Digital Commons Network^™

Raidx: Raid Extended For Heterogeneous Arrays, Andras Fekete

Doctoral Dissertations

The computer hard drive market has diversified with the establishment of solid state disks (SSDs) as an alternative to magnetic hard disks (HDDs). Each hard drive technology has its advantages: the SSDs are faster than HDDs but the HDDs are cheaper. Our goal is to construct a parallel storage system with HDDs and SSDs such that the parallel system is as fast as the SSDs. Achieving this goal is challenging since the slow HDDs store more data and become bottlenecks, while the SSDs remain idle. RAIDX is a parallel storage system designed for disks of different speeds, capacities and technologies. …

Biophysical Mechanisms Of Rhythm Generation In The Pre-Bötzinger Complex, Ryan S. Phillips

Doctoral Dissertations

The pre-Bötzinger complex (pre-BötC) is an essential rhythmogenic brainstem nucleus located in the ventrolateral medulla. Rhythmic output from the pre-BötC is relayed through premotor and motor neurons to the diaphragm and intercostal muscles to drive the active inspiratory phase of breathing. The specific biophysical mechanisms responsible for generating rhythmic bursting and network synchronization are not well understood and remain a highly debated topic within the field. Through extensive experimental and theoretical work two plausible rhythmogenic mechanisms have emerged. One mechanism is based on a slowly inactivating persistent sodium current (INaP) and the other on a calcium activated non-selective cation current …

Examining The Benefits Of Instructional Assessment As Experienced By Secondary Mathematics Teachers, Willem Wallinga

Doctoral Dissertations

Mathematics teachers use a wide variety of assessment tools and methods to measure student understanding and illuminate potential learning gaps (NCTM, 2014). The most frequent and least formal types occur as observations and interactions that provide immediate feedback on the learning process (NRC, 2003, Wiliam, 2007). These Instructional Assessments emerge within the social environment of classroom activity, and serve a formative function by directly impacting the flow of discussion and motivating appropriate teaching interventions. Research has shown that formative assessment improves student performance, but is often challenging for teachers to master (OECD, 2005). The influence of annual high-stakes testing in …

A Study Of The Surface Structure Of Polymorphic Graphene And Other Two-Dimensional Materials For Use In Novel Electronics And Organic Photovoltaics, Maxwell Charles Grady

Doctoral Dissertations

For some time there has been interest in the fundamental physical properties of low- dimensional material systems. The discovery of graphene as a stable two-dimensional form of solid carbon lead to an exponential increase in research in two-dimensional and other re- duced dimensional systems. It is now known that there is a wide range of materials which are stable in two-dimensional form. These materials span a large configuration space of struc- tural, mechanical, and electronic properties, which results in the potential to create novel electronic devices from nano-scale heterostructures with exactly tailored device properties. Understanding the material properties at the …

Size-Sensitive Crystal Plasticity Finite Element Framework For Simulating Behavior Of Lamellar Metal-Metal Composites, Milan Ardeljan

Doctoral Dissertations

Growing demands for materials with enhanced and superb characteristics increase the difficulty and the amount of research necessary to be conducted in many different areas of expertise. The vast field of computational mechanics represents a significant source of valuable solutions to many of these challenges and can provide a smoother transition in the process when a new material is introduced. Experimental techniques are not always able to measure the localized material features due to the very complicated deformation conditions. As an alternative approach, full-field models are developed, such the ones contained in this dissertation that can bridge this gap and …

Self-Similar Properties And Leading Balance Scaling Structure Of Wall-Bounded Turbulent Flows, Ang Zhou

Doctoral Dissertations

Wall-bounded turbulent flows are ubiquitous in numerous technological applications, and thus much effort has been devoted to investigate their properties. Scaling analyses involving the application multiple-scale approaches are effectively used to explore parameters (Reynolds, Prandtl numbers) dependent scaling behaviors of these flows. The objective of this dissertation research is to firstly extend the analysis of self-similar behaviors on the inertial domain as admitted by the mean dynamics in wall-bounded turbulent flows (WBTF). It then mathematically and physically characterizes the existence of a leading order balance structure in both the kinetic energy and passive scalar transport budgets, and subsequently uses this …

Application Of Quantum Monte Carlo Methods To Molecular Potential Energy Surfaces, Andrew Douglas Powell

Doctoral Dissertations

"Various computational methods have been used to generate potential energy surfaces, which can help us simulate and interpret how atoms or molecules behave during a chemical reaction. For accurate work, ab initio wavefunction methods have traditionally been used, which have some disadvantages. For example, highly accurate methods scale poorly with system size (n⁷ or higher) and are mostly not well parallelized for calculations with multiple processors. One alternative method that has more favorable scaling with system size and is well parallelized is a computational technique called quantum Monte Carlo (QMC). QMC methods scale with the number of electrons as …

Receiver Function Imaging Of Mantle Transition Zone Discontinuities Beneath Alaska, Haider Hassan Faraj Dahm

Doctoral Dissertations

"Subduction of tectonic plates is one of the most important tectonic processes, yet many aspects of subduction zone geodynamics remain unsolved and poorly understood, such as the depth extent of the subducted slab and its geometry. The Alaska subduction zone, which is associated with the subduction of the Pacific Plate beneath the North America plate, has a complex tectonic setting and carries a series of subduction episodes, and represents an excellent target to study such plate tectonic processes. Previous seismological studies in Alaska have proposed different depth estimations and geometry for the subducted slab. The Mantle transition zone discontinuities of …

Long-Range Interatomic Interactions: Oscillatory Tails And Hyperfine Perturbations, Chandra Mani Adhikari

Doctoral Dissertations

"We study the long-range interaction between two hydrogen atoms, in both the van der Waals and Casimir-Polder regimes. The retardation regime is reached when the finiteness of the speed of light becomes relevant. Provided that both atoms are in the ground states, the retardation regime is achieved when the interatomic distance, R, is larger than 137 a₀, where a₀ is the Bohr radius.

To study the interaction between two hydrogen atoms in 1S and 2S states, we differentiate three different ranges for the interatomic distance: van der Waals range (a₀ « R « a₀/α, where α is the fine structure …

Design And Theoretical Analysis Of Advanced Power Based Positioning In Rf System, Lei Wang

Doctoral Dissertations

"Accurate locating and tracking of people and resources has become a fundamental requirement for many applications. The global navigation satellite systems (GNSS) is widely used. But its accuracy suffers from signal obstruction by buildings, multipath fading, and disruption due to jamming and spoof. Hence, it is required to supplement GPS with inertial sensors and indoor localization schemes that make use of WiFi APs or beacon nodes. In the GPS-challenging or fault scenario, radio-frequency (RF) infrastructure based localization schemes can be a fallback solution for robust navigation. For the indoor/outdoor transition scenario, we propose hypothesis test based fusion method to integrate …

Geophysical Interpretation And Static Reservoir Modeling Of Structurally Complex Reservoir, Rg Oil Field Area, Sirte Basin, Libya, Abdalla A. Abdelnabi

Doctoral Dissertations

"Cambrian-Ordovician and Upper Cretaceous reservoir formations are found in the central western Sirte Basin, the main oil producing region in the Sirte Basin, Libya. As a result of changes in sedimentary environments and structural activities, a number of irregularities in reservoir continuity have developed, which negatively affected the overall performance of the reservoir. Effective simulation of such complex reservoirs can be achieved by integrating geophysical, geological, and petrophysical data to construct a reliable full-field static model, which has the potential to simulate the vertical and lateral variations in the reservoir formations. In this study, 2D and 3D seismic data acquired …

Advanced Control Architectures For Grid Connected And Standalone Converter Systems, Subhajyoti Mukherjee

Doctoral Dissertations

"This dissertation proposes new control algorithms dedicated towards improving the reliability, computational burden and stability in grid-connected and stand-alone based power electronic converter systems applicable for ac microgrids.

Two voltage sensorless control architectures, one for stand-alone applications and the other for grid-connected application are established in this thesis. The output voltage of a standalone single-phase inverter is controlled directly by controlling the output filter capacitor current without using a dedicated output voltage sensor. A method to estimate the output filter capacitance is also presented. For the grid connected converter, a novel closed loop estimation is presented to estimate the grid …

Phytoforensics: Applications In Vapor Intrusion Assessment, Jordan Lee Wilson

Doctoral Dissertations

"Vapor intrusion (VI) occurs when contaminants in the vapor phase migrate in the shallow subsurface and enter buildings through cracks, seams, and gaps and has been recognized as a serious human-health threat as occupants are exposed to potentially harmful concentrations over long periods of time. The VI pathway has recently (2017) been identified as a primary exposure pathway and implemented into the Hazard Ranking System for inclusion on the Nation Priorities List. However, assessing VI and human exposure is not simple and current methods are time-, cost-, and labor-intensive; intrusive; and temporally and spatially variability. Trees are ideal candidates for …

Numerical And Experimental Study Of New Designs Of All-Vanadium Redox Flow Batteries For Performance Improvement, Mohammed Abdulkhabeer Ali Al-Yasiri

Doctoral Dissertations

"Energy storage is envisioned as a key part of a renewable energy solution incorporated in a grid that overcomes two critical limits of renewable energy: intermittency and uncertainty. Among various technologies, a vanadium redox flow battery (VRFB) offers a promise because of its unique features such as long cycle life, separation of energy and power ratings, and capability of a deep discharge. The remaining challenges, however, include the limited application due to low energy density and complicated geometries. The complex geometry makes it difficult to optimize the performance and can cause a serious concern about leakage of the liquid. The …

A Harmonic M-Factorial Function And Applications, Reginald Alfred Brigham Ii

Doctoral Dissertations

"We offer analogs to the falling factorial and rising factorial functions for the set of harmonic numbers, as well as a mixed factorial function called the M-factorial. From these concepts, we develop a harmonic analog of the binomial coefficient and an alternate expression of the harmonic exponential function and establish several identities. We generalize from the harmonic numbers to a general time scale and demonstrate how solutions to some second order eigenvalue problems and partial dynamic equations can be constructed using power series built from the M-factorial function"--Abstract, page iii.

Electron Impact Excitation-Ionization Of Molecules, Esam Abobakr A. Ali

Doctoral Dissertations

"In the last few decades, the study of atomic collisions by electron-impact has made significant advances. The most difficult case to study is electron impact ionization of molecules for which many approximations have to be made and the validity of these approximations can only be checked by comparing with experiment.

In this thesis, I have examined the Molecular three-body distorted wave (M3DW) or Molecular four-body distorted wave (M4DW) approximations for electron-impact ionization. These models use a fully quantum mechanical approach where all particles are treated quantum mechanically and the post collision interaction (PCI) is treated to all orders of perturbation. …

Multi-Objective Combinatorial Optimization Problems In Transportation And Defense Systems, Hadi Farhangi

Doctoral Dissertations

"Multi-objective Optimization problems arise in many applications; hence, solving them efficiently is important for decision makers. A common procedure to solve such problems is to generate the exact set of Pareto efficient solutions. However, if the problem is combinatorial, generating the exact set of Pareto efficient solutions can be challenging. This dissertation is dedicated to Multi-objective Combinatorial Optimization problems and their applications in system of systems architecting and railroad track inspection scheduling. In particular, multi-objective system of systems architecting problems with system flexibility and performance improvement funds have been investigated. Efficient solution methods are proposed and evaluated for not only …

Biomarker Discovery Using Urinary Metabolomics For Noninvasive Early Cancer Detection, Casey Franklin Burton

Doctoral Dissertations

"The development of new screening methods for the early detection of cancer remains one of the foremost challenges facing modern cancer research. The emergence of new analytical technologies and their application to 'omics'-based approaches has provided researchers with powerful new tools for molecular biomarker discovery that may benefit early screening of cancer. This dissertation outlines several key advances made toward the application of urinary metabolomics to cancer biomarker discovery. The term urinary metabolomics here refers to the investigation of small metabolites in urine as potential disease biomarkers. The advantage of using this approach lies in its noninvasive sampling characteristics and …

Application Of Nearly Linear Solvers To Electric Power System Computation, Lisa L. Grant

Doctoral Dissertations

"To meet the future needs of the electric power system, improvements need to be made in the areas of power system algorithms, simulation, and modeling, specifically to achieve a time frame that is useful to industry. If power system time-domain simulations could run in real-time, then system operators would have situational awareness to implement and avoid cascading failures, significantly improving power system reliability. Several power system applications rely on the solution of a very large linear system. As the demands on power systems continue to grow, there is a greater computational complexity involved in solving these large linear systems within …

In-Situ Assessment Of Concrete Bridge Decks And Pavements Using Stress-Wave Based Methods, Mengxing Li

Doctoral Dissertations

"Concrete infrastructure of United States is aging and deteriorating. Accurate assessment the condition of concrete infrastructure is critical for its maintenance and rehabilitation. Stress-wave based methods, including ultrasonic surface wave (USW) and impact echo (IE), are becoming popular for characterizing defects and mechanical properties of concrete infrastructures. In this dissertation, a comprehensive literature review of seismic wave theory and common types of defects identified in concrete infrastructures, as well as stress-wave based methods used for concrete infrastructure monitoring and characterizing on a selected concrete bridge deck and two concrete pavement segments are present. The utility and reliability of both methods …

Fusion Of Non-Visual And Visual Sensors For Human Tracking, Wenchao Jiang

Doctoral Dissertations

"Human tracking is an extensively researched yet still challenging area in the Computer Vision field, with a wide range of applications such as surveillance and healthcare. People may not be successfully tracked with merely the visual information in challenging cases such as long-term occlusion. Thus, we propose to combine information from other sensors with the surveillance cameras to persistently localize and track humans, which is becoming more promising with the pervasiveness of mobile devices such as cellphones, smart watches and smart glasses embedded with all kinds of sensors including accelerometers, gyroscopes, magnetometers, GPS, WiFi modules and so on. In this …

Mass Transfer Studies In Heavy Oil Recovery Using Solvents, Vijitha Mohan

Doctoral Dissertations

"Heavy oil, sometimes called bitumen, is known for its high viscosity (above 100 cp) and low API gravity (below 22⁰). In most cases, viscosity reduction is needed for the final product. There is a considerable amount of heavy oil in Alberta, Canada and the world's largest heavy oil deposit is in Venezuela. Yet less than 1% of it can be recovered because of its high viscosity. For shallow reservoirs, it is possible to resort to open cast mining. For deeper reservoirs, steam is used at ~ 350 ⁰C which gets the oil viscosity reduced to 1cp, which can now be …

The Use Of Geophysical Methods For Dam Seepage Investigations And Dredged Oyster Deposit Characterization, Stanley Chinedu Nwokebuihe

Doctoral Dissertations

"The dissertation is made up of three papers, which discuss the utility of geophysical tools in earthfill dam investigations and dredged oyster bed characterization.

In the first paper, an earthfill dam in Warren County, Missouri was effectively investigated for seepage through the dam and its outlet works using an integration of the electrical resistivity tomography, induced polarization and spontaneous potential geophysical tools. Recommendations were subsequently made based on the results of the study on grout locations to prevent further seepage. In the second paper, a similar study of earthfill dam seepage was conducted on a different dam in Southern Missouri. …

Rapid Quantification Of Trypsin Inhibitors In Food And Feed Formulations With Electrospray Ionization Mass Spectrometry, Radheshyam Panta

Doctoral Dissertations

"Presence of anti- nutrients deteriorate the nutritional value of animal foods and feed formulations. The important one being trypsin inhibitors. Trypsin inhibitors in food and feed formulations lower the protein supplement and hence the ultimate consequence is the decrease in growth and development of animals. It is therefore, crucial to monitor trypsin inhibitors in animal food and feed formulations. Research work mentioned in this dissertation is based on the development of rapid, more accurate and robust method for determination of trypsin inhibitor in food and feed formulations. The developed method includes extraction of trypsin inhibitor from food and feed formulation …

Environmental Hazard Identification, Assessment And Control For A Sustainable Maritime Transportation System, Lizzette Marie Pérez Lespier

Doctoral Dissertations

"A demand exists to contribute towards the widening awareness of the need for sustainable maritime development and for coordinated maritime policies worldwide. Maritime shipping is considered the most eco-efficient mean of transportation and yet, is responsible for negative environmental impacts.

This dissertation focuses on developing data-driven decision support tools to evaluate the sustainable performance of MTS by focusing on the elements of the MTS that place stress on the environment. The first research contribution is a System Dynamics simulation model that examines the MTS resiliency after an extreme event and determines the sequence needed to restore the ocean-going port to …

Dissolution-Enlarged Fractures Imaging Using Electrical Resistivity Tomography (Ert), Elnaz Siami-Irdemoosa

Doctoral Dissertations

"In recent years the electrical imaging techniques have been largely applied to geotechnical and environmental investigations. These techniques have proven to be the best geophysical methods for site investigations in karst terrain, particularly when the overburden soil is clay-dominated. Karst is terrain with a special landscape and distinctive hydrological system developed by dissolution of rocks, particularly carbonate rocks such as limestone and dolomite, made by enlarging fractures into underground conduits that can enlarge into caverns, and in some cases collapse to form sinkholes.

Bedding planes, joints, and faults are the principal structural guides for underground flow and dissolution in almost …

Layered Crustal And Mantle Structure And Anisotropy Beneath The Afar Depression And Malawi Rift Zone, Cory Alexander Reed

Doctoral Dissertations

"Although a wealth of geophysical data sets have been acquired within the vicinity of continental rift zones, the mechanisms responsible for the breakup of stable continental lithosphere are ambiguous. Eastern Africa is host to the largest contemporary rift zone on Earth, and is thus the most prominent site with which to investigate the processes which govern the rupture of continental lithosphere. The studies herein represent teleseismic analyses of the velocity and thermomechanical structure of the crust and mantle beneath the Afar Depression and Malawi Rift Zone (MRZ) of the East African Rift System. Within the Afar Depression, the first densely-spaced …

Remote Sensing And Localization Of Smart Rocks With Orientation-Controlled Magnets For Real-Time Monitoring Of Bridge Scour And Riprap Effectiveness, Yan Tang

Doctoral Dissertations

"This study aims to develop and implement a novel smart rock technology for real-time monitoring of the maximum scour depth and the effectiveness of riprap mitigation measures. A smart rock is one or more stacked magnets encased in concrete that can automatically roll to the deepest point of a scour hole around a bridge pier and provide its location through remote measurement over time. Once integrated into a riprap measure, the smart rock moves together with natural rocks and is thus a potential indicator of the effectiveness of the riprap measure. Therefore, the localization and movement of smart rocks were …

Contributing Factors To Child Stunting In Guatemala: A Systems Analysis Focused On Enteric Disease Transmission And Mycotoxin Exposure, Lee Emerson Voth-Gaeddert

Doctoral Dissertations

"Child stunting -- low height-for-age -- is a United Nation's indicator for chronic malnutrition that has been linked to both acute and chronic health problems. Data from Guatemala suggests for children under five years of age, 49% are classified as stunted. This dissertation tests the following hypotheses, among children in Guatemala 1) environmental enteric dysfunction (EED) is correlated with height-for-age, 2) aflatoxin B (AFB) exposure is correlated with height-for-age, and 3) AFB exposure is correlated with EED. A network analysis was conducted on data from the US Agency for International Development (USAID) collected in 2012 to identify trends in a …

Optimal Electric Vehicle Scheduling : A Co-Optimized System And Customer Perspective, Maigha

Doctoral Dissertations

"Electric vehicles provide a two pronged solution to the problems faced by the electricity and transportation sectors. They provide a green, highly efficient alternative to the internal combustion engine vehicles, thus reducing our dependence on fossil fuels. Secondly, they bear the potential of supporting the grid as energy storage devices while incentivizing the customers through their participation in energy markets. Despite these advantages, widespread adoption of electric vehicles faces socio-technical and economic bottleneck. This dissertation seeks to provide solutions that balance system and customer objectives under present technological capabilities. The research uses electric vehicles as controllable loads and resources. The …