Effects Of Changes In Parameters Research Articles

Parameter sensitivity analysis of a network model of systemic circulatory mechanics.

A previous analytical model of the systemic circulatory system (Grodins,Quarterly Review of Biology, 1959,34, 93–116) was extended based on recent experimental studies. Major units considered are: large arteries, large veins, and the peripheral circulation. The latter is subdivided into three parallel functional units: (1) nutritional bed, (2) shunt pathway and (3) storage area. By addition of simplified linear descriptions for the heart and pulmonary circulation, the overall cardiovascular system was considered. Parameter values were mainly derived from right heart bypass (Grodins, Stuart, and Veenstra, American Journal of Physiology, 1960198, 552–560) and isolated hindlimb (Satoet al., 1971) experiments. An algebraic equation relating cardiac output to systemic circulatory parameters was derived which provided a convenient means of studying effects of parameter changes. This equation predicted that compliances and unstressed volumes have a unidirectional effect on cardiac output but arterial resistance has a variable effect which depends on the values of resistances and compliances of the parallel pathways. Circulatory responses to exercise were considered by changing compliance and resistance of the nutritional bed in accordance with experimental values obtained with a frequency response method (Vega, Ph.D. Thesis, University of Southern California, 1973). Possible mechanisms for blood flow restoration as required by the resistance change are discussed. In summary, systemic circulatory mechanics appear to influence cardiac output mainly by redistribution of blood volume between different segments rather than by redistribution of blood flow.

Digital/analog simulation of electromechanical devices on a graphics terminal

Computer simulation of electromechanical devices by exercising a suitable mathematical model has advantages in studying the effects of parameter changes. As a specific example, an electromechan ical relay has been chosen for simulation in this investigation. A differential equation model of the relay 1 is developed and simulated on an IBM 1130/2250 graphics terminal using the 1130 Continuous System Modeling Program (CSMP). An optical displacement measuring system was used to measure the armature travel as a function of time while the relay was functioning. These mea sured characteristics were compared with the analogous characteristics of the simulated relay to evaluate the validity and accuracy of the mathematical model. It is concluded that the differential equation model is an adequate appro ximation provided the lumped parameters of the magnetic circuit are appropriately chosen. The influence on the dynamic response of the relay as various relay parameters are changed can easily be predicted from the simulated model in this study.

くま取り極電動機のトルク特性に及ぼす諸定数変化の影響

くま取り極電動機のトルク特性に及ぼす諸定数変化の影響

A discussion on ocean currents and their dynamics - Ocean models

Over the past twenty years or so, a good qualitative description of the ocean circulation has been built up through the use of two-dimensional wind-driven models. These correctly predict the position and sense ot circulation of the major oceanic gyres, and explain the strong western boundary currents. However, the only direct measurements available for quantitative comparison with theory are those of the transport of the Gull Stream. Observed values are considerably larger than those predicted by linear theory, but can be explained by nonlinear models. . Two-dimensional models have their shortcomings, however, because they take no account ot vertical structure. They cannot properly model effects of nonlinearity, bottom topography, or of motions driven by thermohaline effects. They overlook important aspects of the circulation such as the equatorial undercurrent, and upwelling. Three-dimensional numerical models are designed to include these effects, and successfully reproduce, in a qualitative fashion, the major features of the ocean circulation. The models may be used for ‘experiments’ to find possible effects of changing parameters (such as the width and depth of Drake Passage), and to investigate the relative importance of different regions. With presentday computers, however, there are resolution and other problems which limit the degree to which the real ocean’s parameters may be matched.

Parameter sensitivity of systems described by nonlinear ordinary differential equations

AbstractAn approximate analytical method is developed to estimate the parameter sensitivity of the solution of a set of nonlinear ordinary differential equations describing a system which exhibits periodic behavior. An approximate solution is constructed in terms of both the approximate periodic solution determined from Galerkin equations and the envelope and phase of the oscillation away from such a periodic solution. Parameter sensitivity information is then obtained by examining the parameter variation effect on the approximate solution.Examples of two‐ and three‐dimensional nonlinear systems illustrate this procedure and show that the effect of parameter change on the solution is predicted with sufficient accuracy to make this method useful for nonlinear analysis.

Time optimal control of time varying third order plants

It has been shown that time invariant third order plants can be time optimally controlled by a hybrid computer. The computer generates a time optimal switching surface, which it then uses to control the plant. [1] This paper presents an extension of this approach to slow time varying plants, by automatically updating the switching surface. The effects that parameter changes have on the response of the plant and on the switching surface are investigated. It is shown that by rescaling the switching surface, the effects of parameter changes on the plant's response could be minimised. A method is then presented for the time optimal control of time varying plants. The method consists of on-line identification of the time varying parameters and the continuous updating of the switching surface to maintain time optimal control.

Mathematical Model of the Brass-Player's Embouchure

A simple mathematical model of the self-oscillating system comprising the oral cavity, the lips, and the input impedance of an idealized brass instrument has been programmed for a digital computer. The lips are represented by a simple mechanical oscillator with amplitude-dependent damping, similar to the model of the vocal cords used by Flanagan and others in speech studies. The input impedance of the “instrument” is that of a horn whose resonances are precisely harmonically related. This formulation gives a set of coupled nonlinear integral-differential equations that can be solved numerically to give approximate values for the pressure in the oral cavity and in the mouthpiece cup, the volume velocity through the lip orifice, and the area of the lip orifice as a function of time. Although it would not be particularly meaningful to compare the computed waveforms in detail with experimental data, this simple model shows many of the characteristics of real brass instruments and should be useful for studying the effects of parameter changes.

Model for a synchronous p.c.m. transmission complex

One of the proposed synchronisation systems for a large-scale p.c.m. transmission and switching complex uses independent oscillators at each station, which are phase-locked to the average phase of all the incoming lines. This paper derives a simple analogue to the system which allows a sufficient stability condition to be stated by inspection. The effect of parameter changes upon the equilibrium frequency is discussed, and a detailed discussion of the initial conditions shows that, for a 2-oscillator system, there are two stable-equilibrium frequencies that the system may reach. The Appendix contains rigorous proofs of the more intuitive statements in the paper.

Insensitivity of Optimal Linear Control Systems to Persistent Changes in Parameters†

ABSTRACT Previous work on the sensitivity of optimal linear control systems [xdot] = Ax + Bu with quadratic performance index has concentrated on the effects of small changes in parameters. It is shown in this paper that the optimal feedback law u = − Dx is insensitive to (i.e. is unaltered by) a wide variety of persistent changes in A and B. Some explicit expressions for these variations in A and B are presented, including the cases when B is fixed, and when the change in A is known. If A is fixed any change in B results in a change in D, so that the system is more sensitive to changes in B than in A.

Computer Recognition of Handwritten First Names

Alearning program incorporating a version of stimulus-sampling theory was prepared for a digital computer. Handwritten first name signatures coded in a 20 by 48 grid served as inputs to study the effects of parameter changes in the program. Under one main condition the computer with its program examined only those grid cells in which any part of a given pattern fell. Under a second main condition each of the 960 grid cells was examined. Learning of correct pattern names occurred under both conditions. The level of learning achieved under the second condition was higher, although the improvement was gained at the expense of considerably extended running times.

Analysis of the Spectrum of d3 Ions in Trigonal Crystal Fields

The effect of a trigonal crystal field on the energy levels of d3 ions is evaluated within the framework of the crystal-field model. Matrices of the trigonal-field potential for the d3 configuration are presented and used to discuss details of the ruby spectrum. Perturbation expressions for the effect of parameter changes on the energy levels are given. These enable some refinement of electrostatic and crystal-field parameters to be carried out. In particular the effect of the second trigonal parameter is found to be appreciable. Finally, the effect of the spin—orbit interaction is included and the eigenvalues of the total Hamiltonian are found to be in good agreement with the observed energy spectrum of ruby.

Nomograms for the Statistical Summation of Noise in Multihop Communications Systems

Several authors have shown methods for calculating the long-term fluctuation of noise power of multihop systems in which the propagation loss has a log-normal distribution such as in troposcatter FM. However, these methods involve exponentials, the computations are necessarily laborious and time-consuming, and the formulas do not readily reveal the effects of changing parameters. These shortcomings are remedied by two pairs of homographs which eliminate the laborious exponential computations and permit the noise performance calculation to be made within seconds. The nomograms display the effects of varying parameters and clarify the understanding of noise addition. Supplemental data is given reviewing the basis for the calculation, and also in order to enable the reader to extend the nomograms to any other range.

Relay Servomechanisms: The Shunt-Motor Servo With Inertia Load

Abstract This paper develops the theory of the shunt-motor relay servomechanism in terms of dimensionless motor parameters. Operating curves are drawn in the phase plane illustrating the effect of parameter changes on the stability of the servo for three forms of input signal. The first two forms of input signal, a step function and a uniform variation with time, have been discussed before and are included only for completeness. The third form of input signal, a sine function, is of most interest and is treated at greater length. The phase-plane curves, obtained from a differential analyzer, show three modes of operation which have been related to the servomechanism parameters by a relatively simple expression.

Transient Analysis of a Voltage-Regulated Aircraft D-C System

The system consisting of a single generator and a carbon pile voltage regulator is a closed-loop regulating system of the proportional type. As such, its stability and dynamic characteristics can be analyzed by the standard theory of servomechanisms. It is, however, necessary to define the variable quantities very carefully as they are not easily recognizable or measurable. For this system it is convenient to utilize the concept of an error transfer function (defined in this paper) rather than to use the system transfer function common in servomechanism literature. When this is done the criteria for frequency spectrum analysis are altered somewhat, as discussed before. The purpose of the foregoing analysis has been to simplify the problem of improving an existing regulator-generator system. A complete loop transfer function can be written in terms of the regulator and generator parameters. From this it can be seen by inspection whether a given system will be stable. For stable systems the effect of changing parameters can easily be determined by examining equations 2, 10, 21, and 22. It is clear that the regulator characteristics alone do not determine the stability of the system. The generator and regulator characteristics must be considered together instead of separately. When the same regulator is used with two different generators, one system may be stable while the other is not. This can be due to the difference of the generator characteristics alone.