bluuebunny/crossref_metadata_2025 huggingface dataset:
SIMSHAC-a simulation program for solar heating and cooling of buildings
Authors: Winn C. Byron , Johnson Gearold R. , Corder Thomas E.
Published: March 2008

A dynamic simulation model for use in analyzing the performance of specific designs of solar-heated-and- cooled buildings has been developed. The name of the program is SIMSHAC, an acronym for SImulation Model for Solar-Heated-And-Cooled buildings. To use the design program, one has merely to specify the components (that is, each subsystem; for example, collectors, storage units, splitting and mixing valves, house heating and cooling loads, auxiliary heating, auxiliary cooling, heat exchanger, etc.), and the manner in which they are connected and all initial conditions. Program SIMSHAC then writes the program for the specific system to be analyzed. Each subsystem is described by a set of time-dependent differential equations or, possibly, algebraic equations. System state variables include tempera ture, mass flow rate, and enthalpy. The model can handle three types of incident solar radiation data models. These are (1) deterministic (e.g., an algebraic-equation sun model), (2) random simulation (e.g., a model based upon cloud-cover statistics), and (3) actual tabulated input information based upon collected solar data for a specific site. The model has been used for the analysis of five different types of buildings in five locations within the United States. The types include single-family residences, small businesses, three-story apartments, schools, and mobile homes. The locations considered are Atlanta, Georgia; Madison, Wisconsin; Wilmington, Delaware; Mobile, Alabama; and Santa Maria, California. The program has also been used to simulate the solar- heated-and-cooled experimental laboratory presently being built by the National Science Foundation on the campus at Colorado State University.
Experiments with the SIX rule in job-shop scheduling
Authors: Eilon Samuel , Chowdhury I.G. , Serghiou S.S.
Published: March 2008

This paper reports on the results of various experi ments with the loading rule SIx for scheduling jobs and compares its performance with two other, general ly more popular, methods. Several advantages of the SIx rule are discussed.
Advanced nuclear-reactor simulation techniques
Authors: Jimenez R.F. , Benham R.D.
Published: March 2008

This paper presents the single-point kinetic and thermodynamic equations for nuclear reactors which are typically used in safety-analysis studies. The studies here reported were performed on 4K PDP 8 and the larger PDP 11/20 computers with Interactive SimuZation Language (ISL).

The parameters of a former LOFT1 reactor design are used, but the delayed-neutron fractions and decay constants are taken from a paper by Albrecht and Metelmann.2 Simulations are made for six, three, two, and one delayed neutron group for a startup accident. The purpose of the runs is to show the effect of simplifying assumptions on accuracy and on the speed of computer processing. The results show that speed can be increased by a factor of 20 without seriously affecting accuracy. At these speeds, it is possible to simulate the nuclear system five times faster than real time on a PDP 11/20 computer. With extra hardware such as a mul/div unit or a floating- point processor, additional speed is possible.
A simulation of the use of energy and land at the national level
Authors: Watt Kenneth E. F. , Young Jeffrey W. , Mitchiner John L. , Brewer John W.
Published: March 2008

The authors argue that, while detailed econometric- type models will be useful to the implementers of policy, the policy-maker needs a more systems-oriented simulation device. This is true because local prob lems are becoming more intricately related to national (and international) level variables. Also, it is probable that historical trends in important variables (e.g., population growth and energy costs) may soon end and new trends will begin. The authors are assembling a hierarchical systems model for policy- making and describe the national level of the model in this paper. The chief hypothesis being studied with this model is that agricultural exports will expand in order to offset a trade imbalance caused by increased crude-oil import prices. This expansion will trigger a whole sequence of systems-level impacts on variables of diverse character such as domestic wheat prices, urban population density, the fraction of commuters who use public transit, etc. The authors conclude with simulations that demonstrate the drama tic long-term effect of current crude-oil prices.
Simulation of a Metropolitan Bus System
Authors: Veerapandian M. , Ramani S.
Published: March 2008

This paper discusses the use of a GPSS/360 simulation model to analyze the bus service of the metropolitan bus system in Madras, India. The system has been unable to obtain enough buses to keep pace with demand and has waged a constant battle to keep its existing buses rolling. The factors contributing to the system's major operational problems have been identified and incorporated in the model. A comparison of the model's output with historical data shows that it is suitable for analyzing operational pro blems, and it is expected to be useful for tactical planning and for improving future operations.
Multilevel functional simulation
Authors: Bray David W.
Published: March 2008

This paper presents a modification to the functional simulation technique which allows the user to perform simulations of systems at increasing levels of detail by making only minimal changes in the description of the system. Functional simulation is easy to imple ment because the functional simulation model defines all the system control parameters necessary for simu lation. The investigator designing the simulation need not be concerned with implied parameters. To extend the technique of functional simulation to multilevel functional simulation (MLFS) requires only a small amount of additional program, but it provides a significant increase in capability.
Simulation of Energy Flow and Land Use: Speculater 1975
Authors: Brewer John W. , Watt Kenneth E. F. , Young Jeffrey W. , Mitchiner John L. , Ayers Claudia , Hunter Yvonne L.
Published: March 2008

This note is an update of a simulation model (initially described in Simulation Today no. 29 in the January 1975 issue of Simulation) of the interaction of national urban, agri cultural, and energy-use systems. New empirical evidence is provided to substantiate the interactions hypothesized by the authors. The results of simulations of the new version of the model are presented and the implications for public policy are explained.
Litepath-
Authors: Yaffe L.G. , Mode V.A. , Sisson D.H. , McMillan G.G.
Published: March 2008

This paper discusses a computer model of a general spectroscopic optical system that gives the user freedom to analyze a wide variety of arrangements of optical surfaces between a light source and a detec tor. The source may be a point source, or an emitting volume with a linear or nonlinear intensity profile. The optical surfaces may absorb, reflect, refract, filter, or transmit photons. This model has been used to calculate instrument correction factors for fluorescence systems. The model yields results that agree with experimental results.
Some array features of CSMP III
Authors: Wozny Michael J.
Published: March 2008

Two applications are presented which illustrate some of the array features available in CSMP III. The applications show that the array statements not only simplify the programming aspects of systems described in vector-matrix form, but also provide a concise conceptual framework for interpreting the geometrical nature of such problems.
Simulation of Biological Systems: Contraction of Skeletal Muscle
Authors: Noble David F.
Published: March 2008

The simulations to be discussed here assume that force is developed at independent tension generators, and they identify those tension generators with the cross bridges seen in electron micrographs. These simulations attempt to de duce how the cross bridges behave under various circum stances, an essential preparatory step for discovering the actual force-producing phenomena. The mechanical proper ties of each individual cross bridge need not mirror those of the whole muscle. The number of cross bridges partici pating in tension development can vary, and some may be impeding contraction while others aid it. Therefore, one cannot easily predict whether cross bridges with any par ticular kind of behavior will produce behavior characteristic of whole muscle. Such predictions are possible with models and simulation. This review describes two specific cross bridge models, representing two general classes of models. It shows how the predictions of simulations led to a specific experiment whose outcome favored only one of these classes.
A new general-purpose nonlinear component for multivariable function generation for hybrid computers
Authors: Rubin Arthur I.
Published: March 2008

This paper is divided into three main sections which

1. Cover the historical significance of multivaria ble function generation to analog and hybrid computation

2. Describe a new high-speed Multivariable Function Generator (MVFG) for hybrid computation

3. Conclude with a discussion of possible applica tion of the MVFG for general computing use.
Digital simulation of adjustable-frequency ac motor drives
Authors: Murphy John M.D.
Published: March 2008

Simulation techniques are very useful in designing static adjustable-frequency ac drive systems and in evaluating alternative control strategies for them. This paper outlines the basic principles of the modern dc-link static frequency converter, and then describes the implementation of a digital simulation of a complete drive system. The principal components of the drive are programmed as FORTRAN subroutines. The main program uses the IBM Continuous System Model ing Program (CSMP), which is translated into FORTRAN and combined with the FORTRAN subroutines.

Harmonics in the output waveform of the frequency converter can cause design and operating problems under steady-state as well as transient conditions. These problems are discussed and illustrated by results from simulation runs.
Some remarks on the determination of unknown parameters in large nonlinear systems- a problem in spacecraft thermal test evaluation
Authors: Borucki Ludwig , Schwarzott Walter
Published: March 2008

As a special case of large nonlinear systems with many imprecisely known parameters, this paper considers the thermal behaviour of a spacecraft. It is simu lated in the steady state by a mathematical model consisting of a system of nonlinear equations and in the transient state by a system of nonlinear differ ential equations. The system contains a large number of parameters, many of which cannot be calculated or measured directly with satisfactory precision. The estimated parameters of the initial mathematical model can be improved by analysing the results of thermal tests performed on the spacecraft itself. The objective is to minimize the differences between measured and calculated temperatures. Since the temperatures are nonlinear functions of many para meters, the minimization is a difficult task. Methods which transform the nonlinear functions into linear ones may not result in the minimization of the temperature deviations. The major disadvantage of linearizing methods is the restriction of the validity of the first-order terms to the vicinity of the point about which the linearization was made. Therefore there cannot be a universal, straightfor ward procedure to evaluate a great number of unknown parameters in complex nonlinear systems. Engineering methods for special solutions need to be developed and made as general as ingenuity can make them.
A model of community noise pollution
Authors: Burke Richard E.
Published: March 2008

This paper describes a model of the major causes and effects of noise pollution in urban communities. The model is intended to be a preliminary guide to be used by communities in analyzing their noise problems and by academic institutions in conceptual izing the general problem of community noise pollu tion. The use of the model is illustrated by simu lating a fictitious prototype community using a computer program based on the model, and the simula tion is found to yield results which agree with empirical findings for similar communities: (1) air craft constitute the predominant source of community noise when an airport is nearby (8 miles) and (2) attitudinal factors play as large a role as physical ones in determining the degree to which people are annoyed by noise.
Toward a self-sufficient system for human housing
Authors: Loewer O.J. , Colliver D.G. , Duncan G.A. , Mynear D.K. , Cochran W.J.
Published: March 2008

This paper discusses the simulation of a housing system in which most of the food and energy used by the occupants is produced locally. Energy is pro duced by solar collectors and methane generators. Food is produced in greenhouses, gardens, and fish tanks. Wastes are recycled as fertilizer and methane gas. The model uses solar energy submodels, engineer ing descriptions of heating and cooling systems, weather and construction parameters, tables of dietary needs, and food-production rates to obtain estimates of system self-sufficiency. The model uses the methods of system dynamics and the DYNAMO simulation language.
The microprocessor CPU: some unique features
Authors: Leventhal Lance A.
Published: March 2008

This article will briefly describe some of the special features of standard single-chip MOS micro processors. Although these devices are very similar to larger central processing units (CPUs), technolo gical and packaging limitations as well as the needs of some common applications have created some differ ences. An understanding of these differences can often help users decide if microprocessors will be suitable for their applications.

We shall not discuss the general features of CPU architecture. Many adequate descriptions of those features are available.1,2 Instead, we shall briefly describe the functions of CPUs and then concentrate on the implementation of those functions in micropro cessors.
Continuous simulation of a complex queuing system
Authors: Lam Chan F. , Pedersen Janee
Published: March 2008

This paper deals with the continuous simulation of complex queuing systems on a digital computer. Con tinuous-system mathematical models of multicompart ment queuing systems based on a birth-death process consist of large sets of differential equations. A dynamic allocation algorithm can substantially de crease the required computer time and storage by con tinuously adjusting the size of the system of differ ential equations. The applicability of the continuous approach to simulation of complex queuing systems is demonstrated for a four-compartment outpatient clinic.
Safety and Reliability- Analyses of a Breeder Reactor
Authors: Fussell J.B. , Cate C.L. , Wagner D.P.
Published: March 2008

This paper outlines a University of Tennessee indepen dent study of the safety and reliability of the Clinch River Breeder Reactor Plant in Oakridge, Tennessee. The study uses several kinds of models, and analytical computer pro grams, one of which (BACFIRE) is briefly described and illustrated.
A Language Specialist Comments
Authors: Pritsker A. Alan B.
Published: March 2008

Alan Pritsker got involved in a (simulated) air duel in 1956 when he was with Battelle Memorial Institute in Columbus, Ohio. Surviving, he has been associated with Arizona State University, the RAND Corporation, Virginia Polytechnic Institute, Purdue, and-more recently - Pritsker & Associates. Along the way he has developed GASP II, GASP IV, and GASP-PL/1 simula tion languages and the GERT Network Approach as well as the GERT Analysis Programs.
Economic planning and growth of education in developing countries
Authors: Mashayekhi Ali Naghi
Published: March 2008

The criteria for economic planning influence the growth of the educational system, the rate of employ ment of the educated labor force, and the growth of the educated human resource base in developing coun tries. When the use of available human resources is not the major concern in planning, all these factors may display cyclical behavior during periods of moderate economic growth. In contrast, when the orientation in planning is toward maximum utilization of human resources, unemployment and educational growth are stabilized and the expansion of the educa ted human resource base of the country accelerates.
Moving pictures show simulation to user
Authors: Palme Jacob
Published: March 2008

One of the most difficult problems with a simulation program is to gain confidence in the accurateness and reliability of the model. If the program is to be used for important decisions, the decision-makers must feel sure that they can depend on the model. To do this, they have to understand what is happening in the program.

One way of making the users of the simulation more sure about what is happening in the program is to show what is happening during a simulation as a "moving picture" on a terminal. This can easily be done on a simple standard alphanumeric display ter minal.

Our experience is that the extra programming effort is small and that the gain in understanding of the model is high both for the programmer himself and for his client.
A nonlinear Monte Carlo simulation: oxygen transport in the brain
Authors: Hunt Daniel H. , Bruley Duane F.
Published: March 2008

This paper presents a modification of the Monte Carlo method which permits the solution of nonlinear partial differential equations. A hybrid computer implementa tion of the method is used to solve a nonlinear mathematical model of oxygen transport in the capillaries and tissue of the human brain. The tech nique is an alternative to digital computer methods and can greatly reduce the time required to produce a solution.
Man-in-the-loop simulation
Authors: Buck James R. , Deisenroth Michael P. , Alford Edwin C.
Published: March 2008

This paper describes a man-in-the-loop simulation program which can handle many jobs on a variety of computer systems. The program is intended to aid in the design and improvement of man-machine interfaces. An example of an application is the scheduling of ingots into and out of the soaking pits of a steel mill. This example shows how the program can be employed to improve interface design and operating procedure.
Interactive simulation on minicomputers : Part 1- ISIS , a CSSL language
Authors: Hay John L.
Published: March 2008

Continuous System Simulation Languages (CSSLs) are used to program the simulation of dynamic systems that are described by differential equations. Mini computer-based languages are particularly attractive because they generally provide good man-machine interaction. This paper describes an interactive simulation language, ISIS, which provides many of the facilities hitherto restricted to large computers. ISIS is written in FORTRAN and can easily be imple mented on any computer that accepts FORTRAN IV pro grams (the original version runs on a PDP-8). ISIS is designed to offer the user high-level language facilities in the simplest possible form. Line-by- line syntax checking and the built-in editor allow fast interactive development of programs. The execu tion of a simulation can be interrupted by using special commands that allow the user to change the values of variables, modify or introduce OUTPUT and incremental PLOT statements, and produce 'post-mortem' graphs before continuing the simulation. With these and other interactive features, ISIS provides com prehensive facilities for the study of dynamic sys tems on modest minicomputer configurations.
Modeling the control of cell growth
Authors: Alberghina Lilia
Published: March 2008

Cell growth and proliferation are biological phenomena that have not yet been explained. This paper shows how models of the biochemical processes involved can be used both to interpret existing data and to design new experiments. A model is presented that divides the cell into two subsystems: one that synthesizes ribosomes and proteins and a second that performs DNA replication and cell division. Data obtained by simulation, as well as the analytical solution of the model equations, indicate that it is the activity of the first subsystem (the one whose state variables are ribosomes and proteins) and not that of the subsystem that limits the rate of cell proliferation.
A survey of research on the simulation startup problem
Authors: Wilson James R. , Pritsker A. Alan B.
Published: March 2008

To reduce the effects of initial conditions on the results of a simulation experiment, several authors have proposed startup policies that specify how to minimize the warmup period and identify the trunca tion point beyond which observations are to be re corded and analyzed. Other approaches to this prob- Zem have used results from time-series analysis and queueing theory. This paper surveys research on the simulation startup problem; a companion paper which follows presents a procedure for evaluating startup policies when the mean of the truncated sample is to be used to estimate the steady-state mean of the underlying process.
Air-fleet and maintenance facility planning
Authors: Ramchand K. , Mani V. , Sarma V.V.S.
Published: March 2008

This paper describes the use of simulation in the planning and operation of a small fleet of aircraft typical of the air force of a developing country. We consider a single flying base, where the opera tionally ready aircraft are stationed, and a repair depot, where the planes are overhauled. The measure of effectiveness used is "system availability, the percentage of airplanes that are usable. The system is modeled in GPSS as a cyclic queue process. The simulation model is used to perform sensitivity analyses and to validate the principal assumptions of the analytical model on which the simulation model is based.
A digital computation technique for radar scene simulation
Authors: Holtzman Julian C. , Stiles Josephine A. , Frost Victor S. , Kaupp Verne H. , Komp Edward E.
Published: March 2008

This paper describes the Point Scattering Model (PSM) for radar-image simulation and its digital implement ation. The model applies to radar images of real and hypothesized scenes. Simulated radar images of real scenes produced via the PSM correlate very favorably with actual radar images of the same scenes. The simulation model requires information about the terrain in the form of a "ground truth data base" and radar backscatter data. Simulated radar images are compared with actual radar images of the same terrain. Flowcharts of the digital im plementation of the PSM are given.

A major part of the computing consists of independent parallel tasks and is well adapted to processing on a network of microcomputers. The authors hope that readers of this paper can suggest new configurations of the parallel processing equipment suitable for the rapid and economical execution of programs like those described in the paper.
Simulation in the Service of Society
Authors: McLeod John , McLeod Suzette
Published: March 2008

This Newsletter was published independently from January 1971 through August 1976. Back issues are available from SITSOS, 8484 La Jolla Shores Drive, La Jolla, CA 92037, for 75c per copy.
Comparison of simulation and flight-test data for missile systems
Authors: Montgomery Douglas C. , Conard Robert G.
Published: March 2008

Simulation models are frequently used to analyze missile performance. These models produce data that must be compared to corresponding flight-test data. This report describes statistical tests useful in making these comparisons. An application to an actual missile system is presented. The use of these statistical procedures in determining the validity of the model is discussed.
Establishing the credibility of simulations
Authors: Schruben Lee W.
Published: March 2008

A procedure is proposed to promote the acceptance of a simulation model. The procedure actively involves potential users of the simulation. Several alterna tive approaches for the statistical analysis of the experimental results are suggested. Two contrasting experiences in applying the procedure to actual simulation projects are discussed.
Modelling urban vehicle motion to improve performance
Authors: Mazurek Stanislaw , Rudzinska Krystyna
Published: March 2008

A computer simulation method is presented that par tially replaces road testing of engines and other components of the power-drive system of urban buses. To calibrate the model, experiments were performed in the urban traffic of Warsaw using a digital data- acquisition system. Analysis of the recorded data showed that two types of vehicle runs were represent ative of urban traffic; models of them were developed and verified. Specific performance criteria were selected for optimum matching of engines and power- transmission systems. A computational procedure based on the models and performance criteria is described. Finally, the paper presents an applica tion of this simulation method to improving the fuel economy and dynamics of a city bus.
Modelling a model of the tides on the St. Lawrence seaway
Authors: Caldwell Henry G. , Pincock Douglas G.
Published: March 2008

The Hydraulics Laboratory of the National Research Council of Canada uses a hydraulic model of the St. Lawrence River estuary to perform tidal studies. In this model a pump creates the tidal variations at the boundary where the height profile is set to represent actual observed values. The original scheme for controlling the pump was inadequate for periods exceeding one simulated day. In order to experiment with improved control schemes to extend the usefulness of the simulation beyond one day, we needed a computer model of the hydraulic model. This paper describes the development of that model.
Modelling heat flow and thermal stress in ingot casting
Authors: Morgan K. , Lewis R.W. , Seetharamu K.N.
Published: March 2008

Using the finite-element method, we develop a model of heat flow and thermal stress in ingot casting. The model takes into account the intimate contact of ingot and mould in the initial stages and the pres ence of the air gap thereafter, and it handles the effect of the type of lubricant used. The model is general and can deal with different types of bound ary conditions and with variations in material properties. The model is a stress model capable of taking into account time-dependent effects such as creep and of predicting the development of thermal stress fields.

To validate the model, simulation results for a particular problem are compared with the correspond ing results obtained by other workers and with experimental data.
SCS begins a new service : software resources for calculators and personal computers
Authors: Simons Fred O. , Harden Richard C.
Published: March 2008

Modern semiconductor technology has provided us with calculators and personal computers that can perform many complex tasks. Few professionals, however, can use these new devices effectively. The major stum bling block is the lack of ready access to methods for handling common problems. Our intentions here are: (1) to provide a forum for articles on simula tion-oriented software for calculators and personal computers, and (2) to establish standard documenta tion packages that make the software comprehensible and easy to use. We intend to deal with devices ranging from scientific pocket calculators to disk- based personal computers.
Exchange - rate adjustment in a multicurrency monetary system
Authors: Mushin Jeremy D.
Published: March 2008

A multination monetary system like the European Monetary System (EMS) is intended to concentrate trade and employment within the block of member na tions by stabilising internal exchange rates. Each member nation accepts a defined responsibility for intervention by its central bank to maintain exchange rates within a specified band. Since intermember exchange rates are affected by changes in the ex change rates of individual member currencies with respect to major currencies outside the block, monetary systems like the EMS use a formula to allo cate responsibility among the member nations for counteracting such exogenous disturbances of inter- block exchange rates.

Though the rules for assigning responsibility for intervention are clearly stated, their consequences to the member nations are not. For this reason, a simulation model of the EMS was built. (It could, of course, be adapted to represent any similar sys tem.) This paper describes the results of a simula tion study of the EMS based on this model. The study was undertaken to increase understanding of the impact on EMS members of the external economic environment, of changes in the number of members of the EMS, and of changes in their relative trading importance. Simulation was used because the EMS is too complex for conventional mathematical analysis.
Solving Differential Equations By First-Order Explicit Integration
Authors: Meyer George E. , Keener Harold M.
Published: March 2008

A first-order explicit integration technique can be an economical means of solving differential equations numerically. It is easy to implement and requires less computation time than Runge-Kutta integration for stiff equations. Error estimates can be derived and the method converges if the coefficient function is always positive and if it and the forcing function exist every where.
The Control Oriented Language
Authors: Siebert J. Paul , Winning David J.
Published: March 2008

A Control Oriented Language (COL) has been designed to assist engineers in specifying self-contained real-time programs targeted for embedded microprocessor controllers. The language com prises concurrent CSSL-based task segments which support continuouslsequential control and simulation models, and sub- models. A real-time operating system kernel is provided to sched ule these tasks. Low-level hardware access statements and a real- time debugging facility have also been incorporated within the COL.
On simulation modeling for FMS
Authors: Mamalis A.G. , Bilalis N.G. , Konstantinidis M.J.
Published: March 2008

A simulation model capable of representing a large variety of flexible manufacturing systems (FMS) has been developed. The software, written entirely in FORTRAN, can be used during the design and control stages of the FMS development. The several modules of the model are described. The model's validation is primarily examined by comparing its results with those obtained using a model written in a specialized simulation language, namely ECSL. Fifteen control strategies are defined and simulation results discussed.
Use of the Fisher Exact Probability Test in surface-to-air missile (SAM) countermeasures evaluations
Authors: Borden Andrew G.
Published: March 2008

In testing the effectiveness of countermeasures against surface- to-air missile (SAM) systems, the important statistic is the pro portion of simulated missiles whose closest approach to a target is outside the lethal radius of the missile. Small samples are common.

The Fisher Exact Probability Test can be used in this situation. The Fisher Test with Tocher's correction is the uniformly most powerful one-tailed test for differences between two proportions.
Initial conditions and differential equations
Authors: Vibet Claude
Published: March 2008

A new method to investigate initial conditions induced by the application of step commands in linear or nonlinear systems is given in this note.
A simple approximation for the simulation of continuous random variables
Authors: Greenberg Irwin
Published: March 2008

A simple technique is described for simulations and analytical studies where the indication is of a unimodal, right-skewed dis tribution of a continuous random variable, the type of distribu tion often approximated by a gamma distribution. The technique is more realistic and more general than the "simple" techniques described in the simulation literature in that it does not require integer parameters.
ALI: A CSSL/multiprocessor software interface
Authors: Makoui Ali , Karplus Walter J.
Published: March 2008

ALI (A Language Interface) is a software package which translates simulation models expressed in one of the higher-level languages, C5SL-IV or ACSL, into sequences of instructions for each processor of a network of microprocessors. The partitioning of the source program among the processors is automatically accomplished. The code is converted into a data flow graph, analyzed and divided among the processors to minimize the overall execution time in the presence of interprocessor communication delays. This paper describes ALI from the user's point of view and in cludes a detailed example of the application of ALI to a specific dynamic system simulation.
A Prolog-based expert system for modeling with partial differential equations
Authors: Russo Mark F. , Peskin Richard L. , Kowalski A. Daniel
Published: March 2008

Initial results are presented from a project to develop intelligent expert system tools for the construction and execution of com plex mathematical models which employ partial differential equations. This paper reports on that portion of the system, the expert system front end, which is concerned with the represen tation and execution of meta-level knowledge about the model building process itself. The current problem domain is restricted to models involving linear as well as a limited class of nonlinear partial differential equations of up to second order. The system is capable of examining the user's input model for inconsisten cies as well as making judgments about suitable algorithms for stable numerical solutions. The symbolic equations, along with boundary and initial conditions, are represented in the form of Prolog clauses. The input model is analyzed by the expert system for equation type as well as appropriate boundary and initial conditions. Discrete approximation of equation terms is perform ed symbolically and the results are then expanded and simplified into an efficiently computable form. Prolog clauses from the discrete approximation phase are then automatically combined with an appropriate solution stepping scheme to arrive at a fully executable algorithm for numerical solution. The algorithm may then be executed serially for testing or further processed into a form suitable for passing to a separate high-speed processor.
Parameter optimization with ACSL models
Authors: Amyot Joseph R. , van Blokland Gerard
Published: March 2008

A method whereby a parameter optimization program, written in FORTRAN, can be used in conjunction with ACSL (Advanced Continuous Simulation Language) models of dynamic systems is described. The optimization of a projectile's trajectory is used as an example.
SCS Activities: Help us close the loop
Authors: Marr George R.
Published: March 2008

SCS Activities are intended to bring growth and vitality to our organization. Activity vice presidents are Society of ficers charged with insuring the development and effec tiveness of Activities.

Activities are special interest groups — as simple as that, each one a group of people organized around an idea that is of importance to simulation and of interest to the So ciety membership.
Artificial intelligence modelling of control systems
Authors: Lirov Y. , Rodin E.Y. , McElhaney B.G. , Wilbur L.W.
Published: March 2008

The field of control systems simulation needs artificial intelligence technology as much as expert systems need systems simulation tools. A functional approach for the design of Expert Systems that perform model generations and simulations is proposed. A differential games simulator design is chosen to exemplify the above ideas. The discrete-event approach, based on the geometry of the game is proposed. Results are comparable with the simu lation results obtained using the imperative approach, but the interrogative approach offers faster execution and clearer sim ula tor definition. Knowledge representation of the differential games models is described using Semantic Networks. The model genera tion methodology is a blend of several problem-solving para digms, and the hierarchical dynamic goal system construction serves as the basis for model generation. Prolog-based imple mentation of the system is suggested.
State variable analysis of dc-dc converters
Authors: Nelms R.M. , Lollar Louis F. , Grigsby L.L.
Published: March 2008

In spacecraft power systems, different voltage and current levels must be available for different loads. In addition, the source for the spacecraft power system may generate low voltage and high current which must be converted to high voltage and low cur rent for transmission to the loads. Therefore, dc-dc converters are an integral part of dc spacecraft power systems. The power requirements for future spacecraft power systems are such that dc-dc converters may need to be connected in series and parallel to supply the load. To simulate such converter systems, a modular dc-dc converter model is developed using state variable tech niques. The state model for each converter in the system is solved using the state transition matrix method. A test system consisting of two boost converters connected in series supplying a resistive load is simulated and compared to a SPICE simulation.
Storm water simulation: Modeling and analysis of a three-dimensional cloud
Authors: Horibata Yasuyoshi , Kodate Hidemi
Published: March 2008

A simulation of storm water is presented for developing a physical understanding of storm runoff from urban basins. A new three- dimensional cloud model simulates storm rainfall. The model contains nine prognostic equations: three momentum equations, pressure and thermodynamic equations, three moisture and water equations, and a subgrid kinetic energy equation. A par ticular coordinate transformation is used. It maps a simulation domain with an irregular lower boundary onto a rectangular domain. A finite difference scheme which conserves heat, mois ture, water substances, and subgrid-scale motion solves the trans formed equations. The rainfall is averaged in space and time for a basin to obtain the hyetograph. We use the Road Research Lab oratory Hydrograph method (the RRL method) to compute the storm runoff hydrograph for the basin from the hyetograph. A simulation result for a simplified atmospheric condition is presented.
A simulation analysis of an updated version of the assigned-slot listen-before-transmission protocol
Authors: Alshammari Saud A. , Rakes Terry R. , Sen Arun
Published: March 2008

Two situations can occur which would cause computers (or nodes) to transmit messages at the same time. In the first case, both nodes see an idle link and immediately start to send their messages. In the second case, they both see the end of a message transmitted by a third node and again begin sending simulta neously. Both of these situations result in a garbled message called a collision. Protocols, or handshaking rules between nodes, can either handle collisions after they occur and direct re-transmission, or they can schedule messages and avoid collisions.

This paper updates a protocol called the assigned-slot listen- before-transmission scheme by incorporating collision detection capability and the use of message queues. A simulation model of a local area network is used to gauge the performance of this protocol and test its sensitivity to packet length, node groupings, and a range of traffic throughputs.
A PROLOG simulator for interactive flexible manufacturing systems control
Authors: Fan I.S. , Sackett P.J.
Published: March 2008

A simulation model of an in-line Flexible Manufacturing System has been built using the declarative computer programming lan guage PROLOG. The model is a vehicle for the study of dynamic responses of Flexible Manufacturing System control. Animation of system status and powerful user interaction are essential for this application.

A simple but effective structure has been formulated in PROLOG as a core kernel of the simulator. The decision making process is modelled as a set of functional queues. Partitioning of the de cision functions permits modeling of complex peer-to-peer co ordinated decision making in non-trivial control environments. This offers many advantages over traditional manufacturing simu lation systems.

The authors describe appropriate strategies for the realization of acceptable computational performance while retaining the powerful benefits of the PROLOG environment. The result is a practical operational system which features an incremental de velopment upgrade path, quick prototyping, fast and clearly understood code changes.
Unbiased statistics and simulation of continuous mail processing
Authors: Taha Hamdy A. , Goforth R.R.
Published: March 2008

Simulation is used to determine the number of sorting devices needed in an automated postal system facility. The model deals with mail types with great variability in processing characteristics. Interactions between continuously and sequentially processed batches at the sorting stations introduces a bias in conventionally collected statistics. This type of interaction in effect necessitates computation of statistics based on moving averages. Unfortu nately, none of the simulation languages provide this capability as a standard output. Although the logic of the basic simulation is straightforward, the model must be significantly modified to produce unbiased or undistorted statistics. SIMNET and SLAM II are used for independently developed final models.
A general-purpose simulation environment for developing connectionist models
Authors: D'Autrechy C. Lynne , Reggia James A. , Sutton Granger G. , Goodall Sharon M.
Published: March 2008

Developing and evaluating "connectionist models" in artificial intelligence, cognitive science, and neurophysiological model ing is currently a difficult and time-consuming task. To address this issue, as part of a larger research effort, we implemented a software system called MIRRORS/II for developing connec tionist models. MIRRORS/II is distinguished by its support of a very high-level non-procedural language along with user and system libraries for the accumulation of system resources. We describe these features in detail, give a small example of the use of MIRRORS/II, and outline details of the implementation. Fi nally, we discuss current work using MIRRORS/II, future plans for the system and other related connectionist modeling systems.
Visualization of injection molding
Authors: Ellson Richard , Cox Donna
Published: March 2008

Scientific visualization, a computer-generated graphical represen tation of scientific information, provides a global view of simula tion results and helps identify discrepencies between the real and simulated world. This article outlines the scientific visualization method and its application to the study of injection molding flows.
Designing a "Cognizant Interface" between the user and the simulation software
Authors: Treu Siegfried
Published: March 2008

A cognizant interface exhibits artificially intelligent knowledge and behavior toward the parties it is to serve in its interfacing role. These parties are the human user, on one hand, and the computer-based simulation software, on the other. The interface is therefore viewed as two-sided. To enable users who are neither computer specialists nor simulation experts to take advantage of sophisticated tools for system modeling and simulation, new approaches to interface design are necessary. They must encompass state-of-the-art technology (e.g. computer graphics and networks) as well as utilize techniques available in the areas of artificial intelligence and human-computer interaction. This paper has a three-fold purpose: to present results of a structured review of the simulation + ar tificial intelligence literature; to focus on criteria for engineering a modifiable interface; and to add to that interface the ability to adapt to the user. An illustrative prototype is outlined and a simulation-oriented framework of knowledge bases is presented.
A simulation procedure for sample size determination in electric utility load research
Authors: Muralidhar Krishnamurty , Tretter Marietta J.
Published: March 2008

Estimating the customer demand for electricity plays a crucial role in the equitable determination of customer electric utility rates. To estimate the customer demand accurately, it is necessary to determine the appropriate sample size. Due to the unique requirements imposed by the Public Utilities Regulatory Policies Act of 1978, existing procedures to determine sample size fail to provide the optimal sample size that will satisfy the re quirements at the minimum cost. The objective of this study is to develop and describe a simulation based procedure that is capable of achieving both criteria. The effectiveness of the pro cedure is tested for selected distributions of electrical demand. The study also identifies other instances where similar sample size determination problems occur and how the newly developed procedure can be used in these situations as well.
Incorporating natural language descriptions into modeling and simulation
Authors: Beck Howard W. , Fishwick Paul A.
Published: March 2008

We explore an approach to merging simulation and natural language in which conceptual structures are used which can repre sent the structure and meaning of sentences as well as basic mathematical concepts. Sentences can be transformed to these structures, and, via language generation, the structures can be transformed into mathematical equations. The process is illustrated using a text description of a plankton respiration model. The ap proach shows how qualitative natural language statements can be merged with both qualitative and quantitative modeling and simulation.
A computer simulation model for the study of police patrol deployment
Authors: Kern Gary M.
Published: March 2008

Simulation models have been suggested as a means of assist ing patrol administrators making deployment decisions. The simulation model reported here allows the administrator to study the performance of several complex dispatching tactics including multiple unit dis patching, preemption, and in tersector dispatching.

Environmental variables, such as interarrival and service times, can be set to reflect any number of possible probability distributions. Sample reports generated by the model are presented, as is information regarding the model's verification.
Efficient simulation experiments for comparing communication network routing algorithms
Authors: Shaikh Muzaffar A. , Althouse Edwin L.
Published: March 2008

In this paper, we propose efficient statistical designs of simulation experiments and statistical methods for systematically comparing communica tion network routing algorithms via simulation. The design of experiments technique establishes the minimum number of observations or simulation runs without losing much information needed to gain insight into the real world system. Statistical models use this efficient set of observations in providing (1) insight into the intrinsic behavior of the algorithm (i.e., sensitivity of the algorithm to changes in factors), (2) a statistical basis for com paring alternate algorithms that perform common functions, and (3) predictor equations that can be used to predict algorithm performance for the user- specified values of influencing factors. The empha sis in the paper is on the use of statistical testing and comparison methods in a simulation setting and not on the nature of algorithms themselves. These methods should pave the way for perform ance analysis of other algorithms as well.

The testing environment includes a parameter- driven simulator which has the capability to modularly include alternate routing algorithms one at a time. The model generates a threat scenario which transforms into the generation of appropriate messages. The impact analysis of five influencing factors on three measures of perform ance is proposed.