In this paper, we present a digital scheme for fast VLSI range imaging sensor, which is a modification of the analog scheme of existing sensor implemented by T. Kanade. Instead of reading timing information in analog manner, we use a digital scheme which has several advantages over the analog scheme, including area saving, insusceptibility to noise and other undesirable effects. We have implemented a prototype to test feasibility and present its experimental result.

By applying Wigner distribution, which has high time resolution and high random noise reducing capability, to the acoustic bio–signals, the possibility of early diagnosis in both intracranial vascular deformation and prosthetic cardiac valve malfunction increased. Especially in latter case, 1st–order local moment of the distribution showed its effectiveness.

We discuss a processor scheduling problem for parallel logic simulation of combinational circuits. In the processor scheduling problem, to be discussed in this paper, for logic simulation using time–first method, the time needed for each gate evaluation is not given beforehand, and is not constant. This feature distinguishes the processor scheduling problem from typical task scheduling problems. First, we devise newly Algorithm MET to solve the processor scheduling problem. The key idea of Algorithm MET is to determine processor scheduling incrementally and dynamically. Then, experimental evaluations using well–known twelve benchmark combinational circuits show the usefulness of Algorithm, MET, compared with conventional static algorithms. We believe that this is a first step to implement parallel logic simulation of combinational circuits.

We propose an optimal throughput problem using graph transformations to maximize throughput of a pipelined data path with some loops. The upper bound of the throughput, equals to the lower bound of the iteration interval between the start of two successive iterations, is limited by the length of a critical loop. Therefore we can maximize the throughput by minimizing the length of the critical loop. The proposed method first schedules an initial Data Flow Graph (DFG) under the initial iteration interval as few as it can use resources, then it transforms the DFG into the flow graph with the minimal length of the critical loop by rescheduling the given initial scheduling result. If there are any control steps which violate the resource constraints owing to the transformations, then these operations are adjusted so as to satisfy given resource consrtraints. Finally by rescheduling the transformed DFG, it gives a schedule with maximum throughput. Experiments show the efficiency of our proposed approach.

We describe the characteristics of scattering and diffraction of plane E-waves by a lossy dielectric elliptic cylinder. The computational programs for calculating the analytic solutions for the diffraction of a lossy dielectric elliptic cylinder can be achieved. From the calculated results of the backscattering cross section (BSCS) (usually the radar cross section: RCS) and the forward-scattering cross section (FSCS) due to the cross-sectional shape and complex dielectric constant of the elliptic cylinder, the features of the BSCS and FSCS can be clarified as follows. (1) There is a cross-sectional shape of the cylinder which results in a minimum BSCS with a complex dielectric constant of the cylinder. (2) The BSCS and FSCS of the lossy dielectric scatterer approach zero as the scatterer approaches a strip. This result means that no material composing such a strip exists, and the features are very different from those in a perfectly conducting strip. (3) The influence of conductivity, σ, of the cylinder on a scattered wave is small for the relative dielectric constant of εr6. (4) The total scattering cross section of the lossy dielectric elliptic cylinder which causes the minimum BSCS is not small. Hence, it may be considered that the minimum BSCS is determined mainly by interference based on the cross-sectional shape and complex dielectric constant of cylinder, and is not caused by incident wave absorption due to the lossy dielectric.

An efficient full–wave spectral domain moment method is developed to compute the current distribution and the radiation associated with microstrip discontinuities. Two techniques are used to increase the efficiency of the method of moments algorithm so that a transmission line of moderate electrical size can be analyzed in reasonable time.

We present a novel algorithm to reconstruct the refractive-index profile of a circularly symmetric object from measurements of the electromagnetic field scattered when the object is illuminated by a plane wave. The reconstruction algorithm is besed on an iterative procedure of matching the scattered field calculated from a certain refractive-index distribution with the measured scattered field on the boundary of the object. In order to estimate the convergence of the reconstruction, the mean square error between the calculated and measured scattered fields is introduced. It is shown through reconstructing several examples of lossy dielectric cylinders that the algorithm is quite stable and is applicable to high-contrasty models in situations where the Born approximation is not valid.

The mechanical impedance of silicone–gel model or chest surface has been measured and the viscoelasticity and effective vibrating radius have been obtained from the impedance. They depend on the distance between the internal block of the silicone–gel/ribs of right chest and the gel surface/skin surface. The 3–D image of internal structure is reconstructed, based on the relation between the distance from the surface and the effective vibrating radius.

More than 200 papers, two special issues (Journal of Circuits, Systems, and Computers, March, June, 1993, and IEEE Trans. on Circuits and Systems, vol.40, no.10, October 1993), an International workshop on "Chua's Circuit: chaotic phenomena and applications" at NOLTA'93, and a book (Edited by R. N. Madan, World Scientific, 1993) on Chua's circuit have been published since its inception a decade ago. This review paper attempts to present an overview of these timely publications, almost all within the last 6 months, and to identify four milestones of this very active research area. An important milestone is the recent fabrication of a monolithic Chua's circuit. The robustness of this IC chip demonstrates that an array of Chua's circuits can also be fabricated into a monolithic chip, thereby opening the floodgate to many unconventional applications in information technology, synergetics, and even music. The second milestone is the recent global unfolding of Chua's circuit, obtained by adding a linear resistor in series with the inductor to obtain a canonical Chua's circuit--now generally referred to as Chua's oscillator. This circuit is most significant because it is structurally the simplest (it contain only 6 circuit elements) but dynamically the most complex among all nonlinear circuits and systems described by a 21–parameter family of continuous odd–symmetric piecewise–linear vector fields. The third milestone is the recent discovery of several important new phenomena in Chua's Circuits, e.g., stochastic resonance, chaos–chaos type intermittency, 1/f noise spectrum, etc. These new phenomena could have far-reaching theoretical and practical significance. The fourth milestone is the theoretical and experimental demonstration that Chua's circuit can be easily controlled from a chaotic regime to a prescribed periodic or constant orbit, or it can be synchronized with 2 or more identical Chua's circuits, operating in an oscillatory, or a chaotic regime. These recent breakthroughs have ushered in a new era where chaos is deliberately created and exploited for unconventional applications, e.g., secure communication.

The problem of electromagnetic scattering by inductive discontinuities located in rectangular waveguides, in particular when dealing with discontinuous conductors of finite thickness, is analyzed using the modified residue-calculus method, and form of the equation suitable for a numerical calculation is derived. The incident wave is taken to be the dominant mode, and reflection and transmission properties of an asymmetric inductive iris are discussed. After the modal representation of the filed, the modal matching is apply to satisfy the boundary conditions at the discontinuity. And using the modified residue-calculus method, simultaneous infinite equations, which are concerned with the scattered mode coefficients, are derived. Then they are approximated at the thick diaphragm. The solutions obtained take on the form of an infinite product, and a numerical solution based on the method of successive approximations is presented as a technique for concretely determining the reflection coefficients. As confirmation, experiments are also carried out in the X-band and close agreement is shown between the calculated and experimental values.

This paper presents a new numerical procedure for solving the scattering wave by the moving surface. Recently, the author and her colleagues have proposed a novel numerical procedure of grid generation having a coordinate line coincident with an arbitrarily shaped moving boundary. The time dependent curvilinear coordinate system which coincides with a contour of moving boundary in a physical region is transformed into fixed rectangular coordinate system. The simple form for the transformation is made possible to choose the function between the physical region and the rectangular computational region. The FD-TD algorithm is exactly solved in this fixed rectangular coordinate system. In this paper, for the application of the FD-TD algorithm to the body fitted grid generation with moving boundary, the stability criterion of FD-TD algorithm for the body fitted grid generation with moving boundary in three dimensions is derived. The stability criterion is shown an upper bound for time step assuring stable numerical solutions. The study of scattering of electromagnetic and acoustic wave from a moving or a rotating body is very important for electromagnetic probing of moving body. The problem has been investigated in the past by numerous authors. One of them is solved by FD-TD method, where the linear interpolation is introduced for the movement. By using the presented transformation technique where time component is added to the grid generation, the time depending coordinate system can be transformed into fixed rectangular coordinate system. Then the problems are directly solved by FD-TD method in the transformed coordinate system. To verify this numemical technique, scattered field is evaluated in the case when a plane wave is normally incident on a moving perfectly conducting flat plate. The numerical results are compared with the exact ones and excellent agreement between them is obtained.

The authors have studied mechanism of transition from metallic phase to gaseous phase in contact break arc. For further elucidation of the mechanism, we have carried out spectroscopic measurement. The spectrum measurement system which had high time resolution was composed using two monochromators and a bifurcated image fiber, which had one input port and two output ports. The input port received the arc light, and the two monochromators received the arc light from the two output ports, respectively. The spectral sensitivity of the two monochromators was corrected with a standard lamp. We have measured simultaneously two spectra of break arc for Ag in laboratory air, under the condition where source voltage E=48 V, load inductance L=2.3 mH, and closed contact current I0=6 A. As a result, the time-varying tendency of spectrum intensity is similar for the same element, even if the wavelength is different. And from the comparison of time average spectrum intensity, it is clarified that average intensity for gas spectrum does not attain to 10% of that for metallic atomic spectrum (Ag I, 520.91 nm). In addition, the decrease point of Ag II (ion) spectrum has been found to correspond with the peak of Ag I (atom) spectrum.

This paper describes a simple system of measuring the spatial distributions of spectral intensities with AgI-421 nm and AgI-546 nm among many optical spectrums emitted from an arc discharge between separating Ag contacts. In order to detect the intensities of two optical spectrums, the prototype equipment has two sets assembled with a CCD color linear image sensor, a lens and optical filters, which are arranged on rectangularity. The intensities of two spectrums can be recorded with 2 ms time-resolution within a long arc duration on a digital memory. The recorded digital signals are processed by using a personal computer in order to reconstruct two spatial distributions of spectral intensities in a cross section of arc column with the Algebraic Reconstruction Technique.

It is shown that for a class of interval matrices we can estimate the location of eigenvalues in a very simple way. This class is characterized by the property that eigenvalues of any real linear combination of member matrices are all real and thus includes symmetric interval matrices as a subclass. Upper and lower bounds for each eigenvalue of such a class of interval matrices are provided. This enables us to obtain Hurwitz stability conditions and Schur ones for the class of interval matrices and positive definiteness conditions for symmetric interval matrices.

State space explosion is a serious problem in analyzing discrete event systems that allow concurrent occurring of events. A new method is proposed for generating reduced state spaces of systems. This method is an improvement of Valmari's stubborn set method. The generated state space preserves liveness, livelocks, and terminal states of the ordinary state space. Petri nets are used as a model of systems, and a method is shown for generating a reduced state space from a given Petri net.

Reliability of an electric contact can be defined by two parameters, contact resistance and wear, and the parameters of contacts operated in arcing condition are governed by the arc discharge. Thus the measurement on the relationship between the parameters and arc phenomena is necessary to improve the contact performance. The parameters for arcing electric contacts and problems were reviewed, and new concept for electric contact testing systems was proposed. Measurement with such an advanced system should be concurrent parallel measurement, quantitative measurement of degradation, systematic measurement, and analysis of arc discharge phenomena. Some examples of advanced measurement systems and new data obtained with such systems were described. Systematic results on relationships between condition and performance parameters were obtained by systematic measurement with systematically settled conditions, such as opening speed or material condition. A measurement method for the metallic phase arc duration was developed by the authors, and role of the metallic phase arc on contact performance parameters was found from interpretation of obtained data. The real-time surface profile measurement of an operating contact and the optical transient spectrum analyser for arc light radiated from breaking contact were also described.

Experimental optical gain characteristics of an erbium-doped fiber amplifier have not been explained well by conventional laser schemes in the case of two-channel amplification. Modified simple laser schemes including cross relaxation among degenerate levels were valid for the explanation of the optical gain dependence on input signal power and on the erbium-doped fiber length.

In clad contacts of bonded dissimilar metals used in relays and switches, the bonding state affects the switching performance of those devices. Examining the bonding state and analyzing the relationship between the bonding state and the causes of malfunction, such as welding of the contact, leads to improvement in reliability of electromechanical devices. In this experiment we examined, with an ultrasonic microscope, the bonding state in riveted clad contacts which had been subjected to load-breaks of in-rush current, and were able to demonstrate the causal relation of the bonding state with malfunctions of the contacts. The use of the ultrasonic microscope made it possible to perform a hitherto difficult detailed analysis of the bonding state of clad contacts. It was also confirmed that this was an extremely effective method for studying the relationship with switching performance.

Arc discharge between electrodes of relays and switches often causes contact surface damage through material transfer and arc erosion. Especially, material transfer sometimes occurs and brings serious failure even under lower load that is quite smaller than the minimum arc current value of contact material. In this paper, contact surface configuration, material transfer, and arc erosion characteristics of Ag and AgPd 60 contacts were experimentally studied after 0.5 or 1 million switching operations at various load levels. The followings can be made clear. Firstly, it was confirmed that the arcs and material transfer occurred even under such current that was lower than the minimum arc current. Therefore, the definition of the arc occurrence boundary current was newly determined. Secondly, the relation between load conditions (current and power supply voltage) and contact surface configuration (craters and pips) caused by material transfer was studied. The arc erosion behaviors of tested samples could be classified into two types: material transfer type and wear-out type. As one of the primary factors of transition from the former type to the latter one, contact activation was considered. The influences of load conditions and organic gas emitted from relay structure on arc characteristics was experimentally examined. The results indicated that load current greatly influenced the amount of material transfer and that power supply voltage affected the occurrence of the wear-out type significantly. The activation behavior of the contact surface could be found through observing the bridge voltage waveform.

Three-dimensional display technologies that require special glasses are not suitable for telecommunications because wearing glasses is inconvenient and it is defficult to observe facial expressions. Our previous 6.3-inch 3D display was inadequate for presenting images with realistic sensation. In this paper, a direct view 15-inch 3D display is described. The display is made up of a l5-inch TFT LCD and a composite lenticular sheet (LS), and uses the head tracking technique. Quantitative evaluation of the stereoscopic sensation of the display was studied using the 3D display, and better stereoscopic sensation values were obtained compared with a 2D display mode, thus comfirming the display's usefulness.