Production and processing of oil and gas are associated with the formation of a huge bulk of wastewater of complex composition disposed in different ways after thorough treatment. Environmental control of the composition and degree of purification of oil and gas-bearing wastewater requires using effective methods for determining various pollutants, including chloride and fluoride. The object of the study was a sample of wastewater from the largest gas field «Mustakillikning 25 yilligi» in the Surkhandarya region of the Republic of Uzbekistan. It is shown that the sample is salty (dry residue is 34.1 – 31.7 g/dm³) and has a neutral reaction. The method of atomic emission analysis of water revealed high concentrations of potassium, sodium and sulfur, a significant amount of calcium and magnesium, and a significantly small number of other elements contained in water. Study of various methods of sample preparation for ionometric measurements of chloride ion showed that a significant proportion of chlorine is bound with organic components of water. It is shown that boiling (~100°C) or fusing at 800 – 850°C with NaOH eliminates the interfering effect of accompanying components (sulfur, iodine and organic matter) on the chloride determination. The results obtained provide quantitative determination of the total content of chlorine in water both in the form of a free chloride ion and in a bound state, probably in the composition of organochlorine compounds. The presence of fluorine in the organic part of the sample has not been revealed. The possibility of using a single sample preparation (boiling or fusing) for the determination of both chloride and fluoride ions has been shown. The interfering effect of the accompanying elements upon fluorine determination was masked by a buffer solution which regulated the total ionic strength. The developed procedures are easy to use, selective, and cost-effective. The correctness and accuracy of the developed techniques were evaluated and proved using a method of varying sample volume.

The results of studying the composition of glasses from the site of the Zhabinsky factory, one of the first Russian glass factories founded in the north-west of Russia, are presented. More than 200 samples of historical glass fragments of dishes, as well as the remains of glass on the walls of melting pots were studied using X-ray fluorescence analysis. The data obtained made it possible to classify glasses depending on the recipe and the raw materials used in their production. The reliability of the determination of the compositions was confirmed on randomly selected samples by the ICP AES method. The presence of cobalt impurities was qualitatively determined from the characteristic bands in the absorption spectra of the visible region. The main group of finds is represented by potash-calcium glass obtained using plant ash (ash glass) or purified potash (potash glass). A separate group includes potash-lime glasses obtained through addition of lime to the batch. The nature of the coloration of the studied glasses with iron (+2), iron (+3), cobalt (+2), and also due to the charge transfer iron (+3) — sulfur (–2) is discussed. Potassium-lead glasses with a high lead content found at the site of the plant serve as an example of the first Russian colorless lead crystal. The results represent the first systematic study of the composition of glass produced in Russia in the time of Peter the Great. A comparative analysis of the compositions of glasses from the Zhabinsky and Lavinsky factories has been carried out.

Composite materials like «Sibunit» are used as carriers for heterogeneous catalysts. These materials exhibit high mechanical strength, chemical purity, high resistance to aggressive environment, and controlled porous structure. The components of such catalysts are noble metals, and their combinations with oxides of some transition metals. An urgent task in their production is to control the content of the active component in the composition of catalysts. This characteristic affects the phase and electronic state of the metal, the structural and textural characteristics of the carbon carrier, and hence determines the activity and selectivity of catalysts during operation. Quantitative chemical analysis thus becomes one of the main methods for controlling the quality of catalysts. Different options for acid decomposition of mono- (Pd/C, Ru/C, Ga/C) and bimetallic (Pd-Ga/C, Pd-Zn/C, Pd-Ru/C, Pd-Ag/C) catalytic systems based on carbon carrier «Sibunit» are considered. The goal of this study is determination of the content of metals by inductively coupled plasma atomic emission spectrometry. The effect of the main operating parameters of the spectrometer on the intensity of sensitive and non-overlapping spectral lines of the elements being determined was studied. Optimal conditions for measuring the analytical signal were chosen. It is shown that for the studied bimetallic systems, with the exception of Pd-Ru/C, it is possible to choose a sample preparation option that allows simultaneous quantitative determination of two components from one sample. The developed method of quantitative analysis is characterized by rather high accuracy. The relative error of the element determination does not exceed 3 %, the relative standard deviation is not more than 5 %. The results of the study can be used to analyze catalysts of similar chemical composition by inductively coupled plasma atomic emission spectrometry.

The mechanical and thermal properties of heat-resistant ceramic materials based on refractory oxides largely depend on the defect-free nature of their crystal structure, the presence of extraneous phases, the size and orientation of the grains. We present the results of studying the structure of ceramic fibers of mullite-corundum composition during high-temperature heating using optical polarization microscopy. The structural features of a continuous fiber of Al₂O₃ – SiO₂ system heat-treated in a free state and under tension, as well as the structure of short fibers of a similar composition obtained by injecting a solution with subsequent heat treatment of the fiber mass at different temperatures were studied. It is shown that the structure of a continuous fiber after heat treatment in the free state has a multidirectional orientation of the grains, whereas heat treatment at the same temperatures under tension leads to the formation of an oriented uniaxial structure. Thus, the fibers obtained from the same solution and heat-treated at the same temperatures are characterized by different strength values. Moreover, the strength of a fiber with an oriented uniaxial structure is one and a half times higher than that of a fiber with a multidirectional grain orientation, which greatly facilitates its further processing. It is also revealed that structural defects like incomplete crystallization, collective recrystallization, and inhomogeneous inclusions of the second phase, characteristic of short fibers obtained by nozzle spraying, negatively affect the thermal properties of thermal insulation made of such fibers. The results obtained can be used to improve the methods of analyzing the microstructure of aluminum oxide fibers using the method of optical polarization microscopy.

The X-ray technique used in the quality control of soldered joints of injectors with fuel manifold tubes of gas turbine engines (GTE) has a number of limitations and drawbacks. The detectability of flat flaws, e.g., dry solders, strongly depends on their orientation with respect to the direction of X-ray beam propagation. An ultrasonic method which provides increased efficiency of controlling soldered joints of modern gas turbine engines, the manifolds of which usually contain two rows of tubes is presented. A focused high-frequency pencil-type transducer has been used in the study. Samples with artificial reflectors in the form of flat-bottomed holes located in the soldering zone were analyzed. Special delay lines provided the transmission of ultrasonic waves at the angles close to the normal to the surface of the soldered joint. The results of the control obtained using the developed procedure were compared with the data of X-ray method. It is shown that ultrasonic technique provides detection of the flaws not detected by radiographic control. The sensitivity, minimal width of the flaw (dry solder) and possible completeness of the control were determined for the developed technique. The results obtained could be used to improve the method of control of soldered joints of GTE fuel manifolds.

Fibrinogen is synthesized by human liver cells and is constantly present in the blood. Protein is the main factor of blood clotting and largely determines the blood viscosity. Any damage to a blood vessel or tissue in the body triggers hemostasis (blood clotting). Fibrinogen under the action of thrombin is converted into fibrin, an insoluble biopolymer, which is the basis of a blood clot that provides hemostasis. Apart of wound healing, fibrinogen is involved in the pathogenesis of malignant neoplasms. Fibrinogen labeled with ¹²⁵I is used to diagnose thrombosis because it penetrates blood clots. We present the results of studying the structure of fibrinogen in human blood plasma using small-angle X-ray scattering (SAX). The SAX method, widely used in analysis of supra-atomic structures of substances, provides determination of the size of domains present in proteins, their shape, as well as the conformation of segments of chain macromolecules in the form of Gaussian and persistent chains. An important feature of the method is the possibility of studying biological objects in their natural state, without any special pretreatment. It is shown that globular domains of two sizes (diameters — 8.4 and 4 nm, respectively) are present in the structure of fibrinogen. The domains are coupled by polypeptide chains (α, β, γ) twisted in the form of spiral coils. The stiffness of the chains estimated as a persistent length was 3.1. The results obtained can be used in surgical practice and replacement therapy when creating fibrin glue as a hemostatic drug that stops bleeding with minimal invasiveness of intervention, and drugs that eliminate fibrinogen deficiency in the blood.

Experimental and theoretical studies of the fracture regularities under monotonic and alternating loadings, including stress-corrosion fracture, revealed the main scale-structural levels of the brittle fracture (formation of a strip structure, nucleation of microcracks, microstructurally short non-propagating cracks and short propagating cracks, merging of short cracks with a macrocrack nucleation) and viscous fracture (an evolution of dislocation in slip bands, cellular structure formation, nucleation of a pit relief with micropores, merging of pores with a formation of meso-shear bands and initiation of a viscous crack, growing of a viscous crack under inelastic deformation) of crystal bodies. A transition from one level to another is determined by changes in the fracture mechanisms and occurs with varying degrees of probability. The necessity of considering the destruction as a hierarchical random step-by-step process on all scale-structural levels is substantiated. The fracture of plastic materials is considered as the sum of independent or dependent events, namely the initiation and growing of brittle cracks and evolution of pores through various mechanisms. Attaining of the limit states is determined by the statistics of the distribution of inhomogeneities throughout the entire body volume. The results of physical studies (using electron microscopy, X-ray structural analysis, etc.) provide determination of the geometry and density of defects, dislocations, pores, cracks at different levels. Macrocharacteristics of static, long-term and fatigue strength are determined using methods of mechanical tests. The regularities of the fracture evolution of engineering structures are determined using methods of non-destructive testing (ultrasonic analysis, acoustic emission analysis, magnetic flaw detection, etc.). A brief analytical review of the main known physical approaches — dislocation and energy structural theories, dislocation continuous theories, dilaton-frustron models, stochastic physical theories, and phenomenological approaches, including continuum damage theory and fracture mechanics — is presented. The analysis of gained data leads to the necessity of describing fracture in the framework of stochastic multilevel models. We consider the approach according to which the probability of reaching limit sates at each level under arbitrary multiaxial loading is determined by linear functionals of the loading process, kernels of the functionals being random functions of time. For simple proportional loading, the theory of brittle fatigue scale-structural failure is presented.

Nowadays, promising and dynamically developing additive manufacturing of complex parts for small-scale production actively succeeds traditional technologies in many industries including aircraft engineering. A method of selective laser fusing also finds effective application along with a well-known methods of additive manufacturing like selective laser sintering, laser metal deposition, plasma-jet hard-facing and electron beam melting etc. The results of comparing the structural, mechanical and tensile strength properties of materials used for manufacturing complex-shaped products by additive and traditional methods revealed the advantage of additive manufacturing which is the basis for their introduction into industry. The goal of the study is a comparative study of the microstructure, mechanical characteristics, fatigue life and fatigue fracture of the specimens made of EOS PH1 stainless steel produced by additive manufacturing and 30KhGSA hardened steel specimens obtained by a traditional technology. Fatigue resistance tests of the specimens were carried out in conditions of uniaxial longitudinal stretching. The microstructural features of the microsections of the cross sections of the samples were studied using stereomicroscope and scanning electron microscopy. Fractographic study of the macro- and micro fracture patterns of the specimens was carried out to identify the structural features of the fractures, fracture nuclei and their correlation with the microstructural imperfections. It is shown that selective laser melting technology used for manufacturing EOS PH1 stainless steel specimens, provides production of the specimens with a rather high tensile strength characteristics comparable to the characteristics of 30KhGSA hardened steel specimens. Therefore, EOS PH1 stainless steel has a great potential as a material for manufacturing parts and products that have high requirements for the strength, hardness and fatigue life.

The development of laboratory technologies for growing high-quality diamond single crystals, as well as low thermal expansion of a diamond, make it possible to consider this material promising as an element of X-ray optics in designing free electron lasers (XFEL). Diamond crystal-spectrometers of various thicknesses and bending radii are also in demand. In this regard, the issues regarding the mechanical parameters of elastically deformed diamond single crystals require clarification, among them critical stresses in a deformed single crystal and the minimum bending radii for plates of certain geometry. The goal of the study is determination of the elastically deformed state of thin diamond plates with the parameters required in spectrometers for non-invasive diagnostics of X-ray free-electron laser (XFEL) spectra. The samples were cut from the IIa -type crystal of the highest quality grown by the temperature gradient method. Diamond plates with (110) and (111) crystallographic orientations were used in the experiments. The dependences of the stresses and bending radii on deformation value were obtained during bending thin diamond plates with a thickness of 20 μm. The experimental deformations did not exceed 1 mm. The minimum bending radii of thin diamond plates were also determined: for (111) direction — 5.6 mm, and for (110) direction — 4.5 mm. The Young’s moduli were 1198 GPa for (111) direction and 1034 GPa for (110) direction. Critical stresses during bending of thin diamond single crystals (resulting in their destruction) exceeded 2.4 GPa. The dependence of the bending radii of crystals on their thickness was calculated at a stress value of 2.0 GPa. The results of the study make it possible to calculate the allowable deformations for thin diamond plates of arbitrary shape and thickness. The data obtained will contribute to the improvement of modeling and the quality of production of curved spectrometers.

Binary classifiers are studies on balanced text samples. The samplings are formed from scientific publications in the field of Computer Science (Computer Science). The first class contains articles on «Text Data Mining» (the «TDM» class), the second one contains works on other topics of Computer Science (the «non-TDM» class). All the main stages of preliminary processing of text documents are considered, models of their presentation are analyzed. The problem of binary classification is formulated and the quality indicators used in the study are given. A method of sampling from the Russian digital library (Elibrary) is proposed. The generated sampling consists of bibliographic descriptions of documents (title, abstract and keywords). An exploratory analysis was carried out and the sampling structure was studied. «Term clouds» for two classes are constructed and analyzed, documents are visualized using the method of stochastic embedding of neighbors with t-distribution (t-SNE). Based on the review and analysis of known classifiers, the following methods were selected for the study: the K-nearest neighbor method, random forest, gradient boosting, logistic regression, and the support vector method. Profile methods based on the construction of a vector (profile) of the most informative terms determined by the frequency of occurrence of terms and classes are also used in the study. The parameters of the methods were configured using a five-fold cross-validation. The best quality of classification in our sampling demonstrated the methods using the ensemble (collective) decision-making principle (random forest, gradient boosting), as well as the support vector method. The best classifier, gradient boosting, had the proportion of correct answers (accuracy) about 0.98, recall and precision about 0.99. The other (simpler) methods used in the study also generally showed rather good quality of classification (for the least accurate k-nearest neighbor method accuracy, recall and precision were 0.90, 0.81, and 0.91, respectively).

Fizmatlit publishing house published a bookMatvienko Yu. G. Two-parameter fracture mechanics. — Moscow: Fizmatlit, 2021. — 208 p. ISBN 978-5-9221-1899-6 [in Russian]