57 research outputs found
Scalable Algorithms for Laplacian Pseudo-inverse Computation
The pseudo-inverse of a graph Laplacian matrix, denoted as , finds
extensive application in various graph analysis tasks. Notable examples include
the calculation of electrical closeness centrality, determination of Kemeny's
constant, and evaluation of resistance distance. However, existing algorithms
for computing are often computationally expensive when dealing with
large graphs. To overcome this challenge, we propose novel solutions for
approximating by establishing a connection with the inverse of a
Laplacian submatrix . This submatrix is obtained by removing the -th
row and column from the original Laplacian matrix . The key advantage of
this connection is that exhibits various interesting combinatorial
interpretations. We present two innovative interpretations of based
on spanning trees and loop-erased random walks, which allow us to develop
efficient sampling algorithms. Building upon these new theoretical insights, we
propose two novel algorithms for efficiently approximating both electrical
closeness centrality and Kemeny's constant. We extensively evaluate the
performance of our algorithms on five real-life datasets. The results
demonstrate that our novel approaches significantly outperform the
state-of-the-art methods by several orders of magnitude in terms of both
running time and estimation errors for these two graph analysis tasks. To
further illustrate the effectiveness of electrical closeness centrality and
Kemeny's constant, we present two case studies that showcase the practical
applications of these metrics
BEVFormer: Learning Bird's-Eye-View Representation from Multi-Camera Images via Spatiotemporal Transformers
3D visual perception tasks, including 3D detection and map segmentation based
on multi-camera images, are essential for autonomous driving systems. In this
work, we present a new framework termed BEVFormer, which learns unified BEV
representations with spatiotemporal transformers to support multiple autonomous
driving perception tasks. In a nutshell, BEVFormer exploits both spatial and
temporal information by interacting with spatial and temporal space through
predefined grid-shaped BEV queries. To aggregate spatial information, we design
a spatial cross-attention that each BEV query extracts the spatial features
from the regions of interest across camera views. For temporal information, we
propose a temporal self-attention to recurrently fuse the history BEV
information. Our approach achieves the new state-of-the-art 56.9\% in terms of
NDS metric on the nuScenes test set, which is 9.0 points higher than previous
best arts and on par with the performance of LiDAR-based baselines. We further
show that BEVFormer remarkably improves the accuracy of velocity estimation and
recall of objects under low visibility conditions. The code will be released at
https://github.com/zhiqi-li/BEVFormer.Comment: 20 pages, 9 figure
Diversity of genotypes and pathogenicity of H9N2 avian influenza virus derived from wild bird and domestic poultry
IntroductionThe H9N2 subtype is a predominant avian influenza virus (AIV) circulating in Chinese poultry, forming various genotypes (A-W) based on gene segment origins. This study aims to investigate the genotypic distribution and pathogenic characteristics of H9N2 isolates from wild birds and domestic poultry in Yunnan Province, China.MethodsEleven H9N2 strains were isolated from fecal samples of overwintering wild birds and proximate domestic poultry in Yunnan, including four from common cranes (Grus grus), two from bar-headed geese (Anser indicus), and five from domestic poultry (Gallus gallus). Phylogenetic analysis was conducted to determine the genotypes, and representative strains were inoculated into Yunnan mallard ducks to assess pathogenicity.ResultsPhylogenetic analysis revealed that five isolates from domestic birds and one from a bar-headed goose belong to genotype S, while the remaining five isolates from wild birds belong to genotype A. These bird-derived strains possess deletions in the stalk domain of NA protein and the N166D mutation of HA protein, typical of poultry strains. Genotype S H9N2 demonstrated oropharyngeal shedding, while genotype A H9N2 exhibited cloacal shedding and high viral loads in the duodenum. Both strains caused significant pathological injuries, with genotype S inducing more severe damage to the thymus and spleen, while genotype A caused duodenal muscle layer rupture.DiscussionThese findings suggest that at least two genotypes of H9N2 are currently circulating in Yunnan, and Yunnan mallard ducks potentially act as intermediaries in interspecies transmission. These insights highlight the importance of analyzing the current epidemiological transmission characteristics of H9N2 among wild and domestic birds in China
Ranking-Incentivized Quality Preserving Content Modification
The Web is a canonical example of a competitive retrieval setting where many
documents' authors consistently modify their documents to promote them in
rankings. We present an automatic method for quality-preserving modification of
document content -- i.e., maintaining content quality -- so that the document
is ranked higher for a query by a non-disclosed ranking function whose rankings
can be observed. The method replaces a passage in the document with some other
passage. To select the two passages, we use a learning-to-rank approach with a
bi-objective optimization criterion: rank promotion and content-quality
maintenance. We used the approach as a bot in content-based ranking
competitions. Analysis of the competitions demonstrates the merits of our
approach with respect to human content modifications in terms of rank
promotion, content-quality maintenance and relevance.Comment: 10 pages. 8 figures. 3 table
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