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A two-dimensional stationary linear model of flows arising in a stably (neutral) stratified medium over a thermally inhomogeneous flat inclined surface is analyzed analytically. At the lower boundary, temperature deviations are specified, which depend harmonically on the horizontal coordinate transverse to the slope. Explicit analytical solutions are obtained, which make it possible to analyze the regularities of emerging density flows. It is shown that these flows can qualitatively differ depending on the ratio of the slope angle of the lower boundary and the analog of the Rayleigh number, the expression for which includes the horizontal scale of the thermal inhomogeneity region as a spatial scale. An appropriate criterion for distinguishing these currents is established.

The reflection and transmission of harmonic waves is theoretically investigated at the interface between a bubbly liquid and a porous medium saturated with this liquid has been studied theoretically. The influence of the parameters of the system on the coefficients of reflection and transmission through the interface between the two media has been investigated. It has been found that for the interface between the bubbly liquid and the porous medium saturated with the bubbly liquid, there is a range of frequencies in which reflection occurs in the same way as from a free surface and the back reflection as from a rigid wall.

This paper is focused on deriving a common solution to the strain energy release rate for delamination cracks in multilayered inhomogeneous beams under nonlinear creep. The layers of the beams exhibit material inhomogeneity in the thickness direction. The solution is obtained for the nonlinear stress-strain-time relation. The J -integral approach is applied to verify the solution. The variation of the strain energy release rate with time as a result of the nonlinear creep behaviour is analyzed.

The paper considers the solution of the plate flutter problem with mixed boundary conditions. The mathematical formulation of the problem allows taking into account arbitrary directions of the incoming flow vector. For the numerical solution of the problem, a modern numerical algorithm without saturation is proposed, which allows obtaining the critical flutter speed with sufficient accuracy on a sparse grid. The results of calculations for four materials are presented: titanium, steel, aluminum, duralumin. Based on the calculation results, two analytical dependences for the critical flutter speed are obtained: from the direction of the incoming flow vector, as well as from the dimensionless speed of sound in the plate and the thickness of the plate. The eigenforms Re(φ) corresponding to the critical flutter speed are given.

A technology for obtaining hybrid nanocomposite materials with a 7075-T6 aluminum matrix and a filler in the form nanoparticles is proposed. A review of experimental data and computer and theoretical models of crack initiation processes is presented. The mechanisms of microcrack nucleation under uniaxial tensile load are determined. To study the fracture of loaded nanocrystalline materials and determine their mechanisms, a model is proposed that describes the formation and growth of nanocracks near the tips of elliptical cracks in a hybrid nanocomposite material. The dependences between the applied force and the crack length are obtained using the parameters of a modeled crack.

A study was made of the change in the dynamic viscoelastic properties of silicone rubber with the addition of a small fraction (0.05; 0.10%) of single-walled carbon nanotubes. In the region of linear deformation, the elastic modulus and loss factor were measured. It has been established that the addition of nanotubes and the aging of materials lead to an increase in the elastic modulus, and the loss factor can either increase or decrease.

Problems are considered that describe the process of obtaining the residual angle of twist of a rod under creep conditions, taking into account elastic recovery after unloading. It is assumed that a constant linear angle of twist is set for the section being formed, i.e., the section is in conditions of pure torsion, without constraining the ends of the rod. It is believed that strains and stresses depend only on time and two spatial coordinates in the plane of the cross section of the rod. Direct and inverse problems of torsion of a rod with rectangular and angular cross sections in various kinematic creep regimes are considered. The speed of the angle of twist during the entire deformation process is set constant. A method of numerical calculation based on the finite element method is proposed, which makes it possible to obtain the stiffness characteristics of the section under torsion in the case of creep. It is shown that the minimum level of residual stresses is observed in the relaxation mode of deformation. For a rod with a cross-section of the angular type, modes are found in which stresses significantly decrease in the area of their concentration.

In the present study, an experimental approach is developed to study collisions of particles with a fixed air bubble. An air bubble with a diameter of 5.5 mm in deionized water is created, plastic particles (with diameters of 1.5, 2, and 2.5 mm) are released at different heights from the bubble surface, and their collisions with the bubble surface are studied. The results show that the particle size significantly affects the particle velocity and sliding time on the bubble surface. As the particle diameter increases, its sliding velocity on the bubble surface increases, and the particles are detached quickly from the bubble surface. The effects of the drag, capillary, pressure, weight, and buoyancy forces acting on the particles during the attachment-detachment on the bubble surface are also studied. The results show that the particle stays attached if the capillary force is dominant. The effects of the three-phase contact line on the capillary and pressure forces are also analyzed. A modified Bond number is proposed to check the attachment-detachment regimes.

Results of geochemical investigation of drainage waters discharging from the mining objects (dumps, quarries, tailings) of the Orlovskoe tantalum deposit (Transbaikal Territory) are presented. It is determined that the drainage waters from the dumps of overburden rocks and from blast holes are acid and weakly acid, and highly mineralized (TDS up to 4232 mg/L). With respect to the chemical composition, these waters are mainly of sulphate type, with anomalously high concentrations of aluminium, fluorine, chalco- and siderophilic elements. The waters of the tailing storage facility are neutral and weakly alkaline, with increased tungsten and arsenic concentrations. Thermodynamic calculations of the major forms of element migration in drainage waters show that simple cationic forms dominate for most metals, while the second prevailing forms are sulphate and fluoride complexes. The average concentrations of Mn, Al, Be, Zn, Fe, Li, Со, Ni, Cu, W, F^- and SO₄^2- are determined to be substantially higher than the maximum permissible concentrations for water objects for fishery, household, drinking and amenity water usage, which is connected both with the composition of the ores and host rocks of this deposit, and with technogenic activities.

In this study, the conditions for the precipitation of aluminium hydroxide from sodium aluminate solutions obtained from the alkaline solution of raw alunite ore by hydrogen peroxide, an eco-friendly reagent, are studied. Factors influencing the precipitation by H₂O₂ and aluminium hydroxide from diluted aluminate solutions (concentrations of hydrogen peroxide and alkali, volume ratios of hydrogen peroxide and aluminate solution, temperature, time, caustic modulus) are investigated and found under optimal conditions (initial concentration of hydrogen peroxide >15 %; temperature 20-40 °C, V_H2O2/V_sol = (5-20) : 20 mL, alkali concentration 42.33 g/L (according to Na₂O)) precipitation of ~95 % of aluminium in aluminate solution is achieved. The recovery of alkali (sodium hydroxide) after the precipitation of aluminium hydroxide by H₂O₂, its return to the leaching of alunite has been studied, and several difficulties have been eliminated in the precipitation of aluminium hydroxide by other methods. The characteristics of the obtained samples are confirmed by means of XRD, SEM/EDS analysis.