Abstract: A smoke detector includes: a casing; a first light emitting unit; a second light emitting unit; and a light receiving unit. A second scattering angle that is an angle between the reception axis of the light receiving unit and a second extension extending from an intersection of the second emission axis and the reception axis in a direction away from the second light emitting unit is larger than a first scattering angle that is an angle between the reception axis of the light receiving unit and a first extension extending from an intersection of the first emission axis and the reception axis in a direction away from the first light emitting unit.

Abstract: A smoke detector includes: a casing; a first light emitting unit; a second light emitting unit; and a light receiving unit. A second scattering angle that is an angle between the reception axis of the light receiving unit and a second extension extending from an intersection of the second emission axis and the reception axis in a direction away from the second light emitting unit is larger than a first scattering angle that is an angle between the reception axis of the light receiving unit and a first extension extending from an intersection of the first emission axis and the reception axis in a direction away from the first light emitting unit.

Abstract: A roll for a hot-dip metal coating bath has a substantially cylindrical shape. At least an outer peripheral surface of the roll is formed of a ceramic material. A relatively coarse groove is formed on the outer peripheral surface of the roll in a direction crossing the rotation axis. A plurality of relatively fine grooves is formed in the bottom surface of the coarse groove along the longitudinal direction of the coarse groove. In place of the fine grooves extending in the longitudinal direction of the coarse groove, a plurality of rows of fine grooves may be formed along the crosswise direction of the coarse groove.

Abstract: It is an object of the present invention to provide a rotor and a method for manufacturing the same that represent an improvement over the prior art. A roll for hot-dip metal coating bath having a body with a substantially cylindrical appearance, at least an outer peripheral surface thereof being formed of a ceramic material, wherein, on the outer peripheral surface of the body, a groove formed in a direction crossing the rotation axis is formed, and in the bottom surface of the groove, a plurality of rows of a fine groove is formed along the longitudinal direction of the groove. In place of the fine groove along the longitudinal direction of the groove, a plurality of rows of a fine groove are formed along the crosswise direction of the groove.