The present invention relates to novel cephalosporin derivatives represented by Chemical Formula 1. The method includes initiating a job and determining that a printer job channel is not available. A rack is mounted to the frame so as to be vertically movable, and a pair of cross members are mounted to the rack so as to be horizontally movable. A positioning unit sets the image writing unit in the first position and includes a first restriction member, a second restriction member, a third restriction member, and a restriction releasing portion. A groove 26 is provided in the basic body 20 in order to reduce the stress concentration in the region of the joint F. The SSJoin operator can exploit the observation that set overlap can be used effectively to support a variety of similarity functions.