THE PURPOSE. Мutipulse rectifiers are widely used as a nonlinear loads in industrial distribution systems. The advantage of mutipulse rectifiers is low harmonic emission and high power factor. However input currents of mutipulse rectifiers have a wide spectrum including characteristic and noncharacteristic harmonics. This has a negative impact on the power quality. Shunt capacitors are the simplest form of reactive power compensation in industrial power distribution systems. However power systems with nonlinear loads suffer from severe harmonic distortion due to the parallel resonance between capacitors and system inductance. Special compensating devices for reactive power compensation and correction of power system frequency response for resonances damping are necessary. METHODS. In this paper shunt compensating devices for power delivery systems with multipulse nonlinear loads are considered. Proposed devices are composed of 3-5 order parallel connected passive broadband filters. They provide power factor correction, voltage and current harmonics mitigation and resonance modes damping. A general broadband filter design procedure based on frequency and reactive power scaling of normalized filter parameters is developed. RESULTS. Characteristics of different compensating devices configurations using broadband passive filters are discussed. It is shown that broadband filtering devices enable compensation of fundamental frequency reactive power as well as mitigation of voltage harmonic level to values determined by Russian and international standards. Proposed devices have lower fundamental power losses in c omparing with known solutions. CONCLUSION. Proposed analytical design method is applicable to broadband filters of different orders.

THE PURPOSE. Consider the introduction and implementation of lean production technology in the branches of OOO Tatneft - AZS Center. Describe the essence of the technology, consider the problems, the complexity of implementation and propose an algorithm for introducing the technology and involving each employee in the process of optimizing the business and maximizing customer focus. METHODS. At the initial stage, it was decided to start implementing the Lean philosophy with two of its tools: kaizen and 5S. Using the philosophy of continuous improvement Kaizen, a system of kaizen sentences was developed and formalized. In order to provide material incentives for employees at each workplace, the Regulation on the system of continuous improvement of the production system of OOO Tatneft-AZS Center was adopted, which regulates and regulates the process of submitting and evaluating kaizen proposals. For the implementation of the 5S system, the standard "Application of the 5S system in the organization of a workplace" was developed, discussed in all labor collectives and adopted, on the basis of which the implementation of the 5S system was started in all branches of OOO Tatneft-AZS Center. RESULTS. The article describes the use of a fairly wide and varied range of Lean manufacturing tools: kaizen proposals, 5C, standardization, TPM, visualization, SFM-visual management, value stream maps. The tools differ in both the time and duration of implementation and their effectiveness. CONCLUSION. Within the framework of adapting the principles of Lean production to the retail and sales network of oil products of OOO Tatneft-AZS Center, the primary factors are industry and organizational specifics.

Currently, operation control and expansion planning of energy systems occurs separately for local systems and tasks. Traditionally, the considered energy systems unite large energy sources, such as hydro, thermal power plants, combined heat and power plants, boiler plants and electric and pipeline networks distributed over a large area. New trends in the energy sector necessitate a revision of the principles of the construction of energy systems and creating integrated energy systems. THE PURPOSE. Combining existing energy systems into a single integrated system with many interconnected and coordinating elements can contribute to the implementation of new functionalities, the use of more advanced technologies in operation and the active participation of consumers with distributed generation in the energy supply process. METHODS. To study integrated energy supply systems, it is proposed to use a multiagent approach, which is one of the promising areas for the study of complex systems. This approach is used in many subject areas to study systems involving a large number of elements with complex behavior. Such systems include integrated energy systems, the modeling and analysis of which on the basis of a multiagent approach is formed by a multitude of interconnected agents that exchange various data with each other. RESULTS. Based on the research results, the active structure of a multiagent system is proposed for the calculation and optimization of integrated energy systems and, taking into account their main features and properties, in the framework of which the agents of the multiagent system, their goals and objectives are determined. CONCLUSIONS. Based on this structure, a model has been developed that allows modeling integrated energy systems. The experiments carried out using the developed model showed its efficiency, practical applicability and prospects for further development.

Decision-making at the design stage of the distribution network significantly affects the change in the indices of uninterrupted power supply to consumers. The main ones are SAIDI and SAIFI. There is no methodological support for determining the predicted values of the power supply continuity indices. The purpose of the study is to develop a methodology for calculating the predicted values of indicators of uninterrupted supply during design. A feature of the technique is the account of the circuit-mode changes in the 0.4-10 kV distribution network section. The introduction of the developed methodology into project practice is relevant and expedient. An important point is the accounting of distributed generation, which has a significant impact on the operating conditions of power supply systems. Local power systems based on distribution generation and networks 0,4-10 kv are becoming widespread, which can serve as the basis for distributed energy and energy transition in Russia. Their appearance increases the efficiency of the energy sector, including increasing the power supply reliability. However, difficulties arise in justifying distributed generation power distribution schemes, the feasibility of measures to create local power systems and the effectiveness of their integration without appropriate research and methodological support. The developed methodology is based on the use of statistical processing methods, expert systems, the SAIDI method. It is aimed at medium and low voltage distribution networks. The methodology makes it possible to compare measures taking into account changes in the structural and functional reliability of the distribution network and regime restrictions. Verification of the methodology was carried out on the example of a section of the distribution network of a residential neighborhood. Comparison of the results obtained by the methodology and in the software ETAP, proved the adequacy of the proposed methodology and the reliability of the predicted values obtained SAIDI and SAIFI.

THE PURPOSE. To consider the problem of detecting changes in a power grid topology that occurs as a result of the power line outage / turning on. Develop the algorithm for detecting changes in the status of transmission lines in real time by using voltage and current phasors captured by phasor measurement units (PMUs) are placed on buses. Carry out experimental research on IEEE 14-bus test system. METHODS. This paper proposes a method from the field of artificial intelligence such as machine learning in particular "Deep Learning" to solve the problem. Deep Learning arises as a computational learning technique in which high level abstractions are hierarchically modelled from raw data. One of the means to effectively extract the inherent hidden features in data are Convolutional Neural Networks (CNNs). RESULTS. The article describes the topic relevance, offers to apply the method for detecting status of lines using a CNN classifier. The combination of different CNN architectures and the number of time slices from the moment of line status change are used to detect the power grid topology. The effectiveness of the joint use of PMUs and CNN in solving this problem has been proven. CONCLUSION. A solution for the line status change detection in the transient states using a CNN classifier is proposed. A high accuracy of the line status detection was obtained despite the influence of noise on measurement data. A change in the network topology is detected at the very beginning of the transient state almost instantly. It will allow the operator several times during the first seconds to identify the line state in order to make sure that the decisions made are correct.

THE PURPOSE. Consider a renewable energy source. Compare the proposed design with other pyrolysis technologies and make sure that the proposed design will reduce fuel consumption. METHODS. This article proposes the design and technological principle of the process of pyrogenetic wood processing with the production of various compositions of pyrolysis gas and charcoal. RESULTS. The article describes the proposed design, calculates the heat balance for it, and determines the operational parameters of the technological process. CONCLUSION. The main positive difference between the proposed plant design and technology from other pyrolysis technologies is a high level of fuel economy due to heat utilization at intermediate stages of the process. The heat of the cooled charcoa l and the waste products of complete fuel combustion are utilized. The developed design allows reducing fuel consumption, as well as the range of gaseous components obtained as a result of pyrogenetic decomposition of raw wood in a direct -flow pyrolysis plant can be increased.

PURPOSE. Consider the problems and ways of developing hydrogen energy in Russia and in the Republic of Tatarstan. Analyze the main opportunities for the production, transportation, use of hydrogen at the enterprises of Tatarstan. Calculate the economic efficiency of the production of "green" hydrogen by electrolysis at TPP with CCGT in Tatarstan. METHODS. Based on the analysis of literature data and mathematical calculations. RESULTS. Green hydrogen is a promising solution for a decarbonized energy system, and 2020 saw an explosive focus on its use around the world. Tatarstan, as one of the leading economically developed regions of Russia, could take part in the production of "green" hydrogen, the design of electrochemical equipment for its production, the development of technologies for the use of fuel cells, scientific research and training of highly qualified specialists in the field of hydrogen energy. According to the calculations, the production of the most environmentally friendly hydrogen at TPPs with CCGT in Tatarstan will currently cost an average of 2 euros per kilogram, which is significantly lower than the existing market value. CONCLUSION. Tatarstan can become a competitive region for the production and distribution of "green" hydrogen. The main areas of activity should be the production of pure hydrogen, the industrial production of freight transport on fuel cells, the production of megawatt-class electrolysers, the utilization of hydrogen-containing petroleum gases at TPPs in gas turbines or combined cycles with fuel cells.

Voltage dips are quite frequent and dangerous phenomenon, which can lead to disruption of the production process. Ensuring the stability of induction motors during voltage dips is an important task to ensure the continuity of the technological process, as well as to reduce material losses. THE PURPOSE. List the main causes of voltage dips. Develop a simulation model corresponding to a typical power supply scheme for an oil pumping station with a group of asynchronous motors as a load. Perform two series of calculations to determine the parameters of the electrical mode in case of voltage dips and the subsequent restoration of the voltage on the buses of the supply substation. METHODS. When solving the problem, the PSCAD software package was used. RESULTS. The article describes the relevance of the topic, the main causes of voltage dips are given. The simulation of voltage dips resulting from a short circuit on the substation equipment has been performed. A series of calculations were performed, differing from each other in the changed initial data: the place of occurrence of a short circuit, the time delay of automatic transfer of the reserve. The analysis of the obtained results is carried out. CONCLUSION. According to the test results, it can be seen that the decrease in voltage on the low voltage buses of substations after the operation of automatic transfer switch is the lower, the longer the time delay of automatic transfer switch. In this work, the maximum time delay was 7 seconds, while there was no violation of the stability of the induction motors. The need to study the operation of a group of asynchronous motors in case of accidents in an external electrical network is also determined.

THE PURPOSE. Comprehensive research of the slagging intensity is the heating surfaces of the BKZ-420-140 boiler unit with solid slag removal at the Abakan CHP when burning non-project fuels. The relevance of the work is due to the technical necessity and economic feasibility of conversion boiler units to combustion of non-design coals. METHODS. The problem has been analyzed by methodology for conducting complex tests, measurements and processing of experimental data, as well as the results of experimental and computational studies of a boiler unit when operating on coals of various qualities. RESULTS. Qualitative and quantitative parameters for assessing the properties of off-design coals and their behavior in real operating conditions of radiation, semi-radiation and convective conditions, taking into account their modes and design functions, have been obtained. CONCLUSION: A computational analysis of the operating modes of boiler units when burning non-design fuels showed that a promising technology for involving non-design coals in the fuel and energy balance of a thermal power plant is providing a scientifically based mixture of design and nondesign fuels.Analysis of the slagging and polluting properties of non-design coals makes it possible to predict changes in the characteristics of the thermal efficiency of heating surfaces and to develop many practical recommendations for optimizing the parameters of the cleaning equipment installed on the boiler.Also, mixtures of fuels were determined for which the wall temperatures of the metal of the outlet stack of the superheater increase, which significantly reduces the strength characteristics of the surface.The assessment and prediction of the reliability of the heating surface is carried out by calculating the temperature of the metal wall in the most heat-stressed place.

PURPOSE. Perform analysis of the actual heat energy consumption for cold water heating for the hot water utility to the approved standard. Compare different methods of flow control in circulation pipelines of hot water supply systems. Identify ways to improve the efficiency of hot water systems. METHODS. The passive engineering experiment was used to study the operating modes of hot water supply systems of several groups of houses, in which various methods of regulating water consumption in hot water supply systems are implemented. Data collection was carried out using the online system of control and commercial accounting of energy resources. RESULTS. Existing hot water supply systems in residential buildings of Ulyanovsk were inspected under various methods of flow control in circulation pipelines. Features of static and dynamic load control of hot water supply systems were investigated. Analysis of influence of methods of control of thermal load of hot water supply systems on their actual heat consumption was performed. The possibility of bringing the actual operation mode of hot water supply systems to the standard value, on the basis of which consumption is calculated, is estimated. CONCLUSION. Known methods of load control in hot water supply systems and their actual operating conditions do not allow to reach the level of heat consumption that meets the established standards. Conclusions were drawn on the need to revise the regulated indicators of hot water quality and to adjust the method of calculating consumption in hot water supply systems.

THE PURPOSE. The service life duration of wooden tangent towers used on overhead transmission lines with a voltage of up to 35 kV depends on the quality of lumber drying and subsequent impregnation. The drying of tangent tower workpieces is currently carried out by atmospheric or convective methods and is the longest and one of the energy-consuming stages of their production. At the same time, there are promising electrotechnological drying installations that can reduce the duration and improve drying quality at comparable specific energy costs. Such installations include vacuum high-frequency complexes, the wide introduction of which is complicated by a number of unresolved scientific and technical problems like optimizing vacuum high-frequency drying modes and ensuring electromagnetic field uniformity in long workpieces. The purpose of this article is to obtain mathematical tools that simultaneously describe the cross-effects of electromagnetic phenomena and heat and mass transfer processes in long-sized lumber and contribute to the further solution of these problems. METHODS. The positions of the theory of electromagnetic field, heat mass transfer and heat mass exchange, methods of mathematical modeling were used for this purpose. Also the results of previous studies of electromagnetic field distribution in the cross-section and longitudinal sections of the working chamber loading are taken into account. RESULTS. А one-dimensional mathematical model is obtained. It describes the influence of electromagnetic wave distribution along the length of tangent towers and external medium parameters on the temperature and moisture content in the material. This model is characterized by the possibility of using simple algorithms for analyzing differential equation systems based on the finite differe nce method and requiring less initial data on the drying material properties. CONCLUSION. The obtained by using the proposed model and the method of its analysis the numerical study results are compared with the available experimental data. Based on this comparison it is concluded that the obtained model is adequate and more effective relative to other existing models of vacuum high-frequency drying. Generally, further use of the presented mathematical toolkit to optimize the design and modes of vacuum-high-frequency complexes in the task of drying wooden tangent towers will increase the reliability of overhead transmission lines.

THE PURPOSE. Studying the complex issues associated with providing consumers who are away from the central power supply system with environmentally safe renewable energy source, i.e. conversion of wind energy into electrical energy and uninterrupted supply of electricity to consumers. In this area, one of the complex issues is to determine the wind energy resources in the area where it is planned to install a wind farm.

The article deals with the determination of wind energy resources in Turkmenistan. Using databases obtained from meteorological stations over several years, calculations of wind energy resources by region are carried out. This will quickly and in detail analyze the wind energy potential in a particular area to assess the choice of capacity of the projected wind turbines, with the aim of ensuring sustainable development of the region and the reliability of electricity supply.

METHODS. In order to estimate the wind energy resources in the area it is necessary to determine the average wind speed per year. In this research work the average annual wind speeds obtained from meteorological stations installed in different regions of Turkmenistan were used. These data were compared with the actual data obtained from the 2 kW wind power plant installed at the research site of the State Energy institute of Turkmenistan and the relevant graphs were built. The results of the obtained data can be used for optimal selection of wind power plant locations and assessment of wind energy resources of the region. RESULTS.As a result of the calculations, wind energy reserves in the region and for the regions of Turkmenistan were determined, as well as the optimal locations of wind farms.Using the technical characteristics of a 2kW wind power plant, the average annual electricity output of a wind power plant of different capacity is determined.

With the correct definition of wind energy potential, there is an opportunity to solve energy, economic, environmental and social issues of the country. And also there is an opportunity to mitigate climate change on the basis of wind energy installations, and their resources, environmental benefits, goals and objectives on the scientific methodological basis in the field of wind energy for implementation of state programs for energy conservation in Turkmenistan and energy supply of the region.

CONCLUSIONS. On the basis of the carried out scientific work the wind energy resources and technical potentials of wind power plants in the territory of Turkmenistan were determined and the database for compiling the wind energy cadastre was created.

THE PURPOSE. To consider the problems of the increasing dissolved oxygen concentration in feedwater, especially after the condensate pumps. To estimate the opportunity of the vacuum thermic deaeration intensification inside the PT-60-130/13 LMZ steam turbine condenser to reduce the feedwater system rate of corrosion. Perform a thermal test of the external deaerating hotwell, which provides reducing dissolved oxygen concentration by the hot drains and recirculating feedwater. To evaluate the march of the dissolved oxygen concentration in feedwater after the inclusion of the deaerating hotwell. METHODS. The thermal test of the external deaerating hotwell was chosen for evaluating water deaeration. RESULTS. In this paper, the results of the thermal tests are given. The relation of the dissolved oxygen concentration from heating fluid flow is also presented. CONCLUSION. The use of the external deaerating hotwell allows achieving dissolved oxygen concentration below the norms established by the сode of operation for electrical power plants and grids to ensure the maintenance of an acceptable water-chemical regime of the feedwater. During the tests, the dissolved oxygen concentration decreased by 70% and reached a value of 8 mcg/dm3. The deaerating hotwell of the considered type can be recommended for the operation, especially during start-up modes and modes with the low thermal load on the condenser cooling surface.

Thermal power plants (TPPs) burn more than 30% of the produced fuel. Also this fuel is worst in quality. This is usually either high-ash or high-moisture, often high-sulfur coal, or waste from oil refining and associated petroleum gas. If the main fuel at the plant is natural gas, then fuel oil farms are still being built to create a fuel reserve. But even if a gas-oil plant uses only a small part of fuel oil in its fuel balance, the permissible environmental impact is calculated on the maximum use of the dirtiest fuel, i.e. fuel oil. Thus, thermal power plants are either active or potential sources of nitrogen oxide emissions. PURPOSE. Development of methods for decreasing sulfur emissions without installing special desulphurization equipment in the exhaust gas path. In some cases, this is possible if the absorption capacity of the alkaline components of solid fuel ash or the dosing of slaked lime into fuel oil is used to control the permissible emission of solid particles in the absence of ash collectors on gas-and-oil boilers. The developed METHODOLOGY will allow us to trace the entire chain of necessary actions based on the fuel composition before selecting the main parameters of the proposed methods. RESULTS. The formulas for calculating the required degree of purification of combustion products are proposed. Methods decrease sulfur oxides emissions in domestic equipment using for pulverized coal boilers. Solution allows to decrease oxide emissions for boilers that burn fuel oil and do not have ash traps.

THE PURPUSE. To consider the fields of application of electromagnetic treatment of water systems. To analyze the modern literature on the use of constant magnetic fields for dehydration of oil-water emulsions. To develop the design of a device for generating constant magnetic fields and select its parameters. To select the electrical circuit for powering the device. To determine how the energy efficiency of the device changes with an increase in its overall dimensions. METHODS. When solving the problem, the KOMPAS-3D three-dimensional modeling system was used, the magnetic field induction was calculated using the PascalABC programming system, the optimal device parameters were selected using the Microsoft Excel program. RESULTS. The article describes the relevance of the topic, considers the distribution of the magnetic field in the device under development, determines the optimal design parameters for this device and selects the electrical power circuit. CONCLUSION. Calculations have shown that the coefficient taking into account the inhomogeneous distribution of the magnetic field in the device is 0.883. Using the KOMPAS-3D three-dimensional modeling system, a model of the device under development was builttaking into account the obtained relationships.When using a circuit with an uncontrolled rectifier and autotransformer, the power consumed by the device is 2.67 times lower than the power consumed by the device when using a circuit with a controlled rectifier and a transformer. Energy efficiency increases significantly with the increase in device performance.

THE PURPOSE. To consider the problems of reliability of pipeline systems of housing and communal services. To analyze existing methods for assessing the technical condition of pipelines. To develop an improved technique that allows you to search for various types of defects in pipelines. To develop a device for inertial excitation of low-frequency diagnostic vibration vibrations. To develop software in the LabVIEW environment for collecting, storing and processing signals from a sensitive sensor (piezoelectric sensor) installed on a pipeline. To conduct a series of experimental studies to te st the proposed methodology. METHODS. The method of inertial excitation of vibrations was used to excite vibrations in the wall of the investigated pipeline. To search for the natural frequencies of vibrations of the pipeline under study, mathematical mode ling methods were used, implemented in the ANSYS software package. During the experiments, the fast Fourier transform method was used to process the signals coming from the piezoelectric sensor. RESULTS. The article presents a technique for assessing the t echnical condition of pipelines, as well as a device for inertial excitation of vibrations. The article presents the results of experimental studies on a fiberglass pipeline, the results showed that when an oscillatory wave passes through the wall of a defect-free pipeline, its amplitude changes insignificantly. If there is a defect in the wall of the investigated pipeline, the vibration amplitude will be much weaker due to the dissipation of vibrational energy in the place of the defect. Thereby, it is pos sible to determine not only the presence of a defect, but also its size by the degree of attenuation of the signal amplitude CONCLUSION. The proposed technique is the basis for the creation of a new measuring and diagnostic complex for vibration control of pipelines.

THE PURPOSE. In order to control the technical condition of oil-filled electrical equipment, a number of new analytical methods have recently been created to determine the ultra-low concentrations of impurity compounds in transformer oil. An analysis of the literature data showed that at this stage of the analytical procedure significant errors may occur that worsen the quality of control of the technical condition of oil-filled electrical equipment, and in some cases make its results meaningless. The published literature practically does not discuss the problem of sample preparation of transformer oil, which negatively affects the quality of analytical control, that is, the reliability of the results and, accordingly, the diagnosis of oil-filled electrical equipment. METHODS. The paper discusses a sample preparation system for transformer oil, which is based on various methods for extracting target components from it. The adsorption process is used, the preparation of chemical derivatives, various types of extraction, liquid, gas, solid phase and fluid, as well as using low temperatures, extraction in microwave, magnetic, electromagnetic and centrifugal fields. It is shown that liquid extraction with an organic solvent is widely used from all sample preparation methods, with the help of which furan compounds resulting from the destruction of paper insulation are extracted from transformer oil. The disadvantages of sample preparation using liquid-phase extraction and the possibility of using solid-phase extraction on various adsorbents for this purpose are discussed. RESULTS. The results of an experimental study of the sorption properties of various organic solvents with respect to porous materials differing in the structure of their surface are presented. We used zeolite-bearing rocks of the Tatar-Shatrashansky deposit, synthetic zeolites NaX-13^A. Using the ascending variant of liquid column chromatography, the absolute retention values of standard extractants were determined and their dependence on the length of the sorption layer of the porous material was found. CONCLUSIONS. It was shown that the highest retention times for all studied adsorbents are observed for organochlorine extractants, chloroform, carbon tetrachloride, dichloroethane, trichlorethylene. For N. Hexane is a relatively small interaction. Histograms are given of the effect of the retention time of standard sorbates (extractants) on their physicochemical nature.

THE PURPUSE. The paper considers the influence of the nature of organic solvents on the process of separation of an antioxidant additive added to transformer oil at a concentration of up to 0.40% by weight, and organic solvents used as selective extractants. Based on the analysis of literature data, it is shown that mineral transformer oil is a complex hydrocarbon composition that undergoes oxidative degradation during operation, leading to aging of transformer oil and deterioration of technical conditions of operation of transformer electrical equipment. As a result of this process, peroxide compounds appear in transformer oil, which affect its color, oxidation stability, aging resistance, compatibility with structural parts of equipment, etc. Gas -liquid chromatography was used to determine the "Ionol" antioxidant additive and organic extractants in transformer oil. Experiments were performed on a chromatograph of Chromosomes GC -1000 with a flame ionization detector and a quartz capillary column 30 m long, 0.32 mm in diamet er, filled with a fixed liquid phase Valko Bond VB-WAX P/n with a film thickness of 0.5 microns. The sample was dosed into the gas-liquid chromatograph injector using an automatic liquid dispenser DAZH-23, designed for entering up to twenty-three samples of sorbates and controlled by a computer with the appropriate software.

METHODS. Aliphatic alcohols from C₁ to C₅ were studied as extractants of the antioxidant additive, which are well separated from the ionol both under isothermal conditions and in the mode of linear programming of the column temperature from 40 to 220 °C. Under these conditions the chromatogram of the separation of antioxidant additives, and aliphatic alcohols, which are used to calculate their relative retained volumes, the asymmetry of chromatographic peaks and the column efficiency, which depends on the physico -chemical nature of the solutes to be analyzed and the conditions of the chromatographic experiment.

RESULTS. The dependence of the relative volume of retention of aliphatic alcohols on their permittivity, which has a nonlinear form, is established. At the same time, with a decrease in the chain length of alkyl substituents in the aliphatic alcohol molecule, there is a tendency to increase their permittivity. The dependence of the relative retained volume of aliphatic alcohols on the selectivity coefficient of separation with Ionol is linear. In this case, the most optimal separation selectivity, approaching one, is characteristic of the Ionol – Butanol-1 pair. It is shown that the dependence of the logarithm of the retention time of aliphatic alcohols on their boiling points is linear both at a low temperature of the chromatographic column (40 °C) and at a higher temperature (more than 100 °C). CONCLUSION. At the same time, the angle of inclination of the corresponding lines changes in the boiling point of organic solvents, which is associated with a change in the sorption mechanism in a capillary chromatographic column filled with a polar stationary phase.