6,159 research outputs found
Interdisciplinary Monte Carlo Simulations
Biological, linguistic, sociological and economical applications of
statistical physics are reviewed here. They have been made on a variety of
computers over a dozen years, not only at the NIC computers. A longer
description can be found in our new book, an emphasis on teaching in
Eur.J.Phys. 26, S 79 and AIP Conf. Proc. 779, 49, 56, 69 and 75.Comment: 11 pages including many Figs.; for 3rd NIC Symposium, Julich, 3/0
Re-examination of seven-dimensional site percolation thresholds
Monte Carlo simulations alone could not clarify the corrections to scaling
for the size-dependent p_c(L) above the upper critical dimension. Including the
previous series estimate for the bulk threshold gives preference
for the complicated corrections predicted by renormalization group and against
the simple 1/L extrapolation. Additional Monte-Carlo simulations using the
Leath method corroborate the series result for p_c.Comment: 3 pages, 3 figures, submitte
Self-organizing lists on the Xnet
The first parallel designs for implementing self-organizing lists on the Xnet interconnection network are presented. Self-organizing lists permute the order of list entries after an entry is accessed according to some update hueristic. The heuristic attempts to place frequently requested entries closer to the front of the list. This paper outlines Xnet systems for self-organizing lists under the move-to-front and transpose update heuristics. Our novel designs can be used to achieve high-speed lossless text compression
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Parallel data compression
Data compression schemes remove data redundancy in communicated and stored data and increase the effective capacities of communication and storage devices. Parallel algorithms and implementations for textual data compression are surveyed. Related concepts from parallel computation and information theory are briefly discussed. Static and dynamic methods for codeword construction and transmission on various models of parallel computation are described. Included are parallel methods which boost system speed by coding data concurrently, and approaches which employ multiple compression techniques to improve compression ratios. Theoretical and empirical comparisons are reported and areas for future research are suggested
Development of advanced composite structures
Composite structure programs: the L-1011 Advanced Composite Vertical Fin (ACVF), the L-1011 Advanced Composite Aileron, and a wing study program were reviewed. These programs were structured to provide the technology and confidence for the use of advanced composite materials for primary and secondary structures of future transport aircraft. The current status of the programs is discussed. The results of coupon tests for both material systems are presented as well as the ACVF environmental (moisture and temperature) requirements. The effect of moisture and temperature on the mechanical properties of advanced composite materials is shown. The requirements set forth in the FAA Certification Guidelines for Civil Composite Aircraft Structures are discussed as they relate to the ACVF
A simple algorithm to test for linking to Wilson loops in percolation
A simple burning or epidemic type of algorithm is developed in order to test
whether any loops in percolation clusters link a fixed reference loop, a
problem considered recently by Gliozzi, Lottini, Panero, and Rago in the
context of gauge theory. We test our algorithm at criticality in both 2d, where
the behavior agrees with a theoretical prediction, and in 3d.Comment: v1: A third figure added with additional simulation results. Small
corrections als
Local cluster aggregation models of explosive percolation
We introduce perhaps the simplest models of graph evolution with choice that
demonstrate discontinuous percolation transitions and can be analyzed via
mathematical evolution equations. These models are local, in the sense that at
each step of the process one edge is selected from a small set of potential
edges sharing common vertices and added to the graph. We show that the
evolution can be accurately described by a system of differential equations and
that such models exhibit the discontinuous emergence of the giant component.
Yet, they also obey scaling behaviors characteristic of continuous transitions,
with scaling exponents that differ from the classic Erdos-Renyi model.Comment: Final version as appearing in PR
LANDSAT image differencing as an automated land cover change detection technique
Image differencing was investigated as a technique for use with LANDSAT digital data to delineate areas of land cover change in an urban environment. LANDSAT data collected in April 1973 and April 1975 for Austin, Texas, were geometrically corrected and precisely registered to United States Geological Survey 7.5-minute quadrangle maps. At each pixel location reflectance values for the corresponding bands were subtracted to produce four difference images. Areas of major reflectance differences are isolated by thresholding each of the difference images. The resulting images are combined to obtain an image data set to total change. These areas of reflectance differences were found, in general, to correspond to areas of land cover change. Information on areas of land cover change was incorporated into a procedure to mask out all nonchange areas and perform an unsupervised classification only for data in the change areas. This procedure identified three broad categories: (1) areas of high reflectance (construction or extractive), (2) changes in agricultural areas, and (3) areas of confusion between agricultural and other areas
Scaling behavior of explosive percolation on the square lattice
Clusters generated by the product-rule growth model of Achlioptas, D'Souza,
and Spencer on a two-dimensional square lattice are shown to obey qualitatively
different scaling behavior than standard (random growth) percolation. The
threshold with unrestricted bond placement (allowing loops) is found precisely
using several different criteria based upon both moments and wrapping
probabilities, yielding p_c = 0.526565 +/- 0.000005, consistent with the recent
result of Radicchi and Fortunato. The correlation-length exponent nu is found
to be close to 1. The qualitative difference from regular percolation is shown
dramatically in the behavior of the percolation probability P_(infinity) (size
of largest cluster), the susceptibility, and of the second moment of finite
clusters, where discontinuities appears at the threshold. The critical
cluster-size distribution does not follow a consistent power-law for the range
of system sizes we study L 2
for larger L.Comment: v2: Updated results in original version with new data; expanded
discussion. v3: Resubmitted version. New figures, reference
Diffusion in scale-free networks with annealed disorder
The scale-free (SF) networks that have been studied so far contained quenched
disorder generated by random dilution which does not vary with the time. In
practice, if a SF network is to represent, for example, the worldwide web, then
the links between its various nodes may temporarily be lost, and re-established
again later on. This gives rise to SF networks with annealed disorder. Even if
the disorder is quenched, it may be more realistic to generate it by a
dynamical process that is happening in the network. In this paper, we study
diffusion in SF networks with annealed disorder generated by various scenarios,
as well as in SF networks with quenched disorder which, however, is generated
by the diffusion process itself. Several quantities of the diffusion process
are computed, including the mean number of distinct sites visited, the mean
number of returns to the origin, and the mean number of connected nodes that
are accessible to the random walkers at any given time. The results including,
(1) greatly reduced growth with the time of the mean number of distinct sites
visited; (2) blocking of the random walkers; (3) the existence of a phase
diagram that separates the region in which diffusion is possible from one in
which diffusion is impossible, and (4) a transition in the structure of the
networks at which the mean number of distinct sites visited vanishes, indicate
completely different behavior for the computed quantities than those in SF
networks with quenched disorder generated by simple random dilution.Comment: 18 pages including 8 figure
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