Physical Sciences and Mathematics Commons^™

Instrument Performance Enhancement And Modification Through An Extended Instrument Paradigm, Stephen L. Mahan

Doctoral Dissertations

An extended instrument paradigm is proposed, developed and shown in various applications. The CBM (Chin, Blass, Mahan) method is an extension to the linear systems model of observing systems. In the most obvious and practical application of image enhancement of an instrument characterized by a time-invariant instrumental response function, CBM can be used to enhance images or spectra through a simple convolution application of the CBM filter for a resolution improvement of as much as a factor of two. The CBM method can be used in many applications. We discuss several within this work including imaging through turbulent atmospheres, or …

Questing For The Grail: Core Collapse Supernova Simulations With Boltzmann Neutrino Transport, Otis Earl Messer

Doctoral Dissertations

The importance of exact neutrino transport in spherically symmetric core collapse supernova simulations is explored in this dissertation. The primary tool for these studies is the neutrino radiation hydrodynamics code AGILE-BOLTZTRAN (Mezzacappa & Bruenn 1993a,b,c; Mezzacappa & Messer 1998; Liebendörfer 2000). AGILE-BOLTZTRAN couples the solution of the Boltzmann equation for all three flavors of neutrinos and antineutrinos to a one-dimensional, implicit, adaptive grid hydrodynamics code. Emission, absorption, and scattering of neutrinos from nucleons and nuclei, neutrino-electron scattering, and pair production and annihilation are included as neutrino-matter couplings. Details of the code are described, including the equations solved and their finite …

Electronic Excitations In Metals And Semiconductors: Ab Initio Studies Of Realistic Many-Particle Systems, Wei Ku

Doctoral Dissertations

Electronic excitations in metals and semiconductors, measured through inelastic x-ray scattering, electronic energy-loss spectroscopy, and angle-resolved photoemission, provide valuable information about the intrinsic many-body interactions between electrons in the crystal environment. These dynamical interactions are usually analyzed with intuitive simple models. With the problems studied, which correspond to linear response and quasi-particle excitation, it will be shown that ab initio approaches not only can provide more realistic understanding of microscopic processes and mechanisms, but also result in new theoretical interpretations that resolve a number of remarkable "anomalies." Specifically, these problems include the dispersion of the plasmon lifetime in potassium, the …

The Development Of A Lutetium Recovery Plant, Peter Michael Smith

Doctoral Dissertations

This research project focused on the scale-up of an industrial facility for the continuous counter-current solvent extraction (CCCSX) separation of lutetium. CCCSX involves a multistage apparatus for the mixing in each stage of two immiscible liquid phases to transfer an analyte from one phase to the other. The two phases continuously flow in opposite directions in a CCCSX system. In this research, aqueous lutetium solutions, obtained from the acid leaching of lutetium oxyorthosilicate, were mixed with kerosene solutions of phosphorus based metal extractants (e.g. mono-2-ethylhexyl-(2- ethylhexyl) phosphonic acid, MEHEHP). This system extracted the lutetium from the aqueous phase, transferring the …

Laser Spark Ignition Modeling, Ivan George Dors

Doctoral Dissertations

Laser spark phenomena are studied in air and ammonia-oxygen mixtures by the use of a two-dimensional, axially-symmetric, time-accurate computational fluid dynamic model. The initial laser spark temperature distribution is generated to simulate a post-breakdown profile that is consistent with theoretical, experimental, and computational investigations for a nominal 10-ns optical breakdown laser pulse. Thermodynamic properties of various species are extended to 35,000 K to cover the range of the initial temperature distribution. The developed computational model includes a kinetics mechanism that implements plasma equilibrium kinetics in ionized regions.

The computational model time-accurately predicts species concentrations, free electron number density decay, blast …

Evaluation Of Ellipsometric Monitors For Process Control Of High Temperature Superconductors, Kyle John Peterson

Masters Theses

Current methods of manufacturing high temperature thin lm superconductors require increasingly more precise and accurate thin lm diagnostics to ensure high quality superconductors. There are several diagnostic tools for monitoring thin lms. However, due to the complex nature of superconducting thin lm stacks, ellipsometric methods are well suited for this application. This study investigates various ellipsometric methods in simulated process control environments.

A computer program was developed to generate ellipsometric data for given film stack characteristics and experimental geometry, and to analyze simulated ellipsometric data to recover optical parameters of the given film stack. The program was used to investigate …

Scalar Absorption By Spinning D3-Branes, George Siopsis

Physics and Astronomy Publications and Other Works

We discuss absorption of scalars by a distribution of spinning D3-branes. The D3-branes are multi-center solutions of supergravity theory. We solve the wave equation in various cases of supergravity backgrounds in which the equation becomes separable. We show that the absorption coefficients exhibit a universal behavior as functions of the angular momentum quantum number and the Hawking temperature. This behavior is similar to the form of the gray-body factors one encounters in scattering by black holes. Our discussion includes the problematic case of spherically symmetric distributions of D-branes, where resonances arise. We obtain the same universal form for the absorption …