In a RAID system, the power supplied to hard disks can be increased, and a plurality of types of HDDs can be installed. An inner imbalance load inherently developing in the pumping chambers is suppressed or canceled by an outer imbalance load generated by pressurizing fluid introduced into blade ditches formed on an outer periphery of the outer gear. 2 moles acid equivalents per kg powder;extruding the extrudable dough to form extrudates;drying and calcining the extrudates;impregnating the extrudates with an aqueous solution of a nickel compound;drying, calcining and reducing the impregnated extrudates. Additional aspects provide novel ultra-sensitive devices and methods using same for measuring ammonia in air or solution. The wedge portion passes through ring block, spring and pin casing so as to combine those together.