97 research outputs found
Heat conductivity in the presence of a quantized degree of freedom
We propose a model with a quantized degree of freedom to study the heat
transport in quasi-one dimensional system. Our simulations reveal three
distinct temperature regimes. In particular, the intermediate regime is
characterized by heat conductivity with a temperature exponent much
greater than 1/2 that was generally found in systems with point-like particles.
A dynamical investigation indicates the occurrence of non-equipartition
behavior in this regime. Moreover, the corresponding Poincar\'e section also
shows remarkably characteristic patterns, completely different from the cases
of point-like particles.Comment: 7 pages, 4 figure
Self-Similar Solutions for Viscous and Resistive ADAF
In this paper, the self-similar solution of resistive advection dominated
accretion flows (ADAF) in the presence of a pure azimuthal magnetic field is
investigated. The mechanism of energy dissipation is assumed to be the
viscosity and the magnetic diffusivity due to turbulence in the accretion flow.
It is assumed that the magnetic diffusivity and the kinematic viscosity are not
constant and vary by position and -prescription is used for them. In
order to solve the integrated equations that govern the behavior of the
accretion flow, a self-similar method is used. The solutions show that the
structure of accretion flow depends on the magnetic field and the magnetic
diffusivity. As, the radial infall velocity and the temperature of the flow
increase, and the rotational velocity decreases. Also, the rotational velocity
for all selected values of magnetic diffusivity and magnetic field is
sub-Keplerian. The solutions show that there is a certain amount of magnetic
field that the rotational velocity of the flow becomes zero. This amount of the
magnetic field depends on the gas properties of the disc, such as adiabatic
index and viscosity, magnetic diffusivity, and advection parameters. The
solutions show the mass accretion rate increases by adding the magnetic
diffusivity and in high magnetic pressure case, the ratio of the mass accretion
rate to the Bondi accretion rate decreases as magnetic field increases. Also,
the study of Lundquist and magnetic Reynolds numbers based on resistivity
indicates that the linear growth of magnetorotational instability (MRI) of the
flow decreases by resistivity. This property is qualitatively consistent with
resistive magnetohydrodynamics (MHD) simulations.Comment: 18 pages, 3 figures, accepted by JA&
Heat conduction in one dimensional nonintegrable systems
Two classes of 1D nonintegrable systems represented by the Fermi-Pasta-Ulam
(FPU) model and the discrete model are studied to seek a generic
mechanism of energy transport in microscopic level sustaining macroscopic
behaviors. The results enable us to understand why the class represented by the
model has a normal thermal conductivity and the class represented by
the FPU model does not even though the temperature gradient can be established.Comment: 4 Revtex Pages, 4 Eps figures included, to appear in Phys. Rev. E,
March 200
Heat conduction in a 1D harmonic chain with three dimensional vibrations
We study vibrational energy transport in a quasi 1-D harmonic chain with both
longitudinal and transverse vibrations. We demonstrate via both numerical
simulation and theoretic analysis that for 1-D atomic chain connected by 3D
harmonic springs, the coefficient of heat conduction changes it continuously
with its lattice constant, indicating the qualitative difference from the
corresponding 1-D case where the coefficient is independent of the lattice
constant.Comment: 4 pages, 4 figure
- …