The organization of the proposed file and algorithms for search and maintenance of the file are simpler than those of a similar key search file based on B+-tree. An experiment using 230,188 keys with length 1-16 shows the good performance of the file. The storage utilization of the file is about 68%.

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.

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.

There are three viewpoints involved in software project management: process management, quality management and cost management. Software projects must be managed on the basis of these three viewpoints. However, in many cases process management, quality management and cost management systems are built separately as individual systems respectively. Construction of software project management systems which these three functions are integrated has been rare. Therefore, in order to construct a system integrating these functions, the authors clarify the significance of integration of application systems. And then the authors unveil the structure of a software project management system that process management system, quality management system and cost management system are integrated by using an object oriented database.

Object-oriented programming requires different skills from those of traditional structured programming. Thus, a good interactive environment for beginners of object-oriented programming should be provided. We have designed and implemented a visual environment of object-oriented programming for beginners. If a programmer draws a diagram of the tree of the hierarchy of classes visually by using our tool, the relationship between superclasses and subclasses are automatically established. Moreover, in order to prevent careless mistakes to override methods, the prototype environment in the Smalltalk language checks written methods. We conducted an experiment with our tool and evaluated its usefulness.

This paper discusses linear cryptanalysis of LOKI89, LOKI91 and s2DES. Our computer program based on Matsui's search algorithm has completely determined their best linear approximate equations, which tell us applicability of linear cryptanalysis to each cryptosystem. As a result, LOKI89 and LOKI91 are resistant to linear cryptanalysis from the viewpoint of the best linear approximate probability, whereas s2DES is breakable by a known-plaintext attack faster than an exhaustive key search. Moreover, our search program, which is also applicable to differential cryptanalysis, has derived their best differential characteristics as well. These values give a complete proof that characteristics found by Knudsen are actully best.

In this letter we propose a novel method of connection, called the hybrid connection, and find that a resistively coupled oscillator with hybrid connection has stable in-phase and anti-phase synchronized oscillations. Averaging method is used to investigate the stability of the synchronized oscillations. The theory is verified by the experimental results.

A high efficiency and low voltage operation GaAs power amplifier module has been developed for the application to 1.5 GHz Japanese digital cellular phones. This paper summarizes the design method to increase efficiency and to reduce adjacent channel leakage power. Operated at a low drain bias voltage of 4.6 V, the power amplifier module delivers an output power of 1.5 W with 46% power-added efficiency and -52 dBs adjacent channel leakage power.

This paper discusses the performance of non-coherent reception for M-ary spread-spectrum (M-ary/SS) signals in the presence of carrier frequency offset. In general, the M-ary/SS scheme is expected to be of higher spectral efficiency than the conventional DS/SS schemes, but its performance may be degraded by the carrier frequency offset. We, therefore, analyze the effect of carrier frequency offset on the performance of the non-coherent M-ary/SS system with orthogonal modulation using a set of sequences generated by the Hadamard matrix. As a result of the analysis, it has been found that the carrier frequency offset may cause a great deal of degradation in the performance, and that its effect has a distinctive property which is due to the characteristic of Hadamard matrix, at the same time. Making use of this property, we propose two schemes that can mitigate the effect of carrier frequency offset: one is based on choise of the code sequences, the other is on the error correcting code. The effectiveness of the schemes is evaluated in the terms of symbol-error-rates through analysis and computer simulation.

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.

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.

In this work, we present an 8-state trellis code for bit interleaved 16-QAM and the BER performance on Rayleigh fading channel is evaluated. We analyze the BER and show that the effective code length and minimum productive distance are also important criterion for code design on bit interleaved system. We design the code by considering not only minimum Hamming distance but also the effective code length and minimum productive distance. As a result, we found that the scheme employing the code achieves good BER performance on Rayleigh fading channel even with the finite interleaving size.

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 describes, from a system architectural viewpoint, how knowledge-based technologies have been utilized in developing EXLOG (an LSI circuit synthesis system) and SOFTEX (a software synthesis system) inside the authors' projects. Although the system architectures for EXLOG and SOFTEX started from the same production systems, consisting of transformation rules in the middle of the 1980's, both branched off in different directions in the 1990's. Based on experiences with EXLOG and SOFTEX, the differences between LSI and software design models are discussed, and the future directions are indicated for the knowledge-based design system architectures.

With a view to applying to the active matrix displays, micromechanical electrostatic switches having Si-N both-ends-fixed beam of size 1.4 µm by 23 µm grown with LP-CVD on Si wafer were studied about its kinetic switching characteristics, especially its switching speed and hysteresis behavior. Electrostatic beam sticking problems were improved with the additional inverse polarity and short duration pulse following on the turn-on signal. The switching beam deflection of 0.16 µm with the switching time of less than 100 nsec. was measured by tightly focused laser interferometric method. Observed turn-on threshold voltages were more than 30 V, and the on/off hysteresis widths were from one third to two thirds of its threshold voltage. The memory function was experimented for the 2 msec. long holding period with the hold voltage of 25 V following on the writing pulse with the duration of 2 µsec. and the amplitude of 32 V. Now, planarization process has been considered to imtroduce the contact electrodes that were not built-in for these experiments. Although conductive actual switches were not tested, with the obtained results, it seems that the micromechanical electrostatic switch has the large potentials as an active matrix element in display panel especially in electro-luminescent devices or field-emission devices.

The influence of cochannel, adjacent channel and intermodulation constraints on the capacity of the frequency band in the dynamic channel allocation problem is estimated. Algorithms including a backtracking phase with partial reassignment of currently assigned requirements are proposed. Numerical examples show a strong possibility of a 20% capacity improvement compared to the conventional strategies.

A quasi-synchronous (QS) code division multiple access (CDMA) system is proposed for mobile communications. In the proposed method, which uses the time division duplex (TDD) mode of transmission, a mobile receiver can measure propagation delay changes. It then accordingly adjusts its transmission time so its signal can arrive at base station synchronously with other mobile units. A simple control unit is used at the mobile unit in order to reduce any error due to the propagation delay changes. The system operates as follows. At the start of a call, a mobile unit is quasi-synchronised through feedback control from the base station. The mobile unit then maintains synchronous status without any further base station feedback. The degree of the quasi-synchronous accuracy is determined by a clock in mobile units. This paper shows performance results based on using a clock rate of ten times faster than the spreading rate. Orthogonal codes are used for spreading the signals. The results demonstrate that the reverse link CDMA multiuser interference is to a great degree removed.

A photonic/video hybrid system for optical information processing by synthesis of the coherence function is proposed. Optical coherence function can be synthesized to have delta-function-like shape or notch shape by using direct frequency modulation of a laser diode with an appropriate waveform. Therefore, by choosing only the interference component in the interferometer, information processing functions can be obtained. The photonic/video hybrid system proposed provides a novel way to choose the interference component, which can improve the spatial resolution compared with our previous system with holographic technique. Selective extraction two-dimensional (2-D) information from a three-dimensional (3-D) object is successfully performed in basic experiments.

A bottleneck identification methodology is proposed for the performance-oriented design of shared-bus multiprocessors, which are composed of several major subsystems (e.g. off-chip cache, bus, memory, I/O). A subsystem with the longest access time per instruction is the one that limits processor performance and creates a bottleneck to the system. The methodology also facilitates further refined analysis on the access time of the bottleneck subsystem to help identify the causes of the bottleneck. Example performance model of a particular shared-bus multiprocessor architecture with separate address bus and data bus is developed to illustrate the key idea of the bottleneck identification methodology. Accessing conflicts in subsystems and DMA transfers are also considered in the model.

Spectrum scrambling can be applied in vehicle telephones for more secure communication. This letter shows a spectrum scrambling method using real coefficients M band uniform QMF banks. Once QMF banks are designed, spectrum scrambling filters can be realized with simpler procedures. By introducing selectors in the filters, the scrambling scheme may be easily varied in real time processing. Design examples and experimental simulations are included.