845 research outputs found
Adaptive low rank and sparse decomposition of video using compressive sensing
We address the problem of reconstructing and analyzing surveillance videos
using compressive sensing. We develop a new method that performs video
reconstruction by low rank and sparse decomposition adaptively. Background
subtraction becomes part of the reconstruction. In our method, a background
model is used in which the background is learned adaptively as the compressive
measurements are processed. The adaptive method has low latency, and is more
robust than previous methods. We will present experimental results to
demonstrate the advantages of the proposed method.Comment: Accepted ICIP 201
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
1-{(1Z)-1-[6-(4-Chlorophenoxy)hexyloxy]-1-(2,4-difluorophenyl)prop-1-en-2-yl}-1H-1,2,4-triazol-4-ium nitrate
In the title compound, C23H25ClF2N3O2
+·NO3
−, the triazole ring makes dihedral angles of 60.9 (4) and 25.0 (3)° with the 6-chlorophenyl and 2,4-difluorophenyl rings, respectively. The molecule adopts a Z configuration about the C=C double bond. In the crystal, the cations and anions are linked by N—H⋯O hydrogen bonds and weak C—H⋯O interactions
Reconsideration of Second Harmonic Generation from neat Air/Water Interface: Broken of Kleinman Symmetry from Dipolar Contribution
It has been generally accepted that there are significant quadrupolar and
bulk contributions to the second harmonic generation (SHG) reflected from the
neat air/water interface, as well as common liquid interfaces. Because there
has been no general methodology to determine the quadrupolar and bulk
contributions to the SHG signal from a liquid interface, this conclusion was
reached based on the following two experimental phenomena. Namely, the broken
of the macroscopic Kleinman symmetry, and the significant temperature
dependence of the SHG signal from the neat air/water interface. However,
because sum frequency generation vibrational spectroscopy (SFG-VS) measurement
of the neat air/water interface observed no apparent temperature dependence,
the temperature dependence in the SHG measurement has been reexamined and
proven to be an experimental artifact. Here we present a complete microscopic
analysis of the susceptibility tensors of the air/water interface, and show
that dipolar contribution alone can be used to address the issue of broken of
the macroscopic Kleinman symmetry at the neat air/water interface. Using this
analysis, the orientation of the water molecules at the interface can be
obtained, and it is consistent with the measurement from SFG-VS. Therefore, the
key rationales to conclude significantly quadrupolar and bulk contributions to
the SHG signal of the neat air/water interface can no longer be considered as
valid as before. This new understanding of the air/water interface can shed
light on our understanding of the nonlinear optical responses from other
molecular interfaces as well
Shadow-Aware Dynamic Convolution for Shadow Removal
With a wide range of shadows in many collected images, shadow removal has
aroused increasing attention since uncontaminated images are of vital
importance for many downstream multimedia tasks. Current methods consider the
same convolution operations for both shadow and non-shadow regions while
ignoring the large gap between the color mappings for the shadow region and the
non-shadow region, leading to poor quality of reconstructed images and a heavy
computation burden. To solve this problem, this paper introduces a novel
plug-and-play Shadow-Aware Dynamic Convolution (SADC) module to decouple the
interdependence between the shadow region and the non-shadow region. Inspired
by the fact that the color mapping of the non-shadow region is easier to learn,
our SADC processes the non-shadow region with a lightweight convolution module
in a computationally cheap manner and recovers the shadow region with a more
complicated convolution module to ensure the quality of image reconstruction.
Given that the non-shadow region often contains more background color
information, we further develop a novel intra-convolution distillation loss to
strengthen the information flow from the non-shadow region to the shadow
region. Extensive experiments on the ISTD and SRD datasets show our method
achieves better performance in shadow removal over many state-of-the-arts. Our
code is available at https://github.com/xuyimin0926/SADC
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