使用热流传感器对氙离子推力器轴向距离为500、700 mm和900 mm,径向角度为0°~15°(推力器出口平面中心为圆心,推力器出口轴线为0°)范围内羽流热流密度的分布进行了实验研究,获得了热流随角度和半径变化的实验数据。采用PI...使用热流传感器对氙离子推力器轴向距离为500、700 mm和900 mm,径向角度为0°~15°(推力器出口平面中心为圆心,推力器出口轴线为0°)范围内羽流热流密度的分布进行了实验研究,获得了热流随角度和半径变化的实验数据。采用PIC-DSMC (particle in cell direct simulation of Monte Carlo)算法在不同适应系数下对实验条件进行仿真分析,对比仿真结果和实验结果得到适应系数。结果表明:keV能量的Xe粒子对热流传感器表面(铜)的适应系数接近1。展开更多
Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple...Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple linear analysis for the calculation of deflections. This paper presents an investigation of the nonlinear deformation of aluminum bending members using the finite-element analysis （FEA）. The plastic adaptation coefficient, which can be used to limit the residual deflection, is introduced, and the influence of residual deflection is investigated. A method for evaluating the plastic adoption coefficient is proposed. This paper also shows the load-deflection curve of aluminum bending members and the influence of several parameters. A semi-empirical formula is derived, and some numerical examples are given by FEA. The coefficients of the semi-empirical formula are modified by the FEA results using the nonlinear fitting method. Based on these results, two improved design methods for strength and deformation of aluminum bending members are proposed. Through the comparison with test data, these methods are proved to be suitable for structural design.展开更多
针对复杂室内环境下超宽带(Ultra WideBand,UWB)信号传播的非视距(Non Line Of Sight,NLOS)误差问题,本文提出了一种基于无迹卡尔曼滤波(Unscented Kalman Filter,UKF)的环境自适应UWB/DR室内定位方法.该方法通过建立自适应UKF滤波模型,...针对复杂室内环境下超宽带(Ultra WideBand,UWB)信号传播的非视距(Non Line Of Sight,NLOS)误差问题,本文提出了一种基于无迹卡尔曼滤波(Unscented Kalman Filter,UKF)的环境自适应UWB/DR室内定位方法.该方法通过建立自适应UKF滤波模型,将UWB定位信息和航迹推算(Dead Reckoning,DR)定位信息进行融合.依据新息和高斯分布的3σ原则来对UWB定位结果进行非视距检测,再通过新息的实时估计协方差和理论协方差来构建环境适应系数,进而用此系数动态修正UWB定位的观测噪声,使得观测噪声自适应真实环境,降低NLOS误差对融合定位结果的影响.实验结果表明,该方法能有效减小UWB定位的NLOS误差,并且由于环境适应系数的创新引入,比UKF定位和粒子滤波定位(Particle Filtering,PF)有更高的定位精度和更强的抗NLOS误差性能.展开更多
文摘使用热流传感器对氙离子推力器轴向距离为500、700 mm和900 mm,径向角度为0°~15°(推力器出口平面中心为圆心,推力器出口轴线为0°)范围内羽流热流密度的分布进行了实验研究,获得了热流随角度和半径变化的实验数据。采用PIC-DSMC (particle in cell direct simulation of Monte Carlo)算法在不同适应系数下对实验条件进行仿真分析,对比仿真结果和实验结果得到适应系数。结果表明:keV能量的Xe粒子对热流传感器表面(铜)的适应系数接近1。
文摘Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple linear analysis for the calculation of deflections. This paper presents an investigation of the nonlinear deformation of aluminum bending members using the finite-element analysis （FEA）. The plastic adaptation coefficient, which can be used to limit the residual deflection, is introduced, and the influence of residual deflection is investigated. A method for evaluating the plastic adoption coefficient is proposed. This paper also shows the load-deflection curve of aluminum bending members and the influence of several parameters. A semi-empirical formula is derived, and some numerical examples are given by FEA. The coefficients of the semi-empirical formula are modified by the FEA results using the nonlinear fitting method. Based on these results, two improved design methods for strength and deformation of aluminum bending members are proposed. Through the comparison with test data, these methods are proved to be suitable for structural design.
文摘针对复杂室内环境下超宽带(Ultra WideBand,UWB)信号传播的非视距(Non Line Of Sight,NLOS)误差问题,本文提出了一种基于无迹卡尔曼滤波(Unscented Kalman Filter,UKF)的环境自适应UWB/DR室内定位方法.该方法通过建立自适应UKF滤波模型,将UWB定位信息和航迹推算(Dead Reckoning,DR)定位信息进行融合.依据新息和高斯分布的3σ原则来对UWB定位结果进行非视距检测,再通过新息的实时估计协方差和理论协方差来构建环境适应系数,进而用此系数动态修正UWB定位的观测噪声,使得观测噪声自适应真实环境,降低NLOS误差对融合定位结果的影响.实验结果表明,该方法能有效减小UWB定位的NLOS误差,并且由于环境适应系数的创新引入,比UKF定位和粒子滤波定位(Particle Filtering,PF)有更高的定位精度和更强的抗NLOS误差性能.
