4,376 research outputs found
How does dissipation affect the transition from static to dynamic macroscopic friction?
Description of the transitional process from a static to a dynamic frictional
regime is a fundamental problem of modern physics. Previously we developed a
model based on the well-known Frenkel-Kontorova model to describe dry
macroscopic friction. Here this model has been modified to include the effect
of dissipation in derived relations between the kinematic and dynamic
parameters of a transition process. The main (somewhat counterintuitive) result
is a demonstration that the rupture (i.e. detachment front) velocity of the
slip pulse which arises during the transition does not depend on friction. The
only parameter (besides the elastic and plastic properties of the medium)
controlling the rupture velocity is the shear to normal stress ratio. In
contrast to the rupture velocity, the slip velocity does depend on friction.
The model we have developed describes these processes over a wide range of
rupture and slip velocities (up to 7 orders of magnitude) allowing, in
particular, the consideration of seismic events ranging from regular
earthquakes, with rupture velocities on the order of a few km/s, to slow slip
events, with rupture velocities of a few km/day.Comment: 21 pages, 12 figure
DIVERSIFICATION OF REGIONAL MARKETING COOPERATIVES
Agribusiness, Marketing,
Alien Registration- Skinner, Thomas (Portland, Cumberland County)
https://digitalmaine.com/alien_docs/32004/thumbnail.jp
Saturation-Dependence of Dispersion in Porous Media
In this study, we develop a saturation-dependent treatment of dispersion in
porous media using concepts from critical path analysis, cluster statistics of
percolation, and fractal scaling of percolation clusters. We calculate spatial
solute distributions as a function of time and calculate arrival time
distributions as a function of system size. Our previous results correctly
predict the range of observed dispersivity values over ten orders of magnitude
in experimental length scale, but that theory contains no explicit dependence
on porosity or relative saturation. This omission complicates comparisons with
experimental results for dispersion, which are often conducted at saturation
less than 1. We now make specific comparisons of our predictions for the
arrival time distribution with experiments on a single column over a range of
saturations. This comparison suggests that the most important predictor of such
distributions as a function of saturation is not the value of the saturation
per se, but the applicability of either random or invasion percolation models,
depending on experimental conditions
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