图中上方偏左处还能看到埃林顿地，那里被用作多种用于宇航员训练、科研和货物转运的太空署飞行器的机场。

Also visible at image upper left is Ellington Field.This airport services a variety of NASA aircraft used for astronaut training, scientific, and cargo transport purposes.

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图中上方偏左处还能看到埃林顿地，那里被用作多种用于宇航员训练、科研和货物转运的太空署飞行器的机场。

Also visible at image upper left is Ellington Field. This airport services a variety of NASA aircraft used for astronaut training, scientific, and cargo transport purposes.

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特别地，一个没有旋度的力场，就是一个不产生任何旋转运动的力场。

In particular, a force field with no curl is a force field that does not generate any rotation motion.

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