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Articles 3301 - 3330 of 5700
Full-Text Articles in Engineering
Multiple Masks-Based Pixel Comparison Steganalysis Method For Mobile Imaging, Sos S. Agaian, Gilbert L. Peterson, Benjamin M. Rodriguez
Multiple Masks-Based Pixel Comparison Steganalysis Method For Mobile Imaging, Sos S. Agaian, Gilbert L. Peterson, Benjamin M. Rodriguez
Faculty Publications
No abstract provided.
A Comparative Analysis Of Transmission Control Protocol Improvement Techniques Over Space-Based Transmission Media, Joseph M. Lawson
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
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 …
Contingency Planning And An Air Force Space Command Information System, Kaylin Freedman, Michael R. Grimaila
Contingency Planning And An Air Force Space Command Information System, Kaylin Freedman, Michael R. Grimaila
Faculty Publications
No abstract provided.
Managing The Integration Of Space And Information Operations, Daniel F. Gottrich, Michael R. Grimaila
Managing The Integration Of Space And Information Operations, Daniel F. Gottrich, Michael R. Grimaila
Faculty Publications
No abstract provided.
Reliability Of Systems Using Event Occurrence Networks, Gregory M. Steeger
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 …
Numerical Investigation Of Cavity-Vane Interactions Within The Ultra Compact Combustor, Jonathan F. Anisko
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
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
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 …
Risk-Based Decision Model For Determining The Applicability Of An Earned Value Management System In Construction, Mark D. Workman
Risk-Based Decision Model For Determining The Applicability Of An Earned Value Management System In Construction, Mark D. Workman
Theses and Dissertations
New policy mandated by the Undersecretary of Defense for Acquisition, Technology and Logistics has lowered the dollar thresholds of contracts requiring earned value management (EVM). This policy directed that a "risk-based decision" be made to determine if EVM should be used on firm-fixed price contracts under $20 million. Although not previously applicable to Military Construction (MILCON) building projects or other Air Force Civil Engineer (CE) managed contracts, the new threshold requires that CE projects be evaluated for risk. Therefore, the focus of this research was to analyze the risk factors associated with construction contracts in an attempt to build a …
Technology Transition: Guidance Versus Practice, Walter E. Espy
Technology Transition: Guidance Versus Practice, Walter E. Espy
Theses and Dissertations
The transition of technologies ensures that U.S. warfighters have the necessary capabilities to fight ever increasing and changing global threats. The purpose of this study is to discover to what extent the Air Force Research Laboratory (AFRL) is implementing known technology transition best practices. The research will look at the current guidance on technology transition and determine if it is being used by program managers within AFRL. The study will consider the technology transition process or processes expressly exercised within AFRL by surveying the perspectives and knowledge of program managers. An understanding of this process from the science and technology …
Optical Characterization Of Thick Growth Orientation-Patterned Gallium Arsenide, Joshua W. Meyer
Optical Characterization Of Thick Growth Orientation-Patterned Gallium Arsenide, Joshua W. Meyer
Theses and Dissertations
Tunable laser sources in the mid-infrared (MIR) spectral range are required for several Air Force applications. Existing lasers with output in the near-infrared can be converted to more desirable MIR by using nonlinear effects. Orientation patterned gallium arsenide (OPGaAs) is a promising nonlinear conversion material because it has broad transparency and can be engineered for specific pump laser and output wavelengths using quasi-phase matching techniques. This research examines the optical quality of seven OPGaAs crystal samples and explores the design of an optical parametric oscillator (OPO) device. The Air Force Research Laboratory Electro-Optical Countermeasures Technology Branch obtained the samples from …
Investigation Of Copper Contamination And Corrosion Scale Mineralogy In Aging Drink Water Distributions Systems, Nadja F. Turek
Investigation Of Copper Contamination And Corrosion Scale Mineralogy In Aging Drink Water Distributions Systems, Nadja F. Turek
Theses and Dissertations
Research has shown higher levels of copper appear in drinking water conveyed through relatively new copper piping systems; older piping systems typically deliver lower copper levels in their drinking water. This research contributes field data from a real drinking water distribution system, providing a better understanding of this phenomenon, as it relates to treatment considerations and compliance with the Lead and Copper Rule. Copper pipes and copper levels were sampled from drinking water taps of 16 buildings with pipes ranging in age from less than 1 to 48 years. Water samples from each building were collected before and following a …
Assessing The Potential For Improved Scramjet Performance Through Application Of Electromagnetic Flow Control, Martin F. Lindsey
Assessing The Potential For Improved Scramjet Performance Through Application Of Electromagnetic Flow Control, Martin F. Lindsey
Theses and Dissertations
Hypersonic flight using scramjet propulsion bridges the gap between turbojets and rockets. Recent efforts focus on magnetogasdynamic (MGD) flow control to mitigate the problems of high thermomechanical loads and low efficiencies associated with scramjets. This research is the first flight-scale, three-dimensional computational analysis of a realistic scramjet to assess how MGD flow control improves scramjet performance. Developing a quasi-one dimensional design tool culminated in the first open source scramjet geometry. This geometry was tested with the Air Force Research Laboratory's electromagnetic computational code. To increase fidelity, an algorithm was developed to incorporate thermochemistry, resulting in the only open-source model of …
Modeling Study To Quantify The Benefits Of Groundwater Contaminant Source Remediation, David E. Wagner
Modeling Study To Quantify The Benefits Of Groundwater Contaminant Source Remediation, David E. Wagner
Theses and Dissertations
The purpose of this research was to quantify the benefits of groundwater contaminant source remediation by using a model to simulate how reduction of source mass was related to reduction of contaminant concentration at a receptor. This thesis sought to answer three research questions: (1) how are contaminant source mass reduction and reduction of mass flux leaving the source-zone related; (2) how can we quantify the effect of the important natural attenuation processes that act upon the dissolved contaminant as it travels from the source zone to downgradient receptors, and (3) under specified site conditions, what is the maximum contaminant …
Analysis And Simulation Of Hypervelocity Gouging Impacts, John D. Cinnamon
Analysis And Simulation Of Hypervelocity Gouging Impacts, John D. Cinnamon
Theses and Dissertations
In this work, a summary of past and present research efforts, as well as the theoretical foundation, of hypervelocity gouging is presented. As the Holloman AFB High Speed Test Track (HHSTT) sled's speed has increased to Mach 8.5, material interactions develops which causes "gouging" - this can result in catastrophic failure. A characterization of gouging, including a thermodynamic history, is developed from an examination of a gouged rail. An extensive study is performed that determines the specific material flow models for VascoMax 300 and 1080 steel. The models are validated utilizing several experimental tests which are successfully simulated using CTH …
Characterization Of Stress In Gan-On-Sapphire Microelectromechanical Systems (Mems) Structures Using Micro-Raman Spectroscopy, Francisco E. Parada
Characterization Of Stress In Gan-On-Sapphire Microelectromechanical Systems (Mems) Structures Using Micro-Raman Spectroscopy, Francisco E. Parada
Theses and Dissertations
Micro-Raman (µRaman) spectroscopy is an efficient, non-destructive technique widely used to determine the quality of semiconductor materials and microelectromechanical systems. This work characterizes the stress distribution in wurtzite gallium nitride grown on c-plane sapphire substrates by molecular beam epitaxy. This wide bandgap semiconductor material is being considered by the Air Force Research Laboratory for the fabrication of shock-hardened MEMS accelerometers. µRaman spectroscopy is particularly useful for stress characterization because of its ability to measure the spectral shifts in Raman peaks in a material, and correlate those shifts to stress and strain. The spectral peak shift as a function of stress, …
Reducing Uncertainty In Effects-Based Operations, Wilburn B. Mclamb
Reducing Uncertainty In Effects-Based Operations, Wilburn B. Mclamb
Theses and Dissertations
Known as the fog of war, uncertainty has been prevalent in the conduct of military operations throughout human history. Intelligence collection efforts are tasked to reduce this uncertainty through the collection of information. Utilizing Shannon's entropy as a measure of the expected information gain due to an intelligence collection effort, a methodology is developed to prioritize and allocate intelligence assets in an efficient manner. Incorporated in this methodology are target priority and the requirement to reassess dynamic targets. The application area for the methodology is Effects-Based Operations. A generalized state model is developed to conduct adversary system-of-systems analysis. This model …
Radiometric Analysis Of Daytime Satellite Detection, Katherine B. Lilevjen
Radiometric Analysis Of Daytime Satellite Detection, Katherine B. Lilevjen
Theses and Dissertations
A radiometric model for daylight satellite detection is developed and used to evaluate the effects of various parameters on signal-to-noise ratio (SNR). Detection of reflected sunlight from a low-earth orbit, diffuse, planar satellite by a single-pixel infrared photovoltaic detector is considered. Noise considered includes photon noise from the background and signal, as well as thermal noise. Parameters considered include atmospheric conditions, optical parameters, and detector parameters. The Phillips Laboratory Expert-assisted User System, an atmospheric modeling tool that employs the MODTRAN and FASCODE transmission codes, is used to model wavelength-dependent atmospheric transmission and background radiance. The SNR is found to increase …
A Decision Model For Choosing Among Photovoltaic Technologies To Generate Electricity At Grid-Connected Air Force Facilities: A Value-Focused Approach, Mostyn O. Kellner
A Decision Model For Choosing Among Photovoltaic Technologies To Generate Electricity At Grid-Connected Air Force Facilities: A Value-Focused Approach, Mostyn O. Kellner
Theses and Dissertations
The United States is currently consuming fossil fuels faster than natural processes can replace them. Our nation's leaders recognize that a diverse energy portfolio including renewable energy is the key to maintaining our economy, security, and the environment. The federal government is by far the greatest energy consumer; thus, our nation's leaders have directed federal agencies to strive to increase the use of renewable energy at federal facilities. Solar electricity technologies, in the form of photovoltaics, have great potential in the renewable energy mix. Although a major strategy should be integrating photovoltaics into the design of new facilities, an important …
A Graph Theoretic Analysis Of The Effects Of Organizational Structure On Employee Social Networks, John R. Hutzel
A Graph Theoretic Analysis Of The Effects Of Organizational Structure On Employee Social Networks, John R. Hutzel
Theses and Dissertations
A simulation technique was used to investigate the impacts of organizational structure on an organization's social network. By simulating personnel in an organization as vertices in a graph and the aging of the corporation as the aging of the same graph, the maturation of an organization was realized. The characteristic path length of the graph was measured after each year returning an optimistic average organizational distance. Results include the finding that, per this model, an organization's characteristic path length can drop over 50% in a 20 year period with consideration of edges of all strengths. Next a series of random …
Modeling Network Centric Warfare (Ncw) With The System Effectiveness Analysis Simulation (Seas), Jason B. Honabarger
Modeling Network Centric Warfare (Ncw) With The System Effectiveness Analysis Simulation (Seas), Jason B. Honabarger
Theses and Dissertations
Significant technological advances over the past few decades have fueled the continual and rapid development of an information-based world. Network Centric Warfare (NCW) has become the buzzword of the young millennium within the Department of Defense (DoD) and is quickly becoming a popularly shared vision and rallying cry for force transformation among United States military leaders. An essential element in fully implementing this network-centric way of thinking is to develop useful measures to help gauge the effectiveness and efficiency of both our military networks and our strategic NCW doctrine. The goal of this research is first to provide a comprehensive …
An Analysis Of Usaf Aircraft Noise And Hedonic Property Values, Melissa R. Johnson
An Analysis Of Usaf Aircraft Noise And Hedonic Property Values, Melissa R. Johnson
Theses and Dissertations
The primary purpose of the research was to evaluate whether there was a significant difference in housing values of those affected by the noise of USAF aircraft. The secondary purpose was to evaluate whether there was a significant difference in housing values located near USAF bases with and without aircraft noise and to evaluate whether type of aircraft changed the results created by the aircraft noise. This research effort found that homes located within the 65 dB DNL contour of US Air Force installations showed a significant negative impact due to the presence of aircraft noise when studied with the …
Passive Multiple Beam Combination In Optical Fibers Via Stimulated Brillouin Scattering, Kirk C. Brown
Passive Multiple Beam Combination In Optical Fibers Via Stimulated Brillouin Scattering, Kirk C. Brown
Theses and Dissertations
Many active methods of scaling laser brightness have been demonstrated in recent years. The goal of this research was to demonstrate the feasibility of passively combining multiple laser beams using Stimulated Brillouin Scattering (SBS) in a long multimode optical fiber. This method of combination employed a “Gatling gun” fiber array that allowed several collimated beams to be focused by a lens into an optical fiber. The retroreflected Stokes beam is passed through the center of the beam combiner for analysis. In addition to experimental methodology and equipment used, the theoretical and historical background of SBS in optical fibers is provided. …
Terrain And Spatial Effects On Hazard Prediction And Assessment Capability (Hpac) Software Dose-Rate Contour Plot Predictions As Compared To A Sample Of Local Fallout Data From Test Detonations In The Continental United States, 1945-1962, Kevin D. Pace
Theses and Dissertations
Hazard Prediction and Capability (HPAC) Software is validated by comparing modeled predictions to historical test data. Reanalysis weather data is acquired and reformatted for use in HPAC. Simulations are made using various amounts of weather data by use of a spatial domain. Simulations are also varied by levels of terrain resolution. The predicted output of the software is numerically compared to historical test data. The result of this research culminated in the knowledge that HPAC prediction accuracy is improved by using terrain resolutions beyond the flat earth assumption. Furthermore, this research establishes that domain size variation produces no significant advantage …
Using Agent-Based Modeling To Search For Elusive Hiding Targets, Jeffrey E. Rucker
Using Agent-Based Modeling To Search For Elusive Hiding Targets, Jeffrey E. Rucker
Theses and Dissertations
The SCUD hunt problem that emerged during Operation Desert Storm has become a source of great interest to major commands like Air Combat Command. One of the metrics used to measure the effectiveness of our operations in a SCUD hunt is time to detect and target. We use the agent-based System Effectiveness and Analysis Simulation (SEAS) to provide a simulation environment in which all the elements of a SCUD hunt mission can adequately be modeled. Our Blue Force agents are modeled as multirole fighters, satellites and unmanned aerial vehicles (UAV) with various sensor capabilities. The Red Force agents are modeled …
Evaluation Of Energy Costs And Error Performance Of Range-Aware Anchor-Free Localization Algorithms For Wireless Sensor Networks, Gustav Julio Jordt
Evaluation Of Energy Costs And Error Performance Of Range-Aware Anchor-Free Localization Algorithms For Wireless Sensor Networks, Gustav Julio Jordt
Theses and Dissertations
This research examines energy and error tradeoffs in Anchor-Free Range-Aware Wireless Sensor Network (WSN) Localization algorithms. A concurrent and an incremental algorithm (Anchor Free Localization (AFL) and Map Growing) are examined under varying network sizes, densities, deployments, and range errors. Despite current expectations, even the most expensive configurations do not expend significant battery life (at most 0.4%), implying little energy can be conserved during localization. Due to refinement, AFL is twice as accurate, using 6 times the communication. For both, node degree affects communication most. As degree increases, Map Growing communication increases, while AFL transmissions drop. Nodes with more neighbors …
Formal Mitigation Strategies For The Insider Threat: A Security Model And Risk Analysis Framework, Jonathan W. Butts
Formal Mitigation Strategies For The Insider Threat: A Security Model And Risk Analysis Framework, Jonathan W. Butts
Theses and Dissertations
The advancement of technology and reliance on information systems have fostered an environment of sharing and trust. The rapid growth and dependence on these systems, however, creates an increased risk associated with the insider threat. The insider threat is one of the most challenging problems facing the security of information systems because the insider already has capabilities within the system. Despite research efforts to prevent and detect insiders, organizations remain susceptible to this threat because of inadequate security policies and a willingness of some individuals to betray their organization. To investigate these issues, a formal security model and risk analysis …
Analysis Of Photoconductive Properties In Ge2Sb2Te5 (Gst) Chalcogenide Films For Applications In Novel Electronics, John R. V. Chezem
Analysis Of Photoconductive Properties In Ge2Sb2Te5 (Gst) Chalcogenide Films For Applications In Novel Electronics, John R. V. Chezem
Theses and Dissertations
This thesis investigated the thermal phase-change properties in Ge2Sb2Te5 (GST) chalcogenide-based films and determined the feasibility of coupling the GST with photosensitive DNA material for novel optical device applications. Modeling and testing of GST were researched with the approach that GST would react as a resistive mechanism through thermal manipulation. A test structure was fabricated with a 2-micronmeter MEMS fabrication process. GST material was deposited (by RF sputtering) on the surface of the test structures. The GST was analyzed primarily in the amorphous to crystalline transition states due to more distinct changes in the resistance …
Modeling Urban Warfare: Joint Semi-Automated Forces In Urban Resolve, Alexander B. Anastasiou
Modeling Urban Warfare: Joint Semi-Automated Forces In Urban Resolve, Alexander B. Anastasiou
Theses and Dissertations
The United States military is performing operations in urban environments with increasing frequency. Current Department of Defense doctrine is poorly suited to train and equip today's warriors with the tools and experience necessary to fight and win in modern sprawling cities. In order to "close the gap," the U.S. Joint Forces Command's Joint Experimentation Directorate led an effort to run a massively distributed simulation of a synthetic urban environment utilizing human-in-the-loop operators called URBAN RESOLVE. The synthetic environment simulated the city of Jakarta with over 1,000,000 buildings and structures and over 120,000 civilian entities. A Red force retreated into the …