He has done it by exploring, by experimenting, by developing his own model of the grammar of language, by trying it out and seeing whether it works, by gradually changing it and refining it until it does work.
出自-2010年6月听力原文
英语六级真题
The major components of our energy systems, such as fuel production, refining, electrical generation and distribution, are costly installation that have lengthy life spans.
2015年12月六级真题（第一套）阅读 Section B
柯林斯高阶英汉双解学习词典释义
VERB
提炼;精炼
When a substance is refined, it is made pure by having all other substances removed from it.