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Air Force Institute of Technology

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Articles 4411 - 4440 of 5699

Full-Text Articles in Engineering

Metabolic Inhibition Of A Toluene-Enriched Microbial Population Due To Lead (Pb2+): Verification Of A Free Metal Ion Toxicity Model, Patrick J. S. Marbas Dec 1997

Metabolic Inhibition Of A Toluene-Enriched Microbial Population Due To Lead (Pb2+): Verification Of A Free Metal Ion Toxicity Model, Patrick J. S. Marbas

Theses and Dissertations

A dissolved oxygen probe and an ion specific electrode were used to study the lead-induced metabolic inhibition in a toluene-enriched microbial population. Predicted toxicity values were compared to the actual toxicity responses using a free metal ion toxicity model (TM) which linked metabolic inhibition with lead activity. Experimentally derived values for the model parameters (lead activity and a lead distribution coefficient) were used in the TM. It was postulated that cellular metabolism is disrupted by the conformational changes to the cell's plasma membrane produced by lead ion adsorption. The predicted toxicity values were higher than the actual toxicity response. This …

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Cepstral Processing For Gps Multipath Detection And Mitigation, Charles D. Ormsby Dec 1997

Cepstral Processing For Gps Multipath Detection And Mitigation, Charles D. Ormsby

Theses and Dissertations

This work presents a novel approach to code phase multipath mitigation for Global Positioning System (GPS) receivers. It uses the power and complex cepstra for multipath detection and mitigation prior to code phase tracking by a standard non-coherent delay lock loop. Cepstral theory is presented to demonstrate how multipath reflection delays can be detected through the use of the power cepstrum. Filtering can then be performed on the complex cepstrum to remove multipath effects in the cepstral domain. Finally, an inverse complex cepstrum is calculated yielding a theoretically multipath free direct path estimate in the time domain. Simulations are presented …

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Forecasting Methodologies For Usaf Facility Maintenance And Repair Funding Requirements, Gregory R. Ottoman Dec 1997

Forecasting Methodologies For Usaf Facility Maintenance And Repair Funding Requirements, Gregory R. Ottoman

Theses and Dissertations

Eighteen methodologies for forecasting facility maintenance and repair funding requirements were investigated and analyzed to determine which methodology is best suited for use by the United States Air Force (USAF). The literature review identified four primary factors, or criteria, that determine facility maintenance and repair funding requirements. The methodologies were scored against the four criteria with respect to their appropriate application to USAF requirements. An analysis of dominance was accomplished; the results suggested that no one methodology was clearly superior. Fourteen of the methodologies were dominated, and consequently eliminated from further analysis. Four methodologies were non-dominated: the U.S. Army Construction …

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Scattering From Dielectric Bodies, Jeffery M. Parks Dec 1997

Scattering From Dielectric Bodies, Jeffery M. Parks

Theses and Dissertations

The purpose of this study was to develop an RCS measured database of non-PEC targets and provide an example of its use to validate a code, 3D-RCIE. RCS prediction codes that handle penetrable materials require measured data to determine their accuracy. The materials used for this research include polyethylene and polyurethane with dielectric constants around 2.3 and 1.03, respectively. The polyethylene targets include a mini-arrow, ogive, conesphere, conesphere with a gap, sphere, and a large and small cube. The cubes were the only targets made from the polyurethane foam. Additionally, r-card was applied to the cubes and mini-arrow. The material …

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Department Of Defense Hazardous Waste Site Remediation Issues In The Republic Of Korea, Edwin H. Oshiba Dec 1997

Department Of Defense Hazardous Waste Site Remediation Issues In The Republic Of Korea, Edwin H. Oshiba

Theses and Dissertations

The purpose of this research was to provide information to DoD decision makers regarding factors influencing hazardous waste site remediation policy for South Korea. This study addressed: International agreements and U.S. and South Korean laws and policies relevant to hazardous waste sites; objectives of DoD environmental policy makers; extent and effects of soil and groundwater contamination; cleanup precedents set in other foreign countries; availability of resources and technical capabilities to investigate and remediate hazardous waste sites in South Korea; and opportunities for cooperation between the U.S. and South Korean military with regard to hazardous waste site remediation. Data were collected …

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Architecture, Design, And Implementation Of A Rapidly Prototyped Virtual Environment For A Military Spaceplane, Scott A. Rothermel Dec 1997

Architecture, Design, And Implementation Of A Rapidly Prototyped Virtual Environment For A Military Spaceplane, Scott A. Rothermel

Theses and Dissertations

The new Global Engagement vision places increased emphasis on the Air Force's ability to control and exploit space. A military spaceplane combining reliable access to space, high operational tempos, and multi-mission capabilities is in conceptual stages of development. Virtual environment technology provides an opportunity to investigate system requirements and unconventional interface paradigms for this unique vehicle. A virtual environment architecture and design based on support for a rapid prototyping development process, separation of concerns, and user interface development is presented. The rapid prototyping process allowed management of changing requirements via an evolutionary approach to implementation. Separation of the activities performed …

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Optimal Non-Coplanar Launch To Quick Rendezvous, Gregory B. Sears Dec 1997

Optimal Non-Coplanar Launch To Quick Rendezvous, Gregory B. Sears

Theses and Dissertations

The purpose of this study was to determine the feasibility of launching a Delta Clipper-like vehicle on an optimal, non-coplanar trajectory to rendezvous with an earth orbiting object in one orbit or less. The focus of the research was to determine what such a trajectory would look like, and to determine the cost, in payload mass, of flying such a trajectory. A model for the ascent trajectory was developed using the dynamics equations of motion, an atmosphere model, and an aerodynamic model for the DC-Y concept vehicle. A boundary value problem was posed and solved for a coplanar rendezvous. The …

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A Wire Antenna Designed For Space Wave Radiation Over The Earth Using A Genetic Algorithm, Brian S. Sandlin Dec 1997

A Wire Antenna Designed For Space Wave Radiation Over The Earth Using A Genetic Algorithm, Brian S. Sandlin

Theses and Dissertations

A wire antenna is designed for optimal performance at low elevation angles in the presence of a lossy half-space. A simple genetic algorithm (GA) and GENOCOP III software are each integrated with Numerical Electromagnetics Code Version 4.1 (NEC4.1) to optimize a wire antenna geometry for multiple objectives: power gain, azimuthal symmetry, and input impedance. The performance of the two versions of the integrated GA are compared. Several of the resulting antennas are analyzed, and an antenna is proposed for use in a Remote Intrusion Monitoring System (RIMS). Simulations suggest that the proposed antenna, which is well-matched, offers a significant increase …

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Evaluation Of A Maximum A-Posteriori Slope Estimator For A Hartmann Wavefront Sensor, Troy B. Van Caster Dec 1997

Evaluation Of A Maximum A-Posteriori Slope Estimator For A Hartmann Wavefront Sensor, Troy B. Van Caster

Theses and Dissertations

Current methods for estimating the wavefront slope at the aperture of a telescope using a Hartmann wavefront sensor are based upon a centroid shift estimator. The centroid shift estimator determines the displacement, or shift, of the centroid off the optical axis using a moment calculation of the intensity distributions recorded in each subaperture. This centroid shift is proportional to the average slope of the wavefront in each subaperture. A maximum a-posteriori (MAP) slope estimator takes advantage of a-priori knowledge of the wavefront slope statistics and total irradiance falling on the subaperture detector arrays when determining the shift estimate. In order …

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Modeling And Simulation Support For Parallel Algorithms In A High-Speed Network, Dustin E. Yates Dec 1997

Modeling And Simulation Support For Parallel Algorithms In A High-Speed Network, Dustin E. Yates

Theses and Dissertations

This thesis investigates the ability of a simulation model to compare and contrast parallel processing algorithms in a high-speed network. The model extends existing modeling, analysis, and comparison of parallel algorithms by providing graphics based components that facilitate the measurement of system resources. Simulation components are based on the Myrinet local area network standard. The models provide seven different topologies to contrast the performance of five variations of Fast Fourier Transform (FFT) algorithms. Furthermore, the models were implemented using a commercially developed product that facilitates the testing of additional topologies and the investigation of hardware variations. Accurate comparisons are statistically …

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Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler Dec 1997

Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler

Theses and Dissertations

An understanding of spontaneous emission processes within microcavities is crucial in addressing the need to make tomorrow's microlasers more efficient. One approach to improving the device efficiency is to reduce the threshold input energy at which lasing begins to occur. It has been suggested that the threshold in a microcavity laser can be decreased by increasing the fraction of spontaneous emission into the lasing mode, this can be accomplished by preferentially coupling the gain medium of the laser to the electromagnetic cavity mode of interest. It therefore becomes necessary to understand the mechanism by which this coupling takes place. This …

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Measurement Of Ultrafast Carrier Recombination Dynamics In Mid-Infrared Semiconductor Laser Material, William T. Cooley Dec 1997

Measurement Of Ultrafast Carrier Recombination Dynamics In Mid-Infrared Semiconductor Laser Material, William T. Cooley

Theses and Dissertations

Shockley-Read-Hall, radiative, and Auger recombination rates in mid-infrared laser structures are measured and reported using time resolved photoluminescence (TRPL) frequency upconversion. The mid-IR lasers studied were actual InAsSb/InAlAsSb multiple-quantum-well (MQW) diode lasers emitting near 3.3 micrometers which were previously characterized for laser performance. This effort extends the initial studies and reports on the carrier recombination dynamics. Shockley-Read-Hall, radiative and Auger recombination rates at low temperature (77 K) were measured and found to be ASRH ≈ 10 x 107sec-1, Brad ≈ 2 x 10-10 cm3sec-1 and CAuger < 10-29 cm6 …

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An Analysis Of Early Software Reliability Improvement Techniques, John G. Leonard, Ric K. Nordgren Dec 1997

An Analysis Of Early Software Reliability Improvement Techniques, John G. Leonard, Ric K. Nordgren

Theses and Dissertations

This research explores early life cycle software reliability prediction models or techniques to predict the reliability of software prior to writing code, and a method for increasing or improving the reliability of software products early in the development life cycle. Five prediction models and two development techniques are examined. Each model is statically analyzed in terms of availability of data early in the life cycle, ease of data collection, and whether data is currently collected. One model and the two techniques satisfied those requirements and are further analyzed for their ability to predict or improve software reliability. While the researchers …

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Pseudorandom Code Generation For Communication And Navigation System Applications, John F. Brendle Jr. Dec 1997

Pseudorandom Code Generation For Communication And Navigation System Applications, John F. Brendle Jr.

Theses and Dissertations

This research project investigated the design, construction and evaluation of a pseudorandom code generator for communication and navigation system applications. These types of codes include spreading codes, Gold codes, Jet Propulsion Laboratory (JPL) ranging codes, syncopated codes, and nonlinear codes. Such waveforms are typically used in communication and navigation system applications. The code generator uses the Stanford Telecom STEL-1032 Pseudorandom Number (PRN) coder. A coder interface was designed and constructed for manual data entry to the registers of the PRN coder. The code generator is capable of independently clocking and generating all possible codes with lengths up to 4,294,967,295 bits. …

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Pollution Prevention Process Influences In The Weapon System Acquisition Life Cycle, Tedmond B. Grady Dec 1997

Pollution Prevention Process Influences In The Weapon System Acquisition Life Cycle, Tedmond B. Grady

Theses and Dissertations

This research develops a system structure for the pollution prevention acquisition process and uses system dynamics modeling to develop management strategies that optimize life cycle cost. The structure of the pollution prevention acquisition process is developed by identifying primary influences and mechanisms and determining how they interact within the acquisition process. The model structure is based on the premise that rising total projected Life Cycle Cost (LCC) would provide an incentive to perform pollution prevention changes to reduce the overall LCC cost. The model successfully produces the expected reasonable behavior and confidence in the model structure is achieved using standard …

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A Comparative Analysis Of Networks Of Workstations And Massively Parallel Processors For Signal Processing, David C. Gindhart Dec 1997

A Comparative Analysis Of Networks Of Workstations And Massively Parallel Processors For Signal Processing, David C. Gindhart

Theses and Dissertations

The traditional approach to parallel processing has been to use Massively Parallel Processors (MPPs). An alternative design is commercial-off-the-shelf (COTS) workstations connected to high-speed networks. These networks of workstations (NOWs) typically have faster processors, heterogeneous environments, and most importantly, offer a lower per node cost. This thesis compares the performance of MPPs and NOWs for the two-dimensional fast Fourier transform (2-D FFT). Three original, high-performance, portable 2-D FFTs have been implemented: the vector-radix, row-column and pipeline. The performance of these algorithms was measured on the Intel Paragon, IBM SP2 and the AFIT NOW, which consists of 6 Sun Ultra workstations …

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Biodegradation Of Deicing Agents In Various Soil Types, Annmarie Halterman-O'Malley Dec 1997

Biodegradation Of Deicing Agents In Various Soil Types, Annmarie Halterman-O'Malley

Theses and Dissertations

Airports have found that spent deicing fluids eventually reach the airfield's stormwater system and soil surrounding the airfield. Due to toxic effects of spent deicing fluids, containing and collecting the fluid for treatment can be a very costly activity for airports. One alternative to dispose of the used deicing fluid is to institute a land treatment system if it can be proven that the deicing fluid is readily biodegradable in a soil system. The primary concern of this research effort was to monitor the behavior of a simulated aircraft deicing fluid in various soil systems. An automated respirometer monitored the …

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A Cercla-Based Decision Model To Support Remedy Selection For An Uncertain Volume Of Contaminants At A Doe Facility, Christine E. Kerschus Dec 1997

A Cercla-Based Decision Model To Support Remedy Selection For An Uncertain Volume Of Contaminants At A Doe Facility, Christine E. Kerschus

Theses and Dissertations

The Paducah Gaseous Diffusion Plant (PGDP) operated by the Department of Energy is challenged with selecting the appropriate remediation technology to cleanup contaminants at Waste Area Group (WAG) 6. This research utilizes value focused thinking and multi attribute preference theory concepts to produce a decision analysis model designed to aid the decision makers in their section process. The model is based on CERCLA's five primary balancing criteria, tailored specifically to WAG 6 and the contaminants of concern, utilizes expert opinion and the best available engineering, cost, and performance data, and accounts for uncertainty in contaminant volume. The model ranks 23 …

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A Mammographic Registration Method Based On Optical Flow And Multiresolution Computing, Kevin A. Lee Dec 1997

A Mammographic Registration Method Based On Optical Flow And Multiresolution Computing, Kevin A. Lee

Theses and Dissertations

Mammography is a potent weapon in the fight against Breast Cancer, due in large part to its widespread availability and low cost. Despite the fact that mammography can detect small lesions as early as two years before they become palpable on physical exam, between 10 and 30 percent of cancerous lesions go undetected during evaluation by the radiologist. One approach to improving detection rates involves comparing mammograms of the same breast from successive years. Since most forms of breast cancer develop slowly, multiple view techniques might be able to detect subtle changes indicative of cancerous growth. This thesis proposes a …

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A System Dynamics Investigation Of Environmental Attitudes And Behaviors Influencing Solid Waste Reduction, Louis E. Lilley Dec 1997

A System Dynamics Investigation Of Environmental Attitudes And Behaviors Influencing Solid Waste Reduction, Louis E. Lilley

Theses and Dissertations

The relationship between attitudes and behavior is investigated in regard to the reduction of solid waste in a community. The theory of reasoned action, as identified by Ajzen and Fishbein in 1975, is investigated using as system dynamics approach. The closed loop system structure that would produce the expected real world response is established. The structure is then translated into a flow diagram and coded into a mathematical model. The model quantifies the values of beliefs, attitudes, intentions, behaviors, external and demographic variables, perceptions, and waste generation levels in order to illustrate how each changes over time when influenced by …

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Evaluation Of The Natural Biodegradation Of Aircraft Deicing Fluid Components In Soils, Laura M. Johnson Dec 1997

Evaluation Of The Natural Biodegradation Of Aircraft Deicing Fluid Components In Soils, Laura M. Johnson

Theses and Dissertations

This research effort was conducted to analyze the biodegradation of propylene glycol (PG) and tolyltriazole in two different soil types; a sandy soil and a high clay soil. Both an automated respirometer and a high performance liquid chromatograph (H PLO) were used in the analysis. Two separate experiments were conducted. In the first experiment, one level of tolyltriazole was added to the soils to determine whether or not there was a difference in the biodegradation rates of tolyltriazole in the two soils. The respirometer results indicated that there was a significant difference between the respiration rates of the microorganisms in …

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Analytic Transfer Function Of The Forward Propagation Of Diffuse Photon Density Waves In Turbid Media With An Embedded Spherical Inhomogeneity, Deborah L. Lasocki Dec 1997

Analytic Transfer Function Of The Forward Propagation Of Diffuse Photon Density Waves In Turbid Media With An Embedded Spherical Inhomogeneity, Deborah L. Lasocki

Theses and Dissertations

Diffusing photons can be used to detect and localize optical inhomogeneities embedded in turbid media such as clouds, fog, paint and human tissue. This thesis shows that a transfer function derived from an analytic solution of the Helmholtz equation can completely characterize in three dimensions the perturbations in the forward propagation phenomena caused by a spherical defect object in a multiple-scattering medium. Two models of the forward propagation behavior of diffuse photon density waves in homogeneous, infinite, turbid media that contains a spherical inhomogeneity are examined. The first model is an exact analytic solution based on a modal expansion in …

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An Examination Of Elements Necessary For Transfer Of An Environmental Remediation Technology From Full-Scale Demonstration To Implementation, Glenn C. Mandalas Dec 1997

An Examination Of Elements Necessary For Transfer Of An Environmental Remediation Technology From Full-Scale Demonstration To Implementation, Glenn C. Mandalas

Theses and Dissertations

The fact that an innovative environmental remediation technology has been proven feasible in a full scale evaluation does not assure that the technology will be implemented. A number of regulatory, economic, and institutional barriers may impede the transition of a remediation technology from full scale demonstration to implementation. This research explores these barriers, suggesting means to overcome them. Regulators, technology users, and other remediation decision makers apply the nine criteria specified in the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) to evaluate the applicability of an innovative remediation technology at uncontrolled hazardous waste sites. These criteria consider such things …

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A Reconfigurable Superscalar Architecture, Christopher B. Mayer Dec 1997

A Reconfigurable Superscalar Architecture, Christopher B. Mayer

Theses and Dissertations

The invention of the Field Programmable Gate Array (FPGA) has led to a number of interesting developments. One is the idea of providing custom hardware support for applications running on a computer. These reconfigurable computers have been shown to decrease the execution time for some applications. Based on past results, attention has subsequently turned to using reconfigurable computing in general-purpose computers (e.g. desktop and workstation environments). This thesis develops a design for just such a computer. The design, FPGADLX, is based on a hypothetical superscalar computer running the DLX instruction set and is generic enough in principle to be adapted …

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Flow Field And Loading Analysis On A Wrap-Around Fin Missile, Thomas C. Mcintyre Dec 1997

Flow Field And Loading Analysis On A Wrap-Around Fin Missile, Thomas C. Mcintyre

Theses and Dissertations

Wrap-around fin (WAF) missiles offer packaging benefits but experience rolling moments due to the curved fin design. Rolling moments stabilize unguided projectiles, but cause guidance and control problems for future guided applications. Understanding the flow field in the vicinity of the fins is critical to future missiles. Fin pressure profiles were characterized with pressure-sensitive paint. Two rectangular four-fin constructions were tested-one solid and one with a rectangular hole (slotted fin). Static pressure data were divided by free-stream total pressure for presentation. Tests were conducted at Mach numbers of 2.15, 2.28, 2.41, 2.86, 3.25, 3.50 and 3.83. Reynolds numbers based on …

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Atmospheric Turbulence Scintillation Effects On Wavefront Tilt Estimation, James A. Louthain Dec 1997

Atmospheric Turbulence Scintillation Effects On Wavefront Tilt Estimation, James A. Louthain

Theses and Dissertations

A new atmospheric turbulence screen generator is developed for use in performance calculations of adaptive optics systems valid over a wide range of atmospheric turbulence parameters. The screen generator accounts for diffraction effects caused by weak turbulence and incorporates the phase, amplitude, and cross statistics of the perturbed optical field. The wavefront's phase and amplitude perturbations are taken from the correlation functions developed by Lee and Harp and the cross correlation of the phase and amplitude derived in this thesis. The screen generator uses a modal representation to perform a Fourier series expansion of the wavefront phase and amplitude over …

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Applying Flywheel Energy Storage To Solar Electric Orbital Transfers, Mark W. Marasch Dec 1997

Applying Flywheel Energy Storage To Solar Electric Orbital Transfers, Mark W. Marasch

Theses and Dissertations

This study investigated the application of flywheel energy storage to minimum time, constant thrust orbital maneuvers using electric propulsion. The advantages of using stored energy to continue electric thruster operations while in eclipse were explored. The boundary value problems for several schemes of energy use were examined, and numerical solutions were found. Results of simulations utilizing energy storage were compared to results without energy storage. Schemes incorporating energy storage were found to have advantages in terms of propellant mass used, time spent in transit, and deliverable payload.

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Using Cross-Eye Techniques To Counter Radio Frequency Agile Monopulse Processing, Gregory J. Meyer Dec 1997

Using Cross-Eye Techniques To Counter Radio Frequency Agile Monopulse Processing, Gregory J. Meyer

Theses and Dissertations

The purpose of this research was to evaluate how current cross-eye techniques protect an airborne platform versus a pulse-to-pulse Radio Frequency (RF) agile monopulse processing threat and, if necessary, develop a new cross-eye techniques to counter this threat. This research evaluates how both current retrodirective cross-eye techniques and an original technique, namely synchronized cross-eye, hide the true skin return in the time and frequency domain while preserving the necessary phase interferometric effects at the threat radar location. Existing retrodirective cross-eye techniques are inadequate to counter the RF agile threat due to propagation delays. Using modeling and simulation, the research shows …

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Atmospheric Induced Errors In Space-Time Adaptive Processing, Vinod D. Naga Dec 1997

Atmospheric Induced Errors In Space-Time Adaptive Processing, Vinod D. Naga

Theses and Dissertations

This thesis examines the effects of atmospheric turbulence-induced phase perturbations on the performance of ground-based Space-Time Adaptive Processing (STAP) systems. Both Fully Adaptive Joint Domain Optimum and Partially Adaptive Factored-Time Space processing methods are examined. This thesis concentrates on the turbulence effects on STAP applied to ground-based arrays. This thesis further focuses on the capability of STAP to resolve targets at low elevation angles in the presence of turbulence. Only clutter interference and receiver noise are considered. Turbulence effects on the EM phase-front are calculated for turbulence strength Cn(2) values ranging from 5.0 x 10(exp -14) m-2/3 to 5.0 x …

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Fpga Processor Implementation For The Forward Kinematics Of The Umdh, Steven M. Parmley Dec 1997

Fpga Processor Implementation For The Forward Kinematics Of The Umdh, Steven M. Parmley

Theses and Dissertations

The focus of this research was on the implementation of a forward kinematic algorithm for the Utah MIT Dexterous Hand (UMDH). Specifically, the algorithm was synthesized from mathematical models onto a Field Programmable Gate Array (FPGA) processor. This approach is different from the classical, general purpose microprocessor design where all robotic controller functions including forward Kinematics are executed serially from a compiled programming language such as C. The compiled code and subsequent real time operating system must be stored on some form of nonvolatile memory, typically magnetic media such as a fixed or hard disk drive, along with other computer …

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