The post office could simply put seals on the stamps to prevent them from being used again.
邮局只需在邮票上盖上邮戳就能防止邮票被再次使用。
When you want to finish a letter or a book you roll up the scroll and then you put a wax seal at the end of the roll and that seals the book.
当你看完一封信或一本书时，就将书卷卷起，然后在末端用蜡封印，将书封起来。
The concept of inverse radial lip seals is put forward . The sealing capacity of two models of inverse radial lip seals is analyzed.
提出了逆形径向轴封的概念，分析了两种基本的逆形径向轴封模型的密封能力。
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