Numerical studies of reaction–diffusion systems which consist of chaotic oscillators are carried out. The Rössler oscillators are used, which are arranged two–dimensionally and coupled by diffusion. Pacemakers where the average periods of the oscillators are artificially changed are set to produce target patterns. It is found that target patterns emerge from pacemakers and grow up as if they were in a regular oscillatory medium. The wavelength of the pattern can be varied and controlled by changing the parameters (size and frequency) of the pacemaker. The behavior of the coupled system depends on the size of the system and the strength of the pacemaker. When the system size is large, the Poincar return maps show that the behavior of the coupled system is not simple and the orbit falls into a high–dimensional attractor, while for a small system the attractor is rather simple and a one–dimensional map is obtained. Moreover, for appropriate strength of pacemakers and for certain sizes of the systems the oscillations become periodic. It is also found that the largest and local Lyapunov exponents of the system are positive and these values are uniformly distributed over the pattern. The values of the exponents are smaller than that of the uncoupled Rössler oscillator; this is due to the fact that the diffusion reduces the exponents and modifies the form of the attractor. We conclude that the large scale patterns can stably exist in the chaotic medium.

In this paper, we subjects the case that frequency–shift–keying (FSK) modulation and phase locked loop (PLL) demodulator are used in frequency hopped spread spectrum (FH–SS) communication system. So the carrier frequencies of undesired transmitters may come into collision with the carrier frequency of desired transmitter in this communication system, we evaluate the response of PLL by two sinusoidal inputs so as to estimate how the response of PLL demodulator is affected by the collision of carrier frequencies. First, we compute the synchronization diagrams of PLL with two sinusoids. From this, it is indicated that allowable value of amplitude ratio of interference transmitter's signal to disired transmitter's signal decreases with increasing FSK modulation width of desired transmitter. Next, we calculated the output of PLL demodulator with two sinusoids. To this end, it is shown that the allowable value of amplitude ratio is bounded by a constant value even if FSK modulation width is enough small.

The access control method adopted by UNIX is simple, understandable, and useful. However, it is quite possible that unexpected information flows occur when we are cooperating with some group members on UNIX. Introducing notions such as "flow right," "maximal permission" and "minimal umask value", this note proposes a simple method, can be seen as a natural extension of UNIX, to control indirect information flows without losing availability and understandability of UNIX.

Coupling optics for a monolithic array LD module has been developed. High efficient and small sized confocal optics with aspheric lenses based on hyperbolic surfaces has been designed to achieve the uniformity of coupling loss. A small sized (7.2 cc) 4 channel array LD module with this optics was fabricated. This module has low (4.2 dB) and uniform (0.5 dB) coupling loss.

Binary sequences with good correlation properties are required for a variety of engineering applications. We previously proposed simple methods to generate binary sequences based on chaotic nonlinear maps. In this paper, statistical properties of chaotic binary sequences generated by Chebyshev maps are discussed. We explicitly evaluate the correlation functions by means of the ensemble–average technique based on the Perron–Frobenius (P–F) operator. As a consequence, we can confirm an important role of the P–F operator in evaluating statistics of chaos by means of the ensemble-average technique.

This paper presents a new numerical procedure for solving the scattering wave by the moving surface. Recently, the author and her colleagues have proposed a novel numerical procedure of grid generation having a coordinate line coincident with an arbitrarily shaped moving boundary. The time dependent curvilinear coordinate system which coincides with a contour of moving boundary in a physical region is transformed into fixed rectangular coordinate system. The simple form for the transformation is made possible to choose the function between the physical region and the rectangular computational region. The FD-TD algorithm is exactly solved in this fixed rectangular coordinate system. In this paper, for the application of the FD-TD algorithm to the body fitted grid generation with moving boundary, the stability criterion of FD-TD algorithm for the body fitted grid generation with moving boundary in three dimensions is derived. The stability criterion is shown an upper bound for time step assuring stable numerical solutions. The study of scattering of electromagnetic and acoustic wave from a moving or a rotating body is very important for electromagnetic probing of moving body. The problem has been investigated in the past by numerous authors. One of them is solved by FD-TD method, where the linear interpolation is introduced for the movement. By using the presented transformation technique where time component is added to the grid generation, the time depending coordinate system can be transformed into fixed rectangular coordinate system. Then the problems are directly solved by FD-TD method in the transformed coordinate system. To verify this numemical technique, scattered field is evaluated in the case when a plane wave is normally incident on a moving perfectly conducting flat plate. The numerical results are compared with the exact ones and excellent agreement between them is obtained.

We have classified parenchymal echo patterns of cirrhotic liver into 3 types, according to the size of hypoechoic nodular lesions. We have been studying an ultrasonic image diagnosis system using the three–layer back–propagation neural network. In this paper, we will describe the applications of the neural network techniques for recognizing and classifying chronic liver disease, which use the nodular lesions in the Proton density and T2–weighed magnetic resonance images on the gray level of the pixels in the region of interest.

In an image fiber containing a large number of cores, a certain class of crosstalk has been found to decrease with the distance along the fiber axis. This crosstalk is absolutely distinguished from the usual crosstalk that increases with the distance. A theoretical model is presented based on the power transfer between three groups of modes supported by each core. The process of power transfer is described by coupled power equations. Values of the coupling coefficients can be determined from the measurement of the crosstalk. The equations are solved numerically for the transmission of a point image. The results are in good agreement with measurement results.

Introducing a general statistical model of image noise, we present an optimal algorithm for computing 3-D motion from two views without involving numerical search: () the essential matrix is computed by a scheme called renormalization; () the decomposability condition is optimally imposed on it so that it exactly decomposes into motion parameters; () image feature points are optimally corrected so that they define their 3-D depths. Our scheme not only produces a statistically optimal solution but also evaluates the reliability of the computed motion parameters and reconstructed points in quantitative terms.

This paper presents a modified disparity measurement to recover the depth and a robust method to estimate motion parameters. First, this paper considers phase correspondence for the computation of disparity. It has less computation for disparity than previous methods that use the disparity from correspondence and from correlation. This modified disparity measurement uses the Gabor filter to analyze the local phase property and the exponential filter to analyze the global phase property. These two phases are added to make quasi-linear phases of the stereo image channels which are used for the stereo disparity finding and the structure recovery of scene. Then, we use feature-based correspondence to find the corresponding feature points in temporal image pair. Finally, we combine the depth map and use disparity motion stereo to estimate 3-D motion parameters.

Based on a newly proposed notion of relational network, a novel learning mechanism for model acquisition is developed. This new mechanism explicitly deals with both qualitative and quantitative relations between parts of an object. Qualitative relations are mirrored in the topology of the network. Quantitative relations appear in the form of generalized predicates, that is, predicates that are graded in their validity over a certain range. Starting from a decomposition of binary objects into meaningful parts, first a description of the decomposition in terms of relational networks is obtained. Based on the description of two or more instances of the same concept, generalizations are obtained by first finding matchings between instances. Generalizing itself proceeds on two levels: the topological and the predicate level. Topological generalization is achieved by a simple rule-based graph generalizer. Generalization of the predicates uses some ideas from MYCIN. After successful generalization, the system attempts to derive a simple and coarse description of the achieved result in terms of near natural language. Several examples underline the validity of relational networks and illustrate the performance of the proposed system.

A method is presented for reconstructing the surface profile of a perfectly conducting rough surface boundary from the measurements of the scattered far-field. The proposed inversion algorithm is based on the use of the Kirchhoff approximation and in order to determine the surface profile, the Fletcher-Powell optimization procedure is applied. A number of numerical results illustrating the method are presented.

This paper describes a new feature extraction model (Active Model) which is extended from the active contour model (Snakes). Active Model can be applied to various energy minimizing models since it integrates most of the energy terms ever proposed into one model and also provides the new terms for multiple images such as motion and stereo images. The computational order of energy minimization process is estimated in comparison with a dynamic programming method and a greedy algorithm, and it is shown that the energy minimization process in Active Model is faster than the others. Some experimental results are also shown.

This paper proposes new real–time heuristic distributed parallel algorithms for search, which are based on the concepts of propagations and competitions of concurrent waves. These algorithms are characterized by simplicity and clearness of control strategies for search, and distinguished abilities in many aspects, such as real–time performance, wide suitability for searching AND/OR implicit graphs, and ease in hardware implementation.

It is shown that a self–recurrent fuzzy inference can cause chaotic responses at least three membership functions, if the inference rules are set to represent nonlinear relations such as pie–kneading transformation. This system has single input and single output both with crisp values, in which membership functions is taken to be triangular. Extensions to infinite memberships are proposed, so as to reproduce the continuum case of one–dimensional logistic map f(x)=Ax(1–x). And bifurcation diagrams are calculated for number N of memberships of 3, 5, 9 and 17. It is found from bifurcation diagrams that different periodic states coexist at the same bifurcation parameter for N9. This indicates multistability necessarily accompanied with hysteresis effects. Therefore, it is concluded that the final states are not uniquely determined by fuzzy inferences with sufficiently large number of memberships.

In this paper we study the bifurcation phenomena of quasi–periodic states of a model of the human circadian rhythm, which is described by a system of coupled van der Pol equations with a periodic external forcing term. In the system a periodic or quasi–periodic solution corresponds to a synchronized or desynchronized state of the circadian rhythm, respectively. By using a stroboscopic mapping, called a Poincar mapping, the periodic or quasi–periodic solution is reduced to a fixed point or an invariant closed curve (ab. ICC). Hence we can discuss the bifurcations for the periodic and quasi–periodic solutions by considering that of the fixed point and ICC of the mapping. At first, the geometrical behavior of the 3 generic bifurcations, i.e., tangent, Hopf and period doublig bifurcations, of the periodic solutions is given, Then, we use a qualitative approach to bring out the similar behavior for the bifurcations of the periodic and quasi–periodic solutions in the phase space and in the Poincarsection respectively. At last, we show bifurcation diagrams concerning both periodic and quasi–periodic solutions, in different parameter planes. For the ICC, we concentrate our attention on the period doubling cascade route to chaos, the folding of the parameter plane, the windows in the chaos and the occurrence of the type I intermittency.

In this paper, the dispersion characteristics of magnetostatic surface waves (MSSW) in a nonlinear gyromagnetic medium are analytically investigated. Assuming the nonlinearity as the first order perturbation in permeability tensor of the gyromagnetic medium, the perturbation technique based on the multiple scale method is used to deduce the nonlinear dispersion relations for the MSSW. It is observed that for a given propagation constant of the MSSW the frequency decreases with microwave power. It is also observed that group velocity decreases, and as a consequence, delay time increases with power of the microwave. By evaluating the dependence of frequency on power and variation of group velocity on propagation constant within the accuracy of the perturbation theory, it is confirmed that the conditions for formation of bright soliton are not satisfied for the MSSW.

The propagation characteristics of dielectric waveguides with slanted grating structure are analyzed by using the combination of the improved Fourier series expansion method and the approximated multilayer method. The slanted grating region is appoximated by a structure with stratified thin modulated index layers. This method is effective to the guiding problems of the planar slanted grating, because the electromagnetic fields in each layer can be expressed by shifting the phase of the solution in the first layer. In this paper, numerical results are given for the grating with the rectangular and the sinusoidal profile for arbitrary slant angle. The radiation efficiencies for the grating with negative and positive slant angle are also discussed.

This paper describes a segmentation method of liver structure from abdominal CT images using a three–layered neural network (NN). Before the NN segmentation, preprocessing is employed to locally enhance the contrast of the region of interest. Postprocessing is also automatically applied after the NN segmentation in order to remove the unwanted spots and smooth the detected boundary. To evaluate the performance of the proposed method, the NN–determined boundaries are compared with those traced by two highly trained surgeons. Our preliminary results show that the proposed method has potential utility in automatic segmentation of liver structure and other organs in the human body.

We report on an experimental hysteresis in the Hopfield networks and examine the effect of the hysteresis on some important characteristics of the Hopfield networks. The detail mathematic description of the hysteresis phenomenon in the Hopfield networks is given. It suggests that the hysteresis results from fully–connected interconnection of the Hopfield networks and the hysteresis tends to makes the Hopfield networks difficult to reach the global minimum. This paper presents a T–Model network approach to overcoming the hysteresis phenomenon by employing a half–connected interconnection. As a result, there is no hysteresis phenomenon found in the T–Model networks. Theoretical analysis of the T–Model networks is also given. The hysteresis phenomenon in the Hopfield and the T–Model networks is illustrated through experiments and simulations. The experiments agree with the theoretical analysis very well.