The existence of grey spot may cause brittle crack of the joint, therefore, controlling grey spot occupy a decisive position to ensure the quality of rail resistance welding.

灰斑的存在易导致接头的脆性断裂。因此，控制灰斑对保证钢轨接触焊质量举足轻重。

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Besides requiring astronomers to dream up a new mnemonic for their stellar classification, the existence of a grey area between stars and planets reveals the extent to which the processes of planetary and stellar formation are still a mystery.

ECONOMIST: Twinkle, twinkle, giant planet