Let H=(V(H),E(H)) be a directed graph with distinguished vertices s and t. An st-path in H is a simple directed path starting from s and ending at t. Let (H) be defined as { SS is the set of vertices on an st-path in H (s and t are excluded)}. For an undirected graph G=(V(G),E(G)) with V(G) V(H)- { s,t }, if the family of maximal independent sets of G coincides with (H), we call H an MIS-diagram for G. In this paper, we provide a necessary and sufficient condition for a directed graph to be an MIS-diagram for an undirected graph. We also show that an undirected graph G has an MIS-diagram iff G is a cocomparability graph. Based on the proof of the latter result, we can construct an efficient algorithm for generating all maximal independent sets of a cocomparability graph.

Multi-recast techniques make it possible for a voter to participate in a sequence of different designated votings by using only one ticket. In a multi-recastable ticket scheme for electronic voting, every voter of a group can obtain an m-castable ticket (m-ticket), and through the m-ticket, the voter can participate in a sequence of m different designated votings held in this group. The m-ticket contains all possible intentions of the voter in the sequence of votings, and in each of the m votings, a voter casts his vote by just making appropriate modifications to his m-ticket. The authority cannot produce both the opposite version of a vote cast by a voter in one voting and the succeeding uncast votes of the voter. Only one round of registration action is required for a voter to request an m-ticket from the authority. Moreover, the size of such an m-ticket is not larger than that of an ordinary vote. It turns out that the proposed scheme greatly reduces the network traffic between the voters and the authority during the registration stages in a sequence of different votings, for example, the proposed method reduces the communication traffic by almost 80% for a sequence of 5 votings and by nearly 90% for a sequence of 10 votings.

This paper proposes a new design method of a nonlinear filtering algorithm in continuous-time stochastic systems. The observed value consists of nonlinearly modulated signal and additive white Gaussian observation noise. The filtering algorithm is designed based on the same idea as the extended Kalman filter is obtained from the recursive least-squares Kalman filter in linear continuous-time stochastic systems. The proposed filter necessitates the information of the autocovariance function of the signal, the variance of the observation noise, the nonlinear observation function and its differentiated one with respect to the signal. The proposed filter is compared in estimation accuracy with the MAP filter both theoretically and numerically.

We have proposed a non-invasive method for diagnosis of the early stage of atherosclerosis, namely, the detection of small vibrations on the aortic wall near the heart by using ultrasound diagnostic equipment. It is, however, necessary to confirm the effectiveness of such measurement of the pulse wave velocity for quantitative evaluation of the local characteristics of atherosclerosis. It is well known that Young's modulus of a tube wall, estimated from measured pulse wave velocity, depends on inner pressure because of the non-linear relationship between the inner pressure and the change of volume in the tube. The inner pressure, however, changes during the period of one heartbeat. In this experimental study, we found for the first time that Young's modulus of the tube wall, estimated from the measured pulse wave velocity, depends not only on the diastolic pressure but also on the pulse pressure and the pressure gradient of the systolic period.

Rapid system prototyping is one of the main applications for field-programmable gate arrays (FPGAs). At the stage of rapid system prototyping, design specifications can often be changed since they cannot be determined completely. In this paper, layout design change is focused on and a layout reconfiguration algorithm is proposed for FPGAs. The target FPGA architecture is developed for transport processing. In order to implement more various circuits flexibly, it has three-input lookup tables (LUTs) as minimum logic cells. Since its logic granularity is finer than that of conventional FPGAs, it requires more routing resources to connect them and minimization of routing congestion is indispensable. In layout reconfiguration, the main problem is to add LUTs to initial layouts. Our algorithm consists of two steps: For given placement and global routing of LUTs, in Step 1 an added LUT is placed with allowing that the position of the added LUT may overlap that of a preplaced LUT; Then in Step 2 preplaced LUTs are moved to their adjacent positions so that the overlap of the LUT positions can be resolved. Global routes are updated corresponding to reconfiguration of placement. The algorithm keeps routing congestion small by evaluating global routes directly both in Steps 1 and 2. Especially in Step 2, if the minimum number of preplaced LUTs are moved to their adjacent positions, our algorithm minimizes routing congestion. Experimental results demonstrate that, if the number of added LUTs is at most 20% of the number of initial LUTs, our algorithm generates the reconfigured layouts whose routing congestion is as small as that obtained by executing a conventional placement and global routing algorithm. Run time of our algorithm is within approximately one second.

An approximation algorithm composed of a digital neural network (DNN) and a modified greedy algorithm (MGA) is presented for the board-level routing problem (BLRP) in a logic emulation system based on field-programmable gate arrays (FPGA's) in this paper. For a rapid prototyping of large scale digital systems, multiple FPGA's provide an efficient logic emulation system, where signals or nets between design partitions embedded on different FPGA's are connected through crossbars. The goal of BLRP, known to be NP-complete in general, is to find a net assignment to crossbars subject to the constraint that all the terminals of any net must be connected through a single crossbar while the number of I/O pins designated for each crossbar m is limited in an FPGA. In the proposed combination algorithm, DNN is applied for m = 1 and MGA is for m 2 in order to achieve the high solution quality. The DNN for the N-net-M-crossbar BLRP consists of N M digital neurons of binary outputs and range-limited non-negative integer inputs with integer parameters. The MGA is modified from the algorithm by Lin et al. The performance is verified through massive simulations, where our algorithm drastically improves the routing capability over the latest greedy algorithms.

To further increase the capacity of the DS-CDMA reverse-link, this paper investigates the effectiveness of interference rejection weight control (IRWC) for the pilot symbol-assisted coherent multistage interference canceller (PSA-COMSIC) using recursive channel estimation (RCE). First, a bit error rate (BER) expression of the serial (successive) and parallel type hard decision multistage interference canceller (MSIC) with IRWC using Gaussian approximation for multiple access interference (MAI) are presented for no fading channels. It is theoretically shown that IRWC is effective in mitigating the interference replica generation error in hard decision MSIC. Next, the BER performance of PSA-COMSIC using IRWC in a multipath Rayleigh fading channel when channel coding is applied is evaluated by computer simulations. The BER performance and capacity are evaluated not only for the conventional serial and parallel types but also for serial/parallel (S/P) hybrid type and non-linear/linear (N/L) hybrid type schemes, both of which are effective in significantly reducing the demodulation processing delay. The simulation results demonstrate that, in interference-limited channels where the back ground noise is negligible, the capacity of serial type PSA-COMSIC using IRWC is about 10% higher than that without IRWC. It is also found that if we can accept a slight capacity degradation compared to the serial type PSA-COMSIC, S/P hybrid schemes are effective in reducing the demodulation processing delay.

For a given N-vertex graph H, a graph G obtained from H by adding t vertices and some edges is called a t-FT (t-fault-tolerant) graph for H if even after deleting any t vertices from G, the remaining graph contains H as a subgraph. For the n-dimensional cube Q(n) with N vertices, a t-FT graph with an optimal number O(tN+t2) of added edges and maximum degree of O(N+t), and a t-FT graph with O(tNlog N) added edges and maximum degree of O(tlog N) have been known. In this paper, we introduce some t-FT graphs for Q(n) with an optimal number O(tN+t2) of added edges and small maximum degree. In particular, we show a t-FT graph for Q(n) with 2ctN+ct2((logN)/C)C added edges and maximum degree of O(N/(logC/2N))+4ct.

An algorithm for modular division which is suitable for VLSI implementation is proposed. It is based on the plus-minus algorithm which is a modification of the binary method for calculating the greatest common divisor (GCD). The plus-minus algorithm for calculating GCD is extended for performing modular division. A modular division is carried out through iteration of simple operations, such as shifts and addition/subtractions. A redundant binary representation is employed so that addition/subtractions are performed without carry propagation. A modular divider based on the algorithm has a linear array structure with a bit-slice feature and carries out an n-bit modular division in O(n) clock cycles, where the length of clock cycle is constant independent of n.

A floorplan is a partition of a rectangle into subrectangles, each of which is associated with a module. Zero-wasted-area layouts are known to exist when the height and width of modules are constrained only by the area, and several methods have been proposed for deriving such layouts. However, because these methods are global and indirect, they are inherently slow. We propose a new algorithm which simulates the air-pressure mechanics. It begins with a layout, which is not necessarily feasible, and iterates the movement of one wall at a time to the force-balancing position. The key issue is that it is guaranteed that every movement makes a current layout approach a zero-wasted-area layout by the measure of energy which is defined here. Experimental results on the example in several literatures and artificially made complex examples showed very fast convergence. The algorithm is evolved to methods which move all the walls simultaneously, resulting in a further speed enhancement.

We have developed and fabricated an LSI called the FMPP-VQ64. The LSI is a memory-based shared-bus SIMD parallel processor containing 64 PEs, intended for low bit-rate image compression using vector quantization. It accelerates the nearest neighbor search (NNS) during vector quantization. The computation time does not depend on the number of code vectors. The FMPP-VQ64 performs 53,000 NNSs per second, while its power dissipation is 20 mW. It can be applied to the mobile telecommunication system.

In recent years, the rapid advancements of wireless communication technology and computer down-sizing technology have enabled users to utilize computing resources anywhere in the computer network. New applications constructed on the mobile database system are becoming popular. However, the current database systems do not provide special facilities for specific update operations in a mobile computing environment. Moreover, due to the lack of a common data handling method and a mutual communication mechanism, varieties in implementations may cause applications to be incompatible with each other. In this paper, we take up the issue of data handling, in a mobile computing environment, and propose an active mobile database system (AMDS) to solve this issue. First, we review the difficulties of dynamic update of databases in a mobile computing environment, and provide a basic concept of AMDS as a solution for these difficulties. In order to construct an AMDS, we focus on asynchronous events such as the appearance and disappearance of a mobile computer in a wireless communication cell. Then we provide a facility to specify the behavior of each system in Event-Condition-Action(ECA) rules in the same way as normal active database systems. Moreover, we show the architecture and the design of our implementation of AMDS. And, finally AMDS can be easily implemented as a common database infrastructure and work well on heterogeneous systems through indoor experiments.

In this paper, we propose dynamic cepstral representations to effectively capture the temporal information of cepstral coefficients. The number of speech frames for the regression analysis to extract a dynamic cepstral coefficient is inversely proportional to the cepstral order since the cepstral coefficients of higher orders are more fluctuating than those of lower orders. By exploiting the relationship between the window length for extracting a dynamic cepstral coefficient and the statistical variance of the cepstral coefficient, we propose three kinds of windowing methods in this work: an utterance-specific variance-ratio windowing method, a statistical variance-ratio windowing method, and an inverse-lifter windowing method. Intra-speaker, inter-speaker, and speaker-independent recognition tests on 100 phonetically balanced words are carried out to evaluate the performance of the proposed order-dependent windowing methods.

Presently, mobile robots are navigated by means of a number of methods, using navigating systems such as the sonar-sensing system or the visual-sensing system. These systems each have their strengths and weaknesses. For example, although the visual system enables a rich input of data from the surrounding environment, allowing an accurate perception of the area, processing of the images invariably takes time. The sonar system, on the other hand, though quicker in response, is limited in terms of quality, accuracy and range of data. Therefore, any navigation methods that involves only any one system as the primary source for navigation, will result in the incompetency of the robot to navigate efficiently in a foreign, slightly-more-complicated-than-usual surrounding. Of course, this is not acceptable if robots are to work harmoniously with humans in a normal office/laboratory environment. Thus, to fully utilise the strengths of both the sonar and visual sensing systems, this paper proposes a fusion of navigating methods involving both the sonar and visual systems as primary sources to produce a fast, efficient and reliable obstacle-avoiding and navigating system. Furthermore, to further enhance a better perception of the surroundings and to improve the navigation capabilities of the mobile robot, active sensing modules are also included. The result is an active sensor fusion system for the collision avoiding behaviour of mobile robots. This behaviour can then be incorporated into other purposive behaviours (eg. Goal Seeking, Path Finding, etc. ). The validity of this system is also shown in real robot experiments.

Many image-processing techniques are based on texture features or gradation features of the image. However, Landsat images are complex; they also include physical features of reflection radiation and heat radiation from land cover. In this paper, we describe a method of constructing a super-resolution image of Band 6 of the Landsat TM sensor, oriented to analysis of an agricultural area, by combining information (texture features, gradation features, physical features) from other bands. In this method, a knowledge-based hierarchical classifier is first used to identify land cover in each pixel and then the least-squares approach is applied to estimate the mean temperature of each type of land cover. By reassigning the mean temperature to each pixel, a finer spatial resolution is obtained in Band 6. Computational results show the efficiency of this method.

In this paper, we propose a new lemma facility, called the strong contraction rule, for model elimination calculus, and we study some implementation issues of strong contraction in a PTTP-based theorem prover. Strong contraction has the ability to shorten possible proofs and prevent some irrelevant computation to a target goal. Strong contraction never broadens the search space, in principle, and thus, has a stable effect on the acceleration of top-down proof search. However, it is difficult to embed the strong contraction into a PTTP-based theorem prover, because strong contraction imposes a truncation operation of center chains in model elimination calculus. We show a self-truncation-style Prolog code, which makes it possible to retain the high performance of a PTTP-based prover with strong contraction. Finally, we evaluate the performance and effect of strong contraction by performing some experiments.

We introduce a concept of regularization into Genetic Algorithms (GAs). Conventional GAs include no explicit regularizing operations. However, the regularization is very effective in solving ill-posed problems. So, we propose a method of regularization to apply GAs to ill-posed problems. This regularization is a kind of consensus operation among neighboring individuals in GAs, and plays the role of `smoothing the solution. ' Our method is based on the evaluation of macroscopic fitness, which is a new fitness criterion. Conventional fitness of an individual in GAs is defined only from the phenotype of the individual, whereas the macroscopic fitness of an individual is evaluated from the phenotypes of the individual and its neighbors. We tested our regularizing operation by means of experiments with an elastic image mapping problem, and showed the effectiveness of the regularization.

In this paper, a new simulation approach to the analysis of the reflection characteristics on nonuniform transmission lines (NTLs) is presented. The input and output responses in the time domain and the reflection coefficients in the frequency domain are effectively obtained by using the modified central difference (MCD) simulation and the fast Fourier transform (FFT) technique for Gaussian pulse responses. The simulated results for the reflection characteristics of the NTL transformers are in excellent agreements with the theoretical values. By representing both the reflected voltage and the reflection coefficient, it is shown that this approach is useful to analyze for various types of tapered and stepped NTLs.

Theoretical calculations of the pulsing operation and the intensity noise under the optical feedback are demonstrated for operation of the self-sustained pulsation lasers. Two alternative models for the optical feedback effect, namely the time delayed injection model and the external cavity model, are applied in a combined manner to analyze the phenomena. The calculation starts by supposing the geometrical structure of the laser and the material parameters, and are ended by evaluating the noise. Characteristics of the feedback induced noise for variations of the operating parameters, such as the injection current, the feedback distance and the feedback ratio, are examined. A comparison to experimental data is also given to ensure accuracy of the calculation.

A VLSI architecture of a motion estimator is described dedicatedly for the H. 263 low bitrate video coding. Adopting an efficient hierarchical search algorithm, a new motion estimator yields high quality vectors with small area occupancy and at a low operation frequency. A one-dimensional PE (Processing Element) array is devised to be tuned to the H. 263 encoding, which treats both the advanced prediction mode and the PB-frame mode. The proposed motion estimation core is integrated in 1. 55 mm2 by using 0. 35 µm CMOS 3LM technology, which operates at 15 MHz, and hence enables the realtime motion estimation of QCIF pictures.