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In the automotive industry one of the crucial issues is reduction of CO 2 emission to protect environment. A lot of researches have been done to reduce the CO 2 emission of cars by improving efficiency of engine and engine parts or lowering the weight. However, a significant reduction of CO 2 emission of cars can also be obtained from improvement of efficiency of transmission by reducing drag torque or spin loss in disengaged wet clutch. The reduction of drag torque can be achieved by introducing groove on facing of clutch disk and further reduction can be obtained by optimizing the shape of groove. Generally, the optimum shape of groove is decided by trial and error method which requires time, making sample, conducting a lot of tests and wasting a lot of raw materials. In this research, we proposed a new analytical model to predict the drag torque characteristics of a disengaged wet clutch of transmission without making any samples and performing any tests. The feature of the model: It bases on continuity and Navier-Stokes equation, a real time visualization investigation and laminar flow. The model is validated with tests results and the comparison result shows that they are very close to each other. The significance of the model is: it captures the multiphase drag torque characteristic which changes with changing gaps, speeds and oil flow rates. Moreover, the model is a green environment friendly tool to estimate drag torque characteristics without making any samples or conducting any drag tests.

The authors have conducted research regarding ripple formation on an atomically flat cleaved Si surface by low-energy Ar+ ion bombardment. The cleaved atomically flat and smooth plane of a Si wafer was obtained by cutting vertically against the orientation of a Si (100) wafer. Next, the cleaved surface was sputtered by a 1 keV Ar+ ion beam at ion-incidence angles of 0°, 60°, 70°, and 80°. The results confirm the successful ripple formation at ion-incidence angles of 60°–80° and that the wavelength of the ripples increases with the increase of the ion-incidence angle, as well as the inverse of ion doses. The direction of the ripple also changes from perpendicular to parallel to the projection of the ion-beam direction along the surface with the increasing ion-incidence angle. The authors have also observed the dose effects on surface roughness of cleaved Si surface at the ion-incidence angle of 60°, where the surface roughness increases with the increased ion dose. Finally, to understand the roughening mechanism, the authors studied the scaling behavior, measured the roughness exponent α, and compared the evolution of scaling regimes with Cuerno’s one-dimensional simulation results.