bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using simulation in cardiovascular disease control
Authors: Ravindran A. , Sadagopan S. , Petersen Clifford C. , Hatsell Charles P. 
Published: March 2008

The United States Air force is planning a comprehen sive program to reduce the incidence of cardiovascular disease among Air Force personnel. The program will use a risk profile based on the Framingham study to identify high-risk personnel for selective treatment. A risk-reduction program will then provide medication and education for those selected for therapy. To assist the Air Force in designing a cost-effective risk-reduction program, we developed a comprehensive computer simulation model called P-HEART (Purdue Heart Evaluation and Risk Tabulation). P-HEART simu- Zates the USAF population and the processes of identi fying high-risk individuals and selecting appropriate therapies for them. It also calculates the costs and benefits of the cardiovascular disease control pro gram for different risk-reduction policies. This paper describes the simulation model, its validation, and its results.
Hybrid simulation of reactor kinetics in CANDU reactors using a modal approach
Authors: Monaghan Brian M. , McDonnell Frank N. , Hinds H.W. 
Published: March 2008

A hybrid computer model for simulating the behaviour of large CANDU (Canada Deuterium Uranium) reactor cores is presented. The main dynamic variables are expressed in terms of weighted sums of a base set of spatial natural-mode functions with time-varying co efficients. This technique, known as the modal or synthesis approach, permits good three-dimensional representation of reactor dynamics and is well suited to hybrid simulation. The hybrid model provides improved'man-machine interaction and real-time capability. We have used the model in two applications. The first studies the transient that follows a loss of primary coolant and reactor shutdown ; the second is a simulation of the dynamics of xenon, a fission product which has a high absorption cross-section for neutrons and thus has an important effect on reactor behaviour. Comparison of the results of the hybrid computer simulation with those of an all-digital one is good, within 1% to 2%.
Simulation of an oil-pumping ring seal for a Stirling engine
Authors: Smith P.J. , Keith Theo G. 
Published: March 2008

Potentially, the Stirling engine is a more efficient, less polluting replacement for the internal combus tion engine in automobiles, trucks, and buses. However, a critical design problem for this engine is the seal between the working fluid and the lubricat ing fluid. The current approach to solving this problem is to use rolling diaphragm seals to perfect ly separate the working fluid (hydrogen under high pressure) from the lubricating fluid (oil at atmo spheric pressure). The large pressure difference across these rolling diaphragm seals leads to fatigue and failure. This paper reports an investigation of the use of a pumping ring to maintain an oil reservoir on the low-pressure side of the seal. The operation of a pumping ring is simulated, taking into account the axially symmetric unsteady flow in the fluid domain coupled with the elastic distortion of the solid ring. The computer program for solving the mathematical model uses finite differences in the fluid domain and finite-element methods in the solid (pumping ring) domain. The validity of the simulation was checked by comparing its results with analytical solutions for limiting cases. We used the model to investigate the effects of changing various parameters of the ring, such as its geometry, material, rod size and speed, O-ring loca tion, crown spring, and interference fit. Our findings are reported.
The ETH multiprocessor project: parallel simulation of continuous systems
Authors: Halin Hans J. , Bührer Richard , Halg Walter 
Published: March 2008

A new multiprocessor system is currently under con struction at ETH (Swiss Federal Institute of Technol ogy). This multiple-instruction-stream multiple-data stream (MIMD) computer exploits the advantages of low-cost large-scale integrated components. A first model of the ETH multiprocessor featuring a modular expansible architecture will consist of a PDP 11/40 and 16 LS-T-11S. After its completion in 1980 the multiprocessor will be applied mainly to the simula tion of continuous systems. Evaluations of integration schemes for MIMD systems showed the method of power series expansions to be most appropriate. Starting from a FORTRAN-like source code, the differential equations are automatically decomposed into smaller problems. The higher deriva tives of all variables are computed using analytical recursion formulas. Usually many formulas can be evaluated simultaneously, each by a master cooperating with a number of slaves, using the inherent parallel ism in many of these formulas. The time behaviour of the multiprocessor is character ized by dynamically changing hierarchies. To imple ment algorithms efficiently, several principal prob lems of parallel computing were solved in hardware rather than in software. Thus the system features provisions for instantaneous data exchange between processors, protection of data, handling of deadlocks, and performance of operating system tasks. As a result, the ETH multiprocessor simplifies the solu tion of problems from different fields.
Study of large power systems after severe disturbances
Authors: Gelopulos Demosthenes P. 
Published: March 2008

Several types of power-system simulations are de scribed in this paper. Long-term simulations, transient stability studies, and electrical transient and subsynchronous resonance studies are singled out as especially important classes of power-system simulations. The mathematical requirements for carrying out sim plified transient stability simulations of power systems are described in detail. Full-scale simula tions require the simultaneous solution of an elaborate set of differential and transcendental algebraic equations. At present such simulations are time-consuming and costly. This paper discusses several techniques for improving the efficiency of digital programs for this kind of simulation. Further increases in efficiency are still required. Current research in this area is outlined. A large number of related subjects are touched upon, and a list of references is included to help the interested reader.
Using simulation to assign police patrol zones
Authors: Carroll John M. , Laurin Pierre G. 
Published: March 2008

The defining of police patrol zones is a complex problem that can be handled by computer simulation. Typical criteria for establishing zone boundaries are average response time and amount of time avail able for actual patrol duties. Typical constraints include the number of patrol cars and a desired minimum response time. In our application, the criterion was to maximize the amount of time avail able for patrol duties (i.e., repressive patrol); the constraints were the current average time to respond to a call and a limit on the number of patrol cars. We developed a multiple linear regres sion model to forecast calls and a simulator to pre dict performance. The results were reasonable and indicated that, possibly, a small increase in patrol time could be achieved by redefining zone boundaries and that the work load in the zones could be made considerably more uniform. The simulation, however, was undertaken primarily as a training exercise and did not represent the com plete problem. As a result of factors outside of the scope of the work reported here, the findings were not applied. Even so, it can be argued that the study produced benefits that justified its cost.
An interactive simulator for the KIM-1 microcomputer
Authors: Nagata Wesley M. , Miller Donald S. 
Published: March 2008

The KIM-1 simulator is a development tool for the MOS Technology 6502 microprocessor and the KIM-1 microcomputer. It is written in the C programming language and runs under the UNIX operating system on a DEC PDP-11/60. The input to the simulator is ob ject code produced by a cross-assembler. The simu lator helps in debugging 6502 programs by providing the user with the ability to interactively load and display memory and registers, dynamically set and clear breakpoints, handle interrupts, and trace pro gram execution. The simulator is user-oriented; it supplies prompts, English diagnostics, and instructions on usage. Its execution speed and core requirements allow truly interactive debugging. The KIM-1 simulator, in conjunction with the cross- assembler and the actual KIM-1 microcomputers, has been an excellent educational tool for an introduc tory course in computer organization and assembly- language programming. In addition, it has helped researchers using the 6502 microprocessor in appli cations.
Simulating urban obstructions
Authors: Frank Randall S. , Gerding R. Bruce , O'Rourke Patricia A. , Terjung Werner H. 
Published: March 2008

A problem that urban planners have to deal with is the obstruction of sunlight by buildings which may shade streets adjacent to them as well as other near by buildings, thus strongly affecting (1) the need for summer cooling and winter heating at particular sites, and (2) the suitability of sites for particular uses. This problem becomes very complicated when buildings are irregularly shaped and are located in an irregular pattern, and when street widths vary. Doing the necessary calculations by hand is extremely tedious, highly error-prone, and costly. A generalized computer model of great flexibility has been developed to overcome the drawbacks of hand caZ culations of solar shadowing. The program, which is called OBSTRUCT, is modular and is written in FORTRAN IV to run on an IBM 3033 computer. The pro gram is available at no charge. Sample runs for two illustrative cases are included in this report.
Microanalytic simulation models as tools for legislative planning
Authors: Bungers Dieter 
Published: March 2008

Microanalytic simulation models (or micromodels) are useful tools for analyzing and forecasting the social and budgetary effects of government tax and transfer programs. A micromodel actually models the individ ual units passing through the system, rather than dealing with aggregated statistics. The micromodel derives the overall effects of the system by summing its effects on a representative sample of individual units. This type of model is necessary because the complicated interaction of legal regulations and the socioeconomic structure of the population must be modeled in detail if the simulation is to describe all the significant effects of programs. We used the microanalytic approach to develop a planning system for the German Federal Student Aid Program (BAFPLAN). This project required the solu tion of several important methodological problems. These included: (1) the construction of a data file representative of the initial population, (2) the arti ficial aging of the data file, and (3) the modeling of changes in human behavior. Future research will ex tend the use of micromodels in legislative planning and will deal with the problem of access to the requir ed data.
Reduction of time delays in Runge-Kutta integration methods
Authors: Nowack Stefan , Feil Georg 
Published: March 2008

Numerical (digital) integration in a real-time simulation is often performed using explicit Runge-Kutta methods. Real-time system simulation places high demands on computers and integration routines, if data must be sampled from input signals and incor porated into the numerical integration algorithm in order to evaluate the derivatives of the state variables. A modified fourth-order Runge-Kutta (RK4) method, which meets these requirements particularly well is proposed. As an example the routine is applied to a complex flight simulation problem. The results of the modified routine and of the RK4 standard are compared and the specific advantages of the new routine demonstrated.
An expert system framework based on a simulation generator
Authors: Haddock Jorge 
Published: March 2008

Expert Systems (ES) implementations automatically perform tasks for which specially trained or talented people have been re quired. Fifth generation simulation systems integrate the tools developed in the fourth generation and capture the knowledge of the expert programmer as well as that of the simulation model ing expert. Haddock has programmed a user- oriented simula tion generator for the design and control of flexible manufac turing systems (FMS). The development of an ES based on the generator is described in this paper. The system to be described solely requires knowledge of the system to be simulated from the user. FORTRAN written sub routines, incorporated within the software structure of SIMAN, interpret the results of experimental runs and make statistical inferences about the performance measure. Simulation generators can assist simulationists in model develop ment and update, as well as in the analysis of alternative sce narios. A very desirable feature of Intelligent Front Ends (IFEs) is to have the capabilities of analyzing their output. These capa bilities not only reduce the total time required to perform the simulation, but also prevent its misuse.
A hybrid paradigm for modeling of complex systems
Authors: Ruiz-Mier Sergio , Talavage Joseph 
Published: March 2008

The network modeling approach to simulation provides the mo deler with simple and powerful concepts which can be used to capture the significant aspects of the system to be modeled. Yet the most advanced network modeling environments lack ex plicit concepts for the representation of complex behavior such as decision-making. Artificial intelligence research, because of its emphasis on knowledge representation, provides several meth odologies which can be successfully applied to the modeling of decision-making behavior. The approach to modeling complex behavior, outlined in this paper, is based on a hybrid methodology unifying the concepts of Object-Oriented programming, Logic Programming and the discrete event approach to systems modeling. We present SIM YON, an experimental network simulation environment which provides explicit constructs for the representation of complex behavior of real-world systems. SIMYON is implemented by de fining a library of logic objects in the Object-Oriented, Logic Programming environment CAYENE. These objects, which are analogous to the "nodes" of network simulation languages, are the building blocks for modeling. Examples are given in SIMYON to model a job scheduler in a manufacturing situation and an adaptive material handling dis patch mechanism for flexible manufacturing systems.
Interactive graphics in GPSS/PC™
Authors: Cox Springer 
Published: March 2008

GPSS/PC is a recent implementation of the discrete event simula tion language GPSS, the General Purpose Simulation System. With the introduction of Version 2, GPSS/PC has added interac tive graphics and animation to its simulation environment. Its graphics windows are truly interactive, allowing manipulation via an optional pointing device, and assertion of all simulation primitives. All windows are online, providing for a visualization of model dynamics, and one of the windows allows animations of the simulation to be played out in an essentially unbounded virtual screen. In addition, a CAD-based animation postprocessor is scheduled for release in late 1987. It can lend considerable realism to pre viously recorded animations. In accordance with the design goals of the interactive graphics of GPSS/PC, the animation postpro cessor is designed to run with minimal hardware requirements, if necessary. This paper discusses the design alternatives leading to the im plementation of the interactive graphics in GPSS/PC, and the use and limitations of animated simulations.
A fire-spread simulation model developed as an extension of a dynamic percolation process model
Authors: Hirabayashi Fusako , Kasahara Yutaka 
Published: March 2008

A stochastic model of a fire-spreading process has been devel oped to simulate pertinent time-dependent changes. This model has been obtained by extending an existing stochastic model in which the fire-spreading process is described as a percolation process. The extended model considers the time period from ignition to the point at which flames have spread to an unburnt unit. In this model, the above two quantities (the time required for ignition and that required for reading an unburnt unit) are treated as continuous random variables dependent upon the respective probabilities of blaze up and fire spread. To evaluate this model, a Monte Carlo simulation system has been developed. Experiments on hypothetical and real city layouts show that this model is a useful simulation tool in studies con cerned with firefighting.
Turbo-simulation: A technical note
Authors: Korn Granino A. 
Published: March 2008

Many reported computer execution-speed benchmarks involve artificial programs exploring the fixed- and floating-point instruc tion sets. Instead, we report results from two actual dynamic- system simulation problems long used as benchmarks by the simulation community. PHYSBE (Korn and Wait 1978) is a blood- circulation model used in physiological studies, and the Hidinger benchmark (Hidinger 1982) is a practical three-dimensional flight simulation (really a torpedo/ autopilot simulation) developed at the Naval Ocean Systems Center. Such programs can give realistic indications of practical results obtainable with different machines. Specifically, we report on a study of measured and predicted simulation speeds of personal computers with speeded-up clocks and of new 32-bit personal computers. This is a glimpse into a new, bright world of very cost-effective simulation; an 80386/ 387-based PC clone outruns a timeshared VAX 11/780 in the flight-simulation benchmark.
POSE: a Process-Oriented Simulation Environment embedded in SCHEME
Authors: Stairmand Malcolm C. , Kreutzer Wolfgang 
Published: March 2008

POSE is part of a research program to explore potential benefits of new software technologies for various modelling paradigms. It is a SCHEME-based queueing network simulator, whose discus sion serves to demonstrate the suitability of symbolic languages and exploratory programming styles for system simulation. After justifying the use of symbolic languages and an object- oriented approach to model design, basic features of POSE are presented, using a simple example. This is followed by a brief description of the simulator's architecture. A final chapter sum marizes and reflects on our experiences, suggesting that object- oriented simulation environments hosted on powerful personal workstations may well offer major breakthroughs in terms of ef fectiveness and user acceptance. Computational efficiency, while a lesser concern to "investigative simulation," remains unsatisfac tory in simulations used for quantitative predictions. This prob lem may hopefully be overcome through future advances in soft ware and hardware technologies.
Modeling and simulation of an Analog Charge-Pump Phase Locked Loop
Authors: Can Sumer , Sahinkaya Yilmaz E. 
Published: March 2008

We describe a nonlinear computer simulation model of an Ana log Charge-Pump Phase Locked Loop (ACP-PLL). Offsets of the Phase Detector and Analog Charge-Pump are modeled as dis turbances to simulate their effects on the steady-state phase error of the loop. An extensive computer simulation study is carried out for the design of an example Analog CP-PLL using the proposed non linear model and comparing it to the conventional linear model. Results demonstrate the linear model is not sufficient to fully analyze and predict the behaviour of the Analog CP-PLL.
A simulation model for mechanized log harvesting systems
Authors: Wiese Christoph , Olsen Eldon D. , Randhawa Sabah U. 
Published: March 2008

The design, evaluation and control of mechanized harvesting systems is a problem of considerable importance in the forest products industry. However, due to the complexity and diversity of such systems, mathematical analysis of these systems is not computationally feasible. Although the simulation approach to model the harvesting problem has received considerable atten tion, the simulation models developed to date have primarily concentrated on modeling specific components of the system. Furthermore, the simulation models developed for log harvesting have seen little use. This is because the model input requires the user to be familiar with the simulation language, and the simulation results are difficult to interpret in terms of system costs and productivity. The research reported in this paper developed a simulation model for analyzing the entire logging operation (tree-to-mill) in the forest products industry. Using this system, the user is able to define on-line, in an interactive session the configuration of the timber harvesting system the user would like to analyze. A network-based simulation model then performs the simulation and reports the results in an easy to analyze and readable form.
A Comparative study of finite difference and multiquadric schemes for the Euler equations
Authors: Kansa E.J. 
Published: March 2008

We present a true scattered-data, grid free spatial approximation scheme called multiquadrics (MQ) first developed by Hardy. We have modified the original MQ scheme and demonstrated that it is exceptionally accurate for not only surface approximations, but also partial derivative estimates. Unlike familiar polynomial ap proximations, MQ is excellent for moderate to steep gradient regions, but rather poor in relatively flat regions. For that reason, we advocate a hybrid scheme which uses MQ in moderate to steep regions, but switches to the familiar polynomial methods in relatively flat regions. In this paper, we compare the accuracy and operation counts of finite differences and MQ schemes for the solution of time depen dent nonlinear set of hyperbolic partial differential equations. We have demonstrated both from an operations count and accuracy that MQ is superior to the familiar finite difference scheme.
On modelling and differential/algebraic systems
Authors: Mattsson Sven Erik 
Published: March 2008

It is of a vital interest that software for model development and simulation supports models given as differential/algebraic equa tions (DAE), since many models for physical systems are naturally given as sets of ordinary differential and algebraic equations and since, as motivated in the report, the equation form is the only reasonable for model libraries. Unfortunately, most simulation packages of today do not allow models given as DAE systems, but require assignment statements for derivatives and algebraic variables. There are numerical solvers for DAE systems, but they are not as reliable and robust as numerical solvers for ordinary differential equations on state space form. Unfortunately, DAE systems may exhibit bad properties, which make them difficult to solve numerically today. The purpose of the paper is to give an over view of important properties of DAE systems, indicate possible ways to handle difficulties and to motivate others to do research in this area. By means of examples it is illustrated that even small, simple DAE systems can exhibit bad properties. The examples are by no means pathological. They arise naturally during model development. There are many open questions to answer. The questions cover a broad range from theoretical to practical problems. To en courage research in this area, interesting issues are listed.