# Kyiv National University of Construction and Architecture (KNUCA)

• Kyiv, Ukraine
Recent publications
With the development of information technology, electromagnetic radiation becomes a tangible view of the physical (wave) environmental pollution. Modern scientific research aimed at the components of the electromagnetic environment pollution problems mainly involves the anthropocentric approach. There is no procedure for determining the influence of harmful physical factors on biota, in particular in terms of water (Daphnia magna Straus) and air (Drosophila melanogaster L.) environments. A clear system of rationing of maximum permissible levels of electromagnetic radiation, including volume and ecosystems protected areas has not been developed. The article considers the relevant scientific and practical problem of creating a framework for assessing and predicting the negative impact of electromagnetic radiation on the biota related to ethological changes and teratogenesis. The characteristic of all the constituent elements of the system determines the degree of the negative impact of the induction of the magnetic field on the biota: activity, mortality; reproduction; availability, and frequency of Teratology. A method for determining the activity levels of Daphnia and Drosophila total average activity biota was developed and described. The trajectory patterns of Daphnia motion at low activity in the state of stability, with increased activity in the excited state, were created. The results of the research on the negative impact of electromagnetic radiation of industrial frequency on biota were presented. The critical levels of the magnetic field and noise pollution, which cause the depletion and destruction of the test object, the relationship between ethological changes and the occurrence of mutations depending on radiation levels were determined. The biological test objects were proven to minimize the error of the results of determination of electromagnetic effects on the biota, in comparison with the mathematical methods of research.
Banking risk management is considered weak compared to rapid changes in financial markets. In light of the recent global financial crisis, banking risk management has become a significant concern of banking regulators and government agencies. This work aims to build a model for assessing banking risks. The primary study method is economic–mathematical modeling based on the standardized model of the Basel Committee for Operational Risk Management, the modified CAPM model, and the model developed by Shapiro and Cornell for currency risk management. The information base was the financial statements of Bank Credit Agricole (Poland). As a result, an economic–mathematical model is built, which is the optimal combination of operational, currency, and credit risk management models. This model calculates the optimal values of bank balance sheet items, which allows for making the right management decisions. It allowed adjusting the value of the bank profit by 3.6 million US dollars. In conclusion, considering the results of banking risk modeling, the need to build a strategy for the bank’s development is determined.
Industrial equipment is a dynamic system and has deformations not only during installation but also during operation. Under the influence of variable load and displacement of the center of gravity, the soil under the foundation settles unevenly, and accordingly, the equipment deforms unevenly, which is a threat to the equipment, the greater the load corresponds to more subsidence. Separation of partial deformations from full is important for determining the elements of straightening equipment for its uninterrupted and trouble-free operation. The presence of significant total deformation does not affect the performance of the equipment. The most critical deformations are partial deformations. Absolute vertical deformations are calculated as the difference in sediment between adjacent sediment marks, which are fixed on the equipment in the same measurement cycle. Comparing the values of deformations with the allowable technical conditions, decide on the need for straightening and adjustment of equipment. The accuracy of installation is characterized by a tolerance of 0.1÷0.5 mm on the relative position of the equipment, which is conjugate mounted at a distance of several tens or hundreds of meters. For installation of the equipment with such accuracy carry out special geodetic works with use of methods and technical means of measurements specially developed for this purpose in geodesy, metrology and mechanical engineering.
Lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramic powders were synthesized using the sol–gel method. The ceramics thickness was reduced to achieve high-energy storage and large electrocaloric effect in bulk ceramics. Dielectric, ferroelectric, energy storage, and electrocaloric properties were investigated for BCZT ceramic with 400 µm. Here, pure crystalline structure and homogenous microstructure were identified by XRD analysis and SEM measurements, respectively. The dielectric measurements revealed a maximum dielectric constant associated with ferroelectric–paraelectric phase transition. The maximum of εr′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varepsilon^{\prime}_{{\text{r}}}$$\end{document} was 17841, around 352 K. Furthermore, the BCZT ceramic exhibited improved energy storage and electrocaloric properties. A high recoverable energy density Wrec of 0.24 J/cm³ and a total energy density Wtotal of 0.27 J/cm³ with an efficiency coefficient of ~ 88% at 423 K under an electric field of 55 kV/cm were obtained. Besides, The maximum value of ΔT = 2.32 K, the electrocaloric responsivity ζ = 0.42 K mm/kV, the refrigeration capacity RC = 4.59 J/kg and the coefficient of performance COP = 12.38 were achieved around 384 K under 55 kV/cm. The total energy density Wtotal and the temperature change ΔT were also calculated by exploiting the Landau–Ginzburg–Devonshire (LGD) theory. The theoretical results matched the experimental findings. These results suggest that the synthesized BCZT ceramic with reduced thickness could be a promising candidate for energy storage and electrocaloric applications.
The study of dynamical systems chaotic behavior and their routes to chaos was in particular attention at recent years. These phenomena study in non-smooth dynamical system is of the special scientists’ interest. We apply the Continuous Wavelet Transform (hereinafter – CWT) to investigate the intermittent route to chaos, boundary crisis, and transitional regimes under quasi-periodic route to chaos in strongly nonlinear non-smooth discontinuous 2-DOF vibro-impact system. We show that CWT application is very useful to observe the intermittency, chaos and transitional regimes. It allows one to detect and to determine these phenomena with great confidence, reliability, and clearness.
The maximum Lyapunov exponent characterizes the degree of exponential divergence of close trajectories. The presence of a positive Lyapunov exponent in the system indicates a rapid divergence over time of any two close trajectories and sensitivity to the values of the initial conditions. Therefore, the determination of the Lyapunov exponent makes it possible to identify a dynamical system as a system with chaotic dynamics in it. When studying the output signals of dynamic systems, it is often necessary to quantify the degree of randomness of the output signal when equations of the system are unknown. In this paper, the possibilities of accuracy improvement of the numerical algorithms of Benettin and Wolf for estimating the maximum Lyapunov exponents of an attractor of a dissipative dynamical system are shown. Under these procedures a system itself can be specified both analytically (by a system of differential equations) and only by output signal.
The article is devoted to the study of green enterprise logistics management and the circular economy incentives used for the implementation of green environmental projects in the countries of the European Union and Ukraine. The article develops methodological approaches and practical recommendations to improve the management system of the enterprise that collects garbage and makes preparations for garbage cardboard and paper recycling. Such system is based on the principles of “green logistics”, taking into account the competitive environment on Ukrainian market. The objectives of the study are the following: elaboration of methodological approaches to the formation of prospects for the development of an enterprise operating in a highly competitive environment; implementation of the strategy of searching and entering new markets for the purchase of raw materials that requires the improvement of the enterprise management system in the context of “green logistics”. A qualitative assessment of the effectiveness of the implementation of the principles of "green logistics" at the enterprise taking into account the economic, social and environmental effects has been carried out in this research. The system for the enterprise management based on the principles of “green logistics” has been proposed. It is recommended to be used at any enterprise that practices the appropriate type of activities (collecting, pressing and preparing cardboard and paper, as well as high-pressure plastic for processing). This approach of the sustainable development of the municipal solid waste treatment industry can be transferred to the country’s entire economy.
The work carried out complex and systematic studies based on of which the causes of accidental destruction of reinforcement of reinforced concrete structures of hydraulic structures is established, which is that corrosion damage to metal reinforcement is accompanied by its active flooding and embrittlement, resulting in reduced material properties against corrosion and mechanical destruction of reinforced concrete structures, especially after 20-40 years of operation. Based on existing approaches to the assessment of ageing equipment, developed in various branches of mechanical engineering, including the construction industry, identified trends and shortcomings in determining the efficiency of metal structures and their residual life, in connection with which the calculation and experimental methods of using the criteria of crack resistance, sensitive to changes in the structure of the metal during long-term operation. It is established that the decrease in crack resistance characteristics in the surface layers of reinforcement of reinforced concrete structures in contact with the aggressive environment is caused by the degrading effect of hydrogen on the crystal structure of the metal. The calculated-experimental method is offered, allowing to carry out engineering forecast estimation of residual (working) resource of the reinforced concrete designs operated in corrosive-aggressive environments of hydraulic engineering constructions, which adequately reflects physical and mechanical processes in metal which occur during its long operation.
The aim of the article is to assess the effectiveness of the current tools for interaction between public authorities and civil society in Ukraine. A distinctive feature of this study is the use of the content analysis to study the content of consultations of central government bodies with the public, discussions of draft laws, decrees, resolutions, orders, petitions of citizens, as well as recommendations of expert opinions and proposals of public councils and measures for their implementation. The analysis allowed identifying significant shortcomings in organizing work to establish cooperation between central government bodies and the public. These shortcomings involve the dominance of a purely statistical approach to analyzing the petitions of citizens, neglect of public consultations, disregard for the proposals of public expert committees, and a formal approach to the activities of public councils at the ministries. The decreasing effectiveness of interaction between public authorities and civil society in Ukraine is noted, which is caused by the bureaucratization of this process on the one hand, and by the lack of citizens’ skills to defend their position in the legitimate field of social and political relations, on the other hand.
The use of blast furnace cement is an effective way to meet the requirements of sustainable development. However, CEM III/C is characterized by slow strength gain. The problem can be worse for plasticized reinforced blast furnace cement concretes mixed with sea water in view of shorter durability. The mitigation of corrosion in plasticized blast furnace cement concretes mixed with sea water can be provided through a composition of minor additional constituents, with percentage by mass of the main constituents: alkali metal compounds, 2…3; calcium aluminate cement, 1; clinoptilolite, 1. The alkali metal compounds are known to activate hydraulic properties of ground granulated blast furnace slag. A calcium aluminate cement promotes the accelerated chemical binding of Cl− and SO42−-ions with the formation of Kuzel’s salt. A clinoptilolite occludes these aggressive ions. The positive effects of the mentioned minor additional constituents in the blast furnace cement were supported by the increased early strength gain and the higher structural density, as well as by a good state of steel reinforcement, in the plasticized concretes mixed with sea water.
The geofluid temperatures of the most promising geothermal areas of Ukraine are estimated to be less than approximately 130°C . This paper presents the results of a theoretical design study on the thermodynamic cycle parameters of a geothermal power station that would utilize these geothermal resources, and these results are similar to ones given elsewhere. Various configurations of the organic Rankine cycle (ORC) are considered. Thermal schemes of 3-stage geothermal power installations are studied. The effectiveness of geothermal power stations with various working fluids at each stage is investigated. The results of a numerical study of the thermal 3-stage geothermal installation schemes show that at a geothermal liquid temperature of 130°C the possible total specific power output of a turbine is 20.7–20.8 kW per kg/s of a geofluid flow. The combined 3-stage cascaded system with a bottoming cycle can generate about 15% more power than a simple single-stage binary plant at the same brine inlet conditions.
The production of ZrN–Si3N4 and ZrN–Si3N4–TiN composites by spark plasma sintering and the mechanical and tribological properties of the consolidated materials were studied. The densification of the ZrN–Si3N4–TiN composites was found to proceed more intensively in the range 1100–1300°C, and nanocrystalline titanium nitride was the main factor that promoted the densification of these composites. Ceramic 57 wt.% ZrN–43 wt.% Si3N4 and 84 wt.% ZrN–16 wt.% Si3N4 samples with a relative density of 0.95 and 0.93 and (84 wt.% ZrN–16 wt.% Si3N4)–15 wt.% TiN and (57 wt.% ZrN– 43 wt.% Si3N4)–30 wt.% TiN composites with a relative density of ~0.98 were produced. Microstructural studies showed that components of the consolidated ZrN–Si3N4 composites were uniformly distributed over the material with an average grain size of 200–300 nm. The ZrN–Si3N4– TiN composites had a finer structure, TiN grains being smaller than 100 nm. The mechanical properties of the titanium nitride composites were higher than those of the ZrN–Si3N4 materials. Thus, the Vickers hardness and indentation-determined fracture toughness of the composites containing 15 and 30 wt.% TiN were 18.7 ± 1.1 GPa and 5.2 MPa ∙ m1/2 and 19.1 ± 1.9 GPa and 5.8 MPa ∙ m1/2, respectively. The hardness of the ZrN–Si3N4 composites was ~17 GPa. The tribological properties of the composites were tested with the VK6 hardmetal and silicon nitride. The wear resistance of the ceramic samples directly depended on the contents of zirconium nitride and counterface, i.e., on their physicochemical interaction. When the ZrN content increased to 84%, the tribological properties of the composites improved substantially through the lubricating capability of zirconium nitride. The (84 wt.% ZrN–16 wt.% Si3N4)–15 wt.% TiN composite showed the best tribological properties and can be recommended for use in friction units under dynamic loads.
Perovskite-type Ba0.9Sr0.1Ti0.9Sn0.1O3(BSTSn) ceramic was synthesized by the sol-gel method. The P-E hysteresis loops were recorded at different temperatures to investigate the ferroelectric and energy storage properties of BSTSn ceramic. Enhanced recoverable energy density and high energy storage efficiency were found to be 58.08 mJ/cm³ and 84.36%, respectively at room temperature (RT) under a moderate applied electric field of 20 kV/cm. The electrocaloric effect (ECE) in the BSTSn ceramic was explored using two different approaches based on P – E hysteresis loops, and pyroelectric current measurements. The largest electrocaloric (EC) temperature change, ΔTmax ≈ 0.63 K was determined using the Maxwell relationship obtained near RT under 20 kV/cm. The corresponding EC responsivity (ξmax) value of 0.31 K mm/kV is one of the highest reported values in lead-free ferroelectrics near RT. This study demonstrates that the BSTSn ceramic is a promising candidate for solid-state cooling and energy storage applications.
It is shown that for the design of buildings and individual rooms with normative concentrations of light air ions of both polarities, a preliminary estimated assessment of the dynamics of this indicator in space and time is appropriate. In the general case, it is possible to use the continuity equation for weakly ionized plasma for one direction. This is due to the low concentration of air ions in the air. The ratio of molecular kinetic theory of gases is used to determine the necessary indicators - the average lifetime of air ions, free path length. To determine the average speed - Maxwell's distribution. It is shown that the propagation of air ions due to diffusion processes is insignificant, and the corresponding calculations have large errors. Calculations on the propagation of air ions by directed air movement from the source of artificial ionization are given. The distribution of air ion concentrations can be most accurately calculated taking into account their recombination, deposition on heavy air ions and neutral suspended parts (fine dust and aerosols). Relevant coefficients are mostly issued from reference sources. If there are electrostatic fields in the premises, generated due to the triboelectric effect and other factors, it is necessary to take into account the deposition of air ions on these surfaces. In order to correctly determine the concentrations of air ions, in addition to the values of the mobility of negative and positive air ions, data on electrostatic field strengths are required. The values of such fields are unpredictable, so they are measured by appropriate instruments in similar conditions. Verification of calculated data using electrostatic charge meters and air ion counter proved the reasonable convergence of expected and actual data. It is advisable to develop two- and three-dimensional models of the propagation of air ions of both polarities in rooms of different purposes, configurations of equipment placement, the presence of artificial ionization sources and directional air movement.
The geospatial data accuracy and specification requirements for LTE and 5G radio propagation and optimization are much higher than those used in planning 2G and 3G networks. The recommended geospatial data resolution of 1–2 meters allows the display of the smallest parts of geospatial objects. In the article, we describe the technology and its practical implementation to produce an accurate clutter height (raster canopy height model) for the purposes of LTE and 5G radio network propagation and optimization. This technology, which is based on aerial images, may be adapted to use LiDAR data. The technology includes the data integration between the different software. The processing of digital terrain models, obstacles (buildings and vegetation) and DSM cloud points is performed in geographic information systems, such as ArcGIS. The technology was proven by the practical implementation and calculation in multi-technology wireless network design and optimization platform Atoll.
Przedmiotem analiz numerycznych zamieszczonych w pracy jest żelbetowy zbiornik na węgiel brunatny. Pojemność całkowita zbiornika wynosi około 26 tys. ton. W początkowym okresie eksploatacji zasobnika w latach 60. pojawiły się liczne spękania oraz nadmierne deformacje wymuszające podjęcie pilnych działań naprawczych. Wprowadzono wtedy stalowe ściągi podłużne, poprzeczne i ukośne. Skuteczność tych wzmocnień nie była weryfikowana w przeszłości. Inwentaryzacja oraz wykonane w ostatnim czasie badania materiałowe dostarczyły danych użytych w analizach numerycznych, których celem była ocena aktualnego stanu technicznego analizowanego obiektu. Model numeryczny samej konstrukcji został uzupełniony o grunt, na którym zasobnik został posadowiony. Analizy numeryczne zostały wykonane autorskim programem weryfikowanym wcześniej za pomocą innych programów komercyjnych.
The field of Piezoelectric nanogenerators is rapidly growing as promising technology for driving low-power portable devices and self-powered electronic systems by converting wasted mechanical energy into electric energy. In this work, we designed a flexible and self-poled piezocomposite nanogenerator based on lead-free H2(Zr0.1Ti0.9)3O7 (HZTO) nanowires and polylactic acid (PLA) biodegradable polymer. By using a piezoresponse force microscope (PFM), the piezoelectric coefficient (d33) of a single HZTO nanowire was found to be 26 pm V−1. The piezoelectric energy harvesting performances of a self-poled piezocomposite film fabricated by embedding core-shell structured HZTO nanowires by polydopamine into the PLA matrix were tested. The piezoelectric nanogenerator demonstrated enhanced output performances (open-circuit voltage of 5.41 V, short-circuit current of 0.26 µA and maximum power density of 463.5 µW cm−3 at a low resistive load of 2.5 MΩ). Besides, the developed device can charge different capacitors by regular mechanical impartations and can power a red light-emitting LED diode by various biomechanical motions. This work reveals the benefits of combining HZTO nanowires and PLA biopolymer in designing high-performance piezoelectric nanocomposite for biomechanical energy harvesting.
This paper describes the conceptual apparatus for the formation of information spaces of executors of educational projects in a dynamic environment. A multiple model of identification of the executor of an educational project was developed, taking into consideration the competence approach and dynamics of the components of the information space. To assess the competencies of the executors of educational projects, three components are calculated: the grade of the executor’s knowledge, the grade of the executor’s performance, the grade of the executor’s personal qualities. Based on the obtained grades, generalized assessments of the level of competence of each executor are formed. These grades for each executor of a particular educational project are used to determine the level of performance and potential of this project. To find a generalized grade of the project potential, the least square method was used to construct a regression line, which indicates a tendency to develop the competencies of project executors. The stages of building information spaces of executors of educational projects in a dynamic environment were proposed. The hypothesis of the study that the progressive dynamic development of educational project executors has an impact on the potential of these projects was verified experimentally. To verify the described construction method, ten educational projects, which were implemented in the period from 2014 to 2020, were selected. The results indicate that the grade of the competencies of project executors recorded at the time of completion of a project almost completely coincides with the grade of evaluators after completion of the projects. The ranks obtained after the final evaluation of projects and the ranks according to calculated performance grades coincide by 40 %. Evaluation of projects is mainly focused on the reputation and performance of executors and does not sufficiently take into consideration the transformation of the competencies of executors during the implementation of projects.
The innovative content of the components, stages, and results of the construction and implementation of the toolset, which provides a formalized assessment and choice of a rational scenario for reengineering implementation at a modern enterprise in the form of a target project, was displayed. The need for research is caused by the fact that the existing approaches to reengineering business processes in an application for construction enterprises require significant adjustments. The reengineering of a construction enterprise as a target project should be coordinated with the projects and works executed by a construction enterprise. The proposed analytical support makes it possible to determine for each of the construction enterprises an alternative to reengineering adapted for its needs. Modules as part of the proposed analytical support implement a single algorithm of unambiguously formalized substantiation of the construction enterprise renovation project – through a developer reengineering project. This toolset allows rationalizing and adjusting decisions on the coordination of determinative characteristics of the above project – the essence of changes, their duration, estimated cost, investment stages. The presented study provides a clearly formalized management technology for evaluating and selecting reengineering options, determining in advance the future benefits of reengineering transformations, namely, functional-technological, technological, technical, managerial, and economic changes. The created analytical support makes it possible to perform successful administrative support of a reengineering project. Its implementation will ensure an irreversible qualitative "jump" in the trajectory of the life cycle of an enterprise and expected strategic priorities.
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371 members
• Heat-Gas Supply and Ventilation
• Scientific Research Institute for Binders and Materials
• V.D.Glukhovsky Scientific Research Institute for Binders and Materials (SRIBM)
• Department of Geoinformation Systems and Management of Territories
• V. D. Glukhovskii scientific research institute for binders and materials
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