Abstract: For the problem of difficult roof anchor withdrawal at the end of a working face, a static crushing directional anchor withdrawal method at the end of a large-mining-height working face is provided. The method includes the following steps: designing key parameters of boreholes for static crushing, including a borehole position, a spacing between boreholes, a borehole depth, and a borehole diameter at the end of a working face; then determining parameters of a static crushing agent grouting technology device for the construction of a static crushing process; and carrying out an anchor withdrawal operation at the end.

Abstract: Polishing slurries for use in polishing substrates having a nickel or nickel-containing surface, such as those used for magnetic media, are described. The slurries include, in addition to a chemical etchant such as aluminum nitrate and suspended abrasive particles, an oxidizer which converts nickel metal at the surface to nickel oxide, but does not solubilize the nickel oxide in the aqueous medium to any significant degree. Preferred oxidizers include hydrogen peroxide, ferric nitrate and potassium iodate.