This paper presents the device technology for monolithic integration of InP-based resonant tunneling diodes (RTDs) and high electron mobility transistors (HEMTs). The potential of this technology for applications in quantum functional devices and circuits is demonstrated in two integration schemes in which RTDs and FETs are integrated either in Parallel or in series. Based on the parallel integration scheme, we demonstrate an integrated device which exhibits negative differential resistance and modulated peak current. This integrated device forms the foundation of a new category of functional circuits featuring clocked supply voltage. Based on the series integration scheme, resonant-tunneling high electron mobility transistors (RTHEMTs) with novel current-voltage characteristics and useful circuit applications are demonstrated. The high-frequency characteristics of RTHEMTs are also reported.

A multiple classifier system can be a powerful solution for robust pattern recognition. It is expected that the appropriate combination of multiple classifiers may reduce errors, provide robustness, and achieve higher performance. In this paper, high performance Chinese syllable recognition is presented using combinations of multiple classifiers. Chinese syllable recognition is divided into base syllable recognition (disregarding the tones) and recognition of 4 tones. For base syllable recognition, we used a combination of two multisegment vector quantization (MSVQ) classifiers based on different features (instantaneous and transitional features of speech). For tone recognition, vector quantization (VQ) classifier was first used, and was comparable to multilayer perceptron (MLP) classifier. To get robust or better performance, a combination of distortion-based classifier (VQ) and discriminant-based classifier (MLP) is proposed. The evaluations have been carried out using standard syllable database CRDB in China, and experimental results have shown that combination of multiple classifiers with different features or different methodologies can improve recognition performance. Recognition accuracy for base syllable, tone, and tonal syllable is 96.79%, 99.82% and 96.24% respectively. Since these results were evaluated on a standard database, they can be used as a benchmark that allows direct comparison against other approaches.

This paper discusses our newly developed technology for making GaAs/InGaAs/GaAs Tetrahedral-Shaped Recess (TSR) quantum dots. The heterostructures were grown by low-pressure MOVPE in tetrahedral-shaped recesses created on a (111) B oriented GaAs substrate using anisotropic chemical etching. We examined these structures by using cathodoluminescence (CL) measurements, and observed lower energy emissions from the bottoms of, and higher energy emissions from the walls of the TSRs. This suggests carrier confinement at the bottoms with the lowest potential energy. We carried out microanlaysis of the structures by using TEM and EDX, and found an In-rich region that had grown vertically from the bottom of the TSR with a (111)B-like bond configuration. We also measured a smaller diamagnetic shift of the lower energy photoluminecscence (PL) peak in the structure. Based on these results, we have concluded that the quantum dots are formed at the bottoms of TSRs, mainly because of the dependence of InAs composition on the local crystalline structure in this system. We also studied the lateral distribution and vertical alignment of TSR quantum dots by CL and PL measurements respectively. The advantages of TSR quantum dot technology can be summarized as follows: (i) better control in dot positioning in the lateral direction, (ii) realization of dot sizes exceeding limitations posed by lithography, (iii) high uniformity of dot size, and (iv) vertical alignment of quantum dots.

This paper describes an adaptive neural vector quantization algorithm with a deleting approach of weight (reference) vectors. We call the algorithm an adaptive learning and self-deleting algorithm. At the beginning, we introduce an improved topological neighborhood and an adaptive vector quantization algorithm with little depending on initial values of weight vectors. Then we present the adaptive learning and self-deleting algorithm. The algorithm is represented as the following descriptions: At first, many weight vectors are prepared, and the algorithm is processed with Kohonen's self-organizing feature map. Next, weight vectors are deleted sequentially to the fixed number of them, and the algorithm processed with competitive learning. At the end, we discuss algorithms with neighborhood relations compared with the proposed one. The proposed algorithm is also good in the case of a poor initialization of weight vectors. Experimental results are given to show the effectiveness of the proposed algorithm.

This paper describes a circuit analysis technique that includes all circuit elements used in transistor Colpitts quartz crystal oscillators. This technique is applied to a quartz crystal oscillator that has a tank circuit for selecting the oscillation frequency. The results obtained with this technique are compared with SPICE simulation results. Good agreement in the results clearly shows the validity of our technique.

We present a topological framework of stepwise specification for concurrent systems in this paper. Some of description techniques can make topologies on the system space. Such topologies corresponds to abstract levels of those description techniques. Using a family of such description techniques, one can specify systems stepwisely. This framework allows to bridge various DTs and modularizing, so that global properties and module properties of systems become to be related to each other. Within this framework, we show derivation of a LOTOS cpecification from temporal logic formulae. An extended version of LOTOS with respect to concurrency is used in this paper. A semantics including concurrency is introduced to do this in this method. The method presented in this paper is applied to mobile telecommunication.

This paper is devoted to a new design method for infinite impulse response approximate inverse system of a nonminimum phase system. The design is carried out such that the convolution of the nonminimum phase polynomial and its approximate inverse system can be represented by an approximately linear phase all-pass filter. A method for estimating the time delay and order of an approximate inverse system is also presented. Using infinite impulse response approximate inverse systems better accuracy is achieved with reduced computational complexity. Numerical examples are included to show the effectiveness of the proposed method.

This paper presents an efficient queue manager chip for controlling a 16 16 shared buffer ATM switch with a 256-cell buffer. Compared to conventional implementations of queue managers for shared buffer ATM switches, our design eliminates the idle address FIFO and the pre-allocated bubbles at the tails of output queues. The former reduces the storage size required for queue management, while the latter improves the effective buffer capacity. Such modular implementation also provides flexibilities in queue management implementation. Back-pressure with soft-full and hard-full flow control for multi-stage expansion and two priority classes with push-out cell discarding are supported without extra hardware overhead. This chip was designed and fabricated using 0.8µm CMOS technology. It has 35,700 transistors in a chip area of 28.3mm2, with a core of 10.4mm2and 32,960 transistors. Two test sequences were developed during the design phase to fully verify the queue management functions of the prototype chip. The queue manager chip was tested up to 36 MHz, and is able to control a 16 16 shared buffer switch with a 155 MHz link rate.

The fabrication of InAlAs wire structures and InGaAs quantum wire structures on non-planer InP substrates with truncated ridges by molecular beam epitaxy is demonstrated. Indium-rich InAlAs epitaxial layers grown on top of ridges exhibit self-formation of electron-confining InAlAs wire structures. The InAlAs layers on top of the ridges lattice-matched to the substrate are obtained by the control of In flux during the growth. The InGaAs quantum wire structures have been fabricated on thus composition-controlled InAlAs barrier layers. The optical properties of the InGaAs quantum wires with composition-controlled InAlAs barrier layer are found to be better than that of the wires without compositional control.

Photoluminescence characterization with a surface treatment suggests that a reduction in the radiative recombination rate of GaAs nanowhiskers is caused by charge separation in depletion potential. Good agreement is obtained between photoluminescence characteristics and calculations based on self-consistent wavefunctions confined in the depletion potential. The radiative life time of 200-nm GaAs nanowhiskers at 77 K is estimated as short as 0.5 ns if the depletion potential is completely eliminated. Weak size dependence of photoluminescence spectra at 6 K is explained as a sign of band-gap reduction induced by the depletion potential.

In this paper we propose a method for generating Prolog program code and skeleton C code from a specification of requirements written in DFDs (Data Flow Diagram) and DD (Data Dictionary). This generation of code takes two transformation steps. The specification is transformed into a Prolog program and the transformed Prolog is used for generating skeleton C code so that the specification is directly expendable in the conventional programming environment. This work makes it possible to rapidly have a prototype by executing Prolog programs and remove the design stage from the software development life cycle. This has been implemented on UNIX workstation environment with a data flow diagram editor START system.

The edge of a thin SOI (silicon on insulator) film was used to form a very narrow Si-MOS inversion layer. The ultra-thin SOI film was formed by local oxidation of SIMOX wafer. The thickness of the SOI film is less than 15 nm, i.e., the channel width is narrower than 15 nm. At low tempera-tures, clear and large conductance oscillations were seen in this edge channel MOSFET. These oscillations are explained by Coulomb blockade effects in the narrow channel with several effective potential barriers, since the SOI film is so thin that the channel current is seriously affected by small potential fluctuations in the channel. These results suggest that the channel current in edge quantum wire MOSFET can be cut off even with a small controlled potential change. Furthermore, we fabricated a double-gate edge channel Si-MOSFET. In this device, the channel current can be controlled in two ways. One way is to control the electron number inside the isolated electrodes. The other way is to control the threshold voltage of MOSFET. This device enables us to control the phase of Coulomb oscillation.

The multichannel distortions of direct modulated laser diode were studied from the view point of rate equations. A novel technique for compensating the composite second order distortion (CSO) was proposed. Meanwhile, the related calibration procedures were indicated. After the compensation, 10 dB improvement in CSO was obtained

We report on the formation technique and the first observation of visible light emission from silicon nanoparticles (<10nm) embedded in CaF22 Iayers grown on Si(111) substrates by using codeposition of Si and CaF2. It is shown that the size and density of silicon particles embedded in the CaF2 layer can be controlled by varying the substrate temperature and the evaporation rates of CaF2 and Si. The photoluminescence (PL) spectra of Si nanoparticles embedded in CaF2 thin films were investigated. The blue or green light emissions obtained using a He-Cd laser (λ=325nm) could be seen with the naked eye even at room temperature for the first time. It is shown that the PL intensity strongly depends on growth conditions such as the Si:CaF2 flux ratio and the growth temperature. The PL spectra were also changed by in situ annealing process. These phenomena can be explained qualitatively by the quantum size effect of Si nanoparticles embedded in CaF2 barriers.

Quantum Cellular Automaton (QCA), which is one of the candidates for future integrable electron devices, is investigated from the viewpoint of operation temperature. The extended Hubbard model which can extract the physical essence of QCA is used to analyze the inter-cell interaction for a layered cell structure. We found that the operation energy estimated from the energy gap between the ground state and excited states of the layered structure is large enough to allow room temperature operation even if the size of quantum dot is as large as 500. The layered cell structure is found to be suitable for a memory application.

A high-frequency approximate method for calculating the diffraction by a smooth convex surface is presented. The advantage of this method is the validity of it in the caustic region of the creeping rays where the Geometrical Theory of Diffraction (GTD) becomes invalid. The concept used in this method is based on the Method of Equivalent Edge Currents (EEC), and the equivalent line currents for creeping rays which are derived from the diffraction coefficients of the GTD are used. By evaluating the radiation integral of these equivalent line currents, the creeping ray contribution which is valid within the caustic region is obtained. In order to check the accuracy and the validity of the method, the diffraction problem by a perfectly conducting sphere of radius a is solved by applying the method, and the obtained results are compared with the exact and the GTD solutions. It is confirmed from the comparison that the failure of the GTD near the caustic is removed in this method and accurate solution is obtained in this area for high-frequency (ka8). Furthermore, it is also found that this method is valid in the backward region (0θ90, θ is an observation angle mesuered from an incident direction), whereas not in the forward region (90θ180).

This paper presents a new Frequency Shift Keying (FSK) demodulation method using the Short Time-Discrete Fourier Transform (ST-DFT) analysis to combat large frequency offset with time variation in low earth orbit (LEO) satellite communications systems. This demodulation method can demodulate the received signal only by searching for the instantaneous spectrum energy peaks without complicated carrier recovery. In addition, it is insensitive to the signal-to-noise ratio (SNR) degradation caused by the excessively wide bandwidth of the receiver front-end band pass filter. Furthermore, the ST-DFT analysis combined with a differential encoding scheme gives FSK demodulation method a potential robustness against large and fast time-varying frequency offset.

The Guaranteed Bandwidth Protocol (GBW) is an access scheme being proposed for implementation of connection oriented services in DQDB networks. Connection oriented services are expected to handle both constant bit rate (CBR) and variable bit rate (VBR) traffic that have delay and jitter constraints. It has been reported that the GBW protocol can provide guaranteed bandwidth and lower delays compared to the ordinary DQDB protocol. However, the intensity of the jitter introduced by this scheme has not been made clear. This paper compares the jitter results for the GBW scheme to those obtained by a new access method called Modified Guaranteed Bandwidth (MOD_GBW) protocol, which is proposed here. It is shown through simulation that MOD_GBW also provides guaranteed bandwidth and that its delay and jitter characteristics are significantly better than those of the GBW protocol. In the simulation model, the DQDB stations are divided into two groups: 1)Real-Time (RT) stations that generate either CBR or VBR real-time traffic; and 2)Data stations that generate memoryless type of traffic. Data stations operate according to the ordinary DQDB protocol only. The main performance measure adopted here for the real-time traffic is the interdeparture time distribution of consecutive segments from an RT-station. We define the variance of this distribution as jitter. This paper also shows the impact of GBW/MOD_GBW on the performance of the data stations by evaluating their throughput and average bus access delay. Finally, we show that the network performance is weakly related to the number of RT-stations under MOD_GBW, but it depends strongly on the overall loading.

In the paper a new type of Multilayer Perceptron, developed in Quaternion Algebra, is adopted to realize short-time prediction of chaotic time series. The new introduced neural structure, based on MLP and developed in the hypercomplex quaternion algebra (HMLP) allows accurate results with a decreased network complexity with respect to the real MLP. The short term prediction of various chaotic circuits and systems has been performed, with particular emphasys to the Chua's circuit, the Saito's circuit with hyperchaotic behaviour and the Lorenz system. The accuracy of the prediction is evaluated through a correlation index between the actual predicted terms of the time series. A comparison of the performance obtained with both the real MLP and the hypercomplex one is also reported.

Deterministic nonlinear prediction is applied to both artificial and real time series data in order to investigate orbital-instabilities, short-term predictabilities and long-term unpredictabilities, which are important characteristics of deterministic chaos. As an example of artificial data, bimodal maps of chaotic neuron models are approximated by radial basis function networks, and the approximation abilities are evaluated by applying deterministic nonlinear prediction, estimating Lyapunov exponents and reconstructing bifurcation diagrams of chaotic neuron models. The functional approximation is also applied to squid giant axon response as an example of real data. Two metnods, the standard and smoothing interpolation, are adopted to construct radial basis function networks; while the former is the conventional method that reproduces data points strictly, the latter considers both faithfulness and smoothness of interpolation which is suitable under existence of noise. In order to take a balance between faithfulness and smoothness of interpolation, cross validation is applied to obtain an optimal one. As a result, it is confirmed that by the smoothing interpolation prediction performances are very high and estimated Lyapunov exponents are very similar to actual ones, even though in the case of periodic responses. Moreover, it is confirmed that reconstructed bifurcation diagrams are very similar to the original ones.