Mean- Field Approximation and a Small Parameter in Turbulence Theory

Numerical and physical experiments on two-dimensional (2d) turbulence show that the differences of transverse components of velocity field are well described by a gaussian statistics and Kolmogorov scaling exponents. In this case the dissipation fluctuations are irrelevant in the limit of small viscosity. In general, one can assume existence of critical space-dimensionality $d=d_{c}$, at which the energy flux and all odd-order moments of velocity difference change sign and the dissipation fluctuations become dynamically unimportant. At $d<d_{c}$ the flow can be described by the ``mean-field theory'', leading to the observed gaussian statistics and Kolmogorov scaling of transverse velocity differences. It is shown that in the vicinity of $d=d_{c}$ the ratio of the relaxation and translation characteristic times decreases to zero, thus giving rise to a small parameter of the theory. The expressions for pressure and dissipation contributions to the exact equation for the generating function of transverse velocity differences are derived in the vicinity of $d=d_{c}$. The resulting equation describes experimental data on two-dimensional turbulence and demonstrate onset of intermittency as $d-d_{c}>0$ and $r/L\to 0$ in three-dimensional flows in close agreement with experimental data. In addition, some new exact relations between correlation functions of velocity differences are derived. It is also predicted that the single-point pdf of transverse velocity difference in developing as well as in the large-scale stabilized two-dimensional turbulence is a gaussian.Comment: 25 pages, 1 figur

The Clusters Self-Assembled Crystal and Magnetic Structure During the Martensite Transition in Fe86mn13c Alloy

In bulk and thin film state Fe86Mn13C alloy observed experimentally self-assembly of the crystal and magnetic structures on multiscale levels. Offered self-assembly cluster model of atomic structure based on the concept of a liquid-like state of the material in localized areas, formed in the waves of plastic deformation

The Clusters Self-Assembled Crystal and Magnetic Structure During the Martensite Transition in Fe86mn13c Alloy

In bulk and thin film state Fe86Mn13C alloy observed experimentally self-assembly of the crystal and magnetic structures on multiscale levels. Offered self-assembly cluster model of atomic structure based on the concept of a liquid-like state of the material in localized areas, formed in the waves of plastic deformation

Кластерная самоорганизация кристаллической и магнитной структур в процессе мартенситного превращения в сплаве Fe86Mn13C

In bulk and thin film state Fe86Mn13C alloy observed experimentally self-assembly of the crystal and magnetic structures on multiscale levels. Offered self-assembly cluster model of atomic structure based on the concept of a liquid-like state of the material in localized areas, formed in the waves of plastic deformationВ массивных и тонкопленочных образцах сплава Fe86Mn13C экспериментально наблюдается самоорганизация кристаллической и магнитной структур на разномасштабных уровнях. Предлагается кластерная модель атомной самоорганизации, основанная на концепции жидкоподобного состояния материала в локальных участках, образованных волнами пластической деформаци

Infrared photoluminescence from GeSi nanocrystals embedded in a germanium-silicate matrix.

Équipe 104 : NanomatériauxInternational audienceWe investigate the structural and optical properties of GeO/SiO multilayers obtained by evaporation of GeO and SiO powders under ultrahigh vacuum conditions on Si(001) substrates. Both Raman and infrared absorption spectroscopy measurements indicate the formation of GeSi nanocrystals after postgrowth annealing at 800°C. High-resolution transmission electron microscopy characterizations show that the average size of the nanocrystals is about 5 nm. For samples containing GeSi nanocrystals, photoluminescence is observed at 14 K in the spectral range 1500-1600 nm. The temperature dependence of the photoluminescence is studied

Кластерная самоорганизация кристаллической и магнитной структур в процессе мартенситного превращения в сплаве Fe86Mn13C

In bulk and thin film state Fe86Mn13C alloy observed experimentally self-assembly of the crystal and magnetic structures on multiscale levels. Offered self-assembly cluster model of atomic structure based on the concept of a liquid-like state of the material in localized areas, formed in the waves of plastic deformationВ массивных и тонкопленочных образцах сплава Fe86Mn13C экспериментально наблюдается самоорганизация кристаллической и магнитной структур на разномасштабных уровнях. Предлагается кластерная модель атомной самоорганизации, основанная на концепции жидкоподобного состояния материала в локальных участках, образованных волнами пластической деформаци