Engineering Commons^™

Corrosion Protection Mechanisms Of Trivalent Chromium Based Passivations On Γ-Znni Coated Al6061-T6 Alloy, Kevin Foster

Doctoral Dissertations

“The role of cobalt in trivalent chromium passivations (TCPs) to improve corrosion resistance of γ-ZnNi coated steel and aluminum is based on its effect on hexavalent chromium content in the passive layer. Investigations of both a cobalt-containing and cobalt-free TCP on SAE 1008 steel indicated that both passivations protect well for up to 1000 hours in neutral salt spray exposure (SSE). A repetition on Al 6061-T6 alloy indicated that TCP performed much better than cobalt-free TCP implicating the underlying substrate. Optical and electron micrographs indicated physical changes such as crack thickness, crack density, passivation porosity, and passivation thickness existed between …

Modeling Strategy For Emi Filter And Flyback Transformer, Ruijie He

Doctoral Dissertations

“The switch-mode power supply is key to miniaturizing power adapters. However, the switching nature of the circuit introduces issues in conducted emissions. In a flyback converter, the transformer serves as the path for common mode current flowing from the primary side to the secondary side. Different winding technologies have been invented and implemented to reduce the capacitance between the primary side and the secondary side. But the repeatability of the winding is still poor due to the fluctuations of the winding machine. Thus, the resulting conducted emission has a fluctuation that can lead to failure in the compliance tests. EMI …

Characterization And Utilization Of Alkali-Activated Concrete For Sustainable Infrastructures, Eslam Gomaa

Doctoral Dissertations

“This study has investigated the feasibility of using locally available fly ashes (FAs) to synthesize alkali-activated concrete (AAC) for different structural and repair applications. Using AAC made of 100% FA reduces global CO2 emissions, saves energy, and decreases raw material consumption during the production process of ordinary Portland cement. Class C FAs, sourced from Labadie, Jeffery City, Kansas City, Thomas Hill, and Sikeston power plants in the state of Missouri, were used to synthesize the AAC. Sodium silicate (SS), Na2SiO3, and sodium hydroxide (SH), NaOH were used as the alkali activators. Slag, crumb rubber, and air-entraining admixture were used as …

Numerical Simulation Study Of Gel Treatment For Conformance Control From Lab To Field, Jianqiao Leng

Doctoral Dissertations

“Gel treatment has been widely applied to control reservoir conformance and thus improve the sweep efficiency of injection fluids. Quite a few numerical simulations have been conducted to investigate the factors impacting gel treatment and assist to optimize treatment design and predict the performance. However, there exists significant barrier between the simulation approaches and lab experiments. In this study, two comprehensive reviews have been conducted to identify the gaps between lab and current simulations for in-situ polymer treatment and preformed particle gel treatment, separately.

Based on the identified gaps, the effect of a few major factors which are very important …

Depression Of Pyrite In Polymetallic Sulfide Flotation Using Chitosan-Grafted-Polyacrylamide Polymers, Keitumetse Cathrine Monyake

Doctoral Dissertations

“In this work, Chitosan-grafted-Polyacrylamides (Chi-g-PAMs) were studied, for the first time, as selective depressants of pyrite in the flotation of base metal sulfides. Fundamental studies of the adsorption behavior of Chi-g-PAM on model sulfide minerals indicated that Chi-g-PAM was more selective to pyrite’s surfaces as compared to base metal sulfides. Results suggested that the adsorption of Chi-g-PAM at pyrite-water interface was a chemisorption in nature which involved the amine, amide, and hydroxyl groups of Chi-g-PAM. Batch flotation studies of complex sulfide ore of Mississippi Valley Type (MVT) showed that Chi-g-PAM outperformed other pyrite’s depressants at producing less pyrite-diluted concentrates. Statistical …

Characterization Of High Cycle Fatigue And Laser-Aided Machining And Polishing Of Additively Manufactured Materials, Mohammad Masud Parvez

Doctoral Dissertations

“Additive manufacturing (AM) and laser-aided machining and polishing (LAMP) of materials are emerging manufacturing processes both for research and industrial sectors. The AM process can manufacture near-net-shape parts with complex geometries. Meanwhile, the LAMP process integrated with an AM system offers a high processing rate, minimum heat-affected zone, and easily adjustable process parameters during machining and polishing. In mechanical properties characterization of AM metals and alloys, fatigue is a vitally important test method to understand the behavior of materials in cycling loading and unloading circumstances since most mechanical failures of structures are due to fatigue. To characterize AM metal fatigue …

Novel Sensor Platforms Based On Fabry-Perot Resonators For Applications In Environmental Geophysics, Jing Guo

Doctoral Dissertations

"Fabry-Perot resonator sensors have been widely used for various physical and chemical measurements owing to their unique advantages over traditional sensors such as high measurement resolution, mechanically robust, and distributed sensing capabilities. This dissertation focuses on the development of robust fiber optic microwave sensors based on Fabry-Perot resonator mechanism for real-time applications in environmental geophysics.

Firstly, a novel Extrinsic Fabry-Perot Interferometer (EFPI)-based fiber-optic sensor for force measurement using a pre-buckled beam was demonstrated. The axial displacement is transferred and amplified to a horizontal deflection at the middle of the buckled beam, leading to a relatively significant change in the Fabry-Perot …

Distributed Fiber-Optic Temperature Sensors For Applications In The Steel Industry, Muhammad Roman

Doctoral Dissertations

"Steelmaking facilities require continuous temperature measurements throughout the manufacturing process to ensure consistent product quality and high productivity. Motivated by the limitations of conventional temperature sensors, distributed fiber-optic sensors (DFOS) were developed and deployed for various applications in the steel industry. Fiber-optic sensors offer various advantages over conventional sensors, such as the miniaturized size of the optical fiber, immunity to electromagnetic interferences, capability for multiplexing and distributed sensing, and the ability to withstand harsh environments.

Firstly, high-resolution Rayleigh backscattering based DFOS were demonstrated as potential solutions for temperature measurements in steelmaking processes by performing experimental simulations. Additionally, aluminum casting experiments …

Production Of Non-Oriented Electrical Steel Thin Strip Simulating Conditions Of The Direct Twin-Roll Casting Process, Yizhou Du

Doctoral Dissertations

"In this study, a method to cast non-oriented (NGO) electrical steel with conditions of an industrial twin roll thin strip casting (TRSC) process was investigated. A novel vacuum assisted fast cooling (VA) sampling method was developed to produce 2 mm thick strip simulating conditions of an industrial TRSC process. The effects of solidification cooling rate, hot rolling deformation, and annealing time on inclusion distribution, magnetic properties, grain growth, and texture evolution of 3.4 wt.% Si NGO electrical steel with different carbon and sulfur (C&S) levels were analyzed. Samples were thermo-mechanically treated which simulated an industrial TRSC process. After a long …

Engineering Ni/Al2o3 Catalysts By Atomic Layer Deposition For Methane Reforming, Baitang Jin

Doctoral Dissertations

"Dry reforming of methane (DRM) could be a promising choice to utilize natural gas (mainly methane or CH₄), recycle captured CO₂, and produce valuable syngas. Promoters (e.g., CeO₂ and MgO) on Ni/Al₂O₃ prepared by atomic layer deposition (ALD) and ALD-prepared ultrathin overcoating (e.g., ZrO₂ and CeO_x) on Ni/Al₂O₃ prepared by incipient wetness method were investigated for methane reforming.

MgO and CeO₂ prepared by traditional incipient wetness method were used to promote the performance of ALD-prepared Ni nanoparticles (NPs) supported on four-channel α-Al₂O_{3 …}

Signal Integrity Analysis And Electromagnetic Inteference Modeling For Autonomous Vehicles, Yuandong Guo

Doctoral Dissertations

"An autonomous vehicle (AV) may employ various sensors to detect the environment, and the hardware for self-driving should be able to process large volume of sensor data and make real-time decisions. For signal integrity (SI), both the bandwidths and data rates of the high-speed channels should meet the requirements. The electromagnetic interference (EMI) noise may become a major concern with the ever-increasing number of electric modules. This research focuses on both SI analysis and EMI modeling for AVs. The first topic is accurate and broadband three-phase motor modeling. The novel modeling methodology for a typical three-phase motor is presented, using …

Multi-Stage Multi-Market Optimal Bidding Strategy In Electricity Markets, Hossein Mehdipourpicha

Doctoral Dissertations

"Restructuring of power industry created the competitive situations for different MPs through designing appropriate electricity markets. Typically, in pool-based electricity markets, MPs submit their offers, and ISO clears the market and notifies MPs of the cleared power amounts and market prices. In this situation, designing an effective bidding strategy for MPs who seek to maximize their profits has thus become one of the crucial yet difficult tasks that still need further exploration. The majority of recent studies overlooked this problem for the purely financial players. Therefore, designing an efficient strategy for virtual bidder in the pool-based electricity markets is studied …

Evaluation Of Novel Preformed Particle Gels For Conformance Control And Acid Stimulation Through Core Flooding Tests, Shuda Zhao

Doctoral Dissertations

"Acid stimulation and conformance control are two major methods to improve oil production. This study systematically evaluates two newly developed gels: Degradable Preformed Particle Gel (DPPG) and Re-crosslinkable Preformed Polymer Gel (RPPG). DPPG is designed to be a temporary plugging agent for acid stimulation and can self-degrade into a water-like fluid. RPPG is designed for reservoir sweep efficiency improvement and can re-crosslink to each other and form an immobile bulk gel after being placed in fractures or fracture-like conduits.

For DPPG, this study evaluates the effect of monomer, crosslinker, and initiator concentration on the swelling and degradation performance. Results show …

Predicting Radiated Emissions From A Cable Harness Through Component Level Tests, Fuwei Ma

Masters Theses

“In this work, a procedure is developed to predict the radiated emissions from a cable harness using component-level tests. Direct measurement on the engine control unit is utilized to accurately characterize the equivalent common mode source voltages and impedance associated with the device. The cable harness geometry is reduced using the equivalent cable bundle approach by lumping wires according to the source and load impedance compared with characteristic impedance of the harness, which dramatically reduces the measurement effort and allows practical 3D full-wave simulation of the radiated emissions. Radiated emissions are predicted from an engine control unit (ECU) and an …

Effects Of Vacancies And Electron Temperature On The Electron Phonon Coupling In Cubic Silicon Carbide And Their Connection To The Inelastic Thermal Spike, Salah Al-Smairat

Doctoral Dissertations

“The electron-phonon interaction is an important interaction in many solids as it influences transport phenomena and related quantities such as the electrical and thermal conductivities, especially in nuclear and space applications. The importance of the electron-phonon interaction in primary damage production in 3C-SiC is the subject of this research.

The electron-phonon coupling factor was calculated using a hybrid Density Functional Perturbation Theory - Classical Electron Gas model. The coupling factor was calculated as a function of electron temperature in pristine and defective 3C-SiC, and relaxed defective cells. The electron-phonon coupling is found to depend strongly on the electronic temperature and …

Ecological Restoration Of Lead/Zinc/Copper Mine Tailings: Phytomanagement And Amendment Strategies To Enhance Substrate Functionality And Biomass Production, Mariam K. Al-Lami

Doctoral Dissertations

“The extreme physiochemical characteristics of mine tailings inhibit microbial processes and natural plant growth. Consequently, vast and numerous tailings sites remain barren for decades and highly susceptible to wind and water erosion. Phytostabilization is a cost-effective and ecologically productive remediation approach; however, tailings revegetation is generally challenging and must often be assisted with appropriate soil amendments. Amendments applied individually in greenhouse studies discussed herein revealed notable improvement in bioenergy crops growth only with biosolids treatments. Recalcitrant carbon amendments (biochar and humus) showed notable impact only on tailings physichochemical and hydraulic properties. Nevertheless, biosolids may not support sustained vegetation due to …

The Utilization And Loss Of Available Energy In Aerospace Systems, Mohammad Abbas

Doctoral Dissertations

“Theoretical principles and analytical methodology for the control volume-based energy availability methodology for aerospace vehicles are developed; applications are made to jet-propelled and rocket-propelled vehicles as well as to stand-alone engine systems. Energy availability utilization characteristics of a modeled turbojet engine are studied across a wide range of operating conditions of throttle setting, flight altitude, and flight Mach number. The method is also extended to consider jet-powered vehicles. Fundamental principles regarding entropy generation and energy availability are developed, including directly linking entropy generation and maximum range and endurance of a powered aircraft. Theory and application of the energy utilization methodology …

Post-Seismic Response And Repair Of Earthquake-Damaged Reinforced Concrete Bridges, Giacomo Fraioli

Doctoral Dissertations

“In bridge structures, column members are typically designed to be the primary source of energy dissipation during an earthquake. Therefore, reinforced concrete (RC) bridges that are damaged in an earthquake tend to have damage to the column members. While many studies have been conducted on seismic strengthening of RC bridge columns, most are focused on retrofit instead of repair. In addition, the limited research on seismic repair of RC bridges has focused on evaluating the response of individual columns (member level), not the bridge structure (system level), due to limitations in modeling and especially testing of full bridge structures. Local …

Innovative Approach To Use Guayule Resin As A Bio-Based Asphalt Alternative, Ahmed Hemida

Doctoral Dissertations

"Asphalt cement will not last long as the world encounters a diminishment in crude oil. Novel resources can contribute to replacing asphalt with the sustainable, flexible pavement. This study presented guayule resin (guayule) as an innovative bio-based asphalt alternative. Ground tire rubber was used as an asphalt enhancer. To judge the guayule's contribution, guayule-based binders were investigated and compared to control asphalt and asphalt-rubber binders. Binders were assessed according to comprehensive Superpave criteria and advanced rheological tests. Component analysis was performed to link the microscale level with the macroscale level. To validate the novel binder, satisfying mix performance tests were …

Characterizing And Modeling Methods For Power Converters, Anfeng Huang

Doctoral Dissertations

“Stable power delivery is becoming increasingly important in modern electronic devices, especially in applications with stringent requirements of its form factor. With the evolution of technology, the switching frequency in a power converter is pushed to a higher frequency range, e.g., several MHz or even higher, to decrease its size. However, the loss generated in the converter increases drastically due to the high switching frequency. In addition, a wide-band feedback controller is required to accommodate the high switching frequency in the converter. We focus on the characterization or modeling of the feedback control circuits and critical components in a switching …

The Kanarra Fold-Thrust System -- The Leading Edge Of The Sevier Fold-Thrust Belt, Southwest Utah, William Joseph Michael Chandonia

Doctoral Dissertations

“The Jurassic to Eocene Sevier fold-thrust belt is the subject of continued scientific curiosity in tectonics, stratigraphy, and industry. Understanding its development in southwest Utah is hindered in part due to the multiple origins proposed for the Kanarra anticline, a major leading edge structure -- a drag fold along the Hurricane fault, Laramide monocline, Sevier fault propagation fold, or a combination of these -- which have confused its tectonic significance and regional context. This confusion results from the structural complexity of its exposed eastern limb, as well as displacement and burial of its crest and western limb beneath Neogene sediments …

Scale Formation, Properties And De-Scaling In Steelmaking, Richard Osei

Doctoral Dissertations

During continuous castings, reheating, and hot rolling, slab surfaces are exposed to atmospheres containing oxidizing gases which results in scale formation. Inefficient removal of the formed scale during reheating affects product surface quality. The effect of steel composition and operating parameters on scale formation and scale removal efficiencies were investigated. Experimental investigations were carried out using a thermogravimetric (TGA) apparatus designed to replicate the combustion gas atmosphere and temperature in actual industrial slab reheat furnaces. Report on oxidation kinetics, scale structure and properties, and descaling were conducted on laboratory cast and industrial samples. Different characterization techniques were used to analyze …

Array Signal Processing For Source Localization And Enhancement, Sohel J. Patel

Doctoral Dissertations

“A common approach to the wide-band microphone array problem is to assume a certain array geometry and then design optimal weights (often in subbands) to meet a set of desired criteria. In addition to weights, we consider the geometry of the microphone arrangement to be part of the optimization problem. Our approach is to use particle swarm optimization (PSO) to search for the optimal geometry while using an optimal weight design to design the weights for each particle’s geometry. The resulting directivity indices (DI’s) and white noise SNR gains (WNG’s) form the basis of the PSO’s fitness function. Another important …

Advances And Applications In High-Dimensional Heuristic Optimization, Samuel Alexander Vanfossan

Doctoral Dissertations

“Applicable to most real-world decision scenarios, multiobjective optimization is an area of multicriteria decision-making that seeks to simultaneously optimize two or more conflicting objectives. In contrast to single-objective scenarios, nontrivial multiobjective optimization problems are characterized by a set of Pareto optimal solutions wherein no solution unanimously optimizes all objectives. Evolutionary algorithms have emerged as a standard approach to determine a set of these Pareto optimal solutions, from which a decision-maker can select a vetted alternative. While easy to implement and having demonstrated great efficacy, these evolutionary approaches have been criticized for their runtime complexity when dealing with many alternatives or …

Characterization And Modeling Of Esd Events, Risk And Protection, Jianchi Zhou

Doctoral Dissertations

“The ESD (Electrostatic discharge) failures have been raising critical reliability problems in electronic devices design. However, not all the ESD scenarios have been specified by the IEC standard and the characterizations of the ESD risk for different scenarios are essential to evaluate the ESD robustness of the devices in the real word.

The insulation of plastic enclosures provides protection against ESD to the electronic system inside. However, seams between plastic parts are often unavoidable. Different plastic arrangements are constructed to investigate the spark length and current derivatives and to understand the ESD spark behavior for geometries having spark lengths longer …

Evaluation Of Recrosslinkable Preformed Particle Gel (Rppg) As A Fluid Loss Control Material During Drilling Operations, Mohamed Saad M. Ahdaya

Doctoral Dissertations

"One of the most intense, expensive, and time-consuming problems during drilling operations is the loss of circulation, which could result in several consequences, including wellbore collapse, fluid inflow, formation damage, environmental issues, and nonproductive time. This research aims to evaluate novel materials that can mitigate lost circulation and overcome the limitation of other materials. In this research, a comprehensive evaluation of a re-crosslinkable preformed particle gel (RPPG) has been conducted to determine the extent to which it can be used to control drilling fluid losses during drilling operations. The RPPG consists of swellable gel particles that can self-crosslink to form …

Determining Thermal Properties Via Parameter Estimation Of A One-Dimensional, Analytical Model, Lauren B. Tomanek

Doctoral Dissertations

“In thermal applications, thermal conductivity is used to predict how well a material conducts heat. The accuracy of the magnitude of the thermal conductivity becomes increasingly essential to optimize part geometry. Thermal conductivity can vary significantly from the nominal value due to post-processing. The ASTM standards available to measure thermal conductivity are challenging to reproduce because of the insulated and prescribed temperature boundary conditions that are needed. The research introduces two new methods for estimating thermal conductivity that deliver the same accuracy as the existing ASTM standards and are easier to implement. The methods account for losses in the heating …

Advances In Control Of Uncertain Dynamical Systems With Optimal And Adaptive Approaches, Meryem Deniz

Doctoral Dissertations

"This research starts with designing optimal control for uncertain systems, adding the adaptive control input to suppress the uncertainty. It then follows with designing the optimal control for state constraint, designing the optimal nonlinear reference model, designing adaptive control to handle state constraint and uncertainty. Finally, it designs the finite-time controller for uncertain multiagent systems.

It is well known that the design of the control algorithm for an uncertain dynamical system is not trivial. Motivated by this standpoint, this study focuses on optimal and adaptive control approaches with stability and performance guarantees for uncertain sole and multiagent dynamical systems. From …

Design Methods For Pressure Relief Well Systems At Dams And Levees, Andrew Keffer

Doctoral Dissertations

"Flood risk reduction structures such as dams and levees are important systems that provide significant benefits to the nation. Relief wells reduce the substratum water pressures that can compromise them via internal erosion. The U.S. Army Corps of Engineers (USACE) analytical method to design relief well systems by calculating discharge and excess head along an infinite line of wells was developed from the 1930s – 1950s. The research presented here increases our understanding of the method’s history and uses analytical and numerical models to improve current infinite and finite well system design practices. The historical development of this method was …

Joining Of Ultra-High Temperature Ceramics To The Same And Refractory Metals Via Fusion Welding, Jecee Jarman

Doctoral Dissertations

"This research focuses on the joining of ultra-high temperature ceramics to either themselves or refractory metals/alloys via fusion welding and the mechanical strength of produced joints. The ceramics studied consisted of compositions within a diboride-carbide-carbide ternary system while metals studied consisted of molybdenum and a molybdenum alloy. SiC-ZrB2-ZrC ceramics on a binary join between pure SiC and the ternary eutectic composition were found to be weldable when SiC content was below ~57.5 vol%. Compositions above 57.5 vol% SiC were unweldable based on pitting and off-gassing behavior. Welded strength of ceramics was ~180-300 MPa in the SiC-ZrB2-ZrC ternary eutectic composition, ~180-220 …