逆变侧换流变压器网侧接地故障对差动保护影响分析

特高压直流输电系统逆变侧换流变网侧单相接地故障后,网侧电压跌落可能会引发直流系统换相失败,有直流分量流入换流变压器绕组,使变压器铁芯磁通发生偏移,引起换流变饱和,产生故障性涌流,进而影响其安全稳定运行。针对逆变侧换流变网侧单相接地故障产生的故障性涌流问题,通过开关函数理论讨论了换流阀正常换相以及换相失败两种情况下网侧故障电流特征,分析了逆变侧网侧单相接地故障后换流变磁通的变化情况。在此基础上,研究了电流互感器饱和对换流变差动保护的影响。结果表明,换流变网侧区内故障情况下,网侧电流互感器饱和,使得换流变差动电流二次谐波含量超过门槛值,导致差动保护误闭锁。最后通过PSCAD/EMTDC仿真验证了分析的正确性。     

Determination of mechanical parameters for jointed rock masses

Combining with empirical method, laboratory test and numerical simulation, a comprehensive system was presented to determine the mechanical parameters of jointed rock masses. The system has the following four functions: (1) Based on the field investigation of joints, the system can consider rock mass structures, by using network simulation technology. (2) Rock samples are conducted by numerical simulation with the input engineering mechanical parameters of rocks and joints obtained from laboratory tests. (3) The whole stress-strain curve of jointed rock masses under certain normal stress can be plotted from numerical simulation, and then the shear strength parameters of jointed rock masses can be obtained from the whole stress-strain curves under different normal stresses. (4) The statistical values of mechanical parameters of jointed rock masses can be determined according to numerical simulation. Based on the statistical values, combining with engineering experiences and geological investigations, the comprehensive mechanical parameters of jointed rock masses can be achieved finally. Several cases are presented to prove the engineering feasibility and suitability of this system.     

基于元结构和框架优选的数控机床床身结构动态设计研究

提出数控机床大件结构设计元结构和基本框架的概念,把由床身筋板围成的栅格称为筋格,床身的宏观构形为基本框架。筋格的动态特性直接影响机床床身的动态特性。分别以筋格各边长、板厚和清砂孔径为设计变量,以筋格的固有频率为优化目标,进行有限元动态设计,得到相应的筋格的基频随设计变量变化的曲线图;通过有限元分析,忏悔 床身的高度与宽度接近时,床身的动态特性较好。用有限元分析法对简化的床身结构动态特性进行研究,总结出对数控机床身设计具有普遍指导意义的规律,可用于数控机床床身结构初步设计。     

融合极化旋转域特征和超像素技术的极化SAR舰船检测

对海监视是极化SAR的重要应用,密集区域的舰船目标检测是当前面临的主要挑战之一。舰船密集区域受多目标串扰,传统的恒虚警率(CFAR)检测滑窗难以选取纯净的海杂波样本用于确定检测门限,将导致检测性能下降。针对这一问题,该文从特征提取和检测器设计两方面出发,提出一种融合极化旋转域特征和超像素技术的极化SAR舰船检测方法。在特征提取方面,雷达目标的后向散射敏感于目标姿态与雷达视线的相对几何关系,由此带来的散射多样性隐含信息可通过极化旋转域分析进行挖掘。该文利用极化相关方向图及导出的一系列极化旋转域特征,根据目标杂波比(TCR)分析,优选TCR最高的3个极化特征量用于构建目标检测器。在此基础上,该文在检测器设计方面提出了一种基于K均值聚类的杂波超像素筛选方法,有效避免了密集区域舰船目标对邻近杂波的影响,基于筛选的杂波像素点得到舰船目标CFAR检测结果。基于Radarsat-2和高分三号星载全极化SAR数据的对比实验表明,所提方法能有效实现密集区域舰船目标检测,检测品质因数达到95%。      

Highly Processable Ionogels with Mechanical Robustness

Currently, the increasing needs of conductive ionogels with intricate shapes and high processability by individual requirements of next-generation flexible electronics constitute significant challenges. Here, the design of highly processable ionogels is reported with mechanical robustness by self-assembly of a common triblock copolymer into a precursor in functional mixed ionic liquids (ILs) containing conductivity-enhancing and polymerizable strength-enhancing components. The subsequent in situ polymerization of the precursor forms physical-co-chemical cross-linked networks, in which the entanglement between physical and chemical cross-linked networks and microphase separation give rise to mechanical robustness of as-fabricated ionogel. The viscosity of the self-assembled precursor can be rationally tuned, which makes the fabrication process compatible with diverse technologies including inkjet printing, spray coating, and 3D printing. By virtue of highly processable capability of the designed ionogels, an auxetic-structured ionogel can be easily generated using 3D printing, which exhibits greatly improved sensitivity and thus is able to monitor tiny deformations. This study that relies on designing functional mixed ILs as the dispersion phase rather than focusing on synthesizing new-type polymers establishes a new route for versatile and programmable fabrication of high-performance ionogels for broader applications.     

黑龙江上游开江期河道特征对流冰速度的影响

为探究黑龙江上游江段开江期流冰速度沿程变化规律和运移过程，通过抛投微型冰浮标定位器进行流冰追 踪试验，分析黑龙江干流开江期流冰速度分布特征及河道形态对流冰速度的影响规律。结果表明：2019 年开江期 距黑龙江干流源头 69~692?km 河段流冰速度分布为 0.79~3.56?m/s，平均速度为 1.65?m/s，流冰速度与河道宽度、河 道弯曲系数呈负相关关系；在弯曲河段、江心岛河段和弯曲分汊型河段流冰速度降低趋势明显，且河道特征对流 冰速度的影响依次减弱。流冰速度沿程分布规律可为冰坝预测及预防凌汛灾害提供数据支持，研究成果对寒区 河流治理具有十分重要的意义。     

Surface-Diluted LiMn6 Superstructure Units Utilizing PO43− Confined Ni-Doping Sites to Stabilize Li-Rich Layered Oxides

Serious capacity and voltage degradation of Li-rich layered oxides (LLOs) caused by severe interfacial side reactions (ISR), structural instability, and transition metal (TM) dissolution during charge/discharge need to be urgently resolved. Here, it is proposed for the inaugural time that the confinement effect of PO₄³⁻ dilutes the LiMn₆ superstructure units on the surface of LLOs, while deriving a stable interface with phosphate compounds and spinel species. Combining theoretical calculations, diffraction, spectroscopy, and micrography, an in-depth investigation of the mechanism is performed. The results show that the modified LLO exhibits excellent anionic/cationic redox reversibility and ultra-high cycling stability. The capacity retention is increased from 72.4% to 95.4%, and the voltage decay is suppressed from 2.48 to 1.29 mV cycle⁻¹ after 300 cycles at 1 C. It also has stable long cycling performance, with capacity retention improved from 40.2% to 81.9% after 500 cycles at 2 C. The excellent electrochemical performance is attributed to the diluted superstructure units on the surface of LLO inhibiting the TM migration in the intralayer and interlayer. Moreover, the stable interfacial layers alleviate the occurrence of ISR and TM dissolution. Therefore, this strategy can give some important insights into the development of highly stable LLOs.     

Makeup Extraction of 3D Representation via Illumination-Aware Image Decomposition

Facial makeup enriches the beauty of not only real humans but also virtual characters; therefore, makeup for 3D facial models is highly in demand in productions. However, painting directly on 3D faces and capturing real-world makeup are costly, and extracting makeup from 2D images often struggles with shading effects and occlusions. This paper presents the first method for extracting makeup for 3D facial models from a single makeup portrait. Our method consists of the following three steps. First, we exploit the strong prior of 3D morphable models via regression-based inverse rendering to extract coarse materials such as geometry and diffuse/specular albedos that are represented in the UV space. Second, we refine the coarse materials, which may have missing pixels due to occlusions. We apply inpainting and optimization. Finally, we extract the bare skin, makeup, and an alpha matte from the diffuse albedo. Our method offers various applications for not only 3D facial models but also 2D portrait images. The extracted makeup is well-aligned in the UV space, from which we build a large-scale makeup dataset and a parametric makeup model for 3D faces. Our disentangled materials also yield robust makeup transfer and illumination-aware makeup interpolation/removal without a reference image.