Home – Home – Jornals – Advanced Search

The behavior of a three-component electrolyte in a microdevice utilizing a spherical ion-selective granule under an applied electric field and a pressure difference is investigated. In practical applications, one of the electrolyte components corresponds to charged analyte particles present at an initially low concentration. It is shown that the analyte concentration can be increased in the wake of the granule, and the degree of concentration enhancement is independent of the initial concentration. The physical mechanism of this phenomenon is described. This paper also presents the parameter values-such as the potential difference, pressure difference, and the characteristics of the electrolyte and the granule-for which this enhancement is achievable.

Changes in the properties of a DC-excited gas-discharge plasma in uniform weak longitudinal magnetic fields are analyzed. The state and behavior of such a system in a weak magnetic field can be studied using the reaction-diffusion equation, which describes the ionization-recombination equilibrium in the plasma, together with modern concepts of ambipolar diffusion. It is shown that, in the presence of an external magnetic field, the transverse diffusion coefficient decreases, the coherence of emerging plasma states in the system is disrupted, noise or turbulence arises in diffusive and stratified regimes (including contracted ones), and the striation period increases. Complete destruction of the spatiotemporal structure of a striation occurs when the magnetic field strength exceeds a critical value. A similar effect is also achieved by increasing the working gas pressure. The presented findings allow all the above-mentioned behavioral features of the ionized gas to be interpreted as different manifestations of an integrated plasma-field system.

The amplification of a shock wave pulse transmitted through a sand layer is investigated as a function of layer thickness. It is shown that, as the sand layer thickness becomes somewhat higher, the amplitude of the probing pulse first increases and then decreases. Pressure peaks form almost simultaneously throughout the entire sand layer.

Integration in Lagrangian variables is performed for a submodel describing steady-state motions of an ideal gas with constant pressure in the flow region. A general solution is obtained for the invariant submodel of steady-state rotational isobaric motions. Examples of helical gas motions with constant pressure are considered.

A numerical study is performed to investigate the influence of vibrational excitation and relaxation of sulfur hexafluoride (SF₆) molecules on the gas-dynamic structure and stability of high-speed microjets issuing from axisymmetric sonic micronozzles with diameters ranging from 10 to 110 μm. Direct numerical simulation of the gas flow is conducted by solving the unsteady three-dimensional Navier-Stokes equations using a two-temperature model for relaxing flows. The study is carried out over a wide range of Reynolds numbers determined by the micronozzle diameter. The influence of vibrational relaxation of gas molecules on the mode composition and spectral characteristics of disturbances, as well as on the length of the laminar region of the microjets, is observed.

A solution to the problem of the pressure field in an oil and gas reservoir with a hydraulic fracture connecting an injection well and a production well is obtained. The solution is constructed in the Laplace-Carson transform space using an asymptotic method. Analytical expressions for the pressure field in the fracture are derived in the quasi-stationary approximation. An approximate formula for calculating the pressure field in a hydraulic fracture is proposed. Computational experiments are performed using numerical inversion algorithms and the obtained analytical expressions. Spatiotemporal pressure distributions are constructed for realistic values of reservoir and fracture parameters. Based on an analysis of the computational results, the patterns of pressure field formation in a reservoir with a hydraulic fracture are refined. A comparison of the numerical calculations with the analytical relationships shows that the proposed analytical formula provides accuracy sufficient for practical purposes over a time period comparable to the production lifetime of real oil and gas fields.

The nonlocal theory of microstructural deformation of thin plates is applied to derive an equilibrium equation for a thin isotropic nanoplate along with the corresponding boundary conditions. An approach to constructing a solution to this equation for a rectangular nanoplate with simply supported edges is proposed, employing Chebyshev polynomials of the first kind and the collocation method. The deflection of the nanoplate midplane and the bending moments are analyzed as functions of a nonlocal nanoscale parameter.

The catalytic oxidation and extraction of sulphur-containing compounds of the diesel fraction by metal-containing ionic liquids based on imidazolium bromide (IL) and metal salts (FeCl₃, SnCl₄, ZnCl₂, СоС1₂, МnС1₂) have been investigated. The composition of sulphur-containing compounds and polycyclic aromatic hydrocarbons in the initial and purified diesel fraction was determined by gas chromatography - mass spectrometry. The optimal conditions for oxidation and extraction have been determined: temperature 30 °C, extraction time 60 min, the molar ratio IL / metal salt = 1 : 0.25. A higher degree of sulphur-containing compounds removal (80-95 %) is observed in the systems ILFeCl₃, ILSnCl₄, ILZnCl₂. Results of the studies of group and individual composition of dibenzothiophene derivatives have shown that in terms of recovery degree the homologues are ranged as follows: dibenzothiophene > trimethyldibenzothiophene > methyldibenzothiophene > dimethyldibenzothiophene. The efficiency of extraction of naphthalene and phenanthrene homologues is 75-80 %.

The West Siberian oil and gas basin has large reserves of hard-to-recover oil from low-permeability reservoirs. The share of such reserves is more than 80 %, but less than 17 % is currently under development. Statistical analysis of the physicochemical properties and occurrence conditions has been carried out for hard-to-recover Western Siberian oils from deposits characterised by low permeability, the development of which will increase oil production in the region. A set including 1970 oil samples from 488 oilfields of the West Siberian oil and gas basin, taken from the database of the Institute of Petroleum Chemistry SB RAS, was used for analysis. The distribution of oilfields with low-permeability reservoirs in the basin is revealed, and the typification of oilfields with the reservoirs differing in permeability and porosity of rocks is presented. The lithological and stratigraphic distribution of low-permeable deposits of various types is shown. The features of physicochemical characteristics of oils and occurrence conditions have been revealed.

Formulations of composite materials based on aqueous dispersions of petroleum bitumen and plasticised epoxy-diane oligomer, stabilised by oleic acid in an alkaline medium, have been developed. The morphology of composite binder samples, their structural and rheological properties, temperature properties (softening point and brittleness temperature), and adhesive interaction with mineral materials of acidic and basic nature have been studied using granite and dolomite as examples. It is shown that the studied systems have a homogeneous structure, since there is a uniform oligomer distribution throughout the volume of the bitumen binder, with inclusions of light aggregates of epoxy-diane oligomer in the bitumen matrix, the size of which increases with an increase in the amount of the additive. It has been established that in the presence of epoxy oligomer, the temperature range of bitumen plasticity expands to ~20 °C, and the colloidal structure of mixed dispersions exhibits a non-Newtonian flow pattern up to 70 °C, so that with an increase in oligomer concentration (1-20 wt%), the resistance of the colloid system to deformation increases, which is confirmed by an increase in the values of rheological characteristics. The maximum adhesive bond of films (>75 %) is recorded during the interaction of the oligomer-bitumen binder and mineral material with a basic surface nature at an oligomer content of 5 and 15 %. The obtained compositions are promising for use as a film-forming material for construction purposes, which can be used as a sealing and waterproofing protective coating for road and civil construction products and structures, and also as part of a plugging material for cementing, fastening and repairing wells in oil and gas production industry.