In an antenna feed structure for electrically connecting a rotatable antenna to a circuit formed on a circuit board by means of a feeding metallic part, an antenna rotary shaft formed so as to protrude from one end of the antenna and formed of a conductor has a preferably spherical end. The industrial rack system is therefore well suited for storage facilities in which it is not possible or not desired to level an otherwise unleveled floor. The coupling structure includes first, upper coupling elements, which are located on the frame structure, second, lower coupling elements, which are hingedly connected to the frame structure, and connecting elements that are hingedly located on lifting arms of the lifting shaft. The method further includes obtaining the LUT at the determined VRR of the input signal and adjusting the input signal to produce an output signal that compensates for the brightness change for each pixel or sub-pixel in a timing controller based upon the LUT at the determined VRR. The outer ceramic layer consists essentially of zirconia stabilized by about 25 to about 75 weight percent yttria, has a thickness that is less than the thickness of the inner ceramic layer, and has a porosity level that is lower than that of the inner ceramic layer. One of the sides of the key is beveled.