Large number of electronic connectors are widely used in various electronic and telecommunication systems. No matter whether it is optical telecommunications or mobile phone systems, connectors are important links for electronics. Unfortunately connector contacts are exposed in air, they are different from any other electronic components, the contacts are greatly influenced by the environment where they operate. In China, dust and corrosion products are the main contaminants to cause contact failure. Evidently the failed contacts seriously deteriorate the reliability of electronic and telecommunication systems. This paper summarizes the recent achievements obtained by our Lab on the effect of dust and corrosion products to the connector contact failure. Since dust contamination is a very complex problem which is not only popular in China, but also happened in many countries. Continuous studies will be very useful to improve the contact reliability of connectors, setting up new and effective testing methods and standards, building up experimental and computer simulation systems.

We describe a low-cost and extremely stable millimeter-wave transmission system that uses a double-side-band (DSB) millimeter-wave self-heterodyne transmission technique. This technique allows us to use a comparatively low-cost and unstable millimeter-wave oscillator regardless of the modulation format. Furthermore, a transmission band-pass-filter (BPF) is not needed in the millimeter-wave band. The system cost can therefore be substantially reduced. We have theoretically and experimentally evaluated the carrier-to-noise power ratio (CNR) performance that can be obtained when using this technique relative to that attainable through a conventional millimeter-wave self-heterodyne technique where a single-side-band signal is transmitted. Our results show that the DSB self-heterodyne transmission technique can improve CNR by more than 3 dB.

This letter introduces a chaotic circuit consisting of one linear 2-port VCCS, one hysteresis 2-port VCCS, and two capacitors. The circuit has double screw attractors, quad screw attractors and co-existence states of them. Since the system is piecewise linear, attractors existence condition can be described using exact piecewise solutions. Using a simple test circuit, typical phenomena are verified in the laboratory.

This paper deals with a design problem of a robust controller which achieves not only robust stability but also a performance robustness for linear systems with structured uncertainties satisfying matching condition. The performance robustness means that comparing the transient behavior of the uncertain system with a desired one generated by the nominal system, the deterioration of control performance is suppressed. In this approach, the control law consists of a state feedback with the fixed gain designed by using the nominal system, a state feedback with an adaptive gain determined by a parameter adjustment law and a compensation input for the purpose of keeping transient behavior as closely as possible to the desirable one. We show the parameter adjustment law in order to guarantee robust stability and that the condition for the existence of the compensation input is equivalent to the Riccati equation for the standard linear quadratic control problem. Finally, numerical examples are presented.

In this paper, to enhance the power efficiency a new simple space-time coding scheme is devised with application to the OFDM based Wireless LAN system. The basic idea is from the receiver's point of view and is referred to as Virtual Constellation Mapping (VCM). We designed a new combination of the channel coding (Turbo Code) along with multiple transmit antennas (Two antennas) to achieve transmit diversity and space division multiplexing transmission. Computer simulation results showed that with the same transmission data rate, our proposed scheme can achieve better bit error rate (BER) compared with the conventional space-time trellis coded OFDM scheme in high Doppler fading channels.

In this paper, we propose an algorithm that automatically generates the intermediate scenes using the bidirectional disparity morphing (BDM) from the parallel stereo images. The two-step search strategy is used for speeding up the computation of the bidirectional disparity map and three occluding patterns are used for smoothing the computed disparities more elaborately. Using the bidirectional disparity map, we interpolate the left and the right image to their intermediate scenes. Then we dissolve two interpolated images into the desired intermediate scene which the holes are removed and the effect of the disparity estimation errors is minimized. We implemented the proposed algorithm on TM1300 supported by TriMedia using pSOSytem which enables to do multiprocessing. As a result, we can interpolate the high-quality intermediate scenes with real-time process.

A new power and bandwidth efficient modulation technique - Superposed Quadrature Quadrature Amplitude Modulation (SQ2AM) - for use in nonlinear satellite channel is presented. SQ2AM technique expands 2-dimensional SQAM signals into 4-dimensional quadrature modulated signals by using orthogonal baseband waveforms and carriers. The power spectrum and BER performance of SQ2AM are analyzed and compared with those of QPSK, SQAM and Q2PSK in a nonlinearly amplified multi-channel environment.

Gallium nitride (GaN) is one of the wurtzite-type materials and has semiconducting properties. Crystallinities of GaN thin films are usually poor when they are directly grown on polycrystalline metal-foils which are expected as substrates for realizing novel giant microelectronic devices. Improvements of crystal orientations of GaN thin films grown on such polycrystalline metal-foils are tried by using several kinds of intermediate layers. Aluminum nitride (AlN), GaN, silicon dioxide (SiO2) and Si are chosen as materials for the intermediate layers. The crystal orientations of GaN thin films grown by inserting the SiO2 and Si intermediate layers with adequate thicknesses are markedly improved, while those grown on the AlN or GaN intermediate layers are not improved. These differences are not caused by the kinds of the materials used for the intermediate layers but by differences in their crystallinities.

It is well known that Orthogonal Frequency Division Multiplexing (OFDM) scheme is robust to frequency selective fading in wireless channels. However, once delayed signals beyond a guard interval of an OFDM symbol are introduced in a channel with large delay spread, inter-symbol interference causes a severe degradation in the transmission performance. In this paper, we propose a novel pre-Fast Fourier Transform (FFT) OFDM adaptive antenna array, which requires only one FFT processor at a receiver, for suppressing such delayed signals. We analytically derive the optimum weights for the beamformer based on the Maximum Signal-to-Noise-and-Interference power Ratio (SNIR) and the Minimum Mean Square Error (MMSE) criteria, respectively. Computer simulation results show its good performance even in a channel where Directions of Arrival (DoAs) of arriving waves are randomly determined.

Resource-demanding services such as Multi-media-on-Demand (MOD) become possible as Internet and broadband connections are getting more popular. However, as the sizes of multimedia files grow rapidly, storage of such large files becomes a problem. Since multimedia contents will generally become less popular with time, it is desirable to design a prediction algorithm so that the multimedia content can be unloaded from the server if it is no longer popular. This can relieve the storage problem in an MOD system, and hence spare more space for new multimedia files. In this paper, we analyse the MOD viewing trend in order to understand the viewing behaviour of users and predict the viewing trend of a particular category of multimedia based on the knowledge obtained from its trend analysis. In trend analysis, two additive regression models, exponential-exponential-sum (EES) and exponential-power-sum (EPS), are proposed to improve the fitness of the trend. The most suitable model will then be used for trend prediction based on four proposed approaches, namely Fixed Regression Selection (FRS), Continuous Regression Updating (CRU), Historical Updating (HU) and Continuous Regression with Historical Updating (CRHU). From the numerical results, it is found that CRHU, which is constructed by considering historical trend and new incoming data of viewing requests, is in general the best method in forecasting the request trend of a particular category of multimedia clips.

The autocorrelation peak reduction due to wavelength mismatches between an encoder and a decoder in wavelength hopping-time spreading (WH-TS) two-dimensional optical CDMA systems is analyzed and verified by experiments. The tolerance of the wavelength mismatch is then obtained through the analysis of the system bit error rate (BER) performance. The results show that no significant BER performance is degraded only by the wavelength mismatches less than 0.1 nm which corresponds to 25 percent of the typical fiber Bragg gratings' spectral width.

An efficient performance enhancement scheme using the rotation of signal subspace (RSS) and Toeplitz matrix approximation (TMA) methods to enhance the performance of an adaptive antenna array in DS/CDMA systems is proposed. The basis of RSS is to find a transformation matrix in order to recover the desired complex array covariance matrix from a sampled complex array covariance matrix which is contaminated by an interference-plus-noise component. Also, the objective of TMA is to change the output matrix of RSS into a matrix having the theoretical properties such as Toeplitz structure matrix or a positive semidefinite matrix. Consequently, the proposed scheme using RSS and TMA methods can greatly improve the performance of an adaptive antenna array by reducing the interference-plus-noise effect from the sampled complex array covariance matrix of the pre-correlation received signal vector that is used to calculate a weight vector of an adaptive antenna array. Simulation results demonstrate the effectiveness of the proposed scheme.

The demand for wireless mobile communications has grown at a very high rate, recently. In order to solve the non-uniform traffic rates, the use of cell splits is unavoidable for balancing the traffic rate and maximizing total system capacity. For cell planning, a DS-CDMA cellular system can be comprise of different cell sizes because of different demands and population density of the service area. In this paper, we develop a general model to study the forward link capacity and outage probability of a DS-CDMA cellular system with mixed cell sizes. The analysis of outage probability is carried out using the log-normal approximation. When a macrocell is split into the three microcells, as an example, we calculate the multi-cross interferences between macrocells and microcells, and the forward link capacities for the microcells and the neighboring macrocells. The maximum allowable capacity plane for macrocell and microcell is also investigated. The numerical results and discussions with previous published results of reverse link are summarized.

Two implementation schemes for a two-step SOVA (Soft Output Viterbi Algorithm) decoder are proposed and verified in a chip. One uses the combination of trace back (TB) logic to find the survivor state and double trace back logic to find the weighting factor of a two-step SOVA. The other is that the reliability values are divided by a scaling factor in order to compensate for the distortion brought by overestimating those values in SOVA. We introduced a fixed scaling factor of 0.25 or 0.33 for a rate 1/3 and designed an 8-state Turbo decoder with a 256-bit frame size to lower the reliability values. The implemented architecture of the two-step SOVA decoder allows important savings in area and high-speed processing compared with the one-step SOVA decoder using register exchange (RE) or trace-back (TB) method. The chip is fabricated using 0.65 µm gate array at Samsung Electronics and it shows higher SNR performance by 2 dB at the BER 10-4 than that of a two-step SOVA decoder without a scaling factor.

This Letter proposes a timer based ordered registration (TBOR) scheme for CDMA private user zone (PUZ) service. The proposed TBOR scheme solves the problem that both the PUZ system loads and the public system loads are increased due to excessive registration. Also the TBOR scheme is quite simple to implement and compatible with the existing public CDMA system.

This paper describes a design of a Carry Propagation Free Adder/Subtracter (CPFA/S) VLSI using the Adiabatic Dynamic CMOS Logic (ADCL) circuit technology. Using a PSPICE simulator, energy dissipation of the ADCL 1 bit CPFA/S is compared with that of the CMOS 1 bit CPFA/S. As a result, energy dissipation of the proposed ADCL circuits is about 1/3 as high as that of the CMOS circuits. The transistors count, propagation-delay time and energy dissipation of the ADCL 4 bit CPFA/S are compared with those of the ADCL 4 bit Ripple Carry Adder/Subtracter (RCA/S). The transistors count and propagation-delay time are found to be reduced by 7.02% and 57.1%, respectively. Also, energy dissipation is found to be reduced by 78.4%. Circuit operation and performance are evaluated using a chain of the ADCL 1 bit CPFA/S fabricated in a 1.2 µm CMOS process. The experimental results show that addition and subtraction are operated with clock frequencies up to about 1 MHz. In addition, the total power dissipation of the ADCL 1 bit CPFA/S is 28.7 µW including the power supply.

The interconnection problem of binary circuits becomes seriously as the exponential growth of the circuits complexity has been driven by a combination of down scaling of the device size and up scaling of the chip size. Motivated by the problem, there is much research of circuits based on multiple-valued logic. On the other hand, caused by the signal propagation delay, there exist hazards in binary logic circuits. To analyze hazards in binary logic circuits, many multiple-valued logics have been proposed, and studied on their mathematical properties. The paper will discuss on a multiple-valued logic which is suitable for treating static hazards in multiple-valued logic circuits. Then, the paper will show that the prime implicants expressions of r-valued logic functions realize static hazards free r-valued logic circuits.

This paper describes an efficient face recognition method using a combination of the Radon transform and the KL expansion. In this paper, each facial image is transformed into many sets of line integrals resulting from the Radon transform in 2D space. Based on this transformation, a new face-recognition method is proposed by using many subspaces generated from the vector spaces of the Radon transform. The efficiencies of the proposed method are proved by the classification rate of 100% in the experimental results, and the reduction to O(n4) instead of O(n6) of the operation complexity in KL(Karhunen-Loeve) expansion, where n is the size of sample images.

Design patterns can be regarded as an approach to encapsulate and reuse good design practices. However, most design patterns are specified using informal text and examples. To obtain all of the benefits of patterns, formal specification and tool support are indispensable. This paper proposes a Design Pattern Specification Language (DPSL) that is both manageable and effective. The DPSL provides software developers with the capability to treat design patterns as concrete design units without lowering abstraction. To demonstrate the usability of our DPSL and its application in design modeling, we have developed a prototype tool that supports the DPSL in UML diagrams. This prototype allows us to demonstrate the tool's support possibilities and the usability of patterns for software development applications.

We propose a web community chart that is a tool for navigating the Web and for observing its evolution through web communities. A web community is a set of web pages created by individuals or associations with a common interest in a topic. Recent research shows that such communities can be extracted by link analysis. Our web community chart is a graph of whole communities, in which relevant communities are connected by edges. Using this chart, we can navigate through related communities. Moreover we can answer historical queries about topics on the Web and understand sociology of web community creation, by observing when and how communities emerged and evolved. We observe the evolution of communities by comparing three charts built from Japanese web archives crawled in 1999, 2000, and 2001. Several metrics are introduced for measuring the degree of community evolution, such as growth rate, novelty. Finally, we develop a web community evolution viewer that allows us to extract evolving communities using the relevance and metrics. Several evolution examples are shown using this viewer.