非视距传播是无线传感器网络定位中的难题,尤其在复杂的室内环境中,由于视距(Line of Sight,LOS)和非视距(Non-Line of Sight,NLOS)环境的不断切换,对移动目标的精准定位仍是一项难题。文中提出了一种基于平方根无迹卡尔曼滤波和鲁棒扩...非视距传播是无线传感器网络定位中的难题,尤其在复杂的室内环境中,由于视距(Line of Sight,LOS)和非视距(Non-Line of Sight,NLOS)环境的不断切换,对移动目标的精准定位仍是一项难题。文中提出了一种基于平方根无迹卡尔曼滤波和鲁棒扩展卡尔曼滤波并行工作的定位方法,首先对所有节点同一时刻多次采样的TOA测量值进行是否处于非视距环境的判别,如果处于LOS环境,则使用平方根无迹卡尔曼滤波算法进行动态跟踪,若某一节点处于NLOS环境,则采用高斯混合多模型算法对多次采样值进行聚类,并将聚类结果送入并行工作的2个鲁棒扩展卡尔曼滤波器和无迹卡尔曼滤波器,经概率加权后输出定位结果。理论分析和仿真结果表明,本方法具有良好的定位精度。展开更多
An exponential-doping structure is successfully applied to the preparation of AlGaAs/GaAs photocathodes through the metalorganic chemical vapor deposition(MOCVD)technique.The experimental results show that the quantum...An exponential-doping structure is successfully applied to the preparation of AlGaAs/GaAs photocathodes through the metalorganic chemical vapor deposition(MOCVD)technique.The experimental results show that the quantum efficiency in the entire waveband region for the exponential-doping photocathodes grown by MOCVD is remarkably enhanced as compared to those grown by molecular beam epitaxy.As a result of the improved built-in electric fields and cathode performance parameters,the photoemission characteristics for the MOCVD-grown transmission-mode and reflection-mode AlGaAs/GaAs photocathodes are different over the wavelength region of interest.展开更多
文摘非视距传播是无线传感器网络定位中的难题,尤其在复杂的室内环境中,由于视距(Line of Sight,LOS)和非视距(Non-Line of Sight,NLOS)环境的不断切换,对移动目标的精准定位仍是一项难题。文中提出了一种基于平方根无迹卡尔曼滤波和鲁棒扩展卡尔曼滤波并行工作的定位方法,首先对所有节点同一时刻多次采样的TOA测量值进行是否处于非视距环境的判别,如果处于LOS环境,则使用平方根无迹卡尔曼滤波算法进行动态跟踪,若某一节点处于NLOS环境,则采用高斯混合多模型算法对多次采样值进行聚类,并将聚类结果送入并行工作的2个鲁棒扩展卡尔曼滤波器和无迹卡尔曼滤波器,经概率加权后输出定位结果。理论分析和仿真结果表明,本方法具有良好的定位精度。
基金the National Natural Science Foundation of China under Grant Nos 61067001,61240042 and 61261009the Key Science and Technology Project of Henan Province of China under Grant No 112102210202.
文摘An exponential-doping structure is successfully applied to the preparation of AlGaAs/GaAs photocathodes through the metalorganic chemical vapor deposition(MOCVD)technique.The experimental results show that the quantum efficiency in the entire waveband region for the exponential-doping photocathodes grown by MOCVD is remarkably enhanced as compared to those grown by molecular beam epitaxy.As a result of the improved built-in electric fields and cathode performance parameters,the photoemission characteristics for the MOCVD-grown transmission-mode and reflection-mode AlGaAs/GaAs photocathodes are different over the wavelength region of interest.
