• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.297-306
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• 2023

Saemangeum Lake is the largest artificial lake in Korea. The continuous deterioration of lake water quality necessitates the introduction of novel water quality management strategies. Therefore, this study aims to identify the spatiotemporal water quality characteristics of Saemangeum Lake using data from the National Water Quality Measurement Network and provide basic information for water quality management. In the water quality parameters of Saemangeum Lake, water temperature and total phosphorous content were correlated, and salt, total nitrogen content, pH, and chemical oxygen demand were significantly correlated. Other parameters showed a low correlation. The spatial principal component analysis of Saemangeum Lake showed the characteristics of its four zones. The mid-to-downstream section of the river affected by freshwater inflow showed a high nutrient salt concentration, and the deep-water section of the drainage gate and the lake affected by seawater showed a high salt concentration. Two types of water qualities were observed in the intermediate water area where river water and outer sea water were mixed: waters with relatively low salt and high chemical oxygen demand, and waters with relatively low salt and high pH concentration. In the principal component analysis by time, the water quality was divided into four groups based on the observation month. Group I occurred during May and June in late spring and early summer, Group II was in early spring (March-April) and late autumn (November-December), Group III was in winter (January-February), and Group IV was in summer (July-October) during high temperatures. The water quality characteristics of Saemangeum Lake were found to be affected by the inflow of the upper Mangyeong and Dongjin rivers, and the seawater through the Garuk and Shinshi gates installed in the Saemangeum Embankment. In order to achieve the target water quality of Saemangeum Lake, it is necessary to establish water quality management measures for Saemangeum Lake along with pollution source management measures in the upper basin.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.587-597
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• 2023

We evaluated the eutrophication of Saemangeum Lake, which causes abnormal growth of algae, using the Carlson index. Eutrophication characteristics of Saemangeum Lake were analyzed. For the study, water quality surveys were conducted at 7 stations in Saemangeum Lake every month in 2021. The concentration of Chl.a was slightly higher in the Mankyeong water system in winter, and slightly higher in the Dongjin water system in spring and summer, but overall, except for some periods, the concentration was similar to or lower than the lake water quality environmental standard of class 3. COD showed water quality similar to or above the lake quality environmental standard of grade 4 in both the Mankyeong and Dongjin water systems in the summer and Autumn. TOC concentrations were within lake water quality standard 3 at all sites. Total phosphorus concentrations exceeded the lake water quality standard of Class 4 and were higher in January and August after rainfall. In the correlation analysis between water quality factors, the correlation of organic matter, total phosphorus, and total nitrogen to salinity was relatively high. This reflected the water quality characteristics of freshwater, brackish water, and seawater areas due to seawater inflow through the drainage gate and freshwater inflow through upstream rivers. According to the characteristics of eutrophication fluctuations in Saemangeum Lake by trophic state index, the indices of Chl.a, SD, and TN showed water quality in the early stage of eutrophication, while the TP index showed a severe eutrophication state. The magnitude of the eutrophication index among water quality components was TSI(TP) > TSI(TN) > TSI(SD) > TSI(CHL) in all water systems. Quadrant analysis of the deviation of TSI(CHL) from TSI(TP) and TSI(SD) on a two-dimensional plane showed that there was no limiting effect of total phosphorus on algal growth in all water systems. In addition, the factors af ecting light attenuation appeared to be dominated by small particulate matter from outside sources.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.1
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• pp.13-19
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• 2024

An analysis of the coastal water temperature in the Tongyeong waters, the eastern sea of the South Sea of Korea, revealed that the water temperature rose sharply before the typhoon made landfall. The water temperature rise occurred throughout the entire water column. An analysis of the sea surface temperature data observed by NOAA(National Oceanic and Atmospheric Administration) satellites, indicated that sea water with a temperature of 30℃ existed in the eastern waters of the eastern South Sea of Korea before the typhoon landed. The southeastern sea of Korea is an area where ocean currents prevail from west to east owing to the Tsushima Warm Current. However, an analysis of the satellite data showed that seawater at 30℃ moved from east to west, indicating that it was affected by the Ekman transport caused by the typhoon before landing. In addition, because the eastern waters of the South Sea are not as deep as those of the East Sea, the water temperature of the entire water layer may remain constant owing to vertical mixing caused by the wind. Because the rise in water temperature in each water layer occurred on the same day, the rise in the bottom water temperature can be considered as owing to vertical mixing. Indeed, the southeastern sea of Korea is a sea area where the water temperature can rise rapidly depending on the direction of approach of the typhoon and the location of high temperature formation.

• Korean Journal of Remote Sensing
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• v.37 no.6_1
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• pp.1773-1784
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• 2021

In order to minimize damage to oil spill accidents in the ocean, it is essential to collect a spilled area as soon as possible. Thus satellite-based remote sensing is a powerful source to detect oil spills in the ocean. With the recent rapid increase in the number of available satellites, it has become possible to generate a status report of marine oil spills soon after the accident. In this study, the oil spill area was calculated using various satellite images for the Symphony oil spill accident that occurred off the coast of Qingdao Port, China, on April 27, 2021. In particular, improving the accuracy of oil spill area determination was applied using high-resolution commercial satellite images with a spatial resolution of 2m. Sentinel-1, Sentinel-2, LANDSAT-8, GEO-KOMPSAT-2B (GOCI-II) and Skysat satellite images were collected from April 27 to May 13, but five images were available considering the weather conditions. The spilled oil had spread northeastward, bound for coastal region of China. This trend was confirmed in the Skysat image and also similar to the movement prediction of oil particles from the accident location. From this result, the look-alike patch observed in the north area from the Sentinel-1A (2021.05.01) image was discriminated as a false alarm. Through the survey period, the spilled oil area tends to increase linearly after the accident. This study showed that high-resolution optical satellites can be used to calculate more accurately the distribution area of spilled oil and contribute to establishing efficient response strategies for oil spill accidents.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.4
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• pp.343-355
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• 2021

Eelgrass, Zostera marina L., was widely distributed around Sinyangseopji Beach in Bangdu Bay, on the eastern coast of Jeju Island, until breakwater construction in the late 1990s resulted in its complete loss. Six experimental sites were identified for restoration of the Z. marina bed in Bangdu Bay. Using the staple method, 500 Z. marina shoots were transplanted at each site in January 2019 and 2020. The transplants, along with environmental parameters, were monitored for 10 months following transplantation. There were significant differences in underwater irradiance, water temperature, and salinity among the sites, but all were suitable for Z. marina growth. The Ulva species, an opportunistic alga, appeared in spring and accumulated during summer at all sites; however, there was no significant effect of Ulva species on the survival and growth of the eelgrass transplants. Most of the transplanted Z. marina survived, and after 3 months, the density increased by 112.5-300% due to vegetative propagation, with a rapid rate of increase observed during spring and early summer at all sites. For 1-2 months after transplanting, the Z. marina shoots showed signs of transplant shock, after which the shoot density increased at all sites, confirming that all transplants adapted well to the new environment. However, in both 2019 and 2020, during late summer to early fall, the sites experienced heavy damage from typoons (twice in 2019 and three times in 2020) that hit Bangdu Bay. The transplants at two sites located in the center of Bangdu Bay were completely destroyed, but those at three sites located to the west of the bay showed a 192-312% increase in density. Thus, we confirmed that the Bangdu Bay Z. marina bed can be restored, with the highest probability of success for Z. marina restoration on the western side of Bangdu Bay, which is protected from typhoons.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.4
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• pp.352-361
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• 1990

The reducing effect of wind injury was investigated using several wind-break nets in Youngdeok province where cold-wind damage is often occurred during rice growing season. The white-head damage of rice have been often occurred by typhoon during the period between August 15 to September 10 in the cold wind area of the eastern coastal during the last 11 years (1979-1989). This may suggest that the critical period for heading will be by August 15 in the regions. High evaporation coefficient, more than 250 due to typhoon passage over the regions resulted high injury of white head. Generally, the wind injury have been caused by warm and dry westerlies through Fohn apperance in Taebaeg mountains and by cool-humid wind which blows from coast to inland. The frequency of occurrence of the two types of typhoons were 25, 20%, respectively during rice cultivation. The instalation of wind-break net significantly reduced the wind blowing speed, depending on the net mesher with the higher effect in dence net. The distances between the net and cropping area also affect the wind speed: 23% reduction at 1m distance. 34% at 10m and 28% at 20m, respectively. The reducing effect was also observed even at 10 times height of the wind-break net. The instalation of wind-break net gave several effects on climate factor, showing that temperature increased by 0.8$^{\circ}C$(maximum), 0.7$^{\circ}C$(minimum), 0.6$^{\circ}C$(average) : water temperatures increased by 0.5$^{\circ}C$(maximum), 0.6$^{\circ}C$(minimum), 0.5$^{\circ}C$(average) : soil temperature increased 0.4$^{\circ}C$. The earlier heading and increasing growth rate, use of light, culm length, panicle number per hill, spikelet number per panicle, fertility and 1,000 grain weight were observed in the fields with the wind-break nets resulting in 10-15% increase in rice yield using 0.5${\times}$0.5cm nets. The increasing seedlings per hill gave higher grain yield by 13% in the cold wind damage regions of eastern coastals. and the wind-break was more significant in the field without the wind-break net. Wind injury of rice plant in the cold wind regions of eastern coastals in korea could be reduced by selection of tolerant varieties to wind injury, adjustment of transplanting time, and establishment of wind-break nets.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.3
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• pp.188-201
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• 2005

This is the first part of a two-part paper which describes comparison of reliability design methods by application to Donghae Harbor Breakwaters. This paper, Part 1, is restricted to stability of armor blocks, while Part 2 deals with sliding of caissons. Reliability design methods have been developed fur breakwater designs since the mid-1980s. The reliability design method is classified into three categories depending on the level of probabilistic concepts being employed. In the Level 1 method, partial safety factors are used, which are predetermined depending on the allowable probability of failure. In the Level 2 method, the probability of failure is evaluated with the reliability index, which is calculated using the means and standard deviations of the load and resistance. The load and resistance are assumed to distribute normally. In the Level 3 method, the cumulative quantity of failure (e.g. cumulative damage of armor blocks) during the lifetime of the breakwater is calculated without assumptions of normal distribution of load and resistance. Each method calculates different design parameters, but they can be expressed in terms of probability of failure so that tile difference can be compared among the different methods. In this study, we applied the reliability design methods to the stability of armor blocks of the breakwaters of Donghae Harbor, which was constructed by traditional deterministic design methods to be damaged in 1987. Analyses are made for the breakwaters before the damage and after reinforcement. The probability of failure before the damage is much higher than the target probability of failure while that for the reinforced breakwater is much lower than the target value, indicating that the breakwaters before damage and after reinforcement were under- and over-designed, respectively. On the other hand, the results of the different reliability design methods were in fairly good agreement, confirming that there is not much difference among different methods.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.335-347
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• 2013

In February 2008, high storm waves due to a developed atmospheric low pressure system propagating from the west off Hokkaido, Japan, to the south and southwest throughout the East Sea (ES) caused extensive damages along the central coast of Japan and along the east coast of Korea. This study consists of two parts. In the first part, we estimate extreme storm wave characteristics in the Toyama Bay where heavy coastal damages occurred, using a non-hydrostatic meteorological model and a spectral wave model by considering the extreme conditions for two factors for wind wave growth, such as wind intensity and duration. The estimated extreme significant wave height and corresponding wave period were 6.78 m and 18.28 sec, respectively, at the Fushiki Toyama. In the second part, we perform numerical experiments on wave-structure interaction in the Fushiki Port, Toyama Bay, where the long North-Breakwater was heavily damaged by the storm waves in February 2008. The experiments are conducted using a non-linear shallow-water equation model with adaptive mesh refinement (AMR) and wet-dry scheme. The estimated extreme storm waves of 6.78 m and 18.28 sec are used for incident wave profile. The results show that the Fushiki Port would be overtopped and flooded by extreme storm waves if the North-Breakwater does not function properly after being damaged. Also the storm waves would overtop seawalls and sidewalls of the Manyou Pier behind the North-Breakwater. The results also depict that refined meshes by AMR method with wet-dry scheme applied capture the coastline and coastal structure well while keeping the computational load efficiently.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.28-28
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• 2011

국내의 건축물에 관한 통계정보는 국토해양부에 의해서 공표된 통계연보로서 2002년부터 매년마다 제공되고 있다.(국토해양통계누리, https : //stat.mltm.go.kr/potal/stat/yearReport.do) 건축물의 통계연보는 과거부터 2002년까지 매 3년마다 공표된 것으로 알려지고 있다. 이 통계연보에는 건축물 현황과 건축허가착공 통계가 수록되어 있다. 건축물 현황에는 2009년 말을 기준으로 기존 건축물이 전체 6,618,131동으로서 용도별, 층수와 연면적별 그리고 소유구분별 등의 구분에 따라 건축물의 동수에 관한 통계자료가 포함돼 있다. 건축허가 및 착공통계에는 용도별과 구조재료별의 분류에 따라 건축물의 동수에 관한 자료가 신축, 증축 개축 이전 대수선, 용도변경 등으로 분류되어 수록돼 있다. 한편 국내에서 건축물에 대한 내진설계기준이 1988년에 제정됨에 따라 법제화되었다. 이때 내진설계의 의무 대상건축물은 6층 이상 또는 연면적 1만$m^2$이상인 건축물로 규정되었다. 그 이후 내진설계 대상 건축물이 1996년부터 아파트는 5층 이상으로, 판매시설은 연면적 5천$m^2$이상으로 확대되었고, 2000년부터 숙박시설 오피스텔 및 기숙사는 5층 이상으로 확대되었으며, 2005년부터 내진설계 의무화 대상이 3층 이상 또는 1천$m^2$이상으로 확대되었고, 2009년부터 3층 이상 건축물의 구조안전의 확인을 위한 세부절차를 규정하여 내진설계의 실효성을 확보하고 있다. 이와 같이 내진설계의 대상 건축물이 내진설계기준을 제정한 이후 현재까지 시대의 흐름에 따라 6층 이상에서 5층 이상으로 다시 3층 이상으로 계속 확대되어왔다. 이런 환경에서 현재 시점에서 사용 중인 기존 건축물 중에 내진설계가 적용되지 아니한 건축물은 1988년 3월 1일 이전에 건축허가 된 건축물과 그 이후에 건축허가 된 3층 내지 5층 이하인 저층 건축물의 두 가지로 구분할 수 있다. 이들의 내진설계가 미적용 된 건축물에 대해서는 원칙적으로 내진보강 대책 수립 및 추진이 필요한 실정이다. 국내에서는 현재 지진재해대책법에 따라 지진재해로부터 국민의 생명과 재산을 보호하기 위하여 기존 시설물에 대한 내진대책을 추진하는 정책이 시행되고 있다. 앞으로는 이 정책의 일환으로 기존 건축물의 내진성능 확보를 위한 내진보강 대책이 구체적으로 추진될 전망이다. 이와 같이 기존 건축물에 대한 내진보강 대책을 수립하는 데는 무엇보다 그 대상 건축물의 수와 구조형식에 관한 정보가 필요하다. 이는 내진보강의 방법과 소요비용이 건축물의 층수 및 구조형식별 동수에 따라 크게 달라지기 때문이다. 이런 관점에서 살펴볼 때 내진대책의 수립에 필수인 기존 저층 건축물의 층수 및 구조형식별 동수에 관한 통계자료를 현재 건축물의 현황통계에서 손쉽게 찾아 볼 수 있으면 좋겠는데 현실은 그렇지 못한 실정이다. 현재 건축물의 현황통계에는 저층 건축물에 해당하는 층수에 관한 구분이 연대에 따라 다르고 구체적인 층수를 구분하기 어렵게 불분명한 항목으로 구성된 것과 구조형식별 분류항목이 없는 형편이다. 반면에 건축허가 및 착공통계자료에는 구조재료별 건축물 동수와 연면적에 관한 자료가 수록되어있고, 건축물 층수에 따라 분류된 통계자료는 없다. 이 연구에서는, 기존 건축물에 대한 내진보강 대책을 수립하는데 필요한 저층 건축물의 층수 및 구조재료별 동수 등에 관한 구체적인 정보를 파악하기 위하여, 건축물 통계연보에 수록된 건축물 현황통계자료에서 불명확하거나 결여된 정보를 건축허가 및 착공 통계자료로부터 얻은 정보로 보완과 보충하여 제시하고 있다. 따라서 이 연구는 기존 건축물의 내진보강 대책 수립에 필요한 5층 이하의 저층 건축물에 관한 층수별 및 구조형식별 동수에 관한 연도별 통계자료를 추정하여 제안하는데 그 목적이 있다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.3
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• pp.147-153
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• 2011

This study is to measure the differences of the trace-metals resulted from the different ecologies, such as nickel(Ni), copper(Cu), zinc(Zn), cadmium(Cd), plumbum(Pb), arsenic(As) and chrome(Cr) remaining in the parts of Korean Yeongdeok Crab (KYC) and Russian Snow Crab (RSC) based on ICP-MS. The recovery rate of each metal certified the reference materials (CRM) was in the average of 81~99%, which corresponded with the level required in Codex. The level of metals in the parts of KYC was in the order of Ni > As > Zn > Cu > Cr > Cd in the both male and female shell; the order of Zn > As > Cu > Cr > Ni > Cd in the leg flesh; the order of Zn > As > Cu > Cr > Cd > Ni in the body flesh; the order of Cu > Zn > As > Cd > Cr > Ni in the gill; the order of Cu > As > Zn > Cd > Ni > Cr in the male hepatopancreas; the order of Cu > Zn > As > Cd > Cr > Ni in the female hepatopancreas, thereby showing some differences. It was revealed that the levels of most metals (nickel, copper, zinc, arsenic and chrome) were similar between KYC and RSC except cadmium which was somewhat lower than that of KYC. However, the cadmium in RSC was discovered in high level in most of the parts, two times higher in the hepatopancreas, and four times in the gill. It was also revealed that the trace metal contents were changing according to the size of KYC; the metals with the highest level of Ni in shell, Zn in leg and body flesh, Cu in gill tended to decrease as growing, whereas the cadmium contents tended to increase overall and accumulated the most in hepatopancreas. The results showed there was a possibility that the phenomenon of bioaccumulation within hepatopancreas would increase as growing.