Digital Commons Network^™

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 …

Mechanical Properties Of Boride Based Ceramics, Alec Murchie

Doctoral Dissertations

“This research focuses on the elevated mechanical properties of diboride based materials at room and elevated temperatures. These materials include a ZrB₂ ceramic, a ZrB₂-WC-SiC ceramic, and a (Hf,Mo,Nb,Ta,W,Zr)B₂ high entropy boride (HEB). The room temperature flexural strength for the ZrB₂ ceramic was 447 MPa and the fracture toughness was 2.3 MPa·m^1/2. The strength decreased to 196 MPa at 1800°C, and then increased to 360 MPa at 2300°C. The fracture toughness increased to 3.1 MPa·m^1/2 at 2200°C. The strength up to 1800°C was likely controlled by a combination of effects: surface damage …

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 …

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 …

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 …

Investigation Of The Thermodynamics Of Iron Phosphate Melts And Stability Of Iron Phosphate Glasses: Effects Of Composition And Iron Redox Ratio, Melodie Linda Schmitt

Doctoral Dissertations

“Iron phosphate glasses with Fe/P = 0.33 - 0.67, O/P = 3.0 - 3.5 and Fe²⁺/ΣFe = 0.16- 0.52 were prepared by altering batch compositions and melt conditions. Thermal analyses indicate polyphosphate glasses with intermediate chain lengths are most stable against devitrification. Heterogeneous crystallization occurs on the glass surface and is dependent on iron valence state, particle size, heating rate, temperature and oxygen availability in the atmosphere. Oxidation of ferrous iron on the glass surface occurs at temperatures as low as Tg, and thus crystallization behavior and stability can be altered via post-melt heat treatments. A novel preparation …

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 …

Synthesis And Process Optimization Of Colloidal Unimolecular Polymer, Cup, Particle Formation, And Its Interfacial Surface Tension Behavior, Ashish Zore

Doctoral Dissertations

"Colloidal Unimolecular Polymer (CUP) particles are 3-9 nm size single-chain polymer nanoparticles that are made from amphiphilic acrylic co-polymers using the process of water reduction. The formation of CUP particles was driven by the polymer-polymer interactions being greater than polymer-solvent interactions as well as the charge-charge repulsion due to the increasing dielectric of the medium. CUPs provide a surfactant or additive-free nanoparticle system that was useful for studying the interfacial behavior of pure aqueous nanoparticles using a maximum bubble pressure tensiometer. The equilibrium surface tension shows a dependence on concentration and the charge density of the CUP particle. The equilibrium …

Synthesis, Characterization And Chemistry Of Two-Dimensional Transition Metal Carbides And Nitrides (Mxenes), Shuohan Huang

Doctoral Dissertations

"MXenes represent a relatively new and quickly growing family of two-dimensional (2D) early transition-metal carbides and nitrides first synthesized in 2011 from bulk layered crystalline MAX phases. Because of their 2D structure and unique combination of high conductivity and hydrophilicity, MXenes have raised a significant interest for various applications. However, it has been found that in some cases colloidal MXene flakes are not stable and can spontaneously degrade on a time scale from hours to days. In this work, we investigate the crucial factors for MXene degradation and demonstrate gas analysis as a powerful method to gain further insights into …

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 …

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 …

Bulk Nanostructured Steels For Nuclear Reactor And Extreme Environment Applications, Maalavan Arivu

Doctoral Dissertations

"Candidate accident tolerant FeCrAl fuel (ATF) claddings for light water reactors (LWRs) need to be thinner than current Zircaloys owing to higher neutronic penalty, demanding an improvement in strength. Therefore, equal channel angular pressing (ECAP), and high-pressure torsion (HPT) were used to produce bulk ultra-fine grained and nanocrystalline Kanthal-D [KD; Fe-21Cr-5Al-0.026C (wt.%) alloy] which resulted in an improvement in strength of up to 3 times their nominal strength from grain boundary strengthening, and dislocation strengthening. Dynamic recovery was promoted due to ECAP at 520 oC rendering it with a large area fraction of less mobile low angle grain boundaries (LAGBs) …

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 …

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 …

A Three-Dimensional Fully Coupled Hydro-Mechanical Elasto-Plastic Model For Unsaturated Soils With Consideration Of Hysteresis Behavior, Beshoy Sami Moussa Riad

Doctoral Dissertations

"Unsaturated soils are often used as a construction material in transportation infrastructures; in which it is subjected to cyclic traffic loadings and/or seasonal wetting-drying cycles. While mechanical hysteresis is a common feature of soils in general, hydraulic hysteresis is associated with unsaturated soils. Most existing constitutive models paid limited attention to the mechanical and hydraulic hysteresis behavior of unsaturated soils. This research presents a three-dimensional model for unsaturated soils and a chemo mechanical model for saturated soils. The unsaturated soils’ model has the following characteristic features: (a) the hydraulic and mechanical behaviors are fully coupled under 3D conditions; (b) it …

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 …

Peritectic Behavior Detection And Prediction In Fe-C-Si-Mn-Al System, Damilola Balogun

Doctoral Dissertations

"The non-uniformity of shell growth in the continuous casting of peritectic steels constitutes a major barrier to the commercial production of many steel grades such as Advanced high strength steels (AHSS), transformation induced plasticity (TRIP) steels, abrasion-resistant steels, advanced armor plate steels, and many newly proposed steel grades that contain high levels of silicon, manganese, and aluminum.

The shell growth non-uniformity experienced in the continuous casting of peritectic steels results in the formation of defects in the as-cast slab and therefore increases the operating risk from cast aborts and breakouts. The ability to predict and avoid peritectic behavior at the …

Development Of An Interactive Robot For Overground Physical Human-Robot Interaction, Sambad Regmi

Doctoral Dissertations

"The overground interactive robots are potentially beneficial for humans in various areas, such as overground rehabilitation therapies and robotic interactive assistance. However, it is unclear what the expectations and challenges are for a robot to be physically interactive with a human during overground tasks, such as a robot helping an older adult walk. To develop such a robot, one must first build a clear understanding of how the human motor intent is communicated when interacting with another agent. Specifically, how do humans understand the leader’s intention when being led?

Based on previous works, we hypothesized that humans modulate their arm …

Sustainable Face Milling Of Inconel 718 Using Mql And Nanofluids Mql With Vegetable Oil As Base Fluid, Theodore Obumselu Nwoguh

Doctoral Dissertations

"Extreme heat and friction are generated in machining difficult-to-cut metals used in aerospace and nuclear industries leading to poor machinability (high cutting forces, rapid tool wear, shorter tool life, and poor surface integrity). Conventional flood coolant (CEC) used in industry is environmentally unfriendly, hazardous to operators, and unsustainable. These problems motivated this research, which can be mitigated with the use of effective biodegradable cutting fluids, appropriate cutting conditions, and lubrication/cooling strategies. This research provides a sustainable and environmentally friendly replacement to CEC. Firstly, the research characterized three vegetable oils (High Oleic Soybean Oil (HOSO), Low Oleic Soybean Oil (LOSO), and …

Establishing Pteridine Metabolism In A Breast Cancer Cell Model And Quantification Of Silver Nanoparticle Interactions With Yeast Cells Using Mass Spectrometry, Lindsey Katherine Rasmussen

Doctoral Dissertations

"Recent advances in analytical methods have furthered the quantitative insights that can be gleaned from cellular analyses, with applications in cancer and nanoparticle research. In the first part of the research presented, a recently developed HPLC-MS/MS method was advanced to elucidate pteridine metabolism in an isogenic progressive MCF10A breast cancer cell model. The folate-derived pteridine pathway in breast cells was established by individually dosing cell cultures with folic acid and 15 pteridines. Eight potential pteridine biomarkers in breast cancer cells were identified including pterin and isoxanthopterin, which yielded the first in vitro evidence for the cellular metabolisms behind previously reported …

Design And Performance Of Self-Consolidating And Thixotropic Ultra-High-Performance Concrete For Infrastructure Construction And Rehabilitation, Le Teng

Doctoral Dissertations

"The objective of this research is to develop two classes of ultra-high-performance concrete (UHPC), one with self-consolidating consistency and the other with improved thixotropy. Tailoring the rheological properties of low yield stress UHPC can improve dispersion and orientation of steel fibers used in the design of UHPC, hence enhancing the tensile and flexural properties. Similarly, improving the thixotropy of UHPC can enable unique performance for the design of thin bonded bridge deck overlay. The research investigated various thixotropy enhancing admixtures to enhance the structural build-up at rest of UHPC. A total of 16 bonded overlay slab specimens were used to …

Development And Testing Of A New Air-Assisted Flare System For Low Flow Conditions, Hayder Alhameedi

Doctoral Dissertations

"Flare systems provide a safe, efficient, and reliable way to treat unwanted flammable gases that come from relief devices of various chemical processing equipment to ensure the safety of personnel and equipment. Flare systems are classified according to the assist media type as non-assisted (utility), steam-, air-, and pressure-assisted flares. The assist medium enhances mixing between flare gases and surrounding air and induces more air into the combustion zone. An air-assisted flare system is the preferred flare type in regions where steam is unavailable or is costly to supply or ambient temperatures are too low. The environmental protection agency (EPA) …

Data-Driven Modeling And Simulations Of Seismic Waves, Yixuan Wu

Doctoral Dissertations

"In recent decades, nonlocal models have been proved to be very effective in the study of complex processes and multiscale phenomena arising in many fields, such as quantum mechanics, geophysics, and cardiac electrophysiology. The fractional Laplacian(−Δ)^��/2 can be reviewed as nonlocal generalization of the classical Laplacian which has been widely used for the description of memory and hereditary properties of various material and process. However, the nonlocality property of fractional Laplacian introduces challenges in mathematical analysis and computation. Compared to the classical Laplacian, existing numerical methods for the fractional Laplacian still remain limited. The objectives of this research are …

Advanced Materials And Processes For Gas Separation And Storage Applications, Qasim Mohammed Al-Naddaf

Doctoral Dissertations

"Transition to a clean, renewable energy future requires departure from thermally driven separation processes. In that regard, development of new materials that exhibit high adsorption capacity and selectivity, fast kinetics, and long-term durability under multicomponent conditions is becoming attractive for the applications in clean energy. Moreover, novel sorbents and separation systems that can store gases at normal conditions offer a promising approach for stationary or onboard gas storage. Due to the limitations on the surface area and biding energy restrict commercial materials effectiveness as a potential adsorption and storage material. There is significant interest in the properties of hybrid materials …

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 …}

Corrosion Resistance Performance Investigation Of Mild Steel Bar Coated With Magnesium Phosphate Cement Paste, Fan Zhang

Doctoral Dissertations

"In this research study, the anti-corrosion mechanism of reinforcement embedded in magnesium potassium phosphate cement (MKPC) is explored. In addition, one type of additives, metakaolin, and one type of retarder, boric acid, are employed in MKPC to modify its properties in order to further investigate corrosion resistance and to achieve mass-production coating reinforcement at the work site. This coating method may be practical for some underwater construction and some traditional reinforcement concrete structures to reduce the reinforcement corrosion rate and to eventually extend service life in both repair and new construction applications.

By comparing the electrochemical properties of bare ribbed …