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空军工程大学2017年硕士研究生入学试题
考试科目：电机学（A卷）科目代码801 说明：答题时必须答在配发的空白答题纸上，答题可不抄题，但必须写清题号，写在试题上不给分; 考生不得在试题及试卷上做任何其它标记，否则试卷作废；试题必须同试卷一起交回。
一、填空题（30分，每题2分）
1、根据变压器内部磁场的实际分布情况和所起的作用不同，通常把磁通分为和两部分。
前者在闭合，起作用；后者主要通过闭合，起作用。
2、在描述磁场的物理量中，用来描述空间某一点的磁场，用来描述一个给定面上的磁场，与磁场某点处的介质性质有关，而与磁场某点处的介质性质无关。
3、处于交变磁场中的铁磁物质中通常会产生两种损耗：和，由于它们都是在电机铁芯中产生的损耗，通常将它们合在一起，总称为。
一般来说，交变磁场的磁通密度越、交变频率越，这种损耗就越大。
4、在三相变压器原副绕组的连接方法中，Y/Y0-12表示。
5、在交流电机中，采用短距和分布绕组可以削弱或消除谐波磁势，如果想消除6次谐波磁势，则应选择交流绕组的节距（跨距）y= τ，τ表示电机的极距。
6、一台异步电动机的额定转差率为0.03，由定子经气隙传递到转子侧的电磁功率中的 %部分供给转子铜耗，％部分供给总的机械功率。
7、三相绕组的对称条件包括：和。
前者。
第 1 页 共 4 页空军工程大学2017年硕士研究生入学试题考试科目：数字信号处理（A 卷） 科目代码 886 说明：答题时必须答在配发的空白答题纸上，答题可不抄题，但必须写清题号，写在试题上不给分; 考生不得在试题及试卷上做任何其它标记，否则试卷作废；试题必须同试卷一起交回。
一、填空题（每小题2分，共20分）1、正弦序列)4sin()(n n x π=的周期为___________。
2、任意序列)(n x 可用单位脉冲序列)(n δ表示为=)(n x ___________。
3、采样信号的拉普拉斯变换)(s X 与对应序列的Z 变换)(z X 之间存在着从S 平面到Z 平面的映射关系，若S 平面以虚轴为分界线，则S 平面的左半平面映射到Z 平面的___________。
4、已知序列)(n x 只在有限区间21n n n ≤≤内有非零的有限值，此区间外序列值皆为零。
若01≥n 且02>n ，则)(n x 的Z 变换收敛域为___________。
5、若用][⋅DFT 表示序列的N 点离散傅立叶变换，且有)]([)(n x DFT k X =，那么可知=+)](4)(3[n n x DFT δ___________。
6、在时间抽取基2FFT 的计算中，所需要的复数乘法次数为___________。
7、一个典型的模拟信号数字化处理系统通常包括前置预滤波器、A/D 转换器、数字信号处理器、___________和平滑滤波器五个部分。
8、在用双线性变换法设计数字滤波器的过程中，从S 平面到Z 平面之间的单值映射关系可以表示为=s ___________。
9、若FIR 数字滤波器的单位脉冲响应为)(n h ，)(n h 为N 点偶对称实数序列，N 为偶数，则该数字滤波器频率响应的幅度函数)(ωH 在0=ω和πω2=处呈___________（填奇或偶）对称。
10、IIR 数字滤波器的系统函数为∑∑=-=-+=Nk kk N k k kz a z b z H 101)(，该滤波器的直接型结构（即直接II 型结构）中共有___________个延时器。
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空军工程大学2017年硕士研究生入学试题
考试科目：力学综合（A卷）科目代码882 说明：答题时必须答在配发的空白答题纸上，答题可不抄题，但必须写清题号，写在试题上不给分; 考生不得在试题及试卷上做任何其它标记，否则试卷作废；试题必须同试卷一起交回。
一、选择题（每题3分，15分）
1、正立方体的顶角上作用着6个大小相等的力，
此力系向任一点简化的结果是()。
A、主矢等于零，主矩不等于零；
B、主矢不等于零，主矩也不等于零；
C、主矢不等于零，主矩等于零；
D、主矢等于零．主矩也等于零。
2、刚体作定轴转动时，附加动反力为零的充要条件是( )。
A、刚体的质心位于转动轴上；
B、刚体有质量对称平面，且转动轴与对称平面垂直；
C、转动轴是中心惯性主轴；
D、刚体有质量对称轴，转动轴过质心与该对称轴垂直。
3、下列结论中哪些是正确的？(1) 若杆件的各横截面上只有轴力，则该杆件只产生拉伸或压缩变形；(2) 若杆件的各横截面上只有扭矩，则该杆件只产生扭转变形；(3) 若杆件的各横截面上只有弯矩，则该杆件只产生弯曲变形；(4) 若杆件的各横截面上只有正应力，无剪应力，则该杆件不会产生扭转变形。
A、(1)；
B、(1)，(2)；
C、(1)，(2)，(3)；
D、全对。
空军工程大学2017年博士研究生入学试题考试科目：材料物理（A卷）科目代码 3081说明：答题时必须答在配发的空白答题纸上，答题可不抄题，但必须写清题号，写在试题上不给分；考生不得在试题及试卷上做任何其它标记，否则试卷作废，试题必须同试卷一起交回。
一、名词解释（每题5分，共40分）1. 应变2. 比热容3. 热稳定性3. 费米能级5. 饱和磁化强度6. 光吸收7. 压电效应8. 热电效应二、简答题（每题6分，共30分）1. 用能带理论分析碱金属元素Li的导电性优于金属Mg导电性的原因。
2. 什么是霍尔效应？霍尔效应用于判断半导体类型的基本原理是什么？3. 简述BaTiO3电介质在居里温度点以下存在的四种极化机制。
4. 用能量的观点说明铁磁体内形成磁畴的原因。
5. 产生超声波的材料主要有哪几类？三、计算题（每题10分，共30分）1. 一试样长40cm，宽10cm，厚1cm，其杨氏模量为3.5×109 N·m-2，当受到应力为1000N拉力时，能伸长多少?2. 某硅酸铝玻璃的性能为k t=2.1J·m-1·s-1·K-1，α=4.6×10-6K-1，σf=7.0×107N·m-2，E=4.7×107N·m-2，μ=0.25。
求第一及第二热冲击断裂抵抗因子。
3.下图为某一光学材料的透光率曲线，请分析曲线峰谷（位于0.4μm处）形成的原因，并计算该材料的禁带宽度。
（普朗克常数h=4.13×10-15eV·s=6.63×10-34J·s; 光速c=3×108m/s）。
空军工程大学2014年硕士研究生入学试题考试科目：电路信号与系统（A 卷） 科目代码 862说明：答题时必须答在配发的空白答题纸上，答题可不抄题，但必须写清题号，写在试题上不给分; 考生不得在试题及试卷上做任何其它标记，否则试卷作废；试题必须同试卷一起交回。
第一部分 电路分析基础部分（50％）一、填空与选择题：（每题1.5分，共12分）1. 图题1.1电路中的电压U 为 。
(a) 0V (b) 2V (c) 38V (d) –2V图题1.12.在图题1.2所示电路中，已知U S =2V ，I S =2A 。
A 、B 两点间的电压U AB 为 。
Ω2a图题1.2 图题1.33、将图题1.3所示电路化最简电路为 。
4. 叠加定理适合于以下何种电路？应该是电路。
(a) 非时变 (b) 非线性 (c) 时变 (d) 线性5. 图题1.5所示为RLC 串联谐振电路，已知：R = 30Ω，L = 18mH ，电路的谐振频率f 0 = 200kHz ，则电容C = 。
(a) 35.18pF (b) 44.21μF (c) 1.39nF (d) 277.8μF-u图题1.5 图题1.66. 图题1.6所示正弦稳态电路中，各电压表的读数分别为：V 1 = 4V ，V 2 = 10V ，V 3 = 7V ，则电压表V 的读数为 。
(a) 21V (b) 7V (c) 5V (d) 13V7. 正弦稳态电路中，电容上电流和电压之间的正确关系为 。
(a) j i C u ω= (b) C U I ω= (c) C U Iω=∙∙(d) C ui ω= 8. 在R 、L 串联电路中，已知A t t i )3sin 2sin 222(ωω++=，R = 3Ω，ωL = 2Ω，则电阻R 吸收的功率为 。
(a) 210W (b) 110W (c) 27W (d) 15W二、分析与综合计算：（本大题共7小题，共63分）1.（10分）电路如图题2.1所示，列出节点电压方程，并求节点电压1u 、2u 和3u ，已知5S =i A 。
空军工程大学2017年硕士研究生入学试题考试科目：翻译硕士英语（A卷）科目代码211 说明：答题时必须答在配发的空白答题纸上，答题可不抄题，但必须写清题号，写在试题上不给分; 考生不得在试题及试卷上做任何其它标记，否则试卷作废；试题必须同试卷一起交回。
PART I MULTIPLE-CHOICE QUESTIONS [20 POINTS] SECTION A GRAMMARDirections: Beneath each sentence there are four words or phrases marked [A], [B], [C] and [D]. Choose one word or phrase that best completes the sentence. Mark your answers on your ANSWER SHEET.1. Fool _______Helen is, she could not have done such a thing.[A] who [B] as [C]that [D] like2. _____ time, John will make a first-class tennis player.[A] Having [B] Given [C] Giving [D] Had3. Intellect is to the mind _______sight is to the body.[A] what [B] as [C]that [D]like4. After ____ seemed an endless wait, it was his turn to enter the personnelmanager’s office.[A] that [B]there [C] what [D]it5. _____ your timely advice, I would never have known how to go about the work.[A]Unless [B] But for [C] Except for [D] Not for6. Sam is______ hardworking than his sister, but he failed in the exam.[A] no less [B]no more [C]not less [D] no so7. _____for the fact that she broke her leg, Mary might have passed the exam.[A] Had it not been [B] Hadn’t it been [C] Was it not [D] Were it not8. It is futile to discuss the matter further, because ____ going to agree uponanything today.[A]neither you nor I are [B] neither you nor me is[C]neither you nor I am [D] neither me nor you are9. Her strong sense of humor was _______make everyone in the room burst out laughing.[A] so as to [B] such as to [C]so that [D]. such that10. _______at in this way, the present economic situation doesn’t seem so gloomy.[A]Looking [B] Looked [C] Having looked [D] To look11. Acute hearing helps most animals sense the approach of thunderstorms longbefore people _____.[A]do [B] hear [C]do them [D]hearing it12. The meeting was put off because we __________ a meeting without Peter.[A]objected having [B] were objected to having[C]objected to have [D] objected to having13. The oceans ______ divide the world__________ unite it.[A]not…as [B] / …/[C] do not so much … as [D] do so much…than14. Time is what we want most, but what, alas, many use ____________.[A]it [B] worse [C] wisely [D] flexibly15. It is absolutely essential that John ____ his study in spite of some learningdifficulties.[A]will continue [B] continued [C] continue [D] continues SECTION B VACABULARYDirections: There are four words or phrases beneath each sentence. Choose the ONE word or phrase which would best keep the meaning of the original sentence if it were substituted for the underlined part. Mark your answers on your ANSWER SHEET.16.The official promised to be candid, but we wondered.[A]discreet [B] open and frank [C]casual [D] sweet17. Betty advised me to label our luggage carefully in case it gets misplaced intransit.[A]misuse [B]mishandled [C]mistaken [D]mislaid18. His miscellaneous expenses include stamps and haircuts.[A]daily [B] many different [C] additional [D]annual19. In winter, many homeless vagabonds prefer to live in prison rather than to live inthe open.[A]children [B]wanders [C]criminals [D]tramps20. Because the details of the project were rather hazy, they decided to reject theproposal.[A]dubious [B] unobtainable [C] lucrative [D] vague21.The police decided to make every effort to capture the fiend who murdered thechildren.[A]foolish person [B] wicked person[C]hot-headed person [D] suspected person22. His father refused to see anyone and remained a hermit all his life.[A]heretic [B]fugitive [C]recluse [D] veteran23.They found a hamlet in the deep forest with only ten families.[A]an empty space [B]a cottage [C]a small village [D] a tribe24. Does he love his wealthy mother or only pretend for mercenary reasons?[A]personal [B]purely unexplained [C]instinct [D] selfish25. People who live in crowded cities often experience breathing problems duringthe summer when high temperature combined with hoary polluted air.[A]drab [B] stagnant [C]lurid [D]greyish white26. We are at a critical important point in terms of his domestic program.[A]jig [B]martin [C]martini [D] juncture27. If he wins this race, it will make up his recent string of defeats.[A]ameliorate [B] atone [C]asperse [D] ascertain28. Health inspectors criticized severely the kitchen staff for poor standards ofcleanliness.[A]castigated [B]capitulated [C]corroded [D] debilitated29. She was seized the cramps while swimming.[A]sharks [B]swift currents [C]storms [D] sharp pains30. He is one of the young lady's fervent admirers.[A] ardent [B] young [C] first [D] unseenPART II Close Text [10 POINTS] Directions: Read the following text. Choose the best word(s) for each numbered blank and mark A, B, C or D on your ANSWER SHEET.The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, 41 this is largely because, 42 animals, we stand upright. This means that our noses are 43 to perceiving those smells which float through the air, 44 the majority of smells which stick to surfaces. In fact, 45 , we are extremely sensitive to smells, 46 we do not generally realize it. Our noses are capable of 47 human smells even when these are 48 to far below one part in one million.Strangely, some people find that they can smell one type of flower but not another, 49 others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate 50 smell receptors in the nose. These receptors are the cells which sense smells and send 51 to the brain. However, it has been found that even people insensitive to a certain smell 52 can suddenly become sensitive to it when 53 to it often enough.The explanation for insensitivity to smell seems to be that the brain finds it 54 to keep all smell receptors working all the time but can 55 new receptors if necessary. This may 56 explain why we are not usually sensitive to our own smells—we simply do not need to be. We are not 57 of the usual smell of our own house, but we 58 new smells when we visitsomeone else’s. The brain finds it best to keep smell receptors 59 for unfamiliar and emergency signals 60 the smell of smoke, which might indicate the danger of fire.41. [A] but [B] as [C] although [D] while42. [A] besides [B] unlike [C] excluding [D] above43. [A] confined [B] committed [C] dedicated [D] limited44. [A] catching [B] tracking [C] missing [D] ignoring45. [A] anyway [B] though [C] instead [D] therefore46. [A] even if [B] if only [C] only if [D] as if47. [A] determining [B] discovering [C] distinguishing [D] detecting48. [A] diluted [B] dissolved [C] dispersed [D] diffused49. [A] when [B] since [C] for [D] whereas50. [A] unique [B] particular [C] unusual [D] typical51. [A] messages [B] stimuli [C] signs [D] impulses52. [A] at first [B] at all [C] at large [D] at times53. [A] subjected [B] left [C] drawn [D] exposed54. [A] ineffective [B] incompetent [C] inefficient [D] insufficient55. [A] introduce [B] summon [C] trigger [D] create56. [A] still [B] also [C] otherwise [D] nevertheless57. [A] sure [B] stick [C] aware [D] tired58. [A] tolerate [B] repel [C] neglect [D] notice59. [A] suitable [B] reliable [C] identifiable [D] available60. [A] aside from [B] such as [C] along with [D] similar to PART III PROOFREADING & ERROR CORRECTION [10 POINTS] Directions: The passage contains TEN errors. Each indicated line contains a maximum of ONE error. In each case, only ONE word is involved. You should proofread the passage and correct it in the following way:For a wrong word, underline the wrong word and write the correctone in the blank provided at the end of the line. For a missing word, mark the position of the missing word with a“∧” sign and write the word you believe to bemissing in the blank provided at the end of theline.For an unnecessary word, cross out the unnecessary word with a slash “/”and put the word in the blank provided at theend of the line.EXAMPLEWhen ∧art museum wants a new exhibit, (1) an it never buys things in finished form and hangs (2) never them on the wall. When a natural historymuseum wants an exhibition, it must often build (3)exhibitit.Recently, a possible alternative way of producing paper has been suggested by agriculturalists and environmentalists: a plant called hemp.Hemp has been cultivated by many cultures for thousandsof years. It produces fiber which can be made paper, fuel, oils, textiles, food, and rope. For many centuries, it was essential to the economies of many countries because it used to make the ropes and cables used on sailing ships; colonial expansion and the establishment of a world-wide trading network would have been possible without hemp. Nowadays, ships’ cables are usually made from wire or synthetic fibers, and scientists are now suggesting that the cultivation of hemp should be revived for the production of paper and pulp. According to its proponents, four times as that much paper can be produced from land, using hemp rather than trees.However, there is a problem: hemp is illegal in many countries of the world. This plant, so useful for fiber, rope, oil, fuel and textiles, is species of cannabis, related to the plant which marijuana is produced. In the late 1930s, a movement to ban the drug marijuana began to gather force, resulted in the eventual banning of the cultivation not only of the plant used to producing the drug, but also of the commercial fiber-producing 61. __________62. __________63. __________64. __________65. __________66. __________67. __________68. __________69. __________70. __________ hemp plant—despite the fact marijuana cannot be producedfrom the hemp plant, since it contains almost no THC (theactive ingredient in the drug).PART IV READING COMPREHENSION [30 POINTS] Directions: In this part there are four reading passages followed by a total of twenty multiple-choice questions. Read the passages and then mark your answers on the answer sheet.TEXT A (5 points)During the 1970’s and 1980’s political extremism and terrorism frequently focused on “national liberation” and economic issues. The collapse of the Soviet bloc, and the ending of its covert funding and encouragement of terrorism led to a decline in the militant and violent left-wing terrorist groups that was a feature of the age.The 1990s have seen the development of a “new terrorism”. This is not to say that state-backed terrorism has ceased, but rather that the spectrum of terrorism has widened. The new terrorism may seek out military or government targets, but it also seeks out symbolic civilian targets, and the victims have mostly been innocent civilians.Growing concern about this new terrorism has been paralleled by concern about the employment of the new information and communication technologies (ICTs).ICTs offer a new dimension for political extremists and terrorists. They allow the diffusion of command and control; they allow boundless new opportunities forcommunication, and they allow the players to target the information stores, processes and communications of their opponents. The sophistication of the modern nation-state, and its dependency on computer-based ICTs, make the state ever more vulnerable.The use of ICTs to influence, disrupt or damage a nation, its institutions or population by influencing the media, or by subversion, has been called “netwar”. The full range of weapons in the cyberspace armory can be employed in netwar; from propaganda campaigns at one level to interference with databases and networks at the other. What particularly distinguishes netwar from other forms of war is that it targets information and communications, and may be used to alter thinking or disrupt planned actions. In this sense it can be distinguished from earlier forms of warfare — economic wars that target the means of production, and political wars that target leadership and government.Netwar is therefore of particular interest to those engaged in non-military war, or those operating at sub-state level. Clearly nation-states might also consider it as an adjunct to military war or as an option prior to moving on to military war. So far, however, it appears to be of greater interest to extremist advocacy groups and terrorists. Because there are no physical limits or boundaries, netwar has been adopted by groups who operate across great distances or transnationally. The growth of such groups, and their growing powers in relation to those of nation states, suggests an evolving power-based relationship for both. Military strategist Martin Van Creveld has suggested that war in the future is more likely to be waged between such groups and states rather than between states and states.Most modern adversaries of nation states in the realm of low intensity conflict, such as international terrorists, single-issue extremists and ethnic and religious extremists are organized in networks, although their leadership may sometimes be hierarchical. Law enforcement and security agencies therefore often have difficulty in engaging in low intensity conflict against such networks because they are ill suited to do so. Their doctrine, training and modus(形式) of operation have, all too often, been predicated on combating a hierarchy of command, like their own.Only now are low-intensity conflict and terrorism recognized as “strategic” threats to nation-states, and countries which until very recently thought that terrorism was something that happened elsewhere, have become victims themselves.The Tokyo subway attacked by the Aum Shinriko and the Oklahoma City bombing would have been unthinkable a generation ago, and not only was the civil population unprepared, but also law enforcement. And this despite clear warning signs that such attacks were in the offing.The potential for physical conflict to be replaced by attacks on information infrastructures has caused states to rethink their concepts of warfare, threats and national assets, at a time when information is recognized as a national asset. The adoption of new information technologies and the use of new communication media, such as the Internet, create vulnerabilities that can be exploited by individuals, organizations and state.71. Which of the following is a major feature of the new terrorism?[A] It obtains financial support from foreign powers[B] It focuses on military targets of the enemy states.[C] It tends to be organized in a hierarchical manner[D] It may choose important civilian targets to attack.72. Netwar should be understood as a war aimed at __________.[A] disrupting the enemy’s communication systems[B] damaging the institutions of the enemy state[C] manipulating the enemy’s means of production[D] destroying the leadership of the enemy state73. We can infer from the passage that ___________.[A] traditional terrorism was mainly driven by religious fervor[B] ideological differences will continue to be a cause of terrorism[C] attacks from small terrorist groups will increasing[D] the high-tech weapons will greatly facilitate terrorist attacks74. The best title of the passage is ____________.[A] ICT: A New Weapon for Terrorism[B] Netwar: An unfamiliar Form of Warfare[C] Internet: A Vulnerable Target of Extremists[D] “New Terrorism”: A Real Threat to the World75. The main difficulty the police have in combating terrorist groups is _________.[A] their poor equipment[B] the insufficiency of budget[C] the police’s obsolete(陈旧的) way of command[D] the transnational nature of the new terrorismTEXT B (10 points)If you want to stay young, sit down and have a good think. This is the research finding of a team of Japanese doctors, who say that most of our brains are not getting enough exercises and as a result, we are ageing unnecessarily soon.Professor Taiju Matsuzawa wanted to find out why otherwise healthy farmers in northern Japan appeared to be losing their ability to think and reason at a relatively early age, and how the process of ageing could be slowed down.With a team of colleagues at Tokyo National University, he set about measuring brain volumes of a thousand people of different ages and varying occupations.Computer technology enabled the researchers to obtain precise measurements of the volume of the front and side sections of the brain, which relate to intellect and emotion, and determine the human character. (The rear section of the brain, which controls functions like eating and breathing, does not contract with age, and one can continue living without intellectual or emotional faculties.)Contraction of front and side parts as cells die off was observed in some subjects in their thirties, but it was still not evident in some sixty-and seventy-year-olds.Matsuzawa concluded from his tests that there is a simple remedy to the contraction normally associated with age—using the head.The findings show in general terms that contraction of the brain begins sooner in people in the country than in the towns. Those least at risk, says Matsuzawa, are lawyers, followed by university professors and doctors. White collar workers doing routine work in government offices are, however, as likely to have shrinking brainsas the farm worker, bus driver and shop assistant.Matsuzawa's findings show that thinking can prevent the brain from shrinking. Blood must circulate properly in the head to supply the fresh oxygen the brain cells need. “The best way to maintain good blood circulation is through using the brain," he says, “Think hard and engage in conversation. Don’t rely on pocket calculator."76. The team of doctors wanted to find out[A] why certain people age sooner than others.[B] how to make people live longer.[C] the size of certain people's brains.[D] which people are most intelligent.77. On what are their research findings based?[A] A survey of farmers in northern Japan.[B] Tests performed on a thousand old people.[C] The study of brain volumes of different people.[D] The latest development of computer technology.78. The doctor's tests show that[A] our brains shrink as we grow older[B] the front section of the brain does not shrink.[C]sixty-year-olds have better brains than thirty-year-olds.[D]some people's brains have contracted more than other people's79. The word “subjects" in Paragraph 5 means[A] something to be considered.[B] branches of knowledge studied.[C] persons chosen to be studied in an experiment.[D] any member of a state except the supreme ruler.80. According to the passage, which people seem to age slower than the others?[A] Lawyers. [B] Farmers. [C] Clerks. [D] Shop assistants. TEXT C (5 points)Harry Houdini, who died in 1927, was the entertainment phenomenon of the ragtime era. He could escape from chains and padlocks, from ropes and canvas sacks. They put him in a strait-jacket and hung him upside down from a skyscraper and he somehow untied himself. They tied him up in a locked packing case and sank him in Liverpool docks. Minutes later he surfaced smiling. They locked him in a zinc-lined Russian prison van and he emerged leaving the doors locked and the locks undamaged. They padlocked him in a milk churn(搅乳器) full of water and he burst free. They put him in a coffin, screwed down the lid, and buried him and…, well, no, he didn’t pop up like a mole, but when they dug him up more than half an hour later, he was still breathing.Houdini would usually allow his equipment to be examined by the audience. The chains, locks and packing cases all seemed perfectly genuine, so it was tempting to conclude that he possessed superhuman powers. Sir Arthur Conan Doyle’s Sherlock Holmes was the very paragon(模范) of analytical thinking but Conan Doyle believed that Houdini achieved his tricks through spiritualism. Indeed, he wrote to the escapologist(表演脱身术的人) imploring him to use his psychic powers more profitably for the common good instead of just prostituting his talent every night at the Alhambra. However, Houdini repeatedly denounced spiritualismand disclaimed any psychic element to his act.The alternative explanation for his feats of escapism was that Houdini could do unnatural things with his body. It widely held that he could dislocate his shoulders to escape from strait-jackets, and that he could somehow contract his wrists in order to escape from handcuffs. His ability to spend long periods in confined spaces is cited as evidence that he could put his body into suspended animation, as Indian fakirs are supposed to do.This is all nonsense. If you ever find yourself in a strait-jacket, it’s difficult to imagine anything less helpful than a dislocated shoulder. Contracting your wrists is not only unhelpful but, frankly, impossible because the bones of your wrist are very tightly packed together and the whole structure is virtually incompressible. As for suspended animation, the trick of surviving burial and drowning relies on the fact that you can live for short periods on the air in a confined space. The air shifted by an average person in a day would occupy a cube just eight feet square. The build-up of carbon monoxide tends to pollute this supply, but, if you can relax, the air in a coffin should keep you going for half an hour or so.In other word, there was nothing physically remarkable about Houdini except for his bravery, dexterity(灵巧) and fitness. His nerve was so cool that he could remain in a coffin six feet underground until they came to dig him up. His fingers were so strong that he could undo a buckle or manipulate keys through the canvas of a strait-jacket or a mail bag. He made a comprehensive study of locks and was able to conceal lock-picks about his person in a way which fooled even the doctors who examined him. When they locked him in the prison van he still had a hacksaw(钢锯)blade with which to saw through the joins in the metal lining and get access to the planks of the floor. As an entertainer he combined all this strength and ingenuity with a lot of trickery. His stage escapes took place behind a curtain with an orchestra playing to disguise the banging and sawing. The milk churn in which he was locked had a double lining so that, while the lid was locked onto the rim, the rim was not actually attached to the churn. Houdini merely had to stand up to get out. The mail sack he cut open at the seam and sewed up with similar thread. The bank safe from which he emerged had been secretly worked on by his mechanics for 24 hours before the performance.All Houdini’s feats are eminently explicable, although to explain them, even now, is a kind of heresy. Houdini belongs to that band of mythical supermen who, we like to believe, were capable of miracles and would still be alive today were it not for some piece of low trickery. It’s said of Houdini that a punch in his belly when he wasn’t prepared for it caused his burst appendix. Anatomically(在解剖学上), it’s virtually impossible that a punch could puncture your gut, but the story endures. Somehow the myth of the superman has an even greater appeal than the edifice of twenty-first century logic.81. In the first paragraph, what does the writer say Houdini managed to do?[A]. Jump upside down from a skyscraper.[B]. Safely escape from a submerged box.[C]. Break the locks of a prison van from inside.[D]. Escape from a buried coffin unhurt.82. The writer mentions Houdini’s burial alive to show that _________.[A]. his tricks sometimes went disastrously wrong.[B]. he was not always able to do what he claimed he could[C]. he was capable of extraordinary feats of survival[D]. his fear of confined spaces could readily be overcome83. The writer suggests that Conan Doyle __________.[A]. was less analytical about Houdini than one might have expected[B]. asked Houdini if he could include him in a Sherlock Holmes story[C]. felt that Houdini could make more money in other ways[D]. thought there were scientific explanations for Houdini’s feats84. The writer comes to the conclusion that Houdini __________.[A]. had an unusual bone structure[B]. could make parts of his body smaller[C]. could make himself fall asleep easily[D]. was not physically abnormal85. It appears that Houdini was able to escape from a strait-jacket by __________.[A]. hiding a lock-pick in his pocket[B]. undoing its buckles with his fingers[C]. cutting the canvas with a hacksaw[D]. using a blade he had concealedTEXT D (10 points)Austin Texas — The exasperated helpline caller said she couldn’t get her new Dell Computer to turn on. A Dell Computer Corp technician made sure the computer was plugged in and then asked the woman what happened when shepushed the power button. “I’ve pushed and pushed on this foot pedal and nothing happens,” the woman replied. “Foot pedal?” the technician asked. “Yes,” the woman said, “this little white foot pedal with the on switch.” The “foot pedal”, it turned out, was the computer’s mouse, a hand-operated device that helps to control the computer’s operations.Personal computer makers are discovering that it’s still a low-tech world out there. While they are finally having great success selling PCs to households, they now have to deal with people to whom monitors and disk drivers are as foreign as another language.“It is rather mystifying to get this nice, beautiful machine and not know anything about it,” says a technician who helps field consumer calls at Dell’s headquarters here. “It’s going into unfamiliar territory. People are looking for a comfort level.”Only two years ago, most calls to PC help lines came from techniques needing help on complex problems. But now, with computer sales to homes exploding as new “multimedia” functions gain mass appeal, PC makers say that as many as 70% of their calls come from rank novices(新手). Partly because of the volume of calls, some computer companies have started charging helpline users.The questions are often so basic that they could have been asked by opening the manual that comes with every machine. One woman called Dell’s toll-free line to ask how to install batteries in her laptop. When told that the directions were on the first page of the manual, the woman replied angrily. “I just spent $2,000 for this damn thing, and I’m not going to read a book.”Indeed, it seems that these buyers barely refer to a manual when a phone is at hand. If there is a book and a phone and they’re side by side, the phone wins time after time. It’s phenomenon of people wanting to talk to people.And the Computer Corp Compaq’s help center in Houston, Texas, is inundated(淹没) by some 8,000 consumer calls a day, with unbelievable inquiries like this one: a frustrated customer called, who said her brand new Compaq would not work. She had unpacked the unit, plugged it in, opened it up and, sat there for something to happen. When asked what happened when she pressed the power switch, she asked, “What power switch?”Seemingly simple computer features baffle some users. So many people have called to ask where the “any” key is when “Press Any Key” flashes on the screen that Compaq is considering changing the command to “Press Return Key”.Some people can’t figure out the mouse. One consumer complained that her mouse was hard to control with the “dust” cover on. The cover turned out to be the plastic bag the mouse was packaged in. Another consumer held the mouse and pointed it at the screen, all the while clicking madly. He got no response because the mouse works if it’s moved over a flat surface.A customer dutifully compiled with a technician’s request that she send in a copy of defective floppy disk. A letter from the customer arrived a few days later, along with a Xerox copy of the floppy.And at Dell, a technician advised his customer to put his troubled floppy back in the drive and “close the door”. Asking the technician, to “hold on”, the customer put the phone down and was heard walking over to shut the door to his room. The。
空军工程大学2017年硕士研究生入学试题考试科目：电机学（A卷）科目代码801说明：答题时必须答在配发的空白答题纸上，答题可不抄题，但必须写清题号，写在试题上不给分; 考生不得在试题及试卷上做任何其它标记，否则试卷作废；试题必须同试卷一起交回。
一、填空题（30分，每题2分）1、根据变压器内部磁场的实际分布情况和所起的作用不同，通常把磁通分为和两部分。
前者在闭合，起作用；后者主要通过闭合，起作用。
2、在描述磁场的物理量中，用来描述空间某一点的磁场，用来描述一个给定面上的磁场，与磁场某点处的介质性质有关，而与磁场某点处的介质性质无关。
3、处于交变磁场中的铁磁物质中通常会产生两种损耗：和，由于它们都是在电机铁芯中产生的损耗，通常将它们合在一起，总称为。
一般来说，交变磁场的磁通密度越、交变频率越，这种损耗就越大。
4、在三相变压器原副绕组的连接方法中，Y/Y0-12表示。
5、在交流电机中，采用短距和分布绕组可以削弱或消除谐波磁势，如果ττ想消除6次谐波磁势，则应选择交流绕组的节距（跨距）y= ，表示电机的极距。
6、一台异步电动机的额定转差率为0.03，由定子经气隙传递到转子侧的电磁功率中的 %部分供给转子铜耗，％部分供给总的机械功率。
7、三相绕组的对称条件包括：和。
前者是指 ；后者是指 。
8、有一台4极24槽的三相交流电机，则电机的极距= （用槽数表示），每极每相槽数= ，槽距角= 。
9、三相异步电动机的外加电源电压不变，如果定子每相绕组的匝数减少，气隙中每相磁通将 ，空载电流将 。
10、同步发电机三相电动势的相序由 决定，当磁极对数一定时，其感应电势的频率由 决定。
11、直流发电机本质上是一个 发电机，只是多了一套 装置，能够及时地将电势方向即将改变的导体由一条支路换接到另一支路中。
12、直流电动机主要有三种调速方法，它们是 调速、 调速和 调速。
13、当异步电动机的临界转差率为s m 时，其稳定工作范围是 。
