125 research outputs found
Branching mechanism of intergranular crack propagation in three dimensions
We investigate the process of slow intergranular crack propagation by the
finite element method model, and show that branching is induced by partial
arresting of crack front owing to the geometrical randomness of grain
boundaries. A possible scenario for branching instability of crack propagation
in disordered continuum medium is also discussed.Comment: 4 pages, submitted to Phys.Rev.E; v2:corrected typos v3: final
version to be publishe
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
Sub-parsec-scale Accleration of the Radio Jet in the Powerful Radio Galaxy NGC 6251
In order to investigate the genesis of powerful radio jet, we have mapped the
central 10 pc region of the nearby radio galaxy NGC 6251 with a 0.2 pc
resolution using Very Long Baseline Interferometer (VLBI) at two radio
frequencies, 5 GHz and 15 GHz, we have found the sub-parsec-scale counterjet
for the first time in this radio galaxy. This discovery allows us to
investigate the jet acceleration based on the relativistic beaming model.Comment: 7 pages with 7 figures. To appear in PASJ, 52, No. 5, Oct. 25, 200
Heat conduction in the diatomic Toda lattice revisited
The problem of the diverging thermal conductivity in one-dimensional (1-D)
lattices is considered. By numerical simulations, it is confirmed that the
thermal conductivity of the diatomic Toda lattice diverges, which is opposite
to what one has believed before. Also the diverging exponent is found to be
almost the same as the FPU chain. It is reconfirmed that the diverging thermal
conductivity is universal in 1-D systems where the total momentum preserves.Comment: 3 pages, 3 figures. To appear in Phys. Rev.
Divergent Thermal Conductivity in Three-dimensional Nonlinear lattices
Heat conduction in three-dimensional nonlinear lattices is investigated using
a particle dynamics simulation. The system is a simple three-dimensional
extension of the Fermi-Pasta-Ulam (FPU-) nonlinear lattices, in
which the interparticle potential has a biquadratic term together with a
harmonic term. The system size is , and the heat is made to
flow in the direction the Nose-Hoover method. Although a linear
temperature profile is realized, the ratio of enerfy flux to temperature
gradient shows logarithmic divergence with . The autocorrelation function of
energy flux is observed to show power-law decay as ,
which is slower than the decay in conventional momentum-cnserving
three-dimensional systems (). Similar behavior is also observed in
the four dimensional system.Comment: 4 pages, 5 figures. Accepted for publication in J. Phys. Soc. Japan
Letter
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
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