【多选题】直流电动机的调速方法以下说法正确的是
A.
调节电枢电压调速,属于无极平滑调速方法,调速范围宽
B.
电枢回路串电阻只能是有级调速,所串电阻上消耗电能,不经济
C.
弱磁升速,调速范围窄,一般与调压调速相配合使用
【单选题】串级控制系统中包含两个回路,主回路和副回路属于( )
【多选题】下列选项中,属于分程控制系统的应用范围的有( )。
【单选题】The United States is a country made up of many different races. Usually they are mixed together and cant be told from one another. But many of them still, talk about where their ancestors came from. I...
A.
reads at about 245 w. p. m.
C.
reads at about 300 w. p. m.
D.
cannot read difficult works in translation
【单选题】The white races are superior ______ the darker ones.
【简答题】You will watch 2 clips from the film The Color of Friendship, first played on the Disney Channel in 2000. The story is about the friendship between 2 girls from different cultural and ethnic backgroun...
【单选题】循环变应力的循环特性r表达了变应力的变化情况。静应力看作是变应力的特例,其循环特性r为( )