The switches, which must be durable enough to withstand military demands and have special optics for all types of lighting conditions, are often priced as high as $500 each.
这些开关必须足够坚固能满足军用的需要，并且有能适应各种光学环境的专用光学零部件，这些部件的价格可能高达每个500美元。
Cryogenic liquid fluids are widely used in some huge science projects, which usually have very special demands of the purity of those cryogenic liquid fluids.
低温液体常用于许多大型和复杂的科研和工程项目中，在这些场合下对使用的低温流体纯度一般都有特殊要求。
The special devices have been becoming demands because of different process of winding products.
由于制品的工艺要求不同，不同的专用设备日渐成为需求的对象。
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