The share of Americans who smoke has fallen dramatically since 1970, from nearly 40 percent to about 20 percent, but the rate has stalled since about 2004.

自1970年以来，美国吸烟人口的比重大幅下降，从近40%下降到了20%左右。但是，这一比重大约从2004年起就不再下降。

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Some heat release rate formulas are added to the application software for calculation on the properties of the fire smoke flow in building.

将各种非稳态火源热释放速率计算式嵌入建筑物火灾烟流性状预测软件并进行了算例验证。

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Therefore the article recommends that according to fire heat release rate, escape time and control height of smoke layer, the rate of mechanical smoke extraction should be reasonably decided.

文章建议根据火源释热率、火灾发生后的逃生时间、烟气层的控制高度合理确定大空间的机械排烟速率。

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The numbers are even more stark for high school students: in the 1990s, one of every 20 high school students smoked 10 or more cigarettes a day while today, only one out of 71 students smoke at that rate.

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Obama and Buffett are blowing so much smoke over the 15% rate on capital gains and on dividends adopted in the Bush years.

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Although the exact numbers of smokers in housing projects are unknown, about 30 percent of Americans living below the poverty line smoke tobacco, more than 1.5 times the rate of those who live above it.

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