1,994 research outputs found
Nucleon sea in the effective chiral quark model
The asymmetries of both light-flavor antiquark and
strange-antistrange distributions of the nucleon sea are
considered with more details in the effective chiral quark model. We find that
the asymmetric distribution of light-flavor antiquarks
matches the experiment data well and that the asymmetry of strange and
antistrange distributions can bring about 60-100% correction to the NuTeV
anomaly of , which are three standard deviations from the
world average value measured in other electroweak processes. The results on the
correction to the NuTeV anomaly are insensitive to the inputs of the
constituent quark distributions and the cut-off parameters. The ratios of
and are also discussed, and it is
found that the ratio is compatible with the available
experiments with an additional symmetric sea contribution being considered
effectively.Comment: 24 Latex pages, 8 figure
Transit of asteroids across the 7/3 Kirkwood gap under the Yarkovsky effect
Many asteroids in the main belt are continuously pushed by Yarkovsky effect
into regions of different mean motion resonances (MMRs) and then ejected out.
They are considered as the principal source of near-Earth objects. We
investigate in this paper the effects of the 7/3 MMR with Jupiter (J7/3 MMR) on
the transportation of asteroids from Koronis and Eos families that reside
respectively on the inner and outer side of the resonance. The fraction of
asteroids that make successful crossing through the resonance and the escaping
rate from the resonance are found to depend on the Yarkovsky drifting rate, the
initial inclination and the migrating direction. The excitation of eccentricity
and inclination due to the combined influence from both the resonance and
Yarkovsky effect is discussed. Only the eccentricity can be pumped up
considerably, and it is attributed mainly to the resonance. In the
observational data, family members are also found in the resonance and on the
opposite side of the resonance with respect to the corresponding family centre.
The existence of these family members is explained using our results of
numerical simulations. Finally, the replenishment of asteroids in the J7/3 MMR
and the transportation of asteroids by it are discussed.Comment: 10 pages, 10 figures. Accepted by A&
Unsupervised Cross-domain Pulmonary Nodule Detection without Source Data
Cross domain pulmonary nodule detection suffers from performance degradation
due to large shift of data distributions between the source and target domain.
Besides, considering the high cost of medical data annotation, it is often
assumed that the target images are unlabeled. Existing approaches have made
much progress for this unsupervised domain adaptation setting. However, this
setting is still rarely plausible in the medical application since the source
medical data are often not accessible due to the privacy concerns. This
motivates us to propose a Source-free Unsupervised cross-domain method for
Pulmonary nodule detection (SUP). It first adapts the source model to the
target domain by utilizing instance-level contrastive learning. Then the
adapted model is trained in a teacher-student interaction manner, and a
weighted entropy loss is incorporated to further improve the accuracy.
Extensive experiments by adapting a pre-trained source model to three popular
pulmonary nodule datasets demonstrate the effectiveness of our method
Global and partitioned reconstructions of undirected complex networks
It is a significant challenge to predict the network topology from a small
amount of dynamical observations. Different from the usual framework of the
node-based reconstruction, two optimization approaches (i.e., the global and
partitioned reconstructions) are proposed to infer the structure of undirected
networks from dynamics. These approaches are applied to evolutionary games
occurring on both homogeneous and heterogeneous networks via compressed
sensing, which can more efficiently achieve higher reconstruction accuracy with
relatively small amounts of data. Our approaches provide different perspectives
on effectively reconstructing complex networks.Comment: 6 pages, 2 figures, 1 table; revised version; added numerical results
of the PR in Table 1 and expanded Section 4; added 7 reference
Hinge solitons in three-dimensional second-order topological insulators
A second-order topological insulator in three dimensions refers to a
topological insulator with gapless states localized on the hinges, which is a
generalization of a traditional topological insulator with gapless states
localized on the surfaces. Here we theoretically demonstrate the existence of
stable solitons localized on the hinges of a second-order topological insulator
in three dimensions when nonlinearity is involved. By means of systematic
numerical study, we find that the soliton has strong localization in real space
and propagates along the hinge unidirectionally without changing its shape. We
further construct an electric network to simulate the second-order topological
insulator. When a nonlinear inductor is appropriately involved, we find that
the system can support a bright soliton for the voltage distribution
demonstrated by stable time evolution of a voltage pulse.Comment: 11 pages, 6 figure
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