Abstract: A UAV landing system can include a landing pad defining a landing area including a target point; a plurality of positioning radio transmitters positioned in a spaced apart relation and equidistant from the target point, each radio transmitter transmitting a ranging signal; and a position determination and aircraft navigation system at the incoming UAV to receive the ranging signals; determine a range to each positioning radio using the received ranging signals; compute a position of the UAV relative to the target point; determine a course for the UAV to a point above the target point of the landing pad; fly the UAV to the point above the target point of the landing pad, and cause the aircraft to descend vertically toward the target point when the UAV reaches the point above the target point.

Abstract: Oil is recovered from a mercury containing oily solids by mixing the solids with at least a treating agent selected from selected from flocculants, sulfidic compounds, demulsifiers, and combinations thereof, and optionally a solvent, forming a mixture. The mixture is then separated to recover a first phase containing treated oil having less than 50% of the original amount of mercury in the oily solids, and a second phase containing treated solids having a reduced concentration of mercury. The oily solids are selected from drilling muds; oily sediments coating inside of pipelines; sediment deposits on crude oil tanks, vessels, and separators; surface coating on equipment; slop oil from upstream operations; oily solids from heavy oil processing operations; solids recovered from processes for removing mercury from hydrocarbon materials; spill clean-up materials; and mixtures thereof.