In this work, we present a mathematical model of the capture probability of rod-shaped stepped blanks in mechanical disk hopper feeding devices with an inclined disk and tangential pockets. The model must take into account the influence of the design and kinematic parameters of the device on its performance, as well as those of the workpieces. The object of the research was a mechanical disk hopper feeding device having an inclined rotating disk and pockets tangentially located along its periphery, whose active orientation of the mentioned blanks is implemented by overturning them on special supports placed under the rotating disk. The tipping action is carried out under the action of gravity. For the construction of mathematical models, methods based on probability theory, analytical spatial geometry, theoretical mechanics, and general physical laws were used. The methodology for constructing a mathematical model of the probability of capture of rod-shaped step blanks of bodies of revolution in the studied devices with an inclined disk and tangential pockets is described. Algorithms for determining each coefficient of the developed model are presented. The developed model is a product of the probability of finding the rod blanks in a position favorable for their gripping in the direction of the tangentially located pocket, the probable absence of encumbrance during gripping of the blank due to its interlocking with other blanks, and the probable absence of encumbrance as a result of the peripheral speed of the gripping organs of the device. Thus, the developed mathematical models for calculating the capture probability of rod-shaped step blanks of rotational parts can be used at early design stages to estimate with high accuracy the actual productivity of mechanical disk hopper feeding devices with an inclined rotating disk and pockets tangentially located along their periphery.

The study aims to examine the effect of printing direction in the FDM-technology (Fused Deposition Modeling) on the mechanical properties of products. Laboratory tests of type B specimens were conducted in accordance with GOST 11262-2017 using a Shimadzu AGS-10kNXD tensile tester with a loading rate of 2 mm/ min. The specimens were made of ABS (acrylonitrile butadiene styrene) thermoplastic. Under otherwise equal conditions, the printing direction of the specimens was changed. As a parameter representing this factor, the study adopted the inclination angle of printing filaments in the infill of the specimen α to its longitudinal axis. The test results of FDM specimens showed that at different inclination angles α, a consistent variation in experimental data is observed. The specimen comprises two components: the first is the infill of the specimen; the second is the shell of the specimen. An analysis (based on 3D models of specimens in the slicer) of the filament path in the layers and the structure of each layer revealed that the mechanical properties of test specimens are affected by both components. In the shell of the specimen, this effect is produced by its upper and lower edges. A detailed analysis of models representing each layer of the specimens helped explain the variation in the response of specimens with different α to the action of the same tensile load in terms of the magnitude of the failure load. In particular, the features of the infill structure are such that its effect on the magnitude of failure load is limited by an increase in the angle α from 0 to 45°. A further increase in α leads to a mirror repeat pattern. In this case, the effect of the shell on the magnitude of the failure load corresponds to the range of 0°≤α≤90°. Thus, the conducted research provided insights that can help lay the theoretical groundwork for a procedure for producing FDM parts with specified mechanical properties.

The aim was to develop an approach for evaluation and suppression of undesirable self-excited vibrations during the machining process. The suppression efficiency of self-excited vibrations was evaluated by the amount of their internal energy created by the radial cutting force. This force was assumed to be proportional to the difference in the area of the cut metal layer at the tool exit from the workpiece and penetration in each vibration. The research object was a low-rigidity shaft with a diameter of 48 mm, cantilevered with an outreach of 150 mm. Changes in the energy of self-excited vibrations were evaluated using a software package in the SciLab language. The shaft was machined with a cutting tool at a spindle speed of 208 rpm with a feed of 0.122 mm/rev and a cutting depth of 0.8 mm. The modulation frequency of the cutting speed per workpiece revolution was assumed to be 0.5. The difference in the area of the cut metal layer at the tool exit from the workpiece and penetration was calculated sequentially when varying the depth of cutting speed modulation in the range from 0 to 30% with an interval of 1%. The results obtained were used to draw a plot of changes in the relative difference of the cut layer areas (proportional to the internal energy of self-excited vibrations), similar to a cosine curve with a decreasing magnitude. An increase in the depth of cutting speed modulation was established to sharply reduce the internal energy of self-excited vibrations, periodically pulsing around zero values. The local minima of the plot corresponded to the condition of suppression of self-excited vibrations. The fourth local minimum corresponding to the depth of cutting speed modulation equal to 13.5% was selected as a parameter for practical use. At this depth, cutting speed modulation ensured a more than 10-fold decrease in the vibration range and a 12-fold decrease in the vibration amplitude, in comparison with similar parameters at the constant cutting speed. The results obtained confirm the efficiency of the proposed method for evaluating changes in the energy of self-excited vibrations during the machining process. 

This study aims to develop a novel structure of an N-channel adaptive median signal filter with dynamic input exclusion. The proposed design is intended for highly reliable, fault-tolerant modular redundant power supply systems for spacecraft. To investigate the functionality of the proposed N-channel filter, we developed a simulation model for a 7-channel median signal filter using MATLAB Simulink. A model-based design approach was applied to validate the performance of the proposed element using the Altera Cyclone IV EP4CE115F29C7 field-programmable gate array (FPGA). The verification process involved the use of automatic code generation tools within MATLAB Simulink for the FPGA implementation. A novel structure of the N-channel median signal filter was proposed, featuring a dynamic exclusion of unused inputs from the median calculation. This guarantees that only valid input signals from operational modules within the power supply system be included in the median calculation. The simulation results demonstrated that, in contrast to existing counterparts, the proposed filter is capable of reliably outputting the median signal as the number of active input signals decreases from N to 1. The implementation of the filter as an intellectual property (IP) block based on the Altera Cyclone IV EP4CE115F29C7 FPGA demonstrated efficient resource utilisation, occupying 541 logic cells, while fully adhering to the specified operational logic. The proposed structure of the adaptive median signal filter can be employed in highly reliable, fault-tolerant spacecraft redundant power supply systems, maintaining functionality even in the event of multiple module failures, down to the last operational module. The developed solution meets the stringent fault-tolerance requirements of spacecraft power systems.

We aim to determine the applicability of standard microprocessor units of relay protection and automatics for obtaining a digital signal of currents for their subsequent mathematical processing with the purpose of identifying internal faults of electrical equipment. Mathematical processing of experimental data (time series) based on regression analysis approximation in orthogonal basis was carried out. To that end, the weight coefficients of basis functions obtained by the least squares method were compared in terms of multidimensional space vectors, corresponding to the coordinates of this space. The investigated signal was a data set obtained by field experiments conducted with an induction motor, which assumed the possibility of creating artificial internal damage. Experimental data were obtained using two devices with different sampling rates and quantization levels. The first set of data was obtained using a 12-bit PCI board of analog-to-digital converter for installation in a National Instruments 6024E PC at a sampling rate of 10 kHz. The second set of data was obtained using a standard block of microprocessor relay protection and automation at a sampling rate of 2.4 kHz. Indicators for the presence of internal damage to the rotor circuit of an induction motor, which reduces the motor energy characteristics without affecting its operation significantly, were determined. The indicators of the damaged and undamaged state differed by a factor of five. The proposed method for selecting the diagnostic sign of internal damage of electrical equipment of electrical installations detects a 3% deviation in their parameters from the normal state, ignoring the presence of electrical/mechanical load. The diagnostic sign was established to behave similarly in the presence of internal damage, in both sets of signals under study. Thus, the possibility of obtaining a digital signal of acceptable accuracy from standard relay protection units for ensuring reliable identification of internal faults of electrical equipment of electrical installations is confirmed.

The objective is to analyze the sustainability and efficiency of Pakistan’s telecommunication sector by developing a framework for base transceiver stations integrating renewable energy and charging stations. Various renewable energy sources such as solar, wind, biomass and hydropower were considered as the object of research. The following methodological steps were implemented in this work: site analysis; determination of optimal sizing of plants, energy storage systems and electric vehicle charging stations; cost-benefit analysis methods; greenhouse gas emissions estimation; and system design methods for integrating selected renewable energy sources and energy storage solutions, taking into account the operational requirements of the base transceiver stations. It is found that switching to hybrid renewable energy systems can significantly reduce dependence on diesel generators. It is shown that operating costs can be reduced by more than 80% compared to conventional diesel-fueled systems. Also, the introduction of hybrid renewable energy sources can lead to significant reductions in CO₂ emissions. The integration of battery storage systems has been shown to improve the reliability of energy supply by ensuring uninterrupted operation during periods of high demand and blackouts. The proposed structure scheme for base transceiver stations is designed to accommodate future growth in the share of electric vehicles and technological advancements in renewable energy and electric vehicle charging. By prioritizing the integration of renewable technologies along with charging station infrastructure, telecom service providers in Pakistan can reduce their carbon footprint and operational costs. This approach not only addresses the unpredictability of the electricity grid, especially in rural areas, but also positions the telecoms sector as an active participant in global efforts to combat climate change.

A methodology for selecting the composition of generating equipment included in a solar-diesel complex to optimize its operating mode by minimizing the specific fuel consumption of diesel generator units is described. Software developed according to the principle of real-time integer nonlinear programming is used to calculate the minimum operating costs during the operation of the complex. Various restrictions on the operating modes of electrical equipment were taken into account. For a diesel power plant having a minimum capacity not less than 30% of the nominal capacity, the distribution of capacity between diesel generator units takes into account individual consumption characteristics. For an electrical energy storage system whose permissible change in capacity varies from 50 to 100%, the charge/discharge rate is limited to “1C”. For the solar power plant, the change in inverter efficiency was taken into account depending on its load as predicted for a 24-hour period. The research used a model to simulate full-scale equipment of a solar-diesel complex comprising two diesel generator units of 12 and 30 kW, a solar power plant simulator having a capacity of 6.6 kW, an energy storage system, and an active load simulator with a capacity of up to 50 kW. An algorithmic description of the operational principles of an automated control system for ensuring the energy efficiency of solar-diesel complexes in operation is provided. The developed SCADA system is suitable for modeling the operating modes of a solar-diesel complex under conditions close to actual. Depending on the operating conditions of the solar-diesel complex and the equipment parameters (the number of diesel generator units and their nominal capacities, the capacity and power of the electrical energy storage system, as well as the installed capacity of the grid solar power plant), operating mode modeling accuracy can be increased by as much as 30%. Thus, the obtained results of modeling the operating mode of a solar-diesel complex demonstrate the possibility of significantly refining the estimates of the operating parameters of such energy facilities by taking into account the actual energy characteristics of diesel generator units.

The work set out to determine the conditions for the onset of melting and complete melting of the sample (in a stationary setting), as well as to study the dynamic modes of propagation of the melting front at different thermophysical parameters (heating and cooling intensity, change in material properties during melting, geometric characteristics of the sample). A numerical model of the heat conduction process in a heterogeneous medium is used as a research tool. For the numerical solution, non-stationary one-dimensional heat transfer equations are reduced to a differential form, taking the phase transition into account using an enthalpy scheme; in order to improve the stability of the numerical method, the melting and heat conduction processes are separated. The parameters are varied to determine the dependence of the characteristic times of the onset of melting and complete melting of the sample on the process conditions. The trajectories for reaching stationary states, whose solutions were obtained in the first part of the article, were calculated using a numerical model. The melting rate is shown to depend significantly on the ratio of the thermal diffusivity coefficients of the phases, as well as the intensity of heat supply and the thermal effect of melting. Critical values of dimensionless parameters reflecting the relative intensity of heat exchange and heat release obtained for stationary conditions are associated with the effective thermal resistances of the heat-insulating layer and heat transfer to the environment. The model can be used to calculate the dynamics of melting at low enthalpies of fusion (large values of the Stefan number), when the quasi-stationary approximation becomes inapplicable (i.e., when the characteristic time of movement of the melting front is comparable to or less than the thermal relaxation time). The calculations can be used to assess the thermomechanical stability of materials when heated by an internal local energy source (for example, Joule heat). The developed numerical model can be used to investigate melting processes under a wide range of conditions.

The article aims to identify possible directions for developing heat technology systems in Irkutsk Oblast, taking into account the integration of resources of the Irkutsk coal basin with high sulfur content. The study applied a systems analysis of trends in the development of high-capacity coal-fired power boilers, considering the possibility of reducing harmful emissions (NO_x, CO, SO_x) primarily through rational design solutions and the use of coal-water slurry. It is shown that swirl processes realized in fuel combustion schemes that are applied at the TPPs of the Irkutsk power system help to improve the ecological and economic efficiency of heat technology systems, primarily by reducing the combustion temperature and increasing the residence time in the furnace. Experience is available in applying the low-temperature swirl combustion scheme at Ust-Ilimskaya TPP (boiler 6) and a circular furnace at Novo-Irkutskaya TPP (boiler No. 8). It is proposed to redesign the existing power boilers according to the scheme of low-temperature swirl combustion (i.e., the maximum temperature in the furnace is no higher than 1000–1100℃), with the subsequent use of partially demineralized and desulphurized coal-water slurry obtained at the place of extraction and transported by slurry pipeline. Fuel can be burned in a two-stage furnace: it is ignited in its lower part where the low-temperature fluidized bed of inert material is located; then, it is burned completely in the upper part of the furnace at a temperature of 1000–1200℃. Thus, in the context of the growing use of highsulfur coal, the evolution of technological systems in the thermal power industry of Irkutsk Oblast places its cleaning within the scope of activities of power companies. The main method of reducing the emissions of sulfur compounds consists in the low-temperature combustion of fuel using desulfurized coal water slurry.

The paper is aimed at assessing the impact of integrating pumped-storage power stations on the steady-state operation of the Mongolian central power system, as well as its operational reliability, in the context of growing power consumption and the increasing share of renewable energy sources. The study was conducted employing the machine learning method (specifically, ensemble models and statistical ranking models) to build a model of the daily load curve, as well as the power generation of wind and solar power plants. The computations were performed using the Pandapower software, which provided a means to take into account the actual technical characteristics of power grid equipment, analyze normal conditions, and optimize the operating conditions. The modeling results indicate that the integration of four pumped-storage power stations with a total capacity of 250 MW significantly smoothes out the irregularity of the daily output curve of thermal power plants. The irregularity factor indicating the minimum-to-maximum daily load ratio increased from 0.8 to 0.96. An analysis of operating conditions did not reveal overloading of backbone transmission lines or unacceptable node voltage deviation. The total power losses in the central energy system of Mongolia were shown to increase insignificantly with the integration of pumped-storage power stations amounting to 5.54% (5.36% without taking them into account). This fact confirms that the redistribution of significant amounts of power associated with the growing share of renewable energy sources in the Mongolian power system requires a thorough analysis of the technical status of equipment and an increase in transmission line capacity. Thus, the integration of pumped-storage power stations by 2030 will make the control of the Mongolian central power system more flexible. This will increase domestic power generation, reduce ohmic losses in the grid, decrease the volume of power imports from Russia, lower the risks of outages in the central region of Mongolia, and effectively solve the power shortage problem.

The purpose of the study is to develop an approach based on online measurements and the theory of Ritta–Wu characteristic sets from the field of algebraic geometry and computer algebra to solve one of the main tasks of wind energy studies such “abandon wind” caused by wind gusts. The Ritt-Wu theory is effective in studying polynomial systems and their solutions. To obtain an equivalent double-fed induction generator, the following basic steps are used: build the characteristic sets by modeling a wind farm; establish the polynomial rings based on the real-time aggregation data; derive analytical expressions of a model of an equivalent double-fed induction generator; validate of the developed approach to modeling an double-fed induction generator using mathematical modeling in the PSCAD software environment and analysis of a combination of model data and telemetry data. A general solution procedure is used, which can be applied to obtain the analytical expressions of the inductance and impedance of an equivalent wind farm. The expediency and effectiveness of the developed approach is illustrated by the example of a real wind farm with a capacity of 50 MW with 34 double-fed induction generators. The simulation results demonstrate that the obtained parameters of an equivalent double-fed induction generator can accurately follow wind speed fluctuations with a lower error. Thus, this study presents a new effective method for estimating the exact equivalent parameters of a wind farm during wind gusts. The developed method is suitable for obtaining the analytical solutions of equivalent wind farm parameters in real time. Validation of the accuracy and speed of the author’s method has been carried out. Moreover, this study can be applied to any wind farms equipped with double-fed induction generators.

The paper aims to find physicochemical patterns in the separation of liquid smelting products with the melt blasted by side and basal tuyeres installed in the area of a “Pobeda” smelting unit intended for charging and melting copper-containing charge. The study adopted the physical simulation method with the use of transparent media (vegetable oil and colored water) and a glass cuvette. The dynamic similarity between the sample and model was ensured by the constancy of the Archimedes number Ar. The initial ratio between the levels of less and more dense fluids was chosen according to the Weber number We. The Archimedes numbers per one side and one basal tuyere amounted to 5;3 and 12;6 (Variants 1 and 2, respectively). The completeness of phase separation was determined visually through filming the liquid-liquid interface emergence and the settlement front advance, as well as quantitatively via the sampling method with subsequent separation of water and oil through centrifugation. According to the condition Ar = idem, the blasting parameters were determined for the cold model with the installation of six basal and three side tuyeres, which were assumed to be located in the sparging zone of the melt. The phase separation patterns are shown to depend on the duration and intensity of the blast. Under Variant 1, blasting is characterized by the formation of a constant phase immiscibility profile at the end of the experiment, which occurs in a limited area of the settlement zone that is far from the sparging zone. At higher Archimedes numbers (Variant 2), the melt pool acquires a homogeneous structure in a shorter time, and no immiscibility boundaries are observed along the entire length of the melt. Thus, a cold modeling technique was developed to study the patterns of phase separation in the presence of a separate sparging zone in the melt pool. This provides a means to obtain objective parameters for the location of tuyeres and blasting conditions, thus ensuring a reduction in the mechanical losses of copper with slag at a given smelting capacity in the “Pobeda” unit.

The paper aims to study the possibility of using carbide-forming oxides as catalysts for the graphitization of objects used in metallurgy. Published data on the role of catalysts (carbide-forming metals and their oxides) for the graphitization of carbon materials was analyzed. These graphitization catalysts are shown to be able to significantly reduce the graphitization temperature. The physicochemical properties characteristic of carbon materials graphitized without the use of catalysts are preserved. It was revealed that in the case of bulk materials, the graphitization temperature can be reduced to 1200–1500℃ with the use of catalysts (as opposed to 2000ºС and above). The mechanism of catalytic graphitization involving two reactions is described: interaction between a metal (or its oxide) and carbon with the formation of carbide; subsequent formation of pure metal and carbide-like graphite with increasing temperature. The resulting graphite phase constitutes the crystallization nucleus. The main problem associated with the use of catalysts in the production of graphitized objects was identified—the removal of reaction products, including metals. It is shown that additional catalyst charging can be performed at the stage of mixing and forming, which results in the removal of a part of the reaction products at the stage of baking. The mechanism of removing reaction products is expected to be comparable to ash removal from the piece to be graphitized. It was proven effective for objects to contain carbide-forming oxides, even in insignificant amounts (up to 5 wt%). Due to this, as well as given the possibility of catalyst selection, the negative effect of excessive oxide content in the charge can be reduced depending on further operating conditions. Thus, the use of catalysts for the graphitization of electrodes used in metallurgy is a promising way to reduce the process temperature. However, it is required to select the optimal oxide content and adjust the conditions of electrothermal processes in order to adapt the technology for large-sized products.

The paper aims to develop and test a design procedure for setting an electrolytic cell for electrical preheating without current interruption in a series of electrolysis units using aluminum fusible links. For the analysis of a complex electrical circuit, the circuit conversion technique, a direct application of Kirchhoff’s circuit laws, was used. The obtained patterns were identified and determined using graphical and analytical methods. Mathematical modeling was performed by means of approved programs. A design procedure was developed for setting an electrolytic cell for electrical preheating without current interruption in the series of electrolysis units. The computations (mathematical modeling) were performed for two startup variants: without current load interruption in the series of electrolysis units and with the lowering of current load in the series (to 250 kA). Pilot startup tests of two high-amperage electrolytic cells were performed without current interruption in the series of electrolysis units, i.e., at an operating current of 330 kA, as well as the startup of one electrolytic cell with the current load lowered to 250 kA. The study results indicate that the developed method allows a high-amperage electrolytic cell to be set for electrical preheating with the use of fusible links without interrupting the current load or with its lowering in the series of electrolysis units. Successful pilot tests of three high-amperage electrolytic cells operating at a current strength of 330 kA provide a means to extrapolate this preheating method to other high-amperage electrolytic cells operating at current strengths of 400 and 550 kA.

In this work, we aim to obtain a high-alloy product of the Al-Fe-Si-Mn system from scrap and metallized waste, as well as to determine the optimal technological mode of melting for increasing the yield of finished products during complex processing of the melt. The study involved the following methods: X-ray fluorescence (XRF), spectral, X-ray structural, and differential–thermal analysis. Chromatographic and mass-spectrometric analysis of gases released during the remelting of aluminum waste was carried out to determine irrecoverable losses. Analysis data indicate that volatile compounds account for 13–15% of the total mass of aluminum lost during heating and melting of the charge. As a result of the test melts carried out with various aluminum wastes, the obtained castings were shown to correspond to some grades of high-alloy aluminum alloys (for example, 3xxx and 8xxx) mainly belonging to the Al-Fe-Si-Mn system. The metal losses during loading of the charge into the melt at various layer heights in the furnace were determined. Its rational value was established based on the best results, representing 30–40% of the mass of the loaded charge. The implementation of a comprehensive technology for refining and step-by-step processing of the melt produced samples with a yield of 86 to 88%. According to the conducted analysis of the chemical composition, the castings contain a minimal quantity of non-metallic inclusions (SiO₂, CaO, Al₂O₃, TiO₂) with an acceptable hydrogen content (0.08–1.0 cm³/100 g). A study of the structural features characterized all samples as having a complex dendritic structure with the presence of intermetallic phases of the AlFe(Si)Mn type, which have a characteristic appearance known as "Chinese script" and reach sizes from 70 to 120 µm. The structure of the castings, which is generally characterized by its homogeneity and the uniform distribution of agglomerates of nanosized intermetallic compounds in the aluminum matrix, is suitable for obtaining cast blanks and rolled products for a wide range of purposes.