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 …

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 …

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) …

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 …

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 …

Study Of Energy Sampling Weights In The Dø Detector Using Multiparameter Fitting Method, Qun Yu

Doctoral Dissertations

The DØ calorimeter at Fermilab is a sampling calorimeter measuring the energy of particles produced in high energy proton-antiproton collisions. A set of accurate sampling weights is of significant importance to DØ research activity. The objective of this work was to obtain a set of optimized sampling weights for the DØ central calorimeter, the Inter-Cryostat Detector (ICD), the Central Calorimeter Massless Gap (CCMG), and the End Calorimeter Massless Gap (ECMG).

The foundation of the optimization method is that, in high energy physics, the ratio of energy E and the corresponding momentum P of a particle is approximately 1, in units …