Engineering Commons^™

Geometry-Aware Methodology For Coupling Mechanism Analysis And Radiation Mechanism Analysis, Xu Wang

Doctoral Dissertations

"Due to the wide-band spectrum of digital signals, a variety of noise generators, including microprocessors, liquid crystal displays, digital microphones, high-speed traces, and double-data-rate memory modules, are found in consumer electronics products. Noise generated by digital circuits can couple to the antennas and degrade their sensitivity. Additionally, it also couples to metallic housings or heatsinks and produces a significant amount of emission. In this research, methodologies are presented to analyze the coupling and radiation mechanism in electronic devices.

To investigate the coupling between the distributive geometries in the radio frequency interference (RFI) problem, a mesh-dependent partition-based coupling mechanism analysis method …

Intragranular Tungsten-Titanium Carbide Composite Ceramics Via Gas-Solid Displacement Reactions, Ryan Daniel Dempsey

Doctoral Dissertations

"Research presented herein details the synthesis and characterization of nanocomposite ceramics featuring novel heterogeneous microstructures of potential interest in a variety of electrical and structural applications. Specifically, W-TiCy composite ceramics featuring tungsten nanoprecipitates located primarily within TiCy grains have been produced via sintering of intragranular nanocomposite powders produced via reaction processing-based techniques. This dissertation details the thermodynamic basis and applied kinetics of a processing scheme for fabricating nanocomposite ceramics whose morphological heterogeneity reflects that originally developed in the powder state. The first study in this series overviews the motivation for applying metallothermic displacement reactions, conducted through gaseous intermediates, to solid …

Investigation Of Recrosslinkable Preformed Particle Gels For Natural Gas Conformance Control, Ali Abdulmohsen Al Brahim

Doctoral Dissertations

"Recross linkable Preformed Particle Gel (RPPG) is a novel type of preformed particle gel in which particles can bond together to form a strong bulk gel system after being placed in the target formation. In this research, I systematically evaluated the feasibility of using this product to improve gas flooding conformance for mature reservoirs with conduits or fractures. Two RPPG systems were used for the experiment: a CO₂- resistant RPPG (CR-RPPG) synthesized using acrylamide (AM) and 2-acrylamide-2- methylpropane sulfonate acid (AMPS), designed for CO2 flooding; and an acrylamide-co-acrylic acid-based RPPG (LT-RPPG), designed for water flooding. Different experimental apparatuses …

Sustainable Development: A Data Analysis Investigation For A New Conceptual Model, Case Study Comparison And Validation Techniques, Tiffanie Marie Toles

Doctoral Dissertations

"The three pillars model for sustainability, often represented with three intersecting circles described as economic, environmental, and social factors with sustainability being at the center is a complex and philosophically open model [1]. As society promotes efforts to reduce carbon impacts, there becomes a need to critically review the models employed for understanding. This research presents a validated methodology, an updated conceptual configuration of sustainability for overall use, as well as a sustainable development performance measurement system. Using the 2020 Sustainable Development Goals Index Data, 232 indicators from 193 countries were used to evaluate the efficacy of using more than …

A Primal Treatise Of Constant-Force Compliant Segment And Mechanism Design With Applications, Vamsi Lodagala

Doctoral Dissertations

"The evolution of compliant mechanisms propelled the development of constant-force mechanisms (CFMs) for various applications because of their unique characteristics. Many research endeavors have presented different techniques that often involve some optimization to design the CFMs. However, the mechanics of the generation of constant force at the elemental level is not well understood. This research effort theorizes and validates that simple, compliant segment with different boundary conditions, subjected to axial loading, produce near-constant force without the need for design optimization. Analytical models are developed based on the pseudo-rigid-body model (PRBM) concept to predict their force-displacement behavior, and to establish that …

Introduction Of A Variable Inductance Transformer For The Design Of Resonant Power Converters, Angshuman Sharma

Doctoral Dissertations

"Magnetic integration is a hot topic in power electronics that concerns the use of a transformer's leakage and magnetizing inductances purposefully in isolated power electronic converters, thereby giving the opportunity to save the cost and footprint of any additional inductor. This is of prime interest, especially in CLLLC resonant converters which require up to three inductors. For a complete integration of these inductances, the concept of a variable inductance transformer (VIT) is introduced in this thesis. A VIT is an adaptive magnetic structure that facilitates an easy adjustment of both magnetizing and leakage inductances to meet their desired values. However, …

Effects Of Downwash When Measuring Gas Concentration With Uav-Mounted Gas Sensors, Jacob Lane Brinkman

Doctoral Dissertations

"This research concludes that the downwash region of a rotary-wing unmanned aerial vehicle (UAV) does not produce pressure variations substantial enough to cause significant changes in density-based gas concentration measurements. US regulations evaluate gas concentration as a function of gas density, and accurate concentration measurements are critical for protecting health and safety, which means evaluation of actual downwash effects on measured gas concentration is essential.

During experimentation, the UAV was fixed to a stand in a sealed chamber filled with NOx (NO and NO₂) of constant concentration. The UAV rotors ran at hovering speeds, and gas concentrations were …

Co2-Assisted Ethylene Production And Subsequent Purification: A Materials Development, Kinetic Assessment, And Process Performance Investigation, Khaled Baamran

Doctoral Dissertations

"This research focuses on the In-Situ CO₂ capture and utilization in the oxidative dehydrogenation of ethane (ODHE) for ethylene production, and a subsequent ethylene purification through adsorptive separation process. In particular, several dual-function materials (DFMs) were developed, formulated into 3D-structure, and investigated for ODHE reaction to ethylene under various process conditions using CO₂ as a mild oxidant. The DFMs materials were consisted of CaO and metal oxides (e.g., Cr₂O₃ and V₂O₅) supporting H-ZSM-5. The results indicated that higher cell densities lead to better performance due to kinetic enhancement, and the optimum …

Data Analytics Of Wettability Alteration With Surfactants In Carbonate Reservoirs, Ya Yao

Doctoral Dissertations

"Wettability alteration with surfactants has been widely applied to improve oil recovery in carbonate reservoirs. An effective surfactant huff-puff application design requires comprehensive guidelines about where, how, and when this method could be applied. Besides, traditional methods to design an effective application and optimize surfactant performance are dependent on extensive experiments and are time-consuming. This study is to assist in the design of surfactant huff-puff via statistical methods and machine learning techniques.

In this study, a dataset including 402 effective surfactant imbibition tests is established by collecting information from nearly 50 publications. The dataset provides a foundation for further data …

Unsteady Flow Behaviors Generated By Three-Dimensional Lattice Geometries As Measured By Laser Doppler Velocimetry, Yi Qiao

Doctoral Dissertations

"The relation between flow stream turbulence and heat transfer has been known for a long time, that the heat transfer rate is increased if the turbulence or fluctuation level of the flow increases. Open cell foams and compact heat exchangers are two of the most common models applied for heat transfer augmentation. However, the small ligaments of open cell foams limit the heat conducted and smooth passages in compact heat exchangers cannot cause flow unsteadiness. Accordingly, new geometric models are needed to improve the heat transfer enhancement. Three-dimensional (3D) lattice geometries with a range of features and sizes can be …

Phosphate And Borophosphate Glasses For Optical And Biomedical Applications, Parker Tracy Freudenberger

Doctoral Dissertations

"The goal of this work was to connect the network structures of phosphate and borophosphate glasses to the compositional dependence of properties related to biomedical applications. The glasses were characterized by a variety of techniques, including phosphate ion chromatography, Raman spectroscopy, and ¹¹B and ³¹P Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy, which provide qualitative and quantitative information about the phosphate and borate moieties that constitute the network structures. The systematic addition of borate to a phosphate glass initially creates tetrahedral borate sites that replace P-O-P linkages with B-O-P linkages, and the properties of the resulting borophosphate glasses …

Fiber Optic Sensors For Liquid Identifications, Wassana Naku

Doctoral Dissertations

"The fiber optic Fabry-Perot interferometer (FPI) is a widely utilized sensing configuration, offering numerous advantages over conventional electronic sensors, including high accuracy, distributed sensing capabilities, immunity to electromagnetic interference, and compact size. In this study, we propose a remarkably simple fiber optic-tip sensor system combined with machine learning techniques for the identification of pure and volatile organic liquids (VOLs).

A liquid droplet forms an extrinsic FPI (EFPI), with its effective reflectance being a function of the droplet's length. As the droplet evaporates, its length decreases. We conducted immersion tests using optical fiber tip sensors and monitored the time-transient responses of …

Application Of Modeling Methodologies To Improve An Emergency Departments Workflow, Prachita Humane

Doctoral Dissertations

"The healthcare system in the United States is complex and challenging to understand, and the emergency department (ED) serves as a bridge between outpatient and inpatient care. According to the Centers for Disease Control and Prevention, over 130 million people visited emergency rooms in the United States in 2018. The ED is composed of multiple subunits and components that make it difficult to comprehend fully. In this study, a combination of engineering analysis methods was used to identify and understand the issues in the ED.

The first contribution of this research involved collecting data through job shadowing of human entities …

Cfd Analysis For Beyond Bubbly Gas-Liquid Two-Phase Flows In A Large Diameter Pipe, Sungje Hong

Doctoral Dissertations

"Due to the complexity of multiphase flow phenomena, numerical analysis for multiphase turbulent flow is not as reliable as single-phase computational fluid dynamics (CFD). A literature review has revealed that the current efforts on multiphase flow simulation have focused on small diameter channels under very restricted flow conditions and have been conducted without identifying some important procedures. To expand CFD applications to a wide range of two-phase flow conditions in large diameter channels, this study aims to validate the current CFD models for vertical concurrent air-water two-phase flow simulations beyond bubbly flows. First, a numerical model developed to describe dynamical …

Identification, Mapping, Analysis, And Dating Of Composite Mega Landslides In The Colorado Plateau, Conor Maris Watkins

Doctoral Dissertations

"This research consists of three articles focusing on landslide complexes within the Grand Canyon region of the Colorado Plateau. This is a vast and remote region of rugged topography. The landslide complexes in this study are greater than 10 million cubic meters in volume. The slides are located within different areas of the region and consist of differing geology but share multiple commonalities. Stratigraphic and structural controls tend to dictate where the slides occur. All of the landslides occur where carbonates and/or sandstones overlie over consolidated shales. The shales are susceptible to creep and strain softening where lateral confinement has …

Characterization And Improvement Of Powder Properties Through Plasma Spheroidization For Use In The Laser Powder Bed Fusion Process, M. Hossein Sehhat

Doctoral Dissertations

"This research was conducted to characterize the powder properties using different characterization techniques to enhance the powder behavior in the Laser Powder Bed Fusion (LPBF) process. One of the shortcomings of LPBF process is the high cost of gas-atomized powder feedstock. To overcome this downside, the cheaper water-atomized powder was characterized and used in LPBF process, and its performance was compared with those of gas-atomized powder. Also, the plasma spheroidization process was used to improve the powder characteristics; if the spheroidized powder could function as well as the virgin powder, plasma spheroidization process could be applied to the used powders …

Design, Modeling And Analysis Of An Ac-Ac Dual Active Bridge Converter, Kartikeya Jayadurga Prasad Veeramraju

Doctoral Dissertations

"The Solid-State Transformer (SST) is gaining attention as an alternative to conventional iron-core transformers in the power electronic community. The power industry's increasing demands for smaller size, higher efficiency, and greater energy density have made the SST an attractive option. Among various power electronic converter topologies, the Dual Active Bridge (DAB) has become popular for its bidirectional power flow capability and galvanic isolation, primarily in the DC application space. Advancements in semiconductor technologies have introduced new bidirectional switches, opening avenues for novel SST topologies. This research investigates the application of the DAB as a single-stage SST and focuses on advancements …

Development Of A Mission Design Tool For Computing Libration Point Formations Using Differential Corrections Initialized With A Genetic Algorithm, Donna Jennings

Doctoral Dissertations

"The growing interest in deep space spacecraft missions and distributed spacecraft formations has established the need for state-of-the-art advancements in the areas of relative dynamics and mission design. The focus of this research is to develop methods for identifying natural (i.e. ballistic) relative formation trajectories in the vicinity of the collinear libration points. A natural formation decreases the station keeping costs, lowering the consumption of spacecraft resources and extending mission lifetime. This research adapts both numerical and machine learning approaches to the problem of mission design. A genetic algorithm was first used to identify a multi-agent spacecraft formation in the …

Promoting Enhanced Decision-Making And Proactive Management For Modularization In The Construction Industry Using Risk-Based Approach, Analytical Hierarchy Process, And Graph Theory, Mohamad Abdul Nabi

Doctoral Dissertations

"Modularization is an approach that can potentially mitigate many of the current construction industry’s challenges. Despite the documented advantages of modularization, the industry is still not able to capitalize on its full potential and benefits. The latter is due to the outdated decision-making models that may not reflect the multiple factors involved in modular construction, the unique source of risks associated with modular construction methods, need for continuous improvement, and complex contractual requirements and disputes. As such, the goal is to promote the use of modularization in the construction industry by enhancing decision-making and proactive risk management. The associated objectives …