8,953 research outputs found
Radio and X-ray study of two multi-shell Supernova Remnants: Kes79 and G352.7-0.1
We investigate two multi-shell galactic supernova remnants (SNRs), Kes79 and
G352.7-0.1, to understand the causes of such morphology. The research was
carried out based on new and reprocessed archival VLA observations and
XMM-Newton archival data. The surrounding was investigated based on data
extracted from the HI Canadian Galactic Plane Survey, the 13^CO Galactic Ring
Survey and the HI Southern Galactic Plane Survey. The present study revealed
that the overall morphology of both SNRs is the result of the mass-loss history
of their respective progenitor stars. Kes79 would be the product of the
gravitational collapse of a massive O9 star evolving near a molecular cloud and
within the precursor's wind-driven bubble, while G352.7-0.1 would be the result
of interactions of the SNR with an asymmetric wind from the progenitor together
with projection effects. No radio point source or pulsar wind nebula was found
associated with the X-ray pulsar CXOU J185238.6+004020 in Kes79. The X-ray
study of G352.7-0.1, on its hand, revealed that most of the thermal X-ray
radiation completely fills in the interior of the remnant and originates in
heated ejecta. Characteristic parameters, like radio flux, radio spectral
index, age, distance, shock velocity, initial energy and luminosity, were
estimated for both SNRs.Comment: 14 pages, 13 figures. Accepted to be published in Astronomy and
Astrophysic
Peak Effect in Superconductors: Absence of Phase Transition and Possibility of Jamming in Vortex Matter
The magnetic field dependence of the critical current for the
vortex phase of a disordered superconductor is studied numerically at zero
temperature. The increases rapidly near the upper critical field
similar to the peak effect (PE) phenomenon observed in many
superconductors. The real space configuration across the PE changes
continuously from a partially ordered domain (polycrystalline) state into an
amorphous state. The topological defect density
with for . There is no evidence of a phase transition in
the vicinity of the PE suggesting that an order-disorder transition is not
essential for the occurrence of the PE phenomenon. An alternative view is
presented wherein the vortex system with high dislocation density undergoes
jamming at the onset of the PE.Comment: 8 pages and 5 figure
Strongly nonequilibrium flux flow in the presence of perforating submicron holes
We report on the effects of perforating submicron holes on the vortex
dynamics of amorphous Nb0.7Ge0.3 microbridges in the strongly nonequilibrium
mixed state, when vortex properties change substantially. In contrast to the
weak nonequilibrium - when the presence of holes may result in either an
increase (close to Tc) or a decrease (well below Tc) of the dissipation, in the
strong nonequilibrium an enhanced dissipation is observed irrespectively of the
bath temperature. Close to Tc this enhancement is similar to that in the weak
nonequilibrium, but corresponds to vortices shrunk due to the
Larkin-Ovchinnikov mechanism. At low temperatures the enhancement is a
consequence of a weakening of the flux pinning by the holes in a regime where
electron heating dominates the superconducting properties.Comment: 6 pages, 5 figure
Modelling the forming mechanics of engineering fabrics using a mutually constrained pantographic beam and membrane mesh
A method of combining 1-d and 2-d structural finite elements to capture the fundamental mechanical properties of engineering fabrics subject to finite strains is introduced. A mutually constrained pantographic beam and membrane mesh is presented and simple homogenisation theory is developed to relate the macro-scale properties of the mesh to the properties of the elements within the mesh. The theory shows that each of the macro-scale properties of the mesh can be independently controlled. An investigation into the performance of the technique is conducted using tensile, cantilever bending and uniaxial bias extension shear simulations. The simulations are first used to verify the accuracy of the homogenisation theory and then used to demonstrate the ability of the modelling approach in accurately predicting the shear force, shear kinematics and out-of-plane wrinkling behaviour of engineering fabrics
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