how do owen and riggs know each other
Nathan Riggs Nathan Riggs is introduced in the sixth episode of the show's twelfth season as a new cardio attending at Grey-Sloan Memorial. It is quickly learned that he and Owen Hunt (Kevin McKidd) had been friends, but that their friendship ended acrimoniously. It is later revealed that Nathan and Owen's feud was caused by the disappearance of Owen's sister, Megan. Megan, who had been engaged to Nathan at the time of her abduction, had discovered Nathan's infidelity before running off and ultimately getting kidnapped. Owen has long blamed Riggs for the fate of his sister, who has been presumed dead for 10 years now. However, as time goes on, Nathan and Owen learn to work together and eventually tentatively reinstate their friendship.
Kinematic pair A lower pair is an ideal joint that constrains contact between a surface in the moving body to a corresponding surface in the fixed body. A lower pair is one in which there occurs a surface or area contact between two members, e.g. nut and screw, universal joint used to connect two propeller shafts. Cases of lower joints: