钻头规是种周长一定的环型物，它卡紧在钻头的周围，去检测和测量钻头是否磨损，即在钻井过程中是否减少了周长。

Bit gauges, rings of defined circumference, are slipped around drill bits to detect and measure wear, which reduces the circumference of the bit during drilling.

youdao

研究了三角形周长平分弦的性质，得出任一三角形均可确定其最长和最短周长平分弦。

Discuss the properties of the perimeter bisection chord of a triangle, give any triangle, its longest and shortest bisection chords can be determined.

youdao

以下哪个图形的周长与M的周长相等？

Which of the following diagrams has the same perimeter as m.

youdao

And if it is going to be a standing wave then this must be an integral number of wavelengths.

如果这有个驻波的话,那么周长就是个整数。

麻省理工公开课 - 固态化学导论课程节选

I have to have a whole number of wavelengths to get around the circumference.

我必须要有个关于波长的总体数字,测量周长。

麻省理工公开课 - 固态化学导论课程节选

r So the circumference is 2 pi r.

周长=2π

麻省理工公开课 - 固态化学导论课程节选