中心条件推导的间接方法

对于一类多项式系统,给出两类对称条件的推导算法,具体讨论了一类三次系统的中心条件;对于Poincare型系统,给出一类等时中心的充分条件．     

GLOBAL ANALYSIS TO A KIND OF COMPETITION MODEL OF E-COMMERCE SITES

In this paper, we present a competition modei of e-commerce sites with the property of "better for better". Then we qualitatively analyze the special case of two dimensions. So we prove that there does not exist limit cycle, in the first quadrant of the phase plane and all trajectories tend to some singular points.