Physical Sciences and Mathematics Commons^™

Writing And Designing A Chapter On Mercury And Pluto For The Textbook Exploring The Planets (Explanet.Info), Braxton Clark Spilker

Theses and Dissertations

Exploring the Planets (http://explanet.info) is a free online college textbook covering thebasic concepts of planetary science emphasizing the character and evolution of the planetarybodies in the Solar System. The latest edition (3rd edition) was published online in 2007 by EricH Christiansen. Since the release of the third edition, two important planetary missions havebeen completed: MESSENGER (to Mercury) and New Horizons (to Pluto). These missionsprovided new information and fundamental insights into these planetary bodies, which have notyet been included in Exploring the Planets. The modern results based on recent investigations ofMercury and Pluto are critical for our understanding of the nature …

Ion Friction At Small Values Of The Coulomb Logarithm, Robert Tucker Sprenkle

Theses and Dissertations

We create a dual-species ultracold neutral plasma (UNP) by photo-ionizing Yb and Ca atoms in a dual-species magneto-optical trap. Unlike single-species UNP expansion, these plasmas are well outside of the collisionless (Vlasov) approximation. We observe the mutual interaction of the Yb and Ca ions by measuring the velocity distribution for each ion species separately. We model the expansion using a fluid code including ion-ion friction and compare with experimental results to obtain a value of the Coulomb logarithm of Λ= 0.04.

Use Of Phase And Amplitude Gradient Estimation For Acoustic Source Characterization And Localization, Joseph Scott Lawrence

Theses and Dissertations

Energy-based acoustic quantities provide vital information about acoustic fields and the characterization of acoustic sources. Recently, the phase and amplitude gradient estimator (PAGE) method has been developed to reduce error and extend bandwidth of energy-based quantity estimates. To inform uses and applications of the method, analytical and experimental characterizations of the method are presented. Analytical PAGE method bias errors are compared with those of traditional estimation for two- and three-microphone one-dimensional probes. For a monopole field when phase unwrapping is possible, zero bias error is achieved for active intensity using three-microphone PAGE and for specific acoustic impedance using two-microphone PAGE. …

X-Rays From Magnetic B-Type Stars, Corinne Fletcher

Theses and Dissertations

Recent surveys have found that ∼10% of massive stars host strong, mostly dipolar magnetic fields with strengths on the order of a kilogauss. The prominent idea describing the interaction between the stellar winds and the magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the ionized wind material is forced to move along the closed magnetic field loops and collides at the magnetic equator, creating a shock (Δv ∼ 500−800 km s−1). As the shocked material cools radiatively, it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and probing the wind material …

Turbulent Collapse Of Gravitationally Bound Clouds, Daniel William Murray

Theses and Dissertations

In this dissertation, I explore the time-variable rate of star formation, using both numerical and analytic techniques. I discuss the dynamics of collapsing regions, the effect of protostellar jets, and development of software for use in the hydrodynamic code RAMSES. I perform high-resolution adaptive mesh refinement simulations of star formation in self-gravitating turbulently driven gas. I have run simulations including hydrodynamics (HD), and HD with protostellar jet feedback. Accretion begins when the turbulent fluctuations on largescales, near the driving scale, produce a converging flow. I find that the character of the collapse changes at two radii, the disk radius $r_d$, …

Studies In Gravitational-Wave Astronomy And Tests Of General Relativity, Hong Qi

Theses and Dissertations

Modern astronomical data sets provide the opportunity to test our physical theories of the Universe at unprecedented levels of accuracy. This dissertation examines approaches to testing gravitational theories using a) observations of stars orbiting the center of the Milky Way; b) observations of the pulsations of Cepheid variable stars in dwarf galaxies; and c) gravitational-wave observations of compact binary mergers.

Observations of stars orbiting the center of the Milky Way have been used to infer the mass of the putative black hole that exists there. I discuss how well present and future measurements of stellar orbits can constrain the black …

Automated Software For The Detection Of Bolide Events, Elena Botella

Theses and Dissertations

The proper detection and analysis of bolide events ensures that we will once day be prepared for a big, catastrophic impact by a meteor. The data obtained from the analysis of these detected smaller events will provide important information about the meteor’s journey through our atmosphere and its orbit before it crossed the Earth’s path. SkySentinel is one of the All-Sky networks in charge of looking at the skies every night and detecting these objects as they fall. At the moment, SkySentinel’s detection process relies heavily on manpower to check whether their cameras picked up actual bolide events or false …

Thin Film Carbon Nanofuses For Permanent Data Storage, Kevin Robert Laughlin

Theses and Dissertations

We have fabricated nanofuses from thin-film, arc-evaporation carbon for use in permanent data storage. Thin film carbon fuses have fewer fabrication barriers and retain the required resistivity and structural stability to work as a data storage medium. Carbon thin films were characterized for their electrical, microstructural, and chemical bonding properties. Annealing the thin-film carbon in an argon environment at 400°C reduced the resistivity from about 4*10^-2 Ω cm as deposited down to about 5*10^-4 Ω cm, allowing a lower blowing voltage. Nanofuses with widths ranging from 200 nm down to 60 nm were fabricated and tested. They blow …

Development Of A Real-Time Auralization System For Assessment Of Vocal Effort In Virtual-Acoustic Environments, Jennifer Kay Whiting

Theses and Dissertations

This thesis describes the development of the real-time convolution system (RTCS) for a little-studied talker/listener in virtual acoustic environments. We include descriptions of the high-resolution directivity measurements of human speech, the RTCS system components, the measurement and characterization of oral-binaural room impulse responses (OBRIRs) for a variety of acoustic environments, and the compensation filter necessary for its validity. In addition to incorporating the high-resolution directivity measurements, this RTCS improved on that developed by Cabrera et al. [1] through the derivation and inclusion of the compensation filter. Objective measures in the time- and frequency-domains, as well as subjective measures, were developed …

Near Earth Space Object Detection Utilizing Parallax As Multi-Hypothesis Test Criterion, Joseph C. Tompkins

Theses and Dissertations

The US Strategic Command (USSTRATCOM) operated Space Surveillance Network (SSN) is tasked with Space Situational Awareness (SSA) for the US military. This system is made up of Electro-Optic sensors such as the Space Surveillance Telescope (SST) and Ground-based Electro-Optical Deep Space Surveillance (GEODSS) as well as RADAR based sensors such as the Space Fence. While Lockheed Martin’s Space Fence is very adept at detecting & tracking objects in Low Earth Orbit (LEO) below 3000 Km in height [1], gaps remain in the tracking of Resident Space Objects (RSO’s) in Geosynchronous Orbits (GEO) due to limitations associated with the implementation of …

Using An Astrophysical Model To Characterize Nuclear Dust, Anita N. Dunsmore

Theses and Dissertations

Dust clouds resulting from nuclear explosions are complex phenomena, and knowledge on how they form is lacking. Noting the similarities between supernovae and nuclear explosions led to the concept of modeling a nuclear dust cloud using a supernova simulation. MOCASSIN uses a Monte Carlo approach to model photons traveling through a dust cloud, allowing the cloud's characteristics to be discovered by comparing an observed spectrum to a calculated one and then changing input values to make the spectra match. Data files describing two nuclear fireballs of varying yields were created and analyzed using MOCASSIN, but yielded zero energy spectra. After …