8,710 research outputs found
Attention Based Image Compression Post-Processing Convolutional Neural Network
The traditional image compressors, e.g., BPG and H.266, have achieved great
image and video compression quality. Recently, Convolutional Neural Network has
been used widely in image compression. We proposed an attention-based
convolutional neural network for low bit-rate compression to post-process the
output of traditional image compression decoder. Across the experimental
results on validation sets, the post-processing module trained by MAE and
MS-SSIM losses yields the highest PSNR of 32.10 on average at the bit-rate of
0.15.Comment: 4 pages, 2 figures, CVPR Compression Worksho
Classicality and amplification in postselected weak measurement
Nearly thirty years ago the possibility of anomalous weak amplfication (AWA)
was revealed by Aharonov, Albert and Vaidman [1]. Recently two papers presents
two AWA schemes which are beyond the traditional proposal given by them [14,
15]. At the first glance the two papers seems very different. Ref. [14]
discusses the thermal light cross-Kerr effect and finds only postselection can
give the amplification effect without interference of the postselected meter
states, and Ref. [15] shows that only weak interaction itself can give the
amplification effect without postselection. Here the relationships between the
two papers are pointed out and a generalized framework for AWA via
postselecting a pair of orthogonal final states is shown.Comment: Some mistakes are modified, welcome to comments, 4 pages, 4 figure
On mass-dependent subtraction and removal of the ambiguity in QED renormalization
The QED renormalization is restudied by using a mass-dependent subtraction
which is performed at a time-like renormalization point. The subtraction
exactly respects necessary physical and mathematical requirements such as the
gauge symmetry, the Lorentz- invariance and the mathematical convergence.
Therefore, the renormalized results derived in the subtraction scheme are
faithful and have no ambiguity. Especially, it is proved that the solution of
the renormalization group equation satisfied by a renormalized wave function,
propagator or vertex can be fixed by applying the renormalization boundary
condition and of the form as given in the Feynman rules and, thus, an exact
S-matrix element can be expressed in the form as written in the tree diagram
approximation provided that the coupling constant and the fermion mass are
replaced by their effective ones. In the one-loop approximation, the effective
coupling constant and the effective fermion mass obtained by solving their
renormalization group equations are given in rigorous and explicit expressions
which are suitable in the whole range of distance. and exhibit physically
reasonable asymptotic behaviors.Comment: 30 pages, latex, 4 figure
Semileptonic decays in the "PQCD + Lattice" approach
In this paper, we studied the semileptonic decays by employing the PQCD factorization approach, using the newly
defined distribution amplitudes of the meson and the new kind of
parametrization for extrapolation of the form factors , and also taking into
account the lattice QCD results about the relevant form factors at several
points. We found the following main results: (a) the PQCD predictions for the
branching ratios of decays will become a
little smaller by about when the lattice input are taken into
account in the extrapolation of the relevant form factors; (b) the PQCD
predictions for the ratio and the longitudinal
polarization are , and ; and (c) after the inclusion of the lattice input the theoretical
predictions changed slightly: , , and . The theoretical predictions for agree with the measured
one within errors, and other predictions could be tested in the near future
LHCb experiments.Comment: 18 pages, 4 figures and 4 tables. Some important modifications to the
text, new parametrization for extrapolation of the form factors, new
numerical results, new figure, several new references adde
Strain-Induced Room-Temperature Ferromagnetic Semiconductors with Large Anomalous Hall Conductivity in Two-Dimensional Cr2Ge2Se6
By density functional theory calculations, we predict a stable
two-dimensional (2D) ferromagnetic semiconductor CrGeSe, where the
Curie temperature can be dramatically enhanced beyond room temperature
by applying a few percent strain. In addition, the anomalous Hall conductivity
in 2D CrGeSe and CrGeTe is predicted to be comparable
to that in ferromagnetic metals of Fe and Ni, and is an order of magnitude
larger than that in diluted magnetic semiconductor Ga(Mn,As). Based on
superexchange interactions, the enhanced in 2D CrGeSe by
strain can be understood by the decreased energy difference between 3
orbitals of Cr and 4 orbitals of Se. Our finding highlights the microscopic
mechanism to obtain the room temperature ferromagnetic semiconductors by
strain.Comment: 5 pages, 5 figure
Topology optimization of simultaneous photonic and phononic bandgaps and highly effective phoxonic cavity
By using the non-dominated sorting-based genetic algorithm II, we study the
topology optimization of the two-dimensional phoxonic crystals (PxCs) with
simultaneously maximal and complete photonic and phononic bandgaps. Our results
show that the optimized structures are composed of the solid lumps with narrow
connections, and their Pareto-optimal solution set can keep a balance between
photonic and phononic bandgap widths. Moreover, we investigate the localized
states of PxCs based on the optimized structure and obtain structures with more
effectively multimodal photon and phonon localization. The presented structures
with highly focused energy are good choices for the PxC sensors. For practical
application, we design a simple structure with smooth edges based on the
optimized structure. It is shown that the designed simple structure has the
similar properties with the optimized structure, i.e. simultaneous wide
phononic and photonic bandgaps and a highly effective phononic/photonic cavity,
see Figures 8(b) and 8(c).Comment: 9 pages, 8 figure
Topological Superconductors in Correlated Chern Insulators
In this paper, we realize a topological superconductor (TSC) in correlated
topological insulator - the interacting spinful Haldane model. We consider the
electrons on the Haldane model with on-site negative-U interaction and then
study its properties by mean field theory and random-phase-approximation (RPA)
approach. We found that in the intermediate interaction region, the ground
state becomes a TSC with the Chern number 2. We also study its edge states and
the zero modes of the pi-flux.Comment: 13 pages, 14 figure
A classical postselected weak amplification scheme via thermal light cross-Kerr effect
In common sense, postselected weak amplification must be related to
destructive interference effect of the meter system, and a single photon exerts
no effect on thermal field via cross-phasemodulation (XPM) interaction. In this
Letter we present, for the first time, a thermal light cross-Kerr effect.
Through analysis, we reveal two unexpected results: i) postselection and weak
amplification can be explained at a classical level without destructive
interference, and ii) weak amplification and weak value are not one thing.
After postselection a new mixed light can be generated which is nonclassical.
This scheme can be realized via electromagnetically-induced transparency.Comment: Comments are welcome. 6 pages, 11 figure
AndroVault: Constructing Knowledge Graph from Millions of Android Apps for Automated Analysis
Data driven research on Android has gained a great momentum these years. The
abundance of data facilitates knowledge learning, however, also increases the
difficulty of data preprocessing. Therefore, it is non-trivial to prepare a
demanding and accurate set of data for research. In this work, we put forward
AndroVault, a framework for the Android research composing of data collection,
knowledge representation and knowledge extraction. It has started with a
long-running web crawler for data collection (both apps and description) since
2013, which guarantees the timeliness of data; With static analysis and dynamic
analysis of the collected data, we compute a variety of attributes to
characterize Android apps. After that, we employ a knowledge graph to connect
all these apps by computing their correlation in terms of attributes; Last, we
leverage multiple technologies such as logical inference, machine learning, and
correlation analysis to extract facts (more accurate and demanding, either high
level or not, data) that are beneficial for a specific research problem. With
the produced data of high quality, we have successfully conducted many research
works including malware detection, code generation, and Android testing. We
would like to release our data to the research community in an authenticated
manner, and encourage them to conduct productive research
Single photon transfer controlled by excitation phase in a two-atom cavity system
We investigate the quantum interference effects of single photon transfer in
two-atom cavity system caused by external excitation phase. In the proposed
system, two identical atoms (with different positions in the optical cavity)
are firstly prepared into a timed state by an external single photon field.
During the excitation, the atoms grasp different phases which depend on the
spatial positions of the atoms in the cavity. Due to strong resonant
interaction between two atoms and optical cavity mode the absorbed input photon
can be efficiently transferred from the atoms to the resonant cavity mode. We
show that the quantum transfer is highly sensitive to the external excitation
phases of atoms and it leads to quantum interference effects on the cavity mode
excitation. Besides, the quantum transfer is also influenced by the
dipole-dipole interaction dependent to the atomic distance. In this system the
atomic positions also determine the coupling constants between atoms and cavity
mode which causes additional interference effects to the photon exchange
between atoms and cavity. Based on the characteristics of excitation phase we
find that it is a feasible scheme to generate long-lived dark state and it
could be useful for storage and manipulation of single photon fields by
controlling the excitation phase.Comment: 9 pages, 7 figures, 44 reference
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