Because of the much thick wall of large capacity boiler drum, the pressed and weld longitudinal seam is used to manufacture the drum shellring.
由于大容量电站锅炉汽包的壁较厚，所以在汽包筒节制造时常采用压制成两个半圆瓦片再焊接而成的方法。
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"With a laser pulse, you can tap that shell and make it ring like a bell," said physicist Till Rosenband of NIST, who built the existing quantum-logic clock.