Astrophysics and Astronomy Commons^™

Geometric Acoustic Modeling Of The Lds Conference Center, Heather Smith

Theses and Dissertations

This thesis discusses the process of modeling a 21,000 seat fan-shaped auditorium using methods of geometric acoustics. Two commercial geometric acoustics software packages were used in the research: CATT-Acoustic™ 8.0 and EASE™ 4.1. The process first included creating preliminary models of the hall using published absorption coefficients for its surfaces and approximate scattering coefficients based on current best-known techniques. A detailed analysis determined the minimum numbers of rays needed in both packages to produce reliable results with these coefficient values. It was found that 100,000 rays were needed for CATT™ and 500,000 rays were needed for EASE™. Analysis was also …

Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer

Faculty Publications

The m = 1 diocotron mode in non-neutral plasmas has long been thought of as a shifted equilibrium, and its frequency has been approximately calculated in this way by Fine and Driscoll [Phys. Plasmas 5, 601 (1998)]. This article shows that this idea can be coupled with a standard axisymmetric equilibrium calculation on a grid to calculate the frequency of this mode to very high precision including both finite-length and thermal effects, provided that the Debye length is small enough. As the Debye length begins to approach the plasma size not only does the shifted equilibrium calculation fail to predict …

Optical Properties And Application Of Uranium-Based Thin Films For The Extreme Ultraviolet And Soft X-Ray Region, Richard L. Sandberg, David D. Allred, Shannon Lunt, Marie K. Urry, R. Steven Turley

Faculty Publications

Uranium oxide and uranium nitride thin films reflect significantly more than all previously known/standard reflectors (e.g., nickel, gold, and iridium) for most of the 4-10 nm range at low angles of incidence. This work includes measurements of the EUV/soft x-ray (2-20 nm) reflectance of uranium-based thin films (~20 nm thick) and extraction of their optical constants (d and ?). We report the reflectances at 5, 10, and 15 degrees grazing incidence of air-oxidized sputtered uranium, reactively sputtered (O2) uranium oxide, and reactively sputtered (N2) uranium nitride thin films measured at Beamline 6.3.2 at the Advanced Light Source (ALS) at Lawrence …

Analysis And Comparison Of Three Acoustic Energy Density Probes, Lance Lester Locey

Theses and Dissertations

Traditional methods for the investigation of sound fields generally rely on a microphone to convert sound pressure into an electrical signal which can be recorded, displayed, and so forth. The squared sound pressure is directly related to potential energy density. Consequently, the measurement of sound pressure alone does not inherently provide insight into the total energy density of the sound field. Specifically, no information about the kinetic energy density of the sound field is available from this measurement alone. However, it is possible to use two microphones to estimate particle velocity. The squared particle velocity magnitude is directly related to …

Dirac-Fock Energy Levels And Transition Probabilities For Oxygen-Like Fe Xix, V. Jonauskas, F. P. Keenan, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, R. Kisielius, Peter A. M. Van Hoof, P. H. Norrington

Physics and Astronomy Faculty Publications

Multiconfigurational Dirac-Fock calculations are reported for 656 energy levels and the 214 840 electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transition probabilities in oxygen-like FeXIX. The spectroscopic notations as well as the total transition probabilities from each energy level are provided. Good agreement is found with data compiled by NIST.

Mechanical Properties Of Carbon Nanotubes Composites, David Hui, Mircea Chipara, Jagannathan Sankar, K. T. Lau

Physics & Astronomy Faculty Publications

A critical review of theoretical models aiming to explain the physical properties of composites based on polymeric matrices reinforced with carbon nanotubes is presented. Attention is paid to descriptions based on molecular dynamics, continuum mechanics, and finite element analysis. It is shown that both the continuum mechanics approximation and the finite size element analyses fail to describe composites with very thin interfaces, while the performances of molecular dynamics simulations are still restricted by computer's performances. The limitations of the continuum mechanics approximation are analyzed in detail.

Lorentz-Violating Electromagnetostatics, Quentin G. Bailey

Publications

In this talk, the stationary limit of Lorentz-violating electrodynamics is discussed. As illustrated by some simple examples, the general solution includes unconventional mixing of electrostatic and magnetostatic effects. I discuss a high-sensitivity null-type measurement, exploiting Lorentz-violating electromagnetostatic effects, that could improve existing limits on parity-odd coefficients for Lorentz violation in the photon sector.

On The Variability Of The Fine Structure Constant, Jason Lott Evans

Theses and Dissertations

This thesis addresses the issue of the time variability of the fine structure constant, alpha. Recent claims of a varying alpha are set against the established standards of quantum electrodynamical theory and experiments. A study of the feasibility of extracting data on the time dependence of alpha using particles in Penning traps is compared to the results obtained by existing methods, including those using astrophysical data and those obtained in atomic clock experiments. Suggestions are made on the nature of trapped particles and the trapping fields.

Physical Conditions In Orion's Veil, N. P. Abel, C. L. Brogan, Gary J. Ferland, C. R. O'Dell, G. Shaw, Thomas H. Troland

Physics and Astronomy Faculty Publications

Orion's veil consists of several layers of largely neutral gas lying between us and the main ionizing stars of the Orion Nebula. It is visible in 21 cm H I absorption and in optical and UV absorption lines of H I and other species. Toward θ¹ Ori C, the veil has two remarkable properties, a high magnetic field (~100 μG) and a surprising lack of H₂, given its total column density. Here we compute photoionization models of the veil to establish its gas density and its distance from θ¹ Ori C. We use a greatly improved …

Removing Surface Contaminants From Silicon Wafers To Facilitate Euv Optical Characterization, Richard L. Sandberg, David D. Allred, A. L. Jackson, J. E. Johnson, W. Evans, T. Doughty, A. E. Baker, K. Adamson, A. Jacquier, R. E. Robinson

Faculty Publications

The extreme ultraviolet (EUV) is becoming increasingly important. Principal applications include orbital space-based astronomy and lithography for integrated circuit computer chips. A main impediment to further development of efficient mirrors is the lack of reliable optical constants for various materials in this region of the electromagnetic spectrum. One reason for the unreliability of the optical constants is that the sample surfaces are often contaminated with foreign material, especially organic compounds, when exposed to laboratory air. Several cleaning techniques were evaluated, namely: 1) strippable solid optical cleaner (Opticlean®); 2) oxygen plasma etch; 3) high energy UV light/ozone; 4) strippable coating followed …

12C/13C Ratio In Planetary Nebulae From The Iue Archives, R. H. Rubin, Gary J. Ferland, E. E. Chollet, R. Horstmeyer

Physics and Astronomy Faculty Publications

We investigated the abundance ratio of ¹²C/¹³C in planetary nebulae by examining emission lines arising from C III 2s2p³P^o_2,1,0 → 2s²¹S₀. Spectra were retrieved from the International Ultraviolet Explorer archives, and multiple spectra of the same object were co-added to achieve improved signal-to-noise ratio. The ¹³C hyperfine structure line at 1909.6 Å was detected in NGC 2440. The ¹²C/¹³C ratio was found to be ~4.4+/-1.2. In all other objects, we provide an upper limit for the flux of the 1910 Å line. For 23 …

The Effects Of Low-Temperature Dielectronic Recombination On The Relative Populations Of The Fe M-Shell States, S. B. Kraemer, Gary J. Ferland, J. R. Gabel

Physics and Astronomy Faculty Publications

We examine the effects of low-temperature, or Δn=0, dielectronic recombination (DR) on the ionization balance of the Fe M shell (Fe IX-Fe XVI). Since Δn=0 rates are not available for these ions, we have derived estimates based on the existing rates for the first four ionization states of the CNO sequence and newly calculated rates for L-shell ions of third-row elements and Fe. For a range of ionization parameter and column density applicable to the intrinsic absorbers detected in ASCA, Chandra, and XMM-Newton observations of Seyfert galaxies, we generated two grids of photoionization models, with and …

Microsecond Spin-Flip Times In N-Gaas Measured By Time-Resolved Polarization Of Photoluminescence, John S. Colton, T. A. Kennedy, A. S. Bracker, D. Gammon

Faculty Publications

We have observed microsecond spin-flip times in lightly doped n-GaAs, by measuring the photoluminescence polarization in the time domain with pump and probe pulses. Times up to 1.4 μs have been measured. Our results as a function of magnetic field indicated three regions governing the spin relaxation: a low field region, where spin-flip times increase due to suppression of the nuclear hyperfine interaction for localized electrons, a medium field region where spin-flip times increase due to narrowing of the hyperfine relaxation for interacting electrons, and a high field region where spin-flip times begin to level off due to the increasing …

Active Minimization Of Acoustic Energy Density In A Mock Tractor Cab, Benjamin Mahonri Faber

Theses and Dissertations

An active noise control (ANC) system has been applied to the problem of attenuating low-frequency tonal noise inside small enclosures. The intended target application of the system was the reduction of the engine firing frequency inside heavy equipment cabins. The ANC system was based on a version of the filtered-x LMS adaptive algorithm, modified for the minimization of acoustic energy density (ED), rather than the more traditional minimization of squared acoustic pressure (SP). Three loudspeakers produced control signals within a mock cabin composed of a steel frame with plywood sides and a Plexiglas® front. An energy density sensor, capable of …

The Quantum And The Cosmos, Edward (Rocky) W. Kolb, Joseph D. Lykken

IMSA Great Minds Program ®

Fermilab physicists, Dr. Rocky Kolb and Dr. Joe Lykken team up to explain the connection of the physics of the very small to the physics of the cosmos and their discovery of a fundamental contradiction regarding how these mysteries have led to the development of new ideas: string theory, inflation, extra dimensions and Wimpzillas, as well as Higgs boson, and other mysteries that cosmologists care about, like dark energy.

Dr. Rocky Kolb is the founding head of the NASA/Fermilab Astrophysics Group at Fermi National Accelerator Laboratory. He is also a Professor of Astronomy and Astrophysics at The University of Chicago. …

Relativistic Allowed And Forbidden Transition Probabilities For Fluorine-Like Fe Xviii, V. Jonauskas, F. P. Keenan, M. E. Foord, R. F. Heeter, S. J. Rose, P. A. M. Van Hoof, Gary J. Ferland, K. M. Aggarwal, R. Kisielius, P. H. Norrington

Physics and Astronomy Faculty Publications

Energy levels and the corresponding transition probabilities for allowed and forbidden transitions among the levels of the ground configuration and first 23 excited configurations of fluorine-like Fe XVIII have been calculated using the multiconfigurational Dirac-Fock GRASP code. A total of 379 lowest bound levels of Fe XVIII is presented, and the energy levels are identified in spectroscopic notations. Transition probabilities, oscillator strengths and line strengths for electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transitions among these 379 levels are also presented. The calculated energy levels and transition probabilities are compared with experimental data.

Boron Alloying In Gan, Gus L. W. Hart, Laurian Escalanti

Faculty Publications

Using first-principles calculations in the local density approximation, we studied effects of adding up to 6% boron to zinc-blende GaN. We found that the band gap increases monotonically with boron incorporation, in agreement with experiment. A composition-independent band-gap bowing parameter of 4.30 eV was determined, and proved to be large compared to bowing for other mixed cation systems. The formation enthalpy of mixing, ΔH, was determined for BxGa1-xN, BxGa1-xAs, and GaAs1-xNx. A comparison of enthalpies indicates that the production of BxGa1-xN films with boron concentrations of at least 5% may be possible.

Derivation Of Moving-Coil Loudspeaker Parameters Using Plane Wave Tube Techniques, Brian Eric Anderson

Theses and Dissertations

Small-signal moving-coil loudspeaker driver parameters are traditionally derived through electrical impedance measurement techniques. These parameters are commonly called Thiele/Small parameters, after Neville Thiele and Richard Small who are credited with developing industry-standard loudspeaker modeling techniques. However, because loudspeaker drivers are electro-mechano-acoustical transducers, it should be possible to measure their parameters in physical domains other than the electrical domain. A method of measuring loudspeaker parameters from the acoustical domain will be developed. The technique uses a plane wave tube to measure acoustical properties of a baffled driver under test. Quantities such as the transmission loss through the driver are measured for …

Nucleosynthesis, Reionization, And The Mass Function Of The First Stars, Jason Tumlinson, Aparna Venkatesan, J Shull

Physics and Astronomy

We critique the hypothesisthat the first starswere very massive stars(VMSs; M > 140 M).We review the twomajor lines of evidencefor the existence ofVMSs: (1) that therelative metal abundances ofextremely metal-poor Galactic halostars show evidence ofVMS enrichment and (2)that the high electron-scatteringoptical depth (_e) tothe cosmic microwave backgroundfound by the Wilkinson Microwave Anisotropy Probe(WMAP) requires VMSs forreionization in a concordanceCDM cosmology. The yieldpatterns of VMSs explodingas pair-instability supernovae areincompatible with the Fe-peakand r-process abundances inhalo stars. Models includingType II supernovae and/or"hypernovae" from zero-metallicity progenitorswith M = 840 Mcan better explain theobserved trends. We usethe …

Lisa Time-Delay Interferometry Zero-Signal Solution: Geometrical Properties, Massimo Tinto, Shane L. Larson

All Physics Faculty Publications

Time-delay interferometry (TDI) is the data processing technique needed for generating interferometric combinations of data measured by the multiple Doppler readouts available onboard the three Laser Interferometer Space Antenna (LISA) spacecraft. Within the space of all possible interferometric combinations TDI can generate, we have derived a specific combination that has zero response to the gravitational wave signal, and called it the zero-signal solution (ZSS). This is a two-parameter family of linear combinations of the generators of the TDI space, and its response to a gravitational wave becomes null when these two parameters coincide with the values of the angles of …

Grain Size Distributions And Photoelectric Heating In Ionized Media, P. A. M. Vanhoof, J. C. Weingartner, P. G. Martin, K. Volk, Gary J. Ferland

Physics and Astronomy Faculty Publications

Ever since the pioneering study of Spitzer, it has been widely recognized that grains play an important role in the heating and cooling of photoionized environments. This includes the diffuse interstellar medium and H II regions, planetary nebulae and photodissociation regions. A detailed code is necessary to model grains in a photoionized medium since the interactions of grains with their environment include a host of microphysical processes. In this paper we will use the spectral synthesis code CLOUDY for this purpose. A comprehensive upgrade of the grain model has been recently incorporated into CLOUDY. One of these upgrades is the …

Coalescence Remnant Of Spinning Binary Black Holes, J Baker, M. Campanelli, C. O. Lousto, R. Takahashi

Physics & Astronomy Faculty Publications

We compute the gravitational radiation generated in the evolution of a family of close binary black hole configurations, using a combination of numerical and perturbative approximation methods. We evolve the binaries with spins s aligned or counteraligned with the orbital angular momentum from near the innermost stable circular orbit down to the final single rotating black hole. For the moderately spinning holes studied here the remnant Kerr black holes formed at the end of an inspiral process have rotation parameters a/M≈0.72+0.32(s/mH), suggesting it is difficult (though not excluded) to end up with near maximally rotating holes from such scenarios.

Xafs Debye-Waller Factors For Zn Metalloproteins, Nicholas Dimakis, Grant Bunker

Physics & Astronomy Faculty Publications

An accurate and practical method for the calculation and use of thermal x-ray absorption fine structure (XAFS) Debye-Waller factors (DWFs) in active sites of metalloproteins is presented. These factors are calculated on model clusters within the local density functional approximation with nonlocal corrections. The DWFs are mapped out and parametrized as a function of the first shell distance and an angle (where applicable), for all significant single and multiple scattering paths, as well as the sample temperature. This approach is applied to the biologically essential but spectroscopically silent Zn+2 active sites composed of histidines, cysteines, and carboxylate ligands in homogeneous …

Table Of Contents

Journal of the South Carolina Academy of Science

No abstract provided.

President's Message, David J. Stroup

Journal of the South Carolina Academy of Science

No abstract provided.

Scas Officers And Council Members 2004 - 2005

Journal of the South Carolina Academy of Science

No abstract provided.

Bioinformatics: An Undergraduate Research/Teaching Tool., Abhishek Agrawal, Valgene L. Dunham

Journal of the South Carolina Academy of Science

No abstract provided.

Measurement Of Beam-Spin Asymmetries For Π⁺ Electroproduction Above The Baryon Resonance Region, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, S. E. Kuhn, L. M. Qin, F. Sabatié, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration

Physics Faculty Publications

We report the first evidence for a nonzero beam-spin azimuthal asymmetry in the electroproduction of positive pions in the deep-inelastic kinematic region. Data for the reaction e^→pe'π⁺X have been obtained using a polarized electron beam of 4.3 GeV with the CEBAF Large Acceptance Spectrometer at the Thomas Jefferson National Accelerator Facility. The amplitude of the sin ᵠ modulation increases with the momentum of the pion relative to the virtual photon, z. In the range z = 0.5-0.8 the average amplitude is 0.038 ± 0.005 ± 0.003 for a missing mass M_x > 1.1 GeV and 0.037 …

Generation Of The Transient Electrical And Spontaneous Magnetic Fields By Solid State Combustion, Karen S. Martirosyan, J. R. Claycomb, J. H. Miller Jr., D. Luss

Physics & Astronomy Faculty Publications

Experiments revealed that transient electric field intensities up to 2.5 V/cm were generated during the initial period of combustion synthesis of the ferromagnetic products before the maximum temperature was reached. This occurred when the iron particles were partially oxidized and the reaction product was mainly magnetite sFe3O4d. The electromagnetic field caused spontaneous magnetization of the product in the postcombustion zone. Magnetic field values up to 4 µT formed after the sample temperature fell below the Curie temperature and the initial reactants were completely converted to the ferromagnetic phase PbFe12O19. Increasing the volume of the samples increases the absolute residual magnetic …

Setting Upper Limits On The Strength Of Periodic Gravitational Waves From Psr J1939+2134 Using The First Science Data From The Geo 600 And Ligo Detectors, B. P. Abbott, R. Abbott, Mario C. Diaz, Wm. R. Johnston, Joseph D. Romano, Cristina V. Torres

Physics & Astronomy Faculty Publications

Data collected by the GEO 600 and LIGO interferometric gravitational wave detectors during their first observational science run were searched for continuous gravitational waves from the pulsar J1939+2134 at twice its rotation frequency. Two independent analysis methods were used and are demonstrated in this paper: a frequency domain method and a time domain method. Both achieve consistent null results, placing new upper limits on the strength of the pulsar’s gravitational wave emission. A model emission mechanism is used to interpret the limits as a constraint on the pulsar’s equatorial ellipticity.