1,545,789 research outputs found
Linear Solar Models: a simple tool to investigate the properties of solar interior
We describe a simple method to study the dependence of the solar properties
on a generic (small) modification the physical inputs adopted in standard solar
models calculations.Comment: 3 pages, proceeding of the TAUP09 Worksho
Dynamics of particle-particle collisions in a viscous liquid
When two solid spheres collide in a liquid, the dynamic collision process is slowed by viscous dissipation and the increased pressure in the interparticle gap as compared with dry collisions. This paper investigates liquid-immersed head-on and oblique collisions, which complements previously investigated particle-on-wall immersed collisions. By defining the normal from the line of centers at contact, the experimental findings support the decomposition of an oblique collision into its normal and tangential components of motion. The normal relative particle motion is characterized by an effective coefficient of restitution and a binary Stokes number with a correlation that follows the particle-wall results. The tangential motion is described by a collision model using a normal coefficient of restitution and a friction coefficient that are modified for the liquid effects
Vortex states in nanoscale superconducting squares: the influence of quantum confinement
Bogoliubov-de Gennes theory is used to investigate the effect of the size of
a superconducting square on the vortex states in the quantum confinement
regime. When the superconducting coherence length is comparable to the Fermi
wavelength, the shape resonances of the superconducting order parameter have
strong influence on the vortex configuration. Several unconventional vortex
states, including asymmetric ones, giant multi-vortex combinations, and states
comprising giant antivortex, were found as ground states and their stability
was found to be very sensitive on the value of , the size of the
sample , and the magnetic flux . By increasing the temperature and/or
enlarging the size of the sample, quantum confinement is suppressed and the
conventional mesoscopic vortex states as predicted by the Ginzburg-Laudau (GL)
theory are recovered. However, contrary to the GL results we found that the
states containing symmetry-induced vortex-antivortex pairs are stable over the
whole temperature range. It turns out that the inhomogeneous order parameter
induced by quantum confinement favors vortex-antivortex molecules, as well as
giant vortices with a rich structure in the vortex core - unattainable in the
GL domain
Solving the electrical control of magnetic coercive field paradox
The ability to tune magnetic properties of solids via electric voltages instead of external magnetic fields is a physics curiosity of great scientific and technological importance. Today, there is strong published experimental evidence of electrical control of magnetic coercive fields in composite multiferroic solids. Unfortunately, the literature indicates highly contradictory results. In some studies, an applied voltage increases the magnetic coercive field and in other studies the applied voltage decreases the coercive field of composite multiferroics. Here, we provide an elegant explanation to this paradox and we demonstrate why all reported results are in fact correct. It is shown that for a given polarity of the applied voltage, the magnetic coercive field depends on the sign of two tensor components of the multiferroic solid: magnetostrictive and piezoelectric coefficient. For a negative applied voltage, the magnetic coercive field decreases when the two material parameters have the same sign and increases when they have opposite signs, respectively. The effect of the material parameters is reversed when the same multiferroic solid is subjected to a positive applied voltage
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