Abstract: A polygonal three-dimensional building blocks comprises: a main body having a central area and at least three abutment side walls, the central area located among the abutment side walls; the abutment side walls connected to each other in a ring shape and having a slanted surface respectively, each one of the abutment side walls having a first side edge and a second side edge respectively, the first side edge and the second side edge arranged at two opposite sides of each one of the abutment side wall, the central area located between the first side edges of the abutment side walls, the abutment side walls having an inner surface and an outer abutment surface opposite from each other; the main body having a plurality of magnetic attachment areas; a plurality of magnetic members installed at the magnetic attachment areas.

Abstract: A gas sensing method and a gas sensing system are provided. The gas sensing method includes using a gas sensing device to sense a target gas, the gas sensing device having a self-heating region capable of producing a change in resistance in response to the target gas being sensed by the gas sensing device, and controlling a change in supply of current or voltage to the gas sensing device according to the change in resistance, so that the gas sensing device is substantially maintained operating at a predetermined temperature for sensing the target gas.

Abstract: A gas sensing method and a gas sensing system are provided. The gas sensing method includes using a gas sensing device to sense a target gas, the gas sensing device having a self-heating region capable of producing a change in resistance in response to the target gas being sensed by the gas sensing device, and controlling a change in supply of current or voltage to the gas sensing device according to the change in resistance, so that the gas sensing device is substantially maintained operating at a predetermined temperature for sensing the target gas.