【单选题】对称星形负载接于三相四线制电源上,如图所示。若电源线电压为380 V,当在D点断开时, 为( )。
【单选题】对称星形负载接于三相四线制电源上,如下图所示。若电源线电压为380V,当D点断开时,U1为( )
【简答题】According to some researchers,by measuring the levels of NT—proBNP in the blood people may know__________.
【单选题】Researchers disagree whether the 'use it or lose it' philosophy holds for cognitive aging, but there is one evidence that keeping mentally active can slow age-related declines. At Pennsylvania State U...
A.
the role mental stimulation in preventing mental aging,
B.
gradual loss of mental skills with normal aging.
C.
the relationship between mental function and spatial skills.
D.
effective ways to keep intellectual vigor.
【单选题】对称星形负载接于三相四线制电源 ,如图所示。 若电源线电压为 380 V ,当在 D 点断开 时, U 1 为 ( ) 。