G.Huet (1980) showed that a left-linear term-rewriting system (TRS) is Church-Rosser (CR) if P Q for every critical pair where P Q is a parallel reduction from P to Q. But, it remains open whether it is CR when Q P for every critical pair . In this paper, we give a partial solution to this problem, that is, a left-linear TRS is CR if Q P for every critical pair where Q P is a parallel reduction with the set W of redex occurrences satisfying that if the critical pair is generated from two rules overlapping at an occurrence u, then the length |w| |u| for every w W. We also show that a left-linear TRS is CR if Q P for every critical pair generated from two rules overlapping at an occurrence u. Here, Q P is either Q = P or a reduction whose redex occurrence is not greater than u. This condition is incomparable with the previous one and a partial solution to the open problem of ascertaining whether it is CR when Q P for every critical pair .

Polyurethane elastomer (PUE) films similar to polymer gel materials have been found to exhibit the electrostriction effect. We proposed the application their to a moving device such as an actuator without ionic solvent using the electrostriction effect of PUE. The actuators are of monomorph type fabricated by PUE film and metal electrodes evaporated at different thicknesses on the film surface. Because these actuators work at high voltage more than 1 KV, we controlled the molecular structure of the films by doping C60 derivatives (fullerenol) into PUE so that the actuators could operate under a low voltage. In order to clear the bending mechanism of actuators, we measured the space charge of PUE films using the pulsed electroacoustic method.

We present a learning algorithm of the Hopfield neural network for minimizing edge crossings in linear drawings of nonplanar graphs. The proposed algorithm uses the Hopfield neural network to get a local optimal number of edge crossings, and adjusts the balance between terms of the energy function to make the network escape from the local optimal number of edge crossings. The proposed algorithm is tested on a variety of graphs including some "real word" instances of interconnection networks. The proposed learning algorithm is compared with some existing algorithms. The experimental results indicate that the proposed algorithm yields optimal or near-optimal solutions and outperforms the compared algorithms.

This paper describes the design, fabrication, and measurement of a multiple U-shaped slot antenna for Hiper-LAN. The prototype consists of a U-shaped slot and two inverted U-shaped slot. To obtain sufficient bandwidth, a foam layer is inserted between the ground plane and substrate. A measured bandwidth of approximately 7.6% (VSWR 1.5) and gain of 2.9-5.3 dBi are obtained. The experimental far-field patterns are shown to be stable across the pass band, with the 3 dB beam width in azimuth and elevation at 50and 62, respectively.

This paper discusses far-end crosstalk (FEXT) cancellation methods for multicarrier transmission system. A system arrangement and its tap update method are proposed when FEXT cancelers and a frequency-domain equalizer (FEQ) are jointly adapted to combat channel intersymbol interference, FEXT, and other additive noise. We present mathematical formulation of minimum mean-square error (MSE) and the optimum tap coefficients for the FEXT cancelers and the FEQ when FEXT cancellation techniques are introduced for multiuser discrete multitone (DMT) based very high-speed digital subscriber line (VDSL) transmission. It is shown that FEXT cancellation enhances the achievable bit rate in FEXT-limited systems. Computer simulation and analytical results show that the performance of jointly adapted FEXT cancelers and an FEQ is better than that of separately adapted FEXT cancelers and an FEQ.

An analysis of the phase difference spectrum between two images allows precise image shift detection. Image shifts are directly evaluated from the phase difference spectrum without Fourier inversion. In the calculation, the weight function containing the frequency and the cross spectrum is used and an unlapping procedure is carried out. In an experiment using synthetic and real images of typical image patterns, accuracy as high as 0.01-0.02 pixel was achieved stably and reliably for most of the image patterns.

A novel method is presented to compute moments of high-speed VLSI interconnects, which are modeled as coupled RLC trees. Recursive formulae of moments of coupled RC trees are extended to those for coupled RLC trees by considering both self inductances and mutual inductances. Analytical formulae for voltage moments at each node are derived explicitly. The formulae can be efficiently used for estimating delay and crosstalk noise. The inductive crosstalk noise waveform can be accurately and efficiently estimated using the moment computation technique in conjunction with the projection-based order reduction method. Fundamental aspects of the proposed approach are described in details. Experimental results show the increased accuracy of the proposed method over that of the traditional ones.

In this paper, the method of locating multiple transmission zeros by the tap-coupling technique is described for bandpass filters (BPFs), using short-ended λ/2 resonators and its application to a duplexer. First, the method of locating the transmission zero using the short-ended λ/2 resonators is examined with various excitation methods. We focus on four types of short-ended λ/2 resonators: the end-coupling type, tap-coupling type, capacitive tap-coupling type and inductive tap-coupling type. Secondly, the BPFs based on the basic characteristics of the respective resonators are proposed and designed on the basis of a general filter theory with narrow band approximation. Lastly, we propose and design new duplexers consisting of the proposed BPFs. The results lead to the conclusion that the basic characteristics of the short-ended λ/2 resonators are useful for realizing a BPF with multiple transmission zeros and a high-performance duplexer fabricated without increasing the number of elements.

Using various rare earth sesquioxides as additives, silicon nitride (Si3N4) samples were sintered at 1700 for 4 h by millimeter-wave heating performed in an applicator fed by a 28 GHz Gyrotron source under a nitrogen pressure of 0.1 MPa. A comparative study of densification, grain growth behavior and mechanical properties of silicon nitride fabricated by millimeter-wave and conventional sintering was carried out. Bulk densities were measured by Archimedes' technique. Except for the Eu2O3 containing sample, all samples were densified to relative densities of above 97.0%. Microstructure of the specimens was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). To investigate quantitatively the effect of millimeter-wave heating on grain growth, image analysis was carried out for grains in the specimens. Fracture toughness was determined by the indentation-fracture method (IF method) in accordance with Japan Industrial Standards (JIS). Fully dense millimeter-wave sintered silicon nitride presenting a bimodal microstructure exhibited higher values of fracture toughness than materials processed by conventional heating techniques. Results indicate that millimeter-wave sintering is more effective in enhancing the grain growth and in producing the bimodal microstructure than conventional heating. It was also confirmed that localized runaway in temperature, depending upon the sintering additives, can occur under millimeter-wave heating.

A conventional waveguide filter is usually composed of a waveguide which is set with irises and posts inside. When dielectric material is not loaded inside the filter, the filter is too large to mount it on a planar circuit even if the frequency band is as high as the millimeter-wave band. In this paper, we propose a dielectric waveguide filter using LTCC (Low-Temperature Co-fired Ceramics) which can be mounted on a planar circuit. The dielectric waveguide filter using LTCC is composed of a dielectric-loaded waveguide including posts (via holes) and TEM-TE10 converters. The design method of the filter is shown and comparison of the simulated and the experimental results in the 6 GHz band is demonstrated. The simulated results agreed well with the experimental ones. To improve the attenuation characteristics, particularly at the above pass-band frequencies, an attenuation pole is added using a cross patch set inside the LTCC filter in the 25 GHz band. The effect of the cross patch is confirmed using the same simulation method as used for the 6 GHz band. As a result, it is confirmed that the cross patch is very useful for improving the attenuation characteristics at the above pass-band frequencies.

A GaAs HEMT with flip-chip interconnections using a suitable transmission line has been developed. The underfill resin, which was not used for the conventional flip-chip interconnection structure, was adopted between GaAs chip and assembly substrate to obtain high reliability. The underfill resin is effective in relaxing the thermal stress between the chip and the substrate and in encapsulating the chip. There are various possible ground current paths for the GaAs chip in the structure with flip-chip interconnections. An actual ground current path is determined depending on the transmission line type for the chip. For an active device, it is important to utilize an assembly structure capable of realizing excellent high-frequency characteristics. In addition, each transmission line for the chip has its own transmission characterizations such as characteristic impedance. Therefore, it is necessary to choose a suitable transmission line for the chip. We evaluated the high-frequency characteristics of the HEMT test element groups (TEGs) with flip-chip interconnection for three types of transmission lines: with a microstrip line (MSL), with a coplanar waveguide (CPW), and with an inverted microstrip line (IMSL). All three types of TEGs had similar values of a maximum available power gain (MAG) at 30 GHz. However, it was found that the IMSL-type TEG, which had superior characteristics in high-frequency ranges of more than 30 GHz, is the most suitable type. The IMSL-type TEG had an MAG of 10.02 dB and a Rollett stability factor K of 1.20 at 30 GHz.

Vertical stacking is a novel technique for building switching networks, and packing multiple compatible connections together is an effective strategy to reduce network hardware cost. In this paper, we study the crosstalk-free permutation capability of an optical switching network built on the vertical stacking of optical banyan networks to which packing strategy is applied. We first look into the nonblocking condition of this optical switching network. We then study the crosstalk-free permutation in this network by decomposing a permutation evenly into multiple crosstalk-free partial permutations (CFPPs) and realizing each CFPP in a stacked plane of the network such that a crosstalk-free permutation can be performed in a single pass. We present a rigorous proof of CFPP decomposability of a permutation and also a complete algorithm for CFPP decomposition. The possibility of a tradeoff between the number of passes and the number of planes required for realizing a crosstalk-free permutation in this network is also explored in this paper.

We propose an estimation method of crosstalk noise for generic RC trees. The proposed method derives an analytic waveform of crosstalk noise in a 2-π equivalent circuit. The peak voltage is calculated from the closed-form expression. We also develop a transformation method from generic RC trees with branches into the 2-π model circuit. The proposed method can hence estimate crosstalk noise for any RC trees. Our estimation method is evaluated in a 0.13 µm technology. The peak noise of two partially-coupled interconnects is estimated with the average error of 11%. Our method transforms generic RC interconnects with branches into the 2-π model with 14% error on average.

The size of the microscopic electron spot is an important parameter for the white-uniformity of a CRT. It changes as a function of the focus voltage and beam repulsion. This paper explains the mechanism behind this phenomenon. The model is supported by means of measurements.

The adaptive cross-spectral (ACS) technique recently introduced by Okuno et al. provides an attractive solution to acoustic echo cancellation (AEC) as it does not require double-talk (DT) detection. In this paper, we first introduce a generalized ACS (GACS) technique where a step-size parameter is used to control the magnitude of the incremental correction applied to the coefficient vector of the adaptive filter. Based on the study of the effects of the step-size on the GACS convergence behaviour, a new variable step-size ACS (VSS-ACS) algorithm is proposed, where the value of the step-size is commanded dynamically by a special finite state machine. Furthermore, the proposed algorithm has a new adaptation scheme to improve the initial convergence rate when the network connection is created. Experimental results show that the new VSS-ACS algorithm outperforms the original ACS in terms of a higher acoustic echo attenuation during DT periods and faster convergence rate.

A simple non-destructive depth estimation method for a crack on a metal surface has been proposed. This method is based on our finding that the electromagnetic back scattering from a narrow trough (crack model) on the ground plane causes periodical nulls (dips) as the frequency changes, and the first dip occurs when the depth of the crack becomes nearly one half of the incident wavelength. Dependencies of the crack's aperture and the incident angle have also been studied from rigorous and numerical analyses, and considered as our depth estimation parameters. A simple estimation formula for a crack depth has been derived from these studies. Test measurement has been made to check the accuracy of our estimation formula. Time domain gating process is utilized for isolating the crack scattering spectra buried in the measured frequency RCS data. Tested crack types are a narrow rectangular, a tapered, and a stair approximated crack shapes. It is found that the depth of these cracks can be measured within 3 percent error by our estimation method.

One-dimentional equivalent circuit model of a heterostructure InAlAs/InGaAs/InP metal-semiconductor-metal photodetector is discussed. In this photodetector, InGaAs is used as an optical absorption layer and the InAlAs is used for Schottky barrier enhanement. The measured S11 parameter deviates from equi-resistance lines on the Smith chart, indicating the equivalent circuit is different from the conventional equivalent circuit using a series resistance, a depletion region capacitance and a depletion region resistance. The difference is due to band discontinuity at the heterojunctions, and we propose a equivalent circuit taking account of the band discontinuity. The band discontinuity is expressed by parallel combination of a resistance and a capacitance. The measured S11 parameter can be fitted well with the calculated S11 parameter from the proposed equivalent circuit, and we can successfully extract the device parameters from the fitted curve.

A rectangular-to-radial waveguide transformer through a crossed slot is proposed as a feeder of a radial line slot antenna (RLSA) for use in a system of solar power satellite (SPS). The transformer is analyzed and designed by using the MoM with numerical eigenmode basis functions. The measured ripple of the amplitude is 3.0 dB in the φ-direction and a 7.0% frequency bandwidth for rotating mode with the ripple below 6 dB is obtained. This bandwidth is wider than that of conventional ring slot or cavity resonator with a coaxial feeder. The antenna measurements at 5.8 GHz show reasonable rotational symmetry both in the near-field distribution and the far field radiation patterns. The reflection is -27.7 dB at the design frequency and below -15 dB in the 7.0% bandwidth. The gain of the antenna with the diameter of 300 mm is 22.7 dBi and the efficiency is 56%.

The Earth Simulator (ES), developed by the Japanese government's initiative "Earth Simulator project," is a highly parallel vector supercomputer system. In May 2002, the ES was proven to be the most powerful computer in the world by achieving 35.86 teraflops on the LINPACK benchmark and 26.58 teraflops for a global atmospheric circulation model with the spectral method. Three architectural features enabled these great achievements; vector processor, shared-memory and high-bandwidth non-blocking interconnection crossbar network. In this paper, an overview of the ES, the three architectural features and the result of performance evaluation are described particularly with its hardware realization of the interconnection among 640 processor nodes.

For the mass production of GaN-based electronic devices, growth of AlGaN/GaN heterostructures on substrates larger than 100 mm in diameter is indispensable. In this study, we demonstrate the growth of 100-mm-diameter Al0.26Ga0.74N/GaN heterostructures on sapphire substrates by metalorganic vapor phase epitaxy (MOVPE). The obtained films have specular surfaces, good crystal quality and good uniformity of alloy composition across the entire 100-mm-diameter epitaxial wafer. The bowing value of the 100-mm-diameter epitaxial wafer on c-face sapphire substrates is about 40 µm. This bowing value seems to be preferable for electronic device fabrication processes. These epitaxial wafers show good electrical properties.