The cooperative and competitive network suitable for circuit realization is presented, based on the network proposed by Amari and Arbib. To ensure WTA process, the output function of the original network is replaced with the piecewise linear function and supplying the inputs as pulse waveforms is obtained. In the SPICE simulations, it is confirmed that the network constructed by operational amplifiers attains WTA process, even if the scale of the network becomes large.

In this work we study the performance of a distributed GA that incorporates in its core parallel cooperative-competitive genetic operators. A series of controlled experiments are conducted using various large and difficult 0/1 multiple knapsack problems to test the robustness of the distributed GA. Simulation results verify that the proposed distributed GA compared with a canonical distributed GA significantly gains in search speed and convergence reliability with less communication cost for migration.

This letter treats computational complexity of bounded asymmetric choice (AC) net. AC net is a subclass of Petri net that properly includes the class of well-known extended free choice net. It is shown that satisfiability problem of Boolean expressions is polynomial time reducible to liveness problem of bounded AC nets. This implies that the problem is NP-hard.

In this paper, new integrated schemes of scheduling real-time traffic and cell loss control in high speed ATM networks are proposed for multiple priorities based on variable queue length thresholds for scheduling and the Partial Buffer Sharing policy for cell loss control. In our schemes, the queues for buffering arriving cells can be constructed in two ways: one individual queue for each user connection, or one physical queue for all user connections. The proposed schemes are considered to provide guaranteed QoS for each connection and cell sequence integrity for virtual channel/path characteristics. Moreover, these new schemes are quite flexible and can realize different scheduling algorithms. This paper also provides the Stochastic Petri Net models of these integrated schemes and an approximate analysis technique, which significantly reduces the complexity of the model solution and can be applied to real ATM switch models. From the numerical results, we can see that our schemes outperform those well-known schemes such as the head-of-line (HOL) priority control and the queue length threshold (QLT) policy.

Agent technology is widely recognized as a new paradigm for the design of concurrent software and systems. The aim of this paper is to give a mathematical foundation for the design and the analysis of multi-agent systems by means of a Petri-net-based model. The proposed model, called PN2, is based on place/transition nets (P/T nets), which is one of the simplest classes of Petri nets. The main difference of PN2's from P/T nets is that each token, representing an agent, is also a P/T net. PN2's are sufficiently simple for the mathematical analysis, such as invariant analysis, but have enough modeling power.

A workflow is a flow of work carried out by workers, and workflow management is to automate the flow of work. In workflow management, an actual work is carried out based on the workflow, which is called case. In order to effectively meet various requirements, it is necessary to change current workflow dynamically, which is called dynamic workflow change. When the dynamic change is required, there exist cases in the workflow. In order to handle these cases and further to keep the queuing order, the dynamic change takes period of time (called transient time) until the changed workflow becomes steady state again. During the transient time, workers are forced to do irregular work, and therefore it is important to clarify if a change type takes shorter transient time. In this paper, we do the performance evaluation on transient time of dynamic workflow changes. To do so, we first give a definition of transient time, and then propose methods of computing transient time of three change types proposed by Ellis et al. Finally, we do the performance evaluation for 90 dynamic changes by computing the transient times.

Petri net is a mathematical model for concurrent systems. Liveness is one of important properties of Petri net. Liveness problem of general Petri net is of exponential space complexity and subclasses are suggested with less computational complexity. It is well known that liveness problem of bounded (extended) free choice net is solved in deterministic polynomial time. This paper treats liveness problem of AC/DC nets. AC/DC net is a subclass of Petri net that exhibits no confusion (mixture of concurrency and conflict). This class properly includes the class of free choice nets. It is shown that every minimal siphon of an AC/DC net is trap if and only if every strongly connected siphon is a trap. This result shows that monotone liveness of bounded AC/DC net is solved in deterministic polynomial time. It is shown that this result is true of bounded time AC/DC net with static fair condition.

We consider only P-invariants that are nonnegative integer vectors in this paper. An P-invariant of a Petri net N=(P,T,E,α,β) is a |P|-dimensional vector Y with Yt A = for the place-transition incidence matrix A of N. The support of an invariant is the set of elements having nonzero values in the vector. Since any invariant is expressed as a linear combination of minimal-support invariants (ms-invariants for short) with nonnegative rational coefficients, it is usual to try to obtain either several invariants or the set of all ms-invariants. The Fourier-Motzkin method (FM) is well-known for computing a set of invariants including all ms-invariants. It has, however, critical deficiencies such that, even if invariants exist, none of them may be computed because of memory overflow caused by storing candidate vectors for invariants and such that, even when a set of invariants are produced, many non-ms invariants may be included. We are going to propose the following two methods: (1) FM1_M2 that finds a smallest possible set of invariants including all ms-invariants; (2) STFM that necessarily produces one or more invariants if they exist. Experimental results are given to show their superiority over existing ones.

The legal firing sequence problem of Petri nets (LFS) is one of fundamental problems in the analysis of Petri nets, because it appears as a subproblem of various basic problems. Since LFS is shown to be NP-hard, various heuristics has been proposed to solve the problem of practical size in a reasonable time. In this paper, we propose a new algorithm for this problem. It is based on the partial order verification technique, and reduces redundant branches in the search tree. Moreover, the proposed algorithm can be combined with various types of heuristics.

Characteristics of the optical feedback noise in semiconductor lasers under superposition of the HF (High Frequency) current were experimentally examined and theoretically analyzed. The feedback noise was mostly suppressed by superposition of HF current, but still remained when frequency of the HF current coincided with a rational number of the round trip time period for the optical feedback in experimental measurement. Theoretical analysis was also given to explain these characteristic based on the mode competition theory of the semiconductor laser.

Network caches reduce network traffic as well as user response time. When implementing network caches, the object replacement problem is one of the core problems; The problem is to determine which objects should be evicted from a cache when there is insufficient space. This paper first formalizes the problem and gives a simple but sufficient condition for deterministic online algorithms to be competitive. Based on the condition, a general framework to make a non-competitive algorithm competitive is constructed. As an application of the framework, an online algorithm, called Competitive_SIZE, is proposed. Both event-driven and trace-driven simulations show that Competitive_SIZE is better than previously proposed algorithms such as LRU (Least Recently Used).

A halftoning technique that uses a simple GA has proven to be very effective to generate high quality halftone images. Recently, the two major drawbacks of this conventional halftoning technique with GAs, i.e. it uses a substantial amount of computer memory and processing time, have been overcome by using an improved GA (GA-SRM) that applies genetic operators in parallel putting them in a cooperative-competitive stand with each other. The halftoning problem is a true multiobjective optimization problem. However, so far, the GA based halftoning techniques have treated the problem as a single objective optimization problem. In this work, the improved GA-SRM is extended to a multiobjective optimization GA to simultaneously generate halftone images with various combinations of gray level precision and spatial resolution. Simulation results verify that the proposed scheme can effectively generate several high quality images simultaneously in a single run reducing even further the overall processing time.

In this paper agents' interactions are defined in terms of cooperation, coordination and competition. As for cooperation and coordination problems, we focus on knowledge sharing of agents, define agencies as organizations of agents, propose a method to extract organizational knowledge for interacting agents. In case of competition, knowledge sharing is impossible. Therefore, modeling and formalization of strategic decision making and uncertainty management is required. We present an incomplete game theoretical based decision making method for competitive agents.

This paper proposes a public-key cryptography by applying RSA and Petri nets. We introduce RSA and a Petri net based private-key cryptography and then taking the advantages of these two cryptography, we propose a new public-key cryptography, PNPKC. To compare with RSA on security as well as computation order, we do simulation experiments. As the results, the security of PNPKC is as strong as RSA cryptography, and the encryption and decryption of PNPKC are in average 239 times as fast as RSA cryptography from our experiments. Besides, to see if our current PNPKC program can be practically used, we do comparative experiment with PGP, which shows PNPKC takes computation time in average as much as 36 times of PGP cryptography. That means our PNPKC program still needs to be technically improved.

Adaptation of software components to the requirements is one of the key concerns in Component Based Software Development (CBSD). In this paper, we propose a formal approach to compose component based systems which are adaptable to the requirements. We focus on the functional aspects of software components and requirements, which are expressed in S-sorted functions. Those S-sorted functions are transformed into Colored Petri Nets (CPN) models in order to evaluate connectivity between the components, and to evaluate adaptability of composed systems to the requirements. The connectivity is measured based on colors or data types in CPN, while the adaptability is measured based on functional equivalency. We introduce simple glue codes to connect the components each other. The paper focuses on business applications, however the proposed approach can be applied to any other domains as far as the functional adaptability is concerned.

This paper proposes a new heuristic algorithm FMDB for the minimum initial marking problem MIM of Petri nets: "Given a Petri net and a firing count vector X, find an initial marking M0, with the minimum total token number, for which there is a sequence δ of transitions such that each transition t appears exactly X(t) times in δ, the first transition is firable on M0 and the rest can be fired one by one subsequently. " Experimental results show that FMDB produces better solutions than any known algorithm.

It is one of the difficulties in enterprise modeling that we must deal with many fragmented pieces of knowledge provided by various domain-experts, which are usually based on mutually different viewpoints of them. This paper presents a formal approach to integrate those pieces into enterprise-wide model units using Rough Set Theory (RST). We focus on business processes in order to recognize and identify the constituents or units of enterprise models, which would compose the model expressing the various aspects of the enterprise. We defined five model unit types of "resource," "organization," "task," "function," and "behavior. " The first three types represent the static aspect of the enterprise, whereas the last two types represent the dynamic aspect of it. Those units are initially elicited from each domain-expert as his/her own individual model units, then they are integrated into enterprise-wide units using RST. Our approach is methodology-free, and any methodologies can include it in their early stage to identify what composes the enterprise.

We study the performance of oblivious routing algorithms that follow minimal (shortest) paths, referred to as minimal oblivious routing algorithms in this paper, using competitive analysis on a d-dimensional, N = 2d-node hypercube. We assume that packets are injected into the hypercube arbitrarily and continuously, without any (e.g., probabilistic) assumption on the arrival pattern of the packets. Minimal algorithms reduce the total load in the network in the first place and they preserve locality. First we show that the well known deterministic oblivious routing algorithm, namely, the greedy routing algorithm, has competitive ratio Ω(N1/2). Then we show a problem lower bound of Ω(Nlog 2 (5/4)/log5 N). We also give a natural randomized minimal oblivious routing algorithm whose competitive ratio is close to the problem lower bound we provide.

The need for electronic sealed-bid auction services with quantitative competition is increasing. This paper proposes a new method that combines one-way functions and a bit commitment technique for quantitative competitive sealed-bid auctions. Since each modular exponentiation is replaced with a one-way function, the proposed method's computational time is one forty thousandth that of the former methods and the proposed method suits mass bidder systems.

This paper describes two competitive learning algorithms from the viewpoint of deleting mechanisms of weight (reference) vectors. The techniques are termed the adaptivity and sensitivity deletions participated in the criteria of partition error and distortion error, respectively. Experimental results show the effectiveness of the proposed approaches in the average distortion.