12,624 research outputs found
Topological Influence-Aware Recommendation on Social Networks
Users in online networks exert different influence during the process of information propagation, and the heterogeneous influence may contribute to personalized recommendations. In this paper, we analyse the topology of social networks to investigate users’ influence strength on their neighbours. We also exploit the user-item rating matrix to find the importance of users’ ratings and determine their influence on entire social networks. Based on the local influence between users and global influence over the whole network, we propose a recommendation method with indirect interactions that makes adequate use of users’ relationships on social networks and users’ rating data. The two kinds of influence are incorporated into a matrix factorization framework. We also consider indirect interactions between users who do not have direct links with each other. Experimental results on two real-world datasets demonstrate that our proposed framework performs better than other state-of-the-art methods for all users and cold-start users. Compared with node degrees, betweenness, and clustering coefficients, coreness constitutes the best topological descriptor to identify users’ local influence, and recommendations with the measure of coreness outperform other descriptors of user influence.</jats:p
Subdwarf B stars from the common envelope ejection channel
From the canonical binary scenario, the majority of sdBs are produced from
low-mass stars with degenerate cores where helium is ignited in a way of
flashes. Due to numerical difficulties, the models of produced sdBs are
generally constructed from more massive stars with non-degenerate cores,
leaving several uncertainties on the exact characteristics of sdB stars.
Employing MESA, we systematically studied the characteristics of sdBs produced
from the common envelope (CE) ejection channel, and found that the sdB stars
produced from the CE ejection channel appear to form two distinct groups on the
effective temperature-gravity diagram. One group (the flash-mixing model)
almost has no H-rich envelope and crows at the hottest temperature end of the
extremely horizontal branch (EHB), while the other group has significant H-rich
envelope and spreads over the whole canonical EHB region. The key factor for
the dichotomy of the sdB properties is the development of convection during the
first helium flash, which is determined by the interior structure of the star
after the CE ejection. For a given initial stellar mass and a given core mass
at the onset of the CE, if the CE ejection stops early, the star has a
relatively massive H-rich envelope, resulting in a canonical sdB generally. The
fact of only a few short-orbital-period sdB binaries being in the flash-mixing
sdB region and the lack of He-rich sdBs in short-orbital-period binaries
indicate that the flash mixing is not very often in the products of the CE
ejection. A falling back process after the CE ejection, similar to that
happened in nova, is an appropriate way of increasing the envelope mass, then
prevents the flash mixing.Comment: accepted by A&A 12 pages, 11 figure
The effect of discrete breathers on heat conduction in nonlinear chains
Intensive studies in the past decades have suggested that the heat
conductivity diverges with the system size as in one dimensional momentum conserving nonlinear lattices and the
value of is universal. But in the Fermi-Pasta-Ulam- lattices
with next-nearest-neighbor interactions we find that strongly depends
on , the ratio of the next-nearest-neighbor coupling to the
nearest-neighbor coupling. We relate the -dependent heat conduction to
the interactions between the long-wavelength phonons and the randomly
distributed discrete breathers. Our results provide an evidence to show that
the nonlinear excitations affect the heat transport.Comment: 4 pages, 5 figure
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