• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.223-229
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• 2015

Surface modification is a technology to form a new surface layer and overcome the intrinsic properties of the base material by applying thermal energy or stress onto the surface of the material. The purpose of this technique is to achieve anti-corrosion, beautiful appearance, wear resistance, insulation and conductance for base materials. Surface modification techniques may include plating, chemical conversion treatment, painting, lining and surface hardening. Among which, a surface modification process using electrolytes has been investigated for a long time in connection with research on its industrial application. The technology is highly favoured by various fields because it provides not only high productivity and cost reduction opportunities, but also application availability for components with complex geometry. In this study, an electrochemical experiment was performed on the surface of 5083-O Al alloy to determine an optimal electrolyte temperature, which produces surface with excellent corrosion resistance under marine environment than the initial surface. The experiment result, the modified surface presented a significantly lower corrosion current density with increasing electrolyte temperature, except for $5^{\circ}C$ of electrolyte temperature at which premature pores was created.

• 한국해양학회지
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• v.27 no.1
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• pp.78-90
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• 1992

The present study is aimed to investigate the relationship between the distribution of benthic macro fauna and environments in the Mangyung-dongjin tidal flat developed on the west coast of central korea. Samples were taken from 69 sites established on 8 transect lines running perpendicular to the coast. The 69 sites located in the range of -250 to 230 cm height from the mean sea level were categorized into 4 levels of exposure duration. The mean grain sizes of the surface sediments varied from 1.5 to $7.9{\varphi}$. Silty sands and sands were dominant sediment facies on the tidal flat. A total of 64 species of invertebrates was collected and the mean density was $1,335{\;}indiv{\cdot}\textrm{m}^2$. The dominant species was Laternula cf. limicola of Bivalvia (71% of total counts), followed by Umbonium thomasi of Gastropoda (22%), and Lingula anatina of Brachiopoda (2.6%). These 3 species comprised 95.5% of total individual number. The distribution of benthic animals was closely related with the duration of tidal exposure. Perinereis association was the characteristic for the most exposed area, and followed by Macrophthalmus and Bullacta-Mactra-Umbonium association along the degree of exposure duration.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.3
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• pp.238-244
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• 2000

The complete postembryonic developments of copepodid stages of Paramphiascella vararensis T. Scott(Copepoda: Harpacticoida) are described and illustrated based on specimens cultured in laboratory. The copepodites of P. vararensis feed on powder of one of green macro-algae species Ulva pertusa. Developmental time from copepodid stage to adult (copepodid stage) is about 15 days with culture conditions of 33-34 ppt of salinity, 22-23$^{\circ}$C of temperature and feed on algae powder. Sexual characters of the species are distinct on the copepodid stage. Sexual characters appear in size, antennule, pereiopods of second and bases of the fifth and sixth legs. Males are considerably smaller than females in size. In the antennule, the fourth segment of the male extremely is modified and swollen for female. In the segment number of the endopod of second pereiopod, female has 3 segments while male bears 2 segments. The female has 3 setae while the male bears 2 setae on the inner lobe of basis of fifth leg. In the basis of sixth leg, the female has 2 setae while the male has 3 setae.

• 한국해양학회지
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• v.7 no.2
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• pp.74-85
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• 1972

This paper studied the grain size distribution of bottom sediments of Yeongil Bay which is located at the southeastern part of the Korean Peninsula. Sixty four samples collected with snapper and dredger are analyzed by roe Tap Sieve Shaker and Pipette Method. The moment parameters are calculated with the method of Friedman(1961). Most samples are composed of sand size sediments and a few samples are composed of silt and clay. The Yeongil Bay can be divided into gravel-granule zone, sand zone, and silt-clay zone. The sediments near Yeonam- Dong and Hyongsan river are moderately sorted and others are very poorly sorted according to scheme of Friedman91962). In general, sorting values are ranged from 1.0 to 3.5. The samples near Janggigap and Masin-Dong show negative and others show positive skewness values. Skewness values are ranged from -1 to 2. All samples show the leptokurtic distribution except for the samples near Masin- dong and at the deepest place near Janggigap. Kurtosis values are ranged from -1.5 to 21.9. The samples of gravel-granule zone contain more than 50% and those of silt-clay zone contain less than 50% of CaCO$\_$3/. Four different colors, black, yellow, brown and gray, are shown in the sediments of Yeongil Bay.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.4
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• pp.216-230
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• 1999

A Galerkin finite element model for the analysis of harbor oscillation has been developed based on the extended mild-slope equation. Infinite elements are used to accomodate the radiation condition at infinity and joint elements to treat the matching conditions at the harbor entrance which include the energy loss due to flow separation. The numerical tests for rectangular harbors with fully or partially open entrances show that the energy loss at the harbor entrance considerably reduces the the amplification ratios at the innermost parts of the harbors and that the amplification ratios decrease considerably with increasing incident wave heights and jet lengths at the harbor entrance. Application of the model to the Gamcheon harbor show that when the incident wave amplitude is small the amplification ratios rather increase when the entrance energy loss is included than when ignored because of the shift of the resonance periods. Even though the entrance energy loss was insignificant for the measured long-period incident waves, it would be of great importance if the incident waves were large as in the attack of tsunamis. The resonance period of the Helmholtz mode at the Gamcheon Harbor was calculated to be 31 minutes, which agrees well with the measured one between 27 and 33.3 minutes. The measured resonance periods between 9.4 and 12.1 minutes and 5.2 and 6.2 minutes were also calculated by the numerical model as 10.4 minutes and 6.6 or 5.6 minutes, indicating good performance of the model. On the other hand, it was shown that a variety of oscillation modes exists in the Gamcheon Harbor and lateral resonances of considerable amplification ratios also exist at the periods of 3.6 and 1.6 minutes as in the Young-II Bay.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.1
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• pp.16-24
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• 2014

Long-term measured wind data are absolutely necessary to estimate extreme offshore wind speed. However, it is almost impossible to collect offshore wind measured data. Therefore, typhoon simulation is widely used to analyze offshore wind conditions. In this paper, 74 typhoons which affected the western sea of Korea during 1978-2012(35 years) were simulated using Holland(1980) model. The results showed that 49.02 m/s maximum wind speed affected by BOLAVEN(1215) at 100 m heights of HeMOSU-1 (Herald of Meteorological and Oceanographic Special Unit - 1) was the biggest wind speed for 35 years. Meanwhile, estimated wind speeds were compared with observed data for MUIFA, BOLAVEN, SANBA at HeMOSU-1. And to estimate extreme wind speed having return periods, extreme analysis was conducted by assuming 35 annual maximum wind speed at four site(HeMOSU-1, Gunsan, Mokpo and Jeju) in western sea of the Korean Peninsular to be Gumbel distribution. As a results, extreme wind speed having 50-year return period was 50 m/s, that of 100-year was 54.92 m/s at 100 m heights, respectively. The maximum wind speed by BOLAVEN could be considered as a extreme winds having 50-year return period.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.14-24
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• 2015

This study proposed an estimation method of allowable wave height for loading and unloading of the ship and evaluation of effective working days considering moored ship motion that is affected by sip sizes, mooring conditions, wave periods and directions. The method was examined validity by comparison with wave field data at pier $8^{th}$ in Pohang New Harbor. The wave field data obtained with wave height of 0.10~0.75 m and wave period of 7~13 s in ship sizes of 800~35,000 ton when a downtimes have occurred. On the other hand, the results of allowable wave height for loading and unloading of the ship in this method have obtained with wave heights of 0.19~0.50 m and wave periods of 8~12 s for ship sizes of 5,000, 10,000 and 30,000 ton. Thus this method well reproduced the field data respond to various a ship sizes and wave periods. And the results of this in Korea are didn't respond to various the ship sizes and wave periods, and we h method tended to decrease in 16~62 percent when have considered long wave, and it is decreased in 0~46 percent when didn't consider long wave than design standards in case of the ship sizes of 5,000~30,000 ton, wave period of 12 s and wave angle of $75^{\circ}$. The allowable wave heights for loading and unloading of the ship proposed by design standards in Korea have found that overestimated on smaller than 10,000 ton. On the other hand, the rate of effective working days considering ship motion at pier $8^{th}$ in Pohang New Harbor reduced in 6.5 percent when compare with the results without considering ship motion.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.3
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• pp.122-130
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• 2004

Crude oil is complex mixture of thousands of different organic compound formed from a variety of organic materials that are chemically converted under differing geological conditions over long periods of time. Also oil composition varies according to crude source, refining, processing, handling and storage. The oil fingerprint method is application of specific knowledge of petrochemicals and use of sophisticated analytical equipment and techniques to identify the source(s) of oil pollution. KNMPA currently utilizes three primary analytical techniques: Gas Chromatography (GC), Fluorescence Spectroscopy(FL) and Infrared Spectroscopy(IR). Of all these techniques, GC technique are most widely used. Gas Chromatography is used as a primary analytical method because high reliableness, high separating efficiency and repeatability, but it is timeconsumable. The study results of identification of waterborne spilled oil by Fast Gas Chromatograph method showed that analytical time is cut down to 30minutes in comparison with packed column method and chromatograms represent high resolution and high repeatability.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.3
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• pp.146-151
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• 2004

Cyclodextrin compounds including 2-hydroxypropyl-β-cyclodextrin(β-HPCD) though to be accelerate the biodegradation of PAHs molecule by increasing solubility of PAHs through detaining PAHs in their's cavity. However, only this mechanism is not sufficient to explain the enhancement of PAHs biodegradation by β-HPCD. To find out possible additional role of β-HPCD in the enhancement of PAHs biodegradation, biodegradation rates of pyrene and benzo[a]pyrene (B[a]P) by a PAHs degrading Novosphingobium pentaromtivorans US6-1 strain were compared between with and without addition of β-HPCD. Changes of bacterial biomass were also measured simultaneously. In addition catechol 1,2-dioxygenase activity was determined depending on pre-incubation conditions. As a result, β-HPCD accelerate the degradation rate of pyrene by strain US6-1 and especially the β-HPCD amendment was obligatory for the degradation of B[a]p. Bacterial biomass was responsible for β-HPCD, however, PAHs compounds such as pyrene and B[a]P did not contribute to the bacterial biomass. Catechol 1,2-dioxygenase specific activity of US6-l cells pre-cultured in MM2 medium containing l％ β-HPCD was higher than that of cells pre-cultured in ZoBell medium. The former case also showed similar activity compared to that of cells serially starved in MM2 medium after grown in ZoBell medium. These results imply that the presence of β-HPCD accelerate the degradation of PAHs by increasing the bacterial biomass as well as by increasing the water solubility of PAHs.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.4
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• pp.290-298
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• 2013

A Saemangeum Development Project, which is a national project in South Korea, has started with the objective of developing the reclaimed area mainly agricultural land use since the mid'80s. To develop a model of the global eco-reclamation, constructions of the eco-friendly counter facilities such as sluice gates and inner dikes, as well as environmental preservation measures for an estuary reservoir, have been carried out. However, reasonable measures of the water quality management for the Saemangeum area are required. Thus, the purpose of this study is to rigorously analyze and quantitatively evaluate the environmental problems due to the water level management associated with inner dike constructions. To achieve these objectives, the affecting factors on determination of water level management are described and a series of calibrated transient-state numerical simulations was performed to demonstrate the salinity distribution difference in the estuary before and after the construction of inner dikes. The overall salinity reduced about 2~5 psu, and the seawater intrusion was weakened by a well-regulated waterway after construction of the inner dikes compared to before construction of them.