The idea of negative CAPTCHAs is not to ask a user to proof that he is human, but reveal that a spam robot is a bot.

这个消极的CAPTCHA的主意，不是去让用户证明他是一个人，而是让一个机器人证明他是个机器人。

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Giving a new definition for the rate of entropy production is a proof method adopted in some papers published recent years to guarantee that the rate is non-negative.

在过去发表的非平衡热力学文献中所采用的一种方法就是对熵产生的速率重新加以定义，其目的在于确保熵产生的速率为非负值。

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The world has watched admirably at the "wonder from down under, " a seemingly recession-proof economy that avoided a downturn after the global financial crisis and that has not experienced two successive quarters of negative growth for20 years.

BBC: Australia's two-speed economy threatens to hurt growth