This paper puts forward a new method to solve the electromagnetic parabolic equation （EMPE） by taking the vertically-layered inhomogeneous characteristics of the atmospheric refractive index into account. First, the...This paper puts forward a new method to solve the electromagnetic parabolic equation （EMPE） by taking the vertically-layered inhomogeneous characteristics of the atmospheric refractive index into account. First, the Fourier transform and the convo- lution theorem are employed, and the second-order partial differential equation, i.e., the EMPE, in the height space is transformed into first-order constant coefficient differential equations in the frequency space. Then, by use of the lower triangular characteristics of the coefficient matrix, the numerical solutions are designed. Through constructing ana- lytical solutions to the EMPE, the feasibility of the new method is validated. Finally, the numerical solutions to the new method are compared with those of the commonly used split-step Fourier algorithm.展开更多
The general control block diagram ofthe proposed hybrid inverter based ac driveis shown in Fig. 6. The overall control strat-egy is composed of two main control loops.
基金supported by the National Natural Science Foundation of China(Nos.41175025 and41275113)
文摘This paper puts forward a new method to solve the electromagnetic parabolic equation （EMPE） by taking the vertically-layered inhomogeneous characteristics of the atmospheric refractive index into account. First, the Fourier transform and the convo- lution theorem are employed, and the second-order partial differential equation, i.e., the EMPE, in the height space is transformed into first-order constant coefficient differential equations in the frequency space. Then, by use of the lower triangular characteristics of the coefficient matrix, the numerical solutions are designed. Through constructing ana- lytical solutions to the EMPE, the feasibility of the new method is validated. Finally, the numerical solutions to the new method are compared with those of the commonly used split-step Fourier algorithm.
文摘The general control block diagram ofthe proposed hybrid inverter based ac driveis shown in Fig. 6. The overall control strat-egy is composed of two main control loops.
文摘针对高压隔膜泵机械结构复杂,单向阀故障特征信息分布在多尺度上,单一尺度难以全面提取特征的问题,提出了一种基于参数优化变分模态分解(Variational Mode Decomposition,VMD)和增强多尺度排列熵(Enhanced Multi-scale Permutation Entropy,EMPE)的单向阀故障诊断方法。对单向阀振动信号进行VMD分解,以包络熵最小原则对其进行参数优化,获得既定的若干本征模态函数(Intrinsic Mode Function,IMF)分量;计算IMF分量的增强多尺度排列熵,构建故障特征值向量;利用基于变量预测模型的模式识别(Variable Predictive Model Based Class Discriminate,VPMCD)方法对故障特征值向量进行训练和识别,进而实现单向阀的故障诊断。仿真信号和工程实验分析表明,该方法可以准确地识别单向阀的故障类型,具有一定的可靠性和工程应用价值。
