• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.712-720
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• 2022

In this study, we evaluated the production and photoreactivity of CDOM of two polar phytoplanktons - Phaeocystis antarctica and Phaeocystis pouchetii, in order to find out UV effects on phytoplanktons. In visible region, CDOM in media of both phytoplanktons under UV-R decreased during 48hrs incubation period. However, in UV region CDOM decreased 30 % in the media of P. antarctica, but increased 10% in media of P. pouchetii, compared to CDOM concentrations of control after 48 hr incubation. This result indicates that biota in polar environment would not well protected from UV-R harmful effect when P. antarctica is dominant because of loss of CDOM, but when P. pouchetii is dominant species, production of UV absorbing organic matter could play more efficiently for UV screening for marine biota. Also we confirmed that FDOM of humic substance (C-peak) produced by these phtoplanktons under UV-R stress were well matched with fluorescence characteristics of the UV-protecting compound, MAAs. This finding shows that Phaeocystis pouchetti with low photoreactivity would contribute to DOM pool of polar marine environment under stratification by global warming.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.238-246
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• 2012

Once oil is spilled into marine environment, it experiences various weathering processes among which evaporation is the most dominant process in the initial stage of weathering. This study aimed to elucidate the effects of evaporation on the physicochemical properties of spilled oil using standardized laboratory experiments. Laboratory evaporation process was successfully reproduced using controlled rotary evaporation method. In case of Iranian Heavy crude (IHC), evaporation rate after 48 hours was $29.3{\pm}0.4%$ (n=40, p<0.001). Evaporation was simulated using ADIOS2 weathering model and the result was in agreement with laboratory experiment. Chemical composition changes of petroleum hydrocarbons including alkanes, polycyclic aromatic hydrocarbons (PAHs) and biomarkers by evaporation rate were also analyzed. As oil evaporated, low molecular weight alkanes and PAHs decreased, while biomakers showed conservative characteristics. Among biomarkers, $17{\alpha}(H)$, $21{\beta}(H)$-hopane was used for calculation of weathering rates, which matched with evaporative mass losses. Weathering rate calculation using hopane showed that stranded oils of weathering stage I (28.9%) and mesocosm oil weathering experiment till 5 days (26.5%) were mainly affected by evaporation process.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.265-266
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• 2006

The chemical conversion coating formed on magnesium alloy investigated for low cost and harmless in environment by using the colloidal silica as the main component. The film formed in 298 K is thick, the film, which was thought combination of Si-O, was formed. The film formed in 313 K is thinner than that in 298 K. The quantity of film formed at high temperature such as 333 K and 353 K is smaller than dissolved quantity. At the anodic polarization experiment, corrosion resistance in sealing by hot water after chemical conversion treatment in basic solution condition get worse than that in comparison with basic solution condition. In salt spray test, the ratio of black rust on specimen that did not conducted chemical conversion treatment was five times or more compared with those of chemical conversion treated specimen. The film thickness of chemical conversion coating produced by alkali treatment process is thinner than in comparison with that of specimen produced in basic chemical conversion treatment solution condition. It is thought, however, that it showed good corrosion resistance during salt spray test because the area of microcracks is small.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.200-204
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• 2005

The sirocco fan is used to get low noise, and it has been applied to a lot of industry field like the heat engine, the fluid instrument power plant, the food industry, environment industry etc... because there are not any problem even it is mixed with a any kind of liquid, gas, and solid. The flow characteristics in sirocco fan are investigated by PIV. The experiment using PIV measurement for Test section's flow characteristics acquired velocity distribution, .Condition : when sirocco fan in automobile air controller maximum 1450RPM, and a revolution is a variation (1)950RPM, (2)1100RPM, (3)1250RPM. The agreement a experiment shows the validity of this study and the results of this study would be useful to the engineers who design for the flow systems for heating, ventilation and air conditioning.

• Corrosion Science and Technology
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• v.20 no.2
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• pp.85-93
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• 2021

The corrosion damage of materials in marine environment mainly occurs by Cl^- ions due to the breakdown of passive films. Additionally, various characteristics in seawater such as salinity, temperature, immersion time, flow rate, and biological activity also affect corrosion characteristics. In this study, the corrosion characteristics of stainless steels (STS 304 and STS 316L) and anodized aluminum alloys (AA 3003 and AA 6063) were evaluated with seawater temperature parameters. A potentiodynamic polarization experiment was conducted in a potential range of -0.25 V to 2.0 V at open circuit potential (OCP). Corrosion current density and corrosion potential were obtained through the Tafel extrapolation method to analyze changes in corrosion rate due to temperature. Corrosion behavior was evaluated by measuring weight loss before/after the experiment and also observing surface morphology through a scanning electronic microscope (SEM) and 3D microscopy. Weight loss, maximum damage depth and pitting damage increased as seawater temperature increased, and furthermore, the tendency of higher corrosion current density with an increase of temperature attributed to an increase in corrosion rate. There was lower pitting damage and lower corrosion current density for anodized aluminum alloys than for stainless steels as the temperature increased.

• Ocean and Polar Research
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• v.28 no.2
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• pp.145-151
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• 2006

A broadband self-recording hydrophone was developed to conveniently assemble a hydrophone array for use in receiving underwater sound waves. A trigger device with an electromagnetic induction coupler was also developed to control the hydrophone's operation. Main configurations and specifications of the self-recording hydrophone are introduced in this paper. We present experiment results conducted in a water tank to examine the operating behavior of the hydrophone. Some advantages are discussed when the self-recording hydrophones are used to make up a hydrophone array.

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.248-248
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• 2017

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.127-127
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• 2017

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.6
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• pp.584-590
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• 2012

In this study, we have conducted a work on homogenizer development which is operated by high shearing force generated by stator and rotor inside it. To investigate the performance for homogenization and atomization of homogenizer, Bunker-C (IFO 380 cSt) was used as a fuel for experiment. Pre-treatment of bunker-C was carried out with homogenizer developed in this study. Oil purifier was used to investigate effect of oil sludge reduction after pre-treatment. Experimental result showed that the amount of sludge of fuel oil after pre-treatment with homogenizer has decreased by 13 %. To confirm combustion efficiency, Bunker-C which have pre-treatment with homogenizer and purified after are burned in boiler system. The result showed that CO concentration in exhaust gas was decreased. These results mean that if the homogenizer which is developed in this study for marine fuel oil is applied on real vessels, oil costs and operating costs can be reduced.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.459-466
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• 2018

Hazardous and Noxious Substances (HNS) are defined as substances that are likely to create a significant impact on human health and marine ecosystem when they are released into the marine environment. Recently, as the volume of HNS transported by ships increases, the rate of leakage accidents also increases. Therefore, research should be conducted to control and monitor sunken materials from the viewpoint of technology development for hazardous material leakage accident response. In this paper, acoustic detection experiments were carried out using HNS substitute materials in order to confirm the possibility of acoustic detection of sunken HNS on the sediment. The castor oil, which has a similar acoustic impedance with chloroform, is used as a substitute. 200 kHz high frequency signals were used to discriminate the reflected signals and measure reflection loss from the interface between water and castor oil. The reflection loss measured is in good agreement with the modeling results, showing a possibility of acoustic detection for sunken HNS.