bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulating oxygen transport in the microcirculation by Monte Carlo methods
Authors: Halberg Michael R. , Bruley Duane F. , Knisely Melvin H.
Published: March 2008

Oxygen transport in the human cerebral cortex has been simulated previously by considering a single straight capillary and a concentric tissue cylinder as a representa tive sample (the Krogh tissue cylinder). The same geo metric model has been assumed for this study because of its probable accuracy and to allow comparison with previous calculations.

Because of the nonlinear equilibrium relationship be tween dissolved and hemoglobin-bound oxygen (the oxy gen dissociation curve), a differential mass balance yields a nonlinear partial differential equation describing oxy gen transport in the capillary. In the tissue a constant consumption rate is assumed and a linear partial differ ential equation results. The tissue equation and the capillary equation are solved simultaneously, to account for capillary-tissue interaction, thus giving axial and radial oxygen partial pressure profiles for the total system.

The Monte Carlo method has been employed to solve the resulting set of equations on a digital computer. This technique involves a numerical scheme wherein a process is simulated directly by a random walk phenomenon (Markov process). A particular advantage of this method is that solutions may be obtained for one point in space independently of all others. Therefore, an analysis of the transient response of the "lethal corner" is possible with out solving for the entire mesh. Computation time with the Monte Carlo method was considerably less than that with standard deterministic numerical calculation tech niques.

Two models were considered. In the first model the oxygen dissociation curve was linearized, thus giving a linear partial differential equation describing oxygen transport in the capillary. The second model considered the nonlinear nature of the oxygen dissociation curve, and a nonlinear partial differential equation was ob tained. However, because of difficulties with the Monte Carlo method, it was necessary to solve the equations in a quasi-nonlinear manner.

For both the linear and the quasi-nonlinear models, solutions were obtained for the steady state with normal conditions and for dynamic cases. Perturbations of ar terial-oxygen partial pressure and blood flow rate were forced, and the behavior of the system was determined. The pure diffusional model checked with previous de terministic calculations demonstrating very rapid re sponse with time constants in the order of 2 seconds. However, the shapes of the intracapillary and tissue oxy gen tension profiles differed somewhat and no allow ances were made for autoregulatory phenomena such as varying flow rates.
Mass transfer in droplets determined by analog computation
Authors: Wellek R.M. , Kuo J.T. , Waggoner R.C.
Published: March 2008

A mechanism describing the rate of mass transfer to single droplets with a special type of internal circulation is described by a model consisting of a partial differential equation with two independent variables. A Sturm-Liouville system is obtained when the partial differential equation is transformed into a set of ordinary differential equations by the separation-of-variables technique. The eigenvalues and eigenfunctions which determine the solution to this system are obtained by a two variable search procedure on an iterative-analog computer.
The simulation of shot processes
Authors: Daly K.C. , Thomas J.B.
Published: March 2008

Shot processes may be used as models for a wide class of naturally occurring random processes ranging from non-Gaussian impulse processes to nearly Gaussian processes. This paper shows how shot processes with desired spectral properties may be simulated easily. Sev eral models are proposed for using shot processes as locally generated noise sources with statistical charac teristics which conform to many naturally occurring noise processes.

More general models could be considered and the range of applicability can be extended beyond that men tioned in this paper. However, even the basic models treated can provide a much wider range of noise envi ronment than that usually considered in simulation tech niques.
The inverse modeling problem
Authors: Patten Bernard C.
Published: March 2008

In simulation modeling of very large-scale systems, such as social and natural systems, reductions in scale must be so severe that state variables of the abstraction (model) often cannot be translated back to variables that have real-world significance. Model behavior may not much resemble anything that occurs naturally.

If y is a real system and x a model of it, the two can be viewed as related by a set of homomorphic corres pondences M. Then, xMy means x "is a model of" y. Behavior of x pertains to that of y only as M is a valid model, and the relationship is implicit in an inverse model M-1, defined from the fact that xMy implies yM-1x (y "is modeled by" x). To make it explicit, that is to interpret model behavior in terms of real-world variables, means in some sense to be able to identify M-1. One approach to estimating it is suggested, but a definite solution is not reached.
A method for eliminating hidden lines with polyhedra
Authors: McGrath F.J.
Published: March 2008

A method is given to eliminate hidden lines from line drawings of volumes whose surfaces are a union of polygons. Projected polygons are tested pair- wise for overlap by looking for lines with the property that all vertices of one polygon lie on one side of the line and all vertices of the other pdygon lie on the opposite side. When a pair is found to overlap, hidden line endpoints are found by searching a table that was constructed in the test for overlap. Some results of a program written to demonstrate the method are given.
Generalized algorithm for the simulation of unsteady fluid flow in mechanical systems
Authors: Wright E.J.
Published: March 2008

In this article an algorithm is developed to solve the equations for one-dimensional unsteady flow of compressible fluids in the presence of area change, wall friction, heat transfer, and entropy gradients. The algorithm is based on a rectangular mesh solution of the cor responding characteristics equations in the space-time plane. It is arranged in a generalized form to permit convenient application to a variety of engineering systems. A model of the gas exchange process occurring in a two-stroke internal combustion engine with intake and exhaust ducts is used to demonstrate application of the algorithm and to observe the accuracy and stability of solutions with varying mesh-step size.
A solid-state crossbar switch for automatic analog-computer patching by
Authors: Yagi A.
Published: March 2008

An all-electronic crossbar switch consisting of FET series-shunt switches inside the feedback loops of operational amplifiers was designed and constructed. Time-shared solution of five different differential equations was obtained by using four integrators on ASTRAC II, with a new solution being generated 25C times per second.

Crossbar switches for automatic patching

Studies of practical automatic patching schemes for electronic analog computers indicate that it will be economical to employ sets of relatively simple crossbar switches somewhat in the manner of tele phone exchanges. This report describes the con struction and test of a small all-solid-state cross bar switch which permits very fast switching for analog-computer time-sharing, is suitable for integrated-circuit construction, and should be much more reliable than the relay instrumentation sug gested in Reference 1.

The feedback multiplexer

The new crossbar switch is based on the feedback
Simulation—language—generated static checks for hybrid and analog simulations
Authors: Bohn Paul F.
Published: March 2008

Every simulation requires a good static check to be performed to insure that,initially, the equations being simulated match those of the analysis and, subsequently, to be sure that the analog computer's patchboards remain free from wiring errors. Custom arily the static check is prepared by hand using a desk calculator, since the time required for pro gramming a "one-shot" digital program is typically not a good investment. However, by utilizing the capabilities of a suitable simulation language (such as CSMP or DSL/91), digital static checks can be made economically in less time than that required for a hand-calculated check, especially in the case of hybrid computations. Also, with a little ingenuity, the efficiency of hybrid simulation can be greatly increased by combining the static-check calculation and automatic analog setup via the simulation-language static check. (Familiarity with analog programming and the use of simulation languages is assumed.)
Practical considerations in the application of HSU and Howe's method for solving partial differential equations
Authors: Anderson Thomas C.
Published: March 2008

At the 1968 FJCC Hsu and Howe presented an itera tive hybrid method for solving partial differential equations. The method allows the solution of prob lems requiring a large number of nodes in its representation through time-sharing the analog com ponents. The initial attempt to utilize this method showed that the accuracy of the solutions was extremely sensitive to the program parameters. This sensitivity was reduced to acceptable levels through the use of dynamic scaling and incremental equation formulations. The resulting implementa tion has been found to yield solutions of suitable stability and accuracy for practical applications.
Analog simulation of particle trajectories in a cyclone separator
Authors: Cheng Shang-I. , Teller Aaron J.
Published: March 2008

The trajectories of liquid droplets and dust parti cles in a wet cyclonic scrubber were studied via mathematical modeling on TR-20 analog computers. This simulation study was restricted (1) to two- dimensional flow and (2) by the assumption of Stokes' Law behavior.

The penetration of spray droplets into the gas flow field and the time of effective contact with the gas field at high relative velocities were found to be critically dependent on the diameter of the spray droplet and on the angle of injection, in addition to the anticipated dependency on gas flow rate and on projection velocity of the spray particle.

It was found that for small particles (<50μ) the drag forces were so high relative to the initial forces that only insignificant penetration of the vapor body occurred, even at a projection velocity of 200 feet per second.

At an average rotational air velocity of 50 fps a maximum probability of effective interception and impaction of spray and entrained particles occurred in the region of a spray angle of 30° to the tangent.
Modelin and analysis of nonideal polyphase diode converters
Authors: Smith Michael J.
Published: March 2008

The mathematical model of the diode proposed in this investigation for the analysis of nonideal poly phase converters has finite forward and reverse resistances. Since current-dependent diode impedances exist at all times, only one set of piecewise-linear time-invariant state-variable equations is required to describe the nonideal polyphase diode converter completely. A digital computer solution of the state- variable equations was obtained to verify the inte grity and tractability of this method of analysis.
A GASP simulation study of job-shop scheduling
Authors: Ashour Said , Vaswani S.D.
Published: March 2008

The purpose of this paper is to report on a study which involves a simulation of a hypothetical job shop with several machines. The investigation employs GASP-II as a computer language. This simulation study is concerned with: (1) testing a new method of assign ing job due-dates and (2) comparing and evaluating the effect of different processing-time distributions on the performance of a number of scheduling rules.

The most significant results of this study are:

(1) The shortest-imminent-operation rule is superior to others in reducing job lateness and shop flow time (2) The procedure in which the due-date allowance is proportional to the number of operations and work

content of the jobs has proved to be beneficial in the case of the non-due-date rules (3) The operation of a job shop using the shortest-imminent-operation and slack-per-remaining-number-of-operations rules is degraded when the processing-time distribution having Erlang parameter K equal to 4 or 8. However, per formance is better when K = 8 than when K = 4 (4) The GASP-II package works efficiently for large-size shop problems.
Automated programming of analog hybrid computers
Authors: Franklin M.A. , Strauss J.C.
Published: March 2008

The motivation for automated programming, setup and checking facilities for analog/hybrid computers is discussed and the problems involved are classified. The problem of providing better offline and online program preparation and debugging facilities for analog and hybrid computation is selected for fur ther development. Following a brief characteriza tion of the problem, the available literature is reviewed in depth. Suggestions for future work in this area are included where appropriate.
Minicomputer as a circuit-design tool
Authors: Fazarinc Zvonko
Published: March 2008

Lack of interactive capabilities and high processing cost are two main areas of complaints directed against the existing implementations of computer- aided-design packages. The minicomputer promises to remove these serious deficiencies despite its speed and storage limitations. The economics and techniques of interactive minicomputer applications are explored and an integration formula suitable for minicomputer implementation is devised. Several nonlinear networks simulated on a minicomputer are used to demonstrate the long-term stability of the formula.
A comparative study of digital and hybrid simulation of production lines
Authors: Khalil T.M. , Valisalo P.E.
Published: March 2008

This paper describes the application of digital and hybrid simulation to the problem of deliberate unba lancing of production lines to obtain shorter produc tion times.

The paper demonstrates that hybrid simulation tech niques adequately match the accuracy of digital simulation of the same system.

The hybrid provided more flexibility with a reduction in cost.
Digital/analog simulation of electromechanical devices on a graphics terminal
Authors: Sharma Satya P. , Roe C.D.
Published: March 2008

Computer simulation of electromechanical devices by exercising a suitable mathematical model has advantages in studying the effects of parameter changes. As a specific example, an electromechan ical relay has been chosen for simulation in this investigation. A differential equation model of the relay 1 is developed and simulated on an IBM 1130/2250 graphics terminal using the 1130 Continuous System Modeling Program (CSMP).

An optical displacement measuring system was used to measure the armature travel as a function of time while the relay was functioning. These mea sured characteristics were compared with the analogous characteristics of the simulated relay to evaluate the validity and accuracy of the mathematical model. It is concluded that the differential equation model is an adequate appro ximation provided the lumped parameters of the magnetic circuit are appropriately chosen. The influence on the dynamic response of the relay as various relay parameters are changed can easily be predicted from the simulated model in this study.
Multiple-terminal hybrid graphics for control-system analysis
Authors: Stanbery S.R. , Hoberock L.L. , Thompson J.G.
Published: March 2008

Hybrid computation can be extremely efficient, not only in solving certain dynamics and control-system problems, but also in the graphical presentation and analysis of results. Analysis routines, simu lation, and animation can be interactively graphed in a time-shared mode using analog generated dis play with storage-type terminal screens. Many types of control problems amenable to graphical analysis and solution display may not require the large memory and sophistication of all-digital graphics. Hybrid-analog graphics provide an effi cient alternative, as demonstrated with two examples using root-locus and Nyquist diagram analyses. By employing the digital computer on an intermittent basis for calculation of root-locus and Nyquist data, efficient use is made of the analog in solving differential equations describing the system and in generating displays. Parallel effort between the two computers minimizes the total computational time required. Programming of analog logic allows a number of users of terminals to simultaneously select analysis, simulation, or animation options; to set parameter values, initial conditions, and display options; and to change problem configurations. This allows each user interactive graphics for system analysis on a fast, time-shared basis.
An ISL-8 and ISL-15 study of the physiological simulation benchmark experiment
Authors: Benham R.D.
Published: March 2008

PHYSBE is an acroynm for PHYsiological Simulation Benchmark Experiment, and was introduced1 as a suggested standard for evaluating tools and tech niques available for physiological simulation. The mathematical model relates pressure, volume, flow, and resistance in a simplified cardiovascular system.

PHYSBE is an excellent benchmark problem because it is not easy to obtain accurate results with an all-analog or all-digital simulation. The large differences in time-dependent constants (1.63 to 90.0) allow a good check of digital integration routines. Roundoff accumulation errors can be devastating to digital solutions. On the other hand the compliance generators (the driving func tions) are difficult to program with general- purpose diode function generators found on analog computers.

Previous PHYSBE articles2,3,4 have discussed the amount of time it has taken to program with FORTRAN (on a CDC 3600 computer), MIMIC and DSL/90 (on an IBM 7090 computer), CSMP (on an IBM 1130 computer), and DARE I (on a PDP-9 computer). Very little attention has been focused on solution accuracy.

Examination of published results for the all digital simulations of PHYSBE show serious accuracy problems. There appears to be a 5% to 10% difference in pressure and volume values that are published. There is good reason for the FORTRAN, MIMIC, and DSL/90 results to agree, but they do not. Also one would expect the CSMP and DARE I results to agree, but they do not.

This ISL-8 simulation shows that good agreement was obtained with an IBM 1130 CSMP solution after an error was corrected in the CSMP program. Detailed accuracy comparisons with the other solu tions are complicated because not all of the same variables are reported in the same manner. There fore the documentation format suggested by McLeod2 is used here so that ISL-8 and CSMP solutions can be compared with future work with PHYSBE.
Hybrid generation of smooth functions by spline interpolation
Authors: Kharkar Anil N. , Coulman George A.
Published: March 2008

The use of sparse data in hybrid computer simula tion has been provided with a formal procedure for generating smooth approximation functions with excellent reproduction quality. The method is use ful with data records over the independent variable or where a variable diode function generator might be used. The method depends on the theory of spline functions, which provides the specified quality of "smoothness" of the reconstructed function. An analog polynomial circuit receives parameters sequentially from the digital to generate the function. Besides illustrating an efficient method for hybrid function generation, the subject of spline approximation has been introduced to simulators in a simple language.
An optimal design of a soaking-pit rolling-mill system
Authors: Ashour Said , Bindingnavle S.G.
Published: March 2008

While attention in the iron and steel industry has been focused on the study and analysis of the flow of materials through the main productive units (blast furnaces, steel works, and rolling mills), the analysis of this flow through the nonproductive units (the mixer and soaking pits) is generally over looked. These two units would create serious bottle necks in production if their capacities were not properly determined before being installed. This paper considers the soaking-pit/rolling-mill complex as a queueing system in which the soaking pits are viewed as units circulating a cyclic queue, and the rolling mill as the service station. A simulation model representing the pit-mill system is developed:

(1) To predict the improvement in the capacity of the system through adding more pits

(2) To predict the effect of breakdowns and mainte nance or the shutdown of a pit.

Several criteria, including their economic aspects, are used to measure the performance of the system. The optimal capacity of the system is determined such that an economic balance between the cost of service and the cost of waiting for that service is achieved.
Application of Computer Simulation To Research in the Life Sciences
Authors: Garfinkel David , McLeod John , Pring Martin , DiToro Dominic
Published: March 2008

The paper summarizes guidelines for applying computer simulation to life sciences research. It provides brief answers to the following questions:

To what extent can problems be rigorously solved by simu lation—especially complicated problems—and how is this to be done?

What can a given simulation study be expected to accomplish, and when can it be considered complete?

Of what value are the properties of a model in understanding the living system under study?

What should be the proper interaction between simulationists and subject-matter experts in a collaboration?

What constitutes ethical conduct for a simulationist?

To what extent should the same person do both experiments and simu lation?

How should simulationists be trained?
A comparison of numerical methods for solving large sets of simultaneous equations
Authors: Pitts Gerald N. , Crawford Paul B.
Published: March 2008

Many engineering problems require the numerical solution of several hundred to a few thousand simultaneous equations of the Laplace, Poisson, or Fourier types. These equations occur in the solution of many sci entific problems on heat flow, fluid flow, diffusion, and structural problems, etc. There are many methods available for solving these problems; however, there has been little said about core allocations, execu tion times, and programming difficulty of each method. This paper compares five of the best known methods in terms of core allocation, execution times, and program ming difficulty.
A CSMP/360 precompiler for kinetic chemical equations
Authors: Clark R. Lawrence , Groner Gabriel F.
Published: March 2008

CHEMCSMP is a convenient problem-oriented language based on CSMP/360 and is designed specifically to solve problems in kinetic chemical equations. Users' statements, which resemble conventional chemical nota tion, describe slow and fast reactions in multicompartment systems and flows between compartments. CSMP statements may be inter mixed with chemical equations to provide for a variety of computations and convenient output. CHEMCSMP is implemented via a pre compiler which translates the user's pro gram into pure CSMP. The paper describes the use and implementation of CHEMCSMP and provides an illustrative example.
System Simulation and Policy-Making for Economic Development
Authors: Abkin Michael H.
Published: March 2008

The problems of planning for economic develop ment arise from the interplay of the political, social, and economic subsystems of a developing country. These problems are characterized by the uncer tainty necessarily inherent in any process of plan ning for the future — uncertainty arising both from the quantity and quality of available data and from the difficulties of forecasting how a large-scale system of complex interactive and feedback relation ships will respond to policy inputs. In this paper, generalized system simulation is offered as an ap proach to dealing with these problems. It is a flexi ble, iterative, problem-investigating process that includes problem formulation, mathematical modeling, model testing and refinement, and appli cation of the model to solve problems — all in close consultation with decision-makers. As an illus tration, an overview will be given of a policy- oriented system simulation model of the Nigerian economy. The model consists of two detailed re gional agricultural submodels, an aggregated na tional nonagricultural submodel, and components which model Nigeria's population and the inter- regional trade in food. Finally, I shall outline how the generalized system simulation approach could be implemented within the development-planning and policy-making process.
Mass transfer in a packed bed of fibers
Authors: Burley R. , Flower J.R. , Rattee I.D.
Published: March 2008

Commencing with a simple but realistic mathemati cal model of dispersion, absorption, and desorp tion of dye within a cylindrical packed bed of fibers, a finite difference scheme of equations was developed capable of analog solution.

By varying the main kinetic and mass-transfer pa rameters, the dynamic response of the system was determined and preferred changes of operating values were indicated.

We suggest that these methods could be widely ap plied in the study of systems involving mass trans fer and reaction; to determine the individual effect of descriptive physical parameters on a pro cess without recourse to complex mathematical procedures.
The simulation of the neutron diffusion equations over many decades
Authors: Morehouse N.F. , Carter J.C. , Bryant L.T.
Published: March 2008

This paper describes the simulation of a nuclear re actor system using the neutron diffusion equations coupled to the thermodynamic and mechanical equations. In this coupling, representation of the diffusion equation presents considerable difficulty when large power excursions are being simulated. This difficul ty arises from the diverse response times (from 10-8 to 10-1 second) of the coupled equations of the system. In this paper a transformation of the dif fusion equations is developed which permits coupling them to mechanical and thermodynamic equations of much slower response times, thus eliminating the difficulties previously encountered in simulating these coupled sets of equations.

In the transformation, time is the continuous vari able and energy and space are made discrete. The reactor core is divided into concentric cylindrical regions and the energy is divided into bands. The transformtion involves using natural logarithm of the neutron flux in the center region as a refer ence and determining the change in the ratio of the natural logarithm of the neutron fluxes in the other regions to that in the center region as a result of a regional variation in neutron produc tion. The transformation permits a simulation to cover many decades of continuous change in neutron flux. It also gives directly the deviation from the steady-state neutron flux distribution.
Systems analysis applied to a hybrid computer simulation of a missile reentering the atmosphere
Authors: Ricci F.J.
Published: March 2008

This paper presents a tutorial analysis of a hybrid computer model of a missile reentering the atmosphere. An important aspect of the paper is that an example of how to go about analyzing the suitability of a hybrid computer configuration for a particular large- scale simulation is presented from an overall systems point of view. Equations describing a missile (six- degrees of freedom) reentering the atmosphere are given, as is a hybrid computer configuration for solving them. This configuration is then analyzed to establish its suitability for simulation.
Personality traits and success in a general management simulation
Authors: Hodgetts Richard M. , Braskamp Larry
Published: March 2008

Two of the most interesting and challenging questions posed by performance in general management simula tions are: (1) why are some participants successful while others are not, and (2) are there some common characteristics that can be identified through stan dard psychological tests which differentiate success ful and unsuccessful performance? We attempted to answer these questions by testing two classes of seniors in the College of Business at the University of Nebraska-Lincoln. All were scheduled to play the University of Nebraska game TOP MANAGEMENT SIMULATION (TMS).1 This is a general management simulation which requires each team to operate its own company by selling industrial machinery in a finished and in an unfinished goods market. All companies start with identical assets, produce the same product and sell in the same market. The game is of medium complexity requiring ten decisions per period of play in the areas of plant capacity, production, advertising, research and development, pricing, salesmen, distri bution centers, and the financing of operations.
Simulation on large batch and small interactive digital computers
Authors: Franklin Mark A.
Published: March 2008

A simple model for determining the costs of simula tion on two types of simulation systems is developed. One system is the batch-oriented S360/CSMP system operating on an IBM 360/50 computer. The other system is an interactive simulation system operating on a DEC PDP-12 computer. The workload considered includes six problems of varying complexity and is "typical" of those simulation problems encountered in undergraduate and graduate simulation courses. The model indicates that if only a few simulation runs are required, the PDP-12 system is the more cost effective of two systems. The S360/CSMP system, how ever, rapidly becomes more cost effective as the number of simulation runs increases. The factors affecting various cost tradoffs are indicated, and the model is evaluated for a selected set of parameters.
A demographic and economic growth model for Bolivia
Authors: Picardi Anthony C.
Published: March 2008

This paper describes a two-sector population and economic simulation model of Bolivia. Parameters for the population model were arrived at in as rigorous a manner as possible considering the paucity of data. Good agreement with the historical facts was obtained with the population model. The economic model is a more theoretical representation of the dynamic inter actions in a two-sector economy. Sensitivity testing of the model, which has been named BOLIVIA, indicated that average lifetimes and overall growth rates vary considerably in response to public-health and family- planning programs. Unemployment rates, per-capita income, and rural-urban migration rates were found to be sensitive to family planning programs as well as to growth-stimulating economic policies. The response of the model shows the relative weakness of the nega tive feedback loops that restrain population growth, and suggests that family-planning programs and birth- control incentive programs should accompany any pro grams that tend to reduce the death rate.
A nuclear reactor analog simulation for undergraduate nuclear engineering education
Authors: Fenech Henri , Bayne Jay
Published: March 2008

The theory and design of an analog nuclear reactor simulator for undergraduate nuclear engineering edu cation is presented. The simulator mimics the behavior of a 1000-MWe pressurized water reactor and its thermal-to-electrical energy conversion plant. In addition, several model parameters may be hand- selected,allowing for variations in dynamics and power levels and for accidents. Actual simulator results are presented and discussed.
Requirements for interactive simulation systems
Authors: Sohnle R.C. , Tartar J. , Sampson J.R.
Published: March 2008

The evolution of computer hardware and operating systems has made feasible simulation research which benefits from the many advantages of computing in an interactive environment. A general discussion of modelling considerations and the features of discrete simulation systems is followed by a set of basic requirements for interactive simulation languages and monitors. Systems designed for simulation of particular classes of models are briefly contrasted with more general-purpose systems with respect to flexibility, efficiency, and interactive operation. The interactive capability of the language and the communicative function of the monitor emphasize the importance of coordinated design of these elements. To illustrate the principles presented, ceZZ-space modelling and a recently developed interactive ceZZ- space simulation system are discussed.
Discrete-simulation language-users' survey revisited
Authors: Shannon Robert E. , Wyatt Mack W.
Published: March 2008

This paper reanalyzes the results of an earlier survey reported on in SIMULATION. This analysis is based upon an original technique developed for handling opinion survey data where the judges have varying degrees of familiarity with the entities being ranked. The technique utilizes ordinal rankings as opposed to cardinal utilities and is a modification of the Method of Majority Rules. It is bezieved that this presents the results of the original survey in a form more useful and understandable to the reader.
Environmental modeling vs. the "chicken soup" approach: work in progress
Authors: House Peter W.
Published: March 2008

The author wishes to note that the models discussed in this paper are all now under construction. Al though they are all being designed by the Environ mental Studies Division (ESD), there are large num bers of inputs from various other members of the research and policy community. Further, not all of the members of the ESD design team look at the models exactly as the author does. Each member of ESD's teams was chosen because of his unique point of view and the resulting models all represent a meld. Specifically, the SEAS project staff is composed of Martin Brossman, John Gerba, Sam Ratick, and Gene Tyndall; the carrying-capacity team, of Dr. Martin Redding and Robert Livingston; and so forth. Dr. Philip Patterson and I are members of each of these teams. Because the staff is small in number, there is considerable cross-fertilization in each model area. As a result, the points of view in this paper are mine to the extent that team members disagree, and are all of ours when all do agree. The reader is asked to forgive the nonrigorous and informal presentation of the models in this paper. More detailed documentation presented in a more for mal style can be obtained by writing to the author.
Simulation of speech by time-ordered wave function sets
Authors: Carey Bernard J.
Published: March 2008

A simulation of human speech is normally performed to represent the acoustic signal in a form from which meaningful features of interest in the time and frequency domains may be identified and used in attempting to solve research and applications prob- Zems. Frequency-domain simulations related to vocal tract modeling have been the most popular techniques used to date. However, approaches have been investi gated which, for the limited case of voiced sounds, simulate human speech in the time domain by time- ordered time-based wavefunction sets.

This paper discusses the use of a new technique for an accurate, complete simulation of any human speech by the family of Hanning Cosine Modulated (HCM) wavefunctions.

The previous research on wavefunction simulations of speech are first discussed and then, through illus trative examples, it is demonstrated that HCM wave functions may accurately simulate the behavior of speech in either the time or frequency domain.

The actual parameters of the wavefunctions which re present filtered speech may be measured by an auto matic digital signal analysis technique. These parameters then form a data base which, in conjunc tion with the HCM model, provide a closed-form solution in the time or frequency domain for analyzing and synthesizing speech, and they permit a convenient determination of a wide variety of speech features of interest.
The daughter of Celia, the French flag, and the firing squad
Authors: Herman G.T. , Liu W.H.
Published: March 2008

In earlier work we have reported on CELIA, a program for simulating the behavior of linear iterative arrays of cells. The action of a cell is influenced by both its neighbors. Our main application area was biology, where the program can be used to test hypotheses about the developmental rules for organisms.

More recently we have been applying our program to test proposed solutions to some fairly complicated biozogically-based problems. We have investigated whether one can achieve regulative global polarity in organisms without polarity in individual cells, by solving the French flag problem of Wolpert, using only symmetric elements. In our attempted simulation of pigmentation patterns on the shells of sea-snails, we have found it necessary to find a solution to a generalized version of the firing squad synchronization problem, in which the firing squad is growing while it is trying to synchronize itself.

We found that our original program CELIA was some what awkward for simulating such complicated situa tions. A new program has been devised in which the state of the individual ceZZs is described by a set of attributes and each attribute itself may be a list structure.

The present paper reports on these changes and ex plains how they turn out to be useful in the appli cations mentioned above.
Identification and simulation of antenna dynamics
Authors: Kennedy James C. , Cook Gary J.
Published: March 2008

The application of operational analog computers to simulate the dynamic behavior of an antenna is dis cussed. The structural model used is developed from modal as well as nodal equations. The model repre senting motor and control systems is derived from typical drive and control-system equations. The simulation is deliberately more detailed than neces sary in order to establish the effects of parameters that usually are neglected as higher-order effects. The validity of the simulation is achieved by com paring computer results with experimental results. The difficulties encountered in calculating adequate input data and correlating analytical and experimental results are noted.
Simulation of a chemical reaction process using GASP IV
Authors: Hurst Nicholas R. , Pritsker A. Alan B.
Published: March 2008

This paper is a sequel to the preceding paper de scribing the GASP IV language. In this paper, the simulation of a chemical reaction process is used as a vehicle for illustrating the procedures for using GASP IV. The details of the computer coding as well as samples of computer output are included. The in tent of the paper is to illustrate the use of GASP IV to analyze a system involving both continuous varia bles and discrete events.
Simulation and the Planning of Drug-User Services
Authors: Schlenger William E.
Published: March 2008

Public attention has recently been focused on the use and abuse of drugs in America. Community re sponses to the "drug problem" have often been haphazard and poorly planned. This paper proposes a systems framework for studying the provision of services to drug users. The phenomenon of pro viding services to drug users is conceived of as a flow system with four major structural components: (1) the drug-user population, (2) the nonuser popu lation, (3) the service component, and (4) the legal component. A computer model based on this conceptualization is described. The model is used in simulations of four typical strategies for dealing with the drug problem. The relative costs of the strategies and their effects on the size of the drug-user popula tion are discussed.
The construction of a robot investor
Authors: Krolak Patrick D. , Lindahl C.E. , Herndon J.M.
Published: March 2008

The ROBOT INVESTOR is an integrated system of computer heuristics based in part on human experience and port folio management theory. It is designed to receive information about the state of the current stock mar ket and the investor's existing portfolio and to translate this information into actions that will provide a reasonable and stable rate of return. This paper is the next logical step in the process. The robot forecasts the future price behavior of, and estimates risks of, individual stocks. This informa tion is passed to a decision model, which is designed to meet the dynamic real-world problem of continuous portfolio management. The Robot Investor includes a forecaster, a decision model, an accounting section, and an adaptive control section.

The robot has been tested on a randomly selected list chosen from 740 major corporations traded on the New York and American Stock Exchanges and over the counter, using the monthly prices from January 1960 to December 1967. The results are competitive with those of mutual funds over the same period. An advanced model based on this study has significantly improved the performance of an investment club.
Dynamics in a Salmon Culture Pond
Authors: Powers Joseph E.
Published: March 2008

This simulation study of a salmon culture pond at Arcata, California investigated the dynamic interrelationships within the ecosystem of fingerling coho salmon, a small crustacean (an amphipod) that served as the salmon's principal food, the amphipod's food, and the tem perature and salinity of the water in the pond. The simu lations showed that the optimum salinity for maximum growth was 23.5 parts per thousand, and that deviation from this optimum decreases the growth rate of amphipods, which means that more of them are eaten by the fish, because the amphipods are of edible size for a longer time. Competition among the amphipods was great when the density of their food was low. The simulations developed an understanding of the mechanisms at work in the pond ecosystem and resulted in information on which to base suggestions for improved strategies for managing the pond.
Numerical transient-state solutions of queueing systems
Authors: Ashour Said , Jha R.D.
Published: March 2008

When queueing systems can be modeled in the form of a system of simultaneous first-order difference- differential equations and when the transient-state of such a system is likely to defy analysis, it may be wiser, less expensive, less troublesome, and faster to use some numerical method. The outstanding advantage of numerical methods is that it is rela tively easy to estimate the error (due to truncation of higher-order terms) in the results. The argument for seeking a numerical analysis method for solving a wide class of these models has a strong practical appeal. This paper explores the transient solutions to nonhomogeneous Markov processes (those in which the parameters vary with time), using Runge-Kutta and Hamming methods. For illustration, a simple but rather instructive, single queueing model is solved manually. The solutions obtained by these methods are compared with the corresponding analytical solu tions. Several commonly-used queueing models are solved to demonstrate the wide potential applicabil ity of the numerical methods.
Debugging aids for hybrid- computer programmers
Authors: Lew Art
Published: March 2008

We discuss here proposals for two new debugging aids for hybrid-computer programmers. For digital programs, "relevant" post-mortem dumps have long been advocated .1 We propose extending this philoso phy to analog dumps. We describe means of making selective dumps via analysis of the topological structure of analog programs. We also propose a novel analog static-check procedure which takes advantage of the greater computational facilities afforded by a digital computer to solve algebraic equations.

The analog-dump and static-check methods recommended here, at worst, help hybrid programmers with their debugging efforts by automating certain common tac tics. Many errors can thereby be automatically detected and precisely located. In conclusion, we suggest how correction of these errors can be auto mated to some extent.
An algebraic method for simulating legal systems
Authors: Sain Michael K. , Henry Eugene W. , Uhran John J.
Published: March 2008

A primarily algebraic technique for simulating social systems has been developed for combined use by engineers and lawyers and has been applied exten sively to studies of felony processing times in the criminal justice system of two counties in the State of Indiana. As a method of non-Monte-Carlo simulation, the present approach overcomes tradi tional impediments such as determination of loops and multiple-function concatenation. preliminary evidence suggests that the simulator has useful capabilities in initial screening of data and in early qualitative studies of systems in which a priori data is not plentiful .
Some time-saving methods for the digital simulation of highway vehicles
Authors: Bernard James E.
Published: March 2008

Simulation has been used extensively as a tool for the solution of vehicle-dynamics problems. To handle nonlinear simulations of increasing size and complexity, both digital and hybrid methods have been used. As might be expected, purely digital simulation often proves to be more convenient, while hybrid proves to be more economical.

Methods have been developed to provide substantial economies in the digital simulations. Savings by roughly a factor of five may be realized by trans forming the wheel-spin integrations into a solvable set of algebraic equations and by making use of some well-known mechanical characteristics of vehicles to simplify the integration procedure.
A work game for social services
Authors: Algie Jimmy , Hall Anthony S.
Published: March 2008

This paper describes a work game which the authors developed for the National Institute of Social Work (Training), Britain's professional social work train ing institution. Though intended primarily as a training and decision-making device for use by So cial Service managers, it is capable of modification for various planning groups, for example, a British LocaZ Government management group or an American in ter-agency welfare planning committee. It is parti cularly relevant in situations where diverse services are integrated under a new unified structure.

The game focuses on the interplay between rational decision-making and political bargaining which takes place when allocating scarce resources within an integrated social services agency. It comprises a series of rounds, each representing a complete financial year in the life of one such agency. Eight role-players representing key decision- makers negotiate and bargain for policies which they believe the agency should follow. Outcomes of discussions and negotiations are observed by the "God system," four people who represent all aspects of the agency system not otherwise simulated. They make periodic pronouncements as to how agency policy seems to be evolving and how this affects the influence each role-player may exert in subse quent rounds. After several rounds, the experience of the game is discussed in an extensive debriefing session which centres on strategies and tactics employed, the decision-making processes, and the reality reflected in the simulation.
Simulation: From Art To Science for Society
Authors: McLeod John
Published: March 2008

Simulation can be a more effective tool for the study of problems of our times if the practitioners will adopt pro cedures which will make simulation more a science than an art. A big step in that direction would be the develop ment and use of a standard format that would assure ade quate and uniform documentation. Such a format is pro posed, and criticism is solicited.
Real roots of algebraic equations by hybrid computer simulation
Authors: Chinh Nguyen T. , Marin Miguel A.
Published: March 2008

The known methods for solving algebraic equations may be classified in two broad categories: 1) those using numerical techniques and hence a digital com puter, and 2) those using simulation techniques which may be implemented on an analog or hybrid computer.