Abstract: GASP IV is a FORTRAN-based simulation language which provides the framework for modeling systems involving both continuous and discrete phenomena. A general ization of the definition of "event" allows for time to be advanced in a next-event fashion while permit ting a step-wise evaluation of system state variables described by difference or differential equations. Subprograms are included in GASP IV to handle the details of state and event control (including state- variable integration when necessary), information storage and retrieval, collection and analysis of data on system performance, and generation of reports and plots. In this paper, the GASP IV philosophy and modeling approach are described. Descriptions of the subpro grams included in GASP IV and the required user- written subprograms are given. The types of applica tions that have utilized GASP IV are listed. A com panion paper (beginning on p. 71) presents a detailed example of the use of GASP IV for simulating a continuous reaction process in...

Abstract: Pseudo-random sequences can be computed to approximate a distribution or a sample correlation function. How ever, conventional techniques do not allow the control of both distribution and correlati...

Abstract: GSL is a FORTRAN-oriented language which combines the activity and process concepts of a discrete simula tion language with continuous simulation concepts, thereby permitting the simulation of systems which call for combining continuous and discrete simula tion techniques. The basic structural component of GSL is the simulation block, which corresponds either to an activity of a discrete system or a dynamic re gion of a continuous system. Both discrete and con tinuous simulation blocks may have multiple process instances which may be controlled dynamically at run- time. The result is a combined language which re tains the features of both continuous and discrete simulation languages and moreover takes advantage of the desirable features of each to supplement the other. GSL syntax is described by examples which illustrate the application of the language in a typical combined simulation problem and permit the evaluation of the various features of the language.

Abstract: Simulation has been used extensively as a tool for the solution of vehicle-dynamics problems. To handle nonlinear simulations of increasing size and complexity, both digital and hybrid methods have...

Abstract: same t. To take advantage of this, just program the subroutine to remember A and g from the previous t: Use a variable in COMMON with the main program to tell the subroutine it is being called for the very first time. For this t evaluate and store t, A(t), and g(t). Thereafter, every time the subroutine is called it should test the argument t against the t stored. If they are the same, use the stored values of A(t) and g(t). If they are different, reevaluate t, A(t) and g(t), and store them with the new value of t.

Abstract: A system is described that greatly facilitates inter active discrete-time simulation in FORTRAN. The system allows the user to alter and examine the value of any variable during execution. It permits the user to plot any variable as simulation proceeds and to save all variables during simulation. Once a simulation run is complete, the user may go back and look at all previous values of all variables. This system permits the user to restart his simulation at any previous time, with all variables reset to their former values. Many other features are provided to enable novice users to control the simulation with a minimum of external aid. All features are called by simple commands issued during the simulation by the user, or predefined by him in a data file. The features of the system are largely machine-indepen dent and could be easily converted to any time- sharing or batch-processing system. The programming details of the control system are not included, but a general outline of the concepts of its operat...

Abstract: Simulation can be a more effective tool for the study of problems of our times if the practitioners will adopt pro cedures which will make simulation more a science than an art. A big step in that direction would be the develop ment and use of a standard format that would assure ade quate and uniform documentation. Such a format is pro posed, and criticism is solicited.

Abstract: This paper is a sequel to the preceding paper de scribing the GASP IV language. In this paper, the simulation of a chemical reaction process is used as a vehicle for illustrating the procedures for using GASP IV. The details of the computer coding as well as samples of computer output are included. The in tent of the paper is to illustrate the use of GASP IV to analyze a system involving both continuous varia bles and discrete events.

Abstract: Battelle Memorial Institute has initiated a research program to develop an improved set of systematic methods for assisting decision-makers in the identi fication and solution of socioeconomic prob...

Abstract: This paper describes a method for progressing a set of n variables along a constraint curve in n- dimensional real space. The method uses the concept of interdependency of the variables and gives the reasons for doing this. Gradient methods for main taining the accuracy of curve following are azso discussed. The method is suitabze for analog com putation.

Abstract: GSL (Generalized Simulation Language) is a combined continuous-discrete simulation language which permits the simulation of either type of system or a combin ation of the two. The combination leads to powerful new capabilities, including creating and dynamically controlling multiple instances of continuous systems, extensive control over execution and events, and extensive interprocess communication. These capabil ities in turn lead to implementation problems, primarily in the areas of scheduling of multiple continuous simulation blocks, control of interaction between simulation blocks, coordination with discrete blocks, and storage allocation. The resolution of these problems in the GSL implementation is described along with experience with typical problems.

Abstract: A primarily algebraic technique for simulating social systems has been developed for combined use by engineers and lawyers and has been applied exten sively to studies of felony processing times in the criminal justice system of two counties in the State of Indiana. As a method of non-Monte-Carlo simulation, the present approach overcomes tradi tional impediments such as determination of loops and multiple-function concatenation. preliminary evidence suggests that the simulator has useful capabilities in initial screening of data and in early qualitative studies of systems in which a priori data is not plentiful .

Abstract: This paper reanalyzes the results of an earlier survey reported on in SIMULATION. This analysis is based upon an original technique developed for handling opinion survey data where the judges have varying degrees of familiarity with the entities being ranked. The technique utilizes ordinal rankings as opposed to cardinal utilities and is a modification of the Method of Majority Rules. It is bezieved that this presents the results of the original survey in a form more useful and understandable to the reader.

Abstract: 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 computationThe 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 solutionThe 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

Abstract: This simulation study of a salmon culture pond at Arcata, California investigated the dynamic interrelationships within the ecosystem of fingerling coho salmon, a small crustacean (an amphipod) that served as the salmon's principal food, the amphipod's food, and the tem perature and salinity of the water in the pond. The simu lations showed that the optimum salinity for maximum growth was 23.5 parts per thousand, and that deviation from this optimum decreases the growth rate of amphipods, which means that more of them are eaten by the fish, because the amphipods are of edible size for a longer time. Competition among the amphipods was great when the density of their food was low. The simulations developed an understanding of the mechanisms at work in the pond ecosystem and resulted in information on which to base suggestions for improved strategies for managing the pond.

Abstract: This paper describes a simulation of the process of sintering an ore pellet placed in a high-temperature furnace. The sintering kinetics is described via a nonlinear ordinary differential equation with an ill- conditioned initial value. The change in temperature with time in the sintering pellet is described via a partial differential equation (conduction equation) which is coupled with the kinetic equation. The nu merical-solution approach is based on the recently developed repeated-extrapolation technique, which has been shown to be significantly faster than standard finite-difference algorithms. The partial differen tial equation is handled by the classical method of orthogonal eigenfunction expansions. The approach is illustrated by treating the sintering of uranium di oxide spherical pellets. The results clearly indi cate that a significant portion of the shrinkage takes place in the initial non-isothermal heating period. Since the conventional analysis of shrinkage data has been restricted to consta...

Abstract: When queueing systems can be modeled in the form of a system of simultaneous first-order difference- differential equations and when the transient-state of such a system is likely to defy analysis, it may be wiser, less expensive, less troublesome, and faster to use some numerical method. The outstanding advantage of numerical methods is that it is rela tively easy to estimate the error (due to truncation of higher-order terms) in the results. The argument for seeking a numerical analysis method for solving a wide class of these models has a strong practical appeal. This paper explores the transient solutions to nonhomogeneous Markov processes (those in which the parameters vary with time), using Runge-Kutta and Hamming methods. For illustration, a simple but rather instructive, single queueing model is solved manually. The solutions obtained by these methods are compared with the corresponding analytical solu tions. Several commonly-used queueing models are solved to demonstrate the wide potential applic...

Abstract: This paper presents a technique for selecting an optimum alternative from among a limited set of possible alternatives. The method presented is an algorithmic successive-elimination procedure which uses simulation to measure the "cost" of each alter native. The algorithm requires the calculation of estimates of confidence intervals of the mean "cost" for each alternative after each replication of the simulation. By comparing the confidence limits and "costs" for each alternative after each replication, one or more alternatives may be elim inated from consideration. The procedure ends when only one alternative remains or when the criteria used indicate that further analysis would be uneconomical.

Abstract: This invention relates to an arrangement for projecting cantilever sections of multi-sectional bridge supporting structures of steel or prestressed concrete forming the superstructure of the bridge which is supported on bridge piles. The arrangement includes at least one traveling auxiliary beam movably carried on and arranged above the superstructure for spanning between superstructure sections. Two concreting scaffolds each comprising a supporting part having crossbeams and rollers are arranged above the superstructure and carry a platform which is arranged below the superstructure for carrying casings to extend the projecting superstructure sections. A transport device is movably carried on the auxiliary beam and supports the concreting scaffolds for transport between superstructure sections and from the end of a completed section to a bridge pile for beginning construction of a new section. The supporting part of each of the concreting scaffolds has longitudinal girders arranged adjacent the auxiliary beam and crossbars connected to the girders arranged below the auxiliary beam. A pair of supporting blocks for supporting the auxiliary beam on the next succeeding pile are arranged so as to be alternately retractable to allow the supporting part of the scaffolds to pass the bridge pile, and the platform of the scaffolds comprises a bending resistant lattice of crossbeams and girders with means for forming openings therein to allow the platform to pass the pile as the scaffold is transported to the next section.

Abstract: G. HOFFMAN de VISME was born in London in 1923 and was educated at Highgate School, where he studied classics before transferring to the Science Department. He obtained his first degree from London University in 1942 and then joined the Army, serving as a technical officer in the Royal Electrical and Mechanical Engineers until 1946. He then joined the General Electric Company’s Research Laboratories in WembZey and worked on problems connected with radio interference until 1950, when he joined the Education Branch of the Royal Air Force. After serving for 13 years until 1962 mainly as a technical instructor in electronics and radar, he joined the Department of Electrical Engineering and Electronics of the University of Manchester Institute of Science and Technology where he initiated and supervised a postgraduate course in Digital electronics and obtained his PhD degree in the field of digital measurements. In 1971 he was appointed Head of the Department of Electrical and Electronic Engineering at the North Staffordshire PoZytechnic.

Abstract: The programming of differential equations on an ana log or hybrid computer usually requires that the system be scaled in both magnitude and time to pre vent overloading the amplifiers and to obtain the desired speed of solution. This paper, which is tutorial in nature, presents a systematic matrix method which may be used to scale differential equa tions written in state variable format. The proce dure requires estimates of the maximum values of each computer variable, and the technique is shown to be appZicabZe to both linear and nonlinear systems. The description of the method is followed by two illustrative examples, one linear and one nonlinear, and comments on an effective rescaling algorithm.

Abstract: In order to meet the increasing demand for reliable design and expansion of power networks, the use of system simulation must play a leading role in the power industry's future R & D programs. Digital com puters are already widely used in the analysis and design of large power networks. Hybrid computers offer a convenient alternative, especially where fast and accurate simulation of complex nonlinearities is required.In this article, general principles are presented for the computer simulation of interconnected power systems. The technique discussed is directly applicable to an all-digital simulation, but emphasis is also placed on a hybrid implementation in which the transmission por tion of the system is represented digitally, while theintegration and nonlinearities associated with termi nal apparatus are represented on the analog. Example studies are performed to illustrate the technique. Results include voltage waveforms for a three-phase line energization, and the modification of switching transients...

Abstract: A simulation of human speech is normally performed to represent the acoustic signal in a form from which meaningful features of interest in the time and frequency domains may be identified and used in attempting to solve research and applications prob- Zems. Frequency-domain simulations related to vocal tract modeling have been the most popular techniques used to date. However, approaches have been investi gated which, for the limited case of voiced sounds, simulate human speech in the time domain by time- ordered time-based wavefunction sets.This paper discusses the use of a new technique for an accurate, complete simulation of any human speech by the family of Hanning Cosine Modulated (HCM) wavefunctions.The previous research on wavefunction simulations of speech are first discussed and then, through illus trative examples, it is demonstrated that HCM wave functions may accurately simulate the behavior of speech in either the time or frequency domain.The actual parameters of the wavefunctions which re p...

Abstract: An interesting method of involving only two data manipulations per integration step was presented by R. G. E. Franks in his book Modeling and simuzation in chemical engineering. Franks’ method for a transport delay can be best understood if all the data storage positions are visualized as arranged in a slide carrousel with N pockets (see Figure 2). At each integration step the slide carrousel is advanced one position and the information in position N (which is N integration steps old) is read out, and the variable to be delayed is read into this position. Information is available only at discrete intervals.

Abstract: In recent years systems analysis techniques have been applied at an increasing rate to ecosystems.1 1 In particular, modeling and computer simulations are used to study the structure and behavior of ecosystems. Ecosystem modeling is still in its infancy, and considerably more interdisciplinary work needs to be done by biologists and systems scientists to develop ecosystem models which could, one hopes, be used for a most important function: prediction.

Abstract: Publisher Summary The most important factor that differentiates corporate simulation models from other types of simulation models is the fact that corporate simulation models have found their way into the executive suites of some of the largest corporations in the world. There appear to be at least three reasons why risk analysis is not widely used with corporate simulation models. First, the computer run costs are often prohibitively expensive. Second, there are serious problems of validation, experimental design, and data analysis associated with stochastic simulation experiments. Third, risk analysis seems to have only limited appeal to senior corporate executives. The technical problems include (1) the interface between optimization models and simulation models, (2) risk analysis, (3) production planning models, and (4) computer software. The nontechnical problems are (1) ill-defined problem definition, (2) failure to integrate the model into the planning process, and (3) the politics of corporate modeling.

Abstract: San Francisco, California 94120 EDITORIAL 1L’OTE: The article below began a8 one reviewer’s critique of The Construction of a Robot Investor, which appeared in last month’s issue. Then, like Topsy, it &dquo;just growed&dquo;--into a fullscale technical article in its own right. We present it here for readers interested in comparing the investment strategy advocated by the Robot’s authors and the strategy suggested below. NM

Abstract: At the Laboratory of Chemical Technology of the Delft University of Technology, research work is carried out on problems in which multicomponent chemical reactions in a bifunctional catalyst environment are a principal element.Study of the interrelated effects of the many system parameters, as well as the search for possible opti maZ catalyst compositions to maximize output and yield, has made it desirable to have at hand a fast simulation of the reaction system.Hybrid computation appeared to be the logical way to meet the needs of the above Laboratory for easy man- machine interaction and high computation speed. In this report are presented the development and imple mentation of the hybrid simulation together with some of its results as realized at the Delft University Computation Centre. The hybrid model at present simulates a five-component reaction using a bifunc tional catalyst. Much effort has been invested to obtain both easy input/output and the highest possible speed of solution using an Applied ...