Abstract: A spark plug for a gas engine includes a ground electrode body and a center electrode body. A ground electrode of the ground electrode body is welded on a surface of a ground electrode base material opposing to the center electrode body. The ground electrode protrudes toward the center electrode body. The ground electrode is made of a material containing iridium or platinum as a main component. The ground electrode base material is made of a heat-resistant nickel alloy. The ground electrode is impacted in a recess of the ground electrode base material. The spark plug satisfies a condition 0.3?h/H?0.5 when H represents the thickness of the ground electrode base material in an intrusion direction of the ground electrode, and h represents an intrusion length of the ground electrode that defines a length of the ground electrode impacted in the ground electrode base material in the intrusion direction.

Abstract: Each power source switching unit (8) of a electric power system (1) constituted of a power operating system having a power generator (3) driven by an external power source (40) and an engine (4) is constituted of a means for sensing information on a selected power source and supply power in time series, calculating a supply power quantity every power source on the basis of sense data, and storing these sensing and calculated data. This power source switching unit (8), disposed every power load group, comprises a means for communication with another power source switching unit (8). A power source management system, constituted of the power source switching unit (8), comprises a means for transmitting the sensed data or calculated data of each power source switching unit (8) to the control system of the power generating system, a means for receiving data transmitted from the power source management system, and an image display means for displaying the received data by graphing.

Abstract: Each power source switching unit (8) of a electric power system (1) constituted of a power operating system having a power generator (3) driven by an external power source (40) and an engine (4) is constituted of a means for sensing information on a selected power source and supply power in time series, calculating a supply power quantity every power source on the basis of sense data, and storing these sensing and calculated data. This power source switching unit (8), disposed every power load group, comprises a means for communication with another power source switching unit (8). A power source management system, constituted of the power source switching unit (8), comprises a means for transmitting the sensed data or calculated data of each power source switching unit (8) to the control system of the power generating system, a means for receiving data transmitted from the power source management system, and an image display means for displaying the received data by graphing.

Abstract: A spark plug for a gas engine includes a ground electrode body and a center electrode body. A ground electrode of the ground electrode body is welded on a surface of a ground electrode base material opposing to the center electrode body. The ground electrode protrudes toward the center electrode body. The ground electrode is made of a material containing iridium or platinum as a main component. The ground electrode base material is made of a heat-resistant nickel alloy. The ground electrode is impacted in a recess of the ground electrode base material. The spark plug satisfies a condition 0.3?h/H?0.5 when H represents the thickness of the ground electrode base material in an intrusion direction of the ground electrode, and h represents an intrusion length of the ground electrode that defines a length of the ground electrode impacted in the ground electrode base material in the intrusion direction.

Abstract: Pitch substantially free from primary and secondary QI components and solids comprising secondary QI components are prepared by centrifuging coal tar or coal tar pitch at a high temperature, heat-treating the separated supernatant liquid and centrifuging again the liquid at a high temperature.