Distributed shared memory is an attractive option for realizing functionally distributed computing in a wide area distributed environment, because of its simplicity and flexibility in software programming. However, up till now, distributed shared memory has mainly been studied in a local environment. In a widely distributed environment, latency of communication greatly affects system performance. Moreover, bandwidth of networks available in a wide area is dramatically increasing recently. DSM architecture using high performance networks must be different from the case of low speed networks being used. In this paper, distributed shared memory models in a widely distributed environment are discussed and evaluated. First, existing distributed shared memory models are examined: They are shared virtual memory and replicated shared memory. Next, an improved replicated shared memory model, which uses internal machine memory, is proposed. In this model, we assume the existence of a seamless, multi-cast wide area network infrastructure - for example, an ATM network. A prototype of this model using multi-thread programming have been implemented on multi-CPU SPARCstations and an ATM-LAN. These DSM models are compared with SCRAMNetTM, whose mechanism is based on replicated shared memory. Results from this evaluation show the superiority of the replicated shared memory compared to shared virtual memory when the length of the network is large. While replicated shared memory using external memory is influenced by the ratio of local and global accesses, replicated shared memory using internal machine memory is suitable for a wide variety of cases. The replicated shared memory model is considered to be suitable particularly for applications which impose real time operation in a widely distributed environment, since some latency hiding techniques such as context switching or data prefetching are not effective for real time demands.

Throughout the paper, the proper operating of the self-routing principle in 2-D shuffle multistage interconnection networks (MINs) is analysed. (The notation 1-D MIN and 2-D MIN is applied for a MIN which interconnects 1-D and 2-D data, respectively.) Two different methods for self-routing in 2-D shuffle MINs are presented: (1) The application of self-routing in 1-D MINs by a switch-pattern preserving transformation of 1-D shuffle stages into 2-D shuffle stages (and vice versa) and (2) the general concept of self-routing in 2-D shuffle MINs based on self-routing with regard to each coordinate which is the original contribution of the paper. Several examples are provided which make the various problems transparent.

In this study, we discuss a discrete-time cellular neural network (DTCNN) and its applications including convergence property and stability. Two theorems about the convergence condition of nonreciprocal non-uniform DTCNNs are described, which cover those of reciprocal one as a special case. Thus, it can be applied to wide classes of image processings, such as associative memories, multiple visual patterns recognition and others. Our DTCNN realized by the software simulation can largely reduce the computational time compared to the continuous-time CNN.

In this paper, we formulate and solve a discrete-time queueing problem that has two potential applications: ATM multiplexers and DQDB networks. We first consider the modeling of an ATM multiplexer. The object of the analysis is a periodic traffic stream (CBR traffic), which is one of the inputs to the multiplexer. As in previous works of the subject, we consider a memoryless background traffic input. Here, in addition to this background traffic, we take into account the influence of a high-priority traffic, which is time-correlated and requires expedited service. We analyze the influence of these two types of traffic on the statistics of the interdeparture time (jitter process) and the delay of the periodic traffic stream. We obtain their distributions in a form of z-transforms, and from these we derive closed form expressions for the average delay and the variance of the interdeparture time. Our results show that the delay and jitter are very sensitive to the burstiness of the high priority traffic arrival process. We next apply our analytical modeling to a DQDB network when some of its stations are driven by CBR sources. We can obtain interesting results concerning the influence of the physical location of a DQDB station on the jitter.

A performance estimation method has been developed that combines conventional performance evaluation with Bayesian regression analysis. The conventional method is used to estimate performance a priori; this a priori estimate is then updated through Bayesian regression analysis using monitored performance. This method compensates for modeling errors in the conventional technique without recreating complex performance models; it does not require additional traffic measurement or system behavior models. Numerical examples and applications of traffic management in ATM PVC networks have demonstrated its effectiveness.

This paper presents the performance prediction method on sentence recognition system which uses a finite state word automaton. When each word is uttered separately, the relationship between word recognition score and sentence recognition score can be approximated using the number of word sequences at a minimum distance from each sentence in the task. But it is not clear that how we get this number when the finite state word automaton is used as linguistic information. Therefore, we propose the algorithm to calculate this number in polynomial time. Then we carry out the prediction using this method and the simulation to compare with the prediction on the task of Japanese text editor commands. And it is shown that our method approximates the lower limit of sentence recognition score.

An invertible length preserving transducer is called a weakly invertible finite automaton (WIFA for short). If the first letter of any input string of length τ + 1 is uniquely determined by the corresponding output string by a WIFA and its initial state, it is called a WIFA with delay τ. The composition of two WIFAs is the natural concatenation of them. The composition is also a WIFA whose delay is less than or equal to the sum of the delays of the two WIFAs. In this paper we derive various results on a decomposition of a WIFA into WIFAs with smaller delays. The motivation of this subject is from theoretical interests as well as an application to cryptosystems. In order to capture the essence of the decomposability problem, we concentrate on WIFAs such that their input alphabets and their output alphabets are identical. A WIFA with size n of the input and output alphabet is denoted by an n-WIFA. We prove that for any n > 1, there exists an n-WIFA with delay 2 which cannot be decomposed into two n-WIFAs with delay 1. A one-element logic memory cell is a special WIFA with delay 1, and it is called a delay unit. We show that for any prime number p, every strongly connected p-WIFA with delay 1 can be decomposed into a WIFA with delay 0 and a delay unit, and that any 2-WIFA can be decomposed into a WIFA wiht delay 0 and a sequence of k delay units if and only if every state of the 2-WIFA has delay k.

As an optically controlled array antenna, a "two-laser type" using two laser diodes whose frequency difference is set to the desired microwave frequency has been proposed. In this paper, we confirm experimentally that the beamforming network of the two-laser type array antenna has very broadband characteristics by measuring the amplitude and phase of microwave signals at 1.5 GHz, 10 GHz and 20 GHz. Using the optically controlled beam forming network, the radiation pattern of a 4-element linear array antenna was measured at 1.5 GHz.

An optoelectronic beam forming network (BFN) is presented for a single beam, 3-element phased array antenna that utilizes electrically controllable birefringence mode nematic liquid-crystal cells (ECB mode NLC cells) for phase shifting and amplitude control. In the circuit, a microwave signal is carried by a pair of orthogonal linearly polarized lightwaves (signal and reference lightwaves) using the optical heterodyning technique. Birefringence of liquid-crystals is utilized to selectively control the phase of the signal and reference lightwaves. Because an interferometer is formed on a single signal path, the complexity of the optical circuit is much reduced, compared to the BFNs based on arrays of Mach-Zender interferometers. A prototype circuit is built using laser sources of 1.3 µm, and its performance experimentally examined. With small deviations among the three cells, phase shifts of up to 240 degrees are achived for MW signals from 0.9 GHz to 20 GHz with good stability; attenuation of more than 18dB is achieved. An optoelectronic technique for parallel control of amplitude and phase of MW signals was developed.

We present a recursive algorithm for constructing linear discrete-time systems which interpolate the desired 1st-and 2nd-order information. The recursive algorithm constructs a new system and connects it to the previous system in the cascade form every time new information is added. These procedures yield a practical realization of all the interpolants.

In this study, an extraction method of failure sound signal which is strongly contaminated by noise is investigated by genetic algorithm and statistical tests of the frequency domain for the failure diagnosis of machinery. In order to check the extraction accuracy of the failure signal and obtain the optimum extraction of failure signal, the "existing probability Ps (t*k) of failure signal" and statistical information Iqp are defined as the standard indices for evaluation of the extraction results. It has been proven by practical field data and application of the inspection and diagnosis robot that the extraction method discussed in this paper is effective for detection of a failure and distinction of it's origin in the diagnosis of machinery.

We propose a distributed operation system platform for optical cable networks. This distributed platform is an extension of the previously proposed platform for a flexible cable network operation. The concept of the unit platform has been proposed for the distributed operation system platform. By using this concept, we discuss the system upgrade including the connection to other operation systems. We use an object-oriented software technology for designing the distributed operation system platform. The prototype system has been constructed using C++ programing language and the evaluated results are shown.

This paper presents Ternary Decision Diagrams which represent sets of products. This paper also presents manipulating methods for sum-of-products forms and ringsum-of-products forms using Ternary Decision Diagrams, and gives comparison results between Ternary Decision Diagrams and Binary Decision Diagrams.

This paper presents testing methods for a logic synthesis system which supports the standard HDL UDL/I, focusing on conformance test to the language specification. Conformance test, to prove that the system completely satisfies the language specification, is very important to provide a unified design environment for users of CAD tools which support the language. The basic idea of our testing methods is using a logic simulator, due to a limited schedule for the test execution. We classified the test into two: unit test and integration test. Unit test is a test of each individual functionality of the system, and integration test is a test to prove that the whole system works correctly and satisfies the language specification. And we prepared and used various kinds of test data. One of them is the UDL/I Test Suite and it was also utilized to observe progress of language coverage by the system during the test execution.

An analytical framework to study the nonuniformity in geographical distribution of the traffic load in low earth orbit satellite communication systems is presented. The model is then used to evaluate the throughput performance of the system with direct-sequence packet spread-slotted ALOHA multiple-access technique. As the result, it is shown that nonuniformity in traffic makes the characteristics of the system significantly different from the results of uniform traffic case and that the performance of each user varies according to its location. Moreover, the interference reached from users of adjacent satellites is shown to be one of the main factors that limit the performance of system.

This paper proposes a new approach to deal with the various quality of the reference impressions by measuring the seal to register as 3D (three-dimensional) image, that is, range image. By registering a seal as 3D image, it becomes possible to construct various 2D impressions from it according to the affixing conditions of the reference impression such as the affixing slant, the affixing pressure, the state of the ink on the seal surface and so on. Then, the accurate and easy identification of the seals will be possible by comparing the constructed impression with the reference impression. The performance is verified by experiment, and the result shows that plural 2D impressions according to the affixing conditions can be constructed from only one 3D image of the registered seal.

This paper proposes a new method to design an optimal pipelined instruction set processor using formal HW/SW codesign methodology. A HW/SW partitioning algorithm for selecting an optimal pipelined architecture is introduced. The codesign task addressed in this paper is to find a set of hardware implemented operations to achieve the highest performance of an ASIP with pipelined architecture under given gate count and power consumption constraints. The problem formalization as well as the proposed algorithm can be considered as an extension of our previous work toward a pipelined architecture. The experimental results show that the proposed method is quite effective and efficient.

In this paper we propose a new method for removing the characteristic of the piezoelectric transducer from the received signal in the pulse-echo method so that the time resolution in the determination of transit time of ultrasound in a thin layer is increased. The total characteristic of the pulse-echo system is described by cascade of distributed-constant systems for the ultrasonic transducer, matching layer, and acoustic medium. The input impedance is estimated by the inverse matrix of the cascade system and the voltage signal at the electrical port. From the inverse Fourier transform of input impedance, the transit time in a thin layer object is accurately determined with high time resolution. The principle of the method is confirmed by simulation experiments.

We thought that multiple skeletons were inherent in an ordinary three-dimensional object. A thinning method is developed to extract multiple skeletons using 333 templates for boundary deletion based on the hit or miss transformation and 222 templates for checking one voxel thickness. We prepared twelve sets of deleting templates consisting of total 194 templates and 72 one voxel checking templates. One repetitive iteration using one sequential use of the template sets extracts one skeleton. Some of the skeletons thus obtained are identical; however, multiple independent skeletons are extracted by this method. These skeletons fulfill the well-recognized three conditions for a skeleton. We extracted three skeletons from the cube, two from the space shuttle model and four from the L-shaped figure by Tsao and Fu. The digital medial skeleton, which is not otherwise extracted, is extracted by comparing the multiple skeletons with the digital medial-axis-like-figure. One of our skeletons for the cude agreed with the ideal medial axis. The locations of the gravity center of the multiple skeletons are compared with that of the original shape to evaluate how uniform or non-biased skeletons are extracted. For the L-shaped figure, one of our skeletons is found to be most desirable from the medial and uniform points of view.

Efficient retrieval of nested objects is an important issue in advanced database systems. So far, a number of indexing methods for nested objects have been proposed. However, they do not consider retrieval of nested objects based on the set comparison operators such as and . Previouly, we proposed four set access facilities for nested objects and compared their performance in terms of retrieval cost, storage cost, and update cost. In this paper, we extend the study and present refined algorithms and cost formulas applicable to more generalized situations. Our cost models and analysis not only contribute to the study of set-valued retrieval but also to cost estimation of various indexing methods for nested objects in general.