Вестник Башкирского университета

The technique of numerical calculation of geometric characteristics of the cross section of a naturally twisted rod of variable cross section

2025-03-24T09:39:45+00:00

The article describes a technique for numerically calculating the main geometric characteristics of an arbitrary cross-section for a naturally twisted rod: area, center of gravity, axial and central moments of inertia. These parameters are necessary input data for a system of differential equations describing transverse vibrations of a naturally twisted rod. The estimation of the error of the tech- nique is based on numerical results with exact results obtained for the test problem when considering an ellipse-shaped section for which geometric characteristics are determined by precise analytical expressions.

Study of photoconductivity of thin films based on polyaniline derivatives

2025-03-24T10:08:59+00:00

The article studies the optoelectronic properties of a new polymer, polymethylbutenylaniline, with various doping and oxidizing agents. Fluorescence and photoconductivity of thin films based on the obtained materials are studied. Particular attention is paid to the study of absorption and fluorescence spectra, as well as to the measurement of photoconductivity. Photoconductivity of thin films was studied under the action of ultraviolet radiation with a wavelength of 350 nm. Samples of photoresistors were obtained, and such characteristics as photosensitivity and sensitivity were measured.

Study of the inhibitory properties of ketoximes with multiple bonds in hydrogen sulfide-containing media

2025-03-24T10:40:08+00:00

Ketoximes are poorly studied ketone derivatives, products of the interaction of ketones and amino compounds. An important advantage in the context of studying the inhibitory properties of ketoximes is the presence in their structure of a functional group C=N–OH with electronegative N, O atoms and a double bond at the same time, which have good solubility in water, are nontoxic and biodegradable. Selected compounds, in particular butanone oxime (methyl ethyl ketoxime), which is a fairly common organic compound used in industry to inhibit the polymerization process. The effect of a number of ketoximes (with a C4 chain length) on the corrosion resistance of carbon steel in an imitation of NACE formation water saturated with carbon dioxide and hydrogen sulfide was studied. The influence of medium temperature and exposure time on inhibitory properties was established. The influence of the “structure–property”, kinetic and physico-chemical parameters of interaction, as well as the mechanism of adsorption on the metal surface are studied.

Liquid – vapor equilibrium in SYSTEMS NI(PF3)4 – СН2CL2 and NI(PF3)4 – С5Н12

2025-03-24T11:51:47+00:00

Using the methods of circulation distillation and Rayleigh distillation, the liquid-vapor separation coefficients in the systems tetrakis(trifluorophosphine) nickel – dichloromethane and tetrakis(trifluorophosphine) nickel – pentane at 298 K were determined. For the tetrakis(trifluorophosphine) nickel – dichloromethane system the values αcir and αeff are 4.9 ± 0.8 and 11.7, accordingly, for the tetrakis(trifluorophosphine) nickel – pentane system the values are 4.2 ± 0.4 and 20.3, accordingly. The results obtained are consistent with the results of a theoretical assessment of the values αcir and αeff of the vapor-liquid separation coefficient according to Raoult’s law.

The influence of some medicinal compounds on the rheological properties of aqueous solutions of pectin

2025-03-25T08:35:03+00:00

The article is devoted to the study of the rheological behavior of pectin solutions in the presence of medicinal compounds – the antibiotics amikacin and cefazolin. The need for this study is due to the fact that the conformational and supramolecular state of pectin belonging to the class of polyelectrolytes, in addition to temperature, the chemical nature of the polymer and solvent, is largely determined by factors such as the degree of binding of counterions by macroions, as well as the concentration of low molecular weight salts present in the solution. Since medicinal substances are quite often low molecular weight electrolytes, they can have a significant impact on the process of pectin structure formation in solution, and, consequently, on its rheological properties. It was found that the presence of low molecular weight electrolytes of the antibiotics amikacin and cefazolin causes the shielding of the charge on the macromolecular chain and contributes to the strengthening of intra and intermolecular interaction. This fact, in turn, leads to a number of changes in the rheological state of the polymer solution, which must be taken into account when forming biomedical materials based on pectin.

Thermodynamic characteristics of the reaction of aluminum with water in the presence of inorganic salts (copper sulfate and sodium chloride)

2025-03-25T08:51:33+00:00

Metallic aluminum is the most common metal in the Earth’s crust. The chemical reaction between aluminum and water is ac- companied by heat release and leads to the formation of aluminum hydroxide and hydrogen, which can be used for hydrogen energy and heat generation. This article discusses the thermal effect of the oxidation reaction of aluminum with water in the presence of inorganic salts (copper sulfate pentahydrate (II) and sodium chloride). Using the calorimetry method, the dependences of time on temperature were obtained for various qualitative and quantitative compositions of the proposed compositions. A conclusion was made on the calorific value and the most effective ratio of mass. % of components.

Catalytic degradation of rhodamine b dye using hydrogen peroxide over ceramic membrane supported by vanadium (v) oxide layer

2025-03-26T09:46:12+00:00

In this paper, the catalytic degradation of Rhodamine B dye using a ceramic membrane based on α-Al2O3 with a V2O5 supported layer is described. The vanadium-supported layer was prepared using the solgel method. The sol V2O5.1.6H2O was obtained through the thermolysis of V2O5 with H2O2. The ceramic membrane with V2O5 supported layer was characterized using various methods including SEM, XRD, TG/DSC, and ASAP. After thermal treatment, no changes in the phase of V2O5 were observed on the surface of the membrane, where it appeared in the form of dendrite crystals. It was noted that the BET surface area of the supported layer decreased following thermal treatment. The degradation process of Rhodamine B dye was conducted in a batch reactor using the prepared ceramic membrane with supported layers of varying lengths. The degree of degradation of the Rhodamine B dye was assessed by measuring the optical density of the solution with a spectrophotometer.
The degradation rate was analyzed using a first-order kinetic equation. It was found that increasing the length of the supported layer positively influenced the degradation rate.

Antioxidant activity of alcoholic extracts of black currant buds (ribes nigrum l.) of bashkir varieties

2025-03-26T10:05:51+00:00

The effect of alcohol extracts from the buds of black currant (Ribes nigrum L.) varieties of Bashkir verieties on the process of radical chain oxidation of ethanol was studied. The antioxidant activity of alcoholic extracts of currant buds is characterized by the relative decrease in the oxidation rate of the model substrate. The dependence of the antioxidant activity of extracts from the buds on both the currant variety and the time of bud harvesting was established.

Study of kinetic heterogeneity of polymerization catalysts using a genetic algorithm

2025-03-26T10:59:51+00:00

An alternative approach to evaluating the kinetic heterogeneity of polymerization catalysts using heuristic optimization methods is proposed. The assessment is based on the analysis of the molecular weight distribution (MWD) curve, which can be represented as a superposition of several model distributions, each corresponding to a specific active center initiating the polymerization process. The proposed mathematical approach is based on a genetic algorithm to solve inverse problems related to the identification of unknown parameters that determine the contribution of each active center to the overall MWD profile. Unlike classical methods, this approach does not require the determination and analysis of the active center distribution curve. Instead, it assumes that the polymer distribution at each active center follows one of the known model distributions. The methodology was tested in the study of the kinetic heterogeneity of a titanium-containing catalytic system used in the production of 1,4-cis-polyisoprene.