But the survival problem of optical network is still the focus of city rail transit, especially studying and using the ring optical network.
但是光网络的生存性问题仍旧是城市轨道交通关注的焦点，特别是对环形光网络研究和应用。
The wheel band pre-installation used snap ring is wholly buckle installed in the groove of the wheel band relative to the rail car wheel.
所述的轮箍预装用卡环，其整体扣装在轨道机车轮对的轮箍的沟槽中。
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