valve reversal的用法和樣例：
例句
- When the next reversal occurs, the several generations of scientists who study it will know much more about the effects.
當下一次倒轉發(fā)生時(shí)，從事這項研究的幾代科學(xué)家將對有關(guān)的效應知道得更多。 - In order for a reversal to take place there must be a brief time during which the field is non-existent.
為了發(fā)生一次倒轉，必須有一個(gè)很短的時(shí)間沒(méi)有磁場(chǎng)存在。
