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【简答题】
设非线性元件的伏安特性是 i=a0+a1u+a2u2 用此非线性元件作变频器件，若外加电压为 u=U0+USm(1+mcosΩt)cosωst+ULmcosωLt 求变频后中频(ω1=ωL一ωs)电流分量的振幅。
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举一反三
【单选题】沼气发酵调节提高pH的方法不包括( )
A.
经常少量出料并投入同量新料
B.
加入草木灰和适量的氨水
C.
加入氢氧化钠
D.
用石灰水、碳酸钠溶液或碳酸氢钠溶液调节pH值
【单选题】Wherever two or more unusual traits or situations are found in the same place, it is tempting to look for more than a coincidental relationship between them.
A.
vestiges
B.
residues
C.
characteristics
D.
figures
【单选题】When did the latest bomb explosion take place?
A.
It took place just one hour after two other bombings.
B.
It took place on Thursday.
C.
It took place on Tuesday when the train was entering a station.
D.
It took place on Tuesday when the train was leaving a station.
【简答题】The two roads meet________ a market lies. [A] at the place [B] where [C] there [D] at there
【单选题】The World Cup ________ two years after the Olympics. [ ]
A.
is taken place
B.
takes place
C.
held
D.
is holding
【简答题】Stiff vs. Stuff This is too ______; I can’t bend it with my hands. _______ the cushion and then sew up the final seam. They’d been _________ themselves with snacks all afternoon, so they didn’t want a...
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