19,465 research outputs found
Exploiting classical nucleation theory for reverse self-assembly
In this paper we introduce a new method to design interparticle interactions
to target arbitrary crystal structures via the process of self-assembly. We
show that it is possible to exploit the curvature of the crystal nucleation
free-energy barrier to sample and select optimal interparticle interactions for
self-assembly into a desired structure. We apply this method to find
interactions to target two simple crystal structures: a crystal with simple
cubic symmetry and a two-dimensional plane with square symmetry embedded in a
three-dimensional space. Finally, we discuss the potential and limits of our
method and propose a general model by which a functionally infinite number of
different interaction geometries may be constructed and to which our reverse
self-assembly method could in principle be applied.Comment: 7 pages, 6 figures. Published in the Journal of Chemical Physic
The Parallel Complexity of Growth Models
This paper investigates the parallel complexity of several non-equilibrium
growth models. Invasion percolation, Eden growth, ballistic deposition and
solid-on-solid growth are all seemingly highly sequential processes that yield
self-similar or self-affine random clusters. Nonetheless, we present fast
parallel randomized algorithms for generating these clusters. The running times
of the algorithms scale as , where is the system size, and the
number of processors required scale as a polynomial in . The algorithms are
based on fast parallel procedures for finding minimum weight paths; they
illuminate the close connection between growth models and self-avoiding paths
in random environments. In addition to their potential practical value, our
algorithms serve to classify these growth models as less complex than other
growth models, such as diffusion-limited aggregation, for which fast parallel
algorithms probably do not exist.Comment: 20 pages, latex, submitted to J. Stat. Phys., UNH-TR94-0
CoPhy: A Scalable, Portable, and Interactive Index Advisor for Large Workloads
Index tuning, i.e., selecting the indexes appropriate for a workload, is a
crucial problem in database system tuning. In this paper, we solve index tuning
for large problem instances that are common in practice, e.g., thousands of
queries in the workload, thousands of candidate indexes and several hard and
soft constraints. Our work is the first to reveal that the index tuning problem
has a well structured space of solutions, and this space can be explored
efficiently with well known techniques from linear optimization. Experimental
results demonstrate that our approach outperforms state-of-the-art commercial
and research techniques by a significant margin (up to an order of magnitude).Comment: VLDB201
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