SIMULATION: Transactions of The Society for Modeling and Simulation International

Wainer, Gabriel; Qi Liu,

doi: 10.1177/0037549708101182pmid: N/A

We introduce advanced graphical modeling and visualization facilities for Discrete Event System Specification (DEVS) modeling and simulation (M&S) in the CD++ environment. The objective is to provide general users with a variety of easy-to-use environments to facilitate the model analysis process and thereby promoting the adoption of M&S by a wider community of practitioners and researchers. CD++Modeler allows users without much experience in software development to construct rather complex DEVS models and to analyze simulation data using 2D graphics. We also introduce a graphical platform called MAPS designed specifically for urban traffic systems, and other advanced 3D animation tools (CD++/VRML, CD++/Maya, CD++DEVSView, and CD++/Blender) based on both commercial and open-source software packages. We elaborate on the design of these toolkits and demonstrate their capabilities as well as relative merits and limitations with realistic applications. Following a highly modular approach, the resulting architecture can be easily extended to incorporate other modeling and visualization techniques in future development. We show that these facilities can reduce the model development cost significantly, lower the learning curve for general users, and improve the comprehension of continuously evolving models, making them suitable for efficient decision making.

Tyan, Hung-ying; Sobeih, Ahmed; Hou, Jennifer C.

doi: 10.1177/0037549708099998pmid: N/A

In this paper, we present a component-based network simulation environment that provides a systematic way to simulate, with high fidelity, protocol operations in a variety of target network architectures. We take a four-step approach to developing such a composable network simulation environment with reusable components. First, we lay a component-based software architecture, called the autonomous component architecture (ACA). Second, we propose a new real-time, process-driven simulation technique that fits naturally in ACA and simulates the real system realistically. Third, we devise a packet-based network simulation framework, called extensible internetworking framework (INET), on top of ACA. Fourth, we implement in Java both ACA and INET, and several representative suites of protocol components in a variety of network architectures. The resulting codes, along with a scripting framework, constitute a network simulation environment called J-Sim. By virtue of the many desirable features inherited from ACA, the J-Sim environment meets the flexibility, composability, reusability, extensibility and diagnosability requirements. The price J-Sim pays for the many desirable features is, however, the inter-component communication overhead. In this paper, we show (via experimentation) that this overhead is not significant (in the range of 0.2—0.6 μs), and J-Sim achieves better scalability than two other network simulators in the public domains, ns-2 and Scalable Simulation Framework Network Models (SSFNET), in terms of both the experiment setup time and the simulation completion time.

Gohari Sadr, V.; Kouhsari, S.M.

doi: 10.1177/0037549709103897pmid: N/A

In this paper, an adaptive distance relaying strategy based on the global network simulation (GNS) concept is presented. The GNS concept is actually a distributed simulation approach (DSA) for piecewise analysis of large-scale power grids using diakoptics and large change sensitivity (LCS) concepts. To set each utility's relays trip settings adaptively in each power system condition, detailed short circuit analysis is run in the GNS environment. It first updates the pre-fault voltage profile across utilities and then modifies their nodal ZBus in such a way to reflect the effect of the whole network in local fault studies performed by individual utilities; hence, presenting an accurate and secure federative approach on a geographically decomposed grid using local information and computational resources. A set of currently experienced rules in distance coordination is outlined and adaptive as well as conventional relay zone settings in each sub-network are calculated based on the selected rules. An efficient easy-to-implement algorithm to consider the effect of zero sequence mutual impedance among parallel lines is also presented and well integrated into the proposed adaptive approach in the GNS environment. The IEEE 14 bus test system and a real version of a large-scale grid with more than 2,600 buses are used to illustrate the characteristics of the proposed adaptive strategy in terms of security and dependability by comparison with conventional distance protection.

Huang, Chung-Yuan; Tsai, Yu-Shiuan; Sun, Chuen-Tsai; Hsieh, Ji-Lung; Cheng, Chia-Ying

doi: 10.1177/0037549709103775pmid: N/A

Critical thresholds represent one of the most important diffusion indicators of epidemic outbreaks. However, we believe that recent studies have overemphasized ways that the power-law connectivity distribution features of social networks affect epidemic dynamics and critical thresholds. As a result, two important factors have been overlooked: resource limitations and transmission costs associated with social interactions and daily contact. Here we present our results from the simultaneous application of mean-field theory and an agent-based network simulation approach for analyzing the effects of resources and costs on epidemic dynamics and critical thresholds. Our main findings are: (a) a significant critical threshold does exist when resources and costs are taken into consideration, and it has a lower bound whenever contagion events occur in scale-free networks; (b) when transmission costs increase or individual resources decrease, critical contagion thresholds in scale-free networks grow linearly and steady density curves shrink linearly; (c) regardless of whether the resources of individuals obey delta, uniform, or normal distributions, they have the same critical thresholds and epidemic dynamics as long as the average value of usable resources remains the same across different scale-free networks; and (d) the spread of epidemics in scale-free networks remains controllable as long as resources are properly restricted and intervention strategy investments are significantly increased.

doi: 10.1177/0037549709103941pmid: N/A