We have been developing a secure and reliable distributed storage system, which uses a secret sharing scheme. In order to efficiently store data in the system, this paper introduces an optimal share transfer problem, and proves it to be, generally, NP-hard. It is also shown that the problem can be resolved into a Steiner tree problem. Finally, through computational experiments we perform the comparison of heuristic algorithms for the Steiner tree problem.

For a service-oriented architecture-based system, the problem of synthesizing a concrete model (i.e., a behavioral model) for each peer configuring the system from an abstract specification — which is referred to as choreography — is known as the choreography realization problem. In this paper, we consider the condition for the behavioral model when choreography is given by an acyclic relation. A new notion called re-constructible decomposition of acyclic relations is introduced, and a necessary and sufficient condition for a decomposed relation to be re-constructible is shown. The condition provides lower and upper bounds of the acyclic relation for the behavioral model. Thus, the degree of freedom for behavioral models increases; developing algorithms for synthesizing an intelligible model for users becomes possible. It is also expected that the condition is applied to the case where choreography is given by a set of acyclic relations.

The unit commitment problem (UCP) is the problem of deciding up/down and generation-level patterns of energy production units. Due to the expansion of distributed energy resources and the liberalization of energy trading in recent years, solving the distributed UCP (DUCP) is attracting the attention of researchers. Once an up/down pattern is determined, the generation-level pattern can be decided distributively using the alternating direction method of multipliers (ADMM). However, ADMM does not guarantee convergence when deciding both up/down and generation-level patterns. In this paper, we propose a method to solve the DUCP using ADMM and constraint optimization programming. Numerical experiments show the efficacy of the proposed method.

Autonomous distributed manufacturing systems(ADMS) consist of multiple intelligent components with each component acting according to its own judgments. The ADMS objective is to realize more agile and adaptive manufacturing systems. This paper presents the introduction of context-dependent agents (CDAs) in ADMS, and switch strategies depending on system conditions to achieve better performance can be realized by agents that use the same strategies under all system conditions. For the real-time job scheduling problem, the present paper recalls a basic CDA architecture, and presents the results of an extensive empirical evaluation its performance relative to other rule-based schemes based on several common indices for real-time dispatch.

Petri nets are widely recognized as a powerful model for discrete event systems. Petri nets have both graphical and mathematical features. Graphical feature provides an environment to design and to comprehend discrete event systems. Mathematical feature provides an analysis power for verifying several properties of such systems. Several analysis techniques have been proposed so far, such as a reachability (coverability) graph method, a matrix equation approach, reduction or decomposition techniques, a symbolic model method and an unfolding method. The unfolding method was introduced to avoid generating the reachability graph. Unfoldings are often used in the verification of asynchronous circuits. This paper focuses on an analysis of finite state systems, i.e., bounded nets, and discuss a reachability problem and a upper bound problem. Relations between these problems and an unfolding have been clarified to provide a novel method to resolve these problems.

Multi-Car Elevator (MCE) systems, which consist of several independent cars built in the same shaft, are being considered as the elevators of the next generation. In this paper, we present MceSim, a simulator of MCE systems. MceSim is an open source software available to the public, and it can be used as a common testbed to evaluate different control methods related to MCE systems. MceSim was used in the group controller performance competition: CST Solution Competition 2007. This experience has proven MceSim to be a fully functional testbed for MCE systems.

For mission-critical and safety-critical systems such as medical, financial, or administrative information systems, a secure and reliable storage system is indispensable. The main purpose of our research is to develop a highly secure and highly reliable storage system. We have proposed a storage system that utilizes a secret sharing scheme. The storage system is called the Secret Sharing Storage System. So far, we have developed a prototype of the storage system. In this paper, we propose an automatic repair mechanism, and an interval decision method for this system.

Secret sharing is a method for distributing a secret among a party of participants. Each of them is allocated a share of the secret, and the secret can only be reconstructed when the shares are combined together. We have been proposing a secret sharing distributed database system (SSDDB) that uses a secret sharing scheme to improve confidentiality and robustness of distributed database systems. This paper proposes a vertical partitioning algorithm for the SSDDB, and evaluates the algorithm by computational experiments.

In this letter, we introduce a knowledge reuse method to improve the performance of a learning algorithm developed to prevent interference in multi-car elevators. This method enables the algorithm to use its previously acquired experience in new learning processes. The simulation results confirm the improvement achieved in the algorithm's performance.

This paper discusses an on-line Tasks Assignment and Routing Problem (TARP) for Autonomous Transportation Systems (ATSs) in manufacturing systems. The TARP results in a constrained version of the Pickup and Delivery Problem with Time Windows (PDPTW). As an approach to this problem, a cooperative algorithm with autonomous distributed agents has been proposed. The algorithm is able to plan deadlock-free routes even though the buffer capacity is less, but includes reformability at the point that computation time of that case increases drastically. This paper proposes an initial task assignment method to reduce computation time on planning routes. Results of computational experiments show effectiveness of the proposed method.

In this paper, an approach to derive a logic function of asynchronous circuits from a graph-based model called Signal Transition Graphs (STG) is discussed. STG's are Petri nets, whose transitions are interpreted as a signal transition on the circuit inputs or gate outputs, and its marking represents a binary state of the circuit. STG's can represent a behavior of circuit, to derive logic functions, however, the reachability graph should be constructed. In the verification of STG's some method based on Occurrence nets (OCN) and its prefix, called unfolding, has been proposed. OCN's can represent both causality and concurrency between two nodes by net structure. In this paper, we propose a method to derive a logic function by generating substate space of a given STG using the structural properties of OCN. The proposed method can be seem as a parallel algorithm for deriving a logic function.