如果两个等高线相切，说明它们的切线相同，也就是说他们的法向量应该平行，我再在这里画个图。

If the two level curves are tangent to each other that means they have the same tangent line. That means that the normal vectors should be parallel. Let me maybe draw a picture here.

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本文采用聚类分析法，由单谱图象的灰度和纹理参数构成特征向量，进行初始分类。

In this paper, cluster analysis was used for the initial classification in the feature space consisting of intensity of a MR image and its textures.

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