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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The outbreaks will be difficult to detect and control in rural backyard flocks.

在农家后院的鸡群中发现和控制禽流感暴发将是极为困难的。

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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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The costs of providing and managing care, as everyone also knows, can be very difficult to control, and the task of allocating the resources necessary to an effective infrastructure of care is one that the current cartel-like system is not doing very well.

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"I think it will be difficult for them to control the currency, " said Anthony Nafte, a senior economist at CLSA Asia-Pacific Markets in Hong Kong.

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