This paper discuses the simulation of logic circuits with feedback loops for a set of input strings. Logic circuits are modeled as Mealy machines which convert an input string set to an output string set. By the simulation, we obtain a set of output strings which shows the input-output relation of the simulated circuit. The behavior of feedback loops of a logic circuit is shown to be the least-fixed-point on a lattice of string sets. The characteristics of a lattice we have used is also shown in the paper.

Although circuit simulators based on the direct method can be applied to a wide variety of circuits, they are very time consuming. In order to speed up these simulators, the following five techniques are shown to be useful: (1) use of vector processors, (2) modification of the initial value estimation method for Newton's method, (3) improved MOS capacitance model, (4) latency exploitation method and (5) circuit decomposition method. To exploit latency, a new nonlinear equation bypass method (event driven latency checking method) that traces the circuit's active parts intensively and updates only relevant circuit equations will be proposed. It will also be shown that the circuit decomposition method is effective when combined with the latency exploitation method or when the vector processing capability of vector processors can be utilized.

The single layer absorber has the simplest structure among electromagnetic wave absorbers. To have thin and light materials with wide frequency characteristics for this structure, carbon and ferrite are mixed with rubber in different weight ratios. This new material has both dielectric and magnetic losses, which in a single layer structure, has good absorber characteristics . In the C-band, the relative bandwidth is up to 4.6 times wider, and the absorber is thinner, compared with nonmagnetic lossy dielectric material (i.e., 1.0, 0).

Trellis coded modulation (TCM) systems have traditionally employed the signal constellations whose signals are equally probable and uniformly spaced. On the contrary, in this paper, we consider new TCM scheme which employs the signal constellations whose signals are not equally probable and not always uniformly spaced. Such unequally probable signal sets make it possible to increase the minimum Euclidian distance (ED) and other ED's between ajacent signals obtained in equally probable signal sets without increasing average power. As a consequence of gains in ED's, new TCM systems with unequally probable signal sets have shown the superiority of error performace over the corresponding traditional systems. In order to obtain such unequally probable signal sets appropriately, we intentionally introduce intersymbol interference (ISI) to the m-ary PSK system using narrowband pulse shaping filter. The close discussion and simulation results are given for trellis coded QPSK with unequally probable signal sets obtained by introduced ISI, and illustrate that significant coding gains are achieved for a bit error rate of 104 or poorer without degradation of asymptotic error performace at high signal-to-noise ratio relative to the traditional TCM with same spectral efficiency and equal complexity in receiver.

Results of comparative study between compression efficiency of raster and Hilbert scan are presented for several lossless image coding techniques applied to dithered binary images. The-efficient algorithm converting raster binary image file into Hilbert scan file is described. The working coding system HCBI based on Hilbert curve was designed and implemented in Microsoft Quick C. The Lempel-Ziv code, and three models for Q-Coder were compared. Practical conclusions for the use of HCBI are derived. An attempt of theoretical analysis for compression effects on Hilbert curves is performed.

We propose a new type of conditional term rewriting system: the membership-conditional term rewriting system, in which, each rewriting rule can have membership conditions which restrict the substitution values for the variables occurring in the rule. For example, the rule f(χ, χ, y)g(χ, y) if χT' yields the reduction f(M, M, N)g(M, N) only when M is in the term set T'. We study the confluence of membership-conditional term rewriting systems that are nonterminating and nonlinear. It is shown that a restricted nonlinear term rewriting system in which membership conditions satisfy the closure and termination properties is confluent if the system is nonoverlapping.

A new direct algebraic algorithm is developed for the numerical solution of linear differential equations. The differential equations are solved via PL transform by means of an integral operator without iterative calculations. The use of PL transform paves the way, with the aid of symbolic and algebraic manipulation system such as REDUCE for instance, for a simple direct solution for boundary value problems as well as initial value problems of linear differential equations. Examples show that the accuracy of solution is excellent considering the limited length of the PL transform that is used.

Accuracy of PTD is evaluated for a plane wave diffraction from a large circular disk, ten wavelength in diameter. On the analogy of offset reflector antennas, diffracted fields in the incident plane and the plane perpendicular to this is discussed. The excellent accuracy of PTD is demonstrated, while the principal errors are identified as the results of the secondary diffraction. The results by PO are also discussed and its envelope error is given in closed forms. Serious errors of PO in polarization prediction is also pointed out.

This paper describes design and performance of a small-size ribbon-to-single-fiber fanout connector assembled with a fanout unit and push-on type connectors. The structural design for reducing the fanout connector size has been investigated. As a result, the minimum dimensions of the fanout unit and the push-on type connector coupling have been clarified. The constructed fanout connectors have shown average insertion losses of 0.4 dB for multimode 5-fiber ribbons and 0.7 dB for single-mode 10-fiber ribbons. Mechanical and heat-cycle test results were satisfactory for the practical use of the connector.

The coupling coefficient of the directional coupler using small coupling holes for the gyrotron of 100 GHz band is very small to monitor fields. To obtain large coupling coefficient, this paper presents the structure of the rectangular waveguide connected to the overmoded circular waveguide. We analyse it as a boundary value problem, and also present an approximate method. In conclusion of this analysis, we get enough large coupling coefficient and enough small reflective coefficient from this structure.

An adaptive image restoration technique is presented. This is an extended version of the spatially invariant image restoration technique using constrained deconvolution. The aim of the extension is to improve the characteristics of the original filter. The proposed filter partitions the image into three types of regions. For each region this filter has a different impulse response. The most distinctive feature of this filter is that the form of the impulse response varies according to the direction of the edges in the image. It becomes an ordinary inverse filter irrespective of each region, however, when additive noise does not exist in the degraded image. Simulation results show that the observation noise is suppressed, while the edges are preserved.

The capacity of Multi-pulse PPM (MPPM) and performance of Reed-Solomon coded MPPM in optical photon communications are evaluated. Transmission rate, energy efficiency and error probability of MPPM are presented for noiseless channel. It is shown that MPPM yields higher limits of energy efficiencies as well as transmission rate than PPM in band limited channel. Moreover, it is shown that MPPM combined with Reed-Solomon (RS) codes achieves higher energy efficiency of more than twice as that of RS coded PPM, which McEliece studied, in practical range of error probability.

Field induced refractive index variation and the ratio of index to loss variations p' which is an important parameter deciding the loss characteristics of an intersectional optical switch, was analyzed for GaInAs/InP quantum box structure. We found that large index variation and large | p| value(10) with low fundamental absorption, which are required for low insertion loss switch(1 dB), can be attained. Further the usable wavelength range for low loss switching operation is shown to be around 8 nm.

The arithmetic operations over the finite field GF(pn) has many important applications. There is a need for a fast inverter circuit over the finite field GF(pn), because inversion' is must complicated and lengthy operation. In this paper, we will propose a design method of fast inverter circuit that is based on Euclid's algorithm. The inverter circuit is composed of a number of identical basic circuits. Therefore the designed circuit has a regular and expandable feature and has a modular structure.

We solve open problems about synchronized alternating Turing machines. For example, we show that for any L(n)o(log n), there is a set accepted by a loglog n space bounded two-way synchronized alternating Turing machine with only universal states, but not accepted by any L(n) space bounded one-way synchronized Turing machine with only universal states.

The objective of this article is to investigate whether or not a network containing one capacitor, one inductor, and three resistors is able to realize a given biquadratic function. This information should be sought before any synthesis procedure is attempted. It is hoped that the technique may be extended to higher order networks.

In this letter, we investigated in detail the basic characteristics of W type slab waveguide in the vicinity of the cutoff frequency. Concerning with the leaky mode, we obtained some interesting results.

A configuration of multi/demultiplexer using a 4-port optical circulator and interference filters is presented. Owing to the circulator, interference filters for the signal separation can be set normal to the optical signal propagating direction. Demultiplexing operation for 3 wavelength-multiplexed signals, of which wavelength spacings are 1.8 and 4.9 nm, is experimentally confirmed.

Two algorithms are presented for a time-domain analysis of a switching converter which is replaceable with a piecewise-linear system. One of them is for the transient state analysis and the other is for the steady-state analysis. Both of them use the eigen-value and the eigen-vector calculations. The analysis based on these algorithms can be carried out more rapidly and accurately than the conventional analysis using standard fixed or variable step-size integration methods. On the uk converter, the results of the proposed method are compared with those of the Hamming method (a variable step integration method) and of SPICE2 (a general-purpose circuit analysis program using variable step-size integration method).

One of the most important factors indicating the effectiveness of a word clustering method is how commonly it can be applied to different languages. This paper evaluates the applicability of a new word clustering method to the English and Japanese languages using word sets edited from technical summaries. The method employs an iterative clustering routine which increases the number of clustered words. Thus, evaluations are achieved as a function of the number of iterations of the clustering routine from the aspects (a) clustering characteristics determined from the number of clustered words, the number of clusters formed, etc., and (b) performance determined from the average clustering ratio and the average cluster uniformity. Consequently, the applicability of the method to English and Japanese is obtained through evaluations indicating similarities between them for both clustering characteristics and performance. It is also clarified that about fifty percent of the target words can be clustered in less than five iterations of the clustering routine.