Continuous System Model Research Articles

Design and analysis of simulations: practical statistical techniques

Using elementary statistical theory, we discuss sta tistical techniques that can be used to initialize a simulation run and to determine its length, distin guishing between terminating and nonterminating sys tems and between stationary and nonstationary time series. Confidence intervals and hypothesis tests are included (see Section 2). In the case of k sys tem variants (at least 2), multiple comparison proce dures are presented which can be used to obtain simultaneously valid confidence intervals and to select a subset containing the best population, assuming a fixed number of simulation runs. Other wise ranking procedures can be used to determine the number of runs required to select the best system (Section 3). If many parameters and variables exist, selecting a limited number of combinations requires an experimental design, which must be analyzed with a regression metamodel (Section 4). The metamodel of main effects and interactions applies to both quantitative and qualitative factors; its adequacy can be tested (Subsection 4.1). Experimental design is discussed in three steps: (1) screening designs for finding the important factors, namely, 2k-P designs, random, supersaturated, and group-screening designs (Subsection 4.2); (2) augmented 2K-P designs for further exploration (Subsection 4.3); (3) response surface methodology for optimization (Subsection 4.4). Three practical variance reduction techniques are summarized, namely, control variates, antithetics, and common random numbers (Section 5). Some of the statistical methods discussed are also applicable to deterministic models of continuous systems. This paper was written for readers with only an elementary background in statistics.

Simulation of continuous system models in industrial engineering

Many industrial engineering and operations research studies in the creation of continuous dynamic models; that is, models consisting of a system of ordinary differential equations. Such models arise frequently in the analysis of economic, inventory and production control systems. The area of Industrial Dynamics (more recently named Systems Dynamics) is specially oriented toward modeling and simulation of these dynamic systems. The purpose of this paper is to discuss briefly some of the current techniques for modeling and simulation of continuous systems and then to devote major attention to describing a number of difficulties encountered in the actual digital simulation. Finally, a number of specific suggestions will be offered to prevent the occurence of most of these problems.

A First Exposure to Discrete-Time Modelling of Linear Continuous Systems

The growing usage of discrete-time models to simulate continuous and sampled-data systems requires a fundamental and concise introduction in an engineering curriculum. In this paper the discrete-time models are developed from different approximations of the convolution integral representing the response of the continuous system. An example is presented to illustrate the merits of the various models.

Comparison of electrical activity and behavioral correlates of neural networks in the cat and locust

Extensive experimental data are available on the neural activity and behavioral correlates of specific networks in the locust and in the cat and rabbit. Two networks were selected for comparison, one involving visual movement detector interneurons in the locust and the second a hippocampal network in mammals. Both networks receive inputs correlated with motor activity. Each network was simulated using CSMP, a Continuous Systems Modeling program developed initially by IBM. Signals along the two simulated networks were calculated when similar inputs were applied. In addition, approaches toward relating behavior to neural activity were compared in the two networks.

Digital simulation of adjustable-frequency ac motor drives

Simulation techniques are very useful in designing static adjustable-frequency ac drive systems and in evaluating alternative control strategies for them. This paper outlines the basic principles of the modern dc-link static frequency converter, and then describes the implementation of a digital simulation of a complete drive system. The principal components of the drive are programmed as FORTRAN subroutines. The main program uses the IBM Continuous System Model ing Program (CSMP), which is translated into FORTRAN and combined with the FORTRAN subroutines. Harmonics in the output waveform of the frequency converter can cause design and operating problems under steady-state as well as transient conditions. These problems are discussed and illustrated by results from simulation runs.

Dispersion along fiber tracts and in the coupling between tracts and a cortical network

Dispersion in a neuronal cortical network was modeled using CSMP, a Continuous Systems Modeling Program. The signal dispersion over pathways was simulated by use of a serial product approximating the convolution integral. The program was written in a sufficiently general format to be applied to a variety of biological signals. Calculated signals from a fiber tract and activation of a cortical network were compared with experimental data from cats. The network consists of excitatory cells in a forward limb which send collaterals to interneurons that, once excited, feed back to inhibit the excitatory cells. The model was consistent with data from neuronal assemblies in the prepyriform cortex and fibers in the lateral olfactory tract.

The Use of CSMP for Agricultural Engineering Problems

ABSTRACT MANY problems involving continu-ous systems which have seemed so formidable in the past are readily soluble by use of one of the simula-tion languages developed specifically for such systems. This paper provides an introduction to the language Con-tinuous Systems Modeling Program/' (CSMP)* and illustrates its applica-tion to three problems typical of those encountered by Agricultural Engi-neers. While the specifics refer to CSMP, many of the concepts also ap-ply to other existing and similar lan-gauges.

On the non-linear dynamic response of the rhesus to impact

A non-linear discrete parameter mathematical model describing the dynamic behavior of a primate ( Macaca mulatta) has been developed and programmed for solution on the IBM model 360 91 computer using the Continuous Systems Modeling Program (CSMP). The primate is described by a system of discrete anatomical segments connected by translational and rotational springs representing the inter-segment stiffnesses. For example, the neck is represented by three discrete masses, one translational and four rotational springs. The masses, mass moments of inertia, centers of gravity and the neck axial stiffness, were obtained experimentally. The predicted dynamic behavior of the rhesus monkey to blunt head inpact compares favorably with the observations taken from high-speed films of a cerebral concussion experiment. A study of the effect of the point of application and angle of inclination of the forcing function was conducted. The results show that the important response parameters display the expected sensitivity to the location of the blow but are particularly sensitive to its angle of inclination with respect to the plane containing the foramen magnum.

Simulation of the effects of weather on an insect population

This paper describes a digital-computer simulation of the influence of weather on the population of the European corn borer (ECB). The program, which is written in a FORTRAN-based language, defines a basical ly continuous-system model that accommodates discrete events in the weather-ECB ecological system. The principal factors controlling the ECB population are temperature, the daily spread of temperature (i.e., maximum-minimum), and rainfall. The goal of the simu lation is to improve our understanding of crop-ECB ecology and to assist corn-pest managers in reducing crop damage by applying control measures when they will be most effective.

Discrete-time models:Bilinear transform and ramp approximation equivalence

The problem of developing discrete-time models for continuous systems from integral approximations is considered. In particular, the model obtained by approximating the input by a piecewise linear function is developed. By an appropriate approximation of this model, an equivalence between it and the bilinear transform model is established.

Some Design Features Of Continuous System Modelling Program III*

The Continuous System Modelling Program III (CSMP in) has a great many capabilities which were designed to make the program more usable by engineers and scientists who are not computer experts. Most notable of these capabilities is the Graphics Feature, which allows the user to develop and analyse systems models at a graphic display device.The purpose of this paper is to describe a few of the features of CSMP III and some of its graphic capabilities. The paper discusses examples of design decisions in two parts of the program. The design of the main structure of the CSMP HI program is described, showing how the structure aids the user by keeping his interface simple. Then the design of the graphic display panels, and features for controlling the system, are discussed.

Computerized left ventricular mechanics and control system analyses models relevant for cardiac diagnosis

Two left ventricular models, relevant to cardiac diagnosis, are presented. The first is a Computer-based Finite Element Stress Analysis model of the left ventricle (LV) aimed to account for the irregular left ventricular geometry obtainable from single plane cineangiocardiography. The in vivo data for the model consists of instantaneous left ventricular chamber pressure and cine. The calculated wall stresses are compared with idealized geometry models. The finite element model is better able to delineate the stress concentrations at sites of large curvatures. The second model consists of a control system model of the LV, which formulates the interaction of the mechanics of the LV and the lumped parameter circulatory system by the central nervous system's monitoring of the mean arterial pressure, regulation of the heart rate, left ventricular contractility and the perepheral impedance. The model is parametrically simulated for a subject by means of the continuous system modelling program (CSMP); then the simulated model's response to a physiological stress simulating pressure perturbation is determined; the model enables an assessment of the physiological stress sustaining capacity of a subject.

Simulation and short-range scheduling of hydrothermal power systems using system 360 CSMP

The short-range hydrothermal power scheduling problem is set as a problem in optimal control theory. New methods of modeling the upper- and lower-bound con straints on the reservoir capacity are proposed. The general equations that the optimal control satisfies are derived in the form of a constrained 2-point boundary-value problem (TPBVP). Properties of the optimal water usage policy are derived analytically and verified by simulation using the System 360 Continuous Systems Modeling Program.

Electrokinetic movement of suspended colloids in a flowing medium. II. Experimental investigation

An experimental model was constructed to test the theory developed in Part I. In this model, stainless-steel electrodes were utilized in a parallel-plate configuration. The suspensions studied were prepared from colloidal kaolin and deionized water. The influent concentration of suspension was maintained at 60 mg 1 −1. The flow rate of suspension was 250 ml min −1, while the electric field strength between the electrodes was 100 v cm −1. Mass concentration of suspension was measured at various points in the system both in situ on a continuous basis and by withdrawing samples. Both methods involved light transmittance measurements. The following flow characteristics of the medium were measured with a hot-film sensor and related equipment: (a) mean velocity profile, and the (b) root-mean-square (rms), (c) autocorrelation, and (d) spectral density of the random velocity component. The theoretical equations with appropriate boundary conditions were solved on a digital computer using a continuous system modeling program to provide a comparison of theoretical and experimental results. This analysis indicated that the theoretical equations developed in this study for Brownian and convective dispersion conditions provide a valid description of the electrokinetic movement of charged colloids suspended in flowing water.

Control characteristics of regulatory enzyme systems, I: nonlinearities in regulatory enzyme activities

The natures and forms of the nonlinearities in regulatory enzyme activities are presented by the control characteristics of a variety of regulatory enzymes that participate in various metabolic reaction systems. Besides the well-established simple feedback inhibition and feedforward activation, the basic reaction patterns of metabolic control considered include: (i) multivalent feedback inhibition; (ii) cooperative end-product inhibition; (iii) cumulative end-product inhibition; and (iv) compensatory feedback control. The characteristic equations describing these controls are derived and evaluated by computer simulation, using continuous system modelling program (CSMP). The results reveal saturation-type nonlinearities, the functional forms of which are mainly specified by two factors: (a) the type of modifier activity (inhibition, activation or both), and (b) the specific values of kinetic parameters, including stoichiometry, affinity constant, and activation constant (denoted by Q). The question of the possibility and type of metabolite oscillations is treated in terms of the sensitivity or degree of the nonlinearity. Using the oscillatory property of metabolites, the asymmetrical nonlinearities of the control characteristics can be approximated by a quasilinearization method in which a piecewise linear approximation is carried out to represent the given nonlinearity, followed by calculation of the describing function series of its approximation.

Continuous system models of oxygen depletion in a eutrophic reservoir

Continuous system models of oxygen depletion in a eutrophic reservoir

Application of a continuous system modeling program to control system design

Application of a continuous system modeling program to control system design

The System/360 continuous system modeling program

The System/360 continuous system modeling program

Two continuous system modeling programs

The motivation, history, and basic conceptosf user-oriented languages for digital simulation of continuous systems are presented. Reference is made to two illustrative programs, the IBM 1130 and SYSTEM/360 Continuous System Modeling Programs (CSMP). Both programs accept user-oriented input statements for constructing simulation models and controlling simulation runs. The 1130 CSMP also allows on-line interaction by the user. An engineer or scientist at the console can alter the model or change run conditions based on direct observation of simulation outputs. The SYSTEM/36O CSMP is intended for batch-mode operation. It has extended facilities for describing the model and for obtaining automatic program control of successive simulation runs.