1,529 research outputs found
Automated Data Management Information System (ADMIS)
ADMIS stores and controls data and documents associated with manned space flight effort. System contains all data oriented toward a specific document; it is primary source of reports generated by the system. Each group of records is composed of one document record, one distribution record for each recipient of the document, and one summary record
Crossover from 2D to 3D in a weakly interacting Fermi gas
We have studied the transition from two to three dimensions in a low
temperature weakly interacting Li Fermi gas. Below a critical atom number,
, only the lowest transverse vibrational state of a highly anisotropic
oblate trapping potential is occupied and the gas is two-dimensional. Above
the Fermi gas enters the quasi-2D regime where shell structure
associated with the filling of individual transverse oscillator states is
apparent. This dimensional crossover is demonstrated through measurements of
the cloud size and aspect ratio versus atom number.Comment: Replaced with published manuscrip
Self-trapping at the liquid vapor critical point
Experiments suggest that localization via self-trapping plays a central role
in the behavior of equilibrated low mass particles in both liquids and in
supercritical fluids. In the latter case, the behavior is dominated by the
liquid-vapor critical point which is difficult to probe, both experimentally
and theoretically. Here, for the first time, we present the results of
path-integral computations of the characteristics of a self-trapped particle at
the critical point of a Lennard-Jones fluid for a positive particle-atom
scattering length. We investigate the influence of the range of the
particle-atom interaction on trapping properties, and the pick-off decay rate
for the case where the particle is ortho-positronium.Comment: 12 pages, 3 figures, revtex4 preprin
Effect of Level of Surface Spoilage on the Nutritive Value of Maize Silage Diets
This study determined the effect of surface spoilage in the diet on feed intake and nutrient digestibilities using growing steers fed whole-plant maize silage-based diets. A bunker silo, 0.9 m in depth, and a 2.7 m diameter AgBag were filled with alternating loads of chopped forage. After 90 days, the bunker was sealed with a sheet of polyethylene, and this silage was designated “spoiled”. The silage in the AgBag was designated “normal”. The four diets contained 90% silage and 10% supplement (dry matter basis), and the proportions of silage in the diets were A) 100% normal, B) 75% normal: 25% spoiled; C) 50% normal: 50% spoiled; and D) 25% normal: 75% spoiled. Feed intake decreased linearly as the proportion of spoiled silage increased from 0 to 75%. Steers consuming the normal silage diet had the highest nutrient digestibilities. Spoiled silage also had negative associative effects on nutrient digestibilities, and the integrity of the forage mat in the rumen was partially destroyed
Statistical Estimation of Orbital Debris Populations with a Spectrum of Object Size
Orbital debris is a real concern for the safe operations of satellites. In general, the hazard of debris impact is a function of the size and spatial distributions of the debris populations. To describe and characterize the debris environment as reliably as possible, the current NASA Orbital Debris Engineering Model (ORDEM2000) is being upgraded to a new version based on new and better quality data. The data-driven ORDEM model covers a wide range of object sizes from 10 microns to greater than 1 meter. This paper reviews the statistical process for the estimation of the debris populations in the new ORDEM upgrade, and discusses the representation of large-size (greater than or equal to 1 m and greater than or equal to 10 cm) populations by SSN catalog objects and the validation of the statistical approach. Also, it presents results for the populations with sizes of greater than or equal to 3.3 cm, greater than or equal to 1 cm, greater than or equal to 100 micrometers, and greater than or equal to 10 micrometers. The orbital debris populations used in the new version of ORDEM are inferred from data based upon appropriate reference (or benchmark) populations instead of the binning of the multi-dimensional orbital-element space. This paper describes all of the major steps used in the population-inference procedure for each size-range. Detailed discussions on data analysis, parameter definition, the correlation between parameters and data, and uncertainty assessment are included
Momentum distribution of liquid helium
We have obtained the one--body density matrix and the momentum distribution
of liquid He at K from Diffusion Monte Carlo (DMC)
simulations, using trial functions optimized via the Euler Monte Carlo (EMC)
method. We find a condensate fraction smaller than in previous calculations.
Though we do not explicitly include long--range correlations in our
calculations, we get a momentum distribution at long wavelength which is
compatible with the presence of long--range correlations in the exact wave
function. We have also studied He, using fixed--node DMC, with nodes and
trial functions provided by the EMC. In particular, we analyze the momentum
distribution with respect to the discontinuity as well as the
singular behavior, at the Fermi surface. We also show that an approximate
factorization of the one-body density matrix
holds, with and respectively the density matrix of the
ideal Fermi gas and the density matrix of a Bose He.Comment: 10 pages, REVTeX, 12 figure
Two-dimensional array of microtraps with atomic shift register on a chip
Arrays of trapped atoms are the ideal starting point for developing registers
comprising large numbers of physical qubits for storing and processing quantum
information. One very promising approach involves neutral atom traps produced
on microfabricated devices known as atom chips, as almost arbitrary trap
configurations can be realised in a robust and compact package. Until now,
however, atom chip experiments have focused on small systems incorporating
single or only a few individual traps. Here we report experiments on a
two-dimensional array of trapped ultracold atom clouds prepared using a simple
magnetic-film atom chip. We are able to load atoms into hundreds of tightly
confining and optically resolved array sites. We then cool the individual atom
clouds in parallel to the critical temperature required for quantum degeneracy.
Atoms are shuttled across the chip surface utilising the atom chip as an atomic
shift register and local manipulation of atoms is implemented using a focused
laser to rapidly empty individual traps.Comment: 6 pages, 4 figure
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