Digital Commons Network^™

Synthesis And Characterization Of Magnetic Solids Featuring 3d-4f Heterometallic Oxides Comprised Of Spin Chains And 3d-6p Noncentrosymmetric Oxides Templated By Acentric Salt Units, Jennings West

All Dissertations

The studies and syntheses presented in this dissertation were primarily aimed at exploring new magnetic solids comprised of special framework oxides with novel magnetic properties. Low-dimensional magnetic behavior has been of great interest, especially pertaining to molecular solids having single magnetic domains where slow relaxation and quantum properties of magnetization are evident. In attempts to mimic molecular magnets and achieve reduced dimensionality of, in this case 3d-;4f magnetic sublattices, diamagnetic oxyanions, XO_mn-, and A-site cations (A = alkali and alkaline-earth metals) were used as nonmagnetic spacers in hopes of disrupting or confining magnetic interactions in certain dimensions. The …

Thermoelectric Properties Of Silicon Germanium: An In-Depth Study To The Reduction Of Lattice Thermal Conductivity, Daniel Thompson

All Dissertations

Thermoelectric materials provide a solid state route for the direct conversion between thermal and electrical energy. Hence, thermal gradients can be used to generate power of up to several KW, or driven DC power can be used to pump heat in or out of a system. Recent pushes in thermoelectric research are for power generation materials with higher efficiency. These materials can be used to recover energy from the waste heat of vehicles' exhaust systems, and as power generators for extraterrestrial exploration when coupled with a radioactive heat source.
The goal of this dissertation will be to demonstrate a new …

Sparsity Regularization In Diffuse Optical Tomography, John Cooper

All Dissertations

The purpose of this dissertation is to improve image reconstruction in Diffuse Optical Tomography (DOT), a high contrast imaging modality that uses a near infrared light source. Because the scattering and absorption of a tumor varies significantly from healthy tissue, a reconstructed spatial representation of these parameters serves as tomographic image of a medium. However, the high scatter and absorption of the optical source also causes the inverse problem to be severely ill posed, and currently only low resolution reconstructions are possible, particularly when using an unmodulated direct current (DC) source.
In this work, the well posedness of the forward …

Prognostic And Health-Management Oriented Fuel Cell Modeling And On-Line Supervisory System Development, Xian Zhang

All Dissertations

Of the fuel cells being studied, the proton exchange membrane fuel cell (PEMFC) is viewed as the most promising for transportation. Yet until today, the commercialization of the PEMFC has not been widespread in spite of its large expectation. Poor long term performances or durability, and high production and maintenance costs are the main reasons. For the final commercialization of fuel cells in the transportation field, durability issues must be addressed, while costs should be further brought down. At the same time, health-monitoring and prognosis techniques are of great significance in terms of scheduling condition-based maintenance (CBM) to minimize repair …

Inventing Laughter: Comedic Writing Practices And The Limits Of Pedagogical Power, Daniel Liddle

All Theses

This thesis conducts an examination of the writing methods used by stand-up comedians using the lens of the rhetorical canon of invention. The study applies the theories of Thomas Rickert, Diane Davis, Ann Berthoff, and Janice Lauer in order to define the relationship between humor and epistemology, and to consider how this comedic-epistemic perspective can inform pedagogical practices in the composition classroom. This study relies mainly on the rhetorical analysis of 'How To' books on writing comedy, the methodologies of schools of comedy, as well as biographies by/about comedians in order to discuss the relationship between comedians and their 'material.' …

Methods For Producing Stereoscopic Imagery, Matias Volonte

All Theses

This paper describes methodologies for creating computer graphics stereoscopic imagery. This thesis details the positive and negative aspects for producing and post-producing stereoscopic imagery using different stereoscopic tools provided by Autodesk Maya and The Foundry Nuke. Also, in order to increase efficiency and decrease production time, Python tools were developed both for Maya and Nuke. Finally, the methodology proposed in this paper is fully functional and can be adopted by any production.

The Gas/Dust Ratio Of Circumstellar Disks: Testing Models Of Planetesimal Formation, David Horne, Erika Gibb, Terrence W. Rettig, Sean D. Brittain, David Tilley, Dinshaw Balsara

Publications

We present high-resolution, near-infrared NIRSPEC observations of CO absorption toward six class II T Tauri stars: AA Tau, DG Tau, IQ Tau, RY Tau, CW Tau, and Haro 6–5b. 12CO overtone absorption lines originating from the circumstellar disk of each object were used to calculate line-of-sight gas column densities toward each source. We measured the gas/dust ratio as a function of disk inclination, utilizing measured visual extinctions and inclinations for each star. The majority of our sources show further evidence for a correlation between the gas/dust columndensity ratio and disk inclination similar to that found by Rettig et al.

Elastic Properties Of The Zintl Ferromagnet Yb14mnsb11, Sriparna Bhattacharya, D C. Marinescu, James R. Morris, Ivan A. Sergienko, Brian Sales, David Madrus, Veerle Keppens

Publications

We report measurements of the elastic moduli as a function of temperature (5–300) K and magnetic field (0–2 T) for the Zintl ferromagnet Yb14MnSb11, which is believed to be a rare example of an underscreened Kondo lattice. The elastic moduli measured below the Curie temperature in this complex ferromagnet exhibit unusual lattice stiffening that is independent of the magnetic field and can be adequately modeled using the Landau theory.

Vision-Based Tracking Of A Dynamic Target With Application To Multi-Axis Position Control, Carlos A. Montes, Chan Wong, John C. Ziegert, Laine Mears

Publications

Two sub-pixel resolution approaches to measure in-plane displacements and in-plane rotation of a known target, through image processing, are described in this research. A dynamic known target is displayed on a pixel grid, which is attached to one end of the kinematic chain of an XYθZ stage; the latter represents the experimental testbed. At the other end of the kinematic chain, a digital monochrome camera is fixed to the bottom of the stage and provides 3D position information used as the feedback signal to the vision-based control system in charge of the tool’s motion. The illuminated pixels on the display …

Model Of A Mechanical Clock Escapement, John Wagner, David Moline, Eugene Vold

Publications

The mechanical tower clock originated in Europe during the 14th century to sound hourly bells and later display hands on a dial. An important innovation was the escapement mechanism, which converts stored energy into oscillatory motion for fixed time intervals through the pendulum swing. Previous work has modeled the escapement mechanism in terms of inelastic and elastic collisions. We derive and experimentally verify a theoretical model in terms of impulsive differential equations for the Graham escapement mechanism in a Seth Thomas tower clock. The model offers insight into the clock’s mechanical behavior and the functionality of the deadbeat escapement mechanism.

Herschel/Pacs Observations Of Young Sources In Taurus: The Far-Infrared Counterpart Of Optical Jets, L Podio, I Kamp, D Flower, C Howard, G Sandell, A Mora, G Aresu, Sean D. Brittain, W.R.F. Dent, C Pinte, G J. White

Publications

Context. Observations of the atomic and molecular line emission associated with jets and outflows emitted by young stellar objects provide sensitive diagnostics of the excitation conditions, and can be used to trace the various evolutionary stages they pass through as they evolve to become main sequence stars. Aims. To understand the relevance of atomic and molecular cooling in shocks, and how accretion and ejection efficiency evolves with the evolutionary state of the sources, we will study the far-infrared counterparts of bright optical jets associated with Class I and II sources in Taurus (T Tau, DG Tau A, DG Tau B, …

Topological Thermoelectric Effects In Spin-Orbit Coupled Electron- And Hole-Doped Semiconductors, E Dumitrescu, Chuanwei Zhang, D C. Marinescu, Sumanta Tewari

Publications

We compute the intrinsic contributions to the Berry-phase mediated anomalous Hall and Nernst effects in electron- and hole-doped semiconductors in the presence of an in-plane magnetic field as well as Rashba and Dresselhaus spin-orbit couplings. For both systems we find that the regime of chemical potential which supports the topological superconducting state in the presence of the superconducting proximity effect can be characterized by plateaus in the topological Hall and Nernst coefficients flanked by well-defined peaks marking the emergence of the topological regime. The plateaus arise from a clear momentum space separation between the region where the Berry curvature is …

Predicting Nonspecific Ion Binding Using Delphi, Marharyta Petukh, Maxim Zhenirovskyy, Chuan Li, Lin Li, Lin Wang, Emil Alexov

Publications

Ions are an important component of the cell and affect the corresponding biological macromolecules either via direct binding or as a screening ion cloud. Although some ion binding is highly specific and frequently associated with the function of the macromolecule, other ions bind to the protein surface nonspecifically, presumably because the electrostatic attraction is strong enough to immobilize them. Here, we test such a scenario and demonstrate that experimentally identified surface-bound ions are located at a potential that facilitates binding, which indicates that the major driving force is the electrostatics. Without taking into consideration geometrical factors and structural fluctuations, we …

Observations Of Herbig Ae/Be Stars With Herschel/Pacs. The Atomic And Molecular Contents Of Their Protoplanetary Discs, G Meeus, B Montesinos, I Mendigutia, I Kamp, W F. Thi, C Eiroa, C A. Grady, G Mathews, G Sandell, C. Martin-Zaidi, Sean D. Brittain, W.R.F. Dent, C Howard, F Menard, C Pinte, A Roberge, B Vandenbussche, J P. Williams

Publications

We observed a sample of 20 representative Herbig Ae/Be stars and 5 A-type debris discs with PACS onboard Herschel, as part of the GAS in Protoplanetary Systems (GASPS) project. The observations were done in spectroscopic mode, and cover the far-infrared lines of [O i], [C ii], CO, CH+, H2O, and OH. We have a [Oi] 63 μm detection rate of 100% for the Herbig Ae/Be and 0% for the debris discs. The [Oi] 145 μm line is only detected in 25% and CO J = 18–17 in 45% (and fewer cases for higher J transitions) of the Herbig Ae/Be stars, …

Resource Allocation Framework: Validation Of Numerical Models Of Complex Engineering Systems Against Physical Experiments, Joshua Hegenderfer

All Dissertations

An increasing reliance on complex numerical simulations for high consequence decision making is the motivation for experiment-based validation and uncertainty quantification to assess, and when needed, to improve the predictive capabilities of numerical models. Uncertainties and biases in model predictions can be reduced by taking two distinct actions: (i) increasing the number of experiments in the model calibration process, and/or (ii) improving the physics sophistication of the numerical model. Therefore, decision makers must select between further code development and experimentation while allocating the finite amount of available resources. This dissertation presents a novel framework to assist in this selection between …

Delphi: A Comprehensive Suite For Delphi Software And Associated Resources, Lin Li, Chuan Li, Subhra Sarkar, Jie Zhang, Shawn Witham, Zhe Zhang, Lin Wang, Nicholas Smith, Marharyta Petukh, Emil Alexov

Publications

Background

Accurate modeling of electrostatic potential and corresponding energies becomes increasingly important for understanding properties of biological macromolecules and their complexes. However, this is not an easy task due to the irregular shape of biological entities and the presence of water and mobile ions.

Results

Here we report a comprehensive suite for the well-known Poisson-Boltzmann solver, DelPhi, enriched with additional features to facilitate DelPhi usage. The suite allows for easy download of both DelPhi executable files and source code along with a makefile for local installations. The users can obtain the DelPhi manual and parameter files required for the corresponding …

Clemson Commencement Program, May 2012, Clemson University

Clemson Commencement Programs

No abstract provided.

Flushing Of A Dense Fluid From An Isolated Urban Canyon, Zahra Baratian-Ghorghi

All Dissertations

The mechanics of shear-driven flushing of a dense fluid from a canyon is investigated through a series of laboratory experiments. Such a flow has many environmental applications including the removal of dense pollutants trapped in urban canyons and the purging of salt water from bed depressions at river mouths. While there is an extensive literature on flow in canyons and cavities for the neutrally buoyant case, the problem of flushing a dense fluid from canyon has received considerably less attention. To understand the dynamics of the mixing and to quantify the buoyant contaminant flushing rate, a broad range of experimental …

A Collection Of Problems In Combinatorics, Janine Janoski

All Dissertations

We present several problems in combinatorics including the partition function, Graph Nim, and the evolution of strings.
Let p(n) be the number of partitions of n. We say a sequence a_n is log-concave if for every n, a_n2 &ge a_n+1 a_n-1. We will show that p(n) is log-concave for n &ge 26. We will also show that for n<26, p(n) alternatively satisfies and does not satisfy the log-concave property. We include results for the Sperner property of the partition function.
The second problem we present is the game of Graph Nim. We use the Sprague-Grundy theorem to analyze modified versions of Nim played on various graphs. We include progress made towards proving that all G-paths …

Design Of Meta-Materials Outside The Homogenization Limit Using Multiscale Analysis And Topology Optimization, Christopher Czech

All Dissertations

The field of meta-materials engineering has largely expanded mechanical design possibilities over the last two decades; some notable design advances include the systematic engineering of negative Poisson's ratio materials and functionally graded materials, materials designed for optimal electronic and thermo-mechanical performances, and the design of materials under uncertainty. With these innovations, the systematic engineering of materials for design-specific uses is becoming more common in industrial and military uses. The motivation for this body of research is the design of the shear beam for a non-pneumatic wheel. Previously, a design optimization of a finite element model of the non-pneumatic wheel was …

An Optimization Approach To A Geometric Packing Problem, Bradley Paynter

All Dissertations

We investigate several geometric packing problems (derived from an industrial setting) that involve fitting patterns of regularly spaced disks without overlap. We first derive conditions for achieving the feasible placement of a given set of patterns and construct a network formulation that, under certain conditions, allows the calculation of such a placement. We then discuss certain related optimization problems (e.g., fitting together the maximum number of patterns) and broaden the field of application by showing a connection to the well-known Periodic Scheduling Problem. In addition, a variety of heuristics are developed for solving large-scale instances of these provably difficult packing …

Finding A New Continent Versus Mapping All The Rivers: Recognition, Ownership, And The Scientific Epistemological Development Of Practicing Scientists And Engineers, Andrea Verdan

All Dissertations

Maintaining our nation's standing as a leader of innovative and premier science and engineering research requires that those on the trajectory of these careers receive both rigorous and exceptional training. In addition to educating students in the content knowledge of these disciplines, it is also necessary to train them in the professional skills associated with being competent and conscientious scientists and engineers. In the attempts to understand the best strategies to teach these skills, research during the past few decades has shown a steadily increasing interest in improving the scientific literacy of students in science and engineering disciplines. Researchers agree …

Ambiguous Science And The Visual Representation Of The Real, Curtis Newbold

All Dissertations

The emergence of visual media as prominent and even expected forms of communication in nearly all disciplines, including those scientific, has raised new questions about how the art and science of communication epistemologically affect the interpretation of scientific phenomena. In this dissertation I explore how the influence of aesthetics in visual representations of science inevitably creates ambiguous meanings. As a means to improve visual literacy in the sciences, I call awareness to the ubiquity of visual ambiguity and its importance and relevance in scientific discourse. To do this, I conduct a literature review that spans interdisciplinary research in communication, science, …

Development And Application Of Novel Detection Methods For Aqueous Radioactive Iodine, Kelly Grogan

All Dissertations

Novel detection and analysis methods for radioactive iodine concentration and speciation were investigated for aqueous samples. Radioactive iodine is one of the primary risk-drivers at nuclear waste facilities, and regulations for the presence of radioactive iodine in drinking water are stringent. The first phase of this investigation described the development and characterization of a scintillating anion-exchange resin preferential for aqueous iodine in the form of iodide (I-). The resin was incorporated into a radiochromatography flow-cell scintillation detection system that allowed for simultaneous separation, concentration, and detection of aqueous 129I. The performance of this analytical method was characterized with both on-line …

Towards An Understanding Of The Principal-Engaged-With-Policy Using Theories Of Embodiment And The Senses, Amanda Werts

All Dissertations

Federal education policy places increased pressure on the knowledge of today's educational leader. In particular, principals are scrutinized in their ability to implement policy. To aid in successful implementation practice, researchers have provided explanations of and strategies for principals as they engage with policy.
The purpose of this study was to explore the particularities of the sensorial dimension of the principal-engaged-with-policy's subject position. When the principal-engaged-with-policy is represented in research, policy, and leadership preparation literature, it is done with reference not to the lived experiences of the subject position of the individuals who inhabit it, but instead to desired traits …

Algebraic Approaches To Stochastic Optimization, Katherine Hastings

All Dissertations

The dissertation presents algebraic approaches to the shortest path and maximum flow problems in stochastic networks. The goal of the stochastic shortest path problem is to find the distribution of the shortest path length, while the goal of the stochastic maximum flow problem is to find the distribution of the maximum flow value. In stochastic networks it is common to model arc values (lengths, capacities) as random variables. In this dissertation, we model arc values with discrete non-negative random variables and shows how each arc value can be represented as a polynomial. We then define two algebraic operations and use …

The Development Of Freshman College Calculus Students' Mathematics Identity And How It Predicts Students' Career Choice, Jennifer Cribbs

All Dissertations

There is a need for research to explore the connections between students' self-perceptions and their goals and future engagement with mathematics. This is particularly the case when considering that student interest declines as they transition through K-12 and gender differences continue to persist in mathematics related careers. Knowing how students identify with mathematics might provide insight into students' self-perceptions of mathematics and how these perceptions relate to students' career choices.
This quantitative study uses a mathematics identity framework based upon students' self-perceptions related to mathematics. Specifically, students' self-perceptions relating to mathematics interest, recognition by others in mathematics, and mathematical competence …

Using Factors Of Socioeconomic Status, Family Support, And Academic Preparation To Explain The Black-White Gap In Mathematics Achievement And Participation, Charity Watson

All Dissertations

The Black-White achievement and participation gap in mathematics is a major concern for educators in America. In order to understand why these gaps exist and have continued to exist over the years, it is important to identify some of the factors that may contribute to them. However, one of the limitations in identifying factors that influence the disparities in achievement and participation between Black and White students is the issue of finding comparable and representative groups.
This study aspired to move beyond randomized experimental designs to studying a larger representative sample of Black college students who are equivalent to White …

The Racial Rhetoric Of Cuteness As Decorative Decorum, Nicole Mcfarlane

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This work looks at the trope of cuteness as a means of investigating the topological phenomena of race and public space, particularly in regards to African American rhetorical modes of visual and spatial practice. By introducing a sociological coinage known as the 'teddy-bear effect,' this work explores how racialized expressions of cuteness give off the impression of a demurring civility surrounding the social expectations associated with the cultural norms of gender and class. As a preferred characteristic of information design and strategically deployed for the tactic of racialized passings in the face of increasingly regulated forms of 'post-racial' gate-keeping and …

Highly Charged Ion Interactions With Ultrathin Dielectric Films, Russell Lake

All Dissertations

The excitations occurring at a solid surface due to slow highly charged ion (HCI) impacts are interesting from the perspective of fundamental processes in atomic collisions and materials science. This thesis focuses on two questions: 1) How much HCI potential energy deposition is required to form permanent surface modifications?, 2) How does the presence of a thin dielectric surface film change the classical over-the-barrier picture for neutralization above a clean metal?
I describe a measurement of craters in thin dielectric films formed by XeQ+ (26 ≤ Q ≤ 44) projectiles. Tunnel junction devices with ion-irradiated barriers were used to amplify …