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【单选题】
若 x(n) 为实序列, X(e jω ) 是其离散时间叶变换,则()。A.
X(e jω ) 的幅度和相角都是 ω 的偶函数
B.
X(e jω ) 的幅度是 ω 的奇函数，相角是 ω 的偶函数
C.
X(e jω ) 的幅度是 ω 的偶函数，相角是 ω 的奇函数
D.
X(e jω ) 的幅度 和相 角都是 ω 的奇函数
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【简答题】某设备有 2 台电动机,控制要求如下:按下起动按钮,第一台电动机 M1运行10s ,停止 5s ,第二台电动机 M2要求与M1相反,M1运行M2停止,M1停止M2运行,如此反复运行3次,M1和M2均停止,试设计PLC控制程序。
【单选题】Which of the following is TRUE according to the text?
A.
The achievement of Lisbon's goals would precede the elimination of chaos.
B.
The best way to help European firms may be to make it easier for them to fail.
C.
It is high time that the rigid bankruptcy laws in the U.S. were radically changed.
D.
Shutting a weak American company means ending up with a big chunk of assets.
【简答题】A．stopped B．stops C．stopping
【单选题】Which of the following statements is TRUE according to the text?
A.
The reason for the ECB's unwillingness to cut interest rates is that inflation was actually expected to fall in Germany.
B.
In Germany consumer prices were falling.
C.
Last year's oil prices dropping out of the year-on-year calculation directly leads to the drop of inflation.
D.
The European Central Bank is willing to cut interest rate.
【单选题】In the author's opinion,______.
A.
it is true that life in America is much faster than that in any other city
B.
people living outside big cities are lazy and miserable
C.
most American people enjoy living in the suburbs of big cities
D.
those who are busy are not necessarily unfriendly
【简答题】某设备有 3 台电动机,控制要求如下:按下起动按钮,第一台电动机 M1 起动,运行 5s 后,第二台电动机 M2 起动, M2 运行 10s 后,第三台电动机 M3 起动;按下停止按钮, 3 台电动机全部停止。
【单选题】下列关于经典突触的描述,正确的是
A.
属于非定向化学性突触
B.
含各类递质的突触小泡无形态差异
C.
各类递质均在激活区释放
D.
激活区位于前膜上对应于后膜受体的位置
E.
后膜受体都是化学门控通道
【单选题】Which of the following is NOT true about Stevie's childhood?
A.
Stevie often told people that a blind person was not necessarily disabled.
B.
He learnt to concentrate on things that he could do.
C.
He played as often as possible with his brother, who had normal sight.
D.
He tried very hard to train his sense of hearing.
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