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Physical Sciences and Mathematics Commons™

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Physics

Old Dominion University

Series

1999

Articles 1 - 5 of 5

Full-Text Articles in Physical Sciences and Mathematics

Analyzing Mean Transport Equations Of Turbulence And Linear Disturbances In Decaying Flows, W. D. Thacker, T. B. Gatski, C. E. Grosch Jan 1999

Analyzing Mean Transport Equations Of Turbulence And Linear Disturbances In Decaying Flows, W. D. Thacker, T. B. Gatski, C. E. Grosch

CCPO Publications

The decay of laminar disturbances and turbulence in mean shear-free flows is studied. In laminar flows, such disturbances are linear superpositions of modes governed by the Orr-Sommerfeld equation. In turbulent flows, disturbances are described through transport equations for representative mean quantities. The link between a description based on a deterministic evolution equation and a probability-based mean transport equation is established. Because an uncertainty in initial conditions exists in the laminar as well as the turbulent regime, a probability distribution must be defined even in the laminar case. Using this probability distribution, it is shown that the exponential decay of the …

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Role Of Spontaneous Emission In Ultracold Two-Color Optical Collisions, C. I. Sukenik, T. Walker Jan 1999

Role Of Spontaneous Emission In Ultracold Two-Color Optical Collisions, C. I. Sukenik, T. Walker

Physics Faculty Publications

We have observed violet photon emission resulting from energy-pooling collisions between ultracold Rb atoms illuminated by two colors of near-resonant infrared laser light. We have used this emission as a probe of doubly excited state ultracold collision dynamics. By varying the detuning of the lasers, we have clearly identified the effect of spontaneous emission on the collision process.

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Time-Resolved Reflection High-Energy Electron Diffraction Study Of The Ge(111)-C(2×8)-(1×1) Phase Transition, Xinglin Zeng, Bo Lin, Ibrahim El-Kholy, Hani E. Elsayed-Ali Jan 1999

Time-Resolved Reflection High-Energy Electron Diffraction Study Of The Ge(111)-C(2×8)-(1×1) Phase Transition, Xinglin Zeng, Bo Lin, Ibrahim El-Kholy, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The dynamics of the Ge(111)-c(2×8)-(1×1) phase transition is investigated by 100-ps time-resolved reflection high-energy electron diffraction. A laser pulse heats the surface while a synchronized electron pulse is used to obtain the surface diffraction pattern. Slow heating shows that the adatoms in Ge(111)-c(2×8) start to disorder at ∼510 K and are converted to a disordered adatom arrangement at 573 K. For heating with 100-ps laser pulses, the Ge(111)-c(2×8) reconstructed adatom arrangement starts to disorder at 584±16K, well above the onset temperature of ∼510 K for the disordering of Ge(111)-c(2×8) observed for slow …

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Direct Current Glow Discharges In Atmospheric Air, Robert H. Stark, Karl H. Schoenbach Jan 1999

Direct Current Glow Discharges In Atmospheric Air, Robert H. Stark, Karl H. Schoenbach

Bioelectrics Publications

Direct current glow discharges have been operated in atmospheric air by using 100 μm microhollow cathode discharges as plasma cathodes. The glow discharges were operated at currents of up to 22 mA, corresponding to current densities of 3.8 A/cm2 and at average electric fields of 1.2 kV/cm. Electron densities in the glow are in the range from 1012 to 1013  cm−3. Varying the current of the microhollow cathode discharge allows us to control the current in the atmospheric pressure glow discharge. Large volume atmospheric pressure air plasmas can be generated by operating microhollow cathode discharges …

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Factorization And High-Energy Effective Action, Ian Balitsky Jan 1999

Factorization And High-Energy Effective Action, Ian Balitsky

Physics Faculty Publications

I demonstrate that the amplitude for high-energy scattering can be factorized as a convolution of the contributions due to fast and slow fields. The fast and slow fields interact by means of Wilson-line operators—infinite gauge factors ordered along the straight line. The resulting factorization formula gives a starting point for a new approach to the effective action for high-energy scattering in QCD.

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