21,357 research outputs found
Skylab atmospheric contamination control
The Skylab contamination removal systems, preflight analysis and testing, and flight results are described. Results indicate that the combination of materials selection, the onboard removal devices, and the offgassing tests proved to be an effective means of controlling spacecraft contaminant levels
A semiclassical theory of quantum noise in open chaotic systems
We consider the quantum evolution of classically chaotic systems in contact
with surroundings. Based on -scaling of an equation for time evolution
of the Wigner's quasi-probability distribution function in presence of
dissipation and thermal diffusion we derive a semiclassical equation for
quantum fluctuations. This identifies an early regime of evolution dominated by
fluctuations in the curvature of the potential due to classical chaos and
dissipation. A stochastic treatment of this classical fluctuations leads us to
a Fokker-Planck equation which is reminiscent of Kramers' equation for
thermally activated processes. This reveals an interplay of three aspects of
evolution of quantum noise in weakly dissipative open systems; the reversible
Liouville flow, the irreversible chaotic diffusion which is characteristic of
the system itself, and irreversible dissipation induced by the external
reservoir. It has been demonstrated that in the dissipation-free case a
competition between Liouville flow in the contracting direction of phase space
and chaotic diffusion sets a critical width in the Wigner function for quantum
fluctuations. We also show how the initial quantum noise gets amplified by
classical chaos and ultimately equilibrated under the influence of dissipation.
We establish that there exists a critical limit to the expansion of phase
space. The limit is determined by chaotic diffusion and dissipation. Making use
of appropriate quantum-classical correspondence we verify the semiclassical
analysis by the fully quantum simulation in a chaotic quartic oscillator.Comment: Plain Latex, 27 pages, 6 ps figure, To appear in Physica
MEA/A-1 experiment 81F01 conducted on STS-7 flight, June 1983. Containerless processing of glass forming melts
The space processing of containerless, glassforming melts on board the space shuttle flight STS-7 is investigated. Objectives include; (1) obtain quantitative evidence for the supression of heterogeneous nucleation/crystallization, (2) study melt homogenization without gravity driven convection, (3) procedural development for bubble free, high purity homogeneous melts inmicro-g, (4) comparative analysis of melts on Earth and in micro g, and (5) assess the apparatus for processing multicomponent, glass forming melts in a low gravity environment
Spacelab baseline ECS trace contaminant removal test program
An estimate of the Spacelab Baseline Environmental Control System's contaminated removal capability was required to allow determination of the need for a supplemental trace contaminant removal system. Results from a test program to determine this removal capability are presented
- …