Law enforcement is a stressful occupation with both work-related and social-related stressors. Too much stress can negatively affect behaviours, mental states, and job performance. Centralized police organizations limit officers’ individual autonomy, likely increasing stress. This study examined differences in occupational stress in two different European countries and one Middle East country. Participants were 351 male police officers from Serbia (n = 130, age 36 ± 8 years), Russia (n = 121, age 22 ± 4 years), and Lebanon (n = 100, age 36 ± 6 years) who completed the 20-item Operational Police Stress Questionnaire in their own language. Items were averaged and interpreted as low (≤2.0), stress (2.1–3.4), and high stress (≥3.5). Analysis of covariance (ANCOVA) analyses using age as the covariate with Bonferroni post hoc analyses were used. A principal component analysis (PCA) was used to determine stress structure per country. Significant differences were found with lower occupational stress in Russian (P < 0.001) and Lebanon (P = 0.003) than Serbian officers. PCA factor patterns differed by country, with six found for Russian and Lebanese and three for Serbian officers. More work-related stressors were rated higher for the younger Russian officers, while more social-related stressors were rated higher for the older Serbian officers. Results suggest that it is vital to consider officers’ stress sources and overall stress levels.

This paper presents a study of Al2O3–ZrO2 (ZTA) nanocomposites with different contents of reduced graphene oxide (rGO). The influence of the rGO content on the physico-mechanical properties of the oxide composite was revealed. Graphene oxide was obtained using a modified Hummers method. Well-dispersed ZTA-GO nanopowders were produced using the colloidal processing method. Using spark plasma sintering technology (SPS), theoretically dense composites were obtained, which also reduced GO during SPS. The microstructure, phase composition, and physico-mechanical properties of the sintered composites were studied. The sintered ZTA composite with an in situ reduced graphene content of 0.28 wt.% after the characterization showed improved mechanical properties: bending strength was 876 ± 43 MPa, fracture toughness—6.8 ± 0.3 MPa·m1/2 and hardness—17.6 ± 0.3 GPa. Microstructure studies showed a uniform zirconia distribution in the ZTA ceramics. The study of the electrical conductivity of reduced graphene oxide-containing composites showed electrical conductivity above the percolation threshold with a small content of graphene oxide (0.28 wt.%). This electrical conductivity makes it possible to produce sintered ceramics by electrical discharge machining (EDM), which significantly reduces the cost of manufacturing complex-shaped products. Besides improved mechanical properties and EDM machinability, 0.28 wt.% rGO composites demonstrated high resistance to hydrothermal degradation.

This paper discusses the results of a study focused on the nature of the interaction of Me-MeN-(Me,Mo,Al)N coatings (where Me = zirconium (Zr), titanium (Ti), or chromium (Cr)) with a contact medium based on the Ni-Cr system. The studies were carried out during the turning of nickel–chromium alloy at different cutting speeds. The hardness of the coatings was found, and their nanostructure and phase composition were studied. The experiments were conducted using transmission electron microscopy (TEM), X-ray diffraction (XRD), and selected area electron diffraction (SAED). According to the studies, at elevated cutting speeds, the highest wear resistance is demonstrated by the tools with the ZrN-based coating, while at lower cutting speeds, the tools with the TiN- and CrN-based coatings had higher wear resistance. At elevated cutting speeds, the experiments detected the active formation of oxides in the ZrN-based coating and less active formation of oxides in the CrN-based coating. No formation of oxides was detected in the TiN-based coating. The patterns of cracking in the coatings were also studied.

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