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Air Force Institute of Technology

Theses/Dissertations

1995

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Articles 1 - 30 of 83

Full-Text Articles in Physical Sciences and Mathematics

Experimental Investigation And Computer Modeling Of Optical Switching In Distributed Bragg Reflector And Vertical Cavity Surface Emitting Laser Structures, Richard J. Bagnell Dec 1995

Experimental Investigation And Computer Modeling Of Optical Switching In Distributed Bragg Reflector And Vertical Cavity Surface Emitting Laser Structures, Richard J. Bagnell

Theses and Dissertations

The optical switching capabilities of Distributed Bragg Reflector (DBR) structures, including Vertical Cavity Surface Emitting Lasers (VCSELs) are examined. Reflectivity switching is demonstrated using both thermal and carrier generated effects to alter the DBR/VCSEL layers' refractive indices. Optical bistability is demonstrated at room temperature, under CW photopumped excitation. The optical bistability hysteresis is controllable by spectral location of the pump on the stop band edge. In the VCSEL, reflective bistability is also evidenced; additionally, this bistability is accompanied by a bistability in the VCSEL lasing output intensity, spot size, and wavelength. Modeling of the DBR/VCSEL thermally induced bistability was accomplished …

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Effects Of Ammonium Perchlorate On The Thyroid Hormone Levels Of The Sprague-Dawley Rat, James H. King Jr. Dec 1995

Effects Of Ammonium Perchlorate On The Thyroid Hormone Levels Of The Sprague-Dawley Rat, James H. King Jr.

Theses and Dissertations

The purpose of this research was to determine the threshold dose for ammonium perchlorate (AP) in the Sprague-Dawley rat. No dose response data exist for AP and the EPA has studied literature on the subject of perchlorates to determine a provisional reference dose. The Perchiorate Group, a consortium of DoD and industry representatives, believes this provisional reference dose is too conservative. This experiment was executed to provide dose response data on which to base a more accurate reference dose. The study consisted of eight groups of 12 Sprague-Dawley rats, six male and six female, which were exposed to incremental doses …

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Neutron Damage In Distributed Bragg Reflectors And Microcavity Lasers, Mark A. Suriano Dec 1995

Neutron Damage In Distributed Bragg Reflectors And Microcavity Lasers, Mark A. Suriano

Theses and Dissertations

Distributed Bragg Reflectors (DBRs) grown on a gallium-arsenide substrate for a solid state mirror and a vertical cavity surface emitting laser (VCSEL) were subjected to a neutron fluence to determine the sensitivity of the DBRs. The samples were irradiated at Ohio State University's 500 kW research reactor. Relative and absolute reflectance measurements were taken before and after each irradiation over a spectral band of 530 880 µm. Relative reflectance measurements showed that the irradiation did not cause any spectral shift over seven decades of neutron fluences. The reflectivity of the DBRs decreased from their initial measurements after being irradiated. The …

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A Portable Compton Gamma-Ray Camera Design, Brian L. Evans Dec 1995

A Portable Compton Gamma-Ray Camera Design, Brian L. Evans

Theses and Dissertations

The purpose of this research is to investigate the angular resolution, efficiency, and energy resolution possible from a portable Compton camera gamma ray imaging system for possible use in the field of nuclear nonproliferation. The proposed device uses room temperature semiconductor and position sensitive scintillation detectors. The position and energy resolution (and their energy dependence) of a room temperature lithium drifted silicon (Si(Li)) detector and a position sensitive thallium -doped sodium iodide (NaI(Tl)) scintillation detector are investigated. The position and energy resolution of the position sensitive scintillation detector is also modeled computationally, and the results compared to measured data. An …

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The Role Of Frame Selection And Bispectrum Phase Reconstruction For Speckle Imaging Through Atmospheric Turbulence, Elizabeth A. Harpold Dec 1995

The Role Of Frame Selection And Bispectrum Phase Reconstruction For Speckle Imaging Through Atmospheric Turbulence, Elizabeth A. Harpold

Theses and Dissertations

Frame selection using quality sharpness metrics have been shown in previous AFIT theses, to be effective in improving the final product of images obtained using adaptive optics. This thesis extends this idea to noncompensated speckle image data. Speckle image reconstruction is simulated with and without frame selection. Speckle images require the processing of hundreds of data frames. Frame selection is a method of reducing the amount of data required to reconstruct the image. A collection of short exposure image data frames of a single object are sorted based on sharpness metrics. Only the highest quality frames are retained and processed …

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A Point Model Of Aquifer Cleanup With A Distribution Of First-Order Rate Parameters, Jon E. Hodge Dec 1995

A Point Model Of Aquifer Cleanup With A Distribution Of First-Order Rate Parameters, Jon E. Hodge

Theses and Dissertations

Many try modeling groundwater contaminant transport to predict it. Is this possible with rate-limited processes, and under what conditions? On occasion, cleanups go slower than predicted (tailing) and hazardous concentrations reappear after cleanup is thought complete (rebound). Rate-limited transport is blamed by many. When immobile water is present, diffusion from varied sizes and shapes of immobile regions can cause varied rate limitations (due to varied diffusion path lengths). Although known, most modelers represent these varied rate-limiting processes with a single 'representative' rate-parameter. This can yield poor predictions for long-term experiments, and the parameter is generally time and pump-rate dependent. This …

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Photoluminescence And Electroluminescence Of Erbium And Neodymium Implanted Semiconductors, James R. Hunter Dec 1995

Photoluminescence And Electroluminescence Of Erbium And Neodymium Implanted Semiconductors, James R. Hunter

Theses and Dissertations

Low temperature photoluminescence (PL) and electroluminescence (EL) measurements were used to study the excitation of erbium- and neodymium-implanted GaAs and AlxGa1-xAs (x=0. 1, 0.3) pn-junctions. The rare-earth (RE) emissions were investigated as a function of ion dose, aluminum mole fraction, laser excitation power, and applied forward bias voltage for the implanted samples. Low temperature PL was also measured from Er doped silicon grown by the metalorganic chemical vapor-phase deposition (MOCVD) method using various growth parameters.. The MOCVD-grown Si samples were studied as a function of metalorganic source temperature, silane (SiH4) flow, growth time, and …

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A Comparison Of Methods For Estimating Rms Error: A `Brute Force" Approach Versus A Mathematically-Elegant Approach, As Applied To The Calculation Of A Specific Retrieval Error For A Limb-Scanning Microwave Radiometer-Spectrometer, Larry L. Johnson Dec 1995

A Comparison Of Methods For Estimating Rms Error: A `Brute Force" Approach Versus A Mathematically-Elegant Approach, As Applied To The Calculation Of A Specific Retrieval Error For A Limb-Scanning Microwave Radiometer-Spectrometer, Larry L. Johnson

Theses and Dissertations

The Millimeter-wave Atmospheric Sounder (MAS) is a high resolution limb- scanning microwave radiometer-spectrometer which has been flown aboard the Space Shuttle. The instrument was designed to sense the microwave emission from several upper atmospheric constituents, including water vapor and ozone. The resonant frequencies of water vapor and ozone are extremely close (183 and 184 GHz, respectively), so that the high-frequency wing of the water vapor spectrum overlaps the low frequency wing of the ozone spectrum. Consequently, the measured ozone spectrum incorporates a slight water vapor contribution; therefore, the retrieved ozone profile is dependent on the true water vapor profile. The …

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Analysis And Interpretation Of Ion Data Associated With Neutral Gas Releases In The Earth's Ionosphere, Timothy M. Shadid Dec 1995

Analysis And Interpretation Of Ion Data Associated With Neutral Gas Releases In The Earth's Ionosphere, Timothy M. Shadid

Theses and Dissertations

Barium and strontium release experiments were conducted throughout 1991 from the Combined Release and Radiation Effects Satellite (CRRES) to study both natural and man-made disturbances in the earth's ionosphere. A mass spectrometer on the spacecraft counted the Ba and Sr ions as the cloud expanded. In this study, data from the G-1 (in sunlight) and G-11b (in darkness) releases were modeled to understand the source of the ion signals. The model reproduced the Ba+ sun data well assuming photoionization (τ = 28 s) was the primary ionization mechanism. However, it was not able to account for the remaining ion …

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Micromirror Array Control Of A Phase-Locked Laser Diode Array, Carl J. Christensen Dec 1995

Micromirror Array Control Of A Phase-Locked Laser Diode Array, Carl J. Christensen

Theses and Dissertations

A ten element micromirror array has been designed, fabricated, and employed to control the far field irradiance pattern of a phase locked laser diode array. The laser array used in this experiment was a ten element, gain guided array lasing at a nominal wavelength of 828 nm and operating in the it out of phase supermode. The laser's near field irradiance was imaged onto a micromirror array, where the it phase differences between adjacent laser elements were corrected. This was accomplished by moving the micromirrors with individually applied voltages. The result was the desirable single lobed far field pattern, placing …

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An Object-Oriented, Formal Methods Approach To Organizational Process Modeling, Vincent S. Hibdon Dec 1995

An Object-Oriented, Formal Methods Approach To Organizational Process Modeling, Vincent S. Hibdon

Theses and Dissertations

This document presents a methodology for developing an organizational process model which is based on the principles of object oriented design and formal software engineering methods. The methodology begins with the development of an object oriented Rumbaugh model (27). The Rumbaugh model is then formally specified in Z (Zed) schemas. Finally, the Z specifications are translated into an executable model in the Software Refinery Environment(TM). This model is described based on the AF wing domain and developed in this domain. The proposed methodology is then shown to produce a very general model which is extendable across almost any domain. The …

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Evaluation Of The Air Force Installation Restoration Advisory System, Dale M. Fox Dec 1995

Evaluation Of The Air Force Installation Restoration Advisory System, Dale M. Fox

Theses and Dissertations

This research is intended to evaluate the Air Force's Installation Restoration Advisory System Workstation software and documentation. Groundwater modeling is the biggest aid to Air Force Installation Restoration decision makers in making their conclusions about what to do with their hazardous waste sites where the groundwater is contaminated. The Advisory System aids the user in determining if a site poses a potential problem, and if so assists the user in selecting an appropriate groundwater transport model. The decision of what type of model is most suitable is based upon the user's conceptual site model and the decision is made by …

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Macroscale Diffusion-Limited Sorption Modeling--A Preliminary Modeling Exercise For A Dover Afb Site, Jason T. Herman Dec 1995

Macroscale Diffusion-Limited Sorption Modeling--A Preliminary Modeling Exercise For A Dover Afb Site, Jason T. Herman

Theses and Dissertations

A modification was made to the USGS SUTRA code which allowed the simulation of macro scale diffusion effects from specific layers. This modification utilized a split-operator finite element numerical technique to incorporate the macroscale diffusion. The code was applied to a conceptual site developed from a field site at Dover AFB, DL Simulations were done to compare the modified code to the unmodified code which clearly showed the modified code as a closer representation of reality. Simulations were also done to study the effects of pulsed and continuous pumping within the time frame of a field experiment at Dover. These …

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Determining The Effects Of Waste Coal Ash On Landfill Radon Levels, Richard S. Krysiak Jr. Dec 1995

Determining The Effects Of Waste Coal Ash On Landfill Radon Levels, Richard S. Krysiak Jr.

Theses and Dissertations

Coal contains trace amounts of the primary radionuclides 40K, and elements of the 4n (232Th), 4n+2 (238U), and 4n+3 (235U) series including 220Rn and 222Rn. Combustion of coal by electric power and heat plants result in concentration of noncombustible mineral matter, including most of the radionuclides, in the coal ash. The increased radiation due to the concentration of radionuclides is known as technologically enhanced natural radiation. The purpose of this research was to determine the effects of landfilled coal ash on one specific aspect of technologically enhanced natural radiation, radon levels. …

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Study Of The Long-Term Desorption Of Trichloroethylene From Clay Soils Using Infrared Spectroscopy, Mary P. Stager Dec 1995

Study Of The Long-Term Desorption Of Trichloroethylene From Clay Soils Using Infrared Spectroscopy, Mary P. Stager

Theses and Dissertations

Slow desorption of contaminants from soil presents one of the greatest challenges to modeling contaminant fate and transport and implementing effective remediation technologies. The kinetics of long-term desorption of trichloroethylene (TCE) from powdered clay soils were studied to determine the desorption rates and mechanism. Infrared absorption spectroscopy was used to monitor the concentration of TCE desorbed from contaminated flint clay for 71 hours. Observed gas phase TCE concentrations as a function of time were compared to that predicted by a one-site Langmuir desorption mechanism. The Langmuir model, with a single type of bonding site, did not account for the release …

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Model Of Chlorocarbon (Cfc-12) Chemisorption On Solid Rocket Motor Alumina Exhaust Particles, Gary E. Lund Dec 1995

Model Of Chlorocarbon (Cfc-12) Chemisorption On Solid Rocket Motor Alumina Exhaust Particles, Gary E. Lund

Theses and Dissertations

Solid Rocket (SRMs) that power Titan IV rockets and Space Shuttles, exhaust large quantities of potentially ozone damaging pollutants directly into the stratosphere, while in powered flight. In the past, studies on potential stratospheric impact of the exhaust products from aluminum/ammonium perchlorate based SRMs have focused on the effect of gaseous HCl from SRMs on the stratosphere. Until recently, the impact of heterogeneous chemistry on stratospheric ozone was believed to be relatively insignificant. This research investigates the potential heterogeneous process of CFC-12 dissociative chemisorption on alumina surfaces and the release of reactive halogen species known to destroy ozone. Through a …

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Decision Support Model To Optimize Site Characterization Activities Taken In Compliance With The Comprehensive Environmental Response Compensation And Liability Act, Daniel J. Clairmont Dec 1995

Decision Support Model To Optimize Site Characterization Activities Taken In Compliance With The Comprehensive Environmental Response Compensation And Liability Act, Daniel J. Clairmont

Theses and Dissertations

One of the most frequently cited reasons for the slow and costly progress of Superfund cleanups is the remedial investigation and feasibility study process (RI/FS). After each phase of the RI/FS process there are several possible alternatives that may be chosen. This research developed decision support models to help decision makers choose between the feasible alternatives at five different decision points during site characterization activities. The models make recommendations on how to deal with any particular chemical based on the risk posed by that chemical. The models assume that the value of characterizing the site further is a reduction in …

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The Relationship Between Environmental Attitudes And Environmental Behaviors Among Air Force Members, Daniel T. Holt Dec 1995

The Relationship Between Environmental Attitudes And Environmental Behaviors Among Air Force Members, Daniel T. Holt

Theses and Dissertations

A questionnaire was distributed to nearly 2,000 randomly selected active duty Air Force members assigned to locations throughout the continental United States. The survey was designed to determine the extent to which Air Force members expressed support for environmental issues. In addition, the survey measured how frequently Air Force members engaged in specific behaviors that were deemed environmentally protective. Although the Air Force members expressed relatively strong support for environmental issues, they only occasionally engaged in activities that contribute to the preservation or protection of the environment. Correlation analysis revealed that the pro-environmental attitudes were positively linked to the environmentally …

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A Comparison Of Remediation Priorities Developed By The Defense Priority Model, The Relative Risk Evaluation Method, And A Quantitative Risk Assessment Approach, David M. Hunter Dec 1995

A Comparison Of Remediation Priorities Developed By The Defense Priority Model, The Relative Risk Evaluation Method, And A Quantitative Risk Assessment Approach, David M. Hunter

Theses and Dissertations

The Superfund, established by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, seriously underestimated both the number of severely contaminated sites and the associated cleanup cost. The magnitude of projected cleanup costs, coupled with shrinking federal budgets, necessitated the development and use of risk-based prioritization models among some federal agencies. Among these tools, the DOD prioritization models are meant to give priority to sites posing the greatest threat to human health. Their failure to properly rank sites could incorrectly shift the focus from those that pose substantial risk to sites of lesser risk. The DOD site ranking …

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Comparison Of Gravel Substrate Vs Soil Substrate For The Construction Of An Experimental Fen, Carolyn S. Langley Dec 1995

Comparison Of Gravel Substrate Vs Soil Substrate For The Construction Of An Experimental Fen, Carolyn S. Langley

Theses and Dissertations

Under the Clean Water Act Section 404 of 1972 and 33 CFR 320-330 and 40 CFR 230 moderate the destruction of wetlands by the Air Force to make way for other uses. To obtain a permit for a design or construction project which affects a wetland, the Air Force must agree to create new wetlands, or replace lost wetland acreage through wetland creation or restoration. The Air Force is interested in building 'successful' wetlands as inexpensively as possible. It has been common practice to use hydric soil, which often had to be hauled in, as the substrate at the restored …

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A System Dynamics Approach To Modelling The Degradation Of Biochemical Oxygen Demand In A Constructed Wetland Receiving Stormwater Runoff, Leslie A. Mudgett Dec 1995

A System Dynamics Approach To Modelling The Degradation Of Biochemical Oxygen Demand In A Constructed Wetland Receiving Stormwater Runoff, Leslie A. Mudgett

Theses and Dissertations

The objective of this research was to develop a tool to aid the Air Force Environmental Manager in the identification of the design parameters of a constructed wetland system that may be optimized to provide a desired biochemical oxygen demand (BOD) removal efficiency during the treatment of Air Force stormwater runoff. The objective is achieved through the development and use of a system dynamics model which simulates the hydrological functions of a constructed wetland as well as the processes within the wetland responsible for degradation of BOD. Based on literature review, the primary mechanism responsible for the degradation of BOD …

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A Comparison Of Response Surface Methodology And A One-Factor-At-A-Time Approach As Calibration Techniques For The Bioplume-Ii Simulation Model Of Contaminant Biodegradation, Benjamin Shuman Dec 1995

A Comparison Of Response Surface Methodology And A One-Factor-At-A-Time Approach As Calibration Techniques For The Bioplume-Ii Simulation Model Of Contaminant Biodegradation, Benjamin Shuman

Theses and Dissertations

This thesis compared Response Surface Methodology (RSM) to the one-factor-at-a-time approach for calibrating the Bioplume-II simulation model of contaminant biodegradation. The MADE-2 data set from Columbus Air Force Base, Mississippi was used. The one-factor-at-a-time approach reduced the root-mean-squared (RMS) error for the flow to 0.921225 feet in a total of 36 runs of Bioplume-II. The RSM approach reduced the error criterion to 0.918875 in a total of 47 runs. The one-factor-at-a-time approach was unable to reduce the error below 67.1831 parts per billion (ppb) after 21 runs. The RSM approach reduced the RMS error to 67.0327 ppb after 47 runs. …

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Design And Evaluation Of Standard Telerobotic Control Software, Kevin P. Anchor Dec 1995

Design And Evaluation Of Standard Telerobotic Control Software, Kevin P. Anchor

Theses and Dissertations

This thesis represents the first implementation of a proposed Air Force standard telerobotic control architecture. This architecture was developed by the NASA Jet Propulsion Laboratory and the National Institute of Standards and Technology under contract to the Air Force Materiel Command Robotics and Automation Center of Excellence (RACE) as the Unified Telerobotics Architecture Project (UTAP). The AFIT Robotics and Automation Applications Group (RAAG) Lab B facility computational structure was redesigned to be compliant with the UTAP architecture. This thesis shows that the UTAP specification to be implementable. However, if the underlying operating system does not support generic message passing, an …

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Reducing Lag In Virtual Displays Using Multiple Model Adaptive Estimation, David W. Kyger Dec 1995

Reducing Lag In Virtual Displays Using Multiple Model Adaptive Estimation, David W. Kyger

Theses and Dissertations

Multiple Model Adaptive Estimation is an effective method for reducing lag in virtual environment displays. Lag in displays (the time from head motion to the appearance of the proper image on the display) is a significant detriment to realism in virtual environments. Increasing the speed of the computers which control the virtual display is not a final answer. No matter how fast the processors work, there will always be demands to do more. Predicting angular head positions (look-angles) can reduce the lag by allowing the computer to calculate the appropriate scene before it is needed on the display. Single predictors …

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Design And Analysis Of Parallel Hierarchical Battlefield Simulation, Conrad P. Masshardt Dec 1995

Design And Analysis Of Parallel Hierarchical Battlefield Simulation, Conrad P. Masshardt

Theses and Dissertations

The purpose of this research is to determine if hierarchically partitioning a discrete event battlefield simulation reduces runtime and, if reduction exists, to characterize the run time reduction given any particular partition configuration. A hierarchical discrete event simulation of a main battle tank was constructed. Implementations were built for both a single processor and a multiprocessing machine. The implementations used the Message Passing Interface to increase portability to other parallel and distributed configurations. Three test cases were generated and run on three parallel and distributed environments, a network of Sun SparcStation 20's, a Silicon Graphics Power Challenge, and a Paragon …

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Dynamic Transfer Of Control Between Manned And Unmanned Simulation Actors, Neal W. Schneider Dec 1995

Dynamic Transfer Of Control Between Manned And Unmanned Simulation Actors, Neal W. Schneider

Theses and Dissertations

This thesis continues the ongoing research at the Air Force Institute of Technology's Virtual Environments Laboratory in the area of distributed simulation. As the relevance and interest of interactive simulation as a training medium continues to grow, there is a pressing need to provide more realistic and numerous intelligent autonomous agents for simulations. As those autonomous agents mature and become more realistic, the need exists to be able to handle individual agents by taking control of them and operating them as manned agents at certain points within the simulation. The author started with a protocol proposed in a working draft …

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Two-Wavelength Neodymium Based Lasers, Scott H. Mccracken Dec 1995

Two-Wavelength Neodymium Based Lasers, Scott H. Mccracken

Theses and Dissertations

A dual wavelength Q switched laser cavity has been successfully designed and assembled to evaluate the new neodymium (Nd) based materials. Initial characterization has been achieved for Nd:YAG and Nd:YLF. The results indicate that for a fixed pulse repetition frequency, the delay time can be used to adjust the relative energy between the 1.06 and 1.32 micrometer pulses. Any deficiency in the performance of one transition can be made up by performance in the other simply by changing the relative amount of time the population inversion is allowed to build up for each pulse. The best performance was obtained using …

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A Neural Network Approach To The Prediction And Confidence Assignation Of Nonlinear Time Series Classifications, Erin S. Heim Dec 1995

A Neural Network Approach To The Prediction And Confidence Assignation Of Nonlinear Time Series Classifications, Erin S. Heim

Theses and Dissertations

This thesis uses multiple layer perceptrons (MLP) neural networks and Kohonen clustering networks to predict and assign confidence to nonlinear time series classifications. The nonlinear time series used for analysis is the Standard and Poor's 100 (S&P 100) index. The target prediction is classification of the daily index change. Financial indicators were evaluated to determine the most useful combination of features for input into the networks. After evaluation it was determined that net changes in the index over time and three short-term indicators result in better accuracy. A back-propagation trained MLP neural network was then trained with these features to …

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Objectism 3.0: A Software Architecture For The Development Of Portable Visual Simulation Applications, Shawn M. Hannan Dec 1995

Objectism 3.0: A Software Architecture For The Development Of Portable Visual Simulation Applications, Shawn M. Hannan

Theses and Dissertations

A visual simulation software architecture is a reusable design for visual simulation applications. This thesis effort was the third stage in an ongoing refinement of such an architecture, named ObjectSim. The primary goals of this stage were to improve the architecture by eliminating its dependence on two platform-specific graphics libraries (named GL and Performer, from Silicon Graphics, Inc.), and to examine the potential for expanding the architecture to accommodate distributed simulations. The effort resulted in a new version of the architecture which allows the development of visual simulation applications which take full advantage of the aforementioned libraries without calling those …

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Transforming Algebraically-Based Object Models Into A Canonical Form For Design Refinement, Charles G. Beem Dec 1995

Transforming Algebraically-Based Object Models Into A Canonical Form For Design Refinement, Charles G. Beem

Theses and Dissertations

The understandability of object-oriented design techniques and the rigor of formal methods have improved the state of software development; however, both ideas have limitations. Object-oriented techniques, which are semi-formal, can still result in incorrect designs, while formal methods are complex and require an extensive mathematical background. The two approaches can be coupled, however, to produce designs that are both understandable and verifiable, and to produce executable code. This research proposes an approach where object-oriented models are first represented algebraically in a formal specification language such as LARCH and then transformed into a canonical form suitable for design refinement. In the …

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