On global convergence of forced nonlinear delay differential equations and applications

Consider the following nonlinear delay differential equation with a forcing term r(t) : x′(t)+a(t)x(t)+b(t) f (x(t − τ(t))) = r(t), t 0, where a ∈ C[[0,∞), [0,∞)] , b,τ ∈C[[0,∞),(0,∞)] , r ∈C[[0,∞),R] , f ∈ C[(L,∞),(L,∞)] with −∞ L 0 , and limt→∞(t − τ(t)) = ∞ . We establish a sufficient condition for every solution of the equation to converge to zero. By applying the result to some special cases and differential equation models from applications, we obtain several new criteria on the global convergence of solutions.