3,257 research outputs found
Dyad and Triad Census Analysis of Crisis Communication Network
have been found very useful in analyzing structural properties of social networks. This study aims to explore crisis communication network by following dyad and triad census analysis approach to investigate the association of mi- cro-level communication patterns with organizational crisis. This study further tests hypothesis related to the process of data generation and tendency of the structural pattern of transitivity using dyad and triad census output. The changing communication network at Enron Corporation during the period of its crisis is analyzed in this study. Significant dif- ferences in the presence of different isomorphism classes or micro-level patterns of both dyad and triad census are no- ticed in crisis and non-crisis period network of Enron email corpus. It is also noticed that crisis communication network shows more transitivity comppublished_or_final_versio
Network Effects on Scientific Collaborations
Background: The analysis of co-authorship network aims at exploring the impact of network structure on the outcome of scientific collaborations and research publications. However, little is known about what network properties are associated with authors who have increased number of joint publications and are being cited highly. Methodology/Principal Findings: Measures of social network analysis, for example network centrality and tie strength, have been utilized extensively in current co-authorship literature to explore different behavioural patterns of co-authorship networks. Using three SNA measures (i.e., degree centrality, closeness centrality and betweenness centrality), we explore scientific collaboration networks to understand factors influencing performance (i.e., citation count) and formation (tie strength between authors) of such networks. A citation count is the number of times an article is cited by other articles. We use co-authorship dataset of the research field of 'steel structure' for the year 2005 to 2009. To measure the strength of scientific collaboration between two authors, we consider the number of articles co-authored by them. In this study, we examine how citation count of a scientific publication is influenced by different centrality measures of its co-author(s) in a co-authorship network. We further analyze the impact of the network positions of authors on the strength of their scientific collaborations. We use both correlation and regression methods for data analysis leading to statistical validation. We identify that citation count of a research article is positively correlated with the degree centrality and betweenness centrality values of its co-author(s). Also, we reveal that degree centrality and betweenness centrality values of authors in a co-authorship network are positively correlated with the strength of their scientific collaborations. Conclusions/Significance: Authors' network positions in co-authorship networks influence the performance (i.e., citation count) and formation (i.e., tie strength) of scientific collaborations. © 2013 Uddin et al.published_or_final_versio
Density perturbations in f(R) gravity theories in metric and Palatini formalisms
We make a detailed study of matter density perturbations in both metric and
Palatini formalisms in theories whose Lagrangian density is a general function,
f(R), of the Ricci scalar. We derive these equations in a number of gauges. We
show that for viable models that satisfy cosmological and local gravity
constraints (LGC), matter perturbation equations derived under a sub-horizon
approximation are valid even for super-Hubble scales provided the oscillating
mode (scalaron) does not dominate over the matter-induced mode. Such
approximate equations are especially reliable in the Palatini formalism because
of the absence of scalarons.
Using these equations we make a comparative study of the behaviour of density
perturbations as well as gravitational potentials for a number of classes of
theories. In the metric formalism the parameter m=Rf_{,RR}/f_{,R}
characterising the deviation from the Lambda CDM model is constrained to be
very small during the matter era in order to ensure compatibility with LGC, but
the models in which m grows to the order of 10^{-1} around the present epoch
can be allowed. These models also suffer from an additional fine tuning due to
the presence of scalaron modes which are absent in the Palatini case.
In Palatini formalism LGC and background cosmological constraints provide
only weak bounds on |m| by constraining it to be smaller than ~ 0.1. This is in
contrast to matter density perturbations which, on galactic scales, place far
more stringent constraints on the present deviation parameter m of the order of
|m| < 10^{-5} - 10^{-4}. This is due to the peculiar evolution of matter
perturbations in the Palatini case which exhibits a rapid growth or a damped
oscillation depending on the sign of m.Comment: 36 pages including 8 figures. Accepted for publication in Physical
Review
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