"Technical Physics Letters"

Tsukanov, D. A.;Bondarenko, L. V.;Borisenko, E. A.

doi: 10.1134/S1063785010100019pmid: N/A

Abstract Dependence of the surface electric conductivity of the layered Au/Si(111)5.55 × 5.55-Cu structure on the thickness of Au film and exposure in oxygen has been studied using low-energy electron diffraction, Auger electron spectroscopy, and four-point-probe conductivity measurements. The samples were obtained by depositing Au (1–5 monolayers, ML) in vacuum at room temperature onto preliminary prepared Si(111)5.55 × 5.55-Cu surface, after which the structure was kept in oxygen (to a total exposure varied within 0–14000 L) at room temperature. It is established that the increasing oxygen exposure of both the initial and Si(111)5.55 × 5.55-Cu surface and that coated with gold to 1–3 ML leads to a significant decrease in the surface conductivity of samples. In contrast, the conductivity of samples coated with more than 3 ML of gold remains almost unchanged, which is explained by the fact that a continuous Au film is formed in this case on the Si(111)5.55 × 5.55-Cu surface.

Glebova, N. V.;Nechitaĭlov, A. A.

doi: 10.1134/S1063785010100020pmid: N/A

Abstract Features of functionalization of the surface of domestic commercial multiwalled carbon nanotubes by means of the thermal oxidation in air and treatment in nitric acid or a nitric-sulfuric acid mixture has been studied using the method of differential thermal analysis.

Popov, A. L.;Vendik, O. G.;Zubova, N. A.

doi: 10.1134/S1063785010100032pmid: N/A

Abstract The structure of a loop antenna of electrically large diameter with the loop perimeter split by capacitors in the form of planar two-wire (PTW) lines is considered. The antenna characteristics are calculated for one- and two-sided arrangement of the PTW lines and the obtained data are compared to the results of measurements. It is shown that the arrangement of PTW lines significantly influences the distribution of current over the loop perimeter.

Skaldin, O. A.;Timirov, Yu. I.;Lebedev, Yu. A.

doi: 10.1134/S1063785010100044pmid: N/A

Abstract The method of liquid crystal (LC) helix pitch determination from the critical voltage of transition from a homeotropic orientation to a translation-invariant structure in a nematocholesteric LC mixture is considered. It is shown that, in the case of nonrigid homeotropic boundary conditions under which there is azimuthal degeneracy of the director rotation relative to the normal to the LC layer, the helix pitch determined from the critical voltage can significantly differ from the true value.

Bugrova, A. I.;Desyatskov, A. V.;Korobkin, Yu. V.;Lipatov, A. S.;Kharchevnikov, V. K.

doi: 10.1134/S1063785010100056pmid: N/A

Abstract Integral and local characteristics of the laboratory model of a low-power plasma thruster operating in a pulsed regime have been experimentally studied. Rectangular pulses of discharge current with the leading and trailing fronts not exceeding 1 ms have been obtained. At an average supplied electric power of ∼150 W, the propulsion efficiency amounted to 35%. The plasma concentration, electron temperature, and potential distributions in the output plasma jet have been measured using an electric probe. These measurements showed that a well formed plasma jet with a small divergence angle exists behind the thruster edge.

Mirgorod, Yu. A.

doi: 10.1134/S1063785010100068pmid: N/A

Abstract Phase transitions in ensembles of water clusters in aqueous solutions of C11–C28 n-hydrocarbons and C2–C12 amphiphiles have been studied as dependent on the concentration and size of dissolved molecules. A critical size (approximately corresponding to the volume of undecane molecule) for water clusters is determined, which triggers the phase transition that leads to the formation of bistable amphiphile micelles.

Kasumov, M. M.

doi: 10.1134/S106378501010007Xpmid: N/A

Abstract The mass spectrum of the products of arc discharge in helium between graphite electrodes has been studied for various values of the gas flow rate. As the gas flow rate increases, the intensity of C ±60 , C ±70 , C ±84 and C ±90 fullerene peaks increases and that of the C −2 and C +3 cluster radicals decreases, but the total decay in radicals amounts to only 21% of the total growth of fullerenes. From this it follows that a contribution to the formation of fullerenes from the neutral clusters (which are taken into account for the first time) significantly exceeds the contribution due to small radical species.

Kalinin, Yu. A.;Starodubov, A. V.;Volkova, L. N.

doi: 10.1134/S1063785010100081pmid: N/A

Abstract A new generator of broadband chaotic microwave oscillations of medium power on turbulent electron beams is proposed, in which it is possible to tune the generation regime. The characteristics of turbulent electron beams have been studied by experimental and theoretical methods. It is established that drag of the electron beam produces its turbulization, which leads to the generation of broadband chaotic microwave oscillations.

Ponomarenko, V. I.;Prokhorov, M. D.

doi: 10.1134/S1063785010100093pmid: N/A

Abstract Model delay-differential equations for an ensemble of coupled delay-feedback systems have been reconstructed for the first time from their experimental time series.

Danilov, D. S.;Lipatov, I. I.;Tolkachev, G. Yu.

doi: 10.1134/S106378501010010Xpmid: N/A

Abstract Local flow in the boundary layer in the vicinity of a porous surface region has been studied. Mathematical models are formulated and similarity parameters are determined using the asymptotic analysis. Numerical and analytical results that describe the viscid-inviscid interaction of laminar flows near porous surfaces are presented. This method of passive flow control in the boundary layer can be used to eliminate the boundary layer separation and to produce delay of the laminar-turbulent transition. It is shown that the pressure at the point of separation remains virtually unchanged, whereas the pressure gradient grows with increasing coefficient of porosity. This behavior implies that the length of a disturbed flow region decreases when the porosity coefficient increases.