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 the third generation cellular radio system, a variable spreading factor (VSF) and a multi-code (MC) schemes are adopted to support multirate data transmission. Although these schemes affect the statistics of intercell interference and therefore the spectral efficiency, their precise impact is not completely understood. In this letter, a closed-form solution for the moments of the reverse link intercell interference is derived and the spectral efficiency is calculated from the solution. It is shown that the intercell interference gives a bad effect to the spectral efficiency as the portion of high rate user in a cell is increased.

We show how to apply the Feng-Rao decoding algorithm and the Feng-Rao bound for the Ω-construction of algebraic geometry codes to the L-construction. Then we give examples in which the L-construction gives better linear codes than the Ω-construction in certain range of parameters on the same curve.

The reconfiguration latency defined as the time taken for reconfiguring a system upon failure detection or mode change. We evaluate it quantitatively for backup sparing, which is one of the most popular reconfiguration methods, by investigating the effects of key parameters.

A lattice system in this paper is a system whose components are ordered like the elements of (m, n) matrix. A representative example of a lattice system is a connected-(r, s)-out-of-(m, n):F lattice system which is treated as a model of supervision system. It fails if and only if all components in an (r, s) sub lattice fail. We modify the lattice system so as to include a maintenance action and a restriction on the number of failed components. Then, this paper presents availability and MTBF of the repairable system, and reliability when the system stocks spare parts on hand to ensure the specified reliability level.

In this paper, we propose an architecture for environmental information services that make it possible for applications to adapt in dynamically changing environments. These services provide information necessary for applications to adapt to its environment. Unlike other information services, the information provided includes not only raw information but also abstract or policy-applied information. The variety of information enables applications to choose suitable level of information. A simple adaptive application can use highly abstract information instead of detailed raw information required by complicated adaptive applications. The policy-applied information enables adaptive applications to share decisions by the user and cooperate among them. Applications can efficiently adapt to changes in the environment since our architecture provides notification of these changes. This notification does not disturb applications since the conditions for the notification are controlled by each application. We apply the proposed architecture to a mobile internetworking environment and present a prototype implementation of environmental information services called CM1. We also discuss our primary evaluation of CM1 with the Personal File System, which is a network file system with dynamic adaptation features, for mobile internetworking environments.

This paper presents a heuristic algorithm called CLASSIC for the minimization of the control memory width in microprogrammed processors or the instruction memory width of application-specific VLIW (Very Long Instruction Word) processors. CLASSIC results in nearly optimal solutions with the time complexity of O(n2), where n denotes the number of microoperations. In this paper, we also propose the so-called incompleteness relations which are exploited for the minimization of the control memory width. Experiments using various examples have shown that CLASSIC always achieves smaller microprogram widths compared to the earlier techniques based on the maximal compatibility class or the minimal AND/OR set. The results show that CLASSIC can reduce the control memory width by 34.2% on average compared with a heuristic compatibility class algorithm.

Migration transparency is considered in the context of multi-agent systems. A mobile agent architecture is proposed with an Availability service and a Transparency interface. We define mobility as explicit (or proactive) when the agent decides when and where to move and define mobility as implicit (i. e. , transparent or reactive) when it is a consequence of changes in the environment. Implicit mobility of agents is explored in addition to the usual explicit mobility. The search for a target agent (or agency) follows a transparent location and selection. The client agent preferably moves towards the target agent. If not possible, the target agent will move towards the client agent when calling back. If both agents can not move then the execution takes place remotely or is abandoned. Transparency is goal oriented.

Designing control and robotic systems as autonomous decentralized systems introduces a new degree of flexibility in the manufacturing and in the application of such systems. This flexibility is required for the systems to work in environments that are not totally predictable and that can change dynamically. In this paper, we present a new concept for real-time communication that supports this flexibility while still preserving real-time guarantees for hard real-time communication. The concept is designed to work on multiple-access busses. In particular, we consider its application on wireless local area networks and field-busses. The concept addresses requirements of hard-real time, soft real-time and non real-time communication. For this, we extend the TDMA (time- division multiple-access) approach for time-triggered hard-real time communication by the concept of shared channels that support event-triggered communication and coexist with hard real-time channels. A first implementation of concept has been carried out in the context of the CAN-bus.

In cellular systems, autonomous reuse partitioning (ARP) is one of the channel assignment strategy which attains the high spectral efficiency. In the strategy, the movement of mobile stations (MSs) causes the disturbance of reuse partition. Furthermore the smaller cell size causes the spectral efficiency worse. In this paper, we propose a new ARP strategy with reuse partitioning reconstructing, named RP-reconstructing ARP strategy, for microcellular systems. We evaluate the performance of the proposed strategy with blocking rate and forced call termination rate by the computer simulation. The results show that the system with the proposed strategy accommodates 1.5 times as many users as the system with ARP does.

Out-of-head sound localization achieved via binaural earphones is indispensable for a virtual sound system. It is necessary to measure the two transfer functions of each subject, Spatial Sound Transfer Function (SSTF) and Ear Canal Transfer Function (ECTF), for achieving sound localization. It is well known that the quality of sound localization may be poor if the individual transfer functions are not accurately reproduced. This is because each subject has his/her own transfer functions. It is very important to clarify which function includes more individual information, SSTF or ECTF, in order to implement a simpler model. Therefore, we introduce the quantity of "Personal differences" for investigating the subject's transfer functions included in SSTF and ECTF. We measure the transfer functions SSTF and ECTF of 60 subjects in a soundproofed room, and analysis of the data using Principal Component Analysis (PCA) and three subjective assessment tests. This study finds that ECTF differs more widely from person to person than SSTF.

The SDP (Sum of Disjoint Products) approach is a well-known technique for computing network reliability measures. So far several algorithms have been developed based on this approach. In this letter, we present a general framework for parallelization of these SDP algorithms. Based on the framework, we implemented a parallel version of an SDP algorithm called CAREL on a network of workstations. Experimental results show that it works fairly well with almost linear speedups.

It is generally known that the autonomic nervous system regulates the pupil. In this study, we attempted to assess mental workload on the basis of the fluctuation rhythm in the pupil area. Controlling the respiration interval, we measured the pupil area during mental tasking for one minute. We simultaneously measured the respiration curve to monitor the respiration interval. We required the subject to perform two mental tasks. One was a mathematical division task, the difficulty of which was set to two, three, four, and five dividends. The other was a Sternberg memory search task, which had four work levels defined by the number of memory sets. In the Sternberg memory search, the number of memory set changed from five to eight. In such a way, we changed the mental workload induced by mental loading. As a result of calculating an autoregressive (AR) power spectrum, we could observe two peaks which corresponded to the blood pressure variation and respiratory sinus arrhythmia under a low workload. With an increased workload, the spectral peak related to the respiratory sinus arrhythmia disappeared. The ratio of the power at the low frequency band, from 0.05-0.15Hz, to the power at the respiration frequency band, from 0.35-0.4Hz, increased with the work level. In conclusion, the fluctuation of the pupil area is a promising means for the evaluation of mental workload or autonomic nervous function.

Biological object could be trapped by a single laser beam from an optical fiber end inserted at an angle to a sample chamber. Separation/coupling of an individual biological cell was easily achieved using plural optical fibers. From these experimental results, we verify that fiber optic trapping technology can provide new and novel tools for the manipulation of microorganisms and cells without physical contact.

In this paper, the recent development of GaN bulk substrates is reviewed. Among various works on HVPE thick epitaxial growth, the largest free-standing GaN substrates upto 34 cm2 has been first obtained by the HVPE method using NGO substrates, whose lattice constant has a good matching with that of GaN. For developing larger GaN substrates with lower production cost, the ultra-high pressure solution growth method is being developed not only in Poland but also in Japan under "The Light for the 21st Century" national project.

In order to get a perspective to the future of GaN materials, theoretical and experimental knowledge of the optoelectronic activities of dislocations in hexagonal GaN have been reviewed. Although the dislocations in GaN have been thought to be not quite harmful, a growing number of evidences have been accumulated for the intrinsic noxiousness of the dislocations. There are some inconsistencies between experimental data reported by different groups or at different dates, which can be reconciled by a proposed simple model that takes into account the trapping of free excitons. A transmission electron microscopic study revealed that some type of dislocations exhibit the recombination enhanced dislocation glide effect, suggesting the non-radiative recombination activity of the fresh dislocations. Such intrinsic activities of dislocations in GaN, in both electronical and mechanical respects, will possibly cause great difficulties in optoelectronic devices based on this material when the crystal quality becomes improved.

Bit error rates (BER) for playback of (1,7) code employed in optical disc recording were simulated using an ideal (Gaussian) playback waveform, with playback being performed by PRML (Partial Response Maximum-Likelihood) combining a partial response equalizer and a double clock weighted Viterbi decoder. It was found that best BER occurs for PR(2,3,3,2) +7/10 level Viterbi decoding at a weighted value of w = 0.5 for data consisting of 107 symbols. For a minimum bit length of 0.28 µm, BER of 10-4 and less than 10-6 was obtained for SN ratios of 15.6 dB and 17.7 dB, respectively. And for a minimum bit length of 0.26 µm, BER of 10-4 and less than 10-6 was obtained for SN ratios of 16.7 dB and 18.8 dB, respectively. These results demonstrate the feasibility of a minimum bit length of 0.26 µm in current optical disc recorders.

Several methods have be proposed or used to optimize the phase distribution of a kinoform. In this paper, we proposed a fast algorithm for optimization of the kinoform based on simulated annealing to reduce the large computation cost. This method uses a simplified equation to calculate the energy function after perturbation.

Excitonic optical properties of GaN homoepitaxial layers have been studied by means of magneto-luminescence and time-resolved luminescence spectroscopy. The luminescence lines due to the radiative recombination of excitons bound to neutral donors and acceptors have been measured under magnetic field up to 8 T, which was aligned perpendicular and parallel to the hexagonal c-axis. Under the magnetic field aligned perpendicular to the hexagonal c-axis, both the donor- and acceptor-bound-exciton lines clearly split into two components, which originated from the Zeeman splitting. The effective g-factors for both the donor- and acceptor-bound excitons were estimated to be 2.02 and 2.47, respectively. Under the magnetic field aligned parallel to the hexagonal c-axis, slight broadening of the bound-exciton lines was observed and the Zeeman splitting was too small to be detected. On the other hand, the diamagnetic shift for both the donor- and acceptor-bound-exciton luminescence lines was observed under the magnetic field aligned both perpendicular and parallel to the hexagonal c-axis. It was found that the diamagnetic shift of the donor-bound exciton was smaller than that of the acceptor-bound exciton. Furthermore, recombination dynamics of excitonic transitions was measured under high-density excitation. An excitation-density-dependent transition of the dominant radiative recombination process from donor-bound excitons to biexcitons was clearly observed in the temporal behavior. In addition, double-exponential decay of biexciton luminescence was observed, which is one of the characteristics of biexciton luminescence at high excitation densities.