Physical Sciences and Mathematics Commons^™

Computational Magnetohydrodynamic Investigation Of Flux Compression And Implosion Dynamics In A Z-Pinch Plasma With An Azimuthally Opposed Magnetic Field Configuration, Kyle John Peterson

Doctoral Dissertations

Magnetic flux compression is a well established technique for the generation of ultrahigh magnetic fields, large currents, and large energy densities. It has been suggested as a means for power density amplification on Z-pinch generators such as Decade Quad, at Arnold Engineering Development Center, and it may be especially suitable as a means for producing higher powers of K-shell radiation from high atomic number loads such as titanium. Although many one-dimensional models of flux compression on Z-pinch generators exist, an improvement in understanding is needed about the physics and implosion dynamics on a two-dimensional level. To this end, a two-dimensional …

“Design Of Molecular Mechanics Modeling Techniques For Exploring Molecular Recognition Using Cyclodextrins., Shannon Bradley Fox

Doctoral Dissertations

Molecular mechanics modeling techniques have been developed to study the behavior of cyclodextrins (CDs) in capillary electrophoresis (CE) separations. Using the commercial computational package, Sybyl, the mechanisms of molecular recognition between organic analytes and CDs are investigated.

Cyclodextrin-modified capillary electrochromatography (CDCE) experiments were conducted to separate neutral derivitized naphthalene solutes using carboxymethyl-beta-cyclodextrin (CM-b-CD). Grid conformation-searching programs were developed to explore the interaction space between CD and solute and to calculate their interaction energies using molecular mechanics. The interaction energies correlated remarkably well with the separation behavior. It was found that extensive minimization (more than 3000 iterations) was required at each …

A High Shear-Rate Optical Rheometer For Complex Fluids, Khaled S. Mriziq

Doctoral Dissertations

A parallel-plate optical rheometer in a magnetic-disc drive configuration has been designed and constructed of optically transparent materials and operating with a very small gap to obtain rheological and structural measurements at very high shear rates.

The friction force at the disk-slider interface has been measured as a function of sliding speed while the film thickness was monitored in situ using a capacitance technique. The shear rate is calculated from the film thickness and the sliding speed. A thin film can be applied on the disk, which allows very high-shear-rate measurements at low sliding speeds with negligible viscous heating.

Both …

Production In Au-Au Collisions, Robert Jason Newby

Doctoral Dissertations

This thesis presents the first J/ Ψ production analysis of Au+Au reactions at forward rapidity at p √sNN = 200 GeV. In the second year of RHIC running, design energy was achieved in the collisions of both Au+Au ions and proton+proton reactions. The production of the J/Ψ is measured by the PHENIX experiment in Au+Au collisions as well as in proton-proton collisions. The scientific goal is to investigate the nature of hot, dense nuclear matter capitalizing on the unique properties of the J/ Ψ as a probe of this matter. Recent experimental results by the NA50 collaboration at CERN …

3d Visualization Modules For Chemical Engineering – A Web-Based Approach Using Java And Opengl, Sharad Anant Gupta

Masters Theses

The main objective of this work is to implement web-based educational modules for chemical engineering students. Phase behavior is a topic with which the students seem to struggle with, particularly for mixtures, where a 2-D representation of the phase diagram falls far short of the understanding a 3-D model can provide. Using the platform-independence of Java and the graphics capability of OpenGL, three phase diagram Java applets have been developed. Users can view these web-based 3D applets by installing a plug-in. These modules provide users with an ability to rotate the 3D models, slice through them, zoom into them and …

Monte Carlo Simulations And Analysis Of Single-Molecule Detection And Imaging, Peter Williams

Masters Theses

Computer modeling and analysis methods are developed for two modes of operation of an instrument for sensitive fluorescence detection of individual dye-labeled molecules in solution. First, Monte Carlo simulations of experiments for single-molecule imaging (SMI) are extended to include effects of sample flow, sticking of molecules to surfaces, and the finite depth-of-focus of the optics. The results have a bearing on a patented method for high-speed single-molecule DNA sequencing. They indicate that the imaging of freely moving fluorescent labels within a microfluidic flowcell will be considerably more involved than that of immobilized molecules at a surface, which is the usual …

Itera- Tive Reconstruction Framework For High-Resolution X-Ray Ct Data, Thomas Matthew Benson

Masters Theses

Small animal medical imaging has become an important tool for researchers as it allows noninvasively screening animal models for pathologies as well as monitoring dis- ease progression and therapy response. Currently, clinical CT scanners typically use a Filtered Backprojection (FBP) based method for image reconstruction. This algorithm is fast and generally produces acceptable results, but has several drawbacks. Firstly, it is based upon line integrals, which do not accurately describe the process of X-ray attenuation. Secondly, noise in the projection data is not properly modeled with FBP. On the other hand, iterative algorithms allow the integration of more complicated sys- …

A Class Of Functions That Are Quasiconvex But Not Polyconvex, Catherine S. Remus

Masters Theses

In 1991 V. Sverak [11] gave an example of a function that was invariant and quasiconvex but not polyconvex. We have generalized this example to a wide class of functions that meet certain ellipticity and growth conditions. Quasiconvexity is one necessary and sufficient condition for the existence of solutions to the minimization problem in elliptic P.D.E. theory. Invariance is frequently a requirement of the stored energy function in Calculus of Variation approaches to elasticity problems.

Isosurface Extraction In The Visualization Toolkit Using The Extrema Skeleton Algorithm, Subha Parvathy Mahaadevan

Masters Theses

Generating isosurfaces is a very useful technique in data visualization for understanding the distribution of scalar data. Often, when the size of the data set is really large, as in the case with data produced by medical imaging applications, engineering simulations or geographic information systems applications, the use of traditional methods like marching cubes makes repeated generation of isosurfaces a very time consuming task. This thesis investigated the use of the Extrema Skeleton algorithm to speed up repeated isosurface generation in the visualization package, Visualization Toolkit (VTK). The objective was to reduce the number of non-isosurface cells visited to generate …

Cross Sections Fall 2003, Department Of Physics And Astronomy

Cross Sections

No abstract provided.

Strategies For Enhancing The Performance Of Chemical Sensors Based On Microcantilever Sensors, Christopher Tipple

Doctoral Dissertations

Microcantilever (MC) based chemical sensors have become more widely used during the past 10 years due to the advantages they possess over other chemical sensors. One of the most significant characteristics is their extremely high surface to volume ratio. This key facet allows surface forces that can be ignored on a macroscale to become a significant sensing transduction mechanism. MC based sensors also exhibit a higher mass sensitivity to adsorbates than do many other chemical sensor platforms. Under many conditions, MC based sensors directly translate changes in Gibbs free energies due to analyte-surface interactions into mechanical responses. However, the widespread …

Thermodynamics And Kinetics Of Defects At Surfaces, Tianjiao Zhang

Doctoral Dissertations

Fundamental understanding of the various electronic and structural properties at surfaces is a prerequisite for improved control of nanometer-scale patterning of surfaces for potential technological applications. In this dissertation, we have used multi-scale theoretical approaches to investigate the thermodynamic and kinetic properties of a few elemental types of surface defects. The multi-scale approaches range from first-principles calculations within density functional theory to empirical embedded atom method (EAM) to statistical analysis to kinetic Monte Carlo simulations. In studying the thermodynamic properties of intrinsic line defects on a vicinal TaC(910) surface, our Monte Carlo simulations in comparison with scanning tuning microscope (STM) …

Data Access In Wide Area Networks Of Heterogeneous Workstations, Kim Buckner

Doctoral Dissertations

The accessibility of data in wide area networks can be difficult. This research shows the use of the Internet Backplane Protocol (IBP) along with a modified version of the C standard I/O library that can allow data to be easily accessible without having to make major modifications to legacy code. In fact if legacy programs only use standard input and output routines, they need only be recompiled to effect a homogeneous file system. It also demonstrates that this access is predictable enough to make decisions on what data to access and in what fashion that access is most effective.

“Enhancement Of Sensitivity And Selectivity Of Chemical Sensors Through Thin Film Coatings And Surface Modifications, Joseph Jeremy Headrick

Doctoral Dissertations

Chemical sensors have become major analytical tools for how we monitor
and obtain information about the chemical nature of ourselves and our
surroundings. Two characteristics of chemical sensors that are under constant
development and improvement are their selectivity and their sensitivity.
Selectivity is a concern of any chemical sensor, without it the signal obtained by
a chemical sensor cannot be related to the target species concentration with any
confidence. With chemical sensors the selectivity is generally created by the
used of a chemical recognition layer such as a permeable membrane, or a thin
chemical film. The sensitivity of a chemical …

Integrated Visualization Of Diffusion Tensor And Functional Mri, Nathaniel Richard Fout

Masters Theses

To understand the morphology, structure, and function of the human brain and the underlying relationships therein has long been a goal of mankind. Technologies are constantly emerging and evolving in an effort to realize this goal, with each new development potentially providing another piece of the puzzle. Among those technologies are advanced imaging modalities such as Diffusion Tensor MRI (DT-MRI) [2] and Functional MRI (fMRI) [8], whose purpose is to provide deeper insight into the neural network connecting functional units of the cerebral cortex. More specifically, DT-MRI captures a description of the fibrous structures (such as nerve fibers) in the …

Structural And Stratigraphic Investigations At The Southwest End Of The Tellico-Sevier Syncline, Southeast Tennessee, Milan A. Heath Ii

Masters Theses

The southern Appalachian Valley and Ridge is composed of a wedge of Cambrian through Pennsylvanian siliciclastic and carbonate rocks, deformed during latest Paleozoic by the collision of Laurentia and Gondwana. This collision caused the southern Appalachian foreland fold-thrust belt to deform as a critically tapered wedge. This study utilized structural and stratigraphic data to examine the mechanical behavior and timing of emplacement of the southwest end of the Tellico-Sevier syncline within this wedge. The study area is located in southeast Tennessee at the southwest end of the Tellico-Sevier syncline, which is in the first Valley and Ridge thrust sheet west …

Eigenvalue Dependence On Problem Parameters For Stieltjes Sturm-Liouville Problems, Laurie Elizabeth Battle

Doctoral Dissertations

This work examines generalized Stieltjes Sturm-Liouville boundary value problems with particular consideration of self-adjoint problems. Of central importance is determining conditions under which the eigenvalues depend continuously and differentiably on the problem data. These results can be applied to various physical problems, such as constructing beams to maximize the fundamental frequency of vibration, or constructing columns to maximize the height without buckling. These problems involve maximizing the smallest eigenvalues of Sturm-Liouville equations, and the continuous dependence of the eigenvalues on the problem parameters can be used to accomplish this.

We first consider the generalized 2n-dimensional initial value problem dy …

Trochoidal Electron Impact Time-Of-Flight Mass Spectrometry Of Chlorodifluoromethane, Wesley Daniel Robertson

Masters Theses

A Time-of-Fight mass spectrometer (TOF-MS) equipped with both a standard electron gun and a trochoidal electron monochromator was constructed and made operational and used to study ionization processes of the molecule Chlorodifluoromethane (CHF₂Cl). The appearance energies of both the parent ion (CHF₂Cl⁺) and the most intense fragment ion (CHF₂⁺) were carefully analyzed and it was observed that the energy for formation of the parent ion, (CHF₂Cl⁺) at 12.50 eV, was at a higher energy than the fragment ion, (CHF₂⁺) at 12.25 eV. This phenomenon …

Fractal Images Generated By Newton's Method.", Jennifer Corte

Masters Theses

We investigate the behavior of Newton's Method for finding roots applied to complex-valued functions of complex variables. This re- quires an analysis of iteration of rational functions. The fractal nature of Newton's Method in the complex plane gives us intricate and beautiful images. By investigating select functions we attempt to generalize a pattern of behavior.

Computational Models For Diusion Of Second Messengers In Visual Transduction, Harihar Khanal

Doctoral Dissertations

The process of phototransduction, whereby light is converted into an electrical response in retinal rod and cone photoreceptors, involves, as a crucial step, the diffusion of cytoplasmic signaling molecules, termed second messengers. A barrier to mathematical and computational modeling is the complex geometry of the rod outer segment which contains about 1000 thin discs. Most current investigations on the subject assume a well stirred bulk aqueous environment thereby avoiding such geometrical complexity. We present theoretical and computational spatio-temporal models for phototransduction in vertebrate rod photoreceptors, which are pointwise in nature and thus take into account the complex geometry of the …

A Preemption-Based Meta-Scheduling System For Distributed Computing, Sathish Vadhiyar

Doctoral Dissertations

This research aims at designing and building a scheduling framework for distributed computing systems with the primary objectives of providing fast response times to the users, delivering high system throughput and accommodating maximum number of applications into the systems. The author claims that the above mentioned objectives are the most important objectives for scheduling in recent distributed computing systems, especially Grid computing environments.

In order to achieve the objectives of the scheduling framework, the scheduler employs arbitration of application-level schedules and preemption of executing jobs under certain conditions. In application-level scheduling, the user develops a schedule for his application using …

Studies Of Electroosmotic Flow Dynamics During Electrophoretic Separations, Jason Lasseter Pittman

Doctoral Dissertations

Instrumentation and techniques for monitoring electroosmotic flow (EOF) during capillary electrophoretic (CE) separations in both fused-silica capillaries and glass microfluidic devices are presented. These techniques were applied under conventional and sample stacking separation conditions. The instrumentation developed for monitoring EOF was also used to develop optically gated vacancy separations in microfluidic devices.

A recently developed technique for monitoring EOF in capillary electrophoresis by periodic photobleaching of a neutral fluorophore added to the running buffer was further characterized and optimized and then applied to monitoring EOF during a typical capillary electrophoresis separation. The concentration of neutral fluorophore (rhodamine B) added to …

The Role Of Surface States In Electron-Phonon Coupling On The Open Surfaces Of Simple Metals, Shu-Jung Tang

Doctoral Dissertations

Symmetry is the beauty of nature. It is the mirror of the way nature minimizes the energy of the system, and achieves the stable state. In the bulk crystal, 3D symmetry has ensured the minimum of free energy contributed by electrostatic energy, vibrational energy and many body self-energy. When the crystal is broken to form two surfaces, the 3D symmetry is destroyed, leading to high free energy on the surface. In order to minimize the free energy, the electronic charge on or near the surface rearranges to form an electronic and lattice structure quite distinct from the bulk. My research …

“Applications Of Coherent Electron Beams, Alexander Erwin Thesen

Doctoral Dissertations

The use of coherent beams for interferometric measurements has gained great popularity in light optics over the last several decades. The availability of coherent electron sources has now opened the door to apply the concept of holographic imaging in many new areas. Off-axis holograms can now be recorded in field emission transmission electron microscopes equipped with the electron optical equivalent of a biprism. This technique allows the accurate retrieval of phase and amplitude of the electron wave, which has been transmitted through a sample. The sensitivity of the phase of the electron wave to electrical potentials makes it possible to …

Performance Improvements Of Common Sparse Numerical Linear Algebra Computations, Piotr Rafal Luszczek

Doctoral Dissertations

Manufacturers of computer hardware are able to continuously sustain an unprecedented pace of progress in computing speed of their products, partially due to increased clock rates but also because of ever more complicated chip designs. With new processor families appearing every few years, it is increasingly harder to achieve high performance rates in sparse matrix computations. This research proposes new methods for sparse matrix factorizations and applies in an iterative code generalizations of known concepts from related disciplines. The proposed solutions and extensions are implemented in ways that tend to deliver efficiency while retaining ease of use of existing solutions. …

Aspects Of Black Hole Scattering, Suphot Musiri

Doctoral Dissertations

We discuss various aspects of black hole scattering. Firstly, we consider nonextremal rotating black branes. We solve the wave equation for a massless scalar field and calculate the absorption cross section. We obtain a function of two temperature parameters once we move away from extremality, which is similar to the case of Kerr- Newman black holes. We discuss the implications of this result to the AdS/CFT correspondence. Secondly, we study a system of maximally-charged slowly-moving black holes and take the limit of a continuous self-interacting matter distribution (black string). We quantize the system by using the path integral method. We …

Dipole-Bound Anions, Nathanael Isaac Hammer

Doctoral Dissertations

Any molecule with a dipole moment above approximately 2.5 Debye can form a stable negative ion (dipole-bound anion). These anions are best produced by “resonance” charge exchange from atoms in high Rydberg states (Rydberg electron transfer, RET). RET to form dipole-bound anions occurs over a narrow range of effective principle quantum number, n*. Dipole-bound anions for 32 molecules with dipole moments between 2.5 and 6.0 Debye have been studied. The excess electron in such an anion is very diffuse and weakly bound. Binding energies (electron affinities, EAs) are estimated from the narrow range of n* at which charge exchange occurs …

Thermal Evolution Of Planetesimals And Protoplanets In The Terrestrial Planet Region: Code Optimization And Implementation On A Distributed Grid Using Netsolve, Amitabha Ghosh

Masters Theses

A code for asteroidal heat transfer and growth is optimized for performance. The Gauss elimination routine for the solver is replaced by a sparse matrix routine. Finite element matrix assembly operations are rewritten to reduce operations involving 3D arrays to 1D. Advantage is taken of the sparse matrix structure of finite element matrices in reducing 2D arrays to 1D. The number of vector touches are reduced to the extent possible, by carrying over statements from one iteration to the next. The number of do loops are reduced by merging several do loops into one. The optimization reduced the CPU time …

Geology Of Part Of The Southwestern Brushy Mountains, Inner Piedmont, North Carolina, And The Geochemistry Of Western Inner Piedmont Migmatite, James L. Kalbas

Masters Theses

The newly defined boundary between the western and eastern Inner Piedmont belts has been the focus of several recent tectonic studies in the southern Appalachians. Specifically, the Brindle Creek fault was recognized in southwestern North Carolina as a thrust that juxtaposed Siluro-Devonian-age paragneisses (now-known) and Devonian and Mississippian granites atop Neoproterozoic- to Cambrian-age paragneisses, Middle Ordovician volcanic and metasedimentary rocks, and Ordovician intrusive units.

Detailed geologic mapping in the Kings Creek 7.5-minute quadrangle, southwestern Brushy Mountains, Caldwell County, North Carolina, revealed the northeastern continuation of the thrust. Recognition of the northeastern extension of the fault, and analysis of small -scale …

A Coarse-Grain Parallel Implementation Of The Block Tridiagonal Divide And Conquer Algorithm For Symmetric Eigenproblems., Robert M. Day

Masters Theses

Cuppen’s divide and conquer technique for symmetric tridiagonal eigenproblems, along with Gu and Eisenstat’s modification for improvement of the eigenvector computation, has yielded a stable, efficient, and widely-used algorithm. This algorithm has now been extended to a larger class of matrices, namely symmetric block tridiagonal eigenproblems. The Block Tridiagonal Divide and Conquer algorithm has shown several characteristics that make it suitable for a number of applications, such as the Self-Consistent-Field procedure in quantum chemistry.

This thesis discusses the steps taken to implement a coarse-grain parallel version of the Block Tridiagonal Divide and Conquer algorithm, suitable for a parallel supercomputer or …