A convertible wheelchair is provided along with a separable lift module for engaging and elevating the convertible wheelchair to a selected elevation. In a specifically preferred system, the air tank fixing structure includes a first air tank fixing member fixed onto a body frame at one side thereof, and formed with at least one first fixing element in which at least one air tank for the vehicle is fixed at the other side; a second air tank fixing member formed with at least one second fixing element and placed on the air tank. Because the magnetic field is substantially normal to the paths of the charged particles, a force is induced on the charged particles normal to both the path and the magnetic field. A further counter weight is mounted to the drive shaft spaced along the drive shaft from the rotating counter weight to impart a counter moment on the drive shaft and essentially cancel the moment about a moment axis perpendicular to the drive shaft resulting from the axial spacing of the piston and the other two counter weights. An explanation for the matching of matched people that references computer-implemented relationships may be delivered. Capture mode violations are recorded from the timing analysis and are used to go back and form new clock domain groups, thereby repeating the method until no capture mode violations are generated.