Reduction in power output or rotor speed of a wind turbine above a defined limit value, the reduction not being implemented based on the measured wind speed, but on an input value which on one hand is easily detected physically and by control technology and on the other hand is a good indicator of mechanical stresses on the wind turbine. In the semiconductor layer, trenches extending between two neighboring source regions are formed by digging from the source of the semiconductor layer, the inside surface of the trenches are covered by the gate insulating film, and the gate electrodes comprise surface-facing parts, which face the surface of the semiconductor layer, and buried parts, which are buried in the trenches. The data owner can maintain a vector associated with query results returned by the server and can generate a verification synopsis using the vector and a seed. The partial pressure of oxygen is maintained at 0.