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【简答题】
一个LTI系统当且仅当其系统函数H(z)的收敛域包含单位圆｜z｜=1时，该系统是稳定的( )；一个具有有理系统函数的因果LTI系统，当且仅当H(z)的全部极点都位于单位圆内，系统是稳定的( )；即全部极点之模大于等于1时，系统是稳定的( )。
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【多选题】铣削螺旋齿刀具端面齿时,除通常的计算.调整外,还应注意( )等事项。
A.
分度头具有较高的等分精度，需要时能作微量调整
B.
保证端面齿棱带宽度的磨削余量
C.
选用较小直径的铣刀，以免碰伤其他刀齿
D.
选用万能工具铣床，使调整方便，且加工精度高
E.
如果刀具的端面齿呈折线，则棱边的宽度将由铣齿背时予以保证
【单选题】—You shall get an iPhone as long as you come out first in the contest. —Is that a _________? Don't let me down, I hope. [ ]
A.
trick
B.
decision
C.
promise
D.
goal
【单选题】Hairdresser：How would you like to do your hair today?You’re not in a hurry， are you?Mrs．Lee：N0．__________．
A.
Be relaxed
B.
Take it easy
C.
Don，t worry
D.
Take your time
【单选题】---When _______for Guangzhou? ---Next Monday evening.
A.
are you leaving
B.
were you leaving
C.
you are leaving
D.
you were leaving
【单选题】If you fit the ________ averages, by the age of 20 you will have been exposed to at least 20000 hours of television.
A.
statistical
B.
statistics
C.
statistic
D.
statistically
【单选题】At a party or social occasions, how would you indicate that it was time for you to leave someone's house?
A.
I would say, 'It's getting late and I'd better be going.'
B.
I would say, 'I'm sorry. I have to leave now.'
C.
I would wait until the host said something.
D.
I would make up an excuse (e.g. I have to get up early tomorrow, etc.) and thank the hosts.
【单选题】_______ you sit in front of the computer all day while working, you’d better take exercise for at least an hour every day.
A.
Even if
B.
Even though
C.
Now that
D.
As if
【单选题】关于椎管的构成的描述正确的是
A.
椎体、椎间盘和前纵韧带构成椎管前壁
B.
椎间盘位于所有椎骨之间
C.
椎弓板和黄韧带构成椎管的后壁
D.
后纵韧带连于所有棘突的游离端
E.
棘间韧带构成椎管侧壁
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