降低遥信误发率问题常用什么方法?
参考答案:
(1)采用光耦作为隔离手段。
(2)适当提高遥信电源,引入电缆屏蔽,调整RTU防抖时间。
(3)对遥信对象的辅助触点进行清洁处理。
脊髓空洞症首选的辅助诊断方法是()
A.脊柱X线平片
B.脊髓造影
C.延尺脊髓CT扫描
D.脊髓MRI
E.腰穿及脑脊液检查
By the time Bob arrives in Beijing, we have already arrived here for two days.
A.we have been staying here for two days
B.it has been for two days we have stayed here
C.it is already two days before we have arrived here
D.we will have stayed here for two days