• The Journal of Fisheries Business Administration
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• v.24 no.1
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• pp.29-44
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• 1993

The Purpose of this study is to consolidate the management status of Saggoson in the Choson period by literature research, and examined latest status by field investigation. During the Choson period, there were fish distributors such as Saggoson and Kakju. Saggoson took charge of fish distribution from the fishing ground to the land, and handed over the fish to Kakju who sold over them to the whole country: This distibution system of fish was started from and adapted to the yellow-corvenia fishery of Westhern Sea. There were two resons far this. One was that these fish were. caught much from vast fishing grounds and had a very strong demand, for which professional disributors were needed. The thor was that because fishermen had very limited capital, they had to supply the money for fish production from capitalists like Kakju whom they agreed to sell fish directly to. By this time, it was thought that the fish distibution system for the Westhern Sea fishery was determined by the background and tradition. Meanwile, Saggoson, which has been working far a long time in Westhern Sea, is placed in changing circumstances. That is, small scale fishery Saggoson deals with will be getting fewer, because the big scale reclamation projects in this area threatens the fishery's existence. Also, Saggoson, presently, might be forced to become more efficient in its distribution in the future. In this situation, the management status of a Sggoson in the past and present needs to be consolidated and investigated through this study.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.6
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• pp.489-494
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• 2014

Estimation of correct ice load under various operating conditions is important during the design and the operation stages of an icebreaker. Normal operating conditions are expected from the official field ice trials and also from general ice transit action. In this paper ice load for the Korean icebreaking research vessel, ARAON, under normal operating condition, is discussed. Published ice load data from full-scale sea trials of six icebreakers were analysed to derive an empirical ice load prediction formula. The IBRV ARAON had sea ice trials during 2010 and 2012 summer season. Strain gauge signal were recorded during her icebreaking voyage and the measured strain data were converted to the equivalent hull stress values. The effect of ARAON's speed in ice and the hull stresses are investigated. By comparing the empirical formula and ice load calculation based von measured data, it is recommended to use the empirical ice load estimation formula for the initial design stage.

• Journal of the Korean earth science society
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• v.24 no.1
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• pp.7-21
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• 2003

The state-of-art third generation wave prediction model WAM was applied to the Korean seas for a winter monsoon period of January 1997. The wind field used in the present study is the global NSCAT-ERS/NCEP blended winds, which was further interpolated using a bi-cubic spline interpolator to fine grid limited area shallow water regime surrounding the Korean seas. To evaluate and investigate the accuracy of WAM, the hindcasted wave heights are compared with observed data from two shallow water buoys off Chil-Bal and Duk-Juk. A detailed study has been carried with the various meteorological parameters in observed buoy data and its inter-dependency on model computed wave fields was also investigated. The RMS error between the observation and model computed wave heights results to 0.489 for Chil-Bal and 0.417 for Duk-Juk. A similar comparison between the observation and interpolated winds off Duk-Juk show RMS error of 2.28 which suggest a good estimate for wave modelling studies.

• Journal of the korean society of oceanography
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• v.32 no.1
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• pp.1-7
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• 1997

Surface current fields in the eastern East China Sea (ECS) were constructed by analyzing trajectories of 58 satellite-tracked surface drifters released during 1991-1996. Composite trajectories and 20-minute-by-20-minute box-averaged current vectors show that the basic current pattern composes of: the Kuroshio main stream, which turns eastward toward the Tokara Strait; a northward branch current of the Kuroshio on the ECS outer shelf deeper than 100 m; and an anticyclonic circulation in the northern Okinawa Trough west of Kyushu. The northward branch current sharply changes its direction to the northeast when it crosses a line connecting Cheju Island, Korea and Goto Islands, Japan. The basic pattern of current field changes slightly from winter to summer, and the main axis of the Tsushima Current in the Korea Strait is found to shift seasonally. The drifter experiment does not support the claim that the Yellow Sea Warm Current is separated from the northward branch current on the outer shelf southeast of Cheju Island. We suggest that the use of the term 'Tsushima Current' be limited to the northeast channel flow in the Korea Strait. The new term 'Kuroshio Branch Current' is suggested for the northward branch current on the outer shelf south of Cheju-do, which is separated from the Kuroshio.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.29-39
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• 2010

By understanding the construction process of sea dikes and the current state of the thickness and speed of fluid in the bottom layer protection work of final closure gaps, a construction method applicable for the blocking of bottom layer work will be selected. The three construction methods selected will be tested in site through various methods, and the reinforcement of bottom layer protection and impervious effect will be verified. The verification results are as follows: 1) The overall riprap layer were 0.5~1.0m thicker than planned so that the grouting depth and grout input amount increased 2) The applied construction methods permeability of riprap layers were improved from $\alpha{\times}10^{-2}cm/s$ before the construction to $\alpha{\times}10^{-4}cm/s$ after construction. 3) The results of core extraction in order to grossly verify the hardening time and durability allowed the identification of grout injection effect. The amount of filling of the injection was difficult to judge because the slime in many areas made the reading of borehole photography difficult.

• Korean Journal of Remote Sensing
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• v.28 no.1
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• pp.95-100
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• 2012

Big swell is often generated offshore and damages the coasts after travelling long distance. In order to prevent coastal damages, wave measurements should be performed offshore as well as coastal waters around Korea. However, in-situ wave measurements are difficult because of high expense of instruments and high risk of operation. Satellite wave measurements using altimeter make it possible to get wave information from the sea difficult to execute field measurements such as the center of the East Sea or exclusive territorial waters. In order to use wave information from the satellite altimeter, it is important to verify altimeter wave data with in-situ data. This paper examines significant wave height data observed by ENVISAT altimeter by comparing wave data observed at Ieodo station.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.711-714
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• 2002

At the lift-off condition, the combustion and Jet noise of launch vehicle produces a severe acoustic environment and the acoustic loads may be damaging to paylaod and equipments. Prediction of the acoustic environment is thus needed to support the load-resistive design and test-qualification of components. Currently, such a high frequency problem is usually dealt with by using the SEA technique, for which the assumptions should match reasonably well with the vibro-acoustic condition of system. The subsystems of SEA model was composed of 16 flat plates, 8 L-shaped beams, and 2 acoustic cavities. The frequency range was 400 Hz - 4 kHz considering the modal parameter. The experiment was performed in a high intensity acoustic chamber, in which the diffuse acoustic field was assured. By comparing the SEA analysis and the experiments, the error less than 5 dB was observed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.4
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• pp.360-367
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• 2013

The mesh selectivity of the gillnet for Pacific herring (Clupea pallasii) was examined in field experiments with four different mesh sizes (63, 69, 75 and 81mm) from June to July, 2013 in the coastal areas of Imwon in Gangwon province. The fishing performance tests were conducted with a commercial Pacific herring gillnet and a biodegradable gillnet for Pacific herring together selectivity tests. The filed tests were carried out the total 11 times. The master curve of selectivity was estimated by the extended Kitahara's method. In the results, the catch number of Pacific herring was 9,409 (2,203kg) and occupied 84.2% in total catches weight. The optimal mesh size for 50% retention on first maturity size (female, 250mm) of Pacific herring was estimated as 64.5mm by master selectivity curves. The fishing performance of the biodegradable gillnet was showed to be equivalent with commercial gill for Pacific herring.

• The Journal of Korea Robotics Society
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• v.15 no.1
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• pp.16-23
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• 2020

This paper describes an alignment algorithm that estimates the initial heading angle of AUVs (Autonomous Underwater Vehicle) for starting navigation in a sea area. In the basic dead reckoning system, the initial orientation of the vehicle is very important. In particular, the initial heading value is an essential factor in determining the performance of the entire navigation system. However, the heading angle of AUVs cannot be measured accurately because the DCS (Digital Compass) corrupted by surrounding magnetic field in pointing true north direction of the absolute global coordinate system (not the same to magnetic north direction). Therefore, we constructed an experimental constraint and designed an algorithm based on extended Kalman filter using only inertial navigation sensors and a GPS (Global Positioning System) receiver basically. The value of sensor covariance was selected by comparing the navigation results with the reference data. The proposed filter estimates the initial heading angle of AUVs for navigation in a sea area and reflects sampling characteristics of each sensor. Finally, we verify the performance of the filter through experiments.

• Ocean and Polar Research
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• v.36 no.4
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• pp.367-371
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• 2014

In early 1990s, the Korean government has launched a deep-sea research program to secure the stable long-term supply of strategic metallic minerals including Cr, Cu and Ni. Through the pioneering surveys, Korea registered $150,000km^2$ of Mn-nodule field in the Clarion-Clipperton area, the NE equatorial Pacific to the international sea-bed authority (ISA) in 1994. Following the ISA exploration code, the final exclusive exploration area of $75,000km^2$ was assigned in 2002, based on results of eight-year researches of chemico-physical properties of nodules, bottom profiles and sediment properties. Since that time, environmental studies, mining technical developments including robot miner and lifting system and establishment of smelting systems were accompanied with the detailed geophysical studies to decipher the priori mining area until 2009. Major points of the recent Korea Mn-nodule program are deployed on a commercial scale until 2015. In order to meet the goals, we developed a 1/5 scaled robot miner compared to commercial one in 2012 and performed a mining test at the water depth of 1,370 m in 2013. In addition, detailed 25,000 scaled mining maps in the priori area, which can provide operation roots of the miner, will be prepared and an environmental-friendly mining strategy will be pursued based on the environmental impact test and environmental monitoring.