Engineering Commons^™

Investigation Of Shear Modulus And Material Damping Of A Lightly Cemented Silty Sand Representing Offshore Soil, Joshua Jeanjaquet

Theses and Dissertations

Offshore structures remain highly relevant, making the dynamic characterization of offshore soils critical. Since many offshore soils are cemented, understanding their response to dynamic loads is essential for developing accurate models that improve the reliability and cost-effectiveness of offshore structure designs. This study examines the impact of cement content on shear modulus, shear modulus reduction, shear wave velocity, and material damping of lightly cemented fine silty sand. A series of Resonant Column and Torsional Shear tests were conducted. The results were analyzed and compared to existing literature. The modified hyperbolic model was proposed to characterize the shear modulus and damping …

Investigating The Influence Of Volumetric Water Content In The Upper Layer Of Soil On Embankment Factor Of Safety, Kiera Rose Hughes

Theses and Dissertations

Geohazards, including landslides and embankment failures, pose significant risks to railway infrastructure, necessitating early recognition methods for effective risk mitigation. This research explores the relationship between the volumetric water content in the upper soil layer and the embankment's factor of safety (FOS) to improve early detection and stability assessment. A parametric analysis was conducted to evaluate how variations in the soil type (shear strength and hydraulic conductivity), slope geometry (angle and height) and recharge conditions (rainfall intensity and duration) affect the FOS. Using the GeoStudio software, seepage and slope stability analyses were performed for two baseline soils, as well as …

Supercritical Water Oxidation For Removing Pfas Contaminants: A Numerical Study, Ashley Joy Poyner

Theses and Dissertations

Per – and polyfluoroalkyl substances (PFAS) are a group of stable pollutants known for their long lifetimes and resistance to treatment methods used traditionally to remove other contaminants. PFAS and their ability to accumulate in both aquatic and terrestrial environments present threats such as detrimental effects to people and ecosystems due to their ability to penetrate entire systems. Though many methods are being explored to treat PFAS contamination in different systems, Supercritical Water Oxidation (SCWO) is a promising method for both removing and decomposing PFAS, with the ability to completely oxidize these persistent contaminants. This study is a numerical investigation …

Experimental And Numerical Analysis Of Fluidization Of Pelletized Activated Carbon Columns: Effects Of Glass Bead Retention Layer, Amin Nemati Tamar

Theses and Dissertations

In pressure swing adsorption (PSA) processes there is always a desire to process as much gas as possible in the smallest beds possible. This necessarily leads to velocities that, especially during pressure-changing steps, may exceed the adsorbent particle fluidization velocity within the bed. To prevent the possibility of bed expansion and fluidization bed retention systems are usually employed at the top of the bed in the form of dense beads, bags of the same or springs, otherwise the mechanical integrity of the adsorbent might become compromised. PSA process simulation, based on Archimedes’ force balance involving weight, buoyancy and the drag …

Multiscale Modeling Techniques For Electrodynamic Systems, Hunter Teel

Theses and Dissertations

In order to rapidly develop better electromagnetic and electrochemical systems, approaching these complicated topics from multiple perspectives is necessary. The use of mathematical models and numerical simulation offers the ability to evaluate and predict the performance of these systems based off the principles of electrodynamics in an ideal setting. Through the use of Computational Fluid Dynamics (CFD), representative geometries of scales can be created and evaluated to provide insight into the behavior of these systems. Simulation offers a modifiable environment that can approach the relevant physics from both the microscale and macroscale. Conclusions, results, boundary conditions, or other information from …

A Novel Geometric Modeling Kernel For Automated Fiber Placement, Rowen Burney

Theses and Dissertations

Automated Fiber Placement (AFP) is a key manufacturing technique for producing high-performance composite structures, yet existing geometric modeling frameworks lack the specialized functionality required for efficient toolpath planning and laminate optimization. This work presents Knots, a Geometric Modeling Kernel (GMK) developed specifically to address these limitations by providing a unified geometric foundation tailored for AFP. Unlike general-purpose Computer Aided Design (CAD) libraries, Knots is optimized for AFP, offering specialized geometric operations that streamline the transition from design to manufacturing. It directly manages the loading and computation of geometric data, ensuring structured laminate generation while supporting automation and scripting for improved …

Evaluating And Improving U.S. National Water Model Evapotranspiration Estimates Through Eddy-Covariance Flux Tower Observations And Machine Learning Post-Processing, Abin Raj Chapagain

Theses and Dissertations

Despite ET's critical importance in the hydrological cycle, very little has been done to provide ET forecasts at a national level. This study comprises two research chapters examining the National Water Model's (NWM) evapotranspiration (ET) simulations. In Chapter II, we conducted the first comprehensive NWM ET model performance assessment by comparing simulations to eddy-covariance flux tower measurements across the Continental United States (CONUS) on a high-resolution, 1 KM square grid. We clustered results by National Weather Service (NWS) River Forecast Centers (RFCs), land cover classifications, elevation bands, and Köppen-Geiger Climate Zones. The NWM performs best in the Northeast and Ohio …

Modeling And Characterization Of On-Orbit Servicing Architectures For Efficient Mission Planning, Samantha Q. Vi Tang

Theses and Dissertations

As space-based systems become increasingly critical to global infrastructure, efficient satellite maintenance and resource management have become essential to ensuring operational longevity. On-orbit servicing has emerged as a key strategy for extending satellite lifespans, mitigating space debris accumulation, and enhancing the cost effectiveness of space operations. This study presents a comprehensive mixed-integer programming (MIP) model to optimize servicer task assignments and routing while minimizing propellant consumption. The model captures the operational complexities of servicing a network of satellites across multiple orbits by incorporating realistic constraints, such as fuel limitations and task completion time windows. Sensitivity analysis allows mission planners to …

Key Characteristics Of Long-Lived Portland Cement Concrete Airfield Pavements In The United States Air Force Enterprise, Cameron J. Palmer

Theses and Dissertations

The United States Air Force maintains a $30 billion portfolio of airfield pavements essential for national security. Despite their importance, budget constraints have limited average annual repair funding to $260 million over the past decade, requiring pavements to last significantly longer than their typical life span. This project addresses the central question: What design features or characteristics contribute to the longevity of Portland Cement Concrete (PCC) airfield pavements? Utilizing data from AFCEC's Airfield Pavement Evaluation (APE) team and the PAVER sustainment management system, this study employed linear regression, logistic regression, and deep artificial neural network (ANN) modeling techniques to identify …

Imu-Mechanized Discrete Error-State Kalman Filtering With Lie-Group Pose Representations, Daniel P. Koch

Theses and Dissertations

This dissertation investigates methodologies for consistent Kalman filtering with Lie-group based representations of the vehicle pose. Early results are centered around the relative navigation framework, which maintains filter observability and consistency by only tracking the state relative to the latest keyframe of an odometry system such as visual odometry or laser scan matching. A detailed derivation of a relative multiplicative extended Kalman filter, using a quaternion parameterization of the attitude state, is presented for application to multirotor vehicles. The remainder of the dissertation focuses on Kalman filtering using a Lie-group SE(3) pose representation, which improves filter consistency by correctly modeling …

Data-Driven Fusion Of Earth Observation And Hydrologic Data To Forecast Flood Extents At Regional To Continental Scales, Kel N. Markert

Theses and Dissertations

Accurate and timely flood inundation forecasts are crucial for mitigating the devastating impacts of floods, which affect 1.47 billion people globally and cause significant economic losses. While traditional flood forecasting methods, such as hydrologic and hydrodynamic models, have limitations in providing comprehensive and spatially explicit inundation information, recent research has focused on leveraging Earth observation data and machine learning for enhanced flood prediction. This dissertation advances the state-of-the-art in data-driven flood inundation forecasting by exploring the capabilities and scalability of the Forecasting Inundation Extents using Rotated Empirical Orthogonal Function (FIER) framework. This dissertation focuses on investigating different aspects of FIER …

Design And Realization Of Concurrent Cryptosystem For Medical Image Privacy On Reconfigurable Hardware, Vinoth Raj R

Theses and Dissertations

The protection of medical image privacy plays a crucial role in maintaining confidentiality for the secure storage and transmission of patient’s sensitive healthcare data. Medical images are the widely used data type in the e-healthcare sector. Traditional cryptographic algorithms have limitations when applied to large-scale medical image datasets due to their high computational requirements. The primary goal of this research work is to design and implement indigenous algorithms to provide confidentiality for grayscale and color DICOM (Digital Imaging and Communications in Medicine) images through an encryption process. The research leverages the benefits of reconfigurable hardware, namely the Field-Programmable Gate Arrays …

Extraction Of Contact Resistivity For Transition Metal Oxide-Based Silicon Heterojunction Solar Cell, Shanmugam K

Theses and Dissertations

Contact resistivity quantifies the charge transport barrier, which is one of the key parameters for choosing the carrier selective contact for silicon solar cells. Optically transparent and electrically selective contacts such as Transition Metal Oxide (TMO)–based contacts are employed in solar cell applications. Therefore, extracting contact resistivity for such Schottky contacts requires apposite validation.

In this work, the contact resistivity of TiOx/LiFx/Al stack over an n-type c-Si wafer is extracted using two conventional techniques: i) Shockley’s Transfer Length Method (TLM) and ii) Cox and Strack Method (CSM). The extracted contact resistivity is validated by comparing it with the solar cell’s …

Efficiency Of Enzyme Induced Carbonate Precipitation (Eicp) By Crude Extract Urease For Geotechnical And Geoenvironmental Applications, Kaniz Roksana

Theses and Dissertations

Geotechnical engineering is currently facing challenges, including accommodating rapid urbanization, adapting to climate change impacts, and prioritizing sustainability, all while ensuring the safety and stability of critical infrastructure. Biocementation is a recently developed new branch in geotechnical engineering that offers innovative and eco-friendly solutions by leveraging natural processes to enhance soil properties. This dissertation examines the potential of soybean extract urease as a cost-effective substitute for analytical-grade enzymes in Enzyme Induced Carbonate Precipitation (EICP) applications for biocementation. This research examines its effectiveness in various aspects, such as coastal erosion control, desiccation crack remediation, and the removal of heavy metals. Essential …

Comparison Of A Terrestrial And Handheld 3d Laser Scanner In As-Built Building Information Model (Bim) Creation, Cedric Scott Jankowski

Theses and Dissertations

Advances in computer processing have allowed mobile 3D laser scanners to begin to rival terrestrial scanners in terms of accuracy and scanning speed. While terrestrial scanners are the established instrument used in BIM creation for existing buildings, their cost, immobility, and size warrants a comparison to mobile scanners. This evaluation used scans created with both scanner types, the resulting point clouds, and 3D models created by tracing these point clouds to compare the BIM models and resulting floorplans, which were checked against direct on-site measurements. Because terrestrial scanners are considered state-of-the-art, the evaluation focused primarily on comparing mobile scanner and …

Analyzing Lf/Vlf Lightning Waveforms To Estimate D-Region Electron Density Profiles: Process, Application, And Comparison, William R. Smith

Theses and Dissertations

Lightning waveforms in the low frequency (LF; 30-300 kHz) and the very low frequency (VLF; 3-30 kHz) can be exploited to produce data-driven ionospheric Dregion electron density profile (EDP) estimates with significantly higher spatial and temporal coverage than previously available. The lightning waveforms used in this paper are signals detected in the LF/VLF of negative cloud-to-ground lightning by the Earth Networks Total Lightning Detection Network. Each waveform contains a ground wave and a time-delayed ionospheric reflection. The time delay between the ground wave and ionospheric reflection has previously been used to estimate a single specular reflection altitude, where LF/VLF emissions …

Reentry Vehicle Trajectory Analysis & Performance (Re-Tap) Development And Application To Spacex Starship, Emma L. Webb

Theses and Dissertations

A modeling simulation tool for exo-to-endo atmospheric flight is developed to characterize errors associated with varying simulation fidelities from 3 to 6 degrees-of-freedom (DOF). Engineering approximation errors are quantified and compared with flight data from Apollo 10 and the first Space Shuttle Orbiter reentry (STS-1). The reentry reachability optimal control problem (OCP) is formulated in 6DOF and compared with point-mass solutions, revealing that point-mass solutions oversimplify the problem. A cylindrical reentry vehicle (CRV-1), similar to the SpaceX Starship, is introduced with necessary details for 6DOF analysis. The performance and reentry control capabilities of CRV-1 are captured through 6DOF solutions of …

Palindrome: A Bi-Directional Multi-Object Detection Framework For Relative Navigation And Autonomous Docking, Liam A. Weinfurtner

Theses and Dissertations

This work introduces a bi-directional, multi-object detection framework that integrates pose estimates from both receiver- and tanker-mounted cameras to improve accuracy and redundancy. A modular YOLO-based detection pipeline is trained using synthetic and real imagery, leveraging a bootstrap transfer learning approach to enhance sim-to-real performance. System evaluation in both virtual and real-world environments demonstrates improved detection robustness, pose estimation accuracy, and scalability. These advancements contribute to the development of AI-driven vision systems for AAR and other autonomous docking applications.

Thin-Filament Pyrometry In A Rotating Detonation Engine, Theodore B. Guetig

Theses and Dissertations

Rotating Detonation Engine (RDE) proves beneficial by creating a pressure rise across the combustor rather than a pressure drop seen in traditional aircraft combustors. Coupled with this high pressure is a high temperature in the detonation engine that is difficult to measure as it varies spatially and temporally. Thin-Filament Pyrometry (TFP) was performed on a 6-in RDE to measure these high temperatures. Temperature profiles were obtained over a variety of mass flows, equivalence ratios, and different axial locations within the RDE providing insight into the mixing process and where the heat release occurs. Successful determination of these temperature profiles within …

Misalignment Uncertainty In Near-Field Thz Scattering Experiments, Philip Patterson

Theses and Dissertations

This research investigates the effect of misalignment on the near-field scattering of cylinders in the 550-700 GHz frequency band. A Type-1 calibration is performed on previously collected data, using a near-field physical optics solution to simulate scattering at various positions and orientations. The alignment of the cylinders at the time of measurement is predicted by comparing the range profiles of the theoretical and calibrated responses. The data with the most similar range profiles had a mean calibration difference metric of -2.78 dB and a standard deviation of -0.57 dB, demonstrating the presence of sources of error that are dominant over …

Improvement Of Microcracking And Mechanical Properties Of Tungsten Fabricated Via Laser Powder Bed Fusion Through Alloying With Reactive Secondary Constituents, William S. Mockel

Theses and Dissertations

Tungsten (W), a Group VI transition metal, possesses a number of advantageous properties, most notably its impressive mechanical performance at extreme temperatures. While tungsten's nature render traditional manufacturing methods difficult, additive manufacturing through laser powder bed fusion (LPBF) presents a promising avenue for fabricating tungsten components. However, the material’s high ductile-to-brittle transition temperature combined with the embrittling effect of impurities mean that the residual stresses imparted by LPBF result in microcracking in tungsten, degrading its usefulness. This study sought to improve the characteristics of LPBF-W through the removal of embrittling oxygen content via alloying with low concentrations of reactive elements, …

Mechanical Response Of Triply Periodic Minimal Surface Gyroid Structures Under Combined Loading, Jay B. Patel

Theses and Dissertations

This work explored combined tensile and torsional loads applied to additively manufactured Inconel 718 specimens employing Triply Periodic Minimal Surface (TPMS) structures. The gyroid TPMS unit cell was selected with two variations of cylindrical cell maps, a rectangular cell map, and a spherical cell map. All four variants were tested in an axial-torsion test frame at room temperature using equal parts of vertical and angular displacement control until failure. The combined loading in these tests utilized tension and torsion. The data from the tests were compared to finite element analysis (FEA) models to visualize when yielding was predicted. Finally, the …

Impact Of Stochastic Travel Times On The Military Port Selection Problem: A Stochastic Programming Approach, William M. Titus

Theses and Dissertations

This research models and analyzes the impact of stochastic travel times on port selection during a large-scale mobilization of equipment from continental United States installations to deployment locations using sealift ships. A stochastic mixed-integer programming model is developed to minimize the average arrival time of equipment into theater. The model is solved using Sample Average Approximation. In the first stage, the model selects ports to open and assigns installations, equipment, and ships to open ports. In the second stage, travel times are realized, and equipment is assigned to specific ships that are scheduled to depart. Results show that the marginal …

Operational Energy Education: A Thematic Analysis Of Knowledge Area Needs And Educational Gaps, Nana Hene

Theses and Dissertations

Operational Energy (OE) education is vital for national security, military readiness, and fuel energy efficiency. This thesis analyzes the current landscape of OE education and identifies key gaps in awareness, energy knowledge, and curriculum structure. Through a reflexive thematic analysis of interviews with Subject Matter Experts (SMEs), the study underscores the necessity of integrating OE concepts into both educational and professional training programs. A framework is proposed to enhance OE education across various levels in the Air Force, aiming to cultivate a more energy-conscious and strategically prepared force. The findings highlight the critical need for targeted training, curriculum enhancements, and …

Military Entrance Processing Station Location And Capacity Optimization, Micah A. Hurst

Theses and Dissertations

This research optimizes the number, placement, and capacity of Military Entrance Processing Stations (MEPS) to minimize applicant and recruiter travel and improve recruitment efficiency. Using mixed-integer programming, it develops capacitated facility location (CFLP) and maximal covering location (MCLP) models, considering facility capacity, budget, and geographic coverage. Computational testing and scenario evaluations highlight opportunities to reduce travel and balance capacity. For example, the CFLP model adds three new MEPS, reducing annual applicant travel by 1.2 million miles in Florida and Texas and 1.0 million in California, while increasing accessibility within 60 miles of a MEPS. This data-driven approach provides USMEPCOM with …

Practical Estimation Of Action-Generation Mechanisms In Repeated Games, Vladimer Kellachow Iii

Theses and Dissertations

The goal of this research is to gain insight into how players of a game learn their strategy during the course of repeated play. The study employs the Experience Weighted Attraction (EWA) model, developed by Dr. Colin F. Camerer and Dr. Teck-Hua Ho, as the foundational behavioral framework. Using historic observed strategy decisions, the parameter values that define an opponent’s learning process are updated using various inference methods.

The Location Set Covering Disruption Problem, Richard A. Sheldon

Theses and Dissertations

This research models and analyzes a variant of the Location Set Covering Problem (LSCP) in a bilevel, game theoretic setting by posing the LSCP as a non-cooperative attacker-defender Stackelberg game, where facilities are to be emplaced by the defender from a boarder set of potential facility locations to cover a set of demands; however, an attacker removes the possibility of emplacing q specific facility locations with the objective to remove the maximum weighted value demands, and then lexicographically maximize the cost of coverage of remaining demands. A novel methodology leveraging lexicographic programming computed an optimal solution for 98% of all …

Forecasting Army Recruiting Mission Distribution, Maxwell A. Deihl

Theses and Dissertations

The Army’s recruiting landscape has changed markedly in recent years, raising questions about whether forecasting methods of Army contracts remain robust. This thesis recreates the presented models in Joshua McDonald’s 2015 thesis. It replicates and evaluates the models with updated data (2018–2023) to assess their current validity and compare them to novel alternative approaches, such as simpler regression models or neural networks. While the 2015 model remains a valuable baseline, results suggest that either refining its variables or adopting alternative methods can improve predictive accuracy and interpretability. Ultimately, the United States Army Recruiting Command has many options regarding how it …

Lethality And Survivability Of Autonomous Self-Sensing Uavs, Jeffrey T. Wilson

Theses and Dissertations

Unmanned Aerial Vehicles (UAVs) have seen increased usage over the past two decades during the Global War on Terrorism (GWOT), operating in low-risk environments against dispersed enemies with minimal counter-drone capabilities. However, as the U.S. military shifts focus to Multi-Domain Operations (MDO) and Large Scale Combat Operations (LSCO), UAVs face significantly higher risks, including frequent and successful attacks, as well as the exploitation of their technology. Battle damage assessment (BDA) is not new; however, autonomous self-assessment by UAVs represents a novel advancement. Currently, UAV BDA relies on manual inspection, requiring approximately eight hours per drone. By adopting self-sensing technology, UAVs …

Machine Learning Techniques To Detect Anomalies In T-38 Flight Sensor Data, Sydney M. Wekamp

Theses and Dissertations

Accurate sensors are critical for ensuring the safety of aircrew. However, detecting faulty sensors remains a significant challenge for the Test Pilot School at Edwards Air Force Base in California. Current methods rely on either student pilots identifying anomalies or waiting for sensors to fail completely before repairs are made—an approach that lacks reliability and consistency. This research aims to address these shortcomings by implementing machine learning techniques to detect sensor faults proactively. To date, applying machine learning to a dataset of this size, encompassing numerous sensors on the same aircraft, is unprecedented. The project focuses on establishing strong baseline …