Home – Home – Jornals – Journal of Applied Mechanics and Technical Physics 2023 number 2

This paper describes how the method of preparing a composite TiC - n Ni mixture (n = 40, 50, 75% is the volume fraction of nickel) affects the carbide content in the coating material obtained by cold spraying. It is shown that, when coatings are obtained from a powder mixture prepared in a V-shaped mixer, the titanium carbide content is lower than in coatings obtained from powders mechanically processed in a high-energy planetary mill. In the case of mixing the powder mixture in a V-shaped mixer, fine titanium carbide particles do not reach the substrate surface during spraying because they are decelerated in a shock-compressed gas layer when a supersonic jet accumulates on an obstacle. Thus, these particles do not participate in the formation of the coating. Spraying a mechanically treated powder consisting of composite agglomerated TiC-Ni particles allows for a significant (approximately 1.8-fold) increase in the carbide content in the coating

The impact of vibrating manipulation on arterial hemodynamics and mechanical properties is explored by using the finite element method for the fluid-structure interaction. Numerical simulation results show that massage greatly changes the flow behavior of blood within the artery. Under the massage manipulation, the mean blood flow increases by more than 5.34% at a frequency of 2ʄ₀ and by smaller values at frequencies of f0 and 4ʄ₀. The blood flow has obvious disorder characteristics and an obvious wall shear stress concentration in the mixed flow area. The von Mises stress of the artery wall increases, reaching a peak value at the maximum deformation.

This paper describes an approach to modeling the flow velocity distribution at the inlet of a hydro turbine draft tube that can significantly reduce test costs. The flow is modeled using a special apparatus consisting of a combination of two swirlers: fixed and rotating. A previously proposed method for designing swirlers to generate velocity fields corresponding to the velocity distributions behind real hydro turbines was used to design eight blade arrays modeling the velocity distributions in optimal operating modes of hydro turbines of various types. This paper presents a test numerical calculation of flow parameters using the Ansys program and a comparison of the designed velocity distributions with experimental velocity profiles obtained on an aerodynamic rig using a laser Doppler anemometer. The design, calculated, and experimental velocity profiles at the draft tube inlet are in satisfactory agreement. Thus, the promising approach to the experimental modeling of the hydro turbine flow was successfully tested.

Results of experimental and numerical investigations of the flow around an elongated axisymmetric body or revolution in a low-velocity wind tunnel with a closed test section and in a free flow are reported. The Reynolds number based on the body length is varied in the interval 2,75x10⁶ ÷ 9,40x10⁶. The problem is solved numerically under the assumption of an axisymmetric steady incompressible flow with the use of the ANSYS Fluent software. It is demonstrated that the test section walls produce a significant effect on the flow character and aerodynamic characteristics of the body of revolution for the case where the blockage FACTOR of the test section by the body of revolution is formally within 2%.

New analytical solutions for the calculation temperature changes in the liquid flow and in the metal casing string due to induction heating of the string section. The solutions are based on a one-dimensional analytical model, in which convective heat transfer by fluid flow is taken into account, heat transfer between the liquid and the casing string, heat generation in the metal column when the inductor is turned on and losses in cement and rock due to thermal conductivity. To obtain a solution, the integral method was used. Laplace transform in time, inverse transform carried out using the numerical Stefest algorithm. Features explored temperature field during heating and after shutdown inductor, it is shown that the rate of decrease in temperature anomalies increases with increasing liquid flow in the column. Comparison of the results of calculations by the analytical model with numerical simulation results in the Ansys software package Fluent, as well as with experimental data. It is shown that the received analytical solutions can be used in forecasting temperature anomalies caused by induction heating of the casing columns.

The properties of the dispersion relations for two new fully nonlinear weakly dispersive shallow water models are studied, for which, with certain parameters, it is possible to obtain the fourth, sixth, or eighth order of accuracy of the approximation of the phase velocity of the three-dimensional potential current model. For the hierarchy of shallow water models, under the assumption of a slightly changing shape of the bottom, formulas are obtained that establish the relationship between the rate of change in the wave amplitude and the rate of change in the thickness of the liquid layer, and the dependences of the amplitude and length of the incident wave on the depth of the water area are also derived. It is shown that the new model of the fourth order long-wavelength approximation with the eighth order of accuracy of the dispersion relation provides the best approximation of the considered characteristics in the case of both a horizontal bottom and a variable-shaped bottom

A system of the Euler equations that describe two-dimensional steady flows of an ideal fluid is considered. This system is reduced to a nonlinear Laplace equation for the stream function. With the use of the Hirota τ-function, solutions of three elliptical equations (sin-Gordon, sinh-Gordon, and Titeica equations) are found. A simple method of deriving solutions in the form of rational expressions in elliptical functions is proposed. The resultant solutions describe sources in a swirled fluid, jet flows, chains of sources and sinks, and vortex structures. It is shown that the fluid flow rate over a closed curve is quantized in the case of the elliptical sin-Gordon equation.

Based on the turbulence model and the Ffowcs Williams-Hawkings (FW-H) acoustic model, numerical simulations of acoustic characteristics in the Hartmann whistle with the Helmholtz resonator are carried out. The important parameters that control the flow oscillation features of the Hartmann whistle are the stand-off distance, cavity geometry, nozzle pressure ratio, etc. The computational results are compared to experimental data. Under the condition that the jet exit diameter, cavity diameter, nozzle pressure ratio, and stand-off distance remain constant, the mass flow rate and the sound pressure level are calculated as functions of the diameter and length of the Helmholtz resonator. The results show that the sound directivity is similar in the conventional Hartmann whistle and the Hartmann whistle with the Helmholtz resonator, while the sound intensity is higher in the conventional Hartmann whistle. Also, the sound intensity reaches the maximum in the direction perpendicular to the jet. The magnitude of the sound intensity decreases gradually with an increase in the diameter of the Helmholtz resonator, and the decreasing trend in the fundamental resonance frequency is clearly visible. Next, as the length of the Helmholtz resonator increases, the sound intensity first decreases and then increases again. The effect of the resonator length on the fundamental resonance frequency is not large as compared to the resonator diameter.

The flow in a nonuniformly rotating (librating) cylinder with ends symmetrically inclined relative to the cross section is experimentally investigated. Due to librations, inertial waves are supported; at certain frequencies, they are focused on a closed path, called a wave attractor. The velocity of the pulsation flow changes nonmonotonically with frequency and reaches its maximum value when the attractor takes a square shape. With an increase in the oscillation amplitude, new vorticity centers appear in a threshold way, corresponding to inertial waves with a frequency different from the libration frequency. The Fourier analysis of perturbations in the supercritical regime shows that, in addition to the fundamental frequency, the spectrum contains two additional harmonics that satisfy the triadic resonance condition.

The interaction of a step-like pressure wave with a spherical gas-liquid cluster in a cylindrical channel filled with a liquid has been studied numerically. It has been shown that the cluster generates a solitary pressure wave of large amplitude. The influence of a bubble cluster on the dynamics of multiple reflection of a pressure wave from the boundaries of the cylindrical channel has been investigated. The results of numerical calculations are in good agreement with experimental data

The paper reports the results of liquid-fuel model combustor calculations based on different numerical approaches to develop a verified simulation method of combustor operation. Both steady and transient studies were carried using different RANS turbulent models and the detached eddy simulation (DES) method, and their results were compared with experimental data obtained by optical methods. RANS and hybrid eddy-resolving DES approach. Conducted comparison of the obtained results with the data of the non-contact optical experiment. The results show that the the greatest differences experiment and calculations are observed for the near-axial flow field where recirlulation backflow is formed. This vortex structure can be properly resolved in a DES solution as well as in transient calculations based on the SAS SST model. The use of the above-mentioned approaches in combination with the flamelet combustion model provides maximum accuracy in predicting the parameters of a reacting swirling flow including velocity and temperature distributions in the combustion chamber

Results of simulations of supersonic turbulent flows in a channel with due allowance for conjugate heat transfer between the air flow and a copper plate modeling the sensitive element of a thermocouple are reported. Numerical simulations are performed for free-stream Mach numbers M_∞ 3, 4, and 5. It is shown that the simulation results agree well with experimental data obtained in a hotshot wind tunnel. It is found that the conjugate heat transfer with the model walls made of steel can be ignored at times of the order of 100 ms.

A generalized mathematical model for the non-isothermal filtration of natural gas in a porous medium and a modified quasi-stationary model of gas hydrate formation (deposition) in pipelines were used to solve a conjugated problem for the case of joint operation of the “gas-bearing reservoir-well” system and predict the changes in temperature, pressure, gas moisture content, and well flow area. It is found that the presence of a thick permafrost layer accelerates hydrate formation inside the well. It is shown that when taking into account the salinity of formation waters, the duration of complete plugging of the well with hydrates increases

In this study, nonlinear forced vibrations of a bimorph piezoelectric nanobeam are investigated by using the nonlocal elasticity theory. This nanoactuator is modeled using the Euler-Bernoulli beam theory. The Hamilton principle is used to obtain the equations of motion. The derived equations are discretized by applying the mode shapes of multi-span beams as test functions in the Galerkin decomposition method. The discretized equations are then solved using the perturbation method. A parametric study is conducted to show the significance of size effects on the dynamic behavior of nanoactuators. The results show that an increase in the nonlocal parameter leads to a decrease in the fundamental natural frequency of the nanobeam and to an increase in the response amplitude.

By solving the plane problem of the mechanics of a rod strip having a fixed finite-length section on one of its front surfaces, it has been shown that when studying deformation processes with consideration of the compliance of the fixed section, it is necessary to take into account the change in the stress-strain state parameters and the mathematical models used for their description. This change occurs across the boundary between the unfixed and fixed sections. Within the framework of the classical Kirchhoff-Love model, it is impossible to take into account the compliance of the fixed section of the rod. However, within the framework of the simplest refined Timoshenko shear model, this is possible if the section is fixed only on one of the front surfaces. Exact analytical solutions of two simplest linear problems of static transverse bending of a flat rod with fixed sections of finite length on one of the front surfaces are found. One-dimensional finite elements for modeling unfixed sections of flat rods and sections on one of the front surfaces were constructed using the refined Timoshenko shear model. Numerical experiments were performed, showing the necessity of taking into account the change in the rod strain-stress parameters across the boundary between the fixed and unfixed sections.

The boron nitride nanosheet (BNNS), a graphene-like structure with excellent mechanical properties, is one of the most promising candidates for a reinforcement element to design innovative nanocomposites. Herein, we have investigated the BNNS, which serves for surface enhancement of the aluminum matrix via molecular dynamics simulations. The results show that the boron nitride nanosheet coating enlarges the critical yield strength, hardness, and modulus of elasticity. With an increase in the number of boron nitride layers, the strengthening effect is more significant. Meanwhile, a higher system temperature degrades the interfacial energy and weakens the mechanical properties of the BNNS/Al systems.

The problem of stability of cylindrical shells made of composite material, taking into account momentum and nonlinearity of their subcritical stress-strain state. Geometrically non-linear the stability problem is solved by finite element methods and linearization of Newton -Kantorovich. Critical loads are determined in the process of solving a nonlinear problem using Sylvester's criterion. Hypothesized Timoshenko finite elements of composite cylindrical shells natural curvature, in the approximation of displacements of which in explicit form, rigid displacements are highlighted, which significantly affects solution convergence. The stability of the circular cylindrical shell made of polymer composite material, under combined loading by torsional and bending moments and internal pressure. Studied the influence of the laying method monolayers, non-linearity of deformation, internal pressure on critical loads at which buckling occurs shells

This paper proposes a model of static transverse elastic deformations of a magnetic gel sample shaped as a strongly elongated cylinder, which is under the action of a transverse uniform magnetic field and the force of gravity. Theoretical results obtained within the framework of the proposed model are in qualitative agreement with the results of laboratory experiments

A numerical and experimental study of concentrations of combustion products and pollutant emissions in the case of combustion of premixed methane-hydrogen mixtures in a model combustion chamber of a gas-turbine power plant is performed. The mathematical model of combustion of methane--hydrogen mixtures used in the study ensures good qualitative and quantitative agreement between the numerical and experimental data on the main combustion products and also qualitative agreement on emissions of pollutants. In what follows, this mathematical model of combustion combined with the chosen kinetic mechanism of combustion can be used to analyze the emission characteristics of gas-turbine power plant combustion chambers designed for operation on hydrogen-containing mixtures.

The possibility of solving problems of chemical kinetics using artificial neural networks is investigated. The main laboriousness of solving problems of chemical kinetics lies in solving a rigid system of balance equations, whose right side contains the component mass production intensity. This problem can be singled out as a separate stage of solving a system of ordinary differential equations within a common time step of the global problem, and this stage is considered in this paper. A fairly simple model is developed that can solve this problem, which makes it possible to achieve a threefold acceleration of calculations as compared to numerical methods. The resulting neural network operates recursively and can predict the behavior of a chemical multicomponent dynamic system many steps ahead.

The geometric structures, vibration frequencies and relative energies of reactants, products, intermediates, and transients involved in the self-recombination of the indenyl radical were determined using G3(MP2,CC) // B3LYP/6-311G^** quantum chemical calculations. The barrierless association of a pair of indenyl radicals forms the C₁₈H₁₄ complex. The subsequent set of isomerizations of the complex is divided into five reaction channels, which in all cases end in H abstraction but with different four-ring isomers C₁₈H₁₄: in the form of condensed rings-tetraphene, tetracene, chrysene, dibenzoazulene; with an associated internal bond of the rings-dibenzofulvalene. The yield of chrysene prevails since the energy barriers encountered on the pathway of its formation are lower than the barriers on the formation pathways of other products.

Stability of a swirl flame of a premixed methane-air mixture under various gravity conditions is studied. Charts of stable combustion at normal and reverse gravity in the coordinates of the flow velocity and equivalence ratio. It is shown that the limits of stable combustion remain unchanged regardless of using a swirler with and without the central body, but the flame geometries are different. Swirlers are found to produce a minor effect on the flame blowout conditions, especially under the normal gravity condition. It is demonstrated that a swirler allows obtaining a rich lifted flame under the normal gravity condition and a lean lifted flame under the reverse gravity condition. It is found that dilution of the mixture with the fuel leads to expansion of the boundary of combustion stability under the reverse gravity condition as compared to the situation under the normal gravity condition.

The stationary diffusion combustion of a suspension of boron nanoparticles in isopropanol in cocurrent oxygen flow and the pulsed laser photolytic initiation of this combustion were studied. The experiments were carried out using a number of spectroscopic methods. Coherent anti-Stokes light scattering spectroscopy was used to determine the transverse distributions and concentrations of oxygen molecules diffusing into the fuel jet and the flame temperature change at different distances from the edge of the burner nozzle due to the addition of boron nanoparticles into the fuel. The dimensions zones of laser ignition initiation of the combustible mixture were determined by laser-induced fluorescence spectroscopy of electronically excited O₂^* molecules. Chemiluminescence spectroscopy of intermediate products of gas-phase reactions (OH* and BO₂^* radicals) from the ignition region made it possible to characterize the spatio-temporal dynamics of this process. The changes in the temperature field and ignition dynamics due to the addition of boron nanoparticles are explained based on an analysis of the obtained data. In particular, it is assumed that the characteristic rise in temperature in the region of the flame front is primarily due to an increase in the burning rate of the fuel with nanoparticles.

A method of calculating the characteristics of atomization of a liquid fuel by pressure swirl atomizer for setting the boundary conditions of injection into the primary combustion area is proposed. Results of simulating CO emission in a model combustion chamber are presented for two variants of the boundary conditions of liquid fuel injection: (1) with the use of the discrete phase model (DPM), where the parameters of fuel atomization are obtained by modeling a two-phase flow by the volume-of-fluid (VOF) method, and (2) for comparisons, with the use of the semi-empirical method of calculating pressure swirl atomizers developed by H. Lefebvre. The method of determining the boundary conditions of injection proposed in the paper makes it possible to increase the accuracy of predicting CO emissions by several times as compared to the classical semi-empirical method of calculating pressure swirl atomizers.

This paper presents the results of studies of the formation of polyaromatic hydrocarbons (PAHs) and carbon nanoparticles during pyrolysis of mixtures of ethylene with additives of linear ethers: dimethyl ether CH₃OCH₃ (DME), diethyl ether C₂H₅OC₂H₅ (DEE) and dimethoxymethane CH₃OCH₂OCH₃ (DMM). The studies were carried out behind reflected shock waves at temperatures of 1650-2550 K and pressures of 2.7-4.1 atm using optical diagnostic methods: laser-induced fluorescence (LIF) and laser extinction. These additives were found to accelerate the formation of PAHs and carbon nanoparticles. Kinetic modeling results show that this effect is due to the presence of methyl and ethyl groups in the molecules, which promote the formation of PAHs and soot.

Experiments on the filtration combustion of automobile tires mixed with a solid coolant are carried out. The mass content of tire particles in a mixture varies from 10 to 70%. Particles of chemically inert sapphire (Al₂O₃) and sulfur-absorbing marble (CaCO₃) are used as a heat carrier. Optimal conditions for the filtration combustion of automobile tires are determined (the tire content in a mixture is 50%, the combustion temperature is approximately 1 000 ºC, the mass burning rate is 0.40 kg/m³ of supplied air). It is established that the replacement of a solid inert coolant with marble has practically no effect on the combustion temperature. In this case, the composition of combustion products changes: the CO₂ content in gaseous products increases (their combustion heat decreases from approximately 2.5 to 2.2 MJ/m³), the yield of liquid pyrolysis products decreases approximately from 45 to 40%, and the sulfur content in solid combustion products increases from 28 to 40%.

The interaction of flow of burning and smoldering particles with some types of combustible building materials and wood-based structures was studied experimentally. The heat flux generated by glowing particles was determined, and the temperature fields of the most heat-stressed sections of the structures were analyzed. The sample heating rate was estimated based on the data of IR thermography. For the selected parameters of the experiment, the sample simulating a terrace was found to be the most resistant to ignition. Estimation of the temperature in the near-surface layer of the terrace element showed that after 15 min of continuous exposure to burning and smoldering particles, the temperature in the zone of maximum accumulation of particles did not exceed 130 ºC. A wooden guard model was found to the most prone to ignition (its ignition delay time was more than 15% lower than that of the other structures).

It is found that the problem of boundary layer stability with a diffusion flame under the conditions of a constant molecular weight over the boundary layer in the inviscid approximation and in the Dunn-Lin approximation with identical Schmidt numbers can be reduced to a similar problem for a single-component gas. Approximately, this conclusion is also valid for different Schmidt numbers. Calculations of the steady-state parameters of the boundary layer show that there are two generalized inflection points testifying to a necessary condition of the “inviscid” Rayleigh instability. Simulations show that the boundary layer with a diffusion flame is most unstable to two-dimensional disturbances. As the frequency is increased, the phase velocity of the growing wave tends to the value at the generalized inflection point. Despite sufficiently large growth rates, the degree of spatial enhancement of the wave is equal with high accuracy to the ratio of the time degree of enhancement to the group velocity.

This paper describes an experimental study of the operation parameters of a gas-dynamic pressure source with explosive initiation, in which black powder is used as a damping layer.

The enthalpy of formation, density, energy and detonation parameters of hypothetical zwitterionic nitrohydrazine H₃N+N-NO₂ were evaluated. The obtained probable values of the enthalpy of formation (-20 kJ/mol), density (1.90 g/cm³), and detonation velocity (9.4-9.8 km/s) of nitrohydrazine allow it to be considered as a promising energetic compound that justifies efforts to find ways to synthesize it.

Burning of a high-energy paste-like propellant aimed at creating engines with a burning end surface is studied. Specific features determining the burning rate, characteristics of the agglomeration process, and surface layer properties are found. It is demonstrated that these features are similar to those observed for solid propellants based on an active binder with a linear polymer. Possible aspects of improvement of propellants of this type are determined.

This paper describes the method and results of an experimental study of unsteady burning rate of high-energy materials containing metal powder additives under depressurization at a rate of 140-160 MPa/s. A method based on stating and solving the inverse problem of internal ballistics is used to determine the unsteady burning rate. The studies are carried out for high-energy materials, including energy additives in the form of metal powders (ASD-4, ASD-6, and Alex aluminum), aluminum diboride, and dodecaboride. It is shown by analyzing the results of the study that the unsteady burning rate of high-energy materials under sharp depressurization is oscillatory and depends on energy additive type.

On solonetzes and salt marshes of the northern part of Kulunda steppe, cenoses with a predominance of Halimione verrucifera, a dwarf semishrub with succulent leaves of Chenopodiaceae family are often formed. The dynamics of the accumulation of the aboveground mass of this species under different regimes of land use was studied on the example of four plant communities of solonetzsteppe of Northern Kulunda within Novosibirsk region. The description of vegetation was carried out using standard geobotanical methods, the aboveground phytomass was determined by cutting method. It is shown that the aboveground mass of Halimione verrucifera varies greatly from year to year and largely depends on the mode of land use of the steppe communities. During five years of observations, significant correlations were revealed between the mass of Halimione verrucifera and the total aboveground phytomass of communities under absolute protective regime and under weak grazing in certain years. It is noted that during seasons with increased rainfall rapid growth of Halimione verrucifera occurs, and drought resistance allows this species to strengthen in the herbage during dry years in contrast to drying grasses. On pastures Halimione verrucifera is poorly eaten and resistant to trampling. Under long-term moderate grazing, Halimione verrucifera produces numerous small shoots, which can make up the main part of the pasture phytomass. The distribution and conservation of Halimione verrucifera in the solonetz plant communities of Northern Kulunda are mainly determined by soil salinity increase, which can be caused both by its compaction under hard pastoral use and climatic fluctuations.

The bioecological features of Myosotis pseudovariabilis Popov from the section Sylvaticae (Popov ex Riedl) Tzvelev, an endemic of the lover reaches of the Yenisei river (Krasnoyarsk Territory) are considered. Taxonomy, geographical distribution, species protection, and morphological characters of vegetative and generative organs are discussed. Original researches on element composition of green mass of leaves of M. pseudovariabilis in connection with soil composition and ecological conditions of species existence are carried out. Phenological characteristics of the species as well as plant response to abnormal weather conditions were studied for the first time. It has been noted that small populations of M. pseudovariabilis, Heracleum dissectum Ledeb. are confined to shrub thickets in river and stream valleys, while large populations are characteristic of meadows of natural and anthropogenic origin. The conjugate development of cenoses with participation of M. pseudovariabilis and Cirsium helenioides (L.) Hill was revealed. Plant communities M. pseudovariabilis is an explerant; its life strategy is aimed at the formation of long creeping epigeogenic rhizomes that radially take up space due to vegetative rosellate shoots, which have buds of regeneration on the ground surface and are covered by dry leaf debris. At present, due to the reduction of human activity, former hayfields, arable lands and vegetable gardens are overgrown with shrubs and tall grasses, which contributes to creation of favorable conditions for growth of M. pseudovariabilis and increase of its populations, since the main ecological niche of the species is meadow shrub communities of the eutrophic successional vegetation series.

The article presents the results of morphological studies of anthers, as well as live and dehydrated pollen grains of 9 species of the genus Tulipa L. from 4 sections. In the living state, the grains are spherical or elongated-ellipsoidal in shape, ranging in size from 40 to 78 mm. For a spherical shape, the type of aperture is characteristic - a pore, and for an ellipsoid - a colpi. Based on the determination of the place of germination of the pollen tube, which is located only on the distal side and is pore in the species of the sections Leiostemones, Spiranthera, Orithia and a furrow in the species of the section Eriostemnes, it was found that the pollen in the studied species is distal-1-aperture. Aperture without operculum (Leiostemones) or with it (Spiranthera, Eriostemnes, Orithia). The palynomorphological features correspond to the sections of the genus according to the classification of A.I. Vvedensky with additions by Z.P. Bochantseva. The data obtained do not confirm the expediency of including the section Spiranthera.

The species Cetraria crispiformis is very poorly studied in Russia. Only 6 points are indicated on the map of the range of the species for the territory of Russia. The purpose of this study was to revise herbarium materials in order to detect new localities of the lichen, as well as to map the range of the species in Russia. The purpose of this study was to revise herbarium materials in order to detect new localities of the lichen, as well as to map the range of the species on the territory of Russia. The material for the study was herbarium collections, including type materials kept in the Lichenological Herbarium of the Komarov Botanical Institute of the Russian Academy of Sciences (LE), as well as single specimens kept in the Herbarium of the Karelian Scientific Center of the Russian Academy of Sciences (PTZ) and the M.G. Popov Herbarium of the Central Siberian Botanical Garden of the Siberian Branch of the Russian Academy of Sciences (NSK). The study was carried out by a comparative morphological method. The distribution map of the species on the territory of Russia was compiled using the point mapping method. As a result of the revision of the herbarium materials of C. islandica s.l. about 40 (30 new) localities of the species C. crispiformis have been identified. A distribution map of this arctic-northamphiatlantic lichen on the territory of Russia has been compiled, showing that the species is found here almost exclusively along the coasts of the northern seas (Barents, White, Kara) and on the Arctic islands. Outside the coasts (in more continental regions), the species is practically not found, and if it occurs, then in special conditions - in sphagnum bogs. The most remote localities of the species from the coasts are in the Komi Republic on the Timan Ridge and in the Pskov Region on the “Eastern Bog Massif”. As a result of the study of type specimens of intraspecific taxa of C. islandica described by K.A. Rassadina, it was found that the type C. islandica var. polaris f. grumulosa Rass. (LE L127), the name of which was considered by Kärnefelt (1979) as a synonym of C. islandica subsp. crispiformis does not belong to the species C. crispiformis, but represents one of the forms of C. islandica s.l. Synonyms and their type specimens are given.

Ecological monitoring is a regular long-term observation of various environmental parameters. It is one of the tasks of Russian state nature reserves, fixed in legislation. The southern part of the Katunskiy Reserve until its establishment in 1991 was subjected to cattle grazing. The purpose of this research was to estimate the restoration of meadow plant communities in the Reserve after its establishment. Observations of the floristic composition and species cover in the meadow communities of the Katunskiy Reserve were carried out on three Permanent Test Plots (PTP) measuring 10 10 m. Relevés with lists of species and species cover in percentage were made in each PTP in 1999, 2003, 2008, 2017/2018 and 2022. In order to estimate the statistical significance of the species cover changes, the Wilcoxon signed-rank test for paired samples (wilcox.test function in R) was used. Changes of the species composition and, for some species, fluctuations, decrease or increase of the cover were registered in PTPs during the observation period. For two PTPs, the estimation of these changes by Wilcoxon test gave statistical significance above the threshold limit (p-value > 0.05), what does not allow us to admit statistically significant changes. At the third PTP, statistically significant changes in species cover were registered in 2018 and 2022, compared to 1999 (p-value < 0.05). Apparently, this is a result of the restoration of the meadow community, which has been most disturbed by grazing before the reserve establishment. At this PTP, large-leaved species, which were not registered at the first year of observation, were found in subsequent years: Cirsium helenioides, Angelica sylvestris, Rumex aquaticus; as well as other common meadow species: Ranunculus grandifolius, Trollius asiaticus, Polemonium caeruleum, Viola disjuncta. Some species, common for disturbed habitats disappeared from the PTP: Trifolium repens, Carum carvi, Cirsium setosum, what also should be considered as a fact confirming the restoration of the vegetation cover.

According to the results of the expedition routes in 2021-2022, data on the findings of new and rare adventive plant species in the Southern Urals (Republic of Bashkortostan and Orenburg Region) are presented. For the first time for the Southern Urals are given: Carthamus tinctorius, Glycine max and Heliopsis helianthoides. For the Republic of Bashkortostan, the following species are given for the first time: Cotoneaster lucidus, Grindelia squarrosa; for the Orenburg Region: Dracocephalum nutans, Gaillardia aristata, Portulaca grandiflora, Solidago gigantea, Sorghum sudanense, Thladiantha dubia. New localities of 3 rarely occurring adventive plant species (Amaranthus hypochondriacus, Senecio dubitabilis, Setaria italica) in Orenburg Region are given.

Galium zaisanicum Pinzhenina et Kupr. is described as a new species from East Kazakhstan from section Galium. G. zaisanicum grows in Zaisan depression on Kiin-Kerish clays. The material was collected in the East Kazakhstan region of the Republic of Kazakhstan in the intermountain depression, on the clays of Kiin-Kerish. G. zaisanicum shows an external morphological similarity with species G. ruthenicum Willd., G. saurense Litv., but differs by tomentose of stem, length of internodes, shape and pubescence of leaves, shape of corolla lobes, pubescence of corolla, shape of anthers, and sculpture of fruit surface. Data on the surface sculpture of the mericarpies confirm the close relationship of the species G. zaisanicum, G. ruthenicum and G. saurense Litv. G. zaisanicum grows in fine-grained areas with an admixture of quartz sand and kaolin clay scour products in semi-desert communities involving members of the families Poaceae, Amaranthaceae, Asteraceae. For the new species, the holotype, isotypes and paratypes are given. Detailed description, discribution, ecologi, illustrationsas as well as a comparison with morphologically similar species are provided.