Kalashnikov Izhevsk State Technical University

The study analyzes the properties of fluoroanhydrite composition, reinforced with chrysotile-asbestos fiber of grade 7-350 in dispersed manner. The advantage of dispersed reinforcement is high specific surface area of asbestos fibers, which are distributed in inter-pore partitions of composition, excluding pore percolation during the swelling of the binding matrix with a gas generator based on perhydrol. The paper studied microstructure of reinforced composition which showed not only compatibility of asbestos fibers with binding matrix but also formation of secondary new formations on fiber surfaces that stabilize the structure and properties of the composition. The energy-dispersive analysis of the new formations on fiber surfaces showed crystallization of calcium sulfate dihydrate, which is formed during hydration of fluoroanhydrite. The thermal conductivity of the composition was achieved depending on the average density, corresponding to (0.18 – 0.26) W/m·°C. The use of fluorhydrite as a binder is advisable not only because of its physical and mechanical properties, but also in terms of recycling this technogenic product.

This work investigates the application of data driven techniques for classification of misalignment severity using vibration measurements acquired from multiple sensor locations. Experiments were conducted under four operating conditions representing healthy operation and three levels of shaft misalignment at several motor speeds and loads. A set of time-domain and frequency-domain features was extracted and used to train Random Forest classifier. Separate models were developed for two individual sensors as well as for a combined multi-sensor feature set. While overall accuracies were comparable (0.879-0.895), cross-condition validation using Leave-Condition-Out (LCO) revealed that the sensors exhibit different sensitivities to operational changes. Analysis of prediction disagreement showed that 12% of signal segments were correctly identified by only one of the sensors, particularly at the lowest operating speed (20 Hz). This suggests that multi-sensor fusion enhances reliability in scenarios where individual sensor signals are weak. To improve interpretability, SHAP-based explanation techniques were applied to the fusion model. The analysis showed that several physically meaningful features - such as spectral bandwidth, RMS value, vibration range, and form factor - play a dominant role in the classification process and exhibit clear relationships with fault severity. The results demonstrate that while sensor fusion provides marginal gains in average accuracy, it effectively reduces diagnostic “blind spots”, offering a more robust framework for automated misalignment evaluation within the studied operational range.

The article considers the impact of suspended matter concentration on the efficiency of oxygen transfer from air to water under different air flow rates. The authors present experimental data on the dynamics of oxygen saturation obtained in laboratory conditions under different air flow rates (1, 3, 5 L/min) and concentrations of suspended matter, including ceramic sand (0.25, 0.5, and 1 g/L). The results signify that higher suspended matter concentrations can reduce oxygen saturation because of the increased mass transfer resistance on the gas–liquid interface due to the film formation and particle adsorption. Simultaneously, increasing the air flow rate (from 1 to 5 L/min) can partially compensate for the negative effects caused by the suspended matter and reduce the oxygen saturation time. The calculated α и β coefficients confirm that the efficiency of mass exchange is especially sensitive to the suspended matter concentration and can be adjusted by air feed, while oxygen solubility (the β factor) remains virtually the same.

Two mutually exclusive properties of building materials, such as low thermal conductivity and high strength, are com-bined in thermal insulation materials designed for enclosing structures. Currently, much attention is being paid to the ma-terials with industrial waste utilization and low production costs. The aim of the study was to develop a heat-insulating composite material based on porous fluoroanhydrite binder with dispersed reinforcement modified with a hydroactive poly-urethane composition with improved vapor and gas permeability. This scientific study provides the development of a ther-mal insulation material with the simultaneous utilization of two industrial wastes - fluoroanhydrite (waste from the pro-duction of hydrofluoric acid and waste from the production of ultrathin basalt fiber). It is noted that the combination of these two wastes during the porization of the fluoroanhydrite composition with hydrogen peroxide makes it possible to cre-ate a material with a thermal conductivity of 0.114 W/m·°C and average density of 550 kg/m3. The modification of the po-rous composition with hydroactive two-component polyurethane provides the material with increased porosity and water resistance. Vapor and gas permeability is ensured, the pore structure is stabilized due to the dispersed reinforcement of the pore walls with basalt fiber production waste, and the use of aluminum powder for pores formation is eliminated. The developed composition makes it possible to reduce the cost of producing, while simultaneously solving the problems of recy-cling fluoroanhydrite and basalt fiber production waste.

In this article, a method for identifying parameters of a brushless direct current motor based on minimum stable acceleration energy is presented. By “minimum stable consumed acceleration energy,” we mean the energy required to maintain stable rotation of the motor rotor without loss of synchronism. A motor control program based on a digital signal processor has been developed. The novelty lies in the development of a new method for identifying motor parameters in the form of the minimum stable acceleration energy of said motor, obtained experimentally, which can be acquired without direct parameter measurements, which is complex and expensive. Experimental results confirm that changes in motor parameters due to their degradation lead to an increase in the minimum energy consumption, which is a sign of defects. A linear minimally stable acceleration characteristic of the motor is obtained in the form of a dependence of the voltage amplitude on the speed of the rotor The method is primarily intended for operational diagnostics and degradation monitoring rather than primary absolute parameter extraction.