Burning boiler control system is designed in two level control structure: monitoring level and loop level.

锅炉燃烧控制系统设计为两层控制结构：监督级和回路级。

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Searching variables in two level hierarchy, it is possible to avoid the appearance of unfeasible results. So the search space is greatly reduced and efficiency is improved.

通过将需寻优的变量放在内外两个层次进行遗传搜索，可避免无理解的产生，使搜索空间大大缩小，提高了搜索效率。

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Spurred on by funding policies, half of the European research articles had international co-authors in 2007, this is more than twice the level of two decades ago.

在资助政策的推动下，2007年有一半的欧洲研究论文有国际合作作者，这是20年前水平的两倍多。

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The city is more than two thousand meters above sea level, near the southern Rocky Mountains in northern New Mexico.

VOA: special.2009.03.30

So at this point in the story-- at this level in the story, if you will, I've touched one, two, three, four numbers total or I've made two comparisons.

那么这时，我总共已经动过了1，2，3，4个数字,或者说我做了两次比较。

哈佛公开课 - 计算机科学课程节选

So let me rephrase, are these people, are these pair of partners in the firm, or two students working on their homework assignments, are they working more or less than an efficient level?

让我换个表达方式吧,这些企业合伙人,或者两个共同协作做作业的同学,他们是否实现了最优效率了呢

耶鲁公开课 - 博弈论课程节选

Bullish sentiment rose to its highest level in two years, while bearish sentiment fell to its lowest level in about a year in the latest AAII Sentiment Survey.

FORBES: AAII Sentiment: Bullish Sentiment Reaches Two-Year High

The increase was tempered by a decline in the four-week moving average, which smooths out week-to-week volatility and fell to 431, 000, from 436, 750 the week before, its lowest level in two years and approaching the 425, 000 level economists look to as a signal of a sustained decrease in unemployment.

FORBES: Magazine Article

Today its index added 0.4% to 75.04 and is honing in on the highest level in two weeks at 75.38.

FORBES: Confidence Shot As Investors Question 'Kick The Can' Strategies