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The use of non-local self-similarity prior between image blocks can improve image reconstruction performance significantly. We propose a compressive sensing image reconstruction algorithm that combines bilateral total variation and nonlocal low-rank regularization to overcome over-smoothing and degradation of edge information which result from the prior reconstructed image. The proposed algorithm makes use of the preservation of image edge information by bilateral total variation operator to enhance the edge details of the reconstructed image. In addition, we use weighted nuclear norm regularization as a low-rank constraint for similar blocks of the image. To solve this convex optimization problem, the Alternating Direction Method of Multipliers (ADMM) is employed to optimize and iterate the algorithm model effectively. Experimental results show that the proposed algorithm can obtain better image reconstruction quality than conventional algorithms with using total variation regularization or considering the nonlocal structure of the image only. At 10% sampling rate, the peak signal-to-noise ratio gain is up to 2.39 dB in noiseless measurements compared with Nonlocal Low-rank Regularization (NLR-CS). Reconstructed image comparison shows that the proposed algorithm retains more high frequency components. In noisy measurements, the proposed algorithm is robust to noise and the reconstructed image retains more detail information.

Double-ReO3-type structure compound NaSbF6 undergoes a low-temperature rhombohedral to high-temperature cubic phase between 303 and 323 K, as revealed by temperature-dependent X-ray diffractions. Although many double-ReO3-type fluorides exhibit either low thermal expansion or negative thermal expansion (NTE), NaSbF6 exhibits positive thermal expansion (PTE) with a large volumetric coefficient of thermal expansion, αv = 62 ppm/K, in its cubic phase. Raman spectroscopy reveals that the low-frequency transverse vibration of fluorine atoms is stiffened in NaSbF6, compared with the typical NTE compound CaZrF6 with the same structure. The related weak contraction associated with the polyhedral rocking would be overcome by the notable elongation of the Na–F bond length on heating, thus leading to the large volumetric PTE. Unlike ScF3 and CaZrF6 which are insulators with a wide band gap, a relative small band gap of 3.76 eV was observed in NaSbF6. The small band gap can be attributed to the hybridization between ...

As the Mn doping level ( x ) increases in cubic (Ga 0.7 Cu 0.3 ) 1- x Mn x NMn 3 ( x ≤ 0.4) compounds, the temperature window of negative thermal expansion (NTE) is shifted to lower temperatures and broadened due to the strengthening of ferromagnetism. Large coefficient of linear thermal expansion ( α ~ − 22.8 ppm/K) is observed for x = 0.25 and 0.3 at cryogenic temperatures ( x = 0.3 powders, the thermal expansion of epoxy resin is effectively reduced. Nearly zero thermal expansion ( α ~ 1 ppm/K) and remarkably improved thermal conductivity are achieved at cryogenic temperatures in the composite with 50 vol.% addition of the NTE filler.

First principle calculations are performed to study the interfacial photoelectric properties of Ag n /Bi 2 WO 6 (0 0 1) ( n = 1, 2, 3, 4) hybrid photocatalyst. The parallel adsorption of Ag cluster leads to more energetic favorable structures due to stronger interfacial interactions. The positive charged Ag cluster may act as excited electron traps and facilitate the electron⿿hole separation. In particular, hybridization between Ag 5s and O 2p leads to the formation of isolated energy levels above the valence bands, and they become more dispersed with broader bandwidth with the increment of silver cluster size, which is responsible for the enhanced absorption in visible-light region. In the deep valence region, Ag 4d orbital turns more delocalized and hybrid with O 2p states as the cluster size increases, which contributes to more covalent bond feature of Ag⿿O. Moreover, optical spectra demonstrate obvious red-shifts of the absorption edge with the increment of silver content, which enhances efficiently the visible-light photocatalytic activities of Bi 2 WO 6 (0 0 1). The study provides insights into the enhanced photocatalyic mechanism of Ag/Bi 2 WO 6 (0 0 1) and aids in the design of noble metal loaded visible-light plasmonic photocatalyst.

The macromolecular crystallography beamlines at third-generation synchrotron facilities play a central role in solving macromolecular crystal structures and also in understanding the biological function at molecular levels. The MX beamline BL17U at Shanghai Synchrotron Radiation Facility is a typical standard MX beamline with a focused beam size (H × V) of FWHM around 80 μm × 45 μm. However the protein samples brought to the beamline are down to 5-10 m from the important and challenging science project now. These samples require smaller size beam. In order to achieve the mini-size beamline, two mini-beam modes have been developed on BL17U: the pinhole-based mini-beam and the focused mini-beam by compound refractive lens (CRL). Compared to the pinhole-based mode, three times increase in flux is obtained by the CRL mode at a similar beam size. The flux gain obtained by the CRL needs to be considered for data collection strategies. It takes few minutes to switch the beamline from the normal to CRL mini-beam mode.

Normal magnetostriction (MS), which comes from the gradual rotation of magnetic domains in ferromagnets, is anisotropic and smoothly dependent on the applied magnetic field. In cubic antiperovskite compound GaCMn3, a sharp shrink of lattice volume takes place at the antiferromagnetic (AFM) to intermediate magnetic (IM) phase transition. Below the Neel temperature (∼143 K), the AFM-IM transformation can be driven by external magnetic field, leading to a giant isotropic MS of ∼1700 ppm comparable to that of commercial Terfenol-D. In contrast to normal MS, the field-induced magnetostrain exhibits a rapid switch behavior at the critical field. Furthermore, good reversibility and stability were demonstrated for the giant MS of GaCMn3 compound.

Scandium trifluoride (ScF3), adopting a cubic ReO3-type structure at ambient pressure, undergoes a pronounced negative thermal expansion (NTE) over a wide range of temperatures (10 K–1100 K). Here, we report the size effects on the NTE properties of ScF3. The magnitude of NTE is reduced with diminishing the crystal size. As revealed by the specific heat measurement, the low-energy phonon vibrations which account for the NTE behavior are stiffened as the crystal size decreases. With decreasing the crystal size, the peaks in high-energy X-ray pair distribution function (PDF) become broad, which cannot be illuminated by local symmetry breaking. Instead, the broadened PDF peaks are strongly indicative of enhanced atomic displacements which are suggested to be responsible for the stiffening of NTE-related lattice vibrations. The present study suggests that the NTE properties of ReO3-type and other open-framework materials can be effectively adjusted by controlling the crystal size.