Astrophysics and Astronomy Commons^™

Increasing The Computational Efficiency Of Combinatoric Searches, Wiley Spencer Morgan

Theses and Dissertations

A new algorithm for the enumeration of derivative superstructures of a crystal is presented. The algorithm will help increase the efficiency of computational material design methods such as cluster expansion by increasing the size and diversity of the types of systems that can be modeled. Modeling potential alloys requires the exploration of all possible configurations of atoms. Additionally, modeling the thermal properties of materials requires knowledge of the possible ways of displacing the atoms. One solution to finding all symmetrically unique configurations and displacements is to generate the complete list of possible configurations and remove those that are symmetrically equivalent. …

Emission From Black Holes And Supernovae In The Early Universe, Brandon Kerry Wiggins

Theses and Dissertations

To constrain the era when the first galaxies and stars appeared upcoming instruments will rely on the brightest events in the universe: supernovae and brilliant emission from massive black holes. In this dissertation, we investigate the observability of certain types of supernovae of the very first stars (Population III stars) and find that while these events are sufficiently luminous to be observed with deep-sky instruments such as the James Webb Space Telescope (JWST), they may not observe these particular types of events in their lifetimes. We next explore the origins of massive black holes and introduce the direct collapse hypothesis …

Microfabrication With Smooth, Thin Cnt/Polymer Composite Sheets, Nathan Edward Boyer

Theses and Dissertations

Carbon nanotube (CNT)/polymer composite sheets can be extremely high strength and lightweight, which makes them attractive for fabrication of mechanical structures. This thesis demonstrates a method whereby smooth, thin CNT/polymer composite sheets can be fabricated and patterned on the microscale using a process of photolithography and plasma etching. CNT/polymer composites were made from CNTs grown using chemical vapor deposition using supported catalyst growth and floating catalyst growth. The composite sheets had a roughness of approximately 30nm and were about 61¼m or 261¼m depending on whether they were made from supported catalyst grown or floating catalyst grown CNTs. The composites were …

In Situ Magnetic Field Characterization With The Directional Hanle Effect, Jarom Silver Jackson

Theses and Dissertations

We present a novel method of in situ magnetic field mapping related to the Hanle effect. This method uses the change in spatial radiation pattern of scattered light, which we call a 'directional Hanle effect,' rather than the loss of polarization more commonly associated with the Hanle effect. It is particularly well suited for fields in a magneto-optical trap (MOT), requiring only the addition of a narrow slit and a camera to typical MOT components. The use of this method is demonstrated by measuring the gradient through, and location of, the zero-point of the field in our strontium MOT.

Geological Conditions Required For The Fluvial Erosion Of Titan’S Impact Craters, Rebeca M. Kinser

Theses and Dissertations

In comparison to other icy satellites, Titan has a small number of impact craters on its surface. Its dense atmosphere screens smaller impactors from the surface, but this alone does not account for the lack of impact craters, especially at large diameters. This suggests that Titan has a relatively young surface and/or erosional processes have effectively removed craters from its surface. For example, fluvial erosion could degrade craters such that they would be unrecognizable from an orbiting spacecraft such as Cassini. The amount of erosion, however, will depend on a number of factors including the geological and meteorological conditions of …

Reverberation Mapping Of The Dusty Torus In Active Galactic Nuclei, Erich Franz Geisert

Theses and Dissertations

The Dusty Torus is a structure that is believed to exist in Active Galactic Nuclei. The Torus is physically too small to be spatially resolved, so Reverberation Mapping can be performed in order to replace spatial resolution with temporal resolution, yielding observations that can unravel the mystery of the Dusty Torus. One of the unknowns about the Torus is how the dust is distributed. The two competing theories are that either the dust resides in discrete clouds or that there is a solid wall of dust. This thesis presents the results of a year long observation program, starting in August …

Development, Evaluation, And Validation Of A High-Resolution Directivity Measurement System For Played Musical Instruments, K Joshua Bodon

Theses and Dissertations

A high-resolution directivity measurement system at Brigham Young University has been renovated and upgraded. Acoustical treatments have been installed on the microphone array, professional-grade audio hardware and cabling have been utilized, and user-friendly MATLAB processing and plotting codes have been developed. The directivities of 16 played musical instruments and several loudspeakers have been measured by the system, processed, and plotted. Using loudspeakers as simulated musicians, a comprehensive analysis was completed to validate the system and understand its error bounds. A comparison and evaluation of repeated-capture to single-capture spherical systems was made to demonstrate the high level of detail provided by …

Improvements To The Two-Point In Situ Method For Measurement Of The Room Constant And Sound Power In Semi-Reverberant Rooms, Zachary R. Jensen

Theses and Dissertations

The two-point in situ method is a technique for measuring the room constant of a semi-reverberant room and the sound power of a source in that room simultaneously using two measurement positions. Using a reference directivity source, where the directivity factor along any given axis of the source has been measured, one is able to use the Hopkins-Stryker equation to measure both the room constant and the sound power level of another source rather simply. Using both numerical and experimental data, it was found that by using generalized energy density (GED) as a measurement quantity, the results were more accurate …

Rapid Orbit Refinement Of Potential Near-Earth Objects And Recovery Of Nearly Lost Asteroids, Austin Lantz Caughey

Theses and Dissertations

The Minor Planet Center alerts researchers about potential discoveries of new Near-Earth Objects (NEOs) on their NEO Confirmation Page (NEOCP). Most of these are indeed previously unstudied objects, which must be studied very promptly while initial predictions of their motions are still accurate. My thesis project has focused on the observation of these bodies, and the submission of their measured positions to the MPC within a few hours of observation. Data has been obtained using the Skynet Robotic Telescope Network, including the R-COP telescope in Perth, Australia; the PROMPT 3 telescope in La Serena, Chile; and Yerkes Observatory in Williams …

Silicon Carbon Nanotube Lithium Ion Batteries, Lawrence Kent Barrett

Theses and Dissertations

Silicon has the highest theoretical capacity of any known anode material, and silicon coated carbon nanotubes (Si-CNTs) have shown promise of dramatically increasing battery capacity. However, capacity fading with cycling and low rate capability prevent widespread use. Here, three studies on differing aspects of these batteries are presented. Here, three studies on differing aspects of these batteries are presented. The first examines the rate capability of these batteries. It compares the cycling of electrodes hundreds of microns thick with and without ten micron access holes to facilitate diffusion. The holes do not improve rate capability, but thinner coatings of silicon …

Construction Of A 408 Nm Laser System For Use In Ion Interferometry, Lawrence Archibald

Theses and Dissertations

This work reports on the construction of a 408 nm laser system designed to drive stimulated Raman transitions between the F = 4 and F = 5 2 S 1/2 states of 87 Sr + using the 2 P 3/2 state as the intermediate state. This laser system will be used as part of a 87 Sr + ion interferometer. This work also includes a discussion of relevant theory describing the interaction of the ions and laser, along with a calculation of the transition rates as a function of laser power and detuning.

Comparing Theory And Experiment For Analyte Transport In The First Vacuum Stage Of The Inductively Coupled Plasma Mass Spectrometer, Matthew R. Zachreson

Theses and Dissertations

The inductively coupled plasma mass spectrometer (ICP-MS) has been used in laboratories for many years. The majority of the improvements to the instrument have been done empirically through trial and error. A few fluid models have been made, which have given a general description of the flow through the mass spectrometer interface. However, due to long mean free path effects and other factors, it is very difficult to simulate the flow details well enough to predict how changing the interface design will change the formation of the ion beam. Towards this end, Spencer et al. developed FENIX, a direct simulation …

Analysis Of Angular Momentum In Planetary Systems And Host Stars, Stacy Ann Irwin

Theses and Dissertations

The spin angular momentum of single Main Sequence stars has long been shown to follow a primary power law of stellar mass, J ∝ Mα, excluding stars of <2 solar masses. Lower mass stars rotate more slowly with and have smaller moments of inertia, and as a result they contain much less spin angular momentum. A secondary power law describes the upper bound of angular momenta of these less massive stars with a steeper slope. The Solar System’s orbital angular momentum, however, is of the same order of magnitude as the primary law, whereas the Sun’s spin angular momentum is consistent with the secondary relationship. This suggests that planets are an important clue to answering questions about stellar angular momentum loss and transfer. With recent advances in exoplanet discovery and characterization, the angular momenta of exoplanetary systems can now be determined. A method is developed to calculate planetary system angular momenta from the spin and orbital angular momenta of a sample including 426 host stars and 532 planets. To maximize the size of the working sample, systems discovered by both the transit and radial velocity methods are included, and the biases of both techniques are identified. Self-consistent stellar moment of inertia parameters are interpolated from grids of stellar evolutionary models. Main Sequence host stars range from 0.6 to 1.7 solar masses, and their angular momenta are shown to agree well with previous studies of stellar angular momentum, generally falling on or below the appropriate power law, and exhibiting detection method biases. The systems’ angular momenta, including both the planetary orbital and stellar spin components, are widely spread above and below the primary power law, but on average agree well with the primary relationship. The results indicate that the primary power law describes angular momenta of stars of <2 solar masses well, when planetary angular momentum is included. This relationship also holds across host star evolutionary classifications. For 90% of the systems, the angular momentum contained in the planets is greater than the spin angular momentum of the host star, a characteristic shared by the Solar System. Undetected planets contribute significant bias to the system angular momentum as well as to the proportion of angular momentum contained in the planets. This bias is used to identify systems which are likely to harbor additional planets in already known planetary systems, assuming the Solar System’s proportions are typical.

A Search For Planets And Brown Dwarfs Around Post Main Sequence Stars, Tomomi Otani

Theses and Dissertations

So far, the most promising theory for the existence of subdwarf B (sdB) stars is that they were formed during binary star evolution. This research was conducted to test this theory by searching for companions around six sdB pulsators (V391 Peg, HS 0702+6043, EC 20117-4014, PG 1219+534, PG 0911+456, and PG 1613+426) using the Observed-minus-Calculated (O-C) method. A star’s position in space will wobble due to the gravitational forces of any companion. If the star is emitting a periodic signal, the orbital motion of the star around the system’s center of mass causes periodic changes in the light pulse arrival …

A Feasibility Study Of Photometric Reverberation Mapping With Meter-Class Telescopes, Carla June Carroll

Theses and Dissertations

For the past several decades, mass estimates for supermassive black holes hosted by active galactic nuclei (AGN) have been made with the reverberation mapping (RM) technique. This methodology has produced consistent results and has been used to establish several relations that link the characteristics of the host galaxy to the mass of the central black hole. Despite this success, there are less than 50 AGN with black hole masses derived from RM. This low number is generally attributed to the difficulties in coordinating large blocks of telescope time for making simultaneous photometric and spectroscopic observations. Spectroscopic observations also generally require …

Characterization Of Order-Disorder Phase Transition Temperature For Select Nanoparticles, Gregory J. Sutherland

Theses and Dissertations

A method was found for creating ordered nanoparticles whose size and theoretical order-disorder temperature are ideal for study in the TEM. Specifically FePt, NiPt, FeNiPt and AuCu nanoparticles were studied. We were able to show how a nanoparticle's size affects its order-disorder temperature (Tod). When the particles were around 6 nm in diameter there was a shift downward of the Tod of 10-15 percent compared to the bulk. While particles around 10 nm in diameter experienced a downward shift of 0-6 percent compared to the bulk. One can approximate that particles less than 10-15 nm in diameter would show significant …

Characterization Of Cataclysmic Variables And White Dwarfs In The Kepler Field, Trisha Doyle

Theses and Dissertations

We present long baseline Kepler photometry and ground-based Hale 20000 spectroscopy of five known white dwarfs, five newly identified white dwarfs, and a cataclysmic variable, V523 Lyr. Analysis of the photometric and spectroscopic data is used to characterize the white dwarfs and the cataclysmic variable, by determining preliminary fundamental parameters. We model the white dwarfs to determine their fundamental parameters, e↵ective temperature and surface gravity. If the e↵ective temperature of a white dwarf falls within a specific range, the white dwarf is expected to be a pulsator. We verified possible pulsation with complementary Kepler light curves when possible. The modeled …

Supermassive Black Hole Scaling Relations, Ismaeel Abdulla Akhlite Al-Baidhany

Theses and Dissertations

In this dissertation, the determination of the masses of supermassive black holes (SMBHs) and the properties of their host spiral galaxies are focused for the purposes of constraining scaling relations and with the aim of understanding the role of SMBHs in the evolution of galaxies. The several techniques in this work as summarized are focused on in Chapter 2. Direct techniques (reverberation mapping, stellar and gas dynamics, maser modeling) and indirect techniques (the SMBH mass versus stellar/gas velocity dispersion relation and the SMBH mass versus spiral arm pitch angle relation) have been used to estimate SMBH masses. Then the measurement …

Determination Of Resonance Locations In Barred Spiral Galaxies, Amber Sierra

Theses and Dissertations

We applied a method identified by Puerari & Dottori (1997) to find the corotation radii of 57 galaxies. This entailed taking Fourier transforms along radial cuts in the u, g, r, i, and z wavebands and comparing the phase angles as a function of radius between them. The radius at which the phase angles cross indicates the location of the corotation radius. We then calculated the relative bar pattern speed, R and classified the bar as fast, less than 1.4, or slow, greater than or equal to 1.4. Finally, we found that our results were consistent with previously determined values …

Re-Calibration Of The Periods Of Selected Cepheids From The Hubble Space Telescope Key Project Using Time Correction, Muxue Liu

Theses and Dissertations

The Hubble Space Telescope (HST) was originally proposed and funded in the 1970's with a launch planned for the early 1980's. However, the launch finally occurred on April 24, 1990, largely due to the Challenger accident. Once launched in 1990, one of HST's earliest projects was the Key Project. One of the main purposes of the Key Project was to calibrate the distances to nearby galaxies and determine a definitive value of the Hubble constant H0. All secondary distance determination methods were based on the period-luminosity relation of Cepheid variable stars. This thesis examines the Cepheid data from the Key …

Simulations Of Electron Trajectories In An Intense Laser Focus For Photon Scattering Experiments, Grayson J. Tarbox

Theses and Dissertations

An experiment currently underway at BYU is designed to test whether the size of a free electron wave packet affects the character of scattered radiation. Using a semi-classical argument wherein the wave packet is treated as a diffuse charge distribution, one would expect strong suppression of radiation in the direction perpendicular to the propagating field as the wave packet grows in size to be comparable to the wavelength of the driving field. If one disallows the interaction of the wave packet with itself, as is the case when calculating the rate of emission using QED, then regardless of size, the …

Radio Emission Toward Regions Of Massive Star Formation In The Large Magellanic Cloud, Adam Johanson

Theses and Dissertations

Four regions of massive star formation in the Large Magellanic Cloud (LMC) were observed for water and methanol maser emission and radio continuum emission. A total of 42 radio detections were made including 27 new radio sources, four water masers, and eight compact HII regions. The lobes of a radio galaxy were resolved for the first time, and the host galaxy identified. Seven sources were associated with known massive young stellar objects (YSOs). A multi-wavelength analysis using both the infrared and radio spectrum was used to characterize the sources. Mid-infrared color-magnitude selection criteria for ultracompact HII (UCHII) regions in the …

Interdisciplinary Connections Between Science & Theatre, Jessica N. Dotson

Theses and Dissertations

Abstract

INTERDISCIPLINARY CONNECTIONS BETWEEN SCIENCE & THEATRE

Jessica Nicole Dotson

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Fine Arts at Virginia Commonwealth University.

Virginia Commonwealth University, 2015.

Major Director: Dr. Noreen C. Barnes, Director of Graduate Studies, Associate Professor of Theatre

In the 1990s, astronomer Peter Usher was searching for new ways to teach his introductory astronomy class at Pennsylvania State University. He began to engage his students by searching for astronomical connections from other disciplines. His focus was turned to the arts, especially the works of William Shakespeare. Usher found, while …

Algebraic Semi-Classical Model For Reaction Dynamics, Tim Glenn Wendler

Theses and Dissertations

We use an algebraic method to model the molecular collision dynamics of a collinear triatomic system. Beginning with a forced oscillator, we develop a mathematical framework upon which inelastic and reactive collisions are modeled. The model is considered algebraic because it takes advantage of the properties of a Lie algebra in the derivation of a time-evolution operator. The time-evolution operator is shown to generate both phase-space and quantum dynamics of a forced oscillator simultaneously. The model is considered semi-classical because only the molecule's internal degrees-of-freedom are quantized. The relative translation between the colliding atom and molecule in an exchange reaction …

Towards Stronger Coulomb Coupling In An Ultracold Neutral Plasma, Mary Elizabeth Lyon

Theses and Dissertations

Ultracold neutral plasmas are created by photoionizing laser-cooled atoms in a magneto-optical trap (MOT). Due to their large electrical potential energies and comparatively small kinetic energies, ultracold plasmas fall into a regime of plasma systems which are called “strongly coupled.” A priority in the field of ultracold plasmas is to generate plasmas with higher values of the strong coupling parameter Γ, which is given as the ratio of the nearest-neighbor Coulomb potential energy to the average kinetic energy. The equilibrium strong coupling in ultracold plasmas is limited by the ultrafast relaxation of the ions due to spatial disorder in the …

Investigation Of A New Method Of Estimating Acoustic Intensity And Its Application To Rocket Noise, Benjamin Young Christensen

Theses and Dissertations

An alternative pressure-sensor based method for estimating the acoustic intensity, the phase and amplitude gradient estimation (PAGE) method, is presented. This method is similar to the finite-difference p-p (FD) method, in which the intensity is estimated from pressure measurements made using an array of closely spaced microphones. The PAGE method uses the same hardware as the FD method, but does not suffer from the frequency-dependent bias inherent to the FD method. Detailed derivations of the new method and the traditional FD method are presented. Both methods are then compared using two acoustic fields: a plane wave and a three monopole …

Introduction To The Development Of A Radio Astronomy System At Brigham Young University, Daniel Robert Blakley

Theses and Dissertations

The intent of this project was founded upon the need to train students in the techniques of radio astronomy with the purpose of establishing a radio telescope in order to teach the principles and practice of radio astronomy.This document describes the theory, research, to establish the 1st generation radio telescope system within the Department of Physics and Astronomy at Brigham Young University. Included are introductions to: (1) The nature of star forming regions in the spiral arm structure of the galaxy, H I (the hydrogen spin-flip transition) and OH MASERS, (2) The of terminology used with the system components and …

Application Of An Isogeometric Boundary Element Method To The Calculation Of Acoustic Radiation Modes And Their Efficiencies, Candice Marie Humpherys

Theses and Dissertations

In contrast to the structural modes, which describe the physical motion of vibrating structures, acoustic radiation modes describe the radiated sound power. Radiation modes are beneficial in active noise control because reducing an efficiently radiating radiation mode guarantees the reduction of radiated sound power. Much work has been done to calculate the radiation modes for simple geometries, where analytic solutions are available. In this work, isogeometric analysis (IGA) is used to provide a tool capable of analyzing the radiation modes of arbitrarily complex geometries. IGA offers increased accuracy and efficiency by using basis functions generated from Non-Uniform Rational B-Splines (NURBS) …

Spin And Orbital Moments And Magnetic Order In Fe3o4 Nanoparticle Assemblies, Yanping Cai

Theses and Dissertations

Fe3O4 magnetic nanoparticles of 5 to 11 nm in size were prepared by organic methods. Particle size was analyzed by both X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) techniques. Zero Field Cooling (ZFC) / Field Cooling (FC) and magnetization loop measurements were recorded by VSM, and they confirmed superparamagnetic behavior in the sample. The blocking temperature is found to be in the range of 30 K ~ 170 K. It has a dependence on the particle size. ZFC / FC curves also indicate the presence of magnetic coupling between particles. X-ray Magnetic Circular Dichroism (XMCD) measurements of these nanoparticles …

Estimating The Acoustic Power Of Sources In Nonideal Enclosures Using Generalized Acoustic Energy Density, Daniel Ryan Marquez

Theses and Dissertations

Sound power measurements of acoustic sources are generally made in reverberation or anechoic chambers using acoustic pressure measurements as outlined in specific ISO or other standards. A reverberation chamber produces an approximate diffuse-field condition, wherein the sound power is determined from the spatially averaged squared pressure. An anechoic chamber produces an approximate free-field condition, wherein the sound power is estimated from squared pressure over an enveloping measurement surface. However, in many cases it is desirable to estimate sound power within nonideal semi-reverberant spaces. In these environments, both direct and reverberant energies may contribute significantly to the total acoustic field. This …