ko Win - Academia.edu (original) (raw)
Papers by ko Win
Nauka i Obrazovanie, Oct 3, 2016
Nauka i Obrazovanie, May 3, 2016
Инженерный журнал: наука и инновации, May 1, 2019
Приведены постановка задачи и результаты исследований динамических характеристик и устойчивости м... more Приведены постановка задачи и результаты исследований динамических характеристик и устойчивости малых колебаний твердого тела, имитирующего космический заправщик, топливный бак которого содержит криогенную жидкость. Отличительной особенностью криогенной жидкости являются низкая температура и различная плотность ее частиц, что значительно усложняет исследование гидродинамических задач. Криогенная жидкость моделировалась с помощью слоев несмешивающихся жидкостей. Получены уравнения плоского движения твердого тела с полостью, содержащей три несмешивающиеся несжимаемые идеальные жидкости. Исследованы области устойчивости движения твердого полуцилиндра с цилиндрической полостью, наполненной тремя несмешивающимися жидкостями. Приведены результаты экспериментального исследования колебаний полуцилиндра с двумя несмешивающимися жидкостями. Ключевые слова: несмешивающиеся несжимаемые идеальные жидкости, механическая система, область устойчивости, собственная частота колебаний, твердое тело Введение. Задача динамики твердых тел, которые имеют полости, наполненные жидкостью,-одна из классических задач механики [1, 2]. Развитие авиации и космонавтики в 1950-80-е гг. дало новый импульс исследованиям, посвященным динамики тел с полостями, частично заполненными жидкостью. Отметим здесь работы К.
Engineering Journal: Science and Innovation
In this paper, the equations of spherical motion of a solid body with a rotating inhomogeneous in... more In this paper, the equations of spherical motion of a solid body with a rotating inhomogeneous incompressible fluid that fills a completely ellipsoidal cavity are obtained and investigated. The stability of rotation of a solid with an inhomogeneous fluid having a linear density distribution is considered. Arbitrary fields of density and velocity of fluid particles are represented as a power series by spatial variables with coefficients that depend only on time. Sufficient conditions for the stability of the rotation of a solid body with a fluid around the vertical axis of dynamic symmetry are presented. The obtained equations of motion make it possible to study the stability of stationary motions of the system under consideration in order to assess the effect of fluid separation on the dynamics of the body. By analogy with the motion of a solid body, it is stated that the obtained conditions are also necessary and sufficient conditions for stationary rotations of an inhomogeneous fl...
Engineering Journal: Science and Innovation, 2021
The development of rocket and space technology in recent years has led to the widespread use of v... more The development of rocket and space technology in recent years has led to the widespread use of various cryogenic liquids. To increase the shelf life of cryo-products on board spacecraft or in tankers of future space filling stations, it is proposed to create a certain stock of cryo-product, which is simultaneously in a two-phase or three-phase state and forms layers of liquid. The paper considers the problem in a nonlinear formulation about the oscillations of the interface of a two-layer liquid in an arbitrary axisymmetric cavity of a solid body performing angular oscillations around a horizontal axis. For the considered class of cavities with an arbitrary bottom and a lid, the nonlinear problem is reduced to the sequential solution of linear boundary value problems. Nonlinear differential equations describing the oscillations of the interface between two liquids in the vicinity of the main resonance are obtained. In the case of a circular cylindrical cavity with flat bottoms, sol...
Vestnik Tomskogo gosudarstvennogo universiteta. Matematika i mekhanika, 2021
In the paper, the nonlinear oscillations of a two-layer fluid that completely fills a limited tan... more In the paper, the nonlinear oscillations of a two-layer fluid that completely fills a limited tank are theoretically studied. To determine any smooth function on the deflected interface, the Taylor series expansions are considered using the values of the function and its normal derivatives on the undisturbed interface of the fluids. Using two fundamental asymmetric harmonics, which are generated in two mutually perpendicular planes, the differential equations of nonlinear oscillations of the two-layer fluid interface are investigated. As a result, the frequency-response characteristics are presented and the instability regions of the forced oscillations of the two-layer fluid in the cylindrical tank are plotted, as well as the parametric resonance regions for different densities of the upper and lower fluids. The Bubnov-Galerkin method is used to plot instability regions for the approximate solution to nonlinear differential equations. At the final stage of the work, the nonlinear e...
XLIV ACADEMIC SPACE CONFERENCE: dedicated to the memory of academician S.P. Korolev and other outstanding Russian scientists – Pioneers of space exploration, 2021
The proposed paper attempts to give a theoretical explanation of the rotational motion of the int... more The proposed paper attempts to give a theoretical explanation of the rotational motion of the interface in a two-layer liquid. The aim of this work was to obtain the equations of considerable oscillations of the interface of a two-layer liquid and study the stability of the resulting rotational motion of the liquid in a movable cylindrical tank, making reciprocating movements. In this paper, hydrodynamic coefficients of linear and nonlinear problems in integral relations were determined. As a result, the instability regions of forced oscillations of a two-layered liquid in a cylindrical tank occurring in the plane of action of the disturbing force are constructed, as well as the dynamic instability regions of the parametric resonance for different ratios of densities of the upper and lower liquids depending on the amplitudes of liquids from the excitations frequencies.
Engineering Journal: Science and Innovation, 2019
Due to the continued research into chemistry, biology, pharmaceutics and rocket space technology,... more Due to the continued research into chemistry, biology, pharmaceutics and rocket space technology, interest in the study of the dynamics of layered fluids has increased significantly. The paper focuses on oscillations of a three-layer viscous fluid, gives the formulation of the viscous fluid free oscillations problem. Within the research, we determined natural frequencies and damping coefficients of oscillations of the three-layer viscous fluid in a cylindrical vessel by means of the boundary layer method and a mechanical analog. Oscillations of the three-layer viscous fluid were considered as joint oscillations of two partial hydrodynamic systems, one of which corresponds to oscillations of the upper and middle viscous fluids, and the other one - to oscillations of the middle and lower fluids. Then, we determined the coefficients of viscous resistance in partial hydrodynamic systems of a two-layer viscous fluid. Using the mechanical analog of oscillations of the three-layer liquid, ...
Science and Education of the Bauman MSTU, 2016
Asia-Pacific Journal of Public Health, 2002
There is a paucity of information pertaining to oral disease patterns including periodontal disea... more There is a paucity of information pertaining to oral disease patterns including periodontal disease in Cambodia, which is just emerging from a 20-year ruin. A house-to-house survey was conducted to assess the periodontal status of 1948 subjects aged 15-74 years in a rural commune in Cambodia using Community Periodontal Index (CPI) and measuring Attachment Loss (LA). The periodontal status of Cambodians increased with age as indicated by both CPI and LA. Calculus was the most common finding among Cambodians pointing to overall poor oral hygiene levels. Notwithstanding the poor oral hygiene, however, the severe periodontitis as denoted by > or = 6mm periodontal pockets was rare even in the elderly while edentulousness was not frequently observed until 65 years. Preventive programmes targeting periodontal disease in Cambodia should focus on oral health education and simple oral hygiene instructions while the ubiquitous calculus could be dealt with oral prophylaxis.
Asia-Pacific Journal of Public Health, 2004
An analytical cross-sectional study was conducted with 812 subjects aged 35-74 years in Prek Russ... more An analytical cross-sectional study was conducted with 812 subjects aged 35-74 years in Prek Russey commune, Cambodia to detect some factors associated with severe periodontitis. Four calibrated examiners employed Community Periodontal Index (CPI) to ascertain periodontal pocket depth (PD) and loss of epithelial attachment (LA). A questionnaire was used to obtain tobacco and alcohol consumption habits. One hundred (12.3%) subjects had one or more sextants with > or =4 mm PD and > or =6 mm LA (severe periodontitis). Smoking, tobacco chewing and age were significantly associated with severe periodontitis in bivariate analysis while only age and quantified smoking remained significant in a logistic regression analysis. The impact of quantified smoking on severe periodontitis was almost negligible [OR: 1.0006 (95% CI: 1.0001, 1.001)] compared to that of age [OR ranged from 8.3 at 45-54 years to 22 at 65-74 years (95% CI: 3.1, 62.3)]. Nevertheless, both age and quantified smoking can be considered as factors associated with severe periodontitis in rural Cambodians.
Science and Education of the Bauman MSTU, 2016
Nauka i Obrazovanie, Oct 3, 2016
Nauka i Obrazovanie, May 3, 2016
Инженерный журнал: наука и инновации, May 1, 2019
Приведены постановка задачи и результаты исследований динамических характеристик и устойчивости м... more Приведены постановка задачи и результаты исследований динамических характеристик и устойчивости малых колебаний твердого тела, имитирующего космический заправщик, топливный бак которого содержит криогенную жидкость. Отличительной особенностью криогенной жидкости являются низкая температура и различная плотность ее частиц, что значительно усложняет исследование гидродинамических задач. Криогенная жидкость моделировалась с помощью слоев несмешивающихся жидкостей. Получены уравнения плоского движения твердого тела с полостью, содержащей три несмешивающиеся несжимаемые идеальные жидкости. Исследованы области устойчивости движения твердого полуцилиндра с цилиндрической полостью, наполненной тремя несмешивающимися жидкостями. Приведены результаты экспериментального исследования колебаний полуцилиндра с двумя несмешивающимися жидкостями. Ключевые слова: несмешивающиеся несжимаемые идеальные жидкости, механическая система, область устойчивости, собственная частота колебаний, твердое тело Введение. Задача динамики твердых тел, которые имеют полости, наполненные жидкостью,-одна из классических задач механики [1, 2]. Развитие авиации и космонавтики в 1950-80-е гг. дало новый импульс исследованиям, посвященным динамики тел с полостями, частично заполненными жидкостью. Отметим здесь работы К.
Engineering Journal: Science and Innovation
In this paper, the equations of spherical motion of a solid body with a rotating inhomogeneous in... more In this paper, the equations of spherical motion of a solid body with a rotating inhomogeneous incompressible fluid that fills a completely ellipsoidal cavity are obtained and investigated. The stability of rotation of a solid with an inhomogeneous fluid having a linear density distribution is considered. Arbitrary fields of density and velocity of fluid particles are represented as a power series by spatial variables with coefficients that depend only on time. Sufficient conditions for the stability of the rotation of a solid body with a fluid around the vertical axis of dynamic symmetry are presented. The obtained equations of motion make it possible to study the stability of stationary motions of the system under consideration in order to assess the effect of fluid separation on the dynamics of the body. By analogy with the motion of a solid body, it is stated that the obtained conditions are also necessary and sufficient conditions for stationary rotations of an inhomogeneous fl...
Engineering Journal: Science and Innovation, 2021
The development of rocket and space technology in recent years has led to the widespread use of v... more The development of rocket and space technology in recent years has led to the widespread use of various cryogenic liquids. To increase the shelf life of cryo-products on board spacecraft or in tankers of future space filling stations, it is proposed to create a certain stock of cryo-product, which is simultaneously in a two-phase or three-phase state and forms layers of liquid. The paper considers the problem in a nonlinear formulation about the oscillations of the interface of a two-layer liquid in an arbitrary axisymmetric cavity of a solid body performing angular oscillations around a horizontal axis. For the considered class of cavities with an arbitrary bottom and a lid, the nonlinear problem is reduced to the sequential solution of linear boundary value problems. Nonlinear differential equations describing the oscillations of the interface between two liquids in the vicinity of the main resonance are obtained. In the case of a circular cylindrical cavity with flat bottoms, sol...
Vestnik Tomskogo gosudarstvennogo universiteta. Matematika i mekhanika, 2021
In the paper, the nonlinear oscillations of a two-layer fluid that completely fills a limited tan... more In the paper, the nonlinear oscillations of a two-layer fluid that completely fills a limited tank are theoretically studied. To determine any smooth function on the deflected interface, the Taylor series expansions are considered using the values of the function and its normal derivatives on the undisturbed interface of the fluids. Using two fundamental asymmetric harmonics, which are generated in two mutually perpendicular planes, the differential equations of nonlinear oscillations of the two-layer fluid interface are investigated. As a result, the frequency-response characteristics are presented and the instability regions of the forced oscillations of the two-layer fluid in the cylindrical tank are plotted, as well as the parametric resonance regions for different densities of the upper and lower fluids. The Bubnov-Galerkin method is used to plot instability regions for the approximate solution to nonlinear differential equations. At the final stage of the work, the nonlinear e...
XLIV ACADEMIC SPACE CONFERENCE: dedicated to the memory of academician S.P. Korolev and other outstanding Russian scientists – Pioneers of space exploration, 2021
The proposed paper attempts to give a theoretical explanation of the rotational motion of the int... more The proposed paper attempts to give a theoretical explanation of the rotational motion of the interface in a two-layer liquid. The aim of this work was to obtain the equations of considerable oscillations of the interface of a two-layer liquid and study the stability of the resulting rotational motion of the liquid in a movable cylindrical tank, making reciprocating movements. In this paper, hydrodynamic coefficients of linear and nonlinear problems in integral relations were determined. As a result, the instability regions of forced oscillations of a two-layered liquid in a cylindrical tank occurring in the plane of action of the disturbing force are constructed, as well as the dynamic instability regions of the parametric resonance for different ratios of densities of the upper and lower liquids depending on the amplitudes of liquids from the excitations frequencies.
Engineering Journal: Science and Innovation, 2019
Due to the continued research into chemistry, biology, pharmaceutics and rocket space technology,... more Due to the continued research into chemistry, biology, pharmaceutics and rocket space technology, interest in the study of the dynamics of layered fluids has increased significantly. The paper focuses on oscillations of a three-layer viscous fluid, gives the formulation of the viscous fluid free oscillations problem. Within the research, we determined natural frequencies and damping coefficients of oscillations of the three-layer viscous fluid in a cylindrical vessel by means of the boundary layer method and a mechanical analog. Oscillations of the three-layer viscous fluid were considered as joint oscillations of two partial hydrodynamic systems, one of which corresponds to oscillations of the upper and middle viscous fluids, and the other one - to oscillations of the middle and lower fluids. Then, we determined the coefficients of viscous resistance in partial hydrodynamic systems of a two-layer viscous fluid. Using the mechanical analog of oscillations of the three-layer liquid, ...
Science and Education of the Bauman MSTU, 2016
Asia-Pacific Journal of Public Health, 2002
There is a paucity of information pertaining to oral disease patterns including periodontal disea... more There is a paucity of information pertaining to oral disease patterns including periodontal disease in Cambodia, which is just emerging from a 20-year ruin. A house-to-house survey was conducted to assess the periodontal status of 1948 subjects aged 15-74 years in a rural commune in Cambodia using Community Periodontal Index (CPI) and measuring Attachment Loss (LA). The periodontal status of Cambodians increased with age as indicated by both CPI and LA. Calculus was the most common finding among Cambodians pointing to overall poor oral hygiene levels. Notwithstanding the poor oral hygiene, however, the severe periodontitis as denoted by > or = 6mm periodontal pockets was rare even in the elderly while edentulousness was not frequently observed until 65 years. Preventive programmes targeting periodontal disease in Cambodia should focus on oral health education and simple oral hygiene instructions while the ubiquitous calculus could be dealt with oral prophylaxis.
Asia-Pacific Journal of Public Health, 2004
An analytical cross-sectional study was conducted with 812 subjects aged 35-74 years in Prek Russ... more An analytical cross-sectional study was conducted with 812 subjects aged 35-74 years in Prek Russey commune, Cambodia to detect some factors associated with severe periodontitis. Four calibrated examiners employed Community Periodontal Index (CPI) to ascertain periodontal pocket depth (PD) and loss of epithelial attachment (LA). A questionnaire was used to obtain tobacco and alcohol consumption habits. One hundred (12.3%) subjects had one or more sextants with > or =4 mm PD and > or =6 mm LA (severe periodontitis). Smoking, tobacco chewing and age were significantly associated with severe periodontitis in bivariate analysis while only age and quantified smoking remained significant in a logistic regression analysis. The impact of quantified smoking on severe periodontitis was almost negligible [OR: 1.0006 (95% CI: 1.0001, 1.001)] compared to that of age [OR ranged from 8.3 at 45-54 years to 22 at 65-74 years (95% CI: 3.1, 62.3)]. Nevertheless, both age and quantified smoking can be considered as factors associated with severe periodontitis in rural Cambodians.
Science and Education of the Bauman MSTU, 2016