An equivalent circuit for designing a coherent power combiner using a quasi-optical resonator has been developed. In the resonator, large numbers of devices (HEMT, HBT, etc. ) are arrayed two dimensionally and mounted on a surface of a metal grooved-mirror. A newly developed equivalent circuit for the resonator has been constructed using a transmission-line model. Experiments performed at Ku-band have shown that oscillation frequencies in a 33 HEMT array oscillator can be predicted with errors of less than 1% by using this equivalent circuit.

A floorplan is a partition of a rectangle into subrectangles, each of which is associated with a module. Zero-wasted-area layouts are known to exist when the height and width of modules are constrained only by the area, and several methods have been proposed for deriving such layouts. However, because these methods are global and indirect, they are inherently slow. We propose a new algorithm which simulates the air-pressure mechanics. It begins with a layout, which is not necessarily feasible, and iterates the movement of one wall at a time to the force-balancing position. The key issue is that it is guaranteed that every movement makes a current layout approach a zero-wasted-area layout by the measure of energy which is defined here. Experimental results on the example in several literatures and artificially made complex examples showed very fast convergence. The algorithm is evolved to methods which move all the walls simultaneously, resulting in a further speed enhancement.

We have proposed a non-invasive method for diagnosis of the early stage of atherosclerosis, namely, the detection of small vibrations on the aortic wall near the heart by using ultrasound diagnostic equipment. It is, however, necessary to confirm the effectiveness of such measurement of the pulse wave velocity for quantitative evaluation of the local characteristics of atherosclerosis. It is well known that Young's modulus of a tube wall, estimated from measured pulse wave velocity, depends on inner pressure because of the non-linear relationship between the inner pressure and the change of volume in the tube. The inner pressure, however, changes during the period of one heartbeat. In this experimental study, we found for the first time that Young's modulus of the tube wall, estimated from the measured pulse wave velocity, depends not only on the diastolic pressure but also on the pulse pressure and the pressure gradient of the systolic period.

To investigate the possibility of their application to both high density dynamic and nonvolatile ferroelectric random access memories, heteroepitaxial BaxSr1-xTiO3 (BSTO) thin films with various Ba content from x=0 to 1. 0 were prepared on conductive SrRuO3 electrode films, and the crystallographic, dielectric and ferroelectric properties were investigated. The compositional phase boundary between paraelectric and ferroelectric phase at room temperature was located at about x = 0. 12 in the heteroepitaxial films, indicating a quite different composition to that of the bulk (x = 0. 70). At this composition of x = 0. 12, the dielectric constant attained the maximum value of 740 for the BSTO film with a thickness of 77 nm. The composition with a lager Ba content (x 0. 32) showed ferroelectricity at room temperature. The maximum value of remanent polarization of 2Pr = 0. 38 C/m2 was obtained at the composition of x = 0. 70 in this study.

A new type of fiber Fabry-Perot interferometer buried in a fiber connector housing was proposed. The transmission spectra revealed double peaks due to birefringence in the fiber and the peak separation showed a temperature dependence as large as -7. 7 MHz/deg, which was 2 orders of magnitude larger than that estimated from the thermal characteristics of its component materials.

In this paper, we give a new approach to the computation of primary decomposition and associated prime components of a zero-dimensional polynomial ideal (f1,f2,. . . ,fn), where fi are multivariate polynomials on Z (the ring of integer). Over the past several years, a considerable number of studies have been made on the computation of primary decomposition of a zero-dimensional polynomial ideal. Many algorithms to compute primary decomposition are proposed. Most of the algorithms recently proposed are based on Groebner basis. However, the computation of Groebner basis can be very expensive to perform. Some computations are even impossible because of the physical limitation of memory in a computer. On the other hand, recent advance in numerical methods such as homotopy method made access to the zeros of a polynomial system relatively easy. Hence, instead of Groebner basis, we use the zeros of a given ideal to compute primary decomposition and associated prime components. More specifically, given a zero-dimensional ideal, we use LLL reduction algorithm by Lenstra et al. to determine the integer coefficients of irreducible polynomials in the ideal. It is shown that primary decomposition and associated prime components of the ideal can be computed, provided the zeros of the ideal are computed with enough accuracy. A numerical experiment is given to show effectiveness of our algorithm.

Noise cancelation and system identification have been studied for many years, and adaptive filters have proved to be a good means for solving such problems. Some neural networks can be treated as nonlinear adaptive filters, and are thus expected to be more powerful than traditional adaptive filters when dealing with nonlinear system problems. In this paper, two new heterogeneous recurrent neural network (HRNN) architectures will be proposed to identify some nonlinear systems and to extract a fetal electrocardiogram (ECG), which is corrupted by a much larger noise signal, Mother's ECG. The main difference between a heterogeneous recurrent neural network (HRNN) and a recurrent neural network (RNN) is that a complete neural network is used for the feedback path along with an error back-propagation (BP) neural network as the feedforward one. Different feedback neural networks can be used to provide different feedback capabilities. In this paper, a BP neural network is used as the feedback network in the architecture we proposed. And a self-organizing feature mapping (SOFM) network is used next as an alternative feedback network to form another heterogeneous recurrent neural network (HRNN). The heterogeneous recurrent neural networks (HRNN) successfully solve these two problems and prove their superiority to traditional adaptive filters and BP neural networks.

This paper describes the design and evaluation of a high-performance multicast ATM switch and its feasibility study, including its 40 Gbit/s LSI packaging. The multicast switch is constructed using a serial combination of rerouting networks and employs an adapted Boolean interval-splitting scheme for a generalized self-routing algorithm. Analysis and computer simulation results show that the cell loss probability is easily controlled by increasing the number of switching stages. It is shown that the switch configuration can be transformed into other patterns to be built from banyan-based subnetworks of arbitrary size for LSI packaging. It is also shown that an LSI chip integrating an 88 banyan-based subnetwork using 0. 25-µm CMOS/SIMOX technology can attain a 40-Gbit/s switching capability.

This paper proposes implementation methods of fast ATM layer protection switching function. The main problem in attaining fast ATM protection is the number of connections in one transmission path. The transmission delay of the signal for protection negotiation procedure is relatively less than the processing time in the end nodes. Therefore shortening of the processing time in the nodes is a crucial factor for fast rerouting. This paper focuses on this point and presents some suitable implementations on ATM nodes for fast protection switching. These architectures can attain protection time of less than 50 ms after the detection of a failure at an end node. The key is load-sharing of the hardware and firmware. This paper also sums up the effectiveness of ATM protection and the current situation of standardization in ITU-T SG13.

Parallelism on heterogeneous machines brings cost effectiveness, but also raises a new set of complex and challenging problems. This paper addresses the problem of estimating the minimum time taken to execute a program on a fine-grained parallel machine composed of different types of processors. In an earlier publication, we took the first step in this direction by presenting a graph-construction method which partitions a given program into several homogeneous parts and incorporates timing constraints due to heterogeneous parallelism into each part. In this paper, to make the method easier to be applied in a scheduling framework and to demonstrate its practical utility, we present an efficient implementation method and compare the results of its use to the optimal schedule lengths obtained by enumerating all possible solutions. Experimental results for several different machine models indicate that this method can be effectively used to estimate a program's minimum execution time.

Fiat-Shamir's identification and signature scheme is efficient as well as provably secure, but it has a problem in that the transmitted information size and memory size cannot simultaneously be small. This paper proposes an identification and signature scheme which overcomes this problem. Our scheme is based on the difficulty of extracting theL-th roots modn (e. g.L=2 1020) when the factors ofnare unknown. We prove that the sequential version of our scheme is a zero knowledge interactive proof system and our parallel version reveals no transferable information if the factoring is difficult. The speed of our scheme's typical implementation is at least one order of magnitude faster than that of the RSA scheme and is relatively slow in comparison with that of the Fiat-Shamir scheme.

In this paper, we propose a new type of authentication system, one-time zero-knowledge authentication system. Informally speaking, in this authentication system, double usage of the same authentication is prevented. Based on these one-time zero-knowledge authentication systems, we propose a new untraceable electronic cash scheme satisfying both untraceability and unreusablity. This scheme overcomes the problems of the previous scheme proposed by Chaum, Fiat and Naor through its greater efficiency and provable security under reasonable cryptographic assumptions. We also propose a scheme, transferable untraceable electronic cash scheme, satisfying transferability as well as the above two criteria. Moreover, we also propose a new type of electronic cash, untraceable electronic coupon ticket, in which the value of one piece of the electronic cash can be subdivided into many pieces.

The proposed high-power-factor converter is constructed with a flyback converter, and locates the energy-storage capacitor on the secondary side of the transformer. A high power-factor can be obtained without needing to detect any current, and the ZVS operation can be achieved without auxiliary switches. To make the best use of these advantages in the converter, ZVS operations and power-factor characteristics in the converter were analyzed. From the analytical results, the effective control method for achieving ZVS was examined. Using a bread-board circuit controlled by this method, a power-factor of 0.99 and a conversion efficiency of 88% were measured.

Minato has proposed canonical representation for polynomial functions using zero-suppressed binary decision diagrams (ZBDDs). In this paper, we extend binary moment diagrams (BMDs) proposed by Bryant and Chen to handle variables with degrees higher than l. The experimental results show that this approach is much more efficient than the previous ZBDDs' approach. The proposed approach is expected to be useful for various problems, in particular, for computer algebra.

We report on progress in the development of high-current-density all-NbN tunnel junctions for application as submillimeter wave SIS mixers. A very high current density up to 54 kA/cm2, roughly an order of magnitude larger than any reported results for all-NbN tunnel junctions, was achieved in the junctions with a thin aluminum nitride (AIN) tunnel barrier. Even though the junctions have a very high current density, they showed high-quality junction characteristics with a large gap voltage, sharp quasipartical current rise, and small subgap leakage current. The junctions also exhibited good Josephson tunneling behavior, excellent terahertz response, and sensitive heterodyne mixing properties. NbN/AIN/NbN tunnel junctions were integrated with a NbN thin-film antenna to investigate the terahertz responses and the heterodyne mixing properties in a quasioptical mixer testing system. Photon-assisted tunneling steps were clearly observed on the I-V curve with irradiation up to 1 THz, and low-noise heterodyne mixing was demonstrated in the 300-GHz band.

We previously proposed a robust hybrid edge detector which relaxes the trade off between robustess against noise and accurate localization of the edges. This hybrid detector separates the tasks of localization and noise suppresion between two sub-detectors. In this paper, we present an extension to this hybrid detector to determine its optimal parameters, independently of the scene. This extension defines a probabilistic cost function using for criteria the probability of missing an edge buried in noise and the probability of detecting false edges. The optimization of this cost function allows the automatic selection of the parameters of the hybrid edge detector given the height of the minimum edge to be detected and the variance of the noise, σ2n. The results were applied to the 2D case and the performance of the adaptive hybrid detector was compared to other detectors.

We have constructed a new concept device with combination of ferroelectric and ferromagnetic materials by a laser ablation technique. An ideal hetero-epitaxy can be obtained owing to the similar crystal structure of perovskite type ferroelectric Pb (Zr, Ti) O3; (so called PZT) and ferromagnetic (La, Sr) MnO3. The ferromagnetic (La, Sr) MnO3 compounds are well known for their colossal magnetoresistance (CMR) properties. The CMR effect is strongly affected by the lattice stress. The PZT, on the other hand, is famous for its large piezoelectrics. We can introduce the lattice stress easily by applying voltage for the piezoelectric compounds. In the heterostructured ferromagnetic/ferroelectric devices, there are remarkable interesting phenomena. Electric properties of the ferromagnetic material can be controlled by piezoelectric effect via distortion of crystal structure.

A model for estimating the bending loss of 1.3 µm zero-dispersion single-mode fibers at 1.58 µm from the value at 1.55 µm is investigated experimentally and theoretically. An approximated equation for estimating the bending loss ratio of 1.58 µm to 1.55 µm is proposed, which provides good agreement with the experimental results.

We present a high performance AlGaAs/GaAs power HBT with very low thermal resistance for digital cellular phones. Device structure with emitter air-bridge is utilized and device layout is optimized to reduce thermal resistance based on three-dimensional thermal flow analysis, and in spite of a rather thick substrate (100 µm), which achieved a low thermal resistance of 23/W for a multi-finger (440 µm240 fingers) HBT. This 40 finger HBT achieved power added efficiency (PAE) of over 53%, 29.1 dBm output power (Pout) and high associated gain (Ga) of 13.5 dB with 50 kHz adjacent channel leakage power (Padj) of less than -48 dBc under a 948 MHz π/4-shifted QPSK modulation with 3.4 V emitter-collector voltage. We also investigated the difference of RF performance between two bias modes (constant base voltage and current), and found which mode is adequate for each stage in several stage power amplifier for the first time.

A buried gate AlGaAs/InGaAs heterojunction FET (HJFET) with gate breakdown voltage of 30 V was examined for high drain bias (higher than 10 V) operation. High breakdown voltage was realized due to the optimization of the narrow recess depth. A 1.4 mm HJFET has exhibited an output power of 30.2 dBm (1050 mW) with 50% power added efficiency (PAE) and 12.1 dB linear gain at 12 GHz with a 13 V drain bias. An internal matching circuit for a 16.8 mm HJFET was designed using a large-signal load impedance determined from load-pull measurement. The 16.8 mm internally-matched HJFET has delivered 38.9 dBm (7.8 W) output power with 46% PAE and 11.6 dB linear gain at 12 GHz with a drain bias of 13 V. This is the first report of higher than 10 V operation of an X- and Ku-band power HJFET with the excellent power performance.