Nanoscale corundum powders are obtained by first producing an Al2O3 precursor by adding seed crystals to an aqueous solution of an aluminium compound and adding a base and then converting the Al2O3 precursor into corundum by calcination at a high temperature. , the product of 55 Gauss \u03bcm or more of a remnant magnetic flux density and a film thickness, and includes at least a transition metal-rich rare earth-transition metal amorphous alloy layer and a rare earth-rich rare earth-transition metal amorphous layer. For at least a first set of operations that has a start operation and an end operation, the method assigns a particular operation in the first set to a first operational cycle based at least partially on the position of the particular operation with respect to the start and end operations. The method further includes flowing oil between oil sumps of the at least three compressors and along the separate connections to tend to equalize the oil levels among the oil sumps of the at least three compressors.