The fixed-setting face-milled curvilinear cylindrical gear features teeth that are arc-shaped along the longitudinal direction. Some researchers hypothesize that this arc-tooth may enhance the lubrication conditions of the ge... | Find, read and cite all the research you need on Tech Science Press

Hydrogels, with their high water content, tissue-like softness, and excellent biocompatibility, are prime candidates for dynamic load-bearing interfaces such as cartilage replacement and implant coatings. However, the toughening structures introduced to enhance damage resistance often compromise surface lubrication: highly dissipative networks, while suppressing bulk crack propagation, frequently increase interfacial friction and accelerate wear. This toughness–lubrication trade-off constitutes a central bottleneck limiting the long-term service of hydrogels under dynamic contact conditions. This review examines the friction and wear behavior of various hydrogel systems and, from the dual perspectives of bulk mechanical reinforcement and surface lubrication regulation, summarizes the core design mechanisms of toughening and hydration lubrication strategies, respectively. Based on this analysis, this review proposes a functional decoupling design principle: hierarchical structures—ranging from homogeneous to heterogeneous—in which the bulk dissipates mechanical load while the surface maintains hydration lubrication, thereby reconciling mechanical toughness with lubrication. Finally, this review surveys cutting-edge applications of such materials in tissue engineering, device coatings, drug delivery, electronic energy-harvesting and storage devices, and soft actuators, providing a reference for the development of hydrogels that integrate excellent mechanical properties with lubrication functionality.

Quartz is capable of capturing heavy metals (HMs); however, alkaline metals compete with HMs for active adsorption sites during coal combustion. Therefore, this study investigated the influence of alkaline metals (Na₂CO₃, NaCl, and CaO) on the adsorption behavior of HMs (Pb, Cd, Cu, and Zn) onto quartz via tube furnace combustion experiments and the CASTEP module based on density functional theory (DFT). The results showed that the addition of Na₂CO₃ and NaCl was disadvantageous for the retention of HMs in the ash, particularly NaCl. With the increase in NaCl from 0 to 5 wt%, the immobilization efficiencies for Pb and Cd progressively declined from 33.99% and 37.78% to 9.89% and 12.04%, respectively. As the temperature increased from 800 °C to 1200 °C, the fixation rates of Cu, Zn, Pb, and Cd decreased by 19.96%, 27.75%, 23.35%, and 20.68%, respectively, when Na₂CO₃ was present in the coal. The results of the DFT demonstrated that the adsorption energy of alkali metals on quartz-α(001) surfaces was much greater than that of HMs, thus adversely affecting the adsorption of HMs. The adsorption energy of Na₂O reached as high as −924.70 kJ/mol, while that of HMs was generally below −650 kJ/mol. This work contributed to a deeper understanding of the fate, migration, and transformation of HMs, thereby facilitating the mitigation of HMs release and subsequent associated ecological risks.

As an important supporting element of rotating mechanisms, the frictional wear of rolling bearing causes low motion accuracy. To simulate the service statuses of rolling bearing under different lubrication conditions, the wear and frictional behavior between the GCr15 ball-on-disc contact pairs was experimentally analyzed to investigate the effects of rotating speed, loading, supplied oil quantity and air pressure on the friction and wear properties of the point contact pairs. As the experimental results show, the use of oil-air lubrication yields the smallest friction coefficient as compared to those of the grease and the oil lubrication modes, which can suppress the temperature rise effectively and attain the lowest wear rates. The increase of oil volume fraction for the oil-air lubrication led to diminished wear scar depth and low wear rates, while the supplied oil quantity and air pressure were constant, the increase of rotating speed resulted in slight decline of friction coefficient, as well as gradual elevation of temperature and wear rates. Regarding loading, its enhancement made the friction coefficient and wear scar depth went up initially and then reduced, which also caused the wear rates decreased. The findings of this research provide a useful basis for selecting the optimal high-speed bearing lubrication method and their operating parameters.

Although the world is rich in deepwater oil and gas resources, deepwater drilling faces the challenge of a narrow safety density window. Dual-gradient drilling is an effective approach to address this narrow safety density window, and subsea pump-lift dual-gradient drilling is currently one of the most widely used methods. To improve handling capacity and effectiveness under well kick conditions, we established a simplified hydrodynamic model for subsea pump-lift dual-gradient drilling that accounts for the subsea pump’s head-flow performance curve. Based on this hydrodynamic model, we proposed automatic control methods based on throttling regulation and variable-speed regulation and conducted simulation analyses. The results indicate that both control methods can safely, efficiently, and automatically handle well kicks; throttle control has shorter response times and higher precision, while variable-speed control regulates bottom hole pressure by adjusting the subsea pump’s rotational speed and offers better energy-saving performance. These findings provide new insights into handling well kicks in subsea pump-lift dual-gradient drilling.