Experimental and Theoretical Analysis of the Drag Torque in Wet Clutches

Traditional mathematical models cannot predict and explain the phenomenon by which the drag torque(DT)in wet clutches rises in the high-speed zone.In order to evaluate the DT in such conditions,a two-phase air-fluid mathematical model for a DT with grooves was elaborated.The mathematical model was based on the theory of viscous fluid flow.A two-phase volume of fluid model was also used to investigate the distribution and volume fraction of air and fluid.Experiments on three friction plates with different grooves were conducted to validate the resulting mathematical model.It was found that the gap between plates decreased in the high-speed zone,thereby producing an increase of the DT in the high-speed zone.These results support the understanding of the physical phenomena relating to disengaged wet clutches,and provide a theoretical basis for the future improvement of drive systems.

Nonlinear simultaneous inversion of pore structure and physical parameters based on elastic impedance

Carbonate reservoirs have complex pore structures,which not only significantly affect the elastic properties and seismic responses of the reservoirs but also affect the accuracy of the prediction of the physical parameters.The existing rockphysics inversion methods are mainly designed for clastic rocks,and the inversion objects are generally porosity and water saturation.The data used are primarily based on the elastic parameters,and the inversion methods are mainly linear approximations.To date,there has been a lack of a simultaneous pore structure and physical parameter inversion method for carbonate reservoirs.To solve these problems,a new Bayesian nonlinear simultaneous inversion method based on elastic impedance is proposed.This method integrates the differential effective medium model of multiple-porosity rocks,Gassmann equation,Amplitude Versus Offset(AVO)theory,Bayesian theory,and a nonlinear inversion algorithm to achieve the simultaneous quantitative prediction of the pore structure and physical parameters of complex porous reservoirs.The forward modeling indicates that the contribution of the pore structure,i.e.,the pore aspect ratio,to the AVO response and elastic impedance is second only to that of porosity and is far greater than that of water saturation.The application to real data shows that the new inversion method for determining the pore structure and physical parameters directly from pre-stack data can accurately predict a reservoir's porosity and water saturation and can evaluate the pore structure of the effective reservoir.

Vulnerability of Chinese rural-to-urban migrants to social exclusion:Spatial pattern and mechanism

In response to China’s new“people-oriented urbanization”strategy,investigating the current integration situation of rural-to-urban migrants(RUMs)in cities is essential.However,existing studies have not focused on their subjective willingness and adaptive capacity.Moreover,the mechanism of RUMs’urban integration has not been fully explored.The conceptual framework of vulnerability,which originated from the discipline of natural hazards,is perfectly constructive to address these drawbacks.It consists of three main components,including exposure,sensitivity,and adaptive capacity.Vulnerability index has been constructed and calculated by combining the analytic hierarchy process(AHP)and Delphi method.The spatial pattern of vulnerability level is also analyzed with geographic information system(GIS).Furthermore,the underlying mechanism of vulnerability and its associated factors are investigated with the principle component regression.Three major conclusions are reached.First,the vulnerability level of the RUMs to social exclusion presents a heterogeneous pattern between inland and coastal cities in Shandong Province.Second,while the exposure and sensitivity level of each city correlate spatially with the vulnerability level,RUMs’adaptive capacity further moderates it.Lastly,the level of urban development is revealed to be a key factor influencing vulnerability.This study offers meaningful references to promote inclusive urbanization and sustainable urban development.