The problem of hunger worldwide is a hard nut to crack. I'm afraid that scientists need to put in more efforts.

全球性的饥饿问题是个棘手的问题，恐怕科学家们需要付出更多的努力。

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But if any rookie hacker with some time to kill can crack your system, that's a problem.

不过，如果就连一个闲得无聊的菜鸟黑客也能攻陷你的系统的话，这就有问题了。

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Wall crack control is a complex problem that requires the coordination of materials, design, construction and other aspects.

墙体裂缝的控制是一个复杂的问题，需要材料、设计、施工等方面的相互协调、共同配合。

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This is a very tough problem to crack, but a big opportunity.

FORBES: Y Combinator's Spring 2012 Demo Day: No Funding Talk In Pitches, But Plenty Of Funding Interest

WifiSLAM, which is roughly two years old, is among a slew of technology companies trying to crack the problem of how to detect a mobile-phone user's location when the user is indoors and traditional GPS technology doesn't work.

WSJ: Apple Buys Indoor GPS Specialist

But in the bigger picture, the petrol-from-air idea joins a legion of others that are trying to crack the far bigger problem of storing energy produced by renewable sources.

BBC: Petrol from air: Will it make a difference?