First, a number of issues pertaining to analog VLSI implementation of Backpropagation (BP) and Deterministic Boltzmann Machine (DBM) learning algorithms are clarified. According to the results from software simulation, a mismatch between the activation function and derivative generated by independent circuits degrades the BP learning performance. The perfomance can be improved, however, by adjusting the gain of the activation function used to obtain the derivative, irrespective of the original activation function. Calculation errors embedded in the circuits also degrade the learning preformance. BP learning is sensitive to offset errors in multiplication in the learning process, and DBM learning is sensitive to asymmetry between the weight increment and decrement processes. Next, an analog VLSI architecture for implementing the algorithms using common building block circuits is proposed. The evaluation results of test chips confirm that synaptic weights can be updated up to 1 MHz and that a resolution exceeding 14 bits can be attained. The test chips successfully perform XOR learning using each algorithm.

This paper describes a new approach towards the performance-driven layout for analog LSIs. Based on our approach, we developed an automatic performance-driven layout system LIBRA. The performance-driven layout has an advantage that numerical evaluations of performance requirements may exactly specify layout requirements so that a better layout result will be expected with regard to both the size and the performances. As the first step to the final goal, we only concern with the DC characteristics of analog circuits affected by the placement and routing. First of all, LIBRA performs the sensitivity analysis with respect to process parameters and wire parasitics, which are major causes for DC performance deviations of analog LSIs, so as to describe every perfomance deviation by its first order approximation. Based on the estimations of those performance deviations, LIBRA designs the placement of devices. The placement approach here is the simulated annealing method driven by their circuit performance specification. The routing of inter-cell wires is performed according to the priority of the larger total wire sensitivities in the net by the maze router. Then, the simple compaction eliminates the empty space as much as possible. After that, the power lines optimization is performed so as to minimize the ferformance deviations. Finally, an advantage of the performance improvement by our approach is demonstrated by showing a layout result of a practical bipolar circuit and its excellent performance evaluations.

We propose a new distributed signal (analog or digital) transmission system which has the immunity against the noisy channel. An information signal in transmitter is distributed by distributor and the distributed signal is transmitted. Received signal is reconstructed by the inverse distributor in receiver. In this system, an impulsive interference noise which disturbs the transmission signal in the channel passes decoder only, and this interference noise is distributed by the inverse distributor while the transmitted signal is reconstructed. Some appended signals make it possible to estimate the noise components which inversely distributed with the Fourier transformation as the distributor. Basing upon this principle, the transmission system will have an ability to suppress the impulsive interference, and the channel will have high noise immunity. The construction of receiver which can eliminate the impulsive noise is derived.

This paper discusses the trends and future issues in hardware description languages (HDL's) and high-level synthesis systems. First the importance of HDL's and high-level synthesis is described. Then, several HDL's and related CAD systems are briefly introduced. Finally, the requirements to future HDL's and highlevel synthesis systems are discussed from several points of view.

The subject of the paper is to propose a simple O(|V|+|E|) algorithm for finding all 3-edge-components of a given undirected multigraph G=(V, E). An 3-edge-connected component of G is defined as a maximal set of vertices such that G has at least three edge-disjoint paths between every pair of vertices in the set. The algorithm is based on the depth-first search (DFS) technique. For any fixed DFS-tree T of G, cutpairs of G are partitioned into two types: a type 1 pair consists of an edge of T and a back edge; a type 2 pair consists of two edges of T. All type 1 pairs can easily be determined in O(|V|+|E|) time. The point is that an edge set KE(T) in which any type 2 pair is included can be found in O(|V|+|E|) time. All 3-edge-components of G appear as connected components if we delete from G all edges contained in type 1 pairs or in the edge set KE(T).

This paper proposes a designing algorithm for quadrilateral recursive filters which consist of four quarter-plane filters in the four quadrants. This can realize a perfect zero-phase filtering which is essential for image processing. Furthermore, several parallel processing algorithms capable of performing under very high parallel efficiency are developed on line-connected and mesh-connected processor arrays. By these proposals, the advantage of two-dimensional non-causal zero-phase recursive digital filters is made clear.

This paper presents a new fast fault simulation algorithm using a content addressable memory, which deals with zero-delay fault simulation of gate-level synchronous sequential circuits. The computation time of fault simulation for a single vector under the single stuck-at fault model is O(n2) for all the existing fault simulation algorithms on a sequential computers. The new algorithm attempts to reduce the computation time by processing many faults at a time by utilizing a property that a content addressable memory can be regarded as an SIMD type parallel computation machine. According to theoretical estimation, the speed performance of a simulator based on the proposed algorithm is equivalent to a fast fault simulator implemented on a vector supercomputer for a circuit of about 2400 gates.

The subject of the paper is to analyze time complexity of the minimum axiom set problem (MASHC) in the Horn clause propositional logic. MASHC is defined by "Given a set H of Horn clauses and a query Q, all in propositional logic, such that Q is provable over H, find an axiom set of minimum cardinality, HH, with respect to Q, where Q is provable over H if and only if Q can be shown to be true by repeating Modus Ponens starting from clauses of H under the assumption that all of them are originally assumed to be true". If Q is provable over H then H is called an axiom set (with respect to Q). As stated in the definition of MASHC, detecting if Q is provable over H is required. This leads us to a problem, called the provability detecting problem (PDPHC), defined by "Given a set H of Horn clauses and a query Q in propositional logic, determine if Q is provable over H". First an O(σ) algorithm BFSHC for PDPHC is given based on the breadth-first search, where σ is the formula size of a given set of Horn clauses. For MASHC, it is shown that the problem is NP-complete, and an O(σ) approximation algorithm FMAS is given. Its experimental evaluation is also presented.

Since Vendler classified aspect into four categories, state, achievement, activity, and accomplishment, much effort has been made to define the notion of aspect logically. It is commonly agreed that aspect represents the general temporal characteristics of events and states. However, there still remains a considerable amount of disagreement about its formal treatment. One of the major problems is that the aspect of a sentence shifts by certain types of sentence construction. For instance, adding time adverbials to a sentence modifies the original aspect, taking the progressive form of the verb changes the aspect, and so on. These phenomena are known as the aspect shifts. The other is the problem known as the imperfective paradox. The imperfective paradox is a problem of the truth definition of the progressives. The truth condition of the progressive form of the sentence is defined at an internal subinterval of the temporal range of the corresponding non-progressive sentence. If the truth condition of the progressive form of the sentence is defined using the truth condition of the non-progressive form of the sentence, there are logical contradictions of truth definition in a sentence such as "Max was building a house, but he never built it". These problems cause much confusion (1) in the truth definition of aspects, (2) in the definition of aspect operations, such as initiative, terminative, progressive, perfective, etc., and also (3) in the definition of adding time adverbials. This paper reviews the semantic problems with respect to aspect, and presents a consistent mechanism of aspect interpretation in order to settle all these semantic puzzles at once. For the sake of logical clarity, we construct a formal language, Lt, where every meaningful formula is a pair of a meaningful sentence and its aspect. The syntax of Lt describes the phenomenology of aspect shifts. The semantics of Lt defines temporal interpretation for all the meaningful sentences of Lt, with assuming the temporal interpretations of three inherent aspects, state, achievement, and activity. The proposed aspect interpretation gives a reasonable account for aspect shifts, and solves the imperfective paradox by asssuming the time structure to be backwards linear.

Dynamic behavior of a distributed parameter system described by the one-dimensional wave equation with a nonlinear boundary condition is examined in detail using a graphical method proposed by Witt on a digital computer. The bifurcation diagram, homoclinic orbit and one-dimensional map are obtained and examined. Results using an analog simulator are introduced and compared with that of the graphical method. The discrepancy between these results is considered, and from the comparison among the bifurcation diagrams obtained by the graphical method, it is denoted that the energy dissipation in the system considerably restrains the chaotic state in the bifurcation process.

In general, dynamic channel assignment has a better performance than fixed channel assignment in a cellular mobile communication system. However, it is complex to control the system and a lot of equipments are required in each cell when dynamic channel assignment is applied to a large service area. Therefore, it is effective to limit the size of the service area in order to correct the defects of dynamic channel assignment. So, we propose an application of dynamic channel assignment to a part of a service area when fixed channel assignment is applied to the remaining part of the area. In the system, the efficiency of channel usage in some cells sometimes becomes terribly low. The system has such a problem to be improved. We show that the rearrangement of the channel allocation is effective on the problem.

Radiation properties of magnetic noise from the harness wires of a spacecraft (GEOTAIL) have been studied experimentally and theoretically. A simulation experiment on the noise radiation using a minimum set of subsystems of the spacecraft has shown that the intensity and the directional patterns of the noise radiation from the wires were largely changed by the existence of a conductive plate near the harness wires. The change in the noise characteristics is explained by eddy currents induced in the conductive plate by the signal current flowing in the wires. The eddy currents distributed in the conductive plate were calculated by the Finite Element analysis Method (FEM). The magnetic flux densities calculated from both the source signal current and its induced eddy currents for the wiring configuration of the simulation experiment have shown to be consistent with the values obtained in the experiment. The results in the present study have provided us an important information on a wiring method to diminish noise radiation from harness wires.

This paper presents a survey on bicriteria network optimization problems. When there are two conflicting criteria that evaluate the solution, the bicriteria optimization is to find a solution for which these criteria are both acceptably satisfied. Standard approaches to these problems are to combine these two criteria into an aggregated single criterion. Among such problems, this paper first deals with the case in which the aggregated objective function, denoted h(f1(x), f2(x)), is convex in original two objectives f1(x) and f2(x), and, as its special case, it reviews a strongly polynomial algorithm for the bicriteria minimum-cost circulation problem. It then discusses the case in which h is concave and demonstrates that a parametric approach is effective for this case. Several interesting applications in network optimization that belong to this class are also introduced. Finally we deal with the minimum range problems which seek to find a solution such that weights of the components used in the solution are most uniform. We shall present efficient algorithms for solving these problems arised in network optimization.

Optical couplers which are composed of three channel waveguides arranged two-dimensionally are investigated numerically. The mode-matching method that matches the boundary conditions in the sense of least squares is applied to this problem, using the hybrid-modal representation. The precise numerical results of the dispersion relations and field distributions are presented for the lowest three modes near the cutoff. The arrangement of three waveguides can be optimized so as to satisfy the condition for maximum power-transfer efficiency.

It has been recognized that there exist some disparities between properties of continuous control systems and those of discrete ones which are obtained from their continuous counterparts by use of a sampler and zero order hold. This still remains true even if the sampling rate becomes fast enough and sometimes causes unfavorable effects in control systems design. To reconcile with this conflict, use of delta operator has been proposed in place of z-operator recently. This note formulates a delta domain Lyapunov matrix equation and shows that the equation actually mediates the discrete Lyapunov equation and its continuous counterpart.

The authors propose a waveguide π-junction with an inductive post for the element of a multiple-way power divider in a single-layered slotted waveguide array. This π-junction splits part of the power into two branch waveguides through one coupling window, and can excite densely arrayed waveguides at equal phase and amplitude. The power dividing characteristics are analyzed by Galerkin's method of moments and are confirmed experimentally. Reflection from the π-junction is suppressed to the level below 30 dB over 5.4% bandwidth by attaching an inductive post.

A fully integrated digital PLL (Phase Locked Loop) with on-chip CMOS oscillator is described. Nominal division number of the variable divider is automatically tuned in this digital PLL and this feature makes it possible to widen the pull-in range. In general, output jitter may increase if the pull-in range is widened. To overcome this problem, output jitter is reduced by utilizing the dual loop architecture. Wide pull-in range enables us on-chip oscillator, which is not so precise as the expensive crystal oscillator. This CMOS oscillator must be carefully designed to be stable against the temperature and the supply voltage variations. Using these digital PLL techniques, together with the on-chip CMOS oscillator, a fully integrated PLL can be achieved. Circuits are designed for 1.544 Mbit/s ISDN primary rate interface, and 6.25% pull-in range is obtained.

Serious failures of the latest electronic equipments occur easily due to electrostatic discharge (ESD) , which can be caused frequently by the electrification phenomena of human-body walking on the floor. The number of the above damaging incidents has significantly been increasing with an increased use of integrated semiconductor elements with lower operation power. The most effective measures against the ESD consist in preventive ones, which are to obtain dynamic behaviors of the electric charge before the ESD happens, thereby preventing the charge accumulation. From this point of view, this paper describes new approaches for measurement of the static electricity directed toward preventing the ESD. First, a two-dimensional measurement method for visualizing charge distributions is described. This principle is based on visualizing the potential distribution induced in the array electrodes from the electrostatic fields. For showing usefulness of the visualization measurement, a prototype was built and attempts were made on the visualizations for the static electricity distributions of charged bodies. Second, a potential calculation of the human body charged by walking on the floor is described. A model was shown for analyzing the human-body potential on the floor, and the theoretical equation for describing the potential attenuation process was derived in the closed form in the Laplacian transformation domain. In order to obtain the typical half-life of the human-body potential, numerical computations were performed using a reverse Laplacian transformation. The experiments were also conducted for confirming the validity of the computed results. Finally, a new method is described for estimating dynamic behaviors of the occurrence charges of the human body electrified by walking-motions. Statistical measurements of the charges and potentials were made for the fundamental walking-motions specified here. The pace transitions of the potentials due to continuous walking and stepping were also measured and their results were explained from the electrification properties for the fundamental walking-motions.

The effect of the externally reflected light on the mode partition characteristics of 1.3 µm Fabry-Perot laser diodes is studied experimentally and numerically. It is observed that the k-value increases monotonically with the DC bias current and the external reflection coefficient. Based on these experimental results, a numerical model to study the mode partition characteristics of laser diodes in the presence of external reflections is developed. The results calculated using this model agree well with the experimental ones. It is found that the mode partition noise is mainly caused by the interference between the light in the laser diode and the reflected light, and also by the fluctuations of the induced emission and absorption. In the time domain, their contribution to the mode partition noise is almost localized in the time region within 0.1nsec at the time when the optical pulse turns on.