A social networking system includes a question and answer system that displays to a viewing user questions and answers provides by other users of the social networking system. A symmetric multiprocessor data processing system includes multiple processing units. Then, as the network receives a set of data packets, a micro-flow comprising the set of data packets is defined. By way of example, the rotary nut 14 has an outer peripheral surface formed with an annular protrusion 33 of a arcuate longitudinal sectional shape, having a surface thereof formed with a plurality of axially extending surface indentations 33a arranged side by side in a direction circumferentially of the rotary nut 14. More specifically, the present invention relates to a ring-type piezoelectric ultrasonic motor that is driven by a frictional force between rotor and stator, and stator is produced a mechanical displacement by a piezoelectric ceramics applying an alternate electric field with an ultrasonic frequency.