Cтатті КПМ ДІІТ

Permanent URI for this collection

http://crust.ust.edu.ua/handle/123456789/692

ENG: Articles

Browse

Now showing 1 - 20 of 92

Abnormal Effect of Changing the Wetting Angle in Non-Equilibrium Melt–Solid Metal Systems
(G. V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine, Kyiv, 2024) Shtapenko, Eduard Ph.; Syrovatko, Yuliya V.
ENG: The paper deals with the temperature dependence of the contact angle of wetting of a steel substrate with a liquid tin. The experiment shows that the wetting angle is decreased as the temperature rose, and the wettability of this system is improved. However, with the further increase in temperature, the contact angle is increased again that is an abnormal phenomenon. To explain this phenomenon and the process of contact-angle formation in general, we propose the quantum mechanical model based on the Wentzel-Kramers-Brillouin (WKB) conception. In this case, interaction of the melt ions with the substrate atoms is considered indirectly through the formation of a potential barrier with the linear dimensions determined by both the ratio of masses of the atoms of interacting metals and the temperature. From the WKB standpoint, at low temperatures, when the kinetic energy of a generalized particle with the reduced mass is less than the potential barrier, the wave function decays rapidly and, accordingly, the contact angle does not actually change. Quantitative and qualitative changes appear, when the kinetic energy of particles with the reduced mass exceeds the positive barrier values because of increase in temperature. Following the WKB conception, passage or reflection of a particle with the reduced mass over the barrier is determined by the integer or half-integer ratio of the de Broglie wavelength and linear dimensions of the potential barrier. Therefore, qualitative changes in the system, i.e., the wetting threshold and abnormal increase in the contact angle, are described by the processes associated with passage or reflection of a particle with the reduced mass over the barrier. Experimental and theoretical curves of dependences of both the contact angle and the work of adhesion versus temperature show similar dynamics.
About Optimizing of Investments Volume to Improve the Basic Indicators of the Enterprise Effectiveness
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2015) Gasanov, Zakariia M.
EN: Purpose. Profit and profitability of any, including transport enterprises are the main economic indicators of the enterprise effectiveness. These indicators reflect the results and successful performance of the enterprise. On the other hand the enterprise effectiveness in the long term, assurance of rapid development and competitiveness is largely determined by the level of investment activity and the range of investment activity. The purpose of this study is the feasibility of the method to determine optimal investments volume for improving these or others (selectable by the management) principal economic indicators of the enterprise effectiveness. Methodology. The basis of the proposed methodology for determining the optimal investments volume is the theory of optimal control, in particular, the procedure of dynamic programming since a managed development process of the enterprise is a multiple stage. This procedure, using a phased plan, allows not only simplifying the solution of optimization problems, but also solving those, which are impossible to apply the methods of mathematical analysis. Findings. The expediency of performing the calculations to determine the optimal investments volume to ensure high rates of enterprise development was proved, it is a key to the effectiveness of the enterprise in the long term and it improves its competitiveness. Originality. It is shown that using methods of the optimum control theory one can calculate the minimum volume of capital investments for the improvement of economic indicators, which determine the enterprise effectiveness. The proposed method of calculation does not depend on the specific content of economic indicators. The effectiveness of this calculation method is demonstrated on a model example. Practical value. The proposed method of calculating the minimum volume of capital investments to improve the economic effectiveness of enterprises is quite simple, but at the same time enables, on the one hand, to determine priority directions of investment activity of the enterprise. On the other hand it improves the manageability and transparency of business enterprises, increases the head's confidence in the correctness of decisions.
Approximation of Periodic Functions of Many Variables by Functions of a Smaller Number of Variables in Orlicz Metric Spaces
(Springer, 2019) Babich, Yurii P.; Mikhailova, Tetiana F.
EN: For periodic functions of many variables, we propose a method for their approximation in the Orlicz spaces Lφ (T^m). According to this method, the functions are approximated by the sums of functions of smaller number of variables each of which is piecewise-constant in one variable for fixed values of the other variables. A Jackson-type inequality is analyzed for these approximations in terms of the mixed module of continuity.
Concave Shells of Continuity Modules
(Springer, 2019) Pichugov, Sergey A.
EN: We prove the inequality ω¯(t)≤infs>0(ω(s2)+ω(s)st), where ω(t) is a function of the modulus-of-continuity type and ω¯(t) is its smallest concave majorant. The consequences obtained for Jackson’s inequalities in C2πare presented.
Determination of Entropy and Debye Temperature of the Phases of Al-Cu-Co and Al-Ni-Co Decagonal Quasicrystals at the Normal and High Temperatures
(OICC Press, Oxford, UK; Islamic Azad University, Tehran, Iran, 2025) Syrovatko, Yuliya V.; Shtapenko, Eduard Ph.; Syrovatko, Volodymyr
ENG: This paper deals with determination of the entropy of quasicrystalline phases of Al-Cu-Co and Al-Ni-Co alloys by the information-and-statistical method at the temperature of 300 К. Scanned digital images of quasicrystals were processed with the use of this method. Statistical data of the multicomponent structure were divided into separate components of the normal distribution of parameters corresponding to certain phases. We calculated the Gaussian parameters on the basis that dependence of the logarithmic representation of the normal distribution function took the form of a quadratic function. It allowed us to find the mean-square deviation and to calculate the entropy of quasicrystalline phases at 300 К. The resulting values were further used to calculate the Debye temperature of the phases. Decagonal quasicrystals have anisotropic structure. It is assumed that anisotropy manifests itself in the difference of the dispersion laws in the xy plane and in the direction of the z axis, which is described by the model of anisotropic crystals. Using this model, we have found an expression describing the dependence of the entropy on the temperature and Debye temperature of the phases. From here, we calculated the Debye temperature of the phases. Next, using the Debye temperature values, we calculated the entropy of phases at higher temperatures. Therefore, with the use of the presented calculation methods, it is possible to determine the Debye temperature and the entropy of quasicrystalline phases that was done in our study for Al–Cu–Co and Al–Ni–Co quasicrystals.
Development of Method of Multifactor Classification of Transport and Logistic Processes
(НВП ПП «Технологічний центр», Харків, 2018) Bosov, Arkadiy A.; Khalipova, Nataliia V.; Progonyuk, I.; Kuzmenko, V.; Duhanets, V.; Shevchenko, I.
UK: Запропоновано метод для класифікації процесів і об’єктів в транспортно-логістичних системах. Шляхом багатофакторного аналізу і використання системного методу аналізу ієрархій формується комплексний аналітичний показник. На основі логістичного аналізу здійснюється класифікація за ступенем впливу чинників. Проведено класифікацію країн-партнерів України у зовнішній торгівлі на основі аналізу товарообігу окремих груп вантажів за конкретними напрямами.
Formation of Contact Interaction Zones during Infiltration of Composite Materials Depending on Binder Composition
(Chuiko Institute of Surface Chemistry of NAS of Ukraine, Kyiv, 2025) Shtapenko, Eduard Ph.; Syrovatko, Yuliya V.; Levkovich, O. O.
ENG: In the production of macro-heterogeneous composite materials with a metal matrix by the oven infiltration method, it is necessary to control the contact interaction processes occurring at the filler and binder interfaces. The width of the resulting contact interaction zones at the interfaces is an indicator of intensity of these processes. The intensity of contact interaction processes depends on many factors, including the binder alloy composition. The paper examines the effect of binder alloying components on the change in the surface tension of the binder alloy, and, so on the intensity of contact interaction processes occurring at the interfaces during infiltration of composite materials. Calculations of changes in the surface tension of iron-based binder upon alloying with C, P, B and Mo are presented using the formalism of the electrochemical interaction of regular solutions. The iron melt was considered as a solvent, while C, B, P and Mo were considered as dissolved components. It was taken into account that formation of an interface resulted in the appearance of unbalanced charges and energetic influence on the ions distributed in the melt. Adsorption of dissolved components on the filler surface decreased the surface tension of the binder. When estimating the thickness of the layer of excess ion concentration at the surface, we assumed that the binder surface tension depended on the number of adsorbed ions. Our calculations were expressed in accordance with the concept of mole equivalent. It is found that alloying of the Fe–C–B–P binder with Mo causes a decrease in the difference between the surface tension values of the alloyed binder and pure iron melt by 28.5 %, and, accordingly, 22.6 % reduction of thickness of the layer of excess ion concentration. The results obtained were compared with the results of experimental works with regard to composite materials with W–C fillers and iron binders alloyed with C, B, P, and Mo. It is determined that when the Fe–C–B–P binder is alloyed with Mo the width of contact interaction zones in the composite materials decreases by 15–20 %. Therefore, the results of calculations using the proposed method for changing the thickness of the layer of excess ions at the interfaces when alloying the binder correlate with the experimental data for changes in the width of contact interaction zones of composite materials.
Formation of Separate Optimization Models for the Analysis of Transportation-Logistics Systems
(НВП ПП «Технологічний центр», Харків, 2017) Bosov, Arkadiy A.; Khalipova, Nataliia V.
EN: We proposed an algorithm and a procedure of a multi-criterion analysis of the objects of transportation-logistics systems using the vector optimization of functionals, which provide a more complete representation of the properties of objects and processes. The algorithm is based on a statistical analysis of empirical data, analysis of the influential factors and qualitative characteristics of the processes, which makes it possible to more reasonably define the form of a quality function and to form criteria. The essence of the proposed procedure of a multi-criterion analysis is the vector optimization of functionals whose equations are introduced with the characteristics of rate of change in the examined processes. In contrast to the existing procedures that characterize a state of the system and separate elements, the given technique allows us to more fully and objectively estimate dynamic properties of the transportation and logistics processes. Using the movement of cargo flows through the customs warehouse as an example, we have shown the statement of separate mathematical models for simultaneous and independent optimization of several parameters and functionals and the formation of a complete set of effective plans for subsequent analysis by a decision-maker.
Marchaud’s Inequality for Multiple Modules of Continuity in Metric Spaces
(Springer Link, 2020) Pichugov, Sergey A.
ENG: For periodic functions of one variable in the metric spaces LΨ [0, 2π], we establish an analog of Marchaud’s inequality for multiple modules of continuity.
Modeling the Optimization Process of Investments in Development of the Enterprise Taking Into Account Random Costs
(Дніпровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпро, 2019) Gasanov, Z. M.
EN: Purpose. The study aims at substantiating the method to determine the optimal volume of investments for improving basic economic indicators of the enterprise’s performance selected by the company management at random costs at each stage of its development. Methodology. The proposed methodology for determining the optimal investment volume is based on simulation modeling methods and optimal control theory, in particular, the dynamic programming procedure, since the controlled process of the enterprise`s development is a multi-step one. Using step-by-step planning with generation of costs for transitions and statistical processing of results, a solution to optimization problem was obtained, to which the methods of mathematical analysis cannot be applied. Findings. An algorithm has been developed for calculating the minimal volume of capital investments for improving selected economic indicators and constructing the optimal trajectory for the enterprise`s development from the initial economic state to the final desired state. This takes into account unforeseen intermediate costs in the process of enterprise development. Originality. It is shown that using the methods of the theory of optimal control and simulation modeling, it is possible to calculate the minimal amount of capital investments to improve the selected economic indicators that determine the efficiency of the enterprise performance, taking into account the random costs of intermediate transitions by the development stages. Such calculation does not depend on the specific content of economic indicators. Practical value. The proposed methodology for calculating the minimal volume of capital investments is quite simple, but at the same time it allows, on the one hand, determining the priority areas of the enterprise’s investment activities. On the other hand, it increases the manageability and transparency of the enterprise’s economic activity, and increases the manager’s confidence in the correctness of the decisions made.
On Regularity of Weak Solutions to One Class of Initial-Boundary Value Problem with Pseudo-Differential Operators
(Дніпропетровський національний університет ім. Олеся Гончара, 2017) Kogut, Peter I.; Maksimenkova, Julia A.
EN: We discuss the solvability and some extra regularity properties for the weak solutions to one class of the initial-boundary value problem arising in the study of the dynamic of an arterial system.
The Problem of Minimax Estimation of Functionals for Non-Stationary Diffusion Processes
(Український державний університет науки і технологій, м. Дніпро, 2021) Mykhailova, Tetiana F.; Maksymenkova, Yuliia A.
ENG: Purpose. To model the technological process of analysis of energy sources that use random nterference, it is necessary to apply special methods from the theory of minimax estimation and optimal control. The article proposes a method for solving the problem of minimax estimation of functionalities for the systems with distributed parameters with incomplete data for the process of neutron diffusion in a nuclear reactor. Methodology. In practice, in the study of non-stationary controlled processes of functioning of different energy ources there are measurement errors. As a rule, the exact values of errors are unknown, and therefore the desired solution of the equations in partial derivatives describing these processes is determined ambiguously. Therefore, it is advisable to set the task of calculating such an optimal estimate, which would best approximate the unknown value, taking into account the known information about the measurement errors. The best estimate can be achieved by applying a minimax approach to estimating functionals from the solutions of the partial differential equations of parabolic type. Findings. For a mathematical model of the neutron diffusion process in a nuclear reactor, the proposed method allows solving the problem of minimax estimation of the functional determined during the solution of the system describing this process. Since in real conditions of reactor operation there are always random obstacles (both in the equation describing the process and the functionobserved), the method allows finding a minimax estimate of the functional. The problem is reduced to the problem of optimal control with a given quality functionality, which is successfully solved. Originality. Using the methods of minimax estimation and optimal control of systems with distributed parameters, the best a priori estimation of the quality functional of the minimax estimation problem for the mathematical model of neutron diffusion in a nuclear reactor is obtained. Practical value. The method of minimax estimation of functionalities for differential equations of parabolic type proposed in the article allows reducing the problem to the problem of optimal control of the systems with distributed parameters, which can be implemented in Maple package using known algorithms.
Quantum-Mechanical Methodology for Determining the Temperature Dependence of Contact Angle in Melt–Solid Metal Systems
(Oles Honchar Dnipro National University, Dnipro, 2024) Shtapenko, Eduard Ph.; Syrovatko, Yuliya V.; Voronkov, Eugene O. ; Mikhailova, Tetiana F.
ENG: Aim. In order to determine the composite materials’ manufacturing process parameters, it is necessary to evaluate the stability of their structural components and determine the contact angle of wetting of the filler with the molten binder at the infiltration temperature. The development of a theoretical method for determining the dependence of the contact angle of wetting on temperature in melt – solid metal systems makes it possible to reduce the volume of experimental studies. Methods. The paper presents a quantum mechanical methodology for calculating the binding energy of interacting substances, as well as an experimental study of the dependence of the contact angle on temperature for tin – steel systems. The methodology is based on the calculation of the binding energy between atoms of interacting substances using density functional theory. Results. The calculations show an anomalous behavior of contact angle values for the tin–steel system with increasing temperatures. It means that, when the temperature increases, the values of the contact angle initially become lower, and later, in the temperature range of 450-510 °C, an increase in the contact angle is observed. The obtained theoretical and experimental data correlate well with each other. Conclusions. The appearance of extreme regions in the experimental and theoretical temperature dependences is associated with the thermal expansion of interatomic distances in the crystal lattice. The obtained theoretical and experimental data correlate well with each other and base on the thermal expansion of interatomic distances in the crystal lattice.
Sharp Constant in Jackson’s Inequality with Modulus of Smoothness for Uniform Approximations of Periodic Functions
(Pleiades Publishing, 2012) Pichugov, Sergey A.
EN: Abstract—It is proved that, in the space C2π, for all k,n ∈ N, n > 1, the following inequalities hold: 1 − 1 2n k2 + 1 2 ≤ sup f∈C2π f=const en−1(f) ω2(f,π/(2nk)) ≤ k2 + 1 2 . where en−1(f) is the value of the best approximation of f by trigonometric polynomials and ω2(f,h) is the modulus of smoothness of f. A similar result is also obtained for approximation by continuous polygonal lines with equidistant nodes.
Sharp Estimates for the Best Approximations of Smooth Functions in C 2π in Terms of Linear Combinations of the Modules of Continuity of Their Derivatives
(Ukrainian Mathematical Journal, Kyiv, 2022) Babich, Yurii P.; Mykhailova, Tetiana F.
ENG: For the best approximations of en-1(ƒ) functions from C12π by trigonometric polynomials, Zhuk earlier proved the exact Jackson inequality en-1(ƒ),,π/4n*ɷ(ƒ',π/n). This paper proves the following version of Jackson's exact inequality: en-1(ƒ),,π/4n*﴾(1/2ɷ(ƒ',π/2n)+1/2ɷ(ƒ',π/n)﴿.
Автоматизація розрахунків вартості страхових послуг на основі математичних моделей коротко та довгострокового страхування життя
(Хмельницкий університет управління та права, 2014) Послайко, Надія Іванівна; Послайко, Надежда Ивановна; Poslaiko, Nadiia I.; Тичина, О. В.
UK: Розглянуті страхові послуги на основі математичних моделей коротко та довгострокового страхування життя
Аппроксимация анизотропных классов Липшица в метрических пространствах Lψ
(Одеський національний університет, Одеса, 2013) Агошкова, Татьяна Анатольевна; Пичугов, Сергей Алексеевич
RU: Для пространств, определенных функцией ψ-типа модуля непрерывности, доказаны в многомерном случае прямая и обратная теоремы типа Джексона и Бернштейна для усредненных приближений кусочно-постоянными функциями и получена конструктивная характеристика анизотропных классов Липшица при подходящем разбиении тора периода.
Аппроксимация периодических функций многих переменных функциями меньшего числа переменных в метрических пространствах Oрлича
(Інститут математики НАН України, Київ, 2018) Бабич, Юрий Панасович; Михайлова, Татьяна Фёдоровна
RU: Для периодических функций многих переменных предложен метод их приближений в пространствах Орлича Lφ (T^m ) суммой функций меньшего числа переменных, каждая из которых является кусочно-постоянной по одной переменной при фиксированных значениях остальных переменных. Исследуется неравенство типа Джексона для таких приближений в терминах смешанного модуля непрерывности.
Безразмерная тяговая характеристика тепловозов
(Днепропетровский национальный университет железнодорожного транспорта имени академика В. Лазаряна, Днепропетровск, 2006) Босов, Аркадий Аркадьевич; Таран, А. В.
RU: Построена безразмерная математическая модель тяговой характеристики тепловозов.
Векторная оптимизация по двум показателям
(Днепропетровский национальный университет железнодорожного транспорта имени академика В. Лазаряна, Днепропетровск, 2007) Босов, Аркадий Аркадьевич; Кодола, Г. Н.; Савченко, Л. Н.
RU: Используя аналитическое представление конуса Парето, предложен алгоритм решения задачи векторной оптимизации.

Browse

Browsing Cтатті КПМ ДІІТ by Title

Results Per Page

Sort Options