1. The four quarter-circle pieces of plastic can be combined to form a perfect circle that can duty as a coffee table.
做咖啡桌使用的话，把4个夸蒂塑胶块放在一起做成一个完美的圆形就可以了。
2. A two-dimensional plain strain finite element model of infinite plate is developed to investigate the ultrasonic wave propagation and scattering on three kinds of cracks: parallel to the surface, 450 oblique angle to the surface, and quarter-circle.
摘要建立了无限长板的具有吸收边界的二维平面应变有限元模型，在研究了脉冲超声波在无限长板中传播的基础上，对板中平行于表面的裂纹、与表面成45°的斜裂纹和四分之一圆周弧形裂纹三种情况的脉冲超声波散射进行了重点研究。