bluuebunny/crossref_metadata_2025 huggingface dataset:
Dragoman: an expert system to aid users of a simulation model
Authors: Cooley R.E. , El-Hadad K.
Published: March 2008

This paper describes an experiment in constructing an expert system to aid the users of a simulation model. The expert system provides explanations in the form of background information and interpretations of various elements of a model. The approach to explanation is based on an attempt to simplify the model so that the user can think about the behaviour of a subsection of a model during a reduced number of time intervals.
Detailed simulation of a real world job shop with subassembly requirements
Authors: Townsend Miles A. , Lamb Thomas W.
Published: March 2008

A highly-detailed model of a furniture manufacturing plant was constructed to evaluate the effects of various proposed changes and as a long term planning tool. As it turns out, this plant and model have many features of the general class of low- technology job shops with extensive subassembly: poor scheduling, bottlenecks, which are expensive to cure, and an inadequate knowledge of automation. Salient features of this study are the large size and complexity of the model and the diversity it contains. The plant seems to be typical of a low-technology job shop, and the model has the attribute of being about as realistic as can be expected of a simulation.

This paper presents the results of validat ing (matching) the plant and the simulation. Extensive studies which quantify the scheduling priorities are then presented, and some new measures of performance are suggested and evaluated. Further studies on bottleneck removal and adding automation clearly indicate the costs and benefits to the plant. All of these studies would seem to be quite typical of such plants.
Simulation and validation of a contour trackin system using SIMAN
Authors: Sahotay H.S. , Edwards G.L. , Falkner A.H.
Published: March 2008

This paper reports the simulation of a practical system which is being investigated as part of a research program in pattern recognition. It is used to show that the system is feasible and to establish the conditions in which the system is stable. SIMAN is used for the simulation enabling the user to integrate the discrete and continuous parts of the model in one package. The problem being investigated is the tracking of contours of a 2 dimensional object using a beam of light. Z-transforms have been used to model the opto-electronic contouring system. The shape is simulated either by waveform generation or by manual input of numeric data for nonuniform shapes. The paper describes the derivation of the model and the programming behind the simulation together with successful results.
A new family of real-time redictor-corrector integration algorithms
Authors: Howe R.M.
Published: March 2008

This paper describes a variation of the conventional two-pass explicit Adams- Moulton predictor-corrector integration methods which is suitable for real-time simulation. In this new method the first pass through the state equations uses an Adams-Bash forth type of predictor algo rithm to campute an estimate of the state at the n+1/2 frame instead of the n+1 frame, as is customary. This estimate is then used to compute the derivative at the n+1/2 frame which, along with derivatives at the n, n-1, n-2, ... frames is used in the final corrector pass to calculate the state at the n+1 frame. Unlike conventional two-pass Adams- Moulton methods, these new versions are compatible with real-time inputs. The paper shows that they are also superior based on dynamic accuracy measures and stability measures. A three-pass predictor-corrector integration algorithm compatible with real- time inputs is also presented and shown to yield significantly more accurate results than 3rd-order RK (Runge-Kutta) integra tion.
CASED: A simulation package designed for variable speed drives
Authors: McCulloch M.D. , Landy C.F. , Levy W. , MacLeod I.
Published: March 2008

In recent years there has been an increase in the types and usage of AC variable speed drives. However, as the complexity of these systems has increased, so has the occurrence of problems which are often caused by the interaction of the various drive components. The authors have developed CASED which allows users to simulate complete drive systems. An overview is given of the types of models used for the converter and the motor, from which it is seen that three special features are required. Firstly the models are modular in nature, hence the simulator must be able to link the various models. Secondly a combination of discrete and continuous time simulation is required to model the converters, and lastly there may occasionally be a need for specialised stiff differential equation (DE) solvers. It is shown that by choosing the correct DE solver the simulation time can be decreased by more than one hundred fold. CASED has shown itself to be a specialised and powerful tool in variable speed drive analysis.
A simulation approach to finding the stochastic behaviors of a time-dependent attrition process
Authors: Chang Sheng-Lin , Menq Jau-Yeu
Published: March 2008

Today the force-on-force attrition models are widely used to evaluate tactics or appraise equipments. Because of modeling complex ity and computational difficulty, most researches concentrate on deriving solutions to deterministic attrition models. Recently, some computational algorithms have been developed to study the stochastic behaviors of a combat model. However, the attrition rate of a combat could be affected by many factors to become a time-dependent function in reality. A simulation approach is proposed in this paper to explore the time- dependent dynamic behaviors of a combat. Different properties can be computed from the simulation results to gain a more clear insight and understanding. A numerical example is presented as well.
Investigating simulation of hardware at various levels of abstraction and timing back-annotation of dataflow descriptions
Authors: Navabi Zainalabedin , Massoumi Mehran
Published: March 2008

Digital hardware can be described at various levels of abstraction. Functional descriptions merely capture the behavior of the circuit without revealing the details of the architec ture. On the other hand, the gate or switch level models are more robust and include great amounts of detail about the circuit (timing and architecture). Functional models are attractive because they simulate faster than low level models. However, the tradeoff is that the simulation results are not as accurate (primarily from the timing standpoint) as those obtained from low level models. Clearly, having a model that simulates as fast as the functional model and produces accuracies comparable to those of gate level models is desirable.

This paper is an investigation of achieving such models. Two levels of abstractions, dataflow and gate level, are considered and the VHDL language (an industry standard) is used for describing Finite State Machine circuits at both levels. Feasibility of timing back-annotation of dataflow models with the information obtained from gate level is analyzed.
Applications of the collision test to produce results consistent with the spectral test
Authors: Pierce Margaret Anne , Bays Carter
Published: March 2008

The collision test is one of many tests that can be used to check a sequence of numbers for randomness. The current work extends the use of the collision test to produce information about the number of bits of accuracy similar to the powerful spectral test [1]. The spectral test is limited to use with only a few types of generators, but the collision test can be applied to any sequence of numbers. The analysis suggested would be ideal for non-linear congruential types of generators; indeed, one need not know the origin of the number sequence, only the sequence would be needed to perform the analysis.
OpEM distributed simulation
Authors: Clymer John R. , Hernandez Daniel
Published: March 2008

Distributed simulation based on Opera tional Evaluation Modeling (OpEM) is discussed. OpEM, a system design and analysis methodology, uses a two-dimen sional, directed graph language to describe system operation. The OpEM simulation programming system, that implements this methodology, includes object-oriented event processing routines, moving-object routines, an expert system controller, and continuous system simulation routines. These routines are required to model large systems, such as the Strategic Defense Initiative (SDI) systems, that are characterized by closely coupled, context sensitive interactions. These interactions are modeled using a large global state space consisting of both discrete and continuous state variables. Execution of such large, complex models on uniprocessors can be slow; therefore, possible speedup by execution on a multiprocessor system, a set of processors that share memory, is investigated. A generic surface- ship warfare simulation, characteristic of many large models, is executed on a simulation of a multiprocessor system to investigate speedup.
Extending resources to multiple busy states in discrete simulation
Authors: Deuermeyer Bryan L. , Curry Guy L.
Published: March 2008

This paper introduces and develops the concept of multiple busy state resources to simplify the process of stratifying statistics associated with resources. Most simulation languages recognize only busy and idle states. In many applications stratification of the busy state statistics is necessary to account for phenomena such as failures, repairs, maintenance, shift capacity changes, and cost tracking. These ideas are demon strated by way of an implementation in a discrete simulation language.
An empirical evaluation of antithetic variates and quasirandom points for simulating stochastic networks
Authors: Adlakha Veena G.
Published: March 2008

This paper is concerned with simulation procedures for estimating the distribution function of the time to complete stochastic activity networks. A conditional Monte Carlo method using uniformly directed cutsets is considered and combined with antithetic variate sampling and quasirandom points. The efficiency of the two variance reduction techniques is compared using CPU times and mean- square errors. By using three examples the study illustrates the decreasing benefits of using quasirandom points over antithetic variate technique as the network size increases.
The L language for parallel processor machines
Authors: Diehl Joao B. , Bergamini Eduardo W.
Published: March 2008

The programming language L, oriented to parallel computers, is introduced. Principles of parallelism in the solution of problems and the requirements for the computing architecture are presented, for adequate use of the L language. Principles for problem initialization are commented upon, in view of possible real time constraints. The language structure and an example of its application are also presented in this work.
Model input management: a case study
Authors: Standridge Charles R. , Laval David K. , Reust Janet
Published: March 2008

In many cases, model developers deliver models to model users who analyze alterna tives by changing model input values. These model users need software capabilities and an interface that supports the process of data entry and editing as well as selection among input values to define a scenario for analysis. In addition, the interface must use context specific language. Such an interface was developed to unite, for the model user, three inter-related models of a network of petroleum inventories. A database manage ment system, transparent to the model user, was used to implement the capabilities accessed through the user interface. Thus, this case study illustrates requirements for model user software support and one way of meeting them.
CSSL's and simulation of gas well behavior
Authors: Stocker Rudolf K. , Ariel P. Donald , McRae John R. , Stanislav Jaroslav
Published: March 2008

Primitive methods are still sometimes employed in solving engineering problems because of the perceived investment in time required to obtain a more precise solution. Computer modeling with modern simulation languages offers a fast and flexible solution methodology. Modeling of dynamic pressures and gas flow in a single phasegas reservoir illustrates how easily simulation languages can be applied to a problem which is still commonly addressed with graphical methods today. The sample problem is solved with the same simulation language on a variety of machines, widely different in processor speed and memory capacity, demonstrating the portability of the solution code and the flexrbility and generality of the approach to the solution.
Bringing experimental learning to economics
Authors: Saeed Khalid
Published: March 2008

This paper suggests that the possibility to experiment with relationships using system dynamics should lend the method easily to introducing experimental learning in economics and, possibly, also other social science disciplines. This would, however, require modifying teachingformats and creating new text materials and user- friendly computer programs incorporating the possibility to assemble hypothesized relationships by students with little computer or mathematical expertise. The paper reports work in progress towards the development of a simulation laboratory consisting of a text and a user friendly simulation program on issues of economic development as an example of the materials needed for integrating practicum with teaching.
Computer simulation of the coronary circulation: Implications for models and therapeutic Coronary Sinus Intervention
Authors: Schreiner Wolfgang
Published: March 2008

The pulsatile blood flow through the coronary circulation of the human heart has been represented by a simulation model, with classes of blood vessels being lumped together into compartments. Blood flow within the heart muscle was obtained by numerically solving coupled differential equations. The model was particularly designed to represent the venous side of coronary circulation. Several issues, important for the effectiveness of therapeutic coronary sinus interventions, have been the subject of simulation studies in the past. The present article intends to provide a concise summary and discussion of these otherwise dispersed results. In addition to the conclusions regarding therapeutic effectiveness, several general aspects of modeling the coronary blood flow are addressed.
A simulation model for determining maintenance staffing in an industrial environment
Authors: Duffuaa S.O. , Raouf A.
Published: March 2008

In a plant, the size of a maintenance staff initst be related to the level of output. The optimal level of maintenance is essential for maximizing the output of the production process. This paper develops a simulation model to determine the size of a maintenance crew. The heart of the simulation model is the machine servicing model. The model is applied to a local soft drink plant to deter mine the optimal number of their mainte nance crew, and the result of the study is presented.
Impulse response model for a class of distributed parameter systems
Authors: Graham John W. , Sarwal S.N.
Published: March 2008

A mathematical model is developed here for the impulse response of a class of systems represented by a general linear parabolic partial differential equation. Using a generalized eigenfuction expansion and the concept of a sampled-data system, a canonical set of state equations is obtained in discrete form. The impulse inputs may be any known time-varying functions on the given boundaries of the system or may be assumed to be distributed over a finite boundary region. For this computer model, no spatial discretization is required. Each discrete-time equation represents the dynamic behavior of each eigenvalue of the system and the response variable at any discrete location is given by a spatial linear combination of these state variables. Due to the discrete formulation of the system equations, numerical stability is assured. The equations are stable for any sampling time selected and the solution at any particular time desired may be simply obtained by incorporating this value directly into the model equations. The application of this method is demonstrated by solving a two-dimensional heat transfer problem subject to a single impulse input and comparisons were made to the finite element method of solution.
Modeling service distributions in queueing network simulation
Authors: Raatikainen Kimmo E. E.
Published: March 2008

The importance of accurate models for the input processes of simulation is generally recognized. However, the dependencies between the input processes have, at least in queueing network simulation, been paid little attention In this paper, we consider modeling the joint distribution of the input processes required in queueing network simulation Particularly, we propose a method for modeling the dependencies between service demands. In addition, we propose a method for dividing the service demand into service times per visit. These methods are important in simulation modeling of a computer system when accounting files provide the identification data. The experiments reported indicate that the proposed methods produce accurate estimates for quantiles of the system response-time distribution
Knowledge-based model construction for simulating information systems
Authors: Sakthivel S. , Agarwal Ritu
Published: March 2008

The process of constructing a correct simulation model for a system is a difficult and time-consuming task in the simulation life-cycle. Simulation is a widely used methodology for checking the performance requirements of information systems. This paper describes a knowledge-based approach to constructing a simulation model of an information system. The approach consists of two major steps: first, the information system is modeled as a Petri Net and implemented in a logic-based language. Second, the executable representation of the Petri Net is used to automatically construct a simulation model of the information system in GPSS. The approach offers several benefits such as reducing system development time, allowing the flexibility of easy modifications to the information system configuration, and requiring little knowledge of simulation methodology. The knowledge-based system is implemented in PROLOG.
Real-time simulation and animation for dynamic control systems
Authors: Cheok Ka C. , Ningjian Huang
Published: March 2008

Real-time digital simulation and graphic animation limited band-width dynamic control systems can significantly enhance the interpretation and understanding of system responses. This paper outlines an efficient techniques for generating the graphics and the timing in real-time simulation and animation of the dynamic control systems using a high-speed high- performance PC-AT microcomputer. For illustration, the simulation and animation results for the adaptive computer controlled suspension of a combat vehicle and for the gun-turret stabilization and tracking control system for combat vehicle are presented.
Behavioral Simulation of Array Processors in the APES Environment
Authors: Distante Fausto , Piuri Vincenzo
Published: March 2008

APES is an integrated, flexible CAD environment developed for behavioral design, simulation and evaluation of array processor architectures. This paper discusses in detail the core of the system, i.e., the behavioral simulator. This is an interactive subsystem which allows one to set up and run the simulation of the array using the definition of the array architecture supplied by the user. This task computes the output results of the whole array, of each processing element and of each functional unit. The concept of time is also defined and handled by the simulator so to allow subsequent performance evaluation. Functions are available for tracing, for inserting break- points, for step-by-step execution and for selection of display format. The simulator interacts with the other modules of APES (e.g., the Fault Injector, the Reconfiguration Manager) and produces results which can also be post-processed by other modules of APES (e.g., the Diagnostic Evaluator) to aid the designer in evaluating particular characteristics of the architecture.
An object-oriented simulation environment for airbase logistics
Authors: Popken Douglas A.
Published: March 2008

The subject of this paper, the Integrated Model Development Environment (IMDE), addresses basic difficulties experienced in simulating airbase logistics. These difficulties arise during two major modeling activities: 1) developing the conceptual model, and 2) translating the conceptual model to a particular simulation software implementation. The difficulty of the former activity is largely irreducible, a conse quence of the inherent complexity of large, dynamic, and uncertain military systems such as airbase logistics. However, while the latter activity is also complex, key technologies have the potential to simplify this part of the modeling process. This paper discusses how a synergistic combination of object-oriented programming and data bases, graphical programming, software environments, and powerful computer worksta tions can provide significant enhancements to simulation modeling capabilities. In addition, the paper presents the object-oriented decomposi tion of the airbase logistics domain as it is implemented in IMDE. The paper also discusses how the IMDE design meets the needs of airbase logistics modelers with widely differing capabilities and mission requirements. This is accomplished by providing different modeling "levels", each with its own user interface, skill requirements and degree of access to modeling tools. The paper concludes with a description of the current status of this large scale research and development effort.
NEXUS: A simulation environment for large-scale neural systems
Authors: Sajda Paul , Finkel Leif H.
Published: March 2008

NEXUS is a novel simulation environment designed for modeling large neural systems. The simulator allows the user to incorporate complex functional properties and symbolic processing at the level of the individual unit. In addition, NEXUS takes advantage of the principle of topographic map organization, found throughout the mammalian nervous system, to facilitate the modeling and design process. An easy-to-use graphical interface allows the user to interactively build and test models. This paper describes the principles underlying the NEXUS design and its advantages over other current simulation approaches.
A method for computing discrete event simulation performance measures from traces
Authors: Standridge Charles R. , Tsai Jenteng
Published: March 2008

Interactive simulation systems supporting the post-simulation analysis, presentation and interpretation of results have been developed and will continue to evolve. Post- simulation definition and computation of performance measures should be one important capability of such systems. We propose a method for accomplishing this objective. A simulation language neutral form of a discrete event trace contains the information from which the performance measures are computed. Computational procedures for typical performance measures: transaction time delays, numbers of transactions concurrently engaged in an activity or in a queue, time intervals between occurrences of the same event, and the state distribution of resource units are given. A software library for managing traces and performing the needed computations is described. An example shows an illustrative application of the method to three simulation languages: SLAM II, GPSS, and INSIGHT.
Object-Oriented Design of Output Analysis Tools for Simulation Languages
Authors: Mollamustafaoglu Levent , Gurkan Gul , Yonca Ozge A.
Published: March 2008

Contrary to the importance given to simulation modeling, output analysis has seen little implementation effort. Most of the simulation systems and programs have very primitive forms of output analysis facilities. This might result in either statistically insignificant results, if the analyst does not have correct assumptions about the system and uses a very simple output analysis method, or it can discourage the analyst from using the methods because it will be very hard to use them without ready computer help.

This paper analyzes the output analysis methods in literature and reports ways to include them in simulation environments. A generic object-oriented design for output analysis methods is also described. A critical comparison of object-oriented and traditional methods is included.
Process-Dependent Circuit Modeling and Simulation of SOI JFETs: Digital VLSI Applications
Authors: Abdel-Aty-Zohdy Hoda S. , Talkhan Ihab E.
Published: March 2008

Accurate circuit modeling and simulation of Silicon-on-Insulator (SOI) enhancement and depletion Junction Field-Effect transis tors (JFETs) is presented. The nonuniformity in FET device parameters along the channel depth (due to fabrication processes), is taken into account. This is typical in SOI and other thin-film struc tures. Since SOI fabrication processes parameters are represented, in our model, by a closed form mobility variation, improved model accuracy is guaranteed. Simulation results are found to be within less than 3% of actual measurements. Small-signal circuit-model parameters are determined for SOI FJETs and then evaluated for further logic applications. Inverters with a channel Enhancenient-JFET (E-JFET) drivers and n- channel depletion-JFET loads (E/D invert ers) are also considered with different supply voltage values, device parameters and digital applications.
Macro Requirement Within a Simulation Interface
Authors: Munir Ahmad M. , Stam Frank A.
Published: March 2008

The use of simulation has traditionally required a great deal of expertise. Simulation Interfaces to General Purpose Simulation Languages made simulation easier to use. However, for successfully building simulation models, modelling expertise is still required.

Macros have been proposed as a tool within Simulation Interfaces which simplify the building of models. A macro in this context should be seen as a group of SimulationLanguage statements with a data interface to the user.

The questions to be answered were: "What should a macro do and how should it be implemented?" The first objective of the work was to specify the macro functionality more tightly and then develop some macros.

The wide range of macro applications allows categorising. An attempt was made to classify the different types of macros in a hierarchical structure. Implementation of macros in SIMAN® [1], showed difficulties such as nesting, attribute sharing, and code connectivity. To make data input for complete models less laborious, generic data interfaces were proposed. A simple model of a manufacturing cell is discussed, to show some of the above mentioned aspects. It became clear that macros could considetably speed up model building. However, bigger macros could reduce modelling flexibility to some extent.
Chaos and Fractal Algorithms Applied to Signal Processing and Analysis
Authors: Handley J.W. , Jaenisch H.M. , Carruth R.T.
Published: March 2008

Modern signal processing methods strive to maximize signal to noise ratios, even in the presence of severe noise. Frequently, real world data is degraded by under sampling of intrinsic periodicities, or by sampling with unevenly spaced intervals. This results in dropout or missing data, and such data sets are particularly difficul to process using conventional methods. In many cases, one must still extract as much information as possible from a given data set, although the available discrete data is sparse or very noisy. In such cases, we have found the algorithms derived from Chaos and fractal theory to represent a viable alternative to traditional spectral analysis. The data analysis techniques discussed in this work include phase space reconstruction, Poincare projections radius of gyration exponent, artificial insymmetration patterns (AIP), Liapunov spectra, correlation techniques, R/S analysis, K-factor, fractal statistics, maximum entropy method, and wavelets.
Analysis of Envelope-to-Cycle Difference (ECD) in the Far Field
Authors: Peterson B.B. , DeWalt K.M.
Published: March 2008

With the recent mid-continent expansion of LORAN in the United States and the worldwide increase in the use of LORAN in terrestrial and aviation applications, the understanding of propagation over land of LORAN signals has received renewed attention. This study focuses on two aspects of the ability of a LORAN receiver to select the correct zero crossing to track. First, it has long been thought that the negative change in Envelope to Dcyle Difference (ECD) s more rapid over land than seawater. Recent data has shown this not to be true and one purpose of this study is to develop a more accurate model of the variation of ECD with distance and ground conductivity.

Second, with more groundwave attenuation over land than over seawater, skywave to groundwave ratios are larger and skywaves are potentially more of a problem. In our study we have developed a highly accurate model of pulses from solid state transmitters which allows the isolation of skywave from groundwave. This allows us to collect statistical data on skywave to groundwave ratio, skywave delay, and skywave ECD. These statistics, together with a knowledge of the frequency response of the receiver front end and the ECD estimation method, allow us to predict ECD bias and cycle selection problems due to skywave interference.
Loran-C Signal Analysis Test Data and Simulation
Authors: Illgen John D.
Published: March 2008

Modeling, simulation and test data are used to define the accuracy achieved using the Loran-C navigation system. Although Loran was invented prior to WWII, the system has undergone major changes and enhancements over the years. Currently the system offers high accuracy at a very low cost. This paper presents the new nanosecond precision Loran-C system performance and accuracy based on extensive modling, simulation and data analysis.
Software design of 6DOF guidance approximations in 3DOF ascent simulations
Authors: Luke Robert A.
Published: March 2008

Methods are being developed for approximat ing 6DOF (degrees of freedom) motion charac teristics in an operational 3DOF trajectory simulation. The optimizable 3DOF and the nonoptimizable 6DOF simulations are used for launch planning and operations for a current U.S. launch vehicle program. A previous paper [1] discussed the derivation and impact on the 3DOF in terms of vehicle attitude and angle of attack time histories. This paper continues by developing the methodology within the simula tion and optimization software framework. It must take into account both the frequency and the sequencing of calls to various FORTRAN subroutines that model vehicle flight mechanics. These calls and the routines must be planned so as not to violate assumptions upon which the nonlinear programming algorithms used to shape the trajectory are based. Discussion is included on the steps that must be taken to sufficiently simplify the 6DOF booster guidance scheme. In order to do this, a careful review is made of how the trajectory is described and propagated. This description is developed within the context of the various required reference frames and the vehicle attitudes specified with respect to those frames.
The Carbon Budget of the Canadian Forest Sector: Phase I
Authors: Kurz W.A. , Webb T.M. , McNamee P.J. , Apps M.J.
Published: March 2008

An assessment of the contribution of Canadian forest ecosystems and forestry activities to the global carbon budget has been undertaken. The first phase of this study consisted of the development of a computer modeling framework and the use of pub lished information to establish the sector's current role as a net source or a net sink of atmospheric carbon.

The framework includes age-dependent carbon sequestration by living forest biomass, net detrital litter fall of carbon to the forest floor, subsequent accumulation and decomposition release in three soil compartments, retention of carbon in manufactured products derived from harvested forest biomass, and burning of forest biomass for energy.

There is explicit representation of the role of ecosystem disturbances, such as fire, insect-induced stand mortality, and harvesting (clear-cutting, clear- cutting and slash burning, and partial cutting), as they affect carbon releases and transfers to the forest floor and to the forest product sector. Regrowth of biomass and changes in soil decomposition processes following disturbance are also simulated within the model.

In the first phase of the work, national and provin cial data bases were used to provide the first compre hensive estimates of the net carbon exchange between Canadian forest ecosystems and the atmosphere for the reference year 1986.
Simulation of Systolic Arrays on the Connection Machine
Authors: Hemkumar Nariankadu D. , Cavallaro Joseph R.
Published: March 2008

The use of a programming model which extends naturally from the underlying hardware, greatly eases the design and implementation of simulators, especially for those systems that resemble the hardware in the paradigm of computation. Given the characteristics of systolic arrays, SIMD computers which employ the data parallel programming model provide an ideal environment. In this paper, we present a systolic array simulator, a simulation tool written for the Connection Machine *(model CM2), a SIMD machine with pomerful interprocessor communication capabilities. Especially as recent advances have automated the design, there is a need for a verification environment to prototype systolic arrays. Primarily a simulation tool, the systolic array simulator also helps identify inefficiencies and motivates optimal design prior to implementation in either custom VLSI or DSP systems. Currently, we are updating the tool to allow the simulation ofdynamic array reconfiguration algorithms under transient and permanent fault conditions. The simulator is also being ported to the CMS.
Simulation analysis of a Multiple Bus Shared Memory Multiprocessor
Authors: McCarron Christopher W. , Tung Cheng-Hsien
Published: March 2008

The past several years have brought the widespread acceptance of bus based shared memory parallel computer systems. There is a great deal of research which suggests that the limitations of single bus based interconnection networks prohibit effective use of more than perhaps 16 processors. Proposals have been made for several years [7] regarding the use of multiple buses to improve overall bandwidth.

In research conducted during the past two years we have studied the performance gains which could be made by providing additional buses to interconnect processors and memory. In this paper we will present the results of extensive trace driven simulation done using a sample workload. Because a detailed simulation model was created we are able to obtain fine grain detail regarding the operation of the system.
Power Plant Simulators Using Westinghouse Distributed Processing Family Hardware and Software
Authors: Griebenow Ron , Perdeus Matt , Sudduth Al , Fray Roy , Heuser Steve
Published: March 2008

Duke Power Company and the Electric Power Research Institute have embarked on a joint effort to develop plant specific engineering and training simulators to support control replacement projects in Duke's fossil plants. These simulators use low cost personal computer hardware (PCs) and modular process simulation development software, integrated to Westinghouse Distributed Processing Family (WDPF) control hardware and software, to provide an accurate representation of the plant process and controls. Integrating the PC-based process simulation to the control system proved to be a very complex task.

To meet the interface requirements, firmware was modified, and software and interface cards were developed that allow high-speed parallel access to the control system processor memory. In addition, modifications had to be made to provide necessary simulator training functions such as freezing the system, saving snap-shots, and loading initial conditions. This paper provides details on the development of the PC/ WDPF interface and simulator instructor capabilities. In addition, it outlines plans for use of the simulator as an operator training and controls engineering tool.
Elevator Traffic Simulation
Authors: Siikonen Marja-Liisa
Published: March 2008

Passenger waiting time in a lobby and ride time in a car give a good indication of the service capability of an elevator group. If several cars are in the same group, these parameters are too complicated to model in a closed form. In this paper, procedures for modelling elevator performance and passenger traffic in a generic building are described. Elevator dynamics and control, call allocation and passenger traffic modelling are described. Simulated interval and load values are compared with theoretical results, and variances in simulation results are investigated. According to typical simulation results, there is no direct connection between interval and passenger waiting times, as is often assumed. The interval depends on the elevator bank configuration and elevator performance capabilities. Performance indicators, such as the number of starts and cycle times, become saturated even at low traffic intensities. The waiting times, in addition to elevator performance, depend on the passenger traffic patterns and, during heavy traffic, service level is greatly affected by the call allocation algorithm.
Machine Learning and Simulation: Application in Queuing Systems
Authors: Khoshnevis B. , Parisay S.
Published: March 2008

Machine learning algorithins have application potential in simulation at stages of model building, simulation execution monitoring in real-time, and output analysis and model refinement. This article presents the basics of the inductive learning paradigm and the ID3 algorithm, highlights the potential of learning in simulation as means for extracting heuristic rules to be used in expert systems, and demonstrates a sample application in simulation of queuing systems.
Evaluation of New Technologies in a Shoe Manufacturing Plant Using Simulation
Authors: Jacobson I.D. , Townsend M.A. , Allatta J.T.
Published: March 2008

Computer simulations have become popular decision aids in evalitating manufacturing strategies due to the high costs and risks of implementing new technologies. This paper presents a case study of a computer simulation evaluation of the effects of varying operating practices and of incorporating modern equipment and processes in a typical low-technology shoe manufacturing facility.
The Brief Systems Family Therapy Process Model: First Results
Authors: Brown-Standridge Marcia D. , Standridge Charles R. , Poole Yvette M.
Published: March 2008

Family therapy is a process by which therapists help families identify and rectify dysfunctional patterns. A precise under standing and specification of the steps in the family therapy process is critical to helping therapists perform their craft better. A teain of family therapists and simulationists has developed a step by step description of the process of a family therapy session, based on the experience of expert therapists and the published literature. This description forms the basis for a simulation model which has been used in training new therapists. Simulation is an ideal tool for studying family therapy since both are based on systems theory. By observing these thera pists in action, the model is being validated and enhanced.
Modeling Of Multibody Systems For Controls Using General Purpose Simulation Languages
Authors: Zeid Ashraf A. , Overholt James L. , Beck Ronald R.
Published: March 2008

This paper demonstrates how to use an interpretive-type simulation language, such as MATRIXx or SIMULINK, in the simulation of multibody systems. Functional blocks that contain details of the dynamics of a rigid body and of the equations of several joints were created by using the graphical user interface of MATRIXx. Models of complex multibody systems are built by graphically selecting, duplicating, and connecting appropriate blocks of rigid bodies and joints. This modularity is afforded because joints are formulated using the explicit singularly perturbed formulation. The singularly perturbed formulation, originally developed in bond graph language, is based on modeling infinitesimal defonnation in joints, a characteristic of realistic multibody joints.

Bond graphs are graphical models of multi-energy doinain dynamic systems that depict and account for the power structure in the system. In this paper, block diagrams that were obtained from an algorithmic translation of joint bond graphs are coded using the simulation language graphical interface. The methodology is demonstrated by modeling the dynamic behavior of a complex multibody system; namely, a Stewart platform.

Because this formulation is explicit, it sets the stage for the simulation of very large- scale multibody systems by exploiting parallelisin of novel computer architectures.
Importance Sampling Simulation in UltraSAN
Authors: Obal W. Douglas , Sanders William H.
Published: March 2008

Traditional simulation techniques perform poorly when estimating performance measures based on rare events. One solution to this problem is the use of importance sampling. However, two problems that have limited the use of importance sampling are the lack of a formal framework for specifying importance sampling strategies, and the fact that in most cases the simulations must be hand-coded — a very time-consuming process. This paper presents a software tool that facilitates experimentation with importance sampling by addressing these two problems. First, the tool is based on a flexible framework for specifying importance sampling simulations in terms of stochastic activity networks. Second, once specified, the importance sampling simulation program is automatically generated by the tool, freeing the researcher to focus on the modeling problem. The effectiveness of the software is demonstrated through the solution of a machine-repairman model with Weibull distributed failure times and a delayed group repair policy. Orders of magnitude reduction in the CPU time required to obtain a specified relative accuracy were achieved.
Modeling Time-Varied Arrival Rates: An Application Issue in Queuing Systems
Authors: Zhu Zhiwei , McKnew Mark A. , Lee Jim
Published: March 2008

This paper addresses the problem of modeling time-varied arrival rates in gicetcing systems. The approach is to break down a 24-hour period into small time durations such that an average arrival rate during the time duration can be reasonably viewed as constant. Discrete event simulation models were developed using SLAM II to evaluate the selection of the length of time durations. The simulation output data were then compared to real data collected from the Emergency Ambulance Service Center in Shanghai, China, a typical system with time-varied arrivals of service requests. Statistical data analyses on the system performance indicated that the 4-hour duration model with six different arrival rates in 24 hours closely matches the operation characteristics of the Shanghai system.
A Process Oriented Manufacturing System Simulation to Measure the Effect of Shop Control Factors
Authors: Huq Ziaul
Published: March 2008

The objective of this paper is to develop a framework for comparing job shop control policies through simulation analysis. A process based simulation model is developed that uses an object oriented data structure. This paper argues that inventory in a job shop should be divided into three categories, and each category's value would be a more useful performance measure for comparing alternate control policies. An experimental design is presented for determining the appropriate shop control rules that combines the major aspects of shop control decisions. The simulation model is flexible and allows specification of an y number of work stations and job types. The model can accommodate both static and dynamic job processing schemes. The model also outlines statistical procedures to compare alternative shop control policies and provides a hierarchical procedure for selecting these rules. The model's applicability is illustrated by testing some shop control rules in a benchmark job shop.
Induction Of Classification Rules From Noisy Sonar Features
Authors: Clymer John R. , Bandukwala Hussain , Corey Philip D.
Published: March 2008

Developing rules to classify surface ships and submarines based on noisy features extracted from underwater acoustic signals is difficult and time consuming; indeed, it is difficult to generate decision making rules for any complex system. The Operational Evaluation Modeling (OpEM) Simulation Tool Kit including Expert System Controller and Induction Program, discussed in this paper, greatly mitigates this problem for most complex system simulation projects such as airports, factories, or space defense systems. A theory for inductive learning of decision making rules in cybernetic systems is presented to provide a concise way-of thinking about inductive learning. An OpEM directed graph model is presented that describes operation of a sonar detection and classification system. An OpEM Pascal simulation of this system demonstrates how effective classification rules can be that are induced from simulation generated cases, even with noisy features present. The OpEM induction program is described and innovative features are discussed. Rules generated by the OpEM induction program are compared to rules obtained by Ross Quinlan's ID3 induction program. Performance of the OpEM induction program when noisy features are present is compared with ID3.
Using Experimental Design Techniques For Spacecraft Control Simulation
Authors: Gordon Steven C. , Ausink John A. , Berdine Ronald J.
Published: March 2008

Experimental design techniques are used in this work to minimize the number of computer runs required to test a specific spacecraft control algorithm. These techniques save valuable computer simulation time and also produce a regression equation that approximately relates the inputs (assumed error sources) to the output (the control cost over a period of time). When the input data is coded appropriately, the relative sensitivity of the output to the various inputs can then be judged by the relative magnitude of the coefficients in the computed regression equation. This study is concerned with a spacecraft in orbit near libration (Lagrange) point L1 in the Sun- Earth system. In this orbit, the spacecraft remains between the Sun and the Earth and serves as an excellent platform for research relating to the numerous solar effects on the terrestrial environment. Station-keeping using a specified control algorithm is, however, required for this particular type of (unstable) orbit. For a given control routine, error sources, such as tracking errors, solar radiation pressure variations, and planetary mass uncertainties, will have an impact on the station-keeping costs.