Topographical changes induced by optical near-field around photo-irradiated nanoparticles were attained using a pulsed laser with a large peak power as a light source. The arrayed structure of nanoparticles was transcribed on urethane-urea azo copolymer film as dent structure. The experiments by the pulsed laser of different wavelength showed that the topographical change was caused by the light absorption. The dent diameter and the dent depth changed depending on the diameter of nanoparticles.

Photoacoustic spectroscopy (PAS) has recently received much attention especially for plant photosynthesis research, because this technique is capable of performing non-destructive measurement without any pre-treatment of specimens. So far we have developed a PAS system equipped with an open photoacoustic cell (OPC), which allows in situ and in vivo measurements of plant photosynthesis of intact undetached leaves. In this study, we have measured photosynthesis reaction using OPC and developed a Confocal Scanning Photoacoustic Microscopy (CSPAM) system, in which PAS is combined with confocal scanning laser microscopy. The system allows simultaneous measurement of acoustic signal and another signal such as fluorescence, and also gives two- and three- dimensional intensity distributions of these signals, thereby giving two- and three- dimensional information about photosynthetic activity of plants.

In industrial assembly lines, seam sealing is a painting process used for making watertight seals or for preventing rusting. In the process, sealant is painted on seams located at the joints of pressed metal parts. We developed a sealing robot system that adjusts the sealing gun motion adaptively to the seam position sensed by a range sensor (a scanning laser rangefinder which senses profile range data). In this paper, we propose a high-speed and highly reliable algorithm for seam position computation from the sensed profile range data around the seam. It is proved experimentally that the sealing robot system used with the developed algorithm is very effective, especially for reducing wasted sealant.

In 1996, Chiu and Hsu proposed a multi-role-based access control (MRBAC) policy. Nevertheless, the Chiu-Hsu scheme can be further enforced by role list, union, and intersection (i. e. containment) to deal with the problems regarding the MRBAC and the object role with different security ranks. The author presents an improvement of the Chiu-Hsu scheme using more detailed list structure. This improvement offers some significant advantages.

The emergence of nomadic applications have recently generated a lot of interest in wireless network infrastructures which support multimedia services. In this paper, we propose a bandwidth routing algorithm for multimedia support in a multihop wireless network. This network can be interconnected to wired networks (e. g. ATM or Internet) or stand alone. Our bandwidth routing includes bandwidth calculation and reservation schemes. Under such a routing algorithm, we can derive a route to satisfy bandwidth requirement for quality-of-service (QoS) constraint. At a source node, the bandwidth information can be used to decide to accept a new call or not immediately. This is specially important to carry out a fast handoff when interconnecting to an ATM backbone infrastructure. It enables an efficient call admission control. The simulation results show that the bandwidth routing algorithm is very useful in extending the ATM virtual circuit service to the wireless network. Different types of QoS traffic can be integrated in such a dynamic radio network with high performance.

Non-real-time (NRT) services such as nrt-VBR, ABR and UBR traffic are intended for data applications. Although NRT services do not have stringent QoS requirements for cell transfer delay and cell delay variation, ATM networks should provide NRT services while considering other criteria to ensure an excellent performance such as cell loss ratio (CLR), buffer size requirement and service fairness. Service fairness means that networks should treat all connections fairly. That is, connections with low arrival rates should not be discriminated against. In addition, given a fixed buffer size for a connection, reducing the maximum number of cells in a buffer during the lifetime of a connection can lead to a low CLR due to buffer overflow. Thus, these criteria should be considered as much as possible when designing a cell scheduler to provide NRT services. Whereas most of the conventional cell scheduling schemes are usually appropriate for one performance criterion, but inappropriate for another one. In this work, we present a novel cell scheduling scheme, called buffer minimized and service fairness (BMSF), to schedule NRT services in ATM networks. Using probability constraints and selecting a connection with the longest buffer size to transmit first allow BMSF to attain a satisfactory performance with respect to maximum buffer size requirement, CLR, and service fairness in terms of the maximum buffer size and cell waiting delay criteria. Simulation results demonstrate that BMSF performs better than some conventional schemes in terms of these criteria, particularly when NRT services have diverse arrival rates. Thus, the BMSF scheme proposed herein can feasibly schedule NRT services in ATM networks.

Waveguide characteristics of beam-expanders integrated with laser diodes were numerically analyzed by the beam propagation method (BPM) or the finite-difference time-domain (FD-TD) method. It was demonstrated that the vertically and horizontally hybrid tapered structure or an optimized refractive index in the cladding layer improve the trade-off relationship between fiber coupling efficiency and lasing characteristics. It was also demonstrated that exponentially tapering stripe width can reduce device length without sacrificing device properties.

A theoretical study on high slope-efficiency phase-shifted DFB laser diodes is presented. We have proposed a new grating structure called asymmetrically-pitch-modulated (APM) grating, and calculated its slope- efficiency and single-mode-yield. In order to take into account the modulated grating period; we have developed an F-matrix which directly includes a chirped grating structure. APM phase-shifted DFB laser diodes consist of a uniform grating in one half section of the cavity and a chirped grating in the other half. This structure causes asymmetrical field distribution inside the cavity and the optical output power from one facet is larger than that from the other facet. According to the simulation results, when the normalized coupling coefficient κ L is 3.0, the front-to-rear output power ratio is 2.6, while the single-mode-yield remains at 100%, and simultaneously the slope-efficiency improvement becomes 65% better than that of ordinary quarter-wave phase-shifted DFB lasers of the same κ L value.

We propose a device called the Waveguide width abruptly EXpanded Spot-Size-Converter integrated Laser Diode (WEX-SSC-LD) that has been designed to improve lasing characteristics by achieving a steep photoluminescence wavelength change along the cavity. The waveguide parameter was optimized by a three-dimensional beam propagation method to reduce mode conversion and absorption losses. The WEX-SSC-LD's showed superior lasing characteristics such as threshold currents of 5.8 mA at 25C and 19 mA at 85C and operation current of 57.5 mA at an output power of 10 mW for 85C. These excellent lasing characteristics were achieved due to the steeper bandgap-energy shift in the SSC section near the LD section side by introducing the WEX-SSC structure as well as the high-quality MQW active layer grown by selective MOVPE and the precisely controlled pn-pn current blocking structure. The coupling loss to normal single-mode fiber was as low as 1.8 dB while maintaining a large coupling tolerance of 1.8 µm. These excellent coupling characteristics are very promising for passively aligned optical modules.

We describe the fabrication method and characteristics of hybrid external cavity lasers composed of a spot-size converter integrated LD (SS-LD) and a UV written Bragg grating in a planar lightwave circuit (PLC) on a Si substrate. The SS-LD is passively aligned on a Si platform formed in the PLC, and the UV grating is created in the PLC with ArF laser irradiation through a phase mask. This structure enables us to fabricate a stable single-mode laser with a precisely controllable oscillation wavelength. By using the above techniques, we obtained a threshold current of 7-8 mA and a side mode suppression of 37 dB for an external cavity laser operating at 1.3 µm. Moreover, we successfully demonstrated a four-channel external cavity laser with a wavelength interval of 2 nm 0.1 nm by integrating 4 SS-LDs on a PLC and controlling the Bragg wavelengths with ArF laser irradiation without a phase mask.

A 160 GHz colliding-pulse mode-locked laser diode (CPM-LD) was stabilized by injection of a stable master laser pulse train repeated at a 16th-subharmonic-frequency (9.873 GHz) of the CPM-LD's mode-locking frequency. Synchroscan steak camera measurements revealed a clear pulse train with 16-times repetition frequency of the master laser pulse train for the stabilized CPM-LD output, indicating that CPM-LD output was synchronized to the master laser and that the timing jitter was also reduced. The timing jitter of the stabilized CPM-LD was quantitatively evaluated by an all-optical down converting technique using the nonlinearity of optical fiber. This technique is simple and has a wider bandwidth in comparison to a conventional technique, making it possible to accurately measure the phase noise of ultrafast optical pulse train when its repetition frequency exceeds 100 GHz. The electrical power spectra measurements indicated that the CPM-LD's mode-locking frequency was exactly locked by the injection of the master laser pulse train and that the timing jitter decreased as the injection power increased. The timing jitter was reduced from 2.2 ps in free running operation to 0.26 ps at an injection power of 57 mW, comparable to that of the master laser (0.21 ps).

In a client-server system, when LRU or its variant buffer replacement strategy is used on both the client and the server, the cache performance on the server side is very poor mainly because of pages duplicated in both systems. This paper introduces a server buffer replacement strategy which uses a replaced page-id than a request page-id, for the primary information for its operations. The importance of the corresponding pages in the server cache is decided according to the replaced page-ids that are delivered from clients to the server, so that locations of the pages are altered. Consequently, if a client uses LRU as its buffer replacement strategy, then the server cache is seen by the client as a long virtual client LRU cache extended to the server. Since the replaced page-id is only sent to the server by piggybacking whenever a new page fetch request is sent, the operation to deliver the replaced page-id is simple and induces a minimal overhead. We show that the proposed strategy reveals good performance characteristics in diverse situations, such as single and multiple clients, as well as with various access patterns.

File system buffers provide memory space for data being transferred to and from disk and act as caches for the recently used blocks, and the buffer manager usually reads ahead data blocks to minimize the number of disk accesses. However, if several multimedia files with different consumption rates are accessed simultaneously from the file system in which LRU buffer replacement strategy is used, the read-ahead blocks of the low rate file are unloaded from memory to be used for loading a data block of a high data rate file, therefore they should be reloaded again into memory from disk when these blocks are actually referenced. This paper proposes and implements a new buffer cache management scheme for a multimedia file system and analyzes the performance of the proposed scheme by modifying the file system kernel of FreeBSD. In this proposed scheme, initially, some buffers are allocated to each opened multimedia file, privately, then these buffers are reused for other data blocks of that file when they are loaded from the disk. Moreover, the number of private buffers allocated for the file is dynamically adjusted according to its data rate. An admission control scheme is also proposed to prevent opening of a new file which may cause overloads in the file system. Experimental results comparing proposed scheme with the original FreeBSD and a simple CTL-based model show that the proposed buffer management scheme could support the realtime play back of several multimedia files with various data rates concurrently without helps of a realtime CPU and disk scheduling.

The essence of this work is to introduce an interaction between the physical layer and higher network layers, thus enabling a more practical utilization of multiuser detection and supporting services with different QoS parameters. In this paper, a new hybrid TDMA/ Multicode (MC)-CDMA medium access control utilizing multiuser detection is proposed and analyzed. Further, two traffic flow control approaches accompanied the TDMA/MC-CDMA system are proposed. One approach deterministically controls the flow of traffic into the TDMA slots, while the other statistically controls the flow of traffic depending on the instantaneous changes in the traffic load. The two approaches have been examined under a wide range of traffic characteristics where AWGN is only considered besides the mutual interferers from other intracell users. Both approaches show superiority as well as less sensitivity in terms of BER to the traffic changes compared with the conventional system.

This article shows a Boolean Multivalued logical model of varying confirmation by observation of events in human inference and, as an introductory example, applies the model to solve Hempel's paradox of the ravens.

Today's market share of Intelligent Network (IN) service is growing rapidly in wireless networks due to the rapid advances in wireless telecommunication and IN technology. To guarantee network independent IN services, mobility of IN service subscribers has to be taken into account. This paper proposes new designs of Global Service Logic for the IN service enhancement, which increase call completion rates in wired and wireless intelligent networks. In order to apply this logic to wireless service subscribers as well as wired service subscribers, we implement a Queue Manager applied to the call queuing service feature in the Service Control Point (SCP). In the case of wireless service subscribers, the Home Location Register (HLR) handles the service registration flags to notify the Queue Manager of the corresponding service subscribers' mobility. In addition, we present a dynamic queue management mechanism, which dynamically manages the queue size based on the parallel server queuing model as the wireless subscribers roam the service groups due to their mobility characteristics. In order to determine the queue size allocated by the dynamic queue manager, we simulate the relationship between the number of the subscriber's terminals and the drop rate by considering the service increment rate. Moreover, the appropriate waiting time in the queue as required is simulated according to the above relationship. We evaluate call completion rates of the proposed mechanism in the paper by comparing to that of the existing mechanism.

On the Internet, a Quality of Service (QoS) guaranteed services are increasingly being demanded, and the Internet Engineering Task Force (IETF) is developing the specification documents for the QoS services intensively. This overview details the technical rationales underlining the contents of the specification documents developed by the IETF for Differentiated Services (DiffServ)--to provide QoS guarantee services in the large IP networks-- and Policy Framework--to manage DiffServ compliant networks. The IP networks with DiffServ consist of boundary routers and interior routers. These routers are composed of packet classifiers and marker, shaper, and policing function. Many vendors have developed DiffServ-compliant routers with gigabit interfaces. An example of an implementation of a DiffServ-compliant router and a demonstration of a QoS service using this router are presented here. The Policy Framework is expected to be one of the promising management solutions to co-operate with and manage many DiffServ-compliant routers. An experiment that adopts the Policy Framework to a DiffServ compliant network is also outlined.

The increasing diversity in Internet applications necessitates extended Internet architecture that can differentiate forwarding treatment of different types of flows. Diffserv can be a solution to the problem when it is augmented by several additional components. In this paper we describe various issues and possible directions in augmenting Diffserv. We present our analysis of Diffserv architecture, anticipated developments to augment Diffserv architecture, and potential applications of Diffserv.

A novel K-band MMIC frequency doubler has been developed using resistive series feedback circuit. The doubler exhibits much better D/U ratio, smaller output power variation against ambient temperature and lower power consumption than those of the conventional single-ended doubler. This paper presents the simulation results on the effect of the resistive series feedback by harmonic balance methods. To obtain practical and accurate simulation results, newly developed gate charge model for Cgs and Cgd is introduced. The fabricated result of the proposed MMIC is also demonstrated.

In this paper, we propose the high-level service architecture supporting multimedia multicast. The proposed architecture specifies network-oriented and lightweight communication management, which includes group management, multiparty call control and multicast connection/multiple connections control. Many of the existing approaches handling multimedia multicast applications are dependent on specific transport technologies, such as the Internet and ATM, and lack effective communication management. On the other hand, our approach defines flexible and extensible communication management that can be applied to a variety of multimedia multicast applications, independently of transport technologies. Our architecture supports the separation of control from a terminal, which enables remote control and control mobility, so that a user can use a multicast service in a more various way. The architecture is overlaid above legacy transport networks so that the existing network protocols are used for connection control. This minimizes the modification to a legacy transport network and enhances the practicality of the architecture. In addition, terminal manager and virtual device concepts are introduced that hide the details of physical devices from an application designer. The architecture consists of several service components that effectively interact with each other on a distributed platform. To verify and evaluate our architecture, we have prototyped the high-level service architecture on a CORBA platform and analyzed the architecture using a simulation.