The development of the ring-banded spherulites in PTT solution-cast film is a rhythmic growth process, and thus it is consistent with the structural discontinuity model.

At the striking position of the high-speed fluid to the static fluid, a velocity discontinuity appears, which propogates outwards in the film.

Smoothest approximation method, with high precision and capacity of keeping concave and convex feature of original outlines, is used to deal with the derivative discontinuity of gas film thickness.