It is often desired to change the cutoff frequencies of digital filters in some applications like digital electronic instruments. This paper proposes a design of variable lowpass digital filters with wider ranges of cutoff frequencies than conventional designs. Wave digital filters are used for the prototypes of variable filters. The proposed design is based on the frequency scaling in the s-domain, while the conventional ones are based on the z-domain lowpass-to-lowpass transformations. The first-order approximation by the Taylor series expansion is used to make multiplier coefficients in a wave digital filters obtained from a frequency-scaled LC filter become linear functions of the scaling parameter, which is similar to the conventional design. Furthermore this paper discusses the reduction of the approximation error. The curvature is introduced as the figure of the quality of the first-order approximation. The use of the second-order approximation to large-curvature multiplier coefficients instead of the first-order one is proposed.

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.

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.

This is a full text of my presentation titled "Evaluation of Maintenability Improvement by Systems Reliability Growth" at the First Beijing International Conference on Reliability Maintenability and Safety (BICRMS'92). This thesis describes evaluation methods of reliability growth for field working systems by surveying maintenability improvement. And it also touch upon customer satisfaction. As unavailability is suitable for measuring reliability, I use in this thesis a decrease in unavailability per month as a means to evaluate reliability and its growth. "Maintenability" is broadly defined as a system's capability to maintain, repair and recover its functions with the aid of failsoft and RAISIS. The term "Customer satisfaction" is difficult to define, but on the practical market basis it can be fairly easily and objectively measured by examining the cancel rate by customers. This thesis includes topics such as: (1) When a system is in disorder it can restore its original functions although, strictly speaking, such system changes are classified as another systems statistically. (2) Despite this, we need to evaluate a specific system's reliability continously, and study reliability growth, industrial life, and customer satisfaction. Unavailability can be reduced by improving systems through upgrading component.

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.

High variability of object features and bad class separation of objects are the main causes for the difficulties encountered during the interpretation of ground-level natural scenes. For coping with these two problems we propose a method which extracts those regions that can be segmented and immediately recognized with sufficient reliability (core regions) in the first stage, and later try to extend these core regions up to their real object boundaries. The extraction of reliable core regions is generally difficult to achieve. Instead of using fixed sets of features and fixed parameter settings, our method employs multiple local features (including textural features) and multiple parameter settings. Not all available features may yield useful core regions, but those core regions that are extracted from these multiple features make a cntributio to the reliability of the objects they represent. The extraction mechanism computes multiple segmentations of the same object from these multiple features and parameter settings, because it is not possible to extract such regions uniquely. Then those regions are extracted which satisfy the constraints given by knowledge about the objects (shape, location, orientation, spatial relationships). Several spatially overlapping regions are combined. Combined regions obtained for several features are integrated to form core regions for the given object calss.

This paper gives a systematic approach to generate a Markov chain by a discrete-valued auto-regressive equation, which is a a nonlinear auto-regressive equation having a discrete-valued solution. The power spectrum, the correlation function and the transition probability are explicitly obtained in terms of the discrete-valued auto-regressive equation. Some computer results are illustrated in figures.

Phase noise generation in varactor-tuned oscillators is analyzed by an asymptotic perturbation technique. It is found out that 1/f noise and AM noise are converted into phase noise by first- and higher-order nonlinearities of the varactor. The deduced formula can be utilized in CAD for circuit evaluation/optimization of varactor-tuned osicillators.

In the present paper, we focus ourselves on the turning point (TP) algorithm proposed by Mueller and evaluate its performance when applied to a Gaussian signal with definite covariance function. Then the ECG wave is modeled by Gaussian signals: namely, the ECG is divided into two segments, the baseline segment and the QRS segment. The baseline segment is modeled by a Gaussian signal with butterworth spectrum and the QRS one by a narrow-band Gaussian signal. Performance of the TP algorithm is evaluated and compared when it is applied to a real ECG signal and its Gaussian model. The compression rate (CR) and the normalized mean square error (NMSE) are used as measures of performance. These measures show good coincidence with each other when applied to Gaussian signals with the mentioned spectra. Our results suggest that performance evaluation of the compression algorithms based on the stochastic-process model of ECG waves may be effective.

We have developed new DMOS FET (DMOS) and intelligent power devices (IPD) specified for automotive load driving. Their features are extra-high surge immunity and low on-resistance. MOS power semiconductor devices are the most suitable for driving high speed and large current loads in future car electronics, but their high cost is the main obstacle preventing their implementation. To cut the total system cost, we have tried to enhance surge immunity of power semiconductor devices, at the same time reducing ON resistance, which enables us to omit external protection. Enhanced avalanche power dissipation also enables us to lower the breakdown voltage of the device, which also brings lower on-resistance. The drain to source avalanche immunity of vertical type DMOS (VDMOS) has been sharply improved by using the parasitic PN junction of the channel diffusion region as the cellular zener diode. Avalanche power dissipation energy per unit area of this durable DMOS is 10 to 100 times higher than that of conventional VDMOSs. Although the breakdown voltage of this device is only 30V, no external protection device is required in automotive applications. Several fault phenomena which might occur in this device are also described. Two types of IPDs are proposed in this paper. One is a durable and low-cost high-side switch IPD, whose enhanced surge immunity of IC section from VDD line transient is verified by prototypes. Simplification of the fabrication process has also been achieved by lowering its breakdown voltage. The other is an extra-low on-resistance H-bridge IPD. Major on-resistance reduction of an output lateral type DMOS (LDMOS) is achieved because the cell-array structure is realized by applying 2-layer electrode technology to the power section. The on-resistance per unit area of this LDMOS is almost equal to that of VDMOSs in the same voltage class.

This paper describes a novel method to calculate the fields scattered by a polyhedron structure for an incident plane wave. In this method, the fields diffracted by an edge are calculated using the equivalent edge currents which are separated into components dependent on each of the two surfaces which form the edge. The separated equivalent edge currents are based on the Geometrical Theory of Diffraction (GTD). Using this Separated Equivalent Edge Current Method (SEECM) , fields scattered by a polyhedron structure can be calculated without special treatment of the singularity in the diffraction coefficient. This method can be also applied successfully to structures with convex surfaces by modeling them as polyhedron structures.

This paper presents a high-density multiple-valued content-addressable memory (MVCAM) based on a floating-gate MOS device. In the proposed CAM, a basic operation performed in each cell is a threshold function that is a kind of inverter whose threshold value is programmable. Various multiple-valued operations for data retrieval can be easily performed using threshold functions. Moreover, each cell circuit in the MVCAM can be implemented using only a single floating-gate MOS transistor. As a result, the cell area of the four-valued CAM are reduced to 37% in comparison with that of the conventional dynamic CAM cell.

In the future, it will be necessary that robot technology or environmental technology has an auditory function of recognizing sound expect for speech. In this letter, we propose a recognition system for the species of birds receiving birdcalls, based on network technology. We show the first step of a recognition system for the species of birds, as an application of a recognition system for environmental sound.

The inverse problem we consider in this paper seeks, based on the equivalent source method, to determine the shape of perfectly conducting cylinders from the scattered farfield data obtained by using several incident waves. When incident waves of different frequencies are used, the shape of the scatterer can be reconstructed by employing only a few number of observation points. In the reconstruction problem, to determine the shape of the scatterer, the conjugate gradients method is applied. The general approach is applicable to cylindrical scatterers of arbitrary shape. Results of numerical simulations are presented to support the suggested approach.

Recently, a flexible image database retrieval system where image keywords can be captured automatically is strongly required, in order to manage a practical number of image data successfully. However, image recognition/understanding technology level is not generally sufficient enough to achieve this requirement. In order to overcome this problem, a new type of image database framework is proposed in this paper. In the proposed system, image keywords are extracted in fully-automated fashion by the flexible and generalized image recognition system. Image keywords employed in this system are a collection of recognized objects in the image, where achieved recognition levels are allowed to be intermediate or imperfect. The concept of recognition thesaurus" has been introduced to manage these various abstraction level of kerwords successfully. As an embodiment of this concept, an experimental image database with various types of sports scenes has been implemented and various retrieval evaluations have been performed. Experimental results reveal the effectiveness of the proposed method.

As a new method to generate a homogeneous, random, binary image with a rational power spectrum, this paper proposes a discrete-valued auto-regressive equation, of which random coefficients and white noise excitation are all discrete-valued. The average and spectrum of the binary image are explicitly obtained in terms of the random coefficients. Some computer results are illustrated in figures.

A modern architect can not design high performance computer architecture without thinking all factors of performance from hardware level (logic/layout design) to system level (application programs, operating systems, and compilers). For computer architecture design, there are few practical CAD tools, which support design activities of the architect. In this paper, we propose a CAD tool, called COACH, for computer architecture design. COACH supports architecture design from hardware level to system level. To make a high-performance general purpose computer system, the architect evaluates system performance as well as hardware level performance. To evaluate hardware level performance accurately, logic/layout synthesis tools and simulator are used for evaluation. Logic/layout synthesis tools translate the architecture design into logic circuits and layout pattern and simulator is used to get accurate information on hardware level performance which consists of clock frequency, the number of transistors, power consumption, and so on. To evaluate system level performance, a compiler generator is introducd. The compiler generator generates a compiler of a programming language from the desripition of architecture design. The designed architecture is simulated in the behavior level with programs compiled by the compiler, and the architect can get information on system level performance which consists of program execution steps, etc. From both hardware level performance and system level performance, the architect can evaluate and revise his/her architecture, considering the architecture from hardware level to system level. In this paper, we propose a new design methodology which uses () logic/layout synthesis tools and simulators as tools for architecture design and () a compiler generator for system level evaluation. COACH, a CAD system based on the methodology, is discussed and a prototype of COACH is implemented. Using the design methodology, two processors are designed. The result of the designs shows that the proposed design methodology are effective in architecture design.

This article discusses on PDM (Petri net based Development Methodology) which integrates approaches, modeling methods, design methods and analysis methods in a coherent manner. Although various development techniques based on Petri nets have demonstrated advantages over conventional techniques, those techniques are rather ad hoc and lack an overall picture on entire development process. PDM anticipates to provide a refernce process model to develop distributed systems with various Petri net based development methods. Behavioral properties of distrbuted systems can be an appropriate application domain of PDM.

This paper proposes a new method for automatic improvement in image quality through adjusting the image sharpness. This method does not need prior knowledge about image blur. To improve image quality, the sharpness must be adjusted to an optimal value. This paper shows a new method to evaluate sharpness without MTF. It is considered that the human visual system judges image sharpness mainly based upon edge area features. Therefore, attention is paid to the high spatial frequency components in the edge area. The value is defined by the average intensity of the high spatial fequency components in the edge area. This is called the image edge sharpness" value. Using several images, edge sharpness values are compared with experimental results for subjective sharpness. According to the experiments, the calculated edge sharpness values show a good linear relation with subjective sharpness. Subjective image sharpness does not have a monotonic relation with subjective image quality. If the edge sharpness value is in a particular range, the image quality is judged to be good. According to the subjective experiments, an optimal edge sharpness value for image quality was obtained. This paper also shows an algorithm to alter an image into one which has another edge sharpness value. By altering the image, which achieves optimal edge sharpness using this algorithm, image sharpness can be optimally adjusted automatically. This new image improving method was applied to several images obtained by scanning photographs. The experimental results were quite good.

This paper proposes a new subscriber distribution method called FTTA (Fiber To The Area), which uses millimeter-wave radio band to connect subscribers with base station and optical fiber to connect base station with control station in order to obtain broad-band transmission. Usually two main causes of signal degradation, i.e., rainfall attenuation on radio channel and intermodulation distortion on optical channel are considered in this system. Taking into considerations of these two factors, we analyze the available capacity of FTTA system for various 22nQAM modulation levels. The analysis clarifies that there exists an optimum modulation level that can maxize the available capacity, and AGC circuit in the base station is useful to compensate the rainfall attenuation. It is shown that 18.0Gbps is available under the optimum modulation method of the 64QAM with AGC and 12.0Gbps under the 16QAM without AGC when 20 carriers are used.