Digital Commons Network^™

Anion Exchange Membrane Fuel Cell Performance In The Presence Of Carbon Dioxide, Jacob Wrubel

Doctoral Dissertations

Anion Exchange Membrane Fuel Cells (AEMFCs) offer some possible advantages over their Proton Exchange Membrane (PEM) counterparts due to more facile oxygen reduction reaction kinetics (enabling cheaper catalysts), easier water management & balance of plant, cheaper membrane materials, and improved stability of fuel cell stack materials. However, AEMFCs perform significantly worse when exposed to carbon dioxide (CO₂), which is present in most applications. Furthermore, because CO₂ is so pervasive inside the AEMFC system, its effects are difficult to isolate experimentally. Therefore, a modeling approach was developed which can offer independent control of membrane properties and operating conditions, …

Beam-Spin Asymmetry Of Exclusive Coherent Electroproduction Of The Π0 Off 4he, Frank Thanh Cao

Doctoral Dissertations

To understand the partonic structure of nucleons in nuclei, measuring the beam spin asymmetry (BSA) from exclusive processes is important to get at the so-called Generalized Parton Distributions (GPDs) that describe the partons’ behavior inside the nucleon. In particular, BSA in Deeply Virtual Meson Production (DVMP) can offer valuable constraints on the transverse GPDs which are not accessible with other exclusive processes. Furthermore, DVMP measurements on bound nucleons can offer insights into structure modification due to the nuclear environment.

The interpretation of this bounded nucleon DVMP on nuclear targets rests on the assumption of factorization and that higher-order effects are …

Improved Pion Correlation Functions Under Lattice Action, Daniel Hoying

Doctoral Dissertations

We present the first calculation of pion-pion ($\pi\pi$) scattering at physical quark mass from lattice QCD. We simulate QCD in a periodic $\sim 5$ fm box at inverse lattice spacing $a^{-1}=1.015,1.3784$ GeV using zM\"obius/M\"obius Domain Wall Fermions and Iwasaki Gauge Action. We form operators composed of localized hydrogen-like wave functions for scalar ($\overline{\psi}\psi$), pseudoscalar ($\overline{\psi}\gamma_5\psi$), and vector bilinears ($\overline{\psi}\gamma_\mu\psi$) We then calculate all-to-all (A2A) meson field propagators for up to three units of individual particle momenta as well as isospin $I=0,1,2$, with up to (in the $I=0,2$) three units of center of mass momentum. This allows us to project the …

Effective Techniques In Reverse Mathematics, David Nichols

Doctoral Dissertations

We develop the theory of strong reductions in the reverse mathematics zoo and show by means of novel tree labeling constructions that strong computable reduction is sufficient to separate four stable relatives of Ramsey's theorem for 2-colorings of pairs.

Experimental And Numerical Analysis Of Less-Mobile Domain Processes In Naturally Occurring Porous Media, Farzaneh Mahmood Poor Dehkordy

Doctoral Dissertations

The importance of the exchange between surface water (SW) and groundwater (GW) is well known among researchers because of its effects on multiple processes including contaminant transport, biogeochemical reactions, and remediation techniques. Thorough understanding of this exchange can be challenging due to the various factors that can impact GW-SW exchange dynamics; especially considering the possibility of sediment heterogeneity in porous media. In the presence of sediment heterogeneity, pores with different levels of connectivity are expected. Pores that are well connected create “mobile” zones, while poorly connected pores create “less-mobile” zones. Conventional fluid sampling techniques are primarily sensitive to the mobile …

Gaussian Limits And Polynomials On High Dimensional Spheres, Amy Peterson

Doctoral Dissertations

We show in detail that the limit of spherical surface integrals taken over slices of a high dimensional sphere is a Gaussian integral on an affine plane of finite codimension in infinite dimensional space. We then utilize these ideas to show that a natural class of orthogonal polynomials on high dimensional spheres limit to Hermite polynomials.

Investigating Students' Mathematical Needs And Successful Tutoring Strategies, Melissa Newell

Doctoral Dissertations

Quantitative learning centers (QLCs) have emerged on undergraduate around the globe in an attempt to provide necessary support to students enrolled in undergraduate courses that address quantitative literacy. QLCs often provide support through peer tutoring to students in mathematics or related courses. Since QLCs are prevalent on undergraduate campuses and have the potential to impact students from diverse backgrounds and disciplines, it is pertinent that we understand their effects on the learning experience. In the existing literature, QLCs are shown to have an overall positive impact on students both academically and affectively, however studies rarely investigate the needs of the …

Coercing Magnetism Into Diamagnetic Ceramics: A Case Study In Alumina, Erik Nykwest

Doctoral Dissertations

Ceramics are very diverse class of materials whose properties can vary greatly. It is this diversity that make ceramics so useful in advanced technology. The relatively open crystal structure of ceramics makes it possible to impart functionalities via judicious doping. This work focuses on developing a generalized method for introducing magnetism into normally non-magnetic (diamagnetic) ceramics, using the example case of alumina (Al₂O₃). Here, substitutional doping of Al atoms with 3d transition metal in α- and θ-alumina was studied. Density functional theory was used to predict the structural, electronic, and magnetic properties of doped alumina, as …

Prediction Of Supersaturation From Amorphous Drugs And Mechanisms Of Crystallization Inhibition From Supersaturated Solutions, Arushi Manchanda

Doctoral Dissertations

Supersaturating drug delivery systems, especially amorphous formulations, are used to achieve higher oral bioavailability for poorly soluble drugs. However, amorphous formulations, being thermodynamically unstable, recrystallizes upon contact with water, making experimental measurement of amorphous solubility enhancement challenging. In this work, factors affecting the re-crystallization of poorly soluble drugs and amorphous solubility enhancement were studied.

The various approaches in the literature employed in the calculation of amorphous solubility enhancement ratio (R_s) were compared and moreover, the nuances associated with the estimation of R_s, were also explored. Based on the sensitivity and error analysis on the calculated value …

The Trumpet Music Of Eric Nathan, David Wharton

Doctoral Dissertations

The purpose of this thesis is to explore the trumpet works of composer Eric Nathan in terms of their technical and notational elements. This analysis develops an understanding of the musical vocabulary and techniques that will provide insight into the structure, style, and performance of this repertoire and in doing so to discover a historical perspective of the trumpet’s role within solo and chamber music genres in the 21st century. Through this analysis, I suggest that Nathan's music pushed the technical, and therefore expressive boundaries of the instrument. While not exhaustive, the analysis of Cantus, Four Sculptures, and Toying will …

Towards Layerless Printing In Additive Manufacturing, Radu Ioan Corcodel

Doctoral Dissertations

In recent years, Additive Manufacturing (AM) has advanced from its ubiquitous function of design validation to biomedical and biomimetic engineering, rapid tooling, tissue engineering, the arts and even food manufacturing. Though the corresponding scale reduction of the manufactured models did not coincide with improving two of the most important process characteristics, namely print accuracy and build time. This research aims to formulate a computational framework for computing the maximum build volume for given non-circular aperture extruders and printing machines that have 3, or perhaps higher numbers of degrees of freedom (DoF), and also generate suitable print head motions given heuristic …

Teachers' And Students' Perspectives Of School-Based Opportunities For Student Creativity, Laurel Brandon

Doctoral Dissertations

This mixed-methods study examined teachers’ responses on the Imagination, Creativity, and Innovation (ICI) Index instrument’s confirmatory data set (n=220). ICI Index scores represented teachers’ predictions of how students would rate their school’s support for student creativity, which was assumed to represent the teachers’ perspective of the actual support for student creativity at the school. Teachers of grades 6-8 (n=55) had significantly lower ICI Index scores than teachers of grades 3-5 (n=155; pn=151) did not differ significantly from gifted and talented teachers (n=49) on their ICI scores. Qualitative analysis found that, when asked …

Torsion Subgroups Of Elliptic Curves Over Function Fields, Robert John Sweet Mcdonald

Doctoral Dissertations

Let 𝔽 be a finite field of characteristic p, and C/𝔽 be a smooth, projective, absolutely irreducible curve. Let 𝔽(C) be the function field of C. When the genus of C is 0, and p ≠ 2, 3, Cox and Parry provide a minimal list of prime-to-p torsion subgroups that can appear for an elliptic curve E/K. In this thesis, we extend this result by determining the complete list of full torsion subgroups possible for an elliptic curve E/K for any prime p when the genus of C is 0 or 1.

Characterization Of Graphene Oxide, Harish Kumar

Doctoral Dissertations

The conversion of graphite to graphene oxide (GO) is an effective and widely used method for solubilizing and exfoliating graphite. However, the oxidation is not uniform, and wide variations in the degree of oxidation exist between and within batches of GO. In this dissertation, we introduce an approach to both quantify the global degree of oxidation in GO and to separate GO into fractions, each with more uniform extents of oxidation. Using the formation of GO-stabilized oil-in-water emulsions, GO is separated into an emulsion fraction and a water fraction. The results find that the GO sheets that stabilize the emulsion …

Cyber-Physical Networked Microgrids, Yan Li

Doctoral Dissertations

Power grid stability and security are challenging problems with significant economic and social impacts that have been exacerbated in recent years by the increase in extreme weather events and cyberattack concerns. Recently, networked microgrids (NMs) have become an emerging paradigm that demonstrates resiliency benefit to their local customers. U.S. DOE has envisioned that the R\&D of NMs will be the next wave of smart grid research to achieve the nation's grid modernization vision towards climate adaptation and resiliency. However, lack of awareness of stability margin, inadequate capability to respond to grid disturbances, and vulnerabilities to communication failure, delay, and cyberattacks …

Establishing An Injury Determinant Framework In Ncaa Division I Soccer, Ryan M. Curtis

Doctoral Dissertations

The purpose of this work was to 1) examine injury risk, rates and physical and psychological wellbeing; 2) identify risk factors for injury; 3) investigate mechanistic pathways for changes in perceived fatigue and 4) investigate the ability of supervised machine learning techniques to predict injury in women and men’s student-athletes competing in national collegiate athletics association (NCAA) division I soccer. Injuries, workload, psychological well-being, sleep characteristics and physical activity disablement was longitudinally assessed for 256 athletes from 12 separate NCAA division I teams. Absolute injury risk and injury rates were calculated. Multi-level models were used to 1) assess differences in …

Exploratory Studies Of Microbiome Dysbiosis And Plasticity In Mice And Humans, Xin Zhou

Doctoral Dissertations

The human body is cohabitated with large number of microorganisms, which potentially influence the health conditions of the host. Dynamic interactions between microbiome and host are critical for this cohabitation relationship. Among human population, the composition of microbiome shows clear interpersonal variations and intrapersonal plasticity, with patterns and mechanisms that are currently unclear. In the first part of this thesis, we explored the human microbiome variations in relation to healthy aging, aimed to understand if microbiome imbalance, or dysbiosis, is a common phenotype of older adults regardless of the age-related diseases. In the second part, we expanded our investigation on …

Promoting Tolerance Through Learning About Human Evolution And Creation Myths, Afsoon Alishahi

Doctoral Dissertations

The role that religion plays in the lives of humans is complex, contradictory, and deeply impactful. According to Allport (1979), religion has a paradoxical function in that it can either combat or contribute to prejudice. A meta-analysis by Hall, Matz, and Wood (2010) found a significant correlation between being deeply religious and having racial prejudice. Similarly, many social scientific studies since 1940 have concluded that religious individuals are more prejudiced than less religious individuals (Hunsberger & Jackson, 2005).

Therefore, the purpose of this study was to examine whether gaining knowledge about human evolution, creation myths, and their relationship to religious …

Memory Access Efficiency In Distributed Atomic Object Implementations, Theophanis Hadjistasi

Doctoral Dissertations

Distributed data services use redundancy to ensure data availability and survivability. Replication can be used to mask failures, however it introduces the problem of consistency because operations may access different object replicas, possibly containing obsolete values. Atomicity is a venerable notion of consistency, introduced in 1979 by Lamport. Atomicity is the most natural type of consistency because it provides an illusion of equivalence with the serial object type that software designers expect.

We deal with the storage of atomic shared readable and writable data in distributed systems that are subject to perturbations in the underlying distributed platforms composed of computers …

Exploiting Phase Change Memory Nano-Device Properties For Hardware Security Applications, Nafisa Noor

Doctoral Dissertations

Security has become a crucial concern in hardware design due to the growing need of protection in everyday financial transactions and exchanges of private information. Physical unclonable functions (PUFs) utilize the inevitable process variations and other stochastic properties in devices to provide a unique way to verify trusted users during access to hardware devices. Improvements in attack methods have recently moved the field of PUFs from traditional silicon devices toward emerging non-volatile memories, such as phase change memory (PCM). Due to intrinsic cell-to-cell and cycle-to-cycle programming variability and high endurance properties of PCM nano-devices, unpredictable and reconfigurable PUF challenge-response pairs …

Development Of A Counter-Flow Thermal Gradient Microfluidic Device, Shayan Davani

Doctoral Dissertations

This work presents a novel counter-flow design for thermal stabilization of microfluidic thermal reactors. In these reactors, precise control of temperature of the liquid sample is achieved by moving the liquid sample through the thermal zones established ideally through the conduction in the solid material of the device. The goal here is to establish a linear thermal distribution when there is no flow and to minimize the temperature change at flow condition. External convection as well as internal flowinduced effects influence the prescribed thermal distribution. The counter-flow thermal gradient device developed in this study is capable of both stabilizing the …

Support Provided By Administrators For Mathematics Teachers: A Case Study Of One North Louisiana High School, Jessica M. Hunter

Doctoral Dissertations

National and International assessment results as well as general student unpreparedness for college and beyond in terms of mathematical abilities indicate a need for increased student achievement in mathematics (Hart, 2005; National Center for Education Statistics, 2017; Peterson, Woessmann, Hanushek, & Lastra-Anadon, 2011). The purpose of the study was to explore effective leadership traits of secondary school administrators that foster and support teachers of mathematics. Research specifically made connections to instructional and transformational leadership practices, actions, and traits. This exploration was investigated through a case study using interviews completed by high school educators, administrators, and district leaders.

A sample of …

Stakeholders’ Conceptions Of Giftedness, Ashley Y. Carpenter

Doctoral Dissertations

In the world of gifted education, educators must first find students who qualify for gifted services. Various stakeholders in public elementary education often nominate students for gifted identification and ultimately gifted programs. It is important to determine if stakeholders’ conceptions of giftedness are the same or different, as conceptions influence actions. There is substantial research on teachers’ conceptions of giftedness but limited research on parents’ conceptions of giftedness. The purpose of this study was to explore stakeholders’ conceptions of giftedness and answer the research question: How do stakeholder groups describe giftedness? Participants included parents of elementary gifted students (n …

Accelerating Reactive-Flow Simulations Via Vectorized Chemical Kinetic Evaluation, Nicholas Curtis

Doctoral Dissertations

This work details efforts to reduce the cost of using detailed chemical kinetic modeling in realistic reactive-flow simulations, utilizing analytical Jacobian evaluation and vectorized-computing on the central processing unit (CPU), graphics processing unit (GPU) and other hardware-accelerators.

The first part of this thesis investigated GPU-based ordinary differential equation (ODE) methods for stiff chemical kinetics. A fifth-order implicit Runge--Kutta method and two fourth-order exponential integration methods were implemented for the GPU and paired with the analytical chemical kinetic Jacobian software pyJac. The performance of each algorithm was compared with a commonly used CPU-based implicit integrator CVODEs. The implicit Runge--Kutta method running …

Generalized Quasilinear Simulation Of Turbulent Channel Flow, Colleen B. Kellam

Doctoral Dissertations

Direct numerical simulation (DNS) of wall-bounded turbulent flows in physically relevant parameter regimes remains infeasible in many cases of practical interest. Accordingly, this work further establishes the generalized quasilinear (GQL) approximation, introduced by Marston et al. (Phys. Rev. Lett., 116, 2016), as a robust, accurate, and efficient alternative to existing simulation and modeling schemes by investigating its effectiveness as a tool for simulating turbulent channel flow. The GQL reduction is achieved by separating the flow variables into low and high modes via a spectral filter rather than by decomposition into a strict mean and fluctuations, as for the quasilinear (QL) …

I. The Binding Of Cu(Ii) And Zn(Ii) To Poly-N-Isopropylacrylamide And Its Effects On The Phase Transition And Ii. The Synthesis And Characterization Of Nickelalactones Chelated By P-N-P Pincer Ligands, Luke Aaron Fulton

Doctoral Dissertations

The responsive material poly-N-isopropylacrylamide phase-transitions from hydrophilic to hydrophobic conformations above 32 °C in aqueous media. Researchers have successfully tied that responsive behavior to other dissolved species such as pH, metal concentrations, and even glucose concentration. From our interests in developing sensor technologies we ascertained that direct interactions between metal ion and polymer had received little to no attention. Our investigations into this literature gap discovered that dissolved metal ion only slightly shifts the lower critical solution temperature. However, metal ion greatly increases the size of polymer aggregates, and is found to bind directly to the polymer. We present a …

Fatigue Assessment Of Complex Structural Components Of Steel Bridges Integrating Finite Element Models And Field-Collected Data, Maryam Mashayekhizadeh

Doctoral Dissertations

Fatigue damage in welded structural steel components has a complex presentation, which is influenced by the geometric configuration of the component and load path in a structural system. The classic fatigue assessment methods, using nominal stresses and S-N curves, may not capture nor predict the complicated performance of the component with respect to fatigue. Recent novel complex steel structural connections that experience multi-axial behavior or do not fit any conventional fatigue categories are not explicitly addressed in the existing fatigue design codes. An ideal fatigue estimation for the complex structural components is dependent on a thorough understanding of structural performance …

Effects Of Waves, Tides, And Vegetation On The Distribution Of Bed Shear Stress In The Great Bay Estuary, Nh, Salme Cook

Doctoral Dissertations

The goals of this research are to expand our understanding of, and improve predictions of bed shear stress in estuarine environments using both observational datasets and numerical modeling. To accurately predict sediment transport, a good understanding of the bed shear stress that drives the sediment erosion, suspension and deposition is essential. Shear stress is a function of both the hydrodynamics in the system and the characteristics of the sediment that comprise the bed itself. The hydrodynamic forcing is determined by tides, waves, meteorological effects, rivers, or some combination that can change on time scales of a few minutes to a …

Investigating The Use Of Different Types Of Sealant Materials For Cement Remedial Applications, Murad Mohammedahmed Abdulfarraj

Doctoral Dissertations

"The overall objective is to investigate the ability of several material to mitigate cement failures such as channels, fractures, and micro-annuli in oil and gas wells. The sealant material that can also be used in the wells that are used for geologic storage of carbon dioxide CO₂. Evaluating the sealant material is critical to improve the zonal isolation of the wells, which would lead to safer operations. The approach of this dissertation is to utilize particles gel that has been used successfully in conformance control application, and epoxy resin systems, that have superior seal characteristics compared to conventional …

Active-Passive Dynamic Consensus Filters: Theory And Applications, John Daniel Peterson

Doctoral Dissertations

”This dissertation presents a new method for distributively sensing dynamic environments utilizing integral action based system theoretic distributed information fusion methods. Specifically, the main contribution is a new class of dynamic consensus filters, termed active-passive dynamic consensus filters, in which agents are considered to be active, if they are able to sense an exogenous quantity of interest and are considered to be passive, otherwise, where the objective is to drive the states of all agents to the convex hull spanned by the exogenous inputs sensed by active agents. Additionally, we generalize these results to allow agents to locally …