• 한국도로학회논문집
• /
• 제14권4호
• /
• pp.83-91
• /
• 2012

PURPOSES : This study deals with Rotary by Accident Occurrence Location. The purpose of this study is to develop the accident models of rotary by location. METHODS : In pursuing the above, this study gives particular attentions to developing the appropriate models using multiple linear, Poisson and negative binomial regression models and statistical analysis tools. RESULTS : First, four multiple linear regression models which are statistically significant(their $R^2$ values are 0.781, 0.300, 0.784 and 0.644 respectively) are developed, and four Poisson regression models which are statistically significant(their ${\rho}^2$ values are 0.407, 0.306, 0.378 and 0.366 respectively) are developed. Second, the test results of fitness using RMSE, %RMSE, MPB and MAD show that Poisson regression model in the case of circulatory roadway, pedestrian crossing and others and multiple linear regression model in the case of entry/exit sections are appropriate to the given data. Finally, the common variable that affects to the accident is adopted to be traffic volume. CONCLUSIONS : 8 models which are all statistically significant are developed, and the common and specific variables that are related to the models are derived.

• 한국관개배수논문집
• /
• 제19권1호
• /
• pp.87-96
• /
• 2012

Information of local solar radiation is essential for many field, including water resources management, crop yield estimation, crop growth model, solar energy systems and irrigation and drainage design. Unfortunately, solar radiation measurements are not easily available due to the cost and maintenance and calibration requirements of the measuring equipment and station. Therefore, it is important to elaborate methods to estimate the solar radiation based on readily available meteorological data. In this study, two empirical equations are employed to estimate daily solar radiation using Cheongju Regional Meteorological Office data. Two scenarios are considered: (a) sunshine duration data are available for a given location, or (b) only daily cloudiness index records exist. Simple linear regression with daily sunshine duration and cloudiness index as the dependent variable accounted for 91% and 80%, respectively of the variation of solar radiation(H) at 2011. Daily global solar radiation is highly correlated with sunshine duration. In order to indicate the performance of the models, the statistical test methods of the mean bias error(MBE), root mean square error(RMSE) and correlation coefficient(r) are used. Sunshine duration and cloudiness index can be easily and reliably measured and data are widely available.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2011년도 학술발표회
• /
• pp.129-129
• /
• 2011

본 연구에서는 강수예보의 선행시간을 확보하기 위하여 기상청 지상관측망 자료뿐만 아니라 MTSAT-1R 위성영상자료와 수치예보모형인 RDAPS(Regional Data Assimilation and Prediction System) 자료를 활용하고, 입력자료 사이의 물리적인 비선형 상관관계를 효과적으로 고려하기 위하여 인경신경망 기법을 적용한 단시간 강수예측모형을 개발하고자 하였다. 또한 강수의 변화특성을 반영하기 위하여 장마기(6월, 7월)와 태풍기(8월, 9월)로 세분화하여 인공신경망 구축을 위한 학습훈련을 수행하였다. 구축된 모형은 서울지점을 대상으로 선행시간 3, 6, 9, 12시간에 대해서 강수예측을 수행하였다. 2006부터 2008년까지 학습훈련 후 2009년 서울지점의 강수예측결과, 장마기의 상관계수는 각 선행시간에 대해서 0.6998, 0.6498, 0.4434, 0.2961, RMSE(Root Mean Square Error)는 0.7605, 2.8431, 3.1973, 4.2147, 태풍기 상관계수는 0.5368, 0.5089, 0.4164, 0.2392, RMSE는 1.2218, 2.3144, 3.9153, 5.2145로 나타났다. 각 선행시간별로 장마기의 예측결과가 태풍기보다 다소 정확하게 도출되었으며, 선행시간 9시간 이후부터는 정확도가 급격히 낮아지는 결과를 얻었다.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2019년도 학술발표회
• /
• pp.375-375
• /
• 2019

충주댐 유역의 미계측유역을 대상으로 공간분포를 고려한 저류함수법 기반의 유출자료를 활용하여 지역최대홍수량의 추정 가능성을 평가하였다. 유출자료의 공간확장 가능성을 보기위해 2008년부터 2017년까지의 홍수 사상 중에 8개를 선정하였으며, 적절한 비교와 NSE 검증을 위해 충주댐, 영월1, 영춘 수위관측소를 검정지점으로 지정하였다. 또한, 선정한 사상 8개의 계측유역 유출자료를 바탕으로 공간확장방법을 활용하여 미계측유역의 유출자료를 생성하였다. 생성한 유출자료로 충주댐 유역의 홍수 사상과 지역최대홍수량(QRMF) 사이의 상관관계를 분석하여 지역최대홍수량의 발생 가능성과 충주댐 유역의 K값을 추정하였다. NSE 검증결과 유역출구지점인 충주댐에서 0.53으로 만족하여 유출자료 공간확장방법을 활용한 모의유출자료 산정은 적절한 것으로 나타났으며, 모의유출자료의 특성이 실제 유역의 특성과 유사한 것으로 나타났다. 생성한 유출자료와 지역최대 홍수량($Q_{RMF}$)에 대해 피어슨 상관계수와 RMSE를 활용하여 평가한 결과 서로 매우 높은 상관관계를 나타냈으며(Pearson's r> 0.9), 홍수량 산정방법에 있어서 지역최대홍수량($Q_{RMF}$)를 사용하여 산정하는 것이 바람직한 것으로 나타났다(RMSE=1.94). 또한, 충주댐 유역에 대한 지역최대홍수량($Q_{RMF}$)의 K값은 5.298로 산출되었으며, 산출한 K값으로 전체적인 충주댐 유역의 최대홍수량뿐만 아니라 면적이 비교적 작은 소유역의 최대홍수량도 추정할 수 있었다.

• 한국태양에너지학회 논문집
• /
• 제33권3호
• /
• pp.17-26
• /
• 2013

The aim of this study is to analyze the performance of a parabolic trough solar collector (PTC) for water heating and to validate the model performance. The simulated model was compared, calibrated and verified with the experimental results. RMSE (Root mean square error) was used to calibrate the convective heat transfer coefficient between the absorber pipe and the ambient air which was the main factor affecting the heat transfer associated with the PTC. The calibrated model was better fitted with the experimental model. The maximum, minimum and mean deviation between the measured and predicted water temperatures differed only $0.81^{\circ}C$, $0.09^{\circ}C$ and $0.31^{\circ}C$ respectively in the calibrated model. RMSE values were decreased from 0.5389 to 0.4910, 0.0134 to 0.0125 and R-squared was increased from 0.9955 to 0.9956 after calibration. The temperature of water was increased from $33.7^{\circ}C$ to $48^{\circ}C$ in 12hour test. The thermal efficiency of the collector was calculated to be 55%. The calibrated model showed good agreement with the experimental data for model validation.

• 대한원격탐사학회지
• /
• 제33권2호
• /
• pp.111-123
• /
• 2017

피코시아닌(phycocyanin, PC) 색소는 부영양화 된 담수역에서의 남조류를 정량하는 지표로 활용된다. 남조류의 대발생에 의한 잠재적 위험성으로인해 조기 경보 발령이 중요하지만, 혼탁한 수체 내 소량으로 추정되는 PC 농도를 정확하게 산정하는 것은 분광학적으로 매우 복잡하고 어렵다. 이를 위해 현장에서 측정 된 원격반사도로부터 PC 및 물 이외의 입자성 물질에 의한 흡수계수를 분리하여 기존 PC 농도를 추정하는 방법을 개선하여 낮은 농도에서도 향상 된 결과를 보였다. 본 연구에서 제안 된 IOPs 변환 모델 적용 결과 PC 흡수계수 $R^2$는 0.8 이상으로 $a_{pc}(620)$를 적절히 재현하였다. 또한 알고리즘은 기존 널리 사용되는 반경험적 알고리즘에 비해 $0.71{\leq}R^2{\leq}0.85$, $rRMSE{\leq}39.4%$, 그리고 $RE{\leq}78.0%$로 정확도 높은 결과를 보였다. 특히, PC 농도가 $50mg/m^3$ 이하 및 PC: Chl-a ratio가 낮은 조건에서도 잘 예측됨을 확인할 수 있었다.

• Journal of Positioning, Navigation, and Timing
• /
• 제8권4호
• /
• pp.201-208
• /
• 2019

Numerical integration is necessary for satellite orbit determination and its prediction. The numerical integration algorithm can be divided into single-step and multi-step method. There are lots of single-step and multi-step methods. However, the Runge-Kutta method in single-step and the Adams method in multi-step are generally used in global navigation satellite system (GNSS) satellite orbit. In this study, 4th and 8th order Runge-Kutta methods and various order of Adams-Bashforth-Moulton methods were used for GLObal NAvigation Satellite System (GLONASS) orbit integration using its broadcast ephemeris and these methods were compared with international GNSS service (IGS) final products for 7days. As a result, the RMSE of Runge-Kutta methods were 3.13m and 4th and 8th order Runge-Kutta results were very close and also 3rd to 9th order Adams-Bashforth-Moulton results. About result of computation time, this study showed that 4th order Runge-Kutta was the fastest. However, in case of 8th order Runge-Kutta, it was faster than 14th order Adams-Bashforth-Moulton but slower than 13th order Adams-Bashforth-Moulton in this study.

• Journal of Ecology and Environment
• /
• 제38권4호
• /
• pp.485-491
• /
• 2015

This study was conducted to develop stem volume models for the volume estimation of Quercus glauca Thunb. in Jeju Island, Republic of Korea. Furthermore, this study validated the developed stem volume models using an independent dataset. A total of 167 trees were measured for their diameter at breast height (DBH), total height and stem volume using non-destructive sampling methods. Eighty percent of the dataset was used for the initial model development while the remaining 20% was used for model validation. The performance of the different models was evaluated using the following fit statistics: standard error of estimate (SEE), mean bias absolute mean deviation (AMD), coefficient of determination (R²), and root mean square error (RMSE). The AMD of the five models from the different DBH classes were determined using the validation dataset. Model 5 (V = aD^bH^c), which estimates volume using DBH and total height as predicting variables, had the best SEE (0.02745), AMD (0.01538), R² (0.97603) and RMSE (0.02746). Overall, volume models with two independent variables (DBH and total height) performed better than those with only one (DBH) based on the model evaluation and validation. The models developed in this study can provide forest managers with accurate estimations for the stem volumes of Quercus glauca in the subtropical forests of Jeju Island, Korea.

• Journal of Ecology and Environment
• /
• 제37권4호
• /
• pp.177-184
• /
• 2014

This study was conducted to develop allometric equations and to determine the stem density and biomass expansion factor (BEF) for the estimation of the aboveground and belowground biomass of Cryptomeria japonica in Jeju Island, Korea. A total of 18 trees were harvested from the 40-year-old C. japonica stands in Hannam experimental forest, Jeju Island. The mean biomass of the C. japonica was $50.4Mg\;ha^{-1}$ in stem wood, $23.1Mg\;ha^{-1}$ in root, $9.6Mg\;ha^{-1}$ in branch, $4.6Mg\;ha^{-1}$ in needle and $4.3Mg\;ha^{-1}$ in stem bark. The diameter at breast height (DBH) was selected as independent variable for the development of allometric equations. To evaluate the performance of these equations, coefficient of determination ($R^2$) and root mean square error (RMSE) were used and results of the evaluation showed that $R^2$ ranged from 71% (root biomass equation) to 96% (aboveground biomass equation) and the RMSE ranged from 0.10 (aboveground biomass equation) to 0.33 (root biomass equation). The mean stem density of C. japonica was $0.37g\;cm^{-3}$ and the mean aboveground BEF was $1.28g\;g^{-1}$. Furthermore, the ratio of the root biomass to aboveground biomass was 0.32.

• 한국농공학회논문집
• /
• 제58권4호
• /
• pp.9-19
• /
• 2016

The objective of this study was to evaluate the applicability of SWAT (Soil and Water Assessment Tool) model for runoff estimation in the Nam river dam watershed. Input data for the SWAT model were established using spatial data (land use, soil, digital elevation map) and weather data. The SWAT model was calibrated and validated using observed runoff data from 2003 to 2014 for three stations (Sancheong, Shinan, Changchon) within the study watershed. The $R^2$ (Determination Coefficient), RMSE (Root Mean Square Error), NSE (Nash-Sutcliffe efficiency coefficient), and RMAE (Relative Mean Absolute Error) were used to evaluate the model performance. Parameters for runoff calibration were selected based on user's manual and references and trial and error method was applied for parameter calibration. Calibration results showed that annual mean runoff were within ${\pm}5%$ error compared to observed. $R^2$ were ranged 0.64 ~ 0.75, RMSE were 2.51 ~ 4.97 mm/day, NSE were 0.48 ~ 0.65, and RMAE were 0.34 ~ 0.63 mm/day for daily runoff, respectively. The runoff comparison for three stations showed that annual runoff was higher in Changchon especially summer and winter seasons. The flow exceedance graph showed that Sancheong and Shinan stations were similar while Changchon was higher in entire fraction.