11,827 research outputs found
Application development for multicore processor
With multicore processors now in every computer, server, and embedded device, the need for cost-effective, reliable parallel software has never been greater. The efficiency of single core processors does not match the necessary levels for the development of applications
On Spatial Consensus Formation: Is the Sznajd Model Different from a Voter Model?
In this paper, we investigate the so-called ``Sznajd Model'' (SM) in one
dimension, which is a simple cellular automata approach to consensus formation
among two opposite opinions (described by spin up or down). To elucidate the SM
dynamics, we first provide results of computer simulations for the
spatio-temporal evolution of the opinion distribution , the evolution of
magnetization , the distribution of decision times and
relaxation times . In the main part of the paper, it is shown that the
SM can be completely reformulated in terms of a linear VM, where the transition
rates towards a given opinion are directly proportional to frequency of the
respective opinion of the second-nearest neighbors (no matter what the nearest
neighbors are). So, the SM dynamics can be reduced to one rule, ``Just follow
your second-nearest neighbor''. The equivalence is demonstrated by extensive
computer simulations that show the same behavior between SM and VM in terms of
, , , , and the final attractor statistics. The
reformulation of the SM in terms of a VM involves a new parameter , to
bias between anti- and ferromagnetic decisions in the case of frustration. We
show that plays a crucial role in explaining the phase transition
observed in SM. We further explore the role of synchronous versus asynchronous
update rules on the intermediate dynamics and the final attractors. Compared to
the original SM, we find three additional attractors, two of them related to an
asymmetric coexistence between the opposite opinions.Comment: 22 pages, 20 figures. For related publications see
http://www.ais.fraunhofer.de/~fran
New AGNs discovered by H.E.S.S
During the last year, six new Active Galactic Nuclei (AGN) have been
discovered and studied by H.E.S.S. at Very High Energies (VHE). Some of these
recent discoveries have been made thanks to new enhanced analysis methods and
are presented at this conference for the first time. The three blazars 1ES
0414+009, SHBL J001355.9-185406 and 1RXS J101015.9-311909 have been targeted
for observation due to their high levels of radio and X-ray fluxes, while the
Fermi/LAT catalogue of bright sources triggered the observation of PKS 0447-439
and AP Librae. Additionally, the BL Lac 1ES 1312-423 was discovered in the
field-of-view (FoV) of Centaurus A thanks to the large exposure dedicated by
H.E.S.S. to this particularly interesting source. The newly-discovered sources
are presented here and in three companion presentations at this conference.Comment: 8 pages, 3 figures, proceeding from the 25th Texas Symposium on
Relativistic Astrophysics (Heidelberg, Germany, 2010
VHE Gamma-ray Afterglow Emission from Nearby GRBs
Gamma-ray Bursts (GRBs) are among the potential extragalactic sources of
very-high-energy (VHE) gamma-rays. We discuss the prospects of detecting VHE
gamma-rays with current ground-based Cherenkov instruments during the afterglow
phase. Using the fireball model, we calculate the synchrotron self-Compton
(SSC) emission from forward-shock electrons. The modeled results are compared
with the observational afterglow data taken with and/or the sensitivity level
of ground-based VHE instruments (e.g. STACEE, H.E.S.S., MAGIC, VERITAS, and
Whipple). We find that modeled SSC emission from bright and nearby bursts such
as GRB 030329 are detectable by these instruments even with a delayed
observation time of ~10 hours.Comment: Proceeding of "Heidelberg International Symposium on High Energy
Gamma-Ray Astronomy", held in Heidelberg, 7-11 July 2008, submitted to AIP
Conference Proceedings. 4 pages, 3 figures, 1 tabl
Computational Fluid Dynamic Studies of Vortex Amplifier Design for the Nuclear Industry—I. Steady-State Conditions
In this study the effects of changes to the geometry of a vortex amplifier are investigated using computational fluid dynamics (CFD) techniques, in the context of glovebox operations for the nuclear industry. These investigations were required because of anomalous behavior identified when, for operational reasons, a long-established vortex amplifier design was reduced in scale. The aims were (i) to simulate both the anomalous back-flow into the glovebox through the vortex amplifier supply ports, and the precessing vortex core in the amplifier outlet, then (ii) to determine which of the various simulated geometries would best alleviate the supply port back-flow anomaly. Various changes to the geometry of the vortex amplifier were proposed; smoke and air tests were then used to identify a subset of these geometries for subsequent simulation using CFD techniques. Having verified the mesh resolution was sufficient to reproduce the required effects, the code was then validated by comparing the results of the steady-state simulations with the experimental data. The problem is challenging in terms of the range of geometrical and dynamic scales encountered, with consequent impact on mesh quality and turbulence modeling. The anomalous nonaxisymmetric reverse flow in the supply ports of the vortex amplifier has been captured and the mixing in both the chamber and the precessing vortex core has also been successfully reproduced. Finally, by simulating changes to the supply ports that could not be reproduced experimentally at an equivalent cost, the geometry most likely to alleviate the back-flow anomaly has been identified
Exact Thermodynamics of the Double sinh-Gordon Theory in 1+1-Dimensions
We study the classical thermodynamics of a 1+1-dimensional double-well
sinh-Gordon theory. Remarkably, the Schrodinger-like equation resulting from
the transfer integral method is quasi-exactly solvable at several temperatures.
This allows exact calculation of the partition function and some correlation
functions above and below the short-range order (``kink'') transition, in
striking agreement with high resolution Langevin simulations. Interesting
connections with the Landau-Ginzburg and double sine-Gordon models are also
established.Comment: 4 pages, 3 figures (embedded using epsf), uses RevTeX plus macro
(included). Minor revision to match journal version, Phys. Rev. Lett. (in
press
Coexistence of Band Jahn Teller Distortion and superconductivity in correlated systems
The co-existence of band Jahn-Teller (BJT) effect with superconductivity (SC)
is studied for correlated systems, with orbitally degenerate bands using a
simple model. The Hubbard model for a doubly degenerate orbital with the
on-site intraorbital Coulomb repulsion treated in the slave boson formalism and
the interorbital Coulomb repulsion treated in the Hartree-Fock mean field
approximation, describes the correlated system. The model further incorporates
the BJT interaction and a pairing term to account for the lattice distortion
and superconductivity respectively. It is found that structural distortion
tends to suppress superconductivity and when SC sets in at low temperatures,
the growth of the lattice distortion is arrested. The phase diagram comprising
of the SC and structural transition temperatures and versus the
dopant concentration reveals that the highest obtainable for an
optimum doping is limited by structural transition. The dependence of the
occupation probabilities of the different bands as well as the density of
states (DOS) in the distorted-superconducting phase, on electron correlation
has been discussed.Comment: RevTex, 4 pages, 4 figuers (postscript files attached) Journal
Reference : Phys. Rev. B (accepted for publication
Electromagnetic transition from the 4 to 2 resonance in Be measured via the radiative capture in He+He
An earlier measurement on the 4 to 2 radiative transition in Be
provided the first electromagnetic signature of its dumbbell-like shape.
However, the large uncertainty in the measured cross section does not allow a
stringent test of nuclear structure models. The present paper reports a more
elaborate and precise measurement for this transition, via the radiative
capture in the He+He reaction, improving the accuracy by about a factor
of three. The {\it ab initio} calculations of the radiative transition strength
with improved three-nucleon forces are also presented. The experimental results
are compared with the predictions of the alpha cluster model and {\it ab
initio} calculations.Comment: 5 pages and 7 figures, Submitted to Physical Review Letter
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