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Dark reactions featuring continuous activity under light off conditions play a critical role in natural photosynthesis. However, most artificial photocatalysts are inactive upon the removal of the light source, and the artificial photocatalysts with dark photocatalysis abilities have been rarely explored. Herein, we report a Ti-based metal-organic framework (MOF), MIL-125, exhibiting the capability of dark photocatalytic hydrogen production. Remarkably, the introduction of different functional groups onto the linkers enables distinctly different activities of the resulting MOFs (MIL-125-X, X = NH

A high-throughput search for all-inorganic double perovskites by cationic mutation based on first-principles calculations.

The poor stability of organic-inorganic hybrid perovskites hinders its commercial application, which motivates a need for greater theoretical insight into its binding mechanism. To date, the binding mode of organic cation and anion inside organic-inorganic hybrid perovskites is still unclear and even contradictory. Therefore, in this work based on density functional theory (DFT), the binding mechanism between organic cation and anion was systematically investigated through electronic structure analysis including an examination of the electronic localization function (ELF), electron density difference (EDD), reduced density gradient (RDG), and energy decomposition analysis (EDA). The binding strength is mainly determined by Coulomb effect and orbital polarization. Based on the above analysis, a novel 2D linear regression descriptor that E

Here, we report our recent progress in the design, fluid thermodynamics simulation, and high-power test of the2nd harmonic cavity for the China Spallation Neutron Source Phase II. A high-performance and large-size magnetic alloy (MA) core was developed as the load material for the radiofrequency cavity to achieve a high gradient of 40 kV/m. The water-cooling structure and cooling efficiency were studied and improved through numerical analysis and thermal experiments. The long-term stability of the cavity, especially the waterproofness of the MA cores with high heat load, was verified by high power tests.

The application of high-power solid state amplifiers (SSAs) in accelerator facilities is increasing, and equipment failure caused by reflected power is the main risk to their long-term operation. High-power SSAs often comprise multiple power amplifier modules. Full power reflection is more likely to damage the modules in SSAs if the amplitudes of the modules are unequal. Optimization of the power combiners is an effective means for improving the stability of SSAs under high power reflection. This study analyzes the mechanisms and conditions of reflected power generation using the scattering parameters of the combiner and proposes an optimization scheme for the combiner. The simulation and experimental results show that some modules may receive reflected power as high as nearly four times the rated power of one module when the SSA meets certain conditions, which could damage the modules. The maximum reflected power can be effectively reduced and the anti-reflection ability of SSAs can be improved by optimizing the combiner parameters to suppress the maximum reflected power.

In this paper, a novel interference mitigation approach using an autoencoder in combination with a traditional interference detection filter is introduced. It is shown that by employing the gated convolution, the encoder has the ability to learn the signal pattern from the remaining interference-free signal. The decoder can recover the interference-contaminated signal segments from the bottleneck representation as computed by the encoder. Experimental results show that the proposed method can provide a remarkable improvement in signal-to-interference-plus-noise ratio (SINR) and preserves its robustness on real radar measurements in severely disturbed scenarios that are more complex than the training dataset.

The high efficiency of organic–inorganic hybrid perovskites has attracted the attention of many scholars all over the world, the chemical formula of which is ABX3, where A is an organic cation, B is a metal cation, and X is a halogen ion. In addition, the micro-mechanism behind the efficient photoelectric conversion needs more in-depth exploration. Therefore, in this work, based on time-dependent density functional theory (TD-DFT), the electron transfer mechanism from the ground state to the first singlet excited state was systematically investigated by electron and hole analysis and an inter-fragment charge transfer amount method (IFCT). In this work, we optimized and analyzed 99 different perovskite cluster configurations, where A sites are CH3NH3+ (MA+), NH2CHNH2+ (FA+), CH3CH2NH3+ (EA+), NH2CHOH+ (JA+), NH3OH+ (BA+), N(CH3)4+ (DA+), CH3CH2CH2NH3+ (KB+), CH3CH2CH2CH2NH3+ (KC+), C3N2H5+ (RA+), CH(CH3)2+ (TA+), and CH3NH(CH3)2+ (UA+), B sites are Ge2+, Sn2+ and Pb2+, and X sites are Cl−, Br− and I−. According to the analysis of a series of perovskite clusters of the hole–electron distribution, the distribution is mainly concentrated on BX, and electrons and holes are respectively distributed on B and X sites. The exciton binding energy decreases when the metal element changes from Ge to Pb and the halogen element changes from Cl to I. A radar chart including the exciton binding energy, excited energy, amount of net charge transfer, electron and hole overlap index, distance between the centroid of holes and electrons, and the hole and electron separation index was proposed to intuitively describe the electron transmission characteristics of perovskites. Based on that, a comprehensive score index was innovatively proposed to evaluate the photoelectric property of perovskites, providing foundational guidance for the design of high-efficiency organic–inorganic hybrid perovskites.

This paper introduces a novel automotive radar interference mitigation approach using a generative adversarial network (GAN). Instead of tackling the mutual interference in the time domain, a generative adversarial network is trained and used to recover the complex signal in the frequency domain, namely on the complex range profile obtained after the fast Fourier transform of fast-time samples (RFFT spectrum). It is shown that by employing the gated convolution and an attention mechanism, the generator network has the ability to learn the amplitude and phase information for missing data from the remaining signal. Experimental results show that the proposed method can provide a remarkable improvement in signal-to-interference-plus-noise ratio (SINR) and preserves its robustness in severely disturbed scenarios that are much more complex than the training dataset.

Based on the photometric information, a method is proposed for estimating space target attitude and angular velocity under the condition of moving observation platform. Firstly, according to the dynamically changing relative pose relationship among the target, the observation platform and the sun, photometric measurement model is established. Then, in the framework of Unscented Kalman Filter, the joint estimation of target attitude and angular velocity is realized by combining use of quaternion and Modified Rodriguez Parameters. Finally, the feasibility and estimation accuracy of the method are verified by numerical simulation experiments. The results show that the proposed method achieves high accuracy and has certain value in practical application.

Due to its unique properties, such as long carrier diffusion length and adjustable optical band gap, organic-inorganic hybrid perovskite has been a potentially strong photoelectric material for solar cells. However, the challenge of insufficient stability of perovskite materials has not been solved, which in turn, limits its commercial application. Inspired by the strong stability of C3N2H5PbI3 (ImPbI3), we present an innovative doped system, Im(1-x)CsxPbI3 (x = 0.25, 0.5, 0.75), based on the cation-doped strategy, to obtain both strong stability and excellent photoelectric performance. A new perovskite phase ImPbI3 is proposed and verified rationality of existence through formation energy, ab initio molecular dynamics (AIMD), mean square displacement (MSD), and X-ray diffraction (XRD) based on density functional theory (DFT) calculations. For analyzing the photoelectric properties of Im(1-x)CsxPbI3, the bandgap, charge distribution of the frontier molecular orbital, and projected density of states are investigated. To study the stability of Im(1-x)CsxPbI3, geometric configuration, tolerance factor, crystal orbital Hamilton populations (COHP), and AIMD simulations are performed. The results show that the perovskite phase ImPbI3 has strong thermodynamic stability and structural stability, and its optical bandgap value is lower than that of the hexagonal system. When the content of doped Cs does not exceed 50%, the stability of the perovskite phase ImPbI3 is significantly improved. Comprehensive analysis shows that Im0.5Cs0.5PbI3 exhibits encouraging performance with strong stability and high optical absorption coefficient. This theoretical study opens a new avenue for the design of robust organic-inorganic hybrid perovskite materials with strong stability and excellent photoelectric performance based on our findings from perovskite phase ImPbI3 system.

This paper presents a passive measuring method based on monocular trajectory intersection, aimed at realizing the position and velocity measurement of a non-cooperative maritime target for video satellite. Due to the fact that the target’s moving range is relatively small in comparison to that of the satellite during the observation time, a large measuring error results when directly using the monocular trajectory intersection method for 3D motion measurement. Therefore, the dynamic sea surface elevation model is employed to increase the maritime target movement constraints, which simplifies the 3D spatial motion of the target to 2D surface motion. By combining the surface constraint and monocular trajectory intersection method, measurement robustness for a non-cooperative maritime target can be greatly improved. Furthermore, a line-surface intersection method is proposed to obtain the initial solution for motion parameters, which increases the nonlinear optimization efficiency. Simulation experiments are conducted to analyze the effect of different error factors on position and velocity accuracy. The results indicate that the proposed method achieves high measurement accuracy and is feasible in practical applications for video satellite.

Infrared measurement is one of important means for pelagic space instrumentation. Abnormal pixels would impair imaging quality of infrared detector and bring bad influence for display enhancing. In this paper, it presents an abnormal pixel detecting method combing statistics and frequency information and an improved display enhancing method tolerating abnormal pixels based on the detecting result. Real image experiment result shows that it could effectively detect abnormal pixels and improve display enhancing performance.

For through-wall radar imaging (TWRI), the building layout determination is an essential task in practice applications. In this paper, two multi-input multi-output (MIMO) radar with 8 transmitting antennas and 2 receiving antennas under two vertical views are deployed to finish detection, and the generative adversarial nets (GAN) is applied to finish building layout determination. The electromagnetic simulations demonstrate that the GAN achieves great performance in building layout determination.

In synthetic aperture through-the-wall radar imaging, wall penetration effect causes target images defocused and displaced from their true positions. To solve this problem, a wall compensation method based on generative adversarial nets (GAN) is proposed in this paper. Specifically, GAN constructs a spatial structure mapping from the original input images to the output images without wall penetration effect. Electromagnetic simulation show that the proposed method has acceptable computational load and great imaging results in both refocusing and correcting the displacement.

For multi-input multi-output (MIMO) through-wall radar imaging (TWRI), multipath ghosts, side/grating lobe artifacts and wall penetration effect degrade the imaging quality of the obscured targets inside an enclosed building, there in hindering target detection. In this paper, an approach based on generative adversarial nets (GAN) is proposed to achieve multipath ghosts, side/grating lobe artifacts and wall penetration effect suppression with regard to MIMO TWRI. Specifically, the whole task is divided into two steps (Firstly, multipath ghosts and wall penetration effect are suppressed but the side/grating lobes are preserved. Secondly, side/grating lobes are eliminated.) Then a GAN network is applied to solve those two steps. Extensive electromagnetic simulations and comparisons demonstrate that the proposed approach achieves better suppression of multipath ghosts, side/grating lobe artifacts, wall penetration effect and other significant superiorities, including priori wall information not being required and robustness for different array deployments and building layouts.

In this paper, we propose an approach that uses generative adversarial nets (GAN) to eliminate multipath ghosts with respect to through-the-wall radar imaging (TWRI). The applied GAN is composed of two adversarial networks, namely generator G and discriminator D. The generator G learns the spatial characteristics of an input radar image to construct a mapping from input to an output image with suppressed ghosts. The discriminator D evaluates the difference (namely the residual multipath ghosts) between the output image and the ground truth image without multipath ghosts. On the one hand, by training G, the image difference is diminished gradually. In other words, the multipath ghosts are suppressed increasingly in the output image of G. On the other hand, D is trained to improve the ability of evaluating the diminishing difference accompanied with multipath ghosts as much as possible. These two networks G and D fight with each other until G eliminate multipath ghosts. Preliminary simulation results demonstrate GAN can effectively eliminate multipath ghosts in TWRI.

In this paper, we propose an approach that uses generative adversarial nets (GAN) to eliminate multipath ghosts with respect to through-wall radar imaging (TWRI). The applied GAN is composed of two adversarial networks, namely generator G and discriminator D. Generator G learns the spatial characteristics of an input radar image to construct a mapping from an input to output image with suppressed ghosts. Discriminator D evaluates the difference (namely, the residual multipath ghosts) between the output image and the ground-truth image without multipath ghosts. On the one hand, by training G, the image difference is gradually diminished. In other words, multipath ghosts are increasingly suppressed in the output image of G. On the other hand, D is trained to improve in evaluating the diminishing difference accompanied with multipath ghosts as much as possible. These two networks, G and D, fight with each other until G eliminates the multipath ghosts. The simulation results demonstrate that GAN can effectively eliminate multipath ghosts in TWRI. A comparison of different methods demonstrates the superiority of the proposed method, such as the exemption of prior wall information, no target images with degradation, and robustness for different scenes.

3D metrology of a stereovision system requires epipolar rectification to be performed before dense stereo matching. In this study, we propose an epipolar rectification method for a stereovision system with two telecentric lens-based cameras. Given the orthographic projection matrices of each camera, the new projection matrices are computed by determining the new camera coordinates system in affine space and imposing some constraints on the intrinsic parameters. Then, the transformation that maps the old image planes on to the new image planes is achieved. Experiments are performed to validate the performance of the proposed rectification method. The test results show that the perpendicular distance and 3D reconstructed deviation obtained from the rectified images is not significantly higher than the corresponding values obtained from the original images. Considering the roughness of the extracted corner points and calibrated camera parameters, we can conclude that the proposed method can provide sufficiently accurate rectification results.

Photoelectric theodolite is important optical measurement equipment in pelagic aerospace TT&C systems. The visible light imaging method helps capture significant information of the observed target, photometric information is one of them. To achieve expediently and quickly target photometric measuring, it studies and realizes a measuring method, by using stars in the same field of view as the observed target in this paper. Firstly, it calculates the gray values for target and star by image processing algorithm in the image captured by theodolite. Then magnitude information of the star is obtained by using a star catalogue. Lastly, magnitude of the target is calculated by antitheses method. The approach is implemented to investigate the measuring performance and an experiment is carried out by using images containing at least two stars. The result shows good performance of the proposed method.

To further extend the scope of stereo-digital image correlation (stereo-DIC) to more challenging environments, a novel Scheimpflug camera-based stereo-DIC is developed for full-field 3D deformation measurement, wherein the Scheimpflug condition, consisting of tilting the sensor plane with respect to the lens plane for the sake of larger depth of field (DOF) of the camera, is employed. The geometric imaging model of the Scheimpflug camera is described, on the basis of which a robust and effective stepwise calibration strategy is performed to calculate the intrinsic and extrinsic parameters of the stereo Scheimpflug rig. With the aid of a specially tailored stereo triangulation method and well-developed subset-based DIC algorithms, the three-dimensional shape and displacement of the specimen can be retrieved. Finally, practical experiments, including rigid motion tests and three-point bending tests, demonstrate the effectiveness and accuracy of the proposed approach.

A good similarity measure is the key to robust template matching. In this paper, we present a Similarity-Transform invariant Best-Buddies Similarity (SiTi-BBS) to deal with the template matching with obvious geometric distortion. Similar to the BBP, SiTi-BBS still adopts Best-Buddies Pair (BBP) to vote. However, differing from the classic BBS acquiring the point pair via bidirectional matching in xyRGB space, SiTi-BBS takes only the color information (RGB components) to acquire BBPs, while the position information (xy components) of each BBP is employed to calculate the geometric distortion between the template and matching window. To further improve the robustness of template matching, we novelly take advantage of the interval voting to accommodate the case where the two images do not strictly satisfy the similarity transformation. Therefore, SiTi-BBS, to a certain extent, can be applied to the affine and perspective transformation. In this way, the highest number of votes is taken as the similarity measure between the two images. Mathematical analysis indicates that the proposed method is capable of dealing with the case of obvious geometric distortion between images. Furthermore, the test results of simulated and real challenging images show the outstanding performance of the proposed similarity measure for template matching.

The membrane progestin receptor α (mPRα) plays an important role in the regulation of oocyte meiotic maturation in fish. However, the endocrine regulation of multiple spawning in fish with asynchronous ovarian development remains to be determined. We identified four genes (FSHβ, LHβ, CGα and mPRα) that are widely expressed in both the reproductive and non-reproductive tissues of rock bream Oplegnathus fasciatus and examined their expression during ovarian maturation. The level of FSHβ transcripts in the pituitary remained high during vitellogenic stages, when the plasma levels of estradiol-17β reached maximum levels and oocyte development was stimulated. LHβ expression in the pituitary and ovary reached maximum levels during oocyte maturation when the plasma levels of testosterone also reached a maximum. A significant correlation between mPRα transcript levels and the gonadosomatic index was observed during vitellogenesis and final maturation. Brain gonadotropin (FSHβ and LHβ) and mPRα were continuously expressed at different stages of ovarian development. The dynamic and diverse nature of gonadotropins and mPRα gene expression patterns suggests that these genes might jointly regulate ovarian development and maturation through the brain–pituitary–ovary axis in the rock bream endocrine system. J. Exp. Zool. 323A: 430–444, 2015. © 2015 Wiley Periodicals, Inc.

Micro satellites have been widely used in the target monitoring and tracking. Aimed to reduce the ground operator's workload, a target location method based on homography and scene matching is proposed in this paper. For the first time satellite flies over target area, it needs the operator to take a frame as a reference image and extract the target area which is regarded as plane scene. When the satellite scan the area again, we take a frame as a real-time image and calculate the homography induced by the plane. Then rectify the reference image with the homography to reduce distortion between the two images. Finally, locate target on the real-time image using matching method. A significant-feature-point auxiliary positioning method is also proposed to adapt to target area without obvious features. It adopts affine model to calculated target location on the real-time image. Simulation experimental results show accuracy and practical value for engineering of the proposal method.

The structure, composition and mechanical properties of TixCr1-xN coatings have been investigated. Processing by cathodic arc evaporation using cathodes with different arc currents was performed to obtain coatings with compositions x=0.52, x=0.59, x=0.68, x=0.72 and x=0.81, The TixCr1-xN hard coatings were characterized by nanoindentation, scanning electron microscopy and X-ray diffraction. The results showed the coatings consisted of B1-NaCl type cubic structure, the Cr content promoted a (200) preferred crystallographic orientation and has a dramatic influence on the hardness of TixCr1-xN coatings, which indicted the alloy-strengthening of the Cr element on TiN-based coatings.

To simultaneously perform 3D measurement and camera attitude estimation, an efficient and robust method based on trifocal tensor is proposed in this paper, which only employs the intrinsic parameters and positions of three cameras. The initial trifocal tensor is obtained by using heteroscedastic errors-in-variables (HEIV) estimator and the initial relative poses of the three cameras is acquired by decomposing the tensor. Further the initial attitude of the cameras is obtained with knowledge of the three cameras’ positions. Then the camera attitude and the interested points’ image positions are optimized according to the constraint of trifocal tensor with the HEIV method. Finally the spatial positions of the points are obtained by using intersection measurement method. Both simulation and real image experiment results suggest that the proposed method achieves the same precision of the Bundle Adjustment (BA) method but be more efficient.

Two-color DNA microarray platforms are widely used for determining differential amounts of target sequences in parallel between sample pairs. However, the fluorescence (or Forster) resonance energy transfer (FRET) between two fluorophores can potentially result in the distortions of the measured fluorescence signals. Here we assessed the influence of FRET on the two-color DNA microarray platform and developed a reliable and convenient method for the correction of FRET distortion. Compared to current methods of normalization based on the statistical analysis and the hypothesis that only a small part of target sequences are differentially presented between sample pairs, our FRET correction method can recover the undistorted signals by the compensation of fluorescence emission, without considering the number of target sequences differentially presented. The correction method was validated with samples at different target ratios and with microarrays spotted in different probe concentrations. We also applied the FRET correction method to gene expression profiling arrays, and the results show that FRET was present when the content of target sequence was beyond a threshold amount and that the process incorporating our FRET correction method can improve the reliability of the gene expression profiling microarray platform in comparison with the current process without FRET correction.

The membrane progestin receptor α (mPRα) plays an important role in the regulation of oocyte meiotic maturation in fish. However, the endocrine regulation of multiple spawning in fish with asynchronous ovarian development remains to be determined. We identified four genes (FSHβ, LHβ, CGα and mPRα) that are widely expressed in both the reproductive and non-reproductive tissues of rock bream Oplegnathus fasciatus and examined their expression during ovarian maturation. The level of FSHβ transcripts in the pituitary remained high during vitellogenic stages, when the plasma levels of estradiol-17β reached maximum levels and oocyte development was stimulated. LHβ expression in the pituitary and ovary reached maximum levels during oocyte maturation when the plasma levels of testosterone also reached a maximum. A significant correlation between mPRα transcript levels and the gonadosomatic index was observed during vitellogenesis and final maturation. Brain gonadotropin (FSHβ and LHβ) and mPRα were continuously expressed at different stages of ovarian development. The dynamic and diverse nature of gonadotropins and mPRα gene expression patterns suggests that these genes might jointly regulate ovarian development and maturation through the brain-pituitary-ovary axis in the rock bream endocrine system.

Biomolecular interactions can be detected by many established technologies such as fluorescence imaging, surface plasmon resonance (SPR) [1-4] , interferometry and radioactive labeling of the analyte. In this study, we have designed and constructed a label-free, real-time sensing platform and its operating imaging instrument that detects interactions using optical phase differences from the accumulation of biological material on solid substrates. This system allows us to monitor biomolecular interactions in real time and quantify concentration changes during micro-mixing processes by measuring the changes of the optical path length (OPD). This simple interferometric technology monitors the optical phase difference resulting from accumulated biomolecular mass. A label-free protein chip that forms a 4×4 probe array was designed and fabricated using a commercial microarray robot spotter on solid substrates. Two positive control probe lines of BSA (Bovine Serum Albumin) and two experimental human IgG and goat IgG was used. The binding of multiple protein targets was performed and continuously detected by using this label-free and real-time sensing platform.