Power Technology and Engineering

Published by Springer Verlag
Online ISSN: 1570-1468
Print ISSN: 1570-145X
An example of four 0.38-kV overhead distribution lines fed from a 10/0.4-kV transformer substation of the Grodno Electrical Networks (Belarus’) and supplying electricity to a cottage area is used for analyzing energy balances and commercial losses in the networks. It is shown that the reliability of such analysis can be ensured by the use of modern software and electronic energy meters recording a retrospective of half-hourly intervals of active and reactive electric energy.
The requirement that the temperature of the boron solution in water containers of the emergency core-cooling system (ECCS) and in reserve tanks holding the boron solution be maintained at no less than 55°C to provide brittle strength to the housing of the VVÉR-1000 reactor in an emergency where heat-transfer medium is lost and water is subsequently delivered from the ECCS is discussed. The ineffectiveness of the existing design for heating of the water containers in the ECCS is demonstrated experimentally. Deficiencies in the heating systems for the reserve tanks of boron solution, which are employed in the design of the V-428 reactor plant, are indicated. Methods are proposed for heating of the water containers and tanks with the organization of natural circulation in the containers (tanks).
The separation system of a PGV-1000 steam generator is modernized on the basis of bench tests of model PGV-1000 steam generators, full-scale tests of steam generators, and computational analysis of the results of these tests. The changes concern the configuration of the submerged plate and replacement of the louver separator by a receiver baffle. These measures increase the marginal evaporative capacity and the permissible range of variation of the water level, decrease the moisture content at the outlet from the steam generator, and improve the conditions for control and repair of its internal surface.
Limitations in the operation of D u 400 shutter control valves used in the feed system of secondary coolant circuits of VVR-1000 power-generating units are described. A method is suggested for removing these limitations by equipping the control valves with an unloaded gate and anti-cavitation protection of the flowing channel. The technical characteristics and description of the design of the updated D u 400 control valve are presented. Problems in experimental study of the updated valve and its in-situ testing are described. Results of vibroacoustic tests and of measurement of the thickness of branch pipes and adjoining conduits of the valve are presented.
The state of the metal, oxide film, and sediments of shield (screen) pipes in the salt compartment of a TM-104A boiler operating with amine water treatment following damage by thermal bulges. It is shown that this damage is caused by excursions in the thermal flux onto components with high thermal resistance owing to sediments during firing. Recommendations are made for increasing operational reliability. Keywordsboiler–amine water regime–cetamine–shield–piping–metal–oxide film–sediments–bulges
Suggestions concerning updating of main feed pumps of Russian thermal power plants are considered. Causes of pump failure are analyzed and recommendations are given for improving their operating characteristics. The updating of PN 1500-350-1 pumps at the Kaluga Turbine Plant (replacement of eight-channel guide vanes by twelve-channel whole-milled ones, use of 'cellular' seals, additional hydrostatic bearing unit in the middle stage of the rotor, and process measures) has substantially improved the vibration characteristics and increased the reliability. The pump of the 800-MW generating unit of the Perm Regional Hydro Power Plant has run for 5000 h. Recommendations are given for further improvement of the characteristics and the reliability. It is shown that the condensate-feed system can be simplified and made more reliable by realizing a circuit without booster and using preliminary startup of an axial-vortex stage in the feed pump. The updating performed by the KTP is flexible and adaptable to financial possibilities of customers.
New technological schemes for low-temperature swirl combustion of different kinds of fuel in semienclosed furnaces are developed and successfully tested in an operating plant. Data on swirl combustion of bituminous coals, peat, and natural gas in a BKZ-210-13.8 boiler are presented. Keywordsswirl furnace-combustion efficiency-pollutant emissions-slagging
The existing flame processes of dual firing of gas and solid fuel are updated with reconstruction of the burners at the Chelyabinsk TÉTs-2. This is connected with marked worsening of the quality of local coal supplied to the cogeneration plant. Comparative tests of boilers with burners subjected to different degrees of updating have shown that replacement of the now used swirled method of introduction of reagents into the furnace by a uniflow one lowers the heat flows to the metal structures and to the settling of the burner throats making them more reliable. The emission of nitrogen oxides is minimized in the mode of gas firing and the activity of slagging of the furnace and of the platens is reduced in the mode of coal firing, which makes it possible to raise the steam rate of the boiler. Ways for further improvement of burner design with respect to nitrogen oxide emissions in the polydisperse flame are outlined.
The BKZ-210-140F boiler of the West-Siberian Cogeneration Plant was equipped initially with four uniflow tangentially oriented burners and tertiary air nozzles. In order to raise the efficiency of operation and lower harmful emissions the boiler was reconstructed. U-shape aerodynamics was organized in the furnace by mounting 8 burners, 8 secondary air nozzles, and 8 tertiary air nozzles on the front and rear walls of the furnace. The reconstruction ensured higher stability of ignition of pulverized coal without flame division and rated temperatures of the superheater metal, lowered the optimum excess air factor at the outlet from the superheater to 1.2 – 1.25, decreased the concentration of nitrogen oxides in the combustion products to 360 – 380 mg/m3, and increased the gross efficiency of the boiler to 91.5 – 91.7%.
It is shown that the remaining life of bends of steam conduits from steel 15Kh1M1F should be evaluated on the basis of results of estimation of microdamage of the metal performed on a representative sample with allowance for the operating factors.
Steam-gas power unit PGU-170 at the Nevinnomysskii Power Plant includes a high-pressure steam generator VPG-450 consisting of two blocks operating on natural gas and typically has a rather high content of nitric oxide in combustion products. Even in the most typical gas-burning schedule where the excess-air coefficient after the steam superheater is maintained around 1.02 under the nominal load, the concentration of NO x converted to NO 2 reduced to = 1.4 is equal to 1100 – 1200 mg/m 3 . In many domestic boilers of equal rating (the rating of steam generator VPG-450 is 225 ton/h per block) that have balanced draft and operate on natural gas with = 1.4 the concentration of NO x converted to NO 2 has been brought down to 150 – 200 mg/m3 or lower by using rational combustion
This paper describes the arrangements of an international joint industry field study on the ice conditions in the Pechora Sea in 1993. In the near future the Pechora Sea will attract the petroleum industry, and the areas developed then will be offshore structures like pipelines, production structures, a tanker terminal, and ice breaking vessels including tankers and icebreakers. The ice field work in the area started in winter 1992 when a Russian-Finnish expedition (by the Finnish-Russian Offshore Technology Working Group) was made. The main companies involved in the commissioning of the expedition were the Kvrner Masa-Yards Arctic Research Centre (MARC), the Arctic Offshore Research Centre of Helsinki University of Technology (AORC), and the Arctic Marine Geological expedition (AMIGE). During the winter of 1993 the same group and, in addition, the Polar Research Institute of Fishing and Oceanography (PINRO) arranged the second expedition to the Pechora Sea funded by five petroleum companies: AMOCO, EXXON, NESTE, NORSK HYDRO, and TEXACO.
The Kamskaya Hydroelectric Power Plant (KHPP) on the Kama river is an upstream integrated hydro system in the Volga–Kama series of hydroelectric stations. The KHPP is located within the confines of the city of Perm, 3 km downstream the Chusovaya river estuary, a left-side stream of the Kama river. Functionally, the KHPP was mainly intended to generate electric power and to balance the total load in the hydraulic power system with allowance for diurnal and seasonal load fluctuations. Other functions assigned to the KHPP are the proper provision of navigation and timber rafting conditions on the Kama river, flood absorption, and normal operation of intake structures. The average annual stream flow of the Kama river is 51.5 km 3 . The average annual flow rate is 1630 m 3 sec. The KHPP reservoir has a gross storage capacity of 12.2 million m 3 of water; the useful capacity is 9.2 million m 3 of water. The total escapage discharge through the cross-drainage works of the hydraulic power system (with allowance for the transformation of part of the stream flow into reservoir storage): 20,936 m 3 sec — standard design; 25,073 m 3 sec — verification design (ignoring free overflow and horizontal plant unit No. 24). The established KHPP power is 483 MW. The average
Rules governing use of water resources and operating procedures should be approved individually for each reservoir.
How the power systems functioned during the period from 2003 through 2005 is analyzed: an estimate of the dynamics and modes of power demand is given; development of generating capacities and modes of operation at power plants, and balances between capacity and electric power generated by the power systems is analyzed; “bottlenecks” in electrical networks are determined, and trends in prospects for the development and reconstruction of the networks are outlined. Assumptions concerning the introduction of generating capacities and formulation of predicted energy balances, and the development of system-forming networks carrying voltages of 110 kV and higher for the Moscow and Leningradskaya Power Systems are examined during the period from 2006 through 2015. Technico-economic indicators are cited for electrical-network projects planned for introduction, and also for reconstruction and technical refitting.
Prospects of development of the energy economy in Russia are considered up to 2020. The proportion of thermal power plants (TPP) in the structure of the generating capacity of Russia amounts to about 70% (147 mln kW). The proportion of gas in the structure of fuel consumed by TPP amounts to 64%. It is predicted that the fraction of high-quality kinds of fuel (gas and fuel oil) will decrease in the considered period due to maximum involvement of coal in the fuel balance and wider use of combined-cycle and gas-turbine technologies that provide a lower specific consumption of fuel. It is planned to resort to advanced technologies both for reconstructing existing plants and erecting new ones. This paper deals with problems of fuel supply of fossil-fuel-fired thermal power plants in the light of the evolution of the energy economy of Russia. The demand of TPP for different kinds of fossil fuel, i.e., gas, coal, and fuel oil, is estimated for the whole of the country and for its regions according to two variants of development of the generating capacity with planned commissioning of combined-cycle plants with a total output of 32 mln kW and gas-turbine plants with a total output of 61 mln kW in the period of up to 2020. The tasks of the fuel policy to be solved in the considered period are presented.
Aspects of the process of repair of drums, which are virtually irreplaceable boiler units, are very important, especially under the conditions of intense wear and exhaustion of the service life of power equipment. Problems of reconditioning and estimation of the after-repair serviceability of TGME-206-type boilers damaged by through cracks in the zone of the recirculation hole are described. A brief characteristic of the boiler and the steam drum and a detailed description of the damage are presented. The defects are eliminated by mechanical removal of the damaged metal. Control of the repaired zones and of undamaged zones confirms the absence of defects in the metal. Analysis of the results and computation of the cyclic endurance show that the appearance of cracks at a relatively early operation stage is caused by permanent disturbances of the operating conditions of the recirculation line. The processes of repair welding of the drum and subsequent local heat treatment (high-temperature tempering) are described. According to strength computations and a study of the condition of the metal, the reconditioned boiler should operate safely for at least two more years.
The use of numerical simulation and advanced means of computational hydrodynamics (domestic FlowVision software) for simulating the processes of flow and combustion in the systems for air and gas feeding, mixers, burners, and boiler furnaces has made it possible to advance the recirculation system and burners of the TTs-21 cogeneration plant and considerably reduce the NOx emissions.
Data on the use of RCA-2000 (Mark & Vedell, Denmark) stationary analyzers of the content of combustibles in fly ash for optimizing the furnace performance of a TPP-210A boiler and determining the effect of process switchings of the boiler equipment on the quality of the furnace performance are presented.
The authors describe the Vladimirskaya hydroelectric pumped storage power plant that is currently being designed as the pilot Russian power project for the 21st century.
Purification of turbine condensate by mechanical and ion exchange resin (ionite) filters in lumped desalinization units is examined. Loading mechanical filters with styrene copolymer and divinyl benzene ensures efficient removal of petroleum products and iron, but does not fulfil the task of removing polar organic compounds. The ionite part of a lumped desalinization unit ensures removal of easily electrolyzed compounds and silicic acid but is ineffective with regard to capture of organic contamination and iron, which indicates significant contamination of the load in the combination filter by organic compounds. “Cold” (standard) and “hot” regeneration of the anionite load are undertaken. Greater extraction of organic substances is observed with “hot” regeneration.
Results of analysis of operating experience with automatic disconnection of the first domestic 220-kV overhead lines from the Lower Svir’ HPP to a substation in the settlement of Kolpino in the Leningradskaya Oblast’ (two Svir’ 220-kV overheads lines with a length of 247 km) over a period of 21 years (1982–2002) in total volume of 10,400 km · year are presented. Operating indicators are established with respect to specific number of disconnects and stream of failures per 100 km of overhead lines. Indicators of lightning-surge protection on the 220-kV Svir’ overhead lines passing through the same corridor primarily along a swath cut through a forest in periods when the stranded cables were protected by different schemes — stranded cable only on approaches to substations, incomplete and nonuniform protection along the route — are compared. Recommendations are given for optimal cable protection of the 220-kV Svir’ overhead lines.
A procedure for the diagnostics of the insulation of high-pressure oil-filled 220kV and 500kV cable lines approved for use in hydroelectric power plant is presented. The results of the diagnostics and estimation of the residual life of the insulation of such cables, which have been operating for a considerable time in the Toktogul’skaya, Nizhnekamskaya and Bratskaya hydroelectric power plant, are presented. Keywordscable lines–oil-filled cable–insulation diagnostics–residual life
The major equipment in the PGU-230 steam-gas unit at the Heller thermal power plant (Hungary) and its technical characteristics are described. The technologies for startup of the power production system of the steam-gas unit and for switching it from a steam-gas unit cycle to open cycle operation of the steam-gas unit and vice versa are discussed. The regulatory range of the power generation system and its maneuverability characteristics are determined. Keywordspower generation system-steam-gas unit-Hungary-thermal power plant
The results of detailed computations performed for actual electric and heat loads, pressure in the condenser, and other operating parameters are used to consider the changes in the efficiency of operation of a T-250/300–240 turbine after the removal of moving blades of the last stages of the low-pressure cylinder. It is shown that the expediency of running the turbine with removed blades should be determined proceeding from the expected modes of operation of the cogeneration plant in question for the whole year.
The operation of the low-pressure turbine part in variable condensing and extraction regimes is analyzed. The effect of steam parameters at the inlet to the low-pressure part (in the lower extraction chamber) and of operation of the regulating stage of the LPP on the level of wetness in the low-pressure stages is determined. It is shown that the moving blades of the last stages of cogeneration turbines operate under heavier erosion conditions than in condensing turbines. This is one of the main causes of their intense erosion wear.
The paper discusses the condition of 19 turbines operated by the publicly owned joint-stock company Mosénergo, which have exhausted their time to overhaul (220,000 hours, 600 starts). An extension in the time-to-overhaul of all 19 turbines to 300,000 hours or 900 start ups with the condition that a number of mandatory measures be taken is an acknowledged possibility, based on calculations performed and analysis of damage sustained. A number measures, which have themselves been positively recommended for certain turbines, are examined, and a procedure is presented for evaluating the effectiveness of their implementation.
Results of operation of high-voltage variable-frequency asynchronous electric drives of series 1557 MV for blower fans, smoke extractors, and feed pump are considered.
The system for common station regulation of the voltage and reactive power at the Mosénergo TÉTs-27 heating and electric power plant is described briefly. Features of the algorithms for this system, which uses programs and instrumentation from the automatic control system for the electrical equipment in the 450 MW power generation unit No. 3, are examined.
This is a description of experience in the development and introduction of a full-scale process control system for the PGU-450T power production unit of station No. 3 at the TÉTs-27 heat and electric power station of JSC “Mosénergo” based on the latest, fourth generation program package SPPA-T3000, which is being used for the first time in Russia for steam-gas units. The fundamental technical solutions for the structure of the process control system are described, along with the features of the algorithms for control of the main engineering equipment in electric power plants based on the PGU-450.
The effect on the condition of the rotor material owing to multicycle fatigue caused by variable stresses during participation of a power generating unit in grid frequency and power regulation is evaluated using the K-300-23.5 steam turbine as an example. It is shown that during normalized primary frequency regulation the safety factor is at least 50, while during automatic secondary regulation of frequency and power there is essentially no damage to the metal. Keywordselectric power system–steam turbine–frequency and power regulation–rotor–variable stresses–multicycle fatigue
Work done by JSC “Interavtomatika” and the Iriklinskaya GRÉS (State Regional Electric Power Plant) to create automatic frequency and power control systems is reported. This involved reconstructing the turbine regulator systems and modernizing all the regulators for the power generator unit (those coupled to and those not coupled to the automatic frequency and power control systems) and the automatic burner control systems on the basis of a unified Simatic PCS7 PS controller system for the four 300 MW power generation units at the Iriklinskaya GRÉS.
A scheme for compensating the reactive power and controlling the voltage of high-voltage, intermediate-voltage, and low-voltage buses of 330 – 500-kV substations, which consist of static thyristor compensators (STC) on low-voltage autotransformers and controlled shunting reactors on high-voltage lines, is presented. It is shown that the STC can be created step-by-step beginning with the reactive part on substations with low-loaded lines. Results of installation of reactor groups of STC stepwise-controlled by vacuum switches at 330- and 500-kV substations are presented. Tests of the reactor groups have proved their high efficiency.
The basic principles for construction of relay protection of the equipment of 330–750-kV networks and substations with the use of microprocessor devices of series ShÉ2710 produced by the “ÉKRA” Research and Production Enterprise (Cheboksary) are considered.
The necessity for employing nonparametric methods for evaluating statistical data on failures of transmission lines is substantiated. A method for evaluating the reliability of transmission lines based of the life characteristic of the object is suggested. The reliability of 330- and 500-kV transmission lines of Northern Caucasia is evaluated with the help of the methods suggested.
The operation of various types of deaeration systems is analyzed and experience with introducing centrifugal-jet sprayers in the condenser and deaeration towers of boiler drums is described. Keywordssteam-gas unit-deaeration-centrifugal-jet sprayers-operating tests
This is an analysis of computational and analytical studies of the suitability of a wide range of Russian coals, and of industrial-scale combustion tests of several Kuznetsk coals, including a mixture of Krasnobrodskii and Ékibastuz coals in a 1:1 proportion, for use in the 500 MWunits of the Reftinskaya GRÉS (State regional electric power plant), where Ékibastuz coal is traditionally used. Keywordsthermal power station-500 MW unit-coals for power generation-combustion tests
1. The failure of automatically welded joints of 15Cr-1Mo-1V steel in service at 500 and 800 MW power units comes from the depleted strength margin. 2. In exerting safety control over automatically welded joints, the following steps should be made: (i) take a measure of the wall thickness in the welded joint area; (ii) calculate the minimum permissible wall thickness based on the long-term strength for 15Cr-1Mo-V steel; (iii) welded joints that fail to meet the strength requirements should be rewelded or subjected to a standard serviceability test.
Problems concerned with the supply of energy in the Sverdlovskaya Region that have arisen because of the reduced output and higher cost of coal from the Ékibastuz Basin in the early 1990’s have stimulated the search for alternative sources of domestic fuel. In this context, tests were carried out at a number of thermal power plants (Sverdlovénergo Joint-Stock Co.) to see if coals from the Kuznetskii Basin (Kuzbass), mainly of grades SS and OS, could be useful for industrial combustion. Viewed technologically, the results obtained have to be encouraging [1]. The stagnant situation in fuel supply became acutely critical in the late 1999, when the coal stocks at some power plants dropped to an emergency level. The need for using alternative coals came also from other reasons, not always accounted for in full measure when the issue of supplying fuel to thermal power plants (TPPs) was considered [2]: — the service wear at the Sverdlovénergo TPPs, fired by Ékibastuz high-ash coal, is close to critical under the conditions of severe underfunding of the maintenance-and-repair work; — the ash dump sites at most coal-fired Sverdlovénergo TPPs have reached 80 – 90% of their design capacity, so that the use of high-ash coal even at the normal rate may necessitate a reduction of power output in the near future; — further use of Ékibastuz coals for increased power output may lead to environmental problems, at the risk of penal sanctions from environment protection organizations. In this situation, industrial tests for technological applicability of alternative fuel were conducted at P-57 boiler units (500 MW unit) of the Reftinskaya TPP. In the period from 1996 until 2000, tests on the combustion of Kuzbass coals (DG, 1SS, and T grades) and screenings from coal and petroleum cokes were carried out.
Data on the spectral composition and intensity of electromagnetic radiation of corona discharge are obtained in an experimental study performed on the outdoor switchgear of the Shagol 500-kV substation of the Chelyabinsk Enterprise of Trunk Transmission Grids and under a 500-kV Shagol – Kozyrevo overhead transmission line. The electromagnetic environment on the territory of the 500-kV outdoor switchgear is shown to be determined by narrow-band radiations (harmonics of the frequency of electric supply) and wide-band radiations due to corona discharges of high-voltage sources. This means that the personnel experience the action of a commercial-frequency electric field and electromagnetic radiation of a quite wide range, which is not allowed for by the existing guidelines. It is recommended to continue the study in cooperation with medical institutions in order to create guidelines that would allow for the joint action of commercial-frequency electric field and electromagnetic radiation and for the voltage in the line, the current load, the meteorological situation, and other factors.
Technological breakdowns in the Samara electric power networks are analyzed. This enables the statistics to be generalized, reveals the extent of breakdowns and enables the effect of systematic and seasonal factors on the network to be estimated. This provides the possibility of using the results obtained to develop organizational and technical measures to eliminate and prevent the reasons for different forms of technological breakdowns with the aim of increasing the operating efficiency of the power network and its operating reliability, and to reduce the number of breakdowns in the electric power networks. Keywordselectric networks-overhead power lines-technological breakdowns-systematic and seasonal factors-breakdown rate-organizational and technical measures-breakdown rate
The results of the installation of a process control system developed by the Interavtomatika Company (Moscow) for controlling a 500-MW pulverized coal power unit with the use of the Teleperm ME and OM650 equipment of the Siemens Company are described. The system provides a principally new level of automation and process control through monitors comparable with the operation of foreign counterparts with complete preservation of the domestic peripheral equipment. During the 4.5 years of operation of the process control system the intricate algorithms for control and data processing have proved their operational integrity.
The period of commissioning of P-61 boilers at stations Nos. 1 and 2 of the Berezovsk state regional thermal power plant (BGRS-1) and measures for improving the operation of boiler components in order to prolong steady performance of 800-MW power generating units in the load range of 650 – 700 MW are considered. Suggestions of the personnel of BGRS-1 and ZiOSib on modification of the P-67 boiler of unit 3 are presented including reshaping of the platens above the furnace, replacement of the convection superheater by double-stage L-shape platens, corridor arrangement of the loops of the convection superheater, and 30% widening of the surface of the economizer. Planned renovations of the P-67 boiler of units 1 and 2 are discussed.
Thermal layouts are examined for condensation-type steam-gas systems with one, two, and three boiler-utilizer pressure stages based on the GTÉ-65 gas-turbine power generating system and the PT 60-12.7_1.27 steam turbine. The operational efficiency and feasibility of integrating a GTÉ-65 and a Pr-86-13.72-545 boiler-utilizer with a single pressure stage in the existing thermal layout of the TÉTs-9 plant of Mosénergo (a station with crosslinks) within the main housing at the location of a no longer operating R-50-12.7_1.27 steam turbine and PTVM-100 water heating boiler are demonstrated. KeywordsHeating and electric power plant with crosslinks-renovation-gas-turbine power generating system-steam-gas add-on-thermal layouts with one-two and three pressure stages in the boiler-utilizer-cycle thermodynamic efficiency
Experience with the development, study, and manufacturing of cooled blades for the GTÉ-65 high temperature gas turbine is described. Keywordsgas turbine unit-high temperature gas turbine-turbine blades-thermal-hydraulic testing
Thermal configurations for condensation, district heating, and discharge steam-gas systems (PGU) based on the GTÉ-65 gas turbine power unit are described. A comparative multivariant analysis of their thermodynamic efficiency is made. Based on some representative examples, it is shown that steam-gas systems with the GTÉ-65 and boiler-utilizer units can be effectively used and installed in existing main buildings during technical refitting of operating thermal electric power plants.
The development of a modern 660 MW coal-dust generator unit with supercritical steam parameters is described. The major technical solutions that ensure reliability, efficiency, and low emissions of pollutants into the atmosphere are described. Keywordsgenerator unit-supercritical steam parameters-boiler-turbine-thermal layout-electrical precipitator-wet lime sulfur removal-refractory steels-preparation of desalinated water
The rebuilding of the P-67 boiler for an 800 MW unit at the Berezovskaya GRÉS, as well as changes in the thermal engineering characteristics of the coal from the Berezovskii-1 seam and its slagging properties, are described. The results of balance tests of the boiler and changes in the thermal efficiency of heating surfaces during 2006 – 2008, including after mechanical cleaning and modernization of the combined cleaning system, as well as with coal dust coarsening and loading of the lower burner layers and downward blast, are discussed. KeywordsP-67 boiler-800 MW unit-balance tests-thermal efficiency of heating surfaces-aerodynamic drag of convective shafts
Top-cited authors
Mikhail Aivazyan
  • Moscow State Institute of Radio Engineering, Electronics and Automation
Mikhail Petrichenko
  • Saint Petersburg State University
Erast Gaziev
  • Сибирский государственный технологический университет
Georgy Petrov
  • Academy of Sciences of Tajikistan
Dmytro Stefanyshyn
  • National Academy of Sciences of Ukraine