Digital Commons Network^™

Narratives Of Disability And Displacement: Oral Histories Of The Lived Experiences Of Disabled Refugees, Jennifer Lynn Ward

Doctoral Dissertations

Disabled refugees are considered as the most marginalized group of all displaced populations. Disabled displaced people are at particular risk of violence, exploitation, and abuse. Additional barriers to accessing humanitarian assistance, education, health care, and other services exist for disabled displaced people. The purpose of this study was to collaborate with disabled refugees who have resettled in the United States and to create a space for their stories to be told. This research project explores the narratives of the lived experiences of disabled displaced people through the lenses of three theoretical frameworks: human rights, disability justice, and Critical Refugee Studies. …

Exploring Student Engagement For Diverse Student Populations: A Case Study Examining Institutional Logics Of Student Affairs Middle Management Leaders, Frangelo Rominque Ayran

Doctoral Dissertations

This study explores the institutional logics that student affairs middle managers employ to facilitate student engagement programs and resources intended for more diverse student populations. While the positive effects of student involvement and student engagement are both widely documented, disparities between White students and students of color in their rates of engagement continue to illustrate that the effects of student engagement opportunities as forms of high impact practices are dependent upon the racial and ethnic background of students. Higher education institutions faced with the widening divide between low-income students of color in their retention, degree attainment, and engagement rates not …

Incorporating Critical Perspectives In Nonprofit Management Education Programs: How Critical Scholars Of Color Navigate Pressures In Higher Education, Khanh H. Nguyen

Doctoral Dissertations

The nonprofit sector has grown from a few charities, based on religious affiliation, to a multi-billion-dollar sector that supports the United States of America’s economic stability. As a result, the need for nonprofit management education has increased over the last three decades from 1990 to 2019 (O’Neill, 2005; Mirabella, 2014). However, most of the classes taught in nonprofit programs across the US focus on the transactional aspect of nonprofit leadership (Mirabella, 2014; Wang & Ashcraft, 2012). The purpose of this study is to gain a better understanding of the ways critical perspectives are engaged within nonprofit management education programs by …

Source Reconstruction In Near Field Scanning For Rfi Application, Hosseien Rezaei

Doctoral Dissertations

"This research is divided into three major topics. The first topic, mechanical magnetic field generator for communication in the ULF range, is discussed in the first paper. The second topic, source reconstruction in near field scanning for RFI application, is discussed over the course of two papers. The third topic, analysis of imbalanced 2 or 3 Wire VHF LISN, is discussed in the last two papers.

In the first topic, the possibility to use a mechanical system (a rotating magnet) as a source (generator or antenna combined) of the ULF magnetic field is investigated. Ultralow frequency (ULF) communication systems have …

Investigating The Effect Of Operating Condition On Esd-Induced Soft-Failures, Omid Hoseini Izadi

Doctoral Dissertations

"Conflicting observations have been found in the literature regarding the effect of operating conditions on ESD (electrostatic discharge) susceptibility. While some studies have suggested a strong correlation between the two, others observed little to no correlation. In this work, a systematic study has been carried out suggesting the existence of a strong correlation between the ESD susceptibility and operating conditions. It is found that the root cause of this conflict is random ESD noise injection. A measurement approach is proposed to synchronize the noise injection with the system activity such as high/low CPU load. In this approach, the current consumption …

Integrated Solar And Ess Ac/Dc Systems For Various Grid Applications, Phani Ratna Vanamali Marthi

Doctoral Dissertations

"Modular multilevel converters (MMC) have gained prominence for high power applications in recent years due to their technical merits such as voltage scalability, harmonic performance, and high efficiency. Integration of renewable energy sources such as solar photovoltaic (PV) systems and energy storage systems (ESS) to the grid using power electronic (PE) resources is increasing due to the techno-economic successes achieved by such systems. Following these developments, the integration of MMCs with PV plants and ESS systems is one of the dynamic research avenues being pursued. Along these lines, an integrated development of PV plants, ESS, and alternating- and direct-current (ac/dc) …

Thermophysical Properties Of Nominally Phase Pure Boride Ceramics, Austin D. Stanfield

Doctoral Dissertations

"This research focusses on the thermophysical properties of nominally phase pure boride ceramics. As interest in ultra high temperature ceramics increases due to a renewed interest in hypersonic flight vehicles and with the expanding materials design space accompanying interest in high entropy materials, it is imperative to understand the intrinsic properties of boride ceramics. By reducing Hf content in ZrB₂ from the natural abundance, ~1.75 at% in this case, to ~100 ppm, thermal conductivity increased from 88 W/m·K to 141 W/m·K. Removal of Hf allowed the thermal conductivity of ZrB₂ with small transition metal solute additions to be …

Fiber Optic Sensors For Industry And Military Applications, Yiyang Zhuang

Doctoral Dissertations

"Fiber optic sensors (FOSs) have been widely used for measuring various physical and chemical measurands owing to their unique advantages over traditional sensors such as small size, high resolution, distributed sensing capabilities, and immunity to electromagnetic interference. This dissertation focuses on the development of robust FOSs with ultrahigh sensitivity and their applications in industry and military areas.

Firstly, novel fiber-optic extrinsic Fabry-Perot interferometer (EFPI) inclinometers for one- and two-dimensional tilt measurements with 20 nrad resolution were demonstrated. Compared to in-line fiber optic inclinometers, an extrinsic sensing motif was used in our prototype inclinometer. The variations in tilt angle of the …

Mining Haul Road Defect Detection -- Advancement In Automated Road Extent And Response Calibration For Improved Maintenance, Alexander David Douglas

Doctoral Dissertations

Mine haul roads degrade rapidly due to extremely heavy loads on sub optimal construction materials. This research tests two methods of defect detection to determine limitations to current technology: optical detection and vehicle vibration response. Optical defect detection was found to have the least significant limitations for surface defect detection and vehicle vibration response modeling has the least significant limitations for subsurface defects. This research proposes novel methods to eliminate the critical limitations of both technologies.

Unmanned Aerial Vehicles (UAV) equipped with GPS and a high-resolution camera is used to create a 3-D point cloud using a structure-from-motion algorithm. This …

Data And Resource Management In Wireless Networks Via Data Compression, Gps-Free Dissemination, And Learning, Xiaofei Cao

Doctoral Dissertations

“This research proposes several innovative approaches to collect data efficiently from large scale WSNs. First, a Z-compression algorithm has been proposed which exploits the temporal locality of the multi-dimensional sensing data and adapts the Z-order encoding algorithm to map multi-dimensional data to a one-dimensional data stream. The extended version of Z-compression adapts itself to working in low power WSNs running under low power listening (LPL) mode, and comprehensively analyzes its performance compressing both real-world and synthetic datasets. Second, it proposed an efficient geospatial based data collection scheme for IoTs that reduces redundant rebroadcast of up to 95% by only collecting …

Fiber-Optic And Coaxial-Cable Extrinsic Fabry-Perot Interferometers For Sensing Applications, Chen Zhu

Doctoral Dissertations

”The fiber-optic extrinsic Fabry-Perot interferometer (EFPI) is one of the simplest sensing configurations and is widely used in various applications due to its prominent features, such as high sensitivity, immunity to electromagnetic interference, and remote operation capability. In this research, a novel one-dimensional wide-range displacement sensor and a three-dimensional displacement sensor based on fiber-optic EFPIs are demonstrated. These two robust and easy-to-manufacture sensors expand the application scope of the fiber-optic EFPI sensor devices, and have great potential in structural health monitoring, the construction industry, oil well monitoring, and geo-technology.

Furthermore, inspired by the fiber-optic EFPI, a novel and universal ultra-sensitive …

3d-Printed Adsorbents For Gas Separations: A Material Development, Kinetic Assessment, And Process Performance Investigation, Shane Lawson

Doctoral Dissertations

“Adsorbent materials are promising for various gas purification processes, however, forming them into structured contactors is paramount in enhancing mass transfer properties and reducing pressure losses. In this research, various adsorbents were engineered into structured contactors with 3D printing. The overall goal of this research was to improve the formulation methods of 3D-printed adsorbents and understand their performances in gas separation processes. The specific objectives were to 1) develop new adsorbent 3D-printing strategies, 2) understand the kinetic properties of printed adsorbent monoliths, and 3) assess their process performances. Objective one was addressed by developing five 3D printing techniques: i) oxide …

Theoretical Study Of Magnetic Particles In A Shear Flow Subjected To A Uniform Magnetic Field, Christopher A. Sobecki

Doctoral Dissertations

"Magnetic manipulation of non-spherical magnetic microparticles is important for applications in shape-based and magnetic-based separations such as waste management, disease diagnostics, drug delivery, and mining. Manipulations of magnetic microparticles also include chain formation to assemble compositions for electronics, drug loading designs, and magnetorheological fluids for smart armor, hydraulic brakes, and dampers. In microfluidic devices, separation-formation-effectiveness depends on the shape of the channel, the shear rate, and the magnetic field strength and direction.

Particle separation and chain formation involved highly complex and computational expense-demanding studies in microfluidic devices, magnetic fields, and particle- particle/wall interactions. This research took complex experimental studies and …

Pdn Modeling For High-Speed Multilayer Pcb Boards And Decap Optimization Using Machine Learning Techniques, Ling Zhang

Doctoral Dissertations

"In power distribution networks (PDN), there are two main challenges nowadays. One challenge is how to efficiently model and calculate the impedance for arbitrary-shape and multi-layer PDN systems. The second challenge is the optimization of decoupling capacitors in the pre-layout stage. This dissertation proposes novel solutions to these two challenges. To tackle the first challenge, a boundary element method (BEM) is utilized to calculate the quasi-static inductances between vertical vias for arbitrary-shape planes. Then a specialized circuit solver is developed to solve the equivalent circuit of inductances and capacitances for multi-layer PDN structures. Also, a contour integral method (CIM) is …

Receiver Function Imaging Of The 410 And 660 Km Discontinuities And Seismic Azimuthal Anisotropy Revealed By Shear Wave Splitting Beneath The Australian Continent, Kailun Ba

Doctoral Dissertations

"The Australian continent is composed the of Precambrian cratons in the west and Phanerozolc orogens in the east. Despite numerous seismological studies, controversies remain regarding the structure, evolution, and dynamics of the crust and mantle beneath Australia. In this study, we used two techniques, receiver functions and shear wave splitting analyses, to investigate the topography of the mantle transition zone (MTZ) discontinuities and mantle seismic azimuthal anisotropy, respectively. We utilized P-to-S receiver functions to map the 410 and 660 km discontinuities bordering the MTZ. The discontinuity depths obtained show a systematic apparent uplifting for both discontinuities in central and western …

Development Of Tripodal And Bipodal Ligand Frameworks And First-Row Transition Metal Reagents For Selective C-N Bond Construction Methodologies, Anshika Kalra

Doctoral Dissertations

"We present a family of anionic Mn(II) reagents supported by trisphenylamido- amlne frameworks that offer guidance with regards to ligand selection for developing C—N bond construction methodologies (extensively used in the synthesis of petrochemicals, household chemicals) through nitrene- transfer chemistry. We subsequently extend the study to include the corresponding Fe(II), Co(II), and Ni(II) reagents, to gain insights in their comparative reactivity/selectivity patterns. Attenuated levels of electrophilicity of anionic complexes proved to be more suitable for discriminating aromatic from aliphatic olefins for aziridination purposes, especially for Mn(II) complexes. However, in the case of Co(II) reagents, we observe that additional stereoelectronic parameters …

Improving The Data Quality In Gravitation-Wave Detectors By Mitigating Transient Noise Artifacts, Kentaro Mogushi

Doctoral Dissertations

“The existence of gravitational waves (GWs), small perturbations in spacetime produced by accelerating massive objects was first predicted in 1916 as solutions of Einstein’s Theory of General Relativity (Einstein, 1916). Detecting and analyzing GWs produced by sources allows us to probe astrophysical phenomena.

The era of GW astronomy began from the first direct detection of the coalescence of a binary black hole in 2015 by the collaboration of the advanced Laser Interferometer Gravitational-wave Observatory (LIGO) (Aasi et al., 2015) and advanced Virgo (Abbott et al., 2016a). Since 2015, LIGO-Virgo detected about 50 confident transient events of GW signals (Abbott et …

Multi-Fidelity Modeling For Aerothermal Analysis Of Deployable Planetary Entry Technologies, Mario J. Santos

Doctoral Dissertations

“NASA is developing deployable entry technologies in the form of the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) and the Adaptable Deployable Entry Technology (ADEPT) vehicles to support human exploration of Mars. To ensure that these technologies are reliable under uncertain entry conditions and extreme aerothermal environments, uncertainty quantification must be integrated into the design process which typically requires large number of high-fidelity computational fluid dynamics (CFD) simulations with prohibitively high computational cost. To address this challenge, construction of multi-fidelity aerothermal response predictions which combine low-fidelity correlations with fewer high-fidelity CFD models in a way that produces highly accurate surrogates with reduced …

Mantle Flow Systems Associated With Slab Subduction And Absolute Plate Motion In Alaska Constrained By Shear Wave Splitting Analyses, Yuchen Yang

Doctoral Dissertations

"Alaska has long been recognized as a geologically complex region with a sharp contrast in tectonic activity between southern and northern Alaska. While the former is characterized by the subduction of the geometrically varying Pacific-Yakutat plate beneath the North American plate, the latter has a mostly stable cratonic setting. To investigate the mantle flow fields beneath Alaska and understand the influence of the subduction process on regional mantle dynamics, a total of 2790 pairs of well-defined teleseismic shear wave splitting (SWS) measurements recorded from 379 stations are obtained and analyzed. In addition, 247 pairs of SWS results from local earthquake …

Reveal Wind Loading Of Tornadoes And Hurricanes On Civil Structures Towards Hazard-Resistant Design, Ryan Honerkamp

Doctoral Dissertations

"Extreme winds impacting civil structures lead to death and destruction in all regions of the world. Specifically, tornadoes and hurricanes impact communities with severe devastation. On average, 1200 tornadoes occur in the United States every year. Tornadoes occur predominantly in the Central and Southeastern United States, accounting for an annual $1 billion in economic losses, 1500 injuries, and 90 deaths. The Joplin, MO Tornado in 2011 killed 161 people, injured more than 1000, destroyed more than 8000 structures, and caused $2.8 billion of property loss. Hurricanes occur predominantly on the United States East coast regions and along the coast of …

Information-Based Methods And Models For Particle Flow Filtering, Kari Catherine Ward

Doctoral Dissertations

"Recursive estimation methodologies, such as Kalman and Bayesian filters, typically require models of some kind to perform the estimation. This filtering process seeks to improve knowledge surrounding some quantities of interest, or states, over time by incorporation of imperfect observations. The models required pertain to the state dynamics, sensors from which measurements are obtained, and probabilistic models of the underlying stochastic processes. In addition to any number of necessary models, real-world application of a filter is normally accompanied by at least one, if not several, techniques to promote better performance. These methods vary in purpose from expanding the kinds of …

Semi-Empirical Modeling Of Liquid Carbon's Containerless Solidification, Philip C. Chrostoski

Doctoral Dissertations

“Elemental carbon has important structural diversity, ranging from nanotubes through graphite to diamond. Previous studies of micron-size core/rim carbon spheres extracted from primitive meteorites suggest they formed around such stars via the solidification of condensed carbon-vapor droplets, followed by gas-to-solid carbon coating to form the graphite rims. Similar core/rim particles result from the slow cooling of carbon vapor in the lab. The long-range carbon bond-order potential was used to computationally study liquid-like carbon in (1.8 g/cm³) periodic boundary (tiled-cube supercell) and containerless (isolated cluster) settings. Relaxations via conjugate-gradient and simulated-annealing nucleation and growth simulations using molecular dynamics were …

Robustness Against Attacks And Uncertainties In Smart Cyber-Physical Systems, Prithwiraj Roy

Doctoral Dissertations

Cyber-Physical Systems (CPS) are sensing, processing, and communicating platforms, embedded with physical devices that provide real-time monitoring and control. Security challenges in CPS necessitate solutions that are robust against attacks and uncertainties and provide a seamless operation, especially when used in real-time applications to monitor and secure critical infrastructures. CPS mainly consists of a physical component for sensing or monitoring and a cyber component for processing and communicating. The quality of interactions between physical and cyber systems has direct impacts on the system’s performance and reliability.

CPS plays a major role in smart services and applications within a smart living …

Investigating The Focusing Effect Of Charge Geometry With Computer Simulations, Witness Plates, And High-Speed Videography, Kelly Ray Williams

Doctoral Dissertations

"Scaled distance is used to calculate a safe standoff radius from the detonation of a known mass of an explosive. It has been shown that varying only the geometry of the charge significantly overdrives regions of the blast wave potentially resulting in hazardous overpressure levels at scaled distance safe radii. Pressure transducers are used to measure overpressure surrounding spherical, cylindrical, and cubic charges to determine if bridge waves were formed at the edges between flat sides as seen in published studies of cylindrical charges. In the fireball field a witness plate is used to evaluate radial energy distribution with a …

Cyclic Sequential Adsorption Desorption/Thermal-Catalytic Oxidation Of Volatile Organic Compounds: Material Development, Process Advancement/Improvement, And Numerical Modeling, Simulation And Optimization, Busuyi Ojo Adebayo

Doctoral Dissertations

"Volatile organic compounds (VOCs) are a group of useful organic chemicals but when emitted have contributed to air pollution. They affect human health, cause environmental degradation and contaminate our waters and soils, so they need to be controlled. When they exist in dilute concentrations, abatement becomes challenging, thus requiring advanced abatement methods, e.g., sequential adsorption desorption/thermal-catalytic oxidation process. The overall goal of this research was to abate dilute streams of VOCs via the process. The specific objectives were to 1) develop novel adsorbent/catalyst dual-function materials (DFMs) for the process, 2) improve the operability of a one-bed-one-column reactor configuration for the …

Investigating The Impact Of Rock Bridges On The Mechanical Behavior Of Jointed Rock Mass Using Lattice Spring-Based Synthetic Rock Mass (Ls-Srm) Approach, Mariam Salem Alebayat

Doctoral Dissertations

"Rock bridges were defined as a segment of intact rock that separates from discontinuities. Numerous studies are focused on developing methods to quantify their significance in rock mass strength and deformability behavior. This thesis aimed to enhance understanding of the effect of rock bridges on jointed rock masses in both laboratory and slope scales. For this purpose, the lattice spring base Synthetic Rock Mass (LS-SRM) method was adopted to conduct the numerical models, distinguished in computational efficiency, and simulates the brittle failure and roughness of discontinuities.

A robust approach was developed to optimize the calibration procedure to avoid the complex …

Prediction Intervals For Fractionally Integrated Time Series And Volatility Models, Rukman Ekanayake

Doctoral Dissertations

"The two of the main formulations for modeling long range dependence in volatilities associated with financial time series are fractionally integrated generalized autoregressive conditional heteroscedastic (FIGARCH) and hyperbolic generalized autoregressive conditional heteroscedastic (HYGARCH) models. The traditional methods of constructing prediction intervals for volatility models, either employ a Gaussian error assumption or are based on asymptotic theory. However, many empirical studies show that the distribution of errors exhibit leptokurtic behavior. Therefore, the traditional prediction intervals developed for conditional volatility models yield poor coverage. An alternative is to employ residual bootstrap-based prediction intervals. One goal of this dissertation research is to develop …

Analysis Of Turbulence Model Uncertainty For Canonical Flow Problems Including Shock Wave Boundary Layer Interaction Simulations, Aaron James Erb

Doctoral Dissertations

"The purpose of this research is to present results of an uncertainty and sensitivity analysis study of commonly used turbulence models in Reynolds-Averaged Navier-Stokes (RANS) codes due to the epistemic uncertainty in closure coefficients for a set of turbulence model validation cases that represent the structure of several canonical flow problems. The study focuses on the analysis of a 2D zero pressure gradient flat plate, a 2D wall mounted hump, and an axisymmetric shock wave boundary layer interaction, all of which are well documented on the NASA Langley Research Center Turbulence Modeling Resource website. The Spalart-Allmaras (SA), the Wilcox (2006) …

Modeling Time Series With Conditional Heteroscedastic Structure, Ratnayake Mudiyanselage Isuru Panduka Ratnayake

Doctoral Dissertations

"Models with a conditional heteroscedastic variance structure play a vital role in many applications, including modeling financial volatility. In this dissertation several existing formulations, motivated by the Generalized Autoregressive Conditional Heteroscedastic model, are further generalized to provide more effective modeling of price range data well as count data. First, the Conditional Autoregressive Range (CARR) model is generalized by introducing a composite range-based multiplicative component formulation named the Composite CARR model. This formulation enables a more effective modeling of the long and short-term volatility components present in price range data. It treats the long-term volatility as a stochastic component that in …

Investigation Of Packed Bed And Moving Bed Reactors With Benchmarking Using Advanced Measurement And Computational Techniques, Binbin Qi

Doctoral Dissertations

"Trickle bed reactors (TBR), as typical packed bed reactors (PBR), are widely used in various fields. Very limited information regarding the flow behaviors, hydrodynamic, and mathematical models in extrudate catalyst shapes, such as cylinders, trilobes, and quadrilobes, can be found in literatures because the major focus was on spherical shape. Therefore, a hybrid pressure drops and liquid holdup phenomenological model for extrudate catalyst shapes was developed based on two-phase volume averaged equations, which showed high accuracy against experimental data. The maldistribution and dynamic liquid holdup were investigated in quadrilobe catalyst using gamma-ray computed tomography. A pseudo-3D empirical model was developed …