“…Andreev's. [14] mathematical model calculates the polarization of the sphere, and the factors affecting effective magnetic charges are determined by an axially magnetized torus. Yuming Gong analyses and concludes that, for better levitation performance of the field distribution, levitation force, and guiding force, the iron shim with 4 mm thickness is the best among 4, 6, and 8 mm iron shims due to decrease in suspension gap, which is experimented in [15].…”