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

Engineering Commons™

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

Theses and Dissertations

Discipline
Institution
Keyword
Publication Year

Articles 9991 - 10020 of 11503

Full-Text Articles in Engineering

Optimal Wavelet Denoising For High Range Resolution Radar Classification, Brian M. Huether Mar 1999

Optimal Wavelet Denoising For High Range Resolution Radar Classification, Brian M. Huether

Theses and Dissertations

Noncooperative identification (NCTI) of airborne targets is a top priority for the Air Force and this thesis makes a significant contribution to that area. High range resolution radar (HRR) provides an attractive means to perform NCTI. When measured HRR data is used, classification performance is excellent. However, it is often not feasible to acquire measured HRR signatures for a wide set of targets, thus necessitating the use of synthetically generated HRR data. Classification performance suffers severe degradation when using synthetic data. This thesis suggests that a large portion of HRR signature content is non-discriminatory and that this content is a …

Go to article

The Effect Of Registration Errors On Tracking In A Networked Radar System, Bradley J. Mortenson Mar 1999

The Effect Of Registration Errors On Tracking In A Networked Radar System, Bradley J. Mortenson

Theses and Dissertations

To successfully combine information from distributed radar sensors, it is essential that each sensor be correctly referenced in a global coordinate system. If there are biases in the reported position of these sensors, the reported target position will also be biased and the ensuing global estimate of the target position will be degraded. Furthermore, any biases in range or azimuth measurements of these sensors will likewise be reflected in the degradation of global estimate of target position. Registration is the process of ensuring that these errors do not result in the creation of an additional redundant target when only a …

Go to article

Low Grazing Angle Terrain Backscattering Coefficient Generator, William N. O'Connor Mar 1999

Low Grazing Angle Terrain Backscattering Coefficient Generator, William N. O'Connor

Theses and Dissertations

A near-horizon probabilistic terrain backscatter coefficient generator is introduced, combining modified sea-state curves with Weibull-type probability density functions. A total of nine terrain type classifications (soils & rocks, trees, grasses, shrubs, short vegetation, roads, urban areas, dry snow, and wet snow) are supported, for seven radar bands (L, S, C, X, Ku, Ka, and W), and both linear (HH, VV) and cross (HV, VH) polarizations. The Weibull functions are based on measured sigma and match the published data. The functions also provide a probabilistic nature to the generator. Modified sea state curves are used in place of the Weibull functions …

Go to article

A Climatology-Based Model For Long-Term Prediction Of Radar Beam Refraction, Todd S. Pittman Mar 1999

A Climatology-Based Model For Long-Term Prediction Of Radar Beam Refraction, Todd S. Pittman

Theses and Dissertations

The National Air Intelligence Center, WPAFB, OH, needs more accurate predictions of radar beam refraction. A new mode was developed for this thesis replacing the standard atmosphere approach with raytracing and climatology. Usually a microwave radio beam bends towards the earth with a radius of curvature greater than the earth's surface. However, seasonal and climatic variations influence the bending, and at times create temperature or moisture inversions that redirect the energy along the earth's surface leaving radio holes where there is no coverage. This model uses iterative raytracing to determine the most direct path from radar to target through the …

Go to article

Ultra-Wideband Tem Horns, Transient Arrays And Exponential Curves: A Fdtd Look, Troy S. Utton Mar 1999

Ultra-Wideband Tem Horns, Transient Arrays And Exponential Curves: A Fdtd Look, Troy S. Utton

Theses and Dissertations

This research investigates the possibility of applying exponentially curved conducting plates to single-element Transverse Electromagnetic (TEM) horns and their transient arrays to enhance the UWB characteristics already experienced by these radiators. The first part of this study demonstrates the Finite-Difference Time-Domain (FDTD) method's ability to duplicate experimental data, and establishes the baseline models used throughout the remainder of the research. The baseline models consist of the typical flat-triangle shaped conducting plates. The exponential taper models incorporate the exponential curves in the height, the width, and both the height and width directions. One, two- and four-element baseline configurations are compared to …

Go to article

Optimal Pulsed Pumping Schedule Using Calculus Of Variation Methodology, Tay W. Johannes Mar 1999

Optimal Pulsed Pumping Schedule Using Calculus Of Variation Methodology, Tay W. Johannes

Theses and Dissertations

Application of a variational optimization technique has demonstrated the potential strength of pulsed pumping operations for use at existing pump-and-treat aquifer remediation sites. The optimized pulsed pumping technique has exhibited notable improvements in operational effectiveness over continuous pumping. The optimized pulsed pumping technique has also exhibited an advantage over uniform time intervals for pumping and resting cycles. The most important finding supports the potential for managing and improving pumping operations in the absence of complete knowledge of plume characteristics. An objective functional was selected to minimize mass of water removed and minimize the non-essential mass of contaminant removed. General forms …

Go to article

Visualizing Early-Stage Breast Cancer Tumors In A Mammographic Environment Through A 3-Dimensional Mathematical Model, Christopher B. Bassham Mar 1999

Visualizing Early-Stage Breast Cancer Tumors In A Mammographic Environment Through A 3-Dimensional Mathematical Model, Christopher B. Bassham

Theses and Dissertations

In response to the insidious and deadly nature of breast cancer and the less-than-perfect detection ability of mammography, we develop a mathematical model as a foundation to the long-term goal of improving early breast cancer detection. By using modeling and simulation to construct an accurate breast cancer tumor model, we hope to solve the problems associated with mammogram misdiagnosis and, perhaps as a by-product, lend insight to tumor development dynamics. The final tumor model, written in MATLAB, provides realistic tumor growth and 2-dimensional visualization of 3-dimensional structures. Earlier modeling attempts capture slices of the tumor in the 2-dimensional growth spaces. …

Go to article

The Quota Allocation Model: The Linear Optimization Of A Markov Decision Process, David A. Brown Mar 1999

The Quota Allocation Model: The Linear Optimization Of A Markov Decision Process, David A. Brown

Theses and Dissertations

One of the many needs of the Air Force is advanced technical degrees. These degrees can be acquired in three ways: the Air Force can directly recruit personnel with the required degrees; Air Force personnel can obtain them during off duty time from local civilian colleges near their base; or the Air Force can provide advanced academic degrees (AADs) through the Air Force Institute of Technology (AFIT) or AFIT-sponsored programs. In 1995, the AFIT Commandant initiated a re-engineering study to review the AFIT mission. One of the initiatives of that study was the Quota Allocation Model (QuAM). The QuAM model …

Go to article

A Bayesian Decision Model For Battle Damage Assessment, Daniel W. Franzen Mar 1999

A Bayesian Decision Model For Battle Damage Assessment, Daniel W. Franzen

Theses and Dissertations

Battle damage assessment (BDA) is critical to success in any air campaign. However, Desert Storm highlighted numerous deficiencies in the BDA process, and operations since Desert Storm continue to point out weaknesses. We present a review of the Phase I BDA decision, or physical damage assessment, and model the decision process using a Bayesian belief network. Through subject matter expert (i.e., the targeteers) elicitation sessions, imagery was found to be critically important to the BDA process yet this information is generally not retained. This use of "perfect information" is delineated in the BDA process models. We proposed a methodology based …

Go to article

Implementation Of The Metaheuristic Tabu Search In Route Selection For Mobility Analysis Support System, David M. Ryer Mar 1999

Implementation Of The Metaheuristic Tabu Search In Route Selection For Mobility Analysis Support System, David M. Ryer

Theses and Dissertations

This thesis employs a reactive tabu search heuristic implemented in the Java programming language to solve a real world variation of the vehicle routing problem with the objective of providing quality routes to Mobility Analysis Support System (MASS). MASS is a stochastic simulation model used extensively by Air Mobility Command (AMC) to analyze strategic airlift capabilities and future procurement decisions. This dynamic real world problem of strategic and tactical airlift possesses a number of side constraints such as vehicle capacities, route length and time windows in a sizeable network with multiple depots and a large fleet of heterogeneous vehicles. Finding …

Go to article

An Evaluation And Comparison Of The Ace And Brace Airfield Models, David W. Wiliams Mar 1999

An Evaluation And Comparison Of The Ace And Brace Airfield Models, David W. Wiliams

Theses and Dissertations

Airfields are a critical aspect of our military's ability to project power or respond to crises throughout the world. It is crucial that mobility planners have an effective means to estimate the capacity of these airfields. The objective of this research is to examine common mobility metrics and evaluate existing means of measuring them. Currently, Air Mobility Command has two models, the Airfield Capacity Estimator (ACE) and the Base Resource and Capabilities Estimator (BRACE), that were designed to estimate the resource requirements and capacities of an airfield. This study offers a critical evaluation and comparison of the two models. Discrepancies …

Go to article

An Approach For Tasking Allocated Combat Resources To Targets, David A. Koewler Mar 1999

An Approach For Tasking Allocated Combat Resources To Targets, David A. Koewler

Theses and Dissertations

Tasking allocated combat aircraft to strike targets is a complicated and time-consuming process for combat planners. Currently, the process of scheduling missions is a two to four day process. To be able to respond quickly to the changing conditions of the battlefield, the military needs to compress the time that this process requires. Despite efforts to develop computer-based tools to automatically plan missions, combat planners still manually perform most of the tasking and scheduling of aircraft and targets. Unfortunately some of the tools currently available are perceived to be complicated and time consuming to use by the planners. They also …

Go to article

Selection Of Psychophysiological Features Across Subjects For Classifying Workload Using Artificial Neural Networks, Trevor I. Laine Mar 1999

Selection Of Psychophysiological Features Across Subjects For Classifying Workload Using Artificial Neural Networks, Trevor I. Laine

Theses and Dissertations

The issue of pilot workload is important to the United States Air Force because pilot overload or task saturation leads to decreases in mission effectiveness. Additionally, in the most extreme cases, pilot overload may lead to the loss of aircraft and crewmember lives. Current research efforts are utilizing psychophysiological data including electroencephalography (EEG), cardiac, eye-blink, and respiration measures in an attempt to identify workload levels. The primary focus of this effort is to determine if a single parsimonious set of psychophysiological features exists for accurately classifying workload levels between multiple test subjects. To accomplish this objective, the signal-to-noise (SNR) saliency …

Go to article

Analysis Of A Non-Trivial Queueing Network, Kelly Scott Bellamy Feb 1999

Analysis Of A Non-Trivial Queueing Network, Kelly Scott Bellamy

Theses and Dissertations

In studying complex queueing networks, one generally seeks to employ exact analytic solutions to reduce burden on computational resources. Barring the existence of an exact solution, the alternatives include approximation techniques and simulation. Approximation is the more attractive alternative from a time and effort perspective; however, cases exist that are not amiable to this technique. This work increases the flexibility of approximation techniques in obtaining estimates of congestion measures for complex, open queueing networks having several customer classes and class-dependent structures. We accomplish this by providing the procedure to aggregate multiple classes into a single class in order to apply …

Go to article

The Effect Of Particle Properties On The Flow Characteristics Of Electrophotographic Powders, Joseph Pedano Dec 1998

The Effect Of Particle Properties On The Flow Characteristics Of Electrophotographic Powders, Joseph Pedano

Theses and Dissertations

The effect of particle size on the flow characteristics and tribo-electrical charge of dry electrophotographic (toner) powders was investigated. Toner samples, consisting of the same base formulation, but differing in particle size were prepared and studied using commercially available processing and analytical equipment. The effect of post-blending fumed silica into the toner was also investigated as part of this work. The results indicate that toner particle size has a strong effect on toner flow characteristics. The flowability measurements that were most affected by the particle size were the cohesiveness and compressibility properties of the toner powders. The data showed that …

Go to article

Multi-Baseline Interferometric Sar For Iterative Height Estimation, Adam E. Robertson Dec 1998

Multi-Baseline Interferometric Sar For Iterative Height Estimation, Adam E. Robertson

Theses and Dissertations

Multiple SAR interferograms with judiciously selected height sensitivities can be iteratively combined to create a high accuracy digital elevation map. An initial height estimate is refined by iteratively using larger baselines to obtain a height estimation accuracy limited by the spatial decorrelation of the antenna baseline. Spatial filtering is used to reduce the propagation of errors for accurate height estimation. Images containing regions isolated by phase discontinuities, as often found in urban environments, can be resolved by this iterative multi-baseline technique. Computationally demanding and potentially unreliable phase unwrapping is not required to determine scene elevation using SAR inMultiple SAR interferograms …

Go to article

Feature Saliency In Artificial Neural Networks With Application To Modeling Workload, Kelly A. Greene Dec 1998

Feature Saliency In Artificial Neural Networks With Application To Modeling Workload, Kelly A. Greene

Theses and Dissertations

This dissertation research extends the current knowledge of feature saliency in artificial neural networks (ANN). Feature saliency measures allow for the user to rank order the features based upon the saliency, or relative importance, of the features. Selecting a parsimonious set of salient input features is crucial to the success of any ANN model. In this research, several methodologies were developed using the Signal to Noise Ratio (SNR) Feature Screening Method and its associated SNR Saliency Measure for selecting a parsimonious set of salient features to classify pilot workload in addition to air traffic controller workload. Candidate features were derived …

Go to article

Three-Dimensional Calculation Of Contaminant Transport In Groundwater At A Dover Afb Site, Tariq O. Hashim Dec 1998

Three-Dimensional Calculation Of Contaminant Transport In Groundwater At A Dover Afb Site, Tariq O. Hashim

Theses and Dissertations

Macroscale rate-limited sorption modeling was tested using a production transport code, the GMS/FEMWATER ground-water modeling package. The code (Version 1.1 of FEMWATER. dated 1 August 1995) was applied to a 3D conceptual model developed from a field site at Dover AFB, DE. A simulation was performed of a 200 hour contaminant injection pulse followed by clean water flushing. A moment analysis performed on the resulting breakthrough curve validated code self-consistency. Another injection pulse simulation showed that retardation temporally delays the breakthrough peak. Transport simulations of pulsed clean water pumping of the test cell with a prescribed initial contaminant distribution demonstrated …

Go to article

How To Develop An Interactive Electronic Technical Manual: An Industry Perspective, Ali N. Karabulut, Hilmi Oz Dec 1998

How To Develop An Interactive Electronic Technical Manual: An Industry Perspective, Ali N. Karabulut, Hilmi Oz

Theses and Dissertations

Improvements in technology, especially in computer science, in the last two decades have made it possible, and preferable to develop digital technical manuals. A digital manual, which is called an Interactive Electronic Technical Manual (IETM), is a package of information required for the diagnosis and maintenance of a weapon systems, optimally arranged and formatted for interactive screen presentation to the end-user. Being the largest organization in the U.S., the Department of Defense has pioneered in the development of IETM concept as well as in the establishment of its standards. There have been many researches done about different IETM applications and …

Go to article

Development Of An Operations Research Software Package For Army Divisions, Blane C. Wilson Dec 1998

Development Of An Operations Research Software Package For Army Divisions, Blane C. Wilson

Theses and Dissertations

There exists great potential for applying operations research techniques to solve specific problems in the areas of operations, installation support, and training at the Army division level. Because of the operational tempo of today's active-duty and reserve component units, command must focus on accomplishing the daily missions. Also, due their limited knowledge of the field, planners may not be aware of how operations research can be used to enhance planning and operations. Time, training funds, resources, safety, personnel, and equipment are all critical factors in this process. Operations research techniques could be used to improve division-level operations by saving time, …

Go to article

Design Of The Computer Subsystem For The Afit Simulation Satellite (Simsat), Michael P. Hanke Dec 1998

Design Of The Computer Subsystem For The Afit Simulation Satellite (Simsat), Michael P. Hanke

Theses and Dissertations

This document details the systematic development of the computer subsystem for the AFIT Simulation Satellite (SIMSAT) from Concept Exploration to Implementation. This subsystem design effort was conducted as part of a larger four-phase team design effort to implement a fully functional, user-friendly test facility to meet current AFIT teaching and research requirements. Once SIMSAT system integration is complete, control laws will execute on the free-floating "satellite" to reduce communication systems overhead and its impact on control law execution, thereby allowing for more robust control system development and execution. Control law development, simulation, and interactive control of the system will occur …

Go to article

Development Of A Discrete Ordinates Code System For Unstructured Meshes Of Tetrahedral Cells, With Serial And Parallel Implementations, Rodney L. Miller Nov 1998

Development Of A Discrete Ordinates Code System For Unstructured Meshes Of Tetrahedral Cells, With Serial And Parallel Implementations, Rodney L. Miller

Theses and Dissertations

A numerically stable, accurate, and robust form of the exponential characteristic (EC) method, used to solve the time-independent linearized Boltzmann Transport Equation, is derived using direct affine coordinate transformations on unstructured meshes of tetrahedra. This quadrature, as well as the linear characteristic (LC) spatial quadrature, is implemented in our transport code, called TETRAN. This code solves multi-group neutral particle transport problems with anisotropic scattering and was parallelized using High Performance Fortran and angular domain decomposition. A new, parallel algorithm for updating the scattering source is introduced. The EC source and inflow flux coefficients are efficiently evaluated using Broyden's rootsolver, started …

Go to article

An Integer Program Decomposition Approach To Combat Planning, John C. Van Hove Sep 1998

An Integer Program Decomposition Approach To Combat Planning, John C. Van Hove

Theses and Dissertations

Over the last two decades, our military forces have been working to incorporate the latest computer technology into the combat planning process. The earliest efforts use word processors, spreadsheets, and databases to organize planning data and to display high level summaries for commanders. Later efforts perform feasibility checks as missions are planned to insure that the necessary resources are available and that the assets requested are capable of meeting the assigned scheduling requirements. Some of the most recent computer planning tools have included the capability to automatically plan individual missions or groups of missions. These automated efforts have been heuristic …

Go to article

Analysis Of Usaf Medium And Heavylift Space Launch Mission Reliability Requirements, Arthur R. Dawkins Sep 1998

Analysis Of Usaf Medium And Heavylift Space Launch Mission Reliability Requirements, Arthur R. Dawkins

Theses and Dissertations

The launch services that the USAF procures to carry DOD payloads into orbit are characterized by high risks and high costs. If a launch vehicle experiences a catastrophic failure, the cost of the entire launch vehicle, the launch processing, and the payload are completely lost (often in excess of 1,5 billion dollars.) Despite this enormous risk for the payload customer, and indeed the launch provider, launch success rates around the world are not much above 90 percent. The current USAF medium and heavylift launch systems are often based on technology that is 20 years old and older. Furthermore, little historical …

Go to article

The Effects Of Three Media Presentation Systems On Maintenance Task Performance, John W. Chastain Sep 1998

The Effects Of Three Media Presentation Systems On Maintenance Task Performance, John W. Chastain

Theses and Dissertations

Wearable computers and Portable Maintenance Aids (PMAs) may soon be the normal way of doing aircraft maintenance in the Air Force. Currently, the Air Force uses the paper form of Technical Orders (TO's) while doing aircraft maintenance. The purpose of this thesis was to compare the effects of three different media presentations of the information used during aircraft maintenance. The three different presentations compared are the current paper form, a Head Mounted Display (HMD), and an auditory mode. An experiment was conducted to determine if there was a significant difference between the systems (in terms of task completion times and …

Go to article

Electro-Mechanical Fatigue Behavior Of A Quasi-Isotropic Laminate With An Embedded Piezoelectric Actuator, Tse Lin Hsu Sep 1998

Electro-Mechanical Fatigue Behavior Of A Quasi-Isotropic Laminate With An Embedded Piezoelectric Actuator, Tse Lin Hsu

Theses and Dissertations

This study primarily investigated the electro-mechanical fatigue behavior of the embedded piezoelectric actuators in graphite/epoxy laminate with a lay-up of 0 | ± 45 | 90s. A secondary focus was the investigation of the mechanical fatigue effects of the 0 | 0 | ± 45 | 0 | 0 | 90s laminate with embedded PZT under tensile loading. All the fatigue tests were conducted with a triangular loading waveform which had a frequency of 10 Hz and with R=0. 1. In the electro-mechanical testing, the embedded actuator was excited by a -10 V to -100 V or a 10 V …

Go to article

A Comparison Of 8-Hour Vs. 12-Hour Shifts On Performance, Health And Safety In A Usaf Aircraft Maintenance Squadron, Kelly J. Scott Sep 1998

A Comparison Of 8-Hour Vs. 12-Hour Shifts On Performance, Health And Safety In A Usaf Aircraft Maintenance Squadron, Kelly J. Scott

Theses and Dissertations

This study examined the effects of converting a large USAF aircraft maintenance squadron from an 8- hour shift system to a 12-hour shift system. In 1996, the squadron converted its 24-hour operations from three 8-hour work shifts, to two 12-hour work shifts with compressed work weeks. The squadron maintained 12-hour shifts for 19 consecutive months. A comparison was made of organizational performance, worker health and safety measures before, during and after 12-hour shift implementation. Findings indicated that changing from 8- to 12-hour shifts resulted in a slight increase in aircraft Mission Capability rates. However, this benefit appears to have come …

Go to article

Automatic Target Cueing Of Hyperspectral Image Data, Terry A. Wilson Sep 1998

Automatic Target Cueing Of Hyperspectral Image Data, Terry A. Wilson

Theses and Dissertations

Modern imaging sensors produce vast amounts data, overwhelming human analysts. One such sensor is the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) hyperspectral sensor. The AVIRIS sensor simultaneously collects data in 224 spectral bands that range from 0.4µm to 2.5µm in approximately 10nm increments, producing 224 images, each representing a single spectral band. Autonomous systems are required that can fuse "important" spectral bands and then classify regions of interest if all of this data is to be exploited. This dissertation presents a comprehensive solution that consists of a new physiologically motivated fusion algorithm and a novel Bayes optimal self-architecting classifier …

Go to article

An Examination Of The United States Air Service's Logistics Operations, Andrew W. Hunt Sep 1998

An Examination Of The United States Air Service's Logistics Operations, Andrew W. Hunt

Theses and Dissertations

This historical study details the U.S. Air Service's logistics operations at home and abroad in an attempt to determine the relationship between the process and more recently established logistic principles. The information in the study was collected through an extensive review of both first hand accounts and historical compilations of the nature of World War I aviation logistics. Information regarding the production of the De Haviland DH-4 and Liberty Engine serve as the primary case examples of the operation of the logistics system. The established principles required for comparison were extracted from the writings of a number of expert military …

Go to article

Data Storage Devices For Air Force Space Command: A Comparative Analysis, Darryl E. Mosley Sep 1998

Data Storage Devices For Air Force Space Command: A Comparative Analysis, Darryl E. Mosley

Theses and Dissertations

Two of Air Force Space Command's primary missions are ballistic missile warning and global navigation, accomplished by commanding and controlling Defense Support Program and Global Positioning System satellites respectively. The computerized ground control system, called the satellite command and control system (CCS) used to perform command and control of the satellites currently uses antiquated peripheral storage devices. These storage devices are critical components, but are often prone to failure, possibly resulting in adverse mission impact. The Air Force must choose an alternative storage device for use in conjunction with CCS in order to accommodate planned operations tempo increases. This thesis …

Go to article

First Prev Next Last