671 research outputs found
Quantum resource studied from the perspective of quantum state superposition
Quantum resources,such as discord and entanglement, are crucial in quantum
information processing. In this paper, quantum resources are studied from the
aspect of quantum state superposition. We define the local superposition (LS)
as the superposition between basis of single part, and nonlocal superposition
(NLS) as the superposition between product basis of multiple parts. For quantum
resource with nonzero LS, quantum operation must be introduced to prepare it,
and for quantum resource with nonzero NLS, nonlocal quantum operation must be
introduced to prepare it. We prove that LS vanishes if and only if the state is
classical and NLS vanishes if and only if the state is separable. From this
superposition aspect, quantum resources are categorized as superpositions
existing in different parts. These results are helpful to study quantum
resources from a unified frame.Comment: 9 pages, 4 figure
No-Service Rail Surface Defect Segmentation via Normalized Attention and Dual-scale Interaction
No-service rail surface defect (NRSD) segmentation is an essential way for
perceiving the quality of no-service rails. However, due to the complex and
diverse outlines and low-contrast textures of no-service rails, existing
natural image segmentation methods cannot achieve promising performance in NRSD
images, especially in some unique and challenging NRSD scenes. To this end, in
this paper, we propose a novel segmentation network for NRSDs based on
Normalized Attention and Dual-scale Interaction, named NaDiNet. Specifically,
NaDiNet follows the enhancement-interaction paradigm. The Normalized
Channel-wise Self-Attention Module (NAM) and the Dual-scale Interaction Block
(DIB) are two key components of NaDiNet. NAM is a specific extension of the
channel-wise self-attention mechanism (CAM) to enhance features extracted from
low-contrast NRSD images. The softmax layer in CAM will produce very small
correlation coefficients which are not conducive to low-contrast feature
enhancement. Instead, in NAM, we directly calculate the normalized correlation
coefficient between channels to enlarge the feature differentiation. DIB is
specifically designed for the feature interaction of the enhanced features. It
has two interaction branches with dual scales, one for fine-grained clues and
the other for coarse-grained clues. With both branches working together, DIB
can perceive defect regions of different granularities. With these modules
working together, our NaDiNet can generate accurate segmentation map. Extensive
experiments on the public NRSD-MN dataset with man-made and natural NRSDs
demonstrate that our proposed NaDiNet with various backbones (i.e., VGG,
ResNet, and DenseNet) consistently outperforms 10 state-of-the-art methods. The
code and results of our method are available at
https://github.com/monxxcn/NaDiNet.Comment: 10 pages, 6 figures, Accepted by IEEE Transactions on Instrumentation
and Measurement 202
Study on a Strong Polymer Gel by the Addition of Micron Graphite Oxide Powder and Its Plugging of Fracture
It is difficult to plug the fracture water channeling of a fractured low-permeability reservoir during water flooding by using the conventional acrylamide polymer gel due to its weak mechanical properties. For this problem, micron graphite powder is added to enhance the comprehensive properties of the acrylamide polymer gel, which can improve the plugging effect of fracture water channeling. The chemical principle of this process is that the hydroxyl and carboxyl groups of the layered micron graphite powder can undergo physicochemical interactions with the amide groups of the polyacrylamide molecule chain. As a rigid structure, the graphite powder can support the flexible skeleton of the original polyacrylamide molecule chain. Through the synergy of the rigid and flexible structures, the viscoelasticity, thermal stability, tensile performance, and plugging ability of the new-type gel can be significantly enhanced. Compared with a single acrylamide gel, after adding 3000 mg/L of micrometer-sized graphite powder, the elastic modulus, the viscous modulus, the phase transition temperature, the breakthrough pressure gradient, the elongation at break, and the tensile stress of the acrylamide gel are all greatly improved. After adding the graphite powder to the polyacrylamide gel, the fracture water channeling can be effectively plugged. The characteristics of the networked water flow channel are obvious during the injected water break through the gel in the fracture. The breakthrough pressure of water flooding is high. The experimental results are an attempt to develop a new gel material for the water plugging of a fractured low-permeability reservoir
Applications of Schauder’s Fixed Point Theorem to Semipositone Singular Differential Equations
We study the existence of positive periodic solutions of second-order singular differential equations. The proof relies on Schauder’s fixed point theorem. Our results generalized and extended those results contained in the studies by Chu and Torres (2007) and Torres (2007)
. In some suitable weak singularities, the existence of periodic solutions may help
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