A method of regenerating an acidic catalyst is described. With this axial flow fan motor, when two axial flow fan motors are stacked in the axial direction and either one is selectively used, the blades of the other fan motor that is stopped do not obstruct airflow from the fan motor that is being driven. The method further comprises the steps of determining which specific ones of said criteria match none of the items corresponding to said selected point in the hierarchy and unselecting said specific criteria in said second view. Particular aspects of the present invention are described in the claims, specification and drawings. The image elements, generally having the same length and shape as the monopole elements, are connected to a ground reference potential. The inlet orifice may be configured to reduce the relative velocity loss associated with cooling fluids entering the inlet orifice in the rotor, thereby availing the cooling system to the efficiencies inherent in pre-swirling the cooling fluids to a velocity that is greater than a rotational velocity of the turbine rotor body.