53 research outputs found
Parameter estimators of random intersection graphs with thinned communities
This paper studies a statistical network model generated by a large number of
randomly sized overlapping communities, where any pair of nodes sharing a
community is linked with probability via the community. In the special case
with the model reduces to a random intersection graph which is known to
generate high levels of transitivity also in the sparse context. The parameter
adds a degree of freedom and leads to a parsimonious and analytically
tractable network model with tunable density, transitivity, and degree
fluctuations. We prove that the parameters of this model can be consistently
estimated in the large and sparse limiting regime using moment estimators based
on partially observed densities of links, 2-stars, and triangles.Comment: 15 page
Correlation between clustering and degree in affiliation networks
We are interested in the probability that two randomly selected neighbors of
a random vertex of degree (at least) are adjacent. We evaluate this
probability for a power law random intersection graph, where each vertex is
prescribed a collection of attributes and two vertices are adjacent whenever
they share a common attribute. We show that the probability obeys the scaling
as . Our results are mathematically rigorous. The
parameter is determined by the tail indices of power law
random weights defining the links between vertices and attributes
Relationship between Nanostructure and Deformation Behavior of Microphase-Separated Styrene/Butadiene Systems
The relationship between the morphology
and the mechanical properties of nanostructured blends,comprising an asymmetric styrene/butadiene star block copolymer,exhibiting cocontinuous-like morphology and low molar mass homopolymers, was studied by electron microscopy,
microindentation hardness, and tensile testing methods. Results show that the deformation behavior of these systems is significantly modified by the presence of unentangled homopolymer chains, leading partly to a decrease in mechanical properties. In contrast to common polymer
blends, in which usually, the hardness values do not markedly deviate from the additivity law, the H-values in the
system investigated show large deviations from the linear additivity behavior. The observed anomalous behavior is discussed in terms of the enhanced local flow processes
induced by the phase-separated morphology at a nanometer scale.Peer reviewe
Moment-based parameter estimation in binomial random intersection graph models
Binomial random intersection graphs can be used as parsimonious statistical
models of large and sparse networks, with one parameter for the average degree
and another for transitivity, the tendency of neighbours of a node to be
connected. This paper discusses the estimation of these parameters from a
single observed instance of the graph, using moment estimators based on
observed degrees and frequencies of 2-stars and triangles. The observed data
set is assumed to be a subgraph induced by a set of nodes sampled from
the full set of nodes. We prove the consistency of the proposed estimators
by showing that the relative estimation error is small with high probability
for . As a byproduct, our analysis confirms that the
empirical transitivity coefficient of the graph is with high probability close
to the theoretical clustering coefficient of the model.Comment: 15 pages, 6 figure
Bistable polarization switching in mutually coupled vertical-cavity surface-emitting lasers
3 pages.-- OCIS codes: 250.5270, 260.5430.-- Final full-text version of the paper available at: http://dx.doi.org/10.1364/OL.31.000996.We theoretically investigate the polarization-resolved dynamics of two vertical-cavity surface-emitting semiconductor lasers that are mutually
coupled through coherent optical injection. We find a sequence of bistable polarization switchings that can be induced by either
changing the coupling strength or the optical propagation phase. The successive polarization switchings are correlated to the creation
of new compound-cavity modes when these parameters are continuously varied.The authors acknowledge financial support from MEC (Spain) and Feder, project FIS2004-00953. JM
is supported by the CSIC (Spain) through the program I3P-PC2003. MS acknowledges support from UIB (Spain)
On plexus representation of dissimilarities
Correspondence analysis has found widespread application in analysing vegetation gradients. However, it is not clear how it is robust to situations where structures other than a simple gradient exist. The introduction of instrumental variables in canonical correspondence analysis does not avoid these difficulties. In this paper I propose to examine some simple methods based on the notion of the plexus (sensu McIntosh) where graphs or networks are used to display some of the structure of the data so that an informed choice of models is possible. I showthat two different classes of plexus model are available. These classes are distinguished by the use in one case of a global Euclidean model to obtain well-separated pair decomposition (WSPD) of a set of points which implicitly involves all dissimilarities, while in the other a Riemannian view is taken and emphasis is placed locally, i.e., on small dissimilarities. I showan example of each of these classes applied to vegetation data
The Chinese Meaning of Just War and its Impact on the Foreign Policy of the People's Republic of China
Time to pregnancy: results of the German prospective study and impact on the management of infertility
Interaction Between Human Osteoblast Cells and Inorganic Two Dimensional Scaffolds Based on Multiwalled Carbon Nanotubes A Quantitative AFM Study
- …