A Si single electron transistor (SET) was fabricated by converting a one-dimensional Si wire on a SIMOX substrate into a small Si island with a tunneling barrier at each end by means of pattern-dependent oxidation. Since the size of the Si island was as small as around 10 nm owing to this novel technique, the total capacitance of the SET was reduced to a value on the order of 1 aF, which guarantees the conductance oscillation of the SET even at room temperature. Furthermore, a linear relation between the designed wire length and the gate capacitance of SETs was obtained, which clearly indicates that the single island was actually formed in the middle of the one dimensional Si wire. These results were achieved owing to the highly reproducible fabrication process based on pattern dependent oxidation of SIMOX-Si layers. In addition, the fluctuation of the electrical characteristics of the SETs Was studied in relation to the wire size fluctuations. It was found that the fluctuatian is caused predominantly by the roughness of the sidewall surface of the resist pattern.

A three-terminal quantum device utilizing photon-assisted tunneling in a multilayer structure is proposed and analyzed in terms of its high frequency amplification characteristics. The operation principle of this device includes photonassisted tunneling at the input, formation of a propagating charge wave due to the beat of tunneling electrons and its acceleration, and radiation of electromagnetic waves at the output. Analysis of these operations, discussion of similarities and dissimilarities to classical klystrons, and estimation of the power gain and its frequency dependence are given. A simple example demonstrates that amplification up to the terahertz frequency range is possible using this device.

A type of Lienard's equation +µf(x)+x=0, where f(x) is not an even function of x, is studied by Le Corbeiller as a model of various biological oscillations, such as breathing, and called two-stroke oscillators. A distinctive feature of this type of oscillators is that the parameter µ has the upper limit µ0 for the oscillator to have some stable limit cycle. This paper gives a numerical method for calculating this upper limit µ0.

In this paper, we discuss both effective approaches in specification process, formal specification and reuse, and focus on providing an integrated and systematic supportbased on them. Preparing the specification model which mediates an image of the designer and another representation of it in formal method, the designer can specify the target system incrementally and smoothly. As for the specification model, we employ LTS on the early step of specification process because of its understandability for the designer. Moreover, reuse of specification leads to reduction of the cost and time, defining retrieval mechanism of reusable cases from database by mathematically calculating similarity of them. For the reuse mechanism, we define a new concept of similarity on LTS as the criterion of case retrieval, which enables more flexible matching between the besigner's requirement and the existing case than any other traditional schema on LTS, and show the case retrieval algorithm. Integration of two approaches brings us the great improvement of the productivity on system development.

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.

A hardware algorithm for modular division is proposed. It is based on the extended Euclidean algorithm (EEA). The procedure for finding the multiplicative inverse in EEA is modified so that it calculates the quotient. Modular division is carried out through iteration of simple operations, such as shifts and additions. A redundant binary representation is employed so that additions are performed without carry propagation. An n-bit modular division is carried out in O(n) clock cycles. The length of each clock cycle is constant independent of n. A modular divider based on the algorithm has a bit-slice structure and is suitable for VLSI implementation.

The join operation is one of the most expensive operations in relational database systems. So far many researchers have proposed several hash-based algorithms for the join operation. In a hash-based algorithm, a large relation is first partitioned into several clusters. When clusters overflow, that is, when the size of the cluster exceeds the size of main memory, the performance of hash-based algorithms degrade substantially. Previously we proposed the GN hash algorithm which is robust in the presence of overflown clusters. The GN hash join algorithm combines the Grace hash join and hash-based nested-loop join algorithms. We analyze the performance of the GN hash join algorithm when applied to relations with a non-uniform Zipf-like data distribution. The performance is compared with other hash-based join algorithms: Grace, Hybrid, nested-loop, and simple hash join. The GN hash join algorithm is found to have higher performance on non-uniformly distributed relations. In this paper, the robustness of the GN hash algorithm from the point of choosing a run time method is verified. In the GN hash algorithm, the criterion for selecting a run time method from the two algorithm is determined by using the value calculated from the I/O cost formula of the two algorithms. This criterion cannot be guaranteed to be optimal under every data distribution, that is, the optimal criterion may change depending on the data distribution. When the data distribution is unknown, all data has to be repartitioned in order to get an accurate optimal criterion. However, from the view of choosing a method at run time, it is necessary for the GN hash algorithm to determine an appropriate criterion regardless of the data distribution. Thus, we inspect the criterion adopted in our algorithm under a simulation environment. From simulation results, we find that the range of the criterion is very wide under any data distribution and assure that the criterion determined with the assumption of a uniform data distribution can be used even when the data is highly skewed. Consequently, we can conclude that the GN hash algorithm which dynamically selects the nested-loop and Grace hash algorithms provides good performance in the presence of data skew and its performance is not sensitive to the criterion.

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.

Analog computation is a processing method that solves problems utilizing an analogy of a physical system to the problem. As it is based on actual physical effects and not on symbolic operations, it is therefore a promising architecture for quantum processors. This paper presents an idea for relating quantum structures with analog computation. As an instance, a method is proposed for solving an NP-complete (nondeterminis-tic polynomial time complete) problem, the three-color-map problem, by using a quantum-cell circuit. The computing process is parallel and instantaneous, so making it possible to obtain the solution in a short time regardless of the size of the problem.

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.

We have previously reported studies [3], [4] of the steady state system throughput in a slotted ring network. In this paper, we analyze the transient state of packet transmission and derive several characteristics of the network.

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.

Time-domain characteristics of the signal of an open-loop fiber optic gyroscope were analyzed. The waveform moments of the gyroscope signal were dependent upon the rotation-induced Sagnac phase, just as the signal frequency spectra are. The peak positions of the time signal also varied with the supplied rotation, and the Sagnac phase could be read out, with optimum sensitivity, from the intervals between peaks. To demonstrate the time-domain measurement technique, the gyroscope signal was transferred to lower frequencies and the signal period was lengthened. This equivalent-time scheme lowered the operational speed requirement on the signal processing electronics and improved measurement resolution.

In this paper, we propose a camera calibration method that estimates both intrinsic parameters (perspective and distortion) and extrinsic parameters (rotational and translational). All camera parameters can be determined from one or more images of planar pattern consists of parallelogramatic grid points. As far as the pattern can be visible, the relative relations between camera and patterns are arbitrary. So, we have only to prepare a pattern, and take one or more images changing the relative relation between camera and the pattern, arbitrarily; neither solid object of ground truth nor precise z-stage are required. Moreover, constraint conditions that are imposed on rotational parameters are explicitly satisfied; no intermediate parameter that connected several actual camera parameters are used. Taking account of the conflicting fact that the amount of distortion is small in the neighborhood of the image center, and that small image has poor clues of 3-D information, we adopt iterative procedure. The best parameters are searched changing the size and number of parallelograms selected from grid points. The procedure of the iteration is as follows: The perspective parameters are estimated from the shape of parallelogram by nonlinear optimizations. The rotational parameters are calculated from the shape of parallelogram. The translational parameters are estimated from the size of parallelogram by least squares method. Then, the distortion parameters are estimated using all grid points by least squares method. The computer simulation demonstrates the efficiency of the proposed method. And the results of the implementation using real images are also shown.

This paper suggests modified LZSS which is suitable for compressing Hangul data by Hangul character token and the string token with small size based on Hangul properties. The Hangul properties can be described in 2 ways. 1) The structure of a Hangul character consists of 3 letters: The first sound letter, the middle sound letter, and the last sound letter which are called Cho-seong, Jung-seong, and Jong-seong, respectively. 2) The code of Hangul is represented by 2 bytes. The first property is used for making the character token processing Hangul characters which occupies most of the unmatched characters. That is, the unmatched Hangul characters are replaced with one Hangul character token represented by Huffman codes of Cho-seong, Jung-seong, and Jong-seong in regular sequence, instead of 2 character tokens. The second property is used to shorten the size of the string token processing matched string. In other words, since more than 75% of Hangul data are Hangul and Hangul codes are constructed in 2 bytes, the addresses of the window of LZSS can be assigned in 2-byte unit. As a result, the distance field and the length field of the string token can be lessened by one bit each. After compressing Hangul data through these tokens, about 3% of improvement could be made in compression ratio.

We found a novel connecting orbit in the averaged Duffing-Rayleigh equation. The orbit starts from an unstable manifold of a saddle type equilibrium point and reaches to a stable manifold of a node type equilibrium. Although the connecting orbit is structurally stable in terms of the conventional definition of structural stability, it is structually unstable since a one-deimensional manifold into which the connecting orbit flows is unstable. We can consider the orbit is one of global bifurcations governing the differentiability of the closed orbit.

It is well known that extracting parallel loops plays a significant role in designing parallelizing compilers. The execution efficiency of a loop is enhanced when the loop can be executed in parallel or partial parallel, like a DOALL or DOACROSS loop. This paper reports on the practical parallelism detector (PPD) that is implemented in PFPC (a portable FORTRAN parallelizing compiler running on OSF/1) at NCTU to concentrate on finding the parallelism available in loops. The PPD can extract the potential DOALL and DOACROSS loops in a program by invoking a combination of the ZIV test and the I test for verifying array subscripts. Furthermore, if DOACROSS loops are available, an optimization of synchronization statement is made. Experimental results show that PPD is more reliable and accurate than previous approaches.

We propose a method to fuse auditory information and visual information for accurate speech recognition. This method fuses two kinds of information by using Iinear combination after calculating two kinds of probabilities by HMM for each word. In addition, we use full-frame color image as visual information in order to improve the accuracy of the proposed speech recognition system. We have performed experiments comparing the proposed method with the method using either auditory information or visual information, and confirmed the validity of the proposed method.

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.

In this paper we present an efficient method to solve reachability problems for Petri nets based on genetic algorithms and a kind of random search which is called postpone search. Genetic algorithm is one of algorithms developed for solving several problems of optimization. We apply GAs and postpone search to approximately solving reachability problems. This approach can not determine exact solutions, however, from applicability points of view, does not directly face state space explosion problems and can extend class of Petri nets to deal with very large state space in reasonable time. First we describe how to represent reachability problems on each of GAs and postpone search. We suppose the existence of a nonnegative parickh vector which satisfies the necessary reachability condition. Possible firing sequences of transitions induced by the parickh vector is encoded on GAs. We also define fitness function to solve reachability problems. Reachability problems can be interpreted as an optimization ones on GAs. Next we introduce random reachability problems which are capable of handling state space and the number of firing sequences which enable to reach a target marking from an initial marking. State space and the number of firing sequences are considered as factors which effect on the hardness of reachability problems to solve with stochastic methods. Furthermore, by using those random reachability problems and well known dining philosophers problems as benchmark problems, we compare GAs' performance with the performance of postpone search. Finally we present empirical results that GAa is more useful method than postpone search for solving more harder reachability problems from the both points of view; reliability and efficiency.