顶圈
- 网络top ring
顶圈-
电子束焊活塞顶圈毛坯质量的超声波检测
Ultrasonic inspection of quality of pre-machined crown ring for electron-beam welding piston
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圆形降落伞顶孔的孔口圈新技术
New Vent Loop Technology for Annular Parachutes
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在这块花园的正中心，我也以为应当有一座美好的小山，由三级梯磴上达，每一级底顶上留出一圈平地来，其阔足以容四人并肩而行；
I wish also , in the very middle , a fair mount , with three ascents , and alleys , enough for four to walk abreast ;