This paper investigates the problem of constructing a logical multicasting tree which dispatches data to multiple destinations according to their bandwidth requirements. An optimization problem is formulated to minimize the maximum delay between a sender and multiple receivers. An algorithm of finding the optimum branching locations is presented. Performance analysis from the closed queueing network theory is given to evaluate a multicasting tree network based on this proposed algorithm.

Digital-switching noise coupled into sensitive analog circuits is a critical problem in large-scale integration of mixed analog and digital circuits. This paper describes noise coupling of this kind, especially, through the substrate in CMOS integrated circuits, and reviews recent technical solutions to this noise problem. Simplified models have been developed to simulate the substrate coupling rapidly and accurately. A method using a CMOS comparator was proposed for measuring the effects of substrate noise, and equivalent waveforms of actual substrate noise were obtained. A circuit tecnique, called active guard band filtering, that controls the noise source is a new approach to substrate noise decoupling. CAD methods for handling substrate-coupled switching noise are making design verification possible for practical mixed-signal LSIs.

For object analysis and recognition, an original shape often needs to be described by using a small number of vertices. Polygonal approximation is one of the useful methods for the description. In this paper, we propose the curvature-based polygonal approximation (CBPA) method that is an application of the weighted polygonal approximation problem which minimizes the number of vertices of an approximate curve for a given error tolerance (the weighted minimum number problem). The CBPA method considers the curvature information of each vertex of an input curve as the weight of the vertex, and it can be executed in O(n2) time where n is the number of vertices of the input curve. Experimental results show that this method is effective even in the case when relatively few vertices are given as an original shape of a planar object, such as handwritten letters, figures (freehand curves) and wave-form data.

For constructing the next generation education system, we have developed a new human-scale virtual reality interface device called Big-SPIDAR. This device can provide not only the visual and auditory information but also haptic/kinaesthetic display. And it has the capability for the operator or participant to move around inside it. In this paper, we introduce the construction of this interface device and show the evaluation experiments and application systems realized by proposed device.

This study proposes an amplitude limiting type spread spectrum communication to be applied to extremely low power radio wave communicaion and evaluates capability of the code division multiplex. First, changes in output from the correlation device, maximum power, and in allowable noise power are compared by computer simulation for the case where the number of multiplex channels is increased. Second, possible relationship between noise intensity and error rate is measured by actual loading experiments using a device developed for trial purpose. Third, majority decision logic is proposed for the said device to realize amplitude limiting type code division multiplex easily. When the amplitude is limited, the maximum power can be controlled at about 2 dB, and channels with more than half of the number of spread sign can be used. It is revealed that, in the spread spectrum, alteration of the number of multiplex channels is made easy by application of this method.

We developed the computer calligraphy, that is, a computer formation of brush-written Kanji characters using calligraphic knowledge. The style of brush handwriting depends mainly on the way of using a writing brush. Brush writing skills include the direction of brush at the beginning, curvature and turning the brush, the brush-up at the termination point in a stroke. We make up the calligraphic knowledge base according to the above mentioned brush writing skills. For simulating real brush movement, we represent the brush contact form that is the brush shape on the writing plane as a brush-touch. The system can control the size and direction of this brush-touch during the brush simulation. The system simulates the real brush writing to move the brush-touch along the skeleton letter shape in the standard database. We get the brush written Kanji from the locus of the brush-touch movement. We can extend this system to the new on line training system for brush writing using the simulation of brushtouch movement modified by the pressure, speed and rotation of the writing brush, and the skeleton letters written by a learner from the tablet. This system is also useful for students learning how to write Japanese letters beautifully with brush.

This paper proposes the concept of information retrieval for fine arts database system on the fuzzy set theory, especially concerning to sensitive impression and location data. The authors have already reported several important formulations about the data structure and information retrieval models based on the fuzzy set theory for multimedia database. The fuzzy models of the information retrieval are implemented in the fine arts database system, which has the following features: (1) The procedure of information retrieval is formulated in the fuzzy set theory; (2) This database can treat multimedia data such as document data, sensitive impression, location information, and imagedata. (3) It is possible to retrieve the stored data based on sensitive impression and the location data such as "joyful pictures which have a mountain in the center and there is a tree in the right"; (4) Users can input impression words as a retrieval condition, and estimate their grades such as "low," "medium," and "high"; (5) For the result of information retrieval, the satisfaction grade is calculated based on fuzzy retrieval model; and (6) The stored data are about 400 fine arts paintings which are inserted by the textbook of fine arts currently used at the junior high school and high school in Japan. These features of this system give an effects of the fine arts education, and should be useful for information retrieval of fine arts. The results of this study will become increasingly important in connection with development of multimedia technology.

The purpose of our study is to develop an intelligent adaptive instruction system that manages intelligently the learner's estimated knowledge structure and optimizes the selection of problems according to his/her knowledge structures. The system adopts the dynamic problems of high school physics as a material of study, and is intended to operate on a UNIX Work Station. For these purposes, the system is composed of three parts, 1) interface part, 2) problem solving expert part, and 3) optimization expert system part for problem selection. The main feature of our system is that both knowledge structures of learner and teacher are represented by structural graph, and the problem selection process is controlled by the relationship between the learner's knowledge structure and the teacher's knowledge structure. In our system the relationship between these two knowledge structures is handled in the optimization expert system part for problem selection. In this paper the theory of the optimization expert system part for problem selection is described, and the effectiveness of this part is clarified through a simulation experiment of the originally defined matching coefficient.

A formal system-level synthesis model for the concurrent object-oriented design of parallel computer systems, called Multi-token Object-oriented Bi-directional net (MOBnet), is proposed. The MOBnet model extends the standard Petri net by defining (1) multiple tokens to represent different kinds of synthesis control information, (2) object-oriented nodes (places) to denote the system parts under synthesis, and (3) bi-directional arcs to model the design completion check and synthesis rollback operations. In this paper, we first show that MOBnet can serve as a pre-fabrication design methodology analysis tool in ways such as class hierarchy construction, design specification comparison, reachability analysis, and concurrent process management and analysis. We then formally prove MOBnet to be a valid model for concurrent synthesis and give experimental application examples to verify. Finally, solution schemes for the design completion check and synthesis rollback problems are formally validated by analyzing the dynamic behavior of MOBnet, and experimentally illustrated through examples.

For two decades, our colleagues and we have been developing our multiple learning environments in mathematical education for upper secondary school learners, and have been reporting our learner-centered system in the latest four WCCE Conferences (WCCE/1981/1985/1990/1995). In our latest learning multimedia system, individual learners have to meet a complex network structure in which objectives are arranged in the form of non-linear linking and to proceed actively to their own goals. In order to support their exploring learning, we developed several instructional navigation tools from an instructional view point. This paper presents our instructional navigation technology and its tools. The feature of our present system is to provide a supportive environment where individual learners can set up their own goals, create their own paths for their goals through instructional materials, and construct their own instructional structure based on instructional strategies. This feature is remarkably different from a traditional CAI system in which learners are only directed through the courseware via a linear selection of menus. Also this feature fundamentally differs from general navigation technologies by which a user is able to traverse a series of nodes among non-linear network structure, because our navigation must present individual learners with some easily learnable sequences of objectives based on their object and interest. For this purpose, this system has three chracteristic technologies, i.e. focusing, sequencing and clustering ones. These are very useful for them to make their decisions in order to reach their own goals. This paper consists of (1) ideas of instructional navigation, (2) map technology and (3) navigation technology.

Recently, various systems based on agent model architecture have been developed. In these systems, 'agents' with their own goals and functions are embedded, and perform their own tasks through collaboration among them by communication to achieve a goal as the system requires. Using this agent model for the construction of educational systems, adaptive configuration of the system is achieved. The purpose of this study is to propose a methodology for the design of an educational system based on agent model architecture. This paper describes the configuration of the agent model and the communication language and protocol used to represent collaboration among the agents necessary for performing a cooperative task. Moreover, we explain how to organize these agents as an educational system. As a case to show the organization of agents, we discuss the configuration of an intelligent learning environment to support C shell programming in UNIX and explain the collaborative behavior of embedded agents.

Many efforts are currently underway to design wideband mobile communication systems. In this letter, we clarify the received signal level characteristics for wideband mobile radio channels in line-of-sight (LOS) microcells. We conduct several urban-area field experiments to measure the received signal levels for various receiver bandwidths from 300 kHz to 30 MHz and the power delay profile. The experimental results show that the fading depth of the received signal decreases as the normalized rms delay spread, defined as the product of receiver bandwidth and rms delay spread, increases. These results are useful in designing wideband microcell systems for urban areas.

The growing availability of commercial foundry processes allows easy implementation of micro-opto-electro-mechanical systems (MOEMS) for a variety of applications. Such applications go beyond single devices to include whole optical systems on a chip, consisting of mirrors, gratings, Fresnel lenses and shutters, for example. Hinged and rotating structures, combined with powerful and compact thermal actuators, provide the means for positioning and operating these optical components. This paper presents examples of such systems built in a commercial polycrystalline silicon surface-micromachining process, the ARPA-sponsored Multi-User MEMS ProcesS (MUMPS). Examples range from optical sub-components to large mirror arrays, communication components, and micro-interferometers. Using the examples discussed in this paper, a designer can take advantage of commercially available surface-micromachining processes to design and develop MOEMS without the need for extensive in-house micromachining capabilities.

We show that the truth of a prenex normal form Presburger sentence bounded only by existential quantifiers (or an EPP-sentence) involving two variables can be decided in deterministic polynomial time. Specifically, an upper bound of the computation for the decision is O(n3u), where n is the number of atoms of the EPP-sentence, and u is the largest absolute value of all coefficients in the EPP-sentence. In the analysis for the upper bound, the random access machine is assumed for the machine model. Additionally, a uniform cost criterion is assumed. Deciding the truth of an EPP-sentence is an NP-complete problem, when the number of variables is not fixed. Furthermore, whether the truth of an EPP-sentence involving two or more variables can be decided in deterministic polynomial time, when the number of variables is fixed, or not has remained an open problem. We previously proposed a procedure for quickly deciding the truth of an EPP-sentence on the basis of a suggestion by D.C.Cooper. We found the upper bound by analyzing the decision procedure. The procedure can be applied to both automated correctness proof of specification in various design fields and detection of infeasible paths in a program. In the procedure, a matrix denoting coefficients of the variables in the EPP-sentence is triangulated.

Verification of timed bisimulation equivalence is generally difficult because of the state explosion caused by concrete time values. In this paper, we propose a verification method to verify timed bisimulation equivalence of two timed processes using a symbolic technique similar to [1]. We first propose a new model of timed processes, Alternating Timed Symbolic Labelled Transition System (A-TSLTS). In an A-TSLTS, each state has some parameter variables, whose values determine its behaviour. Each transition in an A-TSLTS has a quard predicate. The transition is executable if and only if its guard predicate is true underspecified parameter values. In the proposed method, we can obtain the weakest condition for a state-pair in a finite A-TSLTS, which the parameter values in the weakest condition must satisfy to make the state-pair be timed bisimulation equivalent.

The present paper describes a novel approach to interconnecting and assembling components of MEMS at room temperature. The main drawback of the conventional bonding methods is their rather high process temperatures. The new method, which is referred as the surface activated bonding (SAB), utilizes the phenomena of the adhesion between two atomically clean solid surfaces to enable the bonding at lower temperature or even at room temperature. In the bonding procedure, the surfaces to be bonded are merely brought into contact after sputter-cleaning by Ar fast atom in ultrahigh vacuum conditions. TEM observations of the bonded interfaces show that a direct bonding in atomic scale is achieved in the interface between the micro-components. Based on the concept of this new bonding technology, a micro-assembly system was developed. The micro-assembly system is operated by means of a virtual manipulation system in which 3D model of the micro-components are manipulated virtually in a computer graphics constructed in the world wide web (WWW) scheme. The micro-assembly system will provide a new design tool of three dimensional MEMS by combining the possibility of the flexible assembly and the intuitive operations.

In this paper, an efficient one-way point-to-multipoint communication protocol (PTMP) is proposed. The PTM protocol is helpful to distribute information to many workstations simultaneously and correctly. The PTM protocol is designed for network channels with low error possibility. The PTM protocol utilizes broadcast for data distributing. Re-transmission request for lost packet is returned to the server, and acknowledgment for correctly received packets is not returned to the server. We have applied the protocol to the network presentation system. The network presentation system is intended to display same graphical images to multiple workstations simultaneously on an X window system. This presentation system is able to provide services for at least forty X servers simultaneously, the capacity is limited to X server performance, except for pixmap drawing. For the case of pixmap drawing, the system capacity is limited to the network bandwidth. To solve network bandwidth problem, we combined PTM protocol with the network presentation system. With PTM protocol, system performance is improved and the use of network bandwidth is lowered.

In this paper, we analyze the multiple access interference of a variable processing gain DS/CDMA system and define discrete partial crosscorrelation functions. We also evaluate the bit error rate of the system using Gaussian approximation and bounding technique. Three kinds of spreading codes (long, short, and random codes) are considered in the analysis of the system. It is shown that the bit error rate of a user is not relevant to the processing gain of interfering users: it is relevant only to the processing gain of the user, transmitted powers, PN sequences, and spreading codes. The performance of short codes turns out to be better than that of long and random codes as in other systems.

Effective collaboration in ComputerSupported Collaborative Learning (CSCL) environments is nowadays an important research topic. It deals with two main problems: the configuration of an appropriate learning group and the intelligent task distribution in the practice of domain knowledge. In order to have effective collaboration in a CSCL environment, we have proposed a set of software agents that assist the learners to select their learning tasks, according to their capabilities and the possibilities of collaboration between them. In this paper the cooperation among software agents is presented as the key point for effective collaboration in CSCL environments. In this kind of environments the learner must have enough collaboration and learning possibilities, being motivated with the experience of social knowledge construction. We have been working on the problem of effective collaboration in CSCL environments, based on the cooperation between software agents developed for GRACILE, our Japanese Grammar CSCL environment. Before, we have proposed intelligent agents that assist the learners. Our next step has been the design of the cooperation between agents in order to create possibilities of effective collaboration in a virtual community of practice. In order to evaluate the performance of our agents we made several simulations. The results obtained from these simulations of diverse types of learning groups provided us with guidelines for the configuration of groups in CSCL environments, where effective collaboration is possible.

In this paper we discuss a certain constrained optimization problem which is often encountered in the geometrical optimization. Since these kinds of problems occur frequently, constrained genetic optimization becomes very important topic for research. This paper proposes a new methodology to handle constraints using the Genetic Algorithm through a multiprocessor system (FIN) which has a self-similarity network.