Файл: О.А. Ставцева Английский язык. Методические указания и устные материалы для выполнения контрольных работ №4, 5, 6.pdf

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continually being replaced by rain. And we believe that wind and tides will never cease to exist.

Energy sources are known to be distributed very unequally. Such countries as Norway and Switzerland, for example, are rich in water power while England, being rich in the potential energy of coal, is poor in water resources, and there are few oil wells as well.

A very important factor for man is the possibility of converting energy from one form to another. The form most required by us is mechanical rotational energy. Everyone knows this energy to be used to rotate shafts in a factory for driving various machines as well as for driving the wheels of automobiles and locomotives.

Devices converting energy from one form to another are called engines, which may be of different types. Mechanical rotational energy, for instance, may be produced either by a heat engine converting heat energy or by a turbine or water engine converting the kinetic energy of falling water.

3. CONDUCTORS AND INSULATORS

An electric current was established to be a stream of electrons moving along a conductor. Substances differ in electrical conductivity which depends on the ease with which their atoms give off electrons. Accordingly, they are divided into conductors and insulators.

We know conductors to be the materials with a low resistance so that current easily passes through them. The lower the resistance of the material, the more current can pass through it. The most common conductors are metals, the best of them being silver and copper. Copper being much cheaper than silver, it is widely used to manufacture wire conductors.

It should be taken into consideration that most materials change their resistance with changes in temperature. Electricians know that with the increase of temperature the resistance of metals is also increasing while that of carbon is decreasing. The less is the change of resistance with the change of temperature, the more perfect is the resistance material.

Materials having a very high resistance are called insulators. It is very difficult for current to pass through insulators. The most common insulators include air, paper, rubber, plastics.

Any insulator can conduct current when a high enough voltage is applied to it. But in order to make insulators conduct, currents of great value must be applied to them. The higher the resistance of an insulator, the

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greater the applied voltage has to be. The main function of insulators is to isolate conducting wires and thus to prevent a short between them.

4. TRANSMISSION LINES

Electric energy generated at the power stations is to be transmitted to the consumer. To carry electricity to far-off places it is necessary to have high-voltage power transmission lines. The length of lines varies from area to area, depending on the distance to be covered. Electric power is generally transmitted by using not a direct (d.c.) but an alternating current (a.c.) that reverses direction 25, 50, or 60 times per second.

Thick wires carrying electricity across the country are supported by very high pylons so that nobody would touch them. The best metal conductor is known to be copper, but the wires are usually not copper but aluminium, thirty wires together forming one thick cable. Aluminium being very light, the pylons can easily hold the cables.

Wire conductors offer resistance to the current flow. The longer the wire, the greater is its resistance. Accordingly, the higher the resistance, the greater are the heat losses in the wire. In order to reduce the losses a stepdown (понижающий) transformer can be used.

Electricians distinguish between a «power line» and a «power network». The difference between them is the absence (line) or the presence (network) of parallel branches. According to their functions, power lines and networks are subdivided into transmission lines and distribution ones.

Transmission lines serve to deliver power from a station to distribution centres. They are also used to connect a number of stations together, forming in this way a «power system». Distribution lines deliver power from distribution centres to the consumers.

5. ELECTRIC POWER INTERRUPTIONS

On November 9, 1965, at 5:16 p.m. a backup relay (реле резервной защиты) failed at one of the five main transmission lines at No.2 power station near Toronto, Canada. As the load had shifted to the other four lines, they became overloaded, and as a result the relays failed in all four lines. The failure resulted in the load being shifted to the other power plants in the system. The plants got overloaded, which caused them to shut down. Within minutes, power plants in Canada, New York, and the New England states got out of service. The blackout (перерыв в энергоснабжении) affected 30

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million people and covered an area of 306,000 sq. m. In some areas, such as New York City, power was not restored for about 13 hours.

This massive power blackout was followed by the establishment of the national Electric Reliability Council in June 1958. The task of the council is to set standards for the design, operation, and maintenance of generating and transmission systems. The standards serve to prevent a failure in one power system from spreading to other systems. Yet, local system failures cannot be avoided.

Nowadays in some European countries and in the US there are from 60 to 80 power interruptions a year, in which there is a loss of service for customers for more than 15 minutes. Mostly these interruptions are caused by weather conditions including ice formation, freezing snow, lighting or storm. There can also be failures of equipment such as transformers, relays, insulators and so on. Nevertheless, the reliability of electric service is considered to be extremely high.

6. NUCLEAR SAFETY CONCERNS CONTINUE

Following the nuclear reactor accident at Chernobyl in Ukraine, in April 1986, when radioactive fallout spread across much of Europe, international attention focused on the aging nuclear reactors and uneven implementation of safety standards in the countries belonging to the Commonwealth of Independent States.

The EU (European Union) is particularly concerned about safety of nuclear reactors. In the early 1990s it decided to play a major role in international efforts to help these countries in sustainable improvements in safety by replacing old reactors with alternative energy sources, improving energy efficiency, and helping to modernise the safer reactors.

EU nuclear safety experts believe many reactors designed in Soviet times to have significant safety shortcomings. The older reactors which cannot be upgraded at reasonable cost are planned to be closed and replaced with other energy sources, including new safe nuclear power ones.

The 1999 EU programme consisted of on-site assistance in Kazakhstan, Armenia, Russia and Ukraine. There was also work to deal with environmental problems caused by poor management of radioactive waste and spent nuclear fuel, as well as assistance with the closure of the infamous Chernobyl plant. The EU contributed to efforts to secure the shelter for Unit 4 destroyed in 1986, and to establish independent nuclear regulators.

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Armenia’s government is to close the Medzamor nuclear power plant which it has to keep open until a secure alternative energy source is up and running. The EU focuses on short-term improvements to design safety through on-site projects.

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1. SOLAR POWER STATIONS

The idea of high-capacity SPS (solar power stations – гелиоэлектростанция) is not new. It is based on the thermodynamic transformation of solar radiation with the use of the steam-turbine cycle. We know such stations to be built today in different countries.

An experimental SPS with a capacity of five megawatts, which is as much as was generated by the first atomic power station, was put into operation in the Crimea. It also includes a thermal system with heat accumulators and an automated system of control over the technological processes of the entire station. The capacity of future experimental SPSs is planned to be 200 - 300 megawatts, and that of commercial stations – 5,000 megawatts and more.

Another design of high-capacity installations with direct transformation of solar energy into electricity makes use of a photoeffect. We know modern energetics to be based on units generating high voltage. Russia was the first to develop and test a high-voltage (32,000 volts) photoelectric battery. The efficiency of solar batteries was increased by means of the concentration of solar radiation. This idea (first advanced in 1970) has received universal recognition and is now being studied and developed in many foreign laboratories.

However, the efficiency of the operation of a solar power station is believed to be greatly reduced because of the limited period of its work during the year and weather factors. To overcome these drawbacks the scientists are now working at different combinations of SPSs with traditional stations – thermal, atomic, hydraulic.

2. IMPROVING REACTOR SAFETY

One of the most significant projects in nuclear safety during 1999 was the construction of a test facility for the VVER 440/213 reactors, one of the most recent types used in the CIS (the Commonwealth Independent States).

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The facility, known as a bubble condenser (барботёр-конденсатор), was built at Elektrogorsk in Russia, and allows engineers to test breaks for water and steam line in the event of a nuclear accident at a plant where this type of a reactor is used.

In western countries nuclear power plants have systems which keep accidental radioactivity releases within a contained area. More recent Russian «third generation» reactors have a similar system, but the older first and second generations do not. Many of the second generation reactors have a pressure suppression container system, while the bubble condenser is designed to control both pressure and radioactivity.

The results of testing have been a success. «The test which simulated the maximum load possible during an accident showed that the bubble condenser works. This was something that was needed and was really useful. It proves that this system is safe. Only minor modifications to such plants, costing not more than €100,000 are needed to ensure larger safety margins», says Mr. Kühlwein, who is a project manager for the test. «Everyone benefits if nuclear power plant safety is increased. It is also an opportunity for western industry and the eastern plants to learn about each other and establish business links for the future».

ДЛЯ СТУДЕНТОВ СТРОИТЕЛЬНЫХ СПЕЦИАЛЬНОСТЕЙ

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1. CIVIL ENGINEERING IN KUZBASS

Everyone knows civil engineering to deal with the construction of various kinds of buildings and structures. All buildings constructed nowadays may be divided into three main types: intended for housing, for industrial purposes, for cultural activities of the people. Much attention is paid to providing the region with an adequate infrastructure, including highways, airports, bridges, parking lots and so on.

The first multistoried buildings are known to have been built in Novokuznetsk; today they are being erected all over the region. As for industrial construction much work is to be done in erecting new and reconstructing the existing facilities for coal-mining, metallurgical, and chemical industries.

Civil engineering would be unable to fulfill its tasks without modern machinery and materials. At present there are about 500 building organiza-

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tions in the region. The builders have at their disposal up-to-date earthmoving and building equipment: scrapers, bulldozers, excavators, loaders, etc. Due to mechanization a construction site looks like a huge industrial enterprise.

The main building materials are timber, stone (brick), concrete, steel, lightweight metals, glass and plastics. Building materials industry is represented by nearly 50 enterprises producing cement, asbestos, brick, concrete panels, paints and other materials. Cement and glass are known to be used not only within the country but to be exported abroad.

Availability of new building methods and building materials are of great importance for developing modern architecture, speeding up construction, and decreasing its cost.

2. TOWN PLANNING

Modern town planning is supposed to begin with the development of a master (генеральный) plan. It is the plan which defines the pattern of the town and its relation to the topography. It is to show the principal areas and zones necessary for housing and industry, for business and cultural purposes.

As for the landscape, the master plan should show the agricultural areas surrounding the town and the areas of natural landscape that should be left for passive recreation. The design must respect any feature that has visual significance. It is more than vandalism to fall a tree that has taken years to grow or to demolish a building of fine architectural qualities. Besides, it is necessary to plan the active recreation zones both for the housing areas and for the town as a whole.

Planning a town or a city one should remember that the site of its location should be «healthy», free from dust and smog. The plan must provide the proper standards of space and sunlight to the city’s buildings, and people must move about the town without danger to their life. The town should be so planned that it would be a convenient place for dwelling, working and playing.

Much attention in town planning is paid to the economy factor. But this does not mean that the cheapest scheme is the best scheme.

The «raw materials» for a town planner include a great number of objects: buildings, roads and pavements, lamp posts, trees and so on. Each of them should give a pleasure to look at it.

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3. MODERNIZING CONSTRUCTION

The history of building is inseparably connected with the history of civilization itself. Primitive building required practically no tools and depended upon the material at hand. The invention of tools made it possible to cut stones and timber. The more civilization was developing, the larger and more complex structures could be built. Building has been raised to a higher level due to the creative work of mechanical, technological, and civil engineers. It has become a vital element of national industry, but still it has a number of problems, the greatest of them being minimization of the cost and time of construction works.

An increase in the construction works can be achieved by greater productivity. One of the most important economic results of this would be much faster building.

Modern architecture is characterized by simplicity of line and design. This made it possible to introduce standardized components for buildings and structures erected for different purposes. High quality standardized components for buildings are manufactured by modern house-building plants. Most of the work being done at the plant, the operations on the construction-site, where the conditions may be very difficult, are minimized.

This building method is often called “industrialized building” and includes such aspects as the organization of work, programming, design, wide-scale application of factory-produced panels and other dwelling parts, as well as the increased use of standardized or prefabricated (сборный,

заводского изготовления) components.

4. RESIDENTIAL AND INDUSTRIAL BUILDINGS

In industrialized countries the building industry employs a considerable proportion of the labour force, comprising skilled and unskilled workers, building engineers and architects, designers and managers.

Building industry provides the construction of residential, public and industrial buildings. It holds a considerable place in any country’s national economy and is being carried out on a large scale.

Housing is known to affect the level of living, that is why it is paid much attention to. The ever growing housing demands required new methods of construction with greater emphasis upon standardization, widescale use of prefabrication and reinforced concrete (железобетон) panels.

Prefabricated elements and structures may be classified into two principal groups – for residential houses and industrial buildings.

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Modern designs for residential construction should provide all the conveniences: heating, lighting and ventilating systems, coldand hot-water supply, sanitary fittings.

Industrial buildings are known to comprise laboratories and factories, plants and mines, office buildings and stores, garages and exhibition halls, etc. Each of them demands its own structural solution and techniques. But in general they may be divided into two categories: structures which have to provide enough space for machinery and the ones which have to provide enough space for people.

Reinforced concrete arches, metal frames, glass walls and prefabricated mass-produced elements are known to be widely used in constructing modern industrial buildings.

5. A LITTLE ON ROADS

Today it is hard to imagine our life without highways. Roads are known to have appeared in the far-off times and were first in the form of pedestrian tracks. Then, as civilization was progressing, they became routes along which horse-driven traffic and finally motor vehicle could move.

Roads have always had a dual function serving as traffic routes and as a means of approach to residential and industrial buildings. But since the growth of transport these functions have been seriously in conflict with each other. Today this conflict is extremely great and may result in great danger.

Any town is to be so planned that its citizens would not be injured or killed by moving traffic. The layout of all newly developed areas should take into consideration the safety factor. It is the task of a designer to see that pedestrians and fast moving motor vehicles are isolated, they should never be mixed with each other. When planning a city a designer is to define the principal roads connecting various districts and zones together, the most efficient routes of public transport, the principal pedestrian ways.

Much attention is being paid to road construction in Kuzbass where automobile transportation provides the connection between 20 towns of the region. More than 2.6 thousand automobile companies have at their disposal thousands of trucks, cars and buses.

Different organizations all over the world are experimenting with automated highways. The aim of the research is to provide computercontrolled highways making it possible for vehicles to travel with greater safety at faster speeds and closer to each other.