Mathematical modeling of flow in sound-absorbing structures of resonance type in the presence of a grazing flow

Sound-absorbing structures of resonance type are studied on the basis of integration of the unsteady Reynolds-averaged Navier-Stokes equations. The formation of the boundary layer over a sound-absorbing panel is compared with that on a flat plate in the presence of an incident wave. The dependence of the panel reflection coefficient on the presence of a grazing flow and the boundary layer thickness is investigated. The results of the numerical experiment are compared with the available experimental data.     

Hydrolysis and Condensation of Alkyltrimethoxysilanes in Monomolecular Films

Hydrolysis and condensation of monomolecular alkyloxysilane films by the Langmuir technique is presented. Octadecyltrimethoxysilane formed monolayers on aqueous subphases with different properties depending on the bulk pH. At pH 1 a solid condensed film was directly formed with a molecular area of 23 Ų and a surface pressure/surface area variation similar to that on non-ionized stearic acid. At pH 5.6 and 11 several phase transitions were observed during the compression of the monolayer with a final collapse at a molecular area of 20 Ų. Relaxation measurements confirmed the stability of the films for longer than 12 hours at different surface pressures below a critical value.     

Electrical double layer in surface-inactive electrolyte solution and adsorption of halide ions from 0.1 M solutions on liquid Cd–Ga and In–Ga alloys in gamma-butyrolactone

The double-layer characteristics of liquid renewable Cd–Ga (0.3 at % Cd) and In–Ga (14.2 at % In) electrodes in the gamma-butyrolactone (GBL) solutions of various electrolytes are studied by measuring the differential capacitance and using the method of open-circuit jet electrode. For the (Cd–Ga)/GBL and (In–Ga)/GBL interfaces, the zero-charge potentials, which are not distorted by the specific adsorption of ions, and the chemisorption potential drops of solvent are determined. It is shown that, in spite of the fact that the work function decreases as we pass from (In–Ga) to (Cd–Ga), the chemisorption potential drops of solvent on both electrodes are close. This behavior is explained by a closer approach of GBL dipoles to the surface of (Cd-Ga) electrode providing more effective overlapping of donor–acceptor levels of metal and solvent. It is shown that, in GBL, the adsorption parameters of halide ions and their surface activity series depend on the metal nature. On the (Cd–Ga) and (In–Ga) electrodes, the reversed surface activity series of halide ions is observed: on the Hg electrode in various solvents, the surface activity increases in the series Cl^– < Br^– < I^–, whereas on the (Cd–Ga) and (In–Ga) electrodes in GBL, it varies in the reverse series I^– < Br^– < Cl^–.