• Magazine of the Korean Society of Agricultural Engineers
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• v.21 no.4
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• pp.108-117
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• 1979

In order to obtain the basic data for design of water structures which can be contributed to the planning of water use. Best fitted distribution function and the equations for the probable minimum flow were derived to the annual minimum flow of five subwatersheds along Geum River basin. The result were analyzed and summarized as follows. 1. Type III extremal distribution was considered as a best fit one among some other distributions such as exponential and two parameter lognormal distribution by $x^2$-goodness of fit test. 2. The minimum flow are analyzed by Type III extremal distribution which contains a shape parameter $\lambda$, a location parameter ${\beta}$ and a minimum drought $\gamma$. If a minimum drought $\gamma=0$, equations for the probable minimum flow, $D_T$, were derived as $D_T={\beta}e^{\lambda}1^{y'}$, with two parameters and as $D_T=\gamma+(\^{\beta}-\gamma)e^{{\lambda}y'}$ with three parameters in case of a minimum drought ${\gamma}>0$ respectively. 3. Probable minimum flow following the return periods for each stations were also obtained by above mentioned equations. Frequency curves for each station are drawn in the text. 4. Mathematical equation with three parameters is more suitable one than that of two parameters if much difference exist between the maximum and the minimum value among observed data.

• Water for future
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• v.20 no.2
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• pp.117-126
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• 1987

A Synthetic unit hydrograph method was suggested for the representation of a direct runoff hydrograph with empirical geomorphologic laws and geomorphologic parameters by applying geomorphologic instantaneous unit hydrograph theory and Rossois results of application of GIUH theory to the Nash Model which is a linear reservoir model. The shape parameter m and scale parameter k can be derived by the Horton's empirical geomorphologic laws $R_A,R_B,R_L$ when ordered according to Strahler's ordering Scheme, main stream length and using the maximum velocity for the dynamic characteristics of a river basin, The derived response function was tested on some observed flood datas and showed promising. For the determination of the shape parameter m, eq. (16) was showed applying and m showed a good regression with the size of basin area.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.630-643
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• 1991

The hydrodynamic stability equations are formulated for buoyancy-induced flows adjacent to a vertical, planar, isothermal surface in cold pure water. The resulting stability equations, when reduced to ordinary differential equation by a similarity transformation, constitute a two-point boundary-value(eigenvalue) problem, which was numerically solved for various values of the density extremum parameter R=( $T_{m}$ - $T_.inf./) / ( $T_{o}$ - $T_.inf./). These stability equations have been solved using a computer code designed to accurately solve two-point boundary-value problems. The present numerical study includes neutral stability results for the region of the flows corresponding to 0.0.leq. R. leq.0.15, where the outside buoyancy force reversals arise. The results show that a small amount of outside buoyancy force reversal causes the critical Grashof number $G^*/ to increase significantly. A further increase of the outside buoyancy force reversal causes the critical Grashof number to decrease. But the dimensionless frequency parameter $B^*/ at $G^*/ is systematically decreased. When the stability results of the present work are compared to the experimental data, the numerical results agree in a qualitative way with the experimental data.erimental data.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1996-2000
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• 2006

현재 국내 주요 하천의 홍수예경보시스템 운영과 다목적댐의 홍수조절관리를 위하여 수문학적 모형의 하나인 저류함수모형(storage function model)을 사용하고 있다. 저류함수모형은 산지가 많은 유역에 적합하도록 개발된 모형으로, 계산절차가 간편하고 홍수유출의 비선형성을 고려할 수 있는 방법이므로 선형모형보다 합리적이라고 알려져 있다. 그러나 실제 홍수사상에 저류함수모형을 적용하기 위해서는 적절한 매개변수의 적용이 필요하다. 현재까지 저류함수모형의 매개변수를 보정하기 위한 연구가 많이 되었지만, 실질적으로 보정된 매개변수를 실제 홍수사상에 적용함에 있어서는 많은 어려움이 존재한다. 따라서 이러한 문제점을 해결하고자 본 연구에서는 저류함수 모형 중 유역유출 매개변수를 첨두유량에 대한 상대민감도분석을 통하여 매개변수의 경계조건을 설정하고, 이 경계조건을 바탕으로 최적화기법(optimization technique)을 사용하여 과거 홍수사상에 대하여 보정을 수행하였다. 그리고 보정된 매개변수를 모의 홍수사상에 적용하기 위한 최적매개변수(optimal parameter) 결정을 위한 방법들을 제시 및 적용하여 비교 분석하였다.

• Journal of Korean Society on Water Environment
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• v.25 no.4
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• pp.530-538
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• 2009

The Oxic-Settling-Anaerobic (OSA) treatment process, a modified Conventional Activated Sludge (CAS) process, was developed for the purpose of sludge reduction. The insertion of a sludge holding tank into a sludge return line, an anaerobic reactor, forming an OSA process, may provide a cost-effective way of reducing excess sludge production during a process. The OSA process was evaluated for its sludge reduction ability by kinetic parameter and mass balance, with an observed excess sludge reduction of 63.5%, as $P_{X.VSS}$, compared with the conventional activated sludge process.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.147-153
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• 2006

In this study, the run-up of water waves on slopes of s-berm breakwaters was investigated by performing a series of hydraulic experiments. The run-up height was analyzed in detail by using the effects of wave steepness and surf similarity parameter. In general, the run-up heights were decreased as the height and the width of berm were increased. However, the variation of run-up height was small for change of wave steepness and surf similarity parameter.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.1
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• pp.47-57
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• 2018

This study implemented the rainfall-runoff analysis of the Mekong River basin using the SWAT (Soil and Water Assessment Tool). The runoff analysis was simulated for 2000~2007, and 11 parameters were calibrated using the SUFI-2 (Sequential Uncertainty Fitting-version 2) algorithm of SWAT-CUP (Calibration and Uncertainty Program). As a result of analyzing optimal parameters and sensitivity analysis for 6 cases, the parameter ALPHA_BF was found to be the most sensitive. The reproducibility of the rainfall-runoff results decreased with increasing number of stations used for parameter calibration. The rainfall-runoff simulation results of Case 6 showed that the RMSE of Nong Khai and Kratie stations were 0.97 and 0.9, respectively, and the runoff patterns were relatively accurately simulated. The runoff patterns of Mukdahan and Khong Chaim stations were underestimated during the flood season from 2004 to 2005 but it was acceptable in terms of the overall runoff pattern. These results suggest that the combination of SWAT and SWAT-CUP models is applicable to very large watersheds such as the Mekong for rainfall-runoff simulation, but further studies are needed to reduce the range of modeling uncertainty.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.820-823
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• 2017

This study experimentally investigate how the Reynolds number affect cavitation performance in a turbopump inducer using water. Cavitation performance has been determined by the static pressure measured at the inlet of the inducer. Reynolds number has been varied by varying water temperature and inducer rotational speed to maintain constant non-dimensional thermal parameter. At low non-dimensional thermal parameter, the critical cavitation number is insensitive to Reynolds number. However, at high non-dimensional thermal parameter, the critical cavitation number increased as Reynolds number increases. Thus, cavitation performance is deteriorated as Reynolds number increases when thermal effect exists.

• Journal of Korea Water Resources Association
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• v.31 no.3
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• pp.243-252
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• 1998

In this study, the new dimensionless values were defined and proposed to determine the parameters of urban runoff models based on the relative sensitivity analysis. Also, the sensitivity characteristics of each parameter were investigate. In order to analyze the parameter sensitivities of each model, total runoff ratio, peak runoff ratio, runoff sensitivity ratio, sensitivity ratio of total runoff, and sensitivity ratio of peak runoff were defined. $$Total\;runoff\;ratio(Q_{TR})\;=\;\frac{Total\;runoff\;of\;corresponding\;step}{Maximum\;total\;runoff}$$$$Peak\;runoff\;ratio(Q_{PR})\;=\;\frac{Peak\;runoff\;of\;corresponding\;step}{Maximum\;peak\;runoff}$$$$Runoff\;sensitivity\;ratio(Q_{SR})\;=\;\frac{Q_{TR}}{Q_{PR}}$$ And for estimation of sensitivity ratios based on the scale of basin area, rainfall distributions and rainfall durations in ILLUDAS & SWMM, the reasonable ranges of parameters were proposed.

• Journal of Korea Water Resources Association
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• v.32 no.6
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• pp.657-664
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• 1999

This paper introduced the basic theory of LRCS(Linear Reservoir and Channel System) rainfall runoff model proposed by Korean researchers(Lee and Lee, 1995), and discussed the change of model output according to objective functions in sensitivity analysis and calibration process of model. It proposed "hat" matrix and affluence measures for affluence analysis of parameters in calibration, and investigated relationship between change of model output according to error propagation in parameter estimation, and sensitivity of model output according to variance of model output and change of parameters. Accuracy of parameter estimates was known by analysis of sensitivity coefficient, diagonal element $h_i$ and $D_i$._i$.