Home – Home – Jornals – Russian Geology and Geophysics 2020 number 2

We present results of geochemical and isotope (Rb-Sr, Sm-Nd, and Lu-Hf) studies of the early Paleozoic plagiogranitoid associations in the south of the Lake Zone in Western Mongolia, which formed at the island-arc and accretion-collision stages of the regional evolution. According to the petrogeochemical composition, the early Paleozoic plagiogranitoid associations of the island-arc (Tugrug, Hatan-Hunga, Udzur-Hunga, and Bayasgalant plutons, 531-517 Ma) and accretion-collision (Tugrug, Mandalt, and Dut Uul plutons, 504-481 Ma) stages are high- and low-alumina rocks. The recognized types of plagiogranitoids, with regard to their trace-element composition, indicate that their parental melts were generated from MORB-type metabasites at ≥10-12 kbar, in equilibrium with garnet-containing restite, and at ≤8 kbar, in equilibrium with plagioclase-containing restite. The Sr-Nd isotope data on the rocks and the Lu-Hf isotope parameters of their magmatic zircons show two groups of plagiogranitoids, with different sources of melts. The first group includes plagiogranitoid associations of most plutons (Tugrug, Udzur-Hunga, Hatan-Hunga, Bayasgalant, and Dut Uul) with isotope parameters (ε_Nd = 8.5-4.6, (⁸⁷Sr/⁸⁶Sr)₀ = 0.7034-0.7036, and ε_Hf = 14.7-11.9) indicating the juvenile nature of their sources. The second group includes plagiogranitoids of the Mandalt pluton; their isotope parameters (ε_Nd = 1.4-0.2, (⁸⁷Sr/⁸⁶Sr)₀ = 0.7053, and ε_Hf = 7.2-5.4) indicate that the parental melts were generated mostly from enriched-mantle metabasites. The Hf isotope data on inherited and xenogenic zircons (664-519 Ma) from the early Paleozoic plagiogranitoid associations of the southern Lake Zone permit us to separate these rocks into three groups according to their ε_Hf values (14.5-12.8, 2.9, and 10.6-6.7). The Hf isotope parameters of magmatic and inherited zircons, with regard to their age, indicate that the source of the parental melts lacked rocks with a long crustal history, such as the early Precambrian associations of the Dzavhan microcontinent.

The Kyzyl-Tashtyg deposit and the Kyzyl-Tashtyg ore field are included in the Kyzyl-Tashtyg ore cluster, which is located in the southeastern part of the Ulugoi structure-metallogenic zone. The geologic section of the ore field is composed of lower Cambrian terrigenous and volcanic deposits of the Tumat-Taiga and Tapsa Formations that include a homodromous sequence of early basaltic andesites transitioning to felsic dacite-rhyolite rocks with widespread subvolcanic intrusions. The pyrite-polymetallic mineralization of the ore field spatially associates with a central-type volcanic structure and is localized within the «motley» unit consisting of three lithologic/stratigraphic horizons. The Kyzyl-Tashtyg pyrite-polymetallic deposit is the main ore occurrence of the ore field, which contains the main reserves of pyrite-polymetallic ores. The mineralization outcrops are 650 m in length and 60-65 m in width. The reserves of commercial ore are 12,920 mln tons, with the following average contents of ore metals: Pb-2.8%, Zn-10.3%, Cu-0.65%, Au-1.03 ppm, and Ag-48.71 ppm. The ores have typically simple mineral compositions: pyrite, chalcopyrite, sphalerite, galena, and baryte. Secondary minerals include enargite, hessite, sylvanite, proustsite, and native silver. Based on the dominant mineral or groups of minerals, the ores are classified into sulfur-pyrite (pyrite), copper-zinc (pyrite-chalcopyrite-sphalerite), polymetallic (sphalerite-galena), and baryte-polymetallic (baryte-sphalerite-galena) varieties. The main commercial type is copper-zinc mineralization. The widest range of impurity elements and their highest contents have been identified in copper-zinc and polymetallic ores, in which the main mineral is sphalerite, the carrier of the largest amount of impurity elements. In these ores, commercial contents of gold and silver have been detected: Au-0.8 and 2.3 ppm and Ag-26 and 78 ppm, respectively. Formation temperatures of different types of ores of the deposit range from 400-305 to 270-150 °C. The formation temperatures regularly decrease from sulfur-pyrite to copper-zinc and to baryte-polymetallic ores. This temperature pattern forms a vertical mineralization zoning from bottom to top of the deposit. The formation of the deposit was related to early Cambrian volcanism and included different mechanisms of ore deposition. The hill-like shape of the main ore lode with intense hydrothermal alteration of rocks in its base indicates a hydrothermal and hydrothermal-sedimentary genesis on the floor of a sea basin. The occurrence of tube-like orebodies in the root area of the mineralization zone with veinlet-disseminated and massive ore structures indicates a hydrothermal-metasomatic origin.

We studied the mineralogical and geochemical features and formation conditions of productive mineral assemblages of the Tardan gold-sulfide-quartz deposit located in the endo- and exocontact zone of the Kopto-Bai-Syut gabbro-diorite-plagiogranite massif of the Ordovician Early Tannu-Ola complex (O₁tn). Postskarn mineralization of vein-dissemination type in skarns, quartz diorites, and carbonate rocks is limited by tectonic crushing zones and conjugated with beresitization and listwaenitization of the ore-bearing rocks. Mineralogical and geochemical research has shown the formation of ultrahigh-fineness (986-952‰) and high-fineness (947-918‰) gold at the first productive gold-quartz-calcite substage, of high-fineness gold (918-904‰) → medium-fineness gold (896-809‰) → low-fineness gold (798-756‰) ± hessite Ag₂Te ± volynskite AgBiTe₂ at the second productive gold-telluride-sulfide-quartz-carbonate substage, and of medium-fineness gold (897-802‰) → low-fineness gold (799-717‰) → electrum (691-612‰) → mercurian electrum (471-451 ‰) ± hessite Ag₂Te ± acanthite Ag₂S ± matildite AgBiS₂ at the third productive gold-sulfosalt-sulfide-quartz substage. High- and medium-fineness gold prevails in the ores, ultrahigh- and low-fineness gold is subordinate, and electrum and mercurian electrum are scarce. The fineness of native gold in the ores varies from 451 to 986‰, averaging 858‰. The productive mineral assemblages of the Tardan deposit formed from aqueous fluids containing Mg, Na, and K chlorides (salinity is 6.1-12.9 wt.% NaCl eq.), with a decrease in the mineral formation temperature from 380 to 150 ºC and variations in f _O2, f _S2, f _Se2, and f _Te2.

The Lugokanskoe deposit is located in southeastern Transbaikalia and has been studied for a long time by many researchers. However, the type of its formation is still debatable. In this paper we study the mineral composition of ores by modern methods, recognize and describe the main gold mineral assemblages, and present detailed data on the chemical composition of native gold and sulfide minerals and their isotope composition. We have established that gold-pyrite-chalcopyrite-arsenopyrite and gold-bismuth parageneses localized in skarn deposits are the main productive assemblages. Study of the sulfur isotope composition of sulfide minerals has shown an endogenous source of sulfur of the ore minerals. The carbon and oxygen isotope compositions of carbonates of ore-bearing veins indicate the participation of a magmatic fluid. The established age of the gold mineralization and igneous rocks of the Shakhtama complex, together with direct geological observations, points to their spatial, temporal, and genetic relationships. According to their petrochemical and geochemical characteristics, the igneous rocks of the Shakhtama complex are I -type ilmenite (reduced) granitoids. Study of fluid inclusions by heating and cooling and Raman spectroscopy has shown that the mineral formation was accompanied by a gradual decrease in the content of salts in the ore-forming fluids and by a decrease in their homogenization temperatures. Optical observations demonstrate that the fluid was heterogeneous at the early stages of the mineral formation. The evolution of the ore system was accompanied by a change in the gas phase composition of fluid inclusions from predominantly nitrogen-carbon dioxide to essentially aqueous, with carbon dioxide impurity (H₂O + CO₂ ± ± N₂ → H₂O ± CO₂). The research data testify to the magmatic nature of fluids and the participation of meteoric waters at the late stages of the ore-forming process. The data obtained have led to the conclusion that the Lugokan gold deposit is related to reduced intrusions formed at a shallow depth.

The chemical and isotope compositions of nitric and carbon dioxide thermal waters in Jiangxi Province (China) are considered. The nitric thermal waters are ultrafresh (TDS = 0.26-0.42 g/L) and highly alkaline (pH = 8.73-8.87), with excess of SiO₂, F-, Na, etc. but ultralow concentrations of Ca2+, Mg2+, and Cl-. The carbon dioxide thermal waters are more saline (TDS = 0.3-3.9 g/L) but have lower pH values (6.7-7.8). Major anions in both types of waters are HCO₃^- and Na⁺, but SO₄^2-, F^-, CO₂, and H₂S also play a crucial role. The equilibria of the thermal waters with a complex of secondary minerals (carbonate, fluoride, clay, zeolite, etc.) have been calculated. The thermal-water-rock system is shown to be in the equilibrium-nonequilibrium state. During the transfer into deep horizons and back to the surface, the hydrotherms continuously dissolve all minerals that are in nonequilibrium with them (K-feldspar, anorthite, etc.) and form new minerals, which are in equilibrium with these waters (calcite, albite, etc.). The composition of the solution and the type of secondary minerals change with time because of the change in the proportion of chemical elements: Some elements are removed from the solution, while others continue to accumulate. A dynamic equilibrium between the elements entering and leaving the nitric thermal waters is established very early, when the waters are still ultrafresh, which is due to the high pH and low p _CO2. This equilibrium inhibits an increase in the salinity of the nitric hydrotherms, and they remain lowly mineralized. Owing to the higher p _CO2 and, correspondingly, lower pH values, the carbon dioxide thermal waters reach a dynamic equilibrium at a later stage, when their salinity is higher than 3 g/L; therefore, they are more mineralized.

We study the morphology and sedimentary facies of trace fossils formerly identified as Arctichnus found at the base of the Jurassic section near Cape Airkat (northern Siberia). They are most often found in shoreface silty sand and are similar to Rosselia socialis ichnospecies in morphology, taphonomy, and depositional environments. On the basis of this similarity, the Airkat trace fossils should be identified as Rosselia socialis Dahmer, 1937. Analysis of the type collection of Arctichnus arcticus has revealed new morphological features of the taxon.

Spectral characteristics of the medium around 23 digital strong-motion seismic stations of the Kamchatka region have been studied from local earthquake data relative to a reference bedrock station (Petropavlovsk, PET). Spectra are determined by multiband filtering. In each band peak velocity amplitudes, levels of Fourier S-spectra and mean-square coda amplitudes were compared. Average Fourier spectra were obtained from S-wave energy using Parseval’s equation. The difference in hypocentral distances for pairs of stations was compensated by empirical S -wave attenuation functions. Records of more than 300 events were processed, with M = 5-6 and hypocentral distances mainly 100-600 km. The spectral ratios estimated by the three methods show behavior diversity. Some nonrock stations show expected spectral characteristics at high frequencies. The conditions at other stations can be considered similar to those at PET. Some stations show amplifications of up to 10 times in the 20-30 Hz frequency range. In general, the obtained spectral characteristics within 3-5 Hz are consistent with the expected trends corresponding to known local geology around strong-motion stations.

Magnetotelluric sounding (MTS) usually records variations in five components of the electromagnetic field. Interpretation of distorted MT responses of an inhomogeneous earth may be problematic. The problem can be solved by recording additionally the vertical component E_z of the electric field in order to improve the quality of inversion and to gain more information. Currently E_z variations are estimated by measuring voltage on a vertical line immersed in water. The land measurements of this kind require special drilling or using the existing boreholes, which is not always feasible. Otherwise, a circular electric dipole (CED) can be used as a receiver to record the electric field behavior along the vertical component. Its applicability to MT soundings is analyzed in this paper.

The air flow in the human bronchial tree is simulated in the normal and pathological cases. Analytical formulas are derived to design the full bronchial tree. All surfaces of the bronchial tree are matched with the second order of smoothness (there are no acute angles or ribs). The geometric characteristics of the human bronchial tree in the pathological case are modeled by a “starry” shape of the inner structure of the bronchus; the pathology degree is defined by two parameters: bronchus constriction level and degree of distortion of the cylindrical shape of the bronchus. A numerical technique is proposed for stage-by-stage computing of the air motion in the human bronchial tree. A laminar air flow in the human bronchial tree is computed from the input bronchus to alveoli). It is demonstrated that the pressure decrease in the case of a laminar air flow in the bronchial tree is twice smaller than that in the turbulent case. Distortions of the cylindrical shape of the bronchi in the pathological case lead to a more significant pressure decrease in the bronchial tree.

The filtration of arterial, venous and capillary blood, and cerebrospinal fluid are investigated using a multiphase poroelastic model for the brain matter based on medical data. The model can be used to describe the healthy brain, the state of a brain with hydrocephalus, and the transition between them which occurs when changing model parameters.

A problem of plane-parallel steady motion of a low-viscosity incompressible fluid inside an elliptical cavity with a wall moving along its contour is under consideration. A slip condition with a constant or piecewise-constant slip function is set at the cavity boundary. This problem is solved using the method of merging asymptotic expansions. When the Reynolds number is of the order of Re=1500 and there are no corner points in the flow region, the calculation time decreases by hundreds of times compared with the case where the finite difference method is applied. The flow region is divided into an inviscid core in which vorticity is constant and a “weak” boundary layer. The equation of the “weak” boundary layer by changing variables is reduced to a heat equation whose solution is constructed in the form of a series.

This study compares detailed mode maps during operation using air of two Rank pipes with round and square cross sections of the working channel in the case of identical guides at the inlet and identical outlets. The degree of air expansion and the fraction of flow rate through a cold outlet varies in ranges of 2-8 and 0.2-0.8, respectively. It is observed for both pipes that, as the degree of expansion increases, the dependences of the volumetric flow rate and the cooling coefficient on the fraction of cold flow rate become stable. It is revealed that the cooling coefficient in a round tube is 1.5-2.0 times greater than in a square channel, and the volumetric flow rate therein is approximately 10% lower.

Within the framework of the second approximation of the shallow water theory, the flow of a multilayer fluid stratified in density is under study. A mathematical model for the propagation of near-bottom and near-surface large-amplitude internal waves is constructed, taking into account the influence of the fine structure of thermocline (pycnocline). Using the resulting solutions describing the propagation of solitary waves and wave bores, field data are interpreted.

The aim of this study is to investigate the effect of diversity of particles in the downstream cloud on detonation wave suppression. The multi-component two-phase model for a reacting compressible flow field including clouds of chemically inert solid particles is utilized here. The detonation wave is simulated in a stoichiometric hydrogen and oxygen mixture using a detailed full chemistry model. The finite volume scheme is used in the developed numerical program, where the advection upstream splitting method is used in addition to the Saurel method for the multi-particle cloud in order to compute the particle-phase and gas-phase fluxes. The impact of the detonation wave on the rigid wall is investigated, and the magnitude of the resulting pressure rise is accurately predicted in the case of a head-on collision of two similar waves instead of direct simulation of the wall reflection. The results demonstrate that the impact pressure rise is rather strong and destructive, and using a multi-component particle cloud may have better attenuating features for both short and long action times and require a shorter required propagation length for detonation wave suppression than using a single-component particle cloud.

Interphase momentum exchange of a polydispersed two-phase flow is numerically studied by using a model based on interfacial drag effects of a bulk liquid, ligaments, and droplets entrained in the air flow. A power-law relation is proposed between the droplet velocity and its diameter. The dispersed phase is modeled using the methodology of spray moments of the drop size distribution. All the equations are solved in a Eulerian framework using the finite volume approach, and the phases are coupled with the source terms. The proposed dependence accurately simulates the droplet behavior because droplets with larger diameters experience a higher drag and generally have higher velocities than smaller droplets. The model shows reasonable agreement with experimental and numerical data on the spray tip penetration and Sauter mean radius.

The main objective of this study is to analyze the effect of the solid deposits downstream of the injection hole on the film cooling efficiency by highlighting the impact of several geometrical and physical parameters, such as the blowing ratio, deposit position, and deposit height, by using the ANSYS CFX software. Several configurations are tested by changing the deposit position and deposit height. The turbulence is approximated by the shear stress transport (SST) model. The film cooling effectiveness distributions are presented for different blowing ratios. The numerical results are compared with available experimental data, and good agreement is noted.

Results of an experimental study of how temperature affects the destruction of laser welds of an Al-Cu-Li aircraft aluminum alloy are presented. A comparison is made of the deformation and fracture of welds in the initial state and after two-stage thermal treatment. It is shown that the mechanical characteristics of welded samples have values close to those of the initial alloy.

Constitutive steady-state creep equations are proposed for orthotropic materials with different tensile and compressive resistance properties. Power functions with different exponents for tension and compression are used to describe the resistance. The equations of the problems of tension and shear and the equations of the plane stress problem are given. The model is used to solve the problem of torsion of annular cross-section rods cut from a plate of AK4-1 transversally isotropic alloy in the normal and longitudinal directions by a constant moment at a temperature T = 200oC. Constitutive equations for torsion are obtained. Values of model parameters were obtained in experiments on uniaxial tension and compression of solid round samples cut in various directions. An analytical solution for the rate of torsion angle of an annular cross section rod cut in the normal direction of the plate was obtained for the same exponent index under tension and compression. For a rod cut in the longitudinal direction of the plate, an upper bound of the rate of torsion angle was obtained. The calculation results are in satisfactory agreement with the experimental data.

A mathematical model of viscoelastic-plastic flexural deformation of spatially reinforced plates was developed based on the method of time steps. The viscoelastic behavior of the components of the composition is described by the Maxwell-Boltzmann equations, and plastic behavior by flow theory with isotropic hardening. The low resistance of composite plates to transverse shear is taken into account within the framework of Reddy's theory, and the geometric nonlinearity of the problem is considered in the Karman approximation. The corresponding initial-boundary-value problem is solved using a numerical scheme of the “cross” type. The dynamic viscoelastic plastic bending of spatially reinforced fiberglass rectangular plates under the influence of an air blast wave was investigated. It is shown that for relatively thick plates, replacing a flat reinforcement structure by spatial leads to a significant decrease in the maximum and residual deflections and strain intensities of the binding material, while for relatively thin plates, this replacement is ineffective. It is found that in the initial stage of deformation, the amplitude of oscillation of the composite plate significantly exceeds the residual deflection.

Known models were used to investigate the delamination of a pre-compressed coating from an elastic base, to study in detail the corresponding transcendental equation, prove the existence of a solution in a certain range of parameter values, and obtain simple formulas for the critical value. The supercritical behavior of the coating was studied using the linearization procedure and the Ritz method. It was proposed to simplify the problem by solving the problem for a beam with Winkler type boundary conditions in the delamination area, and an assessment of this simplification was made.

The effect of the cellular core on the stress intensity factor at the tip of a crack in the adhesive layer of a five-layer sandwich composite beam is investigated. A Nomex sheet is used to model the cellular core with honeycomb, square, and triangular cells. The mechanical properties of these cells are obtained by the finite element analysis supported by theoretical two- and three-dimensional equations. Based on the deduced properties, the load-displacement curve is generated for a sandwich beam under mode I fracture. The numerical findings are validated against available experimental data. It is shown that the lowest values of the stress intensity factor are observed for a core with a honeycomb structure as compared to the other two cell shapes used in this study, which are composed of equilateral triangles or squares. An increase in the wall thickness of the cells leads to an increase in the stress intensity factor.

Algorithms for determining the stress intensity factor are developed on the basis of the results of the analysis of asymptotic solutions to the problems of deformation of a homogeneous solid with a cut and a plate with a crack located at an interface between two media,. The proposed algorithms are used to calculate stress intensity coefficients using the results of a numerical solution of the problems of loading various flat and spatial homogeneous cracked solids, as well as a plate with a crack located at the interface between two elastic media. It is shown that the calculation results are in good agreement with the data obtained by other methods.

Regularization techniques for the trace and the traction of elastic waves potentials previously built for domains of the class C² are extended to the Lipschitz case. In particular, this yields an elementary way to establish the mapping properties of elastic wave potentials from those of the scalar Helmholtz equation without resorting to the more advanced theory for elliptic systems in the Lipschitz domains. Scalar Günter derivatives of a function defined on the boundary of a three-dimensional domain are expressed as components (or their opposites) of the tangential vector rotational Δ _{δ Ω}u × n of this function in the canonical orthonormal basis of the ambient space. This, in particular, implies that these derivatives define bounded operators from H^s to H^s-1 (0 ≤ s ≤ 1) on the boundary of the Lipschitz domain and can easily be implemented in boundary element codes. Representations of the Günter operator and potentials of single and double layers of elastic waves in the two-dimensional case are provided.

The peculiarity of the paleogeographic situation in the south of the Vitim plateau of the Transbaikalia led to the formation of landscapes with numerous heaving mounds and thermokarst depressions. The cryolithozone responded to the climate warming by reducing the area, increasing the temperature and depth of seasonal thawing of permafrost. The differentiation of the soil profile in the helix mounds and thermokarst depressions, which led to changes in the morphological, physicochemical properties, which in turn caused the response of the biota, was revealed.

In the Baikal region, warming under conditions of climate continentality is accompanied by increasing of the area of forest fires and the risk of post-pyrogenic ecosystems not turning back into the forest cover. The study of pine forests on sand sediments in the South-Eastern Baikal region showed that ecosystems, located on the territory damaged by fire, develop in different directions depending on the type of a fire and local conditions. After a ground fire, the adult forest stand is preserved and stable signs of pyrogenesis in the soil are developed in the form of charred epipedons. Under these conditions, sparse-grass and dead-cover open stands are formed with almost no signs of renewed young growth and shrubs. The coal influence causes a decrease in soil acidity, an increase in the content of calcium exchange, the formation of humus of humate composition and the base unsaturation. It is proposed to identify the soils with coal epipedons at the level of subtype: psammosoils humus post-perogenic. After a top fire, the plant cover and the soil cover are completely destroyed, the ecosystem begins its development from the 0-moment. Forest renewal in lowlands and on the slopes of shadow and leeward expositions occurs actively in a natural way, as well as against the background of the performed reforestation works. During the post-fire period the soil of Underdeveloped section, psammosoil humus, was formed under the young forest. On the slopes of solar, upwind expositions, despite the actions taken to restore the forest stand, deflation zones, not covered with forest and with no signs of soil formation, are formed. Remote sensing methods made it possible to ascertain that for fifteen years of post-fire development, despite the performed reforestation, the area of uncovered deflation zones has increased in eleven times compared to the pre-fire period. It is recommended to include forest stand restoration in the form of loosening the charred soil on the territories damaged by ground fires, as well as repeated execution of forest planting works in the deflated areas considering protection of the forest edges from wind, into a set of measures to restore forest ecosystems after wildfires.

The article described a variety of psammophyte grass vegetation, in which communities occurs or potentially can recover Pinus sylvestris in Southern Nechernozemye of Russia and identified trends of forming of composition and structure of communities under the influence of leading environmental and coenotical factors. Research realized on the territory of Bryansk, Kaluga and Smolensk regions in 2010-2018; were collected more than 150 relevés of psammophyte grass vegetation. The vegetation belongs to the class of Koelerio-Corynephoretea Klika 1931, which combines dry grasslands on sandy soils and on rocky outcrops of the temperate to boreal zones of Europe, the North Atlantic islands and Greenland. Differences in environmental regimes of habitats of psammophyte communities identified. In most cases, the ecological amplitude of syntaxonomical units in three leading edaphic factors (moisture, reaction, and a soil richness in mineral nitrogen) vary significantly and form a fairly compact environmental space: within syntaxa values of factors vary normally in narrow limits. By method of regression analysis found that species richness of communities shows dependence on significant statistical level only from the richness in mineral nitrogen and soil moisture. Based on the results of the statistical analysis, the number of plants of Pinus sylvestris at any age does not depend on the species richness of the communities, general cover of grasses, separately calculated the cover of mosses and lichens, as well as from environmental factors by H. Ellenberg. The only factor on which the dependence of the number of pine trees at venues, is the distance from the source of the diasporas, which determines the possibility of invasion. The data of phytocoenotic and floristic diversity of psammophyte grass vegetation will be incorporated into a single database for the Southern Nechernozemye of Russia, with the aim of identifying of environmental and botanico-geographical features of this type of plant communities in the region.

The primary successions of vegetation have been investigated in the continental conditions of the North-Chuya center of present-day glaciation (the Central Altai) from the colonization of deglaciated terrains by the first plants and the formation of simple plant groups to the primary plant communities. The observations were carried out for 15 years on the young moraines of the valley glaciers of Maly Aktru (2200-2250 m) and Bolshoi Left Aktru (2370-2500 m above sea level), in chrono-sequences from the ends of glaciers to the moraines of the mid-19th century. Three stages and four sub-stages of the primary succession of vegetation were identified, the species composition of vascular plants, mosses and ground lichens was identified, the dominant species, the peculiarities of primary vegetation were characterized. The ideas about the course of successions and their peculiarities at different altitudes in the upper part of the forest and sub-chalet belts are obtained. It was identified that in the 150 period a young forest community is formed on new moraines in the upper part of the forest belt, and a combination of microcenoses similar to tundra communities are formed in the alpine belt. Primary succession of vegetation on both glacier forelands has some similarities, especially in early stages of ecosystems development (pioneer species composition, three-stage structure of successions); the strong differences appear during the late stages of succession. The primary succession of vegetation on the foreland of the Malyi Aktru glacier involves 146 species of vascular plants, 44 species of mosses and 6 species of lichens; on the foreland of Bolshoi-Levyi Actru 128 species of vascular plants, 26 species of mosses and 8 ground lichens were recorded.

The structure of flora and fauna, which is a standard of the state and dynamics of the taiga forests in humid climatic facies of the Altai-Sayan mountain region is analyzed on the example of the undisturbed mountain Siberian Pine taiga (Eastern Sayan mountains). Ecological-phytocenotic features, floristic and faunistic composition of late succession stage were studied. The dominance of the green moss group of forest types is revealed across the topographic profiles. The forest stands have a different-age structure with Pinus sibirica (Du Tour.) dominance, low productivity (IV-V quality classes prevail), high class of normality (from 0.5 to 1.0) and sufficient regeneration. The floristic, ecological-coenotic analysis of the herb-dwarf-shrub layer, the elements of undergrowth and the moss cover indicates dominance of the humid taiga flora. The species of the taiga ecological-coenotic group (ECG) ( Vaccinium myrtillus , Carex iljinii , Calamagrostis obtusata , Gymnocarpium dryopteris , Phegopteris connectilis , Oxalis acetosella , Aegopodium alpestre , Trientalis europaea , Linnaea borealis , Maianthemum bifolium , Stellaria bungeana et al.), moss-bog ECG ( Ledum palustre , Vaccinium uliginosum , Carex globularis et al.) and bor-taiga ECG ( Vaccinium vitis-idaea , Pyrola rotundifolia , Lycopodium annotinum et al.) form the herb-dwarf-shrub layer in the prevailing forest types. Green mosses ( Hylocomium splendens , Pleurozium schreberi with a mixture of Ptilium crista-castrensis and Rhytidiadelphus triquetrus ) dominate in the moss layer.Polytrichum commune , P. strictum , Dicranum scoparium , D. polysetum and Sphagnum sp. mosses are found in some sites. The increased role of higher spore plants characterized the flora as well-preserved archaic features flora. The Siberian Pine forests coenoflora consists of 224 species and belongs to the Cyperaceae -type. In the structure of the geographical elements of the flora, the leading role belongs to the Palaearctic, European and Siberian elements with an increased role of endemics. The species of typical for the Siberia taiga complex consist the core of the fauna. The most diverse avifauna is represented by 102 species ( Tarsiger cyanurus , Parus montanus , Parus ater , Luscinia calliope , Sitta europaea , Loxia curvirostra , Coccothraustes coccothraustes , Tetrastes bonasia , Phylloscopus proregulus et al.).

The study of the horizontal and vertical distribution of phytoplankton of Lake Sevan was conducted in mid-July 2018, during its maximum blooms of Cyanoprokaryota. The summer biomass of algae in the pelagic zone of the lake were compatible with values of mesotrophic waters. Cyanoprokaryota biomass in Lake Sevan had horizontal and vertical heterogeneity and was related to the depth, morphometry of the lake parts, distribution of currents, transparency, temperature and biomass of Cladocera. In areas where there was water blooms, there was a decrease in the specific number of phytoplankton species and water transparency. The following factors contributed to the increase the average phytoplankton biomass compared to 2013-2017: 1) increased water temperature, 2) weakening of zooplankton press due to the disappearance of Daphnia magna, 3) increased phosphorus load due to increased contribution of D. longispina and Diaphanosoma lacustris in the zooplankton biomass .

Conifer decline ( Abies sibirica Ledeb. stands) as a result of complex biotic effects on the territory of the Krasnoyarsk region by 2018 reached an area of 541,4 thousand hectares; the potential area of further death of A. sibirica is up to 10 million hectares. The main reason is the phytopathogenic fungi Armillaria mellea s. l. and Heterobasidion annosum s. l. when combined with bark beetle Polygraphus proximus . Trees affected by root pathogens are centers of forest dieback, from which pathological outbreaks spread, including due to the effects of P. proximus and its phytopathogenic mycoassociates. Neonectria fuckeliana (C. Booth) Castl & Rossman is among the concomitant pathogens in the scale of the lesion, which causes a resin flow that is similar to the effects of P. proximus attack. The phytopathogenicity of pure cultures of the dominant root pathogens of Armillaria borealis Marxm. & Korhonen and Heterobasidion annosum (Fr.) Bref . , as well as the stem pathogen of N. fuckeliana , has been confirmed by a series of experiments in vitro . Promising natural agents for the regulation of P. proximus abundance are highly virulent aboriginal strains of Beauveria bassiana (Bals.-Criv.) Vuill., resulting in maximum insect death (up to 100 %) for 7-11 days and retaining activity in the temperature range of (16-24) ± 1 °C.

The structure of Thymus petraeus individuals was studied using the architectural approach. It is established that in the South of Siberia the species occurs in similar habitats: in the present, meadow, sandy steppes and their petrophytic variants on the slopes and low rocky peaks of hills. Classification I. G. Serebryakov [1964], T. petraeus - vegetatively-semimobile dwarf shrub with persistent throughout the life system of the main root and with rooting runners. In the structure of individuals T. petraeus identified 3 architectural units that differ in the position of the compound skeletal axis in space (orthotropic-plagiotropic, plagiotropic, orthotropic). Each architectural unit consists of the main compound skeletal axis, the compound skeletal axes of 1st order, formation shoots, branching and enrichment shoots. It is shown that the structure of individuals can be formed by repeating only two architectural units. It is established that in the present steppes and their petrophytic variants the structure of individuals is built at the expense of repetition of orthotropic-plagiotropic and plagiotropic architectural unit; in sandy steppes - at the expense of repetition of plagiotropic and orthotropic architectural unit. The features of T. petraeus development in specific ecological and cenotic conditions are shown. In this regard, characterized by: 1) morphological polyvariance, which is based on changes in the structure of shoots (shortened, elongated) and the composition of architectural units (no compound skeletal axes of the 1st order or enrichment shoots); 2) dimensional polyvariance, manifested in the change in the length and number of compound skeletal axes; 3) dynamic polyvariance, associated with fluctuations in the duration of monopodial growth of shoots formation (from 2 to 5 years) and the architectural unit as a whole (from 6 to 20 years). The revealed modifications of architecture do not lead to a change in the life form of the dwarf shrub, but reflect the mechanisms of its adaptation.

The results of the study of the dynamics of elements of seed productivity amfilikt Hierochloё repens (Host) Beauv. (2 n = 28) and the optional apomict Hierochloё odorata (L.) Beauv. (2 n = 42) (Poaceae) are presented. The plants were grown in the absence of competition and in single-species artificial cenoses with low (5 plants/m²) and high (20 plants/m²) starting density. It was found that plants according to the classification of ecological strategies belong to K-species, the expenses of reproduction was 1.8-5.8 % of the biomass of an individual. The reproductive capacity of two-year cenoses depended on the starting density of plants. In low-density cenoses, plants had 2.4-2.7 times fewer generative shoots compared to high-density cenoses. The influence of species features (F₁) on fruiting abundance varied with age. At two-year coenosis proportion of influence of this factor on the number of generative shoots per unit area was 43,11 % (F₁ = 16,12 %), from three-year - 60,04 % (F₁ = 31,26 %) have a four-year - of 29.19 % (F₁ = 7,24 %; F₀₅ = 4,49; F₀₁ = 8,53). Intrapopulation correlation of indicators of reproduction of the dimension indicators individuals clarified, expressed through the mass and proportion of organ weight from the biomass of individuals. The real seed productivity of H. repens plants was 2.2 times higher in individuals and 1.4 times higher in cenoses compared to H. odorata . Reproductive imbalance in H. odorata is associated with polyploidy and the possibility of apomixis.

In this work, we consider the dynamics of vegetation indices and surface temperature of post-fire areas of different ages in the larch forests of the permafrost zone of Siberia, obtained using long-term Terra/MODIS satellite imagery. Preliminary classification of Landsat/ETM, OLI satellite images was performed to analyze the degree of pyrogenic disturbance in the sample of post-fire sites. An increase of the average temperature of the underlying surface of the post-pyrogenic areas by 3.9-4.6 °C was recorded depending on the degree of disturbance of the litter, which is 15-30 % of the average background values. The deviation (decrease) for the NDVI comparing to background values in the next post-fire year was 22 %, for the NBR index - 72 %. Recovery of the NDVI to background values required 7-10 years after the fire. The recovery period for the surface temperature and the NBR index are significantly higher - 15 years or more. Moreover, for 15-20 years after the fire, the observed temperature anomalies of the underlying surface remain significant.

Results of a pioneering experimental study of the cold spray method used for spraying aluminum traces onto the surface of a brittle erodible material (like brick) are reported. The spraying is performed using a sonic nozzle. Particle velocities near the axis of the two-phase jet are measured, and an approximating formula is derived to describe the dependence of the particle velocity on the stagnation pressure and temperature of the accelerating air. Interaction of the two-phase jet with the substrate surface is studied, and it is shown that an increase in the gas stagnation temperature transforms the process of substrate erosion a coating formation process. Parameter values that can be recommended as working ones for practical spraying are identified.

The preparation of a titanium composite powder containing high-melting TiN nanoparticles using an electric-arc plasma torch is studied. Using an Evo MA15 electron microscope (Carl Zeiss) and a DRON-4.0 diffractometer, both the surface morphology and the internal structure of powder particles are investigated, an X-ray phase analysis of these particles is performed, and a distribution map of the elements both over the surface of the obtained composite particle and over its volume is constructed. It is shown that the nanoparticles are uniformly distributed over the entire volume of titanium particles and are completely clad with Ti. The nanostructured powders obtained in this way and used as nanomodifying additives increase the homogeneity of the distribution of the high-melting elements introduced into the melt, protect the nanoparticles from the direct interaction with ambient medium, increase their wettability, and prolong their shelf life. These factors improve the efficiency of metal and alloy nanomodification.

The paper describes a theoretical study on the influence of filtration of a mixture of gaseous products of pyrolysis and water vapor on the dynamic of ignition of coal-water fuel particles under conditions of high temperature heating. The developed mathematical model offers simulation of the process of ignition of coal-water fuel droplets under conditions close to the furnace space (characterized by intense radiation-convective heating) in typical boilers. Comparisons of experimental data (found previously) and simulation data on the ignition delay time ( t _ign ) demonstrate good compliance. Simulation results show that filtration of water vapor and volatiles is a significant factor (influence up to 40 %) affecting the characteristics and conditions of ignition of coal-water fuel droplets. The higher velocity of the vapor-gas mixture flow through the porous structure of the fuel particle results in a longer ignition delay. The effect of using the “simplified” model of filtration heat transfer on the prognostic estimates of coal-water fuel ignition is analyzed. It is demonstrated that using of rather simple models for filtration heat transfer does not bring any significant errors in calculating the ignition delay time.

Ice layer melting on a vertical substrate heated by a radiation source in the form of a halogen lamp is simulated numerically in a single-phase formulation of the Stefan problem. Ice is presented in the form of a clear, non-scattering, selectively absorbing material with two spectral bands of volume absorption. The computational model takes into account the selective nature of the radiation source. The analysis of calculation results shows the predominant role of incident radiation in the formation of the density field of resultant radiation flux in the medium. Satisfactory agreement between the calculations and experimental data is obtained.

Various issues of increasing the thermodynamic efficiency of generation of produced energy carriers, such as water, hydrogen or compressed air are considered. The proposed technology, called multi-generation, is based on the creation of energy complexes consisting of generation facilities and consumers. The task of generation facilities is to manufacture, along with the traditional energy carriers, such as electricity and heated liquid, other produced energy carries and useful products. In the case of separate generation, they would have been generated either at consumers or at targeted enterprises. The advantages of the multi-generation technology implementation are shown for individual generation facilities and consumers, as well as for the energy supply system as a whole. The change in the specific fuel consumption for electricity and heat production is taken as a criterion for evaluating the thermodynamic efficiency for a separate generation facility. For the power supply system, the criterion is the absolute and relative changes in the exergy efficiency of generation of all produced energy carriers. Formulas for comparative calculation of efficiency for combined and separate generation at accepted evaluation criteria are derived. The accepted conditions and results of calculations of changes in the efficiency of generation of produced energy carriers at the transition from separate to combined generation for the energy complex consisting of the T-100-130 steam turbine unit combined with vapor compression and ammonia-water absorption refrigerating machines are presented.

Results of simulations of air injection into a liquid-filled (water or liquid lead) closed vessel with a high pressure difference are presented. The simulations reveal a big difference in processes of air volume formation and evolution of its boundaries during air injection into air or liquid lead. A comparison of periodic pressure pulsations in the gas volume (simulation results) with pressure pulsations described by a quasi-stationary 1D model demonstrates conservatism of the simplified model. The results of destruction of gas cavities with pressure pulsations for water and liquid lead are compared. Other conditions being identical, the gas volume in water decays faster than that in lead.

The density and thermal expansion of the solid and liquid Inconel 718 alloy are measured by the dilatometer method and gamma-ray attenuation technique over the temperature range 293.15-1730 K. The density change during the solid-liquid phase transition is directly measured. A comparison of the obtained results with literature data is carried out.