Papers - OHIRA Toru

Amplitude Enhancements through rewiring of a non-autonomous delay system Reviewed

Kenta Ohira, Toru Ohira, Hideki Ohira

Chaos: An Interdisciplinary Journal of Nonlinear Science   Vol. 35   page： 041101   2025.4

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DOI： https://doi.org/10.1063/5.0252300

Collective behaviors emerging from chases and escapes Invited Reviewed

Artifitial Life Robotics   Vol. 29   page： 1   2024.1

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Authorship：Lead author  

DOI： https://doi.org/10.1007/s10015-023-00928-1

Dynamics with Transient Resonating Oscillations Reviewed

Kenta Ohira and Toru Ohira

Journal of the Physical Society of Japan   Vol. 92 ( 6 )   2023.6

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DOI： https://doi.org/10.7566/JPSJ.92.064002

Solving a Delay Differential Equation through Fourier Transform Invited Reviewed

Kenta Ohira, Toru Ohira

Physics Letters A   Vol. 531   page： 130138   2025.1

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DOI： https://doi.org/10.1016/j.physleta.2024.130138

Transient Reviving Dynamics with an Exact Solution for Delay Differential Equations Invited Reviewed

Kenta Ohira and Toru Ohira

Journal of the Physical Society of Japan   Vol. 93 ( 9 )   2024.9

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DOI： https://doi.org/10.7566/JPSJ.93.094801

The mechanism of pattern transitions between formation and dispersion Invited Reviewed

Shin Nishihara and Toru Ohira

Journal of Theoretical Biology   Vol. 581   page： 111736   2024.3

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DOI： https://doi.org/10.1016/j.jtbi.2024.111736

Pursuit and Evasion: from singles to groups Invited Reviewed

Sota Yoshihara, Toru Ohira

Sota Yoshihara and Toru Ohira   Vol. 2207   page： 012014   2022.3

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Authorship：Last author,　Corresponding author   Language：English  

DOI： https://doi.org/10.1088/1742-6596/2207/1/012014

Other Link： https://iopscience.iop.org/article/10.1088/1742-6596/2207/1/012014

A simple model of on--demand transporter Invited Reviewed

Yuhei Okubo, Takashi Shimada, Toru Ohira

Proceedings of 40th JSST Annual International Conference on Simulation Technology     page： 32 - 34   2021.9

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

Delayed Gambler's Ruin Invited Reviewed

Tomohisa Imai, Toru Ohira

  Vol. 39 ( 4 ) page： 247 - 251   2020.12

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Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Difficulty Levels of Mathematical Problems and Machine Learning Invited Reviewed

Yuto Toida, Toru Ohira

  Vol. 12 ( 2 ) page： 49 - 53   2020.5

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Zero-correlation entanglement Reviewed

Toru Ohira

Progress of Theoretical and Experimental Physics   Vol. 2020 ( 1 )   2020.1

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© 2020 The Author(s) 2020. Published by Oxford University Press on behalf of the Physical Society of Japan. We consider a quantum entangled state for two particles, each particle having two basis states, which includes an entangled pair of spin 1/2 particles. We show that, for any quantum entangled state vectors of such systems, one can always find a pair of observable operators X, Y with zero correlations (ψ|XY|ψ-ψ|X|ψ (ψ|Y|ψ= 0). At the same time, if we consider the analogous classical system of a "classically entangled" (statistically non-independent) pair of random variables taking two values, one can never have zero correlations (zero covariance, E[XY]-E[X]E[Y] = 0). We provide a general proof to illustrate the different nature of entanglements in classical and quantum theories.

DOI： 10.1093/ptep/ptz149

Scopus

Delayed gambler’s ruin Reviewed

Tomohisa Imai, Toru Ohira

Stability, Control and Application of Time-Delay Systems     page： 333 - 347   2019.1

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Language：Japanese   Publishing type：Part of collection (book)  

© 2019 Elsevier Inc. All rights reserved. We present here a new extended model of the gambler’s ruin problem by incorporating delays in receiving of rewards and paying of penalties. When there is a difference between two delays, an exact analysis of the ruin probability is difficult. We derive an approximate scheme to find an effective shift in the initial assets of the gambler. Through comparison against computer simulations, this approximation is shown to work for small differences between the two delays.

DOI： 10.1016/B978-0-12-814928-7.00016-0

Scopus

On statistical independence and no-correlation for a pair of random variables taking two values: Classical and quantum Reviewed

Toru Ohira

Progress of Theoretical and Experimental Physics   Vol. 2018 ( 8 )   2018.8

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Language：Japanese   Publishing type：Research paper (scientific journal)  

© 2018 The Author(s). It is well known that when a pair of random variables is statistically independent, it has nocorrelation (zero covariance, E[XY]-E[X[E[Y] = 0), and that the converse is not true. However, if both of these random variables take only two values, no-correlation entails statistical independence.We provide here a general proof.We subsequently examine whether this equivalence property carries over to quantum mechanical systems.A counter-example is explicitly constructed to show that it does not. This observation provides yet another simple theorem separating classical and quantum theories.

DOI： 10.1093/ptep/pty086

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Scopus

双方向白色化ニューラルネットワーク Reviewed

藤本勇希, 大平徹

電子情報通信学会論文誌 D   Vol. J101-D ( 1 ) page： 202-210   2018.1

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DOI： 10.14923/transinfj.2017JDP7027

Delays in Gambler's Ruin and Random Relays

Ohira Toru

IFAC PAPERSONLINE   Vol. 51 ( 14 ) page： 207-211   2018

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DOI： 10.1016/j.ifacol.2018.07.224

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A Neural Network Model with Bidirectional Whitening. Reviewed

Yuki Fujimoto,Toru Ohira

Artificial Intelligence and Soft Computing - 17th International Conference, ICAISC 2018, Zakopane, Poland, June 3-7, 2018, Proceedings, Part I     page： 47-57   2018

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A neural network model with bidirectional whitening Reviewed

Yuki Fujimoto, Toru Ohira

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)   Vol. 10841   page： 47 - 57   2018

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Verlag  

We present here a new model and algorithm which performs an efficient Natural gradient descent for multilayer perceptrons. Natural gradient descent was originally proposed from a point of view of information geometry, and it performs the steepest descent updates on manifolds in a Riemannian space. In particular, we extend an approach taken by the “Whitened Neural Networks” model. We make the whitening process not only in the feed-forward direction as in the original model, but also in the back-propagation phase. Its efficacy is shown by an application of this “Bidirectional Whitened Neural Networks” model to a handwritten character recognition data (MNIST data).

DOI： 10.1007/978-3-319-91253-0_5

Scopus

Group chase and escape model with chasers' interaction Reviewed

Takuya Saito, Tomomichi Nakamura, Toru Ohira

PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS   Vol. 447   page： 172 - 179   2016.4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Group chase and escape is a new direction of studying collective behaviors merged with the traditional mathematical problems of chases and escapes proposed by Kamimura and Ohira in 2010. In their model, the chasers recognize only the escapees and pursue the nearest neighbor escapee, and the escapees recognize only the chasers and flee from the nearest neighbor chaser. We call the basic moving rule the nearest opponent interaction (NOI) strategy. In this paper we introduce a new strategy in the model. It is a local interaction that the chasers do not get too close each other, where we call the chasers' local interaction (CLI) strategy. The result of comparisons of the two strategies shows that when the number of the chasers is relatively small compared to the number of the escapees, the trapping time by the CLI strategy is much shorter than that by the NOI strategy. On the other hand, when the number of the chasers is larger than that of the escapees, this advantage of the CLI strategy does not appear. Also, we find that although chasers form clusters (spatial aggregates of chasers) when we apply the NOI strategy, the clusters appear less when we apply the CLI strategy. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physa.2015.12.023

Web of Science

Chases and escapes, and optimization problems Reviewed

Toru Ohira, Tadaaki Hosaka, Tomoaki Nogawa

Artificial Life and Robotics   Vol. 20 ( 3 ) page： 257 - 261   2015.10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer-Verlag Tokyo  

We propose a new approach for solving combinatorial optimization problem by utilizing the mechanism of chases and escapes, which has a long history in mathematics. In addition to the well-used steepest descent and neighboring search, we perform a chase-and-escape game on the ‘‘landscape’’ of the cost function. We have created a concrete algorithm for the Traveling Salesman Problem. Our preliminary test indicates a possibility that this new fusion of chases and escapes problem into combinatorial optimization search is fruitful.

DOI： 10.1007/s10015-015-0220-2

Web of Science

Scopus

Quantum Square Well Bound States Described by Equations with Non-Locality Reviewed

OHIRA Toru

Interdiscip Inf Sci   Vol. 19 ( 1 ) page： 61-64 (J-STAGE)-64   2013.8

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Special Issue: The 4th Young Scientist Meeting on Statistical Physics and Information Processing in Sendai

DOI： 10.4036/iis.2013.61

J-GLOBAL

Random Walks with Delay Reviewed

OHIRA Toru

  Vol. 32 ( 1 ) page： 55-57   2013.3

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Ranking and Winning in Tournaments Reviewed

TOKUYAMA Kichi, MAEMURA Ryuta, YOKOUCHI Kengo, OHIRA Toru

  Vol. 19th   page： 41-43   2013

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J-GLOBAL

Delayed pursuit-escape as a model for virtual stick balancing Reviewed

MILTON John G, FUERTE Andres, BELAIR Christophe, LIPPAI Joshua, KAMIMURA Atsushi, OHIRA Toru

Nonlinear Theory Its Appl IEICE (Web)   Vol. 4 ( 2 ) page： 129-137 (J-STAGE)-137 - 137   2013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

The process of pursuit and escape underlies many biological phenomena ranging from predator-prey interactions, combat and sporting activities. Time delays, τ, arise as a consequence of the time taken to identify the opponent, formulate a strategy, and then act upon it. Here we consider virtual stick balancing (VSB) as a delayed pursuit-escape task. The movements of the target in VSB are programmed to resemble those of balancing a stick at the fingertip. A model of delayed pursuit-escape is developed by assuming that the target movements are governed by a simple random walk and the movements of the pursuer by a delayed random walk biased towards the target when τ=0. When τ > 0 the movements can become transiently biased away from the target. The model reproduces the oscillatory dynamics and statistical properties of VSB. For both model and VSB, transients occur in which the pursuer moves inappropriately causing increases in tracking error. The presence of a signature, or trigger, for impending escape suggests the possibility that escapes can be predicted before they occur.

DOI： 10.1587/nolta.4.129

J-GLOBAL

Group chase and escape with conversion from targets to chasers Reviewed

Ryosuke Nishi, Atsushi Kamimura, Katsuhiro Nishinari, Toru Ohira

PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS   Vol. 391 ( 1-2 ) page： 337 - 342   2012.1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We study the effect of converting caught targets into new chasers in the context of the recently proposed 'group chase and escape' problem. Numerical simulations have shown that this conversion can substantially reduce the lifetimes of the targets when a large number of them are initially present. At the same time, it also leads to a non-monotonic dependence on the initial number of targets, resulting in the existence of a maximum lifetime. As a counter-effect for this conversion, we further introduce self-multiplying abilities to the targets. We found that the longest lifetime exists when a suitable combination of these two effects is created. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physa.2011.08.010

Web of Science

Collective Motions of Chases and Escapes Reviewed

Ohira Toru

PROCEEDINGS OF THE SEVENTEENTH INTERNATIONAL SYMPOSIUM ON ARTIFICIAL LIFE AND ROBOTICS (AROB 17TH '12)     page： 538-540   2012

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Web of Science

Collective Motions of Chases and Escapes Reviewed

Toru Ohira

PROCEEDINGS OF THE SEVENTEENTH INTERNATIONAL SYMPOSIUM ON ARTIFICIAL LIFE AND ROBOTICS (AROB 17TH '12)     page： 538 - 540   2012

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ALIFE ROBOTICS CO, LTD  

We discuss a new take on an old mathematical problem of chase and escape. We consider one group chases another, called "group chase and escape", by presenting simple models. We have found that even a simple model can exhibit rich and complex behavior. The model has been extended to investigate the effects of (1) fluctuations in chasing and escaping movements, (2) reaction delays when chasing, and (3) the conversion of caught escapees to new chasers. We show that these effects can add further complexity and result in unexpected behaviors.

Web of Science

Vulnerability to paroxysmal oscillations in delayed neural networks: A basis for nocturnal frontal lobe epilepsy? Reviewed

Austin Quan, Ivan Osorio, Toru Ohira, John Milton

CHAOS   Vol. 21 ( 4 ) page： 047512   2011.12

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Resonance can occur in bistable dynamical systems due to the interplay between noise and delay (tau) in the absence of a periodic input. We investigate resonance in a two-neuron model with mutual time-delayed inhibitory feedback. For appropriate choices of the parameters and inputs three fixed-point attractors co-exist: two are stable and one is unstable. In the absence of noise, delay-induced transient oscillations (referred to herein as DITOs) arise whenever the initial function is tuned sufficiently close to the unstable fixed-point. In the presence of noisy perturbations, DITOs arise spontaneously. Since the correlation time for the stationary dynamics is similar to tau, we approximated a higher order Markov process by a three-state Markov chain model by rescaling time as t -> 2s tau, identifying the states based on whether the sub-intervals were completely confined to one basin of attraction (the two stable attractors) or straddled the separatrix, and then determining the transition probability matrix empirically. The resultant Markov chain model captured the switching behaviors including the statistical properties of the DITOs. Our observations indicate that time-delayed and noisy bistable dynamical systems are prone to generate DITOs as switches between the two attractors occur. Bistable systems arise transiently in situations when one attractor is gradually replaced by another. This may explain, for example, why seizures in certain epileptic syndromes tend to occur as sleep stages change. (C) 2011 American Institute of Physics. [doi:10.1063/1.3664409]

DOI： 10.1063/1.3664409

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PubMed

Group Chase and Escape Problems Reviewed

KAMIMURA Atsushi, OHIRA Toru

Butsuri   Vol. 66 ( 3 ) page： 205-208 - 208   2011.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

A team approach to undergraduate research in biomathematics: Balance control Reviewed

J. Milton, A. Radunskaya, W. Ou, T. Ohira

Mathematical Modelling of Natural Phenomena   Vol. 6   page： 260-277   2011.1

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The question, how does an organism maintain balance? provides a unifying theme to introduce undergraduate students to the use of mathematics and modeling techniques in biological research. The availability of inexpensive high speed motion capture cameras makes it possible to collect the precise and reliable data that facilitates the development of relevant mathematical models. An in-house laboratory component ensures that students have the opportunity to directly compare prediction to observation and motivates the development of projects that push the boundaries of the subject. The projects, by their nature, readily lend themselves to the formation of inter-disciplinary student research teams. Thus students have the opportunity to learn skills essential for success in today's workplace including productive team work, critical thinking, problem solving, project management, and effective communication. © EDP Sciences, 2011.

DOI： 10.1051/mmnp/20116614

Scopus

Stochastic Resonance with Group Chase and Escape Reviewed

Atsushi Kamimura, Shigenori Matsumoto, Tomoaki Nogawa, Nobuyasu Ito, Toru Ohira

2011 21ST INTERNATIONAL CONFERENCE ON NOISE AND FLUCTUATIONS (ICNF)     page： 200 - 203   2011

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We describe a simple model developed under the new idea of one group chasing another called, "group chase and escape". We will demonstrate that even a simple model can exhibit rather rich and complex behavior. In particular, we show that the appropriate level of fluctuation in each step of the process for chase and escape can minimize the time taken for the entire catch.

Web of Science

Visuomotor tracking tasks with delayed pursuit and escape Reviewed

John Milton, Joshua Lippai, Rachel Bellows, Andrew Blomberg, Atsushi Kamimura, Toru Ohira

Proceedings of the ASME Design Engineering Technical Conference   Vol. 4   page： 419 - 425   2011

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Virtual stick balancing (VSB) is a manual visuomotor tracking task that involves interplay between a human and a computer in which the movements are programmed to resemble those of balancing a stick at the fingertip. Since time delays and random perturbations ("noise") are intrinsic properties of this task, we modeled VSB as a delayed pursuit-escape process: the target movements are described by a simple random walk and those movements controlled by the computer mouse by a delayed random walk biased towards the target. As subjects become more skilled, a stereotyped and recurring pursuit-escape pattern develops in which the mouse pursues the target until it overtakes it, causing the target to move in a different direction, followed, after a lag, by the pursing mouse. The delayed pursuit-escape random walk model captured the qualitative nature of this tracking task and provided insights into why this tracking task always fails at some point in time, even for the most expert subjects. Copyright © 2011 by ASME.

DOI： 10.1115/DETC2011-47312

Scopus

Stochastic Resonance with Group Chase and Escape Reviewed

Kamimura Atsushi, Matsumoto Shigenori, Nogawa Tomoaki, Ito Nobuyasu, Ohira Toru

2011 21ST INTERNATIONAL CONFERENCE ON NOISE AND FLUCTUATIONS (ICNF)     page： 200-203   2011

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Web of Science

Dynamical aspect of group chase and escape Reviewed

Shigenori Matsumoto, Tomoaki Nogawa, Atsushi Kamimura, Nobuyasu Ito, Toru Ohira

NON-EQUILIBRIUM STATISTICAL PHYSICS TODAY   Vol. 1332   page： 226 - +   2011

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Recently, a new concept is proposed for chasing and evading in crowds, called "group chase and escape" through a simple model. In this model, two kinds of players, chasers and escapees, play tag on a two-dimensional square lattice. Each chaser approaches its nearest escapee. On the other hand, each escapee steps away from its nearest chaser. Although there are no communications within each group, players appear to cooperate among themselves to chase or escape. We found relation between this cooperative behavior and group formations depend on the density of chasers and targets.

DOI： 10.1063/1.3569508

Web of Science

J-GLOBAL

A Team Approach to Undergraduate Research in Biomathematics: Balance Control Reviewed

J. Milton, A. Radunskaya, W. Ou, T. Ohira

MATHEMATICAL MODELLING OF NATURAL PHENOMENA   Vol. 6 ( 6 ) page： 260 - 277   2011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EDP SCIENCES S A  

The question, how does an organism maintain balance? provides a unifying theme to introduce undergraduate students to the use of mathematics and modeling techniques in biological research. The availability of inexpensive high speed motion capture cameras makes it possible to collect the precise and reliable data that facilitates the development of relevant mathematical models. An in-house laboratory component ensures that students have the opportunity to directly compare prediction to observation and motivates the development of projects that push the boundaries of the subject. The projects, by their nature, readily lend themselves to the formation of inter-disciplinary student research teams. Thus students have the opportunity to learn skills essential for success in today's workplace including productive team work, critical thinking, problem solving, project management, and effective communication.

DOI： 10.1051/mmmp/20116614

Web of Science

Group chase and escape Reviewed

Atsushi Kamimura, Toru Ohira

NEW JOURNAL OF PHYSICS   Vol. 12   2010.5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We describe here a new concept of one group chasing another, called 'group chase and escape', by presenting a simple model. We will show that even a simple model can demonstrate rather rich and complex behavior. In particular, there are cases where an optimal number of chasers exists for a given number of escapees (or targets) to minimize the cost of catching all targets. We have also found an indication of self-organized spatial structures formed by both groups.

DOI： 10.1088/1367-2630/12/5/053013

Web of Science

Resonance with Stochastic Time Reviewed

Toru Ohira

FRONTIERS OF FUNDAMENTAL AND COMPUTATIONAL PHYSICS   Vol. 1246   page： 154 - 159   2010

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We introduce a resonant phenomenon using a model incorporating delay (temporal non-locality) and stochastic time (temporal stochasticity). Although this model is a very simple linear dynamical differential equation, the addition of these elements makes it very rich. As an illustrative example, we describe a human stick balancing experiment that includes added fluctuations. We discuss how these concepts of temporal non-locality and stochasticity could play a role in characterizing biological and physiological systems, as well as in physics.

DOI： 10.1063/1.3460193

Web of Science

Chase and Escape in Groups Reviewed

Atsushi Kamimura, Shigenori Matsumoto, Nobuyasu Ito, Toru Ohira

CELLULAR AUTOMATA   Vol. 6350   page： 570 - 579   2010

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER-VERLAG BERLIN  

We study here a recently proposed theme of one group chasing another, called "group chase and escape". Rather rich and complex behavior such as self-organized structures can arise from a model with simple rules. We discuss models with various cases of different speeds between the two groups, search ranges, and motion fluctuations.

DOI： 10.1007/978-3-642-15979-4_62

Web of Science

J-GLOBAL

Delay, noise, and resonance: Human balancing and temporal non-locality Reviewed

Toru Ohira

Artificial Life and Robotics   Vol. 15 ( 4 ) page： 436 - 438   2010

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Language：English   Publishing type：Research paper (scientific journal)  

A rather peculiar phenomenon has been observed while a human was balancing a stick on a fingertip. The balancing time improved when the subject moved another object with the other hand. This was particularly so for many subjects with medium stick balancing skills. On the basis of this example, I consider how this seemingly simple task is composed of intricate mixtures of feedback delay, fluctuations, and predictions. I present some simple models of dynamics in which these factors lead to complex behaviors. From these examples, I infer that the concept of "nonlocality" could play an important role in characterizing biological and physiological systems. © 2010 International Symposium on Artificial Life and Robotics (ISAROB).

DOI： 10.1007/s10015-010-0837-0

Scopus

Balancing with Vibration: A Prelude for "Drift and Act" Balance Control Reviewed

John G. Milton, Toru Ohira, Juan Luis Cabrera, Ryan M. Fraiser, Janelle B. Gyorffy, Ferrin K. Ruiz, Meredith A. Strauss, Elizabeth C. Balch, Pedro J. Marin, Jeffrey L. Alexander

PLOS ONE   Vol. 4 ( 10 ) page： e7427   2009.10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Stick balancing at the fingertip is a powerful paradigm for the study of the control of human balance. Here we show that the mean stick balancing time is increased by about two-fold when a subject stands on a vibrating platform that produces vertical vibrations at the fingertip (0.001 m, 15-50 Hz). High speed motion capture measurements in three dimensions demonstrate that vibration does not shorten the neural latency for stick balancing or change the distribution of the changes in speed made by the fingertip during stick balancing, but does decrease the amplitude of the fluctuations in the relative positions of the fingertip and the tip of the stick in the horizontal plane, A(x, y). The findings are interpreted in terms of a time-delayed "drift and act" control mechanism in which controlling movements are made only when controlled variables exceed a threshold, i.e. the stick survival time measures the time to cross a threshold. The amplitude of the oscillations produced by this mechanism can be decreased by parametric excitation. It is shown that a plot of the logarithm of the vibration-induced increase in stick balancing skill, a measure of the mean first passage time, versus the standard deviation of the A(x, y) fluctuations, a measure of the distance to the threshold, is linear as expected for the times to cross a threshold in a stochastic dynamical system. These observations suggest that the balanced state represents a complex time-dependent state which is situated in a basin of attraction that is of the same order of size. The fact that vibration amplitude can benefit balance control raises the possibility of minimizing risk of falling through appropriate changes in the design of footwear and roughness of the walking surfaces.

DOI： 10.1371/journal.pone.0007427

Web of Science

PubMed

The time-delayed inverted pendulum: Implications for human balance control Reviewed

John Milton, Juan Luis Cabrera, Toru Ohira, Shigeru Tajima, Yukinori Tonosaki, Christian W. Eurich, Sue Ann Campbell

CHAOS   Vol. 19 ( 2 ) page： 026110   2009.6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The inverted pendulum is frequently used as a starting point for discussions of how human balance is maintained during standing and locomotion. Here we examine three experimental paradigms of time-delayed balance control: (1) mechanical inverted time-delayed pendulum, (2) stick balancing at the fingertip, and (3) human postural sway during quiet standing. Measurements of the transfer function (mechanical stick balancing) and the two-point correlation function (Hurst exponent) for the movements of the fingertip (real stick balancing) and the fluctuations in the center of pressure (postural sway) demonstrate that the upright fixed point is unstable in all three paradigms. These observations imply that the balanced state represents a more complex and bounded time-dependent state than a fixed-point attractor. Although mathematical models indicate that a sufficient condition for instability is for the time delay to make a corrective movement, tau(n), be greater than a critical delay tau(c) that is proportional to the length of the pendulum, this condition is satisfied only in the case of human stick balancing at the fingertip. Thus it is suggested that a common cause of instability in all three paradigms stems from the difficulty of controlling both the angle of the inverted pendulum and the position of the controller simultaneously using time-delayed feedback. Considerations of the problematic nature of control in the presence of delay and random perturbations ("noise") suggest that neural control for the upright position likely resembles an adaptive-type controller in which the displacement angle is allowed to drift for small displacements with active corrections made only when theta exceeds a threshold. This mechanism draws attention to an overlooked type of passive control that arises from the interplay between retarded variables and noise. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3141429]

DOI： 10.1063/1.3141429

Web of Science

PubMed

Balancing with positive feedback: the case for discontinuous control Reviewed

John Milton, Jennifer L. Townsend, Meredith A. King, Toru Ohira

PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES   Vol. 367 ( 1891 ) page： 1181 - 1193   2009.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC  

Experimental observations indicate that positive feedback plays an important role for maintaining human balance in the upright position. This observation is used to motivate an investigation of a simple switch-like controller for postural sway in which corrective movements are made only when the vertical displacement angle exceeds a certain threshold. This mechanism is shown to be consistent with the experimentally observed variations in the two-point correlation for human postural sway. Analysis of first-passage times for this model suggests that this control strategy may slow escape by taking advantage of two intrinsic properties of a stochastic unstable first-order delay differential equation: (i) time delay and (ii) the possibility that the dynamics can be 'temporarily confined' near the origin.

DOI： 10.1098/rsta.2008.0257

Web of Science

PubMed

Temporal stochasticity and non-locality Reviewed

Toru Ohira

JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT     2009.1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We attempt to consider concepts of 'stochasticity' and 'non-locality' on the time axis. Even though these concepts are more familiar on the space axis, delayed dynamics, for example, can be interpreted as dynamics with temporal non-locality. Along these lines, we present anticipative dynamics as another example of non-locality on the time axis. Two directions are discussed for temporal stochasticity. The first introduces fluctuations at the location of time points, which affects the dynamics. The second takes into consideration the stochasticity in the time flow or variable itself. Through these examples, we show that the combination of stochasticity and non-locality both on the space and time axes can produce rather complex phenomena.

DOI： 10.1088/1742-5468/2009/01/P01032

Web of Science

Resonance with Temporal Stochasticity and Non-locality Reviewed

Toru Ohira

NOISE AND FLUCTUATIONS   Vol. 1129   page： 49 - 52   2009

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We present here a simple model which shows a "resonant" phenomena through stochasticity and non-locality on the time axis. This model incorporates "stochastic time" and "delayed feedback" into its dynamics. We argue that a combination of temporal stochasticity and non-locality can provide rather complex behaviors.

Web of Science

J-GLOBAL

Delayed random walks: Investigating the interplay between delay and noise Reviewed

Toru Ohira, John Milton

Delay Differential Equations: Recent Advances and New Directions     page： 305 - 335   2009

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer US  

A model for a 1-dimensional delayed random walk is developed by generalizing the Ehrenfest model of a discrete random walk evolving on a quadratic, or harmonic, potential to the case of non-zero delay. The Fokker-Planck equation derived from this delayed random walk (DRW) is identical to that obtained starting from the delayed Langevin equation, i.e. a first-order stochastic delay differential equation (SDDE). Thus this DRW and SDDE provide alternate, but complimentary ways for describing the interplay between noise and delay in the vicinity of a fixed point. The DRW representation lends itself to determinations of the joint probability function and, in particular, to the auto-correlation function for both the stationary and the transient states. Thus the effects of delay are manisfested through experimentally measurable quantities such as the variance, the correlation time, and the power spectrum. Our findings are illustrated through applications to the analysis of the fluctuations in the center of pressure that occur during quiet standing. © 2009 Springer-Verlag US.

DOI： 10.1007/978-0-387-85595-0_11

Scopus

Non-locality on the time axis Reviewed

Toru Ohira

FRONTIERS OF FUNDAMENTAL AND COMPUTATIONAL PHYSICS   Vol. 1018   page： 21 - 26   2008

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We consider the question of introducing the concept of "non-locality" in a time variable, which is opposite to the normal description of the concept in space. Simple delayed and anticipative dynamical models are proposed as representatives of non-locality in time. These models show rather complex behaviors as we increase the level of temporal non-locality. We further demonstrate that these models can induce a "resonance" when combined with spatial or temporal noise. Applications to physical and bio-physiological systems are also discussed.

Web of Science

Human and machine stick balancing Reviewed

Shigeru Tajima, Toru Ohira, Yukinori Tonosaki

PROCEEDINGS OF THE ASME INTERNATIONAL DESIGN ENGINEERING TECHNICAL CONFERENCES AND COMPUTERS AND INFORMATION IN ENGINEERING CONFERENCE 2007, VOL 5, PTS A-C,     page： 721 - 727   2008

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC MECHANICAL ENGINEERS  

We compared the similarities and differences in stick balancing for the human fingertip and that by a servo-controlled machine. The motion of the stick in both cases exhibited a swinging or hunting behavior, which appears to be related to feedback delay. However, human stick balancing appears also to be affected by psychological factors, such as attention, which are not present in machine control systems. We discuss how machine control systems compare with human stick balancing. We also discuss about the repulsive delayed random walk as a simplified model of the stick balancing.

Web of Science

Unstable dynamical systems: Delays, noise and control Reviewed

J. G. Milton, J. L. Cabrera, T. Ohira

EPL   Vol. 83 ( 4 )   2008

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY  

Escape from an unstable fixed point in a time-delayed dynamical system in the presence of additive white noise depends on both the magnitude of the time delay, tau, and the initial function. In particular, the longer the delay the smaller the variance and hence the slower the rate of escape. Numerical simulations demonstrate that the distribution of first passage times is bimodal, the longest first passage times are associated with those initial functions that cause the greatest number of delayed zero crossings, i.e. instances where the deviations of the controlled variable from the fixed point at times t and t - tau have opposite signs. These observations support the utility of control strategies using pulsatile stimuli triggered only when variables exceed certain thresholds. Copyright (C) EPLA, 2008.

DOI： 10.1209/0295-5075/83/48001

Web of Science

Scopus

Non-locality on the time axis Reviewed

Ohira Toru

FRONTIERS OF FUNDAMENTAL AND COMPUTATIONAL PHYSICS   Vol. 1018   page： 21-26   2008

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Web of Science

Human and machine stick balancing Reviewed

PROCEEDINGS OF THE ASME INTERNATIONAL DESIGN ENGINEERING TECHNICAL CONFERENCES AND COMPUTERS AND INFORMATION IN ENGINEERING CONFERENCE 2007, VOL 5, PTS A-C,     page： 721-727   2008

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Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Stochasticity and non-locality of time Reviewed

Toru Ohira

PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS   Vol. 379 ( 2 ) page： 483 - 490   2007.6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We present simple classical dynamical models to illustrate the idea of introducing a stochasticity with non-locality into the time variable. For stochasticity in time, these models include noise in the time variable but not in the "space" variable, which is opposite to the normal description of stochastic dynamics. Similarly with respect to non-locality, we discuss the delayed and predictive dynamics which involve two points separated on the time axis. With certain combinations of fluctuations and non-locality in time, we observe a "resonance" effect. This is an effect similar to stochastic resonance, which has been discussed within the normal context of stochastic dynamics, but with different mechanisms. We discuss how these models may be developed to fit a broader context of generalized dynamical systems where fluctuations and nonlocality are present in both space and time. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physa.2007.01.015

Web of Science

Stochasticity and Non-Locality of Time Reviewed

OHIRA Toru

Butsuri   Vol. 62 ( 4 ) page： 260-264 - 264   2007.4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

Stochastic time Reviewed

Toru Ohira

Frontiers of Fundamental Physics   Vol. 905   page： 191 - 194   2007

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We presenta simple dynamical model to addres the question of introducing a stochastic nature in a time variable. This model includes noise in the time variable but not in the "space" variable, which is opposite to the normal description of stochastic dynamics. The notable feature is that these models can induce a "resonance" with varying noise strength in the time variable. Thus, they provide a different mechanism for stochastic resonance, which has been discussed within the normal context of stochastic dynamics.

Web of Science

Predictive dynamical and stochastic systems Reviewed

Toru Ohira

Cooperative Behavior in Neural Systems   Vol. 887   page： 182 - 189   2007

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We study a system whose dynamics are governed by predictions of its future states. A general formalism and concrete examples are presented. We find that the dynamical characteristics depend on how to shape the predictions as well as on how far ahead in time to make them. We also report that noise can induce oscillatory behavior, which we call "predictive stochastic resonance".

Web of Science

Stochastic time Reviewed

Ohira Toru

Frontiers of Fundamental Physics   Vol. 905   page： 191-194   2007

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Web of Science

Predictive dynamical and stochastic systems Reviewed

Ohira Toru

Cooperative Behavior in Neural Systems   Vol. 887   page： 182-189   2007

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Web of Science

Balancing the sticks with fluctuation and delay:Human vs machine Reviewed

Yukinori Tonosaki, Toru Ohira, Shigeru Tajima

2007 IEEE SYMPOSIUM ON FOUNDATIONS OF COMPUTATIONAL INTELLIGENCE, VOLS 1 AND 2     page： 95 - +   2007

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We compared the similarities and differences in stick balancing for the human fingertip and that by a servo-controlled machine. The motion of the stick in both cases exhibited a swinging or hunting behavior, which appears to be related to feedback delay. However, human stick balancing appears also to be affected by psychological factors, such as attention, which are not present in machine control systems. We discuss how machine control systems compare with human stick balancing.

DOI： 10.1109/FOCI.2007.372153

Web of Science

Delayed random walks and control Reviewed

Tadaaki Hosaka, Toru Ohira

FLOW DYNAMICS   Vol. 832   page： 487 - +   2006

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Issues of resonance that appear in non-standard random walk models are discussed. The first walk is called repulsive delayed random walk, which is described in the context of a stick balancing experiment. It win be shown that a type of "resonant" effect takes place to keep the stability of the fixed point better with tuned bias and delay. We also briefly discuss the second model called sticky random walk, which is introduced to model string entanglement. Peculiar resonant effects with respect to these random walks are presented.

Web of Science

Balancing with noise and delay Reviewed

T Hosaka, T Ohira, C Luciani, JL Cabrera, JG Milton

PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   ( 161 ) page： 314 - 319   2006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

Motivated by recent studies in human balance control, we study a delayed random walk with an unstable fixed point. It is observed that the random walker moves away from the unstable fixed point more slowly than is observed in the absence of delay. It is shown that, for given a noise level, there exists an optimal delay to achieve the longest first passage time. Our observations support recent demonstrations that noise has a beneficial role for balance control and emphasize that predicitive strategies are not necessary to transiently control balance.

Web of Science

J-GLOBAL

Balancing with noise and delay Reviewed

T Hosaka, T Ohira, C Luciani, JL Cabrera, JG Milton

PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   Vol. 161 ( 161 ) page： 314 - 319   2006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

Motivated by recent studies in human balance control, we study a delayed random walk with an unstable fixed point. It is observed that the random walker moves away from the unstable fixed point more slowly than is observed in the absence of delay. It is shown that, for given a noise level, there exists an optimal delay to achieve the longest first passage time. Our observations support recent demonstrations that noise has a beneficial role for balance control and emphasize that predicitive strategies are not necessary to transiently control balance.

DOI： 10.1143/PTPS.161.314

Web of Science

Scopus

Delayed random walks and control Reviewed

Hosaka Tadaaki, Ohira Toru

FLOW DYNAMICS   Vol. 832   page： 487-+   2006

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Web of Science

Repulsive delayed random walk Reviewed

Toru Ohira, Tadaaki Hosaka

Artificial Life and Robotics   Vol. 9 ( 4 ) page： 194 - 196   2005.12

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We studied a random walk with delayed feedback around an unstable fixed point. It was found that the random walker can be kept around the fixed point with longer delays. This is in contrast to the normal role of delay, which is generally thought to be a source of instability. We discuss the connection of our model to stick-balancing experiments, and propose new type of control paradigm called "delayed stochastic control." © ISAROB 2005.

DOI： 10.1007/s10015-004-0337-1

Scopus

Control in delayed stochastic systems Reviewed

Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Vol 6, Pts A-C     page： 851-855   2005

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Web of Science

Control in delayed stochastic systems Reviewed

Toru Ohira, Tadaaki Hosaka

Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Vol 6, Pts A-C     page： 851 - 855   2005

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC MECHANICAL ENGINEERS  

This article discusses issues of controlling in situations where fluctuations and delay are present. A new paradigm for control schemes, termed "delayed stochastic controls", is proposed for use in such situations.

Web of Science

遅れを含むランダムウォーク (確率モデルの統計力学) Reviewed

大平 徹

物性研究   Vol. 82 ( 2 ) page： 320-325   2004.5

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遅れを含むランダムウォークについて概説します。とくに拡散の速度や確率分布の振動がおきるような点に着目します。

State-dependent noise and human balance control Reviewed

JL Cabrera, R Bormann, C Eurich, T Ohira, J Milton

FLUCTUATION AND NOISE LETTERS   Vol. 4 ( 1 ) page： L107 - L117   2004.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

The fluctuations observed in the task of stick balancing at the fingertip exhibit many of the properties predicted to occur in parametric stochastic dynamical systems, namely intermittency, truncated Levy flights and truncated Levy distributions. The development of virtual balancing tasks that involve the interplay between a human and computer and that exhibit the same dynamical properties as seen for stick balancing opens the door for experimental investigations into the nature of the neural motor control mechanisms that underlie these phenomena.

DOI： 10.1142/S0219477504001719

Web of Science

Scopus

Non-linear logit models for high frequency currency exchange data Reviewed

N Sazuka, T Ohira

COMPUTATIONAL FINANCE AND ITS APPLICATIONS     page： 297 - 305   2004

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WIT PRESS  

High frequency market data has become available with recent developments in computer technology. These data have some unique characteristics that do not appear in low frequency data. They are important in understanding financial markets. We present evidence of a unique property of high frequency data by proposing a new model. In this paper, we analyze tick-by-tick data, the most high frequency data available, of yen-dollar currency exchange rates. Focusing on the direction of up or down price movement, we show that a non-trivial structure exists in conditional probabilities of binarized data, which is apparently invisible from the price change itself. The probabilistic structure has a strong bias not only in the first order conditional probabilities but also in the higher order ones. Logit models are often applied to the analysis of the direction of price change. However, we found that a conventional logit model was not sufficient for our data due to its non-linear behavior. This motivated us to develop a new extended non-linear logit model to reproduce the binary probabilistic structure. This new model has overcome some of the shortcomings of the conventional analysis such as AR models and logit models. It can successfully show that the structure is such that it refers up to the previous few minutes by a model selection based on Akaike Information Criterion. The empirical result is consistent with dealers' perceptions that their strategies change slowly in the time scale of a few minutes. Our analysis here opens a possibility that this new non-linear logit model can be applied to a wide range of binary time series to extract their non-trivial probabilistic structures. Finally, in order to investigate the generality of our model, we are now analyzing the tick-by-tick GE data on NYSE, which is also one of the most active stocks.

Web of Science

Repulsive delayed random walks Reviewed

T Hosaka, T Ohira

FLUCTUATIONS AND NOISE IN BIOLOGICAL, BIOPHYSICAL, AND BIOMEDICAL SYSTEMS II   Vol. 5467   page： 123 - 130   2004

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We study here a random walk with delayed feedback mound an unstable fixed point. It is found that the random walker can be kept longer around the fixed point with larer delay. This is in contrast to the normal role of delay, which is generally thought to be a source of instability. We discuss a possibility of our model to stick balancing experiments.

DOI： 10.1117/12.548492

Web of Science

Scopus

A dynamical structure of high frequency currency exchange market Reviewed

N Sazuka, T Ohira, K Marumo, T Shimizu, M Takayasu, H Takayasu

PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS   Vol. 324 ( 1-2 ) page： 366 - 371   2003.6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We analyze tick-by-tick data, the most high frequency data available, of yen-dollar currency exchange rates. We show that a dynamical structure can be observed in binarized data indicating the direction of up and down movement of prices, which is not apparently seen from the price change itself. This result is consistent with our previous study that there exists a conditional probabilistic structure in binarized data. The dynamical and probabilistic structure which we found could indicate that dealers' decision making is based on a binary strategy, even if they are unconscious of this fact. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0378-4371(02)01958-1

Web of Science

Scopus

Dynamical systems approach to the Busy Beaver problem Reviewed

E Nameda, T Ohira, T Ikegami

COMPUTER PHYSICS COMMUNICATIONS   Vol. 147 ( 1-2 ) page： 637 - 640   2002.8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The purpose of this paper is to reconsider the Busy Beaver problem, which is a modification of the Turing machine's halting problem, in the light of a dynamical systems approach. Numerical experiments show that the spatio-temporal patterns of machines can be roughly classified into four types. In particular, well-regulated and self-similar patterns are found in most longer-lived machines, which include known best Busy Beaver machines. A relation to the Collatz system is briefly discussed. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0010-4655(02)00356-9

Web of Science

Scopus

研究室の窓 「遅れ」と「ノイズ」の周辺で Reviewed

大平 徹

数理科学   Vol. 40 ( 5 ) page： 79-83 - 83   2002.5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：サイエンス社  

CiNii Books

Predictability of currency market exchange Reviewed

T Ohira, N Sazuka, K Marumo, T Shimizu, M Takayasu, H Takayasu

PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS   Vol. 308 ( 1-4 ) page： 368 - 374   2002.5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We analyze tick data of yen-dollar exchange with a focus on its up and down movement. We show that there exists a rather particular conditional probability structure with such high frequency data. This result provides us with evidence to question one of the basic assumptions of the traditional market theory, where such bias in high frequency price movements is regarded as not present. We also construct systematically a random walk model reflecting this probability structure. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0378-4371(02)00561-7

Web of Science

Scopus

Stochastic three-state model with delay Reviewed

Naoya Sazuka, Toru Ohira

Computer Physics Communications   Vol. 147 ( 1-2 ) page： 641 - 645   2002

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We investigate here a stochastic three-state element whose transition probability depends on its state at a fixed interval in the past. A rich dynamical behavior which does not appear in a binary model is observed in this model. A resonant phenomenon due to the delay appears as well. Furthermore, an analytical expression of this resonant characteristic can be derived in general for an N-state model. We also discuss its application to the dynamical time series of yen-dollar currency exchange. © 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0010-4655(02)00357-0

Scopus

Delayed stochastic resonance with a 1-D ring Reviewed

Toru Ohira

Physica A: Statistical Mechanics and its Applications   Vol. 314 ( 1-4 ) page： 146 - 150   2002

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A one-dimensional ring composed of stochastic binary elements with delayed interaction was studied. The interspike interval histograms and resonance or rhythmic behaviors arise with noise and delay were also studied. It was suggested that the noise and delay accounts for the rhythmic behaviors of network systems.

DOI： 10.1016/S0378-4371(02)01068-3

Scopus

Emergence of a dominant unit in a network of chaotic units with a delayed connection change Reviewed

Junji Ito, Toru Ohira

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics   Vol. 64 ( 6 ) page： 5   2001

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We study here a model of globally coupled units with adaptive interaction weights that has a delay in the updating rule. Simulations show that the model with such delayed synaptic change exhibits dynamical self organization of network structure. With suitably chosen parameters, “dominant” unit emerges spontaneously, in the sense that the connections from such a unit to almost all of the other units are especially strengthened. Such weight structure facilitates the coherent activity among units. © 2001 The American Physical Society.

DOI： 10.1103/PhysRevE.64.066205

Scopus

Resonance between Noise and Delay

OHIRA Toru, SATO Yuzuru

Butsuri   Vol. 55 ( 5 ) page： 360 - 363   2000.5

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/butsuri1946.55.360

CiNii Books

Other Link： https://jlc.jst.go.jp/DN/JALC/00066089421?from=CiNii

Resonance in a stochastic neuron model with delayed interaction Reviewed

Toru Ohira, Toru Ohira, Yuzuru Sato, Jack D. Cowan

Advances in Neural Information Processing Systems     page： 314-320   2000.1

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We study here a simple stochastic single neuron model with delayed self-feedback capable of generating spike trains. Simulations show that its spike trains exhibit resonant behavior between "noise" and "delay". In order to gain insight into this resonance, we simplify the model and study a stochastic binary element whose transition probability depends on its state at a fixed interval in the past. With this simplified model we can analytically compute interspike interval histograms, and show how the resonance between noise and delay arises. The resonance is also observed when such elements are coupled through delayed interaction.

Scopus

Toward encryption with neural network analogy. Reviewed

Toru Ohira

ESANN 2000, 8th European Symposium on Artificial Neural Networks, Bruges, Belgium, April 26-28, 2000, Proceedings     page： 147-152   2000

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Resonance in delayed stochastic dynamics Reviewed

T Ohira, Y Sato

STATISTICAL PHYSICS   Vol. 519   page： 628 - 634   2000

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We first study here a simple stochastic dynamical equation with delayed self-feedback. The model is investigated numerically and we find that its dynamics show an emergent regular "spiking" behavior, by "tuning" its "noise" and "delay". rn order to gain insight into this "resonance", we abstract the model and study a stochastic binary element whose transition probability depends on its state at a fixed interval in the past. With this abstracted model we can analytically capture the time interval histograms between spikes, and discover how the resonance between noise and delay arises. The resonance is also observed when such stochastic binary elements are coupled through delayed interaction.

Web of Science

Resonance in a stochastic neuron model with delayed interaction Reviewed

T Ohira, Y Sato, JD Cowan

ADVANCES IN NEURAL INFORMATION PROCESSING SYSTEMS 12   Vol. 12   page： 314 - 320   2000

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：M I T PRESS  

We study here a simple stochastic single neuron model with delayed self-feedback capable of generating spike trains. Simulations show that its spike trains exhibit resonant behavior between "noise" and "delay". In order to gain insight into this resonance, we simplify the model and study a stochastic binary element whose transition probability depends on its state at a fixed interval in the past. With this simplified model we can analytically compute interspike interval histograms, and show how the resonance between noise and delay arises. The resonance is also observed when such elements are coupled through delayed interaction.

Web of Science

Resonance in a stochastic neuron model with delayed interaction Reviewed

T Ohira, Y Sato, JD Cowan

ADVANCES IN NEURAL INFORMATION PROCESSING SYSTEMS 12   Vol. 12   page： 314 - 320   2000

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：M I T PRESS  

We study here a simple stochastic single neuron model with delayed self-feedback capable of generating spike trains. Simulations show that its spike trains exhibit resonant behavior between "noise" and "delay". In order to gain insight into this resonance, we simplify the model and study a stochastic binary element whose transition probability depends on its state at a fixed interval in the past. With this simplified model we can analytically compute interspike interval histograms, and show how the resonance between noise and delay arises. The resonance is also observed when such elements are coupled through delayed interaction.

Web of Science

Neural network model with delay toward encryption Reviewed

T Ohira

IJCNN 2000: PROCEEDINGS OF THE IEEE-INNS-ENNS INTERNATIONAL JOINT CONFERENCE ON NEURAL NETWORKS, VOL V     page： 417 - 421   2000

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE COMPUTER SOC  

We propose here a new model of encryption of binary data taking advantage of the complexity of dynamics of a model motivated by a neural network with delays. In this scheme, the encryption process is a coupling dynamics with various time delays between different bits (or neurons) in the original data. A simple example has been investigated to show that such a model may possess useful characteristics as an encryption scheme.

DOI： 10.1109/IJCNN.2000.861505

Web of Science

Toward encryption with neural network analogy. Reviewed

Toru Ohira

ESANN 2000, 8th European Symposium on Artificial Neural Networks, Bruges, Belgium, April 26-28, 2000, Proceedings     page： 147-152   2000

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Neural Network Model with Delay toward Encryption. Reviewed

Toru Ohira

IJCNN (5) 2000     page： 417-424   2000

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Delayed stochastic systems Reviewed

Toru Ohira, Toshiyuki Yamane

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics   Vol. 61 ( 2 ) page： 1247 - 1257   2000

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Noise and time delay are two elements that are associated with many natural systems, and often they are sources of complex behaviors. Understanding of this complexity is yet to be explored, particularly when both elements are present. As a step to gain insight into such complexity for a system with both noise and delay, we investigate such delayed stochastic systems both in dynamical and probabilistic perspectives. A Langevin equation with delay and a random-walk model whose transition probability depends on a fixed time-interval past (delayed random walk model) are the subjects of in depth focus. As well as considering relations between these two types of models, we derive an approximate Fokker-Planck equation for delayed stochastic systems and compare its solution with numerical results. © 2000 The American Physical Society.

DOI： 10.1103/PhysRevE.61.1247

Scopus

Resonance in a Stochastic Neuron Model with Delayed Interaction. Reviewed

Toru Ohira,Yuzuru Sato,Jack D. Cowan

Advances in Neural Information Processing Systems 12, [NIPS Conference, Denver, Colorado, USA, November 29 - December 4, 1999]     page： 314-320   1999

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Encryption with delayed dynamics Reviewed

Toru Ohira

Computer Physics Communications   Vol. 121   page： 54 - 56   1999

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Science Publishers B.V.  

We propose here a new model of encryption of binary data taking advantage of the complexity associated with delayed dynamics. In this scheme, the encryption process is a coupling dynamics with various time delays between different bits in the original data. It is shown that decoding of the encrypted data is extremely difficult without a complete knowledge of coupling manner with associated delays for all bits of the data.

DOI： 10.1016/S0010-4655(99)00279-9

Scopus

A Fokker-Planck equation with delay Reviewed

Ohira Toru

  Vol. 70 ( 3 ) page： 448-451   1998.6

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A approximate Fokker-Planck equation which corresponds to a Langevin equation with delay is derived. Our derivation takes an indirect path using an expansion of a corresponding random walk with delayed transition probability dependence(delayed random walk). The derived Fokker-Planck equation is found to contain a derivative term by the delay parameter. An equilibrium solution is also obtained and compared with numerical simulations.

Theory for Systems with Delay and Noise: Delayed Random Walks(Industrial Materials) Reviewed

Ohira Toru

BJSIAM   Vol. 8 ( 1 ) page： 46-49 - 49   1998

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Industrial and Applied Mathematics  

DOI： 10.11540/bjsiam.8.1_46

CiNii Books

Phase transition in a computer network traffic model Reviewed

Toru Ohira, Ryusuke Sawatari

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics   Vol. 58 ( 1 ) page： 193 - 195   1998

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We propose and study here a simple model of computer network traffic that can exhibit a phase transition from a low to high congestion state measured in terms of average travel time of packets as a function of the packet creation rate in the network. In the model, packets are generated with destination addresses, and are transferred from one router to another toward their destinations. The routers are capable of queuing packets and autonomously selecting a path to the next router for a packet. Through simulations on a two-dimensional lattice model network, we found that the phase transition point into the congestion phase depends on how each router chooses a path for the packets in its queue. In particular, an appropriate randomness in path selection can shift the onset of traffic congestion to accommodate more packets in the model network. © 1998 The American Physical Society.

DOI： 10.1103/PhysRevE.58.193

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Delay estimation from noisy time series Reviewed

Toru Ohira, Ryusuke Sawatari

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics   Vol. 55   page： .   1997.12

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We propose here a method to estimate a delay from a time series taking advantage of analysis of random walks with delay. This method is applicable to a time series coming out of a system which is or can be approximated as a linear feedback system with delay and noise. We successfully test the method with a time series generated by a discrete Langevin equation with delay.

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Delay estimation from noisy time series Reviewed

Toru Ohira, Ryusuke Sawatari

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics   Vol. 55   page： .   1997.12

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Language：English   Publishing type：Research paper (scientific journal)  

We propose here a method to estimate a delay from a time series taking advantage of analysis of random walks with delay. This method is applicable to a time series coming out of a system which is or can be approximated as a linear feedback system with delay and noise. We successfully test the method with a time series generated by a discrete Langevin equation with delay.

Oscillatory correlation of delayed random walks Reviewed

Toru Ohira

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics   Vol. 55 ( 2 ) page： R1255 - R1258   1997

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We investigate analytically and numerically the statistical properties of a random walk model with delayed transition probability dependence (delayed random walk). The characteristic feature of such a model is the oscillatory behavior of its correlation function. We investigate a model whose transient and stationary oscillatory behavior is analytically tractable. The correspondence of the model with a Langevin equation with delay is also considered. © 1997 The American Physical Society.

DOI： 10.1103/PhysRevE.55.R1255

Scopus

Distributed Interaction with Computon. Reviewed

Toru Ohira, Ryusuke Sawatari, Mario Tokoro

Agents Breaking Away, 7th European Workshop on Modelling Autonomous Agents in a Multi-Agent World, Eindhoven, The Netherlands, January 22-25, 1996, Proceedings     page： 149-162   1996

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/BFb0031853

Distributed Interaction with Computon. Reviewed

Toru Ohira,Ryusuke Sawatari,Mario Tokoro

Agents Breaking Away, 7th European Workshop on Modelling Autonomous Agents in a Multi-Agent World, Eindhoven, The Netherlands, January 22-25, 1996, Proceedings     page： 149-162   1996

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Language：English   Publishing type：Research paper (scientific journal)  

Complex dynamics and multistability in a damped harmonic oscillator with delayed negative feedback Reviewed

SA Campbell, J Belair, T Ohira, J Milton

CHAOS   Vol. 5 ( 4 ) page： 640 - 645   1995.12

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A center manifold reduction and numerical calculations are used to demonstrate the presence of limit cycles, two-tori, and multistability in the damped harmonic oscillator with delayed negative feedback. This model is the prototype of a mechanical system operating with delayed feedback. Complex dynamics are thus seen to arise in very plausible and commonly occurring mechanical and neuromechanical feedback systems. (C) 1995 American Institute of Physics.

DOI： 10.1063/1.166134

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PubMed

Three-State Stochastic Neural Networkの挙動と解析 (複雑系) Reviewed

大平 徹

物性研究   Vol. 63 ( 6 ) page： p839-849   1995.3

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本論文では、Cowanによって提唱されたニューラルネットワークマスター方程式によって確率動作するニューラルネットの解析をする一手法について考察する。ここでは三つの状態をとるニューロンからなるネットワークを外積表記されたニューラルネットワークマスター方程式を用いて解析する。この解析ではネットワークのモーメントの力学階層式を導き、この階層式を近似する一方法としてネットワーク活動を平均場の中におかれた一つ、もしくは二つの擬似ニューロンによって表現する方法を提案する。これらの近似を単純な構造を持つネットワークに適用し、モンテカーロシミュレーションとの比較を行なった。

Limit cycles, tori, and complex dynamics in a second-order differential equation with delayed negative feedback Reviewed

CAMPBELL S. A.

Journal of Dynamics and Differential Equations   Vol. 7   page： 213-236 - 236   1995.1

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We analyze a second-order, nonlinear delay-differential equation with negative feedback. The characteristic equation for the linear stability of the equilibrium is completely solved, as a function of two parameters describing the strength of the feedback and the damping in the autonomous system. The bifurcations occurring as the linear stability is lost are investigated by the construction of a center manifold: The nature of Hopf bifurcations and more degenerate, higher-codimension bifurcations are explicitly determined. © 1995 Plenum Publishing Corporation.

DOI： 10.1007/BF02218819

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Stochastic single neurons Reviewed

Toru Ohira, Jack D. Cowan

Neural Computation   Vol. 7 ( 3 ) page： 518 - 528   1995

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MIT Press Journals  

We study the stochastic behavior of a single self-exciting model neuron with additive noise, a system that has bistable stochastic dynamics. We use Langevin and Fokker-Planck equations to obtain analytical expressions for the stationary distribution of activities and for the crossing rate between two stable states. We adjust the parameters in these expressions to fit observed histograms of neural activity, thus obtaining what we call an "effective single neuron" for a given network. We construct an effective single neuron from an activity histogram of a representative hidden neuron in a recurrent learning network. We also compare our result with an effective single neuron previously obtained analytically through the adiabatic elimination approximation.

DOI： 10.1162/neco.1995.7.3.518

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Delayed random walks Reviewed

Toru Ohira, John G. Milton

Physical Review E   Vol. 52 ( 3 ) page： 3277 - 3280   1995

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The fluctuations about the stable point in a delayed dynamical system are modeled as a delayed random walk: i.e., a random walk in which the transition probability depends on the position of the walker at a time in the past and transitions in the direction of the stable point are more probable. It is shown that, depending on the magnitude of the delay, the root mean square displacement X2(t) versus time interval approaches a limiting value in either an oscillatory or nonoscillatory fashion. This limiting value of X2(t) is a linear function of. © 1995 The American Physical Society.

DOI： 10.1103/PhysRevE.52.3277

Scopus

Stochastic Dynamics of Three-State Neural Networks. Reviewed

Toru Ohira, D. Cowan

Advances in Neural Information Processing Systems 7, [NIPS Conference, Denver, Colorado, USA, 1994]     page： 271-278   1994

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PATH-INTEGRALS FOR STOCHASTIC NEURODYNAMICS Reviewed

T OHIRA, JD COWAN

WORLD CONGRESS ON NEURAL NETWORKS-SAN DIEGO - 1994 INTERNATIONAL NEURAL NETWORK SOCIETY ANNUAL MEETING, VOL 2     page： B437 - B442   1994

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：LAWRENCE ERLBAUM ASSOC PUBL  

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Stochastic Dynamics of Three-State Neural Networks. Reviewed

Toru Ohira,Jack D. Cowan

Advances in Neural Information Processing Systems 7, [NIPS Conference, Denver, Colorado, USA, 1994]     page： 271-278   1994

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Language：English   Publishing type：Research paper (scientific journal)  

Oscillations and latency in the clamped pupil light reflex Reviewed

John G. Milton, Toru Ohira, Jeff Steck, John Crate, Andre Longtin

Proceedings of SPIE - The International Society for Optical Engineering   Vol. 2036   page： 198-203   1993.12

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It is shown that the pupil latency can be estimated from pupil cycling measurements when the pupil light reflex is clamped with piecewise constant negative feedback. The solution of the mathematical model previously shown to describe these oscillations is utilized to develop a variety of strategies to estimate latency and to evaluate the effects of noise on these estimates. The results demonstrate that the pupil latency shows considerable variation.

Scopus

Master-equation approach to stochastic neurodynamics Reviewed

Toru Ohira, Jack D. Cowan

Physical Review E   Vol. 48   page： 2259-2266   1993.1

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A master-equation approach to the stochastic neurodynamics proposed by Cowan [in Advances in Neural Information Processing Systems 3, edited by R. P. Lippman, J. E. Moody, and D. S. Touretzky (Morgan Kaufmann, San Mateo, 1991), p. 62] is investigated in this paper. We deal with a model neural network that is composed of two-state neurons obeying elementary stochastic transition rates. We show that such an approach yields concise expressions for multipoint moments and an equation of motion. We apply the formalism to a (1+1)-dimensional system. Exact and approximate expressions for various statistical parameters are obtained and compared with Monte Carlo simulations. © 1993 The American Physical Society.

DOI： 10.1103/PhysRevE.48.2259

Scopus

OSCILLATIONS AND LATENCY IN THE CLAMPED PUPIL LIGHT REFLEX Reviewed

J MILTON, T OHIRA, J STECK, J CRATE, A LONGTIN

CHAOS IN BIOLOGY AND MEDICINE   Vol. 2036   page： 198 - 203   1993

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

It is shown that the pupil latency can be estimated from pupil cycling measurements when the pupil light reflex is clamped with piecewise constant negative feedback. The solution of the mathematical model previously shown to describe these oscillations is utilized to develop a variety of strategies to estimate latency and to evaluate the effects of noise on these estimates. The results demonstrate that the pupil latency shows considerable variation.

Web of Science

PERFECT DISTURBING MEASUREMENTS Reviewed

T OHIRA, P PEARLE

AMERICAN JOURNAL OF PHYSICS   Vol. 56 ( 8 ) page： 692 - 695   1988.8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

DOI： 10.1119/1.15502

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