Abstract:
A directional sonar is provided to effectively find out the position of an object by checking both the size of underwater sound and the direction of a sound source, and to cut down the manufacturing cost due to a simple structure. A directional sonar is composed of a sensing unit having a piezoelectric film(110) for detecting the underwater sound received in the opposite direction and a fixing frame(120) for fixing the edge of the piezoelectric film; a support plate(200) rotatably connected with one end of the sensing unit; and a rotating unit(300) for applying rotating power to the sensing unit. The piezoelectric film is piezoelectric polymer consisting of polyvinylidene fluoride. The fixing frame comprises a fixing part for settling the edge of the piezoelectric film and a rotating part connected to the upper center of the fixing unit and supported to the fixing plate.
Abstract:
PURPOSE: An encoding/decoding method using 17 pp run length limited (RLL) modulation code for an error-correction code parity in a magnetic storage device is provided to minimize damage of a code rate and to improve performance better. CONSTITUTION: An encoding/decoding method using 17 pp run length limited (RLL) modulation code fir an error-correction code parity in a magnetic storage device produces user data and parity when passing user data through a low-density parity check code (LDPC) encoding after the user data passes through a multi track recorder (MTR) encoder. The parity (1,7) is passed through an RLL encoder and a channel at the same time. The parity is restored to be the parity of an LDPC code, and finally passed through an MTR decoder after being passed through an LDPC decoder.