A combined Lagrangian method for simulation of axisymmetric gas-particle vortex flows

A combined fully Lagrangian approach for meshless modeling of unsteady axisymmetric vortex flows of a gas-particle mixture with an incompressible carrier phase is developed. The approach proposed is based on the combination of a meshless vortex method for calculating axisymmetric flows of the carrier phase described by the Navier–Stokes (or Euler) equations and the full Lagrangian method for calculating the parameters of the dispersed phase. The combination of these methods reduces the problem of modeling the two phase flows to the solution of a high-order system of ordinary differential equations for the coordinates of toroidal vortex elements in the carrier phase and the particle trajectories, the velocity components, and the components of the Jacobian of transformation from the Eulerian to the Lagrangian variables in the dispersed phase. The application of the method is illustrated by modeling the behavior of an admixture of inertial Stokes particles with a small mass concentration in unsteady flows like solitary vortex rings in a viscous carrier phase and groups of vortex rings in an effectively inviscid carrier phase.     

Dark current-voltage characteristic of triple-junction solar cells: Their relation with the efficiency and the influence of passivating treatments

A correlation between the main parameter of a solar cell, the conversion efficiency, and its dark I–V characteristic is investigated. A formula is derived that expresses an increment (decrement) of the efficiency through a decrement (increment) of the current measured at a certain voltage (here at 2.4 V). Relationships are deduced based on which six methods for passivating the sidewalls of triple-junction InGaP/GaAs/Ge heterostructures grown by metal-organic vapor-phase epitaxy are tested to see how they influence the dark I–V characteristic. The influence of different factors, such as post-growth annealing, damaging radiation, etc., on the solar cell efficiency can be estimated by taking the dark I–V characteristic.     

Fröhlich resonance in the AsSb/AlGaAs system

The optical absorption in a metal-semiconductor metamaterial based on the AlGaAs matrix has been investigated. The key feature of this material is the presence of random arrays of metallic AsSb nanoinclusions modifying its dielectric properties. It has been shown that the presence of such arrays in the material leads to resonance absorption of light by surface plasmons in AsSb nanoinclusions in the incident photon energy range from 1.37 to 1.77 eV. The experimental spectrum of the extinction coefficient at an energy of 1.48 eV exhibits a resonance peak with the half-width equal to 0.18 eV. The extinction coefficient for AsSb nanoinclusions in the AlGaAs matrix has been calculated in terms of the Mie theory. The calculated spectrum of the extinction coefficient also includes a resonance peak with the energy and half-width equal to 1.48 and 0.18 eV, respectively. The calculated plasma energy for free-standing nanoinclusions in vacuum is 7.38 eV.     

Deformation and fracture mechanisms and structural changes in coarse-grained copper under shock-wave loading

Results of experiments on shock-wave deformation of M2 copper under uniaxial loading are presented. Light, scanning, and transmission electron microscopy methods are used to reveal specific features of mechanisms of deformation and fracture of copper during the formation of a main spall crack. The parameters of spall strength, damage, and self-similarity of the spall crack contour are determined.     

Special quadrature rules for Laplace transform inversion

Quadrature rules for Laplace transform inversion are studied that are adapted to the inversion of transforms corresponding to slowly varying long processes characteristic of linear viscoelasticity problems. The convergence of special quadrature rules for Laplace transform inversion is proved.     

Sr<Superscript>+</Superscript> + H<Subscript>2</Subscript>O ↔ SrOH<Superscript>+</Superscript> + H equilibrium in flames with strontium admixtures

Sr⁺ + H₂O ↔ SrOH⁺ + H equilibrium was studied spectrophotometrically. This reaction occurs in natural gas combustion products. Its enthalpy Δ_r H ^○(0) = 61.4 ± 2.8 kJ/mol and bond energy D ₀(Sr⁺-OH) = 432.6 ± 2.8 kJ/mol were determined using the third law of thermodynamics. The experimental data on this reaction obtained earlier in hydrogen flames, Δ_r H ^○(0) = 55.3 ± 10.6 and D ₀(Sr⁺-OH) = 438.7 ± 10.6 kJ/mol, were interpreted anew. The D ₀(Sr⁺-OH) = 432.8 ± 2.7 kJ/mol value was eventually obtained.     

Inertial migration of sedimenting particles in a suspension flow through a Hele-Shaw cell

Within the framework of the model of two interpenetrating continua, a horizontal laminar dilute-suspension flow in a vertical Hele-Shaw cell is investigated. Using the method of matched asymptotic expansions, an asymptotic model of the transverse migration of sedimenting particles is constructed. The particle migration in the horizontal section of the cell is caused by an inertial lateral force induced by the particle sedimentation and the shear flow of the carrier phase. A characteristic longitudinal length scale is determined, on which the particles migrate across the slot through a distance of the order of the slot half-width. The evolution of the particle number concentration and velocity fields along the channel is studied using the full Lagrangian method. Depending on the particle inertia parameter, different particle migration regimes (with and without crossing of the channel central plane by the particles) are detected. A critical value of the particle inertia parameter corresponding to the change in migration regime is found analytically. The possibility of intersection of the particle trajectories and the formation of singularities in the particle number concentration is demonstrated.     

Composition and Properties of Aqueous Fluoroplastic Dispersion for Deposition of Metal–Polymer Coatings

Russian Journal of Applied Chemistry - Formulation of an aqueous dispersion of F-40 tetrafluoroethylene–ethylene copolymer for applying metal–polymer coatings by cathodic...     

Synthesis of 1-alkenyl-3,5-dichloro-1,2,4-triazoles and investigation of their nitration by nitric acid

A method for obtaining 1-alkenyl-3,5-dichloro-1,2,4-triazoles by alkylation of 3,5-dichloro-1,2,4-triazole with chloro- and bromoalkenes was developed. The nitration of 1-alkenyl-3,5-dichloro-1,2,4-triazoles takes place at the double bond of the alkenyl radical; the concentration of the HNO₃ and the percentage of nitrogen oxides in it affect the character and yields of the products.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 933–936, July, 1987.