An estimate of the SN kick velocities for High Mass X-ray Binaries in the SMC

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数学专业英语翻译

第一段翻译(2)：what is the exact value of the number pai?a mathematician made an experiment in order to find his own estimation of the number pai.in his experiment,he used an old bicycle wheel of diameter 63.7cm.he marked the point on the tire where the wheel was touching the ground and he rolled the wheel straight ahead by turning it 20 times.next,he measured the distance traveled by the wheel,which was 39.69 meters.he divided the number 3969 by 20*63.7 and obtained 3.115384615 as an approximation of the number pai.of course,this was just his estimate of the number pai and he was aware that it was not very accurate.数π的精确值是什么？一位数学家做了实验以便找到他自己对数π的估计。

在试验中，他用了一直径63.1厘米的旧自行车轮。

他在车轮接触地面的轮胎上做了标记，而且将车轮向前转动20次。

接下来，他测量了车轮经过的距离，是39.69米。

他用3969除20*63.7得到了数π的近似值3.115384615。

当然，这只是对数π的估计值，并且他也意识到不是很准确。

第二段翻译(5)：one of the first articles which we included in the "History Topics" section archive was on the history of pai.it is a very popular article and has prompted many to ask for a similar article about the number e.there is a great contrast between the historical developments of these two numbers and in many ways writing a history of e is a much harder task than writing one of pai.the number e is,compared to pai,a relative newcomer on the mathematical scene.我们包括在“历史专题”部分档案中的第一篇文章就是历史上的π，这是一篇很流行的文章，也促使许多人想了解下一些有关数e的类似文章。

实用科技英语翻译

I Answer the following quesitions related to EST Translation (3 0’) ( 2 个题)1.What’sthe definit ionof EST (Englishof Science & Technology)?EST (Englishfor Science &Technology or Technical Englishor Scientific English) is a special languagevar iety widely usedinthe fields of science andtechnology. It’sbelievedthatitfirstcame tobeinginthe1950s alongwiththerapiddevelopmentof scienceandtechnology, anditmany researchers andscholarsbegan to conduct investigation of the common features of this special genre including reading comprehension, writing and even translation.2,What are stylistic features of EST?Completely different from other genres such as everyday English, literature English, EST has its own stylistic features due to the specialty in content,field and discourse functions,and partly due to the unique habits of EST writers, which are mostly represented in lexical level and syntactical level.3, What are the general features of CompoundTechnical Terms?A. accuracy (确切性) : accurately reflect the nature of the conceptB. monosemy (单义性) : one sense for one wordC .systematization (系统性):theindividual technical terms ina givenfieldshouldbeina specific levelso as to constitute a common systemD. linguistically correct (语言的正确性) : inaccordancewiththeword-formationinthesamelanguageE. conciseness (简明性) : concise and easy to rememberF. motivation (理据性) : just as the name implies, one can know the meaning of the word.G. stability (稳定性) : stable and unlikely to changeH. productivity (能产性) : onceestablished, itis easy toproducemoreneologisms basedtheoriginalone by means of word-formation4, What are common rules for Technical Term Translation?As such, we should deal with the relationship of the following aspects:A. monosemy vs. conciseness monosemy is the priorityB. motivation vs. accuracy As science knowledge is rather abstract, motivation in translati on is preferredC. stability vs. productivity Productivity is the priorityD. systematization vs. linguistically correctBefore translation of compound technical terms, we should be aware of the nature and traditi on of Chinese word-formation.E. Chinese language trait vs. concisenessAs for the numbers of characters, we prefer to use pair characters (偶数词语) or even 4-chara cter expressions (四字结构) .II. Underline and mark out the themes and rhymes of the following sentences with the capital letters T and R respectively . (10’) ( 2 个题) . Aluminum, though much less strong than steel, can be given a strength approaching that of steel when it is alloyed with small quantities of copper, manganese and magnesium, and subje cted to hot treatment processes.Parallel ：T-R1+R2+R 3… Aluminum, though much less strong than steel, can be given a strengt h approaching that of steel when it is alloyed with small quantities of copper, manganese and ma gnesium, and subjected to hot treatment processes.Each cylinder therefore is encased in a water jacket, which forms part of a circuit through which water is pumped continuously, and cooled by means of air drawn in from the outside atm osphere by large rotary fans, worked off the main crankshaft, or in the large diesel-electric locom otives, by auxiliary motors.3.We, the authors having handled a variety of metals and alloys for over forty years, can reassure those following (Theme) that there is still much scope for craft and ingenuity in metallurgy,by man still call for intensive scientific of metals which are properties e 2) of of the many used despite the fact that great strides have been made in it as a science during the past seventy year s,(Rheme 1) and also that real fundamental understanding(Theme 1) and valid explanations (Themwork (Rheme). (Rheme 2)III.Improve the following translation.As for the first sentence you should provide your impro ved English translation and as for the second sentence you should provide the improved Chinese one. (10’) ( 2 个题).活塞与气缸的配合问题，对发动机的使用寿命影响极大。

The

Under consideration for publication in J. Fluid Mech.
ห้องสมุดไป่ตู้
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The role of unsteadiness in direct initiation of gaseous detonations
By C H R I S A. E C K E T T, J A M E S J. Q U I R K† A N D J O S E P H E. S H E P H E R D‡
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C. A. Eckett, J. J. Quirk and J. E. Shepherd
detonation transition (DDT). The main variable believed to control the success or failure of direct initiation is the magnitude of the initial energy release, provided the energy deposition is suﬃciently fast and the igniter suﬃciently small. Experiments suggest that for a given combustible gas mixture at given uniform premixed initial conditions, the energy release must be above a certain level, known as the critical energy, to successfully initiate a detonation. The same arguments apply for direct initia

专业英语四级-71_真题-无答案

专业英语四级-71(总分100,考试时间90分钟)READING COMPREHENSIONTEXT AIn a recent book entitledThe Psychic Life of Insects, Professor Bouvier says that we must be careful not to credit the little winged fellow with intelligence when they behave in what seems like an intelligent manner. They may be only reacting. I would like to confront the Professor with an instance of reasoning power on the part of an insect which cannot be explained away in any other manner.During the summer, while I was at work on my doctoral thesis, we kept a female wasp at our cottage. It was more like a child of our own than a wasp, except that it looked more like a wasp than a child of our own. That was one of the ways we told the difference.It was still a young wasp when we got it and for some time we could not get it to eat or drink, it was so shy. Since it was female, we decided to call it Miriam.One evening I had been working late in my laboratory fooling around with some gin and other chemicals, and in leaving the room I tripped over a line of diamonds which someone had left lying on the floor and knocked over my card index which contained the names and addresses of all the larvae worth knowing in North American. The cards went everywhere.I was too tired to stop to pick them that night. As I went, however, I noticed the wasp was flying about in circles over the scattered cards. "Maybe Miriam will pick them up", I said half laughingly to myself, never thinking for one moment that such would be the case.When I came down the next morning Miriam was still asleep in her box, evidently tired out. And well she might have been. For there on the floor lay the cards scattered all about just as I had left them the night before. The faithful little insect had buzzed about all night trying to come to some decision about picking them up and arranging them in the boxes for me, and then had figured out for herself that, as she knew practically nothing on larvae of any sort except wasp larvae, she would probably make more of a mess of rearranging them than if she had left them on the floor for me to fix. It was just too much for her to tackle, and discouraged, she went over and lay down in her box, where she cried herself to sleep.1. Professor Bouvier most probably agrees that ______.A. insects" reasoning power has nothing to do with intelligenceB. wasps can only behave in an instinctive mannerC. wasps are different from other winged creaturesD. the issue of insects" intelligence need further research2. The author took the wasp Miriam to his cottage because ______.A. Miriam was treated like a childB. Miriam was the pet of the familyC. the author was studying insects for his doctoral thesisD. the author wanted to prove that insects have intelligence3. When the card index scattered on the floor, the author ______.A. decided to pick them up the next morningB. believed Miriam would pick them upC. didn"t understand why Miriam flew about over the cardsD. found it ridiculous that Miriam would pick them up4. By saying "And well she might have been" (Para. 6), the author thinks that Miriam was ______.A. exhaustedB. intelligentC. energeticD. depressed5. Which of the following statements was based on facts rather than on the author"s pure thinking?A. Miriam cried herself to sleep.B. Miriam had buzzed about all night.C. Miriam could only tell wasp larvae.D. Miriam had left the cards on the floor.An "apple polisher" is one who gives gifts to win friendship or special treatment. It is not exactly a bribe, but is close to it.All sorts of people are apple polishers, including politicians and people in high offices—just about everybody. Oliver Cromwell, the great English leader, offered many gifts to win the support of George Fox and his party, but failed.There are other phrases meaning the same thing as "apple-polishing"—"soft-soaping" or "buttering-up". A gift is just one way to "soft-soap" somebody, or to "butter him up". Another that is just as effective is flattery, giving someone high praise-telling him how good he looks, or how well he speaks, or how talented and wise he is.Endless are the ways of flattery. Who does not love to hear it? Only an unusual man can resist the thrill of being told how wonderful he is. In truth, flattery is good medicine for most of us, who get so little of it.We need it to be more sure of ourselves. It cannot hurt unless we get carried away by it. But if we just lap it up for its food value and nourishment, as a cat laps up milk, then we can still remain true to ourselves.Sometimes, however, flattery will get you nothing from one who has had too much of it. A good example is the famous 12th century legend of King Canute of Denmark and England. The king got tired of listening to the endless sickening flattery of his courtiers. They overpraised him to the skies, as a man of limitless might.He decided to teach them a lesson. He took them to the seashore and sat down. Then he ordered the waves to **ing in. The tide was too busy to listen to him. The king was satisfied. This might show his followers how weak his power.6. Which of the following activities has nothing to do with "apple-polishing"?A. A boy tells his girlfriend how pretty she looks.B. An employee tells her boss how good he is at management.C. A knight is said to be of limitless power by his followers.D. A teacher praises her students for their talent and wisdom.7. What does the writer want to prove with Cromwell"s example?A. Everybody can be an apple-polisher.B. Cromwell was not a good apple-polisher.C. George Fox and his party were not apple-polishers.D. There are people who don"t like being apple-polished.8. Which of the following statements about flattery is true according to the writer?A. Too much flattery can carry us away.B. Flattery is too empty to do people any good.C. Flattery can get you nothing but excessive pride.D. Flattery is one of the ways to apple-polish people.9. King Canute of Denmark and England took his followers to the seashore because ______.A. he was sick of his normal lifeB. he disliked being overpraised any moreC. he wanted them to realize how wise he wasD. he wanted them to see how weak he was as a king10. The author thinks that flattery can do good to those who ______.A. are politicians or in high officesB. lack confidenceC. are really excellentD. think highly of themselvesTEXT BAs medical evidence mounts that we are indeed what we eat, consuming a healthier diet has become almost a national passion in the United States. The food-for-fitness phenomenon began in the late "70s when a U.S. **mittee on nutrition reached grim conclusion that six out of the ten leading causes of death—such as heart disease, cancer, and stroke—might be linked to diet. The government issued dietary guidelines advising Americans to eat a variety of foods, maintain proper weight, and limit intake of fat, salt, sugar, and alcohol.For most Americans, what to eat is a matter of personal choice, rather than one of supply. An excellent nationwide food distribution system assures that fresh produce is readily available in all parts of the country, regardless of the season. Taking advantage of this abundance, many people are forsaking traditional meat-and- potatoes and in favor of lighter meals of salads, fruits, and vegetables.The single most dramatic change in the American diet has been a reduction in consumption of animal fat, which is thought to increase the risk of heart disease and may contribute to the high U.S. incidence of breast and colon cancer. Margarine and vegetable oils have replaced butter and lard in many homes, and half of all milk now drunk in the United States is low-fat. Fish and poultry are increasingly popular sources of protein as consumption of red meat declines. The food industry has responded to concern about fat by producing leaner cuts of meat and cholesterol-free substitutes for eggs.One of the most significant trends in the American way of eating is the healthful change in restaurant food. "One of every two meals in the United States is eaten outside the home," says Donna Watson, president of the American Dietetic Association. "Restaurants are making special efforts to provide low-fat, low-salt, and low-calorie items." Salad bars, loaded with fresh greens and raw fruits and vegetables, are found everywhere, even along-side the burgers and French fries in fast-food restaurants.Most important, the focus on prudent diet has led to an unprecedented national quest for a healthier life style. Americans are smoking less, exercising more, and experimenting with new ways to conquer stress. Eating sensibly, they have discovered, is only one important route to good health.1. It is suggested in the dietary guidelines that ______.A. 60% leading causes of death might be linked to dietB. fat and alcohol should be taken as little as possibleC. eating diverse foods helps maintain proper weightD. sugar and salt should be taken in restricted amount2. Many Americans no longer maintain the meat-and-potatoes diet because ______.A. salads, fruits, and vegetables are more easily preparedB. there is a rich supply of diverse foodsC. such diet is not as healthy as salads, fruits and vegetablesD. diverse foods vary with seasons3. Which of the following can be a way to decrease the consumption of animal fat?A. Using less butter when cooking soup.B. Drinking more milk at breakfast.C. Eating more fish or poultry at dinner.D. Having two eggs at most daily.4. What is the author"s attitude towards restaurant food?A. Optimistic.B. Impersonal.C. Enthusiastic.D. Anxious.5. A nationwide pursuit of a sounder life style began when the American realized ______.A. the disadvantages of smokingB. the advantages of exercisingC. the advantages of prudent dietD. the disadvantages of stressWith increasing prosperity, Western European youth is having a fling that is creating distinctive consumer and cultural patterns.The result has been the increasing emergence in Europe of that phenomenon well known in America as the "youth market". This is a market in which enterprising businesses cater to the demands of teenagers and older youths in all their rock mania and pop-art forms.In Western Europe, the youth market may appropriately be said to be in its infancy. In some countries such as Britain, West Germany and France, it is more advanced than in others. Some manifestations of the market, chiefly sociological, have been recorded, but it is only just beginning to be the subject of organized consumer research and promotion.Characteristics of evolving European youth market indicate dissimilarities as well as similarities to the American youth market.The similarities:The market"s basis is essentially the same—more spending power and freedom to use it in the hands of teenagers and older youth. Young consumers also make up an increasingly high proportion of the population.As in the United States, youthful tastes in Europe extend over a similar range of products—records and record players, transistor radios, leather jackets and "way-out", extravagantly styled clothing, cosmetics and soft drinks. Generally it now is difficult to tell in which direction trans-Atlantic teenage influences are flowing.Also, a pattern of conformity dominates Europe youth as in this country, though in Britain the object is to wear clothes that "make the wearer stand out," but also make him "in," such as tight trousers and precisely tailored jackets.Worship and emulation of "idols" in the entertainment field, especially the "pop" singers and other performers is pervasive. There"s also the same exuberance and unpredictability in sudden fad switches. In Paris, buyers of stores catering to the youth market carefully watch what dress is being worn by a popular television teenage singer to be ready for a sudden demand for copies. In Stockholm other followers of teenage fads call the youth market "attractive but irrational."The most obvious differences between the youth market in Europe and that in the United States is in size. In terms of volume and variety sales, the market in Europe is only a shadow of its American counterpart, but it is a growing shadow.6. The "youth market" is created so as to cater for ______.A. distinctive young consumers and their cultureB. the enterprising businesses in Western EuropeC. the increasingly prosperous European economyD. the emergence of an American phenomenon7. What does the author think about the youth market in Britain, West Germany and France?A. It is more developed than that in Western Europe.B. It is still in its preliminary stage of development.C. More sociological phenomena of the market should be recorded.D. Consumer research and promotion should be based on the market.8. The European youth market and the American one are similar in ______.A. the youth"s spending powerB. the youth"s influences on the marketC. the proportion of the youth populationD. the kinds of products that interest the youth9. Which of the following statements is true about the youth in Britain?A. Their dressing is dominated by a pattern of conformity.B. Their clothing is distinct from the other Europe youth"s.C. Tight trousers and precisely tailored clothes are their favorites.D. They are influenced by the conformity derived from the U.S.A.10. The author mentions the Paris and the Stockholm examples to illustrate ______.A. the prosperity of the youth marketB. the craziness of the fashion followersC. the unpredictable change of fashionD. the popularity of the fashion idolsTEXT CLogistically, it worked out best for me to fly east from Boston Logan to London Heathrow to Tokyo Narita, a trip which involves 26 hours of flight time and another 12 of waiting in airports. The time difference from Eastern Standard Time to Japan Time is 13 hours forward. I arrived at Logan at 3am, the 16th of June, and left Narita at 8am on the 18th. I"m afraid I wasn"t really in the best mental shape once I finally landed; my memories of processing through customs are sketchy reconstructions based on small flashes of recollection.What I remember most about that arrival is my luggage. Terry Pratchett and Neil Stephenson have both written amusingly about unwary travellers carrying too much baggage. I have to say that it"s a lot less amusing when it"s happening to you. I had imagined that the process on arrival would be like arrival at an American airport: I would pull the luggage off the conveyor and put it on a trolley, trundle it 100 yards, and load it into some sort of car. Accordingly, I didn"t really consider space or weight: I had two huge bags, each loaded to the 701b flight luggage limit. I had a giant cardboard box containing a full **puter system and two cubic yards of packing peanuts. I had another big box containing my bicycle. I was moving, after all, and this seemed a fairly minimal set of things to take for a stay of at least a year.The gentleman who **pany sent to greet me at the airport was cheerful about my situation. A lot of people who he met, he told me, had similar situations. There was a shipping office conveniently located within the airport which could freight whichever items weren"t immediately necessary to the apartment which would become mine. It didn"t matter that the larger box had gone squishy and organic, and was slowly leaking peanuts; the **panies were extremely talented here. In fact, he was very nice about everything—but he never once offered to help carry anything.I shipped off my cardboard boxes, but I hadn"t planned for a situation in which it would matter how much luggage I had, so necessary items were scattered between the two bags. We left for **pany guest house where I"d be staying: the cheerful semi-**pany man leading, and me following with 701b in each hand. We rode the train toward Chiba, with each of my bags taking up a pair of seats, and the two of us standing between them. We left the train station and started walking to the house. It wasn"t too far, he told me: less than two kilometers. We had the advantage of good weather, too: the temperature wasn"t expected to break 30 degrees, and the humidity was only 70.**pany man had it easy: he wasn"t carrying anything. As for me, I"ll just say that when you go to experience a foreign land, attempting a 2km walk while carrying 1401b of stuff in the first humidity of summer while exhausted is not the recommended starting point.It"s kind of funny, but I didn"t immediately feel like I was anywhere new. Yes, the roads were narrow, the people were Asian, and the writing was funny, but I"d seen each of those elements before. It wasn"t until the first time I went to get something to eat that I had a really profound understanding that I was in Japan. **pany man told me that I could survive eating prepackaged meals from convenience stores, and showed one to me on the way to the guest house. The first food 1 ate in that country was a strawberry cream sandwich. That sandwich provided my "not in Kansas anymore" moment; it took on a weird significance as my first step in participating in the widespread oddness that is Japanese culture.I slept for 14 hours that night, and woke up at 7am the next morning to a small earthquake. I was now in the Land of the Rising Sun, and those two elements had just cooperated to greet me. It felt good.1. The author found that he had only vague memories about ______.A. how he dealt with his luggageB. how he landed in Narita JapanC. how he passed through the customsD. how he got over the time difference2. The author would most probably describe the experience of unwary travelers with too much luggage other than himself as ______.A. interestingB. ridiculousC. painfulD. pleasing3. When the gentleman greeted the author, ______.A. he took the author"s luggage to the shipping officeB. he told the author he had never expected so much luggageC. he showed the author to the shipping officeD. he refused to help the author with his luggage4. The author didn"t ship off the two bags because ______.A. items in them were of higher valueB. items in them weren"t available in JapanC. they **paratively lighterD. they were of more immediate use5. The author finally realized he was in a foreign country when he ______.A. processed through customsB. ate his first meal in JapanC. got to the guesthouse on foot instead of by taxiD. came to narrow roads and Japanese peopleThe HMS Ontario is one of the most famous shipwrecks and was discovered by two Rochester engineers Jim Kennard, 64, who has spent more than half his life pursuing The HMS Ontario, along with Dan Scoville, 35, a shipwreck diver. They discovered The HMS Ontario deep off the southern shore of Lake Ontario when side-scanning sonar system that Mr. Kennard, a retired Kodak engineer, designed and built himself, showed a picture of something deep in Lake Ontario. The location of the shipwreck had been unknown for 228 years.Experienced shipwreck divers Jim Kennard and Dan Scoville have discovered seven of Lake Ontario"s estimated 500 shipwrecks in the last six years alone. Jim Kennard also designed a microwave-sized remote submersible that they deployed to go down and take the shipwreck"s video. The shipwreck is quite deep in Lake Ontario, so the remote machine with video was very useful."Right away we saw the quarter gallery, the windows in the stem, the cannons," said Jim Kennard. "There was no mistaking. That"s when we started getting excited." The discovery of the ship wreck was confirmed by the HMS Ontario expert Canadian Arthur Britton Smith, who authored the definitive book on the HMS Ontario.The loss of the HMS Ontario, is one of the worst-ever disasters recorded on Lake Ontario. In her time the HMS Ontario was the most-feared ship on the Great Lakes. It was 1780 and the Yankeeswere threatening to storm across Lake Ontario and seize Montreal from the British. But the intimidating 226-ton Ontario--22 cannons, two 80-foot masts, a beamy hull with cargo space for 1000 barrels, was intimidating. On Oct. 31, 1780, she sailed into a storm with around 120 passengers on board and was never seen again. The British tried to keep the news of the ship wreck hush.The HMS Ontario appears to be in perfect shape and the HMS Ontario has aged remarkably well though zebra mussels cover much of the woodwork. Leaning on a 45-degree angle, her masts still jut straight up from her decks where several guns lie upside-down and a brass bell, brass cleats and the stem lantern are perfectly visible. The Seven windows across her stem still have glass. Shipwrecks in cold freshwater are well preserved, that is why great lakes shipwrecks are prized. At 500 feet deep, where the HMS Ontario lies, there is no light and no oxygen to speed up the decomposition, and little marine life to feed on the wood.There was no evidence of the roughly 113 Canadian men, women, children and American prisoners who went down with the ship—the passengers—mostly Canadian soldiers from the 34th regiment—were never found. Nobody knows for sure how many passengers perished on the Ontario; the British kept their prisoner counts secret.Out of worries over looting, Mr. Jim Kennard and Mr. Dan Scoville are not revealing the HMS Ontario"s location. The vessel sits in water up to 500 feet deep and cannot be reached by anyone other than experienced divers. It is not believed to have any shipwreck treasure on it as was reported other than a few shipwreck coins that belonged to the passengers.Kennard said he and his partner have gathered enough ship wreck video of the ship that it will not be necessary to return to the site. He added that they hope to make a documentary about the discovery with the video of the shipwreck.The Great Lakes host many shipwreck locations and there are an estimated 4,700 shipwrecks in total, of which 500 are in Lake Ontario. Freshwater shipwrecks are famous for their preservation of the vessels and make popular diving spots.6. The two discoverers of the HMS Ontario saw its video ______.A. with the help of a scanning sonar systemB. with the help of a remote submersibleC. on an Ontario TV channelD. on a DVD about history7. The HMS Ontario was most probably a ______.A. cruise linerB. fishing boatC. war shipD. cargo ship8. Great Lakes shipwrecks are highly valued because ______.A. they are well protected against decompositionB. they need to be explored with high technologyC. they are of great use to the research of historyD. they have much well-preserved treasure on board9. What is NOT true about the HMS Ontario?A. No trace of human being has been found in the shipwreck.B. The passengers were evacuated before the ship sank.C. The ship used to belong to the British Navy.D. There was not much treasure on the ship.10. What will Jim and Dan do with the HMS Ontario shipwreck?A. They will take it to the surface when they get more financial fund.B. They will make it a popular diving spot.C. They will reveal the location of the ship when the video is released.D. They will leave the shipwreck where it is.11. Which paragraph is NOT about the finding of Jim and Dan?A. Paragraph 3.B. Paragraph 4.C. Paragraph 5.D. Paragraph 6.TEXT DThe 35-year-old Beijing woman is watching an ad showing a giant television made by the **pany Haler. A stream of introduction for the television floats in and out of view, including one about receiving electronic mail over the tube. A suffer tides the waves between skyscrapers, his wash leaving an "@" in the water. The ad is "too direct", she tells an interviewer. "There is this guy talking, telling me all about the product, showing me some images. We get it—but we don"t like it."Since a Shanghai television station aired China"s first TV commercial in 1979, most have been the plain, straightforward, tell-the-name-of-the-product-and-what-it-does kind. Those started disappearing in the U.S. in the late 1960s in favor of more subtle pitches using irony and humor. Now a study says **mercials don"t have to talk down to consumers anymore either—at least the one-third of them living in China"s prosperous cities, and who most interest advertisers.Even the Western agencies that win awards elsewhere for hip, **mercials usually keep it simple in China. After all this country only began flirting with capitalism 20 years ago and is fairly new to advertising. And to consumer culture, too. China is still a developing nation where an income of just $2,000 a year qualifies an urban household as middle-class. On the other hand, city people who once aspired to own the "big three"—a television, refrigerator and washing machine—have already moved up to DVD players and mobile phones. And with a population of 1.3 billion, the world"s largest, China is a huge market. That is why the world"s **panies, from Coca-Cola to Procter & Gamble, are battling it out in China. Advertisers spent more than $500 million dollars through the first half of the year, estimates market researcher, making China the largest advertising market in Asia after Japan.The prevailing view of many of those advertisers and their agencies is that the Chinese don"t yet get clever or subtle advertising and they prefer a straightforward ad with lots of information. But the April survey of almost 500 people in five China"s largest cities discovered "a savvy urban population, tired of a diet of "boring" ads and hungry to be treated as the sophisticated decision-makers they are." In short, the Chinese appreciation of what makes a good ad is no different from their counterparts anywhere else in the world.1. The 35-year-old woman was dissatisfied with the Haier ad because ______.A. there is too much misleading information about itB. its function is too similar to that of a computerC. its advertisement was too difficult to understandD. it has been advertised in a simple-minded way2. By saying that "**mercials don"t have to talk down to consumers", the author suggests that ______.A. the plain and straight-forward way of advertising should be abolishedB. it is not necessary to take up irony and humor in advertisementC. advertisers are more interested in how to attract the high-class citizensD. those disappearing in the U.S. may be just appropriate in China3. What can we learn about the consumer culture in China?A. It is not as complicated as that outside China.B. It has not been fully understood yet.C. Its influence on advertising is still limited.D. It is one of the most important products of capitalism.4. The author will agree that China"s middle-class households ______.A. are interested in inventive ads instead of simple onesB. earn less than the overseas middle-class householdsC. contribute most to China"s consumer marketD. no longer aspire to own the "the big three"5. The passage mainly intends to discuss ______.A. the most effective ways of advertising in ChinaB. the development of advertising styles in ChinaC. consumers" view on the ads in ChinaD. a misconception on the ads in ChinaSome products respond to consumers" needs; others, like Sony"s airboard, seek to create them. Like sending e-mails from the pool, or curling up in bed with your favorite sitcom. This futuristic **bines the functions of a television, a DVD player and the Internet into a portable tablet the size of a place mat. If it catches on, it could change the concept of being digital at home.At 1.5kg, the airboard is light enough to carry anywhere in the house, and can send and receive data wirelessly from a base station hooked up to home-entertainment equipment. A 10.4-inc. (26-cm) LCD screen delivers vivid moving images or can serve as a digital photo album, and a touch-panel display eliminates the need for a keyboard. Sony, which began selling the device in Japan late last year, praises it as the Walkman of the information age. "It is amazing," **pany president Kunitake Ando, who loftily describes the device as a gateway connecting the home to the outside world and eventually linking all appliances within. "The wireless environment will become **mon pretty soon."I tried out the airboard in my Tokyo apartment, and I have to admit: it"s way cool. First of all, airboarding is easy. I didn"t crack the instruction manual once to get the thing set up—and this is from someone who has trouble finding the "record" button on the VCR. Relaxing on my balcony, I could call up the airboard"s on-screen remote control and start playing video. By pressing another button, I could Net surf or check my e-mail account, while a split screen let me simultaneously watch my movie. The airboard"s base station—the size of a shoe box—doubles as a stand and battery charger. There is a slot for inserting a Sony memory stick, the gum-stick-sized cassette used to store photos and other digital files.But the airboard is not for everybody. At $1,065, it costs as much as a laptop but isn"t meant for **puting. Checking e-mail is easy, but a 56-kbps modem makes for pretty slow surfing. The touch panel is fine for sending quick messages, but pushing the on-screen buttons is tedious for anything。

2.4-Viscosity

2.4 ViscosityThe property of viscosity is important to engineering practice because it leads to significant energy loss when moving fluids contact a solid boundary, or when different zones of fluid are flowing at different velocities. Viscosity, µViscosity (also called dynamic viscosity, or absolute viscosity) is a measure of a fluid's resistance to deformation under shear stress. For example, crude oil has a higher resistance to shear than does water. Crude oil will pour more slowly than water from an identical beaker held at the same angle. This relative slowness of the oil implies a low “speed” or rate of strain. The symbol used to represent viscosity is µ (mu). To understand the physics of viscosity, it is useful to refer back to solid mechanics and the concepts of shear stress and shear strain. Shear stress, τ, tau, is the ratio of force/area on a surface when the force is aligned parallel to the area. Shear strain is a change in an interior angle of a cubical element, ∆φ, that was originally a right angle. The shear stress on a material element in solid mechanics is proportional to the strain, and the constant of proportionality is the shear modulus:In fluid flow, however, the shear stress on a fluid element is proportional to the rate (speed) of strain, and the constant of proportionality is the viscosity:Figure 2.1 depicts an initially rectangular element in a parallel flow field. As the element moves downstream, a shear force on the top of the element (and a corresponding shear stress in the opposite direction on the bottom of the element) causes the top surface to move faster (with velocity V + ∆V) than the bottom (at velocity V). The forward and rearward edges become inclined at an angle ∆φ with respect to the vertical. The rate at which ∆φchanges with time, given by φ, is the rate of strain, and can be related to the velocity difference between the two surfaces. In time (∆t) the upper surface moves (V + ∆V)∆t while the bottom surface moves V∆t, so the net difference is ∆V∆t. The strain ∆φ iswhere ∆y is the distance between the two surfaces. The rate of strain isIn the limit as ∆t → 0 and ∆y → 0, the rate of strain is related to the velocity gradient by φ = dV/dy, so the shear stress (shear force per unit area) is(2.6)Figure 2.1 Depiction of strain caused by a shear stress (force per area) in a fluid. The rate of strain is the rate of change of the interior angle of the original rectangle.For strain in flow near a wall, as shown in Fig. 2.2, the term dV/dy represents the velocity gradient (or change of velocity with distance from the wall), where V is the fluid velocity and y is the distance measured from the wall. The velocity distribution shown is characteristic of flow next to a stationary solid boundary, such as fluid flowing through a pipe. Several observations relating to this figure will help one to appreciate the interaction between viscosity and velocity distribution. First, the velocity gradient at the boundary is finite. The curve of velocity variation cannot be tangent to the boundary because this would imply an infinite velocity gradient and, in turn, an infinite shear stress, which is impossible. Second, a velocity gradient that becomes less steep (dV/dy becomes smaller) with distance from the boundary has a maximum shear stress at the boundary, and the shear stress decreases with distance from the boundary. Also note that the velocity of the fluid is zero at the stationary boundary. That is, at the boundary surface the fluid has the velocity of the boundary—no slip occurs between the fluid and the boundary. This is referred to as the no-slip condition. The no-slip condition is characteristic of all flows used in this text.Figure 2.2 Velocity distribution next to a boundary.From Eq. 2.6 it can be seen that the viscosity µ is related to the shear stress and velocity gradient.(2.7)A common unit of viscosity is the poise, which is 1 dyne-s/cm2 or 0.1 N · s/m2. The viscosity of water at 20°C is one centipoise (10-2 poise) or 10-3 N · s/m2. The unit of viscosity in the traditional system is lbf · s/ft2.Kinematic Viscosity, νMany equations of fluid mechanics include the ratio µ/ρ. Because it occurs so frequently, this ratio has been given the special name kinematic viscosity. The symbol used to identify kinematic viscosity is ν (nu). Units of kinematic viscosity ν are m2/s, as shown.(2.8) The units for kinematic viscosity in the traditional system are ft2/s.Temperature DependencyThe effect of temperature on viscosity is different for liquids and gases. The viscosity of liquids decreases as the temperature increases, whereas the viscosity of gases increases with increasing temperature; this trend is also true for kinematic viscosity (see Fig. 2.3 and Figs. A.2 and A.3).Figure 2.3 Kinematic viscosity for air and crude oil.To understand the mechanisms responsible for an increase in temperature that causes a decrease in viscosity in a liquid, it is helpful to rely on an approximate theory that has been developed to explained the observed trends 1. The molecules in a liquid form a lattice-like structure with “holes” where there are no molecules, as shown in Fig. 2.4. Even when the liquid is at rest, the molecules are in constant motion, but confined to cells, or “cages.”The cage or lattice structure is caused by attractive forces between the molecules. The cages may be thought of as energy barriers. When the liquid is subjected to a rate of strain and thus caused to move, as shown in Fig. 2.4, there is a shear stress, τ, imposed by one layer on another in the fluid. This force/area assists a molecule in overcoming the energy barrier, and it can move into the next hole. The magnitude of these energy barriers is related to viscosity, or resistance to shear deformation. At a higher temperature the size of the energy barrier is smaller, and it is easier for molecules to make the jump, so that the net effect is less resistance to deformation under shear. Thus, an increase in temperature causes a decrease in viscosity for liquids.Figure 2.4 Visualization of molecules in a liquid.An equation for the variation of liquid viscosity with temperature is(2.9) where C and b are empirical constants that require viscosity data at two temperatures for evaluation. This equation should be used primarily for data interpolation. The variation of viscosity (dynamic and kinematic) for other fluids is given in Figs. A.2 and A.3.As compared to liquids, gases do not have zones or cages to which molecules are confined by intermolecular bonding. Gas molecules are always undergoing random motion. If this random motion of molecules is superimposed upon two layers of gas, where the top layer is moving faster than the bottom layer, periodically a gas molecule will randomly move from one layer to the other. This behavior of a molecule in a low-density gas is analogous to people jumping back and forth between two conveyor belts moving at different speeds as shown in Fig. 2.5. When people jump from the high-speed belt to the low-speed belt, a restraining (or braking) force has to be applied to slow the person down (analagous to viscosity). If the people are heavier, or are moving faster, a greater braking force must be applied. This analogy also applies for gas molecules translating between fluid layers where a shear force is needed to maintain the layer speeds. As the gas temperature increases, more of the molecules will be making random jumps. Just as the jumping person causes a braking action on the belt, highly mobile gas molecules have momentum, which must be resisted by the layer to which the molecules jump. Therefore, as the temperature increases, the viscosity, or resistance to shear, also increases.Figure 2.5 Analogy of people moving between conveyor belts and gas molecules translating between fluid layers.EXAMPLE 2.2 CALCULATI G VISCOSITY OF LIQUID AS A FU CTIO OF TEMPERATUREThe dynamic viscosity of water at 20°C is 1.00 × 10-3 N · s/m2, and the viscosity at 40°C is6.53 × 10-4 N · s/m2.Using Eq. 2.9, estimate the viscosity at 30°C.Problem DefinitionSituation: Viscosity of water is specified at two temperatures.Find: The viscosity at 30°C by interpolation.Properties:(a) Water at 20°C, µ = 1.00 × 10-3 N · s/m2.(b) Water at 40°C, µ = 6.53 × 10-4 N · s/m2.Plan1. Linearize Eq.2.9 by taking the logarithm.2. Interpolate between the two known values of viscosity.3. Solve for ln C and b in this linear set of equations.4. Change back to exponential equation, and solve for µ at 30°C.Solution1. Logarithm of Eq.2.92. Interpolation3. Solution for ln C and b4. Substitution back in exponential equationAt 30°CReviewNote: This value differs by 1% from the reported value in Table A.5, but provides a much better estimate than would be obtained by arithmetically averaging two values on the table. EXAMPLE 2.3 MODELI G A BOARD SLIDI G O A LIQUID LAYERA board 1 m by 1 m that weighs 25 N slides down an inclined ramp (slope = 20°) with a velocity of2.0 cm/s. The board is separated from the ramp by a thin film of oil with a viscosity of 0.05 N · s/m2.Neglecting edge effects, calculate the space between the board and the ramp.Problem DefinitionSituation: A board is sliding down a ramp, on a thin film of oil.Find: Space (in m) between the board and the ramp.Assumptions: A linear velocity distribution in the oil.Properties: Oil, µ = 0.05 N · s/m2.Sketch:Plan1. Draw a free body diagram of the board, as shown in “sketch.”· For a constant sliding velocity, the resisting shear force is equal to the component ofweight parallel to the inclined ramp.· Relate shear force to viscosity and velocity distribution.2. With a linear velocity distribution, dV/dy can everywhere be expressed as ∆V/∆y, where ∆V isthe velocity of the board, and ∆y is the space between the board and the ramp.3. Solve for ∆y.Solution1. Freebody analysis2. Substitution of dV/dy as ∆V/∆y3. Solution for ∆yAn estimate for the variation of gas viscosity with temperature is Sutherland's equation,(2.10) where µ0 is the viscosity at temperature T0, and S is Sutherland's constant. All temperatures are absolute. Sutherland's constant for air is 111 K; values for other gases are given in Table A.2. Using Sutherland's equation for air yields viscosities with an accuracy of ±2% for temperatures between 170 K and 1900 K. In general, theeffect of pressure on the viscosity of common gases is minimal for pressures less than 10 atmospheres.ewtonian Versus on- ewtonian FluidsFluids for which the shear stress is directly proportional to the rate of strain are called ewtonian fluids. Because shear stress is directly proportional to the shear strain, dV/dy, a plot relating these variables (see Fig. 2.6) results in a straight line passing through the origin. The slope of this line is the value of the dynamic (absolute) viscosity. For some fluids the shear stress may not be directly proportional to the rate of strain; these are called non- ewtonian fluids. One class of non-Newtonian fluids, shear-thinning fluids, has the interesting property that the ratio of shear stress to shear strain decreases as the shear strain increases (see Fig. 2.6). Some common shear-thinning fluids are toothpaste, catsup, paints, and printer's ink. Fluids for which the viscosity increases with shear rate are shear-thickening fluids. Some examples of these fluids are mixtures of glass particles in water and gypsum-water mixtures. Another type of non-Newtonian fluid, called a Bingham plastic, acts like a solid for small values of shear stress and then behaves as a fluid at higher shear stress. The shear stress versus shear strain rate for a Bingham plastic is also shown in Fig. 2.6. This book will focus on the theory and applications involving Newtonian fluids. For more information on the theory of flow of non-Newtonian fluids, see references 2 and 3.Figure 2.6 Shear stress relations for different types of fluids.Copyright © 2009 John Wiley & Sons, Inc. All rights reserved.。

Google开源激光SLAM算法论文原文

I. INTRODUCTION
As-built ﬂoor plans are useful for a variety of applications. Manual surveys to collect this data for building management tasks typically combine computed-aided design (CAD) with laser tape measures. These methods are slow and, by employing human preconceptions of buildings as collections of straight lines, do not always accurately describe the true nature of the space. Using SLAM, it is possible to swiftly and accurately survey buildings of sizes and complexities that would take orders of magnitude longer to survey manually.
1All authors are at Google.
loop closure detection. Some methods focus on improving on the computational cost by matching on extracted features from the laser scans [4]. Other approaches for loop closure detection include histogram-based matching [6], feature detection in scan data,and using machine learning [7].

页岩气文献翻译2

SPE 132371Surface Microseismic Monitoring of Slick-water and Nitrogen FractureStimulations, Arkoma Basin, Oklahoma(表面的微地震监测光滑水面和氮破裂刺激，澳柯玛盆地，奥克拉荷马)Morris Hall, Williams Company, and Jo Ellen Kilpatrick, Microseismic, Inc.（霍尔，威廉姆斯公司，乔·基尔帕特里克，微震，Inc .）Copyright 2010, Society of Petroleum Engineers（版权2010，石油工程师协会）This paper was prepared for presentation at the SPE Unconventional Gas Conference held in Pittsburgh, Pennsylvania, USA, 23–25 February 2010.（本文是介绍了2010年三月23-25日在匹兹堡，宾夕法尼亚，美国举行的非常规天然气会议。

）This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted（提交）by the author(s). （本文介绍了选择一个石油工程师协会项目委员会审查后的信息包含在一个作者提交的抽象概念中）Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s).（本文的内容还没被石油工程师学会审查和作者的更正）The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members.（材料不一定反映石油工程师协会官员或成员的社会地位。

Determination-of-the-viscosity-of-oil 测定油的粘度

P1 Determination of the viscosity of oilIntroductionIn science both liquids and gases are called fluids, because they both can flow. Fluids can flow through tubes, like blood through veins for example, and objects can move through them like aircraft through air. When this happens the moving mass (blood, aircraft) loses energy, so blood has to be continuously pumped by the heart and the aircraft needs an engine or else to glide down, losing potential energy.This energy loss happens in two ways. If velocities are low then the losses are frictional. Close to the moving body the fluid moves with it, but far away it isstationary. As result, layers of liquid slide over each other, like a stack of cards held between your hands being slightly sheared and each card rubbing against its neighbour. If the flow is fast, then turbulent motion of the fluid occurs, giving it kinetic energy. The low speed frictional losses are described by the viscosity , which has dimensions of N m -2 s, or Pa s if you prefer.This experiment finds η for a pump oil by dropping a series of spheres through it. The key equation here is Stokes’ law, which says that the force acting on a sphere with diameter d moving through a fluid with velocity v is3d v ... (1).This theoretical result is accurate so long as the dimensionless Reynolds number R e , given bye dv R (2)is comfortably less than 1, when the losses are dominated by friction. here is the fluid density.Since from equation (1) the drag force on a falling body increases with speed, it will eventually stop the body accelerating. It then falls with a constant speed, called the terminal velocity: for example a human accelerates to a speed of about 120 m.p.h. when falling in air. The downward force due to gravity, allowing for the buoyancy caused by the displaced fluid is volume (σ – ρ)g , where is the density of the body and g the acceleration due to gravity. So writing the volume of a sphere in terms of d , equating the force to the drag given by equation (1) at terminal velocity v T we have336T d g d v , which tidied up gives218T g v d ... (3).If we measure the terminal velocities of a series a spheres with different diameters and plot v T against d 2 we expect a straight line and we can get the value of since the slope is given by equation (3). This is what you will do, using two sorts of spheres, steel and nylon.Measuring the temperatureViscosity is a very temperature dependent property, falling as the temperature rises. There is a digital thermometer immersed in the oil; note its reading.Measuring the densitiesYou will need to measure the density of the oil and of the two sorts of spheres. You have several large balls set aside for their density measurement; do not drop thesein the later measurements. Use the micrometer to measure their diameters, closing the jaws gently by turning the knob the end which will slip as soon as the jaws are shut. Measure the diameters of at least two steel balls. Now put the plastic cup on the scales and press T (the red strip) to zero them. Next weigh together all the large balls. The density of steel is then (6mass)/(d3) divided by the number of balls you weighed.Repeat the above for the large nylon balls.Use the density bottle to find the density of the oil. Weigh it empty, then fill it via the dropper so full that when then stopper is inserted oil flows out of the narrow hole in it. Wipe off any excess and weigh the full bottle. You now know the mass of oil and the bottle has its volume marked on it.Measuring v TBefore you start, have a good look at the oil-filled tube. At the top there is a window that lets you see the oil surface. At the top of the lower window there is a region lit with green light, to help you see the ball as it approaches the measurement region where there are three regions illuminated with blue light, each with a pair of marker lines at the front and at the back. Make sure you are looking at the line and not the edge of the perspex strip it is drawn on. You will need to line up each pair to timethe ball as it crosses each region in turn. The distance between the top and centre lines is 0.25 m as is the distance from centre to bottom. If the time taken to coverthe upper and the lower 0.25 m is the same within the timing errors then the ball has reached terminal velocity and the analysis presented above holds.The timer first needs putting into “lap” mode using the blue button. Leave it like this throughout. When the ball crosses the upper line (use its leading edge or its trailing edge, but do so consistently), press the green button to start timing. As the ball crosses the centre line, press the red button. Finally, as it crosses the lower line press the green button again. At this point the timer shows the time from top to centre, t1 say. Record this, then press the red button to get the centre to bottom time t2. You might want to practise this a few times against a watch before you start measure the spheres, using different intervals so you are sure you know which is which.Pick up the balls with tweezers (this may be easier once the tweezers have oil on them) and release the balls from just below the oil surface and as close to the tube centre as possible.You will notice a near-vertical wire in the oil. This goes to a recovery cup which is only for the lab technician’s use. Before the experiment this wire will have been arranged close to the tube wall; do not move it during the experiment as it might then get in the path of the falling spheres.Nylon and steel spheresThere are 4 sizes of each kind of ball. You may assume the diameters are given by the labels. It is best to measure the drop times for the steel set first and then the nylon. For each set, measure t1 and t2for two balls of each size. If for each member of the pair t1 and t2 are equal then you have reached terminal velocity; if t2 is the same for both drops you can take the average and calculate v T for that size.The nylon balls travel more slowly as their density is closer to that of the oil than for the steel balls. The smallest balls take a long time to travel between the surface window and the lower one, and you will need to be patient whilst this happens. The green lighting is there to help you spot the ball when it reappears.Then plot separate two graphs, one for the steel balls and one for the nylon set. v T should be on the vertical axis and d2 on the horizontal one. Get a value of the viscosity from each of them. Estimate the errors using the regression tool on Excel. Are the viscosities the same within the uncertainties? They should be of course, since the viscosity is a property of the oil and not the spheres.If they are not, which ball-bearing material gives the greater value and which set is on average larger? Think about what the fluid would do if you dropped a very large sphere, not much smaller than the tube. The oil would have to squeeze between the wall and the ball, which would fall more slowly than in a much larger tube, appearing to have a larger viscosity. Does this square with you measurements?Finally use equation (2) above to work out the Reynolds’ number for the largest steel ball and the largest nylon ball of the two sets. If these two have Reynolds numbers comfortably less than one, so will all the rest.TMS13th August 2008。

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a r X i v :a s t r o -p h /0501505v 1 24 J a n 2005Mon.Not.R.Astron.Soc.000,1–4(2002)Printed 2February 2008(MN L A T E X style ﬁle v2.2)An estimate of the SN kick velocities for High Mass X-rayBinaries in the SMCM.J.CoeSchool of Physics and Astronomy,Southampton University,SO171BJ,UKJan 2005ABSTRACTThis work investigates the possible supernova kick velocities imposed on HMXB systems in the Small Magellanic parisons are made between the location of such systems and the locations of young,stellar clusters on the premise that these may represent the birthplace of many of these systems.Measurements of the separation of clusters and HMXBs,and an estimate of the typical lifetimes of these systems,leads to a minimum average space velocity 30km/s.This value is compared to theoretical estimates.Key words:stars:neutron -X-rays:binaries -Magellanic Clouds1INTRODUCTION AND BACKGROUNDThe Be/X-ray systems represent the largest sub-class of massive X-ray binaries.A survey of the literature reveals that of the 115identiﬁed massive X-ray binary pulsar sys-tems (identiﬁed here means exhibiting a coherent X-ray pulse period),most of the systems fall within this Be coun-terpart class of binary.The orbit of the Be star and the com-pact object,presumably a neutron star,is generally wide and eccentric.X-ray outbursts are normally associated with the passage of the neutron star close to the circumstellar disk (Okazaki &Negueruela,2001).A recent review of these sys-tems may be found in Coe (2000).X-ray satellite observations have revealed that the Small Magellanic Cloud (SMC)contains an unexpectedly large number of High Mass X-ray Binaries (HMXB).At the time of writing,47known or probable sources of this type have been identiﬁed in the SMC and they continue to be discov-ered at a rate of about 2-3per year,although only a small fraction of these are active at any one time because of their transient nature.Unusually (compared to the Milky Way and the LMC)all the X-ray binaries so far discovered in the SMC are HMXBs,and equally strangely,only one of the objects is a supergiant system,all the rest are Be/X-ray binaries.2BIRTHPLACES AND KICK VELOCITIESThere is considerable interest in the evolutionary path of High Mass X-ray binary systems (HMXBs),and,in partic-ular,the proper motion of these systems arising from the kick velocity imparted when the neutron star was created.Portegies Zwart (1995)and Van Bever &Vanbeveren (1997)investigate the evolutionary paths such systems might take and invoke kick velocities of the order 100-400km/s.In an investigation into bow shocks around galactic HMXBs Huthoﬀ&Kaper (2002).They then used Hipparcos proper motion data used to derive associated space velocities for Be/X-ray and supergiant systems.From their results,an average value of 48km/s is found for the 7systems that they were able to fully determine the three dimensional mo-tion.Since this is rather lower than the theoretical values it is important to seek other empirical determinations of this motion.This paper addresses what may be learnt about kick velocities by looking at the possible association of HMXBs in the SMC with the nearby young star clusters from which they may have emerged as runaway systems.A review of the properties of the optically (and/or IR)identiﬁed counter-parts to the X-ray pulsars is presented in Coe et al.(2005).In that paper the authors introduce the nomenclature of SXPnnn for the systems,where SXP stands for Small Mag-ellanic Cloud X-ray Pulsar,and the numbers nnn identify the X-ray pulse period in seconds.This simpliﬁed identiﬁ-cation is used here.The SMC cluster data come from an extensive review of the spatial location of stars by Rafelski &Zaritsky (2004).Clusters from this paper are hereafter referred to as RZ clusters.3ANALYSISIt is critical to use the exact position for the SXP sources if distances are to be measured -some have X-ray positional2M.J.CoeFigure1.Distribution of SXPs(shown as crosses)and RZ clus-ters(shown as squares)in the SMC.The rectangular box indicatesthe region used for the random sampling comparison-see text.errors of a few arcminutes.Consequently,only the SXP ob-jects from Coe et al.(2005)which had precise optical coun-terparts were selected for this work.This resulted in an SXPlist of17objects.Firstly the spatial distributions of SXPs and the RZclusters within the SMC were checked to ensure adequatematching coverage around the regions occupied by the SXPobjects.This was found to be satisfactory-see Figure1.The OGLE catalogue of SMC clusters(Pietrzynski et al.,1998)was also considered,but this has restricted coverageand several of the SXP sources fell outside the OGLE region.In order to determine whether the SXP sources mayhave originated from a nearby stellar cluster,the coordi-nates of the SXP objects were compared to those of the RZclusters.For every SXP its position was compared to the lo-cation of all of the RZ clusters and the identiﬁcation of thenearest cluster neighbour obtained.The results from thissearch are presented in Table1.The average distance between the pairs of objects listedin Table1was found to be3.85arcminutes.The histogramof the distances between each SXP source and the nearestRZ cluster is shown in the upper panel of Figure2.Obviously it is important to ensure that the SXP-RZcluster distances are signiﬁcantly closer than a sample ofrandomly distributed points.One way to determine this issimply to just use the RZ cluster data andﬁnd the averagecluster-cluster separation.This gives a value of6.13arcmin-utes.Alternatively,the rectangular region indicated in Fig-ure1was used,and the minimum distance between100,000random points and,in each case,the nearest RZ cluster wasfound.The average value was found to be5.30arcminutesand the corresponding histogram is shown in the lower panelof Figure2.From comparing the two histograms it is clearthat there does exist a much closer connection between SXPsources and RZ clusters than expected randomly.This conclusion may be tested further using either theKolmogorov-Smirnov(K-S)test or the Student t-test toquantify the probability that the two distributions are dis-tinctly diﬀerent.The K-S test gives a probability of9%thatSXP0.92046 3.18SXP3.34150 2.43SXP8.02124 2.87SXP8.8077 4.45SXP9.1360 5.33SXP15.380 3.99SXP59.090 1.40SXP74.7517.38SXP82.472 3.25SXP17268 2.92SXP304133 5.47SXP32366 3.67SXP348150 6.37SXP452130 1.33SXP50496 5.56SXP565101 3.79SXP75657 1.98An estimate of the SN kick velocities for High Mass X-ray Binaries in the SMC3 Figure3.Four examples of theﬁelds around SXP objects showing the nearest RZ cluster.Eachﬁeld is6x6arcminutes in size with North upwards and East to the left.The SXP object is indicated and the associated RZ cluster is shown within the dashed circle.4DISCUSSIONIf the distance of3.85arcminutes is indicative of the dis-tance the SXP pulsar systems have travelled on average since birth,then this value may be used to estimate the kick ve-locity of the systems.To do this oneﬁrst needs to convert the angular separation into a real ing a value of60kpc for the distance to the SMC,then3.85arcmin-utes corresponds to65pc.To compute a velocity one has to have some estimate of the likely travel time of the SXP system since birth.An upper limit on this may be taken from the evolutionary models of Savonije&van den Heuvel (1977)who estimate the maximum possible lifetime of the companion Be star after the creation of the neutron star to be5million years.However,in the same paper they esti-mate the spin down time of the pulsar since creation to be less than600,000years.If we take the lower limit(the spin down time)then the minimum average velocity of the SXP4M.J.Coesystems projected on to the sky is130km/s.This num-ber is signiﬁcantly higher than the numbers presented by other authors,for example van den Heuvel et al.(2000). Those authors interpreted the Hipparcos results for galactic HMXBs(Chevalier&Ilovaisky,1998)in terms of models for kick velocities,and concluded that values around15km/s were more appropriate for such systems.So if,instead,the lifetime number of5million years is used,then transverse velocity components of16km/s are obtained.In either case,assuming the systems are moving in com-pletely random directions compared to our line of sight,then the true average space velocity will be a factor∼2greater, i.e.an average of32km/s in the second case.Finally,the ages of the RZ clusters associated with the SXP sources are of signiﬁcant ing the extinc-tion corrected ages presented in Table2of Rafelski&Zarit-sky(2004)it is possible to determine the mean age to be 130±140Myrs.As can be seen from the histograms pre-sented in their paper,this is very much at the young end of their sample distribution.It therefore reinforces the sug-gestion that the clusters identiﬁed with the SXP sources are very likely to be the correct parent clusters for these objects. 5CONCLUSIONSAs a result of the study of HMXBs in the SMC it has been shown that there exists a convincing link between the these systems and nearby stellar clusters.Accepting this link, leads to a determination of the average space velocity of the systems arising from the SN kick to be∼30km/s.This value is in good agreement with observational and theoreti-cal values.REFERENCESChevalier C.,Ilovaisky S.A.,1998,A&A330,201.Coe M.J.2000in“The Be Phenomenon in Early-Type Stars”,IAU Colloquium175,ASP Conference Proceedings, Vol.214,ed:M.A.Smith H.F.Henrichs.Astronomical So-ciety of the Paciﬁc,p.656.Coe M.J.,Edge W.R.T.E.,Galache J.L.,McBride V.A., 2005,MNRAS(in press).HuthoﬀF.&Kaper L.,2002,A&A383,999.Okazaki A.T.&Negueruela I.,2001A&A377,161. Pietrzynski,G.,Udalski,A.,Kubiak,M.,Szymanski,M., Wozniak,P.,Zebrun,K.,1998AcA48,175.Portegies Zwart S.F.,1995,A&A296,691.Rafelski M.&Zaritsky D.,2004,AJ(in press).Savonije G.J.&van den Heuvel E.P.J.,1997,ApJ214,L19. van den Heuvel E.P.L.,Portegies Zwart S.F.,Bhattacharya D.,Kaper L.,2000,A&A364,563.Van Bever J.,Vanbeveren D.,1997,A&A322,116.This paper has been typeset from a T E X/L A T E Xﬁle prepared by the author.。