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Articles 961 - 990 of 8791
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Potential Solution To Meet Growing Demands Of Refractory Metal: Selective Laser Melting Of Molybdenum-Tungsten Alloy, Jae Yu
Theses and Dissertations
Selective laser melting (SLM) of refractory metals has been of high interest in research due to the metals’ potential desirable characteristics in aeronautical and space applications. In particular, molybdenum and tungsten have been the focus of several studies in the search for high temperature and high strength purposes in applications like supersonic aircraft, re-entry vehicles, nuclear fission, power generation, and other space systems. However, there is still a significant knowledge gap to process defect-free alloys and making use of them in practical engineering functions. The aim of this study is to characterize the relationship between the microstructure and mechanical properties …
Analysis Of Generalized Artificial Intelligence Potential Through Reinforcement And Deep Reinforcement Learning Approaches, Jonathan Turner
Analysis Of Generalized Artificial Intelligence Potential Through Reinforcement And Deep Reinforcement Learning Approaches, Jonathan Turner
Theses and Dissertations
Artificial Intelligence is the next competitive domain; the first nation to develop human level artificial intelligence will have an impact similar to the development of the atomic bomb. To maintain the security of the United States and her people, the Department of Defense has funded research into the development of artificial intelligence and its applications. This research uses reinforcement learning and deep reinforcement learning methods as proxies for current and future artificial intelligence agents and to assess potential issues in development. Agent performance were compared across two games and one excursion: Cargo Loading, Tower of Hanoi, and Knapsack Problem, respectively. …
Thermal Considerations For Film Cooling Materials With Anisotropic Thermal Conductivity, Carol E. Bryant
Thermal Considerations For Film Cooling Materials With Anisotropic Thermal Conductivity, Carol E. Bryant
Theses and Dissertations
Higher performance requirements and reduced core sizes are driving increases in turbine inlet temperature in gas turbine engines, surpassing the melting point of advanced materials. Newer materials, such as composites, are being introduced into the hot sections of gas turbine engines. Components in the hot section use film cooling to prevent melting. One unique aspect of some high-temperature composites is they have a bulk anisotropic thermal conductivity, therefore heat flow differs relative to traditional metallic components. Film cooling designs can be revolutionized by leveraging anisotropy in high-temperature materials. The purpose of this research is to examine thermal considerations for using …
Optimization Of A Multi-Layered Target For A Pulsed Power Neutron Source, Zachary D. Bretz
Optimization Of A Multi-Layered Target For A Pulsed Power Neutron Source, Zachary D. Bretz
Theses and Dissertations
The ability to create neutron environments is critical fora wide variety of applications including national security, materials science, and medical research. It is also helpful in medical, material, and other research. The U.S. Naval Research Laboratory (NRL), Washington, DC, is interested in leveraging their pulsed-power facilities to produce an in-house, relatively inexpensive neutron source. NRL’s facilities produce 2 MeV (from Gamble II) and 5 MeV (from Mercury) protons and deuterons. This research explored combinations of target materials to produce the most neutrons in the forward direction. Models of the reactions involved were first validated against literature experiments, then target designs …
Double Cone Flow Field Reconstruction Between Mach 4 And 12 Using Machine Learning Techniques, Trevor A. Toros
Double Cone Flow Field Reconstruction Between Mach 4 And 12 Using Machine Learning Techniques, Trevor A. Toros
Theses and Dissertations
No abstract provided.
A United States Air Force Site Selection Methodology In A Contested Agile Combat Employment Environment, Zachary T. Moer
A United States Air Force Site Selection Methodology In A Contested Agile Combat Employment Environment, Zachary T. Moer
Theses and Dissertations
The United States Air Force’s (USAF) Agile Combat Employment (ACE) strategy relies on host country access and underlying local infrastructure to facilitate airpower. However, numerous factors, including peer-to-peer threats, complex geopolitics, and intricate supply chain management, often complicate site access and thwart site selection decisions. When shaping the battlespace for future conflict, strategists and planners face the difficult task of identifying optimal locations to conduct adaptive basing operations given these complicating factors. Multi-Criteria Decision Analysis (MCDA) can help strategists appropriately account for competing objectives and maintain a competitive advantage with theater adversaries. This thesis presents an MCDA model that evaluates …
Capability Development For Advanced (N,X) Nuclear Data Measurements, Brian G. Frandsen
Capability Development For Advanced (N,X) Nuclear Data Measurements, Brian G. Frandsen
Theses and Dissertations
Nuclear reaction data are the heart of radiation transport calculations, models, and simulations. Unique approaches are required to improve the measurement capability for many reactions where data are inaccurate or do not exist. First, the newly developed Gamma Energy Neutron Energy Spectrometer for Inelastic Scattering (GENESIS) provides the ability to measure neutron inelastic scattering cross sections on different targets. An initial experiment measuring the 16O(n,n’��) reaction calculated the count rate from the second excited state using the full energy and escape peaks. Second, a set of photocurable scintillator resin formulations capable of neutron-gamma discrimination were developed to support light-based …
Formulation And Characterization Of Fast-Curing Plastic Scintillators With High-Z Loading, Theodore W. Stephens
Formulation And Characterization Of Fast-Curing Plastic Scintillators With High-Z Loading, Theodore W. Stephens
Theses and Dissertations
Development of novel fast-curing plastic scintillators is highly advantageous due to their potential to be manufactured via 3D printing. Several formulations were developed that exhibit enhanced photon sensitivity, producing modest but discernible photopeaks at an incident gamma energy of 122 keV. The photon sensitivity is achieved via bismuth high-Z loading; however, this practice typically results in diminished light yields. Subsequent formulations, which varied the photoinitiator concentration and curing time, demonstrated successful curing with sufficient plastic hardness, reduced purple discoloration, reduced heat buildup during curing, and resulted in less cracking during the curing process, all of which were correlated with lower …
Evaluating Neural Network Decoder Performance For Quantum Error Correction Using Various Data Generation Models, Brett M. Martin
Evaluating Neural Network Decoder Performance For Quantum Error Correction Using Various Data Generation Models, Brett M. Martin
Theses and Dissertations
Neural networks have been shown in the past to perform quantum error correction (QEC) decoding with greater accuracy and efficiency than algorithmic decoders. Because the qubits in a quantum computer are volatile and only usable on the order of milliseconds before they decohere, a means of fast quantum error correction is necessary in order to correct data qubit errors within the time budget of a quantum algorithm. Algorithmic decoders are good at resolving errors on logical qubits with only a few data qubits, but are less efficient in systems containing more data qubits. With neural network decoders, practical quantum computation …
Magnetic Flux Channel Antenna Design In Conformal Applications, William J. Tremblay
Magnetic Flux Channel Antenna Design In Conformal Applications, William J. Tremblay
Theses and Dissertations
Magnetic Flux Channels (MFC) and Magneto-Dielectric Wire Antennas (MDWA) are effective, and in some cases, superior alternatives to traditional metallic antennas, in conformal and electrically small applications at the cost of fabrication and feed complexity. The frequency dispersive nature of magnetic material constituent parameters imposes constraints on the antenna design process, which were not fully developed in prior art. This research quantifies the key differences between the operating regions of magneto-dielectric materials for antenna applications and demonstrates the effectiveness of numerical method augmented modal analysis in the design process, regardless of operating region. Modeling challenges associated with MDWAs are addressed …
Examining Failures Of Kc-135s Using Survival Analysis, Vanessa I. R. Unseth
Examining Failures Of Kc-135s Using Survival Analysis, Vanessa I. R. Unseth
Theses and Dissertations
The United States Air Force manages an inventory of 396 KC-135 Stratotanker aircraft. With mission capability rates falling and total non-mission capability supply rates increasing, it is necessary to take a deeper look at recurrent failures. The study applies non-parametric and semi-parametric survival models to a dataset retrieved from LIMS-EV to look at the duration(s) until failure for the KC-135. Results of non-parametric models show cumulative failure rates increase as sorties or flight hours increase. In addition, semi-parametric models or Cox proportional hazards models with frailty confirm that locations or air bases are not associated with recurrent failures.
Surrogate Modeling Of Computational Aerodynamic Responses For A Generic Hypersonic Vehicle, Jacob R. Johanik
Surrogate Modeling Of Computational Aerodynamic Responses For A Generic Hypersonic Vehicle, Jacob R. Johanik
Theses and Dissertations
In the field of multidisciplinary hypersonic vehicle design, striking the balance between the accuracy and efficiency of a predictive aerodynamic response model is a significant challenge. In response to this challenge, the objective of this thesis is to evaluate the aerodynamic performance of a Generic Hypersonic Vehicle (GHV) using the technique of surrogate modeling Computational Fluid Dynamic data points across a large range of flight conditions. To accomplish this, the full CFD process was conducted by preparing the vehicle geometry, generating a grid, computing the flow, and post-processing the data. A three-dimensional, quasi-random distribution of 1000 points defined the design …
Deep Learning Approach To Multi-Phenomenological Nuclear Fuel Cycle Signals For Nonproliferation Applications, Preston J. Dicks
Deep Learning Approach To Multi-Phenomenological Nuclear Fuel Cycle Signals For Nonproliferation Applications, Preston J. Dicks
Theses and Dissertations
In order to reduce the time required for data analysis and decision-making relevant to nuclear proliferation detection, Artificial Intelligence (AI) techniques are applied to multi-phenomenological signals emitted from nuclear fuel cycle facilities to identify non-human readable characteristic signatures of operations for use in detecting proliferation activities. Seismic and magnetic emanations were collected in the vicinity of the High Flux Isotope Reactor (HFIR) and the McClellan Nuclear Research Center (MNRC). A novel bi-phenomenology DL network is designed to test the viability of transfer learning between nuclear reactor facilities. It is found that the network produces an 84.1% accuracy (99.4% without transient …
Prioritizing Water Distribution Network Asset Maintenance Using Graph Theory Methods, Ashton E. Doyal
Prioritizing Water Distribution Network Asset Maintenance Using Graph Theory Methods, Ashton E. Doyal
Theses and Dissertations
Water distribution networks, like any other large infrastructure system, should be designed for reliability and resilience to resist failure. A literature review of graph theory methods pertaining to water distribution networks reveals a wide scope of mathematical and statistical measures that can be used to identify and classify many important features of a network. From this, an analysis using a combination of graph theory metrics and generated condition indices for the pipes is performed on the Tyndall drinking water system as a case study. The goal is to provide understanding to the risk of the current system and propose asset …
Analysis Of Microscopic Carbon Fiber Fragments, Zachary R. Scott
Analysis Of Microscopic Carbon Fiber Fragments, Zachary R. Scott
Theses and Dissertations
Carbon Fiber (CF) has different tensile strengths and transverse moduli depending on how they are fabricated. Some CF is export controlled as it can be used for weapons, spacecraft, or gas centrifuges for enriching nuclear fuel. This research project explored a new way to prepare micron sized single CF threads to measure their transverse modulus and compare the moduli of non-export controlled CF to that of an export controlled CF. Five total polyacrylonitrile (PAN) fibers were used in this project, one of which was an export controlled fiber.
Simulating Autonomous Cruise Missile Swarm Behaviors In An Anti-Access Area Denial (A2ad) Environment, Kyle W. Goggins
Simulating Autonomous Cruise Missile Swarm Behaviors In An Anti-Access Area Denial (A2ad) Environment, Kyle W. Goggins
Theses and Dissertations
The increasingly sophisticated anti-access area denial (A2AD) threat imposed by the modern integrated air defense system (IADS), coupled with the decreasingly potent advantage provided by high-end stealth platforms, has prompted Air Force senior leaders to invest in radically changing the nature of air power for the year 2030 and beyond. A prominent element of this new vision is weapon swarming, which aims to address this challenge by overwhelming the IADS with huge numbers of low-cost, attritable aerial assets emboldened by autonomous capabilities. This research proposes a framework for classifying the different levels of autonomous capability along three independent dimensions—namely ability …
Neutron Spectral Effect On Microelectronic Performance Response, Wade Kloppenburg
Neutron Spectral Effect On Microelectronic Performance Response, Wade Kloppenburg
Theses and Dissertations
Response of 2N2222 bipolar junction transistors to neutrons from a pulsed thermonuclear or pulsed fission source are researched. Measurements used for comparing performance included the base-collector junction current-voltage and capacitance-voltage characteristics and device gain degradation. Little change was detected in steady-state operation of the base-collector junction, but evidence in the dynamic and capacitance measurements establish effects based on environment. Experimental results are compared to literature results and parameters are explored using a device model simulation code.
Burn Probability And Climate Change: A Quantitative Evaluation Of The Temporal Alterations Of Wildfire, David N. Robinson
Burn Probability And Climate Change: A Quantitative Evaluation Of The Temporal Alterations Of Wildfire, David N. Robinson
Theses and Dissertations
The intensity of extreme weather events, specifically wildfires, along the West Coast has slowly grown overtime due to atmospheric changes caused by climate change. The Air Force, though aware of the threat that is wildfire, does not currently have a quantitative way to assess the hazard to base locations. In this paper, burn probability is quantitatively calculated through the geospatial analysis programs to provide a means of assessing wildfire vulnerability. The FlamMap fire simulator generated burn probabilities for Vandenberg Air Force Base using climate data generated by the remote automated weather station on the base to highlight how the burn …
Measuring Seaport Performance And Congestion In The Republic Of Korea, Derrick J. Lohr
Measuring Seaport Performance And Congestion In The Republic Of Korea, Derrick J. Lohr
Theses and Dissertations
Companies continue to globalize their supply chain operations increasing cargo traffic and creating excessive shipping demand on ports across the globe resulting in port congestion. This increased congestion impacts USTRANSCOM’s cargo movement operations, which compete for use of the same port resources. While the DoD has organic transportation capabilities, most of the cargo is moved by commercial ocean liners. It is, therefore, necessary to understand port operations, identify excess capacity, and exploit it to avoid congestion at ports. The purpose of this study is to identify peak and idle periods by evaluating the comparative performance of seaports using data envelopment …
Analysis Of The Perspective On Syrian Refugees By Neighboring Countries, Norma Ghanem
Analysis Of The Perspective On Syrian Refugees By Neighboring Countries, Norma Ghanem
Theses and Dissertations
Mass migration destabilizes neighboring states, opening the way for fragile state exploitation by enemies, including those that could undermine U.S. national interests. This study investigates an area of the Levant region, specifically countries neighboring Syria, and analyzes their perspective on Syrian refugees for the time frame of 1 June 2019 - 30 June 2020. This analysis may assist in forming policy and creating strategies to address refugee related issues, both domestic and international. There are three main questions addressed. The first inspects dominant refugee framing, the second explores sentiment (dis)similarity within each country and across countries, and the third investigates …
Screening Heuristics For The Evaluation Of Covert Network Node Insertion Scenarios, Andrew E. Pekarek
Screening Heuristics For The Evaluation Of Covert Network Node Insertion Scenarios, Andrew E. Pekarek
Theses and Dissertations
The majority of research on covert networks uses social network analysis (SNA) to determine critical members of the network to either kill or capture for the purpose of network destabilization. This thesis takes the opposite approach and evaluates potential scenarios for inserting an agent into a covert network for information gathering purposes or future disruption operations. Due to the substantial number of potential insertion scenarios in a large network, this research proposes three screening heuristics that leverage SNA measures to reduce the solution space before applying a simple search heuristic.
Assessing The United States Foreign Assistance Activities Impact On Violent Conflicts, Daniel F. Feze
Assessing The United States Foreign Assistance Activities Impact On Violent Conflicts, Daniel F. Feze
Theses and Dissertations
The Global Fragility Act, H.R.2116 116th Cong. (2019), “directs the Department of State to establish the interagency Global Fragility Initiative to stabilize conflict-affected areas and prevent violence globally, and establishes funds to support such efforts”. The United States Agency for International Development (USAID) has identified deteriorating economies, weak or illegitimate political institutions, and competition over natural resources as causes of violence, extremism and instability (USAID, 2021). The agency gives priority to mitigating the causes and consequences of violent conflicts, instability and extremism and funds programs and activities to accomplish that (USAID, 2021). With this study, we aim to quantitatively assess …
Using Generative Adversarial Networks To Augment Unmanned Aerial Vehicle Image Classification Training Sets, Benjamin J. Mccloskey
Using Generative Adversarial Networks To Augment Unmanned Aerial Vehicle Image Classification Training Sets, Benjamin J. Mccloskey
Theses and Dissertations
A challenging task in computer vision is finding techniques to improve the object detection and classification capabilities of ML models used for processing images acquired by moving aerial platforms. This research explores if GAN augmented UAV training sets can increase the generalizability of a detection model trained on said data. To answer this question, the YOLOv4-Tiny Object Detection Model was trained with aerial image training sets depicting rural environments. The salient objects within the frames were recreated using various GAN architectures, placed back into the original frames, and the augmented frames appended to the original training sets. GAN augmentation on …
Examining The Relationship Between An Aging Workforce And Logistics Performance Indicators, Daniel Parkhill
Examining The Relationship Between An Aging Workforce And Logistics Performance Indicators, Daniel Parkhill
Theses and Dissertations
In the United States, 10,000 baby boomers turn 65 every day. The subsequent generation born between 1965 and 1976 is significantly smaller, referred to as the baby bust. As a result, this causes a talent shortage as Baby Boomers retire, leaving a workforce gap which the subsequent generation is not large enough to fill. This issue also has been recognized as a potential problem in the logistics community of the United States Air Force. The purpose of this study is to examine the impact of workers age on key logistics performance indicators (LPIs) such as aircraft availability, product flow days, …
Determination Of Nonlinear Optical Properties For Gallium Arsenide Phosphide Ternary Compounds And For Tin Thiohypodiphosphate, Peter F. Norris
Determination Of Nonlinear Optical Properties For Gallium Arsenide Phosphide Ternary Compounds And For Tin Thiohypodiphosphate, Peter F. Norris
Theses and Dissertations
The Department of Defense and the commercial sector rely on coherent light sources to emit light that transmits through the atmosphere. Nonlinear optical effects in crystalline materials can be used to generate the laser waves, but certain nonlinear effects negatively impact the performance of laser generating materials. This thesis focuses on characterizing nonlinear optical properties for gallium arsenide phosphide ternary compounds and for tin thiohypodiphosphate. The Maker Fringe experiment is used to determine the d-coefficients of the materials, which describe the magnitude of the nonlinear response of the material. The Z-Scan experiment is used to calculate the nonlinear refractive …
Automated Aircraft Visual Inspection With Artificial Data Generation Enabled Deep Learning, Nathan J. Gaul
Automated Aircraft Visual Inspection With Artificial Data Generation Enabled Deep Learning, Nathan J. Gaul
Theses and Dissertations
Aircraft visual inspection, which is essential to daily maintenance of an aircraft, is expensive and time-consuming to perform. Augmenting trained maintenance technicians with automated UAVs to collect and analyze images for aircraft inspection is an active research topic and a potential application of CNNs. Training datasets for niche research topics such as aircraft visual inspection are small and challenging to produce, and the manual process of labeling these datasets often produces subjective annotations. Recently, researchers have produced several successful applications of artificially generated datasets with domain randomization for training CNNs for real-world computer vision problems. The research outlined herein builds …
An Entity-Component System Based, Ieee Dis Interoperability Interface, Noah W. Scott
An Entity-Component System Based, Ieee Dis Interoperability Interface, Noah W. Scott
Theses and Dissertations
In practice, there are several different methods of organizing data within a given software to fulfil its function. The method known as the Entity-Component System (ECS) is a software architecture where data components define entities. These components are stored as organized lists which are operated upon by systems to inject the system's desired behavior. Data is sent across the networks to communicate between simulation nodes as Protocol Data Units (PDUs). When sending PDUs across a network protocol, each simulation represents a common understanding of the world at the desired level of detail. DIS-compliant simulations are commonly written using an Object-Oriented …
Considering Dds In The Domain Of Dis - Pros And Cons, Nathaniel R. Peck
Considering Dds In The Domain Of Dis - Pros And Cons, Nathaniel R. Peck
Theses and Dissertations
DIS is a legacy IEEE standard for defining and structuring PDUs in large scale distributed wargames. Although the standard specifies various QoS appropriate for certain PDUs, a one-size-fits-all transport strategy is traditionally employed via UDP. Since the inception of DIS, the OMG has produced a standard for a DDS which has been implemented by several middleware vendors. DDS middleware offers an abstraction for network communications that allows applications and developers to easily employ configurable QoS by topic. Adoption and use of these QoS in DIS applications may introduce greater compliance with the IEEE standard and enrich the service features available …
Bayesian Convolutional Neural Network With Prediction Smoothing And Adversarial Class Thresholds, Noah M. Miller
Bayesian Convolutional Neural Network With Prediction Smoothing And Adversarial Class Thresholds, Noah M. Miller
Theses and Dissertations
Using convolutional neural networks (CNNs) for image classification for each frame in a video is a very common technique. Unfortunately, CNNs are very brittle and have a tendency to be over confident in their predictions. This can lead to what we will refer to as “flickering,” which is when the predictions between frames jump back and forth between classes. In this paper, new methods are proposed to combat these shortcomings. This paper utilizes a Bayesian CNN which allows for a distribution of outputs on each data point instead of just a point estimate. These distributions are then smoothed over multiple …
Evaluation Of The Armas-Som Framework With Real Data, Brandon M. Blakely
Evaluation Of The Armas-Som Framework With Real Data, Brandon M. Blakely
Theses and Dissertations
The ARMAS framework was created with the goal of developing a framework for all-source sensors which is able to combine detection, identification, calibration, model selection, and independent evaluation into a single system. Stable Observability Monitoring (SOM), augments the original ARMAS framework by enabling ARMAS to detect whether or not its Fault Detection and Exclusion (FDE) capabilities can be trusted and when additional sensor information is required to maintain resiliency. While previously tested with simulated sensor data, SOM has yet to be tested with real-life sensor data. Furthermore, ARMAS has only been tested with real-life GNSS data. This work expands on …