The present invention relates to 3 substituted-2, 3-didehydro-2, 3-dideoxy–L-nucleosides and their pharmaceutically acceptable salts and prodrugs thereof, for the treatment of infectious viral diseases, in general, particularly HBV and HIV viral infections and more particularly, HBV and HIV viral infections that are resistant to other antiviral drugs. A fuel economy determination module determines a plurality of fuel economies for each of the trim positions and determines an efficient trim position from the plurality of fuel economies for each of the trim positions. According to the method, the efficiency of removing nutrient salts is excellent and stable even in the treatment of waste water having low content of influent organisms and low CN ratio. Torque current between the power converter and the motor is also controlled to limit a maximum transient DC bus voltage. Furthermore, the invention is applicable to general integrated-circuit processes as well as various ESD protection devices. An indication is entered in a selected packet among the packets in the sequence, other than the final packet, requesting that a recipient of the packets acknowledge the selected packet.