Structure, phase composition, and optical properties of silicon nanopowders

The nanopowders obtained by sputtering of silicon with a high-power electron beam in nitrogen and argon atmospheres have been investigated by transmission electron microscopy, Raman spectroscopy, photoluminescence spectroscopy, ultrasoft X-ray emission spectroscopy, and X-ray absorption near-edge structure spectroscopy. The sizes of particles and their phase composition have been determined. A mechanism is proposed, which explains the visible photoluminescence of nanopowders.     

Effect of boundary layer thickness before the flow separation on aerodynamic characteristics and heat transfer behind an abrupt expansion in a round tube

Results of numerical investigation of the boundary layer thickness on turbulent separation and heat transfer in a tube with an abrupt expansion are shown. The Menter turbulence model of shear stress transfer implemented in Fluent package was used for calculations. The range of Reynolds numbers was from 5·10³ to 105. The air was used as the working fluid. A degree of tube expansion was (D ₂/D ₁)² = 1.78. A significant effect of thickness of the separated boundary layer both on dynamic and thermal characteristics of the flow is shown. In particular, it was found that with an increase in the boundary layer thickness the recirculation zone increases, and the maximum heat transfer coefficient decreases. The work was financially supported by the Russian Foundation for Basic Research (project codes 07-08-00025 and 06-08-00300).     

Percolation model of an inhomogeneous anisotropic medium

A model of the variation in capillary conductivity is proposed. The change in the permeability of an inhomogeneous medium under load is investigated on the basis of the percolation model [3] and is numerically modeled for cases of hydrostatic compression and nonisotropic loading. The validity of the percolation approach to the determination of the change in flow properties under load is demonstrated.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 67–75, January–February, 1986.     

Modeling of electronic density of states for single-wall carbon and boron nitride nanotubes

The electronic density of states is calculated for all possible geometric configurations of single-wall carbon and boron nitride nanotubes. The calculation is based on the numerical differentiation of the two-dimensional dispersion relations for graphite and hexagonal boron nitride. The differentiation is performed for all allowed values of the wave vector using the π-electron approximation. For the particular carbon nanotubes chosen as examples, a good agreement is demonstrated between the calculated values of energy spacing of the symmetric van Hove singularities in the density of states and the experimental data obtained from the resonance Raman scattering study.     

Recovery of solketal from reaction products by extraction

The extraction of solketal from aqueous glycerol with AI-92 gasoline, toluene, hexane, and 1-hexene was studied. Aromatic compounds and mixtures containing them exhibit the best extracting properties. A flowsheet was suggested for recovering solketal from reaction products by extraction.     

Resonance Raman spectra of M-anions of metalloporphyrins

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 4, pp. 576–584, October, 1990.