It is of important signification to analyse the process of the continental crust evolve with relevant material composition.
而相应的物质构成对分析大陆地壳演化的过程具有重要意义。
The structural characters of steel pipe drilling rod, the signification of welding repair for the rods and the narrow gap welding process and equipment are introduced in the paper.
介绍了钻铤钢管的结构特点、焊接修复的意义，以及窄间隙焊接工艺与设备。
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