sphere of inversion

In addition,a satisfying result is acqtuired by theapplication of BP network to multi-layer densitV interface inversion.

此外，通过修改网络单元的激发函数，增强网络的稳定性和内插功能，使ＢＰ网络在多层密度界面反演中得到满意的结果，模型和实例计算证明了该方法的有效性。