供给X线管的能量,有百分之多少转换成X线()。
A.小于1%
B.4%
C.10%
D.85%
E.99%
参考答案:A
解析:电子束撞击靶面时绝大部分能量(>99%)转变成热。
A disk scheduling mechanism in an operating system causes the disk arm to sweepback and forth across the disk surface servicing all requests in its path. This is a
A.First Come First Serve
B.Shortest Seek Time First
C.Scan
D.None of the above
自来水为什么会发黄?