both sentences are fine.
You can think of the sentences as follows.
1.In the chapter,the priciple of A is introduced, (which is) followed by an analysis on B.
2.This section presents a commonly-used C method,(which is) followed by a modified C with D.
Both (with "which is" or without "which is" ) are acceptable.
1.In the chapter,the priciple of A is introduced, (which is) followed by an analysis on B.
2.This section presents a commonly-used C method,(which is) followed by a modified C with D.
Both (with "which is" or without "which is" ) are acceptable.