Spatial-temporal evolution and peer effects of urban green development efficiency in China.

9 K x = 1 2 π e - x 2 2 Center of gravity and standard deviation ellipse model Center of gravity model The center of gravity model is used to describe the direction and distance of the center of gravity movement of certain attribute values in the region, this model has been widely used in existing literature, for example, Gai and Zhan studied the movement path of the center of gravity of marine eco-efficiency in China's coastal provinces and found that the spatial distribution range of the center of gravity of the efficiency showed a trend of expanding and then shrinking 40 .

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