East japan great disaster tell us the many unfavorable points of the present communication system. Learning from these facts, the design principle of the robust communication system is proposed utilizing the logical structure of the network.

The distributed resource allocation problem is a well known fundamental problem in distributed systems. Many solutions which avoid the deadlock and starvation have been developed. With the progress of computer networks, however, distributed cooperative group activities in a network environment have been increasing, so that several groups may compete for some resources in the network environment and deadlock among groups and starvation of a group may happen. Since previous allocation models are mainly for representation of competition for resources among processes, they cannot reflect clearly the competition for resources among groups of processes. Moreover, though the previous solutions to the distributed resource allocation problem can avoid the deadlock and starvation, they cannot deal with the deadlock among groups and starvation of a group. The authors present a new model which explicitly describes the competition for resources among process groups which may share common processes, and a definition of "Distributed Allocation of Resources to process Group" (DARG) under the model. A solution to DARG is also proposed by extending an acyclic graph approach to the dining philosopher problem. Our solution allocates resources to groups of processes with deadlock among groups and starvation of a group never happening. In addition, our solution guarantees that more than one group works mutually exclusively if a common process belongs to these groups.

The process of development of network computing towards the 21st century is explained. In order to make clear the key technologies required for the development of network computing, the logical model of the system is represented by a site-layer model and the key technologies corresponding to each layer are introduced. For the future development of the information society, the importance and the technologies concerning thin computers and the new platform constructed by the unification of the Internet and broadcasting are also discussed. Finally, the future trends of EC (electronic commerce) is envisioned.

This paper describes a new multimedia LAN protocol, referred to as the buffer insertion/self-token (BIST) protocol, combining buffer insertion and the multiple-self-token ring protocols. The basic buffer insertion ring has the maximum spatial reuse on a ring by allowing stations to transmit packets concurrently. However, it is well known that the buffer insertion method suffers from the possibility of starvation. BIST prevents starvation and maintain fairness by assigning each station individual tokens, called self-tokens. Then a station is allowed to send packets only if it holds its own tokens, that is, each packet transmitted by the station is attached a self-token belonging to the station. That is why packet flow on a ring is regulated, and fairness is adjustable. Asynchronous and synchronous transmissions are supported by using two kinds of self-token, one is for asynchronous transmission and the other is for synchronous transmission. The effectiveness of the proposed protocol is demonstrated via simulation.

As a fundamental study of multiple image processing, the authors have developed a new technique for the analysis of multispectral remote sensing data. Though the basis of the authors' algorithm is similar to a histogram analysis, they have proposed a novel way of the representation of multidimensional image data, which facilitates a nonexpert to locate and assign different classes present in the data set. The authors' experimentation was done with NOAA satellite image data. The brightness of the received data from channels of different frequency bands are the different dimensions of the multispectral image. By using this method, the authors could successfully classify NOAA satellite data received from the northern part of Japan, and locate the plane areas as an exercise. The authors have quantitatively compared their result with official data. The authors' result was found to be only 1 percent in deviation with the official data.>

The authors examine the structural relationship between load and blocking probability for a fully connected homogeneous nonhierarchical network when blocked messages cause retrial and when different alternate routing strategies are employed to overcome congestion. The model employed for analysis is based on the flow approximation. It is found that retrials push the stable equilibrium state away from the zero blocking state, thereby aggravating congestion. The alternate routing strategies accommodate the stable equilibrium state close to the zero blocking state. However, both the retrials and the alternate routing strategies do not alter the fundamental structure of the system, namely, the fold catastrophe. By solving the degenerate equation, the value of appropriate control parameters can be obtained. According to the present model, it is only under schemes with no alternate routing that the system attains stability, in the mathematical sense of the term.>

Store-and-forward techniques in computer communication networks are addressed. The performance estimation and the stability aspects of an input buffer limiting (IBL) scheme are presented. The model is formulated with respect to the state-dependent effective input rate and effective service rate. The computation of the performance parameters with respect to the effective service rate yields satisfactory results when blocking probabilities are not restricted to very low values (>

An attempt is made to design a user-friendly software environment for protocol synthesis based on the FSM (finite state machine), and to show the validity of applying AI (artificial intelligence) techniques to the construction of such a system. For that purpose, the authors have first designed a user-friendly software environment, named SEPS, using the programming language C, which belongs to the procedural programming paradigm. The aim of SEPS is to help a protocol designer to easily design a protocol and avoid logical errors like unspecified receptions and state deadlocks. In order to enhance the productivity of protocol development, a user-friendly interface has been designed which employs the multiwindow mechanism and provides the graphic tools in this system. Consequently, a protocol designer without any experience in protocol synthesis can easily design a protocol without logical errors. The authors have also designed a knowledge-based software environment for protocol synthesis, named KSPS, using the expert system tool OPS83. KSPS has the same functions as SEPS. The advantages of KSPS over SEPS in terms of extension, modification, and maintenance of protocol development systems are shown.>

A numerical method is suggested for estimating the performance parameters of a node with input buffer limiting, throughout the range of blocking probabilities. Congestion is attributed to the sudden increase in the effective service time when the input rate increases. This sudden increase, resulting in the thrashing of the throughput rate, can be related to changes in the shape of the potential function of the node. The methodology of deriving the potential function of the node from its gradient dynamics and dynamic flow conservation considerations is presented. Using the results from catastrophe theory, it is shown that the abrupt changes in the throughput can be expected due to the existence of a catastrophe point in the parameter space. The behavior of a node in a homogeneous network can be characterized by a fold catastrophe. The simulation results are found to agree with the results obtained by the numerical method.>

Stability and throughput are investigated for a combined random-reservation access scheme employed in a satellite-based very small aperture terminal (VSAT) packet communication network. The analysis is based on the use of catastrophe theory by which the system behavior is characterized by the cusp catastrophe. A stable region is given in terms of system and user parameters such as packet generation rate, retransmission rate, channel division ratio and propagation delays. A numerical example is given to illustrate the analysis developed. Simulation results agree with the steady-state throughput of the model.>

The authors attempted to identify fog using image-processing data from the US National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR). AVHRR sensors measure radiation at visible, near-infrared, and infrared wavelengths. Attention is confined to daytime data from channel 1 (CH1), channel 3 (CH3), and channel 4 (CH4) for a detection range of lambda =0.58 approximately 0.68 mu m, lambda =3.55 approximately 3.93 mu m, and lambda =10.5 approximately 11.5 mu m, respectively. The authors have analyzed by image processing the data obtained from CH1, CH3, and CH4 by forming two- and three-dimensional histograms and enhancing them in color.>

The development of the NOAA satellite Advanced Very High Resolution Radiometer (AVHRR) three-dimensional analysis system, in which the problem of drawing a three-dimensional histogram on a two-dimensional CRT was encountered, is discussed. In this case there are two factors: one is the coordinate position given by the brightness level of the three image channels of NOAA AVHRR, the other is the frequency of the points within the images. To decide the semi-optimum value for displaying the processed three-dimensional histogram, the authors tried to relate the frequency and the total number of pixels. It was found that the standard deviation is reasonable. In the analysis using this method, the differences between major components of the images are displayed in the three-dimensional histogram, allowing the identification of features like sea, land, and clouds by a clustering process.>

An intelligent support system, designed to make the development of protocols and communication software easy and user-friendly, is described. The support system is outlined and its accessories (the knowledge-based specification editor, the validation expert system, the software generation expert system, the conformance-testing expert system, and the protocol-conversion expert system) are described in detail. Artificial intelligence techniques are used in the design of each component of the support system. An example which demonstrates the functions of each component in the support system is given.>

A knowledge-based system for protocol synthesis named KSPS is presented. The aim of KSPS is to help the protocol designer design a protocol without logical errors, such as unspecified receptions and state deadlocks. KSPS consists of three major components: a knowledge base, a user interface, and an inference engine. The construction of the knowledge base and the user interface is examined. The knowledge of protocol synthesis represented in the production model and in the procedure programming model is embedded in the knowledge base. A user-friendly interface with a multiwindow mechanism is designed which provides the graphic tools in this system. Consequently, the protocol designer without experience in protocol synthesis can easily design a protocol without logical errors.>

An interactive synthesis algorithm, to construct two communicating finite-state machines (protocols), is presented. The machines exchange messages over two unidirectional FIFI (first-in first-out) channels when the function of the protocol has been given. The synthesis algorithm first constructs the global state transition graph (GSTG) of a protocol to be synthesized and then produces the protocol. It is based on a set of production rules and a set of deadlock avoidance rules, which guarantee that complete reception and deadlock freeness capabilities are provided in the interacting process. This synthesis algorithm prevents a designer from creating unspecified reception and nonexecutable transition, avoids the occurrence of deadlocks, and monitors for the presence of buffer overflow.>

We develop a new tool for performance evaluation of a multiaccess communication system. We give an explicit detailed analytic description of a cusp catastrophe in a computer communication system. An approximate model is formulated for a slotted Aloha system assuming a single buffer, based on the Markovian model studied by Lam [2] and Carleial [3]. Next, we outline the research on quantitative processing of thrashing and its results. Sudden changes, which can be observed in the throughput rate, the average delay, and the average number of backlogged users, are induced by smooth alterations of control parameters in the behavior of a slotted Aloha system. These catastrophic phenomena, such as long lasting periods of vanishing throughput rate and very high delays, are analyzed in line with catastrophe theory. The system behavior in a slotted Aloha system is characterized by the cusp catastrophe. In particular, introducing a new parameter σ in our model, we make it clear why and in what cases these catastrophic phenomena occur. The amount of change is also estimated.

Spatially discrete analogue neural networks and spatially continuous analogue neural networks are considered in this paper in studying the fundamental properties of analogue neural networks. A model of neural networks is discussed.

Some characteristics of the global function of the finite cellular automaton (FCA) are investigated. First, a necessary and sufficient condition for a function from the configuration set to itself to be realized by means of an FCA is given. Next, using these results, the realizability of cycle and tree type transition structures is discussed. Especially, for the system of binary 3-neighbor FCA, the realizability of the maximal cycle length and the bijectivity of the global function are investigated. For the system of FCA, each passive configuration set is defined. An algorithm to obtain the spectrum of a passive configuration set is also discussed. In addition, some examples on the spectrum for the system of binary 3-neighbor FCA are demonstrated.