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【多选题】
在实际工程中，以下哪些构件是需要进行疲劳强度验算的（）A.
吊车梁
B.
框架柱
C.
汽锤基础
D.
钢筋混凝土屋架
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【单选题】某交流发电机正常工作时产生的感应电动势为e=E m sin ωt.若线圈匝数减为原来的1/2,而转速增为原来的2倍,其他条件不变,则产生的感应电动势的表达式是( )
A.
e=E m sin ωt
B.
e=2E m sin ωt
C.
e=2E m sin 2ωt
D.
e=E m sin 2ωt
【单选题】交流发电机在工作时的电动势 e = E m sin ωt . 若将线圈匝数、线圈面积都提高到原来的两倍,其他条件不变,则电动势变为 ( )
A.
． e ＝ 2 E m sin ωt
B.
． e ＝ 4 E m sin ωt
C.
． e ＝ 2 1 E m sin ωt
D.
． e ＝ 4 1 E m sin ωt
【单选题】某交流发电机正常工作时的电动势为e=Emsinωt,如果发电机转子转速提高一倍,线圈匝数也同时增加一倍,其他条件不变,则发电机的电动势为
A.
e=4Emsin2ωt
B.
e=4Emsinωt
C.
e=2Emsin2ωt
D.
e=2Emsinωt
【简答题】That is the day of the ceremony. We have been invited to it.
【简答题】We have two daughters: Kristen is seven years old and Kelly is four. Last Sunday evening, we invited some people home for dinner. I dressed them nicely for the party, and told them that their job was ...
【单选题】Im supposed to go to the meeting, but I have an out—Sam invited me first to come to his wedding. The underlined word means ______.
A.
plan
B.
problem
C.
trouble
D.
excuse
【单选题】交流发电机工作时电动势为e=E m sin ωt,若将发电机的转速提高一倍,同时将电枢所围面积减小一半,其他条件不变,则其电动势变为( )
A.
e′=E m sin
B.
e′=2E m sin
C.
e′=E m sin 2ωt
D.
e′= sin 2ωt
【简答题】We have invited fifty people to our wedding ______________(总共).
【简答题】We have two daughters: Kristen is seven years old and Kelly is four．Last Sunday evening, we invited some people home for dinner．I dressed them nicely for the party, and told them that their job was to...
【简答题】All we invited have arrived, ______________?
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