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Articles 451 - 461 of 461

Full-Text Articles in Other Astrophysics and Astronomy

Slip Length In A Dilute Gas, Alejandro Garcia, D. Morris, L. Hannon Jan 1992

Slip Length In A Dilute Gas, Alejandro Garcia, D. Morris, L. Hannon

Faculty Publications

We study the phenomenon of slip length using molecular dynamics and direct simulation Monte Carlo simulations of a dilute gas. Our work extends the range of Knudsen numbers that have been previously studied. In a recent paper, Bhattacharya and Lie [Phys. Rev. 43, 761 (1991)] suggest a logarithmic dependence of slip length on Knudsen number. By a simple redefinition of the mean free path, we obtain good agreement between simulation results and Maxwell theory for slip length. The anomalies seen by Bhattacharya and Lie appear to be due to their definition of the mean free path.

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Nonequilibrium Processes In Polymers Undergoing Interchange Reactions. Part 2: Reaction-Diffusion Processes, Alejandro Garcia, J. Pojman, D. Kondepudi, C. Van De Broeck Jan 1991

Nonequilibrium Processes In Polymers Undergoing Interchange Reactions. Part 2: Reaction-Diffusion Processes, Alejandro Garcia, J. Pojman, D. Kondepudi, C. Van De Broeck

Faculty Publications

A reactiodffusion system of polymers undergoing interchange reactions is studied. The equation that describes the dynamics of the system is similar to the Boltzmann equation for a gas of hard spheres. We consider a one-dimensionsl system in which the average length and the concentrations at the boundaries are fixed. The resulting steady states are obtained analytically and with numerical integration of equations obtained by using a local equilibrium approximation. Monte Carlo simulations of experimentally realizable conditions were performed and compared. The results reveal a nonlinear distribution of molecular concentration and mass. The entropy of the polymer distributions is calculated as …

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Shadow Casting Phenomena At Newgrange, Frank Prendergast Jan 1991

Shadow Casting Phenomena At Newgrange, Frank Prendergast

Articles

A digital model of the Newgrange passage tomb and surrounding ring of monoliths known as the Great Circle is used to investigate sunrise shadow casting phenomena at the monument. Diurnal variation in shadow directions and lengths are analysed for their potential use in the Bronze Age to indicate the passage of seasonal time. Computer-aided simulations are developed from a photogrammetric survey to accurately show how three of the largest monoliths, located closest to the tomb entrance and archaeologically coded GC1, GC-1 and GC-2, cast their shadows onto the vertical face of the entrance kerbstone, coded K1. The phenomena occur at …

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Hydrodynamic Fluctuations In A Fluid Under Constant Shear, Alejandro Garcia, M. Malek Mansour, G. Lie, E. Clementi, M. Mareschal Jan 1987

Hydrodynamic Fluctuations In A Fluid Under Constant Shear, Alejandro Garcia, M. Malek Mansour, G. Lie, E. Clementi, M. Mareschal

Faculty Publications

No abstract provided.

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Fluctuating Hydrodynamics In A Dilute Gas, Alejandro Garcia, G. Lie, E. Clementi Jan 1987

Fluctuating Hydrodynamics In A Dilute Gas, Alejandro Garcia, G. Lie, E. Clementi

Faculty Publications

Hydrodynamic fluctuations in a dilute gas subjected to a constant heat flux are studied by both a computer simulation and the Landau-Lifshitz formalism. The latter explicitly incorporates the boundary conditions of the finite system, thus permitting quantitative comparison with the former. Good agreement is demonstrated.

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Nonequilibrium Fluctuations Studied By A Rarefied Gas Simulation, Alejandro Garcia Jan 1986

Nonequilibrium Fluctuations Studied By A Rarefied Gas Simulation, Alejandro Garcia

Faculty Publications

A dilute gas under a constant heat flux is studied with use of a Monte Carlo simulation based on the Boltzmann equation. Results for several spatial correlation functions of equal-time fluctuations are reported and compared qualitatively with previous fluctuating hydrodynamics calculations for liquids.

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Membership Of The Rosette Nebula Cluster, Ngc 2244, Laurence A. Marschall, William F. Van Altena, Liang-Tai George Chiu Nov 1982

Membership Of The Rosette Nebula Cluster, Ngc 2244, Laurence A. Marschall, William F. Van Altena, Liang-Tai George Chiu

Physics and Astronomy Faculty Publications

Relative proper motions for 287 stars in the region of the young open cluster NGC 2244, located in the Rsette Nebula, have been determined from plates taken with the Yerkes 40-in. and the Allegheny 30-in. refractors. Probabilities of membership based on these proper motions are derived. Because probable members are chosen primarily from kinematic considerations, the sample should show a minimum photometric bias. Differential extinction across the cluster, however, is identified as a complication in the immediate interpretation of the sample in terms of color-magnitude diagrams or luminosity functions.

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X-Ray Survey Of The Small Magellanic Cloud, F. D. Seward, Melanie Mitchell Feb 1981

X-Ray Survey Of The Small Magellanic Cloud, F. D. Seward, Melanie Mitchell

Computer Science Faculty Publications and Presentations

A region of over 40 square degrees centered on the Small Magellanic Cloud (SMC) has been surveyed with the imaging instruments of the Einstein Observatory. The survey is approximately complete to Lx = 1036 ergs s-1, and the faintest source detected in the SMC, has Lx ≈ 3 x 1035 ergs s-1. Twenty-six sources were clearly seen. Five are identified with objects not associated with the SMC. The only previously known source detected was SMC X-1 which, when in a high state, is the brightest source in the SMC. The second brightest source observed, …

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Development Of Selected Mathematical Instruments Representing Angular, Logarithmic And Arithmetic Computation, Lillian L. Troxell Jan 1927

Development Of Selected Mathematical Instruments Representing Angular, Logarithmic And Arithmetic Computation, Lillian L. Troxell

University of the Pacific Theses and Dissertations

The Sextant in its earliest known form consisted of divided circles and compasses with simply sights. An early Creek astronomer of the second century after Christ, Claudius Ptolemaeus, or more commonly called Ptolemy, wrote a book entitled Megale Syntaxis tes Astron- omias, also known by the Arabic title Almagest. The instrument described in this book was called the Astrolable and was used to measure the angular distance between stars. It was made of two concentric vertical circles, the largest and outer circle was about sixteen inches in diameter with graduated arc; the central ring was movable and carried the two …

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Some Contributions Of Pure Math To Science, Herbert B.E. Case Jan 1897

Some Contributions Of Pure Math To Science, Herbert B.E. Case

Student and Lippitt Prize Essays

An examination of the connection between math and science through discoveries in the subjects of astronomy, mechanics, physics and chemistry.

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Farmer's Almanack 1825, Robert B. Thomas Dec 1824

Farmer's Almanack 1825, Robert B. Thomas

Rare Books

The Farmer's Almanack contains astronomical calculations, a farmer's calendar, military fines, college vacations, table of simple interest, court calendar, agricultural information, Episcopalian holidays, poetry, anecdotes, weather observations, roads and innkeepers and other useful information.

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