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361.
Rami Debouk Stéphane Lafortune Demosthenis Teneketzis 《Discrete Event Dynamic Systems》2003,13(3):263-289
We study the effect of communication delays on the performance of a coordinated decentralized architecture for failure diagnosis of untimed discrete event systems. The architecture consists of local sites communicating with a coordinator that is responsible for diagnosing the failures occurring in the system. A protocol that realizes the architecture is defined by the diagnostic information generated at the local sites, the communication rules used by the local sites, and the decision rule used by the coordinator to infer the occurrence of failures. Our prior work (Debouk et al., 2000) has addressed the performance of a set of protocols under the assumption that messages are received by the coordinator in the order in which they are sent globally. In this work we relax the abovementioned assumption. We modify the coordinator's decision rule for two of the protocols analyzed in Debouk et al. (2000) to account for the reception of out of order messages. We discover conditions on the system structure under which the modified protocols perform as well as the centralized diagnostic scheme proposed in Sampath et al. (1995). 相似文献
362.
This paper addresses the economic benefits of selectively assigning a batch of subassemblies to each other after inspecting and correcting them as needed. Our work is based on optimizing the collective cost of subassembly inspection, rework, scrap, final assembly failure, and the act of subassembly mating. The expected value for the cost is estimated using Monte Carlo Simulation and optimized using a metaheuristic. After each simulation replication where we simulate a batch of subassemblies, we assign the inspected subassembly parts so that the rolled yield throughput is maximized. The complexity of this work is attributed to the fact that we solve an optimization problem for an objective that is estimated using simulation, and in each simulation replication there is another optimization problem to be solved for selective assembly. Significant improvements in assembly lines are predicted to be accomplished when this work is integrated in a real production environment. 相似文献
363.
Mustapha Ait Rami 《Systems & Control Letters》2011,60(9):704-708
This paper addresses the stabilization problem of positive linear systems which have nonnegative states whenever the initial conditions are nonnegative. The synthesis of static output-feedback controllers that ensure the positivity and asymptotic stability of the closed-loop system is investigated. It is shown that this important problem is completely solved for single-input and single-output positive systems. The proposed approach can be applied to multi-input positive systems with controllers having one rank gains. All the provided conditions are necessary and sufficient and can be solved in terms of Linear Programming. 相似文献
364.
A web service-based web application (WSbWA) is a collection of web services or reusable proven software parts that can be discovered and invoked using standard Internet protocols. The use of these web services in the development process of WSbWAs can help overcome many problems of software use, deployment and evolution. Although the cost-effective software engineering of WSbWAs is potentially a very rewarding area, not much work has been done to accomplish short time to market conditions by viewing and dealing with WSbWAs as software products that can be derived from a common infrastructure and assets with a captured specific abstraction in the domain. Both Product Line Engineering (PLE) and Agile Methods (AMs), albeit with different philosophies, are software engineering approaches that can significantly shorten the time to market and increase the quality of products. Using the PLE approach we built, at the domain engineering level, a WSbWA-specific lightweight product-line architecture and combined it, at the application engineering level, with an Agile Method that uses a domain-specific visual language with direct manipulation and extraction capabilities of web services to perform customization and calibration of a product or WSBWA for a specific customer. To assess the effectiveness of our approach we designed and implemented a tool that we used to investigate the return on investment of the activities related to PLE and AMs. Details of our proposed approach, the related tool developed, and the experimental study performed are presented in this article together with a discussion of planned directions of future work. 相似文献
365.
This paper deals with an optimal stochastic linear-quadratic (LQ) control problem in infinite time horizon, where the diffusion term in dynamics depends on both the state and the control variables. In contrast to the deterministic case, we allow the control and state weighting matrices in the cost functional to be indefinite. This leads to an indefinite LQ problem, which may still be well posed due to the deep nature of uncertainty involved. The problem gives rise to a stochastic algebraic Riccati equation (SARE), which is, however, fundamentally different from the classical algebraic Riccati equation as a result of the indefinite nature of the LQ problem. To analyze the SARE, we introduce linear matrix inequalities (LMIs) whose feasibility is shown to be equivalent to the solvability of the SARE. Moreover, we develop a computational approach to the SARE via a semi-definite programming associated with the LMIs. Finally, numerical experiments are reported to illustrate the proposed approach 相似文献
366.
Rami K. Suleiman 《Journal of Adhesion Science and Technology》2020,34(12):1315-1330
AbstractA hybrid organic–inorganic sol–gel coating was successfully prepared and subsequently functionalized individually with five different metal oxide additives. The effect of the incorporated oxides on the corrosion protection performance and scratch-resistance properties of the hybrid base coating on mild steel substrates was investigated using electrochemical techniques, namely electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) as well as mechanical testing. The steel-coated specimens were immersed in 3.5?wt.% NaCl corrosive medium for two weeks and the results reveal an excellent corrosion protection performance by all coating formulations with a significant high corrosion-resistance property for the sample loaded with molybdenum oxide. Scanning electron microscopy (SEM) images proved the absence of corrosion signs, defects, micro cracks, or delamination on the surface of the coated samples. Compared with the pure hybrid coating, all the metal oxide-embedded coatings (except for the sample loaded with yttrium(III) oxide) show comparable aqueous contact angle values as well as enhanced hardness and adherence properties. No noticeable dependence was observed for the surface roughness parameters as a function of the type of incorporated metal oxide within the sol–gel matrix. Overall, the results of this study demonstrate that metal oxides can be advantageous to the desired properties of hybrid sol–gel coatings applied to steel surfaces. 相似文献
367.
Internet has become an essential component of our everyday social and financial activities. Nevertheless, internet users may be vulnerable to different types of web threats, which may cause financial damages, identity theft, loss of private information, brand reputation damage and loss of customer’s confidence in e-commerce and online banking. Phishing is considered as a form of web threats that is defined as the art of impersonating a website of an honest enterprise aiming to obtain confidential information such as usernames, passwords and social security number. So far, there is no single solution that can capture every phishing attack. In this article, we proposed an intelligent model for predicting phishing attacks based on artificial neural network particularly self-structuring neural networks. Phishing is a continuous problem where features significant in determining the type of web pages are constantly changing. Thus, we need to constantly improve the network structure in order to cope with these changes. Our model solves this problem by automating the process of structuring the network and shows high acceptance for noisy data, fault tolerance and high prediction accuracy. Several experiments were conducted in our research, and the number of epochs differs in each experiment. From the results, we find that all produced structures have high generalization ability. 相似文献
368.
Multimedia applications are usually resource intensive, have stringent quality of service requirements, and in many cases involve large groups of participants. Multicasting is poised to play an important role in future deployment of these applications. This paper focuses on developing delay-bounded, minimum-cost multicast trees, linking a source to a set of multicast destination nodes. The approach taken in this paper is efficient, flexible and unique in the sense that it cleverly limits its computation only to paths that originate at multicast nodes, thereby avoiding computing paths that exclusively link non-multicast nodes. The simulation results show that the multicast trees produced by the proposed heuristic are of lower cost than those produced by other well-known heuristics, including those which use an expensive k-shortest-paths procedure to minimize the cost of the multicast tree. Furthermore, the results show that, in comparison to other heuristics, the proposed scheme results in a significant reduction in the computation time required to build the multicast tree. 相似文献
369.
Two‐dimensional finite element method solution of a class of integro‐differential equations: Application to non‐Fickian transport in disordered media
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Rami Ben‐Zvi Harvey Scher Brian Berkowitz 《International journal for numerical methods in engineering》2017,112(5):459-478
A finite element method is developed to solve a class of integro‐differential equations and demonstrated for the important specific problem of non‐Fickian contaminant transport in disordered porous media. This transient transport equation, derived from a continuous time random walk approach, includes a memory function. An integral element is the incorporation of the well‐known sum‐of‐exponential approximation of the kernel function, which allows a simple recurrence relation rather than storage of the entire history. A two‐dimensional linear element is implemented, including a streamline upwind Petrov–Galerkin weighting scheme. The developed solver is compared with an analytical solution in the Laplace domain, transformed numerically to the time domain, followed by a concise convergence assessment. The analysis shows the power and potential of the method developed here. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
370.
A two-stage Ant Colony Optimization algorithm to minimize the makespan on unrelated parallel machines with sequence-dependent setup times 总被引:1,自引:1,他引:0
This paper addresses the non-preemptive unrelated parallel machine scheduling problem with machine-dependent and sequence-dependent
setup times. All jobs are available at time zero, all times are deterministic, and the objective is to minimize the makespan.
An Ant Colony Optimization (ACO) algorithm is introduced in this paper and is applied to this NP-hard problem; in particular,
the proposed ACO tackles a special structure of the problem, where the ratio of the number of jobs to the number of machines
is large (i.e., for a highly utilized set of machines). Its performance is evaluated by comparing its solutions to solutions
obtained using Tabu Search and other existing heuristics for the same problem, namely the Partitioning Heuristic and Meta-RaPS.
The results show that ACO outperformed the other algorithms. 相似文献