KPI Science News

ADAPTATIONS OF RESULTS OF EXPERIMENTAL QUALIFICATION OF PASSIVE SAFETY SYSTEMS OF NUCLEAR POWER PLANTS

Vadym Kondratiuk — Fri, 27 Oct 2023 00:00:00 +0300

Problems. An urgent issue of ensuring the safety of nuclear power plants is the adaptation of the results of experimental qualification of the fittings of passive safety systems in a single-phase environment to emergency conditions of two-phase flows. For most of the equipment of systems important for the safety of nuclear power plants, there is no principled possibility of qualification through direct tests in emergency conditions. The experience of operating nuclear power plants, as well as the results of simulations after design accidents, determined the possible inconsistency of the operating conditions of the fittings in emergency situations and in the modes of operational tests with a single-phase steam-gas environment.Thus, it is necessary to adapt the results of the experimental qualification of the fittings of the emergency steam and gas removal systems in a single-phase environment to the emergency conditions of two-phase flows. The aim of the study. The purpose of this article is sufficient justification of the adaptation of test results on a single-phase environment to the conditions of emergency processes with a two-phase environment. Methodology of implementation. To achieve the goals of the study, deterministic modeling of the conditions and criteria of operation/testing of valves of emergency steam and gas removal systems was used. Research results. T An analysis of the validity of the results of the experimental qualification was performed for the dynamic pressure pressure on the closing device in the test mode (single-phase flow mode) and the dynamic pressure pressure on the closing device in the emergency mode (two-phase flow mode). The adaptation of the results of the experimental qualification for closing the valves of the emergency steam and gas removal systems in a single-phase environment to the emergency conditions of two-phase flows was carried out under the conditions of subsonic and supersonic flow regimes. Conclusions. The conditions for adapting the results of the experimental qualification for closing the valves of the emergency vapor gas removal systems to the emergency conditions of subsonic and transonic flows of two-phase flow in the flow part of the valves have been determined. The dynamic pressure on the closing device of the valve in single-phase flows of operational tests and the dynamic pressure in two-phase flows of emergency modes are considered qualification criteria.

DESIGNS OF HEAT EXCHANGER DEVICES ON TWO-PHASE HEAT TRANSFER ELEMENTS FOR AIR HEAT DISPOSAL IN VENTILATION SYSTEMS: OVERVIEW

Yevhenii Alekseik, Olha Alekseik — Fri, 27 Oct 2023 00:00:00 +0300

Background. Heat exchangers-utilizers for recovery of ventilation air heat are widely used for increasing of buildings energy efficiency. Two-phase elements, such as: thermosyphons, heat pipes and pulsating heat pipes are applied to these heat exchangers for increasing of efficiency of heat transfer between hot and cold air. But such heat exchangers should have high temperature efficiency, enthalpy efficiency and energy efficiency at low aerodynamic drag. Moreover, working conditions of ventilation systems, such as: relatively low working temperatures and low temperature difference between hot and cold air, make it difficult to choose heat carriers for two-phase elements. Thus, it is necessary to solve a number of complex problems for designing of effective heat exchangers-utilizers based on two-phase elements.

Objective. To find out unresolved and understudied issues of designing of heat exchangers-utilizers based on two-phase elements for ventilation systems.

Methods. Analysis of described in literature designs, their characteristics and results of investigations.

Results. General features of two-phase elements based heat exchangers-utilizers designs and a number of issues which need further investigation were detected as a result of literature sources analysis.

Conclusions. Heat exchangers based on two-phase heat transfer elements have wide perspective of applying and provide full heat efficiency up to 85%. But there is a number of unsolved issues connected with: optimization of two-phase elements and heat exchangers design, ribbing optimization, investigation of heat transfer intensity and heat transfer coefficients, investigation of aerodynamic drag, condensate rejecting.

SENSORS BASED ON NANOCELLULOSE FOR BIODEGRADABLE, FLEXIBLE, DISPOSABLE AND WEARABLE ELECTRONICS

Arsenii Naidonov, Viktoriia Koval — Fri, 27 Oct 2023 00:00:00 +0300

Problems. Rapid technical progress has led to a reduction in the useful life of consumer electronics. The introduction of green, flexible, biodegradable electronic devices will prevent an environmental catastrophe. Recently, the use of organic materials instead of inorganic analogues has become increasingly popular, which makes it possible to move from rigid solid-state sensors for multiple use that require disposal to flexible, disposable sensors that are suitable for human wear on the body or clothing and for spontaneous decomposition in nature after using. One of such promising organic materials is nanocellulose.

The aim of the study. Studying the possibility of nanocellulose application for the manufacture of flexible, wearable, disposable sensors of various types of physical and chemical quantities.

Methodology of implementation. In the article the analysis, classification and comparision of various technologies and features of synthesis, as well as the main characteristics of flexible sensors made on the basis of nanocellulose were fulfilled. Also the main parameters of flexible sensors based on nanocellulose were being compared with corresponding analogs of sensors based on artificial polymers.

Research results. The paper established the physical and technological features of using nanocellulose for the manufacture of sensors of various types of physical and chemical quantities in order to improve their performance. It has been established that nanocellulose can be used both as a substrate and as a sensitive element of a sensor. It has also been shown that nanocellulose is suitable for use in sensors based on both electrical physical phenomena and optical effects.

Conclusions. Nanocellulose is a promising biodegradable material on the basis of which flexible, disposable, wearable sensors can be created. The manufacturing technology of such sensors should contain only low-temperature and dry processing processes. For effective use in certain types of sensors, it is advisable to manufacture nanocellulose with a modified surface or in the form of composites with other nanomaterials. Based on the obtained results, it is possible to improve existing and develop new methods of creating flexible wearable disposable sensors that do not require disposal.

THERMOMETRIC MODEL OF DIODE TEMPERATURE SENSOR

Petro Yaganov, Leonid Pavlov — Fri, 27 Oct 2023 00:00:00 +0300

Background. Microelectronic technologies make it possible to create structures with high sensitivity to external influences. In semiconductor microelectronics, these are structures of the type of potential barrier at the p – n Junction. Silicon diode sensors have high temperature sensitivity in a wide temperature range. Both physical and formal mathematical models of the thermometric characteristic of the diode sensor have been developed. The temperature measurement error of some of these methods was not acceptable for the control of many processes. It is relevant to conduct studies of the temperature properties of the p – n Junction in a non-equilibrium state to formalize the new thermometric characteristic of the diode sensor. Objective. The purpose of the work is a model of thermometric characteristics of silicon diode sensors based on the results of measurements of volt-ampere characteristics in the temperature range. Methods. Analysis of methods of calibration of thermometric characteristic of diode sensors by volt-ampere characteristics was carried out, factors affecting temperature measurement accuracy were revealed, regression analysis method for formation of polynomial model of thermometric characteristic was substantiated. Results. As a result of studies of the volt-ampere characteristics of silicon diodes in the temperature range (248... 393) K, it was found that the error in measuring temperature by diode sensors is associated with the dependence of the non-ideality factor of the p – n Junction on temperature. The accuracy of the thermometric characteristic is estimated, where this functional dependence is represented as an approximation polynomial. Conclusions. An alternative model of thermometric characterization of diode temperature sensors by the second degree regression equation is presented. The arguments of the function are the current and voltage of the diode in the direct displacement mode. Current stability in the p – n Junction circuit is not assumed. The temperature determination accuracy in the temperature range (248... 393) K is within ± (0.2... 0,256) K

SIMULATION OF DIFFUSION-DRIFF PROCESSES IN THE ELECTRON-HOLE PLASMA OF THE P-I-N-DIODES ACTIVE REGION UNDER THE CONDITIONS OF A MW PENETRATING IN THE PLASMA BY THE PERTURBATION THEORY METHODS

Igor Moroz, Andriy Bomba — Fri, 27 Oct 2023 00:00:00 +0300

Background. The problem of developing tools for mathematical modeling of the state of electron-hole plasma in the p-i-n structures active region under the influence of an additional factor - a powerful microwave electromagnetic field is considered. The task is important for specialists in the field of microwave electronics, since p-i-n structures are used, in particular, for switching powerful electromagnetic fields and as protective devices for the input paths of radio engineering systems.

Objective. It consists in developing a methodology for modeling the electron-hole plasma concentration distribution in the p-i-n- diodes active region taking into account the effect on the dynamics of charge carriers of microwave radiation penetrating into the active region and developing asymptotic methods for solving the corresponding singularly perturbed nonlinear problems.

Methods. Achieving the goal is ensured by the use of boundary layer method, complex amplitudes method and classical analytic-numerical methods for solving boundary value problems for systems of ordinary differential equations.

Results. A generalized mathematical model of the electron-hole plasma stationary state in the p-i-n diodes active region in the hydrodynamic approximation, which takes into account the effect of microwave radiation on processes in the plasma, is proposed. The model basis is a nonlinear singularly perturbed boundary value problem for the system of electron-hole currents continuity equations and the Poisson. The model boundary value problem is reduced to a recurrent sequence of linear boundary value problems. Solutions of the stated problem are found in the form of asymptotic series containing stationary and non-stationary components. A feature of the proposed mathematical model is that it reflects the effect of detecting an electromagnetic microwave TE-like wave on the charge carrier concentration distribution inhomogeneity in the p-i-n-diode active region.

Conclusions. The methodology for modeling the electron-hole plasma stationary state in the p-i-n-diodes active region taking into account the effect on the charge carriers dynamics of microwave radiation penetrating into the active region has been developed.

SOFTWARE METHODS ANALYSIS OF OPTIMIZING THE LOCAL STATE OF DATA WEB APPLICATIONS MANAGEMENT

Lyubov Оleshchenko, Pavlo Burchak — Fri, 27 Oct 2023 00:00:00 +0300

Background. The use of various libraries often leads to a decrease in the speed of the web application and the complexity of the execution of the program code. The object of this study is the process of storing and managing the data of the client part of the web application, the subject of the research is the software methods of managing the local state of the data of the web application.

Objective. The goal of the article is the reduction in the data processing time of web applications relative to existing software methods.

Methods. The main idea of the proposed method is to use an atomic approach to the state of the web application data. Having an arbitrary entity, in the general state of the web application, a state fragment is created that is responsible only for this entity. Such a fragment is independent of other state fragments and can only work with the encapsulated entity. Using encapsulation, the configuration of an entity is passed to the React Context API as an object containing data and functions that modify it.

Results. The developed framework method was compared with popular state management libraries Redux, MobXState-Tree and Recoil. Comparing each of the test scenarios in a percentage ratio, an average decrease in program execution time by 17% was obtained.

Conclusions. The Redux, MobXState-Tree, and Recoil libraries were selected for the research of existing software methods. The analysis of methods was performed using the SonarQube utility. To evaluate the results of the software methods, the Google Chrome browser utility DevTools was used. The proposed optimized software method allows to reduce the data processing time and optimize the state management of web applications.

Keywords: web application, optimization, local state of data, Redux, MobXState-Tree, Recoil.

APPLICATION OF MODELS OF THE STRUCTURE OF SEPARATION SURFACES IN STEELS WHEN OBTAINING PRODUCTS WITH A GIVEN LIFE CYCLE

Mykola Kuzin, Viacheslav Kopylov, Oleg Kuzin — Fri, 27 Oct 2023 00:00:00 +0300

Background. The development of digital mechanical engineering requires the development and use of interdisciplinary concepts and models of the behavior of heterogeneous polycrystalline materials under the influence of technological and operational loads. In this regard, the development and use of approaches to modeling and analysis of the mechanical behavior of the boundary zones of separation of products, taking into account their energy, becomes important. The development of such approaches makes it possible to solve an actual scientific and technical problem – optimization of the modes of technological processing of products with a given life cycle. Objective. The use of system models of the structure of steels for the development of computational schemes and methods of managing the structural-energy state of the separation surfaces of structural components when obtaining products with increased reliability parameters, taking into account the conditions of their operation. Methods. The analysis of the structure was carried out using the concept of invariant modeling, the results of metallographic and factographic studies, electron microscopy. The assessment of the structural and energetic state of grain separation surfaces after ionplasma etching of the samples was carried out, wear and impact bending tests were carried out, and system computer simulation of the properties of polycrystalline systems was carried out using the FEniCS open finite element analysis package in Python. Results. When applying the energy description of continuous non-local environments, it was established that depending on the angles between the boundaries at the joints of the grains, the structural and energetic state of this region and its ability to form microdefects change. At angles between 140‒180°, zones are formed with a high capacity for the formation of intergranular damage and destruction under load. It is shown that the intensity of wear and intergranular fracture upon impact increases depending on the number of triple joints, in which the boundaries differ significantly in terms of energy level. Steel 40X (5135 Steel) is more sensitive to the formation of triple junctions with a high energy gradient during heat treatment than steels containing nickel, molybdenum and silicon. Conclusions. On the basis of hierarchical modeling of the structure of polycrystals, new approaches are proposed and an algorithm is created to determine the relationships between the structure of the separation surfaces of steels and their operational reliability. Diffuse damage is formed on the separation surfaces between the triple junctions of grains with a high energy gradient. Reducing the share of triple joints, which differ significantly in terms of energy when designing the technological regimes of the quenching and tempering processes, made it possible to increase the wear resistance of improved steels by 48‒53 %.

SOCCER SEASON SIMULATION WITH FIXED MATCHES

Oleg Chertov, Ivan Zhuk — Fri, 27 Oct 2023 00:00:00 +0300

Background. Football is a huge industry comparable to traditional economic sectors. In numerical terms, it is tens of billions of dollars. But one of the most important problems that this industry faces is match fixing (matches with a fixed result).

The most effective way to prevent this threat is a multilateral approach combined with measures aimed at expanding the potential of law enforcement agencies and sports organizations. One of the components of this approach is the use of mathematical methods for identifying suspicious match-fixing results.

Objective. The purpose of the paper is to develop an algorithm for modelling fixed matches related to earnings on bets, which is used to form matches which results are different from the expected ones and can be considered as anomalous.

Methods. Calculation of probabilities of scoring goals by teams during the game based on real data of the season; development of a simulation model of a football season without fixed matches and its analysis by means of statistical modelling; development of an algorithm for modelling fixed matches related to earnings on bets and its analysis.

Results. A simulation model of a football season has been developed, which allows, using probability distributions of the number of goals scored by teams during home or away games obtained on real data, simulating the results of matches, taking into account the strength of the teams and the game type, as well as to simulate the situations of a “fixed” match, replacing the current results. In terms of the overall distributions of match result types and goal differences of all matches, the simulated season is similar to the real season. According to the Kolmogorov-Smirnov test, the difference between the given distributions at the significance level of 0.001 is statistically insignificant.

Conclusions. The developed simulation model of a football season can be used to study the effectiveness of methods for detecting fixed matches and their comparative analysis.

Technology of Repairing the Active Main Pipeline Using Braze-Welded Couplings

Grigoriy Tymchik, Aleksandr Podolian , Kateryna Serhiienko — Fri, 27 Oct 2023 00:00:00 +0300

Background. During operation, the main pipeline needs to be repaired. During periodic diagnostics of the pipeline state defects are detected, some of which are unacceptable. The classic repairing method, that involves the shutdown of the pipeline with subsequent replacement of its defective spots, requires significant financial costs and is associated with a forced pipeline outage and environmental violation.

Objective. The purpose of this article is to improve the technology of reinforcing sections of main high-pressure pipeline with welded couplings, which are filled with molten metal by allowing obtaining high efficiency of pipe strengthening of medium and small diameters.

Methods. Strength improvement of the active pipeline spots is realized by installing brazed-welded couplings on an active main pipeline. Strengthening the pipeline with the coupling consists in the redistribution of the load part from the pipe to the wall of the coupling, which leads to a decrease of the stress level in the pipe wall. The reinforcement efficiency of the pipeline could be evaluated by the degree of reduction of circumferential stresses in the fixed pipe wall.

Results. The article suggests a technique for strength improvement of pipeline spots using couplings filled with a molten metal that has a high elasticity modulus. The operations of formation of under-coupling layer with the parameters that provide achievement of the maximum value of the stresses reduction degree in the reinforced pipe are proposed, while ensuring an even load distribution between the wall of the pipeline spot being repaired and the coupling shell. An improved technology for fixing defective spots of the active pipeline has been proposed, designs for front seals have been proposed that facilitate the formation of under-coupling layer with optimal parameters. The proposed technique makes it possible to increase the efficiency of the pipe strengthening of small and medium diameters.

Conclusions. The article proposes an improved technology of the defective spots reinforcing of the active main pipeline using braze-welded coupling. The focus is on the design of mechanical seals that ensure the tightness of the under-coupling space during the formation of the coupling layer.

Further research would be performed in the direction of developing a mathematical model of the pipeline reinforced with braze-welded coupling, taking into account temperature changes during heating and cooling of the coupling structures during the formation of the under-coupling layer. Some research will be also performed to improve the coupling structures and methods of quality control of their mounting on the pipe.

Automated design of zoom riflescope with extended parameters

Вячеслав Сокуренко, Олег Сокуренко — Fri, 27 Oct 2023 00:00:00 +0300

Background. Designing an arbitrary afocal zoom optical system is a complex and multidimensional problem. It cannot be solved analytically and requires the essential experience and efforts of the designer. Objective. The purpose of the paper is to present and verify by simulation the method and means to perform an automated design of complex multi-lens afocal zoom optical systems having variable parameters and characteristics. Methods. Using the developed specialized software with implemented modification of the adaptive Cauchy differential evolution algorithm for the parametric synthesis of multi-component optical systems of zoom riflescopes with extended functional parameters. Results. The developed optical system of the riflescope provides the 5× magnification ratio and the angular field of view in the object space from 3.26° to 0.83°. It has a reticle located in the first focal plane, the entrance pupil diameter of 60 mm, the eye relief within the range of 106...111 mm, and the maximum system length of 390 mm. The riflescope contains 13 lenses in 10 components. The performed simulations showed that the time interval required for the direct automated design of the riflescope’s optical system is about 30–40 hours for the total number of unknown parameters (variables) equal to 91. The root-mean-square values of the angular aberrations of axial beams in all (five) configurations of the synthesized zoom system do not exceed 1.25 arc minute in the whole spectral range. The algorithm helps to determine the prescription data of optical systems, considering the technical requirements and restrictions specified by the designer. Conclusions. Computer simulations of the development of the zoom riflescope with the magnification of 5-25×, the entrance pupil diameter of 60 mm, and the reticle located in the first focal plane have confirmed the effectiveness of the proposed algorithm to design automatically complex multi-lens optical systems with variable parameters. The obtained results proved the high image quality of the generated 13-lens riflescope with the long eye relief. The implemented modification of the adaptive Cauchy differential evolution method can be considered a powerful tool that helps to automate the parametric synthesis of multicomponent optical systems of zoom riflescopes, taking into account the requirements set by the designer. Future research should test the feasibility of the automated design of other riflescopes containing more lenses and providing extreme performances.

CORROSION RESISTANCE OF GALVANIC NICKEL DEPOSITS AND ELECTROCHEMICAL ACTIVITY OF THEIR CORROSION PRODUCTS

Fri, 27 Oct 2023 00:00:00 +0300

Background. Bright galvanic nickel coatings, with high sulphur content, are less corrosion resistant than matte. Bright nickel coatings are particularly susceptible to corrosion damage in conditions that simulate tropical humid climates and are characterized by the presence of acetic acid vapours.

Objective. The purpose of the paper is to investigate: corrosion resistance of galvanic nickel deposits in concentrated acetic acid and its vapours, electrochemical activity of sulphide-containing corrosion products of bright nickel coatings.

Methods. Potentiodynamic and cyclic volt-amperometry have been used to study the electrochemical activity of galvanic nickel deposits and their corrosion products. The corrosion rate of galvanic nickel deposits has been determined by gravimetric method. Investigation of surface morphology and composition of galvanic deposits were performed using scanning electron microscopy and X-ray fluorescence analysis.

Results.The increased electrochemical activity of sulphide corrosion products of bright nickel coatings is evidenced by an order of magnitude higher cathodic current densities of CVA curves obtained in acetate buffer solutions, in comparison with bright and matte nickel galvanic deposits. It has been shown that at the deposition of sulphide corrosion products of bright nickel coatings on matte nickel foil the corrosion rate of last one increase at the exposition in concentrated acetic acid and its vapours.

Conclusions. Significant intensifying effect of sulphur on the corrosion of galvanic nickel deposits in concentrated acetic acid and its vapours has been established. In particular, this can be explained by the decomposition of nickel sulphide (which incorporates in the coating) in acetic acid. Sulphur in the oxidation state (-2) interacts with passive oxide coatings to form an adsorbed monolayer, which leads to the transition of nickel to the active state. Further research will focus on a deeper study of the electrochemical properties of corrosion products of bright nickel coatings.