In this paper, we implemented practical resource adaptation mechanism for broadband application environment especially suitable for portable computers (note PCs) with limited power supply. Continuous development of portability enhancement and increasing computation with less power consumption for battery operating environment in note PC equips with intelligent resource controlling mechanism embedded inside the hardware. In such environment, where occasional environmental changes take in place rapidly, adaptive and collaborative controls of resources are required. Optimization of resource based on power supply management is dedicated to the operating environment. Bi-directional, user, application, operating system and device aware interface for resource configuration/management is extended to the current Unix operating system by implementing application programming interface of Advanced Configuration and Power Interface (ACPI). Traditional operating system conceals the active device probing and controlling method autonomously. Implementation of "State handler daemon" interface enables applications and application users to monitor and adapt the resources available during the operation. Thick collaboration between application and devices that are reserved in its limited environments economizes the consuming device utilization resulting: for example, life extension of battery life and effective network bandwidth adaptation. We focused on DVTS (Digital Video Transport System) as a typical broadband application. Evaluation shows 125 minutes of continuous battery operation with battery life extension compared to 70 minutes with traditional systems. Collaboration with network device management enables 100% packet transfer compared to 89% without any Resource adaptations.

A new type of triple-band antenna is introduced by combing a tab monopole antenna (TMA) and a planar inverted F antenna (PIFA). The antenna configuration is shown to operate at three discrete frequencies: GSM 900, GSM 1800 (DCS) and GSM 1900 (PCS). The performance of an antenna is presented as well as the results of the computer simulations with a software package based on the Finite Element Method. The simulated results with the real antenna's experimental results. The advantage of the design suggested in this paper is its simplicity of manufacturing and low cost.

The Fat-Btree which is a new parallel B-tree structure has been proposed to improve the access performance of shared-nothing parallel database systems. Since the Fat-Btree has only a part of index nodes on each processing element, it can reduce the synchronization cost in update operations. For these reasons, both retrieval and update operations can be processed at high throughput compared to previously proposed parallel B-tree structures for shared-nothing computers. Though we tried to apply some conventional concurrency control methods to the Fat-Btree, e.g., B-OPT and ARIES/IM, which were designed for shared-everything machines, we found that these methods are not always appropriate for the Fat-Btree. In this paper, it is shown that the conventional methods are not suitable for the Fat-Btree and other parallel B-trees. We propose a new deadlock free concurrency control protocol, named INC-OPT, to improve the performance of the Fat-Btree more effectively than the B-OPT and ARIES/IM. Furthermore, in order to prove that the Fat-Btree provides the impact on the performance of shared-nothing parallel databases, we compare the real performance of three types of parallel B-tree structures, Fat-Btree, Copy-Whole-Btree, and Single-Index-Btree, on an nCUBE3 machine where the INC-OPT is applied.

To elucidate the mechanism of topographic organization, we propose a simple topographic mapping formation model from generalized cell layer to generalized cell layer. Here generalized cell layer means that we consider arbitrary cell neighborhood relations. In our previous work we investigated a topographic mapping formation model between one dimensional cell layers. In this paper we extend the cell layer structure to any dimension. In our model, each cell takes a binary state value and we consider a class of learning principles which are extensions of Hebb's rule and Anti-Hebb's rule. We pay special attention to correlation type learning rules where a synaptic weight value is increased if pre and post synaptic cell states have the same value. We first show that a mapping is stable with respect to the correlational learning if and only if it is semi-embedding. Second, we introduce a special class of weight matrices called band type and show that the set of band type weight matrices is strongly closed and such a weight matrix can not yield a topographic mapping. Third, we show by computer simulations that a mapping, if it is defined by a non band type weight matrix, converges to a topographic mapping under the correlational learning rules.

This paper introduces the concept of hierarchical testability of data paths for delay faults. A definition of hierarchically two-pattern testable (HTPT) data path is developed. Also, a design for testability (DFT) method is presented to augment a data path to become an HTPT one. The DFT method incorporates a graph-based analysis of an HTPT data path and makes use of some graph algorithms. The proposed method can provide similar advantages to the enhanced scan approach at a much lower hardware overhead cost.

Sports scheduling concerns how to construct a schedule of a sports competition mathematically. Many sports competitions are held as round-robin tournaments. In this paper, we consider a particular class of round-robin tournaments. We report some properties of round-robin tournaments and enumerate home-away tables satisfying some practical requirements by computer search.

Most conventional studies on self-stabilization have been indifferent to the vulnerability under convergence. This paper investigates how mutual exclusion property can be achieved in self-stabilizing rings even for illegitimate configurations. We present a new method which uses a state with a large state space to detect faults. If some faults are detected, every process is reset and not given a privilege. Even if the reset values are different between processes, our protocol mimics the behavior of Dijkstra's unidirectional K-state protocol. Then we have a fast and safe mutual exclusion protocol. Simulation study also examines its performance.

A new rewritable medium utilizing a guest-host (G-H) polymer-dispersed liquid-crystal (PDLC) film has been developed in our laboratory. The medium is thermally written and electrically erased. It is portable, like paper, and can store recorded data because of the memory effect of smectic-A liquid crystal (SmA LC), which exhibits bistable states of homeotropic and focal conic alignment. Dichroic dye is added to the SmA LC to form the G-H type. An evaluation of the characteristics revealed that this medium exhibits both high contrast and good reliability.

Various types of wavelength-selectable light sources (WSLs) and wavelength-tunable laser diodes (LDs) have been developed, and the one based on an array of distributed feedback (DFB) laser diodes (LDs) has the advantage of tuning that is both simple and stable tuning. It requires only the selection of a DFB-LD and a temperature control. We report on monolithically integrated WSLs with a DFB-LD array, multimode interference (MMI) coupler, semiconductor optical amplifier (SOA), and electro-absorption (EA) modulator. To make them compact, we introduced microarray structures and to ensure that they were easy to fabricate, we used selective area growth. For the WSL with an integrated EA modulator, we developed a center-temperature-shift method that optimizes the detuning wavelength between the lasing wavelength and the absorption edge wavelength of the EA-modulator. Using this method, we obtained a uniform extinction ratio and were able to demonstrate error-free 2.5-Gb/s transmission over a 600-km fiber span. A CW-WSL without an EA-modulator should provide enough output power to compensate the loss caused by the external modulators, but the high-power operation of a CW-WSL is sensitive to optical feedback from the front facet. We therefore used an angled facet in our WSLs and eliminated a mode hop problem. More than 20 mW of fiber-coupled power was obtained over 23 ITU-T channels on a 50-GHz grid.

Clustering is one of the most important topics in the field of knowledge discovery from databases. Especially, hierarchical clustering is useful since it gives a hierarchical view of a whole database and can be used to guide users in browsing a huge database. In many cases, clustering can be modeled as a graph partitioning problem. When an appropriate distance function between database objects is given, a database can be viewed as an edge-weighted complete graph, where vertices are database objects and weights of edges are distances between them. Then a process of MST (Minimal Spanning Tree) construction can be viewed as a process of a single-linkage agglomerative clustering process for database objects. In this paper, we propose an efficient MST construction method for a large complete metric graph, which is derived from a database with a metric distance function defined on it. Our method utilizes a metric index to reduce the number of distance calculations. The basic idea is to exclude those edges less probable to be a part of an MST by using the metric postulate. For this purpose, we introduce a new metric index named MetricMatrix. Experimental results show that our method can drastically reduce the number of distance calculations needed for MST construction in comparison with the classical method.

A novel rough neural network (RNN) structure and its application are proposed in this paper. We principally introduce its architecture and training algorithms: the genetic training algorithm (GA) and the tabu search training algorithm (TSA). We first compare RNN with the conventional NN trained by the BP algorithm in two-dimensional data classification. Then we compare RNN with NN by the same training algorithm (TSA) in functional approximation. Experiment results show that the proposed RNN is more effective than NN, not only in computation time but also in performance.

In this paper, we consider optimal mirror allocation problems for the purpose of load balancing in network servers. We focus on constructing high-reliability networks and propose the optimal mirror allocation model such that the system reliability is maximized subject to costs and delays, in view of the trade-off between the reliability and cost. This optimization model is capable of dealing with various kinds of network topologies, although for simplicity, we assume the read-only situation. We formulate this optimization problem into a 0-1 integer programming model, and we use an approximate method for numerical analysis in order to analyze more large-scale systems. Our objective is to find the optimal mirror allocation by solving this model, and to show quantitatively the general characteristics of the load balancing and the improvement of the system reliability by the distributed mirror allocation.

A cascode crystal oscillator is widely used for the stable frequency source of mobile communication equipments. Recently, IC production of the cascode crystal oscillator has become necessary. The cascode crystal oscillator is composed of a colpitts crystal oscillator and a cascode connected base-common buffer amplifier. The base bypass condenser prevents the area size reduction. In this paper, we have proposed the new structures of the cascode crystal oscillator suitable for integrated circuits. The proposed circuits have the advantages on reduction of the area size and start-up time without deteriorating the frequency stability against the load impedance variation and other performances. The simulation and experiment have shown the effectiveness of the proposed circuits.

A highly stable oven-controlled crystal oscillator (OCXO) with low phase-noise characteristics has been developed using a dual-mode SC-cut quartz crystal oscillator. The OCXO uses a conventional oven-control system for coarse compensation and a digital-correction system, which uses B-mode signal in an SC-cut resonator as a temperature sensor, for fine compensation. Combining these two forms of compensation greatly improves the stability of the C-mode frequency without requiring a double-oven system. The experimental results indicated that the frequency stability of the proposed OCXO, including the frequency-temperature hysteresis, is ten times better than that of a conventional, free-running OCXO. The results also indicated that the proposed OCXO has good frequency retraceability and low phase-noise characteristics.

Recently, Kasahara and Murakami proposed new product-sum type public-key cryptosystems with the Chinese remainder theorem, Methods B-II and B-IV. They also proposed a new technique of selectable encryption key, which is referred to as 'Home Page Method (HP Method).' In this paper, first, we describe Methods B-II and B-IV. Second, we propose an effective attack for Method B-II and discuss the security of Methods B-II and B-IV. Third, applying the HP Method to Methods B-II and B-IV, we propose new product-sum type PKC with selectable encryption key. Moreover, we discuss the security of the proposed cryptosystems.

Several gateway-based congestion control mechanisms have been proposed to support an end-to-end congestion control mechanism of TCP (Transmission Control Protocol). One of promising gateway-based congestion control mechanisms is a RED (Random Early Detection) gateway. Although effectiveness of the RED gateway is fully dependent on a choice of control parameters, it has not been fully investigated how to configure its control parameters. In this paper, we analyze the steady state behavior of the RED gateway by explicitly modeling the congestion control mechanism of TCP. We first derive the equilibrium values of the TCP window size and the buffer occupancy of the RED gateway. Also derived are the stability condition and the transient performance index of the network using a control theoretic approach. Numerical examples as well as simulation results are presented to clearly show relations between control parameters and the steady state behavior.

We propose a frequency stabilization system for laser diodes (LD's), in which the major parameters in the stabilization process can be controlled in respond to the monitored frequency noise characteristics in real-time basis. The performance of this system was also tested through stabilizing a 35 mW visible LD. The center frequency of the LD has been stabilized by negative electrical feedback based on Pound-Drever-Hall technique. The linewidth of the LD has been reduced by adapting optical feedback from resonant confocal Fabry-Perot (CFP) cavity. The controlling parameters, especially gain levels and frequency responses of the negative electrical feedback loop can be manipulated to remove the instantaneous frequency noise by monitoring power spectral density (PSD) of the frequency error signals in the real-time basis. The achieved PSD of frequency noise of a sample LD stabilized by the present system was less than 1105 Hz2/Hz for the Fourier frequency < 10 MHz. The reduced linewidth was estimated to be narrower than 400 kHz. The achieved minimum square root of the Allan variance was 3.910-11 at τ = 0.1 msec.

This paper describes the recent progress made in developing wavelength tunable semiconductor light sources for WDM applications. Wide and quasi-continuous wavelength tunings were investigated for a wavelength-selectable laser and a wavelength tunable distributed Bragg reflector (DBR) laser having a super structure grating (SSG). A wavelength-selectable laser consisting of a DFB laser array, a multi-mode interferometer (MMI), and a semiconductor optical amplifier (SOA) demonstrated a quasi-continuous tuning range of 46.9 nm by using temperature control. A wavelength-tunable DBR laser with SSG exhibited a quasi-continuous tuning range of 62.4 nm by using three tuning current controls. Wavelength stabilization was also demonstrated under the temperature variations of 5.

A feedback-based congestion control mechanism is essential to realize an efficient data transfer service in packed-switched networks. TCP (Transmission Control Protocol) is a feedback-based congestion control mechanism, and has been widely used in the current Internet. An improved version of TCP called TCP Vegas has been proposed and studied in the literature. It can achieve better performance than TCP Reno. In previous studies, performance analysis of a window-based flow control mechanism based on TCP Vegas only for a simple network topology has been performed. In this paper, we extend the analysis to a generic network topology where each connection is allowed to have a different propagation delay and to traverse multiple bottleneck links. We first derive equilibrium values of window sizes of TCP connections and the number of packets waiting in a router's buffer. We also derive throughput of each TCP connection in steady state, and investigate the effect of control parameters of TCP Vegas on fairness among TCP connections. We then present several numerical examples, showing how control parameters of TCP Vegas should be configured for achieving both stability and better transient performance.

The problem of detecting straight lines arises frequently in image processing and computer vision. Here we consider the problem of extracting lines from range images and more generally from sets of three-dimensional (3D) points. The problem is stated as follows. Given a set Γ of points in 3D space and a non-negative constant , determine the line that is at a distance at most ε from the maximal number of points of . The extraction of multiple lines is achieved iteratively by performing this best line detection and removing at each iteration the points that are close to the line found. We consider two approaches to solve the problem. The first is a simple approach that selects the best line among a randomly chosen subset of lines each defined by a pair of edge points. The second approach, based on tabu search, explores a larger set of candidate lines thus obtaining a better fit of the lines to the points. We present experimental results on different types of three-dimensional data (i) range images of polyhedral objects (ii) secondary structures (helices and strands) of large molecules.