• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.319-324
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• 2005

This study was carried out for the purpose of proposing the guideline for the non-mischief and comfortable coastal leisure activities to reduce the marine pollution caused by sea fishing and strengthen the marine management and supervision for the fishing activity. In research method, a extensive reference was examined and analyzed, and the questionnaire investigation and field work were carried out to recognize the present conditions and problems concerning the environmental pollution caused by sea fishing. At the same time, the guideline for the safe and comfortable activities was proposed by diagnosing of actual evil conditions of marine environment due to the sea fishing activity and by analyzing of foreign mangement cases. On the basis of these research results, it is useful to contrive a management criteria for the realities investigation on the pollution of coastal activities. It also contributes to develop the regional economy by controlling coastal leisure activities effectively and systematically through the national publicity for the prevention of marine pollution.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.2
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• pp.207-217
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• 2022

The accurate calibration of broadband echo sounders is essential for providing high quality acoustic information for fisheries applications. The increased range resolution of broadband echo sounder systems improves the detection and characterization of targets near boundaries, such as fish near the seabed. Most echo sounder systems are calibrated using tungsten-carbide (WC) spheres. For accurate calibration, it is necessary to select WC spheres of optimized diameters used frequently to calibrate echo sounder systems. For these purposes, the measured and simulated target strength (TS) data for seven WC spheres of different sizes were compared across a bandwidth of 100-200 kHz. The frequency-dependent TS pattern for the specular wave measured from two WC spheres using the fractional Fourier transform was also estimated and analyzed. Comparative results are presented for all the spheres and the best average precision of 0.15 dB was obtained for the 22 mm WC sphere.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.20-21
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• 2016

Aids to Navigation (AtoN) is marine traffic safety facility to facilitate the safe and efficient movement of shipping and enhance the protection of the marine environment by the regulation or guideline of The International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA). By IALA NAVGUIDE, the term "New Danger" is defined as newly discovered hazards not yet shown in nautical documents and includes naturally occurring obstructions such as sandbanks or rocks or man-made dangers such as wrecks. 'New Dangers' should be appropriately marked using Lateral, Cardinal, Isolated Danger marks or by using the Emergency Wreck Marking Buoy. However, the Emergency Wreck Marking Buoy has difficulties with implementation conditions in terms of speed and accuracy to install the buoy. In case of sinking accidents, it is difficult immediately to install the Emergency Wreck Marking Buoy because of weather conditions, marine environments and accident position. This paper studies Auto Releasing New Danger Mark Buoy on the deck which can be automatically to release from the deck of a vessel and float in the water and quickly install the accident position in case of sinking accidents. The buoy will be to reduce the risk of navigation and prevent secondary collisions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.810-819
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• 2017

The purpose of this study is to evaluate port use and the distribution of risk factors in 15 major ports in Korea, delineating the risk of each port after classifying the ports into four risk groups based on estimated risks. The placement of response vessels is then analyzed accordingly. Based on the results, danger was estimated to be especially high in ports where large-scale petrochemical facilities are located, such as Yeosu Gwangyang ports (1.85), Ulsan port (1.33) and Daesan port (1.25). The ports showing the next highest degree of danger were Pusan (0.95) and Incheon (0.83), which have significant vessel traffic, followed by Mokpo (0.71) and Jeju (0.49), which expanded their port facilities recently and saw an increase in large vessel traffic. Next is Masan (0.44), for which many fishing permits in the vicinity. When the relative ratios of each port were graded based on the Yeosu Gwangyang Ports, which showed the highest risk values, and risk groups were classified into four levels, the highest risk groups were Yeosu Gwangyang, Ulsan, Daesan and Pusan, with Incheon, Mokpo, Jeju, and Masan following. Pyeongtaek Dangjin, Pohang, Gunsan, and Donghae Mukho were in the mid-range danger group, and the low risk groups were Samcheonpo, Okgye, and Changsungpo. Among these, all response vessel placement ports specified by current law were above the mid-range risk groups. However, we can see that ports newly included in mid-range risk group, such as Mokpo, Jeju, and Donghae Mukho, were excluded from the pollution response vessel placement system. Therefore, to prepare for marine pollution accidents these three ports should be designated as additional response vessel placement ports.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.1
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• pp.16-25
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• 2015

Visual census and hydro-acoustic survey was carried out at Ulju small scale marine ranching area (MRA) to estimate demersal fish aggregations on September and November 2013. In this hydro-acoustic survey, the authors combined an image sonar with a scientific echo sounder to monitor an underwater situation and compare two acoustic data. Consequently, visual census survey was useful to estimate fish species composition for hydro-acoustic survey, because it is easy to identify aggregated fish species and overcome limits on a fishing depth and ability of an conventional fishing gear like a bottom gill-net or a fish trap at marine ranching area. Mean fish density was estimated as $0.757g/m^2$ on September and $0.219g/m^2$ on November and Fish abundance was finally calculated as 1.51ton (coefficient of variation, CV=13.1%) on September and 0.44ton (CV=47.7%) on November, respectively. Hydro-acoustic survey combined with the image sonar was useful to monitor fish aggregations and estimate fish stocks around artificial reefs at shallow coastal MRA. We were able to easily identify the underwater structures like an artificial reef and a fishing rope as well as fish aggregations from image sonar data. Therefore, the method was effective to separate unwanted echo signals in acoustic data of scientific echo sounder.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.1
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• pp.29-37
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• 2011

PIV measurements of the velocity field, pressure field, vorticity, and turbulent intensity in the rear of curved section of an oil fence with current speed showed that the flow directions in the rear of flow boundary area were similar to those in the front of it. As the current speed increased, the patterns of pressure distribution were changed, and the turbulent flow became more irregular. CFD simulations under the same conditions as the PIV tests showed that the flow patterns of the wake were similar to those by PIV tests in speed of 0.3 m/s and less, but were distinctively deviated from those in 0.4 m/s due to the flexibility of the oil fence, which was not properly taken care of in CFD modeling.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.2
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• pp.106-112
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• 2022

As a series of basic research to draw the pilot design measures for developing the habitat apparatus of Sulculus diversicolor supertexta inhabiting the coastal area of Jeju island, this study conducted a water tank experiment to understand the habitat marine environment of Sulculus diversicolor supertexta and the preference of habitat space focusing on the research fisheries performing the discharge of marine products. In the composition degree of marine algae in both fisheries, Donggwi-ri showed the highest gulfweed (79.3%) as brown algae and there were some coralline algae (17.2%) as red algae. Hansu-ri yielded the highest gulfweed (48.1%) as brown algae, which was followed by sea lettuce (10.4%) as green algae. In the preference of habitat space, the shelter angles 40° showed the highest adhesion as number of 82.9, which was followed by 60° and 70° as 69.2 and 68.2 respectively (P<0.05) by reviewing the environmental characteristics of habit of Salculus diversicolor supertexta in the coastal fishery of Jeju Island, when considering the adhesion rate in each of five shelters with different angles. In the future, there should be continuous research and monitoring for designing the fish shelters suitable for the coastal fisheries of Jeju island, and it would be also necessary to add the field-centered sustainable concrete research.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.2
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• pp.152-159
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• 2017

Rockfish was a commercially important fish specie in marine ranching areas in Korea. To estimate density and biomass of rockfish using acoustic method, target strength (TS) information is required on the species. This study measured TS dependence on tilt angle and size on 14 live rockfish individuals at 38, 70, and, 120 kHz by ex-situ measurement (tethered method) and acoustic scattering model (Krichhoff ray mode, KRM). The swimbladdered angle ranged from 18 to $30^{\circ}$ ($mean{\pm}s.d.=26{\pm}4^{\circ}$). The mean TS for all individuals was highest -35.9 dB of tilt angle $-17^{\circ}$ at 38 kHz, -35.4 dB of tilt angle $-25^{\circ}$ at 70 kHz, and -34.9 dB of tilt angle $-22^{\circ}$ at 120 kHz. The ex-situ TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-67.1$, $TS_{70kHz}=20log_{10}(TL)-68.6$, and $TS_{120kHz}=20log_{10}(TL)-69.9$, respectively. The model TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-66.4$, $TS_{70kHz}=20log_{10}(TL)-67.0$, $TS_{120kHz}=20log_{10}(TL)-67.0$. The two measurements between the ex-situ TS and KRM model for TS-tilt angle and fish size were found to be significantly correlated.

• Strategy21
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• s.43
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• pp.175-199
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• 2018

Recent marine territorial disputes in the East China Sea and the South China Sea have come to us as a great threat. China, which has recently established the China Coast Guard and has rapidly developed maritime security forces, is trying to overcome the various conflict countries with its power. Japan is also strengthening intensively its maritime security forces. Since Korea, China, and Japan are geographically neighboring and sharing maritime space in Northeast Asia, there is no conflict between maritime jurisdiction and territorial rights among the countries. The struggle for initiative in the ocean is fierce among the three coastal nations in Northeast Asia. therefore, Korea needs more thorough preparation and response to protect the marine sovereignty. As the superpowers of China and Japan are confronted and the United States is involved in the balance of power in strategic purposes, the East Asian sea area is a place where tension and conflict environment exist. China's illegal fishing boats are constantly invading our waters, and they even threaten the lives of our police officers. The issue of delimiting maritime boundaries between Korea and China has yet to be solved, and is underway in both countries, and there is a possibility that the exploration activities of the continental shelf resources may collide as the agreement on the continental shelf will expire between Korea and Japan. On the other hand, conflicts in the maritime jurisdictions of the three countries in Korea, China and Japan are leading to the enhancement of maritime security forces to secure deterrence rather than military confrontation. In the situation where the unresolved sovereignty and jurisdiction conflicts of Korea, China and Japan continue, and the competition for the strengthening of the maritime powers of China and Japan becomes fierce, there is a urgent need for stabilization and enhancement of the maritime forces in our country. It is necessary to establish a new long-term strategy for enhancing the maritime security force and to carry out it. It is expected that the Korean Coast Guard, which once said that it was a model for the establishment of China's Coast Guard as a powerful force for the enforcement of the maritime law, firmly establishes itself as a key force to protect our oceans with the Navy and keeps our maritime sovereignty firmly.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.1
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• pp.37-45
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• 2011

Reduction of ship's rolling is the most important performance requirement for improving the safety of the crew on board and preventing damage to cargo as well as improving the comfort of the ride. It is a common experience for mariners, to see that steering with a rudder generally induces rolling of the ship, though the original aim of the rudder is to keep the ship's heading to the required course. At the first stage, when a rudder is steered, usually a ship heels in an inward direction, due to the roll moment acting on the rudder. At the next stage in steering, the main heel may change to an outward. This coupling between rudder and roll motion has become an attractive problem from the point of view of roll stabilization using the rudder, because it is a natural in sight that if the rudder action is skillfully related to the change of roll as well as to the course deviation, the roll can be reduced to a certain degree. The main aim of this paper is to discuss the results of the actual full-scale sea trials carried out on steer gear No.1 and No.1 2, the individual quartermaster and to make clear their statistical properties, using the actual data which included measurement of roll angle, roll rate and the comparative tests were carried out immediately after each other, in order to minimize any statistical variation in sea conditions. It can be concluded that the steer gear No. 1 2 reduced the roll motion on average by about 21% in comparison with the No.1 and confirmed the some difference as per a ability of quarter-master's maneuver.