bluuebunny/crossref_metadata_2025 huggingface dataset:
Air traffic control system—digital simulation facility
Authors: Vander Veer John R. , Bona Louis J.
Published: March 2008

The Federal Aviation Administration, at its National Aviation Facilities Experimental Center, has recent ly completed a new air traffic control system Digital Simulation Facility. The facility allows for improved real-time systems simulation and is currently being used to support two important pro jects aimed at improving control and safety of air traffic: It is being used to evaluate the inter action between a proposed airborne collision avoidance system and the air traffic control system, and to validate the various levels of automation in the air-terminal automation development program.

The facility was developed for simulating present and proposed air traffic control systems and has twelve digital displays, five used as pilot consoles and seven as controlleer consoles. Each is equip ped with data entry devices for communicating with the computer which controls the simulation.

This article describes the operation of the system, the hardware which comprises it, and the software required to control the equipment, to simulate air craft flights, and to collect and reduce data. Advantages of the new simulation facility over prior ones are discussed, as are plans for its use and expansion.

The new facility provides an environment for con ducting simulations required in developing improved air traffic control systems to meet the needs of our increasing air traffic.
Computer simulation and parameter optimization of phase-locked loops (PLL)
Authors: Ricci Fred
Published: March 2008

The automatic control and simulation of phased- locked loops (PLL) is treated with particular em phasis on the use of analog and digital computer simulation techniques. The object is to obtain an adequate mathematical model for the PLL and then to use this model to optimize parameters and investi gate pull-in performance. Results are presented for the second-order loop, with ramp, step, random noise, and sinusoidal inputs.

The significant result is that an optimization of the PLL loop parameters is obtained using computer techniques.
Simulating the Viatron 2140/2150 on the IBM 360
Authors: Mallach Efrem G.
Published: March 2008

This paper describes the process ofdeveloping an instruction-level simula tion of a digital computer for program checkout, with particular reference to a simulation of the Viatron 2140/2150 minicomputers on the IBM 360. The architecture of these computers is described. Design decisions to be made in simulator development are then covered, including programming language, data representation, approach to timing, and debugging facil ities. A method ofreducing the size of the simulator by "paging" the simu lated memory into and out of the host computer's core memory is discussed. Results of operational use of the simulator are given. Through out, emphasis is placed on those factors which tend to differentiate the simulation of a minicomputer from the simulation of a commercial data- processing computer.
A simulation model for the rent-or-buy decision
Authors: Krolak Patrick D. , Melton James D.
Published: March 2008

The decision to rent or buy a home is probably the most important in family finance. Yet the analysis of this problem in the literature has been superfi cial and subject to many criticisms. This paper will develop a complete simulation model to investigate this decision and to look at many related questions such as the type of loan best suited to the family's financial policies, the price range that a given family can afford, and the type of other investments consistent with this decision.

The model simulates the family income, expenses, and investment portfolio on a monthly basis over the planning period. The results are compared to a deterministic analysis based on a capital budgeting model of the family. Finally, a case study based on data obtained from a real family will be present ed. Further use of the simulation model to study many other capital budgeting problems associated with family finance will also be discussed.
An analogue computer model for the insulin response to glucose infusion
Authors: Cerasi Erol , Andersson Bertil
Published: March 2008

An analogue computer model has been constructed for the analysis of the interrelationship between blood glucose and plasma insulin concentrations during glucose infusion. The model presented gives quantitative information on the effect of plasma insulin on glucose uptake, the total amount of glucose taken up by the tissues at a given time, the effect of blood glucose on the release of stored and newly formed insulin, and the rapidity by which plasma insulin is increased in response to hyperglycaemia.

Such an analogue computer model might be a useful tool in the investigation of the various dynamic factors involved in the glucose- insulin interrelationship.
Interactive simulation terminals to the IBM 360/91 computer
Authors: Bohn P.F.
Published: March 2008

This paper explains the multiprocessing-via-the- terminal approach to interactive simulation taken at the Applied Physics Laboratory. Two systems are discussed: (a) the simulation console (SIMCON) used for all-digital interactive computing, and (b) the 680 hybrid computer used for analog/digital computing. Hardware configura tion, software, operational characteristics, and cost of operation are detailed for these systems, which are operat ing as time-sharing terminals into an IBM 360/91 from a simulation laboratory 800 feet distant from this central processor. (Cable lengths are actually 1000 feet to allow for future movement of equipment within buildings. )
Hybrid Monte Carlo techniques with a minimal interface
Authors: Jermann William H. , Calhoun Malcolm D. , Thomas Richard C.
Published: March 2008

Hybrid Monte Carlo Techniques for the solution of elliptical and parabolic partial differential equa tions have been developed. This paper primarily con cerns the implementation of these techniques with a small, general-purpose digital conputer, a modest analog computer, and a minimal interface.
Analog simulation of a digital three-mode controller
Authors: Clemence C.R.
Published: March 2008

Textbook designs of digital systems are often based on classical responses produced by specific closed- loop transfer functions, and offer little assistance to the "analog" engineer who is required to convert a number of analog loops to digital control while maintaining product specifications. To ensure uni form operation of the plant during the conversion, it is desirable to have as little change as possible in the response of individual loops in order to minimize unexpected side effects.

This paper describes a simulation procedure which enables the engineer to incorporate the familiar analog concepts of proportional, derivative, and integral modes into the digital software and to identify the mode coefficients with corresponding software variables. Thus the digital controller can be tailored to provide mode emphasis similar to that of the analog device being replaced. The whole sys tem, including the digital software, is simulated by analog means and the gain of each mode is adjusted independently until the desired response is obtained.
Dynamic stability analysis of linkages with elastic members via analog simulation
Authors: Seevers J.A. , Yang A.T.
Published: March 2008

Small-amplitude flexural vibration of a slightly deformable binary link in a planar linkage is governed by a fourth-order parabolic partial differential equation. Specifically, for a slider- crank mechanism with an elastic connecting rod, stability charts are obtained via analog simulation on the basis of the principal modal equation of vibration. It is found that stability of the mechanism depends on three nondimensional parameters - length ratio, mass ratio, and rigidity-speed ratio. The procedure of dynamic stability analysis via analog simulation for the slider-crank may be applied to other planar linkages with elastic binary links.
A program for simulating the dispersion of platoons of road traffic
Authors: Seddon Philip A.
Published: March 2008

Digital simulation studies have been carried out on many traffic phenomena because, being stochastic, they are frequently too complex to be represented by a reasonable mathematical model. Furthermore, empirical laws are difficult to obtain because con ditions on the road rarely remain stable for a sufficient time to obtain reliable data. Most simulations have been carried out to determine maximum flows, queue length, delays, etc. in terms of conflicting traffic flow, driver behaviour para meters, etc. A number of examples of this type of simulation are mentioned in the paper. The author's simulation program, however, was written to give information on vehicle behaviour within the platoon dispersion process. Having modelled starting condi tions at the stopline and arrival patterns at points along the road sufficiently well, it was assumed that vehicle behaviour within the process was also being accurately modelled. The queues of vehicles at stopline are of random length with randomly selected vehicle type and random performance para meters. Leading vehicles in each lane accelerate according to an exponential law, and other vehicles are given accelerations according to one or other of the car- following laws. A novel technique allows driver reaction time to be taken into account. Vehicles may turn from the main road and overtake, the simulation program giving data on every vehicle's position, speed, and acceleration at each scan. The paper describes in detail the more important of the steps which make up the whole complex dispersion process and the various measures taken to verify the simulation.
A practical automatic patching system for a time-shared hybrid computer
Authors: Shoup Jerry F. , Adams William S.
Published: March 2008

This paper describes a digitally controlled MOSFET switching array capable of programming a module of 37 analog computer components for a hybrid compu ter system. Using the patching scheme to program the analog portion of a hybrid computer has allowed full time-sharing of the system. A time- sharing monitor has been developed allowing remote access to the system.
The fitting, calibration, and validation of simulation models
Authors: Wigan M. Ramsay
Published: March 2008

The validation of simulation models is not often treated to any great depth in reports on their use. This paper considers the problems involved in the validation and calibration of several classes of simulation models. Particular stress is laid on the checking of the internal consistency of the model against the problem as posed by the model designer. Distinctions are drawn between fitting, calibration, and validation of a model, and some of the implica tions for forecasting using such a model are discuss ed. Systematic errors may be introduced in any of these stages, and it is argued that the estimation of their magnitude is an intrinsic part of the validation process. Distinctions are drawn between validation procedures appropriate to discrete-event and continuous-simulation models, and to dynamic and cross-sectional structures in the systems modelled.
DARE IIIB — a CSSL-type batch-mode simulation language for CDC 6000-series computers
Authors: Trevor Alexander B. , Wait John V.
Published: March 2008

This paper describes a batch-mode FORTRAN-based continuous-system simulation language possessing most of the desirable features specified by the Simulation Council's CSSL committee.

Of course, there are already many continuous-system simulation languages, such as DSL/90 and CSMP (block- oriented), MIMIC, SL-1, CSSL III, etc.; however, to the writers' knowledge, only MIMIC and CSSL III are currently available for CDC-6000 series systems. MIMIC, while equation-oriented, is not as powerful as CSSL III, is somewhat rigid in format, and hard to modify. CSSL III usage involves a surcharge to the program originator, and is thus not attractive for educational applications.

DARE IIIB, locally developed under NSF sponsorship, is a modern CSSL-type language, almost as powerful as CSSL III, that is available to any potential user for the cost of a magnetic tape. DARE IIIB is structured to permit convenient user modification, e.g., it is relatively easy to add new integration rules, run-time strategies, or special library subprograms.

Problem equations are entered in a form close to ordinary mathematical notation; the associated proce dural language is FORTRAN. User-chosen variable names in the problem description are accommodated by a translation phase. Run-time data is entered via standard FORTRAN IV namelist data cards. A variety of output options are provided, including line- printer listings and plots, and CalComp plotter dis plays.

Single- or multiple-run problems may be specified, with storage files used for saving output data for subsequent cross-plotting, reentry into future runs, etc. In addition to an internal collection of library functions, special functions may be specified in FORTRAN, and one-or-two variable table lookup function generation is provided. DARE IIIB provides a choice of several internal fixed- and variable-step integra tion rules; the user can insert his own run-time con trol subroutine for special application.

The system is presently implemented on a CDC 6400 with 65K of core memory (SCOPE 3.2 operating system), and an off-line CalComp plotter. DARE IIIB can accommodate problems with 100 parameters, 200 state variables, and 350 output variables.

This paper describes the major features of the lan guage, and presents basic user information, and several examples.

Inquiries regarding this software package should be addressed to Professor John V. Wait.
FLAP, a simplified simulation system for time-share users
Authors: Elliott Irving B.
Published: March 2008

FLAP, which stands for "FORTRAN-Language Analog Pro gram," is a skeletal simulation program and package of subroutines that can be modified and used for con tinuous system simulation. The FLAP system was created to enable engineers familiar with FORTRAN to write their own simulation programs and to run them in a time-sharing environment; however, FLAP can be run on any small or large computing system having FORTRAN capability. The advantages of FLAP are that it provides a simple algebraic language for continuous system simulation, it can be run on virtually any com puter, and its repertoire of operators can easily be expanded.
Poiseuille flow with variable physical properties — a simulation approach
Authors: Cheng S.C. , Birta L.G. , Kumar A.
Published: March 2008

This paper investigates two computational approaches to the solution of a particular nonequilibrium fluid problem of Poiseuille flow. In the problem formula tion considered, the viscosity μ and the thermal con ductivity k are taken to be functions of temperature. By incorporating certain assumptions, the fundamental partial differential equations describing the phys ical situation can be simplified to a pair of non linear ordinary differential equations. The problem solution, however, is embedded in a two-point boundary value problem whose solution is complicated by an ill-behaved region at one end of the solution trajectory.

Solutions to the problem are obtained using both an analog/hybrid computer and the S/360 CSMP package. The mechanisms provided in both these computational environments for handling logic signals provides the means for coping with the ill-behaved feature inher ent in the solution trajectory. The results obtained in both approaches compare favorably with previously reported results based on the Picard method.

Each of the two approaches has its inherent advan tages and disadvantages in the context of the prob lem considered. With little doubt, the high "inter activity" of the analog/hybrid approach represented its most noteworthy asset, while the relative ease with which the basic problem dynamics could be pro grammed was the most advantageous feature of the CSMP approach. However, the relative difficulty in handling the two-point boundary value problem in the CSMP approach complicated the total programming effort required.
Visual simulation of dynamic three dimensional systems using the vector network
Authors: Savage Gordon J. , Andrews Gordon C.
Published: March 2008

This paper describes briefly a digital simulation program developed at the University of Waterloo, Canada. The program accepts the description of a dynamic three-dimensional mechanical system as input (presently limited to particle masses) and then formulates and integrates the equations of motion of the system. The resulting dynamic response is displayed on a CRT screen for observa tion. The theoretical basis for the program is the vector-network model, a recently-developed formula tion process based on graph theory. The computer graphics subroutines include a novel package for previewing and photographing the dynamic sequences on 16-mm motion-picture film. With some further development, the program could become a useful engineering tool for the design of dynamic mechanical systems.
Simulating transistor and other nonlinear circuits
Authors: Barker J.R.
Published: March 2008

Analog simulations of nonlinear systems involving al gebraic loops or high-gain amplifiers are often unsta ble. Simple stabilizing measures, which are often successful, are suggested, and a method is given for producing alternative flow diagrams in cases of difficulty. The illustrations are of simulations of transistor circuits with exponential functions de scribing the DC junction characteristics and of a varactor circuit with a square-root law for the charge-voltage relationship.
Simulation of a sintering pellet
Authors: Fahidy T.Z. , Wynnyckyj J.R.
Published: March 2008

This paper describes a simulation of the process of sintering an ore pellet placed in a high-temperature furnace. The sintering kinetics is described via a nonlinear ordinary differential equation with an ill- conditioned initial value. The change in temperature with time in the sintering pellet is described via a partial differential equation (conduction equation) which is coupled with the kinetic equation. The nu merical-solution approach is based on the recently developed repeated-extrapolation technique, which has been shown to be significantly faster than standard finite-difference algorithms. The partial differen tial equation is handled by the classical method of orthogonal eigenfunction expansions. The approach is illustrated by treating the sintering of uranium di oxide spherical pellets. The results clearly indi cate that a significant portion of the shrinkage takes place in the initial non-isothermal heating period. Since the conventional analysis of shrinkage data has been restricted to constant temperature conditions, the approach presented in this paper should lead to a more sophisticated treatment of sintering.
Air-pollution forcasting by an adaptive method
Authors: Horie Y. , Fan L.T.
Published: March 2008

The unsteady state of urban air pollution is described by a simple first-order ordinary differential equa tion that is derived from the fundamental equations of fluid-dynamics under the assumptions of homogeneity of source distribution and horizontal concentration distribution. The short-term prediction of a regional average concentration is carried out for a four-day period based on the unsteady-state equation with use of an adaptive prediction method. One- to six-hour predictions of the regional average concen tration are in good agreement with the observed concentrations.
A control system for FORTRAN simulation programming
Authors: Hilborn Ray
Published: March 2008

A system is described that greatly facilitates inter active discrete-time simulation in FORTRAN. The system allows the user to alter and examine the value of any variable during execution. It permits the user to plot any variable as simulation proceeds and to save all variables during simulation. Once a simulation run is complete, the user may go back and look at all previous values of all variables. This system permits the user to restart his simulation at any previous time, with all variables reset to their former values. Many other features are provided to enable novice users to control the simulation with a minimum of external aid. All features are called by simple commands issued during the simulation by the user, or predefined by him in a data file. The features of the system are largely machine-indepen dent and could be easily converted to any time- sharing or batch-processing system. The programming details of the control system are not included, but a general outline of the concepts of its operation are given.
Example of function optimization via hybrid computation
Authors: Volz Richard A.
Published: March 2008

Iterative techniques for function optimization have been considered extensivezy for use in all-digital computation. Relatively little has been done to take advantage of the much higher integration speed of hybrid computation systems. This paper demonstrates application of one simple procedure in a hybrid envi ronment and compares the results to those obtained by an efficient digital procedure. Even though a much more efficient procedure was used on the digital, time-saving factors between 8 and 2 were obtained via the simpler hybrid implementation. Since the dollar cost of the hybrid is much less than that of the digital, the hybrid has a large advantage per solution.
Computer solution of queueing models
Authors: Black J.R. , Even J.C.
Published: March 2008

This paper explores a rapid, low-cost approach to the solution of queueing models. The mutually-exclusive state differential equations are derived with the aid of a Markov transition matrix and then solved on an analog computer. The computer solution is obtained in graphical form as a function of time on an x-y plotter. A detailed derivation and method of solu tion is given for a two-phase single-service model. The analog solution has the advantage of including the transient region, an area difficult to analyze by classical mathematical techniques.
Curve following in n—dimensional Euclidean space
Authors: Jones John Rees
Published: March 2008

This paper describes a method for progressing a set of n variables along a constraint curve in n- dimensional real space. The method uses the concept of interdependency of the variables and gives the reasons for doing this. Gradient methods for main taining the accuracy of curve following are azso discussed. The method is suitabze for analog com putation.
Analog simulation of frequency response of digital control system
Authors: Corripio A.B. , Smith C.L. , Murrill P.W.
Published: March 2008

The frequency response of a linear digital control system is studied by simulating a plant (represented by a first-order lag plus dead-time) on the analog computer. The digital controller is simulated with analog track-and-store units and parallel logic components. The high speed of the analog computer allows it to display the sinusoidal signals on an oscilloscope in order to observe instantaneously the effect on the frequency response of changing various system parameters. This paper describes the simulation techniques we used, the results we obtained, and how the analog simulation helped us to get the "big picture" of the problem in only a few hours of simulation runs. We turned to analog simulation only after spending several months in an unsuccessful attempt to solve the problem by digital simulation. The reasons for this lack of success are cited.
Simulation in Animal-Pasture Ecosystem Research
Authors: Vickery P.J. , Hedges D.A.
Published: March 2008

Animal-pasture ecosystems can be studied by the use of modelling and simulation. This paper describes one such model to illustrate the advantages and problems of this approach. In the course of our work some important areas which require further data were revealed, and we discuss their effect on the future development of the model. We found the model to be highly sensitive to certain factors and these receive particular attention. The value of simu lation in conventional agriculture research is illustrated by using the model to compare the possible outcomes of sev eral management strategies.
Analyzing the Use of Wilderness
Authors: Smith V. Kerry , Webster David , Heck Norman
Published: March 2008

Increasing demand for low-density or wilderness recrea tion has caused the problems of management and alloca tion of undeveloped public lands to become an important problem. This paper describes a large-scale traffic- simulation model developed to evaluate the implications of alternative management strategies for the quality of the recreational services provided by wilderness areas. The model is capable of simulating recreational patterns in real-world systems and has been applied to the Spanish Peaks Primitive Area in Montana.
An Overview of Cornmod: a Dynamic Simulator of Corn Production
Authors: Baker Charles H. , Horrocks R.D.
Published: March 2008

CORNMOD is a comprehensive mathematical model that not only simulates energy and gas ex change at the plant-air interface but also predicts the consequences of decisions (e.g., when to plant, when to irrigate). An extensive search of the litera ture revealed many models that antedate CORN MOD, and many of them were adequate for biological applications. However, the search also revealed many inadequacies in our understanding of the environment within the plant canopy.

CORNMOD is a simulator of agricultural crop- production systems and it forms a basic framework for a model that will eventually be able to analyze more complex agricultural systems. At present the model is still being developed, and much work remains to be done.
When is GERTS an attractive choice for simulating systems?
Authors: Whitehouse Gary E.
Published: March 2008

This article attempts to give the analyst some guidelines for making the choice between GERTS (Graphical Evaluation and Review Technique Simula tion program) and general-purpose simulation tech niques. GERTS allows the analyst to simulate without performing any programming. GERTS also represents a system in a network model which aids communications with nonsimulators. Examples are given of the types of problems in which GERTS is preferred to general- purpose simulation techniques. The approximation of complicated systems using GERTS is also considered.
Land Use and Energy Flow At the National Level
Authors: Young Jeffrey W. , Mitchiner John L. , Watt Kenneth E. F. , Brewer John W.
Published: March 2008

Simulation models can be used to examine hypothetical long-term causal pathways. This note describes such a model of the interaction of the agricultural and energy sectors at the national level. The indication is that crude-oil prices could have dramatic effects on the long-term and transient values of modal split, wheat exports, urban land conversion rates, and many other systems variables.
Modeling demographic-employment interactions in an urban economy
Authors: Markland Robert E. , Grandstaff Peter J.
Published: March 2008

This paper describes a simulation model of the economy of the St. Louis Standard Metropolitan Statistical Area. The model focuses on the opera tion of the area's labor market. It uses (a) an age-specific regimen for predicting changes in population and (b) the concept that the area's unemployment level is inversely related to the area's exports.

The validity of the model is tested by setting its initial conditions to the 1960 values of the vari ables in the model and running it forward to 1970. The resultant errors are then analyzed and, with two exceptions, found to be small. The exceptions are analyzed and hypotheses to explain them are outlined.

The authors conclude that the model should be useful in finding the key areas in the local economy and in experimenting with economic policies to assess the long-term impact of alternate policies on the local economy.

A systematic simulation study is then designed, and approximately 100 runs are made. Analysis of these runs indicates (a) that the transportation-equipment industry is the key industry in the area and (b) that increasing its growth rate by 2 percent annually over the USA national average for that industry, combined with a 0.1 decrease in the relative cost ratio (compared to the national average) of labor in the durable-fabrication area, would have a very marked effect in reducing unem ployment in the St. Louis area.
BASIC external function for the control of an analogue computer system
Authors: Eatock Robert , Al-Dabass David
Published: March 2008

This paper discusses an external function program that has been developed to enable a PDP11-BASIC user to control the operations of a general-purpose analo gue computer and other external devices using the EXF statement. The result is in effect a digital/analogue hybrid computing facility that can play an important role in undergraduate education and postgraduate research in the department.
Using pseudo-linearization in simulating the dynamics of a multicomponent distillation column
Authors: Ju Haeho , Finkelstein Stanley
Published: March 2008

This paper describes a method for using the S/360 CSMP digital simulation language to implement the computer simulation of a nonlinear model of a multi component distillation column. The method makes it unnecessary to linearize the nonlinear vapor-liquid equilibrium relationship by employing a "pseudo- linearization" approach to this nonlinearity. This approach yields a computer simulation capable of operating over the complete range of the original model. The method is applied to a model of a ternary (benzene-toluene-xylene) distillation column which consists of 11 plates, a condenser, and a reboiler. The simulation results are then compared to known experimental results as a means of validating the simulation. Except for initial transients, the two sets of results are in close agreement, which sug gests that the pseudo-linearization technique pro duces a satisfactory model of the distillation column.
Simulation of Traffic Delays At a T-Juntion With Various Alternative Forms of Layout
Authors: Ashworth R. , Goodwin R.P. , Cheung N.C.
Published: March 2008

The computer simulation model which has been developed for the study of traffic delays at a T-junction can be varied to accommo date a single-lane or dual-lane approach on the minor road and to allow the major road to be either a single or dual carriage-way. In the latter case, the amount of waiting space for right-turning vehicles within the central reserve is also variable. The simulation enables the traffic engineer to estimate the economic value of improving the traffic-handling capacity of a T-junction.
Identification of multivalued and memory nonlinearities in dynamic processes
Authors: Sehitoglu Hasan , Klein Richard E.
Published: March 2008

This paper presents a new approach to the identifica tion of multivalued and memory types of functions (such as hysteresis) in a class of nonlinear dynamic processes which can be represented by a set of ordi nary differential equations. This approach leads to the direct identification of an unknown nonlinear coefficient or unknown nonlinear term. Four examples illustrate applications of the method: a hysteresis loop, a relay with hysteresis, a second-order system with hysteresis and an unknown nonlinear "constant," and a relay with hysteresis and an unknown dead zone. This paper uses standard CSMP function notation. The four systems were simulated and identified with adequate accuracy for many engineering purposes. The method is applicable to a broad class of mechan ical processes and dynamic mechanisms, including many common vibration phenomena involving nonlinear springs and nonlinear energy dampers. A CSMP digital computer program was used to simulate the dynamics of the physical systems and to implement the identifica tion technique.
An interactive digital simulation and optimization package: FORTRAN programs MINISIM and OPTSIM
Authors: Roach John R. , Chow Ee-Pan
Published: March 2008

MINISIM is a general-purpose interactive digital simulation program which is written in FORTRAN and is suitable for both interactive and batch use. The program currently utilizes a fixed-step 4th-order Runge-Kutta integration algorithm. The program has proved to be suitable as a replacement for an analog computer in both teaching and research activities. OPTSIM is an extension of MINISIM that permits optimizing simulated systems automatically while making use of the MINISIM integration routines. The same problem-description subroutine (SUBROUTINE EQUATN ) may be used with either MINISIM or OPTSIM.

Detailed examples are given of the simulation and optimization of a control system and also of the solution of a two-point boundary-value optimization problem.
Simulating the use of space in a hospital surgical suite
Authors: Kwak N.K. , Kuzdrall Paul J. , Schmitz Homer H.
Published: March 2008

This paper describes a simulation procedure for determining the number of patients that the recovery room must accommodate in a hospital with a given number of operating rooms. The particular case simu- Zated was that of Deaconess Hospital in Saint Louis, which has 505 beds and 5 operating rooms. The statistics on the use of the operating rooms and the recovery room were collected from hospital records and incorporated in the simulation. They take into account the types of surgery performed, the number of patients receiving each type of surgical treatment, the patients' need for the recovery room, and the length of time patients need to stay in the recovery room (a statistical function of the type of surgery).

The simulation uses Monte Carlo techniques. Its results closely duplicated the hospital's experience and were accepted by management as the basis for deciding the capacity of the recovery room that would be required after the hospital expanded its facilities. It was found that with 5 operating rooms this hospital required a recovery room with a capacity for 13 patients. The simulation is a general one that can be applied to other hospitals.

This paper includes the principal results of the simulation of the operation of the Deaconess Hospital's surgical suite as it affects the number of patients served by the recovery room.
Simulation of an investment in convertible bonds
Authors: Roberts Darrell D.
Published: March 2008

A general-purpose quantitative model of an investment in convertible bonds (corporation bonds which the holder may convert into stock) selling below par value (usually $ 1000) was developed using the GPSS simulation language. The simulation was written in such a way that all the variables are changeable as desired.

The model assumes an investor who manages his own account and purchases convertible bonds, using an account in which monthly investments are accumulated. The computation assumes that the maximum allowable amount is borrowed from the brokerage firm for the purchase using the purchased bonds as security for the loan, and that the account maintains itself (i.e., the the interest on and capital gains from the converti ble bonds pay the brokerage firm's interest charges and the income taxes on capital gains and on the interest earned by the bonds).

The results of the simulation runs, which cover a 20-year time period, give quantities for many items. An example of some of the quantitative values resulting from an exercise of the model are the following: the number of convertible bonds owned by the investor at the end of the time period, the amount of income from interest, the amount of interest paid on borrowed money, taxes paid on interest and capital-gains income, and many other quantities of interest when such an investment is undertaken.
A decision-tree framework for estimating the costs of simulation
Authors: Gray Paul , Rezek Ronald E. , Young Donovan
Published: March 2008

This paper presents a framework for analyzing the anticipated costs of simulation before committing resources. The viewpoint taken is that of a manager who must decide whether to solve a problem by simu lation or some other means. The decision-analysis model that is formulated allows the manager to deter mine the minimum-cost method of simulation within the operating and policy constraints of his firm. Two examples are discussed.
Solving the equations for unsteady gas flow by two methods
Authors: MacLaren J.F.T. , Tramschek A.B. , Pastrana O.F. , Sanjines A.
Published: March 2008

The paper discusses briefly a number of methods available to solve the hyperbolic partial differential equations which describe unsteady compressible fluid flow. Equations describing unsteady one-dimensional flow in a pipe, accounting for heat transfer, gradual area change, and friction are presented in conserva tion-law, normal, and characteristic form. The pres sure pulsations at locations in a single-stage reci procating air compressor system are predicted, employ ing both the method of characteristics and a composite scheme utilising the Two-Step Lax-Wendroff method within the pipes and the method of characteristics at the boundaries. The composite scheme was simpler to apply, required much less computational time, and yielded results in closer agreement with data obtained experimentally.
Implicit integration for CSMP III and the problem of stiffness
Authors: Watson H.D.D. , Gourlay A.R.
Published: March 2008

The phenomenon of stiffness in differential systems is described, and the problem of instability in the numerical integration of such systems is discussed. The need for implicit integration methods is demon strated together with the consequential requirement for the extensive use of sparse-matrix techniques.

A specific implementation of an implicit stiff- system integration routine, STIFFX, based on Gear's algorithm and designed for use with the IBM continuous system simulation language CSMP III is described, and its efficiency is compared with that of the STIFF routine which is a part of CSMP III.
Modeling biological systems by means of flowgraphs
Authors: Wiitanen Wayne
Published: March 2008

This brief article is intended to expose the biologi cal modeler to a powerful technique for writing models and for the notation, dimensional analysis, simulation, and solution of biological models. The technique is based on the well-known engineering tecnhique of flowgraph analysis and uses flowgraph notation.
Simulation of the Respiratory Control System
Authors: Milhorn H.T.
Published: March 2008

This paper describes the development over the last two decades of mathematical models of the mamalian respira tory system.
Simulation of Heart Muscle Contraction
Authors: Sagawa Kiichi , Nakayama Kiyoshi
Published: March 2008

This paper describes several of the mathematical models that have been used to study cardiac muscle contraction.
SIMPAK —
Authors: Birta L.G. , Raymond J. , Haqqani M.A.M.
Published: March 2008

A software system for continuous system simulation, having an interactive graphics capability, is described. Inasmuch as the system uses reasonably priced, commercially available graphics hardware, it has wide potential utility. The system uses the IBM 360 Continuous System Modeling Program (CSMP) and has a simple command language to control the CSMP problem. The user enters commands at the key board of the graphics terminal to initiate simulation runs, change parameter values, and display graphs of problem variables. The system maintains a file which permits the user to display curves from earlier runs and thereby to readily obtain insight into the effect of parameter changes.
A controlled Markov chain model for nursing homes
Authors: López-Toledo Alejandro A.
Published: March 2008

This paper deals with the modeling of the patient admission policy in a nursing home as a Markov deci sion process. There are two different charges for care in the home, i.e., two kinds of patients k1 and k2; patients arrivals follow a Poisson process; lengths of stay are exponential or Erlang; and, finally, the home decides whether or not to admit a patient on the basis of maximizing its expected dis counted returns. Computer simulation experiments show interesting results: the optimal policy is not very sensitive to different discount rates, average length of stay, home size, charges for care, or k1 to-k2 arrival ratios. To investigate the validity of the model, computer experiments for a system of several nursing homes in a competitive situation were run, using real data from homes in Rhode Island. These experiments included comparisons of real length-of-stay distributions with assumed distribu tions and analyses of statistics such as backlog in hospitals and average occupancy of nursing homes for different values of the system's utilization factor.
Software for simulation of combined continuous and discrete systems: a state-of-the-art review
Authors: Ören Tuncer I.
Published: March 2008

This paper is a state-of-the-art review of software for combined continuous/discrete systems simulation. The following 18 languages or packages are discussed:
A Computer Model of Cell Clone Growth
Authors: Ransom Robert
Published: March 2008

A model simulating the growth of clones of cells in two dimen sions is described. This model includes an algorithm that simulates the displacements which occur when interior cells divide in a cell mass; the model uses an algorithm which allows more realistic simulation than did previous models that did not possess this facil ity. Applications of the model are discussed, and details are given of the execution of the program on refresh display video, allow ing dynamic observation of the modelled cell division process.
Simulation in the Service of Society
Authors: McLeod John , McLeod Suzette
Published: March 2008

This Newsletter was published independently from January 1971 through August 1976. Back issues are available from SITSOS, POB 994, La Jolla, CA 92038, for 75ç per copy.
Applying simulation to highway intersection design
Authors: Varol Yaacov L. , Kaufman Arie A. , Hanani Michael Z.
Published: March 2008

This paper describes a simulation model of driver- vehicle behaviour at an intersection and two versions (one batch, one interactive) of its implementation. The model offers the user considerable flexibility in specifying the intersection, the traffic control techniques, and the volume and other characteristics of the traffic. It incorporates some of the latest findings of human factors research concerning the driving task, and represents the driver's perceptual, decision-making, and response processes as the driver approaches, passes through, and leaves the intersec tion. Driver behaviour is based on various percep tual cues and on psychophysical judgements derived from them.

We rejected gap-acceptance distribution as the basis for driver behaviour at the intersection because we formulated the model for intersection design. vali dation tests showed that the model created gap- acceptance data statistically equivalent to field data. Two implementations of the conceptual model have been built. They are modular in design and are programmed in FORTRAN because of its transportability and proven efficiency in use of CPU time and of memory for traffic simulation. The batch-mode version runs on any computer having a FORTRAN IV compiler; it has already been used successfully in the complete rede sign of an old intersection. The interactive version runs on a minicomputer with a graphics display; it is being considered for driver re-education.
A random number generator for microprocessors
Authors: Mueller R.A. , Georg D.D. , Johnson G.R.
Published: March 2008

An algorithm is presented for generating uniformly distributed random deviates on microprocessors or minicomputers utizizing memories with a small word- Zength. other alternative solutions are discussed, and the statistical quality of sample streams of generated numbers is evaluated and compared with the quality of other widely used generators.
Statistical estimation of feedback models
Authors: Senge Peter M.
Published: March 2008

This paper considers the accuracy of conventional econometric techniques in estimating parameters in a feedback model. Evaluation of the estimation techni ques is accomplished by an experimental procedure in which a nonlinear feedback model generates synthetic data which is then used to estimate the parameters in the data-generating model. Comparison of the estimated and "true" parameter values provides a measure of the accuracy of the estimation technique.

Experiments with ordinary and generalized least- squares estimation (OLS and GLS) show that the parameter estimates derived from these methods are highly sensitive to errors in data measurement, especially when a model's feedback structure is not completely known. Further tests of OLS and GLS with different feedback models, as well as experimental evaluations of other estimation techniques, should help to determine the proper role of statistical methods in modeling feedback systems.
Simulation of semiconductor devices
Authors: Akers Lex A.
Published: March 2008

The simulation of semiconductor devices is a powerful means for optimizing the performance of semiconduc tor circuits and devices. various classes of semi conductor models exist, but accurate simulations re quire exact ("total") computer models. The exact models allow the use of arbitrary initial conditions and internal distributions and describe the device accurately over wide ranges of operation.

This article discusses the leading numerical formula tions used to generate exact semiconductor models and describes the simulation of an NP junction, a bipolar transistor, and a MOS field effect transistor using exact models.
A GASP IV model of steel ingot processing
Authors: Surh Dae S. , Talavage Joseph J.
Published: March 2008

This paper describes a GASP IV model of part of a steel mill. The processes modeled include pouring molten steel into molds, removing (stripping) the hot ingots from the molds, and sending them to the soaking pits and finally to the primary rolling mill. Molds move from a preparation area to the furnaces, thence to the stripping cranes, and back to the pre paration area. Rail trains transport ingots and molds.

The major problem is how to dispatch a limited number of rail engines to pull trains so that materials and molds are at the right places at the right times for efficient operation. A set of 32 experiments (indi vidual simulation runs) was devised to find an opti mum combination of number of engines, number of transportation zones, and dispatching rules for a particular steel mill.

The set of experiments showed (not surprisingly) that the use of a single transportation zone (so that all engines were able to go wherever they were needed) and a larger number of engines resulted in the greatest percentages of on-time deliveries and (somewhat surprisingly) that random and priority selection of engines worked equally well and were better than selecting the nearest engine, even when that choice was modified by a priority rule.
Microprocessors and microprogramming: a review and some suggestions
Authors: Leventhal Lance A. , Leventhal Lance A.
Published: March 2008

Microprocessors and microprogramming are both impor tant new topics in the design and development of computer systems. This paper discusses the relation ships between these two topics. Microprocessors have been used in the design of microprogrammed systems which emulate minicomputers, act as high-speed con trollers, handle special-purpose tasks in such areas as signal processing and simulation, and allow for the distribution of computing power. Microprogramma ble computers can, in turn, provide valuable support in the design of microprocessors, other associated devices, microprogrammed systems, and ordinary micro processor-based systems.
Modified BASIC for all-digital hybrid computing
Authors: Morse M.J. , Gilbert B.R.
Published: March 2008

A number of advantages may be gained when a digital replacement for an analogue computer is used in a hybrid computing system. This paper describes the interfacing characteristics of the MBD-24 parallel digital simulator and the language which has been developed to control it from a Data General NOVA 820 minicomputer. The language uses the CALL statement of Data General's extended BASIC and the necessary format of these statements is explained. To illus trate the use of the hybrid system and the language, the simulation and measurement of the transfer func tion of the active filter is described.