Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Air Force Institute of Technology

Theses/Dissertations

1997

Discipline
Keyword

Articles 1 - 30 of 143

Full-Text Articles in Engineering

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

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 …

Go to article

Speaker Verification In The Presence Of Channel Mismatch Using Gaussian Mixture Models, Robert B. Reid Dec 1997

Speaker Verification In The Presence Of Channel Mismatch Using Gaussian Mixture Models, Robert B. Reid

Theses and Dissertations

A channel compensation method is sought for use in speaker identification (ID) and verification applications under matched and mismatched training and testing conditions. This work expands on previous work on matched conditions by investigating three techniques on matched and mismatched conditions using the TIMIT and NTIMIT speech databases. First, previous results on 168 speakers are reproduced for matched conditions using Gaussian mixture models (GMM) and mel-frequency cepstral coefficients. Next, cepstral mean subtraction with band limiting (CMSBL) is investigated. The third method, developed in this thesis uses a modified Wiener filtering approach to channel compensation. New GMMs are created for each …

Go to article

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 …

Go to article

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 …

Go to article

Effects Of Liquid Transpiration Cooling On Heat Transfer To The Diverging Region Of A Porous-Walled Nozzle, Daniel J. Schieb Dec 1997

Effects Of Liquid Transpiration Cooling On Heat Transfer To The Diverging Region Of A Porous-Walled Nozzle, Daniel J. Schieb

Theses and Dissertations

This research effort investigated the effects of evaporation of water on the heat transferred to the wall of the diverging portion of a porous walled nozzle The AFIT High Pressure Shock Tube was used with a two-dimensional Mach 3 nozzle. One flat surface of the nozzle was fitted with a layer of porous stainless steel from the nozzle throat to the exit. This porous material was saturated with water to simulate liquid transpiration cooling. Surface temperature data was taken in this region using fast response coaxial thermocouple. Heat transfer was determined from the surface temperature history. Data was taken for …

Go to article

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 …

Go to article

Constrained Model Predictive Control Of A Nonlinear Aerospace System, Christopher M. Shearer Dec 1997

Constrained Model Predictive Control Of A Nonlinear Aerospace System, Christopher M. Shearer

Theses and Dissertations

Recent research efforts have applied the receding horizon Model Predictive Control (MPC) strategy to linearized high performance aerospace systems. The research contained in this thesis used these recent results in order to apply the MPC strategy to a nonlinear high performance aerospace system, specifically an F-16 fighter aircraft model. The model was commanded to follow dynamic trajectories of roll angle and altitude. Further, adaptive constraint techniques were used to improve system tracking. To accomplish these tasks, code and block diagrams were generated using the commercial software packages of Matlab and Simulink. Numerous simulations were conducted with the goal of achieving …

Go to article

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 …

Go to article

A System Dynamics Model Of The Bioavailability Of Metals In Constructed Wetland Sediment, Timothy S. Wood Dec 1997

A System Dynamics Model Of The Bioavailability Of Metals In Constructed Wetland Sediment, Timothy S. Wood

Theses and Dissertations

Constructed wetlands used for storm water treatment accumulate metals primarily in their sediment. This sediment has the potential to produce toxic effects in benthic organisms at some period in time. Bioavailability of metals in sediment is directly linked to pore water metal activity. The mechanisms that influence pore water metal activity are included in physical, chemical, and biological processes. A system dynamics model was developed to represent these processes and the major influences affecting pore water metal activity in a treatment wetland receiving storm water influent. The model structure and behavior was tested and validated using several system dynamics validation …

Go to article

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 …

Go to article

The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson Dec 1997

The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson

Theses and Dissertations

The rational resolution analysis RRA is introduced and developed as a generalization of the integer, dilation multiresolution analyses MRA developed by Mallat and Meyer. Rational dilation factors are achieved by relaxing the condition on MRAs that successive approximation spaces be embedded. Conditions for perfect reconstruction are discussed and it is shown that perfect reconstruction is possible with specific constraints on the scaling function the scaling filter must have its roots on the unit circle. Furthermore, the required arrangement of the roots indicate the scaling function must be derived from a B-spline of some degree. It is proven the only compactly …

Go to article

Microelectromechanical Optical Beam Steering Systems, David M. Burns Dec 1997

Microelectromechanical Optical Beam Steering Systems, David M. Burns

Theses and Dissertations

The development of microelectromechanical systems (MEMS) has matured to the point where the fabrication of micron sized devices is feasible. State of the art MEMS construction processes now support the fabrication of novel optical devices that could not previously be built. This dissertation reports on the development of innovative micro optical devices such as Variable Blaze Gratings (VBGs) using state of the art MEMS construction processes. The principle application of the micro optical devices described in this dissertation is steering optical beams; however other applications such as spectral analysis are identified. Specific optical beam steering systems developed and characterized in …

Go to article

Space Shuttle East Coast Abort Modes For High Inclination Launches, Richard K. Neufang Dec 1997

Space Shuttle East Coast Abort Modes For High Inclination Launches, Richard K. Neufang

Theses and Dissertations

This study investigated the possibility of abort landing the Space Shuttle at east coast airports when launched at inclinations of 51.6 degrees or more. Computer modeling was used to characterize both the Shuttle launch out of Cape Canaveral and two methods of unpowered abort descents from various points in the launch following Solid Rocket Booster SRB separation. The first method used varying values of pitch and roll held constant to control the descent. By plotting the latitude and longitude of the point in the descent when the nominal landing altitude was achieved against locations of east coast airports it was …

Go to article

Message-Bundle Converting In Intenet Protocol Multicast-Based High Level Architecture Exercises, Tracy A. Bobo Dec 1997

Message-Bundle Converting In Intenet Protocol Multicast-Based High Level Architecture Exercises, Tracy A. Bobo

Theses and Dissertations

The Department of Defense is pushing for more wide-spread and realistic interactive training simulations which increases the demand on network capacity and resources. While network bandwidth is a measurable resource, packet bandwidth, or the number of packets-per-second (Pk/s) a host can handle, is a shifting commodity. This research analyzes host performance characteristics under varying data loads. The hosts include SGI single and multi-processor systems and Intel Pentium platforms using both Windows 95 and Linux Operating Systems. The networking media covers Ethernet, ATM and FDDI. For the ATM network, both AAL5 and IP over ATM were analyzed. With the data from …

Go to article

Microelectromechanical Scanner Using A Vertical Cavity Surface Emitting Laser, Joseph G. Bouchard Jr. Dec 1997

Microelectromechanical Scanner Using A Vertical Cavity Surface Emitting Laser, Joseph G. Bouchard Jr.

Theses and Dissertations

Optical scanners play a prominent role in the commercial and military industries. The scanner's size, cost and reliability are critical characteristics. In this research a microoptical scanning system was fabricated by incorporating a vertical cavity surface emitting laser (VCSEL) onto a surface machined microelectromechanical die. The micro optics for laser beam steering includes a 135 deg mirror, a Fresnel lens, a lateral scanning rotating mirror, and a vertical scanning fan mirror. The VCSEL was attached to the die by solder and electrical connection was provided by wire bonding. Based on far field measurements the scanner had a lateral scan angle …

Go to article

Velocity Profiles And Skin Friction On A Ribletted Flat Plate In Adverse Pressure Gradient., Richard D. Branam Dec 1997

Velocity Profiles And Skin Friction On A Ribletted Flat Plate In Adverse Pressure Gradient., Richard D. Branam

Theses and Dissertations

This project investigated the flow field characteristics over a flat, ribletted plate and the effects of an adverse pressure gradient on this flow field. Testing examined the development of the flow over the ribletted plate from laminar through fully turbulent flow fields. The flow field states (laminar, transitional, and turbulent) were determined using local turbulence intensity values and boundary layer profiles. Several parameters were examined to help better describe the flow characteristics, boundary layer profiles, and influence on skin friction drag. The skin friction drag coefficients were calculated using a numerical integration technique to determine an average value and scaled …

Go to article

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. …

Go to article

Modeling Uptake And Translocation Of Lead (Pb) In Maize For The Purposes Of Phytoextraction, Mark A. Brennan Dec 1997

Modeling Uptake And Translocation Of Lead (Pb) In Maize For The Purposes Of Phytoextraction, Mark A. Brennan

Theses and Dissertations

Phytoextraction is a remediation technology that uses plants to remove heavy metals from soil. This technology has the potential to decrease the costs of remediating contaminated sites by several orders of magnitude compared to traditional technologies. To effectively implement this technology requires an understanding of the plant processes that control uptake and translocation of metals from the soil. Currently these processes are poorly understood, and especially so for Pb. The purpose of this thesis was to gain insights concerning the plant mechanisms that control uptake and translocation of Pb and how these mechanisms interact to control levels of Pb accumulation …

Go to article

Visualization And Animation Of A Missile/Target Encounter, Jeffrey T. Bush Dec 1997

Visualization And Animation Of A Missile/Target Encounter, Jeffrey T. Bush

Theses and Dissertations

Existing missile/target encounter modeling and simulation systems focus on improving probability of kill models. Little research has been done to visualize these encounters. These systems can be made more useful to the engineers by incorporating current computer graphics technology for visualizing and animating the encounter. Our research has been to develop a graphical simulation package for visualizing both endgame and full fly-out encounters. Endgame visualization includes showing the interaction of a missile, its fuze cone proximity sensors, and its target during the final fraction of a second of the missile/target encounter. Additionally, this system displays dynamic effects such as the …

Go to article

Development And Validation Of An Experimental Test Rig For Electrohydrodynamic Enhancement Of Forced Convective Heat Transfer, William T. Caldwell Dec 1997

Development And Validation Of An Experimental Test Rig For Electrohydrodynamic Enhancement Of Forced Convective Heat Transfer, William T. Caldwell

Theses and Dissertations

This report details the development of a facility for the experimental investigation of electrohydrodynamic (EHD) enhancement of forced convection heat transfer. The test facility was developed for the Thermal and Transparencies Laboratory (TATLAB), Air Force Research Laboratory (AFRL), for use in future research into the applicability of EHD for the miniaturization of Air Force heat exchangers. During this research, a closed l6op, medium scale electrohydrodynamic test rig was developed and brought online. The test fluid loop was integrated with a data acquisition and parameter control system. Basic loop and fluid performance testing was accomplished through the use of a 3mm …

Go to article

Orbit Estimation Using Track Compression And Least Squares Differential Correction, Vincent J. Chioma Dec 1997

Orbit Estimation Using Track Compression And Least Squares Differential Correction, Vincent J. Chioma

Theses and Dissertations

This thesis develops two methods of compressing a track of radar observations of a satellite into a single state vector and associated covariance matrix, and a method of estimating orbits using results from multiple tracks. The track compression uses least squares differential correction to determine a state vector at the central observation time. The resulting state vectors and covariance matrices are then used to estimate the satellite's orbit, also using least squares differential correction. Numerical integration using two-body, J2 and an atmospheric drag model is used to represent the dynamics. This orbit estimation produces a state vector which includes …

Go to article

A Modeling Study For The Implementation Of In Situ Cometabolic Bioremediation Of Trichloroethylene-Contaminated Groundwater., John A. Christ Dec 1997

A Modeling Study For The Implementation Of In Situ Cometabolic Bioremediation Of Trichloroethylene-Contaminated Groundwater., John A. Christ

Theses and Dissertations

The limitations of conventional groundwater remediation technologies have led to the development of innovative technologies which may achieve national hazardous waste site remediation goals. Before an innovative technology can be implemented in the field, remedial project managers, regulators and other stakeholders require adequate modeling tools to help assess the applicability of the technology at a particular site. This modeling study investigates how an innovative technology, in situ cometabolic bioremediation, might be implemented to remediate a TCE-contaminated site, under different site conditions. A steady-state model is developed which couples an analytical expression to simulate the effect of flow between multiple pumping …

Go to article

Fatigue Behavior Of A Quasi-Isotropic Graphite/Epoxy Laminate Embedded With A Piezoelectric Sensor, Jon M. Coleman Dec 1997

Fatigue Behavior Of A Quasi-Isotropic Graphite/Epoxy Laminate Embedded With A Piezoelectric Sensor, Jon M. Coleman

Theses and Dissertations

This study primarily investigated the mechanical effects of embedding piezoelectric sensors on the tensile and fatigue strength of a quasi-isotropic, carbon-epoxy laminate. A secondary focus was the investigation of the sensor degradation under tensile loading. A [0 | ±45 | 90]s laminate was fabricated from Hercules AS4/3501-6 pre-preg tape. Specimens were first tested monotonically to obtain an average ultimate tensile strength and to detail the progression of damage. The fatigue tests were tension-tension, R=0.1, 10 Hz, constant amplitude. Results indicated that the embedded piezoelectric sensors did not have a significant effect on the tensile strength of the laminate. Specimens …

Go to article

Multiple Model Adaptive Estimation And Control Redistribution Performance On The Vista F-16 During Partial Actuator Impairments, Curtis S. Clark Dec 1997

Multiple Model Adaptive Estimation And Control Redistribution Performance On The Vista F-16 During Partial Actuator Impairments, Curtis S. Clark

Theses and Dissertations

Multiple Model Adaptive Estimation with Control Reconfiguration (MMAE/CR) capability to estimate and compensate for partial actuator failures, or "impairments" is investigated using the high-fidelity, nonlinear, six-degree-of-freedom, VISTA F-16 simulation which currently resides on the Simulation Rapid-Prototyping Facility (SRF). After developing a model for inserting partial actuator impairments into the VISTA F-16 truth model, research begins with a battery of single actuator impairment tests. This stage of research explores the capability of the existing MMAE algorithm to estimate single, partial actuator impairments, and helps to define refinements and expansions needed in the MMAE algorithm for the second phase of research: the …

Go to article

Next Last