Periodic Solutions Of Some Classes Of Differential Equations

The dissertation is composed of three chapters. It mainly studies the periodic solutions of some types of differential equations. A series of new findings are acquired in it. And some of them improve or extend the related results in the literatures.Chapter 1 mainly focuses on the periodic and almost periodic solutions of a nonautonomous perdator-prey system with stage-structure and cannibalism. By using the new method, it relaxes the restriction of the related results in the Pa-per[31],extends the mainly results of the Paper[31], obtains the existence and uniqueness of a positive periodic solution, proves the existence and the uniform asymptotic stability of the almost periodic solutions of the studying model.Chapter 2 concerns the existence of the periodic solutions of a class of neutral Lotka-Volterra systems . In this paper, it not only relaxes the strict restrictions of the conefficients in Paper[39], but also extends the main results of Paper[37-40]. What's more, by changing the condition of the coefficients A;, obtains the new results.Chapter 3 studies the existence of periodic solutions for higher order nonlinear neutral impulsive functional differential equations . It develops the related results in the recent Paper[41,43], relaxes the restriction of the coefficient c in Paper[42].