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.

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 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.

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.

This paper describes the Profit-Sharing, a reinforcement learning approach which can be used to design a coordination strategy in a multi-agent system, and demonstrates its effectiveness empirically within a coil-yard of steel manufacture. This domain consists of multiple cranes which are operated asynchronously but need coordination to adjust their initial plans of task execution to avoid the collisions, which would be caused by resource limitation. This problem is beyond the classical expert's hand-coding methods as well as the mathematical analysis, because of scattered information, stochastically generated tasks, and moreover, the difficulties to transact tasks on schedule. In recent few years, many applications of reinforcement learning algorithms based on Dynamic Programming (DP), such as Q-learning, Temporal Difference method, are introduced. They promise optimal performance of the agent in the Markov decision processes (MDPs), but in the non-MDPs, such as multi-agent domain, there is no guarantee for the convergence of agent's policy. On the other hand, Profit-Sharing is contrastive with DP-based ones, could guarantee the convergence to the rational policy, which means that agent could reach one of the desirable status, even in non-MDPs, where agents learn concurrently and competitively. Therefore, we embedded Profit-Sharing into the operator of crane to acquire cooperative rules in such a dynamic domain, and introduce its applicability to the realistic world by means of comparing with RAP (Reactive Action Planner) model, encoded by expert's knowledge.

This paper presents a framework for the nonblocking supervisory control of nondeterministic discrete event systems (DESs) using multiple deterministic model. Necessary and sufficient conditions for the existence of a multiple model nonblocking supervisor are obtained for a multiple deterministic model. We show that a multiple model nonblocking supervisor guarantees the nonblockingness of an original nondeterministic system.

High accuracy, high reliability, and high performance have to be simultaneously satisfied to achieve high productivity of the latest processing equipment. High flexibility is also required because many options are available and processing equipment is modified frequently. A high-assurance-system (HAS) model for processing equipment has been developed according to the concept of an Autonomous Decentralized System (ADS). Heterogeneous devices, that have same function and diverse qualities, are utilized to assure the different requirements of high accuracy, high reliability, and high performance simultaneously. The Data Property (DP) and Assurance Manager (AM) are proposed in this model. Different accuracy, reliability, and performance indices characterize each device, and the DP describes the differences of the properties of the data transmitted from these heterogeneous devices. The AM assures not only high reliability but also high performance and high accuracy by utilizing the heterogeneity of data described by the DP. The HAS model was applied to a device-level system used in processing equipment, and its effectiveness was verified by simulating a pressure-control system.

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 shall put forward a novel circularly connected synergetic neural network extending the previously studied auto-correlation or cross-correlation dynamics so as to realise a group memory retrieval. The present model is substantially based on a top-down approach of the dynamic rule of an analog neural network in the similar manner to the conventional synergetic dynamics early proposed by Haken. It will be proved that a complete association can be assured up to the same number of the embedded patterns as the minimal number of neurons of the linked synergetic neural networks. In addition, one finds that a searching process of a couple of embedded patterns can be also realised by means of controlling attraction parameters as was previously reported in the autoassociative synergetic models.

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.

The need for responsive, flexible agents is pervasive in many application domains due to their complex, dynamic, and uncertain nature. Dynamic Adaptive Autonomy allows Sensible Agents to reorganize themselves during system operation to solve different problems in the face of these complex and dynamic environments. This paper presents both functional and implementation architectures for Sensible Agent systems. The functional architecture supports concepts from the distributed computing community by separating internal agent functionality into a discrete set of modules whose interactions are formally specified using the Interface Definition Language (IDL) from the Common Object Request Broker Architecture (CORBA). These four modules are: (1) Perspective Modeler--which contains the agent's explicit model of its local, subjective view of the world, (2) Autonomy Reasoner--determines the appropriate decision-making framework for each of the agent's goals, (3) Action Planner--interprets domain-specific goals, plans to achieve these goals and executes the generated plans, and (4) Conflict Resolution Advisor--identifies, classifies, and recommends possible solution strategies for resolving conflicts between this agent and other agents. The implementation architecture has been realized in a testbed that promotes (1) language and platform independence, (2) parallel development, (3) rapid integration of evolving representations and algorithms implementing agent functionality, (4) repeatable experimentation and testing, (5) environment and agent visualization, and (6) inter-domain application portability. The testbed uses the Inter-Language Unification (ILU) ORB from Xerox to provide the CORBA layer of inter-module and inter-agent communication. A three-dimensional visualization of the domain is provided with a CORBA-connected Virtual Reality Modeling Language (VRML) model while low-level data collection is accomplished using a CORBA-connected Java application. The combination of a distributed functional architecture with a distributed implementation architecture provides a high level of flexibility, visualization ability and experimental fidelity for evaluating the performance of Sensible Agents in complex, dynamic and uncertain environments.

In a decentralised system the problems of fault tolerance, and in particular error recovery, vary greatly depending on the design assumptions. For example, in a distributed database system, if one disregards the possibility of undetected invalid inputs or outputs, the errors that have to be recovered from will just affect the database, and backward error recovery will be feasible and should suffice. Such a system is typically supporting a set of activities that are competing for access to a shared database, but which are otherwise essentially independent of each other--in such circumstances conventional database transaction processing and distributed protocols enable backward recovery to be provided very effectively. But in more general systems the multiple activities will often not simply be competing against each other, but rather will at times be attempting to co-operate with each other, in pursuit of some common goal. Moreover, the activities in decentralised systems typically involve not just computers, but also external entities that are not capable of backward error recovery. Such additional complications make the task of error recovery more challenging, and indeed more interesting. This paper provides a brief analysis of the consequences of various such complications, and outlines some recent work on advanced error recovery techniques that they have motivated.

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.

The homogeneous structure of field programmable gate arrays (FPGAs) suggests that the defect tolerance can be achieved by shifting the configuration data inside the FPGA. This paper proposes a new approach for tolerating the defects in FPGA's configurable logic blocks (CLBs). The defects affecting the FPGA's interconnection resources can also be tolerated with a high probability. This method is suited for the makers, since the yield of the chip is considerably improved, specially for large sizes. On the other hand, defect-free chips can be used as either maximum size, ordinary array chips or fault tolerant chips. In the fault tolerant chips, the users will be able to achieve directly the fault tolerance by only shifting the design data automatically, without changing the physical design of the running application, without loading other configurations data from the off-chip FPGA, and without the intervention of the company. For tolerating defective resources, the use of spare CLBs is required. In this paper, two possibilities for distributing the spare resources (king-shifting and Horse-allocation) are introduced and compared.

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.

In this letter, we propose an approximate calculation formula for the resonant frequency of a microstrip antenna with meshed ground plane, which is derived by perturbational technique and is expressed by a simple closed form. The calculated results are in good agreement with FDTD-calculated and measured ones. Therefore, it is confirmed that the proposed formula is valid for approximate evaluation of the resonant frequency of microstrip antenna with meshed ground plane.

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.

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.