The birds move constantly, slowly rotating from the cold outside rings to the warm, wind-free center.

这些雄帝企鹅不断地移动着，从寒冷的外圈慢慢地转动到温暖无风的中心部位。

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Huddle forms when hundreds, even thousands, of males crowd together.The birds move constantly, slowly rotating from the cold outside rings to the warm, wind-free center.

当成百上千只雄帝企鹅挤在一起时就形成了一个大“团”。这些雄帝企鹅不断地移动着，从寒冷的外圈慢慢地转动到温暖无风的中心部位。

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A number of designs use two rings of stubby, counter-rotating blades made from composite materials.

有许多设计采用了两圈短而粗的、反向对转的采用复合材料制作的叶片。

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One way to increase the efficiency of a high-bypass jet engine is to turn the fan into an open rotor, a bit like returning to propellers, but using two rings of stubby counter-rotating blades.

ECONOMIST: A new way to build a greener jet engine