bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of reciprocating gas compressors with automatic reed valves
Authors: Wambsganss M.W. , Coates Donald , Cohen Raymond
Published: March 2008

The simulation of high-speed reciprocating refrigeration compressors was motivated by the needs of design engi neers. In this paper a mathematical model describing the dynamic behavior of a reciprocating compressor is pre sented. The model is semianalytic in that two types of empirical factors are required to relate phenomena not yet analytically predictable. One type is obtained from steady- state tests and the other by trial and error based on com parison with experimental results. Both analog and digital computers were considered as means of simulating the model. Due to nonlinearities in the model, the digital com puter, using Fortran IV, was selected. To evaluate the sim ulation, a one-quarter horsepower 3600-rpm stock com pressor was modified and used as a laboratory vehicle. A typical correlation between the computer simulation and experimental results is given. In general, good correlation was achieved.
A computer algorithm for frequency response calculations
Authors: Daneels A.J.H.A. , Spear R.C.
Published: March 2008

This paper shows how the state variable description of linear dynamical systems can be used to develop a general digital computer program for frequency response calcula tions. State variables are first introduced in the time domain, and a straightforward application of the Fourier Transform yields equations suitable for programming on a digital computer. Data input is discussed, and an algorithm given which will allow this data to be the coefficients of polynomial transfer functions. The selection of frequency values at which the response is to be calculated is covered, and an indication of possible numerical pitfalls is given. An example is presented.
Accurate analog computer generation of Bessel functions for large ranges
Authors: Hausner Arthur
Published: March 2008

The generation of Bessel functions Jn(x) is required when simulating many systems on an analog computer. Because of an indeterminate expression at the origin, however, they have not been amenable to an accurate generation for the range 0 ≤ x ≤ Xmax for large Xmax.

This paper extends an idea of Van Remoortere to use an approximation for 0 ≤ x ≤ X 1 and solve a differential equation for X1 ≤ x ≤ Xmax, combining both phases by switching. The technique described here uses Chebyshev polynomials to minimize equipment in the approximation phase and generates the function 1/x by an integration process in the differential-equation phase to extend the range. The examples given for J0 and J9 indicate excellent accuracy for at least 0 ≤ x ≤ 100.
A mathematical model of heat transfer in continuous casting
Authors: Kung E.Y. , Pollock J.C.
Published: March 2008

This paper presents a mathematical model of dynamic and steady-state heat transfer in the continuous casting process which considers heat transfer through both dimensions of the cross section of the cast section. The steady-state ver sion of the model has been tested against heat transfer and operating data reported in the literature.
Library simulation: The computer locates the data needle in the journal haystack
Authors: Mangino Joseph J.
Published: March 2008

Developments in the information technology make pos sible the use of computer searching of normal text, to locate the articles of interest to match a professional pro file. These profiles are computer equivalents of an indi vidual's description of his work assignment, and are stored in the computer to be compared with new or current data being processed in normal text by the computer. The data is the author's/publisher's abstract of the article in the orig inal form. The computer reads the data and compares it with over 2500 profiles. When a match occurs, the abstract is selectively printed out and sent to the individual. This is an operational system used in the IBM Technical Informa tion Retrieval Center to keep IBMers aware of the state-of- the-art in their specialty. Feedback statistics are included to indicate the high response and satisfaction criteria of the users.
A medium-scale hybrid interface
Authors: Marston G.P. , MacDonald J.S.
Published: March 2008

A flexible, low-cost hybrid interface linking a DEC PDP-9 digital computer with an EAI 231 R-V analog computer is described. The interface includes provision for complete mode control of the 231 R-V by the PDP-9, as well as signal selection and potentiometer setting facilities. Data transfer is accomplished by using double-buffered D/A registers with provision for controlling the transfer of data from either the analog or digital side of the interface. In addi tion, provision is made for the updating of several D/A channels simultaneously. A sixteen channel analog multi plexer with a settling-time of less than two microseconds has been designed and is employed with a twelve-bit twenty-microsecond A/D converter for high-speed analog- to-digital data transfer.
The design of an automatic patching system
Authors: Starr David A. , Jonsson Jens J.
Published: March 2008

An automatic patching system for analog computers is proposed. The system patches any set of component ter minals together, yet size and cost are practical. The design is accomplished in three steps:

First, a "model" analog computer is defined and its components divided into modules. Components within a module connect to one another through an "intraface" which allows any terminal to connect to any other ter minal. Problem sections are patched within the modules and then joined together by an "intermodular" trunking system.

Secondly, the principle of module chaining permits in dividual modules to access a limited number of other modules, rather than all other modules. This reduces the number of patching switches required by the intermodular trunking system and reduces the overall number of switches required.

The third step, called concentration, brings the required number of patching switches down to a practical value by assuming that all analog computer terminals will not be in use at once. Switching devices called "concentrators" exploit this fact to reduce switch requirements.

The automatic patching system is driven by a digital computer under control of specialized software, and to gether with the automatic patching control system it can patch large problems in times of the order of fifteen sec onds. The information in this paper is a result of work done for a Master of Science thesis.1
Computer simulation of automobile accidents ... a new research tool
Authors: McHenry Raymond R.
Published: March 2008

Simulation programs are currently being developed by the Cornell Aeronautical Laboratory, Inc. (CAL) to implement analytical studies of the dynamics of automobile accidents.

One CAL digital computer program simulates responses of the crash victim during a longitudinal collision (i.e., a frontal or rear impact). The eleven-degree-of-freedom non linear mathematical model is being used to evaluate the effects of belt-type restraints and energy absorption prop erties of vehicle interiors and structures.

In another CAL research program, an eleven-degree-of- freedom nonlinear mathematical model of an automobile traversing irregular terrain and encountering obstacles has been formulated and programmed for a digital computer. This simulation provides an analytical means of evaluating existing and proposed roadside energy-conversion systems.

The two simulation programs are described and their outputs are compared with experimental responses.
A flexible sinusoidal response analyzer
Authors: Sprague Clyde H.
Published: March 2008

Clyde Sprague was selected by the SCi Awards Committee as a winner of the EAI Student Papers Competi tion for the paper on the sinusoidal response analyzer which follows. At the time that the paper was written, the author was a doctoral candidate under another SIMULATION contributor, Dr. Robert H. Kohr, at Purdue. To appreciate the significance of this award, see the rules on page iv. JM
Trajectory optimization by a direct descent process
Authors: Fogarty L.E. , Howe R.M.
Published: March 2008

The problem considered is that of trajectory optimization using step-by-step descent to minimum cost along the direction of the cost gradient with respect to the control. Using a hybrid computer, the gradient is computed di rectly as the response to nearly impulsive control perturba tions. A method is presented for computing the gradient when several terminal constraints are enforced. Examples of application of the method are presented. It is concluded that the direct gradient computation method has some significant advantages over other methods.
Presenting
Authors: Valisalo P.E.
Published: March 2008

This paper describes a systems engineering laboratory that consists of a hybrid computer system and a group of industrial measuring and control equipment, all of which can be used as one integrated whole. It uses a special-purpose software system for internal communi cations. The laboratory's plan of organization for super vision, maintenance, and operation within a university environment is explained. A concise description of how the laboratory has been used in undergraduate and grad uate teaching is given.
A review of numerical methods for digital simulation
Authors: Benyon P.R.
Published: March 2008

This review is based on an extended study of the litera ture and experience in the detailed simulation of guided missiles and similar systems. After a brief recapitulation of the main ideas behind the classical methods for numer ically solving ordinary differential equations, the recent literature on this subject is surveyed and discussed. Pre dictor, predictor-corrector, and Runge-Kutta methods of various orders are then compared experimentally and theoretically. The theoretical comparison is based on the performance in computing the steady-state frequency response of linearized systems and includes consideration of accuracy, numerical stability, recovery of continuous outputs from sampled outputs, and computing time per step. The factors determining the optimum order are brought out. Other procedures such as different step lengths in different parts of the problem, special-purpose difference equations for "stiff" linear sections of the prob lem, and procedures for inserting wideband noise are dis cussed. The methods currently in use with a number of simulation languages are then summarized, and it is found that there is little consensus on "best" methods. It is concluded that further development is needed of meth ods for handling (a) stiff equations, including the non linear case, (b) mixed step lengths, (c) noise insertion, (d) discontinuities, and (e) recovery of continuous out puts. A list of 75 references is given.
Protracted military conflict and politico- economic stability
Authors: Rastogi P.N.
Published: March 2008

The computer simulations used in this paper were car ried out using the CTSS system of Project MAC at MIT. The study stems from the author's interest in developing a cybernetic model of the Indian social system. See, for example, his "A cybernetic model of total Indian so ciety," Center for International Studies, MIT (no. C/ 67-23), October, 1967. The present study deals with a hypothetical underdeveloped country and situation. The focus is on developing a general framework linking a protracted military conflict with its politico-economic concomitants.

The modeling philosophy adopted for the simulations described in this paper is based on feedback systems theory. The approach used, known as Industrial Dynam ics, was developed at MIT under the leadership of Jay Forrester.
A Comparative Study of Digital Integration Methods
Authors: Martens Hinrich R.
Published: March 2008

This paper is a brief report on an investigation into the performance of integration routines used in the simula tion of dynamic systems by general-purpose digital simu lation programs. The performance is compared with respect to overall speed, accuracy, and convenience. Several routines are considered, including rectangular, Runge-Kutta, Runge-Kutta-Blum, Runge-Kutta-Mer son, and Adams-Moulton methods. The last two may use either fixed- or variable-step-size methods. The Tus tin method and the State-Transition method are also included.

By examining the performance of the routines through tests on representative systems, it is shown that for the simulation of linear systems the state transition method works best. For the general simulation of linear and non linear systems the variable-step-size Runge-Kutta-Mer son method proves to be most accurate and most efficient. The variable-step-size method may be designed to gen erate outputs at uniform intervals, thus greatly enhanc ing its value when synchronous interaction with other parts of a simulation is required.
Simulation of the effects of load on hydraulic servo actuators
Authors: Glickman Myron
Published: March 2008

Control system analysts are frequently called upon to include a hydraulic servo actuator as part of the loop in a complex closed-loop system simulation. This article presents a general description of several common types of hydraulic servo actuators and several methods for inclusion of the effects of load on the simulation of the actuator in the control loop. These methods are pre sented in block diagram form and are suitable for inclu sion in a larger simulation loop. The block diagrams themselves may be somewhat condensed and modified before inclusion in a larger simulation, but are presented here with all the details shown explicitly for clarity.
Simulation models for flexible spinning bodies
Authors: Childs Dara
Published: March 2008

The objective of the analysis which follows is the deriva tion of simulation models for flexible spinning bodies. The analysis employed is based on relatively simple con cepts of vector mechanics and results in a lumped-param eter simulation model. The simulation models which are first derived are subsequently simplified by invoking the small deflection assumptions of the theory of elasticity. A final section deals with some analysis steps used in adapting the basic simulation model for the description of turbine rotors.
An investigation of optimally stable numerical integration methods with application to real time simulation
Authors: Nigro Bart J.
Published: March 2008

An approach for deriving numerical integration methods which possess extended ranges of absolute stability and arbitrarily small truncation error coefficients is given. In particular, a family of three-step methods which have these properties and which are classical to the second degree is derived. The derivation of this family of meth ods forms a generalization of a corresponding family of methods which have extended ranges of absolute sta bility and are classical to the third degree.

Suitable perturbations of the coefficients of these methods allow their reduced range of relative stability to be increased and the resulting techniques may be considered to be optimum from the stability viewpoint. Such methods have particular application in real-time simulation where we seek maximum integration steps.

The complete derivation scheme employed has gen eral application in the construction of numerical integra tion algorithms of arbitrary step number.
A predictive time-optimal controller for second-order systems with time delay
Authors: Mellichamp D.A.
Published: March 2008

This paper presents a method of interactive or real-time predictive control which can be implemented without a stored program computer. By restricting the process dy namic model to a second-order-plus-dead-time format, a configuration which is satisfactory for many chemical or petroleum processing systems, a time-optimal controller can be built entirely on a small analog/hybrid computer. For set-point changes, the controller utilizes an analog model of the process to search out the predicted optimum input switching sequence and continuously maintains the process on the time-optimal trajectory. Because of the predictive nature of the method there is no necessity to include the time-delay term in the high-speed model; the predicted switches in the process input are simply ad vanced in time by the amount of the time-delay.
The water immersion facility
Authors: Hammersley Vernon C.
Published: March 2008

The water immersion technique is a major training tool for extra-vehicular activities and man's physical move ment inside and around the spacecraft while in space. This technique is also very useful for hardware devel opment and procedures verification. The water immer sion technique involves the balancing of buoyant forces with gravitational forces for zero g (simulated space travel) or overcoming the buoyant forces with grav itational forces by some fraction, such as one-sixth g, for simulated lunar-surface training. When the present-day space suit filled with a man and air is submerged in the water, several imbalances can be expected. These are usually resolved by rebalancing the suited subject.

The Water Immersion Facility (WIF), Figure 7, at the Manned Spacecraft Center consists chiefly of a water tank, a control room, and a small medical installation. For spacecraft exercises, mockup trainers with special provisions for viewing, submersion, and safety are used in the water tank.
Partial gravity simulators
Authors: Johnson Harold I. , Trader Arthur G.
Published: March 2008

This article covers two partial-gravity simulators being used at the Manned Spacecraft Center to acquaint astronauts with the dynamics of moon walking. The first simulator discussed, the Partial Gravity Simulator (PGS), Figures 7 and 8, is a 5 + degrees-of-freedom simulator built into a 14 x 60 foot room which is 60 feet high. The second simulator described, the Mobile Partial Gravity Simulator (MPGS), Figure 9, is a full six- degrees-of-freedom simulator utilizing a one-ton truck as the primary horizontal motion system. Construction and specific uses of the simulators are described. One astronaut, Alan Bean, reporting directly from the moon after a moon-walk, called these simulators "real good trainers."
The command module simulators
Authors: Prude George
Published: March 2008

Three Command Module Simulators (CMS), Figure 15, two located at Cape Kennedy, Florida and the third at Houston, Texas, were designed and built to provide training for the Apollo astronauts in their goal of landing on the moon.

Each CMS is identical and consists of a digital computer complex that provides dynamic representations of spacecraft systems, a complete and accurate presentation of exterior visual scenes, and an exact replica of the spacecraft interior. The CMS's are capable of integration into the Mission Control Center computational complex, thereby providing a total training exercise between the astronauts and flight controllers.

The simulators are designed with extreme flexibility for modification. The computer complex is readily adjustable to changing mission objectives which require a change in a Command Module subsystem. Any alteration of a particular system or of a mathematical model is programmed and fed into the computer. No variation in computer hardware is required. The required updating is thus accomplished with a minimum loss of training time.
Simulation in the analysis and control of a cardio-circulatory assist device
Authors: Spyker D.A.
Published: March 2008

Several of the important fluid dynamics problems en countered in the design, analysis, and control of cardio- circulatory assist devices are well suited to examination (and solution) by hybrid computer simulation.

The simulation approach to the analysis and control synthesis for a particular left ventricular assist blood pump, pneumatic drive system, and experimental animal is presented. This includes a hybrid computer simulation of this system, sensitivity analysis, solution for control parameters, and description of a computer monitoring and control system to regulate the assist device.
3-D Visual simulation
Authors: Goldstein Robert A. , Nagel Roger
Published: March 2008

This paper describes a visual simulation technique by which fully computer-generated perspective views of three-dimensional objects may be produced. The method is based on a relatively simple geometric modeling technique for the mathematical representa tion of the three elements essential to the picture- taking process, namely, a camera, a light source, and the object or objects to be photographed. Once these three basic components have been defined, geometric ray tracing is employed to compute a "picture" of the object as it appears in the simu- Zated camera. In essence, individual light rays are traced from their source to the surface of the object. The reflected component of each ray is computed and traced to its point of intersection with the film plane. Thus, each reflected ray pro vides the intensity at a single point on the pic ture, and, when a sufficient number of points have been computed, the entire area of intensity data may be displayed on a cathode ray tube. Several examples of the pictorial output of this process are shown, and the application to the computer- generated films is discussed.
Compufilms: A computer animation process
Authors: Lieberman Lawrence I.
Published: March 2008

Compufilms is a computer-generated animation tech nique developed jointly by Pennsylvania Research Associates Inc. (PRA) and film producer, Stanley Rose. A medium-scale general-purpose digital compu ter (RCA Spectra 70/46) is used to generate display instructions for a Digital Equipment Corporation PDP 8/338 connected as a satellite computer via telephone lines. The DEC 338 CRT display is photographed with a motor-driven motion picture camera having a "single frame" feature. Special effects and color are added at this point.

The basic movie generating softwave was written at the Moore School of Electrical Engineering, Univer sity of Pennsylvania, on sponsored projects. The developers have been able to extend the use of this software and combine it effectively with special animation and cinemagraphic processes to create Compufilms. This article describes the system and its operation, and illustrates its use as a practi cal animation process.
Stability of tubular reactors
Authors: Clough David E. , Ramirez W. Fred
Published: March 2008

This paper investigates the stability of tubular reactors by both theoretical and computational techniques. Liapunov's second method using a Liapunov functional of the general norm is used to show that tubular reactors without diffusion and without temperature effects and reactors with diffusion and without temperature effects are globally, uniformly asymptotically stable. The theorem fails for reactors with temperature effects. The results of computer simulations show that the system with temperature effects is not uni formly stable.
Minimum altitude visibility diagram —MAVD
Authors: Shannon Robert E. , Ignizio James P.
Published: March 2008

An essential part of almost all air-defense computer simulation models is the visibility subroutine. This subroutine performs the necessary computations and provides the data required to determine whether enemy aircraft or missiles may be detected by stationary ground-based air-defense system sensors- that is, whether they are within sensor range and whether their visibility is obstructed by terrain irregularities and/or the curvature of the earth. This paper presents a new approach to the visibility subroutine, entitled MAVD (Minimum Altitude

Visibi Zi ty Diagram). MAVD provides a visibility subroutine which could be incorporated into existing models relatively easily. The authors believe that it would result in a more realistic simulation and provide a significant reduction in computer time, in comparison with other simulation methods with which the authors are familiar.
From simulation model to public policy
Authors: Kadanoff Leo P.
Published: March 2008

Forrester's model is described and critically analyz ed with a view to understanding the relationship between his conclusions and his normative scheme. He claims that his model produces "counterintuitive" results; it is argued here that the main results follow directly from his goals. An alternative method of evaluating the results of the model is pro posed, based upon the model's calculation of the city's attractiveness for various groups. This alternative normative scheme leads to quite different conclusions from those reached by Forrester.
Simulation of the switching behaviour of P-N junction diodes
Authors: Olive Graham
Published: March 2008

The simulation of p-n junction transient behaviour using an analogue computer is described. The dif fusion controlled model, mathematical treatment, computer mechanization and typical results are presented.
A second survey of users' views of discrete simulation languages by
Authors: Kleine Henry , Palme Jacob
Published: March 2008

This simulation language survey is a followup of the survey published in SIMULATION, in May 1970, p. 225. The previous report generated much inter est, criticism pro and con, and most importantly some additional responses. Consequently the responses summarized below, including the 30 re sponses from the original survey, now total 103. Responses were solicited by direct request, the generous efforts of others (notably Ira Key of Southern Simulation Service, Inc.), and a "Dear John" letter published in the October 1970 issue of SIMULATION.
Library policy structure: an industrial dynamics study
Authors: Nance Richard E. , Baker Norman R.
Published: March 2008

An industrial dynamics model of a university library, developed originally to investigate the effect of library control policies, is described. The model is used to analyze the effect of two policies pro posed by the Physics Library at Purdue University. After having operated under extremely crowded con ditions for the past several years, the Physics Library will move in 1971 into new, more spacious quarters. The policies for loans from the library collection have been rather free, control over the collection has been lax, and penalties for users failing to comply with library policies have been mild. The reasoning behind these policies was that if all loaned materials were returned, sufficient shelf space was unavailable.

With the space limitations removed in the new quarters, the Physics Librarian can adopt one of two general policies:

Policy 1 - Closer control over the library collection, more restrictive loan policies, more staff, and longer operating hours

Policy 2 - Less control over the collection with more extended loan policies and increased purchases of multiple copies.

Analysis of the two policies shows that Policy 1 effects a reduction in delays in return of loaned material at the expense of incurring user dissatis faction with the library and that Policy 2 results in even higher user satisfaction than is presently experienced.
Hybrid solution of partial differential equations by application of invariant imbedding to the serial method
Authors: Nelson Paul , Altom Donald W.
Published: March 2008

This paper presents a hybrid computational method in which invariant imbedding is used to effect analog solution of the boundary-value problems which typically result from time discretization of a partial differential equation. The method is developed from fundamentals, scaling rules are derived, computational results are presented and discussed, and possible extensions are mentioned.
OLDAS: An On-Line Digital Analog Simulator
Authors: Cullen Richard P. , Green Daniel T.
Published: March 2008

OLDAS is a conversational system that provides a user with the means to construct, modify, and run programs written in the continuous simulation language MIMIC.

OLDAS operates in a multiprogrammed mode on an IBM 360/40 computer. The user terminal consists of an IBM 2250 CRT display with a light pen and alphanumeric keyboard. An IBM 2311 disk pack drive is utilized for storage of user programs and data. MIMIC source programs are entered via the alpha numeric keyboard, displayed on the CRT, and stored on the disk in the form of pages, of which there are three types: Parameter, Program, and Arbitrary Function. To facilitate manipulation and reuse of a program, several versions of it may be stored in the some file on the disk.

The principal form of output is a graphical display of results which the user monitors during execution. The user can halt execution at any time, change pro gram parameters and integration options, and specify new results to be plotted. Options which allow a user to display results digitally and to print on- line are available. Results can also be saved on the disk for processing by off-line programs.
A survey of random methods for parameter optimization
Authors: White R.C.
Published: March 2008

A class of algorithms known as random search methods has been developed for obtaining solutions to para meter optimization problems. This paper provides a guide to the literature in this area, while describ ing some of the theoretical results obtained as well as the development of practical algorithms. Included are brief descriptions of the problems associated with inequality constraints, noisy measurements, and the location of the global optimum. An attempt is made to indicate types of problems for which random search methods are especially attractive.
On-line simulation experiments
Authors: Armstrong J.S.
Published: March 2008

This paper reviews the software and hardware requirements for on-line computing. It shows these facilities can be used to conduct on-line simulation experiments of models of agricultural systems. The general problems associated with modelling are indicated and the advantages of the on-line approach are discussed.

Key words and phrases: on-line computing, modelling agricultural systems, systems analysis in agricul ture.
On the analog simulation of a pure time delay
Authors: Davies W.D.T.
Published: March 2008

In the investigation of many physical systems, it becomes necessary to simulate the time-delay phenomenon on the computer. This phenomenon arises in such investigations as shock waves in mechanical systems, sound waves in acoustical systems, and more generally in connection with the flow of materials in chemical processes and heat exchangers. Since information about such systems is not available until a finite time after certain actions have been performed, it is essential to represent this time-delay phenomenon adequately.

Various methods have been used to do this, depend ing on the value of the time delay involved and the frequencies contained in the variable quantity passing through the delay. This paper discusses the application of operational amplifiers to form time-delay approximations for those applications where the delay is more or less constant.

A number of such approaches are discussed and the resulting approximations are brought into a common form and scale, so that comparisons between the different approximations may be easily accomplished.
HYBRID—a user-developed hybrid interpretive language
Authors: Holst Per A.
Published: March 2008

An interpretive hybrid programming language, HYBRID, has been developed by The Foxboro Company, for use in a small hybrid computer system. The TELETYPE* oriented language comprises a command structure resembling FOCAL and offers hybrid instructions similar to HOI. It provides features seldom found in software for small (mini) computers with limited core, such as computed (variable) part and step numbers in go-to instructions, foreground- background operational modes, monitor functions, and a full assortment of hybrid and interrupt handling capabilities.

The HYBRID program occupies approximately 4K of core in a PDP-7t 18-bit computer and includes routines for drum (disc) and paper tape input- output of source and data files. It permits the use of assembly (machine) language routines to be called by source program commands. The variable list (Symbol Table) is referenced in a binary search mode, which results in fast execution speed as well as efficient running of the source program. The language contains a number of error-checking and source-program protection provisions to make it as user-friendly and fault-tolerant as possible .
Simulation of the human cardiovascular system: a model with normal responses to change of posture, blood loss, transfusion, and autonomic blockade
Authors: Boyers David G. , Cuthbertson James G. , Luetscher John A.
Published: March 2008

The model of the human circulation here used consists of the minimum number of compartments required to simulate the distribution and flow of blood under different conditions. In the model the peripheral circulation consists of four parallel vascular compart ments, each with a typical inflow resistance and compliance. Each of the peripheral compartments is in equilibrium with an interstitial fluid compartment. Blood returning from the peripheral circulation flows into the great veins and pulmonary vessels, from which it is pumped by the heart into the high-pressure aorta and arteries. The distribution and flow of blood are regulated by the autonomic nervous system, which receives inputs from arterial pressure and pulmonary blood volume, and which controls cardiac output and the resistance and compliance of each peripheral vascular compartment.
The use of hydrological simulation and remote sensing in an integrated program for water-resource systems
Authors: Byron Winn C.
Published: March 2008

A statewide water resources data bank and an associated integrated program for water-resource systems (IPWRS) is being developed for the State of Colorado. IPWRS is to be an open-ended system of digital computer modules unified under the control of an executive pro gram. This executive program will permit an analyst to prescribe which modules should be exercised, the order in which they are to be used, and the form in which output is to be presented. This computing sys tem provides a valuable tool for the management of the limited-water resources of the state. This paper presents a summary of the philosophy behind IPWRS and the results of a phase of the program concerned with the prediction of streamflow runoff in mountainous regions. The prediction involves the use of a self- calibrating snowmelt simulation model, which is one of the digital computer modules in the IPWRS system.
The dynamics of natural resource utilization
Authors: Behrens William W.
Published: March 2008

The limited reserves of mineral resources will soon become a problem facing all the countries of this globe. In an attempt to plan for the needed supply, the static reserve life index of a resource has been used as a measure of future availability. This static index is an inadequate measure of resource availability, one which could cause severe misjudg ments concerning resource supplies. Long-term re source planning requires a better understanding than that afforded by the static reserve life index. This paper illustrates that knowledge already available about the relationships governing the supply of and demand for resources is sufficient to develop a frame work, a simulation model, which can form the basis for more meaningful analysis of long-term resource utili zation.
Modifications to a digital simulation program to facilitate automatic patching
Authors: Rigas H.B. , Coombs D.J.
Published: March 2008

One factor of importance in a complete auto matic analog-computer patching system is a software package to provide the actual patching information for a model described in a high-level language.

Several approaches to this problem have been proposed. One such program, PATCH, differs from the others in that it not only uses a continuous simulation language as a means of describing the model to be patched, but also actually uses the simulation processor as an integral part of the patching program.

The simulator which was used for the imple mentation of the patching program is S/360 CSMP. Since PATCH was first described in the literature, many have inquired about the possibility of using another simulator such as CSSL or MIMIC in the same way.

We will attempt here to outline the modifi cations made to CSMP and their purpose so that one intimately familiar with another simulator could make similar alterations to that program.

PATCH itself is a subroutine written in FORTRAN IV and could readily be modified to accept input from other simulators.
A simulation of the shortgrass prairie ecosystem
Authors: Patten Bernard C.
Published: March 2008

Ecosystem modeling for simulation and systems analy sis is complicated by (i) size and complexity of ecosystems, (ii) lack of data and methods for obtain ing needed measurements, and (iii) inadequacies of modeling theory for macrosystem applications. This paper presents an S/360 CSMP simulation of a gener alized shortgrass prairie scaled large enough to preserve meaningful biological detail, but still small enough for computer implementation. Both nomi nal and small perturbation behaviors are described, together with a modeling rationale tied to the closed-loop recycling structure of ecosystems. The model, which is piecewise linear and piecewise stationary, demonstrates in the context of system complexity and insufficient data the potential of linear methods for successfully characterizing ecosystem dynamics.
Simulation of Ill-Defined Systems: Some Problems and Progress
Authors: Innis George
Published: March 2008

This paper addresses some problems and progress in the develop ment of mathematical simulation models in which the mathe matical relations are not fully understood — in particular, models of biological systems. Three types of utility of models are defined, as are sharp and fuzzy laws. With these concepts in mind, models of various sizes are discussed. Modeling is analyzed from the point of view of making concepts specific, of sharpening fuzzy laws, and of producing useful results. The practical difficulties encountered when a team of experts in different fields attempt to develop a model are considered. Finally, the question of cost is addressed vis-à-vis the benefits that can accrue as a result of modeling activity.
GSL - a combined continuous and discrete simulation language
Authors: Golden D.G. , Schoeffler J.D.
Published: March 2008

GSL is a FORTRAN-oriented language which combines the activity and process concepts of a discrete simula tion language with continuous simulation concepts, thereby permitting the simulation of systems which call for combining continuous and discrete simula tion techniques. The basic structural component of GSL is the simulation block, which corresponds either to an activity of a discrete system or a dynamic re gion of a continuous system. Both discrete and con tinuous simulation blocks may have multiple process instances which may be controlled dynamically at run- time. The result is a combined language which re tains the features of both continuous and discrete simulation languages and moreover takes advantage of the desirable features of each to supplement the other. GSL syntax is described by examples which illustrate the application of the language in a typical combined simulation problem and permit the evaluation of the various features of the language.
Hybrid simulation of multicomponent chemical reactions in multifunctional catalyst systems
Authors: Buis J.P.
Published: March 2008

At the Laboratory of Chemical Technology of the Delft University of Technology, research work is carried out on problems in which multicomponent chemical reactions in a bifunctional catalyst environment are a principal element.

Study of the interrelated effects of the many system parameters, as well as the search for possible opti maZ catalyst compositions to maximize output and yield, has made it desirable to have at hand a fast simulation of the reaction system.

Hybrid computation appeared to be the logical way to meet the needs of the above Laboratory for easy man- machine interaction and high computation speed. In this report are presented the development and imple mentation of the hybrid simulation together with some of its results as realized at the Delft University Computation Centre. The hybrid model at present simulates a five-component reaction using a bifunc tional catalyst. Much effort has been invested to obtain both easy input/output and the highest possible speed of solution using an Applied Dynamics AD4, an IBM 1800, and interface equipment. How this was done is described in some detail.
Business games off the shelf
Authors: Eiloart Tim , Searle Nigel
Published: March 2008

Computer-based modelling and simulation techniques are now enjoying widespread application. Computer programs for corporate financial planning and invest ment appraisal could provide the breakthrough in gaining acceptance for computers in the business world as machines capable of more than routine clerical work. The computer time-sharing services are in the forefront in providing these programs to the user.

At present the models are being used to answer clear- cut "What if...?" questions (gut-feeling and experi ence are still needed in marginal cases). As yet, models capable of generating "optimum" solutions are still only in the research stage. Most commercial packages, however, do include sophisticated fore casting techniques, allowing the user to answer problems such as "What level of sales and monthly growth rate would be needed to double sales in three years?"

All told, the arrival of routine models for business simulation is becoming the first tentative step in delegating social decision-making to machines--per haps the real beginnings of providing computer power for the public generally.
Diagnostic simulation of a pneumatically controlled blowdown wind tunnel
Authors: Pitkin Edward T.
Published: March 2008

The nonlinear differential equations required to correctly model the plenum pressure history of a pneumatically controlled blowdown wind tunnel are derived,and arguments in favor of digital simulation of the full nonlinear equations as opposed to conven tional linearized analysis are presented. Operation aZ data for a real system are then compared to com puter-simulated data to show by example how digital simulation can be employed as a most economical and effective diagnostic tool, in this case being used to uncover the source of undesired oscillations not predicted by conventional linear analyses.
Use of the S/360 CSMP package in solving an external boundary-layer flow problem
Authors: Kumar Ashok , Cheng S.C. , Birta L.G.
Published: March 2008

External boundary-layer flow problems with constant heat flux and variable physical properties are, in general, difficult to deal with computationally. In this study, a particular problem of this type is investigated using the S/360 CSMP package. A varia tional formulation based on the concept of local potential is first applied to transform the two fundamental coupled nonlinear partial differential equations into two more-tractable ordinary differen tial equations. The study has yielded information concerning flow performance as well as information on the sensitivity of thermal conductivity and viscosity to the local Nusselt number and local friction factor. Wherever possible a comparison has been made between the results from this study and those obtained from the literature. Close agreement has been obtained in all cases. The CSMP program has proved to be a very convenient and effective tool in this study, and it is felt that the package would be equally useful in the study of similar boundary-layer flow problems.
The Club of Rome — the new threshold
Authors: Peccei Aurelio
Published: March 2008

The purpose of this note is to recapitulate the con cern and convictions of the members of the Club with regard to the present state of world society, to assess the position reached by our initial efforts, to discuss the strengths and weaknesses inherent in the nature and concept of the Club, and to enumerate some of the problem areas which we feel demand urgent investigation.
Digital and hybrid computer simulation of power systems
Authors: Carroll Dennis P.
Published: March 2008

In order to meet the increasing demand for reliable design and expansion of power networks, the use of system simulation must play a leading role in the power industry's future R & D programs. Digital com puters are already widely used in the analysis and design of large power networks. Hybrid computers offer a convenient alternative, especially where fast and accurate simulation of complex nonlinearities is required.

In this article, general principles are presented for the computer simulation of interconnected power systems. The technique discussed is directly applicable to an all-digital simulation, but emphasis is also placed on a hybrid implementation in which the transmission por tion of the system is represented digitally, while the

integration and nonlinearities associated with termi nal apparatus are represented on the analog. Example studies are performed to illustrate the technique. Results include voltage waveforms for a three-phase line energization, and the modification of switching transients by surge arresters in a single-phase system.
Magnitude- and time-scaling of state-variable equations for analog/hybrid computation
Authors: Cannon Michael R.
Published: March 2008

The programming of differential equations on an ana log or hybrid computer usually requires that the system be scaled in both magnitude and time to pre vent overloading the amplifiers and to obtain the desired speed of solution. This paper, which is tutorial in nature, presents a systematic matrix method which may be used to scale differential equa tions written in state variable format. The proce dure requires estimates of the maximum values of each computer variable, and the technique is shown to be appZicabZe to both linear and nonlinear systems. The description of the method is followed by two illustrative examples, one linear and one nonlinear, and comments on an effective rescaling algorithm.
GASP IV: A combined continuous - discrete FORTRAN-based simulation language
Authors: Pritsker A. Alan B. , Hurst Nicholas R.
Published: March 2008

GASP IV is a FORTRAN-based simulation language which provides the framework for modeling systems involving both continuous and discrete phenomena. A general ization of the definition of "event" allows for time to be advanced in a next-event fashion while permit ting a step-wise evaluation of system state variables described by difference or differential equations. Subprograms are included in GASP IV to handle the details of state and event control (including state- variable integration when necessary), information storage and retrieval, collection and analysis of data on system performance, and generation of reports and plots. In this paper, the GASP IV philosophy and modeling approach are described. Descriptions of the subpro grams included in GASP IV and the required user- written subprograms are given. The types of applica tions that have utilized GASP IV are listed. A com panion paper (beginning on p. 71) presents a detailed example of the use of GASP IV for simulating a continuous reaction process involving discrete startups and shutdowns.
Simulation of a squegging oscillator
Authors: Stollberg Richard F. , Steber George R.
Published: March 2008

This paper presents an analog-computer simulation of a circuit familiar to many radio and electronics engineers — the squegging oscillator. A relatively simple model of a nonlinear transistor is shown to be sufficient to investigate stability conditions associated with the oscillator and to accurately duplicate the phenomenon of squegging. The success of the transistor model in this application also suggests its use in other simulations involving transistors.