Along with the improvement of micro processors and local area networks, a distributed system becomes useful to realize a telecommunication system. It has potential advantage to achieve both high performance and high reliability. However, the design of a distributed system tends to be more complicated compared to a conventional centralized system. For the purpose of the standardization of distributed processing, ISO and ITU-T study the Open Distributed Processing (ODP) and are currently standardizing the Basic Reference Model of ODP (RM-ODP). To avoid dealing with the complexity of distributed systems, RM-ODP defines five viewpoints. The viewpoint approach of RM-ODP is proposed as a framework for the design of a distributed system. Although some previous works give the design methods of distributed systems based on the ODP viewpoint approach, the detailed design method has not been fully specified or all of the five viewpoints are not taken into account. In this paper, we describe a detailed design method for a distributed telecommunication system based on the ODP viewpoint approach. The method applies the five viewpoints to the three phases of design of a distributed system, that is, requirement analysis, functional design and detailed design phase. It clarifies what specifications for the target system should be made from the individual viewpoints and how the specifications are related each other. It also takes account of the platform which provides the distribution support, and gives the design method for both the platform and the application specific functions on the platform. The design method is examined by applying it to the design of a distributed MHS system supporting X.400 series protocols. In this example, the remote procedure call based on the client-server model is selected as the base of the platform. The result shows that our method is useful to simplify the complexity of the design for a distributed telecommunication system.

In this paper, a novel coupler-type wavelength demultiplexer composed of the K+-ion diffused waveguides, which has an adjustment function for optimizing the diffusion depth, is proposed to achieve reliably the high extinction ratio. The optimization in the diffusion depth is made by repeating the K+-ion diffusion and extinction-ratio measurement alternatively, and the high extinction ratios more than 20 dB are measured reliably at both operation wavelengths of 0.6328 and 0.83 µm. Experimental results on the polarization dependence in the extinction-ratio adjustment are also reported.

A coupled-mode analysis of a symmetric planar nonlinear directional coupler (NLDC) is presented by using a singular perturbation scheme. The effects of linear coupling and nonlinear modification of refractive index are treated to be small perturbations, and the modal fields of isolated linear waveguides are employed as the basis of propagation model. The self-consistent first-order coupled-mode equations governing the transfer of optical power along the NLDC are obtained in analytically closed form. It is shown that tha critical power for optical switching derived from the coupled-mode equations is in close agreement with that obtained by the numerical analysis using the finite difference beam propagation mathod.

On ranging system on short distance using spread spectrum, we examine waveform responses to predict the state of electromagnetic waveform propagation while the signal is received after scattered by a target. Then this system and the numerical results are discussed.

It is known that homogeneous networks are ones which perform parallel algorithms, and the dynamics of neural networks are applied to practical problems including combinatorial optimization problems. Both homogeneous and neural networks are parallel networks, and are composed of Boolean elements. Although a large number of studies have been made on the applications of homogeneous threshold networks, little is known about the relation of the dynamics of these networks. In this paper, some results about the dynamics, used to find the lengths of periodic and transient sequences, as built by parallel networks including threshold and homogeneous networks are shown. First, we will show that for non–restricted parallel networks, threshold networks which permit only two elements to transit at each step, and homogeneous networks, it is possible to build periodic and transient sequences of almost any lengths. Further, it will be shown that it is possible for triangular threshold networks to build periodic and transient sequences with short lengths only. As well, homogeneous threshold networks also seem to build periodic and transient sequences with short lengths only. Specifically, we will show a sufficient condition for symmetric homogeneous threshold networks to have periodic sequences with the length 1.

We propose and demonstrate an excellent linearly frequency-swept laser diode (LD) for sensing system utilizing frequency-moduleted continuous-wave (FMCW) technique. In order to linearly sweep the optical frequency, we adopt a reference interferometer and an electric phase comparator. The interference beat signal of the reference interferometer is phase-compared with an external reference rectangular signal having a fixed frequency near the interference beat signal frequency by a lock-in amplifier. The error signal from the lock-in amplifier is fed back to the modulating signal of the injection current of the LD. Thus, a phase-locked loop composed of optical and electric circuits can be established, and the beat signal frequency is locked to the frequency of the reference signal. The optical frequency of the LD is, therefore, excellently linearly swept in time. In order to experimentally confirm the linearlity of the proposed method, we apply this light source to the FMCW reflectometry. Resultingly, the improvement of the linearity is estimated to be about 10 dB. And the theoretically limited spatial resolution of the FMCW reflectometry is achieved.

This letter presents the results of an analysis concerning the global, dynamical structure of a second order phase–locked loop (PLL) in the presence of the continuous wave (CW) interference. The invariant manifolds of the PLL equation are focused and analyzed as to how they are extended from the hyperbolic periodic orbits. Using the Melnikov integral which evaluates the distance between the stable manifolds and the unstable manifolds, the transversal intersection of these manifolds is proven to occur under some conditions on the power of the interference and the angular frequency difference between the signal and the interference. Numerical computations were performed to confirm the transversal intersection of the system–generated invariant manifolds for a practical set of parameters.

We propose two methods to fuse auditory information and visual information for accurate sppech recognition. The first method fuses two kinds of information by using linear combination after calculating two kinds of probabilities by HMM for each word. The second method fuses two kinds of information by using the histogram which expresses the correlation of them. We have performed experiments comparing the proposed methods with the conventional method and confirmed the validity of the proposed methods.

Synchronization has been one of the problems in M–ary spread spectrum communication systems. In this letter, we propose the frame synchronization method using the Hadamard matrix and a frame synchronization method of PCM communication systems. Moreover, we analyze the probabilities of keeping synchronous state and frame renewal rates, and we evaluate the relationship between these probabilities and the number of stages of counters.

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 introduce recurrent networks that are able to learn chaotic maps, and investigate whether the neural models also capture the dynamical invariants (Correlation Dimension, largest Lyapunov exponent) of chaotic time series. We show that the dynamical invariants can be learned already by feedforward neural networks, but that recurrent learning improves the dynamical modeling of the time series. We discover a novel type of overtraining which corresponds to the forgetting of the largest Lyapunov exponent during learning and call this phenomenon dynamical overtraining. Furthermore, we introduce a penalty term that involves a dynamical invariant of the network and avoids dynamical overtraining. As examples we use the Hnon map, the logistic map and a real world chaotic series that correspond to the concentration of one of the chemicals as a function of time in experiments on the Belousov–Zhabotinskii reaction in a well–stirred flow reactor.

We discuss a processor scheduling problem for parallel logic simulation of combinational circuits. In the processor scheduling problem, to be discussed in this paper, for logic simulation using time–first method, the time needed for each gate evaluation is not given beforehand, and is not constant. This feature distinguishes the processor scheduling problem from typical task scheduling problems. First, we devise newly Algorithm MET to solve the processor scheduling problem. The key idea of Algorithm MET is to determine processor scheduling incrementally and dynamically. Then, experimental evaluations using well–known twelve benchmark combinational circuits show the usefulness of Algorithm, MET, compared with conventional static algorithms. We believe that this is a first step to implement parallel logic simulation of combinational circuits.

This paper proposes a new class of unidirectional byte error locating codes, called single symmetric bit error correcting and single unidirectional byte error locating codes, or SEC–SUbEL codes. Here, "byte" denotes a cluster of b bits, where b2. First, the necessary and sufficient conditions of the codes are clarified, and then code construction method is demonstrated. The lower bound on check bit length of the SEC–SUbEL codes is derived. Based on this, the proposed codes are shown to be very efficient in some range of the information length. The code design concept presented for the SEC–SUbEL codes induces the generalized unidirectional byte error locating codes with single symmetric bit error correction capability.

This paper proposes a methodology for fine evaluation of the uncertain behaviors of systems affected by any fluctuation of internal structures and internal parameters, by the use of a new concept on the fuzzy mapping. For a uniformly convex real Banach space X and Y, a fuzzy mapping G is introduced as the operator by which we can define a bounded closed compact fuzzy set G(x,y) for any (x,y)∈X×Y. An original system is represented by a completely continuous operator f defined on X, for instance, in a form xλ(f(x)) by a continuous operator λ: YX. The nondeterministic fluctuations induced into the original system are represented by a generalized form of the fuzzy mapping equation xGβ (x,f(x)) {ζX|µG(x,f(x))(ζ)β}, in order to give a fine evaluation of the solutions with respect to an arbitrarily–specified β–level. By establishing a useful fixed point theorem, the existence and evaluation problems of the "β–level-likely" solutions are discussed for this fuzzy mapping equaion. The theory developed here for the fluctuation problems is applied to the fine estimation of not only the uncertain behaviors of system–fluctuations but also the validity of system–models and -simulations with uncertain properties.

An optimal control theory has been applied to a biological compartment system to show a method to analyze the control principle of biological system represented by compartments. Present theory has been proposed to afford a theoretical back ground and validity for the strategy of drug administration or control of the anesthetic agent in practical medicine. The instantaneous change of the concentration of a given material within a biological system has been expressed by differential equations. Each compartment has been set to be transferred a material from all other compartments and conversely each compartment sends it to all other compartments. The control input was restricted to be one kind. The performance function involved the deviation from the target value, the rate of change in concentration and the amount of the control variables. The biological system was defined to operate optimally only when the performance function has been minimized during a given time period. By the optimal control theory of Pontoriagin, above biological problem has been converted to a mathematical problem and was solved numerically by multiple shooting method. The calculated trajectory of the optimal control has been asymmetric parabolic one with the maximum at its initiation and the minimum at the middle of total reaction time. This pattern has been consistent with that of probable transient change of the concentration of anesthetic agent when it has been inhalated under the most up to date "Rapid Inhalation Induction" method. The optimal trasient change of the concentration at each compartment has beeb affected by the difference in time dependent nature and the magnitude of the transfer rate. Present theory afforded a method to analyze the control strategy of biological system expressed by compartments model and showed an availability for actual clinical medicine. The optimal control principle must be a most adequate one to describe the Homeostasis in biological system.

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.

We propose an optimal throughput problem using graph transformations to maximize throughput of a pipelined data path with some loops. The upper bound of the throughput, equals to the lower bound of the iteration interval between the start of two successive iterations, is limited by the length of a critical loop. Therefore we can maximize the throughput by minimizing the length of the critical loop. The proposed method first schedules an initial Data Flow Graph (DFG) under the initial iteration interval as few as it can use resources, then it transforms the DFG into the flow graph with the minimal length of the critical loop by rescheduling the given initial scheduling result. If there are any control steps which violate the resource constraints owing to the transformations, then these operations are adjusted so as to satisfy given resource consrtraints. Finally by rescheduling the transformed DFG, it gives a schedule with maximum throughput. Experiments show the efficiency of our proposed approach.

More than 200 papers, two special issues (Journal of Circuits, Systems, and Computers, March, June, 1993, and IEEE Trans. on Circuits and Systems, vol.40, no.10, October 1993), an International workshop on "Chua's Circuit: chaotic phenomena and applications" at NOLTA'93, and a book (Edited by R. N. Madan, World Scientific, 1993) on Chua's circuit have been published since its inception a decade ago. This review paper attempts to present an overview of these timely publications, almost all within the last 6 months, and to identify four milestones of this very active research area. An important milestone is the recent fabrication of a monolithic Chua's circuit. The robustness of this IC chip demonstrates that an array of Chua's circuits can also be fabricated into a monolithic chip, thereby opening the floodgate to many unconventional applications in information technology, synergetics, and even music. The second milestone is the recent global unfolding of Chua's circuit, obtained by adding a linear resistor in series with the inductor to obtain a canonical Chua's circuit--now generally referred to as Chua's oscillator. This circuit is most significant because it is structurally the simplest (it contain only 6 circuit elements) but dynamically the most complex among all nonlinear circuits and systems described by a 21–parameter family of continuous odd–symmetric piecewise–linear vector fields. The third milestone is the recent discovery of several important new phenomena in Chua's Circuits, e.g., stochastic resonance, chaos–chaos type intermittency, 1/f noise spectrum, etc. These new phenomena could have far-reaching theoretical and practical significance. The fourth milestone is the theoretical and experimental demonstration that Chua's circuit can be easily controlled from a chaotic regime to a prescribed periodic or constant orbit, or it can be synchronized with 2 or more identical Chua's circuits, operating in an oscillatory, or a chaotic regime. These recent breakthroughs have ushered in a new era where chaos is deliberately created and exploited for unconventional applications, e.g., secure communication.