Engineering Commons^™

Elucidating Differences In Constitutionally Isomeric Diamine- And Bisphenol-Based Polybenzoxazine Networks, Benjamin L. G. Morasch

Dissertations

This dissertation aims to expand the fundamental understanding of diamine-based benzoxazine chemistry by examining how synthesis influences the network properties of 4,4’-ddm and phenol-based (P-ddm) benzoxazine, compared to the constitutionally isomeric bisphenol-F and aniline-based (BF-a) benzoxazine. While bisphenol-based benzoxazines such as BF-a have been studied more extensively, diamine-based benzoxazines are still relatively unexplored due to the competition with the formation of 1,3,5-hexahydrotriazine intermediates and the inconsistent thermal and mechanical properties reported in the literature. These inconsistencies stem from factors including synthetic methods, curing conditions, and degradation during polymerization that have been overlooked.

To address these issues, this dissertation is organized …

Upcycling Commodity Polymers To Advanced Materials For Energy And Environmental Sustainability, Anthony Griffin-Espinoza

Dissertations

Synthetic polymers play an essential role in nearly every aspect of our lives. Extending beyond single-use packaging, polymeric material design has progressed to attain tailorable architectures granting exceptional performance across advanced applications, including carbon-fiber reinforced polymer composites for aerospace, conductive materials for soft electronics, and drug carriers for biomedicine. While highly promising, intricately designed polymers needed to achieve excellent performance often have limited processability, complex synthetic methods, and expensive precursors. Furthermore, due to a lack of recyclability, commodity polymer waste streams result in both environmental impacts and a substantial loss of economic value. This dissertation focuses on developing robust strategies …

Privacy Preserving-Based Artificial Intelligence For Precision Agriculture, Partha P. Sengupta

Dissertations

The research work finds a solution to precision agriculture of cotton cultivation using artificial intelligence (AI) models. Two sets of model performance based on the application are selected namely a low resource and a high resource setting. This is because using drone surveys to capture images identifying the classes of stressed and unstressed cotton plantation requires limited model architecture and CPU based computation. Thus, traditional AI models were selected for low resource settings. Again, for high computation intensive models like transfer learning-convolution neural network (CNN) based architectures were grouped into high resource settings. There was another issue of class imbalance …

Understanding Crystallization Behaviors Of Polyethylene-Derived Vitrimers, Sara Valdez

Dissertations

Polyolefins (POs), particularly polyethylene (PE) and polypropylene (PP), are among the most widely utilized polymers globally, valued for their low production costs and favorable mechanical properties stemming from their semicrystalline microstructure. However, their extensive use and improper disposal have raised serious environmental and human health concerns. In response, PO-derived covalent adaptable networks (CANs) have emerged, integrating dynamic chemistries to enable recyclability and sustainable end-of-life strategies. While existing literature has largely focused on novel CAN systems, structure–property relationships, and network rearrangement in relation to thermal transitions (e.g., topological freezing temperature), the influence of network formation on crystallinity and crystallization kinetics remains …

Steel-Concrete Composite Girder Experiments To Isolate Interface Load Transfer Effects On Stud Fatigue Life, Marc Crespi Hromcova

Graduate Theses and Dissertations

Metal fatigue resulting from repeated loading is a primary limit state that affects the quantity of headed shear studs required in the composite design of steel bridge girders. While concrete-deck-to-steel-superstructure load transfer is only considered through stud bearing in the American Association of State Highway Transportation Officials (AASHTO) design standards, friction and interface interlocking effects may also contribute. This study aims to experimentally quantify the effect of interface conditions on the fatigue life of headed studs within composite girders. In this study, two full-scale composite girder specimens having the same geometry and material properties are tested with two interface conditions. …

Optimizing Indigenous Timber Short-Gap Crossing Designs By Minimizing Wood Moisture Content, Robert Greenwood

Graduate Theses and Dissertations

Reducing moisture content increases wood strength and reduces the weight of timber members. An accurate and efficient method for measuring moisture content is important for the design and construction of indigenous timber short-gap crossings. This study evaluates different methods for measuring moisture content in timber, describes a methodology for developing a representative moisture content value for a timber log, and approaches for quickly drying large timber logs. The results of this thesis will support activities in developing a representative moisture content of a log for structural design purposes and reducing weight for constructability purposes. The approaches discussed were developed considering …

Toward A Better Understanding Of Friction, Adhesion, And Stud Bearing Shear Transfer At The Steel-Concrete Interface Of Composite Bridge Girders, Callie Grace James

Graduate Theses and Dissertations

Following curing of the concrete deck, load transfer between the concrete and steel components in a composite bridge girder is possible through three mechanisms: 1) mechanical contact (bearing) between the embedded shear connectors and surrounding cured concrete, 2) adhesion between the cured concrete and steel-section top flange, and 3) friction between the contacting materials Understanding the mechanisms of bearing, adhesion, and friction shear transfer at the steel-concrete interface of composite bridge girders is necessary for efficient proportioning of headed shear connectors (or studs) in design. To better understand the roles that stud bearing, adhesion, and friction play in composite girder …

Computational Fluid Dynamics Based Optimization Method Applied To Hydrokinetic Turbine Devices, Stuart Glenn Fletcher

Graduate Theses and Dissertations

This thesis presents a computational investigation of optimal kinematic operating parameters governing various hydrokinetic turbines (HKT) systems for the use of power generation within river and tidal environments. Two separate studies are performed. The first study investigates optimal cycle parameters for simple and complex kinematic modes governing the motion of oscillating foil energy harvesters (OFEH). An iterative gradient-ascent optimization method is used to search for local efficiency optima based on an initial set of kinematic parameters. To search the operational space for up to eight degrees of freedom (DOF), a maximin space filling condition was implemented to efficiently compute initial …

Validation Studies Of A Dynamic Hybrid Rans-Les Turbulence Modeling Strategy For Cfd Simulation Of Gas Turbine Component Film Cooling, Cole Simmonds

Graduate Theses and Dissertations

Computational prediction of the flow physics associated with gas turbine film cooling is important for ensuring effective heat transfer design. These flow fields are highly turbulent and anisotropic, making the accuracy and efficiency of the chosen turbulence model an important aspect of performing high quality computational fluid dynamics (CFD) based analysis. Current industry standard Reynolds-averaged Navier-Stokes (RANS) turbulence models such as RANS k-ω SST, while computationally efficient, are subject to relatively high levels of uncertainty in their ability to predict these turbulent flow fields. In contrast, high fidelity methods such as Large Eddy Simulation (LES) are computationally very expensive, while …

Optimal Control Of Human Exercise Using An Individualized Physiological Three-Tank Model And Dynamic Programming, Asal Lotfi

All Theses

This thesis develops a physiologically inspired three-tank model of human bioenergetics to describe and optimize fatigue and recovery during exercise. The aerobic, phosphagen, and glycogen systems are modeled as coupled reservoirs whose states constrain instantaneous power output. Building on this representation, dynamic programming is used to compute pacing strategies that respect physiological limits while maximizing task-specific goals such as peak power or total work over a fixed duration, enabling individualized, goal-driven exercise prescriptions. The three-tank dynamics are formulated in continuous time and then discretized under a zero-order-hold assumption for simulation and optimal control. Model parameters are linked to standard field …

Dynamic Modeling And Simulation Of A Power Generation Steam Rankine Cycle For A Fluoride Salt-Cooled High-Temperature Reactor Nuclear Power Plant, William R. Ton

Master's Theses

Nuclear Fluoride Salt-Cooled High-Temperature Reactors (FHRs) have the potential to greatly improve nuclear technology in terms of safety and cost. By combining molten salt coolant technology from the Molten Salt Reactor (MSR) and TRISO fuel technology from the Very High Temperature Gas Reactor (VHTR), FHRs may operate at significantly lower pressures than Light Water Reactors (LWRs) and with a more robust fuel source that is excellent at containing fission products. However, as no FHR has been built, there are still many design questions to address. This thesis uses transient computer modeling and simulation to investigate how an FHR could potentially …

Reverse Design Of Solid Rocket Grain Geometry, Yechan Kang

Master's Theses

The reverse design of solid rocket motors remains a challenging process due to the nonlinear relationship between the grain geometry and the internal ballistics. The reverse design process involves obtaining an optimal grain geometry given a target performance curve set by mission requirements, which is the inverse problem of the forward design. The purpose of this study is to assess the validity and implementation of neural network and simulated annealing algorithms to perform the reverse design process. A modified phase field model of the eikonal equation is derived to simulate the evolution of combustion surfaces over time, enabling burn back …

Using Scenario-Based Design Activities To Explore Sociotechnical Thinking In Engineering Professionals, James M. Whealan

Master's Theses

Sociotechnical thinking is the ability to recognize the interconnectedness of both technical and non-technical dimensions such as environmental, economic, social, cultural, and political factors. Although traditional engineering curriculum often emphasizes technical knowledge and skills, research suggests that engineering work is inherently sociotechnical. While sociotechnical thinking is a critical engineering skill, relatively little is understood about the nature of it or the different aspects comprised within it. To that end, this study addresses the following research question: What sociotechnical factors do engineering professionals consider in a collaborative scenario-based design activity? To answer this question, we conducted a qualitative study of engineering …

Hallucination Techniques For Self-Supervised Synthetic Datasets For Mobile Robots, Wyatt D. Colburn

Master's Theses

Classical techniques in autonomous navigation struggle in tightly constrained spaces. Machine learning has been shown to perform better in these difficult environments but most techniques require large amounts of navigation experience for training. Using a new machine learning paradigm learning from hallucination (LfH), training data can be collected in a safe environment and not require supervision. Data is collected in real time while an agent performs a random walk in free space, supervision is not required as there are no obstacles for the robot to run into. After a random walk a post processing pipeline will hallucinate a safety corridor …

Time-Domain Symmetrical Components For Detection And Analysis Of Unbalanced Faults In Three-Phase Systems, Ryan Pospichal

Master's Theses

Unbalanced faults in three-phase power systems degrade performance, increase losses, and threaten equipment reliability. Traditional frequency-domain approaches using phasor analysis and symmetrical components offer valuable steady-state insights but respond too slowly for transient or rapidly changing conditions. This thesis investigates time-domain symmetrical components (ISCs) as a faster, physically interpretable method for detecting and analyzing unbalanced faults directly from instantaneous voltages and currents. Two ISC computation techniques were developed and compared: a polar-form method, applying one-third and two-thirds cycle time delays, and a rectangular-form method, which achieves equivalent phase shifts using only a quarter-cycle delay. Simulations in Microsoft Excel verified both …

Development Of A Kytc Highway Geometric Design Workshop, Jill Asher, Jeff Jasper, Travis Thompson, Chris Van Dyke

Kentucky Transportation Center Research Report

In-depth knowledge of geometric design principles is a prerequisite for delivering road projects that provide safe and efficient multimodal mobility for all users. Historically, Kentucky Transportation Cabinet (KYTC) early-career design staff arrived at the agency with little design experience. The agency has relied on a combination of short courses and mentorship provided by experienced personnel to bring early-career design staff up to speed on design best practices. However, this approach to training carries limitations. Employee turnover and imposing workloads make it challenging for early- and even mid-career design professionals to receive guidance from seasoned designers who have long tenures at …

The Importance Of Leader-Member Exchange And Psychological Contracts In Highly Qualified Researchers, Robin L. Ingerick Dba

Theses & Dissertations

This study examined the significance of the relationship between leader-member exchange (LMX) and psychological contracts in United States-based research organizations. When the organization-manager-employee relationship deteriorates, psychological contract breaches can occur, negatively affecting employee outcomes and the organization's financial success and stability. Existing knowledge highlights several factors that influence relationships, including reciprocated treatment, work behaviors and reactions, trust, professional respect, affect, mutual interaction, work autonomy, communication, job satisfaction, and fulfillment. The study sought to determine to what extent is there a predictive relationship between LMX and psychological contracts (employee obligations, employer obligations, fulfillment, and contract transitions) of highly qualified United States-based …

Development And Validation Of A Thermal Model For An Electric Vehicle Transmission, Ghazal Rajabikhorasani

Dissertations

This research investigates the thermal behavior of a high-speed electric vehicle (EV) helical gearbox with the goal of improving the prediction accuracy of component temperatures and total power losses under a range of operating conditions. The study focuses on developing a physics-based lumped-parameter thermal network model capable of capturing the main heat generation and dissipation mechanisms within the transmission. The model integrates experimentally validated loss correlations for gears, bearings, seals, and churning, as well as convective and radiative heat transfer paths.

The thermal network model was coded in MATLAB and validated through a series of controlled experiments performed on an …

Investigation Of Laser Based Flow Diagnostics With Metastable Argon, Sterling S. Gordon

Physics Theses & Dissertations

The overarching motivation of this work is the development of seedless, non-intrusive, laser-based diagnostics for supersonic airflow in wind tunnels. To advance this goal, this dissertation fo-cuses on three-photon excitation in a research-grade argon beam within a tabletop vacuum system, which offers a controlled environment for testing and refining the approach. The chosen excitation scheme drives argon atoms to the 3d[5/2]₃ state using a pulsed Ti:Sapphire laser system, enabling time-of-flight (ToF) measurements on atoms that subsequently undergo a multi-step decay to the metastable 4s[3/2]₂ state. Although full realization of this excitation scheme was hindered by technical …

Design And Assessment Of A Single-Blade Rotary Wing For Use In Vertical Takeoff And Landing (Vtol) Aircraft, William C. Mcmasters

Mechanical & Aerospace Engineering Theses & Dissertations

A single-bladed propeller was designed to determine its efficacy in increasing efficiency of quadplane aircraft in the cruise configuration while still providing sufficient vertical lift for the vertical takeoff portion of flight. Aerodynamic theory predicts higher efficiency for single-blade propellers, resulting in a lower power requirement. A counter-weighted single-blade was modeled after a 10x5 model aircraft propeller used in small unmanned vehicles with a steel counterweight to balance centrifugal forces. The propeller was tested in the ODU wind tunnel to determine performance at various Advance Ratios (J). The research suggests that single-blade propellers show comparable performance compared to two-bladed propellers …

On The Scalability Of Anisotropic Mesh Adaptation On Distributed And Shared Memory Architectures For Numerical Approximations, Kevin Mark Garner Jr.

Computer Science Theses & Dissertations

Mesh generation is a critical component in numerical approximations of Partial Differential Equations (PDEs). One such example includes Computational Fluid Dynamics (CFD), as CFD simulations in turn are crucial for applications in many industries, such as personalized healthcare and the design of aerospace vehicles. Generating high quality meshes for large-scale CFD problems presents a significant bottleneck in the CFD workflow. This dissertation proposes “fast,” parallel 3D mesh generation methodologies that are designed to leverage the concurrency offered by emerging High-Performance Computing (HPC) architectures. First, a distributed memory method is presented that integrates a sequential state-of-the-art isotropic, advancing front local reconnection-based …

Component Model Development Of Heat Exchangers, Expanders, And Control Valves For Autonomous Cryogenics Plant Cool-Down, William Harris Buhrig Iv

Mechanical & Aerospace Engineering Theses & Dissertations

The traditional method of cryogenic plant cool-down involves having continuous on-call staff to head into the office at any time to modify the existing multi-layered PID control systems if the on-call staff member detects a significant deviation from the cool-down plan. This thesis aims to outline an effective method for modeling the structure of systems with performance characteristics that deviate from design requirements and from ideal inlet-outlet correspondence, enabling the adjustment and modification of existing control structures across all Thomas Jefferson National Accelerator Facility (JLab) cryogenic refrigeration plants. Analytical Modeling and Gaussian Process Regression (GPR) are applied to model the …

Machine Learning For Anomaly Detection In Neural Network Security And Srf Cavities, Hal Ferguson

Electrical & Computer Engineering Theses & Dissertations

This dissertation explores the development and deployment of machine learning approaches to address critical challenges in anomaly detection across two distinct domains: neural network security in federated learning settings and cavity behavior analysis in particle accelerator operations at Jefferson Lab in Newport News, Virginia. Anomaly detection identifies deviations from expected patterns, safeguarding systems in cybersecurity, industry, and research against malicious activities and failures. This dissertation demonstrates how our machine learning approaches enhance detection accuracy and efficiency in both neural network security and industrial applications.

First, we investigate vulnerabilities in deep neural networks deployed in federated learning. Although federated learning preserves …

Comparative Analysis Of Emergent Behaviors Of Three Drone Swarm System Models For Targeting Using Agent-Based Modeling And Simulation, Arsenio T. Gumahad Ii

Engineering Management & Systems Engineering Theses & Dissertations

This dissertation introduces a novel computational simulation framework for evaluating the emergent behaviors of three swarm drone models using Agent-Based Modeling and Simulation (ABMS). The three swarm models are a Leader-Follower swarm model based on Bruckstein's antline theory, a Flocking model based on a simplified Reynolds 'Boids’ model, and a Stigmergic model with pheromone-based coordination. The primary objective of the simulation is to evaluate the performance of these models in delivering a user-defined number of drones of each type to a target area of interest in four separate scenarios, resulting in 50,000 separate simulation trials. Each scenario was structured to …

Development Of A Handy Tool For The Selection Of Urban Stormwater Best Management Practices, Aaron T. Kenny

Civil & Environmental Engineering Theses & Dissertations

The City of Norfolk, Virginia faces substantial stormwater management challenges due to shallow groundwater, tidal influence, dense urban development, and limited right-of-way. These constraints limit the applicability of many Best Management Practices (BMPs) and require the early identification of feasible practices before detailed hydrologic modeling. This thesis introduces a decision-support tool that quickly and systematically identifies and prioritizes BMPs that are both feasible and well-suited to Norfolk’s Municipal Separate Storm Sewer System (MS4) program, streamlining early-stage selection and saving time and resources.

The tool implements a two-stage methodology. First, feasibility gates are applied using catalog attributes derived from the Virginia …

Human Identification And Action Recognition Using Small Data And Deep Domain Adaptation, Alexander M. Glandon

Electrical & Computer Engineering Theses & Dissertations

Human identification and human action recognition problems are two important research areas for real-world security and surveillance applications. In both human identification and action recognition, it is necessary to operate by collecting small datasets in the field, possibly in a short time window of observation. This dissertation studies and develops computational modeling and high-performance machine learning (ML) and deep learning (DL) models for human identification and human action recognition using small amounts of data. These methods and computational models may be useful for different security and surveillance applications.

This dissertation on human recognition develops a ML computational model to estimate …

Separating The Control Of Moving And Holding In Human Post-Stroke Arm Paresis, Alkis M. Hadjiosif, Kahori Kita, Scott T. Albert, Robert A. Scheidt, Reza Shadmehr, John W. Krakauer

Biomedical Engineering Faculty Research and Publications

Moving and holding-still (holding) have been posited to be separately controlled. The paretic arm after stroke exhibits different abnormalities during rest vs. movement, providing an opportunity to ask whether control of these behaviors is independently affected in stroke. We quantified resting postural abnormalities in human stroke patients by measuring their biases in force production as they held their hand still in various locations in a planar workspace and then assessed whether these resting force biases influenced reaching in the same workspace. Patients displayed marked resting force biases at each location, even when the arm was supported. However, these …

Effects Of Wc Additions On The Phase Formation Of (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B2 High Entropy Dual Phase Ceramics, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas

Materials Science and Engineering Faculty Research & Creative Works

High entropy dual phase (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B2 ultra-high temperature ceramics were produced from powders synthesized by boro-carbothermal reduction. Systematic additions of 2.5 wt%, 5 wt%, and 10 wt% WC were incorporated after powder synthesis. Additions of 2.5 wt% and 5 wt% WC dissolved into the host ceramics, resulting in complete solid solution formation and nearly full densification. In contrast, a secondary monoboride phase evolved for the composition with 10 wt% WC, in addition to the main high entropy carbide and diboride phases. Thermodynamic analysis revealed that WB formation was favorable for WC additions in the presence of metal diborides at the sintering …

Thermal Properties Of High Entropy Dual Phase (Hf,Nb,Ta,Ti,Zr,)C-(Hf,Nb,Ta,Ti,Zr)B2 Ceramics: Comparison With The High Entropy Single-Phase Ceramics And The Effect Of Wc Additions, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas

Materials Science and Engineering Faculty Research & Creative Works

The heat capacity, thermal diffusivity and thermal conductivity of (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B₂ high entropy dual phase ceramics were evaluated from room temperature to 1800 °C and compared with the constituent high entropy single phase ceramics of the same nominal compositions. Thermal conductivity of the (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B₂ dual phase ceramic increased from 17.7 W m⁻¹ K⁻¹ at room temperature to 54 W m⁻¹ K⁻¹ at 1800 °C. The addition of WC to the dual phase ceramic reduced its thermal conductivity. For the addition of 5 wt% WC, room temperature thermal conductivity was 16.8 W m⁻¹ K^{−1 …}

Micro/Nanomechanical Properties Of Top-Seeded Melt Grown Ybco Single Crystals Determined Using Depth Sensing Indentation, Ugur Kolemen, Cafer Mert Yesilkanat, Fikret Yilmaz, Fatih Dogan, Orhan Uzun

Materials Science and Engineering Faculty Research & Creative Works

Mechanical properties of the bulk YBa2Cu3O7-x (YBCO) single crystal superconductor, prepared by using the Top Seeded Melt Growth (TSMG) method, were determined. Property measurements were conducted by the nanoindentation method under various loads and the micro indentation method at different temperatures. Hardness (H) and reduced elastic modulus (Er) values were calculated by using the Oliver–Pharr method. According to hf/h max values found from load- displacement curves, there is a sink in behavior around outer rim of the indents that was confirmed by atomic force microscopy (AFM) analysis. Nanoindentation analyses conducted on upper section, middle section and subsection revealed that all …