A novel strategy for the preparation of yttria-stabilized zirconia powders: Deposition and scratching of thin films obtained by the sol-gel method

In the present work, an alternative to the traditional sol-gel method is reported. The gel is deposited on a wide flat glassy surface so that a very thin film of solid is obtained after evaporation of the solvent. The yttria-stabilized zirconia powders are recovered by removing the referred film from the glassy surface and subsequent milling. The samples have been characterized by Scanning Electron Microscopy (SEM), nitrogen adsorption at −196 °C and Fourier Transform Infrared (FT-IR) spectroscopy. The experimental results show that the 3 mol% yttria-stabilized zirconia (3YSZ) powders prepared by drying of thin films at 100 °C exhibit extremely low values of specific surface area and pore volumes. Furthermore, the proportion of solvent or the type of alcohol used in the preparation of the powders play a very important role in the textural properties of the 3YSZ powders. In this connection, for samples prepared by varying the propanol proportion an increase in the volume of this solvent leads to larger values of specific surface area and pore volumes. On the other hand, an increase in the molecular size of the alcohol used as the solvent leads to a noticeable development of the textural parameters.     

一种改进的视觉传感器与激光测距雷达特征匹配点提取算法

激光测距雷达与视觉传感器的配准是视觉图像与激光距离信息融合的前提。激光测距雷达与视觉传感器的配准可分为点匹配与平面匹配。由于混合像素和非结构空间特征激光点丢失现象,使得基于点匹配的视觉传感器与激光测距雷达配准算法精度难以提高。通过对混合像素和非结构空间特征激光点丢失问题的分析,提出了一种结合平面建模思想,利用假想激光光束与平面模型相交提取匹配特征点的方法。验证了实验结果并进行了算法精度比较。实验结果表明,这种改进的特征匹配点提取算法解决了特征点缺失,并且提高了点匹配的精度,使匹配性能大大地改善。     

Luminescence of Ce3+ in lanthanum silicon oxynitride

The luminescence properties of lanthanum silicon oxynitride(La-Si-O-N) series doped by trivalent Ce ions have been investigated to seek for tunable wavelength-conversion phosphor for white light emitting diode applications.Four compound hosts of LaSiO2N,La4Si2O7N2,La5Si3O12 N,and La2Si6O3N8 were synthesized and examined in this work.Crystallographic examination for the equal amount of Ce 3+ substitution indicated that the covalency degree decreased in a sequence LaSiO2 N > La2Si6O3N8 > La4Si2O7N2 > La5Si3O12 N,not simply in correlation to the ratio of N3/O2.Excitation and emission spectrum measurements showed the main features of Ce3+ luminescence in the series:the centre of gravity of 5d bands depends on crystal-field splitting more strongly than that on covalency of Ce-N bonding;nephelauxetic effect could not be observed clearly for the investigated series;to some extent Stokes shift was dominated by crystal-field splitting rather than Ce-N covalency degree.     

SrF2-CaF2混合物薄膜的物理及红外光学特性研究

采用热蒸发和电子束蒸发两种沉积方式分别沉积了相同厚度的SrF₂-CaF₂ (比例为1∶1) 的混合物薄膜,对其物理和光学特性进行了研究,并定量地给出了其在红外波段的光学常数,填补了这一数据的空白. 同时提供了一种获得不同低折射率薄膜的方法.文中还以该比例的混合物作为低折射率材料,研制出具有很好的光学性能的长波红外宽光谱增透膜.     

基于比率的三种群混合扩散模型的动力学行为

讨论了一类基于比率的非自治三种群混合扩散模型,三种群间既有捕食关系又有竞争关系.我们研究了该模型的动力学行为:包括一致持久性,全局渐近稳定性,周期解,概周期解的存在唯一性.表明即使食饵种群在某些孤立的斑块中可能绝灭,也可以通过适当选取扩散率来保证系统持续生存.