The effect of intragranular microstress in Al2O3—SiC nanocomposites

A theoretical model is established to investigate the intragranular particle residual stress in Al2O3-SiC nanocomposites.Using this model,we calculate the average compressive stress on the Al2O3 grain boundary(GB) and the average tensile stress within Al2O3 grains caused by SiC nanoparticles.The normal compressive stress strengthens the GB,and the average tensile stress weakens the grains.The model gives a reasonable interpretation of the strength changes of Al2O3-SiC nanocomposites with the number of SiC particles.     

The effect of intragranular microstress in A1203-SiC nanocomposites

A theoretical model is established to investigate the intragranular particle residual stress in A1203-SiC nanocom-posites. Using this model, we calculate the average compressive stress on the A1203 grain boundary （GB） and the average tensile stress within A1203 grains caused by SiC nanoparticles. The normal compressive stress strengthens the GB, and the average tensile stress weakens the grains. The model gives a reasonable interpretation of the strength changes of A1203-SiC nanocomposites with the number of SiC particles.     

船用星敏感器星点质心精确提取方法

 从星空图像中提取星点质心是星敏感器工作的重要基础,针对船用星敏感器所获取的星空图像噪声情况复杂的特点,提出一种基于重心法的星点质心精确提取方法。通过块扫描的阈值分割和星象连续性的噪点剔除,引入灰度信息参考的星象提取以及重心法质心坐标计算等步骤,从星空图像中提取星点质心。对于30幅海上实拍星图实验,该方法能够100%提取出至少10颗星点,质心坐标提取精度达到1/20像素,并且可以实现对视频图像的实时处理,满足船用星敏感器的应用需求。     

船用星敏感器探测灵敏度计算及分析

星敏感器作为一种被广泛应用于各种载体上的高精度自主导航定位设备,探测灵敏度影响着其工作效率及测量精度。与航天器载体上的星敏感器不同,船用星敏感器工作在海平面环境下,其探测灵敏度不仅由镜头及成像传感器的各项参数决定,还要受到夜空背景以及大气透射等外部因素的影响。为了给船用星敏感器的研制与应用提供理论依据,通过对星光传播、传感器成像以及信号提取过程的研究分析,推导出了船用星敏感器探测灵敏度的计算模型,并通过实验验证了该模型的有效性,在此基础上,分析了各项因素对船用星敏感器探测灵敏度的影响情况,根据分析结果对船用星敏感器系统的设计研制提出了相应建议。     

The effect of intragranular microstress in Al₂O₃-SiC nanocomposites

A theoretical model is established to investigate the intragranular particle residual stress in Al2O3-SiC nanocomposites.Using this model,we calculate the average compressive stress on the Al2O3 grain boundary(GB) and the average tensile stress within Al2O3 grains caused by SiC nanoparticles.The normal compressive stress strengthens the GB,and the average tensile stress weakens the grains.The model gives a reasonable interpretation of the strength changes of Al2O3-SiC nanocomposites with the number of SiC particles.