Rostov State Transport University

In the age of rapidly developing technologies and the digital revolution, modern society needs highly qualified workers capable of continuous self-development, the ability to learn throughout life, solve non-standard problems, show persistence and initiative, take responsibility for their actions, and possess the skills of working in a team. This causes an increase in requirements for the professional competencies of graduates of secondary vocational education organizations. The effectiveness of learning depends on both external (social, pedagogical) and internal (psychological) factors. Interest is the basis on which the learning process is built, helps to study successfully, master a profession, and influences personal development. Motivation helps maintain interest. Using observation and analysis methods, the reasons why modern students do not want to learn have been identified and discussed. Solutions to training problems in secondary vocational education organizations are proposed. These include meetings with representatives of the chosen profession, and the skill of a teacher who uses a variety of approaches, forms and methods of work, technologies and teaching tools, and the organization of leisure activities for students (involvement in various forms of cultural, sports, and volunteer activities, participation in shows -competitions, educational and research projects, quizzes, games, seminars, etc.).

Currently, one of the major trends in the construction industry is the creation of structures with increased strength and durability. The solution is the use of nanomaterials as modifiers for cementitious composites. The aim of this study is to produce concretes with a variable structure modified with a combination of aluminum oxide (NA) and titanium oxide (NT) nanoparticles with improved properties. A variatropic structure is characterized by differences in properties across the cross-section of the material. Concretes were produced using vibration (V), centrifugation (C), and vibrocentrifugation (VC) technologies. Modification was carried out with NA particles from 0% to 4.0% in increments of 1.0% and NT from 0% to 2.0% in increments of 0.5% of the binder mass. Through experimental study, the impact of combined nanomodification on the compressive strength, water absorption, and frost resistance of concrete created with different technologies was investigated. The most effective modification dosages with NA and NT particles were determined to be 2% and 1%. The determination of concrete properties and the statistical processing of experimental results were carried out in accordance with the requirements of standardized methods. Compared to control samples, the maximum compressive strengths for V, C, and VC concretes were 12.4%, 17.5%, and 20.3% higher, reaching 48.9 MPa, 58.4 MPa, and 62.9 MPa, respectively. The lowest water absorptions for V, C, and VC concretes were 5.21%, 4.24%, and 3.76%, which are 18.5%, 24.4%, and 29.2% lower than those of the control samples. After a series of freeze-thaw cycles-6 for V, 8 for C, and 10 for VC-the losses in compressive strength and mass of the nanomodified composites were less than those of the control samples, indicating an increase in the frost resistance of concrete. The influence of concrete production technology on the effect of nanomodification with NA and NT particles was proven. Nanomodified C and VC concretes have improved physical and mechanical properties compared to V concretes. Nanomodified concretes with a variable structure have a more organized microstructure with a greater number of clusters of calcium silicate hydroxides. The resulting variable-structure concrete has improved properties and can be used to manufacture columns, piles, and transmission line supports.

High-performance concrete (HPC) is an important construction material that can be improved with nano-additives. In this study, the modification of HPC with KHA-HC nanodiamond and nano aluminum oxide (NA) admixtures was investigated; the admixture rate was applied in the range of 0-1.4% in 0.2% increments. The rheology, density, compressive and flexural strength, water absorption, and microstructure properties were investigated; the results showed that the KHA-HC nanodiamond showed higher efficiency than NA. Compared with HPC without nano-additives, the strength properties of HPC with the most optimal content of nano-additives, 0.6% KHA-HC and 1.0% NA, were improved by 47.1% and 17.0% for compressive strength and by 44.9% and 16.3% for flexural strength. Water absorption decreased by 33.0% and 26.0%, respectively. Also, with optimal dosages of nano-additives, an improvement in the rheology of the HPC mixture was recorded. The complex modification of HPC 0.6% KHA-HC and 1.0% NA provides a synergistic effect and maximum improvements in properties: the increase in compressive strength was 58.2%; flexural strength - 54.1%; decrease in water absorption - 49.1%. HPC modified by nano-additives has an improved macro- and microstructure. The two types of nano-additives’ effectiveness, KHA-HC and NA, both separately and together in HPC technology for additional improvement of their operational properties, has been proven.

We have studied diamond-like carbon coatings produced by vacuum ion-plasma deposition. The coatings were doped with Ti ions via arc evaporation of a titanium cathode in parallel with laser arc evaporation of carbon from a graphite cathode. The titanium-doped diamond-like coatings were grown on 40CrNi steel substrates with a sorbite structure. The Ti content of the metal–carbon coatings thus prepared was in the range 1.5–5.5 wt %. The coating thickness was widely varied in our experiments, in the range δ = 0.5–4.5 μm. The effect of the parameter δ on tribological characteristics of the coatings was one of the key aspects of this research. The structure of the coatings was studied by high-resolution electron microscopy and their mechanical properties were studied using continuous indentation. The tribological properties of the coatings were assessed in ball-on-disk sliding friction tests on a tribometer at friction loads in the range F = 1–10 N. In analyzing the experimental data obtained, we used a computational analysis model which allowed us to construct critical state diagrams of various materials and coatings. The results demonstrate that such diagrams can be used for reliably predicting the minimum coating thickness δmin needed for preventing premature failure of coatings in tribological tests. In addition, titanium doping of diamond-like carbon coatings (in the range of Ti concentrations studied) was shown to help stabilize the coating thickness: no spontaneous cracking of the coatings was detected at thicknesses of up to δ = 4.5 μm, and their microstructure remained sufficiently uniform, without any signs of formation of secondary carbide phases.

The growing environmental concern over waste tire accumulation necessitates innovative recycling strategies in construction materials. Therefore, this study aims to develop and evaluate sustainable concrete by integrating waste tire rubber (WTR) aggregates of different sizes and recycled waste tire steel fibers (WTSFs), assessing their combined effects on the mechanical and microstructural performance of concrete through experimental and analytical approaches. WTR aggregates, consisting of fine (0–4 mm), small coarse (5–8 mm), and large coarse (11–22 mm) particles, were used at substitution rates of 0–20%; WTSF was used at volumetric dosages of 0–2%, resulting in a total of 40 mixtures. Mechanical performance was evaluated using density and pressure resistance tests, while microstructural properties were assessed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The findings indicate systematic decreases in density and compressive strength with increasing WTR ratio; the average strength losses were approximately 12%, 20%, and 31% at 5%, 10%, and 20% for WTR substitution, respectively. Among the WTR types, the most negative effect occurred in fine particles (FWTR), while the least negative effect occurred in coarse particles (LCWTR). The addition of WTSF compensated for losses at low/medium dosages (0.5–1.0%) and increased strength by 2–10%. However, high dosages (2.0%) reduced strength by 20–40% due to workability issues, fiber clumping, and void formation. The highest strength was achieved in the 5LCWTR–1WTSF mixture at 36.98 MPa (≈6% increase compared to the reference/control concrete), while the lowest strength was measured at 16.72 MPa in the 20FWTR–2WTSF mixture (≈52% decrease compared to the reference/control). A strong positive correlation was found between density and strength (r, Pearson correlation coefficient, ≈0.77). SEM and EDX analyses confirmed the weak matrix–rubber interface and the crack-bridging effect of steel fibers in mixtures containing fine WTR. Additionally, a hybrid prediction model combining physics-informed neural networks (PINNs) and CatBoost, supported by data augmentation strategies, accurately estimated compressive strength. Overall, the results highlight that optimized integration of WTR and WTSF enables sustainable concrete production with acceptable mechanical and microstructural performance.

In the present work, the mechanical properties and tribological characteristics of TiN (monolayer) and TiN/a‑C (bilayer; two variants of combinations of elastoplastic properties of the layers) coatings were investigated using experimental and theoretical approaches. The microstructure of the synthesized coatings and the topography of the surface were characterized by scanning electron microscopy. Characterization of the a‑C coating was carried out by the diffuse total internal reflection (DTIR) method using a Fourier‑transform infrared (FT‑IR) spectrometer. Hardness and reduced modulus were obtained by continuous (instrumented) indentation with a Berkovich indenter. Wear rate and coefficient of friction were determined in sliding friction tests. The results of the comprehensive experimental study of the coatings served as the basis for developing a finite‑element model of indentation of a bilayer elastoplastic medium with various combinations of elastic and plastic properties and different relative layer thicknesses. A correlation between coating parameters H/E and H3/E2 and the wear rate was established experimentally. Functional dependences of hardness and reduced modulus on the relative thickness of the surface metastable a‑C layer were determined theoretically. The optimal ratio of the thicknesses of the constituent layers in the TiN/a‑C coating for given elastoplastic material properties, yielding the best tribological performance, was identified.

Aim. To study the process of operation of the existing level crossing devices. To examine a detailed barrier operation algorithm that takes into account the proper operation of each component. The existing level crossing protection systems use simplified operation algorithms. To focus on the process of crossing warning generation when a train enters the warning section. To examine in detail the work of operators who identify the distance to a vehicle and, consequently, the barrier activation time. That will allow adjusting the barrier activation time and, consequently, reduce the rolling stock downtime. Methods . The paper suggests a method that involves continuously measuring the vibration displacements of the rails at the crossing using an accelerometer. By continuously measuring the values of vibration velocity (V) and vibration acceleration (a) at the boundary of a crossing, a set of measured values Vi and ai is generated. These values are used for making a system of equations for the train location coordinate, whose right part is equated to the values of the train coordinates. By solving the system of train coordinate equations using the values of vibration velocity (V) and vibration acceleration (a) at the boundary of a crossing at the approach of a train, the coordinate of the vehicle can be defined at specific points in time. Consequently, the speed and nature of its movement can be identified throughout the warning section. Out of the obtained values, the time of the train’s head clearing the crossing can be identified. By comparing the estimated barrier activation time with the time derived from the nature of a train’s movement, the moment of crossing barrier activation can be identified. Results . The study showed that the existing level crossing warning systems deployed within stations normally activate barriers in advance. That may cause motor vehicles to spend excessive amounts of time before a crossing. If the length of the approach section is fixed, the actual warning time is inversely proportional to the train’s speed and may significantly exceed the minimum required time. Excessive warning time may have negative consequences, which requires a solution. If a crossing is regularly closed for long periods of time, drivers will be attempting to cross faster once the restrictive signal has turned on, which may lead to accidents, train-to-motor vehicle collisions. Should data on the actual time of a train’s arrival to a crossing be available, the time spent by motor vehicles at closed crossings will be able to be reduced down to the estimated closing time and the time it takes for the train to clear the crossing. The average train speed in the Russian Federation is 35.7 km/h [1], while warnings are calculated for the top speed. Conclusion. The time spent by vehicles before a barrier can be reduced about 3 to 4 times. Consequently, the number of accidents at crossings can be reduced as well.