但是，有关循环经济系统的演化及动力等问题的研究目前还较少。

But related question of circulation economy system evolution and power research at present is still blank.

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在具有社会关系结构的经济系统及通讯网络系统等许多现实的系统中，人们经常关注节点集在系统中的重要性问题。

Nodes' importance is often concerned in many real world systems, such as economic systems with social relation structure and communication networks.

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