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This paper presents an extension of a previously-described framework for the specification and manipulation of models of systems. The original framework and its extension include a convenient application programming interface (API), and this paper describes examples of the use of this API in the context of graphical simulation. These examples include the simulation of objects whose definition involves torques, and a brief description of the simulation of air and smoke by means of a model involving particles moving in fluid. [Copyright &y& Elsevier]

Abstract: This paper demonstrates the use of a semi-discretization technique for obtaining a discrete-time analogue of an exponentially convergent network that is subject to impulses with large magnitude. Prior to implementing the analogue for computer simulations, we investigate its exponential convergence towards a unique equilibrium state and thereby obtain a family of sufficiency conditions governing the network parameters and the impulse magnitude and frequency. Although the time-step does not appear in the conditions that govern the network parameters, its value needs to be sufficiently small in order for the analogue displays correct convergence behaviour of the network when subjected particularly to large impulses. [Copyright &y& Elsevier]

Abstract: This paper investigates the chaos synchronization problem for drive–response Chua''s systems coupled with dead-zone nonlinear input. Using the sliding mode control technique, an adaptive control law is established which guarantees projective synchronization even when the dead-zone nonlinearity is present. Computer simulations are provided to demonstrate the effectiveness of the proposed synchronization scheme. [Copyright &y& Elsevier]

This paper describes the development and the validation of two computational fluid dynamics (CFD) frameworks for multidisciplinary and multi-scale simulations. The first framework is an overset grid topology with a six-degree of freedom rigid body dynamics library for both structured-grid and unstructured-grid approaches. This framework will enable the CFD flow solver to simulate the problems involving relative motions between multiple bodies such as the stage/store separation process, etc. The second framework is a hybrid scheme that integrates a direct simulation Monte-Carlo (DSMC) method for rarefied gas flows and a Navier–Stokes (NS) solver for continuum flows. The hybrid DSMC–NS numerical framework can greatly improve the computational efficiency for simulation of problems with disparate length scales or a wide range of Knudsen numbers. A density-based Navier–Stokes flow solver, HYB3D, and a pressure-based Navier–Stokes flow solver, FDNS, were employed in this study to demonstrate the capability, strength, and accuracy of these two frameworks. Numerical simulations of benchmark test cases were conducted as the preliminary evaluation for these two frameworks, and the numerical results are presented. [Copyright &y& Elsevier]

The trunsored model, which is a new incomplete data model regarded as a unified model of the censored and truncated models in lifetime analysis, can not only estimate the ratio of the fragile population to the mixed fragile and durable populations or the cured and fatal mixed populations, but also test a hypothesis that the ratio is equal to a prescribed value with ease. Since SARS showed a severe case fatality ratio, our concern is to know such a case fatality ratio as soon as possible after a similar outbreak begins. The epidemiological determinants of spread of SARS can be dealt with as the probabilistic growth curve models, and the parameter estimation procedure for the probabilistic growth curve models may similarly be treated as the lifetime analysis. Thus, we try to do the parameter estimation to the SARS cases for the infected cases, fatal cases, and cured cases here, as we usually do it in the lifetime analysis. Using the truncated data models to the infected and fatal cases with some censoring time, we may estimate the total (or final) numbers of the patients and deaths, and the case fatality ratio may be estimated by these two numbers. We may also estimate the case fatality ratio using the numbers of the patients and recoveries, but this estimate differs from that using the numbers of the patients and deaths, especially when the censoring time is located at early stages. To circumvent this inconsistency, we propose a mixed trunsored model, an extension of the trunsored model, which can use the data of the patients, deaths, and recoveries simultaneously. The estimate of the case fatality ratio and its confidence interval are easily obtained in a numerical sense. This paper mainly treats the case in Hong Kong. The estimated epidemiological determinants of spread of SARS, fitted to the infected, fatal, and cured cases in Hong Kong, could be the logistic distribution function among the logistic, log-normal, gamma, and Weibull models. Using the proposed method, it would be appropriate that the SARS case fatality ratio is roughly estimated to be 17% in Hong Kong. Worldwide, it is roughly estimated to be about 12–18%, if we consider the safety side without the Chinese case. Unlike the questionably small confidence intervals for the case fatality ratio using the truncated models, the case fatality ratio in the proposed model provides a reasonable confidence interval. [Copyright &y& Elsevier]

Abstract: This paper addresses the problem of chaos synchronization from a control theoretic point of view. The main idea is to construct an augmented dynamical system from the synchronization error system, which is itself uncertain. A new dynamic output feedback is applied to perform synchronization in spite of master/slave mismatches. In this way, the nonidentical chaotic synchronization can be attained. The advantage of this method over the existing results is that the feedback controller has a predictable synchronization delay. The synchronization time is explicitly computed. Computer simulations are provided to verify the operation of the designed synchronization algorithm. [Copyright &y& Elsevier]

Abstract: Nowadays, most scientists and engineers rely on computer simulations to analyze, design, and prototype complex systems. Scientific and engineering system models are implemented in a variety of simulation environments; however, limited model libraries are often provided to users who are compelled to create their own customized models. Developing customized simulation models is a time-consuming and error-prone task which requires software developer skills. The difficulty of creating customized models presents the need for user-friendly tools that assist users in their code development process. This paper describes a tool named RCMAG that automatically builds customized models for the Virtual Test Bed (VTB) [http://vtb.engr.sc.edu/, The Virtual Test Bed Overview, Architecture, and Downloads] simulation environment. VTB is an interactive software system that provides a problem-solving environment (PSE) for simulation, prototyping, and advanced visualization of large-scale multi-disciplinary systems. VTB complies with a simulation standard named VHDL-AMS to enforce natural (circuit), signal, and data coupling between entities from diverse disciplines. The PSE tool RCMAG automatically builds naturally coupled or circuit-based VTB entities from input data provided by the user. RCMAG accepts both numeric and symbolic input data from the user, manages it to create code, and releases the compiled model object, which is ready to be added to the VTB model library and be used in a simulation. [Copyright &y& Elsevier]

Abstract: Based on both the theories of cellar biology and the results of experimental observations a dynamical model of birth and death-diffusion type has been suggested for popular growth of bacillus and evolution of nutrition in the single-species bacillus system with a growth–propagation source. It has been verified that the single-species bacillus system in the process of growth–propagation has the biological wave behaviors from the experimental observation. Furthermore, under a special initial values and boundary conditions corresponding to the point-source growth in a closed culture-container, the evolutionary equations of this dynamical model in the single-species bacillus system with a growth–propagation source and the combination of biological waves in the single-species bacillus system with two growth–propagation sources are analyzed by means of the computer simulation, respectively. It shows that the popular growth of single-species bacillus systems governed by birth and death-diffusion dynamical equation is characterized by the spatial-temporal quasi-periodicities which is consistent with the traveling wave solution of above evolutionary equations. It turns out that these results of computer simulation, we obtain could qualitatively copy and describe the phenomenon from experimental observations. The results reported in this paper are a powerful support to the famous argument of the biological wave about the popular growth of bacteria based on lab-observation in ecology. [Copyright &y& Elsevier]

Discrete dynamical systems based on dependency graphs have played an important role in the mathematical theory of computer simulations. In this paper, we are concerned with parallel dynamical systems (PDS) and sequential dynamical systems (SDS) with the OR and NOR functions as local functions. It has been recognized by Barrett, Mortveit and Reidys that SDS with the NOR function are closely related to combinatorial properties of the dependency graphs. We present an evaluation scheme for systems with the OR and NOR functions which can be used to clarify some basic properties of the dynamical systems. We show that for forests that does not contain a single edge the number of orientations equals the number of different OR-SDS. [Copyright &y& Elsevier]