Recent developments in mixed lubrication

This paper reviews the advances in the study of mixed lubrication in recent years, both in theoretical modelling and in experiments, especially those marking substantial progress. The advances support the mode of mixed lubrication proposed by the author more than ten years ago which exhibited thinning, mixed and partial films and mixed contacts in modern mixed lubrication under severe operating conditions. The paper outlines recently achieved progress in the field, which revealed new phenomenon such as: the elastoplastic deformation of the surface asperities, the boundary film interfacial slippage, the boundary lubrication effect and the interfacial shear stress effect on the contact surface deformation. Also, the mixed lubrication with designed surface roughness and the load-carrying mechanism of mixed lubrication are reviewed

Topological classes of black holes in de-Sitter spacetime

In this paper, we investigate the topological number of de-Sitter black hole solutions with different charges $(q)$ and rotational $(a)$ parameters. By using generalized free energy and Duan's $\phi$-mapping topological current theory, we find that the topological numbers of black holes can still be classified as three types. In addition, we interestingly found the topological classes for de-Sitter $($dS$)$ spacetime with distinct horizon, i.e, black hole event horizon and cosmological horizon, will be different. Moreover, we also investigate topological classifications of dS black hole solutions in higher dimensions with or without Gauss-Bonnet term.Comment: 18 pages, 14 figure

Surface Roughness Effect in Hydrodynamic Thrust Bearing with Ultra Low Clearance

In the hydrodynamic thrust bearing with ultra-low clearance, even the nanoscale surface roughness is comparable to the bearing clearance, and its effect can be very significant. In this paper, the calculations are made for the performance of this bearing when the surface roughness is on the 1nm scale. It was found that the surface roughness effect in the bearing is strongly dependent on the physical adsorption of the fluid to the bearing surface determined by the interaction strength (or potential) between the fluid molecules and the molecules of the bearing surface; it can considerably enhance the load-carrying capacity of the bearing for the strong interaction between the fluid and the bearing surfaces