hollow core

基本解释

The riser’s inner hollow core (a pipe within a pipe) is reserved for the drill string.
立管内部核心是空心的（管中管），留给钻柱使用。
The core of the propellant is hollow and it burns out from the middle so that the gas accelerates through the hollow core out of the back of the solid rocket booster.
推进剂的内核是中空的，它从内部中间开始燃烧以至于气体加速流过中空的内核而从固体火箭推进器的后端喷出。
Simple and enormous intersecting walls give a balanced symmetry but are also the means by which the structure stands at the height of a 14-storey building, with an entirely hollow core.
简单而巨大的相交墙赋予了平衡的对称性，但也意味着结构具有14层高建筑物的高度，具有完全空心的核心。

Despite Ahmadinejad's success in maintaining his grip on power, it is an indisputable fact that regime opponents succeeded these past few weeks as never before in destabilizing the regime and in demonstrating its hollow core.
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