Home – Home – Jornals – Russian Geology and Geophysics 2026 number 10

The Mid-Atlantic Ridge within Iceland differs significantly from others by its structures. It consists of a few active rift zones with different kinematics and internal structure. At the same time, there are also several inactive rift zones, separated by block uplifts. This structural diversity is caused by the thermal influence of the Icelandic plume, which manifests itself in conditions of asymmetric spreading. Physical modeling was used to identify the conditions for the development of Icelandic rift zones and the features of their structure in relation to the cyclicity of plume activity. The resulting model reflects the structure and development of Icelandic rift zones over the last 21.5 Myr. Results show that the kinematics and internal structure of rift zones are a consequence of the development of multi-scale overlaps of spreading centers. Between them, block uplifts arise, which in the present-day topography are expressed as elevated peninsulas, mainly in the northern part of the island. The sizes of block uplifts depend on the distance between overlapping spreading axes. As the distance decreases, large uplifts are replaced by a series of small en-echelon blocks. The formation of this structural ensemble is the result of periodic increase in plume activity and its eastward displacement relative to the boundary of the lithospheric plates, which is caused by spreading asymmetry. There are two cycles of plume activity with different durations. The period of 7-8 Myr reflects the complete cycle of formation and development of overlappings, and the period of 2-3 Myr determines the evolution of the rift zone structure within the entire structural ensemble.

This paper presents a synthesis of published and new geological, geochronological, biogeographic, paleomagnetic, and petrological-geochemical data. The goal is to substantiate the tectonic zoning of the Central Asian Fold Belt and its Vendian-Paleozoic geodynamic evolution as a complex folded structure composed of deformed fragments of collisional and accretionary orogens. It is shown that the belt formed at the junction of the collisional and accretionary margins of the Siberian Craton. This setting is analogous to the modern tectonic interactions between the Indo-Atlantic and Pacific global tectonic segments of the Earth and their respective interactions with Eurasia. During the Vendian and Early Ordovician, two active margins existed along the periphery of the Siberian Craton: the collisional Tuva-Mongolian margin and the accretionary Kuznetsk-Altai margin. These margins separate the craton from the tectonic plates of the Paleo-Asian Ocean (Indo-Atlantic segment) and the Paleo-Pacific Ocean (Pacific segment), respectively. A distinctive feature of the Paleo-Asian Ocean plate is its complex structure, which includes fragments of oceanic crust and Precambrian Gondwanan continental blocks that contain fragments of the Grenvillian orogeny. Grenvillian detrital zircons (1.3-0.9 Ga) are widely found in Vendian-Paleozoic sedimentary deposits from various geodynamic settings of the collisional orogen. In contrast, a distinctive feature of the accretionary orogen is the widespread presence of oceanic crust fragments and the absence of Precambrian Gondwanan blocks. Consequently, there are no Grenvillian detrital zircons in the Vendian-Paleozoic sedimentary rocks of various geodynamic settings that represent the accretionary orogen. The early to middle Paleozoic Charysh-Terekta-Ulagan-Sayan-Olkhon suture-strike-slip zone separates the collisional orogen from the shelf of a back-arc basin. This basin is located in the northern part of the Altai-Sayan Folded Area, which frames the Siberian Craton. The suture-strike-slip zone consists of fragments of Vendian-early Paleozoic oceanic crust from a back-arc basin, Ordovician blueschist, and Ordovician-Silurian turbidite, as well as late Silurian-Devonian collisional metamorphic rock and granite. Based on the structural position of the suture-strike-slip zone, petrology, and geochronology, this zone is interpreted as a subduction-collision complex. It formed in the back-arc basin of the Vendian-Cambrian Tuva-Mongolian island arc. Late Paleozoic strike-slip faults and thrusts manifested in the Central Asian Fold Belt during the Late Devonian and early Carboniferous. These structures resulted from the collision of the Kazakhstan-Baikal orogen (a composite continent) with the Siberian Craton, which led to the formation of the North Asian continent. Subsequently, during the late Carboniferous and Triassic, the collision of the East European and North Asian continents led to the formation of Eurasia. As a result of these collisional events, the originally linear structures of the collisional and accretionary orogens were deformed into large oroclinal folds. These structures were further fragmented by strike-slip faults and thrusts into numerous blocks. Within these blocks, the Vendian-Paleozoic structures are complicated by thrust-fold deformations.

Analysis of the hypsometric positions of lava flows of different ages (~8 and ~4 Ma) in the Iya-Uda volcanic field indicates that the main phase of intense relief dissection and activation of block movements along the Main Sayan Fault within the Biryusa Block occurred from the Late Miocene to the Pliocene. The geochemical characteristics of the lavas, including elevated FCKANTMS values (0.46-0.77) [Yang et al., 2019] and the positions of data points on CaO-MgO and TiO₂/Al₂O₃-SiO₂ diagrams, point to melting of a garnet-pyroxenite mantle source rather than a typical peridotite mantle. The trace-element composition of the rocks is consistent with OIB-type intraplate basalts. Variations in Th/Nb and TiO₂/Yb ratios suggest that the role of garnet in the melting zone increases for the 4 Ma lavas, whereas the contribution of the lithospheric mantle is more significant for the 8 Ma magmas. The origin of the enriched pyroxenite component in the lithosphere of the Biryusa Block is most likely linked to Cenozoic tectonic convergence and rifting. These processes led to foundering dipping of lower crustal material into the mantle of the Siberian Craton. Volcanism in the (dripping) Iya-Uda interfluve is thus the result of melting of a heterogeneous and enriched lithospheric mantle.

Experimental studies modeling the interaction of garnets from eclogitic and lherzolitic parageneses with reduced and oxidized sulfur-rich fluids were conducted using a split sphere multianvil high-pressure apparatus (BARS). The experiments were performed in garnet-sulfur-carbon and garnet-anhydrite-carbon systems at a pressure of 6.3 GPa and temperatures of 1150, 1300, and 1450 °C, using graphite capsules as well as platinum capsules with a buffering hematite container. We demonstrated that interaction of both reduced and oxidized sulfur-rich fluids with garnets of mantle paragenesis leads to their partial dissolution and recrystallization, resulting in the formation of zoned crystals with reduced iron concentrations in the rims. In addition, this metasomatic interaction results in (1) garnet carbonation, accompanied by the formation of a magnesite ± dolomite + kyanite + coesite assemblage or a carbonate-silicate melt, and (2) garnet sulfidation, with the formation of pyrite (1150-1300 °C) or a sulfide melt (1450 °C) as inclusions within garnet and in the interstitial space. The experiments yielded indicator characteristics for mantle-paragenesis garnets that have been affected by sulfur-bearing fluids. These characteristics include decreased FeO contents in the peripheral zones of the crystals relative to their cores, as well as the formation of sulfide inclusions that trace the boundaries between zones. Here we present the first study of diamond dissolution features under lithospheric mantle P-T conditions in a silicate-sulfur-carbon system that models mantle metasomatic alteration of garnet-bearing rocks by sulfur-rich fluids. We conclude that, under these conditions, diamond crystals undergo partial dissolution, producing characteristic etch pits in the form of negative trigons on {111} and rectangles on {100}.

We studied chemical and isotope (C, O, Sr) compositions of carbonate sediments in three sections of the lower Baratal Group in the southeast of Gorny Altai, which are considered to be one of the oldest known fragments of the carbonate cover of oceanic uplifts preserved in the structure of the Central Asian Orogenic Belt. The contents of Fe, Mn, Sr and their ratios to each other, and to isotope parameters indicate postsedimentary alterations varying within and between studied sections. For the least altered Akkaya section, the δ¹³C values are -0.4…+0.7‰, and the ⁸⁷Sr/⁸⁶Sr ratios vary from 0.70818 to 0.70833; this limits the age of sedimentation to the range of 550-520 Ma. In the Kurai and Chagan-Uzun sections, along with similar values, anomalously low values of ⁸⁷Sr/⁸⁶Sr down to 0.70662-0.70701 are documented, which are often accompanied by a decrease in δ¹⁸O values and an increase in Mn content. These unusual isotope and geochemical characteristics of carbonates are supposed to be the result of the influence of metasomatic fluids due to underlying basalt and spatially related to the Kurai regional fault zone. In the Kurai section, skeletal small shelly fossils Cambrotubulus were found, which are not known to be older than 550 Ma; this confirms the Precambrian-early Phanerozoic age of the basal sequences of the Baratal Group.

We introduce a new method for constructing a structural model of an oil and gas field, focused on the consistent integration of well and seismic data represented in different domains-depth and time. To address the problem of reconciling heterogeneous data, we propose the application of 3D approximation methods such as 3D splines and collocated cokriging. These methods combine well and seismic data in a single variable space. This approach simplifies the workflow for structural model construction by eliminating the need for both explicit generation of average velocity maps and introducing adjustments to regression relationships. We have also compared the quality of structural models obtained by the proposed methods - 3D spline approximation and collocated cokriging with results produced by traditional approaches, including linear regression and methods based on average velocity maps generated in various ways. The comparison is based on error analysis using cross-validation. The 3D spline method, which has not previously been applied to structural mapping problems, provides the best results. The traditional approach based on linear regression with subsequent modification of the structural map using interpolation and adjustments demonstrates a comparable accuracy. We have obtained the results by structural modeling of the upper part of the Bazhenov Formation in the Kazan oil and gas condensate field. High well density allows us to assess the accuracy of different structural modeling methods according to varying levels of well data availability, typical for different stages of field development.

This paper presents the results of developing a pulse height analyzer for a downhole geophysical instrument intended for spectrometric gamma-ray logging. The module is implemented using a field-programmable gate array and enables real-time signal processing. An algorithm for converting biexponential responses of a scintillation detector into trapezoidal pulses is proposed. The efficiency of the implemented algorithm has been demonstrated in resolving pile-up pulses with a time delay of 300 ns. Using calibrated gamma-ray sources - Am²⁴¹, Eu¹⁵², Cs¹³⁷, Co⁶⁰, and Th²²⁸ - the system’s energy coverage in the range of 50 to 3000 keV is confirmed. The pulse height analyzer features universal architecture and is compatible with various types of gamma-ray detectors.

There is the Tira Horizon, represented by the Chistyakov, Omoro, and Oskoba Formations in different facies zones, widespread in the central and southwestern parts of the Siberian Platform. Deposits of the Tira Horizon in most sections of the Southwestern Siberian Platform are differ significantly in lithology from the underlying Nepa and overlying Danilov Horizons. In this paper considers the most complete section in the eastern part of the Angara Folded Zone, which serves as a key section. There are three main transgressive-regressive cycles, separated by sequence boundaries, are noted in the Tira interval. Three members correspond to these cycles. The first member records an abrupt change in facies from coastal to deep-sea, containing organic-walled microfossils of the first assemblage with Vanavarataenia insolita. The second member, formed in a coastal marine environment, exhibits an increase in carbonate and sulfate content, the appearance of chert lenses and nodules with microfossils, and the second assemblage with Tinnajaphyton amplum (lower submember). The third member is characterized by upper littoral, sabkha, and continental-deltaic deposits. The identified associations of microfossils, along with the features of the lithological composition and isotopic characteristics, allow them to be used as benchmarks in regional constructions on the Siberian platform, and possibly also beyond its borders. A carbon isotope anomaly of up to -11.3‰ (EPDB) was detected in dolomites of the Oskoba Formation at the Kamo Arch of the Baikit Anteclise. This may indicate a restructuring of the ecosystem in the paleobasin, accompanied by the appearance of certain microbiota groups and points to global climate change.

The problem of forecasting the filtration-capacitance properties (FCP) of target horizons (porosity, effective thickness, oil saturation) using methods capable of learning on large volumes of heterogeneous data is considered. 3D seismic data, both full-stack (seismic attributes extracted from a seismic cube) and partial-stacks (synchronous inversion), are used, limited to the target horizons interval, obtained at one of the offshore fields in the north of Sakhalin. The large data volume and the strong interdependence of the extracted features required dimensionality reduction of the seismic parameters. The novelty of the developed approach lies in the application of factor analysis prior to performing FCP forecasting. As a result, 92% of the data variations associated with reservoir properties were represented by five main factors. Subsequent application of neural networks to the forecasting problem demonstrated that the identified factors are significant predictors of porosity, oil saturation, and effective thickness. Cross-validation identified zones with low accuracy in FCP estimation – resulting from the strong influence of gas on seismic data – as well as zones with high accuracy in FCP estimation, which were subsequently used to determine optimal weights and the final forecasts. Based on the results of FCP forecasting using factor analysis and neural networks, correlation coefficients at test well locations ranged from 0.92 to 0.93, and forecast accuracy – verified following the drilling of two production wells – fell within the 85–93% range, thereby demonstrating the effectiveness of the proposed technology.

The article presents new data on a complex study of the composition of quartzites and gneisses of the Olkhon terrane. It has been established that the quartzites are typical metasedimentary rocks characterized by Cr–V mineralization—derived from volcanic exhalations—that is unevenly distributed throughout the stratigraphic section. The presence of organic matter in the sedimentary basin facilitated the precipitation of vanadium and chromium, as well as their subsequent sorption by clayey-organic material. The presence of quartzites with Cr-V and manganese mineralization in a single section may indicate alternation of oxidizing and reducing conditions in the sedimentation basin and the active tectonic regime during precipitation accumulation.
The morphological features of zircon from quartzite and its rare element composition suggest its age ~516 Ma as a result of a tectonothermal event, which contributed to the recrystallization of siliceous sediments with the formation of Cr-V mineralization (garnets, mica-roscoelites, chromium-vanadium oxides). The youngest population of detrital zircon from a biotite gneiss sample is 538 Ma, indicating that the sedimentary sequence formed within a narrow time of 538-516 Ma.

Quartz gabbroic rocks are generally considered as a rare variety of mafic plutonic rocks. Their occurrences have been reported, among other settings, in Precambrian gneiss complexes. This study presents the first detailed petrological investigation of quartz gabbronorites from two small intrusive bodies hosted within the gneissic sequence of the Kem-Ludy area of the Archean-Paleoproterozoic Belomorian Mobile Belt (BMB), Karelia. The studied quartz gabbronorites exhibit variable degrees of metamorphic overprint, ranging from low to complete. In two samples, primary magmatic minerals (clinopyroxene, orthopyroxene, plagioclase, and quartz) are preserved in significant amounts, while metamorphic alteration is locally developed. In contrast, garnet amphibolite from the marginal zone of the quartz gabbronorite body is completely devoid of primary magmatic minerals; only inclusions of relic clinopyroxene within garnet are observed. Geothermobarometric data and phase equilibrium modelling indicate that crystallization of the quartz gabbronorites occurred at temperatures of approximately 1100 °C and pressures of ~0.7 GPa, followed by subsequent subisobaric cooling to ~850°С. These estimates suggest that the rocks formed under lower- to mid-crustal conditions, either through fractional crystallization or in its absence. The results imply that the distribution of quartz gabbronorites within the Belomorian Mobile Belt may be significantly underestimated.

More than 30 years have passed since the current Working Stratigraphic Framework for the Kuril Islands was approved. Over this period, extensive age data (from diatom analysis, K-Ar dating, and other methods) have been obtained for the rocks composing the islands of the Greater Kuril Ridge, through both regional geological mapping and targeted research projects. In addition, the upper boundary of the Neogene was revised in 2011. Consequently, to synthesize these data, it became necessary to draw up an updated Neogene-Quaternary stratigraphic framework and a correlative intraregional chart for the magmatic rocks of the Greater Kuril Ridge. Based on comprehensive diatom biostratigraphy, radioisotope dating, and geological correlation of volcanic complexes, the following have been developed: (1) a new Unified Stratigraphic Framework for the Neogene-Quaternary deposits, and (2) a new intraregional correlation chart for the magmatic assemblages. The diatom and radioisotope data confirmed the absence of a stratified Paleogene–Early Miocene "Green Tuff Complex" previously recognized by researchers at the base of the exposed section of the Greater Kuril Ridge. Diatom analysis of the oldest stratigraphic subdivisions (the Rybakovsky Volcanic Complex and the Shumnovskaya Formation) of the Greater Kuril Ridge – specifically, the identification of the Thalassionema schraderi and Neodenticula kamtschatica diatom zones – indicates that the rocks composing the islands of the Greater Kuril Ridge began to form in the Tortonian (Late Miocene).

To improve the insulating properties of the solid-liquid dielectric interface and to reduce the risk of surface discharges, partial discharges in the liquid dielectric, and dendrite growth in the solid dielectric, it is proposed to minimize polarization and ionic charges at the solid-liquid dielectric interface. For this purpose, nonpolar solid dielectrics with the same permittivity ε as the liquid dielectric are used. Polypropylene and polyethylene, both with ε = 2.3, are suitable for transformer oil with ε = 2.3. Polypropylene has relatively high mechanical strength and is easy to machine, while polyethylene is flexible and deforms without cracking, making it suitable for wire sheaths. This approach makes it possible to increase the dielectric strength of high-voltage pulsed devices, improve insulation reliability, and reduce device dimensions.

A 2.3-mm-thick coating based on titanium aluminides with Cr, Nb, and Si additions is formed on the surface of a VT20 titanium alloy by out-of-vacuum electron-beam surfacing. Energy-dispersive X-ray diffraction combined with energy-dispersive X-ray spectroscopy is used to assess the homogeneity of the coating thickness. The concentrations of aluminum and alloying elements in the deposited layer are found to vary slightly across its thickness, which affects the ratios of the main phases (γ-TiAl, α₂-Ti₃Al, Ti₅Si₃) formed in the coating, while the composition remains qualitatively unchanged. Such variations are not expected to have a significant effect on the coating properties across its thickness. The wear resistance of the deposited layer under dry sliding friction is found to be 2.5-fold higher than that of the base metal, and its mass gain at 1100 °C is 6.5-fold lower than that of the VT20 titanium alloy.

A numerical study is performed to investigate the effect of laser radiation parameters on the dissolution of titanium diboride (TiB₂), a refractory compound used for surface hardening. A spherical TiB₂ particle placed in a titanium melt containing nanoscale refractory modifier particles is considered. The simulation accounts for the nonuniform heating typical of laser powder surfacing. The dependence of the TiB₂ particle dissolution time on laser power and surfacing speed is determined. A comparison with the dissolution of titanium carbide particles is made. The physical properties of TiB₂ are shown to significantly affect the nature and time of its dissolution.

For a multidimensional quantum waveguide with a cylindrical outlet at infinity, various upper and lower bounds on the multiplicity of its discrete spectrum are presented. Some estimates based on the eigenvalues of the integral-differential problem on a resonator are absent from the literature. At the same time, the problem under consideration makes it possible to obtain a sharper sufficient condition for nonemptiness of the discrete spectrum of the waveguide and an estimate of its multiplicity.

A gas-dynamic calculation of the thermal loads and flux parameters of a single-phase flow in the duct of a supersonic exhaust diffuser is performed using a commercial numerical simulation code. The computational model and the challenges of calculating heat fluxes in the pseudo-shock region are described. A combined method for calculating heat fluxes is proposed, based on solving the integral relations for the boundary layer in the supersonic flow region and using the derived engineering formulas for the pseudo-shock region. The proposed approach is tested on a small profiled diffuser. Comparison of the calculated and experimental data shows a difference not exceeding 20 %.

The effect of secondary flows in the form of a paired spiral-vortex structure, formed by flow swirling in an annular channel, on heat transfer is investigated. Local and average heat transfer characteristics in an annular channel under swirling flow conditions are determined experimentally and numerically. The formation of the paired spiral-vortex structure and the resulting nonuniformity in the Nusselt number distribution are examined. The data obtained are compared with known calculated correlations. The largest difference between the numerical simulation results and the experimental data for the distribution of the average heat flux density in the annular channel does not exceed 16 %. Secondary flows are found to form a complex local heat transfer pattern that is not described by existing correlations for the average Nusselt number.

A transient model is proposed for the sedimentation of solid drill cuttings particles in the annulus of a well with arbitrary geometry after circulation of the drilling fluid has stopped. The possibility of plug formation in the annulus is taken into account. The fluid rheology is described by a power-law non-Newtonian model. A numerical scheme is developed that allows the equations of motion to be solved rapidly and efficiently. Examples of modeling particle sedimentation and bed formation are presented for straight, deviated, and J-shaped wellbores. The code developed on the basis of the proposed model makes it possible to determine the distributions of bed thickness and velocity, as well as the suspension density-parameters that can be used to assess the feasibility of wellbore cleanout upon resumption of fluid circulation.

Experimental data on the interaction of weak shock waves with the sharp leading edge of a flat plate and the bow shock at a Mach number M = 2.5 are presented. Measurements are performed with a constant-resistance hot-wire anemometer. Spatial distributions of the mean mass flow rate and its fluctuations under the action of an N-wave are determined in the incoming flow, in the flow above the model, and in the boundary layer. Spectral and statistical analyses of the resulting data are performed. The experimental results show that, when an N-wave passes through the bow shock, its amplitude decreases in the flow above the plate. The statistical distributions of the fluctuation signal in the vicinity of the N-wave fronts deviate significantly from a normal distribution. Outside the N-wave, the probability density distribution of the fluctuation signal is normal. The propagation angles of the N-wave fronts are estimated. The leading front of the N-wave is found to propagate in the incoming flow at an angle of 24.9 ± 0.5°, which agrees with the results of optical measurements. The trailing front of the N-wave propagates at the Mach angle.

The evolution of small perturbations in the joint motion of two uniformly stretched layers of ideal incompressible fluids is investigated. Kinematic and dynamic conditions are satisfied at the free boundaries of the layers and at their interface. The problem of small perturbations in Lagrangian coordinates is shown to admit separation of variables. A system of amplitude equations is derived that contains three Weber numbers, the density ratio and initial thickness ratio of the layers, and the wave numbers, making it possible to determine the evolution of the perturbed motion. Numerical results from an analysis of the amplitude equations are presented, indicating the instability of the motion under consideration.

The feasibility of using physics-informed neural networks (PINNs) to modify the Reynolds-averaged Navier-Stokes (RANS) equations for solving a heat transfer problem in a square channel is explored. A method for approximating solutions to differential equations based on the PINN approach is studied for estimating the mean flow temperature field with various heat transfer fluids. We consider a fully developed turbulent flow at a high Reynolds number (Re = 6100) and small to moderate Prandtl numbers (Pr = 0.025-1.000), typical of fuel elements using liquid metals and gas mixtures as coolants. Two models employing different approaches to approximating the turbulent heat flux are implemented: the gradient diffusion hypothesis (GDH) and an improved GDH hypothesis with two trainable coefficients that accounts for the shortest distance to the channel wall. The use of the PINN approach is shown to allow a significant reduction in computational cost. Model training takes approximately 2 h on a single GPU, whereas direct numerical simulation (DNS) of a similar problem on a supercomputer cluster requires several weeks of computation. The proposed approach is shown to be effective for parametric optimization, especially at small Prandtl numbers. When PINNs are used with DNS data, the accuracy of solving the RANS equations is higher than with conventional RANS modeling. The highest accuracy is achieved by the model using the modified GDH approximation.

The problem of unsteady bilinear flow of a Newtonian fluid in a reservoir with a finite-length vertical automatic hydraulic fracture connecting an injection and a production well is investigated. One well operates at constant pressure, while the other maintains a constant flow rate. Using the Laplace transform, analytical solutions are obtained for the pressure fields in the automatic hydraulic fracturing and in the reservoir, for the flow velocity in the fracture, and for the seepage rate. Conditions for the existence of a bilinear flow regime are determined. A simplified model of fracture flow using specified leakages is proposed, and analytical solutions in which time is a parameter are found.

The problem of proving the local-in-time existence and uniqueness of shock wave solutions to hyperbolic systems of conservation laws with many spatial variables is examined. This problem specifically pertains to the task of finding conditions on the initial data, such that, at each point on the surface of the initial shock wave, a smooth solution to the corresponding free boundary problem exists for small time. Examples of systems of conservation laws in continuum mechanics include the equations of gas dynamics and the equations of elastodynamics for compressible neo-Hookean materials.

The aerodynamic characteristics of a cone-shaped spacecraft model with and without an emergency escape system are compared. The freestream Mach number is M = 2. Jets issuing from the nozzles are shown to significantly affect the aerodynamic characteristics of the model. Compared with the cone-shaped model, the model with the escape system exhibits up to a 5.8-fold reduction in the drag coefficient.

Direct numerical simulation of the laminar-turbulent transition in a zero-pressure-gradient supersonic boundary layer and in the interaction of the boundary layer with an incident shock wave is performed. Transition scenarios caused by the development of a pair of oblique Tollmien - Schlichting waves at the frequency of the most unstable wave of linear theory, as well as by a wave packet, are investigated. Using the method of proper orthogonal decomposition, we performed a comparative analysis of the laminar-turbulent transition scenarios for a zero-pressure-gradient boundary layer and for a flow with a shock wave. Differences in the energy distribution of the flow fluctuations over the eigenmodes in the transition zone and in the wake are demonstrated.

A numerical study is performed on the development of disturbances in weakly underexpanded vibrationally nonequilibrium and equilibrium SF₆ jets issuing from axisymmetric sonic micronozzles into an SF₆ medium. The numerical simulation is based on solving unsteady three-dimensional Navier - Stokes equations using a two-temperature model of relaxing flows. Spectral analysis of the velocity disturbances in the mixing layer with respect to frequencies and azimuthal wave numbers shows that the initial disturbance level of the first asymmetric azimuthal mode determines the position of the laminar-turbulent transition. In a nonequilibrium microjet, this level is an order of magnitude lower than in an equilibrium one, which leads to a longer laminar section of the microjet.

Results of an experimental study of a Bunsen flame using planar laser-induced fluorescence (PLIF) are presented. A conical flame is visualized in the absence and in the presence of a weak transverse electric field. Premixed methane-air and ammonia-hydrogen-air mixtures are used with Reynolds numbers Re = 1000 and 600 and air equivalence ratios φ = 0.92 and 1.00, respectively. Using the PLIF method for two-line OH, an estimate of the temperature field is obtained for the studied regimes in the absence and in the presence of the electric field. The visualization results indicate that, under the action of a weak electric field, the upper part of the flame front of the methane-air mixture becomes rounded and deflected toward the cathode. The effect of a weak electric field on the ammonia-hydrogen-air flame produces no significant changes in the shape of the flame front and no significant deflection toward the electrodes. The temperature field estimate indicates that, in the studied regimes, a weak electric field has no effect on the temperature distribution in the combustion products.

The stabilization of a diffusion flame of gaseous hydrocarbons and hydrogen-containing mixtures is studied both for free discharge into the atmosphere and under the action of an external electric field. Current-voltage characteristics of the flame in an electric field are obtained for various hydrogen volume fractions. A change in the stabilization regime is observed when a constant electric field is applied. The relationship between the flame lift-off height and the homochronicity criterion is examined. The electrohydrodynamic effect on the flame is found to be dual in nature: in addition to the ionic wind, there is another mechanism by which the electric field influences the flame, associated with the induction of a space charge in the reaction region by the external field.

Computational studies of temperature variations in permafrost soils under various external boundary conditions are performed. The calculations use the results of laboratory studies of the thermophysical characteristics of soils in the thawed and frozen states, as well as the results of in situ soil temperature measurements in Norilsk, Russia. The boundary conditions of the computational model at the outer soil surface are specified using the snow cover thickness and the radiation balance. The variation of the radiation balance over the annual cycle is obtained for Norilsk's climatic conditions. A decrease in the moisture content of the surface soil layers is shown to reduce the influence of phase transitions on the thermal inertia of the soil, leading to an increase in the thickness of the soil layer with annual temperature fluctuations, an increase in the thaw depth, and a drop in the soil temperature below the thaw zone. Data are obtained on the temperature distribution over the depth of permafrost soils under various boundary conditions over a long-term cycle for Norilsk's climate.

Within the framework of antiplane shear theory, the equilibrium problem of an elastic composite body containing many thin gradient-elastic inclusions is considered. Each inclusion is geometrically represented by a straight-line segment with endpoints on the edges of the body. The inclusions-fibers or rods-are parallel to one another, and the problem contains a small positive parameter ε describing the distance between two adjacent inclusions. Using a variational formulation of the problem, the behavior of a family of its solutions as ε tends to zero is investigated. The limiting passage as ε → 0+ is justified using the two-scale convergence method. As a result, a correct averaged model of an anisotropic gradient-elastic composite body is constructed. This model describes the effective behavior on a macroscopic scale: on a scale at which it is not necessary to take each individual inclusion into account. Additional smoothness of the solution to the averaged model is proven, and an equivalent mixed formulation is derived on the basis of this proof. Finally, for the averaged problem in the mixed formulation, a numerical algorithm is proposed, and a series of numerical experiments is carried out to confirm the validity of the theoretical conclusions.

The problem of torsion of orthotropic circular rods under a constant torque in the creep regime is considered. Solutions are compared for three types of rods made from a transversely isotropic plate: (1) an isotropic rod with properties corresponding to those in the plane of the plate; (2) a rod oriented normal to the plate, taking into account the transversely isotropic properties of the material; (3) a rod oriented in the longitudinal direction of the plate, taking into account the transversely isotropic properties of the material. In a two-dimensional formulation, analytical solutions and estimates for the angular velocity of twist are obtained under the assumption of steady-state creep and no constraint of displacements at the rod ends along its axis. The resulting solutions are compared with the results of three-dimensional finite element calculations in the ANSYS software package. The possibility of estimating the stress-strain state by the method of characteristic parameters for rods of all three types is demonstrated. The resulting analytical dependences make it possible to determine the shear parameters of the material from torsion tests.

A numerical simulation of non-Newtonian fluid flows with various rheological parameters in a straight microchannel is performed to assess its suitability as a rheometer. Calculations are performed using a rectangular microchannel that is 40 μm high, 400 μm wide, and 13 mm long. A power-law fluid with a consistency index ranging from 0.006-0.6 Pa·sⁿ and a flow index ranging from 0.4 to 0.8 is considered. The Reynolds numbers range from 1 to 100. Based on the simulation data, a correlation is obtained for the constant in the expression for the friction coefficient, and equations are derived for calculating the rheological coefficients of the power-law model from the measured flow rate and pressure drop.

With a view to developing activities aimed at dust reduction in coal mine air, various mechanisms of dust catching with finely dispersed water droplets are discussed. Efficiency of wet dust suppression is estimated theoretically as function of density of dust particles, diameter ratio of water droplets and dust particles, and their collision velocity. The authors determine the minimal velocity of a water droplet to catch a dust particle, as well as the limit velocities of a water droplet relative to a dust particle, when no kickback and fragmentation of water droplets takes place. Dependence of dust suppression along a mine roadway on the parameters of dust particles and air flow is determined, and the start conditions for the secondary dust loss are determined.

As the scope of apatite-nepheline ore extraction expands, the diversity and quantity of complex ores, particularly those from fracture zones, are steadily increasing, which adversely affects ore processing. Research into apatite-nepheline ore revealed differences in the mineral constitution of deposits located in two distinct sections of the main ring-shaped foidolite structure. These differences stem from varying degrees of hydrothermal alteration, specifically in the ore from the Apatity Circus and Rasvumchorr Plateau deposits compared to the Kukisvumchorr and Yukspor deposits, and also from different amounts of finely dispersed secondary minerals, such as zeolites, clay minerals, and hydromicas. Petrographic and electron-microscopic analyses demonstrate that fluorapatite within zones of intense nepheline zeolitization has undergone partial dissolution, recrystallization, and redeposition, resulting in the formation of fine- to very fine-grained aggregates and complex intergrowths with zeolites. Based on these mineralogical and processing characteristics, the apatite-nepheline ore from the Apatity Circus and Rasvumchorr Plateau deposits is predicted to be more rebellious.

The issues of improving gold ore processing technology through the implementation of a crushing technique based on repeated dynamic impacts are examined. This study focuses on a seasonal modular processing plant, in which quartz-vein gold ore from the Maltan deposit is treated. A comparative analysis between the current ore preparation flowsheet with crushers SMD-116 and Barmac B-5000 and a proposed flowsheet with crusher DKD-300 is carried out. Material flows, circulating loads, processing performance, and economic efficiency of the new technology are calculated. The use of crusher DKD-300 reduced the total circulating load and the energy intensity of ore preparation. The crushing resulted in a complete liberation of gold particles coarser than 100 μm, which enabled pre-treatment of the crushed material. The flowsheet upgrade increased end-to-end gold recovery from 75.17% to 83.11%. The high technological and investment attractiveness of crushing by repeated dynamic impacts is confirmed at gold processing facilities.

The microstructural features of compacts made from milled refractory waste of fused aluminous product were analyzed. Structural and morphological changes in compacts when milled with a modifying agent were studied and determined. Test results indicate that compacts produced from modified powder exhibit a more homogeneous structure. The coarsening of subgrains during dry milling with a modifier suggests the formation of dense and strong inter-particle contacts; consequently, compacts made from the modified material will experience reduced surface stresses and strains in roasting, thereby enhancing the quality of finished products manufactured from man-made waste. The findings provide a basis for the development of aluminous waste processing and recycling technologies.

The promising varieties of quartz raw materials from the Southern Urals were processed. The textural and structural characteristics as well as mineral inclusions were studied. Two processing flowsheets were employed: the first involved microwave decrepitation and magnetic separation, while the second utilized thermal crushing. Compared to the first flowsheet, the second yielded more efficient processing results, achieving a 11-24% higher degree of purification in terms of total impurity content. The quartz concentrates produced by thermal crushing contain less than 20 ppm of total impurities, which meets the standards required for applications in the semiconductor, fiber-optic, lighting, optical, photovoltaic, and microelectronics industries.

The results of numerical modeling regarding the formation and atmospheric dispersion of a dust-gas cloud from a large-scale blasting in a quarry are presented. A total explosive mass of 6.500 kg was used. The modeling was divided into two stages: at the first stage, the formation of a blast cloud was analyzed using the Eulerian approach for multiphase media, starting from the time of explosive charges (each weighing 200 kg) detonation in boreholes, and ending with the time when the cloud completed its atmospheric rise. The second stage included calculating the subsequent transfer of rock particles within the dust-gas cloud; the wind speed, gravitational settling, and turbulent diffusion were taken into account. The diffusion was calculated using the Monte Carlo method. Airborne particle concentrations at different times and particle deposition densities at different distances from the pit wall were studied. The extent of dust particle deposition downwind outside the quarry boundaries was estimated.

A test bench is developed to study the stress-strain behavior of rocks under complex loading. The stress state within a cylindrical sample is generated by applying an axial compressive load and a torque. The sequence of application and the ratio between the axial load and the torque can be varied according to the experimental program. During testing, axial strain, circumferential strain, and the angle of twist are measured by novel sensors. Principal strains are determined using specially oriented strain gauges glued to the sample surface. Designed to operate in conjunction with uniaxial compression presses, this test bench enables the study of stress-strain and rheological properties of rocks. The use of rigid presses allows testing under both hard and soft loading conditions.