26,295 research outputs found
Process Flow Diagram of an Ammonia Plant as a Complex Network
Complex networks have attracted increasing interests in almost all
disciplines of natural and social sciences. However, few efforts have been
afforded in the field of chemical engineering. We present in this work an
example of complex technological network, investigating the process flow of an
ammonia plant (AP). We show that the AP network is a small-world network with
scale-free distribution of degrees. Adopting Newman's maximum modularity
algorithm for the detection of communities in complex networks, evident modular
structures are identified in the AP network, which stem from the modular
sections in chemical plants. In addition, we find that the resultant AP tree
exhibits excellent allometric scaling.Comment: 15 pages including 4 eps figure
Network analysis identifies weak and strong links in a metapopulation system
The identification of key populations shaping the structure and connectivity of metapopulation systems is a major challenge in population ecology. The use of molecular markers in the theoretical framework of population genetics has allowed great advances in this field, but the prime question of quantifying the role of each population in the system remains unresolved. Furthermore, the use and interpretation of classical methods are still bounded by the need for a priori information and underlying assumptions that are seldom respected in natural systems. Network theory was applied to map the genetic structure in a metapopulation system by using microsatellite data from populations of a threatened seagrass, Posidonia oceanica, across its whole geographical range. The network approach, free from a priori assumptions and from the usual underlying hypotheses required for the interpretation of classical analyses, allows both the straightforward characterization of hierarchical population structure and the detection of populations acting as hubs critical for relaying gene flow or sustaining the metapopulation system. This development opens perspectives in ecology and evolution in general, particularly in areas such as conservation biology and epidemiology, where targeting specific populations is crucial
Scale-free trees: the skeletons of complex networks
We investigate the properties of the spanning trees of various real-world and
model networks. The spanning tree representing the communication kernel of the
original network is determined by maximizing total weight of edges, whose
weights are given by the edge betweenness centralities. We find that a
scale-free tree and shortcuts organize a complex network. The spanning tree
shows robust betweenness centrality distribution that was observed in
scale-free tree models. It turns out that the shortcut distribution
characterizes the properties of original network, such as the clustering
coefficient and the classification of networks by the betweenness centrality
distribution
Spanning Trees and bootstrap reliability estimation in correlation based networks
We introduce a new technique to associate a spanning tree to the average
linkage cluster analysis. We term this tree as the Average Linkage Minimum
Spanning Tree. We also introduce a technique to associate a value of
reliability to links of correlation based graphs by using bootstrap replicas of
data. Both techniques are applied to the portfolio of the 300 most capitalized
stocks traded at New York Stock Exchange during the time period 2001-2003. We
show that the Average Linkage Minimum Spanning Tree recognizes economic sectors
and sub-sectors as communities in the network slightly better than the Minimum
Spanning Tree does. We also show that the average reliability of links in the
Minimum Spanning Tree is slightly greater than the average reliability of links
in the Average Linkage Minimum Spanning Tree.Comment: 17 pages, 3 figure
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