A new kind of radar has been developed for space-age travelers. A working laboratory model - 试题答案网问答

第1题

A new kind of radar has been developed for spaceship travelers. A working laboratory model

of a new system of radar that makes use of a beam of light is said to be ten thousand times more accurate than the best comparable system of radar that uses microwaves.

The model has shown that this radar system, known as laser-dopple radar, can measure with absolute precision speeds varying from spaceship orbital injection(进入) velocities(速度) of five miles per second down to virtual stops-speeds of less than one-thousandth of an inch per second. According to the scientists who are developing this system, such fine measures of velocity are of prime importance in space missions. In a rendezvous(对接) between two spaceships, or in a landing approach by a vehicle onto an orbiting space station, a bump could rip open a ship's skin, or a nudge could knock the station out of its orbit.

The light-beam radar, which operates at a frequency of trillions of cycles(百万兆) per second, could easily detect and measure the movement of a vehicle edging up to a satellite space station. A control system using so precise a signal as this would allow a huge vehicle to dock at a space station as lightly as a feather.

Laser-dopple radar ______.

A．measures the movement of a spaceship by means of light beam

B．makes use of microwaves

C．makes use of sound waves

D．both A and B

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第2题

Laser-dopple radar is especially valuable in space missions because it ______ .A．is one th

Laser-dopple radar is especially valuable in space missions because it ______ .

A．is one thousand times more precise than microwave radar

B．provides precise measures of the velocity of space vehicles

C．is a new system of radar

D．can measure the movement of a spaceship less accurately than a microwave radar

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第3题

A．Discovering new life in space.B．Studying meteorites.C．Plotting the courses of astero

A．Discovering new life in space.

B．Studying meteorites.

C．Plotting the courses of asteroids.

D．Developing radar telescopes.

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第4题

Laser-dopple radar is especially valuable in space missions because it ______.A．is one tho

Laser-dopple radar is especially valuable in space missions because it ______.

A．is one thousand times more precise than microwave radar

B．provides precise measures of the velocity of space vehicles

C．is a new system of radar

D．can measure the movement of a spaceship less accurately than a microwave radar

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第5题

Please Fasten Your Seatbelts Severe turbulence （湍流) can kill aircraft passengers. Now,

Please Fasten Your Seatbelts Severe turbulence (湍流) can kill aircraft passengers. Now, in test flights over the Rocky Mountains, NASA (美国航空航天局) engineers have successfully detected clear-air turbulence up to 10 seconds before an aircraft hits it.

Clear-air turbulence often catches pilots by surprise. Invisible to radar, it is difficult to forecast and can hurl (用力抛出去) passengers about the cabin. In December 1997, one passenger died and a hundred others were injured when unexpected rough air caused a United Airlines flight over the Pacific to drop 300 metres in a few seconds.

However, passengers can avoid serious injury by fastening their seatbelts. “It is the only antidote (对策) for this sort of things,” says Rod Bogue, project manager at NASA’s Dryden Flight Research Center in Edwards, California.

The centre’s new turbulence detector is based on lidar, or laser radar, Laser pulses are sent ahead of the plane and these are then reflected back by particles in the air. The technique depends on the Doppler effect. The wavelength of the light shifts according to the speed at which the particles are approaching. In calm air, the speed equals the plane’s airspeed. But as the particles swirl (打漩) in rough air, their speed of approach increases or decreases rapidly. The rate of change in speed corresponds to the severity (激烈程度) of the turbulence.

In a series of tests that began last month, a research jet flew repeatedly into disturbed air over the mountain ridges (山脉) near Pueblo, Colorado. The lidar detector spotted turbulence between 3 and 8 kilometres ahead, and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountered.

Bogue says that he had “ a comfortable amount of time” to fasten his seatbelt. The researchers are planning to improve the lidar’s range with a more powerful beam. The system could be installed on commercial aircraft in the next few years.

第6题：What does “clear-air turbulence” probably mean？（Paragraph 1）

A．A not very rough storm.

B．Unexpected disturbed air.

C．A kind of visible storm.

D．A storm over mountain ridges.

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第6题

Please Fasten Your SeatbeltsSevere turbulence （湍流) can kill aircraft passengers. Now, in

Please Fasten Your Seatbelts

Severe turbulence (湍流) can kill aircraft passengers. Now, in test flights over the Rocky Mountains; NASA (美国航空航天局) engineers have successfully detected clear-air turbulence up to 10 seconds before an aircraft hits it.

Clear-air turbulence often catches pilots by surprise. Invisible to radar, it is difficult to forecast and can hurl (用力抛出去) passengers about the cabin. In December 1997, one passenger died and a hundred others were injured when unexpected rough air caused a United Airlines flight over the Pacific to drop 300 metres in a few seconds.

However, passengers can avoid serious injury by fastening their seatbelts. "It is the only antidote (对策) for this sort of thing," says Rod Bogue, project manager at NASA's Dryden Flight Research Center in Edwards, California.

The centre's new turbulence detector is based on lidar, or laser radar. Laser pulses are sent ahead of the plane and these are then reflected back by particles in the air. The technique depends on the Doppler effect. The wavelength of the light shifts according to the speed at which the particles are approaching. In calm air, the speed equals the plane's airspeed. But as the particles swirl (打漩) in rough air, their speed of approach increases or decreases rapidly. The rate of change in speed corresponds to the severity (激烈程度) of the turbulence.

In a series of tests that began last month, a research jet flew repeatedly. into disturbed air over the mountain ridges (山脉) near Pueblo, Colorado. The lidar detector spotted turbulence between 3 and 8 kilometres ahead, and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountered.

Bogue says that he had "a comfortable amount of time" to fasten his seatbelt. The researchers are planning to improve the lidar's range with a more powerful beam. The system could be installed on commercial aircraft in the next few years.

What does "clear-air turbulence" probably mean？ (Paragraph 1)

A．A not very rough storm.

B．Unexpected disturbed air.

C．A kind of visible storm.

D．A storm over mountain ridges.

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第7题

In the eyes of anthropologist PaysonD.Sheets,_____.A．because grasses that made up the that

In the eyes of anthropologist PaysonD.Sheets,_____.

A．because grasses that made up the thatched roof of the dwelling were still new, that the structure was recent.

B．he left the site, located northwest of San Salvador, the capital, in 1980 unwillingly.

C．by sending radar signals through the ground in order to detect buried objects, he located 22 additional structures still buried in ash.

D．When the teeth were found, he said that throwing teeth on the roof is a tradition still practiced by some people in rural El Salvador today.

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第8题

回答题。 Electromagnetic Energy1. White light seems to be a combination of all colors. Th

回答题。

Electromagnetic Energy

1. White light seems to be a combination of all colors. The energy that comes from a source of light is not limited to the kind of energy you can see. Heat is given off by a flame or an electric light. On a cloudy day it is possible to get a sunburn even though you feel cool. Visible light and the kind of energy that produce warmth and sunburn are examples of electromagnetic energy.

2. The sun is 93 million miles from the earth. Yet we can use energy from the sun because electromagnetic energy travels through space.

3. Many other kinds of energy are also types of electromagnetic energy. Radio, television, and radar signals travel from transmitters to receivers as low-energy electromagnetic waves. Infrared (红外线的 ) radiation is an electromagnetic wave. When it is absorbed by matter, heat is produced. Waves of infrared and visible light have more energy than waves of radio, television, or radar. Ultraviolet rays (紫外线 ) and X-rays are electromagnetic waves with even greater amounts of energy. Infrared radiation is used in cooking food and heating buildings. Sunlight and electric lights are part of our requirements for normal living. Ultraviolet radiation is useful in killing certain disease organisms. X-rays and gamma rays have so mush energy that they travel right through solid objects. They can be used to detect and treat cancer. X-rays are used in industry to find hidden cracks in metal, and in medicine to reveal broken bones.

4. Usually we use electricity to generate electromagnetic energy. The source of most of our energy is the sun. Heat from the sun causes water to evaporate. When the water falls to the earth as rain, some of it is trapped behind dams and then used to operate electric generators. Other generators are powered by coal, but the energy stored in coal came from the sun, too.

5. Until recently, the source of the tremendous amount of energy given off by the sun was a puzzle. If the sun depended on chemical reactions, it would have used up all its energy long ago. Experiments with electromagnetic radiation led to the theory that mass can be converted into energy. About forty years after the theory was proposed, nuclear energy was harnessed (利用 ) by man. Chemical energy comes from electron (电子 ) rearrangement. Nuclear energy comes from a change in the nucleus of an atom. Compared with chemical reactions, nuclear reactions release millions of times more energy per pound of fuel. We now believe that the sun&39;s energy comes from the nuclear reactions in which hydrogen is changed into helium (氦 ) .

6. Nuclear energy is beginning to compete with coal as an economical source of power to generate electricity. It is also being used to operate engines in large ships. Scientists continue to seek new and better methods of obtaining and using energy.

Paragraph 3__________ 查看材料

A.Nuclear reactions as the lasting source of the sun"s energy

B.The most important source of energy

C.Types of electromagnetic energy

D.The machines used for energy generation

E.Seeking new sources of energy

F.The use of ultraviolet radiation in medicine

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第9题

Please Fasten Your Seatbelts Severe turbulence （湍流) can kill aircraft passengers. N

Please Fasten Your Seatbelts

Severe turbulence (湍流) can kill aircraft passengers. Now, in test flights over the Rocky Mountains, NASA (美国航空航天局) engineers have successfully detected clear-air turbulence up to 10 seconds before an aircraft hits it.

Clear-air turbulence often catches pilots by surprise. Invisible to radar, it is difficult to forecast and can hurl (用力抛出去) passengers about the cabin. In December 1997, one passenger died and a hundred others were injured When unexpected rough air caused a United Airlines flight over the Pacific to drop 300 metres in a few seconds.

However, passengers can avoid serious injury by fastening their seatbelts. "It is the only antidote (对策) for this sort of thing," says Rod Bogue, project manager at NASA's Dryden Flight Research Center in Edwards, California.

The centre's new turbulence detector is based on lidar, or laser radar. Laser pulses are sent ahead of the plane and these are then reflected back by particles in the air. The technique depends on the Doppler effect. The wavelength of the light shifts according to the speed at which the particles are approaching. In calm air, the speed equals the plane's airspeed. But as the particles swirl (打漩) in rough air, their speed of approach increases or decreases rapidly. The rate of change in speed corresponds to the severity(激烈程度) of the turbulence.

In a series of tests that began last month, a research jet flew repeatedly into disturbed air over the mountain ridges (山脉) near Pueblo, Colorado. The lidar detector spotted turbulence between 3 and 8 kilometres ahead, and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountered.

Bogus. says that he had "a comfortable amount of time" to fasten his seatbelt. The researchers are planning to improve the lidar's range with a more powerful beam. The system could be installed on commercial aircraft in the next few years.

第 36 题 What does "clear-air turbulence" probably mean？ (Paragraph 1)

A．A not very rough storm.

B．Unexpected disturbed air.

C．A kind of visible storm.

D．A storm over mountain ridges.

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第10题

The fruit of the new tomato doesn't taste salty because ______.A．The new kind of tomato do

The fruit of the new tomato doesn't taste salty because ______.

A．The new kind of tomato doesn't need to be watered.

B．The new kind of tomato can store salts in its leaves.

C．The new kind of tomato can store salts in its roots.

D．The new kind of tomato is planted with special water.

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