灰阶平衡 base nearization
低生育水平阶段 a steady low fertility in the population growth
一阶平稳过程 first order stable process
二阶平衡B树 two-order balance B tree
二阶平稳 second order stationary
一阶平均球近似 First-order mean-spherical approximation ; FMSA
二阶平稳性 second order stationarity
一阶平均球形近似 FMSA
结合一阶平均球近似 First-order mean-spherical approximation
吴阶平 prognosis
本文从推广的二阶耦合波理论出发，对平条纹面光栅衍射这一物理过程进行分析。
The physical process of diffraction by planar gratings'is analysed, based on the generalized second-order coupled-wave theory.
还指出仅当柱面或平面光栅时，才能形成二阶子午无离焦平场和弧矢无象散圆场谱面。
It is also shown that only when the gratings are cylinder or plane ones, the second order sagittal anastigmatic circular field and meridional non defocus flat field spectral images can be formed.
应用推荐