Multifunctional Organic Potassium Salt Additives as the Efficient Defect Passivator for High-Efficiency and Stable Perovskite Solar Cells

Despite the rapid developments are achieved for perovskite solar cells (PSCs), the existence of various defects in the devices still limits the further enhancement of the power conversion efficiency (PCE) and the long-term stability of devices. Herein, the efficient organic potassium salt (OPS) of para-halogenated phenyl trifluoroborates is presented as the precursor additives to improve the performance of PSCs. Studies have shown that the 4-chlorophenyltrifluoroborate potassium salt (4-ClPTFBK) exhibits the most effective interaction with the perovskite lattice. Strong coordination between  BF₃⁻/halogen in anion and uncoordinated Pb²⁺/halide vacancies, along with the hydrogen bond between F in  BF₃⁻ and H in FA⁺ are observed. Thus, due to the synergistic contribution of the potassium and anionic groups, the high-quality perovskite film with large grain size and low defect density is achieved. As a result, the optimal devices show an enhanced efficiency of 24.50%, much higher than that of the control device (22.63%). Furthermore, the unencapsulated devices present remarkable thermal and long-term stability, maintaining 86% of the initial PCE after thermal test at 80 °C for 1000 h and 95% after storage in the air for 2460 h.     

一种基于Arnold置乱和DCT编码的无载体信息隐藏方法北大核心CSCD

近年来十分火热的搜索映射式无载体信息隐藏虽具有一定的鲁棒性,但其隐藏容量较低、传输负载大且算法复杂度高。针对以上问题,该文章提出一种基于Arnold置乱和离散余弦变换(discrete cosine transform,DCT)编码的无载体信息隐藏方法。该算法先对图片进行Arnold置乱,再对DCT后的低频系数进行编码,接着更换置乱参数来构建索引表。选择索引表中与秘密信息相同的编码值所对应的参数构建候选队列,最后筛选出鲁棒性强的参数作为密钥发送给接收方。实验结果表明,该方法与现有方法相比大大提高了嵌入容量,拥有更强的抗JPEG压缩性能。并且减少了传输负载,算法简捷,具有较强的应用价值。     

Occluded Video Instance Segmentation: A Benchmark

International Journal of Computer Vision - Can our video understanding systems perceive objects when a heavy occlusion exists in a scene? To answer this question, we collect a large-scale dataset...     

Mixed graph convolution and residual transformation network for skeleton-based action recognition

Action recognition based on a human skeleton is an extremely challenging research problem. The temporal information contained in the human skeleton is more difficult to extract than the spatial information. Many researchers focus on graph convolution networks and apply them to action recognition. In this study, an action recognition method based on a two-stream network called RNXt-GCN is proposed on the basis of the Spatial-Temporal Graph Convolutional Network (ST-GCN). The human skeleton is converted first into a spatial-temporal graph and a SkeleMotion image which are input into ST-GCN and ResNeXt, respectively, for performing the spatial-temporal convolution. The convolved features are then fused. The proposed method models the temporal information in action from the amplitude and direction of the action and addresses the shortcomings of isolated temporal information in the ST-GCN. The experiments are comprehensively performed on the four datasets: 1) UTD-MHAD, 2) Northwestern-UCLA, 3) NTU RGB-D 60, and 4) NTU RGB-D 120. The proposed model shows very competitive results compared with other models in our experiments. On the experiments of NTU RGB?+?D 120 dataset, our proposed model outperforms those of the state-of-the-art two-stream models.

     

Feed-direction ultrasonic vibration−assisted milling surface texture formation

The formation mechanism of surface texture for feed-direction ultrasonic vibration?assisted milling (UVAM) was investigated in this study by establishing a kinematic model and a pressing model of UVAM. The kinematic model showed that the cutter tip, which was supposed to be totally sharp, produced closed scratches by crossed trajectories. The variation trends of the interval for closed textures were of sine function. A comparative experiment was carried out by UVAM and conventional milling. A dividing line close to the X coordinate divides the surface feature into two parts. The pressing model showed that the tool minor cutting edge left clear traces with certain width because of the tool minor cutting edge angle. Scratches by tool minor cutting edge were intermittent and regularly varied when feed-direction vibration was introduced. All the surface feature changes are in the radial direction and the trajectory intersections shall always be the scratch grooves or ridges. The ratio between ultrasonic vibration frequency and spindle speed, tool radius, and the located cutter rotation angle affected the changing rule of scratches by tool minor cutting edge. The analytical models and the experimental results proved to each other reasonable.     

The Effects of Initial Conditions on Photoacoustic Waveforms Generated by a Gaussian Heating Source Moving in One Dimension

Although the photoacoustic effect is almost universally generated by radiation whose intensity is varied in time either by amplitude modulation of a continuous optical source or through the use of pulsed irradiation, it is possible to produce sound by movement of a continuous source in space. Here, the characteristics of sound production by movement of a light source in one dimension are discussed by solution to the wave equation for pressure. Solutions to the wave equation for the velocity potential, from which the acoustic pressure can be determined, are found using the D’Alembert integral and by Fourier transformation of the wave equation. The characteristics of the waveform generated by a Gaussian heat source moving uniformly in space are found to depend on the initial conditions for movement of the source.     

反蛋白石结构光子晶体及其应用的研究

反蛋白石结构光子晶体因具有完全光子带隙、制备材料广泛、特殊的周期结构、大的比表面积和连通的孔洞结构,近年来在自发辐射的调制、提高光催化反应速率和染料敏化太阳能电池反应速率等领域成为研究热点之一,并且在光、电、催化、传感、显示、检测等领域有着巨大的应用价值。介绍了反蛋白石结构光子晶体的基本概念及制备方法,阐述了反蛋白石结构在材料自发辐射的调制、能量传递的调制、促进物理化学反应、外界环境响应材料等方面的作用及其应用。     

GPS测量系统误差分析

本文引出了GPS姿态测量,介绍了GPS测量原理,根据GPS测量系统的特点分析了测量过程中的各种误差,并提出了相应的误差消除措施。