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Abstract Using the 1H NMR examination of a representative set of crude oils (86 samples, 54 oil fields and exploration areas) from the North Caucasus oil-and-gas basin, we obtained, for the first time, the structural-group composition of crude oils over the entire basin. Distribution density plots were presented for all the composition parameters measured. It was demonstrated that, because none of the parameters obeys normal distribution, non-parametric statistical analysis is needed for the data processing. In particular, medians and median confidence intervals (the latter being determined by signed-rank test), rather than means or root-mean-square deviations, should be relied upon. The North Caucasus oils were found to have a markedly lower content of aromatics (both monocyclic and bi-/polycyclic) than the crude oils from Western Siberia and Volga–Urals. Compared with the Eastern Siberia basin, the North Caucasus oils are distinguished by a slightly higher presence of bicyclic and polycyclic aromatics. At the same time, the North Caucasus oils exhibit the highest content of normal and monomethylated alkanes among the four basins under consideration. The North Caucasus oils were classified into three stratigraphic groups according to their oil composition. The first group consists of Triassic and Jurassic reservoirs. These crude oils have the lowest content of aromatics and the highest content of normal and monomethylated alkanes. The second group is the Cretaceous sediments, and the third group includes Paleogenic and Neogenic deposits. The content of aromatics increases consistently from the bottom to the top of the section.

Goals and objectives. Graphical models have proven to be a reliable, clear and convenient tool for creating sketch models of databases. Most of the existing notations are designed for the relational data model, the dominant data model for the last thirty years. However, the development of information technologies has led to an increase in the popularity of non-relational data models, primarily the document model. One of the problems of its application in practice is the lack of suitable tools that allow performing graphical modeling of the database, taking into account the features of the document model, at the stage of logical design. The development of appropriate tools is an important and actual task, since their application in practical research makes it possible to identify, classify and analyze typical modeling errors that allow the designer to reduce the risk of their occurrence in the future. The purpose of this article is to develop a graphical notation that, on the one hand, providing convenience for the designer, and on the other hand, taking into account the peculiarities of creating and functioning of the noSQL document storage model.Materials and methods. The materials for the study were numerous publications devoted to the development of graphical notations in problems and their application to database design for various information systems. The selected materials were analyzed and the main graphical notations used to describe the relational data model were identified. Three notations were selected from them, a set of graphic stereotypes, which were most different from each other, the analysis of which allowed us to identify the main image patterns of the components of the relational model.The resulting patterns were applied to the main elements of the document database, which were obtained by analyzing the documentation of the popular MongoDB DBMS.Results. The result of the research was the creation of a new tool for modeling document databases at the logical level, which consists of a set of graphic stereotypes and rules for their application. On the one hand, the development is well known to practitioners who have previously worked with relational data models, since its development took into account many years of experience in using graphical models in the field of relational database design, and on the other hand, it reflects the features of the structure of the document model.Conclusion. The practical application of the developed model has shown the convenience of its use both in the process of designing document databases and in the process of teaching students within this subject area. The use of graphical models constructed in the proposed graphical notation will allow researchers to create and illustrate typical patterns of document databases, which will undoubtedly have a positive impact on the dynamics of the development of promising data storage technologies.

Samples of rhodium nanoparticles supported on the surface of highly oriented pyrolytic graphite (HOPG) are prepared by vacuum deposition; their interaction with nitrogen dioxide is studied by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). In the initial state, metallic rhodium particles with a size of about 2–5 nm are combined into aggregates localized on the steps and terraces, apparently, in the region of localization of structural defects. After treatment in NO2 at room temperature and pressures of 10−6 and 10−5 mbar, carbon oxidation accompanied by the degradation of the structure of 12–15 graphene layers on the HOPG surface is observed. Under these conditions, rhodium remains in the metallic state, and the Rh particles are encapsulated with carbon. The results are compared with data on the interaction of NO2 with Pt and Pd nanoparticles supported on the HOPG surface.

—A comprehensive study of Domanik deposits of the Timan–Pechora Basin has been carried out. The examined composition of hydrocarbon biomarkers, chemical structure of kerogen, carbon isotope composition, and rock lithology, the Rock-Eval pyrolysis data, and the contents of bitumen and Corg in the rocks give an insight into the geochemical processes in the oil window in the Domanik deposits, which took place at Tmax = 435–450 °C. The bitumen coefficient βCB is maximum in this temperature interval, reaching 30%. The obtained data on the distribution of polycyclic biomarkers in the Domanik rocks and the bitumen and Rock-Eval pyrolysis data allowed determining the boundary values of biomarker maturity coefficients in the study of the maturation of organic matter of the rocks. The carbon isotope composition of bitumen fractions in the Domanik rocks is considered, and the bimodal distribution of the δ13C values of the bitumen is shown.

More than 75 % of the drinking water demand in the territory of the former USSR is met by underground water reserves. Along with a serious approach to the pollution of surface waters, soils, atmospheric air, the ecological state of underground waters is given an unjustifiably small importance. The availability of fresh, environmentally friendly water in sufficient quantities is the basis for the life of both humans and all ecosystem participants. The current ecological situation in the Shchuchansky district in the Kurgan region is formed under the influence of numerous factors of natural and manmade origin. The purpose of the research was to assess the quality of underground water located on the territory of the Shchuchansky district in the Kurgan region. The theoretical material of the ecological state of the territory in the Shchuchansky district has been presented in the article. Descriptions of laboratory studies of underground water have been given, and sources of pollution have been indicated. The conducted evaluation of the quality of underground water according to hydrochemical indicators did not reveal the excess of permissible concentrations of pollutants. The underground waters of Chumlyak, Kolmakovo-Miasskoye and the town Shchuchye are more susceptible to pollution. The lowest content of chlorides and sulfates in wells and boreholes has been found in the Petrovskoye and in the Puktysh, nitrites and nitrates in the Nikitino, and ammonium nitrogen in the Naumovka. Studies of the concentrations of heavy metals in underground sources have been shown an increased iron content in them at the level of 1,1-1,6 maximum allowable concentration. The content of copper, zinc and manganese in underground waters did not exceed the maximum allowable concentration. The highest concentration of copper has been found in wells and boreholes in the Kolmakovo-Miasskoye, and manganese in boreholes in the town Shchuchye.

The distributions of the 13C NMR-measured structural-group composition parameters of the Lena–Tunguska basin crude oils were obtained. All these distributions were shown to be far from normal, many of them being asymmetric and/or bimodal. These oils exhibit a significantly lower content of aromatics than the Volga–Urals and Western Siberia oils. The principal maximum of Car distribution lies in the distribution tail areas of the other two basins. The Lena–Tunguska oils are free of fluids with low content (below 14 abs %) of n-alkyl structures. It was also demonstrated that the crude oils sampled from the basin’s two major tectonic structures, namely the Baikit anteclise and the Nep-Botuob anteclise, differ significantly from one another in the concentrations of aromatics and n-alkyl structures.

Oils in Tatarstan were determined to have been generated in at least two source rock formations, whose organic matter (OM) differed in genesis, redox conditions of sedimentation, and maturity. The oils of type 1 are hosted in Devonian terrigenous reservoir rocks, whereas the oils of type 2 occur in overlying reservoirs. Differences between the oils are reliably identified in most compositional parameters of saturated biomarkers, with the values of the two oil groups not overlapping for two parameters: Ts/Tm and t22/t21. The maturity of the group-1 oils is statistically significantly higher than that of the group-2 ones. The source rocks are identical at the macrolevel: the original organic matter was deposited in marine sedimentation environments under reducing conditions, which is consistent with literature data. Comparison of the compositions of the oils and OM of the Domanik Formation indicates that rocks of the Mukhanovo–Erokhov trough were not involved in producing oil accumulations in Tatarstan. Differences were also detected between genetic characteristics of oils from the terrigenous Devonian rocks and Domanik Formation in the arch part of the area. Organic matter in the arch part of the territory could be significantly involved in the generation of oil accumulations hosted in reservoirs in the Semiluk and higher horizons. It is demonstrated that earlier conclusions that the source rocks of certain oil groups differed in lithology are groundless. To estimate the confidence interval for the median values, a criterion of signs was proposed, which has never before been employed in organic geochemistry.

Increasing of production performance of production systems and equipment in the meat-processing industry is integrally linked to maintenance activities. The article analyzes the influence of technological effectiveness, level of hygiene, reliability and simplicity of equipment design on the main parameters of meat products quality. Here it is shown that the strategy of Total Productive Maintenance (TRM) and Lean production is important tool for assessment of parameter of the Overall Equipment Effectiveness (OEE), which is used to assess the main types of losses that reduce the equipment productivity. The link of influence between the structural and mechanical properties of food masses, the moisture content of the initial food raw material, the temperature and viscosity, the processing pressure, and the density for the optimal operating terms of the equipment are analyzed in this research. With the help of OEE concept, the time losses related to the features of the equipment functioning are determined. The types of losses are classified as follows: downtime and readjustment (availability or readiness for operation) of equipment, short-term shutdown of equipment and a decrease in processing speed (productivity or performance rate of the equipment), product rejects and product losses (quality losses) during startup of equipment. While analyzing of the operation of vacuum filler for sausages production, the values of parameters of equipment availability, it productivity and product quality are calculated. The availability index is 0.79, the productivity index is 0.76, and the product quality index is 0.95. Taking into account the obtained data on equipment availability, productivity and product quality, it is determined that the overall equipment effectiveness (OEE) accounts for 57%. The application of this method for studying the overall equipment effectiveness operation can be applied to any technological equipment used in the meat-processing industry and allows eliminating many problems that arise during the operation of technological equipment, improving its technical and economic parameters, and developing a system of measures for improvement of its maintenance and repair.

Transients in a high- and medium-voltage power-supply network due to switching operations and short circuits are accompanied by high-frequency overvoltage pulses. Their amplitude and frequency characteristics are needed to select proper protection devices. Only experimental study can give us reliable data on such characteristics. The paper presents overvoltage spikes experimental study data in switchgears of 6–500 kV. The spikes were measured by means of recorder with noncontact capacitive sensors. Experimental studies at power-engineering facilities showed that most hazardous phenomena are high-frequency resonances. In this case, the overvoltage values are over ten times higher than nominal voltage amplitude. The usual method of connecting protection device to mains via a conductor a few meters long was shown to be inadequate to provide equipment protection. RC circuits are needed for this situation.

This bibliographical review represents the published data on the composition and structure of aluminate ions in solutions with varied Al(III) and NaOH concentrations. The results of investigations of the partial and integral properties of aluminate solutions regarded as a ternary NaOH–NaAl(OH)4–H2O system are given. The phase diagrams of the ternary Na2O–Al2O3–H2O system for temperatures of 30, 95, 110, 130, 150, and 180°C are presented, and the compositions of the solid phases existing in equilibrium with the corresponding saturated aluminate solutions are specified.

A technique for forming Au/SiO2 core/shell nanoparticles is developed. A long-wavelength shift of the extinction spectrum peak from 520 nm to 538 nm with increasing SiO2 shell thickness from a monolayer to 10 nm is established. It is experimentally shown that the anomalous spectral shift of the extinction spectrum peak of Au/SiO2 nanoparticle arrays from 538 nm to 720 nm, observed with increasing the SiO2 shell thickness, is caused by the formation of Au nanoparticle di- and trimers within one SiO2 shell. This effect is theoretically explained for the case of Au nanoparticle dimers.

The effect of laser radiation with a wavelength near 1.55 µm on the photoluminescence properties of “nitrogen-vacancy” (NV) color centers in diamond has been studied experimentally. The effect of radiation of an infrared laser on the charge state of color centers redistributes the spectral intensity of photoluminescence in the ensemble of NV centers. In the case of neutral NV centers, the quenching of photoluminescence reaching about 60% has been observed. A feature of the laser excitation of NV centers by this method is the absence of competition with stimulated emission and two-photon excitation, which is observed with an increase in the power of infrared radiation at other wavelengths.

The contact surfaces of the banding shelves of adjacent steam turbine blades made of titanium VT6 alloy after operation are studied by fractography, micro-X-ray and microstructural analysis and determination of mechanical properties. The different types of destruction of the contact surfaces are analyzed and explained. It is shown that the reason for intensive abrasion of the turbine blades' binding meshes is violation of the welding mode in the station conditions.

This article presents the results of the creation of laboratory equipment for the production of nano- and microfibres by the method of multi-layer electrospinning, a detailed description of the parts of the resulting device is given, such as a device for feeding a polymer solution into the electrospinning zone and a collector assembly. The main parameters of the device, the principle of operation and modes of electrospinning are described. Comparison with similar devices, advantages and disadvantages of different options for supplying solutions to the electroforming zone are presented. The results of experimental studies on this installation are presented on the example of aqueous solutions of sodium alginate and polyvinyl alcohol, and their mixtures. The regimes of stable electrospinning are experimentally determined. Samples of nanomaterials were obtained from mixtures of these polymer solutions. A morphological analysis of the obtained materials and a histogram of the fibre diameter distribution were carried out.

We report the results of systematic experimental and theoretical studies of structural and dynamical properties of short-period GaN/AlN superlattices. The multilayer structures with the thicknesses of the constituent layers varying from two to several monolayers are grown using the submonolayer digital molecular beam epitaxy technique. In the framework of density functional theory, the lattice dynamics properties of the superlattices are studied. Good agreement between the experiment and theory is found, which made it possible to establish unambiguously a relationship between the features observed in the Raman spectra and the microscopic nature of the acoustic and optical phonon modes. The results obtained enhance the capabilities of Raman spectroscopy as a fast and non-destructive characterization method of short-period GaN/AlN superlattices and can be used to optimize growth process parameters for the fabrication of structurally perfect low-dimensional heterostructures.

The luminescence properties of colloidal Ag2S quantum dots (QDs) with ZnS or SiO2 shells coated with thioglycolic or 2-mercaptopropionic acids are comparatively analyzed. It is demonstrated that the quantum yield of the IR recombination luminescence of colloidal Ag2S QDs increases by a factor of up to 35 as a result of formation of ZnS or SiO2 shells with a simultaneous increase in the average luminescence lifetime. It is shown that the radiative and nonradiative recombination constants for core/shell Ag2S/ZnS QDs coated with thioglycolic acid decrease, which is explained by localization of electrons in the shell and localization of holes in the core. In core/shell Ag2S/SiO2 QDs coated with 2-mercaptopropionic acid, the radiative recombination constant increases and the nonradiative recombination constant decreases. In this case, the increase in the radiative recombination constant is caused by localization of electrons and holes in the core. The decrease in the nonradiative recombination constant is explained by passivation of interface defects of QDs upon the shell formation.

The main contribution to the luminescence of LiNbO3 : Zn (0,04 ÷ 2,01 mol. %) at 420 and 440 nm was established to be due to two electro-hole pairs of Nb4+–O-in niobium octahedron. Moreover, the luminescence weakly depends on Li / Nb ratio and Zn concentration. The increase of Zn concentration to 2,01 mol. % ZnO leads to monotonically increasing intensity in long-wave region of the photoluminescent spectra. This fact indicates that there are shallow energy levels near bottom of the conductivity band. Also the features of hydrogen bonds in LiNbO3structure effects on the location of the shallow energy levels as the complex defects caused by OH-group in the structure can contribute to the photoluminescence.

The photoluminescence intensity in lithium niobate crystals close to the stoichiometric composition being lower than in a congruent crystal was established. The increase of Li / Nb ratio leads to shifting the photoluminescence bands to the short-wavelength region of the spectrum and changing the fundamental absorption edge of the crystals under study. It was shown that, in addition to point defects in the cationic sublattice, complex defects due to the presence of OH groups and compensation defects (VLi / VNb) in the structure can also contribute to photoluminescence.

We consider the manufacturing process of forgings for turbine blades of extra-large dimensions (length >2 m) from electroslag remelting steel 15H11MF-Sh. With an increase of the workpiece dimensions (weight >450 kg), we face the problem of choosing the technology for obtaining the original billet. The production technology is known to affect the structure of the material and, as a consequence, the final properties of the product. We present the results of studying the influence of the method of obtaining the original metal blanks (hot-rolled steel bars and forged billets) on the properties of large-sized forgings of turbine blades. The mechanical characteristics, microstructure properties, chemical composition and content of δ -ferrite were determined by examining the initial samples of long products and forged rods. It is shown that billet in the forged state exhibit higher strength characteristics. However, after the stamping process, the properties of the blades equalize, i.e., after stamping and heat treatment, the same structure is formed, regardless of the method of obtaining the original workpiece. The results obtained can be used in the serial production of large-sized turbine blades of a new profile.

A sample of palladium nanoparticles with an average size of ~5 nm on the surface of highly oriented pyrolytic graphite (HOPG) was prepared by vacuum deposition. With the use of X-ray photoelectron spectroscopy (XPS), it was found that the interaction of the resulting Pd/HOPG sample with nitrogen dioxide at room temperature and a pressure of 10–6 mbar led to the oxidation of graphite. In this case, palladium particles retained their metallic state. A comparison with the behavior of a palladium sample supported onto HOPG activated by ion etching under similar conditions showed that structural defects on the graphite surface did not play a decisive role in the oxidation of graphene layers. A comparison with the results obtained upon the interaction of NO2 with Pt nanoparticles supported on the HOPG surface was made.

We analyze the features of nonlinear refraction in colloidal solutions containing Ag2S quantum dots capped with thioglycolic acid (Ag2S/TGA) or L-cysteine (Ag2S/L-Cys), with the quantum-dot (QD) sizes ranging from 1.7 to 5.5 nm and their concentration in the solution being 0.1%. The Z-scans of the samples were obtained using 10 ns pulses of 532 nm radiation. For samples with various average sizes and positions of the characteristic feature in the optical density spectrum, both self-focusing and self-defocusing of radiation were observed. The contribution of thermal refraction to the recorded Z-scans was estimated, and the impact of thermal effects on the observed nonlinear refraction was shown to be negligible. The solutions of the Ag2S/TGA QDs with the ground state exciton absorption peaked at 590 nm exhibit self-focusing. The samples with recombination luminescence and the ground state exciton absorption peaked at 750 nm reveal self-defocusing. We show that nonlinear refraction in the case of nanosecond pulses is predominantly nonthermal in nature and is due to absorption by free charge carriers, as well as due to the band filling effect in the Ag2S QDs, which involves localized states of impurities.