Showing papers on "Modeling and simulation published in 1998"

Computational Materials Science: The Simulation of Materials Microstructures and Properties

Abstract: INTRODUCTION AND FUNDAMENTALS. Modeling and Simulation in Materials Science. Fundamentals and Solution of Differential Equations. SIMULATION TECHNIQUES AT THE NANO-MICRO SALE. Fundamentals. Statistical Mechanics in Atomic-Scale Simulations. Monte Carlo Simulation and Integration. Molecular Dynamics. SIMULATION TECHNIQUES AT THE MICRO-MESO SCALE. Discrete Dislocation Statics and Dynamics. Ginzburg--Landau-Type Phase Field Kinetic Models. Cellular Automata. Mesoscale Kinetic Monte Carlo and Potts Models. Geometrical and Component Models. Topological Network and Vertex Models. SIMULATION TECHNIQUES AT THE MESO-MACRO SCALE. Finite Element and Difference Methods at the Meso-Macroscale. Polycrystal Elasticity and Plasticity Models. INTEGRATED MODELING AND SIMULATION. Fundamentals. Space and Time Scales in Microstructure Simulation. Appendices.

Theory of quantized systems: formal basis for DEVS/HLA distributed simulation environment

Abstract: In the context of a DARPA ASTT project, we are developing an HLA-compliant distributed simulation environment based on the DEVS formalism. This environment will provide a user- friendly, high-level tool-set for developing interoperable discrete and continuous simulation models. One application is the study of contract-based predictive filtering. This paper presents a new approach to predictive filtering based on a process called 'quantization' to reduce state update transmission. Quantization, which generates state updates only at quantum level crossings, abstracts a sender model into a DEVS representation. This affords an alternative, efficient approach to embedding continuous models within distributed discrete event simulations. Applications of quantization to message traffic reduction are discussed. The theory has been validated by DEVSJAVA simulations of test cases. It will be subject to further test in actual distributed simulations using the DEVS/HLA modeling and simulation environment.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Methodology for the Modeling and Simulation of Microsystems

Abstract: From the Publisher: Methodology for the Modeling and Simulation of Microsystems is the first book to give an overview on the problems associated with modeling and simulation of microsystems. It introduces a new methodology, which is supported by several examples. It should provide a useful starting point for both scientists and engineers seeking background information for efficient design of microsystems.

Computational fluid dynamics applied to water and wastewater treatment facility modeling

Abstract: The major issues in water and wastewater industry are to meet quality requirements, to guarantee treatment process efficiency, to contain investment and operating costs. This implies the use of powerful predictive modeling and simulation tools which are able to account for the multiple interaction between all the water quality and process design parameters. Computational Fluid Dynamics modeling tools have already been widely used in other industries but their application in water industry is quite recent. This paper presents different applications of CFD modeling to the study of the hydro-dynamic and mass transfer performance of single- or two-phase flow reactors used in water and wastewater treatment. Numerical simulations, together with experimental measurements, have been performed on laboratory and full-scale plants in order to gain a better under-standing of the physical phenomena (mixing, interfacial transfer) occurring in these systems. Numerical simulations are systematically validated by experiments. The paper shows how CFD can be helpful in order to improve the design of existing water treatment plants and the process efficiency. In this scope, CFD enables designs more reliable and cost effective water treatment processes which remain basic environmental policy issues.

Modeling and simulation of an electronic component manufacturing system using hybrid Petri nets

Abstract: Modelling and analysis for the design and operation of manufacturing systems is a vital need. For semiconductor manufacturing systems, which are large scale systems, discrete Petri nets do not constitute an adequate tool for modeling and analysis. In fact, use of discrete Petri nets is confronted with tile state explosion and the high cost of simulation. In this paper, hybrid Petri nets are presented as powerful tools for modeling and simulation of semiconductor manufacturing systems. This model has been used for modeling and simulation of a real life electronic components manufacturing system. It provides an accurate and first simulation of this system.

Introduction to Intelligent Simulation: The RAO Language

Abstract: From the Publisher: Introduction to Intelligent Simulation: The RAO Language focuses on an unique approach in modeling and simulation of complex systems. In the volume features are considered of complex systems and processes, their mathematical description, and modeling. Theoretical foundations of RAO (Resource-Action-Operation) language as well as its syntax and utilisation are given. Examples of simulation models of different complexity levels, related to different fields, are presented as well.

Traffic simulation based on the high level architecture

Abstract: Interoperability and reusability are features supported by the new High Level Architecture for Modeling and Simulation (HLA). While the traditional approach of monolithic traffic simulation modeling has proven to be successful, distributed traffic simulations gain more attention. The first part of the paper describes our work with distributed traffic simulation based on the High Level Architecture and the lessons learned from enhancing classic simulation and animation tools for HLA and our first HLA prototypes. The second part elaborates on the additional flexibility that architectures for distributed simulation offer, focusing on the dynamic integration of information relevant to the overall simulation into the dynamic event space. A promising outlook concludes the paper.

An energy-based model reduction methodology for automated modeling

Abstract: Commercial competition demands a reduction in the development time of new products. While it has been recognized for a number of years that the development process can be accelerated with the use of computer simulation based on mathematical models of the product, the lack of appropriate modeling tools has limited the effectiveness of this approach. It is the premise of this work that a new modeling metric able to handle nonlinear dynamic systems and all types of energy elements, will improve the effectiveness of modeling tools. A new modeling metric, activity, which is based on energy, is developed in this work. This metric is used to rank the importance of all energy elements in a system. The ranking of the energy elements provides the relative importance of the model parameters and this information can be used to reduce the size of the model. The metric is implemented in an algorithm called Model Order Reduction Algorithm (MORA). MORA is applied to a nonlinear quarter car model showing that elements with low activity can be eliminated without any significant change in model accuracy. MORA is also applied to linear systems, where the steady state activity to sinusoidal inputs is considered. It is shown that the activity varies with frequency, and thus, a series of reduced models can be generated as a function of the excitation frequency. For multibody systems, the activity metric can be applied to each DOF of the rigid bodies. The activity metric is applied to a heavy-duty tractor-semitrailer to demonstrate that a significant number of the model parameters are insignificant, and therefore, that a substantial reduction in the model size can be achieved. Finally, an interpretation algorithm based on the activity metric is developed to provide the user with physical meaning of each low activity element eliminated. In addition, the use of the activity metric to rank the energy elements augments the insight into the model, since the engineer can focus on a smaller number of elements that are identified by MORA as important to the system behavior. In conclusion, this work develops an automated modeling algorithm, MORA, which can be used to rank model parameter importance, reduce model complexity and help provide physical insight into a system. MORA extends the applicability of automated modeling to systems that can be represented by nonlinear dynamic models and it should improve the use of modeling and simulation for product development.

Uncertainty quantification in computational structural dynamics : A new paradigm for model validation

Abstract: We present an overview of new research efforts underway at Sandia National Laboratories to understand the sources of uncertainty and error in computational structural dynamics and other physics simulations, and to quantify their effects on predictive accuracy. In order to establish confidence in computational simulations as these simulations move further from the established experimental database, a new approach to modeling and simulation validation is needed. In particular, when simulations are used to qualify the safety and reliability of systems, we believe that validation should be based upon a comprehensive quantification of uncertainties and errors from all phases of the modeling and simulation process. Uncertainty and error quantification is a two-step process, the first step being the identification of all uncertainty and error sources in each phase of modeling and simulation. The second step is the assessment and propagation of the most significant uncertainties and errors through the phases of the modeling and simulation process to the predicted response quantities. This paper outlines the phases of modeling and simulation, the distinction between uncertainty and error, and a categorization of uncertainty and error sources in each phase of modeling and simulation. We also address the question of how uncertainties in the form or structure of the model might be assessed using multiple models. Examples from linear structural dynamics are given to illustrate these concepts.

Modeling and simulation of the interaction of plants with the environment using l-systems and their extensions

Abstract: The simulation of plant-environment interactions has been recognized as one of the main problems in the domain of plant modeling. This dissertation presents the results of my work, which include recognizing general mechanisms of the interaction between a real plant and its environment and incorporating them into an existing plant modeling formalism based on Lindenmayer systems (L-systems). The first step was the extension of the L-system formalism by the introduction of environmentally-sensitive L-systems which are able to simulate the development of a plant affected by the environment. The next step was the design of a modeling framework which can capture all aspects of the plant-environment interaction, including the effects of the plant on the environment. This framework consists of two separate processes, one simulating the plant and the other modeling the environment. The L-system formalism is extended by creating open L-systems which can communicate with the environment through a well defined interface. The communication library provided with the framework makes it easy to create new programs simulating the environment. The modeling capabilites of both environmentally-sensitive L-systems and the framework based on open L-systems are validated on many examples of plant models interacting with their environment. Most of these examples reproduce results presented in the literature proving the usability of the proposed modeling framework. Many of the models are modified, improving the realism of their visualization by incorporating various new graphical features of the modeling software, or making the algorithms which simulate the environment more effective.

Simulation Based Acquisition: A New Approach

Abstract: : Program Managers have long been applying modeling and simulation tools to efforts within the various stages of their programs. Recently, declining defense budgets have increased the pressure on the acquisition community to find cheaper ways to develop and field systems. The objective of this book is to convince program managers that Simulation Based Acquisition is a smarter way of doing business.

Markov Modeling for Reliability Analysis

Abstract: From the Publisher: "Markov modeling has long been accepted as a fundamental and powerful technique for the fault tolerance analysis of mission-critical applications. However, the elaborate computations required have often made Markov modeling too time-consuming to be of practical use on these complex systems. With this hands-on tool, designers can use the Markov modeling technique to analyze safety, reliability, maintainability, and cost-effectiveness factors in the full range of complex systems in use today.Featuring ground-breaking simulation software and a comprehensive reference manual, MARKOV MODELING FOR RELIABILITY ANALYSIS helps system designers surmount the mathematical computations that have previously prevented effective reliability analysis. The text and software compose a valuable self-study tool that is complete with detailed explanations, examples, and a library of Markov models that can be used for experiments and as derivations for new simulation models. The book details how these analyses are conducted, while providing hands-on instruction on how to develop reliability models for the full range of system configurations.Computer-Aided Rate Modeling and Simulation (CARMS) software is an integrated modeling tool that includes a diagram-based environment for model setup, a spreadsheet like interface for data entry, an expert system link for automatic model construction, and an interactive graphic interface for displaying simulation results."

Efficient large-scale process-oriented parallel simulations

Abstract: Process oriented views are widely recognized as very useful for modeling, but difficult to implement efficiently in a simulation system, as compared to event oriented views In particular, the complexity and run-time overheads of the implementation have prevented the widespread use of process oriented views in optimistic parallel simulations Here, we review the conventional approaches to implementing process-oriented views, and outline some of the sources of problems in those approaches We also identify an approach that we call stack reconstruction, which is most suited for portably and efficiently supporting optimistic process-oriented views Benchmark simulations using our preliminary implementation, which is incorporated in the TED modeling and simulation system, confirms the low overheads of this approach, and demonstrates its capability to simulate over one million processes in a process-oriented model

Applied modeling and simulation : an integrated approach to development and operation

Abstract: Introduction to Modelling and Simulation Systems Science and Systems Engineering A Framework for Modelling and Simulation Defining the Need for Models and Simulations Creating a Modelling and Simulation Baseline Developing an Acquisition Strategy A Conceptual Approach to Developing Models and Simulations Designing Models Producing and Managing Data Implementing Models and Simulations in Hardware and Software Verification, Validation and Accreditation Integrating and Executing Simulations Establishing Standards and Specifications Adapting to Changing Technology Network Issues in Distributed Simulation Interactive Simulation - Inserting Humans into Distributed Virtual Environments Information Security in Simulator Design and Operation Appendix A - Estimating Cost and Schedule Appendix B - Software Design Appendix C - Statistical Analysis and Experimental Design

Discrete-event simulation for the design and evaluation of physical protection systems

Abstract: Explores the use of discrete-event simulation for the design and control of physical protection systems for fixed-site facilities housing items of significant value. The paper begins by discussing several modeling and simulation activities currently being performed in designing and analyzing these protection systems and then discusses the capabilities that design/analysis tools should have. The authors then discuss in detail how some of these new capabilities have been implemented in software to achieve a prototype design and analysis tool. The simulation software technology provides a communications mechanism between a running simulation and one or more external programs. In the prototype security analysis tool, these capabilities are used to facilitate human-in-the-loop interaction and to support a real-time connection to a virtual reality model of the facility being analyzed. This simulation tool can be used for both training (in real-time mode) and facility analysis and design (in fast mode).

A Multilevel Product Model for Simulation-Based Design of Mechanical Systems

Abstract: This paper presents a multilevel product model that supports Simulation-Based Design (SBD) of mechanical systems, from pre liminary to detailed design stages The pnmary goal of the SBD is to achieve product designs featuring better performance and greater du rability and reliability through computer-based modeling, engineering analysis, and design trade-off. A Computer-Aided Design (CAD) model combined with engineering parameters and mathematical equations that simulate physical behavior of the mechanical system constitute its product model for SBD. For preliminary design, improvement of system performance, including dynamics and human factors, is usually the primary focus A CAD model with reasonably accurate physical parameters, such as mass properties of major components or assemblies, is defined as the base definition of the product model for SBD. A number of simulation models are derived from the base definition to sup port simulation of the mechanical system performance A parametric study can be cond...

Modeling, simulation, and design methodology of the interconnect and packaging of an ultra-high speed source synchronous bus

Abstract: In this paper, we describe the modeling, simulation and design methodology of the interconnect and packaging for a 400 MHz L2 level cache. Since the bus is source synchronous or "self timed", the signal integrity, and hence the electrical performance of the package and board interconnects is a major limiter to the bus speed. To this end, we present circuit design techniques to alleviate packaging problems such as the implementation of a dynamically controlled driver impedance and edge rate. The timing equations for the source synchronous I/O bus are written in terms of the basic fundamental limitations of the silicon, package, and board processes. The interconnect performance modeling and simulation methodologies used to optimize these equations are described.

General Purpose Discrete Event Simulation using

Abstract: We discuss the use of the stochastic process algebra (spades) for discrete event simulation, and report on a prototype simulation algorithm that has been implemented. The use of process algebraic techniques in offers a number of advantages with respect to existing simulation techniques. The compositional nature of allows an on-the-fly construction of the simulation model, and hence only the current state need to be saved. , moreover, allows us to model and simulate on a general purpose basis, as the simulation algorithm applies to any well founded process specified in . Finally, specifications in are also amenable to traditional process algebraic analysis of their functional behaviour, like e.g. absence of deadlocks. We illustrate our result with a simulation example of a nontrivial system.

Modeling and simulation of flexible flight vehicles

Abstract: Theeffectsofe exibility on thee ightdynamicsoflargeaircraft havebeen shown to bequitesignie cant, especially as the frequencies of the elastic modes become lower and approach those of the rigid-body modes. The handling characteristics of such vehicles are altered signie cantly from those of a rigid vehicle, and the design of the e ightcontrol system may become drastically more complex. Consequently, the need to model accurately the dynamics of such vehicles, and to develop valid simulations, is becoming particularly acute. The theoretical development of a generic e exible-aircraft model is reviewed. This modeling technique allows for the e exible degrees of freedom to be added to an existing simulation model of the vehicle’ s rigid-body dynamics. The data necessary for modeling a specie c vehicle include aerodynamic stability derivatives, aerodynamic ine uence coefe cients, elastic mode shapes, modal frequencies and damping, and generalized masses. Two case studies are presented, both involving the developmentofmotion-basedsimulationsinNASALangleyResearchCenter’ ssimulationfacility.Thee rstexample investigatesanaircraftsimilaringeometrytotheB-1,whereasthesecondinvestigatesalargehighspeedcommercial transport. The dynamic responses (time and frequency domain ) for these vehicles are presented, along with the evaluations of the effects of dynamic aeroelasticity on their handling characteristics. The vehicle responses are critical to evaluating hardware and software requirements for simulation e delity, for example, visual and motion cues. Finally, a brief assessment of the effects of limitations of the simulation facility is presented. Limitations considered include digital time delay, motion hardware bandwidth, and motion washout logic.

Modeling a die bonder with Petri nets: a case study

Abstract: The process of designing complex manufacturing machines involves problems of interdisciplinary communication, design space exploration as well as design evaluation and analysis that can best be solved by integrating modeling and simulation stages into the development process. Requirements necessary for a modeling environment are: support for hierarchical and modular structuring, module reuse, configurability of the model, executability of the model with a notion of time, and intuitive usability. The CodeSign object-oriented, temporal Petri net formalism with its associated tool is a modeling and simulation environment to meet those requirements. A case study conducted in an industrial setting is described that demonstrates the applicability of the CodeSign approach to the modeling of semiconductor manufacturing equipment with step-wise refinement. Results are given to show the accuracy of simulation results with respect to data actually measured on the machine. The CodeSign simulation results are shown to have superior accuracy compared to the output of a previous spreadsheet model of the same machine.

Efficient techniques for accurate modeling and simulation of substrate coupling in mixed-signal IC's

Abstract: Industry trends aimed at integrating higher levels of circuit functionality have triggered a proliferation of mixed analog-digital systems. Magnified noise coupling through the common chip substrate has made the design and verification of such systems an increasingly difficult task. In this paper we present a fast eigen-decomposition technique that accelerates operator application in BEM methods and avoids the dense-matrix storage while taking all of the substrate boundary effects into account explicitly. This technique can be used for accurate and efficient modeling of substrate coupling effects in mixed-signal integrated circuits.

STEADY-STATE modeling and simulation of pipeline networks for compressible fluids

Abstract: This paper presents a model and an algorithm for the simulation of pipeline networks with compressible fluids. The model can predict pressures, flow rates, temperatures and gas compositions at any point of the network. Any network configuration can be simulated; the existence of cycles is not an obstacle. Numerical results from simulated data on a proposed network are shown for illustration. The potential of the simulator is explored by the analysis of a pressure relief network, using a stochastic procedure for the evaluation of system performance.

Modeling, simulation and design of convective industrial dryers

Abstract: The use of computers to perform simulations of chemical engineering processes has lead to the development of software tools that perform most tedious computations in the field of process analysis, mathematical modeling and design. In the case of dryers, these mathematical programming aspects can be dealt in a straightforward way. The mathematical models of all popular convective dryers are presented and analysed. The transport and thermophysical properties of materials and air involved in the developed mathematical models are briefly discussed. The simulation of convective drying processes facilitated by modern computer technology is outlined and discussed. Design of convective industrial dryers is described and performed through the simulation tools developed. Short-cut design techniques are introduced allowing concentrated information on design results for various levels of process parameters and variables to be integrated in generalized design curves that produce values of optimal dryer struct...

The effects of complexity on business processes reengineering: values and limitations of modeling and simulation technologies

Abstract: Argues that the value of simulation and modeling technology tends to be contingent on creating models that can offer a systematic, well-defined way of representing the structure of a firm's business processes. As such, the behavior of stable systems can be predicted through modeling and simulation. Stable business processes can reach an equilibrium over time. Complexity (hierarchical processes) and random changes within complex processes, however, tend to create dynamic systems that have a tendency not to reach an equilibrium. Hence, simulation and modeling of complex and dynamic systems tend to add less value in the predictability of such systems.

Precorrected-DCT techniques for modeling and simulation of substrate coupling in mixed-signal IC's

Abstract: Industry trends aimed at integrating higher levels of circuit functionality have triggered a proliferation of mixed analog-digital systems. Magnified noise coupling through the common chip substrate has made the design and verification of such systems an increasingly difficult task. In this paper we present a new method based on a precorrected-DCT algorithm that extends an eigendecomposition-based technique and can be used to accelerate operator application in BEM methods. This method is shown to avoid storage of a dense matrix, as is typical in BEM methods, while at the same time taking all of the substrate boundary effects into account explicitly. This technique can be used for accurate and efficient modeling of substrate coupling effects in mixed-signal integrated circuits.