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

Digital Commons Network™

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

Air Force Institute of Technology

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 7351 - 7380 of 8791

Full-Text Articles in Entire DC Network

A Comparison Of Loose And Tight Gps/Ins Integration Using Real Ins And Gps Data, Warren H. Nuibe Dec 1995

A Comparison Of Loose And Tight Gps/Ins Integration Using Real Ins And Gps Data, Warren H. Nuibe

Theses and Dissertations

An extended Kalman filter (EKE) is used to combine the information obtained from a Global Positioning System (GPS) receiver and an Inertial Navigation System (INS) to provide a navigation solution. This research compares the results of a tightly-coupled GPS/INS integrated system with a loosely-coupled integrated system, using real world data. A fair comparison is accomplished by using the same sets of data, and keeping the integration structures as close as possible. Both integrations are feedforward and have the same error states in the navigation Kalman filters. Differences between the two, such as navigation solutions and tuning values, are shown in …

Go to article

Design Of Flight Control Laws For Aircraft With Flexible Wings Using Quantitative Feedback Theory, Christina L. Osmon Dec 1995

Design Of Flight Control Laws For Aircraft With Flexible Wings Using Quantitative Feedback Theory, Christina L. Osmon

Theses and Dissertations

Aircraft composed of lightweight composite materials are extremely enticing since their structural weight is greatly reduced. However, the control of these aircraft is complicated by the resultant flexibility of the wings. Two avenues of approach are possible; stiffen the wings thus losing some of the weight reduction benefits, or design the lateral/directional flight control system cognizant of the wing's flexibility. In this thesis the second approach is taken. The design of three lateral/directional flight control systems for the sub-sonic flight envelope of the F-18 is presented. The Quantitative Feedback Theory (QFT) robust control design technique is used. These designs incorporate …

Go to article

Three Dimensional Inverse Synthetic Aperture Radar Imaging, Jack D. Pullis Dec 1995

Three Dimensional Inverse Synthetic Aperture Radar Imaging, Jack D. Pullis

Theses and Dissertations

This research investigates the generation, display, and interpretation of three-dimensional (3-D) Synthetic Aperture Radar images. Three-dimensional assumes that the data collected consists of one temporal dimension and two orthogonal angular dimensions. From this data, a three dimensional reflectivity map, or 3-D image, of a target can be constructed. This thesis effort develops and applies a three-dimensional imaging algorithm on actual radar data measured on a one-third scale model of a C-29 aircraft. Two-dimensional slices of the three-dimensional image as well as three-dimensional isosurfaces are compared to the physical properties of the target. The results demonstrate the ability to produce three-dimensional …

Go to article

Electroencephalography: Subdural Multi-Electrode Brain Chip, John E. Rosenstengel Dec 1995

Electroencephalography: Subdural Multi-Electrode Brain Chip, John E. Rosenstengel

Theses and Dissertations

In October 1995, a CMOS brain chip consisting of two 8 x 17 multiplexed sub-arrays designed to measure electrical potentials at the cortical column level, was implanted on the somatosensory cortex of a laboratory rhesus monkey. Electroencephalograph (EEG) and averaged evoked response (AEG) data were taken over a period of 40 minutes. The brain chip was replaced with an identical chip, and data were again taken for 40 minutes. In both instances AEG signals of approximately 150 µVpp were recorded. Additionally, the first implanted chip recorded three phases of data: (1) AEG; (2) large clock noise (during a period …

Go to article

Maximum Likelihood Estimation Of Wave Front Slopes Using A Hartmann-Type Sensor, Scott A. Sallberg Dec 1995

Maximum Likelihood Estimation Of Wave Front Slopes Using A Hartmann-Type Sensor, Scott A. Sallberg

Theses and Dissertations

Current methods for estimating the wave front slope at the pupil of a telescope equipped with a Hartmann-type wave front sensor (H-WFS) are based on a simple centroid calculation of the intensity distributions (spots) recorded in each subaperture of the H-WFS. The centroid method does not include any knowledge concerning correlation properties of the slopes over the subapertures or the amount of light collected by the telescope and diverted to the H-WFS for wave front reconstruction purposes. This thesis devises a maximum likelihood (ML) estimation of the spot centroids by incorporating statistical knowledge of the spot shifts. The light level …

Go to article

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 …

Go to article

Characterization Of Atmospheric Turbulence Over Long Horizontal Paths Using Optical Slope Measurements, Eric E. Silbaugh Dec 1995

Characterization Of Atmospheric Turbulence Over Long Horizontal Paths Using Optical Slope Measurements, Eric E. Silbaugh

Theses and Dissertations

Atmospheric turbulence has long been recognized as one of the fundamental factors affecting optical systems operating through the atmosphere. Turbulence over vertical paths has been well characterized, both theoretically and experimentally. Much less is known about turbulence over long, horizontal paths. Perturbations of the wave front phase can be measured using a Hartmann wave front sensor (H-WFS). Theoretical expressions for the tilt removed structure function of the H-WFS slope measurements were derived and evaluated using quadrature. These slope structure functions are functions of the phase structure function. The Kolmogorov turbulence model was assumed. Simulated H-WFS slope measurements were generated using …

Go to article

Multiple Model Adaptive Control Of The Vista F-16, Michael J. Stepaniak Dec 1995

Multiple Model Adaptive Control Of The Vista F-16, Michael J. Stepaniak

Theses and Dissertations

Multiple model adaptive control (MMAC) is investigated using the high-fidelity, nonlinear, six-degree-of-freedom Simulation Rapid-Prototyping Facility VISTA F-16. Detection of single actuator and sensor failures is considered, with an MMAC algorithm initially pursued which allows a controller specifically designed for each particular failure condition to replace the standard F-16 Block 40 flight control system (FCS) once the failure is detected. The synthesis of certain discrete-time LQG/PI controllers (those using control variables linearly dependent on state derivatives) is shown to be unattainable due to numerical difficulties. A novel control technique, termed control redistribution, is introduced which redistributes control commands (that would normally …

Go to article

Improving The Morse Intercept Operator's Audio Display, Jesse M. Washburn Dec 1995

Improving The Morse Intercept Operator's Audio Display, Jesse M. Washburn

Theses and Dissertations

This thesis improves the audio display for multiple Morse communications. Factors considered to improve the audio display are frequency of source, volume level of source, and methods of unmasking. The best frequency and volume level of a Morse source is 500 Hz at 70 dB sound pressure level (spi). Two types of masking are researched: frequency masking and expectation driven masking. Experiments showed by amplifying high pitched sources the effects of frequency masking are minimized. Other methods to compensate for frequency masking are 3-D sound and the placement of a source out of phase between the ears. Morse code recognition …

Go to article

Computer Aided Detection Of Microcalcifications Utilizing Texture Analysis, Ronald C. Dauk Dec 1995

Computer Aided Detection Of Microcalcifications Utilizing Texture Analysis, Ronald C. Dauk

Theses and Dissertations

A comparative study of texture measures for the classification of breast tissue is presented. The texture features investigated include Angular Second Moments, Power Spectrum Analysis and a novel feature, Laws Energy Ratios. The texture study was accomplished as part of the development of a Model Based Vision (MBV) system for the automatic detection of microcalcifications. An overview of the Microcalcification Detection System is presented, which applies image differencing techniques, feature selection methods, and neural networks for locating microcalcification clusters in mammograms. The Power Spectrum Analysis feature set had the best overall performance with an 83% Probability of Detection and an …

Go to article

Computer-Aided Diagnosis Of Mammographic Masses, William E. Polakowski Dec 1995

Computer-Aided Diagnosis Of Mammographic Masses, William E. Polakowski

Theses and Dissertations

A new Model-Based Vision algorithm was developed to find possibly cancerous regions of interest (ROIs) in digitized mammograms and to correctly identify the malignant masses. This work has shown a sensitivity of 92 percent for locating malignant ROIs. The database contained 272 images (12 bit, 1OO microns) with 36 malignant and 53 benign mass images. Of the 53 biopsied benign cases, 74 percent were correctly classified. The Focus of Attention (segmentation) Module algorithm used a physiologically motivated Difference of Gaussians (DoG) filter to highlight mass-like regions in the mammogram. The Index Module labeled the regions by their hypothesized class: large …

Go to article

Effects Of Neutron Radiation On Resonant Cavity Light-Emitting Diodes, Daniel S. Hinkel Dec 1995

Effects Of Neutron Radiation On Resonant Cavity Light-Emitting Diodes, Daniel S. Hinkel

Theses and Dissertations

Resonant Cavity Light Emitting Diodes (RCLEDs) were irradiated in Ohio State University's nuclear reactor to determine the effects of Neutron displacement damage. The RCLEDs were characterized both before and after irradiation by their current versus voltage curves (I-V curves) and external light power versus current curves (L-I curves). The I-V curves showed an increase in the "knee voltage" at a neutron fluence of 1.45x1017 neutrons/cm2. Logarithmic decreases in external light power and differential quantum efficiency were observed. Significant decreases in external light power were observed at neutron fluences greater than 5.1x1013 neutrons/cm2. Equations were …

Go to article

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 …

Go to article

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 …

Go to article

Space Object Identification Using Spatio-Temporal Pattern Recognition, Gary W. Brandstrom Dec 1995

Space Object Identification Using Spatio-Temporal Pattern Recognition, Gary W. Brandstrom

Theses and Dissertations

This thesis is part of a research effort to automate the task of characterizing space objects or satellites based on a sequence of images. The goal is to detect space object anomalies. Two algorithms are considered - the feature space trajectory neural network (FST NN) and hidden Markov model (HMM) classifier. The FST NN was first presented by Leonard Neiberg and David P. Casasent in 1994 as a target identification tool. Kenneth H. Fielding and Dennis W. Ruck recently applied the hidden Markov model classifier to a 3D moving light display identification problem and a target recognition problem, using time …

Go to article

Design And Analysis Of A Navigation System Using The Federated Filter, Stephen J. Delory Dec 1995

Design And Analysis Of A Navigation System Using The Federated Filter, Stephen J. Delory

Theses and Dissertations

The purpose of this paper was to design and analyse a federated filter design, to be used for retrofit of an Embedded GPS/INS (EGI) navigation unit into an existing Kalman filter-based air navigation system. A design was selected and simulations were conducted in the Distributed Kalman Filter Simulation software (DKFSIM). As well, a centralized Kalman filter design was simulated under identical conditions for comparison purposes. The federated filter was shown to be a feasible design, with accuracy in position and velocity very close to centralized Kalman filter values. The federated filter design also showed some attractive fault detection and isolation …

Go to article

A Methodology To Assess Post-Launch Efforts To Counter Mobile Tactical Ballistic Missile Launchers, Wayne H. Hayes Dec 1995

A Methodology To Assess Post-Launch Efforts To Counter Mobile Tactical Ballistic Missile Launchers, Wayne H. Hayes

Theses and Dissertations

The Department of Defense has a requirement to quantify the force enhancement effects from various configurations of an envisioned multilayered Theater Missile Defense (TMD) system. TMD research accomplished to date has focused primarily on the pre-launch and in-flight tactical ballistic missile (TBM) operational phases while ignoring the post-launch phase during which mobile transporter-erector-launchers (TELs) are vulnerable to attack. No methodology currently exists to measure the effectiveness of various post-launch counter-TEL system configurations or their potential contribution to the overall TMD mission. This research uses the decision analysis technique of influence diagrams to model the post-launch counter-TEL process using notional variable …

Go to article

Exmis: An Expert System For The Autonomous Onboard Command System (Aocs), Kevin D. Benedict Dec 1995

Exmis: An Expert System For The Autonomous Onboard Command System (Aocs), Kevin D. Benedict

Theses and Dissertations

The primary objective of this study is the creation of a prototype expert system called EXMIS (EXpert MIssile System) that performs the flight termination logic sequence of the Autonomous Onboard Command System (AOCS). The AOCS is a proposed system that would take the "man-in-the-loop" out of the self-destruct decision making process and place the entire decision on the launch vehicle. Through the use of a six degree of freedom trajectory program called BOOST, simulated flight data for four different flight scenarios is obtained. The launch vehicle selected for the simulations is the Peacekeeper ICBM. EXMIS is developed using an expert …

Go to article

Analysis Of Gravity-Gradient Satellite Attitude Inversion, Jules-Francois D. Desamours Dec 1995

Analysis Of Gravity-Gradient Satellite Attitude Inversion, Jules-Francois D. Desamours

Theses and Dissertations

The purpose of this research is to understand and describe the process by which the 1986 Polar BEAR gravity- gradient research satellite of John Hopkins University/Applied Physics Laboratory achieved an orbital attitude correction (re-inversion) from an inverted orientation through the utilization of its momentum wheel. Understanding this process provides an analytical foundation from which a universal attitude inversion process for other gravity-gradient satellites with similar anomalous motions may be sought and developed. The equations of motion for a gravity-gradient satellite with a momentum wheel are derived and implemented in FORTRAN for simulation of the dynamics of the spacecraft. Several re-inversion …

Go to article

Systems Analysis Of Gps Electrical Power System Redesign, Kevin J. Walker Dec 1995

Systems Analysis Of Gps Electrical Power System Redesign, Kevin J. Walker

Theses and Dissertations

A systematic analysis is applied to the electrical power subsystem of the Global Positioning Satellite (GPS) system. Results determined the most appropriate power source and conversion system Options. Photovoltaic solar arrays, the current power system, were not included in the analysis. The best electrical power subsystem options found in the analysis include a solar power source with either a dynamic or direct conversion technique, and a direct conversion nuclear source. The two solar options are designed, at a low level of detail, to provide the same level of power the current GPS photovoltaic solar array system provides. These two designs …

Go to article

The Comparative Effectiveness Of Computer-Mediated Communication Supplemented Satellite Distance Education And Traditional Face-To-Face Education, Megan C. Block Dec 1995

The Comparative Effectiveness Of Computer-Mediated Communication Supplemented Satellite Distance Education And Traditional Face-To-Face Education, Megan C. Block

Theses and Dissertations

Satellite distance education delivery typically has one main drawback -- limited student-to-student and student-to-instructor interaction. Telecommunications technology, more specifically computer-mediated communication (CMC), has made it possible for educational institutions to overcome this drawback. This research examines the comparative effectiveness of CMC supplemented satellite distance education delivery and traditional face-to-face education delivery. The three dependent variables that were measured to compare the two educational delivery methods included: performance, interaction, and attitude outcomes. Pre- and post-course instruments were administered in a non-equivalent quasi-experimental design to students enrolled in an Air Force Institute of Technology's School of Systems and Logistics software engineering Professional …

Go to article

A Solid Surface From Which To Explore: The Executive Summary As The Frontispiece Of A Technical Hyperdocument, Alicia M. Williams Dec 1995

A Solid Surface From Which To Explore: The Executive Summary As The Frontispiece Of A Technical Hyperdocument, Alicia M. Williams

Theses and Dissertations

This research analyzes the purpose and organization of a well-written executive summary, reviews the characteristics of hypermedia, and compares the strengths and weaknesses of a typical executive summary published originally on paper and now under consideration for transition to hypermedia in order to determine which elements of an executive summary are essential before effective transition to hypermedia. The executive summary of a technical report is a stand-alone description of what was done, how it was done, what the results were, why they matter, and where further information is found in the report body. Executive summaries have a wider audience than …

Go to article

Multimedia And Audience: Implications For Executive Summaries, Donna M. Grudziecki Dec 1995

Multimedia And Audience: Implications For Executive Summaries, Donna M. Grudziecki

Theses and Dissertations

In an effort to put technical reports into a multimedia format, this thesis explored audience analysis and multimedia issues related to executive summaries. While multimedia has been shown to be effective at conveying complex information in certain environments, little research has been done to apply this technology to technical reporting. This thesis concentrates on the executive summary audience because the executive summary is the most read and most important section of a report. To analyze the audience, I conducted telephone interviews with report readers using an interview form I developed based on Mathes and Stevenson's guidelines for conducting an audience …

Go to article

Re-Engineering The Acquisition Process Of Manufactured On-Demand Only Spares, Mark E. Koesters Dec 1995

Re-Engineering The Acquisition Process Of Manufactured On-Demand Only Spares, Mark E. Koesters

Theses and Dissertations

The purpose of this study is to explore potential alternatives to the current Department of Defense (DoD) acquisition process for low demand, high dollar value, not commercially stocked, spare parts in order to better utilize diminishing resources, reduce cycle costs, and sustain the defense industrial base. Demand for these items is insufficient to justify maintaining inventory, while the buy on-demand alternative results in long lead- times and increased costs due to the labor intensiveness of the current process, lack of willing manufacturing sources, and higher prices paid for small quantities of material. An exploratory case study method was used to …

Go to article

Three Dimensional Localization Of Lesions From Digitized Mammograms, Amy L. Magnus Dec 1995

Three Dimensional Localization Of Lesions From Digitized Mammograms, Amy L. Magnus

Theses and Dissertations

This thesis describes new algorithms to localize regions-of-interests (ROIs) three dimensionally from a pair of digitized mammograms. This work is intended to add a layer of sophistication to computer aided diagnosis by putting to use the fixed and measurable parameters of mammographic imaging. The fixed parameters are the source to film orientation and the podium-image distance. Measurable parameters are the rotation angle of the x-ray tube from the horizontal and the compression depth (the distance from compression paddle to contact podium distance) at the time of imaging. As an additional benefit, three dimensional localization algorithms alleviate the confusion radiologists may …

Go to article

Thermal Stresses In End-Heated Layered Media, Jerry R. Couick Dec 1995

Thermal Stresses In End-Heated Layered Media, Jerry R. Couick

Theses and Dissertations

Thermal stresses in semi-infinite layered beams heated on the end are calculated using an extension to simple bimetallic thermostat theory. Recently, researchers have used the concept of interfacial compliance to determine interlaminar stresses in a simple thermostat of finite length subjected to a uniform temperature increase. In the present work, the thermostat theory is extended to apply to the beams of interest. A closed-form solution to the problem is obtained. It is not applicable within about one beam thickness (St Venant boundary region) of the end. Various classes of layered materials are analyzed to determine if significant stresses exist outside …

Go to article

How Location And An Action Standard On A Risk Ladder Affect Perceived Risk, Lonny P. Baker Dec 1995

How Location And An Action Standard On A Risk Ladder Affect Perceived Risk, Lonny P. Baker

Theses and Dissertations

Efforts to explain risk magnitudes often rely on a risk ladder in which exposure levels and associated risk estimates are arranged with low levels at the bottom of the ladder and high levels at the top. An experiment was conducted to test the hypotheses that perceived threat varies with the location of a subject's assigned level on the risk ladder, and that perceived threat varies with the presence of an action standard on the risk ladder. Air Force Institute of Technology Professional Continuing Education students were asked to assume a particular level of a hypothetical hazard in their residences, to …

Go to article

A Case Study Of The Environmental Impacts Of The Beddown Of The C-17 Globemaster Iii At Charleston Afb, Richard H. Houghton Jr. Dec 1995

A Case Study Of The Environmental Impacts Of The Beddown Of The C-17 Globemaster Iii At Charleston Afb, Richard H. Houghton Jr.

Theses and Dissertations

Unites States Air Force acquisition environmental planning has changed significantly since the passage of the National Environmental Policy Act in 1969. This research examined the role of environmental planning in weapon system acquisition. It focused on environmental planning performed for the C-17 Globemaster III prior to its beddown at Charleston Air Force Base. The case study of the C- 17 beddown included interviews, archival record reviews, and direct observations at the base. Evidence was collected to determine what environmental impacts occurred during the beddown. An environmental postaudit compared actual impacts with those predicted in environmental planning documentation. Impacts were analyzed …

Go to article

Design, Fabrication And Characterization Of Micro Opto-Electro-Mechanical Systems, Darren E. Sene Dec 1995

Design, Fabrication And Characterization Of Micro Opto-Electro-Mechanical Systems, Darren E. Sene

Theses and Dissertations

Several micro-opto-electro-mechanical structures were designed using the Multi-User MEMS Process (MUMPS). Specific design techniques were investigated for improving the capabilities of elevating flip up structures. The integration of several flip up microoptical structures into a microoptical system was explored with emphasis on the development of a microinterferometer. The thermal effects on the Modulus of Elasticity were determined by detecting the resonant frequency for a square Flexure Beam Micromirror Device. The resonance of the device was found to match theory to within 0.1 % and the Modulus of Elasticity was found to decrease by 0.041 GPa/K from 290 to 450 K. …

Go to article

Development And Testing Of A New Optimum Design Code For Hypersonic Wind Tunnel Nozzles, Including Boundary Layer, Turbulence, And Real Gas Effects, Ralph C. Tolle Nov 1995

Development And Testing Of A New Optimum Design Code For Hypersonic Wind Tunnel Nozzles, Including Boundary Layer, Turbulence, And Real Gas Effects, Ralph C. Tolle

Theses and Dissertations

A robust and efficient optimization code is developed and validated. The code is used to redesign an existing Mach 12 wind tunnel nozzle and utilizes response surface methodology (RSM) techniques. Explicit, globally second-order, flux-difference-splitting algorithms are used to solve the Navier-Stokes (NS) and Parabolized Navier-Stokes (PNS) flow solvers incorporated into the optimizer code. Either the Baldwin-Lomax or the Yang-Shih k-s turbulence model may be employed in the optimization code. First, 2-D/axisymmetric NS and PNS flow solvers are developed/modified and account for perfect gas/nonequilibrium chemically reacting flows. All solvers are validated against Computational Fluid Dynamics (CFD) and experimental data. The optimization …

Go to article

First Prev Next Last