5,050 research outputs found
Uniqueness of the thermodynamic limit for driven disordered elastic interfaces
We study the finite size fluctuations at the depinning transition for a
one-dimensional elastic interface of size displacing in a disordered medium
of transverse size with periodic boundary conditions, where
is the depinning roughness exponent and is a finite aspect ratio
parameter. We focus on the crossover from the infinitely narrow () to
the infinitely wide () medium. We find that at the thermodynamic
limit both the value of the critical force and the precise behavior of the
velocity-force characteristics are {\it unique} and -independent. We also
show that the finite size fluctuations of the critical force (bias and
variance) as well as the global width of the interface cross over from a
power-law to a logarithm as a function of . Our results are relevant for
understanding anisotropic size-effects in force-driven and velocity-driven
interfaces.Comment: 10 pages, 12 figure
Frictional dynamics of viscoelastic solids driven on a rough surface
We study the effect of viscoelastic dynamics on the frictional properties of
a (mean field) spring-block system pulled on a rough surface by an external
drive. When the drive moves at constant velocity V, two dynamical regimes are
observed: at fast driving, above a critical threshold Vc, the system slides at
the drive velocity and displays a friction force with velocity weakening. Below
Vc the steady sliding becomes unstable and a stick-slip regime sets in. In the
slide-hold-slide driving protocol, a peak of the friction force appears after
the hold time and its amplitude increases with the hold duration. These
observations are consistent with the frictional force encoded
phenomenologically in the rate-and-state equations. Our model gives a
microscopical basis for such macroscopic description.Comment: 10 figures, 7 pages, +4 pages of appendi
Coastal Area Prone to Extreme Flood and Erosion Events Induced by Climate Changes: Study Case of Juqueriquere River Bar Navigation, Caraguatatuba (Sao Paulo State), Brazil
Tuning spreading and avalanche-size exponents in directed percolation with modified activation probabilities
We consider the directed percolation process as a prototype of systems
displaying a nonequilibrium phase transition into an absorbing state. The model
is in a critical state when the activation probability is adjusted at some
precise value p_c. Criticality is lost as soon as the probability to activate
sites at the first attempt, p1, is changed. We show here that criticality can
be restored by "compensating" the change in p1 by an appropriate change of the
second time activation probability p2 in the opposite direction. At
compensation, we observe that the bulk exponents of the process coincide with
those of the normal directed percolation process. However, the spreading
exponents are changed, and take values that depend continuously on the pair
(p1, p2). We interpret this situation by acknowledging that the model with
modified initial probabilities has an infinite number of absorbing states.Comment: 9 pages, 11 figure
Seismic cycles, size of the largest events, and the avalanche size distribution in a model of seismicity
We address several questions on the behavior of a numerical model recently
introduced to study seismic phenomena, that includes relaxation in the plates
as a key ingredient. We make an analysis of the scaling of the largest events
with system size, and show that when parameters are appropriately interpreted,
the typical size of the largest events scale as the system size, without the
necessity to tune any parameter. Secondly, we show that the temporal activity
in the model is inherently non-stationary, and obtain from here justification
and support for the concept of a "seismic cycle" in the temporal evolution of
seismic activity. Finally, we ask for the reasons that make the model display a
realistic value of the decaying exponent in the Gutenberg-Richter law for
the avalanche size distribution. We explain why relaxation induces a systematic
increase of from its value observed in the absence of
relaxation. However, we have not been able to justify the actual robustness of
the model in displaying a consistent value around the experimentally
observed value .Comment: 11 pages, 10 figure
Lone Wolf Riots: Social Frustration & U.S. Mass Violence
Through various life events and circumstances, some individuals find themselves at a disconnect with their surroundings—unable to relate to peers, socially awkward, and socially isolated and outcast. As a result, socially constructed basic human needs (BHNs) of meaning, recognition, and justice can seem even more difficult if not impossible to satisfy. The resulting relative deprivation becomes more problematic for these individuals as they navigate pursuit of these BHNs absent the value opportunities provided by social bonds, such as shared experience, collaborative problem solving, emotional outlets, networking, and alternate perspectives. Simultaneously, empathy and bonding toward their communities are damaged or erased. Relative deprivation draws the lone wolf inward, where altered realities both further isolate the individual and seek to selfsatisfy unmet needs. Having exhausted their limited resources, violence itself becomes a value opportunity. The consistent thread of unsatisfied needs and frustration align lone wolf USMV more consistently with riot or lone wolf terrorist behavior than with a copycat syndrome. Understanding USMV from the standpoint of lone wolf riots provides a basis for examining how social and cultural structures contribute to the isolation and emergence of lone wolf rioters, and how social, structural, and cultural changes may help stem the phenomena
Analysis of ischaemic crisis using the informational causal entropy-complexity plane
In the present work, an ischaemic process, mainly focused on the reperfusion stage, is studied using the informational causal entropy-complexity plane. Ischaemic wall behavior under this condition was analyzed through wall thickness and ventricular pressure variations, acquired during an obstructive flow maneuver performed on left coronary arteries of surgically instrumented animals. Basically, the induction of ischaemia depends on the temporary occlusion of left circumflex coronary artery (which supplies blood to the posterior left ventricular wall) that lasts for a few seconds. Normal perfusion of the wall was then reestablished while the anterior ventricular wall remained adequately perfused during the entire maneuver. The obtained results showed that system dynamics could be effectively described by entropy-complexity loops, in both abnormally and well perfused walls. These results could contribute to making an objective indicator of the recovery heart tissues after an ischaemic process, in a way to quantify the restoration of myocardial behavior after the supply of oxygen to the ventricular wall was suppressed for a brief period.Fil: Legnani, Walter. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Universidad Nacional de Lanús; ArgentinaFil: Traversaro Varela, Francisco. Instituto Tecnológico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Redelico, Francisco Oscar. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Cymberknop, Leandro Javier. Instituto Tecnologico de Buenos Aires. Departamento de Bioingenieria; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Armentano, Ricardo Luis. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Instituto Tecnologico de Buenos Aires. Departamento de Bioingenieria; ArgentinaFil: Rosso, Osvaldo Aníbal. Universidad de los Andes; Chile. Universidade Federal de Alagoas; Brasil. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Universal interface width distributions at the depinning threshold
We compute the probability distribution of the interface width at the
depinning threshold, using recent powerful algorithms. It confirms the
universality classes found previously. In all cases, the distribution is
surprisingly well approximated by a generalized Gaussian theory of independant
modes which decay with a characteristic propagator G(q)=1/q^(d+2 zeta); zeta,
the roughness exponent, is computed independently. A functional renormalization
analysis explains this result and allows to compute the small deviations, i.e.
a universal kurtosis ratio, in agreement with numerics. We stress the
importance of the Gaussian theory to interpret numerical data and experiments.Comment: 4 pages revtex4. See also the following article cond-mat/030146
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