1. Three dimensional characterization of grinding surfaces is measured, the heights of summits follow the Gaussian distribution.
2. An apparatus is designed to measure real contact area.
3. Relation between real contact area and normal load is measured.
4. The statistical characteristics of atomic friction are illuminated.
5. A semi-analytical model is advanced for the friction of nanosized asperity
6. Dependence of frictional coefficient on load for rough surfaces