Military logistics systems are large and complex systems that can be difficult to control. Control theories provide a potentially powerful means.

军事后勤系统是一类控制复杂的大系统，控制理论为复杂大系统提供了一个有效的控制方法。

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Due to the high polarity of vinyl ester chemistry, it is known to be difficult to control the rheology with normal thickening additives or hydrophilic fumed silica.

但由于乙烯基酯树脂的高化学极性，用普通增稠剂和亲水性气相法二氧化硅对其实现很好的流变性控制是相当困难的。

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Boys, of course, attract more abuse, such as beating, because, once again, parental expectations are high, and boys tend to be more energetic and difficult to control than girls.

当然，男孩会受到更多的虐待，比如殴打，因为父母的期望又很高，而且男孩往往比女孩更有活力，更难控制。

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There may be circumstances under which it's the case but it's often difficult to control.

可能在某些环境下可以做到,但是通常情况下很难控制。

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They may have certain inclinations which are powerful, and which may be difficult to control.

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Criminality has already taken on a life of its own which would be difficult to control even if Chavez were no longer president.

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With thousands of foreign journalists due to cover the Olympics in August, officials would have feared that any outbreak of unrest close to that date would be difficult to control because of intense media scrutiny.

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