This study was designed to evaluate localized muscular fatigue induced during mouse operation in a VDT task. Ten male undergraduates from 19 to 23 years old participated in the experiment. The subject performed a pointing task with a PC mouse for about 4 hours. The EMG measurements and psychological rating of fatigue were conducted before the experimental task and after each 30-minutes block during the experimental task. The changes in the Mean Power Frequency (MPF) and Percentage Maximum Voluntary Contraction (%MVC)-shift for the constant cumulative probability in the Amplitude Probability Distribution Function (APDF) with time were explored. The correspondence between the index (MPF or APDF) and the subjective rating of localized muscular fatigue was also examined. The performance was nearly constant across all blocks. The psychological rating of fatigue tended to increase with time. The MPF tended to increase with time, although the main effect of block (time) was not statistically significant. The %MVC-shift tended to increase with time. The correspondence with the perceived sensation of localized muscular fatigue was higher when using the %MVC-shift than when using the MPF. Based on the results, the effectiveness of the indexes used for evaluating localized muscular fatigue was discussed. The %MVC-shift obtained from the APDF was found to be a sensitive index of localized muscular fatigue and corresponded well with the subjective rating of localized muscular fatigue.

The High Tc SQUID was used in an unshielded environment to make eddy current nondestructive testing measurement on a multi-layer aluminum structure. As a demonstration of their capabilities, subsurface defects in a multilayer aluminum structure have been located and mapped using phase shift with no magnetic shielding around the specimen.

A combining method for receiver diversity, followed by a Bayesian decision feedback equalizer, is proposed. This eigenvector based combining maximizes the desired part energy of combined channel, on which the equalizer performance mainly depends. The validity of the proposed method is demonstrated by simulations.

Recently, multi-carrier code division multiple access (MC-CDMA) has been attracting much attention for the broadband wireless access in the next generation mobile communications systems. In the case of uplink transmissions, the orthogonality among users' signals is lost since each user's signal goes through different fading channel and hence, multi-access interference (MAI) is produced, thereby significantly degrading the transmission performance compared to the downlink case. The use of frequency-domain equalization at the receiver cannot sufficiently suppress the MAI. In this paper, we propose frequency-domain pre-equalization transmit diversity (FPTD), which employs pre-equalization using multiple transmit antennas with transmit power constraint, in order to transform a frequency-selective channel seen at a receiver close to the frequency-nonselective channel. We theoretically analyze the bit error rate (BER) performance achievable with the proposed FPTD and the analysis is confirmed by computer simulation.

In the Multi Carrier (MC)-CDMA system, the frequency diversity gain is obtained by its being spread in the frequency domain. The frequency interleaving technique can improve the frequency diversity gain. In this paper, the bit error rate (BER) performance in the MC-CDMA system which adopts the frequency interleaving scheme in the frequency selective fading channel is evaluated by computer simulation. In this simulation, orthogonal restoration combining (ORC) and minimum mean square error combining (MMSEC) are considered as frequency equalization combining techniques. This paper shows that BER performance with the frequency interleaver is better than without it in various environments.

A new data-aided carrier frequency offset (CFO) estimation technique is presented for correlative coded OFDM systems in the presence of strong multipath. Different from traditional data-aided estimation techniques, the technique estimates CFO by detecting amplitude of pilots rather than their phase shift and removes effects on CFO estimation due to intercarrier interference by an iterative compensation method. A theoretical analysis of its performance has been derived and simulation results comparing the new technique with a traditional data-aided estimation technique are presented.

This paper proposes a distributed adaptive routing algorithm that may be applied to inter-domain calls passing over any type of network topology, traffic management and switching techniques on the path, while carrying bidirectional traffic with multiple QoS requirements. The path is searched within a contour area restricted by the number of hops between source and destination while the end-to-end admission of calls is controlled at source node and each hop's admission at each node, reflecting the latest resources availability and network conditions for the given QoS requirements. Performance analysis in various conditions shows good applicability in real networks.

Multi-carrier code division multiplexing (MC-CDM) is one of promising multiplexing techniques for fourth-generation mobile downlink communications systems, where high data rate services should be provided even for high speed-cruising mobiles. For MC-CDM-based packet communication, a frequency scheduling method, which adaptively assigns different sub-carriers to different users, is proposed. This paper proposes a frequency scheduling method, which utilizes pre-assignmented subcarriers in the frequency domain for the MC-CDM scheme. Furthermore, the performance of the proposed system in frequency selective fading channels is compared with that of a no-scheduled MC-CDM scheme by computer simulation in both single- and multi-cell environments. From the results, it is found that the proposed system achieves better bit error rate performance than the no-scheduled MC-CDM scheme and can control quality of service (QoS) for active users.

The electric currents on the upper, lower and side surfaces of the patch conductor in a circular microstrip antenna are calculated by using the integral equation method and the characteristic between the electric currents on the upper and lower surfaces is compared. The integral equation is derived from the boundary condition that the tangential component of the total electric field due to the electric currents on the upper, lower and side surfaces of the patch conductor vanishes on the upper, lower and side surfaces of the patch conductor. The electric fields are derived by using Green's functions in a layered medium due to a horizontal and a vertical electric dipole on those surfaces. The result of numerical calculation shows that the electric current on the lower surface is much bigger than that on the upper surface and the input impedance of microstrip antenna depends on the electric current on the lower surface.

OFDM, MC-CDMA and DS-CDMA are being researched vigorously as the prospective signaling technique for the next generation mobile communications systems, which will be characterized by the broadband packet technology. With packet transmissions, hybrid ARQ (HARQ) will be inevitable for error control. HARQ with rate compatible punctured turbo (RCPT) codes is one of the promising techniques. Data rate equivalent to the OFDM system can be attained with MC-CDMA and DS-CDMA by assigning all the available codes to the same user resulting in what is commonly referred to as multicode MC-CDMA and multicode DS-CDMA. A rake receiver is used for receiving the DS-CDMA signals. However, recently minimum mean square error frequency-domain equalization (MMSE-FDE) has been proposed for the reception of DS-CDMA signals. In this paper, we introduce RCPT HARQ to DS-CDMA with MMSE-FDE and compare its throughput performance with OFDM, multicode MC-CDMA and multicode DS-CDMA with rake combining. MMSE weight for packet combining is introduced and the soft value generation for turbo coding in MC-CDMA and DS-CDMA with MMSE-FDE is presented. The throughput is theoretically evaluated for the uncoded case. For RCPT-HARQ, the comparison is done by computer simulations. It is found that the throughput of HARQ using DS-CDMA with MMSE-FDE is the same as or better than using MC-CDMA. However, with higher level modulation, type I HARQ using OFDM is better than using either MC-CDMA or DS-CDMA; for type II HARQ without redundancy in the first transmission, however, MC-CDMA and DS-CDMA gives a higher throughput.

An improved method for extracting translation equivalents from bilingual comparable corpora according to contextual similarity was developed. This method has two main features. First, a seed bilingual lexicon--which is used to bridge contexts in different languages--is adapted to the corpora from which translation equivalents are to be extracted. Second, the contextual similarity is evaluated by using a combination of similarity measures defined in opposite directions. An experiment using Wall Street Journal and Nihon Keizai Shimbun corpora, together with the EDR bilingual dictionary, demonstrated the effectiveness of the method; it produced lists of candidate translation equivalents with an accuracy of around 30% for frequently occurring unknown words. The method thus proved to be useful for improving the coverage of a bilingual lexicon.

While CDMA systems are proven to be excellent solutions for cellular communications, they suffer from severe multi-path interferences and are hard to support high-data-rate transmissions over frequency-selective fading channels. This letter introduces a novel downlink transmission method for next generation mobile communication systems. The proposed method can provide significantly improved performance in a hot-spot area while maintaining the backward compatibility with the 3rd generation CDMA systems.

An equivalent MOSFET circuit with a wide input range is proposed. The proposed circuit is suitable for a realization of a wide input range under a low power supply voltage. The circuit consists of a MOSFET array and level shift circuits. The sum of drain currents of the MOSFET array is used as an equivalent drain current. The equivalent drain current is represented by K(VGS-VT)2 even when its drain-to-source voltage is quite small and some MOSFETs in the array are in the non-saturation region or the cut-off region. The input range of the proposed circuit realized by k-MOSFET array is k times as wide as that of a single MOSFET. It is confirmed through HSPICE simulations that the proposed circuit is effective in applications with a wide dynamic range.

This paper presents an improved architecture of the multistage multibit sigma-delta modulators (ΣΔMs) for wide-band applications. Our approach is based on two resonator topologies, high-Q cascade-of-resonator-with-feedforward (HQCRFF) and low-Q cascade-of-integrator-with-feedforward (LQCIFF). Because of in-band zeros introduced by internal loop filters, the proposed architecture enhances the suppression of the in-band quantization noise at a low OSR. The HQCRFF-based modulator with single-bit quantizer has two modes of operation, modulation and oscillation. When the HQCRFF-based modulator is operating in oscillation mode, the feedback path from the quantizer output to the input summing node is disabled and hence the modulator output is free of the quantization noise terms. Although operating in oscillation mode is not allowed for single-stage ΣΔM, the oscillation of HQCRFF-based modulator can improve dynamic range (DR) of the multistage (MASH) ΣΔM. The key to improving DR is to use HQCRFF-based modulator in the first stage and have the first stage oscillated. When the first stage oscillates, the coarse quantization noise vanishes and hence circuit nonidealities, such as finite op-amp gain and capacitor mismatching, do not cause leakage quantization noise problem. According to theoretical and numerical analysis, the proposed MASH architecture can inherently have wide DR without using additional calibration techniques.

This paper presents the selective orthogonal matrix least-squares (SOM-LS) method for representing a multiport network characterized by sampled data with the rational matrix, improving the previous works, and providing new criteria. Recently, it is needed in a circuit design to evaluate physical effects of interconnects and package, and the evaluation is done by numerical electromagnetic analysis or measurement by network analyzer. Here, the SOM-LS method with the criteria will play an important role for generating the macromodels of interconnects and package in circuit simulation level. The accuracy of the macromodels is predictable and controllable, that is, the SOM-LS method fits the rational matrix to the sampled data, selecting the dominant poles of the rational matrix. In examples, simple PCB models are analyzed, where the rational matrices are described by Verilog-A, and some simulations are carried out on a commercial circuit simulator.

Multi-Carrier CDMA (MC-CDMA) has been considered as a combination of the techniques of Code Division Multiple Access (CDMA) and Orthogonal Frequency Division Multiplex (OFDM). However, even until now, the efficient MC-CDMA scheme is still under study because of the inherent bugs in OFDM, such as the troubles caused by Multiple Access Interference (MAI) and Peak to Average Power Ratio (PAPR). In this paper, we present a novel two-dimensional spreading sequence named "Two Dimensional Combined Complementary Sequence" (TDC). If we take this kind of sequences as spreading codes, several prominent advantages can be achieved compared with traditional MC-CDMA. First, it can achieve MAI free in the multi-path transmission both in uplink and downlink. Second, it offers low PAPR value within 3 dB with a quite simple architecture. The last but not the least, the proposed MC-CDMA scheme turns out to be an efficient approach with high bandwidth efficiency, high spreading efficiency and flexible transmission rate enriched by a special shift-and-add modulation. Meanwhile, an algorithm that constructs TDC sequences is discussed in details. Based on above results, we can get the conclusion that the novel TDC sequences and corresponding MC-CDMA architecture have great potential for applications in next generation wireless mobile communications, which require high transmission rate in hostile and complicated channels.

A frequency selection algorithm leveraging the capability of a handset to autonomously select idle channels of a public communication system for use in a private communication system was previously proposed, and its effectiveness was verified through experiments conducted in a metropolitan area. This paper describes the results of an experiment verifying the algorithm's effectiveness in rural areas with relatively low public communication system traffic.

In downlink MC-CDMA, orthogonal variable spreading factor (OVSF) codes can be used to allow multirate communications while maintaining the orthogonality among the users with different data rates. In this paper, we point out that simple selection of the OVSF codes results in degraded performance. We show that this happens because simple code selection results in power concentration over certain consecutive subcarriers; severe power loss in the received signal occurs when these subcarriers experience a deep fade in a frequency selective fading channel. In addition, we show two effective techniques to avoid the performance degradation: random code selection and frequency interleaving; which technique provides a better performance depends on modulation level, code multiplexing order, and presence of channel coding.

We propose a new diversity scheme for orthogonal frequency division multiplexing/multi-input multi-output (OFDM/MIMO) systems. The proposed scheme, named turbo layered space-frequency coded OFDM (TLSFC-OFDM), exploits the turbo principle with space hopping (SH). The TLSFC-OFDM system with SH provides a spatial coding so that we can obtain the transmit diversity. We also introduce a successive interference cancellation (SIC) algorithm that requires no ordering and fewer iterations to converge. As a result, this scheme reduces computational complexity. Computer simulation results show that the unordered SIC-based TLSFC-OFDM system outperforms the OFDM/H-BLAST system. It is also shown that the proposed system can operate even with fewer receive antennas than transmit antennas.

To enable the use of passive transmission lines (PTLs) for the interconnection of single-flux-quantum (SFQ) circuits, we have implemented a driver and a receiver and have developed a method for designing SFQ circuits with passive interconnections. Basic components and properties of passive interconnections, such as the frequency characteristics of the driver and receiver, the PTL delay, and the crosstalk between PTLs, have been experimentally verified. Our developed components and design method have been applied to actual SFQ circuits, such as a 44 switch having block-to-block passive interconnections and a 22 switch having gate-to-gate passive interconnections. We have also shown the advantages of PTLs over Josephson transmission lines (JTLs). We also discuss the prospects of SFQ circuits having passive interconnections.