SWAT-CUP을 이용한 SWAT 모형 검·보정 III: 다중 관측 지점 및 변수를 고려한 분석

조영현,Cho, Younghyun 한국수자원학회 2020 한국수자원학회논문집 Vol.53 No.12

In this study, a criteria for the SWAT model calibration method in SWAT-CUP which considers multi-site and multi-variable observations was presented. For its application, the SWAT model was simulated using long-term observed flow, soil moisture, and evapotranspiration data in Yongdam study watershed, investigating the hydrological runoff characteristics and water balance in the water cycle analysis. The model was calibrated with different parameter values for each sub-watershed in order to reflect the characteristics of multiple observations through one-by-one calibration, appropriate settings of model simulation run/iteration number (1,000 simulation runs in the first iteration and then 500 simulation runs for the following iterations), and executions of partial and all run in SWAT-CUP. The flow simulation results of watershed outlet point, ENS 0.85, R2 0.87, and PBIAS -7.6%, were compared with the analysis results (ENS 0.52, R2 0.54, and PBIAS -22.4%) applied in the other batch (i.e., non one-by-one) calibration approach and showed better performances of proposed method. From the simulation results of a total of 15 years, it was found that the total runoff (streamflow) and evapotranspiration rates from precipitation are 53 and 39%, and the ratio of surface runoff and baseflow (i.e., sum of lateral and return flow, and recharge deep aquifer) are 35 and 65%, respectively, in Yongdam watershed. In addition, the analytical amount of available water (i.e., water yield), including the total annual streamflow (daily average 21.8 m3/sec) is 6.96 billion m3 per year (about 540 to 900 mm for sub-watersheds).

2000년대 기계공학분야 특허출원동향 분석

조영현(CHO Younghyun) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

This paper aims to analyze recent trends in application and approval of patents in the field of mechanical engineering. This analysis is based on the International Patent Classification(IPC), a hierarchical system of patent classification. Created under the Strasbourg Agreement (1971), IPC has 8 sections from A to H, among which the section F covers the area of mechanical engineering. Through the analysis presented in this paper, we will find a significant phenomena in regards to the patents listed under the section B and section F. Conspicuously enough, the patents related to the mechanical engineering (and therefore listed under the section B and section F) tend to fall under multiple segments at the same time, especially since 2000. This not only intimates an important trends in R&D and patent applications in the field of mechanical engineering, but also lets us have critical prospects and strategical minds for the decades to come.

수문기상 정보를 이용한 가뭄 전이 분석: 기상학적 가뭄에서 농업적 가뭄

유명수,조영현,김태웅,채효석,Yu, Myungsu,Cho, Younghyun,Kim, Tae-Woong,Chae, Hyo-Sok 한국수자원학회 2018 한국수자원학회논문집 Vol.51 No.3

Drought is a complex phenomenon caused by various factors which can be classified into natural and anthropogenic causes. In Korea, the natural drought typically occurs when the high pressure of the Pacific Ocean develops rapidly or becomes stronger than usual in summer, resulting in a short-lived monsoon season. Drought also can be classified into meteorological, agricultural, hydrological, and socioeconomic drought depending on the development process and consequences. Each type of droughts can influence the other drought types directly or indirectly. Drought propagation refers a phenomenon that changes from meteorological drought to agricultural or hydrological drought. In this study, the occurrence and patterns of drought propagation are evaluated. The relationship between meteorological and agricultural droughts was assessed using hydrometeorological data. We classified the types of drought into five categories to evaluate the occurrence and characteristics of drought propagation. As results, we found drought propagation did not occur or delayed until three months, depending on the type of drought. The further generalized relationship of drought propagation is expected to be used for predicting agricultural drought from the preceding meteorological drought. 가뭄은 여러 가지 요인에 의해 복합적으로 발생하는 현상으로 자연적 원인과 인위적 원인으로 구분할 수 있다. 우리나라는 기후학적 특성상 여름철에 태평양 고기압의 발달 시기가 빠르거나 평년보다 강하면 장마 기간이 짧아져 자연적인 원인에 의해 가뭄이 발생한다. 가뭄은 발생과정과 피해 영향에 따라 기상학적, 농업적, 수문학적, 사회경제적 가뭄으로 구분할 수 있으며 직 간접적으로 다른 가뭄에 영향을 미친다. 가뭄의 종류가 기상학적 가뭄에서 농업적 가뭄 혹은 기상학적 가뭄에서 수문학적 가뭄으로 변화되는 현상을 가뭄 전이라 한다. 본 연구에서는 국내의 가뭄 전이 발생 여부와 발생 패턴을 검토하기 위해 수문기상 정보를 이용하여 기상학적 가뭄에서 농업적 가뭄으로의 전이 관계를 분석하였다. 가뭄 전이 발생 현황 및 특성 분석을 위해 가뭄 발생의 유형을 5가지로 구분하였으며, 유형에 따라 가뭄 전이가 발생하지 않거나 최대 3개월까지 지체되는 것을 확인하였다. 향후 더 많은 가뭄 지표들과의 분석을 통해 가뭄 전이 관계를 일반화한다면 기상학적 가뭄 발생 시 농업적 가뭄 예측을 위한 인자로 활용할 수 있을 것으로 기대된다.

위성기반 증발산량 및 토양수분량 산정 국내 연구동향

최가영,조영현,Choi, Ga-young,Cho, Younghyun 대한원격탐사학회 2022 大韓遠隔探査學會誌 Vol.38 No.6

The application of satellite imageries has increased in the field of hydrology and water resources in recent years. However, challenges have been encountered on obtaining accurate evapotranspiration and soil moisture. Therefore, present researches have emphasized the necessity to obtain estimations of satellite-based evapotranspiration and soil moisture with related development researches. In this study, we presented the research status in Korea by investigating the current trends and methodologies for evapotranspiration and soil moisture. As a result of examining the detailed methodologies, we have ascertained that, in general, evapotranspiration is estimated using Energy balance models, such as Surface Energy Balance Algorithm for Land (SEBAL) and Mapping Evapotranspiration with Internalized Calibration (METRIC). In addition, Penman-Monteith and Priestley-Taylor equations are also used to estimate evapotranspiration. In the case of soil moisture, in general, active (AMSR-E, AMSR2, MIRAS, and SMAP) and passive (ASCAT and SAR)sensors are used for estimation. In terms of statistics, deep learning, as well as linear regression equations and artificial neural networks, are used for estimating these parameters. There were a number of research cases in which various indices were calculated using satellite-based data and applied to the characterization of drought. In some cases, hydrological cycle factors of evapotranspiration and soil moisture were calculated based on the Land Surface Model (LSM). Through this process, by comparing, reviewing, and presenting major detailed methodologies, we intend to use these references in related research, and lay the foundation for the advancement of researches on the calculation of satellite-based hydrological cycle data in the future.

SWAT-CUP을 이용한 SWAT 모형 검·보정 I: 목적함수에 따른 불확실성 분석

유지수,노준우,조영현,Yu, Jisoo,Noh, Joonwoo,Cho, Younghyun 한국수자원학회 2020 한국수자원학회논문집 Vol.53 No.1

This study aims to quantify the uncertainty that can be induced by the objective function when calibrating SWAT parameters using SWAT-CUP. SWAT model was constructed to estimate runoff in Naesenong-cheon, which is the one of mid-watershed in Nakdong River basin, and then automatic calibration was performed using eight objective functions (R², bR², NS, MNS, KGE, PBIAS, RSR, and SSQR). The optimum parameter sets obtained from each objective function showed different ranges, and thus the corresponding hydrologic characteristics of simulated data were also derived differently. This is because each objective function is sensitive to specific hydrologic signatures and evaluates model performance in an unique way. In other words, one objective function might be sensitive to the residual of the extreme value, so that well produce the peak value, whereas ignores the average or low flow residuals. Therefore, the hydrological similarity between the simulated and measured values was evaluated in order to select the optimum objective function. The hydrologic signatures, which include not only the magnitude, but also the ratio of the inclining and declining time in hydrograph, were defined to consider the timing of the flow occurrence, the response of watershed, and the increasing and decreasing trend. The results of evaluation were quantified by scoring method, and hence the optimal objective functions for SWAT parameter calibration were determined as MNS (342.48) and SSQR (346.45) with the highest total scores.

SWAT-CUP을 이용한 SWAT 모형 검·보정 II: 모의 실행 및 반복 횟수에 따른 불확실성 분석

유지수,노준우,조영현,Yu, Jisoo,Noh, Joonwoo,Cho, Younghyun 한국수자원학회 2020 한국수자원학회논문집 Vol.53 No.5

본 연구에서는 SWAT-CUP 프로그램을 이용한 SWAT 모형 매개변수 검·보정 수행 시 적은 계산 소요시간으로 모의 성능을 극대화할 수 있는 매개변수 보정 방안을 결정하기 위해 모의 실행 횟수에 따라 Case1~3(250, 500, 1,000번) 및 Case4(초기 1,000번, 이후 500번)로 구분하고, 이들 모의의 반복에 따른 보정 결과를 비교하였다. 선정한 목적함수에 대하여 모의 성능을 평가한 결과 각 모의 수행의 4번째 반복 이후 Case2와 Case3의 목적함수가 같은 값(MNS 0.64)에 도달했으며, 8번째 이후부터는 Case1의 목적함수도 유사한 값에 도달하는 것을 확인하였다. 그러나 매개변수의 최종 산정 값은 Case1~3이 모두 상이하게 나타났으며, Case3과 Case4의 결과만 유사하게 수렴되는 것을 확인하였다. 이의 분석을 통해 보정 결과는 매개변수 값 산정을 위한 초기 모의 실행 횟수에 큰 영향을 받는다는 것을 알 수 있었다. 반면, 초기의 매개변수 변화 폭과는 다르게 이의 반복을 통한 SWAT 모의 수행 결과는 크게 달라지지 않았다. 이와 같은 결과를 종합하여 Case4와 같이 1,000번 이상의 충분한 모의 실행 횟수 설정 후 초기 1-2회 정도 반복 수행하고, 그 이후는 모의 횟수를 줄여서 반복하는 것을 가장 효율적인 SWAT-CUP을 이용한 SWAT 모형 검·보정 방안으로 제시할 수 있었다.

해양환경에 적합한 수중 통신 기술의 특허 동향

전용철(Jun Yongcheul),최준우,조영현(Cho Younghyun),남일구(Nam Ilku) 한국통신학회 2013 한국통신학회 학술대회논문집 Vol.2013 No.1

생명보험산업 보험료 성장률 예측계량모형 비교

전성주 ( Sungju Chun ),조영현 ( Younghyun Cho ) 한국금융연구원 2015 금융연구 Vol.29 No.3

In this article we evaluate the performance of forecasting models to predict the Korean life insurance premium growth rates. Comparisons are made for the Vector Auroregressive (VAR) predictive model, the multivariate leading indicator model, and the diffusion index model proposed by Stock and Watson (2002) against the Univariate Autoregressive (AR) predictive model as a benchmark. We compare each model’s predictability for the total premium incomes and the initial premium incomes of three types in the individual insurance; protection, endowment and annuity. The complete quarterly data spans from the second quarter of 1986 to the first quarter of 2014. The lag selection for AR and VAR forecasting models depends on the Bayesian Information Criteria (BIC) with the maximum number of lags set to 4. For the multivariate leading indicator model, we use 4 leading indicators of GDP growth rates, inflation, education, and age. In order to avoid data mining concerns, we select the variables that have been found to be the determinants of life insurance demands by previous studies. The diffusion index model is an approximate dynamic factor model that relates the future life insurance premium growth rates to a number of factors estimated by principal components using a large number of macroeconomic variables. The set of macroeconomic variables consists of 57 variables representing 6 main categories of macroeconomic time series: demand for final output; balance of payments and international trade; price indexes; money, interest rates and financial markets; labor, production and population; and world variables. We also include in the data set the variables related to the life insurance industry such as the industry’s total asset returns, claims paid and etc. In predicting total premium income growth rates, the AR predictive model produces the smallest mean squared predictive errors (MSPEs). For the premium incomes of protective insurance all the forecasting models have the MSPEs less than 3%. But they become unreliable in predicting the premium incomes of annuity with producing the MSPEs more than 10%. When we test the null hypothesis of no difference in MSPEs, it is rejected at 5% significance level for the VAR and the diffusion index predictive models when we forecast the total premium income growth rates of protective insurance. In predicting initial premium income growth rates, we find that there are no statistically significant differences in the MSPEs of each model. In addition, all the models have MSPEs more than 10% so that we may not be able to depend on any model to forecast in practice. We conclude that it may not be beneficial to take advantage of the information contained in macroeconomic variables for predicting life insurance premium growth rates. It may be due to the fact that most of the insurance contracts in Korea charge monthly premiums, which induces heavy autocorrelations among quarterly insurance premium data and makes an AR forecast very effective. Rho and Shin (1998) also found that macroeconomic variables are not likely to influence on insurance demands as is largely determined by insurer’s push-marketing. Policy holders cannot surrender their insurance contracts without heavy penalties, which makes them not so much responsive to macroeconomic environments. Lastly, life insurance demands are very sensitive to changes in insurance regulation and taxation, which could not be controlled for by our estimation procedure due to the lack of time series observations.

An optimal design for the local back contact pattern of crystalline silicon solar cells by using PC1D simulation

오성근(Oh, Sungkeun),임충현(Lim, Chung-Hyun),조영현(Cho, Younghyun) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.11

In the crystalline silicon solar cells, the full area aluminum_back surface field(BSF) is routinely achieved through the screen-printing of aluminum paste and rapid firing. It is widely used in the industrial solar cell because of the simple and cost-effective process to suppress the overall recombination at the back surface. However, it still has limitations such as the relatively higher recombination rate and the low-to-moderate reflectance. In addition, it is difficult to apply it to thinner substrate due to wafer bowing. In the recent years, the dielectric back-passivated cell with local back contacts has been developed and implemented to overcome its disadvantages. Although it is successful to gain a lower value of surface recombination velocity(SRV), the series resistance(R_{series}) becomes even more important than the conventional solar cell. That is, it is a trade off relationship between the SRV and the R_{series} as a function of the contact size, the contact spacing and the geometry of the opening. Therefore it is essential to find the best compromise between them for the high efficiency solar cell. We have investigated the optimal design for the local back contact by using PC1D simulation.

1차원 비정상 수질모형을 이용한 플러싱방류에 따른 수질개선 효과 분석

노준우(Noh Joonwoo),정성태(Jung Sungtae),조영현(Cho Younghyun),성영두(Sung Youngdu) 대한토목학회 2008 대한토목학회 학술대회 Vol.2008 No.10