These included the first use of "hard hats" to protect the workers' heads and special glasses to protect their eyes.

VOA: special.2010.07.23

Now for the hacker edition, if you are feeling up to a bit more of a challenge you'll find that when you run the game, one it's not all that hard to use some ASCII art just make it a little fancier as the teaching fellow who implemented this solution did.

对于升级版，如果你能应付更大的,挑战，你会发现当你在玩这个游戏时，用一些字符画把它做得,比那些教学人员做的更有新意,并不是那么困难。

哈佛公开课 - 计算机科学课程节选

There's been a lot of work done on these over the years, but in fact, it's pretty hard to invent a good hash function. So my advice to you is, if you want to use something was a hash, go to a library. Look up a good hash function.

已经做过了很多的尝试和努力,但是事实是，很难发明出一个好的哈希函数,所以我给你们的建议是,如果你们想使用哈希功能,到函数库中查找一个好的哈希函数。

麻省理工公开课 - 计算机科学及编程导论课程节选

He says the campaign aims to change consumer behavior through the use of soft power, not hard power.

VOA: standard.2009.10.19

I think so. But video phone has been very hard to achieve. It's either been to be expensive, or too crowded, or can we use the internet to finally introduce video phone and this is different from video on-demand.

我也这么认为，但视频电话要成功很困难,它要么很贵，要么很拥堵，或者我们是否可以使用互联网引入视频电话,这与随需视频是不同的。

麻省理工公开课 - 媒体、教育、市场课程节选

And there's two you could use to attack through, easy or hard.

同样他也有两条路入侵途径,平坦之途和崎岖之途

耶鲁公开课 - 博弈论课程节选

Some customers want to use your safe because safes are hard and expensive to get and some -and then you've got all this gold, so you might as well lend it out.

顾客需要使用你的保险箱,因为对个人而言保险箱既昂贵又难以获得,这样你就拿到他们的金子,然后你可以把金子借出去

耶鲁公开课 - 金融市场课程节选

Well, now one of the things farmers in history discovered is that it's very hard to do well as a farmer if all you do is grow the crops, because people normally don't use what you grow in the form in which you grow it.

关于农民我们在历史上能够得知的一件事是,当好农民很困难,特别是只种农作物的农民,因为人们一般不会将,你从地里种出来的东西留作种子

耶鲁公开课 - 古希腊历史简介课程节选