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Full-Text Articles in Engineering

Arctic Construction Under Climatological Constraints: A Decision Support System For Expeditionary Construction Site Selection In The Arctic Environment, Zachary S. Wontrop Mar 2023

Arctic Construction Under Climatological Constraints: A Decision Support System For Expeditionary Construction Site Selection In The Arctic Environment, Zachary S. Wontrop

Theses and Dissertations

The natural physical barriers present in the Arctic are being eroded by climate change, increasing near peer adversaries' abilities to exploit this region for strategic and economic gain. To maintain the Arctic as a region of strategic and economic international cooperation, increased infrastructure investment by the United States and its allies are required. No methodology currently exists to quantify construction-limiting climatological factors over time and space. Decision support systems can provide actionable information to guide decision makers during site selection. This research employs geographic, and time-coded historical climatology applied to a project case study, to develop a site selection decision …


Applications Of Fragile Curves To Water Distribution Networks, Danielle M. Van Lanen Mar 2023

Applications Of Fragile Curves To Water Distribution Networks, Danielle M. Van Lanen

Theses and Dissertations

Water distribution networks are of critical importance to provide uninterrupted services to a city. Not only do they provide potable drinking water to customers they also are used for fire services and other emergency support functions. By the year 2039, the United States’ drinking water investment gap is estimated to grow to $136 billion dollars. As the gap between available funding and funding required, being able to prioritize assets for investments is critical. Unfortunately, water distribution networks are typically managed reactively rather than proactively. This paper showcases a methodology for a proactive approach to asset management through the use of …


Decontamination Of Perfluoroalkyl Substances From Stainless Steel Piping Used In Aqueous Film Forming Foam Fire Suppression Systems, Ryan M. Register Mar 2023

Decontamination Of Perfluoroalkyl Substances From Stainless Steel Piping Used In Aqueous Film Forming Foam Fire Suppression Systems, Ryan M. Register

Theses and Dissertations

This study examines the removal of perfluoroalkyl substances (PFAS) from legacy hangar fire suppression systems which utilized PFAS containing aqueous film forming foam (AFFF). Hundreds of these systems are currently in place throughout the Department of Defense, with planned phase-out occurring by 2024. The estimated cost of replacing these systems is $2.1 billion dollars. To mitigate this cost, a triple-rinse method of decontamination has been proposed. This thesis explores the release of PFAS from AFFF systems during a triple-rinse decontamination, and the continued removal of PFAS after a triple-rinse is complete while simultaneously analyzing methylene blue dye as a potential …


U.S. Army Force Structure Optimization And Sufficiency Analysis, Francis P. Gargin Mar 2023

U.S. Army Force Structure Optimization And Sufficiency Analysis, Francis P. Gargin

Theses and Dissertations

The United States Army perpetually deploys rotational forces across the globe in support of the National Security Strategy. These forces meet a set of discrete mission demands over an extended time period before redeploying, modernizing, and preparing for the next deployment. The U.S. Army now utilizes the Regionally Aligned Readiness and Modernization Model to execute these cyclical stages for unit deployments. Specific emphasis is placed on aligning forces against a Geographic Combatant Command, which allows units to build readiness and lethality oriented towards the same series of threats, physical terrain, and civilian considerations. This research provides an Integer Programming model …


Rate Effects In Aircraft Learning Curves, Caleb J. Ahern Mar 2023

Rate Effects In Aircraft Learning Curves, Caleb J. Ahern

Theses and Dissertations

Across the Department of Defense (DoD), a wide variety of analytical tools are employed by cost analysts to estimate weapon system costs. One of the techniques widely employed by practitioners is the learning curve (LC). Although learning curves have been widely studied, using rate-adjustments or production rate effects (PRE), their usage have only intermittently been evaluated in place of using the traditional learning curve. Previous studies analyzing production rate found mixed results. This research aims to examine aircraft production data to determine if production rate model is preferrable in United States Air Force programs. Additionally, this PRE research seeks to …


Angle Resolved Photoelectron Spectroscopy Study Of Germanium Tin: Experimentally Determined Electronic Band Gap And Surface Analysis, Jeremy M. Hunter Mar 2023

Angle Resolved Photoelectron Spectroscopy Study Of Germanium Tin: Experimentally Determined Electronic Band Gap And Surface Analysis, Jeremy M. Hunter

Theses and Dissertations

The germanium tin band gap is responsive to wavelengths in the mid to near infrared spectrum; this shows promise in meeting the detection demands of the next generation infrared detectors. Recent developments in germanium tin (GeSn) alloy growth techniques have peaked the scientific community’s interest in GeSn based optoelectrical and detection devices. Detection materials made entirely of group IV elements are compatible with complementary metal-oxide semiconductor manufacturing techniques. Understanding the surface chemistry of this alloy is fundamental for solid state device design and must be analyzed to optimize device performance. Studies have shown that with the addition of tin, the …


Influence Of Dilute Silicon Carbide Nanoparticle Additions To The Microstructure And Mechanical Properties Of Laser Powder Bed Fusion Molybdenum, Nathan E. Ellsworth Mar 2023

Influence Of Dilute Silicon Carbide Nanoparticle Additions To The Microstructure And Mechanical Properties Of Laser Powder Bed Fusion Molybdenum, Nathan E. Ellsworth

Theses and Dissertations

Consolidation of pure molybdenum through laser powder bed fusion and other additive manufacturing techniques is complicated by a high melting temperature, thermal conductivity, and ductile-to-brittle transition temperatures. Nano-sized silicon carbide particles (0.1 wt%) were homogeneously mixed with molybdenum powder and the printing characteristics, chemical composition, microstructure, and mechanical properties were compared to pure molybdenum for scan speeds of 100, 200, 400, and 800 mm/s. The addition of silicon carbide improved the consolidation and mechanical properties and the oxygen content was reduced. Two mechanisms of oxygen reduction were identified as responsible for the improvements: oxidation of free carbon and the creation …


Classification And Analysis Of Twitter Bot And Troll Accounts, Callan P. Mccormick Mar 2023

Classification And Analysis Of Twitter Bot And Troll Accounts, Callan P. Mccormick

Theses and Dissertations

This research trains, tests, and analyzes bot and troll classification models using publicly available, open source datasets. Specifically, it applies decision tree, random forest, feed forward neural networks, and long-short term memory neural networks with hyperparameters tuned via designed experiment to five labeled bot datasets created between 2011 and 2020 and one dataset labeling state-sponsored disinformation accounts or trolls. The first three models utilize account profile features, while the last model applies natural language processing techniques, specifically GloVe embedding, to analyze a user’s Tweet history. Results indicate that the random forest model outperforms the other three models with an average …


Exploring Variations In Fast Curing Plastic Scintillator Formulations: Optimizing Tpo And Evaluating The Effects Of High-Z Loading And Novel Waveshifters, Andrew K. Nesbitt Mar 2023

Exploring Variations In Fast Curing Plastic Scintillator Formulations: Optimizing Tpo And Evaluating The Effects Of High-Z Loading And Novel Waveshifters, Andrew K. Nesbitt

Theses and Dissertations

Organic plastic scintillators are widely used due to their relative low cost, physical robustness, and fast timing properties, but typically provide lower light yields and photon sensitivity compared to other alternatives. Photocuring novel plastics offers a viable method for producing fast curing plastic scintillators. The current formulations include an acrylic polymer base and utilize diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) as the photo-initiator for polymerization; however at higher concentrations of TPO may adversely affect scintillator light output. The present research refined the optimal TPO concentrations that fully cure these acrylic-base scintillators and maximize light production to 0.4-0.5% by weight. Additionally, this …


Characterizing Gesn Alloys By Sem/Eds And Photoluminescence Spectroscopy, Christopher M. Sutphin Mar 2023

Characterizing Gesn Alloys By Sem/Eds And Photoluminescence Spectroscopy, Christopher M. Sutphin

Theses and Dissertations

Germanium tin (GeSn) alloys are being studied as potential transition metal (Group IV) photoelectric semiconductors or optical detectors. GeSn alloys could be employed as an optically active material within a computer. Compared to current technologies, a direct band gap GeSn alloy can be engineered to operate with higher thermal stability and efficiency. The GeSn alloy studied was composed of Ge and Si substrates with various Sn percentages grown using remote plasma-enhanced chemical vapor deposition (RPECVD). Photoluminescence spectroscopy (PL) techniques were initially used to determine the GeSn properties, including the band gap. The Ge91.2Sn8.8 PL spectra suggested the …


An Analysis Of Aircraft Maintenance Leading Indicator Metrics To Unit-Level Aircraft Availability Rates, William C. Hardy Mar 2023

An Analysis Of Aircraft Maintenance Leading Indicator Metrics To Unit-Level Aircraft Availability Rates, William C. Hardy

Theses and Dissertations

The purpose of this research is to improve the usefulness of data that is already collected within aircraft maintenance organizations to better identify trends, and outliers, and possibly better explain relationships between leading and lagging indicator metrics. Specifically, this graduate research paper sought to answer two research questions addressing what aircraft maintenance metrics significantly impact aircraft availability, and how to measure those to understand which metrics impact aircraft availability most. The research questions were answered through a comprehensive literature review, and the use of multiple linear regression analysis on data from two specific aircraft maintenance organizations from the same location. …


Lunar Search And Rescue: The Next Step For Human Spaceflight Recovery, Benjamin J. Johnis Mar 2023

Lunar Search And Rescue: The Next Step For Human Spaceflight Recovery, Benjamin J. Johnis

Theses and Dissertations

Humans return to the Moon in 2024 under the NASA Artemis mission. Commercial space explorations are rapidly expanding. The sudden increase of human spaceflight calls for increased emphasis on space rescue. These revelations drove an AFRL/AFIT capability gap assessment to provide specific proposals for a modern space rescue program guided by Transaction Cost Economics Theory. The mission analysis arms USSPACECOM and NASA to coordinate an interagency approach to Lunar Search and Rescue, positioning America to compete in the new space race. The strategic consequences of failing to act could fundamentally jeopardize American leadership in space.


Pattern Of Life Modeling On Maritime Vessels With Bayesian Inferencing, Miles A. Kelly Mar 2023

Pattern Of Life Modeling On Maritime Vessels With Bayesian Inferencing, Miles A. Kelly

Theses and Dissertations

Despite decades of research, maritime traffic models’ limited predictive power continues to constrain their operational utility. We build on previous pattern of life modeling algorithms and contribute a Bayesian inferencing model for anomaly detection. Our probabilistic approach provides decision makers the capability to tailor the belief threshold for identifying anomalies and to enact a measured response based on the degree of abnormality. We perform a case study to evaluate the results, verifying that our Bayesian inferencing method accurately refines its probability when given the location and time of a ship of interest, and serving as a proof of concept for …


Integrating Ace And Mca Requirements Into The Civil Engineer Officer Occupational Competency Framework, Stone D. Williford Mar 2023

Integrating Ace And Mca Requirements Into The Civil Engineer Officer Occupational Competency Framework, Stone D. Williford

Theses and Dissertations

The Air Force Civil Engineer officer career field has made dedicated efforts to the professional development of its company grade officers. In response to the 2015 Air Force Strategic Master plan, the Civil Engineer officer career field adopted a competency-based education approach. In 2020, the Civil Engineer Officer Career Field Education and Training Plan was published, officially integrating the career field’s operational requirements into a competency framework. However, since 2020, the Air Force has adopted an updated force generation strategy, and with it, changes to the way the Air Force assets are employed in contingency environments. This new scheme of …


Hierarchical Federated Learning On Healthcare Data: An Application To Parkinson's Disease, Brandon J. Harvill Mar 2023

Hierarchical Federated Learning On Healthcare Data: An Application To Parkinson's Disease, Brandon J. Harvill

Theses and Dissertations

Federated learning (FL) is a budding machine learning (ML) technique that seeks to keep sensitive data private, while overcoming the difficulties of Big Data. Specifically, FL trains machine learning models over a distributed network of devices, while keeping the data local to each device. We apply FL to a Parkinson’s Disease (PD) telemonitoring dataset where physiological data is gathered from various modalities to determine the PD severity level in patients. We seek to optimally combine the information across multiple modalities to assess the accuracy of our FL approach, and compare to traditional ”centralized” statistical and deep learning models.


Air Force Cadet To Career Field Matching Problem, Ian P. Macdonald Mar 2023

Air Force Cadet To Career Field Matching Problem, Ian P. Macdonald

Theses and Dissertations

This research examines the Cadet to Air Force Specialty Code (AFSC) Matching Problem (CAMP). Currently, the matching problem occurs annually at the Air Force Personnel Center (AFPC) using an integer program and value focused thinking approach. This paper presents a novel method to match cadets with AFSCs using a generalized structure of the Hospitals Residents problem with special emphasis on lower quotas. This paper also examines the United States Army Matching problem and compares it to the techniques and constraints applied to solve the CAMP. The research culminates in the presentation of three algorithms created to solve the CAMP and …


Uncertainty Quantification In Federated Learning For Persistent Post-Traumatic Headache, Byungmoo Brian Kim Mar 2023

Uncertainty Quantification In Federated Learning For Persistent Post-Traumatic Headache, Byungmoo Brian Kim

Theses and Dissertations

A post-traumatic headache (PTH), resulting from a mild traumatic brain injury (mTBI), potentially develops into persistent post-traumatic headache (PPTH). Although no known cure for PPTH exists, research has shown that receiving treatment at earlier stages of PTH lowers the risk of patients developing PPTH. Previous studies have shown machine learning (ML) models capable of predicting a patient’s PTH progression, but none have considered the issue of protecting patient privacy. Due to patient privacy, ML models only have access to data within the institution. Federated learning (FL) harnesses data from separate institutions without sacrificing patient privacy as institutions can run ML …


Examining Fuel Service System Failures Of The Usaf R11 Using Survival Analysis, Roed M.S. Mejia Mar 2023

Examining Fuel Service System Failures Of The Usaf R11 Using Survival Analysis, Roed M.S. Mejia

Theses and Dissertations

Recent events show that fuel supply is a large contributor to the success or failure of a military operation in response to a contingency. Any future near-peer conflict will stress the supply chain and require fully operational vehicles to be ready for the primary mission sets they support. In the United States Air Force (USAF), the readiness of fuel distribution trucks is crucial to meeting those mission sets in global operations. Utilizing non-parametric and semi-parametric survival models, which do not assume specific probability distributions, this study analyzes maintenance data for R-11 trucks that refuel aircraft.


Predicting Success Of Pilot Training Candidates Using Interpretable Machine Learning, Alexandra S. King Mar 2023

Predicting Success Of Pilot Training Candidates Using Interpretable Machine Learning, Alexandra S. King

Theses and Dissertations

The United States Air Force (USAF) has struggled with a sustained pilot shortage over the past several years; senior military and government leaders have been working towards a solution to the problem, with no noticeable improvements. Both attrition of more experienced pilots as well as wash out rates within pilot training contribute to this issue. This research focuses on pilot training attrition. Improving the process for selecting pilot candidates can reduce the number of candidates who fail. This research uses historical specialized undergraduate pilot training (SUPT) data and leverages select machine learning techniques to determine which factors are associated with …


A Transformer Based Architecture For Indonesian Sentiment Analysis - Exploring Indobert Variations, Training Size, And Self-Supervised Model Training, Connor F. Shaw Mar 2023

A Transformer Based Architecture For Indonesian Sentiment Analysis - Exploring Indobert Variations, Training Size, And Self-Supervised Model Training, Connor F. Shaw

Theses and Dissertations

There is strong motivation in both civilian and military circles to understand the attitudes, motivations, feelings, and emotions of a population of interest. Social media is a rich source of self-disclosed information by individuals from all walks of life about virtually every domain of the human experience, but the vast quantity of data is impossible to effectively analyze without advanced natural language processing algorithms. This research creates a transfer learning based emotion classification model for Indonesian language Twitter data. Transfer learning consists of two steps: pre-training and fine tuning. Three variations of Indonesian Bidirectional Encoder Representations from Transformers (IndoBERT) are …


Examining Failures Of Kc-135 Boom Assemblies Using Survival Analysis, Benjamin D. Miller Mar 2023

Examining Failures Of Kc-135 Boom Assemblies Using Survival Analysis, Benjamin D. Miller

Theses and Dissertations

The purposes of this study are to confirm the applicability of survival analysis for predicting recurrent failures of a component of a military aircraft and to provide practical insights to maintenance managers and mission planners. The results of this study also can help the United States Department of Defense improve the CBM+ program. This study was able to predict recurrent failures of the component using Nelson-Aalen cumulative estimates. In addition, this study used a Cox proportional hazards regression model with shared frailty for measuring the effect of covariates on recurrent failures and unidentified heterogeneity in the model, which warranted future …


Simulating Autonomous Drone Swarm Behaviors In An Anti-Access Area Denial (A2ad) Environment, Alexander L. Martinez Mar 2023

Simulating Autonomous Drone Swarm Behaviors In An Anti-Access Area Denial (A2ad) Environment, Alexander L. Martinez

Theses and Dissertations

Army senior military leaders are invested in acquiring modernized aerial platforms and equipment to augment the U.S. Army’s ability to overcome A2AD threats imposed by modern IADS. A prominent element of this modernization effort is the employment of autonomous drones to defeat IADS threats while minimizing risk to Army Soldiers. This research utilizes a framework for classifying the levels of autonomous capability along three dimensions: the ability to act alone, the ability to cooperate, and the ability to adapt. A virtual combat model, created using the AFSIM, simulates the engagement between an enemy IADS and a friendly formation comprised of …


Estimation Of Optimal Flight Trajectory In A Total Power Loss Scenario Using Proximal Policy Optimization, Eidahn Eliash Mar 2023

Estimation Of Optimal Flight Trajectory In A Total Power Loss Scenario Using Proximal Policy Optimization, Eidahn Eliash

Theses and Dissertations

Recent research has been conducted in using deep reinforcement learning algorithms to generate closed form optimal control laws for helicopters in power loss scenarios. The control laws could allow for design of various cockpit visual pilot aids if proven successful. Such pilot aids are predicted to reduce pilot workload during execution of an emergency powerless landing, and to overall increase the probability of landing safely in such an event. The proposed topic discusses the use of the PPO algorithm in order to find an optimal control policy for a helicopter in a total power loss emergency landing scenario. The task …


Concept Of Operations Of Cislunar Mirror Satellites To Provide Augmented Lighting Of Dim Space-Based Objects, Alec E. Cook Mar 2023

Concept Of Operations Of Cislunar Mirror Satellites To Provide Augmented Lighting Of Dim Space-Based Objects, Alec E. Cook

Theses and Dissertations

The imaging and inspection of Resident Space Objects (RSOs) is an increasingly important mission as space-faring nations and commercial enterprises alike seek to develop means to repair and refuel spacecraft, as well as de-orbit RSOs to reduce orbital debris. Lighting conditions are not always advantageous for an imaging/inspection or repair/refuel spacecraft; therefore, the use of mirror spacecraft to reflect solar energy is proposed to illuminate dimly lit RSOs. The present research investigates the efficacy of space-based reflectors at examining spacecraft in the cislunar environment. Specific assessments include target spacecraft in geosynchronous Earth orbit and periodic orbits around selected Lagrange points, …


Performance Analysis And Recommended Improvements Of A Cubesat Resistojet, Alexander M. Petrocelli Mar 2023

Performance Analysis And Recommended Improvements Of A Cubesat Resistojet, Alexander M. Petrocelli

Theses and Dissertations

A small resistojet design was evaluated for its current performance and assessed for design and operational improvements. This resistojet is designed to operate on AFIT CubeSats with the intent of providing 100-200 mN of thrust at a specific impulse between 66-104 seconds. Using previously collected data and studies conducted on the design, analysis was performed to determine the current performance of this first-generation design. This provided a starting point for performance analysis over a variety of operational temperatures and pressures. This process was conducted for various heat exchanger path lengths of both the current design and two adapted path geometries. …


Experimental And Computational Bearing Strength Of Fiber Metal Laminate With And Without Film Adhesive, Christopher L. Bellanova Jr. Mar 2023

Experimental And Computational Bearing Strength Of Fiber Metal Laminate With And Without Film Adhesive, Christopher L. Bellanova Jr.

Theses and Dissertations

This research characterized the performance of a fiber metal laminate composed of carbon fiber and stainless steel without film adhesive and compared it to a similar, previously tested, fiber metal laminate including film adhesive. Removal of the adhesive layers reduced the localized thickness, simplified manufacturing, and allowed for a 20% increase in foil thickness. Quasi-static testing was conducted in double shear, single shear protruding, and single shear countersunk configurations. The results were compared to adhesive hybrid and control samples. To study the affects of bolt tension, samples at low torque in double shear were also tested. Progressive failure samples revealed …


Anisotropic Characterization Of Additively Manufactured Ti 6-4 Via Tension, Compression, And Three Point Bend Experimentation, James M. Gunderson Mar 2023

Anisotropic Characterization Of Additively Manufactured Ti 6-4 Via Tension, Compression, And Three Point Bend Experimentation, James M. Gunderson

Theses and Dissertations

Titanium's ability to fill existing material gaps because of its higher strength and higher melting temperature compared to other common materials used in aircraft structures requires a need to understand the behavior of the material. Titanium's properties and the development of additive manufacturing also open an opportunity for it to be used in aerospace systems of the future in applications where traditionally manufactured titanium cannot meet the desired system requirements. Compressive, tensile, and three point bend experimental data collected from this research under varying temperatures, print orientations, print layer build heights, and surface finishes were analyzed to determine favorable material …


Direct Collocation Methods For Comparison Of Aerothermodynamic Models Effect On Hypersonic Trajectory Optimization By The Process Of Continuation, Noor K. Khan Mar 2023

Direct Collocation Methods For Comparison Of Aerothermodynamic Models Effect On Hypersonic Trajectory Optimization By The Process Of Continuation, Noor K. Khan

Theses and Dissertations

An algorithm was created to optimize trajectories of hypersonic glide vehicles with selected cost functions by applying the process of continuation to direct orthogonal collocation methods. The trajectory was optimized to maximize the range of launch position given a fixed terminal location. The hypersonic glide vehicle system dynamics were modeled with three-dimensional, three degree of freedom equations of motion assuming no thrust and a non-rotating Earth with the control as bank angle. Three aerothermodynamic models were compared when input as path constraints to calculate the stagnation point heating rate at the nose as well as integrated for heat load. Use …


Optimal Gyroid Infill For Space Launch, Jose R. Lopez Cordell Mar 2023

Optimal Gyroid Infill For Space Launch, Jose R. Lopez Cordell

Theses and Dissertations

This research characterizes the optimal gyroid infill design for the 1st frequency response of composite sandwich panels. Structural performance may be improved by designing the gyroid infill within the sandwich panel to have a 1st mode resonance frequency above typical launch vehicle vibrations. Ensuring a component generates a natural frequency response above a designed threshold is mandatory for space launch systems to prevent damage. The gyroid, a Triply Periodic Minimal Surface (TPMS), has the potential to provide close to isotropic stiffness in the principal axes with a minimal amount of material, making it an attractive choice for this application. This …


Critical Infrastructure System Resiliency Modeling Using Multi-Layer Network Optimization, Spencer R. Figge Mar 2023

Critical Infrastructure System Resiliency Modeling Using Multi-Layer Network Optimization, Spencer R. Figge

Theses and Dissertations

ccurately modeling the interdependent operation of critical infrastructure systems is an effective and efficient way of proactively evaluating system vulnerabilities and resiliency. Infrastructure systems are designed to transport essential commodities from where they are produced to where they are consumed and network flow-based models are one of the most effective ways to simulate and quantify infrastructure performance. The literature is populated with proposed models that must balance accuracy of interdependent operations, capability to include real-world considerations, and computational cost. This research proposes an alternative network-flow based model called the Critical Infrastructure System Resiliency Model (CISRM) that focuses on modeling a …