2,608 research outputs found
Optimization and resilience of complex supply-demand networks
Acknowledgments This work was supported by NSF under Grant No. 1441352. SPZ and ZGH were supported by NSF of China under Grants No. 11135001 and No. 11275003. ZGH thanks Prof Liang Huang and Xin-Jian Xu for helpful discussions.Peer reviewedPublisher PD
STGIN: Spatial-Temporal Graph Interaction Network for Large-scale POI Recommendation
In Location-Based Services, Point-Of-Interest(POI) recommendation plays a
crucial role in both user experience and business opportunities. Graph neural
networks have been proven effective in providing personalized POI
recommendation services. However, there are still two critical challenges.
First, existing graph models attempt to capture users' diversified interests
through a unified graph, which limits their ability to express interests in
various spatial-temporal contexts. Second, the efficiency limitations of graph
construction and graph sampling in large-scale systems make it difficult to
adapt quickly to new real-time interests. To tackle the above challenges, we
propose a novel Spatial-Temporal Graph Interaction Network. Specifically, we
construct subgraphs of spatial, temporal, spatial-temporal, and global views
respectively to precisely characterize the user's interests in various
contexts. In addition, we design an industry-friendly framework to track the
user's latest interests. Extensive experiments on the real-world dataset show
that our method outperforms state-of-the-art models. This work has been
successfully deployed in a large e-commerce platform, delivering a 1.1% CTR and
6.3% RPM improvement.Comment: accepted by CIKM 202
Electron interaction-driven insulating ground state in Bi2Se3 topological insulators in the two dimensional limit
We report a transport study of ultrathin Bi2Se3 topological insulators with
thickness from one quintuple layer to six quintuple layers grown by molecular
beam epitaxy. At low temperatures, the film resistance increases
logarithmically with decreasing temperature, revealing an insulating ground
state. The sharp increase of resistance with magnetic field, however, indicates
the existence of weak antilocalization, which should reduce the resistance as
temperature decreases. We show that these apparently contradictory behaviors
can be understood by considering the electron interaction effect, which plays a
crucial role in determining the electronic ground state of topological
insulators in the two dimensional limit.Comment: 4 figure
Power-Law Decay of Standing Waves on the Surface of Topological Insulators
We propose a general theory on the standing waves (quasiparticle interference
pattern) caused by the scattering of surface states off step edges in
topological insulators, in which the extremal points on the constant energy
contour of surface band play the dominant role. Experimentally we image the
interference patterns on both BiTe and BiSe films by measuring
the local density of states using a scanning tunneling microscope. The observed
decay indices of the standing waves agree excellently with the theoretical
prediction: In BiSe, only a single decay index of -3/2 exists; while in
BiTe with strongly warped surface band, it varies from -3/2 to -1/2 and
finally to -1 as the energy increases. The -1/2 decay indicates that the
suppression of backscattering due to time-reversal symmetry does not
necessarily lead to a spatial decay rate faster than that in the conventional
two-dimensional electron system. Our formalism can also explain the
characteristic scattering wave vectors of the standing wave caused by
non-magnetic impurities on BiTe.Comment: 4 pages, 3 figure
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