Engineering Commons^™

High-Power Power Conditioning Systems For Medium-Voltage Applications, Ahmed Rahouma Fares Rahouma

Graduate Theses and Dissertations

The purpose of this dissertation is to address the background, theoretical analyses, design methodologies, and evaluation techniques relevant to high-power power conditioning systems (PCSs) tailored for medium-voltage (MV) applications. Conventional PCSs, reliant on line-frequency transformers (LFTs), suffer from many problems including low power densities, inflexible designs, and scalability constraints. Employing multilevel converters (MLCs), particularly cascaded H-bridge topology, eliminates the need for these LFTs. A key focus lies in minimizing the number of cascaded building blocks by harnessing MV power switching modules. The dissertation makes two primary contributions: firstly, it offers a design methodology for MV-PCS, facilitating the selection of the …

Modeling, Optimization, And Characterization For Choke Horn Antennas, Ibrahim Nasser I Alquaydheb

Graduate Theses and Dissertations

This dissertation presents a comprehensive study focusing on the modeling, optimization, and characterization of choke horn antennas (CHAs). An analytical model designed to capture the parameters of CHA and derive the total radiated fields from the choke and waveguide elements is primarily focused on in this work. Compared to the use of simulation software, such as ANSYS HFSS (High Frequency Structure Simulator) or CST Studio, which employs numerical methods to simulate and calculate antenna performance, numerous advantages are offered by the analytical model. Analytical models provide deeper insight into electromagnetic interactions and the principles governing antenna behavior, leading to a …

Development Of A High-Throughput Screening Platform To Profile Gene Delivery And Transcriptional Control In Macrophages, Alexis Ivy

Graduate Theses and Dissertations

Macrophages are an important cell type in the body responsible for orchestrating the inflammatory response and return to homeostasis. Macrophages are often implicated in a multitude of disease pathologies including delayed wound healing, excessive fibrosis, autoimmune disease, and immunosuppression within the tumor microenvironment. Although macrophages have been targeted for therapeutic applications, success in utilizing them has remained elusive due to their relative ease of phenotype switching between inflammatory and anti-inflammatory. The challenge that remains is developing clinically relevant delivery vehicles that can target macrophages without causing a phenotypic switch counter-productive to the desired response. This is especially important when targeting …

Molecular Beam Epitaxy Of Gesn On Iii-V Substrates For Photonic Applications, Calbi Gunder

Graduate Theses and Dissertations

This dissertation explores the advancement of germanium-tin (GeSn) as a tuneable narrow bandgap material, crucial for the development of high-efficiency photodetectors and laser devices in near- and mid-infrared technologies. We investigate the synthesis challenges, particularly the lattice mismatch between GeSn alloys and substrates, which significantly affects their crystalline and optical qualities. Through molecular beam epitaxy, we examine the growth of Ge and GeSn on GaAs (001) substrates, employing Ge/GaAs and Ge/AlAs buffer layers to investigate these challenges. Our findings, characterized by X-ray diffraction, atomic force microscopy, reflection high-energy electron diffraction, and photoluminescence, demonstrate the production of high-quality Ge layers, achieving …

Application Of Electrical Impedance Tomography To Cementitious Composites, Hugo Zazueta

Theses and Dissertations

This thesis explores the feasibility of using Electrical Impedance Tomography (EIT) for detecting damage in cementitious composites. Cementitious composites, such as concrete and cement mortar, are insulating; any conductive properties arise from the moisture within their pores and capillary structures. The proposed concept herein is that formed internal damages in cementitious composites consequently alter their pore and capillary structure, which can then be detected through EIT imaging. To construct tomographic images, the Gaussian Newton (GN) reconstruction algorithm, enhanced with priors, was employed. The results were then compared across different reconstruction processes. Cylindrical cement pastes and cement mortar samples were prepared, …

Hardware-Oriented Protection And Acceleration For Machine Learning Application, Antian Wang

All Dissertations

The security of Machine Learning (ML) grows along with the development of high-performance models and expanding application scenarios. Numerous users are benefiting from the convenience brought by transformative ML applications. In the meantime, various attackers are trying to find vulnerabilities within ML deployment service models, thereby undermining the performance of ML and jeopardizing stakeholders’ interests. The dissertation focuses on the two aspects of secure ML applications: acceleration and protection. Homomorphic Encryption (HE) emerges as a widely recognized security primitive suitable for the cloud computing service model, where the computation can be performed over ciphertext without decryption. However, evaluations in the …

The Role Of Kinases Signaling In Organogenesis, Fatemeh Nasehi

All Dissertations

Kinases are crucial regulators of organ development and differentiation. This thesis investi- gates the roles of TAK1, TGFbeta-Activate Kinase 1 (TAK1/Map3K7), and Akt3 kinases in skeletal, cardiac muscle, and cartilage. TAK1 is pivotal for the differentiation of various organ systems, including sinoatrial node and cartilage, and is responsible for phosphorylat- ing a diverse array of downstream kinases. We identified several novel proteins, including phospho-Akts, that are upregulated in response to TAK1 activation. We discovered severe Dilated Cardiomyopathy (DCM) and cartilage defects in Akt3 mutant mice. Although this mouse mutant has been studied for over two decades, we are the first …

Identification And Validation Of A Measurement Of Emergency Physician Workload During End Of Shift Patient Handoffs, Steven Foster

All Dissertations

Recent increases in emergency physician (EP) workload have been identified as contributors to increased EP burnout, increased staff attrition, decreased patient safety, and increased patient admission rates. Patient handoffs have been extensively researched as critical points in patient care, with existing research primarily focusing on communication errors and interventions designed to standardize handoff communication protocols.

While end of shift handoffs in hospital emergency departments (EDs) intuitively represent a transfer of patient caseload from an outgoing EP to an incoming EP, there is a fundamental lack of literature examining how such handoffs contribute to EP workload, and a similar lack of …

Computer Vision Algorithms For Assessment Of Surgical Suturing Skill Using Hand And Needle Motion, Jianxin Gao

All Dissertations

Surgical suturing skill assessment is a crucial part of surgical education. Vascular surgery educators have developed a simulation-based examination called Fundamentals of Vascular Surgery, which includes a clock-face model for assessing open surgical suturing skills. The clock-face model, however, requires the valuable time of expert surgeons to determine examinees' skills. Moreover, expert surgeons have different judgments for appropriate sutures, which leads to inconsistent grading. These limitations motivate us to use sensors to measure examinees' needle motions and hand motions during the clock-face suturing exercises, and then use the measurements for objective suturing skill assessment.

To assess suturing skills based on …

Novel Meta-Materials Application For Pressure-Offloading Of Diabetic Foot Ulcers, Kyle Walker

All Dissertations

Diabetes and its associated complications have seen their prevalence sharply rise in the United States over the past few decades. In fact, the prevalence of diagnosed diabetes has nearly doubled from 5.1% of the US population in 1988, to 9% in the most recent CDC report, which does not include the large percentage of the population with undiagnosed or prediabetes. Of this diabetic population, it is estimated that up to 34% will experience at least one foot ulcer during their lifetime. In worst case scenarios, these ulcers can become infected and eventually require amputation of a portion of, or the …

On The Structure, Energy, And Segregation Behavior Of Grain Boundaries In Metallic Systems, Yasir Mahmood

All Dissertations

Nearly all structural metallic systems are multi-component polycrystalline aggregates; their microstructures are composed of crystalline grains that are internally joined at grain boundaries (GBs). This thesis focuses on GB structure, energy, and chemistry, as these greatly influence many material properties and processes, including boundary dynamics during processing treatments or under operating conditions.

Using atomistic simulations, we examine the impact of metastable GB structures on solute segregation. A wide range of GB geometries and metastable structures are used in our study. The Al-Mg alloy is used because it is of interest for light weighting. The atomistic simulation results are used to …

The Development Of A Novel Cartilage Analog Scaffold For Chondral Regeneration, Vishal Thomas

All Dissertations

Focal Chondral Defects (FCDs) are cartilage injuries that affect about 900,000 Americans every year. Left untreated, these may lead to osteoarthritis and eventually necessitate painful knee replacements. Current treatment options are limited in terms of durability, cost, and availability of grafts. Tissue engineering, using natural scaffolds, are a highly attractive alternative promising cost efficiency, abundance, and long-term benefits. However, their low mechanical strength and dense matrices are impediments that could lead to sub-optimal repair.

In this work, a natural biomaterial, the bovine nucleus pulposus (bNP), derived from intervertebral disc tissue, was identified as a candidate scaffold for cartilage regeneration. Mechanical …

Monitoring Vehicle Seat Occupancy Status And Tracking Human Passenger Activities Inside Vehicle Passenger Cabins, Rahul Prasanna Kumar

All Dissertations

An autonomous vehicle (AV) is a promising engineering innovation that can operate without a human driver. Nonetheless, to ensure passenger safety and comfort in the absence of human drivers, the vehicle must continuously monitor and predict how the cabin’s state will evolve in the immediate future. The two major factors influencing the cabin’s state are the occupancy statuses of vehicle seats and the activities of human passengers occupying them. Therefore, this dissertation presents a system employing a capacitance-sensing mat and a machine learning unit to monitor vehicle seat occupancy status and track passenger activities non-intrusively. While the mat integrates with …

Vision-Based Autonomy Stacks For Farm Tractors And Intelligent Spraying Systems In Orchards, Shengli Xu

All Dissertations

Autonomous tractors equipped with intelligent sprayers have become a pivotal aspect of smart farming (SF), marking a transformative shift in traditional agricultural practices and holding the potential to revolutionize the farming industry. With 2,453,620 fruit-bearing acres in the United States as of 2022, there is a pressing need for the implementation of autonomous systems for farm tractors and intelligent spraying systems in orchards. These advancements can significantly reduce labor costs, address labor shortages, and minimize spray loss. Furthermore, to enhance profitability and productivity, it is essential to develop low-cost yet effective vision-based autonomy systems that can operate efficiently across various …

Efficient And Secure Data Transmissions In Emerging Heterogeneous Wireless Networks, Sihan Yu

All Dissertations

The widespread deployment of wireless devices facilitates the Internet of everything, greatly enhancing communication efficiency and improving people’s daily experiences. The interconnectivity of wireless devices relies on wireless communication technologies. With the development of various emerging communication technologies, wireless networks have become increasingly vast and complex, giving rise to numerous new challenges such as efficiency and security concerns.

In wireless networks, different devices may utilize different communication protocols, resulting in heterogeneous wireless networks. Communication among heterogeneous devices is challenging, often leading to conflicts and low communication efficiency when utilizing limited communication resources (e.g., spectrum resources). Moreover, the coexistence of heterogeneous …

Convex Approach To Data-Driven Optimal Control With Safety Constraints Using Linear Transfer Operator, Joseph Raphel Moyalan

All Dissertations

This thesis is concerned with the data-driven solution to the optimal control problem with safety constraints for a class of control-affine nonlinear systems. Designing optimal control satisfying safety constraints is a problem of interest in various applications, including robotics, power systems, transportation networks, and manufacturing. This problem is known to be non-convex. One of this thesis's main contributions is providing a convex formulation to this non-convex problem. The second main contribution is providing a data-driven framework for solving the control problem with safety constraints. The linear operator theoretic framework involving Perron-Frobenius and Koopman operators provides the convex formulation and associated …

Physics-Informed Machine Learning Methods For Inverse Design Of Multi-Phase Materials With Targeted Mechanical Properties, Yunpeng Wu

All Dissertations

Advances in machine learning algorithms and applications have significantly enhanced engineering inverse design capabilities. This work focuses on the machine learning-based inverse design of material microstructures with targeted linear and nonlinear mechanical properties. It involves developing and applying predictive and generative physics-informed neural networks for both 2D and 3D multiphase materials.

The first investigation aims to develop a machine learning method for the inverse design of 2D multiphase materials, particularly porous materials. We first develop machine learning methods to understand the implicit relationship between a material's microstructure and its mechanical behavior. Specifically, we use ResNet-based models to predict the elastic …

Data-Driven Enhanced Energy Management System Applications For Energy Control Centers, Dulip Madurasinghe

All Dissertations

This dissertation explores the pressing needs of modern bulk power system operation and control and delves into enhancements to EMS applications with minimal infrastructure development. The dissertation investigates three main EMS application enhancements. The transmission network topology processing (TNTP) is a foundational application of the EMS. A physics-based hierarchical transmission network topology processing (H-TNTP), including substation configuration identification, to improve efficiency and reliability is proposed. Secondly, a multi-level distributed linear state estimation (D-LSE) approach solely based on PMUs is proposed utilizing H-TNTP as the network modeling tool. The D-LSE can conduct linear state estimation (LSE) at either substation, area or …

Integrating Artificial Intelligence And Augmented Reality For Enhanced Task Performance In The Construction Industry, Aasish Chandrika Bhanu

All Dissertations

The Architecture, Engineering, and Construction (AEC) sector, characterized by its complex tasks, often faces challenges in adopting cutting-edge technologies, a trend that can significantly hinder productivity improvements compared to other industries. This dissertation explores the emerging integration of Artificial Intelligence (AI) and Augmented Reality (AR) within the AEC domain, investigating how effectively this can be implemented to potentially revolutionize industry practices. AI could be used in the AEC domain for advanced analytical and decision-making processes, while AR could be used for training, visualization, and remote collaboration.

In scenarios where construction site workers require expert guidance, these technologies could be helpful. …

Opioid Overdose Epidemic Modeling, Chelsea Spence

All Dissertations

The opioid overdose crisis in the United States has led to thousands of lost lives and thousands more people struggling with opioid dependence. Disease modeling allows researchers to examine the course that the disease may take and to investigate policies to determine the effects they may have. Disease models can be used to model non-communicable diseases and have been used to study opioid use disorder. Many types of disease models exist with their own inherent benefits and drawbacks.

In this dissertation, we provide a scoping review of the disease models that have been used to study the opioid overdose epidemic. …

Emerging Technologies And Advanced Analyses For Non-Invasive Near-Surface Site Characterization, Aser Abbas

All Graduate Theses and Dissertations, Fall 2023 to Present

This dissertation introduces novel techniques for estimating the soil small-strain shear modulus (G_max) and damping ratio (D), crucial for modeling soil behavior in various geotechnical engineering problems. For G_max estimation, a machine learning approach is proposed, capable of generating two-dimensional (2D) images of the subsurface shear wave velocity, which is directly related to G_max. The dissertation also presents a method for estimating frequency dependent attenuation coefficients from ambient vibrations collected using 2D arrays of seismic sensors deployed across the ground surface. These attenuation coefficients can then be used in an inversion process …

Computational Fluid Dynamics Modeling Of Air Demand For Fixed Cone Valve In Energy Dissipating Structure, Matthew S. Harames

All Graduate Theses and Dissertations, Fall 2023 to Present

Fixed cone valves are commonly installed as low-level outlet devices to discharge water from reservoirs. When discharging water, the fixed cone valves require an air vent to properly operate and maintain the valve. There is a current lack of published information regarding the accuracy of model studies to properly estimate the air demand on the full-size prototype. This research aims to help close that gap by providing data comparison between a model and prototype. Furthermore, computational fluid dynamics (CFD) simulations may be used to estimate the air demand, but the results of such have not been verified nor is information …

Utilizing Bayesian Optimization In Technoeconomic Analyses For Integrated Energy Systems, Anthoney Griffith

All Graduate Theses and Dissertations, Fall 2023 to Present

Technoeconomic analysis is a key element in the study of integrated energy systems. The goal of this analysis is the sizing of technologies resulting in the best economic outcome for the system. The evaluation of this system involves sizing the components and simulating the resulting market to determine an outcome. This simulation incorporates multiple possible values of uncertain parameters like grid price and wind generation. This problem is currently approached with the gradient descent optimization method. An alternative approach, Bayesian optimization, sees success on simple problems of a similar nature to technoeconomic analyses. These results motivate applying Bayesian optimization as …

Ensemble Machine Learning At The Edge Using The Codec Classifier Structure And Weak Learners Guided By Mutual Information, Aj Beckwith

All Graduate Theses and Dissertations, Fall 2023 to Present

The Codec Classifier is a low-computation, low-memory tree ensemble method that dramatically improves feasibility of image classification on resource-constrained edge devices. It achieves advantages over other tree ensemble methods due the separation of encoder and decoder tasks in the classifier. The encoder partitions feature space, and the decoder labels the regions in the partition. This functional separation of tasks enables the encoder design (partitioning) to be guided by maximizing the mutual information (MI) between class labels and the features (i.e. the encoded representation of the data) without regard to the error performance of the classifier. Experiments show maximizing MI leads …

A Position Allocation Approach To The Battery Electric Bus Charging Problem, Alexander Brown

All Graduate Theses and Dissertations, Fall 2023 to Present

With an increasing adoption of Battery Electric Bus (BEB) fleets, developing a reliable charging schedule is vital to a successful migration from their fossil fuel counterparts. In this work, a BEB charging scheduling framework that considers fixed route schedules, multiple charger types, and battery dynamics is modeled as a Mixed Integer Linear Program (MILP). The MILP is modeled after the Berth Allocation Problem (BAP) in a modified form known as the Position Allocation Problem (PAP). The optimization coordinates BEB charging to ensure that each vehicle remains above a specified charge percentage. The model also minimizes the total number of chargers …

Method Development For The Extraction And Analysis Of Per- And Polyfluoroalkyl Substances (Pfas) In Wastewater And Biosolids, Victoria Krull

All Graduate Theses and Dissertations, Fall 2023 to Present

Per and poly-fluorinated alkyl substances (PFAS) are manufactured chemicals that have water and grease repellant properties and do not readily biodegrade. PFAS are present in many consumer products and end up in waste systems and the environment. Studies have shown that PFAS can have adverse health effects on humans and animals.

There are many challenges to processing and analyzing samples containing PFAS including: adsorption of PFAS to equipment, contamination from equipment containing PFAS, and the high sensitivity needed to analyze for PFAS in the parts per trillion detection range. The United States Environmental Protection Agency (EPA) has been developing methods …

Development Of A High-Throughput Methodology For Vibration-Based Fatigue Tests, Brandon Alexander Furman

All Graduate Theses and Dissertations, Fall 2023 to Present

Global efforts towards the development of additively manufactured materials, biomaterials, metamaterials, self-healing materials, and composites have reached a staggering pace. With new materials being developed on a near-daily basis, it is more important than ever to be able to quickly and precisely quantify their mechanical performance. However, one of the most important mechanical properties, fatigue life, is notoriously time consuming to measure. Consequently, fatigue parameters are often calculated based on small sample sizes, resulting in high uncertainty of the measured parameters. In this dissertation a high-throughput approach to fatigue measurements is developed. This technique allows for multiple samples to accumulate …

Defining Engineering Leadership And Engineering Leadership Skills From The Perspectives Of Abet Leaders And Professional Engineers, Yemisi Victoria Oyewola

All Graduate Theses and Dissertations, Fall 2023 to Present

Leadership within the engineering domain has gained significant recognition in recent years due to calls from the literature, industry, and engineering professional bodies to incorporate leadership training into the engineering curriculum. In response to these calls and despite various approaches that have been implemented by engineering institutions to teach engineering leadership, research indicates that there remains a lack of consensus on the definition of engineering leadership and the specific skills that should be emphasized in the teaching of engineering leadership. Also, there is evidence in the literature that there exists a debate regarding the nature of engineering leadership, with some …

Understanding Ion Rejection Mechanism Of Freeze Desalination By Molecular Dynamics Simulation, Mahbuba Jannat

All Graduate Theses and Dissertations, Fall 2023 to Present

This study explores a method called freeze desalination, which uses the natural process of ice formation to remove salt from water at lower than freezing temperature of water, which is 235K (Freezing temperature of this water model is 249K), making it safe for potable water. Unlike traditional methods, freeze desalination can be more efficient and environmentally friendly, but how it rejects salt at the molecular level is not very clear to understand. Using molecular dynamics simulation, this research aims to uncover the details of this process. We focused on understanding how water molecules interact with salt ions during freezing. Our …

Improving The Long-Term Maintenance And Durability Of Pervious Concrete Pavements, Kate Elizabeth Christiansen

All Graduate Theses and Dissertations, Fall 2023 to Present

Impervious concrete is constructed for most new infrastructure such as housing developments, commercial projects, and industrial facilities, which prevents stormwater runoff from infiltrating into groundwater storage. Pervious concrete is a sustainable, economical, and safe alternative to collect runoff and prevent the issues resulting from increased land development.

Although pervious concrete has the benefit of a large porous structure for water infiltration, this high porosity leads to issues with debris, sand, and other materials clogging the porous areas. Pervious concrete also has the challenge of non-standardized material preparation techniques, testing, and construction practices. As such, more research is needed to improve …