ON SOME PROPERTIES OF SOLUTIONS FOR CERTAIN FOURTH-ORDER NON-LINEAR DIFFERENTIAL EQUATIONS
In this paper, we use the frequency-domain method to generalize earlier results to some fourth-order non-linear differential equations. The properties of solutions considered are:(i) the existence of a unique solution which is, as well as its first three derivatives bounded and globally exponentially stable, and (ii) the periodicity (or almost periodicity) of the solution whenever the forcing term is periodic (or almost periodic). AMS (1980) Classification: 34-C-25.