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Using the three-dimensional linearized theory of stability and piecewise-homogeneous medium model, this study has investigated near-surface buckling in the laminated composite materials, as well as local buckling in the vicinity of interlayer macrocracks. The effects of macrocrack size and position on critical loads and buckling modes have been thoroughly analyzed. It has been demonstrated that, as the macrocrack size increases reaching a certain value, the near-surface buckling mode abruptly changes over to local buckling. To solve the problem numerically, a mesh-based method and a modified variational-difference approach have been applied. A computational experiment has been conducted using both sequential and parallel implementations of the Cholesky method to solve the resulting system of linear algebraic equations, as well as the subspace iteration method to solve the generalized eigenvalue problem.

The cost of the graphite electrodes amounts greater proportion in the final value of the finished product. This calls for finding opportunities to reduce the maintenance costs of AC and DC furnaces used in foundries. The aim of the study is the creation of a mathematical model and the analysis of the efficiency of the evaporative cooling method in reducing the amount of the graphite electrodes used in small capacity arc furnaces. The mathematical model and the computer program allow determining the thermal state of the electrode and the melting loss of the graphite, the model is developed for a primarily cylindrical electrode and takes into account: the current passing through an electrode, the time of the electrode being in the electrified furnace, and the parameters of the water evaporative cooling. The paper presents the received data about the melting loss of the graphite per ton of steel against the water consumption during the evaporative cooling. The graphite consumption in the arc furnaces of 10-12 tons' capacity is reduced by 40 %. The recommended water consumption for the evaporative cooling of electrodes for all types of foundry furnaces is 0.1-0.2 m3/h.

In the present work, we studied in detail the thermochemistry, thermal stability, mechanical sensitivity, and detonation performance for 20 nitro-, cyano-, and methyl derivatives of 1,2,5-oxadiazole-2-oxide (furoxan), along with their bis-derivatives. For all species studied, we also determined the reliable values of the gas-phase formation enthalpies using highly accurate multilevel procedures W2-F12 and/or W1-F12 in conjunction with the atomization energy approach and isodesmic reactions with the domain-based local pair natural orbital (DLPNO) modifications of the coupled-cluster techniques. Apart from this, we proposed reliable benchmark values of the formation enthalpies of furoxan and a number of its (azo)bis-derivatives. Additionally, we reported the previously unknown crystal structure of 3-cyano-4-nitrofuroxan. Among the monocyclic compounds, 3-nitro-4-cyclopropyl and dicyano derivatives of furoxan outperformed trinitrotoluene, a benchmark melt-cast explosive, exhibited decent thermal stability (decomposition temperature >200 °C) and insensitivity to mechanical stimuli while having notable volatility and low melting points. In turn, 4,4′-azobis-dicarbamoyl furoxan is proposed as a substitute of pentaerythritol tetranitrate, a benchmark brisant high explosive. Finally, the application prospects of 3,3′-azobis-dinitro furoxan, one of the most powerful energetic materials synthesized up to date, are limited due to the tremendously high mechanical sensitivity of this compound. Overall, the investigated derivatives of furoxan comprise multipurpose green energetic materials, including primary, secondary, melt-cast, low-sensitive explosives, and an energetic liquid.

New composite materials were obtained on the basis of segmental copoly(urethane-imides) and carbon particles of various types: amorphous carbon (carbon black), carbon nanofibers, and graphene. The matrix copoly(urethane-imides) were prepared by known procedures starting from toluylene 2,4-diisocyanate-terminated poly(propylene glycol), pyromellitic dianhydride, and 4,4′-diaminodiphenyl ether (the first matrix) and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride and m -phenylenediamine (the second matrix). The thermal stability and mechanical and electrical properties were determined; the structural features of film composite surface were characterized. It was shown that the composites behave as high-strength elastomers. The elongation at rupture is 100–1000%, and the specific bulk conductivity reaches 1.1 S m −1 . Regarding the mechanical and electrical properties, the composite based on propylene glycol, pyromellitic dianhydride, and 4,4′-diaminodiphenyl ether containing 20 wt. % carbon black was found to be optimal among the investigated film samples as an elastomer planar electrode. Using methyl thiazolyl tetrazolium (MTT) assay, the material was found to be nontoxic to human dermal fibroblasts, which is significant for the intended use of the composite in wearable medical and cosmetic devices.

Chitosan and composite fibers containing chitin nanofibrils have been developed for use in cosmetology. The tensile strength of the chitosan multifilaments is 160.6 ± 19.0 MPa, and of the composite multifilaments containing chitin, nanofibrils are 198.0 ± 18.4 MPa. Chitin nanofibrils introduced into the chitosan solution contribute to the creation of a new spatial arrangement of chitosan chains and their denser packing. The studies carried out by optical, scanning electron, and atomic force microscopy has shown that the serum, consisting of a mixture of lactic acid and sodium lactate, contains extended oriented structures—“liquid filaments”. It has been also shown that a mixture of serum and composite fibers based on chitosan and chitin nanofibrils has mucoadhesive, film-forming properties. The introduction of composite fibers containing chitin nanofibrils into the serum promotes the reinforcing effect of liquid filaments, the lifting effect of the film. The obtained composition can be used in cosmetology as a skin care product.

This work presents research results of the technology development in applying electroconductive wear-resistant coatings using supersonic cold gas-dynamic spraying method.

The article considers stochastic mathematical models for thermolysis kinetics of complex oil-like hydrocarbon systems using mathematical statistics and the theory of random processes. Mathematical modeling shows that the thermolysis process is collective, nonergodic, and nonstationary. The criteria for which hydrocarbon systems obey the first order and Avrami kinetic laws are established. Using the example of thermolysis of high-viscosity Al’shacha oil, it is shown that the kinetics of the release of gaseous products of thermolysis are better described by models of stationary kinetics, and the yield of residues and distillates is better described by models of nonstationary kinetics. The established regularities can be used in modeling thermal and thermocanalytic processes of petrochemistry and oil refining.

A significant part of the cost of released products in the smelting of steel is the cost of graphite electrodes, so reducing their specific consumption is an urgent task. The aim of the work is to study on a computer model and analyze the efficiency of using evaporative cooling to reduce the consumption of graphite electrodes in electric arc furnaces of three-phase alternating and direct current of small capacity. A computer simulation of the thermal state and fame of graphite electrodes for arc furnaces of three-phase and direct current with the capacity of 12 tons was performed. The efficiency of using evaporative cooling of graphite electrodes was revealed. It is established that for arc furnaces operating on direct and three-phase alternating current, the use of electrodes water cooling allows to reduce the consumption of graphite by about one and a half times. It is established that the water supply to the evaporative cooling system is the most rational during 1–2 minutes after the current is turned on. The use of evaporative cooling of graphite electrodes in arc furnaces can be recommended to reduce their consumption on operating and designed small capacity alternating and direct current arc furnaces.

The effect of implantation of argon, oxygen, and nitrogen ions on the physicochemical structure of the surface and the corrosion and electrochemical behavior of chromium-nickel steel 03Cr18Ni11 has been studied. Methods of electrochemical polarization (EP), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were used. Ion implantation of argon, oxygen, and nitrogen leads to an increase in the corrosion resistance of steel 03Cr18Ni11 both in a neutral environment and in the presence of a corrosion activator (chloride anions), while irradiation with argon ions is most effective. It is found that, after implantation of argon ions, a partial etching of the steel surface occurs, i.e., an increase in the true surface. This, in turn, facilitates the onset of the passive state. At the same time, the use of oxygen and nitrogen ions leads to smoothing of the surface. AFM data indicate that the studied steel treated with argon ions exhibits the greatest resistance to local corrosion. The implantation of oxygen and argon ions reduces the overall corrosion to the greatest extent. It is important to note that deep craters and traces of pitting corrosion do not form on the surface of the steel. The XPS data show that after ion implantation, there is a change in the concentration of the elements that make up the steel in the near-surface layers of the material in the depth of the implanted layer compared with the unirradiated sample. It is established that the surface layers of steel are enriched in chromium atoms during ion implantation. This process occurs most intensively when samples are treated with argon ions. In this case, mixed chromium and iron oxides are formed, contributing to the passivation of the steel surface. Also, the process of ion implantation is accompanied by oxidation of the surface of the steel under study. This is confirmed by an increase in the oxygen content in the surface layers. To the greatest extent, this process occurs during the implantation of oxygen ions. After corrosion tests, an increased chromium content is also observed on the surface of steel treated with Ar+ ions, which confirms the formation in this case of stable chromium oxides that remain on the surface during the corrosion of steel. The analysis of the fine structure of the XPS spectra showed that, under the action of argon ions, the oxygen of surface oxides is redistributed in favor of chromium atoms and the formation of stable mixed iron and chromium oxides of the spinel type, including Fe2+, Fe3+, Cr3+, and Cr6+ compounds. It is important to note that, although chromium oxides are also formed during oxygen implantation and in the same quantities as during argon implantation, the protective properties of the resulting compounds are noticeably lower. Therefore, not only the chemical composition but also the structure of the resulting layers are important. It can be assumed that the high kinetic energy of heavy argon ions affects both the formation of developed surface relief and the formation of stable mixed iron and chromium oxides of the spinel type.

The article considers the synthesis of the optimal voltage regulator for the electric power supply system of the electromechanical complex of the submersible apparatus with the power transmission through the cable line. Based on the reduced linearized model of the multidimensional nonlinear control object the regulator with adjustable parameters is synthesized, providing the DC voltage stabilization at the power supply system load. The variant of building proportional feedback on output state variables is used for the regulator in the system with parametric and external disturbances. Due to the technical impossibility of measuring the voltage on the load, a combined optimal regulator with negative feedback is organized, which makes it possible to stabilize the voltage at the payload within the specified limits when receiving data from the output filter of voltage source inverter.