Existence Of Positive Periodic Solutions For Some Functional Differential Equations

In this paper, we study the periodicity of solutions of some functional differential equations.In chapter two, By using the coincidence degree theory, we study the delay Lotka-Volterra predator-prey system with Beddington-type functional and stock:Some suifficient conditions that gurantee the existence of positive periodic solutions of the system are obtained.By using the method of coincidence degree, in chapter three, we study the periodicity of a class of mathematical models with cannibalism arising bioeconomics:By using comparison theorem and the monotonicity, in chapter four, we study a nonautonomous predator-prey model with functional response and impulses:Some sufficient conditions which guarantee the permanence and asymptotic behavior of this system are obtained.