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Air Force Institute of Technology

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Articles 3271 - 3300 of 5700

Full-Text Articles in Engineering

Blind Deconvolution Of Anisoplanatic Images Collected By A Partially Coherent Imaging System, Adam Macdonald Jun 2006

Blind Deconvolution Of Anisoplanatic Images Collected By A Partially Coherent Imaging System, Adam Macdonald

Theses and Dissertations

Coherent imaging systems offer unique benefits to system operators in terms of resolving power, range gating, selective illumination and utility for applications where passively illuminated targets have limited emissivity or reflectivity. This research proposes a novel blind deconvolution algorithm that is based on a maximum a posteriori Bayesian estimator constructed upon a physically based statistical model for the intensity of the partially coherent light at the imaging detector. The estimator is initially constructed using a shift-invariant system model, and is later extended to the case of a shift-variant optical system by the addition of a transfer function term that quantifies …

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Characterization Of Passivated Indium Antimonide, Catherine Ann Taylor Jun 2006

Characterization Of Passivated Indium Antimonide, Catherine Ann Taylor

Theses and Dissertations

Infrared absorption and photoluminescence measurements have been used to optically characterize bulk-grown, 680-μm thick, indium antimonide (InSb), both as-grown and after passivation by either anodization or a 700-Å layer of silicon oxide (SiOx). Spectra were obtained using Fourier transform infrared (FT-IR) spectroscopy. Results include the effects of sample temperature in the range of 10 to 300 K and 4.636 μm laser pump power in the range of 28 mW to 1.43 W for the photoluminescence spectrum.

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Managing Bandwidth And Traffic Via Bundling And Filtration In Large-Scale Distributed Simulations, Roberto C. Sánchez Jun 2006

Managing Bandwidth And Traffic Via Bundling And Filtration In Large-Scale Distributed Simulations, Roberto C. Sánchez

Theses and Dissertations

Research has shown that bandwidth can be a limiting factor in the performance of distributed simulations. The Air Force's Distributed Mission Operations Center (DMOC) periodically hosts one of the largest distributed simulation events in the world. The engineers at the DMOC have dealt with the difficult problem of limited bandwidth by implementing application level filters that process all DIS PDUs between the various networks connected to the exercise. This thesis examines their implemented filter and proposes: adaptive range-based filtering and bundling together of PDUs. The goals are to reduce the number of PDUs passed by the adaptive filter and to …

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Active Fpga Security Through Decoy Circuits, Bradley D. Christiansen Jun 2006

Active Fpga Security Through Decoy Circuits, Bradley D. Christiansen

Theses and Dissertations

Field Programmable Gate Arrays (FPGAs) based on Static Random Access Memory (SRAM) are vulnerable to tampering attacks such as readback and cloning attacks. Such attacks enable the reverse engineering of the design programmed into an FPGA. To counter such attacks, measures that protect the design with low performance penalties should be employed. This research proposes a method which employs the addition of active decoy circuits to protect SRAM FPGAs from reverse engineering. The effects of the protection method on security, execution time, power consumption, and FPGA resource usage are quantified. The method significantly increases the security of the design with …

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Optimal Geometric Deployment Of A Ground Based Pseudolite Navigation System To Track A Landing Aircraft, Matthew P. Crawford Jun 2006

Optimal Geometric Deployment Of A Ground Based Pseudolite Navigation System To Track A Landing Aircraft, Matthew P. Crawford

Theses and Dissertations

With much of the military and civilian communities becoming dependent on GPS technology to navigate it has become imperative that the navigation systems be tested in situations in which GPS does not work. This testing is especially necessary for precise tasks such as landing an aircraft. Currently, research is being conducted into using a pseudolite-based reference system to use as a truth model for the GPS jamming test. Pseudolite systems have been proven to provide sub-centimeter level accuracy in the horizontal plane; however in the vertical plane the position error is still in the decimeter to meter level range. This …

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Evaluation Of Microbial Diversity In Wetland Through Polymerase Chain Reaction (Pcr) And Restriction Fragment Length Polymorphism (Rflp), Gregory K. Joseph Jun 2006

Evaluation Of Microbial Diversity In Wetland Through Polymerase Chain Reaction (Pcr) And Restriction Fragment Length Polymorphism (Rflp), Gregory K. Joseph

Theses and Dissertations

The diversity of microbial communities in wetlands has not been fully measured. These communities may offer tools to naturally remediate sites polluted with chlorinated compounds. Polmerase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP) are genomic techniques that are capable of rapidly characterizing bacteria communities and can provide valuable information about the diversity of microbial communities.

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Technology Transfer: A Qualitative Analysis Of Air Force Office Of Research And Technology Applications, David C. Trexler Jun 2006

Technology Transfer: A Qualitative Analysis Of Air Force Office Of Research And Technology Applications, David C. Trexler

Theses and Dissertations

Everyday within United States Air Forces’ research laboratories there are hundreds of scientists and engineers whose research and development activities contribute to the advancement of science and technology for mankind. The opportunities for successful technology transfer within these research activities are unbounded. This thesis examines the Air Force Office of Research and Technology Applications (ORTA’s) involvement with technology transfer, the complexities they face, the importance of their position, and what best practices ORTAs use to facilitate technology transfer. Air Force concerns and initiatives are detailed to provide perspective on balancing technology transfer with mission requirements and adherence to United States …

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Development And Validation Of Reentry Simulation Using Matlab, Robert E. Jameson Jr. Jun 2006

Development And Validation Of Reentry Simulation Using Matlab, Robert E. Jameson Jr.

Theses and Dissertations

This research effort develops a program using MATLAB to solve the equations of motion for atmospheric reentry and analyzes the validity of the program for use as a tool to expeditiously predict reentry profiles. The reentry vehicle is modeled as a point mass with constant aerodynamic properties as defined by the user. The equations of motion for reentry are based on the two-body problem. The atmosphere is modeled as a single layer exponentially decreasing in density. The MATLAB program has the ability to derive the initial trajectory conditions from the position and velocity relative to the rotating surface of the …

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Particle Image Velocimetry Using A Novel, Non-Intrusive Particle Seeding, Charles J. Delapp Ii Jun 2006

Particle Image Velocimetry Using A Novel, Non-Intrusive Particle Seeding, Charles J. Delapp Ii

Theses and Dissertations

The purpose of this research effort was to study the use of non-intrusive particle seeding for Particle Image Velocimetry (PIV). Current seeding material and techniques involve the use of either solid particles or liquid mixtures which can contaminate or damage closed circuit wind tunnels, and in some cases can introduce a potential fire or explosive hazard. The proposed method is based on creating seed particles utilizing Carbon Dioxide (CO2). The CO2 would be dispensed into the flow as a liquid, immediately condensing to solid seed particles as they leave the spray nozzle. The advantage of using these particles is that …

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The Determination Of Remaining Satellite Propellant Using Measured Moments Of Inertia, Jason W. Geitgey Jun 2006

The Determination Of Remaining Satellite Propellant Using Measured Moments Of Inertia, Jason W. Geitgey

Theses and Dissertations

This research is designed to demonstrate that a change in satellite propellant can be determined using measured moments of inertia (MOI) from a satellite. Because satellites are currently incapable of being refueled in orbit it is important to have multiple methods to determine the remaining fuel onboard. This research can also support satellite operator selection of control-system gains to improve performance or recover the spacecraft. To meet the research objectives, new mathematical models of the Air Force Institute of Technology's Simulated Satellite (SimSat) were developed. These models were created using dynamic response analysis techniques on the reaction wheel and SimSat …

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Wear Analysis Of Cu-Al Coating On Ti-6al-4v Under Fretting, Karl N. Murray Jun 2006

Wear Analysis Of Cu-Al Coating On Ti-6al-4v Under Fretting, Karl N. Murray

Theses and Dissertations

The effects of changes in the coefficient of friction (CoF) between the contacting surfaces on the fretting wear characteristics of Cu-Al coating on Ti-6Al-4V were investigated. This Cu-Al coating is part of a system that is applied to titanium turbine blades to reduce fretting at the interface. In the application, there is a solid lubricant that is added on top of the coating as an assembly aid and to help reduce the friction while the lubricant remains within the contact. Previous studies have researched the characteristics of the coating without the additional lubricant. In this study, liquid motor oil was …

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An Investigation Into Robust Wind Correction Algorithms For Off-The Shelf Unmanned Aerial Vehicle Autopilots, Brent K. Robinson Jun 2006

An Investigation Into Robust Wind Correction Algorithms For Off-The Shelf Unmanned Aerial Vehicle Autopilots, Brent K. Robinson

Theses and Dissertations

The research effort focuses on developing methods to design efficient wind correction algorithms to "piggyback" on current off-the-shelf Unmanned Aerial Vehicle (UAV) autopilots. Autonomous flight is certainly the near future for the aerospace industry and there exists great interest in defining a system that can guide and control aircraft with high levels of accuracy. The primary systems required to command the vehicles are already in place, but with only moderate abilities to adjust for dynamic environments (i.e. wind effects), if at all. The goal of this research is to develop a systematic procedure for implementing efficient and robust wind effects …

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Dynamic Nonlinear Bending And Torsion Of A Cantilever Beam, Michael S. Whiting Jun 2006

Dynamic Nonlinear Bending And Torsion Of A Cantilever Beam, Michael S. Whiting

Theses and Dissertations

This effort sought to measure the dynamic nonlinear bending and torsion response of a cantilever beam. The natural frequencies of a cantilever beam in both chord and flap directions were measured at different static root pitch angles with varying levels of weights attached at the free end. The results were compared with previous experimentation to validate the data and testing procedures while lowering the associated error bands. Additionally, methodology for measuring mode shapes was set forth and mode shapes were measured for a few test cases with zero degrees of root pitch.

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Molecular Characterization Of Wetland Soil Bacterial Community In Constructed Mesocosms, Ethan C. Bishop Jun 2006

Molecular Characterization Of Wetland Soil Bacterial Community In Constructed Mesocosms, Ethan C. Bishop

Theses and Dissertations

The use of wetlands to effectively remediate aquifers contaminated with chlorinated solvents is an emerging technique, which shows high promise. In order to better understand this process and test its legitimacy, a treatment wetland was constructed at Wright-Patterson AFB, Dayton, Ohio and, in a joint effort with Wright State University (WSU), has previously shown the effective removal of PCE. The purpose of this research was to characterize the soil bacterial community, pre-PCE injection, among three wetland plant species from the sedge family (Cyperaceae) within constructed wetland mesocosms and to identify any bacterial dominance. Carex comosa, Scirpus atrovirens, and Eleocharis erythropoda …

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Effects Of Frequency And Environment On Fatigue Behavior Of An Oxide-Oxide Ceramic Matrix Composite At 1200°C, Griffin Hetrick Jun 2006

Effects Of Frequency And Environment On Fatigue Behavior Of An Oxide-Oxide Ceramic Matrix Composite At 1200°C, Griffin Hetrick

Theses and Dissertations

Advances in aeronautical engineering in the 21st century depend upon materials that can perform well in extreme environments such as high temperatures and oxidizing conditions. Nextel™720/Alumina (N720/A) is an oxide/oxide ceramic matrix composite with a porous alumina matrix that has been identified as a candidate material for such applications. This research investigated the effects of frequency on fatigue response of N720/A at 1200°C in both air and steam environment. Prior investigation of this material by Eber [8] in 2005 studied fatigue behavior at 1200°C in air and in steam environments at the frequency of 1.0 Hz. The current research focused …

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Theoretical Modeling Of The Transient Effects Of A Towline Using The Method Of Characteristics, Christopher A. Hill Jun 2006

Theoretical Modeling Of The Transient Effects Of A Towline Using The Method Of Characteristics, Christopher A. Hill

Theses and Dissertations

The use of decoys in combat has become more advanced in recent years. Some of the newest military aircraft, such as the US Navy's F/A-18E/F Superhornet, have the capability to deploy a towline with an attached decoy when entering hostile territory as a defense mechanism against enemy threats. In steady state, the towline extends behind and below the aircraft. A major concern is the position of the towline, as aircraft maneuvers can cause the line to enter the engine plume. The high exhaust heat can cause problems, such as damaging electrical equipment and severing the line. In order to better …

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Characterization Of Uav Performance And Development Of A Formation Flight Controller For Multiple Small Uavs, Patrick A. Mccarthy Jun 2006

Characterization Of Uav Performance And Development Of A Formation Flight Controller For Multiple Small Uavs, Patrick A. Mccarthy

Theses and Dissertations

The Air Force Institute of Technology's (AFIT) Advanced Navigation Technology (ANT) Center has recently delved into the research topic of small Unmanned Aerial Vehicles (UAV). One area of particular interest is using multiple small UAVs cooperatively to improve mission efficiency, as well as perform missions that couldn't be performed using vehicles independently. However, many of these missions require that the UAVs operate in close proximity of each other. This research lays the foundation required to use the ANT Center's UAVs for multi-vehicle missions (e.g. cooperatively) by accomplishing two major goals. First, it develops test procedures that can be used to …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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