• International Journal of Contents
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• v.8 no.3
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• pp.34-41
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• 2012

The concept of vegetation freeboard equivalence (VFE) is presented from the comparison between the rise in stage with/without vegetation and the freeboard height under design discharge conditions. In South Korea, the freeboard height of large, medium and small rivers is defined as a function of river discharge. Two models are used for this analysis of flood stage with and without vegetation: the 1-D model HEC-RAS and the 2-D model RMA-2. Both models are applied to three river study sites of the Geum River in South Korea as representative sites for a large, a medium and a small river. The analysis shows that without vegetation, both models provide comparable results and the calculated results are in very good agreement with the design configuration. The vegetation effects on the medium river are less significant, and the freeboard is adequate to contain the rise in stage from the added floodplain vegetation in large rivers. The concept of vegetation freeboard equivalence is therefore useful for the analysis of flood river stages after the restoration of channels with increased floodplain vegetation.

• Water Engineering Research
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• v.1 no.4
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• pp.279-291
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• 2000

A mathematical model using dynamic programming approach is applied to an optimal unit commitment problem. In this study, the units are treated as stages instead of as state dimension, and the time dimension corresponds to the state dimension instead of stages. A considerable amount of computer time is saved as compared to the normal approach if there are many units in the basin. A case study on the Lower Colorado River Basin System is presented to demonstrate the capabilities of the optimal scheduling of hydropower units.

• Water for future
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• v.26 no.3
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• pp.75-85
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• 1993

In this study, reach boundaries in QUAL2E Model were set by the locations of point-waste discharge or tributary input and measured or direct calculated hydrologic factors were used in computation as much as possible. South Platte Experimental River in Colorado, USA was selected as a target river and data collected during September 1991 and January 1992 periods were used for calibration and verification, respectively. Constituents modeled in this study are 5-day carbonaceous biochemical oxygen demand(CBOD$) and dissolved oxygen(DO). The good agreement was obtained between a calculated using this model and observed, less than 5% to DO and about 20% to CBOD$. According to the result of water-quality prediction, experimental river is classified as the 4th category by the criteria of environmental protection agency in the USA in 2001.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.5
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• pp.53-67
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• 1999

In this study, regional frequency analysis is used to determine each subbasin drought frequency with watershed runoff which is calculated with Tank Model in Nakdong river basin. L-Monments methd which is almost unbiased and nearly normal distribution is applied to estimate paramers of drought frequency analysis of monthly runoff time series. The duration of '76-77 was the most severe drought year than othe rwater years in this study. To decide drought frequency of each subbasin from the main basin, it is calculated by interpolaing runoff from the frequency-druoght runoff relationship. and the linear regression analysis is accomplished between drought frequency of main basin and that of each subbasin. With the results of linear regression analysis, the drought runoff of each subbasin is calculated corresponing to drought frequency 10,20 and 30 years of Nakdong river basin considering safety standards for the design of impounding facilities. As the results of this study, the proposed methodology and procedure of this study can be applied to water budget analysis considering safety standards for the design of impounding facilities in the large-scale river basin. For this purpose, above all, it is recommanded that expansion of reliable observed runoff data is necessary instead of calculated runoff by rainfall-runoff conceptual model.

• Journal of Wetlands Research
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• v.21 no.1
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• pp.1-8
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• 2019

In this study, the multi-objective optimization method is attemped to optimize the hydrological model to estimate the runoff through two hydrological processes. HL-RDHM, a distributed hydrological model that can simultaneously estimate the amount of snowfall and runoff, was used as the distributed hydrological model. The Durango River basin in Colorado, USA, was selected as the watershed. MOSCEM was used as a multi-objective optimization method and parameter calibration and hydrologic model optimization were tried by selecting 5 parameters related to snow melting and 13 parameters related to runoff. Data from 2004 to 2005 were used to optimize the model and verified using data from 2001 to 2004. By optimizing both the amount of snow and the amount of runoff, the RMSE error can be reduced from 7% to 40% of the simulation value based on the initial solution at three SNOTEL points based on the RMSE. The USGS observation point of the outflow is improved about 40%.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2002.05a
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• pp.125-130
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• 2002

우리의 언어생활을 비추어 볼 때 한자어 정보처리는 많은 연구가 이루어야 함에도 불구하고 고유어 언구에 비해 소흘해 다루어져 왔다. 본 연구는 단일 한자어를 구성하는 각 음절이 단어의 재인에 어떤 영향을 미치는지 점화과제를 통하여 알아보았다. 본 실험은 기존의 한자어 연구에 빈도특성과 고유어와 외래어의 글자특성까지 고려하여 종합적으로 살펴보았다. 먼저 실험1의 어휘판단관제에서는 고유어와 한자어의 양상이 비슷하며 외래어는 다른 처리를 하는 것으로 드러났다. 고유어와 한자어는 빈도에 따라 영향을 받지만 외래어는 빈도의 영향에 변함없이 일정하게 나타났다. 이런 결과는 한국인은 고유어와 한자어를 동일한 양상으로 처리하며 이런 이유는 외래어의 한국어와는 다른 음운규칙이나 음절규칙의 영향으로 해석할 수 있겠다. 실험 2에서는 한자어 형태소와 의미적으로 유사한 조건(강도-강력)과 철자적 유사 조건(강도-강변), 고유어 유사 조건(강도-강정)조건을 점화과제를 이용하여 어휘판단을 하게 하였다. 실험 결과 모든 조건이 통제조건에 비하여 빠르게 나왔다. 그리고 의미적 유사 조건이 촉진적 점화효과를 일으키고, 철자적 유사조건은 억제 효과를 일으켰으며 고유어는 특이하게도 판단시간이 빠르게 나와 한자어와는 다른 처리과정이 있음을 보여주고 있다. 이런 결과는 지연조건에서도 동일하게 일어나고 있다. 이런 결과는 한자어는 어휘접근 이후에도 실험의 과제 특성상 한자어 형태소는 단어 수준 아래 위치하기는 힘든 반면, 고유어는 단어 수준 아래에 존재한다고 할 수 있다. 결국 한자어와 고유어는 기본적으로 외래어와 다른 처리를 보이면 한자어와 고유어 내에서도 한자어는 단어접근 전에 의미접근의 단계를 거쳐야 하지만 고유어는 각 음절이 형태소가 아니기 때문에 바로 어휘에 접근하는 것이라고 할 수 있겠다.ulic geometry and sediment transport has been applied to: (1) gravel-bed transport measurements in a cobble-bed stream at Little Granite Creek, Wyoming; (2) sand and gravel transport by size fraction in the sharp meander bends of Fall River, Colorado; (3) changes in sand dune geometry and resistance to flow during major floods of the Rhine River in the Netherlands; (4) changes in hydraulic geometry of the Rio Grande downstream of Cochiti Dam, New Mexico; and (5) analysis of the influence of water temperature and the Coriolis force on flow velocity and sediment transport of the Lower Mississippi River in Louisiana. Recent developments also include two textbooks on "Erosion and Sedimentation" and "River Mechanics" by the author and state-of-the-art papers in the ASCE Journal of Hydraulic Engineering.rk on is diversified, the importance of skills are diversified in each field of jobs.

• Water Engineering Research
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• v.4 no.2
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• pp.99-109
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• 2003

Since bed elevation changes are mainly dependent on the flow velocity and corresponding shear stress, it is possible to predict bed elevation numerically using velocity components. For the scour analysis due to channel contraction, a bed load transport model is developed and applied to estimate scour depth around coffer dam in the Mississippi River. During Phase I of the Lock & Dam No. 26 replacement project, a coffer dam was constructed to reduce the flow area approximately by 50%. Flow velocity increases due to the flow area reduction yields significant lowering (erosion) of the channel bed elevation. The proposed numerical model solves the sediment continuity equation using the finite element method to evaluate scour process in the vicinity of the coffer dam

• Journal of Wetlands Research
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• v.5 no.1
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• pp.67-78
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• 2003

The unsteady 2D convection and diffusion equation is solved numerically for the real-time simulation of suspended load propagation. The streamlined upwind scheme efficiently reduces numerical oscillations due to the high Peclet number in the convection dominant flow. By using the mixed boundary condition to express the external source terms or externally induced suspended load as a function of time in the algorithm, the model is capable of handling not only continuous load cases but also non-continuous suspended load influx. The suspended load transport modelwas verified using a case study for which an analytical exact solution is available and was applied to the real-time simulation of a suspended load influx case on the Mississippi River. The model algorithm can provide a framework upon which water quality as well as contaminant transport models can be built.

• Journal of Electrical Engineering and Technology
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• v.6 no.5
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• pp.585-594
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• 2011

This paper presents the use of sequential outage checkers to identify the potential cascading processes that might lead to large blackouts. In order to analyze cascading outages caused by a combination of thermal overloads, low voltages, and under-frequencies following an initial disturbance, sequential outage checkers are proposed. The proposed sequential outage checkers are verified using the AEP 9-bus system, New England 39-bus system, and IEEE 118-bus system.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.488-488
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• 2015

Intermittent streamflow is common phenomenon in arid and semi-arid regions. To manage water resources of intermittent streamflows, stochactic simulation data is essential; however the seasonally stochastic modeling for intermittent streamflow is a difficult task. In this study, using the periodic Markov chain model, we simulate intermittent monthly streamflow for occurrence and the periodic gamma autoregressive and copula models for amount. The copula models were tested in a previous study for the simulation of yearly streamflow, resulting in successful replication of the key and operational statistics of historical data; however, the copula models have never been tested on a monthly time scale. The intermittent models were applied to the Colorado River system in the present study. A few drawbacks of the PGAR model were identified, such as significant underestimation of minimum values on an aggregated yearly time scale and restrictions of the parameter boundaries. Conversely, the copula models do not present such drawbacks but show feasible reproduction of key and operational statistics. We concluded that the periodic Markov chain based the copula models is a practicable method to simulate intermittent monthly streamflow time series.