• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.140-141
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• 2005

This study describes the postinstallation maintenance technology of artificial reefs and their improvement. The maintenance technology of artificial reefs consists of four steps; the investigation of volumes of installed reefs, the removal of fishing gears entangled in reefs, the estimation of reef functions, and the establishment of surveyed results in the data base. The proper understandings of their steps is the key to improve the maintenance technology of artificial reefs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2307-2312
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• 2014

Artificial reef refers to various structures that facility to construction field format and spawning of marine organisms, sea ranch, forest of the sea, and sea jungle artificially in water, Build a production stable base of marine products, thereby contributing to an increase in the income of fishermen. In the management of an artificial reef, the calculation of the number of square reefs may be that it is a method to perform the submersible is an important part of maintenance is correct. However, cost and diving personnel, depending on the diving situation, there is a difficult thing to implement to coast across the country. Therefore, In this study, We calculated the volume using the multi-beam Echo Sounder and side scan sonar for the reefs of the rectangle are the existing installation. And proposes the improvement of the estimation in accordance with the volume coefficient reef.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.139-147
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• 2022

In this study, we designed a high-strength, low-alkali type cement composite for artificial reef by mixing various binders and evaluated whether it is possible to manufacture it with an ME method 3D printer. As a result of the tests, it is found that it is important to control the water-binder ratio, the silica sand-binder ratio, and the type of silica sand in order to control the fluidity of the cement composites to enable 3D printing. The surface quality of 3D printer output can be achieved by adjusting the amount of viscosity agent added while obtaining printable fluidity. In the cement composites mixing proportion using the alpha-type hemihydrate gypsum, a setting control agent needs to be used to control the quick setting effect. It is also necessary to derive the time to maintain the fluidity, and to apply it when printing. To obtain the required strength, the mix proportion needs to be modified while satisfying the fluidity level of 3D-printable cement composites. In the present study, 3D-printable mix proportions were designed by the use of multi-component binders including alpha-type hemihydrate gypsum a for low-alkali type artificial reefs, and the printability was confirmed. A further study needs to be performed to quantitatively evaluate the alkali reduction effect.

• Ocean and Polar Research
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• v.31 no.4
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• pp.305-318
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• 2009

A marine ranching project in Tongyoung was established in 1998, lasting 9 years to 2006. Project activities included the deployment of artificial reefs, the release of young fishes like jacopever and rockfish, and input/output control for specific marine ranching areas in Tongyoung. This report focuses on the economic feasibility of the project in hindsight. Analysis concentrates on three aspects; (a) direct economic benefits, such as increasing effects of fisheries income and savings in harvesting costs, (b) indirect benefits, including increasing effects of recreational fishing and saving R&D costs, and (c) costs, including releasing and purchasing costs of artificial reef and juvenile fish, R&D costs, maintenance costs and harvesting costs. Results show that NPV=4.7 billion won, IRR=8.55% and B/C ratio=1.286 under Scenario 1, which considers the saving effects of R&D costs, and NPV=0.9 billion won, IRR=6.03% and B/C ratio=1.11 under Scenario 2, which does not consider the saving effects of R&D costs, based on 5.5% of the social rate of discount. According to sensitivity analysis, the economic feasibility is very sensitive to the recapture rate.

• Journal of the Korea Society of Computer and Information
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• v.12 no.5
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• pp.321-326
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• 2007

The contents of reef container face a risk of being damaged if the interior temperature and certain maintenance conditions for the shipments cannot be met. Currently, the temperature and other conditions within a reefer container is checked manually and periodically by someone in charge of it. Since it means that there is no real-time checking of the conditions, if something goes wrong, there is no immediate means of correcting the problem. This paper introduces reefer container monitoring system, that checks interior temperature of container on real-time by sensor nodes attaching reefer container using wireless sensor network. It senses the temperature, amount of light, motion and the change in speed of the objects that distributes sensors throughout the desired places and sends the data wirelessly to anyone interested. Because the prosed technique can check the temperature and other conditions within a reefer container on real-time basis, it enables efficient and effective maintenance of temperature and other conditions

• Spatial Information Research
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• v.16 no.3
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• pp.331-342
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• 2008

The countries are trying to expand the sea limit such as the territorial sea, fishing zone or the exclusive economic zone as far as the Law of the Sea permit to do for the benefit of their national interest. Especially, they are eager to claim the base point where it locates far from the coastline even if it is uninhabited island or reef under the sea. The baseline has been claimed to maximize the territorial sea. Another way to expand the sea limit is to lower the vertical datum to change the land limit. China claimed Dongdo which is located about 79 miles far from the coast as the base point. Japan also claimed many uninhabited island or the reef which is located very far from the coast such as Okino Dorishima. As Korea is the party who negotiate the maritime limit with Japan and China, we should be keen and sensitive on the issues claimed by neighboring countries in terms of base point and the baseline. This paper is to review the characteristics of the base points or baselines of neighboring countries and to suggest the views how to maintain and to relocate our base points. As western coast of Korean peninsula is one of the largest tide fluctuation zone in the world, with long tidal record to prove the vertical datum adjustment, Korea can find the way to lower the vertical datum especially in Yellow Sea. So, major and critical tidal station has to be set up along the western coast to verify tide fluctuation record which can be met with international standard.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.67-72
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• 2022

Concrete prevents corrosion of reinforcing bars due to its strong alkalinity. However, in the sea, strong alkali components with a pH of 12 to 13 are eluted, which adversely affects the ecological environment and growth of marine organisms. In this study, the mechanical properties and durability of the low alkali mortar were evaluated for the development of a low alkali mortar for the 3D printed artificial reefs. As a result of evaluation of strength characteristics, the α-35 mixture, which were produced with fly ash, silica fume and α-hemihydrate gypsum, satisfied the strength requirement 27 MPa in terms of compressive strength. As a result of pH measurement, it was found that mixing with alpha-type hemihydrate gypsum resulted in minimizing pH due to the the formation of calcium sulfate instead of calcium hydroxide production. As a result of the chloride ion penetration resistance test, the α-35 mixture exhibited the best performance, 3844C. As a result of measuring the length change over time, the α-35 mixture showed the shrinkage 33.5% less compared to the Plain mix.

• Journal of Korea Port Economic Association
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• v.37 no.1
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• pp.1-18
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• 2021

A coastal marine ranching project in Uleungdo had been conducted for 5 years from 2013 to 2017 with investment costs of 5 billion won, for the special purpose of the deployment of artificial reefs, the release of young fishes. The paper focuses on an ex-post analysis of the economic feasibility for the project after completing the project, which is apart from a preliminary viability. For economic analysis, the economic benefits are derived from direct benefits including increasing effects of fisheries income and saving effects of harvesting costs, and indirect benefits including increasing effects of recreational fishing and preservation effects of coastal marine ecosystems while economic costs include releasing and purchasing costs of artificial reef and juvenile fish, R&D costs, maintenance costs and harvesting costs. The result shows that the project should not be accepted according to NPV=-0.125 billion won, IRR=4.5% and B/C ratio=0.98 under Scenario 1 which considers direct benefits and indirect benefits excluding the preservation values, while the project should be accepted under Scenario 2 indicating NPV=30.9 billion won, IRR=11.3% and B/C ratio=1.49 which considers the direct benefits as well as the indirect ones including the preservation values, based on 4.5% of the social rate of discount.