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Full-Text Articles in Physical Sciences and Mathematics

Testing The Adequacy Of A Semi-Markov Process, Richard S. Seymour Sep 2015

Testing The Adequacy Of A Semi-Markov Process, Richard S. Seymour

Theses and Dissertations

Due to the versatility of its structure, the semi-Markov process is a powerful modeling tool used to describe complex systems. Though similar in structure to continuous time Markov chains, semi-Markov processes allow for any transition time distribution which enables these processes to t a wider range of problems than the continuous time Markov chain. While semi-Markov processes have been applied in fields as varied as biostatistics and finance, there does not exist a theoretically-based, systematic method to determine if a semi-Markov process accurately fits the underlying data used to create the model. In fields such as regression and analysis of …


Temperature Dependent Rubidium-Helium Line Shapes And Fine Structure Mixing Rates, Wooddy S. Miller Sep 2015

Temperature Dependent Rubidium-Helium Line Shapes And Fine Structure Mixing Rates, Wooddy S. Miller

Theses and Dissertations

Diode Pumped Alkali Lasers (DPALs) are a new type of laser that uses alkali metal vapor as a gain medium and a buffer gas to control the line shape and kinetics. While these systems were first demonstrated in 2003 [48] they have just recently been scaled to the kilowatt power levels in 2012 [18]. To achieve these powers, the design of the gain cell relied on a set of incomplete line shape and kinetic data. The current focus areas of DPAL research are the continued power scaling of the systems and basic science research into the rates involved within the …


An Analysis Of Conus Based Deployment Of Pseudolites For Positioning, Navigation And Timing (Pnt) Systems, Justin H. Deifel, Albert J. Pena Sep 2015

An Analysis Of Conus Based Deployment Of Pseudolites For Positioning, Navigation And Timing (Pnt) Systems, Justin H. Deifel, Albert J. Pena

Theses and Dissertations

The Global Positioning System (GPS) developed and operated by the United States Air Force (USAF) provides a way for users to determine position, navigation and timing (PNT). GPS provides an extraordinary capability that has become instrumental in all aspects of our day to day lives. As new technologies such as automated vehicles and unmanned aircraft continue to be developed, a reliable back up to GPS is required to ensure the PNT data generated in these systems is accurate. This research studies a potential architecture for deploying a nationwide network of ground based pseudolites that would act to supplement and backup …


Sediment Loss And Its Cause In Puerto Rico Watersheds, Y. Yuan, Y. Jiang, E. V. Taugas, Eric G. Mbonimpa Sep 2015

Sediment Loss And Its Cause In Puerto Rico Watersheds, Y. Yuan, Y. Jiang, E. V. Taugas, Eric G. Mbonimpa

Faculty Publications

A major environmental concern in the Commonwealth of Puerto Rico is increased sediment load to water reservoirs, to estuaries, and finally to coral reef areas outside the estuaries. Sediment deposition has significantly reduced the storage capacity of reservoirs, and sediments, with their associated contaminants and nutrients that are adsorbed, can stress corals and negatively impact reef health. To prevent and manage sediment loss it is therefore important to understand local soil erosion and sediment transport processes. The main objective of this study was to determine the influence of landscape characteristics on sediment loss. We analyzed available precipitation and sediment data …


Experimentally Generating Any Desired Partially Coherent Schell-Model Source Using Phase-Only Control, Milo W. Hyde Iv, Santasri Basu, David G. Voelz, Xifeng Xiao Sep 2015

Experimentally Generating Any Desired Partially Coherent Schell-Model Source Using Phase-Only Control, Milo W. Hyde Iv, Santasri Basu, David G. Voelz, Xifeng Xiao

Faculty Publications

A technique is presented to produce any desired partially coherent Schell-model source using a single phase-only liquid-crystal spatial light modulator (SLM). Existing methods use SLMs in combination with amplitude filters to manipulate the phase and amplitude of an initially coherent source. The technique presented here controls both the phase and amplitude using a single SLM, thereby making the amplitude filters unnecessary. This simplifies the optical setup and significantly increases the utility and flexibility of the resulting system. The analytical development of the technique is presented and discussed. To validate the proposed approach, experimental results of three partially coherent Schell-model sources …


Experimental And Theoretical Basis For A Closed-Form Spectral Brdf Model, Samuel D. Butler Sep 2015

Experimental And Theoretical Basis For A Closed-Form Spectral Brdf Model, Samuel D. Butler

Theses and Dissertations

The microfacet class of BRDF models is frequently used to calculate optical scatter from realistic surfaces using geometric optics, but has the disadvantage of not being able to consider wavelength dependence. This dissertation works toward development of a closed-form approximation to the BRDF that is suitable for hyperspectral remote sensing by presenting measured BRDF data of 12 different materials at four different incident angles and up to seven different wavelengths between 3.39 and 10.6 micrometer. The data was intended to be fit to various microfacet BRDF models to determine an appropriate form of the wavelength scaling. However, when fitting the …


Improved Terahertz Modulation Using Germanium Telluride (Gete) Chalcogenide Thin Films, Alexander H. Gwin, Christopher H. Kodama, Tod V. Laurvick, Ronald Coutu Jr., Philip F. Taday Jul 2015

Improved Terahertz Modulation Using Germanium Telluride (Gete) Chalcogenide Thin Films, Alexander H. Gwin, Christopher H. Kodama, Tod V. Laurvick, Ronald Coutu Jr., Philip F. Taday

Faculty Publications

We demonstrate improved terahertz (THz) modulation using thermally crystallized germanium telluride (GeTe) thin films. GeTe is a chalcogenide material that exhibits a nonvolatile, amorphous to crystalline phase change at approximately 200 °C, as well as six orders of magnitude decreased electrical resistivity. In this study, amorphous GeTe thin films were sputtered on sapphire substrates and then tested using THz time-domain spectroscopy (THz-TDS). The test samples, heated in-situ while collecting THz-TDS measurements, exhibited a gradual absorbance increase, an abrupt nonvolatile reduction at the transition temperature, followed by another gradual increase in absorbance. The transition temperature was verified by conducting similar thermal …


Identifying The Experimental And Theoretical Effective Characteristics Of Nonaligned Anisotropic Metamaterials, Michael R. Benson Jun 2015

Identifying The Experimental And Theoretical Effective Characteristics Of Nonaligned Anisotropic Metamaterials, Michael R. Benson

Theses and Dissertations

Previous research into anisotropic materials has assumed certain properties in order to make the underlying mathematics tractable. One of the assumptions is the alignment of the optical axes with the laboratory frame of reference, such as split-ring resonators lying at on the material plane. This assumption does not hold true for many metamaterials, such as tilted nanorods. Techniques such as ellipsometry are needed to analyze the effective characteristics of these highly anisotropic structures. In this research, tilted nanorods are analyzed using generalized ellipsometry to extract the indices of the optical axes. The underlying physics of ellipsometry is then used to …


Coupling Nuclear Induced Phonon Propagation With Conversion Electron Mössbauer Spectroscopy, Michael J. Parker Jun 2015

Coupling Nuclear Induced Phonon Propagation With Conversion Electron Mössbauer Spectroscopy, Michael J. Parker

Theses and Dissertations

Mössbauer spectroscopy is a very sensitive measurement technique (10-8 eV) which prompted motivation for the experiment described in this thesis. Namely, can a sensitive detection system be developed to detect nuclear recoils on the order of 10 to 100 of eVs? The hypothesis that this thesis tests is: Nuclear induced phonon bursts caused by Rutherford scattered alphas, decayed from 241Am, in a type-310 stainless steel material can couple with 7.3 keV conversion electron Mössbauer events at the other end of the material which will have a statistically significant effect on a Mössbauer spectrum. The phonon bursts produced by …


Auto-Concealment Of Supersymmetry In Extra Dimensions, Savas Dimopoulos, Kiel Howe, John March-Russell, James A. Scoville Jun 2015

Auto-Concealment Of Supersymmetry In Extra Dimensions, Savas Dimopoulos, Kiel Howe, John March-Russell, James A. Scoville

Faculty Publications

In supersymmetric (SUSY) theories with extra dimensions the visible energy in sparticle decays can be significantly reduced and its energy distribution broadened, thus significantly weakening the present collider limits on SUSY. The mechanism applies when the lightest supersymmetric particle (LSP) is a bulk state — e.g. a bulk modulino, axino, or gravitino — the size of the extra dimensions ≳ 10−14 cm, and for a broad variety of visible sparticle spectra. In such cases the lightest ordinary supersymmetric particle (LOSP), necessarily a brane-localised state, decays to the Kaluza-Klein (KK) discretuum of the LSP. This dynamically realises the compression mechanism …


A Boost For The Ew Susy Hunt: Monojet-Like Search For Compressed Sleptons At Lhc14 With 100 Fb-1, Alan Barr, James A. Scoville Apr 2015

A Boost For The Ew Susy Hunt: Monojet-Like Search For Compressed Sleptons At Lhc14 With 100 Fb-1, Alan Barr, James A. Scoville

Faculty Publications

Current Large Hadron Collider (LHC) analyses are blind to compressed supersymmetry (SUSY) models with sleptons near the lightest super partner (LSP) in mass: {m}_{\tilde{l}}-{m}_{{\tilde{\chi}}_1^0} ≡ Δm ≲ 60 GeV. We present a search sensitive to the very compressed range 1 3 GeV < Δm < 24 GeV using the channel pp\to {\tilde{l}}^{+}{\tilde{l}}^{-} + jet → {l}^{+}{l}^{-}{\tilde{\chi}}_1^0{\tilde{\chi}}_1^0 + jet with soft same-flavor leptons and one hard jet from initial state radiation (pJT > 100 GeV). The sleptons recoil against the jet boosting them and their decay products, making the leptons detectable and providing substantial missing transverse momentum. We use the kinematic variable mT2 along with a different-flavor control region to reduce the large standard model backgrounds and control systematic uncertainty. We find the analysis should allow LHC14 with 100 …


Interstitial Silicon Ions In Rutile Tio2 Crystals, Eric M. Golden, Nancy C. Giles, Shan Yang, Larry E. Halliburton Apr 2015

Interstitial Silicon Ions In Rutile Tio2 Crystals, Eric M. Golden, Nancy C. Giles, Shan Yang, Larry E. Halliburton

Faculty Publications

Electron paramagnetic resonance (EPR) is used to identify a new and unique photoactive silicon-related point defect in single crystals of rutile TiO2. The importance of this defect lies in its assignment to interstitial silicon ions and the unexpected establishment of silicon impurities as a major hole trap in TiO2. Principal g values of this new S=1/2 center are 1.9159, 1.9377, and 1.9668 with principal axes along the [¯110],[001], and [110] directions, respectively. Hyperfine structure in the EPR spectrum shows the unpaired spin interacting equally with two Ti nuclei and unequally with two Si nuclei. These silicon …


Symmetry Groups For Linear Programming Relaxations Of Orthogonal Array Problems, David M. Arquette Mar 2015

Symmetry Groups For Linear Programming Relaxations Of Orthogonal Array Problems, David M. Arquette

Theses and Dissertations

Integer linear programs arise in many situations, and solving such problems can be computationally demanding. One way to solve them more efficiently is by exploiting the symmetry within their formulation. This paper proves that the symmetry group for the linear programming relaxation of 2-level orthogonal array problems of strength 2 is a particular semidirect product.


Accuracy Of Time Phasing Aircraft Development Using The Continuous Distribution Function, Gregory E. Brown Mar 2015

Accuracy Of Time Phasing Aircraft Development Using The Continuous Distribution Function, Gregory E. Brown

Theses and Dissertations

Early research on time phasing primarily focuses on the theoretical foundation for applying the continuous distribution function, or S-curve, to model the distribution of development expenditures. Minimal methodology is provided for estimating the S-curve's parameter values. Brown, White, and Gallagher (2002) resolve this shortcoming through regression analysis, but their methodology has not been widely adopted by aircraft cost analysts, as it is judged as overly broad and not specific to aircraft. Instead, analysts commonly apply the 60/40 rule of thumb to aircraft development, assuming 60 percent expenditures at 50 percent schedule. It is currently unknown if the 60/40 heuristic accurately …


The Unified Behavior Framework For The Simulation Of Autonomous Agents, Daniel M. Roberson Mar 2015

The Unified Behavior Framework For The Simulation Of Autonomous Agents, Daniel M. Roberson

Theses and Dissertations

Since the 1980s, researchers have designed a variety of robot control architectures intending to imbue robots with some degree of autonomy. A recently developed architecture, the UBF, implements a variation of the three-layer architecture with a reactive controller to rapidly make behavior decisions. Additionally, the UBF utilizes software design patterns that promote the reuse of code and free designers to dynamically switch between behavior paradigms. This paper explores the application of the UBF to the simulation domain. By employing software engineering principles to implement the UBF architecture within an open-source simulation framework, we have extended the versatility of both. The …


Constructing Cost-Effective And Targetable Ics Honeypots Suited For Production Networks, Michael M. Winn Mar 2015

Constructing Cost-Effective And Targetable Ics Honeypots Suited For Production Networks, Michael M. Winn

Theses and Dissertations

Honeypots are a technique that can mitigate the risk of cyber threats. Effective honeypots are authentic and targetable, and their design and implementation must accommodate risk tolerance and financial constraints. The proprietary, and often expensive, hardware and software used by Industrial Control System (ICS) devices creates the challenging problem of building a flexible, economical, and scalable honeypot. This research extends Honeyd into Honeyd+, making it possible to use the proxy feature to create multiple high interaction honeypots with a single Programmable Logic Controller (PLC). Honeyd+ is tested with a network of 75 decoy PLCs, and the interactions with the decoys …


Tactical Ai In Real Time Strategy Games, Donald A. Gruber Mar 2015

Tactical Ai In Real Time Strategy Games, Donald A. Gruber

Theses and Dissertations

The real time strategy (RTS) tactical decision making problem is a difficult problem. It is generally more complex due to its high degree of time sensitivity. This research effort presents a novel approach to this problem within an educational, teaching objective. Particular decision focus is target selection for a artificial intelligence (AI) RTS game model. The use of multi-objective evolutionary algorithms (MOEAs) in this tactical decision making problem allows an AI agent to make fast, effective solutions that do not require modification to the current environment. This approach allows for the creation of a generic solution building tool that is …


Recent Advances In Compressed Sensing: Discrete Uncertainty Principles And Fast Hyperspectral Imaging, Megan E. Lewis Mar 2015

Recent Advances In Compressed Sensing: Discrete Uncertainty Principles And Fast Hyperspectral Imaging, Megan E. Lewis

Theses and Dissertations

Compressed sensing is an important field with continuing advances in theory and applications. This thesis provides contributions to both theory and application. Much of the theory behind compressed sensing is based on uncertainty principles, which state that a signal cannot be concentrated in both time and frequency. We develop a new discrete uncertainty principle and use it to demonstrate a fundamental limitation of the demixing problem, and to provide a fast method of detecting sparse signals. The second half of this thesis focuses on a specific application of compressed sensing: hyperspectral imaging. Conventional hyperspectral platforms require long exposure times, which …


Examining The Return On Investment Of Test And Evaluation, Nathan C. Smith Mar 2015

Examining The Return On Investment Of Test And Evaluation, Nathan C. Smith

Theses and Dissertations

This research examined the return on investment of Department of Defense test and evaluation. The thesis analyzed the return on investment of the cost avoidance achieved if an issue discovered late in the program had been discovered and corrected during developmental test and evaluation. The methodology utilized two case study examples from the Joint Primary Training Aircraft System to calculate the potential cost avoidance and the potential return on investment if the program had discovered and corrected the issues during developmental test and evaluation. The result of one case was a 9,260% return on investment. The other case results ranged …


Unified Behavior Framework For Discrete Event Simulation Systems, Alexander J. Kamrud Mar 2015

Unified Behavior Framework For Discrete Event Simulation Systems, Alexander J. Kamrud

Theses and Dissertations

Intelligent agents provide simulations a means to add lifelike behavior in place of manned entities. Generally when developed, a single intelligent agent model is chosen, such as rule based, behavior trees, etc. This choice introduces restrictions into what behaviors agents can manifest, and can require significant testing in edge cases. This thesis presents the use of the UBF in the AFSIM environment. The UBF provides the flexibility to implement any and all intelligent agent models, allowing the developer to choose the model he/she feels best fits the experiment at hand. Furthermore, the UBF demonstrates several key software engineering principles through …


Evaluating Machine Learning Classifiers For Hybrid Network Intrusion Detection Systems, Michael D. Rich Mar 2015

Evaluating Machine Learning Classifiers For Hybrid Network Intrusion Detection Systems, Michael D. Rich

Theses and Dissertations

Existing classifier evaluation methods do not fully capture the intended use of classifiers in hybrid intrusion detection systems (IDS), systems that employ machine learning alongside a signature-based IDS. This research challenges traditional classifier evaluation methods in favor of a value-focused evaluation method that incorporates evaluator-specific weights for classifier and prediction threshold selection. By allowing the evaluator to weight known and unknown threat detection by alert classification, classifier selection is optimized to evaluator values for this application. The proposed evaluation methods are applied to a Cyber Defense Exercise (CDX) dataset. Network data is processed to produce connection-level features, then labeled using …


Git As An Encrypted Distributed Version Control System, Russell G. Shirey Mar 2015

Git As An Encrypted Distributed Version Control System, Russell G. Shirey

Theses and Dissertations

This thesis develops and presents a secure Git implementation, Git Virtual Vault (GV2), for users of Git to work on sensitive projects with repositories located in unsecure distributed environments, such as in cloud computing. This scenario is common within the Department of Defense, as much work is of a sensitive nature. In order to provide security to Git, additional functionality is added for confidentiality and integrity protection. This thesis examines existing Git encryption implementations and baselines their performance compared to unencrypted Git. Real-world Git repositories are examined to characterize typical Git usage and determine if the existing Git encryption implementations …


Effects Of Data Replication On Data Exfiltration In Mobile Ad Hoc Networks Utilizing Reactive Protocols, Corey T. Willinger Mar 2015

Effects Of Data Replication On Data Exfiltration In Mobile Ad Hoc Networks Utilizing Reactive Protocols, Corey T. Willinger

Theses and Dissertations

A swarm of autonomous UAVs can provide a significant amount of ISR data where current UAV assets may not be feasible or practical. As such, the availability of the data the resides in the swarm is a topic that will benefit from further investigation. This thesis examines the impact of le replication and swarm characteristics such as node mobility, swarm size, and churn rate on data availability utilizing reactive protocols. This document examines the most prominent factors affecting the networking of nodes in a MANET. Factors include network routing protocols and peer-to-peer le protocols. It compares and contrasts several open …


Utilizing Four Dimensional Lightning And Dual-Polarization Radar To Develop Lightning Initiation Forecast Guidance, Andrew J. Travis Mar 2015

Utilizing Four Dimensional Lightning And Dual-Polarization Radar To Develop Lightning Initiation Forecast Guidance, Andrew J. Travis

Theses and Dissertations

Lightning initiation is a major forecast challenge faced by Air Force's 45th Weather Squadron (45 WS), which provides weather support to Cape Canaveral Air Force Station and Kennedy Space Center (KSC). Prior studies by Thurmond (2014) and Woodard (2011) have shown that dual-polarization (DP) radar can be used to identify the presence of hydrometeors indicative of cloud charging, leading to improved lightning initiation forecasts. The 45 WS currently employs empirical lightning initiation forecast rules which state that in-cloud lightning is likely when radar reflectivity meets or exceeds 37.0 dBZ above the -10°C height. This study examined 249 convective cells from …


Scaling Of An Optically Pumped Mid-Infrared Rubidium Laser, Paul J. Moran Mar 2015

Scaling Of An Optically Pumped Mid-Infrared Rubidium Laser, Paul J. Moran

Theses and Dissertations

An optically pumped mid-infrared rubidium (Rb) pulsed laser has been demonstrated in a heat pipe along the 62P3/2 - 62S1/2 transition at 2.730 µm and the 62P1/2 - 62S1/2 transition at 2.790 µm. The bleached limit, slope efficiency, and maximum laser output energy of the mid-IR Rb laser have been shown to scale linearly with increasing Rb density, contrary to prior laser demonstrations. A maximum output energy of 5 nJ per pulse had previously been observed before a rollover occurred in the scaling of output energy with Rb …


Absorption Spectroscopy Of Rubidium In An Alkali Metal Dispenser Cell And Bleached Wave Analysis, James M. Rosenthal Mar 2015

Absorption Spectroscopy Of Rubidium In An Alkali Metal Dispenser Cell And Bleached Wave Analysis, James M. Rosenthal

Theses and Dissertations

An absorption spectrum of a rubidium alkali metal dispenser (AMD) cell was obtained in order to determine the system s suitability for use in a diode pumped alkali laser (DPAL) and use in high-temperature spectroscopic studies. The AMD produced a concentration of 3.65 0.16 1010 cm-3, which is in the ideal range for Beer s Law region absorption spectroscopy, but too low to make a high-power DPAL in a 10 cm cell with a poor Q resonator. Before AMDs can be used to determine pressure broadening and shifting coefficients, issues concerning contamination and producing rubidium vapor at pressure must be …


Photon Sieve Bandwidth Broadening By Reduction Of Chromatic Aberration Effects Using Second-Stage Diffractive Optics, Christopher M. Tulip Mar 2015

Photon Sieve Bandwidth Broadening By Reduction Of Chromatic Aberration Effects Using Second-Stage Diffractive Optics, Christopher M. Tulip

Theses and Dissertations

A photon sieve is a lightweight diffractive optic which can be useful for space-based imaging applications. It is limited by chromatic aberration and a narrow bandwidth. A Fresnel zone plate is used to counteract this effect in a manner similar to that accomplished with a traditional holographic corrector. First, a radiometric analysis established a target for bandwidth improvement. Next, a sieve was designed, fabricated, and characterized. Third, the bandwidth-broadening correction scheme was developed to correct primary chromatic aberration. Finally, a zone plate was designed, fabricated, and tested. Performance of the corrected system was measured over the target bandwidth. The corrected …


The Use Of Ultra-Violet (Uv) Light Emitting Diodes (Leds) In An Advanced Oxidation Process (Aop) With Brilliant Blue Fcf As An Indicator, Robert W. Scott Iv Mar 2015

The Use Of Ultra-Violet (Uv) Light Emitting Diodes (Leds) In An Advanced Oxidation Process (Aop) With Brilliant Blue Fcf As An Indicator, Robert W. Scott Iv

Theses and Dissertations

Water contamination can result from terrorist acts, industrial accidents, or natural phenomena. Advanced Oxidation Processes (AOPs) represent a potentially useful method for water decontamination. This research explored the application of Brilliant Blue FCF as a witness dye in an Advanced Oxidation Process (AOP) employing Ultra-Violet (UV) Light Emitting Diodes (LEDs) with peroxide (H2O2). In addition to exploring the attributes of Brilliant Blue FCF within this application, this research employed this dye to evaluate the effect of varied UV LED duty cycles (pulsing) on the reaction rates of a UV/H2O2 AOP. Experiments performed using …


Distributed Kernelized Locality-Sensitive Hashing For Faster Image Based Navigation, Scott A. Hutchison Mar 2015

Distributed Kernelized Locality-Sensitive Hashing For Faster Image Based Navigation, Scott A. Hutchison

Theses and Dissertations

Content based image retrieval (CBIR) remains one of the most heavily researched areas in computer vision. Different image retrieval techniques and algorithms have been implemented and used in localization research, object recognition applications, and commercially by companies such as Facebook, Google, and Yahoo!. Current methods for image retrieval become problematic when implemented on image datasets that can easily reach billions of images. In order to process extremely large datasets, the computation must be distributed across a cluster of machines using software such as Apache Hadoop. There are many different algorithms for conducting content based image retrieval, but this research focuses …


Assessing Predictive Ability Of Three Auroral Precipitation Models Using Dmsp Energy Flux, Cory T. Lane, Ariel O. Acebal, Yihua Zheng Feb 2015

Assessing Predictive Ability Of Three Auroral Precipitation Models Using Dmsp Energy Flux, Cory T. Lane, Ariel O. Acebal, Yihua Zheng

Faculty Publications

Our study statistically compares the total energy flux outputs of Newell et al.'s (2010a) oval variation, assessment, tracking, intensity, and online nowcasting (OVATION) Prime model, Hardy et al.'s (1991) Kp‐based model, and a coupled Space Weather Modeling Framework ring current model to energy flux data obtained from 2198 Defense Meteorological Satellite Program (DMSP) satellite passes in the Northern Hemisphere. Our DMSP data set includes 28 days grouped into continuous 3 and 4 day periods between 2000 and 2008 and encompasses magnetic local times (MLTs) between 04:00 and 21:00. We obtain the most equatorward magnetic latitude coordinate, where a DMSP satellite …