Abstract: The present invention provides a method for preparing spherical carbon comprising step of heat-treating a mixture of a carbon precursor and dispersion media, a spherical non-graphitizable carbon using the same, and a method for preparing spherical artificial graphite.

Abstract: The present invention provides a method for preparing spherical carbon comprising step of heat-treating a mixture of a carbon precursor and dispersion media, a spherical non-graphitizable carbon using the same, and a method for preparing spherical artificial graphite.

Abstract: A user key management method for a broadcast encryption includes assigning node path identifiers (IDs) to nodes arranged in sequence; assigning random seed value keys to the nodes according to the node path IDs; generating key values by repeatedly applying a hash function to the assigned random seed value keys; and assigning the generated key values to the nodes in sequence. Accordingly, it is possible to reduce the transmission overhead that is most important matter in the broadcast encryption to less than the number of the revoked users. Further, there is an advantage that the transmission overhead of the exemplary embodiments of the present invention is remarkably reduced compared with the Subset Difference method.

Abstract: An ornithopter with an airframe structure that is lightweight, simple and stable and can generate sufficient lift and thrust. The ornithopter comprises a body, a main wing attached to an upper portion of a front section of the body, and a tail wing attached to a rear section of the body. The ornithopter further comprises a power source and a power transmission mechanism installed within a housing of the body. The main wing includes a wing frame composed of a plurality of frame rods and a skin attached to the wing frame for forming an outline of the main wing. The wing frame of the main wing is supported by a support means exposed to the outside at the upper portion of the front section of the body. The power transmission mechanism includes a gear train for adjusting the rotational motion of the power source at a proper speed and transferring it to the main wing, and connecting rods for converting the rotational motion into a swing motion of the main wing.

Abstract: Disclosed are copolymers including an alkylene carbonate, and a method of preparing the same. The copolymers are represented by Formulas 1 and 2, and they are prepared with terpolymerized lactide or delta-valerolactone, carbon dioxide, and alkylene oxide, in the presence of a catalyst. (wherein, —O—A— is an opened alkylene oxide structure, the alkylene oxide being selected from the group consisting of ethylene oxide, propylene oxide, 1-butene oxide, 1,1-dimethylethylene oxide, cyclopentene oxide, cyclohexene oxide, 1-phenylethylene oxide, 1-vinylethylene oxide, and 1-trifluoromethylethylene oxide; and x and y are independently an integer being equal to or less than 2,000, n is an integer, and n=(z-x-y), wherein z is an integer being equal to or less than 20,000.).

Abstract: The present invention provides a method for preparing spherical carbon comprising step of heat-treating a mixture of a carbon precursor and dispersion media, a spherical non-graphitizable carbon using the same, and a method for preparing spherical artificial graphite.

Abstract: An ornithopter with an airframe structure that is lightweight, simple and stable and can generate sufficient lift and thrust. The ornithopter comprises a body, a main wing attached to an upper portion of a front section of the body, and a tail wing attached to a rear section of the body. The ornithopter further comprises a power source and a power transmission mechanism installed within a housing of the body. The main wing includes a wing frame composed of a plurality of frame rods and a skin attached to the wing frame for forming an outline of the main wing. The wing frame of the main wing is supported by a support means exposed to the outside at the upper portion of the front section of the body. The power transmission mechanism includes a gear train for adjusting the rotational motion of the power source at a proper speed and transferring it to the main wing, and connecting rods for converting the rotational motion into a swing motion of the main wing.

Abstract: A power-driven ornithopter piloted by a remote controller wherein a takeoff and landing motion, a climbing and descending motion, and a turning motion of the ornithopter can be controlled using the remote controller. The ornithopter comprises a body, a main wing attached to an upper portion of a front section of the body, and tail wings attached to a rear section of the body. An electric motor, a power transmission mechanism, a battery, first and second servo motors and a controller are installed within a housing of the body. A crank arm is connected to a rotating shaft of the first servo motor and a connecting rod attached to a free end of the crank arm is then pivotally connected to a lower edge of the horizontal tail support. The second servo motor is mounted into a recess formed at an upper side of a rectangular parallelepiped of the horizontal tail support and a rotating shaft of the second servo motor is disposed on a central axis of the horizontal tail.

Abstract: Disclosed are copolymers including an alkylene carbonate, and a method of preparing the same. The copolymers are represented by Formulas 1 and 2, and they are prepared with terpolymerized lactide or delta-valerolactone, carbon dioxide, and alkylene oxide, in the presence of a catalyst.

Abstract: A coupling device of synchronous cable for making the frequency to be mutually coincided by connecting a frequency of induced voltage generated from FBT to a set.