6,832 research outputs found
Learning a Dilated Residual Network for SAR Image Despeckling
In this paper, to break the limit of the traditional linear models for
synthetic aperture radar (SAR) image despeckling, we propose a novel deep
learning approach by learning a non-linear end-to-end mapping between the noisy
and clean SAR images with a dilated residual network (SAR-DRN). SAR-DRN is
based on dilated convolutions, which can both enlarge the receptive field and
maintain the filter size and layer depth with a lightweight structure. In
addition, skip connections and residual learning strategy are added to the
despeckling model to maintain the image details and reduce the vanishing
gradient problem. Compared with the traditional despeckling methods, the
proposed method shows superior performance over the state-of-the-art methods on
both quantitative and visual assessments, especially for strong speckle noise.Comment: 18 pages, 13 figures, 7 table
Research on the Rotary Ultrasonic Facing Milling of Ceramic Matrix Composites
AbstractCeramic matrix composites (CMC) has got increasing importance in many fields of industry, especially in the aerospace. However, due to the special properties, the conventional machining methods are generally very challenging for CMC. The rotary ultrasonic machining (RUM) is a high efficiency processing technology for these advanced materials. This paper carried out research on the rotary ultrasonic facing milling of C/SiC and developed the cutting force simulation software to optimize the cutting parameters. Verification experiments were conducted showing that the efficiency improved by RUM is 5.8 times while the surface quality is improved by 54.4% compared with the conventional milling
Tuning the flat bands by the interlayer interaction, spin-orbital coupling and electric field in twisted homotrilayer MoS
Ultraflat bands have already been detected in twisted bilayer graphene (TBG)
and twisted bilayer transition metal dichalcogenides (tb-TMDs), which provide a
platform to investigate strong correlations. In this paper, the electronic
properties of twisted trilayer molybdenum disulfide (TTM) are investigated via
an accurate tight-banding Hamiltonian. We find that the highest valence bands
are derived from -point of the constituent monolayer, exhibiting a
graphene-like dispersion or becoming isolated flat bands. The lattice
relaxation, local deformation, and electric field can significantly tune the
electronic structures of TTM with different starting stacking arrangements.
After introducing the spin-orbital coupling (SOC) effect, we find a
spin-valley-layer locking effect at the minimum of conduction band at K- and
K-point of the Brillouin zone, which may provide a platform to study
optical properties and magnetoelectric effects
TBPLaS: a Tight-Binding Package for Large-scale Simulation
TBPLaS is an open-source software package for the accurate simulation of
physical systems with arbitrary geometry and dimensionality utilizing the
tight-binding (TB) theory. It has an intuitive object-oriented Python
application interface (API) and Cython/Fortran extensions for the performance
critical parts, ensuring both flexibility and efficiency. Under the hood,
numerical calculations are mainly performed by both exact diagonalizatin and
the tight-binding propagation method (TBPM) without diagonalization.
Especially, the TBPM is based on the numerical solution of time-dependent
Schr\"odinger equation, achieving linear scaling with system size in both
memory and CPU costs. Consequently, TBPLaS provides a numerically cheap
approach to calculate the electronic, transport and optical properties of large
tight-binding models with billions of atomic orbitals. Current capabilities of
TBPLaS include the calculation of band structure, density of states, local
density of states, quasi-eigenstates, optical conductivity, electrical
conductivity, Hall conductivity, polarization function, dielectric function,
plasmon dispersion, carrier mobility and velocity, localization length and free
path, Z2 topological invariant, wave-packet propagation, etc. All the
properties can be obtained with only a few lines of code. Other algorithms
involving tight-binding Hamiltonians can be implemented easily thanks to its
extensible and modular nature. In this paper, we discuss the theoretical
framework, implementation details and common workflow of TBPLaS, and give a few
demonstrations of its applications.Comment: 54 pages, 16 figure
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