Abstract: Thus there is provided a method of installing rotor blades of a wind turbine to a rotor hub of the wind turbine. The wind turbine has a tower having a tower longitudinal axis. The rotor hub has a first, a second and a third rotor blade connection. The rotor hub is rotated until the first rotor blade connection is at an angle of 90° or 270° with respect to the tower longitudinal axis. The first rotor blade is lifted substantially horizontally and fixed to the rotor blade connection. The rotor hub is rotated so that the second rotor blade connection is at an angle of 90° or 270° with respect to the tower longitudinal axis. The second rotor blade is lifted substantially horizontally and fixed to the second rotor blade connection. The rotor hub is further rotated until the third rotor blade connection is at an angle of 60° or 300° with respect to the tower longitudinal axis. The third rotor blade is lifted at an angle of ?=30° with respect to a horizontal and fixed to the third rotor blade connection.

Abstract: A method for increasing the wear-resistance of a work piece involves connecting the work piece to a non-formable core material having a greater hardness than that of the work piece material. In order to improve the connection while simultaneously reducing the costs, the core material is connected in a form-fitting manner to the work piece by means of cold extrusion or hot extrusion of the work piece material.

Abstract: A valve disk of silicon-infiltrated silicon carbide material for control elements for regulating liquid flows is suitable in particular for service-water mixer valves. The silicon carbide material contains 70 to 90% by weight of silicon carbide and 8 to 30% by weight of silicon with a content of most 0.2%, by weight of free carbon and contains at most 0.1% by volume of closed pores. The valve disk has a functional surface having the optical appearance in the form of isolated islands of bearing surfaces surrounded by a level lying lever with respect to the isolated islands, the functional surface having the following microtopographical characteristics over its entire region: R.sub.a : 0.02 to 0.80 .mu.m, preferably 0.15 to 0.40 .mu.m; R.sub.t : 0.50 to 6.00 .mu.m,; R.sub.z : 0.20 to 100 .mu.m: flatness: 0.0002 to 0.01 mm; t.sub.pi : 40 to 80% (at 0.3 .mu.m cut depth); t.sub.pa : 10 to 60% (at 0.3 .mu.m cut depth). The invention also relates to a process for producing the valve disk.