题目内容

对于欠阻尼二阶系统，无阻尼自然振荡频率ωn保持不变时（）。

A. ξ越大，调整时间ts越大
B. ξ越大，调整时间ts越小
C. ξ越大，调整时间ts不变
D. ξ越大，调整时间ts不定

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单位反馈系统稳态速度误差的正确含义是（）。

A. 在r(t)=Rx1(t)时，输出速度与输入速度的稳态误差
B. 在r(t)=Rx1(t)时，输出位置与输入位置的稳态误差
C. 在r(t)=Vx1(t)时，输出位置与输入位置的稳态误差
D. 在r(t)=Vx1(t)时，输出速度与输入速度的稳态误差

已知其系统的型别为v，输入为r(t)=tn（n为正整数），则系统稳态误差为零的条件是（）

A. v≥n
B. v＞n
C. v≤n
D. v＜n

Listen to a short passage concerning the meaning of life and fill in the missing information.[音频]Life is never just being. It is becoming a relentless, flowing on. Our parents live on through us, and we will live on through our children. The ___1_ we build endure, and we will endure through them. The beauty we fashion cannot be 2 by death. Our flesh may perish,our hands will wither,but that which they create in beauty and _3_ and truth lives on for all time to come.[音频]Don’t spend and waste your lives 4 objects that will only turn to dust and ashes. Pursue not so much the material as the ideal, for ideals alone _5_ life with meaning and are of _6_. Add love to a house and you have a home. Add righteousness to a city and you have a 7. Add truth to a pile of red brick and you have a school.[音频]Add religion to the humblest of edifices and you have a sanctuary. Add justice to the far-flung round of human endeavor and you have 8__. Put them all together, exalt them above their present _9___, add to them the vision of humankind redeemed, forever free of need and strife and you have a future _10___ with the radiant colors of hope.

Google（www.google.com，见图1-3），中文翻译为谷歌，是公认的全球最大、业界领先的搜索引擎。

A. 对
B. 错