Sapphire, belonging to hexagonal crystal system, is typically anisotropic which makes it direction-sensitive. To research the effects of growth directions on properties of sapphire, c-[0001] seed（c-sapphire） and a-[...Sapphire, belonging to hexagonal crystal system, is typically anisotropic which makes it direction-sensitive. To research the effects of growth directions on properties of sapphire, c-[0001] seed（c-sapphire） and a-[11-20] seed（a-sapphire） were used to prepare sapphire by edge-defined film-fed growth（EFG） method. The samples were analyzed through lattice integrity, dislocation and corrosion performance by double-crystal XRD, OM, AFM, SEM and EDX. It was shown that the lattice integrities of two growth-direction crystals were both well due to the small FWHM values. While the average densities of dislocation in c-sapphire and a-sapphire were 9.2×103 and 3.9×103 cm-2 respectively, the energy of dislocation in c-sapphire was lower than that in a-sapphire. During Strong Phosphoric Acid（SPA） etching, the surface of c-sapphire basically kept smooth but in a-sapphire there were many point-like corrosion pits where aluminum and oxygen atoms lost by 2：1. Our work means that it will be promising for growing c-[0001] seed sapphire by EFG if aided by parameter optimization.展开更多
为解决现有测向系统体积大、运算量高、成本高、同步采集困难等问题,设计了一种低成本高精度二维测向系统,由五阵元十字型天线阵列及HackRF One同步采集子系统组成。该测向系统通过外接频率源、引入时间同步信号以及初始相位校准分别实...为解决现有测向系统体积大、运算量高、成本高、同步采集困难等问题,设计了一种低成本高精度二维测向系统,由五阵元十字型天线阵列及HackRF One同步采集子系统组成。该测向系统通过外接频率源、引入时间同步信号以及初始相位校准分别实现了接收设备间频率同步、时间同步、相位同步,然后将同步的采集信号采用多重信号分类(Multiple Signal Classification,MUSIC)算法进行处理,估计出二维波达方向。实验结果表明,系统的同步误差可控制在一个采样周期内,定位误差小于2°,可广泛应用于雷达、声呐、室内定位等多种领域。展开更多
基金Funded by the Special Fund of Jiangsu Province for the Transformation of Scientific and Technological Achievements(No.BA2012049)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Sapphire, belonging to hexagonal crystal system, is typically anisotropic which makes it direction-sensitive. To research the effects of growth directions on properties of sapphire, c-[0001] seed（c-sapphire） and a-[11-20] seed（a-sapphire） were used to prepare sapphire by edge-defined film-fed growth（EFG） method. The samples were analyzed through lattice integrity, dislocation and corrosion performance by double-crystal XRD, OM, AFM, SEM and EDX. It was shown that the lattice integrities of two growth-direction crystals were both well due to the small FWHM values. While the average densities of dislocation in c-sapphire and a-sapphire were 9.2×103 and 3.9×103 cm-2 respectively, the energy of dislocation in c-sapphire was lower than that in a-sapphire. During Strong Phosphoric Acid（SPA） etching, the surface of c-sapphire basically kept smooth but in a-sapphire there were many point-like corrosion pits where aluminum and oxygen atoms lost by 2：1. Our work means that it will be promising for growing c-[0001] seed sapphire by EFG if aided by parameter optimization.
文摘为解决现有测向系统体积大、运算量高、成本高、同步采集困难等问题,设计了一种低成本高精度二维测向系统,由五阵元十字型天线阵列及HackRF One同步采集子系统组成。该测向系统通过外接频率源、引入时间同步信号以及初始相位校准分别实现了接收设备间频率同步、时间同步、相位同步,然后将同步的采集信号采用多重信号分类(Multiple Signal Classification,MUSIC)算法进行处理,估计出二维波达方向。实验结果表明,系统的同步误差可控制在一个采样周期内,定位误差小于2°,可广泛应用于雷达、声呐、室内定位等多种领域。
