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Another one sight of this park is The wall of 9 dragons was constructed in 1756 by the emperor Qianlong. This is the most ancient construction about 25.22 meters long, 5.96 meters height, 1.6 meters thickness. The wall of nine dragons is decorated the mosaic from a brick with 424 seven-color glazed tiles with relief images of nine dragons. Close the wall looks incredibly majestically and characterizes all power and grandness of the imperial power. If we speak about the most known and visited parks of Beijing, the Beihai Park occurs to one of the first. This is beautiful, very green and incredibly quiet place.

The next place of our research is located in the most popular city in the USA. Central Park [Picture 2] was the first artificial landscaped public park in the United States. Between 1821 and 1855, New York City nearly quadrupled in population. As the city expanded northward up Manhattan, people were drawn to the few existing open spaces, mainly cemeteries, to get away from the noise and chaotic life in the city.

The park was established in 1857 on 778 acres (315 ha) of city-owned land. In 1858, Frederick Law Olmsted and Calvert Vaux, a landscape architect and an architect, respectively, won a design competition to improve and expand the park with a plan they titled the "Greensward Plan". Construction began the same year and the park's first area was opened to

the public in the winter of 1858.

Now the Park is located on the island of Manhattan between 59th and 110th street and Fifth and Eighth avenues and therefore has a rectangular shape. The length of the Park — 4 kilometers,

width — 800 meters, total area is 3.4 km2. The Park is visited by approximately 25 million people a year, it is the most visited Park in the United States, and its showing in many

movies and television shows made the Park one of the most famous in the world.

The park is entirely man-made, although it looks natural. The park contains several natural-looking lakes and reservoirs that have been artificially created, extensive walking trails, two skating rinks for ice skating (one of which is a swimming pool in July and August), Central Park Zoo, Central Park Garden, wildlife sanctuary, large area natural forests, the Delacorte Theater, which hosts summer festivals. The attractions of the Central Park are: the Belvedere Castle, the Swedish Cottage Theater, and the historic Carousel. In addition, there are seven main lawns and many children's playgrounds for children.

According to the idea of the architects, the Central Park should become the embodiment of democratic principles and freedoms, for which the country has struggled for many years. Social equality - this was and the main idea when designing a park. This is particularly expressed in the joint parallel passage of pedestrian roads, where the poor and rich people moved together. Central Mall -

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the only direct avenue leading to the heart of the park Bethesda terrace, a wide pedestrian area with benches and places for street performances - also had to be a place of mixing people of different classes.

The Central Park has several entrances, which required names. That is why the architects chose the occupations of ordinary people who participated in the construction of the park. The park has gates of Scientists, Artists, Craftsmen, Traders, Farmers,

Hunters, Miners, Foresters, Engineers, Inventors, Military, etc.

Today the park is one of the most beloved places of the inhabitants of the city, where everyone will find entertainment for themselves. The park has more than 80 kilometers of pedestrian and 10 kilometers of

racetracks, 36 unique stone and cast-iron bridges, several open-air theaters, a tennis center, many free outdoor sports facilities and many others.

Also we should say about the most majestic and magnificent park on our planet. Park Güell [Picture 4]

is located in Barcelona and it is one of the most beautiful places in Spain. This park was built is one of at the initiative of Eusebio Guell. He decided to

make a housing estate for prosperous citizens, which look like garden city. Guell bought 17 hectares in Muntanya Pelada in 1899. The project of architectural and landscape composition was created by the great architect of that time Antoni

Gaudi. Park Guell is one of the most famous Gaudi’s creations and in 1984 it was entered in the list of the World heritage of UNESCO.

At a main entrance to the park, we can see two pavilions: office and for the gatekeeper. These buildings were made by Antonio Gaudi in rural style and were decorated with medallions and decorative eaves from a beaten ceramic tile. Also beaten tile has trimmed roofs and a tower.

The next park sights are a big ladder and a mosaic sculpture of a salamander. Gaudi often gave preference to this amphibious entity. The ladder conducts to the "Hall of hundred columns" decorated with a set of decorative elements with symbolical value. "The hall of hundred columns" literally stuns with the majestic ensemble from 86 Doric columns 6 meters high. They are made of an artificial stone and support a massive esplanade of a mosaic ceiling, which has the wavy form. In the place of missing four columns the ceiling is decorated with mosaic medallions.

Over the hall there is the esplanade which Gaudi named "Greek Theatre". From the sea, this place is fenced off by a bench, and from mountains - natural grottoes. Gaudi used a set of materials for construction of a long and wavy bench: glass pieces, faience, a facing tile, the broken plates and cups.

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Since then has passed almost century. During this time the park wasn't exposed reconstruction, to capital repairs. It seems that Gaudi was able to build in full sense for ages.

In addition, we should say about parks in Russia. One of St. Petersburg's most famous and popular visitor attractions, the palace and park at Peterhof

(also known as Petrodvorets) are often referred to as "the Russian Versailles" [Picture 5]. The idea of creating a summer residence came to Peter 1 in 1714. He needed not just a residence. Peter decided the luxury and beauty of Peterhof to eclipse the most famous palaces of France.

Since Peter often went to Kronstadt to watch the erection of fortifications, and weather the sea posed many dangers, and he desided to build a house in the place from which the move would be more comfortable and not far.

Peter the Great, as is known, was a very active monarch. He himself made decrees relating to the construction of a country residence. Preserved drawings and drawings with marks of the emperor, that's why it is called the first architect of Peterhof. The king ordered abroad sculptures and paintings to decorate his palaces and parks. In addition, Peter personally developed a fountain system.

Every year several million tourists come to the Northern Capital of Russia to admire the legendary fountain complex in Peterhof. Today the complex consists of 4 cascades and 173 fountains, the main place among which is undoubtedly "Samson". After the death of Peter I in 1725, Empress Catherine established this group, which symbolized Russia's victory over Sweden in the Northern War. The first fountain was cast from lead and only under the emperor Paul was replaced by a bronze sculpture

The war was a terrible test for Peterhof. Fascist barbarians destroyed and blasted everything that they could not take out of Russia. But the Leningraders managed to keep the fountains of Peterhof. Their reconstruction began immediately after the Victory. Every Leningrad were working: they cleaned the broken trees, cleaned the park, restored sculptures and fountains. 38 fountains began to work already in August 1946. And a year later, the Samson Fountain took its place and took its place.

In conclusion, we would like to say that certainly one of the first places, which tourists visit are parks. That is why they must be beautiful and comfortable. It is an opportunity to be closer to nature and provide cultural centers for yourself and your friends. Today, the problem of the status and development of parks is important. Every cities tries to improve their general places of rest and make them more available.

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Ivanova E.V., Mikhailova E.B.

Nizhny Novgorod State University of Architecture and Civil Engineering

WIND TURBINE GENERATORS

Wind energy is playing a crucial role in the establishment of an environmentally sustainable low carbon economy. This work presents an overview of wind turbine generator technologies and compares their advantages and drawbacks used for wind energy utilization.

Traditionally, DC machines, synchronous machines and squirrel-cage induction machines have been used for small scale power generation. For medium and large wind turbines (WTs), the doubly-fed induction generator (DFIG) is currently the dominant technology while permanent magnet (PM), switched reluctance (SR) and high temperature superconducting (HTS) generators are all extensively researched and developed over the years. In this work, the topologies and features of these machines are discussed with special attention given to their practical considerations involved in the design, control and operation, quick reference guidelines for developing wind turbine generation systems are provided.

Our basic objective is to study construction and design of wind turbine generators, to compare their types, and to analyze their advantages, disadvantages and future prospects.

The tasks that face us are as follows:

To learn new facts about wind turbines ;

To think about the future of wind turbine generators.

We are going to achieve these goals by analyzing information about wind turbine generators.

The use of wind energy to generate electricity first appeared in the late 19th century but did not gain ground owing to the dominance of steam turbines in electricity generation. The interest in wind energy was renewed in the mid1970s following the oil crises and increased concerns over resource conservation. Initially, wind energy started to gain popularity in electricity generation to charge batteries in remote power systems, residential scale power systems, isolated or island power systems, and utility networks. These wind turbines themselves are generally small (rated less than 100 kW) but could be made up to a large wind farm (rated 5 MW or so). It was not until the early 1990s when wind projects really took off the ground, primarily driven by the governmental and industrial initiatives. In the 1990s there seemed a shift of focus from onshore to offshore development in major wind development countries, especially in Europe. Offshore wind turbines were first proposed in Germany in 1930s and first installed in Sweden in 1991 and in Denmark in

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1992. By July 2010, there were 2.4 GW of offshore wind turbines installed in Europe.

Compared to onshore wind energy, offshore wind energy has some appealing attributes such as higher wind speeds, availability of larger sites for development, lower wind sheer and lower intrinsic turbulence intensity. But the drawbacks are associated with harsh working conditions, high installation and maintenance costs. For offshore operation, major components should be marinized with additional anti-corrosion measures and dehumidification capacity. In order to avoid unscheduled maintenance, they should also be equipped with fault-ride-through capacity to improve their reliability.

Over the last three decades, wind turbines have significantly evolved as the global wind market is growing continuously and rapidly. By the end of 2009, the world capacity reached a total of 160 GW. In the global electricity market, wind energy penetration is projected to rise from 1% in 2008 to 8% in 2035. This is achieved simply by developing larger wind turbines and employing more in the wind farm. In terms of the size, large wind turbines of 178 Advances in Wind Power the MW order began to appear in the EU, the US and now in China and India. Nowadays, modern wind turbines are reliable, quiet, cost-effective and commercially competitive while the wind turbine technologies are proven and mature. At present, technical challenges are generally associated with evergrowing wind turbine size, power transmission, energy storage, energy efficiency, system stability and fault tolerance.

Clearly, wind energy is high on the governmental and institutional agenda. However, there are some stumbling blocks in the way of its widespread usage. Wind turbines come with different topologies, architectures and design features. Some options of wind turbine topologies are as follows:

•Rotor axis orientation: horizontal or vertical;

•Rotor position: upwind or downwind of tower;

•Rotor speed: fixed or variable;

•Hub: rigid, teetering, gimbaled or hinged blades;

•Rigidity: still or flexible;

•Number of blades: one, two, three or even more;

•Power control: stall, pitch, yaw or aerodynamic surfaces;

•Yaw control: active or free.

Wind turbines include critical mechanical components such as turbine blades and rotors, drive train and generators. They cost more than 30% of total capital expenditure for offshore wind project. In general, wind turbines are intended for relatively inaccessible sites placing some constraints on the designs in a number of ways. For offshore environments, the site may be realistically accessed for maintenance once per year. As a result, fault tolerance of the wind turbine is of importance for wind farm development. One of key components in the wind turbine is its drive train, which links aerodynamic rotor and electrical output terminals. Optimization of wind turbine generators cannot be realized

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without considering mechanical, structural, hydraulic and magnetic performance of the drive train. Drive train topologies may raise the issues such as the integration of the rotor and gearbox/ bearings, the isolation of gear and generator shafts from mechanical bending loads, the integrity and load paths. Although it may be easier to service separate wind turbine components such as gearboxes, bearings and generators, the industry is increasingly in favor of system design of the integrated drive train components.

A variety of new wind projects were installed in the U.S. in the late 90s, including a cluster of Zond Z-40 turbines operated for a utility in southwest Texas, a wind plant of 46 Vestas machines planned for Big Spring, Texas, a 10megawatt wind plant in Northern Colorado, a number of plants in the upper midwest, and the "re-powering" of some projects in California. Some of these involve foreign machines manufactured in the U.S. There is a sense that the industry is finally on the move again, with over 2000 megawatts of new capacity in the U.S. alone. Existing and planned U.S. projects can be explored using the Wind Project Map maintained by the American Wind Energy Association.

The cost of energy from larger electrical output wind turbines used in utility-interconnected or wind farm applications has dropped from more than $1.00 per kilowatt-hour (kWh) in 1978 to under $0.05 per kWh in 1998, and is projected to plummet to $0.025 per kWh when new large wind plants come on line. The hardware costs of these wind turbines have dropped below $800 per installed kilowatt in the past five years, underpricing the capital costs of almost every other type of power plant.

It's difficult to accurately compare the costs of wind plants and fossil fuel plants because the cost drivers are so different. Low installed-cost-per-kilowatt figures for wind turbines are somewhat misleading because of the low capacity factor of wind turbines relative to coal and other fossil-fueled power plants. Capacity factors of successful wind farm operations range from 0.20 to 0.35. These can be compared with factors of more than 0.50 for fossil-fuel power plants and over 0.60 for some of the new gas turbines.

However, the use of “capacity factor” is also misleading because wind has a “rubber” capacity factor that varies with the density of the wind resource. But that wind resource is constant for the life of the machine and is not subject to manipulation or cost increases. One reason why fossil fuels are so popular with investors is that many of the risks are passed on to consumers. Fossil fuel shortages result in an increase in revenues for investors, who are actually rewarded for: 1) speeding the depletion of a nonrenewable resource or 2) not investing enough of their profits in support infrastructure, which drives up prices. If a big oil coal or gas company could start charging for the wind, they would make sure that wind power development happened. In late 1996, with the purchase of Zond Systems by Enron (a now-defunct gas mining and distribution company), the possibility of this happening became very real.

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Even though Enron proved to be a poor steward for the Zond technology, the subsequent purchase of what was one of the only viable Enron divisions by GE Energy in 2003 maintained U.S. visibility in the large wind turbine market. In 2015, GE was still the largest U.S. manufacturer of wind turbines, although recently overtaken by the Danish company Vestas as the largest manufacturer and installer in the world.

Wind energy has attracted much attention from research and industrial communities. One of growth areas is thought to be in the offshore wind turbine market. The ongoing effort to develop advanced wind turbine generator technologies has already led to increased production, reliability, maintainability and cost-effectiveness. At this stage, the doubly fed induction generator technology (equipped with fault-ride-through capacity) will continue to be prevalent in medium and large wind turbines while permanent magnet generators may be competitive in small wind turbines. Other types of wind turbine generators have started to penetrate into the wind markets to a differing degree. The analysis suggests a trend moving from fixed-speed, geared and brushed generators towards variable-speed, gearless and brushless generator technologies while still reducing system weight, cost and failure rates.

In conclusion, there may not exist the best wind turbine generator technology to tick all the boxes. The choice of complex wind turbine systems is largely dictated by the capital and operational costs because the wind market is fundamentally cost-sensitive. In essence, the decision is always down to a comparison of the material costs between rare-earth permanent magnets, superconductors, copper, steel or other active materials, which may vary remarkably from time to time.

Zimina S.S., Mikhailova E.B.

Nizhny Novgorod State University of Architecture and Civil Engineering

ULTRAVIOLET AND ULTRASOUND AS THE NEWEST METHODS

OF URBAN WASTEWATER DISINFECTION

The work deals with the field of wastewater disinfection, particularly, the basic criteria for water disinfection. The subject of the work is relevant because the use of water depends on its properties and composition.

The work relevance is also defined by the necessity of water treatment from various impurities. Water supply and sewerage are known to be set of measures of water industry to provide to the population, transport and agriculture. Quality of water is characterized by its physical, chemical and bacteriological properties: color, turbidity, odor, bacterial count, pH and temperature.

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The purpose of our work is to consider and choose the most effective method of disinfection of urban wastewater.

We consider the following tasks:

-to analyze the newest methods of disinfection of urban wastewater;

-to compare the chlorination method and ultraviolet irradiation;

-to consider: disinfection of sewage with ultraviolet irradiation, disinfection of sewage with ultrasound;

-to choose from the methods presented the most effective for sewage disinfection.

We use the following methods: analyses and comparison.

According to the World Health Organization, up to 80% of infectious diseases are transmitted by water.

The main source of pollution of water is wastewater. Pathogenic microorganisms can not be completely removed at the facilities for complete biological treatment of urban wastewater. Therefore, effective disinfection is a priority in wastewater treatment processes. The existing methods of disinfection of sewage can be divided into two groups - chemical and physical (Table 1).

The real practical technologies of sewage disinfection that have been tested at existing treatment facilities are: chlorination, ozonization and ultraviolet irradiation. Promising are - ultrasonic treatment, electropulse discharge, gamma radiation.

The use of the traditional method of disinfection with chlorine is currently being questioned, since the fact of the formation of organochlorine compounds in water with chlorination, which have high toxicity, mutagenicity and carcinogenicity in relation to humans, is found in water. In addition, chlorination is the least effective against viruses and spore-forming bacteria. Ozone has a high virucidal effect of disinfection, but ozonation of sewage water also produces by-products (ketones, aldehydes, phenols) classified as toxic. In this regard, currently the preference is given to the methods of physical impact on water.

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Ultraviolet irradiation, unlike oxidative technologies, does not change the chemical composition of water. Numerous studies have shown no harmful effects after irradiation of water, even at doses far exceeding practically necessary.

The effect of disinfection with ultraviolet is based on the action of ultraviolet rays with a wavelength λ = 200-300 nm. It is caused by photochemical reactions, which result in irreversible damage to DNA and other cell structures. The bactericidal effect depends on the direct action of ultraviolet rays on each bacterium.

The only condition for the application of the method of ultraviolet disinfection is the correctly chosen dose of irradiation, that is, the amount of ultraviolet energy that is necessary for the destruction of microorganisms in the water. The choice of the dose of ultraviolet irradiation is determined experimentally and depends on the quality of the water entering the disinfection. For urban wastewater, the dose is at least 30 mJ / cm2. The effectiveness of disinfection is affected by the presence of suspended solids in water. Practical experience of operation has shown that the content of suspended matter in the water of secondary sedimentation tanks should be 15-20 mg / l. The recommended level of suspended matter is 10 mg / l.

Ultraviolet irradiation destroys most bacteria, viruses, spores and parasitic protozoa. The method is safe for people, there is no need for reagent farming. The operating costs are significantly lower than in chlorination and ozonation.

Comparative characteristics of the effect of chlorine and UV irradiation on various types of pathogenic microorganisms are shown in Figure 1.

As sources of ultraviolet radiation, mercury lamps of low and high pressure are used. When using low-pressure mercury lamps for UV disinfection, no toxic by-products are formed in the medium, whereas under the influence of UV radiation from high-pressure mercury lamps, the chemical composition of water can vary due to the bactericidal effect of photochemical transformations of dissolved substances. The ultraviolet method of wastewater treatment has found the greatest application as a non-reagent and environmentally friendly method of decontamination.

Disinfection and purification of water by ultrasound is considered one of the newest methods of disinfection, although this method was first proposed in 1928.

Ultrasound is elastic vibrations and waves whose frequency is above 1520 kHz. When ultrasound is applied to a liquid, specific physical, chemical and biological effects arise - cavitation, dispersion, emulsification, disinfection, local heating, and others. The bactericidal action of ultrasonic radiation is mainly associated with cavitation. Cavitation is the appearance in the fluid of a mass of pulsating gas bubbles. With ultrasound, the cavitation bubble reaches its maximum size. Then the bubble bursts, creating shock waves. If the shock wave

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encounters an obstacle in its path, it destroys its surface. Cavitation occurs at intensities of the sound field above the threshold value of 0.3-1 W / cm2.

Fig. 1. Relative doses of chlorine and UV irradiation, which are necessary for the disinfection of sewage.

A single theory, explaining the bactericidal effect of ultrasound, does not exist to the present day. However, most researchers are of the opinion that in the ultrasonic field there is a predominantly mechanical destruction of bacteria as a result of ultrasonic cavitation.

The advantage of using ultrasound in front of many other means of disinfection of wastewater is its insensitivity to high turbidity and color of water, the nature and quantity of microorganisms and the presence of dissolved substances in the water. Additional useful functions are performed by active radicals formed during cavitation. These compounds accelerate the oxidation process.

For ultrasonic disinfection, there are no criteria and methods for controlling the process, regulatory documents that regulate its use for water disinfection. Purification and disinfection of water by ultrasound is also limited by the norms of domestic effective safety standards.

Currently, the Russian market presents industrial equipment for water disinfection, combining ultraviolet and ultrasound treatment.

On the basis of the work carried out, we have come to the following conclusion that ultraviolet irradiation is the most effective method of disinfecting sewage. Disinfection by means of ultrasound does not have normative documents regulating its use, as well as ultrasound water disinfection is limited by the norms of the current safety standards.

We must conclude that, after ultraviolet irradiation of water, a large number of bacteria, viruses, spores and parasitic protozoa are killed in it, and it is also safe for humans.

References

1.World Health Organization - http://www.who.int/ru.

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