New focused ion beam (FIB) methods for microscopic cross-sectioning and observation, microscopic crosssectioning and elemental analysis, and aluminum film microstructure observation are presented. The new methods are compared to the conventional methods and the conventional FIB methods, from the four viewpoints such as easiness of analysis, analysis time, spatial resolution, and pinpointing precision. The new FIB methods, as a result, are shown to be the best ones totally judging from the viewpoints shown above.

Expressions for electromagnetic fields generated by vertical and horizontal electric dipoles located in the air or in a lossy half-space near its boundary with air are obtained from Hertz vectors by the method of operators under the condition |n|31, where 1/n is the refractive constant of the lossy space. These can be applied up to the near fields under the additional conditions, |n|21 and cos2θ1, where θ is the zenith angle of the point of observation. As for recent works inclusive of expressions of lateral waves their weak points are pointed out.

This paper applies the principle of radar polarimetry to the synthetic aperture frequency modulated continuous wave radar. First, the principle of monochromatic wave radar polarimetry using scattering matrix and polarization ratio necessary for introducing polarimetric imaging is given. In order to accommodate this principle to a wideband radar, a scattering matrix must be introduced, because FM-CW radar utilizes a wideband signal. This paper points out that the polarimetric target reflection coefficient obtained by the synthetic aperture FM-CW radar works as the scattering matrix element. This replacement, i.e., polarimetric reflection coefficient = the scattering matrix element, was verified by an experiment based on the polarization ratio which maximizes and minimizes a target. A radar system operative in the microwave X-band was successfully applied to the polarimetric detection of a metallic pipe of different orientations, demonstrating the validity of FM-CW radar polarimetry, and indicating an establishment of full polarimetric radar system.

When we use the finite-difference time-domain (FD-TD) method to study time-domain electromagnetic fields in the unbounded surroundings, we frequently use a radiation boundary condition (RBC) by means of one-way wave equations. The reflection coefficient by the RBC is independent of frequency, but the reflection coefficient of the finite difference approximation for the RBC depends on a frequency also; this study examines how the reflection characteristics are affected by the frequency, and the study presents the coefficients used in the RBC which gives expected reflection characteristics for a frequency, and presents the application to simulation of the matched termination of a rectangular waveguide.

In Spread Spectrum Packet Radio Networks (SS/PRNs), different spreading codes are required for different stations for transmitting packets. Therefore multihop SS/PRNs with a large number of stations would require a large number of codes and hence a large channel bandwidth. In this paper we design a code assignment algorithm which could reduce the number of codes required to about 22%. Further reducing the number of codes is found to cause little throughput degradation. The Coded Tone Sense protocol is designed for using these codes in multihop PRNs. Simulation result shows that in a 80 node network using only 5 spreading codes, the maximum network throughput is about 73% higher than the BTMA protocol.

This paper proposes a high-speed VP bandwidth control scheme for ATM networks that utilizes a distributed control mechanism. First, the characteristics of VPs are compared with those of digital paths in STM networks. A distributed control scheme is adopted for rapid control. The basic elements and the necessary distributed function, the control algorithm, and the message transmission mechanism, are elucidated. The bandwidth alteration time with the proposed algorithm is estimated by considering network element processing and queuing delay. The proposed VP bandwidth control scheme can be applied to both public networks and leased line services. Finally, this paper focuses on its application to leased line services, and discusses the resource reduction effects of the proposed scheme.

In this paper, we propose a plausible software reliability growth model by applying a mathematical technique of stochastic differential equations. First, we extend a basic differential equation describing the average behavior of software fault-detection processes during the testing phase to a stochastic differential equation of ItÔ type, and derive a probability distribution of its solution processes. Second, we obtain several software reliability measures from the probability distribution. Finally, applying a method of maximum-likelihood we estimate unknown parameters in our model by using available data in the actual software testing procedures, and numerically show the stochastic behavior of the number of faults remaining in the software system. Further, the model is compared among the existing software reliability growth models in terms of goodness-of-fit.

This paper is concerned with an ITS designed for augmenting a student's capability in problem solving. Discussions are concentrated on helping students acquire strategic knowledge and assisting them to build it in their heads. In this paper, many kinds of strategies are treated from a unified point of view. Based on this consideration, a teaching paradigm of strategic knowledge is presented. The paradigm is realized in an ITS as a training environment for strategic knowledge. Assisting students to learn strategic knowledge, the system sets up an appropriate environment and gives them some appropriate advice in each environment. It is realized as a function of giving them appropriate problems and hints about it. In general, strategic knowledge is a kind of heuristics so that it is not easy to describe their application conditions deterministically and explicitly. For this reason, an ITS for strategic knowledge is required to be designed so as to cover not only the case where expertise is represented explicitly as an executable model but also the case where it is represented only implicitly. To realize this teaching paradigm, situation-dependent knowledge called reminding pattern is prepared in the system. It is represented by a triple of a strategy, a situation, and a key symbol in the situation. It denotes that the key usually reminds students of the strategy in the situation. The system gives students problems including positive/negative examples of applications of each strategy in its problem solving process and hints which remind them of an appropriate strategy and makes them resume the problem solving when they fall into an impasse. In this paper, the structure of the system realizing this teaching paradigm is explained in the domain of proving propositional formulas.

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.

In this paper, we study the knowledge tightness of zero-knowledge proofs. To this end, we present a new measure for the knowledge tightness of zero-knowledge proofs and show that if a language L has a bounded round zero-knowledge proof with knowledge tightness t(|x|) 2 - |x|-c for some c 0, then L BPP and that any language L AM has a bounded round zero-knowledge proof with knowledge tightness t(|x|) 2-2-O(|x|) under the assumption that collision intractable hash functions exist. This implies that in the case of a bounded round zero-knowledge proof for a language L BPP, the optimal knowledge tightness is "2" unless AM = BPP. In addition, we show that any language L IP has an unbounded round zero-knowledge proof with knowledge tightness t(|x|) 1.5 under the assumption that nonuniformly secure probabilistic encryptions exist.

Experimental evidence of a two-step enhancement in electromigration lifetime is presented through pulsed testing that extends over a wide frequency range from 7 mHz to 50 MHz. It is also found, through an accompanying failure analysis, that the failure mechanism is not affected by current pulsing. Test samples were the lowew metal lines and the through-holes in double-level interconnects. The same results were obtained for both samples. The testing temperature of the test conductor was determined considering the Joule heating to eliminate errors in lifetime estimation due to temperature errors. A two-step enhancement in lifetime is extracted by normalizing the pulsed electromigration lifetime by the continuous one. The first step occurs in the frequency range from 0.1 to 10 kHz where the lifetime increases with (duty ratio)-2 and the second step occurs above 100 kHz with (duty ratio)-3. The transition frequency in the first-step enhancement shifts to the higher frequency region with a decrease in stress temperature or an increase in current density, whereas the transition frequency in the second step is not affected by these stress conditions. The lifetime enhancement is analyzed in relation to the relaxation process during the current pulsing. According to the two-step behavior, two distinct relaxation times are assumed as opposed to the single relaxation time in other proposed models. The results of the analysis agree with the experimental results for the dependence on the frequency and duty ratio of pulses. The two experimentally derived relaxation times are about 5 s and 1 µs.

Server aided secret computation (SASC) protocol also called the verifiable implicit asking protocol, is a protocol such that a powerful untrusted auxiliary device (server) can help a smart card (client) for computing a secret function efficiently. In this paper, we extend the concept of addition sequence to the secure addition sequence and develop an efficient algorithm to construct such sequence. By incorporating the secure addition sequence into the SASC protocol the performance of SASC protocol can be further enhanced.

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.

This paper presents a novel model of optical associative memory using an optoelectronic neurochips, which detects and processes a two-dimensional input image at the same time. The original point of this model is that the optoelectronic neurochips allow direct image processing in terms of parallel input/output interface and parallel neural processing. The operation principle is based on the nonlinear transformation of the input image to the corresponding the point attractor of a fully connected neural network. The learning algorithm is the simulated annealing and the energy of the network state is used as its cost function. The computer simulations show its usefulness and that the maximum number of stored images is 150 in the network with 64 neurons. Moreover, we experimentally demonstrate an optical implementation of the model using the optoelectronic neurochip. The chip consists of two-dimensional array of variable sensitivity photodetectors with 8 16 elements. The experimental results shows that 3 images of size 8 8 were successfully stored in the system. In the case of the input image of size 64 64, the estimated processing speed is 100 times higher than that of the conventional optoelectronic neurochips.

This paper presents a hypermedia English learning environment, called HELEN (Hypermedia Environment for Learning ENglish), which integrates traditional methods of learning English, audio-visual facilities for both listening and watching and intelligent tutoring functions for suitable advice to each learner based on natural language understanding. HELEN consists of an authoring stage and a learning stage. In order to support multimodal learning, at the authoring stage HELEN gets voice and video scenes from a video disc and text sentences from an image scanner, then analyzes the sentences both syntactically and semantically by a natural language processing module so that necessary information for conversation, error identification and example sentence retrieval may be extracted. Thus at the learning stage, HELEN is able to aid learners to learn hearing, reading, writing, watching, consulting and noting. Besides these facilities HELEN also supports two facilities for tests in English: One is the test facilities of dictating sentences and the other is QA (questions and answers) facilities to make learner's comprehension state clear. According to the results of these tests, HELEN identifies learner's illegal usage of syntax or semantics, and piles them in a student model. The illegal usage in the model is used as resources for generating questions, treating errors, determining topics, etc. The main part of this paper concerns with the representation method for syntax and semantics of correct and incorrect sentences.

The learning environment called IPE (Interactive Physical Environment) for Dynamics is developed on the computer. IPE can understand the simulated phenomena started from the arbitrary conditions set up by the learner. IPE has several scripts which describe the dynamical phenomena. The understanding of the simulated phenomena by IPE is obtained by matching these scripts with status list and phenomena list which are generated by the simulator using difference scheme. IPE gives the learner the explanation sentences which explain the features of simulated phenomena. This explanation strongly assist the learner in recognizing the details of result of the simulation.

This paper describes the development of an environmental ICAI system for English conversation learning, which is equipped with a simulation-based learning environment and an advisor function. Recently there have been various educational applications or tools for adult second language education, where the learning target is the acquisition of formal knowledge of a language. When considering the implementation of a practical CAI system, methods for developing communicative competence in learners are required. Although there are a number of ICAI systems for conversation learning, often the methodologies which they apply are not completely suitable for the acquisition of the required fundamental knowledge. Our system, based on the architecture of environmental CAI, enhances communication skill acquisition. The system has a learning environment with the following features: (1) A simulation of language activities, implemented in the role-playing game style, which helps to promote a learner's motivation. (2) Educational behavior of the system is varied through the modification of the learning environment and changes in the simulation progress and control commands. (3) An induction strategy, which can cause learners to fail to achieve a learning target, is executed by an advisor mechanism. The system is a prototype architecture for application in environmental ICAI systems for simulation based learning. We believe that the architecture of this system is an efficient framework for linguistic education.

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.

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 discusses the design of an ITS to realize a load-oriented tutoring to enhance the student's explanation understanding. In the explanation understanding, it is to be hoped that a student not only memorizes the new information from an explanation, but also relates the acquired information with his/her own knowledge to recognize what it means. This relating process can be viewed as the one in which the student structures his/her knowledge with the explanation. In our ITS, we regard the knowledge-structuring activities as the explanation understanding. In this paper, we propose an explanation, called a load-oriented explanation, with the intention of applying a load to the student's knowledge-structuring activities purposefully. If the proper load is applied, the explanation can induce the student to think by himself/herself. Therefore he/she will have a chance of gaining the deeper understanding. The important point toward the load-oriented explanation generation is to control the load heaviness appropriately, which a student will bear in understanding the explanation. This requires to estimate how an explanation promotes the understanding activities and how much the load is applied to the activities. In order to provide ITS with the estimation, we have built an Explanation Effect Model, EEM for short. Our ITS consists of an explanation planner and a self-explanation environment. The planner generates the load-oriented explanation based on EEM. The system also makes a student explain the explanation understanding process to himself/herself. Such self-explanation is useful to let the student be conscious of the necessity of structuring his/her knowledge with the explanation. The self-explanation environment supports the student's self-explanation. Furthermore, if the student reaches an impasse in self-explaining, the planner can generate the supporting explanation for the impasse.