closed type concave

例句：

1. 1. Thedesign of the closed-type concave is very elegant and practical.
   这种封闭型凹面的设计风格既优雅又实用。
2. 2.The closed-type concave has a smooth surface that makes it easy to clean.
   这种封闭型凹面的表面光滑，使得清洁变得容易。
3. 3. The closed-type concave is often used in jewelry making to create intricate designs.
   封闭型凹面常被用于珠宝制作中，以创造复杂的设计。