Positive periodic solutions for fully third-order ordinary differential equations

In this paper the existence results of positive ωω-periodic solutions are obtained for the fully third-order ordinary differential equation u‴(t)=f(t,u(t),u′(t),u″(t)),t∈R where f∈C(R×(0,∞)×R×R,R)f∈C(R×(0,∞)×R×R,R) is ωω-periodic in tt, and f(t,u,v,w)f(t,u,v,w) may be singular at u=0u=0. The discussion is based on a fixed point theorem in cones.