Principles of Tribology is a compilation of current developments from the tribology research results with tribology fundamentals and applications, including lubrication theory, lubrication design, friction mechanism, wear mechanism, friction control, and their applications. Besides classical tribology content, the book also covers intersecting research areas of tribology, as well as the regularities and characteristics of the tribological phenomena in practice. Furthermore, it presents the basic theory, numerical analysis methods and experimental measuring techniques of tribology as well as their application in engineering. The tribological processes in nano-tribology results in the following: Thin film lubrication and its applications.