3. And the ball must contain an adequate vent to the pressure port opposite of the downstream sealing port. 球体必须包含一个适当的排气口，对着与下游密封端口相反的压力端口。
1. a word that expresses a meaning opposed to the meaning of another word, in which case the two words
2. a relation of direct opposition
3. a contestant that you are matched against
4. something inverted in sequence or character or effect adj.
1. being directly across from each other; facing
2. of leaves etc; growing in pairs on either side of a stem
3. moving or facing away from each other
4. the other one of a complementary pair
5. altogether different in nature or quality or significance
6. characterized by opposite extremes; completely opposed adv.
1. directly facing each other