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Kang D.,Maritime Security Research Center | Lim S.,Maritime R and nter | Lee H.,Maritime Security Research Center | Doh J.,Maritime R and nter | And 2 more authors.
Ocean and Polar Research | Year: 2013

The toxic, Harmful Algal Blooms (HABs) caused by the Cochlodinium polykrikoides have a serious impact on the coastal waters of Korea. In this study, the acoustic detection system was developed for rapid HABs detection, based on the acoustic backscattering properties of the C. polykrikoides. The developed system was mainly composed of a pulser-receiver board, a signal processor board, a control board, a network board, a power board, ultrasonic sensors (3.5 and 5.0 MHz), an environmental sensor, GPS, and a land-based control unit. To evaluate the performance of the system, a trail was done at a laboratory, and two in situ trials were conducted: (1) when there was no red tide, and (2) when there was red tide. In the laboratory evaluation, the system performed well in accordance with the number of C. polykrikoides in the received level. Second, under the condition when there was no red tide in the field, there was a good correlation between the acoustic data and sampling data. Finally, under the condition when there was red tide in the field, the system successfully worked at various densities in accordance with the number of C. polykrikoides, and the results corresponded with the sampling data and monitoring result of NFRDI (National Fisheries Research & Development Institute). From the laboratory and field evaluations, the developed acoustic detection system for early detecting HABs has demonstrated that it could be a significant system to monitor the occurrence of HABs in coastal regions.

Oh Y.R.,Gwangju Institute of Science and Technology | Oh Y.R.,Electronics and Telecommunications Research Institute | Kim Y.G.,Gwangju Institute of Science and Technology | Kim Y.G.,Maritime R and nter | And 5 more authors.
IEICE Transactions on Information and Systems | Year: 2011

In this paper, we propose a text corpus design method for a Korean stereo super-wideband speech database. Since a small-sized text corpus for speech coding is generally required for speech coding, the corpus should be designed to comply with the pronunciation behavior of natural conversation in order to ensure efficient speech quality tests. To this end, the proposed design method utilizes a similarity measure between the phoneme distribution occurring from natural conversation and that from the designed text corpus. In order to achieve this goal, we first collect and refine text data from textbooks and websites. Next, a corpus is designed from the refined text data based on the similarity measure to compare phoneme distributions. We then construct a Korean stereo super-wideband speech (K-SW) database using the designed text corpus, where the recording environment is set to meet the conditions defined by ITU-T. Finally, the subjective quality of the K-SW database is evaluated using an ITU-T super-wideband codec in order to demonstrate that the K-SW database is useful for developing and evaluating super-wideband codecs. Copyright © 2011 The Institute of Electronics, Information and Communication Engineers.

Kim K.-P.,Maritime R and nter | Ahmed M.R.,University of The South Pacific | Lee Y.-H.,Korea University
Renewable Energy | Year: 2012

There is a growing interest in utilizing tidal currents for power generation which has led to extensive research on this source of renewable energy. The amount of energy that can be extracted from tidal currents has been a topic of considerable interest to researchers for many years; still, there is no consensus on the extent to which this resource can be exploited. A turbine generates no power if it presents no resistance to the flow or if it presents so much resistance that there is no flow through it. At the same time, the estimation of exploitable resource should take into consideration the environmental, economic and social constraints. In view of these, the design of efficient turbines driven by bi-directional tidal currents has been a challenge to researchers for some time. There appears to be a general agreement among researchers that a number of turbines spread over the width of the channel can extract more energy compared to an isolated turbine. The present work is aimed at quantifying the improvement in the performance of a given type of turbine by utilizing a larger area of the channel. Numerical experiments were performed using the commercial CFD code ANSYS-CFX to study the performance of a bi-directional cross-flow turbine by simulating two cases of i) a single turbine and ii) a number of equally spaced turbines. It was found that the Coefficient of Power can be increased significantly by employing a larger area of the channel. © 2012 Elsevier Ltd.

Kim D.W.,Hanbat National University | Lee H.J.,Inha University | Kim M.H.,Maritime R and nter | Lee S.-Y.,Maritime R and nter | Kim T.-Y.,Maritime R and nter
International Journal of Control, Automation and Systems | Year: 2012

This paper presents a new direct discrete-time design methodology of a robust sampled-data fuzzy controller for a class of nonlinear system with parametric uncertainties that is exactly represented by Takagi-Sugeno (T-S) fuzzy model. Based on an exact discrete-time fuzzy model in an integral form, sufficient conditions for a robust asymptotic stabilization of the nonlinear system are investigated in the discrete-time Lyapunov sense. It is shown that the resulting sampled-data controller indeed robustly asymptotically stabilizes the nonlinear plant. To illustrate the effectiveness of the proposed methodology, an example, a sampled-data depth control of autonomous underwater vehicles (AUVs) is provided. © 2012 Institute of Control, Robotics and Systems and The Korean Institute of Electrical Engineers and Springer-Verlag Berlin Heidelberg.

Kim Y.G.,Maritime R and nter | Kim Y.,Maritime R and nter | Lee S.H.,Maritime R and nter | Moon S.-T.,Maritime R and nter | And 2 more authors.
2016 1st International Workshop on Sensing, Processing and Learning for Intelligent Machines, SPLINE 2016 - Proceedings | Year: 2016

In this paper, an underwater acoustic sensor fault detection method is proposed that determines whether or not each sensor of multi-channel line array hydrophones malfunctions for passive sonar systems. To this end, the proposed method first measures a short-time root mean square (RMS) value of input signal for each channel. Then, it analyzes the RMS difference between the adjacent channels. In addition, the crossing rate of RMS values (RMSCR) is computed for each channel, and then the average value of RMSCR over all the channels is obtained. Some faulty sensors are identified by comparing the RMS difference with a threshold, and others by comparing the ratio between RMSCR of each of them and the average value of RMSCR with a threshold. In order to evaluate the performance of the proposed method, the precision of detecting fault sensors is measured. Consequently, it is shown that the proposed method works well in underwater environments with average RMS of -18.6 and -9.7 dB. © 2016 IEEE.

Song S.H.,Maritime R and nter | Rho S.H.,Korea Aerospace University | Jung C.H.,Korea Aerospace University | Kwag Y.K.,Korea Aerospace University
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2010

Spaceborne SAR (Synthetic Aperture Radar) image inherently contains geo-location errors which are caused by SAR image acquisition geometry, imaging mode, characteristics of reflectivity and image formation process. Since the geo-location error caused by SAR image acquisition geometry is inevitable, these errors are should be considered and corrected during the image formation process. In this paper, a geo-location error correction method is presented to analyze and correct the azimuth skew and ground range non-linearity error, and orientation error. This scheme does not require the aids of GCP and DEM, and instead directly extract the key correction parameters from the SAR raw data. Using RADARSAT-1 image, a simulation is performed to evaluate the proposed geo-location algorithm. To analyze the effect of proposed correction method, the corrected SAR images are compared with the reference image by RMSE values. © 2010 IEEE.

Yoo T.S.,Maritime R and nter | Yoon S.I.,Maritime R and nter
Journal of Institute of Control, Robotics and Systems | Year: 2013

The purpose of this paper is to design a DVL-RPM based VKF (Velocity Kalman Filter) design for a performance improvement underwater integrated navigation system. The proposed approach relies on a VKF, augmented by a altitude from Echo-sounder based switching architecture to yield robust performance, even when DVL (Doppler Velocity Log) exceeds the measurement range and the measured value is unable to be valid. The proposed approach relies on two parts: 1) Indirect feedback navigation Kalman filter design, 2) VKF design. To evaluate proposed method, we compare the results of the VKF aided navigation system with simulation result from a PINS (Pure Inertial Navigation System) and conventional INS-DVL method. Simulations illustrate the effectiveness of the underwater navigation system assisted by the additional DVL-RPM based VKF in underwater environment. © ICROS 2013.

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