A method and system are provided for simulating the metabolic consumption of oxygen contained in a breathable gas. The glass substrate has a through-hole 3 communicating with a front surface and a rear surface of the glass substrate, and filled with a metal material. The request is distributed to processing nodes of the Howard Cascade in a time sequence order in a manner to minimize the time to so expand the Howard Cascade. The flange has a plurality of first mounting holes and the bearing housing has a plurality of second mounting holes corresponding to the first mounting holes, respectively, whereby the stator is bolted to the bearing housing.