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Articles 1 - 8 of 8
Full-Text Articles in Physics
Observation Of Beam-Induced Changes In The Polarization Of Balmer-Α Radiation Emitted Following Beam--Tilted-Foil Transmission, Wang Qi, David D. Allred, Larry V. Knight, Douglas L. Harper, Royal G. Albridge, Norman H. Tolk
Observation Of Beam-Induced Changes In The Polarization Of Balmer-Α Radiation Emitted Following Beam--Tilted-Foil Transmission, Wang Qi, David D. Allred, Larry V. Knight, Douglas L. Harper, Royal G. Albridge, Norman H. Tolk
Faculty Publications
Measurements of the circular polarization of Balmer-α radiation emitted by excited hydrogen atoms, following the transmission of (20-50)-keV protons through thin, tilted amorphous carbon foils, exhibit markedly unexpected behavior as a function of exposure of the foil to the proton beam. Specifically, the circular polarization changes from an initially well understood tilt-angle dependence to a behavior which, for low tilt angles, gives the opposite handedness of circular polarization from that predicted. In addition, the degree of alignment, indicated by the linear Stokes parameter M/I, is enhanced also as a function of dose. These changes in the tilt-angle dependence of the …
Numerical Calculation Of Axisymmetric Electrostatic Modes For Cold Finite-Length Non-Neutral Plasmas, Johnny K. Jennings, Ross L. Spencer, K. C. Hansen
Numerical Calculation Of Axisymmetric Electrostatic Modes For Cold Finite-Length Non-Neutral Plasmas, Johnny K. Jennings, Ross L. Spencer, K. C. Hansen
Faculty Publications
A numerical calculation of mode frequencies for cold, non-neutral plasmas is reported. The numerical method can be applied to any axisymmetric plasma shape in a trap. Here, it is used to study axisymmetric electrostatic modes in a long conducting cylinder. These modes were previously studied by Prasad and O'Neil [Phys. Fluids 26, 665 (1983)] and by Dubin [Phys. Rev. Lett. 66, 2076 (1991)]. In contrast to Dubin's calculation, the effects of a nearby cylindrical wall, including its influence on the shape of the plasma equilibrium, are considered. It is found that for plasmas with aspect ratios (length divided by diameter) …
Computer Simulation Study Of The Permeability Of Driven Polymers Through Porous Media, Grace M. Foo, Ras B. Pandey
Computer Simulation Study Of The Permeability Of Driven Polymers Through Porous Media, Grace M. Foo, Ras B. Pandey
Faculty Publications
A computer simulation model is used to study the permeability of polymer chains driven by a biased flow field through a porous medium in two dimensions. The chains are modeled by constrained self-avoiding walks, which reptate through the heterogeneous medium with a biased probability imposed by the driven field. A linear response description is used to evaluate an effective permeability. The permeability σ shows an unusual decay behavior on reducing the porosity ps. We find that the permeability decreases on increasing the bias above a characteristic value Bc. This characteristic bias shows a logarithmic decay on …
Computer-Simulation Study Of The Permeability Of A Porous Sediment Model, Ras B. Pandey, Jeffrey L. Becklehimer
Computer-Simulation Study Of The Permeability Of A Porous Sediment Model, Ras B. Pandey, Jeffrey L. Becklehimer
Faculty Publications
A computer simulation model is used to study the permeability of fluid flow through porous media generated by the random distribution of the sediments in a two-dimensional lattice. Fluid particles are confined to pore space with the sediments forming the rigid barriers at the pore boundaries. An interaction between the fluid particles and the pore substrate is introduced to incorporate the additional drag in the pore space. The pressure gradient causes a bias to drive the fluid and the Metropolis algorithm is used to hop the fluid particles. The permeability of this system is studied as a function of the …
Comment On 'Simulation Of A Two-Dimensional Rayleigh-Bénard System Using The Direct Simulation Monte Carlo Method, Alejandro Garcia, F. Baras, M. Malek Mansour
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.
A Consistent Boltzmann Algorithm, Alejandro Garcia, F. Alexander, B. Alder
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
Xenon 147-Nm Resonance Ƒ Value And Trapped Decay Rates, H. M. Anderson, Scott D. Bergeson, D. A. Doughty, J. E. Lawler
Xenon 147-Nm Resonance Ƒ Value And Trapped Decay Rates, H. M. Anderson, Scott D. Bergeson, D. A. Doughty, J. E. Lawler
Faculty Publications
The absorption oscillator strength of the xenon 147-nm resonance transition is measured to be 0.264±0.016. This value is from direct absorption measurements with equivalent widths from ≈ 1 to ≈ 10 cm-1. This ƒ-value measurement is compared to others in the literature and is used in Monte Carlo simulations of trapped decay rates. The simulations include an angle-dependent partial frequency redistribution. The simulation results are compared to trapped decay rates in the literature.
Waterjet Cutting Of Cross-Linked Glass, Fang Yuan, John A. Johnson, David D. Allred, Robert H. Todd
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 …