Abstract: A method for producing pig iron using a blast furnace comprising a tuyere, the method including: charging a first layer containing an iron ore material and a second layer containing coke alternately in the blast furnace; and reducing and melting the iron ore material in the stacked first layer while injecting an auxiliary reductant into the blast furnace by hot air blown from the tuyere, in which: the iron ore material contains a plurality of reduced iron molded products obtained by compression molding reduced iron; the reduced iron molded product is in a rectangular shape chamfered in a plan view, having on both faces a bulge resulting from a center portion being thicker than a peripheral portion; and a length ratio of a longer side to a shorter side of the reduced iron molded product in the plan view is less than or equal to 1.5.

Abstract: In a bass intensifying device for a speaker system, a passive radiator (5) constructed by a speaker having a voice coil (7) is disposed at a location where it receives a sound pressure from a main speaker (1) driven by a main amplifier (4). A motion feed-back circuit independently of the main amplifier (4) for driving the main speaker (1) is connected to this passive radiator (5). Since the motion feed-back circuit is closed only in the passive radiator (5), it is possible to reinforce the bass while preventing the motion feed-back circuit from degrading the sound quality of the main speaker (1). The selection of the main amplifier 4 for driving the main speaker is free.