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IMPRESSIONS OF MODERN ARCHITECTURE.
(A LETTER FROM ENGLAND).
1. You ask what I think of modern architecture. I don't know very much about modem architecture in Europe, but styles are probably similar in most countries today. I think this is because now architects have no opportunities they had in the past. They are seldom asked to design buildings like wonderful churches and cathedrals of the Middle Ages. Architects today have to design schools, hospitals and huge blocks of flats and offices. If they, are asked to make plans for houses, these are usually all alike or nearly alike.
2. Boxes - that's what a good deal of modern architecture reminds me of. The blocks of flats in our big towns are huge boxes, whether the fronts and sides are square or oblong. A man who lives in one of these boxes works in another big box, high up in the air. If he falls ill, he goes to another big box called a hospital.
3. Architects have done some very good work in designing new schools. Many of these are prefabricated, which means that as much of the building work as possible is done not on the building site, but in factories where mass production methods can be used. The parts are taken to a site and put together there. Children who attend the best of these new schools are very happy. Their classrooms are light and big, and they have a fine large assembly hall. The children have dinner at school, and there is a dining-hall completed with modern kitchen.
4. I began this letter by saying that many modern buildings, especially the blocks of flats and business offices, were like big boxes. They do look like boxes from the outside, but when we go inside, we find them very well planned for their purposes. An architect today has to be an engineer too. The best modern buildings help us to live and work in comfort. They save plenty of unnecessary work. There is central heating, for example, instead of the dusty open fires we used to have, with coal to be carried up long stairs and ashes to be carried down.
5.1 have given my opinion on what I have seen in England. I know a lot of interesting work has been done in Scandinavia, and, of course, I've read about the work of Le Corbusier in France and I'd like to see what American architects are doing now. You may know the work of the American architect Frank Lloyd Wright. He designed the Imperial Hotel in Tokyo. It was designed to resist earthquakes and it proved so strong that it did. It was one of the few buildings in Tokyo that did not fall in the terrible earthquake of 1923.
1. Man has always been a builder. This kind of house he built depended upon the climate, upon his enemies, and upon the building materials at hand. The first houses in many parts of the world were made of wood, for in those days the greater part of the Earth was covered with forests. Men tied together the tops of several trees and covered them with the skins of animals
It appears that the most ancient homes on the territory of Russia were earthenhouses. One such home was discovered near Voronezh m 1927. It consisted of a shallow hole of oval shape. The floor was covered with limestone slabs.1 The roof had been conical and stood on poles (столб) covered by branches or animal skins. Such dwellings existed in that part of the country in the Upper Paleolithic Period (from 40,000 to 12,000 years ago).
2. The ancient Egyptians built very simple houses, by present standards. Having dried the bricks in the sun, they put up four walls, and above these they placed a flat roof. The roof was flat because there was very little rain in Egypt. Although their buildings were simple in construction, the Egyptian art of building was very beautiful. Their pyramids and monuments, sphinxes and palaces arouse our admiration to this day. An important part in the history of building has been played by the column, and it was ancient Egypt that gave the world its first lessons in the art of making columns.
The Greeks learned much from Egypt. But they did not borrow the flat roof. They built a slanting roof because there was much rain in their) country. The Greeks made the roof slant in two directions from the middle. They also improved on Egypt's columns and soon became the teachers of the world in column making.
The Romans, in turn, learned much from the Greeks. First of all they borrowed the slanting roof and the columns. But they added the arch, thus adding much strength and beauty to their buildings.
3. In Ancient Russia architecture flourished for the first time in Kiev Russ. Unfortunately only a few of the church buildings of that period have remained, among them the famous Cathedral of St Sophia, the cornerstone of which was laid in 1037 to commemorate the victory over the Pechenegs. The churches of that time were strong buildings with thick walls and small windows. They often had to serve as fortresses against enemy invasions. During the Second World War the finest ancient architectural monuments were destroyed and great effort has gone into restoring them.
4. In the Middle Ages in Europe numerous wars between different nations caused great damages to the houses of crowded Medieval towns. Therefore many monarchs and nobles built castles as a form of defence. Those castles had very strong walls, narrow windows and projecting fortifications.
5. The Renaissance, which was a European movement, lasted roughly from the 14th to the 17th century. During this period, arts and sciences underwent great changes. In architecture these changes were marked by a return to classical forms and proportions of ancient Roman buildings.
6. Buildings of the 19th century are characterized by the use of new materials and by a great diversity of architectural styles. From the end of the 18th century iron and steel became widely used as alternatives to wood, for by that time many countries experienced shortage of this material. Later the Industrial Revolution brought mass-production of building parts which were manufactured at a factory and then simply assembled at a site.2
7. The 20th century is notable for widespread use of steel - reinforced concrete.3 Huge reinforced concrete units manufactured in heated factory premises4 are brought to the site which becomes something like an assembly shop.5 This technique has many advantages over other building methods. First of all it cuts the labour needed for building by 60 to 70% and extends the building season what is very important for countries where winter lasts for many months Furthermore the duration of building is greatly cut. All this makes the building process less expensive and much less labourous
Architecture of the 20th century is characterized by very high buildings - particularly skyscrapers6- and by great diversity of styles which completely differ from those of the past.
1 limestone slab - известняковая плита
2 were simply assembled at a site - просто собирались на строительной площадке
3 reinforced concrete - железобетон
4 heated factory premises - отапливаемые заводские помещения
5 assembly shop - сборочный цех 4
6skyscrapers - небоскребы
THE EGYPTIAN PYRAMIDS.
Architecture is the art which makes buildings beautiful to look at as well as useful. A man who designs (проектировать) buildings and makes the plans for them is called an architect. He has to think not only of what he wants the building to look like when it is finished, but also what it is to be used for. He must not forget the sort of material to be used in the building. This may be stone, brick, wood or steel and concrete.
There have been many different styles or kinds of architecture in the past and there are many different styles today in different parts of the world.
The oldest monuments which are met within architecture are the colossal pyramids of Egypt most of which were constructed about 6,000 years ago.
The pyramids are large triangular (треугольный) buildings which were placed over the tombs (могила) of Egyptian kings. The best known of the pyramids are a group of three built at Giza south of Cairo. The largest of these is 482 feet high. They tell us of the advanced civilization of ancient Egypt which is much spoken about even in our days.
It was a country which had expert mathematicians and engineers, where
The country was rich in hard and durable (прочный) stone, but poor in timber and metal, so that the main material used for construction was granite, and this was the reason for the durability of the pyramids.
Large blocks of stone were transported over long distances by land and water, and placed into position with the help of the most primitive equipment. That was done by slaves (рабы) working for thirty or forty years. All this great amount of work was done, masses of material and a large territory sometimes of about 52,000 square meters were used, only for protecting the body of a dead king and constructing a dwelling place for his happy life in the "other world".
AIR POLLUTION AND SMOG ARE THE PROBLEMS OF MODERN CITIES.
The word smog comes from smoke and fog. Smog is a sort of fog with other substances mixed in. Smog has been here a long time. Billions of years ago, volcanoes sent millions of tons of ash and smoke into the air. Winds whipped up dust clouds. Animal and vegetable matter decayed, adding polluting gases.
When people came along, they began to produce their own kind of air pollution. They discovered fire. In the Middle Ages, people in cities such as London used soft coal to heat their homes. The smoke from these fires, combined with moisture in the air, produced dense layers of smog. The smog would blanket the city for days, particularly in winter. The heat generated in large cities tends to circulate air within a dome-like shape. This traps the smog and holds it over the city.
Smog, and the chemicals and other substances in it, can be harmful, even deadly. Smog blurs vision. It irritates the eyes, the throat, and the lungs. Eyes water, throats get sore, people cough. Smog can make people ill. And it can make sick people sicker. Air pollution has been linked to eczema, asthma, emphysema, cardiovascular difficulties, and lung and stomach cancer. It also has a harmful effect on the environment. Food crops and animals suffer. Paint may peel from houses. It is obvious that we must do everything possible to reduce man-made atmospheric pollutants and smog.
Smog, along with smoke, is the most visible evidence of atmospheric pollution. But some atmospheric pollution is not visible and may not become visible until it is mixed with moisture. Lead compounds from leaded gasoline, hydrocarbons (unburned gasoline), carbon monoxide, and other gases may pollute the air without being seen. All air is polluted to some extent. That is, all air carries some polluting substances. Much of it is natural: smoke and ash from volcanoes, dust stirred up by the wind, compounds given off by growing vegetation, gases given off by rotting animal and vegetable matter, salt particles from the oceans, and so on. Man adds to these pollutants by burning coal, oil, gas, gasoline, and many other things.
Before we get to the automobile, however, let us review what we know about combustion. Most fuels, such as coal, gasoline, and wood, contain hydrogen and carbon in various chemical combinations. During combustion, oxygen unites with the hydrogen and carbon to form water (H20), carbon monoxide (CO), and carbon dioxide (C02).
In addition, many fuels contain sulfur; this burns to produce sulfur oxides. Also, in the heat of combustion, some of the nitrogen in the air combines with oxygen to form nitrogen oxides (NO). Some of the fuel may not burn completely, so that smoke and ash are formed. Smoke is simply particles of unburned fuel and soot, called particulates, mixed with air.
Altogether, it is estimated that 200 million tons of man-made pollutants enter the air every year in the United States alone. This is about a ton for every man, woman, and child in the country!
This man-made pollution is what clean-air laws are aimed at.
Consider Los Angeles, a large city set in a basin, with about 7,000,000 inhabitants. It is surrounded on three sides by mountains, and on the fourth by the Pacific Ocean. When the wind blows out over the ocean, it sweeps away pollutants. But at other times, the air is stagnant. Smoke and other pollutants from industry and automobiles do not blow away. They just build up into a thick, smelly, foggy layer of smog. The location of Los Angeles, plus all the people and industry there, make it one of the biggest "smog centers" in the country. And it is Los Angeles which has led in measures to reduce smog.
Los Angeles has banned unrestricted burning, for example, burning trash. Incinerators without pollution controls were outlawed. Industry was forced to change combustion processes and add controls to reduce pollutants coming from their chimneys. Laws were passed that required the addition of emission controls on automobiles. All these measures have significantly reduced atmospheric pollution in the Los Angeles area.
If not controlled, the automobile can give off pollutants from four places. Pollutants can come from the fuel tank, the carburetor, the crank-case, and the tail pipe. Pollutants from the fuel tank and carburetor consist of gasoline vapors. Pollutants from the crankcase consist of partly burned air-fuel mixture that has blown by the piston rings. Pollutants from the tail pipe consist of partly burned gasoline (HC), carbon monoxide (CO), nitrogen oxide (NO), and - if there is sulfur in the gasoline - sulfur oxides (SO).
The Story of American Schools.
The first schools in America started in the 1600s. The Puritans, that is people who left England because of their religious beliefs, wanted each person in New England to know the Bible. So they organized schools to teach religion and basic subjects. But by the 19th century large numbers of children did not attend school. The problem of children's education started a great debate in America. There were three groups of people who had different ideas.
One group said that young people should spend their time at home helping their families. As most Americans lived on farms there was always much agricultural work to be done.
The second group, mostly businessmen, believed that children should work at factories. America's Industrial Revolution had begun, and this group knew that there would be many jobs in manufacturing. Some young people were already working at factories. They were children from 7 to 16 years old and their working day lasted up to 13 hours.
The third group said that to help create a better society, young people should know how to write and express their own ideas. Therefore each state should develop a system of public schools, called free schools, or common schools. This idea had been supported by Thomas Jefferson, the third president, and later by Abraham Lincoln who said that education was very important for people.
In 1839 Horace Mann, a Massachusetts-born educator, a lawyer by profession, opened the first common school in the United States. He devoted his life to this idea and soon a lot of common schools were opened throughout the state of Massachusetts. His example attracted national attention. Before long many states were doing what Massachusetts had done. The free school supporters had won the debate.
Вариант № 1.
Farm Electric Motors Selection According to Starting Requirements.
Single-phase electric motors1 are not inherently self-starting. Some special component part or style of winding must be incorporated into their design before they will start themselves and any attached load. Various electrical principles are used to accomplish this purpose, and all except one of the single-phase electric motors are named after the principle employed. This fact accounts for the following names: split-phase, capacitor-start induction run capacitor motor, two-value capacitor motor, repulsion motor2, repulsion-induction motor, repulsion-start induction motor, shaded-pole motor, and the one exception - the universal motor.
Since different electrical-starting principles are employed, it is understandable that the motors could very likely have different abilities to start a load. That is exactly the situation. Therefore, the name not only indicates a certain starting principle but also designates the motor's ability to develop starting torque. Furthermore, since one of the motor's jobs is to start the load, the selection of a motor to perform this duty is made according to the name of the motor.
The actual selection of a motor for starting a certain farm load is commonlyу made from the three types of motors shown in Figs. 1 and 2 and three-phase type 3of Fig. 3. The other types of motors are not as widely used, or are available only with their associated equipment.
Machines that must be started with a part or all of their operating load attached, or machines which in themselves present a fairly large amount of resisting torque during the starting period, are said to be h a r d t о s t a r t. This category includes such machines as a meat grinder, the vacuum pump of a milking machine,
Fig. 3. Three-phase squirrel-cage induction motor. It is used when three-phase service is available. This motor will not start or operate satisfactory on a single-phase system. Notice that the bearings of this particular motor are lubricated for life.
a small air compressor, a piston-type water pump, and a large-diameter attic fan. The smaller sizes of feed grinders and conveyers are also classed as h a r d to start. Loads of this type require a motor that develops a high-starting torque. The capacitor-star induction motor and the three-phase induction (squirrel cage) motor fulfill this requirement. For the average farm a three-phase supply is not available so the capacitor-star motor is the suggested solution to the selection problem.
The capacitor-start induction motor is commonly available in sizes ranging from 1.6 to 5 hp. However, loads in this category do not usually require a motor larger than 1 hp. This motor develops more starting torque than an equivalent-size split-phase motor and at the same time has less input current while starting. It has a greater initial cost than the split-phase motor, from one and one half to two times more, but other than starting, its operating characteristics are the same.
Many farm machines offer a very large resisting torque when being started, since they must be started while completely loaded, or under conditions which cause even greater loads than normal. Such machines as large air compressors or refrigeration compressors, small feed grinders (up to 1 hp), certain elevator conveyers, and many of the larger water pumps fall into this category.
The capacitor-start motor described in the previous section may be satisfactory for these jobs. However, the repulsion-start induction-type motor develops more starting torque and is best adapted for the h a r d e s t-t o-s t a r t loads. The repulsion-start motor develops about 20 per cent more starting torque than the capacitor-start motor, and even then it requires less input current. The lower value of input current is very important since it means less voltage drop in the lines which serve the motor. This line-voltage-drop factor validates still further the selection of a repulsion-start induction motor for the very-hard-starting loads.
The repulsion-start induction motor has more parts than the capacitor-start motor and may be 7 to 12 per cent more expensive in the smaller sizes, but the cost from 1.2 hp and upward is usually the same. This motor has brushes and a commutator which may require occasional attention and, in general, a variety of sizes are not readily available in many electrical stores. The larger stores usually stock the motor in sizes ranging from 1.6 to 10 hp. Its principal advantage is that it has the highest starting torque per input ampere of any of the single-phase induction motors.
Larger loads such as ensilage cutters, large feed mills, conveyers, gutter cleaners4, mixers, and blowers are usually hard or very hard to start, and require motor sizes such as 1.5, 2, 3, and 5 hp. This type of load is separated from the others since the driving motor must develop a large running torque and consequently will also develop a large starting torque. One type of motor which was previously described, the repulsion-start type, will also be satisfactory for these larger loads. In addition, two other types, the capacitor-start capacitor-run motor and the three-phase induction motor (squirrel-cage type), are quite well adapted for these applications.
The capacitor-start capacitor-run type (also termed a two-value capacitor motor) has essentially the same starting characteristics as the capacitor-start motor but has better running performance. It has a higher efficiency and a higher power factor and is in effect an improved capacitor-start motor for the larger-horsepower sizes. The cost is approximately the same as that of the repulsion-start motor, and the motor is normally available in sizes from 1.2to 10 hp.
For sizes over 1 hp the three-phase induction motor is the least expensive of the three types. It has about the same starting torque as the capacitor type and is the most rugged, reliable, and satisfactory motor of the group. This motor is highly recommended if three-phase power is available. It is manufactured in sizes ranging from 1.6hp upward.
1single-phase motor – однофазный мотор
2repulsion motor – репульсионный мотор
3three-phase motor – трехфазный мотор
4gutter cleaner - канавоочиститель
Farm Electric Motors Selection According to the Surroundings.
After having determined the horsepower rating of the motor for driving the load and the type of motor that will satisfactorily start the load, the remaining decisions involve those selections which are related to the location and surroundings in which the motor will be operated.
Enclosures1. The enclosure, or housing, is most important in protecting the working parts of the motor. Frequently motor failures occur or the life of the motor is greatly reduced because the type of enclosure was not given proper consideration. There are six standard types of enclosures, but unless the farm motor application is most exceptional, only three of these types need to be considered. These are the open-dripproof, the splashproof, and the totally enclosed types.
The most common type of enclosure for electric motors is the open-dripproof type2. The motors of Figs. 1 and 2 have this type of enclosure. It is applicable for locations in which the atmosphere is relatively free from foreign particles or splashing liquids. It should not be selected if the motor is to operate near a water spray, in the rain, or in areas containing lint, dust, or metallic or grain particles. In general, if the atmosphere bothers the operator, it is certain to be too much for this type of enclosure. The ventilation openings are near the base of the enclosure and provide for air circulation which cools the motor's windings. If excessive amounts offoreign particles, water, or oil are pulled inside through these openings, they destroy the insulation on the windings by causing overheating of the wires. The foreign particles may also get into the bearings and cause excessive wear.
Regardless of this limitation, the open-dripproof enclosure is suggested for general-purpose use around the farm.
The splashproof type3 of enclosure provides more" protection against water and dust than does the dripproof type. This enclosure is especially well suited for the dairy farm and for processing rooms where washing of the equipment is required. It is also installed outdoors but should be covered when not in use. The housing protects the motor against water and particles, with the exception of the small amounts I hat may enter at an angle upward from the floor. The over-lead and sides are completely shielded. The splashproof enclosure is shown in Fig. 4.
The totally enclosed type of enclosure affords the most reliable protection for the motor of any of these types. (No air is circulated through the motor since there are no external openings, but the cooling is accomplished by direct radiation and by convection.) The totally enclosed motor should be used in many places around the farm, but so far its use is not too common. It is a good selection for the driving motor of a feed grinder or similar machine where the atmosphere is filled with dust and small pieces of grain, and it is also adapted to areas subjected to water sprays. A motor having a totally enclosed housing is shown in Fig. 5.
Overload Protection. An overload means that the amount of current flowing to the motor is greater than the value of current marked on the nameplate of the motor. A motor must have current in order to produce torque, but the current also produces heat. The insulation on the motor's windings is not injured if the motor temperature is within the rated limits (usually 40°C above room temperature) but is damaged by higher temperatures. It is only logical that proper protection against excessive current be provided before operating the motor. Excessive current flows to a motor owing to any one of- the following reasons:
1. the connected load is too great or becomes jammed;
2. the belt is too tight;
3. the bearings are worn or need lubrication;
4. the input voltage to the motor is too low;
5. the (V-type) pulleys are cut of line;
6. alignment of the bearings is faulty owing to unequal tightening of the end shields or base.
It may appear that these items can be avoided, but it is quite unlikely that they could all be avoided over a period of years.
There are four types of overload protection for farm electric motors. One of these is installed by the manufacturer and is known as built-in-overload protection. Most types and sizes of motors for farm use are available with this protection. It is primarily suggested for motor sizes of 1 hp and less and is available in two styles - the automatic reset and the manual reset4. The automatic reset stops the motor in case of an overload and starts it again after it has cooled. This reset is not used for motors driving machines around which people are working, as there is a possibility of someone attempting to clear or clean the machine just as it starts again. Motors equipped with a manual-reset built-in overload are restarted by pressing a small button on the motor frame. These overload controls operate on the bimetallic-strip principle, and a certain length of time for cooling is necessary before the motor can be restarted.
A second type of overload protection is the time-delay fuse. It is the cheapest of the four types so far as initial cost is concerned but must be replaced after it has performed its function. The correct ampere size for the time-delay fuse is obtained by multiplying the motor-nameplate current value by 1.15 or by selecting a fuse rating which exactly corresponds with the nameplate value.
The manually operated motor starting switch is a very excellent type of overload control for motor sizes up to 1 hp. A similar switch with a larger frame is manufactured for sizes up to 3 hp. This overload control consists of a metal enclosure, a switch, bimetallic strips or a solder-and-ratchet wheel mechanism and a heater coil. The ampere rating of the heater coil or strip is selected by multiplying 1.15 by the motor-nameplate current value. The motor current flows through the heater coil, and the coil is designed to supply the necessary amount of heat to trip the switch mechanism if excessive current flows to the motor. The overload heater coil upon installation its ampere-rating tab should be retained and fastened to the switch, either in the switch lever or on the coil itself. The life of the coil is indefinite, but owing to the wide variety of types and sizes, replacements are not usually stocked locally, so it is well to include a spare with the initial order.
The fourth type of overload protection for farm electric motors is the magnetic starting switch. The overload protection is once again gained as a result of heat generated by a heater coil or strip. When a predetermined amount of heat is being developed by the heater, the overload contacts open, thereby interrupting the flow of current to the main coil of the switch. Deenergizing the main coil breaks the contacts to the motor. The magnetic switch is operated with pushbutton control or with a single-pole toggle switch5. The pushbutton control is available as an integral part of the magnetic-switch enclosure or as a separate unit which can be remotely located for the convenience of the operator. It is always good practice to have a switch instead of using the plug cap of the attached cable as a switch. The larger the motor size, the more necessary a switch becomes, and one should be used for all sizes from 1.2 hp upward. The magnetic starting switch is especially suggested for the 3- and 5-hp motors and is recommended for use with the 1.5 - and 2-hp sizes. It is a very satisfactory type of switch and provided for no-voltage protection as well as protection against excessive current. Compared to the contacts of a double-pole manually operated switch, the fast-operating, positive-acting contact points of a magnetic switch perform much better and last longer.
1enclosure – кожух, корпус, вид исполнения двигателя
2open – dripproof – каплезащитное исполнение
3splash – proof – брызгонепроницаемое исполнение
4reset – возврат
5single – pole toggle switch – однополюсный рычажный выключатель
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