1,407 research outputs found
Sparse representation for pose invariant face recognition
Face recognition is easily affected by pose angle. In order to improve the obustness to pose angle, we need to solve the pose estimation, face synthesis and recognition problem. Sparse representation can represent a face image with linear combination of atom faces. In this paper, we construct different pose dictionaries using face images captured under the same pose angle to estimate pose angle and synthesize front face images for recognition. Experimental results show that sparse representation can estimate pose angle accurately, synthesize near frontal faces very well and significantly improve the recognition rate for large pose angles
Transverse-momentum-dependent wave functions and Soft functions at one-loop in Large Momentum Effective Theory
In large-momentum effective theory (LaMET), the transverse-momentum-dependent
(TMD) light-front wave functions and soft functions can be extracted from the
simulation of a four-quark form factor and equal-time correlation functions. In
this work, using expansion by regions we provide a one-loop proof of TMD
factorization of the form factor. For the one-loop validation, we also present
a detailed calculation of perturbative corrections to
these quantities, in which we adopt a modern technique for the calculation of
TMD form factor based the integration by part and differential equation. The
one-loop hard functions are then extracted. Using lattice data from Lattice
Parton Collaboration on quasi-TMDWFs, we estimate the effects from the one-loop
matching kernel and find that the perturbative corrections depend on the
operator to define the form factor, but are less sensitive to the transverse
separation. These results will be helpful to precisely extract the soft
functions and TMD wave functions from the first-principle in future
Does global value chain engagement improve export quality? Evidence from Chinese manufacturing firms
Using a firm-level data set of Chinese manufacturing sector, we
examine whether global value chain (G.V.C.) engagement induces
firms to upgrade the quality of the goods that they export.
Empirical results show that G.V.C. participation has positive impact
on export product quality, and this finding is consistent across
several robustness checks. However, the influence of G.V.C.
embedment on export quality presents an ‘inverted-U’ shape. The
mechanism analysis demonstrates that the effect of G.V.C. participation
on export quality is driven by competition effect and firms’
willingness to import high-quality intermediates. Furthermore, the
quality effect of G.V.C. embedment differs depending on firm
characteristics. This article therefore contributes to a better understanding
of the benefits of participation in G.V.C.s for manufacturing
firms from developing countries
Formation of Nanofoam carbon and re-emergence of Superconductivity in compressed CaC6
Pressure can tune material's electronic properties and control its quantum
state, making some systems present disconnected superconducting region as
observed in iron chalcogenides and heavy fermion CeCu2Si2. For CaC6
superconductor (Tc of 11.5 K), applying pressure first Tc increases and then
suppresses and the superconductivity of this compound is eventually disappeared
at about 18 GPa. Here, we report a theoretical finding of the re-emergence of
superconductivity in heavily compressed CaC6. The predicted phase III (space
group Pmmn) with formation of carbon nanofoam is found to be stable at wide
pressure range with a Tc up to 14.7 K at 78 GPa. Diamond-like carbon structure
is adhered to the phase IV (Cmcm) for compressed CaC6 after 126 GPa, which has
bad metallic behavior, indicating again departure from superconductivity.
Re-emerged superconductivity in compressed CaC6 paves a new way to design
new-type superconductor by inserting metal into nanoporous host lattice.Comment: 31 pages, 12 figures, and 4 table
Terahertz Wave Guiding by Femtosecond Laser Filament in Air
Femtosecond laser filament generates strong terahertz (THz) pulse in air. In
this paper, THz pulse waveform generated by femtosecond laser filament has been
experimentally investigated as a function of the length of the filament.
Superluminal propagation of THz pulse has been uncovered, indicating that the
filament creates a THz waveguide in air. Numerical simulation has confirmed
that the waveguide is formed because of the radially non-uniform refractive
index distribution inside the filament. The underlying physical mechanisms and
the control techniques of this type THz pulse generation method might be
revisited based on our findings. It might also potentially open a new approach
for long-distance propagation of THz wave in air.Comment: 5 pages, 6 figure
QED contributions to the mixing
We explore the QED corrections to the mixing within
the framework of light-front quark model (LFQM) in the three-quark picture.
After explicitly investigating the relation between the
mixing and the flavor and heavy quark symmetry breaking, we
derive the QED contributions to the mixing angle. Numerical results indicate
the QED contribution is smaller than the one from the mass difference between
the strange and up/down quark provided by a recent Lattice QCD analysis. Adding
these contributions together we find that at this stage the
mixing is small and still incapable to account for the
large symmetry breaking in the semi-leptonic decays.Comment: 7 pages, 4figure
Singing Voice Synthesis with Vibrato Modeling and Latent Energy Representation
This paper proposes an expressive singing voice synthesis system by
introducing explicit vibrato modeling and latent energy representation. Vibrato
is essential to the naturalness of synthesized sound, due to the inherent
characteristics of human singing. Hence, a deep learning-based vibrato model is
introduced in this paper to control the vibrato's likeliness, rate, depth and
phase in singing, where the vibrato likeliness represents the existence
probability of vibrato and it would help improve the singing voice's
naturalness. Actually, there is no annotated label about vibrato likeliness in
existing singing corpus. We adopt a novel vibrato likeliness labeling method to
label the vibrato likeliness automatically. Meanwhile, the power spectrogram of
audio contains rich information that can improve the expressiveness of singing.
An autoencoder-based latent energy bottleneck feature is proposed for
expressive singing voice synthesis. Experimental results on the open dataset
NUS48E show that both the vibrato modeling and the latent energy representation
could significantly improve the expressiveness of singing voice. The audio
samples are shown in the demo website
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