This paper expands the non-linear observation function in Taylor's series, takes to the quadraticterm and obtains the form of the linear-quadraticterm.
本文将非线性观测值函数泰勒级数展开，并取至二次项，得到线性一二次项形式。
2
On the other hand, it also derives the covariance propagation formula of non-linear function containing quadraticterm in matrix form using the matrix theory etc.
另一方面又利用矩阵理论等推导出含有二次项的非线性函数的协方差传播公式的矩阵形式。
3
Firstly part of quadraticterm of Taylor series is chosen; a low-dimension surface is used to approximate limit state surface; and the modified reliability formula is derived.