A polished glass disk medium substrate suitable for use as a substrate for a hard disk, a hard disk containing the substrate and methods for making the substrate. Together with measurements of cathode temperature, such measurements of cathode fall may inform a determination of cathode heater voltage as a function of discharge current that avoids both sputtering and excess-evaporation. The first conducting strip protrudes rearward from the cover plate and is configured to contact a first terminal of a receptacle, where the first terminal connects the receptacle to a power source. The inflatable member is mounted against the vehicle wheel rim. The simulated wastewater may be transferred to the simulated wastewater treatment plant through a simulated sewage pipeline network. As the result, when the hand strap 4 which is made of conductive material and is formed into a ring shape, is attached, the hand strap 4 and the antenna element 2 are electro-magnetically coupled, and thereby, the antenna has a high gain.