A method for protecting powder metallurgy alloy elements from oxidation andor hydrolyzation during sintering. and are plastically deformable at room temperature. A novel feature of the central segment or central segment group is that its maximum horizontal dimension significantly exceeds the height of the just-mentioned horizontal bar and the thickness of the arms of any displayable addition symbol. In one aspect, sensors such as gyroscopes output camera movement data, which a controller uses to rotate the curved image sensor about its center of curvature, e. A reflective layer prevents light emerging from the second face. When the pressure sensing signal and the touch sensing signal are generated, the control unit outputs a first clicking signal representing that the first side is clicked.