• Journal of Korea Water Resources Association
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• v.56 no.3
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• pp.165-171
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• 2023

The Nakdong Estuary Barrage is a tidal river environment where freshwater and seawater meet. This requires systematic monitoring of both surface water discharged from the estuary barrage and submarine groundwater discharge. In this study, upstream hydrograph and water balance analysis were used to calculate the change in water storage and discharge of the Nakdong Estuary Barrage. Submarine groundwater discharge was also calculated based on remote sensing-based digital elevation model data and hydrological modeling data, and compared with the estimated surface water discharge for analysis. Our proposed method can be efficiently applied to water resource management by utilizing remote sensing-based altimeter data other than field measurement. Because submarine groundwater discharge plays a significant role on the coastal environment as well as surface water discharge from an estuary barrage, studies on groundwatersurface water interactions in a river estuary should be sufficiently considered in monitoring the ecosystem of the Nakdong Estuary Barrage.

• Journal of Wetlands Research
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• v.14 no.1
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• pp.75-87
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• 2012

Hyporheic zone is a region beneath and alongside a stream, river, or lake bed, where there is mixing of shallow groundwater and surfacewater. Hyporheic exchange controls a variety of physical, biogeochemical and thermal processes, and provides unique ecotones in a aquatic ecosystem. Field and experimental observations, and modeling studies indicate that hyporheic exchange is mainly in response to pressure gradients driven by the geomorphological features of stream beds. In the reach scale of a stream, pool-riffle structures dominate the exchange patterns. Flow over a pool-riffle sequence develops recirculation zones and stagnation points, and this flow structures make irregular pressure gradient which is driving force of the hyporheic exchange. In this study, 3 D hydro-dynamic model solves the Reynolds-averaged Navier-Stokes equations for the surface water and Darcy's Law and the continuity equation for ground water. The two sets of equations are coupled via the pressure distribution along the interface. Simulation results show that recirculation zones and stagnation points in the pool-riffle structures dominantly control the upwelling and downwelling patterns. With decrease of recirculation zones, length of donwelling zone formed in front of riffles is reduced and position of maximum downwelling point moves downward. The numerical simulation could successfully predict the behavior of hyporheic exchange and contribute the field study, river management and restoration.

• Korean Journal of Remote Sensing
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• v.33 no.6_2
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• pp.1139-1149
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• 2017

Measuring tree's volume is very important input data of various environmental analysis modeling However, It's difficult to use economical and equipment to measure a fragmented small green space in the city. In addition, Trees are sensitive to seasons, so we need new and easier equipment and quantification methods for measuring trees than lidar for high frequency monitoring. In particular, the tree's size in a city affect management costs, ecosystem services, safety, and so need to be managed and informed on the individual tree-based. In this study, we aim to acquire image data with UAV(Unmanned Aerial Vehicle), which can be operated at low cost and frequently, and quickly and easily quantify a single tree using SfM-MVS(Structure from Motion-Multi View Stereo), and we evaluate the impact of reducing number of images on the point density of point clouds generated from SfM-MVS and the quantification of single trees. Also, We used the Watertight model to estimate the volume of a single tree and to shape it into a 3D structure and compare it with the quantification results of 3 different type of 3D models. The results of the analysis show that UAV, SfM-MVS and solid model can quantify and shape a single tree with low cost and high time resolution easily. This study is only for a single tree, Therefore, in order to apply it to a larger scale, it is necessary to follow up research to develop it, such as convergence with various spatial information data, improvement of quantification technique and flight plan for enlarging green space.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.445-453
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• 2005

Relative importance between bottom-up and top-down controls on phytoplankton dynamics was investigated in the Juam Reservoir, Chonnam based on the results from statistical analyses including regression and artificial neural network (ANN) modeling. Effects of nutrients on size-structured phytoplankton dynamics were explored by simple linear regression analysis and relative importance between bottom-up and top-down controls was estimated based on results from the artificial neural network analyses. Although there is a limitation in determining direct grazing effects since chlorophyll a : pheopigments ratios, indirect index for grazing activity rather than grazing rates or herbivores biomass were used, the results from regression analysis showed that nutrients especially orthophosphates were positively correlated with the phytoplankton biomass and chlorophyll a : pheopigments ratios were also positively correlated with the phytoplankton biomass at lower coefficient of determination ($r^2$) compared to orthophosphates. The simulation results from ANN suggested that the bottom-up mechanisms including water temperature and availability of nutrients, especially orthophosphates were more important than top-down mechanisms such as grazing in the phytoplankton dynamics.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.358-368
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• 2011

Responses of plankton populations to nutrient enrichment in mesocosm experiments in Shihwa lake were simulated using FVCOM. Dissoloved oxygen module was added to the FVCOM to simulate impacts of its decreased levels. The ecological model included the major components of the pelagic ecosystem including nutrients, phytoplankton (pico-, nano-, micro-), zooplankton (two groups of protozoa, mesozooplankton), particulate organic matter, dissolved organic matter and bacteria, and was calibrated using trophodynamic data collected from Gyeonggi Bay and Shihwa Lake. The model was able to reproduce major responses of plankton populations to nutrient enrichment, including phytoplankton of different size groups, change of dominance of protozoa from < 20 ${\mu}m$ oligotrichs to scuticociliates, and reponses to bacteria and low levels of dissolved oxygen in water column of the mesocosms.

• Journal of Korean Society of Forest Science
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• v.104 no.1
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• pp.1-13
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• 2015

Korea now boasts a vastly forested landscape resulting from a successful forest restoration projects carried out in the past several decades. However, Korea's forest now face new challenges, such as the rapidly increasing mature forests, climate change, and various novel forest disturbances with both natural and anthropogenic causes. Considering the extensive spatial and temporal scale of the forests and the challenges it face, it is necessary to utilize a tool that can properly tackle the issues with such nature. This brings our attention to Forest Landscape Models, which have been actively developed and used to improve our understanding of how forests respond to a variety of changes and to satisfy the society's demand on forests and its ecosystem services. A large variety of Forest Landscape Models exist, with a wide spectrum of algorithms, various selections of ecological processes they simulate, and the spatial and temporal scale they utilize, so that any researcher may find a model that fits one's use. However, it is important to properly understand the properties of such models so that the right model is used and the results are aptly interpreted. In this study, we describe and characterize the various Forest Landscape Models based on their historical roots, lineages, and development, ecological characteristics, and computational aspects, and discuss how they can be classified and what limits should be recognized to assist in model selection and utilization.

• Journal of Korea Water Resources Association
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• v.41 no.3
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• pp.293-303
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• 2008

Reservoir turbidity flows degrade the efficiency and sustainability of water supply system in many countries located in monsoon climate region. A decision support system called RTMMS aimed to assist reservoir operations was developed for the real time monitoring, modeling, and management of turbidity flows induced by flood runoffs in Daecheong reservoir. RTMMS consists of a real time data acquisition module that collects and stores field monitoring data, a data assimilation module that assists pre-processing of model input data, a two dimensional numerical model for the simulation of reservoir hydrodynamics and turbidity, and a post-processor that aids the analysis of simulation results and alternative management scenarios. RTMMS was calibrated using field data obtained during the flood season of 2004, and applied to real-time simulations of flood events occurred on July of 2006 for assessing its predictive capability. The system showed fairly satisfactory performance in reproducing the density flow regimes and fate of turbidity plumes in the reservoir with efficient computation time that is a vital requirement for a real time application. The configurations of RTMMS suggested in this study can be adopted in many reservoirs that have similar turbidity issues for better management of water supply utilities and downstream aquatic ecosystem.

• The Journal of the Korea Contents Association
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• v.21 no.4
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• pp.26-37
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• 2021

This study conducted a big data analysis on news to identify the agenda of media literacy, which has been socially discussed, and on which relevant policy directions will be proposed. To this end 1,336 articles from January 1, 2019 to September 30, 2020 were collected and a topic modeling analysis was conducted according to four periods. Five topics for each period were derived through the analysis, and implications based on the results are as follows. First, the government should implement a nation-level systematic approach to media literacy education according to life cycle stages to generate economic and cultural value. Second, local communities and schools should provide systematic support and education guidance activities to ensure a sustainable ecosystem for media literacy and prevent an educational gap and loss in learning. Third, efforts should be made in various aspects to minimize the side effects resulting from constantly providing media literacy education; furthermore a culture of desirable media application should be established. Finally, a research environment for scientific research on media literacy, active exchange of experience and value obtained in the field, and long-term accumulation of research results should be encouraged to develop a robust knowledge exchange culture.

• Knowledge Management Research
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• v.25 no.2
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• pp.177-191
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• 2024

This study aims to analyze policy changes over time by conducting a textual analysis of the basic plan for activating convergence research and development. By examining the basic plan for convergence research development, this study looks into changes in convergence research policies and suggests future directions, thereby exploring strategic approaches that can contribute to the advancement of science and technology and societal development in our country. In particular, it sought to understand the policy changes proposed by the basic plan by identifying the relevance and trends of topics over time. Various analytical methods such as TF-IDF analysis, topic modeling (LDA), and network (CONCOR) analysis were used to identify the key topics of each period and grasp the trends in policy changes. The analysis revealed clustering of topics by period and changes in topics, providing directions for the convergence research ecosystem and addressing pressing issues. The results of this study are expected to provide important insights to various stakeholders such as governments, businesses, academia, and research institutions, offering new insights into the changes in policies proposed by previous basic plans from a macroscopic perspective.

• Korean Journal of Ecology and Environment
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• v.49 no.1
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• pp.51-61
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• 2016

This study was carried out to assess the carbon budget of two urban parks and one natural park and to prepare the plan for improving the ecological functions of the park including carbon sink. Net Ecosystem Production (NEP) of those study sites was calculated from the relationship between Net Primary Production (NPP) and soil respiration of each study site. To understand carbon budget of the whole area designated as the park, carbon budget of the urban park was analyzed by classifying the vegetated and the non-vegetated zones. NEP of the Nohae and the Sanggye parks calculated by reflecting areal size that the non-vegetated zones occupy were shown in -1.0 and $0.6\;ton\;C\;ha^{-1}yr^{-1}$, respectively. On the other hand, NEP of Mt. Bulam natural park as a reference site was in $2.3\;ton\;C\;ha^{-1}yr^{-1}$. Based on the result, the Nohae park was assessed as carbon source rather than carbon sink. On the other hand, the Sanggye park was classified as carbon sink but the role was poor compared with natural park. The result is, first of all, due to lower NPP of the vegetation introduced for the parks compared with natural vegetation. The other reason is due to wide arrangement of non-vegetated zone. To solve those problems and thereby to create the urban park with high ecological quality, selection of plant species suitable for the ecological characteristic of the park, their arrangement imitated natural vegetation, and ecological zoning were recommended.