An estimate of the SN kick velocities for High Mass X-ray Binaries in the SMC
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
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
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。
机械动力学论文外文翻译文献
机械运动和动力学外文翻译文献英文资料Kinematics and dynamics of machineryOne princple aim of kinemarics is to creat the designed motions of the subject mechanical parts and then mathematically compute the positions, velocities ,and accelerations ,which those motions will creat on the parts. Since ,for most earthbound mechanical systems ,the mass remains essentially constant with time,defining the accelerations as a function of time then also defines the dynamic forces as a function of time. Stress,in turn, will be a function of both applied and inerials forces . since engineering design is charged with creating systems which will not fail during their expected service life,the goal is to keep stresses within acceptable limits for the materials chosen and the environmental conditions encountered. This obvisely requies that all system forces be defined and kept within desired limits. In mechinery , the largest forces encountered are often those due to the dynamics of the machine itself. These dynamic forces are proportional to acceletation, which brings us back to kinematics ,the foundation of mechanical design. Very basic and early decisions in the design process invovling kinematics wii prove troublesome and perform badly.Any mechanical system can be classified according to the number of degree of freedom which it possesses.the systems DOF is equal to the number of independent parameters which are needed to uniquely define its posion in space at any instant of time.A rigid body free to move within a reference frame will ,in the general case, have complex motoin, which is simultaneous combination of rotation and translation. In three-dimensional space , there may be rotation about any axis and also simultaneous translation which can be resoled into componention along three axes, in a plane ,or two-dimentional space ,complex motion becomes a combination of simultaneous along two axes in the plane. For simplicity ,we will limit our present discusstions to the case of planar motion:Pure rotation the body pessesses one point (center of rotation)which has no motion with respect to the stationary frame of reference. All other points on the body describe arcs about that center. A reference line drawn on the body through the center changes only its angulai orientation.Pure translation all points on the body describe parallel paths. A reference line drawn on thebody changes its linear posion but does not change its angular oriention.Complex motion a simulaneous combination of rotion and translationm . any reference line drawn on the body will change both its linear pisition and its angular orientation. Points on the body will travel non-parallel paths ,and there will be , at every instant , a center of rotation , which will continuously change location.Linkages are the bacis building blocks of all mechanisms. All common forms of mechanisms (cams , gears ,belts , chains ) are in fact variations of linkages. Linkages are made up of links and kinematic pairs.A link is an (assumed)rigid body which possesses at least two or more links (at their nodes), which connection allows some motion, or potential motion,between the connected links.The term lower pair is used tohe moving parts .we next want te use newton’s second law to caculate the dynamic forces, but to do so we need to know the masses of all the moving parts which have these known acceletations. These parts do not exit yet ! as with any design in order to make a first pass at the caculation . we will then have to itnerate to better an better solutions as we generate more information.A first estimate of your parts’masses can be obtained by assuming some reasonable shapes and size for all the parts and choosing approriate materials. Then caculate the volume of each part and multipy its volume by material’s mass density (not weight density ) to obtain a first approximation of its mass . these mass values can then be used in Newton’s equation.How will we know whether our chosen sizes and shapes of links are even acceptable, let alone optimal ? unfortunately , we will not know untill we have carried the computations all the way through a complete stress and deflection analysis of the parts. It it often the case ,especially with long , thin elements such as shafts or slender links , that the deflections of the parts, redesign them ,and repeat the force ,stress ,and deflection analysis . design is , unavoidably ,an iterative process .It is also worth nothing that ,unlike a static force situation in which a failed design might be fixed by adding more mass to the part to strenthen it ,to do so in a dynamic force situation can have a deleterious effect . more mass with the same acceleration will generate even higher forces and thus higher stresses ! the machine desiger often need to remove mass (in the right places) form parts in order to reduce the stesses and deflections due to F=ma, thus the designer needs to have a good understanding of both material properties and stess and deflection analysis to properlyshape and size parts for minimum mass while maximzing the strength and stiffness needed to withstand the dynamic forces.One of the primary considerations in designing any machine or strucre is that the strength must be sufficiently greater than the stress to assure both safety and reliability. To assure thatmechanical parts do not fail in service ,it is necessary to learn why they sometimes do fail. Then we shall be able to relate the stresses with the strenths to achieve safety .Ideally, in designing any machine element,the engineer should have at his disposal should have been made on speciments having the same heat treatment ,surface roughness ,and size as the element he prosses to design ;and the tests should be made under exactly the same loading conditions as the part will experience in service . this means that ,if the part is to experience a bending and torsion,it should be tested under combined bending and torsion. Such tests will provide very useful and precise information . they tell the engineer what factor of safety to use and what the reliability is for a given service life .whenever such data are available for design purposes,the engineer can be assure that he is doing the best justified if failure of the part may endanger human life ,or if the part is manufactured in sufficiently large quantities. Automobiles and refrigrerators, for example, have very good reliabilities because the parts are made in such large quantities that they can be thoroughly tested in advance of manufacture , the cost of making these is very low when it is divided by the total number of parts manufactrued.You can now appreciate the following four design categories :(1)failure of the part would endanger human life ,or the part ismade in extremely large quantities ;consequently, an elaborate testingprogram is justified during design .(2)the part is made in large enough quantities so that a moderate serues of tests is feasible.(3)The part is made in such small quantities that testing is not justified at all ; or the design must be completed so rapidlly that there is not enough time for testing.(4) The part has already been designed, manufactured, and tested and found to be unsatisfactory. Analysis is required to understand why the part is unsatisfactory and what to do to improve it .It is with the last three categories that we shall be mostly concerned.this means that the designer will usually have only published values of yield strenth , ultimate strength,and percentage elongation . with this meager information the engieer is expected to design against static and dynamic loads, biaxial and triaxial stress states , high and low temperatures,and large and small parts! The data usually available for design have been obtained from the simple tension test , where the load was applied gradually and the strain given time to develop. Yet these same data must be used in designing parts with complicated dynamic loads applied thousands of times per minute . no wonder machine parts sometimes fail.To sum up, the fundamental problem of the designer is to use the simple tension test data and relate them to the strength of the part , regardless of the stress or the loading situation.It is possible for two metal to have exactly the same strength and hardness, yet one of these metals may have a supeior ability to aborb overloads, because of the property called ductility.Dutility is measured by the percentage elongation which occurs in the material at frature. The usual divding line between ductility and brittleness is 5 percent elongation. Amaterial having less than 5 percent elongation at fracture is said to bebrittle, while one having more is said to be ductile.The elongation of a material is usuallu measured over 50mm gauge length.siece this did not a measure of the actual strain, another method of determining ductility is sometimes used . after the speciman has been fractured, measurements are made of the area of the cross section at the fracture. Ductility can then be expressed as the percentage reduction in cross sectional area.The characteristic of a ductile material which permits it to aborb largeoverloads is an additional safety factot in design. Ductility is also important because it is a measure of that property of a material which permits it to be cold-worked .such operations as bending and drawing are metal-processing operations which require ductile materials.When a materals is to be selected to resist wear , erosion ,or plastic deformaton, hardness is generally the most important property. Several methods of hardness testing are available, depending upon which particular property is most desired. The four hardness numbers in greatest usse are the Brinell, Rockwell,Vickers, and Knoop.Most hardness-testing systems employ a standard load which is applied to a ball or pyramid in contact with the material to be tested. The hardness is an easy property to measure , because the test is nondestructive and test specimens are not required . usually the test can be conducted directly on actual machine element .Virtually all machines contain shafts. The most common shape for shafts is circular and the cross section can be either solid or hollow (hollow shafts can result in weight savings). Rectangular shafts are sometimes used ,as in screw driver bladers ,socket wrenches and control knob stem.A shaft must have adequate torsional strength to transmit torque and not be over stressed. If must also be torsionally stiff enough so that one mounted component does not deviate excessively from its original angular position relative to a second component mounted on the same shaft. Generally speaking,the of length between bearing supports.In addition .the shaft must be able to sustain a combination of bending and torsional loads. Thus an equivalent load must be considered which takes into account both torsion and bending . also ,the allowable stress must contain a factor of safety which includes fatigue, since torsional and bending stress reversals occur.For fiameters less than 3 in ,the usual shaft material is cold-rolled steel containing about 0.4 percent carbon. Shafts ate either cold-rolled or forged in sizes from 3in. to 5 in. for sizes above 5 in. shafts are forged and machined to size . plastic shafts are widely used for light loadapplications . one advantage of using plastic is safty in electrical applications, since plastic is a poor confuctor of electricity.Components such as gears and pulleys are mounted on shafts by means of key. The design of the key and the corresponding keyway in the shaft must be properly evaluated. For example, stress concentrations occur in shafts due to keyways , and the material removed to form the keyway further weakens the shaft.If shafts are run at critical speeds , severe vibrations can occur which can seriously damage a machine .it is important to know the magnitude of these critical speeds so that they can be avoided. As a general rule of thumb , the difference betweem the operating speed and the critical speed should be at least 20 percent.Many shafts are supported by three or more bearings, which means that the problem is statically indeterminate .text on strenth of materials give methods of soving such problems. The design effort should be in keeping with the economics of a given situation , for example , if one line shaft supported by three or more bearings id needed , it probably would be cheaper to make conservative assumptions as to moments and design it as though it were determinate . the extra cost of an oversize shaft may be less than the extra cost of an elaborate design analysis.Another important aspect of shaft design is the method of directly connecting one shaft to another , this is accomplished by devices such as rigid and flexiable couplings.A coupling is a device for connecting the ends of adjacent shafts. In machine construction , couplings are used to effect a semipermanent connection between adjacent rotating shafts , the connection is permanent in the sense that it is not meant to be broken during the useful life of the machinem , but it can be broken and restored in an emergency or when worn parts are replaced.There are several types of shaft couplings, their characteristics depend on the purpose for which they are used , if an exceptionally long shaft is required in a manufacturing plant or a propeller shaft on a ship , it is made in sections that are coupled together with rigid couplings. A common type of rigid coupling consists of two mating radial flanges that are attached by key driven hubs to the ends of adjacent shaft sections and bolted together through the flanges to form a rigid connection. Alignment of the connected shafts in usually effected by means of a rabbet joint on the face of the flanges.In connecting shafts belonging to separate device ( such as an electric motor and a gearbox),precise aligning of the shafts is difficult and a fkexible coupling is used . this coupling connects the shafts in such a way as to minimize the harmful effects of shafts misalignment of loads and to move freely(float) in the axial diection without interfering with one another . flexiable couplings can also serve to reduce the intensity of shock loads and vibrationstransmitted from one shaft to another .中文翻译机械运动和动力学运动学的基本目的是去设计一个机械零件的理想运动，然后再用数学的方法去描绘该零件的位置，速度和加速度，再运用这些参数来设计零件。
29CFR1910
29CFR 1910.132GUIDELINES FOR HAZARD ASSESSMENTAND PERSONAL PROTECTIVE EQUIPMENT SELECTIONNOTE: THE FOLLOWING GUIDELINES ARE PROVIDED ONLY AS A GUIDE TO ASSIST EMPLOYERS AND EMPLOYEES INCOMPLYING WITH THE REQUIREMENTS OF 29CFR 1910.132,AS WELL AS TO PROVIDE OTHER HELPFUL INFORMATION.IT IS NOT INTENDED TO SUPERSEDE THE REQUIREMENTSOF THE STANDARD. EMPLOYERS SHOULD REVIEW THESTANDARD FOR PARTICULAR REQUIREMENTS WHICH AREAPPLICABLE TO THEIR SPECIFIC SITUATION.This Guide is intended to provide compliance assistance for employers and employees in implementing requirements for a hazard assessment and the selection of personal protective equipment.1. CONTROLLING HAZARDSPPE devices alone should not be relied on to provide protection against hazards, but should be used in conjunction with guards, engineering controls, and soundmanufacturing practices.2.ASSESSMENT AND SELECTIONIt is necessary to consider certain general guidelines for assessing the foot, head, eye and face, and hand hazard situations that exist in an occupational or educationaloperation or process, and to match the protective devices to the particular hazard. It should be the responsibility of the safety officer to exercise common sense andappropriate expertise to accomplish these tasks.3. ASSESSMENT GUIDELINESIn order to assess the need for PPE the following steps should be taken:a. SurveyConduct a walk-through survey of the areas in question. The purpose of the surveyis to identify sources of hazards to workers and co-workers. Consideration shouldbe given to the basic hazard categories:(1) Impact(2) Penetration(3) Compression (roll-over)(4) Chemical(5) Heat(6) Harmful dust(7) Light (optical) radiationb. SourcesDuring the walk-through survey the safety officer should observe:(1) sources of motion; i.e., machinery or processes where any movement of tools,machine elements or particles could exist, or movement of personnel thatcould result in collision with stationary objects;(2) sources of high temperatures that could result in burns, eye injury or ignition ofprotective equipment, etc.;(3) types of chemical exposures;(4) sources of harmful dust;(5) sources of light radiation, i.e., welding, brazing, cutting, furnaces, heat treating,high intensity lights, etc.;(6) sources of falling objects or potential for dropping objects;(7) sources of sharp objects which might pierce the feet or cut the hands;(8) sources of rolling or pinching objects which could crush the feet;(9) layout of workplace and location of co-workers; and(10) any electrical hazards. In addition, injury/accident data should be reviewed tohelp identify problem areas.anize dataFollowing the walk-through survey, it is necessary to organize the data andinformation for use in the assessment of hazards. The objective is to prepare for an analysis of the hazards in the environment to enable proper selection ofprotective equipment.d.Analyze dataHaving gathered and organized data on a workplace, an estimate of the potential for injuries should be made. Each of the basic hazards (paragraph 3.a.) should be reviewed and a determination made as to the type, level of risk, and seriousness of potential injury from each of the hazards found in the area. The possibility ofexposure to several hazards simultaneously should be considered.4. SELECTION GUIDELINESAfter completion of the procedures in paragraph 3, the general procedure forselection of protective equipment is to:a. Become familiar with the potential hazards and the type of protective equipmentthat is available, and what it can do; i.e., splash protection, impact protection, etc.;b. Compare the hazards associated with the environment; i.e., impact velocities,masses, projectile shape, radiation intensities, with the capabilities of theavailable protective equipment;c. Select the protective equipment which ensures a level of protection greater thanthe minimum required to protect employees from the hazards; andd. Fit the user with the protective device and give instructions on care and use of thePPE. It is very important that end users be made aware of all warning labels forand limitations of their PPE.5. FITTING THE DEVICECareful consideration must be given to comfort and fit. PPE that fits poorly will not afford the necessary protection. Continued wearing of the device is more likely if it fits the wearer comfortably. Protective devices are generally available in a variety of sizes.Care should be taken to ensure that the right size is selected.6. DEVICES WITH ADJUSTABLE FEATURESAdjustments should be made on an individual basis for a comfortable fit that will maintain the protective device in the proper position. Particular care should be taken in fitting devices for eye protection against dust and chemical splash to ensure that the devices are sealed to the face. In addition, proper fitting of helmets is important to ensure that it will not fall off during work operations. In some cases a chin strap may be necessary to keep the helmet on an employee's head. (Chin straps should break at a reasonably low force, however, so as to prevent a strangulation hazard). Where manufacturer's instructions are available, they should be followed carefully.7. REASSESSMENT OF HAZARDSIt is the responsibility of the safety officer to reassess the workplace hazard situation as necessary, by identifying and evaluating new equipment and processes, reviewing accident records, and reevaluating the suitability of previously selected PPE.8. SELECTION CHART GUIDELINES FOR EYE AND FACE PROTECTIONSome occupations (not a complete list) for which eye protection should be routinely considered are: carpenters, electricians, machinists, mechanics and repairers,millwrights, plumbers and pipe fitters, sheet metal workers and tinsmiths, assemblers, sanders, grinding machine operators, lathe and milling machine operators, sawyers, welders, laborers, chemical process operators and handlers, and timber cutting and logging workers. The following chart provides general guidance for the properselection of eye and face protection to protect against hazards associated with the listed hazard "source" operations.9. SELECTION GUIDELINES FOR HEAD PROTECTIONAll head protection (helmets) is designed to provide protection from impact andpenetration hazards caused by falling objects. Head protection is also available which provides protection from electric shock and burn. When selecting head protection, knowledge of potential electrical hazards is important. Class A helmets, in addition to impact and penetration resistance, provide electrical protection from low-voltage conductors (they are proof tested to 2,200 volts). Class B helmets, in addition to impact and penetration resistance, provide electrical protection from high-voltage conductors (they are proof tested to 20,000 volts). Class C helmets provide impact and penetration resistance (they are usually made of aluminum which conductselectricity), and should not be used around electrical hazards. Where falling object hazards are present, helmets must be worn. Some examples include: working below other workers who are using tools and materials which could fall; working around or under conveyor belts which are carrying parts or materials; working below machinery or processes which might cause material or objects to fall; and working on exposed energized conductors. Some examples of occupations for which head protection should be routinely considered are: carpenters, electricians, linemen, mechanics and repairers, plumbers and pipe fitters, assemblers, packers, wrappers, sawyers,welders, laborers, freight handlers, timber cutting and logging, stock handlers, and warehouse laborers.10. SELECTION GUIDELINES FOR FOOT PROTECTIONSafety shoes and boots which meet the ANSI Z41-1991 Standard provide bothimpact and compression protection. Where necessary, safety shoes can be obtained which provide puncture protection. In some work situations, metatarsal protectionshould be provided, and in other special situations electrical conductive or insulating safety shoes would be appropriate. Safety shoes or boots with impact protection would be required for carrying or handling materials such as packages, objects, parts or heavy tools, which could be dropped; and, for other activities where objects might fall onto the feet. Safety shoes or boots with compression protection would berequired for work activities involving skid trucks (manual material handling carts) around bulk rolls (such as paper rolls) and around heavy pipes, all of which could potentially roll over an employee's feet. Safety shoes or boots with puncture protection would be required where sharp objects such as nails, wire, tacks, screws, largestaples, scrap metal etc., could be stepped on by employees causing a foot injury.Some occupations (not a complete list) for which foot protection should be routinely considered are: shipping and receiving clerks, stock clerks, carpenters, electricians, machinists, mechanics and repairers, plumbers and pipe fitters, structural metalworkers, assemblers, drywall installers and lathers, packers, wrappers, craters,punch and stamping press operators, sawyers, welders, laborers, freight handlers, gardeners and grounds-keepers, timber cutting and logging workers, stock handlers and warehouse laborers.11. SELECTION GUIDELINES FOR HAND PROTECTIONGloves are often relied upon to prevent cuts, abrasions, burns, and skin contact with chemicals that are capable of causing local or systemic effects following dermal exposure. OSHA is unaware of any gloves that provide protection against all potential hand hazards, and commonly available glove materials provide only limited protection against many chemicals. Therefore, it is important to select the most appropriate glove for a particular application and to determine how long it can be worn, andwhether it can be reused. It is also important to know the performance characteristics of gloves relative to the specific hazard anticipated; e.g., chemical hazards, cuthazards, flame hazards, etc. These performance characteristics should be assessed by using standard test procedures. Before purchasing gloves, the employer should request documentation from the manufacturer that the gloves meet the appropriate test standard(s) for the hazard(s) anticipated. Other factors to be considered for glove selection in general include:(A) As long as the performance characteristics are acceptable, in certaincircumstances, it may be more cost effective to regularly change cheapergloves than to reuse more expensive types; and,(B) The work activities of the employee should be studied to determine the degree ofdexterity required, the duration, frequency, and degree of exposure of thehazard, and the physical stresses that will be applied. With respect to selectionof gloves for protection against chemical hazards:(A) The toxic properties of the chemical(s) must be determined; in particular, theability of the chemical to cause local effects on the skin and/or to pass throughthe skin and cause systemic effects;(B) Generally, any "chemical resistant" glove can be used for dry powders;(C ) For mixtures and formulated products (unless specific test data are available),a glove should be selected on the basis of the chemical component with theshortest breakthrough time, since it is possible for solvents to carry activeingredients through polymeric materials; and,(D) Employees must be able to remove the gloves in such a manner as to prevent skincontamination.12. CLEANING AND MAINTENANCEIt is important that all PPE be kept clean and properly maintained. Cleaning is particularly important for eye and face protection where dirty or fogged lenses could impair vision. For the purposes of compliance with 1910.132 (a) and (b), PPE should be inspected, cleaned, and maintained at regular intervals so that the PPE provides the requisite protection. It is also important to ensure that contaminated PPE which cannot be decontaminated is disposed of in a manner that protects employees from exposure to hazards.。
2020年高考英语真题重点语法和题型分类汇编精讲第09题 阅读理解(解析版)
第09题阅读理解A number of Americans predict that driverless cars will revolutionize the form of travelling in cities and on highways However, recent experiments have shown that autonomous vehicles also have the potential to improve the quality of life for millions of Americans, especially the elderly and disabled, so long as the government and lawmakers carry out smart policiesA retirement community in Alabama which has been transformed by a small group of driverless taxis shows the potential of self-driving cars to change people's lives in America. Although the modified Ford Fusions are currently limited to a two-mile road, residents are already having the benefits of them to take part in socialactivities which they would otherwise be unable to enjoy simply because they could not get to them.When the experimental run finally reaches 15 miles of road, these residents whose average age is 77 will also have a convenient and reliable new way to keep their appointments. Because these cars continue to serve residents there, it is not difficult to understand why California is gradually simplifying regulations for the business.In New Jersey, ahead-thinking policies have the potential to unlock other hidden benefits of autonomous vehicles, especially for those with physical disabilities . The New Jersey Disability Righted for the development of this technology , saying that it could give people with disabilities greater opportunities in the workforce and enable them to lead more satisfying and independent lives.Many Americans admit that autonomous vehicles will be the future of transportation, but it is too often overlooked that this future cannot arrive fast enough for millions of Americans on others for day-to-day travel. The policymakers should follow the lead of places like California and New Jersey, and pass regulations to unlock these hidden benefits of driverless cars.1. What's the attitude of most American people to the future of autonomous vehicles?A. Uncertain.B. Doubtful.C. Indifferent.D. Optimistic.【答案】D【解析】推理判断题。
Journal of Molecular Structure THEOCHEM
Video sensor networks (VSNs) has become the recent research focus due to the rich information it provides to address various data-hungry applications. However, VSNimplementations face stringent constraints of limited communication bandwidth, processing capability, and power supply. In-network processing has been proposed as efficient means toaddress these problems. The key component of in-network processing, task mapping and scheduling problem, is investigated in this paper. Although task mapping and scheduling in wired networks of processors has been extensively studied, their application to VSNs remains largely unexplored. Existing algorithms cannot be directly implemented in VSNs due to limited resource availability and shared wireless communication medium. In this work, an application-independent task mapping and scheduling solution in multi-hop VSNs is presented that provides real-time guarantees to process video feeds. The processed data is smaller in volume which further releases the burden on the end-to-end communication. Using a novel multi-hop channel model and a communication scheduling algorithm, computation tasks and associated communication events are scheduled simultaneously with a dynamic critical-path scheduling algorithm. Dynamic voltage scaling (DVS) mechanism isimplemented to further optimize energy consumption. According to the simulation results, the proposed solution outperforms existing mechanisms in terms of guaranteeing application deadlines with minimum energy consumption.Article Outline1. Introduction2. Preliminaries2.1. Network assumptions2.2. Application and energy consumption model 2.3. Problem statement3. The proposed scheduling solution3.1. Hyper-DAG extension and multi-hop channel modeling 3.2. Communication scheduling algorithms 3.3. Scheduling with DCTMS algorithmPurchase$ 31.503.3.1. DCOS procedure 3.3.2. OSTA procedure 3.4. The DVS algorithm 4. Simulation results 4.1. Simulation parameters4.2. Simulation with a real-life application example 4.3.Simulation with randomly generated DAG 4.3.1. Effect of the application deadlines 4.3.2. Effect of the cluster size 4.3.3. Effect of the number of tasks 4.3.4. Comparison with EbTA 5. Conclusion Acknowledgements References170Evaluation of service management algorithms in adistributed web search system Original Research ArticleComputer Standards & Interfaces , Volume 29, Issue 2,February 2007, Pages 152-160Ahmed Patel, Muhammad J. KhanClose preview | Related articles | Related reference work articlesAbstract | Figures/Tables | ReferencesAbstractThe World Wide Web interconnected through the internet today offers numerous specialist topic-oriented or regional search engines and systems in a largely federated heterogeneous environment. Old ones continue to exist and new ones appear in spite of the tremendous progress achieved by their generic Web-wide rival competitors, because they produce better results in their areas of specialisation. However, finding and choosing the best specialised search engines or systems for a particular information need is difficult. This is made even more complicated by the fact that these enginesPurchase $ 31.50and systems would want to carve out a niche market that generates maximum revenue for themselves. The ADSA (Adaptive Distributed Search and Advertising) Web research project has investigated the problem at some depth and had put forward a search architecture which allows many search engines to be independently owned and controlled, offering advantages over existing centralised architectures. One aspect of the architecture has been to evaluate the service management algorithms that were designed to support competing autonomous systems in a cooperative marketplace. Here we present ADSA economic model and the service management strategies that can lead to maximum revenue generation, by making informative and intelligent decisions on search price adjustments of key quantitative parameters, as well as the results of evaluation experiments and briefly discuss the need for standardised interfaces which are required if this concept is to ease development and implementation of such a marketplace in a large scale.Article Outline1. Introduction2. ADSA economic model and pricing function2.1. The pricing function3. Evaluation3.1. Tests3.2. Performance criteria4. Experimental results5. Need for standard interfaces for administrative service management6. Conclusions and future workReferencesVitae171 Geophysical wavelet library: Applications of the continuous wavelet transform to the polarization anddispersion analysis of signals Original Research ArticleComputers & Geosciences , Volume 34, Issue 12,December 2008, Pages 1732-1752M. Kulesh, M. Holschneider, M.S. DialloClose preview | Related articles | Related reference work articlesAbstract | Figures/Tables | ReferencesAbstractIn the present paper, we consider and summarize applications of the continuous wavelet transform to 2C and 3C polarization analysis and filtering, modeling the dispersed and attenuated wave propagation in thetime –frequency domain, and estimation of the phase and group velocity and the attenuation from a seismogram. Along with a mathematical overview of each of the presented methods, we show that all these algorithms are logically combined into one software package “Geophysical Wavelet Library” developed by the authors. The novelty of this package is that we incorporate the continuous wavelet transform into the library, where the kernel is the time –frequency polarization and dispersion analysis. This library has a wide range of potential applications in the field of signal analysis and may be particularly suitable in geophysical problems that we illustrate by analyzing synthetic, geomagnetic and real seismic data.Article Outline1. Introduction2. GWL structure and implementation technology3. The CWT3.1. The direct wavelet transform 3.2. Wavelets3.3. The inverse wavelet transform 3.4. Wavelet transform of a complex signalPurchase $ 19.954. Polarization properties of two-component data and polarization filtering 4.1. Polarization analysis in the time domain 4.2. Complex trace method in the wavelet domain 4.3. Two-component polarization filter4.4. Application to the analysis of geomagnetic data5. Polarization analysis and filtering of 3C data 5.1. CWT-based polarization properties of an ellipse5.2. CWT-based polarization properties of an ellipsoid 5.3. Application to the analysis and filtering of seismic signals6. Modeling of wave propagation using a diffeomorphism in wavelet space 6.1. Linear diffeomorphism of the wavelet spectrum6.2. Describing wave dispersion and attenuation with non-linear diffeomorphism6.3. The case for non-linear frequency-dependent attenuation6.4. Modeling wave propagation in the space of polarization parameters 6.5. Parametrization of dispersion and attenuation7. An estimate of phase and group velocities and attenuation 7.1. Wavelet-based frequency –velocity analysis7.2. Inversion for the dispersion and attenuation characteristics of the medium 7.3. Application to experimental data 8. Conclusion Acknowledgements Appendix A. List of symbols References172A software framework for model predictive control with GenOpt Original Research ArticleEnergy and Buildings , Volume 42, Issue 7, July 2010, Pages 1084-1092Brian Coffey, Fariborz Haghighat, Edward Morofsky, Edward KutrowskiPurchase$ 35.95Close preview | Related articles | Related reference work articlesAbstract | Figures/Tables | ReferencesAbstractThere is a growing interest in integrated control strategies for building systems with numerous responsive elements, such as solar shading devices, thermal storage and hybrid ventilation systems, both for energy efficiency and for demand response. Model predictive control is a promising way of approaching this challenge. This paper presents a flexible software framework for model predictive control using GenOpt, along with a modified genetic algorithm developed for use within it, and applies it to a case study of demand response by zone temperature ramping in an office space. Various areas for further research and development using this framework are discussed.Article Outline1. Introduction2. Background2.1. Model predictive control in buildings research2.2. Simulation, optimization and controls software3. Framework3.1. Generic problem definition3.2. Framework overview3.3. The organizational layer3.4. Virtual testing environment4. Example algorithm4.1. Basic genetic algorithm description4.2. Using the optimization instructions file5. Example application study5.1. Demand response with zone temperature ramping5.2. Case study description 5.3. Results6.Discussion6.1. Appropriate complexity level for application studies 6.2. Improving optimization results6.3. Imperfect models, initializations and predictions6.4. Other potential research areas with SimCon7. Conclusions Acknowledgements References173Design and implementation of an environmentaldecision support systemEnvironmental Modelling & Software , Volume 16, Issue 5,July 2001, Pages 453-458W. G. Booty, D. C. L. Lam, I. W. S. Wong, P. SiconolfiClose preview | Related articles | Related reference work articlesAbstract | Figures/Tables | ReferencesAbstractAn environmental decision support system is a specific version of an environmental information system that is designed to help decision makers, managers, and advisors locate relevant information and carry out optimal solutions to problems using special tools and knowledge. The RAISON (Regional Analysis by Intelligent Systems ON microcomputers) for Windows decision support system has been developed at the National Water Research Institute, Environment Canada, over the last 10 years. It integrates data, text, maps, satellite images, pictures, video and other knowledge input. A library of software functions and tools are available for selective extraction of spatial and temporal data that can be analysed using spatial algorithms, models, statistics, expert systems, neural networks, and other information technologies. ThePurchase $ 19.95system is of a modular design which allows for flexibility in modification of the system to meet the demands of a wide range of applications. System design and practical experiences learned in the development of a decision support system for toxic chemicals in the Great Lakes of North America are discussed. Article Outline1. Introduction2. RAISON for Windows decision support system3. Great Lakes toxic chemical decision support system3.1. Databases3.1.1. Parameters3.1.2. Site_Info3.1.3. SiteDesc3.2. Modelling3.3. Neural network3.4. Expert system3.5. Optimization3.6. Data visualization4. DiscussionAcknowledgementsReferences174 DSP instrument for transient monitoring Original Research Article Computer Standards & Interfaces, Volume 33, Issue 2, February 2011, Pages 182-190Tomasz Tarasiuk, Mariusz Szweda应届生-算法工程师)|公司行业： 通信/电信运营、增值服务 计算机软件公司性质： 国企公司规模： 150-500人比比你的竞争力发布日期：2011-03-10工作地点：北京 招聘人数：2工作年限：应届毕业生 语言要求： 英语 熟练 日语 熟练学 历：硕士职位描述算法工程师招聘人数：2人工作地点：北京、上海职位描述：负责交通信息预测和海量数据分析。
volumeflowrate容积流量
Volumeflow rateDisya Ratanakorn∗,Jesada KeandaoungchanDivision of Neurology,Department of Medicine,Faculty of Medicine Ramathibodi Hospital,Mahidol University,Bangkok,ThailandKEYWORDSVolumeflow rate; Doppler method; Color velocity imagingquantification; Quantitativeflow measurement system; Angle-independent Doppler technique by QuantixND system Summary Vascular imaging of carotid and vertebral arteries may not be sufficient to evaluate the patients with stroke and other cerebrovascular disorders.Cerebral bloodflow measurement can add information to increase the accuracy in diagnosis,assessment,and plan of management in these patients.There are many noninvasive quantitative methods to measure cerebral blood flow including volumeflow rate measured by ultrasound.This article addresses mainly the dif-ferent ultrasound techniques to measure cerebral bloodflow.Clinical applications,volumeflow rate in normal and abnormal conditions with a case example,and advantage and disadvantage of the ultrasound techniques are also described.©2012Elsevier GmbH.IntroductionVascular imaging of carotid and vertebral arteries may not be sufficient to evaluate the patients with stroke and other cerebrovascular disorders.Cerebral bloodflow(CBF)mea-surement can add information to increase the accuracy in diagnosis,assessment,and plan of management in these patients.Methods for measurement of cerebral bloodflowThere are many noninvasive quantitative methods to measure CBF including stable xenon-enhanced computed tomography,single-photon emission computed tomogra-phy,positron-emission tomography,and magnetic resonance imaging.These methods are reliable and accurate for CBF measurement.However,they are rather expensive and requiring to transfer patients to the imaging or radio-nuclei facility which may be a limitation in the critical ill,sedated, or ventilated patients[1].∗Corresponding author.T el.:+6622012318;fax:+6622011645.E-mail address:****************.th(D.Ratanakorn).Volumeflow rate measurement by ultrasound Several ultrasound methods have been used to measure vol-umeflow rate(VFR)of CBF such as Doppler method[2],color velocity imaging quantification(CVIQ)[3],quantitativeflow measurement system(QFM)[4,5],and angle-independent Doppler technique by QuantixND system[6].The common carotid artery(CCA)is quite accessible and reliable to mea-sure VFR,whereas it is more difficult to obtain reliable VFR in the internal carotid artery(ICA)or vertebral artery(VA) due to the deeper vessels.VFR measurements are usually obtained at1.5—2.0cm below carotid bifurcation in CCA, 1—2cm above carotid bifurcation in ICA,and between the 4th and5th cervical vertebra in the inter-osseous segment of VA using high-resolution linear probe with pulsed Doppler imaging[7].Doppler methodDoppler method can estimate VFR at a specific point in a vessel by multiplying theflow velocity with cross-sectional lumen diameter at that specific point in time(Fig.1). However,Doppler method does not provide a profile of instantaneous peak velocities across the entire vessel and2211-968X©2012Elsevier GmbH./10.1016/j.permed.2012.03.008Open access under CC BY-NC-ND license.Open access under CC BY-NC-ND license.204 D.Ratanakorn,J.KeandaoungchanFigure1VFR measurements using Doppler method in CCA(A), ICA(B),and VA(C)with large sample volumes across the entire vessel lumens.cannot adjust for changes in theflow lumen throughout the cardiac cycle.Color velocity imaging quantificationCVIQ measures VFR by using time-domain processing with color velocity imaging combined with a synchronous M-mode color display to provide an instantaneous profile of the peak velocities across theflow lumen as well as a continuous estimate of the diameter of theflow lumen throughout the cardiac cycle(Fig.2).By assuming a circular vessel and axial symmetricalflow,CVIQ can be calculated automatically with built-in software.Quantitativeflow measurement systemQFM is comprised of two components.One component uses one transducer with ultrasonic echo tracking tomeasure Figure2VFR measurement using CVIQ in CCA with the opti-mal color box across the entire lumen in M-mode display(A) and synchronous instantaneous peak velocities across theflow lumen(B).With permission from Professor Charles H.T egeler.vessel diameter,and the other uses three transducers with continuous Doppler independent of incident angles to mea-sure absolute bloodflow velocity.QFM can be calculated using a vessel diameter in cross-sectional area and the abso-lute bloodflow velocity.Angle-independent Doppler technique by QuantixND systemQuantixND system is an angle-independent Doppler tech-nique which employs dual ultrasound beams within one insonating probe in a defined angle to each other.The real time information is stored automatically and analyzed by the computer.VFR measured by CVIQ and Doppler method The mean values of VFR in50healthy subjects as mea-sured by CVIQ and Doppler method are340.9±75.6and 672.8±152.9ml/min for CCA,226.9±65.0and316.2±89.1 for ICA,and92.2±36.7and183.5±90.8for ECA,respec-tively[2].VFR is higher in male compared to those in female and decreasing with increasing age.Doppler method tends to overestimate VFR and CVIQ seems to be more accurate than Doppler method to measure the carotid artery VFR. However,CCA VFR measured by CVIQ and Doppler method has no difference in0-95%ICA stenosis but CCA VFR byVolumeflow rate205Figure3CCA VFR measured by Doppler method in a46-year-old male with right ICA occlusion.Colorflow imaging shows right ICA occlusion(A)and normal left ICA(B)with right CCA VFR of159ml/min(C),and left CCA VFR of493ml/min(D).Doppler method is higher than that measured by CVIQ in 95—100%ICA stenosis[8].Clinical applicationsVFR measurement can be useful for grading carotid stenosis especially with coexisting contra-lateral carotid stenosis or occlusion to avoid overestimation of degree stenosis by using onlyflow velocity criteria,evaluating collateralflow and cerebrovascular reserve,identification of feeders and use as follow-up study in intra-cranial arteriovenous malforma-tion,quantification of hemodynamic changes in subclavian steal syndrome,assessment of vasospasm in subarachnoid hemorrhage,and monitoring of CBF before and after carotid endarterectomy[9,10].In addition,there is a direct corre-lation between middle cerebral artery meanflow velocity (MCA Vm),CCA VFR,and end-expiratory CO2in normal sub-jects.The MCA Vm and CCA VFR increase6.1%and5.3%per mmHg increase in end-expiratory CO2,respectively,and the MCA Vm increases0.3cm/s for each1ml/min increase in CCA VFR[11].Therefore,measurement of CCA VFR changes during CO2inhalation may be an alternative method to mea-sure cerebral vasoreactivity in the patients with inadequate temporal windows.VFR in carotid stenosisCCA VFR measured by Doppler method and CVI-Q at different degree of carotid stenosis are359±130and 337±96ml/min,respectively,for the individuals without ICA stenosis,310±99and293±133ml/min for50—75%ICA stenosis,347±80and195±131ml/min for75—95% ICA stenosis,152±36and63±25ml/min for95—99%ICA stenosis,and125±47and58±22ml/min for ICA occlusion [8].The reduction of ipsilateral CCA VFR is present in the patients with severe ICA stenosis of75—99%or ICA occlusion as shown in Fig.3.ConclusionsWhen comparing with other brain perfusion imaging tech-niques,VFR obtained with ultrasound does not provide values for each brain region,but represents only one value for each supplying vessel[10].It may be limited by oper-ator dependent,extra examination time,requirement for patient cooperation,extensive plaque formation,turbulent flow,and tortuous and asymmetrical vessels.Nevertheless, VFR measured by ultrasound is still the easiest,feasible, noninvasive,and repeatable bedside examination with no exposure to contrast media or radiation.Appendix A.Supplementary data Supplementary data associated with this article can be found,in the online version,at /10.1016/ j.permed.2012.03.008.References[1]Markus HS.Cerebral perfusion and stroke.J Neurol NeurosurgPsychiatry2004;75:353—61.206 D.Ratanakorn,J.Keandaoungchan[2]Ho SSY,Metreweli C.Preferred technique for blood vol-ume measurement in cerebrovascular disease.Stroke 2000;31:1342—5.[3]Eicke BM,T egeler CH,Howard G,Myers LG.In vitro reliablityofflow volume measurements with color velocity imaging.J Ultrasound Med1993;12:543.[4]Furuhata H,Sugano R,Kodaira K,Aoyagi T,Matsumoto H,Hayashi J,et al.An ultrasonic Doppler method designed for the measurement of absolute blood velocity values.Med Elec Bioeng1978;16:264—8.[5]Mizukami M,Yamaguchi K,Yunoki K.Evaluation of occlu-sive cerebrovascular disease using ultrasonic quantitativeflow measurement.Stroke1981;12:793—8.[6]Schebesch KM,Simka S,Woertgen C,Brawanski A,Rotho-erl RD.Normal values of volumeflow in the internal carotid artery measured by a new angle-independent Doppler tech-nique for evaluating cerebral perfusion.Acta Neurochir(Wien) 2004;146:983—6.[7]Peter Scheel MD,Christian Ruge,Uwe R,Petruch MD,MartinSchöning MD.Color Duplex measurement of cerebral bloodflow volume in healthy adults.Stroke2000;31:147—50.[8]Likittanasombut P,Reynolds P,Meads D,T egeler C.Volumeflowrate of common carotid artery measured by Doppler method and color velocity imaging quantification(CVI-Q).J Neuroimag-ing2006;16:34—8.[9]T egeler CH,Ratanakorn D,Neurosonology.In:Fisher M,Bogousslavsky J,editors.T extbook of neurology.Newton,MA: Butterworth Heinemann;1998.p.101—18.[10]Wintermark M,Sesay M,Barbier E,Borbély K,Dillon WP,Eastwood JD,et parative overview of brain perfusion imaging techniques.Stroke2005;36:e83—99.[11]Ratanakorn D,Greenberg J,Meads DB,T egeler CH.Middlecerebral arteryflow velocity correlates with common carotid artery volumeflow rate after CO2inhalation.J Neuroimaging 2001;11:401—5.。
巨灾模型介绍
巨灾模型介绍汇报内容⏹巨灾模型简介⏹台风模型（RMS）一、巨灾模型简介巨灾模型的历史Hurricane Hugo,1989Loma PrietaEarthquake,1989Hurricane Andrew,1992巨灾模型迅速发展的原因ProprietaryHAZUSOpen Source （陈克平，巨灾模型的结构（陈克平，2004）the Insurance Coverage Modulethe Science Module the EngineeringModuleSimulating thephysical characteristics ofa specificcatastrophe ②Determining the damage to exposuresKozlowski R.T. , Mathewson S.B. ,Measuring and Managing Catastrophe RiskCalculate DamageQuantify Financial LossGenerate Stoch .EventsApply ExposureQuantification of hazard (hazard parameter footprint)Exposure geographical distributionTypeValueDamage to buildings ContentBIFinancialimplication to the insurer and re-insurerHazard Module Stochastic Vulnerability Module Financial ModuleExposure Input Define Hurricane Assess WindSpeedRMSStochastic Event Set Module⏹Stochastic Event Set☐Exhaustive list of events that can impact theregion of interest⏹Location⏹Size⏹Rate⏹For each event☐Characterize the “footprint”of the event☐Calculate the damage to the exposure⏹For all events together☐Quantify the financial lossesProbabilistic CAT Modeling Outputs ⏹An estimate of the probability of exceedinggiven amount of losses in any given year⏹An estimate of the average annual loss (AAL)due to the peril modeled in a given region⏹An estimate of the loss cost⏹Capability of processing these quantities withinthe context of specific insurance andreinsurance structures for decision makingExceedance Probability Definitions ⏹Occurrence Exceedance Probability (OEP)☐Probability that the single largest event loss in ayear will exceed a loss threshold⏹Aggregate Exceedance Probability (AEP)☐Probability that the aggregate event losses in ayear will exceed a threshold☐Includes the contribution of all events in a yearEP Curves with High Event Frequency When the overall event frequencyincreases, the split between AEP andOEP increases风险分担机制损失程度全球再保险小灾中灾大灾巨灾SWISSRE, 2007L3L2 L1$100 million$30 million$5 million $0ReinsurerInsurer Home-ownerAverage Annual Loss (AAL)⏹AAL: the annual loss potential from all events inthe stochastic set☐Measurement of overall catastrophe risk (includesboth frequency and severity)☐Same as Pure Premium⏹Calculated as:☐Sum over all events of (Loss * Rate)⏹Can be obtained:☐For a whole portfolio☐By regions (province, county, postal code)CAWAUTNVORMTNMWYIDAZCO00.250.50.751Relative Risk by State Based on Industry ExposureRISK MANAGEMENTSTRATEGIES Risk Reduction Risk TransferDECISION PROCESSES of Key Stakeholders CATASTROPHEMODEL(Risk Assessment)基于巨灾模型的风险管理框架二、案例-台风模型（RMS）Assess WindSpeedDefine HurricaneQuantify Financial Loss90%$ LossCalculate Damage Stochastic Hazard Module Vulnerability Financial ModuleRadius to Maximum Wind Filling Rate after LandfallConfidentialBasin-wide Track Modeling –Storm TypesType 1Type 2Type 3Type 4Type 5Examples:Type 1: Hugo 1989, Floyd 1999Type 2: Galveston 1900, Gilbert 1988Type 3: Bob 1991, Dennis 1999Type 4: Camille 1969, Mitch 1998Type 5: Opal 1995, Bret 1999Mean Forward Velocities –Type 1 HurricanesLongest A rrow: Array15 m/s(34 mph) Tracks simulated without“turbulence”ConfidentialSmoothing of Historical DataConfidentialType 1 Stochastic TracksStochasticHistoryComplete track allows for:-Clash-Bypassing stormsWIND FIELD RECONSTRUCTION : MIREILLE The maximum winds footprint and theassociated wind directions arereconstructed and used for damagecalculations.DepartamentoBarrio(BogotaBuildingBuilding Roofcovering Roof covering Roof-wallanchor Roof -wall anchor Windowprotection Window protection FoundationFoundation RoofframingRoof framing Building-specificvulnerability functionsBuilding -specific vulnerability functions mphM D R (%)mph M D R (%)mph M D R (%)mph M D R (%)mphM D R (%)mph M D R (%)Calculate FloodDepths Calculate DamageDefine EventQuantify Financial Loss90%$ LossStochastic Hazard VulnerabilityModule Financial Module<2 4 6 8 10 mm<2 4 6 8 10 mm<2 4 6 8 10 mm<2 4 6 8 10 mm<2 4 6 8 10 mmStochastic Module: Example of Stochastic Event<2 4 6 8 10 mm<2 4 6 8 10 mm<2 4 6 8 10 mm<2 4 6 8 10 mmCalculate FloodDepthsF l o w Downstream IncreasingF l o w Mean drainage length =Time to peak = 14 hr Mean slope = 0.25Mean drainage length = 29.7kmTime to peak = 28 hrFlood wave routed downstreamlarge lakes treated explicitlyHazard Module: Flood Depth Calculations ❑Flow vs. depth calculated for each river segment (rating curves)❑Uses RMS hydrodynamic model at 50mx50m resolution –enhanced to 0.1m for depth calculations❑Flood depth derived for each exposure unit of resolutionVisual Display of EP Curves & Return Period Losses⏹The EP curve provides a visual interpretation ofloss potential⏹Each point of the curve has an associatedthreshold and probability of exceedance。
职称英语考试真题阅读判断
职称英语考试真题阅读判断New Understanding of Natural Silk’s MysteriesNatural silk, as we all know, has a strength that manmade materials have long struggled to match. In a discovery that sounds more like an ancient Chinese proverb than a materials science breakthrough, MIT researchers have discovered that silk gets its strength from its weakness. Or, more specifically, its many weaknesses. Silk gets its extraordinary durability and ductility from an unusual arrangement of hydrogen bonds that are inherently very weak but that work together to create a strong, flexible structure.Most materials -- especially the ones we engineer for strength -- get their toughness from brittleness. As such, natural silks like those produced by spiders have long fascinated both biologists and engineers because of their light weight, ductility and high strength (pound for pound, silk is stronger than steel and far less brittle). But on its face, it doesn't seem that silks should be as strong as they are; molecularly, they are held together by hydrogen bonds, which are far weaker than the covalent bonds found in other molecules.To get a better understanding of how silk manages to produce such strength through such weak bonds, the MIT team created a set of computer models that allowed them to observe the way silk behaves at the atomic level. They found that the arrangement of the tiny silk nanocrystals is such that the hydrogen bonds are able to work cooperatively, reinforcing one another against external forces andfailing slowly when they do fail, so as not so allow a sudden fracture to spread across a silk structure.The result is natural silks that can stretch and bend while retaining a high degree of strength. But while that's all well and good for spiders, bees and the like, this understanding of silk geometry could lead to new materials that are stronger and more ductile than those we can currently manufacture. Our best and strongest materials are generally expensive and difficult to produce (requiring high temperature treatments or energy-intensive processes).By looking to silk as a model, researchers could potentially devise new manufacturing methods that rely on inexpensive materials andweak bonds to create less rigid, more forgiving materials that are nonetheless stronger than anything currently on offer. And if you thought you were going to get out of this materials science story without hearing about carbon nanotubes, think again. The MIT team is already in the lab looking into ways of synthesizing silk-likestructures out of materials that are stronger than natural silk -- like carbon nanotubes. Super-silks are on the horizon.参考译文：我们都知道，蚕丝具有的韧性是人造织物长期奋力追求的目标。
小 波阻抗 差 avo 反射 英文
小波阻抗差avo 反射英文全文共3篇示例，供读者参考篇1Wave impedances are important parameters in wave mechanics and are crucial for understanding the behavior of waves when they encounter boundaries or interfaces. One commonly used wave impedance is the acoustic velocity impedance (AVO), which describes the ratio of the acoustic pressure to the acoustic velocity in a medium. AVO plays a crucial role in seismic exploration, where it helps in determining the contrasts in rock properties that can indicate the presence of hydrocarbons underground.In seismic exploration, one key concept that is frequently encountered is the reflection coefficient, which describes the ratio of the reflected wave to the incident wave when a wave encounters a boundary. The reflection coefficient is dependent on the wave impedances of the two media on either side of the boundary and can be used to predict the behavior of waves at interfaces.One important application of wave impedances and reflection coefficients is in seismic inversion, where the goal is to infer the properties of the subsurface rocks from seismic data. By analyzing the reflections of seismic waves at interfaces and their velocities and amplitudes, geophysicists can reconstruct the subsurface structure and identify potential oil and gas reservoirs.Additionally, wave impedances play a crucial role in reservoir characterization, where they are used to assess rock properties such as porosity, permeability, and lithology. By analyzing the variations in wave impedances and reflection coefficients across a reservoir, geoscientists can better understand the reservoir properties and improve their reservoir modeling and production strategies.In conclusion, wave impedances, especially AVO and reflection coefficients, are essential tools in wave mechanics and seismic exploration. By understanding these parameters and their relationships, geophysicists and geoscientists can better interpret seismic data, characterize reservoirs, and improve their understanding of the subsurface geology.篇2A Study on Small Wave Impedance Discrepancy and AVO ReflectionIntroductionIn exploration geophysics, the amplitude variation with offset (AVO) technique is widely used to evaluate subsurface properties by analyzing the reflection amplitudes of seismic waves at different offsets. The AVO response is affected by various factors such as lithology, fluid content, and the presence of small-scale heterogeneities. One important factor that influences the AVO response is the small wave impedance discrepancy, which refers to the difference in wave impedance between neighboring rock layers.Small Wave Impedance DiscrepancyWave impedance is a property that characterizes the ability of a medium to transmit seismic waves. It is defined as the product of the density and seismic velocity of the medium. When seismic waves encounter a boundary between two rock layers with different wave impedances, part of the wave energy is reflected back to the surface, leading to amplitude variations in the recorded seismic data. The small wave impedance discrepancy refers to the difference in wave impedance betweenadjacent rock layers that is too small to be resolved by conventional seismic data processing techniques.AVO ReflectionThe AVO response of a rock layer is determined by its angle-dependent reflectivity, which is influenced by the small wave impedance discrepancy. When the wave impedance discrepancy between two adjacent rock layers is small, the AVO response becomes more sensitive to changes in the angle of incidence of the seismic waves. This sensitivity is characterized by the AVO anomaly, which is a deviation from the expected AVO response based on the properties of the rock layers.Case StudyTo investigate the relationship between small wave impedance discrepancy and AVO reflection, a case study was conducted in a sedimentary basin with alternating layers of sandstone and shale. Seismic data were acquired using a marine seismic survey and processed to estimate the wave impedances of the rock layers. The AVO response was then analyzed to identify any anomalies that could be attributed to the small wave impedance discrepancy.ResultsThe analysis of the seismic data revealed that the small wave impedance discrepancy between the sandstone and shale layers was indeed influencing the AVO response. In areas where the wave impedance discrepancy was significant, the AVO anomaly was more pronounced, indicating a higher sensitivity of the reflectivity to changes in the angle of incidence. This result highlights the importance of incorporating the small wave impedance discrepancy in AVO analysis to improve the accuracy of subsurface property estimation.ConclusionThe study on small wave impedance discrepancy and AVO reflection provides valuable insights into the factors that influence the AVO response in seismic data. By considering the wave impedance discrepancy between adjacent rock layers, geophysicists can better interpret the AVO anomalies and improve the characterization of subsurface properties. Further research is needed to explore the implications of small wave impedance discrepancy on other seismic attributes and develop more advanced processing techniques to account for this phenomenon.篇3Small Wave Impedance Difference AVO ReflectionIntroductionThe study of small wave impedance difference AVO reflection has significant implications for the exploration and production of oil and gas reservoirs. AVO, or amplitude versus offset, refers to the variation in seismic amplitudes with offset and is a key tool in seismic data analysis. By analyzing the small wave impedance difference AVO reflection, geophysicists can gain valuable insights into subsurface rock properties, fluid content, and potential hydrocarbon reserves.Small Wave Impedance DifferenceImpedance is the product of the velocity and density of a material and is a fundamental property that influences the reflection of seismic waves. In the context of small wave impedance difference AVO reflection, geophysicists are interested in the variation in impedance between different layers of rock. By analyzing the impedance contrast at small scales, researchers can derive information about the subsurface geology with high precision.AVO ReflectionAVO reflection refers to the changes in seismic amplitudes as a function of offset. In the context of small wave impedance difference AVO reflection, geophysicists are interested in the relationship between the amplitude of the reflected waves and the impedance differences between adjacent layers. The AVO response can be characterized by various attributes, such as the AVO gradient, intercept, and curvature, which provide valuable information about the subsurface properties.Applications in Oil and Gas ExplorationThe study of small wave impedance difference AVO reflection has numerous applications in oil and gas exploration. By analyzing the AVO response, geophysicists can identify potential hydrocarbon traps, estimate reservoir properties, and improve the accuracy of seismic imaging. The detection of small-scale impedance variations can also help in delineating subtle structural features and predicting lithology changes.Case Study: North SeaIn the North Sea region, the study of small wave impedance difference AVO reflection has played a crucial role in the exploration and development of oil and gas fields. By integrating AVO analysis with well data and seismic interpretation, geoscientists have been able to improve reservoircharacterization and reduce exploration risks. The identification of subtle stratigraphic traps and fault compartments has led to the discovery of significant reserves in the area.Future DirectionsAs technology advances, the study of small wave impedance difference AVO reflection is expected to become even more sophisticated. With the development of advanced seismic imaging techniques and machine learning algorithms, geophysicists will be able to extract valuable insights from the seismic data with greater accuracy and efficiency. The integration of multi-component seismic data and rock physics modeling will further enhance the understanding of subsurface properties and improve reservoir prediction.ConclusionIn conclusion, the study of small wave impedance difference AVO reflection is a valuable tool in oil and gas exploration. By analyzing the variation in impedance at small scales and correlating it with the AVO response, geophysicists can gain valuable insights into subsurface properties and improve reservoir characterization. With continued research and technological advancements, the field of small wave impedancedifference AVO reflection is poised to make significant contributions to the oil and gas industry in the years to come.。
CUPT题目翻译
CUPT题⽬翻译CUPT题⽬1. Gaussian cannon ⾼斯炮A sequence of identical steel balls includes a strong magnet and lies in nonmagnetic channel. Another steel ball is rolled towards them and collides with the end ball .the ball at the opposite end of the sequence is ejected at a surprisingly high velocity .optimize the magnet’s position for the greatest effect.⼀列相同的钢球含有⼀个强磁铁并置于⽆磁通道中。
另有⼀个钢球向他们滚动并碰撞序列末尾的球。
在另⼀端末尾的球被迫以极⾼的速度离开。
请优化磁铁的位置使碰撞产⽣最佳效果。
2. Cutting the air切割空⽓When a piece of thread (e.g. nylon) is whirled around with a small mass attached to its free end, a distinct noise is emitted.study the origin of this noise and the relevant parameters.⼀段线（例如尼龙）的⾃由端系上⼀个重物，当线被旋转时会形成明显的噪声。
研究这种噪声的产⽣原因及相关参数。
3. String of beads串珠A long string of beads is released from a breaker by pulling a sufficiently long part of the chain over the edge of the breaker. Due to gravity the speed of the string increases. At a certain moment the sting no longer touches the edge of the breaker (see picture). Investigate andexplain the phenomenon.⼀长串珠⼦从烧杯⾥释放，具体释放⽅式是将⾜够长的珠链拉出烧杯的边缘，这样由于重⼒作⽤串珠的速度增⼤。
泛珠综合试试题及答案-solution-14
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bytetrack计算流程
bytetrack计算流程英文回答：The calculation process of ByteTrack involves several steps. First, the input video is analyzed frame by frame to detect and track objects. This is done using deep learning algorithms, specifically convolutional neural networks (CNNs). The CNN model is trained on a large dataset of labeled images to learn the features and characteristics of different objects.Once the objects are detected and tracked, the nextstep is to estimate their positions and trajectories. Thisis done by applying mathematical algorithms and techniques, such as Kalman filters, to predict the future positions of the objects based on their current positions and velocities.After the positions and trajectories are estimated, the system can perform various tasks, such as object classification and behavior analysis. For example, thesystem can classify objects into different categories, such as cars, pedestrians, or bicycles, based on their appearance and motion patterns. It can also analyze the behavior of objects, such as detecting abnormal or suspicious activities.The final step in the calculation process is togenerate the output, which can be in the form of visualizations or data. For example, the system cangenerate a video with bounding boxes around the detected objects or provide data on the number of objects, their positions, and other relevant information.Overall, the calculation process of ByteTrack involves object detection and tracking using deep learning algorithms, estimation of object positions and trajectories, object classification and behavior analysis, and generation of output in the form of visualizations or data.中文回答：ByteTrack的计算流程包括几个步骤。
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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.。