Boundedness and periodicity in impulsive ordinary and functional differential equations (Q855478)

Periodicity and boundedness are studied for the impulsive ordinary differential equation \[ {\begin{cases} x'(t)=f(t,x),& t\not=t_k,t\geq 0\\ x(t_k)=I_k(x(t_k^-)),&k\in N, \end{cases}} \] and for a similar functional differential equation. Horn's fixed point theorem is applied to establish Hale-Yoshizawa type criteria for the existence of periodic solutions.