One approach to develop software efficiently is to reuse existing software by modifying a part of it. However, modifying software will often introduce unexpected side effects into other parts of it. As a result, it costs much time and care to modify the software. So, in order to modify software efficiently, we have proposed a functional model to represent information about side effects caused by modification and a model based supporting system for modifying software. So far, however, an expert software developer must describe the entire functional model of the target software through the analysis of practical modifying processes. This will be an unnecessary burden on him. Moreover, the larger target software becomes, the harder the model construction becomes. Therefore, an automatic constructing method of the functional model is needed in order to solve this problem. So, this paper considers a method of acquiring useful interaction information by learning from training examples of modification. However, in our application domain, it seems that it is impossible to make complete domain theory and to prepare a large number or training examples in advance. Therefore, our learning method involves an integration of explanation-based learning (EBL) from positive examples of modification generated by the user and Similarity-based learning (SBL) from positive or negative examples generated by the user and the learning system. As a result, our method can acquire valid knowledge about the interaction from not so many examples under incomplete theory. Then, this paper presents a constructing method, in which our proposed learning method is incorporated, of a functional model. Finally, this paper demonstrates construction of the functional model in the domain of an event-driven queueing simulation program according to our learning method.

Information systems to support cooperative work among people should be first designed to help humam communication. However, there are few systems based on the analysis of human communication. Standing on this situation, we propose a meeting support system for the participants' understandings by indicating the suitable information about the topic of the scene". Our system provides only useful information by monitoring each statement without complex methods. To show something useful multi-media information for members, we propose the following structure of the meeting on the basis of the analysis of communication. Each statement is classified into two levels, either; a statement about the progress" of the meeting (context-level utterances) or, a statement about objects" (content-level utterances). Further, content-level utterances are classified into two types, position utterances and argument utterances. Using this classification of statements, the proceeding of the meeting is represented as the tree model which is called a context-tree". If the structure of meetings is fixed, it is possible to select only useful information from all shared information for members by analyzing each content-level utterance. The system introduced in this paper shows appropriate multi-media information about the topic of the scene" by using the above model. We have implemented a prototype system based on the above ideas. Moreover, we have mode some experiments to show the effectiveness of this system. Those results show that our method is effective to improve the productivity" of meetings.

In this paper, we study the following node-to-node fault tolerant routing problem: In the presence of up to n-1 faulty nodes, find a fault-free path which connects any two non-faulty nodes s and t in an n-connected graph. For node-to-node fault tolerant routing in n-dimensional hypercubes Hn, we give an algorithm which finds a fault-free path s t of length at most in O(n) time, where d(s, t) is the distance between s and t. We also show that a fault-free path s t in Hn of length at most d(s, t)2i, 1i, can be found in time. For node-to-node fault tolerant routing in n-dimensional star graphs Gn, we give an algorithm which finds a fault-free path s t of length at most min{d(Gn)3, d(s, t)6} in O(n) time, where is the diameter of Gn. It is previously known that, in Hn, a fault-free path s t of length at most d(s, t) for d(s, t)n and at most d(s, t)2 for d(s, t)n can be found in O(d(s, t)n) time, and in Gn, a fault-free path s t of length at most min{d(Gn)1, d(s, t)4}can be found in O(d(s, t)n) time. When the time efficiency of finding the routing path is more important than the length of the path, the algorithms in this paper are better than the previous ones.

The effect of an optical hard-limiter on the performance of direct-detection optical synchronous code-division multiple-access (CDMA) systems with M-ary pulse position modulation (PPM) signaling is analyzed. Moreover, the effect of the error correction coding on the performance of direct-detection optical synchronous CDMA systems with PPM signaling is analyzed: Reed-Solomon (RS) codes and convolutional codes (CC's) with soft-decision Viterbi decoding are employed. We analyze the performance under the assumption of Poisson shot noise model for the receiver photodetector and the noise due to the detector dark currents is considered. We analyze the performance under average power and bit rate constraints. Our results show that the optical hard-limiter is not effective for improving the performance of the optical CDMA systems with PPM signaling. Moreover, RS codes are shown to be more effective than CC's with soft-decision Viterbi decoding to reduce an asymptotic floor to the error probability of the system with large M, while CC's with soft-decision Viterbi decoding is more effective than RS codes for the system with small M. Furthermore, we show that as the code rate of the error correction code increases, the required average energy to achieve the bit error probability Pb105 for the RS coded PPM/CDMA system appreciably increases compared with that for the convolutional coded PPM/CDMA system when M16.

In this paper, we discuss computational methods for obtaining the bifurcation points and the branch directions at branching points of solution curves for the nonlinear resistive circuits. There are many kinds of the bifurcation points such as limit point, branch point and isolated point. At these points, the Jacobian matrix of circuit equation becomes singular so that we cannot directly apply the usual numerical techniques such as Newton-Raphson method. Therefore, we propose a simple modification technique such that the Newton-Raphson method can be also applied to the modified equations. On the other hand, a curve tracing algorithm can continuously trace the solution curves having the limit points and/or branching points. In this case, we can see whether the curve has passed through a bifurcation point or not by checking the sign of determinant of the Jacobian matrix. We also propose two different methods for calculating the directions of branches at branching point. Combining these algorithms, complicated solution curves will be easily traced by the curve tracing method. We show the example of a Hopfield network in Sect.5.

This paper proposes novel optical path accommodation design algorithms for networks wherein the number of wavelengths multiplexed into a fiber is restricted. This algorithm optimizes both optical path route and wavelength assignment in VWP/WP networks. It minimizes optical path cross-connect (OPXC) system scale in terms of incoming/outgoing fiber port numbers. A comparison in terms of required OPXC system scale between the WP and VWP schemes is demonstrated for the first time.

The periodic correlation properties of M sequences coded by channel codes are discussed. As for the channel codes, the Manchester code and the eight DC free codes in the FM family codes, which include the conventional FM code and the differential Manchester code, are adopted. The M sequences coded by the DC free codes in the FM family codes are referred to as FM coded M sequences. The periodic correlation properties of all combinations of the FM coded M sequences are checked, and the combinations which can provide almost the same or better properties as compared with those of the preferred pairs of M sequences are described. An example of code design using the FM coded M sequences for asynchronous direct sequence/spread spectrum multiple access systems is also discussed.

Optical switching networks to transport vast amounts of information are important for B-ISDN services. Wavelength division multiplexing (WDM) is emerging as the dominant technology for future optical networks. A large capacity photonic ATM switch architecture using WDM technology is proposed in this paper. The proposed switch is suitable for WDM optical ATM networks, that is, an input and an output of the switch are wavelength division multiplexed. The basic switch module of the proposed switch has a simple architecture, and reduces the amount of a buffer hardware by introducing the WDM concept.

This paper proposes a requirement description and elicitation approach for communication services. Requirements are described in natural language, refined with a knowledge base, and converted to a formal language for program generation. A model for communication services is made as a set of three items: terminal state, terminal action and the response of the communication system to the action. This set, in turn, corresponds to natural language syntax that expresses two conditions (terminal state and action) and their result. These conditions and result are expressed as a sequence of simple sentences that describe the relationship between a terminal and a communication system. Thus, by defining such a description style to reflect the features of communication services, it should be possible to achieve both a high level of description and mechanical processing capabilities at the same time. However, requirement descriptions usually include omission and inconsistency. This problem cannot be solved by merely introducing natural language for the descriptions. Knowledge about the target domain of requirements is needed to resolve it. This paper reports on a knowledge base that stores constraints existing between conditions and results in communication services. This knowledge base is shown to be effective in supplementing omissions and resolving inconsistency. This paper also presents a technique for converting the elicited requirements in natural language to descriptions in a formal language that can be used to generate a program.

High rate binary coset codes are investigated. The binary coset (BC) code is a binary convolutional code with parallel path. In our previous research of concatenated trelliscoded modulation (TCM) scheme, we have found that the effective minimum distance of inner code is more important than the minimum free distance when TCM is used as inner code. In this paper, for inner code, we construct the high rate BC codes by maximizing the effective minimum distance. With the new inner codes, we can decrease the decoding complexity of the inner code compared with conventional best convolutional code while maintaining the overall decoding performance.

This paper proposes a novel phase ambiguity resolver with combining a very low power Viterbi decoder employing a scarce state transition scheme to realize cost effective receivers for the PCM sound broadcasting satellite service. The theoretical analyses on phase decision performance show that the proposed resolver achieves the symbol-by-symbol phase detection and decides correctly phases of the demodulated data even if the bit error probability of 710-2. The resolver also reduces the phase decision time to below 1/1000 of that of the conventional resolver. Furthermore, experimental results of the power consumption estimate that the prototype Viterbi decoder consumes only 60mW at the data rate of 24.576Mbit/s.

This paper proposes a technique for estimating the harmonic frequencies based on instantaneous frequency (IF) of speech signals. The main problem is how to decompose the speech signal into the harmonic components. For this purpose, we use a set of bandpass-filters, each of whose center frequencies changes with time in order to track the instantaneous freuency of its output. As a result, the outputs of the band-pass filters become the harmonic components, and the instantaneous frequencies of the harmonics are accurately estimated. To evaluate the effectiveness of the approach, we apply it to pitch determination of speech. Pitch determination is simply accomplished by selecting the correct fundamental frequency out of the harmonic components. It is confirmed that the pitch extraction using the proposed pitch determination algorithm (PDA) is stable and accurate. The most significant feature of the PDA is that the extracted pitch contour is smooth and it requires no post-processing such as nonlinear filtering or any smoothing processes. Several examples are presented to demonstrate the capability of the harmonics estimation technique and the PDA.

We propose an algorithm for image decomposition based on Hadamard functions, realized by answer-in-weights neural network, which has simple architecture and is explored with steepest decent method. This scheme saves memory consumption and it converges fast. Simulations with least mean square (LMS) and absolute mean (AM) errors on a 128128 image converge within 30 training epochs.

Time-frequency representations (TFRs) have been developed as tools for analysis of non-stationary signals. Signal dependent TFRs are known to perform well for a much wider range of signals than any fixed (signal independent) TFR. This paper describes customised and sequential versions of the signal dependent TFR proposed in [1]. The method, which is based on the use of the Radon transform at distance zero in the ambiguity domain, is simple and effective in dealing with both simulated and real data. The use of the described method for time-scale analysis is also presented. In addition, the paper investigates a simple technique for detection of noisy chirp signals using the Radon transfrom in the ambiguity domain.

We propose an accurate FET model for microwave nonlinear circuit simulation, which has been modified from the Statz model. We have greatly enhanced the accuracy of both dc and capacitance expressions, especially in the knee voltage region where Ids begins to saturate. In the expression of dc characteristics, our model improves the accuracy by incorporating the drain-source voltage dependence of pinch-off voltage, the gate-source voltage dependence of knee voltage, and the non-square dependence of drain current against the gate-source voltage. The non-square-root voltage dependence of gate capacitances is considered as well. All modifications are simple and the parameter extraction is kept as simple as that of the Statz model. By using this model, good agreement has been obtained between simulated and measured characteristics of a GaAs FET. For the dc characteristics and the S-parameters, each of estimated error is within 5% and 10%. The model accuracy has been verified by comparison of simulated and measured results of power amplifier performances over a wide range of operating conditions.

Intelligent Tutoring Systems (ITS) represents a wide class of computer based tutoring systems, designed with an extensive use of the technology of modern Artificial Intelligence. Successful applications of various expert systems and other knowledge based systems of AI gave rise to a new wave of interests to ITS. Yet, many authors conclude that practically valuable achievements of ITS are rather modest despite the relatively long history of attempts to use knowledge based systems for tutoring. It is advocated in this paper that some basic obstacles for designing really successful ITS are due to the lack of well understood and sound models of the education process. The paper proposes to overcome these problems by borrowing the required models from AI and adjacent fields. In particular, the concept of Learning Levels from AI might be very useful both for giving a valuable retrospective analysis of computer based tutoring and for suggestion of some perspective directions in the field of ITS.

A novel series-tapered nonlinear directional coupler is proposed to improve all-optical switching characteristics. Its switching characteristics are analyzed by using a beam propagation method based on the Galerkin's finite element technique. It is presented that the critical power of the series-tapered nonlinear directional coupler is smaller than conventional uniform symmetric and tapered nonlinear directional couplers.

We study all-to-all broadcasting in hypercubes with randomly distributed Byzantine faults. We construct an efficient broadcasting scheme BC1-n-cube running on the n-dimensional hypercube (n-cube for short) in 2n rounds, where for communication by each node of the n-cube, only one of its links is used in each round. The scheme BC1-n-cube can tolerate (n-1)/2 Byzantine faults of nodes and/or links in the worst case. If there are exactly f Byzantine faulty nodes randomly distributed in the n-cabe, BC1-n-cube succeeds with a probability higher than 1(64nf/2n) n/2. In other words, if 1/(64nk) of all the nodes(i.e., 2n/(64nk) nodes) fail in Byzantine manner randomly in the n-cube, then the scheme succeeds with a probability higher than 1kn/2. We also consider the case where all nodes are faultless but links may fail randomly in the n-cube. Broadcasting by BC1-n-cube is successful with a probability hig her than 1kn/2 provided that not more than 1/(64(n1)k) of all the links in the n-cube fail in Byzantine manner randomly. For the case where only links may fail, we give another broadcasting scheme BC2-n-cube which runs in 2n2 rounds. Broadcasting by BC2-n-cube is successful with a high probability if the number of Byzantine faulty links randomly distributed in the n-cube is not more than a constant fraction of the total number of links. That is, it succeeds with a probability higher than 1nkn/2 if 1/(48k) of all the links in the n-cube fail randomly in Byzantine manner.

This paper investigates the error correcting capabilities of concatenated codes employing algebraic geometry codes as outer codes and time-varying randomly selected inner codes, used on discrete memoryless channels with maximum likelihood decoding. It is proved that Gallager's random coding error exponent can be obtained for all rates by such codes. Further, it is clarified that the error exponent arbitrarily close to Gallager's can be obtained for almost all random selections of inner codes with a properly chosen code length, provided that the length of the outer code is sufficiently large. For a class of regular channels, the result is also valid for linear concatenated codes, and Gallager's expurgated error exponent can be asymptotically obtained for all rates.

The background concepts and methodologies of the knowledge-based program understander ALPUS is discussed. ALPUS understands user's buggy Pascal programs using four kinds of programming knowledge: the knowledge on algorithms, programming techniques, the Pascal language, and logical bugs. The knowledge on algorithms, the key knowledge, is represented in a form of hierarchical data structure called Hierarchical Procedure Graph (HPG). In HPG each node represents a chunk of operations called process," which is consisted of sub-processes. The other knowledge is maintained as independent knowledge bases and linked to associated processes of the HPG. The knowledge about bugs acquired by cognitive experiment is grouped into three categories: bugs on algorithms, programming techniques, and the Pascal language, and connected to associated elements of programming knowledge respectively. ALPUS tries to understand user's buggy programs, detects logical bugs, infers user's intentions, and gives advices for fixing bugs. Program understanding is achieved by three steps: normalization, variable identification, and process and technique identification. Normalization results in improving flexibility of understanding. Variable, process and technique identifications are achieved by knowledge-based pattern matching. Intentions are inferred by means of information attached to buggy patterns. The result of comprehension is reported to a user (i.e., student). Experimental results using Quicksort programs written by students show that the HPG formalism is quite powerful in understanding algorithm-oriented programs. The ALPUS's way of program comprehension is useful in the situation of programming education in an intermediate class of an engineering school. The ALPUS system is a subsystem of the intelligent programming environment INTELLITUTOR for learning programming, which was implemented in the frame-based knowledge engineering environment ZERO on a UNIX workstation.