摘要

Perturbing the cubic polynomial differential systems (x) over dot = -y (a(1)x + a(0)) (b(1)y + b(0)), (y) over dot = x (a(1)x + a(0)) (b(1)y + b(0)) having a center at the origin inside the class of all polynomial differential systems of degree n, we obtain using the averaging theory of second order that at most 17n + 15 limit cycles can bifurcate from the periodic orbits of the center.