The attenuation of X-ray through the object is non-linear and the gray level of image is non-linear response of object thickness.
射线穿过物体的衰减是非线性的，经过影像系统得到的图像灰度与物体厚度是非线性的关系；
2
If a proper non - linear change of the instantaneous frequency is realized, we can get a frequency spectrum whose input is the mean of the reciprocals of bed attenuation coefficients.
如果把瞬时频率作适当的非线性变化，就可以得到一个以地层衰减率的倒数的平均值为输入的频谱。
3
And simulation results show that to what extent the performance of the novel multistage non-linear PIC based on attenuation factors can be improved.