西南科技大学线性系统理论2019年考博真题试题
(完整word版)《线性系统理论》试卷及答案
R C 2《线性系统理论》试卷及答案1、（20分）如图所示RLC 网络,若e(t ）为系统输入变量r （t)，电阻R 2两端的电压为输出量y(t),选定状态变量为 x 1（t)=v 1（t ），x 2(t ）=v 2(t)，x 3（t)=i （t)要求列写出系统的状态空间描述。
2、(15分)求出下面的输入输出描述的一个状态空间描述。
y （4)+4y （3）+3y （2）+7y （1）+3y=u (3）+ 2u （1）+ 3u3、（15分）计算下列线性系统的传递函数。
[]210X 13101X y -⎡⎤⎡⎤=+⎢⎥⎢⎥-⎣⎦⎣⎦=4、(10分）分析下列系统的能控性.0111X X u a b •⎡⎤⎡⎤=+⎢⎥⎢⎥-⎣⎦⎣⎦5、（10分）分析下列系统的能观性。
[]1110a X X y Xb •⎡⎤==-⎢⎥⎣⎦6、（15分)判断下列系统的原点平衡状态x e 是否大范围渐近稳定。
12221123x x x x x x==--7、（15分）已知系统的状态方程为221012000401X X u •--⎡⎤⎡⎤⎢⎥⎢⎥=-+⎢⎥⎢⎥⎢⎥⎢⎥-⎣⎦⎣⎦试确定一个状态反馈阵K,使闭环极点配置为λ1*=—2、λ2*=-3、λ3*=—4.答案：1、（20分）如图所示RLC 网络，若e （t ）为系统输入变量r （t ）,电阻R 2两端的电压为输出量y （t ），选定状态变量为 x 1(t)=v 1（t)，x 2(t ）=v 2（t ）,x 3（t)=i （t ）要求列写出系统的状态空间描述。
2、（15分）求出下面的输入输出描述的一个状态空间描述。
列出向量表示形式解出解出解出r x x x L R x x x rx LR x x x xx x C R x x x C xC x r x R x L L LL⎥⎥⎥⎦⎤⎢⎢⎢⎣⎡+⎥⎥⎥⎦⎤⎢⎢⎢⎣⎡⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎣⎡--=⎥⎥⎥⎦⎤⎢⎢⎢⎣⎡+--=-=+=+==++1321113211311132122222112211333113000xy x xLy （4）+4y (3）+3y （2)+7y (1）+3y=u （3）+ 2u （1)+ 3u[]得出了状态空间表达式列出向量表示形式，就求导，有选取状态变量令有令⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎣⎡=++=⎪⎪⎩⎪⎪⎨⎧+----=========⎩⎨⎧++==++++++++=++++++===43211025233375y ~y ~x y ~x y ~...y ~x y ~x y ~3y ~2y ~y ~3y ~7y ~3y ~4y ~u 3734p 1y ~3734p 32p y d/dtp 4214321(4)43(2)22(1)1(3)4(1)21(1)(3)(1)(2)(3)(4)2342343x x x x x x x y u x x x x x x x x y u p p p u p p p p(完整word 版)《线性系统理论》试卷及答案3、(15分）计算下列线性系统的传递函数.[]Xy u X 10103112X =⎥⎦⎤⎢⎣⎡+⎥⎦⎤⎢⎣⎡--=[][][]计算得出传递函数⎥⎦⎤⎢⎣⎡⎥⎦⎤⎢⎣⎡-------=-=⎥⎦⎤⎢⎣⎡-------=⎥⎦⎤⎢⎣⎡--=--==⎥⎦⎤⎢⎣⎡=⎥⎦⎤⎢⎣⎡--==⎥⎦⎤⎢⎣⎡+⎥⎦⎤⎢⎣⎡--=----1021131)3)(2(110)()(21131)3)(2(13112)()()(1010311210103112X 1111s s s s B A Is C s G s s s s s s A Is BA Is C s G CB A Xy u X(完整word 版)《线性系统理论》试卷及答案4、（10分）分析下列系统的能控性。
2019年西南大学考博英语真题(回忆版)
2019年西南大学考博英语真题回忆Many objects in daily use have clearly been influenced by science, but their form and function, their dimensions and appearance, were determined by technologists, artisans, designers, inventors, and engineers – using nonscientific modes of thought. Many features and qualities of the object that a technologist thinks about cannot be reduced to unambiguous verbal descriptions; they dealt with in the mind by a visual, nonverbal process. In the development of Western technology, it has been nonverbal thinking, by the large, that has fixed the outlines and filled in the details of our material surroundings. Pyramids, cathedrals, and rockets exist not because of geometry or thermodynamics, but because they were first a picture in the minds of those who built them.The creative shaping process of a technologist’s mind can be seen in nearly every artifact that exists. For example, in designing a diesel engine, a technologist might impress individual ways of nonverbal thinking on the machine by continually using an intuitive sense of rightness and fitness. What would be the shape of the combustion chamber? Where should be valves be replaced? Should it have a long or short piston? Such questions have a range of answers that are supplied by experience, by physical requirements, by limitations of available space, and not least by a sense of form. Some decisions such as wall thickness and pin diameter, may depend on scientific calculations, but the nonscientific component of design remains primary.Design courses, then, should be an essential element in engineering curricula. Nonverbal thinking, a central mechanism in engineering design, involves perceptions, the stock-in-trade of the artist, not the scientist. Because perceptive processes are not assumed to entail hard thinking, nonverbal thought is sometimes seen as a primitive stage in the development of cognitive processes and inferior to verbal or mathematical thought. But it is paradoxical that when the staff of the Historical American Engineering Record wished to have drawings made of machines and isomeric views of industrial processes for its historical record of American engineering, the only college students with the requisite abilities were not engineering students, but rather students attending architectural schools.If courses in design, which in a strongly analytical engineering curriculum provide the background required for practical problem-solving, are not provided, we can expect to encounter silly but costly errors occurring in advanced engineering systems. For example, early models of high-speed railroad cars loaded with sophisticated controls were unable to operate in a snowstorm because a fan sucked snow into the electrical system. Absurd random failures that plague automatic control systems are not merely trivial aberrations; they are a reflection of the chaos that results when design is assumed to be primarily a problem in mathematics.26. In the text, the author is primarily concerned with ()A) identifying the kinds of thinking that are used by technologistB) stressing the importance of nonverbal thinking in engineering design.C) proposing a new role for nonscientific thinking in engineering design.D) contrasting the goals of engineers with those of technologists.27.It can be inferred that the author thinks engineering curricula are ()A) strengthened when they include courses in design.B) weakened by the substitution of physical science courses for courses designed to developmathematical skills.C)strong because nonverbal thinking is still emphasize by most of the courses.D)strong despite the errors that graduates of such curricula have made in the development of automatic control system.28.which of the following statements best illustrates the main point of the first two paragraphs of the text?()A) When a machine like a rotary engine malfunctions, it is the technologist who is best equipped to repair it.B) Each component of an automobile – for example, the engine or the fuel tank – has a shape that has been scientifically de termined to be best suited to that component’s function.C) A telephone is a complex instrument designed by technologists using only nonverbal thought.D) The distinctive features of a suspension bridge reflect its designer’s conceptualization as well as the physical requirements of its site.29.Which of the following statements would best serve as an introduction to the text?()A) The assumption that the knowledge incorporated in technological developments must be derived from science ignore the many nonscientific decisions made by technologists.B) Analytical thought is no longer a vital component in the success of technological development.C) As knowledge of technology has increased, the tendency has been to lose sight of the important role played by scientific thought in making decisions about form, arrangement, and texture.D)A movement in engineering colleges toward a technician’s degree reflects a demand for graduates who have the nonverbal reasoning ability that was once common among engineers.30.The author calls the predicament faced by the Historic American Engineering Record paradoxical (line 6, paragraph 3) most probably because ()A) the publication needed drawings that its own staff could makeB) architectural schools offered but did not require engineering design courses for their studentC) college students were qualified to make the drawings while practicing engineers were not.D) engineering students were not trained to make the type of drawings needed to record thedevelopment of their own disciplineThe remarkable progress of science and technology in the 20st century has brought enormous benefits to humankind. Long and healthy lives, economic prosperity and a pleasant and convenient living environment have resulted from technological progress based on advances in scientific knowledge. This progress will continue or may even accelerate in the future, because both the number of scientists and their activities are expanding throughout the world. We may expect, therefore, that science and technology will continue to contribute to the development of human society.At the same time, rapid scientific advances may raise some difficult problems. First of all, the disparity in scientific knowledge between those in scientific and technical professions and those in other areas will continuously expand. This may create a communications gap between the two groups that could affect obtaining public consent on important issues, such as the use of genetically engineered plants or human embryonic stem cells. Secondly, the 21st century will be characterized by a knowledge-based society and a knowledge of science will be required for many professions. Those who lack scientific knowledge will have fewer opportunities for good jobs. Thirdly, the enormous increase in scientific information will become a burden for children who must study science. Already young people seem to be losing interest in science, and this trend may increase in the future. Over the past several years, enrollment in high-school physics courses in Japan has been decreasing, which suggests that many young people are losing interest in physics or avoiding subjects that require diligent study. Finally, scientific research in the next century will require increasing levels of public investment because sophisticated research is usually expensive. If the public loses interest in, science or does not understand the importance of research, it will become difficult for scientists to obtain sufficient financial support.Because of these considerations, I think that we need to carefully review present science education at different levels and to improve it in order to meet the expected rapid progress of science in the 21st century. At the level of primary education, the’ most important task is to stimul ate children’s interest in nature. Naive surprise at the wonders of nature will hopefully lead to a later interest in science. During their secondary education, students must learn logic and the principles of natural phenomena. They will gradually separate into groups of those who like and those who dislike science. It will be difficult to provide the latter students with the scientific basics that would be useful throughout their lives. This is also the case in university education.It is becoming a goal of general university education to give students who are not majoring in natural science and engineering some level of scientific literacy. In the future, all citizens, especially those expected to lead diverse areas of society should have a sound basis for understanding the progress of science. Because the pace of progress will accelerate further, continuing science education for the public is also of great importance.1.The first paragraph aims at _____A.Overstating the importance of science and technology.B.Highlighting the crucial role scientists play in the development of science and technology.C.Introducing the problems brought about by rapid scientific advances whiles stating theenormous benefits brought about by the progress of science and technology.D.Predicting the trend of the development of science and technology.2.According to the text, that young people seem to be losing interest in science_____.A.Causes the lack of scientists throughout the world in future.B.Is mainly due to the explosion of scientific information.C.Hinders the development of human society.D.Increases the communications gap between young people and scientists.3.The second paragraph is to denote_____A.The gap between scientific and technical professional and non-professionals.B.The difficulties faced by young people in finding jobs.C.The difficulties problems raised by rapid scientific advances.D.Scientific research in the 21th century.4.To which of the following statements is the author most unlikely to agree?A.It is a sheer waste of time and money to force those who dislike science to learn science.B.Stimulating children’s interest in nature is the top priority for primary and secondaryschool authorities.C.Secondary school students should learn logic and the principles of natural phenomena.D. A knowledge of science will be required for many professional in the 21st century5.The best title for this text might be_____A.Science education for the publicB.Science and technology in the 21st centuryC.Scientific advance and ensuing problemsD.The goal of primary, second and higher education还有一篇阅读是讲迈克杰克逊的歌曲，专辑。
2019年西南大学博士研究生入学考试《英语》试题及答案详解
西南大学博士研究生入学考试《英语》试题及答案详解Part Two: Structure and Written Expression20Directions: In each question decide which of four choices given will most suitably complete the sentence if inserted at the place marked. Mark your choices on the ANSWERSHEET.21.The nuclear family __________ a self-contained, self-satisfying unit composed of father, mother and children.A. refers toB. definesC. describesD. devotes to22.Some polls show that roughly two-thirds of the general public believe that elderly Americans are________ by social isolation and loneliness.A. reproachedB. favoredC. plaguedD. reprehended23.In addition to bettering group and individual performance, cooperation ________ the quality of interpersonal relationship.A. ascendsB. compelsC. enhancesD. prefers24.In the past 50 years, there ________ a great increase in the amount of research _____on the human brain.A. was…didB. has been…to be doneC. was…doingD. has been…done25.“I must have eaten something wrong. I feel like _____ .”“We told you not to eat at a restaurant. You’d better _______ at home when you are not in the shape.”A. to throw up…to eatB. throwing up…eatingC. to throw up…eatD. throwing up…eat26. Parent shave to show due concerns to their children’s creativity and emotional output; otherwise what they think beneficial to the kids might probably _______ their enthusiasm and aspirations.A. hold backB. hold toC. hold downD. hold over27. According to psychoanalysis, a person’s attention is attracted ________ by the intensity of different signals ________ by their context, significance, and information content.A. not less than…asB. as…just asC. so much…asD. not so much…as28.They moved to Portland in1998 and lived in a big house, _______ to the south.A. the windows of which openedB. the windows of it openedC. its windows openedD. the windows of which opening29.The lady who has_______ for a night in the dead of the winter later turned out to be a distant relation of his.A. put him upB. put him outC. put him onD. put him in30.By standers,_______,_________ as they walked past lines of ambulances.A. bloody and covered with dust, looking dazedB. bloodied and covered with dust, looked dazedC. bloody and covered with dust, looked dazedD. bloodied and covered with dust, looking dazed31. Hong Kong was not a target for terror attacks, the Government insistedyesterday, as the US________ closed for an apparent security review.A. ConsulationB. ConstitutionC. ConsulateD. Consular32. American fans have selected Yao in a vote for the All-Star game ______the legendary O’Neal,who ______ the “Great Wall”at the weekend as the Rockets beat the Los Angeles Lakers.-A. in head of, ran onB. in head of, ran intoC. ahead of, ran ontoD. ahead of, ran into33. Professional archivists and librarians have the resources to duplicate materials in other formats and the expertise to retrieve materials trapped in _________ computers.A. abstractB. obsoleteC. obstinateD. obese34. She always prints important documents and stores a backup set at her house. “I actually think there’s something about the______ of paper that feels more comforting.” She said.A. tangibilityB. tanglednessC. tangentD. tantalization35.“They said what we always knew,”said an administration source,___________.A. he asked not to be namedB. who asked not to be namedC. who asked not be namedD. who asked not named36.In Germany, the industrial giants Daimler Chrysler and Siemens recently_______ their unions into signing contracts that lengthen work hours without increasing pay.A. muscledB. movedC. mushedD. muted37. He argues that the policy has done little to ease joblessness, and has left the country_______.A. energizedB. EnervatedC. NervedD. enacted38. The more people hear his demented rants, the more they see that he is a terrorist_______.A. who is pure and simpleB. being pure and simpleC. pure and simpleD. as pure and simple39. This expansion of rights has led to both a paralysis of the public service and to a rapid and terrible ________ in the character of the population.A. determinationB. deteriorationC. desolationD. desperation40._______ a declining birthrate, there will be an over-supply of 27,000 primary school places by 2010, _______ leaving 35 school sidle.B. Coupling with, equivalent toC. Coupled with, equivalent toD. Coupling with, equals toPart Three: Reading Comprehension 10Passage One The HeroMy mother’s parents came from Hungary, but my grandfather could trace his origin to Germany and also he was educated in Germany. Although he was able to hold a conversation in nine languages, he was most comfortable in German. Every morning, before going to his office, he read the German language newspaper, which was American owned and published in New York.My grandfather was the only one in his family to come to the United States with his wife and children. He still had relatives living in Europe. When the first world war broke out, he lamented the fact that if my uncle, his only son had to go, it would be cousin fighting against cousin. In the early days of the war, my grandmother begged him to stop taking the German newspaper and to take an English language newspaper, instead. He scoffed at the idea, explaining that the fact it was in German did not make it a German newspaper, but only an American newspaper, printed in German. But my grandmother insisted, for fear that the neighbors may see him read it and think he was German. So, he finally gave up the German newspaper.One day, the inevitable happened and my uncle Milton received notice to join the army. My grandparents were very upset, but my mother, his little sister, was excited. Now she could boast about her soldier brother going off to war. She was ten years old at the time, and my uncle, realizing how he was regarded by his little sister and her friends, went out and bought them all service pins, which meant that they had a loved one in the service. All the little girls were delighted. When the day came for him to leave, his whole regiment, in their uniforms, left together from the same train station. There was a band playing and my mother and her friends came to see him off. Each one wore her service pin and waved a small American flag, cheering the boys, as they left.The moment came and the soldiers, all very young, none of whom had hadany training, but who had never the less all been issued uniforms, boarded the train. The band played and the crowd cheered. The train groaned as if it knew the destiny to which it was taking its passengers, but it soon began to move. Still cheering and waving their flags, the band still playing, the train slowly departed the station.It had gone about a thousand yards when it suddenly ground to a halt. The band stopped playing, the crowd stopped cheering. Everyone gazed in wonder as the train slowly backed up and returned to the station. It seemed an eternity until the doors opened and the men started to file out. Someone shouted, “It’s the armistice. The war is over.” For a moment, nobody moved, but then the people heard someone bark orders at the soldiers. The men lined up and formed into two lines. They walked down the steps and, with the band playing behind, paraded down the street, as returning heroes, to be welcomed home by the assembled crowd. The next day my uncle returned to his job, and my grandfather resumed reading the German newspaper, which he read until the day he died.41. Where was the narrator’s family when this story took place?A. In Germany.B. In Hungary.C. In the United StatesD. In New York.42.His grandfather ____________.A. could not speak and read English well enoughB. knew nine languages equally wellC. knew a number of languages, but felt more kin to GermanD. loved German best because it made him think of home43. His grandmother did not want her husband to buy and read newspapers in German, because ________.A. it was war time and Germans were their enemyB. the neighbors would mistake them as pro-GermanC. it was easier to get newspapers in English in AmericaD. nobody else read newspapers in German during the wartime44. The narrator’s mother wanted her brother to go to fight in the war, because________.A. like everybody else at the wartime, she was very patrioticB. she hated the war and the Germans very muchC. all her friends had relatives in war and she wanted to be like themD. she liked to have a brother she could think of as a heroPassage TwoWaking Up from the American DreamsThere has been much talk recently about the phenomenon of “Wal-Martizatio n”of America, which refers to the attempt of America’s giant Wal-Mart chain store company to keep its cost at rock-bottom levels. For years, many American companies have embraced Wal-Mart-like stratagems to control labor costs, such as hiring temps (temporary workers) and part-timers, fighting unions, dismantling internal career ladders and outsourcing to lower paying contractors at home and abroad.While these tactics have the admirable outcome of holding down consumerprices, they’re costly in other ways. More than a quarter of the labor force, about 34 million workers, is trapped in low-wage, often dead-end jobs. Many middle-income and high-skilled employees face fewer opportunities, too, as companies shift work to subcontract or sand temps agencies and move white-collar jobs to China and India.The result has been an erosion of one of America’s most cherished value: giving its people the ability to move up the economic ladder over their life times. Historically, most Americans, even low-skilled ones, were able to find poorly paid janitorial or factory jobs, then gradually climbed into the middleclass as they gained experience and moved up the wage curve. But the number of workers progressing upward began to slip in 1970s. Upward mobility diminished even more in the 1980s as globalization and technology slammed blue-collar wages.Restoring American mobility is less a question of knowing what to do than of making it happen. Experts have decried schools’in adequacy for years, but fixing them is a long, arduous struggle. Similarly, there have been plenty of warnings about declining college access, but finding funds was difficult even in eras of large surpluses.45. The American dream in this passage mainly refers to____________.A. there are always possibilities offered to people to develop themselves in the societyB. Americans can always move up the pay ladderC. American young people can have access to college, even they are poorD. the labor force is not trapped in low-wage and dead-end jobs46. Wal-Mart strategy, according to this passage, is to___________.A. hire temps and part-timers to reduce its costB. outsource its contracts to lower price agencies at home and abroadC. hold down its consumer price by controlling its labor costsD. dismantle the career ladder and stop people’s mobility upward47. Which of the following statements is NOTTRUE?A. Wal-Martization has been successful in keeping costs at rock-bottom levels.B. Upward mobility for low-skilled workers has become impossible in the U.S.C. More business opportunities are given to low-cost agencies in China and India.D. Although people know how to restore American mobility, it’s difficult to change the present situation.Passage Three Seniors and the CityTens of thousands of retirees are pulling up stakes in suburban areas and fashioningtheir own retirement communities in the heart of the bustling city. They are looking for what most older people want: a home with no stairs and low crime rates. And they are willing to exchange regular weekly golf time for rich cultural offerings, young neighbors and plenty of good restaurants. Spying an opportunity, major real-estate developer shavebroken ground on urban sites they intended to market to suburban retirees. These seniors are already changing the face of big cities. One developer, Fran Mc Carthy asks: “Who ever thought that suburban flight would be roundtrip?”The trickle of older folks returning to the city has grown into a steady stream. While some cities, especially those with few cultural offerings, have seen an exodus of seniors, urban planners say others have become retirees magnets. Between 1999 and 2000, the population of 64-to-75-year-olds in downtown Chicago rose 17 percent. Austin, New Orleans, and Los Angeles have seen double-digit increases as well. There may be hidden health benefits to city living. A study reveals that moving from suburbs to the city can ward off the byproduct of aging--- social isolation. In the next six years, downtowns are expected to grow even grayer. For affluent retirees, city life is an increasingly popular option.48. Retired seniors are moving back into the city because____________.A. they find there are too many crimes in the suburbsB. unlike the flats in the city, their country house have stairs to climbC. they are no longer interested in playing golfD. in the city, they have more social and cultural life against loneliness49. From the passage we can infer that_________.A. the real-estate developers have broken their original contracts of construction with senior retireesB. a life in the downtown city is expensive, and most of those retirees who moved back into the city are very well-offC. with more older people living in the city, the city will become gray and less beautifulD. very soon the American suburban areas will face their low population crisis50. Fran Mc Carthy’s question means: nobody ever thought that__________.A. people who moved out of the city decades ago now would move backB. suburban dwellers when moving back into the city must take roundtripC. suburban flight years ago would go in circlesD. senior people’s moving back into the city would take place all over the United StatesDirections: Read the following passage carefully and then explain in your own English the exact meaning of the numbered and underlined parts. Put your answers on ANSWERSHEET(2)15(51) Being angry increases the risk of injury, especially among men, new research says.There searchers gathered data on more than 2,400 accident victims at three Missouri hospitals. They interviewed each subject to determine the patient’s emotional state just before the injury and 24 hours earlier, gathering data on whether the patients felt irritable, angry or hostile, and to what degree. Then they compared the results with a control groupof uninjured people.(52)Despite widespread belief in “road rage,”anger did not correlate with injuries from traffic accidents.(53)Not surprisingly, anger was strongly associated with injuries inflicted deliberately. But other injuries–those neither intentionally inflicted nor from falls or traffic accidents–also showed strong associations with anger.(54)The correlations were significantly weaker for women than for men, but there were no differences by race. The authors acknowledge that their data depend on self-reports, which are not always reliable.(55)Why anger correlates with injury is not known. “I can speculate that the anger may have prompted some behavior that led to the injury, or may have simply distracted the person, leading indirectly to the injury,”said the study’s lead author.Part Four: Cloze Test10Directions: Read the following passage carefully and then fill in each numbered blank with ONE suitable word to complete the passage. Put your answers on ANSWERSHEET (2).Last year French drivers killed(56)_______ than 5,000 people on the roads for the first time in decades. Credit goes largely(57)________ the 1,000 automated radar cameras planted on the nation’s high ways since 2003, which experts reckon(58)_______ 3,000 lives last year. Success, of course breeds success: the government plans to install500(59)______radar devices this year.So it goes with surveillance these days. Europeans used to look at the security cameras posted in British cities, subways and buses(60)_______ the seeds of an Orwellian world that was largely unacceptable in Continental Europe. But last year’s London bombing, in which video cameras(61)________a key role in identifying the perpetrators, have helped spuraseachange. A month(62)_______ the London attacks, half of Germans supported EU-wide plans to require Internet providers and telecoms to store all e-mail, Internet and phone data for “anti-terror”(63)______.In a British poll, 73 percent of respondents said they were(64)_______ to give up some civil liberty to improve(65)________.Part Five: Proof reading 10Directions: In the following passage, there are altogether 10 mistakes, ONE in each numbered and underlined part. You may have to change a word, add a word, or just delete a word. If you change a word, cross it with a slash(/) and write the correct word beside it. If you add a word, write the missing word between the words (in brackets) immediately before and after it. If you delete a word, cross it out with a slash(/). Put your answer on ANSWERSHEET(2).Examples:eg.1(66)The meeting begun 2 hours ago.Correction put on the ANSWERSHEET(2):(66) begunbeganeg.2(67) Scarcely they settled themselves in their seats in the theatre when the curtain went up.Correction put on the ANSWERSHEET(2):(67)(Scarcely) had (they)eg.3(68)Never will I not do it again.Correction put on the ANSWERSHEET(2):(68)not(66)Application files are piled highly this month in colleges across the country.(67) Admissions officers are poring essays and recommendation letters, scouring transcripts and standardized test scores.(68)But anything is missing from many applications: a class ranking, oncea major component in admissions decisions.In the cat-and-mouse maneuvering over admission to prestigious colleges and universities, (69) thousands of high schools have simply stopped providing that information, concluding it could harm the chances of their very better, but not best, students.(70)Canny college officials,in turn, have found a tactical way to response.(71) Using broad data that high schools often provide, like a distribution of grade averages for entire senior class, they essentially recreate an applicant’s class rank.(72)The process has left them exasperating.(73)“If we’re looking at your son or daughter and you want us to know that they are among the best in their school, with a rank we don’t necessarily know that,”said Jim Bock, dean of admissions and financialaid at Swarthmore College.(74)Admissions directors say strategy can backfire.When high schools do not provide enough general information to recreate the class rank calculation, (75) many admissions directors say they have little choice and to do something virtually no one wants them to do: give more weight to scores on the SAT and other standardized exams.Part Six: Writing15Directions: Write a short composition of about 250 to 300 words on the topic given below. Write it neatly on ANSWERSHEET(2).Recently, a newspaper carried an article entitled: “We Should No Longer Force Gong Li and Zhang Yimou to Take Part in National Politics”. The article argued that some artists and film stars are unwilling or unqualified to represent the people in the People’s Congress or the People’s Political Consultative Conference, and they should not be forced to do so. What do you think?56. fewer 57. to 58. saved 59. more 60. as 61. played 62. after 63. purposes 64. ready/ willing 65. security北京大学2006年博士入学考试试题答案Listening0.5each)1-5 BCAAD 6-10 BADCA11-15 CBADA 16-20 BDCBＣC1:immune C11:insufficientC2:range C12:accidentsC3:quarter C13:wheelC4:uninterrupted C14:shiftC5:tossing C15:riskC6:destined C16:deterioratesC7:claim C17:snatchC8:fooling C18:skepticalC9:deprivation C19:substituteC10:correlation C20:insomnia Structureandwrittenexpression1pointeach)21-25accdd 26-30adaab 31-35cdbab 36-40abcbcReading1pointeach)41-45ccbda 46-50cbdbaParaphrasing:(3pointseach)51.According to new research, getting angry adds to the chances of getting physically hurt, particularly for male.52.even people generally believe that people easily get angry when driving on the road, but anger didn’t have much/anything to do with injuries from traffic accidents,/ but not many injuries from traffic accidents are the results of anger on the road.53.It is not at all surprising that anger is a very important reason for people who intentionally hurt themselves.54.We see this strong link between anger and injury more in men than in women, but different races of people did not show much variation.55. People do not know yet why anger is associated with injury. Cloze:(1pointeach)56.Fewer57.To 58.Saved 59.More 60.As 61.Played 62.After63.Purposes 64.Ready 65.SecurityProofreading:(1pointeach)66.Highly-high67.Pore-poreover68.Anything-something69.Better-good70.Response-respond71.Forentire-foranentire72.Exasperating-exasperatedbS73.With-without 74.Strategy-thestrategy 75.And-butWriting:(15points)。
线性系统理论多年考题和答案
线性系统理论多年考题和答案2019级综合大题⎡400⎤⎡1⎤⎥x +⎢1⎥u x =⎢0-21⎢⎥⎢⎥⎢⎢⎣00-1⎥⎦⎣0⎥⎦y =[112]x1 能否通过状态反馈设计将系统特征值配置到平面任意位置？2 控规范分解求上述方程的不可简约形式？3 求方程的传递函数；4 验证系统是否渐近稳定、BIBO 稳定、李氏稳定；（各种稳定之间的关系和判定方法！）5 可能通过状态反馈将不可简约方程特征值配置到-2，-3？若能，确定K ，若不能，请说明理由；6 能否为系统不可简约方程设计全阶状态观测器，使其特征值为-4，-5； 7画出不可简约方程带有状态观测器的状态反馈系统结构图。
参考解答： 1.判断能控性：能控矩阵M =⎡⎣B可控，不能任意配置极点。
2按可控规范型分解AB⎡1416⎤⎢1-24⎥, rank (M ) =2. 系统不完全A 2B ⎤=⎦⎢⎥⎢⎣000⎥⎦⎡1⎢3140⎡⎤⎢1⎢⎥-1取M 的前两列，并加1与其线性无关列构成P =1-20，求得P =⎢⎢⎥⎢6⎢⎥⎢⎣001⎦⎢0⎢⎣2⎤⎡08⎢3⎥⎡1⎤⎢⎥1⎢⎥-1-1进行变换=PAP ⎢12-⎥, =PB =0, =cP =[222]⎢⎥⎢6⎥⎢⎢⎥⎣0⎥⎦001⎢⎥⎢⎥⎣⎦2⎤0⎥3⎥1-0⎥⎥6⎥01⎥⎥⎦⎧⎡08⎤⎡1⎤⎪x =⎢⎥x +⎢0⎥u12所以系统不可简约实现为⎨⎣⎦⎣⎦⎪y =[22]x ⎩3.G (s ) =c (sI -A ) -1B =4.2(s -1)(s +1) 2(s -1)=(s -4)(s +2)(s +1) (s -4)(s +2)det(sI -A ) =(s -4)(s +2)(s +1) ，系统有一极点4，位于复平面的右部，故不是渐近稳定。
G (s ) =c (sI -A ) -1B =2(s -1)，极点为4，-2，存在位于右半平面的极点，故系统不(s -4)(s +2)是BIBO 稳定。
系统发散，不是李氏稳定。
西南科技大学2019-2020-工学类-1线性代数B毕业生补考2
…⎝ ⎭⎝ ⎭2 3 西南科技大学 2019-2020-1 学期 《线性代数 B 》本科期末考试试卷（B 卷）课程代码 L X 1 6 0 8 5 0 命题单位理学院:工程数学教研室一 二 三 11 12 1314151617总分一、填空题（每小题 3 分，共 15 分）1、六阶行列式中乘积 a 35a 21a 13a 66 a 42 a 54前面应加的符号是。
2、设三阶方阵 A 的行列式为 A = 2, A *为 A 的伴随矩阵,则行列式 (3A )-1- A *=。
3、设方阵 A 满足 A2A 5E 0,则 A1。
⎛ 1 0 0 ⎫⎛ 1 2 3 ⎫ 4、 0 -100 0 ⎪ 4 5 6 ⎪=。
⎪ ⎪ 0 0 1 ⎪ 7 8 9 ⎪5、设向量组 a 1= (1,2, 3)T , a= (2, 4, 0)T , a = (2, 4, 6)T，则该向量组的线性相关性为（线性相关或线性无关）。
二、选择题（每小题 3 分，共 15 分）6、设a 11a 21 a 31a 12 a 22a 32a 13 a 23 a 331 则D 4a 114a 214a 312a 1 2a 2 2a 33a 12 3a 22 3a 32a 13 a 23a 33（）.( A )0； (B ) ―12； (C ) 12；(D )1.7、设 A, B 都是n 阶矩阵，则必有（）.( A ) A B AB ；(B ) ABBA ；(C ) AB BA ；(D )( A B )1A1B 1.8、设 A 经过初等列变换变为 B ，则（）. (下面的 R ( A ), R (B )分别表示矩阵 A , B 的秩)。
学院 _____________班级名称_______________学号_____________姓名_____________ 教师________________ 序号________________………密……………封……………线……………以……………内……………答……………题……………无……………效……………1 2 3 4D ⎪ ⎝ ⎭( A )R (3A ) < R (B )； (B ) R ( A ) = R (7B )；(C ) R (3A ) > R (B )；(D ) 无法判定R ( A )与 R (B )之间的关系.9、设0 1 0 0，则 A 3的秩为（ ）。