966 research outputs found
Disassortative mixing in online social networks
The conventional wisdom is that social networks exhibit an assortative mixing
pattern, whereas biological and technological networks show a disassortative
mixing pattern. However, the recent research on the online social networks
modifies the widespread belief, and many online social networks show a
disassortative or neutral mixing feature. Especially, we found that an online
social network, Wealink, underwent a transition from degree assortativity
characteristic of real social networks to degree disassortativity
characteristic of many online social networks, and the transition can be
reasonably elucidated by a simple network model that we propose. The relations
among network assortativity, clustering, and modularity are also discussed in
the paper.Comment: 6 pages, 5 figures, 1 tabl
Geo-Social Group Queries with Minimum Acquaintance Constraint
The prosperity of location-based social networking services enables
geo-social group queries for group-based activity planning and marketing. This
paper proposes a new family of geo-social group queries with minimum
acquaintance constraint (GSGQs), which are more appealing than existing
geo-social group queries in terms of producing a cohesive group that guarantees
the worst-case acquaintance level. GSGQs, also specified with various spatial
constraints, are more complex than conventional spatial queries; particularly,
those with a strict NN spatial constraint are proved to be NP-hard. For
efficient processing of general GSGQ queries on large location-based social
networks, we devise two social-aware index structures, namely SaR-tree and
SaR*-tree. The latter features a novel clustering technique that considers both
spatial and social factors. Based on SaR-tree and SaR*-tree, efficient
algorithms are developed to process various GSGQs. Extensive experiments on
real-world Gowalla and Dianping datasets show that our proposed methods
substantially outperform the baseline algorithms based on R-tree.Comment: This is the preprint version that is accepted by the Very Large Data
Bases Journa
Research on transmission coefficient property of coupled beam structure
This study investigates the transmission coefficient of coupled beam structure which has been widely used in engineering problems. Although the power flow is continuous at the coupled point, the waveform and energy density often show sudden changes. These changes can be utilized to create an understanding of the system. By treating the two-beam coupled structure as two infinite beams and considering the coupling between the bending wave and the torsion one, the conversion of wave types at the coupled interface is discussed. Further, the transmission coefficient is also computed. Furthermore, investigate the effects of coupling angle, beam height and the excitation frequency of incident wave on the conversion of wave type and energy transmission. Numerical results indicate that the coupling angle and beam height have great influences on the conversion of wave type. The component of torsion wave grows with the excitation frequency and cannot be ignored in high frequencies
How people make friends in social networking sites - A microscopic perspective
We study the detailed growth of a social networking site with full temporal
information by examining the creation process of each friendship relation that
can collectively lead to the macroscopic properties of the network. We first
study the reciprocal behavior of users, and find that link requests are quickly
responded to and that the distribution of reciprocation intervals decays in an
exponential form. The degrees of inviters/accepters are slightly negatively
correlative with reciprocation time. In addition, the temporal feature of the
online community shows that the distributions of intervals of user behaviors,
such as sending or accepting link requests, follow a power law with a universal
exponent, and peaks emerge for intervals of an integral day. We finally study
the preferential selection and linking phenomena of the social networking site
and find that, for the former, a linear preference holds for preferential
sending and reception, and for the latter, a linear preference also holds for
preferential acceptance, creation, and attachment. Based on the linearly
preferential linking, we put forward an analyzable network model which can
reproduce the degree distribution of the network. The research framework
presented in the paper could provide a potential insight into how the
micro-motives of users lead to the global structure of online social networks.Comment: 10 pages, 12 figures, 2 table
PolyA_DB: a database for mammalian mRNA polyadenylation
Messenger RNA polyadenylation is one of the key post-transcriptional events in eukaryotic cells. A large number of genes in mammalian species can undergo alternative polyadenylation, which leads to mRNAs with variable 3Ⲡends. As the 3Ⲡend of mRNAs often contains cis elements important for mRNA stability, mRNA localization and translation, the implications of the regulation of polyadenylation can be multifold. Alternative polyadenylation is controlled by cis elements and trans factors, and is believed to occur in a tissue- or disease-specific manner. Given the availability of many databases devoted to other aspects of mRNA metabolism, such as transcriptional initiation and splicing, systematic information on polyadenylation, including alternative polyadenylation and its regulation, is noticeably lacking. Here, we present a database named polyA_DB, through which we strive to provide several types of information regarding polyadenylation in mammalian species: (i) polyadenylation sites and their locations with respect to the genomic structure of genes; (ii) cis elements surrounding polyadenylation sites; (iii) comparison of polyadenylation configuration between orthologous genes; and (iv) tissue/organ information for alternative polyadenylation sites. Currently, polyA_DB contains 45â565 polyadenylation sites for 25â097 human and mouse genes, representing the most comprehensive polyadenylation database till date. The database is accessible via the website (http://polya.umdnj.edu/polyadb)
The Evolution of Sustainable Business Model Innovation:Evidence from a Sharing Economy Platform in China
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