National Aviation University
  • Kyiv, Kyiv, Ukraine
Recent publications
Modern materials science has faced the problem of reducing the cost of raw materials and labor costs while obtaining basic construction materials (cement concrete) with increased performance properties. The article aims to substantiate the use of carbon nanotubes of fly ash as a cement concrete modifier to be reasonable for solving the above problem. Experimental studies are carried out using standard and special methods. The technological properties of cement concrete mixtures are determined in accordance with the European and American standards. The study investigates the impact of carbon nanotubes of fly ash on the structure and properties of the mineral Portland cement binder. The article provides the examination of structural and rheological characteristics of nano-modified cement concrete mixtures. The effect of a carbon nano-modifier on the strength, deformation, and performance properties of cement concrete mixtures is defined. As a result, the optimal composition of nano-modified cement concrete mixture has been developed that meets the criteria of concrete compressive strength and flowability. Positive research results allow determining the areas of application of the obtained compositions in civil engineering.
The multi-rotors have a limited operational period and generate too much noise, which is insufficient for complex tasks and adversely affects humans’ and animals’ health. Nevertheless, their market has become increasingly popular. Therefore, low-noise products are more competitive, and aerodynamic and acoustic improvements are critical. This investigation aims to design a small bioinspired propeller with the same power input as a conventional propeller to achieve the same or better aerodynamic performance while decreasing noise. Accordingly, an experiment investigated the impacts of operation conditions and varied geometric parameters on six small propellers' aeroacoustic performances with a unique planform shape inspired by five insects and one plant seed, such as Blattodea, Hemiptera, Hymenoptera, Neuroptera, Odonata, and maple seed. Each propeller was operated at eleven rotational speeds ranging from 3000 to 8000 RPM with no freestream velocity for simulating hover conditions. Compared to the baseline propeller, the results demonstrate that all bioinspired propellers produce more thrust for the same power supply, reduce harmonic and broadband noise, and provide a better noise level. Also, their rotational speed is lower and their figure of merit is higher than the baseline propeller at hover flight with 3N thrust. They all outperform the baseline propeller in terms of hover efficiency at all thrust values considered. Besides, the Neuroptera propeller is more efficient than other propellers, decreasing 5.5 W of power and reducing 7.9 dBA at hover flight with 3N thrust and 1.5 meters distance, compared to the baseline propeller.
Nowadays situation at the universities in Ukraine and all other countries round the world are faceted with different challenges almost every new quarter of the year. The very vivid example of it was the pandemic period, which determined transforming of forms of education and different approaches to education. Moreover, the Pandemia provoke the huge wave of challenges for scientific and pedagogical staff of universities. A great number of changes took place at the system of educational process organization: pandemic has exacerbated the need for digital, technology-enabled education experiences, new types of online-classes appared and new ways to scale them etc. But after pandemic period and all these transmitions in universities their appared the need for analyses of challenges which we are going to face with, when we come back to ordinary style of teaching? what problems are we going to solve? To answer these questions, we created a Questionnaire for teaching staff and students of different Universities in Ukraine in different regions. We asked them to give their feedbacks, opinions and feelings of the quarantine restrictions of COVID-19, what difficulties they had durining the next few months. The investigation helped to distinguish challenges to scientific and pedagogical staff of higher educational institutions, the nature of which is the peculiarities of the professional activities of teachers and challenges to the scientific and pedagogical staff of higher educational institutions, the nature of which are the features of the educational activities of students.
In this paper the algorithm for constructing the discrete (0,1)-sequent functions constituting the whole symmetric systems of orthogonal equidistant functions on the example of the eighth-order systems developed. Discrete sequential functions form by replacing their piecewise constant values +1 or -1 in the time domain (from the original space) with numerical values 0 and 1 in the image space. We refer to Walsh-like functions as (0,1)-sequent functions in which the number of zeros and ones in each half of the definition interval is not necessarily the same as in classical Walsh functions. By the directed search method, each of the 30 formed whole groups of equidistant sequent functions unfolds, like the group of classical Walsh functions of the eighth order, into 28 symmetric systems of sequent functions. The main result achieved in this work should consider an expansion of the set of Walsh-like systems of the eighth order by more than an order of magnitude. The algorithm's simplicity for synthesizing such systems of sequential functions and the high speed of spectral processing of discrete signals provided by the proposed bases open the Walsh-like systems for broad prospects of application in various fields of science and technology.
In 2019, Yuval Harari, an Israeli historian and bestselling author, appeared in the center of a media debate provoked by the discovery of considerable differences between the English text of his 21 Lessons for the 21st Century and its Russian translation. A comparative study of the English and Russian texts of the book featured in this paper revealed five major issues which turned out to be sensitive for the Russian censorship, namely, homosexuality, liberalism, U.S.S.R.–U.S. “tug-of-war,” Putin and Putin’s Russia, and Putin’s aggression against Ukraine and Georgia. It is in the presentation of these topics that Yuval Harari’s English text suffered essential transformation and reduction in the Russian edition. The conducted analysis contributes to the long-lived debate about the author’s and the translator’s responsibility before their readers, and the boundaries, beyond which mutilation of the source text no longer allows regarding the resulting text as a translation. The author argues that the escalating information wars targeted at people’s minds in the twenty-first century impose ever-increasing requirements to authors and translators of such books as Yuval Harari’s 21 Lessons for the 21st Century in terms of intellectual integrity and professional ethics.
Currently, the areas of application of polymethyl methacrylate plastic (acrylic) owing to its unique properties (most notably, lightness, plasticity, exceptional transparency and high impact resistance) range widely from modeling, lighting technology and medicine, automotive industry and watchmaking to aviation, shipbuilding, rocket engineering and production of military equipment. Mechanical characteristics of polymethyl methacrylate plastic, like most polymers, change significantly over time when exposed to temperature. The temperature impact extends to all volume of the material and leads to its “heat aging”, which should be considered when designing the products made of polymethyl methacrylate plastic. The process of thermal destruction is long enough, so it is reasonable to predict the changes in the properties of polymethyl methacrylate plastic using accelerated methods of material specimen aging with subsequent testing under simple loading. The paper deals with the experimental study of the process of changing of physical and mechanical characteristics of polymethyl methacrylate plastic during thermal destruction. Heat aging of the material is identified with the process of the thermal oxidative destruction occurring at a constant rate and specified temperature. It is assumed that the change in polymer’s mechanical properties is proportional to the change in number of its functional groups. The tests were performed on cylindrical specimens with fillets at the ends at three levels of temperature: 40, 70 and 100°C. Specimens were held at each temperature for 2; 5; 10; 20 and 30 days. According to results of statistical processing of experiments, we obtained the average values of ultimate strains for each temperature-time regime. The obtained ultimate strain values were the basis for the construction of long-term aging curves. For the minimum allowable value of ultimate strain in operation, the period of operation of polymethyl methacrylate plastic was determined for different aging temperatures. At the operating temperature of 20oС the period of operation was 12 years. During this period, the ultimate deformability of polymethyl methacrylate plastic decreases to 3%, which is approximately equal to elastic deformations. The results will allow us to predict the period of operation of polymethyl methacrylate plastic products for different values of the ultimate strain and operating temperature.
The greatest difficulties in creating a new structure or upgrading an old one are associated with designing joints and connecting parts of the structure, especially composite and metal ones. Nowadays, the problem of designing and improving such joints is timely and is being actively studied so that the best solutions are found. The article presents the research carried out to determine the main parameters of elements of mechanical joints made of polymer composite materials, as factors affecting the requirements for precision of connection compliance estimation. There has been found the influence of the number of fastener rows on estimating the maximum forces which act in the joint, as well as the influence of the ratio of the connection compliance to the compliance of the part. A field of possible states of the joint has been built. Within the field, the following areas have been identified: the area of high sensitivity to precision of estimating the parameters of the joint elements, requiring experimental confirmation and more accurate models; the area of average sensitivity of the joint to precision of estimating the parameters of its elements, permitting the use of known dependences; and the area of low sensitivity, where simplified models can be used. In the course of the developed model testing, joint samples were tested to evaluate the force connection compliance, and a reference variant was calculated using the Douglas formula. The reference variant of the joint sample was chosen based on the principle of equal compliances of the parts to be joined, presented by a series of samples assembled from a composite package of 80 layers and two surface layers made of 3.98 mm-thick steel. The parts were connected with steel bolts with a diameter of 6 and 8 mm. Numerically, the ratio of the connection compliance to the part compliance is 85...96 for the experimental data, and 9...10 for the calculated data. This indicated that the joint was in the transition area between high and medium sensitivity of the joint to the accuracy of compliance estimation, which requires continuous refinement of the connection parameters.
Conventional process schemes of municipal sewage water treatment, advantages, and disadvantages of the methods applied when removing biogenic elements were considered. It was shown that the existing shortcomings cause additional explicit costs and difficulties when disposing of the resulting waste. Low efficiency of the removal processes themselves causing residual concentrations of biogenic elements in the treated sewage water was also shown. A process scheme for treating municipal sewage water was proposed. It includes the use of a photobioreactor of a proposed design for the removal of biogenic elements due to the metabolism of microalgae. It was experimentally shown that the use of Euglena gracilis strain for removal of phosphates in initial concentrations of 4, 7, and 14 mg/dm3 from sewage water is the most efficient way. It makes it possible to reduce these concentrations to residual 0…0.55 mg/dm3 in four days. A 3.75…5.58 times increment of microalgae biomass during this period was also shown. A mathematical model was constructed for calculating the time of staying the sewage water and microalgae mixture in a photobioreactor to achieve the required degree of removal of biogenic elements. Based on the proposed model and experimental studies, the required time of staying in the rector working area was calculated. It was shown that with the use of Euglena gracilis strain but without removal of biogenic elements at previous purification stages (process schemes including only mechanical purification), the time of mixture staying in the working zone was 37.81 hrs. With partial removal of biogenic elements at the stage of biological treatment (0.55 mg/dm3 total nitrogen, 0.91 mg/dm3 ammonium nitrogen, 0.44 mg/dm3 phosphates), this time was reduced to 26.66 hrs. It was found that the use of Euglena gracilis strain instead of Chlorella vulgaris (FC-16) in the removal of phosphates results in a 2-time increase in the process efficiency and a 50 % decrease in time of mixture staying in the working zone. Recommendations for calculating geometric parameters of photobioreactors of the proposed design were given for use in the process schemes
The article is devoted to the analysis of the constitutional principles of implementation of the Association Agreement between Ukraine and the European Union. It is determined that the important factors of constitutional support for the implementation of the Association Agreement between Ukraine and the European Union are, first, the consolidation of the pro-European foreign policy of the state, which is a kind of constitutional guarantee of continuity and consistency in implementation and association activities in Ukraine EU and, secondly, the improvement of constitutional provisions on the interaction of national and international law, in particular those governing the implementation of international treaties into the national legal system. Attention is drawn to the need for more systematic constitutional and legal regulation of international and domestic law, in particular, it is proposed to include in the formation of a «package» of systemic constitutional changes, items on the relationship between international and national law, which will create the basis for: 1) to consolidate the superiority (primacy) of properly implemented international legal norms over the national law of Ukraine (except for the Constitution of Ukraine, which should have supremacy and priority in the national legal system); 2) to regulate the application of other sources of international law in Ukraine (first of all, generally accepted principles and norms of international law, as well as acts of international organizations); 3) specify the forms of expressing consent to the binding nature (methods of implementation) of an international agreement for Ukraine; 4) determine the place of international treaties of Ukraine in the hierarchy of normative legal acts; 5) to expand the range of subjects of implementation of international agreements and to regulate the status and hierarchy of intergovernmental and interdepartmental agreements accordingly. The ongoing process of constitutional reform in Ukraine creates a legal basis for the systematic elimination of shortcomings and gaps in the Constitution of Ukraine in the field of interaction between national and international law. Key words: Constitution of Ukraine, Constitutional Reform, Constitutionalization, European Union, Association Agreement between Ukraine and the EU, Implementation.
This paper presents results of a study investigating worm gears consisting of polymer worm wheels and steel involute and Archimedes worms. The author uses his own calculation method to predict polymer wheel wear, gear life and maximum contact pressure in mesh. The effect of tooth correction and wear on gear life and contact pressure is considered. Cases of double and triple tooth engagement are analysed. The worm wheel is made of non-reinforced polyamide PA6. Quantitative and qualitative relationships are established between the maximum initial contact pressure along tooth profile and the tooth correction coefficient. Tooth wear causes a considerable decrease in contact pressure, with the highest decrease observed at the exit of engagement. The maximum contact pressure is generated at the exit of engagement. The same trend is observed for tooth wear. The minimum gear life is observed at the exit of engagement. It increases linearly with increasing the coefficient of tooth correction. The gear life significantly increases (by approx. 56%) in triple tooth engagement compared to double tooth engagement.
Services, where clients are served simultaneously in one space, require new approaches for customer service value management. Total customer service value management is a new management concept in the service industry. On the example of suburban passenger transportation, the authors try to prove that it can be an effective tool for customer and transport behavior management. Encouraging drivers of private cars to increase the frequency of public transport usage can reduce harmful emissions, reduce cost of the development of car infrastructure, reduce drivers’ and passengers’ transport fatigue and increase traffic safety. The implementation of purely economic measures aimed at private car owners’ (residents of the suburbs) transport behavior change, can have the effect of increasing the share of those who use public transport. However, this effect may be temporary, as people will gradually return to usage of private cars if they are not satisfied with the value and content of transport customer service value offered by the suburban passenger carrier. Therefore, in order to increase the sustainability of such switching effect, local and state authorities should encourage the suburban carrier to regulate the customer service value of transportation service provided by it, in a certain way. In this way there is a problem of measuring human attitudes to the transportation service offered by the carrier, and developing on this basis the optimal management influence (budget of changes, project implementation time, the magnitude of the effect of switching drivers of private cars to use public transport, combination of these optimization criteria). The largest suburban traffic flow to the capital of Ukraine, Kyiv, is generated by the satellite town Brovary, so the transport situation here is tense. The marketing research results of the possibilities of private cars drivers switching to the use of public transport in this connection are presented.
The object of this study is the assessment of total uncertainty during calibration in terms of assessing the component due to the competence of the personnel. The problems addressed here related to the lack of regulatorily-defined decision criteria regarding the materiality of the impact of the study component; improvement of existing statistics that would minimize errors of the first and second kinds to make a decision on the impact of personnel competence on uncertainty during calibration. A brief interpretation of the results obtained regarding errors of the first and second kinds and insufficient power of En, the statistics, which are most often used by calibration laboratories, alternative statistics are explained by violation of the conditions of their use. The proposed method based on the modified En-statistics shows the power of more than 95 % and the absence of parcels of the first and second kinds. This is due to the developed modification, which makes it possible to take into consideration the maximum permissible uncertainty. The peculiarity is the flexibility of the formula since the maximum permissible uncertainty is chosen according to metrological rules for the selection of standards. It differs for various measuring instruments; a specialist can be allowed to calibrate a less accurate measuring equipment tools and is not allowed to have high-precision ones. The scope of use of the obtained results can be certified calibration laboratories. This procedure will make it possible to obtain reliable data to devise internal methods for assessing uncertainty during calibration. The conditions for the practical use of the proposed method of assessing the impact of personnel based on the modified En-statistics in calibration laboratories are the presence of calibration methods that largely depend on the competence of the personnel, such as measurement of linear and mechanical quantities
This paper reports a study into the quantitative values and dynamics of physical factors in premises and workplaces of stationary and portable computers. The factors that are practically not perceived by the senses of operators were investigated. It is established that modern monitors do not generate electromagnetic fields of hygienically significant levels. System units generate electric fields (18‒22 V/m) and magnetic fields (220‒245 nT) that are approaching the maximum permissible. Sources of uninterruptible power supply and fluorescent lighting systems generate excess magnetic fields (up to 2250 nT and 2300 nT), respectively. The main excessive factor for portable computers is electric fields (up to 9 kV/m), which is the cause of air deionization in the user's zone of stay. It is shown that one system unit in the normative volume of the room (20 m3) deionizes air (into 100 cm-3 positive and 200 cm-3 negative). The generation of ions by modernized laser printers and photocopiers of various models (up to 1500 cm-3 and 2800 cm-3, respectively) was investigated. The distances at which the ionic composition of the air corresponds to the background values (1.0‒1.5 m) were determined. That requires the introduction of artificial air ionization in workplaces of users and a decrease in the levels of electrostatic fields. The spectral composition and amplitudes of magnetic fields of external power supplies of laptop computers were determined. It is shown that the difference in sound levels measured on the scales "Lin" and "A" reaches 24 dB, which indicates a significant impact of infrasound on users. Membrane-type protective panels configured for maximum resonant frequencies of low-frequency sound and infrasound have been proposed
The most important parameters for determining the state of real gas and the thermodynamic properties of the working fluid in a pure liquid region are pressure, specific volume, enthalpy and entropy. The paper presents a modified Redlich-Kwong-Aungier equation of state for determining pressure, specific volume, enthalpy and entropy in the pure liquid phase of real gas. CO2 was selected as the studied working fluid. When solving this problem, the author identified the main parameters of liquid carbon dioxide thermo-dynamics with the least error in comparison with experimental data in a wide range from 220 K to 300 K. It is possible to calculate pressure, specific volume, density, enthalpy and entropy of liquid CO2 with the help of the proposed method, for which the initial data are temperature, density, critical properties, molar mass and acentric factor of the working fluid. In particular, a modified Redlich-Kwong-Aungier equation is used to calculate the pressure of the working fluid. The author proposes a correlation equation of the scale correction, which is used in the Redlich-Kwong-Aungier equation for CO2 in the region of pure liquid phase. The results obtained for the pressure, enthalpy and entropy of liquid CO2 showed good agreement with the basic values, which provides the application of the proposed method in the field of pure liquid CO2, limited by the temperature range from 220 K to 300 K. The simplicity of the equation of state and the small number of empirical coefficients allows to use this method to solve practical problems of computational gas dynamics without spending a lot of time on calculations.
The spatial problem of the elasticity theory is studied for a layer with two infinite circular solid cylindrical inclusions that are parallel to each other and to the layer boundaries. The physical characteristics of the layer and the inclusions are different from each other and they are homogeneous, isotropic materials. The spatial function of stresses is given at the upper boundary, and the function of displacements is given at the lower layer boundary. Circular cylindrical elastic inclusions are rigidly connected to the layer. It is necessary to determine the stress-strain state of the composite body. The problem solution is based on the generalized Fourier method, which uses special formulas for the transition between the basic solutions of the Lamé equation in different coordinate systems. Thus, the layer is considered in the Cartesian coordinate system, the inclusions – in the local cylindrical ones. Satisfying the boundary and conjugation conditions, systems of infinite integro-algebraic equations were obtained, which were subsequently reduced to linear algebraic ones. The resulting infinite system is solved by the reduction method. After deter-mining the unknowns, it is possible to find the stress values at any point of the elastic composite body. In numerical studies, a comparative analysis of the stress state in the layer and on the surfaces of inclusions at different distances between them is carried out. The analysis showed that when the inclusions approach each other, the stress state in the layer practically does not change. However, its significant change is observed in the bodies of inclusions, so with dense reinforcement ((R1 + R2) / L > 0.5), it is necessary to take into account the distances be-tween the reinforcing fibers. At stress values from 0 to 1 and the order of the system of equations m=10, the accuracy of meeting the boundary conditions was 10-4. With an increase in the system order, the accuracy of meeting the boundary conditions will increase. The given analytical-numerical solution can be used for high-precision determination of the stress-strain state of the given type of problems, and also as a reference for problems based on numerical methods.
The ongoing events of the Russian invasion of Ukraine seriously impacted on the environment in all areas: ground, air, water, flora and fauna. First of all, this war has created a massive increase in air pollution. The Russian attack has caused many fires at oil depots, industrial complexes, equipment and ammunition stockpiles, the forests, residential areas, etc. In addition to this, many bridges, hydraulic and other structures destroyed that seriously affected water bodies such as rivers and lakes which were seriously polluted. These events were studied by using publicly available remote sensing data, as well as from the media. Much attention is paid to the data provided by NOAA-2, Suomi NPP, Aqua and Terra satellites. In addition, the research used data from Sentinel and Landsat satellites, which are making it better to visualizate the consequences of the Russian military invasion.
The microstructure evolution of the 30MnB5 steel, tempered at the different temperatures, the micromechanical properties and wear resistance was studied. The correlation between results of sclerometry and wear resistance of steel was found. Minimal work of plastic deformation (29.42·10-8 J) accompanies the maximal wear resistance of steel. This makes it possible to use sclerometry as an express method for testing steel for wear resistance after various types of heat treatment. The abrasive wear resistance of 30MnB5 steel depends on its hardness which provides resistance of material to micro-cutting by abrasive grain. Maximal wear resistance of steel is observed after quenching and tempering at 200°C, when its hardness is 54 and 49 HRC. The abrasive wear of quenched and tempered at 200°C steel 30MnB5 is the result of micro-cutting and micro-ploughing. The plastic deformation, displacement of material along the grooves, pit holes and chipping of the brittle components are observed on the friction surface of steel after tempering at 400°C and 600°C. Surface damage at the friction tests with an unfixed abrasive is less than with a fixed abrasive.
Statistical data show that over 90% hip implants have the acetabular cup made of ultra-high molecular weight polyethylene (UHMWPE), while the femoral head is made of stainless steel, CoCrMo alloy, titanium and ceramics. The values of Young’s modulus for stainless steel, CoCrMo alloy and titanium differ from that for UHMWPE by 100–200 times, while Young’s modulus of ceramics differs from the Young’s modulus value of UHMWPE by up to 400 times. Young’s modulus of UHMWPE can also differ by up to 3 times, which considerably affects contact parameters. Therefore, the problem of assessing the impact of the elastic characteristics of UHMVE on the contact pressure in the prostheses of the hip joint is relevant. A new calculation method is used to determine the effect of Young’s modulus and Poisson’s ratio (UHMWPE) on maximum contact pressures in a hip implant. This study undertakes an analysis of the relationship between elastic properties of UHMWPE and contact pressures, considering a Grade2 TDN (thermo-diffusion nitrided titanium) femoral head diameter and radial clearance. Quantitative and qualitative relationships are established between contact pressures and Young’s modulus and Poisson’s ratio for the UHMWPE acetabular cup. The proposed calculation method can be used at the stage of hip implant selection to estimate contact pressures depending on the implant load (patient’s weight and muscular force) and geometry (femoral head diameter and radial clearance in the implant). Contact pressures also have a significant impact on the wear rate of an UHMWPE acetabular cup, as well as on hip implant service life.
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.
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1,434 members
Alexander M. Puziy
  • Department of Chemistry and Chemical Technology
Nikolaj Glazunov
  • Faculty of Electronics
Vladimir Ulansky
  • Department of Electronics Robotics Monitoring and IoT Technologies
Влерий Конин
  • Институт аэронавигации
Sergey Ignatovich
  • Aircraft Structure Department
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Address
Kosmonavta Komarova 1, 03058, Kyiv, Kyiv, Ukraine
Head of institution
Volodymyr Isaienko
Website
https://nau.edu.ua/