Masahiro Agu

Geometrical Correction Factor for Semiconductor Resistivity Measurements by Four-Point Probe Method

Geometrical correction factors are derived for semiconductor resistivity measurements by the four-point probe method on rectangular parallelepipeds. The conformal transformation method leads to the same numerical values as that obtained from the solutions of Poissons equation in the lower limit of the sample thickness. Some numerical results are given as a function of the width, length, and thickness of the rectangular parallelepiped, the probe separation, and the probe position.

A Measure of Complexity for 1/f Fluctuation

A measure of complexity for 1/fβ fluctuation is proposed using the block entropy of a sequence of correlated symbols generated by 1/fβ fluctuation. This measure of complexity represents the diversity of sequences of correlated symbols. It is shown that the measure of complexity has the maximum value for 1/f fluctuation among 1/fβ fluctuations when the length of sequence of correlated symbols is chosen appropriately.

Energy and Power Flow of a Wave in a Moving Dispersive Medium

The transformation laws have been derived for the energy density W , the power-flow density S and the time rate of energy density dissipation Q of a wave in an anisotropic dispersive medium which is in motion. It has been found that to the zeroth order in \(\tilde{\varepsilon}^{a}\) (antihermitian part of the reduced permittivity) the action density W /ω (ω is the frequency) and the action-flow density S /ω transform in the same way as the energy and momentum of a particle do relativistically. Response of a medium against motion of a test charge immersed in the medium is calculated and conditions in which the negative-energy wave behaves as an active was are discussed.

Asymmetrical Property of 1/f Resistance Fluctuation for Time Inversion

The 1/f resistance fluctuations of carbon fiber are observed under four different nonequilibrium conditions controlled by the heat diffusion from the fiber to the external environment. A higher-order correlation function of an observed 1/f time series is analyzed and compared with those of three different types of computer-generated 1/f time series. It is found that the higher-order correlation function related to the time-inversion asymmetry of the 1/f resistance fluctuation shows the same statistical property as that of a one-dimensional diffusion system. Further more, the higher-order correlation function of the 1/f resistance fluctuations with the same 1/f spectra is shown to be affected by the heat diffusion from the carbon fiber.

A continuous-time asynchronous Boltzmann machine

We propose an asynchronous neural network model having the same structure as the binary Hopfield model. Each neuron operates with continuous time and randomly changes its state according only to its membrane potential. The proposed model settles in a steady-state fluctuation, in which the probability distribution of the global state is identical to that of the serial Boltzmann machine with the same synaptic weights. Copyright 1997 Elsevier Science Ltd.

Multimatched filtering using a microlens array for an optical–neural pattern recognition system

In the optical-neural recognition system proposed for flexible parallel information processing, a planar microlens array is used to form simultaneously many identical Fourier transforms of an input pattern; from each transform the feature extraction of the input pattern is performed in parallel through optical correlations with memorized standard spatial filters. In this paper, it is experimentally shown that the multimatched filtering system, as the optical feature extracting part of the proposed system, can be composed of a planar array of graded index microlenses of 1.05-mm diameter and 2.6-mm focal length.

A parallel-processing optical-digital recognition system as a model of biological visual perception

Abstract An optical-digital pattern recognition system is proposed as a model of biological visual perception. The optical part of this system extracts in parallel the geometrical features of each divided part of a pattern by using multi-matched filters made by an integrated small lens array. The fundamental experiments on the miniaturized matched filter of reflection type with a small lens of 3.3 mm diameter is reported, which show the feasibility to achieve the optical part of the proposed system.

1/f Resistance Fluctuation of a Carbon Fiber

1/f resistance fluctuations of carbon fiber are measured under the condition that tension of the carbon fiber is changed. The deformation of the fiber extends from an elastic region to a plastic one. It is found that the intensity of 1/f resistance fluctuations increases significantly as the applied tension increases, while the change of the mean value of the resistance is very small. The increase of the 1/f intensity is considered to originate from the change of the nonlinear potential caused by the applied tension.

Digital system for 1/f fluctuation-speed control of a small-fan motor

To produce a comfortable breeze similar to a natural one, a digital open-loop control system was utilized to control the speed of a small fan motor with 1/f fluctuation. The system was modeled as a first-order lag element with a time constant of 1.1 s. The output was controlled by commands and produced 1/f fluctuations, even though it was an open-loop system when the holding time of the data for 1/f fluctuation was set at more than 2 s. >

Prediction of catastrophes in bistable systems using externally applied random force

A method is proposed to forecast the catastrophic changes of the states of bistable systems with the use of externally applied Gaussian random force. The prediction is based on the fact that the probability distribution function of the states of a bistable system under the influence of Gaussian random force becomes far from Gaussian in the vicinity of its catastrophe. In other words, the anomalous increase of the variance of the probability distribution function in the vicinity of the catastrophe can be utilized as a precursory phenomenon to predict the catastrophe. The anomaly of the probability distribution function is caused by the nonlinear property of the bistable system.