bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Space Shuttle ground operations
Authors: Wilson James R. , Vaughan David K. , Naylor Edward , Voss Robert G.
Published: March 2007

To assess the feasibility of proposed launch schedules for the Space Shuttle, we have developed a simulation model of the flow of activities comprising Shuttle turn around processing. Considering queueing delays caused by the limited capacity of ground facilities, the model estimates flight starting dates needed to meet a given launch schedule with a specified level of confi dence. The results of an extensive sensitivity analysis indicate that the currently projected schedules are optimistic and that the turnaround time will substan tially exceed the current goal of 28 days.
Simulation and graphics on microcomputers
Authors: Miller Ronald R.
Published: March 2007

It is difficult to relate the output of a simulation model to the physical system it describes. Graphic representa tions of results can make simulations more credible and more interesting. On most large computers, how ever, there are software and hardware barriers between the user and graphical output. Microcomputers, on the other hand, are easy to use, and simple graphics are easy to produce without help from a programmer or systems specialist. Examples show bar charts, snap shots, dot plots, bit density plots, and contour plots of simulation results generated using an Atari 800 micro computer, a color television, and an Epson MX-80 printer (costing about $600) with graphics capability. All the user must do to obtain such plots is write short programs (less than 100 statements) in BASIC.
Simulation of a high-gain adaptive speed-regulating system for an internal combustion engine
Authors: El-Imam Yousif Ali
Published: March 2007

An analog computer has been used to simulate a high-gain adaptive control method for regulating the speed of an internal combustion engine. A nonlinear element (an on-off relay) main tains the high gain in the forward loop that is necessary to produce a one-to-one relationship between input and output. Such high gain leads to limit-cycle behaviour in the model. A high-frequency dither at the relay input acts as a stabilizing signal to deal with this problem.
Use of models for water resources management, planning, and policy
Authors: Pratt Charles A.
Published: March 2007

The U.S. Office of Technology Assessment (OTA) recently sent a report brief to this office that I would like to share with our readers. It presents yet another instance in which the importance of computer modeling is being recognized. Because the brief is only part of a full report, * / have chosen to reproduce it in its entirety rather than to "excerpt the excerpt."
Simulation in the Service of Society
Authors: McLeod John , McLeod Suzette
Published: March 2007

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 75ç per copy.
Validation of multivariate response models using Hotelling's two-sample T2 test
Authors: Balci Osman , Sargent Robert G.
Published: March 2007

A procedure is given for using Hotelling's two-sample T2 test to test the validity with respect to the mean behavior of a multivariate response simulation model that represents an observable system. A tradeoff analysis can be made to help the modeler decide on a data collection method and budget, the number of observations to collect, and suitable model builder's and user's risk levels for testing the validity under a given set of experimental conditions. A model of an M/M/1 queuing system with two performance measures serves as an example for the validation procedure.
Simulation of robotic manufacturing cells: a modular approach
Authors: Medeiros Deborah J. , Sadowski Randall P.
Published: March 2007

This research provides a general modeling approach for the design and analysis of computer-controlled manufacturing cells containing robots, sensors, automatic machines, and orientation devices. The development process is described and alternative concepts are discussed. The developed ap proach allows a simulation model to be constructed by se lecting appropriate modules from an available library and linking them together. A demonstration manufacturing cell developed by McDonnell Douglas for the Air Force In tegrated Computer-Aided Manufacturing (ICAM) program is utilized to illustrate the concepts and a more complex exam ple is presented to illustrate the versatility. This approach is flexible because alternative configurations can be modeled quickly and easily. Individuals with significant expertise in cell design but little experience in simulation can create simulation models of manufacturing cells and perform mean ingful analysis.
Simulating Saudi Arabia's oil export strategy
Authors: Picardi Anthony C. , Shorb Alan McK.
Published: March 2007

A system dynamics model of Saudi Arabia's oil export strategy has been constructed. Besides providing estimates of future oil exports, this work demonstrates the application of stochas tic simulation models with feedback to the examination of de cisions involving multiple objectives. Such models can be used in real-world strategic planning where decisions affect the achievement of many goals simultaneously, and where tradeoffs must be made between different objectives. Since strategic planning occurs in an environment of uncertain events, it is necessary to explore the limits of the system behavior so best and worst case scenarios can be defined.

Our model, called the Saudi Oil Decision Model, uses inter views with informed people to estimate probable values of ex ternal factors and to validate the system structure. The model considers seven Saudi national objectives, four of which are advanced by increasing exports and three by decreasing ex ports. The feedback structure balances increases and de creases in exports according to criteria that measure the achievement of all seven objectives.

The model was simulated in a Monte Carlo mode, and the results were examined to determine which combinations of ex ternal events produced the largest changes in oil exports. Analysis shows that large increases in Saudi oil exports are unlikely, given their national objectives as evidenced in past behavior. The reason for this derives from the dynamics of compromise between conflicting objectives. The Saudi Oil Decision Model is the first multi-objective model to be ap plied to the political-economic problem of oil exports from Saudi Arabia.
Evaluating the reliability and availability of photovoltaic systems
Authors: Huss William R.
Published: March 2007

SOLREL, a new reliability/availability simulation model, incor porates design, reliability, cost, and maintenance information to predict annual maintenance cost and energy production for photovoltaic [PV] power systems. SOLREL considers failures, lost production, and both scheduled and unscheduled mainte nance. Combined with initial cost and operating cost informa tion, the model predicts levelized cost per kWh. It gives photovoltaic system designers a way to evaluate design trade- offs and minimize life-cycle energy cost.

Large terrestrial photovoltaic power systems (over 50 kWp) are a recent development. Thus, failure rate, repair time, and cost data are lacking for many subsystems and components. In spite of this, reliability/availability models can still aid in design decisions by allowing designers to estimate changes in life-cycle energy costs for alternative subsystems and con figurations. As more test and field data become available, the models can be made more detailed and more accurate. At present, their principal value is to emphasize reliability and maintainability early in system design, with resulting im provements in component selection and subsystem design.
Three-dimensional simulation of tumor growth
Authors: Düchting Werner , Vogelsaenger Thomas
Published: March 2007

A new three-dimensional model of tumor growth and treatment includes (1) models of the life cycles of normal cells and tumor cells, (2) cell-cell interaction and production rules, and (3) algorithms that account for different avenues of tumor treat ment. Illustrative examples show the simulation of tumor growth and treatment by chemotherapy. The model could make it possible to optimize treatment schedules using computer simulation prior to clinical therapy.
A system dynamics simulation of educational finance policies
Authors: Andersen David F.
Published: March 2007

What happens when two different simulation approaches are used to explore the same social policy question?1 This question is explored using the problem of school finance reform with an emphasis on special education finance as an example. The out put from two simulation models is briefly described. A static simulation model, based on an extensive data base, provides one-year projections on a locality-by-locality basis. A pilot system dynamics model provides multi-year aggregate fore casts, but fails to provide detailed locality-by-locality projec tions and relies upon several empirically uncertain relation ships. Where one technology excels, the other falls short. Pilot results appear promising and development work continues on the system dynamics approach to simulating school finance questions.
A preliminary review of batch sizes in a job shop using a digital simulation model
Authors: Browne Jim , Davies B.J.
Published: March 2007

A previous paper 1 described the design of a simulation model. This model, written in GASP IV, allows the management of a large machine shop to try out policies under realistic assump tions without disrupting operations.

This paper outlines the results of approximately 30 "runs" on the model, which are designed to provide an insight into the ef fects of modifying the batch sizes used in the machine shop. The results obtained suggest that the major impact of increased batch sizes is on the flow of work through the plant. The overall conclusion is that the current manufacturing system cannot ac commodate larger batch sizes. The presently used batch sizes suit the configuration of work centres and the deployment of labour in the job shop.
Use of computer simulation in oil spill response training
Authors: Peabody C.H. , Goodman R.H.
Published: March 2007

Response to recent oil spill incidents has shown the need for augmenting the training of oil spill response teams. At the spill site, the On-Scene Commander attempts to correlate all the available information for prompt implementation of the op timum clean-up strategy.

A new technique using Computer-Assisted Learning has been developed for the training of On-Scene commanders, which dramatically simulates the time pressures involved in an oil spill. The Computer-Assisted Learning system will complement ac tual hands-on training field exercises.

A forty-eight hour scenario is simulated in four hours of actual time, during which the On-Scene Commander responds to the spill situation by requesting weather information, spill trajec tories, deploying booms and skimmers, and solving other prob lems in a time-pressured situation. All commands are input through a touch-sensitive screen, eliminating problems ex perienced by users unfamiliar with a keyboard.

At the end of the simulated response, data is provided on the amount of oil recovered, the amount of shoreline oiled, and the total cost of the cleanup. The trainee can then evaluate his actions as recorded by the computer throughout the simula tion and as presented to him in the form of graphs at the end of the simulation.

The Computer-Assisted Learning program has proven to be a useful adjunct to our usual training program; it provides the On- Scene Commander trainee the opportunity to experience the time pressures and decision-making associated with an oil spill.
A simulation model of stock exchange trading
Authors: Cohen Kalman J. , Maier Steven F. , Schwartz Robert A. , Whitcomb David K.
Published: March 2007

A simulation model of stock exchange trading is used to test the impact of various stabilization policies on a stock's market per formance characteristics (price volatility, the size of its bid-ask spread, and autocorrelation patterns in the security's returns). Market participants include large and small traders, a pure stabilizer, and a speculating stabilizer. The "market architecture" includes the arrival of market and limit orders the maintenance of a limit order book, and the handling of trade execution. Each type of stabilizer improves the operating characteristics of the market, with the speculating stabilizer having a bigger impact and realizing more profits than the pure stabilizer. Using the mechanism of simulation to eliminate other sources of the stabilizer's profit, we find that stabilization per se is an un profitable activity. We then suggest additional ways in which the simulation model could be developed and further uses for it.
Digital simulation of guidance and control system of an advanced supersonic fighter
Authors: Lin Ching-Fang , Hsu Khai-Li
Published: March 2007

This paper discusses automatic guidance and control system of a supersonic fighter and presents results obtained from real-time digital simulation of a wide range of problems of practical in terest in optimal aircraft maneuvering. The optimal maneuvers simulated include (1) maximum-range glide, (2) minimum-time zoom climb, (3) minimum-time vertical turns (i.e., loop, half- loop, split-S), and 4) minimum-time three-dimensional turn (i.e., chandelle). The aircraft model used in the simulation is a lightweight, high thrust-to-weight ratio supersonic fighter. Both the off-line optimization approach and the on-line optimization approach are used. The computer used for the simulation is the AD 70, which is a very high-speed special-purpose computer designed specifically for time-critical simulation of very large and complex models of dynamic systems such as the aircraft.
A methodology for building a simulation model for efficient design and performance analysis of local area networks
Authors: Chlamtac Imrich , Jain Raj
Published: March 2007

This paper proposes a general methodology for building a soft ware tool to aid in the design and performance modeling of local computer networks. At the core of the modeling approach lies a distributed view of the network consisting of independently modeled network functional components—protocols, nodes, and resources. The network components communicate through model defined or user provided interfaces. As a consequence, the effect of network changes, component deletions, or addi tions are localized and the network model can be easily altered to highlight certain components while reducing others as re quired in different design phases. The result is that long simula tion runs of a large and fully detailed model are replaced by shorter runs of several smaller "function oriented" network models. The inherent partitioning of the system model into relatively independent functional units makes it also a poten tial candidate for a distributed simulation implementation.

The given methodology is exemplified with an actual implemen tation of an Ethernet* based system configuring tool. The methodology can also be applied to other distributed systems to build efficient modular simulator programs.
The simulation of a master-slave event set processor
Authors: Comfort John Craig
Published: March 2007

Event set manipulation may consume a considerable amount of the computation time spent in performing a discrete-event simulation. One way of minimizing this time is to allow event set processing to proceed in parallel with the remainder of the simulation computation. This paper describes a multiprocessor simulation computer, in which all non-event set processing is performed by the principle processor (called the host). Event set processing is coordinated by a front end processor (the master) and actually performed by several other functionally identical processors (the slaves). A trace-driven simulation pro gram modeling this sytem was constructed, and was run with trace output taken from two different simulation programs. Out put from this simulation suggests that a significant reduction in run time may be realized by this approach. Sensitivity analysis was performed on the significant parameters to the system (number of slave processors, relative processor speeds, and in terprocessor communication times). A comparison between ac tual and simulated run times for a one-processor system was used to assist in the validation of the simulation.
Simulation of speech intonation by Legendre orthogonal polynomials
Authors: Zhou S.M. , Suen C.Y. , Bui T.D.
Published: March 2007

A method of fitting and synthesizing speech intonation by means of Legendre orthogonal polynomials has been proposed and simulated. When applied to pitch curves and intensity curves, the fitting error was small. Using the fitting coefficients, the in tonation of different types of spoken Chinese sentences was syn thesized satisfactorily.
DPS — A digital simulation language for the process industries
Authors: Wood R.K. , Thambynayagam R.K.M. , Noble R.G. , Sebastian D.J.
Published: March 2007

A digital simulation language program, DPS, developed for the unsteady state simulation of multicomponent process systems, is described. Although a continuous system simulation language, the program allows for the specification of a variety of discrete events of the type encountered in process applications. Typical of these events are the opening/closing of valves, starting/stop ping pumps, etc. DPS uses powerful graphical techniques for sorting and sieving the model equations. The use of DPS is demonstrated by simulating the dynamic behaviour of two dif ferent types of systems: a simple multicomponent mixing pro cess and a control system described by transfer functions.
Simulation of nonlinear differential equation systems
Authors: Belmont Michael R. , Lindsay-Stewart W. Andrew , Boyle J.D.
Published: March 2007

A low-cost hybrid method is described for implementing delays and convolution integrals as part of nonlinear differential equa tions on an analogue computer. A Z80 based unit is employed for storage of data tables and kernel functions and mode con trol of the problem. The technique is illustrated using the logistic equation and its generalisation.5 The results are compared with analytic approximations which are developed later in this paper.
Computer simulation of patient flow in obstetrical/gynecology clinics
Authors: Mahachek Arnold R. , Knabe Terry L.
Published: March 2007

Management's plan to combine two clinics is analyzed by com puter simulation based upon present patient flow data and specific planned operational changes. The specific areas ex amined or tested are provider staff size/ratio, effect of new pro vider type, facility size/composition requirement, patient sched uling methodology, personnel utilization, staff arrival/departure effects, patient waiting time, and direct labor unit costs. Pro cedure duration and patient arrival time are gathered using log sheets for 2,000 patients; direct observation supplements logged data loss. The simulation system is GPSS. Model results con tribute substantially to all eight target areas. The planned com bining of the two clinics is postponed until adequate space is available.
Simulation to develop and test queue approximations: A case study
Authors: Albin Susan L.
Published: March 2007

We use simulation to both develop and test approximation for mulas for the operating charactertistics of a queue that occurs in queuing network models. In this context, the main simula tion issues are design of simulation experiments and evaluation of the difference between approximations and simulation esti mates. The simulation experiments described here have specific goals, use analytic results to reduce the number of factors, and are performed sequentially with initial experiments generating questions to address in later experiments. The difference between simulation estimates and approximations are evaluated by two summary measures: average absolute percentage error and a measure of simulation variability. In addition, another measure is examined: percent of cases where the approximation falls out side a 95% confidence interval computed from simulation esti mates. While this measure is commonly used by others, especially in graphs, work here suggests it is inappropriate.
Using the Interactive Financial Planning System (IFPS) for stochastic simulation
Authors: Gray Paul
Published: March 2007

In recent years, many financial planning languages have been developed that contain capabilities for fixed-time interval simula tion. These languages differ from ordinary programming lan guages and from existing simulation languages in that they are much more English-like, produce spread sheet output, and have built-in WHAT IF and other capabilities for sensitivity analysis. These languages are simple, easy to learn, and easy to use to com municate with other professionals and with managers.

This paper describes the capabilities of one of these languages, the Interactive Financial Planning System (IFPS), for simulation. These capabilities include, among others, the means for gener ating probability distributions and scenarios, providing statistical outputs as a function of time, and graphical presentation of out put distributions. Typical models written in this language are used for illustration.
An efficient generator of uniformly distributed random variates between zero and one
Authors: Thesen Arne
Published: March 2007

A random number generator particularly well suited for simula tion work on microcomputers is presented. The generator dif fers from conventional generators in that the floating point representation of the variate is constructed directly without first going the way of an equivalent integer representation of the variate.

Implementations of the generator in FORTRAN-77 and PASCAL/MT+ for the IBM PC are presented, and the results of extensive empirical tests of the generator are provided. The generator is shown to be about as fast as conventional 16-bit congruential generators but with substantially better statistical properties and at least one order of magnitude longer period.
A new method for the computation of digital filter coefficients — Part I
Authors: Forsythe William
Published: March 2007

A new method tor computing the coefficients ot a digital algorithm to simulate a continuous transfer function is shown in a number of examples to be simple to apply and highly effec tive in operation. The poles of the function of s are mapped directly into the z-plane, but the positions of the z-plane zeros (which may be equal in number to the poles, or greater) are derived by a more complex process involving the use of the Taylor series expansion.
A simulation model of railroad reliability
Authors: Kesling G.D. , Whittaker I.C.
Published: March 2007

A simulation model is used to study the relative reliability of struc tures subject to failure caused by fatigue cracking. This general model can be applied to most structures maintained by periodic inspections, including airplanes, bridges, pressure vessels, and nuclear reactors. The models of initiation and growth of cracks and the resulting fractures use a grid of stress cells to approx imate the cross-sectional shape of the structural components. Included in the analysis is a general model of the probabilitistic detection of cracks during an inspection. The reliabiltiy of struc tural components can be combined in the analysis to obtain overall structural reliability.

The model was applied to railroad rails as a subcontract for the Department of Transportation. 29 Measurements of the rail's material characteristics and operating environment are used to estimate its reliability for a specified inspection schedule. The crack growth model selected for the rail application performs well for steel compositions, though alternative growth models are recommended for other materials. For the rail application, a model for computing the stress exposure of railroad rails is also included. Results from the rail application and use of these results to improve efficiency of resource allocations are presented.
A hybrid graphical-simulation analysis of a health systems application
Authors: Nelson Barry , Ravindran A.
Published: March 2007

Computer simulation is often used to optimize practical network queuing models. In many situations the number of possible alter natives that could be simulated is large, and individual runs may be expensive. A simple approximation technique can be used to reduce the number of options actually simulated by providing a pictorial representation of the service process in a network of queues under simplifying assumptions. A simulation experiment can then be performed for detailed analysis of the selected subset of alternatives. This hybrid graphical-simulation approach was used in the design of a United States Air Force health improve ment program.
ESL - A new Continuous System Simulation Language
Authors: Crosbie R.E. , Javey S. , Hay J.L. , Pearce J.G.
Published: March 2007

ESL is a new Continuous System Simulation Language (CSSL) which is being developed under contract from the European Space Agency. It is based on the concepts outlined in Refer ence 6. The main features of the new language are:

(1) Models can be built from submodels (2) Separation of model and experiment (3) Advanced discontinuity-handling (4) A parallel segment feature.

The implementation of ESL requires both an interpreter and a translator version of the language. The interpreter translates the user's program into an intermediate code (H-code) which is then interpreted at run-time. The translator may be used to convert the H-code to FORTRAN-77 to produce a more efficient ex ecutable program of production runs. The entire system (with the exception of a few low-level routines) is being written in FORTRAN-77.

A prototype version of the language was installed in August 1983 and is currently undergoing evaluations. Details of this version are given with examples of its use.
Applications of supercomputers in the petroleum industry
Authors: Absar Ilyas
Published: March 2007

Supercomputers are becoming a useful and important tool in the finding and developing of oil and gas reserves. Applications of supercomputers in the petroleum industry involve two im portant aspects: enormous computational power and massive data management. Vector computers are being used in petroleum engineering to simulate the flow of oil and gas in a reservoir, the faster performance of the vector machines mak ing many, heretofore, unmanageable calculations possible. In ex ploration for oil and gas, supercomputers are being used to store, classify, and interpret huge amounts of geophysical seismic data.
Linear systems revisited
Authors: Conley William
Published: March 2007

An elegant and well-developed theory exists for solving systems of linear equations. It has been applied successfully for decades in industrial and scientific applications and it forms the basis for linear programming. However many systems of linear equations for industrial applications may require all of the variables to be nonnegative or in an even more restricted area, and/or to be whole numbers. These conditions can create difficulties for the standard approach. So presented here is a new absolute value transformation and a multi-stage Monte Carlo simulation solu tion technique for dealing with the nonnegativity solution re quirement and other conditions. The new approach has the ad ditional advantage of working on nonlinear problems. The system of equations is transformed into a statistic (where the minimum of the statistic is the solution of the system). Then solving the system of equations becomes a problem of finding a way across the sampling distribution to the minimum, which will solve the system of equations.

Regular Monte Carlo simulation to solve a system or optimiza tion problem suffers from only being able to roughly approx imate the answer. Multi-stage Monte Carlo simulation overcomes this obstacle by using a more sophisticated sampling scheme and additionally exploiting the well-behaved nature of the sampling distributions of transformed systems of equations.
DATATRAN: A data base management and executive program for use by the nuclear industry
Authors: Bailey Patrick G. , Kopp Harold J. , Cordes Gail
Published: March 2007

A BSTRACT The DATATRAN data base and executive program is currently under development by the Electric Power Research Institute (EPRI) for use and application by the nuclear utility industry. Since 1966, the computer code system has been under develop ment and has been extensively used by the Naval Reactors Pro gram. DATATRAN is being developed for use in a large number of general applications, including: (1) storage of experimental and plant transient data in hierarchical data set form, (2) auto matically linking data sets between computer codes, and (3) act ing as a program executive in executing series of computer codes while maintaining organization of the data between all of the codes. Various potential uses of the DATATRAN system, specific applications, and future research and development plans are reviewed in this paper.
Simulation of an Ethernet interface using micro PASSIM
Authors: Vayda Thomas P. , Wear Larry L.
Published: March 2007

Micro PASSIM, a GPSS-based simulation system, was transported from the Apple II to the HP 9836; this paper discusses the prob lems associated with moving a large program from one UCSD Pascal system to another. Micro PASSIM was transported to the HP system so that an Ethernet to HPIB interface board could be modeled. The model is described and the results obtained from the simulation are discussed. Discussion on the advantages and disadvantages of using micro PASSIM rather than a standard language, such as GPSS, is also included.
On the specification of diverse models in APL
Authors: Cundiff W.E.
Published: March 2007

APL (A Programming Language), developed by Dr. Kenneth Iverson of Harvard in the 1960s, has not been a computer language often associated with the mainstream of the simulation community. An interpreted language with its own symbol set, APL was normally passed over in favor of specialised simulation languages or compiler-based general-purpose programming languages. Four contrasting approaches to modelling and their embodiment in APL are presented, with emphasis on APLs versatility and capacity to specify complex models very concisely and quickly. High-performance interpreters, 16/32 bit microprocessors, dedicated APL engines and parallel processor architecture combine to make APL a more sensible choice for simulation in the 1980s.
A simulation model for bed allocation to hospital inpatient departments
Authors: Vassilacopoulos G.
Published: March 2007

A general simulation model can be used to determine the bed complement in hospital inpatient departments to meet a pre determined demand for service. Certain operational constraints were considered in this version of our model: (1) emergency pa tients should be admitted without delay, (2) occupancy should not fall below a prespecified level, and (3) the waiting list length should not exceed a predetermined number. Extensions and modifications of the model are briefly discussed. Three case studies on the general medical, general surgical and orthopaedics departments at St. Peter's Hospital, Chertsey, Surrey (England), illustrate how this model may be utilised.
A discrete simulation model of electrocardiograms
Authors: Malík Marek , Cochrane Thomas
Published: March 2007

A discrete simulation model reproducing electropotential changes within the heart and imitating the generation of the ECG signal has been developed using the SIMULA** language. Used for computational experiments, the current version is writ ten in FORTRAN IV because of lower memory demands and for installation on a desk-top computer. However, the FORTRAN version saves all important SIMULA methodology and enables different pathological situations of the cardiac conduction system to be modeled in a comparatively easy way. The present ver sion of the model is especially suited for projects studying car diac rhythm and its disorders. A large set of such experiments has been performed. This paper concisely describes the simulated system with special attention devoted to a description of the model principles and program results. Comparison is made be tween existing models of electrocardiogram generation, and some experimental results are shown. External validation of the model and advantages that have been obtained by transmitting the SIMULA model into FORTRAN are also discussed.
Project engineering and management for procurement of nuclear training simulators
Authors: Chou Q.B. , Payne C.A.J. , Davis R.M. , Acchione P.N.
Published: March 2007

A comprehensive project engineering and management system has been developed and used by Ontario Hydro for the acquisi tion of nuclear generating station training simulators. This system was instrumental in the successful completion, on schedule and within budget, of the Bruce A and Pickering B Training Simulators and is presently being implemented on two other simulator projects.

The developed engineering and management system includes some unique features such as a two-phased project, a project "core group" which actively monitors and controls the work, and joint buyer/vendor work procedures.

Application of the project management system throughout the full simulator project cycle is described.
The probability distribution as a performance criterion when comparing alternative systems
Authors: Friedman Linda Weiser , Friedman Hershey H.
Published: March 2007

The Kolmogorov-Smirnov test is used to determine whether the output distributions of two simulated systems are significantly different. The advantages of using this statistical procedure, and the danger in making comparisons between the systems with only the mean as a critical performance measure, are dem onstrated.

Two queuing systems were simulated and results analyzed first by comparing means and, then, distributions. Results showed that, even if the means of two alternative systems are equivalent, the systems may still prove to be significantly different from each other if the entire distribution is examined.
Simulation of flexible manufacturing systems
Authors: Cheng T.C.E.
Published: March 2007

In this note we first discuss the role of computer simulation in flexible manufacturing systems (FMS) design. In using computer simulation to evaluate alternative FMS performance, we find it useful to distinguish two levels of system definition, namely: macro- and micro-level for gross and detailed simulation results, respectively. Finally, we report on the development of a microcomputer-based simulator aimed at providing industrial designers with a rapid and cost-effective aid for FMS design and appraisal.
The impact of advanced information processing on simulation — An illustrative review
Authors: Kerckhoffs E.J.H. , Vansteenkiste G.C.
Published: March 2007

Advanced Information Processing (AIP) techniques are felt to play an important role in next generation simulation tools. Here we will review and illustrate the incorporation of two such AIP techniques in modelling and simulation. Simulation-oriented information-base management systems are considered to auto matize one of the major activities, peripheral to large-scale modelling and model implementation : the management of the descriptive and quantitative data involved. On the other hand, attention is paid to the impact of artificial intelligence techniques in modelling and simulation. Knowledge-based simulation, Al supported model synthesis and some additional topics with respect to integrating Al and the system analysis approach are briefly reviewed.

Some concepts are illustrated on the basis of research activities in the Benelux countries.
Expert systems for industrial applications — Part 2
Authors: Foster Warren
Published: March 2007

"Applications of artificial intelligence" was featured on page 306 in the June 1985 SIMULATION. A section titled, "Expert systems for industrial applications, by Warren Foster, looked at the basic perspective of artificial intelligence (Al) and how it is used in solving industrial problems. This current article focuses on the evaluation of six expert system shells that are currently available for in dustrial applications.
Hierarchical decomposition and simulation of manufacturing cells using Ada
Authors: Antonelli Charles J. , Volz Richard A. , Mudge Trevor N.
Published: March 2007

A useful tool in the development of flexible automation is a system description language which can generate a complete func tional description of a manufacturing cell of arbitrary complexity. We propose a description system based on the concept of hierar chical decomposition utilizing the Ada programming language in conjunction with established diagrammatical decomposition methods. The distinguishing aspect of our work is that it takes advantage of certain features of Ada (such as type checking) to create a description that can be automatically verified for con sistency Simulation is often an indispensable tool in the develop ment of manufacturing systems. We show how a simulation of the operation of the manufacturing cell can be embedded in its description. Finally, we apply the methodology to a specific instance of a manufacturing cell.
Strategy-related characteristics of discrete-event languages and models
Authors: Hooper James W.
Published: March 2007

In regard to available features, discrete-event simulation languages differ in many respects. There is, however, one aspect of a simula tion language that transcends all others in significance - namely, the strategy (or strategies) employed for "next event" selection. Strategy determines how a modeler must view a system which is to be modeled (i.e., determines the "world view"). The three generally recognized strategies are event scheduling, activity scan ning, and process interaction. Modern simulation languages may include combinations of these strategies.

Analyses of the three strategies have been made, including the development of algorithms for each of the three strategies, and the use of the algorithms for in-depth comparisons of the char acteristics of languages employing each strategy. Models using different strategies have been compared relative to their develop ment characteristics and performance characteristics. Journal and conference Proceedings' articles spanning many years have been reviewed to obtain observations of simulation experts concern ing the impact of strategy on simulation languages and models.

It is hoped that the perspective of strategies afforded by this discussion can lead to better-informed choices and more effec tive use of modeling tools and methods.
A simulation model for analyzing service times in a rotational position sensing disk system
Authors: Herring Bruce E. , Prather Wanda
Published: March 2007

The performance of a computer system is often directly depen dent on the performance of the disk subsystems supporting it. Therefore, we have developed a model to aid in the evaluation of disk subsystem performance, with special emphasis on the rotational position sensing (RPS) feature due to its widespread use.

The model produces I/O service times broken down by device within the disk subsystem, which can be used as a basis for design and placement decisions for critical applications. The model also produces channel and device utilizations and other measures of disk performance.

Data-driven, the model uses data obtained from direct measure ment of the operating system in use. Thus the analyst need not know or make assumptions about the characteristics of the existing devices in the subsystem. Validation is accomplished through direct measurement of an existing system.

In a wide-range of initial applications, the model has proven to be a valuable tool for the analysis of disk subsystems.
The application of small peripheral array processors to the modeling of distributed parameter systems
Authors: Karplus Walter J. , Shibata Yoshitaka
Published: March 2007

In the modeling of distributed parameter systems, it is sometimes necessary to utilize system observations to identify or estimate the boundary conditions of the field. For example, in dealing with water resources systems, it may be desired to identify and characterize sources of water pollution on the basis of measure ments of pollution concentrations downstream from suspected sources. A computational technique based on pattern recogni tion has been found to be relatively effective in this application. However, the algorithms involved are highly computation- intensive and therefore tend to place a considerable burden on most conventional digital computer facilities. Array processors, though primarily designed for signal processing are playing an increasingly important role in the modeling and simulation of physical systems. It is a purpose of this paper to describe the ap plication of a relatively small and inexpensive peripheral array processor to this problem and to evaluate its performance.
Pasion
Authors: Raczynski Stanislaw
Published: March 2007

PASION is a process and event-oriented simulation language designed for those who already know and use Pascal. The lan guage has a two-level (process/event) structure and permits all the Pascal structures. PASION provides all necessary facilities needed to handle sequences of random events, queues, and quasi-parallel processes, both discrete and continuous. A PASION program consists of a sequence of process declara tions. At run-time the program generates objects that represent model processes due to the process declarations. Compared with Simula, PASION is rather simple and offers similar compromise between simplicity and flexibility as does Pascal when compared to Algol.
A network simulation model of a fish processing facility
Authors: Jonatansson Elias , Randhawa Sabah U.
Published: March 2007

Quick-freezing, the single, most important production method in the fish processing industry, involves a number of production workstations. The mathematical analysis of such a system not only involves the process flow but also includes such factors as scheduling priorities, machine failures, and types of inputs and outputs. The resulting mathematical analysis is extremely com plex to conduct and difficult to explain to the production managers.

A network-based simulation model is developed to analyze a fish processing facility, and the quick-freezing process in a typical fish processing plant is described. The network simulation model is then developed using the Simulation Language for Alternative Modeling (SLAM). Among the results from the model are statistics on utilization of machines and workers in the process, size of in-process inventory at different locations in the process, and throughput times. Sensitivity analysis is performed on some of the major factors that can affect the efficiency of the system. A front-end interface to the simulation model is developed which facilitates the user in entering input parameters to the model without the need to learn the simulation language. The model provides a methodology for evaluating alternative production strategies for a fish processing facility, and provides the production manager with a tool to develop short-term production policies.
Simulation and social theory
Authors: Bronson Richard , Jacobsen Chanoch
Published: March 2007

Currently, there are many social theories but none which have been formally tested because, in macrosociology, replication under genuinely comparable conditions has not been possible. A research strategy based on computer simulations is described that gives sociologists a practical quantitative technique for testing social theories and for comparing alternative hypotheses under identical research conditions. The strategy is demonstrated on a social theory of change in normative systems and illustrated with one of the empirical data sets that have been used to test the theory.
Comparison of the CRAY X-MP-4, Fujitsu VP-200, and Hitachi S-810/20
Authors: Dongarra Jack J. , Hinds Alan
Published: March 2007

A set of programs, gathered from major Argonne computer users, was run on the current generation of supercomputers: the CRAY X-MP-4 is a consistently strong performer over a wide range of problems. The Fujitsu and Hitachi computers excel on highly vectorized programs and offer an attractive opportunity to sites with IBM-compatible computers.
A SLAM II simulation study of a simplified flow shop
Authors: Barrett Robert T. , Barman Samir
Published: March 2007

Control of jobs being processed in a flow shop is important to management. Shop performance is affected by shop congestion, processing time variation, and the dispatching rule used to load the jobs. Most previous research has concentrated on the effects of varying these parameters in a job shop setting. A SLAM II net work model and simulation analysis of these parameter varia tions was applied in a two-work center flow shop. Performance of the flow shop was tested using combinations of 5 dispatching rules, 3 shop load levels, and 2 levels of processing time varia tion. Based on a series of performance measures, the shop using the shortest processing time dispatching rule in one work center and the due data based rule in the other compares favorably with the shop that used the shortest processing time rule in both work centers. Results indicate that shop congestion and process ing time variation affect the performance of the flow shop as well. Performances between the flow shop and job shop are com pared, and results indicate that the flow shop performance closely follows the job shop performance under the same dis patching rule at all work centers.
One hundred differential equations execute directly on the IBM PC
Authors: Korn Granino A.
Published: March 2007

Inexpensive personal computers (IBM PC/XT/AT and com patibles) can do very respectable dynamic-system simula tions at remarkable speed, as shown in this brief technical note. The direct-executing ENHANCED DESIRE system solves up to one hundred ordinary differential equations typed and edited on the CRT screen, without noticeable delay for program translation. Monochrome or color graph ics are produced.
The simulation of material handling systems
Authors: Banks Jerry
Published: March 2007

This article describes the simulation of material handling (MH) systems using simulation languages and simulators. We first show how to construct a simulation of a MH system using the standard blocks available in two general purpose simulation languages. When building models in this manner, an accurate emulation of the real system can be accomplished. Modeling can be accomplished more rapidly using built-in MH capabilities provided in several simulators and simulation languages and some of these are described in the article. Lastly, we discuss a simulation package that has the capability to model material han dling systems with great accuracy.
The Surface of Cotton Fibers
Authors: Tripp Verne W. , Moore Anna T. , Rollins Mary L.
Published: March 2007

The topography of unmoditied cotton fibers has been examined microscopically by means of surface replica techniques. The outstanding characteristic of the surface is a system of roughly parallel ridges and grooves spiraling around the fiber at an acute angle (usually 20 30 ) to its axis. The pattern of the surface is a reflection of the spiral fibrillar structure of the cellulose beneath the primary wall of the fiber. The average height and distance between ridges is approximately 0.5 micron. and many of the ridges are 10 or more microns in length.

The surfaces of most native cottons are quite similar, although statistically significant differences in the average distance between ridges were found between certain samples The surface of fibers from unopened bolls is relatively smooth, but assumes the roughness of the typical fiber on drying for the first time. A characteristic surface formation ap peared to be associated with fibers known to have undergone compression. Drastic abrasion largely obliterates the normal appearance of the fiber surface.