No abstract

Rolling friction and wear behaviours of a surface densified Fe-2Cu-0.6C powder metallurgy material were investigated. Results indicated that friction coefficient and wear were significantly decreased after rolling. Wear rate tended to be steady as the rolling cycle increases. Under light load, wear was caused by delamination and ploughing. Delamination crack initiated on material surface. Under heavy load, wear was caused by delamination and pits. Cracks initiated at the surface and subsurface. However, due to the hardened surface layer and a lower porosity, probability of subsurface crack initiation was reduced and crack locations were closer to surface. Crack propagation distance also was shortened. The surface densified layer plays an important role in improving the rolling wear resistance of the material.

In this letter we analysed the efficient exchange of orbital angular momentum (OAM) of light in a double V-type semiconductor quantum well via electron spin coherence. We found that due to the four-wave mixing (FWM) mechanism the OAM state of the vortex light can transfer from applied lights to a new generated signal beam when the efficiency of the FWM processes is enough high. We also shown that the absorption spectrum of the new generated light depends on the OAM number and azimuthal angle of the optical vortex light. We realized that for some specific parametric conditions the absorption spectrum of the generated light becomes negative which corresponds to the lasing without inversion.

The nonextensive statistical ensembles are revisited for the complex systems with long-range interactions and long-range correlations. An approximation, the value of nonextensive parameter (1-q) is assumed to be very tiny, is adopted for the limit of large particle number for most normal systems. In this case, Tsallis entropy can be expanded as a function of energy and particle number fluctuation, and thus the power-law forms of the generalized Gibbs distribution and grand canonical distribution can be derived. These new distribution functions can be applied to derive the free energy and grand thermodynamic potential in nonextensive thermodynamics. In order to establish appropriate nonextensive thermodynamic formalism, the dual thermodynamic interpretations are necessary for thermodynamic relations and thermodynamic quantities. By using a new technique of parameter transformation, the single-particle distribution can be deduced from the power-law Gibbs distribution. This technique produces a link between the statistical ensemble and the quasi-independent system with two kinds of nonextensive parameter having quite different physical explanations. Furthermore, the technique is used to construct nonextensive quantum statistics and effectively to avoid the factorization difficulty in the power-law grand canonical distribution.