52,681 research outputs found
Near-earth thermal environmental criteria study
A study was made to determine improved values and definitions to be used for thermal environmental design parameters for a spacecraft in near-earth orbit. An algorithm was used to derive a total earth thermal radiation based on a mathematical relationship. Several albedo and earth thermal radiation grid maps were produced on seven track digital magnetic tape. Each map contained the values obtained during a 24 hour period over the entire earth. The output statistics are summarized, and the data processing program is described
Correlation of stress-wave-emission characteristics with fracture in aluminum alloys, 1 September - 1 December 1969
Cryogenic testing of aluminum alloy specimens for fracture toughness and stress wave dat
Newtonian and Relativistic Cosmologies
Cosmological N-body simulations are now being performed using Newtonian
gravity on scales larger than the Hubble radius. It is well known that a
uniformly expanding, homogeneous ball of dust in Newtonian gravity satisfies
the same equations as arise in relativistic FLRW cosmology, and it also is
known that a correspondence between Newtonian and relativistic dust cosmologies
continues to hold in linearized perturbation theory in the marginally
bound/spatially flat case. Nevertheless, it is far from obvious that Newtonian
gravity can provide a good global description of an inhomogeneous cosmology
when there is significant nonlinear dynamical behavior at small scales. We
investigate this issue in the light of a perturbative framework that we have
recently developed, which allows for such nonlinearity at small scales. We
propose a relatively straightforward "dictionary"---which is exact at the
linearized level---that maps Newtonian dust cosmologies into general
relativistic dust cosmologies, and we use our "ordering scheme" to determine
the degree to which the resulting metric and matter distribution solve
Einstein's equation. We find that Einstein's equation fails to hold at "order
1" at small scales and at "order " at large scales. We then find the
additional corrections to the metric and matter distribution needed to satisfy
Einstein's equation to these orders. While these corrections are of some
interest in their own right, our main purpose in calculating them is that their
smallness should provide a criterion for the validity of the original
dictionary (as well as simplified versions of this dictionary). We expect that,
in realistic Newtonian cosmologies, these additional corrections will be very
small; if so, this should provide strong justification for the use of Newtonian
simulations to describe relativistic cosmologies, even on scales larger than
the Hubble radius.Comment: 35 pages; minor change
The Molonglo Galactic Plane Survey (MGPS-2): Compact Source Catalogue
We present the first data release from the second epoch Molonglo Galactic
Plane Survey (MGPS-2). MGPS-2 was carried out with the Molonglo Observatory
Synthesis Telescope at a frequency of 843 MHz and with a restoring beam of 45
arcsec x 45 arcsec cosec(dec), making it the highest resolution large scale
radio survey of the southern Galactic plane. It covers the range |b| < 10 deg
and 245 deg < l < 365 deg and is the Galactic counterpart to the Sydney
University Molonglo Sky Survey (SUMSS) which covers the whole southern sky with
dec 10 deg).
In this paper we present the MGPS-2 compact source catalogue. The catalogue
has 48,850 sources above a limiting peak brightness of 10 mJy/beam. Positions
in the catalogue are accurate to 1 arcsec - 2 arcsec. A full catalogue
including extended sources is in preparation. We have carried out an analysis
of the compact source density across the Galactic plane and find that the
source density is not statistically higher than the density expected from the
extragalactic source density alone.
We also present version 2.0 of the SUMSS image data and catalogue which are
now available online. The data consists of 629 4.3 deg x 4.3 deg mosaic images
covering the 8100 deg^2 of sky with dec 10 deg. The
catalogue contains 210,412 radio sources to a limiting peak brightness of 6
mJy/beam at dec -50 deg. We describe the
updates and improvements made to the SUMSS cataloguing process.Comment: 12 pages, 9 figures, to be published in MNRAS Note that Figures 8 and
9 are much lower resolution than in the published versio
Quantum and Classical in Adiabatic Computation
Adiabatic transport provides a powerful way to manipulate quantum states. By
preparing a system in a readily initialised state and then slowly changing its
Hamiltonian, one may achieve quantum states that would otherwise be
inaccessible. Moreover, a judicious choice of final Hamiltonian whose
groundstate encodes the solution to a problem allows adiabatic transport to be
used for universal quantum computation. However, the dephasing effects of the
environment limit the quantum correlations that an open system can support and
degrade the power of such adiabatic computation. We quantify this effect by
allowing the system to evolve over a restricted set of quantum states,
providing a link between physically inspired classical optimisation algorithms
and quantum adiabatic optimisation. This new perspective allows us to develop
benchmarks to bound the quantum correlations harnessed by an adiabatic
computation. We apply these to the D-Wave Vesuvius machine with revealing -
though inconclusive - results
1-loop contribution to the dynamical exponents in spin glasses
We evaluate the corrections to the mean field values of the and the
exponents at the first order in the -expansion, for . We find
that both and are decreasing when the space dimension decreases.Comment: 12 pages 3 Postscript figure
Monitoring of crack growth in Ti-Al-4v alloy by the stress wave analysis technique
Stress wave analysis techniques for monitoring crack growth in Ti-6Al-4V alloy pressure vessel wall
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