Tokushima University / Educator and Researcher Directory --- Ueta, Tetsushi

Personal Web Page

https://risa.is.tokushima-u.ac.jp/

https://researchmap.jp/read0017423 (researchmap)

https://orcid.org/0000-0001-5810-437X (ORCID)

Field of Study

○	Nonlinear Engineering, Nonlinear Circuit Technology, Nonlinear System Engineering, Field Informatics

Subject of Study

○	Analysis on Bifurcations and Chaos in Nonlinear Dynamical Systems, Engineering applicaitons of chaos, Visualization of Nonlinear Phenomena, Strategies of Information Security, Administration of Information Systems (bifurcation, chaos, numerical computation, nonlinear dynamical system, chaos control, Information Security Management System)

Book / Paper

Book:

1.	Motohiro Ishida, Shinki Oyabu, Tetsushi Ueta, Hidekazu Kakei, Kazuhide Kanenishi, Hiroki Tanioka, Shin-ichi Nakayama and Akihiro Haga : 情報科学入門統計・データサイエンス・AI, 技術評論社, Mar. 2021.
2.	Hiroyuki Asahara, Takuji Kousaka and Tetsushi Ueta : Analysis of bifurcation in oscillatory circuits, --- Oscillator Circuits: Frontiers in Design, Analysis and Applications, Y. Nishio (ed.) ---, Inspec/Iee, London, Dec. 2016. (Summary) In this chapter, we investigate the bifurcation phenomena observed in oscillatory circuits. The stability and bifurcation phenomena in autonomous systems are introduced by focusing on the equilibrium point and the fixed point. The characteristics and conditions of the saddlenode bifurcation, Hopf bifurcation, and pitchfork bifurcation are discussed for the equilibrium point. Likewise, the characteristics and conditions of the saddle-node bifurcation, period-doubling bifurcation, Neimark Sacker bifurcation, and pitchfork bifurcation are introduced for the fixed point. The method for computing the bifurcation points of the equilibrium point and the periodic points is also introduced, and an example of an application is presented. (Link to Publication Site) ● Publication site (DOI): 10.1049/PBCS032E_ch2 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1049/PBCS032E_ch2 (DOI: 10.1049/PBCS032E_ch2)
3.	Yusuke Nishiuchi and Tetsushi Ueta : Bifurcation Analysis of a Simple 3D BVP Oscillator and Chaos Synchronization of Its Coupled Systems, Chapter 9, Handbook of Applications of Chaos Theory, CRC Press, Boca Raton, Jun. 2016. (Link to Publication Site) ● Publication site (DOI): 10.1201/b20232-12 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1201/b20232-12 (DOI: 10.1201/b20232-12)
4.	Ken'ichi Fujimoto, Tetsuya Yoshinaga, Tetsushi Ueta and Kazuyuki Aihara : Parametric Control to Avoid Bifurcation Based on Maximum Local Lyapunov Exponent, --- K. Aihara, J. Imura and T. Ueta (eds), Analysis and Control of Complex Dynamical Systems ---, Springer, Tokyo, Mar. 2015. (Keyword) bifurcation (Link to Publication Site) ● Publication site (DOI): 10.1007/978-4-431-55013-6_5 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1007/978-4-431-55013-6_5 (DOI: 10.1007/978-4-431-55013-6_5)
5.	Miki Kobayashi, Tetsushi Ueta and Kazuyuki Aihara : Feedback control method based on predicted future states for controlling chaos, --- K. Aihara, J. Imura and T. Ueta (eds), Analysis and Control of Complex Dynamical Systems ---, Springer, Tokyo, Mar. 2015. (Keyword) controlling chaos / hybrid system / switching threshold (Link to Publication Site) ● Publication site (DOI): 10.1007/978-4-431-55013-6_9 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1007/978-4-431-55013-6_9 (DOI: 10.1007/978-4-431-55013-6_9)
6.	Daisuke Ito, Tetsushi Ueta, Takuji Kousaka, Jun'ichi Imura and Kazuyuki Aihara : Threshold control for stabilization of unstable periodic orbits in chaotic hybrid systems, --- K. Aihara, J. Imura and T. Ueta (eds), Analysis and Control of Complex Dynamical Systems ---, Springer, Tokyo, Mar. 2015. (Summary) Stabilization of unstable periodic orbits within a given chaotic hybrid dynamical system is realized by a variable threshold value. In the conventional chaos control methods, a control input is proportional to the difference between the target orbit and the current state and it is added to a specific system parameter or the state as a small perturbation. Thus the whole system consumes a certain control energy as the amount of such input values during the transition state. We propose a new control method that changing the threshold value dynamically to stabilize the chaotic orbit. No actual control input is added into the system unlike the OGY method and the delayed feedback control. When the orbit hits the threshold, the state-feedback only determines the next threshold value to convey the controlled orbit to the target unstable periodic orbit enventually. Thus the orbit starting from the current threshold value reaches the next controlled threshold value without any control energy. We obtain the variation of the threshold value from the composite Poincar´e map, and the controller is designed by the linear feedback theory with this variation. We demonstrate this method in simple hybrid chaotic systems and show its control performances with evaluating basins of attraction. (Keyword) controlling chaos / hybrid system / switching threshold (Link to Publication Site) ● Publication site (DOI): 10.1007/978-4-431-55013-6_6 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1007/978-4-431-55013-6_6 (DOI: 10.1007/978-4-431-55013-6_6)
7.	Clara Gracio, Daniele Fournier-Prunaret, Tetsushi Ueta and Yoshifumi Nishio : Nonlinear Maps and their Applications; Selected Contributions from the NOMA 2011 International Workshop, Springer, New York, Mar. 2014. (Link to Publication Site) ● Publication site (DOI): 10.1007/978-1-4614-9161-3 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1007/978-1-4614-9161-3 (DOI: 10.1007/978-1-4614-9161-3)
8.	Tetsushi Ueta : Manifolds and global bifurcations, Controlling Chaos, 朝倉書店, 東京, Aug. 2013. (Summary) 非線形力学系の平衡点・固定点に関する多様体とそれにまつわる大域的分岐について解説している．また，カオス中の不安定周期軌道を安定化するカオス制御について基本的な技術を解説している．
9.	Haruki Inoue, Takahiro Hasegawa, Shinya Mizuno, Hiroyuki Ishii, Masaki Nagata, Keiko Suzuki, Tomoyuki Sakata, Naoyo Sugiura, Misaki Asano, Mutumi Seki, Tetsuhiko Ichikawa, Tetsushi Ueta and Yoshiki Mihara : BCPを支えるクラウド情報基盤, 静岡学術出版, Shizuoka, Jun. 2012.
10.	Kenji Matsuura, Naka Gotoda, Tetsushi Ueta and Yoneo Yano : Design of the Community Site for Supporting Multiple Motor-Skill Development, Springer-Verlag, Heidelberg, Germany, Oct. 2011. (Link to Publication Site) ● Publication site (DOI): 10.1007/978-3-642-23190-2_15 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1007/978-3-642-23190-2_15 (DOI: 10.1007/978-3-642-23190-2_15)
11.	Tetsushi Ueta : 1-1 力学系，相空間，1-2 保存系，可積分系，散逸系，2-1-3 ローレンツシステム，レスラーシステム, Institute of Electronics, Information and Communication Engineers, 東京, Sep. 2010. (Summary) 力学系および相空間の定義を，写像や微分方程式を基に与える．続いて力学系の構造に基づき，保存系，可積分系，散逸系について性質を述べる．また，二つのカオス的力学系について，発見の歴史的経緯，分岐構造等について解説する．
12.	Masanori Miyata, Koichiro Tsuchiya, Toshiki Takeuchi and Tetsushi Ueta : テスト問題·レポート課題作成ハンドブック, Center for University Extension, Tokushima, Jan. 2004. (Summary) 大学の授業で成績評価をする際のテスト問題やレポート課題を作成するためのハンドブックです． (Keyword) テスト問題 / レポート課題
13.	Tetsushi Ueta, Tohru Kawabe, Hiroshi Kawakami and Guanrong Chen : Calculation and Control of Unstable Periodic Orbits in Piecewise-Smooth Dynamical Systems., --- G. Chen, D. J. Hill, and X. Yu (eds), (Chaos and Bifurcation Control: Theory and Applications ---, Springer-Verlag, Berlin, Jul. 2003. (Summary) This chapter describes a simple method for calculating unstable periodic orbits (UPOs) and their control in piecewise smooth autonomous systems. The algorithm can be used to obtain any desired UPO embedded in a chaotic attractor, and the UPO can be stabilized by a simple statefeedback control. Some illustrative examples are shown for demonstration. (Link to Publication Site) ● Publication site (DOI): 10.1007/978-3-540-44986-7_14 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1007/978-3-540-44986-7_14 (DOI: 10.1007/978-3-540-44986-7_14)
14.	Tetsushi Ueta and Hiroshi Kawakami : Numerical approaches to bifurcation analysis, --- G. Chen and T. Ueta (eds), in Chaos in Circuits and Systems, Chapter 28 ---, World Scientific, Singapore, Jul. 2002. (Summary) This chapter investigates direct methods for evaluating the bifurcation parameter values of periodic solutions in nonlinear systems. The method can numerically calculate parameter values with high convergence rate and accuracy, at which local bifurcations; tangent, period-doubling, Neimark-Sacker and pitchfork bifurcations are occurred. The method uses some basic properties of the characteristic equation for a fixed point of the corresponding Poincare map. The location and parameter value of the fixed point are used as independent variables in the computation that employs quadratically convergency in Newton method. In addition, in the case of Neimark-Sacker bifurcation, the argument of the complex conjugate multiplier or the other parameter is used as the independent variable. This direct method utilize accurate solution of variational equations with numerical integration, thus implementaion of algorithm becomes very simple. Some numerical examples are given. (Link to Publication Site) ● Publication site (DOI): 10.1142/9789812705303_0028 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/9789812705303_0028 (DOI: 10.1142/9789812705303_0028)
15.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Nonlinear dynamical systems with interrupted characteristics: Bifurcation and control, --- G. Chen and T. Ueta (eds), in Chaos in Circuits and Systems, Chapter 19 ---, World Scientific, Singapore, Jul. 2002. (Summary) 断続特性および非線形特性をもつ回路について，生じる周期解の発生，分岐について検討している．回路のクラスを周期外力を加える系，自律系に分けて分岐現象をのべ，分岐パラメータの計算方法を提案し，計算例を示している．区分非線形系の分岐問題について，その数値計算について例題を用いて説明している文献は他に例をみない．ポアンカレ写像の構成方法，不可微分点でのヤコビ行列の求積方法に新規性がある．また，断続系に特有な分岐現象についてもその数値計算方法について述べている． (Link to Publication Site) ● Publication site (DOI): 10.1142/9789812705303_0019 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/9789812705303_0019 (DOI: 10.1142/9789812705303_0019)
16.	合原一幸 and Tetsushi Ueta : 4章カオスと分岐，5章カオスとフラクタル, 放送大学教育振興会, 東京, Apr. 2001. (Summary) 非線形常微分方程式および非線形差分方程式で記述される力学系において，カオスの発生するメカニズムを分岐理論の立場から説明している．簡単な一次元差分方程式による周期点やその分岐，カオスの発生について述べ，その数理を説明している．カオスアトラクタの視覚化や分岐パラメータの数値計算方法も言及する．カオスの持つ状態空間やパラメータ空間における自己相似性やフラクタルの性質を，計算結果のグラフィクス表現とともに詳述している．この本の4，5章に掲載されている．1997年の「カオスの数理と技術」の改訂版であるが，全面的に内容を刷新し，補助的なデータを掲載している．
17.	Tetsushi Ueta and Guanrong Chen : Chaos and Bifurcation in Coupled Networks and Their Contol, --- Controlling Chaos and Bifurcations in Engineering Systems ---, CRC Press, Boca Raton, Jul. 1999. (Summary) This chapter investigates the complex dynamics and control of chaos in a system of strongly connected neural oscillators. More specifically, the existence and stability of some simple equilibria of a coupled-neuron system is first discussed. The system periodic solutions are then analyzed by using the Poincare mapping method. Bifurcation diagrams and topological properties for these periodic solutions are obtained, where synchronization phenomena are classified. Finally, a simple feedback control method for stabilizing an in-phase synchronizing periodic solution embedded in the chaotic attractor of a higher-dimensional model of such coupled neural oscillators is presented.
18.	Tetsushi Ueta and 合原一幸 : 4章カオスと分岐，5章カオスとフラクタル, 放送大学教育振興会, 東京, Apr. 1997. (Summary) 非線形常微分方程式および非線形差分方程式で記述される力学系において，カオスの発生するメカニズムを分岐理論の立場から説明している．簡単な一次元差分方程式による周期点やその分岐，カオスの発生について述べ，その数理を説明している．カオスアトラクタの視覚化や分岐パラメータの数値計算方法も言及する．カオスの持つ状態空間やパラメータ空間における自己相似性やフラクタルの性質を，計算結果のグラフィクス表現とともに詳述している．この本の4，5章に掲載されている．
19.	Hiroshi Kawakami and Tetsushi Ueta : C によるカオス CG, サイエンス社, Tokyo, Apr. 1994. (Summary) 非線形差分方程式で記述されるさまざまな力学系について，パラメータに依存して生じる固定点，周期点，カオスなどのアトラクタを視覚化する．状態空間におけるカオス軌道の表現方法，周期点アトラクタへの吸引集合の視覚化，パラメータにおける分岐集合の計算方法について述べる．C言語のソースをすべて添付し，研究入門者や初学者にも実験できるよう配慮されている．計算結果は高精度グラフィクスにより描画され，多数掲載されている．アトラクタの安定性やその解析方法，分岐パラメータの計算方法もソースコードとともに詳述し，専門家への参考図書としてもなり得る．

Academic Paper (Judged Full Paper):

1.	Michiru Katayama, Kenji Ikeda and Tetsushi Ueta : Stabilization of laminars in chaos intermittency, International Journal of Bifurcation and Chaos, Vol.34, No.2, 2450024-1-2450024-14, 2024. (Summary) Chaos intermittency is composed of a laminar regime, which exhibits almost periodic motion, and a burst regime, which exhibits chaotic motion; it is known that in chaos intermittency, switching between these regimes occurs irregularly. In the laminar regime of chaos intermittency, the periodic solution before the saddle node bifurcation is closely related to its generation, and its behavior becomes periodic in a short time; the laminar is not, however, a periodic solution, and there are no unstable periodic solutions nearby. Most chaos control methods cannot be applied to the problem of stabilizing a laminar response to a periodic solution since they refer to information about unstable periodic orbits. In this paper, we demonstrate a control method that can be applied to the control target that laminar phase of a dynamical system exhibiting chaos intermittency. This method records the time series of a periodic solution prior to the saddle node bifurcation as a pseudo-periodic orbit and feeds it to the control target back. We report that when this control method is applied to a circuit model, laminar motion can be stabilized to a periodic solution via control inputs of very small magnitude, and robust control can be obtained. (Keyword) chaos control / chaos intermittency / bifurcation / OGY method / laminar regime (Tokushima University Institutional Repository) ● Metadata: 118840 (Link to Publication Site) ● Publication site (DOI): 10.1142/S021812742450024X (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S021812742450024X (Tokushima University Institutional Repository: 118840, DOI: 10.1142/S021812742450024X)
2.	Seiya Amoh, Tetsushi Ueta and Hiroshi Kawakami : Transient Responses to Relaxation Oscillations in Multivibrators, IEEE Access, Vol.12, 471-482, 2024. (Summary) The multivibrator is an electronic circuit that has three oscillation states: astable, monostable, and bistable; these circuits typically contain opamps. These states are often modeled using hybrid systems, which contain characteristics of both continuous and discrete time. While an ideal opamp possesses both continuous and discrete characteristics, actual opamps exhibit continuous properties, which necessitate indepth modeling. The relaxation oscillations produced by the multivibrator, characterized by periodic, rapid state changes, are typically modeled by considering slow fast dynamical systems. In these systems, the phenomenon whereby the amplitude of the signal changes rapidly is referred to as a ``canard explosion''. By considering this phenomenon, it is possible to understand the process of relaxation oscillations in the multivibrator. In this work, we model the multivibrator by considering a slow fast dynamical system and observe canard explosions through numerical experiments. This study indicates that the oscillatory changes in the multivibrator are continuous, which explains the onset of relaxation oscillations. Additionally, circuit experiments are conducted using affordable opamps; in this experimental work, canard explosions are observed. (Keyword) bifurcation analysis / canard / multivibrator / singular perturbation / slow-fast dynamical systems (Tokushima University Institutional Repository) ● Metadata: 118852 (Link to Publication Site) ● Publication site (DOI): 10.1109/ACCESS.2023.3345840 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1109/ACCESS.2023.3345840 (Tokushima University Institutional Repository: 118852, DOI: 10.1109/ACCESS.2023.3345840)
3.	Yuu Miino and Tetsushi Ueta : Structurally unstable synchronization and border-collision bifurcations in the twocoupled Izhikevich neuron model, International Journal of Bifurcation and Chaos, Vol.33, No.16, 2330040, 2023. (Summary) This study investigates a structurally unstable synchronization phenomenon observedin the two-coupled Izhikevich neuron model. As the result of varying the systemparameter in the region of parameter space close to where the unstablesynchronization is observed, we find significant changes in the stability of its periodicmotion. We derive a discrete-time dynamical system that is equivalent to the originalmodel and reveal that the unstable synchronization in the continuous-time dynamicalsystem is equivalent to border-collision bifurcations in the corresponding discrete-timesystem. Furthermore, we propose an objective function that can be used to obtain theparameter set at which the border-collision bifurcation occurs. The proposed objectivefunction is numerically differentiable and can be solved using Newton's method. Wenumerically generate a bifurcation diagram in the parameter plane, including theborder-collision bifurcation sets. In the diagram, the border-collision bifurcation setsshow a novel bifurcation structure that resembles the `strike-slip fault' observed ingeology. This structure implies that, before and after the border-collision bifurcationoccurs, the stability of the periodic point discontinuously changes in some cases butmaintains in other cases. In addition, we demonstrate that a border-collision bifurcationsets successively branch at distinct points. This behavior results in a tree-like structurebeing observed in the border-collision bifurcation diagram; we refer to this structure asa border-collision bifurcation tree. We observe that a periodic point disappears at theborder-collision bifurcation in the discrete-time dynamical system and is simultaneouslyreplaced by another periodic point; this phenomenon corresponds to a change in thefiring order in the continuous-time dynamical system. (Keyword) two-coupled Izhikevich neuron model / structurally unstable synchronization / border-collision bifurcation (Tokushima University Institutional Repository) ● Metadata: 118725 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127423300409 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127423300409 (Tokushima University Institutional Repository: 118725, DOI: 10.1142/S0218127423300409)
4.	Masaki Yoshikawa, Kentaro Ono and Tetsushi Ueta : Bifurcations in a forced Wilson-Cowan neuron pair, Nonlinear Theory and Its Applications, IEICE, Vol.E14-N, No.2, 366-377, 2023. (Summary) We investigate bifurcations of periodic solutions observed in the forced Wilson Cowan neuron pair by both the brute-force computation and the shooting method. By superimposing the results given by both methods, a detailed topological classification of periodic solutions is achieved that includes tori and chaos attractors in the parameter space is achieved. We thoroughly explore the parameter space composed of threshold values, amplitude, and angular velocity of an external forcing term. Many bifurcation curves that are invisible when using brute-force method are solved by the shooting method. We find out a typical bifurcation structure including Arnold tongue in the angular velocity and the amplitude of the external force parameter plane, and confirm its fractal structure. In addition, the emergence of periodic bursting responses depending on these patterns is explained. (Keyword) Wilson-Cowan model / bifurcation / brute-force analysis / torus / chaos / entrainment (Tokushima University Institutional Repository) ● Metadata: 117907 (Link to Publication Site) ● Publication site (DOI): 10.1587/nolta.14.366 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/nolta.14.366 (Tokushima University Institutional Repository: 117907, DOI: 10.1587/nolta.14.366)
5.	Rina Yano, Hiroki Tanioka, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : Quantitative Measurement and Analysis to Computational Thinking for Elementary Schools in Japan, Information Engineering Express, IIAI International Journal Series, Vol.8, No.1, IEE658, 1-17, 2022. (Summary) In Japan, programming education has been made compulsory in elementary schools since 2020. The Programming Education Guide (GPE) explains the purpose of programming education and the abilities that can be fostered through programming education. In addition, the Portal Site for Programming Education Focusing on Elementary Schools introduces various examples of programming education. However, there is little information measuring whether programming classes are effective in improving OTWP (Objective Thinking as a Way of Programming) abilities based on CT (Computational Thinking), except for reports of improvement after simple statistical analysis. Therefore, we prepared 30 CT questions, 12 basic and 18 applied, for the CT test considering four key techniques, decomposition, pattern recognition, abstraction, and algorithms, of which 14 questions were pre-test and seven questions were assessment test. In the experiment, 18 elementary school students from grades 1st to 6th were given a short workshop only once, and the analysis of the effect was done statistically, considering their habituation to the problems. The results of the experiment showed that there was no effect of the one-time workshop, unlike other reports of improvement that used simple statistical methods. It became clear that the CT ability was not improved by the short education. On the other hand, a new finding is that females may be inferior to males in three techniques: decomposition, algorithm, and abstraction. (Keyword) Programming education / Computational thinking / Learning analytics (Tokushima University Institutional Repository) ● Metadata: 116887 (Link to Publication Site) ● Publication site (DOI): 10.52731/iee.v8.i1.658 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.52731/iee.v8.i1.658 (Tokushima University Institutional Repository: 116887, DOI: 10.52731/iee.v8.i1.658)
6.	Yuu Miino and Tetsushi Ueta : Calculation method for unstable periodic points in two-to-one maps using symbolic dynamical system, Nonlinear Theory and Its Applications, IEICE, Vol.E13-N, No.2, 215-220, 2022. (Summary) In this study, we have focused on the two-to-one maps and developed the numerical method to calculate the unstable periodic points (UPPs), based on the theory of the symbolic dynamical system. The core technique of the method is the definition of a non-deterministic map G. From the experimental result of three typical maps: logistic map, tent map, and Bernoulli map, we have confirmed the proposed method works very well within the defined errors. Our method has the following advantages: the method converges rapidly as the period of the target UPP is larger; we can choose the target UPP regardless of its cause (any bifurcation is not a matter); we can find the UPPs that are always unstable in the given parameter range. The convergence of the method is guaranteed by two standpoints: the corresponding symbolic dynamical system, and the asymptotic stability of UPP of G. Hereby, the error of the convergence is scalable according to the numeric precision of the software. (Keyword) chaos / two-to-one map / unstable periodic point / symbolic dynamical system (Tokushima University Institutional Repository) ● Metadata: 116701 (Link to Publication Site) ● Publication site (DOI): 10.1587/nolta.13.215 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/nolta.13.215 (Tokushima University Institutional Repository: 116701, DOI: 10.1587/nolta.13.215)
7.	Yuu Miino and Tetsushi Ueta : Homoclinic bifurcation analysis for logistic map, Nonlinear Theory and Its Applications, IEICE, Vol.E13-N, No.2, 209-214, 2022. (Summary) In this study, we have developed the method to obtain the homoclinic bifurcation parameter of an arbitrary targeted fixed point in the logistic map Tr. We have considered the geometrical structure of Tr around x = 0.5 and derived the core condition of the bifurcation occurrence. As the result of numerical experiment, we have calculated the exact bifurcation parameter of the fixed point with ℓ<= 256. We have also discussed the Feigenbaum constants found in the bifurcation parameter and the fixed point coordinate sequences. This fact implies the local stability of the fixed point and global structure around it are in association via the constants. (Keyword) homoclinic bifurcation / logistic map / global bifurcation / Feigenbaum constants (Tokushima University Institutional Repository) ● Metadata: 116702 (Link to Publication Site) ● Publication site (DOI): 10.1587/nolta.13.209 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/nolta.13.209 (Tokushima University Institutional Repository: 116702, DOI: 10.1587/nolta.13.209)
8.	Seiya Amoh, Miho Ogura and Tetsushi Ueta : Computation of bifurcations: Automatic provisioning of variational equations, Nonlinear Theory and Its Applications, IEICE, Vol.E13-N, No.2, 440-445, 2022. (Summary) In the conventional implementations for solving bifurcation problems, Jacobian matrix and its partial derivatives regarding the given problem should be provided manually. This process is not so easy, thus it often induces human errors like computation failures, typing error, especially if the system is higher order. In this paper, we develop a preprocessor that gives Jacobian matrix and partial derivatives symbolically by using SymPy packages on the Python platform. Possibilities about the inclusion of errors are minimized by symbolic derivations and reducing loop structures. It imposes a user only on putting an expression of the equation into a JSON format file. We demonstrate bifurcation calculations for discrete neuron dynamical systems. The system includes an exponential function, which makes the calculation of derivatives complicated, but we show that it can be implemented simply by using symbolic differentiation. (Keyword) chaos / bifurcation / symbolic differentiation (Tokushima University Institutional Repository) ● Metadata: 116700 (Link to Publication Site) ● Publication site (DOI): 10.1587/nolta.13.440 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/nolta.13.440 (Tokushima University Institutional Repository: 116700, DOI: 10.1587/nolta.13.440)
9.	Atsuo Maki, Yuu Miino, Naoya Umeda, Masahiro Sakai, Tetsushi Ueta and Hiroshi Kawakami : Nonlinear dynamics of ship capsizing at sea, Nonlinear Theory and Its Applications, IEICE, Vol.E13-N, No.1, 2-24, 2022. (Summary) Capsizing is one of the worst scenarios in oceangoing vessels. It could lead to a high number of fatalities. A considerable number of studies have been conducted until the 1980s, and one of the discoveries is the weather criterion established by the International Maritime Organization (IMO). In the past, one of the biggest difficulties in revealing the behavior of ship-roll motion was the nonlinearity of the governing equation. On the other hand, after the mid-1980s, the complexity of the capsizing problem was uncovered with the aid of computers. In this study, we present the theoretical backgrounds of the capsizing problem from the viewpoint of nonlinear dynamics. Then, we discuss the theoretical conditions and mechanisms of the bifurcations of periodic solutions and numerical attempts for the bifurcations and capsizing. (Keyword) capsizing / regular sea / safe-basin boundary / global bifurcation (Tokushima University Institutional Repository) ● Metadata: 116263 (Link to Publication Site) ● Publication site (DOI): 10.1587/nolta.13.2 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/nolta.13.2 (Tokushima University Institutional Repository: 116263, DOI: 10.1587/nolta.13.2)
10.	Seiya Amoh, Xu Zhang, Guanrong Chen and Tetsushi Ueta : Bifurcation Analysis of a Class of Generalized Henon Maps with Hidden Dynamics, IEEJ Transactions on Electrical and Electronic Engineering (TEEE), Vol.16, No.published online, 2021. (Summary) Although continuous systems such as the Chua circuit are known as systems with hidden attractors, hidden attractors also exist in classical discrete maps, such as a generalized Henon map. A hidden attractor is an attractor that does not overlap with its own attracting region in its vicinity, which makes it difficult to visualize. In this paper, a local bifurcation analysis method for discrete maps is described, and the bifurcation analysis of the generalized Henon map is performed using the method. The bifurcation structure, as the parameters are changed, shows a certain law, and the interesting Neimark-Sacker bifurcation and period-doubling bifurcation are confirmed to occur simultaneously. It was also found that the hidden attractors exist in the rectangular characteristic chaotic regions, and they appear relatively frequently near the window of chaos. (Keyword) hidden attractor / bifurcation analysis / chaos (Tokushima University Institutional Repository) ● Metadata: 116264 (Link to Publication Site) ● Publication site (DOI): 10.1002/tee.23480 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1002/tee.23480 (Tokushima University Institutional Repository: 116264, DOI: 10.1002/tee.23480)
11.	Yuu Miino, Daisuke Ito, Tetsushi Ueta and Hiroshi Kawakami : Locating and stabilizing unstable periodic orbits embedded in the horseshoe map, International Journal of Bifurcation and Chaos, Vol.31, No.4, 2150110, 2021. (Summary) Based on the theory of symbolic dynamical systems, we propose a novel computation method to locate and stabilize the unstable periodic points (UPPs) in a two-dimensional dynamical system with a Smale horseshoe. This method directly implies a new framework for controlling chaos. By introducing the subset based correspondence between a planar dynamical system and a symbolic dynamical system, we locate regions sectioned by stable and unstable manifolds comprehensively and identify the speci ed region containing a UPP with the particular period. Then Newton's method compensates the accurate location of the UPP with this region information as an initial guess. On the other hand, the external force control (EFC) is known as an e ective method to stabilize the UPPs. By applying the EFC to the located UPPs, robust controlling chaos is realized. In this framework, we never use ad hoc approaches to nd target UPPs in the given chaotic set. Moreover, the method can stabilize UPPs with the speci ed period regardless of the situation where the targeted chaotic set is attractive or not. As illustrative numerical experiments, we locate and stabilize UPPs and the corresponding unstable periodic orbits in a horseshoe structure of the Du ng equation. In spite of the strong instability of UPPs, the controlled orbit is robust and the control input retains tiny in magnitude. (Keyword) chaos / horseshoe map / symbolic dynamics / unstable periodic point / numerical computation / controlling chaos (Tokushima University Institutional Repository) ● Metadata: 115874 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127421501108 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127421501108 (Tokushima University Institutional Repository: 115874, DOI: 10.1142/S0218127421501108)
12.	Takafumi Bando, Hironori Takeuchi, Tetsushi Ueta and Kenji Matsuura : A management of the support life cycle for client operating systems in Tokushima University, Journal for Academic Computing and Networking, No.24, 48-57, 2020. (Summary) 大学など研究機関は，常にサイバー攻撃の脅威にさらされており，水際であるPC，および搭載OSのセキュリティ対策の需要が高まっている．本学では，構成員が使用しているクライアント機器の OSについて，新たな方針の策定と，既存の情報システムを利用したOS更新の促進のための施策を実施した．これら施策は，大学組織の構成員の多様性を考慮して設計されている．学内の認証基盤の網羅性に着目し，そのログを用いて利用者と利用OSを推定，対象となるOSの利用者に対しては個別メールによるOS更新の周知促進を行った．本論文では，その実践事例と効果，今後の課題について述べる． (Keyword) OS / Windows / macOS / Shibboleth (Tokushima University Institutional Repository) ● Metadata: 115736 (Link to Publication Site) ● Publication site (DOI): 10.24669/jacn.24.1_48 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.24669/jacn.24.1_48 (Tokushima University Institutional Repository: 115736, DOI: 10.24669/jacn.24.1_48)
13.	Seiya Amoh, Daisuke Ito and Tetsushi Ueta : A method to suppress local minima for symmetrical DOPO networks, Nonlinear Theory and Its Applications, IEICE, Vol.11, No.4, 580-589, 2020. (Summary) Coherent Ising machine (CIM) implemented by degenerate optical parametric oscillator(DOPO) networks can solve some combinatorial optimization problems. However, whenthe network structure has a certain type of symmetry, optimal solutions caused by pitchforkbifurcations are not always detected since local minima grasp the search process. In addition,a uniform pump rate for DOPOs in the conventional control operation cannot overcome thisproblem. In this paper proposes a method to avoid trapping of the local minima by applying acontrol input in a pump rate of an appropriate node. This control may break the symmetricalproperty and the bifurcation structure temporarily, then it guides the trajectory into the globalminima. We show several simulation results. (Keyword) coherent Ising machine / bifurcation / control (Tokushima University Institutional Repository) ● Metadata: 115318 (Link to Publication Site) ● Publication site (DOI): 10.1587/nolta.11.580 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/nolta.11.580 (Tokushima University Institutional Repository: 115318, DOI: 10.1587/nolta.11.580)
14.	Yuu Miino, Tetsushi Ueta and Hiroshi Kawakami : Bending angles of a broken line causing bifurcations and chaos, Nonlinear Theory and Its Applications, IEICE, Vol.11, No.3, 359-371, 2020. (Summary) We replace the cubic characteristics in the Duffing equation by two line segments connected at a point and investigate how an angle of that broken line conducts bifurcations to periodic orbits. Firstly we discuss differences in periodic orbits between the Duffing equation and a forced planar system including the broken line. In the latter system, a grazing bifurcation split the parameter space into the linear and nonlinear response domains. Also, we show that bifurcations of non-resonant periodic orbits appeared in the former system are suppressed in the latter system. Secondly, we obtain bifurcation diagrams by changing a slant parameter of the broken line. We also nd the parameter set that a homoclinic bifurcation arises and the corresponding horseshoe map. It is clari ed that a grazing bifurcation and tangent bifurcations form boundaries between linear and nonlinear responses. Finally, we explore the piecewise linear functions that show the minimum bending angles exhibiting bifurcation and chaos. (Keyword) local and global bifurcation analysis / piecewise linear dynamical system / hybrid dynamical system / Duffing equation (Tokushima University Institutional Repository) ● Metadata: 114909 (Link to Publication Site) ● Publication site (DOI): 10.1587/nolta.11.359 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/nolta.11.359 (Tokushima University Institutional Repository: 114909, DOI: 10.1587/nolta.11.359)
15.	Yuu Miino and Tetsushi Ueta : Influence of bifurcation structures revealed by refinement of a nonlinear conductance in Josephson junction element, Complexity, No.8931525, 2018. (Summary) We conduct a bifurcation analysis of a single-junction superconducting quantum interferometer with an external flux. We approximate the current-voltage characteristics of the conductance in the equivalent circuit of the JJ by using two types of function: a linear function and a piecewise linear (PWL) function. We describe a method to compute the local stability of the solution orbit and to solve the bifurcation problem. As the result, we reveal the bifurcation structure of the systems in a two-dimensional parameter plane. By making a comparison between the linear and PWL cases, we find a difference in the shapes of their bifurcation sets in the two-dimensional parameter plane even though there are no differences in the one-dimensional bifurcation diagrams or the trajectories. As for the influence of piecewise linearization, we discovered that grazing bifurcations terminate the calculation of the local bifurcations, because they drastically change the stability of the periodic orbit. (Tokushima University Institutional Repository) ● Metadata: 112949 (Link to Publication Site) ● Publication site (DOI): 10.1155/2018/8931525 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1155/2018/8931525 (Tokushima University Institutional Repository: 112949, DOI: 10.1155/2018/8931525)
16.	Yuu Miino, Daisuke Ito, Hiroyuki Asahara, Takuji Kousaka and Tetsushi Ueta : A general method to stabilize unstable periodic orbits for switched dynamical systems with a periodically moving threshold, International Journal of Circuit Theory and Applications, 1-14, 2018. (Summary) In the previous study, a method to control chaos for switched dynamical systems with constant threshold value has been proposed. In this paper, we extend this method to the systems including a periodically moving threshold. The main control scheme is based on the pole placement, then a small control perturbation added to the moving threshold value can stabilize an unstable periodic orbit embedded within a chaotic attractor. For an arbitrary periodic function of the threshold movement, we mathematically derive the variational equations, the state feedback parameters, and a control gain by composing a suitable Poincaré map. As examples, we illustrate control implementations for systems with thresholds whose movement waveforms are sinusoidal and sawtooth-shape, and unstable one and two periodic orbits in each circuit are stabilized in numerical and circuit experiments. In these experiments, we confirm enough convergence of the control input. (Keyword) controlling chaos / switched dynamical system / numerical simulation / circuit implementation (Tokushima University Institutional Repository) ● Metadata: 112951 (Link to Publication Site) ● Publication site (DOI): 10.1002/cta.2573 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1002/cta.2573 (Tokushima University Institutional Repository: 112951, DOI: 10.1002/cta.2573)
17.	Atsuo Maki, Lawrence Virgin, Naoya Umeda, Tetsushi Ueta, Yuu Miino and Hiroshi Kawakami : On the loss of stability of periodic oscillations and its relevance to ship capsize, Journal of Marine Science and Technology, 2018. (Summary) This research aims to analytically investigate beam seas roll motion. So far, in the analytical investigation for this topic, the softening Duffing equation has been often utilized because of its similarity to the ship equation of motion, and considerable number of researches have been reported. In this research, we focus on the loss of stability of periodic oscillation and its relevance to ship capsize. In the past researches, the threshold of saddle-node bifurcation, flip bifurcation and heteroclinic bifurcation has been obtained. Among them, the condition with respect to flip was derived from the negative stiffness condition in the variational equation having the form of Mathieus equation. On the other hand, in this paper, the authors reconsider the phenomenon and then that threshold is identical with that of pitchfork bifurcation. Furthermore, the practical capsizing threshold was introduced by using the solution after pitchfork bifurcation. The result shows the fairly good agreement with the numerically obtained capsizing boundary. It means that applying the unsymmetric solution after pitchfork bifurcation into capsizing assessment is reasonable. (Keyword) Nonlinear dynamics / Softening Duffing equation / Capsizing / Pitchfork bifurcation (Tokushima University Institutional Repository) ● Metadata: 113428 (Link to Publication Site) ● Publication site (DOI): 10.1007/s00773-018-0591-x (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1007/s00773-018-0591-x (Tokushima University Institutional Repository: 113428, DOI: 10.1007/s00773-018-0591-x)
18.	Daisuke Ito, Tetsushi Ueta and Kazuyuki Aihara : Bifurcation analysis of eight coupled degenerate optical parametric oscillators, Physica D: Nonlinear Phenomena, Vol.372, 22-30, 2018. (Summary) A degenerate optical parametric oscillator (DOPO) network realized as a coherent Ising machine can be used to solve combinatorial optimization problems. Both theoretical and experimental investigations into the performance of DOPO networks have been presented previously. However a problem remains, namely that the dynamics of the DOPO network itself can lower the search success rates of globally optimal solutions for Ising problems. This paper shows that the problem is caused by pitchfork bifurcations due to the symmetry structure of coupled DOPOs. Some two-parameter bifurcation diagrams of equilibrium points express the performance deterioration. It is shown that the emergence of non-ground states regarding local minima hampers the system from reaching the ground states corresponding to the global minimum. We then describe a parametric strategy for leading a system to the ground state by actively utilizing the bifurcation phenomena. By adjusting the parameters to break particular symmetry, we find appropriate parameter sets that allow the coherent Ising machine to obtain the globally optimal solution alone. (Keyword) bifurcation analysis / degenerate optical parametric oscillators / symmetry-breaking bifurcations (Tokushima University Institutional Repository) ● Metadata: 112111 (Link to Publication Site) ● Publication site (DOI): 10.1016/j.physd.2018.01.010 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1016/j.physd.2018.01.010 (Tokushima University Institutional Repository: 112111, DOI: 10.1016/j.physd.2018.01.010)
19.	Daisuke Ito, Hiroyuki Asahara, Takuji Kousaka and Tetsushi Ueta : Clock pulse modulation for ripple reduction in buck-converter circuits, Chaos, Solitons & Fractals, Vol.111, 138-145, 2018. (Summary) DC-DC switching converters which are frequently treated as hybrid dynamical systems exhibit complex behavior due to nonlinear and interrupt characteristics. For synchronous buck-converters, we propose a method to control chaotic behavior by pulse frequency modulation. An input voltage, a duty ratio of PWMs, and so on, affect to the regulation characteristics of converters directly, but a frequency of PWMs is determined by the frequency characteristics of the converter and is set as a fixed value. The proposed chaos-control method suppresses chaotic responses by slightly perturbing the pulse frequency alone, therefore our method can stabilize unstable periodic orbits without influence on the voltage regulation scheme. To simplify the feedback controller, the condition of dimension reduction for the controlling gain vector is derived. The proposed controller acheves the stabilization without a current sensor. Numerical simulation and circuit implementation demonstrate the validity of this method. (Keyword) controlling chaos / buck converter / pulse-frequency modulation (Tokushima University Institutional Repository) ● Metadata: 112108 (Link to Publication Site) ● Publication site (DOI): 10.1016/j.chaos.2018.04.015 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85045703294 (Tokushima University Institutional Repository: 112108, DOI: 10.1016/j.chaos.2018.04.015, Elsevier: Scopus)
20.	Yuu Miino, Tetsushi Ueta and Hiroshi Kawakami : Nonlinear resonance and devil's staircase in a forced planer system containing a piecewise linear hysteresis, Chaos, Solitons & Fractals, Vol.111, 75-85, 2018. (Summary) The Duffing equation describes a periodically forced oscillator model with a nonlinear elasticity. In its circuitry, a saturable-iron core often exhibits a hysteresis. However, a few studies about the Duffing equation has discussed the effects of the hysteresis because of difficulties in their mathematical treatment. In this paper, we investigatea forced planer system demonstrating the Duffing equation containing the hysteresis. For simplicity, we approximate the hysteresis to a piecewise linear function. Since the solutions are expressed by combinations of some dynamical systems and switching conditions, a finite-state machine is derived from the hybrid system approach, and then bifurcation theory can be applied to it. We topologically classify periodic solutions and compute local and grazing bifurcation sets accurately. In comparison with the Duffing equation, we discuss the effects caused by the hysteresis, such as the devil's staircase in resonant solutions. (Keyword) bifurcation analysis / hybrid system / nonlinear resonance / Duffing equation / devil's staircase / chaos (Tokushima University Institutional Repository) ● Metadata: 111897 (Link to Publication Site) ● Publication site (DOI): 10.1016/j.chaos.2018.04.007 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85045410451 (Tokushima University Institutional Repository: 111897, DOI: 10.1016/j.chaos.2018.04.007, Elsevier: Scopus)
21.	Tomohiro Takeda, Kenji Ohira, Hiroki Tanioka, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : A Method to Detect Rogue Access Points in a Campus without Decrypting WLAN Frames, The Transactions of the Institute of Electronics, Information and Communication Engineers B, Vol.J101-B, No.2, 90-99, 2018. (Summary) Security problems of rogue APs exist because there are many wireless access points (APs) in a campus. In many cases, there are not only university-wide network administrators but also subnet administrators and the former ones usually do not know details of each subnet. We propose a method for the university-wide network administrators to detect rogue APs without decrypting WLAN frames. HTTP packets of captive portal detection are used in this method. As a result of our evaluation, we confirmed that it is possible to associate an IP address as seen from wired upstream network and a frame from WLAN. (Keyword) campus network / rogue access point / captive portal / wireless LAN (Tokushima University Institutional Repository) ● Metadata: 113976 (Link to Publication Site) ● Publication site (DOI): 10.14923/transcomj.2017GTP0013 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050845763785488256 ● Search Scopus @ Elsevier (DOI): 10.14923/transcomj.2017GTP0013 (Tokushima University Institutional Repository: 113976, DOI: 10.14923/transcomj.2017GTP0013, CiNii: 1050845763785488256)
22.	Takeshi Kojima, Tetsushi Ueta and Tetsuya Yoshinaga : Multivalued discrete tomography using dynamical system that describes competition, Mathematical Problems in Engineering, Vol.2017, No.Article ID 8160354, 9-pages, 2017. (Summary) Multivalued discrete tomography involves reconstructing images composed of three or more gray levels from projections. We propose a method based on the continuous-time optimization approach with a nonlinear dynamical system that effectively utilizes competition dynamics to solve the problem of multivalued discrete tomography. We perform theoretical analysis to understand how the system obtains the desired multivalued reconstructed image. Numerical experiments illustrate that the proposed method also works well when the number of pixels is comparatively high even if the exact labels are unknown. (Tokushima University Institutional Repository) ● Metadata: 114381 (Link to Publication Site) ● Publication site (DOI): 10.1155/2017/8160354 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1155/2017/8160354 (Tokushima University Institutional Repository: 114381, DOI: 10.1155/2017/8160354)
23.	Masahiko Sano, Kenji Matsuura, Tetsushi Ueta and Kanae Yagi : BCP Test Results and Problems of Information Systems in Tokushima University, Journal for Academic Computing and Networking, Vol.20, No.1, 119-127, 2016. (Summary) 徳島大学の所在地である徳島県は南海・東南海地震の発生確率が高いとされており，大規模災害を想定した事業継続計画(BCP)の策定とその実施は重要である．本学では情報システムのBCPの一環として，DCを活用したネットワーク基盤及び広域無線の整備を平成25年度末に実施した．これは，被災確率の高いキャンパスに集中する基盤情報システムやネットワークを再設計し，被災時の可用性及び事業継続性の向上を目的としている．徳島大学情報センターでは，情報センターのISMS運用に従い，対策の有効性確認と試験のため，平成26年度，27年度に情報システムのBCPテストを実施した．本論文では，これらテスト結果と改善課題および情報システムのBCPへのリスクの影響について考察する. (Keyword) 情報系システム / BCPテスト / ISMS / リスク管理 (Tokushima University Institutional Repository) ● Metadata: 115737 (Link to Publication Site) ● Publication site (DOI): 10.24669/jacn.20.1_119 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390282763041457408 ● Search Scopus @ Elsevier (DOI): 10.24669/jacn.20.1_119 (Tokushima University Institutional Repository: 115737, DOI: 10.24669/jacn.20.1_119, CiNii: 1390282763041457408)
24.	Ken'ichi Fujimoto, Tomohiro Otsu, Hiroyuki Kitajima and Tetsushi Ueta : Control Technique of Maximum Local Lyapunov Exponent on Stable Periodic Solution in Continuous-Time Non-Autonomous Dynamical Systems, International Journal of Computing Communication and Instrumentation Engineering, Vol.3, No.2, 349-353, 2016. (Summary) We previously proposed a parametric controller to avoid undesirable bifurcations of stable fixed and periodic points in discrete-time dynamical systems. The parameter regulation is derived from an optimization problem on the maximum local Lyapunov exponent and a method of steepest descent. In this paper, on the basis of the ideas and a stroboscopic mapping that transforms the trajectory of a continuous-time periodic solution into a sequence of points, we propose a technique to control the maximum local Lyapunov exponent on stable periodic oscillations in continuous-time non-autonomous dynamical systems. (Keyword) Maximum local Lyapunov exponent / parametric control / stroboscopic mapping / stable periodic oscillation / continuous-time non-autonomous dynamical system (Tokushima University Institutional Repository) ● Metadata: 112040 (Link to Publication Site) ● Publication site (DOI): 10.15242/IJCCIE.AE0616114 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.15242/IJCCIE.AE0616114 (Tokushima University Institutional Repository: 112040, DOI: 10.15242/IJCCIE.AE0616114)
25.	Daisuke Ito, Tetsushi Ueta, Takuji Kousaka and Kazuyuki Aihara : Bifurcation Analysis of the Nagumo-Sato Model and its Coupled Systems, International Journal of Bifurcation and Chaos, Vol.26, No.3, 1630006-1-1630006-11, 2016. (Summary) The Nagumo-Sato model is a simple mathematical expression of a single neuron, and it is catego- rized as a discrete-time hybrid dynamical system. To compute bifurcation sets in such a discrete- time hybrid dynamical system accurately, conditions for periodic solutions and bifurcations are formulated herewith as a boundary value problem, and Newton's method is implemented to solve that problem. As the results of the analysis, the following properties are obtained: border- collision bifurcations play a dominant role in dynamical behavior of the model; chaotic regions are distinguished by tangent bifurcations; and multi-stable attractors are observed in its coupled system. We demonstrate several bifurcation diagrams and corresponding topological properties of periodic solutions. (Keyword) discrete-time hybrid dynamical system / Nagumo-Sato model / border-collision bifurcation (Tokushima University Institutional Repository) ● Metadata: 112119 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127416300068 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-84962638018 (Tokushima University Institutional Repository: 112119, DOI: 10.1142/S0218127416300068, Elsevier: Scopus)
26.	Yusuke Tone, Hiroyuki Asahara, Daisuke Ito, Tetsushi Ueta, Kazuyuki Aihara and Takuji Kousaka : Calculation Method of Local Bifurcation Point in Piecewise Nonlinear Discrete-Time Dynamical Systems, Electronics and Communications in Japan, Vol.99, No.3, 22-30, 2016. (Summary) This paper proposes a method for calculation of localbifurcation points in discrete-time dynamical systems withpiecewise nonlinear characteristics (PNDDS). First, ann-dimensional PNDDS, which has two piecewise nonlinearmaps, is shown and its variational equation is derived. Next,a calculation method for the local bifurcation points thatutilizes the conditional equation for the periodic solutionand the characteristic equation is proposed. It is essential tocalculate the derivatives of the map with an initial value andwith a bifurcation parameter to obtain the bifurcation pointscontinuously in the parameter space. The above calculationprocess is a key component of the proposed method, and isexplained in detail. Finally, we apply the proposed methodto a two-dimensional PNDDS and calculate the local bifurcationpoints in order to confirm the validity of the proposedmethod. (Keyword) piecewise nonlinear discrete-time system / local bifurcations / bifurcation analysis (Link to Publication Site) ● Publication site (DOI): 10.1002/ecj.11771 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-84958691300 (DOI: 10.1002/ecj.11771, Elsevier: Scopus)
27.	Tetsushi Ueta, Daisuke Ito and Kazuyuki Aihara : Can a Pseudo Periodic Orbit Avoid a Catastrophic Transition?, International Journal of Bifurcation and Chaos, Vol.25, No.13, 1550185-1-1550185-10, 2015. (Summary) We propose a resilient control scheme to avoid catastrophic transitions associated with saddlenode bifurcations of periodic solutions. The conventional feedback control schemes related to controlling chaos can stabilize unstable periodic orbits embedded in strange attractors or suppress bifurcations such as period-doubling and Neimark-Sacker bifurcations whose periodic orbits are kept existing through bifurcation processes. However, it is impossible to apply these methods directly to a saddle-node bifurcation since the corresponding periodic orbit disappears after such a bifurcation. In this paper, we define a pseudo periodic orbit which can be obtained using transient behavior right after the saddle-node bifurcation, and utilize it as reference data to compose a control input. We consider a pseudo periodic orbit at a saddle-node bifurcation in the Duffing equations as an example, and show its temporary attraction. Then we demonstrate suppression control of this bifurcation, and show robustness of the control. As a laboratory experiment, a saddle-node bifurcation of limit cycles in the BVP oscillator is explored. A control input generated by a pseudo periodic obit can restore a stable limit cycle which disappeared after the saddle-node bifurcation. (Keyword) catastrophic transition / saddle-node bifurcation / unstable periodic orbit / pseudo periodic orbit / suppression of bifurcation (Tokushima University Institutional Repository) ● Metadata: 112060 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127415501850 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127415501850 (Tokushima University Institutional Repository: 112060, DOI: 10.1142/S0218127415501850)
28.	Yuu Miino, Daisuke Ito and Tetsushi Ueta : A computation method for non-autonomous systems with discontinuous characteristics, Chaos, Solitons & Fractals, Vol.77, No.8, 277-285, 2015. (Summary) We propose a computation method to obtain bifurcation sets of periodic solutions in non-autonomous systems with discontinuous properties. If the system has discontinuity for the states and/or the vector field, conventional methods cannot be applied. We have developed a method for autonomous systems with discontinuity by taking the Poincare mapping on the switching point in the preceded study, however, this idea does not work well for some non-autonomous systems with discontinuity. We overcome this difficulty by extending the system to an autonomous system. As a result, bifurcation sets of periodic solutions are solved accurately with a shooting method. We show two numerical examples and demonstrate the corresponding laboratory experiment. (Keyword) bifurcation phenomena / numerical analysis / nonlinear non-autonomous system / discontinuity (Tokushima University Institutional Repository) ● Metadata: 111895 (Link to Publication Site) ● Publication site (DOI): 10.1016/j.chaos.2015.06.014 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-84934760766 (Tokushima University Institutional Repository: 111895, DOI: 10.1016/j.chaos.2015.06.014, Elsevier: Scopus)
29.	Daisuke Ito, Tetsushi Ueta, Takuji Kousaka, Jun'ichi Imura and Kazuyuki Aihara : Controlling chaos of hybrid systems by variable threshold values, International Journal of Bifurcation and Chaos, Vol.24, No.10, 1450125-1-1450125-12, 2014. (Summary) We try to stabilize unstable periodic orbits embedded in the given chaotic hybrid dynamical system by perturbation of a threshold value. In the conventional chaos control methods, a control input is designed by state-feedback value which is proportional to the difference between the target orbit and the current state, and it is applied into the specific system parameter as a small perturbation. During transition state, the control system consumes a certain control energy given by integration of such perturbations. In our method, we changes the threshold value dynamically to control the chaotic orbit. Unlike OGY method or the delayed feedback control, no actual control input is added into the system. The state-feedback is utilized only to determine the dynamic threshold value, thus the orbit starting from the current threshold value reaches the next controlled threshold value without any control energy. We obtain the variation of the threshold value from the composite Poincare map, and the controller is designed by the linear feedback theory with this variation. We demonstrate this method in simple hybrid chaotic systems and show performances with evaluating basins of attractions. (Keyword) controlling chaos / hybrid system / switching threshold (Tokushima University Institutional Repository) ● Metadata: 112118 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127414501259 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-84908626145 (Tokushima University Institutional Repository: 112118, DOI: 10.1142/S0218127414501259, Elsevier: Scopus)
30.	Masahiko Sano, Kanae Yagi and Tetsushi Ueta : Effects of ISMS on the Center for Administration of Information Technology, Tokushima University, Journal for Academic Computing and Networking, Vol.18, No.18, 90-98, 2014. (Summary) 徳島大学情報センターでは，平成24年度3月に国立大学法人内の組織としては4番目にISMS認証を取得した．ISMS認証は情報セキュリティマネジメントの国際標準として知られており，国内の多数の組織が取得している．また，ISMSは情報セキュリティポリシーを運用する仕組みとしても効果的である．本センターはISMS構築後3年経過したことから本センターにおけるISMSの効果について検証と考察を行った．その結果，本センターのISMS導入および運用の効果が確認された．本論文ではその詳細について述べる． (Keyword) ISMS / effect / operation examples / Satellite Communication (Tokushima University Institutional Repository) ● Metadata: 115738 (Link to Publication Site) ● Publication site (DOI): 10.24669/jacn.18.1_90 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390564238052309632 ● Search Scopus @ Elsevier (DOI): 10.24669/jacn.18.1_90 (Tokushima University Institutional Repository: 115738, DOI: 10.24669/jacn.18.1_90, CiNii: 1390564238052309632)
31.	Kenji Matsuura, Tetsushi Ueta, Masahiko Sano, Yosuke Seki, Takeshi Matsumura and Kanae Yagi : Information System BCP and Long Distance Wireless Access Preparing for Disaster Recovery by Tokushima University, Journal for Academic Computing and Networking, Vol.18, No.18, 99-107, 2014. (Summary) <p>A geographical issue of Tokushima University gives the alarm on preparing for expected natural disasters near Nankai-Trough area. However, the university was slow to act so far according to several problems to be solved. The impact of the Great East Japan Earthquake in 2011 made us change our mind of the priority for investments relatively. The university has actually installed and prepared the BCP infrastructure with wireless communication networks on the whole. This paper describes such integrated environments taking geographical conditions into account.</p> (Keyword) BCP for Information Systems / Virtualization Infrastructure / Long Distance Wireless LAN / Satellite Communication (Tokushima University Institutional Repository) ● Metadata: 115739 (Link to Publication Site) ● Publication site (DOI): 10.24669/jacn.18.1_99 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390845713027345536 ● Search Scopus @ Elsevier (DOI): 10.24669/jacn.18.1_99 (Tokushima University Institutional Repository: 115739, DOI: 10.24669/jacn.18.1_99, CiNii: 1390845713027345536)
32.	Yusuke Tone, Hiroyuki Asahara, Daisuke Ito, Tetsushi Ueta, Kazuyuki Aihara and Takuji Kousaka : Calculation Method of Local Bifurcation Point in Piecewise Nonlinear Discrete-Time Dynamical Systems, IEEJ Transactions on Electronics, Information and Systems, Vol.134-C, No.5, 729-736, 2014. (Summary) This paper proposes a calculation method of local bifurcation points for discrete-time dynamical systems with piecewise nonlinear characteristic (PNDDS). First, an n-dimensional PNDDS, which has two piecewise nonlinear maps, is shown and its variational equation is defined. Next, the calculation method of the local bifurcation points is proposed using the conditional equation of the periodic solution and the characteristic equation. Here, we have to calculate derivatives of the map with an initial value and with a bifurcation parameter to obtain the bifurcation points continuously in the parameter space. The above calculation process is a key of the proposed method, and we explain it in detail. Finally, we apply the proposed method to a two-dimensional PNDDS and calculate the local bifurcation points for confirming its validity. (Keyword) piecewise nonlinear discrete-time system / local bifurcations / bifurcation analysis (Link to Publication Site) ● Publication site (DOI): 10.1541/ieejeiss.134.729 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390001204608142080 ● Summary page in Scopus @ Elsevier: 2-s2.0-84899800127 (DOI: 10.1541/ieejeiss.134.729, CiNii: 1390001204608142080, Elsevier: Scopus)
33.	Atsuo Maki, Naoya Umeda and Tetsushi Ueta : Melnikov integral formula for beam sea roll motion utilizing a non-Hamiltonian exact heteroclinic orbit: analytic extension and numerical validation, Journal of Marine Science and Technology, Vol.19, No.3, 257-264, 2014. (Summary) In the research field of nonlinear dynamical system theory, it is well known that a homoclinic/heteroclinic point leads to unpredictable motions, such as chaos. Melnikov's method enables us to judge whether the system has a homoclinic/heteroclinic orbit. Therefore, in order to assess a vessel's safety with respect to capsizing, Melnikov's method has been applied for investigations of the chaos that appears in beam sea rolling. This is because chaos is closely related to capsizing incidents. In a previous paper (Maki et al. in J Mar Sci Technol 15:102 106 2010), a formula to predict the capsizing boundary by applying Melnikov's method to analytically obtain the non-Hamiltonian heteroclinic orbit was proposed. However, in that paper, only limited numerical investigation was carried out. Therefore, further comparative research between the analytical and numerical results is conducted, with the result being that the formula is validated. (Keyword) Melnikov's method / Beam seas / Roll motion / Non-Hamiltonian exact heteroclinic orbit (Tokushima University Institutional Repository) ● Metadata: 113430 (Link to Publication Site) ● Publication site (DOI): 10.1007/s00773-013-0244-z (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-84906786692 (Tokushima University Institutional Repository: 113430, DOI: 10.1007/s00773-013-0244-z, Elsevier: Scopus)
34.	Atsuo Maki, Naoya Umeda, Renilson Martin and Tetsushi Ueta : Analytical methods to predict the surf-riding threshold and the wave-blocking threshold in astern seas, Journal of Marine Science and Technology, Vol.19, No.4, 415-424, 2014. (Summary) For the safe design and operation of high-speed craft, it is important to predict the behavior of these craft in following and astern quartering seas as it is well known that serious problems can occur when a vessel is forced by the waves to travel at wave speed. The surf-riding threshold is the lower speed limit above which the vessel will be forced to travel at wave speed (usually on the face of the wave) which is generally accepted to be a prerequisite for broaching. While a vessel travelling below this speed will experience significant changes in its longitudinal speed in the wave, it will not be forced to travel at wave speed. For high-speed craft, the wave-blocking threshold also becomes important. This is the upper speed, below which the vessel will also be forced to travel at wave speed (usually on the back of the wave) and is related to the possibility of bow diving. By the application of a polynomial approximation to the waveinduced surge force, including the nonlinear surge equation, an analytical formula to predict both the surf-riding and the wave-blocking thresholds is proposed. Comparative results of the surf-riding threshold and wave-blocking threshold predicted utilizing the proposed formula and the thresholds predicted using numerical bifurcation analysis indicate fairly good agreement. In addition, previously proposed analytical formulae are examined. (Keyword) Surf-riding / Wave-blocking / Analytical formula / Nonlinear dynamics (Tokushima University Institutional Repository) ● Metadata: 113431 (Link to Publication Site) ● Publication site (DOI): 10.1007/s00773-014-0257-2 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-84912126257 (Tokushima University Institutional Repository: 113431, DOI: 10.1007/s00773-014-0257-2, Elsevier: Scopus)
35.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : Classification of Bifurcations and Oscillations in Coupled BVP Oscillators, Journal of Signal Processing, Vol.18, No.1, 39-48, 2014. (Summary) Bonoh¨oeffer-van der Pol (BVP) oscillator is a planer nonlinear model exhibiting a rich variety of bifurcation phenomena for both equilibria and limit cycles. Since it has two ports regarding its state variables, many topologically different coupled systems are obtained even when two identical BVP oscillators are resistively coupled. Although individual coupled systems have been already studied, it is not able to compare them because models of nonlinearity and normalizations are different. In this paper, we firstly unify them, and investigate their bifurcations of equilibria and synchronization modes of limit cycles. As results, common bifurcations of equilibria for all coupled structures are found, and some properties on parameter ranges, synchronization modes and their stabilities are clarified. (Keyword) coupled BVP oscillator / nonlinear autonomous system / bifurcation phenomenon / chaos attractor / coupled BVP oscillator / nonlinear autonomous system / bifurcation phenomenon / chaos attractor (Link to Publication Site) ● Publication site (DOI): 10.2299/jsp.18.39 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390001204465040512 ● Search Scopus @ Elsevier (DOI): 10.2299/jsp.18.39 (DOI: 10.2299/jsp.18.39, CiNii: 1390001204465040512)
36.	Tetsushi Ueta and Akihisa Tamura : Bifurcation Analysis of a Simple 3D Oscillator and Chaos Synchronization of its Coupled Systems, Chaos, Solitons & Fractals, Vol.45, No.12, 1460-1468, 2012. (Summary) Tamasevicius et al. proposed a simple 3d chaotic oscillator for educational purpose. In fact the oscillator can be implemented very easily and it shows typical bifurcation scenario so that it is a suitable training object for introductory education for students. However, as far as we know, no concrete studies on bifurcations or applications on this oscillator have been investigated. In this paper, we make a thorough investigation on local bifurcations of periodic solutions in this oscillator by using a shooting method. Based on results of the analysis, we study chaos synchronization phenomena in diffusively coupled oscillators. Both bifurcation sets of periodic solutions and parameter regions of in-phase synchronized solutions are revealed. An experimental laboratory of chaos synchronization is also demonstrated. (Keyword) chaotic oscillator / bifurcation analysis / synchronization (Tokushima University Institutional Repository) ● Metadata: 112038 (Link to Publication Site) ● Publication site (DOI): 10.1016/j.chaos.2012.08.007 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1016/j.chaos.2012.08.007 (Tokushima University Institutional Repository: 112038, DOI: 10.1016/j.chaos.2012.08.007)
37.	Kunichika Tsumoto, Tetsushi Ueta, Tetsuya Yoshinaga and Hiroshi Kawakami : Bifurcation analyses of nonlinear dynamical systems: From theory to numerical computations, Nonlinear Theory and Its Applications, IEICE, Vol.3, No.4, 458-476, 2012. (Summary) In this paper, we explain how to compute bifurcation parameter values of periodic solutions for non-autonomous nonlinear differential equations. Although various approaches and tools are available for this problem nowadays, we introduce the simplest method composed by computational algorithms appeared in textbooks for beginner's, i.e., the Newton's method and Runge-Kutta method. We formulate the given bifurcation problem as a boundary value problem and use the Newton's method as a solver consistently. All derivatives required in each iteration are obtained by solving variational equations about the state and the parameter. Thank to quadratic convergence ability of the Newton's method, accurate results can be obtained without using any sophisticated mathematical library or software. If a discontinuous periodic force is applied to the system, we can take the same strategy to solve the bifurcation problem. The key point of this method is deriving a differentiable composite map from consideration of the various information about the problem such as the location of sections, the periodicity, the Poincaré mapping, and so on. (Keyword) nonlinear dynamical system / bifurcation / boundary value problem / variational equation / Newton's method (Tokushima University Institutional Repository) ● Metadata: 114910 (Link to Publication Site) ● Publication site (DOI): 10.1587/nolta.3.458 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/nolta.3.458 (Tokushima University Institutional Repository: 114910, DOI: 10.1587/nolta.3.458)
38.	Tetsushi Ueta : Invariant patterns in a non-invertible chaotic map by the directional coloring, Nonlinear Theory and Its Applications, IEICE, Vol.3, No.4, 497-507, 2012. (Summary) We propose a visualization method called the directional coloring for chaotic attractors in planer discrete systems. A color in the hue circle is assigned to the argument determined by the current point and its n-th mapped point. Some unstable n-periodic points embedded in the chaotic attractor become visible as radiation points and they can be accurately detected by combination of this coloring and the Newton's method. For a chaotic attractor in a non-invertible map, we found out invariant patterns around the fixed point and detect its nearest unstable n-periodic point. The computed results of their locations show a fractal property of the system. (Tokushima University Institutional Repository) ● Metadata: 114911 (Link to Publication Site) ● Publication site (DOI): 10.1587/nolta.3.497 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/nolta.3.497 (Tokushima University Institutional Repository: 114911, DOI: 10.1587/nolta.3.497)
39.	Kenji Matsuura, Tetsushi Ueta and Masahiko Sano : Proposing User Experience based on WEB-SSO with Multiple Backends of Authentication/Authorization Engine, Journal for Academic Computing and Networking, Vol.16, No.16, 138-145, 2012. (Summary) 個人のIDが複数存在する場合の個人認証には，単一の認証源に登録されている場合だけでなく，複数の異なる内容での認証源に登録されている事もある．これをシングルサインオンのバックエンド情報源として利用する際には，その特性や扱う属性に注意しながら慎重に実装しなければならない．これらはセキュリティを考慮しつつ利便性および対障害性を高めるための設計方針および運用方針を要し，本論文では本学での実装について述べる．さらに，異なるシングルサインオン技術を用いた異なるカテゴリでの統合的な操作環境について述べる． (Keyword) WEB-SSO / Shibboleth / Kerberos / ADFS (Tokushima University Institutional Repository) ● Metadata: 115740 (Link to Publication Site) ● Publication site (DOI): 10.24669/jacn.16.1_138 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390845713038666624 ● Search Scopus @ Elsevier (DOI): 10.24669/jacn.16.1_138 (Tokushima University Institutional Repository: 115740, DOI: 10.24669/jacn.16.1_138, CiNii: 1390845713038666624)
40.	Daisuke Ito, Tetsushi Ueta and Kazuyuki Aihara : Bifurcation analysis with threshold values for interrupt autonomous systems, The Transactions of the Institute of Electronics, Information and Communication Engineers A, Vol.J94-A, No.8, 596-603, 2011. (Summary) スイッチや状態変数の跳躍で表される断続力学系の研究が盛んに行われている．複数の異なるベクトル場が接合して力学系を構成する場合，しばしばしきい値が接合面(断続面)の位置を決める条件となる．系に現れる周期軌道は，しきい値をパラメタとしたとき，その値の変化に対して様々な分岐現象を生じる．状態変数やパラメタが断続面において微分不可能となる断続系では，従来の解析手法の適用に困難をもたらすが，断続面を局所断面とし局所座標系を構成するPoincare 写像を定義すれば，シューティング法による分岐解析が行なえることが示されている．しかしながら，しきい値の定義式は一般にモデル方程式に陽に含まれないため，分岐パラメタ値としてのしきい値に対するシューティング解法は知られていない．本論文では，断続系の分岐理論を拡張し，しきい値をパラメタとする変分方程式を導出し，求積する手法について述べる．さらに，具体例として結合Izhikevich ニューロンモデルを取り上げ，分岐構造の詳細を説明する (Keyword) interrupt dynamical systems / Poincare map / threshold analysis / coupled Izhikevich moderl (Tokushima University Institutional Repository) ● Metadata: 110725 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050564287419585024 (Tokushima University Institutional Repository: 110725, CiNii: 1050564287419585024)
41.	Atsuo Maki, Naoya Umeda, Martin Renilson and Tetsushi Ueta : Analytical formulae for predicting the surf-riding threshold for a ship in following seas, Journal of Marine Science and Technology, Vol.15, No.3, 218-229, 2010. (Summary) Making use of Melnikov's method, a generalized formula for predicting the surf-riding threshold is developed as an extension to the applications of Kan and Spyrou. A new analytical formula for calculating the surfriding threshold of a ship in following seas is also proposed in light of nonlinear dynamical system theory. By applying a continuous piecewise linear approximation to the waveinduced surge force, a heteroclinic bifurcation point is obtained analytically with an uncoupled surge equation. Results calculated using these formulae are presented, and they show good agreement with those obtained utilizing numerical bifurcation analysis. Further, it was confirmed that the surf-riding threshold obtained using the proposed formulae agrees reasonably well with that obtained experimentally for an unconventional vessel. (Keyword) Analytical formulae / Surf-riding threshold / Heteroclinic bifurcation / IMO vulnerability criteria / Following seas (Link to Publication Site) ● Publication site (DOI): 10.1007/s00773-010-0085-y (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1570854176225674240 ● Search Scopus @ Elsevier (DOI): 10.1007/s00773-010-0085-y (DOI: 10.1007/s00773-010-0085-y, CiNii: 1570854176225674240)
42.	Akihisa Tamura, Tetsushi Ueta and Shigeki Tsuji : Bifurcation Analysis of Izhikevich Neuron Model, Dynamics of Continuous, Discrete and Impulsive Systems. Series A: Mathematical Analysis, Vol.16, No.6, 849-862, 2009. (Summary) An autonomous differential equation with jumps has been proposed by Izhikevich for a demonstration of various spiking waves by changing its parameters. Some well-known firing patterns of this model are shown by numerical simulations, however bifurcation analysis of the model has not been investigated in detail. In this paper, we apply our numerical computation algorithm to this model. Although it is a challenge to manage jumps with the Poincar´e mapping and we obtain bifurcation parameter values by a shooting method. As a result, we conclude that some spiking modes are caused by local bifurcation of limit cycles. (Keyword) bifurcation / ODE with jumps / Poincare mapping (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-73249132565 (Elsevier: Scopus)
43.	Takuji Kousaka, Ken'ichi Fujimoto, YUE MA, Tetsushi Ueta and Hiroshi Kawakami : Bifurcations observed in BVP oscillator with periodically switched RC circuit, Dynamics of Continuous, Discrete and Impulsive Systems. Series A: Mathematical Analysis, Vol.16, No.6, 811-824, 2009. (Summary) Many works have been devoted to the study of the behavior of the Bonhoe er-van der Pol (BVP) oscillator in physiological and biochemical modeling studies. In this paper, bifurcation and chaos in BVP oscillator, which is intermittently connected to a parallel RC load, is investigated. By using the periodicity of switching action we introduce a composite discrete mapping as the Poincar´e mapping that is useful for the analysis of piecewise nonlinear systems. Adjusting the switching period close to the integral multiple of the period of self-oscillation, we find various synchronizations. In particular the fundamental synchronization is discussed. Under the appropriate switching ratios, we illustrate that the synchronized state bifurcates to chaotic states by the period doubling cascades or the torus breaking down. (Keyword) nonlinear circuits / periodic switch / composite Poincare mapping / chaos / bifurcation (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-73249140949 (Elsevier: Scopus)
44.	Atsuo Maki, Naoya Umeda and Tetsushi Ueta : Melnikov integral formula for beam sea roll motion utilizing a non-Hamiltonian exact heteroclinic orbit, Journal of Marine Science and Technology, Vol.15, No.1, 102-106, 2009. (Summary) The chaos that appears in the ship roll equation in beam seas known as the escape equation has been intensively investigated because it is closely related to capsizing incidents. In particular, many applications of the Melnikov integral formula have been reported in the literature; however, in all the analytical works concerning the escape equation, the Melnikov integral is formulated utilizing a separatrix for the Hamiltonian part or a numerically obtained heteroclinic orbit for the non-Hamiltonian part of the original escape equation. To overcome such limitations, this article attempts to utilise an analytical expression for the non-Hamiltonian part. As a result, an analytical procedure is provided that makes use of a heteroclinic orbit of the non-Hamiltonian part within the framework of the Melnikov integral formula. (Keyword) Escape equation / Chaos phenomenon / Melnikov integral formula / analytical formula / Non-Hamiltonian heteroclinic orbit (Tokushima University Institutional Repository) ● Metadata: 113429 (Link to Publication Site) ● Publication site (DOI): 10.1007/s00773-009-0076-z (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1571417126178539904 ● Search Scopus @ Elsevier (DOI): 10.1007/s00773-009-0076-z (Tokushima University Institutional Repository: 113429, DOI: 10.1007/s00773-009-0076-z, CiNii: 1571417126178539904)
45.	Takuji Kousaka, Tetsushi Ueta and YUE MA : Chaos Control Implementation by Interrupted Electric Circuit with Switching Delay, International Journal of Bifurcation and Chaos, Vol.19, No.7, 2359-2362, 2009. (Summary) We have demonstrated that the chaotic circuit with a switching delay is modeled by a return map, and a controller for the suppression of chaos is proposed. A circuit representing a controller stabilizing a period-1 unstable periodic orbit in an interrupted electric circuit with a certain switching delay is also discussed. (Tokushima University Institutional Repository) ● Metadata: 112117 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127409024128 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127409024128 (Tokushima University Institutional Repository: 112117, DOI: 10.1142/S0218127409024128)
46.	Tetsushi Ueta : Submission and edition system orienting low-cost publishing of conference proceedings, Academic Information Processing Environment Research, Vol.12, 27-33, 2009. (Summary) 国際会議，研究集会などの会議録を生成するシステムをウェブアプリケーション等と組み合わせて実現した．投稿，査読，再投稿プロセスを，フリーウェアにパッチを施した投稿システムで運用する．内部で使用されるデータベースから必要な情報を取得し，各論文PDF へのリンクを埋め込んだ講演プログラム目次ページを自動的に生成する．採択論文はPDFlib を用いてページ番号やロゴ，様々なページへのしおりが埋め込まれる．いくつかの会議で実際に本システムを運用し，出版コストを金銭的にも人的にも低く抑えることができた．本稿では上記システムの概要を報告する． (Keyword) 会議録 / 出版業務 / 投稿システム / PDFlib / LaTeX (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1523951030828454912 (CiNii: 1523951030828454912)
47.	Quentin Brandon, Tetsushi Ueta, Daniele Fournier-Prunaret and Takuji Kousaka : Numerical Bifurcation Analysis Framework for Autonomous Piecewise-Smooth Dynamical Systems, Chaos, Solitons & Fractals, Vol.42, No.1, 187-201, 2009. (Summary) In this paper, we consider a numerical method for the bifurcation analysis method of nonlinear piecewise-smooth systems. While linear piecewise-smooth systems can be analyzed rigorously, nonlinear piecewise-smooth systems cannot lead to an analytical solution. Derived from both continuous and discrete system analysis approaches, our method uses a Poincar´e map to transform the results of partial analysis over the continuous components into those issued from a discrete mapping. We then apply conventional methods in order to find critical parameter values and obtain bifurcation diagrams in the parameter space. The numerical procedure is fully described and illustrated by the analysis results of various versions of the Alpazur oscillator. (Keyword) Bifurcation Analysis / Numerical Methods / Piecewise-smooth Systems / chaos (Link to Publication Site) ● Publication site (DOI): 10.1016/j.chaos.2008.11.013 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1016/j.chaos.2008.11.013 (DOI: 10.1016/j.chaos.2008.11.013)
48.	Tetsuya Yoshinaga, Yoshihiro Imakura, Ken'ichi Fujimoto and Tetsushi Ueta : Bifurcation Analysis of Iterative Image Reconstruction Method for Computed Tomography, International Journal of Bifurcation and Chaos, Vol.18, No.4, 1219-1225, 2008. (Summary) Of the iterative image reconstruction algorithms for computed tomography (CT), the power multiplicative algebraic reconstruction technique (PMART) is known to have good properties for speeding convergence and maximizing entropy. We analyze here bifurcations of fixed and periodic points that correspond to reconstructed images observed using PMART with an image made of multiple pixels and we investigate an extended PMART, which is a dynamical class for accelerating convergence. The convergence process for the state in the neighborhood of the true reconstructed image can be reduced to the property of a fixed point observed in the dynamical system. To investigate the speed of convergence, we present a computational method of obtaining parameter sets in which the given real or absolute values of the characteristic multiplier are equal. The advantage of the extended PMART is verified by comparing it with the standard multiplicative algebraic reconstruction technique (MART) using numerical experiments. (Link to Publication Site) ● Publication site (DOI): 10.1142/S021812740802094X (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S021812740802094X (DOI: 10.1142/S021812740802094X)
49.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcation analysis of current coupled BVP oscillators, International Journal of Bifurcation and Chaos, Vol.17, No.3, 837-850, 2007. (Summary) The Bonhöffer van der Pol (BVP) oscillator is a simple circuit implementation describing neuronal dynamics. Lately the diffusive coupling structure of neurons attracts much attention since the existence of the gap-junctional coupling has been confirmed in the brain. Such coupling is easily realized by linear resistors for the circuit implementation, however, there are not enough investigations about diffusively coupled BVP oscillators, even a couple of BVP oscillators. We have considered several types of coupling structure between two BVP oscillators, and discussed their dynamical behavior in preceding works. In this paper, we treat a simple structure called current coupling and study their dynamical properties by the bifurcation theory. We investigate various bifurcation phenomena by computing some bifurcation diagrams in two cases, symmetrically and asymmetrically coupled systems. In symmetrically coupled systems, although all internal elements of two oscillators are the same, we obtain in-phase, anti-phase solution and some chaotic attractors. Moreover, we show that two quasi-periodic solutions disappear simultaneously by the homoclinic bifurcation on the Poincaré map, and that a large quasi-periodic solution is generated by the coalescence of these quasi-periodic solutions, but it disappears by the heteroclinic bifurcation on the Poincaré map. In the other case, we confirm the existence a conspicuous chaotic attractor in the laboratory experiments. (Tokushima University Institutional Repository) ● Metadata: 112115 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127407017586 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127407017586 (Tokushima University Institutional Repository: 112115, DOI: 10.1142/S0218127407017586)
50.	Yasuo Miyoshi, Takahiro Oie, Tetsushi Ueta, Masanori Hirotomo, Yoneo Yano and Hiroshi Kawakami : Construction of e-Syllabus Supporting the Discovery of Learning Path by Using EDB, Journal of University Education Research, No.3, 1-9, 2006. (Summary) In Tokushima University, the syllabus has been published and opened on the web using an Educator and Researcher Information Database (EDB). We are now developing an e-Syllabus system that represents graphically and dynamically the relationships between lectures. This development represents one of the improvements of infrastructure for education and learning. In order to construct the e-Syllabus, three new columns have been added to each lecture of the syllabus: keywords, preceding lectures and relational lectures. XML is used as a storage format for EDB; it allows us to represent the structured data within on a text file that can be stored on a CD-ROM. Thus, without accessing the web, it is possible to represent graphically and discover the relations between the lectures. This representation of the syllabus supports the students in the discovery of learning-paths and the definition of learning plan. Thus, the e-Syllabus system improves the convenience of using the syllabus. (Keyword) Learning Path / Syllabus / Lecture Outline / EDB / XML (Tokushima University Institutional Repository) ● Metadata: 82383 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050564287417193344 (Tokushima University Institutional Repository: 82383, CiNii: 1050564287417193344)
51.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : Stable torus and its bifurcation phenomena in a Three-Dimensional Autonomous Circuit, Chaos, Solitons & Fractals, Vol.27, No.4, 941-951, 2006. (Summary) It is well known that a stable torus is observed as a result after the system meets the super-critical Neimark Sacker bifurcation for a limit cycle. Although tori are easily observed in two-dimensional and periodically forced dynamical systems, there is a few papers about stable tori in three-dimensional autonomous systems. Besides, as physical circuit implementations, such circuits contain very special active elements, or have difficulty in realizing. In this paper, we show a very simple circuit of three-dimensional autonomous system, an extended Bonhöffer van der Pol (BVP) oscillator, which is demonstrating a stable torus. Firstly we explain a discovery of the torus in a computer simulation of the model equation. To implement it as a circuitry, we design a new nonlinear resistor. Although this contains an FET and an op-amp, it is simpler than any other nonlinear resistors proposed in previous papers. We confirm that this BVP oscillator can generate a stable torus in a real circuitry. We thoroughly investigate the bifurcation phenomena of various limit cycles and tori in this circuit, i.e., a super-critical Neimark Sacker and tangent bifurcations of limit cycles are concretely obtained, furthermore, phase locking and chaos regions are clarified in a bifurcation diagram. (Link to Publication Site) ● Publication site (DOI): 10.1016/j.chaos.2005.04.092 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-24344472635 (DOI: 10.1016/j.chaos.2005.04.092, Elsevier: Scopus)
52.	Takuji Kousaka, Tetsushi Ueta, YUE MA and Hiroshi Kawakami : Control of chaos in a piecewise smooth nonlinear system, Chaos, Solitons & Fractals, Vol.27, No.4, 1019-1025, 2006. (Summary) This paper shows the stabilization of the unstable periodic orbit of any given piecewise smooth system with linear and/or nonlinear characteristics. By utilizing the periodicity of the switching action, we construct the Poincare´ mapping including all information of the original system. This mapping offers a first step toward extending a novel technique for controlling chaos based on the appropriate state feedback in piecewise smooth nonlinear systems. We also apply this approach to Rayleigh type oscillator described by the piecewise smooth nonlinear systems. (Link to Publication Site) ● Publication site (DOI): 10.1016/j.chaos.2005.04.068 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-24344480901 (DOI: 10.1016/j.chaos.2005.04.068, Elsevier: Scopus)
53.	Takuji Kousaka, Tetsushi Ueta, YUE MA and Hiroshi Kawakami : Bifurcation analysis of a piecewise smooth system with non-linear characteristics, International Journal of Circuit Theory and Applications, Vol.33, No.4, 263-279, 2005. (Summary) In previous works, there are no results about the bifurcation analysis for a piecewise smooth system with non-linear characteristics. The main purpose of this study is to calculate the bifurcation sets for a piecewise smooth system with non-linear characteristics. We first propose a new method to track the bifurcation sets in the system. This method derives the composite discrete mapping, Poincare mapping. As a result, it is possible to obtain the local bifurcation values in the parameter plane. As an illustrated example, we then apply this general methodology to the Rayleigh-type oscillator containing a stateperiod- dependent switch. In the circuit, we can find many subharmonic bifurcation sets including global bifurcations. We also show the bifurcation sets for the border-collision bifurcations. Some theoretical results are verified by laboratory experiments. (Link to Publication Site) ● Publication site (DOI): 10.1002/cta.320 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1002/cta.320 (DOI: 10.1002/cta.320)
54.	Masahiko Sano, Kenji Matsuura, Tetsushi Ueta and Shunichiro Oe : A Study of Database Support for enacting the Security Policy, Journal for Academic Computing and Networking, Vol.8, No.8, 25-32, 2004. (Summary) <p>Various and many incidents, which like infections by the computer virus and leakage of personal information, threat our information society nowadays. The number of organization enacting the security policy for protecting themselves from those threats is rising. At the security policy planning, high cost and manpower are required for investigating their property and assessing their risk. Therefore, we have developed the security policy support database system to decreasing the cost of manpower. In this paper, we describe the requirements to construct a support database system and the results of out construction and operation.</p> (Keyword) 構築支援 / Security Policy / Construction support / Database (Tokushima University Institutional Repository) ● Metadata: 115742 (Link to Publication Site) ● Publication site (DOI): 10.24669/jacn.8.1_25 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390001288156120704 ● Search Scopus @ Elsevier (DOI): 10.24669/jacn.8.1_25 (Tokushima University Institutional Repository: 115742, DOI: 10.24669/jacn.8.1_25, CiNii: 1390001288156120704)
55.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : A design method of bursting using 2-parameter bifurcation diagrams in FitzHugh-Nagumo model, International Journal of Bifurcation and Chaos, Vol.14, No.7, 2241-2252, 2004. (Summary) Spiking and bursting observed in nerve membranes seem to be important when we investigate information representation model in the brain. Many topologically different bursting responses are observed in the mathematical models and their related bifurcation mechanisms have been clarified. In this paper, we propose a design method to generate bursting responses in FitzHugh Nagumo model with a simple periodic external force based on bifurcation analysis. Some effective parameter perturbations for the amplitude of the external input are given from the two-parameter bifurcation diagram. (Keyword) bifurcation / bursting / FitzHugh-Nagumo model / periodic external force / OSCILLATIONS (Tokushima University Institutional Repository) ● Metadata: 112113 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127404010564 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127404010564 (Tokushima University Institutional Repository: 112113, DOI: 10.1142/S0218127404010564)
56.	Yoko Uwate, Yoshifumi Nishio, Tetsushi Ueta, Tohru Kawabe and Tohru Ikeguchi : Performance of Chaos and Burst Noises Injected to the Hopfield NN for Quadratic Assignment Problems, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E87-A, No.4, 937-943, 2004. (Summary) In this paper, performance of chaos and burst noises injected to the Hopfield Neural Network for quadratic assignment problems is investigated. For the evaluation of the noises, two methods to appreciate finding a lot of nearly optimal solutions are proposed. By computer simulations, it is confirmed that the burst noise generated by the Gilbert model with a laminar part and a burst part achieved the good performance as the intermittency chaos noise near the three-periodic window. (Keyword) chaos / intermittency / burst noise / neural network / combinatorial optimization problems / QAP (Tokushima University Institutional Repository) ● Metadata: 110705 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050845762396289280 ● Summary page in Scopus @ Elsevier: 2-s2.0-2342627371 (Tokushima University Institutional Repository: 110705, CiNii: 1050845762396289280, Elsevier: Scopus)
57.	Tetsushi Ueta, Hisayo Miyazaki, Takuji Kousaka and Hiroshi Kawakami : Bifurcation and chaos in coupled BVP oscillators, International Journal of Bifurcation and Chaos, Vol.14, No.4, 1305-1324, 2004. (Summary) Bonh¨offer van der Pol(BVP) oscillator is a classic model exhibiting typical nonlinear phenomena in the planar autonomous system. This paper gives an analysis of equilibria, periodic solutions, strange attractors of two BVP oscillators coupled by a resister. When an oscillator is fixed its parameter values in nonoscillatory region and the others in oscillatory region, create the double scroll attractor due to the coupling. Bifurcation diagrams are obtained numerically from the mathematical model and chaotic parameter regions are clarified. We also confirm the existence of period-doubling cascades and chaotic attractors in the experimental laboratory. (Keyword) bifurcation / chaos / BVP oscillator / coupling (Tokushima University Institutional Repository) ● Metadata: 112055 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127404009983 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127404009983 (Tokushima University Institutional Repository: 112055, DOI: 10.1142/S0218127404009983)
58.	Takuji Kousaka, Yasuhara Yoshihito, Tetsushi Ueta and Hiroshi Kawakami : Experimental Investigation of Controlling Chaos using Pole Assignment in the Forced BVP Oscillator, IEEJ Transactions on Electronics, Information and Systems, Vol.124-C, No.2, 495-501, 2004. (Summary) In previous work(1), we proposed a control method of the chaotic attractor in the non-autonomous systems and stabilized the unstable periodic orbits observed in the Duffing's equation. Our method can be used as a general technique for controlling chaos, however, the control function was not demonstrated in the laboratory experiments. With this in mind, in this paper, we consider the experimental control of the chaotic behavior in the circuit model, called the forced BVP oscillator. The pole assignment for the corresponding discrete system derived from such a non-autonomous system via Poincaré mapping works effectively, and the control unit is easily realized by the window comparator, sample-hold circuits, and so on. In particular, we try to stabilize the unstable 1 and 3-periodic orbits in the chaotic attractor in the numerical and experimental simulations. (Keyword) non-autonomous system / forced BVP oscillator / controlling chaos / circuit implementation / forced BVP oscillator / controlling chaos / circuit implementation (Link to Publication Site) ● Publication site (DOI): 10.1541/ieejeiss.124.495 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390282679582944384 ● Search Scopus @ Elsevier (DOI): 10.1541/ieejeiss.124.495 (DOI: 10.1541/ieejeiss.124.495, CiNii: 1390282679582944384)
59.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcation of Burst Response in an Amari-Hopfield Neuron Pair with a Periodic External Force, Electrical Engineering in Japan, Vol.146, No.2, 43-53, 2004. (Keyword) excitatory-inhibitory neuron pair model / bifurcation / a periodic external force / burst response / MODEL / OSCILLATIONS (Link to Publication Site) ● Publication site (DOI): 10.1002/eej.10217 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1002/eej.10217 (DOI: 10.1002/eej.10217)
60.	Takahiro Oie, Tetsushi Ueta, Youji Ochi and Yoneo Yano : Education and research database in Tokushima University, --- Development and operation of the database orienting periodical publication and information disclosure ---, The Journal of University Evaluation of National Institution for Academic Degrees and University Evaluation, Research in University Evaluation, Vol.3, 31-50, 2003. (Summary) 大学機関では，紀要や各種総覧，シラバスなどの定期刊行物や，大学評価，外部評価，自己点検評価など，多くの報告書が編集され出版されている．これら出版物を制作するためのデータは，例えば学歴，職歴のように職員個人にとっては不変の情報であったり，著作リストのように既存のデータを追加するだけで済む情報である．しかし，個人のデータの記録書式や，編集者のデータ収集方法を統一することは困難であり，よって，出版物ごとにデータの再入力が強いられ，結果，編集・校正に長い期間を要し，データ入力者のみならず編集者にとっても多大な負担となる．そこで本学では，上記出版物の網羅すべき項目を洗いだし，「情報の再利用」を設計思想として，ユーザの入力と出版物の編集作業の援用を指向した教職員データベースシステム(EDB; Education and research database)を構築した．EDBは当初，徳島大学工学部においてのみ運用されていたが，大学評価や自己点検評価の資料を含む多くの出版物編集に利用された．その実績を受け，現在では全学レベルの運用に引き上げられている．本稿では，このEDBのコンセプトや提供される機能について述べ，入力から出版までの流れ，既出版物の概要，今後の展望について解説する．また，運用までの経緯や問題点について述べる． (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050845762563877248 (CiNii: 1050845762563877248)
61.	Takuji Kousaka, Tetsushi Ueta, Hiroshi Kawakami and Minoru Abe : Implementation and Analysis of a Simple Circuit Causing Border-Collision Bifurcation, IEEJ Transactions on Electronics, Information and Systems, Vol.122-C, No.11, 1908-1916, 2002. (Summary) ecently, a new type of bifurcation phenomena called Border-Collision (abbr. BC) bifurcation has been discovered for one or two-dimensional one-parameter families of discrete-time systems. A skewed tent map is the simplest model exhibiting the BC bifurcation and the existence of break point (undifferentiable point) in the map is an essential for BC bifurcation. In some continuous systems, BC bifurcation is also confirmed. In particular, many interesting bifurcation phenomena including BC bifurcation are observed in the power electronic systems. Since power electronic circuits with current or voltage feedback have wide industrial ap plications, indeed, theoretical and experimental analysis in such systems are very important in practical point of view. In this paper, we propose a system interrupted by own state and a periodic interval, and show that the system has much variety of bifurcation phenomena, including BC bifurcation. To analyze properties of the dynamics, we derive a one-dimensional map explicitly. We show some theorem and the regions of periodic solution within two parameter space. Some of theoretical results are verified by laboratory experiments. (Keyword) Border-Collision bifurcation / Return map / Bifurcation diagram (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390282679587897600 (CiNii: 1390282679587897600)
62.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcation of Burst Response in Amari-Hopfield Neuron Pair with a Periodic External Force, IEEJ Transactions on Electronics, Information and Systems, Vol.122-C, No.9, 1506-1514, 2002. (Summary) 本論文では一般的な解析によく用いられている Amari-Hopfield 型ニューロンモデルについて，バースト応答の分類と対応を調べ，バースト発生機構を構築している．入力は周期外力とし，これがパラメータ分岐図における各種分岐曲線をまたがって摂動する場合，さまざまなバーストが発生する．周期外力をパラメータとし，その振幅と周波数による分岐図を求めた．バースト発振の発生·消滅·バーストのパルス数は主に接線分岐により増減することを示した．分岐のパターンによって，バースト発振を分類した．これにより，バースト応答の設計が可能となり，仕様を満たすバースト応答を自由に実現できる． (Keyword) excitatory-inhibitory neuron pair model / bifurcation / a periodic external force / burst response (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390001204609985536 (CiNii: 1390001204609985536)
63.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Controlling chaos in a state-dependent nonlinear system, International Journal of Bifurcation and Chaos, Vol.12, No.5, 1111-1119, 2002. (Summary) In this paper, we propose a general method for controlling chaos in a nonlinear dynamical system containing a state-dependent switch. The pole assignment for the corresponding discrete system derived from such a nonsmooth system via Poincar e mapping works effectively. As an illustrative example, we consider controlling the chaos in the Rayleigh-type oscillator with a state-dependent switch, which is changed by the hysteresis comparator. The unstable one- and two-periodic orbits in the chaotic attractor are stabilized in both numerical and experimental simulations. (Tokushima University Institutional Repository) ● Metadata: 112109 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127402004942 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127402004942 (Tokushima University Institutional Repository: 112109, DOI: 10.1142/S0218127402004942)
64.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Chaos and Control of Periodically Switched Nonlinear Systems, The Latin American Applied Research Journal, Vol.1, No.31, 211-218, 2001. (Summary) This paper discusses chaos and its control in periodically switched nonlinear systems. Since the trajectory of the system is not differentiable at break points, the Poincar sections should be naturally attached at these points and then the Poincar mapping is derived as a composite of local mappings defined among these sections. This map enable us to calculate the location and its stabilities of the periodic points in the chaotic attractor. We also consider chaos control problem based on the Poincar map. The controlled system is fully described as the differentiable map, there fore the controller can be designed by using conventional pole assignment technique. As an illustrated example, we consider a Rayleigh type oscillator containing a periodic switch. We firstly discuss bifurcation sets of the system. The dynamic properties of periodic or bits and chaotic attractors e clarified. We also investigate bifurcation structure of phase locked regions along a Neimark-Sacker bifurcation set. Some theoretical results are con firmed by laboratory experiments. Secondly we try to stabilize one and two-period unstable periodic orbits by using the proposed method. The controller is calculated easily because all information can be obtained from the Poincar map. The results of numerical simulations are demonstrated.
65.	Keng C. Yap, Guanrong Chen and Tetsushi Ueta : Controlling bifurcations of discrete maps, The Latin American Applied Research Journal, Vol.1, No.31, 157-162, 2001. (Summary) Bifurcation control has attracted increasing attention in recent years. A simple and unfied state-feedback methodology is developed in this paper for various bifurcation controls for discrete-time systems. The control task can be either shifting an existing bifurcation or creating a new one, for transcritical, pitchfork, saddle-node, and period- doubling bifurcations. Some computer simulations are included to illustrate the methodology and verify the theoretical results.
66.	Tetsushi Ueta, Eiji Izumida and Hiroshi Kawakami : Visualization of Bifurcation Surfaces of Periodic Solutions in Nonlinear Dynamical Systems, Transactions of the Visualization Society of Japan, Vol.21, No.4, 65-70, 2001. (Summary) 本論文では， n次元非線形常微分方程式系に含まれる3次元パラメータ空間において，周期解に関する分岐集合(分岐曲面)を計算し， CG として視覚化する方法について述べる．分岐曲面は一種の等値面とみなせるが，一般の等値面構成問題とは異なり，数値積分とn+3 次元方程式の求解を要し，ボクセル判定法は計算コストの観点から用いることができない．そこで，計算コストの削減を念頭においた分岐曲面の構成方法を二つ提案する．構成方法 I は，第 3 パラメータのさまざまな値で第 1, 2 パラメータによる平面で分岐集合をもとめ，それらを接続してポリゴンを生成する手法である．また，構成方法IIは，初期値となるパラメータ平面の分岐集合から自律的に 3次元分岐曲面を探索してゆく手法である．両手法の詳細を述べ，特徴を比較した．これらの可視化手法よって，パラメータ空間中における各種解の存在領域の形状，その発生消滅，カオスの存在位置などの大域的性質が理解でき，系の設計，解析の手助けとなる． (Link to Publication Site) ● Publication site (DOI): 10.3154/tvsj.21.65 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.3154/tvsj.21.65 (DOI: 10.3154/tvsj.21.65)
67.	Tetsushi Ueta, Tetsuya Yoshinaga, Hiroshi Kawakami and Guanrong Chen : A Method to Calculate Neimark-Sacker Bifurcation in Autonomous Systems, The Transactions of the Institute of Electronics, Information and Communication Engineers A, Vol.J83-A, No.10, 1141-1147, 2000. (Summary) 自律系にみられるリミットサイクルにおいて，パラメータの変化により特性乗数が複素単位円を横切る場合， Neimark-Sacker 分岐を生じる．本論文ではこの分岐パラメータ値を求める新しい計算方法を提案する．固定点条件，ポアンカレ断面条件に加えて，共役複素数の特性乗数を代入した特性方程式を実部と虚部に分離し，それぞれを独立した条件として採用する．これら条件式を連立させ，ニュートン法により解く．新たな独立変数として，共役複素な特性乗数の偏角を用いた．ニュートン法のヤコビ行列の各要素は，複素数演算，数値微分を用いることなく，変分方程式の解と行列操作によって求めることができるため，ニュートン法の収束性もよい．例として8次元自律系のリミットサイクルのNeimark-Sacker分岐の計算結果を挙げる． (Tokushima University Institutional Repository) ● Metadata: 110721 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050564287419583872 (Tokushima University Institutional Repository: 110721, CiNii: 1050564287419583872)
68.	Tetsushi Ueta and Guangrong Chen : Bifurcation Analysis of Chen's Equation, International Journal of Bifurcation and Chaos, Vol.10, No.8, 1917-1931, 2000. (Summary) Anticontrol of chaos by making a nonchaotic system chaotic has led to the discovery of some new chaotic systems, particularly the continuous-time three-dimensional autonomous Chen's equation with only two quadratic terms. This paper further investigates some basic dynamical properties and various bifurcations of Chen's equation, thereby revealing its different features from some other chaotic models such as its origin, the Lorenz system. (Tokushima University Institutional Repository) ● Metadata: 112046 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127400001183 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-0034238522 (Tokushima University Institutional Repository: 112046, DOI: 10.1142/S0218127400001183, Elsevier: Scopus)
69.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation of Switched Nonlinear Dynamical Systems, IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing, Vol.CAS-2, No.7, 878-885, 1999. (Summary) This paper proposes a method to trace bifurcation sets for a piecewise-defined differential equation. In this system, the trajectory is continuous, but it is not differentiable at break points of the characteristics. We define the Poincare mapping by suitable local sections and local mappings, and thereby it is possible to calculate bifurcation parameter values. As an illustrated example, we analyze the behavior of a two-dimensional nonlinear autonomous system whose state space is constrained on two half planes concerned with state dependent switching characteristics. From investigation of bifurcation diagrams, we conclude that the tangent and global bifurcations play an important role for generating various periodic solutions and chaos. Some theoretical results are confirmed by laboratory experiments (Link to Publication Site) ● Publication site (DOI): 10.1109/82.775383 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1109/82.775383 (DOI: 10.1109/82.775383)
70.	Takuji Kosaka, Yutaka Umakoshi, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation of Nonlinear Circuits with Periodically Operating Switch, The Transactions of the Institute of Electronics, Information and Communication Engineers A, Vol.J81-A, No.5, 836-843, 1998. (Summary) 本論文では，レイリー型の発振器部分とスイッチで制御される直流電源部分から構成される Alpazur 発振器の分岐集合を数値計算により求めた．従来法による分岐パラメータの計算方法では，スイッチの断続条件が軌道の連続微分性を失わせていしまい，そのままの適用はできない．そこでスイッチング動作の周期性を利用して，たくみにポアンカレ写像を構成し，分岐パラメータを計算することに成功した．定式化とアルゴリズムについて述べる．さらには Neimark-Sacker 分岐に沿って生じる位相同期解とカオスについて詳細に解析した． (Tokushima University Institutional Repository) ● Metadata: 110720 (Tokushima University Institutional Repository: 110720)
71.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Synchronization of Electric Fireflies by using Square Wave Generators, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E81-A, No.5, 656-663, 1998. (Summary) In this article, we propose a square wave generator whose switching threshold values are switched by external inputs. This circuit is designed to simulate the synchronized luminescence of coupled fireflies. We investigate the behavior of the solutions in two coupled oscillators. The dynamics are demonstrated by a linear autonomous equation piecewisely, therefore, a one-dimensional return map is derived. We also prove the existence of stable in-phase synchronization in the coupled oscillator by using the return map, and we show the existence of regions of periodic solutions within a parameter space. Some theoretical results are confirmed by laboratory measurements. (Tokushima University Institutional Repository) ● Metadata: 110701 (Tokushima University Institutional Repository: 110701)
72.	Yoshio Tanaka, Hiroshi Kawakami and Tetsushi Ueta : Nonlinear Phenomena in Overhead-Crane-Type One-Link Manipulator, Transactions of The Japan Society of Mechanical Engineers, Series C, Vol.63, No.7, 2360-2367, 1997. (Summary) The dynamics of an overhead-crane-type one-link manipulator with a passive joint is essentially described by nonlinear ordinary differential equations including trigonometric functions. Under certain conditions, therefore, it is predicted that a manipulator performing repetitive tasks will exhibit typical nonlinear phenomena, such as the coexistence of several periodic vibrations and chaotic states of vibrations. In this paper, periodic motions of the manipulator are studied numerically, and their bifurcation diagrams in several parameter planes are calculated using the algorithms based on the geometric approach of ordinary differential equations. Period-doubling bifurcation leading to chaotic motions are observed in some parameter areas.
73.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation phenomena in the Josephson junction circuit coupled by a resistor, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E79-A, No.10, 1546-1550, 1996. (Summary) Bifurcation phenomena observed in a circuit containing two Josephson junctions coupled by a resistor are investigated. This circuit model has a mechanical analogue; Two damped pendular linked by a clutch exchanging kinetic energy of each pendulum. In this paper, firstly we study equilibria of the system. Bifurcations and topological properties of the equilibria are clarified. Secondly we analyse periodic solutions in the system by using suitable Poincare mapping and obtain a bifurcation diagram. There are two types of limit cycles distinguished by whether the motion is in S1 * R3 or T2 * R2, since at most two cyclic coordinates are included in the state space. There is a typical structure of tangent bifurcation for 2-periodic solutions with a cusp point. We found chaotic orbits via the period-doubling cascade, and a long-period stepwise orbit. (Tokushima University Institutional Repository) ● Metadata: 110695 (Tokushima University Institutional Repository: 110695)
74.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : A Method to Generatr a Chaotic Attractor by Destabilization, The Transactions of the Institute of Electronics, Information and Communication Engineers A, Vol.J79-A, No.8, 1418-1426, 1996. (Summary) 本論文では，自律系にみられる安定平衡点やリミットサイクルに対し，不安定化制御を行う．これは，線形制御理論の極配置法において，不安定極を指定することによって達成され，結果としてカオスアトラクタを得ることができる．安定平衡点の場合は，安定平衡点周りの特性方程式の極を不安定に指定した制御器を取り付け，制御を印加する時間を適当に与える．また，リミットサイクルに対しては，ポアンカレ写像を定義し，それによって得られる差分方程式系の固定点を不安定化し, カオスを発生させる．これらの手法の適用例として，勾配系回路, van der Pol方程式，拡張BVP発振器のモデルにそれぞれ不安定化制御を施し，得られたカオスについて検討した． (Tokushima University Institutional Repository) ● Metadata: 110719 (Tokushima University Institutional Repository: 110719)
75.	Tetsushi Ueta, Hiroshi Kawakami and Ikuro Morita : A Study of the Pendulum Equation with a Periodic Impulsive Force, --- Bifurcation and Control ---, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E78-A, No.10, 1269-1275, 1995. (Summary) The pendulum equation with a periodic impulsive force is investigated. This model described by a second order differential equation is also derived from dynamics of the stepping motor. In this paper, firstly, we analyze bifurcation phenomena of periodic solutions observed in a generalized pendulum equation with a periodic impulsive force. There exist two topologically different kinds of solution which can be chaotic by changing system parameters. We try to stabilize an unstable periodic orbit embedded in the chaotic attractor by small perturbations for the parameters. Secondly, we investigate the intermittent drive characteristics of two-phase hybrid stepping motor. We suggest that the unstable operations called pull-out are caused by bifurcations. Finally, we proposed a control method to avoid the pull-out by changing the repetitive frequency and stepping rate. (Tokushima University Institutional Repository) ● Metadata: 110694 (Tokushima University Institutional Repository: 110694)
76.	Yoshio Tanaka, Tetsushi Ueta, Hiroshi Kawakami and Takashi Sumitomo : A Robotic Truck Crane with Vibration Sensors, Journal of Robotics and Mechatronics, Vol.7, No.3, 213-217, 1995. (Summary) To solve the problems of the shortage and increasing age of skilled operators in Japan, we propose a new concept of "robotic crane system" or "intelligent crane system" and develop the prototype system under laboratory conditions. This paper describes the hardware of the robotic crane system, control design of the flexible rotary crane using vibration sensors, and the first experimental results. In order to simulate the crane's load swing efficiently and develop a 3-D simulator for cranes with a spherical pendulum such as a rotary crane, an efficient dynamic simulation method is also presented. This method was applied to the prototype system.
77.	Tetsushi Ueta and Hiroshi Kawakami : Composite dynamical system for controlling chaos, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E78-A, No.6, 708-714, 1995. (Summary) We propose a stabilization method of unstable periodic orbits embedded in a chaotic attractor of continuous-time system by using discrete state feedback controller. The controller is designed systematically by the Poincare mapping and its derivatives. Although the output of the controller is applied periodically to system parameter as small perturbations discontinuously, the controlled orbit accomplishes C^0. As the stability of a specific orbit is completely determined by the design of controller, we can also use the method to destabilize a stable periodic orbit. The destabilization method may be effectively applied to . escape from a local minimum in various optimization problems. As an example of the stabilization and destabilization, some numerical results of Duffing's equation are illustrated. (Tokushima University Institutional Repository) ● Metadata: 110693 (Tokushima University Institutional Repository: 110693)
78.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation of an inductively coupled Josephson junction circuit, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E77-A, No.11, 1758-1763, 1994. (Summary) Some qualitative properties of an inductively coupled circuit containing two Josephson junction elements with a dc source are investigated. The system is described by a four-dimensional autonomous differential equation. However, the phase space can be regarded as S^1×R^3 because the system has a periodicity for the invariant transformation. In this paper, we study the properties of periodic solutions winding around S^1 as a bifurcation problem. Firstly, we analyze equilibria in this system. The bifurcation diagram of equilibria and its topological classification are given. Secondly, the bifurcation diagram of the periodic solutions winding around S^1 are calculated by using a suitable Poincare mapping, and some properties of periodic solutions are discussed. From these analyses, we clarify that a periodic solution so-called "caterpillar solution" [1] is observed when the two Josephson junction circuits are weakly coupled. (Tokushima University Institutional Repository) ● Metadata: 110689 (Tokushima University Institutional Repository: 110689)
79.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation of heteroclinic orbits in a circuit containing a Josephson junction element, Electronics and Communications in Japan, Part 3 : Fundamental Electronic Science, Vol.77, No.2, 85-93, 1994. (Summary) The circuit equation of the circuit containing a Josephson junction and the equation of motion of a pendulum in which an elastic restoring force is applied in the direction of rotation are described in terms of a second-order ordinary differential equation containing the sum of a trigonometric term on the state and a linear term. In such a dynamic system, the number of saddles and sinks changes according to the parameter values and no periodicity exists with respect to the location of the saddles and sinks, thus analysis is difficult. In this paper, a circuit containing a Josephson junction is chosen as an example of such a dynamic system. Classification by the tangent bifurcation of the saddles and sinks and the results of the analysis based on the heteroclinic orbits on the phase plane are presented. The heteroclinic orbit presents a global bifurcation on the phase plane due to its structural instability. The parameters generated by this orbit are used as the values for the bifurcation, and the bifurcation set was derived on the parameter plane. As a result, the unique linking number is defined for a particular parameter region surrounded by the bifurcation curve. This value can be used as a guideline for rotation of the orbit on the phase plane. Further, by combining it with the bifurcation ensemble, a classification of the stable sinks in the basin is made possible. (Link to Publication Site) ● Publication site (DOI): 10.1002/ecjc.4430770209 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1002/ecjc.4430770209 (DOI: 10.1002/ecjc.4430770209)
80.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation of Heteroclinic Orbits in a Circuit Containing a Josephson Junction Element, The Transactions of the Institute of Electronics, Information and Communication Engineers A, Vol.J76-A, No.10, 1450-1456, 1993. (Summary) ジョセフソン接合素子を含む回路の回路方程式や，回転方向に弾性復元力の働く振り子の運動方程式などは，状態に関する三角関数の項と線形項の和を含んだ2階の常微分方程式で記述される．このような力学系は，平衡点の数がパラメータの値によって変わり，平衡点の位置に関して周期性を持たなくなるため解析が難しい．本論文では，この力学系の例としてジョセフソン接合素子を含む回路を取り上げ，平衡点の接線分岐による分類，および相平面上に生じるヘテロクリニック軌道に着目した解析の結果を述べる．ヘテロクリニック軌道は，その構造不安定性により，相平面上での大域的な分岐を表す．この軌道の生じるパラメータを分岐の値として，パラメータ平面で分岐集合を求めた．その際，分岐曲線によって囲まれる1つのパラメータ領域に，唯一決まるまつわり数を定義した．これは，軌道の相平面での回転の指標として用いることができ，さらに分岐集合と組み合わせることによって，安定平衡点の引力圏の分類を可能にした． (Tokushima University Institutional Repository) ● Metadata: 110718 (Tokushima University Institutional Repository: 110718)
81.	Yoshio Tanaka, Yasuo Yoshida, Tetsushi Ueta and Hiroshi Kawakami : Vibration suppressing control of flexible rotary crane using tip position sensor, Journal of Robotics and Mechatronics, Vol.4, No.6, 520-525, 1993. (Summary) For vibration suppressing control of flexible rotary cranes, two control methods by the use of a tip position sensor have been proposed. One is a control system that suppresses transient vibrations generated by the impact of switching of driving speeds when Bang-Bang control, open-loop anti-swing control, is completed. The other is a servo system to which vibration suppressing feedback is added. Experiments have confirmed that either system is remarkably effective in suppressing vibration.
82.	Yoshio Tanaka, Tetsushi Ueta and Hiroshi Kawakami : Efficient Dynamic Simulation Method of Cranes with a Spherical Pendulum, Transactions of The Japan Society of Mechanical Engineers, Series C, Vol.59, No.3, 186-190, 1993. (Summary) 旋回型クレーンにおいて，クレーン本体と吊り荷を一つの開ループリンク機構としてモデリングを行うことを提案している．受動関節と仮想リンクという新しい概念を導入し，従来使用されている開ループリンク機構ロボット用に開発された高速シミュレーション方法が適用可能となった．本文ではリンクの構成問題の詳述と，適用例，それらの数値計算結果を示している．適用例では，実験用に製作したクレーンの実パラメータを用いてシミュレーションを行い，実機とシミュレーションとの差違についても検討している．また，結果の3次元ソリッドモデルによるグラフィクス表示も試みている．

Academic Paper (Unrefereed Paper):

1.	Hiroki Tanioka, Kenji Matsuura, Tetsushi Ueta and Fumiaki Kawano : Challenges and Improvements in a Workshop-Type Class in BYOD, Journal of University Education Research, No.16, 18-23, 2019. (Keyword) BYOD / workshop / group learning / information literacy (Tokushima University Institutional Repository) ● Metadata: 113256 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050845763146058880 (Tokushima University Institutional Repository: 113256, CiNii: 1050845763146058880)
2.	Tetsushi Ueta : A Consideration of an ICT Tool for Chalk and Talk Lectures, Journal of University Education Research, No.14, 62-68, 2017. (Summary) Many teachers notice that it is important to represent abstract images, development of equations, and summaries on a blackboard in lectures for promotion of students' understanding. On the other hand, visual aids are also effective since figures and pictures encourage intuitive comprehension. We report new possibilities and problems with this tool through experience of operations in several lectures including remote lectures and massive classrooms (Keyword) ICT tool / visual aid / digital teaching material (Tokushima University Institutional Repository) ● Metadata: 110950 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050564287419657984 (Tokushima University Institutional Repository: 110950, CiNii: 1050564287419657984)
3.	Mihoko Teshigawara and Tetsushi Ueta : Improving the Quality of a Graduate-Level Content Course Taught in English, --- A Description of Student Support and Questionnaire Survey Results ---, Journal of University Education Research, No.5, 123-127, 2008. (Summary) 英語による大学院レベルの専門授業において行った，受講生に対する支援講義の内容を記述し，アンケート調査により得られた支援講義に対する評価をまとめた． (Keyword) Content course taught in English / student language support / questionnaire survey results (Tokushima University Institutional Repository) ● Metadata: 82681 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050282812440492032 (Tokushima University Institutional Repository: 82681, CiNii: 1050282812440492032)

Academic Letter:

1.	Yosuke Seki, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : A Questionnaire System with An Authentication Framework Considering Online Activities of Users, IEEJ Transactions on Electrical and Electronic Engineering (TEEE), Vol.13, No.7, 1071-1072, 2018. (Summary) It is difficult to distribute online questionnaire adequately to those subjects who satisfy requirements of investigations. In addition, low questionnaire response rates, because of factors such as overlooking request emails and noncooperation to answer the questionnaires, sometimes annoy the investigators. Now that today's organizational systems adopt a unified authentication framework of which logging function stores authentication records of users in federated systems, the possible solution for these problems arises by utilizing the log data and adding the questionnaire process to the framework. The present paper proposes a flow controlling mechanism arranged in a major unified authentication framework and describes how to utilize log data on the framework to select target persons for questionnaires and increase the response rates. (Keyword) questionnaires / Shibboleth authentication / questionnaire response rates (Tokushima University Institutional Repository) ● Metadata: 111611 (Link to Publication Site) ● Publication site (DOI): 10.1002/tee.22665 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1002/tee.22665 (Tokushima University Institutional Repository: 111611, DOI: 10.1002/tee.22665)
2.	Yosuke Seki, Kenji Matsuura, Masahiko Sano, Tetsushi Ueta and Hiroaki Tatei : A Method of Providing PC Operations for Stimulating Recalls of Past Operating Process and Results, Japan Journal of Educational Technology, Vol.40, No.Suppl., 113-116, 2016. (Summary) Web検索やファイル編集作業に対して，統合的に作業記録する常駐のツールと，後日それを活用して過去作業の関連作業を支援するビューワを提案する．過去に実施・経験した知的作業を想起することで，現在の作業効率が高まることや相対的な成果物の充実などが期待される． (Keyword) 作業履歴 / 想起 / web検索 / ビューワ / ロガー (Tokushima University Institutional Repository) ● Metadata: 111602 (Link to Publication Site) ● Publication site (DOI): 10.15077/jjet.S40065 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.15077/jjet.S40065 (Tokushima University Institutional Repository: 111602, DOI: 10.15077/jjet.S40065)
3.	Daisuke Ito and Tetsushi Ueta : Steady state analysis of the TCP network with RED algorithm, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.EA99, No.6, 1247-1250, 2016. (Summary) The transmission control protocol with a random early detection (TCP/RED) is an important algorithm for a TCP congestion control. It has been expressed as a simple second-order discrete-time hybrid dynamical model, and shows unique and typical nonlinear phenomena, e.g., bifurcation phenomena or chaotic attractors. However, detailed behavior is unclear due to discontinuity that describes the switching of transmission phases in TCP/RED, but we have proposed its analysis method in previous study. This letter clarifies bifurcation structures with it. (Keyword) TCP/RED / S-model / border-collision bifurcation (Tokushima University Institutional Repository) ● Metadata: 110707 (Link to Publication Site) ● Publication site (DOI): 10.1587/transfun.E99.A.1247 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/transfun.E99.A.1247 (Tokushima University Institutional Repository: 110707, DOI: 10.1587/transfun.E99.A.1247)
4.	Kenji Hishikawa, Daisuke Ito and Tetsushi Ueta : Bifurcations and Phase Differences of Nonlinear Coupled Dictyostelium Systems, Journal of Signal Processing, Vol.19, No.4, 99-102, 2015. (Summary) Nagano proposed a mathematical model of coupled Dictyostelium systems and demonstrated the strong tendency of in-phase synchronization. In this study, we investigate the mechanisms of this phenomenon by obtaining bifurcation sets and analyzing the phase differences of responses. From the analysis results, the model has a wide parameter range giving a stable 1-periodic solution. Thus, the one-to-one synchronization is maintained regardless of changes in the environment parameters. For example, even if the frequency ratio of two oscillators is extremely unbalanced, the model with an appropriate coupling factor shows a 1-periodic solution. (Link to Publication Site) ● Publication site (DOI): 10.2299/jsp.19.99 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.2299/jsp.19.99 (DOI: 10.2299/jsp.19.99)
5.	Takayuki Fujii, Hiroyuki Asahara, Daisuke Ito, Tetsushi Ueta and Takuji Kousaka : Computational Method of Border-collision Bifurcation Point for Piecewise Nonlinear Discrete-Time Dynamical Systems, IEEJ Transactions on Electronics, Information and Systems, Vol.135, No.4, 468-469, 2015. (Keyword) piecewise nonlinear discrete-time dynamical system / border-collision bifurcation (Link to Publication Site) ● Publication site (DOI): 10.1541/ieejeiss.135.468 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-84928191587 (DOI: 10.1541/ieejeiss.135.468, Elsevier: Scopus)
6.	Norihide Oda, Takuji Kousaka, Tetsushi Ueta and YUE MA : Controlling Chaos in a Simple Circuit with Switching Delay, Journal of Signal Processing, Vol.11, No.4, 329-332, 2007. (Summary) Recently, the control of chaos in piecewise smooth systems has been attracting increasing attention. In the previous study, we proposed a method of stabilizing the unstable periodic orbit in the piecewise smooth system with an ideal switching action. In most practical cases, however, switching events do not behave ideally. In particular, switching delay, large or small, indeed exists and cannot be ignored. So far, there is little work on controlling chaos in such kinds of systems. In this paper, we proposes a method of stabilizing the unstable periodic orbit in a simple circuit with switching delay. (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1520291855157814912 (CiNii: 1520291855157814912)
7.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami, Hiroshi Fujii and Kazuyuki Aihara : Bifurcations in two-dimensional Hindmarsh-Rose type model, International Journal of Bifurcation and Chaos, Vol.17, No.3, 985-998, 2007. (Summary) We analyze a two-dimensional Hindmarsh Rose type model exhibiting properties of both Class 1 and Class 2 neurons. Although the system is two-dimensional and contains only four parameters, the obtained bifurcation diagrams show that the bifurcation structure satisfies conditions for emergence of both features with constant stimuli. (Tokushima University Institutional Repository) ● Metadata: 112116 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127407017707 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127407017707 (Tokushima University Institutional Repository: 112116, DOI: 10.1142/S0218127407017707)
8.	Yu Toyosaki, Tetsushi Ueta and Takuji Kousaka : Switch Synchronizing Occasional Delayed Feedback Control for Piecewise Linear Systems, Journal of Signal Processing, Vol.10, No.412, 235-238, 2006. (Summary) This paper proposes Switch Synchronizing Delayed Feedback Control(abbr. SSDFC) in the piecewise linear systems. This control method weeds out the unsuitable control input from the different piecewise continuous functions. As an illustrated example, we then apply this general methodology to a simple circuit containing state-period dependent switch. The unstable periodic orbit is stabilized effectively in the computer simulations. Finally, the performance of SSDFC is compared with Delayed Feedback Control(DFC). (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1523669554771534848 (CiNii: 1523669554771534848)
9.	Tetsushi Ueta and Hiroshi Kawakami : Chaos in cross-coupled BVP oscillators, International Journal of Bifurcation and Chaos, Vol.15, No.10, 3359-3366, 2005. (Summary) In this letter, we investigate the cross-coupled BVP oscillators. A single BVP oscillator has two terminals which can extract an independent state variable, so in the preceding works, several coupling systems have been studied. Synchronization modes and chaos in these systems are classified as results of bifurcation problems. We revisit a coupled oscillator, and clarify new results which have not been reported before, i.e. stable tori and its breakdown, and chaotic motions. Also classification of synchronized periodic solutions is done by a bifurcation diagram. (Tokushima University Institutional Repository) ● Metadata: 112058 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127405013940 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127405013940 (Tokushima University Institutional Repository: 112058, DOI: 10.1142/S0218127405013940)
10.	Takuji Kousaka, Yoshihito Yasuhara, Tetsushi Ueta and Hiroshi Kawakami : Experimental Realization of Controlling Chaos in the Periodically Switched Nonlinear Circuit, International Journal of Bifurcation and Chaos, Vol.14, No.10, 3655-3660, 2004. (Summary) This letter presents an experimental confirmation of controlling the chaotic behavior of a target unstable periodic orbit when the periodically switched nonlinear circuit has a chaotic attractor. The pole assignment for the corresponding discrete system derived from such a nonautonomous system via Poincar´e mapping works effectively, and the control unit is easily realized by the window comparator, sample-hold circuits, and so on. (Tokushima University Institutional Repository) ● Metadata: 112114 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127404011508 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127404011508 (Tokushima University Institutional Repository: 112114, DOI: 10.1142/S0218127404011508)
11.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation in asymmetrically coupled BVP oscillators, International Journal of Bifurcation and Chaos, Vol.13, No.5, 1319-1327, 2003. (Summary) BVP oscillator is the simplest mathematical model describing dynamical behavior of the neural activity. The large scale neural network can often be described naturally by coupled systems of BVP oscillators. However, even if two BVP oscillators are merely coupled by a linear element, the whole system exhibits a complicated behavior. In this paper, we analyze coupled BVP oscillators with asymmetrical coupling structure, with each oscillator having a different internal resistance. We present a complete four-dimensional system, which shows a rich variety of bifurcation phenomena, and strange attractors. We calculate bifurcation diagrams and confirm relaxation phenomena in the laboratory experiments. We also briefly report a conspicuous strange attractor. (Tokushima University Institutional Repository) ● Metadata: 112053 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127403007199 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127403007199 (Tokushima University Institutional Repository: 112053, DOI: 10.1142/S0218127403007199)
12.	Tetsushi Ueta and Guanrong Chen : On Synchronization and Control of Coupled Wilson-Cowan Neural Oscillators, International Journal of Bifurcation and Chaos, Vol.13, No.1, 163-175, 2003. (Summary) This paper investigates the complex dynamics, synchronization and control of chaos in a system of strongly connected Wilson Cowan neural oscillators. Some typical synchronized periodic solutions are analyzed by using the Poincar e mapping method, for which bifurcation diagrams are obtained. It is shown that topological change of the synchronization mode is mainly caused and carried out by the Neimark Sacker bifurcation. Finally, a simple feedback control method is presented for stabilizing an in-phase synchronizing periodic solution embedded in the chaotic attractor of a higher-dimensional model of such coupled neural oscillators. (Tokushima University Institutional Repository) ● Metadata: 112051 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127403006406 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127403006406 (Tokushima University Institutional Repository: 112051, DOI: 10.1142/S0218127403006406)
13.	Tohru Kawabe, Tetsushi Ueta and Yoshifumi Nishio : Solving Abilities of Chaotic Noise and Iterative Simulated Annealing for TSP, Transactions of the Institute of Systems, Control and Information Engineers, Vol.15, No.9, 510-512, 2002. (Summary) Hopfild型ニューラルネットワークを巡回セールス問題の解探索マシンとして適用した場合，系の運動は多くの場合局所解に陥ってしまう．このマシンに対し，カオスノイズを印加すると，大域的最適解を見いだせる可能性が他の文献によって示されている．本論文では，焼き鈍し技法で用いられる確率型ノイズと，決定論によるカオスノイズと性能を比較している．カオスノイズの何の性質がこれらの問題に有効であるのか，その断片が明らかにされる． (Keyword) hopfield neural netowrk / chaotic noise / simulated annealing / traveling salesman problem (Link to Publication Site) ● Publication site (DOI): 10.5687/iscie.15.510 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390001205166567936 ● Search Scopus @ Elsevier (DOI): 10.5687/iscie.15.510 (DOI: 10.5687/iscie.15.510, CiNii: 1390001205166567936)
14.	Tetsushi Ueta, Akira Takeuchi and Kenji Terada : Image Pattern Retrieval Method using Fractal Coding, The Transactions of the Institute of Electronics, Information and Communication Engineers A, Vol.J85-A, No.2, 253-257, 2002. (Summary) フラクタル符号化の原理を用いて画像中から，与えられた画像パターンと同じようなパターンを検索する手法を提案する．全ての画像には，部分的に互いに相似な場所が存在しているが，その性質を利用して圧縮する方式をフラクタル符号化と言う．本手法ではフラクタル符号化の圧縮データに含まれる画像中の相似な場所の位置関係を示すデータ群を利用して，決められた画像パターンを検索するものである．本手法により人間や複雑であいまいな形状の画像パターンを，背景などの模様に影響を受けることなく精度良く抽出することができる． (Keyword) フラクタル符号 / IFS / 画像領域分割 / 画像パターン検索 (Tokushima University Institutional Repository) ● Metadata: 110724 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050001337466163328 (Tokushima University Institutional Repository: 110724, CiNii: 1050001337466163328)
15.	Shigeki Tsuji, Tetsushi Ueta, Tetsuya Yoshinaga and Hiroshi Kawakami : A Calculation Method of the Fixed Point with a Specified Argument and Its Application, The Transactions of the Institute of Electronics, Information and Communication Engineers A, Vol.J84-A, No.3, 441-443, 2001. (Summary) 非線形力学系において，系に含まれるパラメータが変化し，固定点の特性乗数が複素単位円外に出ることにより各種の局所的分岐現象を生じる．本報告では，複素共役な特性乗数をもつ固定点に対して，偏角を指定してその位置，動径，パラメータ値を数値計算する方法を述べる．また，その応用として，Neimark-Sacker 分岐パラメータ値を求める計算方法を提案する．本稿では，連続力学系のポアンカレ写像または離散力学系を対象とし，指定した偏角をもつ固定点(周期点)の等高線をパラメータ平面で計算する方法を提案する．固定点条件，共役複素数の特性乗数を代入した特性方程式を実部と虚部に分離し，それぞれを独立した条件として連立させ，ニュートン法で固定点位置，パラメータ値について解く．また，この手法の応用として，指定した偏角をもつNS分岐を求める手法について述べる．これらのツールにより，固定点とNS分岐，周期引き込み領域との関係をより直接的に調べることができる． (Keyword) 固定点 / 偏角 / Neimark-Sacker 分岐 / ニュートン法 (Tokushima University Institutional Repository) ● Metadata: 110723 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1050282812442873856 (Tokushima University Institutional Repository: 110723, CiNii: 1050282812442873856)
16.	Takuji Kousaka, Shoichi Tahara, Tetsushi Ueta, Hiroshi Kawakami and Minoru Abe : Chaos in a Simple Hybrid System and its Control, Electronics Letters, Vol.37, No.1, 1-2, 2001. (Summary) A simple hybrid system exhibiting chaos is developed and a chaos control method realised. It is shown that, since the dynamics can be expressed by a return map, the system has an observable chaos. The control method, which is based on the pole assignment technique, can stabilise any unstable periodic orbit in the chaos. The theoretical result is verified by laboratory experiments. (Link to Publication Site) ● Publication site (DOI): 10.1049/el:20010033 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1049/el:20010033 (DOI: 10.1049/el:20010033)
17.	Zhi-Hong Guan, Guanrong Chen and Tetsushi Ueta : On Impulsive Control of a Periodically Forced Chaotic Pendulum System, IEEE Transactions on Automatic Control, Vol.45, No.9, 1724-1727, 2000. (Summary) We consider impulsive control of a periodically forced pendulum system which has rich chaos and bifurcation phenomena. A new impulsive control method for chaos suppression of this pendulum system is developed. Some simple sufficient conditions for driving the chaotic state to its zero equilibrium are presented, and some criteria for eventually, exponentially asymptotical stability are established. This work provides a rigorous theoretical analysis to support some early experimental observations on controlling chaos in the periodically forced pendulum system. (Link to Publication Site) ● Publication site (DOI): 10.1109/9.880633 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1109/9.880633 (DOI: 10.1109/9.880633)
18.	Akira Takeuchi, Tetsushi Ueta and Kenji Terada : Image Segmentation Using Fractal Coding with Resizable Domain Blocks, The Transactions of the Institute of Electronics, Information and Communication Engineers D, Vol.J83-D2, No.7, 1695-1700, 2000. (Summary) フラクタル符号化の原理を用いて画像中の同じ性質の領域ごとに分割していく手法を提案する．全ての画像は部分的には互いに相似な場所があるが，その性質を利用した画像データ圧縮方式をフラクタル符号化と言う．本手法ではフラクタル符号化の圧縮データ中に含まれる画像中の相似な場所同士の位置関係情報を利用して，画像を領域分割していくものである．従来，フラクタル符号化では相似な部分をある一定の大きさごとで検索していたが，本手法では相似領域の大きさを変化させることで，領域分割の精度の向上を実現した． (Keyword) image processing / computer vision / フラクタル / 符号化 (Tokushima University Institutional Repository) ● Metadata: 110722 (Tokushima University Institutional Repository: 110722)
19.	Toshikazu Masaki, Tetsushi Ueta and Kenji Terada : フラクタル符号を用いた指紋による個人認識の一手法, The Journal of the Institute of Image Electronics Engineers of Japan, Vol.29, No.2, 147-152, 2000. (Summary) フラクタル符号化された指紋画像データを用いて，個人識別を行なう手法を提案する．指紋は完全なフラクタル図形ではないが，部分的な自己相似性を有している．フラクタル符号化は部分的自己相似性を利用して圧縮する技術であるが，本手法ではこの圧縮の原理を用いて個人固有の指紋の特徴を抽出する．すなわちフラクタル符号の部分自己相似を探索するアルゴリズムにより，データ取得の際の指紋の位置や向き，指の状態や押しつける強さの違いによって生じる画像中の指紋の大きさや太さ，かすれなどの影響を受けないように個人特徴を抽出することを実現した． (Keyword) image processing / computer vision / フラクタル / 符号化 / バイオメトリクス
20.	Tetsushi Ueta, Guanrong Chen and Tohru Kawabe : A Simple Approach to Calculation and Control of Unstable Periodic Orbits in Chaotic Piecewise Linear Systems, International Journal of Bifurcation and Chaos, Vol.11, No.1, 215-224, 2000. (Summary) This paper describes a simple method for calculating unstable periodic orbits (UPOs) and their control in piecewise-linear autonomous systems. The algorithm can be used to obtain any desired UPO embedded in a chaotic attractor, and the UPO can be stabilized by a simple state feedback control. A brief stability analysis of the controlled system is also given. (Tokushima University Institutional Repository) ● Metadata: 112049 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127401002092 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127401002092 (Tokushima University Institutional Repository: 112049, DOI: 10.1142/S0218127401002092)
21.	Guanrong Chen and Tetsushi Ueta : Yet Another Chaotic Attractor, International Journal of Bifurcation and Chaos, Vol.9, No.7, 1465-1466, 1999. (Summary) This Letter reports the finding of a new chaotic at tractor in a simple three-dimensional autonomous system, which resembles some familiar features from both the Lorenz and Rossler at tractors. (Tokushima University Institutional Repository) ● Metadata: 112044 (Link to Publication Site) ● Publication site (DOI): 10.1142/S0218127499001024 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1142/S0218127499001024 (Tokushima University Institutional Repository: 112044, DOI: 10.1142/S0218127499001024)
22.	Tetsushi Ueta, Masafumi Tsueike, Hiroshi Kawakami, Tetsuya Yoshinaga and Yuji Katsuta : A computation of bifurcation parameter values for limit cycles, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.EA80, No.9, 1725-1728, 1997. (Summary) This letter describes a new computational method to obtain the bifurcation parameter value of a limit cycle in nonlinear autonomous systems. The method can calculate a parameter value at which local bifurcations; tangent, period-doubling and Neimark-Sacker bifurcations are occurred by using properties of the characteristic equation for a fixed point of the Poincare mapping. Conventionally a period of the limit cycle is not used explicitly since the Poincare mapping needs only whether the orbit reaches a cross-section or not. In our method, the period is treated as an independent variable for Newton's method, so an accurate location of the fixed point, its period and the bifurcation parameter value can be calculated simultaneously. Although the number of variables increases, the Jacobian matrix becomes simple and the recurrence procedure converges rapidly compared with conventional methods. (Tokushima University Institutional Repository) ● Metadata: 110699 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-0031220919 (Tokushima University Institutional Repository: 110699, Elsevier: Scopus)
23.	Tetsushi Ueta and Hiroshi Kawakami : On Unstable Saddle-Node Connecting Orbit in a Planer Autonomous System, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E79-A, No.11, 1581-1586, 1996. (Summary) We found a novel connecting orbit in the averaged Duffing-Rayleigh equation. The orbit starts from an unstable manifold of a saddle type equilibrium point and reaches to a stable manifold of a node type equilibrium. Although the connecting orbit is structurally stable in terms of the conventional definition of structural stability, it is structually unstable since a one-dimensional manifold into which the connecting orbit flows is unstable. We can consider the orbit is one of global bifurcations governing the differentiability of the closed orbit. (Keyword) saddle-node connecting orbit / bifurcation / topological classification of flows (Tokushima University Institutional Repository) ● Metadata: 110696 (Tokushima University Institutional Repository: 110696)

Review, Commentary:

1.	Atsuo Maki, Masahito Sakai and Tetsushi Ueta : Review of the analytical prediction method of surf-riding threshold in following sea, and its relation to IMO second-generation intact stability criteria, Nonlinear Theory and Its Applications, IEICE, Vol.15, No.3, (in-press), Jul. 2024. (Summary) High-speed ship operations have a significant risk of the broaching phenomenon when navigating in following/quartering seas. The occurrence of this phenomenon can result in a violent yaw motion, regardless of the steering effort. Centrifugal forces due to the yaw motion could cause large roll motion and even capsizing in some cases. A necessary condition for the occurrence of broaching is the surf-riding phenomenon. Therefore, the International Maritime Organization (IMO) has set up criteria to include theoretical formulas for estimating the occurrence of surf-riding phenomena. The theoretical equation used in the IMO Second-Generation Intact Stability criteria (SGISC) to estimate the surf-riding threshold is based on the authors' method, and in its derivation process, Melnikov's method. is utilized. This paper deals with nonlinear equations describing the surge motions of a ship. However, such equations cannot be directly solved; therefore, prior researchers and authors have proposed various approximate methods to predict the surf-riding threshold, including the methods based on Meknikov's method. In this paper, first, the authors describe the mechanism of the surfing phenomenon. Then, the authors explain in detail the derivation of the estimation methods for the surf-riding phenomenon that have been proposed by the prior researchers and the authors. Finally, the authors show the relationship between the theoretical prediction method of the surf-riding threshold based on Melnikov's method and the IMO SGISC. (Keyword) surf-riding / analytical solution / heteroclinic bifurcation / Melnikov's method
2.	Tetsushi Ueta and Seiya Amoh : To Tackle Bifurcation Problems with Python, IEICE ESS Fundamentals Review, Vol.16, No.3, 139-146, Jan. 2023. (Summary) 機械学習やデータサイエンスを実践する基盤プログラミング言語としてPython が注目されている．本解説では非線形問題，特に系にみられる周期解の分岐問題について，Python を用いたアプローチの詳細を述べる．分岐計算アルゴリズムを可読性高く実装でき，計算機やOS に依存せず，対話処理による試行錯誤が可能となる．いくつかの特徴的なコードを示しながら，分岐問題に対するPython の優位点を述べる．また，Neimark-Sacker 分岐におけるbialtenate 積を用いた解法のコンパクトな実装，及びSympy を用いたヘシアン生成自動化過程についても述べる． (Keyword) Python / bifurcation analysis / tensor / bialternate product (Tokushima University Institutional Repository) ● Metadata: 117893 (Link to Publication Site) ● Publication site (DOI): 10.1587/essfr.16.3_139 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/essfr.16.3_139 (Tokushima University Institutional Repository: 117893, DOI: 10.1587/essfr.16.3_139)
3.	Tetsushi Ueta : 粗悪雑誌と業績評価, 徳島大学機関リポジトリ, Mar. 2021. (Summary) 本コラムでは著者の経験や主観に基づく，粗悪雑誌が選択される仕組み，粗悪雑誌を回避する方法について述べる．以下では粗悪雑誌についての定義は了解されているものと仮定した上で話を進める．研究分野によって実情と合わない点も多いかと思うが，ご容赦願いたい． (Link to Publication Site) ● Publication site (DOI): 10.15000/115857 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.15000/115857 (DOI: 10.15000/115857)
4.	Tetsushi Ueta : Ramble on about NOLTA Society, IEICE ESS Fundamentals Review, Vol.13, No.1, 5-6, Jul. 2019. (Tokushima University Institutional Repository) ● Metadata: 113463 (Link to Publication Site) ● Publication site (DOI): 10.1587/essfr.13.1_5 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1587/essfr.13.1_5 (Tokushima University Institutional Repository: 113463, DOI: 10.1587/essfr.13.1_5)
5.	Hiroshi Kawakami, Tetsushi Ueta and Tetsuya Yoshinaga : 区分非線形系にみられる不連続応答の分岐とカオス制御, Journal of Signal Processing, Vol.3, No.6, 367-371, Jun. 1999.
6.	Hiroshi Kawakami, Tetsuya Yoshinaga and Tetsushi Ueta : 力学系の計算機シミュレーション, 応用数理, Vol.3, No.6, 49-57, Dec. 1997.

Proceeding of International Conference:

1.	Seiya Amoh and Tetsushi Ueta : Design and Development of Bifurcation Analysis Software Using Python, Proc. NOLTA2023, 699-702, Catania, Sep. 2023. (Summary) There are several software packages for solving bifurcation problems of nonlinear dynamical systems, but they are built on Fortran or old version of MATLAB. They often require users to prepare in advance, and their interfaces are not modern. In this paper, we present the design of a bifurcation computation package using Python. Python provides numerical calculation libraries ported from Fortran and other languages, and the trade-off between speed and readability is well balanced. The proposed package includes interactive phase-portrait drawing software, the main calculation part of the bifurcation analysis, and tools for grapher that can be used in academic papers. (Link to Publication Site) ● Publication site (DOI): 10.34385/proc.76.D2L-21 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.34385/proc.76.D2L-21 (DOI: 10.34385/proc.76.D2L-21)
2.	Tetsushi Ueta : Python Expressions of Variational Equations, Proc. NOLTA2023, 663-666, Catania, Sep. 2023. (Summary) Python is gaining attention as a fundamental programming language for machine learning and data science. This paper describes a detailed Python approach to nonlinear problems, especially the bifurcation problems of periodic solutions. It is a highly readable implementation of the bifurcation algorithm, independent from the computer and the operating system, and it allows an interactive trial-and-error processing. (Link to Publication Site) ● Publication site (DOI): 10.34385/proc.76.D1L-22 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.34385/proc.76.D1L-22 (DOI: 10.34385/proc.76.D1L-22)
3.	Michiru Katayama, Kenji Ikeda and Tetsushi Ueta : Laminar stabilization control in chaos intermittency, Proc. NOLTA2023, 17-20, Catania, Sep. 2023. (Summary) Intermittency gives the irregular switching of almost periodic (laminar) and chaotic (burst) motions, and can be confirmed in every physical system within a certain parameter range. In this paper, by utilizing a method stabilizing a periodic motion which have been vanished by a saddle node bifurcation, a laminar motion in the intermittency is stabilized by a tiny control input. Apseudo periodic orbit composed by the vanished orbit or laminar motion is applied as a reference for the linear feedback control. We demonstrate the control for a circuit model and show robust stabilization responses. (Link to Publication Site) ● Publication site (DOI): 10.34385/proc.76.A2L-15 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.34385/proc.76.A2L-15 (DOI: 10.34385/proc.76.A2L-15)
4.	Seiya Amoh and Tetsushi Ueta : Multivibrator with Slow-Fast Dynamics, Proc. NOLTA2023, 13-16, Catania, Sep. 2023. (Summary) In this paper, we discusses slow-fast dynamical systems, which are ordinary differential equations with very different time constants. Such systems can exhibit a canard solution, which results in explosive amplitude increases for small parameter changes. We explores the canard explosion parameters using a multivibrator circuit as a slow-fast dynamical system, and presents numerical simulation results and a real circuit realization of the canard based on the simulations. The study focuses on the transition from the periodic solution generation process by Hopf bifurcation to canard explosion. (Link to Publication Site) ● Publication site (DOI): 10.34385/proc.76.A2L-14 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.34385/proc.76.A2L-14 (DOI: 10.34385/proc.76.A2L-14)
5.	Yuri Lucas Direbieski, Hiroki Tanioka, Kenji Matsuura, Hironori Takeuchi, Masahiko Sano and Tetsushi Ueta : Security Impact Analysis of Degree of Field Extension in Lattice Attacks on Ring-LWE Problem, COMPSAC 2023 Workshop: The 1st IEEE International Workshop on Data Science & Machine Learning for Cybersecurity, IoT & Digital Forensics (DSML), 1441-1446, Turin, Jun. 2023. (Summary) Modern information communications use cryptography to keep the contents of communications confidential. RSA (RivestShamirAdleman) cryptography and elliptic curve cryptography, which are public-key cryptosystems, are widely used cryptographic schemes. However, it is known that these cryptographic schemes can be deciphered in a very short time by Shors algorithm when a quantum computer is put into practical use. Therefore, several methods have been proposed for quantum computer-resistant cryptosystems that cannot be cracked even by a quantum computer. A simple implementation of LWE-based lattice cryptography based on the LWE (Learning With Errors) problem requires a key length of O(n2) to ensure the same level of security as existing public-key cryptography schemes such as RSA and elliptic curve cryptography. In this paper, we attacked the Ring-LWE (RLWE) scheme, which can be implemented with a short key length, with a modified LLL (Lenstra-Lenstra-Lova sz) basis reduction algorithm and investigated the trend in the degree of field extension required to generate a secure and small key. Results showed that the lattice-based cryptography may be strengthened by employing Cullen or Mersenne prime numbers as the degree of field extension. (Keyword) lattice-cipher / ring-LWE / LLL-basis-reduction (Link to Publication Site) ● Publication site (DOI): 10.1109/COMPSAC57700.2023.00221 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1109/COMPSAC57700.2023.00221 (DOI: 10.1109/COMPSAC57700.2023.00221)
6.	Kenji Matsuura, Kohta Jobe, Hiroki Tanioka, Hironori Takeuchi and Tetsushi Ueta : Performed-Tactics Detection of a Basketball Match using Multi-Object Tracking Technology Applicable for a Movie, Elizabeth Langran (Ed.), Proceedings of Society for Information Technology & Teacher Education International Conference, 676-680, New Orleans, LA, US, Mar. 2023.
7.	Masaki Yoshikawa, Kentaro Ono and Tetsushi Ueta : Bifurcations in a forced Wilson-Cowan neuron pair, Proc. NOLTA 2022, 155-158, Online, Dec. 2022. (Summary) We investigate bifurcations of periodic solutions observed in the forced Wilson-Cowan neuron pair by both the brute-force computation and the shooting method. By super-imposing results given by both methods, a detailed topological classification of periodic solutions is achieved. Totally different shapes of bifurcation sets compared with other literature are found. (Link to Publication Site) ● Publication site (DOI): 10.34385/proc.71.A4L-E-04 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.34385/proc.71.A4L-E-04 (DOI: 10.34385/proc.71.A4L-E-04)
8.	Tetsushi Ueta : Locating and Controlling Chaotic Saddles, The 14th International Workshop on Complex-Systems for Future Technologies and Applications (IWCFTA2021), Zhanjiang (online), Dec. 2021. (Summary) Some planar discrete nonlinear systems may have a horseshoe structure with stable and unstable manifolds associated with a saddle fixed point. Under this situation, as is well known, there are infinitely many unstable periodic points around the saddle. By making correspondence of the cross sections of manifolds and symbolic dynamics, one can obtain a ``candidate area'' containing an unstable periodic point whose period is given by the gray code. These unstable periodic points can be stabilized by applying any chaos control technique into that candidate area, for which the external force control method exhibits a very robust control performance. In this talk, a horseshoe structure derived by Poincaré mapping for a two dimensional nonautonomous hybrid system is analyzed as an example. A a locating scheme for unstable periodic points is demonstrated, and their control results are presented.
9.	Yuu Miino and Tetsushi Ueta : Calculation method for unstable periodic points in unimodal maps using symbolic dynamical system, Proc. NSLW2021, 16, Online, Dec. 2021. (Summary) We have developed a novel method to calculate unstable periodic points in unimodal maps based on symbolic dynamical system. In the numerical experiments, we have correctly discovered the points in 10^{-12} tolerance.
10.	Miino Yuu and Tetsushi Ueta : Homoclinic bifurcation analysis for logistic map, Proc. NSLW2021, 15, Online, Dec. 2021. (Summary) We have proposed the numerical method to calculate the homoclinic bifurcation parameter of the logistic map. From the experiments, we have exhibited the target parameters in the bifurcation diagram.
11.	Amoh Seiya, Ogura Miho and Tetsushi Ueta : A Method to Obtain Variational Equations Automatically by Applying Symbolic Differentiation, Proc. NSLW2021, 17, Online, Dec. 2021. (Summary) In the conventional implementations for solving bifurcation problems, Jacobian matrix and its partial derivatives regarding the given problem should be provided manually. This process is not so easy, thus it often induces human errors like computation failures, mistakes of copies, especially if the system is higher order. In this paper, we develop a preprocessor that gives the Jacobian matrix and partial derivatives symbolically by using SymPy packages on the Python platform. Possibilities about the inclusion of errors are minimized by symbolic derivations and reducing loop structures. It imposes a user only on putting an expression of the equation into a JSON fomat file. We demonstrate bifurcation calculations for discrete neuron dynamical systems. The system includes an exponential function, which makes the calculation of derivatives complicated, but we show that it can be implemented simply by using the symbolic differentiation.
12.	Tetsushi Ueta : Backward-Time Dynamics in an RLC Circuit with an Inverted Diode, Proc. NSLW2021, 8, Online, Dec. 2021.
13.	Shunya Izumi and Tetsushi Ueta : Secret Sharing Scheme Using Chaotic Neural Network, Proc. NCSP2021, 1-4, Online, Mar. 2021. (Summary) To avoid risks about transportation of secret keys for the chaos common-key encryption scheme, we proposed a chaos-based secret sharing scheme. However it is designed by a one-dimensional difference equation, so the threshold of the scheme has to be lowered. The risk of leaking the plaintext is higher compared to the conventional secret sharing scheme. In this paper, we will propose a secret sharing scheme using the high-dimensional chaotic neuron model. Since the config- uration of this model is chargeable, the whole dimension can be chosen. By changing the dimension, the number of shares required for decoding, that is the threshold, can be adjusted. The effect of changing the dimensionality of the model on the variance and recovery results is confirmed. The performance is evaluated by comparing with the previous study. (Keyword) secret share / chaotic neural networks / chaos encryption
14.	Yuu Miino and Tetsushi Ueta : Devil's staircase and multistability in a hybrid harmonic oscillator, Proc. NOLTA 2020, 501-504, Online, Nov. 2020. (Summary) In this study, we introduce a simple hybrid dynamical system showing complex behavior. Only hav- ing two harmonic oscillators with a stable node, this system exhibits rich kinds of nonlinear phenomena: bifurcations, chaos, multistable state, and devil's staircase. We observe them in phase portraits, bifurcation diagrams, and the ro- tation number, via the numerical experiments. Through the bifurcation analysis, we clarify the relation between the grazing bifurcation and the devil's staircase, and summa- rize the scenario to the chaos. (Link to Publication Site) ● Publication site (DOI): 10.34385/proc.74.D2L-C-3 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.34385/proc.74.D2L-C-3 (DOI: 10.34385/proc.74.D2L-C-3)
15.	Miho Ogura and Tetsushi Ueta : A Cryptographic Hash Function Based on a Chaotic Map, Proc. NOLTA 2020, 150-153, Online, Nov. 2020. (Summary) In a chaotic system, the sensitivity of the initialvalues, and a uniform distribution of mapped points aredesirable properties for hashing. In the conventional hashfunctions based on chaotic maps, an initial key given by theparameter values or initial state is required, however, theexistence of this initial key becomes a certain vulnerability.We developed a key-less hashing function based on a tentmap iteration. The parameter values and the initial valuesare obtained by exclusive-ORing each 32-bit character with64 constants. We evaluate its security and performance bythe confusion-diffusion analysis. The results assert that theproposed function is better than SHA-256 under appropriateconditions. (Keyword) cryptography / chaotic map (Link to Publication Site) ● Publication site (DOI): 10.34385/proc.74.A4L-D-3 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.34385/proc.74.A4L-D-3 (DOI: 10.34385/proc.74.A4L-D-3)
16.	Seiya Amo and Tetsushi Ueta : Bifurcation analysis of 3D hybrid autonomous system, Proc. NOLTA 2020, 493-496, Online, Nov. 2020. (Summary) In this paper, an analysis method for highdimensional piece-wise nonlinear autonomous systems is proposed. The method is more accurate than the conventional methods since we newly introduce durations as independent variables. We show the explanation of this method and the bifurcation analysis results of the piece-wise linear system. (Keyword) bifurcation (Link to Publication Site) ● Publication site (DOI): 10.34385/proc.74.D2L-C-1 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.34385/proc.74.D2L-C-1 (DOI: 10.34385/proc.74.D2L-C-1)
17.	Rina Yano, Hiroki Tanioka, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : Quantitative Measurement and Analysis to Thinking as a Way of Programming for Elementary School in Japan, Proceedings of IIAI-AAI2020, 163-168, Kitakyushu, Sep. 2020. (Summary) Programming education will be compulsory in elementary schools in Japan from 2020, but it is still little information on how to measure the effects of lessons conducted for students. In this study, to measure objectively and quantitativelythe educational effect of programming education, we developed a test of measuring the ability of thinking as a way of programming. In this paper, we evaluate the measurability of the test using Fishers exact test for elementary school students answers, focusing on the grade, the programming experience, and the difference between the results before and after the workshop. (Keyword) Learning Analytics / Programming Education / Elementary School (Link to Publication Site) ● Publication site (DOI): 10.1109/IIAI-AAI50415.2020.00040 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85107198127 (DOI: 10.1109/IIAI-AAI50415.2020.00040, Elsevier: Scopus)
18.	Seiya Amo, Daisuke Ito and Tetsushi Ueta : A method to suppress excited states for high symmetrical DOPO networks, Proc. NOLTA 2019, 173-176, Kuala Lumpur, Dec. 2019. (Summary) A network coupled with degenerate optical parametric oscillator (DOPO) can be used as a coherent Ising machine (CIM). Since some classes of combinatorial optimization problems can be encoded into the network configuration of DOPOs, a very fast computation is expected. However, the CIM cannot result the optimum solutions always because of bifurcation structure of the system influenced from the symmetry of the network configuration. Especially, it is impossible to avoid trapping into local minima by controlling with a uniform pomp rate. In this paper, we propose a method to suppress local minima by adjusting a pomp rate of the specific DOPO whereas the pump rates of other DOPOs are uniformvalues. This control may break the symmetrical property and the bifurcation structure temporarily and guide the trajectory into the global minima. We show several simulation results.
19.	Kohei Kawanaka, Felicia Misamanana Rabarison, Hiroki Tanioka, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : Improving Animal Recognition Accuracy using Image De-fencing, The 7th International Conference on Smart Computing and Artificial Intelligence (SCAI 2019), 534-537, Toyama, Jul. 2019. (Summary) When a computer recognizes an animal on an image, an accuracy of animal recognition decreases if a part of the animals body is covered by fences. On the other hand, when a human recognizes an object on the image, it is known to be possible to remove the fences and supplement the removed areas, and recognize the object, even if a part of the object is covered by fences. In this research, we aim to improve the accuracy of animal recognition using de-fencing on computer. (Keyword) Noice reduction / Image complement / Animal recognition (Link to Publication Site) ● Publication site (DOI): 10.1109/IIAI-AAI.2019.00114 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85080896317 (DOI: 10.1109/IIAI-AAI.2019.00114, Elsevier: Scopus)
20.	Kaoru Kimura, Felicia Misamanana Rabarison, Kawanaka Kohei, Hiroki Tanioka and Tetsushi Ueta : Animal Stamp Rally Application using Image Recognition, The 7th International Conference on Smart Computing and Artificial Intelligence (SCAI 2019), 1077-1078, Toyama, Jul. 2019. (Summary) Tokushima zoo is a municipal zoo housing a lot ofanimals for educational purpose. Thus, Tokushima city wantsvisitors to observe animals as many as possible whilst havingfun. The animal stamp rally is a game that visitors collect aseries of stamps at around animals which visitors have observed.Not to provide real stamps, tables and stamp cards, we developan animal stamp rally application. Thanks to the ConvolutionalNeural Network (CNN), the application can recognize stampsfrom snapshots of real animals instead of real stamps or QRcodes. Additionally, to improve animal recognition accuracy, theapplication uses GPS information. In this paper, we describesa progress of our development of the animal stamp rallyapplication, and estimates its recognition accuracy. (Keyword) Image Recognition / GPS Camera / Stamp Rally (Link to Publication Site) ● Publication site (DOI): 10.1109/IIAI-AAI.2019.00234 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85080922805 (DOI: 10.1109/IIAI-AAI.2019.00234, Elsevier: Scopus)
21.	Atsuo Maki, Yuuki Maruyama, Naoya Umeda, Yuu Miino, Toru Katayama, Masahiro Sakai and Tetsushi Ueta : A perspective on theoretical estimation of stochastic nonlinear rolling, Proc. of 17th International Ship Stability Workshop, 39-46, Helsinki, Jun. 2019. (Summary) Development of the probabilistic assessment method for nonlinear ship motion in irregular seas is essential. Particularly, theoretical based method is useful for practical and wider application such as stability evaluation in preliminary design stage. In this research, the method in which Monte Carlo Simulation and theoretical method were combined is newly proposed. Here, from the limited number of Monte Carlo Simulation (MCS) realizations, the unknown coefficients containing in the theoretically obtained non-Gaussian probability density function (PDF) were successfully determined. In this research, the results on roll motion in beam sea condition and parametric rolling in longitudinal waves were shown. Then, it was found that this approach is capable of determining the PDF, and the tail of the obtained PDF shows good agreement with the theoretical results. (Keyword) extreme roll motion / capsizing / parametric rolling / probability density function
22.	Kimura Kaoru, Felicia Misa Rabarison, Kawanaka Kohei, Hiroki Tanioka and Tetsushi Ueta : Local Zoo Animal Stamp Rally Application using Image Recognition, IEEE International Conference on Computational Photography 2019, Tokyo, May 2019.
23.	Kohei Kawanaka, Felicia Misa Rabarison, Hiroki Tanioka, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : Improving Animal Recognition Accuracy using Deep Learning, IEEE International Conference on Computational Photography 2019, Tokyo, May 2019.
24.	Yuu Miino, Tetsushi Ueta, Hiroshi Kawakami, Atsuo Maki and Naoya Umeda : Local stability and bifurcation analysis of the softening Duffing equation by numerical computation, Proc. 13th International Conference on the Stability of Ships and Ocean Vehicles, 397-403, Osaka, Sep. 2018.
25.	Yuu Miino, Tetsushi Ueta and Hiroshi Kawakami : Bifurcations in a sinusoidally driven LCR circuit with a hysteresis, Proc. NOLTA 2018, 247-250, Tarragona, Spain, Sep. 2018. (Summary) We investigate a driven LCR circuit with ahysteresis. We describe the circuit by a hybrid dynamicalsystem. The coil is modeled by a piecewise linear hysteresis, and the changes of the condition of the coil (magnetizedor not) are described by a finite state machine. We computelocal bifurcations accurately by taking a suitable Poincaremapping. Appearance patterns of the tangent and grazingbifurcations characterize this model.
26.	Mamoru Sakai, Hiroki Tanioka, Kenji Matsuura, Masahiko Sano, Kenji Ohira, Tetsushi Ueta and Sakaguchi Hiroaki : Evaluating Hitting Skills of NPB Players with Logistic Regression Analysis, CSCE'18 Proceedings, 313-319, Las Vegas, Jul. 2018. (Summary) Luck or unluck is supposed to exist in baseball. In this paper, we consider unpredictable "lucky" or "un-lucky" cases which are occurred on the ground in order to find out authentic ability of batters. If all cases are observable, hit probabilities can be calculated. However, it is impossible to gather all the information on the ground. Therefore, "luck" is defined as influence of information that cannot be observed. To provide more appropriate evaluation for NPB 1 players, this paper proposes a predicted BABIP using Logistic Regression and describes the predicted BABIP reducing the influence of luck on the assessment of hitting ability. Analysis results show that there is a possibility of appropriate evaluation on hitting abilities of NPB players using the predicted BABIP. (Keyword) baseball / hitting / performance / evaluation / logistic regression
27.	Takeshi Kojima, Tetsushi Ueta and Tetsuya Yoshinaga : An attempt to enlarge basin in discrete tomographic dynamics with a competitive term, Proc. of NCSP'18, 604-607, Honolulu, Mar. 2018.
28.	Yuu Miino, Tetsushi Ueta and Hiroshi Kawakami : Global bifurcation analysis in a simple piecewise linear non-autonomous dynamical system, Proc. NOLTA 2017, 629-632, Cancun, Mexico, Dec. 2017. (Summary) In this study, we construct a simple piecewise linear dynamical system and analyze their global bifurcation phenomena. From the parameter dependency, we derive the scenario of local and global bifurcation phenomena.
29.	Yuu Miino and Tetsushi Ueta : Five-segment PWL conductance in a Josephson junction, Proc. IEEE TJCAS 2017, Okayama, Aug. 2017.
30.	Hiroki Tanioka, Takafumi Bando, Kenji Matsuura, Kenji Ohira, Masahiko Sano and Tetsushi Ueta : Improving Document Availability in Storage, --- Where're our important documents for daily business operations? ---, The 9th International Conference on E-Service and Knowledge Management (ESKM 2017), 997-1000, Hamamatsu, Jul. 2017. (Summary) This paper provides a case study of improving availability for searching documents in an academic facility. Every day some documents are needed for our business and academic activities in the Center for Administration of Information Tech- nology (AIT) in Tokushima University. AIT has been employing and operating Information Security Management System (ISMS) since 2014. ISMS requires to maintain Confidentiality, Integrity and Availability. Particularly, AIT places importance on Avail- ability. However, time-consuming is a problem to find documents in the daily operation. A case study was conducted to put a full-text search engine in the facility, considering the objective and efficiency about finding documents in the file-server. In the process, it was found out that document freshness is important to academic office workers for their job. Then, the effectiveness of a score of TF-IDF with document freshness was assessed. Therefore, availability for finding documents was significantly improved using a full-text search engine with document freshness. (Keyword) Document management / information retrieval / Elasticsearch (Link to Publication Site) ● Publication site (DOI): 10.1109/IIAI-AAI.2017.139 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85040546313 (DOI: 10.1109/IIAI-AAI.2017.139, Elsevier: Scopus)
31.	Michitomo Morii, Hiroki Tanioka, Kenji Ohira, Masahiko Sano, Kenji Matsuura, Yosuke Seki and Tetsushi Ueta : Research on Integrated Authentication Using Passwordless Authentication Method, COMPSAC Workshops 2017 Student Research Symposium, 682-685, Torino, Jul. 2017. (Summary) Currently, authentication methods using ID and password are widely used and fulfilled central roles in various information systems and services. Our university also uses ID and password for authentication of most services. However, passwords have various problems such as reuse, phishing and leakage. This research is a practical experiment in order to implement an integrated authentication system without password. Shibboleth is introduced to our university, providing capabilities of web single sign-on and attribute exchange framework for organizational services. The Fast IDentity Online (FIDO) is adopted into Shibboleth as an external authentication, to realize passwordless authentication. Furthermore, we held a feasibility test of an integrated authentication system without password, and considered problems of the passwordless authentication method using FIDO. (Keyword) Authentication / Passwordless / Shibboleth / FIDO (Link to Publication Site) ● Publication site (DOI): 10.1109/COMPSAC.2017.198 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85031916565 (DOI: 10.1109/COMPSAC.2017.198, Elsevier: Scopus)
32.	Yuu Miino and Tetsushi Ueta : Synchronized bifurcation in a two-coupled Izhikevich neuron model, Proc. NOLTA 2016, 354-357, Yugawara, Nov. 2016. (Summary) In a coupled Izhikevich neuron model, there are some parameter regions where each neuron arises fir- ing at the same time. We observed discontinuous changes of stability of the solutions in these regions. In this study, we regard these changes as a bifurcation phenomena. We present their examples and condition of the bifurcation. Fi- nally we calculate sets of the bifurcation.
33.	Hiroyuki Fukue, Takuji Kousaka, Tetsushi Ueta, Hirokazu Ohtagaki and Hiroyuki Asahara : A Switching Ripple Reduction Technique for Current-Controlled 1-Dimensional DC/DC Boost Converter, Proc. NOLTA 2016, 149-151, Yugawara, Nov. 2016. (Summary) In this paper, we demonstrate a switch- ing ripple reduction technique for current-controlled one- dimensional DC/DC boost converter. First, we show the circuit model, and then we explain behavior of the wave- form. Next, we define the discrete map by sampling the inductor current at clock interval. Based on the discrete map, we derive a controlling gain. Finally, we try to re- duce switching ripple of inductor current, and confirm the effectiveness of our controlling method. (Keyword) firefly
34.	Ryo Takeno, Yosuke Seki, Masahiko Sano, Kenji Matsuura, Kenji Ohira and Tetsushi Ueta : A Route Navigation System for Reducing Risk of Traffic Accidents, Proceedings of IEEE 5th GCCE, 640-644, Kyoto, Oct. 2016. (Keyword) learning support / combination of primitive motions / feedback (Link to Publication Site) ● Publication site (DOI): 10.1109/GCCE.2016.7800543 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85010465159 (DOI: 10.1109/GCCE.2016.7800543, Elsevier: Scopus)
35.	Yuu Miino and Tetsushi Ueta : A difficulty from chattering in bifurcation analysis of the circuit with a Josephson junction including piecewise linear property, Proc. IEEE TJCAS 2016, Tainan, Aug. 2016.
36.	Tetsushi Ueta and Yuu Miino : Automatic threshold adjustment for limit cycles holding a specified stability in hybrid systems, Proc. NCSP2016, 672-673, Honolulu, Mar. 2016. (Summary) In this paper, we propose a method to compute the threshold value satisfying the given stability criterion. If this method is established, one can strengthen the limit cycle without changing any explicit parameter. In electronic circuit implementations, since such threshold value is usually realized by a reference voltage, thus no actual control energy is consumed regarding this adjustment. (Keyword) hybrid system / stability
37.	Kyosuke Miyamoto, Daisuke Ito, Hiroyuki Asahara, Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Circuit Experiments for Bifurcation of TimeWaveforms on Forced LED Fireflies, Proc. NOLTA 2015, 836-839, Hong Kong, Dec. 2015. (Summary) Creatures with rhythm phenomenon is shown mutual emphasis and combination, this is called synchronization phenomenon that is one of typical phenomenon in nonlinear systems. As the example of creatures causing synchronization phenomenon, there are group emissions of light of fireflies and chorus of crickets [1] [2] [3]. In this paper, we observe bifurcation phenomenon of periodic solutions on forced LED fireflies that constructed from an RC square wave generator with a periodic external force in order to simulate the synchronization of fireflies. On forced LED fireflies, characteristic periodic solutions called isolation periodic solution is observed at broad parameter regions. It can be considered these solutions causes synchronization phenomenon. Waveforms and periods of them are changed by border-collision bifurcations that are occurred by varying the frequency of an external force. Moreover, chaotic waveforms are observed at certain parameters. There can observe chaos waveform by a certain parameter. (Keyword) LED / fireflies
38.	Tomoyuki Sasada, Daisuke Ito, Tetsushi Ueta, Hirokazu Ohtagaki, Takuji Kousaka and Hiroyuki Asahara : Controlling Unstable Orbits via Varying Switching Time in a Simple Hybrid Dynamical Systems, Proc. NOLTA 2015, 475-478, Hong Kong, Dec. 2015. (Summary) In this paper, we discuss a controlling method of the switching time in the state- and perioddependent interrupted electric circuit. There are many state- and period-dependent interrupted electric circuits in the electrical engineering eld. Therefore, the controlling method reported in this paper is able to apply the practical circuits such as the dc/dc converters and dc/ac inverters. First, we explain the algorithm. Next, we show an example of the application by demonstrating the proposed algorithm to a simple state- and period-dependent interrupted electric circuit with one dimensional topology. Finally we discuss validity of the method. (Keyword) hybrid system
39.	Daisuke Ito, Munehisa Sekikawa, Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Bursting of transition dynamics on series coupled two operational amplifiers, Proc. NOLTA 2015, 181-184, Hong Kong, Dec. 2015. (Summary) Abstract\|An operation ampli er (op-amp) is used in various electrical circuits and one of the most famous electronic devices. In general applications, op-amps behave as differential amplifiers, but in parameter miss matching or miss connections, the op-amp occurs complex high frequency oscillations. We nd complex oscillation phenomena in the modi ed simple oscillator with the op-amp, and that these phenomena depend on the dynamics of circuits and throughrates of op-amps. (Keyword) firefly
40.	Yuu Miino and Tetsushi Ueta : Laboratory experiment for bifurcation phenomena of the forced Alpazur oscillator, Proc. NOLTA 2015, 169-172, Hong Kong, Dec. 2015. (Summary) This paper shows some results of laboratory experiment for bifurcation phenomena on the forced Al- pazur oscillator. The oscillator denotes some special phe- nomena in some parameter settings and are called chaos or bifurcation. The chaos is defined as the state of disorder and occurred by the bifurcation. Therefore the bifurcation should almost always be avoided to occur. Especially in these days, an idea to solve these problems on the forced Alpazur oscillator is proposed. However laboratory experi- ments for the idea have never been done. Laboratory exper- iments are important to confirm whether numerical analy- ses are correct or not. (Keyword) bifurcation / forced Alpazur oscillator / external force
41.	Yosuke Seki, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : Providing flexible authorization for shared group spaces by the attribute registration system, Proc. of the 17th Asia-Pacific Network Operations and Management Symposium, 256-261, Busan, Aug. 2015. (Link to Publication Site) ● Publication site (DOI): 10.1109/APNOMS.2015.7275436 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-84957534699 (DOI: 10.1109/APNOMS.2015.7275436, Elsevier: Scopus)
42.	Shota Mano, Daisuke Ito and Tetsushi Ueta : Circuit implementation of controlling chaos using pseudo periodic orbit, Proc. NCSP 2015, 405-408, Kuala Lumpur, Mar. 2015.
43.	Kenji Hishikawa, Daisuke Ito and Tetsushi Ueta : Bifurcations and Phase Differences of Nonlinear Coupled Dictyostelium System, Proc. NCSP 2015, 401-404, Kuala Lumpur, Mar. 2015.
44.	Daisuke Ito and Tetsushi Ueta : Stability control with a threshold value of the stepping motor, Proc. NCSP 2015, 397-400, Kuala Lumpur, Mar. 2015.
45.	Yu Miino, Daisuke Ito and Tetsushi Ueta : Bifurcation analysis for the forced Alpazur oscillator, Proc. NCSP 2015, 158-161, Kuala Lumpur, Mar. 2015.
46.	Kenji Matsuura, Yosuke Seki, Masahiko Sano and Tetsushi Ueta : Design and Implementation of Organizational Authorization for a Network Monitoring System, Proceedings of the Second International Symposium on Computing and Networking, 605-607, Shizuoka, Japan, Dec. 2014.
47.	Yuu Miino, Daisuke Ito and Tetsushi Ueta : Bifurcation analysis of coupled Izhikevich neuron model with an external periodic force, Proc. NOLTA2014, 807-810, Luzern, Sep. 2014. (Summary) The neuron model is an important when sim- ulating the behavior of the neurons. There are so many models developed (e.g., Fitz-Hugh-Nagumo, Integrated and Fire model, BVP, etc.) and there are also so many studies about these models[1] [5]. Especially, the model developed by Izhikevich[1] is focused recently because it can decrease numerical costs at simulation and express all patterns of burstings. In addition, the nonlinear phenom- ena, e.g. bifurcation phenomena or chaotic attractor, occur at this model since this is nonlinear non-autonomous sys- tem. In this paper, we focus on the nonlinear phenomena of coupled Izhikevich neuron model with external periodic force. (Keyword) bifurcation / Izhikevich neuron model / external force
48.	Shota Mano, Daisuke Ito and Tetsushi Ueta : Pseudo periodic orbits and their stabilization, Proc. NOLTA2014, 775-778, Luzern, Sep. 2014. (Summary) In a chaotic attractor, some orbits looking like unstable periodic orbit are recognized. We call them pseudo periodic orbits and they are not proper periodic orbits but, we consider that they pre- serve similar properties to unstable periodic orbits. In this paper, we propose the method stabilizing the pseudo periodic orbit by using the external force con- trol. Although, the pseudo periodic orbit is an approx- imative unstable periodic orbit but it is found easily without any analytic approaches. We demonstrate the chaos controlling by using the pseudo periodic orbit for the Duffing equation with hysteresis characteristics. (Keyword) Pseudo periodic solution / bifurcation / chaos
49.	Kenji Hishikawa, Daisuke Ito and Tetsushi Ueta : Bifurcation Analysis of Coupled Dictyostelium Oscillators, Proc. NOLTA2014, 419-422, Luzern, Sep. 2014. (Summary) In recent years, a new rhythm synchroniza- tion has been reported. The generalization of the function for receptors in the Dictyostelium by a nonlinear coupled oscillators realizes the synchronization. After that, this phenomena were investigated qualitatively by the averag- ing method. However, a relationship between synchroniza- tion modes and bifurcation phenomena has not been stud- ied. In this paper, we feature van der Pol equation into Nagano's model, and investigate bifurcation phenomena of the periodic solution and classify synchronization modes. We show bifurcation diagrams and some typical attractors. (Keyword) Dictyostelium discoideum / bifurcation / synchronization
50.	Daisuke Ito and Tetsushi Ueta : Border-collision bifurcations for the mathematical model of the TCP-RED, Proc. NOLTA2014, 779-782, Luzern, Sep. 2014. (Summary) The transmission control protocol with the random early detection (TCP/RED) is an important algo- rithm for the TCP congestion control [1]. It has been mod- eled as a simple second-order discrete-time model, and it performs unique and typical nonlinear phenomena, e.g., bifurcation phenomena, or a chaotic attractor [2, 3]. In this paper, we focus on the discrete-time model of the TCP/RED, and investigate bifurcation structures of it. (Keyword) TCP/IP / bifurcation
51.	Yu Miino, Daisuke Ito and Tetsushi Ueta : Bifurcation phenomena of forced Izhikevich neuron model, Proc. NCSP 2014, 413-416, Honolulu, Mar. 2014.
52.	Daisuke Ito, Tetsushi Ueta, Shigeki Tsuji and Kazuyuki Aihara : Attractor-Preserving Control to Avoid Saddle-Node Bifurcation, Proc. NOLTA 2013, 150-153, Santa Fe, Sep. 2013. (Link to Publication Site) ● Publication site (DOI): 10.15248/proc.2.150 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.15248/proc.2.150 (DOI: 10.15248/proc.2.150)
53.	Ken'ichi Fujimoto, Tomohiro Otsu, Tetsuya Yoshinaga, Tetsushi Ueta, Hiroyuki Kitajima and Kazuyuki Aihara : Controlling Method to Avoid Bifurcations of Periodic Points Using Maximum Lyapunov Exponent, Proc. of 2013 International Symposium on Nonlinear Theory and its Applications, 158-161, Santa Fe, Sep. 2013. (Link to Publication Site) ● Publication site (DOI): 10.15248/proc.2.158 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.15248/proc.2.158 (DOI: 10.15248/proc.2.158)
54.	Tetsushi Ueta, Daisuke Ito and Kazuyuki Aihara : Restoration control for disappeared periodic solutions, Proc. of 5th Int. Conf. Frontiers of Nonlinear Physics, 34-35, Nyzhny Novgrod, Jul. 2013.
55.	Jumpei Inaba, Yusuke Nishiuchi and Tetsushi Ueta : Numerical validation for blurred basin of symmetric equilibria in a 3D autonomous system, Proc. of 2013 RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing, 361-364, Kona, Mar. 2013.
56.	Daisuke Ito, Tetsushi Ueta and Kazuyuki Aihara : Bifurcation analysis of a chaotic map with a controller, Proc. of 2013 RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing, 57-60, Kona, Mar. 2013. (Summary) Chaos controlling techniques are intended to stabilize un- stable periodic orbits (UPOs). They are embedded into the chaotic attractor originally. Even as the system is attached the controller, there is possible that the system generate bi- furcation phenomena by the parameter perturbation. How- ever, Analysis of bifurcation phenomena on the system with controller are less discussed. In this paper, we consider the chaos controlling by using a pole assignment method for the logistic map, and investigate bifurcation phenomena on this system with controller. Additionally, by the bifurcation struc- ture, we indicate system and controller parameters with the robustness.
57.	Tomohiro Otsu, Ken'ichi Fujimoto, Daisuke Ito and Tetsushi Ueta : Evaluation and Comparison of Controlling Energy, Proc. of 2013 RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing, 673-676, Kona, Mar. 2013.
58.	Tomohiro Otsu, Ken'ichi Fujimoto, Daisuke Ito and Tetsushi Ueta : Evaluation and Comparison of Controlling Energy, Proceedings of The 2012 IEEE Workshop on Nonlinear Circuit Networks, 14-17, Tokushima, Dec. 2012. (Summary) OGY and delayed-feedback methods proposed at the beginning of 1990s are well known as the original methods of controlling chaos. One of the authors et al. also proposed a method of controlling chaos using Poincare map and linear control theory. All the methods can stabilize unstable periodic motions by making small perturbations of available system parameters. However, from the viewpoint of controlling energy needed to stabilize such motions, to evaluate the amount of required parameter perturbations has not been reported as far as the authors know. In this report, using three indices based on state variables, control input, and electric power (i.e. energy), we evaluated controlling costs to stabilize an unstable periodic motion observed in a continuous-time dynamical system such that the amount of parameter perturbations can be converted to electric power.
59.	Yusuke Tone, Hiroyuki Asahara, Tetsushi Ueta, Kazuyuki Aihara and Takuji Kousaka : A Method for the Computation of Border Collision Bifurcation Point in a Piecewise Linear System with Interrupted Characteristics, Proc. NOLTA 2012, Vol.1, 828-831, Palma, Spain, Oct. 2012. (Summary) This paper proposes a simple method for analyzing the border-collision bifurcation point in a piecewise linear interrupted system. First, we show the system dynamics, and then we derive the Poincare map. Next, we explain the method for calculating the border-collision bifurcation point based on the Poincare map approach. Finally, we apply the method to the current mode controlled buck-boost converter. The analysis result will show the validity of the method. (Link to Publication Site) ● Publication site (DOI): 10.15248/proc.1.828 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.15248/proc.1.828 (DOI: 10.15248/proc.1.828)
60.	Y Yamamoto, Hiroyuki Asahara, Daisuke Ito, Tetsushi Ueta, Kazuyuki Aihara and Takuji Kousaka : Experimental Control of Chaos via Switching Threshold in an Interrupted Electric Circuit, Proc. ITC-CSCC 2012, No.B-T2-05, Sapporo, Oct. 2012.
61.	Munehisa Sekikawa, Akinori Tsuji, Keiko Kimoto, Ikku Aihara, Daisuke Ito, Tetsushi Ueta, Kazuyuki Aihara and Hiroshi Kawakami : Optically coupled oscillators (OCOs) -- LED fireflies, Proceedings of the 2012 ACM Multimedia Conference, MM'12, 1485-1486, Nara, Oct. 2012.
62.	Daisuke Ito, Tetsushi Ueta, Jun'ichi Imura and Kazuyuki Aihara : Energy saving controlling chaos, Proc. ISCAS 2012, 405-408, Seoul, May 2012. (Summary) An energy saving control of unstable periodic orbits embedded in a hybrid chaotic system is proposed. The conventional controlling chaos methods utilize small perturbations of states or parameters as control input, however, quick time responses cannot be expected since the corresponding basins of attractions for higher periodic solutions become tiny. While If one allows a large perturbation to improve the time response, rather the total controlling energy which is proposed to the distance between the target orbit and the current orbit may increases. In this paper, when we consider the chaotic hybrid system, we noticed that we could utilize the perturbation of the referenced value for controlling, i.e., only a threshold value (Poincare mapping surface) is updated in control. No control input as a perturbation of the state or parameter value is applied to the system. In fact, the threshold value is used instantly when the feedback system determines the next updated threshold value. The variation of the threshold value can be obtained numerically by computing variational equations, and the control matrix is designed with the linear control theory. Since no affection to the state and parameters, it is emphasized that the total behavior of the controlled system is different from the conventional methods, especially it is unlike the impulsive control methods. We demonstrate this control method in a simple hybrid system and show that a large basin of attraction for the control is realized. (Keyword) controlling chaos / threshold control (Link to Publication Site) ● Publication site (DOI): 10.1109/ISCAS.2012.6272048 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1109/ISCAS.2012.6272048 (DOI: 10.1109/ISCAS.2012.6272048)
63.	Yoshinori Kitano, Tetsushi Ueta, Yoshifumi Nishio, Guoan Yang and Yang Yang : On Investigation of the Intensity Scaling Factor in Fractal Image Coding, Proc. NCSP 2012, 273-276, Honolulu, Mar. 2012.
64.	Daisuke Ito, Nakanishi Takaya, Akinori Tsuji, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation Phenomena of a Light Coupled Oscillator with a Clock Pulse Input, Proc. NCSP 2012, 675-679, Honolulu, Mar. 2012.
65.	Kazutoshi Kinoshita, Tetsushi Ueta, Hiroshi Kawakami, Jun'ichi Imura and Kazuyuki Aihara : Bifurcation phenomena of coupled piecewise affine system with hysteresis properties, Proc. NOLTA 2011, 407-410, Kobe, Sep. 2011.
66.	Takaya Nakanishi, Daisuke Ito, Tetsushi Ueta, Shigeki Tsuji, Jun'ichi Imura and Kazuyuki Aihara : Delayed feedback control for dynamic systems with jumping characteristics, Proc. NOLTA 2011, 615-618, Kobe, Sep. 2011.
67.	Daisuke Ito, Tetsushi Ueta, Jun'ichi Imura and Kazuyuki Aihara : Analysis and controlling of interrupt chaotic systems by a switching threshold, Proc. NOLTA 2011, 577-580, Kobe, Sep. 2011.
68.	Kazutoshi Kinoshita, Tetsushi Ueta, Hiroshi Kawakami, Jun'ichi Imura, Kazuyuki Aihara and Kazuyuki Aihara : Bifurcation phenomena of piecewise affine systems with hysteresis properties, Proc. ISIMM2011, 109, Tokyo, Mar. 2011.
69.	Takaya Nakanishi, Daisuke Ito, Tetsushi Ueta, Shigeki Tsuji, Jun'ichi Imura and Kazuyuki Aihara : Delayed feedback control for dynamical systems with jumping characteristics, Proc. ISIMM2011, 108, Tokyo, Mar. 2011.
70.	Daisuke Ito, Tetsushi Ueta, Jun'ichi Imura and Kazuyuki Aihara : Analysis and controlling of interrupt chaotic systems by a switching threshold, Proc. ISIMM2011, 107, Tokyo, Mar. 2011.
71.	Kenji Matsuura, Naka Gotoda, Tetsushi Ueta and Yoneo Yano : Bridging Multiple Motor-Skills in a Community Site, Knowledge-Based Intelligent Information and Engineering Systems, Vol.LNAI 6279, 145-152, Cardiff, UK, Sep. 2010. (Summary) This paper touches upon the design issue for multiple skill development of human beings in an online community environment. It focuses on motor skills such as rope-skipping, running, swimming and so forth in the physical world. The approach attempts to adopt social networking service for mutual contribution on that purpose as the base of online communication. In order to treat various sorts of skill, the web-based system allows community authors to handle several types of media for storing records of skill training of individuals and representing them in the system. This study developed such an environment and made trial use for the first stage.
72.	Tetsushi Ueta and Kei Nagao : Accurate Formulas Locating Unstable Periodic Points in Chaos, Proc. NOLTA2010, 111-114, Cracow, Sep. 2010. (Summary) We have studied fractal nature of patterns given by the directional coloring for chaotic attractors. With this method, unstable periodic points are visualized as concentrated points or crossing points in the state space. A fractal pattern around the specific unstable fixed point are identified as a formula derived from relationship among neighbor unstable periodic points. In this paper, we try to model an accurate formula giving locations of unstable periodic points. Higher periodic points are predicted by the obtained formula. Some numerical examples are shown.
73.	Kazutoshi Kinoshita and Tetsushi Ueta : Bifurcation Analysis of Coupled Nagumo-Sato Models, Proc. NOLTA2010, 488-491, Cracow, Sep. 2010. (Summary) The Nagumo-Sato model is one of mathe- matical neuron models described by a piecewise linear dif- ference equation. Since there is a conditional character which is discontinuous at the threshold value, the system can be classified as a hybrid dynamical system. Bifurca- tion phenomena are occurred by changing internal param- eters and chaotic attractors are also given. The dynamical properties were exactly studied analytically. In this paper, we investigate the bifurcations of diffusively-coupled Nagumo-Sato models. By using com- plementarity a shooting algorithm and brute-force method, complete bifurcation diagrams are obtained. In spite of the discontinuities inside the coupled system, our shoot- ing method can solve bifurcation problems. A period- locking regions edged by border-collision bifurcation sets are found, and chaotic regions are distinguished by a tan- gent bifurcation. We discuss on changing bifurcation struc- tures with parameter variations.
74.	Daisuke Ito and Tetsushi Ueta : Bifurcation Analysis of Two Coupled Izhikevich Oscillators, Proc. NOLTA2010, 627-630, Cracow, Sep. 2010. (Summary) A simple oscillator of spiking neurons is pro- posed by Izhikevich. By some numerical experiments, all firing patterns which have been observed in the brain are confirmed at the origin of the mathematical model. Al- though, a detailed bifurcation analysis has been given by the author, no investigation on its coupling system has been done. In this paper, we consider two Izhikevich neurons coupled by a gap junction. By choosing an appropriate Poincare section, we can compute bifurcation set for limit cycles. As a result, period-doubling bifurcation and its cas- cade to chaos is observed by changing the coupling coeffi- cient. We show bifurcation diagrams and numerical simu- lation results.
75.	Daisuke Ito and Tetsushi Ueta : Design of the Poincare Mapping of Piecewise Linear Systems, Proc. NCSP 2010, 125-128, Honolulu, Mar. 2010.
76.	Tetsushi Ueta and Yoshifumi Nishio : A Pilot Project toward Implementation of a Short-Term Exchange Program between an Affiliated University and The University of Tokushima, Proceedings of the Fourth International Symposium on the Development of the Global Double Degree Program (GDDP), 33-35, Tokushima, Dec. 2009.
77.	Kei Nagao and Tetsushi Ueta : A Structural Detection of Unstable Periodic Points in Chaotic Attractors by the Directional Coloring, Proc. NOLTA'09, 419-422, Sapporo, Oct. 2009. (Summary) We propose an application of the visualization method called directional coloring by using mapping direction of the difference equation. An invariant pattern can be detected for a given chaotic attractor with this coloring. Unstable periodic points(UPPs) are visualized as a crossing points of different colors and these locations are determined by the pattern. With this property and thanks to Newton's mehtod, we can compute UPPs systematically and accurately. We show numerical results and their fractal nature.
78.	Kazutoshi Kinoshita and Tetsushi Ueta : Bifurcation Analysis of the Lozi Map, --- as a Hybrid System ---, Proc. NOMA'09, 111-113, Urbino, Italy, Sep. 2009. (Summary) We analyze bifurcations observed in the Lozi system. Since the state space is not differentiable at x = 0, the system becomes non invertible, and the solution and corresponding variations are not expressed by elementary functions, although the system is described by a piecewise linear equation. The system is classified as one of hybrid systems because of this non-smoothness. In spite of this factor, the orbit and variations can be differentiable at any moment except for x = 0, 1st and 2nd variations are obtained numerically, thus, in this paper, we compute bifurcations of the Lozi map by using a shooting method. We also report a special degenerated stable attractors keeping the Lyapunov stability criterion.
79.	Tetsushi Ueta : Synchronization of Coupled BVP Oscillators, No proceedings, Hong Kong, May 2009. (Keyword) bifurcation
80.	Satoshi Nishioka and Tetsushi Ueta : Bifurcation Analysis of Chaos Synchronization in Coupled BVP Oscillators, Proc. NOLTA'08, 529-532, Budapest, Sep. 2008. (Summary) In this paper, we investigate three chaotic BVP oscillators which are resistively coupled as a ring. Since all parameters of oscillators are identical, attractors appeared in the system have a strong symmetrical properties observed in the individual oscillator. We found completely in-phase synchronization for periodic solutions and chaos. Also 3-phase synchronized tori and self-switching synchronized chaos. We show some bifurcation diagrams to explain the parameter regions exhibiting these attractors.
81.	Akihisa Tamura and Tetsushi Ueta : Bifurcation analysis of Izhikevich model, Proc. NOLTA'08, 529-532, Budapest, Sep. 2008. (Summary) A simple model of spiking neurons is proposed by Izhikevich. As some experimental results, origin of the mathematical model, firing pattern of all known types of neurons a re reported. However bifurcation analysis has not been investigated in details. In this paper, in order to discuss dynamical properties of this model, we compute bifurcation sets by using bifurcation theory. We clarify non-oscillatory, oscillatory and chaotic regions in the parameter plane.
82.	Quentin Brandon, Tetsushi Ueta, Takuji Kousaka and Daniele Fournier-Prunaret : Numerical Bifurcation Analysis of Systems with Variable Switching Conditions, Proc. NOLTA'08, 160-163, Budapest, Sep. 2008. (Summary) In this paper, we consider a method of numerical bifurcation analysis of nonlinear switched autonomous systems. Its development is motivated by several factors: linear systems can be studied through analytical approaches; smooth and non-autonomous systems can be studied using a standard periodical Poincar´e map. Our goal is to develop a method as general as possible and implement it as a computer-based tool. The main evolution we will describe this time is the possible treatment of variable switching conditions.
83.	Tetsushi Ueta, Quentin Brandon, Akihisa Tamura and Takuji Kousaka : Bifurcation and chaos in switched autonomous systems, Proc. NDES'08, 25-28, Nizhny Novgorod, Jul. 2008. (Summary) In the fields of circuits and systems, there are many discontinuous situations in their characteristics or operations. Rather we affirmatively utilize these property to obtain quick responses or apply various signal processing. Switching, impulsive trains, break points, bending points, borders, hystereses, threshold values, and cut-in voltages are example factors making the systems discontinuous. Especially analysis on a nonlinear circuit with these discontinuity becomes a very difficult problem. In addition, continuous characteristics for derivatives of the state and parameters are required for the general way of analysis for nonlinear systems, thus even the case using a periodic rectangular wave source cannot be treated directly. Bifurcation problems in circuits with above characteristics are discussed within very limited categories1;2. Piecewise linear systems have been intensively investigated for two decades because solutions the systems and their derivatives are obtained exactly, for instance, various converters, Chua's circuit3, hysteresis circuits and so on. Only a numerical computation of the return time or the period is required for bifurcation analysis. Approximation of the piecewise linear characteristics by smooth functions is often tried, especially for the Chua's circuit. While, discontinuous characteristics are also observed in physical systems, e.g., impulsive behavior in neuronal and biological activities. The problem is loosing continuity of the state, or its variations. In general, smooth functions are naturally assumed in analyzing process, in fact, without this assumption, it is unable to obtain derivatives of the state and its variations needed for Jacobian matrix in the shooting method. Above approximation is avoidance of this difficulty. Even if the given system equation and the state are continuous, computation of information about dynamical behavior requires continuity of their derivatives. Assume that we have now a piecewise autonomous nonlinear system. The system equation may be given in nonlinear ordinary differential equations with some conditional statements. Then the following equation is held piecewisely, such as dx/dt = fk(x), k = 0, 1, 2, . . .m, x(0) = x0. We have developed a general framework of bifurcation analysis for dynamical systems including discontinuous characteristics4. For piecewise nonlinear autonomous systems, more careful treatment is needed. Indeed the characteristic equation directly induced from the Jacobian matrix of the composite Poincar´e map does not contains correct multipliers of the limit cycle.
84.	Tetsushi Ueta and Hiroshi Kawakami : Visualization of unstable periodic points embedded in chaotic attractors by the directional coloring, Proc. NOMA'07, 25-28, Toulouse, Dec. 2007. (Summary) We propose a new visualization method called directional coloring for chaotic attractors in two-dimensional discrete systems. The argument defined by the current point of the solution orbit and its n-th mapped point is assigned into the hue circle in the HSV color system. For a given system, the vector field of the n-th powered system is visualized by this method. As singular points, n-periodic points are emerged as concentrating points of colors. We also reduce the computation time by featuring the brute-force method for the directional coloring, and illustrate a detection method of unstable periodic points in a chaotic attractor as an application.
85.	Quentin Brandon, Tetsushi Ueta and Daniele Fournier-Prunaret : Method of Bifurcation Analysis of Hybrid Nonlinear Systems, Proc. NOMA'07, 59-62, Toulouse, Dec. 2007. (Summary) Systems showing continuous and discrete dimensions, in other words hybrid systems, are present in many domains such as mechanical (apparition of frictions) or electronic systems (switching component). The solution function usually remains continuous but presents points of non-derivability where discrete changes occur. Some of the most widely studied applications are usually related to electrical engineering, such as power converters investigated as piecewise smooth systems by di Bernardo [1], Tse [2] or Banerjee [3][4]; or some PLL models as introduced By Acco [5], refering to this type of model as ``hybrid sequential.'' Little work has been done in the bifurcation analysis of nonlinear hybrid models, apart from Kawakami, Ueta and Kousaka [7][8]. As for hybrid linear models, they can be analysed using rigorous analytical methods, so exact solutions are obtained and used for analyses of the total dynamical behavior, as did Kabe [6]. But the nonlinear characteristics of many systems make this option possible only for approximations. Instead, we prefer using numerical methods. We propose using a Poincar´e map in order to obtain a discrete linearized approximation and conduct the bifurcation analysis using conventional methods. We consider the analysis results of the Alpazur oscillator, which reveals an unsual bifurcation structure: the interactions between the equilibrium point at some state and the corresponding switching condition make appear a fractal bifurcation structure, with an infinite number of bifurcation curves focusing towards a limit set.
86.	Akihisa Tamura and Tetsushi Ueta : Bifurcation analysis for a simple chaotic circuit and its coupled systems, Proc. NOLTA'07, 529-532, Vancouver, Sep. 2007. (Summary) Tamasevicius et. al proposed a very simple chaotic oscillator. Some experimental results, origin of the mathematical model, and numerical simulations are reported. However, bifurcation analysis has not been investigated in details. In this paper, we compute bifurcation sets of this model by using bifurcation theory and discuss its dynamical properties. The bifurcation structures are identified in various parameter planes. Moreover we investigate chaos synchronization in its coupled system. Synchronization of periodic and chaotic states are depicted in the bifurcation diagram, and it is clarified that the period-doubling bifurcation is deeply related to desynchronization.
87.	Fatima Guezar El, Hassane Bouzahir, Tetsushi Ueta and Pascal Acco : Chaos in a Switched Dynamical System: Scicos as a Modeler and Simulator, Proc. NOLTA'07, 164-167, Vancouver, Sep. 2007. (Summary) In this paper, we explore some modeling capabilities of Scicos. Our aim is to generate chaos from a simple hybrid dynamical system. We give the chaotic dynamics of the current-programmed boost converter in open-loop circuit as a case study. By considering two bifurcation parameters the current reference and the voltage input, we observe that the obtained Scicos simulations show that the boost converter is prone to subharmonic behavior and chaos. We also present the corresponding bifurcation diagrams. We use Scicos because it provides a much clearer understanding of the way the model will behave during simulation reducing considerably the risk of ambiguity.
88.	Quentin Brandon, Tetsushi Ueta, Takuji Kousaka and Daniele Fournier-Prunaret : Local Bifurcations of Nonlinear Hybrid Systems, Proc. NOLTA'07, 160-163, Vancouver, Sep. 2007. (Summary) As most analysis tools for nonlinear dynamical systems are dedicated to either continuous or discrete models, we propose an analysismethod for hybrid systems. Using the Poincar´e map, we transform the results of partial analysis over the continuous components into a discrete mapping. We can then apply more conventionalmethods in order to seek for critical values and obtain bifurcation diagrams in the parameters space. In this paper, we describe this method, discuss different approaches to conduct such analysis, and finally present an application example with a 3-state Alpazur oscillator.
89.	Masaaki Mizumoto, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation Analysis of Duffing-Rayleigh Equation, Proc. NDES2007, 90-93, Tokushima, Jul. 2007. (Summary) This paper deals with the bifurcation of the periodic solution and the generation of chaotic states of the solution for Duffing-Rayleigh equation. We calculate bifurcation diagram under both of increasing and decreasing time and calculate stable and unstable manifolds. From these analysis, we explain the generation of crisis.
90.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation Structure of Capacitive Coupled BVP, Proc. NDES2007, 90-93, Tokushima, Jul. 2007. (Summary) We have investigated a variety of coupled two oscillators. In previous reports, we explained many bifurcation structures of coupling types when two BVP oscillators are connected by linear resistor. In this report we investigate a bifurcation structure, when two BVP oscillators are connected by capacitor. Additionally, each current Port of oscillators is connected. This system becomes five-dimensional autonomous system unlike other coupling. We illustrate attractors and bifurcation phenomena of this system, and we compare bifurcation structures of coupled oscillators.
91.	Hassane Bouzahir, El Fatima Guezar and Tetsushi Ueta : On Scicos simulation of a hybrid dynamical system, Proc. NDES2007, 62-65, Tokushima, Jul. 2007. (Summary) This paper reports on a numerical study of an example of piecewise linear systems that constitute a class of hybrid systems. Precisely, we study the dynamics of the current-programmed boost converter circuit in an open-loop. Our modeling techniques are based on the new French native modeler and simulator for hybrid systems called Scicos (Scilab Connected Object Simulator) which is a Scilab (Scientific Laboratory) package. Scicos provides a much clearer understanding of the way the model will behave during simulation reducing considerably the risk of ambiguity. Taking into account the hybrid nature of the circuit is also a new approach in this paper.
92.	Quentin Brandon, Toshiyuki Kumano and Tetsushi Ueta : Method of repellers detection by applied computation over basin of attraction, Proc. NDES2007, 241-244, Tokushima, Jul. 2007. (Summary) This paper proposes a new visualization method for chaotic attractors and detection of repellers in the basin of attraction of discrete nonlinear dynamical systems. Conventionally it is expressed by plotting the solution orbit into a plane as a set of dots. In the case of color figures, a pixel is usually colored based on the location of the orbit, hitting statistics, and so on. In some other approaches, a pixel is colored by n-time map direction. This method is called directional coloring. However, it requires much time to calculate both the solution and the n-time map direction. We use an argument defined by a current orbit and an n-time mapped point is used for coloring in initial plane. This method can decrease the computation time, and can render a direction map where all solutions within the range arbitrarily specified. This method can visualize repeller as well as directional coloring. The position of repellers can be detected by automatically setting up the candidate point based on visualized repellers.
93.	Tetsushi Ueta, Takuji Kousaka and Shigeki Tsuji : Occasional Delayed Feedback Control for Switched Autonomous Systems, Proc. of ISCAS2007, 2474-2477, New Orleans, May 2007. (Summary) We propose the occasional delayed feedback control for chaotic circuits with interrupt characteristics. The control input generated by the difference between the current state and the delayed state is added to the system occasionally, i.e., during a certain interval defined by the switching policy. This control is reasonable for chaotic systems including some switches since they are not always feasible to admit the control input, e.g., a fixed control input terminal may be separated according to the switching action. We apply the control method to a chaotic switched circuit and demonstarate availability by some numerical experiments.
94.	Yasuo Miyoshi, Takahiro Oie, Hiroshi Kawakami, Tetsushi Ueta and Yoneo Yano : e-Syllabus System Supporting the Discovery of Learning Paths, Proceedings of E-Learn 2006, 784-789, Honolulu, Oct. 2006. (Summary) We have developed an e-Syllabus system that represents graphically and dynamically the relationships between lectures. This development represents one of the improvements of infrastructure for education and learning. In order to construct the e-Syllabus, three new columns have been added to each lecture of the syllabus: keywords, preceding lectures and relational lectures. XML is used as a storage format; it allows us to represent the structured data within on a text file that can be stored on a CD-ROM. Thus, without accessing the web, it is possible to represent graphically and discover the relations between the lectures. This representation of the syllabus supports the students in the discovery of learning-paths and the definition of learning plan. Thus, the e-Syllabus system improves the convenience of using the syllabus.
95.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Dependence of Synchronous Activities in Coupled Inhibitory Neurons upon Excitability Classes, Proc. of NOLTA2006, Bologna, Italy, Sep. 2006.
96.	YUE MA, Soumitro Banerjee, Takuji Kousaka and Tetsushi Ueta : Classification and Analytical Method of Switched Dynamical Systems, Proc. of NOLTA2006, Bologna, Italy, Sep. 2006.
97.	Kazuya Kusaka, Takao Hanabusa, Satoshi Kiriyama, Tetsushi Ueta, Akio Tsuneda and Takuo Nagamachi : Mutual evaluation of presentation skills between two distant universities by giga-bit network, Abstract of 6th Asian-Pacific Conference on PBL, 79, Tokyo, May 2006.
98.	Yu Toyosaki, Tetsushi Ueta and Takuji Kousaka : Switch Synchronizing Delayed Feedback Control for Piecewise Linear Systems, Proc. of ISCAS2006, 3702-3705, Island of Kos, Greece, May 2006.
99.	Toshiyuki Kumano, Tetsushi Ueta and Hiroshi Kawakami : Pattern Emergence in Strange Attractor by Directions of Mappings, Proc. of ISCAS2006, 2737-2740, Island of Kos, Greece, May 2006. (Summary) This paper proposes a new visualization method to given chaotic attractors in discrete nonlinear dynamical systems. Conventionally it is expressed by plotting the solution orbit into a plane as a set of dots. In the case of color figures, a pixel is colored by the location of the orbit, histogram of hitting, and so on. We use an argument defined by a current orbit and an n-time mapped point is utilized for coloring. This can depict orientation or tendency of the orbit within the chaotic attractor. In this visualization process, an remarkable pattern emergence phenomenon is observed. We illustrate these color figures and discuss similarity to basins of attraction.
100.	Kimiyasu Shiotsu, Tetsuya Kobayashi, Tetsushi Ueta, Shigeki Tsuji, Kazuyuki Aihara and Hiroshi Kawakami : Bifurcations of periodic solutions in the forced genetic toggle switch system, Proc. of NCSP2006, 251-254, Honolulu, Mar. 2006.
101.	Hirokazu Komatsu, Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcational classification for type-I and II activities in a forced planar H-R model, Proc. of NCSP2006, 325-328, Honolulu, Mar. 2006.
102.	Hiroki Yoshii, Tetsushi Ueta and Hiroshi Kawakami : Visualization and stereolithography system of bifurcation sets, Proc. of NCSP2006, 361-364, Honolulu, Mar. 2006.
103.	Yu Toyosaki, Tetsushi Ueta and Takuji Kousaka : Switch synchronizing occasional delayed feedback control for piecewise linear systems, Proc. of NCSP2006, 203-206, Honolulu, Mar. 2006.
104.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation phenomena of capacitive coupled BVP oscillators, Proc. of NCSP2006, 243-246, Honolulu, Mar. 2006.
105.	Toshiyuki Kumano, Masaaki Mizumoto, Yusuke Nishiuchi, Kunichika Tsumoto, Shigeki Tsuji, Tetsushi Ueta, Tetsuya Yoshinaga, Hiroshi Kawakami and Kazuyuki Aihara : Development of an ODE solver orienting a bifurcation analysis package, Proc. of NCSP'06, 297-300, Honolulu, Mar. 2006.
106.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcations in Class 1 neuron models interconnected by inhibitory and electrical synapses, Proc. of NOLTA'05, Vol.1, 317-320, Bruges, Oct. 2005.
107.	Yoshihiro Imakura, Tetsushi Ueta and Tetsuya Yoshinaga : Bifurcations of a Dynamical System Defined by PMART, Proc. of NOLTA'05, Vol.1, 38-51, Bruges, Oct. 2005.
108.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcations in Modified BVP Neurons Connected by Inhibitory and Electrical Coupling, Proc. ISCAS2005, 6058-6061, Kobe, May 2005.
109.	Yu Toyosaki, Takuji Kousaka, Tetsushi Ueta and Sang-Ho Hyon : Partial Delayed Feedback Control for Autonomous System, Proc. of NCSP2005, 483-486, Honolulu, Mar. 2005.
110.	Yusuke Nishiuchi, Shigeki Tsuji, Tetsushi Ueta and Hiroshi Kawakami : On Synchronization in Cross Coupled BVP Oscillators, Proc. NCSP2005, 109-112, Honolulu, Mar. 2005.
111.	Hiroki Yoshii, Tetsushi Ueta and Hiroshi Kawakami : A New Scheme for Construction of 3D Bifurcation Diagrams, Proc. of NCSP2005, 65-68, Honolulu, Mar. 2005.
112.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Spatio-Temporal Complex Behavior in Inhibitory Modified BVP Neurons Connected by Gap-Junction, Proc. NCSP2005, 29-32, Honolulu, Mar. 2005.
113.	Tetsushi Ueta, Takuji Kousaka, Tohru Kawabe and Sang-Ho Hyon : Partial External Force Control for Piecewise Smooth Dynamical Systems, Proc. of 2004 IASTED CSS, Clearwater, Florida, Nov. 2004.
114.	Sang-Ho Hyon, Takashi Emura and Tetsushi Ueta : Detection and stabilization of hybrid periodic orbits of passive running robots, Proc. Mechatronics and Robotics, 1309-1314, Archen, Germany, Sep. 2004.
115.	Sang-Ho Hyon, X Jiang, Takashi Emura and Tetsushi Ueta : Passive running of planar 1/2/4-legged robots, Proc. IEEE/RS IROS, 3532-3539, Sendai, Sep. 2004. (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-14044268217 (Elsevier: Scopus)
116.	Tetsushi Ueta, Yu Toyosaki, Shigeki Tsuji and Takuji Kousaka : Partial delayed feedback control and its DSP implementation, Prod. MWSCAS'04, 629-632, Hiroshima, Jul. 2004.
117.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcations in current coupled BVP oscillators, Proc. NDES2004, 348-351, Evora, Portugal, May 2004.
118.	Tetsushi Ueta and Hiroshi Kawakami : An aspect of oscillatory conditions in linear systems and Hopf bifurcations in nonlinear systems, Proc. NDES2004, 352-355, Evora, Portugal, May 2004.
119.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcations in Modified BVP Neurons Coupled by Gap-Junctions, Proc. of NCSP'04, 495-498, Honolulu, Mar. 2004.
120.	Atsushi Tsuda, Shigeki Tsuji, Tetsushi Ueta and Hiroshi Kawakami : On Basin Boundary of Composite Dynamical System with Pole Assignment, Proc. of NCSP'04, 363-366, Honolulu, Mar. 2004.
121.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : A Blurred Boundary and its Manifolds in the Extended BVP oscillator, Proc. of NCSP'04, 515-518, Honolulu, Mar. 2004.
122.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : On a stable torus in a three dimensional autonomous system, Proc. of ECCTD'03, Vol.1, 82-85, Cracow, Sep. 2003.
123.	Tetsushi Ueta and Hiroshi Kawakami : Chaos in cross-coupled BVP oscillator, Proc. ISCAS2003, Vol.3, 68-72, Bangkok, May 2003.
124.	Atsushi Tsuda, Yusuke Nishiuchi, Akinori Tsuji and Tetsushi Ueta : Applications of nonlinear signal processing by DSP, Proc. of NOLTA'02, Vol.2, 1009-1012, Xi'an, Oct. 2002.
125.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : On basin boundary of the extended BVP oscillator, Proc. of NOLTA'02, Vol.1, 311-314, Xi'an, Oct. 2002.
126.	Shigeki Tsuji, Tetsushi Ueta, Tetsuya Yoshinaga, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcations in gap-junctionally coupled BVP neurons driven by periodic external force, Proc. of NOLTA'02, Vol.1, 307-310, Xi'an, Oct. 2002.
127.	Tohru Kawabe, Tetsushi Ueta and Yoshifumi Nishio : Comparison between Chaotic Noise and Iterative Simulated Annealing for Combinatorial Optimization Problems, Proceedings of International Symposium on Nonlinear Theory and its Applications (NOLTA'02), Vol.1, 447-450, Xi'an, Oct. 2002.
128.	Yoko Uwate, Yoshifumi Nishio, Tetsushi Ueta, Tohru Kawabe and Tohru Ikeguchi : Performance of Chaos Noise Injected to Hopfield NN for Quadratic Assignment Problems, Proceedings of International Symposium on Nonlinear Theory and its Applications (NOLTA'02), Vol.1, 267-270, Xi'an, Oct. 2002. (Summary) 本論文では，二次割り当て問題を解く Hopfield Neural Network にカオスノイズを注入した際の性能についての調査を行っている．特に，カオスのパラメータを変化させることにより，どのようなカオスノイズが有効であるかについて論じている．また，その性能を評価するために，最適解に近い解をいかに多く見つけるかを判断することができる評価方法を提案している．
129.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation behavior in a nonlinear circuit with a state-period dependent switch, Proc. NDES2002, 3-1-3-4, Izmir, Turkey, Jun. 2002.
130.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation and chaos in the extended BVP oscillator, Proc. NDES2002, 3-5-3-8, Izmir, Turkey, Jun. 2002.
131.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : An advanced design method of bursting in FitzHugh-Nagumo model, Proc. ISCAS2002, Vol.1, 389-392, Phoenix, AZ, May 2002.
132.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation and chaos in asymmetrically coupled BVP oscillators, Proc. ISCAS2002, Vol.2, 544-547, Phoenix, AZ, May 2002.
133.	Yoko Uwate, Yoshifumi Nishio, Tetsushi Ueta, Tohru Kawabe and Tohru Ikeguchi : Solving Ability of Hopfield Neural Network with Chaotic Noise and Burst Noise for Quadratic Assignment Problem, Proceedings of IEEE International Symposium on Circuits and Systems (ISCAS'02), Vol.3, 465-468, Phoenix-Scottsdale, U.S.A., May 2002. (Summary) 本論文では，二次割り当て問題を解く Hopfield Neural Network にカオスノイズとバーストノイズを注入した際の性能についての調査を行っている．コンピュータシミュレーションの結果，インターミッテンシー·カオスのラミナー部とバースト部の存在をモデリングしたギルバートモデルによって得られるバーストノイズが 3周期窓付近のインターミッテンシー·カオスと同様のよい性能であることが確認されている． (Link to Publication Site) ● Publication site (DOI): 10.1109/ISCAS.2002.1010261 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-0036287607 (DOI: 10.1109/ISCAS.2002.1010261, Elsevier: Scopus)
134.	Tohru Kawabe, Tetsushi Ueta and Yoshifumi Nishio : Iterative Simulated Annealing for Hopfield Neural Network, Proceedings of IASTED International Conference on Modelling and Simulation, 59-62, Marina del Rey, U.S.A., May 2002.
135.	Shouichi Tahara, Takuji Kousaka, Tetsushi Ueta, Minoru Abe and Hiroshi Kawakami : Experimental Control of Chaotic Behavior in State-Dependent Nonlinear Circuit, Proc. of NOLTA2001, Zaou, Miyagi, Japan, Oct. 2001.
136.	Takahiro Oie, Youji Ochi, Tetsushi Ueta, Yoneo Yano and Hiroshi Kawakami : A Database Orienting Information Disclosure on Campus Network, Proceedings of 2nd International Conference on Information Technology Based Higher Education and Training, Kumamoto, Jul. 2001.
137.	Tetsushi Ueta, Takuji Kousaka and Hiroshi Kawakami : Strange attractor in resistively coupled BVP oscillators, Proc. of Progress on Nonlinear Science, Nizhny Novgorod, Jun. 2001.
138.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Controlling chaos in a state-dependent nonlinear circuit, Proc. of First Asia-Pacific Workshop on Chaos Control and Synchronization, 26-27, Shanghai, Jun. 2001.
139.	Hiroshi Kawakami, Tetsuya Yoshinaga and Tetsushi Ueta : Counting and classifying synchronized patterns in symmetrical network, Proc. of First Asia-Pacific Workshop on Chaos Control and Synchronization, 3, Shanghai, Jun. 2001.
140.	Tetsushi Ueta, Shigeki Tsuji, Tetsuya Yoshinaga and Hiroshi Kawakami : Calculation of the isocline for the fixed point with a specified argument of complex multipliers, Proc. ISCAS2001, Vol.III, 281-284, Sydney, May 2001.
141.	Takuji Kousaka, M Matsumoto, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation Analysis in Hybrid Nonlinear Dynamical Systems, Proc. ISCAS2001, Vol.III, 281-284, Sydney, May 2001.
142.	Tetsushi Ueta, Ei'ichiro Okahisa, Tohru Kawabe and Yoshifumi Nishio : Construction of Effective Noise for TSP, Proceedings of IEEE International Conference on Industrial Electronics, Control and Instrumentation (IECON'00), 2135-2140, Nagoya, Oct. 2000. (Link to Publication Site) ● Publication site (DOI): 10.1109/IECON.2000.972606 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-84969188071 (DOI: 10.1109/IECON.2000.972606, Elsevier: Scopus)
143.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcation of Burst response in Forced Wilson-Cowan Neuron Model, Proc. NOLTA'00, Vol.1, 285-288, Dresden, Germany, Sep. 2000.
144.	Tetsushi Ueta, Guanrong Chen and Zhi-Hong Guan : mpulsive Control of a Chaotic Pendulum, Proc. NOLTA'00, Vol.1, 225-228, Dresden, Germany, Sep. 2000.
145.	Tetsushi Ueta and Guranrong Chen : Bifurcation and chaos of Chen's equation, Proc. ISCAS00, Vol.5, 505-508, Geneva, May 2000.
146.	Tetsushi Ueta, Guranrong Chen, Hiroshi Kawakami and Tetsuya Yoshinaga : Bifurcation and Bursting Response in Coupled Neural Oscillators, Proc. ISCAS00, Vol.3, 475-478, Geneva, May 2000. (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-0033714204 (Elsevier: Scopus)
147.	Takuji Kousaka, Takashi Kido, Tetsushi Ueta, Hiroshi Kawakami and Minoru Abe : Analysis of Border-Collision Bifurcation in a Simple Circuit, Proc. ISCAS00, Vol.2, 481-484, Geneva, May 2000.
148.	Takuji Kousaka, Shouichi Tahara, Tetsushi Ueta, Hiroshi Kawakami and Minoru Abe : Controlling Chaos of Nonlinear Hybrid System with a State-Period Depended Switch, AFSS 2000, Vol.1, 363-368, Tsukuba, Japan, May 2000.
149.	Katsuya Shimoji, Tohru Kawabe, Tetsushi Ueta and Yoshifumi Nishio : Solving Abilities of Hopfield Neural Network with Chaotic Noise versus with Simulated Annealing for Traveling Salesman Problem, Proceedings of Asian Fuzzy Systems Symposium (AFSS'00), Vol.2, 909-913, Tsukuba, May 2000.
150.	Shuji Baba, Naoki Urushihara, Yoshifumi Nishio, Tohru Kawabe and Tetsushi Ueta : Solving Ability of the Hopfield NN with Burst Noise, Proceedings of Asian Fuzzy Systems Symposium (AFSS'00), Vol.2, 914-917, Tsukuba, May 2000.
151.	Takashi Kido, Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Efficient Construction of 3D Bifurcation Diagrams for Nonlinear Dynamical Systems, Proc. NOLTA'99, Vol.1, 93-96, Hawaii, USA, Dec. 1999.
152.	Eiji Izumida, Tetsushi Ueta and Hiroshi Kawakami : Efficient Construction of 3D Bifurcation Diagrams for Nonlinear Dynamical Systems, Proc. NOLTA'99, Vol.1, 257-260, Hawaii, USA, Dec. 1999.
153.	Toshikazu Masaki, Tetsushi Ueta and Kenji Terada : Fingerprint Identification using Fractal Coding, Proceddings of the Nonlinear Theory and Its Applications(NOLTA'99), Vol.1, 143-146, Hawaii, Dec. 1999. (Summary) In this paper, we propose a novel method of identification of fingerprint by using fractal coding. Automatic identification of person is one of important techniques for information and security systems. Such features bases on persons physiological or behavioral characteristics are called biometrics. Fingerprint is the most suitable information as a biometric; everyone has own immutable coding technique is applied to data compression of images. We pay attentions to the basic concept of this coding method - self-similar property in a fingerprint. We develop an identification system using the compressed data of fingerprint image. We can do identifying process for compensation image by using fractal coding, and it is abstract for feature value by compressed data. Practical experiments of fingerprint extracted feature finding from compressed data are performed and experimental results are presented. (Keyword) image processing / computer vision / human sensing / バイオメトリクス / pattern recognition
154.	Akira Takeuchi, Tetsushi Ueta and Kenji Terada : An Improvement of Image Segmentation by using Fractal Coding, Proceedings of the Nonlinear Theory and Its Applications(NOLTA'99), Vol.1, 347-350, Hawaii, USA, Dec. 1999. (Summary) This paper presents improvements for conventional image segmentation algorithm by using fractal coding. The compressed data with fractal coding is a set of parameters of affine mapping. This algorithm utilizes this compressed data to split an original image into some segments which have different feature. Image segmentation can be achieved by calculation for basins of attractions in the dynamical system computing the inverse affine mapping. The higher quality segmentation image can be obtained by adding a small perturbation to inverse affine mappings. This note describes the proposed method and shows some segmentat8oin results by using this algorithm. (Keyword) image processing / computer vision / フラクタル / 符号化
155.	Tetsushi Ueta, Guanrong Chen and Tohru Kawabe : An Approach to Calculation and Control of Unstable Periodic Orbits in Chaotic Piecewise Linear Systems, Proc. NOLTA'99, Vol.1, 9-12, Hawaii, USA, Dec. 1999.
156.	Katsuya Shimoji, Tohru Kawabe, Tetsushi Ueta and Yoshifumi Nishio : On the Properties of Hopfield Neural Networks with Chaotic Noise for Traveling Salesman Problem, Proceedings of International Symposium on Nonlinear Theory and its Applications (NOLTA'99), Vol.1, 9-12, Hawaii, USA, Nov. 1999.
157.	Shuji Baba, Yoshifumi Nishio, Tohru Kawabe and Tetsushi Ueta : Hopfield Neural Network with Various Burst Noise for TSP, Proceedings of International Symposium on Nonlinear Theory and its Applications (NOLTA'99), Vol.1, 13-16, Waikoloa, U.S.A., Nov. 1999.
158.	Ei'ichiro Okahisa, Hiroyuki Kitajima, Tetsushi Ueta and Hiroshi Kawakami : Spatiotemporal Chaotic Motion in Lower Dimensional Coupled Maps, Proc. KES'99, Vol.1, 867-870, Aderade, Australia, Aug. 1999.
159.	Tetsushi Ueta, Guanrong Chen, Tetsuya Yoshinaga and Hiroshi Kawakami : A Numerical Algorithm for Computing Neimark-Sacker Bifurcation Parameters, Proc. ISCAS'99, Vol.5, 503-506, Orlando, FL, USA, May 1999. (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-0032673064 (Elsevier: Scopus)
160.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation of a Nonlinear Circuit with a State-Dependent Switch, Proc. NOLTA'98, Vol.1, 867-870, Crans-Montana, Switzerland, Sep. 1998.
161.	Tetsushi Ueta, Takuji Kousaka and Hiroshi Kawakami : Bifurcation of Switched Nonlinear Dynamical Systems, Proc. of ISCAS'98, Vol.3, 465-468, Monterey, CA, USA, May 1998.
162.	Tetsushi Ueta, Yoshifumi Nishio and Tohru Kawabe : Comparison between Chaotic Noise and Burst Noise on Solving Ability of Hopfield Neural Networks, Proceedings of International Symposium on Nonlinear Theory and its Applications (NOLTA'97), Vol.1, 409-412, Honolulu, Nov. 1997.
163.	Tetsushi Ueta, T Okubo and Hiroshi Kawakami : Nonlinear resonant circuit with phase-controlled periodic signal, Proc. NOLTA'97, 487-490, Hawaill, USA, Nov. 1997.
164.	Ken'ichi Fujimoto, Takuji Kousaka, Hiroyuki Kitajima, Tetsushi Ueta and Hiroshi Kawakami : BVP oscillator with periodically switched RC circuit, Proc. of 1997 International Symposium on Nonlinear Theory and its Applications, 479-482, Hawaii, USA, Nov. 1997.
165.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Controlling chaos in nonlinear dynamical systems with non-smooth characteristics, Proc. NOLTA'97, 471-474, Hawaii, USA, Nov. 1997.
166.	Makoto Shiota, Tetsushi Ueta and Hiroshi Kawakami : Computation of three-dimensional bifurcation diagrams for dynamical systems, Proc. NOLTA'97, 69-72, Hawaill, USA, Nov. 1997.
167.	Tetsushi Ueta and Hiroshi Kawakami : Chaos synchronizing control in the invariant subspaces, Proc. COC'97, 69-72, St. Petersbrug, Russia, Aug. 1997.
168.	Tetsushi Ueta, Hiroshi Kawakami, Tetsuya Yoshinaga and Yuuji Katsuta : A computation of bifurcation parameter values for limit cycles, Proc. of ISCAS'97, Vol.2, 801-804, Hong Kong, Jun. 1997. (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-0030700186 (Elsevier: Scopus)
169.	Masafumi Tsueike, Tetsushi Ueta and Hiroshi Kawakami : Bifurcations of Coupled Neural Oscillators, Proc. of NOLTA'96, 365-368, Kochi, Oct. 1996.
170.	Takuji Kousaka, Hiroshi Kawakami and Tetsushi Ueta : Synchronization of Electric Fireflies of Square Wave Generators, Proc. of NOLTA'96, 321-324, Kochi, Oct. 1996.
171.	Tetsushi Ueta and Hiroshi Kawakami : A Control to Enlarge the Region of Frequency Entrainment in a Nonautonomous System, Proc. of NOLTA'96, 73-74, Kochi, Oct. 1996.
172.	Tetsushi Ueta and Hiroshi Kawakami : Unstable saddle-node connecting orbits in the averaged Duffing-Rayleigh equation, Proc. of ISCAS'96, Vol.3, 288-291, Atlanta, May 1996.
173.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Destabilizing control of stable orbits, Proc. NOLTA'95, Vol.2, 997-1000, Las Vegas, Nov. 1995.
174.	Masafumi Tsueike, Tetsushi Ueta and Hiroshi Kawakami : Basin of attractions in controlled chaotic system, Proc. NOLTA'95, Vol.2, 985-988, Las Vegas, Nov. 1995.
175.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation phenomena in the Josephson junction circuit coupled by a resistor, Proc. NOLTA'95, Vol.1, 343-346, Las Vegas, Nov. 1995. (Summary) Bifurcation phenomena observed in a circuit containing two Josephson junctions coupled by a resistor are investigated. This circuit model has a mechanical analogue: Two damped pendula linked by a clutch exchanging kinetic energy of each pendulum. In this paper, firstly we study equilibria of the system. Bifurcations and topological properties of the equilibria are clarified. Secondly we analyze periodic solutions in the system by using suitable Poincare mapping and obtain a bifurcation diagram. There are two types of limit cycles distinguished by whether the motion is in S^1 x R^3 or T^2 x R^2, since at most two cyclic coordinates are included in the state space. There is a typical structure of tangent bifurcation for 2-periodic solutions with a cusp point. We found chaotic orbits via the period-doubling cascade, and a long-period stepwise orbit.
176.	Hiroshi Kawakami and Tetsushi Ueta : Stabilization and Destbilization of Chaotic Systems, Proceedings of ICIAM 95 in Zeitschrift fur Angewandte Mathematik und Mechanik, 210-213, Hamburg, Jul. 1995.
177.	Yoshio Tanaka, Tetsushi Ueta and Hiroshi Kawakami : A robotic truck crane with vibration sensors, Proc. JFCM'04, 731-734, Takamatsu, Jun. 1994.
178.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation of an inductively coupled Josephson junction circuit, Proc. NOLTA'93, Vol.3, 1019-1022, Honolulu, Dec. 1993.

Proceeding of Domestic Conference:

1.	FUJIMOTO Shintaroh and Tetsushi Ueta : ハミルトン力学系を用いたカオス暗号, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, No.16-1, 215, Sep. 2023.
2.	Masato Saitoh, Seiya Amoh and Tetsushi Ueta : 電磁誘導Hindmarsh-Rose モデルの分岐, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, No.1-4, 43, Sep. 2023.
3.	Ryuto Ishigaki and Tetsushi Ueta : Basin boundary 構造変化の3 次元視覚化, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, No.1-3, 42, Sep. 2023.
4.	Hironori Takeuchi, ONO Kentaro, Kenji Matsuura and Tetsushi Ueta : Study of designing a tactical learning system by mathematical modeling, 教育システム情報学会2023年全国大会講演論文集, 225-226, Aug. 2023. (Keyword) フィールドスポーツ / 戦術学習 / 学習支援
5.	MICHIRU Katayama and Tetsushi Ueta : 間欠性カオスのラミナーを微小制御量で安定化させる, NOLTAソサイエティ大会, No.NLS-21, Jun. 2023.
6.	ZHANG QUANKAI and Tetsushi Ueta : 生物スイッチの数理モデルにおける分岐現象解析, NOLTAソサイエティ大会, No.NLS-4, Jun. 2023.
7.	Seiya Amoh and Tetsushi Ueta : マルチバイブレータにおけるカナール爆発現象とその実回路応答, NOLTAソサイエティ大会, No.NLS-31, Jun. 2023.
8.	Tetsushi Ueta : Locating and Controlling Chaotic Saddles, IEICE English Webinar, Mar. 2023.
9.	Ono Kentaro and Tetsushi Ueta : 強制Wilson-Cowanニューロン対の分岐現象, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, 26, Sep. 2022.
10.	Tetsushi Ueta : 連鎖律のPython実装について, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, 8, Sep. 2022.
11.	MICHIRU Katayama, Seiya Amoh and Tetsushi Ueta : シナプス結合 FitzHugh-Nagumo モデルにおける周期解の分岐, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, 2, Sep. 2022.
12.	Masaki Yoshikawa, seiya Amoh and Tetsushi Ueta : Pythonを用いた分岐解析ツールの開発, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, 1, Sep. 2022.
13.	Tetsushi Ueta : 学生に育てられたカオス研究者の半生, NOLTAソサイエティ大会, Jun. 2022.
14.	Seiya Amoh, Tetsushi Ueta and Hiroshi Kawakami : マルチバイブレータとカナール, NOLTAソサイエティ大会, No.NLS-019, Jun. 2022.
15.	Tetsushi Ueta : Locate Theoretically and Stabilize Firmly, Saddles in a Chaotic Set, IRCN Salon, Univ. of Tokyo, Mar. 2022.
16.	Takahiko Kojo, Masahiko Sano, Kenji Matsuura, Hiroki Tanioka and Tetsushi Ueta : Classification of Research Fields, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, 210, Sep. 2021. (Summary) 科学研究費助成事業(以下，科研)のデータベース(KAKEN)[2]を基に研究組織の研究を分類し，科研と所属組織の各研究分野への注力度合いとその推移を可視化する場合において，分類基準が変更になった際の時系列的に連続した分類とする分類手法の提案と実装
17.	Tetsushi Ueta : ダイオードを含む回路の逆時間ダイナミクス, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, 16, Sep. 2021.
18.	Rikiya Yamaguchi, Yuu Miino, Daisuke Ito and Tetsushi Ueta : 定トルクを加えた減衰単振り子の大域的分岐, Shikoku-Section Joint Convention Record of the Institutes of Electrical and Related Engineers, 13, Sep. 2021.
19.	Seiya Amoh, Tetsushi Ueta and Hiroshi Kawakami : マルチバイブレータのカナール発生機序, Proc. SJCIEE 2021, 12, Sep. 2021.
20.	Miho Ogura and Tetsushi Ueta : Swish関数を用いた離散系ニューラルネットワークの分岐解析, Proc. SJCIEE 2021, 11, Sep. 2021.
21.	Hiroki Tanioka, Takafumi Bando, Kenji Matsuura, Tetsushi Ueta, Masahiko Sano and Kensuke Inai : Electronic Application System for Security Export Control Procedures, 国立大学法人情報系センター協議会 (NIPC), Sep. 2021. (Keyword) Security Export Control / Electronic Application / Online / Digital Transformation Promotion
22.	Rina Yano, Hiroki Tanioka, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : Development of an online test aiming quantitatively measurement of computational thinking, The 45th Annual Conference of JSiSE, 43-44, Sep. 2020. (Summary) 2020 年度より小学校ではプログラミング教育が必修化されたが，学習者の能力の成長を定量的に測定する手法は確立されていない．本研究ではプログラミング教育によって養われるとされるプログラミング的思考には計算論的思考が含まれると考え，計算論的思考力を客観的・定量的に測定するためのテストを開発してきたが，小学校教育の現状を鑑みて遠隔授業等にも導入できるようオンライン形式で公開した．本稿では，事前調査として大学生 38 名を対象に行ったテスト結果について報告する． (Keyword) Programming Education / ICT / Learning Analytics
23.	Shunya Izumi and Tetsushi Ueta : テント写像を用いた秘密分散法の研究, Proceedings of the 2020 IEICE General Conference, Mar. 2020.
24.	小林崇弘, Masahiko Sano, Kenji Matsuura, Hiroki Tanioka, Kenji Ohira and Tetsushi Ueta : 希望研究室選択時の研究内容調査支援システム, 第82回全国大会講演論文集, No.4ZF-03, Mar. 2020.
25.	Yuu Miino and Tetsushi Ueta : Unstable Periodic Points in the Tent Map Based on Symbolic Dynamics, Proc. 2019 IEEE Workshop on Nonlinear Circuit Networks, 23-25, Dec. 2019.
26.	Hiroki Tanioka, Rina Yano, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : A Workshop Based Programming Educational Practice, --- Welcome to CoderDojo Tokushima ---, The 44th Annual Conference of JSiSE, 195-196, Sep. 2019. (Summary) CoderDojo Tokushima は 2017 年 12 月から継続的に開催されている.CoderDojo は小学生~高校生がプログラミングを学習する場としてアイルランドで生まれ，110 ヶ国，国内は 169 ヶ所で開催されている.参加者から参加費を徴収しないことを除いて，内容については主催者に委ねられているため，我々は，参加者の自主的な学習や情報交換の促進を重視し，ワークショップ形式を用いている.毎回のアンケートの統計情報からその効果と課題について述べる. (Keyword) workshop / Programming Education / CoderDojo / Questionnaire Analysis
27.	Yu Miino and Tetsushi Ueta : A computation method to calculate the stable manifold of a ship dynamical system, NOLTAソサイエティ大会, No.NLS-12, Jun. 2019.
28.	Seiya Amo, Daisuke Ito, 美井野優 and Tetsushi Ueta : Isingマシンにおけるポンプレート分散調節による最適解探索, NOLTAソサイエティ大会, No.NLS-31, Jun. 2019.
29.	Shunya Izumi, 美井野優 and Tetsushi Ueta : カオスを用いた秘密分散法の研究, NOLTAソサイエティ大会, No.NLS-44, Jun. 2019.
30.	平松孝雄, Masahiko Sano, Kenji Matsuura, Hiroki Tanioka, Kenji Ohira and Tetsushi Ueta : ゼミ議事録と研究成果物の蓄積と利用の支援システムの開発, 第81回全国大会講演論文集, No.5ZH-05, Mar. 2019.
31.	小林崇弘, Masahiko Sano, Kenji Matsuura, Hiroki Tanioka, Kenji Ohira and Tetsushi Ueta : 研究室選択時の意思決定支援システム, 第81回全国大会講演論文集, No.5ZH-09, Mar. 2019. (Summary) 多くの大学では研究室調査を学生が各自で行い，学生が行きたいと思う研究室を選択する．本研究室ではWebサービスを用いて入力されたキーワードに関する論文を本学が保有する研究者情報DBより取得し，利用者に提示することによる研究室の配属の支援を行っている．しかし，先行研究では幾つかの課題があり，その一つに日本語キーワードから英語論文が検索できない問題点があった．本研究では単語翻訳機能を用いて関連する英語論文を提示する機能を追加する．また，先行研究の有用性の追跡調査を行い評価する
32.	Nishimura Yuki, Masahiko Sano, Kenji Matsuura, Hiroki Tanioka, Kenji Ohira and Tetsushi Ueta : A Management Method of Research Results Metadata, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 232, Sep. 2018. (Summary) 研究活動における論文や実験データなどの研究成果物を蓄積と再利用を支援するため，CMSの一つであるMaharaを機能拡張することを目的とする．研究成果物情報をRDF化してDBに集積することにより，研究情報成果物に対するメタ情報の効率的な利活用の管理を支援する．
33.	Hiramatsu Takao, Masahiko Sano, Kenji Matsuura, Kenji Ohira, Hiroki Tanioka and Tetsushi Ueta : A Management System for Reusing Meeting and Research Results, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 233, Sep. 2018. (Summary) 大学研究室での学生のゼミ活動でにおいて，その議論内容の時間経過による忘失を防止するため，テキストや映像・音声データなどによりゼミ議事録として記録される．本研究では，ゼミ議事録と研究成果物の参照や再利用を活性化し研究活動の効率化を支援するため，ゼミ議事録にメタデータを付与することで機械的に整理して管理し，メタデータを利用した情報検索を行うシステムの開発を目的とする．
34.	野村悠佑, 美井野優 and Tetsushi Ueta : 2次元自律系におけるリミットサイクルの一設計方法, 2018電気関係学会四国支部連合大会論文集, 9, Sep. 2018.
35.	Miino Yuu, Tetsushi Ueta, Hiroshi Kawakami, Atsuo Maki and Naoya Umeda : Local stability and bifurcation phenomena in the softening Duffing equation, NOLTAソサイエティ大会, No.NLS-25, Jun. 2018.
36.	Hiroki Tanioka, Kenji Matsuura, Tetsushi Ueta and Fumiaki Kawano : BYOD環境によるワークショップ型実習の試みとその課題, 大学教育カンファレンス in 徳島, Jan. 2018. (Summary) 2017年度前期に，徳島大学歯学部1年生を対象とした実習ベースの授業科目「医療情報処理」全16回の講義の11回分の講義と実習及び成績評価までを担当し，いくつかの知見が得られたので，その結果と課題について報告する．本講義は，受講者全員(歯学科40名，口腔衛生学科15名)が個人PCを持ち込むワークショップ形式1) の講義であったため，BYOD環境を全学展開する上での試金石となったので，これもあわせて報告する． (Keyword) BYOD / workshop
37.	Ryo Takeno, Masahiko Sano, Kenji Matsuura, Hiroki Tanioka, Kenji Ohira, Yosuke Seki and Tetsushi Ueta : Visualization of Research Field in Research Unit, AXIES2017, Dec. 2017. (Summary) 研究組織において，自組織及び学界での研究の動向を把握しておくことは重要である．本研究では，科学研究費助成事業による分野分類を用いて研究組織の研究分野を推定し，各分野における注力度合いを可視化する．
38.	Shin Maruyama, Kenji Ohira, Masahiko Sano, Hiroki Tanioka, Kenji Matsuura and Tetsushi Ueta : Management solution of PC classroom to balance unification of desktops and terminal's speed, IPSJ SIG Technical Report, Vol.2017-IOT-39, No.14, 1-6, Sep. 2017.
39.	Tetsushi Ueta and Takafumi Bando : Raspberry Pi によるディジタルサイネージの構築と運用, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 241, Sep. 2017.
40.	Yuu Miino and Tetsushi Ueta : Josephson 接合素子特性の 5 区分線形化, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 24, Sep. 2017.
41.	西村友基, Masahiko Sano, Kenji Matsuura, Hiroki Tanioka, Kenji Ohira, Yosuke Seki and Tetsushi Ueta : A metadata management method of arifacts in Mahara, Forum on Information Technology, 349-351, Sep. 2017. (Summary) 大学における研究活動では，論文や発表スライド，実験データなどの研究成果物が生成・収集される．収集データを利活用する際には，成果物内の情報あるいは成果物に付与されるメタ情報を検索に用いる．本研究では，付与されたメタ情報同士の関係性を解析し，利用者に提示することにより，研究活動の効率化を目的とする．本論文では，eポートフォリオであるMaharaを対象としてメタ情報管理のための手法を提案する．メタ情報はメタ情報記述のための枠組みであるRDFに基づき表現することで，意味に基づいた検索や，他の公開されているメタ情報との連携を可能とする．
42.	Miino Yuu, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation phenomena and homoclinic states of a simple piecewise linear dynamical system, NOLTAソサイエティ大会, No.NLS-18, Jun. 2017.
43.	Tomohiro Takeda, Kenji Ohira, Hiroki Tanioka, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : A Rogue Access Point Detection Method with Estimation and Trace of Internet Reachability Check Packets, 情報処理学会全国大会講演論文集, 3-161-3-162, Mar. 2017.
44.	Izumi Nishina, Kenji Ohira, Hiroki Tanioka, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : A Security Warning System Associating Detected Actions with their Risks to Motivate Users to Take Countermeasures, 情報処理学会全国大会講演論文集, 3-601-3-602, Mar. 2017.
45.	Hirokazu Nakano, Kenji Ohira, Hiroki Tanioka, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : A method of two-factor authentication with a student ID card and a password to WLAN client authentication, 情報処理学会全国大会講演論文集, 3-573-3-574, Mar. 2017.
46.	Kensuke Nakagiri, Yuu Miino and Tetsushi Ueta : Newton法を用いたポアンカレ写像点の算出, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 3, Sep. 2016.
47.	Yuu Miino and Tetsushi Ueta : Synchronized bifurcation in the two-coupled Izhikevich neuron model with an external force, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 11, Sep. 2016.
48.	Miino Yuu and Tetsushi Ueta : Synchronization of firing in coupled Izhikevich neuron model, NOLTAソサイエティ大会, No.NLS-13, Jun. 2016.
49.	Takuya Nomura, Masahiko Sano, Kenji Matsuura, Yosuke Seki and Tetsushi Ueta : Relationship analysis support system between the data in Mahara, Proceedings of the 2016 IEICE General Conference, 112, Mar. 2016. (Summary) 本研究ではMaharaを用いて収集したデータにメタ情報を付与し，データ間の関係性解析支援システムを提案した．研究室や研究機関といったグループの枠にとらわれることなく論文やその他のデータ間の関係性を可視化し，研究情報の共有を行う．論文間の関係性を可視化するために論文を4つの型に分類しグラフ化を行う．SPARQLを用い論文を検索し，論文作成過程で使用・生成された関連データの提示を行う．
50.	Ryo Takeno, Yosuke Seki, Masahiko Sano, Kenji Matsuura, Kenji Ohira and Tetsushi Ueta : Route navigation system reflecting traffic accident probability and transportation of the user, Proceedings of the 2016 IEICE General Conference, 144, Mar. 2016. (Summary) 交通事故の発生には，安全不確認や道路の形状，周囲の環境等による操作・判断ミスなど様々な要因がある．本研究では，様々な要因の中でも環境的要因により交通事故発生の危険性が高いと想定される地点を「危険地点」，各危険地点の危険度合いを「危険度」と定義し，危険地点の危険度を把握し注意，回避させることでより安全な移動の実現を目的とする．そして，日常生活下における移動者の危険地点回避を支援の対象とし，登録された危険地点に関する情報から移動者の移動手段等を考慮した，より安全な移動経路を提案するシステムを構築する．
51.	宮本恭介, Tetsushi Ueta and Hiroshi Kawakami : 2 つのコンパレータを用いたRC 方形波発振回路, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 300, Sep. 2015.
52.	Yuu Miino and Tetsushi Ueta : Bifurcation Analysis for Duffing Equation with Non- smooth Hysteresis Characteristics, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 200, Sep. 2015.
53.	竹野凌, Yosuke Seki, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : Route navigation system reflecting traffic accident probability a nd present situation of the user, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 295, Sep. 2015. (Summary) 交通事故の原因には，本人の操作ミスや道路の形状，周囲の環境など様々な要因がある．本研究では，環境的要因により事故発生の危険性が高いと想定される地点を「危険地点」，各地点の危険度合いを「危険度」と定義し，危険地点と危険度を把握し注意，回避させることでより安全な移動の実現を目的とする．危険地点を把握した移動に関する先行研究として，地震災害時に利用者からの提供情報を元に，危険度の高い地点を回避する安全な移動経路を案内する研究[1]が報告されているが，適用場面が地震災害時に限られている．また，個々の危険地点が移動者自身に直接関係するかは考慮されていない．本研究では，日常生活下での移動における危険地点回避を支援の対象とし，登録された交通事故に関する情報をもとに，移動者を考慮したより安全な移動経路を案内するシステムを提案する
54.	野村卓哉, Masahiko Sano, Kenji Matsuura, Tetsushi Ueta and Yosuke Seki : Maharaにおけるメタデータ構造解析支援システム, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 296, Sep. 2015. (Summary) 課題レポートや研究の実験データ，参考文献など多くの成果物や参考資料等が大学生活では生成，収集される．eポートフォリオシステムはこれらの情報を記録でき，学習・研究活動の振り返り，第三者への成果物の共有などを可能とする．収集データのメタデータ同士の関係性を構築し，その関係性の解析結果を利用者に提示することができれば，利用者の学習・研究活動の効率化や深化を期待できる．そこで本研究では，今回Maharaを対象とした，収集データ及びメタデータの構造解析を支援するシステムを提案する．
55.	Yosuke Seki, Kenji Matsuura, Tetsushi Ueta, Masahiko Sano and Yuichi Ogata : Demand Forecast of Computer Terminals by Time Series Data Analysis, 情報処理学会第77回全国大会講演論文集, 27-28, Mar. 2015.
56.	Akinori Tsuji, 藤岡慧明, Daisuke Ito, 木本圭子, 合原一究, 関川宗久, Tetsushi Ueta, Kazuyuki Aihara and Hiroshi Kawakami : LEDホタルによる自然ホタルの強制同期, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 12, Sep. 2014.
57.	Hiroaki Tatei, Tetsushi Ueta, Masahiko Sano and Kenji Matsuura : Student Support System using Working Logger on PC, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 342, Sep. 2014. (Summary) 大学生は，復習を授業単位取得において必要とされる等，復習は大学での勉学において重要である．大学生が作成するレポート課題についても，復習は有用である．例えば，ポートフォリオの作成や，別の新しいレポート作成のための参考文献として利用することや，自分自身の学校生活の記録や成果として参照することもできる．そのため復習を考慮しながらレポートに取組むことも多い．レポート作成をコンピュータ(PC)上で行う場合，大抵は複数のソフトウェアを用いて複数の情報源を参照しつつ作業を行う．非常に多くの情報に触れながらレポートを作成するため，復習の際に，有用な情報をレポートから読み取れないことも多く，質の良い復習を阻害し，学生の復習意欲を減退させている．本研究では，復習の質を向上させ，復習意欲を促進するシステムを提案する．
58.	Yoshihiro Nakayashiki, Tetsushi Ueta, Masahiko Sano and Kenji Matsuura : Event information sharing system utilizing personal schedule data, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 339, Sep. 2014. (Summary) 近年，学生の大学における活動において，講演会や演奏会，就職対策セミナーなど，不定期で開催されるイベント情報は，授業内のアナウンス，公式ウェブ，学内SNS，メールなどのメディアによって伝達される．イベント情報にはタイトル，概要，場所，時間といった，ユーザが参加の判断に必要な情報が含まれている．しかし，ユーザはこれらの情報を各種メディアを適切に使いこなし，能動的に見つけなければならない．そのため，開催場所を地図上で明示し，イベント情報を共有するシステム[1]が注目を浴びている．しかしながら，開催時間に至っては場所情報とは異なり直感的に把握できるようには設計されていない．また，ユーザがそのイベントに参加可能かどうかも考慮されていない．そこで本研究は，イベント情報を本システムに集約し，ユーザが物理的・合理的にそれらに参加できるよう，場所と時間情報を組み合わせた上で地図上に表示させ，イベント情報を容易に共有できるシステムを提案する．
59.	Yuichi Ogata, Tetsushi Ueta, Kenji Matsuura and Masahiko Sano : Demand Forecast of Computer Terminals by Time Series Analysis, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 330, Sep. 2014. (Summary) 大学等高等教育機関では，講義のために数多くのPC端末が存在する．講義時間外においては，それらを自由に利用させることもあり，レポート課題など様々な用途に使用できる．しかしながら，学生が講義時間外の空席状況を事前に知る方法が無い場合には，現在の利用状況[1]のみの情報では端末室の利用予定を自身のスケジュールに組む込むことが困難である．そこで，本研究では学生の利便性を向上させるため，端末室の利用状況を予報するシステムを提案する．
60.	Daisuke Ito, Shota Mano and Tetsushi Ueta : Stabilization of pseudo periodic orbits in chaotic dynamical systems, Proceedings of the 2014 IEICE General Conference, SS57-SS58, Mar. 2014.
61.	Tetsushi Ueta and Daisuke Ito : Obtaining Bifurcation Sets, Proceedings of the 2014 IEICE General Conference, SS35-SS38, Mar. 2014. (Summary) 非線形関数を含む常微分方程式や差分方程式によって記述される力学系では，発生する平衡点や周期解がパラメータの変動によって容易に分岐するであろう．物理的対象から，数理モデル(力学系) が一旦導かれれば，数値計算を用いて分岐集合(分岐図)が計算でき，その力学系の定性的性質を特徴付けることができよう．本稿では分岐パラメータ値の計算方法を紹介する．
62.	Yosuke Seki, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : 属性管理とセキュリティレベルの多重化について, 情報・システムソサイエティ特別企画学生ポスターセッション予稿集, 119, Mar. 2014.
63.	Daisuke Ito, Tomohiro Otsu, Ken'ichi Fujimoto, Tetsushi Ueta, Kazuyuki Aihara and Tetsuya Yoshinaga : Avoidance of Bifurcations of Stable Fixed Point Using the Maximum Lyapunov Exponent, Proceedings of 1st Multi Symposium on Control Systems, 742-745, Mar. 2014. (Summary) Topological properties of the limit set are characterized by the Lyapunov exponent of the orbit on the dynamical system. In discrete-time dynamical system is described by ordinary differential equations, authors translate avoidance of bifurcations controlling problem of a stable fixed point, periodic point into minimization problem that the evaluation function the maximum Lyapunov exponent. The authors had proposed the controller to avoid the unbeseeming bifurcation phenomena that is caused by the variation of system parameters by change in environment. We have reported results that it is applied to the period- doubling bifurcation of the periodic point on the H enon map. In this paper, avoidance of bifurcations method is applied to the Kawakami map. We confirm that the controller can avoid the tangent bifurcation and Neimark-Sacker bifurcation. (Keyword) Avoidance of bifurcation / Maximum Lyapunov exponent
64.	Tomohiro Otsu, Ken'ichi Fujimoto, Tetsushi Ueta, Kazuyuki Aihara and Tetsuya Yoshinaga : Avoidance of Bifurcations of Stable Fixed Point Using the Maximum Lyapunov Exponent, Proceedings of the 2014 IEICE General Conference, SS49-SS50, Mar. 2014. (Summary) 動的システムにみられる極限集合の位相的性質は解軌道のリアプノフ指数によって特徴づけられる．著者らは，常差分方程式で記述される離散時間力学系において，安定な固定点・周期点の分岐回避制御問題を最大リアプノフ指数を評価関数とした最小化問題に帰着させ，環境変動等に起因するシステムパラメータ変化によって発生しうる不適切な分岐を回避するための制御系を提案し，Henon写像にみられる安定固定点・周期点の周期倍分岐回避に適用した実験結果を報告している．本稿では，その分岐回避制御系を川上写像に適用し，安定固定点の接線分岐とNeimark-Sacker分岐が回避できることを例証する．
65.	Akinori Tsuji, Daisuke Ito, 木本圭子, 合原一究, 関川宗久, Tetsushi Ueta, Kazuyuki Aihara and Hiroshi Kawakami : LEDホタルによるゲンジボタルの発光同期パタンの解析, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 3, Sep. 2013.
66.	Tetsushi Ueta, Masahiko Sano and Kanae Yagi : JGN-Xを利用した緊急時情報発信機構の確保, 平成25年度電気関係学会四国支部連合大会講演論文集, 340, Sep. 2013.
67.	Kenji Hishikawa, Tetsushi Ueta, Yoshifumi Nishio, Akihiro Ushida and Shuichi Aono : モバイル端末における身体活動観測ツールの開発, 平成25年度電気関係学会四国支部連合大会講演論文集, 301, Sep. 2013.
68.	Shota Mano and Tetsushi Ueta : 方向彩色による周期点抽出支援ツールの開発, 平成25年度電気関係学会四国支部連合大会講演論文集, 9, Sep. 2013.
69.	Jumpei Inaba, Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : ある4次元発振器で見られるバースト発振について, 平成25年度電気関係学会四国支部連合大会講演論文集, 2, Sep. 2013.
70.	Masahiko Sano, Kanae Yagi and Tetsushi Ueta : 徳島大学情報化推進センター ISMS 活動事例, 第17回学術情報処理研究集会発表論文集, 17-20, Sep. 2013. (Summary) 徳島大学情報化推進センターは平成24年3月にISMS認証(ISO/IEC 27001:2005 JIS Q 27001:2006)を取得し，一年以上経過した．取得後一年の間には，対象範囲の変更審査や記載内容変更など2回も登録証の記載変更を行うなど，ISMS構築時には想定外の事項や問題点に直面した．本稿では，当センターのISMSの活動を，認証取得後1年目の状況について紹介し，2年目の取組みについて概要を述べる．
71.	Tetsushi Ueta, Kenji Matsuura, Masahiko Sano, Takeshi Matsumura and Yosuke Seki : 大学コミュニケーションポータルの運用と課題, 第17回学術情報処理研究集会発表論文集, 5-9, Sep. 2013. (Keyword) communication portal / SNS / cloud
72.	Daisuke Ito and Tetsushi Ueta : 結合南雲・佐藤モデルにおける分岐解析, 回路とシステムワークショップ論文集, 285-288, Aug. 2013.
73.	Takaya Nakanishi, Daisuke Ito and Tetsushi Ueta : 馬蹄形写像におけるカオス制御, 回路とシステムワークショップ論文集, 1-6, Aug. 2013.
74.	Daisuke Ito, Akinori Tsuji, 木本圭子, 合原一究, 関川宗久, Tetsushi Ueta, 合原一幸 and Hiroshi Kawakami : LEDホタルの引き込み現象:ホタルはエッジで同期する, LED総合フォーラム2013 in徳島論文集, 87-88, Apr. 2013.
75.	Daisuke Ito, Tetsushi Ueta, Junichi Imura and Kazuyuki Aihara : 接線分岐回避・補償制御のロバスト性, Proceedings of the 2013 IEICE General Conference, SS52-SS53, Mar. 2013. (Summary) 本研究では,接線分岐直後に存在する周期解の残骸を利用した分岐補償制御を提案する.具体的には,周期解の残骸の特徴を利用し,フィードバック制御を適用することで,接線分岐後も周期解を存続させることを試みる.一般に,接線分岐が発生すると,突然振幅の大きな周期解に遷移したり,カオスが発生するなど,実際の系においては事後に望ましくない振る舞いとなることがありえる,本手法を適用することで,これらリスクを回避もしくは低減できる可能性がある.
76.	Yosuke Seki, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : Designing Flexible Secure-Authorization based on Shibboleth, 情報処理学会第75回全国大会講演論文集, 577-578, Mar. 2013.
77.	Ken'ichi Fujimoto, Tetsuya Yoshinaga, Tetsushi Ueta, Hiroyuki Kitajima and Kazuyuki Aihara : Control to Avoid Bifurcations of Periodic Points Using Maximum Lyapunov Exponent, Proceedings of the 2013 IEICE General Conference, SS50-SS51, Mar. 2013. (Summary) 動的システムにみられる極限集合の位相的性質は解軌道のリアプノフ指数によって特徴づけられる．本稿では，安定な固定点・周期点の分岐回避制御問題を最大リアプノフ指数を評価関数とした最小化問題に帰着させ，環境変動等に起因するシステムパラメータ変化によって発生しうる不適切な分岐を回避するための制御系を提案する．
78.	Yoshinori Kitano, Tetsushi Ueta, Yoshifumi Nishio, Yang Guoan and Yang Yang : 二値画像に対するフラクタル符号化における輝度値変換パラメータの性質, 平成24年度電気関係学会四国地区連合大会講演論文集, 39, Sep. 2012.
79.	Jumpei Inaba, Yusuke Nishiuchi and Tetsushi Ueta : 3次元自律系の対称平衡点に関するベイスン崩壊の数値検証, 平成24年度電気関係学会四国支部連合大会講演論文集, 36, Sep. 2012.
80.	Tomohiro Out and Tetsushi Ueta : カオス力学系に対する最適制御, 平成24年度電気関係学会四国支部連合大会講演論文集, 13, Sep. 2012.
81.	Yoshinori Miyaji, Daisuke Ito and Tetsushi Ueta : モデル方程式を用いないカオス制御, 平成24年度電気関係学会四国支部連合大会講演論文集, 12, Sep. 2012.
82.	Masahiko Sano and Tetsushi Ueta : Our activities after the ISMS certificated, Journal for Academic Computing and Networking, Vol.16, 205-206, Sep. 2012. (Summary) 情報化推進センターは，平成24年3月に情報セキュリティマネジメントシステム(ISMS)を取得した．これは，我々が管理・運用する情報システムを，適切に運用するための活動及び体制を国際標準規格の下で確立するプロジェクトであった．ISMSを取得した時点では，その物理的な適用範囲は情報化推進センター棟に限定しており，本来含めるべき情報化推進センター蔵本分室を適用外としていた．今回，適用外としていた蔵本分室を適用範囲に含めるため，ISMSの変更審査を受審(変更審査は9月)するため活動を行ったので，その事例を紹介する． (Keyword) ISMS (Tokushima University Institutional Repository) ● Metadata: 115741 (Tokushima University Institutional Repository: 115741)
83.	Bolortsetseg Ganbat, Tetsushi Ueta, Kenji Matsuura, Masahiko Sano and Shinsuke Uno : The Design of a Dynamic Virtual Organization, 2012年電子情報通信学会通信ソサイエティ大会, 142, Sep. 2012.
84.	Shinsuke Uno, Kenji Matsuura, Masahiko Sano, Tetsushi Ueta and Bolortsetseg Ganbat : Discussion about authorization function based on Shibboleth, FIT2012講演論文集, No.4, 183-184, Sep. 2012.
85.	Tetsushi Ueta : ポストカオス制御に向けた取り組み, 回路とシステム(淡路島)ワークショップ論文集, 9-14, Jul. 2012.
86.	Akinori Tsuji, Daisuke Ito, 木本圭子, 関川宗久, 喜多順三, Tetsushi Ueta, 合原一幸 and Hiroshi Kawakami : LEDホタルの同期現象:自律的に動く光パタンの生成, LED総合フォーラム2012 in徳島論文集, 99-100, Apr. 2012.
87.	Yosuke Seki, Kenji Matsuura, Takeshi Matsumura, Tetsushi Ueta, Masahiko Sano and Yoneo Yano : ネットワーク監視システムのShibboleth化, 大学ICT推進協議会2011年度年次大会論文集, 255-256, Dec. 2011.
88.	Miyuki Sawamura and Tetsushi Ueta : Computation of periodic points embedded in horseshoe map, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-12, 12, Sep. 2011.
89.	Takaya Nakanishi and Tetsushi Ueta : Computation of periodic points embedded in horseshoe map, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-11, 11, Sep. 2011.
90.	Kazutoshi Kinoshita, Tetsushi Ueta, Hiroshi Kawakami, Jun'ichi Imura and Kazuyuki Aihara : Bifurcation Phenomena of a Piecewise Affine Map with Hysteresis Properties, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-10, 10, Sep. 2011.
91.	Daisuke Ito and Tetsushi Ueta : Controlling chaos by parallel parameter variations, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-9, 9, Sep. 2011.
92.	Jamsran Altanzul and Tetsushi Ueta : On 7th Power in Duffing Equation, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-8, 8, Sep. 2011.
93.	Yusuke Miyaji and Tetsushi Ueta : 線形予測を用いた遅れ時間カオス制御, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-7, 7, Sep. 2011.
94.	Shinsuke Uno, Kenji Matsuura, Tetsushi Ueta and Masahiko Sano : The Design of a Dynamic Virtual Organization, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 269, Sep. 2011.
95.	Takaya Nakanishi, Daisuke Ito, Tetsushi Ueta, 井村順一 and Kazuyuki Aihara : 断続系のためのdelayed feedback control の応用, 自動制御連合講演会講演論文集, 783-788, Oct. 2010.
96.	Miyuki Sawamura and Tetsushi Ueta : Effects of a nonlinear conductance in a Josephson Junction Circuit, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.18-22, Sep. 2010.
97.	Daisuke Ito, Tetsushi Ueta and Kazuyuki Aihara : Neimark-Sacker bifurcation in a 3D BVP Oscillator with a switch, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.18-21, Sep. 2010.
98.	Takaya Nakanishi, Daisuke Ito, Tetsushi Ueta and Kazuyuki Aihara : インパルス系への delayed feedback control の適用と問題, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.8-5, Sep. 2010.
99.	Kazutoshi Kinoshita, Tetsushi Ueta and Jun'ichi Imura : カオスを利用したランダムIFSによるフラクタル生成, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-3, 10, Sep. 2010.
100.	Daisuke Ito, Tetsushi Ueta, Jun'ichi Imura and Kazuyuki Aihara : Izhikevich ニューロンの Gap Junction結合系における分岐解析, 電気学会電子・情報・システム部門大会講演論文集, Sep. 2010.
101.	Kenji Matsuura, Toshihiro Hayashi, Kenji Kume, Tetsushi Ueta, Kazuhide Kanenishi and Yoneo Yano : Authenticatino and Authorization for Distributed LMS, 教育システム情報学会第35回全国大会講演論文集, 339-340, Aug. 2010.
102.	Kei Nagao and Tetsushi Ueta : Analysis of Invariant Pattern in a Non-Invertible Chaotic Map with Directional Coloring, 平成21年度電気関係学会四国支部連合大会講演論文集, No.18-23, 347, Sep. 2009.
103.	Satoshi Nishioka and Tetsushi Ueta : Controlling Chaos Synchronization in Coupled Nonlinear Oscillators, 平成21年度電気関係学会四国支部連合大会講演論文集, No.18-22, 346, Sep. 2009.
104.	永尾景 and Tetsushi Ueta : 方向彩色法による2次元非線形写像における不変パターンの視覚化と解析, 平成21年電気学会電子・情報・システム部門大会講演論文集, No.MC13-5, 947-950, Sep. 2009.
105.	西岡聡 and Tetsushi Ueta : FFTを用いた結合非線形発振器にみられる同期現象の判別, 平成21年電気学会電子・情報・システム部門大会講演論文集, No.TC4-4, 82-86, Sep. 2009.
106.	Kenji Matsuura, Kazuhide Kanenishi, Takahiro Oie, Tetsushi Ueta, Masahiro Nakagawa and Yoneo Yano : Designing authentication and authorization for federated systems, Proceedings of the 2009 IEICE General Conference, S-141-S-142, Mar. 2009. (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1573387452362391168 (CiNii: 1573387452362391168)
107.	Satoshi Nishioka and Tetsushi Ueta : Bifurcation analysis of Synchronization Phenomena in Coupled BVP Oscillators, 平成20年度電気関係学会四国支部連合大会講演論文集, No.17-12, 381, Sep. 2008.
108.	Kei Nagao and Tetsushi Ueta : Detection of the unstable periodic point in the chaos using direction coloring, 平成20年度電気関係学会四国支部連合大会講演論文集, No.17-16, 385, Sep. 2008.
109.	Quentin Brandon, Tetsushi Ueta, Takuji Kousaka and Fournier-Prunaret Daniele : Bifurcations of the Alpazur Oscillator with variable switching thresholds, 平成20年度電気関係学会四国支部連合大会講演論文集, No.17-17, 386, Sep. 2008.
110.	Quentin Brandon, Tetsushi Ueta and Takuji Kousaka : Local Bifurcations of 3-state Alpazur Oscillator, 平成19年度電気関係学会四国支部連合大会講演論文集, No.17-59, 389, Sep. 2007.
111.	Masaaki Mizumoto, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation Analysis of Duffing-Rayleigh Equation, 平成19年度電気関係学会四国支部連合大会講演論文集, No.17-58, 388, Sep. 2007.
112.	Satoshi Nishioka and Tetsushi Ueta : Homoclinic structure about the origin of a simple discrete system, 平成19年度電気関係学会四国支部連合大会講演論文集, No.17-57, 387, Sep. 2007.
113.	Akitoshi Tamura and Tetsushi Ueta : Chaos synchronization of coupled simple oscillators, 平成19年度電気関係学会四国支部連合大会講演論文集, No.17-52, 297, Sep. 2007.
114.	Akitoshi Tamura and Tetsushi Ueta : Bifurcation of the simple third-order automomous system, 平成18年度電気関係学会四国支部連合大会講演論文集, No.17-1, 297, Sep. 2006.
115.	Tetsushi Ueta, Takuji Kousaka and Shigeki Tsuji : 区分非線形系と部分遅延カオス制御について, 平成18年度電気関係学会四国支部連合大会講演論文集, No.1-11, 11, Sep. 2006.
116.	Masaaki Mizumoto, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation analysis of modified Duffing-van der Pol equation, 平成18年度電気関係学会四国支部連合大会講演論文集, No.17-3, 299, Sep. 2006.
117.	Toshiyuki Kumano, Tetsushi Ueta and Hiroshi Kawakami : A detection of repelles by applied computation for basin of attractions, 平成18年度電気関係学会四国支部連合大会講演論文集, No.17-2, 298, Sep. 2006.
118.	Masayasu Shiotsu, Tetsushi Ueta, Tetsuya Kobayashi, Shigeki Tsuji, Kazuyuki Aihara and Hiroshi Kawakami : On bistability of forced gene toggle switch, 平成18年度電気関係学会四国支部連合大会講演論文集, No.17-5, 301, Sep. 2006.
119.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : Bifurcation and Chaos in Simplification Circuit of `v`-`i` Coupled BVP Oscillators, 平成18年度電気関係学会四国支部連合大会講演論文集, No.17-4, 300, Sep. 2006.
120.	Yasuo Miyoshi, Takahiro Oie, Tetsushi Ueta, Masanori Hirotomo, Yoneo Yano and Hiroshi Kawakami : Support for Finding Learning Path by Relevant Lectures in e-Syllabus, JSiSE Research Report, Vol.20, No.4, 7-12, Nov. 2005. (Summary) 徳島大学では教育·研究者情報データベース (EDB) を利用してシラバスを作成してきた．現在，EDBに登録されたXML形式のシラバス情報を元に科目間の関連性をグラフ表示するLearning Path Finderの開発を行っている．これにより履修時の学習経路検索が支援されシラバスの使い勝手が向上する． (Keyword) Learning Path / Syllabus / XML / XML / Relational Database
121.	Kimiyasu Shiotsu, Tetsushi Ueta, Shigeki Tsuji, Kazuyuki Aihara and Hiroshi Kawakami : 遺伝子スイッチモデルの強制系に見られる周期解とその分岐現象, 平成17年度電気関係学会四国支部連合大会講演論文集, 4, Oct. 2005.
122.	Hirokazu Komatsu, Shigeki Tsuji, Tetsushi Ueta and Hiroshi Kawakami : 2次元ニューロンモデルの発火特性とその分類, 平成17年度電気関係学会四国支部連合大会講演論文集, 5, Oct. 2005.
123.	Toshiyuki Kumano, Tetsushi Ueta and Hiroshi Kawakami : カオスアトラクタ内の軌道履歴の視覚化, 平成17年度電気関係学会四国支部連合大会講演論文集, 12, Oct. 2005.
124.	Yu Toyosaki, Tetsushi Ueta and Takuji Kousaka : 区分的に滑らかな系に対するスイッチ同期型遅延制御法, 平成17年度電気関係学会四国支部連合大会講演論文集, 15, Oct. 2005.
125.	Yoshihiro Imakura, Tetsushi Ueta and Tetsuya Yoshinaga : PMART力学系の分岐, 平成17年度電気関係学会四国支部連合大会講演論文集, Oct. 2005.
126.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : 変形BVP発振器でみられる引力圏境消失について, 平成17年度電気関係学会四国支部連合大会講演論文集, 10, Oct. 2005.
127.	Hiroki Yoshii, Shigeki Tsuji, Tetsushi Ueta and Hiroshi Kawakami : Homotopy法をもちいた分岐局面の自動追跡, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, Sep. 2005.
128.	Yoshihiro Imakura, Tetsushi Ueta and Hiroshi Kawakami : Brusselator にみられるカオス現象, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, Sep. 2005.
129.	Shota Nakagawa, Kousaka Takuji, YUE MA and Tetsushi Ueta : 時刻依存型断続動作特性を有する力学系にみられるカオスの制御と回路実装, 平成17年度電気関係学会中国支部連合大会講演論文集, Sep. 2005.
130.	Yasuo Miyoshi, Takahiro Oie, Tetsushi Ueta and Yoneo Yano : Publication of Syllabus with Educators and Researchers' Information Database in Tokushima University, 教育システム情報学会30周年記念全国大会講演論文集, 553-554, Aug. 2005. (Summary) 徳島大学では，情報の再利用を設計思想とした教育·研究者情報データベース(EDB: Educators and Researchers' Information Database, 以下 EDB)を独自に開発，運用を行っている．大学においては，種々の定期刊行物(紀要，教育要覧，研究要覧など)を出版しているが，EDBの各種刊行物のためのLaTeX形式の出力機能により，それにかかるコスト削減に成功している．具体的には，教員が登録した情報から冊子の版下までをEDBで作成できるため，校正が不要となり，冊子を印刷するための時間と費用が節約できる． (Keyword) syllabus / 講義概要 / XML / Relational Database
131.	Yu Toyosaki, Shigeki Tsuji, Tetsushi Ueta and Takuji Kousaka : 部分的遅延制御と部分的外力印加制御の組合せによるカオス制御, Proceedings of IEICE Society Conference, Vol.A, Sep. 2004.
132.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : ネットワークルータの輻輳制御における非線形性の導入, Proceedings of IEICE Society Conference, Vol.A, Sep. 2004.
133.	Tetsushi Ueta, Takuji Kousaka, Tohru Kawabe and Sanghoo Hyon : 部分的外力印加法によるカオス制御, 年度電子情報通信学会ソサイエティ大会講演論文集, Vol.A, No.2-14, Sep. 2004.
134.	Sanghoo Hyon, Suguru Emura and Tetsushi Ueta : elayed feedback control of one-legged passive running robot, Proc. of SICE Annual Conference, 949-954, Aug. 2004.
135.	Tetsushi Ueta and Hiroshi Kawakami : 拡張BVP発振器における振動停止現象について, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 14, Oct. 2003.
136.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : 変形BVP発振器でみられるトーラス, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 13, Oct. 2003.
137.	Shigeki Tsuji, Tetsushi Ueta and Hiroshi Kawakami : 電流結合型 BVP発振器対の分岐とカオス, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 11, Oct. 2003.
138.	Atsushi Tsuda, Tetsushi Ueta, Takuji Kousaka and Hiroshi Kawakami : 極配置法カオス制御におけるベイスンについて, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 10, Oct. 2003.
139.	Takahiro Oie, Tetsushi Ueta and Yoneo Yano : Development and operation of education and research database in Tokushima University, 平成15年度工学·工業教育研究講演会講演論文集, 633-636, Sep. 2003. (Summary) 大学においては，教育・研究活動を広報する目的で，紀要，教育要覧，研究要覧などの定期刊行物(以下，刊行物)を出版している．刊行物に収録することにより読者に効果的にアピールできる項目としては，構成員の業績リストが挙げられる．一方で，大学の構成員に対する業績調査も頻繁に行われており，教職員はその都度調書の作成を行っている．これの刊行物や調書を制作するためのデータは，例えば学歴，職歴のように職員個人にとっては不変の情報であったり，著作リストのように既存のデータを追加するだけで済む情報である．しかし，個人のデータの記録書式や，編集者のデータ収集方法を統一することは困難であり，よって，刊行物ごとにデータの再入力が強いられ，結果，編集・校正に長い期間を要し，データ入力者のみならず編集者にとっても多大な負担となる．そこで本学では，上記刊行物の網羅すべき項目を洗いだし，「情報の再利用」を設計思想として，ユーザの入力と刊行物の編集作業の援用を指向した「教育・研究者情報データベース」(EDB; Education and research database, 以下，EDB)を構築した．本稿ではこの EDB の開発と運用について述べる． (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390001206110975744 (CiNii: 1390001206110975744)
140.	Yoko Uwate, Yoshifumi Nishio, Tetsushi Ueta, 河辺徹 and 池口徹 : 組み合わせ最適化問題を解く Hopfield NN にカオスノイズを適用した場合の性能評価, 電子情報通信学会総合大会講演論文集, No.A-2-6, 40, Mar. 2003.
141.	Tohru Kawabe, Tetsushi Ueta and Yoshifumi Nishio : Chaotic Noise and Iterative Simulated Annealing for TSP, SICE Annual Conference Proceedings, 2909-2912, Aug. 2002.
142.	Tetsushi Ueta, Akinori Tsuji and Shunichiro Oe : DSPを用いたカオス力学系の信号抽出, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 22, Oct. 2001.
143.	Yoshihito Yasuhara, Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : 周期開閉スイッチを有する非線形回路に発生するカオスの制御, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 17, Oct. 2001.
144.	Shoichi Tahara, Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : ハイブリッドシステムに発生するカオスの制御, 電気関係学会中国支部連合大会論文集, 10, Oct. 2001.
145.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : 状態依存型断続特性を有する非線形力学系に発生するカオスの実験的制御, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 12, Oct. 2001.
146.	Hisayo Miyazaki, Tetsushi Ueta and Hiroshi Kawakami : 非対称結合BVP発振器の分岐とカオス, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 13, Oct. 2001.
147.	漆原直樹, Yoshifumi Nishio, 河辺徹 and Tetsushi Ueta : バーストノイズ注入型 Hopfield NN を用いた TSP 解探索能力, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-4, 4, Sep. 2001.
148.	Shoichi Tahara, Takuji Kousaka, Tetsushi Ueta, Hiroshi Kawakami and Minoru Abe : On an Electric Circuit Interrupted by Own State and a Periodic Interval, --- Control ---, IEICE Technical Report, Vol.NLP2000, No.100, 57-62, Nov. 2000. (Summary) In this report, we propose a control method of chaos in nonlinear dynamical system interrupted by own state and a periodic interval. We derive the composite discrete mapping as Poincare mapping. It enable us to calculate the unstable fixed or periodic point in a chaotic attractor. The controller is designed with the pole assignment technique which is usually applied in many linear control system. As an illustrate examples, we try to control the chaos in the system which has an observable chaos. This system is described by one dimensional piecewise linear system interrupted by own state and a periodic interval. Some theoretical results are verified by laboratory experiment.
149.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : 周期外力を印加したニューロン対におけるバースト応答とその分岐, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 10, Oct. 2000.
150.	Shoichi Tahara, Takuji Kousaka, Tetsushi Ueta, Hiroshi Kawakami and Minoru Abe : ハイブリッドシステムに発生するカオスの制御, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 5, Oct. 2000.
151.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : ニューロン対発振器の周期外力応答, 電子情報通信学会総合大会講演論文集, Vol.A, 61, Mar. 2000.
152.	Tetsushi Ueta, Guanrong Chen, Tetsuya Yoshinaga and Hiroshi Kawakami : 強結合ニューロン対に生じるneimark-sacker分岐と同期モード, 電子情報通信学会総合大会講演論文集, Vol.A, 412-413, Mar. 2000.
153.	馬場秀司, Yoshifumi Nishio, 河辺徹 and Tetsushi Ueta : Gilbert モデルによるバーストノイズを与えた Hopfield Neural Network, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-9, 9, Oct. 1999.
154.	Toshikazu Masaki, Tetsushi Ueta and Kenji Terada : フラクタル符号化された指紋画像を用いた個人識別, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 234, Oct. 1999.
155.	Akira Takeuchi, Tetsushi Ueta and Kenji Terada : フラクタル符号化を用いた画像中人間領域抽出, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 233, Oct. 1999.
156.	Eiji Izumida, Tetsushi Ueta and Hiroshi Kawakami : 非線形力学系における3次元分岐図の自動作成, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 14, Oct. 1999.
157.	Takashi Kido, Takuji Kousaka, Hiroshi Kawakami and Tetsushi Ueta : Border-Collision分岐を生じる簡素な回路, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 13, Oct. 1999.
158.	Tetsushi Ueta and Guanrong Chen : Chen 方程式の分岐とカオス, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 12, Oct. 1999.
159.	武内朗, Tetsushi Ueta and Kenji Terada : フラクタル符号化を用いた画像中人間領域抽出, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.13-27, 233, Oct. 1999.
160.	下地克弥, 河辺徹, Tetsushi Ueta and Yoshifumi Nishio : 巡回セールスマン問題におけるカオスノイズ注入型ニューラルネットワークの解探索能力の解析, 計測自動制御学会学術講演会予稿集, No.2, 483-484, Jul. 1999.
161.	Eiichiro Okahisa, Kenji Terada, Tetsushi Ueta and Shunichiro Oe : 口の形状と動き情報を用いた母音認識法, National Convention Record I.E.E. Japan, Vol.3, 138, Mar. 1999.
162.	Toshikazu Masaki, Tetsushi Ueta and Kenji Terada : フラクタル符号化を用いた指紋識別, National Convention Record I.E.E. Japan, Vol.3, 134, Mar. 1999.
163.	Eiji Izumida, Tetsushi Ueta and Hiroshi Kawakami : 非線形力学系における3パラメータ分岐曲面求解の自動化, National Convention Record I.E.E. Japan, Vol.1, 31, Mar. 1999.
164.	Toshikazu Masaki, Tetsushi Ueta and Kenji Terada : フラクタル符号を用いた諮問識別の試み, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 232, Oct. 1998.
165.	岡久英一郎, Tetsushi Ueta, Yoshifumi Nishio and 河辺徹 : ノイズ注入型ニューラルネットワークの探索能力, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.15-2, 261, Oct. 1998.
166.	Eiji Izumida, Tetsushi Ueta and Hiroshi Kawakami : 3-パラメータ空間における非線形力学系の分岐構造の視覚化, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 10, Oct. 1998.
167.	Takashi Kido, Takuji Kousaka, Hiroshi Kawakami and Tetsushi Ueta : 方形波発振器の同期現象の解析, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 15, Oct. 1998.
168.	Takuji Kousaka, Hiroshi Kawakami and Tetsushi Ueta : DC-DCコンバータ回路における分岐計算法, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 82, Oct. 1998.
169.	Tetsushi Ueta, Takuji Kousaka and Guanrong Chen : new numerical algorithm for Neimark-Sacker bifurcation, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 93, Oct. 1998.
170.	武内朗, Tetsushi Ueta and Kenji Terada : フラクタル力学系の不安定化を用いた画像の領域分割, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, No.1-6, 6, Oct. 1998.
171.	Tetsushi Ueta : 力学系における分岐現象の解析, 回路とシステム(軽井沢)ワークショップ論文集, 257-262, Apr. 1998.
172.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : 状態に依存したスイッチで制御される非線形断続回路のカオス制御, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 115, Oct. 1997.
173.	Makoto Shiota, Tetsushi Ueta and Hiroshi Kawakami : Duffing方程式における分岐集合曲面の3次元表示, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 34, Oct. 1997.
174.	Tetsushi Ueta and Hiroshi Kawakami : 3個の結合された2次写像の時空カオス的挙動, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 21, Oct. 1997.
175.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : 不連続な非線形特性を持つ系にみられるリミットサイクルの分岐, 電子情報通信学会総合大会講演論文集, Vol.A, 93, Mar. 1997.
176.	Makoto Shiota, Tetsushi Ueta and Hiroshi Kawakami : 2 次元離散力学系における周期アトラクタ領域の σ-等高線による解析, 電子情報通信学会総合大会講演論文集, Vol.A, 92, Mar. 1997.
177.	Masafumi Tsueike, Tetsushi Ueta and Hiroshi Kawakami : 結合ニューロン発振器の同期現象, 電子情報通信学会総合大会講演論文集, Vol.A, 76, Mar. 1997.
178.	Makoto Shiota, Tetsushi Ueta and Hiroshi Kawakami : 2次元離散系における σ-等高線の計算, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 21, Oct. 1996.
179.	Takuji Kousaka, Hiroshi Kawakami and Tetsushi Ueta : 方形波発振器を用いた電子ホタルの同期現象, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 20, Oct. 1996.
180.	Tetsushi Ueta and Hiroshi Kawakami : On saddle-node connectiong orbit in nonlinear dynamical systems, 電子情報通信学会総合大会講演論文集, Vol.A, 435-436, Mar. 1996.
181.	Masafumi Tsueike, Tetsushi Ueta and Shunichiro Oe : カオスアトラクタの可聴領域における表現, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 342, Oct. 1995.
182.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Destabilizing orbits by controlling chaos, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 125, Oct. 1995.
183.	Tetsushi Ueta and Hiroshi Kawakami : A control to enlarge the synchronized region of nonlinear dynamics, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 124, Oct. 1995.
184.	Tetsushi Ueta and Hiroshi Kawakami : 周期外力を印加した倒立振子のカオスとその制御, 電子情報通信学会総合大会講演論文集, Vol.A, 75, Mar. 1995.
185.	Takuji Kosaka, Tetsushi Ueta and Hiroshi Kawakami : BVP発信器に見られる分岐現象の解析, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 13, Oct. 1994.
186.	Tetsushi Ueta and Hiroshi Kawakami : Stabilizing periodic orbits embedded in a chaotic attractor of continuous dynamical systems, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 129, Oct. 1994.
187.	Hiroshi Kawakami and Tetsushi Ueta : Controlling unstable fixed point in chaotic state of discrete dynamical systems, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 128, Oct. 1994.
188.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation phenomena in a Josephson junction circuit coupled by a resistor, 電子情報通信学会春季全国大会講演論文集, Vol.A, 75, Mar. 1994.
189.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation of an inductively coupled Josephson junction circuit, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 13-14, Oct. 1993.
190.	Tetsushi Ueta and Hiroshi Kawakami : 準回転力学系のヘテロクリニック軌道, 電子情報通信学会春季全国大会講演論文集, A85, Mar. 1993.
191.	Tetsushi Ueta and Hiroshi Kawakami : 準回転運動を行なう力学系の解析, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 13-14, Oct. 1992.
192.	Yoshio Tanaka, Masato Tanaka, Yasuo Yoshida, Tetsushi Ueta and Hiroshi Kawakami : 振動センサを利用した旋回型クレーンの振動制御, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 287-288, Oct. 1991.
193.	Tetsushi Ueta, Yoshio Tanaka and Hiroshi Kawakami : クレーンの吊り荷揺れと揺れのパラメトリック制御, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 277-278, Oct. 1991.
194.	Tetsushi Ueta, Yoshio Tanaka and Hiroshi Kawakami : クレーンの本体と吊り荷揺れの統一的解析法Ⅱ, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 213-214, Oct. 1990.
195.	Yoshio Tanaka, Tetsushi Ueta and Hiroshi Kawakami : クレーンの本体と吊り荷揺れの統一的解析法I, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 211-212, Oct. 1990.
196.	Kazumasa Imai, Kiyoo Shibuya, Taku Yoshida and Tetsushi Ueta : 高知高専の校内パソコンネットワークについて, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 401-402, Oct. 1987.
197.	Kazumasa Imai, Tetsushi Ueta and Kozin Okamoto : パソコンLANによる地球観測衛星ランドサット画像データ処理システムの開発, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 403-404, Oct. 1987.
198.	Kazumasa Imai and Tetsushi Ueta : 16ビットパソコンによる地球観測衛星ランドサット画像データ処理システムの開発, Journal of Shikoku-Section Joint Convention of the Institutes of Electrical and Related Engineers, 317-318, Oct. 1986.

Et cetera, Workshop:

1.	ISHIGAKI Ryuto and Tetsushi Ueta : Visualization of a 2-dimensionally stable manifold of an equilibrium in 3 dimensional autonomous system, IEICE Technical Report, Vol.NLP2023, No.121, 174-177, Jan. 2024. (Summary) In various field such engineering and biology, to analyze systems, people have been analyzing them by buildingmodels. In this paper, I visualize 2-dimensionally stable manifold. Target is saddle of 3 dimensional autonomous system.Stable manifold is separatrix. So, it is basin boundary of attraction and gives us basin of attraction in state space. That is why Icalculate stable manifold. If a manifold is one dimension, all you need is to chase orbits that depart from eigen vector of saddlefor plus or minus time. But, if it is two dimensions, you have to approximate with a curved surface. In this paper, I explainmethod that is referenced by previous research. And I visualize 3 autonomous systems, Lorenz equation, Chens equation, andequation of S. Dadras et al. (Keyword) 3 dimensional autonomous system / 2-dimensionally stable manifold
2.	Seiya Amoh and Tetsushi Ueta : Canard Cycles in Multivibrators with Piece-wise Constant Identical Operational Amplifier, IEICE Technical Report, Vol.NLP2023, No.106, 106-109, Jan. 2024. (Summary) The multi-vibrator is an electronic circuit with multiple stable states, often built using operational amplifiers. Thereare three types of stable states: unstable, monostable, and bistable, and transitions between these modes can be achievedthrough parameter changes. Conventionally, the output response of multi-vibrators is considered a hybrid system. In thisstudy, we similarly configure the system as a hybrid system by modeling the amplification characteristics of the operationalamplifier as piecewise constant or piecewise linear characteristics. Furthermore, the system is constructed as a time-delayeddynamical system by considering the first-order delay characteristics of the operational amplifier. During the transition fromthe monostable state to the unstable state, a unique solution specific to slowfast dynamical systems, canard, is observed. (Keyword) Slow-fast dynamics / canard / multivibrator / bifurcation / operational amplifier
3.	Masaki Yoshikawa, Seiya Amoh and Tetsushi Ueta : Bifurcation of three Wilson-Cowan neuron models, IEICE Technical Report, Vol.NLP2023, No.89, 30-33, Jan. 2024. (Summary) In recent years, there has been a lot of interest in analyzing the activity between neurons by schematizing neuronalmodels. In this study, we numerically analyze and discuss a three-dimensional Wilson-cowan neuron model. The generaltwo-dimensionalWilson-cowan model reproduces simple responses between neurons by assuming one group of excitatory andone group of inhibitory neurons. In this study, we performed numerical experiments using the general Wilson-Cowan modelwith one excitatory neuron group. The results showed that the local branching structure changed as the excitatory neuronsvalue fluctuated. The stability of the equilibrium point also supports the global stability proposed by Hoppensteadt et al. (Keyword) Wilson-Cowan neuron model / numerical analysis / bifurcation
4.	MICHIRU Katayama and Tetsushi Ueta : On inverse-time responses and bifurcations in 2-dimensional non-autonomus, IEICE Technical Report, Vol.NLP2023, No.96, 66-69, Jan. 2024. (Summary) A dynamical system represented by the signal response of an electric circuit is expressed as a non-autonomoussystem. Some non-autonomous systems have strange attractors in their phase space, and their bifurcation structures are of greatinterest in chaos theory. In this paper, we consider the transformation to analyze bifurcation structures. The Poincar´emap of the periodic solution has a fixed point, which is a condition for non-hyperbolicity, in common with the forward andbackward time systems, and the stability of the fixed points is interchanged. As an example, we perform numerical analysis offorward and backward time systems in a two-dimensional non-autonomous electrical circuit. As a result, we confirmed that theparameter regime that corresponds to the divergent regime in the forward time system can sometimes be observed as a periodicsolution in the backward time system. We also report that there are strange attractors in the phase space of the backward timesystem that cannot be seen in the forward time direction. (Keyword) diode / bifurcation phenomena / chaos
5.	ZHANG QUANKAI and Tetsushi Ueta : Bifurcation analysis and simulation of a biological switch model, IEICE Technical Report, Vol.NLP2023, No.23, 45-48, Jun. 2023. (Summary) Using a mathematical model of biological switches, we examine the phenomenon of cell differentiation under a cyclic external force as a circadian rhythm. In order to understand the differentiation state of cells with different parameters in the mathematical model, a bifurcation analysis of the periodic solution is investigated, and the topological classification of the periodic solution is performed by means of a bifurcation diagram. We also show that a period-doubling cascade chain occurs, resulting in different states of Delta concentration, or differentiation, in the cell. The response of the mathematical model under a cyclic external force as a circadian rhythm is investigated by computer simulations. In the bistable region, the attraction regions are separated from each other by a high potential, and the amplitude of a cyclic external force as a circadian rhythm cannot merge the attraction regions with each other, indicating that the switch structure does not collapse. (Keyword) biological switch / cell differentiation / mathematical model / bifurcation analysis
6.	Seiya Amoh and Tetsushi Ueta : Multivibrator as Slow-fast Dynamics, --- Canard Explosion and its Circuit Response ---, IEICE Technical Report, Vol.NLP2023, No.27, 61-64, Jun. 2023. (Summary) Intermittency gives the irregular switching of almost periodic (laminar) and chaotic (burst) motions, and can be confirmed in every physical system within a certain parameter range. In this paper, by utilizing a method stabilizing a periodic motion which have been vanished by a saddle node bifurcation, a laminar motion in the intermittency is stabilized by a tiny control input. A pseudo periodic orbit composed by the vanished orbit or laminar motion is applied as a reference for the linear feedback control. We demonstrate the control for a circuit model and show robust stabilization responses. (Keyword) Slow-fast dynamics / canard / multivibrator / bifurcation
7.	MICHIRU Katayama, Kenji Ikeda and Tetsushi Ueta : Laminar stabilization control in chaos intermittency, IEICE Technical Report, Vol.NLP2023, No.28, 65-68, Jun. 2023. (Summary) Intermittency gives the irregular switching of almost periodic (laminar) and chaotic (burst) motions, and can be confirmed in every physical system within a certain parameter range. In this paper, by utilizing a method stabilizing a periodic motion which have been vanished by a saddle node bifurcation, a laminar motion in the intermittency is stabilized by a tiny control input. A pseudo periodic orbit composed by the vanished orbit or laminar motion is applied as a reference for the linear feedback control. We demonstrate the control for a circuit model and show robust stabilization responses. (Keyword) chaos control / chaos intermittency
8.	Rikiya Yamaguchi, Daisuke Ito, Yuu Miino and Tetsushi Ueta : 2 リンクロボットにおける大域的分岐, IEICE Technical Report, Vol.NLP2022, No.113, 37-42, Mar. 2023. (Summary) A two-link robot is modeled as a four-dimensional autonomous system, and its motion is chaotic. The global motion of the robot starts from an unstable manifold near a saddle equilibrium point and is separated by a homoclinic orbit connecting to its own saddle equilibrium point. In this study, we analyze and observe homoclinic orbits in a system where friction and constant torque are applied to the joints of the robot. (Keyword) 2リンクロボット / 動力学 / 大域的分岐 / ホモクリニック軌道
9.	Ryuichi Yoshida, Seiya Amoh and Tetsushi Ueta : A scenario obtaining periodic solutions from third-order autonomous system without equilibrium points, IEICE Technical Report, Vol.NLP2022, No.113, 31-36, Mar. 2023. (Summary) The generation of periodic solutions is one example of a bifurcation in an autonomous system. Usually, periodic solutions are generated by a Hopf bifurcation at an equilibrium point. In this paper, we focus on a system with periodic solutions but no equilibrium point, and explore the mechanism by which periodic solutions are generated. In one scenario, a Hopf bifurcation was confirmed by adding a new parameter to the system, and the mechanism of the periodic solution was found. For the desired unstable complex conjugate root in the characteristic equation We will consider adding a parameter to generate a Hopf bifurcation for the desired unstable complex conjugate roots in the characteristic equation. Therefore, this paper presents an example of adding a parameter to generate a Hopf bifurcation in a system without equilibrium. Key words no equilibrium points, bifurcation analysis (Keyword) 分岐解析
10.	Tetsushi Ueta : Revisit on Computations for Bifurcation Problems, --- A follow-up ---, IEICE Technical Report, Vol.NLP2022, No.88, 36-41, Jan. 2023. (Summary) Python is gaining attention as a fundamental programming language for machine learning and data science. This report describes a detailed Python approach to nonlinear problems, especially the bifurcation problems of periodic solutions. It is a highly readable implementation of the bifurcation algorithm, independent from the computer and the operating system, and it allows an interactive trial-and-error processing. We describe advantages of Python for bifurcation problems with some illustrated codes. (Keyword) Python / 分岐解析 / テンソル
11.	Seiya Amoh, Tetsushi Ueta and Hiroshi Kawakami : Multivibrator and Slow-fast Dynamics, --- Basic bifurcation phenomena and Canard solutions ---, IEICE Technical Report, Vol.NLP2022, No.15, 72-77, Jun. 2022. (Summary) Slow-fast dynamical systems are systems of ordinary differential equations involving different time constants. Systems with slow-fast characteristics may have a characteristic solution called the Canard solution. The evolution of the solution depending on the parameter change is interesting. In this paper, we treat a multivibrator, which is a slow-fast dynamical system that can be easily implemented as an electronic circuit. If the operational amplifiers of the multivibrator have dynamic output characteristics, the system behaves as a slow dynamics system. We investigate the basic bifurcation phenomena that occur at the equilibrium point and the process of generating Canard solutions. (Keyword) Slow-fast dynamics / canard / multivibrator / bifurcation
12.	Tetsushi Ueta : Revisit on Computations for Bifurcation Problems, IEICE Technical Report, Vol.NLP2021, No.55, 56, Dec. 2021. (Summary) We are developing a bifurcation analysis tool written by Python. In this computer language, reliable functions which have been imported from FORTRAN implementation are available. Variational equations and related derivatives are expressed simply without loops. A GUI required for interactive operation is also provided by matplotlib. The tool can be OS independent. We introduce the tool in detail and discuss further development and prospects. (Keyword) bifurcation / numerical computation / python
13.	Rina Yano, Hiroki Tanioka, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : Quantitative Measurement and Analysis to Thinking as a Way of Programming for Elementary School in Japan, IPSJ SIG Technical Report, Vol.2020-CLE-30, Mar. 2020. (Summary) Programming education will be compulsory in elementary schools in Japan from 2020, but thereis still little information on how to measure the effects of lessons conducted for students. In this study, inorder to objectively and quantitatively measure the educational effect of programming education, we developed a test of measuring an ability of thinking as a way of programming. In this paper, we evaluate themeasurability of the test using the Fishers exact test for elementary school students answers, focusing onthe grade, the programming experience, and the difference between the results before and after the workshop. (Keyword) Programming Education / evaluation / analysis
14.	Shohei Miyazaki, Yuu Miino, Tetsushi Ueta and Hiroshi Kawakami : 馬蹄型写像の同定とカオス制御, IEICE Technical Report, Vol.NLP2019, No.58, 117-122, Sep. 2019. (Summary) 1 つのサドル型固定点から伸びる安定多様体と不安定多様体の交わりであるホモクリニック点が存在するとき，馬蹄形写像が存在している．馬蹄形写像内部には可算無限個の不安定周期点が存在しており，ホモクリニック点をNewton 法の初期値として任意周期の不安定周期点を計算することができる．本研究では，導出した不安定周期点を用いたExternal Force Control で馬蹄形写像内部の不安定周期点を制御することを目的とする． (Keyword) Henon map / horse shoe map / unstable periodic orbit / homoclinic point / かおすせいぎょ
15.	Yuu Miino and Tetsushi Ueta : 記号力学系に基づいたlogistic map における不安定周期点の数値的導出法, IEICE Technical Report, Vol.NLP2019, No.36, 11-14, Sep. 2019. (Summary) 本研究では，logistic map に対応する記号力学系を基に，カオス中に埋め込まれた不安定周期点(unstable periodic point; UPP) を算出する数値的手法を提案する．logistic map を逆写像に持つ2 つの写像を定義することで，時間過去方向の解軌道に自由度をもたせ，所望の記号列に対応したUPP を導出する．1 から6 の周期を持つ周期点及び 10-周期点，20-周期点に対して数値実験を行い，手法の有効性を示す．また，計算の収束性を示す指標を導入し，提案手法の適用可能性も吟味する． (Keyword) logistic map / 不安定周期解 / chaos / numerical analysis / 記号力学系
16.	Kawanaka Kohei, Rabarison Misamanana Felicia, Hiroki Tanioka, Kenji Ohira, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : Improving Animal Recognition Accuracy using De-fencing, IPSJ SIG Technical Report, Vol.2019-ICS-194, No.9, 1-6, Mar. 2019. (Summary) When a computer recognizes an animal on an image, an accuracy of animal recognition decreases if a part of the animal's body is covered by fences. On the other hand, when a human recognizes a object on the image, it is known to be possible to remove and supplement the fences, and recognize the object, even if a part of the object is covered by fences. In this research, we aim to improve the accuracy of animal recognition using de-fencing on computer. (Keyword) Noice reduction / Image complement / Animal recognition
17.	Felicia Misamanana Rabarison, Kohei Kawanaka, Hiroki Tanioka and Tetsushi Ueta : Local Zoo Guide Application using Image Recognition, IEICE Technical Report, Vol.PRMU2018-118, No.459, 21-26, Feb. 2019. (Summary) Most of the information for guide in the Tokushima zoo is in Japanese. However, it is difficult to understand Japanese guide for foreign tourists. Therefore, we need to develop an animal guide application or robot without language query for foreign visitors. One of the ideas is that Convolutional Neural Network (CNN) is employed for image recognition for making image query on the application. The application is available to display instantly information about animals in an image or video. For our experiment, pictures including 30 kinds of animals are collected. Around 4,000 pictures were taken from Tokushima zoo for the purpose of this experiments. (Keyword) Convolutional Neural Network / Image Recognition / VGG-16 / Fine-tuning
18.	Hiroki Tanioka, Kenji Matsuura, Tetsushi Ueta and Fumiaki Kawano : Report for Learning Email Etiquette in Group, JSiSE Resaeach Report, Vol.33, No.4, 21-22, Oct. 2018.
19.	Shohei Miyazaki, Yuu Miino, Tetsushi Ueta and Hiroshi Kawakami : エノン写像における馬蹄形写像のホモクリニック点と不安定周期点との位置関係, IEICE Technical Report, Vol.NLP2018, No.70, 91-96, Aug. 2018. (Summary) 馬蹄形写像内部の不安定周期点をあるホモクリニック点の座標情報を用いて計算する手法が開発されている．しかし，両者の位置的関係についての調査は未だ行われていなかった．本研究では，馬蹄形写像に埋め込まれた不安定周期点を6周期点まで算出し，これらと算出に用いるホモクリニック点との位置関係を調査する．Hénon 写像を例に取り，ホモクリニック点及び周期点は数値的に導出し，極座標形式による座標評価を行う． (Keyword) Henon map / horse shoe map / unstable periodic orbit / homoclinic point
20.	Yuu Miino, Tetsushi Ueta, Hiroshi Kawakami, Atsuo Maki and Naoya Umeda : 船舶転覆問題にみられる分岐現象, IEICE Technical Report, Vol.NLP2018, No.55, 15-19, Aug. 2018. (Summary) 船舶の運動安定性の分野においては，船舶転覆問題を議論するために軟化型Duffing 方程式が用いられる．しかしながら，軟化型Duffing 方程式を扱う多くの研究は近似的解法を用いており，実際の物理系の振る舞いにそぐわない結果を導くことも少なくない．本報では，非線形分野で古くから発展してきた数値的解法を用いて，軟化型 Duffing 方程式を解析する．適切なPoincaré 写像を定義し，系で観測される周期解の安定性や安定・不安定多様体を導出し，局所または大域分岐について議論する．結果として，系の二次元パラメタ空間における分岐構造を明らかにし，分岐現象が状態空間のベイスンに及ぼす影響について議論する． (Keyword) 軟化型Duffing方程式 / numerical computation / local stability / local bifurcation / global bifurcation
21.	Mamoru Sakai, Hiroki Tanioka, Kenji Matsuura, Masahiko Sano, Kenji Ohira, Tetsushi Ueta and Sakaguchi Hiroaki : Evaluating Hitting Skills of NPB Players with Logistic Regression Analysis, IPSJ SIG Technical Report, Vol.2018-MPS-119, No.8, Jul. 2018. (Summary) When we watch a baseball game, we often witness scenes that a line drive flies out in front of a fielder. On the other hand, a pop fly falls between infielders and outfielders. In such a scene, we viewers express unlucky or lucky for the batter. Therefore, luck is supposed to be existing in baseball. In other words, it is hard to say that hitting records depend on only the ability of the batters. In this paper, lucky or unlucky is occurred in unpredictable cases with human eyes. Hence, we consider that luck exists in a phenomenon beyond observers expected based on their observable information. (Keyword) baseball / hitting / performance / evaluation / logistic regression
22.	Takao Hiramatsu, Masahiko Sano, Kenji Matsuura, Kenji Ohira, Hiroki Tanioka and Tetsushi Ueta : A Meeting Recording System Concidered for Utilization, IPSJ SIG Technical Report, Vol.2018-CLE-24, No.17, 1-4, Mar. 2018. (Summary) 蓄積されたゼミ議事録や研究成果物が有効に利活用されていない問題に対して，それらの利活用や関連情報の再検索における手間の低減を目的とした手法を提案する．提案手法では，ゼミ議事録にメタデータを付与しながらの作成と，関連研究成果物との連携により，利活用する際の手間の低減を図る．本稿では，その提案手法とその実験システムの開発状況について述べる．
23.	Kana Okada, Masahiko Sano, Kenji Matsuura, Kenji Ohira, Hiroki Tanioka and Tetsushi Ueta : Support System for Laboratory Selection using Researchers Database, IPSJ SIG Technical Report, Vol.2018-CLE-24, No.7, 1-6, Mar. 2018. (Summary) 大学生の研究室配属前の希望度と配属後の満足度のミスマッチが問題となっている．本研究では，事前調査の結果，その理由の一つが希望研究室の調査不足であることに着目し，学生の調査不足を大学が所有する研究者情報データベースを活用して支援する希望研究室選択支援手法について提案する．本稿では，その提案手法とその実験システムを著者らが所属する組織にて評価した結果について述べる．
24.	Takuma Horiuchi, Kenji Ohira, Hiroki Tanioka, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : スマートデバイス向けサードパーティーアプリの危険性検証ツールの提案, IEICE Technical Report, Vol.IA2017, No.75, 1-6, Mar. 2018.
25.	Takahiro Oriishi, Kenji Ohira, Michitomo Morii, Hiroki Tanioka, Masahiko Sano, Kenji Matsuura and Tetsushi Ueta : FIDOにおけるオーセンティケータ登録のパスワードフリーな運用に関する設計と実装, IEICE Technical Report, Vol.IA2017, No.74, 1-6, Mar. 2018.
26.	Kenji Ohira, Hirokazu Nakano, Hiroki Tanioka, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : A Study on Application of Two-Factor Authentication to Campus WLAN Connections, IPSJ SIG Technical Report, Vol.2017-IOT-38, No.3, 1-6, Jun. 2017.
27.	Michitomo Morii, Hiroki Tanioka, Kenji Ohira, Masahiko Sano, Kenji Matsuura, Yosuke Seki and Tetsushi Ueta : Research on authentication cooperation using passwordless authentication method, IPSJ SIG Technical Report, Vol.2017-IOT-37, No.8, 1-6, May 2017. (Keyword) Shibboleth / FIDO / Authentication / Password
28.	Yuu Miino, Tetsushi Ueta and Hiroshi Kawakami : 簡素な区分線形力学系に発現するホモクリニック点の分岐, IEICE Technical Report, Vol.NLP2017-15, No.18, 73-76, May 2017. (Summary) In a certain case, a piecewise linear dynamical system shows rich nonlinear phenomena. In this study, we discuss the homoclinic point and its bifurcation observed in a simple piecewise linear dynamical system. We adapt the hybrid system approach and calculate the homoclinic point and its bifurcation sets. (Keyword) piecewise linear / bifurcation analysis / hybrid system / homoclinic point
29.	Kenji Matsuura, Masahiko Sano, Kenji Ohira, Hiroki Tanioka, Tetsushi Ueta and Yuki Nishimura : Descussion on Management and Application of Daily Academic Activity at a University, IPSJ SIG Technical Report, Vol.2016-CLE-20, Nov. 2016.
30.	Yuu Miino, Tetsushi Ueta and Hiroshi Kawakami : Nonlinear phenomena observed in the piecewise hysteresis Duffing equation, IEICE Technical Report, Vol.NLP2016, No.50, 31-36, Sep. 2016. (Keyword) hysteresis phenomena / Duffing equation / bifurcation analysis / hybrid system / nonlinear resonance
31.	Daisuke Ito and Tetsushi Ueta : Controlling chaos and its stability analysis for Lorenz model with external force control, IEICE Technical Report, Vol.NLP2016, No.17, 83-86, May 2016. (Keyword) external force control method / Lorenz model / bifurcation analysis
32.	Hiroyuki Fukue, Takuji Kousaka, Tetsushi Ueta, Daisuke Ito, Hirokazu Ohtagaki, Koh Utsunomiya and Hiroyuki Asahara : Controlling ON/OFF-Time in Current-Controlled DC/DC Boost Converter, IEICE Technical Report, Vol.NLP2016, No.16, 77-81, May 2016. (Keyword) DC/DC converter / unstable periodic orbit / discrete map / bifurcation phenomena / chaos control
33.	Kyosuke Miyamoto, Tetsushi Ueta and Hiroshi Kawakami : Synchronization mechanism of optical-coupled oscillators, IEICE Technical Report, Vol.NLP2016, No.10, 45-50, May 2016. (Keyword) LED firefly / synchronization
34.	Yuu Miino and Tetsushi Ueta : Synchronization firing phenomena and bifurcation in coupled Izhikevich neuron model, IEICE Technical Report, Vol.NLP2016, No.11, 51-56, May 2016. (Keyword) Izhikevich neuron model / coupled systems / bifurcation analysis / hybrid system
35.	Yosuke Seki, 野村卓哉, 曽我部紗也香, Masahiko Sano, Kenji Matsuura, Kenji Ohira and Tetsushi Ueta : 研究活動の持続的成長を支援するeポートフォリオシステムの提案, IPSJ SIG Technical Report, Vol.2016-CLE-18, No.7, 1-6, Feb. 2016.
36.	Daisuke Ito, 美井野優 and Tetsushi Ueta : 双極型ロジスティックカオスニューロンを用いたIsingネットワークの分岐, IEICE Technical Report, Vol.NC2015-27, 59,-62, Oct. 2015.
37.	Kanae Yagi, Masahiko Sano and Tetsushi Ueta : ISMS新規格における徳島大学情報センターの対応事例, 国立大学情報系センター協議会第13回ISMS研究会資料, Sep. 2015.
38.	Yosuke Seki, Kenji Matsuura, Masahiko Sano and Tetsushi Ueta : A questionnaire distribution system referring access logs and authentication processes, IPSJ SIG Technical Report, Vol.2015-IOT-30, No.2, 1-6, Jun. 2015.
39.	Hiroyuki Asahara, Tetsushi Ueta, Daisuke Ito and Takuji Kousaka : スイッチング回路のON/OFF時間制御に関する一考察, IEICE Technical Report, Vol.115, No.34, 35-38, May 2015.
40.	Daisuke Ito, Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : 周期外力を印加した電子ホタルにみられる時間応答波形, IEICE Technical Report, Vol.114, No.414, 113-116, Jan. 2015. (Keyword) Electronic firefly / isolated periodic orbit / quasi-periodic orbit
41.	Tomohiro Otsu, Ken'ichi Fujimoto, Tetsushi Ueta and Kazuyuki Aihara : Bifurcation Avoidance of Stable Periodic Oscillations in Continuous-Time Duffing Equation, IEICE Technical Report, Vol.114, No.348, 69-74, Nov. 2014. (Summary) We previously proposed a parametric control method to avoid bifurcations of stable fixed and periodic points in discrete-time dynamical systems. The parameter regulation to avoid bifurcations is derived from an optimization problem on the maximum local Lyapunov exponent and the method of steepest descent. This method allows us to predict occurrence of bifurcations caused by unexpected parameter change and to avoid it without directly analyzing bifurcations in advance. In this report, on the basis of the ideas and a stroboscopic mapping that discretizes the trajectory of a continuous-time solution, we propose a methodology to avoid bifurcations of stable periodic oscillations in continuous-time non-autonomous dynamical systems. We also demonstrate that the proposed method can avoid bifurcations of stable periodic solutions in Duffing equation. (Keyword) maximum local Lyapunov exponent / stable periodic oscillation / avoidance of bifurcation / continuous time non-autonomous dynamical system / stroboscopic mapping
42.	Kenji Hishikawa, Daisuke Ito and Tetsushi Ueta : 非線形結合における同期特性, IEICE Technical Report, Vol.114, No.250, 171-174, Oct. 2014. (Keyword) Dictyostelium discoideum / nonlinear coupling / chaos / 同期特性
43.	Yuu Miino, Daisuke Ito and Tetsushi Ueta : 外力を印加した結合ニューロンモデルの応答, IEICE Technical Report, Vol.114, No.250, 119-123, Oct. 2014. (Keyword) coupled neurons / bifurcation analysis / chaos
44.	Shota Mano, Daisuke Ito and Tetsushi Ueta : 疑似周期軌道を用いたカオス制御とその実装, IEICE Technical Report, Vol.114, No.250, 125-128, Oct. 2014. (Keyword) pseudo periodic orbits / UPO / chaos control
45.	Daisuke Ito and Tetsushi Ueta : ネットワークルータの輻輳制御における分岐現象の解析, IEICE Technical Report, Vol.114, No.250, 175-178, Oct. 2014. (Summary) ランダム初期検知を用いた転送制御は TCP 通信における輻輳制御問題で重要な手法であり,数理モデルとしてモデル化する研究もなされている.それらのモデルにおいて,カオスや分岐現象といった,非線形力学系固有の現象が観測された.本報告では,離散時間モデルである S-モデルを対象に分岐構造を調査する. (Keyword) border-collision bifurcation / TCP/RED / S model
46.	Yosuke Seki, Kenji Matsuura, Tetsushi Ueta and Masahiko Sano : Development and practical use of GakuNin application system at Tokushima University, 第18回学術情報処理研究集会発表論文集, 51-56, Sep. 2014.
47.	Shota Mano, Daisuke Ito and Tetsushi Ueta : Emergent Control of Pseudo Periodic Orbits in Chaotic Dynamical Systems, IEICE Technical Report, Vol.113, No.341, 55-58, Dec. 2013. (Keyword) pseudo periodic orbits / UPO / controlling chaos
48.	Jumpei Inaba, Yusuke NIshiuchi, Tetsushi Ueta and Hiroshi Kawakami : An analysis of bursting oscillations in a 4D autonomous system, IEICE Technical Report, Vol.113, No.271, 199-204, Oct. 2013. (Summary) Bursting oscillations are important in considering the behavior of neuron,the mathematical models are devised variously.And bursting oscillations are realized by a coupling or applying an external periodic forcing to the system,however,what can be implemented easily in actual circuit is not many. In the studying for the BVP oscillator for generating a quasi-periodic, we were able to propose the bursting oscillator of 4-dimensional autonomous system. whose number of components is small and be easy to implement.In this paper, we showed periodic orbits, quasi-periodic orbits, and let compared with the responses of the actual circuit and numerical simulations on how to change burst oscillations are dependent on the parameters. Next we analyzed the bifurcation of periodic solutions, and characterized the topological properties of the bursting oscillations. (Keyword) バースト発振 / 4次元発振器 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1520853834200712192 (CiNii: 1520853834200712192)
49.	Yusuke NIshiuchi, Tetsushi Ueta and Hiroshi Kawakami : Characteristics of bifurcations and oscillations in coupled BVP oscillators, IEICE Technical Report, Vol.113, No.271, 117-122, Oct. 2013. (Summary) BVP 発振器は単純な回路構成で発振状態を観測できる有名な非線形モデルである．BVP 発振器は二つの状態変数に関係したポートを持つため，二つの同一 BVP 振器を結合する場合でも，結合方式の違う結合発振器が複数存在する．これらの結合発振器のうち，基本的なものは既に研究されているが，非線形特性や正規化手法が違うため，その結果を単純に比較し特徴を求めることはできない．そこで，本研究では基本的な結合方式について，同一条件で平衡点やリミットサイクルの分岐，同期発振の状態を調べ，結合方式による特徴を明らかにする． (Keyword) 結合BVP発振器 / nonlinear systems / bifurcation phenomena
50.	Daisuke Ito, Tetsushi Ueta, Shigeki Tsuji and Kazuyuki Aihara : On compensation of attractors vanished by tangent bifurcation, IEICE Technical Report, Vol.112, No.301, 19-22, Nov. 2012.
51.	Ken'ichi Fujimoto, Tomohiro Otsu, Daisuke Ito, Tetsushi Ueta and Tetsuya Yoshinaga : Evaluation and comparison of controlling costs on controlling chaos, IEICE Technical Report, Vol.112, No.301, 1-6, Nov. 2012. (Summary) OGY and delayed-feedback methods proposed at the beginning of 1990s are well known as the original methods of controlling chaos. One of the authors et al. also proposed a method of controlling chaos using Poincare map and linear control theory. All the methods can stabilize unstable periodic motions by making small perturbations of available system parameters. However, from the viewpoint of controlling energy needed to stabilize such motions, to evaluate the amount of required parameter perturbations has not been reported as far as the authors know. In this report, using three indices based on state variables, control input, and electric power (i.e. energy), we evaluated controlling costs to stabilize an unstable periodic motion observed in a continuous-time dynamical system such that the amount of parameter perturbations can be converted to electric power.
52.	Jumpei Inaba, Yusuke Nishiuchi and Tetsushi Ueta : Numerical validation for blurred basin of symmetric equilibria in a 3D autonomous system, IEICE Technical Report, Vol.NLP2012-74, No.112, 99-104, Sep. 2012. (Keyword) BVP発振器
53.	Yoshihiko Yamamoto, Hiroyuki Asahara, Daisuke Ito, Tetsushi Ueta, Kazuyuki Aihara and Takuji Kousaka : Experimental Confirmation of Controlling Chaos Utilizing the Threshold, IEICE Technical Report, Vol.112117, No.112, 13-16, Jul. 2012. (Summary) Controlling chaos has attracted considerable attention, and many researchers have proposed the controlling methods. In recent years, a controlling method that focused on the threshold in the composite dynamical system has been proposed. Although its effectiveness was confirmed, the experimental verification is insufficient. In this paper, we experimentally confirm of controlling chaos in an interrupted electric circuit by adding the controlling signal into the threshold. First, we explain the circuit model and basic behavior of the waveform. Next, we show the design of the controller. Finally, we confirm the controlling method based on the experimental results. (Keyword) Interrupted electric circuit / Controlling chaos / Threshold (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1520009408783062528 (CiNii: 1520009408783062528)
54.	Yusuke Miyaji, Daisuke Ito and Tetsushi Ueta : Controlling Chaos by linear prediction and data lists, IEICE Technical Report, Vol.112, No.117, 7-12, Jul. 2012. (Summary) In this study, we propose a chaos controlling with a linear prediction and lists. A linear prediction model is the technique that can predict the future state of systems by using past states. It is suitable for the prediction of time series. We apply this for a chaos controlling, and propose the chaos controlling by using prediction value. However, a linear prediction model is ruled unfit to predict of nonlinear systems like chaos. Thus, in highly non-linearity systems, the prediction accuracy become diminished and performance of controller negatively affect. So, The return value of target systems is kept as lists and list data is used for the controlling in highly non-linearity region. By this way, even if the systems has highly non-linearity, our controller can be stabilized from chaos, and can be improved the performance. (Keyword) chaos control (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1520572356992237824 (CiNii: 1520572356992237824)
55.	Yoshinori Kitano, Tetsushi Ueta, Yoshifumi Nishio, Yang Guoan and Yang Yang : コントラストの高い白黒二値画像に対するフラクタル符号の重みについて, IEICE Technical Report, Vol.NLP2012-4, No.112, 19-24, Apr. 2012.
56.	Tetsushi Ueta and Masahiko Sano : 組織評価とISMS, IPSJ SIG Technical Report, Vol.2012-IOT-16, No.41, 1-6, Mar. 2012. (Summary) 徳島大学情報化推進センターでは，ISMS 導入にむけ，2011 年度当初から準備を始め，最終的に2012 年1 月に認証機関より適合判定を受けた．ISMS 取得は，並行して行われた新コンピュータシステム調達(2012 年3 月稼働予定)との2 大事業であり，クラウド導入に関するデータセンターの利用，SLA 締結におけるセキュリティ要件の管理において重要な役割を果たす．時期を同じくして本センターは組織評価(外部評価)を受審したが，評価資料における組織，人的セキュリティ，経営陣の責任等の体制構築，情報セキュリティ対策および関連プロジェクトなど各種取り組みの情報はISMS 受審には大いに役立った．情報セキュリティ関係業務は本センターの主業務であるため，ISMS をターゲットに取りまとめた資料は，組織評価資料の作成に多いに貢献した．本稿では情報系センターの組織評価におけるISMS の価値や必要性と，大学における情報マネジメントの関係について述べる．
57.	Daisuke Ito, Akinori Tsuji, Tetsushi Ueta and Hiroshi Kawakami : 周期外力を加えた電子ホタルにおける分岐と同期現象, IEICE Technical Report, Vol.NLP2011-138, No.111, 81-86, Jan. 2012. (Summary) Cooperative or conjoint action of creatures with autonomous oscillation can be considered as synchronization phenomena which are one of typical nonlinear dynamic properties. For example, there are a group singing of crickets, self-organized light synchronizations of fireflies and so on. Especially, fireflies can be modeled as optically coupled oscillators(OCOs) by using LEDs and photo interruptor. Synchronization phenomena of a couple of these oscillators were already investigated, however, synchronization of the single oscillator is not discussed. In this study, we model the firefly as OCO, and add the periodic external force input for one. (Keyword) electrical firefly / interrupt dynamical system / bifurcation phenomena (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1520572357095635328 (CiNii: 1520572357095635328)
58.	Takaya Nakanishi, Daisuke Ito, Tetsushi Ueta, Hiroshi Kawakami, Jun'ichi Imura and Kazuyuki Aihara : 馬蹄形写像を利用した周期点の特定と制御, IEICE Technical Report, Vol.NLP2011-120, No.111, 19-24, Dec. 2011.
59.	Tetsushi Ueta and Masahiko Sano : 徳島大学情報化推進センターにおけるISMS構築について, IPSJ SIG Technical Report, Vol.2011-IOT-14, No.5, 1-2, Jul. 2011.
60.	Daisuke Ito, Tetsushi Ueta, Jun'ichi Imura and Kazuyuki Aihara : しきい値の変分を利用したカオス制御, IEICE Technical Report, Vol.NLP2011-59, No.106, 193-198, Jul. 2011.
61.	Kazutoshi Kinoshita, Tetsushi Ueta, Hiroshi Kawakami, Jun'ichi Imura and Kazuyuki Aihara : ヒステリシス特性を持つ区分的アファインシステムについての分岐現象, IEICE Technical Report, Vol.NLP2011-13, No.62, 62-64, May 2011.
62.	Masafumi Tsuji, Shigeki Tsuji, Tetsushi Ueta and Takuji Kousaka : スイッチング遅れを伴う断続力学系に対する遅延フィードバック制御の有効性, IEICE Technical Report, Vol.NLP2010-110, No.299, 21-24, Nov. 2010.
63.	Kazutoshi Kinoshita, Tetsushi Ueta, Jun'ichi Imura and Kazuyuki Aihara : 南雲・佐藤モデルの二個結合系における分岐と特性, IEICE Technical Report, Vol.NLP2010-110, No.165, 166, 117-122, Aug. 2010.
64.	Daisuke Ito, Tetsushi Ueta and Kazuyuki Aihara : 結合Izhikevichニューロンにおける分岐現象, IEICE Technical Report, Vol.NLP2010-110, No.165, 166, 159-164, Aug. 2010.
65.	Takaya Nakanishi, Daisuke Ito, Tetsushi Ueta, Jun'ichi Imura and Kazuyuki Aihara : 断続特性をもつ系におけるdelayed feedback controlの検討, IEICE Technical Report, Vol.NLP2010-110, No.165, 166, 111-116, Aug. 2010.
66.	Yusuke Nishiuchi and Tetsushi Ueta : LC回路によって結合されたBVP発振器で起こる非線形現象, IEICE Technical Report, Vol.NLP2010-110, No.165, 166, 105-110, Aug. 2010.
67.	Toyoaki Nabeshima, Kenji Matsuura, Naka Gotoda, Tetsushi Ueta and Yoneo Yano : Design of Skill Bank: Flexible Online-Communities for Motor Skill, IEICE Technical Report, Vol.109, No.453, 59-64, Mar. 2010.
68.	Ippei Nakata, Kenji Matsuura, Naka Gotoda, Tetsushi Ueta and Yoneo Yano : Development of a web-community site for sharing academic review, IEICE Technical Report, Vol.109, No.453, 65-70, Mar. 2010.
69.	Kei Nagao and Tetsushi Ueta : 2次元離散系の不安定周期点近傍における自己相似性, IEICE Technical Report, Vol.NLP2009, No.167, 83-87, Aug. 2009.
70.	Satoshi Nishioka and Tetsushi Ueta : 非線形発振器結合系におけるカオス同期化制御法, IEICE Technical Report, Vol.NLP2009, No.167, 1-5, Aug. 2009.
71.	Akihisa Tamura and Tetsushi Ueta : Izhikevich モデルにおける状態の跳躍の取り扱いと分岐, IEICE Technical Report, Vol.NLP2008, No.45, 63-66, Aug. 2008.
72.	Quentin Brandon, Tetsushi Ueta and Takuji Kousaka : Numerical Bifurcation Analysis of Systems with Affine Switching Conditions, IEICE Technical Report, Vol.NLP2008, No.44, 57-62, Aug. 2008.
73.	Satoshi Nishioka and Tetsushi Ueta : 結合された BVP 発振器にみられる多様な同期現象, IEICE Technical Report, Vol.NLP2008, No.40, 39-44, Aug. 2008.
74.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : 特異な応答における Basin Boundary 構造の消失と数値演算誤差について, IEICE Technical Report, Vol.NLP2008, No.29, 53-56, Jul. 2008.
75.	Kei Nagao and Tetsushi Ueta : 解の写像方向の視覚化を用いた非線形系方程式の周期点検出, IEICE Technical Report, Vol.NLP2008, No.27, 41-46, Jul. 2008.
76.	Quentin Brandon, Tetsushi Ueta and Takuji Kousaka : Bifurcations is a 3-state Piecewise Smooth Dynamical Systems, IEICE Technical Report, Vol.NLP2007, No.25, 13-17, Jun. 2007.
77.	Akitoshi Tamura and Tetsushi Ueta : 簡素な3次元カオス発生器の分岐構造とその結合系に関するカオス同期, IEICE Technical Report, Vol.NLP2006, No.452, 11-16, Jan. 2007.
78.	Toshiyuki Kumano and Tetsushi Ueta : 写像の方向と回数を利用した周期点抽出機構, IEICE Technical Report, Vol.NLP2006, No.451, 81-86, Jan. 2007.
79.	Kimiyasu Shiotsu, Tetsushi Ueta, Shigeki Tsuji, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcations in a gene toggle switch model, IEICE Technical Report, Vol.NLP2005, No.114, 93-98, Jan. 2006.
80.	Hirokazu Komatsu, Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Analysis of type-I and II characteristics of a forced two-dimentional HR neuron model, IEICE Technical Report, Vol.NLP2005, No.113, 87-92, Jan. 2006.
81.	Yoshihiro Imakura, Tetsushi Ueta and Tetsuya Yoshinaga : Estimating Suitable Parameter of Dynamical System Defined by PMART with Eigenvalue, IEICE Technical Report, Vol.NLP2005, No.106, 49-54, Jan. 2006.
82.	Hiroki Yoshii, Tetsushi Ueta and Hiroshi Kawakami : Automatic Tracking Scheme of 3D Bifurcation Diagrams for Nonlinear Dynamical Systems, IEICE Technical Report, Vol.NLP2005, No.103, 55-60, Jan. 2006.
83.	Toshiyuki Kumano, Tetsushi Ueta and Hiroshi Kawakami : Information Extraction by Visualization of Transient States in Chaotic Attractors, IEICE Technical Report, Vol.NLP2005, No.107, 55-60, Jan. 2006.
84.	Yu Toyosaki, Tetsushi Ueta and Takuji Kousaka : Implementation of Switch Synchronizing Occational Delayed Feedback Control with DSP, IEICE Technical Report, Vol.NLP2005, No.115, 99-104, Jan. 2006.
85.	Yu Toyosaki, Tetsushi Ueta and Takuji Kousaka : H-Bridgeインバータに対するスイッチ同期型カオス部分的遅延制御, 電気学会技術報告, Nov. 2005.
86.	Hirokazu Komatsu, Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Bifurcational classification for type-I and II activities in a forced planar H-R model, Int. Symp. Complexity Modelling and its Applications, Nov. 2005.
87.	Koji Sakamoto, Takuji Kousaka, YUE MA and Tetsushi Ueta : Bifurcation and Chaos in an H-Bridge Inverter, IEICE Technical Report, Vol.NLP2005, No.2, 7-12, May 2005. (Summary) In this paper, we discuss a bifurcation and chaos in a H-Bridge Inverter. At first, we show a H-bridge inverter with PWM controller and derive a return map. The fundamental bifurcation phenomena of the periodic points is confirmed by the bifurcation diagrams in one- and two-dimensional parameter plane.
88.	Yusuke Nishiuchi, Tetsushi Ueta and Chikara Ohta : 非線形曲線を導入したネットワークルータにおける輻輳制御, IEICE Technical Report, Vol.NLP2004, No.107, 43-48, Jan. 2005.
89.	Hiroki Yoshii, Tetsushi Ueta and Hiroshi Kawakami : ニュートンホモトピー法を応用した3次元分岐局面の構成法について, IEICE Technical Report, Vol.NLP2004, No.91, 15-20, Jan. 2005.
90.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : 電気シナプスと抑制性シナプスによって結合される変形BVPニューロンモデルにみられる同期現象について, IEICE Technical Report, Vol.NLP2004, No.84, 49-54, Nov. 2004. (Summary) Electrical coupling among inhibitory interneurons has been discovered in various regions of the brain. Since these local networks indicate the sophisticated activity by the interplay between electrical and inhibitory synapses, the emergence of synchronous phenomena have been investigated by many researchers. We propose coupled neuronal models connected by both inhibitory and electrical synapses and investigate the emergence of various synchronous phenomena and its bifurcational structures by the bifurcation analysis.Although it is generally known that strong gap junction synchronize coupled neurons, we show in-phase and anti-phase phenomena in coupled neurons connected by both inhibitory and electrical synapses, and they change to chaotic solutions via period-doubling and pitchfork bifurcations.
91.	Yu Toyosaki, Tetsushi Ueta, Shigeki Tsuji and Takuji Kousaka : Partial Delayed Feedback Control and its DSP Implementation, IEICE Technical Report, Vol.NLP2004, No.14, 23-28, Jun. 2004. (Summary) This paper propose the partial delayed feedback control for chaos circuits with interrupt characteristics. The control input is added during the certain period defined by the switching policy. The total consumed energy may be saved compared with the conventional delayed feedback control system.¥r¥nThis method is easily realized by a digital signal processor (DSP) since the delayed information can be generated by storing the state of the system into the memory in the DSP with a sufficient high-speed sampling rate. As an illustrative example, we apply the control method to a chaotic piecewise smooth circuit.
92.	Sanghoo Hyon, Suguru Emura and Tetsushi Ueta : 脚式走行ロボットにおける非線形振動, IEICE Technical Report, Vol.NLP2004, No.50, 47-52, May 2004. (Summary) In this paper, we report on the analysis and orbital stabilization of periodic gaits of a planar one-legged robot. The robot is installed with linear springs at the telescopic knee joint and torsional springs at the hip joint. Two stabilizing controllers that asymptotically stabilize periodic passive gaits are derived. The main part of the second controller is based on ``energy-preserving principle¥" and generates interesting quasi-periodic running gaits, which can be seen in Hamiltonian system. With an additional adaptive scheme similar to delayed feedback in chaotic system, the controller achieves orbitaly stabilization to (unknown) passive running gaits.
93.	Kenji Matsuura, Tetsushi Ueta, Masahiko Sano and Shunichiro Oe : A Study on Polishing up the Security Policy Documents in accordance with Information Security Management System, 情報処理学会研究報告, Vol.2004-DSM-33, 59-64, May 2004. (Summary) 現在セキュリティ対策は，個人情報保護のみならず，知的財産の管理保護や情報資産の活用といった側面からも重要であり，大学組織においても取り組まれているところである．特に，ポリシ文書はセキュリティ規範となるものであり，その運用においてはISMS認証制度などに準拠した運用体制の確保とサイクリックな監査が行われる事が望ましい．徳島大学では，ISMS準拠のセキュリティ対策とポリシの策定を目的として，全学展開による活動を行っている．また，そのための運用システムを開発した．そこで本稿では，大学におけるISMS規格準拠のセキュリティ運用手法を考察する．
94.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : Gapjunction 結合ニューロンモデルにみられる分岐現象について, IEICE Technical Report, Vol.NLP2003, No.139, 5-10, Dec. 2003.
95.	Tetsushi Ueta and Hiroshi Kawakami : 線形回路の発振条件と非線形回路の Hopf 分岐に関する考察, IEICE Technical Report, Vol.NLP2003, No.84, 7-12, Oct. 2003.
96.	Atsushi Tsuda, Shigeki Tsuji, Tetsushi Ueta and Hiroshi Kawakami : 極配置法カオス制御におけるベイスンについて, IEICE Technical Report, Vol.NLP2003, No.78, 49-54, Sep. 2003.
97.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : 単純な3次元自律系に生じるトーラス, IEICE Technical Report, Vol.NLP2003, No.52, 41-46, Jul. 2003.
98.	Shigeki Tsuji, Tetsushi Ueta and Hiroshi Kawakami : 電流結合型BVP発振器対にみられる分岐現象とカオス, IEICE Technical Report, Vol.NLP2003, No.49, 23-28, Jul. 2003.
99.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : 変形BVP発振器における引力圏形成モデル, IEICE Technical Report, Vol.NLP2003, No.3, 13-18, May 2003.
100.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : 3次元自律系ニューロンモデルにみられるバースト発火とその分岐, IEICE Technical Report, Vol.NLP2003, No.5, 25-30, May 2003.
101.	Yoshihito Yasuhara, Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : 状態と時刻に依存したスイッチを有する非線形回路の解析, IEICE Technical Report, Vol.NLP2002, No.76, 43-48, Nov. 2002.
102.	Yusuke Nishiuchi, Tetsushi Ueta and Hiroshi Kawakami : 変形BVP発振器にみられる特異な応答とその Basin Boundary について, IEICE Technical Report, Vol.NLP2002, No.15, 45-50, Jun. 2002.
103.	Atsushi Tsuda, Yusuke Nishiuchi, Akinori Tsuji and Tetsushi Ueta : DSPを用いた非線形信号処理応用, IEICE Technical Report, Vol.NLP2002, No.9, 7-12, Jun. 2002.
104.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : 周期外力で駆動される Gap Junction 結合 BVP 発振器, IEICE Technical Report, Vol.NLP2002, No.14, 39-44, Jun. 2002.
105.	Yoko Uwate, Yoshifumi Nishio, Tetsushi Ueta, Tohru Kawabe and Tohru Ikeguchi : Solving Ability of Hopfield Neural Networks with Chaotic Noise and Burst Noise for QAP, IEICE Technical Report, Vol.NLP2002, No.109, 59-64, Mar. 2002.
106.	Hideaki Harada, Takuji Kousaka, Minoru Abe, Hiroshi Kawakami and Tetsushi Ueta : Calculation of the Bifurcation sets in the Buck Converter, IEICE Technical Report, Vol.NLP2002, No.100, 472-54, Jan. 2002. (Summary) Recently, various bifurcation phenomena have been observed in the simple power electronics circuits. Since current or voltage controlled converters have wide industrial application, it is a important problem to clarity the property of the power electronics systems in the mathematical point of view. However, there are very few methods being developed in the literature for the bifurcation analysis and its property. In this paper, we investigate the bifurcation phenomena in a simple DC-DC buck converter. We have also propose a method to trace the local bifurcation sets in such converters. Some of theoretical results are verified by laboratory experiments.
107.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation and Chaos of Periodic Solutions in the Custom BVP Oscillator, IEICE Technical Report, Vol.NLP2001, No.63, 71-78, Nov. 2001.
108.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : The design and its implementation of the bursting in BVP oscillator, IEICE Technical Report, Vol.NLP2001, No.57, 27-34, Nov. 2001. (Summary) Bursting observed in nerve membranes is regarded to be important when the information representation problem in brain is considered. Until now, various bursting responses are illustrated in the mathematical model, and accordingly their related bifurcation mechanisms have been clarified. In this paper, we propose an oscillator showing bursting response with a simple circuitry, the circuit equation is represented as a BVP(FitzHugh-Nagumo)model equation. Firstly we investigate bifurcation structure in the autonomous system. Then an effective and reasonable perturbation of theh external force to this bifurcation structure to generate various bursting responses. Secondly we show various burst oscillations are observed by changing the frequency and amplitude of sinusoidal wave. Finally we show a laboratory experiments of the circuit.
109.	Hisayo Miyazaki, Tetsushi Ueta, Takuji Kousaka and Hiroshi Kawakami : Bifurcation in Coupled BVP Oscillators, IEICE Technical Report, Vol.NLP2001, No.56, 35-42, Sep. 2001. (Summary) BVP oscillator is the simplest mathematical model describing a neural activity. However, even if two BVP oscillators are merely compled by a linear element, the whole system exhibits complicated behavior. For studying such coupled system, identical oscillators are often used as an oscillator unit since symmetrical properties sometimes reduce the bifurcation problem about equilibria and periodic solutions. In this paper, we analyze a coupled BVP oscillators with asymmetrical coupling structure, besides, each oscillator has different internal registance. We should the whole four-dimensional system, but the system shows strange attractors. We calculate bifurcation diagrams and confirm relevant phenomena in the laboratory experiments. Furthermore, we try to reduce the system dimension by removing passive and active elements.
110.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : The generating mechanism of bursting in FitzHugh-Nagumo model and design of its external force, IEICE Technical Report, Vol.NLP2001, No.44, 27-34, Sep. 2001. (Summary) Firing phenomenon called spiking and bursting observed in nerve cell membranes are regarded to be important when the information representation problem in brain is considered. Until now, various bursting responses observed in the mathematical model have been classified, and accordingly their related bifurcation mechanisms on have been clarified. In this papaer, we propse a FitzHugh-Nagumo model with a simple periodic external force. The external input gives periodic activity to the autonomous system, and it is expected that the generating mechanism of bursting is constructed. The parameter regions sectioned by bifurcation curves are obtained as bursting or spiking regions.
111.	Yoshihito Yasuhara, Takuji Kousaka, Tetsushi Ueta, Minoru Abe and Hiroshi Kawakami : Experimental Control of Chaotic Behavior in a State-Dependent Nonlinear Circuit, IEICE Technical Report, Vol.NLP2001, No.8, 51-58, May 2001. (Summary) There have been numerous theoretical and experimental investigations on the controlling chaos in the piecewise linear systems. This paper reports a method for controlling chaos in the nonlinear dynamical systems with interrupted characteristics. Some of theoretical results are confirmed by experiment al laboratory.
112.	Shigeki Tsuji, Tetsushi Ueta, Hiroshi Kawakami and Kazuyuki Aihara : 周期外力を付加したAmari-Hopfieldニューロン対におけるバースト応答の分岐, IEICE Technical Report, Vol.NLP2000, No.167, 25-32, Mar. 2001. (Summary) When considering the mechanism of an information processing mechanism in the brain of a living body, the problem of information coding of a neuron, etc., the mathematical model of a neuron is indispensable. According to a point of view and the purpose, various models are formulized until now, and analysis is advanced. In this paper, correspondence is investigated about a classification of bifuracation by Izhikevich et al., and a burst response in an Amari-Hopfield model. It is thought that it is important to investigate the various burst response type which realizes a burst response of the given specification, and it becomes information useful as a design problem of a burst response to solve the bifurcation diagram according to the parameter of external force.
113.	Tetsushi Ueta, Takuji Kousaka, Hisayo Miyazaki and Hiroshi Kawakami : Bifurcation and Chaos in Coupled BVP Oscillators, IEICE Technical Report, Vol.NLP2000, No.166, 17-24, Mar. 2001. (Summary) BVP oscillator is one of classic model exhibiting typical nonlinear phenomena in the planar autonomous system and it has been studied for last three decades. This report shows bifurcation and chaos in resistively coupled BVP oscillators. Each oscillator has different value of internal resister, i.e., different frequency oscillators are coupled. Bifurcation diagrams are obtained numerically from mathematical model and chaotic parameter regions are clarified. This result also points out that the coupling system of identical oscillators does not behave chaotically with reasonable parameter range. We also confirm the existence of period-doubling cascades and chaotic attractors in experimental laboratory.
114.	Takuji Kousaka, Tetsushi Ueta, Hiroshi Kawakami, Shoichi Tahara and Minoru Abe : On an Electric Circuit Interrupted by Own State and a Periodic Interval, --- Control ---, IEICE Technical Report, Vol.NLP2000, No.100, 57-62, Nov. 2000. (Summary) This report consider a system interrupted by own state and a periodic interval. We know above system has prospects of occurrence of border-collision bifurcation. Firstly, we propose a simple model that occurs border-collision bifurcation, and consider periodic orbits, their stabilities and bifurcations. Some of theoretical results are verified by laboratory experiments. Secondly, we analyze dc-dc converter. Finally, We propose a method to trace bifurcation sets for a piecewise nonlinear equation interrupted by own state and periodic interval.
115.	Shigeki Tsuji, Hisayo Miyazaki, Tetsushi Ueta and Hiroshi Kawakami : Calculation of the Isocline for the Fixed Point with a specifiled Argument of Complex Multipliers, IEICE Technical Report, Vol.NLP2000, No.102, 69-74, Nov. 2000. (Summary) This paper proposes a calculation method to obtain the location of the fixed point in given nonlinear discrete system when the argument of complex multipliers is specified. We can calculate isoclines corresponding to the specified arguments, then the stability and instantaneous phase around the fixed point is clarified. As an application, we also propose a new calculation method of NS bifurcation parameter values with specified argument. In addition, cross points of a cusp in a periodic entrainment region and the NS bifurcation curve is identified by this application.
116.	Takuji Kousaka, Takashi Kido, Tetsushi Ueta and Hiroshi Kawakami : On an Electric Circuit Interrupted by Own State and a Periodic Interval, --- Bifurcation ---, IEICE Technical Report, Vol.NLP99, No.123, 31-38, Nov. 1999. (Summary) This report consider a system interrupted by own state and a periodic interval. We know above system has prospects of occurrence of border-collision bifurcation. Firstly, we propose a simple model that occurs border-collision bifurcation, and consider periodic orbits, their stabilities and bifurcations. Some of theoretical results are verified by laboratory experiments. Secondly, we analyze dc-dc converter. Finally, We propose a method to trace bifurcation sets for a piecewise nonlinear equation interrupted by own state and periodic interval.
117.	Tetsushi Ueta, Guanrong Chen and Tohru Kawabe : 区分線形力学系における不安定軌道の効果的な計算方法とカオス制御, IEICE Technical Report, Vol.NLP99, No.27, 9-16, Jun. 1999. (Summary) This paper describes a simple method for calculating unstable periodic orbits (UPOs) and their control in piecewisc-linear autonomous systems. The algorithm can be used to obtain any desired UPO embedded in a chaotic a. ttractor ; and the UPO can be stabilized by a simple state feedback control. A brief stability analysis of the controlled system is also given.
118.	武内朗, Tetsushi Ueta and Kenji Terada : 相似領域可変型フラクタル符号化の画像領域分割への応用, IEICE Technical Report, Vol.NLP99, No.25, 85-92, Jun. 1999.
119.	Takashi Kido, Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Border-collision 分岐を生じる簡素な構成の回路について, IEICE Technical Report, Vol.NLP99, No.123, 31-38, May 1999.
120.	Toshikazu Masaki, Tetsushi Ueta and Kenji Terada : フラクタル符号化を用いた指紋識別の試み, IEICE Technical Report, Vol.NLP99, No.32, 39-44, May 1999.
121.	武内朗, Tetsushi Ueta and Kenji Terada : フラクタル力学系に基づいた画像の領域分割, IEICE Technical Report, Vol.PRMU99, No.211, 143-148, Jan. 1999.
122.	岡久英一郎, Tetsushi Ueta, Yoshifumi Nishio and 河辺徹 : 組合せ最適化問題におけるカオスノイズ注入型ニューラルネットワークの探索能力の検討, IEICE Technical Report, Vol.NLP98, No.38, 1-8, Jul. 1998.
123.	Takuji Kousaka, Hiroyuki Kitajima, Tetsushi Ueta, Tetsuya Yoshinaga and Hiroshi Kawakami : 不連続性をもつ力学系における分岐計算法, IEICE Technical Report, Vol.NLP98, No.30, 1-8, Jul. 1998.
124.	Takashi Kido, Takuji Kousaka, Hiroshi Kawakami and Tetsushi Ueta : 抵抗で結合した方形波発振器の同期現象, IEICE Technical Report, Vol.NLP98, No.92, 9-16, May 1998.
125.	武内朗, Tetsushi Ueta and Kenji Terada : フラクタル力学系を用いた画像の領域分割, IEICE Technical Report, Vol.NLP98, No.6, 37-44, May 1998.
126.	塩田真, Tetsushi Ueta and Hiroshi Kawakami : 3次元パラメータ空間における分岐図の構成と視覚化, IEICE Technical Report, Vol.NLP97, No.97, 93-100, Oct. 1997.
127.	高坂拓司, Tetsushi Ueta, Hiroshi Kawakami, Ken'ichi Fujimoto and 林保幸 : 断続RC回路を持つBVP発振器について, IEICE Technical Report, Vol.NLP97, No.112, 103-108, Oct. 1997.
128.	高坂拓司, 馬越豊, Tetsushi Ueta and Hiroshi Kawakami : 状態に依存したスイッチで切り替わる非線形系の分岐, IEICE Technical Report, Vol.NLP97, No.14, 97-104, May 1997.
129.	Tetsushi Ueta and Hiroshi Kawakami : 2自由度マニュピュレータの繰り返し動作にみられるカオス的振動, IEICE Technical Report, Vol.NLP97, No.112, 103-108, May 1997.
130.	馬越豊, 高坂拓司, Tetsushi Ueta and Hiroshi Kawakami : 外力と状態で動作するスイッチを含む発振回路の解析, IEICE Technical Report, Vol.NLP96, No.169, 77-84, Mar. 1997.
131.	Takuji Kousaka, Hiroshi Kawakami and Tetsushi Ueta : 結合した2つの異なる方形波発振器に生じる周期解の解析, IEICE Technical Report, Vol.NLP96, No.145, 33-40, Feb. 1997.
132.	杖池雅史, Tetsushi Ueta and Hiroshi Kawakami : 結合ニューロン発振器の同期現象, IEICE Technical Report, Vol.NLP96, No.137, 101-107, Feb. 1997.
133.	杖池雅史, Tetsushi Ueta and Hiroshi Kawakami : 結合した興奮抑制対ニューロン回路の同期, IEICE Technical Report, Vol.NLP96, No.61, 23-28, Jul. 1996.
134.	杖池雅史, Tetsushi Ueta and Yoshifumi Nishio : カオス的 2 次元写像を用いた暗号系の電子メイルへの応用, IEICE Technical Report, Vol.NLP96, No.19, 61-66, May 1996.
135.	杖池雅史, Tetsushi Ueta and 坂本敏幸 : 非線形写像の引力圏の動画像化について, IEICE Technical Report, Vol.OSF96, No.7, 39-44, May 1996.
136.	Tetsushi Ueta and Hiroshi Kawakami : 2次元自律系における解軌道の位相的分類, IEICE Technical Report, Vol.NLP96, No.25, 105-110, May 1996.
137.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : 方形波発振器を用いた電子ホタルの同期現象, IEICE Technical Report, Vol.NLP96, No.5, 27-32, May 1996.
138.	Tetsushi Ueta and Hiroshi Kawakami : 結合系のカオス制御, IEICE Technical Report, Vol.NLP95, No.81, 133-139, Oct. 1995.
139.	Tetsushi Ueta and Hiroshi Kawakami : リミットサイクルに関する分岐の一計算法, IEICE Technical Report, Vol.NLP95, No.43, 47-52, Oct. 1995.
140.	杖池雅史, 高坂拓司, 曽根直人, Tetsushi Ueta, Yoshifumi Nishio and Masakatu Morii : カオスを用いた暗号機構のMIMEへの実装, IEICE Technical Report, Vol.OSF95, No.10, 11-16, May 1995.
141.	Takuji Kousaka, Tetsushi Ueta and Hiroshi Kawakami : Destabilization of Stable Orbits by Controlling Chaos, IEICE Technical Report, Vol.NLP94, No.102, 51-58, Mar. 1995. (Summary) We propose a method of destabilizing stable equilibria and limit cycles by using controlling chaos.A chaotic state can be easily generated from stable states by our method.A stable orbit is destabilized by a linear feedback technique with unstable pole assignment.As illustrated examples,a stable limit cycle of the van der Pol equation and stable equilibria of BVP equation are destabilized to chaos.Gradient system is also destabilized and a technique to escape from local minimum is discussed.
142.	Tetsushi Ueta and Hiroshi Kawakami : 高階自律系におけるカオス制御, IEICE Technical Report, Vol.NLP94, No.79, 71-78, Dec. 1994.
143.	Hiroshi Kawakami and Tetsushi Ueta : Control theory as applied to controlling discrete chaotic dynamical systems, IEICE Technical Report, Vol.NLP94, No.63, 175-182, Oct. 1994.
144.	Tetsushi Ueta and Hiroshi Kawakami : Stabilization method of controlling chaotic systems, IEICE Technical Report, Vol.NLP94, No.62, 167-174, Oct. 1994.
145.	森本修, Tetsushi Ueta and Hiroshi Kawakami : 不連続波形を印加した非線形系の分岐現象の追跡法とそのBVP方程式への応用, IEICE Technical Report, Vol.NLP94, No.2, 9-14, May 1994.
146.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation phenomena in a Josephson junction circuit coupled by a resistor, IEICE Technical Report, Vol.NLP93, No.91, 47-54, Mar. 1994.
147.	Tetsushi Ueta and Hiroshi Kawakami : Bifurcation of Heteroclinic Orbits in a Circuit containing a Jasephson Junction Element, IEICE Technical Report, Vol.NLP92, No.105, 43-48, Mar. 1993. (Summary) Similar equation is obtained from a simple pendulum with an elastic restoring force.In such a system there exist many saddles and sinks affected by the sinusoidal restoring term.In this paper we investigate heteroclinic bifurcations correlated with separatrices of the saddle points.The topological classification of the heteroclinic orbit is achieved by defining a linking number between the heteroclinic orbit and a suitable cross section.

Report:

1.	Tetsushi Ueta : マネジメントシステムの情報セキュリティ版がもたらすもの, SS研ニュースレター選集, Vol.15, 17-27, May 2015.
2.	Satoshi Kiriyama, Takao Hanabusa, Hideo Araki, Koichi Nakamura, Shingo Kuroiwa, Shoichiro Fujisawa, Masanobu Haraguchi, Toshiaki Tamaki, Tatsuji Haneji, Yoshihisa Takaishi, Seishi Kitayama, Makoto Ohashi and Tetsushi Ueta : 特色ある大学教育支援プログラム「進取の気風」を育む創造性教育の推進平成17年度報告書, 特色ある大学教育支援プログラム「進取の気風」を育む創造性教育の推進平成17年度報告書, Tokushima, Mar. 2006.
3.	Hiroshi Kawakami, Tetsuya Yoshinaga and Tetsushi Ueta : Nonlinear Science Laboratory, Supplemental report of Kaken, Tokushima, Feb. 2002.
4.	Hiroshi Kawakami, Tetsuya Yoshinaga and Tetsushi Ueta : 有限群の表現を用いた対称結合非線形回路の合成法に関する研究, 平成11-13年度科学研究費補助金(基盤研究(C)(2))研究成果報告書, Tokushima, Feb. 2002.
5.	Tetsushi Ueta : 電気回路系にみられるカオスの制御実装, 財団法人実吉奨学会研究助成受給者研究報告集, Vol.16, 37-40, Tokyo, Mar. 1999.
6.	Hiroshi Kawakami, Tetsuya Yoshinaga and Tetsushi Ueta : 系の構造に基づく非線形回路の解析法に関する研究, 平成8-9年度科学研究費補助金(基盤研究(C)(2))研究成果報告書, Tokushima, Feb. 1998.

Grants-in-Aid for Scientific Research (KAKEN Grants Database @ NII.ac.jp)

データサイエンスに基づくチームスポーツ戦術モデルとスキル学習支援 (Project/Area Number: 22K12314 )
Stabilization of natural motions embedded in chaotic responses of a multilink robot; Applications of bifurcation theory (Project/Area Number: 21K04109 )
持続的研究の効率化を支援するシステムの研究 (Project/Area Number: 18K11572 )
Study on portfolio to support sustainable growth of research community (Project/Area Number: 15K12168 )
A design method and applications of periodic solutions in hybrid systems by variations of threshold values (Project/Area Number: 25420373 )
Construction of a new technology and science education system (Project/Area Number: 21500878 )
Aggregation of bifurcation analysis methods for piecewise nonlinear dynamical systems (Project/Area Number: 19560385 )
非線形回路における特異な応答とぼやけた引力圏境の解析 (Project/Area Number: 15760293 )
非線形力学系の不安定化制御を応用した創発システムの研究 (Project/Area Number: 12750365 )
Synthesis of Symmetrical Nonlinear-Circuits with Finite Group Representaion (Project/Area Number: 11650383 )
区分非線形力学系の分岐現象の解析 (Project/Area Number: 10750301 )
情報処理系へのカオス制御の応用に関する研究 (Project/Area Number: 08750483 )
Study on Methods of Analysis of Nonlinear Circuits with Symmetrical Structure (Project/Area Number: 08650431 )
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Professor : Ueta, Tetsushi

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Grants-in-Aid for Scientific Research (KAKEN Grants Database @ NII.ac.jp)