In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that ...In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that the high/low speed streaks are directly related to the hairpin or horseshoe-like vortices. This observation can give a better understanding of the physical mechanism in the turbulent boundary layer.展开更多
针对建筑物三维模型建立自动化程度与效率无法并存的问题,本文提出一种自动提取机载激光雷达(light detection and ranging,LiDAR)点云的建筑物关键点算法,针对规则建筑物实现快速三维重建。该方法通过阿尔法-形状(Alpha-Shape)边缘检...针对建筑物三维模型建立自动化程度与效率无法并存的问题,本文提出一种自动提取机载激光雷达(light detection and ranging,LiDAR)点云的建筑物关键点算法,针对规则建筑物实现快速三维重建。该方法通过阿尔法-形状(Alpha-Shape)边缘检测算法和屋顶分割算法完成建筑物关键点提取,再利用夏普·格尔(SharpGL)工具包完成基于关键点建筑物的三维重建。并与经典建筑三维重建方法做对比实验,结果表明本文方法在建筑物提取与三维重建中具有较高的效率,实现0.05 km^(2)区域的建筑物三维重建仅耗时6 min。展开更多
采用常规射频等离子体增强化学气相沉积方法,以高氢稀释的Si H4为源气体和以PH3为掺杂剂,制备了磷掺杂的氢化纳米晶硅薄膜。结果表明,薄膜的生长速率随PH3/Si H4流量比（Cp）增加而显著减小。Raman谱的研究证实,随Cp增加,薄膜的晶化率...采用常规射频等离子体增强化学气相沉积方法,以高氢稀释的Si H4为源气体和以PH3为掺杂剂,制备了磷掺杂的氢化纳米晶硅薄膜。结果表明,薄膜的生长速率随PH3/Si H4流量比（Cp）增加而显著减小。Raman谱的研究证实,随Cp增加,薄膜的晶化率经历了先增大后减小的过程,当Cp=1.0%,晶化率达到最大值45.9%。傅里叶变换红外吸收谱测量结果显示,薄膜中的H含量在Cp=2.0%时达到最低值9.5%。光学测量结果表明,本征和掺P的氢化纳米晶硅薄膜在可见光谱范围呈现出良好的光吸收特性,在0.8~3.0 e V范围内,nc-Si（P）∶H薄膜的吸收系数显著大于c-Si。和α-Si∶H薄膜相比,虽然短波范围的吸收系数较低,但是在hν〈1.7 e V区域,nc-Si（P）∶H薄膜的吸收系数要高两到三个量级,显示出优良的红光响应。电学测量表明,适当掺P会显著提高氢化纳米晶硅薄膜的暗电导率,当Cp=0.5%时,薄膜的暗电导率可达5.4 S·cm-1。展开更多
文摘In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that the high/low speed streaks are directly related to the hairpin or horseshoe-like vortices. This observation can give a better understanding of the physical mechanism in the turbulent boundary layer.
文摘采用常规射频等离子体增强化学气相沉积方法,以高氢稀释的Si H4为源气体和以PH3为掺杂剂,制备了磷掺杂的氢化纳米晶硅薄膜。结果表明,薄膜的生长速率随PH3/Si H4流量比（Cp）增加而显著减小。Raman谱的研究证实,随Cp增加,薄膜的晶化率经历了先增大后减小的过程,当Cp=1.0%,晶化率达到最大值45.9%。傅里叶变换红外吸收谱测量结果显示,薄膜中的H含量在Cp=2.0%时达到最低值9.5%。光学测量结果表明,本征和掺P的氢化纳米晶硅薄膜在可见光谱范围呈现出良好的光吸收特性,在0.8~3.0 e V范围内,nc-Si（P）∶H薄膜的吸收系数显著大于c-Si。和α-Si∶H薄膜相比,虽然短波范围的吸收系数较低,但是在hν〈1.7 e V区域,nc-Si（P）∶H薄膜的吸收系数要高两到三个量级,显示出优良的红光响应。电学测量表明,适当掺P会显著提高氢化纳米晶硅薄膜的暗电导率,当Cp=0.5%时,薄膜的暗电导率可达5.4 S·cm-1。
