5,105 research outputs found
Progress satellite: An automatic cargo spacecraft
The requirement for resupplying long term orbital space stations is discussed. The operation of Progress (an unmanned automatic resupply spacecraft) is described. It concludes that the development of Progress is a major contribution of Soviet science to domestic and world aeronautics
Precision Quantum Hall Resistance Measurement on Epitaxial Graphene Device in Low Magnetic Field
Precision quantum Hall resistance (QHR) measurements were performed on
large-area epitaxial graphene device at low magnetic fields (B = 2 T - 8 T) at
temperature T = 1.5 K. Hall resistance was measured using Cryogenic Current
Comparator resistance bridge with high biasing current Isd = 40 micro ampere.
The results showed that at B = 8 T the relative deviation of Hall resistance
from the expected quantized value h/2e2 is within experimental uncertainty of
3.5 parts in 108 and remained below 0.35 parts per million (ppm) down to B = 3
T
Transport of the repulsive Bose-Einstein condensate in a double-well trap: interaction impact and relation to Josephson effect
Two aspects of the transport of the repulsive Bose-Einstein condensate (BEC)
in a double-well trap are inspected: impact of the interatomic interaction and
analogy to the Josephson effect. The analysis employs a numerical solution of
3D time-dependent Gross-Pitaevskii equation for a total order parameter
covering all the trap. The population transfer is driven by a time-dependent
shift of a barrier separating the left and right wells. Sharp and soft profiles
of the barrier velocity are tested. Evolution of the relevant characteristics,
involving phase differences and currents, is inspected. It is shown that the
repulsive interaction substantially supports the transfer making it possible i)
in a wide velocity interval and ii) three orders of magnitude faster than in
the ideal BEC. The transport can be approximately treated as the d.c. Josephson
effect. A dual origin of the critical barrier velocity (break of adiabatic
following and d.c.-a.c. transition) is discussed. Following the calculations,
robustness of the transport (d.c.) crucially depends on the interaction and
barrier velocity profile. Only soft profiles which minimize undesirable dipole
oscillations are acceptable.Comment: 10 pages, 8 figures, accepted by Laser Physis. arXiv admin note: text
overlap with arXiv:1312.2750 The replaced version has a few corrections and
additional reference
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