In this paper, we show that the method of monotone iterative technique is valid to obtain two monotone sequences that converge uniformly to extremal solutions to second order periodic boundary value problems and periodic solutions of functional difference equations. We obtain some new results under the lower solution a and upper solution βwith α≤β.
Abstract With the help of a continuation theorem based on Gaines and Mawhin’s coincidence degree,westudy the global existence of positive periodic solutions of a "food-limited" population model with toxicants andtime delays.Some new results are obtained.
Meng Fan, Ke WangDepartment of Mathematics, Key Laboratory for Vegetation Ecology of the Ministry of Education of China, Northeast Normal University, Changchun 130024, China
