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With the prevalence of net-centric environments, Service-Oriented Architectures (SOAs) have emerged as a paradigm that greatly impacts the modeling and simulation (M&S) community. This paper has two interrelated goals. The first is to give a comprehensive review of various service-oriented simulation frameworks to help researchers select the appropriate one for their specific purpose. The second goal is to combine the common features derived from the review into one unifying framework that can describe and prescribe various specific approaches. The focus of this paper is on the common functionalities of service-oriented simulations reflected in the review and unifying framework. In particular, we emphasize the way SOAs and M&S are combined, and the interoperability and composability challenges of distributed M&S services. We describe some fundamental concepts first. Then we present a comprehensive survey of several classical frameworks, including formalism-based, model-driven, interoperability protocol based, eXtensible Modeling and Simulation Framework (XMSF), Open Grid Services Architecture (OGSA) based, and ontology-driven frameworks. Based on the review, we propose a novel three-dimensional reference model that can unify the ad hoc approaches into a common framework. The model can be used as a guideline or an analytic means to find potential and possible future directions. In particular, the model inspects the crossover between the disciplines of M&S, service-orientation, and software/systems engineering. Based on the model, we present a detailed comparison of the reviewed frameworks. Finally the significance of the paper is discussed and future directions are recommended. [ABSTRACT FROM PUBLISHER]

Road safety barriers are roadside structures installed on certain sections of the road to improve highway safety by preventing a vehicle from leaving the road and colliding with roadside hazards. Road safety barriers are an effective solution for reducing the risk of injuries on modern roads. A road safety barrier must meet minimum standards of construction and materials design. Normally, they must undergo crash tests according to the European standard EN 1317 or the Manual for Assessing Safety Hardware by the American Association of State Highway and Transportation Officials. On the basis of these standards, each safety barrier must pass standardized crash tests as mandated in their approval procedures. Currently, computer simulation methods are typically used by researchers to analyze the performance of roadside safety barriers. Advancement in computer technology could facilitate the finite element method in replacing expensive experimental tests. This paper presents an approach for constructing and evaluating a finite element model for road safety barriers according to European standard EN 1317 by using the finite element code LS-DYNA. Excellent agreement between real-world test data and simulation results was achieved for behavior and impact severity values. The results obtained using the model ensure the exactness of the proposed method and prove that the numerical method is a practical approach for eliminating road safety barrier problems. Furthermore, the model was able to replace experimental tests for developing road safety barriers, thus reducing time and money. [ABSTRACT FROM AUTHOR]

Weld line is aesthetically unpleasant and affects the mechanical strength of injection molded parts. Because of the ever-increasing requirements for parts performance, lots of researchers have performed various studies related to the weld lines optimization. However, research about the computer determination of weld lines in injection molding remains scarce. In this paper, a weld line computer determination method based on filling simulation with surface model is proposed, from which the positions and lengths of the weld lines can be predicted. According to the characteristics of the surface model, all weld lines are classified into two different types. Initial welding node searching and revision algorithms for the two different types of weld lines are first developed. Starting from initial welding nodes, weld lines are then extended by a pre-extension algorithm and an extension algorithm. In the weld line extension algorithm, 135° is set as a welding angle threshold for forming weld lines. Finally, the effects of cavity thickness, process parameters, and mesh densities have been investigated. Moreover, Moldflow simulation results and real parts in production have been conducted to verify the proposed determination method, which demonstrate that the proposed method is correct and effective in actual production. [ABSTRACT FROM PUBLISHER]

This paper presents a novel analytical approach to calculate the saturation throughput of the Distributed Queuing Medium Access Control protocol for Ad Hoc Networks (DQMAN) in single-hop scenarios. DQMAN integrates a near-optimum MAC protocol into a passive clustering algorithm based on Carrier Sensing Multiple Access (CSMA). Therefore, based on models of both CSMA and centralized MAC protocols, a new model is presented to accurately calculate the saturation throughput of DQMAN in single-hop networks. In addition, the model presented can be extended to any MAC protocol based on the spontaneous clustering concept of DQMAN. The accuracy of the overall model has been assessed through link-level computer simulations. A performance evaluation of the protocol under different configurations is also presented together with a performance comparison with the IEEE 802.11 standard. [ABSTRACT FROM AUTHOR]

Computer simulation has become an efficient and cost-effective tool for the liquid composite molding (LCM) processes, including the RTM, VARTM, and resin infusion, compared to trial-and-error. The purpose of simulation is to accurately reflect the real situation. Since the simulation is predominantly based on the control volume finite element method (CVFEM), the boundary conditions such as gate and vent definition need to be properly defined. In this paper, the errors of the CVFEM based mold filling simulation were analyzed. The error sources were identified as the mesh near gates and vents, and gate definition. By conducting 3-D and 2-D simulation case studies, the influence of the gate definition on the simulation result was studied. Because many composite parts are shells and can be regarded as surfaces. 2-D simulation is favorable because of the better efficiency and simpler pre-processing. For this purpose, a method for mold filling simulation incorporating the gate size effect the effective gate method (EGM) - was developed. This method was validated through case studies. It shows that the EGM provides an effective and efficient approach to the CVFEM mold filling simulation incorporating the effect of injection gate size. [ABSTRACT FROM AUTHOR]