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Theses and Dissertations

Theses/Dissertations

1996

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Articles 1 - 30 of 88

Full-Text Articles in Physical Sciences and Mathematics

Modeling And Simulation Of Optical Characteristics Of Microelectromechanical Mirror Arrays, Peter C. Roberts Dec 1996

Modeling And Simulation Of Optical Characteristics Of Microelectromechanical Mirror Arrays, Peter C. Roberts

Theses and Dissertations

MEMS (Micro-Electro-Mechanical Systems) micromirror devices can be used to control the phase of a propagating light wavefront, and in particular to correct aberrations that may be present in the wavefront, due to either atmospheric turbulence or any other type of fixed or time and space varying aberrations. In order to shorten the design cycle of MEMS micromirror devices, computer software is developed to create, from MEMS micromirror device design data, a numerical model of the MEMS device. The model is then used to compute the far field diffraction pattern of a wavefront reflected from the device, and to predict the …

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On Unifying Time And Uncertainty: The Probabilistic Temporal Network, Joel D. Young Dec 1996

On Unifying Time And Uncertainty: The Probabilistic Temporal Network, Joel D. Young

Theses and Dissertations

Complex real-world systems consist of collections of interacting processes/events. These processes change over time in response to both internal and external stimuli as well as to the passage of time. Many domains such as real-time systems diagnosis, (mechanized) story understanding, planning and scheduling, and financial forecasting require the capability to model complex systems under a unified framework to deal with both time and uncertainty. Existing uncertainty representations and existing temporal models already provide rich languages for capturing uncertainty and temporal information, respectively. Unfortunately, these partial solutions have made it extremely difficult to unify time and uncertainty in a way that …

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Student Modeling In An Intelligent Tutoring System, Jeremy E. Thompson Dec 1996

Student Modeling In An Intelligent Tutoring System, Jeremy E. Thompson

Theses and Dissertations

This thesis explores a new approach to modeling the student in an intelligent tutoring system (ITS), by providing a student model which learns new solutions from the student. A prototype of the new approach to ITS is demonstrated in the Euclidean geometry domain. Complete C++, CLIPS, and Tcl/Tk code listings are included in the appendices for reference. Adaptable multiple software agents were targeted for implementation, based on current literature. However, the student model is found to be maintainable without multiple software agents, while still allowing for tracking several possible solution paths when monitoring student solutions. This capability contradicts previous research …

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Algebraic Algorithm Design And Local Search, Robert P. Graham Jr. Dec 1996

Algebraic Algorithm Design And Local Search, Robert P. Graham Jr.

Theses and Dissertations

Formal, mathematically-based techniques promise to play an expanding role in the development and maintenance of the software on which our technological society depends. Algebraic techniques have been applied successfully to algorithm synthesis by the use of algorithm theories and design tactics, an approach pioneered in the Kestrel Interactive Development System (KIDS). An algorithm theory formally characterizes the essential components of a family of algorithms. A design tactic is a specialized procedure for recognizing in a problem specification the structures identified in an algorithm theory and then synthesizing a program. Design tactics are hard to write, however, and much of the …

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Electrical Characterization Of Intrinsic And Induced Deep Level Defects In Hexagonal Sic, James D. Scofield Dec 1996

Electrical Characterization Of Intrinsic And Induced Deep Level Defects In Hexagonal Sic, James D. Scofield

Theses and Dissertations

Deep level defects in hexagonal SiC were studied using digital deep level transient spectroscopy (DLTS) methods over the temperature range of 100 to 800 deg K. New centers were found in bulk and epitaxial 6H-SiC with ionization energies between 0.38 to 1.3 eV, and levels from 0.2 to 0.856 eV were identified in 4H-SiC epitaxy. Direct correlation between inequivalent lattice sites was identified for energetic pairs associated with both vanadium and ion implanted Mg impurities. Nonradioative carrier capture mechanisms were studied and deep level trapping was found to proceed via lattice relaxation multi-phonon emission, indicating efficient electronic lattice coupling in …

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Unfolding The High Energy Electron Flux From Crres Fluxmeter Measurements, Brian D. Mckellar Dec 1996

Unfolding The High Energy Electron Flux From Crres Fluxmeter Measurements, Brian D. Mckellar

Theses and Dissertations

The Combined Release and Radiation Effects Satellite (CRRES) was launched on 25 July 1990 to collect measurements in the earth's radiation belts. One instrument, the High Energy Electron Fluxmeter (HEEF), measured the flux of electrons in 10 channels with energies between 1 MeV and 10 MeV. The channel sensitivities, Ri(E), have been calibrated and partially re-calibrated. We explore the errors introduced in unfolding the electron flux spectrum from the channel measurements and the propagation and growth of calibration and measurement errors. Using numerical experimentation, we fold the responses with known spectra to obtain simulated measurements, add random measurement and calibration …

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Pulse Coupled Neural Networks For The Segmentation Of Magnetic Resonance Brain Images, Shane L. Abrahamson Dec 1996

Pulse Coupled Neural Networks For The Segmentation Of Magnetic Resonance Brain Images, Shane L. Abrahamson

Theses and Dissertations

This research develops an automated method for segmenting Magnetic Resonance (MR) brain images based on Pulse Coupled Neural Networks (PCNN). MR brain image segmentation has proven difficult, primarily due to scanning artifacts such as interscan and intrascan intensity inhomogeneities. The method developed and presented here uses a PCNN to both filter and segment MR brain images. The technique begins by preprocessing images with a PCNN filter to reduce scanning artifacts. Images are then contrast enhanced via histogram equalization. Finally, a PCNN is used to segment the images to arrive at the final result. Modifications to the original PCNN model are …

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Requirements, Design, And Development Of A Rapidly Reconfigurable, Photo-Realistic, Virtual Cockpit Prototype, Terry A. Adams Dec 1996

Requirements, Design, And Development Of A Rapidly Reconfigurable, Photo-Realistic, Virtual Cockpit Prototype, Terry A. Adams

Theses and Dissertations

The United States Air Force uses aircraft flight simulators for pilot training and mission rehearsal. They use a variety of simulators for this task ranging with prices ranging from $400,000 to $30,000,000. These simulators have specialized hardware that restricts reuse of their components and increases maintenance costs. Air Education and Training Command wants to reduce simulators cost and improve availability to the operational commands by supporting research in virtual reality flight simulators. This thesis looks at the development of a reconfigurable virtual cockpit in a distributed virtual environment that can be used for different aircraft as well as training scenarios. …

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A Domain Independent Framework For Developing Knowledge Based Computer Generated Forces, James L. Benslay Jr. Dec 1996

A Domain Independent Framework For Developing Knowledge Based Computer Generated Forces, James L. Benslay Jr.

Theses and Dissertations

Computer Generated Forces (CGFs) are important players in Distributed Interactive Simulation (DIS) exercises. A problem with CGFs is that they do not exhibit sufficient human behaviors to make their use effective. The SOAR approach has yielded a human cognitive model that can be applied to CGFs, but this is extremely complex. The product of the research reported in this thesis is a much less complex behavioral framework for a CGF that is easy to validate, revise, and maintain. To support this, an existing, domain independent CGF architecture is discussed and applied to an experimental CGF. Techniques for modeling the knowledge …

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Inference Algorithm Performance And Selection Under Constrained Resources, Brett J. Borghetti Dec 1996

Inference Algorithm Performance And Selection Under Constrained Resources, Brett J. Borghetti

Theses and Dissertations

Knowing that reasoning over probabilistic networks is, in general, NP-hard, and that most reasoning environments have limited resources, we need to select algorithms that can solve a given problem as fast as possible. This thesis presents a method for predicting the relative performance of reasoning algorithms based on the domain characteristics of the target knowledge structure. Armed with this knowledge, the research shows how to choose the best algorithm to solve the problem. The effects of incompleteness of the knowledge base at the time of inference is explored, and requirements for reasoning over incompleteness are defined. Two algorithms for reasoning …

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Design And Prototype Of The Afit Virtual Emergency Room: A Distributed Virtual Environment For Emergency Medical Simulation, Brian W. Garcia Dec 1996

Design And Prototype Of The Afit Virtual Emergency Room: A Distributed Virtual Environment For Emergency Medical Simulation, Brian W. Garcia

Theses and Dissertations

Due to the increasing complexity of emergency medical care, medical staffs require increasingly sophisticated training systems. Virtual environments offer a low cost means to achieve a widely usable yet sophisticated training capability. The Defense Advanced Research Projects Agency (DARPA) has sponsored the Virtual Emergency Room (VER) project to develop a simulation system that enables emergency department personnel within level I and II emergency rooms to practice emergency medical procedures and protocols. The VER is a simulation facility that uses a distributed virtual environment architecture to enable real-time, multi-participant simulations. The potential advantages of this system include the ability to evaluate …

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Dynamic Relevance Filtering In Asynchronous Transfer Mode-Based Distributed Interactive Simulation Exercises, David T. Hightower Dec 1996

Dynamic Relevance Filtering In Asynchronous Transfer Mode-Based Distributed Interactive Simulation Exercises, David T. Hightower

Theses and Dissertations

As Distributed Interactive Simulation (DIS) exercises continue to grow in scale, the need to support a large number of players has become apparent. The demands on the network and the simulation hosts in large exercises, though, have proved to be prohibitive, requiring significant computational overhead to filter through the information and extract what is relevant to a particular simulation. Some mechanism is needed to reduce irrelevant network traffic received by a system, while increasing the bandwidth available for the DIS exercise. Previous research efforts in this area have centered primarily on fixed geographic partitions of the battlespace to reduce the …

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Analysis And Design Of Standard Telerobotic Control Software, Matthew L. June Dec 1996

Analysis And Design Of Standard Telerobotic Control Software, Matthew L. June

Theses and Dissertations

The Robotics and Automation Center for Excellence (RACE) has defined an open telerobotics control architecture. This architecture, called the Unified Telerobotic Architecture Project (UTAP), is a proposed standard for all Air Force telerobotic systems. Implementation of UTAP will reduce the cost of robotic applications by increasing software modularity, portability, and reusability. This thesis continued the effort to prove the feasibility of UTAP. In December, 1995, 1st Lt Anchor implemented a portion of the UTAP specification on a PUMA robot. The UTAP-compliant controller exhibited some degradation in the system performance. However, the performance degradation was not fully measured. This thesis extended …

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Molecular Articulation In Response To Interactive Atomic Forces In Docker, Todd R. Kellett Dec 1996

Molecular Articulation In Response To Interactive Atomic Forces In Docker, Todd R. Kellett

Theses and Dissertations

Molecular docking aids in the design of materials supporting the current and future needs of the warfighter by simulating the real-world results of combining molecules. Specifically, it supports research and development in novel non-linear optical materials for laser-hardening and other advanced optical applications. Potential uses for these materials range from personnel and optical system laser protection to holographic information displays. DOCKER, our baseline docking system, minimizes the computational overhead of the simulation by modeling the molecules as rigid objects. This simplification can cause DOCKER's solutions to disagree with the real-world results, because molecules flex as they react to one another …

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Implementation Of An Ada95 Crosscompiler For The Real-Time Executive For Military Systems (Rtems), Kendall M. Lemley Jr. Dec 1996

Implementation Of An Ada95 Crosscompiler For The Real-Time Executive For Military Systems (Rtems), Kendall M. Lemley Jr.

Theses and Dissertations

This thesis represents a continuation of the assessment of the Unified Telerobotics Architecture Project (UTAP), a proposed Air Force standard. This architecture was developed by the NASA Jet Propulsion Laboratory and the National Institute of Standards under contract to the Air Force Materiel Command Robotics and Automation Center of Excellence at Kelly AFB, Texas. Due to operating system constraints, the only UTAP implementation to date has required a separate software interface layer, adding complexity and overhead to the overall system, while reducing portability. This thesis proposes a long term effort to design and implement UTAP-compliant application software devoid of this …

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Integrating The Capability Maturity Model For Software And The Quality Air Force Criteria, Marshall B. Messamore Dec 1996

Integrating The Capability Maturity Model For Software And The Quality Air Force Criteria, Marshall B. Messamore

Theses and Dissertations

As defense budgets decrease and it is required to do more with less, the Air Force has chosen to use the Malcolm Baldrige National Quality Award (MBNQA) as the basis for implementing quality principles. The Air Force program is known as Quality Air Force (QAF), and the criteria are referred to as the QAF criteria DEPA95b. At about the same time the Department of the Air Force implemented QAF, the software leaders in the Air Force adopted the Capability Maturity Model for Software (CMM) as the internal standard for Air Force software organizations MOSE9l. Software organizations strapped with both sets …

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A Specific Network Link And Path Likelihood Prediction Tool, Gary K. Moy Dec 1996

A Specific Network Link And Path Likelihood Prediction Tool, Gary K. Moy

Theses and Dissertations

Communications have always been a crucial part of any military operation. As the pace of warfare and the technological complexity of weaponry have increased, so has the need for rapid information to assess battlefield conditions. Message passing across a network of communication nodes allowed commanders to communicate with their forces. It is clear that an accurate prediction of communication usage through a network will provide commanders with useful intelligence of friendly and unfriendly activities. Providing a specific network link and path likelihood prediction tool gives strategic military commanders additional intelligence information and enables them to manage their limited resources more …

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Survivability Analysis Of The Iridium Low Earth Orbit Satellite Network, Douglas K. Stenger Dec 1996

Survivability Analysis Of The Iridium Low Earth Orbit Satellite Network, Douglas K. Stenger

Theses and Dissertations

This thesis evaluates the survivability of the proposed Iridium Low Earth Orbit (LEO) Satellite Network. In addition to the complete Iridium constellation, three degraded Iridium constellations are analyzed. This analysis occurs via the use of simulation models, which are developed to use three dynamic routing algorithms over three loading levels. The Iridium network models use a common set of operating assumptions and system environments. The constellation survivability was determined by comparing packet rejection rates, hop' counts, and average end to end delay performance between the various network scenarios. It was concluded that, based on the established scenarios, the proposed Iridium …

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Collaborative Workspaces Within Distributed Virtual Environments, William D. Wells Dec 1996

Collaborative Workspaces Within Distributed Virtual Environments, William D. Wells

Theses and Dissertations

In warfare, be it a training simulation or actual combat, a commander's time is one of the most valuable and fleeting resources of a military unit. Thus, it is natural for a unit to have a plethora of personnel to analyze and filter information to the decision-maker. This dynamic exchange of ideas between analyst and commander is currently not available within the distributed interactive simulation (DIS) community. This lack of exchange limits the usefulness of the DIS experience to the commander and his troops. This thesis addresses the commander's isolation problem through the integration of a collaborative workspace within AFIT's …

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Speaker Recognition By Hidden Markov Models And Neural Networks, Erik J. Zeek Dec 1996

Speaker Recognition By Hidden Markov Models And Neural Networks, Erik J. Zeek

Theses and Dissertations

As humans, we develop the ability to identify people by their voice at an early age. Getting computers to perform the same task has proven to be an interesting problem. Speaker recognition involves two applications, speaker identification and speaker verification. Both applications are examined in this effort. Two methods are employed to perform speaker recognition. The first is an enhancement of hidden Markov models. Rather than alter some part of the model itself, a single-layer perceptron is added to perform neural post-processing. The second solution is the novel application of an enhanced Feature Space Trajectory Neural Network to speaker recognition. …

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An Incremental Language Conversion Method To Convert C++ Into Ada95, Ding-Yuan Sheu Dec 1996

An Incremental Language Conversion Method To Convert C++ Into Ada95, Ding-Yuan Sheu

Theses and Dissertations

This thesis develops a methodology to incrementally convert a legacy object oriented C++ application into Ada95. Using the experience of converting a graphic application, called Remote Debriefing Tool (RDT), in the Graphics Lab of the Air Force Institute of Technology (AFIT), this effort defined a process to convert a C++ application into Ada95. The methodology consists of five phases: (1) reorganizing the software application, (2) breaking mutual dependencies, (3) creating package specifications to interface the existing C++ classes, (4) converting C++ code into Ada programs, and (5) embellishing. This methodology used the GNAT's C++ low level interface capabilities to support …

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Local Effects Of Solid Rocket Motor Exhaust On Stratospheric Ozone Concentrations, Brian K. George Dec 1996

Local Effects Of Solid Rocket Motor Exhaust On Stratospheric Ozone Concentrations, Brian K. George

Theses and Dissertations

Solid Rocket Motors (SRMs) power the initial flight of the Space Shuttle and Titan IV rocket. During those first two minutes after liftoff, the exhaust plumes from these motors emit large quantities of chlorine compounds and alumina particles into the atmosphere. For years scientists have argued that such a large chlorine input, injected directly into the stratosphere, would photochemically react with the surrounding air to cause significant ozone depletion. To answer the question of whether SRM exhaust causes a significant ozone depletion, Version 7 data from the Total Ozone Mapping Spectrometer (TOMS) instrument was analyzed for the 30 days prior …

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Evaluating The Hazardous Materials (Hazmat) Pharmacy Among Air Force Majcoms Using Waste Reductions And Activity Indicators, W. Edward Iseman Jr. Dec 1996

Evaluating The Hazardous Materials (Hazmat) Pharmacy Among Air Force Majcoms Using Waste Reductions And Activity Indicators, W. Edward Iseman Jr.

Theses and Dissertations

The Hazardous Materials (HazMat) Pharmacy has been designed as an environmentally friendly vehicle to handle, store, dispense, track, recycle, and dispose of hazardous materials in the Air Force. This thesis effort proposed a method in which valuable feedback for the pharmacy can be obtained. Because it is still in the early stages of implementation, there has been little feedback on the pharmacy. An activity index that uses a variable most closely associated with the generation of hazardous waste in a MAJCOM is proposed. Using an aircraft maintenance related variable, like maximum take-off weight, the fluctuations in mission over time can …

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The Biodegradation Characteristics Of Proposed Fuel Systems Icing Inhibitors (Fsii), Charles E. Meshako Dec 1996

The Biodegradation Characteristics Of Proposed Fuel Systems Icing Inhibitors (Fsii), Charles E. Meshako

Theses and Dissertations

The biodegradation characteristics of three fuel system icing ihhibitors (FSII) were evaluated. FSII are jet fuel additives that partition into water readily and are present in the water drained from storage tank bottoms in concentrations approaching 40%. These concentrations raise concerns as to the disposal and handling of these wastes. The current FSII, DiEGME was evaluated along with two new candidates, dipropylene glycol and glycerol formal. DiEGME appeared to be moderately but not completely biodegradable. It is likely that much of it would be removed in a wastewater treatment plant. Dipropylene glycol only showed signs of degradation after more than …

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An Activity Driver Based Analysis Of Hazardous Materials Usage At Wright-Patterson Afb, Charles D. Perham Dec 1996

An Activity Driver Based Analysis Of Hazardous Materials Usage At Wright-Patterson Afb, Charles D. Perham

Theses and Dissertations

As the Air Force has progressed and succeeded in the realm of pollution prevention, the opportunities for further progress have become more challenging. With the 'low-hanging fruit' now gone from the pollution prevention tree, new methods to identify opportunities must be adopted. This research effort applied a subset of activity based costing, activity driver analysis, to reveal pollution prevention opportunities in regards to hazardous materials usage. A sample of base organizations (civil engineering and aircraft maintenance), and a sample of the hazardous chemicals (Class C or most hazardous) used by those organizations were investigated to determine the drivers behind usage.

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Modeling Marine Exposure To Polychlorinated Biphenyls From Sunken Ships, Charles N. Wendt Dec 1996

Modeling Marine Exposure To Polychlorinated Biphenyls From Sunken Ships, Charles N. Wendt

Theses and Dissertations

In the past, the U.S. Navy has routinely conducted SINKing EXercises (SINKEX) for training, weapon effectiveness tests, and economic disposal of aging assets. Recent concern over polychlorinated biphenyl (PCB) chemicals aboard such target vessels has resulted in a suspension of SINKEX. The U.S. Navy has approximately 200 vessels currently requiring such disposal. Environmental legislation and health concerns preclude selling such vessels to foreign governments or scrapping. This work attempted to model the fate and transport of these PCBs by examining their transport to coastal water and their accumulation in the marine food chain. The model includes biodegradation, upwelling, partitioning of …

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Analysis Of Multimode Low-Probability-Of-Intercept (Lpi) Communications With Atmospheric Effects, Ala Ghordlo Dec 1996

Analysis Of Multimode Low-Probability-Of-Intercept (Lpi) Communications With Atmospheric Effects, Ala Ghordlo

Theses and Dissertations

This research expanded Low Probability of Intercept (LPI) communications analysis in two areas. First, multimode communication was included to account for ground to ground and air to ground links in addition to the standard air to air links traditionally used in LPI analysis. The propagation equations for the three modes of interest were derived and included in LPI analytic models in the form of a mode quality factor to account for multimode LPI scenarios. This new quality factor was used in studying several communication and interception link combinations. Variations due to differences between the communication and interception modes were presented …

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Performance Analysis Of A Hartman Wavefront Sensor Used For Sensing Atmospheric Turbulence Statistics, Toby D. Reeves Dec 1996

Performance Analysis Of A Hartman Wavefront Sensor Used For Sensing Atmospheric Turbulence Statistics, Toby D. Reeves

Theses and Dissertations

Atmospheric turbulence parameters, such as Fried's coherence diameter, the outer scale of turbulence, and the turbulence power law, are related to the wavefront slope structure function (SSF). The SSF is defined as the second moment of the wavefront slope difference as a function of both time and position. Knowledge of the SSF allows turbulence parameters to be estimated. Hartmann wavefront sensor (H-WFS) slope measurements composed of both signal and noise, allow the SSF to be estimated by computing a mean square difference of H-WFS slope measurements. The quality of the SSF estimate is quantified by the signal-to-noise ratio (SNR) of …

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Weighted Mahalanobis Distance For Hyper-Ellipsoidal Clustering, Khaled S. Younis Dec 1996

Weighted Mahalanobis Distance For Hyper-Ellipsoidal Clustering, Khaled S. Younis

Theses and Dissertations

Cluster analysis is widely used in many applications, ranging from image and speech coding to pattern recognition. A new method that uses the weighted Mahalanobis distance (WMD) via the covariance matrix of the individual clusters as the basis for grouping is presented in this thesis. In this algorithm, the Mahalanobis distance is used as a measure of similarity between the samples in each cluster. This thesis discusses some difficulties associated with using the Mahalanobis distance in clustering. The proposed method provides solutions to these problems. The new algorithm is an approximation to the well-known expectation maximization (EM) procedure used to …

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Graphical Display Of A Missile Endgame Scenario, Joseph E. Moritz Dec 1996

Graphical Display Of A Missile Endgame Scenario, Joseph E. Moritz

Theses and Dissertations

Traditionally, computer programs to model and simulate air-to-air missile endgame engagements have focused on improving the underlying probability of kill models. This focus, however, understates the benefits of current computer graphics technology for visualization and direct manipulation of missile endgame parameters and building engagement understanding through real-time, three dimensional simulation of the endgame. Our research has been to develop a versatile simulation system to display the missile endgame parameters and allow graphical interaction with these parameters. This program also allows the user to view animated engagements of previously designed endgames. The current project scope is to provide user feedback of …

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