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Vestnik NSU. Series: Physics. 2015. V10, i 1 |
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Physics of Field, Neutral and Ionized Gases |
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Rudyak V. Ya. Modern Status of Researches of Nanofluids Viscosity In present paper the regular review of researches of nanofluids viscosity is made. Known experimental data and data of molecular dynamic simulation are considered. It is shown, that nanofluid viscosity is not described by the classical theories. All experimental data and molecular dynamics simulations suggest that at a fixed volume concentration of nanoparticles, the nanofluid viscosity is significantly higher than the viscosity of conventional suspensions. Generally it depends not only on concentration наночастиц, but also from their size. The viscosity coefficients increase with decreasing nanoparticle size. It was shown by molecular dynamics method that the viscosity coefficient of nanofluid depends on the nanoparticles material. At low and moderate concentrations of nanoparticles, the relative viscosity coefficient does not change with increasing temperature. In this case the temperature dependence of nanofluid viscosity is determined by the corresponding dependence of based fluid. The nanofluid prepared on distilled water with CuO nanoparticles has the non-Newtonian rheology if the concentration of the particles is more than 0.25 in the volume. It was established that their rheology is well described by the power law fluid model. With an increase in concentration of nanoparticles, nanofluid index decreases, but the consistency parameter K, on the contrary, increases. The correlation defining dependence of the viscosity coefficient on nanoparticles concentration and their size is offered. The reasons of nonclassical behavior of nanofluids are in detail discussed. |
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Litvinenko М. V., Litvinenko Yu. А., Vikhorev V. V. Hot-Wire Measurements on the Round Jet Formed by Curved Pipe The results of experimental studies of round jet formed by a curved pipe are presented. The hot-wire measurements of three-dimensional profile of mean and fluctuating streamwise mean velocity components at the nozzle outlet and downstream. The effect of Dean vortices on the jet development are shown. The frequency spectrum for some cross-sections are analyzed. The receptivity of the jet to the low-frequency part of the spectrum are shown. |
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Pavlenko A. N., Volodin O. A., Serdyukov V. S. The Features of the Film Flow of Liquid Nitrogen over the Structured Surfaces Experimental results on hydrodynamics of cryogenic liquid film flow over the surface of the single elements of the structured packing are presented. Based on the comparison of experimental data, the effect of microtexture and perforation on the zones of liquid film spreading over a corrugated surface is shown for different values of the film Reynolds number. The results of experiments on dependence of a relative portion of liquid held in a single irrigated channel of the corrugated plates with different thicknesses on irrigation degree are presented. It is shown that microtexture, its direction relative to the gravity has a significant effect on redistribution of the local flow rate of liquid flowing over the surface with complex geometry. |
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Pavlenko A. N., Volodin O. A., Serdyukov V. S. Effect of the Rib Inclination Angle on Liquid Film Spreading over the Structured Surface Results of experimental studies on hydrodynamics of the film flow of liquid nitrogen over the surface of the single elements of structured packing are presented. The effect of inclination angle of the large ribs and perforation on the zones of liquid film spreading over the corrugated surface with microtexture at different Reynolds numbers of the film is shown based on a comparison of experimental data. It is shown that the angle of large rib inclination has a significant influence on redistribution of the local flow rate of liquid flowing on the surface with complex geometry. Analysis of results of the high-speed video revealed that in a vicinity of the vertical lateral edges of corrugated plates, the intense rivulet flows are formed, including those with separation from the film flow surface. This negative factor can lead to significant liquid accumulation and flow near the vertical edges of the structured packing and on the inner wall of the heat exchanging apparatuses and, finally, to a significant increase in the degree of maldistribution of local liquid flow rate over the crosssection, for instance, of the distillation columns. |
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Solid-State and Semiconductor Physics, Physics of Nanostructures |
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Kuz’min V. I., Nikolaev S. V. Investigation of Anomalies in the Electronic Dispersion of the Hubbard Model, t–J and t–J* Models within the Cluster Perturbation Theory in the X-Operator Representation The electronic structure with the spectral line broadening corresponding to the angle-resolved photoemission spectroscopy
resolution has been calculated for the Hubbard model, t–J and t–J* models within the norm-conserving cluster perturbation
theory. The electronic dispersion anomalies similar to the high-energy kinks observed in the angle-resolved photoemission
spectroscopy experiments are obtained at the energy scale of order of the hopping integral t. The doping
dependence of the high-energy anomalies for different Coulomb repulsion values is discussed. The influence of the threesite |
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Savelkaev S. V., Airapetyan V. S., Litovchenko V. A. Three Sectional Drift-Diffusion Mathematical Model of the Field Effect Transistor with a Schottky Barrier Three sectional drift-diffusion mathematical model of the field effect transistor with a Schottky barrier is proposed. It
takes into account the accumulation of charge carriers in the additionally introduced third section, which significantly |
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Nikitin S. E., Popkov S. I., Petrov M. I., Terent’ev K. Yu., Semenov S. V., Shaikhutdinov K. A. Features of Magnetoresistance in the Bilayer Single Crystal Manganite La1,4Sr1,6Mn2O7 We investigate magnetoresistance of single-crystal bilayer lanthanum manganite La1,4Sr1,6Mn2O7 at a transport current flowing along the crystal c axis and in external magnetic fields applied parallel to the crystal c axis or ab plane. It is demonstrated that the La1,4Sr1,6Mn2O7 manganite exhibits the positive magnetoresistance effect in the magnetic field applied in the ab plane of the sample at the temperatures T < 60 K. The mechanism of this effect is shown to be fundamentally different from the colossal magnetoresistance effect typical of lanthanum manganites. The positive magnetoresistance originates from spin-dependent tunneling of carriers between the manganese-oxygen bilayers and can be explained by features of the magnetic structure of the investigated compounds. |
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