In a distributed-memory parallel-processing system, the overhead of data transfer among the processors is so large that it is important to reduce the data transfer. We consider the data transfer in evaluating an expression consisting of data distributed among the processors. We propose some algorithms which assign the operators in the expression to the processors so as to minimize the number or the cost of data transfers, on the condition that the data allocation to the processors is given. The basic algorithm is given at first, followed by some variations.

This paper discusses a way of identifying the network configuration of ATM-LANs, which are composed of a number of ATM hubs. In general, a Network Management System (NMS) sets and gets the necessary data to and from the network elements. In managing an ATM-LAN, the ATM connection between the NMS and each network element, namely the ATM hub, must be established in order to get and set the necessary data. This forms a remarkable contrast with conventional LANs such as the IEEE802.3 LAN, which is a shared media network and enables broadcast communication without setting up any connection. This paper proposes a new protocol and a procedure that establishes the ATM connection between the NMS and each ATM hub, while identifying the overall network configuration. First, this paper makes clear the peculiarity of the ATM-LAN in terms of automatically identifying the network configuration. Next, the identification protocol that achieves the required properties is precisely explained. Then, the proposed identification protocol is evaluated in terms of required bandwidth and identification time.

This paper describes a new method to estimate traffic load of communication nodes, such as switching systems. The new method uses the system identification, which is often used in designing control systems of real systems. First, this paper makes clear that, under certain conditions, the input and output relation of a communication system, which is composed of a number of communication nodes, is formulated into a dynamic state equation that is classed as a time-invariant, single-input single-output, discrete-time system. Next, it is explained that traffic load information is estimated by identifying the dynamic state equations of the communication system. Then, the traffic load estimator is synthesized using the system identification in it. Finally, it is clarified by computation simulations that the proposed method is very applicable in estimating the traffic load of each communication node.

We consider a communication system in which a transmitter is connected to a receiver through parallel channels, and the Go-Back-N ARQ scheme is used to handle transmission errors. A packet error on one channel results in retransmission of packets assigned to other channels under the Go-Back-N ARQ scheme. Therefore, the channel-grouping (a grouped-channel is used to transmit the same packet at a time), would affect the throughput performance. We analyze the throughput performance, and give a tree-algorithm to efficiently search for the optimal channel-grouping which makes the throughput to become maximum. Numerical results show that the throughput is largely improved by using the optimal channel-grouping.

It has become more important to shorten development periods of high performance computer systems and their LSIs. During debugging of computer prototypes, logic designers request very frequent LSI refabrication to change logic circuits and to add some functions in spite of their extensive logic simulation by several GFLOPS supercomputers. To meet these demands, an automated on-chip direct wiring modification system has been developed, which enables wire-cut and via-digging by a precise focused ion beam machine, and via-filling and jumper-writing by a laser CVD machine, directly on pre-redesign (original) chips. This modification system was applied to LSI reworks during the development of Hitachi large scale computers M-880 and S-3800, and contributed to shorten system debugging period by four to six months.

The photonic Space-Division (SD) switching network is attractive for constructing flexible broadband networks. This paper first describes possible applications of the network. A broadband STM switching system, Digital Cross-connect System (DCS) and Video signal distribution switch, especially for HDTV signals, are attractive near term applications. Recent activities on photonic SD switching network developments aiming at these application are also reviewed. A 128 line prototype switching system has been developed. This system utilizes LiNbO3 photonic switch matrices, semiconductor traveling wave amplifiers (TWAs) and three dimensional optical interconnections for multi stage switching networks. It is confirmed that the system has been operating in providing 150Mb/s TV phone services and 600Mb/s HDTV distribution services with high stability. An experimental optical Digital Crossconnect System (optical DCS) has also been demonstrated. Line failure restoration operation at 2.4Gb/s has been successfully demonstrated. These experimental demonstrations prove that practical photonic switching systems are feasible with current technologies.

A new mobility model dependent upon electron concentration is presented for studying the screening effect on ionized impurity scattering. By coupling this model with the drift-diffusion and Hartree models, the effects of self-consistent and quasi-equilibrium screening on carrier transport in heavily doped systems are revealed for first time. The transport mechanism is found to be dominated by the electron-concentration-dependent mobility, and transconductance is shown to be determined by effective mobility and changes from degraded to enhanced characteristics with electron concentration modulation.

In this paper, we present some novel concepts and photonic devices for use in optical interconnects. First, we review the progress of surface emitting lasers while featuring materials and performances including thresholds, power output, RIN, linewidth, and so on. Advanced technology for aiming at spontaneous emission control, photon recycling, polarization control, wavelength tuning, integration etc. will be considered. Then we touch on some other possible devices for optical interconnects. Lastly, we discuss on lightwave subsystems applying these devices and concepts.

This study is intended to investigate a method to diagnose the student model in the domain of procedural problem solving. In this domain, the goal of an instruction should be to understand the processes of solving given problems, and to understand the reasons why problems can be solved by using sertain knowledge; the acquisition of problem solving skills might not be the intrinsic instructional goals. The tutoring systems in this domain must understand the effect of each problem solving operators, as well as when to implement these operators in order to effectively solve given problems. We have been studying and developing a system which deals with student modelling in the domain of procedural problem solving. We believe that the two types of knowledge should be clearly defined for the diagnosing tasks; effective knowledge (EK) and principle knowledge (PK). The former is the knowledge which is explicitly applied by students throughout problem solving processes, and the latter is the one which gives the justifications of the EK. We have developed a student model diagnosing system which infers students' knowledge structure pertaining to PK, based on the precedently manipulated student model about EK. This student model diagnosing method requires knowledge which argues the relationship between the PK and the EK. This knowledge plays the very important role in our system, and it's hard to describe such knowledge properly by hand. In this paper, we provide a student model diagnosing system which has the knowledge acquiring function to learn the relationship between EK and PK. The system acquires this knowledge through its own problem solving experience. Based on the student model and the acquired relational knowledge, the system can give students proper instructions about construction of EK with explanations in terms of PK. The system has been partly implemented with CESP language on a UNIX workstation.

This paper presents an improved current-mode circuit for implementation of a chaotic neuron model. The proposed circuit uses a switched-current integrator and a nonlinear output function circuit, which is based on an operational transconductance amplifier, as building blocks. Is is shown by SPICE simulations and experiments using discrete elements that the proposed circuit well replicates the behavior of the chaotic neuron model.

This paper describes the current situations and future directions of intelligent CAI researches/development in Japan. Then necessity of intelligence in CAIs/Educational systems are thought over corresponding to the model of teaching and the cognitive model of human learning like the situated learning, knowledge construction and so on. Originally, the main aims of ITSs/ICAIs are to tealize the high level environment of individual teaching/learning. So it is the most important to incorporate the intellectual function of teaching into the system. Whatever kinds of teaching purposes ITSs have, they have the quite complex structure which consists of the domain knowledge base (Expert system), student model, the tutoring knowledge base, the powerful human interface, and sophisticated inference engine with plural functions by artificial intelligence technology. In this paper, the technological and educational points of view are discussed, surveyed and summarized based on intelligent teaching functions of ITSs/ICAIs. Moreover, the meaning of new paradigm from ITSs to ILE are mentioned under the new technology of networking and multi-media.

This paper describes the concepts and methodologies of the INTELLITUTOR system which is an integrated intelligent programming environment for learning programming. INTELLITUTOR attempts to work as a human programming tutor to guide a user, i.e., a student, in writing a computer program, to detect logical errors within it, and to make advices not only for fixing them but also for letting him notice his misunderstandings. The system consists of three major modules, i.e., GUIDE, ALPUS and TUTOR. GUIDE is a guided editor for easy coding, ALPUS is an algorithm-based program understander, and TUTOR is an embedded-intelligent tutoring system for programming education. The ALPUS system can infer user's intentions from buggy codes in addition to detecting logical errors by means of knowledge-based reasoning. ALPUS uses four kinds of programming knowledge: 1) knowledge on algorithms, 2) Knowledge on programming techniques, 3) Knowledge on a programming language, and 4) Knowledge on logical errors. These knowledge are organized in a hierarchical procedure graph (HPG) as a multi-use knowledge base. The knowledge on logical errors was obtained by means of cognitive experiments. The student model is built by means of the results of ALPUS and interactions between a student and the system. Teaching is done based on the student model. Because the ITS subsystem, i.e., TUTOR, is embedded within the intelligent programming environment interactions for creating the student model could be minimized. Although the current system deals with the PASCAL language, most of the knowledge is applicable to those of procedure-oriented programming languages. The INTELLITUTOR system was implemented in the frame-based knowledge engineering environment ZERO and working on a UNIX workstation for system evaluation.

This paper is concerned with the continuous relation between models of the plant and the predicted performances of the system designed based on the models. To state the problem more precisely, let P be the transfer matrix of a plant model, and let A be the transfer matrix of interest of the designed system, which is regarded as a performance measure for evaluating the designed responses. A depends upon P and is written as A=A(P). From the practical point of view, it is necessary that the function A(P) should be continuous with respect to P. In this paper we consider the linear quadratic optimal servosystem with integrators (LQI) scheme as the design methodology, and prove that A(P) depends continuously on the plant transfer matrix P if the topology of the family of plants models is the graph topology. A numerical example is given for illustrating the result.

In this paper an identity-based non-interactive key sharing scheme (IDNIKS) is proposed in order to realize the original concept of identity-based cryptosystem, of which secure realization scheme has not been proposed. First the necessary conditions for secure realization of IDNIKS are considered from two different poinrts of view: (i) the possibility to share a common-key non-interactively and (ii) the security for entity's conspiracy. Then a new non-interactive key sharing scheme is proposed, of which security depends on the difficulty of factoring. The most important contribution is to have succeeded in obtaining any entity's secret information as an exponent of the obtainer's identity information. The security of IDNIKS for entity's conspiracy is also considered in details.

In this paper, we investigate the knowledge complexity of interactive proof systems and show that (1) under the blackbox simulation, if a language L has a bounded move public coin interactive proof system with polynomially bounded knowledge complexity in the hint sense, then the language L itself has a one move interactive proof system; and (2) under the blackbox simulation, if a language L has a three move private coin interactive proof system with polynomially bounded knowledge complexity in the hint sense, then the language L itself has a one move interactive proof system. These results imply that as long as the blackbox simulation is concerned, any language L AM＼MA is not allowed to have a bounded move public coin (or three move private coin) interactive proof system with polynomially bounded knowledge complexity in the hint sense unless AM = AM. In addition, we present a definite distinction between knowledge complexity in the hint sense and in the strict oracle sense, i.e., any language in AM (resp. IP) has a two (resp. unbounded) move public coin interactive proof system with polynomially bounded knowledge complexity in the strict oracle sense.

Mean Time Between Failures (MTBF) is an important measure of practical repairable systems, but it has not been obtained for a repairable linear consecutive-k-out-of-n: F system. We first present a general formula for the (steady-state) availability of a repairable linear consecutive-k-out-of-n: F system with nonidentical components by employing the cut set approach or a topological availability method. Second, we present a general formula for frequency of system failures of a repairable linear consecutive-k-out-of-n: F system with nonidentical components. Then the MTBF for the repairable linear consecutive-k-out-of-n: F system is shown by using the frequency of system failure and availability. Lastly, we derive some figures which show the relationship between the MTBF and repair rate µorρ(=λ/µ) in the repairable linear consecutive-k-out-of-n: F system. The figures can be easily used and are useful for reliability design.

This paper proposes an optimal free-sensors allocation problem (OFSAP) in safety monitoring systems. OFSAP is the problem of deciding the optimal allocation of several sensors, which we call free sensors, to plural objects. The solution of OFSAP gives the optimal allocation which minimizes expected losses caused by failed dangerous (FD)-failures and failed safe (FS)-failures; a FD-failure is to fail to generate an alarm for unsafe object and a FS-failure is to generate an alarm for safe object. We show an unexpected result that a safer object should be monitored by more sensors under certain conditions.

A simulation-based ITS (Intelligent tutoring system), SRIM, has been developed for the purpose of providing individualized learning to students of PID control. We first indicate that the following two steps will be a burden to the student during personal use of simulators: 1) Selection of operational goals and 2) Interpretation of the simulation results. In order to reduce the burden of students in learning with a simulator, SRIM guides the learning process by providing local goals for PID controller tuning and by giving messages. Two tutoring strategies: i.e. the exercise style strategy and the illustrating style strategy, are employed in SRIM. In the exercise style strategy, a local goal for tuning a PID controller is first given to the student. A local goal is defined as one which can be satisfied by a single operation step such as Decrease the off-set." The student selects his operation and executes the simulation. By observing the simulation, the student understands whether his operation was a success or a failure. The illustrating style strategy is invoked to repair the student's erroneous knowledge when a contradiction is detected in the student model or a wrong operation is selected repeatedly. The architecture of ITS is employed to perform the local goal selection and the tutoring strategy switching, in a natural, well timed manner. The performance of SRIM was evaluated for the purpose of demonstrating the effectiveness of the teaching strategy. The evaluation experiment was carried out in the following steps: 1) Pre-test, 2) Learning and 3) Post-test. The teaching effect of SRIM was compared with other learning methods such as simple use of simulators or a textbook from the results of the pre-test and the post-test. The results showed that SRIM is effective in providing individualized learning with simulators.

For systems in which the probability that an incorrect output is observed differs with input values, we adopt the redundant usage of n copies of identical systems which we call the n-redundant system. This paper presents a method to find the optimal redundancy of systems for minimizing the probability of dangerous errors. First, it is proved that a k-out-of-n redundancy or a mixture of two kinds of k-out-of-n redundancies minimizes the probability of D-errors under the condition that the probability of output errors including both dangerous errors and safe errors is below a specified value. Next, an algorithm is given to find the optimal series-parallel redundancy of systems by using the properties of the distance between two structure functions.

The student model component of intelligent tutoring systems (ITSs) used to be considered central: it was the means by which the ITS could individually adapt the learning experience to suit the learner's perceived needs. However, the practical difficulty of building reliable student models, the evolution away from the knowledge communication style of ITSs towards a more constructivist philosophy, and the development of new media to support learning interactions have all combined to question the role (if any) for student models in current interactive learning environments (ILEs). In this paper we will explore the new role of student models by considering the lessons learned from five Lancaster projects (SAFE, EPIC, PEOPLEPOWER, CLORIS and SMILE). The main issues revolve (as usual) around the questions of control and learning objectives.