Astronomers who study star clusters have noticed that the speed at which a star of a given mass spins (measured by tracking cool, dark spots on the surface) also seems to vary predictably with age.
研究星团的天文学家已经注意到质量一定的行星(通过追踪表面阴暗冷却斑点来测量)，其旋转速度随着其星龄呈现可预测性的变化。
For this reason, the speed of a grinding wheel should not exceed the safe surface speed limit specified by the manufacturer.
基于此原因，砂轮的速度不应超过制造商规定的安全表面速度的限制。
Carried by H-5 bomber or Q-5 attacker, the Yu-2 was designed to fly using rocket engine in air at high speed before it hits the water at a very close distance to the surface target.
由轰- 5型轰炸机或强- 5型强击机携带，鱼- 2型设计采用火箭发动机在空中高速飞行，当在非常接近到水面目标的距离时进入水面。
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