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Astrophysics and Astronomy

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Selected Works

1994

Articles 1 - 6 of 6

Full-Text Articles in Physical Sciences and Mathematics

Electron Energy Loss In Oxygen Plasmas, G. A. Victor, John C. Raymond, Jane L. Fox Nov 1994

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.

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Evidence For A Disk In The Wind Of Hd 93521: Uv Line Profiles From An Axisymmetric Model., Richard Ignace Oct 1994

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 …

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Vv 114: Making Of An Ultraluminous Galaxy?, Min S. Yun, N Z. Scoville, R A. Knop Aug 1994

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 …

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Velocity Distribution Among Colliding Asteroids, W F. Bottke, M C. Nolan, R Greenberg, Robert A. Kolvoord Jan 1994

Velocity Distribution Among Colliding Asteroids, W F. Bottke, M C. Nolan, R Greenberg, Robert A. Kolvoord

Robert A Kolvoord

No abstract provided.

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Direct Simulation Monte Carlo For Thin Film Bearings, Alejandro Garcia, B. Alder, F. J. Alexander Jan 1994

Direct Simulation Monte Carlo For Thin Film Bearings, Alejandro Garcia, B. Alder, F. J. Alexander

Alejandro Garcia

The direct simulation Monte Carlo (DSMC) scheme is used to study the gas flow under a read/write head positioned nanometers above a moving disk drive platter (the slider bearing problem). In most cases, impressive agreement is found between the particle-based simulation and numerical solutions of the continuum hydrodynamic Reynolds equation which has been corrected for slip. However, at very high platter speeds the gas is far from equilibrium, and the load capacity for the slider bearing cannot be accurately computed from the hydrodynamic pressure.

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Microscopic Simulation Of Dilute Gases With Adjustable Transport Coefficients, Alejandro Garcia, F. Baras, M. Malek Mansour Jan 1994

Microscopic Simulation Of Dilute Gases With Adjustable Transport Coefficients, Alejandro Garcia, F. Baras, M. Malek Mansour

Alejandro Garcia

The Bird algorithm is a computationally efficient method for simulating dilute gas flows. However, due to the relatively large transport coefficients at low densities, high Rayleigh or Reynolds numbers are difficult to achieve by this technique. We present a modified version of the Bird algorithm in which the relaxation processes are enhanced and the transport coefficients reduced, while preserving the correct equilibrium and nonequilibrium fluid properties. The present algorithm is found to be two to three orders of magnitude faster than molecular dynamics for simulating complex hydrodynamical flows.

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