A答案
机械原理复习题A(附答案)
AC1=b-a AC2=b+a 由此得曲柄a和连杆b的长度。
4．已知曲柄摇杆机构的行程速比系数K＝1.25，摇杆长lCD=40mm，摇杆摆角Ψ=60º,机架长lAD=55mm。作图设计此曲柄摇杆机构，求连杆和曲柄的长度。
3．飞轮是如何调节周期性速度波动的？
答：
飞轮实质是一个能量储存器。当机械出现盈功速度上升时，飞轮轴的角速度只作微小上升，它将多余的能量储存起来；当机械出现亏功速度下降时，它将能量释放出来，飞轮轴的角速度只作微小下降。
4．造成转子不平衡的原因是什么？平衡的目的又是什么？
答：原因：转子质心与其回转中心存在偏距；
机械原理复习题A及答案
一、单项选择题（共18分，每小题2分）
1、____ B _是构成机械的最小单元，也是制造机械时的最小单元。
A．机器B．零件C．构件D．机构。
2、曲柄摇杆机构的死点发生在__ C ___位置。
A．主动杆与摇杆共线B．主动杆与机架共线
C．从动杆与连杆共线D．从动杆与机架共线
3、偏心轮机构是由铰链四杆机构_ A ____演化而来的。
A．扩大转动副B．取不同的构件为机架
C．化转动副为移动副D．化低副为高副
4、渐开线齿轮齿条啮合时，其齿条相对齿轮作远离圆心的平移时，其啮合角___ B __。
A．加大B．不变C．减小D．不能确定
5、用齿条型刀具加工αn=20°、,ha*n =1、β=30°的斜齿圆柱齿轮时不产生根切的最少数是____ B ____。
解：
θ=180*（k-1）/(k+1)=2 0°
1)按已知条件作DC1、DC2； 2)作直角三角形及其外接圆如图；
英语答案A
ClozeDirections: In this part there is a passage with 20 blanks in it. For each blank there are four choices marked A, B, C and D. You are required to choose the one that best fills into the passage and mark the corresponding letter on the Answer Sheet with a single line through the center.In primitive societies sick people had to reply on medicine men and witch doctors. It was believed that a person was sick because he had been attacked by evil spirits. The witch doctor’s job was to___1___these spirits.His method ___2___ a combination of three methods, the firs of ___3___ was religious. He chanted magic words and used good luck charms which he thought had power ___4___ the evil spirits that supposedly had entered the patient’s body.___5___, he ___6___ fed the patient mixtures, which ___7___ often dirty and ___8___, to make the evil spirits ___9___ uncomfortable that they could gladly ___10___ and so ___11___ the patient to get well.The third method was to give the patient medicines ___12___ from certain plants and herbs similar ___13___ shape or texture to the various organs of the body.___14___ our point of view, this was the only method ___15___ had any value. Modern scientific study has shown that some of these remedies had ___16___ usefulness in ___17___ sickness, or ___18___ in ___19___ pain, but not for the reasons ___20___ by the witch doctor.题目选项：1、drive back drive off take back take off 正确答案：B2、illustrated suggested presented involved 正确答案：D3、them whom that which 正确答案：D4、above over across around 正确答案：B5、Furthermore Besides In addition Secondly 正确答案：D6、deliberately instinctivelydistinctivelydelightedly正确答案：A7、has been had been were was 正确答案：C8、satisfying disgusting amusing exciting 正确答案：B9、to be too so only too 正确答案：C10、run out run away run over run down 正确答案：B11、make force enable induce 正确答案：C12、got obtained prepared attained 正确答案：C13、to with about in 正确答案：D14、Accordingly From In As for 正确答案：B15、as but what that 正确答案：D16、true little genuine real 正确答案：C17、recovering diagnosing curing preventing 正确答案：C18、at most at best at least at worst 正确答案：C19、reliving relieving releasing rejecting 正确答案：B20、confirmed represented stored advanced 正确答案：D阅读理解Reading ComprehensionDirections: In this part there are four passages. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You are required to decide on the choice that best answers the question or completes the statement.Passage 1Questions 1 to 5 are based on the following passage.Very high waves are destructive when they strike the land. Fortunately, this seldom happens. One reason is that outat sea, waves moving in one direction almost always run into waves moving in a different direction. The two sets of waves tend to cancel each other out. Another reason is that water is shallower near the shore. As a wave gets closer to land, the shallow bottom helps reduce its strength.But the power of waves striking the shore can still be very great. During a winter gale, waves sometimes strike the shore with the force of 6,000 pounds for each square foot. That means a wave, 25 feet high and 500 feet along its face, may strike the shore with a force of 75 million pounds.Yet the waves, no matter how big or how violent, affect only the surface of the sea. During the most raging storms, the water a hundred fathoms (600 feet) beneath the surface is just as calm as on a day without a breath of a wind.题目选项：1. According to the passage, destruction caused by high waves occurs ________.A、regularlyB、rarelyC、alwaysD、predictably正确答案：B2. We know from this passage that out at sea, when waves going in opposite directions meet, their force ________.A、causes great damageB、extends to the ocean floorC、is liable to lessenD、increases rapidly正确答案：C3. It is clear from the passage that coastal depth ________.A、is the only factor influencing the strength of high wavesB、influences the power of high wavesC、has no influence upon the strength of very high wavesD、is irrelevant to the question of the power of high waves正确答案：B4. From the second paragraph of the passage we know that the power of very high waves striking the shore is ________.A、constantB、equalizedC、variableD、perpetual正确答案：C5. From your reading of the passage, which of the following is true?A、At a depth of 1,200 feet the effects of a violent surface storm are frightful.B、A submarine commander navigating his vessel at a depth of 700 feet will not be affected by a raging surface storm.C、A typhoon 500 miles out at sea can stir up the ocean floor.D、If high waves can strike the shore with a horizontal force of 75 million pounds, the vertical force of such waves can have an even greater effect upon the ocean floor.正确答案：BPassage 2Questions 6 to 10 are based on the following passage.Man’s first real invention, and one of the most important inventions in history, was the wheel. All transportation and every machine in the world depend on it.The wheel is the simplest yet perhaps the most remarkable of all inventions, because there are no wheels in nature ― no living thing was ever created with wheels. How, then, did man come to invent the wheel?Perhaps some early hunters found that they could roll the dead body of a heavy animal through the forest on logs more easily than they could carry it. However, the logs themselves weighed a lot.It must have taken a great prehistoric thinker to imagine two thin slices of log connected at their centers by a strong stick. This would roll along just as the logs did yet be much lighter and easier to handle. Thus the wheel and axle came into being, and with them the first carts.题目选项：6. The wheel is important because ________.A、it was man’s first real inventionB、all transportation depends on itC、every machine depends on it.D、both B and C正确答案：D7. The wheel is described as ________.A、simpleB、complicatedC、strangeD、light正确答案：A8. It was remarkable of man to invent the wheel because ________.A、it led to many other inventionsB、man had no use for it thenC、there were no wheels in natureD、it was very complicated正确答案：C9. This passage says that the first wheel might have been a ________.A、round piece of stoneB、heavy logC、piece of metalD、slice of log正确答案：D10. The idea of making wheels might have come from ________.A、chasing an animalB、watching a rolling trunkC、watching running animalsD、rolling the dead body of an animal on logs正确答案：DPassage 3Questions 11 to 15 are based on the following passage.Although no one is certain why migration occurs, there are several theories. One theory is based upon the premise that prehistoric birds of the northern Hemisphere were forced south during the Ice Age, when glaciers covered large parts of Europe, Asia, and North America. As the glaciers melted, the birds came back to their homelands, spent the summer, and then went south again as the ice advanced in winter. In time, the migration became a habit, and now, although the glaciers have disappeared, the habit continues.Another theory proposes that the ancestral home of all modern birds was the tropics. When the region became overpopulated, many species were crowded north. During the summer, there was plenty of food, but during the winter, scarcity forced them to return to the tropics.A more recent theory, known as photoperiodism, suggests a relationship between increasing daylight and the stimulation of certain glands in the birds’ bodies that may p repare them for migration. One scientist has been able to cause midwinter migrations by exposing birds to artificial periods of daylight. He has concluded that changes occur in the bodies of birds due to seasonal changes in the length of daylight.题目选项：11. According to one theory, when the glaciers disappeared, birds ________.A、stopped migratingB、continued migratingC、began migrating againD、migrated south and stay there正确答案：B12. The author states that birds left the tropics because ________.A、there was not enough food there in the winterB、there were too many birdsC、there were too many glaciersD、there was too much daylight正确答案：B13. Why did one scientist expose birds to artificial daylight?A、To test the relationship between daylight and a disease of the glands common to birds.B、To test the relationship between daylight and migration.C、To test the relationship between migration and temperature.D、To test the relationship between daylight and changes in the season.正确答案：B14. According to the theory of photoperiodism, ________.A、birds should migrate in the middle of the winterB、longer days cause changes in the bodies of birdsC、seasonal changes in the length of days do not affect migrationD、increasing daylight increases the distance of migration正确答案：B15. This passage supports the belief that ________.A、exact reasons for migration are not knownB、birds migrate because of changes in temperatureC、the ancestral home of all birds was the tropicsD、glaciers caused birds to migrate正确答案：APassage 4Questions 16 to 20 are based on the following passage.The Arctic Circle is an imaginary line about 1,650 miles from the North Pole. About one million people live within the area bounded by the Arctic Circle. The land there is the great tundra region of the world. Tundra is a Russian word which means “marshy plain”. For nine months of the year, the tundra is a great white plain. The ground is frozen hard. But in summer the tundra is covered with flowers, thick grass, and moss.A surprisingly large number of animals live in the tundra area. Rein deer are used for transportation, food, and clothing by the northern peoples. Other animals are polar bears, musk oxen, Arctic hares, and lemmings. In the summer, wolves and foxes migrate to the tundra.Some of the tundra region is very much like the deserts of the world. To be sure, tundra temperatures are low while desert temperatures are usually high. But in both regions there is little rainfall, not much plant life, and few people.题目选项：16. What topic is treated in this passage?A、The North Pole.B、The animals living in the tundra area.C、The tundra region and the deserts of the world.D、The tundra area within the Arctic Circle.正确答案：D17. According to the passage, the great tundra region of the world is ________.A、always a great white plainB、a marshy plain of Soviet RussiaC、bounded by the Arctic CircleD、a densely populated area正确答案：C18. The animals used for food by the native people are ________.A、bears and musk oxenB、wolves and foxesC、rein deerD、Arctic hares and lemmings正确答案：C19. The tundra region differs from the deserts of the world in that ________.A、there is much plant life at the tundra while there is not any in the desertsB、there are a variety of animals at the tundra while there are no animals in the desertsC、tundra temperatures are low while desert temperatures are usually highD、tundra temperatures are high while desert temperatures are usually low正确答案：C20. In paragraph 3, the author develops his main idea by ________.A、explaining the relationship between the tundra and the desertsB、listing the things the tundra and the deserts share in commonC、comparing the tundra with the desertsD、listing the things in which the tundra and the deserts differ from each other正确答案：CVocabulary and StructureSection A (10%)Directions: In this section there are 20 incomplete sentences. For each sentence there are four choices marked A, B, C and D. You are required to choose the one that best completes the sentence and mark the corresponding letter on the Answer Sheet with a single line through the center.题目选项：1. Tom was extremely angry, but cool-headed enough to ________ storming into the boss’s office.A、preventB、prohibitC、refrainD、avoid正确答案：D2. A magician’s talk creates a(n) ________ of attention so that people don’t see how he does his tricks.A、interactionB、illusionC、diversionD、difference正确答案：C3. To his great __________, his son again failed to pass the examination.A、impatienceB、promotionC、disappointmentD、excitement正确答案：C4. Johnnie’s hard work and popularity led to his rise in salary and _____________ in position.A、privilegeB、complimentsC、promotionD、advantage正确答案：C5. She told me to use my dict ionary to ________ anything I didn’t understand.A、look outB、look upC、look forD、look at正确答案：B6. This exercise is certainly not so difficult as it ______________.A、showsB、appearsC、expectsD、happens正确答案：B7. Too much ____________ to X-rays can cause skin burns, cancer or other damage to the body.A、disclosureB、exhibitionC、contactD、exposure正确答案：D8. Alice _______ her father that both she and her husband would be happy if he would live with them.A、convincedB、convictedC、demandedD、required正确答案：A9. There in the rural area, we established our first revolutionary ________.A. B. C. D.A、fundB、baseC、foundationD、basis正确答案：B10. A dentist _______ the pupil’s teeth twice a year.A、insertsB、respectsC、inspectsD、insects正确答案：C11. Smoking in bed ________ l000 fires a year.A、burnsB、catchesC、keepsD、causes正确答案：D12. The United States ________ a population of over 200 million.A、possessesB、containsC、ownsD、has正确答案：D13. In a sudden ________ of anger, the man tore up everything within reach.A、attackB、burstC、splitD、blast正确答案：B14. He is late again today. I can ________ that he will be late tomorrow.A、suspectB、gambleC、betD、swear正确答案：C15. We don’t believe that those special kinds of leaves are _______.A、compulsiveB、edibleC、ridiculousD、actual正确答案：B16. The plan had been ________, which made him very angry.A、called offB、called upC、called inD、called on正确答案：A17. Despite their good service, most inns are less costly than hotels of ________ standards.A、equivalentB、alikeC、uniformD、likely正确答案：D18. Some people either ________ avoid questions of right and wrong or remain neutral about them.A、violentlyB、enthusiasticallyC、sincerelyD、deliberately正确答案：D19. Mother needs ________ help in the kitchen on weekends when all of us get together.A、traditionalB、practicalC、ordinaryD、additional正确答案：D20. The children were allowed to watch television to their hearts’ ________.A、satisfactionB、comfortC、contentD、amusement正确答案：CSection BDirections: Complete the following sentences with appropriate words or expressions or with the proper forms of the given words in the brackets. Write your answer on the Answer Sheet.1. We do not do much _________ with him. ( business)正确答案：business2. _____ Suez Canal joins the Red Sea and the Mediterranean.正确答案：The3. Anyone can attend the meeting if _____ is interested.正确答案：he4. The book was strange. It was _____ from all the other books I’ve ever read. (differ)正确答案：different5. I _____ if you were free this evening. (wonder)正确答案：wondered6. I’ll have to put the car to the side of the road because we _____ if we leave it here. (fine)正确答案：will be fined7. That was so serious a matter that I had no choice but _____ the police. (call in)正确答案：to call in8. You think you are funny, _____ you?正确答案：don’t9. Before their exploring, they armed themselves _____ possible danger.正确答案：against10. It was yesterday _____ he came to see me.正确答案：thatTranslationDirections: In this part there five sentences which you should translate into Chinese. These sentences are all taken from the reading passages you have just read in Part III. You can refer back to the passages so as to identify their meanings in the context. You should write your answer on the Answer Sheet.1. Yet the waves, no matter how big or how violent, affect only the surface of the sea.正确答案：然而，不管水波多大、多猛烈，只对海面造成影响。
七年级上册英语提分a计划答案2024版
七年级上册英语提分a计划答案2024版English:The Grade 7 English Booster Plan for the 2024 Edition includes a comprehensive study schedule that focuses on improving reading, writing, listening, and speaking skills. The plan incorporates various learning materials such as textbooks, workbooks, audiovisual aids, and online resources to provide a well-rounded learning experience. The study schedule is divided into daily, weekly, and monthly tasks, allowing students to practice and review key concepts regularly. Additionally, the program includes regular assessments and feedback sessions to monitor students' progress and provide necessary support. The plan also emphasizes the importance of independent learning and critical thinking, encouraging students to explore and analyze English language and literature independently. Overall, the Booster Plan aims to enhance students' English proficiency and confidence through systematic and engaging learning activities.中文翻译:《2024年版七年级英语提分计划》包括一项全面的学习计划，侧重于提高阅读、写作、听力和口语能力。
《互联网金融》试题A及参考答案
《互联网金融》试题A 及参考答案1.填空题（每空一分，共10分）1. 从功能的角度来看，任何金融体系的主要功能都是为了帮助人们在一个不确定的环境里进行跨、跨的资源配置。
（地域、时间）2. 深圳前海微众银行和浙江网商银行是我国第一批形式的银行。
（纯互联网、民营）3. 在异步交换中，第三方支付是一种支付托管行为，第三方担当和监督职能。
（中介保管）4. P2P 网络贷款实际上是一种型众筹的模式。
（债权）5. 根据《最高人民法院关于审理非法集资刑事案件具体应用法律若干问题的解释》（2010年），非法集资有、、、四个基本特征。
（非法性、公开性、利诱性、社会性）2.单项选择题（每题2分，共10分）1.“二次脱媒”“二次脱媒”理论是指在互联网的冲击下，理论是指在互联网的冲击下，理论是指在互联网的冲击下，金融运行正在脱离金融运行正在脱离：（D ）A.商业银行B.资本市场C.证券公司D.金融中介2. 狭义的互联网金融往往不包括以下哪种金融模式：（B ）A.第三方互联网支付B.网络保险C. P2P 网贷D.互联网众筹3. P2P 网络借贷是属于：（A ）A.直接融资B.间接融资C. 无风险融资D.低成本融资4. 下述描述不符合我国直销银行特点的是：（C ）A.不设物理网点 B.不发实体卡 C. 与原有银行无关 D.远程开户5. 互联网金融门户利用“”的方式，将各家金融机构的产品放在平台上，供用户对比挑选适合自己的产品和服务。
（B ）A.团购+预售B.搜索+比价C.点对点D.线上+线下3.多项选择题（每题2分，错选、多选、漏选均不给分，共10分）1. 互联网金融借助于互联网技术，秉承“开放、平等、协作、分享”的互联网精神，是实现精神，是实现 等功能的新兴金融服务模式。
（ACD ） A.支付结算支付结算 B.信用创造信用创造 C. 资源配置资源配置 D.信息处理信息处理2. 第三方支付机构可以从事的支付业务主要有以下几种第三方支付机构可以从事的支付业务主要有以下几种 ： A.网络支付网络支付 B.预付卡预付卡 C.银行卡收单银行卡收单 D.清算中心清算中心3. 股权型众筹的运营模式一般有以下种类股权型众筹的运营模式一般有以下种类 ：（ABCD ） A.凭证式凭证式 B.会员式会员式 C. 直接股权式直接股权式 D.基金间接股权式基金间接股权式4. 互联网金融风险的叠加性体现在互联网金融风险的叠加性体现在 等风险的叠加上：（BD ） A.操作风险操作风险 B.金融风险金融风险 C.市场风险市场风险 D.互联网风险互联网风险5. 芝麻信用评分体系体现了大数据在金融征信领域的应用，它构建了个人的信用历史、人脉关系以及用历史、人脉关系以及 等评分维度。
(完整word版)泛函分析试题A及答案
莆期末考试一试卷（A）卷2010—— 2011 学年第1学期课程名称：泛函剖析合用年级 / 专业07数学试卷类型：开卷（√）闭卷（）学历层次：本科考试用时：120 分钟《考生注意：答案要所有抄到答题纸上，做在试卷上不给分》．．．．．．．．．．．．．．．．．．．．．．．．．．．一、填空题（每题 3 分，共 15 分）%是胸怀空间， T 是 X 到 Y 中的映照，x0X ,1. 设 X = ( X , d)， Y = (Y, d)假如 _________________________________________________则,称 T 在x0连续。
2.设 X 和 Y 是两个赋范线性空间， T 是 X 到 Y 中的线性算子，假如 _______________, 则称 T 是 X 到 Y 中的无界限性算子。
3.设 X 是赋范线性空间，称为 X 的 Hilbert 空间。
4.设 M 是 Hilbert 空间 X 中的规范正交系，若___________________________________则称 M 是 X 中的完整规范正交系。
5.设 X 是赋范线性空间， X 是 X 的共轭空间，泛函列 f n X (n1,2,L ) ，假如则,称点列 f n弱*收敛于f。
二、计算题（ 20 分）表达 l1空间的定义，并求 l 1上连续线性泛函全体所成的空间？。
三、证明题（共65 分）1 、（ 14分）设 C[0,1] 表示闭区间 [0,1] 上连续函数全体，对任何 x, y C[0,1]，令d ( x, y)1y(t ) | dt , 证明 ( x, d ) 成为胸怀空间。
| x(t)n2、（12 分）证明R n按范数|| x || max |i|构成的赋范线性空间X与R n按范数|| x ||| i |i i1试卷第 1 页共 2 页构成的赋范线性空间Y 共轭。
3、（ 15 分）设X是可分Banach空间，M是X中的有界集，证明M中每个点列含有一个弱 * 收敛子列4、（ 12 分）设H是内积空间，M为H的子集，证明M在H中的正交补是H中的闭线性子空间。
2021年全国中学生数学奥林匹克竞赛初赛一试A卷参考答案及评分标准
2021年全国中学生数学奥林匹克竞赛（初赛）暨2021全国高中数学联合竞赛 一试（A 卷）参考答案及评分标准说明：1. 评阅试卷时，请依据本评分标准. 填空题只设8分和0分两档；其他各题的评阅，请严格按照本评分标准的评分档次给分，不得增加其他中间档次.2. 如果考生的解答方法和本解答不同，只要思路合理、步骤正确，在评卷时可参考本评分标准适当划分档次评分，解答题中第9小题4分为一个档次，第10、11小题5分为一个档次，不得增加其他中间档次．一、填空题：本大题共8小题，每小题8分，满分64分．1. 等差数列{}n a 满足202120211a a a ，则1a 的值为 ．答案：19814001．解：设的公差为d ．由条件知1120201,2391,a d a d 解得119814001a ． 2. 设集合{1,2,}A m ，其中m 为实数．令 2B a a A ，C A B ．若C 的所有元素之和为6，则C 的所有元素之积为 ．答案：8 ．解：由条件知21,2,4,,m m （允许有重复）为C 的全部元素．注意到，当m 为实数时，221246,1246m m m ，故只可能是{1,2,4,}C m ，且1246m ．于是1m （经检验符合题意），此时C 的所有元素之积为124(1)8 ．3. 设函数()f x 满足：对任意非零实数x ，均有(2)()(1)1f f x f x x，则()f x 在(0,) 上的最小值为 ．答案1．解：令1,2x ，分别得(1)(1)(2)1f f f 与(2)(2)2(1)12f f f，解得3(2)1,(1)4f f ．从而对0x ，有31()14f x x x．当(0,)x时，()11f x，当3x 时等号成立．所以()f x 在(0,)1．4. 设函数2()cos log (0)f x x x x ，若正实数a 满足()(2)f a f a ，则(2)(4)f a f a 的值为 ．答案：3 或1 ．解：由条件得2222cos log cos2log 22cos 11log a a a a a a ，所以{}n a2cos 2cos a a ，进而得cos 0a 或12，相应有2cos22cos 11a a 或12． 于是222(2)(4)cos2log 2cos4log 4cos22cos 2f a f a a a a a a a3,cos 21,11,cos 2.2a a 若若5. 在ABC 中，21,2,3AB AC B C，则ABC 的面积为 ．答案：14．解：由正弦定理知sin 2sin B AC C AB ，又23B C，故212sin sin sin sin 322C B C C C ，即5sin 22C C，所以tan 5C ．记ABC 的面积为S ．注意到23A B C C，故11sin sin cos 2sin 2222S AB AC A A C C ．由tan 5C知2221tan 112tan cos 2,sin 21tan 141tan 14C C C C C C ，从而11121421414S． 6. 在平面直角坐标系中，抛物线的焦点为，过上一点（异于）作的切线，与轴交于点．若，则向量OP 与OQ的数量积为 ．答案：32．解：设2,(0)2t P t t p ，则 的切线PQ 的方程为22t yt p x p．令0x ，得2t y ，故0,2t Q．又F 坐标为,02p ，进而 222p tFP p ，FQ 结合可分别得224p t p ，224p t ．所以21,3p t ．于是2322t OP OQ ．xOy 2:2(0)y px p F P O y Q 2,1FP FQ 2,1FP FQ7. 一颗质地均匀的正方体骰子，六个面上分别标有点数．随机地抛掷该骰子三次（各次抛掷结果相互独立），所得的点数依次为，则事件“”发生的概率为 ．答案：14．解：注意到12233113132max 2min i i i i a a a a a a a a ．因此，掷得的三个点数123,,a a a 满足条件，当且仅当最大数与最小数之差为3，即123,,a a a 是,,3x x d x 的一个排列，其中{1,2,3},{0,1,2,3}x d ．对每个{1,2,3}x ，当0d 或3d 时，,,3x x d x 各有3种不同的排列；当1d 或2d 时，,,3x x d x 各有6种不同的排列．因此，满足条件的点数123,,a a a 有3(2326)54 种情况．从而所求概率为354164 ．8. 设有理数(0,1)pr q，其中,p q 为互素的正整数，且pq 整除3600．这样的有理数r 的个数为 ．答案：112．解：设集合*,,,(,)1,|3600p r r p q p q pq q N． 考虑 的任一元素r 的最简分数形式pq，因3600的标准分解为422235 ，可设235,235A B C a b c p q ，其中min{,}min{,}min{,}0A a B b C c ，且4,2,2A a B b C c ．这样的数对(,)A a 共有9种取法，数对(,)B b 共有5种取法，数对(,)C c 共有5种取法．所以 的元素个数955225 ．满足条件的有理数的全体为(0,1) ．注意到，r 当且仅当1r，特别地，1 ．因此，\{1} 中的元素可按乘积为1配成 111122对，每对中恰有一数属于(0,1)，即恰有一数满足条件．从而所求有理数r 的个数为112．二、解答题：本大题共3小题，满分56分．解答应写出文字说明、证明过程或演算步骤．9.（本题满分16分）已知复数列{}n z 满足：11,(1i)(1,2,)2n n n z z z z n， 其中i 为虚数单位．求2021z 的值．解：对*N n ，设i (,)R n n n n n z a b a b ，则222111i (1i)i i ()i n n n n n n n n n n n a b z z z z z a b a b ，因此2211,n n n n n n a a b a b b ． ……………4分1,2,3,4,5,6123,,a a a 1223316a a a a a a又由12z知，11,02a b，所以2n a ，进而 2134n n n b b b ， ……………8分即221111242n n n n b b b b． 所以当2n 时，1122111112222n n n b b121122n ． ……………12分 于是2020202120212021211i 2i 2z a b． ……………16分 10. （本题满分20分）在平面直角坐标系中，函数11x y x的图像上有三个不同的点位于直线l 上，且这三点的横坐标之和为0．求l 的斜率的取值范围．解：当0x 时，1y ；当0x 时，11x y x关于x 严格递增且小于1．设直线:l y kx b ，则条件等价于方程11x kx b x ①有三个不同的实数解123123,,()x x x x x x ，满足1230x x x ．首先有0k （否则，l 只能是1y ，但此时l 与函数11x y x 图像的任意三个公共点的横坐标之和必大于0，不合题意）． ……………5分当0x 时，方程①可整理为2(1)10kx k b x b ， ②至多两个负数解． ……………10分当0x 时，方程①即为1kx b ， ③至多一个非负解．这表明方程②有两个不同的负数解12,x x ，其中121k b x x k，方程③有非负解31bx k．由1230x x x ，可知2k b ．进而有312bx b，由30x 得01b ． ……………15分方程②变为22(1)10bx b x b ，由判别式2(1)42(1)(1)(19)0b b b b b ，并结合01b ，可知109b （经检验，此时12,x x 确实为负数，符合题意）．综上，l 的斜率(2)k b 的取值范围是209k ． ……………20分11. （本题满分20分）如图，正方体ABCD EFGH 的棱长为2，在正方形ABFE 的内切圆上任取一点1P ，在正方形BCGF 的内切圆上任取一点2P ，在正方形EFGH 的内切圆上任取一点3P ．求122331PP P P P P 的最小值与最大值．解：以正方体的中心为原点，DA 、DC 、DH 的方向分别为x 轴、y 轴、z 轴的正方向，建立空间直角坐标系．根据条件，可设111222333(1,cos ,sin ),(sin ,1,cos ),(cos ,sin ,1)P P P ．约定4141,P P ．记1(1,2,3)i i i d PPi ，则 222211(1sin )(1cos )(sin cos )i i i i i d ． ①……………5分记122331f PP P P P P ．先求f 的最小值．对1,2,3i ，根据①与平均值不等式得2222111(1sin )(1cos )(1sin )(1cos )2i i i i i d ，故1(2sin cos )2i i i d ．于是312311(2sin cos )2i i i f d d d31(sin cos )2i i i31sin 4i i3 ． 当(1,2,3)4i i时，f可取到最小值3． ……………10分再求f 的最大值．由①知21142cos 2sin 2sin cos i i i i i d ．注意到sin 1,cos 1(1,2,3)i i i ，有33332111111122sin cos sin cos i i i i i i i i i d 33311111122sin cos sin cos i i i i i i i 311182(1sin )(1cos )18i i i ．由柯西不等式知22221233()54f d d d，故f ．当(1,2,3)i i 时，f可取到最大值．综上所述，f的最小值为3，最大值为． ……………20分2。
综合教程4-Unit 3 Text A 课后习题答案
Unit 3 Text APage 70Pair Work1.What is the writer according to what he says at the beginning of the text?He runs a manufacturing company.2.What kind of answers did he get from the college graduate who wanted a job?Almost all of them were no.3.What conclusion did the writer draw from the young applicant’s answers?This applicant was ill prepared for the job he was applying for and therefore ill qualified.4.What is the first suggestion the writer gives to job applicants?Prepare to win.5.What changes have taken place with employees since the writer’s college days?They now have to switch jobs frequently.6.What example does the writer use in support of his second suggestion?A 90-year-old player who wanted to work on his weakness—backhand court.7. What is the writer’s third suggestion mainly concerned with?Believe in yourself, even when no one else does.8.Why does the writer talk about the cabs in New York when he gives his fourthsuggestion?Because he will mention a cab driver who is different.9.What was it about the cabdriver that particularly impressed the writer?His efforts to make a difference.10.What made the writer travel with his mentor Curt Carlson in Carlson’s jet andwhat happened on the day of departure?He was offered a ride on a day when Minnesota was hit with one of the worst snowstorm in years and the international airport there was closed for the first time in decades.11.Why was Curt Carlson so happy when they were taxiing down the runway?Because there were no tracks left in the snow, which means he was the first person to take off from there.12.What point does the writer want to make by talking about his mentor, CurtCarlson?Carlson was excited about being first, which is exactly what the writer recommends to job applicants.Page 71Working on Your Own1.Part One Paras. 1-6 An ill-prepared college graduate failed his interview. Part Two Paras. 7-27 Four pieces of advice on being a successful interviewee. Part Three Paras. 28-31 Make your own tracks in whatever you do.2.Suggestions Examples1) Prepare to win 1) Michael Jordan2) Never stop learning 2) a 90-year-old tennis player3) Believe in yourself, even when no one else does 3) the four-minute mile, the NewYork Marathon and theVietnam veteran4) Find a way to make a difference 4) a New York cabdriver Page 72Language Sense Enhancement1.(1) checked with (2) interview (3) grill (4) clippings (5) be right for (6) follow up (7) indicating (8) hand-delivered (9) prepared (10) prospective Page 75V ocabularyI1.1) rude 2) physically 3) structure 4) made a difference 5) blurted (out) 6) chuckling 7) measurable 8) prospective9) preparations 10) sparkled 11) took a crack at 12) partner2.1) go after 2) look back at / on 3) be put up 4) stood for 5) build in 6) follow up 7) be hooked up to 8) closed up Page 763.1) Mary’s parents grilled her about where she had been all night.2) Before the appearance of her Fairly Godmother, it was beyond Cinderella’s wildest dreams that she could one day dance in the King’s palace.3) The translation of the popular novel has just been finished and a Chinese versionwill be in readers’ hands soon.4) As with anything else, it is important to do your homework before going on an interview.5) Jim’s car broke down last week and the repair cost was in the neighborhood of 150 dollars.Page 774.1) applicants / veteran / the prospective2) From his standpoint / has made every endeavor to go after3) as the saying goes / to have a crack at / barelyPage 77II Words with Multiple Meanings1.behave2. keep (used to avoid repetition)3. clean4. get along5. perform / complete6. perform / complete7. study 8. be enough 9. be acceptable Page 79III Usage1.There is so much to say and it is hard to know where to begin. OK, I’ll talk aboutmyself first.2.Thank you very much, John, for your beautiful Christmas card. By the way, Ihave something here for you.3.The new computer language can be quite easily understood by anyone who canread the daily newspaper. Now, why is this an advantage?4.I’m going to work out the outline and will let you know how it goes. By the way,I will see you in February, as I plan to attend your seminar in Shanghai.5.Ok, you got the job. Now, how to maximize your profits with as little effort aspossible?6.Chris is back from Australia. Incidentally, those pictures you sent me arewonderful.Page 80I Cloze(1) prospective (2) As I see it (3) done your homework (4) beforehand (5) endeavor (6) structure (7) partners (8) Respond (9) take a crack (10) from the standpoint (11) make a difference (12) follow upPage 812.(1) encouraging (2) inquiry (3) relevant (4) samples (5) references (6) advice (7) preparing (8) seriously (9) probably (10) exhibit Page 81II Translation1.1) Despite the inadequate length of the airstrip in this emergency landing, the veteran pilot managed to stop the plane after taxiing for only a short while.2) Grilled by the reporters, the movie star eventually blurted (out)that she hadundergone two plastic surgeries.3) We have the technology and our partner has the capital. Working together, we’llhave the future in our hands.4) If I had known that you would bring so many friends home, I would have made better preparations. You see, I have barely enough food and drinks for a snack. 5) People gave generously upon learning that new school rooms with strongerstructures were to be built in the earthquake-stricken area.2.Well begun, half done, as the saying goes.It is extremely important for a job applicant to do his homework while seeking employment. From my standpoint, whether or not one has done his homework clearly makes a difference in his chance of success.I have a friend who is earning somewhere in the neighborhood of100,000 dollars a years in a large computer software company. He told me that from his own experience the decision makers who interview prospective employees like people who are well prepared. Those who make no endeavor to learn as much about his prospective employer as possible don’t have much of a chance of success.。
算法设计与分析期末考试卷及答案a
算法设计与分析期末考试卷及答案a-CAL-FENGHAI.-(YICAI)-Company One1考生 信 息 栏 ＿＿＿＿＿＿学院＿＿＿＿＿＿系＿＿＿＿＿＿ 专业 ＿＿＿＿＿＿年级姓名＿＿＿＿＿＿学号＿＿装订线考生 信息栏＿＿＿＿＿＿学院＿＿＿＿＿＿系＿＿＿＿＿＿ 专业 ＿＿＿＿＿＿年级姓名＿＿＿＿＿＿学号＿装订线pro2(n) ex1(n/2) end if return end ex1 3．用Floyd 算法求下图每一对顶点之间的最短路径长度，计算矩阵D 0，D 1，D 2和D 3，其中D k [i, j]表示从顶点i 到顶点j 的不经过编号大于k 的顶点的最短路径长度。
三．算法填空题（共34分） 1．（10分）设n 个不同的整数按升序存于数组A[1..n]中，求使得A[i]=i 的下标i 。
下面是求解该问题的分治算法。
算法 SEARCH 输入：正整数n ，存储n 个按升序排列的不同整数的数组A[1..n]。
输出：A[1..n]中使得A[i]=i 的一个下标i ，若不存在，则输出 no solution 。
i=find ( (1) ) if i>0 then output i else output “no solution ” end SEARCH 过程 find (low, high) // 求A[low..high] 中使得A[i]=i 的一个下标并返回，若不存在，考生 信息栏＿＿＿＿＿＿学院＿＿＿＿＿＿系＿＿＿＿＿＿ 专业 ＿＿＿＿＿＿年级姓名＿＿＿＿＿＿学号＿＿＿＿＿装订线《算法设计与分析》期考试卷(A)标准答案一. 填空题：1. 元运算 考 生 信息栏＿＿＿＿＿＿学院＿＿＿＿＿＿系＿＿＿＿＿＿ 专业 ＿＿＿＿＿＿年级姓名＿＿＿＿＿＿学号＿＿＿＿＿装订线2. O3. ∑∈nD I I t I p )()(4. 将规模为n 的问题分解为子问题以及组合相应的子问题的解所需的时间5. 分解，递归，组合6. 在问题的状态空间树上作带剪枝的DFS 搜索（或：DFS+剪枝）7. 前者分解出的子问题有重叠的，而后者分解出的子问题是相互独立（不重叠）的8. 局部9. 高10. 归并排序算法11. 不同12. v=random (low, high); 交换A[low]和A[v]的值随机选主元13. 比较n二. 计算题和简答题：1. 阶的关系：(1) f(n)= O(g(n))(2) f(n)=Ω(g(n))(3) f(n)=Ω(g(n))(4) f(n)= O(g(n))(5) f(n)=Θ(g(n))阶最低的函数是：100阶最高的函数是：n 32. 该递归算法的时间复杂性T(n)满足下列递归方程：⎩⎨⎧>+===1n ,n log T(n/2)T(n)1n , 1T(n)2 将n=k 2, a=1, c=2, g(n)=n log 2, d=1代入该类递归方程解的一般形式得： T(n)=1+∑-=1k 0i i 22n log =1+k n log 2-∑-=1k 0i i =1+ k n log 2-2)1k (k -=n log 2122+n log 212+1 所以，T(n)= n log 2122+n log 212+1=)(log 2n Θ。
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全国2010年4月自学考试计算机网络原理试题 课程代码：04741 一、单项选择题(本大题共24小题，每小题1分，共24分) 在每小题列出的四个备选项中只有一个是符合题目要求的，请将其代码填写在题后的括号内。错选、多选或未选均无分。 1．下列关于通信服务的说法错误的是（B） A．通信服务分为面向连接服务和无连接服务 B．面向连接数据传输因收发数据顺序改变故通信效率不高 C．面向连接服务在数据传输过程前必须建立、维护和释放连接 D．无连接服务中在数据传输过程不需要建立、维护和释放连接 2．下列不属于多路复用技术的是（A） A．码分多路复用 B．时分多路复用 C．频分多路复用 D．波分多路复用 3．ADSL调制解调器采用的主要调制方式是（D ） A．ASK B．FSK C．PSK D．QAM 4．下列有关数据交换技术的说法中不正确的是（A ） A．电路交换方式具有数据传输迅速、数据较易丢失的特点 B．报文交换网络可以把一个报文发到多个目的地 C．报文交换网络可以进行速度和代码的转换 D．分组交换的方式分为虚电路交换和数据报交换 5．提高物理信道的信噪比可以减少的差错是（A ） A．随机差错 B．突发差错 C．丢失差错 D．干扰差错 6．BSC协议为实现字符同步，要求所发送的数据必须跟在至少（B ） A．1个SYN字符之后 B．2个SYN字符之后 C．3个SYN字符之后 D．5个SYN字符之后 7．HDLC监控帧(S帧)控制字段的第3、4位组合中，不包括（ D） A．“00”接收就绪 B．“01”拒绝 C．“10”接收未就绪 D．“11”应答 ：应为选择拒接 8．从保证质量和避免拥塞的角度，虚电路的优势是（A） A．可以提前预留资源 B．易于实现资源分配 C．可以终止失效路由 D．分组可以沿虚电路建立路径 9．下列各组设备中属于网间连接器的是（A ） A．转发器、网桥、路由器、网关 B．转发器、网桥、路由器、交换机 C．网桥、路由器、网关、交换机 D．转发器、路由器、网关、交换机 10．因特网互连层的功能不包含（D ） A．寻址 B．数据包的分割和组装 C．路由选择 D．数据交换 11．ICMP协议工作在TCP／IP协议栈的（ B） A．主机—网络层 B．互连层 C．传输层 D．应用层 12．由用户群组成不需要基站、无固定路由器的移动通信网是（D ） A．蜂窝式通信网 B．无线局域网 C．微波通信网 D．Ad hoc网 13．ARP协议的主要功能是（A ） A．将IP地址解析为物理地址 B．将物理地址解析为IP地址 C．将主机域名解析为IP地址 D．将IP地址解析为主机域名 14．在TCP／IP参考模型中，传输层的主要作用是为应用进程提供（C ） A．点到点的通信服务 B．网络到网络的通信服务 C．端到端的通信服务 D．子网到子网的通信服务 15．下列有关“域名”的叙述中不正确的是（A ） A．域名反映计算机所在的物理地点 B．域名是字符形式的IP地址 C．域名采用层次结构的命名方案 D．因特网上的主机，都有惟一的域名 16．如果使用UDP协议进行数据传输，则承担全部可靠性方面工作的协议是（D ） A．数据链路层协议 B．网络层协议 C．传输层协议 D．应用层协议 17．WWW浏览器和WWW服务器之间传输网页使用的协议是（B ） A．IP B．HTTP C．FTP D．TELNET 18．千兆以太网对介质访问采用的工作方式是（ D） A．单工 B．半双工 C．全双工 D．半双工和全双工 半双工：适用于共享介质的连接方式，仍采用CSMA/CD协议解决信道的争用问题
19．远程登录服务协议TELNET使用的端口号是（A ） A．23 B．70 C．80 D．110 20．光纤分布式数据接口FDDI采用的拓扑结构是（B ） A．星形 B．环形 C．总线形 D．树形 21．在采用CSMA／CD控制方式的网络中（ A） A．不存在集中控制结点 B．存在一个集中控制结点 C．存在多个集中控制结点 D．可存在或不存在集中控制结点 22．逻辑链路控制与适应协议(L2CAP)位于（ C） A．电话控制协议层之上 B．核心协议层之上 C．基带协议层之上 D．电缆替代协议层之上 23．网络安全中的完整性是指（ C） A．避免拒绝授权访问和拒绝服务 B．保护信息不泄露给非授权用户 C．保护信息不被非授权用户修改或破坏 D．避免信息被用户修改或破坏 24．网络安全攻击中的被动攻击的主要目的是（B ） A．检测主动攻击 B．窃听和监视信息的传输并存储 C．修改数据 D．创建虚假数据流 二、填空题(本大题共15小题，每小题1分，共15分) 请在每小题的空格中填上正确答案。错填、不填均无分。 25．所谓“三网合一”所融合的三网包括传统电信网、计算机网络和___广播电视网___。 26．为了满足多媒体信息的传输要求，多媒体网络必须要满足交互性和__实时性____。 27．环型拓扑网络采用的控制策略是_令牌帧__。 28．OSI参考模型包括的三级抽象是体系结构、服务定义和__协议规范____。 29．TCP／IP参考模型的最底层是_主机---网络层_____。 30．物理层规范EIA RS-232C对信号线的命名方法采用__字母组合，数字和英语缩写____。 31．数据链路层连接的建立、维持和释放被称作__链路管理____。 32．引起传输差错的噪声分两类，一类为冲击噪声，另一类为___热噪声___。 33．网络层实现的最基本功能是_ 两个端系统之间数据透明的传输___。 34．拥塞控制的任务是确保通信子网能够承载所到达的_流量____。 35．作用于网络层，提供网络层的协议转换，在不同网络之间进行分组的存储与转发的网络互连设备是___路由器___。 36．TCP段结构中端口地址的比特数为__16位____。 37．DNS是一个分布式数据库系统，它的三个组成部分是地址转换请求程序、域名空间和__地址转换____。 38．局域网中负责差错与流量控制的子层是__LLC____。 39．IEEE802.3的MAC帧中，目的地址字段为全“1”表示___为广播地址___。 三、简答题（本大题共4小题，每小题5分，共20分） 40．简述最短路由选择算法的基本思想。 最短路由算法：建立一个子网图，图中的每个节点代表一台路由表，每条弧线代表一条通信线路，弧上的数字代表该线路的权重。为了在一对给定的路由之间选择一条路由路径，路由算法只需在图中找到这对节点之间的最短经即可。 距离适量路由算法：每个路由器维护一张路由表，它予以网中的每个路由器为索引，表中列出了当前已知的路由器到目标路由器的最佳距离，以及使用的线路。通过在邻居之间相互交换信息，路由器不断地更新它们内部的路由表。 链路状态路由算法： 1. 发现邻居节点 2. 测量线路开销 3. 创建链路状态分组 4. 发布链路状态分组 5. 计算新的路由 41．简述数据报子网中拥塞控制的措施。 虚电路子网的动态拥塞控制方法 防止已经拥塞的子网进一步恶化的技术是准入控制 虽然允许建立新的虚电路，但要谨慎地选择路由，使所有新的虚电路都绕开有问题的区域 进行资源预留 数据报子网中的拥塞控制 1》 警告位 2》 抑制分组 3》 逐跳抑制分组 42．简述UDP的段结构中各个字段的名称及其含义。 4》 源端口 16bit 标明发送端地址 5》 目的端口 16bit 标明接收端地址 6》 长度 16bit 指明包括UDP的头在内的数据段的总长度。 7》 校验和 16bit 可选项
43．简述I-坚持CSMA的基本思想。 8》 I-坚持CSMA 当一个节点要发送数据时，首先监听信道；如果信道空闲就立即发送数据；如果信道忙则等待，同时继续监听直至信道空闲；如果发生冲突，则随机等待一段时间后，再重新开始监听信道。 9》 非坚持CSMA 当一个节点要发送数据时，首先监听信道；如果信道空闲就立即发送数据；如果信道忙则放弃监听。随机等待一段时间，再开始监听信道。 10》 P-坚持CSMA 用于时分信道，当一个节点要发送数据时，首先监听信道，如果信道忙则坚持监听到下一个时隙；如果信道空闲，便以概率P发送数据，以概率1-p推迟到下一个时隙；如果下一个时隙仍然空闲，则以P的概率发送数据。以概率1-p推迟推迟到下一个时隙。 44．有一受随机噪声干扰的信道，其信噪比为30dB，最大数据传输速率为30Kbps。试求出该信道的带宽。 3k=30Kbps/10=C=H*/log(1+1030/10)2 45．设信道上数据传输速率为4Kbps，数据帧长为240bit，信道的传播时延为20ms，采用停等协议，帧的控制信息、确认帧长及帧处理时间均忽略不计。试求出信道的利用率。 240/(4kbps*20*2*10-3+240)=60% 停等协议 是发一次，等待确认后 再发一次。信道延时就应该*2
46．有一个电缆长度为1Km的CSMA/CD局域网，数据传输速率为1Gbps，信号传播速度为2×105Km/s。试求出最小帧长度。 (1km/2×105Km/s)*1Gbps*2=10000bit
47．一组N个站点共享一个56Kbps的纯ALOHA信道， 每个站点平均每100s输出一个1000bit的帧。试求出N的最大值。 0.184->信道的利用率 0.184*56Kbps=10.304Kbps 可用总带宽 1000bit/100s=10bps 1站占有的带宽 10304/10=1030 五、应用题（本大题共3小题，每小题7分，共21分） 48．说明域名解析过程及域名服务器的类型。 当应用程序需要将主机域名映射成IP地址时，就调用域名解析函数，解析函数将请求放在DNS请求中，以UDP报文方式发给本地域名服务器，如果本地域名查找到响应的域名后，将对应的IP地址放入应答UDP报文中一起返回。若不能回答请求，则此域名服务器将暂时成为DNS中的另一个客户，直到找到回答该请求的域名服务器为止。 49．请给出ATM和ATM信元的特点、ATM信元头的内容以及ATM与分组交换、帧