正方形是二维的，立方体是三维的。
A square is two-dimensional and a cube is three-dimensional.
本文介绍了采用三维光弹性应力冻结法，对旋转正方形试样半边裂纹应力强度因子进行研究的成果。
This paper introduces a research result on the stress intensity factors of crackles on single side of revolving square sample with the stress freezing in three-dimensional photoelasticity.
有六个正方形或长方形侧面的三维形状。
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