The speed with which Facebook hit the 500 million mark is a sign of its accelerating growth.

Facebook达到5亿用户的速度反映了其惊人的增长率。

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The most ominous sign that something big was brewing under the mountain developed on its north side. Within four weeks, this flank bulged out with hitherto unknown speed (see Figure 1).

最明显的征兆是山体下面的北侧在酝酿着某种活动，四个星期之内，这个侧翼以前所未有的速度膨胀出来(见图1)。

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"I have not moved for five hours," said Zhang Xingping, 27, standing outside his cab near a road traffic sign mockingly warning him to obey the 100km per hour speed limit.

“我一动不动已经有五小时了”27岁的张兴平说。讽刺的是，离他车子不远处的交通标志牌却一直警告着他时速切勿超过100公里。

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Remember, you've got to keep track of the sign of acceleration, so if you're picking up speed towards the ground, a is negative, so it will be g plus a, but a is a negative number.

记住,一定要注意加速度的符号,所以当你加速下降的时候,a 是负的,还是 g 加上 a,但是 a 是负数

耶鲁公开课 - 基础物理课程节选

We filmed 15 vehicles including a bus, a post van and numerous cars which, according to a flashing speed warning sign, were breaking the limit.

BBC: Will a borough-wide 20mph speed limit work?

It also coaxed 200, 000 new U-verse TV subscribers and 613, 000 high-speed internet users to sign up with Ma 'Bell.

ENGADGET: AT&T sells 4.7 million iPhones and 1.4 million other smartphones, makes $3.6 billion profit in Q3

They argued that widespread violation of the national 55 mph. speed limit was a sign that law was too restrictive.

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