题目内容

流体阻力的大小只取决于流体的黏性。

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往复泵的流量随扬程增加而减少。

扬程为20m的离心泵，不能把水输送到20m的高度。

Uponstartingyourdatabase，youreceivethefollowingerror：
SQL＞startupORACLEinstancestarted.
TotalSystemGlobalArea171581440bytesFixedSize1298640bytesVariableSize146804528bytesDatabaseBuffers20971520bytesRedoBuffers2506752bytesDatabasemounted.
ORA-00313：openfailedformembersofloggroup1ofthread1
ORA-00312：onlinelog1thread1：’/oracle01/oradata/orcl/redo01.log’ORA-00312：onlinelog1thread1：’/oracle01/oradata/orcl/redo01a.log’
Youcanchoosefromthefollowingsteps：
a.Restorethedatabasedatafiles.
b.Issuethealterdatabaseclearunarchivedlogfilegroup1command.
c.Issuethealterdatabaseopencommand.
d.Issuethealterdatabaseopenresetlogscommand.
e.Recoverthedatabaseusingpoint-in-timerecovery.
f.IssuetheStartupMountcommandtomountthedatabase.
g.Backupthedatabase.
Whichisthecorrectorderofthesestepsinthiscase？（）

用一U形管差压计测某一压强差，现换一口径比原来大的U形管差压计来测量同一压强差，指示液与前U形管相同，则所测得的读数R/与前U形管的读数R相同。