Coordinate gap and bidualily

For a varietyX inP ⁿ, we define a numberb ₂, called coordinate gap number,and prove thatb ₂>2 only ifX is not reflexive. Then, for a smooth surface inP ³, we obtain a concrete sufficient and necessary condition forb ₂>2, which enables us to discuss the biduality of surfaces inP ³.     

Extraordinary plasticity of ductile bulk metallic glasses

Shear bands generally initiate strain softening and result in low ductility of metallic glasses. In this Letter, we report high-resolution electron microscope observations of shear bands in a ductile metallic glass. Strain softening caused by localized shearing was found to be effectively prevented by nanocrystallization that is in situ produced by plastic flow within the shear bands, leading to large plasticity and strain hardening. These atomic-scale observations not only well explain the extraordinary plasticity that was recently observed in some bulk metallic glasses, but also reveal a novel deformation mechanism that can effectively improve the ductility of monolithic metallic glasses.     

珠三角产业转移与广西承接产业转移清单

从产业集聚指数的视角,预测了广州、深圳等珠江三角洲地区的9个城市的产业转移趋势.从产业吸引力指数的视角,计算了广西所属的14个地级市分别承接珠江三角洲9个城市中转移产业的吸引力指数,分析了广西在承接珠江三角洲产业转移中的产业分布范围,确定了承接产业转移清单.产业转移承接地的资源禀赋将影响其承接产业转移的能力.承接产业转移的能力取决于承接地的投资环境、自然资源、交通便捷、技术创新、劳动力成本等方面的因素.对广西的14个地级市的资源禀赋进行了分析,测算了其承接产业转移的能力.     

A facile processing way of silica needle arrays with tunable orientation by tube arrays fabrication and etching method

A simple method to fabricate silica micro/nano-needle arrays (SNAs) is presented based on tube-etching mechanism. Using silica fibers as templates, highly aligned and free-standing needle arrays are created over large area by simple processes of polymer infiltration, cutting, chemical etching and polymer removal. Their sizes and orientations can be arbitrarily and precisely tuned by simply selecting fiber sizes and the cutting directions, respectively. This technique enables the needle arrays with special morphology to be fabricated in a greatly facile way, thereby offers them the potentials in various applications, such as optic, energy harvesting, sensors, etc. As a demonstration, the super hydrophobic property of PDMS treated SNAs is examined.     

木粉/聚乙烯复合材料的等离子体表面处理——等离子体处理时间对复合材料表面特性的影响

为改善木粉/聚乙烯复合材料的表面粘接性,实现木粉/聚乙烯复合材料的无缝连接,利用低温等离子体处理技术,对木粉/聚乙烯复合材料进行了表面处理.采用接触角测试、傅立叶变换红外光谱分析(FTIR)以及X射线光电子能谱分析(XPS)研究了等离子体处理前后复合材料表面性能的变化.试验结果表明,经等离子体处理后,复合材料表面的接触角减小,表面润湿性得以改善;FTIR分析结果表明,经等离子体处理后,复合材料表面有—OH、—C=O和—O—C=O基团生成;XPS分析表明,经等离子体处理后,复合材料表面含氧基团的含量增加,在较短的时间内表面氧元素含量增加会达到平衡,且生成大量的—O—C=O基团。     

Ab initio study of the bonding and elastic properties of Ti2CdC

The chemical bonding and elastic properties of Ti₂CdC were investigated by means of a first-principles pseudopotential total energy method. The calculated results for the lattice constants and internal coordinate agree with experimental values very well. Ti₂CdC is conducting, and the Cd-d states have little effect on the chemical bonding. The elastic properties were estimated from the individual elastic constants by Voigt approximation. The calculated shear-modulus of Ti₂CdC, 70 GPa, is the lowest value among all MAX phases. The lower shear-modulus and shear-modulus-to-bulk-modulus ratio are related to the weaker Ti–Cd bond, which indicates the lower coefficient of friction. This suggests that Ti₂CdC would be a potential electrical frictional material.     

Computational analysis of three-dimensional flow and mass transfer in a non-standard configuration for growth of a KDP crystal

Computational analysis of three-dimensional flow and mass transfer in a non-standard configuration for growth of a KDP crystal was conducted. The results show that the surface shear stress is mainly affected by the inlet velocity, and the distribution of the surface supersaturation is determined by the bulk supersaturation and the inlet velocity. By adjusting the inlet velocity, the homogeneity of surface supersaturation can be improved, which is helpful for reducing the occurrence of inclusions and enhancing the crystal quality. The thickness of solute boundary layer is closely related to the flow intensity, but it is almost free from the impact of the bulk supersaturation.     

An Entropy-Based Anti-Noise Method for Reducing Ranging Error in Photon Counting Lidar

Photon counting lidar for long-range detection faces the problem of declining ranging performance caused by background noise. Current anti-noise methods are not robust enough in the case of weak signal and strong background noise, resulting in poor ranging error. In this work, based on the characteristics of the uncertainty of echo signal and noise in photon counting lidar, an entropy-based anti-noise method is proposed to reduce the ranging error under high background noise. Firstly, the photon counting entropy, which is considered as the feature to distinguish signal from noise, is defined to quantify the uncertainty of fluctuation among photon events responding to the Geiger mode avalanche photodiode. Then, the photon counting entropy is combined with a windowing operation to enhance the difference between signal and noise, so as to mitigate the effect of background noise and estimate the time of flight of the laser pulses. Simulation and experimental analysis show that the proposed method improves the anti-noise performance well, and experimental results demonstrate that the proposed method effectively mitigates the effect of background noise to reduce ranging error despite high background noise.