Abstract: A multi-stage froth flotation process is provided for concentrating sulphide minerals or middlings containing non-ferrous metal values such as nickel, cobalt and copper, which co-exist with significant amounts of pyrrhotite. The process is carried out without relying on any specific reagent as pyrrhotite depressant, but rather by exploiting the natural pulp environment with low REDOX potentials generated by mild steel grinding media in the grinding step preceding the froth flotation. The concentrate from the flotation stage(s) in which the REDOX potential rises above a predetermined value, is recycled back to the grinding step and/or to preceding flotation stage(s) from which concentrate is collected as the final product or is subjected to an up-grading in a further cleaning stage.

Abstract: An apparatus which simulates signals received by a radar antenna and which is used for teating radar equipment and for training purposes, Two stores are provided to hold the horizontal and vertical polar diagram characteristics of an antenna, respectively. The appropriate values are read out of these stores by signals representing the azimuth and elevation angles of an imaginary target and the antenna, which may be real or imaginary. The outputs from the stores are combined to give a realistic simulated signal. Since the polar diagram characteristics of an antenna may be different for transmission and reception, each store may be provided in duplicate and the outputs from all four stores combined to produce the simulated signal.