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We have studied the macrocomponent composition of pore solutions in hydrothermal clays forming extended thick strata in the thermal fields of the Pauzhetka geothermal system. Two zones have been identified in the vertical sections of the clay strata, which differ in the physicochemical parameters, composition, and formation conditions of pore solutions. It is shown that the pH of the solutions plays a crucial role in the change of their macrocomponent composition with depth. The conclusion is drawn that the pore solutions resulted from the direct impact of deep-level infiltrating thermal waters on the matrix of hydrothermal clays, which led to the redistribution of elements between the rock and the contact solution. Along with the general regularities, we have established significantly different conditions of formation of pore solutions in the Upper Pauzhetka and East Pauzhetka thermal fields, which is due to the different geologic positions and hydrogeochemical regimes of these fields.

Sulfosalts of the tetrahedrite and enargite groups from the Maletoyvayam epithermal Au-Ag deposit were studied using optical and scanning electron microscopy. We conclude that they were crystallized from acidic magmatic volcanogenic hydrothermal fluids under conditions of elevated oxygen level. Early sulfosalts of the pre-gold stage of the Maletoyvayam deposit, argentotetrahedrite-(Zn,Fe) and tetrahedrite-(Zn,Fe), associated with pyrite, arsenopyrite and galena, evolved with their enrichment in Te, Se and Cu. Increased activity of these elements caused by an increase in the oxidation potential of the environment led to the crystallization of subsequent stibiogoldfieldite, arsenogoldfieldite, and minerals of the enargite group, where the excess Cu content increased as the ore-forming system evolved. Au-bearing minerals are paragenetically associated with sulfosalts of the final stage of this evolution. The crystallization trend of sulfosalts (As→Sb→Te) at the Maletoyvayam deposit is also characteristic of other acid-sulfate type deposits, such as the Ozernovskoe and Prasolovskoe deposits, in contrast to the reverse trend (Te→Sb→As) typical for sulfosalts from adularia-sericite type epithermal Au-Ag deposits.

Active faults under permafrost conditions in the highland part of Gorny Altai (South Chuya and Kubadru fault zones) and the Lena River delta (Primorsky Fault Zone) were studied using the electrical resistivity tomography technique. The method proved to be effective in identifying active fault zones to depths up to the first hundreds of meters under permafrost conditions. However, the presence of ice-rich rocks with a resistivity greater than 100 kΩ·m limits its application because of the screening effect of the insulating unit. The main criterion for identifying active faults in geoelectric sections is the existence of subvertical zones of reduced electrical resistivity against the background of high-resistivity permafrost rocks. This concerns both the young seismic ruptures formed during the 27 September 2003 Chuya earthquake ( M_s = 7.3) in the South Chuya Fault Zone and the older Holocene primary seismic deformations in the zones of the Kubadru and Primorsky faults. At the same time, the electrical resistivity values in the zones of active faults and seismic ruptures are too high to assume their saturation with free water. The decrease in electrical resistivity in such zones relative to the host permafrost frame may be due to (1) intensive fracturing of rocks and sediments; (2) occurrence of finely grated material in the core and damage fault zones, on particles of which adsorbed unfrozen water is concentrated; (3) residual thermal anomalies in the case of modern fault activations, so that negative temperatures have already been restored, but the process of frozen strata aggradation is not complete yet; (4) saturation of the geologic section with sand-silty material as a result of liquefaction and fluidization processes during earthquakes. The revealed regularities can be used not only to confirm the zones of morphologically distinctive segments of active faults but also to search for their buried segments in the permafrost areas typical of seismically active highland and Arctic regions in Russia and worldwide.

The article considers the results of mathematical modeling of transient electromagnetic cross-borehole monitoring data for civil and industrial cryolithozone facilities containing thaw zones (taliks) in their vicinity. A solution to the direct problem is presented based on the Sumudu integral transform and the vector finite-element method for two types of borehole sources: induction coils and a less common electric current line, taking into account the frequency dispersion of the electrical conductivity of permafrost. Three-dimensional numerical modeling of the transient signals is performed in realistic geoelectric models of a gas-producing borehole and a residential building on piles. Based on the modeling results, we have revealed the main features and differences of transient cross-borehole monitoring with coils or a line as the source.

The phenomenon of increased burning velocity of a laminar fuel-rich ethanol flame with droplet injection was investigated numerically, and the results were compared with calculations for ethanol combustion without injection with the same mass fuel consumption. The calculations show that the presence of a dispersed phase in the form of 14 μm droplets with a mass flow rate of 0.5 g/min and a gas flow rate of 1.6 g/min significantly increases the flame propagation velocity compared to the combustion of gaseous ethanol with a flow rate of 2.1 g/min. The laminar flame speed increases from 23 cm/s in the combustion of only the gaseous fuel to 42 cm/s in the combustion with droplet injection. This effect correlates with a more than threefold increase in atomic hydrogen concentration in the flame and with a twofold increase in HCO concentration.

The dynamics of gas temperature was studied using as an example a single cylindrical channel with a diameter of 2 mm - a Raschig ring - placed in a porous medium made of such rings. The gas and thermocouple wire temperatures on the channel axis and the temperature distribution in the channel were calculated for two processes: the first is the pressure rise in a closed vessel during flame propagation in the space free of the porous medium, and the second is the cooling of the gas after the flame passage through the channel. For both processes, the gas temperature and the equilibrium temperature of the gas and the porous medium were measured using a thermocouple with a wire diameter of 15 μm in a cylindrical pore with a diameter of 2 mm. It was shown that during gas compression at a constant low rate, the thermocouple provided adequate measurements of steady-state gas temperature. However, when reaching the steady-state value, the larger the wire diameter, the longer was the thermocouple lag. During cooling of the instantaneously heated gas, the thermocouple measurements of gas temperature were found to be significantly underestimated. This is due to the higher heat capacity of the thermocouple wire as compared to the heat capacity of the gas in the pore. During the heating of the thermocouple, the gas cools down due to heat transfer into the pore walls.

Based on the large-eddy-simulation (LES) turbulence model, the shock wave propagation process in the roadway with branch structure was studied, focusing on the changes of overpressure under different explosion intensities and a different number of branches. Four conditions of gas accumulation length of 5, 10, 15, and 20 m are used in four models to reveal the influence of the branch structure. The results show that the shock attenuation coefficient of the main roadway no longer changes linearly with the gas accumulation length when there are branch structures in the roadway. When the gas accumulation length is constant, the increase of the number of branches can effectively reduce the rise rate of the impact overpressure value within a certain propagation distance. The overpressure in the branch roadway away from the explosion site is less affected. Due to the influence of multi-branch structure of adjacent roadway, its fluctuation is more chaotic than that of main roadway.

A closed mathematical model of continuous spin detonation of a synthesis gas---air mixture is formulated in a three-dimensional unsteady gas-dynamic formulation, and an algorithm for numerically solving the problem is developed. The model is verified using experimental data on ignition delay at high temperatures and the results of one-dimensional numerical calculations of the Chapman---Jouguet detonation parameters. For three stoichiometric compositions in an annular cylindrical combustor 306 mm in diameter, single-wave continuous spin detonation modes are obtained and the three-dimensional structure and the main flow parameters are analyzed. The minimum possible flow rates for continuous detonation are obtained in the case of variable specific mixture flow rates in a range of 90 ÷ 260 kg/(s · m²). The resulting data are compared with existing experimental data.

The methodology of calculating the problem of detonation initiation in acetylene-oxygen mixtures by a small-diameter sphere flying with a velocity greater than the Chapman-Jouguet detonation velocity is presented. A reduced kinetic scheme of chemical reactions is tested against experimental data on the ignition delay time, detonation propagation velocity, and detonation cell size. Regimes of oblique detonation and combustion in an acetylene-oxygen mixture diluted by argon are obtained in experiments in the pressure range from 21.1 to 60.7 kPa. The energy of detonation initiation by a high-velocity projectile is estimated, which demonstrates good agreement between analytical, numerical, and experimental data. Based on this estimate, the initiation of oblique detonation by a high-velocity projectile in an acetylene-oxygen mixture is calculated. A correlation between the numerically predicted flow regimes and analytical estimates is obtained.

Flows with multiheaded rotating detonation in a combustor in the form of an annular gap between plates are numerically studied. It is assumed that a homogeneous propane-air mixture enters the combustor from a reservoir with specified stagnation parameters through elementary nozzles uniformly filling the outer ring that limits it. The gas-dynamic parameters of this mixture are determined as functions of the stagnation parameters and static pressure in the gap. The study of multiheaded rotating detonation is carried out under the following conditions: the number of waves is 1, 2, 4, and 8, while the stagnation pressure slowly decreases over time according to a linear law. It is revealed that shock-wave structures can be qualitatively different, depending on the stagnation pressure, and that detonation ceases at a stagnation pressure lower than the critical pressure. The dependences of the power characteristics of the traction equipment on time are presented. Calculations are performed on the Lomonosov supercomputer at the Moscow State University using an original software package implementing a modified Godunov method and a one-step reaction kinetic model.