• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.209-215
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• 2015

Miraculous victory of Myeongnyang sea battle turned the tide of the Joseon's entire war against Japan and it is regarded as one of the most remarkable sea victories in the world history. In the sea battle of Myeongnyang, on September 16, 1597(lunar calender), the Joseon navy with 13 battle ships, led by Admiral Yi Sun-sin, won the Japanese navy with their fleet of 133 warships. There were several reasons why Admiral Yi decided on this location for battle. Myeongnyang strait is so narrow and had currents so powerful that many ships could not pass strait simultaneously. Therefore, despite being vastly outnumbered, Admiral Yi used terrain and tidal current advantage to defeat Japanese navy's numerical advantage. In order to find out the tidal state of Myeongnyang strait on September 16, 1597, topological phase of sun and moon was studied by orbital period of earth and moon. The tidal state of Myeongnyang strait on September 16, 1597 is estimated based on the theories of tide and tide tables. As a result of this study, time of slack water were found to be 0636, 1248, 1906 and time/speed of maximum tidal current were found to be 0930/8.3kts(NW), 1612/9.9kts(SE).

• Journal of Korean Society of Environmental Engineers
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• v.38 no.9
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• pp.482-496
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• 2016

Algal blooms of cyanobacteria (blue-green Algae) due to the eutrophication of rivers and lakes can cause not only the damage by its biological toxins but also the economic loss in drinking water treatment. The natural algae coagulant, a commercial product known as W.H. containing the algicidal and allelopathic material derived from oak, can control algal problems proactively through the coagulation flotation process. However, because there have been no applications of the process for pre-treatment in drinking water plants, we could find no report on the optimum injection dose of W.H.. In this study, we have conducted several sets of jar-tests while changing W.H. dose and concentration of chl-a for (1) Han-river samples and (2) subcultured cyanobacteria samples, and monitored the removal mechanisms of algae intensively. Based on these jar-test results, two linear equations with variables of chl-a and turbidity have been deduced to predict the optimal W.H. dose after the multiple regression analysis using IBM-SPSS. Also, prototypes of automatic control logic have been suggested to inject the optimal W.H. dose promptly in response to the variation of water quality.

• Smart Media Journal
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• v.7 no.1
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• pp.45-51
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• 2018

Avian influenza (AI) is notorious for its rapid infection rate, and has a serious impact on consumers and producers alike, especially in poultry farms. The AI outbreak, which occurred nationwide at the end of 2016, devastated the livestock farming industries. As a result, the prices of eggs and egg products had skyrocketed, and the event was reported by the media with heavy emphasis. The purpose of this study was to investigate the correlation between the egg price fluctuation and the keyword changes in online news articles reflecting social issues. To this end, we analyzed 682 cases of AI-related online news articles for fourteen weeks from November 2016 in South Korea. The results of this study are expected to contribute to understanding the relationship between the actual price of eggs and the keywords from news articles related to social issues.

• 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.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.269-276
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• 2003

The study was performed to understand the relationships of cyanobacterial bloom and environmental factors in Lake Daechung. The samples were collected weekly from June to October in 2001. The cyanobacterial bloom was divided into the three phases of the early phase, the middle phase and the late phase by phytoplankton standing crops. For the early phase, the correlation coefficients between chl- a and TP, and chl- a and $PO_4$-P were 0.986 and 0.894 respectively. Therefore, phosphorus was a main environmental factor in the development of cyanobacterial bloom. Zeu/Zm ratio and chl-a showed negative correlation of r = -0.995. At the late phase, $PO_4$-P showed the highest relationship (r = 0.958), and TP and temperature showed relatively high relationships (r = 0.857 and r = 0.813). At the late phase, $NH_3$-N showed highly positive relationship (r = 0.921). It was confirmed that $PO_4$-P was the most important contribution factor for the bloom through the regression analysis on the environmental factors. As the result, the decrease of Zeu/Zm ratio and the increase of P concentration influenced cyanobacterial bloom developed rapidly in the early phase. Also the cyanobacterial bloom was decreased in proportion to decreasing of $NH_3$-N concentration in the late phase. It was expected that observation of $NH_3$-N may be a very useful factor on monitoring of the decreasing situation of the bloom.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.4
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• pp.56-65
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• 2000

This paper deals with the experimental study on the characteristics of current in the ocean engineering basin of KRISa, The unsteady characteristics of the flow is examined by analyzing time histories of streamwise velocity at some points. The major frequency of the fluctuating velocity was found by the spectral analysis of the measured data. The vertical and spanwise distributions of time averaged velocities were also examined. Especially, vertical distributions of the streamwise velocities with guide vanes are compared with those without guide vanes and it confirms the effeciency of the guide vane to improve the uniformity of the vertical profile of streamwise velocity. Finally, the measured data are regressed to give the relation between revolutions per minute(r.p.m.) and mean velocity.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.358-358
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• 2016

본 연구에 앞서 가뭄에 따른 충청남도 서부권의 물 부족을 해결하기 위하여 금강 본류로부터 보령댐으로 일정 유량을 도수(diversion)하는 계획이 금강 본류에 미치는 수리적 영향을 1차원 비정상류 해석(unsteady flow analysis)을 통하여 분석하였으며, 본 연구에서는 수리모형 결과와 연계하여 수질 모형을 구축하여 금강 본류 수질에 미치는 영향을 알아보고자 하였다. 조위 영향에 따른 염도의 역류 모의를 위하여 전자해도와 위성영상자료를 활용하여 금강 하굿둑에서 외해 방향으로 약 9km에 이르는 모의 구간을 확장하였으며, 상류단의 진두수위표를 포함한 8개 지천의 유입유량 및 수질, 하구의 조위와 염도, 농공용수 취수시설의 취수량 및 회귀수 수질, 금강 배수갑문 운영, 대상 구간에 인접한 기상대의 기상자료 등을 고려하고 금강 본류를 따라 9개 수질측정소의 수질자료를 이용하여 모형의 보정을 실시하였다. 또한 대상 구간 내 2015년의 갈수기 유황 분석을 토대로 비선형 회귀분석식을 도출하여 2016년 갈수기 예측 유량과 함께 수질-유량 관계식을 도출하여 대상 구간의 수온, 염도, 용존산소(DO), BOD, 조류 등 영향을 분석하였다. 수온 분석 결과, 지점에 따라 2015년 유황 대비 평균 수온 1.79~3.83도, 최고 수온 1.74~4.30도 상승할 것으로 모의되었으며, 염도는 2016년 갈수기 동안의 금강 하굿둑 외해 염도는 담수 방류량의 감소로 전년 동기 대비 평균 53% 증가하는 것으로 모의되어 기수역 생태계에 상당한 영향을 줄 것으로 분석되었으며, 갈수기 동안의 금강 하굿둑 내수의 염도는 배수갑문 개방 빈도, 개방 시간, 개방 정도의 감소에 따른 해수 역류의 감소로 전년 동기 대비 크게 감소할 것으로 모의되었다. 용존산소는 2016년 갈수기 동안의 용존산소 농도는 지점에 따라 전년 동기 대비 평균 4~11% 감소하는 것으로 모의되었으며, 2016년 갈수기 동안의 BOD 농도는 지점에 따라 전년 동기 대비 평균 30~57% 증가하는 것으로 분석되었다. 조류는 지점에 따라 전년 동기 대비 평균 29~67% 증가하는 것으로 모의되었다. 유량의 감소에 따른 수온 증가 및 수질 악화의 영향이 있을 것으로 분석되나, 도수에 따른 영향은 상대적으로 제한적인 것으로 분석되었다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.4
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• pp.310-321
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• 2016

This study describes the spatial distribution of dinoflagellate cyst assemblages from the fishing ports along Jeju Island. Surface sediment samples from 22 stations revealed the occurrence of 29 species involving the Groups Protoperidinioid (44.8%), Gonyaulacoid (31.0%), Calciodineloid (10.3%), Gymnodinioid (6.9%), Diplosalid (3.5%) and Tuberculodinioid (3.5%). The cyst abundance recorded here is very low ($13{\sim}220cysts\;g-dry^{-1}$) as compared to Korean coastal regions. The abundance of heterothophic cysts increased in several fishing pots with fine sediments and anthropogenic tidal pools. And cyst abundance was well correlated with the grain-size composition of surface sediments. The dinoflagellate cyst assemblages in Jeju fishing ports were characterized by the dominant species, cyst of Gymnodinium sp., cyst of Pyrodinium bahamense and cyst of Scrippsiella trochoidea in 2012, Protoperidinium sp. (Brigantedinium sp.), cyst of Scrippsiella sp./trochoidea and cyst of Gymnodinium sp. in 2014, and Protoperidinium sp. (Echinidinium sp. and Brigantedinium sp.) in 2016. The advent of the toxic dinoflagellate, Pyrodinium bahamense were recorded for the first time in Jeju coastal waters. As a results, we are determined should be to monitoring and management measures for new toxic dinoflegallates from tropical or subtropical reigions and anthropogenic tidal pools by industrial activities.

• Journal of Environmental Impact Assessment
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• v.26 no.6
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• pp.470-478
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• 2017

This study was classified into two groups, normal season group and drought season group, by the cluster analysis using the weather and water quality data from 2012 to 2015, using SPSS 18 version. Also each cluster was classified into three spaces, Gangcheon, Yeoju and Ipoh weir. We performed the multiple regression analysis with each monthly data that concentration of Chl-a was more than algae warming level. 6 groups classified in time and space were analyzed by the correlation analysis between concentration of Chl-a and 3 weather, 11 water quality and discharge factors. We developed Chl-a prediction equations of each group with independent variables of the multiple regression analysis applying to the correlation result. The result of cluster analysis was that the period was divided into two groups, normal group(2012-2013) that total annual precipitation rate was normal and drought group(2014-2015) that total annual precipitation rate was less than 1,000 mm/hr, in time. The months that concentration of Chl-a was more than algae warming level in each group classified by cluster analysis were that the normal group was 3~8 and drought group was 3 and 6~10. The correlation result between Chl-a and weather, water quality and discharge factors for each 6 group was that relationships between Chl-a and water, discharge factors were high in the drought group more than in normal group at all weirs. This was influenced by velocity reduction and increasing HRT according to the intense drought. Weather, water quality and discharge factors that were high correlation with Chl-a were applied to independent variables of Chl-a prediction equations and each equations were developed. Among them, Each adjusted R square of Prediction equations for Chl-a in each group at Ipoh weir where is located in Namhan river downstream and is directly connected to Paldang dam were normal group = 0.920 and drought group = 0.818. It's showed the high linear.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.246-247
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• 2018

Since the routes within VTS areas include harbour limit of major ports, there are sections where the traffic volume increases and the routes are normally narrow according to the geographical conditions. In the case of ports and VTS areas located on the west coast of Korea, it is affected by strong current due to large tidal differences. In this paper, we propose a method to produce useful information according to the change of navigation environment by analyzing the characteristics of ship's movement according to tidal stream or current. The SVR seaway model, support vector regression, and grid search were conducted in order to extract models.