• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.2
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• pp.237-243
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• 2019

Floating platforms made of PE (PolyEthylene) are often located in shallows of seas, rivers or lakes. They are widely used for marine pensions, marine pontoons, marine bridges, etc. These products are characterized by good flexibility, recyclability, chemical resistance and weatherability with corrosion resistance. Existing PE floating platforms have a simple structure in which one pipe is fastened to one bracket, but this has limited application, even if a user modifies the arrangement. Therefore, we developed a structure that allows buoyancy pipes of various sizes to be fastened to one bracket and verified the structural safety of the product using the finite element method. From the results of structural analysis for buoyancy pipes of different diameters, the maximum stress ratio was 0.78 compared with allowable criteria of 1.0, which represented sufficient safety for a model with 500 mm diameter pipes. Based on the results of this study, further research to evaluate the structural safety of various floating platforms can be carried out in the further; it will also be necessary to establish related evaluation criteria.

• Proceedings of the Korean Society for Information Management Conference
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• 2017.08a
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• pp.103-103
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• 2017

생태학 분야에서는 생물의 분포, 변동, 서식환경요인의 변화, 등의 여러 종류의 데이터들이 수집되고 있는데 데이터의 형태가 다양하여 데이터의 관리와 활용형태도 다양하게 나타나고 있다. 근래에 들어 각 종 측정기기들이 개발되면서 생태조사 분야에서도 데이터의 양이 급증하는 시점에 있다. 수생태계 분야에서도 전통적인 생물상조사의 데이터는 크게 증가하지 않고 있지만 자동측정센서가 개발된 항목의 경우에는 데이터가 급증하는 단계에 있다. 수생태계에서 흔히 조사되는 플랑크톤의 군집구조 자료를 보면 하나의 조사대상 시료에서 출현하는 종의 수가 50 종정도에 이르며 각 개체의 종을 육안으로 확인하고 있으므로 종조성조사는 아직 자동화가 어렵다. 그러므로 플랑크톤 자료의 특성은 조사의 시료수(case)는 적고 측정항목(변수 variable)이 많은 특성을 가진다. 반면에 센서가 개발된 수질과 관련된 항목들은 자동측정설비가 확대되고 있어 변수는 적지만 장기간의 time series 들이 수집되고 있다. 녹조현상이 관심을 끌면서 여러 곳에 식물플랑크톤의 양을 측정하는 chlorophyll 센서가 설치되고 있는 것이 대표적인 사례이다. 그 외에 정량화되지 못하는 정성적 자료들도 수집되고 있으며 자료수집방법의 표준화도 미흡한 예가 많이 있고, 자료의 형태가 다양하여 데이터의 관리와 활용을 어렵게 한다. 환경부는 전국의 주요 하천 지점에서 정기적으로 수질을 측정하여 공개하고 있으며, 일부 지점에는 자동수질측정시설을 설치하여 측정의 빈도를 높이고 있다. 하천이나 호수에서 센서를 이용한 고빈도 모니터링은 그 동안 인지하지 못하였던 단기적 생태계 변화에 대해 새로운 정보를 제공하여 연구의 장르를 넓혀 가고 있다. 도시하천에서 산소를 측정한 사례를 보면 강우 시에 일시적으로 산소가 고갈되는 현상이 관찰되며, 부영양한 호수와 하천에서는 주야간 산소의 급격한 변동이 생태계 스트레스 요인으로 작용하고 있음을 알 수 있었다. 식물플랑크톤 센서의 연구에 의해 단기적인 변동이 크게 나타나고 있음이 새로이 밝혀지기도 하였다. 데이터의 수집과 활용도를 높이려는 노력도 이루어지고 있다. 과거에는 개인단위로 이루어지던 연구가 이제는 데이터를 수집하고 공유하는 플랫폼이 만들어 지면서 공동연구가 확대되고 있고, 국제적으로 지역을 초월하는 공동연구도 가능하게 되었다. 국제호수관측망학회(Global Lake Ecological Observatory Network, GLEON)이 그 사례이며 세계 여러 나라의 학자들이 참여하여 국제적으로 데이터를 공유하고 공동연구를 촉진하는 역할을 하고 있다. 생태계데이터의 증가는 생태학자들의 연구역량을 초과하는 데이터의 관리와 활용의 능력을 요구할 것이며 환경 생태 IT 분야의 융합연구의 필요성이 크게 대두되고 있다. 그간 데이터베이스의 구축에는 일부 성과가 있었으나 아직 수집된 데이터의 활용도를 높이고 타분야와의 협력연구 시너지를 확대하려는 노력은 부족하다. 이제는 데이터의 수집과 저장뿐 아니라 데이터의 활용도를 높일 수 있도록 학제적 협력연구를 촉진하는 off-line 모임도 확대할 때이다.

• Convergence Security Journal
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• v.17 no.5
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• pp.143-151
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• 2017

The purpose of this study is to provide the future development of the PRC Marine Corps by analyzing the changing functions via its historical development. The PRCMC is an elite regular military forces and was established by the Central Military Commission(China) in 1953 in order to project the national military power toward the enemy's territory by overcoming maritime obstacles such as seas and lakes. The PRCMC is relatively smaller personnel strength compared with the whole size of the PRC military forces. Thus its functions were limited in the areas of amphibious and land operations, island and land defense against Taiwan before the PRC pursues expanding policy toward outside. However, in the 2000s, China pursues its policy for obtaining absolute national interest so that its functions are rapidly enlarged into defense of the forward naval bases, and those for evolving its power toward outside according to not only the island territorial dispute with Japan, but also Xi Jinping's active expanding policy what we call 'the one belt and one road'. So its personnel strength is slowly increased. If the increasement of the PRC Navy and Marine Corps would develop into the level of which they can contain the status and influence of the US military power in Asia-Pacific area, it is possible that the security environment of the North-east Asia including the Korean peninsula will be fluctuated. Consequently, the ROK also needs to reevaluate the functions and the size of the joint strength of the ROK Navy and Marine Corps considering the transition of the changing security environment.

• Journal of Korean Society of Disaster and Security
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• v.12 no.1
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• pp.23-34
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• 2019

It is an urgent issue to manage and reduce non-point pollution sources for improving the water quality of stream and lakes in rural areas. In this study, in order to reduce non-point pollution sources in rural area, Gabion mattresses was proposed to provide protection of riverbanks with anaerobic and aerobic area. The utilization of this was assessed by lab scale model test and pilot plant test. After filling the inside of the gabion mattresses with aggregate, the filtration zone under anaerobic and aerobic conditions was formed to treat the contaminants. In addition, vegetation was deposited on the surfae of the gabion to prevent the inflow of soil and to promote purification by the plant. COD and nitrogen content (T-N, $NH_4{^+}$, -N, $NO_3{^-}N$) were monitored in model and field tests. The lab scale model test showed removal efficiency of 17% of TCOD, 35% of SCOD, 14% of TN, 62% of $NH_4{^+}$, -N, and 33% of $NO_3{^-}$ N. Also, pilot plant test showed removal efficiency of 24% of TCOD, 29% of SCOD, 47% of TN, 50% of $NH_4{^+}-N$, 33% of $NO_3{^-}$, N and 29% of TP.

• Journal of Korean Society on Water Environment
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• v.37 no.5
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• pp.381-397
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• 2021

Off-flavor materials (geosmin and 2-methylisoborneol (2-MIB)) produced by microorganisms, such as, cyanobacteria and actinomycetes, cause freshwater use problems worldwide. Due to unpleasant taste and odor, these microorganisms have raised issues especially in drinking water resources. Recently, there has been increasing concern about 2-MIB and causal cyanobacteria, namely, Pseudanabaena, in Korea. However, material production and ecological dynamics remain largely unexplored. This study reviewed the distribution of Pseudanabaena, its species diversity, and the research trend of molecular ecology related to 2-MIB production in Korea. Based on published literature, we found that seven species of Pseudanabaena which include P. mucicola, P. limnetica, P. redekei, P. catenata, P. galeata, P. yagii, and P. cinerea appeared to occur in a variety of Korean water systems. All of these Pseudanabaena species were found in the North-Han River system (Lakes Soyang, Chuncheon, Uiam, and Paldang). Some of these species were also detected in other watersheds, but the precise species diversity was not identified. Species belonging to the Pseudanabaena genus are hard to classify through general microscopic alpha taxonomy, due to their very small cell size and similar morphological characters. Moreover, the potential of 2-MIB production cannot be detected by microscopic observation. Combining molecular ecological techniques, such as, environmental genomic materials (eDNA, eRNA) analyses to conventional methods could be useful to better understand the off-flavor material production and dynamics, thereby providing more efficient management strategies of freshwater systems.

• Journal of Korean Society on Water Environment
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• v.27 no.4
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• pp.491-498
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• 2011

We investigated the ranges of total cellular microcystins content of cyanobacterial blooms collected in Korean lakes and rivers from 2005 to 2009. The amount and composition of microcystins of Korean cyanobacteria varied depending on the sampling water bodies and dominant cyanobacterial genera. Toxic cyanobacterial cell numbers equivalent to $1{\mu}g$ MCYSTs/L using total cellular microcystin content of Korean cyanobacteria were in the range of 2,348 to 66,980,638 cells/mL. Only four samples among forty nine samples showed less cell numbers than current criterion of Harmful Algae Alert System, 5,000 cells/mL indicating current criterion do not reflect properly the microcystins content of Korean cyanobacteria. Anabaena and Aphanizomenon spp. showed three to six times higher cell numbers equivalent to $1{\mu}g$ MCYSTs/L than Microcystis spp. To propose criteria of Harmful Algae Alert System for Korean toxic cyanobacteria, we calculated about 50% selective geometrical means of cyanobacterial cell numbers equivalent to $1{\mu}g$ MCYSTs/L in order of toxic content. The proposed criteria for Microcystis, Oscillatoria, Anabaena, and Aphanizomenon spp., are 10,000, 20,000, 40,000, and 80,000 cells/mL, respectively.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.38 no.4
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• pp.39-48
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• 2020

This study examined the type, the structural shapes, and the representation of Sandae, which was the stage for traditional performing arts and constructed for the purpose of imperial processions, ritual ceremonies, banquets, etc. from the Goryeo Dynasty to the Late Joseon Dynasty, and the implications of Seokgasan, which was built in the same era. First, through the history and meaning of Sandae, it was confirmed that Sandae has a homogeneity with Seokgasan, which attempted to imitate the shape of "Mountain" in the outer space. The construction of Sandae was deeply related to the tradition of famous mountains. This is consistent with the fact that 'Famous mountains and lakes" in China was symbolically replicated on the Seokgasan in the front yard of the "Cheongyeongak" in the Goryeo Dynasty. Second, Sandae and Seokgasan differed in their structural shapes, materials, and production methods, but they were used as a stage background for national events by constructing in the shape of the mountain, and appeared in various types. It can be seen that the interest in gardens and art of those days has resulted in various formative expressions of nature through the shape and symbolic meaning of the Sandae that mimics the mountain. Third, it is presumed that the square pond with lotus flowers, which is believed to have been located in the center of the garden of Shin Jaehyo's old house, and the Sugak and Seokgasan adjacent to it were not only elements of the garden, but also functioned as a background for the training and performance stage of Shin Jaehyo's students.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.39 no.4
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• pp.66-76
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• 2021

The purpose of this study was to analyze the transition process of Gyeongpo lake and to analyze the viewing characteristics of each period in the pavilion. The view characteristics at pavilion were analyzed by overlapping classification maps of landscape types by period with the view range map from pavilion. The circumference and area of Gyeongpo lake have been reduced to 15.2km and 3.9km² in the 1750s, 9.0km and 1.7km² in the 1933, and now 4.41km and 1.0km². By period, the largest decrease in the proportion of Gyeongpo lake viewed from Pavilion was Hwanseonjeong, which decreased by 48.0% from the 1750 to 2017. Hwallaejeong, Haeunjeong, and Hohaejeong were found to be impossible to view Gyeongpo lake as some of the adjacent lakes were changed to agricultural land. Pavilion has great significance as a space for traditional culture created in the background of humanities and natural environments. For the succession and development of Pavilion culture, it is necessary to use it as a cultural resource, to continuously manage the building, and to partially restore Gyeongpo lake considering the function of each pavilion.

• Journal of Korean Society on Water Environment
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• v.38 no.1
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• pp.19-30
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• 2022

Climate change has increased the average air temperature. Rising air temperature are absorbed by water bodies, leading to increasing water temperature. Increased water temperature will cause eutrophication and excess algal growth, which will reduce water quality. In this study, long-term trends of air and water temperatures in the Han-river basin over the period of 1997-2020 were discussed to assess the impacts of climate change. Future (~2100s) levels of air temperature were predicted based on the climate change scenarios (Representative concentration pathway (RCP) 2.6, 4.5, 6.0, and 8.5). The results showed that air and water temperatures rose at an average rate of 0.027℃ year^-1 and 0.038℃ year^-1 respectively, over the past 24 years (1997 to 2020). Future air temperatures under RCP 2.6, 4.5, 6.0, and 8.5 increased up to 0.32℃ 1.18℃, 2.14℃, and 3.51℃, respectively. An increasing water temperature could dissolve more minerals from the surrounding rock and will therefore have a higher electrical conductivity. It is the opposite when considering a gas, such as oxygen, dissolved in the water. Water temperature also governs the kinds of organisms that can live in rivers and lakes. Fish, insects, zooplankton, phytoplankton, and other aquatic species all have a preferred temperature range. As temperatures get too far above or below this preferred range, the number of individuals of the species decreases until finally there are none. Therefore, changes of water temperature that are induced by climate change have important implications on water supplies, water quality, and aquatic ecosystems of a watershed.

• Journal of Korea Water Resources Association
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• v.54 no.spc1
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• pp.1037-1051
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• 2021

Biochemical oxygen demand (BOD) concentration, one of important water quality indicators, is treated as the measuring item for the ecological chapter in lakes and rivers. This investigation employed novel two-stage hybrid paradigm (i.e., wavelet-based gated recurrent unit, wavelet-based generalized regression neural networks, and wavelet-based random forests) to predict BOD concentration in the Dosan and Hwangji stations, South Korea. These models were assessed with the corresponding independent models (i.e., gated recurrent unit, generalized regression neural networks, and random forests). Diverse water quality and quantity indicators were implemented for developing independent and two-stage hybrid models based on several input combinations (i.e., Divisions 1-5). The addressed models were evaluated using three statistical indices including the root mean square error (RMSE), Nash-Sutcliffe efficiency (NSE), and correlation coefficient (CC). It can be found from results that the two-stage hybrid models cannot always enhance the predictive precision of independent models confidently. Results showed that the DWT-RF5 (RMSE = 0.108 mg/L) model provided more accurate prediction of BOD concentration compared to other optimal models in Dosan station, and the DWT-GRNN4 (RMSE = 0.132 mg/L) model was the best for predicting BOD concentration in Hwangji station, South Korea.