6,249 research outputs found
Tidal Stripping of a White Dwarf by an Intermediate-Mass Black Hole
During the inspiralling of a white dwarf (WD) into an intermediate-mass black
hole (~ 10^{2-5} M_sun), both gravitational waves (GWs) and electromagnetic
(EM) radiation are emitted. Once the eccentric orbit's pericenter radius
approaches the tidal radius, the WD would be tidally stripped upon each
pericenter passage. The accretion of these stripped mass would produce EM
radiation. It is suspected that the recently discovered new types of
transients, namely the quasi-periodic eruptions and the fast ultraluminous
X-ray bursts, might originate from such systems. Modeling these flares requires
a prediction of the amount of stripped mass from the WD and the details of the
mass supply to the accretion disk. We run hydrodynamical simulations to study
the orbital parameter dependence of the stripped mass. We find that our results
match the analytical estimate that the stripped mass is proportional to
z^{5/2}, where z is the excess depth by which the WD overfills its
instantaneous Roche lobe at the pericenter. The corresponding fallback rate of
the stripped mass is calculated, which may be useful in interpreting the
individual flaring light curve in candidate EM sources. We further calculate
the long-term mass-loss evolution of a WD during its inspiral and the
detectability of the GW and EM signals. The EM signal from the mass-loss stage
can be easily detected: the limiting distance is ~ 320(M_h/10^4 M_sun) Mpc for
Einstein Probe. The GW signal, for the space-borne detectors such as Laser
Interferometer Space Antenna or TianQin, can be detected only within the Local
Supercluster (~ 33 Mpc).Comment: 18 pages, 13 figures, Accepted for publication in Ap
Improving the Transferability of Adversarial Examples with Arbitrary Style Transfer
Deep neural networks are vulnerable to adversarial examples crafted by
applying human-imperceptible perturbations on clean inputs. Although many
attack methods can achieve high success rates in the white-box setting, they
also exhibit weak transferability in the black-box setting. Recently, various
methods have been proposed to improve adversarial transferability, in which the
input transformation is one of the most effective methods. In this work, we
notice that existing input transformation-based works mainly adopt the
transformed data in the same domain for augmentation. Inspired by domain
generalization, we aim to further improve the transferability using the data
augmented from different domains. Specifically, a style transfer network can
alter the distribution of low-level visual features in an image while
preserving semantic content for humans. Hence, we propose a novel attack method
named Style Transfer Method (STM) that utilizes a proposed arbitrary style
transfer network to transform the images into different domains. To avoid
inconsistent semantic information of stylized images for the classification
network, we fine-tune the style transfer network and mix up the generated
images added by random noise with the original images to maintain semantic
consistency and boost input diversity. Extensive experimental results on the
ImageNet-compatible dataset show that our proposed method can significantly
improve the adversarial transferability on either normally trained models or
adversarially trained models than state-of-the-art input transformation-based
attacks. Code is available at: https://github.com/Zhijin-Ge/STM.Comment: 10 pages, 2 figures, accepted by the 31st ACM International
Conference on Multimedia (MM '23
Structural deformation of shale pores in the fold-thrust belt: The Wufeng-Longmaxi shale in the Anchang Syncline of Central Yangtze Block
The gas-rich Wufeng-Longmaxi shale has been intensely deformed within the fold-thrust belt of the Yangtze Block. To better understand the impact of structural deformation on the shale pore system, this paper systematically investigated the matrix components, porosity and pore structures in core samples from theWufeng-Longmaxi shale, newly collected from various structural domains in the first commercial shale gas field of the Central Yangtze Block, the Anchang Syncline. The shale porosity generally showed a positive relationship with total organic carbon content. Nevertheless, even at a constant total organic carbon content, the shale porosity decreased from the syncline limb to the syncline hinge zone and with a decreasing interlimb angle in the syncline hinge zone, which aligned with the structural deformation strain during folding. The artificial axial compression of shale samples also confirmed that the decrease in shale porosity was stronger at an elevated axial compression stress and was relatively higher in samples with higher total organic carbon content. The organic pore size decreased with higher structural deformation strain, but the aspect ratio of the pore shape increased. Even quartz failed to resist the effective stress under the intensive structural deformation, changing the correlation between porosity and quartz from positive to negative. In contrast, pore spaces generated by the slipping between clay flakes under intensive deformation accounted for a positive relationship between clay content and bulk porosity. Considering the shale porosity reduction caused by the intensive structural deformation of shale pores, the Wufeng-Longmaxi shale, that is rich in fracture networks between roof and floor layers, may still be an excellent exploration target in the fold-thrust belt of the Yangtze Block.Cited as: Guo, X., Liu, R., Xu, S., Feng, B., Wen, T., Zhang, T. Structural deformation of shale pores in the fold-thrust belt: The Wufeng-Longmaxi shale in the Anchang Syncline of Central Yangtze Block. Advances in Geo-Energy Research, 2022, 6(6): 515-530. https://doi.org/10.46690/ager.2022.06.0
Enhancing Security Patch Identification by Capturing Structures in Commits
With the rapid increasing number of open source software (OSS), the majority
of the software vulnerabilities in the open source components are fixed
silently, which leads to the deployed software that integrated them being
unable to get a timely update. Hence, it is critical to design a security patch
identification system to ensure the security of the utilized software. However,
most of the existing works for security patch identification just consider the
changed code and the commit message of a commit as a flat sequence of tokens
with simple neural networks to learn its semantics, while the structure
information is ignored. To address these limitations, in this paper, we propose
our well-designed approach E-SPI, which extracts the structure information
hidden in a commit for effective identification. Specifically, it consists of
the code change encoder to extract the syntactic of the changed code with the
BiLSTM to learn the code representation and the message encoder to construct
the dependency graph for the commit message with the graph neural network (GNN)
to learn the message representation. We further enhance the code change encoder
by embedding contextual information related to the changed code. To demonstrate
the effectiveness of our approach, we conduct the extensive experiments against
six state-of-the-art approaches on the existing dataset and from the real
deployment environment. The experimental results confirm that our approach can
significantly outperform current state-of-the-art baselines
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