Yoko Uwate

Analog electronic cochlea with mammalian hearing characteristics

Systems close to bifurcations can be used as small-signal amplifiers. Biophysical measurements suggest that the active amplifiers present in the mammalian cochlea are systems close to a Hopf bifurcation. The pure tone and transient signal output of our electronic hearing sensor based on this observation provides output that is fully compatible with the electrophysiological data from the mammalian cochlea. In particular, it reproduces all salient nonlinear effects displayed by the cochlea.

Chaos glial network connected to Multi-Layer Perceptron for Solving Two-Spiral Problem

Some methods using artificial neural network were proposed for solving to the Two-Spiral Problem (TSP). TSP is a problem which classifies two spirals drawn on the plane, and it is famous as the high nonlinear problem. In this paper, we propose a chaos glial network which connected to Multi-Layer Perceptron (MLP). The chaos glial network is inspired by astrocyte which is glial cell in the brain. By computer simulations for solving TSP, we confirmed that the proposed chaos glial network connected to MLP gains better performance than the conventional MLP.

SYNCHRONIZATION PHENOMENA IN VAN DER POL OSCILLATORS COUPLED BY A TIME-VARYING RESISTOR

In this study, synchronization phenomena observed in van der Pol oscillators coupled by a time-varying resistor are investigated. We realize the time-varying resistor by switching a positive and a negative resistor periodically. By carrying out circuit experiments and computer calculations, interesting synchronization phenomena can be confirmed to be generated in this system. Namely, the synchronization states change according to the switching frequency of the time-varying resistor.

From Hearing to Listening: Design and Properties of an Actively Tunable Electronic Hearing Sensor

An important step towards understanding the working principles of the mammalian hearing sensor is the concept of an active cochlear amplifier. Theoretical arguments and physiological measurements suggest that the active cochlear amplifiers originate from systems close to a Hopf bifurcation. Efforts to model the mammalian hearing sensor on these grounds have, however, either had problems in reproducing sufficiently close essential aspects of the biological example (Magnasco, M.O. Phys. Rev. Lett. 90, 058101 (2003); Duke, T. & Jülicher, F. Phys. Rev. Lett. 90, 158101 (2003)), or required complicated spatially coupled differential equation systems that are unfeasible for transient signals (Kern, A. & Stoop, R. Phys. Rev. Lett. 91, 128101 (2003)). Here, we demonstrate a simple system of electronically coupled Hopf amplifiers that not only leads to the desired biological response behavior, but also has real-time capacity. The obtained electronic Hopf cochlea shares all salient signal processing features exhibited by the mammalian cochlea and thus provides a simple and efficient design of an artificial mammalian hearing sensor.

SHRIMPS: OCCURRENCE, SCALING AND RELEVANCE

Shrimps are islands of periodicity within a chaotic sea in phase and parameter spaces of dimensions larger than one. Islands of different periodicities have recently been shown to be connected by spirals that emanate from a joint focal point, paving ways to wander around in parameter space without ever crossing the chaotic sea. We discuss the shrimp building and scaling principles as well as the influence of individual system properties. While the emergence of shrimps has abundantly been demonstrated for artificial systems, we discuss here in detail evidence of rich hierarchies of shrimps in experimental systems. We finally pinpoint the importance of shrimps in the field of bioinformatics.

Synchronization in Several Types of Coupled Polygonal Oscillatory Networks

In this study, synchronization phenomena observed in several types of coupled polygonal oscillatory networks by sharing branches are investigated by both computer simulations and circuit experiments. We focus on the power consumption of coupling resistors of the whole system. By using theoretical analysis, we confirm that the phase differences of the coupled oscillators are solved by finding the minimum value of the power consumption function.

Multi-Layer Perceptron with positive and negative pulse glial chain for solving two-spirals problem

A glia is a nervous cell existing in a brain. The brain is composed of the relationship with glias and neurons. By an ion concentration, the glia transmits signal to neurons and neighboring glias. In this study, we propose the MLP with positive and negative pulse glial chain which is inspired from features of the biological glia.We add the MLP to the positive and negative pulse glial chain. In the positive and negative pulse glial chain, the glias are connected to the neurons one by one. The glia generates pulse when the glia is excited by the connected neurons output. If the connected neuron has large amount of output, the glia generates positive pulse. Moreover, if the connected neuron has small amount of output, the glia generates the negative pulse. The positive and negative pulse are propagated to the connected neuron and neighboring glias. We consider that the positive and negative pulse glial chain give the relationships of position of neurons in a same layer. By solving a Two-Spirals Problem (TSP), we confirm that the proposed MLP has better a learning performance and a generalization capability than the conventional MLP.

Clustering phenomena in complex networks of chaotic circuits

In this study, we investigate synchronization phenomena in coupled chaotic circuits which are connected with distance information. We confirm that the chaotic circuits arranged in the near distance are synchronized at in-phase state, and the coupled circuits with the far distance could not be synchronized. Namely, clustering phenomena of coupled chaotic circuits is observed on two-dimensional place.

Solving ability of Hopfield neural network with chaotic noise and burst noise for quadratic assignment problem

Solving combinatorial optimization problems is one of the important applications of the neural network. Many researchers have reported that exploiting chaos achieves good solving ability. However, the reason for the good effect of chaos has not been clarified yet. In this article, intermittent chaos noise near three-periodic window and burst noise generated by the Gilbert model are applied to the Hopfield neural network for quadratic assignment problem. By computer simulations we confirm that the burst noise generated by the Gilbert model is effective to solve the quadratic assignment problem and we can say that the existence of the laminar part and the burst part is one reason of the good performance of the Hopfield NN with chaos noise.

COMPLEX PATTERN IN A RING OF VAN DER POL OSCILLATORS COUPLED BY TIME-VARYING RESISTORS

Synchronization phenomena in coupled oscillatory systems are very important models to describe various higher-dimensional nonlinear phenomena in the field of natural science. In this paper, phase synchronization in a ring of van der Pol oscillators coupled by time-varying resistors is studied. The coexistence of in-phase and anti/N-phase states and various interesting phase synchronization patterns are observed when the parameters are changed. Further, the influence of duty cycle of time-varying resistors for the observed phase synchronization patterns is investigated.