149 research outputs found
On Properties of Boundaries and Electron Conductivity in Mesoscopic Polycrystalline Silicon Films for Memory Devices
We present the results of molecular dynamics modeling on the structural
properties of grain boundaries (GB) in thin polycrystalline films. The
transition from crystalline boundaries with low mismatch angle to amorphous
boundaries is investigated. It is shown that the structures of the GBs satisfy
a thermodynamical criterion. The potential energy of silicon atoms is closely
related with a geometrical quantity -- tetragonality of their coordination with
their nearest neighbors. A crossover of the length of localization is observed.
To analyze the crossover of the length of localization of the single-electron
states and properties of conductance of the thin polycrystalline film at low
temperature, we use a two-dimensional Anderson localization model, with the
random one-site electron charging energy for a single grain (dot), random
non-diagonal matrix elements, and random number of connections between the
neighboring grains. The results on the crossover behavior of localization
length of the single-electron states and characteristic properties of
conductance are presented in the region of parameters where the transition from
an insulator to a conductor regimes takes place.Comment: 8 pages, 3 figure
Filling a silo with a mixture of grains: Friction-induced segregation
We study the filling process of a two-dimensional silo with inelastic
particles by simulation of a granular media lattice gas (GMLG) model. We
calculate the surface shape and flow profiles for a monodisperse system and we
introduce a novel generalization of the GMLG model for a binary mixture of
particles of different friction properties where, for the first time, we
measure the segregation process on the surface. The results are in good
agreement with a recent theory, and we explain the observed small deviations by
the nonuniform velocity profile.Comment: 10 pages, 5 figures, to be appear in Europhys. Let
Multi-component lattice-Boltzmann model with interparticle interaction
A previously proposed [X. Shan and H. Chen, Phys. Rev. E {\bf 47}, 1815,
(1993)] lattice Boltzmann model for simulating fluids with multiple components
and interparticle forces is described in detail. Macroscopic equations
governing the motion of each component are derived by using Chapman-Enskog
method. The mutual diffusivity in a binary mixture is calculated analytically
and confirmed by numerical simulation. The diffusivity is generally a function
of the concentrations of the two components but independent of the fluid
velocity so that the diffusion is Galilean invariant. The analytically
calculated shear kinematic viscosity of this model is also confirmed
numerically.Comment: 18 pages, compressed and uuencoded postscript fil
Spurious diffusion in particle simulations of the Kolmogorov flow
Particle simulations of the Kolmogorov flow are analyzed by the
Landau-Lifshitz fluctuating hydrodynamics. It is shown that a spurious
diffusion of the center of mass corrupts the statistical properties of the
flow. The analytical expression for the corresponding diffusion coefficient is
derived.Comment: 10 pages, no figure
Galilean invariance of lattice Boltzmann models
It is well-known that the original lattice Boltzmann (LB) equation deviates
from the Navier-Stokes equations due to an unphysical velocity dependent
viscosity. This unphysical dependency violates the Galilean invariance and
limits the validation domain of the LB method to near incompressible flows. As
previously shown, recovery of correct transport phenomena in kinetic equations
depends on the higher hydrodynamic moments. In this Letter, we give specific
criteria for recovery of various transport coefficients. The Galilean
invariance of a general class of LB models is demonstrated via numerical
experiments
Hydrodynamics of thermal granular convection
A hydrodynamic theory is formulated for buoyancy-driven ("thermal") granular
convection, recently predicted in molecular dynamic simulations and observed in
experiment. The limit of a dilute flow is considered. The problem is fully
described by three scaled parameters. The convection occurs via a supercritical
bifurcation, the inelasticity of the collisions being the control parameter.
The theory is expected to be valid for small Knudsen numbers and nearly elastic
grain collisions.Comment: 4 pages, 4 EPS figures, some details adde
Quantum interference experiments, modular variables and weak measurements
We address the problem of interference using the Heisenberg picture and
highlight some new aspects through the use of pre-selection, post-selection,
weak measurements, and modular variables, We present a physical explanation for
the different behaviors of a single particle when the distant slit is open or
closed: instead of having a quantum wave that passes through all slits, we have
a localized particle with non-local interactions with the other slit(s). We
introduce a Gedankenexperiment to measure this non-local exchange. While the
Heisenberg picture and the Schrodinger pictures are equivalent formulations of
quantum mechanics, nevertheless, the results discussed here support a new
approach which has led to new insights, new intuitions, new experiments, and
even the possibility of new devices that were missed from the old perspective
Shock-Like Dynamics of Inelastic Gases
We provide a simple physical picture which suggests that the asymptotic
dynamics of inelastic gases in one dimension is independent of the degree of
inelasticity. Statistical characteristics, including velocity fluctuations and
the velocity distribution are identical to those of a perfectly inelastic
sticky gas, which in turn is described by the inviscid Burgers equation.
Asymptotic predictions of this continuum theory, including the t^{-2/3}
temperature decay and the development of discontinuities in the velocity
profile, are verified numerically for inelastic gases.Comment: 4 pages, 5 figures, revte
The Influence of Superpositional Wave Function Oscillations on Shor's Quantum Algorithm
We investigate the influence of superpositional wave function oscillations on
the performance of Shor's quantum algorithm for factorization of integers. It
is shown that the wave function oscillations can destroy the required quantum
interference. This undesirable effect can be routinely eliminated using a
resonant pulse implementation of quantum computation, but requires special
analysis for non-resonant implementations.Comment: 4 pages, NO figures, revte
- …