A current continuity equation is proposed as the additional equation for the GTD-MM hybrid technique formulation to acquire the uniqueness of the solution which were nonexistent in the conventional formulation with the matching-point equation. The current continuity equation, which ensures the current continuity and satisfies the boundary condition, can directly be written down through equating the MM-region current to the GTD-region current at the regions boundary. It is proved that the current continuity equation is equivalent to the matching-point equation of special case when the matching-point located very close to the boundary, which were able to give the best solution in the conventional formulation with the matching-point equation as explained by Burnside et al. The validity of the new equation is confirmed through the numerical results.

We produced a double-layer thin-film heater to detrap magnetic flux in a SQUID sensor. The heater is integrated on a sensor chip, and consists of a lower resistor layer and an upper superconducting layer to cancel the magnetic field produced by the heater current. The SQUID sensor is cooled below its critical temperature with a temperature gradient to detrap the flux completely. To make the gradient, we had to decrease heater power to zero over an interval exceeding 10-4 second in our experiment, which is almost equal to the sensor chip's thermal time constant. The integrated heater effectively controls the temperature profile and detraps flux in the sensor.

High efficiency amplifier construction techniques are investigated focusing on UHF band transmitting power amplifiers intended for cellular portable telephones and the state of the art amplifiers are presented. First, it is shown that high efficiency amplifiers are indispensable to attain pocket sized portable units through a theoretical analysis using a simple model. When about 1 W of transmitting power is required, it is desirable for the amplifier to operate with an efficiency of over 40%. Secondly, the switching mode scheme is described as the most effective technical means to achieve high amplifier efficiency. State of the art switching mode amplifiers, the Harmonic Reaction Amplifier (HRA) and the Linearized Saturation Amplifier with Bidirectional Control (LSA-BC), are presented as examples of nonlinear and linear amplifiers respectively. Basic operation mechanisms are shown. Experimental HRA and LSA-BC are constructed to determine their practically attainable efficiencies. Power-added efficiencies of 75% and 40% are recorded from a 1.7 GHz band 3 W HRA for CW and a 1.5 GHz band 1 W LSA-BC for π/4 QPSK respectively. These values indicate that these types of amplifier can be applied to pocket sized portable radio units.

Efficient device simulation methods to realize circuit level analyses have been proposed. Highly conductive wire regions, the current source, and lumped elements such as resistances and capacitances can be handled within the framework of a present device simulation software. Additionally, the simulation area can be reduced and computational efforts can be saved by adopting the inner Neumann boundary condition between devices which affect each other very little except through the wire region. The regularity of the coefficient matrix can be preserved in all cases, so it is possible to get stability of matrix solver and save computer memory. The advantage of matrix regularity is enhanced to speed up when using a vector-concurrent computer. Hence, the computational cost can be saved considerably. These numerical techniques have been implemented in the authors' device simulation software.

Markov Renewal Process (MRP) is an extremely powerful analyzing tool for concurrent systems. But it is often difficult to determine the correct Markov model for even moderately complex systems. Petri net is very descriptive and flexible in modeling various kinds of systems of concurrency and asynchronization. This paper presents an aggregate approach of Markov Renewal Process and Extended Stochastic Petri Net (ESPN) model, which allows incorporation of arbitrary time distributions. Using a descriptive "language" like the ESPN for specifying a Markov model of a system, the analyzing power of MRP can be exploited more easily. Moreover, an Abstract Partial Reachability Graph (APRG) is introduced to simplify the Markov solution. In addition, the aggregate approach of MRP and ESPN is applied to analyze a parallel message system.

A self-healing method to overcome memory address errors due to bit errors in a shared buffer memory switch is proposed. A shared buffer memory switch is one of the most useful switches for asynchronous transfer mode (ATM) networks because of its highly efficient memory usage and small hardware size. However, this switch has a basic problem. This is due to switching control mechanism in which the memory addresses are circulated between the idle address queueing buffer and the assigned address queueing buffers. Once a bit error occurs in the address, duplicate address values may appear and permanently circulate. This causes frequent cell discard and mis-routing due to cell overwriting at the same address. The proposed self-healing method can detect and discard the erroneous address and correct the address error without reducing throughput. To detect an erroneous address, a check memory is introduced. A buffer identifier in which an address is queued is memorized in the check memory. If duplicate address values appear, the memorized identifier is overwritten and changes into different one. Therefore, the erroneous address is detected by identifier mismatch when it is read out from the queueing buffer. Any queueing buffer is prohibited to store the erroneous address and that address is discarded. The correct address is restored by searching the lost address and inserting it as a correct idle address. The performance of the proposed method is simulated. It shows that the number of cells lost during the error detecting process is negligible.

Hopfield's neural networks are known to have a potentiality to solve combinatorial optimization problems. It is however found that the networks often fail to get the optimum solution. The present paper intends to clarify the exact cause of such failure from a mathematical point of view. A normal form of the objective function to be minimized is introduced. It is shown that almost all of combinatorial optimization problems can be reduced to minimum search problems of real-valued quadratic functions of two-valued variables excluding linear terms. A dynamical system, which is implemented by an idealized neural network consisting of massively connected neurons, is induced from the extension of the objective function to a multidimensional Euclidean space. The asymptotically stable states of this dynamical system are shown to lie in the vertices of a hyper cube that correspond to minimal points of the objective function. Hence, if the initial state were rightly selected, then the state of the dynamical system would approach to the minimum point of the objective function, and the corresponding optimization problem could be completely solved. This indicates that only the problem how to find a right initial state remains to be investigated. Through computer simulation, a conjecture on initial state selection is given such that the probability for the minimum search with a randomly selected initial state from the hyper cube, of which center is located at the origin of the state space, to be successful converges to 1 as the cube becomes 0 in size.

A new statistical test has been recently presented for determining whether a binary sequence into which a real-valued sequence to be tested is transformed precisely mimics Bernoulli trials B (p, q) with probabilities of 0 and of 1, p and q, or not. This paper gives a theoretical test based on such a stringent test and shows its usefulness. This method uses the ensemble average technique under the assumption that the pseudorandom-number generator is mixing with respect to an absolutely continuous measure. The existence of such a measure permits us to theoretically calculate the ensemble average of several statistics by using the Perron-Frobenius integral operator. Furthermore, this operator releases us from cumbersome and tedious procedures to calculate multivariate distributions, in connection with several statistical tests. Three kinds of tests, the runs test, poker test, and serial correlation test are presented. The Galerkin approximation to the operator on a suitable functional space is also introduced which provides a finite dimensional matrix (referred to as a Galerkin-approximated matrix of the Perron-Frobenius operator). The largest eigenvalue of the matrix, nearly equal to 1, corresponds to the existence of the measure. Each theoretical value of three tests for B (p, q) shows that the magnitude of the second largest eigenvalue plays an important role in determing randomness of the sequence generated by the generation.

Bifurcations of phase-locked modes for diffusively coupled van der Pol equations are investigated. It is known that in-phase and out-of-phase modes are typically observed in the system if two oscillatory equations are identical. There have been many studies on the behavior of diffusively coupled equations of van der Pol type. Many of these, however, persist in the limits of weakly nonlinearity and weak coupling. In this paper we study global feature of bifurcation sets of the modes under relatively wide range of variation of system parameters: coefficient of nonlinear term, parameter related to the frequency of the uncoupled equations, diffusion coefficient and so on.

After the brief review on nonlinear phenomena in chemistry, our attention is focused on two oscillatory systems which are typical examples of nonlinear, nonequilibrium chemical oscillations: (1) oscillation at membrane and at interface as a model of self-oscillation of a living cell, and (2) interference and entrainment between chemical oscillations, as an example of a spatio-temporal self-organization of multicellular organisms.

The paper clarifies the bifurcation mechanism responsible for a repeated appearance of period-one attractors in an R-L-Diode circuit driven by a sinusoidal voltage source E sin 2πft. Extensive measurements are performed to observe bifurcation diagrams in the f-E parameter space. After several simplifications of the dynamics, exact bifurcation equations are derived and analyzed. A major finding is that all the period-one attractors of our interest belong to the same family in the f-E parameter-space.

Recently, most of the difficult problems which prevented the realization of soliton communication have been solved by using the so-called erbium-doped optical fiber amplifiers (EDFAs). These amplifiers can provide a larger gain with a lower pumping power than the Raman process. In this paper, we describe how we were able to realize an actual soliton transmission system which utilizes lumped amplifiers instead of distributed amplifiers. A data transmission experiment at 10 Gbit/s 300 km is presented.

The first successful imaging by laser absorption computed tomography of in vitro specimens has been achieved by means of the Coherent Detection Imaging (CDI) method realized with the optical heterodyne detection technique and image reconstruction from back projection of the data obtained via optical absorption measurements in a parallel beam geometry.

The problem of embedding two-dimensional grids into hypercube parallel computers is the main subject of this work. Two methods (called dilation 1 and dilation 2 embedding) are used to embed a grid and their performances are evaluated. In dilation 1 (d1) embedding a grid edge connecting 2 points is mapped into one hypercube link, and in dilation 2 (d2) embedding there are cases in which one grid edge is mapped into two hypercube links. Generally, this makes the performance of d2 embedding poorer than that of d1 embedding, as communication between some adjacent grid points have to be forwarded through an intermediate link. However, there are cases where d2 embedding allows a more efficient use of the hypercube, as more processors can be used in the embedding. Thus, it is necessary to find out what kind of embedding achieves the best performance. We assume that the number of grid points is larger than the number of processors, and then propose a method to divide the grid in rectangular parts of arbitrary size called fragments, which are actually embedded into a processor. Using the parameters of a commercial hypercube, the performances of several grids embedded under different conditions are evaluated. As a result, the relation between hypercube size and grid size is found to have a strong influence on the choice of the embedding method.

The nonstationary electron transports in the BP-SAINT GaAs MESFETs with submicron gate lengths have been studied under the various conditions at 300 K by an ensemble Monte Carlo simulation. It is shown that the calculated drain currents fairly agree with the experiments. It has been found that Wang's effective saturation velocity of electrons, which is defined as 0.8 Vmax, depends not only on the gate length, but alsos on the gate voltage, the drain voltage, and the doping concentration of the channel, where Vmax is the maximum velocity in the channel. The dependence of the effective saturation velocity upon a gradient of the electric field is discussed. The spatial distributions of the valley population ratio (or the effective mass for the effective-single valley model) and the kinetic energy of electrons under the gate are studied by the ensemble Monte Carlo method to evaluate the validity of the relaxation time approximation for these device simulations. It is shown that the effective mass cannot be always specified as a fuction of the mean energy only and that the kinetic energy is not negligibly small around the middle of the channel compared with the thermal energy.

The performance guarantees of the Hopfield networks are given for two simple graph problems. A lower bound of the cutsize is evaluated for the maximum cut problem through the analysis of the eigenvalues at equilibrium states. The condition of constraint satisfaction and an upper bound of the cutsize are also given for the graph bipartitioning problem. In addition an effective numerical scheme is proposed to integrate the differential equations of the Hopfield networks by using backward Euler formula with one-step Gauss-Seidel relaxation. Theoretical estimates of the performance of the algorithm are verified experimentally.

This paper addresses thecurrent research and recent trends of image communications research that fall into the theme of intelligent communications in two parts --Intelligent Image Coding and Communications with Realistic Sensations. In Part , the theme of intelligent image coding and the particular example of encoding of human facial images using an intelligence-based approach is presented. A classification of the different generations--five generations--of image coding systems is first given. First and second generations are the direct wave-form coding and the statistical encoding methods. The third and fourth generations are the use of model-based anaylsis-synthesis and recognition/reconstruction methods, respectively. The fifth generation is the full intelligent coding system that can understand the semantics, intention, motives and other factors in an image. The progress in the model-based analysis-synthesis approach to image coding is reviewed and the particular example of its application to the encoding of human facial images is examined. In this example, the methods of modeling human face, the extraction of feature points and the tracing of motion in a facial image, as well as the analysis and synthesis of facial expressions are discussed. In Part , the current research in the new paradigm of telecommunication--Communications with Realistic Sensations is introduced. The progress in the research of a Virtual Space Teleconference System as an example of this new paradigm is presented. The possibility of delivering a very high level of sensation realism to a receiver is made real by recent advances in computer graphics and computer animation techniques, in stereoscopic display techniques that enable life-size images to be displayed on a wide screen and in computer human interface technologies, particularly, for recording human hand, head and eye positions. Progress of these technologies in the context of the research on the Virtual Space Teleconference System are discussed. The research on how to communicate and manipulate 3-D objects in a such an environment is examined.

This paper describes the dynamic behavior of a trench capacitor dRAM cell, named the SCC (Surrounded high-Capacitor Cell). A transient three-dimensional simulation reveals the raising of the substrate potential and the leakage current in the low-to-high state operation. The simulation results are verified by the experimental data using a test device. The characterization of this phenomenon allows design consideration of the scaled SCC.

In statistical tests, the uniform distribution property is frequently requested. Two well-known procedures are discussed for transforming nonuniform good random sequences into uniform ones. Results of a recently proposed randomness tests are also shown to be invariant under these transformations.

In Japan extensive efforts have been made for the practical application of the 1125/60 HDTV system for broadcasting and non-broadcasting uses. In this paper recent progress in the 1120/60 HDTV is reviewed focusing on the studio standard and the developments of HDTV equipment such as very high sensitivity pick-up tubes, HDTV CCD devices and a 33-inch flat panel plasma display. Then the transmission of HDTV signals via broadcasting satellite, communications satellite and CATV are described in addition to the digital transmission of HDTV signals. Finally some examples of non-broad-cast application of the 1125/60 HDTV are briefly discussed.