The purpose of the research described herein is to prototype a software system that aids a simulationist in developing a general purpose discrete event simulation model. A literature review has shown the need for an integrated visual simulation system that provides for the graphical definition and interactive specification of the model while maintaining application independence. The General Purpose Visual Simulation System (GPVSS) prototyped in this research meets this need by assisting a simulationist to: (1) graphically design the model and its M visualization, (2) interactively specify the model's logic, and (3) automatically generate the executable version of the model, while maintaining domain independence. GPVSS is prototyped on a Sun 3/160C computer workstation using the SunView graphical interface. It consists of over 11,000 lines of documented code. GPVSS has been successfully tested in three different case studies that are described in this work. / Master of Science

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The Department of Defense has always had an interest in simulation systems for training and analysis. Recently, simulation usage in training has been stressed. Simulation systems provide an easy and effective way for trainees to learn military doctrine and small unit tactics. In order to be effective, a simulation must accurately represent the real world. Sensory perception is one important real world influence that should be modeled. Modular Semi-Automated Forces (ModSAF) is a highly advanced computer simulation system that can model the movement, formations, equipment and other aspects of armed forces with precise calculations. In spite of all of the advances in ModSAF and other systems like it, the behaviors of sound and how they affect the warfighter have been scarcely modeled. The goal of this project is to investigate how sound is produced, propagated, and detected (acoustics), the behavioral effects sound has on the human psyche, and model the findings. It includes the development of a computer model of the physical phenomenon relating to sound, to be incorporated within ModSAF or another similar constructive simulation system.

Several panel methods are developed to model subsonic aerodynamics. The vorticity panel method for two-dimensional problems is capable of handling general unsteady, potential, lifting flows. The lifting surface is modelled with a vortex sheet and the wakes by discrete vortices. As an imitation of the conditions at the trailing edge, stagnation conditions on both surfaces are used. The over-determined system is solved by an optimization scheme. The present predictions are in good agreement with experimental data and other computations. Moreover the present approach provides an attractive alternative to those developed earlier. Two panel methods for three-dimensional nonlifting problems are developed. One uses source distributions over curved elements and the other vorticity distributions over flat elements. For the source formulation, the effect of weakly nonlinear geometry on the numerical results is shown to accelerate the convergence of numerical values in general. In addition, the extensive comparisons between two formulations reveal that the voticity panel method is even more stable and accurate than the curved source panel method. Another vorticity panel method is developed to study the lifting l flows past three-dimensional bodies with sharp edges. The body is modelled by single vortex sheet for thin bodies and two vortex sheets for thick bodies while the wakes are modelled with a number of strings of discrete vortices. The flows are assumed to separate along the the sharp edges. The combination of continuous vorticity on the lifting surface and discrete vortices in the wakes yields excellent versatility and the capability of handling the tightly rolled wakes and predicting continuous pressure distributions on the lifting surface. The method is applied to thin and thick low-aspect-ratio delta wings and rectangular wings. The computed aerodynamic forces and wake shapes are in quantitative agreement with experimental data and other computational results. / Ph. D.

The purpose of this thesis is to develop a software tool for the Simulation Model Development Environments (SMDE) research project, called the Premodels Manager, which enables information associated with completed simulation studies and models to be reused effectively. This research began by classifying the potential users of a Premodels Manager and determining the various types of information required by these user classes. The required information was then organized into a detailed simulation life-cycle documentation outline and each item of this outline was carefully associated with various user classes. Once the information required by Premodels Manager users was identified, the premodels database was developed to store this information. Evolutionary prototyping was used to uncover the system requirements for the Premodels Manager. An initial prototype administered the tables within the premodels database directly; however, this prototype was unable to accommodate changes to the premodels database. To overcome this inflexibility, a second prototype was developed which administered the premodels database based on table and field classifications. The second prototype provided adequate retrieval capabilities and was easily modified but did not assist with the installation of information into the premodels database. The third and current prototype, referred to as simply the Premodels Manager, provides the flexibility of the second prototype plus additional installation facilities. The Premodels Manager was evaluated from both the perspective of a user and of a software developer. The Premodels Manager ' s user interface is simple and consistent which allows even novice or infrequent users to retrieve pertinent information. Several completed simulation studies have been installed using the Premodels Manager, and information associated with these simulation studies has been retrieved using the various retrieval facilities. The design and implementation of the Premodels Manager is elegant and robust. Carefully planned modules enhance both maintainability and transportability while allowing the full power of underlying software packages to be exploited. The Premodels Manager provides a sound foundation for future work. Future enhancements are anticipated and provided for in the design of the Premodels Manager. The extensive research into the information requirements for various user classifications is applicable to numerous information management systems. Finally, the implementation contains independent modules and functions which have been well tested and can easily be adapted to other programming efforts. / M.S.

The aim of this research was to identify promising areas for international cooperative development work in the area of integrated harvesting systems which incorporate the recovery of logging residues. The Harvesting Analysis Technique, a computer simulation package, was used to model seven harvesting systems on forest stands in five participating countries. The simulation results indicated that on good terrain with short skidding distances mechanical felling and grapple skidding was the best available method to deliver full trees to a landing. Processing trees at the landing accounted for at least 50 percent of the harvesting cost, indicating that if full trees or tree sections could be efficiently transported on public roads, then centralized processing may be the best alternative. Where logging residues consisted primarily of cull trees, full tree chippers were found to be an effective means for comminution. Residues consisting of tops and branches are more problematic due to their small piece size, lack of uniform linear orientation, and low bulk density. Compaction prior to chipping was proposed as one possible solution to this problem. Alternatively, residue processing could be combined with the merchandising of the full tree. Five problem areas were identified which could be of interest for future international cooperative projects: 1. Compacting tree sections, full trees or residues on trucks. 2. Delimbing tree sections with a mobile unit. 3. Systems for handling and processing residues at a landing. 4. Integrated systems for processing full trees at a landing. 5. Chip fractioning techniques. In addition, the development of a standard format for data collection in equipment evaluations would expedite comparisons of equipment originating in different countries. / M.S.