995 research outputs found
It\u27s a Small World: Enhancing Human Cognition through Virtual Dioramas
2008 S.C. Water Resources Conference - Addressing Water Challenges Facing the State and Regio
Learning from the Success of MPI
The Message Passing Interface (MPI) has been extremely successful as a
portable way to program high-performance parallel computers. This success has
occurred in spite of the view of many that message passing is difficult and
that other approaches, including automatic parallelization and directive-based
parallelism, are easier to use. This paper argues that MPI has succeeded
because it addresses all of the important issues in providing a parallel
programming model.Comment: 12 pages, 1 figur
Evaporative Cooling of a Two-Component Degenerate Fermi Gas
We derive a quantum theory of evaporative cooling for a degenerate Fermi gas
with two constituents and show that the optimum cooling trajectory is
influenced significantly by the quantum statistics of the particles. The
cooling efficiency is reduced at low temperatures due to Pauli blocking of
available final states in each binary collision event. We compare the
theoretical optimum trajectory with experimental data on cooling a quantum
degenerate cloud of potassium-40, and show that temperatures as low as 0.3
times the Fermi temperature can now be achieved.Comment: 6 pages, 4 figure
Comparison between three-dimensional linear and nonlinear tsunami generation models
The modeling of tsunami generation is an essential phase in understanding
tsunamis. For tsunamis generated by underwater earthquakes, it involves the
modeling of the sea bottom motion as well as the resulting motion of the water
above it. A comparison between various models for three-dimensional water
motion, ranging from linear theory to fully nonlinear theory, is performed. It
is found that for most events the linear theory is sufficient. However, in some
cases, more sophisticated theories are needed. Moreover, it is shown that the
passive approach in which the seafloor deformation is simply translated to the
ocean surface is not always equivalent to the active approach in which the
bottom motion is taken into account, even if the deformation is supposed to be
instantaneous.Comment: 39 pages, 16 figures; Accepted to Theoretical and Computational Fluid
Dynamics. Several references have been adde
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Cosmic Ray Background Analysis for a Cargo Container Counter.
We have developed a new model for calculating the expected yield of cosmic-ray spallation neutrons in a Cargo Container Counter, and we have benchmarked the model against measurements made with several existing large neutron counters. We also developed two versions of a new measurement uncertainty prediction code based on Microsoft Excel spreadsheets. The codes calculate the minimum detectability limit for the Cargo Container Counter for either neutron singles or doubles counting, and also propagate the uncertainties associated with efficiency normalization flux monitors and cosmic ray flux monitors. This paper will describe the physics basis for this analysis, and the results obtained for several different counter designs
Scattering of short laser pulses from trapped fermions
We investigate the scattering of intense short laser pulses off trapped cold
fermionic atoms. We discuss the sensitivity of the scattered light to the
quantum statistics of the atoms. The temperature dependence of the scattered
light spectrum is calculated. Comparisons are made with a system of classical
atoms who obey Maxwell-Boltzmann statistics. We find the total scattering
increases as the fermions become cooler but eventually tails off at very low
temperatures (far below the Fermi temperature). At these low temperatures the
fermionic degeneracy plays an important role in the scattering as it inhibits
spontaneous emission into occupied energy levels below the Fermi surface. We
demonstrate temperature dependent qualitative changes in the differential and
total spectrum can be utilized to probe quantum degeneracy of trapped Fermi gas
when the total number of atoms are sufficiently large . At smaller
number of atoms, incoherent scattering dominates and it displays weak
temperature dependence.Comment: updated figures and revised content, submitted to Phys.Rev.
Sympathetic cooling of an atomic Bose-Fermi gas mixture
Sympathetic cooling of an atomic Fermi gas by a Bose gas is studied by
solution of the coupled quantum Boltzmann equations for the confined gas
mixture. Results for equilibrium temperatures and relaxation dynamics are
presented, and some simple models developed. Our study illustrate that a
combination of sympathetic and forced evaporative cooling enables the Fermi gas
to be cooled to the degenerate regime where quantum statistics, and mean field
effects are important. The influence of mean field effects on the equilibrium
spatial distributions is discussed qualitatively.Comment: 8 pages, 9 figures, accepted for publication in Phys.Rev.Let
Moving Forward: Refinement of the INTELLIGENT RIVER, A Basin-Scale Monitoring Instrument
2012 S.C. Water Resources Conference - Exploring Opportunities for Collaborative Water Research, Policy and Managemen
Leftovers:The presence of manufacture-derived aquatic lipids in Alaskan Pottery
Lipids preserved within the walls of ancient pottery vessels are routinely analysed to reveal their original contents. The provenience of aquatic lipids in pottery is generally connected to vessel function (e.g., for cooking or storing fish, shellfish and aquatic mammals). However, ethnographic reports from early historic Alaska mention the use of aquatic oils for waterproofing low-fired pottery. Results of lipid residue studies on Alaskan pottery reflect an exclusive function of pottery to process aquatic resources. However, can one be sure these residues are the product of vessel function and not a remnant of the manufacturing process? The study presents the results of an experiment where the preservation of aquatic lipids during the firing process at different temperatures was measured. It was found that nearly all lipids were removed at firing temperatures of ℠400°C. Petrographic analysis of Alaskan pottery samples indicates that firing temperatures were generally > 550°C but < 800°C. The contribution of pre-firing manufacture-derived lipids to samples fired at these temperatures may be regarded as negligible. While the possible presence of aquatic lipids from post-firing surface treatments cannot be excluded, such treatments appear unnecessary for well-fired pottery.</p
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