Well, a man named Hausdorff in 1919 introduced a number which was just a mathematical joke, and I found that this number was a good measurement of roughness.
那么，1919年，一个名叫豪斯多夫的人 介绍了一个数字，这个数字简直是一个数学笑话。 我发现这个数字 是一个很好的测量粗糙度的值。