Digital Commons Network^™

Experimental And Modeling Studies Using Packed Bed Reactors: Liquid Phase Ethylene Production By Hydrogenation Of Acetylene, Humayun Shariff

Doctoral Dissertations

"Gas-phase catalytic hydrogenation of acetylene to produce ethylene, commonly practiced in industries, has green oil formation, which leads to catalyst deactivation and sometimes reactor runaway risks due to high exothermicity. To overcome these issues as well as to increase the selectivity and conversion, liquid-phase hydrogenation of acetylene was investigated in packed bed reactors (PBR) using a commercial catalyst. The reactor performance of two-phase flow PBRs was assessed experimentally complemented by a validated mathematical model at different scales.

The selective hydrogenation of acetylene in the liquid phase over a commercial 0.5 wt% Pd/Al₂O₃ catalyst was investigated in a …

Stabilization Dynamics Of The Ozone Molecular System, Sangeeta Sur

Doctoral Dissertations

"The observation of larger-than-expected concentrations of heavier isotopologues of ozone known as 'ozone isotopic anomaly' in the stratosphere is a mass-independent effect (in contrast to most kinetic isotope effects familiar to chemists) that is traced back to the recombination process in the formation of ozone in the Chapman cycle. Understanding the relative efficiencies (often approximated as equal for different isotopologues) of the stabilization step (some of the details of which are still a mystery) which involves energy transfer from a highly excited ozone molecule to a third body, M (argon atom in this case) to form stable ozone is a …

Design Of X-Ray Source For Real-Time Computed Tomography, Wesley William Tucker

Doctoral Dissertations

"The reduction of motion blur in computed tomography (CT) drives the current research for multisource CT. Due to their compact nature, the current multisource systems utilize stationary angled anodes. Unfortunately, these configurations neither simplify the imaging geometry, nor satisfy the need for managing the high thermal loads demanded by real-time CT (30 acquisition frames per second). To add to the current field of knowledge, two x-ray tube concepts are presented in this dissertation. First, a simulation of transient thermal analysis was performed on a compact transmission-type x-ray tube anode operating in pulse-mode. A correlation was found between deposited beam power …

A Broad Iceland Plume Associated With Two Phase Transitions At The 660 Km Discontinuity: Constraints From Receiver Functions, Dan Wang

Doctoral Dissertations

"In spite of the fact that Iceland is frequently regarded as the archetypal example of mantle plumes, the existence, depth extent, origin, dimension and excess temperature of the hypothesized plume remain enigmatic and hotly debated. The controversy mostly originates from the limited vertical resolution of seismic tomography techniques and the associated uncertainty in the depth and lateral extents of the lower wavespeed anomaly. Here we utilize a robust receiver-function-based technique to image the topography of the 410 and 660 km discontinuities bordering the mantle transition zone beneath Iceland and surrounding oceanic regions, and construct thermal and seismic wavespeed models of …

System Si/Pi Modeling And Analysis, Biyao Zhao

Doctoral Dissertations

"A physics-based circuit modeling methodology for 3D IC/packages is proposed here. The method is based on partial element equivalent circuit (PEEC) and layered Green's function (LGF). The LGFs are calculated from discrete complex image method (DCIM) with three terms, direct coupling, complex images, and surface wave, extracted to analyze the wave behavior. The dominate terms for LGFs are analyzed for four stack-ups in 3D IC/packages. Analytical formulas that include the contribution of complex images are proposed for partial capacitance calculation, with the complex image extracted from LGFs. A chip PDN geometry is used to illustrate the use of LGF in …

Trajectory Control Of A Wheeled Robot Using Interaction Forces For Intuitive Overground Human-Robot Interaction, George Leno Holmes Jr.

Doctoral Dissertations

"Effective and intuitive physical human robot interaction (pHRI) requires an understanding of how humans communicate movement intentions with one another. It has been suggested that humans can guide another human by hand through complex tasks using force information only. However, no clear and applicable paradigm has been set forth to understand these relationships. While the human partner can readily understand and adhere to this expectation, it would be difficult for anyone to explain their intuitive motions with strict rules, algorithms, or steps. Uncovering such a procedural framework for the control of robotic systems to execute expected performance simply from force …

Frequency Selective Surface-Based Sensing: Theory And Applications, Mahboobeh Mahmoodi

Doctoral Dissertations

"Frequency selective surfaces (FSS) are periodic arrays of resonant elements with a specific (resonant) reflection/transmission response when illuminated by electromagnetic energy. FSSs have been utilized for different applications such as spatial filters, reflectors, lenses, radomes, and more recently, as sensors. FSS-based sensors have shown potential for numerous applications in structural health monitoring such as crack detection, concurrent strain and temperature sensing, normal and shear strain sensing, inspection of layered structures, etc. As FSS-based sensing is largely undeveloped, there are many critical aspects that must be fully understood before this sensing approach can be fully utilized. Therefore, the goal of this …

Polymeric Nanoparticle As A New Platform For High Removal Of Endotoxins From Biopharmaceutical Solutions, Sidharth Razdan

Doctoral Dissertations

"Presently, approximately one-third of all biopharmaceutical drugs are derived from biological sources like gram-negative bacteria. Gram-negative bacteria like E.coli are much cheaper to cultivate and provide higher biotherapeutic yield compared to mammalian cells. On extracting the useful biotherapeutics from the gram-negative bacterial cells (E.coli), endotoxin present in the bacteria is released in the surrounding media thus contaminating the lifesaving biotherapeutics. Application of the endotoxin-contaminated therapeutics to humans or animals can cause serious health issues like septic shock, tissue injury and ultimately death. Hence, thorough purification of biotherapeutics before parenteral application is necessary. Although there are multiple methods for …

Characterization Of Neutron Irradiated Accident Tolerant Nuclear Fuel Cladding Silicon Carbide & Radiation Detector Deadtime, Bader Almutairi

Doctoral Dissertations

“In part I, the pulse shape characteristics generated by a Geiger Muller (GM) detector and recorded by an oscilloscope manually, were investigated. The objective of part I was (1) to find a correlation between pulse shape and the operating voltage; and (2) to assess if pulse shape properties followed distinct patterns comparable to detector deadtime findings reported by a previous study. It was observed that (1) there is a strong correlation between pulse shape and operating voltage, and (2) pulse shape falls in three distinct regions similar to detector deadtime. Furthermore, parts II and III are companions and share the …

Modeling A Nuclear Research Reactor And Radiation Dose Estimation In An Accident Scenario, Abdulaleem Abdulmajeed Bugis

Doctoral Dissertations

“A detailed, flexible three-dimensional (3D) model of the Missouri S&T Reactor (MSTR) with a heterogeneous core geometry was developed using the Standardized Computer Analyses for Licensing Evaluation (SCALE). A Graphical User Interface (GUI) was developed for SCALE, which allows the user to generate an input file automatically. The SCALE model was validated with a Monte Carlo N-Particle Transport (MCNP) model of the MSTR. The validation process was based on the criticality calculations using the Criticality Safety Analysis Sequence (CSAS6). Three geometrical models were examined. The SCALE model that has the full detailed geometry showed a good agreement with the MCNP …

Development Of A System Architecture For The Prediction Of Student Success Using Machine Learning Techniques, Tatiana A. Cardona

Doctoral Dissertations

“ The goals of higher education have evolved through time based on the impact that technology development and industry have on productivity. Nowadays, jobs demand increased technical skills, and the supply of prepared personnel to assume those jobs is insufficient. The system of higher education needs to evaluate their practices to realize the potential of cultivating an educated and technically skilled workforce. Currently, completion rates at universities are too low to accomplish the aim of closing the workforce gap. Recent reports indicate that 40 percent of freshman at four-year public colleges will not graduate, and rates of completion are even …

Understanding The Deformation Mechanisms In Ni-Based Superalloys With Using Crystal Plasticity Finite Element Method, Tianju Chen

Doctoral Dissertations

“Ni-based superalloy is considered as a good candidate due to its excellent resistance to elevated temperature deformation for long term period application. Understanding the deformation and failure mechanisms of Ni-Based superalloys is very helpful for providing design guidelines for processing Ni-based superalloys. Experimental characterization indicates that the deformation mechanisms of Ni based superalloy is strongly microstructure dependent. Besides, damage transform from the void nucleation to the macro cracks by voids growth leading to the failure of the Ni-based superalloys are also showing strong microstructure sensitivity. Therefore, this work focuses on the prediction and comprehension of the deformation and void growth …

Symmetry-Breaking In The Multi-Photon Ionization Dynamics Of Oriented Atoms, Aruma Handi Nishshanka Chandrajith De Silva

Doctoral Dissertations

“Laser cooling and trapping, femtosecond light creation, and coincident electron and ion momentum imaging was combined in a world-wide unique experimental setup. These state-of-the-art techniques were used to control atomic systems and analyze the few-body quantum dynamics in multi-photon ionization of lithium. An all-optical, near-resonant laser atom trap (AOT) was developed to prepare a lithium gas at milli-Kelvin temperatures. The atoms can be resonantly excited to the state 2² P_3/2(ml = +1) with a high degree of polarization and are used as a target to study atomic multi-photon ionization in the field of an intense laser source …

Synthesis And Thermodynamic Characterization Of Free And Surface Water Of Colloidal Unimolecular Polymer (Cup) Particles Utilizing Dsc And Tga, Peng Geng

Doctoral Dissertations

“Colloidal Unimolecular Polymer (CUP) is spheroidal nanoscale polymer particle (3-9 nm) with charged hydrophilic gruops on the surface and a hydrophobic core. The formation of CUPs involves a simple free radical polymerization and a water reduction process. CUPs are thermodynamically stable in water, molecular weight, particle size and charge density can be designed and controlled. CUPs have a layer of surface associated water, due to the small particle size, the surface water/CUP volume ratio is ultra-high. Therefore, CUP is a very promising candidate to investigate the thermodynamic of surface water characteristics. In addition, CUP solution is free of surfactant and …

Predicting Complex System Behavior Using Hybrid Modeling And Computational Intelligence, Vinayaka Gude

Doctoral Dissertations

“Modeling and prediction of complex systems is a challenging problem due to the sub-system interactions and dependencies. This research examines combining various computational intelligence algorithms and modeling techniques to provide insights into these complex processes and allow for better decision making. This hybrid methodology provided additional capabilities to analyze and predict the overall system behavior where a single model cannot be used to understand the complex problem. The systems analyzed here are flooding events and fetal health care. The impact of floods on road infrastructure is investigated using graph theory, agent-based traffic simulation, and Long Short-Term Memory deep learning to …

Acoustic Confinement And Characterization Of A Microwave Plasma, Seth Lee Pree '09

Doctoral Dissertations

High amplitude acoustic fields are used to confine, characterize, and manipulate collisional plasmas with temperatures of a few thousand Kelvin. This dissertation describes the theory, experimental techniques, and apparatus necessary both to generate high amplitude sound in a few thousand Kelvin plasma and to use that sound field to manipulate the plasma within a resonant acoustic cavity. The acoustic field in a spherically symmetric oscillating plasma has been measured to have a Mach number of .03, which is sufficient to cause acoustic radiation pressure effects to confine the plasma to the center of its container. This field also generates convection …

Extraction And Analysis Of Data For Fragility Fracture Patients To Help Determine The Likelihood Of Follow-Up With A West Michigan Fragility Fracture Service, Michael Joseph Lamphere

Doctoral Dissertations

Fragility fractures and secondary fractures are a large physical, financial, and emotional drain on the individuals and families affected. Improving post fragility fracture care and increasing follow-up rates with specialty services, such as a fracture liaison service, may promote post-fracture recovery and help prevent future fractures. The purpose of this doctoral project was to increase and improve post osteoporotic fracture care by increasing appropriate referrals and follow-up care. Patient data was retrieved and analyzed on 60 fragility fracture patients referred to a local fracture liaison service. The analysis found that patient gender, fracture site, and history of a previous fracture …

Modification Of The Optical Response Of Alpha Quartz Via The Deposition Of Gold Nanoparticles In Etched Ion Tracks, Maria C. Garcia Toro

Doctoral Dissertations

”This study addresses the experimental methods used to develop and characterize plasmonic devices capable of modifying the optical response of alpha quartz via the deposition of gold nanoparticles in etched ion tracks. In the first part of the research, the microstructural characterization of latent and etched ion tracks produced in alpha quartz (α-SiO₂) is presented. Single crystals of α-SiO₂ were irradiated with two highly energetic ions to different nominal fluences. As expected, the morphology of the resulting ion tracks depends on the energy of the incident ion and their stopping powers within the target material. Subsequent chemical …

Time- And Space-Dependent Uncertainty Analysis And Its Application In Lunar Plasma Environment Modeling, Xinpeng Wei

Doctoral Dissertations

”During an engineering system design, engineers usually encounter uncertainties that ubiquitously exist, such as material properties, dimensions of components, and random loads. Some of these parameters do not change with time or space and hence are time- and space-independent. However, in many engineering applications, the more general time- and space-dependent uncertainty is frequently encountered. Consequently, the system exhibits random time- and space-dependent behaviors, which may result in a higher probability of failure, lower average lifetime, and/or worse robustness. Therefore, it is critical to quantify uncertainty and predict how the system behaves under time- and space- dependent uncertainty. The objective of …

Mesh Networking And Full-Duplex Communication For Wireless Networks, Arul Mathi Maran Chandran

Doctoral Dissertations

“Connectivity with large coverage area; and an increase in spectral efficiency of communications are highly desired features for any wireless network. The presented research work addresses these two feature improvements. First, the work analyzed mesh networks to enhance connectivity for wireless networks. The work analyzed both homogeneous and heterogeneous mesh networks. The work includes the development of an Android application to enable smartphones with multiple interfaces, such as Wi-Fi, Bluetooth, and cellular services, to become convergence devices. These convergence devices are then used to build a heterogeneous mesh network improving connectivity and coverage area. Second, the work explored full-duplex communications, …

Analysis And Modeling Of Power Supply Induced Jitter For High Speed Driver And Low Dropout Voltage Regulator, Yin Sun

Doctoral Dissertations

”With the scaling of power supply voltage levels and improving trans-conductance of drivers, the sensitivity of drivers to power supply induced delays has increased. The power supply induced jitter (PSIJ) has become one of the major concerns for high-speed system. In this work, the PSIJ analysis and modeling method are proposed for high speed drivers and the system with on-die low dropout (LDO) voltage regulator. In addition, a jitter-aware target impedance concept is proposed for power distribution network (PDN) design to correlate the PSIJ with PDN parasitic.

The proposed PSIJ analysis model is based on the driver power supply rejection …

Isospin Dependence Of Nucleon-Nucleon Short-Range Correlations In Inclusive Scattering With Tritium And Helium-3, Shujie Li

Doctoral Dissertations

The nucleon-nucleon (NN) potential has a strong repulsive core. When a two-nucleon (sub)system falls into this range, they will interact strongly at short distance, and move away from each other with momenta above the Fermi level. This is called the NN Short-range Correlations (SRCs).

Previous experiments reported a neutron-proton pair (isosinglet) dominance in high-momentum nucleons. In inclusive electron scattering, this np dominance will cause a scaling behavior of cross sections at 1.4

Fat In The Academy: Reimagining The Experience Of The Fat Academic, Danielle Marie Lavendier

Doctoral Dissertations

This dissertation gives teachers with stigmatized bodies space to enter into a conversation that is often had without them by media and medical providers. Fat bodies are maligned in contemporary American society and, for a number of reasons, including American ideas about independence and self-control, European-based standards of beauty, media representation, and more, fat people (especially women) are seen as pathological, out-of-control and as draining to the greater society. Within academia, there are pressures for fat folks, as well. This qualitative interview-based study focuses on self-identified fat, female professors and graduate students in Composition and Rhetoric. These women are high …

Becoming ‘We’: Disembodied Trauma And A Community Of Globalized Reading In Contemporary Asian American Novels And Graphic Narratives, Jin Lee

Doctoral Dissertations

Historical narratives often focus on the victors of major global conflicts and leave out the mention of the oppressed. But trauma theorists note that literary arts can effectively offer insight to unremarked histories. My dissertation examines how contemporary Asian American novels and graphic narratives represent underrepresented historical trauma, with a particular focus on Maxine Hong Kingston’s The Woman Warrior, Lois-Ann Yamanaka’s Blu’s Hanging, GB Tran’s Vietnamerica, Fred Chao’s Johnny Hiro, and Gene Luen Yang’s American Born Chinese. I focus on what I call “disembodied trauma,” a phenomenon which encourages readers to recognize silenced histories in the texts. Specifically, “disembodied trauma,” …

From Believing To Doing: Teacher Ownership Of Inclusive Education Practices A Grounded Theory Case Study, Maria Agorastou

Doctoral Dissertations

The purpose of the current qualitative study was to explore the in-depth experiences of school teachers in an urban public elementary school in Greece, looking at 1) their role as change agents, as it pertains to inclusive education practices, and 2) their conception of ownership toward this change

This case study utilized a Straussian grounded-theory design to guide the collecting and coding of interview data in order to identify emerging categories and generate substantive theory. The researcher collected data through interviews with 15 teachers, administrators and parents of the school community.

Adhering to a constant comparative analysis of the data, …

Tuning Surface Properties Of Titanium Dioxide For Carbon Monoxide Oxidation Over Copper-Titanium Dioxide, Guoqiang Cao

Doctoral Dissertations

Besides being widely used as a probe reaction, carbon monoxide (CO) oxidation has been playing a crucial role in multiple industrial applications, including automotive emission elimination, chemical production, and abatement of toxic waste. Copper (Cu) based catalysts have been extensively investigated for CO oxidation, because of its low cost and comparable activity to precious metal-based catalysts. Meanwhile, the surface properties, such as the oxidation state of copper species and oxygen species, depend on the synthesis process. Surface properties would eventually impact the catalytic performance. Therefore, it is desirable to build the property-activity relationship to understand factors that can affect the …

Strategies In Ligand Design For Carbon Dioxide Reduction Catalysts, Sebastian Andrew Pantovich

Doctoral Dissertations

There is a growing concern over emission of carbon dioxide into the atmosphere and its implication in global climate change. Natural sinks for carbon dioxide, such as oceans and vegetative growth, cannot compete with anthropogenic source emissions. Efforts to counteract carbon dioxide emission involve photochemical and electrochemical reduction of carbon dioxide into value increased feedstock chemicals. The high bond strength of carbon-oxygen bonds and energy needed for structural rearrangement from a linear to bent conformation after reduction result in high overpotentials, thus making the process inefficient. Transition metal catalysts and proximal protons sources have been shown to stabilize the bent …

Experimental And Numerical Failure Analysis Of Deep Steel Column Sections, Shokoufeh Zargar Zargar Shoushtari

Doctoral Dissertations

The availability of reliable numerical models is essential to reduce the uncertainties present in the prediction of structural behavior. Experimental studies allow the calibration and development of numerical models capable of characterizing the realistic behavior of structural elements and components until the limit state of collapse is approached. Exterior columns in perimeter steel moment-resisting frame structures that are exposed to strong earthquakes experience bending moment demands with high levels of axial load due to overturning. Deep wide flange sections can be used as exterior columns to increase the lateral stiffness of moment frames without significantly increasing the overall weight of …

Effects Of Rumen-Protected Amino Acids And Levels And Sources Of Energy On Milk Production And Nutrient Utilization In Dairy Cattle Fed Metabolizable Protein-Deficient Diets, Yu Zang

Doctoral Dissertations

Lactating dairy cows are characterized by poor N efficiency and dietary N not captured in milk protein is excreted in urine and feces, which then contribute to environmental N pollution. Nitrogen losses also shrink profit margins for dairy producers due to costly protein sources. Additionally, the dairy industry is an important anthropogenic source of greenhouse gases such as CO2 and CH4, with CH4 representing a potent greenhouse gas and non-negligible energy losses in dairy cattle. Thus, my PhD program has focused on developing nutrition-based approaches to improve milk production efficiency (e.g., milk yield/dry matter intake) and reduce N excretion and …

Future Hydrological Failure Probability Of Dams In New England Under Land Use And Climate Change, Iman Hosseini-Shakib

Doctoral Dissertations

Floods lead to the overtopping of dams which is the main cause of dam failures and can result in significant loss of lives and property. This study investigates how the hydrological failure probability of dams in New England may change with future changes in climate and land use. Non-stationarity of future precipitation caused by the anthropogenic climate change and altered watershed concentration times caused by anthropogenic alterations such as urbanization, industrialization or deforestation can impact the mechanisms of runoff production and transfer. This can potentially change the frequency, magnitude, or duration of floods. Therefore, due to different flood patterns and …