bluuebunny/crossref_metadata_2025_split huggingface dataset:
The simulation of structural and thermal systems via flow graphs
Authors: Feeser Larry J. , Feng Chuan C. 
Published: March 2008

This paper presents a study of simulation of structural systems and heat flow problems by use of oriented flow graphs. Linear elastic structural systems are transformed into graph representation using two kinds of parametric analyses. In one case, flexibility parameters of structural components are used as branch transmittances of the or iented graphs, and geometric displacements are the ex ternal sources or inputs to the graph. In the other ap proach, stiffness coefficients as graph transmittances and unbalanced residual loads as source inputs lead to relax ation operations which can be represented by feedback analysis. Each of these approaches is the dual of the other in a topological sense. Two-dimensional problems governed by the Laplacian partial differential equation are solved by using first-order central difference analysis to transform the governing equation into an oriented graph. The graph networks of physical systems of this type can be constructed by in spection of the mesh network without recourse to the difference equations. Initial boundary values are treated as independent source inputs to the graph. A solution of the steady-state heat flow in a thin plate is presented. The simulation of physical systems by oriented flow graphs treats the system as an entity in which the physical characteristics are transformed topologically into graph representations. Oriented graphs are essentially analog setups from which numerical results can be obtained by analog computers. If use is made of the loop-rule equa tions of graph theory, efficient use of the digital computer is indicated. The nature of design of structural systems is complex because of the range of parameters to be con sidered and because of required accuracy. Flow graph simulation can give information on the effect of variation of parameters by way of sensitivity analysis and can be an aid in the study of design.
Microwave radar and electronic environment simulator
Authors: Katsura Tomio 
Published: March 2008

A facility capable of direct synthesis of radar systems and their electromagnetic environments operating concurrently with missile flight simulations, range instrumentation sim ulations, and related test-range experiments has been needed for many years. This paper describes the design, development, and ap plication of a general-purpose Radar and Electromagnetic Environment Simulator operating under the combined control of digital and analog computers. This simulator is one of the more recent developments of the Analyses and Computation Directorate, White Sands Missile Range. In this system the combined operation of computers and microwave hardware is utilized to create realistic dynamic radio-frequency environmental effects based on time de lay, doppler shift, and RF-signal-power equations com bined with simulated radar and missile flight geometry dynamics and kinematics. Associated radar antenna pat terns, target backscatter patterns, clutter, and other target- induced RF phenomena are included. The simulator includes a flexible system for simulating RF signal generation and receiver signal-processing and provides a broad range of adjustment of radar parameters. The simulated transmitter signals are propagated through the computer-controlled environment simulation and are received and tracked by the receiver signal-processing equipment as in normal radar operations. Prototype radar subsystems and components, tracking beacons, jammers, counter-countermeasure receivers, and many other devices can be coupled into the simulator to be studied within the confines of the simulation laboratory.
A modified Runge-Kutta method
Authors: Chai A.S. 
Published: March 2008

It is possible to replace k2 in a 4th-order Runge-Kutta for mula (also Nth-order 3 ≤ N ≤ 5) by a linear combination of k1 and the ki's in the last step, using the same procedure for computing the other ki's and y as in the standard R-K method. The advantages of the new method are: It re quires one less derivative evaluation, provides an error estimate at each step, gives more accurate results, and needs a minor change to switch to the RK to obtain the starting values. Experimental results are shown in verification of the for mula.
Techniques for the design of linear digital simulations
Authors: Gagné R.E. , Baxter D.C. 
Published: March 2008

This paper presents an operational approach to the design of digital simulations of linear dynamic systems which allows the design to be carried out using concepts familiar to the engineer. Traditional evaluations of numerical ap proximations to continuous operations are generally diffi cult to interpret in the engineering environment, and the operational approach presented allows discrete system evaluation using more familiar methods. A method of digital modeling is derived which allows the digital transfer function of the discrete model to be obtained directly from the transfer function to be simu lated. From this digital transfer function can be obtained information on stability, frequency response, transient response, root mean square modeling error, as well as the numerical algorithm itself. The method is illustrated by examples of the digital simulation of several linear systems using several traditional numerical integration algorithms.
Digital simulation of space missions for Monte Carlo analysis
Authors: Mullin Frank J. 
Published: March 2008

This paper describes a set of computer programs devel oped for Monte Carlo analysis of a complete space mis sion. The results of such an analysis are used in mission planning (for example, in the determination of how various errors affect the trajectory, midcourse-correction fuel re quirements, and other parameters). In Monte Carlo analysis, a sample mission is simulated a large number of times, with the various stochastic pa rameters assuming different random values for each run. The resulting data is then processed statistically to yield useful probabilistic statements regarding output param eters of interest. Three programs are described. The first derives, edits, and formats the input data required for simulation of a particular mission. The second is the simulation proper, generating a set of output parameters for each run. The third program processes the data from the simulation to derive the required statistical error-analysis data. The first and third programs are relatively straightforward and are briefly described; the simulation is described in more detail. In general, the simulation operates by ordering all the events of the mission and using a set of standard mathe matical descriptions called PROP boxes to compute the state vector at the end of each event from its state at the beginning of the event. It uses the deviations of the pa rameters from those of a reference trajectory rather than the values of the parameters themselves, thereby simplify ing the mathematical treatment and reducing the comput ing time by orders of magnitude.
Mathematical programming in economics by physical analogies
Authors: Franksen Ole I. 
Published: March 2008

This article is the first of a series of three in which we establish and solve a physical analogy of the economic model underlying mathematical programming. Basically, the first article is a reexamination of the fundamental assumptions underlying quasi-static models in economics and engineering, with a view to the estab lishment of a conceptual framework common to both disciplines. At the microscopic level it is demonstrated that the assumptions of perfect competition can be cast in a form analogous to the one used in statistical physics. At the macroscopic level it is shown that measurements in economics and physics can be classified in identical manners with the result that derived relationships, like Ohm's law and demand curves or electric power and total revenue, can be made analogous concepts. On this basis it is then asserted that underlying economics we find two basic laws which, apart from a single change in sign, are completely analogous to the well-known first and second laws of thermodynamics.
Mathematical programming in economics by physical analogies
Authors: Franksen Ole I 
Published: March 2008

REVIEW OF PART I AND PREVIEW OF PART II This article is the second of a series of three in which we establish and solve a physical analogy of the economic model underlying mathematical programming. Basically, the first article (published in SIMULATION last month) was a reexamination of the fundamental assumptions underlying quasi-static models in economics and engineering, with a view to the establishment of a conceptual framework common to both disciplines. At the microscopic level it was demonstrated that the assumptions of perfect competition can be cast in a form analogous to the one used in statistical physics. At the macroscopic level it was shown that measure ments in economics and physics can be classified in iden tical manners with the result that derived relationships, like Ohm's law and demand curves or electric power and total revenue, can be made analogous concepts. On this basis it was then asserted that underlying economics we find two basic laws which, apart from a single change in sign, are completely analogous to the well-known First and Second Laws of thermodynamics. The present article is primarily a reformulation of the Walrasian economic model, which underlies mathemati cal programming, into an analogue electrical network. In accordance with the tradition of physics, the Wal rasian system of equations is derived from the postulates of the First and Second Laws of economics. The advan tage of this approach, which differs from conventional economic expositions, is that it permits a nearly auto matic establishment, term for term, of the corresponding electrical network model. The constraints and state-functions of the electrical analogue are formulated by modern network techniques in order to separate, in the economic formulation of the Walrasian system, the analytical aspects from those more general aspects which are involved in the design of an economic production system.
Sampling errors in closed-loop hybrid computer programs
Authors: Hammond Joseph L. , Alford Cecil O. 
Published: March 2008

This paper applies a previously derived equation for sampling error in hybrid systems to the case of hybrid computer systems which use first-order analog hold de vices. Explicit expressions for sampling error are ob tained for a general hybrid computer program and for several classes of programs corresponding to particular cases. The equations apply for most types of hybrid com puter operation including the case for which the digital computer is used to integrate one or more of the prob lem equations. The error equations are used to examine the effect of various allocations of computing operations, both in general terms and through use of a particular example. The results, while providing no new insight into gross effects, give quantitative relations which sharpen intui tive guidelines for programming a hybrid computer. The equations place in evidence the following facts which are not apparent from a qualitative study: (1) The major components of sampling error depend on the first power of the sampling period, making the hybrid computer a first-order numerical method. (2) Digital execution time has an effect on error which is similar to that of the sampling period, but is weighted twice as heavily. (3) A numerical integration method in the digi tal computer produces negligible error in relation to other error sources if it is of order 2 or higher.
Hybrid computer simulation of xenon spatial oscillations
Authors: Wozny M.J. , Bartells P.S. , Bailey R.E. 
Published: March 2008

This paper is concerned with a hybrid computer simulation of the space-time xenon oscillation problem. Such prob lems are important in large thermal nuclear power reactors. The basic nuclear reaction is modeled by three slightly nonlinear partial differential equations-a diffusion equa tion describing the neutron flux concentration, and two first-order partial differential equations which contain only partials with respect to time and which describe the gen eration and decay of iodine and xenon. The continuous-space discrete-time approximation is used to implement the equations on the hybrid computer. By discretizing the time variable the xenon and iodine equations are reduced to algebraic expressions and the flux equation is reduced to a boundary value problem. The algebraic equations are decoupled from the boundary value problem and, therefore, solvable on the digital computer, by invoking the assumption that the nonlinear flux terms change slowly with respect to the time step. This assump tion also simplifies the boundary value problem which is solved on the analog computer in conjunction with digital function storage. The simulation effectively displays the space-time xenon oscillatory behavior resulting from an initial spatial per turbation of the flux shape. This information is used to study the stability of the local changes in the xenon con centration and, hence, the spatial variations of reactivity in the core.
On the simulation of distributed parameter systems
Authors: Schuchmann Heinz 
Published: March 2008

This paper presents analog, hybrid, and digital simulation techniques for one-dimensional flow, diffusion, and wave- type systems. These techniques also provide the basis for the simulation of more complex distributed-parameter systems. Many of the techniques considered are well known; however some of them are just recently devel oped. The various techniques result from either discretiza tion and transformation of the original partial differential equations or from application of the method of charac teristics. From this point of view, it is possible to fit the techniques into a general framework. It will be indicated by means of the properties of each technique which type of computer will best implement it and which system can be treated by it most advantageously.
Hybrid computation in the university
Authors: Strauss Jon C. , Greenberg David B. 
Published: March 2008

One of the primary goals of the Carnegie-Mellon University Hybrid Computation Laboratory has been to study hybrid computation per se, from both an application and automation viewpoint. To date, the work has concentrated on automation of hybrid computer programming and on methods for solving partial differential equations. During the course of the design, installation, and operation of its hybrid computation laboratory, CMU has obtained a wealth of experience (both objective and subjective) with the use of hybrid computation in the university environment. In light of growing univer sity interest in hybrid computation, this article describes the experience of CMU and presents certain conclusions concerning the appropri ateness of university use of hybrid computation.
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.
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.
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.
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.