bluuebunny/crossref_metadata_2025_split huggingface dataset:
A demonstration hybrid computer for real-time flight simulation
Authors: Connelly Mark E. 
Published: March 2008

A hybrid, real-time simulation facility has been de signed, constructed, and demonstrated, using as a test vehicle the complete aerodynamic and engine equations for a high-performance military aircraft. The analog-digital configuration employs peripheral analog equipment to represent a linear, skeleton version of the aircraft and the PDP-1 digital com puter to carry out engine simulation, decision man agement, and corrections for nonlinear effects. To provide an all-digital reference against which the hybrid simulation could be compared, the air craft model was also simulated in real-time on the PDP-1 alone. It was found that the solution rate of 20 per second employed in the all-digital study could be reduced substantially without deleterious effects when the hybrid configuration was used. Such a re duction demonstrates that supplementing a digital computer by relatively inexpensive analog peripheral equipment greatly increases the real-time capacity of the digital computer in complex simulation appli cations. Moreover, because a number of key variables are computed continuously in the analog domain, the introduction of analog equipment results in a net decrease in the complexity of the interface.
Software for hybrid computers
Authors: McGhee R.B. , Lew A.Y. 
Published: March 2008

Efficient use of a hybrid computer for the solution of a wide variety of problems requires that the computer hardware be complemented by a comprehensive software package. Such software ought to assist not only in the preparation of programs, but in their execution as well. For open-shop operation of a hybrid facility, it is important that a widely- understood high-level procedure-oriented language be made available to users. From a practical point of view, FORTRAN and its various derivatives are the only lan guages satisfying this requirement at the present time. Expansion of a purely digital programming language into a hybrid programming language may be accomplished either by rewriting the processor or by attaching a suitable subroutine library. The software system of the System Simulation Laboratory at the University of Southern Cali fornia furnishes a concrete example of the latter approach.
The DIAN digital I simulation program
Authors: Farris George J. , Burkhart Lawrence E. 
Published: March 2008

Although DIAN can be used for almost any type of simula tion problem, it has been used most where it had a particu lar advantage over other available methods of solution. Thus, it has been used to transfer an analog problem to a digital computer when the problem grew too large for the existing facilities, where a large number of transport delays or where long transport delays were involved, and when the simulation problem was very large. The DIAN flowsheet is almost the same as an analog computer flowsheet, the coding of the input cards is straightforward, and except for a boundary value problem, no compilation is necessary. Iterative solutions of boundary value problems can be solved using DIAN and several problems can be handled sequentially in a multifile run. The use of DDA-type integrators permits flexibility in non linear function generation and output format may be var ied since the format is supplied as input information with each problem.
A computational compensation for measuring system dynamics
Authors: Mason Maughan S. , Clary George W. 
Published: March 2008

This paper is concerned with the general problem of de termining the time history of an unknown input signal, given only the recorded response of a known physical sys tem excited by the unknown input. The particular case considered is determination of true thrust from the re corded test stand response, with the physical system re sponse noise superimposed upon the thrust data. Passive or numerical filtering can smooth the trace, but these methods will attenuate the signal within a particular fre quency band, and thus may distort the data content of the recorded response. The paper describes analog computer techniques that can be used to reconstruct data distorted by such physical system response. The data may be recovered through an "active filtering" process, even when it contains compo nents of a higher frequency than the response noise being removed. Several examples are shown, including one case where the original signal was recovered intact even though the input signal excited a system resonance by passing through the natural frequency of the simulated test stand. The method described is not restricted to linear systems, but can take into account such nonlinearities as changing rocket booster mass, and nonlinear damping and spring force versus deflection relationships. The major require ment is to obtain sufficient information to permit deriva tion of a realistic mathematical model of the physical sys tem used for test and measurement purposes.
A new digital attenuator system for hybrid computers
Authors: Pracht Conrad Paul 
Published: March 2008

Digital attenuators are simple multiplying digital-to-analog converters used to replace coefficient-setting potentiome ters in modern analog/hybrid computers. This report de scribes a new digital attenuator system employing low- phase-shift miniature metal-film ladder networks. They are switched by latching reed relays which give the system a nondestructive coefficient memory even when the com puter is switched off. New digital control logic employs serial data transmission and requires only one address line per 14-bit attenuator. It permits one to set all 200 attenuators of a typical hybrid computer installation within 20 milliseconds. For maximum contact life, relay contacts are switched only when no current is flowing. The digital computer static-check routine can readily check individual relays to simplify maintenance. Particular emphasis in this report is on a digital-attenu ator system designed for a very fast repetitive computer in the Analog/Hybrid Computing Laboratory at the Uni versity of Arizona. The same design approach is readily applied to "slow" analog computers and appears to be even more advantageous there.
Educational demonstration
Authors: Soudack Avrum , Greenberg David B. 
Published: March 2008

A year has now passed since the initiation of this section, Computers in educa tion. During this time we have published articles on analog and digital simu lation in undergrad programs, on a prototype hybrid computer for undergrad use, on conducting tank and conducting sheet analogs, and on a student's research project. With the beginning of the second year of CIE, we are inaugurating a sub section of CIE entitled Educational demonstrations and experiments. The object of this section will be to present in detail upper level experiments suitable for in-class demonstrations and in-lab projects. We hope to complement the excel lent job John Evans of ACEUG is doing in publication of the ACEUG applications. A second object of our second year is to solicit and publish material from both graduate and undergraduate students. In this way, we hope to get fresh viewpoints and ideas. To continue the success of CIE, we require the interest and enthusiasm of all those concerned with the educational aspects of computers. I thus ask my colleagues to submit interesting and meaningful experiments and extend the opportunity to students who wish to express their ideas and discuss their work.
Mermaid... the development of a medium scale hybrid monitor
Authors: Anderson Tom 
Published: March 2008

In the Fall of 1965, it was decided that an existing facility of adjacent analog and digital computers would be up graded to provide hybrid computation capability. The Mermaid Monitor System, which provides the executive control functions and hybrid communications features, was developed in the very brief period during which the interface equipment was built. The initial version of Mer maid was written by digital systems programmers with no direct experience with analog computation who consulted with analog programmers with no digital or hybrid expe rience. Despite the general lack of knowledge and expe rience, the initial version was a workable monitor system which was used for over a year. Since the initial version of Mermaid was not an ideal monitor, a two-stage updating was undertaken to incor porate additional equipment and to strengthen Mermaid's capabilities in the area of hybrid inputloutput. On com pletion of this development cycle, the system will be com pletely disk oriented, and it will provide a maximum of convenience in programming for hybrid applications.
Optimization by parameter-perturbation correlation
Authors: Gonzalez Robert , Muterspaugh Milo 
Published: March 2008

This paper describes a simple method of steepest-descent optimization of a criterion functional F(α1, α2,...) depend ing on the state variables y i(t;α1,α2,...) of a dynamic system with design parameters α 1, α 2.... The system is simulated on a fast analog computer and the parameters are given mutually orthogonal sequences of binary pertur bations during successive computer runs. Simple correla tion of each parameter perturbation with the criterion functional value at the end of each computer run yields ap proximations for the gradient components ∂ F/∂α k needed for steepest-descent optimization with a minimum- of dig ital logic. As an example, two- and three-parameter model- matching problems are solved by iterative computation at 1000 iterations per second. A course term-paper for first-year graduate students
Four-gimbal systems for simulation display
Authors: Wilson John W. 
Published: March 2008

The utility of a four-gimbal system for positioning two reference frames with respect to each other without gim bal lock has long been recognized. As early as 1954 such a system to isolate an inertial platform was proposed by Arnold and Schlesinger1 . However, the exact law for driving the fourth angle has been a question. The situa tion had not improved through 1962 where, in Reference 2, "gimbal flip" (an instantaneous rotation of 180 de grees in two axes, similar to the three-axis gimbal be havior at gimbal lock) appears as an inherent part of the fourth angle's driving law. Clearly this behavior is not desirable for platform isolation or visual display systems used for vehicle motion cues in simulation. This paper describes developments made at Langley (NASA) in the last several years. A driving law for the fourth angle is developed for two different four-gimbal systems. The first is similar to the gimbal systems de scribed in References 1 and 2 and has advantages in design and implementation for platform isolation. The second is specifically designed to minimize occlusion in visual display systems3. In each system, the fourth angle driving law is a direct consequence of maximizing the angle between the two axes causing the singularity. Thus, a necessary differ ential constraint is found to maintain a nonsingular solu tion. A sufficiency condition for a nonsingular solution is also found. The second four-gimbal system that mini mizes occlusion has the interesting result that the maxi mum angle between the singularity-forming axes is not always 90 degrees.
Mathematical programming in economics by physical analogies
Authors: Franksen Ole I. 
Published: March 2008

This article is the third of a series of three in which we establish and solve a physical analogy of the economic model underlying mathematical programming. In the third article the concept of equilibrium is de rived from the basic notion of a static mechanical system at rest, and it is shown how, by refining this concept, it can be extended to dynamic physical systems. In this process it is also explained why an extremum value of a state-function determines an equilibrium state of a system. From an economic viewpoint the physical concept of equilibrium is identified with that of a perfectly competi tive market, and it is demonstrated how this concept dif fers from the equilibrium concept of a monopolist. For comparison, industries with one and two outputs are considered. From a mathematical programming viewpoint both linear and quadratic problems are discussed in terms of methods of classical mechanics. In particular it is shown that the simplex method can be derived from Fourier's inequality for equilibrium on a boundary and that the Kuhn-Tucker conditions are statements analogous to Kirchhoff's mesh law for an electrical network.
A decision procedure for selecting among proposed automatic analog computer patching systems
Authors: Gracon T.J. , Strauss J.C. 
Published: March 2008

In the recent literature, a paper1 and a contract report2 indicate that automatic analog computer patching sys tems have become economically and technologically feasible. In anticipation of the development of a variety of proposed patching systems, a specific decision pro cedure is developed for the rational evaluation of com peting automatic analog patching systems. The design procedure described in this paper facilitates selection of the patching system best suited for a partic ular computer and a particular problem class. Sufficient information is abstracted from a typical problem set to determine the number of relays required for (and thus to assign a cost figure to) each possible patching system without requiring the actual design of each system. Nom inally, the best system is that with the lowest cost figure. It is recognized, however, that there are many subjective decisions (e.g., captive vs. free pots) involved in the de sign process that are not quantified in this overall cost figure. This problem is met in part by providing inter mediate information relating to the optimal module size, combinations of proposed systems, etc. to help estab lish some of the sensitivity properties of the optimal system. The procedure is illustrated by applying it to a particu lar case and evaluating a number of alternative switching systems.
A general purpose digital traffic simulator
Authors: Blum A.M. 
Published: March 2008

The described vehicle traffic simulator is designed to fa cilitate analysis of traffic flow and to experiment with postulated traffic control systems. It offers users a large amount of flexibility in specifying network, intersection, vehicle, and control parameters. The logical flow of ve hicles, as well as much of the control system, is prepro grammed. Vehicles varying in size may change lanes, turn, change velocity (including reaction and acceleration delays), and merge. Input volumes may be varied, turns may be eliminated, and vehicles may be routed through the network. The user supplies the geometrical character istics and input information unique to his particular net work in data cards for the program. Some applications to real traffic networks (including a validation procedure) and a simple control experiment are discussed. The model, programmed in a special version of GPSS II and in FAP for the IBM 7090/94 systems, can be used in the simulation of single intersec tions, arterial routes, grid networks, and, for some special cases, limited access roadways.
The translation and docking simulator
Authors: Williams Wayne K. 
Published: March 2008

This article describes the Translation and Docking Sim ulator (TDS) used to support the Gemini as well as the Apollo space flight programs. The simulator was origi nally conceived, designed, built, and operated as a Gem ini simulator. The six-degrees-of-freedom relative mo tion of the crew station was simulated with an actual out-the-window view of docking and with the actual spacecraft controls as major parts of the simulation. Then at the conclusion of the Gemini program, the simulator was modified to simulate the Lunar Module (LM) active lunar orbital docking with the Command and Service Module (CSM) for the Apollo program. A LM crew station replaced the Gemini as the active vehi cle, and a CSM mockup replaced the Agena as the pas sive, or target vehicle. Again, primary attention was given to simulation of the out-the-window view of dock ing and to controls in the crew station. Typical opera tions consist of one-hour to one-and-a-half-hour train ing sessions. During the session lighting configurations are varied and system malfunctions are simulated. In the Gemini and Apollo programs docking is ac complished by a crew member using onboard maneuver ing systems while relying on his own judgment of relative positions and rates as determined by viewing the target vehicle through a spacecraft window. To develop the skill required, crew members have used several training devices, one of which is the TDS.
General management simulations: an approach for the seventies
Authors: Hodgetts Richard M. 
Published: March 2008

The great surge of enthusiasm and research in gaming during the sixties provided us with some of the most sophisticated general-management simulations ever. In the seventies we will undoubtedly witness even more interest in these games. However, the value of many of them is questionable because: (a) the time needed to memorize mechanistic rules is excessive and (b) the difficulty in interpreting feedback leads to an inability to draw cause-effect relationships. If these games are to be of real value we need more emphasis in game design upon giving the participants data that can be analyzed, cause-and-effect relationships that can be determined, and situations in which intelligent strategy can be devel oped. In short, less doing and more thinking. The concept of Key Equations as used in TOP MAN AGEMENT SIMULATION, a general management game developed at the University of Nebraska, may serve as a model for these games during the seventies.
Simulation of the evolution of stellar systems
Authors: Hohl Frank 
Published: March 2008

Computer models for isolated disk galaxies and for infi nite doubly periodic stellar systems are used to study the self-consistent motion of large numbers of interacting stars as they move in the plane of the galactic disk. The doubly periodic model is used to investigate the develop ment of the gravitational instability for a plane stellar system. The results obtained show that the initial con densations which form are about two Jeans lengths in diameter. An isolated, initially cold, balanced disk is found to be violently unstable. Adding a sciffcient amount of ve locity dispersion will stabilize all small-scale disturb ances. Most disks investigated are found to be unstable against slowly growing long wavelength modes, and after about two rotations the disks tend to assume a bar- shaped structure. It is also found that the final mass distribution for most disks can be closely approximated by an exponential variation irrespective of the initial mass distribution.
Time path of total society systems — the case of US society (1951—1972)
Authors: Rastogi P.N. 
Published: March 2008

This paper seeks to structure the problem of mea surement and prediction in total society systems. A macrosociological model comprising a limited num ber of variables is developed and applied to five diverse societies of the globe - Brazil, France, India, Nigeria and the USA. The rationale of the model and the methodology are provided by cyberne tic concepts; it permits making qualified predic tions. The model that is developed can be run for ward or backward in time. In the latter use the results of the simulation were compared with available official data for prior years, and the agreement was found to be generally good. The performance of the model is illustrated here with particular reference to US society for a period of over two decades. In the simulation the time path of a society consists of its viability status (Z)GS and essential variables as functions of time. The predictions obtained by running the model forward in time depend for their validity on the fit of the simulation to historical data when time runs backward. For 1972 and the USA, this applies particularly to empirical variables like government change, economic growth, price rise, and unemployment. The generality and validity of the model are reinforced by the con sistent results obtained for the other four societies (which differ markedly from the USA) when the model for them is run backward in time. The model encompasses exogenous pressures, internal system processes, and endogenous events. The latter are interpreted as processes extended in time.
Digital simulation of the rotation of a moving triad with a known matrix spin vector
Authors: Massoud M.F. , Youssef Y.A. 
Published: March 2008

This paper discusses the numerical evaluation of the elements of the transformation matrix of an orthogonal rectilinear triad moving with respect to a similar fixed system, when the former rotates with a known spin vector. Typical governing equations are formu lated in terms of Euler angles, in terms of quater nions, and in terms of direction cosines and their derivatives. Emphasis is placed on the latter formu lation for solution by digital computation. The governing equations are reformulated into a homogeneous and linear matricial state variable equa tion of the first order, with a skew symmetric coefficient matrix called the rotation operator. The transition matrix of this state equation gives the required rotation matrix. The characteristics of the skew-symmetric matrices are used in the development of a suitable algorithm for the solution. The exact rotation matrix can be obtained for cases of constant spin vector and for special cases of variable spin vectors. For the general case of a variable spin vector, a discrete-variable numerical solution based upon a mean coefficient value is used. The algorithm is based upon a recursive formula giving the elements of the rotation matrix at any arbitrary value of the independent variable. Errors resulting from the use of this method are compared (for a particular example) with those resulting from a fourth-order Runge-Kutta integration algorithm. The state equation for systems of higher degrees of free dom is discussed.
Advanced nuclear-reactor simulation techniques
Authors: Jimenez R.F. , Benham R.D. 
Published: March 2008

This paper presents the single-point kinetic and thermodynamic equations for nuclear reactors which are typically used in safety-analysis studies. The studies here reported were performed on 4K PDP 8 and the larger PDP 11/20 computers with Interactive SimuZation Language (ISL). The parameters of a former LOFT1 reactor design are used, but the delayed-neutron fractions and decay constants are taken from a paper by Albrecht and Metelmann.2 Simulations are made for six, three, two, and one delayed neutron group for a startup accident. The purpose of the runs is to show the effect of simplifying assumptions on accuracy and on the speed of computer processing. The results show that speed can be increased by a factor of 20 without seriously affecting accuracy. At these speeds, it is possible to simulate the nuclear system five times faster than real time on a PDP 11/20 computer. With extra hardware such as a mul/div unit or a floating- point processor, additional speed is possible.
A new general-purpose nonlinear component for multivariable function generation for hybrid computers
Authors: Rubin Arthur I. 
Published: March 2008

This paper is divided into three main sections which 1. Cover the historical significance of multivaria ble function generation to analog and hybrid computation 2. Describe a new high-speed Multivariable Function Generator (MVFG) for hybrid computation 3. Conclude with a discussion of possible applica tion of the MVFG for general computing use.