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2 ( 092501, 091501, 080402)

WHAT CAN COMPUTERS DO?

Computers in present use range considerably: from tiny things to big fellows. The microcomputer, for example is the smallest and the newest member of the computer family. It usually consists of several integrated circuit chips, including a microprocessor chip, memory chips, and input/output interface chips, which are a result of tremendous advance in large-scale integration.

Minicomputers are larger than microcomputers, they are widely used in industrial control systems, scientific institution, and research laboratories. Although more expensive than microcomputers, minicomputers continue to be widely used because they are generally faster and possess more capabilities.

The largest computers ("maxicomputers") are those found in research centers, large scientific laboratories, and big universities.

Most of the computer principles and concepts are common to all categories of computers, although there can be tremendous variations from computer to computer.

A question sometimes arises whether computers are able to think. As a matter of fact they do not think. The computer programmer provides a program of instructions and data which specifies every detail of what to do, how to do, and with what to do it. The computer is simply a high-speed machine which can manipulate data, solve problems, and make decisions, all under the control of the programmer. If the programmer makes a mistake in the program or puts in the wrong data, the computer will produce wrong results.

 

3 ( 070801)

Chernobyl

Electricity is all around us - in thunder storms, in our bodies, in all things alive or dead. However, it is not easy to make and control electricity for us to use in our homes and in industry. Nuclear power is a way of making electricity that seems to be cheap and clean.

Chernobyl was a nuclear power station in the Ukraine (which used to be part of the USSR). The power station in Chernobyl was made in a way that has not been accepted in other parts of the world. British scientists had looked at the design but decided that it was dangerous, because the reactor did not have enough protection in case anything went wrong.

In the middle of a nuclear power station are one or more reactors, which get extremely hot. If they get too hot, the reactors blow up.

Very late at night on Friday 25th April 1986, some of the scientists at the Chernobyl power station decided to try a dangerous experiment. They changed the pressure in one reactor, which caused the temperature to rise. The reactor blew up.

Twenty people were working there at the time. One person was killed immediately, and his body has never been found. Several other people were killed soon after-some of them were fire-fighters who were helping to put out the fire. Other fire-fighters succeeded in putting out the fire before it reached the other three reactors at Chernobyl.

At first, the scientists and the government did not want to say that a really serious accident had happened. However, in the next days and weeks after the accident, the government of the Ukraine agreed that the air, food and water around Chernobyl were radioactive, and that it was dangerous for people to stay there. During the next few weeks, people in the city of Kiev, a hundred kilometres south of Chernobyl, wondered why there were no buses in their city! In fact, 1,200 buses from Kiev, and other towns, were being used to take people to a safer place. Later, 135,000 people were moved from around Chernobyl.

The rest of Europe first heard about the Chernobyl accident not from the USSR, but from Sweden, where radioactivity was noticed at the Forsmark nuclear power station. Denmark and Norway also reported an increase in radioactivity, and the scientists of western Europe finally realized that the radioactivity must be coming from near Kiev in the USSR.

 

IV

. , 䳺-. .

1. The automatic equipment is being installed in our shop.

2. Radioactive isotopes have been made in nuclear reactor.

3. The construction of this house will be completed in a month.

4. The engineer was asked about the new technology used at the plant.

. , it, that, one.

1. The successes in chemistry made it possible to obtain a lot of new materials.

2. One must apply the materials that can be machined easily.

3. It is the energy of falling water that is used to drive turbines.

. , .

1. I think the drawing will be ready by tomorrow.

2. Every substance a man comes in contact with consists of molecules.

IV. . , ᒺ ᒺ .

1 The crew is reported to have carried out a great deal of scientific experiments.

2. We know the wave theory of light to be first proposed by the English physicist Robert Hooks in 1665.

3. Nearly all refrigerators to be used at home are based upon the principle that the rapid evaporation of a liquid or the expansion of a gas produce cooling.

V. . 䳺 .

1. A curve showing the behavior of metal is given in Fig. 21.

2. About 100 years ago, a French scientist Pierre Curie subjecting certain crystalline materials to pressure, observed that they produced an electric charge.

3. The computer's electronic memory recording all the operator's commands, the picture of deviations was produced.

VI. . .

1. If one looks at his own face in a mirror, the image observed is technically described as perverted.

2. If the service life of the instrument had been prolonged, the economic effect would have been increased many times.

3. It would be impossible to ensure the full supply of energy without atomic power stations.

VII. . .

1 ( 090520, 090507)

THE PRINCIPLE OF A REFRIGERATING MACHINE

A compressor refrigerating machine has four essential parts: compressor, condenser, expansion valve and evaporator.

The refrigerant circulates in the system in the following way. Gas from the evaporator is drawn in by the compressor and compressed, with a result that its temperature rises. The compressed gas flows to the condenser, where it is cooled by water or air, changes into a liquid state.

The liquid refrigerant is led from the condenser to the expansion valve, where pressure falls as it passes through a small orifice.

Owing to the drop in pressure, some of the refrigerant evaporates and its temperature thus falls. The cold refrigerant proceeds to the evaporator, where the rest of the liquid evaporates by extracting heat from the surroundings, which are thus cooled. The vapour formed when the refrigerant boils is drawn in through the compressor suction pipe and once more compressed.

It may be said that the task of the compressor is to pump heat from the low temperature in the evaporator to the high temperature in the condenser in order that the heat absorbed in the evaporator may be carried away by the cooling water or air. The greater the difference between the evaporation and condensation temperatures, the greater is the work required for a given refrigerating capacity. The work of compression is converted into heat, which of course is carried away in the condenser.

2 ( 092501, 091501, 080402)

HOW ROBOTS APPEARED

1. The word "robot" is an invention of fiction. It was taken from the Czech word "robotnik" meaning a slave or a serf and used by Karel Capek in play R.U.R. (Rossum's Universal Robots) which introduced the word robot into the English language. The playwright created the word to mean forced labour, the machines in his play resembled people, but worked twice as hard.

The term industrial robot appeared in the 1970s. But it is true to think that robotics has its roots in ancient times when attempts were made to build automata-humanlike devices: moving figurines, mechanical servants and the like.

Early robots were not entirely self-regulating. They were on-off devices. They could perform only one action and they were unable to operate under a variety of conditions.

The idea of the first industrial robot was to build a machine that was flexible enough to do a variety of jobs automatically and could be easily taught or programmed. Robots combine computer intelligence, modem sensors and manipulator arms to provide flexible devices that can economically increase the productivity of manufacturing processes.

 

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