Showing papers in "Simulation in 1977"
TL;DR: This paper reviews the application of multiple re sponse surfaces to multiple-variable optimization problems and describes how these techniques may be used in analyzing computer simulation experiments.
Abstract: This paper reviews the application of multiple re sponse surfaces to multiple-variable optimization problems and describes how these techniques may be used in analyzing computer simulation experiments. An example with four response surfaces illustrates the method. In it a simulation of a tank duel is analyzed to determine the values of two independent (input) variables that will optimize four dependent (output) variables simultaneously. The problem examined is that of training battle-tank crews, and the optimization procedure used is based on the Geoffrion-Dyer interactive vector maximal algorithm.
92 citations
TL;DR: An introduction to catastrophe theory is provided and the principal condi tions required for its application are defined and the basic prop erties of bimodality, discontinuity (catastrophe), hysteresis, and divergence are defined using the simplest structures of the theory.
Abstract: Catastrophe theory is a new field in mathematical topology that allows the formulation of comprehensive qualitative models of systems which have previously eluded rigorous mathematical formulation Because the models have a topological foundation, many seem ingly dissimilar phenomena can be related to a common underlying topological structure The properties of that structure can then be studied in a convenient form and the conclusions related back to the original problem This paper provides an introduction to catastrophe theory and defines the principal condi tions required for its application The basic prop erties of bimodality, discontinuity (catastrophe), hysteresis, and divergence are defined and illustra ted using the simplest structures of the theoryIn this paper the spruce budworm/forest ecosystem of eastern Canada illustrates how catastrophe theory may be applied in ecology With only a minimum of general descriptive information about the budworm system, a qualitative catastrophe theory model
47 citations
TL;DR: This work, which was done at the University of California at Davis, has cost about $2,000,000 and has been supported by the Ford foundation, the U.S. National Science Foundation, the Subcommittee on Energy and Power of the House of Representatives, and a Senior Fellowship from the East-West Center in Honolulu.
Abstract: For the past eight years I have been an active participant in developing large-scale computer simulation models of society. This work, which was done at the University of California at Davis, has cost about $2,000,000 and has been supported by the Ford Foundation, the U.S. National Science Foundation, the Subcommittee on Energy and Power of the House of Representatives, and a Senior Fellowship which I received from the East-West Center in Honolulu. Some 51 people worked on various aspects of the models at one time or another, 17 of them contributing to the conceptual models that now guide our research, and only one of themmehas been on the team the whole time. By 1978 I will be the only person left on this project.
40 citations
TL;DR: The leading numerical formula tions used to generate exact semiconductor models are discussed and the simulation of an NP junction, a bipolar transistor, and a MOS field effect transistor using exact models is described.
Abstract: The simulation of semiconductor devices is a powerful means for optimizing the performance of semiconduc tor circuits and devices. various classes of semi conductor models exist, but accurate simulations re quire exact ("total") computer models. The exact models allow the use of arbitrary initial conditions and internal distributions and describe the device accurately over wide ranges of operation.This article discusses the leading numerical formula tions used to generate exact semiconductor models and describes the simulation of an NP junction, a bipolar transistor, and a MOS field effect transistor using exact models.
38 citations
TL;DR: Using elementary statistical theory, techniques that can be used to initialize a simulation run and to determine its length are discussed and three practical variance reduction techniques are summarized, namely, control variates, antithetics, and common random numbers.
Abstract: Using elementary statistical theory, we discuss sta tistical techniques that can be used to initialize a simulation run and to determine its length, distin guishing between terminating and nonterminating sys tems and between stationary and nonstationary time series. Confidence intervals and hypothesis tests are included (see Section 2). In the case of k sys tem variants (at least 2), multiple comparison proce dures are presented which can be used to obtain simultaneously valid confidence intervals and to select a subset containing the best population, assuming a fixed number of simulation runs. Other wise ranking procedures can be used to determine the number of runs required to select the best system (Section 3). If many parameters and variables exist, selecting a limited number of combinations requires an experimental design, which must be analyzed with a regression metamodel (Section 4). The metamodel of main effects and interactions applies to both quantitative and qualitative factors; its adequacy ca...
28 citations
TL;DR: This paper is a state-of-the-art review of software for combined continuous/discrete systems simulation with the following 18 languages or packages discussed.
Abstract: This paper is a state-of-the-art review of software for combined continuous/discrete systems simulation. The following 18 languages or packages are discussed:
28 citations
TL;DR: Experiments with ordinary and generalized least- squares estimation (OLS and GLS) show that the parameter estimates derived from these methods are highly sensitive to errors in data measurement, especially when a model's feedback structure is not completely known.
Abstract: This paper considers the accuracy of conventional econometric techniques in estimating parameters in a feedback model Evaluation of the estimation techni ques is accomplished by an experimental procedure in which a nonlinear feedback model generates synthetic data which is then used to estimate the parameters in the data-generating model Comparison of the estimated and "true" parameter values provides a measure of the accuracy of the estimation techniqueExperiments with ordinary and generalized least- squares estimation (OLS and GLS) show that the parameter estimates derived from these methods are highly sensitive to errors in data measurement, especially when a model's feedback structure is not completely known Further tests of OLS and GLS with different feedback models, as well as experimental evaluations of other estimation techniques, should help to determine the proper role of statistical methods in modeling feedback systems
26 citations
TL;DR: The subprogram module is an enhancement to CSSL-based simulation software and relies on its host software for the specification and solution of the dynamic equations of the system under study.
Abstract: This paper describes a subprogram module which sim plifies the implementation of parameter optimization studies in continuous dynamic systems. The module is an enhancement to CSSL-based simulation software and relies on its host software for the specification and solution of the dynamic equations of the system under study. The module includes several different optimization algorithms -a feature which can be of great value in difficult problems. It has output documentation routines and is organized so as to be transparent to the user.
24 citations
TL;DR: The effect of initial conditions and the warm-up period on the design of simulation experiments for the simple case of a single-server queuing system with Poisson input and exponential service times is explored.
Abstract: The simulation of complex queuing systems is an im portant application for discrete-event digital simula tion. In many cases, the object of the analysis is estimation of steady-state measures (e.g....
21 citations
TL;DR: This paper shows what is happening during a simulation as a "moving picture" on a terminal so that the users of the simulation can feel sure that they can depend on the model.
Abstract: 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.
19 citations
TL;DR: Three inexact methods that are commonly used to generate arrivals for a nonstation ary Poisson process are described and an exact method is shown to produce accurate results.
Abstract: This paper describes three inexact methods that are commonly used to generate arrivals for a nonstation ary Poisson process and compares them to an exact method. Different patterns are assumed for the arrival rate as a function of time. The exact method is shown to produce accurate results, whereas all three inexact methods produce results that are sig nificantly different in a statistical sense. All four methods require similar amounts of computer time.
TL;DR: Analysis of a study directed to the specification and procurement of a new cockpit simulator for an advanced class of heli copters showed that a particularly cost-effective approach is to employ a large minicomputer acting as host and controller for a special-purpose digital peripheral processor.
Abstract: This paper describes some of the results of a study directed to the specification and procurement of a new cockpit simulator for an advanced class of helicopters. A part of the study was the definition of a challenging benchmark problem, and detailed analyses of it were made to assess the suitability of a variety of simulation techniques. The analyses showed that a particularly cost-effective approach to the attainment of adequate speed for this extremely demanding application is to employ a large minicomputer acting as host and controller for a special-purpose digital peripheral processor. Various realizations of such peripheral processors, all employing state-of-the-art electronic circuitry and a high degree of parallelism and pipelining, are available or under development. The types of peripheral processors array processors, simulation-oriented processors, and arrays of processing elements - are analyzed and compared. They are particularly promising approaches which should be suitable for high-speed simulations of all kinds, the cockpit simulator being a case in point.
TL;DR: The multiple-instruction stream/ multiple-data stream (MIMD) Wisconsin parallel array computer (WISPAC) makes use of current, low-cost microprocessor technology and is intended to meet future needs in large-scale simulation.
Abstract: This paper discusses the multiple-instruction stream/ multiple-data stream (MIMD) Wisconsin parallel array computer (WISPAC). The design of the computer makes use of current, low-cost microprocessor technology and is intended to meet future needs in large-scale simulation. A modular approach is taken where smaller configurations are meant as direct competi tive replacements of current hybrid systems. Larger configurations will allow high-speed solution of large-scale simulation problems using a one-to-one correspondence of each microprocessor to each node of the system being modeled. A three-dimensional configuration is used to allow a high degree of iso morphism between the computer setup and the model to be investigated. These schemes simplify programming requirements and overall machine conceptualization. New techniques of high-speed internode communication utilizing a serial "pass-through" scheme are des cribed. The scheme allows general cross-array com munication that is competitive with cross-point ...
TL;DR: It is now practical to combine many analog operations into groups of input/output functions, and many traditional programming and operating difficulties are eliminated.
Abstract: tors can simplify programming, provide special features for the operator, and reduce costs. It is now practical to combine many analog operations into groups of input/output functions. When simulations are divided into categories (mechanical, chemical, physiological, etc.), there are usually recurring loops that can be treated as independent subprograms. These subprograms may then be programmed as physical or mathematical functions rather than as analog computing components. Many traditional programming and operating difficulties are thus eliminated.
TL;DR: A philosophical overview of simulation is presented, with an emphasis on the nature of the relation between models and the systems they represent, and the problem of validation of the results of a simulation.
Abstract: This paper presents a philosophical overview of simulation, with an emphasis on the nature of the relation between models and the systems they represent. Model-making is shown to be an essential feature of human thinking. The “abstraction ladder,” which leads from observations of reality to mathematical models, is reviewed from a semantic viewpoint. The problem of validation of the results of a simulation is then outlined. The paper concludes with same philosophical observations on the relation of model and reality.
TL;DR: A model simulating the growth of clones of cells in two dimen sions is described, which includes an algorithm that simulates the displacements which occur when interior cells divide in a cell mass.
Abstract: A model simulating the growth of clones of cells in two dimen sions is described. This model includes an algorithm that simulates the displacements which occur when interior cells divide in a cell mass; the model uses an algorithm which allows more realistic simulation than did previous models that did not possess this facil ity. Applications of the model are discussed, and details are given of the execution of the program on refresh display video, allow ing dynamic observation of the modelled cell division process.
TL;DR: Jay W. Forrester developed system dynamics, a methodology which makes use of computer modeling and simulation to study corporate and social systems.
Abstract: Jay W. Forrester began his simulation work when he was directing development of the Whirlwind computer for the study of engineering systems at MIT, circa 1950, and the SAGE man/machine air-defense system at MIT's Lincoln Laboratories. Later, as professor of management at MIT, he developed system dynamics, a methodology which makes use of computer modeling and simulation to study corporate and social systems.
TL;DR: Physiological models are older and better developed than biochemical models because they have had an analytic outlook while physiology has been synthetic and quantitative.
Abstract: Much computer simulation of biological systems has been at the physiological level, i.e., it has involved the functioning of a major organ or organ system. Simulation at the biochemical level has lagged by comparison. This lag has not been the result of a lack of biochemical information, as biochemical research has flourished recently,. Rather it is the result of the different approaches of the two sciences. Biochemistry has had an analytic outlook while physiology has been synthetic and quantitative. Since many physiological results can be described in numerical terms and be represented by relatively simple mathematical functions, engineering techniques for system identification and parameter estimations have been applied directly to physiological problems. The display of events as functions of time is traditional in physiology but not in biochemistry, which fact affects the applicability to biochemistry of methods concerned with functions of time. For these reasons physiological models are older and better developed than biochemical models.
TL;DR: An algorithm is presented for generating uniformly distributed random deviates on microprocessors or minicomputers utizizing memories with a small word- Zength and the statistical quality of sample streams of generated numbers is evaluated and compared with the quality of other widely used generators.
Abstract: An algorithm is presented for generating uniformly distributed random deviates on microprocessors or minicomputers utizizing memories with a small word- Zength. other alternative solutions are discussed, and the statistical quality of sample streams of generated numbers is evaluated and compared with the quality of other widely used generators.
TL;DR: In this article, a digital computer simulation of an experiment which measures the energy-intensity distribution of noble gas ions scattered by crystalline solids is described, emphasizing the simulation techniques employed (in particular, the choice of integration method), the methods of relating computer input data to the experimental variables, and the transformation of computer results into a form directly comparable to experimental data.
Abstract: Digital computer simulation of an experiment is described which measures the energy-intensity distribution of noble gas ions scattered by crystalline solids. The discussion emphasizes the simulation techniques employed (in particular, the choice of integration method), the methods of relating computer input data to the experimental variables, and the transformation of computer results into a form directly comparable to experimental data.
TL;DR: Many types of simulation games and management techniques are now available to business and industry as mentioned in this paper, which range from general management simulations to industry games to functional area games (marketing, production, finance etc.).
Abstract: Many types of simulation games and management techniques are now available to business and industry. These games range from general management simulations to industry games to functional area games (marketing, production, finance, etc.). The management techniques include the Delphi technique, envelope forecasting, and scenario writing, which are used to help predict future occurrences. All these games and techniques have one common characteristic : they are designed to help the participant in the deci-
TL;DR: In this paper, the authors discuss and measure the use of simulation in decision support systems in the U.S.A. and identify specific areas within each of the business functions where simulation is being used.
Abstract: This article both discusses and measures the use of sim ulation modeling in decision support systems in major cor porations in the U.S.A. The effective use of quantitative techniques requires that managers develop decision sup port systems which include both adequate data bases and the capability of structuring decision models compatible with their corporations' information systems. Since simu lation is one of the most widely used quantitative tech niques, its use in such decision support systems is exam ined. Specifically, this paper attempts (1) to measure the development and use of simulation at all decision- making levels (operational, tactical, and strategic), (2) to examine the use of simulation within each functional area of business, and (3) to identify specific areas within each of the business functions where simulation is being used.
TL;DR: A new deterministic integration method is presented which will accurately and rapidly produce the solution to a differential equation of the form x(t)= Ax(t) + Bu(t), where A and B are constants.
Abstract: A common problem in system simulation is producing the solution to a differential equation of the form x(t)= Ax(t) + Bu(t), where A and B are constants. In particular, simulation often requires solutions for a step, ramp, or constant-acceleration forcing function. Standard numerical integration methods may fail or be extremely slow when implemented on a mini computer because of its short wordlength. This paper presents a new deterministic integration method which will accurately and rapidly produce the solution. Some numerical experiments are shown to demonstrate the new method.
TL;DR: A simulation model of driver- vehicle behaviour at an intersection and two versions (one batch, one interactive) of its implementation, which incorporates some of the latest findings of human factors research concerning the driving task, and represents the driver's perceptual, decision-making, and response processes as the driver approaches, passes through, and leaves the intersec tion.
Abstract: This paper describes a simulation model of driver- vehicle behaviour at an intersection and two versions (one batch, one interactive) of its implementation. The model offers the user considerable f...
TL;DR: Many years ago, a customs man asked my occupation and when I told him I worked for a computer manufacturer, he unhesitatingly queried “Analog or digital?” Not only would customs people fail to appear so knowledgeable today, but one would be very hardpressed indeed to find any group outside the SCS that is aware of the distinction.
Abstract: Many years ago, I was enroute to Canada on a sales call for Beckman. A customs man asked my occupation and when I told him I worked for a computer manufacturer, he unhesitatingly queried &dquo;Analog or digital?&dquo; Not only would customs people fail to appear so knowledgeable today, but one would be very hardpressed indeed to find any group outside the SCS &dquo;family&dquo; that is aware of the distinction. Even
TL;DR: In a simulation the use of complementary antithetic random variates in the generation of component lifetimes reduces the vari ance of the sample mean number of replacements in a multiple-component multiple-period replacement process in which the components may be either new or used.
Abstract: Prediction of replacement requirements for components (such as manufacturing equipment or engines) requires analysis of a replacement process. Unfortunately, unless component lives are exponentially distributed, that analysis requires transform methods, approxima tions, or simulation. Only simulation or approxima tion may be used for prediction of replacement re quirements when the replacement process is complicat ed, when it is subdivided into several periods of time, when replacements are not all new, or when several identical components that operate simulta neously are supplied from the same stock of spares.This paper shows that in a simulation the use of complementary antithetic random variates in the generation of component lifetimes reduces the vari ance of the sample mean number of replacements in a multiple-component multiple-period replacement process in which the components may be either new or used. Reducing the variance results in more accurate predictions for fixed simulation runtimes or, alt...
TL;DR: A stochastic model of the right- turn-on-red (RTOR) policy for a high-density urban area consisting of one-way streets is outlined and specific recommendations on when to use RTOR are developed for typical urban conditions.
Abstract: This paper outlines a stochastic model of the right-turn-on-red (RTOR) policy for a high-density urban area consisting of one-way streets. This model is used to investigate the effects of (1) cross-street traffic volume, (2) right-turn lane traffic volume, (3) pedestrian arrival rate, and (4) balking rate for right-turning vehicles. The model provides the methodology for studying the RTOR maneuver under various conditions. Specific recommendations on when to use RTOR are developed for typical urban conditions. Language: en
TL;DR: In this article, the authors describe the modelling of variables usually treated as exogenous parameters in regional simulation models, and identify the areas where those variables are particularly important, and discuss a multiregional model for Great Britain.
Abstract: This paper describes the modelling of variables usually treated as exogenous parameters in regional simulation models, and identifies the areas where those variables are particularly important. A multi regional approach allows the direct modelling of interregional migration, unemployment differentials, and industrial growth changes; the paper describes the equations involved and discusses a multiregional model for Great Britain. Results from initial experimentation with the model are presented, and its ability to replicate real data is tested. The model permits the incorporation of policy decisions and programmes; simulation results show the application of a development area policy and a migration assist ance programme. Further development of the model by more detailed breakdown of the population and indus trial sectors is outlined.
TL;DR: The Interactive Simulation Language (ISL) is a power ful and easy-to-use software system for hybrid com puters using any of several different minicomputers.
Abstract: The Interactive Simulation Language (ISL) is a power ful and easy-to-use software system for hybrid com puters using any of several different minicomputers. Its principal features are:
TL;DR: In this article, a GASP IV model of part of a steel mill is described and the major problem is how to dispatch a limited number of rail engines to pull trains so that materials and molds are at the right places at right times for efficient operation.
Abstract: This paper describes a GASP IV model of part of a steel mill. The processes modeled include pouring molten steel into molds, removing (stripping) the hot ingots from the molds, and sending them to the soaking pits and finally to the primary rolling mill. Molds move from a preparation area to the furnaces, thence to the stripping cranes, and back to the pre paration area. Rail trains transport ingots and molds.The major problem is how to dispatch a limited number of rail engines to pull trains so that materials and molds are at the right places at the right times for efficient operation. A set of 32 experiments (indi vidual simulation runs) was devised to find an opti mum combination of number of engines, number of transportation zones, and dispatching rules for a particular steel mill.The set of experiments showed (not surprisingly) that the use of a single transportation zone (so that all engines were able to go wherever they were needed) and a larger number of engines resulted in the greatest percentage...