In this paper, we present an access scheme for packet-typed wireless networks, called DQRUMA/PAR (Distributed-Queueing Request Update Multiple Access with Periodically Automatic Reservation), which can transmit multimedia traffic efficiently. Here, we deal with three kinds of traffic i. e. voice, data and still picture. DQRUMA/PAR introduces the transmission scheme that mobile stations for voice communications reserve the transmission capacity periodically during their talkspurts. The transmission control process of DQRUMA/PAR will become easier than the one of DQRUMA, and the delay characteristic of voice is improved. Furthermore, we study two enforced protocols on DQRUMA/PAR. One is the more enforced protocol for voice communications. We call this as Voice Enforced mode (VE mode) on DQRUMA/PAR. The other is the more enforced protocol for data communications. We call this as Data Enforced mode (DE mode) on DQRUMA/PAR. The transmission delay of voice will become reduced significantly by introducing VE mode. On the other hand, the transmission delay characteristic of data will be improved by introducing DE mode. We carry out the performance comparisons of pure DQRUMA/PAR with PRMA and DQRUMA and show the considerable improvement of the protocol numerically. Next we make the performance comparisons between pure DQRUMA/PAR and two enforced modes on DQRUMA/PAR and show the considerable improvements of these enforced protocols, respectively.

A hierarchical structure of the statistical models involving the parametric, state space, generalized state space, and self-organizing state space models is explained. It is shown that by considering higher level modeling, it is possible to develop models quite freely and then to extract essential information from data which has been difficult to obtain due to the use of restricted models. It is also shown that by rising the level of the model, the model selection procedure which has been realized with human expertise can be performed automatically and thus the automatic processing of huge time series data becomes realistic. In other words, the hierarchical statistical modeling facilitates both automatic processing of massive time series data and a new method for knowledge discovery.

We propose a universal NAND logic gate based on single flux quantum (SFQ) logic. The NAND gate enables the construction of any logic circuits. In the proposed gate, three superconducting loops share two Josephson junctions (JJs). The critical currents of the JJs were designed to allow each of any two loops to trap an SFQ at the same time. We simulated dynamic operation of this NAND gate. The results show that the NAND gate can operate with a delay time of 45 ps, and the power consumption of this circuit is close to 0.06 µW/gate.

We propose an untraceable electronic money system. Our system uses the partially blind signature based on the discrete logarithm problem, and applies secret key certificates to the payment protocol.

An analytical solution of the London equation for the weakly coupled grain model of high Tc superconducting thin films has been obtained in the case of finite thickness by taking full account of anisotropic conductivities. Using the solution, we provide general expressions for the transmission-line parameters of high Tc superconducting transmission lines. Dependences of the inductance and resistance on the grain size, coupling strength and film thickness have been numerically evaluated and discussed.

The paper shows some of benefits of multi-unitary decomposition in signal analysis applications. It is emphasized that decompositions of complex discrete-time signals onto a single basis provide an incomplete and in such way potentially misleading image of the signals in signal analysis applications. It is shown that the multi-unitary decimated filter banks which decompose the analyzed signal onto several bases of the given vector space can serve as a tool which provides a more complete information about the signal and at the same time the filter banks can enjoy efficient polyphase component implementation of maximally decimated, i. e. nonredundant, filter banks. An insight into the multi-unitary signal decomposition is provided. It is shown that the multiple-bases representation leads to an efficient computation of frequency domain representations of signals on a dense not necessarily uniform frequency grid. It is also shown that the multiple-bases representation can be useful in the detection of tones in digital implementations of multifrequency signaling, and in receivers of chirp systems. A proof is provided that there are possible benefits of the multiple-bases representations in de-noising applications.

The arrangement graph An,k is not only a generalization of star graph (n-k=1), but also more flexible. Designing efficient broadcasting algorithm on a regular interconnection network is a fundamental issue for the parallel processing techniques. Two contributions are proposed in this paper. Initially, we elucidate a first result to construct n-k edge-disjoint spanning trees in an An,k. Second, we present efficient (one/all)-to-all broadcasting algorithms by using constructed n-k spanning trees, where height of each spanning tree is 2k-1. The arrangement graph is assumed to use one-port and all-port communication models and packet-switching (or store-and-forward) technique. Using n-k spanning trees allows us to present efficient broadcasting algorithm in the arrangement graphs and outperforms previous results. This is justified by our performance analysis.

This paper is intended as an investigation of scientific discoveries from a philosophical point of view. In the first half of this century, most of philosophers rather concentrated on the logical analysis of science and set the problem of discovery aside. Logical positivists distinguished a context of discovery from a context of justification and excluded the former from their analysis of scientific theories. Although Popper criticized their inductivism and suggested methodological falsificationism, he also left the elucidation of discovery to psychological inquiries. The problem of scientific discovery was proprely treated for the first time by the "New Philosophy of Science" school in the 1960's. Hanson reevaluated the method of "retroduction" on the basis of Peirce's logical theory and analysed Kepler's astronomical discovery in detail as a typical application of it. Kuhn's theory of paradigm located discoveries in the context of scientific revolutions. Moreover, he paid attention to the function of metaphor in scientific discoveries. Metaphorical use of existing terms and concepts to overcome theoretical difficulties often plays a decisive role in developping new ideas. In the period of scientific revolution, theoretical metaphors can open up new horizons of scientific research by way of juxtapositions of heterogeneous concepts. To explicate such a complicated situation we need the "rhetoric" of science rather than the "logic" of science.

A multilayer perceptron is usually considered a passive learner that only receives given training data. However, if a multilayer perceptron actively gathers training data that resolve its uncertainty about a problem being learnt, sufficiently accurate classification is attained with fewer training data. Recently, such active learning has been receiving an increasing interest. In this paper, we propose a novel active learning strategy. The strategy attempts to produce only useful training data for multilayer perceptrons to achieve accurate classification, and avoids generating redundant training data. Furthermore, the strategy attempts to avoid generating temporarily useful training data that will become redundant in the future. As a result, the strategy can allow multilayer perceptrons to achieve accurate classification with fewer training data. To demonstrate the performance of the strategy in comparison with other active learning strategies, we also propose an empirical active learning algorithm as an implementation of the strategy, which does not require expensive computations. Experimental results show that the proposed algorithm improves the classification accuracy of a multilayer perceptron with fewer training data than that for a conventional random selection algorithm that constructs a training data set without explicit strategies. Moreover, the algorithm outperforms typical active learning algorithms in the experiments. Those results show that the algorithm can construct an appropriate training data set at lower computational cost, because training data generation is usually costly. Accordingly, the algorithm proves the effectiveness of the strategy through the experiments. We also discuss some drawbacks of the algorithm.

Measurement of the viscosity of liquid using a piezoelectric disk is described. Experiments with a radial expansion mode of a piezoceramic disk were carried out for water-glycerin mixture samples. Resonant resistance has linearity to the square root of the product of density and viscosity of a liquid around 113 kHz.

A new efficient two-dimensional warping algorithm is presented, in which sub-optimal warping is attained by iterating DP-based local optimization of warp on partially overlapping subplane sequence. From an experimental comparison with a conventional approximation algorithm based on beam search DP, relative superiority of the proposed algorithm is established.

This paper presents a simulated annealing (SA)-based algorithm for fast and robust block motion estimation. To reduce computational complexity, the existing fast search algorithms move iteratively toward the winning point based only on a finite set of checking points in every stage. Despite the efficiency of these algorithms, the search process is easily trapped into local minima, especially for high activity image sequences. To overcome this difficulty, the new algorithm uses two sets of checking points in every search stage and invokes the SA to choose the appropriate one. The employment of the SA provides the search a mechanism of being able to move out of local minima so that the new algorithm is less susceptible to such a dilemma. In addition, two schemes are employed to further enhance the performance of the algorithm. First, a set of initial checking points which exploit high correlations among the motion vectors of the temporally and spatially adjacent blocks are used. Second, an alternating search strategy is addressed to visit more points without increasing computations. Simulation results show that the new algorithm offers superior performance with lower computational complexity compared to previous works in various scenarios.

High-speed low-power matched filter plays an important role in the fast despreading of spread-signals in wideband code division multiple access (W-CDMA) mobile communications. In this paper, we describe the algorithm and the VLSI-architecture of a complex matched filter chip implemented by our proposed digital-controlled analog parallel operational circuits. The complex matched filter VLSI with variable taps from 4 to 128 is developed for despreading QPSK-modulated spread-signals for W-CDMA communications, which is fabricated by a 2-metal 0.8 µm CMOS technology. The dissipation power of the chip is 225 mW and 130 mW when it operates at the chip-rate of 20 MHz with the supply voltages of 3.0 V and 2.5 V, respectively, and it can be furthermore reduced to 62 mW at chip rate of 10 MHz when the supply voltage is lowered to 2.2 V. The 3-dB cut-off frequency of the fabricated chip is higher than 20 MHz for both 3.0 V and 2.5 V supplies. Comparing to pure digital matched filters, the massive and high-speed despreading operations of the spread-signals are directly carried out in analog domain. As a result, two high-speed analog-to-digital (A/D) converters operating at chip rate are omitted, the inner signal paths and the total dissipation power are greatly reduced.

The outage probability of a forward link DS-CDMA cellular system with fast transmit power control (TPC) based on signal-to-interference ratio (SIR) is investigated. The expression for SIR at the output of RAKE receiver is developed, and the outage probability is evaluated by using Monte Carlo simulation. We consider two kinds of channel models: random delay resolvable path model and tapped delay line model which are suitable models for a few distinct paths channel and highly frequency-selective-channel model, respectively. The outage probability of a system with fast TPC based on SIR is compared to that without fast TPC. The use of orthogonal spreading codes is compared to that of the random spreading codes in terms of outage probability. The effects of the maximum and minimum transmit powers and the dispersive loss of signal power on the outage probability are also investigated.

This paper reports the design and characteristics of an aerial optical drop cable incorporating electric power wires, which was developed for a new π-system. The new system is called the power supply HUB π-system, in which commercial AC electric power is received at a central location of several optical network units (ONUs), and is distributed to each ONU by the aerial optical/electric drop cable. We describe the requirements for the cable, which guarantee a 20-year lifetime. We designed the cross-sectional structure of the cable, based on system requirements and operation requirements, and determined the strength wire type and diameter, based on the optical fiber failure prediction theory and a cable strain requirement. We confirmed that the cables, manufactured as a trial, have stable characteristics, which satisfy the above requirements. The optical/electric drop cables will be introduced in autumn 1999.

Watermarking methods that employ orthogonal transformations are very robust against non-geometrical modifications such as lossy compression, but attaining robustness against image translation or cropping is difficult. This report describes a watermarking method that increases robustness against geometrical modifications such as image translation and cropping by embedding watermark data in the frequency component of an image and detecting that data by considering the phase difference of the coefficients that results from translation of the image. Experimental results demonstrate the robustness of this method against both non-geometrical image changes and image translation and cropping.

Diffraction pattern functions of an E-polarized scattering by a wedge composed of perfectly conducting metal and lossless dielectric with arbitrary permittivity are analyzed by applying an improved physical optics approximation and its correction. The correction terms are expressed into a complete expansion of the Neumann's series, of which coefficients are calculated numerically to satisfy the null-field condition in the complementary region.

We have developed a parameter optimization tool, Monte Carlo Josephson simulator (MJSIM), for rapid single flux quantum (RSFQ) digital circuits based on a Monte Carlo yield analysis. MJSIM can generate a number of net lists for the JSIM, where all parameter values are varied randomly according to the Gaussian distribution function, and calculate the circuit yields automatically. MJSIM can also produce an improved parameter set using the algorithm of the center-of-gravity method. In this algorithm, an improved parameter vector is derived by calculating the average of parameter vectors inside and outside the operating region. As a case study, we have optimized the circuit parameters of an RS flip-flop, and investigated the validity and efficiency of this optimization method by considering the convergency and initial condition dependence of the final results. We also proposed a method for accelerating the optimization speed by increasing 3σ spreads of the parameter distribution during the optimization.

Accurate current analysis is required in circuit designs to analyze electromigration failure rate, power consumption, voltage drop, and so on. A charge-based current model for CMOS gates is presented in this paper. The current waveform of a CMOS gate during a transition consists of three components: one occurs when the input changes and the others exist only when the output changes. These three components are characterized by triangular pulses with four parameters which can be easily obtained after timing simulation. This model has been embedded into our switch-level timing simulator to generate the current waveform. The simulated current waveform helps solve the VLSI reliability problems due to electromigration and excess voltage drops in the power buses. When comparing the results obtained by using SPICE with those by our model, we find agreement, especially on the time points at which current pulses occur.

This paper reviews design aspects of computational discovery systems through the analysis of some successful discovery systems. We first review the concept of viewscope/view on data which provides an interpretation of raw data in a specific domain. Then we relate this concept to the KDD process described by Fayyad et al. (1996) and the developer's role in computational discovery due to Langley (1998). We emphasize that integration of human experts and discovery systems is a crucial problem in designing discovery systems and claim together with the analysis of discovery systems that the concept of viewscope/view gives a way for approaching this problem.