They hope to reduce both the number of components needed in a construction job and their weight—by replacing solid supports with hollow tubes, for example.

他们希望减少建筑工作所需的部件数量和重量，例如，用空心管代替实心支架。

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A iron bar is solid; a pipe is hollow.

铁条是实心的，管子是空心的。

《新英汉大辞典》

Since the solid wood design didn’t resonate as much as hollow body guitars, you could crank one up nice and loud without it feeding back.

因为是实心木头琴体不像空心吉他那样产生共鸣，你可以在声音毫无反馈叠加的情况下调大音量。

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The rest of the vertical column is made from a material called syntactic foam - a solid made mostly of hollow "microballoons" - giving it enough buoyancy to float back up.

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Though it's predominantly made of matte and glossy-finished plastic, it still feels solid and not at all hollow.

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Objects which hitherto had to be cast in solid metal can be manufactured as hollow shapes, reducing their weight and the amount of precious metal used.

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