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1993

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Articles 91 - 120 of 1974

Full-Text Articles in Physical Sciences and Mathematics

Quantile-Locating Functions And The Distance Between The Mean And Quantiles, D. Gilat, Theodore P. Hill Dec 1993

Quantile-Locating Functions And The Distance Between The Mean And Quantiles, D. Gilat, Theodore P. Hill

Research Scholars in Residence

Given a random variable X with finite mean, for each 0 < p < 1, a new sharp bound is found on the distance between a p-quantile of X and its mean in terms of the central absolute first moment of X. The new bounds strengthen the fact that the mean of X is within one standard deviation of any of its medians, as well as a recent quantile-generalization of this fact by O'Cinneide.

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Recombination Of 2-Dimensional Electrons With Free Light And Heavy Holes In Alxga1-Xas-Gaas Single Heterojunctions In A Magnetic-Field, D. C. Reynolds, David C. Look, B. Jogai, C. E. Stutz Dec 1993

Recombination Of 2-Dimensional Electrons With Free Light And Heavy Holes In Alxga1-Xas-Gaas Single Heterojunctions In A Magnetic-Field, D. C. Reynolds, David C. Look, B. Jogai, C. E. Stutz

Physics Faculty Publications

Landau-level oscillations are observed in the photoluminescence from an AlxGa1-xAs-GaAs single heterojunction in an applied magnetic field. Extrapolating the oscillations back to zero field gives the energy of the transition from the two-dimensional (2D) electrons to the free heavy holes (hh1 and hh2) and free light holes (lh) weakly confined in the GaAs active layer. The measured energy separation between hh1 and lh is 1.8 meV, which agrees very well with the calculated value of 2.2 meV. The measured energy separation between hh1 and hh2 is 3.8 meV, in good agreement with the calculated value of …

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Correctness Proof Of A Geometric Constraint Solver, Ioannis Fudos, Christoph M. Hoffmann Dec 1993

Correctness Proof Of A Geometric Constraint Solver, Ioannis Fudos, Christoph M. Hoffmann

Department of Computer Science Technical Reports

No abstract provided.

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Object-Orientation In Multidatabase Systems, Evaggelia Pitoura, Omran Bukhres, Ahmed K. Elmagarmid Dec 1993

Object-Orientation In Multidatabase Systems, Evaggelia Pitoura, Omran Bukhres, Ahmed K. Elmagarmid

Department of Computer Science Technical Reports

No abstract provided.

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Collaborative Multimedia Game Environments, Vinod Anupam, Chandrajit L. Bajaj Dec 1993

Collaborative Multimedia Game Environments, Vinod Anupam, Chandrajit L. Bajaj

Department of Computer Science Technical Reports

No abstract provided.

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Dynamic Decision Modeling In Medicine: A Critique Of Existing Formalisms, Tze-Yun Leong Dec 1993

Dynamic Decision Modeling In Medicine: A Critique Of Existing Formalisms, Tze-Yun Leong

Research Collection School Of Computing and Information Systems

Dynamic decision models are frameworks for modeling and solving decision problems that take into explicit account the effects of time. These formalisms are based on structural and semantical extensions of conventional decision models, e.g., decision trees and influence diagrams, with the mathematical definitions of finite-state semi-Markov processes. This paper identifies the common theoretical basis of existing dynamic decision modeling formalisms, and compares and contrasts their applicability and efficiency. It also argues that a subclass of such dynamic decision problems can be formulated and solved more effectively with non-graphical techniques. Some insights gained from this exercise on automating the dynamic decision …

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Asynchronous Transaction Commitment In Federated Database Systems, San-Yih Hwang, Ee Peng Lim, Jaideep Srivastava Dec 1993

Asynchronous Transaction Commitment In Federated Database Systems, San-Yih Hwang, Ee Peng Lim, Jaideep Srivastava

Research Collection School Of Computing and Information Systems

We propose a new (and restricted) model for global transactions which allows asynchronous commitment of subtransactions. Our model requires each global transaction to have a fixed structure with update to the data in at most one database. Based on this transaction model, we present two concurrency control algorithms, namely Asynchronous Site Graph and Asynchronous VirtGlobalSG, which employ asynchronous commitment and achieve global serializability. Compared to other proposed algorithms, our algorithms employ asynchronous commitment so as to increase transaction performance. Furthermore, our algorithms do not put restrictions on transaction data access or local histories.

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The Structural Homogeneity Of Boron Carbide Thin Films Fabricated Using Plasma-Enhanced Chemical Vapor Deposition From B5H9+Ch4, Sunwoo Lee, J. Mazurowski, W.L. O'Brien, Q.Y. Dong, J.J. Jia, T.A. Callcott, K.E. Miyano, D.L. Ederer, D.R. Mueller, Peter A. Dowben Dec 1993

The Structural Homogeneity Of Boron Carbide Thin Films Fabricated Using Plasma-Enhanced Chemical Vapor Deposition From B5H9+Ch4, Sunwoo Lee, J. Mazurowski, W.L. O'Brien, Q.Y. Dong, J.J. Jia, T.A. Callcott, K.E. Miyano, D.L. Ederer, D.R. Mueller, Peter A. Dowben

Peter Dowben Publications

Boron carbide thin films of several B/C ratios have been deposited on Si(111) using plasma-enhanced chemical vapor deposition from nido-pentaborane(9) (B5H9) and methane (CH4). X-ray diffraction studies of boron carbide thin films on Si(111) exhibited characteristic microcrystalline diffraction lines. Soft x-ray emission spectroscopy was used to verify that the local electronic structure and composition of each sample corresponded to a homogeneous solid solution boron carbide phase.

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Thermodynamic Properties Of Mixtures Of Aqueous Solutions Of Hydrochloric Acid And Cadmium Chloride, Copper Chloride, Manganese Chloride, And Zinc Chloride, Samia A. Kosa Dec 1993

Thermodynamic Properties Of Mixtures Of Aqueous Solutions Of Hydrochloric Acid And Cadmium Chloride, Copper Chloride, Manganese Chloride, And Zinc Chloride, Samia A. Kosa

Masters Theses

The densities of mixtures of aqueous solutions of hydrochloric acid and cadmium chloride, copper chloride, manganese chloride, and zinc chloride have been measured at constant ionic strengths of 1.0 and 3.0 molal at 25 °C. In the case of HCl, CdCl2 , and ZnCl2 the literature data were refit using Pitzer' s apparent molal volume equation and the binary solution parameters were determined. Density data were used to determine the volume of mixing (∆Vm). Data from Torok and Berecs were combined with our data for the mixtures with CuCl2 and MnCl2. Pitzer's volume …

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Spectroscopic And Vibrational Energy Transfer Studies In Molecular Bromine, Courtney D. Holmberg Dec 1993

Spectroscopic And Vibrational Energy Transfer Studies In Molecular Bromine, Courtney D. Holmberg

Theses and Dissertations

Vibrational transfer and electronic quenching in the lower vibrational levels (v' < 3) of the B3π(0u+) state of 79Br2 were investigated using spectrally resolved, temporally resolved laser induced fluorescence techniques. Spectrally resolved emissions from collisionally populated Br2(B) vibrational levels were observed for Br2 and rare gas collision partners. Vibrational transfer was efficient in the non-predissociative vibrational levels and was adequately described by the Montroll-Shuler model for harmonic oscillators. A single fundamental rate coefficient for vibrational transfer from v' = 1 to v' = 0, kv(1,0), characterizes vibrational relaxation. For Br2, the …

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A Non-Homogeneous, Spatio-Temporal, Wavelet Multiresolution Analysis And Its Application To The Analysis Of Motion, Thomas J. Burns Dec 1993

A Non-Homogeneous, Spatio-Temporal, Wavelet Multiresolution Analysis And Its Application To The Analysis Of Motion, Thomas J. Burns

Theses and Dissertations

This research presents a multiresolution wavelet analysis tool for analyzing motion in time sequential imagery. A theoretical framework is developed for constructing an L2R wavelet multiresolution analysis from three non-identical spatial and temporal L2R wavelet multiresolution analyses. This framework provides the flexibility to tailor the spatio-temporal frequency characteristics of the three dimensional wavelet filter to match the frequency behavior of the analyzed signal. An unconventional, discrete multiresolution wavelet decomposition algorithm is developed which yields a rich set of independent spatio-temporally oriented frequency channels for analyzing, the size and speed characteristics of moving objects. Unlike conventional wavelet decomposition methods, this algorithm …

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Air Pollution Transport Modeling, David M. Paal Dec 1993

Air Pollution Transport Modeling, David M. Paal

Theses and Dissertations

This research effort addresses modeling of the transportation of air pollution in the atmosphere and the numerical analysis of the partial differential equations used in such modeling. Three Gaussian models are examined and compared using example problems. Several finite difference schemes are developed to solve the partial differential equations used in air pollution transport modeling. This study examines three Gaussian models SCREEN, AFTOX, and the program GAUSPLUM. The model GAUSPLUM is developed in this study and uses the Ada programming language and the analytic solution to the advection- diffusion equation. Numerical analysis of the partial differential equations PDE used in …

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Design And Construction Of The Aerobot Robotic Manipulator (Arm), William L. Cochran Dec 1993

Design And Construction Of The Aerobot Robotic Manipulator (Arm), William L. Cochran

Theses and Dissertations

This thesis designed, constructed, and tested a robotic arm for the Aerobot Aerial Robot. The main purpose of the ARM is to enable the Aerobot to retrieve objects for use in an annual robotics competition. Design of the ARM involved synthesizing the characteristics of simplicity, weight, strength, and size. The result was a three-degree-of-freedom manipulator that uses electric motors, cable linkages, and telescoping tubes to access a work space below the Aerobot. Forward and inverse kinematics were investigated to enable automation of the ARM. Data was collected from infrared sensors to validate the model. Manipulation of the ARM is presently …

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Shock Wave Interaction With L-Shaped Structures, Richard C. Miller Dec 1993

Shock Wave Interaction With L-Shaped Structures, Richard C. Miller

Theses and Dissertations

This study investigated the interaction of shock waves with L-shaped structures using the CTH hydrodynamics code developed by Sandia National Laboratories. Computer models of shock waves traveling through air were developed using techniques similar to shock tube experiments. Models of L-shaped buildings were used to determine overpressures achieved by the reflecting shock versus angle of incidence of the shock front. An L-shaped building model rotated 45 degrees to the planar shock front produced the highest reflected overpressure of 9.73 atmospheres in the corner joining the two wings, a value 9.5 times the incident overpressure of 1.02 atmospheres. The same L-shaped …

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The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch Dec 1993

The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch

Theses and Dissertations

Vertical Cavity Surface Emitting Lasers VCSELs are a type of semiconductor laser with a cavity oriented orthogonally to the planes of material growth. These lasers differ from conventional edge emitting lasers in several important ways. They have symmetric output beams and they are easily built into two dimensional arrays, making them very attractive as photonic components. The characteristic of interest in this thesis is polarization. While the asymmetric cavities of edge emitters exhibit a clear preference for light polarized in a particular direction, the cylindrically symmetric cavity of a VCSEL has no clear preference. Therefore, it should be relatively easy …

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Vibrational Energy Transfer Within The B3Π(0+U) State Of 79Br2 Upon Collision With N2, O2, No, And Sf6, Gregory S. Williams Dec 1993

Vibrational Energy Transfer Within The B3Π(0+U) State Of 79Br2 Upon Collision With N2, O2, No, And Sf6, Gregory S. Williams

Theses and Dissertations

Vibrational transfer and electronic quenching in the lower vibrational levels of the 79Br2(B; v'≤3) were investigated using spectrally resolved, temporally resolved pulsed laser induced fluorescence techniques. Spectrally resolved emissions from collisionally populated Br2(B) vibrational levels were observed for N2, O2, NO, and SF6collision partners. The vibrational transfer was efficient in the nonpredissociative vibrational levels and is adequately described by the Montroll-Shuler model. An average fundamental vibrational transfer rate coefficient of kv(l,0)=3.4(±0.6) x 10-11 cm3/molec-sec predicts the vibrational transfer rates for the 0≤v'≤3 collisions with …

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Vulnerability Assessment Using A Fuzzy Logic Based Method, Richard W. Fleming Dec 1993

Vulnerability Assessment Using A Fuzzy Logic Based Method, Richard W. Fleming

Theses and Dissertations

This thesis demonstrates the feasibility of using qualitative analysis methods to evaluate computer security vulnerabilities. Although many risk analysis systems exist, few provide for the adequate analysis of identified vulnerabilities. While the main focus of this thesis is to evaluate computer security vulnerabilities, the methods involved have application in other areas requiring evaluation using qualitative methods. It is proposed, and demonstrated by this thesis, that the use of qualitative analysis using linguistic variables to describe the impact of computer security vulnerabilities is not only feasible, but intrinsically easier to understand and use than quantitative methods.

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Developing Realistic Cooperative Behaviors For Autonomous Agents In Air Combat Simulation, Dean P. Hipwell Dec 1993

Developing Realistic Cooperative Behaviors For Autonomous Agents In Air Combat Simulation, Dean P. Hipwell

Theses and Dissertations

This thesis investigated, developed and implemented cooperative decision-making behaviors in an air combat simulation by using a knowledge-based system. Knowledge-based systems were well suited for this task because of built- in features such as inference engines and rule-based constructs. This thesis addresses the specific problem of generating autonomous forces for inclusion in the Advanced Research Projects Agency Distributed Interactive Simulation program. Existing autonomous forces implementations lacked flexibility, realistic behaviors, real-time planning and other features. The simulation system in this thesis addresses the problem of realistic behavior by modeling pilot decision processes rather than aircraft platforms. The system is based on …

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Developing Realistic Behaviors In Adversarial Agents For Air Combat Simulation, George S. Hluck Dec 1993

Developing Realistic Behaviors In Adversarial Agents For Air Combat Simulation, George S. Hluck

Theses and Dissertations

This thesis describes an initial effort into creating a rule-based, reactive system for air combat simulation. This program uses the object-oriented extension of the expert system tool known as the C Language Integrated Production System CLIPS. This effort rose out of the need for creating and integrating semi-autonomous forces for the Distributed Interactive System DIS. This thesis describes the basic maneuvers a pilot uses in present air-to-air combat. The methodology includes the design decisions, knowledge-base development, phase architecture, and maneuver architecture development. The actual implementation of the selected architecture is described. This thesis also discusses the results of experimental runs …

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Investigation Into Formalization Of Domain-Oriented Parallel Software Development, Daniel P. King Dec 1993

Investigation Into Formalization Of Domain-Oriented Parallel Software Development, Daniel P. King

Theses and Dissertations

This research investigates the conceptual design of a semi-automated platform for parallel software development. The proposed semi-automated environment applies transformational techniques and domain-specific knowledge to a parallel software development process. Domain-specific and software design knowledge interact within the transformational development process in the creation of a software application. The underlying parallel specification language requires a set of parallel composition operators in order to capture an application’s concurrent properties. A set of parallel composition operators is proposed that consists of parallel composition, parallel enumeration, nondeterministic choice, sequential composition specific communication and synchronization variable types are also proposed. A semi-automated environment based …

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Developing A Sophisticated User Interface To Support Domain-Oriented Application Composition And Generation Systems, Jay A. Cossentine Dec 1993

Developing A Sophisticated User Interface To Support Domain-Oriented Application Composition And Generation Systems, Jay A. Cossentine

Theses and Dissertations

This research refined the visual presentation and usability of a previously developed visual interface for a domain-oriented application composition and generation system. The refined visual interface incorporated domain-specific bit-mapped graphics and sophisticated user interface design concepts to reduce user workload. User workload was reduced through object layout, window design, and color utilization techniques; by combining repetitive procedures into single commands; and reusing, rather than recreating, composition information throughout the application composition process. The Software Refinery environment, including its graphical interface tool INTERVISTA, was used to develop techniques for visualizing and manipulating objects contained in a formal object base. INTERVISTA was …

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A Parallel Computational Fluid Dynamics Unstructured Grid Generator, Deborah E. Davis Dec 1993

A Parallel Computational Fluid Dynamics Unstructured Grid Generator, Deborah E. Davis

Theses and Dissertations

This research addressed the development of a parallel computational fluid dynamics unstructured grid generator using Delaunay triangulation. The generator is applied to simple elliptical and cylindrical two-dimensional bodies. The methodologies used included Watsons point insertion algorithm, Holmes and Snyders point creation algorithm, a discretized surface definition, Andersons clustering function, and a Laplacian smoother. The first version of the software involved a processor boundary exchange at the end of each iteration with no inter-processor communications during the iterations The second version used inter-processor communication during each iteration instead of the boundary exchange. Version 1 demonstrated a speedup of 1.8 for some …

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A Distributed Interactive Simulation Based Remote Debriefing Tool For Red Flag Missions, Michael T. Gardner Dec 1993

A Distributed Interactive Simulation Based Remote Debriefing Tool For Red Flag Missions, Michael T. Gardner

Theses and Dissertations

Air Force leaders, recognizing the need for improved training following the Vietnam War, implemented the Red Flag exercises at Nellis AFB. At the heart of this training is the Red Flag Measurement and Debriefing System RFMDS and its capability to accurately reconstruct the elements of an intense exercise fought over the deserts of Nevada. This thesis uses the technology of distributed interactive simulation DIS to transmit aircraft telemetry onto computer networks, allowing the monitoring and analysis of live Red Flag missions at any site with compatible communications equipment and thesis software. The use of standard DIS protocols enables simulators to …

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Alternative Architectures For Domain-Oriented Application Composition And Generation Systems, Warren E. Gool Dec 1993

Alternative Architectures For Domain-Oriented Application Composition And Generation Systems, Warren E. Gool

Theses and Dissertations

This thesis presents a formalized framework for comparing the structure and semantics of software architectures. The framework uses object diagrams for analyzing the structure of the architectures and the axiomatic approach for analyzing the semantics. This framework is used to compare the Object Connection Update OCU model developed by the Software Engineering Institute against four other software architectures VHDL defined by Lipsett, MetaH defined by Honeywell, microRapide defined by Luckham, and hierarchical software systems as defined by Batory. The goal of the comparison was to evaluate the OCU model for suitability within prototype application composition and generation systems. This research …

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Performance Measurement Of Three Commercial Object-Oriented Database Management Systems, Timothy J. Halloran Dec 1993

Performance Measurement Of Three Commercial Object-Oriented Database Management Systems, Timothy J. Halloran

Theses and Dissertations

The goal of this thesis was to study the performance of three commercial object-oriented database management systems. The commercial systems studied included Itasca, sold by Itasca Systems Incorporated Matisse, sold by Intellitic International and ObjectStore, sold by Object Design Incorporated. To examine performance of these database management systems two benchmarks were run the OO1 benchmark and a new AFIT Simulation benchmark. The OO1 benchmark was designed, implemented, and run on all three database management systems. ObjectStore was our top performer on all configurations of the OO1 benchmark. The AFIT Simulation benchmark was designed, implemented, and run on the ObjectStore database …

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Integration And Enhancement Of The Saber Wargame, Karl S. Mathias Dec 1993

Integration And Enhancement Of The Saber Wargame, Karl S. Mathias

Theses and Dissertations

The Saber wargame is a theater-level air/land battle wargame written in Ada that is being developed for the Air Force Wargaming Center at Maxwell AFB, AL. This thesis documents how the user interface and simulation engine were integrated. Integration was accomplished by developing a portable object-oriented database system (OODBMS) interface. The interface was implemented in Ada and tied to an OODBMS also written in Ada. Using the interface, both subsystems were able to work from a consistent database and exchange information. The user interface was enhanced by converting it from the Software Technology for Adaptable Reliable Systems Ada/X Window System …

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Developing A Graphical User Interface To Support A Real-Time Digital Signal Processing System, Jeffrey C. Miller Dec 1993

Developing A Graphical User Interface To Support A Real-Time Digital Signal Processing System, Jeffrey C. Miller

Theses and Dissertations

A graphical software user interface for a VMEbus-based real-time digital signal processing system was designed. Use, requirements were defined and the Rumbaugh object-oriented analysis and design technique was applied to analyze the requirements and produce an object-oriented design. The software design includes a graphical, mouse- and keyboard driven user interface, specialized hardware driver modules, and operating system interfaces. An implementation plan was also developed to map the design into the C programming language using existing system code, automatically generated code, and newly written code. Based on the implementation plan, a limited software system prototype w successfully developed and demonstrated. The …

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A Prototype Architecture For An Automated Scenario Generation System For Combat Simulations, Mark W. Pfefferman Dec 1993

A Prototype Architecture For An Automated Scenario Generation System For Combat Simulations, Mark W. Pfefferman

Theses and Dissertations

This research effort examines the problem of automating the scenario generation process and presents a prototype architecture for an automated scenario generation system. This architecture is designed using an object- oriented approach which leads to a modular and modifiable design. The architecture provides a mechanism for automatically generating scenario files from a textual US Army operation order. This translation process occurs in two phases. First, the text operation order is translated into an intermediate format called the mission file. In the second phase, the system reads the mission file, instantiates intelligent entities, and assigns missions to those entities. The intelligent …

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Design Of A Shared Coherent Cache For A Multiple Channel Architecture, John A. Reisner Dec 1993

Design Of A Shared Coherent Cache For A Multiple Channel Architecture, John A. Reisner

Theses and Dissertations

The Multiple Channel Architecture MCA is a recently proposed computer architecture which uses fiber optic communications to overcome many of the problems associated with interconnection networks. There exists a detailed MCA simulator which faithfully simulates an MCA system, however, the original version of the simulator did not cache shared data. In order to improve the performance of the MCA, a cache coherency protocol was developed and implemented in the simulator. The protocol has two features which are significant: (1) a time-division multiplexed TDM communication bus is used for coherency traffic, and (2) the shared data is cached in an independent …

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Object Interaction In A Parallel Object-Oriented Discrete-Event Simulation, Walter G. Trachsel Dec 1993

Object Interaction In A Parallel Object-Oriented Discrete-Event Simulation, Walter G. Trachsel

Theses and Dissertations

This thesis investigates object interaction issues involved in developing an object-oriented parallel discrete-event simulation and develops a simulation model that provides object interaction capabilities. The research covers issues in object representation, object interaction, object management. discrete-event simulation, and parallel simulation. There are three primary types of objects that the research discusses. The first type is a basic simulation object, whose size and behavior is insignificant compared to the size of the simulation as a whole. The second type is an aggregate object which consists of smaller component objects that interact and affect the performance of the larger object as a …

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