• 한국농공학회논문집
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• 제60권1호
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• pp.11-20
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• 2018

This study is to calibrate the SWAT (Soil and Water Assessment Tool) water quality of SS (Suspended Solid), T-P (Total Phosphorus), and T-N (Total Nitrogen) by focusing on 2014~2015 drought periods and identify the important parameters. For Gongdo watershed ($366.5km^2$), the SWAT was calibrated for 2 cases of 2002~2006 normal year focusing calibration and 2014~2015 drought focusing calibration respectively. The parameters of N_UPDIS (Nitrogen uptake distribution parameter) and CMN (Rate factor for humus mineralization of active organic nutrients) played important roles for T-N calibration during drought periods. The SWAT SS, T-N, and T-P average $R^2$ (Coefficient of determination) results by focusing on 2014~2015 drought periods calibration showed 0.71, 0.65 and 0.62 while 2002~2006 normal year focusing calibration showed 0.63, 0.58 and 0.50 respectively. Also SWAT SS, T-N, and T-P model efficiency NSE (Nash-Sutcliffe efficiency) results by focusing on drought period (2014~2015) calibrated showed 0.76, 0.77, 0.87 respectively. Even though the SS, T-P parameters were unchanged during the calibration, the SS and T-P results were improved by the hydrological parameters (SCS-CN, SOL_K, SLSOIL) during the drought periods. The SWAT water quality calibration needs to be considered for the movement of SS and nutrients transport especially focusing on the drought characteristics.

• 한국식품저장유통학회지
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• 제6권1호
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• pp.29-36
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• 1999

Using Fuji apple fruits cultivated in Kyungpook prefecture, the calibration model for firmness evaluation of fruits by near infrared(NIR) reflectance spectroscopy was developed, and the various influence factors such as instrument variety, measuring method, sample group, apple peel and selection of firmness point were investigated. Spectra of sample were recorded in wavelength range of 1100∼2500nm using NIR spectrometer (InfraAlyzer 500), and data were analyzed by stepwise multiple linear regression of IDAS program. The accuracy of calibration model was the highest when using sample group with wide range, and the firmness mean values obtained in graph by texture analyser(TA) were used as standard data. Chemometrics models were developed using a calibration set of 324 samples and an independent validation set of 216 samples to evaluate the predictive ability of the models. The correlation coefficients and standard error of prediction were 0.84 and 0.094kg, respectively. Using developed calibration model, it was possible to monitor the firmness change of fruits during storage frequently. Time, which was reached to firmness high value in graph by TA, is possible to use as new parameter for freshness of fruit surface during storage.

• 한국농림기상학회지
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• 제23권2호
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• pp.122-133
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• 2021

작물 모형의 품종모수를 추정하기 위한 기상자료는 일반적으로 생육 관측 자료가 수집된 시험지의 인근에 위치한 종관기상 관측자료가 사용되어왔으나, 지형적인 원인이나 시험지와 기상관측소 사이의 거리로 인해 실제 시험지의 기상과 차이가 발생할 수 있다. 반면, 비교적 높은 밀도로 분포하는 방재기상 관측자료를 활용할 경우 이러한 문제점을 보완할 수 있을 것이다. 본 연구에서는 종관기상 관측자료와 방재기상 관측자료를 각각 사용하여 출수기에 영향을 미치는 DSSAT 모형의 모수들을 추정하고, 추정된 모수들의 신뢰도를 비교하고자 하였다. 모수 추정을 위해 사용한 재배관리 및 생육 관측값은 지역장려품종 선발시험과 작황시험으로부터 수집하였다. 모수 추정은 Generalized Likelihood Uncertainty Estimation (GLUE) 방법을 사용하였으며, 불확실성을 고려하여 100번의 반복 추정을 통해 100개의 모수 집합을 생성하였다. 모수 추정에 소요되는 시간을 단축하기 위해 도커 컨테이너를 기반으로 병렬적으로 GLUE를 구동하였다. 추정된 모수들을 사용하여 모의된 출수기의 평균은, 방재기상자료를 사용하였을 때 최대 4일로, 종관기상자료를 사용하였을 때 최대 오차가 7일이었던 것에 비하여 크게 개선되었다. 그러나, 방재기상자료의 원활한 활용을 위해서는 해당 자료에 대한 접근성이 향상되어야 할 것으로 예상되었다.

• 한국물환경학회지
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• 제29권5호
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• pp.681-690
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• 2013

Watershed models have been increasingly used to support an integrated management of land and water, non-point source pollutants, and implement total daily maximum load policy. However, these models demand a great amount of input data, process parameters, a proper calibration, and sometimes result in significant uncertainty in the simulation results. For this reason, uncertainty analysis is necessary to minimize the risk in the use of the models for an important decision making. The objectives of this study were to evaluate three different uncertainty analysis algorithms (SUFI-2: Sequential Uncertainty Fitting-Ver.2, GLUE: Generalized Likelihood Uncertainty Estimation, ParaSol: Parameter Solution) that used to analyze the sensitivity of the SWAT(Soil and Water Assessment Tool) parameters and auto-calibration in a watershed, evaluate the uncertainties on the simulations of runoff and sediment load, and suggest alternatives to reduce the uncertainty. The results confirmed that the parameters which are most sensitive to runoff and sediment simulations were consistent in three algorithms although the order of importance is slightly different. In addition, there was no significant difference in the performance of auto-calibration results for runoff simulations. On the other hand, sediment calibration results showed less modeling efficiency compared to runoff simulations, which is probably due to the lack of measurement data. It is obvious that the parameter uncertainty in the sediment simulation is much grater than that in the runoff simulation. To decrease the uncertainty of SWAT simulations, it is recommended to estimate feasible ranges of model parameters, and obtain sufficient and reliable measurement data for the study site.

• 한국습지학회지
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• 제22권1호
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• pp.15-23
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• 2020

본 연구에서는 다중최적화기법을 이용하여 분포형 수문모형의 매개변수 보정 과정에서 분포형의 정도가 융설과 유량의 최적화에 어떠한 영향을 미치고 있는 가를 연구하였다. 분포형 수문모형으로는 HL-RDHM를 이용하였고, 분포형 정도에 따라 집중형, 준분포형, 완전분포형 등 3개의 모형을 구성하여 최적 매개변수를 산정하였다. 유역은 108개의 격자로 구성되며, 격자별로 융설과 관련하여 15개, 유출량 관련 13개의 매개변수를 다중최적화기법인 MOSCEM를 이용하여 최적화하였다. 최적 매개변수 산정을 위하여 2004-2005년의 기상학적 자료와 융설량과 유출량 관측자료가 이용되었고, 최적화된 매개변수를 2001-2004년의 자료를 이용하여 검증하였다. 다중최적화기법 적용 결과 집중형의 경우, 초기 값에 의한 결과로 부터 RMSE 값이 융설량은 평균 35%, 유출량은 약 42% 개선되었고, 준분포형과 완전분포형의 경우는 융설량은 평균 40%, 유출량은 약 43% 정도의 RSME 값이 향상되었다. 전반적으로 집중형보다는 분포형 모형이 최적화 과정에서 융설과 유출량 예측에 더 나은 성과를 보여주었지만, 준포형과 완전분포형의 경우 최적화 성과에서 큰 차이를 보이지 않았고, 유출보다는 융설에서 분포형 정도에 따른 모형의 민감도가 더 높은 것을 확인되었다.

• Structural Engineering and Mechanics
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• 제42권1호
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• pp.1-12
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• 2012

In this study, Pasternak foundation model, which is a two parameter foundation model, is used to analyze the behavior of laterally loaded beams embedded in semi-infinite media. Total potential energy variation of the system is written to formulate the problem that yielded the required field equations and the boundary conditions. Shear force discontinuities are exposed within the boundary conditions by variational method and are validated by photo elastic experiments. Exact solution of the deflection of the beam is obtained. Both foundation parameters are obtained by self calibration for this particular problem and loading type in this study. It is shown that, like the first parameter k, the second foundation parameter G also depends not only on the material type but also on the geometry and the loading type of the system. On the other hand, surface deflection of the semi infinite media under singular loading is obtained and another method is proposed to determine the foundation parameters using the solution of this problem.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.2215-2219
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• 2009

For model calibration in rainfall-runoff modeling, streamflow data at a specific outlet is obviously required but is not sufficient to identify parameters of a model since numerous parameter combinations can result in very similar model performance measures (i.e. objective functions) and indistinguishable simulated hydrographs. This phenomenon has been called 'equifinality' due to inherent parameter uncertainty involved in rainfall-runoff modeling. This study aims to investigate catchment responses in time and space to various uncertain parameter sets in distributed rainfall-runoff modeling. Seven plausible (or behavioral) parameter sets, which guarantee identically-good model performances, were sampled using deterministic and stochastic optimization methods entitled SCE and SCEM, respectively. Then, we applied them to a computational tracer method linked with a distributed rainfall-runoff model in order to trace and visualize potential origins of streamflow at a catchment outlet. The results showed that all hydrograph simulations based on the plausible parameter sets were performed equally well while internal catchment responses to them showed totally different aspects; different parameter values led to different distributions with respect to the streamflow origins in space and time despite identical simulated hydrographs. Additional information provided by the computational tracer method may be utilized as a complementary constraint for filtering out non-physical parameter set(s) (or reducing parameter uncertainty) in distributed rainfall-runoff modeling.

• 한국산림과학회지
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• 제95권5호
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• pp.569-579
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• 2006

This study focuses on the application of multi-criteria performance measures based on the concept of equifinality to the calibration of the rainfall-runoff model TOPMODEL in a small deciduous forest catchment. The performance of each parameter set was evaluated by six performance measures, individually, and each set was identified as a behavioral or non-behavioral parameter set by a given behavioral acceptance threshold. Many behavioral parameter sets were scattered throughout the parameter space, and the range of model behavior and the sensitivity for each parameter varied considerably between the different performance measures. Sensitivity was very high in some parameters, and varied depending on the kind of performance measure as well. Compatibilities of behavioral parameter sets between different performance measures also varied, and very few parameter sets were selected to be used in making god predictions for all performance measures. Since different behavioral parameter sets with different likelihood weights were obtained for each performance measure, the decision on which performance measure to be used may be very important to achieve the goal of study. Therefore, one or more suitable performance measures should be selected depending on the environment and the goal of a study, and this may lead to decrease model uncertainty.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.60-63
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• 2006

Geostationary Ocean Color Imager (GOCI) is under development to provide a monitoring of oceancolor around the Korean Peninsula from geostationary platforms. It is planned to be loaded on Communication, Ocean, and Meteorological Satellite (COMS) of Korea. In this paper radiometric calibration concept of the GOCI is introduced. The GOCI radiometric response is modeled as a nonlinear system in order to reflect a nonlinear characteristic of detector. In this paper estimation approaches for radiometric parameters of GOCI model are discussed. For the GOCI, the offset signal depends on each spectral channel because dark current offset signal is a function of integration time which is different from channel to channel. The offset parameter can be estimated by using offset signal measurements for two integration time setting is described.

• 한국농공학회지
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• 제45권4호
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• pp.89-97
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• 2003

Using inference models developed for estimation of the parameters necessary to implement the Runoff Block of the Stormwater Management Model (SWMM), a number of alternative inference scenarios were developed to assess the influence of inference model complexity and structure on the calibration of the catchment modelling system. These inference models varied from the assumption of a spatially invariant value (catchment average) to spatially variable with each subcatchment having its own unique values. Fur-thermore, the influence of different measures of deviation between the recorded information and simulation predictions were considered. The results of these investigations indicate that the model performance is more influenced by model structure than complexity, and control parameter values are very much dependent on objective function selected as this factor was the most influential for both the initial estimates and the final results.