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【简答题】
某液体在内径为d1的水平管路中稳定流动，其平均流速为u1，当它以相同的体积流量通过等长的内径为d2(d2=d1/2)的管子时，若流体为层流，则压降Dp为原来的 倍。
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【简答题】小题1:Many athletes won gold medals in the Olympics, they are our national h__________. 小题2:Tom didn’t finish _____________( write) his test because he ran out of the time. 小题3:The girl is a mode...
【单选题】It is known to us that it was such great efforts _______ all the Chinese athletes had made _______ helped them get 51 gold medals in the 2008 Beijing Olympic Games. [ ]
A.
as, that
B.
that, which
C.
that, as
D.
which, which
【单选题】What accounts for black athletes' failure to obtain a college degree, according to the man?
A.
Coaches lack the incentive to graduate them.
B.
College degrees do not count much to them.
C.
They have little interest in academic work.
D.
Schools do not deem it a serious problem.
【单选题】Although there were only five athletes ____ in the race, it was a rather exciting one.
A.
competing
B.
having been competed
C.
to compete
D.
to be competed
【多选题】P、V操作是操作系统提供的具有特定功能的原语。利用P、V操作可以( )。
A.
保证系统不发生死锁
B.
实现资源的互斥使用
C.
推迟进程使用共享资源的时间
D.
提高资源利用率
E.
协调进程的执行速度
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