南京航空航天大学878数字电路和信号与系统(A卷)2017年考研真题

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西南交大考研试题(信号与系统)

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3序列f（k）＝e j2πk/3＋e j4πk/3是（）。[西安电子科技大学2012研] A．非周期序列 B．周期N＝3 C．周期N＝6 D．周期N＝24 【答案】B查看答案 【解析】f1（k）＝e j2πk/3的周期N1＝2π/（2π/3）＝3，f2（k）＝e j4πk/3的周期N2＝2π/（4π/3）＝3/2，由于N1/N2＝2为有理数，因此f（k）为周期序列，周期为2N2＝N1＝3。 4积分[西安电子科技大学2011研] A．2 B．1 C．0 D．4 【答案】A查看答案 【解析】 一电路系统H（s）＝（10s＋2）/（s3＋3s2＋4s＋K），试确定系统稳定时系数K 的取值范围（）。[山东大学2019研]

A．K＞0 B．0＜K＜12 C．K＞－2 D．－2＜K＜2 【答案】B查看答案 【解析】H（s）＝（10s＋2）/（s3＋3s2＋4s＋K）＝B（s）/A（s），其中A（s）＝s3＋3s2＋4s＋K，系统稳定需要满足K＞0，3×4＞K，因此0＜K＜12。7信号f（t）＝6cos[π（t－1）/3]ε（t＋1）的双边拉普拉斯变换F（s）＝（）。[西安电子科技大学2012研] A． B． C． D． 【答案】C查看答案 【解析】信号f（t）变形为

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who got a cold, the ones who felt greater social support and Cohen, a professor of psychology at Carnegie. Hugging "is a benefits of hugging to the release of oxytocin, often called "the relationships, including that between mother and their newborn babies. Oxytocin is made primarily in the central lower part of the brain , and some of it is released into the bloodstream. But physiology. 1.[A] Unlike [B] Besides [C] Despite [D] Throughout 【答案】[B] Besides 2.[A] connected [B] restricted [C] equal [D] inferior 【答案】[A] connected

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2017年考研英语一试题 Section Ⅰ Use of English Directions: Read the following text. Choose the best word(s) for each numbered blank and mark A, B, C or D on the ANSWER SHEET. (10 points) Could a hug a day keep the doctor away? The answer may be a resounding "yes!"_____（1）helping you feel close and _____（2）to people you care about, it turns out that hugs can bring a _____（3）of health benefits to your body and mind. Believe it or not, a warm embrace might even help you _____（4）getting sick this winter. In a recent study _____（5）over 400 healthy adults, researchers from Carnegie Mellon University in Pennsylvania examined the effects of perceived social support and the receipt of hugs_____（6）the participants' susceptibility to developing the common cold after being_____（7）to the virus. People who perceived greater social support were less likely to come_____（8）with a cold, and the researchers_____（9）that the stress-reducing effects of hugging _____（10）about 32 percent of that beneficial effect. _____（11）among those who got a cold, the ones who felt greater social support and received more frequent hugs had less severe_____（12）. "Hugging protects people who are under stress from the _____（13）risk for colds that's usually _____（14）with stress," notes Sheldon Cohen, a professor of psychology at Carnegie, Hugging " is a marker of intimacy and help _____（15）the feeling that others are there to help_____（16）difficulty." Some experts_____（17）the stress-reducing, health-related benefits of hugging to the release of oxytocin, often called "the bonding hormone"_____（18）it promotes attachment in relationships, including that between mothers and their newborn babies. Oxytocin is made primarily in the central lower part of the brain, and some of it is released into the bloodstream. But some of it _____（19）in the brain, where it _____（20）mood, behavior and physiology. 1. A．Besides B．Unlike C．Throughout D．Despite 2. A．equal B．restricted C．connected D．inferior 3. A．view B．host C．lesson D．choice 4. A．avoid B．forget C．recall D．keep 5. A．collecting B．affecting C．guiding D．involving 6. A．on B．in C．at D．of 7. A．devoted B．attracted C．lost D．exposed 8. A．along B．across C．down D．out 9. A．imagined B．denied C．doubted D．calculated 10.A．served B．restored C．explained D．required 11.A．Thus B．Still C．Rather D．Even 12.A．defeats B．symptoms C．errors D．tests 13.A．highlighted B．increased C．controlled D．minimized

2017年考研英语一真题及答案

2017年考研英语一真题及答案 Section Ⅰ Use of English Directions:Read the following text.Choose the best word(s)for each numbered blank and mark A,B,C or D on the ANSWER SHEET.(10 points) Could a hug a day keep the doctor away? The answer may be a resounding "yes!"_____（1）helping you feel close and_____（2）to people you care about,it turns out that hugs can bring a_____（3）of health benefits to your body and mind.Believe it or not,a warm embrace might even help you_____（4）getting sick this winter. In a recent study_____（5）over 400 healthy adults,researchers from Carnegie Mellon University in Pennsylvania examined the effects of perceived social support and the receipt of hugs_____（6）the participants' susceptibility to developing the common cold after being_____（7）to the virus.People who perceived greater social support were less likely to come_____（8）with a cold, and the researchers_____（9）that the stress-reducing effects of hugging_____（10）about 32 percent of that beneficial effect._____（11）among those who got a cold,the ones who felt greater social support and received more frequent hugs had less severe_____（12）. "Hugging protects people who are under stress from the_____（13）risk for colds that's usually_____（14）with stress,"notes Sheldon Cohen,a professor of psychology at Carnegie,Hugging"is a marker of intimacy and help_____（15）the feeling that others are there to help_____（16）difficulty." Some experts_____（17）the stress-reducing, health-related benefits of hugging to the release of oxytocin, often called"the bonding hormone"_____（18）it promotes attachment in relationships, including that between mothers and their newborn babies. Oxytocin is made primarily in the central lower part of the brain, and some of it is released into the bloodstream. But some of it_____（19）in the brain, where it_____（20）mood, behavior and physiology. 1. A．Besides B．Unlike C．Throughout D．Despite 2. A．equal B．restricted C．connected D．inferior 3. A．view B．Host C．lesson D．choice 4. A．avoid B．forget C．recall D．keep 5. A．collecting B．affecting C．guiding D．involving 6. A．on B．in C．at D．of 7. A．devoted B．attracted C．lost D．exposed 8. A．along B．across C．down D．out 9. A．imagined B．denied C．doubted D．calculated 10. A．served B．Restored C．explained D．required 11. A．Thus B．Still C．Rather D．Even 12. A．defeats B．symptoms C．errors D．tests 13. A．Highlighted B．increased C．controlled D．minimized 14. A．Presented B．equipped C．associated D．compared 15. A．assess B．Generate C．moderate D．record