702 research outputs found
Dynamical heat channels
We consider heat conduction in a 1D dynamical channel. The channel consists
of a group of noninteracting particles, which move between two heat baths
according to some dynamical process. We show that the essential thermodynamic
properties of the heat channel can be evaluated from the diffusion properties
of the underlying particles. Emphasis is put on the conduction under anomalous
diffusion conditions. \\{\bf PACS number}: 05.40.+j, 05.45.ac, 05.60.cdComment: 4 figure
Anomalous kinetics and transport from 1D self--consistent mode--coupling theory
We study the dynamics of long-wavelength fluctuations in one-dimensional (1D)
many-particle systems as described by self-consistent mode-coupling theory. The
corresponding nonlinear integro-differential equations for the relevant
correlators are solved analytically and checked numerically. In particular, we
find that the memory functions exhibit a power-law decay accompanied by
relatively fast oscillations. Furthermore, the scaling behaviour and,
correspondingly, the universality class depends on the order of the leading
nonlinear term. In the cubic case, both viscosity and thermal conductivity
diverge in the thermodynamic limit. In the quartic case, a faster decay of the
memory functions leads to a finite viscosity, while thermal conductivity
exhibits an even faster divergence. Finally, our analysis puts on a more firm
basis the previously conjectured connection between anomalous heat conductivity
and anomalous diffusion
Thermal conductivity of one-dimensional lattices with self-consistent heat baths: a heuristic derivation
We derive the thermal conductivities of one-dimensional harmonic and
anharmonic lattices with self-consistent heat baths (BRV lattice) from the
Single-Mode Relaxation Time (SMRT) approximation. For harmonic lattice, we
obtain the same result as previous works. However, our approach is heuristic
and reveals phonon picture explicitly within the heat transport process. The
results for harmonic and anharmonic lattices are compared with numerical
calculations from Green-Kubo formula. The consistency between derivation and
simulation strongly supports that effective (renormalized) phonons are energy
carriers in anharmonic lattices although there exist some other excitations
such as solitons and breathers.Comment: 4 pages, 3 figures. accepted for publication in JPS
Long time, large scale limit of the Wigner transform for a system of linear oscillators in one dimension
We consider the long time, large scale behavior of the Wigner transform
W_\eps(t,x,k) of the wave function corresponding to a discrete wave equation
on a 1-d integer lattice, with a weak multiplicative noise. This model has been
introduced in Basile, Bernardin, and Olla to describe a system of interacting
linear oscillators with a weak noise that conserves locally the kinetic energy
and the momentum. The kinetic limit for the Wigner transform has been shown in
Basile, Olla, and Spohn. In the present paper we prove that in the unpinned
case there exists such that for any the
weak limit of W_\eps(t/\eps^{3/2\gamma},x/\eps^{\gamma},k), as \eps\ll1,
satisfies a one dimensional fractional heat equation with . In the pinned case an analogous
result can be claimed for W_\eps(t/\eps^{2\gamma},x/\eps^{\gamma},k) but the
limit satisfies then the usual heat equation
Compact Modeling and Mitigation of Parasitics in Crosspoint Accelerators of Neural Networks
In-memory computing (IMC) can accelerate data-intensive tasks, such as matrix-vector multiplication (MVM) or artificial neural networks (ANNs) inference, by means of the crosspoint memory array, allowing to reduce time and energy consumption. IMC accuracy, however, is affected by nonidealities, such as variability of the conductive weights or IR drop along wires due to parasitic resistances, whose impact steeply increases with the increase of array size. This work proposes a compact model to assess the impact of nonidealities for various circuital implementations, together with architectural schemes for their mitigation based on replicated arrays. The proposed mitigation techniques allow to restore the ANN accuracy from 72.7% to 94.9%, close to the software accuracy of 96.9%, in view of an increased area and energy consumption
Controlling the energy flow in nonlinear lattices: a model for a thermal rectifier
We address the problem of heat conduction in 1-D nonlinear chains; we show
that, acting on the parameter which controls the strength of the on site
potential inside a segment of the chain, we induce a transition from conducting
to insulating behavior in the whole system. Quite remarkably, the same
transition can be observed by increasing the temperatures of the thermal baths
at both ends of the chain by the same amount. The control of heat conduction by
nonlinearity opens the possibility to propose new devices such as a thermal
rectifier.Comment: 4 pages with figures included. Phys. Rev. Lett., to be published
(Ref. [10] corrected
Temperature dependence of thermal conductivity in 1D nonlinear lattices
We examine the temperature dependence of thermal conductivity of one
dimensional nonlinear (anharmonic) lattices with and without on-site potential.
It is found from computer simulation that the heat conductivity depends on
temperature via the strength of nonlinearity. Based on this correlation, we
make a conjecture in the effective phonon theory that the mean-free-path of the
effective phonon is inversely proportional to the strength of nonlinearity. We
demonstrate analytically and numerically that the temperature behavior of the
heat conductivity is not universal for 1D harmonic lattices
with a small nonlinear perturbation. The computer simulations of temperature
dependence of heat conductivity in general 1D nonlinear lattices are in good
agreements with our theoretic predictions. Possible experimental test is
discussed.Comment: 6 pages and 2 figures. Accepted for publication in Europhys. Let
Anomalous thermal conductivity and local temperature distribution on harmonic Fibonacci chains
The harmonic Fibonacci chain, which is one of a quasiperiodic chain
constructed with a recursion relation, has a singular continuous
frequency-spectrum and critical eigenstates. The validity of the Fourier law is
examined for the harmonic Fibonacci chain with stochastic heat baths at both
ends by investigating the system size N dependence of the heat current J and
the local temperature distribution. It is shown that J asymptotically behaves
as (ln N)^{-1} and the local temperature strongly oscillates along the chain.
These results indicate that the Fourier law does not hold on the harmonic
Fibonacci chain. Furthermore the local temperature exhibits two different
distribution according to the generation of the Fibonacci chain, i.e., the
local temperature distribution does not have a definite form in the
thermodynamic limit. The relations between N-dependence of J and the
frequency-spectrum, and between the local temperature and critical eigenstates
are discussed.Comment: 10 pages, 4 figures, submitted to J. Phys.: Cond. Ma
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