Special Purpose Analog Computer Research Articles

Chaos from switched-capacitor circuits: Discrete maps

A special-purpose analog computer made of switched-capacitor circuits is presented for analyzing chaos and bifurcation phenomena in nonlinear discrete dynamical systems modeled by discrete maps x <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n + 1</inf> = f(x <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> ) Experimental results are given for four switched-capacitor circuits described by well-known discrete maps; namely, the logistic map, the piecewise-linear unimodal (one-hump) map, the Hénon map, and the Lozi map.

Nonlinear programming without computation

Using the Kuhn-Tucker conditions from mathematical programming theory, a canonical nonlinear programming circuit for simulating general nonlinear programming problems has been developed. This circuit is canonical in the sense that its topology remains unchanged and that it requires only a minimum number of 2-terminal nonlinear circuit elements. Rather than solving the problem by iteration using a digital computer, we obtain the answer by setting up the associated nonlinear programming circuit and measuring the node voltages. In other words, the nonlinear programming circuit is simply a special purpose analog computer containing a repertoire of nonlinear function building blocks. To demonstrate the feasibility and advantage of this approach, several circuits have been built and measured. In all cases, the answers are obtained almost instantaneously in real time and are accurate to within 3 percent of the exact answers.

Electrical network analogue for determining the optimal flows in multiterminal communication networks

An electrical network model of a multiterminal communication network is described which can be used as a special-purpose analogue computer to determine the optimal distribution of information flow. It provides an alternative to digital-computer methods for which the computation time increases very rapidly with increasing network complexity, and which are therefore impractical for large networks.

Simulation for training and decision-making in large-scale control systems

The present generation of special-purpose computer hardware for power-system trainers consists of a hybrid computer comprised of a general-purpose digital computer and a special-purpose analog computer. These hybrid simulators use analog models of generators, transmission lines, loads, etc., and they provide training experience in performing such procedures and functions as load following, intrapool exchanges of power, reconfiguration of systems for maintenance, voltage control, load shedding, and other emergency procedures, economic dispatch, fast generation pickup, and coping with incomplete or distorted information during a simulated blackout episode. The history of simulator use is discussed, along with present day hardware and software and future trends. 5 references, 1 figure, 1 table.

Use of a model for simulating individual aortic dynamics in man

A simulation model is suggested for the analysis of aortic dynamics in man. The aortic model consists of six segments and is part of a larger model of the closed-loop human circulation. The model is simulated on a special-purpose analogue computer. Three parameters are employed to characterise the arterial system; peripheral resistance, aortic compliance and peripheral damping. Using a method for adapting the model to the individual patient, measurements of aortic pressure, cardiac output and pulse transmission time from 29 patients were used to test the validity of this approach. The model is able to simulate the pressure course along the aorta satisfactorily. The compliance calculated from the transmission properties of the aorta was compared with the complicance calculated from the stroke volume and pressure pulse. An adequate correlation (r=0.98) was found between these two independent methods. The mean compliance of the total aorta was 0.6 ml/mm Hg at a mean pressure of 104 mm Hg. The compliance showed large individual variations and decreasing values with increasing age of the patient. It is concluded that the model enables simulation of the individual aorta.

An inexpensive blood pressure-heart rate computer for laboratory or teaching use.

A special-purpose analog computer circuit is described that, given a signal proportional to arterial blood pressure, generates signals equal to systolic, diastolic, pulse, and mean pressure at a calibration of 100 mmHg/V. Heart period and rate are also derived at calibration of 1 s/V and 100 bpm/V, respectively. The outputs are step-function beat-by-beat changes in these six variables suitable either for analog recording, or presentation to a panel meter for digital display.

An analog computer for calculating the shunt impedance of a resonant cavity

We have developed a small, special-purpose analog computer for automatically calculating the shunt impedance of a resonant cavity from phase-shift perturbation data. Accuracy is limited by the size of the perturbing bead and precision is about 2% for a fixed experimental configuration.

The precision of a special purpose analog computer in clinical cardiac output determination.

Three hundred dye-dilution curves taken during our first year of clinical experience with the Waters CO-4 cardiac output computer were analyzed to estimate the errors involved in its use. Provided that calibration is accurate and 5.0 mg of dye are injected for each curve, then the percentage standard deviation of measurement using this computer is about 8.7%. Included in this are the errors inherent in the computer, errors due to baseline drift, errors in the injection of dye and acutal variation of cardiac output over a series of successive determinations. The size of this error is comparable to that involved in manual calculation. The mean value of five successive curves will be within 10% of the real value in 99 cases out of 100. Advances in methodology and equipment are discussed which make calibration simpler and more accurate, and which should also improve the quality of computer determination. A list of suggestions is given to minimize the errors involved in the clinical use of this equipment.

Simulation in the Teaching of Concepts of Respiratory Gas Exchange

Summary The study of pulmonary gas exchange involves understanding factors which influence the performance of a complex non‐linear system. Experimentation with a realistic simulation gives the student insight which is very difficult to obtain by conventional teaching methods. A dynamic model of carbon dioxide transport has been developed and implemented on both a special purpose analog computer and a digital computer. The special purpose analog computer has significant advantages for this application.

A Direct-Reading Colorimeter for Color-Television Picture Tubes

An instrument for measurement of color of cathode ray tube screens has been developed and evaluated. It consists of four filters and photocells coupled to a special purpose analog computer with readout directly in C.I.E. x and y on a pair of digital panel meters. Accuracy is within one percent of the spectroradiometer used for calibration. Possible future developments and applications include set-up and tracking white on color receivers, measurement in terms of C. I. E. uniform chromaticity system and, perhaps, incorporation of direct readout in brightness.

An analogue device for measuring the pre-ejection period (PEP).

A special purpose analogue computer for beat by beat determination of the pre-ejection period of cardiac systole is described.

The Computer Application for the Metal Heating Optimization

The metal heating conditions influence significantly the economic indices of hot treatment of metal under pressure. In order to optimize these indices, oxidization (and/or decarbonization) of the metal, heating costs in the furnaces (fuel and fire resistant material), rolling costs (power and tools), capital investments into equipment (furnaces, the mill) as well as the process rate and the impact of heating conditions on the product quality should be taken into account.Problems involving the above factors are very complicated and cannot be solved without computers.The paper formulates the approach to the solution of this kind of problems and discusses four specific problems: of the optimal operating conditions and heating duration to the billets temperature specified; of finding the optimal capacity of the metal heating section; of the optimal heating condition and temperature of billets at the start of rolling with allowance for the characteristics of the mill; of the design of an optimal scale-free heating furnace.These problems were solved on an M-220 computer for models of specific industrial furnaces, a ring scale-free open flame furnace and a multi-zone continuous slab reheating furnace. The solutions obtained led to considerable savings.In order to obtain optimal operation, a genzaeral-purpose digital computer is not obligatory. For instance, a special-purpose analog computer actually controls a multi-zone slab reheating furnace.

THE RESPIRATORY EFFECTS OF A POTENT ANALGESIC (GPA 2087) IN MAN

SUMMARY The respiratory depressant effects of a potent analgesic (GPA 2087) were compared with morphine in a randomized double-blind cross-over study in human volunteers. Using a rebreathing technique, carbon dioxide response curves were plotted automatically with a special-purpose analog computer. The respiratory depressant relative potency of GPA 2087 to morphine was found to be 1.21 with lower and upper 95 per cent confidence limits of 0.88 and 2.04. Our best estimate based on the displacement of the respiratory response curve is that GPA 2087 8 mg is the equivalent of morphine 10 mg in our population of volunteers.

An on-line hybrid computing system for dynamic respiratory response studies

This paper describes a hybrid computing system for on-line human respiratory studies. A digital computer dictates the subject's inspired CO 2 concentration through a servocontrolled breathing chamber. The inspired CO 2 is varied so that the alveolar CO 2 concentration has a useful dynamic perturbation. A special purpose analog computer system measures and displays respiratory response data in real time and an on-line digital system accumulates these data on a breath-to-breath basis. A digitally controlled breath sound simulator is used to study the subject's voluntary interaction with his involuntary CO 2 response. Examples of experimental data are presented. The system is presently in use in ongoing studies of the normal and drug-altered respiratory control system.

Void fraction and stability of natural circulation water boiling in a vertical annulus heated internally: I. Axial phase and amplitude distribution of void fraction with uniform heat flux

Void fraction and inlet flowrate in a natural circulation boiling water loop have been analysed in terms of their relative dependence. Power spectra were calculated by means of a special-purpose analogue computer. The independent variables were channel power and inlet subcooling. Increasing power beyond certain values generated spontaneous hydraulic oscillations. The experiments covered both stable and unstable behaviour of the system. The amplitude of the signals indicated an obvious transition between both regions, but the relative phases did not change. No rapid change of phase between any two signals was observed. Knowledge of the phase offered the possibility of calculating void propagation velocities. The results affirmed the physical inconsistency of a boiling boundary.

A Special-Purpose Analog Computer for Vectorcardiography [Summary

A Special-Purpose Analog Computer for Vectorcardiography [<i>Summary</i>

Meridional refractometry. II. Data reduction.

Three methods for simplifying the solution of the equations used in meridional refractometry are outlined: solution by time-sharing, multiple-access digital computers; solution by special-purpose analogue computer; and solution by nomogram. The advantages and the disadvantages of each method are discussed. It is suggested that a special-purpose analogue computer is the most feasible data reduction device for meridional refractometry.

Rapid Stress-Induced Crystallization in Natural Rubber

Abstract Stress-induced crystallization in a rapidly stretched natural rubber gum vulcanizate has been studied using thermal techniques to follow the development of crystallinity. A special-purpose analog computer has been assembled and used online to process the thermal and mechanical data obtained in high speed tensile testing. Roughly first-order room temperature crystallization kinetics curves were obtained having time constants of 50–60 msec in the range of 400–540% extension. While the rate of this rapid, presumably primary crystallization appears rather insensitive to elongation in this limited range, the extent of crystallization at 400 msec increases smoothly from zero at 340% elongation to around 18% at 540% elongation. It is shown that our high-speed tensile tester can stretch this vulcanizate fast enough that most of the crystallization takes place after extension has been completed. Stress—strain curves obtained at this high rate are compared with those obtained at lower rates where crystallization takes place during the stretching.

Analog Computer for Calculation of Second Moments in NMR

A special purpose analog computer is described for calculating the second moment of the NMR absorption spectrum drawn out by a wide-line spectrometer with an integrating phase-sensitive detector (PSD). An experimental check on NH4Cl yielded a mean second moment within 1% of a previous value, and a standard error over 50 observations of 2%. The integrating PSD enabled these spectra to be recorded over 100-sec sweeps with a signal-to-noise ratio comparable to that obtained using conventional techniques with sweep times at least an order of magnitude longer.

Real-Time Fourier Spectroscopy

The operation and performance of a system to perform Fourier spectroscopy in real time is described. The interferogram is sampled and the spectrum is simultaneously synthesized by the summation of a series of cosine functions with amplitudes and frequencies determined by the sample points. A digital memory oscilloscope performs the summation, and the spectral distribution is presented at 1000 points. An error of 2% of the full scale output can be expected and is caused by several inaccuracies in the components of the system. Several ir spectra were investigated, and the results produced by the real-time system are compared with those obtained with a digital and a special purpose analog computer.