Periodicity in a generalized semi-ratio-dependent predator-prey system with time delays and impulses

摘要

With the help of a continuation theorem based on coincidence degree theory, we establish necessary and sufficient conditions for the existence of positive periodic solutions in a generalized semi-ratio-dependent predator-prey system with time delays and impulses, which covers many models appeared in the literature. When the results reduce to the semi-ratio-dependent predator-prey system without impulses, they generalize and improve some known ones.