level set的用法和样例：
例句
- The model based on the implicit variational level set methods can handle topological changes automatically.
它基于隐式水平集变分方法，能够自动处理曲面拓扑结构的变化。 - A new level set way based on GVF was proposed, in order to solve the problem that the level set evolving curve will often stop on the local maximum or isolated edge.
摘要针对传统水平集分割图像会出现演化曲线停止于梯度的局部极大值或孤立的边缘处的缺点，对速度停止项进行了改进。
