Planes must zigzag from one ground beacon to the next, and ascend and descend in steps at each stage obtaining permission from the ground.

飞机从一个地面信标到下一个信标曲折飞行，在每一阶段都要经过地面的许可才能上升和下降。

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Sea gliders move slowly, at around 1kph, tracing a saw-tooth pattern through the water as they constantly ascend and descend.

海洋滑翔器移动较慢，大概每小时航行1公里，当它们持续的上浮和下沉时，轨迹是一个锯齿形的图案。

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The elevator that runs from the ground floor to the fifth floor will be replaced and will ascend and descend in a new, fire-resistant shaft.

原从 地面至五楼的电梯将被更新，同时风井将改为防火的。

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From the late afternoon to early evening, an elevator outfitted with regen will generate power continuously as lightly loaded and often empty elevators ascend to pick up office workers and crowded elevators descend as workers stream out of the building.

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