• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.413-413
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• 2019

하천과 호수에서 남조류의 이상 과잉증식 문제(이하 녹조문제)는 담수생태계의 생물다양성을 감소시키며, 음용수의 이취미 원인물질을 발생시켜 물 이용에 장해가 된다. 또한 독소를 생산하는 유해남조류가 대량 증식할 경우에는 가축이나 인간의 건강에 치명적 해를 끼치기도 한다. 그 동안 국내에서 녹조문제는 댐 저수지와 하구호와 같은 정체수역에서 간헐적으로 문제를 일으켰으나, 4대강사업(2010-2011)으로 16개의 보가 설치된 이후 낙동강, 금강, 영산강 등 대하천에서도 광범위하게 발생되고 있어 중요한 사회적 환경적 이슈로 대두되었다. 한편, 대하천에 설치된 보 구간에서 빈번히 발생하는 녹조현상의 원인에 대해서는 전 지구적 기온상승에 따른 기후변화의 영향이라는 주장과 유역으로부터 영양염류의 과도한 유입, 가뭄에 따른 유량감소, 보 설치에 따른 체류시간 증가 등 다양한 의견이 제시되고 있으나, 대상 유역과 수체의 특성에 따라 녹조 발생의 원인이 상이하거나 또는 다양한 요인이 복합적으로 작용하기 때문에 보편적 해석(universal interpretation)이 어려운 것이 현실이다. 따라서 각 수계별, 보별 녹조현상에 대한 정확한 원인분석과 효과적인 대책 마련을 위해서는 집중된 실험자료와 데이터마이닝 기법에 근거로 한 보다 과학적이고 객관적인 접근이 이루어져야 한다. 본 연구에서는 2012년 보 설치 이후 남조류에 의한 녹조현상이 빈번히 발생하고 있는 낙동강 4개보(강정고령보, 달성보, 합천창녕보, 창녕함안보)를 대상으로 집중적인 현장조사와 실험분석을 수행하고, 수집된 기상, 수문, 수질, 조류 자료에 대해 통계분석과 다양한 데이터모델링 기법을 적용하여 보별 남조류 우점 환경조건과 이를 제어하기 위한 주요 조절변수를 규명하는데 있다. 연구대상 보 별 수질과 식물플랑크톤의 정성 및 정량 실험은 2017년 5월부터 2018년 11월까지 2년에 걸쳐 실시하였으며, 남조류 세포수 밀도와 환경요인과의 상관성 분석을 실시하고, 단계적 다중회귀모델(Step-wise Multiple Linear Regressions, SMLR), 랜덤포레스트(Random Forests, RF) 모델과 재귀적 변수 제거 기법(Recursive Feature Elimination using Random Forest, RFE-RF)을 이용한 변수중요도 평가, 의사결정나무(Decision Tree, DT), 주성분분석(Principal Component Analysis, PCA) 기법 등 다양한 모수적 및 비모수적 데이터마이닝 결과를 바탕으로 각 보별 남 조류 우점 환경요인을 종합적으로 해석하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.487-487
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• 2018

본 연구에서는 2017년 5월부터 12월까지 주단위로 낙동강 수계 5개 보 구간(칠곡보~창녕함안보)에서 본류와 유입지천의 유기물(BOD, $COD_{Mn}$, TOC) 분석 및 상관관계 조사하였으며, 강정고령보~창녕함안보의 대표지점에 대해서는 용존유기물(DOC)의 분해특성을 조사하였다. 본류의 유기물 농도는 BOD $2.7mgO_2/L$($2.3{\sim}3.1mgO_2/L$), $COD_{Mn}$ $5.6mgO_2/L$($5.0{\sim}6.2mgO_2/L$), TOC 4.7 mgC/L($4.2{\sim}5.2mgO_2/L$), 유입지천은 BOD $3.4mgO_2/L$($1.1{\sim}5.6mgO_2/L$), $COD_{Mn}$ $7.1mgO_2/L$($2.5{\sim}10.9mgO_2/L$), TOC $5.7mgO_2/L$(2.3~8.7 mgC/L)로 각각 나타났다. 유기물간 상관성 분석결과 본류의 BOD와 COD, TOC 상관계수(r)은 각각 0.97, 0.98, COD와 TOC는 0.91, 유입지천의 BOD와 COD, TOC는 각각 0.81, 076, COD와 TOC는 0.99로 나타났다. 본류 구간에서 탄소로 환산된 BOD-C/TOC 산화율은 21.5%(20.4~22.5%), COD-C/TOC 45.7%(44.3~48.0%), 유입지천의 BOD-C/TOC 산화율은 23.6%(13.1~31.0%), COD-C/TOC 48.0%(41.3~53.3%)로 각각 나타났다. 강정고령보~창녕함안보 대표지점의 DOC 분해특성은 DOC 중 R-DOC가 86.9%(74.5~94.3%), L-DOC 13.0%(5.7~25.5%)로 나타났다. L-DOC의 분해속도(k)는 0.21 /day(0.11~0.38 /day)로 계산되었으며, 보별 평균 분해속도는 합천창녕보(0.25 /day) > 강정고령보(0.22 /day) > 창녕함안보(0.21 /day) > 달성보(0.18 /day)순으로 나타났다. 유기물 농도는 본류에서는 하류로 갈수록 증가하는 경향을 보였으며, 유입지천은 지점별로 다양하게 나타났다. 유기물간 상관성은 유입지천보다 본류구간이 상관계수가 높게 나타났다. TOC에 대한 BOD와 $COD_{Mn}$산화율은 본류구간 보다 유입지천에서 큰 변동을 보였으며, 실제 유기물 총량 대비 BOD와 $COD_{Mn}$은 각각 77.0%, 52.7% 낮게 나타났다. DOC 중 난분해성 유기물이 대부분을 차지하였으며, 타 보 대비 달성보 내에 난분해성 유기물이 높은 것으로 나타났다.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.21-28
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• 2018

Despite a number of studies on consolidation behavior that have been carried out in the Nakdong River estuary in Busan, these are focused on the prediction of final settlement during ground improvement process, and there is almost no research on the long-term settlement occurring after that. For the practical study on the long-term settlement, the field monitored settlement data that measured over 10 years in the Busan new port facilities area were used, and the final settlement and predicted time-settlement line were constituted by hyperbolic function. As a result, the measured settlements depend on the thickness of clayey soils, and the pattern were similar to each other and good agreement with the predicted time-settlement line using hyperbolic method. Also, the settlement in the lower non-improved layer occupied 62-76% of total settlement. Information about above results would be quite helpful to understand the long-term settlement behaviors as well as the non-improved layer's settlement is more careful consideration needed at design phase.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.240-246
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• 2019

The noise generated by construction machinery operating at construction sites is a major cause of environmental disputes with nearby residents. To reduce construction site noise, low noise construction machinery and low noise methods are recommended to be used first. In addition, the possible noise should be predicted and preventive measures suitable for the noise source should be taken. This study analyzed the sound power level of an excavator, which is used most frequently at construction sites. The sound power level of 297 excavators sold in Korea after 2008 were analyzed and the sound power level was classified according to the type, output (kW), and production site of the excavator engine based on the measured data. As a result, the sound power level decreased by 1 dBA depending on the change in engine type and the sound power level increased by approximately 3 dB (A) when the engine output was doubled. In addition, the sound power level was low in small-sized products of less than 55 kW for overseas products and medium and small-sized products of 55 to 104 kW for domestic products.

• Journal of the Korean Geotechnical Society
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• v.35 no.1
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• pp.31-42
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• 2019

About 3% of Casein is included in milk and it accounts for 80% of milk's protein. It has an adhesive property when mixed with calcium hydroxide and sodium hydroxide solutions. It has been usually used to bond woods under dry condition but becomes weak when exposed to moisture. Such weakness is very critical when casein is applied for soil cementation under groundwater condition. Therefore, this study was aimed to protect such weakness by changing or adding certain ingredients of casein adhesive. Two types of cemented specimens were prepared with Nakdong river sand and tested for unconfined compressive strength and durability. Each specimen was mixed with casein or cement. Ingredients of casein binder suggested by the University of Wisconsin, which is called a standard casein recipe, was also prepared. This study tried 6 different types of casein binder recipe. Among them, one with 30% hydroxide calcium increase and 50% hydroxide sodium decrease compared with the standard casein was most effective. Based on the most effective casein recipe, cemented sand with 1-4% of casein ratio was prepared and tested. The unconfined compressive strength and durability index were 6,253kPa and 92% for the specimen with 4% of casein ratio and 1,500kPa and 62% for the one with 8% of cement ratio. Therefore, casein cemented sand showed better performance. In addition, over 3% of casein cemented sand had over 80% durability index.

• Korean Journal of Environment and Ecology
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• v.35 no.2
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• pp.126-134
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• 2021

It is necessary to set a management period by analyzing growth trends for individual species because the time taken for planted trees to become established differs by species. The purpose of this study was to suggest an appropriate management period through the analysis of the annual growth of Pinus densiflora planted in the riverine eco belt. The average annual growth before planting was 0.6cm. The growth after planting showed an increase of 0.3cm in the 1st and 2nd year, 0.5cm in the 3rd and 4th year, and 0.7cm after the 5th year. Since P. densiflora was confirmed to go through poor growth stages in the 1st and 2nd year, a recovery stage in the 3rd and 4th year, and a normal growth stage in the 5th year, management should pay more attention to improve inappropriate environmental conditions until at least the 4th year, unlike the growth of hardwood. Since the period required for activation by species may vary, the management period of each species will need to be set through growth research.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.493-502
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• 2021

Recently, because of changes in temperature and rising water temperatures due to increased pollution sources, many algae have been produced in the water system. Therefore, there has been a lot of research using satellite images for the generation and monitoring of green algae. However, in prior studies, it is difficult to consider the optical properties of the local water system by using only a single index, and by using medium and low-resolution satellite images to conduct large-scale algae detection, there is a problem of accuracy in narrow, broad rivers. Therefore, in this work, we utilize high-resolution images of Sentinel-2 satellites to perform green algae detection on a single index (NDVI, SEI, FGAI) and development index (NDVI & SEI, FGAI & SEI) that mixes single indices. In this study, POD, FAR, and PC values were utilized to evaluate the accuracy of green algae detection algorithms, and the FGAI & SEI index showed the highest accuracy with 98.29% overall accuracy PC.

• Journal of Wetlands Research
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• v.23 no.2
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• pp.133-143
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• 2021

This study aims to classify the plant communities of the Gudam wetland, a riparian wetland in Nakdong River basin, and to identify the characteristics of the communities according to the veritical structure to prepare management plan. In the Gudam wetland, a total of 19 plant communities were found through physiognomical vegetation, and were analyzed by dividing into tree dominant community, shrub dominant community, and herbaceous dominant community according to the vertical structure. When examining the results of the community characteristics analysis, the species diversity index was the highest in the tree dominant communities but there was concern about a decrease in species diversity due to the influx of exotic plants such as Sicyos angulatus. The shrub dominant community tended to have a biased species diversity index on shrub plants. The herbaceous dominant communities ware divided into wetland herbaceous communities and dryland herbaceous communities according to the species diversity index, and measures were needed to reduce the species diversity index due to artificial disturbances. The importance value was the highest in the arboreal Salix genus in the tree dominant communities, and the exotic plants such as Amorpha fruticosa were the highest in the shrub dominant communities. In the herbaceous dominant communities, wetland herbaceous plants such as Phragmites japonicus were high. As a result of the analysis according to ordination the tree dominant communities and shrub dominant communities were differentiated by exotic plant factors, and the herbaceous dominant communities were differentiated by hierarchy number and slope.

• Korean Journal of Environment and Ecology
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• v.35 no.3
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• pp.277-284
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• 2021

This study surveyed the ecological characteristics of Squalidus gracilis majimae at Nakdong River tributary Sinan Stream from January to December 2020. The species inhabited the riverbed that was mostly covered with gravel and sand. The water depth was 27-158 cm, and the average was rather deep at 54 cm. The stream velocity was slow at 0.41±0.19 (0.24-0.86) m/sec. The gender ratio of females to males was 1:0.73. According to the total length-frequency distribution, the age indicated that the group with less than 50 mm in total length was one year old, the group with 70-69 mm was two years old, and the group over 70 mm was three years old. The total length of sexually mature fishes was 50 mm for females and 60 mm for males. The spawning season was from June to July, and the water temperature was 20.9-23.4℃ during the period. The prosperous spawning season was July. The average number of eggs in the ovaries was 1,009 (595-1,630) per matured female, and the matured eggs were yellowish and spherical with a mean diameter of 0.78±0.08 (0.57-0.83) mm. The live foods were S. gracilis majimae Protozoa, attached algae, zooplankton, and aquatic insects. The feeding habits of S. gracilis majimae are omnivorous, but more than 80% of the stomach content was aquatic insects, Chironomidae spp. The larger the size of this species, the greater the amount and frequency of eating aquatic insects, which are animal feeds. The population that ate aquatic insects did not eat vegetable food.

• Journal of Environmental Impact Assessment
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• v.31 no.2
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• pp.95-105
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• 2022

Busan, where the coastal ecosystem health is deteriorating due to high development pressure and intensity of use, needs ecosystem management that considers humans and the natural environment together for sustainable use and ecosystem preservation of the coastal areas. In this study, the InVEST model was applied to assess the habitat status of the coastal land and coastal sea to manage the ecosystem based on habitats. As a result of the assessment of the coastal land, the habitat quality of Gadeok-do, Igidae, and Sinseondae, Gijang-gun are high, and Seo-gu, Jung-gu, Dong-gu, and Suyeong-gu are low. In the case of the coastal sea, the habitat risk of the Nakdong river estuary is low, and some areas of Yeongdo-gu, Saha-gu, Gangseo-gu are high. Therefore, for the sustainable use and preservation of coastal ecosystems, it is necessary to prepare ecosystem-based management measures to improve damaged habitats and reduce threats. In addition, the impact on coastal seas should be fully considered when planning coastal land development. The results of the InVEST habitat quality model in coastal land show similar tendencies to the biotope and environmental conservation value assessment map. The results of the habitat risk assessment in the coastal sea are expected to be utilized to identify habitats in the coastal sea and management of threat factors.