Introduction. Cement production is responsible for approximately 8% of anthropogenic CO₂ emissions, while annual losses from sulfate corrosion account for 2–4% of the global GDP [1]. Studies have confirmed the influence of SiO₂ and additives on the sulfate resistance of multi-component cements (MCCs). However, there is a lack of high-SiO₂ systems, and there is no consensus on the effects of individual additives. The absence of long-term field experiments hinders an empirical solution to this problem. The present study addresses these gaps. The aim of this research is to develop predictive models to substantiate the optimal composition of MCCs based on their sulfate resistance and environmental performance. The tasks include: synthesizing data on MCC compositions, performing ANOVA and regression analysis, and constructing and validating the models.

Materials and Methods. The data sources were thematically structured and analyzed. Experiments were conducted on eight compositions in accordance with patent RU 2079458 C1 and standards GOST 310.1.76 and GOST 310.4.81. The samples were grouped by SiO₂ levels. ANOVA and linear regression were used to model the dependence of sulfate resistance and self-stress on SiO2 content.

Results. The statistical significance of SiO₂ influence on the sulfate resistance and strength of MCCs was proven (F = 248.6795, p = 3.5612e–25). The regression model (Sr = 6.2644 + 0.08 ∙ SiO₂, R² = 0.983) demonstrated a linear dependence of sulfate resistance (ranging from 8.04 to 9.62 conventional units) on SiO₂ content (21–44%). For SiO₂ content > 22%, the addition of pozzolans was recommended to compensate for reduced strength at early stages of hardening. Compressive strength ranged from 35.0 to 44.0 MPa. The reduction of C₃A content to ≤8% enhanced sulfate resistance. The introduction of 50% granulated blast-furnace slag as a binder optimized the cement structure and reduced the carbon footprint by 27.5% (to 388.2 kg CO₂/t). An increase in silica in the composition:

• by 22.15–28% enhanced sulfate resistance by 0.468 units;
• by 37–40% — 6.2644;
• 42% — 9.6244.

Discussion. The model explains 98.3% of the variance in sulfate resistance through changes in silicon dioxide content. The model remains robust with an increased number of observations, as indicated by the adjusted R₂ of 0.981.
The F-statistic indicates the high statistical significance of the model. The normal distribution of residuals and the high precision of the coefficient estimates were confirmed. The limitations on additives in cement specified by GOST 22266-2013 are no longer up to date. This new approach will allow for an increase in cement durability in sulfate environments, a reduction in production costs by 30–50%, and a decrease in CO₂ emissions by 27.5%. It enables the selection of a concrete composition based on either economic or environmental priorities.

Conclusion. SiO₂ content is the key factor in enhancing sulfate resistance. This approach offers a new methodological perspective by overcoming the shortcomings of the GOST standard. Variations in slag composition and the absence of thermal activation may limit the model's reproducibility, necessitating further research.

Introduction. Researchers at the Southern Scientific Center of the Russian Academy of Sciences have repeatedly observed abundant microalgae blooms in Taganrog Bay, which negatively impact the health of people, animals, the environment, as well as the economy. Given the increasing depletion of biodiversity and deterioration of water quality in the Azov Sea due to reduced freshwater inflow, rising water temperatures, and increased nutrient runoff, the risk of toxic phytoplankton populations is increasing. This threatens the ecosystem, regional economy, and health of local residents. The rise in average annual temperatures and increased nitrogen and phosphorus runoff caused by urbanization and agriculture leads to accelerated growth of cyanobacteria, particularly during warmer months. This results in abundant blooms with the potential for toxicity, especially in Taganrog Bay. Models of phytoplankton population dynamics exist at the lag-phase and reactive norm levels. However, their adaptation to the conditions of the Azov Sea requires the consideration of the specific variations in depth, salinity, and seasonal characteristics. The aim of this study is to construct medium-term forecasts for the development of cyanobacteria using an integrated approach based on the application of mathematical modeling methods.

Materials and Methods. Phytoplankton population dynamics were predicted using a three-dimensional, non-stationary mathematical model based on a system of non-stationary partial differential equations with nonlinear source functions. The input data for the model included values of water flow vector components from a hydrodynamic model, as well as measurements of salinity, temperature, nutrient concentrations, and phytoplankton populations from long-term observations. Difference approximation of the model was performed using explicit-implicit splitting schemes. A depth interpolation method was used to construct a three-dimensional computational domain. The described method was also applied to interpolate salinity and temperature values based on cartographic information.

Results. A numerical experiment yielded three-dimensional distributions of cyanobacteria and green algae in Taganrog Bay during the growing season. The experiment considered the effects of salinity and temperature, as well as the nutrient limitation of phytoplankton populations. The interpolation method resulted in a depth map, salinity, and temperature distributions that were relatively smooth at the junction points, and served as input data for the model.

Discussion. The mathematical model of the dynamics of phytoplankton populations presented in this paper takes into account the conditions for the development of blue-green and green algae and their environmental impact. It allows us to create a three-dimensional image of plankton distribution and determine the areas where blue-green and green algae are most abundant in Taganrog Bay and the Azov Sea.

Conclusion. The described mathematical model and mathematical modeling methods have been integrated into a software package. This allows us to simulate and predict all changes that have occurred and will occur in the waters of Taganrog Bay. This, in turn, will undoubtedly contribute to informed decision-making in the future development of the Azov Sea.

Introduction. In today's world, fire safety has become a top priority for public administration in every country. The challenges of providing professional fire protection are addressed, among other measures, through the institution of volunteer firefighting both in Russia and abroad. Problems in ensuring the activities of volunteer firefighters are generally quite typical, regardless of the level of socio-economic development of the territory. Thus, in modern conditions in the Russian Federation, there are quite noticeable imbalances in the level of fire safety. These issues are particularly acute for small, remote settlements, where it is quite resource-intensive to maintain professional fire protection. Nevertheless, the principle of equal access and quality of public services is a key component of state policy and regional administration. The activities of volunteer fire brigades play an essential role in the fire safety system in Russia and abroad. However, as practice shows, there is a significant problem of ignorance and, in general, unwillingness of citizens to participate in voluntary fire protection and to assist in the development of this institution. In this regard, this study aims to investigate the role of volunteer firefighting societies (hereinafter referred to as VFFS) and analyze the specifics of their activities abroad in order to identify common practices and assess the perception of this institution by the population.

Materials and Methods. The research plan consisted of two interconnected parts. First, we planned to study the sources devoted to evaluating the role of volunteer firefighters in other countries and analyze the activities of volunteer firefighting organizations in the Russian Federation. Then, we conducted a sociological survey and processed the results. The processing of responses involved summarizing the collected data and identifying the reasons and motives behind the responses received. For the regional part of the study, statistical data on the activities of voluntary firefighting societies and the dynamics of the number of volunteers were analyzed in order to assess the contribution of voluntary firefighting societies to the fire safety system.

Results. It has been revealed that the institute of volunteer firefighters is widespread in the fire extinguishing system both in Russia and abroad. It has been found that approaches to the organization, financing and financial incentives of volunteer firefighters from different countries have both similarities and some differences, including the subjective perception of this institution by the population. It was found that the number of VFFS branches and the participation of VFFS units in extinguishing fires in the Russian Federation have increased significantly in the Russian Federation. This indicates the relevance and effectiveness of their work. An analysis of the distribution of the number of fires by fire extinguishing participants showed that the proportion of volunteer fire brigades participating in firefighting has been growing annually. However, the analysis has also showed a decrease in the overall number of volunteer firefighters in the Udmurt Republic. According to the sociological survey conducted, the vast majority of respondents were generally not ready to participate in voluntary fire protection and assist in the development of this institution.

Discussion. This work has shown that the institution of volunteer firefighters is a highly sought-after and socially significant phenomenon both in Russia and abroad. However, there are clear problems at both the national and regional levels with the organization of the VFFS system itself. Generally, the population is not very willing to join volunteer firefighting groups, and the reasons why people do not join these groups have been identified. The analysis revealed the motivations and conditions under which respondents were willing to participate in volunteer firefighting activities. The results show the need for a comprehensive approach to developing measures to improve the status of volunteers. It is also necessary to develop a set of measures to increase the appeal of the image of a volunteer firefighter to attract young people into this field.

Conclusions. The research confirms the important role of volunteer firefighters in ensuring fire safety in the subject area under study, both in Russia and abroad. The review showed that the key problems in organizing the work of voluntary firefighting services are identical for most countries. These conclusions are supported by the results of the analysis. The main results of the study include data on the dynamics of the number of volunteers in the region as well as factors that determine the motivation of the population to participate in volunteer firefighting activities. The practical significance of the research lies in its application in predicting additional measures to attract more volunteers to volunteer firefighting organizations. Further research will aim to develop mechanisms to promote volunteer firefighting activities.

Introduction. Ignoring the systemic nature of a reservoir can lead to ineffective and damaging management decisions. However, the study of such objects often focuses on individual factors. The predictive potential of graph models is limited by a lack of expert information and outdated databases of indicators. This work aims to address these issues by evaluating the effectiveness of measures to improve the condition of the Tsimlyansk Reservoir. The solution is based on the author's graph model that takes into account the interaction of anthropogenic and biotic characteristics of the object.

Materials and Methods. The literature sources and information on hydrobiochemistry and species composition of fish were analyzed. A model was created that took into account 20 factors related to the state of the Tsimlyansk Reservoir. A hydrobiological analysis allowed us to create graph G(V, E, Y). V — set of vertices, v_k ∊ V, k = 1̅, ̅2̅0. E — set of oriented edges e_k = (v_i, v_j) in the form of ordered pairs of length 2, i ≠ j. Y — mapping, Y : V → V. A weight matrix was created based on an integral assessment of each factor by experts. The weighting coefficients (±0.5–±1) were calculated using information from hydrobiological and chemical databases.

Results. We investigated how the removal of zebra mussels would affect the facility during a single cleaning (scenario 1) and a three-year cleaning (scenario 2). We visualized the dynamics of pulses for the state of the water (v₁₅) and changes in the concentration of biological substances (v₁₈). In the first scenario, for the first factor, the maximum pulse (0.5) was fixed from the third year of exposure; the minimum (0) was during the first year. For the second factor, the pulse increased from a minimum (–0.5) to a maximum (0.25) over the third year. In the second scenario, both factors did not change in the first year. Then the pulse for v₁₅ increased (to 0.75), v₁₈ fell in the second year to –0.5, and then increased to –0.25.

Bream reproduction with v₅ feeding was evaluated for a year (scenario 3) and five years (scenario 4). The state of spawning fish v₁, replenishment of juveniles v₂, fishing v₇, and eutrophication v₁₄ were taken into account. v₂, v₇, and v₁₄ pulses remained zero for two years. Then v₂ and v₇ grew to one, and in the fourth year they fell to zero. The eutrophication pulse dropped to –1, and returned to zero by the end of the fourth year. With a five-year feeding, v₁ pulse dropped to –1 in the first year, v₁₄ — in the third, and its value did not change, and v₁ returned to 0 in the fifth year of modeling. The pulse for v₂ and v₇ grew from zero to one in three years.

Discussion. Annual cleaning of a reservoir from zebra mussel was more effective for improving the water condition and less effective for the concentration of nutrients. One-time feeding would increase the number of juveniles and fishing. Eutrophication would decrease, but there would be no sustainable results. Annual feeding would increase the number of juveniles, reduce eutrophication and lead to the development of fishing.

Conclusion. The proposed solution makes it possible to predict potential benefits or harm of anthropogenic activities on the reservoir. The model can be improved by fine-tuning the weighting coefficients, taking into account non-linear and threshold effects as well as other indicators.

Introduction. The problem of containers overturning off railway platforms has become more acute with the development of logistics and climate change, and is attracting the attention of researchers. This paper examines the situations at various logistics facilities and different capacities. It is known how the risk of overturning depends on the strength of the wind, the curvature of the track, and the height of the rail. There are methods to calculate losses from these incidents. The results of the survey are useful for logistics management, but implementing such solutions takes time and significant resources, so they are rarely implemented in practice. The approach described in this article addresses these limitations by its technical simplicity. Its aim is to demonstrate the effectiveness of adjusting three platform parameters: the lateral gap at the edge, as well as the height and thickness of the stationary stops.

Materials and Methods. The literature on the subject was analyzed, including state standards, technical specifications, and building codes and regulations. The connection between the fitting and the stop, as well as the container's parameters necessary for calculations, were visualized in diagrams. The equations took into account the strength of the wind, its lateral load on the container, and regional characteristics. We used data on a 40-foot container with dimensions of approximately 12.2 meters in length, 2.6 meters in height, and 3.9 tons in weight, with spacing between fittings of approximately 2.3 meters. Regional wind patterns were determined using the “Zoning of the Territory of the Russian Federation by Wind Pressure” map.

Results. It has been proven that a technically simple change in platform stops would significantly reduce the risks of container overturning under significant wind load. It was necessary to minimize the lateral play at the edge of the platform, increase the height of the stationary stop to 106 mm, and its thickness to 56 mm. Without these upgrades, a 40-foot container would overturn at a wind speed of 120 Pa. With the proposed configuration, the stability of the container on the platform was significantly improved. In dry conditions, the container remained stable under wind forces of »834 Pa, with precipitation — »500 Pa. This represented a gain of 7 times and 4.2 times, respectively, in stability.

Discussion. In the initial configuration, a 40-foot container overturns at a wind speed of 11.9 m/s, or in wind zone I, as in Moscow or Minsk. The modernization proposed by the author will allow the container to withstand wind speeds of 37 m/s (zone VII). In rain and snow, the container will overturn at a wind speed of 29.5 m/s. This is zone IV (Kazakhstan and the coast of the Caspian Sea). Currently, there is active automobile and railway traffic here. Cargo traffic is expected to increase in the future due to the implementation of the Silk Road project.

Conclusion. The implementation of the proposed innovation will significantly reduce the likelihood of emergencies due to containers falling from railway platforms and, consequently, increase transportation safety. The solution is characterized by technological simplicity and versatility. The container design remains the same. Individual elements of the platform change minimally.

Introduction. When heating with high-frequency currents (HFCs) at high speeds, more significant strengthening effects can be observed compared to using machine generators. Therefore, hardening at high frequencies is more efficient. However, the increase in the generator frequency results in a decrease in the depth of penetration of eddy currents and an increased unevenness of heating across the cross-section. The application of a constant external magnetic field during HFC hardening can increase the depth of eddy current penetration and create more uniform heating. Unfortunately, there is not enough information available on the effect of the external magnetic field on HFC heating processes and phase transformations in steel. Currently, there are no quantitative estimates for the impact of an external magnetic field on changes in the kinetics of electric heating and the penetration depth of eddy currents. In connection with the above, the aim of this paper is to investigate changes in the kinetics of high-frequency heating of iron-carbon alloys when an external constant magnetic field is applied and, and, based on this, to consider the potential for technological applications.

Materials and Methods. Theoretical assessment of the influence of an external magnetic field on the change in the kinetics of electric heating and the penetration depth of eddy currents is based on the general theory of induction heating kinetics. An experimental study of the influence of a magnetic field on the kinetics of high-frequency current heating was performed on samples of 45 steel, pearlitic gray (SCh30), and ferritic malleable cast iron (KCh30-6). The temperature distribution over the cross-section of ferromagnetic materials during induction heating with an external magnetic field has been studied using special samples of iron, 45 steel, and SCh30 gray pearlitic cast iron. Electric tempering processes have been investigated on samples of U8A steel using a vacuum tube generator (heating temperature — 450℃, heating rate — 750℃/s). Changes in austenite grain size after high-speed heating with external magnetization have been examined on samples of reduced-hardenability 55PP steel. To study the processes of thermal treatment in a magnetic field during experiments involving heating samples using high-frequency currents, a specially designed electromagnet was created to apply an external constant magnetic field.

Results. Theoretical curves were constructed for heating conditions with and without an external constant magnetic field. Experimental data on the effect of an external constant magnetic field on induction heating in the surface layer of various materials were summarized in kinetic diagrams. Evidence that the observed changes were due to increased depth of penetration of eddy currents came from experiments on cylindrical samples of 45 steel with different wall thicknesses. Kinetic curves were provided for estimating the temperature field (at 6 points at different depths) during high-frequency current heating with and without external magnetization. The paper presents experimental data on the micro-hardness distribution across the cross-section of a U8 steel sample after quenching, quenching and electric tempering, quenching and electric tempering with external magnetization, and quenching and bulk tempering. It also includes the results of the study of the austenite grain size of 55PP steel after high-speed heating with external magnetization and conventional (slow) deep heating.

Discussion. The application of a high-intensity external constant magnetic field during the first quasi-stationary process resulted in a decrease in the rate of induction heating of the ferromagnetic material and an increase in the depth of its uniform heating. However, above the Curie point, the effect of the magnetic field was negligible due to the low magnetic susceptibility of the material, and the heating rate remained unchanged as if there was no field present. In addition, due to the insignificant difference in the values of magnetic permeability below and above the Curie point during heating in the field, the thermal curve did not exhibit the characteristic inflection typical of kinetic curves observed during the transition of the surface layer to a paramagnetic state. Experiments with electric tempering have demonstrated that by applying an external field, it was possible to temper a material to the desired depth and it could be done on a single high-frequency current setup. The size of the austenite grains after high-speed heating with magnetization was reduced compared to conventional deep heating of steel with low hardenability, eliminating the issue of induction heating for low-hardenability steel.

Conclusion. The results of the study demonstrated that the use of an external magnetic field enabled the achievement of strengthening effects during heating at higher frequencies, thereby eliminating the drawbacks of such heating methods.