转动节流针形阀的手轮,调节针形阀的开度,就改变了阀体中阀针与阀座之间的间隙和气流的(),而且由于节流阀还改变了气体的流动方向,故能起到调节气体流量和压力的作用。
参考答案:流通面积
There are forty-eight students in our class. There are twenty-three boys and twenty-five girls. Some students live near the school, and some others live very far from the school. About half of the students come to school by bike. They often get to school at a quarter to seven. About ten students often come to school by bus. They often go to school very early, too. Another ten students come to school on foot. Their homes are near the school, but they are often late for school, because they get up very late.
小题1:More than half of the students usually come to school .
A.very late
B.very early
C.by bus
D.on foot小题2:Some students are often late for school because .
A.their homes are far from the school
B.they go to school on foot
C.they get up very late
D.they don’t like going to school小题3:About students go to school by bike.
A.forty-eight
B.ten
C.twenty
D.twenty-four小题4:About ten students often come to school by bus because .
A.their homes are not near the school
B.they don’t have any bikes
C.they can’t ride bike
D.they want to go to school very early小题5:How many students get to school by bus and on foot?
A.About thirty-eight
B.About twenty
C.About ten.
D.About twenty-five
若积分环节时间常数为T,则输出量随时间的增长而不断地增加,增长斜率为()
A.T
B.1/T
C.1+1/T
D.1/T2