15,973 research outputs found
A new class of -d topological superconductor with topological classification
The classification of topological states of matter depends on spatial
dimension and symmetry class. For non-interacting topological insulators and
superconductors the topological classification is obtained systematically and
nontrivial topological insulators are classified by either integer or .
The classification of interacting topological states of matter is much more
complicated and only special cases are understood. In this paper we study a new
class of topological superconductors in dimensions which has
time-reversal symmetry and a spin conservation symmetry. We
demonstrate that the superconductors in this class is classified by
when electron interaction is considered, while the
classification is without interaction.Comment: 5 pages main text and 3 pages appendix. 1 figur
Improved three-dimensional color-gradient lattice Boltzmann model for immiscible multiphase flows
In this paper, an improved three-dimensional color-gradient lattice Boltzmann
(LB) model is proposed for simulating immiscible multiphase flows. Compared
with the previous three-dimensional color-gradient LB models, which suffer from
the lack of Galilean invariance and considerable numerical errors in many cases
owing to the error terms in the recovered macroscopic equations, the present
model eliminates the error terms and therefore improves the numerical accuracy
and enhances the Galilean invariance. To validate the proposed model, numerical
simulation are performed. First, the test of a moving droplet in a uniform flow
field is employed to verify the Galilean invariance of the improved model.
Subsequently, numerical simulations are carried out for the layered two-phase
flow and three-dimensional Rayleigh-Taylor instability. It is shown that, using
the improved model, the numerical accuracy can be significantly improved in
comparison with the color-gradient LB model without the improvements. Finally,
the capability of the improved color-gradient LB model for simulating dynamic
multiphase flows at a relatively large density ratio is demonstrated via the
simulation of droplet impact on a solid surface.Comment: 9 Figure
Non-canonical statistics of finite quantum system
The canonical statistics describes the statistical properties of an open
system by assuming its coupling with the heat bath infinitesimal in comparison
with the total energy in thermodynamic limit. In this paper, we generally
derive a non-canonical distribution for the open system with a finite coupling
to the heat bath, which deforms the energy shell to effectively modify the
conventional canonical way. The obtained non-canonical distribution reflects
the back action of system on the bath, and thus depicts the statistical
correlations through energy fluctuations
Modeling thermal response of polymer composite hydrogen cylinders subjected to external fires
With the anticipated introduction of hydrogen fuel cell vehicles to the market, there is an increasing need to address the fire resistance of hydrogen cylinders for onboard storage. Sufficient fire resistance is essential to ensure safe evacuation in the event of car fire accidents. The authors have developed a Finite Element (FE) model for predicting the thermal response of composite hydrogen cylinders within the frame of the open source FE code Elmer. The model accounts for the decomposition of the polymer matrix and effects of volatile gas transport in the composite. Model comparison with experimental data has been conducted using a classical one-dimensional test case of polymer composite subjected to fire. The validated model was then used to analyze a type-4 hydrogen cylinder subjected to an engulfing external propane fire, mimicking a published cylinder fire experiment. The external flame is modelled and simulated using the open source code FireFOAM. A simplified failure criteria based on internal pressure increase is subsequently used to determine the cylinder fire resistance
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