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Theses and Dissertations

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Full-Text Articles in Engineering

Experimental Investigation Of The Aerodynamic Ground Effect Of A Tailless Lambda-Shaped Ucav With Wing Flaps, Jason T. Mostaccio Jun 2006

Experimental Investigation Of The Aerodynamic Ground Effect Of A Tailless Lambda-Shaped Ucav With Wing Flaps, Jason T. Mostaccio

Theses and Dissertations

This experimental study adequately identified the ground effect region of a lambda-shaped unmanned combat air vehicle (UCAV). The lambda planform used in this study was originally tested in a previous experiment to determine the stability and control characteristics generated out-of-ground-effect. The following study extends the existing database by analyzing the inherent aerodynamic behavior that is produced by employing trailing edge flap deflections while flying in-ground-effect (IGE). To accomplish this objective, static ground effect tests were performed in the AFIT 3? x 3? subsonic wind tunnel where a ground plane was used to simulate the forces and moments on the UCAV …


A Wind Tunnel Investigation Of Joined Wing Scissor Morphing, Christopher C. Dike Jun 2006

A Wind Tunnel Investigation Of Joined Wing Scissor Morphing, Christopher C. Dike

Theses and Dissertations

The Air Force Research Laboratory's Munitions Directorate has been looking to extend the range of its small smart bomb. Corneille [6] has conducted tests to determine the aerodynamic characteristics of joined wings on a missile and determine if joined wings are more beneficial than a single wing configuration. The concept of retrofitting wings on the bomb introduced an interesting problem: storage before deployment. This study conducted steady-state low speed wind tunnel testing of a joined wing configuration that morphed from a compact configuration for storage to a full extension. These steady-state tests examine differing sweep angles of the same joined …


Situational Awareness And Synthetic Vision For Unmanned Aerial Vehicle Flight Testing, Joseph M. Dugan Jun 2006

Situational Awareness And Synthetic Vision For Unmanned Aerial Vehicle Flight Testing, Joseph M. Dugan

Theses and Dissertations

The Advanced Navigation Technology (ANT) Center at the Air Force Institute of Technology (AFIT) is currently exploring ways to develop and advance the employment of autonomous Unmanned Aerial Vehicles (UAV) by the Department of Defense for military purposes. The research in this thesis describes the development of a tool that enhances situational awareness and provides synthetic vision in a program called the Aviator Visual Display Simulator (AVDS) during UAV flight. During flight testing, the Situational Awareness and Synthetic Vision Relay Tool (SASVRT) developed provides the test coordinator and pilot, as well as the safety observers, with the most pertinent information …


A Comparative Analysis Of Single-Stage-To-Orbit Rocket And Air-Breathing Vehicles, Benjamin S. Orloff Jun 2006

A Comparative Analysis Of Single-Stage-To-Orbit Rocket And Air-Breathing Vehicles, Benjamin S. Orloff

Theses and Dissertations

This study compares and contrasts the performance of a variety of rocket and air breathing, single-stage-to-orbit, reusable launch vehicles. Fuels considered include bi-propellant and tri-propellant combinations of hydrogen and hydrocarbon fuels. Astrox Corporation's HySIDE code was used to model the vehicles and predict their characteristics and performance. Vehicle empty mass, wetted area and growth rates were used as figures of merit to predict the procurement, operational and maintenance cost trends of a vehicle system as well as the system's practicality. Results were compared to those of two-stage-to-orbit reusable launch systems using similar modeling methods. The study found that single-stage-to-orbit vehicles …


An Experimental Study Of A Pulsed Dc Plasma Flow Control Actuator, Jennifer D. Wall Jun 2006

An Experimental Study Of A Pulsed Dc Plasma Flow Control Actuator, Jennifer D. Wall

Theses and Dissertations

An experiment on the effects of a pulsed DC plasma actuator on a separated flow in a low speed wind tunnel was conducted. The actuator consisted of two asymmetric copper electrodes oriented normal to the flow separated by a dielectric barrier and mounted on a flat plate in the center of the tunnel. A contoured insert was constructed and used to create an adverse pressure gradient in the test section comparable to a Pak-B low pressure turbine blade distribution. Suction was applied from the upper wall to induce separation along the flat plate over the electrodes. The DC power supply …


Characterizing A Co-Flow Nozzle For Use In A Filtered Rayleigh Scattering System, David S. Miceli Jun 2006

Characterizing A Co-Flow Nozzle For Use In A Filtered Rayleigh Scattering System, David S. Miceli

Theses and Dissertations

Research was conducted on the flow field exiting a co-annular flow nozzle for use in filtered Rayleigh scattering flow visualizations. More specifically, the flow visualizations were of the flow field exiting a coflow nozzle and illuminated by a tunable, nominal 4.2 watt narrow line width Argon laser operating at 514.5nm. ND:YAG lasers are typically used in this application, but some of the properties of a tunable Argon laser make it an attractive alternative. Before generating flow visualizations, the coflow nozzle was characterized both experimentally and computationally. Due to a flow asymmetry in the outer annulus flow field, the nozzle was …


Effect Of Environment On Creep Behavior Of An Oxide/Oxide Cfcc With ±45° Fiber Orientation, Gregory T. Siegert Jun 2006

Effect Of Environment On Creep Behavior Of An Oxide/Oxide Cfcc With ±45° Fiber Orientation, Gregory T. Siegert

Theses and Dissertations

Aerospace applications require materials capable of maintaining superior mechanical properties while operating at high temperatures and oxidizing environments. Nextel™ 720/A (N720/A), an oxide/oxide ceramic matrix composite (CMC) with a porous alumina matrix was developed specifically to provide improved long-term properties and performance at 1200°C. This research evaluated the creep behavior of N720/A with a ±45° fiber orientation at 1200°C in: laboratory air, steam, and argon environments. Creep-rupture tests at the creep stress levels of: 45, 40, 35, and 15 MPa were conducted in each environment.
The ultimate tensile strength of N720/A with ±45° fiber orientation was 55 MPa, the elastic …


High Altitude Airship Station-Keeping Analysis, Douglas P. Kondrack Jun 2006

High Altitude Airship Station-Keeping Analysis, Douglas P. Kondrack

Theses and Dissertations

Lighter-than-air vehicles were once widely utilized by most major militaries. The airship’s extended range and flight endurance made them the optimal vehicle for surveillance and reconnaissance. These flight characteristics have created new interest in using lighter-than-air vehicles as high altitude surveillance and communications platforms. Future Department of Defense plans include high altitude airships that will operate at near space altitudes and take advantage of the low wind region in the upper atmosphere located at approximately 24 km. A high altitude airship could provide 24-hour coverage of a target area if operated in this low wind region. This study investigated the …


Modeling A Reparable Supply Chain And Applying Cpfr Concepts, Sandra A. Mayhall Jun 2006

Modeling A Reparable Supply Chain And Applying Cpfr Concepts, Sandra A. Mayhall

Theses and Dissertations

The Air Force supply chain includes parts required to build, fix, or maintain aircraft delivered to the warfighter to carry out missions. Industry has shown that following Collaborative Planning, Forecasting, and Replenishment (CPFR) concepts, particularly reducing inventory through accurate demand forecasts, has increased profits in part by lowering the holding costs of inventory and increasing sales. This is analogous to the Air Force increasing aircraft availability. There is scant evidence that demand forecasts generated at any level in the Air Force are shared with the intent of coordinating replenishment. This thesis uses a simple discrete-event stochastic simulation model to show …


Evaluation Of The Effects Of Predicted Associativity On The Reliability And Performance Of Mobile Ad Hoc Networks, Esteban Francisco Sanchez Jun 2006

Evaluation Of The Effects Of Predicted Associativity On The Reliability And Performance Of Mobile Ad Hoc Networks, Esteban Francisco Sanchez

Theses and Dissertations

Routing in Mobile Ad Hoc Networks (MANETs) presents unique challenges not encountered in conventional networks. Predicted Associativity Routing (PAR) is a protocol designed to address reliability in MANETs. Using associativity information, PAR calculates the expected lifetime of neighboring links. Nodes use this expected lifetime, and their neighbor's connectivity to determine a residual lifetime. The routes are selected from those with the longest residual lifetimes. In this way, PAR attempts to improve the reliability of discovered routes. PAR is compared to AODV using a variety of reliability and performance metrics. Despite its focus on reliability, PAR does not provide more reliable …


Mitigating Insider Threat Using Human Behavior Influence Models, Anthony J. Puleo Jun 2006

Mitigating Insider Threat Using Human Behavior Influence Models, Anthony J. Puleo

Theses and Dissertations

Insider threat is rapidly becoming the largest information security problem that organizations face. With large numbers of personnel having access to internal systems, it is becoming increasingly difficult to protect organizations from malicious insiders. The typical methods of mitigating insider threat are simply not working, primarily because this threat is a people problem, and most mitigation strategies are geared towards profiling and anomaly detection, which are problematic at best. As a result, a new type of model is proposed in this thesis, one that incorporates risk management with human behavioral science. The new risk-based model focuses on observable influences that …


Maneuver Estimation Model For Geostationary Orbit Determination, Brian J. Hirsch Jun 2006

Maneuver Estimation Model For Geostationary Orbit Determination, Brian J. Hirsch

Theses and Dissertations

As an increasing number of geostationary satellites fill a limited number of orbital slots, collocation of satellites leads to a risk of close approach or misidentification. The ability to detect maneuvers made by these satellites using optical observations can help to prevent these problems. Such a model has already been created and tested using data from the Air Force Maui Optical and Supercomputing site. The goal of this research was to create a more robust model which would reduce the amount of data needed to make accurate maneuver estimations. The Clohessy-Wiltshire equations were used to model the relative motion of …


Fast Video Stabilization Algorithms, Mohammed A. Alharbi Jun 2006

Fast Video Stabilization Algorithms, Mohammed A. Alharbi

Theses and Dissertations

A fast and robust electronic video stabilization algorithm is presented in this thesis. It is based on a two-dimensional feature-based motion estimation technique. The method tracks a small set of features and estimates the movement of the camera between consecutive frames. It is used to characterize the motions accurately including camera rotations between two imaging instants. An affine motion model is utilized to determine the parameters of translation and rotation between images. The determined affine transformation is then exploited to compensate for the abrupt temporal discontinuities of input image sequences. Also, a frequency domain approach is developed to estimate translations …


Cement Stabilization Of Aggregate Base Materials Blended With Reclaimed Asphalt Pavement, Ashley Vannoy Brown May 2006

Cement Stabilization Of Aggregate Base Materials Blended With Reclaimed Asphalt Pavement, Ashley Vannoy Brown

Theses and Dissertations

The purpose of this research was to investigate the effects of reclaimed asphalt pavement (RAP) content and cement content on the strength and durability of recycled aggregate base materials. Specifically, the unconfined compressive strength (UCS) and final dielectric value in the Tube Suction Test (TST) were measured in a full-factorial experimental design including five RAP contents, five cement contents, and three replicate specimens of each possible treatment. Specimen mixtures consisted of 0, 25, 50, 75, or 100 percent RAP and 0.0, 0.5, 1.0, 1.5, or 2.0 percent Type I/II Portland cement. Both the RAP and base materials were sampled from …


A Study Of Model Integration In Conjunction With The Extensible Model Definition Format, Melanie A. Fife May 2006

A Study Of Model Integration In Conjunction With The Extensible Model Definition Format, Melanie A. Fife

Theses and Dissertations

A considerable amount of research has been done to connect or integrate separate numerical models. The Environmental Modeling Research Laboratory (EMRL) has developed a generic file format, the eXtensible Model Data Format (XMDF). One of the objectives of the XMDF project is to facilitate the spatial interpolation and data-sharing necessary when linking models. The objective of this research is to investigate how model linking capabilities can be added to the XMDF by defining a Model Linkage Object (MLO) that is compatible with current model linking frameworks. A potential design for an MLO is defined in this thesis after a detailed …


Fpga-Based Experiment Platform For Hardware-Software Codesign And Hardware Emulation, Yajuvendra Nagaonkar May 2006

Fpga-Based Experiment Platform For Hardware-Software Codesign And Hardware Emulation, Yajuvendra Nagaonkar

Theses and Dissertations

An FPGA-based experiment platform for hardware-software codesign experiments was developed. The proposed platform would be used by an engineer who can be affiliated with academia, research or industry for codesign experiments or hardware emulation. The platform utilizes a combination of a microcontroller and a FPGA device to enable sufficient flexibility in exploring the design space to implement codesign experiments. The FPGA device operation is integrated with that of the microcontroller to provide an overall embedded solution for codesign experimentations. It is anticipated that the platform will be used in academia for educating the students the concepts of computer architecture and …


Evaluation And Modeling Of Repeated Load Test Data Of Asphalt Concrete For Mechanistic-Empirical Flexible Pavement Design, Stephen Price Apr 2006

Evaluation And Modeling Of Repeated Load Test Data Of Asphalt Concrete For Mechanistic-Empirical Flexible Pavement Design, Stephen Price

Theses and Dissertations

The Mechanistic-Empirical Pavement Design Guide (MEPDG) uses a power model that incorporates Dynamic Modulus (DM) as a factor in predicting rutting performance of asphalt concrete. The rutting model is empirical and the rutting profiles obtained from the model are largely based on the adjustment of calibration constants not the DM. Various DM values would be capable of producing similar rutting profiles based on the current model. This study evaluated using accumulated strain data obtained from the Repeated Load Test (RLT) as an alternative to using DM. In addition, a model to represent the accumulated strain data obtained from the RLT …


In-Situ Testing Of A Carbon/Epoxy Isotruss Reinforced Concrete Foundation Pile, Sarah Richardson Apr 2006

In-Situ Testing Of A Carbon/Epoxy Isotruss Reinforced Concrete Foundation Pile, Sarah Richardson

Theses and Dissertations

This thesis focuses on the field performance of IsoTruss®-reinforced concrete beam columns for use in driven piles. Experimental investigation included one instrumented carbon/epoxy IsoTruss®-reinforced concrete pile (IRC pile) and one instrumented steel-reinforced concrete pile (SRC pile) which were driven into a clay profile at a test site. These two piles, each 30 ft (9 m) in length and 14 in (36 cm) in diameter, were quasi-statically loaded laterally until failure. Behavior was predicted using three different methods: 1) a commercial finite difference-based computer program called Lpile; 2) a Winkler foundation model; and, 3) a simple analysis based on fundamental mechanics …


Increasing Speed Limit Compliance In Reduced-Speed School Zones, Kelly Grant Ash Apr 2006

Increasing Speed Limit Compliance In Reduced-Speed School Zones, Kelly Grant Ash

Theses and Dissertations

Reduced-speed school zones greatly improve the safety of young children commuting to and from school and provide larger gaps in traffic for children to cross the street. The main focus of this study was to determine effective methods for increasing speed compliance in reduced-speed school zones. This objective was accomplished through an in-depth literature review, a public opinion survey of Utah drivers, and an evaluation of the effects of speed monitoring displays (SMDs) in school zones. The main focus of the literature review was to determine how to increase and maintain speed limit compliance within school zones. Information about the …


A Comparative Analysis Of Transmission Control Protocol Improvement Techniques Over Space-Based Transmission Media, Joseph M. Lawson Apr 2006

A Comparative Analysis Of Transmission Control Protocol Improvement Techniques Over Space-Based Transmission Media, Joseph M. Lawson

Theses and Dissertations

The purpose of this study was to assess the throughput improvement afforded by the various TCP optimization techniques, with respect to a simulated geosynchronous satellite system, to provide a cost justification for the implementation of a given enhancement technique. The research questions were answered through model and simulation of a satellite transmission system via a Linux-based network topology; results of the simulation were analyzed primarily via a non-parametric method to ascertain performance differences between the various TCP optimization techniques. It was determined that each technique studied, which included the Space Communication Protocol Standard-Transport Protocol (SCPS-TP), window scale, selective acknowledgements (SACKs), …


Performance-Metric Driven Atmospheric Compensation For Robust Free-Space Laser Communication, Peter N. Crabtree Apr 2006

Performance-Metric Driven Atmospheric Compensation For Robust Free-Space Laser Communication, Peter N. Crabtree

Theses and Dissertations

The effect of turbulence on laser propagation is a significant challenge to current electro-optical systems. While atmospheric compensation techniques in space object imaging and high-energy laser weapons have been thoroughly investigated, optimizing these techniques for Laser Communication (LaserCom) has not been examined to the same degree. Average Strehl ratio is the typical design metric for current atmospheric compensation systems. However, fade probability is the relevant metric for LaserCom. This difference motivated the investigation into metric-driven atmospheric compensation. Metric-based tracking techniques for fade mitigation is the first major focus of this research. In a moderate range air-to-air scenario, focal plane spot …


Ignition Delay Of Oxygenated Fuel Droplets: Development Of A 1 Second Drop Tower And Initial 1-G Test Results, Matthew Hammill Mar 2006

Ignition Delay Of Oxygenated Fuel Droplets: Development Of A 1 Second Drop Tower And Initial 1-G Test Results, Matthew Hammill

Theses and Dissertations

United States' dependency on petroleum fuels, much of it imported, has remained at the same level even as alternative fuels become more readily available to the consumer market. One alternative to petroleum based fuel is biodiesel. Biodiesel has been shown to have lower carbon monoxide, hydrocarbon, and particulate matter emissions than standard fuels, but show an increase in the formation of nitrous oxide gases. It has been theorized that several of the physical properties, which are governed by the chemical makeup of the fuel, have an adverse affect on NOx production. But until that time when a thorough chemical …


Assessing The Economic Impacts Of Transportation Improvement Projects, Andrew L. Stewart Mar 2006

Assessing The Economic Impacts Of Transportation Improvement Projects, Andrew L. Stewart

Theses and Dissertations

In that a transportation system can influence an economy for good or bad a system that enhances economic vitality becomes a crucial element in maintaining or developing economic prosperity. To provide a methodology to include economic development impacts of transportation improvement projects in the decision making process and the tools and alternatives available are here explored. Primary contributions of this document are results of a literature review, transportation professional and decision maker survey, economic modeling tool evaluation, and development of approach alternatives. The following thesis introduces the purpose and need for the given research, the procedure that was followed, the …


Full Scale Static Lateral Load Test Of A 9 Pile Group In Sand, Dustin Shaun Christensen Mar 2006

Full Scale Static Lateral Load Test Of A 9 Pile Group In Sand, Dustin Shaun Christensen

Theses and Dissertations

Much research has been done to study the effects of spacing in laterally loaded pile groups and how the pile spacing affects lateral resistance of the piles. In this test a 9-pile group of steel piles was installed in a 3x3 configuration in sand. The piles were spaced from center-to-center at a distance of 5.65 pile diameters in the direction of the load. The pile group was laterally loaded and instrumented to collect deflection, load, and strain data. A separate single pile was similarly instrumented and tested for comparison to the pile group. The soil profile consisted of a top …


Reliability Of Systems Using Event Occurrence Networks, Gregory M. Steeger Mar 2006

Reliability Of Systems Using Event Occurrence Networks, Gregory M. Steeger

Theses and Dissertations

The study of a system's reliability has played a crucial role in business and industry since the dawn of modern technology. Current graphical models utilized in reliability theory are limited in that no one model or technique allows for a thorough analysis of system reliability. This research introduces a new graphical model and methodology to be used in the field of reliability that addresses this concern. Event Occurrence Networks (EONs) and their solution methodologies provide an all-inclusive graphical model that allows for the manipulation of several important reliability measures. An EON is a probabilistic network that represents the superposition of …


Full-Scale-Lateral-Load Test Of A 1.2 M Diameter Drilled Shaft In Sand, Amy Jean Taylor Mccall Mar 2006

Full-Scale-Lateral-Load Test Of A 1.2 M Diameter Drilled Shaft In Sand, Amy Jean Taylor Mccall

Theses and Dissertations

The soil-structure interaction models associated with laterally loaded deep foundations have typically been based on load tests involving relatively small diameter foundations. The lateral soil resistance for larger diameter foundations has been assumed to increase linearly with diameter; however, few, if any load tests have been performed to confirm this relationship. To better understand the lateral resistance of large diameter deep foundations in sand, a series of full scale, cyclic, lateral load tests were performed on two 1.2 m diameter drilled shafts and a 0.324 m diameter steel pipe pile in sand. Although the tests involve two different foundation types, …


Numerical Investigation Of Cavity-Vane Interactions Within The Ultra Compact Combustor, Jonathan F. Anisko Mar 2006

Numerical Investigation Of Cavity-Vane Interactions Within The Ultra Compact Combustor, Jonathan F. Anisko

Theses and Dissertations

A numerical analysis and design optimization of the Ultra Compact Combustor (UCC) has been conducted. The UCC is a combustor designed to incorporate high-g loadings to increase flame propagation speed while reducing flame length, thereby helping to significantly reduce the size of a combustor. A commercial CFD package with a k-Ⲉ turbulence model has been used to develop design rules for the construction of future UCCs. There have been several versions of UCC that have been designed, built and tested by AFRL/PRTC. Since real experimental tests are expensive and construction time is prohibitive to test many different design configurations, CFD …


Adaptive Illumination Patterns For Radar Applications, Phillip M. Corbell Mar 2006

Adaptive Illumination Patterns For Radar Applications, Phillip M. Corbell

Theses and Dissertations

The fundamental goal of Fully Adaptive Radar (FAR) involves full exploitation of the joint, synergistic adaptivity of the radar's transmitter and receiver. Little work has been done to exploit the joint space time Degrees-of-Freedom (DOF) available via an Active Electronically Steered Array (AESA) during the radar's transmit illumination cycle. This research introduces Adaptive Illumination Patterns (AIP) as a means for exploiting this previously untapped transmit DOF. This research investigates ways to mitigate clutter interference effects by adapting the illumination pattern on transmit. Two types of illumination pattern adaptivity were explored, termed Space Time Illumination Patterns (STIP) and Scene Adaptive Illumination …


Uncertainty Estimation For Target Detection System Discrimination And Confidence Performance Metrics, David R. Parker Mar 2006

Uncertainty Estimation For Target Detection System Discrimination And Confidence Performance Metrics, David R. Parker

Theses and Dissertations

This research uses a Bayesian framework to develop probability densities for target detection system performance metrics. The metrics include the receiver operating characteristic (ROC) curve and the confidence error generation (CEG) curve. The ROC curve is a discrimination metric that quantifies how well a detection system separates targets and non-targets, and the CEG curve indicates how well the detection system estimates its own confidence. The degree of uncertainty in these metrics is a concern that previous research has not adequately addressed. This research formulates probability densities of the metrics and characterizes their uncertainty using confidence bands. Additional statistics are obtained …


The Storage Of Parametric Data In Product Lifecycle Management Systems, Jonathan Gary Lund Mar 2006

The Storage Of Parametric Data In Product Lifecycle Management Systems, Jonathan Gary Lund

Theses and Dissertations

Product development companies are continually seeking methods to increase efficiency while maintaining quality. Distributed development is also more important than ever before as industries globalize. These forces have driven firms to adopt formal data management practices that allow groups and individuals to work from singular, centralized data source that are secure, reliable, and support collaboration. This thesis proposes a methodology to leverage globalized infrastructures for the efficient storage of product variations. The methodology is proved through a working prototype using the market leader in Product Lifecycle Management (PLM) systems, Teamcenter Engineering. First, paradigms are set forth for the storage of …