278 research outputs found
Zero Temperature Hysteresis in Random Field Ising Model on Bethe Lattices: approach to mean field behavior with increasing coordination number z
We consider the analytic solution of the zero temperature hysteresis in the
random field Ising model on a Bethe lattice of coordination number , and
study how it approaches the mean field solution in the limit z-> \infty. New
analytical results concerning the energy of the system along the hysteresis
loop and first order reversal curves (FORC diagrams) are also presented.Comment: 4 pages, 4 figures, Submitted to PR
A new structured mathematical model of the composting process
Postprint (published version
Work distributions in the T=0 Random Field Ising Model
We perform a numerical study of the three-dimensional Random Field
Ising Model at T=0. We compare work distributions along metastable
trajectories obtained with the single-spin flip dynamics with the distribution
of the internal energy change along equilibrium trajectories. The goal is to
investigate the possibility of extending the Crooks fluctuation theorem to zero
temperature when, instead of the standard ensemble statistics, one considers
the ensemble generated by the quenched disorder. We show that a simple
extension of Crooks fails close to the disordered induced equilibrium phase
transition due to the fact that work and internal energy distributions are very
asymmetric
1D-Space dynamic mathematical model of the composting process
Mathematical modelling is a helpful tool to analyse complex systems, but its development and application to the composting process has been rather scarce up to date. The use of mathematical models is common in
complex biological processes such as the activated sludge wastewater treatment and the anaerobic digestion process, both systems operating on a single isothermal phase.Postprint (published version
Puntuación entre iguales para la evaluación del trabajo en equipo
La entrada en el EEES y la adopción de un sistema
de evaluación basado en competencias, algunas de
ellas no técnicas, hace que nos tengamos que plantear
algún tipo de cambio, no solo en la forma de enseñar,
sino también en la forma de evaluación. Evaluar,
por ejemplo, la actitud ante el trabajo, el trabajo
en equipo o la capacidad de innovación mediante un
examen resulta a todas luces poco apropiado, si no
imposible.
Es en este sentido que hemos experimentado durante
dos semestres la posibilidad de evaluación entre
iguales para la competencia genérica “trabajo en
equipo”. En este trabajo, presentamos la experiencia
y conclusiones extraídasPeer Reviewe
Line creep in paper peeling
The dynamics of a "peeling front" or an elastic line is studied under creep
(constant load) conditions. Our experiments show an exponential dependence of
the creep velocity on the inverse force (mass) applied. In particular, the
dynamical correlations of the avalanche activity are discussed here. We compare
various avalanche statistics to those of a line depinning model with non-local
elasticity, and study various measures of the experimental avalanche-avalanche
and temporal correlations such as the autocorrelation function of the released
energy and aftershock activity. From all these we conclude, that internal
avalanche dynamics seems to follow "line depinning" -like behavior, in rough
agreement with the depinning model. Meanwhile, the correlations reveal subtle
complications not implied by depinning theory. Moreover, we also show how these
results can be understood from a geophysical point of view.Comment: 22 pages, 14 fig
The magnetization-driven random field Ising model at T=0
We study the hysteretic evolution of the random field Ising model (RFIM) at
T=0 when the magnetization M is controlled externally and the magnetic field H
becomes the output variable. The dynamics is a simple modification of the
single-spin-flip dynamics used in the H-driven situation and consists in
flipping successively the spins with the largest local field. This allows to
perform a detailed comparison between the microscopic trajectories followed by
the system with the two protocols. Simulations are performed on random graphs
with connectivity z=4 (Bethe lattice) and on the 3-D cubic lattice. The same
internal energy U(M)is found with the two protocols when there is no
macroscopic avalanche and it does not depend on whether the microscopic states
are stable or not. On the Bethe lattice, the energy inside the macroscopic
avalanche also coincides with the one that is computed analytically with the
H-driven algorithm along the unstable branch of the hysteresis loop. The output
field, defined here as dU/dM, exhibits very large fluctuations with the
magnetization and is not self-averaging. Relation to the experimental situation
is discussed.Comment: 11 pages, 13 figure
Dynamic hysteresis in the rheology of complex fluids
Recently, rheological hysteresis has been studied systematically in a wide range of complex fluids combining global rheology and time-resolved velocimetry. In this paper we present an analysis of the roles of the three most fundamental mechanisms in simple-yield-stress fluids: structure dynamics, viscoelastic response, and spatial flow heterogeneities, i.e., time-dependent shear bands. Dynamical hysteresis simulations are done analogously to rheological ramp-up and -down experiments on a coupled model which incorporates viscoelasticity and time-dependent structure evolution. Based on experimental data, a coupling between hysteresis measured from the local velocity profiles and that measured from the global flow curve has been suggested. According to the present model, even if transient shear banding appears during the shear ramps, in typical narrow-gap devices, only a small part of the hysteretic response can be attributed to heterogeneous flow. This results in decoupling of the hysteresis measured from the local velocity profiles and the global flow curve, demonstrating that for an arbitrary time-dependent rheological response this proposed coupling can be very weak.Peer reviewe
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