Trying to apply new methods to projects that have established deadlines is difficult, and often impossible.

在确定了最终期限的项目中运用新的方法是相当困难的，通常是不可能的。

youdao

Too often, rules are so vague and complex as to make replication impossible.

规则是如此模糊和复杂，通常不太可能得到复制验证。

youdao

This is limiting as it requires the alteration of a document about which the claim is being made — often undesirable, and if the document format isn't RDF, impossible.

这是有限制的，因为它需要对文档的有关声明是怎么产生的进行改动，这常常是不合需要的，而且如果文档格式不是RDF，则不可能发生改动。

youdao

But the prime minister also admits that in a country where HIV and AIDS victims are often abandoned by their families, fear of the disease could make it almost impossible to stop its spread.

VOA: standard.2009.04.04

These linkages are largely unknown and often impossible to observe, quantify and measure.

FORBES: The hidden dangers of outsourcing

The necessary problem-solving skills are difficult to teach, and the experience is often impossible to acquire because so much is new.

FORBES: Does It Matter That Apple and GE Are Bringing Back Manufacturing?

Often they make it impossible for mothers with pushchairs, and often walking small children, to pass without dangerously going out into the road.

BBC: Parking - Your Thoughts