The possibility of using a new graphene-based carbon monolith for searching new oil deposits or branches adjacent to the already registered oilfields by areal geochemical survey is demonstrated. The material has been developed at the Faculty of Chemistry of M. V. Lomonosov Moscow State University. Sorption of volatile organic compounds (VOCs) from soil air at the oilfield was carried out using two sorbents (carbon adsorbent and Tenax-TA traditionally used for such analyses) with subsequent determination by gas chromatography with mass spectrometric detection and thermal desorption as a way of sample injection (TD/GC/MS). The new material absorbs more hydrocarbons (n-alkanes and monoaromatics) in the range from C₈ to C₁₆ than Tenax-TA, the intensities of the chromatographic peaks of the compounds also being higher. The phenomenon of irreversible sorption from carbon materials is observed for VOCs from C₁₇ and more. However, the concentration of such substances in the soil air is rather low due to the low pressure of saturated vapors of these compounds under normal conditions. Hence, the chromatogram of carbon monolith reflects the macro-characteristics of this oil deposit better than Tenax-TA. To increase the sensitivity of the determination, a preliminary optimization of thermal desorption conditions was carried out. The values of the helium flow rate through the sorbent sample and the desorption time of the compounds are chosen to get the largest peak area. The regeneration of sorbent samples is carried out to provide the possibility of their reusage. Tenax-TA decomposes at lower temperatures compared to carbon sorbent and thus cannot be purified completely unlike the new monolith. The graphene-based sorbent is reusable and much cheaper in the manufacture than imported polymer Tenax-TA since it is made of domestic materials.

Study of the elemental composition of the soil-grape-wine chain and correlation relationships between the chain links is presented. The objects of the study were grapes of the Muscat, Cabernet and Merlot varieties, wine samples produced from them and soils of the viticultural areas. Concentrations of Li, Mg, Al, K, Ca, V, Mn, Fe, Ni, Co, Cu, Zn, Rb, Cd, Pb, Ba, Na, Ti and Sr in soils, grapes and wines were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Relationships between the elemental composition of the objects under study were assessed by statistical modelling using the STATISTICA software. The character of metal distribution in the soil-grape chain was studied for three forms of the element extraction from soils. We determined their gross content, the content of acid-soluble and mobile forms. The degree of absorption of mobile forms of metals by grapes was estimated using «biological absorption coefficient»., Values of the biological absorption coefficient (BAC) of different metals depend on the grape variety. High BAC values are observed for Rb, Ti, Mg, Zn, Cu, Na, Fe, Al, and Sr in Merlot grapes; K, Pbm and Ni in Muscat; and for V and Mn in Cabernet. The lowest BAC values were observed for Co, Ba, and Ca in all grape varieties under study. Each grape variety formed its own individual elemental image due to the different nature of absorption of the studied metals. The transfer of metals from grape to wine for all considered varieties was accompanied by a decrease in the concentrations of Mg, Al, K, Ca, Mn, Ni, Cu, Zn, Rb, Ba, Ti, and Sr and by an increase in the content of V, Fe, Co, Pb, and Na. Discriminant analysis revealed the metals with the highest identification properties, considering their form present in the soil. The results obtained can be used when setting markers determining the varietal and regional origin of wines.

Materials based on rare earth elements (REE) are of great importance due to their unique chemical and physical properties, but the effectiveness of their use depends on the quality of raw materials. Therefore, further development of the methods of analytical control in relation to rare-earth materials is aimed at increasing the accuracy and sensitivity of the methods, as well as at expanding the nomenclature and concentration range of the determined elements. Cerium oxide is used in glasses, ceramics, catalysts, phosphors, composite and scintillation materials, as well as in medicine. The problem of developing a new arc spectral method is extremely urgent to match modern requirements for the accuracy and sensitivity of the impurity determination for monitoring the purity of cerium oxide. A technique for arc atomic emission analysis of cerium oxide which meets modern requirements for the accuracy and sensitivity of the impurity determination has been developed. The range of impurities to be determined is significantly expanded compared to the standardized technique of the 1970s. The goal of this work is to study and develop a modern method for arc optical emission spectral analysis of cerium oxide using the instrumental capabilities of the atomic emission complex «Grand Globula». To specify compromise conditions for the determination of 15 REE impurities and 19 elements more, analytical lines were selected and the dependence of their intensity on the operating mode of the generator, the shape and size of the electrodes, the interelectrode distance, the ratio of the masses of the analyzed sample and graphite powder, as well as on the presence of various carriers (Ga₂O₃, NaCl, NaF, KCl, S, GeO) was analyzed. Application of the considered methodological approach to the selection of conditions made it possible to develop a method for spectral analysis of cerium oxide without preliminary dissolution of the sample with an extended range of determinable impurities. When studying the curves of the impurity evaporation, an exposure time was chosen to be sufficient for their complete evaporation (100 – 120 sec). The study has shown the 0promising character and feasibility of the developed arc spectral techniques applicable to the analysis of REE-based materials as an alternative to the methods for analysis of solutions. The metrological characteristics of the proposed procedure for the analysis of cerium oxide were evaluated in comparison with the standardized technique.

The oligomer microstructure, reflecting the configuration of the elementary units (cis-1,4-, trans-1,4-, and 1,2-) and their distribution order in the polymer chain, decisively affects the physicochemical and rheological properties of the oligomer. Parameters of microstructure-dependent transitions (glass transition) characterize the oligomer behavior under abnormal low-temperature conditions. We present the results of studying the microstructure of low-molecular rubbers. We determined the content of cis-1,4- and trans-1,4-structural links of poly-divinyl-isoprene-urethane-epoxy oligomer. The structure of polybutadiene HTPB-IV with terminal hydroxyl groups was analyzed using NMR and IR spectroscopy. A comparative analysis of the microstructure of the poly-divinyl-isoprene-urethane-epoxy oligomer and low molecular rubbers with a known content of structural units has been carried out. The obtained results can be used to obtain oligomers with the desired physicochemical and mechanical properties.

Technologies of automated laying out of fibers (Automated Fiber Placement — AFP) and tapes (Automated Tape Laying — ATL) are used in the manufacture of blanks from polymer composite materials (PCM) for subsequent autoclave or other type of molding. The frequency of defect formation upon laying depends on the complexity of the certain part and the technological parameters (the tape width, speed of laying and idle time, temperature, deviations from the calculated trajectory, etc.). We present a review of the main defects thus formed along with the analysis of the reasons for their appearance and their effect on the physical and mechanical properties of composite materials. It is shown that the defects change the thickness and reduce the strength of the PCM under tension and compression. Moreover, the inaccuracy of fiber placement when using the AFP technology has a negative effect on the quality of the materials. The results presented can be used in the further study of the effect of defects on the PCM properties and reasons for defect formation, as well as in developing promising universal computational program that can provide reduction of the number of corresponding experimental tests.

In free space, the permittivity of materials is usually determined by the value of the Brewster angle using the angular dependences of the amplitude and phase of the wave reflected from the material plate. An expression corresponding to materials without dielectric and magnetic losses is used as a calculation model. Experimental studies of the parameters of the wave reflected from dielectric materials show the discrepancies with theoretical calculations known as deviations from the Fresnel laws. We present the results of determining the Brewster angle of the wave reflected from a plate made of a material with dielectric losses. The angular dependences of the amplitude and phase of the reflected wave were calculated using the numerical solution of the problem of falling at an arbitrary angle of a plane linearly polarized wave with an electric field vector lying in the plane of incidence on a plate of a dielectric material with complex values of the dielectric and magnetic permittivity. They were used to determine the angles corresponding to the minimum reflection coefficient depending on the dielectric losses of the plate material. The differences between the numerical calculations and the data obtained using the Brewster angle formula were noted, which increased with increasing dielectric losses of the material. From the condition that the modulus of the reflected wave amplitude is equal to zero, a different formula for calculating the Brewster angle for a material with losses is analytically obtained. The results of calculations using this formula coincided with the calculations for the reflected wave when solving the classical problem of the inclined incidence of a plane wave on a plate of a dielectric material in the framework of geometric optics. The results obtained can be used to determine the Brewster angle for a wave reflected from a plate with magnetic and dielectric losses.

Fatigue damage to babbitt layers of plain bearings is often manifested during operation. The goal of the study is to develop a model for accumulation of the fatigue damage and destruction of antifriction materials and layers of plain bearings. A generalized fatigue diagram of tin-based babbitts including the main stages of fatigue damage and a diagram of the fatigue damage development in the antifriction layer of plain bearings are presented. The generalized model of V. V. Bolotin for damage accumulation and destruction is modified with regard to antifriction materials containing rather large structural elements. An explicit (direct) modeling of damage processes appeared possible for such materials. The model describes dissipated accumulation of microcracks (interpreted as destruction of the elements of the material structure), initiation and development of a system of short cracks, initiation and development of macro-cracks up to the limit state of the object. The model suggests discretization of the volume into sections with constant levels of complex stress state and discretization of the time axis into the intervals (blocks of loading cycles). The problem of identifying the parameters of a multistage model of the fatigue damage accumulation in the alloy is solved proceeding from the analysis of the results of testing babbitt specimens. We used the simplest optimization procedure, i.e., the method of deformable polyhedron. The parameters of the power function in the dependence of the rate of microdamage accumulation on the level of stresses are obtained. The parameters of the initiation and development of the crack system in the babbitt layer are obtained from the analysis of experimental results of studying steel-babbitt samples. The problem of calculating the durability of antifriction babbitt layers required the development of a new software. The program is examined by comparing calculated and experimental values of the durability of fatigue-tested bearing specimens forced against a rotating shaft by varying cyclic load. The calculated values of the durability match the experimental which confirms the performance of the calculated model.

The results of computation and experimental studies of changes in the regularities of the strain resistance and damage accumulation in conditions of the irregular low cycle loading are presented and compared with similar data for a regular cyclic elastoplastic deformation at the same loading. The irregular mode of low cycle loading implemented in the study is adopted in the form of an equiprobable distribution of changes in the stress amplitudes within a given range between maximum and minimum levels at the symmetric form of the cycles. This mode was reproduced on test equipment through introduction of the corresponding functional dependence of changes in the stress amplitude in the cycles into the control program. The data on a cycle-by-cycle kinetics of both cyclic and unilaterally accumulated strains obtained under irregular mode of loading were recorded in a databank and then compared with the data for a regular loading. This provided the possibility of their analytical description by the corresponding equations of state with the correction of the parameters of the diagrams of cyclic elastoplastic deformation taking into account the conditions of irregularity of loading modes. The results of the experiments are presented in the form of diagrams of the tests modes, curves of a low cycle fatigue of the studied material at the soft and hard loading modes, diagrams of a cycle-by-cycle kinetics of the cyclic and accumulated strains at the regular and irregular modes, and also as kinetic diagrams of damages accumulation for these conditions. Using the summation criteria expressed through the deformation characteristics of accumulated damage, it is shown that taking into account change in the character of the strain development under irregular low-cycle loading, the criterion dependences can be used to assess the durability and compare it with the similar data under regular modes when accepting the condition of attaining the limiting state.

The anisotropy of the properties of a ceramic cutting insert (for three faces) obtained by the lithography-based technology from the Al₂O₃ + ZrO₂ composite has been studied. The study was carried out using the indentation method and Mayer’s law. This method, in contrast to the bending test, excludes the sample destruction. All the studies were carried out on three faces of a ceramic cutting insert made of a composite Al₂O₃ + ZrO_2. The behavior of the Mayer index was studied in the range of loads from 2 to 20 kg and from 0.2 to 1 kg. The results of studying the density, phase composition and microstructure of each face of the sample are presented. The study of the adhesion of the printed layers were also carried out using a Knoop indenter. No anisotropy of the hardness was observed in the load range up to 10 kg. It is shown that a layered structure present in the sample, contributes to the hardness anisotropy under the load of 20 kg and more. No anisotropy of the fracture toughness is observed in the load range of 2 – 20 kg. The results of using a Knoop indenter revealed a high adhesion between 3D printed layers. Studies using a Knoop indenter have indicated high adhesion between the layers of 3D printing.

We define risk as an unwanted opportunity and divide risk theory into three stages — risk analysis, risk estimation, risk management. Safety and risk are directly related to each other, being like a «mirror image» of each other which necessitates developing both the general theory of risk and particular theories of risk in specific areas. General risk theory allows for a uniform approach to the analysis, estimation and management of risks in specific situations. Currently, three main approaches to accounting for the uncertainty and describing risks are used — probabilistic and statistical approach, fuzzy sets, and the approach based on interval mathematics. The methods of risk estimation primarily based on probabilistic and statistical models are considered. The mathematical apparatus for estimating and managing risks is based on nonparametric formulations, limit relations, and multi-criteria optimization. Asymptotic nonparametric point estimates and confidence limits for the probability of a risk event are constructed on the base of binomial distribution and the Poisson distribution. Rules for testing statistical hypotheses regarding the equality (or difference) of two probabilities of risk events are proposed. An additive-multiplicative risk estimation model based on a hierarchical risk system based on a three-level risk system has become widespread: private risks — group risks — final risk. For this model, the role of expert estimation is revealed. The prospects of using (in the future) the theory of fuzzy sets are shown. The article deals with the main components of the mathematical apparatus of the theory of risks, in particular, the mathematical support of private theories of risks related to the quality management, innovations and investments. The simplest risk assessment in a probabilistic-statistical model is the product of the probability of a risk event and the mathematical expectation of the accidental damage. Mathematical and instrumental methods for studying global economic and environmental risks are discussed.