bluuebunny/crossref_metadata_2025 huggingface dataset:
A statistical expert system for simulation analysis
Authors: Mellichamp Joseph M. , Park Young H.
Published: March 2008

Efforts on a number of fronts are being made to enhance the usefulness of simulation as a tool for analysis. Graphical input, animation, automated program generation, model management utilities, and user interactive environments all address the issue of ease of use. Even with the current emphasis in this regard, simulation suffers from several shortcomings which preclude even greater application of the methodology. One of the more signifi cant limitations is the dependence of simulation on statistical methodologies. Practically every phase of simulation analysis in volves one or more statistical issues. And the fact of the matter is that many simulation practitioners have neither the statistical skills nor the access to qualified statisticians to effectively address these crucial issues.

The obvious solution to this problem would be to have an ex pert statistician available during every simulation study to answer any questions concerning statistical issues. A more practical alter native is to make available an expert system which could func tion as a statistical advisor to simulation analysts. This option seems ideally suited for expert system techniques since it is well- defined and narrowly bounded and an appropriate body of statistical knowledge exists.

The objective of this research was to develop such an expert statistical consultant. The system would be able to advise as well as perform appropriate computations for a variety of statistical issues including input data analysis, design of experiments, and output analysis. An overview of the proposed system is given and illustrations of the capabilities of the system are presented.
CLUSTERT — A simulation-based expert
Authors: Pinkowski Ben
Published: March 2008

Cluster analysis consists of applying statistical and heuris tic methods in an attempt to discover the group composition of a data set. Users of traditional clustering software often find non-intelligent packages difficult to use because of the many parameters that must be specified before an analysis can begin; these include a distance or similarity metric, a method for stopping group amalgama tion or division, and a particular clustering algorithm. CLUSTERT is an expert system for solving cluster analysis problems that was developed because of this difficulty. Unlike most expert systems, however, CLUSTERT is primarily based on knowledge generated by simulation experiments. The system also provides suggestions and an intelligent environment for conducting additional simulations that may reinforce
A methodology for simulation of database systems
Authors: Eich Margaret H. , Fan Chin-Feng , Sun Wei-Li , Rafiqi Sohail
Published: March 2008

This paper presents a methodol ogy for performing database system simulations which is based on the Wisconsin Bench- marks. Use of this approach provides very realistic represen tations for transactions, hard ware, and software aspects of a target database environment. The flexibility built into the approach also facilitates exami nation of many different database environments with few changes to the basic model. The method described equips researchers with the first standard simulation approach which can be used on any database system. We describe the approach, its implementation using SLAM II, and then provide an overview of its use.
A User-Friendly Interactive Turbo Pascal Simulation Toolkit
Authors: Tavernini Lucio
Published: March 2008

A Turbo Pascal-based simulator specifically designed for continuous-time models with time delays and hysteretic phenomena is presented and its use illustrated with examples. Delays can be time- and state-dependent.

For models with hysteretic (multi-valued) behavior, use is made of a recently introduced mathematical paradigm: the differential automaton. For models defined by differ ential or delay-differential equations with jumps in the derivatives, the differential automaton formalism can be bypassed by using a switch function to indicate points of low differentiability in the model. The switch function interacts with the simulator to approximate each point of discontinuity where the numerical integrator is to be reini tialized. This interaction, transparent to the user and implemented via side effects of the switch function, replaces the explicit scheduling of state events by the user.

For models with time delays, a global approximation is constructed for each delayed state variable. Each global ap proximation is partitioned into sufficiently smooth seg ments and a smoothness index is associated with the boundary separating any two such segments. Whenever a delay crosses between two adjacent segments, should the value of the smoothness index require it, the time of crossing is approximated iteratively, the numerical integra tor is reinitialized, and a new segment is started in the partition. A new segment is also started whenever a switching takes place.

The simulator graphical output interface is self-config uring at execution time with respect to the video display adapter-display combination in use. Interactive plotting programs with on-line documentation are also provided to retrieve, then plot, problem data from save files generated during a simulation.
Simulation for emergency management: Taking advantage of automation in emergency preparedness
Authors: Walker J. Andrew , Ruberg George E. , O'Dell John J.
Published: March 2008

Industrial facilities operate in an en vironment of increased public awareness of hazards, and added regulatory demands. Public awareness and new regulations result from concerns over the effec tiveness o f safety systems and the consequences of their failure. Increasingly the public, government regulators, insurers, and stockhold ers require evidence that a facility can be operated safely and that accidents can be managed effec tively. Recent federal environ mental and occupational safety regulations reflect the increasing attention. This requirement may be addressed by proposing a cost- effective approach, which applies simulation techniques in three phases to take advantage of advances in emergency prepared ness automation. The approach will both train and provide some means of validating those persons responsible for effectively managing emergencies when they occur.
A Model for the Management of Building Evacuation
Authors: Weinroth Jay
Published: March 2008

The process of emergency evacuation of large buildings has been modeled by computing the theoretically most efficient paths for occupants and then attempt ing to realise this recommenda tion in evacuation planning and management. A simulation approach is presented which reverses this sequence. The evacuation behavior of occu pants is modeled to predict and analyze the choices that lead to serious bottlenecks and an improvement strategy is developed from these results. An explanation of the basis for the model is presented, followed by examination of results of applying the model to Pauls' evacuation data and to a university building with complex exit structures.
Law Enforcement Simulation System
Authors: McDonald Craig J.
Published: March 2008

This article describes a model (known as COPS, COuntywide Police Simulation System) which simulates the receipt of police, fire, and emergency medical calls at a public safety communications center, with subse quent dispatch of law enforcement officers to police events. The delivery of police services involves the processing of an event, or call-for-service, from the moment that the call is received at an emergency communications center through disposition of the call by police officers. This process involves telecom municators, dispatchers, and police officers.

From the telecommunicator perspective, it includes the receipt of a request for police service at a public safety communications center, the assignment of the call to an available telecommunicator, the interview of the calling party by the telecommunicator, and the transfer of the event in formation to a police dispatcher. The dispatcher is then responsible for selecting the most appropriate police unit(s) for dispatch. The police officer must travel to the scene, service the complainant, clear from the call, and return to preventive patrol.

The model examines the interaction of external variables, including the type of call, the frequency of calls, the number of telecommunicators on duty, the number of police cars in service, the deployment pattern of the officers, the number of cars to be dispatched, and the dispatch plan.

By modifying the values that these variables can hold, the distribution of workload among police officers can be observed, response times and service times can be examined, and dispatching policies can be evaluated. Sensitivity analysis can be performed without disrupting the life-critical nature of the live operation.
Simulation of power converter devices with nonlinear elements
Authors: Nelms R.M. , Reid Brad B. , Grigsby L.L.
Published: March 2008

This paper presents a technique for modeling and simulating power converters which contain nonlinear elements such as saturable inductors. Each nonlinear element is modeled by an ideal sampler, a variable gain, and a clamp. A state variable is added for each nonlinearity. A homogeneous state model is then formulated for the power converter. This state model is solved using a state transition matrix ap proach. A jump matrix J is utilized to account for the ideal sampler operations.
Evaluation of probabilistic consultation systems by simulation
Authors: Nordbotten Svein
Published: March 2008

This paper reports on an evaluation of alternative inference models applied in probabilistic consultation systems by simulation. In the first section some general remarks about consultation systems are made in order to set the specific system discussed in a wider context. Section 2 gives a description of the different inference models tested. The next section specifies simula tion experiments which aim at an evaluation of the inference algo rithms. Section 4 outlines the actual experiments and in Section 5 the results of the experiments are presented. The main conclusions supported by the experiments are: the rule value model gives more successful predictions than simpler inference models, that a model applying the complete Bayes' formula performs better than one which instead makes use of complementary probabilities in the denominators, and that the estimates of prediction probabilities in models ignoring the statistical dependence among symptoms tend to be highly biased and cannot be expected to be useful reliability indicators.
Verifying and validating complex simulation models by analogy
Authors: Banks Jerry
Published: March 2008

This paper describes a procedure used to develop verifi cation and validation techniques for very large simulation models. The procedure uses analogies from other systems to stimulate analogies which can then be implemented in the simulation environment.

Sixteen systems were studied and some 64 analogies were developed. Several of the analogies are currently being considered for possible extension and application to complex simulation models.
MOSES: Manufacturing Organization Simulation and Evaluation System
Authors: Pruett James M. , Vasudev Vinay K.
Published: March 2008

The key to the successful "factory of the future" will be the effective coordination of managerial functions and production operations. The simulation model described in this paper addresses this "coordination" issue, especially in terms of managing the impact of interrelated alternatives and activities in an information-rich environment. An evolutionary simulation modeling program, MOSES (Manufacturing Organization Simulation & Evaluation System), has been developed for the purpose of describing, analyzing, and understanding manufacturing organizations.

MOSES is both a program and a concept. As a program, it is a menu-driven, interactive, discrete-simulation modeling tool. MOSES users are able to simulate any discrete-product manufacturing environment. As a concept, MOSES is a blend of simulation modeling and information-based management. It is structured around the idea that all manufacturing organization functions can be categorized into one of four areas—marketing, production, inventory, and accounting—and that organizational success depends on decisions made by managers of those areas. MOSES users manage the organization by observing, experimenting with, and modifying the simulation-driven activities. This user interaction may take place before, during, or after the simulation process.

MOSES is evolutionary in several ways: (1) the user is able to build a meaningful manufacturing organization simulation model without writing any computer code; (2) the model spans the entire manufacturing organization, not just the production function; (3) the model includes optimization techniques and heuristics along with traditional logical modeling principles; (4) the model' stores and manipulates data using database technology rather than more traditional file techniques ; (5) the system includes the user as an integral part of the simulation process.
Modeling and simulation in the operational test and evaluation process
Authors: Keck Eric
Published: March 2008

The continuous use of modeling and simulation (M/S) throughout the operational test and evaluation (OT&E) process is presented as a means to improve the efficiency and effectiveness of OT&E. The utility of using M/S from understanding the problem at the beginning of a test program to maximizing the utility of test information after the test is discussed along with some problem areas and potential solutions.
Modeling and simulation in support of Navy operational test and evaluation
Authors: Loyd LCDR Robert C.
Published: March 2008

OPTEVFOR is chartered by CNO as the Navy's independent test organiza tion to conduct actual field test of new procurement systems. Prior to DOT&E's issuance of new policy guidance, any test issue which OPTEVFOR could not address during OT&E was left unresolved or limited comment was made based on extracts of precise technical information from pristine and less complex developmental tests. DOT&E has now recognized the contribution that logically applied modeling and simulation can make toward the evaluation of new warfare systems at each decision point in the procurement and implementation cycle. This use of M&S to supplement rather than replace operational testing is interpreted by DOT&E as being within the spirit and intent of the law. This brings about a significant change in the way OPTEVFOR does business. To in corporate a modeling and simulation capability at OPTEVFOR, a new organization has been established: the Modeling and Simulation Branch. The M&S Branch representative works with the OTD and advises him on the integration of M&S into OT&E, primarily to support those areas where actual testing is inadequate to provide answers to effectiveness or suitability issues, but also, to aid in OT&E test design and devise new system tactics. Major systems in development now using M&S to aid in early program as sessments include SSN-21, using the NUSC SIM II model, and Standard Missile (SM-2) Block IV with its series of flyout and endgame portrayal models developed through the coordination of Raytheon.
Dynamic and control behavior of multicomponent distillation columns
Authors: Yiu Y.S. , Carling G.A. , Wood R.K.
Published: March 2008

A general purpose digital simulator that can be used for studying either the transient response or control behavior of multicomponent tray distillation columns has been developed. The DYCONDIST simulator, written in FORTRAN 77, utilizes a column model that solves the coupled nonlinear material and energy balance equations for each stage. Control performance of any column is analyzed by the user deciding upon a control strategy and then invoking one or more or the existing control algorithms or employing a user-written control algorithm. Features of the simulator are described and its use is illustrated for studying the open loop (dynamic) behavior and control behavior of a 29 tray depropanizer.
An autocorrelation function test for out put validation
Authors: Barlas Yaman
Published: March 2008

Output validation is a major aspect of simulation validation in general. In continu ous simulation (e.g., System Dynamics), output validation involves demonstrating that the model is able to reproduce the dynamic time patterns that have been observed in the behavior of the real system. But standard sta tistical tests cannot be readily used to make such dynamic time pattern com parisons (i.e. periodicities, amplitudes, trends...) In this paper, we propose an output validity test that addresses the above need. The test consists of comparing the autocorrelation functions of the observed and model-generated outputs. Using simulation experiments, we demonstrate the application of the test to different situations, such as systems with large noise, observation errors, and models with parameter errors. The test is shown to detect significant errors in the fundamental periods of the observed and model-generated outputs. The test can also determine if the observed output has high frequency noise components (such as observa tion errors) not present in the model output. Experiments also demonstrate that interpreting the results of the autocorrelation function test is rather intuitive and simple, which is a major advantage of the test.
Simulation of transmission line transients with a distributed-parameter model using a personal computer
Authors: Nelms R.M. , Sheblé G.B. , Newton Steven R. , Grigsby L.L.
Published: March 2008

This paper presents a state space technique for the solution of electromag netic traveling wave equations. By dividing the transmission line into a series of π -section segments, a set of state equations is written in vector-matrix form. Each section segment consists of a series resistance and inductance with a shunt conductance and capacitance placed at the terminal ends of the segment. The state variables are chosen as the inductor currents and the capacitor voltages. The trapezoidal method of numerical integra tion is used to convert the state equations to a set of linear difference equations. Finally, LU factorization is used to update the difference equations. The state space technique presented is readily imple mented on a personal computer.
Predicting beef cattle stocking rates and live weight gains on Eastern Oregon rangelands: Description of a model
Authors: McInnis Michael L. , Quigley Thomas M. , Vavra Martin , Reed Sanderson H.
Published: March 2008

A simple deterministic model was developed to predict animal unit months (AUM's) and live weight gains of beef cattle grazing specific range types in eastern Oregon. The model can provide values for 3 levels of spatial resolution (pasture, mapping unit, and slope/ proximity to water "cells" within map ping units) and 5 monthly periods from May 15 to October 14. Operation of the model begins by calculating forage availability as a factor of forage biomass, usable acres, and desired forage utiliza tion. Grazing capacity (AUM's) is calculated by comparing forage availabil ity with the dry matter forage requirement of a 1,000 lb animal unit for 30 days. Live weight gains are calculated by comparing forage availability to dry matter forage intake, crude protein intake, and digestible energy intake of yearling heifers. The model can be used in planning range improvements and coordinating livestock management with other rangeland activities.
A software stimulator for a knowledge-based ESM system
Authors: Hood Stephen T. , Mason Keith P. , Mildren Wayne J.
Published: March 2008

A computer simulation of a receiver intercepting radar emissions in a tactical maritime environment has been developed as a means of stimulating a knowledge-based system for signal interpretation. The development of the model from concept, through a prototype in Prolog, to the current version in C is described in this paper. The model is designed to run in a multi processing environment providing real-time simulation of the signal environment to allow the performance of the knowledge- based system to be evaluated. The model provides a language for specifying scenarios in an object-oriented style, and uses inter process communication facilities provided by the UNIX operating system to connect to the application system. Interactive tools to control the runtime characteristics of the simulation are also provided.
The entity - connection approach to modelling and simulation
Authors: Pflug Georg Ch. , Prohaska Michael
Published: March 2008

To cope with the huge complexity of many simulation programs, a series of description, implementation and documentation tools have been invented to support the whole software development process. The tools range from simulation model specification and documenta tion languages, through program generators, to knowledge-based advanced simulation environ ments or model management systems. Most of these tools transform meta-information about the model into a code in an existing simulation language. Little attention is, however, paid to the question which concepts of a computer simula tion language are appropriate to support meta- programming (i.e. module combination, alteration, replication etc.). In this paper a modular concept for a discrete event simulation language is presented. This language contains abstraction mechanisms, namely the entity and the connection module, which are at the same time data and control abstractions. To each such module there corresponds a graphically displayable icon. The graphic representation is such that the consistency of the model is equivalent to a correctly assembled representa tion graph. The aims of this new concept are to present a new structure for simulation program ming, to create an appropriate software engineering tool and to provide a graphical representation technique for simulation models, which enhances modularity and decomposition for parallelization.
Multiprocessor implementation of algorithms for ordinary differential equations
Authors: Dimitriadis Socrates , Karplus Walter J.
Published: March 2008

Multiprocessor computers constitute a cost-effective alternative to supercomputers for applications that require the solution of large sets of ordinary differential equations. The efficient use of multiprocessor comput ers however, requires tools for generation of parallel applications. This paper presents a general methodology for parallelization of the integration algorithms through a heuristic procedure for static multiprocessor scheduling of the computations involved. The procedure partitions, distributes and schedules the entire computation, based on decomposition of the mathematical models. Both problems are addressed: (i) minimize the completion time for a specified number of processors, and (ii) minimize the number of processors required to achieve a specified performance. The procedure combines high performance and simplicity for a wide variety of mathematical models, numerical algorithms and multiprocessor architec tures.
A multiprocessor system for dynamic system simulation
Authors: Malbasa Veljko
Published: March 2008

The basic goal of the project reported in. this paper was to design and implement an experimental multimicroprocessor system dedicated to the real-time parallel simulation of dynamic systems of various degrees of complexity. The implemented multimicroprocessor called RAMS is also used to study the parallelization concepts of dynamic system models. Potential applica tion of RAMS is in the process control area. The RAMS hardware architecture and software concepts, in particular the auto matic synthesis of RAMS application software, are given in some detail. The problems of both task creation and schedul ing in the non-deterministic RAMS environment are addressed. The experimen tal results show the power of RAMS through the parallel simulation of a case study dynamic system.
An expert system prototype assisting the statistical validation of simulation models
Authors: Deslandres V. , Pierreval H.
Published: March 2008

The validation stage is often neglected in a simulation project, due to the high level of knowledge which is necessary. In this paper, the expert system approach is proposed to assist the simulation user in selecting an appropriate validation method, application of this method in the appropriate way, and interpreting the results. The main objective of such a system is to regroup validation techniques, scattered in literature, into the same knowledge base, and then to complete it with knowledge in statistics, simulation, and validation techniques, coming from experts. This study is part of a more general study on an Intelligent Environment for Simulation. Due to the difficulty in designing such a validation expert system, the application domain is restricted to the validation of observable discrete systems (particularly manufacturing systems), and to methods based on statistical tests. The functions of the expert system and the chosen knowledge representation are outlined and a prototype developed using K.E.S. software, is introduced. A brief example is given which illustrates the system capabilities. Finally the conclusion states that the expert system approach is adapted, due to restrictions which were imposed.
Discrete event simulation of object movement and interactions
Authors: Corey Philip D. , Clymer John R.
Published: March 2008

A set of routines is described that assist a programmer in modeling object movement and interactions. Interactions occur when objects move in range or leave range of other objects. Interaction events are rescheduled automatically as objects change vectors. Routines are written in Pascal to take advantage of its dynamic memory allocation capability and minimize memory require ments. An airport simulation demonstrates use of the routines.
A performance study of the hypercube parallel processor architecture
Authors: Lamanna Catherine A. , Shaw Wade H.
Published: March 2008

This simulation study investigated the relationship between workload characteris tics and process speedup obtainable on a hypercube parallel processor architecture. There were two goals: the first was to determine the functionat relationship between workload characteristics and speedup, and the second was to show how simulation could be used to model the concurrently executing processes to allow estimation of such a relation. The hypercube implementation used in this study was a packet-switched network with predeter mined routing and a balanced computa tional workload. Three independent vari ables were controlled: total computational workload, number of processors and the message traffic load. A benchmark program was used to estimate the fundamental timing models and to validate a discrete event simulation. Results of this study are useful to software designers seeking to predict the degree of performance improve ment attainable on a hypercube class machine. The methodology and results can be extended to other parallel processing architectures.
CAUSIM: A rule-based causal simulation system
Authors: Fu Li-Min
Published: March 2008

Researchers have felt that expert perfor mance must also rest on knowledge of deep models which relate underlying causal variables to observable facts. Simulation based upon causal knowledge is an impor tant method to infer possible consequences from given situations. This paper presents a rule-based causal simulation system called CAUSIM, which basically offers two kinds of simulation: backward simulation and forward simulation. Backward simulation is used to infer the instant behavior of specific attributes, whereas forward simulation is taken to arrive at possible overall scenarios. In addition, CAUSIM invokes constraint rules which describe incompatible behavior and values among related variables before applying simulation rules in order to obviate the inconsistencies between the simulation result and existing facts. The strength of CAUSIM lies in the capability of perform ing both qualitative and quantitative causal simulation in an integrated environment.
A mathematical model to simulate small boat behaviour
Authors: Browning Andrew W.
Published: March 2008

The use of mathematical models and associated computer simulation is a well established technique for predicting the behaviour of large marine vessels. For a variety of raisons, mainly related to effects of scale, existing models are unable to ad equately predict the manoeuvring character istics of smaller vessels. The accuracy with which the performance of a boat under autopilot control can be predicted also leaves much to be desired. The paper presents a mathematical model to simulate small boat behaviour and so can assist with the design and testing of boat autopilots.

The boat model is presented in six degrees- of-freedom, which, with suitable wave disturbance terms, allows motions such as broaching to be analysed. Instabilities in the performance of an autopilot arising from such sea-induced yaw motions can be assessed with a view to improving the control algorithms and methodology.

The research rectifies the glaring omission of a small boat mathematical model, the framework of which could be expanded to encompass other marine vehicles. Initial results are promising and show good agreement with real data.
MDL: A system for fast simulation of large layered neural networks
Authors: Teeters Jeffrey Lee
Published: March 2008

The Model Development Language (or MDL) is a simulation language and system which uses an assignment statement notation tailored for 2-dimensional layered neural networks. The key features are: (1) Operations occur on 2-dimensional arrays which correspond to the layout of many brain structures. (2) A spatial convolution operation models spatial summation occurring in dendritic trees. (3) Arbitrary time invariant expressions and differential equations may be specified by simple assignment statements. (4) Numerical methods are automatically taken care of in the MDL environment rather than in the user's specification of the model. These features allow high level modeling using leaky integrator model neurons and modeling of detailed biophysical properties, such as the Hodgkin-Huxley equations and voltage clamp experiments. Conciseness of the language allows specification of a moderately complex retina model in only one or two pages of code. The parallel structure of the language allows highly optimized implementation on parallel or vector processing computers. Use of the language is illustrated through two ex amples.
Real-time simulation of air traffic control radar terminal with trainer interface
Authors: Kornecki A. , Cieplak J. , Schneider A.
Published: March 2008

The Airway Science Simulation Labora tory (ASSL) was established in 1987 at. Embry Riddle Aeronautical University. The objective of this laboratory is to further develop and promote aviation education. One project that has emerged from this laboratory is the described below Air Traffic Control Simulation System (ATCSS). The ATCSS is designed to facilitate an environ ment in which students participate and interact as both pilots and air traffic controllers. This interaction simulates the real-time teamwork between pilots and air traffic controllers.

The purpose of this paper is to describe the simulation design concept, its components, and its potential for a variety of aviation uses. This description will include: the methods of interfacing, software and hardware requirements, feasibility of operating in multitasking environment, parallel processing, and ATC requirements with respect to oriented-towards-human- factors aviation training.
Artificial noise in read-write simulation of optical disk and drive
Authors: Chao Shiuh , Yang Tsong-Yo
Published: March 2008

When the mathematical model of the read write(R/W) simulation of write once and read many (WORM) optical disk and drive was formulated and numerical analysis and software implementation of the simulation were carried out for the noise-free R/W process, it was found that the numerical process of the simulation introduced artificial noise in the read back signal. The artificial noises were due to finite precision of integration, finite density of written spot, and finite number of pits simulated. The noises can be reduced, but at the expense of computational time.
Storing data from simulation runs for compactness and quick retrieval
Authors: Norman Theodore A.
Published: March 2008

Simulation models can generate tremendous quantities of data. This paper describes data compression and file organization tech niques which were developed to reduce the disk space required by these data. The compression techniques, which include prefix encoding, differencing and scaling, reduced one file of state variable histories by 73%. Also described is a method which allows histories of many variables to share a single file without requiring individual recorded values to be identified as to their source. This technique reduced by 99% the time to extract the history of a single variable from a file of histories of 600 state variables.
An integrated framework for knowledge-based modeling and simulation of natural systems
Authors: Rozenblit Jerzy W. , Jankowski Piotr L.
Published: March 2008

This paper proposes a new approach to simula tion modeling of natural systems in the context of water quality modeling in streams affected by point source pollution. The approach has a potential for application to other domains of natural resource modeling. Its conceptual basis is knowledge-based simulation and systems analysis. In the approach presented in this paper, a stream or its section is viewed as a collection of components, i.e. stream segments. The structure of a stream is its segments and their couplings. For each stream segment, a single constituent model describing processes affecting the segment's water quality is defined. Models are coupled in a hierarchical manner. The hierarchi cal, modular model specification results in a stream model comprised of a finite number of sub-segment models. Fundamental theoretical concepts supporting such a specification are described. A prototype simulation modeling environment to support prediction of water quality in streams has been implemented and tested. The proposed approach differs from other natural systems modeling frameworks in that it offers a) modular model specification facilities, b) high degree of model reusability, and c) support for model selection and coupling.
An experimental design strategy for designing robust systems using discrete-event simulation
Authors: Wild Rosemary H. , Pignatiello Joseph J.
Published: March 2008

Well designed experiments can dramatically improve the statistical accuracy of simula tion output data and facilitate the statistical analysis. In this paper we propose an experimental design strategy for designing robust systems using discrete-event simulation. The proposed strategy is motivated by Genichi Taguchi's strategy for improving product and process quality in manufacturing. Robust systems are systems that not only satisfy performance criteria, but also are not sensitive to uncontrollable environmental conditions or noise in the system's environment. We demonstrate the proposed experimental design strategy with a jobshop example and discuss the potential benefits of employing such a strategy for designing robust systems in general.
Workstation for integrated system design and development
Authors: Cosic K. , Kopriva I. , Miler I.
Published: March 2008

Hardware in the loop simulation has been proven as a very cost effective method in design, development, modification and testing of sophisticated industrial control systems. The Workstation for Integrated System Design and Development presented in this article allows: highly efficient real time simulation of dynamic systems using the available multiprocessor resources, micropro cessor control system design and implementa tion using suitable software package for synthesis and code generation, testing and verification of microprocessor based controller using real time interaction with multiproces sor simulator. The hardware configuration of Workstation for ISDD is based on inexpensive general purpose single board computers, which are very attractive and more favorable in speed/cost ratio in relation to the other powerful single processor solution. The appropriate examples show the applicability of these multi-microprocessor resources in: real time simulation of linear time invariant systems, comparative analysis of different discretization techniques and digital control system design and testing.
Modeling and simulation of a six-legged walking robot power system
Authors: Nair Satish S.
Published: March 2008

Reliable models and simulation enhance design and optimization capabilities considerably for complex systems. This study is concerned with such issues for a six-legged rough terrain walking vehicle power system that includes the associated control systems. The power system of the vehicle can be divided into three broad categories: leg systems, mechanical transmission system, and the primary power source and energy storage system. Modeling techniques, detailed analytical models, and a comprehensive nonlinear digital simulation are developed for precise performance predictions, interaction studies, parametric studies, and to aid in the mechanical and control design process. Validation of the models is provided by several experiments performed on a prototype leg and the vehicle. The models and simulatian predictions have resulted in a significant improvement in vehicle performance.
Hierarchical non-linear bond graphs: a unified methodology for modeling complex physical systems
Authors: Cellier François E.
Published: March 2008

Bonds graphs have been around for a quarter of a century. While originally intended for modeling mechanical systems, they have meanwhile found widespread applications in many areas of physical system modeling. Bond graphs are a very appealing tool for modeling physical systems, because they represent the flow of power through a system. Since energy and mass are the only tradable goods in our physical universe, a bond graph model is more likely to reflect physical reality than a model derived by use of any other modeling methodology. However, bond graphs, like all graphical techniques, become unwieldy when applied to complex sys tems. Also, bond graphs were traditionally used to model predominantly linear systems. This paper introduces new concepts for modeling complex physical systems through hierarchical bond graphs which can include arbitrary non-linearities. It introduces a software tool that can be used to implement these hierarchical non-linear band graphs. Finally, a new application area for bond graphs will be discussed. It will be demonstrated how these hierarchical non-linear bond graphs can be used to model chemical reaction kinetics and chemical thermodynamics together in very general terms also farther away from equilibrium than traditional approaches would permit.
A simulation technique for estimation in perturbed stochastic activity networks
Authors: Adlakha V.G. , Arsham H.
Published: March 2008

We are concerned with what-if analysis in estimating the expected value and the distribution function of completion time in stochastic activity networks. Widely used Monte Carlo simulation models of stochastic networks are often subject to errors caused by the estitnated parameter(s) of underlying input distribution function. " What-if' analysis is needed to establish confidence with respect to small changes in the parameters of the input distributions. However, traditional "what-if'analysis requires a separate simulation run for each input value. Recently, a method based on Likelihood Ratio (LR) for estimating performance function far several scenarios using a single-run extrapolation has been presented. In this paper, we experiment the use of this LR method in a network with exponential arc durations. We also consider the method with a nonlinear control random variate (NCRV) and compare it to crude Monte Carlo. The results show that the NCRV method induces variance reduction and is an effeetive filter to stabilize statisti cal variation of this single-run estimate.
Study of modeling and simulation for a chemical production system
Authors: Habchi Georges , Deloule Françoise
Published: March 2008

The purpose of this paper is to demonstrate the advantages that may be obtained through the use of simulatian tools in the design of a production workshop and more specifically, in validating a structure for production and a logic for control in the field of chemical processes. Such simulation concerns a type of production which is totally different from manufacturing type, as the former are continuous processes that can be rendered discrete. After a rapid presentation of the various theoretical approaches to modeling and simulation tools that may be used in this field, we will describe the system to be designed and its characteristics. Then we will go on to the approach to modeling we have retained and the simulation carried out in order to study the system dynamically. Finally, we will present the results we reached and we will draw some conclusions on the advantages and the limits of the study made.

This study, which aims at designing and evaluating the performances of a production unit in an international class plant specializ ing in the production of liquid chemical products, was carried out with the help of the SIMAN-CINEMA (3.5) simulation generator and decision assistance tool widely used in the design and set up of manufacturing type production systems.
Simulation modeling of human behavior in buildings
Authors: Ozel Filiz
Published: March 2008

A simulation model (BGRAF) capable of representing the emergency egress behavior of people in fires was developed at the University of Michigan. The software, written in Fortran, can be used to test different hypothesis about human behavior in fires. The cognitive effects of the physical environment were also incorporated into the decision making process simulated in this model. The graphic output animates the actions of the simulated people on a building plan on the screen. Tabular output is also provided. A building data base created by CAEADS computer-aided design software developed at the University of Michigan with partial funding from the U.S. Army Corps of Engineers is accessed by BGRAF during the input phase. The use of a CAD data base to model the physical environment was critical in creating an accurate model, since the actions of the simulated persons hinged upon the limitations of the physical environment.
The simulation of decentralized control: a hostless resource allocation model
Authors: Gagliano Ross A. , Fraser Martin D. , Schaefer Mark E.
Published: March 2008

In this article, an alternative approach to control for computing systems, with possible distributed, parallel, or multilprocess application, is proposed and evaluated through simulation. Functions normally handled by centralized controllers, schedulers, arbiters and priority schemes are accomplished through a decentral ized model of control. Resource allocation, one important control function, is resolved within a Challenge Ring (CR) in which individual computing tasks independently (or without a host, hence their interaction is called hostless) exercise algorithms to gain access to computing resources.

Simulated system performance is monitored by analyzing individual task processing times, total system times, resource availability, resource utilization, and system efficiency. Our preliminary experimental results indicate that such decentralized (or hostless) models can be superior to some standard centralized (or hosted) versions. Moreover, tasks in CR networks that interact through cooperative strategies in some cases exhibit better performance. Our overall results encourage the further exploration of decentralized control models which could be useful in the continuing pursuit of alternative machine constructs (e.g. non-von Neumann architectures) and new distributed operational schemes (e.g. hostless network operating systems).
SARPI: A simulator for assessing cognitive tasks in process control
Authors: Ketcham Michael G. , Hooper Kevin , Coury Bruce
Published: March 2008

SARPI is a computer-based simulation of a fluid processing plant, used to evaluate operator performance in managing process controls. SARPI represents a highly stylized facility, consisting of tanks, pumps, and valves where an operator can control valve settings to optimize system output or keep the system in equilibrium. It has been designed to meet the experimental requirements of researchers investigating cognitive tasks for operators and the impact of alternative display formats on operator performance. Experiments with SARPI have shown that simple modeling constructs can accurately represent complex cognitive tasks.
A general purpose simulation environment for neural models
Authors: Mesrobian E. , Skrzypek J.
Published: March 2008

Current interest in neural networks has produced a diverse set of algorithms and architectures that vary in connectivity pattern, temporal behavior, update rules, and convergence properties. We have designed a flexible simulation system that can support the implementation of a wide range of neural network approaches. The UCLA-SFINX simulator is especially suited for the exploration of structured, irregular, and layered connectivity patterns. Func tions, such as those in early vision, are modeled using the regular connectivity of center/surround antagonistic receptive fields and can be implemented as the difference of concentric gaussians. Higher level cognitive functions, such as supervised and unsuper vised learning, have more irregular, dynamic connectivity structures and update mechanisms that are also supported. To visualize weight spaces, input/output training sets, image data, or other network characteristics, SFINX provides an X- windows based graphical output that assists in rapidly assessing the consequences of altering connectivity patterns, parameter tuning, and other experiments.
A comparative study between Petri Net and SLAM
Authors: Taqi A.A.Q. , Al-Sammak A.J. , Khan A.A. , Ahmed N.
Published: March 2008

The purpose of this paper is to illustrate the techniques of converting SLAM (Simulation Language for Alternative Modeling) models to Petri Nets and vice versa. Conversion of SLAM models into Petri Nets will allow the modeler to represent complex systems graphically. On the other hand, conversion of Petri Nets into SLAM will result in quick and efficient generation of statistical results with very little programming effort. For demonstration purposes a SLAM model of a simple queuing system has been converted into a PN one and con trasted. A PN model of CPU-IO interaction was converted into SLAM model, where the results obtained usig both tools are shown to be identical.
A large scale simulation model for analyzing the production of pipe valves and fittings
Authors: Evans Gerald W. , Biles William E. , Alexander Suraj M.
Published: March 2008

This paper describes a large-scale SLAM II- FORTRAN simulation model of a manufacturing plant that produces pipe valves and fittings. The model represents the functional areas of manufacturing (machining, heat treating, electropolishing, assembly, test and material movement) as well as the production planning and control system. The model allows for experimentation in a variety of areas, including production control, capacity planning, and layout design. Results of model experimentation indicate the advantages of conversion to a new single- floor facility over the existing multi-floor facility, as well as the advantages of a reduction in inventory levels for the plant.