bluuebunny/crossref_metadata_2025 huggingface dataset:
Visual interactive fitting of bounded Johnson distributions
Authors: DeBrota David J. , Dittus Robert S. , Roberts Stephen D. , Wilson James R.
Published: March 2008

We present a visual, interactive method for specifying a bounded Johnson (SB) probability distribution when little or no data are available for formally identifying and fitting an input process. Using subjective information, the modeler provides values for familiar characteristics of an envisioned target distribution. These numerical characteristics are transformed into parameter values for the probability density function. The parameters can then be indirectly manipulated, either by revising the desired numerical values of the function's specifiable characteristics or by directly altering the shape of the displayed curve. Interaction with a visual display of the fitted density permits the modeler to conveniently obtain a more realistic representation of an in put process than was previously possible. The techniques involved have been packaged into a public-domain microcomputer-based software system called VISIFIT.
Automatic model generation for production-distribution systems using natural language
Authors: Austin Wanda M. , Khoshnevis Behrokh
Published: March 2008

Simulation is a powerful tool for system analysis and decision sup port. Managers need sophisticated simulation tools to support time-critical decisions. This paperpresents an intelligent simula tion environment which provides the manager with analytical sup port through a user friendly interface. Using natural language, the user can build system dynamics simulation models. The applica tion domain is multi-level production distribution systems. DYNAMO code for the model is automatically generated.
An automatic programming approach to simulating prelaunch activities
Authors: Zhang Shou-Xiang , Schroer Bernard J. , Tseng Fan T.
Published: March 2008

This paper presents the develop ment of an automatic program ming (AP) system for simulat ing prelaunch activities. The Automatic Network Program ming System (ANPS) is a tool to assist the modeler define a problem and then to automati cally generate the corresponding code in the target simulation language.
Simulation models of ecological economics developed with energy language methods
Authors: Odum Howard T.
Published: March 2008

The energy-systems language method of modelling and simula tion, because of its energy con strained rules, is a means for trans ferring homologous concepts be tween levels of the hierarchies of nature. Mathematics of self-organi zation may justify "emulation" as the simulation of systems overview without details. Here, these methods are applied to the new fields of "ecological economics" and "ecological engineering." Since the vitality of national economies depends on the symbiotic coupling of environmental resources and human economic behavior, the energy language is adapted to develop overview models of nations relevant to public policies. An overview model of a developing nation is given as an example with simulations for alternative policies. Maximum economic vitality was obtained with trade for external resources, but ultimate economic carrying capacity and standard of living was determined by indige nous resources, optimum utilization and absence of foreign debt.
The binary derivative test: noise filter, crypto aid, and random-number seed selector
Authors: Carroll John M.
Published: March 2008

Random noise obscuring digit ized images or text can be removed by a new technique that recognizes the appearance o f randomness in short bit strings. This test makes uses binary derivatives. The derivative of a bit string is formed by recur sively XORing the bits pair- wise. The measure of random ness depends is the maximum range of the one's ratio (p) among various order deriva tives. Random pixel strings in digital images can be zeroed out leaving outlined regions where image details can be recovered by edge-detection or other tech niques. Binary derivatives can also assist cryptographers and cryptanalysts. And they can help simulationists avoid selecting random-number generator seeds that would bias their results.
On Fly-by-Wire Control System and statistical analysis of system performance
Authors: Hammond Ronald A. , Newman David S. , Yeh Y.C.
Published: March 2008

The flight control system proposed for future Boeing commercial airplanes is a Fly-By-Wire (FBW) system. The entirely electronic FBW system will replace the mechanical cable/quadrant/pushrod system used on earlier airplanes. The FB W system, also called an Electronic Flight Control System (EFCS), must meet extremely high standards of integrity and reliabil ity. The heart of the FBW concept is the use of redundant, dissimilar computing and communication channels.

Predicting the performance of such a system is beyond the capabilities of conventional simulation and control system design methods. Moreover, the number of independent, random parameters in the system makes straight forward Monte Carlo analysis prohibitively expensive. This paper describes the simulation methods used to model the EFCS, and the use of statistically designed experiments to extract more infor mation about the performance of the EFCS with a smaller number of simulation runs than is possible with a less structured approach. The results of the analysis defined the performance of the EFCS, especially the tails of the distribu tions of the performance measures, with much greater confidence than could have been gained by more conventional methods.
Modular Control System Simulator
Authors: Ovaska Seppo J.
Published: March 2008

In this paper, we introduce a modular control system simulator for positioning servo applications. The program package was originally written for elevator car positioning simulations, but because of its straightforward modular structure it can easily be tailored for other types of applications as well. The simulator contains all the necessary functions needed to design an appropriate positioning servo when an estimate of the system model is known. The numerical system model is assumed to be a rational z-domain transfer function and it can be identified a priori from measured excitation and response signals by using some prediction error type algorithm. Although all the internal computations are performed using floating-point numbers, the simulator has built-in A/D and D/A converters to quantize the input and output sequences artificially. The simulator also has a programmable noise generator to generate additive measurement error to the simulated feed-back signal. The control and noise- filtering algorithms can be changed by replacing the existing modules with user-written FORTRAN subroutines. All the data transfers between individ ual modules are well defined to ensure easy modifiability of the overall system. The simulation software runs in a desk top personal computer.
A Simulation Assistant for Modeling Manufacturing Systems
Authors: Schroer Bernard J.
Published: March 2008

This paper presents a structured approach to modeling manufac turing systems. The structured approach is accomplished through a simulation assistant consisting of a set of predefined GPSS simulation macros, a user interface, and an automatic code generator.
Development and training of a learning expert system in an autonomous mobile robot via simulation
Authors: Spelt P.F. , Lyness E. , deSaussure G.
Published: March 2008

The Center for Engineering Systems Advanced Research (CESAR) conducts basic research in the area of intelligent machines. Recently at CESAR a learning expert system was created to operate on board an autonomous robot working at a process control panel. A two- computer simulation system was used to create, evaluate and train this learning system. The simulation system has a graphics display of the current status of the process being simulated, and the same program which does the simulat ing also drives the actual control panel. Simulation results were validated on the actual robot. The speed and safety values of using a computerized simulator to train a learning computer, and future uses of the simula tion system, are discussed.
Dynamic models of the AIDS epidemic
Authors: Ahlgren David J. , Stein Alex C.
Published: March 2008

This paper describes HIV transmission models built using STELLA, a new language for the Apple Macintosh. These include a basic model, or template, of sexual transmission of HIV; a model of heterosexual transmission constructed from the template; and a model which simulates transmission caused by needle sharing. The paper also describes a computer program, based on the template rate equations, which optimizes key epidemiological parameters associated with the early epidemic in San Francisco. With this program we have shown that the per contact transmission probability (infectivity) of the antigen- positive first stage of infection may be significantly higher than the infectivity of the antibody- positive subsequent stage. This finding stresses the importance of screening for viral antigens to detect first stage infection in high risk groups.
A simple model for estimating the prevalence of HIV-infected persons
Authors: Kotva Milan , Zdenková B.
Published: March 2008

It is not possible to ascertain directly the exact actual value of prevalence of HIV-infected persons without clinical symptoms of AIDS. Therefore a very simple simulation model was developed for the estimation of this value in the early stage of the epidemic. This model is based on the principles of the general method of multicompartmental models and its core is the so-called one-way transport segment which imitates very faithfully the supposed transition of HIV-infected persons through the stage from the transmission of infection to AIDS manifestation. The number of AIDS cases is represented in the model by a compartment. The essence of the estimation procedure is also very simple —it consists in the finding of such shape of the time-dependent parameter of exponential input function of the transport segment for which the course of the compartment measure values agree with the ascertained or prognosti cated data about the numbers of AIDS cases. The dependence of the exponen tial function parameter on the product of the average probability that the infection is transmitted from the infected to the receptive individual and of the average rate at which new sexual partners are required can be shown.
PRE-PRIM as a pre-processor to simulations: a cohesive unit
Authors: Gardenier Turkan K.
Published: March 2008

Large scale computer simula tions are in widespread and growing use in government, business and science. Large numbers of parameters may initially appear to be needed in simulations; the user needs the flexibility to evaluate as many parameters as possible. Mathe matical and statistical tools can reduce the final set of parame ters to an efficient minimum. This paper describes the con cepts underlying PRE-PRIM, a preprocessor to simulations integrated by the present author. PRE-PRIM assures that (a) a wide number of parameters can be analyzed with a minimum number of simulation runs, (b) efficiency and replicability in the coefficients of these parameters is established, and (c) a protocol for the sequence of simulation runs is determined.
Applying the object-oriented paradigm to discrete event simulations using the C++ language
Authors: Eldredge David L. , McGregor John D. , Summers Marguerite K.
Published: March 2008

This paper demonstrates the appropriateness of an object- oriented programming lan guage, C++, for developing discrete event simulations. An introduction to the concept of object-oriented programming and the C++ language is followed by an example simula tion of a single-server queuing system. The example shows the general advantages of the C++ language for simulations.
A Prolog simulation for combustion control
Authors: Fogarty Terence C.
Published: March 2008

This paper describes the simulation of the effect on overall carbon monoxide and oxygen readings of alterations to the air inlet valve of each of a number of burners sharing a common flue. Built as part of the development program of a rule-based system for combustion control in a multiple burner furnace in the steel industry it has proved to be an invaluable tool. It is now being used to aid the adaptation of the rule-based system for use on other multiple burner furnaces and on boiler plants.

Every burner in the installation is represented by a number of perfect burners which in turn are represented by Prolog facts in a relational database. Changes to the burners and readings of carbon monoxide and oxygen from the common flue are accomplished by Prolog predicates operating on the database as are changes in firing level and degeneration of the burners over time. Prolog was initially chosen for ease of interfacing with the rule-based system but was found to be an ideal language for writing the simulation although elegance of expression often had to be sacrificed to brute force for it to run effi ciently on a micro computer.

The output of the functional simulation of a two burner installation under the control of the rule-based system is compared with that of a two burner boiler under the control of the same system. The response of the two is shown to be similar under a broad range of operating conditions.
Modeling and simulation in the test and evaluation process
Authors: Atkinson James H.
Published: March 2008

An integral part of most major weapon systems is some form of a C3I technology. This utilization and its complexity are presenting the Department of Defense (DoD) Test and Evaluation (T&E) with major performance evaluation challenges. These challenges will require the utilization of complementary computer models and simulations (M/S) with testing. To effectively complement testing, it is necessary that the methodology for employing MIS with testing be clearly understood throughout the life cycle of the weapon system. Also, there are four basic M/S characteristics which will require special attention during the development and utilization of the M/S capability. These characteristics are: (1) Degree of Representation, (2) Practicality, (3) Validation and (4) Configura tion control. These characteristics will need to receive top priority at all times if MIS is to become a complementary tool for the DoD T&E communities.
Digital models and simulation in the test and evaluation process — A new emphasis
Authors: Oldham Loel E.
Published: March 2008

A new and increased empha sis on the use of modeling and simulation as a direct and significant part of the Opera tional Test and Evaluation (OT&E) Process has recently been established in the Depart ment of Defense. A comprehen sive policy statement was issued by the Director, Opera tional Test and Evaluation, on 24 Jan 1989. In line with this policy the US Air Force has initiated a broad series of actions ranging from develop ment programs to application of modeling and simulation in actual test and evaluation. This paper summarizes these actions and provides some limited commentary on the causes and effects of the new policy emphasis.
Economic and financial simulation for small business: A discussion of the small business economic, risk, and tax simulator
Authors: Cochran Mark J. , Richardson James W. , Nixon Clair
Published: March 2008

A simulation model designed to perform economic, risk, and tax analysis for small busi nesses organized as sole proprie torships is presented. The SERTS model can be run deter ministically or stochastically and has the ability to monitor numerous performance vari ables over the entire planning horizon. The model can be used by managers to rank alternative management strategies for risk efficiency. Risk efficiency is identified with generalized stochastic dominance. Alterna tively it can perform impact analysis on government programs and macroeconomic conditions for use by the public policy process.
Performance of Fourier series in line transect simulations
Authors: Pinkowski Ben
Published: March 2008

Performance of Fourier Series is assessed for density estimation problems involving the line transect census method. Simu lated populations of objects characterized by various distributions (Poisson, aggre gated, and uniform) are gener ated to examine important stochastic variables, including detection function, sample size, object movement, and several kinds of observer measurement errors. Circumstances are identified where FS performance is generally acceptable and where alternate models should be sought.
A concise algorithm to solve over-/under-determined linear systems
Authors: Lord Eric A. , Sen S.K. , Venkaiah V. Ch.
Published: March 2008

An O(mn2) direct algorithm to compute a solution of a system of m linear equations Ax=b with n variables is presented. It is concise and matrix inversion- free. It provides an in-built consistency check and also produces the rank of the matrix A. Further, if necessary, it can prune the redundant rows of A and convert A into a full row rank matrix thus preserving the complete information of the system. In addition, the algo rithm produces the unique projection operator that projects the real (n)-dimensional space orthogonally onto the null space of A and that provides a means of computing a relative error bound for the solution vector as well as a nonnegative solution.
A numerical simulation of a free mixing layer
Authors: Sod Gary A.
Published: March 2008

A numerical method is pre sented that can resolve a compressible flow field at high Reynolds number. It is used to compute the free mixing layer of a flat plate of finite length with unequal free stream velocities above and below the plate. The computed flow field is shown to be dominated by large scale vortices which have been observed unexperiments. These results are shown to be in close agreement with experiments.
Modeling and simulation of robot dynamics using transputer-based architectures
Authors: Zomaya A.Y. , Morris A.S.
Published: March 2008

Advanced control strategies require the inclusion of the dynamical model of the robot arm in the control law. However, the dynamics consist of a highly coupled and non-linear set of equations. Thus, this complexity has always presented a major obstacle in real-time dynamic control applications. The computation ally efficient solution of this problem will lead to a better comprehension of the key factors effecting robot operations. This work describes a solution of this problem by employing a parallel processing approach. The dynamics are computed by using a semi-customized Newton-Euler formulation. The algorithm is distributed over a highly- coupled multiple™ instruction multiple-data steram (MIMD) computer architecture. The computer system is constructed from general purpose (VLSI) building blocks called the (TRANSPUTER). The cost-effective ness and speed of the scheme is demon strated by a case study (PUMA 560 robot arm). The communication issues between the different processors and discussed. Speed-up results are included to show the superiority and advantages of the parallel approach.
Combining an expert system with simulation to enhance planning for banking networks
Authors: Coats Pamela K.
Published: March 2008

This application paper shows how bankers who are planning to operate a local electronic funds transfer (EFT) network can use simulation and an expert system to improve their EFT decisions. The key to making good EFT decisions is understanding the tradeoffs between the costs and performance of different network possibilities. Being able to explore network choices in light of a bank's service and profit goals, prior to the actual commitment of resources, is essential to that understanding. However, there are no published EFT studies which attempt to combine both technical and economic con cerns, particularly the representation of intangible benefits and costs, in a single methodology. The simulation process de scribed here illustrates a computer model that approximates the performance and economics of alternative local EFT designs. Expert system technology is incorporated to give bankers the convenience of interacting with the model in a natural language format. It should be noted that the work described here is based on the author's current research and ongoing model development for client banks. Every attempt is made to be as informative as possible without breaching confidentiality.
An efficient method for handling time-dependent boundary conditions with the DSS/2 differential equation solver
Authors: Bainian Liu  , Aguirre Fernando J.
Published: March 2008

This paper discusses an efficient method for handling time dependent boundary conditions with the DSS/2 differential equation solver. The method was evaluated by using it in the numerical solution of a diffusion problem. The proposed method is also particularly useful for boundary conditions in which only derivatives of the depend ent variables are involved. The method is based on transforming the boundary conditions at the interface to a set of algebraic equations which must be solved simultaneously at each integra tion step. Both algebraic and numerical solutions of this set of equations are discussed, and the relative merits of each one of these solutions are evaluated. The proposed method provides significant improvements in computation times and is capable of handling more complex boundary conditions as compared to other conventional methods.
Syntactic modeling and simulation
Authors: Green David G.
Published: March 2008

Formal languages are powerful modeling tools in their own right. Applications to biological processes such as growth and behavior emphasize the ability of syntactic models to capture organization clearly, concisely and accurately. This ability can be exploited by designing generic systems ("em bodiments") that simulate whole families of processes. Within an embodiment, specific models are defined by formal languages whose semantics relate to the real-world systems being modelled, rather than computational details. The most powerful embodiment systems are object-oriented hierarchies based on key theoretical concepts, such as directed graphs, cellular automata, and neural nets. Benefits of the embodiment approach include simplifying the development of simulation models; permitting the use of formal languages as modeling tools; and stimulating the develop ment of theory in particular areas of application.
Fawsim
Authors: Brown Terrance J. , Shub Charles M.
Published: March 2008

This paper describes a flexible artificial workload simulator in use both as a pedagogic aid in a teaching environment and as a tool in a software prototype test facility. The background motivations behind the development of the tool are presented first. This is followed by a delineation of the goals derived from the motivations and examination of related work. Next the design choices are pre sented and justified. This is followed by a brief description of the tool. The presenta tion continues with a description of the choices made during the implementation phase. Particular attention is paid to how the sequencing of workload components was achieved. The discussion of implemen tation is concluded with some necessary low level details. The validation pro cedures are described. Finally the opera tion of the tool is explained and conclu sions are given.
A procedure for interactive simulation using mnemonic identifiers and index mapping functions
Authors: Mukundan R. , Swamy S.S.
Published: March 2008

A method for interactive simula tion of continuous systems using index mapping functions is presented. State variables, their differential forms and function outputs are represented by elements of a mnemonic set which constitute the building blocks in system modeling. Mapping functions are used to assign each mnemonic a unique pointer to its value location, and also to translate user defined equations into index matrices. Outputs of functions pertaining to any specific problem domain can be easily mapped to the variable list. Procedural details are illustrated with examples of second order sys tems.
Simulation methodology for intermodal freight transportation terminals
Authors: Kondratowicz Ludwik J.
Published: March 2008

This paper presents the issue of general methodology for modeling and simulation of seaport and inland terminals in intermodal freight transportation systems. The report documents a phase of the on-going more comprehensive effort aimed at developing a generalized modeling capability to provide strategic and tactical decision support for transportation logistics and intermodal terminals.

By providing the object-oriented process of simula tion modeling with the coherent and uniform methodo logical basis, it was possible to construct a practical tool "TRANSNODE," The Simulator of Intermodal Transportation Terminals which allows one to model and simulate any transportation terminal, or a group of interconnected terminals, large or small, multipurpose or specialized, at optional scale. Knowledge-base and artificial intelligence concepts were incorporated in the simulator.

Different from traditional simulation modeling, which combines data, knowledge and control program ming, the data-driven simulation modeling approach of the TRANSNODE system treats data and control logic as distinct parts. The resulting model is a generic simulator which can be used in many different application scenarios without requiring user simulation knowledge to modify the program. The only thing the user must do is supply the input data in the specified format through data files. Different terminal configura tions can be simulated merely by changing the input data.

The developed technology is expected to be used by the industry for supporting their strategic and tactical decisions, by engineering firms in evaluating the design of their client facilities, their policies, and by the universities and research institutes in supporting and furthering their research.
SLONN: A Simulation Language for modeling of Neural Networks
Authors: DeLiang Wang  , Hsu Chochun
Published: March 2008

This paper presents a general purpose Simulation Language for modeling Of Neural Networks (SLONN) which has been implemented in our laboratory. Based on a new neuron model, SLONN can represent both spatial and temporal summation of a single neuron and synaptic plasticity. By introducing fork to describe a connection pattern between neurons and by using repetition connec tion, module type and module array to specify large networks, SLONN can be used to specify both small and large neural networks effectively. This language is distinguished by its hierarchical organiza tion, which makes it possible to catch very general aspects at higher levels as well as very specific properties at lower levels. As an example to demonstrate some features of SLONN, we have modeled the habitua tion and sensitization behaviors in Aplysia.
Graphical description and a program generator for queuing models
Authors: Raczynski Stanislaw
Published: March 2008

The Queuing Model Generator (QMG), described in this article, is a module of the environment of the simulation language PASION. It contains a block-diagram editor which permits the user to define the structure of the model, and a program generator which generates the corresponding PASION code. This code is automatically translated to PASCAL. QMG is transpar ent, (i.e. the languages PASION and PASCAL are not visible for "non-program mer" users.) However, if the user knows PASION or PASCAL, then he can work with the resulting code, creating more complex models. An application in flexible manufacturing systems design is described.
BOOK REVIEW A review by Dr. Dean Uyeno, SIMULATION Book Review Editor, Faculty of Commerce, University of British Columbia, Vancouver, Canada, V6T IW8 : Getting Started with GPSS/H
Authors: Banks J. , Carson J.S. , Sy J.N.
Published: March 2008

The Red Book lies quietly on my shelf, its cover frayed through years of heavy use, some pages torn.

The book and I were both young once. Before 1974 when Tom Schriber was still pregnant with the ideas for the book, I employed a pre-publication version to equip bright and eager students with the skills to practically apply this innovative problem-solving tool, GPSS.

As the years went by, however, the book and I both became grayer. Updated versions of GPSS appeared on various computer platforms. Microcomputers became the tool of choice and friendlier versions of GPSS became available. Through it all, the Red Book never changed, although its price always rose. Rumor had it that Tom Schriber wanted to revise and expand the book so we waited and remained loyal, but nothing happened. We were very patient, but now it is 1990.
Improving the reliability of confidence limits for the mean of positive random variables
Authors: Le Minh Do , Sherif Y.S.
Published: March 2008

This paper presents a simple method to obtain a strictly positive lower confidence limit for the mean of a positive random variable. Although this method involves some approxi mations, it is shown empiri cally that it works well for a large number of cases.
Interactive simulation of backpropagation and creeping-random-search learning in neural networks
Authors: Korn Granino A.
Published: March 2008

A new environment for interactive neural-network experiments on personal computers, DESIRE/NEUNET combines a readable matrix language with very fast "direct execution". Experimenters enter and screen-edit simulation programs and run immediately, without the usual annoying delays for compilation and linking. Simula tions still run much faster than Microsoft FORTRAN. Users can compose their own help screens and interactive menus. DESIRE/ NEUNET permits conventional dynamic-system simulation (up to 1000 differential equations) as well as, or in conjunction with, neural-net simulation and has been used to simulate Hopfield and bidirectional associative memories, transver sal predictors, and various competitive- learning schemes. This report exhibits the classical XOR training experiment with backpropagation and creeping-random- search learning.
Operational Evaluation Modeling
Authors: Clymer John R. , Corey Philip D. , Nili Nafise
Published: March 2008

A graphical parallel process language is described that assists a system designer in visualization of system operation. Visual ization is essential when building an operational model to experiment with alternative system operation and architec tures and to evaluate design tradeoffs. Such visualization is also essential for the knowledge engineering necessary to implement object oriented, rule based decision making in a simulation program. A Pascal simulation programming system is discussed that has been developed to implement the graphical language and rule based control.
An interactive debugging expert system for GPSS/H simulation models
Authors: Mellichamp Joseph M. , Venkatachalam A.R.
Published: March 2008

Many enhancements to simulation methodol ogy which will reduce the burden on the simulation analyst are likely to come as a result of the integration of expert systems methodol ogy with simulation. One phase of the simulation approach which appears to have particular promise for the integration of expert systems methodology is the model development task. This is perhaps the most time consuming step in the simulation approach and probably requires the highest level of expertise. Interest ingly, the piece of the model development task which is almost certainly the most frustrating to the analyst — program debugging — has attracted very little attention from an expert system perspective. Thus, it would appear that there is both a need and an opportunity for expert systems that could assist system analysts in the program debugging task. The major objective of this research was to develop an expert system which could function as a debugging advisor to simulation analysts. A second objective was to evaluate the expert system and from the evaluation try to make generalizations about the most viable form and structure for such systems in order to guide future research efforts in this area.
Modular simulation of the static portion of the leaf energy budget
Authors: Tichenor Lee H.
Published: March 2008

The ability to simulate the static energy budget of the green leaf is needed before any of the dynamic leaf functions such as stomatal control or the interactions among the intermediates of photosynthesis can be studied on the computer. This program uses a windowed interface, interactive control of 23 environmental and structural variables, and a modular design to build such a simulation. The modular design allowed by the newer implementation environments, such as Borland's Turbo Pascal V, means that further dynamic functions which require elements of the static energy budget can be simply added as additional modules.
Smulation Network News
Authors: Fishwick Paul
Published: March 2008

This column focuses on a single topic within the field of computer simulation. All the material comes directly from the electronic news group (bulletin board) called Simulation Digest. The Digest can be obtained over INTERNET by accessing the news group 'comp.simulation' or by sending e-mail to: 'simulation request@bikini.cis.ufl.edu'
ISI - An environment for the engineering use of general purpose simulation languages
Authors: Nolan Paul J. , Lane Gearóid M. , Fegan Joseph M.
Published: March 2008

Present day approaches to discrete event simulation can be broadly classified as using either special purpose data-driven simula tion systems or general purpose simulation languages. Although the latter embrace a far wider range of applications and offer much greater flexibility in modeling for a particu lar application, their user base is restricted by the high level of expertise required.

An Expert System interface to general purpose simulation languages, ISI (the Intelligent Simulation Interface), is pre sented here. Models are constructed and simulation runs are performed in an integrated environment comprising interactive menu-driven graphics, a knowledge base system and a general purpose simulation language. The features of ISI include hierarchical model construc tion, interactive experiment specification, automatic code generation, run-time animation and interactive graphical post- processing of results. An example case study is presented illustrating the main aspects of ISI. The ISI interface is shown to extend a general purpose language into an intelligent simulation environment.
A simulation model for management of operations in the pharmacy of a hospital
Authors: Mukherjee Arup K.
Published: March 2008

A need exists for a readily usable tool for different operations management strategies in a pharmacy of a hospital. A simulation model of a pharmacy, incorporating the major activities in relation to processing of regular orders, emergency orders and outdoor orders has been presented. The model has been programmed using the simulation language SIMAN. Several complexities like getting clarifications on drug orders and preparation of I.V. drugs have been included. Turnaround times of orders and utilizations of pharmacist, order technician and order entry technician have been investigated and found to be comparable to a real life pharmacy. Detailed description has been presented about how an operating manager may use the model to evaluate various operating strategies. Sensitivity analysis of a few parameters has been presented to illustrate some important relationships. Performance measures estimated by the model are found to be very similar to a real life hospital pharmacy.
Graphical programming of simulation models in an object-oriented environment
Authors: Ozden Mufit H.
Published: March 2008

Graphical programming, which is used here to mean creation of simulation models graphically, has been used in conjunction with conventional simulation languages via block diagrams or activity networks. Its beneficial effects on model development in simulation have been generally accepted. However, none of these conventional simulation languages has reached a level of graphical programming that would impact the user's programming task substantially. Today, this is possible with the current software and hardware technology. An interactive incremental programming environment supported by a good graphical programming system that helps automatic model development, specification and verification would be greatly appreciated in modeling in general, but especially in simulation of complex real-life systems. Such a visual system could essentially be a conceptual framework for analysis of the problem at hand and become a means of communication among the people who are involved in development and management of systems. It can also be the friendly interface that forms a communication medium between the modeler and the computer for automatic programming.

In this research paper, a prototype graphical programming methodology for modeling and automatic interpretation of simulation problems is developed in the object-oriented environment of the Smalltalk-80 language. The modeler uses a high-level graphical representation formalism based on the activity-cycle diagrams to define simulation models in an interactive mode. These activity-cycle diagrams can then be interpreted into the underlying program ming language and executed automatically. Thus, the modeler does not have to know the underlying Smalltalk 80 language in order to use our prototype simulation system. The future expansions to this system will include a simulation object editor, a graphical output view system and a richer high-level concept base for modeling purpose.
On simulating a die toss with coin flips
Authors: Pugh G. Allen
Published: March 2008

In this paper a general method for the generation of discrete uniform random deviates from random binary digits is examined. A measure of efficiency is developed and an improvement on the fundamental technique is also explored.
Simulation Network News
Authors: Fishwick Paul
Published: March 2008

This column focuses on a single topic within the field of computer simulation. All the material comes directly from the electronic news group (bulletin board) called Simulation Digest. The Digest can be obtained over INTERNET by accessing the news group 'comp.simulation' or by sending e-mail to: 'simulation-reguest@bikini.cis.ufledu'
Dynamic process plant simulation and scheduling: an expert systems approach
Authors: Sztrimbely W. Marcus , Weymouth Peter J.
Published: March 2008

The secure operation of a complex industrial process, such as a Steelmaking Meltshop or Nickel Smelter, depends almost entirely on a harmonic working relationship between the human operator and the real time process control environment. The introduction of sophisticated real time monitoring systems and faster than real time decision making modules, requires a new approach to dynamic process plant simulation, scheduling and production optimization under varying operating constraints. Based on the proven Expert Systems Methodologies of Knowledge Engineering and Rule-Based Logistics, The ADSI Scheduling Advisor has been successfully implemented on the shop floor of serveral major base metals producing facilities.
A non-linear pattern generator for testing digital VLSI circuitry
Authors: Robinson John P.
Published: March 2008

A digital pattern generator suggested by the boundary scan structure was examined using Fortran simulation. The scan register is closed to form a circular shift register. Each logic output is exclusive-ored between two boundary scan stages. The resulting circuit is a large, usually non-linear, sequential circuit suitable for built-in self- test. Earlier analysis using an independent input model demonstrated that this circular form will provide a rich collection of input test patterns. Our simulation indicates that typical circuits perform even better as pattern generators than the independent model predicts. Specifically the minimum sequence length necessary to cover all possible combinations of K variables was observed to be half or less than the length obtained from the independent model.
Simulation Network News
Authors: Fishwick Paul
Published: March 2008

This column focuses on a single topic within the field of computer simulation. All the material comes directly from the electronic news group (bulletin board) called Simulation Digest. The Digest can be obtained over INTERNET by accessing the news group 'comp.simulation' or by sending e-mail to: 'simulation request@bikini.cis.ufl.edu'
Parallel simulation of neural networks
Authors: Wang Chia-Jiu , Wu Chwan-Hwa
Published: March 2008

We simulate five neural networks on a vector multiprocessor. The training time can be reduced significantly especially when the training data size is large. These five neural networks are: 1) the ART1 network, 2) the ART 2 network, 3) the feedforward network, 4) the recurrent network, and 5) the Hopfield network. The training algorithms are programmed in such a way to best utilize 1) the inherent parallelism in neural computing, and 2) the vector and concur rent operations available on the parallel machine. To prove the correctness of parallelized training algorithms, each neural network is trained to perform a specific function. ART 1 and ART 2 are trained to recognize binary and analog patterns. The feedforward network is trained to perform the Fourier transform, the recurrent network is trained to predict the solution of a delay differential equation, the Hopfield network is trained to solve the traveling salesman problem. The machine we experiment with is the Alliant FX/80.
Simulation of epiphytic bacterial growth under field conditions
Authors: Caristi james , Sands David C. , Georgakopoulos Dimitrios G.
Published: March 2008

A model of the growth of bacteria on leaf surfaces was developed using a combined continuous and discrete simulation ap proach. It is important to understand the population dynamics of these bacteria under field conditions because of their role in causing disease and frost damage to plants, and their potential as biological control agents and enhancers of precipitation. The model incorporates many of the necessary field variables, and is designed to be part of a larger ecological model involving arrivals and departures, inimical organisms, and involvement in atmospheric processes. Historical validation indicates a reasonable correlation between predicted and observed population levels in the field. Analysis of simulation results suggests an explanation for the observed lognormal distribution of bacteria in the simuland.
Simulation of a distributed processing system: A case study
Authors: Vemuri V.
Published: March 2008

Many modern computer systems require a continual monitoring of their projected performance from the design phase until the system becomes operational. This means forecasting system performance with very little data available during the early design phase and continually updating the forecast as the design matures. While designing computer systems with time-critical performance constraints, the timing requirements are hard to meet if crucial decisions are not made at the design stage. Experience with the Over The Horizon— Backscatter radar data processing project is used as an example to illustrate how these decisions are made using a variety of techniques such as benchmark testing, paper-pencil analysis, and simulation.
GIBSS: A model specification framework for multi-stage, manufacturing system design
Authors: De Meter Edward C. , Deisenroth Michael P.
Published: March 2008

Heterogeneous simulation models are used in the initial, multistage design of discrete parts manufacturing systems. Current research is directed toward the development of an object-oriented, model-base environ ment which will facilitate heterogeneous modeling. To this end, the GIBSS (General ized Interaction Based Simulation Specifica tion) frameworks have been developed. The GIBSS conceptual frameworks permits the modular specification of heterogeneous models through the logical assemblage of entity, interaction, and transition objects. The GIBSS logic framework defines the synchronous execution of objects which use various mixtures of continuous and discrete event simulation techniques and/or manage multiple attribute sets. This paper describes the GIBSS frameworks and provides a case study of their application.
The Role of JSC Engineering Simulation in the Apollo Program
Authors: Lawrence James A. , Smith H. Edward
Published: March 2008

Presently, the Space Exploration Initiative has captured the attention of the manned space community. The approach to the accomplishment of such a demanding mission causes recall of the development of the Apollo mission, the synergism with the SEI, and the role that JSC's Engineering Simulations took in the Lunar Landing systems definition and development.
Real-Time Simulation of the Space Station Freedom Attitude Control System
Authors: Pope Tonya
Published: March 2008

Software in the Systems Engineering Simulator at NASA's Johnson Space Center must be updated frequently to insure reliability and accuracy of the simulation. The Attitude Control System of the Space Station Freedom is one large component of the station simulation which must likewise undergo upgrades and maintenance. The baseline McDonnell Douglas Space Systems Co. (MDSSC)/Honeywell Attitude Control System has been integrated into the laboratory as a new system rather than modifying the older, existing version. Because this was replacing the older version, testing and verification were simplified as the existing task interfaces could be retained. This prevented many errors while at the same time provided a realistic capability for the laboratory.
Space station rendezvous and berthing
Authors: Cook John , Wicks David
Published: March 2008

This paper describes the application of johnson Space Center's Systems Engineer ing Simulator to model a complex spacecraft rendezvous and capture scenario. In this real-time scenario, an operator in one space vehicle made use of a telerobotic manipulator to capture and berth another, smaller vehicle. The goals of the study were to determine if the task could be reliably completed and to provide design and performance data on the manipulator.

The study results demonstrate that it is feasible to use a telerobotic manipulator to berth an incoming Shuttle to Space Station Freedom.
The engineering applications of fractals
Authors: Diab Hassan , Abboud Nikola
Published: March 2008

Fractal geometry principles and mathematical models based upon the theory of Mandelbrot [1] are commonly used today in search of a more realistic simulation of natural phenomena. This paper presents the simulation of various engineering applications by using fractals. In agriculture and civil engineering, underground seepage simulation is used to determine the critical distance between the different subsurface seepage pipes in order to avoid pondage due to overlay of the seepage cones. This is done by simulating the phreatic line — the boundary of the saturated region of the soil — using fractal interpolation. A second application is the simulation of settling tanks based on fractal geometry. Settling tanks are used in civil engineering to remove impurities from water. The main objective is to find the efficiency of the tank based on the shape of the sludge zone. Using fractal interpolation techniques, the shape of this zone can be determined. The package simulates discrete particles entering the settling tank. These particles accelerate until an equilibrium is reached between the drag force induced due to the particle's mass and the driving force of water flow. The fractal interpolation algorithm uses the corrdinates of the settled particles to determine the shape of the sludge zone. A third application that this paper presents is a computer graphics simulation of the formation and growth of coral reef based on the Diffused-Limited Aggregation (DLA) algorithm, which produces a certain class of fractals based on a stochastic model.