的确，我们不再像我们的祖先一样打猎，且城市里有很多自然界不存在的‘危险’，但我们仍然可以从我们的祖先那学到一些东西——鞋仅仅是人们为了在某些特殊场合保护足底而设计的，对我们的祖先来说，穿鞋这一行为是临时性的。
True, our urban environments are full of 'unnatural' dangers. But we can still learn from our origins - footwear was designed to protect the soles of the feet where necessary, and it was temporary.
在一些特殊场合对金属硬密封蝶阀的密封提出了更高的要求，必须双向承压。
In some special occasions for metal hard seal butterfly valve seal put forward higher request, must be two-way under pressure.
在一些特殊场合对金属硬密封蝶阀的密封提出了更高的要求，必须双向承压。
In some special occasions for metal hard seal butterfly valve seal put forward higher request, must be two-way under pressure.
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