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A history of development of various cycloidal rotors used as aircraft propellers is presented. The operating principle of a cycloidal rotor with a swinging blade is described. Differentpapers on this issue are reviewed, quantitative data are summarized and analyzed, and the most important parameters affecting the characteristics of a cycloidal rotor with a swinging blade are identified. Optimal values of the main parameters for improving the characteristics of a CR with a swinging blade are obtained. A method for the engineering evaluation of the thrustof a cycloidal rotor with a swinging blade is proposed

Functionally graded B₄C-CrB₂ material with a CrB₂ concentration gradient along the thickness equal to 5, 15, and 25 % was produced by reactive hot pressing of a mixture of boron carbide, chromium oxide, and a carbon material with high specific surface area. A general view of the microstructure and the size distribution of chromium diboride particles in each layer are presented. The change in mechanical properties with an increase in the CrB₂ concentration is shown to be non-monotonic due to the features of boron carbide reduction.

This paper presents an algorithm for the developed overdetermined method of constructing the asymptotics of the stress field near a nanocrack tip in an anisotropic linear elastic body with cubic symmetry. For the problem of combined loading (normal separation and transverse shear) of a nanoplate of monocrystalline copper and aluminum with a central cut, a molecular dynamics solution was obtained and used to derive an asymptotic representation for the stress tensor components. The atomistic stresses in the vicinity of the crack tip were calculated, and the coefficients of the series representing the stress field were determined using the values of the atomistic stress tensor components. The molecular dynamics calculations were performed for a temperature of~10~K to exclude the appearance of a zone of nonlinear elastic deformation near the crack tip. The stress fields in the atomistic and analytical solutions were compared. The stresses at different distances from the nanocrack tip are in good agreement with the solutions of problems of macroscopic classical theory of anisotropic elasticity and can be described using a series that extends the Williams series to anisotropic media. In the series extended to anisotropic materials, the regular (non-singular) terms were taken into account and the series coefficients of these terms were determined. It is shown that the developed algorithm can be used to effectively determine the coefficients of the higher-order terms of the series

An approach to the simulation and evaluation of the parameters of thin elastic open shells and plates under postcritical deformation is proposed. A finite element model of the longitudinal bending of a plate with a trough-shaped profile is considered. A numerical simulation of the behavior of a plate with quasi-zero stiffness was performed, and the effectiveness of such a plate as an elastic element of a vibration isolation mechanism was studied. Finite element simulation results were compared with the results of calculations using analytical models and with experimental data. The possibilities of adjusting the quasi-zero stiffness of plates were analyzed. The results obtained indicate that such elastic elements can be widely used in vibration isolation systems for ground and onboard equipment

The assessment of material toughness is governed by codes based largely on rigorous experimental results. However, the problem of transferability from the laboratory specimen to field-scale structures limits the extent to which these results can be used. The present work is a developmental contribution to a new approach for assessing the toughness of pipeline steels. The procedure concerns the interaction between material fracture curve based on the three-parameter fracture criterion (K-T-A₃) and the surface longitudinal notch driving force of a pipe under internal pressure. This could be applied as an important engineering parameter for assessing the structural integrity of pipelines during long-term operation.

An unsteady problem of heat conduction for a rod is considered. The classical heat conduction equation based on the assumption of temperature differentiability with respect to time and coordinate is derived. A solution of a model problem with boundary conditions of the second kind is obtained, which determines the temperature distribution in the thermally insulated rod over its length and in time. For the classical formulation of the problem, the temperature change rate at the initial time is found to be singular, and the condition of temperature differentiability with respect to time is not satisfied. A modified form of the heat conduction equation is proposed, which is based on nonlocal determination of temperature as a time-dependent function. In contrast to the traditional definition of temperature, this function is not the temperature value at a fixed time; instead, it is the mean value on a finite time interval called the nonlocal temperature. As a result of using such an approach, the heat conduction equation retains the classical form, but contains the nonlocal temperature rather than the traditionally used temperature. Traditionally, the temperature is determined by means of solving the Helmholtz equation including an unknown time interval over which the temperature is averaged and which is determined experimentally. The classical and nonlocal solutions are compared with experimental data. The nonclassical Maxwell--Cattaneo equation of heat conduction is discussed, which implies a finite rate of temperature propagation in time.

A number of new formulas are obtained for vector fields and vector analysis used in geometry and the vector field characteristics used in differential geometry: curvature vector, associated vector field, degree of nonholonomy, and the Laplacian value. Non-classical characteristics such as the vector potential of the curvature vector field of a vector field and the sum of three curvature vectors of vector lines of the Frenet unit vector fields of a family of curves are also studied. It is shown that all the listed quantities are related to Aminov's divergent representations for the Gaussian curvature or for the total curvature of the second kind. The obtained formulas can be considered as properties of the family of curves. Some formulas have divergence form, which makes it possible to derive differential conservation laws for the family of curves as well as for the eikonal equation and Euler's hydrodynamic equations

At present, in connection with the active development of the Russian Arctic, issues related to prevention and elimination of the consequences caused by disturbances of vulnerable northern ecosystems are becoming increasingly urgent. Soils deserve attention on the first-priority basis. On the one hand, soils are the basis of any terrestrial ecosystem, on the other hand, under the harsh conditions of the Far North, their self-restoration is slow, and effective reclamation measures are costly. In the work, the most common environmental problem of the northern territories of Siberia is considered: the pollution of soils with oil products. The properties of automorphous and hydromorphous organogenic, loamy, stony, sandy, and sandy loam soils widely occurring in the cryolithozone are investigated. It is noted that among soil properties, the greatest role in the fixation of oil products is played by total carbon content and cation exchange capacity, while the increased density of soils prevents the introduction and accumulation of oil products. Based on the analysis of literature data and statistical processing of own materials, recommendations on soil remediation at the sites contaminated with oil products to different extents are proposed.

Electrochemical properties of a cell with carbon highly porous electrodes and a solid polymer electrolyte based on polyurethane elastomer filled with a solution of an organic salt of N,N-methyl-propyl-piperidinium in N-methyl-2-pyrrolidone have been studied. The values of specific capacitance of the electrode material in contact with the polymer electrolyte, which reach 45 F/g, were determined by cyclic voltammetry (CVA) in the voltage range from -4.5 to 4.5 V and galvanostatic charge-discharge. Analysis of the dependence of capacitance on the potential sweep rate has shown that the main contribution to the capacitance is the pseudocapacitance due to surface electrochemical processes, the nature of which is still unclear. The CVA data are in good agreement with the data obtained by impedance spectroscopy. The obtained polymer solid electrolyte based on polyurethane elastomer can be used to create flexible polymer supercapacitors operating in a wide voltage range.

The possibility to increase the adsorption capacity of the sorbent Purolat-Standard, a cheap anthracite-based carbon material (CM), towards iron(II) ions was studied. Sulphuric acid, aminoethanoic acid, and their combination were used as modifiers. The effect of modification on the porous structure and surface state of the analysed sorbents was examined. It has been found that only treatment with sulphuric acid has a significant impact on the structural characteristics of the carbon material. A comparison of microphotographs of the samples before and after iron ion adsorption suggests its adsorption on the surface of macropores. It is shown with the help of X-ray diffraction analysis that the chosen modification methods do not change the phase composition of the sorbents. According to the data of spectroscopic studies, modification of sorbent samples leads to changes in the qualitative and quantitative composition of surface groups. The adsorption of iron(II) ions on the initial and modified samples of carbon material was studied under equilibrium conditions. It was found that using AEA as a modifier fundamentally alters the shape of the metal ion adsorption isotherms. The use of aminoethanoic acid as a modifying agent has been determined to strongly alter the shape of metal ion adsorption isotherms, which is due to different composition of functional groups on the sample surface and changes in the sorbent-sorbate interaction type. Using the Langmuir model and a modified Dubinin-Radushkevich equation for ion adsorption, the main adsorption characteristics were calculated. It is assumed that for the initial sorbent and the sample treated with sulphuric acid, as well as for the samples modified with aminoethanoic acid, in the case of low equilibrium iron concentration, adsorption proceeds via ion exchange. At higher equilibrium concentrations, the formation of iron ion complexes with the modifier is possible for the sorbents treated with the amino acid. It is established that the most promising sample for use as a sorbent for extracting iron ions from groundwater is the carbon material modified with both sulphuric and aminoethanoic acids (by sequential impregnation), which demonstrates the highest adsorption capacity.