Physical Sciences and Mathematics Commons^™

Comment On 'Simulation Of A Two-Dimensional Rayleigh-Bénard System Using The Direct Simulation Monte Carlo Method, Alejandro Garcia, F. Baras, M. Malek Mansour

Faculty Publications

No abstract provided.

Three-Dimensional Fabry-Perot Imaging Spectroscopy Of The Crab Nebula, Cassiopeia A, And Nova Gk Persei, Stephen S. Lawrence, Gordon M. Macalpine, Alan Uomoto, Bruce E. Woodgate, Larry W. Brown, Ronald J. Oliversen, James D. Lowenthal, Charles Liu

Astronomy: Faculty Publications

Three-dimensional spatial models of the line-emitting gas in the Crab Nebula, Cassiopeia A, and the nova remnant of GK Persei have been developed from imaging spectroscopy taken with the Goddard Fabry-Perot Imager mounted on the McGraw-Hill 1.3 m and Hiltner 2.4 m telescopes of the Michigan-Dartmouth-MIT Observatory. The spatial model of the Crab Nebula in [O III] λ5007 emission reveals the thin, annular morphology of the "high-helium torus," the association of this torus and other bright filament loops with north-south bipolar asymmetry of the remnant shell, the structure of the filamentary shell at the boundary with the inner synchrotron cavity, …

Exclusive Electron Scattering From Deuterium At High Momentum Transfer, H. J. Bulten, P. L. Anthony, R. G. Arnold, J. Arrington, E. J. Beise, E. Belz, K. Van Bibber, P. E. Bosted, J.F.J. Van Den Brand, M. S. Chapman, K. P. Coulter, F. S. Dietrich, R. Ent, M. Epstein, B. W. Filippone, H. Gao, R.A. Gearhart, D. F. Geesaman, J.-O. Hansen, R. J. Holt, H. E. Jackson, C. E. Jones, C. E. Keppel, E. Kinney, S. E. Kuhn, K. Lee, W. Lorenzon, A. Lung, N.C.R. Makins, D. J. Margaziotis, R.D. Mckeown, R. G. Milner, B. Mueller, J. Napolitano, J. Nelson, T.G. O'Neill, V. Papavassiliou, G. G. Petratos, D. H. Potterveld, S. E. Rock, M. Spengos, Z. M. Szalata, L. H. Tao, J. L. White, B. Zeidman

Physics Faculty Publications

Cross sections are presented for the reaction ²H(e,e′p)n for momentum transfers in the range 1.2 ≤Q²≤ 6.8 (GeV/c)2 and for missing momenta from 0 to 250 MeV/c. The longitudinal-transverse interference structure function has been separated at Q²=1.2(GeV/c)². The observables are compared to calculations performed in nonrelativistic and relativistic frameworks. The data are best described by a fully relativistic calculation.

Comment On 'Simulation Of A Two-Dimensional Rayleigh-Bénard System Using The Direct Simulation Monte Carlo Method, Alejandro Garcia, F. Baras, M. Malek Mansour

Alejandro Garcia

No abstract provided.

A Consistent Boltzmann Algorithm, Alejandro Garcia, F. Alexander, B. Alder

Alejandro Garcia

The direct simulation Monte Carlo method for the Boltzmann equation is modified by an additional displacement in the advection process and an enhanced collision rate in order to obtain the exact hard sphere equation of state at all densities. This leads to consistent thermodynamic and transport properties in the low density (Boltzmann) regime. At higher densities transport properties are comparable to the predictions of the Enskog model. The algorithm is faster than molecular dynamics at low and moderate densities and readily run on a parallel architecture

A Consistent Boltzmann Algorithm, Alejandro Garcia, F. Alexander, B. Alder

Faculty Publications

The direct simulation Monte Carlo method for the Boltzmann equation is modified by an additional displacement in the advection process and an enhanced collision rate in order to obtain the exact hard sphere equation of state at all densities. This leads to consistent thermodynamic and transport properties in the low density (Boltzmann) regime. At higher densities transport properties are comparable to the predictions of the Enskog model. The algorithm is faster than molecular dynamics at low and moderate densities and readily run on a parallel architecture

Dynamic Phase Steepening In Alfven Waves, Stephen R. Granade

Honors Theses

Our solar system contains more activity and complexity than can be seen through a telescope. One such "invisible" phenomenon is the solar wind, created by a steady stream of particles blasted away from the sun in all directions. The sun's donut-shaped magnetic field lines channel this stream. Particles moving along the field lines perform an intricate helical dance, with ions winding one way and electrons the other.

The solar wind shapes and is shaped by the magnetic fields of the planets and the sun. If left undisturbed by outside influences, the earth's magnetic field, like the sun's, would resemble a …

A Theoretical Study Concerning The Solar Cycle Dependence Of The Nightside Ionosphere Of Venus, Zoltan Dobe, Andrew F. Nagy, Jane L. Fox

Physics Faculty Publications

We modeled the chemical and physical processes taking place in the nightside ionosphere of Venus by solving the one dimensional coupled continuity and momentum equations for 12 ion species [CO₂⁺, O₂⁺, O⁺, H⁺, NO⁺, CO⁺, N₂⁺, N⁺, He⁺, C⁺, O⁺ (²D) and O⁺ (²P)]. We investigated the relative importance of the two major processes responsible for maintaining the nightside plasma densities: atomic ion transport from the dayside and impact ionization due to energetic electron precipitation. …

Shock Study In Fully Relativistic Isothermal Flows. Ii, Ruixin Yang, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The isothermal shocks and their stabilities in fully relativistic accretion wedge flows onto black holes are studied. The jump condition across the shock is modified by the relativistic effects when the sound speed is comparable to the speed of light. With a new kind of instability analysis, it is found that only one of the two possible shocks is stable. The results are applied to the QPO behavior in galactic black hole candidates such as Cygnus X-1.

Using Fritiof To Model Nucleus-Nucleus Interactions In A Cosmic Ray Detector, Carlos A. Sanchez, Kazuhiko Murai, Donald C. Wold

Journal of the Arkansas Academy of Science

Ascintillating optical fiber calorimeter (SOFCAL) isbeing developed by NASA/Marshall Space Flight Center for use in experiments to study the spectrum of high-energy cosmic rays and gamma rays from 100 GeV to 1,000 TeV. SOFCAL willnot saturate for long exposures and this calorimeter inthese balloon-borne emulsion chambers willbe helpful for the study of the composition of primary cosmic-ray nuclei. For primary nuclei with energies much greater than 1014 eV, nucleus-nucleus interactions are likely to exhibit characteristics of a quark-gluon plasma (QGP). Aparticle event generator was used tomodel the collision of a cosmic-ray nucleus with a target nucleus inan emulsion chamber. FRITIOF …

Creation And Implementation Of A Tracking Module For A Small-Geometry, Vertex Time Projection Chamber, Christine A. Byrd, Wilson H. Howe, Amber D. Climer, Wilfred J. Braithwaite

Journal of the Arkansas Academy of Science

A charged-particle tracking module was written and tested using pixel data generated from CERN's Monte Carlo detector-modeling program GEANT. This tracking module was customized for testing the design of a micro-strip gas time project chamber, designed by Drs. Margetis and Wieman of the Relativistic Nuclear Collisions Group at Lawrence Berkeley Laboratory. This low-mass, high-resolution, small-geometry vertex time projection chamber was designed for possible use with a larger instrument in an experiment using the relativistic heavy ion collider, RHIC, under construction at Brookhaven National Laboratory in New York. Implementing this tracking module involved generating tables and source code in a manner …

Waterjet Cutting Of Cross-Linked Glass, Fang Yuan, John A. Johnson, David D. Allred, Robert H. Todd

Faculty Publications

The cutting of cross-linked glasses such as silica and Corning 7059 can be difficult. We conducted an experimental study to determine the feasibility of using a high-speed waterjet to cut thin Corning 7095 glass. Cutting using either pure de-ionized high pressure water at 380 MPa (55 000 psi) or de-ionized water with entrained garnet abrasive was studied. The roughness of the cut surfaces was measured and compared. Photomicrographs were taken of glass examples cut at different traversing rates with pure water and with the abrasive entrained waterjet. Comparative studies of cutting with and without the entrained abrasive material showed that …

Using Geant To Model Calrimeter Response For Electromagnetic Cascades From Nucleus-Nucleus Interactions In A Cosmic Ray Detector, Kazuhiko Murai, Carlos A. Sanchez, Donald C. Wold

Journal of the Arkansas Academy of Science

Ascintillating optical fiber calorimeter (SOFCAL) is being developed by NASA/Marshall Space Flight Center for use in balloon-borne experiments to study the spectrum of high-energy cosmic rays and gamma rays. SOFCAL will not saturate for long exposures and the calorimeter willbe useful in emulsion chambers to study primary cosmic-ray nuclei with energies from 100 GeV to 1,000 TeV. The event generator FRITIOF was used to model the collision of a cosmic-ray projectile with a target nucleus inan emulsion chamber. The measurements of charged particles from the interaction in the emulsions are related to the energy of the primary cosmic ray nucleus-nucleus …

Evidence For Virtual Compton Scattering From Proton, J.F.J. Van Den Brand, R. Ent, P. L. Anthony, R. G. Arnold, J. Arrington, E. J. Beise, J. E. Belz, P. E. Bosted, H. J. Bulten, M. S. Chapman, K. P. Coulter, F. S. Dietrich, M. Epstein, B. W. Filippone, H. Gao, R. A. Gearhart, D. F. Geesaman, J.-O. Hansen, R. J. Holt, H. E. Jackson, C. E. Jones, C. E. Keppel, E. R. Kinney, S. Kuhn, K. Lee, W. Lorenzon, A. Lung, N.C.R. Makins, D.J. Margaziotis, R.D. Mckeown, R.G. Milner, B. Mueller, J. Napolitano, J. Nelson, T. G. O'Neill, V. Pavavassiliou, G. G. Petratos, D. H. Potterveld, S. E. Rock, M. Spengos, Z. M. Szalata, L. H. Tao, K Van Bibber, D. A. Wasson, J.L. White, B. Zeidman

Physics Faculty Publications

In virtual Compton scattering an electron is scattered off a nucleon such that the nucleon emits a photon. We show that these events can be selected experimentally, and present the first evidence for virtual Compton scattering from the proton in data obtained at the Stanford Linear Accelerator Center. The angular and energy dependence of the data is well described by a calculation that includes the coherent sum of electron and proton radiation.

Osse Observations In Blazars, K. Mcnaron-Brown, W. N. Johnson, G. V. Jung, R. L. Kinzer, J. D. Kurfess, M. S. Strickman, C. D. Dermer, D. A. Grabelsky, W. R. Purcell, M. P. Ulmer, Menas Kafatos, P. A. Becker, R. Staubert, M. Maisack

Mathematics, Physics, and Computer Science Faculty Articles and Research

Results are reported on observations obtained with the Oriented Scintillation Spectrometer Experiment (OSSE) instrument on the Compton Gamma Ray Observatory (CGRO) of 17 active galactic nuclei (AGNs) known to exhibit blazar properties at other wavelengths. These observations span the period from 1991 June through 1994 May. Of the 33 high-confidence EGRET detections of blazars during CGRO observing phases 1 and 2 (1991 May 16-1993 September 7), OSSE has observed eight and detected five, namely 3C 273, 3C 279, PKS 0528+134, CTA 102, and 3C 454.3. Additionally, OSSE has detected the BL Lac sources H1517+65.6 and PKS 2155-304, which were not …

Multiwavelength Observations Of Markarian 421 During A Tev/X-Ray Flare, D. J. Macomb, C. W. Akerlof, H. D. Aller, M. F. Aller, D. L. Bertsch, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

A Te V flare from the BL Lac object Mrk 421 was detected in May of 1994 by the Whipple Observatory air Cherenkov experiment during which the flux above 250 GeV increased by nearly an order of magnitude over a 2-day period. Contemporaneous observations by ASCA showed the X-ray flux to be in a very high state. We present these results, combined with the first ever simultaneous or nearly simultaneous observations at Ge V gamma-ray, UV, IR, mm, and radio energies for this nearest BL Lac object. While the GeV gamma-ray flux increased slightly, there is little evidence for variability …

Density Of States Of A Damped Quantum Oscillator, Andreas Hanke, W. Zwerger

Physics and Astronomy Faculty Publications and Presentations

We calculate the density of states of a damped quantum-mechanical harmonic oscillator which is described by a Caldeira-Leggett type model with Ohmic dissipation and a Drude-like cutoff. From the exact expression for the associated partition function, we derive the asymptotic behavior of the density of states using Tauberian theorems. An effective algorithm to evaluate the density of states is presented and examples are given. It is pointed out that the calculated density of states is an experimentally accessible quantity.

Ultraviolet Temporal Variability Of The Peculiar Star R Aquarii, S. R. Meier, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

This paper is a comprehensive study of all far-UV spectra obtained with the International Ultraviolet Explorer (IUE) satellite of the symbiotic star R Aquarii (R Aqr) covering a 13 yr period between 1979 and 1992. We have analyzed the ultraviolet emission for the compact H II region and the NE and SW extended "jetlike" filamentary structures. The results of our ultraviolet analysis indicate that the H II region and features A, B, and D of the NE jet are increasing in intensity, while the SW counterjet, feature A', has declined in intensity. We have found much stronger evidence that the …

Implications Of Gamma-Ray Transparency Constraints In Blazars: Minimum Distances And Gamma-Ray Collimation, P. A. Becker, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

We develop a general expression for the γ-γ absorption coefficient, αγγ, for γ-rays propagating in an arbitrary direction at an arbitrary point in space above an X-ray-emitting accretion disk. The X-ray intensity is assumed to vary as a power law in energy and radius between the outer disk radius, R0 , and the inner radius, Rm., which is the radius of marginal stability for a Schwarzschild black hole. We use our result for αγγ to calculate the γ-γ optical depth, Tγγ, for γ-rays created at height z and propagating at angle Φ relative to the disk axis, and we show …

Precision Measurement Of Relative Dipole Matrix Elements In Atomic Sodium, Rodney P. Meyer

Physics Theses & Dissertations

Relative dipole matrix elements are measured by means of a new spectroscopic technique called polarization interference spectroscopy. It is a two-color two-photon nonresonant process that maps the matrix elements into the energy domain by means of quantum mechanical interference. The technique measures the relative magnitude of the reduced matrix elements, particularly those involving excited states, to accuracies that are an order of magnitude better than previously available. Also, for the first time the relative phase of the reduced matrix elements is measured. The ratio of reduced matrix elements for the transitions 3s ²S_1/2 →3P ²P_3/2 →5s …

Tracking And Impact Prediction Of Earth-Crossing-Objects (Ecos) On A Collision Course With Earth, Gregory A. Bishop

Theses and Dissertations

This study investigated the effectiveness of Earth-based angles only observations in determining the orbit of various hypothetical Earth-Crossing-Objects (ECOs). 'True' trajectories were simulated specifically for Earth-Crossing- Comets (ECCs) by numerically integrating in a Restricted Three Body system. Starting at Earth impact points, the state vectors were reverse-propagated" to a proposed detection time. Observations (obs), with state-of-the-art accuracy, were then simulated with error induced by a Gaussian random number generator; these were used in a least- squares differential corrector to estimate the positions of the ECOs. State vectors and covariance matrices were then propagated to the impact times and axis lengths …

Effects Of Photon Noise On Unconstrained Minimization Techniques For Iterative Blind Deconvolution, Derek K. Davis

Theses and Dissertations

In recent years, imaging through atmospheric turbulence has interested military scientists seeking to improve optical surveillance of satellites. Adaptive optics was a step toward achieving diffraction-limited resolution from ground-based telescopes. Unfortunately, adaptive optics only partially compensate for atmospheric blurring, therefore post processing of images is required. Processing methods in use today require knowledge of the impulse response of the optical system to reconstruct imagery, but this information is seldom known. This thesis looks at a new metal of processing compensated imagery, called blind deconvolution, which assumes very little or no a priori information about the impulse response. In particular, this …

Orbital Studies Of The Cataclysmic Variables Cz Orionis, V1193 Orionis And Bz Ursae Majoris, F. A. Ringwald, J. R. Thorstensen, R. M. Hamwey

Dartmouth Scholarship

Time-resolved spectroscopy reveals the orbital periods of three cataclysmic variables. CZ Ori has an orbital period of 0.2189 d. This is within 3 per cent of a prediction relating orbital period and dwarf nova outburst decline time. We find the M2.5 ± 1.0 secondary, and infer an absolute magnitude for CZ Ori in RKc of 8.5 ± 1.0 and a distance of 260 ± 110 pc. V1193 Ori, also called Hamuy's Blue Variable, has an orbital period of 0.165 d. In 1988, Ha emission line profile variations suggested red star illumination. In 1989, this line's red wing flared at orbital …

Electron Energy Loss In Oxygen Plasmas, G. A. Victor, John C. Raymond, Jane L. Fox

Jane L. Fox

The results of calculations of the energy deposition of energetic electrons in oxygen plasmas are given. In a pure oxygen plasma even with large fractional ionization, much of the electron energy results in the production of additional ionization and excited electronic states. Results are given for separate calculations using theoretical and experimental cross sections for the important O I excitations of ¹S and ¹D because the theoretical and experimental data are not in agreement. These results are useful for understanding the spectra of oxygen-rich supernova remnants.

Chromospherically Active Stars. Xiii. Hd 30957: A Double Lined K Dwarf Binary, Francis C. Fekel, Virgiljus Dadonas, Julius Sperauskas, Todd R. Vaccaro, L. Ronald Patterson

Information Systems and Engineering Management Research Publications

HD 30957 is a double-lined spectroscopic binary with a period of 44.395 days and a modest eccentricity of 0.09. The spectral types of the components are K2-3 V and K5 V. The measured v sin i for both components is less than or equal to 3 km/s and the orbital inclination is estimated to be 69 deg. The system is relatively nearby with a parallax of 0.025 sec or a distance of 40 pc. Space motions of the system indicate that it does not belong to any of the known moving groups. Absolute surface fluxes of the Ca II H …

Evidence For A Disk In The Wind Of Hd 93521: Uv Line Profiles From An Axisymmetric Model., Richard Ignace

Richard Ignace

Recently it has been suggested (Massa 1992; Howarth & Reid 1993), from the C IV ultraviolet resonance line profile of HD 93521, that there is a high-speed component in the polar outflow from the star as well as a low-speed component in the equatorial regions. In this paper we present theoretical calculations of the line profiles that would be produced by such a model. We find from Hubble Space Telescope (HST) Goddard High Resolution Spectrograph (GHRS) observations of HD 93521 that the observed C IV profile can be produced if the star has an inclination angle very close to 90 …

Extraordinary Line-Emitting Knots In The Crab Nebula, Gordon M. Macalpine, Stephen S. Lawrence, Beth A. Brown, Alan Uomoto, Bruce E. Woodgate, Larry W. Brown, Ronald J. Oliversen, James D. Lowenthal, Charles Liu

Astronomy: Faculty Publications

Extraordinary, semistellar, line-emitting knots are apparent in images of the Crab Nebula which were obtained with the Goddard Fabry-Perot imager at the Michigan-Dartmouth-MIT Observatory. The knots are most prominent for [O III] λ5007 emission through a 5.3 Å (FWHM) bandpass centered at 5015.3 Å, with representative fluxes of roughly 10-14 ergs cm-2 s-1. They are aligned in arcs, seven to the north and four to the south, from the pulsar. The northern group appears to be in a bounded corridor through the filamentary structure. Measurements over a 2 year baseline yield proper motions of order 0″.1 yr-1, corresponding to transverse …

Effects Of Aberrations On Spatially Modulated Fourier Transform Spectrometers, R Glenn Sellar, James Bruce Rafert

Aerospace, Physics, and Space Science Faculty Publications

Spatially modulated Fourier transform spectrometers (FTS) have a throughput advantage over dispersive spectrometers, since an FTS does not require a slit in order to achieve spectral resolution. The traditional implementation of FTSs employs a scanning Michelson interferometer, but since this interferometer is temporally modulated, it is difficult or impossible to use with a target whose spatial and/or spectral signature is changing rapidly. The less common spatially modulated approach to FTS allows all spectral channels to be acquired simultaneously, but cylindrical optics are required to create an imaging version a FTS (IFTS). This combination of cylindrical and spherical optics, used to …

Vv 114: Making Of An Ultraluminous Galaxy?, Min S. Yun, N Z. Scoville, R A. Knop

Min S. Yun

High-resolution (Theta = 4 arcseconds .4 x 3 arcseconds .1) CO observations of the IR luminous system VV 114 (IC 1623) using the Owens Valley Millimeter array reveal 5.1 x 1010 Solar masses of H2 in a 5.9 x 3.1 kpc (15 arcseconds x 8 arcseconds) bar with two 4-6 kpc long tails (D = 80 Mpc for H 0= 75). The wide separation (6 kpc) of the merging optical galaxies, the extended gas distribution, and the noncircular gas kinematics suggest that VV 114 is in an early stage of a gas-rich merger. The concentration of gas and its dominance …

Chromospherically Active Stars. Xii. Ads 11060 C: A Double Linked K Dwarf Binary In A Quintuple System, Francis C. Fekel, Gregory W. Henry, Melissa L. Hampton, Robert E. Fried, Mary D. Morton

Information Systems and Engineering Management Research Publications

ADS 11060 C is a double lined spectroscopic binary with a period of 25.7631 days and an eccentricity of 0.565. Spectral types of the two stars are estimated as K7 V and MO V with a magnitude difference of about 0.55 mag in V. The stars appear to be somewhat metal rich with respect to the Sun. Despite the relatively large masses of 0.53 and 0.51 solar mass, our photometric observations find no evidence for eclipses and we estimate an inclination of 77 deg plus or minus 11 deg. ADS 11060 C is, however, photometrically variable with a period of …