大径指过外螺纹牙顶或内螺纹牙底的圆柱面直径。

The root of the external thread or the crest of the inner thread .

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结果表明，牙顶处金属材料受到丝锥棱齿的压力相对较小，并且金属流向牙顶两侧上方的区域时受到的阻力最小；

Through metallographic analysis of the material, microstructure change and deformation mechanism of crest, flank and root of the thread along the layer depth direction were obtained.

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1988年奥运会女子马拉松比赛的金牌得主是一名葡萄牙选手，她反戴着一顶白色的画家便帽，原因是为了让她的头发不影响视线并且给她的脖子防晒。

A female athlete from Portugal won the women's marathon in 1988. She would wear a white painter's cap back-to-front to keep her hair out of her eyes and shade her neck from the sun.

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