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Aiming at the problem of inaccurate feature extraction of low illumination images, a method is proposed that fuses Scale Invariant Feature Transform into SuperPoint. Firstly, the low illumination image is light-enhanced. Secondly, SuperPoint and SIFT features are fused at feature map level, changing the deep neural network weight by labeling the prob output of the network with the SIFT of input image as the maximum of the current prob at pixel-level. Finally, the loss function is constructed based on homography transformation, its principle between image pairs is used to realize the constraint on network parameters. The training and evaluation are conducted on ExDark dataset, tests and comparisons are conducted on multiple indicators of SOTA on HPatches common dataset. The experimental results show that our method improves the precision and recall than SuperPoint, and performs well in multiple evaluation indicators. &nbsp

After more than half century development, remarkable achievements have been made in the study of earth's interior electrical structure by using the magnetotelluric (MT) method. The majority of these research results are based on the electrical isotropic assumption. However, the electrical anisotropy phenomenon is prevalent in the earth interior, and the presence of such anisotropy in the crust and upper mantle is an important link factor among geoelectric models, underground structure and tectonic models. In this paper, the tensor conductivity is first introduced by starting from the Maxwell equations, then we deduce a set of partial differential equations with respect to Ex and Hx according to the characteristic of two-dimensional electrical anisotropic structure. By using the partial differential equations, the appropriate solutions of Ex and Hx are solved, and other field components are obtained on the basis of Ex and Hx. In order to recognize the characteristics of electromagnetic propagation under common and special geological conditions, the influence on the measured MT data is studied by the forward simulation on ordinary and special two-dimension anisotropic electrical structure, which lays theoretical foundation for the subsequent processing and interpretation of MT data. Finally, the electrical anisotropy theory is introduced into processing and interpretation of MT data based on the results in the paper, and the widespread existence of electrical anisotropy is illuminated, and the exactness of this theory and practicability of the algorithm are verified by means of the two-dimension forward fitting interpretation on the MT data from Xinjiang. This work would provide theoretical basis and technical guidance for analyzing and explaining the electrical anisotropy in MT data and help opens approaches for processing of measured MT data.

The segmented mirror telescope is widely used. The aberrations of segmented mirror systems are different from single mirror systems. This paper uses the Fourier optics theory to analyse the Zernike aberrations of segmented mirror systems. It concludes that the Zernike aberrations of segmented mirror systems obey the linearity theorem. The design of a segmented space telescope and segmented schemes are discussed, and its optical model is constructed. The computer simulation experiment is performed with this optical model to verify the suppositions. The experimental results confirm the correctness of the model.

This paper analyses the dynamic residual aberrations of a conformal optical system and introduces adaptive optics (AO) correction technology to this system. The image sharpening AO system is chosen as the correction scheme. Communication between MATLAB and Code V is established via ActiveX technique in computer simulation. The SPGD algorithm is operated at seven zoom positions to calculate the optimized surface shape of the deformable mirror. After comparison of performance of the corrected system with the baseline system, AO technology is proved to be a good way of correcting the dynamic residual aberration in conformal optical design.

Conformal domes that are shaped to meet aerodynamic requirements can increase range and speed for the host platform. Because these domes typically deviate greatly from spherical surface descriptions, a variety of aberrations are induced which vary with the field-of-regard (FOR) angle. A system for correcting optical aberrations created by a conformal dome has an outer surface and an inner surface. Optimizing the inner surface is regard as static aberration correction. A deformable mirror is placed at the position of the secondary mirror in the two-mirror all reflective imaging system, which is the dynamic aberration correction. An ellipsoidal MgF2 conformal dome with a fineness ratio of 1.0 is designed as an example. The FOR angle is 0°− 30°, and the design wavelength is 4 μm. After the optimization at 7 zoom positions by using the design tools Code V, the root-mean-square (RMS) spot size is reduced to approximately 0.99 to 1.48 times the diffraction limit. The design results show that the performances of the conformal optical systems can be greatly improved by the combination of the static correction and the dynamic correction.

Background: Calycosin-7-O-β-D-glucopyranoside (CG) is a natural isoflavone found in traditional Chinese medicines Astragali Radix (AR). Objective: Calycosin-7-O-β-D-glucopyranoside, an isoflavone isolated from AR, has been found to have potent antioxidantive effects. This study was designed to investigate whether CG prevents oxidative stress induced by thioacetamide (TAA). Materials and Methods: BRL-3A cells were pretreated with different concentrations of CG (10, 20, 40 mg/mL) for 12 h and then exposed to 0.18 mol/L TAA for 2 h. The cell viability were examined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium assay, total antioxidant capacity, malondialdehyde (MDA) and the activity of antioxidant enzymes, including catalase, glutathione peroxidase and superoxide dismutase were determined by microplate method. Reactive oxygen species (ROS) generation was quantified by the 2’,7’-dichlorofluorescin-diacetate method. Protein and mRNA expression of CYP2E1 were determined by western blotting and real-time PCR. Results: The cell oxidative stress was significantly increased after 2 h of TAA exposure. Pretreatment of BRL-3A cells with CG significantly increased the activities of antioxidant enzymes, scavenged ROS and reduced MDA production. CG decreased the expression of CYP2E1, and ultimately decreased TAA-induced BRL-3A cells oxidative stress. Conclusions: Calycosin-7-O-β-D-glucopyranoside has a protective effect against TAA-induced oxidative stress in BRL-3A cells, and that the underlying mechanism involves in scavenging of ROS and the modulating expression of CYP2E1.

A uniform distribution of light is expected in many illumination systems. There are several factors influencing the uniformity of light distribution : the intensity distribution of light sources, the aberration of optical systems, and the variability of reflecting index and absorbing index[1].

The electrical anisotropy in the crust and the upper mantle is the main link among geoelectrical model, underlying structure, and tectonic model. In recent years, great attention was paid to this phenomenon, which promotes the new research towards the structure model of electrical anisotropy and inversion theory. According to the Marquardt's inversion theory, in the paper we first improve the weighting factor and apply it to the apparent resistivity and impedance phase joint inversion. Then, the detailed example analysis of them proves the corrctness of the mentioned theory. Additionally, the processing and the interpretation of the measured magnetotelluric data in northwest of china not only indicate the practicability of the theory, but also provide a new method for the future research of deep electrical structures.