Systems and methods for optimizing marketing strategies. An earth terminal is provided at one edge of the cutout and is brought into elastic contact with an earth contact provided on one side of the circuit board when the circuit board is covered with the metal cover. Additionally, the amount of rank that any particular node can contribute to another node may be capped at a threshold level, thus tending to prevent some nodes from unduly influencing the ranking values. The second voltage generating circuit receives a fan rotary speed signal and generates a second voltage signal according to the fan rotary speed signal.