14,135 research outputs found
A data storage, retrieval and analysis system for endocrine research
This retrieval system builds, updates, retrieves, and performs basic statistical analyses on blood, urine, and diet parameters for the M071 and M073 Skylab and Apollo experiments. This system permits data entry from cards to build an indexed sequential file. Programs are easily modified for specialized analyses
The importance of the classical channel in the impurity transport of optimized stellarators
In toroidal magnetic confinement devices, such as tokamaks and stellarators,
neoclassical transport is usually an order of magnitude larger than its
classical counterpart. However, when a high-collisionality species is present
in a stellarator optimized for low Pfirsch-Schl\"uter current, its classical
transport can be comparable to the neoclassical transport. In this letter, we
compare neoclassical and classical fluxes and transport coefficients calculated
for Wendelstein 7-X (W7-X) and Large Helical Device (LHD) cases. In W7-X, we
find that the classical transport of a collisional impurity is comparable to
the neoclassical transport for all radii, while it is negligible in the LHD
cases, except in the vicinity of radii where the neoclassical transport changes
sign. In the LHD case, electrostatic potential variations on the flux-surface
significantly enhance the neoclassical impurity transport, while the classical
transport is largely insensitive to this effect in the cases studied.Comment: 10 pages, 2 figure
Ice/frost detection using millimeter wave radiometry
A series of ice detection tests was performed on the shuttle external tank (ET) and on ET target samples using a 35/95 GHz instrumentation radiometer. Ice was formed using liquid nitrogen and water spray inside a test enclosure containing ET spray on foam insulation samples. During cryogenic fueling operations prior to the shuttle orbiter engine firing tests, ice was formed with freon and water over a one meter square section of the ET LOX tank. Data analysis was performed on the ice signatures, collected by the radiometer, using Georgia Tech computing facilities. Data analysis technique developed include: ice signature images of scanned ET target; pixel temperature contour plots; time correlation of target data with ice present versus no ice formation; and ice signature radiometric temperature statistical data, i.e., mean, variance, and standard deviation
Vortex crystals
Vortex crystals is one name in use for the subject of vortex patterns that move without change of shape or size. Most of what is known pertains to the case of arrays of parallel line vortices moving so as to produce an essentially two-dimensional flow. The possible patterns of points indicating the intersections of these vortices with a plane perpendicular to them have been studied for almost 150 years. Analog experiments have been devised, and experiments with vortices in a variety of fluids have been performed. Some of the states observed are understood analytically. Others have been found computationally to high precision. Our degree of understanding of these patterns varies considerably. Surprising connections to the zeros of 'special functions' arising in classical mathematical physics have been revealed. Vortex motion on two-dimensional manifolds, such as the sphere, the cylinder (periodic strip) and torus (periodic parallelogram) has also been studied, because of the potential applications, and some results are available regarding the problem of vortex crystals in such geometries. Although a large amount of material is available for review, some results are reported here for the first time. The subject seems pregnant with possibilities for further development.published or submitted for publicationis peer reviewe
Three body problem in a dilute Bose-Einstein condensate
We derive the explicit three body contact potential for a dilute condensed
Bose gas from microscopic theory. The three body coupling constant exhibits the
general form predicted by T.T. Wu [Phys. Rev. 113, 1390 (1959)] and is
determined in terms of the amplitudes of two and three body collisions in
vacuum. In the present form the coupling constant becomes accessible to
quantitative studies which should provide the crucial link between few body
collisions and the stability of condensates with attractive two body forces
Generalized Mean Field Approach to a Resonant Bose-Fermi Mixture
We formulate a generalized mean-field theory of a mixture of fermionic and
bosonic atoms, in which the fermion-boson interaction can be controlled by a
Feshbach resonance. The theory correctly accounts for molecular binding
energies of the molecules in the two-body limit, in contrast to the most
straightforward mean-field theory. Using this theory, we discuss the
equilibrium properties of fermionic molecules created from atom pairs in the
gas. We also address the formation of molecules when the magnetic field is
ramped across the resonance, and present a simple Landau-Zener result for this
process.Comment: 35 page
Duality Between Spatial and Angular Shift in Optical Reflection
We report a unified representation of the spatial and angular Goos-Hanchen
and Imbert-Fedorov shifts that occur when a light beam reflects from a plane
interface. We thus reveal the dual nature of spatial and angular shifts in
optical beam reflection. In the Goos-Hanchen case we show theoretically and
experimentally that this unification naturally arises in the context of
reflection from a lossy surface (e.g., a metal).Comment: 4 pages, 3 figure
Connection between effective-range expansion and nuclear vertex constant or asymptotic normalization coefficient
Explicit relations between the effective-range expansion and the nuclear
vertex constant or asymptotic normalization coefficient (ANC) for the virtual
decay are derived for an arbitrary orbital momentum together with
the corresponding location condition for the () bound-state energy. They
are valid both for the charged case and for the neutral case. Combining these
relations with the standard effective-range function up to order six makes it
possible to reduce to two the number of free effective-range parameters if an
ANC value is known from experiment. Values for the scattering length, effective
range, and form parameter are determined in this way for the O+,
and He collisions in partial waves where a bound state
exists by using available ANCs deduced from experiments. The resulting
effective-range expansions for these collisions are valid up to energies larger
5 MeV.Comment: 17 pages, 6 figure
Microwave soil moisture measurements and analysis
An effort to develop a model that simulates the distribution of water content and of temperature in bare soil is documented. The field experimental set up designed to acquire the data to test this model is described. The microwave signature acquisition system (MSAS) field measurements acquired in Colby, Kansas during the summer of 1978 are pesented
Statistical fluctuations of the parametric derivative of the transmission and reflection coefficients in absorbing chaotic cavities
Motivated by recent theoretical and experimental works, we study the
statistical fluctuations of the parametric derivative of the transmission T and
reflection R coefficients in ballistic chaotic cavities in the presence of
absorption. Analytical results for the variance of the parametric derivative of
T and R, with and without time-reversal symmetry, are obtained for both
asymmetric and left-right symmetric cavities. These results are valid for
arbitrary number of channels, in completely agreement with the one channel case
in the absence of absorption studied in the literature.Comment: Modified version as accepted in PR
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