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2023

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Articles 6511 - 6540 of 9778

Full-Text Articles in Engineering

An Analysis On Recommended United States Air Force Additive Manufacturing Construction Unit Type Code Package For Expeditionary Deployment, Caleb G. Dann Mar 2023

An Analysis On Recommended United States Air Force Additive Manufacturing Construction Unit Type Code Package For Expeditionary Deployment, Caleb G. Dann

Theses and Dissertations

Additive Manufacturing Construction (AMC) is an emerging technology in the construction industry which utilizes 3-D printing to reduce costs, labor requirements and deviations in quality. This technology has the ability to rapidly produce repeatable construction projects while tailoring each to specific requirements through the use of 3-D designs. One of the primary objectives of the 2018 National Defense Strategy (NDS) is to continue meeting mission demands with a greater focus on the efficient use of resources. AMC has the ability to satisfy the requirements of this objective. The United States Air Force has begun initial print trials but have not …

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Investigation Of Rhine Pointing As A Solution To The Aircraft Human Machine Interface Problem, Alexandra C. Dobranski, Samuel J. Medvec Mar 2023

Investigation Of Rhine Pointing As A Solution To The Aircraft Human Machine Interface Problem, Alexandra C. Dobranski, Samuel J. Medvec

Theses and Dissertations

The human machine interface in 5th generation aircraft has not evolved proportionally with advances in display size and data density. The traditional cursor slew method fails to rapidly relocate the cursor, especially on large displays. Previous studies at the Air Force Test Pilot School and Air Force Institute of Technology identified methods that have the potential to improve the human machine interface. This research expanded upon those studies by providing an assessment of head tracking technology as a secondary method of cursor manipulation. Specifically, this study examined the effects that visual feedback (visible and invisible head tracking cursors) and cursor …

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Temporal And Spatial Variability Of Specific Energy Consumption For Atmospheric Water Generators, Anthony T. Brenes Mar 2023

Temporal And Spatial Variability Of Specific Energy Consumption For Atmospheric Water Generators, Anthony T. Brenes

Theses and Dissertations

Atmospheric Water Generators (AWG) produce potable water from the moisture in the air, providing a potentially viable water source in austere locations or emergency response scenarios. In this study, the operating constraints of three existing commercially available AWG devices are investigated, compared to historical weather data from across the continental United States. Utilizing linear regression modeling and weather station data for the years of 1985-2019, the monthly and spatial trends of energy demand to produce water from these devices are evaluated. Energy and water production efficiencies for the devices are highly dependent on environmental conditions with relative humidity and temperature …

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A Systems Modeling Approach To Support Human-Agent Team Performance For Combat Identification, Clayton W. Couch Mar 2023

A Systems Modeling Approach To Support Human-Agent Team Performance For Combat Identification, Clayton W. Couch

Theses and Dissertations

Combat Identification (CID) in an air-to-air combat context is a highly complex cognitive task that requires the operator to make rapid, high consequence decisions. To accomplish CID, fighter aircrew must attend to and perceive a broad range of information while concurrently building situation awareness (SA) and conducting other tasks. While existing automated agents are available to help fighter aircrew with this CID task, they are designed for a very narrow subset of the overall task and are not well suited for human-agent teaming. An interdependence analysis of the human operator and supporting machine agents conducted for this task support the …

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Mission Dependency Weighted Water Distribution Networks, Payten A. Connally Mar 2023

Mission Dependency Weighted Water Distribution Networks, Payten A. Connally

Theses and Dissertations

How does the United States Air Force (USAF) assess and plan to replace their most critical drinking water infrastructure? The historical answer is to wait for it to break and then replace or repair the failed pipe. While this has been the process in the past, it is no longer a sustainable approach with resources and funding becoming more constrained in the public and private sectors, and aging assets approaching the end of their usable life. The USAF has taken the first step in asset management to identify their underground water lines, but they have not developed ways to convey …

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Climate-Informed Idf Curve Updates And Impact On Design Policy, Douglas C. Jaks Mar 2023

Climate-Informed Idf Curve Updates And Impact On Design Policy, Douglas C. Jaks

Theses and Dissertations

Stormwater systems across the United States (US) are aging with the American Society of Civil Engineers awarding a grade of D for the state of the infrastructure. Additionally, these aging systems are under-designed for climate-induced non-stationarity of rainfall. Several studies indicate a global increase of extreme rainfall events as a result of climate change, driving the need for future stormwater management designs that account for a changing climate. Specifically, this research generates climate-change informed intensity-duration-frequency (IDF) curve change factors through downscaled climate scenario change factors. While previous work has identified processes for predicting future IDF curves, this study generated curves, …

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Comparison Of Federated Kalman Filter And Autonomous Resilient Management Of All-Source Sensors (Armas) Framework For Fault Detection And Exclusion, Flavio Fernandes Mar 2023

Comparison Of Federated Kalman Filter And Autonomous Resilient Management Of All-Source Sensors (Armas) Framework For Fault Detection And Exclusion, Flavio Fernandes

Theses and Dissertations

In recent times, there is a great demand for resilient and robust PNT solutions. Current navigation systems rely heavily on GNSS to provide this solution. This dependence is a major concern and therefore it is prudent to use additional aids to provide the best solution possible. However, traditional methods to address this need require a nontrivial number of Kalman filters to maintain a fault-free solution. The federated filter approach provides an attractive alternative to the current solutions. In this thesis, we examine the use of the federated filter design to address this need in today’s integrated navigation systems. We compared …

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Team And Skill Matching For Disaster Recovery Operations, Emily B. Frahm Mar 2023

Team And Skill Matching For Disaster Recovery Operations, Emily B. Frahm

Theses and Dissertations

United States Air Force (USAF) bases are key power projection platforms that ensure mission readiness and help bring humanitarian aid to locations in need. Recovering airfields after attack or natural disaster is a key mission of USAF civil engineers, and accomplishing this repair as swiftly as possible is key to maintaining our position in the global order. Accomplishing a disaster recovery project is a set of teams, each assigned to a specific task, and made up of a series of personnel. The question answered within this paper is: how do we match the right person with the appropriate skills to …

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An Analysis Of A Modular Open System Approach On Program Management Metrics For Cost And Schedule, Kayla I. Vogler Mar 2023

An Analysis Of A Modular Open System Approach On Program Management Metrics For Cost And Schedule, Kayla I. Vogler

Theses and Dissertations

A modular open system approach (MOSA) and its inclusion of open architecture are among the prevailing acquisition strategies for cost and schedule management. This approach involves the incorporation of reusable, modular packages that can be incrementally added and upgraded throughout programs’ lifecycles. Many practitioners throughout the acquisitions community find that MOSA enables better opportunities for affordability, rapid acquisition, flexibility, enhanced competition, and innovation. A literature review reveals that few studies examine the interaction between MOSA and the extent to which it influences cost and schedule performance. However, no studies to date examine open architecture’s impact via programmatic evaluation of Earned …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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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. …

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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.

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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 …

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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 …

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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.

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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 …

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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 …

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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.

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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 …

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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 …

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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 …

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