• Journal of Korea Water Resources Association
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• v.53 no.5
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• pp.383-393
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• 2020

The main objective of this study is to provide a robust model for estimating parameters of the Clark unit hydrograph (UH) using the observed rainfall-runoff data in the Soyangang dam basin. In general, HEC-1 and HEC-HMS models, developed by the Hydrologic Engineering Center, have been widely used to optimize the parameters in Korea. However, these models are heavily reliant on the objective function and sample size during the optimization process. Moreover, the optimization process is carried out on the basis of single rainfall-runoff data, and the process is repeated for other events. Their averaged values over different parameter sets are usually used for practical purposes, leading to difficulties in the accurate simulation of discharge. In this sense, this paper proposed a hierarchical Bayesian model for estimating parameters of the Clark UH model. The proposed model clearly showed better performance in terms of Bayesian inference criterion (BIC). Furthermore, the result of this study reveals that the proposed model can also be applied to different hydrologic fields such as dam design and design flood estimation, including parameter estimation for the probable maximum flood (PMF).

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.307-311
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• 2010

지구 온난화로 인한 이상기후 현상이 지속적으로 발생됨에 따라 풍수해의 저감과 수자원의 효율적인 활용에 대한 관심이 높아지고 있다. 국내의 경우 주요지점의 상류에 댐을 건설하고 댐 상류의 저류공간을 이용하여 홍수를 저감하고 수자원을 확보하는 것이 가장 일반적으로 사용되고 있는 홍수대응과 수자원 활용 방안이다. 수자원 문제를 해결하기 위한 다양한 기법들이 연구되고 적용되고 있지만, 수자원 문제는 불확실성과 애매모호함을 내포하고 있어 풍수해 피해 저감과 한정된 수자원의 효율적인 활용을 어렵게 하고 있다. 본 연구에서는 수자원 문제에 내포되어 있는 불확실성과 애매모호함을 해결하기 위해, 인간의 사고과정과 유사한 추론과정을 통해 애매모호함을 처리하는 데 강점을 가진 퍼지추론기법을 적용하여 저수지 퍼지최적운영 모형을 개발하는 것을 목적으로 하였다. 또한 기후변화를 고려하기 위해, 일반적으로 발생하고 있는 홍수뿐만 아니라 이상홍수 발생의 경우도 고려하여 저수지 운영모형을 개발하였다. 저수지 운영모형 개발을 위해 다음과 같은 과정을 통해 퍼지최적운영모형을 개발하였다. 우선 선형계획법을 사용해 일반적인 홍수와 이상 홍수 유입시 저수지 최적연계운영을 실시하여 최적운영규칙을 추출하였다. 그리고, 최적운영을 통해 추출된 각각의 운영규칙을 퍼지기법을 도입하여 퍼지운영규칙으로 정리하였다. 마지막으로, 정리된 각각의 퍼지운영 규칙을 조합하여 이상홍수를 고려한 저수지 운영규칙을 구성하였다. 본 연구에서는 낙동강 상류에 위치한 다목적댐인 안동댐과 임하댐 유역을 시험유역으로 선정하여 모형을 개발하였고, 일반적인 홍수로는 안동댐과 임하댐에 각각 100년 빈도의 홍수가 유입되는 것을 가정하였으며, 이상홍수로는 각의 댐에 극한홍수(PMF)가 유입되는 것으로 설정하였다. 개발된 저수지 운영모형을 통해 시험유역의 저수지 운영을 모의한 결과 각 댐의 유입량자료와 저수지 저류량 자료, 하류지점의 유량자료만을 사용하여 간편하고 신속하게 저수지 운영을 수행 할 수 있었다.

• Journal of Venture Innovation
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• v.7 no.3
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• pp.45-63
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• 2024

The success of a company in the market is linked to the value it delivers to its customers. However, that value is not always constant. As the environment changes, so do customer experiences and requirements, and eventually the value they seek also evolves. Thus, a timely, clear, and effective value proposition, along with the associated benefits, becomes the functional, psychological, and economic foundation of a business. Therefore, the customer value proposition is crucial in terms of Product-Market Fit (PMF), establishing competitive differentiation, and delivering consistent messaging. Despite this, the most widely known and utilized model related to the Customer Value Proposition (CVP) in general businesses is the Value Proposition Canvas (VPC) by Osterwalder and Pigneur. Apart from that, there are only a few other models used by scholars and experts. In this paper, I selected the VPC model, which is widely used by business practitioners globally, and two other major CVP models well-known to experts. I conducted a detailed analysis of these models and derived the essential elements and key features of a customer value proposition. These were then combined with the Lean Startup methodology, which is frequently used for innovation today, to design an integrated CVP model that startups can easily utilize. The framework proposed in this study is a comprehensive CVP model that incorporates the strengths, weaknesses, characteristics, and commonalities of the three existing CVP models. It is designed to flexibly adapt depending on the business direction or strategic characteristics of the company by comprehensively considering all circumstances of the entire company or a specific product/service. Additionally, it systematically manages the contents of customers' wants & needs, strategic focus, and growth horizons, even after application. The Integrative-Lean CVP Model, designed for easy use by startups, is expected to help them with limited funding and marketing capabilities identify value proposition elements for timely PMF, fostering the creation of a new startup ecosystem.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4B
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• pp.221-232
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• 2012

In this study, the model enhancing the safety of reservoirs and reducing the downstream flood damage by reservoirs system operation during abnormal flood was developed. Linear programming was used for the optimal reservoirs system operation during an abnormal flood and fuzzy inference system was introduced to solve the uncertainty problem which is included in hydrological factors like inflow, water level and inflow variation of reservoir operation. The linear programming model determined the optimal reservoir system operation rules and could be used in situation where water demands varies rapidly during the abnormal flood events using fuzzy control technique. In this study, the optimal reservoirs system operation for Andong and Imha reservoirs located in the upper basin of Nakdong river was performed in order that the design flood discharge at Andong city would not be exceeded for the design flood of 100 year and PMF(Probable Maximum Flood). And the model that determines the release according to the downstream flow discharge, the reservoir storage, the inflow and the inflow variation of each reservoir was developed using the optimal system operation result and fuzzy control technique. The developed model consisted of 224 fuzzy rules according to the conditions of Andong reservoir, Imha reservoir and Andong city. And the release from each reservoir could be determined when the current data are used as input data through the developed GUI.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.449-453
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• 2008

This research focused on analyzing and comparing between the results of hydraulic physical modeling and the results of numerical modeling of Grass Concrete which is newly developed in-situ block system. The physical model was built as a scale of 1:50 by Froude similitude measuring the water levels and the water velocities for before and after vegetation and the effects were analyzed after reviewing the results. In consequence, the water velocities were observed to decrease meanly 19.1%, and the water depth were determined to increase meanly 27.8% in case of the of design flood, $Q=200m^3/sec$. Moreover, the velocities were produced reduction effects of 27.2%, and the water levels were derived from addition effects of the highest 31.3% in case of the probability maximum flood(PMF), $Q=600m^3/sec$. To verifying the hydraulic physical modeling, the numerical modeling was conducted for a close examination of before and after vegetation. HEC-RAS model was for 1 dimensional numerical analysis and RMA-2 was for 2 dimensional numerical analysis. The results of the numerical simulation, under the condition of roughness coefficient calibration, shows similar results of the physical modeling. These satisfactory results show that the accomplished results of hydraulic modeling and the predicted results of numerical modeling corresponded reasonably each others.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.4
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• pp.459-476
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• 2013

Receptor models have been rapidly developed to manage the ambient air quality and to establish effective emission reduction strategies. The models are used to identify various emission sources and apportion quantitatively the ambient pollutant mass based on various measured physico-chemical properties of the air pollutants at the receptor site. Many types of receptor models have been applied to estimate source contributions since those provide fundamental information when establishing reasonable environmental policies in Korea and Foreign countries. In this paper, we will introduce the basic concept and principal of the receptor model, various types of existing models with discussing strong and weak points for each model, and performance procedure of PMF model as the most popular model in the world. Further the trends of receptor modeling studies in Korea and other countries were provided. Finally, the improvement directions of the modeling works for the national and local air quality management were suggested in this paper.

• Journal of Wetlands Research
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• v.17 no.2
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• pp.130-138
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• 2015

According to the "Safety Evaluation Detailed Instructions (Dam)", a precise safety inspection is carried out for dams that exceed a certain scale. However, as the Hydrological Safety Evaluation from various evaluation standards is designed to evaluate the safety of existing dams considering PMF(Probable Maximum Flood), the evaluation is much less applicable for most agricultural reservoirs. Therefore, the Hydrological Safety Guidelines for agricultural reservoirs are expected to be re-evaluated considering the diverse risk factors with the coefficient model and AHP(Analytic Hierarchy Process) in this study. The coefficient model has been developed by selecting the hydrological safety superordinate subordinate evaluation factors to reflect diverse risk factors of agricultural reservoirs. This study indicated that in the short term, improving the safety check condition evaluation grade will be useful to improve the hydrological safety of the agricultural reservoir because it can be performed immediately.

• Membrane and Water Treatment
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• v.9 no.1
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• pp.63-68
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• 2018

Molecular dynamics simulations were used to study the removal of Cd(II) as a heavy metal from wastewater using armchair carbon nanotube, boron nitride nanotube and silicon carbide nanotubes under applied electric field. The system contains an aqueous solution of $CdCl_2$ as a heavy metal and a (7,7) nanotube as a nanostructured membrane, embedded in a silicon nitride membrane. An external electric field was applied to the considered system for the removal of $Cd^{2+}$ through nanotubes. The simulation results show that in the same conditions, considered armchair nanotubes were capable to remove $Cd^{2+}$ from wastewater with different ratios. Our results reveal that the removal of heavy metals ions through armchair carbon, boron nitride and silicon carbide nanotubes was attributed to the applied electric field. The selective removal phenomenon is explained with the calculation of potential of mean force. Therefore, the investigated systems can be recommended as a model for the water treatment.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1604-1608
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• 2008

최근 기상이변 등에 따라 빈번히 발생하는 이상홍수에 대비하여 댐의 안정성 확보를 위한 댐설계기준이 강화되었고, 이에 따라 가능최대홍수량(PMF) 유입시 댐의 항구적인 안전성 확보를 위하여 치수능력 증대사업이 필요하게 되었다. 본 연구에서는 안동댐의 치수능력 증대사업의 일환으로 계획된 비상여수로에 대하여 2차원, 3차원 수치모형실험을 통해 비상여수로의 수리학적 안정성과 기능성을 검토하였다. 최적의 설계안을 결정하는데 필요한 자료를 제공하기 위하여 접근수로의 유황, 월류위어의 방류능력, 급경사수로 및 감세공의 유황을 검토하였다. 특히, 월류위어의 교각형상에 따른 수면형상, 조절부의 제원에 따른 방류량 검토, 조절부의 평면형상에 따른 유황, 급경사수로의 종단경사에 따른 유황, 저유량 방류시 플립버킷부에서의 사출궤적 등에 대한 검토 등을 수행하였다. 본 연구결과, 수치모형실험은 설계자에게 실용적인 해석도구로 사용될 수 있음을 보일 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1205-1208
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• 2007

본 연구에서는 3차원 CFD 모형인 FLOW-3D 모형을 이용하여, 군남 홍수조절지 접근수로의 안정성과 웨어의 월류능력을 검토하였다. 이를 위해서 현지측량자료와 1:5,000도의 수치지도를 이용하여 지형과 기본계획 설계(안)의 여수로를 구성하였다. 지형은 모델링 범위를 충분히 포함하도록 홍수조절지의 상 하류에 걸쳐 작성하였으며, 연직범위는 가능 최대 홍수량(PMF)시 저수지의 최고수위를 초과하는 범위까지 재현하였다. 모델링 범위는 웨어와 같은 구조물 주변에서는 조밀한 격자를 사용하여 정밀한 흐름현상을 재현토록 하였으며, 저수지 부분과 하류하천 부분에 대하여는 느슨한 격자망을 적용하여 최종적으로 2가지 격자망으로 모델링 전체범위에 대하여 격자를 구성하였다. 상류 경계조건으로는 저수지 수위를 경계조건으로 설정하였고, 하류 경계조건으로는 군남 홍수조절지가 일반댐과 달리 상 하류의 표고차가 크지 않아 방류시 하류하천 수위 상승으로 인하여 통수능에 영향을 줄 것으로 판단되므로, 방류량 대 하류하천 형성수위 관계식을 산정하여 방류량에 따른 하류하천의 수위를 하류경계조건으로 설정하였다.