Periodic Solutions for a Kind of Second-Order Neutral Differential Equation on Time Scales

In this paper, the existence of periodic solutions and nonnegative periodic solutions for a kind of second-order neutral differential equation on time scales is considered. The partial increment is a fixed constant if the time scale is the real number set and is a multiple of the periodic of the time scale if the time scale is not the real number set. By means of a fixed point theorem due to Krasnoselskii, some sufficient conditions are obtained.