An automatic transmission includes a thrust bearing \u03b1 disposed between a third sun gear of a third planetary gear mechanism and a second sun gear of a second planetary gear mechanism. The process comprises the steps of forming a supercritical solvent containing ions of an alkali metal in an autoclave; and dissolving a feedstock in this supercritical solvent to form a supercritical solution, and simultaneously or separately crystallizing aluminum nitride on the face of a crystallization seed. Based on the designated characteristics, the new user profile is associated with a particular Vornoi cluster region of existing user profiles.