Tailoring the Molecular Properties with Isomerism Effect of AIEgens

It is challenging to achieve precise control on the properties of organic π‐functional materials to widen their practical applications. On the other hand, the study of aggregation‐induced emission luminogens (AIEgens) helps achieve such goals because of inherent relationships between their luminescence behaviors and conformational variations that allow for the visual monitoring of the changes in the material properties. Inspired by this, in this work, three AIE isomers are fabricated in structures consisting of tetraphenylpyrazine and triphenylethene units with para‐, meta‐, and ortho‐position linkages, respectively. The isomerism effect brings about significantly decreased luminescence efficiency, subtly blueshifted emission, basically reduced AIE effect but boosted porosity in the aggregate state as the conformation of AIEgens evolves from an extended to a folded one. Based on the distinct properties, their respective use in blue organic light‐emitting diodes, nanofluorescent probes, and molecule‐capturing porous crystals are investigated. This work not only achieves precise property control by using the isomerism effect of AIEgens but also provides useful information on the future design of π‐conjugated materials with advanced functionalities.     

Interface Engineering for Both Cathode and Anode Enables Low‐Cost Highly Efficient Solution‐Processed CdTe Nanocrystal Solar Cells

Low‐cost solution‐processed CdTe nanocrystal (NC) solar cells always suffer from a high interface energy barrier and unbalanced hole/electron transport as well as anisotropic atom diffusion on the CdTe surface due to the limited amount of hole/electron interface materials or the difficulty in interface processing. In this work, a novel strategy is first adopted with gradient electron transport layer (CdS/CdSe) modification in the cathode and a new crosslinkable hole transport polymer (P‐TPA) implantation in the anode. The carrier recombination at interfaces is greatly decreased and thus the carrier collection is increased. Moreover, the light harvesting is improved both in short and long wavelength regions, making J_sc and V_oc increase simultaneously. A champion solar cell shows a very high power conversion efficiency of 9.2% and an outstanding J_sc of 25.31 mA cm^?2, which are among the highest values for all solution‐processed CdTe NC solar cells with a superstrate structure, and the latter value is even higher than that of traditional thick CdTe thin‐film solar cells (2 µm) via the high temperature close space sublimation method. This work demonstrates that facile surface modifications in both the cathode and anode with stepped extraction and organic–inorganic hybridization are very promising in constructing next‐generation highly efficient NC photovoltaic devices.     

Polymer Template Synthesis of Flexible BaTiO3 Crystal Nanofibers

BaTiO₃ crystals are attractive materials due to their high dielectric properties, but they are brittle and inelastic ceramics, which limits their broader applications in emerging fields, such as flexible electronics. A scalable strategy for the fabrication of ultra‐flexible crystalline BaTiO₃ nanofiber (NF) films by a sol–gel electrospinning method, followed by a brief calcination, is reported. It facilitates the formation of perovskite BaTiO₃ crystals with intricate grain boundaries at a low temperatures by growing them within polymer NF templates. The ceramic films have a polymer‐like softness of 50 mN, a large Young's modulus of 61 MPa, and an elastic strain of 0.9%. Moreover, they have a low density of 28 mg cm^?3 and demonstrate superior softness without fracture after deformation. Piezoelectric sensors fabricated based on these films exhibit a high sensitivity of 80 ms with an output voltage of 1.05 V at a pressure of 100 kPa. This approach allows for the large‐scale fabrication of flexible BaTiO₃ crystal NF films.     

基于三角面元模型的复杂目标棱边提取

等效边缘电磁流法是计算超电大目标电磁散射特性的有力工具之一。当目标为复杂目标时,目标棱边提取是分析中的重要一环。文中根据目标模型特征提出了一种棱边提取的方法。使用商业软件Hypermesh建模并输出模型三角面元数据,采用穷举法给出所有三角面元及与其相邻的三角面元信息,通过设定角度阀值确定属于目标棱边的三角面元,接着判断该面元所含棱边的凹凸性,完成棱边提取。数值结果表明,该方法可以精准提取复杂目标棱边的数据信息。     

主动学习半监督聚类入侵检测算法

针对聚类的入侵检测算法误报率高的问题,提出一种主动学习半监督聚类入侵检测算法.在半监督聚类过程中应用主动学习策略,主动查询网络中未标记数据与标记数据的约束关系,利用少量的标记数据生成正确的样本模型来指导大量的未标记数据聚类,对聚类后仍未能标记的数据采用改进的K-近邻法进一步确定未标记数据的类型,实现对新攻击类型的检测.实验结果表明了算法的可行性及有效性.     

基于天线分集和空-时编码的抗舰载卫星天线指向损耗方法研究

本文针对舰载卫星天线指向损耗问题,将接收分集和空-时编码技术应用于舰艇卫星通信中。构建了舰船卫星通信信道模型,分析了舰载天线随机指向损耗特点,研究了接收分集和空-时编码技术,进行了舰船卫星MIMO通信性能仿真。研究结果表明,将MIMO技术应用于舰艇卫星通信可以有效改善舰载卫星天线指向损耗的不良影响。     

低温退火对具有HfO2/TiN栅结构的MOS电容电学性能的影响

The effects of low temperature annealing,such as post high-k dielectric deposition annealing(PDA),post metal annealing(PMA)and forming gas annealing(FGA)on the electrical characteristics of a metal–oxide–semiconductor(MOS)capacitor with a TiN metal gate and a HfO2dielectric are systematically investigated.It can be found that the low temperature annealing can improve the capacitance–voltage hysteresis performance significantly at the cost of increasing gate leakage current.Moreover,FGA could effectively decrease the interfacial state density and oxygen vacancy density,and PDA could make the flat band positively shift which is suitable for P-type MOSs.     

宽光谱、大视场小畸变望远系统设计

设计了一个应用于成像光谱仪的望远系统,针对成像光谱仪的特点,由前置望远镜及后置光谱仪组成。前置望远系统的参数以及成像质量对整个成像光谱仪应用显得非常重要。设计了一个谱段范围1～2.5 m、视场为28.10.3、相对口径为1/4、焦距长度为60 mm的望远系统。系统在谱段1～2.5 m宽谱段范围内通过玻璃的匹配校正了色差及二级光谱,畸变控制在0.2%以内,很好地保证了与后续光谱仪的对接,此设计可用于航空领域进行大视场、高分辨率成像。     

CMOS图像传感器中电荷非完全转移的影响分析

A method to judge complete charger transfer is proposed for a four-transistor CMOS image sensor with a large pixel size.Based on the emission current theory,a qualitative photoresponse model is established to the preliminary prediction.Further analysis of noise for incomplete charge transfer predicts the noise variation.The test pixels were fabricated in a specialized 0.18μm CMOS image sensor process and two different processes of buried N layer implantation are compared.The trend prediction corresponds with the test results,especially as it can distinguish an unobvious incomplete charge transfer.The method helps us judge whether the charge transfer time satisfies the requirements of the readout circuit for the given process especially for pixels of a large size.     

Modal cutoff in rare-earth-doped photonic crystal fibers with multi-layer air-holes missing in the core

The various mode effective indices of the doped photonic crystal fibers (PCFs) are compared, the mode field distributions of the fundamental mode and the second-order mode are analyzed, and the single-mode condition is presented. The mode effective indices of large-core doped PCFs with different core indices and structure parameters are simulated by the finite element method (FEM). The relations of the core index with the fiber structure parameters of pitch, hole-to-pitch ratio and core diameter are obtained for single-mode propagation. In the design and fabrication of the doped PCF, we can adjust the core index and fiber structure parameters to achieve large mode area and single-mode propagation.