A detailed numerical solution of the design criteria of in-phase lateral and single-longitudinal-mode operation GaInAsP/InP DFB laser arrays is presented. The analysis, including broad-area pumped and stripe-geometry pumped index-guided arrays, was carried out on the basis of the eigenvalue equation method. It is shown that there exists a cut-off array pitch co, at which all of the higher-order array modes are cut off. For the pitch larger than the cut-off pitch co, the modal discrimination is evaluated by the threshold gain difference between the in-phase lateral and higher-order array modes. As a result, the modal discrimination was found to decrease with the increase of the number of elements and the array pitch which is limited to be smaller than twice the cut-off pitch co to attain a stable in-phase lateral- and single-longitudinal-mode operation.

In high-speed packet networks, protocol processing overhead time becomes remarkable in determining the system performance. In this paper, we present a new Selective-Repeat ARQ scheme (called Block SR-ARQ sheme), in which a packet is transmitted or retransmitted in the same way as basic SR-ARQ scheme, but a single acknowledgement packet is used to acknowledge a block of packets. The maximum number of packets acknowledged by an acknowledgement packet is defined as block size. We analyze the system throughput and the average packet delay over the system, and the accuracy of approximately analyzed results is validated by simulation. Furthermore, we show that there exists an optimal block size which obtains both the maximum throughput and the minimum average packet delay.

This paper investigates a two-class priority queue with decrementing service of a parameter (k1=, k2=k,1k) which operates as follows: Starting once a class-1 message service, a single server serves all messages in queue 1 until it becomes empty. After service completion in queue 1, the server switches over to queue 2 and continues serving messages in queue 2 until either queue 2 becomes empty, or the number of messages decreases to k less than that found upon the server's arrival at queue 2, whichever occurs first. It is assumed that arrival streams are Poissonian, message service times are generally distributed, and switch-over times are zero. We derive queue-length generating functions and LSTs of message waiting time distributions.

This paper describes the endurance of a ceramic hydrophone to measure high acoustic pressures at the focal point of Extracorporeal Shockwave Lithotripter (ESWL).

The demand for mobile communications is continuing to grow, but there is a limit on the radio frequency resources. Micro cellular systems are a strong solution to this problem. However, Forced Call Termination (FCT) and Channel Changing (CC) occur frequently in these systems because of their small cell size. This paper proposes a new Dynamic Channel Assignment (DCA) strategy which uses information of moving direction of Mobile Stations (MSs) to reduce FCT and CC. This strategy, the MD (Moving Direction) strategy, is compared with other major DCA strategies by simulating a one-dimensional service area covering a road, such as an expressway. The simulation shows that the MD strategy performs better than the other strategies with regard to FCT, CC, and carried load. FCT is an especially important factor in the quality of service. The MD strategy reduces FCT and has the largest carried load of the strategies, which means that it has the most efficient channel usage. This is an attractive characteristic of the MD strategy for micro cellular systems.

In the present paper we present a mathematical theory for the transient analysis of probabilistic models relevant to communication networks. First we review the z-transform method, the matrix method, and the Laplace transform, as applied to a class of birth-and-death process model that is relevant to characterize network traffic sources. We then show how to develop transient solutions in terms of the eigenvalues and spectral expansions. In the latter half the paper we develop a general theory to solve dynamic behavior of statistical multiplexer for multiple types of traffic sources, which will arise in the B-ISDN environment. We transform the partial differential equation that governs the system into a concise form by using the theory of linear operator. We present a closed form expression (in the Laplace transform domain) for transient solutions of the joint probability distribution of the number of on sources and buffer content for an arbitrary initial condition. Both finite and infinite buffer capacity cases are solved exactly. The essence of this general result is based on the unique determination of unknown boundary conditions of the probability distributions. Other possible applications of this general theory are discussed, and several problems for future investigations are identified.

Modeling and performance analysis have played an important role in the economical design and efficient operation of switching systems, and is currently becoming more important because the switching systems should handle a wide range of traffic characteristics, meeting the grade of service requirements of each traffic type. Without these techniques we could no longer achieve economy and efficiency of the switching systems in complex traffic characteristic environments. From the beginning of research on electronic switching systems offering circuit-switched applications, Stored Program Control (SPC) technology has posed challenges in the area of modeling and performance analysis as well as queueing structure, efficient scheduling, and overload control strategy design. Not only teletraffic engineers and performance analysts, but also queueing theorists have been attracted to this new field, and intensive research activities, both in theory and in practice, have continued over the past two decades, now evolving to even a broader technical field including traditional performance analysis. This article reviews a number of important issues that have been raised and solved, and whose solutions have been reflected in the design of SPC switching systems. It first discusses traffic problems for centralized control systems. It next discusses traffic problems inherent in distributed switching systems.

Processors are important resources of stored program control (SPC) switching systems, and estimation of their workload level is crucial to maintaining service quality. Processor utilization is measured as processor usage per unit time, and workload level is usually estimated from measurement of this utilization during a given interval. This paper provides an approximate distribution of processor utilization of SPC switching systems, and it provides a method for designing an overload detection scheme. This method minimizes the observation interval required to keep overload detection errors below specified values. This observation interval is obtained as an optimal solution of a linear programming.

The velocity overshoot and hot carrier effects in thin-film SOI-nMOSFETs have been studied using a two-dimensional device simulator based on the energy transport model. It has been found that the velocity overshoot effect in a nearly-intrinsic device becomes pronounced in the short channel region because of their high carrier mobility. The distribution of the electron velocity in a 0.2 µm channel length SOI device shows that the velocity overshoot takes place over the whole channel region, which enhances the drive capability significantly. The behaviors of hot carriers injected into the gate oxide and the back oxide have been simulated for the first time by using the energy distribution functions of electrons and holes at the SOI-SiO2 interface and solving the current continuity equation in the oxide layer. It has been found that hot carriers are injected not only into the gate oxide but also into the back oxide, which can degrade hot-carrier reliability in small-featured thin-film SOI-MOSFETs.

The embedded Markov processes associated with Markovian queueing systems are closely related, and their relationships are important for establishing an analytical basis for performance evaluation techniques. As a first step, we analyze the embedded processes associated with a general M/M/1 queueing system. Linear transformations between the infinitesimal generators and the transition probability matrices of embedded processes at arrival and departure times are explicitly derived. Based upon these linear transformations, the equilibrium distributions of the system states at arrival and departure times are obtained and expressed in terms of the equilibrium distribution at arbitrary times. The approach presented here uncovers an underlying algebraic structure of M/M/1 queueing systems, and establishes an algebraic methodology for analyzing the equilibrium probabilities of the system states at arrival and departure times for more general Markovian queueing systems.

A multicast error control protocol proposed by Metzner is generalized and the performance of the proposed protocol on random error channels (binary symmetric channels) is analyzed. The proposed protocol adopts an encoding procedure based on a product code structure, whith enables each destined user terminal to decode the received frames with the Reddy-Robinson algorithm. As a result, the performance degradation due to the re-broadcasting of the replicas of the previously transmitted frames can be circumvented. The numerical results for the analysis and the simulation indicate that the proposed protocol yields higher throughput and less degradation of throughput with an increase of the number of destined terminals.

Separability is a valuable property of nonlinear mappings. By exploiting this property, computational complexity of many numerical algorithms can be substantially reduced. In this letter, a new algorithm is presented that detects the separability of nonlinear mappings using the concept of "computational graph". A hybrid algorithm using both the top-down search and the bottom-up search is proposed. It is shown that this hybrid algorithm is advantageous in detecting the separability of nonlinear simultaneous functions.

We fabricated a 4 GHz thin-base (120 nm) lateral bipolar transistor on bonded SOI by applying our sidewall self-aligning base process. By applying this device to BiCMOS circuits, bipolar transistor base junction capacitance, and MOSFET source and drain capacitance were very small. Furthermore, MOSFET and bipolar transistors are completely isolated from each other. Thus, it is easy to optimize MOS and bipolar processes, and provide protection from latch-up problems and soft errors caused by α-particles. In this paper, we describe device characteristics and discuss the crystal quality degradation introduced by ion implantation, and two dimensional effects of base diffusion capacitance.

For the connection request procedure in mobile communication systems, a previous study had shown that the 3-channel systems provide the haighest maximum of stable per channel throughput. In this paper, we propose and study a new algorithm, called the Parallel Collision Resolution Algorithm, which can be implemented in a Q-channel connection request environment, where Q3. For the implementation, the channels are arranged in R groups, where R is a positive integer. The collision resolution scheme distributes the collided messages over all the groups so that throughput and delay measures can be improved. At any point in time, there can be a maximum of R collision resolution schemes operational irrespective of the channel or the group number over which collisions occurred. The performance measures are estimated by computer simulation. Under the new algorithm, almost the same level of the perchannel stable throughput measure of a 3-channel network can be achieved in networks for which Q3. This feature allows freedom to the network designer to employ a higher number of connection request channels without forfeiting high channel utilization rates. When Q is an integral multiple of 3, the maximum stable per channel throughput level achieved can be the same as that achieved by the 3 channel system, if the grouping of channels is such that each group consists of 3 channels. When Q is not an integral multiple of 3, the intuitive strategy of organizing the channels in such a way that Q/3 groups consist of 3 channels each and one group consists of (Q mod 3) channels, may result in much degraded performance. It is found that, if the channels are so organised that no group is composed of (Q mod 3) channels, the performance levels can be substantially enhanced. Also, under the new algorithm, the delay measure is significantly improved, particularly in schemes like the mobile satellite systems with high propagation delays. We conclude that the new scheme presents a promising collision resolution methodology for connection request procedures.

One model of a laser is a set of differential equations called the Maxwell-Bloch equations. Actually, in a physical system, causing a chaotic behavior is very difficult. However the chaotic behavior can be observed easily in the system which has a mirror to feedback the delayed output.

Frequency Selective Screens (FSS) with conductor or complementary aperture array are investigated. The electric current distribution on conductor or the magnetic current distribution on aperture is determined by the moment method in the spectral domain. In addition, the power reflection coefficients are calculated and the scattering properties are considered.

In this paper, we propose a new network organizing method for packet radio networks, a layered self-organizing method. In the layered self-organizing network, whole service area is divided into multiple sub-areas and one base station is settled in each sub-area. Communication links are settled in shorter time than the conventional self-organizing method. We evaluate the network organizing performance of the method by using simulations.

Heat recovery methods and the amount of heat that can be recovered from fuel cell exhaust gas is described. The cooling performance of an absorption refrigerator that uses fuel cell waste heat is also described. Two heat recovery methods from the exhaust gas are considered: one uses heat recovery from mixed exhaust gas from the cathode side of the cells and the reformer (mixed type); the other uses separate heat recovery from these sites (separate type). Simulation shows that the amount of heat recovered between 60 and 75 with the separate type of heat recovery is greater than with the mixed type of heat recovery. The cooling capacity of the refrigerator using the separate type heat recovery and recovering heat between 65 and 85 is about 2.5 times that of one using a generator (heat source) with a constant 85 temperature.

Signature analysis using a Multiple-Input LFSR as the output response compaction circuit is widely adopted in actual BIST schemes. While aliasing probabilities for random errors are usually very small, MI-LFSRs are tend to fail detecting diagonal errors. A spot error, which include the diagonal error as a particular case, is defined as multiple bit crrors adjacent in space and in time domain. Then, shuffling of interconnection between CUT output and MI-LFSR input is studied as a scheme to prevent aliasing for such errors. The condition for preventing aliasing due to a predetermined size of single spot error is shown. Block based shuffling and the shortened one are proposed to realize required distance properties. Effect of shuffling for multiple spot errors is examined by simulation showing that shuffling is effective also for a certain extend of multiple spot errors.

CFGs (context-free grammars) with various types of memory are introduced and their generative capacities are investigated. For an automata-theoretic characterization, a new type of automaton called partitioning automaton is introduced and it is shown that the class of languages generated by CFGs with memory type X is equal to the class of languages accepted by partitioning automata of type X.