Учебник английского языка для технических университетов и вузов Издание шестое, стереотипное
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To be read after Lesson 3 Nuclear Power? Well, Yes Although nuclear reactors have generated electricity commer cially for more than 40 years and nearly 400 now in operation, two major accidents — in the US in 1979 and Chernobyl in the USSR in 1986 — have put the industry under a radioactive cloud. In the popular imagination, reactors are nuclear bombs; even if they don’t explode, they go on accumulating waste that will finally cause a global catastrophe. As a result, an energy source once considered as the fuel of the future became questionable. But not everywhere. Nuclear power provides nearly a quarter of the electricity generated in the indus trialized Western world by the 24-member countries of the Organi zation for Economic Cooperation and Development. In France more than 76 % of electric power is nuclear-generated, in Belgium — 62 %, Sweden — 50 %, Germany, Switzerland, Spain and Fin land come in at one third, Japan — a little less; Britain, the US and Canada — under 20 %. Some countries have no nuclear power plants at all and don’t want any. Not only the strong emotions of fear have worked against nu clear power. Energy demand grew more slowly than expected in the past decade. Prices of oil and coal have reduced. However, energy prices can rise. Moreover, supplies of fossil fuel are limited, while energy needs and tide (прилив) can’t meet the increasing require ments. Besides, nuclear power doesn’t add to global warming. All this causes the people to believe that the world can’t live and work without nuclear power. To be read after Lesson 4 Telecommunication A group of people enter a room, the lights go down, the screens come... the videoconference is under way. Tomorrow’s scientific fiction has become today’s new technol ogy -a daily reality for global companies who recognise the impor tance of regular communication between groups of people in different locations around the world. Essentially the videoconference room resembles a usual confer ence room. Delegates sit along one side of a table facing their col leagues on screen on the other side. They can see, hear and talk to each other simultaneously and can present slides of diagrams, even pieces of equipment. The technology is relatively simple. A device called videocodec takes the picture, digitalizes it for transmission over a special network and reforms the picture at the other end. The problem today is to manufacture codec to the new interna tional standard and to improve picture quality through faster trans mission speeds. Research and development is also focusing on mobile videoconferencing with broadcast quality pictures which enable to have instant communication with colleagues around the world. There is no doubt about the effectiveness of videoconferencing, as the videoconference eliminates the working time lost through travel. The First Travelling Post Office The first travelling post office in the United States was Abra ham Lincoln’s hat. That was a strange place, indeed, for mail; but that is where it was kept. Lincoln was appointed postmaster of New Salem, a small Western town, about the year 1833. The postman visited the place once a week and brought the mail — a dozen let ters, perhaps, and two or three newspapers — in his saddle (седло) bags. He was always met by Postmaster Lincoln who put the letters into his hat for safekeeping. Lincoln was also the clerk in the coun try store, so he had a good opportunity to distribute the mail. But if people did not come for it, he put on his hat and delivered it. So New Salem was the first town in the US to have rural free delivery, even though the postmaster received very small pay for his work. At that time, stamps and envelopes were not used. When the sender of a letter paid the postal charges, the postmaster wrote PAID in the large letters on the face of the letter. But the postal rates were so high that the sender seldom paid them. Thus, the mailing charges were usually collected from the person who received the mail. The postmaster always held his postal receipts until a government rep resentative came for them. The Internet The Internet is a magnificent global network with millions and millions of computers and people connected to one another where each day people worldwide exchange an immeasurable amount of information, electronic mail, news, resources and, more impor tant, ideas. It has grown at a surprising rate. Almost everyone has heard about it and an increasing number of people use it regularly. The current estimate is that over 70 million people are connected, in some way, to the Internet — whether they know it or not. With a few touches at a keyboard a person can get access to ma terials in almost everywhere. One can have access to full-text news papers, magazines, journals, reference works, and even books. The Web is one of the best resources for up-to-date information. It is a hypertext-based system by which you can navigate through the Internet. Hypertext is the text that contains links to other docu ments. A special program known as «browser» can help you find news, pictures, virtual museums, electronic magazines, etc. and print Web pages. You can also click on keywords or buttons that take you to other pages or other Web sites. This is possible because browsers understand hypertext markup language or code, a set of commands to indicate how a Web page is formatted and displayed. Internet Video conferencing programs enable users to talk to and see each other, exchange textual and graphical information, and collaborate. Internet TV sets allow you to surf the Web and have e-mail while you are watching TV, or vice versa. Imagine watching a film on TV and simultaneously accessing a Web site where you get in formation on the actors of the film. The next generation of Internet-enabled televisions will incorporate a smart-card for home shopping, banking and other interactive services. Internet- enabled TV means a TV set used as an Internet device. The Internet is a good example of a wide area network (WAN). For long-distance or worldwide communications, computers are usually connected into a wide area network to form a single inte grated network. Networks can be linked together by telephone lines or fibre-optic cables. Modern telecommunication systems use fi bre-optic cables because they offer considerable advantages. The cables require little physical space, they are safe as they don’t carry electricity, and they avoid electromagnetic interference. Networks on different continents can also be connected via sat ellites. Computers are connected by means of a modem to ordinary telephone lines or fibre-optic cables, which are linked to a dish ae rial. Communication satellites receive and send signals on a trans continental scale. To be read after Lesson 5 Harnessing (обуздание) the Speed of Light When American engineer Alan Huang revealed his plans to build an optical computer, most scientists considered this idea as hopeless. It was impractical, if not possible, they said, to create a general-purpose computer that could use pulses of light rather than electrical signals to process data. During one of the scientist’s lec tures on the subject, a third of the audience walked out. At another one, some of the scientists laughed, calling the researcher a dreamer. 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
Yet many scientists are predicting that the device will 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 in terference. 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 work on more than one problem at a time instead of one after another, as today’s new gen eration 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 microproces sors. At their most basic level, transistors may seem simple. But their development actually required many years of thorough research. Be fore 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 created the first inte grated 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 oper ating positions, on and off. This on/off function enables the pro cessing of information in a computer. The only information computers understand are electrical sig nals that are switched on and off. To understand how transistors work, it is necessary to have an understanding of how a switched electronic circuit works. Switched electronic circuits consist of sev eral 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 com pleting or breaking the circuit’s pathway. Transistors have no mov ing parts and are turned on and off by electrical signals. The on/off switching of transistors facilitates the work performed by micropro cessors. Something that has only two states, like a transistor, can be re ferred 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 1 ’s and 0’s generated by multiple transistors can repre sent letters, numbers, colours and graphics. This is known as binary notation. More complex information can be created such as graphics, au dio 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 allow electrical current to flow through them are called in sulators. Pure silicon, the base material of most transistors, is con sidered 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 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 tran sistor. To be read after Lesson 6 Ceramic Application The application which has captured the imagination of engi neers, 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 prob lems of cost and reliability. Steady progress is being made in the in crease 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 ser vice still needs to be defined for those applications where the mate rial 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, ceramic heat exchangers for chemical plants. Ceramics finds application in bearings and engine parts be cause 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 ex pensive 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 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 expen sive 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 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 can not 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 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 bend ing 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. |