The analysis presented in [1, 2] is extended to sedimenting low-inertia tracers advected by random divergence-free hydrodynamic flows. The key feature of the process is the clustering of the tracers due to the divergence of tracer-velocity field. This phenomenon has probability one; i.e., it takes place in almost every realization of the process. Both spatial diffusivity and diffusivity in the density space (responsible for clustering) are calculated. The low inertia of the tracers does not affect the spatial diffusivity. The indispensable use of a finite velocity correlation time leads to an anisotropic spatial diffusivity. The calculations performed in the study are based on a diffusion approximation. 相似文献
The Green’s function method is used to derive general equations for describing effects of pairing in Fermi systems where there are two types of interaction, two-particle and quasiparticle-phonon interaction. These equations generalize Bardeen-Cooper-Schrieffertheory to the case of complex configurations involving “strong” phonons. In the approximation of weak coupling to phonons, realistic equations that make it possible to describe excited states of nonmagic even-even nuclei with allowance for a single-particle continuum and complex configurations of the two quasiparticles ? phonon type are formulated for the first time. These equations are solved for an isovector E 1 resonance in the stable isotope 120 Sn and in the unstable isotopes 104,132Sn. It is shown that complex configurations must be taken into account in order to describe E1 excitations—in particular, in a broad energy region around the nucleon binding energy.
Different techniques for the fabrication of structures containing ensembles of ultrasmall germanium nanoclusters distributed with a high density over the substrate surface are discussed. How to control the morphology and ordering of these ensembles is also discussed. 相似文献
Single crystals of lead gallium germanate Pb3Ga2Ge4O14 are grown from their own solution melts. The propagation of bulk acoustic waves is investigated, and the elastic, piezoelectric, and dielectric constants are calculated. The temperature dependences of the dielectric constants of this compound are analyzed. 相似文献
The main theoretical aspects of detonation decomposition of powerful mixed explosives with a negative oxygen balance accompanied by the formation of nanodiamonds (ultrafine-dispersed diamonds, UDDs) are described. The basic UDD synthesis parameters are considered, and the expediency of using trotyl-hexogen alloys is shown. The conditions of diamond phase conservation in the detonation products are specified. Various versions of industrial detonation synthesis of UDDs are considered. The most efficient technology of chemical cleaning of UDDs (with nitric acid at high temperatures and pressures) for producing UDDs with the highest purity is described.
Superhard nanodiamond-SiC ceramics are prepared by infiltrating liquid Si into porous nanodiamond compacts under pressure.
Synthesized samples are 2.2 mm thick and 3–4 mm in diameter. The effect of particle size of dynamically synthesized nanodiamond
powders on silicon infiltration and SiC phase formation is studied. It is established that silicon does not penetrate into
the pores of nanodiamond powders if the original particle size is smaller than 0.5–1.0 μm. The critical pore size for infiltration
is 100–200 nm. A study of the microstructure of the samples showed the presence of the nanometer-and submicron-scale SiC phase.
The ultrasound velocities are measured in the prepared compacts, and the elastic moduli are calculated.
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Translated from Fizika Tverdogo Tela, Vol. 46, No. 4, 2004, pp. 734–736.
Original Russian Text Copyright ? 2004 by Ekimov, Gromnitskaya, Mazalov, Pal’, Pichugin, Gierlotka, Palosz, Kozubowski. 相似文献
The terahertz absorption spectra of plasmon modes in a grid-gated double-quantum-well field-effect transistor structure is analyzed theoretically and numerically using the scattering matrix approach and is shown to faithfully reproduce strong resonant features of recent experimental observations of terahertz photo-conductivity in such a structure. 相似文献
Growth of thin Ti films on (100)W and the kinetics of their oxidation are studied using thermal-desorption spectroscopy and Auger electron spectroscopy. Titanium films grow nearly layer by layer on the (100)W face at room temperature. The activation energy for desorption of Ti atoms decreases from 5.2 eV for coverage θ=0.1 to 4.9 eV in a multilayer film. Oxidation of a thin (θ=6) titanium film starts with dissolution of oxygen atoms in its bulk to the limiting concentration for a given temperature, after which the film oxidizes to TiO, with the TiO2 oxide starting to grow when exposure of the film to oxygen is prolonged. The thermal desorption of oxides follows zero-order kinetics and is characterized by desorption activation energies of 5.1 (TiO) and 5.9 eV (TiO2). 相似文献
The history of the discovery of nanodiamond synthesis, the investigation of nanodiamond properties, and the application and organization of their production in the second half of the 20th century is expounded. It is noted that this history is unique, since nanodiamond synthesis was discovered in the USSR three times over 19 years: first by K.V. Volkov, V.V. Danilenko, and V.I. Elin at the VNIITF (Snezhinsk) in 1963 and then, in 1982, by A.M. Staver and A.I. Lyamkin at the Institute of Hydrodynamics, Siberian Division, Academy of Sciences of the USSR (Novosibirsk), and by G.I. Savvakin at the Institute of Problems of Materials Science, Academy of Sciences of the UkSSR (Kiev). All of these researchers discovered nanodiamond synthesis accidentally while studying diamond synthesis by shock compression of nondiamond carbon modifications in blast chambers. The priority of work by Russian scientists in this field is demonstrated. 相似文献