ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница

ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница

That was several years ago. Now the scientist demonstrated his experimental computing machine based on optics. It took him five years to develop it. The device — a collection of lasers, lenses and prisms — can serve as the basis for future optical computers 100 to 1,000 times as powerful as today's most advanced supercomputers. The potential applications are remarkable: robots that can see, computers that can design aircraft, processors that can convert spoken words into written text and vice versa. Such practical opti­cal computers are still years away — some would say light-years.

Yet many scientists are predicting that the device will ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница have an impact similar to that of the integrated circuit which made small personal computers possible.

Photons, the basic unit of light beams, can in theory be much better than electrons for moving signals through a computer. First of all, photons can travel about the times as fast as electrons. And

while electrons react with one another, beams of photons, which have no mass or charge, can cross through one another without in­terference. Thus, photons can move in free space. This could open the door to radically new and different computer designs, including so-called parallel processors that could ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница work on more than one problem at a time instead of one after another, as today's new gen­eration computers do.

How Transistors Work

Microprocessors are essential to many of the products we use every day such as TVs, cars, radios, home appliances and of course, computers. Transistors are the main components of microproces­sors. At their most basic level, transistors may seem simple. But their development actually required many years of thorough research. Be­fore transistors, computers relied on slow, inefficient vacuum tubes and mechanical switches to process information. In 1958, engineers put two transistors onto a silicon crystal and ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница created the first inte­grated circuit that led to the microprocessor. Here on a tiny silicon chip there are millions of switches and pathways that help computers make important decisions and perform helpful tasks.

Transistors are miniature electronic switches. They are the building blocks of the microprocessor which is the brain of the computer. Similar to a basic light switch, transistors have two oper­ating positions, on and off. This on/off function enables the pro­cessing of information in a computer.

The only information computers understand are electrical sig­nals that are switched on and off. To ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница understand how transistors work, it is necessary to have an understanding of how a switched electronic circuit works. Switched electronic circuits consist of sev­eral parts. One is the circuit pathway where the electrical current flows — typically through a wire. Another is the switch, a device that starts and stops the flow of electrical current by either com­pleting or breaking the circuit's pathway. Transistors have no mov­ing parts and are turned on and off by electrical signals. The on/off switching of transistors facilitates the work performed by micropro­cessors.

Something that has only two ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница states, like a transistor, can be re­ferred to as binary. The transistor's «on» state is represented by a 1 and the «off» state is represented by a 0. Specific sequences and patterns of l's and 0's generated by multiple transistors can repre­sent letters, numbers, colours and graphics. This is known as binary notation.

More complex information can be created such as graphics, au­dio and video using the binary, or on/off action of transistors.

Many materials, such as most metals, allow electrical current to flow through them. These are known as conductors. Materials that do not ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница allow electrical current to flow through them are called in­sulators. Pure silicon, the base material of most transistors, is con­sidered a semiconductor because its conductivity can be modulated by the introduction of impurities.

Adding certain types of impurities (примесь) to the silicon in a transistor changes its crystalline structure and improves its ability to conduct electricity.

The binary function of transistors gives microprocessors the ability to perform many tasks; from simple word processing to video editing. Microprocessors have developed to a point where transistors can carry out hundreds of millions of instructions per second on a ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница single chip. Automobiles, medical devices, televisions, computers and even the Space Shuttle use microprocessors. They all rely on the flow of binary information made possible by the tran­sistor.



To be read after Lesson б

Ceramic Application

The application which has captured the imagination of engi­neers, as well as the general public, is certainly the ceramic engine, that is the adiabatic turbo-diesel engine and the ceramic turbine for automotive use. There are some successful phototypes on the road, however, applications on a large scale have been held back by prob­lems of cost and reliability. Steady progress is being made in ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница the in­crease of the reliability of ceramics. But the cost factor is likely to remain a problem for some time.

One should mention here that the long-term reliability in ser­vice still needs to be defined for those applications where the mate­rial must withstand very high temperatures and dynamically changing mechanical and thermal loads in a chemically aggressive environment.

Ceramic engines and turbines are but the top of the pyramid with respect to applications. At lower levels of performance there are numerous other applications, in which the operating conditions are less severe, for example ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница, ceramic heat exchangers for chemical plants. Ceramics finds application in bearings and engine parts be­cause of its high hardness and high abrasion resistance.

There are three main materials used in making pipes: metal, rubber and plastic.

Metal is stronger than rubber and plastic. It is also heavier and more rigid than rubber and plastic. Metal is the strongest material, but it is also the heaviest, and the most rigid. It is also the most ex­pensive of the three materials.

Rubber is weaker than metal or plastic. It is also more flexible than the other two materials. Rubber is the most ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница flexible of the three materials, but it is the weakest.

Plastic is lighter than metal. It is also less expensive than steel or rubber. Plastic is the lightest material. It is also the least expen­sive of the three materials.

Glass is used for making windows because you can see through it, and it is very hard and therefore cannot be cut easily. But at the same time it is very brittle and therefore it can break easily.

Wood is soft and therefore it can be cut easily. It can be used in fires because it is ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница combustible.

Car tyres are made of rubber because rubber is flexible.

A car panel is made by three methods. First, sheet steel is made. This is done by pushing a piece of steel between two rollers, which squeeze the metal and make it longer and thinner. This method is called rolling. Not all metals can be rolled. For example, iron can­not be rolled because it is too brittle. But steel can be rolled because it is tough and malleable (ковкий) enough.

Next, the steel is cut into a flat shape. This is done by placing the sheet onto a ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница die, and then cutting a hole in it with a punch. The method is called punching. The steel can be cut easily because it is now very thin.

Finally, the sheet steel is bent and pressed into a rounded shape. This is done by putting the sheet onto a die and then bend­ing the sheet around the die with a press. This method is called pressing. It is not difficult to press sheet steel because it is thin and malleable.

To be read after Lesson 7

Electric Car

The electric car is not a new idea. It had ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница success with American women in the early 1900s. Women liked electric cars because they were quiet and, what was more important, they did not pollute the air. Electric cars were also easier to start than gasoline-powered ones. But the latter was faster, and in the 1920s they became much more popular.

The electric car was not used until the 1970s, when there were serious problems with the availability of oil. The General Motors Co. had plans to develop an electric car by 1980. However, soon oil became available again, and this car was never produced.

Today there is a new interest in ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница the electric car. The Toyota Co. recently decided to spend $800 million a year on the development of new car technology. Many engineers believe that the electric car will lead to other forms of technology being used for transportation.

Car companies are working at developing a supercar. A super- efficient car will have an electric motor. Four possible power sources are being investigated. The simple one is batteries. Another possibility is fuel cells, which combine oxygen from air with hydro­gen to make electricity. Yet another approach would be a flywheel (маховик), an electric generator consisting of free-spinning wheels ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница with magnets in the rims that can produce a current. A fourth pos­sible power source for the super-car would be a small turbine en­gine, running on a clean fuel like natural gas. It would run at a constant speed, generating electricity for driving vehicles or for feeding a bank of batteries, storing energy for later use.

Engines

Do you know what the first engine was like? It was called the «water wheel». This was an ordinary wheel with blades fixed to it, and the current of a river turned it. These first engines were used ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница for irrigating fields.

Then a wind-powered engine was invented. This was a wheel, but a very small one. Long wide wooden blades were attached to it. The new engine was driven by the wind. Some of these ones can still be seen in the country.

Both of these, the water- and wind-operated engines are very economical. They do not need fuel in order to function. But they are dependent on the weather.

Many years passed and people invented a new engine, one op­erated by steam. In a steam engine, there is a furnace and a boiler ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница. The furnace is filled with wood or coal and then lit. The fire heats the water in the boiler and when it boils, it turns into steam which does some useful work.

The more coal is put in the furnace, the stronger the fire is burning. The more steam there is, the faster a train or a boat is moving.

The steam engine drove all sorts of machines, for example, steam ships and steam locomotives. Indeed, the very first aeroplane built by A.F. Mozhaisky also had a steam engine. However, the steam engine had its disadvantages. It was too ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница large and heavy, and needed too much fuel.

The imperfections of the steam engine led to the design of a new type. It was called the internal combustion engine, because its fuel ignites and burns inside the engine itself and not in a furnace. It is smaller and lighter than a steam engine because it does not have a boiler. It is also more powerful, as it uses better-quality fuel: petrol or kerosene.

The internal combustion engine is now used in cars, diesel lo­comotives and motor ships. But to enable aeroplanes to fly faster than the speed ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница of sound another, more powerful engine was needed. Eventually, one was invented and it was given the name «jet en­gine». The gases in it reach the temperature of over a thousand de­grees. It is made of a very resistant metal so that it will not melt.

To be read after Lesson 8

The Driving Lesson Miss Green: Good afternoon. My name is Miss Green and I'm your

driving instructor. Is this your first lesson?

Simon:

It is my first lesson at this driving school.

M.

G.:

Oh, you've been to another one?

S.:

Yes. The ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница Greenwich school of driving. But I stopped going there.

M.

G.:

Why? Weren't the lessons good enough?

S.:

They were good but my instructor left.

M.

G.:

Really? Well, let's see what you can do. I want you to drive down this road and turn left at the end.

S.:

Yes, all right.

M.

G.:

You drive very well! I'm sure you'll pass your test. All my pupils pass their tests. Oh, look out! That lorry!

S.:

You said turn left at the end.

M.

G.:

When you want to turn a corner, slow down and look first ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница. You nearly hit that lorry. Please, be careful. Now turn right at the traffic lights... Right, not left!

S.: Sorry it was too late. I've turned left now.

M. G.: Didn't you see the No Entry sign? This is a one-way street.

S.: Why are those drivers shouting?

M. G.: Because you're driving the wrong way down a one-way street. Stop the car, please, and turn it round.

S.: I'm not very good at that.

M. G.: Mind that red car!

S.: Madman! He nearly hit me!

M. G.: He was right ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница and you were wrong. Why didn't you wait? Now you are blocking the road. You want re­verse gear. Turn the wheel... more ... more ... Not too fast! Oh, what have you done now?

S.: It is all right. I went into the lamp-post but it is still

standing. I didn't knock it down.

M.G.: Oh, but look at the back of the car.

S.: Sorry, but you said «reverse».

M.G.: I didn't say «drive into the lamp-post». Well, you've turned the car round now, so drive back to the traffic lights ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница and go straight across.

S.: Are we going to the park?

M.G.: The roads are quiter near the park. Oh, not too fast!

S.: The lights are green.

M.G.: Slow down! The lights are changing!

S.: I can't slow down. There! We are across.

M.G.: The lights were red!

S.: It's all right. There were no policemen.

M.G.: I know why your last instructor left. He wanted to stay alive.

S.: That's not a very nice thing to say. And it's not true.

He left because he wasn't very well ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница.

M.G.: Stop the car, please. Oh, gently!

S.: Sorry. Did you hit your head on the roof?

M.G.: No. Luckily I was wearing the seat belt. Now I want you to practise driving backwards. Reverse the park gates. Look first, than reverse in.

S.: Right.

M.G.: Oh, you've hit the gate!... Now you are driving on the grass!

S.: I'm going backwards down the hill and I can't stop!

Help me!

M.G.: Use the brakes! Don't drive into the lake!

S.:

M.G.:

S.:

Too late.

Look what you've done. You ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница reversed into a lamp post. You hit the park gate. Now you've driven into the lake. Oh, why didn't you stay with the other driv­ing school?

They had no more cars left.




Heavy-Lift Dirigible

Unlike other new dirigible projects the giant CargoLifter CL 160 (Germany) is aimed at heavy-lift cargo applications, not at tourism or advertising. It will be the beginning of a new era in freight transport.

The 260-meter-long, 65-meter-diameter semi-rigid airship will be capable of transporting 160 ton loads-equivalent to 36 standard 40-ft containers — to out-of-the-way (remote) construction ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница sites 10,000 km away. With a cruise speed of just 80-120 km/hr the CL 160 would not get the load to its destination nearby as fast as a heavier-than-air craft such as Antonov An-124, but it would also not require the landing facilities needed for the unusually large air­craft.

Moored (причаливать) above the delivery site, the airship will lower loads using an onboard crane without actually having to touch down. A crew of five, including navigator and two cargo- masters (высококвалифицированные рабочие) would man the ship.

In fact, the CargoLifter project was born of a logistics need ex­pressed ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница by manufacturers of electric generators, turbines and other outsized (i.e., larger than the usual size) machinery.

Rolls-Royce-Turbomeca turboshaft engines are to be used for maneuvering the big airship, cruise being provided by diesel power- plants.

What Is GPS?

The Global Positioning System (GPS) is a satellite-based navi­gation system made up of a network of 24 satellites. GPS was origi­nally intended for military applications, but now the systems is available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day.

GPS satellites circle the earth twice a day ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница in a very precise orbit and transmit signal information to Earth. GPS receivers take this information and use triangulation to calculate the user's exact lo­cation. Essentially, the GPS receiver compares the time a signal
was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map.

A GPS receiver must be locked on to the signal of at least three ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница satellites to calculate a 2D position (latitude and longitude) and track (прослеживать) movement. With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). Once the user's position has been deter­mined, the GPS unit can calculate other information, such as speed, bearing (пеленг), track, trip distance, distance to destina­tion, sunrise and sunset time and more.

Today's GPS receivers are extremely accurate within an aver­age of three to five meters thanks to their parallel multi-channel design.

The 24 satellites that make up the GPS space segment are orbit ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница­ing the earth about 12,000 miles above us. They are constantly moving, making two complete orbits in less than 24 hours. These satellites are travelling at speeds of roughly 7,000 miles an hour.

GPS satellites are powered by solar energy. They have backup batteries onboard to keep them running in the event of a solar eclipse (затмение), when there's no solar power. Small rocket boosters on each satellite keep them flying in the correct path.

Here are some other interesting facts about the GPS satellites:

1. The first GPS satellite was launched in 1978.

2. A full constellation (созвездие) of 24 satellites ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница was achieved in 1994.

3. Each satellite is built to last about 10 years. Replacements are constantly being built and launched into orbit.

4. A GPS satellite weighs approximately 2,000 pounds and is about 17 feet across with the solar panels extended.

5. Transmitter power is only 50 watts or less.

GPS satellites transmit two low power radio signals. The signals travel by line of sight, meaning they will pass through clouds, glass and plastic but will not go through most solid objects such as build­ings and mountains.

A GPS signal contains three different bits of information — a pseudorandom code, ephemeris data and almanac data.

Some ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница factors that can degrade the GPS signal and thus affect accuracy include the following:

1. The satellite signal slows as it passes through the atmosphere.

2. The GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors.

3. A receiver's built-in clock is not as accurate as the atomic clocks onboard the GPS satellites. Therefore, it may have very slight timing errors.

4. The more satellites a GPS receiver can «see,» the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница foliage (листва) can block signal reception, causing po­sition errors or possibly no position reading at all. GPS units typi­cally will not work indoors, underwater or underground.

To be read after Lesson 9

Getting into Deep Water

The dark depths of the Gulf of Mexico, once frequented by only the sea creatures, are now alive with human activity. Miniature submarines and robot-like vehicles move around the ocean bottom while divers make their way around incredible underwater struc­tures — taller than New York City skyscrapers, but almost totally beneath the surface of the waves. Modern-day explorers are ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница using technology worth of Jules Verne and Jacques Cousteau to find fresh supplies of oil and natural gas.

Until recently, drilling in the Gulf was concentrated close to shore in water as deep as 9 m. But now the scientists are looking to hundreds of meters deep and 160 km and more from land.

The deep water research began in 1984. Since then many Ame­rican companies have built the world's deepest production plat­forms of more than 100 storeys high. Finding gas and oil deposits at large depth is not an easy technological task.

Voyage to the Bottom of the Sea

There is an ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница American project of one-person submarine, which will «fly» to the bottom on inverted wings rather than simply sink­ing under its own weight as the bathyscaphes did. This design is more like an aeroplane than a balloon. It could one day make ex­ploring the ocean depth as easy as flying a plane is today.

The most difficult problem is to find a material that is also light enough to allow the craft to float back to the surface if there is a loss of power or some other emergency. Alumina, a hard ceramic, was chosen for the ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница vessel.

The pilot's capsule is about a meter in diameter, 5 centimeters thick and about 2 meters long. It is capped at one end with a ce­ramic hemisphere and at the other with a glass viewing dome. The rest of the craft, including the wings on either side and the casing at the rear for the motors, are made of a lightweight composite material.

In addition to the pilot, the pressure vessel houses the controls and instrument panel, the life-support system and a 24-volt power supply. The pilot effectively operates the craft by radio control.

The batteries feed ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница a pair of electric motors that can drive the craft at up to 14 knots (25 kilometers per hour). The craft could dive vertically but this would be uncomfortable for the pilot who lies face downwards in the cylindrical chamber. So it descends at an angle of up to 45°. «Deep Flight» is designed to be as stream­lined as possible. This means making the submarine's cross section as small as possible and providing as little equipment as possible on the hull.

At a cruising speed of 10 knots «Deep Flight» will descend at a rate of 200 meters per minute and ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница reach 11,000 meters in about an hour in the Mariana Trench (Марианская впадина), the deepest site on Earth. The weight of the craft is 2.5 tonnes, which is about the same as a large car. This will allow it to be launched from any vessel.

To be read after Lesson 10

Laser Technology

In the last decade there was outstanding progress in the devel­opment of laser technology and its application in science, industry and commerce. Laser cutting, welding and machining are begin­ning to be big business. The market for laser systems represents around 2.5 % of the world machine tool market.

Which country ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница is the biggest producer and consumer of lasers? Why, Japan, naturally: Japan produced 46 % of world's lasers in 1989, while figures for Europe and the USA are 32 % and 22 %. Ja­pan is building 1,200 to 2,000 CO2 lasers per year of which some 95 % are over 500 W power and 80 % of them are used for cutting operations.

Europe is the second largest user and the third largest producer. In 1990 Europe's market for lasers was $128 million, of which Germany consumed about $51 million, and Italy — $12 million.

The Germany met 90 % of its demands through domestic produc­ers. Growth rate of the European market is estimated at 10 to ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница 15 % per year.

In the future the main trend influencing the industry will be la­ser source prices. The prices are dropping. There appear lasers of modular construction. The complexity of laser machines is rising. Multi-axes systems are in more use now. Recently a 7-axis CNC la­ser machining center has been introduced. In addition to X,Y and Z axes, there are two rotary axes, A and C, and two more linear axes, U and V, to give a trepanning (прорезать большие отвер­стия) motion to the laser.

Optical Disks and Drives

Optical disks can store information at much ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница higher densities than magnetic disks. Thus, they are ideal for multimedia applica­tions where images, animation and sound occupy a lot of disk space. Besides, they are not affected by magnetic fields. This means that they are secure and stable, e.g. they can be transported through airport metal detectors without damaging the data. However, opti­cal drives are slower than hard disks. While there are hard drives with an average access time of 8 milliseconds (ms), most CD-ROM drives have an access time of 150 to 20 ms.

There are various types of optical drives, which have become a reality. CD-ROM ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница systems use optical technology. The data is re­trieved using a laser beam. To read CD-ROM disks, you need an optical drive (a CD-ROM player). A typical CD-ROM disk can hold 650 MB (megabytes) of sound, text, photographs, music, mul­timedia materials and applications. In addition, most CD-ROM drives can be used to play audio CDs. Do you remember that CD stands for compact disk?

Yet CD-ROM technology has one disadvantage. The data on a CD-ОМ cannot be changed or «written» to, i.e. it is impossible to add your own material to ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница what is on the disk. It is like a music CD. It is not designed for you to write on, it is designed to hold a lot of information that the user doesn't need to change.

Magneto-optical (MO) drives use both a laser and an electro­magnet to record information. Consequently, MO disks are rewritable, that is they can be written to, erased, and than written again. They are available in two formats. Their capacity may be more than 2 GB (gigabyte) or 230 to 640 MB. Such combined de­vices are good for back up purposes and storage of large ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница amounts of information such as a dictionary or encyclopaedia.

To be read after Lesson 11

Space Cooling

A new method of cooling that can generate cryogenic tempera­tures of 200 °C below zero without the use of electricity and with almost no moving parts has been tested at the Jet Propulsion Labo­ratory in Pasadena, California. The refrigerator used for the pur­pose was recently tested to — 253 °C, only 20 degrees above absolute zero, the lowest possible temperature.

In space such cooling system could increase the life of future space station refuelling ports by cooling the large liquid-hydrogen fuel tanks which ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница are likely to be in service.

In future earth applications it could be used for cooling hydro­gen-powered cars and planes, as well as for cooling superconduct­ing motors and computers.

According to the JPL (Jet Propulsion Laboratory) experts the key lies in the use of hydrides, materials that interact with hydro­gen. These materials absorb tremendous amounts of hydrogen gas at room temperature. The engineers of the JPL have taken advan­tage of this property to build a series of devices that act as compres­sors and provide a continuous cooling stream of liquid hydrogen.

The system saves ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница weight in space since it can use direct solar heat instead of electricity from heavier, inefficient electric systems. Because it has so few moving parts and uses the same supply of gas in a closed cycle, it could operate for many decades. Because of its long potential lifetime, the system could be used to cool infrared sensors during missions to the other planets, which may take 10 years or more to complete.

The Propulsion Challenge1

Magsails are a form of solar sails that use a completely different type of physical interaction with the Sun. Magsail is a ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница simple loop (петля, контур) of high-temperature superconducting wire carry­ing a persistent2 current. The charged particles in the solar wind are deflected3 by the magnetic field, producing thrust. Although the thrust density in the solar ion wind flux is 5,000 times less than the thrust density in the solar photon flux4, the mass of a solar sail goes directly with the area, whereas the mass of the magsail rises with the perimeter of the enclosed area.

The effective cross-sectional area of the magnetic field around the magsail is about a hundred times the physical area of the loop ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ 20 страница. As a result, preliminary calculations show the thrust-to-weight ra­tio of a magsail can be an order of magnitude (порядок величины) better than a solar sail. Recent thermal balance calculations indi­cate that a properly Sun-shielded5 cable can be passively main­tained at a temperature of 65 К in space, well below the supercon­ducting transition point for many of the new high temperature su­perconductors.

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