Faculty Profiles - OHIRA Toru

Papers - OHIRA Toru

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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

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

Neural Network Model with Delay toward Encryption. Reviewed

Toru Ohira

IJCNN (5) 2000 page： 417-424 2000

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

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

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

Encryption with delayed dynamics Reviewed

Toru Ohira

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

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

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

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

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

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

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

Scopus

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

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.

Scopus

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

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

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

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

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

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

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

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

Web of Science

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

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

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

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

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

Scopus

Stochastic single neurons Reviewed

Toru Ohira, Jack D. Cowan

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

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

Scopus

Delayed random walks Reviewed

Toru Ohira, John G. Milton

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

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

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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