9,989 research outputs found
Nonequilibrium structures and dynamic transitions in driven vortex lattices with disorder
We review our studies of elastic lattices driven by an external force in
the presence of random disorder, which correspond to the case of vortices in
superconducting thin films driven by external currents. Above a critical force
we find two dynamical phase transitions at and , with
. At there is a transition from plastic flow to smectic flow
where the noise is isotropic and there is a peak in the differential
resistance. At there is a sharp transition to a frozen transverse solid
where both the transverse noise and the diffussion fall down abruptly and
therefore the vortex motion is localized in the transverse direction. From a
generalized fluctuation-dissipation relation we calculate an effective
transverse temperature in the fluid moving phases. We find that the effective
temperature decreases with increasing driving force and becomes equal to the
equilibrium melting temperature when the dynamic transverse freezing occurs.Comment: 8 pages, 3 fig
Anisotropic finite-size scaling of an elastic string at the depinning threshold in a random-periodic medium
We numerically study the geometry of a driven elastic string at its
sample-dependent depinning threshold in random-periodic media. We find that the
anisotropic finite-size scaling of the average square width and of
its associated probability distribution are both controlled by the ratio
, where is the
random-manifold depinning roughness exponent, is the longitudinal size of
the string and the transverse periodicity of the random medium. The
rescaled average square width displays a
non-trivial single minimum for a finite value of . We show that the initial
decrease for small reflects the crossover at from the
random-periodic to the random-manifold roughness. The increase for very large
implies that the increasingly rare critical configurations, accompanying
the crossover to Gumbel critical-force statistics, display anomalous roughness
properties: a transverse-periodicity scaling in spite that ,
and subleading corrections to the standard random-manifold longitudinal-size
scaling. Our results are relevant to understanding the dimensional crossover
from interface to particle depinning.Comment: 11 pages, 7 figures, Commentary from the reviewer available in Papers
in Physic
Integrated model for the hydro-mechanical effects of vegetation against shallow landslides
Shallow landslides are instability events that lead to dramatic soil mass wasting in sloping areas and are commonly triggered by intense rainfall episodes. Vegetation may reduce the likelihood of slope failure through different hydro-mechanical mechanisms that take place at the soil-plant-atmosphere interface. However, while vegetation’s mechanical contribution has been widely recognized, its hydrological effects have been poorly quantified. In addition, most of the existing models lack a holistic approach, require difficult to measure parameters or are commercially based, making them hardly transferable to land planners and other researchers.In this paper an integrated, robust and reproducible model framework is proposed and evaluated with the aim of assessing the hydro-mechanical effects of different vegetation types on slope stability using easily measureable and quantifiable input parameters. The output shows that the model framework is able to simulate the hydro-mechanical effects of vegetation in a realistic manner and that it can be readily applied to any vegetation, soil and climate types. It also demonstrates that vegetation has positive hydro-mechanical effects against shallow landslides, where plant biomass and evapotranspiration play an important role
Green for Brown (G4B): a novel tool for evaluating phytoextraction in soils polluted by heavy metals
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