A narrow-band digital land mobile system has been developed that operates in the frequency bands of 150 and 400 MHz, which are commonly used by transportation-related companies, local government, and public-sector organizations--and are therefore very congested. The number of users that can be accommodated in these bands is almost doubled by reducing the channel separation to 6.25 kHz, about half that of a conventional FM system. A carrier bit rate of 9.6 kbps is achieved by using π/4 shift QPSK modulation with a roll-off factor of 0.2. Laboratory and field testing showed that: (1) Without propagation delay spread, a BER of 10-2 was obtained without using space diversity. (2) With a propagation delay spread of 10 µs, a BER of 610-3 was obtained without space diversity. These measurements confirmed the technical feasibility of this narrow-band system. Its widespread implementation will help mitigate the congestion in private radio systems.

Localization properties of mode waves in an off-diagonally disordered waveguide system are presented. The disorder is introduced by taking spacings between cores to be random variables. Coupled mode equations are transformed into a matrix eigenvalue problem and eigenvalues and eigenvectors are numerically obtained. Correspondences between the natures of modes and the modal density of states are discussed. The system is divided into several sections which behave effectively as isolated systems. Modes in the entire system are a superposition of modes associated with the sections. A section is divided into several elements, which do not only behave apparently as isolated systems but also couple with each other. When an element includes two cores coupled strongly with each other due to a narrow spacing, modes are strongly localized there. The extent of the modes is almost independent of the disorder of the system. In a system with small disorder strongly localized modes can exist. The modes appear outside the propagation constant band of the ordered system composed of identical cores of equal spacing. Modes near the center of the band are extended over a number of elements and have the relatively large extent. Many modes appear near the center of the band and the modal density of states has a sharp peak there.

With conventional dynamic routing algorithms, many query messages are required in a distributed environment for efficient multicast routing of any traffic volume. We have developed a dynamic routing algorithm that uses a predetermined path search in which an appropriate multicast path is dynamically constructed by searching only a few nodes. This algorithm can construct an efficient multicast tree for any traffic volume. Simulation has shown that the proposed algorithm is advantageous compared with conventional dynamic routing algorithms when nodes are added to or removed from the multicast group during steady-state simulation.

This paper presents the effect of stress on device degradation in metal-oxide-semiconductor field-effect transistors (MOSFETs) due to stud bumping. Stud bumping above the MOSFET region generates interface traps at the Si/SiO2 interface and results in the degradation of transconductance in N-channel MOSFETs. The interface traps are apparently eliminated by both nitrogen and hydrogen annealing. However, the hot-carrier immunity after hydrogen annealing is one order of magnitude stronger than that after nitrogen annealing. This effect is explained by the termination of dangling bonds with hydrogen atoms.

This paper reviews recent progresses in the research and development of planar photonic band-gap (PBG) structures, also called electromagnetic crystals, for microwave and millimeter-wave applications. Planar electromagnetic crystals are particularly attractive and intensively investigated because of their easy fabrication, low cost, and compatibility with standard planar circuit technology. Two configurations and their applications are described in this paper: a square lattice of holes etched in a ground plane and the recently developed Uniplanar Compact PBG (UC-PBG) structure. Basic properties as well as applications to microwave circuits are reported. These include harmonic tuning in power amplifier, leakage suppression in conductor-backed coplanar waveguide (CB-CPW), realization of planar slow-wave structure, and performance improvement in microstrip filters and patch antennas.

The present paper modifies the algorithm to estimate harmful event frequencies and examines the definition of modes of operation in IEC 61508. As far as the continuous mode concerns, the calculated results coincide with those obtained based on the standard. However, for the intermediate region of medium demand frequencies and/or medium demand durations, the standard gives much higher harmful event frequencies than the real values. In order to avoid this difficulty, a new definition of modes of operation and a shortcut method for allocation of SILs are presented.

Printed transmission lines have been extensively examined so far, but results obtained there are all concerned with the waveguiding conductors with no loss and zero thickness, except very few results. We have recently studied the transmission characteristics of printed transmission lines in detail, when the waveguiding conductors have finite conductivity and thickness, and we have found an unexpected effect that we call a "mode extinction effect. " This effect results in significant changes in the dispersion behavior of the printed-transmission-line fundamental mode. For a critical thickness, it may turn out that such transmission line can not use in open structural configuration, but must always be used by putting into a packaging box. In this paper, we discuss thoroughly this important effect and related results from the standpoints of both the dispersion behavior and the vector field plots. We also show the measured results of the attenuation constant.

In this paper we present an analysis based on the indirect Lyapunov criteria, that is used to study the convergence of an infinite impulse response (IIR) adaptive digital filter (ADF) based on estimation of the allpass system. The analysis is then extended to investigate the necessity of directly estimating the transfer level of the unknown system. We consider two cases of modeling the ADF. In the first system, the allpass section of the ADF estimates only the real poles of the unknown system while in the second system, both real and complex poles the allpass section are estimated. From the analysis and computer simulation, we realize that the poles of the ADF converge selectively to the poles of the unknown system, depending on the sign of the step size of adaptation. Using these results we proposed a new method to control the convergence of the poles the IIR ADF based on estimation of the allpass system.

A novel protocol scheme is proposed here to compile a program or run a software package. It is a modification where a file can be detected by checking the consistency of the original file with its accompanying digital signature. When an executable program is created it may get infected with some viruses before the signature is attached to it. The infection cannot be detected by signature verification and the origin of the infection cannot be specified either. We propose a signature scheme that let one can sign right in atomic step after the creation of an executable program. Our security-related and cryptographic protocol is used to establish secure communication over insecure open networks and distributed systems. When a server compiles a source program, the compiler automatically creates both the executable program and its signature. Thus no virus can infect the executable programs without being detected. In our proposed signature scheme, the server signature is created a set of proxy secret integers, which is calculated from a compiler maker's secret key. Each server compiler is possessed by its corresponding client user and it is used only when a server secret value is fed into it. The infections of files can be detected by the ordinary server digital signatures. The proposed signature scheme together with the digital signature against infection in the preprocessing step enables us to specify the origin of the infection. Besides that, we also provide the message recovery capability to recover the original file to save the infected files. The most natural extension of this novel protocol scheme is a server-based signature that integrated together with application packages will allow client and the server to commit themselves to one another.

Abnormal IDDQ (Quiescent VDD supply current) indicates the existence of physical damage in a circuit. Using this phenomenon, a CAD-based fault diagnosis technology has been developed to analyze the manufacturing yield of logic LSI. This method to detect the fatal defect fragments in several abnormalities identified with wafer inspection apparatus includes a way to separate various leakage faults, and to define the diagnosis area encircling the abnormal portions. The proposed technique progressively narrows the faulty area by using logic simulation to extract the logic states of the diagnosis area, and by locating test vectors related to abnormal IDDQ. The fundamental diagnosis way employs the comparative operation of each circuit element to determine whether the same logic state with abnormal IDDQ exists in normal logic state or not.

This paper describes an improved complementary beamforming microphone array based on the new noise adaptation algorithm. Complementary beamforming is based on two types of beamformers designed to obtain complementary directivity patterns with respect to each other. In this system, during a pause in the target speech, two directivity patterns of the beamformers are adapted to the noise directions of arrival so that the expectation values of each noise power spectrum are minimized in the array output. Using this technique, we can realize the directional nulls for each noise even when the number of sound sources exceeds that of microphones. To evaluate the effectiveness, speech enhancement experiments and speech recognition experiments are performed based on computer simulations with a two-element array and three sound sources under various noise conditions. In comparison with the conventional adaptive beamformer and the conventional spectral subtraction method cascaded with the adaptive beamformer, it is shown that (1) the proposed array improves the signal-to-noise ratio (SNR) of degraded speech by more than 6 dB when the interfering noise is two speakers with the input SNR of below 0 dB, (2) the proposed array improves the SNR by about 2 dB when the interfering noise is bubble noise, and (3) an improvement in the recognition rate of more than 18% is obtained when the interfering noise is two speakers or two overlapped signals of some speakers under the condition that the input SNR is 10 dB.

This paper considers two simulation models for simple unreliable file systems with checkpointing and rollback recovery. In Model 1, the checkpoint is generated at a pre-specified time and the information on the main memory since the last checkpoint is back-uped in a secondary medium. On the other hand, in Model 2, the checkpointing is executed at the time when the number of transactions completed for processing is achieved at a pre-determined level. However, it is difficult to treat such models analytically without employing any approximation method, if queueing effects related with arrival and processing of transactions can not be ignored. We apply the generalized stochastic Petri net (GSPN) to represent the stochastic behaviour of systems under two checkpointing schemes. Throughout GSPN simulation, we evaluate quantitatively the maintainability of checkpoint models under consideration and examine the dependence of model parameters in the optimal checkpoint policies and their associated system availabilities.

In December 1996, JR East introduced "ATOS" the latest Autonomous Decentralized System, on its Chuo Line. This system, named after Athos, the mountain which is sacred to the Greek Orthodox Church, is considered as a sanctuary of the railway technology in the current information society. ATOS or the Autonomous Decentralized System is not only an application, on a huge scale, of the concept of an epoch making network computing to the downsizing, but is also highly innovative in terms of the diversity and complexity of the technology applied, of its capacity for expansion, and of its complementary functions. The system not only controls the day-to-day operation of 6,200 trains over 1,100 kilometers of track, delivering information which is essential to the company's passengers and work force, but also serves as a safety system covering maintenance work, including track repairs and the inspection of electrical facilities. Total investment in ATOS is expected to reach $360 million. This railway operation control system, which is a comprehensively revamped version of the CTC system used on many lines including the Shinkansen, is a digital application of analog technology at its best. It is among the most sophisticated and interesting applications of an autonomous decentralized system in the industry.

The Monte Carlo simulation is applied to fault tree analyses of the sequential failure logic. In order to make the validity of the technique clear, case studies for estimation of the statistically expected numbers of system failures during (0, t] are conducted for two types of systems using the multiple integration method as well as the Monte Carlo simulation. Results from these two methods are compared. This validates the Monte Carlo simulation in solving the sequential failure logic with respectably small deviation rates for those cases.

A large-scale primarily public system requires in addition to high reliability, a broad range of applications from control to information services. As construction is phased-in this system must be flexible, changeable and able to grows as the needs arise. However, a changing a system may lead to loss of reliability. A system that is able to change and grow in a reliable and stable manner is called an assurance system and the technology it uses is called assurance technology. This paper describes the basic technology, phased-in system construction and so on of assurance technology based on an autonomous decentralized system. It further discusses application of assurance technology to ATOS as an example of a large-scale transport operation control system. Note: ATOS; Autonomous Decentralized Transport Operation Control System

In supervised learning, one of the major learning methods is memorization learning (ML). Since it reduces only the training error, ML does not guarantee good generalization capability in general. When ML is used, however, acquiring good generalization capability is expected. This usage of ML was interpreted by one of the present authors, H. Ogawa, as a means of realizing 'true objective learning' which directly takes generalization capability into account, and introduced the concept of admissibility. If a learning method can provide the same generalization capability as a true objective learning, it is said that the objective learning admits the learning method. Hence, if admissibility does not hold, making it hold becomes important. In this paper, we introduce the concept of realization of admissibility, and devise a realization method of admissibility of ML with respect to projection learning which directly takes generalization capability into account.

A 20 GHz-band GaAs MMIC receiver module has been developed using 0.15 µm HEMT technology process. It incorporates two front end low noise amplifiers, a double balanced diode mixer, and filters. The RF input frequency ranges 20.1 to 21 GHz and the IF output 1.1 to 2 GHz. Test results show an overall conversion gain of more than 27 dB, and less than a 2.2 dB noise figure. The image-rejection ratio greater than 21 dB has been obtained. The isolation between RF and IF ports is better than 27 dB, and between LO and IF is more than 50 dB.

This report introduces a new approach to the time domain analysis of the magnetostatic wave in ferrite materials. The time domain analysis is carried out by the finite difference time domain (FDTD) method. To include the gyromagnetic properties which is the origin of magnetostatic wave, direct differentiation of magnetic dipole moment equation in time and space domains without any approximation are carried out and is combined with Maxwell's equation under the FDTD method. As a result, the possibilities of the analysis on the magnetostatic wave with the FDTD method are confirmed and the validities of this approach are confirmed by some inspections. In addition, the analyses of the nonlinear characteristics on the magnetostatic backward volume waves (MSBVW) are carried out and clarify the dependance of the space profile on the input power.

Standard client-server workflow management systems have an intrinsic scalability limitation, the central server, which represents a bottleneck for large-scale applications. This server is also a single failure point that may disable the whole system. We propose a fully distributed architecture for workflow management systems. It is based on the idea that the case (an instance of the process) migrates from host to host, following a process plan, while the case activities are executed. This basic architecture is improved so that other requirements for Workflow Management Systems, besides scalability, are also contemplated. A CORBA-based implementation of such architecture is discussed, with its limitations, advantages and project decisions described.

In this letter, a simple design of a discrete-time chaos circuit realizing a tent map is proposed. The proposed circuit can be constructed with 13 MOSFET's and 2 capacitors. Concerning the proposed circuit synthesized using switched-current (SI) techniques, the validity of the circuit design is analyzed by SPICE simulations. Furthermore, the proposed circuit is built with commercially-available IC's. The proposed circuit is integrable by a standard CMOS technology.