首页 > 学历类考试

网友您好，请在下方输入框内输入要搜索的题目：

请输入或粘贴题目内容搜题

搜题

拍照、语音搜题，请扫码下载APP

题目内容（请给出正确答案）

[主观题]

Among the question of design, construction, and operation remaining to be solved before co

mmercial airliners travel faster than sound is the difficult problem of sonic boom (声震) , the explosive sound generated when an object moves through the air at supersonic speed(超音速).

A sound is a pressure disturbance: a sonic boom, like other explosive sounds, is the result of an abrupt change in pressure. An airplane in subsonic flight produces weak changed in pressure, but because these disturbances travel at the speed of sound, they move faster than the airplane and stay in front of it. In effect, these disturbances warn the air to get out of the way, and the an does just jet, however, gets ahead of its own pressure disturbances. Consequently a wave of suddenly com pressed air--a shock wave--builds up and is thrown off like the wave ;hat spreads from the bow of a speedboat.

Can sonic booms be eliminated？ The answer is a categorical negative--they are an innerent(内在的) part of supersonic flight--but the sonic boom probably can be reduced; government and private research is now under way to improve understanding of the sonic boom. If and when the booms can be reduced to tolerable levels, commercial supersonic transports can come rata service.

Before commercial airliners travel faster than sound, problems must 0e solved regarding ______.

A．design

B．Construction

C．operation

D．all of the above

答案

查看答案

发布时间：2021-08-24

更多“Among the question of design, construction, and operation remaining to be solved before co”相关的问题

第1题

The question of whether war is inevitable is one which has concerned many of the world's g

reat writers. Before considering this question, it will be useful to introduce some related concepts. Conflict, defined as opposition among social entities directed against one another, is distinguished from competition, defined as opposition among social entities independently striving for something which is in inadequate supply. Competitors may not be aware of one another, while the parties to a conflict are. Conflict and competition are both categories of opposition, which has been defined as a process by which social entities function in the disservice of one another.

Opposition is thus contrasted with cooperation, the process by which social entities function in the service of one another. These definitions are necessary because it is important to emphasize that competition between individuals or groups is inevitable in a world of limited resources, but conflict is not. Conflict, nevertheless, is very likely to occur, and is probably an essential and desirable element of human societies.

Many authors have argued for the inevitability of war from the premise that in the struggle for existence among animal species, only the fittest survive. In general, however, this struggle in nature is competition, not conflict. Social animals, such as monkeys and cattle, fight to win or maintain leadership of the group. The struggle for existence occurs not in such fights, but in the competition for limited feeding areas and for occupancy of areas free froth meat-eating animals. Those who fail in this competition starve to death or become victims to other species. This struggle for existence does not resemble human war, but rather the competition of individuals for jobs, markets, and materials. The essence of the struggle is the competition for the necessities of life that are insufficient to satisfy all.

Among nations there is competition in developing resources, trades, skills, and a satisfactory way of life. The successful nations grow and prosper; the unsuccessful decline. While it is true that this competition may induce efforts to expand territory at the expense of others, and thus lead to conflict, it cannot be said that war-like conflict among nations is inevitable, although competition is.

In the first paragraph, the author gives the definitions of some terms in order to ______.

A．argue fur the similarities between animal societies and human societies

B．smooth out the conflicts in human societies

C．distinguish between two kinds of opposition

D．summarize the characteristic features of opposition and cooperation

点击查看答案

第2题

QUESTION 48以下哪些存储子系统的参数可以影响华为桌面云用户的体验（）

A.硬盘性能

B.读写I/O下盘比例

C.硬盘容量

D.读写I/O比例

点击查看答案

第3题

The question of whether war is inevitable is one which has concerned many of the world's g

reat writers. Before considering this question, it will be useful to introduce some related concepts. Conflict, defined as opposition among social entities directed against one another, 'is distinguished from competition, defined as opposition among social entities independently striving for something that is in inadequate supply. Competitors may not be aware of one another, while the parties to a conflict are. Conflict and competition are both categories of opposition which has been defined as a process by which social entities function in the disservice of one another. Opposition is thus contrasted with cooperation the process by which social entities function in the service of one another. These definitions are necessary because it is important to emphasize that competition between individuals or groups is inevitable in a world of limited resources, but conflict is not. Conflict, nevertheless, is very likely to occur, and is probably an essential and desirable element of human societies.

Many authors have argued for the inevitability of war from the premise that in the struggle for existence among animal species, only the fittest survive. In general, however, this struggle in nature is competition, not conflict. Social animals, such as monkeys and cattle, fight to win or maintain leadership of the group. The struggle for existence occurs not in such fights, but in the competition for limited feeding areas and for the occupancy of areas free from meat-eating animals. Those who fail in this competition starve to death or become victims to other species. This struggle for existence does not resemble human war, but rather the competition of individuals for jobs, markets, and materials. The essence of the struggle is the competition for the necessities of life that are insufficient to satisfy all.

Among nations there is competition in developing resources, trades, skills, and a satisfactory way of life. The successful nations grow and prosper; the unsuccessful decline. While it is true that this competition may induce efforts to expand territory at the expense of others, and thus lead to conflict, it cannot be said that war-like conflict among nations is inevitable, although competition is.

In the first paragraph, why does the author give the definitions of some terms？_____

A．Argue for the similarities between animal societies and human societies

B．Smooth out the conflicts in human societies

C．Distinguish between two kinds of opposition

D．Summarize the characteristic features of opposition and cooperation

点击查看答案

第4题

How much sleep does a person need？【31】the physiological bases of the need for sleep remain

conjectural (猜想), rendering conclusive answers to this question impossible, much evidence has been gathered on how much sleep people do in fact obtain. Perhaps the most important conclusion to be【32】from this evidence is【33】there is great variability among individuals in total sleep time. For adults,【34】between six and nine hours of sleep as a nightly average is not unusual, and 7.5 hours probably best expresses the norm. Such norms, of course, forms inevitably vary with the criteria of sleep employed, The most【35】and reliable figures on sleep time, including those cited here, come from studies in sleep laboratories, where EEG criteria are employed.

【36】consistently has been associated with the varying amount, quality, and pattern of electrophysiologically defined sleep. The newborn infant may spend an average of about 16 hours of each 24-hour period in sleep,【37】the sleep time drops sharply; by two years of age, it may【38】from nine to 12 hours. Decreases to approximately six hours have been observed among the elderly.

【39】will be discussed from below, EEG sleep studies have indicated that sleep can be considered to consist of several different stages. Developmental changes in the relative proportion of sleep time【40】in these sleep stages are as striking as age-related changes in total sleep time.

(31)

A．As

B．Despite

C．While

D．Whether

点击查看答案

第5题

How much sleep does a person need？【31】the physiological bases of the need for sleep remain

conjectural (猜想), rendering conclusive answers to this question impossible, much evidence has been gathered on how much sleep people do in fact obtain. Perhaps the most important conclusion to be【32】from this evidence is【33】there is great variability among individuals in total sleep time. For adults,【34】between six and nine hours of sleep as a nightly average is not unusual, and 7.5 hours probably best expresses the norm. Such norms, of course, forms inevitably vary with the criteria of sleep employed. The most【35】and reliable figures on sleep time, including those cited here, come from studies in sleep laboratories, where EEG criteria are employed.

【36】consistently has been associated with the varying amount, quality, and pattern of electrophysiologically defined sleep. The newborn infant may spend an average of about 16 hours of each 24-hour period in sleep,【37】the sleep time drops sharply; by two years of age, it may【38】from nine to 12 hours. Decreases to approximately six hours have been observed among the elderly.

【39】will be discussed from below, EEG sleep studies have indicated that sleep can be considered to consist of several different stages. Developmental changes in the relative proportion of sleep time【40】in these sleep stages are as striking as age-related changes in total sleep time.

(31)

A．As

B．Despite

C．While

D．Whether

点击查看答案

第6题

If it were only necessary to decide whether to teach elementary science to everyone on a m

ass basis or to find the gifted few and take them as far as they can go, our task would be fairly simple. The public school system, however, has no such choice, for the jobs must be carried on at the same time. Because we depend so heavily upon science and technology for our progress, we must produce specialists in many fields. Because we live in a democratic nation, whose citizens make the policies for the nation, large numbers of us must be educated to understand, to support, and when necessary, to judge the work of experts. The public school must educate both producers and users of scientific services.

In education, there should be a good balance among the branches of knowledge that contribute to effective thinking and wise judgment. Such balance is defeated by too much emphasis on any one field. This question of balance involves not only the relation of the natural sciences, the social sciences, and the arts but also relative emphases among the natural sciences themselves.

Similarly, we must have a balance between current and classical knowledge. The attention of the public is continually drawn to new possibilities in scientific fields and the discovery of new knowledge; these should not be allowed to mm our attention away from the sound, established materials that form. the basis of courses for beginners.

According to the first paragraph, the task of education is fairly complicated because ______.

A．the current public school system is too complicated to be understood

B．the public school system has no choice of what to teach

C．it is difficult to decide whether elementary science should be taught in public schools

D．the educators have to take care of both ordinary and gifted students

点击查看答案

第7题

What Is Death？ People in the past did not question the difference between life and de

What Is Death？

People in the past did not question the difference between life and death. They could see that a person died when his heart stopped beating. People have learned, however, that the body does not die immediately when the heart stops beating. They discovered that we remain alive as long as our brain remains active. Today the difference between life and death is not as easy to see as in the past. Modern medical devices can keep the heart beating and the lungs breathing long after the brain stops. But is this life？

This question has caused much debate among citizens in the United States. Many of them want a law that says a person is dead when the brain dies. A person should be considered dead when brain waves stop even if machines can keep the body alive. Such a law would permit doctors to speed removal (切除) of undiseased (没病的) organs for transplant (移植) operations.

The brain is made of thousands of millions of nerve cells. These cells send and receive millions of chemical and electrical messages every day. In this way the brain controls the other body activities. Nerve-cell experts say it is usually easy to tell when the brain has died. They put small electrodes (电极) on a person's skull (头骨) to measure the electrical signals that pass in and out of the brain. These brain waves are recorded on a television screen or on paper. The waves move up and down every time the brain receives messages from the nerve cells. The brain is dead when the waves stop moving.

Although there are people who oppose the idea of a law on brain block for various reasons, the idea of brain wave activity as a test of death is slowly being accepted.

第 31 题 People in the past held that the difference between life and death

A．did not exist.

B．was easy to tell.

C．lay in the brain.

D．was open to debate.

点击查看答案

第8题

One of the questions that is coming into focus as we face growing scarcity of resources of

many kinds in the world is how to divide limited resources among countries. In the international development community, the conventional wisdom has been that the 2 billion people living in poor countries could never expect to reach the standard of living that most of us in North America enjoy, simply because the world does not contain enough iron ore, protein, petroleum, and so on. At the same time, we in the United States have continued to pursue super affluence as though there were no limits on how much we could consume. We make up 6 percent of the world's people; yet we consume one-third of the world's resources.

As long as the resources we consumed each year came primarily from within our own boundaries, this was largely an internal matter. But as our resources come more and more from the outside world, "outsiders" are going to have some stay over the rate at which and terms under which we consume. We will no longer be able to think in terms of "our" resources and "their" resources, but only of common resources.

As Americans consuming such a disproportionate share of the world's resources, we have to question whether or not we can continue our pursuit of super affluence in a world of scarcity. We are now reaching the point where we must carefully examine the presumed link between our level of well-being and the level of material goods consumed. If you have only one crust of bread, then an additional crust of bread doesn't make that much different. In the eyes of most of the world today, Americans have their loaf of bread and are asking for still more. People elsewhere are beginning to ask why. This is the question we're going to have to answer, whether we're trying to persuade countries to step up their exports of oil to us or trying to convince them that we ought to be permitted to maintain our share of the world fish catch.

The prospect of a scarcity of, and competition for, the world's resources require that we reexamine the way in which we relate to the rest of the world. It means we find ways of cutting back on resource consumption that is dependent on the resources and cooperation of other countries. We cannot expect people in these countries to concern themselves with our worsening energy and food shortages unless we demonstrate some concern for the hunger, illiteracy and disease that are diminishing life for them.

The writer warns Americans that ______.

A．their excessive consumption has caused world resource exhaustion

B．they are confronted with the problem of how to obtain more material goods

C．their unfair share of the world's resources should give way to proper division among countries

D．they have to discard their cars for lack of fossil fuel in the world

点击查看答案

第9题

IV. Reading Comprehension （60 points) Directions: There are five reading passages in

IV. Reading Comprehension (60 points)

Directions: There are five reading passages in this part. Each passage is followed by four questions. For each question there are four suggested answers marked A, B, C and D. Choose one best answer and blacken the corresponding letter on the Answer Sheet.

Passage One

Wild and farm birds often get a flu virus. Yet they usually are able to carry the virus without getting sick.

In 1997 six people in Hong Kong died of a different kind of bird flu virus. It is called the h-five-n-one virus. The Hong Kong government quickly ordered the killing of all farm birds there. That stopped the spread of h-five-n-one to people in Hong Kong.

Yet the virus bad already spread to other parts of Asia. It was found in 16 countries between 2003 and 2006.

The h-five-n-one virus first appeared in Africa. This raised many concerns about the spread of the disease. Scientists do not know exactly how bird flu came to Africa. At first, they thought wild birds were to blame. Now, officials with the U. N. Food and Agriculture Organization believe the main cause is trade in farm birds.

The bird flu virus is found in the waste and liquids of infected birds. The virus spreads when healthy birds or people touch sick birds or nay infected (被感染了的) part of sick birds. Right now, the virus is not spreading among person to person. But the virus could change and start spreading among people. Health officials believe that it is even more possible now that bird flu has spread in Africa, and that is why international organizations are working so hard to stop its spread.

The best way to stop the spread of bird flu is to kill all the chickens in an area where bird flu has been discovered. More than 145 000 chickens have been killed in Nigeria since bird fin was first found one year ago.

36. The passage focuses on ______.

A. wild and farm birds

B. a fin virus

C. bird flu

D. infected birds

点击查看答案

第10题

The Great Fire of London started in the very early hours of September 1666 In four days

it destroyed more than three-quarters of the old city, where most of the houses were wooden and close together. One hundred thousand people became homeless, but only a few lost their lives. The fire started on Sunday morning in the house of the King’s baker(面包师) in Pudding Lane. The baker, with his wife and family, was able to get out through a window in the roof. A strong wind blew the fire from the bakery (面包房) into a small hotel next door. Then it spread quickly into Thames Street. That was the eginning. By eight o’clock three hundred houses were on fire. On Monday nearly a kilometer of the city was burning along the River Thames. Tuesday was the worst day. The fire destroyed many well-known buildings, old St Paul’s and the Guildhall were among them. Samuel Pepys, the famous writer, wrote about the fire. People threw their things into the river. Many poor people stayed in their houses until the last moment. Birds fell out of the air because of the heat. The fire stopped only when the King finally ordered people to destroy hundreds of buildings in the paths of the fire. With nothing left to burn , the fire became weak and finally died out. After the fire, Christopher Wren ,the architect , wanted a city with wider streets and fine new houses of stone. In fact, the streets are still narrow, but he did build more than fifty churches, and the new St Paul’s is among them. The fire caused great pain and loss, but after it London was a better place : a city for the future and not just of the past.

1The fire began in ____.

A.a hotel

B.the palace

C.Pudding Lane

D.Thames Street

2The underlined word “family” in the second paragraph means _____.

A.home

B.children

C.wife and husband

D.wife and children

3It seems that the writer of the text was most sorry for the fact that______.

A.some people lost their lives

B.the birds in the sky were killed by the fire

C.many famous buildings were destroyed

D.the King’s bakery was burned down

4Why did the writer cite (引用)Samuel Pepys ？

A.Because Pepys was among those putting out the fire.

B.Because Pepys also wrote about the fire.

C.To show that poor people suffered most.

D.To give the reader a clearer picture of the fire.

5How was the fire put out according to the text？

A.The King and his soldiers came to help.

B.All the wooden houses in the city were destroyed.

C.People managed to get enough water from the river.

D.Houses standing in the direction of the fire were pulled down.

点击查看答案

账号：尚未登录

登录没有账号？去注册

购买搜题卡

下载APP

关注公众号

TOP