bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Mathematical Model of Short-Term Memory
Authors: Adey W. Ross , Findler N.V. 
Published: March 2008

It is attempted in this paper to give a mathematical description of the short-term memory. Instead of using the microscopic properties of individual neu rons, such as the number of interconnections, neuron density, threshold value, etc., the cerebral cortex is regarded as a "neuron gas" that is a vast conglomer ate of neurons with statistically distributed charac teristics. Stimuli from the environment cause the receptor neurons to emit virtual electromagnetic waves into the brain. A self-optimizing process of the brain tis sue is here described by which the useful, informa tion-carrying energy reaching the long-term memory tends to maximum. It is emphasized that in the following a brain model is described and the physical processes in volved may have no direct equivalent in reality.
The DES-1A New Digital Computer for Solving Differential Equations
Authors: Levine Leon 
Published: March 2008

The DES-1 is a new digital computer system, espe cially designed for the solution of ordinary differ ential equations. The major components are (1) the SDS 9300, a high-speed digital computer, ( 2) a mathe matical operator language, and (3) a console. The mathematical operator language is analogous to the computing elements of the analog computer. Thus both the DES-1 and analog computer can be programmed the same way (although the DES-1 has several more operations). Consequently an analog computer operator can learn to program the DES-1 easily and can use much of the programming expe rience acquired on the analog computer. Further more, the use of floating-point arithmetic eliminates all need for amplitude scaling. The console provides rapid communication between the operator and the DES-1 and allows problem mode control and changes even as the com putations are being made. Some of the modes are RESET, OPERATE, and HOLD, while typical changes include parameters, initial conditions, and even equa tion structure. The DES-1, therefore, combines the advantages of the digital computer 1. Accuracy 2. Reliability 3. Ease of program and data storage 4. Ability to perform algebraic operations with those of the analog computer 1. Convenience of programming through use of the mathematical operator language 2. Rapid communication between operator and computer to produce a computer which has advantages over both conventional analog and digital computers in solving differential equations.
Using Pontryagin's Maximum Principle to Solve One-Dimensional Optimization Problems, with and without Constraints, on an Iterative Analog Computer
Authors: Steinmetz Hans L. 
Published: March 2008

An analog computer technique is presented which enables application of Pontryagin's maximum prin ciple to the problem of optimizing control systems. The key problem in using Pontryagin's maximum principle is the extremization of the Hamiltonian function at every instant of time. Since the analog computer is an excellent differential equation solver, it is of advantage to convert this task into a dynamic problem. The technique used to do this is based upon the steepest ascent method. The method is applied to a one-dimensional control problem; higher-di mensional control problems can be treated using the same approach. The argument that an analog computer can solve differential equations with only one independent variable, corresponding to machine time, is true only in a technical sense. In practice it is feasible for cer tain types of problems to integrate one set of differ ential equations sufficiently fast enough so that, while integrating another set of differential equations at a much slower rate, the solution error associated with this approach remains within acceptable limits. When using the analog computer in this way, one time domain always corresponds to the solution time required for solving the differential equations de scribing the system; a second time domain corre sponds to the solution time required for solving an auxiliary set of differential equations which has no direct relationship with the system. Technological improvements and innovations made in the analog computer field during the recent past have contributed to the successful application of this approach.
Study on time-shared analog computation technique
Authors: Miura Takeo , Iwata Junzo 
Published: March 2008

Methods of time-sharing computing elements or cir cuits to achieve economy in analog computing are studied. The conventional method of time-sharing is to scan inputs and outputs with synchronized switches and to hold the computer solutions after each scan ning. This method is practical only when the scanning interval is short enough compared to the period of solution to reduce error to an acceptable level. The method presented here allows elimination of hold circuits and keeps good accuracy even with long scanning intervals. In particular, this method is shown to be without phase lag, and this is confirmed by experiments. For the conventional method, the equivalent dead time (the predominant source of error) is calculated, and several compensation techniques are presented. Comparisons of all these methods are also made.
Analog simulation of Hanford dual-purpose reactor plant
Authors: Coughren K.D. , Swanson C.D. , Thieme G.G. 
Published: March 2008

An analog simulation of the dual-purpose Hanford N-reactor was undertaken.1 Studies were performed to determine the dynamic characteristics of the plant and to determine the effects of possible plant, oper ator, and control-system malfunctions. Various op erational procedures and proposed design changes were also studied. The simulation of the reactor plant was made up of a series of subsystems which were coupled to gether. Each subsystem had been studied in detail previous to being assembled into the total reactor plant simulation.
Pulsed prediction filters applied to digital and hybrid simulation
Authors: Matlock David L. 
Published: March 2008

The increasing use of digital computers in the simulation of dynamic systems presents a number of new problems. In particular, the inclusion of a digital computer in a predominantly analog environment introduces time base problems. The digital computer appears to the analog circuitry to be a particular pulsed filter. Time delays due to sampling, computation, and output appear dynamically as ideal transportation delays. The effects of time delays1 can be compensated for at the digital-to-analog or analog-to-digital interfaces by either analog2 or digital lead filters. Considerations with respect to problem constraints and the available equip ment dictate where and by what means the compensation is to be mechanized. Problem constraints involve the num ber of variables to be interfaced, the characteristics of the variables to be predicted (i.e., not highly nonlinear or dis continuous) and the effects of prediction errors on the variables. Digital simulation of a system of equations usu ally results in a higher order system of difference equations. The attendant problem of stability and attenuation or am plification of prediction errors may make compensation at the D/A interface more desirable. Equipment availability in terms of amplifiers, computation time and the number and type, sequential or parallel, of converter channels in fluence the choice of analog or digital filters. The purpose of this paper is to apply both classical numerical analysis methods and phase and gain error cri teria to the problem of digital time prediction. A modified maximally flat phase criterion is applied to prediction co efficients to illustrate a filter used in a common simulation problem. Finally, phase and amplitude curves are included to show the advantages of the derived filters for simulation purposes as compared to classical polynomial extrapola tion.
Digital simulation of paper machine dynamics
Authors: Sullivan P.R. , Schoeffler J.D. 
Published: March 2008

This paper presents a technique for simulation of the stock preparation and Fourdrinier dynamics which is flexible, convenient, and detailed enough to allow the user to study physical process modifications and transient response dur ing upsets and "furnish" (fibers with different character istics, fillers, dyes, etc.) changes and to evaluate simplified mathematical models and control schemes. The technique uses digital simulation in a block diagram form, each block of which corresponds to one type of physical unit in the process (e.g., cleaner or tanks). Simu lation of a particular process then involves specification of the particular parameters of each physical unit together with the way in which they are interconnected. Individual components of the furnish may be traced through the whole process. A complete wet-end configuration, including the white water recovery system, is simulated using the technique described in the paper, and typical results obtained during grade changes and disturbances are presented.
A hybrid computer technique for power spectrum analysis
Authors: Thomas Lee C. 
Published: March 2008

A technique is presented by which the power density spectrum of an analog computer waveform may be meas ured to a specified amplitude precision and frequency resolution. The procedure involves sampling the wave form, storing the samples in a digital computer, and dig itally computing the autocorrelation function and the cosine transform of the autocorrelation function to yield the power spectrum. The theory required for selection of the parameters of sampling and computation is presented as are the required methods of data smoothing and proces sing. A description is given of an application of the tech nique to the design of a solid-state frequency multiplier. The computational system is designer-controlled and is capable of giving rapid indications of the effect of changes in the process being simulated on the analog computer.
Optimization using a remote control console for a digital computer
Authors: Kirby D.B. 
Published: March 2008

A general-purpose optimization program, using the meth ods of steepest descent and multidimensional Newton- Raphson, has been developed for the IBM 7094. The program can be used independently or as part of a man- machine optimization system in which the engineer can quickly appraise the effect of changes in problem param eters. Man-machine interaction at a remote location is provided through an experimental console which con sists of a Packard-Bell PB-250 computer and associated input-output equipment. The program and equipment configuration used for interaction will be described and an example of network optimization using this system will be presented. An optimization scheme which is designed for a digital computer offers a more sophisticated strategy and better accuracy than a scheme designed for an analog computer. The current interaction system is of limited form; never theless, work done with it has aided in defining the ob jectives for a more flexible man-digital machine interac tion system.
Solution of optimal control problems on a high-speed hybrid computer
Authors: Maybach Richard L. 
Published: March 2008

This paper presents a method for finding the solutions to minimum-time optimal control problems. The procedure is to implement Pontryagin's Maximum Principle on an iterative hybrid computer. The state and adjoint equations as well as the control law are simulated using conven tional analog components. The troublesome two-point boundary-value problem, which is always associated with Maximum Principle, is solved by iteration, using a digital parameter optimizer. Thus, a manual trial-and-error search for the proper initial values of the adjoint variables is un necessary. We show that, for a large class of systems, it is not necessary to generate the Hamiltonian, because the neces sary condition that it normally must satisfy is redundant. This allows many problems to be greatly simplified. We also present an optimizing routine that solves the boun dary-value problem. This permits the proposed method to be used on any hybrid computer that incorporates a general-purpose digital computer. The solutions to two problems show that the proposed method is feasible. Average convergence times range from less than one second to about 70 seconds. These vary with the initial conditions on the state variables. The examples were solved using ASTRAC II, a small (40 amplifier), high speed (up to 1000 solutions per second), iterative hybrid computer with only modest component accuracy (0.25 per cent). Although the discussion and examples are limited to a minimum-time performance index, the method is easily extended to cover other criteria.
Hybrid-oriented Simulation programs
Authors: Dames R.T. 
Published: March 2008

Both existing and newly proposed digital analog simulator programs have a rather minimal hybrid orientation. This lack of emphasis is attributed to the numerous types of analog interfaces and the various "modi operandi" of different installations. Nevertheless, it is ironic that the hybrid user, who seems to have received the least software attention, is yet frequently the one who could use it most. The intent of this paper is to point out at least two direc tions in which the hybrid user might extend a simulator program. The extensions, either as proposed or in modified form, would tend to simplify several hybrid programming tasks.
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.
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.
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.
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.
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.
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.
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.