n.改良者；改善者；改进剂
A paving asphalt penetration ratio improver was introduced. 介绍了一种提高道路沥青针入度比的改进剂。
Cyclohexyl nitrate is an effective cetane number improver for diesel oil. 硝酸环己酯是一种有效的柴油十六烷值改进剂。
