也就是，这个向量场等价于,从原点指向给定位置的向量，所以它是以原点为心向外辐射的。
Well, , see, that is a vector field that is equal to the vector from the origin to the point where I am, so it is pointing radially away from the origin.
本文研究了平面多项式向量场的全局与局部分叉，旨在研究高次平面非线性动力系统多极限环的存在性以及极限环的个数及其相对位置关系；
The main aim of this dissertation is to study the exist of limit cycles of plane nonlinear dynamic system of high degree and the number and the configurations of limit cycles.
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