Based on the Marshall-Palmer, Weibull raindrop size distribution and Mie electromagnetic scattering model, the relationships of attenuation coefficient of terahertz (THz) atmospheric window waves with precipitation rate and temperature are studied. Furthermore, combined with the loss of electromagnetic wave transmission in free space, the attenuation of THz communication and the transmission of current mobile communication signals through rain are compared and analyzed. The results show that the attenuation coefficient of THz transmission is increased with increasing precipitation rate, the difference of attenuation coefficient at different THz window waves is small, and the maximum difference is about 3 dB. The rain attenuation of THz wave is first decreased and then increased with increasing temperature, but the temperature has little effect on it. The attenuation of THz wave through rain is much larger than that of mobile communication signal.

悬垂结构是选区激光熔化成型存在的固有几何限制, 其容易导致成型件形状与尺寸精度变差。为了掌握悬垂面成型出现缺陷的原因, 在自主研发的选区激光熔化成型设备上, 采用316L不锈钢粉末, 进行了高速与低速条件下成型不同倾斜角度和不同扫描线长度的悬垂结构实验。结果表明, 倾斜角越小和扫描速度越小, 翘曲变形越严重, 理论分析了最小成型角度与可靠成型角度分别与高速扫描、低速扫描的实验结果吻合。高速扫描可成型具有最小成型角度的悬垂面, 而低速扫描下只能成型可靠成型角度的悬垂面。悬垂面沿着长线扫描方向更容易发生翘曲变形。通过对悬垂面进行局部成型参量控制, 可以明显改善成型质量。本研究从工艺与设计的角度为选区激光熔化技术成型悬垂面提供了依据, 并给出了初步解决方法。

为了能用波长为1.064μm的Nd∶YAG激光器对高反射率的超薄T2紫铜进行激光焊接，通过设计激光脉冲波形中的各个参量，并在纯氮保护、离焦量为+2mm、焊接速率为1.5mm/s的条件下，应用正交试验方法研究了脉冲峰值电流、脉冲峰值时间、脉冲频率的变化对焊接试件可承受的最大剪切应力的影响。通过实验研究，得出了脉冲峰值电流、脉冲峰值时间、脉冲频率对最大剪切应力的影响规律；并观察了焊缝表面及其显微组织。结果表明，通过设计激光脉冲波形等工艺参量，采用波长为1.064μm的Nd∶YAG激光器可以对高反射率的超薄紫铜进行很好的点焊。