• Environmental Engineering Research
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• v.24 no.4
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• pp.582-590
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• 2019

Currently, the waterfront facility was constructed in New Songdo City, South Korea. It has the various water leisure areas and especially an artificial urban canal with filtered seawater by re-circulating flow system. However, due to excessive amount of nutrients from seawater combined with complicated geometry, it is highly vulnerable to deterioration of water quality. In this study, flow characteristics and pollutant transport were analyzed with comprehensive numerical models, MIKE 3 FM and ECO-lab. Based on these numerical results, notable sampling points were selected for field measurements and comparison between modeling and measured results were conducted. In addition, the integrated water quality evaluation index, Water Quality Index was applied to analyze various water quality issues. We also set up scenarios to control the two kinds of water quality factors, dissolved oxygen (DO), and total phosphorus (TP). As a result, the effect of 20% reduction of TP was less than 10% and it was almost ineffective for a year but it was reduced by up to 40% in case of scenario which DO is increased by 20%. Therefore, it was recommended to control the DO concentration, usually by applying re-aeration facility, rather than TP in artificial urban canal with seawater.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.683-688
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• 2001

In case of constructing the concrete structures under seawater environment, the concrete suffers from deterioration due to penetration of various ions such as chloride, sulfate and magnesium in seawater. Tn the present study, Immersion tests with artificial seawater were carried out to investigate the resistance to seawater attack of antiwashout underwater concrete. From the results of compressive strength, it was found that blended cement concrete due to mineral admixtures such as fly ash(FA) and ground granulated blast-furnace slag(SGC), were superior to ordinary portland cement concrete with respect to the resistance to seawater attack. Moreover, XRD analysis indicated that the formed reactants of ordinary portland cement paste by sulfate and magnesium ions led to the deterioration of concrete. As expected, however, the blended cements with FA or SGC have a good resistance to seawater attack. This paper would discuss the mechanism of seawater deterioration and benefical effects of antiwashout underwater concretes with mineral admixtures.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.2
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• pp.96-103
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• 2009

The biodegradability in water of the artificial baits for blue crab pots which were made of intestines of mackerel, tuna and grinded krill were studied. The biodegradability of artificial bait was evaluated with the effective capacity of 10L water tank which was made of acryl pipe at the velocity of 1m/d and hydraulic retention time of 12 hours. For the 23 days operation time, all artificial baits were degraded fast at the early stage of operation time and stabilized within 5 days after start up. The rates of biodegradation were different depending on the raw materials of artificial baits. In terms of degradation rate of organic matter which can be expressed as COD, artificial bait made of tunas intestine showed the fastest degradation rate. On the other hand, in terms of degradation rate of nitrogenous matter which can be expressed as ammonia nitrogen, artificial bait made of mackerels intestine showed the fastest degradation rate. In order to evaluate the effect of artificial bait on marine ecosystem, seawater qualities including SS, COD, DO, nitrogen, phosphorus were determined depending on depth and location during 2 days test operation period. It is apparent that the effect of artificial bait on seawater quality was negligible when comparing seawater quality of test operation area with control area.

• Development and Reproduction
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• v.13 no.1
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• pp.35-41
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• 2009

In the present study, we investigated the effects of rearing condition during the winter period on artificial maturation and reproduction of cultured female eel, Anguilla japonica. The female eel was adapted by combination of environmental conditions (seawater/low temperature, $10^{\circ}C$; seawater/high temperature, $20^{\circ}C$; freshwater/low temperature, $10^{\circ}C$; freshwater/high temperature, $20^{\circ}C$) during 8 weeks of the winter period. Then, the female eel cultivated by different conditions during the winter were transferred to seawater at $20^{\circ}C$ for induction of artificial maturation by salmon pituitary extraction (SPE) injection. The results shown that gonadosomatic index (GSI) and plasma levels of estradiol-$17{\beta}$ (E2) were significantly higher in female eel were reared in seawater than in freshwater, and were the highest at eel adapted by seawater/low temperature. Also, reproduction coefficient were higher in seawater/low temperature than in the other groups. These results will provide valuable information for elevation of the artificial maturation and reproduction coefficient in the cultured female eel.

• Journal of Ocean Engineering and Technology
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• v.26 no.1
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• pp.78-83
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• 2012

The abundant nutrients contained in deep seawater are delivered by natural upwellings from the deep sea to the surface sea. However, the natural upwelling phenomenon is limited to specific areas of the sea; in other areas, the thermocline separates the surface sea from the lower layer. Thus, the surface layer is often deficient in nutritive salts, causing the deterioration of its primary productivity and ultimately leading to an imbalance in the marine ecosystem. Without a consistent supply of nitrogenous nutritive salts, they are absorbed by phytoplankton, resulting in a considerable problem in primary productivity. To solve this issue, a floating type of artificial upwelling system is suggested to artificially pump up, distribute, and diffuse deep seawater containing rich nutritive salts. The key technologies for developing such a floating artificial upwelling system are a floating offshore structure with a large diameter riser, self-supplying energy system, density current generating system, method for estimating the emission and absorption of CO2, and way to evaluate the primary production variation. Strengthening the primary production of the sea by supplying deep seawater to the sea surface will result in a sea environment with abundant fishery resources.

• Journal of Environmental Science International
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• v.18 no.10
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• pp.1065-1070
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• 2009

Experimental design for ecological restoration approach was investigated from the P' company's slag dumping area with higher pH value. The degree of pH recovery was measured by the injection of carbon dioxide from the LNG exhaust gas, and the residual carbon, for example, calcium and carbonate which can be controlled by artificial seaweed beds. The degree of adaptability from 3 algaes (Undaria pinnatifida, Sargassum horneri and Ecklonia stolonifera) and uptake nutrient function of Ecklonia stolonifera chosen in the first treatment were measured in the laboratory to determine the transplanting algae in artificial seaweed beds. The higher value of pH was decreased to 7.0~8.5 by injection of LNG exhaust gas with flow rate $20\;m^3/min$. In the experiment design at laboratory, the upper part of frond of Undaria pinnatifida and Sargassum horneri began to decay, and the color changed after 10 days. However, those of Ecklonia stolonifera were after 14~20 days. The uptake rate of nutrient from Ecklonia stolonifera was higher than those of other algaes, and those was similar pattern in the control (e.g. seawater); The DIN concentration uptake of Ecklonia stolonifera was $1.88\;{\mu}g/L/hr$ avg. in leachate, but $2.19\;{\mu}g/L/hr$ avg. in seawater. However, the ${PO_4}^3$-P concentration uptake was $0.18\;{\mu}g/L/hr$ avg. in leachate, but $0.31\;{\mu}g/L/hr$ avg. in seawater. These result indicated Ecklonia stolonifera uptaked these nutrients in the leachate as well as in seawater, and it may suggested for this species to transplant for constructing artificial seaweed beds.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.49 no.4
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• pp.349-354
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• 2023

Sunscreen is a product that protects against ultraviolet rays by blocking and scattering ultraviolet rays, and has now become a daily necessity beyond cosmetics. Applying sunscreen is a common and easy way to prevent skin damage caused by ultraviolet rays. Due to its significance, the evaluation of sunscreen has evolved since its regulation by the FDA in 1978, progressing to standardized methods established by ISO. Additionally, to assess the loss of sunscreen due to activities such as water exposure or sweating, the Ministry of Food and Drug Safety in Korea and ISO have established protocols for evaluating the water-resistant sun protection factor (SPF). However, existing evaluations of water resistance have been mainly confined to test methods involving plain water, and methods accounting for the impact of seawater during activities like beach leisure, sports, and recreation are yet to be established. Based on the existing guidelines for testing the water-resistant UV protection index, this study compared the water-resistant UV protection index in water, artificial seawater (salt water) and natural seawater (sea water) to evaluate the UV protection index in real-world situations such as marine leisure, sports, and leisure activities. Through these results, we were able to compare the differences between water resistance sun protection index tests in ordinary water, artificial seawater, and natural seawater, and suggest a method for water resistance sun protection index tests using natural seawater.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.637-640
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• 1998

Generally, the durability of the reinforced concrete structures reduce when they are constructed in marine environments. The Mg ions and sulfate ions in seawater cause chemical attacks in concrete and the cracks in concrete result from corrosion of steel due to chlorides. In this study, the mortar specimens made from 5 different types of cement were immersed in artificial seawater of 2 times concentration and then we measured the compressive strength, the length change and the weight change. As a result of this study, we found that the compressive strength ratio decreased in the immersed 56days. We also found the longer the immersed days were, the more the increase of weight ratio and the length change were.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.1
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• pp.46-54
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• 2022

A magnetohydrodynamic (MHD) seawater propulsion thruster has been proposed to reduce propeller noise, propeller pitting, and vessel vibration originated from the propeller cavitation. The MHD thruster was also focused to overcome the limitation of propulsion velocity for the special purpose of marine ships. The research trends and key technologies in the worldwide leading countries are reviewed for the development of MHD propulsion thrusters in Korea. A small performance test device was developed firstly with a conventional solenoid magnet of ≤0.6 Tesla and a helical-type cylindrical duct(inner diameter of 5 cm) of thruster. The artificial seawater was fabricated by a salt solution including a conductivity of 5~6 S/m. The measured flow velocity of artificial seawater in the test device was 0.03~0.42 m/s (0.06~0.84 Knot) with a magnetic field strength of 0.6 Tesla and the applied currents of 10~80 A including the change of anode materials. It was found that the flow direction of seawater was reversed by the directional change of applied current in the solenoid magnet.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.4 s.148
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• pp.467-475
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• 2006

Fatigue strength of hull structural steel plate, extracted from longitudinal bulkhead of a 17-year-old ore/oil carrier for renewal, was investigated in air and in artificial seawater condition. The surface of the plate was covered with corrosion pits and they proved to be crack initiation sites by fractography using SEM. From this research, it was found that the evaluation method for fatigue strength of virgin mild steel plates in air and in artificial seawater can also be applied to the evaluation of the fatigue strength of mild steel plates those were long-term exposed to a corrosive environment and their surfaces had been rusted intensively.