For L 2, M 8, and transmission rate R = (log2M-1) bit/sym, a method for constructing GU trellis codes with L MPSK constellations is proposed and it is shown that the maximally achievable free distance is twice larger than it was previously reported for GU codes. Basides being geometrically uniform, these codes perform as good as Pietrobon's non-GU trellis codes with multidimensional MPSK constellations.

Photovoltaic devices capable of generating more than 200 volts with an area of 1 cm2 have been developed for directly driving microactuators such as piezoelectric or electrostatic actuators. The micro-devices interconnect 285 micro cells (unit cell size: about 0.5 mm 2.0 mm) in series, and have an open circuit voltage (Voc) of 207 volts, a short circuit current (Isc) of 36.6 µA, a maximum output power (Pmax) of 4.65 mW and a fill factor (F.F.) of 0.615 under AM (Air Mass) 1.5 and 100 mW/cm2 illumination. This voltage is the highest in the world for the area of 1 cm2. The series connection is precisely processed by a focused laser beam, thereby significantly reducing the area needed for device connections. It has been confirmed that a piezoelectric polymer can be directly driven by the electrical output in evaluating the potential of the devices to be used as a microactuator's power source.

Significant traffic variations occur in telecommunication networks. This paper focuses on hour-to-hour traffic variations during 24 hours and investigates the possibility of using idle periods effectively by introducing non-realtime service at a discount rate. In order to provide non-realtime service, memory is placed at each telecom center. When immediate service is not available, messages of non-realtime calls are stored in the memory and served later when network resources are available. Realtime calls are served with preference. A basic model and a method of dimensioning the memory capacity are presented. The basic model is extended to the network model, and methods of designing a minimum cost network and pricing and profit issues are presented. The results for a basic model are verified by traffic simulation. Numerical examples are given to show the effectiveness of non-realtime service.

This paper is concened with the design and implementation of a 2-channel, 2-dimensional filter bank using rectangular (analog/digital) and quincunx (digital/digital) sampling. The associated analog low-pass filters are separable where as the digital low-pass filters are non-separable for a minimum sampling density requirement. The digital low-pass filters are Butterworth type filters, N = 9, realized as LWDFs. They, when itterated, approximate a valid scaling function (raised-consine scaling function). The obtained system can be used to compute a discrete wavelet transform.

The millimeter wave (MMW) radar has good compromise characteristics of both microwave radar and optical sensors. It has better angular and range resolving abilities than microwave radar, and a longer penetrating range than optical sensors. We used the MMW radar to detect targets located in the sea and among sea ice clutter based on fractals, wavelets, and neural networks. The wavelets were used as feature extractors to decompose the MMW radar images and to extract the feature vectors from approximation signals at different resolution levels. Unsupervised neural classifiers with parallel computational architecture were used to classify sea ice, sea water and targets based on the competitive learning algorithm. The fractal dimensions could provide a quantitative description of the roughness of the radar image. Using these techniques, we can detect targets quickly and clearly discriminate between sea ice, sea water, and targets.

The polymer matrix for the number of N in-puts/outputs, N stages and 2x2-switches is denoted as the 1-D Spanke-Benes (SB) network. Throughout the paper, the 1-D SB-network, which equals the diamond cellular array, is extended to arbitrary dimensions by a mathematical transformation (a 1-D network provides the interconnection of 1-D data). This transformation determines the multistage architecture completely by providing size, location, geometry and wiring of the switches as well as it preserves properties of the networks, e.g., the capability of sorting. The SB-networks of dimension 3 are analysed and sorting is applied.

We investigate bifurcations of the periodic solution observed in a phase converter circuit. The system equations can be considered as a nonlinear coupled system with Duffing's equation and an equation describing a parametric excitation circuit. In this system there are two types of solutions. One is with x = y = 0 which is the same as the solution of Duffing's equation (correspond to uncoupled case), another solution is with xy0. We obtain bifurcation sets of both solutions and discuss how does the coupling change the bifurcation structure. From numerical analysis we obtain a codimension two bifurcation which is intersection of double period-doubling bifurcations. Pericdic solutions generated by these bifurcations become chaotic states through a cascade of codimension three bifurcations which are intersections of D-type of branchings and period-doubling bifurcations.

A method is presented for reconstructing the surface profile of a two dimensional rough surface boundary from the scattered far field data. The proposed inversion algorithm is based on the Kirchhoff approximation and in order to determine the surface profile, the numerical results illustrating the method are presented.

It is thought that we have generally succeeded in establishing learning algorithms for neural networks, such as the back-propagation algorithm. However two major issues remain to be solved. First, there are possibilities of being trapped at a local minimum in learning. Second, the convergence rate is too slow. Chang and Ghaffar proposed to add a new hidden node, whenever stopping at a local minimum, and restart to train the new net until the error converges to zero. Their method designs newly generated weights so that the new net after introducing a new hidden node has less error than that at the original local minimum. In this paper, we propose a new method that improves their convergence rate. Our proposed method is expected to give a lower system error and a larger error gradient magnitude than their method at a starting point of the new net, which leads to a faster convergence rate. Actually, it is shown through numerical examples that the proposed method gives a much better performance than the conventional Chang and Ghaffar's method.

Most research on the estimation of direction of arrival (DOA) has been performed based on the assumption that the signal sources are point sources. In some real surroundings, signal source localization can more adequately be accomplished with distributed source models. When the signal sources are distributed over an area, we cannot directly use well-known DOA estimation methods, because these methods are established based on the point source assumption. In this paper, we propose a 3-dimensional distributed signal source model, in which a source is represented by two parameters, the center angle and degree of dispersion. Then, we address the estimation of the elevation and azimuth angles of distributed sources based on the parametric distributed source modeling in the 3-dimensional space.

An image obtained by ultrasonic medical equipment is poor in quality because of speckle noise, that is caused by the quality of ultrasonic beam and so on. Thus, it is very difficult to detect internal organs or the diseased tissues from a medical ultrasonic image by the processing, which is used only gray-scale of the image. To analyze the ultrasonic image, it is necessary to use not only gray-scale but also appropriate statistical character. In this paper, we suggest a new method to extract regions of internal organs from an ultrasonic image by the discrimination function. The discrimination function is based on gray-scale and statistical characters of the image. This function is determined by using parameters of the multi-dimensional autoregressive model.

This paper proposes a three-dimensional (3-D) band-limiting technique for a conversion of Simple Cubic Sampling into Body-Centered Cubic Sampling. Based on spectral distribution of the original signal, the proposed method adaptively varies the passband shape of a band-limiting filter in order to preserve informations of the original picture. By applying this method to 3-D moving pictures, we can preserve resolution on each axis without introducing heavy aliasing error and avoid degradation of picture quality such as ringing in still pictures or blurring in moving pictures. The examples given in this paper demonstrate these advantages.

This paper proposes a design technique for 3-D non-separable QMF banks with Face-Centered Cubic Sampling (FCCS) and Body-Centered Cubic Sampling (BCCS). In the proposed technique, 2-D McClellan transformation is applied to a suitably designed 2-D prototype QMF to obtain 3-D QMFs. The design examples given in this paper demonstrate advantages of the proposed method.

The local moment functions for discrete Wigner trispectrum are examined in ambiguity and in time-frequency domain. A concept of multiple and multidimensional circular convolution in frequency domain is introduced into the discrete Wigner higher order time-frequency signal representation of any order. It is shown that this concept based on the 1st order spectra of the signal offers an insight into the properties of inconsistent local moment functions and their representation both in ambiguity and time-frequency domain. It allows to prove that midfrequency crossterms of a multicomponent signal can not be removed by any generalized 4th order ambiguity function which employ kernel function in the ambiguity domain. It is shown, that the concept of multiple convolution in frequency domain can lead to the crossterm-reduced discete time-frequency representations of any order

Recently applications of Hilbert curves are studied in the area of image processing, image compression, computer hologram, etc. We have proposed a fast Hilbert scanning algorithm using lookup tables in N dimensional space. However, this scan is different from the one of previously proposed scanning algorithms. Making the lookup tables is a problem for the generation of several Hilbert scans. In this note, we describe a method of making lookup tables from a given Hilbert scan which is obtained by other scanning methods.

In this paper, electromagnetic scattering by infinite double two-dimensional periodic array of resistive upper and lower elements is considered. The electric field equations are solved by using the moment method in the spectral domain. Some numerical results are shown and frequency selective properties are discussed.

A two-dimensional recording method that achieves double recording density by reducing the track pitch is described. This method uses a flat disk and the data are recorded with circular marks on lattice points. Two-dimensional interference consisting of crosstalk and inter-symbol interference is reduced by two-dimensional equalization. To minimize the two-dimensional interference, the optimum equalization coefficients are calculated dynamically with the reproduced signal of the training marks. Reproduction was simulated and this showed that the signal-to-noise ratio of the processed signal was 24.3 dB under ideal conditions and 19.8 dB under worst-case conditions with the usual magneto-optical media using double recording density. These simulation results were checked by a recording/reproduction experiment. The experimental result for the signal-to-noise ratio of the processed signal was 23.6 dB with an areal density of 2.3 Gbit/in2.

We believe that virtual world communication will subsume BBS and visual communication. Accordingly, we proposed the networked virtual world "Interspace" for visual communication. If we are to achieve education and training in this world, techniques to receive and transmit information without any special training are necessary. The traditional "easy" ways of transmitting information are talking and drawing. In Interspace, users can already talk each other. In this paper we focus on drawing. In daily life we communicate through drawings in various situations. At this time it is important to recognize who is drawing and where the participants are watching. It is difficult to realize these functions using conventional media, but it is possible to realize them in virtual space. In virtual space, the system can clearly represent who is drawing and where participants are watching; expressing topics in virtual space frees us from many physical restrictions. In this paper we discuss the process of drawing when many participants share topics in virtual space; the necessary conditions for our system are considered. We design a system that offers functions to make drawing sheets, to display the view fields of participants, and to share visual fields. Furthermore, we propose the mode of InterSheet called "InterMirror" which shows mirror images of partners and their drawings. We make a prototype and evaluate it. The results indicate the synergistic effect of drawing with voice and the usefulness of drawing for communication in virtual space.

In this paper, we present for the first time two three-dimensional analytical electrostatic Green's functions for shielded and open arbitrarily multilayered medium structures. The analytical formulas for the Green's functions are simply expressed in the form of Fourier series and integrals, and are applicable to the arbitrary number of dielectric layers. In combination with the complex image charge method, we demonstrate an efficient application to analyze microstrip discontinuities in a three-layered dielectric structure. Numerical results for the capacitance associated with on open-end discontinuity show good agreement with those from a previous paper and the effectiveness of using the analytical Green's functions to analyze three-dimensional electrostatic problems.

A numerical scheme to analyze a three-dimensional perfectly conducting body that has edges and corners is presented. The geometry of the body can be arbitrary. A new formulation using boundary element method has been developed. This formulation allows that a scatterer has edges and corners, where the behavior of the electromagnetic fields become singular.