Abstract: An electric field sensor for underwater, including a sensing unit that senses a change in an electric field and transfers a sensing signal of the electric field to a signal line, a waterproof sealing unit that keeps a signal transferring portion of the sensing unit in a waterproof state, and a water-passing protection unit that shields and protects an exposed portion of the sensing unit. The sensing unit includes a nonconductive hollow pipe connected to the signal line, a sheet of carbon fiber that is wound around the outer surface of the hollow pipe and that senses an electric field, and a terminal ring that is electrically conductively installed at an end portion of the sheet of carbon fiber to provide a connection portion of the signal line and that is watertightly sealed by the waterproof sealing unit.

Abstract: An electric field sensor for underwater, including a sensing unit that senses a change in an electric field and transfers a sensing signal of the electric field to a signal line, a waterproof sealing unit that keeps a signal transferring portion of the sensing unit in a waterproof state, and a water-passing protection unit that shields and protects an exposed portion of the sensing unit. The sensing unit includes a nonconductive hollow pipe connected to the signal line, a sheet of carbon fiber that is wound around the outer surface of the hollow pipe and that senses an electric field, and a terminal ring that is electrically conductively installed at an end portion of the sheet of carbon fiber to provide a connection portion of the signal line and that is watertightly sealed by the waterproof sealing unit.

Abstract: Provided is a homogeneous catalytic system for use in preparing an ethylene homopolymer or a copolymer of ethylene and ?-olefin, and more particularly a Group 4 transition metal compound in which a cyclopentadienyl derivative 3,4-positions of which are substituted with alkyls and an electron-donating substituent are crosslinked around a Group 4 transition metal. Also provided is a method of preparing an ethylene homopolymer or a copolymer of ethylene and ?-olefin, having high molecular weight, under high-temperature solution polymerization conditions using the catalytic system including such a transition metal compound and a co-catalyst composed of an aluminum compound, a boron compound or a mixture thereof. The catalyst according to present invention has high thermal stability and enables the incorporation of ?-olefin, and is thus effective in preparing an ethylene homopolymer or a copolymer of ethylene and ?-olefin, having various properties, in industrial polymerization processes.

Abstract: Provided is a homogeneous catalytic system for use in preparing an ethylene homopolymer or a copolymer of ethylene and ?-olefin, and more particularly a Group 4 transition metal compound in which a cyclopentadienyl derivative 3,4-positions of which are substituted with alkyls and an electron-donating substituent are crosslinked around a Group 4 transition metal. Also provided is a method of preparing an ethylene homopolymer or a copolymer of ethylene and ?-olefin, having high molecular weight, under high-temperature solution polymerization conditions using the catalytic system including such a transition metal compound and a co-catalyst composed of an aluminum compound, a boron compound or a mixture thereof. The catalyst according to present invention has high thermal stability and enables the incorporation of ?-olefin, and is thus effective in preparing an ethylene homopolymer or a copolymer of ethylene and ?-olefin, having various properties, in industrial polymerization processes.

Abstract: Provided is a homogeneous catalytic system for use in preparing an ethylene homopolymer or a copolymer of ethylene and ?-olefin, and more particularly a Group 4 transition metal compound in which a cyclopentadienyl derivative 3,4-positions of which are substituted with alkyls and an electron-donating substituent are crosslinked around a Group 4 transition metal. Also provided is a method of preparing an ethylene homopolymer or a copolymer of ethylene and ?-olefin, having high molecular weight, under high-temperature solution polymerization conditions using the catalytic system including such a transition metal compound and a co-catalyst composed of an aluminum compound, a boron compound or a mixture thereof. The catalyst according to present invention has high thermal stability and enables the incorporation of ?-olefin, and is thus effective in preparing an ethylene homopolymer or a copolymer of ethylene and ?-olefin, having various properties, in industrial polymerization processes.

Abstract: Provided are a bridged metallocene compound particularly suitable for copolymerization of ethylene and alpha-olefin or cyclic olefin, a process of preparing the metallocene compound, and a process of preparing polyolefin using the metallocene compound. The bridged metallocene compound has low steric hindrance and good (co)polymerization activity, and thus, exhibits good activity in copolymerization of ethylene and alpha-olefin such as 1-hexene or 1-octene. Furthermore, the process of preparing the bridged metallocene compound is simplified, and thus, suitable for mass production.

Abstract: There are provided a method of simply preparing a 1,4,6-substituted, 1,4-substituted, 1,6-substituted, or 1-substituted fulvene compound, the intermediates of the fulvene compound, and a method of preparing an ansa-metallocene compound in which two cyclopentadienyl ligands are bridged by one carbon and there are substituents only at positions adjacent to the bridging point of a cyclopentadienyl ligand, using the fulvene compound.

Abstract: Provided are a bridged metallocene compound particularly suitable for copolymerization of ethylene and alpha-olefin or cyclic olefin, a process of preparing the metallocene compound, and a process of preparing polyolefin using the metallocene compound. The bridged metallocene compound has low steric hindrance and good (co)polymerization activity, and thus, exhibits good activity in copolymerization of ethylene and alpha-olefin such as 1-hexene or 1-octene. Furthermore, the process of preparing the bridged metallocene compound is simplified, and thus, suitable for mass production.

Abstract: There are provided a method of simply preparing a 1,4,6-substituted, 1,4-substituted, 1,6-substituted, or 1-substituted fulvene compound, the intermediates of the fulvene compound, and a method of preparing an ansa-metallocene compound in which two cyclopentadienyl ligands are bridged by one carbon and there are substituents only at positions adjacent to the bridging point of a cyclopentadienyl ligand, using the fulvene compound.