Abstract: A method for recovering rare-earth mud including steps of: (A) penetrating a mud gathering pipe into a layer containing rare-earth mud under the seafloor, (B) preparing a slurry containing a rare earth by loosening rare-earth mud in the mud gathering pipe, and (C) transferring the slurry through a mud raising pipe. A rare-earth mud recovery system including: a mud gathering pipe configured to penetrate into a layer containing rare-earth mud under a seafloor; a stirring device configured to loosen rare-earth mud in the mud gathering pipe; and a mud raising pipe connected to the mud gathering pipe.

Abstract: A concave section such as an extension section, a cutting section, and a notch section is provided to receive a lid of a float valve in an inside of outer tube assembly of a drill string. Thus, when the float valve is provided for the drill string, it is made possible to collect a core with a larger diameter by a thinner drill string, by expanding the inner diameter of the drill string.

Abstract: A concave section such as an extension section, a cutting section, and a notch section is provided to receive a lid of a float valve in an inside of outer tube assembly of a drill string. Thus, when the float valve is provided for the drill string, it is made possible to collect a core with a larger diameter by a thinner drill string, by expanding the inner diameter of the drill string.

Abstract: An automatic vessel position holding control method for holding a vessel position and a vessel heading of a vessel on the ocean in order to reduce a positional deviation and a heading deviation sharply as compared with the conventional automatic vessel position holding control by performing feedforward control for estimating and then compensating for at least one of a wave drifting force and a wave drifting moment that act on the vessel, wherein a vessel position holding control is performed that includes such controls as estimating waves entering the vessel from motion thereof, calculating at least one of the wave drifting force and the wave drifting moment from the estimated waves and performing feedforward control for at least one of the calculated wave drifting force and the calculated wave drifting moment.

Abstract: An automatic vessel position holding control method for holding a vessel position and a vessel heading of a vessel on the ocean in order to reduce a positional deviation and a heading deviation sharply as compared with the conventional automatic vessel position holding control by performing feedforward control for estimating and then compensating for at least one of a wave drifting force and a wave drifting moment that act on the vessel, wherein a vessel position holding control is performed that includes such controls as estimating waves entering the vessel from motion thereof, calculating at least one of the wave drifting force and the wave drifting moment from the estimated waves and performing feedforward control for at least one of the calculated wave drifting force and the calculated wave drifting moment.

Abstract: An automatic vessel position holding control method for holding a vessel position and a vessel heading of a vessel on the ocean in order to reduce a positional deviation and a heading deviation sharply as compared with the conventional automatic vessel position holding control by performing feedforward control for estimating and then compensating at least one of a wave drifting force and a wave drifting moment that act on the vessel, wherein a vessel position holding control is performed that includes such controls as estimating waves entering the vessel from motion thereof, calculating at least one of the wave drifting force and the wave drifting moment from the estimated waves and performing feedforward control for at least one of the calculated wave drifting force and the calculated wave drifting moment.