With time , plumes become progressively more diffuse .

随着时间的推移，烟羽逐渐弥散。

The 30-year era of progressively cheaper capital is nearing an end .

30年来资本成本逐步降低的时代已行将结束。

That may be one reason why the relatively tranquil north has become progressively more dangerous .

这也许是阿富汗原本相对宁静的北方地区变得日益危险的原因之一。

The energy mix will progressively change .

能源构成将逐渐发生变化。

A small mercy is that successive iterations of the legislation have become progressively less extreme .

一个小小的幸运之处在于，对该法案的反复重提已逐渐不那么极端。