A Study of Early Stage Self-Loosening of Bolted Joints
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题型组合训练Ⅰ.单项填空1.(2024苏锡常镇二模)It’s reported that in many countries there are rescue centers for girls who are forced into early marriages, and boys who to look after farm animals.A.drop inB.drop awayC.drop offD.drop out答案 D 考查动词短语。
句意:据报道,在许多国家有为了帮助那些被迫早婚的女生或者是辍学去照看农场动物的男生(而建立)的救助中心。
drop in顺便探望;drop away削减,减弱;drop off削减;打瞌睡;drop out辍学。
2.(2024泰州中学二模)Much disappointed as he is in the job interview, he still keeps his confidence.A.to have failedB.failedC.having failedD.failing答案 A 考查非谓语动词。
句意:尽管他工作面试失败很悲观,但他仍旧保持自信。
as/though的倒装:形容词/状语/动词+as/though+主谓,本句中形容词disappointed提前,be disappointed to do sth.做某事感到悲观。
由he still keeps his confidence(他仍旧保持自信)可知此处强调这件事带来的结果对后面产生了影响,因此用现在完成时态。
3.(2024苏锡常镇二模)—What do you think of Steven Hawking?—Well, despite his disabled body, he was a man of scientific nature, worthy of admiration.A.oneB.whoC.thatD.this答案 A 句意:——你认为斯蒂芬·霍金怎么样?——嗯,尽管身体残疾,但他是一个有科学天赋的人,一个值得钦佩的人。
高二年级英语心理学初探单选题50题1. The state of being extremely sad and losing interest in life is often related to ______.A. AnxietyB. DepressionC. ObsessionD. Hallucination答案:B。
解析:A选项Anxiety是焦虑的意思,通常表现为过度担忧、不安;B选项Depression是抑郁,其特征包括极度悲伤、对生活失去兴趣等,符合题意;C选项Obsession是痴迷、困扰的意思,与悲伤和对生活失去兴趣无关;D选项Hallucination是幻觉,与题干所描述的心理状态无关。
2. A person who has an unreasonable fear of a particular thing is said to have ______.A. PhobiaB. ParanoiaC. AmnesiaD. Dementia答案:A。
解析:A选项Phobia指恐惧症,即对特定事物有不合理的恐惧;B选项Paranoia是偏执狂,主要表现为过度猜疑等,与对特定事物的恐惧无关;C选项Amnesia是失忆症,与恐惧无关;D选项Dementia是痴呆,与题干描述的对特定事物的恐惧不相关。
3. Which term refers to the ability to understand and share the feelings of others?A. EmpathyB. SympathyC. ApathyD. Antipathy答案:A。
解析:A选项Empathy是同理心,强调理解并分享他人的感受;B选项Sympathy更多是同情,只是表示对他人的不幸表示怜悯,并不一定理解和分享感受;C选项Apathy是冷漠,与理解和分享感受相反;D选项Antipathy是反感,与题干表达的意思完全不同。
2024年1月普通高等学校招生全国统一考试英语养成良好的答题习惯,是决定成败的决定性因素之一。
做题前,要认真阅读题目要求、题干和选项,并对答案内容作出合理预测;答题时,切忌跟着感觉走,最好按照题目序号来做,不会的或存在疑问的,要做好标记,要善于发现,找到题目的题眼所在,规范答题,书写工整;答题完毕时,要认真检查,查漏补缺,纠正错误。
总之,在最后的复习阶段,学生们不要加大练习量。
在这个时候,学生要尽快找到适合自己的答题方式,最重要的是以平常心去面对考试。
第一部分听力(共两节,满分30分)做题时,先将答案标在试卷上。
录音内容结束后,你将有两分钟的时间将试卷上的答案转涂到答题纸上。
第一节(共5小题:每小题1.5分,满分7.5分)听下面5段对话。
每段对话后有一个小题,从题中所给的A、B、C三个选项中选出最佳选项。
听完每段对话后,你都有10秒钟的时间来回答有关小题和阅读下一小题。
每段对话仅读一遍。
例:How much is the shin?A. £19.15.B. £9.18.C. £9.15.答案是C。
1. What does the man do?A. A computer technician.B. A hotel receptionist.C. A shop assistant.2. Where does the conversation take place?A. At the grocer’s.B. At the tailor’s.C. At the cleaner’s.3. How did the speaker come to Seattle?A. By plane.B. By car.C. By train.4. What will the speakers have for dinner today?A. Fried rice.B. Noodles.C. Steak.5. How is Sophie feeling now?A. Confused.B. Worried.C. Disappointed.第二节(共15小题:每小题1.5分,满分22.5分)听下面5段对话或读白。
第 1 页 共 8 页《基础英语四》考试试卷B适合专业: 考试日期:所需时间: 120分钟 闭卷考试 试卷总分:100分 I. Vocabulary (10×0.5=5 points )Directions:Please match each word in the left column with the corresponding explanation inthe right one.1. irreverent A. to look with the eyes partly open2. oblige B. to make it necessary for you to do sth3. proximate C. having a lack of respect for certain organization, beliefs, customs4. squint D. to shine brightly5. necessitate E. to conquer6. glisten F. unsuitable7. subjugate G . to do sth for sb as a favor or small service 8. inept H. heavier, larger on one since than on the other 9. lopsided I. extremely enthusiastic 10. zealous J. nearest in time, order, etc II. Rhetorical devices (5×1=5 points )Directions: Point out what kind of rhetorical device is used in the following sentences.A. metonymyB. parallelismC. personificationD. hyperboleE. alliterationF. euphemism G .. metaphor H. irony I. oxymoron J. paradox 11.The world is watching closely what the White House will do next. ( ) 12.. “Yes,” said the Dog. “Stand to one side. You are blocking the sunlight.” ( ) 13. Globalization's other problem is political, cultural and social. ( )14. In Orlando you develop a throat of iron, and you just put back your head and put it down, in case the police should arrive. ( ) 15. Live and let live. ( )III. Grammar & Vocabulary (20×0.5=10 points )Directions: For each blank there are four choices marked A, B, C and D. You should choose the one that best fits into the sentence. Then mark the corresponding answer on ANSWER SHEET.16. The people living in these apartments have free _______ to that swimming pool. A. access B. excessC. excursionD. recreation17. He is quite sure that it ’s ______ impossible for him to fulfill the task within two days. A. absolutely B. exclusively C. fully D. roughly 18. To drive safely, you should check and _____ the brakes regularly. A. achieve B. attach C. adjust D. admire19. Residents were cutting their lawns, washing their cars and otherwise ________a pleasant, sunny day.A. idling awayB. taking awayC. chasing awayD. driving away20. John cannot afford to go to university, _______going abroad. A. not to speak of B. anything butC. nothing butD. nothing to speak of21. He waited in the _____ of the building until the rain stopped. A. lobby B. muddy C . ruby D. hobby22. The police are trying to find out the _____ of the woman killed in the traffic accident. A. evidence B. recognition C. status D. identity 23. A person ’s calorie requirements vary _____ his life. A. withinB. overC. throughoutD. across24. Before he started work, I asked the builder to give me an _____ of the cost of repairing the roof. A. assessmentB. estimateC. announcementD. evaluation25. With great effort of the peace-loving people all over the world; Iraq ______ the war. A. survived B. survived from C. survival D. survived to 26. I am not too ____ jazz.A. keen onB. keen inC. fond onD. fond to院系: 班级: 姓名: 学号:装 订 线27. The ______ stuck on the envelope says “By Air”A. diagramB. labelC. signalD. mark28. I usually listen to the weather _______, though I have little faith in it.A. broadcastB. predictionC. forecastD. announcement29. Politics and religion are always interesting ____ of conversation.A. ideasB. titlesC. topicsD. questions30. Everyone agreed that the woman in the photo was_____. It was easy to see why she had won the beauty contest.A. gorgeousB. spaciousC. luxuriousD. bossy31. All things ____, the planned trip will have to be called off.A. consideredB. be consideredC. consideringD. having considered32. After the Arab states won independence, great emphasis was laid on expandingeducation, with girls as well boys____ to go to school.A. to be encouragedB. been encouragedC. being encouragedD. be encouraged33. We booked rooms at the hotel ________we should find no vacancies on our arrival.A. wheneverB. ifC. sinceD. lest34. Techniques for ________sleep would involve learning to control both mind and body sothat sleep can occur.A. cultivatingB. promotingC. pushingD. strengthening35. It is important to ________between the rules of grammar and the conventions of written language.A. determineB. identifyC. exploreD. distinguishIII. Cloze (15×1=15 points)Directions: There are 20 blanks in the following passage. For each blank there are four choices marked A, B, C and D. You should choose the one that best fits into the passage. Then mark the corresponding answer on ANSWER SHEET.The kids who grew up on “Star Trek” can’t find ___36___ way around Earth. Americans can___37___direct to England, but only half can find it on a map of Europe. They can fly almost___ 38___in the United States for a few hundred dollars, but they put New York State in 37 placed on both coasts. When they look for the United States__39___ , they spot it in China, Australia, Brazil, the Soviet Union, India and Botswana. For people who are supposed to be leaders of the__40 __world, Americansare ___41 ___ dumb, according to a survey conducted for the National Geographic Society. In many school systems, geography has been mixed with history___42___melted down into social studies. Social studies has been processed into “teacher resource packages” and___43___of good writing, excitement, color and any ideas that aren’t simplistic, too __44___and too deadening to hold students’ attention.In the last few years, evidence of America’s educational__45___has prompted hundreds of studies, generated baskets___46___legislation and moved parents into advocacy groups. But there’s little to show that the trend has been___47___. No matter___48___you try, you can’t make it seem funny that many Americans say pandas come from Panama, the Summer Olympic Games were held in Vietnam or___49___ Iraq, and Columbus was trying to get to Europe when he bumped into ___ 50___.36. A. it’s B. the C. their D. a37. A. write B. fly C. dial D. drive38. A. somewhere B. anywhere C. anytime D. everywhere39. A. itself B. themselves C. for themselves D. by itself40. A. tough B. free C. cruel D. real41. A. geographically B. especially C. somewhat D. extremely42. A. and B. or C. which D. while43. A. dreamed B. consisted C. cheated D. robbed44. A. dark B. bright C. yellow D. gray45. A. priority B. inferiority C. short backs D. controversy第 2 页共8 页46. A. full of B. with C. according to D. out of47. A. stopped B. followed C. reversed D. appreciated48. A. how B. if C. whether D. don’t49. A. may be B. on the contrary C. instead D. maybe50. A. the Pacific B. Spain C. the Atlantic D. AmericaIV. Reading Comprehension (20×1.5=30 points)Directions: In this section there are four passages followed by questions or unfinished statements, each with four suggested answers marked [A], [B], [C] and [D]. Choose the one that you think is the best answer. Mark your answers on your ANSWER SHEET.TEXT AIt is possible for students to obtain advanced degree in English while knowing little or nothing about traditional scholarly methods. The consequences of this neglect of traditional scholarship are particularly unfortunate for the study of women writers. If the canon-the list of authors whose works are most widely taught-is ever to include more women, scholars must be well trained in historical scholarship and textual editing. Scholars who do not know how to read early manuscripts, locate rare books, establish a sequence of editions, and so on are lacking crucial tools for revising the canon.To address such concerns, an experimental version of the traditional scholarly methods course was designed to raise students' consciousness about the usefulness of traditional learning for any modern critic or theorist. To minimize the artificial aspects of the conventional course, the usual procedure of assigning a large number of small problems drawn from the entire range of historical periods was abandoned, though this procedure has the obvious advantage of at least superficially familiarizing students with; a wide range of reference sources. Instead students were engaged in a collective effort to do original work on a neglected eighteenth century writer, Elizabeth Griffith, to give them an authentic experience of literary scholarship and to inspire them to take responsibility for the quality of their own work.Griffith's work presented a number of advantages for this particular pedagogical purpose. First, the body of extant scholarship on Griffith was so tiny that it could be all read in a day, thus students spent little time and effort mastering the literature and had a clear field for their own discoveries. Griffith's play-The Platonic Wife exists in three visions, enough to provide illustrations of editorial issues but not too many for beginning students to manage. In addition, because Griffith was successful in the eighteenth century, as her continued productivity and favorable reviews demonstrate, her exclusion from the canon and virtual disappearance from literary history also helped raise issues concerning the current canon.The range of Griffith's work meant that each student could become the world's leading authority on a particular Griffith text. For example, a student studying Griffith's Wife in the Right obtained a first edition of the play and studied it for some weeks. This student was suitably shocked and outraged to find its title transformed into A Wife in the Night in Watt's Bibliotheca Britannica. Such experiences, inevitable and common in working on a writer to whom so little attention has been paid serve to vaccinate the students-I hope for a lifetime-against credulous use of reference sources.51. The author of the passage is primarily concerned with ______.A. revealing a commonly ignored deficiencyB. proposing a return to traditional methodC. describing an attempt to correct a shortcomingD. assessing the success of a new pedagogical approach52. Which of the following is a disadvantage of the strategy employed in the experimental scholarly methods course?A. Students were not given an opportunity to study women writers outside the canon.B. Students had little background knowledge for further research.C. Most of the students in the course had little opportunity to study 18th century literature.第 3 页共8 页D. Students were not given an opportunity to encounter certain sources of information that could prove useful in their future studies.53. The "particular pedagogical purpose" mentioned in Paragraph 3 is to ______.A. minimize the trivial aspects of the traditional scholarly methods courseB. encourage scholarly rigor in students' own researchC. reestablish Griffith's reputation as an authorD. bridge the gap between the new method and the traditional approach54. It can be inferred that the author expects, that the experience of the student mentioned as having studied Wife in the Right would have the effect that ______.A. it would lead the student to have a clear understanding of the editorsB. it would teach the student to question the accuracy of certain kinds of information sources when studying neglected authorsC. it would teach the student to avoid the use of reference sources in studying neglected authorsD. it would enhance the student's appreciation of the works of authors not include in the canon55. What is the function of the last paragraph in relation to the passage as a whole?A. It summarizes the benefits students can derive from the experimental scholarly methods course.B. It provides additional reasons why Griffith's works raises issues having to do with the canon of authors.C. It provides an illustration of the immediate nature of the experiences students can derive from the experimental scholarly methods course.D. It contrasts the experience of a student in the experimental scholarly methods course with the experience of a student in the traditional course.TEXT BCultural norms so completely surround people, so permeate thought and action that we never recognize the assumptions on which their lives and their sanity rest. As one observer put it, if birds were suddenly endowed with scientific curiosity they might examine many things, but the sky itself would be overlooked as a suitable subject; if fish were to become curious about the world, it would never occur to them to begin by investigating water. For birds and fish would take the sky and sea for granted, unaware of their profound influence because they comprise the medium for every fact. Human beings, in a similarly way, occupy a symbolic universe governed by codes that are unconsciously acquired and automatically employed. So much so that they rarely notice that the ways they interpret and talk about events are distinctively different from the ways people conduct their affairs in other cultures.As long as people remain blind to the sources of their meanings, they are imprisoned within them. These cultural frames of reference are no less confining simply because they cannot be seen or touched. Whether it is an individual neurosis that keeps an individual out of contact with his neighbors, or a collective neurosis that separates neighbors of different cultures, both are forms of blindness that limit what can be experienced and what can be learned from others.It would seem that everywhere people would desire to break out of the boundaries of their own experiential worlds. Their ability to react sensitively to a wider spectrum of events and peoples requires an overcoming of such cultural parochialism. But, in fact, few attain this broader vision. Some, of course, have little opportunity for wider cultural experience, though this condition should change as the movement of people accelerates. Others do not try to widen their experience because they prefer the old and familiar, seek from their affairs only further confirmation of the correctness of their own values. Still others recoil from such experiences because they feel it dangerous to probe too deeply into the personal or cultural unconscious. Exposure may reveal how tenuous and arbitrary many cultural norms are; such exposure might force people to acquire new bases for interpreting events. And even for the many who do seek actively to enlarge the variety of human beings with第 4 页共8 页whom they are capable of communicating there are still difficulties.Cultural myopia persists not merely because of inertia and habit, but chiefly because it is so difficult to overcome. One acquires a personality and a culture in childhood, long before he is capable of comprehending either of them. To survive, each person masters the perceptual orientations, cognitive biases, and communicative habits of his own culture. But once mastered, objective assessment of these same processes is awkward, since the same mechanisms that are being evaluated must be used in making the evaluations.56. The examples of birds and fish are used to ______.A. show that they, too, have their respective culturesB. explain humans occupy a symbolic universe as birds and fish occupy the sky and the seaC. illustrate that human beings are unaware of the cultural codes governing themD. demonstrate the similarity between man, birds, and fish in their ways of thinking57. The term "parochialism" (Line 3, Para. 3) most possibly means ______.A. open-mindednessB. provincialismC. superiorityD. discrimination58. It can be inferred from the last two paragraphs that ______.A. everyone would like to widen their cultural scope if they canB. the obstacles to overcoming cultural parochialism lie mainly in people's habit of thinkingC. provided one's brought up in a culture, he may be with bias in making cultural evaluationsD. childhood is an important stage in comprehending culture59. Which of the following statements is TRUE according to the passage?A. Individual and collective neurosis might prevent communications with others.B. People in different cultures may be governed by the same cultural norms.C. People's visions will be enlarged if only they knew that cultural differences exist.D. If cultural norms are something tangible, they won't be so confining. 60. The passage might be entitled "______."A. How to Overcome Cultural MyopiaB. Behavioral Patterns and Cultural BackgroundC. Harms of Cultural MyopiaD. Cultural Myopia-A Deep-rooted Collective NeurosisTEXT CA Holy Week procession (Settimana Santa) is an event taking place in Holy Week, most often in a country with traditional Roman Catholic culture. This tradition goes back a long way, to a Christian use in medieval times and in some cases there are testimonies dating back to the XVI century. The Easter period is an incredibly important time in the calendar of this largely Roman Catholic nation, and events are used to mark the occasion throughout Italy. One of the most important of these occurs in Rome on Good Friday, when the Pope leads a procession past the Colosseum and the Roman Forum right up to the ancient Palatine Hill. Then on Easter Sunday the Pontiff holds Mass and gives a blessing to the crowd from the balcony of St Peter's Basilica.Around of the country Italians celebrate the Easter period with processions and plays depicting Christ's final hours. Easter feasts are also a part of Italian celebrations; typical fare includes spring lambs and lots of sweet bread, cakes and special chocolates.In today's world where the festivals can often be taken for granted as just a great party, it is the novena, and the other religious aspects that keep the true link to the past alive. Our secular society is often at odds with the value systems that brought about these religious festivals and yet it seems that the younger generations still enjoy participating. The older generations often lament the loss of faith in the young people and wonder how religious festivals can survive without losing their soul. However, the fact is nothing in human culture is static and every generation celebrates in their own way, often against the wishes of the elders. Some of the larger festivals have become annual tourist attractions, bringing in needed revenue to the old Italian American communities that hold the events and often第 5 页共8 页benefiting the city as a whole.61. Which of the following is INCORRECT?A. This procession has a long history.B. The procession has wide influence.C. The procession occurs in countries with traditional Roman Catholic culture only.D. The procession may originate from 16th century.62. Which of the following is the activity held in Easter period?A. ProcessionsB. PlaysC. FeastsD. All of the above.63. The author's attitude towards the modern secular society is ______.A. CommendatoryB. objectiveC. incredulityD. absurd64. Which of the following is true?A. Nowadays the festivals are purely commercial.B. Young people enjoy the festivals because they are religious.C. The older generations are worried about the death of these festivals.D. The older generations are concerned about the change of these festivals.TEXT DParkour is a physical activity that is difficult to categorize. It is not an extreme sport, but an art or discipline that resembles self-defense in the martial arts. According to David Belle, "the physical aspect of parkour is getting over all the obstacles in your path as you would in an emergency. You want to move in such a way, with any movement, as to help you gain the most ground on someone or something, whether escaping from it or chasing toward it.① Thus, when faced with a hostile confrontation with a person, one will be able to speak, fight, or flee. As martial arts are a form of training for the fight, parkour is a form of training for the flight. Because of its unique nature, it is often said that parkour is in its own category: "Parkour is parkour."An important characteristic of parkour is efficiency. Practitioners move not only as fast as they can, but also in the least energy-consuming and most direct way possible. This characteristic distinguishes it from the similar practice of free running, which places more emphasis on freedom of movements, such as acrobatics. Efficiency also involves avoiding injuries, short and long-term, part of why parkour's unofficial motto is tre et durer (to be and to last).Tracers claim that parkour also influences one's thought process by enhancing critical thinking skills that allow one to overcome everyday physical and mental obstacles.There are fewer predefined movements in parkour than gymnastics, as it does not have a list of appropriate "moves." Each obstacle a tracer faces presents a unique challenge on how they can overcome it effectively, which depends on their body type, speed and angle of approach, the physical make-up of the obstacle, etc. Parkour is about training the body mind to react to those obstacles appropriately with a technique that works. Often that technique cannot and need not be classified and given a name. In many cases effective parkour techniques depend on fast redistribution of body weight and the use of momentum to perform seemingly impossible or difficult body maneuvers at speed. Absorption and redistribution of energy is also an important factor, such as body rolls when landing which reduce impact forces on the legs and spine, allowing a tracer to jump from greater heights than those often considered sensible in other forms of acrobatics and gymnastics.There are many basic techniques that are emphasized to beginners for their versatility and effectiveness. Most important are good jumping and landing techniques. The roll, used to limit impact after a drop and to carry one's momentum onward, is often stressed as the most important technique to learn. Many tracers develop joint problems from too many large drops and rolling incorrectly. Due to large drops parkour has sometimes received criticism for its questionable safety. Several communities in Great Britain have been warned by law enforcement or fire and rescue of the potential dangers of parkour. Although David Belle has never been seriously injured while practicing parkour, there is no careful study about the health issues of large drops and tracers stress gradual progression to avoid any problems.第 6 页共8 页65. Parkour participators ______.A. aim to exploit their potential strengthB. move the longest distance they can endureC. practice prescriptive movementsD. choose different paths to the terminals by themselves66. According to the passage," critical thinking skills" (Line 1, Para. 3) refers to skills of __A. judging and giving comments on somethingB. decisive thinkingC. conquering crisisD. finding out essentials67. Which of the following is NOT a determinant to the effectiveness of parkour?A. Participator's figure.B. Participator's relative location to the obstacle.C. Participator's reaction to the obstacle.D. Participator's experience of parkour.68. The following are parkour techniques EXCEPT ______.A. reducing energy waste during the processB. making poses while moving at speedC. fighting against someone blocking the pathD. preventing oneself from being injured or hurt69. What can we learn from the passage?A. Participators believe long-term effective practice can help avoid injuries.B. Beginners should train their endurance above all.C. To parkour participators, speed is much more important than safety.D. Large drops is the most difficult techniques of parkour.70. Which of the following activities is mostly close to parkour?A. Jogging.B. Obstacle race.C. Gymnastics.D. Acrobatic performanceVI. Translation (20 points)Section A: (5×2=10 points)Directions:Put the following into English.71. 认为太阳绕着地球转的观点统治了古代学术界达一千多年。
高中英语学术调研单选题50题1. In academic research, it is essential to be precise and ______ in data collection.A. accurateB. approximateC. roughD. casual答案:A。
本题考查形容词词义辨析。
“accurate”意为“精确的,准确的”,在学术研究中,数据收集需要精确准确,A 选项符合语境。
“approximate”表示“大约的,近似的”;“rough”指“粗糙的,粗略的”;“casual”意思是“随便的,偶然的”,这三个选项都不符合学术研究中对数据收集的要求。
2. The scholar spent years conducting ______ studies to prove his theory.A. extensiveB. intensiveC. expensiveD. expansive答案:B。
“intensive”有“集中的,深入的”之意,在学术研究中,进行深入的研究才能证明理论,B 选项符合。
“extensive”侧重于“广泛的”;“expensive”是“昂贵的”;“expansive”意为“广阔的,扩张的”,均不符合本题学术研究的语境。
3. The ______ of this academic paper was highly praised by the experts.A. formatB. contentC. styleD. structure答案:D。
本题考查名词词义。
“structure”表示“结构”,学术论文的结构受到高度赞扬,D 选项恰当。
“format”指“格式”;“content”是“内容”;“style”为“风格”,相比之下,结构更能被整体评价和赞扬。
4. To make the academic research more ______, a large sample size was needed.A. reliableB. unstableC. questionableD. doubtful答案:A。
白天看到一个太阳晚上看到无数个星星的英语作文全文共3篇示例,供读者参考篇1The Celestial Dance: Marveling at the Sun and StarsEver since I was a little kid, I've been fascinated by the celestial dance that plays out in the sky day and night. During the day, the magnificent sun reigns supreme, radiating its brilliant warmth and light. But when night falls, the sun's solo performance gives way to an ensemble cast of twinkling stars that illuminate the inky blackness with their mesmerizing glow. This dynamic contrast between day and night has captivated my imagination for as long as I can remember.The rising sun heralds the start of each new day, gently peeking over the horizon and gradually bathing the world in its radiant splendor. As the morning progresses, the sun climbs higher into the sky, casting its golden rays upon the earth and breathing life into every corner of our world. I've spent countless hours simply gazing up at the sun, marveling at its sheer power and majesty. Despite its immense size and distance from Earth,the sun's brilliance is so intense that I can scarcely look directly at it without squinting.Yet, as awe-inspiring as the sun is during the day, it's the night sky that truly sets my soul alight with wonder and curiosity. As the sun dips below the horizon, the inky blackness of space slowly unveils its celestial treasures, one twinkling star at a time. Before long, the entire night sky is awash in a dazzling display of countless pinpricks of light, each one a distant sun like our own, shining across the vast expanse of the cosmos.I've spent many a night lying on my back, gazing up at the stars in quiet contemplation. Their sheer number is staggering, and the realization that each one represents an entire solar system, or even an entire galaxy, is simply mind-boggling. As I trace the familiar constellations with my eyes, weaving together the ancient mythological tales they represent, I can't help but feel a profound sense of humility and insignificance in the face of such cosmic grandeur.But the stars' allure extends far beyond their sheer abundance and mythological associations. Each one is a unique and fascinating entity, with its own story to tell. Some burn with a brilliant white-hot intensity, while others radiate a warm, reddish glow. Some appear to twinkle and dance, while others shine witha steady, unwavering light. And some even explode in spectacular fashion, their dying gasps visible from Earth as fleeting bursts of brilliance before fading back into the cosmic darkness.As I ponder the celestial dance of the sun and stars, I can't help but feel a deep sense of awe and reverence for the natural world and the vast, unknowable mysteries of the universe. The sun, our nearest star, sustains all life on Earth with its warmth and light, while the countless other stars that adorn the night sky hint at the existence of countless other worlds, some perhaps even harboring their own forms of life.Yet, for all their grandeur and magnificence, the sun and stars also serve as a humbling reminder of our own fragility and insignificance in the grand scheme of the cosmos. We are but tiny specks in a vast, ever-expanding universe, our existence a mere blink of an eye in the cosmic timeline. And yet, we are also inextricably linked to the celestial dance that unfolds above us, our very existence made possible by the fusion reactions that power the stars and the elements they forge and disperse throughout the cosmos.As I gaze up at the heavens, I can't help but feel a profound sense of connection to something larger than myself, somethingthat transcends the boundaries of our tiny planet and spans the entire universe. The sun and stars are not just mere celestial objects, but rather the embodiment of the fundamental forces that govern our existence and the very fabric of reality itself.In the end, my fascination with the sun and stars is more than just a passing fancy or casual interest. It is a deep, abiding love and respect for the natural world and the cosmic mysteries that surround us. It is a recognition of our place in the grand tapestry of the universe, and a reminder that even in our most profound moments of existential crisis or personal struggle, we are part of something larger, something ancient and enduring, something that will endure long after we are gone.So, whether I'm basking in the warmth of the sun's radiant glow or losing myself in the twinkling tapestry of the night sky, I am forever in awe of the celestial dance that unfolds above me, a dance that has been playing out for billions of years and will continue to do so for billions more. And in those quiet moments of contemplation and wonder, I feel a profound sense of connection to the cosmos, a connection that transcends the boundaries of time and space and reminds me of the beauty, majesty, and mystery that surrounds us all.篇2The Wonders of the Celestial Worlds AboveHave you ever really stopped to ponder the celestial wonders that surround us? I must admit, for most of my life I took the beauty of the heavens for granted. The sun rose each morning, and I went about my day without much thought. The stars twinkled at night, and I paid them little mind. It wasn't until I was a bit older that I began to appreciate the trulyawe-inspiring marvels overhead.During the day, the sun is the star of the show - quite literally! That blazing orb in the sky is what makes life possible on our planet. As I gaze up at the sun, I'm amazed by its immense power and scale. It is a whirling sphere of hot plasma, fusing hydrogen nuclei into heavier atoms through nuclear fusion. This continuous reaction pours out tremendous amounts of energy in the form of light and heat.The sun is absolutely colossal - its diameter spans nearly 1.4 million kilometers! To put that in perspective, you could line up 109 Earths across the sun's disk. Despite its gargantuan size, the sun is actually considered an average-sized star. There are many larger stars out there burning even more ferociously in the cosmos.Yet from our vantage point here on Earth, the sun appears to be just the right size and brightness for life to flourish. Its heat warms our world to the perfect temperature for liquid water to exist. Its light allows plants to grow through photosynthesis, providing the base for virtually all food chains. The sun's rays even help generate Vitamin D in our bodies. Truly, the sun is the giver of life itself.Of course, we can't stare directly at the sun's brilliant face for long. Its dazzling light is simply too intense for our weak eyes. But that doesn't stop me from admiring the sun through a proper filter during the day. I've seen images of sunspots - dark blotches on the sun caused by intense magnetic activity. I've watched footage of solar flares bursting from the sun's surface, sending charged particles hurtling through space at millions of miles per hour. The sun is not just a static ball of fire - it is a roiling, chaotic sphere of plasma constantly changing and shifting in mind-boggling ways.Then, when night falls, an entirely new kind of spectacle emerges overhead. The inky black canvas of the night sky becomes a sparkling tapestry woven with thousands - no, millions - of twinkling stars. Every one of those pinpricks of light is a searing star, not so different from our own sun. Some areyounger, bluer, and more energetic. Others are older, redder, and nearing the ends of their stellar lives. A few may have burned out long ago, now existing as dense remnants invisible to our eyes. Together, they form the vast, sweeping spiral arms of our home galaxy, the Milky Way.On a clear night away from city lights, I could spend hours outside gazing upon the breathtaking expanse of the Milky Way arching across the heavens. Within its billion-mile diameter are hundreds of billions of stars. Our sun is just one solitary, unremarkable resident among that multitudinous stellar population. Yet our sun has qualities that make it rare and precious - it resides in one of the Milky Way's sparse outer arms, far from the galaxy's chaotic, crowded core. It is situated in a relatively uncrowded region of space with very little interstellar dust and gas to obscure the view. And most篇3The Great Celestial ShowHave you ever really stopped to ponder the heavens? I mean, have you truly taken the time to gaze up at the cosmic wonders that grace our skies? If you haven't, you're missing out on one of the greatest shows nature has to offer – a spellbinding spectaclethat plays out in the celestial theater twice a day, every single day.Let me set the stage for you. It's early morning, that magical time when night is loosening its grip and day is stirring awake. You step outside, and there it is – the star of the show itself, the sun! Ah, that brilliant golden orb, regal and radiant, slowly cresting over the horizon. It's like the curtain rising on an epic performance, revealing our solar system's reigning diva ready to deliver yet another showstopping turn.As the sun continues its stately ascent into the sky's dome, you can't help but be awestruck by its dazzling light and warmth caressing your face. This is no mere lightbulb in the heavens, my friends. No, this is a true celestial superstar, a searing sphere of plasma measuring over a million miles across and burning at temperatures that would make the heart of a raging furnace feel like a lazy summer afternoon. Mind-boggling, isn't it?Yet for as hypnotic as the sun's morning unveiling is, it's just the opening act. You see, the real mind-blowing extravaganza unfolds after that fiery diva has had her time in the spotlight and decided to call it a day, exiting the celestial stage as regally as she arrived. As night falls and the sky's inky curtain draws closed,an entirely new effervescent ensemble begins to assemble, ready to enchant us with the evening's performance.First, a few bright harbingers twinkle to life as night's dusky veil settles over the horizon, sending shivers of goosebumps along your arms. Those pinpoint blazes of brilliance are likely the evening's featured players – Venus, Jupiter, Mars, perhaps –warming up with their solo sets before the real celestial chorus kicks into full revelry. Watching those first few golden gems wink into existence is always a breathtaking thrill for me, a tantalizing preview of the cosmic magic about to unfold.Then, as the velvet backdrop of night grows complete, it begins – a veritable tsunami of starlight, an incandescent explosion rendering the sky alive with thousands upon thousands of shimmering fires. Out they pop, wave after wave of twinkling pinholes piercing the celestial dark, a blizzard of blazing lanterns strewn across the heavens like a glittering wildsown spangling of celestial diamonds flung from some divine jeweler's satchel. It's utterly breathtaking, an excessive embarrassment of riches calculated to leave your gaping senses reeling and your overbrimmed mind struggling to take in such undreamt-of splendor.And that's just the big picture view from Earth's surface. Zoom in a little closer on those glimmering specks with a telescope, and a vast new dimension of overwhelming grandeur comes spinning into focus. Whirlpools of stars wheel across your view, entire galaxies of unfathomable size and composition blooming into view like titanic celestial cities, each one an inconceivable conflagration burning with the fire of billions upon billions of individual suns in a single colossal congregation of stellar light and heat and raw power.Whole clusters of these galactic leviathans parade across the eyepiece in intricate winding whirlpools of unfurling light, pulled into frenzied pirouettes by the relentless cyclonic tugs of gravity, all dancing together in an eternal cosmic ballet of dizzying revolutions. The human eye, so accustomed to the modest scale of our Earthly surroundings, simply cannot compute the immensities it's witnessing, the unimaginable abysses of space and time that these colossal pinwheels occupy, the ludicrous volumes of matter they contain, the wild pyrotechnics of atomic fire at their bright hearts. It's a privilege just to glimpse these marvels, a humbling opportunity to brush up against the achingly beautiful complexities of a universe so much vaster than our tiny planet-bound senses could ever have allowed us to conceive.And to think, this is just the grand finale sky show that plays after that celestial diva, the sun, has had her turn! The heavens' dual performance is a true cosmic double-header, a chance to daily witness both the mighty warmth-giver during her solar solo act as well as the dazzling encore chorus of stellar gemfire after she has departed the stage. It's a festival for the eyes and the soul, an extravagant twice。
高等教育自学考试自考《英语二》模拟试题与参考答案一、阅读判断(共10分)第一题Passage:In the era of globalization, English has become the dominant language in international communication. As a result, the importance of learning English has been increasingly recognized worldwide. The following passage discusses the benefits of learning English and the challenges faced by language learners.1.English has become the primary language for international communication.2.Learning English is not as important as it used to be.3.The passage mentions the benefits of learning English.4.The passage talks about the challenges faced by language learners.5.The passage suggests that the importance of learning English is decreasing.Questions:1、The passage states that English has become the dominant language for international communication. Which of the following statements is true according to the passage?A. English is not the primary language for international communication.B. English has become the primary language for international communication.C. The passage does not mention anything about the role of English in international communication.D. The importance of English is decreasing in international communication.2、The passage discusses the benefits of learning English. Which of the following statements is true according to the passage?A. Learning English has no benefits.B. The passage mentions the benefits of learning English.C. The passage does not discuss the benefits of learning English.D. The benefits of learning English are not mentioned in the passage.3、The passage talks about the challenges faced by language learners. Which of the following statements is true according to the passage?A. The passage does not mention any challenges faced by language learners.B. The passage discusses the challenges faced by language learners.C. The challenges faced by language learners are not mentioned in the passage.D. The passage suggests that language learners face no challenges.4、The passage suggests that the importance of learning English is decreasing. Which of the following statements is true according to the passage?A. The importance of learning English is decreasing.B. The passage does not mention anything about the importance of learning English.C. The passage suggests that the importance of learning English isincreasing.D. The passage suggests that the importance of learning English remains the same.5、Which of the following statements is true according to the passage?A. English is not as important as it used to be.B. The passage does not mention the importance of learning English.C. The passage suggests that learning English is more important now than ever before.D. The passage states that learning English is not as important as it used to be.Answers:1、B2、B3、B4、A5、C第二题Read the following passage and then answer the questions by choosing the correct answer (True, False, or Cannot be determined) from the options given.Passage:The evolution of the internet has revolutionized the way we communicate and access information. With the advent of social media platforms, people can nowconnect with others from all over the world in real-time. This has had a significant impact on global culture and society, as it has made information more accessible and has facilitated the exchange of ideas.1、The internet has had a major impact on global culture and society.A. TrueB. FalseC. Cannot be determined2、Social media platforms allow people to connect with others from different parts of the world.A. TrueB. FalseC. Cannot be determined3、The internet has made information less accessible.A. TrueB. FalseC. Cannot be determined4、The exchange of ideas has been hindered by the internet.A. TrueB. FalseC. Cannot be determined5、The evolution of the internet has not changed how we communicate.A. TrueB. FalseC. Cannot be determinedAnswers:1、A. True2、A. True3、B. False4、B. False5、B. False二、阅读理解(共10分)Read the following passage and answer the question that follows.The advent of the internet has revolutionized the way we communicate and access information. One of the most significant impacts of the internet is the ease with which we can now learn new skills and knowledge. Online learning platforms and courses have made education more accessible and flexible than ever before.Online courses offer several advantages over traditional classroom settings. Firstly, they provide students with the convenience of learning at their own pace and in their own time. This flexibility is particularly beneficial for working professionals and those with family commitments. Secondly, online courses often offer a wide range of subjects and topics, allowing students to explore areas of interest that may not be available in their local educationalinstitutions. Additionally, online learning platforms often provide interactive tools and resources that enhance the learning experience.However, despite these benefits, online learning also presents certain challenges. One of the main concerns is the lack of face-to-face interaction, which can be crucial for building a strong foundation in certain subjects. Additionally, the self-discipline required to complete online courses without the structure of a traditional classroom can be a barrier for some students.Many educational institutions have recognized the potential of online learning and have started to offer their own online courses and degrees. This has expanded the reach of higher education and made it more inclusive. Moreover, governments around the world have been investing in online learning initiatives to bridge the education gap and improve literacy rates.Question:What is one of the main advantages of online courses mentioned in the passage?A)They require more self-discipline than traditional courses.B)They lack the interactive tools and resources of traditional classrooms.C)They offer the flexibility of learning at one’s own pace and in one’s own time.D)They are less likely to be beneficial for working professionals.Answer:C) They offer the flexibility of learning at one’s own pace and in one’s own time.三、概况段落大意和补全句子(共10分)第一题Passage:The following passage is from a book about the history of higher education in the United States. Read the passage carefully and then answer the questions that follow.In the United States, higher education has a rich and complex history. The first colleges were established in the 17th century, and they were primarily founded by religious institutions. These early colleges were small, with a focus on classical education and religious training. Over time, however, the scope of higher education expanded significantly. The 19th century saw the rise of the research university, which combined teaching and research in a new way. Today, higher education in the U.S. includes a wide range of institutions, from small liberal arts colleges to large research universities.Questions:1、The passage discusses the history of higher education in the United States. Which of the following is NOT mentioned as a factor in the early establishment of colleges?A. Religious institutionsB. Classical educationC. Professional trainingD. Religious training2、The 19th century marked a significant change in higher education. What was this change characterized by?A. The decline of religious institutionsB. The rise of the research universityC. The increase in the number of studentsD. The focus on vocational education3、The passage mentions that early colleges were “small.” What does the author imply by this statement?A. Early colleges were not well-funded.B. Early colleges were only for the wealthy.C. Early colleges had limited resources.D. Early colleges were more exclusive.4、The author states that “Today, higher education in the U.S. includesa wide range of institutions.” What is the author suggesting about the current state of higher education?A. Higher education is becoming less diverse.B. There is a trend towards larger, more specialized institutions.C. Higher education is more accessible to a wider population.D. Higher education is becoming more expensive.5、The passage concludes with a comparison of early colleges to contemporary institutions. What is the author’s purpose in making this comparison?A. To show the continuity of higher education over time.B. To highlight the differences between early and modern colleges.C. To emphasize the importance of religious education in early colleges.D. To discuss the role of research in modern higher education.Answers:1、C2、B3、C4、C5、A第二题Read the following paragraph and then answer the questions that follow.Paragraph:The rapid advancement of technology has significantly transformed the way we live and work. In the field of education, online learning platforms have gained immense popularity, offering flexibility and accessibility to students worldwide. These platforms provide a wide array of courses, ranging from basic skills to advanced professional development. However, despite the benefits, some challenges persist, such as the need for self-discipline and potential lack of personal interaction. Additionally, the increasing reliance on technology in education raises concerns about the future of traditional classroom settings.1.What is the main topic of the paragraph?A) The benefits of traditional classroom settings.B) The challenges of online learning platforms.C) The transformation of education through technology.D) The future of online learning platforms.2.According to the paragraph, what are the advantages of online learning platforms?A) They require high levels of self-discipline.B) They limit personal interaction between students.C) They offer flexibility and accessibility.D) They are less effective than traditional education.3.What challenge is mentioned in the paragraph regarding online learning platforms?A) The need for frequent updates.B) The potential lack of personal interaction.C) The high cost of online courses.D) The difficulty in assessing student progress.4.The paragraph discusses the impact of technology on what aspect of education?A) Teaching methods.B) Student engagement.C) The physical classroom environment.D) The availability of resources.5.What is one of the concerns raised about the reliance on technology in education?A) The decline in student attention spans.B) The future of traditional classroom settings.C) The potential for increased cyberbullying.D) The reliance on outdated teaching materials.Answers:1.C) The transformation of education through technology.2.C) They offer flexibility and accessibility.3.B) The potential lack of personal interaction.4.C) The physical classroom environment.5.B) The future of traditional classroom settings.四、填空补文(共10分)Reading PassageIn the modern world, language learning has become increasingly important. English, in particular, is considered a global language, and proficiency in Englis h is often a key factor in career success. One way to improve one’s English skills is through self-study. The self-study examination system for higher education, known as “self-study examination” or “self-study degree examination,” allows individuals to st udy and take exams independently. In this passage, we will discuss the English subject for the second level of self-study examination.The English subject for the second level of self-study examination focuses on the development of reading, writing, listening, and speaking skills. Theexamination aims to test candidates’ comprehensive English proficiency and ability to apply English in practical situations.Fill in the blanks with the appropriate options:1.The self-study examination system for higher education is also known as the _______.A. English examinationB. self-study examinationC. degree examinationD. comprehensive examination2.The English subject for the second level of self-study examination is designed to improve_______skills.A. mathematicsB. ChineseC. EnglishD. physics3.The examination aims to test candidates’_______proficiency.A. mathematicalB. ChineseC. EnglishD. scientific4.One way to improve one’s English skills is through _______.A. traditional classroom learningB. self-studyC. group studyD. online learning5.English is considered a_______language in the modern world.A. localB. regionalC. globalD. nationalAnswers1.B. self-study examination2.C. English3.C. English4.B. self-study5.C. global五、填词补文(共15分)第一题Read the following passage and complete the sentences with the appropriate words in the box below.In the bustling city of New York, there are numerous 1 that attract tourists from all over the world. Times Square, with its 2 of neon lights and towering skyscrapers, is a symbol of 3 and modernity. The 4 of Broadway theaters offers a wide range of performances, from classic plays to contemporary musicals. The5 of Central Park provides a6 escape from the urban jungle, offering serene walks and beautiful landscapes.A. attractionsB. shimmeringC. vibrancyD. repertoireE. oasis1.__________2.__________3.__________4.__________5.__________6.__________Answers:1.A. attractions2.B. shimmering3.C. vibrancy4.D. repertoire5.E. oasis6.E. oasis第二题阅读内容:In today’s fast-paced world, 1, it is crucial for individuals tocontinuously 2 their knowledge and skills. One such way is through self-study examinations, which allow learners to progress at their own pace. The following passage is about the benefits of self-study examinations.If you are preparing for the self-study examination known as “English Level Two,” you should be familiar with the following vocabulary and phrases that are commonly used in the test.Fill in the blanks with the appropriate words from the list below:a)broadenb)pursuingc)adaptd)accessiblee)motivatedf)effectiveg)enhanceh)fundamentali)diversej)comprehensivePassage:The self-study examination for 1 has become increasingly 2 for professionals and students alike. It offers a 3 and flexible learning environment, allowing individuals to 4 their learning experience according to their own needs and schedules. The examination covers a wide range of topics, ensuring that learners gain 5 knowledge and skills in English.1.__________2.__________3.__________4.__________5.__________Answers:1.d) accessible2.e) motivated3.j) comprehensive4.a) broaden5.f) enhance六、完型补文(共15分)第一题Read the following passage and fill in the blanks with the most suitable words from the options given below.James was an intelligent and ambitious young man who always dreamt of traveling the world. He knew that to achieve his goal, he needed to learn a new language. After much research, he decided to take the self-study examination for college English, specifically the second level (CET-4).James spent hours studying every day, focusing on improving his vocabulary and grammar. He also practiced listening and speaking to become more fluent.One day, while he was reading an article about language learning, he came across a tip that suggested reading newspapers and magazines in the target language could be very helpful.1、James decided to start reading newspapers and magazines in English to improve his ________.A. vocabularyB. grammarC. listening skillsD. speaking skills2、By reading newspapers and magazines, James hoped to become more ________.A. intelligentB. ambitiousC. fluentD. ambitious3、James believed that reading newspapers and magazines in English would________his learning process.A. complicateB. simplifyC. frustrateD. hinder4、After a few months of consistent practice, James noticed a significant improvement in his ________.A. vocabularyB. grammarC. listening skillsD. speaking skills5、James’ hard work and dedication eventually paid off when he________the self-study examination with flying colors.A. passedB. failedC. postponedD. canceled答案:1、A2、C3、B4、A5、A第二题The following passage has eight blanks. For each blank there are four choices marked A, B, C, and D. You should choose the one that best fits into the passage.Reading passage:In the past few decades, the internet has revolutionized the way we communicate and access information. From social media to online shopping, ithas become an integral part of our daily lives. However, this digital age has also brought about several challenges, one of which is the issue of online privacy.1、__________, many users are concerned about the security of their personal information when using online services.A. As a resultB. For instanceC. In additionD. On the other hand2、__________, data breaches have become increasingly common, leading to the exposure of sensitive information.A. FurthermoreB. HoweverC. ConsequentlyD. Moreover3、__________, it is crucial for individuals to take steps to protect their online privacy.A. Despite the above challengesB. In order to overcome these challengesC. As a result of the digital ageD. In light of the current situation4、__________, using strong passwords and enabling two-factorauthentication can help reduce the risk of unauthorized access.A. For one thingB. For anotherC. On the one handD. On the other hand5、__________, it is important to be cautious about the information we share online.A. FinallyB. In conclusionC. In the endD. UltimatelyAnswers:1.A2.A3.D4.A5.A七、写作(30分)Task: Write an essay of about 200 words on the following topic:“Online learning has become increasingly popular in recent years. Discuss the advantages and disadvantages of online learning, and give your opinion onwhether it can fully replace traditional classroom teaching.”Sample Essay:Online learning has undoubtedly revolutionized the way we acquire knowledge and skills. There are several advantages to this mode of education. Firstly, it offers flexibility, allowing students to study at their own pace and schedule. This is particularly beneficial for working professionals or those with family commitments who cannot attend regular classes. Secondly, online learning provides access to a vast array of resources, including e-books, videos, and interactive tools, which can enhance the learning experience. Lastly, it encourages self-motivation and independence, as students must take responsibility for their own learning.However, there are also disadvantages to consider. One major drawback is the lack of face-to-face interaction, which can hinder the development of communication skills. Additionally, some students may struggle withself-discipline and time management when learning independently. Moreover, not all subjects are well-suited for online learning, and certain practical skills might require hands-on experience that cannot be replicated online.In my opinion, while online learning can be a valuable supplement to traditional classroom teaching, it is unlikely to fully replace it. The social and collaborative aspects of classroom learning are crucial for personal and academic growth. However, with advancements in technology, online learning can be integrated into traditional education to create a more comprehensive learningexperience.Parsing:•The essay begins with a statement of the topic and then introduces the advantages of online learning.•The advantages are presented with clear and concise points, each followed by a brief explanation.•The essay then turns to the disadvantages of online learning, again using clear and structured sentences.•The author’s opinion is clearly stated, followed by a logical argument supporting the viewpoint.•The conclusion summarizes the main points and reinforces the author’s stance on the topic.•The essay is coherent, well-organized, and adheres to the word limit requirement.。
绝密★启用前2024届高三1月大联考考后强化卷(新课标II卷)英语(考试时间:100分钟试卷满分:120分)第一部分阅读(共两节,满分50分)第一节(共15小题;每小题2.5分,满分37.5分)阅读下列短文,从每题所给的A、B、C和D四个选项中,选出最佳选项。
AScience Books for Kids of All AgesTo help you choose the perfect educational books for your child, we’ve created this handpicked list of the best science books for kids. The titles featured here spark curiosity, encourage learning, and are lots of fun, too.About Time: A First Look at Time and ClocksAuthor: Bruce Koscielniak; Price: US $8.55Long ago people used the sun, the moon, and the water to tell time. Soon after we began using our knowledge about the natural world to build clocks and to create calendars made up of months and years. Centuries later, we have clocks and calendars all around us. This book tells the amazing story of how it all happened!Animalium: Welcome to the MuseumAuthor: Katie Scott; Price: US $8.99This book opens the doors of the natural history museum for your child all year round! It features 200 full-color specimens (样本) accompanied by lively, informative text and more. Discover the animal kingdom in glorious detail with unique illustrations that combine science and art.Bang!: How We Came to BeAuthor: Michael Rubino; Price: US $16.00“Bang! And that was it, the beginning of everything.” So begins this beautifully illustrated story of evolution. This book conveys not only the facts but also the excitement of the scientific explanation of our world, from the origin of the universe to the present reality of our planet.Bedtime Math: The Truth Comes OutAuthor: Laura Overdeck; Price: US $10.99This book makes learning about math as fun as dessert after dinner! It combines math and cool facts for one fun and wild adventure. Now kids can discover the science behind all their favorite things: marshmallows, soda, ice cream, and more. With over 100 math problems on a variety of topics, kids will find math isn’t just fun — it can be found everywhere!1. What can kids learn in the book About Time?A. The tough life of ancestors.B. The origin of the sun and the moon.C. The old ways to measure time.D. The wildlife in the natural world. 2. What do Animalium and Bang! have in common?A. They are children’s novels.B. They are popular for cheap price.C. They are collected in the museum.D. They are illustrated stories for kids.3. Which book can make numbers fun and easy?A. Bang!.B. Bedtime Math.C. Animalium.D. About Time.BOn November 7, Lewis Pugh completed a one-kilometer swim in the freezing waters of King Edward Cove, off South Georgia in Antarctica. He was wearing only his swimming glasses, cap and Speedo!Pugh is an advocate for our oceans and seas, working to protect these ecosystems with their large diversity of marine life. When asked why he doesn’t w ear a wetsuit (防寒泳衣), Pugh says, “I ask world leaders to do everything they can to protect our oceans. Sometimes the steps they need to take are difficult and unpopular. If I’m asking them to be courageous, I must also be. Swimming in a wetsuit would not send the right message.”It took Pugh about 19 minutes to complete the one-kilometer swim in Antarctica where the water averaged about 1.6 degrees Celsius. He says that his body can only tolerate about 20 minutes in the freezing waters before it starts shutting down. As he swims, his body temperature steadily drops, which in turn causes his muscle control to drop, slowing him down. When he is done with his swim, his support team rushes him to a hot shower and it takes almost an hour for his body temperature to return to normal.Doctors and Pugh caution that one must receive months of training to swim in such cold waters. Even expert swimmers who are unused to freezing waters can drown within minutes because of the physical shock experienced by the body. Pugh says he trained for six months before this swim.This is not the first time that Pugh has swum in dangerous conditions. In 2007, he swam one kilometer in the North Pole to draw attention to the melting Arctic ice due to climate change. In 2015, he swam in the Bay of Whales in Antarctica’s Ross Sea as part of his successful campaign to help set up a marine reserve there.4. Why did Lewis Pugh swim without a wetsuit?A. To show his bravery.B. To swim faster.C. To build up his body.D. To have overnight fame.5. What does the underlined word “it” in Paragraph 3 refer to?A. His body temperature.B. His body.C. The water.D. The water temperature.6. What’s Pugh’s advice about swimming in freezing waters?A. One should be expert at swimming.B. One must be used to long-distance swimming.C. One should be ready to take on challenges.D. One must be adequately prepared for it.7. What can be the best title for the text?A. Lewis Pugh: achieving the impossibleB. How to survive a swim in cold watersC. Lewis Pugh: swimming for a causeD. How to prepare for extreme swimmingCGirls should take part in competitive sport to build confidence, and the leaders of a group of girls’ schools will argue this week. Helen Fraser, director of the Girls’ Da y School Trust (GDST), will tell the group that sport can help girls deal with failure.“All girls, not just the sporty ones, should take physical exercise,” Ms. Fraser says. Research that girls are far less active than boys is worrying, she argues. Ms. F raser will tell the group that she supports “sport for all”. “That’s why I love it when our schools have A, B, C and D teams and beyond,” she says.The GDST draws on research from the Women’s Sport and Fitness Foundation which suggests only a quarter of girls in England meet basic levels of activity each week. One in five girls does no activity at all, twice the proportion of boys, the research suggests.Ms. Fraser says other research suggests that more than 80% of women business leaders played sports while growing up. She uses the examples of former US Secretary of State Condoleezza Rice, who once was a skater and tennis player, and the head of the International Monetary Fund, Christine Lagarde, who was in the French national swimming team. Ms. Fraser says Olympic medalists like Jessica Ennis and Katherine Grainger are excellent role models for young women but says women’s sport needs more money and more news reports.Valerie Dunsford, head of Sheffield High School for Girls, part of GDST, said it was important to offer a large number of sports to attract different types of girls. “Not everyone wants to be out playing the hockey,” said Ms. Dunsford.8. Which of the following would Ms. Fraser agree with?A. Boys are born to be sport lovers.B. Girls are less confident than boys.C. More should be done to make girls do sports.D. Those taking part in the sport are always successes.9. What’s the proportion of boys who never take exercise?A. 1/10.B. 1/5.C. 1/4.D. 2/5.10. Ms. Fraser mentions those famous women to show __________.A. hard work will pay offB. it’s not easy to be greatC. sport can help girls to succeedD. it’s necessary to balance work and sport11. What’s the purpose of the text?A. To explain the key to success.B. To show the importance of sport.C. To introduce more sports to girls.D. To encourage more girls to do sports.DWe’ve been told for years that self-driving cars are just approaching. But it’s time to accept the truth, said Darrell Etherington on TechCr unch: they “aren’t going to happen” in our lifetimes.I’ve long been excited about the potential of this technology, but my remaining optimism left me finally last month when Ford and V olkswagen announced they were stopping running Argo AI, their autonomous driving tech joint firm. Argo was considered a leader in the field. But Ford feels that “producing profitable, fully autonomous vehicles on a large scale is a long way off”, and it could no longer stomach the increasing costs. This is just the latest setback.It is true that General Motors is making progress in trialing driverless vehicles on the roads, but only on a small scale. Tesla is pushing ahead with its self-driving technology, but its ambitions can be limited by an investigation that is looking into some accidents inv olving its “Autopilot” system. Some of the firmest believers in self-driving technology have turned nonbelievers. State-of-the-art robot cars still “struggle” with construction sites, road blocks, and sometimes even simple left turns.I recently took a ride in a self-driving taxi in the city of Chandler, Arizona. There was an undeniable horror-movie aspect of sitting in the back of a vehicle and watching the steering wheel turn autonomously. To my relief, it slowed when other vehicles behaved improperly. I was just about to feel relaxed and text a co-worker when the taxi came to a sudden stop at one point. A truck stopped in front of us and wanted to go backwards in order to take a missed turning. Unclear about what to do next, the taxi “chirped (吱吱叫) to call a human specialist to solve the situation”. Fortunately, the truck driver decided to drive on and we continued our way. My driverless experience made me believe this technology may never be possible to make passengers relaxed when they are in a driverle ss vehicle. Even so, I won’t undervalue the technological advances that have been made— after all, who knows what the future will look like.12. What can we infer from Darrell Etherington’s words?A. Self-driving cars will be replaced by other technology.B. Self-driving cars will change our travel mode.C. Self-driving cars are approaching us.D. Self-driving cars are just a dream now.13. What does the underlined word “stomach” probably mean in Paragraph 2?A. Endure.B. Reduce.C. Regain.D. Remove.14. Why are General Motors and Tesla mentioned in Paragraph 3?A. To state self-driving technology has made big progress.B. To prove self-driving technology has a long way to go.C. To show self-driving technology is totally impractical.D. To stress self-driving technology has great potential.15. What is the author’s attitude towards the self-driving technology?A. Critical.B. Conventional.C. Favorable.D. Indifferent.第二节 (共5小题;每小题2.5分,满分12.5分)阅读下面短文,从短文后的选项中选出可以填入空白处的最佳选项。
[考研类试卷]英语专业(语言学)历年真题试卷汇编28.doc[考研类试卷]英语专业(语言学)历年真题试卷汇编28一、填空题1 The type of language constructed by second or foreign language learners who are still in the process of learning a language is often referred to as______. (中山大学2008研)2 ______is formed when the leaner attempts to learn a new language, and it has features of both the first language and the second language but is neither. (中山大学2006研)3 Hymes' theory leads to notion/function-based syllables, and a step further,______syllabuses. (中山大学2005研)4 Error is the grammatically incorrect form; ______ appears when the language is correct grammatically but improper in a communicational context. (中山大学2008研)5 As a compromise between the "purely form-focused approaches" and the "purely meaning-focused" approaches, a recent movement called______seems to take a more balanced view on the role of grammar in language learning. (中山大学2011年研)二、单项选择题6 In Krashen's monitor theory, "i" in "i + 1" hypothesis of second language acquisition refers to ______. (对外经贸2006研) (A)interaction(B)interference(C)input(D)intake7 The______is a syllabus in which the language content is arranged in terms of speech acts together with the languageitems needed for them. (西安外国语学院2006研)(A)structural syllabus(B)situational syllabus(C)notional syllabus(D)functional syllabus8 Negative transfer in learning a second language is known as______.(A)interference(B)interlanguage(C)fossilization(D)acculturation9 ______sees errors as the result of the intrusion of L1 habits over which the learner had no control.(A)error analysis(B)performance analysis(C)contrastive analysis(D)discourse analysis三、简答题10 How do you understand interlanguage? (西安交通大学2008研)11 What are the four obvious barriers to adult 12 acquisition? (浙江大学2003研)12 Linguists have taken an internal and/or external focus to the study of language acquisition. What is the difference between the two?(北外201 1研)13 What is the difference between mistakes and errors?14 What are the distinctions between interlingual and intralingual errors?15 What are the different views of input hypothesis and interaction hypothesis on discourse's contribution to languageacquisition?四、名词解释16 Applied linguistics (武汉大学2006研)17 Interlanguage (北外2010研;北航2010研;上海交大2005研)18 Contrastive analysis (北航2010研;浙江大学2004研)19 face validity (南开大学2011年研)20 Error Analysis (中山大学2011年研)五、举例说明题21 Krashen's Input Hypothesis and Language Learning.(北交大2006研)22 Explain one of the teaching approaches that you're familiar with and discuss its advantages and disadvantages. (浙江大学2004研)23 What do you think are the similarities and dissimilarities between learning a first anda second language? (北外2003研)24 What is communicative competence? How should we develop it in our foreign lauguage learning? (四川大学2009研)25 Read the following paragraphs and then answer four questions. (北外201 1年研) The idea behind the experiential vision of learning is that the use of the target language for communicative purposes is not only the goal of learning, but also a means of learning in its own right. This may clearly involve students using language which they may not have fully mastered, and contrasts with other more ' traditional' approaches which emphasize part practice (i. e., isolating parts of the whole for explicit study and learning)leading up in a more or less controlled manner to integrated language use for communicative purposes. An experientialapproach to learning may therefore involve a degree of what Johnson (1982) refers to as an ' in at the deep end strategy'. Simply throwing learners into wholly uncontrolled and undirected language use is, of course, as dubious a strategy with respect to language learning as doing the same with someone who is learning to swim. For this reason, considerable effort has been devoted by methodologists, material writers, and teachers in recent decades to the way in which two sets of factors can be combined. One is the basic insight that language use can serve a significant role in promoting learning, and the other is the acknowledgement that use of the language needs to be structured in a coherent and pedagogically manageable way. The experiential vision of learning has evolved in a variety of ways since the 1960s and is now encountered in a number of differing forms. Nevertheless, most experiential approaches to learning rest on five main principles which were developed in the earlier days of the communicative movement, even if certain receive more attention in one variant than in another. These principles are the following: message focus, holistic practice, the use of authentic materials, the use of communication strategies, and the use of collaborative modes of learning. (Tudor 2001: 79) An analytical view of learning posits that according explicit attention to the regularitiesof language and language use can play a positive role in learning. Each language manifests a number of structural regularities in areas such as grammar, lexis and phonology, and also with respect to the ways in which these elements are combined to communicate messages. The question, therefore, is not whether languages have structural regularities or not, but whether and in which way explicit attention to such regularitiescan facilitate the learning of the language. An analytical approach to learning rests on a more or less marked degree of part practice, i. e. , isolating parts of the whole for explicit study and learning, even if its ultimate goal remains the development of learners' abilityto put these parts together for integrated, holistic use. At least, two main considerations lend support to an analytical approach to learning. First, in terms of learning in general , the isolation and practice of sub-parts of a target skill is a fairly common phenomenon. ... Second, explicit identification of regularities in a language has advantages which Johnson (1996: 83) refers to as 'generativity' and ' economy'. Mastering a regularity in a language gives learners access to the generative potential of this regularity in new circumstances. ... Explicit presentation or discovery of the structural regularities of a language can therefore represent a short-cut to mastery of this language and support learners' ability to manipulate these regularities for communicative purposes. (Tudor 2001: 86-7)1. What are the differences between experiential and analytical modes of language learning?2. What serves as the theoretical foundation for the experiential mode of language learning and what are its advantages and disadvantages?3. What serves as the theoretical foundation for the analytical mode of language learning and what are its advantages and disadvantages?4. How would you balance the two modes of learning in your teaching or learning of a foreign language?26 How many types of data analysis have been employed in language acquisition research? How are these types of dataanalysis significant in SLA research?。
Yanyao Jiange-mail:yjiang@Ming Zhang Mechanical Engineering,University of Nevada,Reno,NV89557Chu-Hwa LeeFord Motor Company,Advanced Engineering Center,20000Rotunda Drive,Dearborn,MI48121A Study of Early StageSelf-Loosening of Bolted JointsBoth experimental investigation andfinite element analysis were conducted to explore the mechanisms for the early stage self-loosening of bolted joints under transverse cyclic loading.The nuts were glued to the bolts using a strong thread locker in the self-loosening experiments to ensure that no backing-off of the nut occurred.Depending on the loading magnitude,the clamping force reduction ranged from10%to more than40%of the initial preload after200loading cycles.Three-dimensional elastic-plasticfinite element analysis was conducted with the implementation of an advanced cyclic plasticity model.Thefinite element results revealed that the local cyclic plasticity occurring near the roots of the engaged threads resulted in cyclic strain ratcheting.The localized cyclic plastic deforma-tion caused the stresses to redistribute in the bolt,and the result was the gradual loss of clamping force with loading cycles.Thefinite element results agreed with the experimen-tal observations quantitatively.When the two clamped plates started to slip and the slip displacement was controlled,both experiments andfinite element simulations suggested that the friction between the clamped plates has an insignificant influence on the early stage self-loosening.͓DOI:10.1115/1.1586936͔IntroductionBolted joints are the most commonly used components in ma-chines and structures.The fasteners generally represent the largest single cause of the warranty claims faced by the automobile manufacturers͓1͔.Often,potential durability problems in a ma-chine or structure are proportional to the number of the boltedjoints used.Two failure modes are found in bolted joints subjectedto cyclic loading:fatigue and self-loosening.Fatigue is a majorfailure form for a bolted joint subjected to tensile load and self-loosening is often found in a bolted joint subjected to transverseor shear load.Self-loosening is the gradual loss of the clampingforce in the bolted connections under cyclic external loading,es-pecially transverse loading.It can result in a decrease in structuralstiffness or the separation of clamped members.Experimental observations reveal that self-loosening starts witha gradual relaxation of initial preload.Only when the clampingforce has fallen below a certain critical value does the nut actuallystart to back off͓1͔.Loosening is rapidly beyond this point.Fig-ure1shows a typical self-loosening sequence due to transversecyclic loading from an experiment͓2͔.The symbol P representsthe clamping force,P0denotes the initial clamping force or pre-load,andis the rotation angle of the nut against the bolt.Two distinct stages can be identified from Fig.1.During thefirst ͑early͒stage,there is no relative motion between the nut and the bolt.Loosening is caused by material deformation.For the caseswith large slip between the two clamped plates,thefirst stage canbe very short͓2͔.The other stage is characterized by the obviousbacking-off of the nut and rapid loosening of the clamping force.There is a possible transition in between the two stages whereboth material deformation and the backing-off of the nut contrib-ute to the loosening.The current investigation attempted to under-stand the mechanisms governing the early stage self-loosening.Early investigations concentrated on the behavior of boltedjoints under axial dynamic loading͓3͔.Junker͓4͔was thefirst tonotice the importance of the transverse dynamic load on the oc-currence of self-loosening.It is generally asserted that the clamp-ing force serves as the source of internal off-torque force whichresults in the rotational loosening of the bolt or the nut.Such ahypothesis has been the most convincing explanation for self-loosening.However,since the relative rotation between the bolt and the nut is a necessary condition,the theory cannot explain the experimental observation that significant loss of preload can occur before the nut starts to back off.Most investigations tried to understand how the nut slides on the bolt thread due to internal clamping force and the external loading on the bolted joints.Yamamoto and Kasei͓5͔developed quantitative models based on a two-stage theory for the nut to slide along the thread of the bolt.However,no quantitative results were provided for the verification of the models.Following Junk-er’s basic assumptions,Sakai͓6,7͔proceeded to conduct a theo-retical analysis,trying to derive the conditions necessary for a bolt to loosen by self-rotation.It was concluded that unless the friction coefficient was less than0.03,the bolt would not rotate loosely.It was found that one of the causes of the clamping force reduction was the fretting wear between contact surfaces.Vibration models were proposed to explain self-loosening of bolted joints.Daadbin and Chow͓8͔studied the loosening due to impact load using a mass-spring model.It was argued that in the occurrence of resonance,the nut thread would separate from the thread of the bolt and the nut would undergo a freeflight until it touched the inclined surface again.A series of experiments were conducted to verify the theory.However,the preload applied in the experiments was between10and40N while the realistic preload should be around10kN for the bolt sizes used in their experiments.Other investigators͓9–11͔used mass-spring-damper models to study the effect of damping on self-loosening and op-timal preload for a bolted joint.Hess and co-workers͓12–14͔developed models to describe the motion of the threaded components loaded by gravity and sub-jected to axial harmonic vibrations.A single bolt assembly with zero or small clamping force was tested in a shaker.Depending on the testing frequencies and amplitudes,the nut was found to move up or down.It was then concluded that a bolted joint would loosen or tighten due to vibration.The results may help to under-stand the later stage self-loosening when the clamping force has been dropped to a very low level.Kasei et al.͓15͔were thefirst to study self-loosening focusing on the initial stage of the loosening.The original loss of the clamping force was attributed to the repeated twist of the nut relative to the bolt shank due to the slippage between the bolt and nut threads.Koga and Isono͓16͔studied the self-loosening from the aspect of impulsive friction.It was suggested that when a bolt was subjected to axial impacts,the pressure waves created on theContributed by the Reliability,Stress Analysis and Failure Prevention Committeefor publication in the J OURNAL OF M ECHANICAL D ESIGN.Manuscript receivedMay2002;rev.Feb.2003.Associate Editor:J.C.Moosbrugger.518ÕVol.125,SEPTEMBER2003Copyright©2003by ASME Transactions of the ASMEbolt flank would propagate within the bolt.After being reflected at the free end of the bolt,the pressure waves changed into tensile stresses and returned to the pressure flank on the other side of the bolt.These tensile stress waves caused the axial clamping force to decrease as a result of bolt loosening.Zadoks and Yu ͓17,18͔challenged this hypothesis as being contradictory to the general experimental observation that the axial vibrations seldom caused loosening.Many efforts have been made to understand the self-loosening of bolted joints;yet,the mechanisms responsible for the self-loosening process remain unexplored.None of the existing theo-ries can explain the general experimental observations that no relative motion occurs between the bolt and nut in the early stage of clamping force reduction and it is the transverse load instead of the axial load that causes self-loosening.No quantitative evalua-tion of bolted joints for the self-loosening is available that can capture the essential characteristics of the experimentally ob-served loosening phenomenon.The concentration of the current investigation was to study the early stage self-loosening where the nut did not have a relative motion to the bolt.Three-dimensional elastic-plastic finite element models as well as self-loosening experiments were conducted to study the cyclic plastic deformation involved in the early stage self-loosening.Self-Loosening ExperimentSelf-loosening experiments were conducted using a custom de-signed testing fixture.The experimental setup is shown in Fig.2.Two plates made of the high strength AISI 4340steel were clamped with a bolt and a nut.Each plate had a thickness of 13mm.One plate was fixed at one end and a shear load was applied at the end of the other plate.A low profile washer-type compres-sion load cell ͑capacity 15000lb for 0.5inch bolt ͒was attached between the bolt head and the fixed plate and was used for the measurement of the clamping force.The load cell was specifically designed to match SAE bolt sizes and strengths.The thickness of the load cell was 15mm.As a result,the effective bolt length was 41mm.An extensometer with a gage length of 50.8mm was attached to the plates,with one leg of the extensometer being attached to one plate and the other leg to the other plate.In this way,the relative displacement of the two clamped plates with-in a gage length of 50.8mm can be controlled and measured experimentally.A half an inch ͑12.7mm ͒͑tpi ϭ13͒bolt made of 1070steel was used in the experiments.The bolt had a length of 57mm and the length with threads was 25mm.All the bolts for the self-loosening experiments were machined from the hot-rolled round bars that had been heat-treated at 880°for four hours followed by air-cooling.The 0.2%offset yield strength of the material from the monotonic stress-strain is 449MPa.To maintain a good sur-face finish,the threads of the bolts were ground.The Grade 8hex nuts used in the experiments were commercially purchased.The hardness of the nut is HRC 26ϳ34.An Instron material testing system with computer control and data acquisition was used for the self-loosening experiments.Pre-load was applied through tightening the nut slowly.The testing frequency was 0.25ϳ0.5Hz.Two types of self-loosening experiments were conducted.In the load-controlled tests,the fully reversed transverse load was the controlling parameter.It was applied by the actuator and was mea-sured by the load cell in the testing machine.A sine waveform was used in the control of load.For the load-controlled experi-ments,no lubricant was added to the interface between thetwoFig.1Self-looseningsequenceFig.2Experimental setup for self-loosening experiment;…a …Sectional view,…b …Three-dimensional viewJournal of Mechanical DesignSEPTEMBER 2003,Vol.125Õ519clamped parts.The dry static friction allowed for a large trans-verse load to be applied without slip occurring between the two clamped plates.In the displacement-controlled self-loosening experiments,the relative displacement between the two clamped parts within a gage length of 50.8mm was controlled and measured by the at-tached extensometer.A strong thread locker,Threadlocker 262,was used to glue the nut to the bolt.This adhesive is generally used for heavy shock and vibration applications.Removal of the nut requires a special tool.The use of the thread locker ensured that no backing-off of the nut occurred during the self-loosening experiments.A sine waveform was used in the control of displace-ment.A grease lubricant was added to the contact surfaces of the two clamped plates to reduce friction.A low friction is necessary in order to minimize the wear of the contact surfaces of the two clamped plates.According to Bickford ͓1͔and Eccles ͓19͔,an appropriate level of preload corresponds to an axial stress equal to 50–75%of the nominal yield strength of the bolt.Based on this,the desired range of preload for a half an inch bolt ͑1070steel ͒is 25ϳ40kN.Experimental Observations.The experimental results of the clamping force reduction with the number of the transverse load-ing cycles are shown in Fig.3for a total of nine different loading combinations.In the figure,P 0denotes preload,Q is the trans-verses load,⌬Q /2is the amplitude of the transverses load,and ⌬␦/2represents the displacement amplitude within the gage length of 50.8mm between the two clamped plates.Depending on the loading magnitude and initial preload,the loss of clamping force ranged from a few percents to up to 41%after 200repeated trans-verse loading cycles.It should be noted that the logarithmic scale was used for the horizontal axes in Fig.3.The first transverse loading cycle resulted in the most signifi-cant reduction in clamping force.The rate of loosening in clamp-ing force decreased with increasing number of loading cycles.For the load-controlled experiments with no slip between the two clamped plates,self-loosening was minimal after the first few loading cycles.For the displacement-controlled experiments,self-loosening was a gradual process.With the same preload,a larger displacement amplitude between the two clamped plates resulted in larger self-loosening.Slip was observed on some load-controlled experiments.However,no slip occurred for the load-controlled case reported in this paper.Slip between the two clamped plates was monitored by the attached extensometer ͑see Fig.2͑b ͒͒.The variations of the transverse loading amplitude with the number of loading cycles are shown in Fig.4for selected displacement-controlled experiments.For the dry contact case without lubrication between the two contact surfaces of the clamped parts,the transverse load increased dramatically during the first 10loading cycles.When lubricant was applied between the sliding surfaces,the transverse load did not change signifi-cantly during the first 100loading cycles.The transverse load was increased dramatically after about 200loading cycles.For the displacement-controlled experiments,the increase in shear load amplitude is an indication of the increase in friction between the two sliding surfaces.There were two displacement-controlled experiments shown in Fig.3͑b ͒which had a preload of 41kN and an identical displace-ment amplitude of 0.46mm.One experiment was conducted with dry contact between the two clamped plates.In the other case,a grease lubricant was added.It can be deduced from the results shown in Fig.4for the shear load that the two cases had very different frictions between the two clamped plates.However,the self-loosening behavior was very similar for the two cases.This suggests that the friction between the two plates does not play an important role in the self-loosening of the bolted joints when the relative displacement of the two clamped plates is controlled.Finite Element SimulationsFinite Element Model.A three-dimensional ͑3-D ͒finite ele-ment ͑FE ͒model was created with the software package Hyper-mesh ͓20͔͑Fig.5͒.The threads in the bolt and nut were simplified into circumferential grooves.Because the load and geometry were symmetrical with respect to the x -y plane,only one half of the structure was modeled.Accordingly,all the displacements of the nodes located in the x -y (z ϭ0)plane should be fixed in the z direction.There were six engaged threads in the FE mesh model.According to a previous FE simulation ͓21͔,the first engaged thread carries more than 30%of the total load.Therefore,the first engaged thread root is the critical area for possible plastic defor-mation whose behavior should be studied carefully.The mesh in this area was the finest.Eight nodes were created on the root of the first engaged thread while four nodes were used in the second engaged thread root ͑Fig.5͑b ͒͒.One node was used elsewhere.There are a total of 10836nodes and 8395eight-node solid brick elements in the mesh model.Eight-node elements are gen-erally preferred for an analysis involving surface contacts.To avoid singularity in the numerical analysis when slip occurs be-tween the two clamped plates,a spring element was attachedtoFig.3Experimentally observed clamping force reduction with number of loadingcyclesFig.4Variation of transverse load amplitude with number of loading cycles for displacement-controlled experiments520ÕVol.125,SEPTEMBER 2003Transactions of the ASMEthe upper plate.The spring element had a stiffness of 100N/mm.The small force produced by the spring element does not affect the results in the bolted structure.The contact in the bolted structure was simulated by the penalty function method and it was realized by using the input file in ABAQUS ͓22͔.A total of 10pairs of contact couplings were usedto simulate the contact surfaces.They were the contacts between the six engaged threads of the bolt and the nut,the contact be-tween the nut and its bearing surface,the contact between the two camped plates,the contact between the lower plate and the load cell,and the contact between the bolt head and its bearing surface.In order to simulate the sticking behavior between the engaged threads of the nut and bolt,the relative slip on the contact surface was restrained by a set of high critical shear stresses.In the defi-nition of contact pairs,the contact surface of male ͑bolt ͒threads with finer meshes was assigned to be the slave surface and the contact surface of the female ͑nut ͒threads with coarser meshes served as the master surface.Friction Model.In the bolted structure under consideration,slip was allowed only between the two clamped members.The finite slip between the two plates was described by the Coulomb friction model.The translation of friction coefficient from the stick to slip status followed the exponential rule ͓23͔,ϭk ϩ͑s Ϫk ͒e Ϫd c ␥˙(1)where s is the static friction coefficient,k is the kinetic frictioncoefficient,d c is the decay coefficient,and ␥˙represents the slip rate.This model has a smooth continuity that causes no numerical problems.Therefore,the model can be adopted to describe the reversed translation process.According to the experimental results that will be discussed,s ,k and d c were taken to be 0.6,0.2,and 10,respectively.Plasticity Model.A cyclic plasticity model developed by Jiang and Sehitoglu ͓24,25͔was used in the FE simulations for the self-loosening of bolted joints.The basic mathematical equations in the plasticity theory are listed in Table 1.The major reason to adopt the plasticity model is due to its capability of describing the general cyclic material behavior including cyclic strain ratcheting and stress relaxation that occur in a bolted joint.A detailed de-scription of the plasticity model and the determination of material constants can be found in references ͓24,25͔.The plasticity model was implemented into the general-purpose finite element package ABAQUS ͓22͔through the user-defined subroutine UMAT.A backward Euler algorithm was used in an explicit stress update algorithm.The algorithm reduced the plas-ticity model into a nonlinear equation that can be solved by New-ton’s method.The corresponding consistent tangent operator was derived for the global equilibrium iteration,which ensured the quadratic convergence of the global Newton-Raphson equilibrium iteration.Detailed formulation for the implementation of the plas-ticity theory into the FE code can be found in Ref.͓26͔.The material properties of 1070steel were obtained through uniaxial strain-controlled experiments on smooth round speci-mens.The material for the testing specimens had an identical heat treatment as the bolts used in the self-loosening experiments.The material constants obtained from the cyclic deformationexperi-Fig.5Finite element mesh model;…a …Complete model,…b …Enlarged view near the first threadTable 1Plasticity model used in the finite element simulationYield Functionf ϭ͑S ˜Ϫ␣˜͒:͑S ˜Ϫ␣˜͒Ϫ2k 2ϭ0S ˜ϭdeviatoric stress␣˜ϭbackstress k ϭyield stress in shear Flow Lawd ˜pϭ1h ͗dS ˜:n ˜͘n˜n ˜ϭnormal of yield surfaceh ϭplastic modulus ˜p ϭplastic strainHardeningRule␣˜ϭ͚i ϭ1M␣˜͑i ͒d ␣˜͑i ͒ϭc ͑i ͒r ͑i ͒ͩn ˜Ϫͩʈ␣˜͑i ͒ʈr ͑i ͒ͪ͑i ͒ϩ1␣˜͑i ͒ʈ␣˜͑i ͒ʈͪdp͑i ϭ1,2,...,M ͒␣˜(i )ϭi th backstress part M ϭnumber of backstress parts dp ϭequivalent plastic strain increment c (i ),r (i ),(i )ϭmaterial constantsJournal of Mechanical Design SEPTEMBER 2003,Vol.125Õ521ments on smooth round specimens were used in the cyclic plas-ticity model.They are listed in Table ponents other than the bolt were found to deform elastically and the elastic-plastic material properties for these components were not needed.Preload.Preloading the bolted joint was simulated by apply-ing a temperature to the upper plate of the two clamped members.The FE package ABAQUS ͓22͔allows for the use of orthotropic thermal expansion material properties.A thermal expansion coef-ficient for axial direction was non-zero while the thermal expan-sion coefficients in the other two directions were set to be zero.In this way,the material expanded in one direction only,thus simu-lating the tightening process.The level of the preload can be eas-ily adjusted through modifying either the value of the expansion coefficient of the material or the value of the temperature applied.Cyclic Transverse Loading.To simulate the transverse load,the lower part of the bolted joint was fixed.A uniformly distrib-uted pressure or displacement was applied at the left end of the upper plate ͑refer to Fig.5͑a ͒͒.A full cycle of transverse loading was composed of four steps:loading in positive direction to its maximum from zero position,unloading to zero,loading in the opposite direction to its maximum,and returning from minus maximum to the initial zero position.Depending on the loading magnitude,approximately 15to 20loading increments were used for the application of the transverse load in each step.Origin 2000computers in NCSA at the University of Illinois were used for the FE simulations.It took approximately 200CPU hours for the completion of one simulation of 32loading cycles.Finite Element Results.FE simulations were conducted for several loading cases.For each loading case,a total of up to 32transverse loading cycles was simulated after the initial preload wasestablished.Fig.6Axial stress contours during a transverse loading cycle;…a …Upon application of preload …unit:MPa …,…b …After reaching a maximum transverse load …unit:MPa …,…c …After the transverse load reached minus maximum …unit:MPa …,…d …After returning to zero from minus maximum …unit:MPa …Table 2Material constants of 1070steel used in the plasticity modelE ϭ206.8GPa,ϭ0.3,k ϭ130.0MPac (1)ϭ1633.0,c (2)ϭ493.4,c (3)ϭ149.1,c (4)ϭ45.0,c (5)ϭ13.6r (1)ϭ85.4MPa,r (2)ϭ76.6MPa,r (3)ϭ88.3MPa,r (4)ϭ96.7MPa,r (5)ϭ141.1MPa (1)ϭ(2)ϭ(3)ϭ(4)ϭ(5)ϭ5.0522ÕVol.125,SEPTEMBER 2003Transactions of the ASMEThe contours for the stress in the axial ͑y ͒direction in the x -y (z ϭ0)cross section in the bolt are shown in Fig.6.The preload was P 0ϭ41.7kN and the transverse displacement ampli-tude was ⌬␦/2ϭ0.46mm.Figure 6͑a ͒depicts the stress distribu-tion after the preload was established in the bolt.It is noted that the stress distribution is symmetric with respect to the y -axis.The maximum axial stress value is 950MPa and it occurs in the first engaged thread root.Plastic deformation can be observed near the thread roots due to stress concentrations.After the transverse load was applied to its maximum in the x direction,the axial stress distribution was shown in Fig.6͑b ͒.This picture reveals that the bolt was subjected to a combined axial and bending load and the bending moment was introduced by the transverse loading.The maximum axial stress occurs on the first engaged thread root with a value of 1090MPa and the equivalent von Mises stress at this point was found to be far beyond the yield stress of 1070steel.Figure 6͑c ͒illustrates the axial stress distribution over the x -y plane after the transverse load was applied in the opposite x di-rection to its maximum.Figure 6͑d ͒shows the axial stress distri-bution after the transverse load was released to zero.A loading cycle was completed at this point.The material near the root of the first engaged thread in the bolt experienced the largest cyclic plasticity in the bolt and the stresses and strains in this area varied with increasing number of loading cycles.Figure 7shows the stress-strain hysteresis loops obtained for the material point at the root of the first engaged thread in the bolt.Clearly,both stress relaxation and cyclic strain ratcheting occurred in this area.The axial stress in this particular location kept decreasing while the axial strain at the same material point increased with increasing number of transverse loading cycles.The result of the cyclic plasticity in the small area near the roots of the engaged threads is the redistribution of the stresses with time.Figure 8exhibits the variation of the axial stress distribution along the central line ͑x-axis ͒on the first engaged thread root cross section for the selected loading cycles.The loading condi-tions were P 0ϭ41.7kN and ⌬␦/2ϭ0.46mm.The axial stress dis-tributions shown in Fig.8were obtained after a full loading cycle was completed,i.e.,the transverse load returned from minus maximum to zero.The redistribution of the axial stress over the cross section introduced by local cyclic plasticity contributes to the reduction of the clamping force.The clamping force can be calculated through the integration of the axial stresses across the cross-section of the bolt.The clamp-ing force variation with the loading cycles can be obtained.Figure 9summarizes the clamping force reduction with increasing load-ing cycles obtained from the FE simulations together with the experimental results.Clearly,the FE results agree well with the general experimental observation on the early stage self-loosening of bolted joints.Influence of Friction.It should be pointed out that in a bolted joint the friction coefficient is not simply the ratio of the transverse load over the clamping force.This is because the trans-verse load needs to overcome the geometric constraint produced by the bolted joint in addition to the friction between the two clamped parts.The geometric constrain of the bolted jointrefersFig.7Axial stress-strain response at the notchrootFig.8Redistribution of axial stress with loadingcyclesFig.9Comparison of FE predictions with experimental clamp-ing forcereductionFig.10Schematic illustration of the transverse load versus displacement relationshipJournal of Mechanical Design SEPTEMBER 2003,Vol.125Õ523to the additional resistance against the relative movement of the two clamped plates provided by the bolt connection.Even if there is no friction between the two clamped plates,a transverse force is needed to translate one plate over the other.A schematic of the hysteresis loop for the transverse load versus the relative displace-ment between the two clamped plates is shown in Fig.10.AB and CD in the figure represent the overall stiffness of the structure when there is no slip.BC and DA correspond to the period when slip occurs.The slopes of BC and AD reflect the geometric con-straint of the bolted joint.If the constraint is minimal,the slopes of BC and AD should be zero.On the other hand,when there is no friction between the two clamped plates,the hysteresis loop shown in Fig.10will be reduced to a line passing through the origin.At B and D,slip is to start.It should be noted that slip could occur in the positive direction when the transverse load is still negative,or in the negative direction when the transverse load is still positive,just as schematically shown in Fig.10.The hys-teresis loop for the relationship between the transverse load and the relative displacement depends on the materials,geometry,de-tailed dimensions of all the components in the joint,and the fric-tions between the two clamped plates.Realistic friction coefficients can be obtained by comparing the curves of the transverse load versus relative displacement of the two clamped parts obtained from an FE simulation and the experi-ments.Shown in Fig.11is a comparison of the FE results with the experimental observations.With a trial-and-error method used in the selection of the coefficients in Eq.͑1͒,the FE results agree well with the experimental observations.The procedure can be used to determine the friction coefficients indirectly.It was noted that the decay coefficient,d c ,in Eq.͑1͒has an insignificant in-fluence on the FE simulation results.The results shown in Fig.3indicate that for the lubricated and non-lubricated cases,self-loosening results were similar when the controlled displacements were identical.This was confirmed by the FE simulations.Shown in Fig.12are the simulation results fora case with a preload of 36kN and a relative displacement am-plitude of 0.3mm.It can be found that the simulation results are very similar when the kinetic friction coefficient ranges from 0.3to 0.8.DiscussionComparing the load-controlled experiments with the displacement-controlled experiments,it can be observed that it is the relative displacement between the two clamped plates that contributes most to the self-loosening.Self-loosening is not sig-nificant when there is no slip between the clamped parts.This is consistent with many reported experimental observations.Effec-tively preventing the clamped parts from slipping can successfully minimize the possibility of significant self-loosening of a bolted joint.Embedment can cause the clamping force reduction.Embed-ment refers to the removal of the high spots and indentation in the contact areas.Plastic deformation and creep are responsible for embedment.It was found ͓27͔that most embedment occurred immediately after the application of the preload.In the current experimental study,the reduction of the clamping force after tight-ening the nut occurred within a period of a few seconds.The maximum reduction of the clamping force was 2%of the preload.No further reduction of clamping force was observed within a few hours after preloading.Creep of the materials can cause the re-duction in clamping force.However,none of the materials used in the bolted joint in the current investigation displays any creep at room temperature.In addition,indentation can be accommodated in the elastic-plastic modeling.The current study reveals that the maximum contact pressure occurs on the contact surfaces of the first engaged thread.The maximum contact pressure is 550MPa.The contact pressure causes an insignificant indentation during the tightening process.The finite element ͑FE ͒simulations indicate that the further indentation of the contact surfaces is minimal during the cyclic transverse loading.It can be therefore con-cluded that embedment is not a significant factor influencing the early stage self-loosening behavior observed in the current investigation.The FE results agree with the experimental observations very well.The theoretical simulations not only capture the significant decrease of clamping force during the first few loading cycles,but also the general tendency of decay in clamping force reduction with increasing loading cycles.The success of the current FE simulations was mainly due to the implementation of a realistic cyclic plasticity model that captures the essential stress relaxation and strain ratcheting behavior of the material.Most existing cyclic plasticity models are not capable of describing the long-term strain ratcheting behavior of a material ͓24,25,28,29͔.1070steel displays stable stress-strain properties with minimal cyclic transient behavior.The bolts used in the experimental in-vestigation were ground so that the residual stresses were insig-nificant.Although more complex material models are available nowadays to deal with such cyclic properties as non-proportional hardening and transient cyclic hardening or softening,the imple-mentation of such cyclic plasticity models into the finite element calculations is still a difficulty.More importantly,the current com-puter power does not allow for a very complex material model to be used to simulate a three-dimensional structure under repeated loading for a number of cycles.A simple material without the involvement of residual stresses facilitated the modeling and has led to the exploration of the major mechanism responsible for the early stage self-loosening.It is noted that most bolts in engineer-ing applications are rolled.The rolling process introduces signifi-cant residual stresses in the threads.The consideration of the re-sidual stresses in the rolled threads will alter the quantitative values of the results.However,the manufacturing processes will not alter the general conclusions made in the current study on the mechanism of early stageself-loosening.Fig.11Comparison of experimental transverse load versus displacement relation with FEpredictionFig.12Influence of friction on FE self-loosening prediction524ÕVol.125,SEPTEMBER 2003Transactions of the ASME。