For a disk to be readable, the session must be "closed."
要使盘可读，就必须“关闭”段。
2
A type of quick-opening valve whose orifice is opened and closed by a disk that pivots on a shaft in the throat of the valve.
一种快开式阀门，其孔口的开启和关闭靠装在阀门颈部枢轴上的圆盘。
3
The Company closed the main supply monitoring, surveillance cameras, monitoring equipment, hard disk recorders, network cameras, smart ball, ball speed, infrared cameras, micro-cameras and so on.