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Search Results: 1 - 10 of 315800 matches for " L. V. Shevchuk "
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Whirl Interaction of a Drill Bit with the Bore-Hole Bottom  [PDF]
Nabil W. Musa, V. I. Gulyayev, L. V. Shevchuk, Hasan Aldabas
Modern Mechanical Engineering (MME) , 2015, DOI: 10.4236/mme.2015.53005
Abstract: This paper deals with the theoretic simulation of a drill bit whirling under conditions of its contact interaction with the bore-hole bottom rock plane. The bit is considered to be an absolutely rigid ellipsoidal body with uneven surface. It is attached to the lower end of a rotating elastic drill string. In the perturbed state, the bit can roll without sliding on the bore-hole bottom, performing whirling vibrations (the model of dynamic equilibrium with pure rolling when maximum cohesive force does not exceed the ultimate Coulombic friction). To describe these motions, a nonholonomic dynamic model is proposed, constitutive partial differential equations are deduced. With their use, the whirling vibrations of oblong and oblate ellipsoidal bits are analyzed, the functions of cohesive (frictional) forces are calculated. It is shown that the system of elastic drill string and ellipsoidal bit can acquire stable or unstable whirl modes with approaching critical Eulerian values by the parameters of axial force, torque and angular velocity. The analogy of the found modes of motions with ones of the Celtic stones is established. It is shown that the ellipsoidal bits can stop their whirling vibrations and change directions of their circumferential motions in the same manner as the ellipsoidal Celtic stones do. As this takes place, the trajectories of the oblate ellipsoidal bits are characterized by more complicated paths and irregularities.
V. Vovk,D. Shevchuk,N. Macuk,M. Borisenko
Proceedings of National Aviation University , 2012,
Abstract: It is propound a new method of assessment casual parameters of complex, unstable, moveable object for problems with structural identification of own object and synthesis of optimal, by structure, object stabilization system. Предложен новый метод оценки случайных параметров сложных, нестабильных, подвижных объектов для задач структурной идентификации собственных объектов и синтеза оптимальных по структуре объектов системы стабилизации. Розглянуто можлив сть орган зац мон торингу аеродинам чного стану л така в польот . Визначено, чим в др зняються сили, як д ють на неушкоджене крило та при його пошкодженн сторонн ми об’ ктами. Об рунтувано склад груп датчик в для д агностування аеродинам чного стану л така в польот .
Review of fluid flow and convective heat transfer within rotating disk cavities with impinging jet
Souad Harmand,Julien Pellé,Sébastien Poncet,Igor V. Shevchuk
Physics , 2013, DOI: 10.1016/j.ijthermalsci.2012.11.009
Abstract: Fluid flow and convective heat transfer in rotor-stator configurations, which are of great importance in different engineering applications, are treated in details in this review. The review focuses on convective heat transfer in predominantly outward air flow in the rotor-stator geometries with and without impinging jets and incorporates two main parts, namely, experimental/theoretical methodologies and geometries/results. Experimental methodologies include naphthalene sublimation techniques, steady state (thin layer) and transient (thermochromic liquid crystals) thermal measurements, thermocouples and infra-red cameras, hot-wire anemometry, laser Doppler and particle image velocimetry, laser plane and smoke generator. Theoretical approaches incorporate modern CFD computational tools (DNS, LES, RANS etc). Geometries and results part being mentioned starting from simple to complex elucidates cases of a free rotating disk, a single disk in the crossflow, single jets impinging onto stationary and rotating disk, rotor-stator systems without and with impinging single jets, as well as multiple jets. Conclusions to the review outline perspectives of the further extension of the investigations of different kinds of the rotor-stator systems and their applications in engineering practice.
Використання волоконно-оптичних нтелектуальних структур д агностування техн чного стану зовн шн х обвод в л така FIBER-OPTIC INTELLIGENCE STRUCTURES FOR THE TECHNICAL CONDITIONS DIAGNOSIS OF THE OUTSIDE OF THE AIRPLANE Использование волоконно-оптических интеллектуальных структур диагностирования те
Vasyliy M. Kazak,Dmytro O. Shevchuk,Мaryna L. Ostapchuk
Proceedings of National Aviation University , 2009,
Abstract: Розглянуто можлив сть використання волоконно-оптичних нтелектуальних структур для д агностування техн чного стану зовн шн х обвод в л така. Article is devoted to the possibilities of usage of the fiber-optic intelligence structure for the diagnosis of the technical conditions of the outside of the airplane. Рассмотрена возможность использования волоконно-оптических интеллектуальных структур для диагностирования технического состояния внешних обводов самолета.
O. Shevchuk
Economics of Development , 2012,
Abstract: Today, a modern economic system is characterized by the transition to a new type of socio-economic development, which is based on knowledge. This is connected with the fact that the economic activity is transformed in the process of creation, dissemination and use of knowledge, which are on the one hand, can be considered as a resource, and on the other – as the final product. The knowledge itself become a direct productive force, the driving force for development and a major factor of increase of competitiveness. At the same time, the development of science, creation of new technologies and science-intensive industries can increase the requirements to the educational level and professional qualification of each employee. In these conditions, the cycle of creation of a product becomes shorter, and the need for innovation increases. This means that the knowledge economy dictates new requirements to the manufacturers in the context of the development of international trade and enhancing the competitiveness of products. So far, in modern conditions – part of the mental labor increases, and physical – on the contrary – reduces, respectively, the first plan is taken by the ability of people to learn and their ability to correct application of a special kind of monopoly – a monopoly on knowledge. In other words, the basis for profitability, increase in profits and a privileged status as any of the Corporation and for the country as a whole – is the monopoly of knowledge, which is achieved due to use of own intellectual capacity, as a part of human capital.
Zinaida Shevchuk
Obrana a Strategie , 2011,
Abstract: Book review
Study of oxidative desulphurization process of coal with different metamorphism degrees

燃料化学学报 , 2012,
Abstract: The oxidative desulphurization process of coal with different metamorphism degrees treated by an air-steam mixture has been studied.It has been shown that the pyrite present in black coal and anthracite is oxidized with the sulphur dioxide formation,and the process chemical mechanism does not depend on the quality of organic matter.The medium-metamorphized coal,capable of turning into a plastic state and cake in the range of investigated temperatures(350~450 ℃),is desulphurized with the greatest difficulty.The chemical mechanism dealing with the transformations of pyritic sulphur present in brown coal differs from similar processes taking place in black coal and anthracite,because FeS2 is converted with hydrogen sulphide formation at desulphurization.
Synthesis of Hydroxyapatite Nanoparticles with Initiating Centers in Polymer Shell
Shevchuk O.M.,Chobit M.R.,Bukartyk N.M.,Tokarev V.S.
Proceedings of the International Conference Nanomaterials : Applications and Properties , 2012,
Abstract: This research work was devoted to the synthesis of hydroxyapatite nanoparticles with initiating centres in polymer shell. Marcroinitiators comprised by heterofunctional copolymers containing either pendant peroxidic groups or benzoin pieces attached to the backbone chain were used as surface modifiers of hydroxyapatite. Their use in the stage of synthesis of the mineral particles makes possible a control over size and the surface properties of particles. The effect of copolymer nature and its concentration, as well as the synthesis conditions on hydroxyapatite particle size and the copolymer adsorption value was studied. Both types of functional groups namely peroxide and benzoin in structure of copolymers immobilized at the hydroxyapatite surface were used for initiation of polymerization processes at elevated temperature (in the first case) or under UV-irradiation (in another case). These techniques of bioceramics modification allowed to form polymer compatibilizing layer of proper structure and thickness bonded with the mineral particles that enhanced compatibility of mineral filler and polymer matrix of different nature and as a result obtaining composite materials with improved physico-mechanical properties.
Determination of Metal Nanoparticles Size Distribution in Gold Hydrosols of Plasmonic Absorption Spectra
Journal of Nano- and Electronic Physics , 2012,
Abstract: Substantiated method determining the distribution of metal particle size on the optical absorption data for composites consisting of dielectric medium and metallic inclusions and tested this method on hydrosols of gold nanoparticles compared to the data obtained by microscopic examination.
A Limit on the Number of Isolated Neutron Stars Detected in the ROSAT All-Sky Survey Bright Source Catalog
Monica L. Turner,Robert E. Rutledge,Ryan Letcavage,Andrew S. H. Shevchuk,Derek B. Fox
Physics , 2010, DOI: 10.1088/0004-637X/714/2/1424
Abstract: Using new and archival observations made with the Swift satellite and other facilities, we examine 147 X-ray sources selected from the ROSAT All-Sky-Survey Bright Source Catalog (RASS/BSC) to produce a new limit on the number of isolated neutron stars (INSs) in the RASS/BSC, the most constraining such limit to-date. Independent of X-ray spectrum and variability, the number of INSs is <=48 (90% confidence). Restricting attention to soft (having an effective temperature of < 200 eV), non-variable X-ray sources -- as in a previous study -- yields an all-sky limit of <=31 INSs. In the course of our analysis, we identify five new high-quality INS candidates for targeted follow-up observations. A future all-sky X-ray survey with eROSITA, or another mission with similar capabilities, can be expected to increase the detected population of X-ray-discovered INSs from the 8 to 50 in the BSC, to (for a disk population) 240 to 1500, which will enable a more detailed study of neutron star population models.
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