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In the early 1950s the researchers who produced the first clad glass optical fibers were not thinking of using them for communications. (1) H____, fiber optics was already a well-established commercial technology when the famous paper by Kao and Hockham, (2)____(claim) the use of low-loss optical fibers for communication, appeared in 1966. The first low-loss silica fiber was described in (3)____ which appeared in October of 1970. The date of this publication is sometimes (4)____(cite) as the beginning of the era of fiber communication. Although this development did receive (5)____(consider) attention in the research community at the time, it was far from inevitable that a major industry would evolve. The technological barriers appeared formidable because there were serious doubts as to (6) wh_____ these fiber components could ever be produced economically enough, but the market potential was very significant. (7)____(consequence), research and development activity expanded rapidly, and a number of important issues were (8) re_____ during the early 1970s. During the middle and late 1970s，the rate of progress towards marketable products accelerated as the emphasis (9)____(shift) from research to engineering. Fibers with losses (10) app____ the Rayleigh limit of 2 dB/km at a wavelength of 0.8μm were produced. By 1980 improvement in component performance, cost, and reliability led to major commitments on the part of telephone companies.
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更多 “问答题In the early 1950s the researchers who produced the first clad glass optical fibers were not thinking of using them for communications. (1) H____, fiber optics was already a well-established commercial technology when the famous paper by Kao and Hockham, (2)____(claim) the use of low-loss optical fibers for communication, appeared in 1966. The first low-loss silica fiber was described in (3)____ which appeared in October of 1970. The date of this publication is sometimes (4)____(cite) as the beginning of the era of fiber communication. Although this development did receive (5)____(consider) attention in the research community at the time, it was far from inevitable that a major industry would evolve. The technological barriers appeared formidable because there were serious doubts as to (6) wh_____ these fiber components could ever be produced economically enough, but the market potential was very significant. (7)____(consequence), research and development activity expanded rapidly, and a number of important issues were (8) re_____ during the early 1970s. During the middle and late 1970s，the rate of progress towards marketable products accelerated as the emphasis (9)____(shift) from research to engineering. Fibers with losses (10) app____ the Rayleigh limit of 2 dB/km at a wavelength of 0.8μm were produced. By 1980 improvement in component performance, cost, and reliability led to major commitments on the part of telephone companies.” 相关考题
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The text is written mainly for those_____________.A. who go to work early B. who want to lose weightC. who stay up late D. who eat before sleep
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Who will write up a report on Mangrove Rivulus?A．Patricia WrightB．Researchers in GuatemalaC．Scientists from BelizeD．Scott Taylor
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1.Some of the most commonly used medicines for high blood pressure are drugs called ACE inhibitors（抑制剂）.Doctors have given these drugs to patients for twenty-five years.A government study in the United States found that the use almost doubled between 1 995 and 2000.2.Doctors have known for years that women should not take ACE inhibitors during the last six months of pregnancy（怀孕）.The medicine can injure the bahy.ACE inhibitors,though,have been considered safe when taken during the first three months.But a new study has found that women who take these drugs early in their pregnancy still increase the risk of hirth disorders（先天性疾病）.Thestudyshowsthat,comparedtoothers,theirbabieswerealmostthreetimesaslikely to be horn with major problems.These included problems with thefo朋ation of the brain and nervous system and holes in the heart.3.The researchers say they found no increased risk in women who took other blood pressure medicines during the first three months.Researchers at Vanderbilt University in Tennessee and Boston University did the study. The New England Journal of Medicine published the results.The researchers studied the records of almost thirty thousand births between 1985 and 2000.Two hundred nine babies were born to women who took ACE inhibitors during the first three months of their pregnancies.Eighteen of the babies,or almost nine percent,had major disorders.4.ACE inhibitors are often given to patients with diabetes（糖尿病）.But diabetes during pregnancy can result in birth defects（先天性缺陷）.So the study did not include any women known to be diabetic. ACE inhibitors suppress a protein called angiotensin-converting enzyme（血管紧张素转化酶）,or ACE. This enzyme produces a chemical in the body that makes blood passages narrow. The drugs increase the flow of blood,so pressure is reduced.5.New drugs are tested on pregnant animals to see if they might cause birth defects in humans. But experts say these tests are not always dependable.The United States Food and Drug Administration helped pay for the study.The FDA says women who might become pregnant should talk with their doctor about other ways to treat high blood pressure.Paragraph 4__________A:Effects of ACE and ACE inhibitorsB:Wide use of ACE inhibitorsC:How to deal with high blood pressure in pregnant womenD:Damage to pregnant women's future babiesE:Suggestions on stopping the use of ACE inhibitorsF: Relative safety for women during the first three months of pregnancies
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第三篇Scientists Make Sweet DiscoveryGood news for chocoholics:the treat preferred by millions all over the world is good for you,according to American researchers at the University of California. Chocolate contains substances called flavonoids（类黄 酮)that can help maintain a healthy heart and good circulation.The researchers have discovered that cocoa acts like aspirin and that eating a bar of chocolate once in a while may contribute to a healthy diet. Chocolate has also been shown to release endorphins（内啡肽) in the body: these chemicals help to reduce pain andstress and make you feel happy.But who first discovered this wonderful way of keeping healthy?The Olmec Indians of Mexico and CentralAmerica were the first to grow cocoa beans,in about 1500 BC,and the Mayas were drinking unsweetened cocoa hundreds of years before it became fashionable in Europe.The word chocolate comes from the Nahuatl word xocolati,which means"bitter water".In 1544,a delegation of Mayan nobles visited Philip of Spain and gave him jars of cocoa as a gift. Cocoa soon became fashionable in Spain and Portugal.The Spanish were the first to add sugar to their cocoa drink. In the 17th century,chocolate was becoming fashionable with the middle-classes,not only as a drink but also as a medicine.By the middle of the century,solid chocolate was becoming familiar. In 1753,a Swedish scientist re- named cocoa theobroma or" food for the gods".In 1765,James Baker and John Hanan opened the first choco- late mill in the United States,introducing chocolate to the average citizen.In 1876,in Switzerland,Daniel Peter had the idea of adding milk in the chocolate,making process and produced the first milk chocolate.Since then,chocolate has grown enormously in popularity. One of the biggest chocolate-eating nations isBritain where the average man,woman,and child eats nine kilos of chocolate a year!In fact,chocolate is the number one comfort food and there are more"chocoholics"in Britain than anywhere else in the world.Re- searchers warn that although chocolate is good for you,it should be eaten in small quantities and with noadded milk.What did James Baker and John Hanan do about chocolate?A:They produced the first milk chocolate.B:They introduced chocolate to Europe.C:They added sugar to make chocolate bars.D:They made chocolate accessible to the average man.
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The Beginning of American Literature America has always been a land of beginnings.After Europeans"discovered"America in the fifteenth century,the mysterious New World became for many people a genuine hope of a new life,an escape from poverty and persecution,a chance to start again.We can say that,as a nation,America begins with that hope.When,however,does American literature begin? American literature begins with American experiences.Long before the first colonists arrived,before Christopher Columbus,before the Northmen who"found"America about the year 1000,native Americans lived here.Each tribe's literature was tightly woven into the fabric of daily life and reflected the unmistakably American experience of linking with the land.Another kind of experience,one filled with fear and excitement,found its expression in the reports that Columbus and other explorers sent home in Spain, French and English.In addition,the journals of the people who lived and died in the New England wilder- ness tell unforgettable tales of hard and sometimes heartbreaking experiences of those early years. Experience,then, is the key to early American literature.The New World provided a great variety of experiences,and these experiences demanded a wide variety of expressions by an even wider variety of early American writers.These writers included John Smith,who spent only two-and-a-half year on the American continent.They included Jonathan Edwards and William Byrd,who thought of themselves as British subjects,never suspecting a revolution that would create a United States of America with a literature of its own.American Indians,explorers,Puritan ministers,frontier wives,plantation owners-they are all the creators of the first American literature.What does"that hope"in the first paragraph refer to?A:The hope that America would be discovered.B:The hope to start a new life.C:The hope to see the mysteries of the New Worid.D:The hope to find poverty here.
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Kicking the HabitWhat is a bad habit?The most common definition is that it is something that we do regularly,almost without thinking about it,and which has some sort of negative consequence.This consequence could affect those around us,or it could affect us personally.Those who deny having bad habits are probably lying. Bad habits are part of what makes us human.Many early habits,like sucking our thumb,are broken when we are very young.We are either told to stop doing it by our parents,or we consciously or subconsciously observe that others do not have the same habit,and we gradually grow out of it.It is when we intentionally or unintentionally pick up new habits in our later childhood or early adulthood that it becomes a problem.Unless we can break that habit early on,it becomes a part of our life,and becomes"programmed"into our brain.A recent study of human memory suggests that no matter how hard we try to change our habits,it is the old ways that tend to win,especially in situations where we are rushed,stressed or overworked.Habits that we thought we had got rid of can suddenly come back.During the study programme,the researchers showed a group of volunteers several pictures,and gave them words to associate with them.They then showed the volunteers the same pictures again,and gave them new words to associate with them.A few days later,the volunteers were given a test.The researchers showed them the pictures,and told them to respond with one of the words they had been given for each one.It came as no surprise that their an- swers were split between the first set of words and the second.Two weeks later,they were given the same testagain.This time,most of them only gave the first set of. words.They appeared to have completely forgotten the second set.The study confirms that the responses we learn first are those that remain strongest over time.We may try to change our ways,hut after a while,the response that comes to mind first is usually the first one we learned.The more that response is used,the more automatic it becomes and the harder it becomes to respond in any other way.The study therefore suggests that over time,our had habits also become automatic,learned behavior. This is not good news for people who picked up bad habits early in life and now want to change or break them.Even when we try to put new,good intentions into practice,those previously learned habits remain stronger in more automatic,unconscious forms of memory.The study suggests that it is more difficult to respond to what we learn first?A:RightB:WrongC:Not mentioned
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Kicking the HabitWhat is a bad habit?The most common definition is that it is something that we do regularly,almost without thinking about it,and which has some sort of negative consequence.This consequence could affect those around us,or it could affect us personally.Those who deny having bad habits are probably lying. Bad habits are part of what makes us human.Many early habits,like sucking our thumb,are broken when we are very young.We are either told to stop doing it by our parents,or we consciously or subconsciously observe that others do not have the same habit,and we gradually grow out of it.It is when we intentionally or unintentionally pick up new habits in our later childhood or early adulthood that it becomes a problem.Unless we can break that habit early on,it becomes a part of our life,and becomes"programmed"into our brain.A recent study of human memory suggests that no matter how hard we try to change our habits,it is the old ways that tend to win,especially in situations where we are rushed,stressed or overworked.Habits that we thought we had got rid of can suddenly come back.During the study programme,the researchers showed a group of volunteers several pictures,and gave them words to associate with them.They then showed the volunteers the same pictures again,and gave them new words to associate with them.A few days later,the volunteers were given a test.The researchers showed them the pictures,and told them to respond with one of the words they had been given for each one.It came as no surprise that their an- swers were split between the first set of words and the second.Two weeks later,they were given the same testagain.This time,most of them only gave the first set of. words.They appeared to have completely forgotten the second set.The study confirms that the responses we learn first are those that remain strongest over time.We may try to change our ways,hut after a while,the response that comes to mind first is usually the first one we learned.The more that response is used,the more automatic it becomes and the harder it becomes to respond in any other way.The study therefore suggests that over time,our had habits also become automatic,learned behavior. This is not good news for people who picked up bad habits early in life and now want to change or break them.Even when we try to put new,good intentions into practice,those previously learned habits remain stronger in more automatic,unconscious forms of memory.We can only break bad habits if others tell us to do so.A:RightB:WrongC:Not nientioned
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The Beginning of American Literature America has always been a land of beginnings.After Europeans"discovered"America in the fifteenth century,the mysterious New World became for many people a genuine hope of a new life,an escape from poverty and persecution,a chance to start again.We can say that,as a nation,America begins with that hope.When,however,does American literature begin? American literature begins with American experiences.Long before the first colonists arrived,before Christopher Columbus,before the Northmen who"found"America about the year 1000,native Americans lived here.Each tribe's literature was tightly woven into the fabric of daily life and reflected the unmistakably American experience of linking with the land.Another kind of experience,one filled with fear and excitement,found its expression in the reports that Columbus and other explorers sent home in Spain, French and English.In addition,the journals of the people who lived and died in the New England wilder- ness tell unforgettable tales of hard and sometimes heartbreaking experiences of those early years. Experience,then, is the key to early American literature.The New World provided a great variety of experiences,and these experiences demanded a wide variety of expressions by an even wider variety of early American writers.These writers included John Smith,who spent only two-and-a-half year on the American continent.They included Jonathan Edwards and William Byrd,who thought of themselves as British subjects,never suspecting a revolution that would create a United States of America with a literature of its own.American Indians,explorers,Puritan ministers,frontier wives,plantation owners-they are all the creators of the first American literature.What can we learn from the literature of the tribes of the native Americans?A:About the everyday life of the native Americans.B:About the arrival of Columbus.C:About the experience of the first European settlers.D:About the experience of those who died in the New England wilderness.
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Kicking the HabitWhat is a bad habit?The most common definition is that it is something that we do regularly,almost without thinking about it,and which has some sort of negative consequence.This consequence could affect those around us,or it could affect us personally.Those who deny having bad habits are probably lying. Bad habits are part of what makes us human.Many early habits,like sucking our thumb,are broken when we are very young.We are either told to stop doing it by our parents,or we consciously or subconsciously observe that others do not have the same habit,and we gradually grow out of it.It is when we intentionally or unintentionally pick up new habits in our later childhood or early adulthood that it becomes a problem.Unless we can break that habit early on,it becomes a part of our life,and becomes"programmed"into our brain.A recent study of human memory suggests that no matter how hard we try to change our habits,it is the old ways that tend to win,especially in situations where we are rushed,stressed or overworked.Habits that we thought we had got rid of can suddenly come back.During the study programme,the researchers showed a group of volunteers several pictures,and gave them words to associate with them.They then showed the volunteers the same pictures again,and gave them new words to associate with them.A few days later,the volunteers were given a test.The researchers showed them the pictures,and told them to respond with one of the words they had been given for each one.It came as no surprise that their an- swers were split between the first set of words and the second.Two weeks later,they were given the same testagain.This time,most of them only gave the first set of. words.They appeared to have completely forgotten the second set.The study confirms that the responses we learn first are those that remain strongest over time.We may try to change our ways,hut after a while,the response that comes to mind first is usually the first one we learned.The more that response is used,the more automatic it becomes and the harder it becomes to respond in any other way.The study therefore suggests that over time,our had habits also become automatic,learned behavior. This is not good news for people who picked up bad habits early in life and now want to change or break them.Even when we try to put new,good intentions into practice,those previously learned habits remain stronger in more automatic,unconscious forms of memory.If we develop bad habits early in life,they are harder to get rid of.A:RightB:WrongC:Not mentioned
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Kicking the HabitWhat is a bad habit?The most common definition is that it is something that we do regularly,almost without thinking about it,and which has some sort of negative consequence.This consequence could affect those around us,or it could affect us personally.Those who deny having bad habits are probably lying. Bad habits are part of what makes us human.Many early habits,like sucking our thumb,are broken when we are very young.We are either told to stop doing it by our parents,or we consciously or subconsciously observe that others do not have the same habit,and we gradually grow out of it.It is when we intentionally or unintentionally pick up new habits in our later childhood or early adulthood that it becomes a problem.Unless we can break that habit early on,it becomes a part of our life,and becomes"programmed"into our brain.A recent study of human memory suggests that no matter how hard we try to change our habits,it is the old ways that tend to win,especially in situations where we are rushed,stressed or overworked.Habits that we thought we had got rid of can suddenly come back.During the study programme,the researchers showed a group of volunteers several pictures,and gave them words to associate with them.They then showed the volunteers the same pictures again,and gave them new words to associate with them.A few days later,the volunteers were given a test.The researchers showed them the pictures,and told them to respond with one of the words they had been given for each one.It came as no surprise that their an- swers were split between the first set of words and the second.Two weeks later,they were given the same testagain.This time,most of them only gave the first set of. words.They appeared to have completely forgotten the second set.The study confirms that the responses we learn first are those that remain strongest over time.We may try to change our ways,hut after a while,the response that comes to mind first is usually the first one we learned.The more that response is used,the more automatic it becomes and the harder it becomes to respond in any other way.The study therefore suggests that over time,our had habits also become automatic,learned behavior. This is not good news for people who picked up bad habits early in life and now want to change or break them.Even when we try to put new,good intentions into practice,those previously learned habits remain stronger in more automatic,unconscious forms of memory.Researchers were surprised by the answers that the volunteers gave in the first test.A:RightB:WrongC:Not mentioned
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The Beginning of American Literature America has always been a land of beginnings.After Europeans"discovered"America in the fifteenth century,the mysterious New World became for many people a genuine hope of a new life,an escape from poverty and persecution,a chance to start again.We can say that,as a nation,America begins with that hope.When,however,does American literature begin? American literature begins with American experiences.Long before the first colonists arrived,before Christopher Columbus,before the Northmen who"found"America about the year 1000,native Americans lived here.Each tribe's literature was tightly woven into the fabric of daily life and reflected the unmistakably American experience of linking with the land.Another kind of experience,one filled with fear and excitement,found its expression in the reports that Columbus and other explorers sent home in Spain, French and English.In addition,the journals of the people who lived and died in the New England wilder- ness tell unforgettable tales of hard and sometimes heartbreaking experiences of those early years. Experience,then, is the key to early American literature.The New World provided a great variety of experiences,and these experiences demanded a wide variety of expressions by an even wider variety of early American writers.These writers included John Smith,who spent only two-and-a-half year on the American continent.They included Jonathan Edwards and William Byrd,who thought of themselves as British subjects,never suspecting a revolution that would create a United States of America with a literature of its own.American Indians,explorers,Puritan ministers,frontier wives,plantation owners-they are all the creators of the first American literature.The main purpose of the last paragraph is to tell the readers that______.A:in the early days most American writers were from Great BritainB:people with rich life experience became writersC:there were many writers in the early days of American historyD:early-day experience provided the foundation for American literature
考题
Why did the early settlers come to America? Who were the Pilgrims? Who were the Puritans? What were the features in the colonial period which had influence on later American development?
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单选题According to Hudson Institute researchers, the effect of the early retirement of qualified workers in the U. S. economy is ______.A
constructiveB
significantC
inconclusiveD
detrimental
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单选题Jackie Robinson, the first Black American who was to play baseball in the majorleagues, joined the Brooklyn Dodgers in 1947.A
the first and a Black American whoB
was the first Black AmericanC
the first Black AmericanD
the Black American who first
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单选题When is a driver likely to have a sleep-related accident according to researchers?A
In the middle of the morning is 10 times as likely as those driving in the evening.B
Very early in the evening is as likely as those driving early in the morning.C
Very early in the morning is much more likely than those driving early in the evening.D
In the middle of the evening is 10 times as likely as those driving early in the morning.
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单选题The first question we now discuss is _____ we should go there so early tomorrow.A
whetherB
whereC
whatD
whom
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单选题According to the passage, short feature films produced as early as 1992 ______.A
were recorded by optical sensorsB
put musicians out of workC
were only effective for dialogue sequencesD
preceded talking pictures
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单选题Who has a lower risk of developing Alzheimer’s disease?A
People who have received little education.B
People who have mentally active jobs.C
People who first have good memories.
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问答题An employee at a company was given the task of making a large number of copies. He spent the first 45 minutes making copies at a constant rate on copier A, but copier A broke down before the task was completed. He then spent the next 30 minutes finishing the task on copier B, which also produced copies at a constant rate. How many total minutes would the task hare taken had copier A not broken down? (1) Copier A produced twice as many copies in its first 5 minutes of operation as copier B produced in its first 15 minutes. (2) Copier B produces 10 copies per minute.
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单选题What does the author mean by moms to be in the last paragraph?A
Women who are pregnant, especially for the first time.B
Women who dream of having babies for the first time.C
Women who already have children.D
Women who have just got babies for the first time.
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单选题As sought after for speaking ability, African Grey parrots, being considered valuable by both researchers and pet owners.A
As sought after for speaking ability, African Grey parrots, being considered valuable by both researchers and pet owners.B
African Grey parrots sought after for their ability to speak who are considered valuable by both researchers and pet owners.C
Sought after for their speaking abilities, African Grey parrots are considered valuable by both researchers and pet owners.D
Sought after for their speaking abilities, researchers and pet owners consider African Grey parrots valuable.E
Sought after because of their speaking ability, researchers and pet owners who are considering African Grey parrots valuable.
考题
问答题Why did the early settlers come to America? Who were the Pilgrims? Who were the Puritans? What were the features in the colonial period which had influence on later American development?
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