Abstract: To provide a zirconia mill blank for dental cutting and machining which has excellent machinability in a thin workpiece such as an inlay, an onlay and a veneer, and may impart high strength and high translucency to a zirconia perfect sintered body without a special sintering such as HIP treatment, and a preparing method thereof. The zirconia mill blank for dental cutting and machining has a porosity within a range of 15 to 30%.

Abstract: To provide a zirconia mill blank for dental cutting and machining which has excellent machinability in a thin workpiece such as an inlay, an onlay and a veneer, and may impart high strength and high translucency to a zirconia perfect sintered body without a special sintering such as HIP treatment, and a preparing method thereof. The zirconia mill blank for dental cutting and machining has a porosity within a range of 15 to 30%.

Abstract: A deterioration determination unit determines whether a catalyst in an exhaust passage of an engine is deteriorated; a first determination unit determines whether there is an air-fuel ratio variation among cylinders of the engine on the basis of distortion in waveform of the air-fuel ratio on the upstream side of the catalyst; and a second determination unit determines whether there is an air-fuel ratio variation among the cylinders on the basis that the air-fuel ratio on the downstream side of the catalyst remains on the lean side. A determination mode switching unit makes the first determination unit execute a determination process concurrently with determination by the deterioration determination unit, and it is determined by the determination process that there is an air-fuel ratio variation among the cylinders, makes the second determination unit execute a determination process in priority to determination of deterioration of the catalyst.

Abstract: During normal engine operation, a temporary determination mode is executed in which whether or not there is an air-fuel ratio variation among cylinders is determined on the basis of distortion in output waveform of an LAF sensor, concurrently with determination of deterioration of a three-way catalyst, under a control condition of normal learning sensitivity of the learned value of a stoichiometry correction factor. If it is determined in the temporary determination mode that there is an air-fuel ratio variation, the determination mode is switched to a main determination mode and the learning sensitivity of the learned value of the stoichiometry correction factor is set to the sensitive side to determine whether or not there is an air-fuel ratio variation among the cylinders with higher reliability on the basis of the learned value of the stoichiometry correction factor (=the value of an enrichment process counter C2) which increases rapidly due to the air-fuel ratio variation among the cylinders.