Pulsating stochastic flows accompanying microwave filament/supersonic shock layer interaction

The details of pulsating stochastic flows accompanying the interaction of a microwave filament (regarded as a heated rarefied channel) and an aerodynamic body in supersonic flow are examined numerically using the Euler equations. Symmetrical and asymmetrical filament locations relative to the aerodynamic body are considered. The flowfields are characterized by large scale pulsations and small scale stochastic fluctuations. The mechanisms of the formation of these flow structures are discussed. Two qualitatively different kinds of flowfields are observed depending on the magnitude of the filament radius, with domination of the pulsations of flow parameters or stochastic phenomena. Flow instabilities inherent to the problems under interest are described. The problems are considered in both plane and cylindrical configurations for a wide class of filament characteristics and freestream Mach numbers equal to 1.89 and 3.     

Ellipsometry of precision optical surfaces and mirror coatings

The possibility of testing a surface damaged layer and the cleaning quality of precision optical surfaces using the monochromatic ellipsometry method is discussed. The results of ellipsometric measurements of the thickness homogeneity of nanofilms deposited by the ion-beam sputtering method are analyzed. The results of calculations of the film thicknesses and parameters of surface layers performed by solving an inverse ellipsometric problem are presented. The results of measurements of the thickness of thin films by the profilometric and ellipsometric methods are compared.     

Xerogels modified with l-(2-Pyridylazo)-2-naphthol and dimethylglyoxime: Indicator tubes for determining nickel

A simple and rapid sol-gel method was proposed for preparing xerogels modified with l-(2-pyrilylazo)-2-naphthol and dimethylglyoxime. Reactions between nickel and xerogels modified with l-(2-pyrilylazo)-2-naphthol and dimethylglyoxime were studied by solid-phase spectrophotometry, and the optimal conditions were found. Procedures for determining nickel in solution by solid-phase spectrophotometry and tests based on indicator tubes containing powdered xerogel modified with l-(2-pyrilylazo)-2-naphthol were developed. The analytical ranges for nickel in the above methods were 0.1–2 and 0.2–30 mg/L, respectively. The interference from cobalt(II) was eliminated by its adsorption on hydrophobic C₁₆ and C_phenyl silica gels modified with l-(2-pyrilylazo)-2-naphthol. The interference of copper(II) and iron(III) was eliminated by the addition of a mixture of Na₂S₂O₃ and NH₄F.     

Simulation of stochastic pulsating flows with instabilities using minimum-stencil difference schemes

Pulsating flows with contact discontinuity instabilities and generated regions of turbulent-like gas parameter fluctuations were numerically simulated. The flows were driven by the interaction of an infinite heated rarefied channel with a shock layer. Pulsating flow regimes were analyzed for an energy source located symmetrically or asymmetrically relative to the body. Averaged steady flows characterized by stagnation point oscillations about a new position at the end face were examined, and steady-state flow structures with gas parameter nonmonotonicities near the body end face were studied. The simulation was based on minimum-stencil modified schemes.     

Direct numerical simulation of one type of compressible turbulence interacting with a shock wave

Direct numerical simulations of compressible turbulence interacting with an initially plane shock wave are presented. The underlying model is based on the numerical solution of the Euler equations combined with direct statistical simulation. Steady-state isentropic isotropic turbulence is considered. The amplification factors for fluctuations of the thermodynamic variables, velocity, vorticity, and kinetic energy of fluctuations are analyzed; and the correlation coefficients between flow variables are studied for Mach numbers ranging from 1.2 to 3.     

A minimum-stencil difference scheme for computing two-dimensional axisymmetric gas flows: Examples of pulsating flows with instabilities

A minimum-stencil difference scheme for computing two-dimensional axisymmetric gas flows is described. The scheme is explicit, conservative, and second-order accurate in space and time. The numerical results obtained for pulsating flows and contact discontinuity instabilities are discussed. The mechanisms of flow pulsation and instability generation are described.     

A New Method of Synthesis of Nanosized Boehmite (AlOOH) Powders with a Low Impurity Content

A new method of synthesis of nanosized aluminum oxyhydroxide (AlOOH, boehmite) powders has been suggested through a hydrothermal treatment of nanosized γ-Al₂O₃ powder in water and a 1.5 wt % HCl solution at different temperatures. It has been found that hydrothermal treatment in a 1.5 wt % HCl solution leads to the purification of the starting material; different treatment durations allow one to obtain boehmite particles of different shape. It has been demonstrated that a nanosized boehmite powder is obtained upon the hydrothermal treatment of a nanosized γ-Al₂O₃ in water above 80°С. The nanosized boehmite powders synthesized at different temperatures have been studied by various methods.