threshold mass的用法和樣例：
例句
- The same ideas of critical size and critical mass apply to bombs.
同樣的臨界尺寸概念和臨界質(zhì)量概念適用于原子彈。 - A chain reaction can be initiated by inserting more and more fuel elements into the reactor core until the critical mass is attained.
只要在反應堆中加入越來(lái)越多的燃料并且一直加到臨界質(zhì)量為止，就可以發(fā)生連鎖反應。
