低轨卫星导航增强系统在实现高精度定位时,导航增强信号和低轨导航增强载荷正常接收信号会产生自干扰,针对此问题,提出了一种基于改进的迭代变步长最小均方(Improved Iterative Variable Step-size Least Mean Square,IIVSSLMS)的数字...低轨卫星导航增强系统在实现高精度定位时,导航增强信号和低轨导航增强载荷正常接收信号会产生自干扰,针对此问题,提出了一种基于改进的迭代变步长最小均方(Improved Iterative Variable Step-size Least Mean Square,IIVSSLMS)的数字域自干扰对消算法。在初始阶段设置较大的步长因子以提高收敛速度,并基于箕舌线函数建立步长因子和迭代次数之间的非线性关系,同时利用当前误差信号和上一步误差信号之间的自相关估计协同控制步长因子。利用步长因子、误差信号和发射信号得到估计的自干扰信道冲激响应,并根据已知的发射信号重构自干扰信号。从接收信号中去除重构的自干扰信号,实现数字域自干扰对消。仿真结果表明,该算法与已有变步长最小均方(Least Mean Square,LMS)算法相比,收敛速度提高2.5倍,干扰对消比提高7.4 dB,性能提升显著。展开更多
Wetland is a unique habitat with great biodiversity and important ecological functions between land and water on the earth. With the irrational utilization of wetland resources, the ecological destruction and pollutio...Wetland is a unique habitat with great biodiversity and important ecological functions between land and water on the earth. With the irrational utilization of wetland resources, the ecological destruction and pollution of wetland are becoming more and more serious. To evaluate the pollution of heavy metals in the sediments of Longjiang Wetland in Binzhou City, chromium(Cr), copper(Cu), zinc(Zn), cadmium(Cd) and lead(Pb) were measured by inductively coupled plasma mass spectrometry. Concentrations of Cr, Cu, Zn, Cd and Pb in the sediments were 5.3–13.6, 5.6–15.0, 16.6–33.0, 0.1–0.4 and 7.9–24.9 mg/kg dry weight, respectively. The concentrations of heavy metals in Longjiang Wetland was lower than soil background values of Shandong Province and in lower level compared with those reported in sediments/soils of wetlands in some other locations. Based on geo-accumulation index(Igeo), Cr, Cu, Zn and Pb showed low levels of contamination at all stations, while Cd was observed at a moderate pollution degree. Potential ecological risk factor(E_r^i) and risk index(RI) values showed low ecological risk of heavy metals in sediments of the wetland.展开更多
文摘低轨卫星导航增强系统在实现高精度定位时,导航增强信号和低轨导航增强载荷正常接收信号会产生自干扰,针对此问题,提出了一种基于改进的迭代变步长最小均方(Improved Iterative Variable Step-size Least Mean Square,IIVSSLMS)的数字域自干扰对消算法。在初始阶段设置较大的步长因子以提高收敛速度,并基于箕舌线函数建立步长因子和迭代次数之间的非线性关系,同时利用当前误差信号和上一步误差信号之间的自相关估计协同控制步长因子。利用步长因子、误差信号和发射信号得到估计的自干扰信道冲激响应,并根据已知的发射信号重构自干扰信号。从接收信号中去除重构的自干扰信号,实现数字域自干扰对消。仿真结果表明,该算法与已有变步长最小均方(Least Mean Square,LMS)算法相比,收敛速度提高2.5倍,干扰对消比提高7.4 dB,性能提升显著。
基金Sponsored by the Natural Science Foundation of Shandong Province(ZR2018PD002)
文摘Wetland is a unique habitat with great biodiversity and important ecological functions between land and water on the earth. With the irrational utilization of wetland resources, the ecological destruction and pollution of wetland are becoming more and more serious. To evaluate the pollution of heavy metals in the sediments of Longjiang Wetland in Binzhou City, chromium(Cr), copper(Cu), zinc(Zn), cadmium(Cd) and lead(Pb) were measured by inductively coupled plasma mass spectrometry. Concentrations of Cr, Cu, Zn, Cd and Pb in the sediments were 5.3–13.6, 5.6–15.0, 16.6–33.0, 0.1–0.4 and 7.9–24.9 mg/kg dry weight, respectively. The concentrations of heavy metals in Longjiang Wetland was lower than soil background values of Shandong Province and in lower level compared with those reported in sediments/soils of wetlands in some other locations. Based on geo-accumulation index(Igeo), Cr, Cu, Zn and Pb showed low levels of contamination at all stations, while Cd was observed at a moderate pollution degree. Potential ecological risk factor(E_r^i) and risk index(RI) values showed low ecological risk of heavy metals in sediments of the wetland.
