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1
Wu, Zhi Qiang, und Jun Fang Zhao. „The Design of Plate Mills Hydraulic Lubricating and Monitoring System“. Advanced Materials Research 1006-1007 (August 2014): 643–49. http://dx.doi.org/10.4028/www.scientific.net/amr.1006-1007.643.
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Plate mills hydraulic system is made up of several hydraulic stations, lubrication stations and grease stations, these hydraulic stations and lubrication stations are distributed around the mills. Each hydraulic station possesses qualities of successive long working time, high reliability and signal complexity, and it can satisfy diverse demands of high grade pressure or temperature control, etc. This paper is based on these demands, assembling control missions of hydraulic and lubricating stations. Several PLC S7-300 were chosen to match the need of controlling mills hydraulic and lubricating system for a certain plate factory, and the HMI monitoring system for mill hydraulic and lubricating stations was developed by WINCC, which achieved central control and monitoring the hydraulic and lubricating system of plate mills.
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Neville, A., A. Morina, T. Liskiewicz und Y. Yan. „Synovial joint lubrication — does nature teach more effective engineering lubrication strategies?“ Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 221, Nr. 10 (30.09.2007): 1223–30. http://dx.doi.org/10.1243/09544062jmes724.
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Nature shows numerous examples of systems which show energy efficiency, elegance in their design and optimum use of materials. Biomimetics is an emerging field of research in engineering and successes have been documented in the diverse fields of robotics, mechanics, materials engineering, and many more. To date little biomimetics research has been directed towards tribology in terms of transferring technologies from biological systems into engineering applications. The potential for biomimicry has been recognized in terms of replicating natural lubricants but this system reviews the potential for mimicking the synovial joint as an efficient and durable tribological system for potential engineering systems. The use of materials and the integration of materials technology and fluid/surface interactions are central to the discussion.
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Czarny, Ryszard. „THE EFFECT OF THE TYPE OF WALL MATERIAL AND GREASE COMPOSITION PAIRING ON SHEAR STRESSES IN BOUNDARY LAYER“. Tribologia 284, Nr. 2 (30.04.2019): 27–36. http://dx.doi.org/10.5604/01.3001.0013.4146.
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The paper presents the results of research on the influence of fillers introduced into plastic greases on the rheological properties of the boundary layer of the resultant lubricant compositions. The fillers were PTFE and MoS2 powders. They are added to lubricants to improve their tribological properties; however, these fillers also affect the rheological properties of the composition. This affects the change of the shear stress value in the lubricant during its flow in the lubrication system. Knowledge of this value, especially during the flow of the lubricant composition in the boundary layer, has a significant impact on the operation of automated central lubrication systems in which these compositions can be used. Measurements were carried out by means of a rotary rheometer (Rheotest 2.1). Tests were performed on lithium and bentonite greases (without additives) as well as compositions of these greases containing various percentage of the fillers mentioned above. Test results showed that both the type of grease and the type of filler introduced into this grease affect the rheological properties in the boundary layer of the produced lubricating compositions.
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CZARNY, Ryszard. „INFLUENCE OF FILLERS ON THE RHEOLOGICAL PROPERTIES OF THEIR COMPOSITIONS WITH LUBRICATING GREASES“. Tribologia 273, Nr. 3 (30.04.2018): 47–55. http://dx.doi.org/10.5604/01.3001.0010.6120.
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The paper presents the results of studies on the influence of fillers, introduced into lubricating greases, on the rheological properties of resultant grease compositions. These fillers were graphite and PTFE powders. They are added to greases in order to improve their tribological properties. They also affect their rheological properties, and they mainly change the value of the shear stress in grease during its flow in a lubrication system. Knowledge of this value is important in designing automated central lubrication systems in which these compositions may be used. Measurements during experimental tests were performed by means of a rotary rheometer Rheotest 2.1. Tests were performed on pure lithium and bentonite greases, with the addition of oxidation and corrosion inhibitors as well as compositions of these greases with different shares of the above mentioned fillers. These tests were performed by changing the gradient of shearing rate. Test results have shown that both the kind of grease and the kind of filler introduced into this grease affect the rheological properties of produced grease compositions.
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Li, Feng, Feng Guo, Guan Gyuan Liu und Zhang Gang. „Design and Experiment Study on a New Type of Lubrication Simulation System for Thrust-Ball Bearing in Confined Space“. Applied Mechanics and Materials 873 (November 2017): 303–7. http://dx.doi.org/10.4028/www.scientific.net/amm.873.303.
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Many machine components work within an elastohydrodynamic lubrication (EHL) regime. Unconfined space is widely used in EHL formulas for to evaluate film thickness, which is related to operating conditions and material properties. In classical theoretical EHL studies, film pressure matches the loading balance and the location of the lubricated components can be adjusted. In the present study, the lubrication performance is analyzed based on a confined space. A thrust ball bearing lubrication simulation system is designed and used to examine the relationship between velocity and film thickness. It was found that the central film thickness and minimum film thickness increased as entrainment velocity increased. Fluctuations in the film thickness curve were observed, which may have arisen from slight gap variations in the ball-plate contact area.
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Huo, Junzhou, Jianjun Zhou, Tao Li, Zhichao Meng und Wei Sun. „Thermal EHL Characteristics Investigation on Axle Box Bearings of Railway Vehicle Based on Slicing Method“. Shock and Vibration 2019 (02.04.2019): 1–14. http://dx.doi.org/10.1155/2019/6981482.
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Lubrication failures of axle box bearings can lead to accidents, such as bearing burnout and hot axle cutting. Presently, the modeling of the vehicle-track system dynamics rarely considers the nonlinear contact load of axle box bearings, and this leads to imperfection in the vehicle-track system dynamics calculation. And then, the load distribution and lubrication characteristics of axle box bearings are difficult to obtain. Therefore, in this paper, we fully consider the time-varying nonlinear contact load of bearings and track irregularity in establishing the bearing-wheel-rail system coupling-dynamics model. The dynamic response of axle box bearings is obtained by taking the vertical, strong impact-time-varying load on the carrying saddles as the external excitation. The load-balance equation of dynamic pressure lubrication is then obtained, according to the slicing method of bearing rollers. Finally, the elastohydrodynamic lubrication (EHL) model of axle box bearings is established considering thermal and scale effects. The results show that the central film thickness under thermal EHL was decreased by 13.61% compared with that under isothermal EHL. As the velocity of the contact pair increases, the thickness difference between thermal and isothermal EHL became larger. Thermal effects should be considered in the EHL model, in order to truly reflect the characteristics of EHL under a high speed.
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Glazunov, D. V. „Development of the lubricant for side-mounted rail flange lubricators for traction rolling stock“. Vestnik of the Railway Research Institute 78, Nr. 1 (13.05.2019): 59–64. http://dx.doi.org/10.21780/2223-9731-2019-78-1-59-64.
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Specificity of operating conditions of the rolling stock defines a number of requirements for lubricants intended for the wheel-rail tribosystem. Lubricants are used for “wheel — rail” contact, the aggregate state of which varies from liquid to solid. When evaluating the lubrication properties of these materials, a significant number of factors must be taken into account, in particular, influence of the environment, method of application, condition of the rail surface. The paper discusses the main operational requirements for lubricants operating in a wheel-rail tribosystem. Temperature ranges of the lubricants used for the “wheel — rail” contact on the railway network of the Russian Federation are given. As a result of the research, it was determined that none of the materials used for lubrication of the wheel-rail system satisfies the operating temperature conditions of the traction rolling stock. To solve this problem a lubricant was developed and tested in an industrial environment at the Rostov State University of Railway Transport. Its lubricant composition allows to significantly expand the temperature range of the lubricant. Complex of experimental studies and method of orthogonal central composite plan of the 2nd order established the optimum values of the thickness of the working shell of the 0.846 mm lubricating rod and the 50.411 % percentage of plastic lubricant, allowing to extend the temperature range of lubricant rods and, in particular, completely eliminate the lubricant flow to achieve a temperature of 126.034 °C. Proposed composition of the lubricant was tested on a freight electric locomotive of the VL80T series, equipped with non-power lubricators, under the conditions of the Bataysk — Likhaya section of the North Caucasus Railway. Intensity of wear of the wheel flanges of the traction rolling stock lubricated by the proposed material, compared with the intensity of wear of the wheel flanges without the use of lubrication systems is reduced by 2 times.
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Zhai, Liming, Zhengwei Wang, Yongyao Luo und Zhongjie Li. „TEHD analysis of a bidirectional thrust bearing in a pumped storage unit“. Industrial Lubrication and Tribology 68, Nr. 3 (11.04.2016): 315–24. http://dx.doi.org/10.1108/ilt-07-2015-0092.
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Purpose The purpose of this paper is to analyze lubrication characteristics of a bidirectional thrust bearing in a pumped storage, considering the effect of the thermal elastic deformation of the pad and collar. Design/methodology/approach This study used the fluid–solid interaction (FSI) technique to investigate the lubrication characteristics of a bidirectional thrust bearing for several typical operating conditions. The influences of the operating conditions and the thrust load on the lubrication characteristics were analyzed. Then, various pivot eccentricities were investigated to analyze the effects of the pivot position. Findings It is found that the effect of the radial tilt angle of the collar runner on the oil film is compensated for by the radial tilt of the pad. The central pivot support system is the main factor limiting the loads of bidirectional thrust bearings. Originality/value This paper has preliminarily revealed the lubrication mechanism of bidirectional tilting-pad thrust bearings. A three-dimensional FSI method is suggested to evaluate the thermal–elastic–hydrodynamic deformations of thrust bearings instead of the conventional method, which iteratively solves the Reynolds equation, the energy equation, the heat conduction equation and the elastic equilibrium equation.
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Lu, Junjie. „Theoretical optimization and experiment on lubrication of floating microgroove cylindrical seal“. Industrial Lubrication and Tribology 72, Nr. 10 (10.06.2020): 1217–26. http://dx.doi.org/10.1108/ilt-02-2020-0048.
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Purpose The purpose of this paper is to analyze and improve the lubrication performance of a floating cylindrical seal by investigating micro spiral groove. Design/methodology/approach The lubrication model of is solved by finite difference, considering the influence of convergence eccentricity and Rayleigh step on the gas film period. A lubrication model, which is a gas film of floating microgroove cylindrical seal, is solved under high-precision central difference (finite-difference method-center) for the critical problems of convergence eccentricity and Rayleigh step. And then, an idea on the opening-leakage ratio is proposed, and a multiobjective optimization model is established. Finally, an experiment is conducted on a narrow gap to determine the gas film opening force and leakage by the modules of testing system, and the theoretical results are verified by real tests. Findings The theoretical calculation results agree well with the experimental data, which proves the correctness of the lubrication optimization model, and the optimized groove has better lubrication performance. On the other hand, the sealing pressure plays a more important role in the seal operation. Originality/value The theoretical model carries out low complexity and high sparseness, thus being very suitable for large-scale gas film problems. A multiobjective optimal function is established based on the opening-leakage ratio for optimizing groove. Finally, a curved groove of high precision and gas film opening force is obtained completely. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2020-0048/
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KOWALEWSKI, Piotr, Anna BROŃCZYK und Wojciech WIELEBA. „A TRIBOLOGICAL TEST RIG FOR FIBRES, CABLES, AND PLAITINGS“. Tribologia 271, Nr. 1 (28.02.2018): 51–55. http://dx.doi.org/10.5604/01.3001.0010.6363.
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The paper presents a description of the mechanical construction, measuring and control systems and the possibilities of a new type tribological testing device. The design was developed and built at the Department of Fundamentals of Machine Design and Tribology of Wroclaw University of Science and Technology. Described tester allows the investigate a friction and wear of components such as fibrous tapes, ropes, plaitings or fibers themselves in contact with solid materials. The paper describes in detail the construction of drive and the load pneumatic system. The innovative system of the device such measurement equipped with piezoelectric sensors and an experimental fixing unit of tested components also have been described. Work includes diagrams of used control and measurement systems and the central lubrication system. As a test the polyethylene cable in contact with brass rods has been examined. The results of this studies were been also presented in the paper.
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Buczek, Bronislaw, und Anna Zajezierska. „Biodegradable lubricating greases containing used frying oil as additives“. Industrial Lubrication and Tribology 67, Nr. 4 (08.06.2015): 315–19. http://dx.doi.org/10.1108/ilt-07-2013-0082.
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Purpose – The aim of this paper was to investigate the possibility of reusing frying oil, obtained during thermal treatment of food in fast-food restaurants for production of plastic greases. Design/methodology/approach – In accordance with the proposed research concept, the used frying oil was to be the base oil of biodegradable plastic greases thickened with calcium 12-hydroxystearate and lithium 12-hydroxystearate. These studies included the determination of the effect of variable amounts of used oil component in the base oil on the properties of the resultant plastic greases. Findings – It was found that the optimum amount of the component in the base oil is 10-15 per cent. Calcium and lithium greases prepared in such a way possess a quality to that of greases prepared with fresh rapeseed oil. Research limitations/implications – Higher concentrations of used frying oil in the base oil adversely affect the degree of thickening, thixotropic properties and dropping point of the grease, as well as, creating technological problems. Practical implications – The investigations, beside their research goals have also a practical character – recycling waste material in place of its present method of disposal. Originality/value – One of the least expensive material, and most commonly used to produce biodegradable lubricants are vegetable oils. In recent years, besides introducing biodegradable lubricating oils, increasing interest is observed in the use of plastic greases of high biodegradability. Now, it is possible to obtain such greases with additive of used frying oils. Biodegradable greases are used as lubrication of open gear, food production equipment, central lubrication system in cars and railway engineering.
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Kozdrach, Rafał. „The influence of base oil type on the rheological properties of ecological lubricating greases“. Nafta-Gaz 77, Nr. 2 (Februar 2021): 127–35. http://dx.doi.org/10.18668/ng.2021.02.07.
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The article presents the results of research on the influence the type of base oil in lubricating compositions has on the rheological parameters of selected lubricants. Vegetable, mineral, and synthetic dispersion phases were used to produce lubricating greases. The modified amorphous silica was used as the dispersed phase. However, as a modifying additive was used a substance containing the antioxidants, corrosion inhibitors, and EP/AW additives. The experiments on rheological properties were carried out using a Physica MCR 101 rotational rheometer (manufactured by Anton Paar), equipped with a diffusion air bearing and connected to a pneumatic supply – an oil-free Jun-Air compressor and air drying block. The device is equipped with a Peltier system for temperature control in the range of –20°C to 200°C and an external thermostatic VISCOTHERM V2 system, working in the temperature range of –20°C to 200°C. The rheometer control and measurement data analysis were performed using Rheoplus software. The tests were carried out using a cone-plate measuring system with a shear rate range of 0.01–100 s-1 at 20°C for lubricating compositions prepared on various oil bases. To evaluate the value of rheological parameters, the results of tests of the dependence between shear stress and shear rate (flow curves) were used. For the theoretical determined on the flow curves, the following rheological models were used: Bingham, Herschel–Bulkley, Casson, and Tscheuschner. The values of the shear stress (yield point) in depending on the type of dispersion phase has changed. This proves that the use of a base oil with the appropriate functional properties does not weaken, but reinforces the spatial structure of a lubricating grease. It has an important meaning when selecting construction parameters when designing a central lubrication system with grease made from a vegetable oil base (Abyssinian oil). The rheological properties of the lubricating grease are influenced by the type of base oil and thickener, any additives in the grease, the production technology of the grease, and the conditions in which it is used. The tests revealed an important influence of the base oil on the rheological parameters that describe the behaviour of lubricating compositions subjected to stresses and strains in a lubricating system.
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Kennedy, Francis E., Douglas W. Van Citters, Khanittha Wongseedakaew und Mongkol Mongkolwongrojn. „Lubrication and Wear of Artificial Knee Joint Materials in a Rolling∕Sliding Tribotester“. Journal of Tribology 129, Nr. 2 (14.11.2006): 326–35. http://dx.doi.org/10.1115/1.2464130.
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This paper describes the influence of lubrication on wear during testing of materials for artificial knee joints in a rolling∕sliding tribotester built to simulate contact conditions in a total knee replacement. The test configuration consists of parallel cylinders (pucks) of ultrahigh molecular weight polyethylene (UHMWPE) and polished cobalt-chrome alloy in oscillatory rolling∕sliding contact in a bath of dilute (25%) bovine serum. Wear tests of three different UHMWPE materials were run under constant load at 40% sliding for 1.5 million oscillation cycles at 1.5cycles∕s. Wear of the UHMWPE was determined by measuring the profile of the cylindrical contact surface of the puck before and after each test. Profile measurements were repeated after at least 53days to eliminate the contribution from creep. Differences between initial and final profiles were attributed to wear of the UHMWPE. It was found that the largest wear depth in the lubricated tests occurred near the ends of the oscillatory contact area, while dry (unlubricated) tests of the same materials showed a peak wear depth near the center of the contact area. In the lubricated tests, the worn depth was lowest for the most heavily irradiated material. Analysis of the elastohydrodynamic lubrication in the rolling∕sliding contact was carried out assuming a line-contact situation with smooth cylindrical surfaces. The time-dependent modified Reynolds equation and the elasticity equation with initial conditions were solved numerically using a multigrid technique with full approximation scheme, and using a Newton Raphson method to solve the highly nonlinear system of equations. The thickness of the lubricating film of bovine serum was determined for points along the length of the wear track. It was found that the smallest film thickness (hmin) occurs very close to the location in the oscillating contact where the greatest wear occurs, owing to the very low entraining velocity near the ends of the oscillation cycle. The coefficient (K) for wear of the UHMWPE was found to be relatively constant over the central section of the oscillatory motion, but increased to a higher value where hmin decreased to near zero. Thus, the important influence of lubrication on wear of artificial knee bearings was demonstrated.
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Babin, Alexander, Alexey Kornaev, Alexey Rodichev und Leonid Savin. „Active thrust fluid-film bearings: Theoretical and experimental studies“. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 234, Nr. 2 (23.07.2019): 261–73. http://dx.doi.org/10.1177/1350650119862074.
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Research in the field of active fluid-film bearing has been recently getting more and more attention, integration of control systems becoming one of the most promising means of enhancement of rotor-bearing nodes' characteristics. It has been determined that the vast majority of papers published on active fluid-film bearing only consider radial bearings, and very few focus on thrust bearings. This lack of attention along with the obvious necessity to fill the said gap has triggered the present research. In cases of rotor machines that experience extensive axial loading due to various reasons, e.g. various turbine engines (aero and spacecraft) and hydraulic pumps (crude oil extraction facilities), such research could prove the feasibility of application of a control system to significantly increase the performance of the whole machine. Moreover, extensive wear during start up and shut down could be eliminated by means of rotor position control, thus life time of a rotor-bearing system could be significantly increased. The present paper features a complex mathematical model of an active thrust fluid-film bearing with a central feeding orifice, a developed test rig designed to verify the presented mathematical model allowing a series of numerical tests to be carried out. Numerical studies focus on the hypothesis of a possibility to use active control in thrust bearings to decrease power loss due to friction and extensive axial vibrations by means of identification of an energy efficient area of axial gaps based on the lubrication regime and its maintenance by means of application of controlled lubrication principles.
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Kruszewska, Natalia, Piotr Bełdowski, Piotr Weber, Steven Yuvan, Marcin Drechny und Marcin Kośmieja. „Formation of Protein Networks between Mucins: Molecular Dynamics Study Based on the Interaction Energy of the System“. Energies 12, Nr. 18 (06.09.2019): 3448. http://dx.doi.org/10.3390/en12183448.
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Molecular dynamics simulations have been performed for a model aqueous solution of mucin. As mucin is a central part of lubricin, a key component of synovial fluid, we investigate its ability to form cross-linked networks. Such network formation could be of major importance for the viscoelastic properties of the soft-matter system and crucial for understanding the lubrication mechanism in articular cartilage. Thus, the inter- and intra-molecular interaction energies between the residues of mucin are analyzed. The results indicate that the mucin concentration significantly impacts its cross-linking behavior. Between 160 g/L and 214 g/L, there seems to be a critical concentration above which crowding begins to alter intermolecular interactions and their energies. This transition is further supported by the mean squared displacement of the molecules. At a high concentration, the system starts to behave subdiffusively due to network development. We also calculate a sample mean squared displacement and p-variation tests to demonstrate how the statistical nature of the dynamics is likewise altered for different concentrations.
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Wei, Biao, Yi Zhuo, Chaobin Li und Menggang Yang. „Parameter Optimization of a Vertical Spring-Viscous Damper-Coulomb Friction System“. Shock and Vibration 2019 (14.04.2019): 1–19. http://dx.doi.org/10.1155/2019/5764946.
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A vertical spring-viscous damper-concave Coulomb friction isolation system was firstly proposed, and their parameters were firstly optimized to achieve the best performance under earthquakes. An incremental dynamic analysis method (IDA) and a performance-based assessment framework were used to calculate the system and assess its seismic vulnerability, respectively. Results show that both the friction force and the horizontal component of spring force gradually increase when an earthquake enforce the isolator to slide from its central location. Although other papers propose that an increase of spring force and a decrease of friction force can reduce the structural residual displacement, this paper can minimize the residual displacement value to be 0 by using a super lubrication in the middle of contact surface and a variable increment ratio of concave friction distribution. The reason is that the horizontal component of spring force is always greater than the friction force within any relative displacement between the structure and the ground in this paper. As for the peak relative displacement and peak acceleration of structure, one is reduced while the other is increased when selecting the optimal isolation parameters. If the structure is very sensitive to the acceleration response, a low friction parameter, a small spring constant, and a small and even zero damping constant could be adopted to yield a small peak acceleration of system. The tightness of vertical spring can be adjusted to be appropriately loose to continuously reduce the structural acceleration response.
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Liu, Yuchuan, Q. Jane Wang, Wenzhong Wang, Yuanzhong Hu und Dong Zhu. „Effects of Differential Scheme and Mesh Density on EHL Film Thickness in Point Contacts“. Journal of Tribology 128, Nr. 3 (02.03.2006): 641–53. http://dx.doi.org/10.1115/1.2194916.
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This paper investigates the effects of differential scheme and mesh density on elastohydrodynamic lubrication (EHL) film thickness based on a full numerical solution with a semi-system approach. The solution variation with different schemes and mesh sizes is revealed based on a set of numerical cases in a wide range of central film thickness from several hundred nanometers down to a few nanometers. It is observed that when the film is thick, the effects of differential schemes and mesh density are not significant. However, if the film becomes ultra-thin, e.g., below 10–20 nanometers, the influence of mesh density and differential schemes becomes more significant, and a proper dense mesh and differential scheme may be highly desirable. The present study also indicates that the solutions from the 1st-order backward scheme give the largest film thickness among all the solutions from different schemes at the same mesh size.
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Polycarpou, Andreas A., und Andres Soom. „Two-Dimensional Models of Boundary and Mixed Friction at a Line Contact“. Journal of Tribology 117, Nr. 1 (01.01.1995): 178–84. http://dx.doi.org/10.1115/1.2830597.
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Two-dimensional dynamic friction models at a lubricated line contact, operating in boundary and mixed lubrication regimes, are developed. The friction coefficient is shown to be a function of the sliding velocity and the instantaneous separation of the sliding bodies, normal to the sliding direction. The models are based on unsteady friction experiments carried out under constant normal loads and under time-varying sliding velocities. The normal motions at the sliding contact were detected indirectly by contact resistance measurements. The contact resistance is related to the theoretical central film thickness for smooth surfaces. An advanced system identification technique (Minimum Model Error) is implemented to identify the most important terms in a number of nonlinear friction models. Two friction models are then nondimensionalized and parameterized. The validity and range of application of the models are then tested, by comparing them with experiments and with selected models proposed by other researchers.
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Gil, Antonio, Andrés Omar Tiseira, Luis Miguel García-Cuevas, Tatiana Rodríguez Usaquén und Guillaume Mijotte. „Fast three-dimensional heat transfer model for computing internal temperatures in the bearing housing of automotive turbochargers“. International Journal of Engine Research 21, Nr. 8 (15.10.2018): 1286–97. http://dx.doi.org/10.1177/1468087418804949.
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Each of the elements that make up the turbocharger has been gradually improved. In order to ensure that the system does not experience any mechanical failures or loss of efficiency, it is important to study which engine-operating conditions could produce the highest failing rate. Common failing conditions in turbochargers are mostly achieved due to oil contamination and high temperatures in the bearing system. Thermal management becomes increasingly important for the required engine performance. Therefore, it has become necessary to have accurate temperature and heat transfer models. Most thermal design and analysis codes need data for validation; often the data available fall outside the range of conditions the engine experiences in reality leading to the need to interpolate and extrapolate disproportionately. This article presents a fast three-dimensional heat transfer model for computing internal temperatures in the central housing for non-water cooled turbochargers and its direct validation with experimental data at different engine-operating conditions of speed and load. The presented model allows a detailed study of the temperature rise of the central housing, lubrication channels, and maximum level of temperature at different points of the bearing system of an automotive turbocharger. It will let to evaluate thermal damage done to the system itself and influences on the working fluid temperatures, which leads to oil coke formation that can affect the performance of the engine. Thermal heat transfer properties obtained from this model can be used to feed and improve a radial lumped model of heat transfer that predicts only local internal temperatures. Model validation is illustrated, and finally, the main results are discussed.
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Akpan, Umoren, Aniefiok, Eyo, Emmanuel Okon und Akpan, Sunday Brownson. „Investigating the nexus between Non-Performing Loans in the Nigerian Banking System and Lending to Micro-Small Medium Enterprises“. International Journal of Contemporary Research and Review 9, Nr. 06 (01.06.2018): 20778–91. http://dx.doi.org/10.15520/ijcrr/2018/9/06/516.
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Micro-Small and Medium Enterprises (MSMEs) constitute vital ingredients for the lubrication of the development process of any economy. Therefore, Micro-Small and Medium Enterprises are bedrocks of emerging economies as they exact vital roles in promoting and sustaining growth and development. However, in Nigeria MSMEs are facing myriad of challenges and difficulties in funding their activities. Rising trends in Non-performing loans (NPLs) adversely affected availability of loans and advances to economic agents in the Nigerian economy thereby constraining financial intermediation and economic activities hence growth. The study investigated the nexus existing between NPLs in the Nigerian banking system and lending to MSMEs sub-sector in Nigeria from 1981-2015. Time series data used in the study were collected from annual statistical bulletin of the Central Bank of Nigeria (CBN). These data were subjected to descriptive and inferential methods. The results of the graphical presentations indicated irregular fluctuations in NPLs. The graphs indicated positive trends in respect to lending to MSMEs and the productivity of MSMEs. The estimated OLS results showed negative nexus between non-performing loans and lending to MSMEs. This negative nexus led to concomitant low MSMEs productivity in Nigeria. The study recommended that CBN should increase its financial surveillance over the sectors and also ensure timely resolutions of the NPLs challenges CBN should increase arrays of financial intervention that would address paucity in funds in the MSMEs sub-sector
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Khan, Aqib Mashood, Muhammad Jamil, Mozammel Mia, Danil Yurievich Pimenov, Vadim Rashitovich Gasiyarov, Munish Kumar Gupta und Ning He. „Multi-Objective Optimization for Grinding of AISI D2 Steel with Al2O3 Wheel under MQL“. Materials 11, Nr. 11 (13.11.2018): 2269. http://dx.doi.org/10.3390/ma11112269.
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In the present study, the machinability indices of surface grinding of AISI D2 steel under dry, flood cooling, and minimum quantity lubrication (MQL) conditions are compared. The comparison was confined within three responses, namely, the surface quality, surface temperature, and normal force. For deeper insight, the surface topography of MQL-assisted ground surface was analyzed too. Furthermore, the statistical analysis of variance (ANOVA) was employed to extract the major influencing factors on the above-mentioned responses. Apart from this, the multi-objective optimization by Grey–Taguchi method was performed to suggest the best parameter settings for system-wide optimal performance. The central composite experimental design plan was adopted to orient the inputs wherein the inclusion of MQL flow rate as an input adds addition novelty to this study. The mathematical models were formulated using Response Surface Methodology (RSM). It was found that the developed models are statistically significant, with optimum conditions of depth of cut of 15 µm, table speed of 3 m/min, cutting speed 25 m/min, and MQL flow rate 250 mL/h. It was also found that MQL outperformed the dry as well as wet condition in surface grinding due to its effective penetration ability and improved heat dissipation property.
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Raymond, C. F. „Energy balance of ice streams“. Journal of Glaciology 46, Nr. 155 (2000): 665–74. http://dx.doi.org/10.3189/172756500781832701.
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AbstractAnalysis of the cross-flow transmission of force from the central parts of a well-lubricated ice stream to its margins shows that there is a corresponding shift in the lateral location of motion-induced heat generation. The rate of basal heat generation in the center can be substantially smaller than the local rate of potential energy loss given by driving stress times the speed of downslope motion. The basal heating is a maximum for an intermediate level of lubrication for which speed is about 40% of the speed over a friction-less bed and base stress is about 25% of the driving stress. Stable and unstable balances between meltwater production and drainage on the bed are identified. A stable steady state with a speed less (more) than that giving maximum heat generation is termed drainage-(production-) limited, since an increase in speed would lead to increased (decreased) basal melting and must (need not) be balanced by increased drainage. It is shown that gradual evolution of the basal water drainage system and the factors affecting basal melting can cause discontinuous jumps between fast- and slow-moving states. A simplified analysis applied to six cross-sections of West Antarctic Ice Streams B, D, E and Rutford Ice Stream shows them to be diverse in the level of support from the sides and corresponding shift of mechanical heating sideward from their central parts. The cross-sections of Ice Stream B near “Upstream B” may be production-limited, because of especially high lubrication and related support from the sides. Cross-sections in the upper part of Ice Stream D, Ice Stream E and Rutford Ice Stream are in a drainage-limited condition. Substantial reduction of basal heat generation by side drag (in most cases) and expected high heat flow into the basal ice associated with low thickness (in some cases) tends to favor basal freezing. Nevertheless, all of the examined cross-sections except one are expected to experience basal melting with a modest geothermal heat-flux density of 60 m W m−1 or less in some cases. The lower part of Ice Stream B is an exception, where the analysis indicates that geothermal flux density must exceed 80–100 m W−1 m to maintain melting. If this high geothermal flux is not present, then the base of the lower part of Ice Stream B may be freezing, which would suggest continued deceleration of this part of Ice Stream B.
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Armeni, Anastasia K., Konstantinos Assimakopoulos, Dimitra Marioli, Vassiliki Koika, Euthychia Michaelidou, Niki Mourtzi, Gregoris Iconomou und Neoklis A. Georgopoulos. „Impact of estrogen receptor α gene and oxytocin receptor gene polymorphisms on female sexuality“. Endocrine Connections 6, Nr. 1 (Januar 2017): 44–52. http://dx.doi.org/10.1530/ec-16-0090.
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Over the past decades, research attention has increasingly been paid to the neurobiological component of sexual behavior. The aim of the present study was to investigate the correlation of estrogen receptor α (ERA) gene polymorphism (rs2234693-PvuII) (T→C substitution) and oxytocin receptor gene polymorphism (rs53576) (G→A substitution) with sexuality parameters of young, healthy women. One hundred thirty-three Greek heterosexual women, students in higher education institutions, 20–25 years of age, sexually active, with normal menstrual cycles (28–35 days), were recruited in the study. Exclusion criteria were chronic and/or major psychiatric diseases, use of oral contraceptive pills (OCs), polycystic ovary syndrome (PCOS), thyroid diseases as well as drugs that are implicated in hypothalamus–pituitary–gonadal axis. T allele (wildtype) of rs2234693 (PvuII) polymorphism of ERA gene was correlated with increased levels of arousal and lubrication, whereas A allele (polymorphic) of rs53576 (OXTR) polymorphism was correlated with increased arousal levels. The simultaneous presence of both T allele of rs2234693 (PvuII) and A allele of rs53576 (OXTR) polymorphisms (T + A group) was correlated with increased arousal, orgasm levels as well as female sexual function index full score. To our knowledge, this is the first study to investigate the interaction between ERA and OXTR with regard to sexual function in women. Female sexuality is a complex behavioral trait that encompasses both biological and psychological components. It seems that variability in female sexual response stems from genetic variability that characterizes endocrine, neurotransmitter and central nervous system influences.
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CZARNY, Ryszard. „RELATION BETWEEN SHEAR STRESS AND SHEARING TIME IN SELECTED LUBRICANT COMPOSITIONS“. Tribologia 279, Nr. 3 (01.07.2018): 25–33. http://dx.doi.org/10.5604/01.3001.0012.7004.
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The paper presents the results of studies of the influence of fillers introduced into lubricating greases on changes in values of shear stresses in resulting lubricant compositions. These fillers were powders of graphite, molybdenum disulphide, and PTFE. They are added to grease to improve their tribological properties. They also impact the rheological properties of lubricating compositions, especially on the course of the shear stress, whose value decreases with the duration of the flow of these compositions. Knowledge of changes in the value of this stress is essential in designing central lubrication systems in which these compositions may be used. Tests were performed on lithium grease without fillers as well as on a composition of this grease with the fillers mentioned above. Measurements were carried out using a Rheotest 2.1 rheometer by changing the shearing time at selected gradients of shear rate. Test results have shown that both the kind of filler and the shearing time have an impact on the value of shear stress in the tested lubricant composition.
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Kodnyanko, Vladimir, Stanislav Shatokhin, Andrey Kurzakov, Yuri Pikalov, Iakov Pikalov, Olga Grigorieva, Lilia Strok und Maxim Brungardt. „Numerical Modeling on the Compliance and Load Capacity of a Two-Row Aerostatic Journal Bearing with Longitudinal Microgrooves in the Inter-Row Zone“. Applied Sciences 11, Nr. 12 (20.06.2021): 5714. http://dx.doi.org/10.3390/app11125714.
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Aerostatic bearings are attractive, with minimal friction losses, high durability, and environmental friendliness. However, such designs have a number of disadvantages, including low load-bearing capacity and high compliance due to high air compressibility and limited injection pressure. The article proposes a double-row aerostatic journal bearing with an external combined throttling system and longitudinal microgrooves in the inter-row zone. It is hypothesized that the use of microgrooves will reduce the circumferential flows of compressed air, as a result of which the compliance should decrease and the bearing capacity should increase. To test the hypothesis, we carried out the mathematical modeling, calculations, and theoretical study of stationary operation modes of the bearing for small shaft eccentricities in the vicinity of the central equilibrium position of the shaft and bearing capacity for arbitrary eccentricities. Formulas were obtained for the numerical evaluation of compliance for bearings with a smooth bushing surface and with longitudinal microgrooves. Iterative finite-difference methods for evaluating the fields of the squared pressure are proposed, on the basis of which the load capacity of the bearings is calculated. Experimental verification of the bearing’s theoretical characteristics was carried out, which showed satisfactory agreement between the compared data. The study of the compliance and load capacity of a microgroove bearing yielded impressive results. We show that the positive effect from the application of the improvement begins to manifest itself already at four microgrooves; the effect becomes significant at six microgrooves, and at twelve or more microgrooves, the circumferential flows in the bearing gap practically disappear; therefore, the bearing characteristics can be calculated on the basis of one-dimensional models of air lubrication longitudinal flow. Calculations have shown that for a length of L = 1, the maximum load capacity of a bearing with microgrooves is 1.5 times higher than that of a conventional bearing; for L ≥ 1.5, the bearing capacity increases twice or more. The result obtained allows us to recommend the proposed improvement for practical use in order to increase the load capacity of aerostatic journal bearings significantly.
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Kumar, Niraj, und Punit Kumar. „New equations for enhanced film thickness in line contacts under pressurized ambient conditions“. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 231, Nr. 5 (05.09.2016): 616–22. http://dx.doi.org/10.1177/1350650116667345.
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An elastohydrodynamic lubrication model is proposed for line contacts under pressurized ambient conditions often encountered in hydraulic pumps, submarine machinery and many other submerged systems. It has been demonstrated that the film forming behavior under such conditions is essentially different from that in conventional elastohydrodynamic lubrication contacts. The numerical simulation results are regressed to develop new central and minimum film thickness equations for Newtonian fluids as functions of ambient pressure, speed, load, and material parameters. An alternative approach is also discussed which involves the use of existing film thickness formulas with ambient viscosity and pressure–viscosity coefficient pertaining to the desired pressure range. A film thickness enhancement of more than 100% over conventional elastohydrodynamic lubrication case is observed. This enhancement is shown to be highly sensitive to the pressure–viscosity coefficient. Besides, the effect of shear-thinning behavior is also investigated and it is found to lower the film thickness enhancement, especially at high ambient pressures.
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Chandran Suja, V., A. Kar, W. Cates, S. M. Remmert, P. D. Savage und G. G. Fuller. „Evaporation-induced foam stabilization in lubricating oils“. Proceedings of the National Academy of Sciences 115, Nr. 31 (16.07.2018): 7919–24. http://dx.doi.org/10.1073/pnas.1805645115.
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Foaming in liquids is ubiquitous in nature. Whereas the mechanism of foaming in aqueous systems has been thoroughly studied, nonaqueous systems have not enjoyed the same level of examination. Here we study the mechanism of foaming in a widely used class of nonaqueous liquids: lubricant base oils. Using a newly developed experimental technique, we show that the stability of lubricant foams can be evaluated at the level of single bubbles. The results obtained with this single-bubble technique indicate that solutocapillary flows are central to lubricant foam stabilization. These solutocapillary flows are shown to originate from the differential evaporation of multicomponent lubricants—an unexpected result given the low volatility of nonaqueous liquids. Further, we show that mixing of some combinations of different lubricant base oils, a common practice in the industry, exacerbates solutocapillary flows and hence leads to increased foaming.
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Molokov, Nikolai Sergeevich, Gennadiy Petrovich Kicha und Andrei Veniaminovich Nadezkin. „Influence of lubricating oil centrifugal separation intensity in combined cleaning systems on marine diesel engine“. Vestnik of Astrakhan State Technical University. Series: Marine engineering and technologies 2020, Nr. 3 (19.08.2020): 23–32. http://dx.doi.org/10.24143/2073-1574-2020-3-23-32.
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The article considers the rationality of combined lubricating oil cleaning system in the automatically operated marine diesel engines. The system includes a self-recovering filter and
a self-cleaning centrifugal purifier. This combination is found to obtain resource-saving oil using coupled with minimum engine wear and increased reliability. The full-flow filtration of oil in a die-sel engine lubricating system is necessary to protect its friction couples (bearings) from abrasive wear. Centrifugal separation contributes deep oil purification i.e. removal of insoluble impurities reducing lubricating oil service life. By means of experimental simulation there has been found
a minimum value of centrifugal purifier capacity index, when engine wear reaches the lowest level and keeps stable. The dependence of engine wear on the fuel quality and centrifugal purification intensity represented by centrifugal purifier capacity index is displayed. The adequacy variance was calculated, the adequacy of the found model being checked by using Fisher criterion. The experimental design and processing of the results have been carried out using orthogonal central composite plan of the second order. Specificity of polynomial when all the points of extremum show the minimum value of engine wear was presented. The model is designed to select the proper oil purifier for forced marine diesel engines with average and increased revolutions.
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Rowland, David L. „Neurobiology of Sexual Response in Men and Women“. CNS Spectrums 11, S9 (2006): 6–12. http://dx.doi.org/10.1017/s1092852900026705.
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AbstractSexual desire, arousal, and orgasm are mediated by complex—and as yet not fully understood—interactions of the somatic and autonomic nervous systems, operating at cerebral, spinal, and peripheral levels. Furthermore, neural activity within these systems is modulated by the presence of steroid and peptide hormones, which affect male and female response differentially. At the central level, dopaminergic and serotonergic systems appear to play a significant role in various components of sexual response, although adrenergic, cholinergic, nitergic, γ-aminobutyric acidergic, and other neuropeptide transmitter systems may contribute as well. At the peripheral level, adrenergic, cholinergic, and nitergic activation mechanisms control vascular changes that underlie vaginal lubrication and penile erection. In addition, these systems respond to descending brain and spinal influences that generate orgasmic response. Disruption of endocrine, neural, or vascular response—caused by aging, disease, surgery, or medication—has the potential to lead to sexual inadequacy. At the same time, psychological and relationship factors play an important role in healthy sexual response and may enhance or impair sexual functioning.
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Okokpujie, Imhade Princess, und Lagouge Kwanda Tartibu. „Performance Investigation of the Effects of Nano-Additive-Lubricants with Cutting Parameters on Material Removal Rate of AL8112 Alloy for Advanced Manufacturing Application“. Sustainability 13, Nr. 15 (28.07.2021): 8406. http://dx.doi.org/10.3390/su13158406.
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The implementation of nano-additives in machining fluid is significant for manufacturers to attain a sustainable manufacturing process. The material removal rate (MRR) is a significant process of transforming solid raw materials into specific shapes and sizes. This process has many challenges due to friction, vibration, chip discontinuity when machining aluminum alloy, which has led to poor accuracy and affected the fatigue life of the developed material. It is worth noting that aluminum 8112 alloy is currently being applied in most engineering applications due to its lightweight-to-strength ratio compared to some other metals. This research aims to compare the effects of copra oil-based-titanium dioxide (TiO2)- and Multi-walled Carbon Nanotubes (MWCNTs)-nano-lubricant with cutting parameter interactions by conducting a study on MRR for advanced machining of aluminum 8112 alloys. The biodegradable nano-additive-lubricants were developed using two-step preparation techniques. The study employed a quadratic rotatable central composite design (QRCCD) to carry out the interaction study of the five machining parameters in the three lubrication environments on MRR. The results show that the copra-based-TiO2 nano-lubricant increases the MRR by 7.5% and 16% than the MWCNTs and copra-oil-lubrication machining environments, respectively. In conclusion, the eco-friendly nano-additive-lubricant TiO2-Copra oil-based should be applied to manufacture machine parts for high entropy applications for sustainable production systems.
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Chappie, P. J. „Modelling of a Radial-Piston Hydraulic Motor“. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 206, Nr. 3 (August 1992): 171–80. http://dx.doi.org/10.1243/pime_proc_1992_206_328_02.
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The paper is concerned with the theoretical modelling of the torque-producing mechanism in a radial-piston, eccentric-type, hydraulic motor for low-speed operation. The major difficulty in such an analysis is the description of the frictional losses which, at low speeds, principally result from boundary lubrication conditions. The level of friction is also dependent on the distribution of the transferred forces and the amount of distortion in the bearings These forces vary during the pressure cycle, and squeeze-film effects are introduced between the bearing faces during the period of time following the introduction of pressure into the cylinder. The interaction between the frictional effect in the connecting rod bearing and the operation of the hydrostatic slipper is central to the modelling process. Friction coefficients in the bearings are determined that predict similar efficiencies to those obtained from test measurements on a low-speed motor. The evaluation of internal motor parameters is then carried out using these coefficient values in the model. Such a model is invaluable for establishing critical areas in the mechanism and for predicting the effect of component design changes on the motor performance.
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Glennie, Simon, Tom Leeson, Ian Rowson und Bevan Morrison. „Rigless well intervention and trees on wire from a DPII vessel: a case study“. APPEA Journal 49, Nr. 2 (2009): 564. http://dx.doi.org/10.1071/aj08037.
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The Vincent field development is typical subsea development with 11 subsea wells required to be tied back to a central production facility. In 350–400 m of water all subsea operations would be diver-less and the well costs associated with using a semi-submersible rig would be a major element of the total field cost. Sequencing construction vessel and drill rig activities, and aligning this sequence with availability of suitable vessels is often a major challenge on such projects. This was accentuated on this development by the shortage of suitable vessels. In addition to this, multiple mobilisations—potentially incorporating lengthy, expensive transits from Singapore—drove a desire to minimise the use of specialist vessels. The challenges in reducing well costs by using rigless operations are both technical and commercial. Technically, the operations and proposed equipment must be matched to the capabilities and functionality of the vessel. Commercially, sufficient work needs to be identified to justify the one-off costs of preparing and mobilising the vessel and equipment, preparing the operations program, and training and familiarising the personnel. In this instance, the operator identified sufficient work to make the vessel mobilisation and equipment preparation worthwhile while not committing to a long-term deployment. Recognising the multi-role capability of the vessel permitted additional work on nearby assets. These removed the need to mobilise additional vessels to the field and improved vessel’s economy in well intervention mode. Other factors that ensured value was gained from the rigless approach included: the rig schedule being de-coupled from product delivery; the drilling program with limited drilling assets was accelerated, protecting first oil; and, the need to re-configure or modify a rig for Xmas tree (XT) handling was removed. Initial preparations for the planned operations began in the latter part of 2006. The main activities were to: confirm the specification of the subsea lubricator system and its deployment system; undertake a detailed hazard and risk assessment process on all operations; undertake an operability study for crane and deployment system; complete the modifications to the vessel for its intervention role; and, prepare detailed well programs and procedures for equipment operation. The design and fabrication of project-specific interface equipment between the subsea lubricator and the subsea Xmas trees, and specification of the required well services equipment such as wireline, pumping and fluid handling services were also required. As this represented the first time such operations had been undertaken in the region by the contractor or by the operator, a large number of supporting systems were required to be developed, adopted and managed, most notably: well control and barrier philosophies; emergency shutdown and disconnection (ESD) philosophy; project management processes; and, personnel training and familiarisation programs.
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Радченко, Андрій Миколайович, Анатолій Анатолійович Зубарєв, Сергій Георгійович Фордуй, Володимир Володимирович Бойчук und Віталій Васильович Цуцман. „АНАЛІЗ ЕФЕКТИВНОСТІ ОХОЛОДЖЕННЯ ПОВІТРЯ КОГЕНЕРАЦІЙНОГО ГАЗОПОРШНЕВОГО МОДУЛЯ УСТАНОВКИ АВТОНОМНОГО ЕНЕРГОЗАБЕЗПЕЧЕННЯ“. Aerospace technic and technology, Nr. 7 (31.08.2019): 76–80. http://dx.doi.org/10.32620/aktt.2019.7.10.
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The analysis of the efficiency of cooling air of cogeneration gas-piston module of installations for combined production of electric energy, heat, and cold is performed. The installation for energy supply includes two JMS 420 GS-N.LC GE Jenbacher cogeneration gas-piston engines manufactured as cogeneration modules with heat exchangers for removing the heat of exhaust gases, scavenge gas-air mixture, cooling water of engine and lubricating oil. The heat of hot water is transformed by the absorption lithium-bromide chiller AR-D500L2 Century into the cold, which is spent on technological needs and for the operation of the central air conditioner for cooling the incoming air of the engine room, wherefrom it is sucked by the turbocharger of the engine. The temperature of the scavenge gas-air mixture at the entrance to the working cylinders of the engine is maintained by the system of recirculating cooling with the removal of its heat into surroundings by the radiator. Because of significant heat influx from working engines and other equipment, as well as through the enclosures of the engine room from the outside to the air-cooled in the central air conditioner in the engine room, from where it is sucked by a turbocharger, the air temperature at the inlet of the turbocharger is quite high: 25...30 °C. At elevated temperatures of the ambient air at the inlet of the radiator for cooling scavenge gas-air mixture and the air at the turbocharger inlet the fuel economy of engine is falling, which indicates the need for efficient cooling of air. The efficiency of cooling the air of the gas-piston module was estimated by a reduction in the consumption of gaseous fuel and the increase in electric power of the engine. For this purpose, the data of monitoring on the fuel efficiency of the gas-piston engine with the combined influence of the ambient air temperature at the inlet of the radiator and the air at the turbocharger inlet were processed to obtain data on their separate effects and to determine the ways to further improve the air cooling system of the gas-piston module.
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Радченко, Андрій Миколайович, Анатолій Анатолійович Зубарєв, Сергій Георгійович Фордуй, Володимир Володимирович Бойчук und Андрій Вікторович Коновалов. „АНАЛІЗ ЕФЕКТИВНОСТІ ОХОЛОДЖЕННЯ ПОВІТРЯ НА ВХОДІ КОГЕНЕРАЦІЙНОГО ГАЗОПОРШНЕВОГО МОДУЛЯ НА ЧАСТКОВИХ НАВАНТАЖЕННЯХ“. Aerospace technic and technology, Nr. 8 (31.08.2019): 54–58. http://dx.doi.org/10.32620/aktt.2019.8.08.
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The fuel efficiency of the reciprocating gas engine deteriorates with the increase of ambient air temperatures at the inlet to the radiator of the recirculating cooling water system for cooling the scavenge gas/air mixture at the inlet of the working cylinders and the air at the inlet of the scavenge air turbocharger. The peculiarity of cogeneration reciprocating gas modules of plants for combined production of electricity, heat, and cold is the operation mainly at partial loads according to the schedules of consumption of electricity, heat, and cold. The efficiency of cooling air of cogeneration gas module on the partial loads was analyzed on the example of an integrated power supply installation, which includes two cogeneration reciprocating gas engines JMS 420 GS-N.LC GE Jenbacher, manufactured as the cogeneration modules with exchangers using the heat of exhaust gases, scavenge gas-air mixture, cooling water of the engine shirt and lubricating oil for heating water. Hot water heat is transformed by the AR-D500L2 Century absorption lithium-bromide chiller into a cold that is spent on technological needs and for the operation of a central air conditioner that cools the engine room income air from where it is sucked by a scavenge air turbocharger. Because of significant heat influx from working engines and other equipment, as well as through the enclosures of the engine room from the outside to the air-cooled in the central air conditioner in the engine room, from where it is sucked by a turbocharger, the air temperature at the inlet of the turbocharger is quite high: 25...30 °C. At elevated temperatures of the ambient air at the inlet of the radiator for cooling scavenge gas-air mixture and the air at the turbocharger inlet the fuel economy of engine is falling, which indicates the need for efficient cooling of air. The efficiency of cooling the air of the reciprocating gas module was estimated by a reduction in the consumption of gas fuel and an increase in electric power of the engine. For this purpose, the data of monitoring on the fuel efficiency of the reciprocating gas engine with the combined influence of the ambient air temperature at the inlet of the radiator and the air at the turbocharger inlet were processed to obtain data on their separate effects and to determine the ways to further improve the air cooling system of the reciprocating gas module.
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Фордуй, Сергій Георгійович, Андрій Миколайович Радченко, Анатолій Анатолійович Зубарєв, Володимир Володимирович Бойчук und Олексій Валерійович Остапенко. „РЕЗЕРВИ ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ТРАНСФОРМАЦІЇ ТЕПЛОТИ УСТАНОВКИ АВТОНОМНОГО ЕНЕРГОЗАБЕЗПЕЧЕННЯ“. Aerospace technic and technology, Nr. 4 (31.08.2019): 25–30. http://dx.doi.org/10.32620/aktt.2019.4.05.
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It is analyzed the efficiency of heat conversion in the integrated electricity, heat and cooling supply of the enterprise. The installation for energy supply includes two JMS 420 GS-N.LC GE Jenbacher cogeneration gas engines manufactured as cogeneration modules with heat exchangers for removing the heat of exhaust gases, scavenge gas-air mixture, cooling water of engine and lubricating oil. The heat of hot water is transformed by the absorption lithium-bromide chiller AR-D500L2 Century into the cold, which is spent on technological needs and for the operation of the central air conditioner for cooling the incoming air of the engine room, where from it is sucked by the turbocharger of the engine. The presence of significant heat losses, which account for about 30% of the total heat removed from the cogeneration gas piston module and is due to the inconsistency of the joint operation modes of the absorption lithium-bromide chiller and the gas piston engine, was revealed. This inconsistency is caused by the contradictory conditions of their effective operation according to the temperature of the return coolant at the outlet of the absorption lithium-bromide chiller and the entrance to the engine cooling system. The thermal state of the gas piston engine is ensured by maintaining the temperature of the return coolant at the entrance to it is not higher than 70 °C. At the same time, during the transformation of the heat of the coolant into the cold in an absorption lithium-bromide chiller, the temperature decreasing in the machine is no more than 10 ... 15 °С, that is, up to 75 ... 80 °С, if the temperature of the heat coolant outlet from the cogeneration gas piston module, i.e. at the inlet of the absorption lithium-bromide chiller, 90 °С. Therefore, the return coolant is additionally cooled in the "emergency heat release" radiator by removing its heat into surroundings. It is shown the possibility of increasing the cooling capacity of the system by conversion of the return coolant exhaust heat into cold in absorption lithium-bromide and ejector chillers through the data procession of monitoring the heat conversion system in the integrated energy plant.
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Вержбицкий, А. Н., und М. Г. Лахтюхов. „Lubrication system of central gearboxes of the axle drive gear“. Engineering Journal: Science and Innovation, Nr. 25 (Dezember 2013). http://dx.doi.org/10.18698/2308-6033-2013-12-1126.
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Chu, Li-Ming, Chi-Chen Yu, Qie-Da Chen und Wang-Long Li. „Elastohydrodynamic Lubrication Analysis of Pure Squeeze Motion on an Elastic Coating/Elastic Substrate System“. Journal of Tribology 137, Nr. 1 (01.01.2015). http://dx.doi.org/10.1115/1.4028916.
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A rigid sphere approaching a lubricated flat surface with a layer of elastic coating on the elastic substrate is explored under constant load conditions. The transient pressure profiles, film shapes, elastic deformation, von Mises stress (σvon) during the pure squeeze process under various operating conditions in the elastohydrodynamic lubrication (EHL) regime are discussed. The simulation results reveal that the greater the Young's modulus of coating is, the greater the pressure distribution is, the smaller the contact area is, and the greater the maximum stress (σvon) value is. As the Young’s modulus of coating decreases, the central elastic deformation at the surface (Z = 0) increases and the deformation at the interface of coating/substrate (Z = −1) decreases. For hard coating cases, the maximum central pressure increases to an asymptotic value and minimum film thickness decreases to an asymptotic value as the coating thickness increases. For soft coating cases, this phenomenon reverses. A thicker and stiffer coating leads to a higher maximum stress. At the deformation recovery stage, the positions of the maximum stress would begin to offset downwards and closer to the coating/substrate interface. Moreover, the position of maximum stress varies from the coating to the subsurface as the Young’s modulus of coating increases. The EHL with stress analysis can prevent the chance of fracture in coating or substrate. These characteristics are important for the lubrication design of mechanical elements with coatings.
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Park, K., A. Tixier, A. H. Christensen, S. F. Arnbjerg-Nielsen, M. A. Zwieniecki und K. H. Jensen. „Viscous flow in a soft valve“. Journal of Fluid Mechanics 836 (11.12.2017). http://dx.doi.org/10.1017/jfm.2017.805.
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Fluid–structure interactions are ubiquitous in nature and technology. However, the systems are often so complex that numerical simulations or ad hoc assumptions must be used to gain insight into the details of the complex interactions between the fluid and solid mechanics. In this paper, we present experiments and theory on viscous flow in a simple bioinspired soft valve which illustrate essential features of interactions between hydrodynamic and elastic forces at low Reynolds numbers. The set-up comprises a sphere connected to a spring located inside a tapering cylindrical channel. The spring is aligned with the central axis of the channel and a pressure drop is applied across the sphere, thus forcing the liquid through the narrow gap between the sphere and the channel walls. The sphere’s equilibrium position is determined by a balance between spring and hydrodynamic forces. Since the gap thickness changes with the sphere’s position, the system has a pressure-dependent hydraulic resistance. This leads to a nonlinear relation between applied pressure and flow rate: flow initially increases with pressure, but decreases when the pressure exceeds a certain critical value as the gap closes. To rationalize these observations, we propose a mathematical model that reduced the complexity of the flow to a two-dimensional lubrication approximation. A closed-form expression for the pressure drop/flow rate is obtained which reveals that the flow rate $Q$ depends on the pressure drop $\unicode[STIX]{x0394}p$, sphere radius $a$, gap thickness $h_{0}$, and viscosity $\unicode[STIX]{x1D702}$ as $Q\sim \unicode[STIX]{x1D702}^{-1}a^{1/2}h_{0}^{5/2}(1-\unicode[STIX]{x0394}p/\unicode[STIX]{x0394}p_{c})^{5/2}\unicode[STIX]{x0394}p$, where the critical pressure $\unicode[STIX]{x0394}p_{c}$ scales with the spring constant $k$ as $\unicode[STIX]{x0394}p_{c}\sim kh_{0}a^{-2}$. These predictions compared favourably to the results of our experiments with no free parameters.
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Maiti, Giridas, und Nibir Mandal. „Early Miocene Exhumation of High-Pressure Rocks in the Himalaya: A Response to Reduced India-Asia Convergence Velocity“. Frontiers in Earth Science 9 (26.02.2021). http://dx.doi.org/10.3389/feart.2021.632806.
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Low-viscosity channel flow, originating from a melt-weakened mid-crustal layer, is one of the most popular tectonic models to explain the exhumation of deep-seated rocks in the Greater Himalayan Sequence (GHS). The driving mechanism of such channel flow, generally attributed to focused erosion in the mountain front, is still debated, and yet to be resolved. Moreover, the channel flow model cannot explain eclogites in the GHS. In this study, we present a new two-dimensional thermo-mechanical numerical model, based on lubrication dynamics to demonstrate the exhumation process of deep crustal rocks in GHS. The model suggests that a dynamic-pressure drop in the Himalayan wedge, following a large reduction in the India-Asia convergence velocity (15 cm/yr at 50 Ma to nearly 5 cm/yr at ∼22 Ma) localized a fully developed extrusion zone, which controlled the pressure-temperature-time (P-T-t) path of GHS rocks. We show that the wedge extrusion, originated in the lower crust (∼60 km), was initially bounded by two oppositely directed ductile shear zones: the South Tibetan Detachment systems (STDS) at the top and the Higher Himalayan Discontinuity (HHD) at the bottom. With time the bottom shear boundary of the extrusion zone underwent a southward migration, forming the Main Central Thrust (MCT) at ∼17 Ma. Our model successfully reproduces two apparently major paradoxical observations in the Himalaya: syn-convergence extension and inverted metamorphic isograds. Model peak P (10–17 kb) and T (700–820°C) and the exhumation P-T-t path estimated from several Lagrangian points, traveling through the extrusion zone, are largely compatible with the petrological observations in the GHS. The model results account for the observed asymmetric P-T distribution between the MCT and STDS, showing peak P-T values close to the MCT. The lubrication dynamics proposed in this article sheds light on the fast exhumation event (>1 cm/yr) in the most active phase of crustal extrusion (22-17 Ma), followed by a slowed-down event. Finally, our model explains why the extrusion zone became weak in the last 8-10 Ma in the history of India-Asia collision.
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Gayathri, N., G. Premnath, S. Kiruthika, Mano j. Vasudevan und Geeta Anusha Loya. „Lagophthalmos- A Rare Presenting Sign in a Case of Childhood Pontine Glioma“. JOURNAL OF CLINICAL AND DIAGNOSTIC RESEARCH, 2020. http://dx.doi.org/10.7860/jcdr/2020/44925.13967.
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Brain stem glioma is a rare central nervous system tumour arising from glial cells which occur mostly in children. Diffuse Intrinsic Pontine Gliomas (DIPG) and Focal glioma are the two types of pontine glioma. DIPGs are highly aggressive. The clinical features are not the same in every child. It commonly has a grave prognosis as most children die within 18 months of diagnosis. Hereby, Authors present a case of 10-year-old male child complaining of watering from the left eye for four days. There was no history suggesting involvement of any other cranial nerves and there was no episode of any seizure or similar history. On examination patient was found to have left lagophthalmos. Magnetic Resonance Imaging (MRI) of brain showed features of pontine glioma with mass effect. To prevent exposure keratopathy, the child was started on lubricating drops/gel and lid taping and referred immediately to a cancer centre for further management. Patients with pontine gliomas usually complain of gait disturbance, headache, limb weakness and double vision. To Authors’ knowledge no other documented case has presented with lagophthalmos. This case is presented for the rarity of the presenting symptom and to stress the importance of picking early ophthalmic signs.