【简答题】稠油氧化降粘法可用的主剂为 和 ,助剂为 和 。
【单选题】What does Dr Thomas probably think about the cost of the new weight?
A.
It is a small amount to pay for so much precious metal.
B.
It is difficult to judge the value of such an object.
C.
It is reasonable for an object with such an important function.
D.
It is too high for such a light weight.
【单选题】What does the passage say about the predictions made by Thomas Robert Malthus and Paul Ehrlich?
A.
They proved to be useful.
B.
They have not come true.
C.
They proved to be accurate.
D.
They have not drawn enough attention.
【单选题】—Why does Thomas speak through every discussion but never listen to the others? —That's what he ________ do. We used to hate that, but are used to it now.
【单选题】关于戴维宁定理的应用,下列叙述中错误的是 ( )
A.
戴维宁定理可将复杂的有源线性-端电路等效为-个电压源与电阻并联的电路模型
B.
求戴维宁等效电阻是将有源线性二端电路内部所有的独立源置零后,从端口看进去的输入电阻
C.
为得到无源线性二端网络, 可将有源线性二端网络内部的独立电压源短路、独立电流源开路
D.
在化简有源线性二端网络为无源线性二端网络时 , 受控源应保持原样,不能置于零
【单选题】关于戴维宁定理的应用,下列叙述错误的是()。
A.
戴维宁定理可将复杂的有源线性二端电路等效为一个电压源与电阻串联的电路模型。
B.
戴维宁等效电路中的电压源是有源线性二端网络端口的开路电压。
C.
用戴维宁等效电路替代有源二端网络,对外电路(端口以外的电路)求解没有任何影响。
D.
当有源二端网络含有受控源时,求戴维宁等效电阻,可以将受控源置为零。