第一个是积分的对象，称为积分要素。

One is whatever you integral is called the integrant.

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它的实质是以轨道要素的平均变化率为基础的微分方程，而方程的右端包含定积分。

The essence of this method is a group of differential equations based on the average change rate of orbit elements, and the right sides of these equations contain definite integrals.

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核心区内森林景观要素面积较大，但各景观要素之间的面积分配极不均匀，周长也表现出相同的规律。

The forest landscape elements cover a quite large area, nevertheless, the areas of various elements are extremely uneven, and their perimeters demonstrate the same regularity as well.

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