PRNet:Pyramid Restoration Network for RAW Image Super-Resolution

Typically, image super-resolution (SR) methods are applied to the standard RGB (sRGB) images produced by the image signal processing (ISP) pipeline of digital cameras. However, due to error accumulation, low bit depth and the nonlinearity with scene radiance in sRGB images, performing SR on them is sub-optimal. To address this issue, a RAW image SR method called pyramid restoration network (PRNet) is proposed in this paper. Firstly, PRNet takes the low-resolution (LR) RAW image as input, and generates a rough estimation of the SR result in the linear color space. Afterwards, a pyramid refinement (PR) sub-network refines image details in the intermediate SR result and corrects its colors in a divide-and-conquer manner. To learn the appropriate colors for displaying, external guidance is extracted from the LR reference image in the sRGB color space, and then fed to the PR sub-network. To effectively incorporate the external guidance, the cross-layer correction module (CLCM), which fully investigates the long-range interactions between two input features, is introduced in the PR sub-network. Moreover, as different frequency components decomposed from the same image are highly correlated, in the PR sub-network, the refined features from a lower layer are utilized to support the feature refinement in an upper layer. Extensive experiments presented in this paper demonstrate that the proposed method is capable of recovering fine details and small structures in images while producing vivid colors that align with the output of a specific camera ISP pipeline

Normal-mode splitting in the optomechanical system with an optical parametric amplifier and coherent feedback

Strong coupling in optomechanical systems is the basic condition for observing many quantum phenomena such as optomechanical squeezing and entanglement. Normal-mode splitting (NMS) is the most evident signature of strong coupling systems. Here we show the NMS in the spectra of the movable mirror and the output field in an optomechanical system can be flexibly engineered by a combination of optical parametric amplifier (OPA) and coherent feedback (CF). Moreover, the NMS could be enhanced by optimizing the parameters such as input optical power, OPA gain and phase, CF strength in terms of amplitude reflectivity of beam splitter.Comment: 8 pages, 7 figure

Emergent topological quantum orbits in the charge density wave phase of kagome metal CsV3_3Sb5_5

The recently discovered kagome materials $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs) attract intense research interest in intertwined topology, superconductivity, and charge density waves (CDW). Although the in-plane $2\times2$ CDW is well studied, its out-of-plane structural correlation with the Fermi surface properties is less understood. In this work, we advance the theoretical description of quantum oscillations and investigate the Fermi surface properties in the three-dimensional CDW phase of CsV$_3$Sb$_5$. We derived Fermi-energy-resolved and layer-resolved quantum orbits that agree quantitatively with recent experiments in the fundamental frequency, cyclotron mass, and topology. We reveal a complex Dirac nodal network that would lead to a $\pi$ Berry phase of a quantum orbit in the spinless case. However, the phase shift of topological quantum orbits is contributed by the orbital moment and Zeeman effect besides the Berry phase in the presence of spin-orbital coupling (SOC). Therefore, we can observe topological quantum orbits with a $\pi$ phase shift in otherwise trivial orbits without SOC, contrary to common perception. Our work reveals the rich topological nature of kagome materials and paves a path to resolve different topological origins of quantum orbits.Comment: The Supplementary is available at the end of the main tex

Electronic nematicity without charge density waves in titanium-based kagome metal

Layered crystalline materials that consist of transition metal atoms on a kagome network have emerged as a versatile platform to study unusual electronic phenomena. For example, in the vanadium-based kagome superconductors AV3Sb5 (where A can stand for K, Cs, or Rb) there is a parent charge density wave phase that appears to simultaneously break both the translational and the rotational symmetry of the lattice. Here, we show a contrasting situation where electronic nematic order - the breaking of rotational symmetry without the breaking of translational symmetry - can occur without a corresponding charge density wave. We use spectroscopic-imaging scanning tunneling microscopy to study the kagome metal CsTi3Bi5 that is isostructural to AV3Sb5 but with a titanium atom kagome network. CsTi3Bi5 does not exhibit any detectable charge density wave state, but comparison to density functional theory calculations reveals substantial electronic correlation effects at low energies. Comparing the amplitudes of scattering wave vectors along different directions, we discover an electronic anisotropy that breaks the six-fold symmetry of the lattice, arising from both in-plane and out-of-plane titanium-derived d orbitals. Our work uncovers the role of electronic orbitals in CsTi3Bi5, suggestive of a hexagonal analogue of the nematic bond order in Fe-based superconductors.Comment: This is the submitted version. Final manuscript will appear in Nature Physic

Theoretical study of vector-vortex field generated by quasi-periodic planar structure

This study presents a rigorous analysis of the vector-vortex field generated by quasi-periodic planar structure (qpps) based on the vectorial Huygens's principle. This letter focuses on the longitudinal component of electrical fields arising from the qpps. We show theoretically that such component is comparable to transverse components in the near field of qpps. Moreover, we demonstrate that the longitude field is also of vortex, with different topological charge from that by transverse components. Selected results are presented to verify the derived theory. ? 2014 IEEE.EI

A Deep-Learning Model with Learnable Group Convolution and Deep Supervision for Brain Tumor Segmentation

The segmentation of brain tumors in medical images is a crucial step of clinical treatment. Manual segmentation is time consuming and labor intensive, and existing automatic segmentation methods suffer from issues such as numerous parameters and low precision. To resolve these issues, this study proposes a learnable group convolution-based segmentation method that replaces convolution in the feature extraction stage with learnable group convolution, thereby reducing the number of convolutional network parameters and enhancing communication between convolution groups. To improve utilization of the feature maps, we added a skip connection structure between learnable group convolution modules, which increased segmentation precision. We used deep supervision to combine output images in the network output stage to reduce overfitting and enhance the recognition capabilities of the network. We tested the proposed algorithm model using the open BraTS 2018 dataset. The experiment results revealed that the proposed model is superior to 3D U-Net and DMFNet and has better segmentation results for tumor cores than No New-Net and NVDLMED, the winning methods in the BraTS 2018 challenge. The segmentation precision of the proposed method with regard to whole tumors, enhancing tumors, and tumor cores was 90.25%, 80.36%, and 86.20%. Furthermore, the proposed method uses fewer parameters and a less complex model

Impact of Public Service Quality on the Efficiency of the Water Industry: Evidence from 147 Cities in China

Nowadays, water service marketization has become a global trend, and the quality of public services has gradually become an important factor affecting the input and output of urban water utilities. This paper defines the connotation of service quality at the technical and public aspects innovatively, builds on the service quality system of water utilities, establishes the relationship between the quality and output efficiency model, and studies the impact of service quality on the efficiency of water utilities. Then, based on 147 cities’ water supply data during the 2005–2016 period in China, the data envelopment analysis model and Tobit panel data model were used in the empirical research to measure the efficiency characterized by the quality dimension. The results show that: (1) The service quality of the water industry is reflected in two aspects: technical and publicity. At the technical level, the service quality of the water industry can be represented by the supply capacity of water and infrastructure, and at the public level, by the penetration rate. (2) The overall comprehensive efficiency of urban water utilities in China is in the middle level of 0.5–0.7, the scale efficiency is at a high level of 0.8–1, and the pure technical efficiency is relatively low. The opportunity cost of maintaining service quality in China’s water sector is 5.21% of the potential output. (3) Public service quality is significantly positively correlated with the efficiency of China’s water utilities, and the improvement of service quality will promote the improvement of efficiency

Two Novel Schiff Base Manganese Complexes as Bifunctional Electrocatalysts for CO₂ Reduction and Water Oxidation

One mononuclear Mn(III) complex [MnIIIL(H2O)(MeCN)](ClO4) (1) and one hetero-binuclear complex [(CuIILMnII(H2O)3)(CuIIL)2](ClO4)2·CH3OH (2) have been synthesized with the Schiff base ligand (H2L = N,N′-bis(3-methoxysalicylidene)-1,2-phenylenediamine). Single crystal X-ray structural analysis manifests that the Mn(III) ion in 1 has an octahedral coordination structure, whereas the Mn(II) ion in 2 possesses a trigonal bipyramidal configuration and the Cu(II) ion in 2 is four-coordinated with a square-planar geometry. Electrochimerical catalytic investigation demonstrates that the two complexes can electrochemically catalyze water oxidation and CO2 reduction simultaneously. The coordination environments of the Mn(III), Mn(II), and Cu(II) ions in 1 and 2 were provided by the Schiff base ligand (L) and labile solvent molecules. The coordinately unsaturated environment of the Cu(II) center in 2 can perfectly facilitate the catalytic performance of 2. Complexes 1 and 2 display that the over potentials for water oxidation are 728 mV and 216 mV, faradaic efficiencies (FEs) are 88% and 92%, respectively, as well as the turnover frequency (TOF) values for the catalytic reduction of CO2 to CO are 0.38 s−1 at −1.65 V and 15.97 s−1 at −1.60 V, respectively. Complex 2 shows much better catalytic performance for both water oxidation and CO2 reduction than that of complex 1, which could be owing to a structural reason which is attributed to the synergistic catalytic action of the neighboring Mn(III) and Cu(II) active sites in 2. Complexes 1 and 2 are the first two compounds coordinated with Schiff base ligand for both water oxidation and CO2 reduction. The finding in this work can offer significant inspiration for the future development of electrocatalysis in this area