Based on the forging principle of divided-flow and with the method of secondary divided-flow, the two-stage forming technology of cylindricalstraight inner gear was put forward.

The magnetic particles prepared through coprecipitation suspend stably in the fluid of polydimethylsiloxane after twice dispersing,and so the polydimethylsiloxane based ferrofluid is prepared.

Using the method of quadratic differential,we obtain that the Affine transformation in angle region is not an extremal mapping with its boundary values,and give explicitly an unique extremal Teichmller mapping with the same boundary values as the Affine transformation.

Extraction of impacted mandibular third molars with two times dividing crown;