refine

Oil is refined to remove naturally occurring impurities.

油经过提炼去除天然生成的杂质。

At the same time, more of this newly discovered oil is of the type that requires a greater investment to refine.

与此同时，这些新发现的石油中有更多属于需要加大投资才能提炼的类型。

Surgical techniques are constantly being refined.

外科手术技术正在不断得到完善。

He has done it by exploring, by experimenting, by trying it out and seeing whether it works, by gradually changing it and refining it until it does work.

他通过探索、实验、尝试并观察它是否有效、逐步改变并完善它，直到它起作用。

Instead of trying to refine old formulas, they invent new ones.

他们不是试图改进旧的公式，而是发明新的公式。