There is provided self piercing rivet comprising a substantially planar metal body portion having deformable tabs symmetrically disposed about a slit as per the first embodiment. The system includes a database and a server including a processor. The frequency of the magnetic writing pulse signal and the frequency of a driving pulse signal of the stepper motor are in a linear relationship. The cyclonic airflow chamber causes the suction airstream to travel in a cyclonic path such that the entrained contaminants are separated therefrom and deposited into a dirt container that defines the chamber. A battery module 200 has a configuration in which a plurality of cells 100 as secondary batteries are housed in a case 90 having a plurality of housing parts housing, but not in contact with, the cells 100, and when a gas is generated in one of the cells 100 to cause the cell 100 to expand, this cell 100 comes into contact with the associated one of the housing parts.