9 research outputs found
Scaling Model of Annihilation-Diffusion Kinetics for Charged Particles with Long-Range Interactions
We propose the general scaling model for the diffusio n-annihilation reaction
with long-range power-law i
nteractions. The presented scaling arguments lead to the finding of three
different regimes, dep ending on the space dimensionality d and the long-range
force power e xponent n. The obtained kinetic phase diagram agrees well with
existing simulation data and approximate theoretical results.Comment: RevTEX, 7 pages, no figures, accepted to Physical Review
A Carbon Corrosion Model to Evaluate the Effect of Steady State and Transient Operation of a Polymer Electrolyte Membrane Fuel Cell
A carbon corrosion model is developed based on the formation of surface
oxides on carbon and platinum of the polymer electrolyte membrane fuel cell
electrode. The model predicts the rate of carbon corrosion under potential hold
and potential cycling conditions. The model includes the interaction of carbon
surface oxides with transient species like OH radicals to explain observed
carbon corrosion trends under normal PEM fuel cell operating conditions. The
model prediction agrees qualitatively with the experimental data supporting the
hypothesis that the interplay of surface oxide formation on carbon and platinum
is the primary driver of carbon corrosion
Efficient search by optimized intermittent random walks
We study the kinetics for the search of an immobile target by randomly moving
searchers that detect it only upon encounter. The searchers perform
intermittent random walks on a one-dimensional lattice. Each searcher can step
on a nearest neighbor site with probability "alpha", or go off lattice with
probability "1 - \alpha" to move in a random direction until it lands back on
the lattice at a fixed distance L away from the departure point. Considering
"alpha" and L as optimization parameters, we seek to enhance the chances of
successful detection by minimizing the probability P_N that the target remains
undetected up to the maximal search time N. We show that even in this simple
model a number of very efficient search strategies can lead to a decrease of
P_N by orders of magnitude upon appropriate choices of "alpha" and L. We
demonstrate that, in general, such optimal intermittent strategies are much
more efficient than Brownian searches and are as efficient as search algorithms
based on random walks with heavy-tailed Cauchy jump-length distributions. In
addition, such intermittent strategies appear to be more advantageous than
Levy-based ones in that they lead to more thorough exploration of visited
regions in space and thus lend themselves to parallelization of the search
processes.Comment: To appear in J. Phys.: Condensed Matter, special issue on "Random
Search Problem: Trends and Perspectives", eds.: MEG da Luz, E Raposo, GM
Viswanathan and A Grosber
Combined hydrophobicity and mechanical durability through surface nanoengineering
This paper reports combined hydrophobicity and mechanical durability through the nanoscale engineering of surfaces in the form of nanorod-polymer composites. Specifically, the hydrophobicity derives from nanoscale features of mechanically hard ZnO nanorods and the mechanical durability derives from the composite structure of a hard ZnO nanorod core and soft polymer shell. Experimental characterization correlates the morphology of the nanoengineered surfaces with the combined hydrophobicity and mechanical durability, and reveals the responsible mechanisms. Such surfaces may find use in applications, such as boat hulls, that benefit from hydrophobicity and require mechanical durability