Hongjun Joo - Academia.edu (original) (raw)
Papers by Hongjun Joo
Proceedings of the Korea Water Resources Association Conference, 2016
Proceedings of the Korea Water Resources Association Conference, 2010
The finger language is the part of the sign language, which is a language system that expresses v... more The finger language is the part of the sign language, which is a language system that expresses vowels and consonants with hand gestures. Korean finger language has 31 gestures and each of them needs a lot of learning models for accurate recognition. If there exist mass learning models, it spends a lot of time to search. So a real-time awareness system concentrates on how to reduce search spaces. For solving these problems, this paper suggest a hierarchy HMM structure that reduces the exploration space effectively without decreasing recognition rate. The Korean finger language is divided into 3 categories according to the direction of a wrist, and a model can be searched within these categories. Pre-classification can discern a similar finger Korean language. And it makes a search space to be managed effectively. Therefore the proposed method can be applied on the real-time recognition system. Experimental results demonstrate that the proposed method can reduce the time about three times than general HMM recognition method.
Han-gukbangjaehakoenonmunjip, Aug 31, 2014
This study has evaluated the stream gauge network which is considered the total hydrological info... more This study has evaluated the stream gauge network which is considered the total hydrological information and the importance class of stream gauge stations, and is applied to Namgang Dam basin. The total hydrological information and the importance class of stream gauge stations are two different physical parameters. We adopt the Euclidean distance method to consider them simultaneously. An equation obtained by the Euclidean distance method is used as the objective function in multiobjective optimization method to determine the optimal combination of the stream gauge stations for satisfying the both criteria: the maximum total amount of the hydrological information and the importance class of stream gauge stations. To evaluate the optimal stream gauge network, the representative unit hydrograph which is derived by real rainfall-runoff analysis is transferred into probability density function for the application of entropy theory concept. The importance class of stream gauge stations is determined by referring the result of MLIT (2010). As result of applying to Namgang Dam basin, The optimal stream gauge network obtained by the suggested method shows more satisfied the importance of stream gauge station purpose than the optimal stream gauge network obtain by the entropy theory only. This result implies that the optimal steam gauge network by the suggested method can consider both the total hydrological information and the importance class of stream gauge station. It is found that Namgang Dam basin needs at least 8 steam gauge stations among 12 steam gauge stations.
Proceedings of the Korea Water Resources Association Conference, 2016
Korean Society Of Hazard Mitigation, Jun 1, 2020
Nepalese Journal of Ophthalmology, 2021
Introduction: Ocular tuberculosis as choroidal tuberculoma is a rare event. It creates a clinical... more Introduction: Ocular tuberculosis as choroidal tuberculoma is a rare event. It creates a clinical diagnostic dilemma when there is no systemic involvement. Case: A 22-year-old man presented with the chief complaints of discomfort and blurring of vision of right eye for one week. On fundus examination under mydriatics of his right eye, a solitary mass which measured approximately 2DD (Disc Diameter) was appreciated at the superotemporal quadrant with the surrounding localized retinal detachment. Choroidal tuberculoma was suspected by a positive Mantoux test. Physician consultation and laboratory investigations ruled out the pulmonary and systemic manifestation of tuberculosis and other aetiology. Anti-tubercular treatment was started and this led to the improvement of vision and shrinkage of the choroidal mass into a flat chorioretinal scar at 3 months of anti-tubercular treatment . Conclusion: Solitary choroidal tuberculoma though rare, can occur in a healthy, immunocompetent pat...
Entropy, 2019
Stream gauge stations are facilities for measuring stream water levels and flow rates, and their ... more Stream gauge stations are facilities for measuring stream water levels and flow rates, and their main purpose is to produce the data required to analyze hydrological phenomena. However, there are no specific criteria for selecting the locations and installation densities of stream gauge stations, which results in numerous problems, including regional imbalances and overlapping. To address these issues, a stream gauge network was constructed in this study considering both the transinformation of entropy (objective function 1) and the importance of each stream gauge station (objective function 2). To account for both factors, the optimal combinations that satisfied the two objective functions were determined using the Euclidean distance. Based on the rainfall runoff analysis results, unit hydrographs reflecting stream connectivity were derived and applied to entropy theory. The importance of each stream gauge station was calculated considering its purposes, such as flood control, wate...
Water, 2019
The purpose of this study is to reduce the uncertainty in the generation of rainfall data and run... more The purpose of this study is to reduce the uncertainty in the generation of rainfall data and runoff simulations. We propose a blending technique using a rainfall ensemble and runoff simulation. To create rainfall ensembles, the probabilistic perturbation method was added to the deterministic raw radar rainfall data. Then, we used three rainfall-runoff models that use rainfall ensembles as input data to perform a runoff analysis: The tank model, storage function model, and streamflow synthesis and reservoir regulation model. The generated rainfall ensembles have increased uncertainty when the radar is underestimated, due to rainfall intensity and topographical effects. To confirm the uncertainty, 100 ensembles were created. The mean error between radar rainfall and ground rainfall was approximately 1.808–3.354 dBR. We derived a runoff hydrograph with greatly reduced uncertainty by applying the blending technique to the runoff simulation results and found that uncertainty is improved...
E3S Web of Conferences
The purpose of this study is to suggest a structural plan for improving the utilization of inacti... more The purpose of this study is to suggest a structural plan for improving the utilization of inactive storage in dam reservoirs, to mitigate extreme drought. Inactive storage in the dam is composed of emergency storage and dead storage. The emergency storage can be used in emergencies such as drought. But, in general, the dead storage for sedimentation is not used, even in an emergency. Therefore, we developed a methodology to determine how the dead storage space can be partially used during extreme drought periods when the sedimentation has not occurred yet. We call this partial space in a dam reservoir “drought storage”. An accurate analysis of sediment levels needs to be performed before calculating drought storage, and so the present sediment level in the dam reservoir was estimated using SED-2D linked with the RMA-2 model of SMS. After considering the additional available storage capacity based on the estimated sediment level, drought storage was finally determined. We also predi...
Water
As flood damage is becoming more frequent and severe worldwide, efficient flood control of dams h... more As flood damage is becoming more frequent and severe worldwide, efficient flood control of dams has been highlighted. The purpose of the study is to establish a simple method for dam operators to estimate the flood control capacity and predischarge level required for flood response. The cumulative probability distribution (CDF) pair with the same return period for 12 major dams located in South Korea were estimated using the frequency matching method. A Ratio of Storage volume to Flood inflow (RSF) concept was suggested and applied for each dam, and they were classified into three types: Linear, Estranged, and Vague according to the water storage characteristics. Using the method presented in this study, we suggested the required amount of flood control capacity and target water level for each dam. The results demonstrated that there is no linear relationship between flood and storage of dam when the ratio of watershed area to a storage capacity of the dam is 2.0 or more, or the rat...
Wetlands play a crucial role in maintaining human life and ecosystems. In order to conserve and m... more Wetlands play a crucial role in maintaining human life and ecosystems. In order to conserve and manage wetlands in a quantitative way, their sustainability needs to be evaluated. With this background, this study assessed the sustainability of the Binae wetland, located along the Namhan River, Korea. More specifically, we developed a wetland sustainability index (WSI), taking into account water environments, hydrometeorological factors, and the plant and animal habitats in the wetland area. Sustainability of the Binae wetland was assessed based on the WSI, which showed favorable results in general. The wetland was expected to have high sustainability in water environments and hydrometeorological factors, a moderate or low sustainability for plant habitat, and very low sustainability for animal habitat. Therefore, it can be concluded that more attention and management efforts need to be paid to the wetland’s animal habitats to make the region more sustainable.
Membrane Water Treatment, 2019
The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) predicted that... more The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) predicted that recent extreme hydrological events would affect water quality and aggravate various forms of water pollution. To analyze changes in water quality due to future climate change, input data (precipitation, average temperature, relative humidity, average wind speed and sunlight) were established using the Representative Concentration Pathways (RCP) 8.5 climate change scenario suggested by the AR5 and calculated the future runoff for each target period (Reference:1989-2015; I: 2016-2040; II: 2041-2070; and III: 2071-2099) using the semi-distributed land use-based runoff processes (SLURP) model. Meteorological factors that affect water quality (precipitation, temperature and runoff) were inputted into the multiple linear regression analysis (MLRA) and artificial neural network (ANN) models to analyze water quality data, dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen de...
Energies, 2021
Small hydropower (SHP) plants are advantageous as they have a short construction period and can b... more Small hydropower (SHP) plants are advantageous as they have a short construction period and can be easily maintained. They also have a higher energy density than other alternative energy sources as environmentally-friendly energy sources. In general, hydropower potential is estimated based on the discharge in the river basin, and the discharge can be obtained from the stage station in the gaged basin. However, if there is no station (i.e., ungaged basin) or no sufficient discharge data, the discharge should be estimated based on rainfall data. The flow duration characteristic model is the most widely used method for the estimation of mean annual discharge because of its simplicity and it consists of rainfall, basin area, and runoff coefficient. Due to the characteristics of hydroelectric power depending on the discharge, there is a limit to guaranteeing the accuracy of estimating the generated power with only one method of the flow duration characteristic model. Therefore, this stud...
Journal of Hydrology, 2021
Abstract This study proposes a complex networks-based method to determine the connections among t... more Abstract This study proposes a complex networks-based method to determine the connections among the stations in a streamflow monitoring network and assess the importance of the individual stations. For implementation, 13 streamflow stations in the Pyeongchang River basin in South Korea are studied, and daily flow (discharge) data are analyzed. Three different centrality measures are employed to identify the connections in the streamflow network: degree centrality, closeness centrality, and betweenness centrality. The links between the nodes can significantly change depending upon the centrality method used and the threshold considered. Therefore, an integrated centrality method is proposed using a Bayesian network. The integrated centrality results show that stations situated along the main stream in the middle of the basin have high centrality, while the tributary stations have low centrality. To assess the importance of stations, the integrated centrality is used with community-based clusters. This assessment on the importance of the individual streamflow stations through their centrality is useful to establish strategies for their effective and efficient maintenance.
Stochastic Environmental Research and Risk Assessment, 2020
Stream gauging stations are important in hydrology and water science for obtaining water-related ... more Stream gauging stations are important in hydrology and water science for obtaining water-related information, such as stage and discharge. However, for efficient operation and management, a more accurate grouping method is needed, which should be based on the interrelationships between stream gauging stations. This study presents a grouping method that employs community detection based on complex networks. The proposed grouping method was compared with the cluster analysis approach, which is based on statistics, to verify its adaptability. To achieve this goal, 39 stream gauging stations in the Yeongsan River basin of South Korea were investigated. The numbers of groups (clusters) in the study were two, four, six, and eight, which were determined to be suitable by fusion coefficient analysis. Ward’s method was employed for cluster analysis, and multilevel modularity optimization was applied for community detection. A higher level of cohesion between stream gauging stations was obser...
Journal of Hydrology: Regional Studies, 2021
Proceedings of the Korea Water Resources Association Conference, 2016
Proceedings of the Korea Water Resources Association Conference, 2010
The finger language is the part of the sign language, which is a language system that expresses v... more The finger language is the part of the sign language, which is a language system that expresses vowels and consonants with hand gestures. Korean finger language has 31 gestures and each of them needs a lot of learning models for accurate recognition. If there exist mass learning models, it spends a lot of time to search. So a real-time awareness system concentrates on how to reduce search spaces. For solving these problems, this paper suggest a hierarchy HMM structure that reduces the exploration space effectively without decreasing recognition rate. The Korean finger language is divided into 3 categories according to the direction of a wrist, and a model can be searched within these categories. Pre-classification can discern a similar finger Korean language. And it makes a search space to be managed effectively. Therefore the proposed method can be applied on the real-time recognition system. Experimental results demonstrate that the proposed method can reduce the time about three times than general HMM recognition method.
Han-gukbangjaehakoenonmunjip, Aug 31, 2014
This study has evaluated the stream gauge network which is considered the total hydrological info... more This study has evaluated the stream gauge network which is considered the total hydrological information and the importance class of stream gauge stations, and is applied to Namgang Dam basin. The total hydrological information and the importance class of stream gauge stations are two different physical parameters. We adopt the Euclidean distance method to consider them simultaneously. An equation obtained by the Euclidean distance method is used as the objective function in multiobjective optimization method to determine the optimal combination of the stream gauge stations for satisfying the both criteria: the maximum total amount of the hydrological information and the importance class of stream gauge stations. To evaluate the optimal stream gauge network, the representative unit hydrograph which is derived by real rainfall-runoff analysis is transferred into probability density function for the application of entropy theory concept. The importance class of stream gauge stations is determined by referring the result of MLIT (2010). As result of applying to Namgang Dam basin, The optimal stream gauge network obtained by the suggested method shows more satisfied the importance of stream gauge station purpose than the optimal stream gauge network obtain by the entropy theory only. This result implies that the optimal steam gauge network by the suggested method can consider both the total hydrological information and the importance class of stream gauge station. It is found that Namgang Dam basin needs at least 8 steam gauge stations among 12 steam gauge stations.
Proceedings of the Korea Water Resources Association Conference, 2016
Korean Society Of Hazard Mitigation, Jun 1, 2020
Nepalese Journal of Ophthalmology, 2021
Introduction: Ocular tuberculosis as choroidal tuberculoma is a rare event. It creates a clinical... more Introduction: Ocular tuberculosis as choroidal tuberculoma is a rare event. It creates a clinical diagnostic dilemma when there is no systemic involvement. Case: A 22-year-old man presented with the chief complaints of discomfort and blurring of vision of right eye for one week. On fundus examination under mydriatics of his right eye, a solitary mass which measured approximately 2DD (Disc Diameter) was appreciated at the superotemporal quadrant with the surrounding localized retinal detachment. Choroidal tuberculoma was suspected by a positive Mantoux test. Physician consultation and laboratory investigations ruled out the pulmonary and systemic manifestation of tuberculosis and other aetiology. Anti-tubercular treatment was started and this led to the improvement of vision and shrinkage of the choroidal mass into a flat chorioretinal scar at 3 months of anti-tubercular treatment . Conclusion: Solitary choroidal tuberculoma though rare, can occur in a healthy, immunocompetent pat...
Entropy, 2019
Stream gauge stations are facilities for measuring stream water levels and flow rates, and their ... more Stream gauge stations are facilities for measuring stream water levels and flow rates, and their main purpose is to produce the data required to analyze hydrological phenomena. However, there are no specific criteria for selecting the locations and installation densities of stream gauge stations, which results in numerous problems, including regional imbalances and overlapping. To address these issues, a stream gauge network was constructed in this study considering both the transinformation of entropy (objective function 1) and the importance of each stream gauge station (objective function 2). To account for both factors, the optimal combinations that satisfied the two objective functions were determined using the Euclidean distance. Based on the rainfall runoff analysis results, unit hydrographs reflecting stream connectivity were derived and applied to entropy theory. The importance of each stream gauge station was calculated considering its purposes, such as flood control, wate...
Water, 2019
The purpose of this study is to reduce the uncertainty in the generation of rainfall data and run... more The purpose of this study is to reduce the uncertainty in the generation of rainfall data and runoff simulations. We propose a blending technique using a rainfall ensemble and runoff simulation. To create rainfall ensembles, the probabilistic perturbation method was added to the deterministic raw radar rainfall data. Then, we used three rainfall-runoff models that use rainfall ensembles as input data to perform a runoff analysis: The tank model, storage function model, and streamflow synthesis and reservoir regulation model. The generated rainfall ensembles have increased uncertainty when the radar is underestimated, due to rainfall intensity and topographical effects. To confirm the uncertainty, 100 ensembles were created. The mean error between radar rainfall and ground rainfall was approximately 1.808–3.354 dBR. We derived a runoff hydrograph with greatly reduced uncertainty by applying the blending technique to the runoff simulation results and found that uncertainty is improved...
E3S Web of Conferences
The purpose of this study is to suggest a structural plan for improving the utilization of inacti... more The purpose of this study is to suggest a structural plan for improving the utilization of inactive storage in dam reservoirs, to mitigate extreme drought. Inactive storage in the dam is composed of emergency storage and dead storage. The emergency storage can be used in emergencies such as drought. But, in general, the dead storage for sedimentation is not used, even in an emergency. Therefore, we developed a methodology to determine how the dead storage space can be partially used during extreme drought periods when the sedimentation has not occurred yet. We call this partial space in a dam reservoir “drought storage”. An accurate analysis of sediment levels needs to be performed before calculating drought storage, and so the present sediment level in the dam reservoir was estimated using SED-2D linked with the RMA-2 model of SMS. After considering the additional available storage capacity based on the estimated sediment level, drought storage was finally determined. We also predi...
Water
As flood damage is becoming more frequent and severe worldwide, efficient flood control of dams h... more As flood damage is becoming more frequent and severe worldwide, efficient flood control of dams has been highlighted. The purpose of the study is to establish a simple method for dam operators to estimate the flood control capacity and predischarge level required for flood response. The cumulative probability distribution (CDF) pair with the same return period for 12 major dams located in South Korea were estimated using the frequency matching method. A Ratio of Storage volume to Flood inflow (RSF) concept was suggested and applied for each dam, and they were classified into three types: Linear, Estranged, and Vague according to the water storage characteristics. Using the method presented in this study, we suggested the required amount of flood control capacity and target water level for each dam. The results demonstrated that there is no linear relationship between flood and storage of dam when the ratio of watershed area to a storage capacity of the dam is 2.0 or more, or the rat...
Wetlands play a crucial role in maintaining human life and ecosystems. In order to conserve and m... more Wetlands play a crucial role in maintaining human life and ecosystems. In order to conserve and manage wetlands in a quantitative way, their sustainability needs to be evaluated. With this background, this study assessed the sustainability of the Binae wetland, located along the Namhan River, Korea. More specifically, we developed a wetland sustainability index (WSI), taking into account water environments, hydrometeorological factors, and the plant and animal habitats in the wetland area. Sustainability of the Binae wetland was assessed based on the WSI, which showed favorable results in general. The wetland was expected to have high sustainability in water environments and hydrometeorological factors, a moderate or low sustainability for plant habitat, and very low sustainability for animal habitat. Therefore, it can be concluded that more attention and management efforts need to be paid to the wetland’s animal habitats to make the region more sustainable.
Membrane Water Treatment, 2019
The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) predicted that... more The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) predicted that recent extreme hydrological events would affect water quality and aggravate various forms of water pollution. To analyze changes in water quality due to future climate change, input data (precipitation, average temperature, relative humidity, average wind speed and sunlight) were established using the Representative Concentration Pathways (RCP) 8.5 climate change scenario suggested by the AR5 and calculated the future runoff for each target period (Reference:1989-2015; I: 2016-2040; II: 2041-2070; and III: 2071-2099) using the semi-distributed land use-based runoff processes (SLURP) model. Meteorological factors that affect water quality (precipitation, temperature and runoff) were inputted into the multiple linear regression analysis (MLRA) and artificial neural network (ANN) models to analyze water quality data, dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen de...
Energies, 2021
Small hydropower (SHP) plants are advantageous as they have a short construction period and can b... more Small hydropower (SHP) plants are advantageous as they have a short construction period and can be easily maintained. They also have a higher energy density than other alternative energy sources as environmentally-friendly energy sources. In general, hydropower potential is estimated based on the discharge in the river basin, and the discharge can be obtained from the stage station in the gaged basin. However, if there is no station (i.e., ungaged basin) or no sufficient discharge data, the discharge should be estimated based on rainfall data. The flow duration characteristic model is the most widely used method for the estimation of mean annual discharge because of its simplicity and it consists of rainfall, basin area, and runoff coefficient. Due to the characteristics of hydroelectric power depending on the discharge, there is a limit to guaranteeing the accuracy of estimating the generated power with only one method of the flow duration characteristic model. Therefore, this stud...
Journal of Hydrology, 2021
Abstract This study proposes a complex networks-based method to determine the connections among t... more Abstract This study proposes a complex networks-based method to determine the connections among the stations in a streamflow monitoring network and assess the importance of the individual stations. For implementation, 13 streamflow stations in the Pyeongchang River basin in South Korea are studied, and daily flow (discharge) data are analyzed. Three different centrality measures are employed to identify the connections in the streamflow network: degree centrality, closeness centrality, and betweenness centrality. The links between the nodes can significantly change depending upon the centrality method used and the threshold considered. Therefore, an integrated centrality method is proposed using a Bayesian network. The integrated centrality results show that stations situated along the main stream in the middle of the basin have high centrality, while the tributary stations have low centrality. To assess the importance of stations, the integrated centrality is used with community-based clusters. This assessment on the importance of the individual streamflow stations through their centrality is useful to establish strategies for their effective and efficient maintenance.
Stochastic Environmental Research and Risk Assessment, 2020
Stream gauging stations are important in hydrology and water science for obtaining water-related ... more Stream gauging stations are important in hydrology and water science for obtaining water-related information, such as stage and discharge. However, for efficient operation and management, a more accurate grouping method is needed, which should be based on the interrelationships between stream gauging stations. This study presents a grouping method that employs community detection based on complex networks. The proposed grouping method was compared with the cluster analysis approach, which is based on statistics, to verify its adaptability. To achieve this goal, 39 stream gauging stations in the Yeongsan River basin of South Korea were investigated. The numbers of groups (clusters) in the study were two, four, six, and eight, which were determined to be suitable by fusion coefficient analysis. Ward’s method was employed for cluster analysis, and multilevel modularity optimization was applied for community detection. A higher level of cohesion between stream gauging stations was obser...
Journal of Hydrology: Regional Studies, 2021