Abstract: A light-emitting diode element includes a semiconductor substrate having a first surface and a second surface on a side opposite to the first surface, a semiconductor lamination portion formed on the first surface of the semiconductor substrate, a first electrode connected to a part of the semiconductor lamination portion on the semiconductor substrate side, and a second electrode connected to a part of the semiconductor lamination portion on a side opposite to the semiconductor substrate. The semiconductor lamination portion includes an n-type semiconductor layer, an active layer having a p-type conductivity and laminated on the n-type semiconductor layer, and a p-type semiconductor layer laminated on the active layer on a side opposite to the n-type semiconductor layer. The active layer has a multiple quantum well structure constituted of barrier layers including AlInAs and well layers including InAsSb alternately laminated therein.

Abstract: The spark plug includes: an insulator having an axial hole extending in an axial direction; a center electrode disposed at a front end in the axial direction of the axial hole and having a front end portion that protrudes from a front side of the axial hole; a tubular metal shell holding the insulator; and a ground electrode having one end portion that is fixed to a through hole provided in the metal shell, the ground electrode having another end portion that forms a discharge gap between the other end portion and the front end portion of the center electrode. The through hole extends toward the front side in the axial direction, in a direction from an outer peripheral surface toward an inner peripheral surface of the metal shell. The one end portion is located on a rear side relative to the other end portion in the axial direction.

Abstract: This spark plug inhibits excessive increase in the temperature of a ground electrode to inhibit occurrence of pre-ignition. The spark plug includes: an insulator in which an axial hole extending in an axial line direction is formed; a center electrode disposed at a front end in the axial line direction of the axial hole and having a front end portion that protrudes from a front side of the axial hole; a tubular metal shell holding the insulator; and a ground electrode having one end portion that is fixed to a through hole provided in the metal shell, the ground electrode further having another end portion that forms a discharge gap between the other end portion and the front end portion of the center electrode. The through hole extends toward the front side in the axial line direction, in a direction from an outer peripheral surface toward an inner peripheral surface of the metal shell. The one end portion is located on a rear side relative to the other end portion in the axial line direction.

Abstract: In a grinding wheel truing method of an aspect of the present invention, an outer peripheral surface of a grinding wheel is trued while a position of a truer with respect to the grinding wheel is moved from one end side toward the other end side in the axial direction of the grinding wheel. In the truing, a relative movement speed of the truer when a position of the outer peripheral surface of the grinding wheel which grinds a large-diameter portion of a conical surface of a work is trued is lower than a relative movement speed of the truer when a position of the outer peripheral surface of the grinding wheel which grinds a small-diameter portion of the conical surface of the work is trued.