Introduction. The increased intensity of noise and vibration of railway traffic may become not only an urgent problem in the field of occupational safety, but also a serious environmental problem in the near future due to the constant need to increase the weight of freight trains, the speed of passenger trains and the capacity of railway lines. Recently, a lot has been done to minimize the negative effects of noise and vibration in railway transport. However, the problem of exceeding the indicators of vibration noise factors remains relevant. Reducing the harmful effects helps to improve the working conditions of train crew employees and improve the comfortable conditions of transport passengers. As a rule, the main focus of the analysis is on the external impact of vibroacoustic factors on residential areas and less attention is paid to the impact on rolling stock. However, these studies do not provide a complete picture of how noise and vibration actually affect the train in motion. The aim of the study was to obtain the result of an analysis of the impact of vibroacoustic factors on train crew workers and to propose a method of comprehensive protection based on the use of vibration damping materials.Materials and Methods. In the course of the work, regulatory documents were studied, a comprehensive analysis of relevant information on this topic was carried out, and methods for calculating vibration and vibration acceleration were used. The values of the sound pressure levels were obtained using a SPM-101 sound level meter. The object of the study was a carriage of the "reserved seat" type in the process of movement. As part of the research plan, sound pressure was measured at selected sites and a class of working conditions was determined.Results. The result of the analysis of the impact of vibroacoustic factors on train crew workers indicated the need to strengthen comprehensive measures to protect them. The obtained calculation of the vibration force became the basis of the method proposed by the authors to minimize the harmful effects of vibroacoustic factors, which was based on the use of vibration and sound insulation materials suitable for the necessary acoustic parameters in the construction of the car. In particular, it was proposed to cover the floor of the car with dense rubber and the ceiling of the car with an inorganic fiber material for sound insulation. The work also provides an economic assessment of the effectiveness of measures to minimize harmful vibration noise effects.Discussion and Conclusion. The proposed methods for minimizing noise and vibration impacts can help reduce the level of sound pressure and vibration indicators to standard values, which will significantly reduce the negative impact of vibroacoustic factors on train crew workers and railway passengers. The considered complex for minimizing vibration and noise includes a set of methods in which affordable materials based on recycled substances have found application.

Introduction. The issues of ensuring optimal fuel consumption modes are the subject of constant research in the field of vehicle operation. Works in the field of reducing fuel consumption in most cases are devoted to the study of the design of power units, transmission or aerodynamic features of the body of cars. At the same time, the issues of determining the optimal laws of control of unsteady movement from the point of view of the synthesis of algorithms for controlling the movement of a car have not been considered. To optimize the transmission ratio of cars with unsteady movement, the authors of the work carried out analytical calculations to simplify the synthesis of motion control algorithms, which in turn allowed reducing fuel consumption. The aim of the work was to determine the optimal transmission ratio, which allowed solving the problem of synthesizing vehicle control to reduce fuel consumption.Materials and Methods. The synthesis of algorithms for controlling the movement of a car considered in the work was based on the application of the needle variation of L.S. Pontryagin to invariant features of the real movement. An analytical method was used to estimate energy efficiency of vehicle performance, which was based on determination of optimal transmission ratio of motor vehicles taking into account minimum fuel consumption. The presented method took into account the amount of torque transmitted from the engine crankshaft to the transmission elements, which, depending on the engine power, was realized in the form of traction force on the wheels of the car.Results. The law of optimal change in the transmission gear ratio during acceleration of the car in a minimum time was built. The problem of determining the optimal transmission ratio of the vehicle in the case of driving the vehicle at a constant speed and constant fuel supply and in the case of accelerating the vehicle to a given speed at a constant fuel supply, when the condition ε = const was met, was solved. The result of the considered case of applying the optimal law of change in the transmission gear ratio was the minimization of fuel consumption under restrictions on acceleration (traction force) and speed of the car.Discussion and Conclusion. The use by the authors of the analytical method for determining the transmission ratio of a car, as well as the use of this method in practical calculations for a car with given characteristics, showed the possibility of solving the problem of synthesizing vehicle control using a mathematical apparatus. This was confirmed by the built graphical dependence based on the results of the calculations. The considered cases of movement made it possible to determine the analytical dependencies of the optimal transmission ratio and the speed of the car. The initial data obtained by analytical relationships are applicable for cars with a mixed control mode.

Introduction. It makes practical sense to change the properties of steels with a bainite structure, as with bainite transformation under the influence of a magnetic field, it is possible to improve the ductility of the steel while maintaining or even increasing its strength. Scientific research in this area has focused on the influence of the magnetic field on thermodynamics and on the change in the phase transformation scenario. However, there is no detailed description in open sources of the effect of a magnetic field on the structure and properties of the products of intermediate bainite transformation. The aim of the work is to study the peculiarities of the influence of an external magnetic field on the scenario and kinetics of phase transformation of steel.Materials and Methods. The study was conducted using samples made of 65G steel. Their chemical composition was monitored using a Magellan Q8 optical emission spectrometer. Heat treatment (resistive heating) was carried out in an IMASH 20–75 installation for high-temperature research. The heating temperature was approximately 1000 degrees 1000°C, and the holding time was 10 minutes. The sample was cooled down using water-cooled electrical contacts. An external magnetic field with a strength of 400 kA/m and 800 kA/m was created by an electromagnet integrated into the vacuum chamber of the installation.Results. The experiments confirmed the potential for altering the transformation pathway from pearlite into bainite in the presence of an external magnetic field of up to 1 MA/m. Images of the microstructure and surface relief of samples after cooling in a magnetic field were obtained. Kinetic changes and dependencies of the volumetric transformation rates on the duration of isothermal exposure were analyzed. It has been found that exposure to a constant magnetic field of 1.6 MA/m increased the volumetric transformation rate by 1.808 times (for 65G steel) and by 1.687 times (for 45H steel).Discussion and Conclusion. The results of observations of changes in the surface relief during cooling in the absence of a magnetic field, and in magnetic fields of various strengths, were recorded. This has allowed us to draw the conclusion that the external magnetic field stimulates the bainitic transformation instead of the original pearlitic one. Microstructural changes can be explained by the influence of the magnetic field on the initial phase magnetic state.

Introduction. Sulfur is found in the organic and mineral parts of all types of solid fuels, and its concentration determines the extent of the hazardous characteristics of mine seams. Therefore, research on the determination of sulfur content in fossil fuels has not lost its relevance. The total sulfur content and its varieties has been studied in most cases in terms of the efficiency of fuel processing processes, the quality and environmental safety of coal products. Less attention was paid to the hazardous properties of mine seams, forecasting and developing preventive measures for endogenous fires in coal mines. This work aims to develop an engineering method to calculate the elemental sulfur content in the mineral mass of coal to predict the hazardous properties of mine seams.Materials and Methods. According to the results of the correlation analysis, we established how the sulfur content in the combustible part of the fuel depended on the total sulfur. We analyzed data on coals from almost all mine seams of the Donetsk and Lviv-Volyn coal basins. We presented the ash ratios for the formation and basin samples, as well as the information about the total sulfur and sulfur content in the combustible part. This allowed us to estimate the sulfur content in mineral impurities by calculation. The initial data for developing the method were taken from reference and regulatory documents.Results. Seven sets were considered, which included from 149 to 1827 mine seams. For each, reference and calculation data were summarized:- sulfur content — total (Std) and in the combustible part of the fuel (Sг);- conditional points for adjusting the indicators to avoid obtaining negative average values;- empirical equations that describe the calculated and corrected dependencies based on the ratio of Std and Sг;- correlation of these indicators;- ranges of change in ash yield.All this information was presented for clean and raw coals, for ash yields of more and less than 10%. In one case, satisfactory results were noted for determining the calculated sulfur content in a conditionally non-combustible mass. This was a set of 149 mine layers. For 13 of them, the difference in indicators (Std – Sг) was greater than or equal to zero. For 136 — less than zero. For 81, the sulfur content in the conditionally non-combustible part of the fuel Sн was less than zero. At the same time, there was a sufficient level of correlation (0.79) and a limited range of changes in ash yield (2.4–10). The empirical equation corresponding to this set was recommended for predicting the hazardous properties of mine seams with an ash yield of less than 10%.Discussion and Conclusion. The results of this study can be used to improve regulations for the safe conduct of mining activities, taking into account sulfur content in organic matter and in mineral impurities of fossil coal.

Introduction. Harmful components of ore dust, formed during the unloading of products in the preparation of iron ore concentrate (PPIOC) at the mixing stage, cause damage to both workers and equipment. To address this issue, liquid aerosol spraying using nozzles with large diameters (>20 μm) is used. However, this method proves ineffective in capturing fine-dust particles. Therefore, enhancing the efficiency of the dust deposition method through PPIOC dust spraying becomes a pressing challenge. The aim of this study is to investigate the impact of the Dry Fog technology, generating liquid droplets up to 20 μm in size, during the unloading stage of PPIOC at a mining and metallurgical enterprise in the precipitation of suspended fine-dust particles. The primary goal of this research was to assess the effectiveness and potential advantages of applying the Dry Fog technology for dust spraying with subsequent precipitation, as this technology has not been previously applied to PPIOC dust.Materials and Methods. The experiment on the PPIOC dust deposition was conducted in a specially designed laboratory setup. Through physical modeling in the laboratory setup, parameters of the precipitation process were obtained. Subsequently, the results were analyzed to understand the dependence of dust precipitation over time, taking into account the influence of the Dry Fog technology. An experiment program was developed for physical modeling. According to the devised program, dust was uniformly loaded into the interior of the laboratory setup (from the top), distributed in the air stream throughout the volume of the setup by a fan, and an instrument located at the bottom recorded changes in concentration over time. Experiments on dust precipitation were then conducted using liquid spraying (filtered water as the liquid) introduced into the setup through nozzles generating droplets with sizes of 10 and 15 μm, concurrently with the loading of dust into the laboratory setup. The effectiveness of the Dry Fog technology in the deposition of PPIOC dust was determined visually and further analyzed based on a comparison of graphs. The dynamics of changes in the average dust concentrations depending on time was studied both during precipitation without spraying and using the Dry Fog technology. During the experiment, the characteristics of the microclimate inside the laboratory setup (humidity, temperature and air velocity) and the parameters of two nozzles — their operating pressure and the supplied liquid spraying time — were recorded.Results. The comparison of the results showed a reduction in the dust precipitation time by 40 % and 75 % when using nozzles with sizes of 10 μm and 15 μm, respectively.Discussion and Conclusion. The experiment results confirm the effectiveness of the Dry Fog technology for PPIOC dust precipitation during unloading at the mixing stage. Fundamental findings have been obtained, providing a basis for further assessment of the efficiency of dust precipitation with the additional application of pulsating ventilation. In such a combination, an additional 20–25 % increase in precipitation efficiency is anticipated compared to the results presented in this article. The obtained results will support the justification of rational parameters and the implementation of the described method in production to enhance dust precipitation efficiency. Additionally, they will aid in developing a methodology to accelerate the PPIOC dust precipitation using the pulsating ventilation method.

Introduction. The main disadvantage of traditional processes of diffusion surface hardening of steel products is its long duration. Therefore, the problem of intensification of such processes is relevant. To solve it, the use of high-energy effects on the material is proposed, which allows us to obtain a hardened surface layer from a coating composed of ferroalloy powders containing alloying elements. There is no data in the literature on the required content and dispersion of such powders in the composition of the coating. The aim of this study was to select the particle size of ferroalloys and their concentration in the coating to achieve the most effective hardening of the processed product.Materials and Methods. For experimental studies, cylindrical samples made of steel 20 with a diameter of 12 mm and a length of 35 mm were used. On the surface of these samples, an alloying coating containing ferroalloy powders and an electrically conductive gel as a binder was applied. After that, the samples were immersed vertically for half their length into a metal container, which was then filled with carbon powder with a particle size of 0.4–0.6 mm. Then an electric current of 2.5 to 3.0 A was passed in the circuit power source — container — carbon powder — sample. The duration of the process was 2–8 minutes.Results. The calculated estimation of the electrical conductivity of coal powder was performed, and the thermophysical parameters of microarc heating of steel were calculated. These include the power released by electric current on the surface of the steel product, the density of the heat flux, and the energy of a single microarc discharge. The expressions for calculating the particle size of ferroalloy powder were obtained, as well as the experimental dependencies of the diffusion layer thickness on the particle size of ferroalloys and their content in the coating.Discussion and Conclusion. The results of this study have allowed us to determine the size range of ferroalloys and their content in the coating. This information is essential for optimizing the alloying process and ensuring the most efficient surface hardening treatment for steel products. The data collected will be used to develop improved technological processes for the surface hardening process, leading to improved product quality and performance.

Introduction. Intra-laboratory comparison tests play an important role in ensuring the quality and reliability of research outcomes in laboratories. These tests allow researchers to evaluate the accuracy and reproducibility of the methods they use in their work, as well as to identify potential sources of error and inconsistency. The results of these tests are shared with experts to confirm competence within the accreditation. Typically, comparison tests are carried out in laboratory conditions in a familiar and calm environment for the testers. However, when laboratories conduct research as part of a special assessment of working conditions (SAWC) they are required to conduct on-site comparisons at real-world facilities, where customers may unwittingly disrupt the process and directly affecting the quality of the measurements. The aim of this study is to evaluate the quality of on-site intra-laboratory comparison tests using the example of determining the dust content in a bricklayer's work environment on a construction site, and to determine the minimum number of measurements necessary and sufficient for this purpose.Materials and Methods. To determine the dustiness of the bricklayer's workplace, a weighing method was used. This involved collecting dust on filters and then weighing them to determine the concentration. The quality assessment of intra-laboratory tests was conducted in accordance with GOST R ISO 5725-1-2002 "Accuracy (trueness and precision) of measurement methods and results. Part 1. General principles and definitions".Results. At the bricklayer's workplace, a 1.6-fold excess of the one-time maximum permissible dust concentration was detected. The average dust concentration at the workplace under study was: Kp2 = 9.57 ± 0.81 mg/m3, the convergence of the results obtained was r = 8.68 %, the relative error δ = 8.50 %. It was revealed that the maximum allowable difference between the results of the two tests was 0.84 mg/m3. The difference in direct measurements of the mass of the two samples should be no more than 0.1 mg.Discussion and Conclusion. The results obtained demonstrated the possibility of conducting a minimum number of measurements that, under reproducible conditions, are considered satisfactory and could be provided to experts for confirming the competence of the laboratory. As part of a special assessment of working conditions, employees of the object under study are recommended to use personal respiratory protection equipment that offers protection against highly dispersed dust particles.

Introduction. Mathematical modelling is effective in the analysis of industrial safety at metallurgical plants, in particular for tracking problems of the man — machine system. To introduce the time factor, recurrence relations (in a discrete model) and differential relations (in a continuous model) are used. However, it is also necessary to solve the problem of linking the model parameters to the real conditions of the production environment and to the human factor.The aim of this study is to create a method for determining the parameters of simulation mathematical models of the dynamics of the operator’s psychophysiological indicators affecting the work.Materials and Methods. The operator’s psychophysiological state (PPS) was assessed by performance, fatigue levels, and error rate. The data were collected by the Digital Correction Task (DCT) test. Based on the obtained results, the experimental values of the operator’s PPS indicators, which were reduced to the normalized scale [0, 1], were calculated. These indicators for a particular respondent, the mathematical model and the developed algorithm were used to determine the numerical values of the model parameters. In order to interpret the indicators of performance, fatigue and error rate, we introduced scales with five gradations.Results. The use of the authors’ modified version of the mathematical model showed a significant improvement in its prognostic properties. Out of 10 participants the best result was shown by respondent no. 7, the worst result was shown by respondent no. 8. During the first working hour (from 9.00 to 10.00) their performance increased almost equally, from 0.5–0.55 to almost 0.6. Then the score of respondent no. 7 increased and remained well above the “good” level until the end of the day. The score of respondent no. 8 dropped and was below average from 14.00 to 15.00. The difference was largely determined by the operators’ chronotypes. Their chronophysiological characteristics also affected fatigue and error rate. The model’s quality varied for different participants in the experiments. In one case it was excellent (mean relative error ≤5%), in three cases it was good (≤10%) and in four it was satisfactory (≤15%).Discussion and Conclusion. The proposed approach allows us to obtain the dynamic profiles of psychophysiological characteristics for every individual, to assess their interrelationships and to perform a prediction on the basis of a modified mathematical model. However, in order to extend the functionality of the models to the real working conditions of the metallurgical plant operator, it is necessary to increase the sample size, reduce the discrete time step and conduct studies for different working conditions, considering technological, climatic, environmental, psychological and other factors.

Introduction. When determining the number and technical equipment of fire departments, regulatory documents on fire safety do not take into account natural, climatic and geographical features of the subjects of the Russian Federation in an explicit form. At the same time, there is some information in scientific literature about the influence of certain natural and climatic factors on the effectiveness of fire protection actions in extinguishing fires. The aim of this study was to determine the influence of the system of natural, climatic and geographical characteristics of the subjects of the Russian Federation on the rapid response indicators of territorial fire departments. The results obtained are recommended for further use in rationing the number and technical equipment of fire departments.Materials and Methods. A factor analysis of statistical data for 2020–2022 was carried out. The statistical data were obtained from the Federal State Information System "Federal Database "Fires", from the website of the Federal State Statistics Service of the Russian Federation and from other sources. For the analysis, the authors selected ten indicators characterizing natural, climatic and geographical features of the subjects of the Russian Federation, two indicators of the rapid response of territorial fire departments and four indicators of the fire situation.Results. Five significant factors were identified, the change of which explained the change in the observed indicators. The first factor characterized the relationship of climatic conditions with fire situation indicators. The second factor connected the indicators of the rapid response of fire departments with the terrain features of the subjects of the Russian Federation. The third factor described the relationship between fire situation indicators and rapid response indicators with population density and forest cover of the territory. Other factors did not significantly contribute to the indicators of fire situation and rapid response.Discussion and Conclusion. By means of mathematical analysis and factor modeling, the authors investigated the interdependence of natural, climatic and geographical features of the subjects of the Russian Federation, fire situation indicators and indicators of rapid response of fire departments. The most significant factors influencing these indicators were identified. They included the average air temperature, the area covered by forest, the presence of mountain ranges, and population density. These indicators should be taken into account when determining the number and technical equipment of fire departments to increase the efficiency of their functioning.

   Introduction. The pivot assembly provides connection between the rotating and non-rotating parts of machines and mechanisms such as cranes, excavators, trailers, railway rolling stocks. In relation to rolling stock, it connects the load-carrying part of the car with the bogie and is one of the most critical and wear-out friction units. Its technical condition affects the intensity and form of wear of the surfaces themselves, the amount of resistance to rotation of the bogie when the car moves in curved sections of the track, the amplitude of the lateral rocking of the car, the intensity of wear of the wheel flanges and, as a consequence, the safety of operation of the rolling stock as a whole. Until now, periodic grease is used for this unit, which, even with a short mileage, manages to be squeezed out of the contact zones and, thereby, creates conditions for the predominance of dry friction. Until now, various proposals to solve this problem have not found application in mass production for a number of reasons, and therefore the search for ways to reduce wear in the pivot assembly of cars is still relevant. This study proposes a solution to this problem that does not require structural changes to the pivot assembly itself.   The aim of this work was to develop a technologically advanced anti-friction coating with good adhesion, which will be applied to the surface of a replaceable disk installed between the rubbing surfaces of the pivot assembly during scheduled repairs of the car chassis.   This approach will reduce the friction force and wear rate in the unit when lubrication shortage occurs due to squeezing out of the grease.   Materials and Methods. Antifriction characteristics of the developed coating was observed on a friction machine providing specific loads on the test sample up to 5000 N and a sliding speed from 0.13 m/s. The samples were examined by scanning electron microscopy (FEI Quanta 200 microscope). SEM images were acquired in a back-scattered electron (BSE) mode using a semiconductor detector. To analyze the elemental composition of beam samples, an energy dispersive spectrometer (EDAX Element EDS system) was used.   Results. A three-layer functional phosphorus-containing composite coating of the surfaces of the unit was developed, which made it possible to significantly reduce the coefficient of friction and, as a consequence, the intensity of wear of the pivot unit surface during dry friction. The optimal conditions for obtaining composite coating layers were determined. The influence of the thickness of each layer and the conditions for its production on its functional characteristics was studied.   Discussion and Conclusion. The proposed solution is manufacturable and, with appropriate adaptation, can be used to reduce wear in any open pivot assembly without radically changing its design. The methods for producing coating layers are accessible and technologically advanced for serial use.