The subject of the paper is to propose two approximation algorithms FM_SPLA, FM_DPLA for priority-list scheduling in timed Petri nets. Their capability is compared with that of existing algorithms SPLA, DPLA through experimental results, where SPLA and DPLA have previously been proposed by the authors.

Thin Si films grown on anodized porous silicon have been characterized using a high-energy ion scattering technique with related simulations of MeV ions in solids. It turned out that the simulations are necessary and very usuful for quantitative and nondestractive analysis of thin films with thicknesses less than 100 nm. In the case of the epitaxial Si films examined, it is often insufficient for the characterization of crystalline quality to measure only the channeling minimum yield, and therefore, it is emphasized that angular scans over the critical angle in the vicinity of a channeling direction must be performed for the analysis of possible imperfections in thin films. The possible imperfections observed in the epitaxial specimen are treated quantitatively.

This letter proposes an improvement of the equivalent source method in order to give an accurate solution for the scattering of an electromagnetic plane wave by a conducting cylinder with edges.

An accurate numerical solution is presented for the electromagnetic scattering from infinite strip gratings attached to both sides of a dielectric slab. This structure is a model of polarization discriminating devices. The period of the strips is common to both planes, but the widths and the axes may be different. The direction of propagation and the polarization of an incident plane wave are arbitray. We derive a set of singular integral equations and solve it by the moment method, where the Chebyshev polynomials are successfully used as the basis and the testing functions. This method is accurate and effective owing to the incorporation of the edge condition and the decomposition of the kernel functions into the singular and the regular parts. Numerical calculations are carried out for the purpose of designing polarization discriminators, and it is shown that the band width is widened by decreasing the permittivity of the slab. The cross-polarization characteristics at skew incidence are also discussed.

Microcrystalline silicon embedded in silicon oxide has been prepared by means of a wet oxidation of porous silicon (PS) anodically produced from degenerate Si wafers in a HF solution. As the oxidation proceeded, optical absorptions of the PS specimen in the visible light region shifted obviously to the higher energy side. Visible light emission from the oxidized specimen was observed at room temperature with photoexcitation by a He-Cd laser while the as-prepared specimen emitted no visible lights. These results are discussed in relation to the quantum size effect of the microcrystalline silicon confined in the oxide matrix as well as visible emissions from as-prepared specimens produced from non-degenerate Si wafers.

A Ge/Si structure grown by chemical vapor deposition (CVD) is angle-lapped and characterized by the micro-Raman spectroscopy. Near the interface, the phonon mode due to the Si-Ge bond is clearly observed, which indicates that a SiGe alloy is formed by the solid-phase interdiffusion at the interface. The thickness of the interfacial alloy layer is about 0.2 µm. Amount of residual strain is estimated by comparing the measured phonon frequencies with those predicted from the composition profie, but the shift due to the residual strain is not appreciable. Both the interdiffusion at the interface and the nearly complete relaxation of the lattice mismatch are attributed to the high growth temperature of the CVD sample.

Fiber-optic subscriber loops are beginning to be constructed worldwide as an infrastructure for the 21st century. Making the most of the superior transmission capabilities of optical fiber cable, high-speed and broadband services such as so-called Broadband-ISDN (B-ISDN) services are expected to be achieved. We review current trends in fiber-optic systems and discuss how fiber-optic subscriber loops should be implemented from the points of view of services and technology. First, prospective services offered over fiber-optic subscriber loops and resulting requirements for such loops are presented. Various kinds of services produced through fiber-optic subscriber loops will further develop the information-oriented society and have a major influence not only on the industrial world but on family life as well. Next, basic concepts of totally fiber-optic subscriber loops and proposals for shifting from the existing metallic cable network to totally fiber-optic subscriber loops are discussed. In this regard, we must consider the advantages of optical fiber cables and improve upon the disadvantages of the existing metallic cable network. In particular, a Digital Loop Carrier (DLC) system or a Passive Double Star (PDS) have been proposed to shift from the existing metallic cable network to totally fiber-optic subscriber loops effectively and economically. Finally, line configuration topology and latest fiber-optic technologies such as high-count cable, construction techniques and operation systems for use in achieving totally fiber optic subscriber loops are shown. We believe a single star configuration is the most appropriate for totally fiber-optic subscriber loops.

The effect of mesage-class dependent threshold-type scheduling on queueing delay and resequencing delay for the M/M/n queueing system is analyzed. We first derive the expressions for the state transition equations, mean queueing delay, resequencing delay and total delay for the M/M/n queueing system shared by C different message classes under a threshold-type scheduling in which the threshold values depend on the message class at the head of queue and the number of messages in the buffer. Next, the numerical calculation and the computer simulation are carried out for the queueing system with two servers. It is found that the message-class dependent threshold-type scheduling is effective to reduce the resequencing delay of some specific message class, which can not be attained under the conventional threshold-type scheduling, and thus, the proposed scheduling can satisfy the different requirements of the different message classes, such as minimizing only queueing delay or total delay including resequencing delay.

This paper proposes a hierarchical Digital Signal Processor (DSP) Code Generator VIRGO for large scale general signal processing algorithms. Hierarchical structured Vectorized Signal Flow Graph (V-SFG) description is used as input specifications. Ths DSP independent optimization procedure for both the program size and the execution time is performed each module by each hierarchically with regard to operation order, memory assignment and register allocation. The efficient code generation is demonstrated by comparing both instruction steps and dynamic steps of a practical ADPCM encoder/decoder with a conventional method.

In this paper, we present an automatic implementation method by which executable communication programs in C can be generated from protocol specifications in LOTOS. The implementation method consists of two parts: 1) An implementation strategy and 2) a set of translation rules. The first part consists of the basic ideas on how to realize the primary mechanisms in LOTOS specifications. The second part formulates the implementation method by way of the translation rules based on the implementation strategy. The characteristics of our method can be summarized as follows: We formulate our implementation method by way of translation rules. These rules are defined topdown in the form of syntax-directed translation function. The mechanism for controlling concurrency and communication among the user processes corresponding to the processes in LOTOS specification is easily realized by using UNIX operating system functions. The translation rules have been implemented on the AS 3000 (SUN3) workstation. An application of this implementation method is demonstrated by a simplified token-ring-protocol.

Based on the Fornasini-Marchesini second model, an efficient algorithm is developed to derive the characteristic polynomial and the inverse of the system matrix from the state-space parameters. As a result, the external description of the Fornasini-Marchesini second model is clarified. A technique for designing 2-D recursive digital filters in the frequency domain is then presented by using the Fornasini-Marchesini second model. The resulting filter approximates both magnitude and group delay specifications and its stability is always guaranteed. Finally, three design examples are given to illustrate the utility of the proposed technique.

An arborescence-net N is a directed connected communication network with arborescence structure. Some information to be distributed through N is supposed to have been written in a file and the written file is denoted by J, where the file means an abstract concept of information carrier. In this letter, we consider a problem of distributing copies of J through N from the root vertex to every vertex, where the cost of transmitting a copy of J through each arc, the cost of making a copy of J at each vertex and the number of copies of J needed at each vertex in N are defined. Definig a file transfer on N, we give a method for designing an optimal file transfer by which we mean a file transfer whose total cost of transmitting and making copies of J is minimum on N.

This paper describes a method of evaluating operations effort for fiber optic subscriber loops, such as the Central Terminal/Remote Terminal (CT/RT) system, which can economically provide a variety of telecommunication services. Four system configurations with different operation procedures are evaluated by simulation. By evaluating the operating costs associated with service provisioning, it is shown that automatic distributing frames are cost effective in subscriber loops with CT/RT systems. Moreover, the most economical operation strategies for installing and extending subscriber boards are discussed in terms of facility and operations cost.

In general, a two-dimensional display is defined by two orthogonal unit vectors. In developing the display, discriminant analysis has a shortcoming that the extracted axes are not orthogonal in general. First, in order to overcome the shortcoming, we propose discriminant analysis which provides an orthonormal system in the transformed space. The transformation preserves the discriminatory ability in terms of the Fisher criterion. Second, we present a necessary and sufficient condition that discriminant analysis in the original space provides an orthonormal system. Finally, we investigate the relationship between orthogonal discriminant analysis and the Karhunen-Loeve expansion in the original space.

This paper designs and evaluates highly parallel VLSI processors for real time 2-D state-space digital filters using hierarchical behavioral description language and synthesizer. The architecture of the 2-D state-space digital filtering system is a linear systolic array of homogeneous VLSI processors, each of which consists of eight processing elements (PEs) executing 1-D state-space digital filtering with multi-input and multi-output. Hierarchical behavioral description language and synthesizer are adopted to design and evaluate PE's and the VLSI processors. One 16 bit fixed-point PE executing a (4, 4)-th order 2-D state-space digital filtering is described on the basis of distributed arithmetic in about 1,200 steps by the description language and is composed of 15 K gates in terms of 2 input NAND gate. One VLSI processor which is a cascade connection of eight PEs is composed of 129 K gates and can be integrated into one 1515 [mm2] VLSI chip using 1 µm CMOS standard cell. The 2-D state-space digital filtering system composed of 128 VLSI processors at 25 MHz clock can execute a 1,0241,024 image in 1.47 [msec] and thus can be applied to real-time conventional video signal processing.

For the development of a practical device simulation, it is necessary to solve the large sparse linear equations with a high speed computation of direct solution method. The use of parallel computation methods to solve the linear equations can reduce the CPU time greatly. The Multi Step Diakoptics (MSD) algorithm, is proposed as one of these parallel computation methods with direct solution, which is based on Diakoptics, that is, a tearing-based parallel computation method for sparse linear equations. We have applied the MSD algorithm to device simulation. This letter describes the partition and connection schedules in the MSD algorithm. The evaluation of this algorithm is done using a massively parallel computer with distributed memory (AP1000).

Over the past few years, the drive towards optimization and globalization of business activities has mandated the integration of various services, an increase in system scale, and the networking of a variety of systems. These requirements can only be satisfied by the introduction of systems that are able to accommodate and control multiple media and integrate LANs and PBXs synergistically. This paper proposes an architecture for next generation private networks called ANS (Areal Networking System) that is targeted at achieving flexible customization in an effort to meet a wide variety of user requirements as well as the ability to efficiently handle multimedia services. Based upon the clarification of various requirements on the ANS architecture, this paper defines two models for the ANS architecture. These models introduce modular building blocks in hierarchical structures that facilitate the custom design of networks. The key technologies for the ANS architecture are also discussed; for example, schemes for logically networking control functions by using virtual connections and a way to implement the LAN function.

Bifurcations of the periodic solutions of the space-clamped Hodgkin-Huxley equations for the muscle membrane are studied regarding the chloride conductance as a parameter. A limit cycle appears at a Hopf bifurcation and disappears at a homoclinic orbit. With high sodium permeability, a subcritical period doubling bifurcation occurs before it disappears.

In the approximate learning model introduced by Valiant, it has been shown by Blumer et al. that an Occam algorithm is immediately a PAC-learning algorithm. An Occam algorithm is a polynomial time algorithm that produces, for any sequence of examples, a simple hypothesis consistent with the examples. So an Occam algorithm is thought of as a procedure that compresses information in the examples. Weakening the compressing ability of Occam algorithms, a notion of weak Occam algorithms is introduced and the relationship between weak Occam algorithms and PAC-learning algorithms is investigated. It is shown that although a weak Occam algorithm is immediately a (probably) consistent PAC-learning algorithm, the converse does not hold. On the other hand, we show how to construct a weak Occam algorithm from a PAC-learning algorithm under some natural conditions. This result implies the equivalence between the existence of a weak Occam algorithm and that of a PAC-learning algorithm. Since the weak Occam algorithms constructed from PAC-learning algorithms are deterministic, our result improves a result of Board and Pitt's that the existence of a PAC-learning algorithm is equivalent to that of a randomized Occam algorithm.

Thermal desorption spectroscopy (TDS) is applied to analyze the oxidation reactions of hydrogen-terminated Si(100) surfaces in both the heating and cooling processes after hydrogen desorption. The oxidation reaction of oxygen and water with a silicon surface after hydrogen desorption shows hysteresis in the heating and cooling processes. In the cooling process, oxidation finishes when the silicon surface is adequately oxidized to about a 10 thickness. Oxidation continues to occur at lower temperatures when the total volume of oxygen and water is too small to saturate the bare silicon surface. The reaction of water with silicon releases hydrogen at more than 500. Hydrogen does not adsorb on the silicon oxide surface. A trace amount of oxygen, less than 110-6 Torr, roughens the surface.