Many digital signal processors (DSPs) employ indirect addressing using address registers (ARs) to indicate their memory addresses, which often leads to overhead. This paper presents methods to efficiently allocate addresses for variables in a given program so that overhead in AR update operations is reduced. Memory addressing model is generalized in such a way that AR can be updated at the codes without memory accesses. An efficient memory address allocation is obtained by a method based on the graph linearization algorithm, which takes account of the number of possible AR update operations for every memory access. In order to utilize multiple ARs, methods to assign variables into ARs are also investigated. The proposed methods are applied to the compiler for µPD77230 (NEC) and generated codes for several examples prove effectiveness of these methods.

This paper first investigates a relationship between inkdot-depth and inkdot-size of inkdot two-way alternating Turing machines and pushdown automata with sublogarithmic space, and shows that there exists a language accepted by a strongly loglog n space-bounded alternating pushdown automaton with inkdot-depth 1, but not accepted by any weakly o (log n) space-bounded and d (n) inkdot-size bounded alternating Turing machine, for any function d (n) such that limn [d (n)log n/n1/2] = 0. In this paper, we also show that there exists an infinite space hierarchy among two-way alternating pushdown automata with sublogarithmic space.

This paper presents a new CLSP/CC (Channel Load Sensing Protocol/Channel Clearance) in order to obtain better performances in spread slotted ALOHA networks. This protocol can decrease a wasteful utilization of channel by prohibiting continuous transmission of the packets destroyed in previous slot, with little added network complexities. For channel clearance technique, hub station broadcasts NAK to all mobile stations when the number of packets transmitted in a slot exceeds the channel capacity, and mobile stations cease own packet transmissions at NAK broadcast. The performances of the proposed CLSP/CC are obtained and compared with those of conventional CLSP by simulations. The performances include network throughput, average processing time and the number of mobile stations in backlogged state. As simulation results, the proposed CLSP/CC outperforms conventional CLSP, especially in highly offered load environment. Also as the proposed CLSP/CC obtain maximum throughputs at higher offered loads and the larger number of mobile stations in backlogged state than the conventional CLSP, it is found that our protocol can support more mobile stations and higher occurrence probabilities.

A slotted ALOHA direct sequence spread spectrum system with random signatures is considered. The system is applicable in cases where a large number of terminals transmit to a single hub station like in cellular digital radio, personal mobile systems and wireless LANs. It is shown that significant improvements in packet throughput capacity are obtained if the adaptive receiver structures are used. Systems for the comparison are the spread spectrum slotted ALOHA system and the conventional slotted ALOHA system.

The performance of a constrained (that is, minimal order) Yule-Walker (CYW) single tone frequency estimator is studied. A closed form expression for the asymptotic error variance is derived. It is shown that CYW does not satisfactorily utilize the informaiton in data, and estimators with improved performance are proposed. Simulation results which lend support to the theoretical findings are included.

We consider the situation that plural degraded images are obtained. When no prior knowledge about original images are known, these images are individually restored by an optimum restoration filter, for example, by Wiener Filter or by Projection Filter. If correlations between original images are obtained, some restoration filters based on Wiener Filter or Projection Filter are proposed. In this paper, we deal with the case that some pixels or some parts of original images overlap, and propose a restoration method using a formulae for overlapping. The method is based on Partial Projection Filter. Moreover, we confirm an efficacy of the proposed method by numerical examples.

This paper proposes high-speed similitude retrieval schemes for a viewpoint-based similarity discrimination system (VB-SDS) and presents analytical and experimental performance evaluations. The VB-SDS, which contains a huge set of semantic definitions of commonly used words and computes semantic similarity between any two words under a certain viewpoint, promises to be a very important module in analogical and case-based reasoning systems that provide solutions under uncertainty. By computing and comparing similarities for all words contained in the system, the most similar word for a given word can be retrieved under a given viewpoint. However, the time this consumes makes the VB-SDS unsuitable for inference systems. The proposed schemes reduce search space based on the upper bound of a similarity calculation function to increase retrieval speed. An analytical evaluation shows the schemes can achieve a thousand-fold speedup and confirmed through experimental results for a VB-SDS containing about 40,000 words.

This paper extends left-incompatible term rewriting systems defined by Toyama et al. It is also shown that the functional strategy is normalizing in the class, where the functional strategy is the reduction strategy that finds index by some rule selection method and top-down and left-to-right lazy pattern matching method.

From the standpoint of reducing the electromagnetic (EM) absorption in the human head for portable telephones, a ferrite sheet is proposed to use as a protection attachment between the antenna and the head. By using an anatomically based head model and a realistic portable telephone model, the effects of the ferrite sheet on both the reduction of EM absorption and antenna radiation pattern are numerically analyzed by the finite-difference time-domain (FDTD) method. The results show that a ferrite sheet can result in a reduction over 13% for the spatial peak SAR averaged over one gram of tissue relative to a degradation below 0.6 dB for the antenna radiation pattern.

Producing realistic images and animations of flames is one of the most interesting subjects in the field of computer graphics. In a recent paper, we described a two-dimensional particle-based visual method of simulating flames. In the present paper, we first extend the simulation method, without losing any of its desirable features, in such a way that it functions in three-dimensional space. We then present an efficient method of producing an image of the scene, including flames acting as volume light sources, which normally requires a large amount of computing time in the usual simulation approaches. Finally, we demonstrate the capabilities of our visual simulation method by showing sample images generated by it, which are excerpted from an animation.

Recently, progress has been made in the area of electrical modeling of conductors embedded in arbitrary dielectrics using circuit oriented techniques. These models usually occur in conjunction with VLSI type circuits. Many different applications exist today for such models in the EMI, EIP (Electrical Interconnect and Package) analysis as well as for the microwave circuit area. Practical problems involve a multitude of hardware components and they demand a wide spectrum of both time as well as frequency domain solution techniques. In this paper we consider circuit oriented techniques for the solution of these problems. Specifically, we give an outline of the three dimensional Partial Element Equivalent Circuit (PEEC) full wave modeling approach and review the recent progress in this area.

The transmission performance of DS-CDMA forward link with orthogonal spreading and Rake combining is evaluated under multipath fading environments. A simple-to-use expression for the conditional instantaneous signal-to-interference plus background noise power ratio (SIR) is derived, assuming an M-finger Rake combiner. Using the derived expression, the forward link SIRs of either orthogonal spreading or random spreading can be conveniently computed. The link performance in terms of the average bit error rate (BER) and capacity (the maximum number of allowable users) is evaluated by a Monte Carlo simulation assuming ideal BPSK data modulation. In frequency selective multipath fading, the orthogonality of the forward link is destroyed to some extent and link performance approaches that of random spreading. The extent of orthogonality destruction depends on the multipath channel power delay profile shape and number of resolved paths (for an exponential profile, it is defined as the number of stronger resolved paths that capture 90% of the total received power); so their influences on the link performance are discussed. Also simulated is the distribution of the BERs in a radio coverage area taking into account the path loss and shadowing to evaluate the link capacity at a certain outage probability.

Electromagnetic field diffracted by conducting circular disk and circular hole in the conducting plate is formulated by the method of Kobayashi potential. The field is expressed by linear combination of functions which satisfy the required boundary conditions except on the disk or hole. Thus the functions may be regarded as eigen functions of the configuration. By imposing the remaining boundary conditions, we can derive the matrix equations for the expansion coefficients. It may be verified readily that each eigen function satisfies edge conditions for induced current on the disk and for aperture field distribution on the hole. It may also be verified that the solutions for the disk and the hole satisfy Babinet's principle. Matrix elements of the equations for the expansion coefficients are given by two kinds of infinite integrals and the series solutions for these integrals are derived. The validity of these expressions are verified numerically by comparing with the results obtained from direct numerical integrations.

In this paper, scattering problem of the directional coupler for the slab waveguides are analyzed by the mode-matching method in the sense of least squares for the lowest order even TE mode incidence. It is considered that the analysis of this coupler for the slab waveguides presents the fundamental data to design the directional coupler for the three dimensional waveguides. This directional coupler is composed of three parallel slabs which are placed at equal space in the dielectric medium. Respective slabs are core regions of three respective waveguides. The periodic groove structure of finite extent is formed on the both surfaces of core region of the central waveguide among them. The power of incident TE mode is coupled to other two waveguides through periodic groove structure. The coupled TE mode propagates in the other waveguides to the same or opposite direction for the direction of incident mode which propagates in the waveguide having periodic structure when the Bragg condition is selected appropriately. The scattered field of each region of this directional coupler is described by the superpositions of the plane waves with bandlimited spectra, respectively. These approximate wave functions are determined by the minimization of the mean-square boundary residual. This method results in the simultaneous Fredholm type integral equations of the second kind for these spectra. The first order approximate solutions of the integral equations are derived and the coupling efficiency and scattered fields are analyzed on the basis of those solutions in this paper.

The integral kernel expansion method is applied to an analysis of scattering of magnetostatic forward volume waves (MSFVWs) by an array with any number of metal strips. In this method, first the integral kernel of the Fourier integral is expanded in terms of orthogonal polynomials to obtain moment equations. Then a system of algebraic equations is derived by applying the Galerkin's method. In the process, interaction between strips is naturally taken into account and real current distributions on the strips are determined such that boundary conditions are satisfied. Calculus confirmation through the energy conservation principle shows that numerical results are quite satisfactory. A comparison shows that theoretical results are in good agreement with experimental ones except the vicinity of lower and upper limits of the MSFVW band. It is shown that an infinite number of propagation modes is excited even if a wave of single mode is incident. Dependence of the scattering on dimension of arrays and on frequency and mode of an incident wave is obtained.

The H-polarized diffraction by a wedge consisting of perfect conductor and lossless dielectric is investigated by employing the dual integral equations. Its physical optics diffraction coefficients are expressed in a finite series of cotangent functions weighted by the Fresnel reflection coefficients. A correction rule is extracted from the difference between the diffraction coefficients of the physical optics field and those of the exact solution to a perfectly conducting wedge. The angular period of the cotangent functions is changed to satisfy the edge condition at the tip of the wedge, and the poles of the cotangent functions are relocated to cancel out the incident field in the artificially complementary region. Numerical results assure that the presented correction is highly effective for reducing the error posed in the physical optics solution.

Polarization transformation characteristics of a statified slab consisting of uniaxial chiral layers are investigated. It is assumed that a plane electromagnetic wave with arbitrary polarization is normally incident from free space on the stratified slab, which is located on a dielectric substrate. Note that the electric field inside a uniaxial chiral layer is expressed as a sum of four plane waves with different wavenumbers. The wavenumbers are found by seeking non-trivial solutions of the constitutive relations with Maxwell's equations. The electric field components of the transmitted and reflected waves can be obtained from a chainmatrix formalism. The powers and the Stokes parameters of the two waves are represented in terms of their electric field components. As is well known, the Stokes parameters uniquely describe every possible state of polarization of a plane wave. Numerical results are presented for two types of uniaxial chiral structure. The cross- and co-polarized powers and the Stokes parameters of the transmitted and reflected waves are computed for the incident plane wave of linear polarization. The results demonstrate a significant polarization transformation of the transmitted wave. Then it is shown that the stratified slab can be used as efficient polarization-transformation transmission filters active at some frequency band.

In this paper, a quite general systematic procedure is presented for defining incremental field contributions, that may provide effective tools for describing a wide class of scattering and diffraction phenomena at any aspect, whthin a unitary, self-consistent framework. This is based on a generalization of the localization process for cylindrical canonical problems with elementary source illumination and arbitrary observation aspects. In particular, it is shown that the spectral integral formulation of the exact solution may also be represented as a spatial integral convolution along the axis of the cylinder. Its integrand is then directly used to define the relevant incremental field contribution. This procedure, that will be referred to as a ITD (Incremental Theory of Diffraction) Fourier transform convolution localization process, is explicitly applied to both wedge and circular cylinder canonical configurations, to define incremental diffiraction and scattering contributions, respectively. These formulations are asymptotically approximated to find closed form high-frequency expression for the incremental field contributions. This generalization of the ITD lacalization process may provide a quite general, systematic procedure to find incremental field contributions that explicitly satisfy reciprocity and naturally lead to the UTD ray field representation, when it is applicable.

In this paper, we illustrate the analysis of microstrip structures with a large number of unknowns using the sparse-matrix/canonical grid method. This fast Fourier thansform (FFT) based iterative method reduces both CPU time and computer storage memory requirements. We employ the Mixed-Potential Integral Equation (MPIE) formulation in conjunction with the RWG triangular discretization. The required spatial-domain Green's functions are obtained efficiently and accurately using the Complex Image Method (CIM). The impedance matrix is decomposed into a sparse matrix which corresponds to near interactions and its complementary matrix which corresponds to far interactions among the subsectional current elements on the microstrip structures. During the iterative process, the near-interaction portion of the matrix -vector multiplication is computed directly as the conventional MPIE formulation. The far-interaction portion of the matrix-vector multiplication is computed indirectly using fast Fourier transforms (FFTs). This is achieved by a Taylor series expansion of the Green's function about the grid points of a uniformly-spaced canonical grid overlaying the triangular discretization.

In this paper a new class of single error-correcting fixed block-length (d, k) codes has been proposed. The correctable error types are peak-shift error, insertion or deletion error, symmetric error, etc. The basic technique to construct codes is a systematic construction algorithm of multilevel sequences with a constant Lee weight (TALG algorithm). The coding rate and efficiency are considerably good, and hence the proposed new codes will be very useful for improving the reliability of high density magnetic recording.