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Laser Intensity Scaling Through Stimulated Scattering In Optical Fibers, Timothy H. Russell
Laser Intensity Scaling Through Stimulated Scattering In Optical Fibers, Timothy H. Russell
Theses and Dissertations
The influence of stimulated scattering on laser intensity in fiber optic waveguides is examined. Stimulated Brillouin scattering (SBS) in long, multimode optical waveguides is found to generate a Stokes beam that propagates in the fiber LP01 mode. Additionally, the same process is found to combine multiple laser beams into a single spatially coherent source. Limitations in beam cleanup and combining are also investigated to identify ways to overcome them. The last portion of the dissertation theoretically examines suppression of stimulated Raman scattering in fibers to eliminate the restriction this imposes on the power of a fiber laser or amplifier. The …
Reduced Order Modeling For High Speed Flows With Moving Shocks, David J. Lucia
Reduced Order Modeling For High Speed Flows With Moving Shocks, David J. Lucia
Theses and Dissertations
The use of Proper Orthogonal Decomposition (POD) for reduced order modeling (ROM) of fluid problems is extended to high-speed compressible fluid flows. The challenge in using POD for high-speed flows is presented by the presence of moving discontinuities in the flow field. To overcome these difficulties, a domain decomposition approach is developed that isolates the region containing the moving shock wave for special treatment. The domain decomposition implementation produces internal boundaries between the various domain sections. The domains are linked using optimization-based solvers which employ constraints to ensure smoothness in overlapping portions of the internal boundary. This approach is applied …
Modeling Axisymmetric Optical Precision Piezoelectric Membranes, James W. Rogers Jr.
Modeling Axisymmetric Optical Precision Piezoelectric Membranes, James W. Rogers Jr.
Theses and Dissertations
The US Department of Defense (DOD), as well as the National Aeronautics and Astronautics Administration (NASA) and the Jet Propulsion Laboratory (JPL) are interested in developing and deploying precise, compliant, light-weight, space-based structures. More specifically, the Air Force’s core competencies ‘Aerospace Superiority’ and ‘Information Superiority’ demand ever-increasing depth and breadth of capability. Whether used for energy transmission or optical reconnaissance, current launch restraints limit rigid space-based optical reflector size. To support this requirement, the Air Force Research Laboratory (AFRL) is developing a large space-based optical membrane telescope. Inflatable reflectors can conceptually break this barrier, but controlling such a compliant structure …
Analysis And Numerical Solution Of An Integral Equation Method For Electromagnetic Scattering From A Cavity In A Ground Plane, Eric T. Howe
Analysis And Numerical Solution Of An Integral Equation Method For Electromagnetic Scattering From A Cavity In A Ground Plane, Eric T. Howe
Theses and Dissertations
In this research the electromagnetic scattering of a plane wave from a two-dimensional cavity embedded in an infinite, perfectly conducting ground plane is investigated. The plane wave is assumed to be under transverse electric (TE) polarization with respect to the x-axis. The cavity may be empty or filled with an arbitrary homogeneous, lossy material. A coupled set of scalar integral equations that govern the electromagnetic scattering is implemented. An approximate solution to the scalar integral equations is found via a Method of Moments (MoM) algorithm. The algorithm is implemented in a computer code, and approximations to the total magnetic field …
Theater-Level Stochastic Air-To-Air Engagement Modeling Via Event Occurrence Networks Using Piecewise Polynomial Approximation, David R. Denhard
Theater-Level Stochastic Air-To-Air Engagement Modeling Via Event Occurrence Networks Using Piecewise Polynomial Approximation, David R. Denhard
Theses and Dissertations
This dissertation investigates a stochastic network formulation termed an event occurrence network (EON). EONs are graphical representations of the superposition of several terminating counting processes. An EON arc represents the occurrence of an event from a group of (sequential) events before the occurrence of events from other event groupings. Events between groups occur independently, but events within a group occur sequentially. A set of arcs leaving a node is a set of competing events, which are probabilistically resolved by order relations. An important EON metric is the probability of being at a particular node or set of nodes at time …
Microcavity Surface Emitting Laser, Stewart Feld, John P. Loehr, James A. Lott
Microcavity Surface Emitting Laser, Stewart Feld, John P. Loehr, James A. Lott
AFIT Patents
A three-dimensional waveguiding structure for a microcavity surface-emitting laser is described in which native aluminum oxide layers provide control of intracavity waveguiding and the laser optical mode structure of the emitted beam. Microcavity lasers described herein account for the blueshift of the emission wavelength as the laser lateral dimensions are reduced to or below the emission wavelength.
Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay
Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay
Theses and Dissertations
In the world of semiconductor photonic device fabrication, one important objective may be to extract as much light as possible from the device. In these devices, photons are created when electrons recombine with holes by transitioning from a high-energy state to a lower one. Unfortunately, electron-hole recombination does not always result in the formation of a photon. There are three basic types of recombination: the first results in the formation of a photon and is called radiative recombination; and the second and third, known as Shockley-Read-Hall and Auger recombination, result in the heating of the device and do not produce …
Single-Sided Noninvasive Inspection Of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography, Matthew A. Lange
Single-Sided Noninvasive Inspection Of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography, Matthew A. Lange
Theses and Dissertations
As aircraft age, corrosion forms upon unobservable surfaces, particularly at the junction of the sheet aluminum and the steel rivets used to attach the sheets to the airframe, degrading the aircraft s airworthiness. Previous research developed a noninvasive technique for the evaluation of the material composition of aluminum surfaces, utilizing the information encoded in the energy spectra of Compton-scattered gamma emissions. The spectra are gathered by a six-element, high purity germanium detector array. A, first principles, deterministic computer code is used to reconstruct a two-dimensional map of the electron density of aluminum samples. Previous efforts, to image pure aluminum samples, …
Hidden Markov Models For Visual Speech Synthesis In Limited Data, Harold A. Arb
Hidden Markov Models For Visual Speech Synthesis In Limited Data, Harold A. Arb
Theses and Dissertations
This work presents a new approach for estimating control points (facial locations that control movement) to allow the artificial generation of video with apparent mouth movement (visual speech) time-synced with recorded audio. First, Hidden Markov Models (HMMs) are estimated for each visual speech category (viseme) present in stored video data, where a category is defined as the mouth movement corresponding to a given sound and where the visemes are further categorized as trisemes (a viseme in the context of previous and following visemes). Next, a decision tree is used to cluster and relate states in the HMMs that are similar …
Spectroscopic Constants, Lifetimes And Predissociation Rates For Bi2A(0+U), Michael W. Dolezal
Spectroscopic Constants, Lifetimes And Predissociation Rates For Bi2A(0+U), Michael W. Dolezal
Theses and Dissertations
More than 100,000 spectral features from a Bi2(X1 Σ+g → A(0+u)) absorption spectrum, encompassing 0 ≤ v' ≤ 91, 0 ≤ v" ≤ 7 and J2(A). Ground state constants, reported by Barrow et al. [1], remain unchanged. The new constants are used to redefine the A-state potential using traditional RKR methods and to set the dissociation energy at De = 29,913 cm"1, which correlates A-state dissociation products to 4S + 2D atoms. A pulsed dye laser apparatus was used to obtain lifetime data for Bi2A(0+u) …
Evolution Of Cloud-To-Ground Lightning Discharges In Tornadic Thunderstorms, Wendy L. Seaman
Evolution Of Cloud-To-Ground Lightning Discharges In Tornadic Thunderstorms, Wendy L. Seaman
Theses and Dissertations
Air Force operations are directly impacted by weather on a daily basis. Erroneous forecasts negatively impact mission readiness and consequently cost the government time, in terms of wasted man-hours, and money. Advanced forecast lead-time could make a difference to minimize loss to both USAF personnel and assets. This study examined lightning data from 64 storm events from 1995-2000 in search of unique lightning signatures indicative of tornadic activity. Overall flash rates, percentage of positive flashes, positive and negative peak currents and multiplicity for each case were separated into two categories based on tornado intensity and season of occurrence. Based on …
Validation And Characterization Of Ionospheric Densities Measured By Dmsp, Herbert L. Keyser
Validation And Characterization Of Ionospheric Densities Measured By Dmsp, Herbert L. Keyser
Theses and Dissertations
Future models of the thermosphere-ionosphere-magnetosphere system will require near real-time assimilation of ionospheric parameters to specify% and forecast these regions One of the current sensors that will be used in the GAIM model is the DMSP SSIES. Knowledge of the SSIES's reliability and data characteristics is key to using the data when relying on automated processes to ingest the data. To validate the DMSP value, the DMSP-measured density is compared to ground-based ISR measurements from solar minimum to solar maximum. The DMSP data are compared to data from the ISRs located at the Millstone Hill Observatory in Massachusetts and Sondrestrom …
Design And Specification Of Dynamic, Mobile And Reconfigurable Multiagent Systems, Athie L. Self
Design And Specification Of Dynamic, Mobile And Reconfigurable Multiagent Systems, Athie L. Self
Theses and Dissertations
Multiagent Systems use the power of collaborative software agents to solve complex distributed problems. There are many Agent-Oriented Software Engineering (AOSE) methodologies available to assist system designers to create multiagent systems. However, none of these methodologies can specify agents with dynamic properties such as cloning, mobility or agent instantiation. This thesis starts the process to bridge the gap between AOSE methodologies and dynamic agent platforms by incorporating mobility into the current Multiagent Systems Engineering (MaSE) methodology. Mobility was specified within all components composing a mobile agent class. An agent component was also created that integrated the behavior of the components …
Comparative Analysis Of Traditional Versus Computer-Based Survey Instrument Response, Albert E. Franke Iv
Comparative Analysis Of Traditional Versus Computer-Based Survey Instrument Response, Albert E. Franke Iv
Theses and Dissertations
The purpose of this study was to determine if survey medium (paper versus computer) affected responses and response rates in Air Force personnel. The study compared responses and response rates from 900 randomly selected Air Force active-duty members using a paper-based survey, a computer-based survey, and a more complex computer-based survey. The first computer-based survey minimized the differences between itself and the paper-based survey to more accurately quantify any bias due solely to the computer medium. The more complex survey served to maximize differences between itself and the other computer-based survey to more accurately quantify any bias due to programmatic …
A Process For Vectoring Offensive Information Warfare As A Primary Weapon Option Within The United States Air Force, Sheila G. Bennett
A Process For Vectoring Offensive Information Warfare As A Primary Weapon Option Within The United States Air Force, Sheila G. Bennett
Theses and Dissertations
Consistently and comprehensively using Information Operations (IO) capabilities as primary weapon option within the Air Force is the next step to operationalizing IO within the Air Force. Doctrine and official guidance has set the variables of mission and concepts of operations, organizational structure, and IW players in place. The missing variable to operationalizing IO and probably the most difficult is the 'how' or process of the equation. This research will introduce a useable process that can be incorporated within the Air Force for integrating offensive IW activities into the current and given environment. The process is the basis for further …
A Traffic Pattern-Based Comparison Of Bulk Image Request Response Times For A Virtual Distributed Laboratory, David B. Hooten
A Traffic Pattern-Based Comparison Of Bulk Image Request Response Times For A Virtual Distributed Laboratory, David B. Hooten
Theses and Dissertations
Various agencies throughout the Department of Defense possess intelligence imagery and electrooptical signature data required by researchers in the field of automatic target recognition (ATR). The Air Force Research Laboratory, Sensors Directorate, as been tasked with creating a virtual distributed laboratory (VDL) which will make this data available to ATR researchers via high speed networks such as the defense research and engineering network (DREN). For this research, a model for simulating potential operational network configurations and collaboration scenarios was developed and implemented using OPNET. The results of the simulations were analyzed using statistical methods to determine the impact on performance …
Analysis Of Cloud-Free Line-Of-Sight Probability Calculations, Joseph J. Golemboski Iii
Analysis Of Cloud-Free Line-Of-Sight Probability Calculations, Joseph J. Golemboski Iii
Theses and Dissertations
Cloud-free line-of-sight probabilities were calculated using two separate methods. The first was a variation of a method developed by the Rand Corporation in 1972. In it, CFLOS probabilities were calculated using empirical data based on five years of photograms taken over Columbia, Missouri and forecasted cloud amounts rather than climatological values. The second was a new approach using the Cloud Scene Simulation Model developed by Phillips Laboratory. Cloud scenes were generated using forecasted cloud fields, meteorological inputs, and thirty random numbers. Water content files were produced and processed through a follow-on program to determine the extinction coefficients at each grid …
A Low Power Application-Specific Integrated Circuit (Asic) Implementation Of Wavelet Transform/Inverse Transform, Daniel N. Harvala
A Low Power Application-Specific Integrated Circuit (Asic) Implementation Of Wavelet Transform/Inverse Transform, Daniel N. Harvala
Theses and Dissertations
A unique ASIC was designed implementing the Haar Wavelet transform for image compression/decompression. ASIC operations include performing the Haar wavelet transform on a 512 by 512 square pixel image, preparing the image for transmission by quantizing and thresholding the transformed data, and performing the inverse Haar wavelet transform, returning the original image with only minor degradation. The ASIC is based on an existing four-chip FPGA implementation. Implementing the design using a dedicated ASIC enhances the speed, decreases chip count to a single die, and uses significantly less power compared to the FPGA implementation. A reduction of RAM accesses was realized …
The Affect Of Varying Arousal Methods Upon Vigilance And Error Detection In An Automated Command And Control Environment, Brent T. Langhals
The Affect Of Varying Arousal Methods Upon Vigilance And Error Detection In An Automated Command And Control Environment, Brent T. Langhals
Theses and Dissertations
This study focused on improving vigilance performance through developing methods to arouse subjects to the possibility of errors in a data manipulation information warfare attack. The study suggests that by continuously applying arousal stimuli, subjects would retain initially high vigilance levels thereby avoiding the vigilance decrement phenomenon and improving error detection. The research focused on which methods were the most effective as well the impact of age upon the arousability of the subjects. Further the implications of vigilance and vigilance decrement for correct detections as well as productivity were explored. The study used a simulation experiment to provide a vigilance …
Solving The Protein Structure Prediction Problem With Fast Messy Genetic Algorithms (Scaling The Fast Messy Genetic Algorithm To Medium-Sized Peptides By Detecting Secondary Structures), Steven R. Michaud
Theses and Dissertations
The ability to accurately predict a polypeptide's molecular structure given its amino acid sequence is important to numerous scientific, medical, and engineering applications. Studies have been conducted in the application of Genetic Algorithms (GAs) to this problem with promising initial results. In this thesis report, we use the fast messy Genetic Algorithm (fmGA) to attempt to find the minimization of an empirical CHARMM energy model and generation of the associated conformation. Previous work has shown that the fmGA provided favorable results, at least when applied to the pentapeptide Met-Enkephalin. We extend these results to a larger Polyalinine peptide by utilizing …
Using A Distributed Object-Oriented Database Management System In Support Of A High-Speed Network Intrusion Detection System Data Repository, Phillip W. Polk
Using A Distributed Object-Oriented Database Management System In Support Of A High-Speed Network Intrusion Detection System Data Repository, Phillip W. Polk
Theses and Dissertations
The Air Force has multiple initiatives to develop data repositories for high-speed network intrusion detection systems (IDS). All of the developed systems utilize a relational database management system (RDBMS) as the primary data storage mechanism. The purpose of this thesis is to replace the RDBMS in one such system developed by AFRL, the Automated Intrusion Detection Environment (AIDE), with a distributed object-oriented database management system (DOODBMS) and observe a number of areas: its performance against the RDBMS in terms of IDS event insertion and retrieval, the distributed aspects of the new system, and the resulting object-oriented architecture. The resulting system, …
A Model For Palladium Catalyzed Destruction Of Chlorinated Ethenes In Contaminated Groundwater, Christopher M. Stoppel
A Model For Palladium Catalyzed Destruction Of Chlorinated Ethenes In Contaminated Groundwater, Christopher M. Stoppel
Theses and Dissertations
Groundwater contamination by chlorinated ethenes is a widespread environmental problem. Conventional remediation technologies have shortcomings that have prompted further research into the development of novel treatment technologies. A palladium/ alumina catalyst in the presence of dissolved molecular hydrogen (referred to hereafter as a PD/H2 system) has been demonstrated to rapidly destroy chlorinated ethene contaminated groundwater. First-order kinetics have been used to model chlorinated ethene destruction in a PD/H2 reactor. However, catalyst deactivation and regeneration are important processes that also need to be modeled in order to better understand their effect on treatment efficiency. This study presents a model …
Photoluminescence Of Single Quantum Well Structures In Gallium Arsenide, Christian A. Bartholomew
Photoluminescence Of Single Quantum Well Structures In Gallium Arsenide, Christian A. Bartholomew
Theses and Dissertations
The continued development of state-of the-art semiconductor technologies and devices by the United States Air Force and the Department of Defense requires accurate and efficient techniques to evaluate and model these new materials. Of particular interest to the Air Force are quantum well structures which can be used for small-scale laser sources in fly-by-light applications, as efficient infrared countermeasures to heat-seeking missiles, or as advanced seekers in optically guided missiles. This thesis provides the initial experimental procedures and data necessary to begin producing accurate yet robust models. Although carrier effective masses could not be evaluated using hot-electron photoluminescence, photoluminescence excitation …
Use Of Quantum Mechanical Calculations To Investigate Small Silicon Carbide Clusters, Jean W. Henry
Use Of Quantum Mechanical Calculations To Investigate Small Silicon Carbide Clusters, Jean W. Henry
Theses and Dissertations
Density Functional Theory (DFT) method was employed to model silicon carbide small clusters. Comparing the DFT calculation results with experimental results that observed by using photoelectron spectroscopy (PES), DFT predicts the same structures that experiment observed. For electron affinity, DFT results are in good agreement with experimental results, the root mean square negative offset 0.1 eV found using medium size of basis set (cc-pVDZ+) calculation. DFT results for vibrational frequencies are in good agreement with experiment results; the root mean square error is 72.5 cm-1 wave number. 16 ground state structures of SimCn (m ≤ 4, …
Lifecycle Energy And Air Emission Differences Between Electric And Internal Combustion Vehicles, David L. Mccleese
Lifecycle Energy And Air Emission Differences Between Electric And Internal Combustion Vehicles, David L. Mccleese
Theses and Dissertations
The U.S. Federal Government has encouraged shifting from internal combustion engine vehicles (ICEVs) to electric vehicles (EVs) with three objectives, reducing foreign oil dependence, greenhouse gas emissions, and criteria pollutant emissions. This thesis uses Monte Carlo simulation to predict lifecycle emissions and energy consumption differences per kilometer driven from replacing ICEVs with three EV options: lead acid, nickel cadmium (Ni-Cd), and nickel metal hydride (NiMH). All three EV options reduce U.S. foreign oil dependence by shifting to domestic coal. The probabilities that lifecycle energy consumption per km driven improve are lead acid 76%, Ni-Cd 64%, and NiMH 90%. The probabilities …
Software Domain Model Integration Methodology For Formal Specifications, Joel C. Nonnweiler
Software Domain Model Integration Methodology For Formal Specifications, Joel C. Nonnweiler
Theses and Dissertations
Using formal methods to create automatic code generation systems is one of the goals of Knowledge Based Software Engineering (KBSE) groups. The research of the Air Force Institute of Technology KBSE group has focused on the utilization of formal languages to represent domain model knowledge within this process. The code generation process centers around correctness preserving transformations that convert domain models from their analysis representations through design to the resulting implementation code. The diversity of the software systems that can be developed in this manner is limited only by the availability of suitable domain models. Therefore it should be possible …
Selecting A Software Engineering Methodology Using Multiobjective Decision Analysis, Scott A. O'Malley
Selecting A Software Engineering Methodology Using Multiobjective Decision Analysis, Scott A. O'Malley
Theses and Dissertations
With the emergence of agent-oriented software engineering methodologies, software developers have a new set of tools to solve complex software requirements. One problem software developers face is to determine which methodology is the best approach to take to developing a solution. A number of factors go into the decision process. This thesis defines a decision making process that can be used by a software engineer to determine whether or not a software engineering approach is an appropriate system development strategy. This decision analysis process allows the software engineer to classify and evaluate a set of methodologies while specifically considering the …
Traveling Salesman Problem For Surveillance Mission Using Particle Swarm Optimization, Barry R. Secrest
Traveling Salesman Problem For Surveillance Mission Using Particle Swarm Optimization, Barry R. Secrest
Theses and Dissertations
The surveillance mission requires aircraft to fly from a starting point through defended terrain to targets and return to a safe destination (usually the starting point). The process of selecting such a flight path is known as the Mission Route Planning (MRP) Problem and is a three-dimensional, multi-criteria (fuel expenditure, time required, risk taken, priority targeting, goals met, etc.) path search. Planning aircraft routes involves an elaborate search through numerous possibilities, which can severely task the resources of the system being used to compute the routes. Operational systems can take up to a day to arrive at a solution due …
Malicious Hackers: A Framework For Analysis And Case Study, Laura J. Kleen
Malicious Hackers: A Framework For Analysis And Case Study, Laura J. Kleen
Theses and Dissertations
Recent years have seen an increase in the number and severity of Information Operations (IO) attacks upon DoD resources. At a higher level, the US as a whole has come under cyber attack by individuals and groups seeking thrills, monetary gain, publicity for their causes, and myriad other goals. This effort develops a first cut model of individual hacker mentality that can be utilized to improve threat assessment, mitigate Information Assurance (IA) vulnerabilities, and improve risk assessment. Further, it is a first step toward automated characterization of Information Warfare (IW) attacks based upon hacker types. All hackers are not the …
Dissolution Of Chromium From Inhalable Primer Paint Particles Into A Simulated Lung Fluid, David A. Kauth
Dissolution Of Chromium From Inhalable Primer Paint Particles Into A Simulated Lung Fluid, David A. Kauth
Theses and Dissertations
The use of chromate as a corrosion inhibitor in primer paint is an essential component for the protection of aluminum-skinned aircraft and the primary source of hexavalent chromium (Cr (VI)) exposure to USAF aircraft painters. The objective of this research was to quantify the dissolution of chromate from freshly sprayed paint particles into a simulated lung fluid (SLF). Two primer paints were sprayed with a paint spray gun to generate overspray particles for collection into impingers filled with SLF. Particles were allowed to soak in SLF for 24 and 48 hours and then the particles were removed by centrifugation. The …