• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1340-1346
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• 2005

A water quality modeling study was performed for Chunggye stream during combined sewer overflow(CSO) period, utilizing the diagnostic system for water management in small watershed, CREEK-1(Cyber River for Environment and Economy in Korea). This system integrated geogaphic information system, data base, landscape ecological model(FRAGSTATS), watershed model(SWMM), water quality model (WASP5), and computer graphic. In this study, the watershed model and water quality model were extensively utilized so as to simulate water qualities and flow in Chunggye stream during wet periods. The Chunggye stream watershed was divided into 18 sub-basins in the watershed model and the stream reach into 11 segments in the water quality model. The watershed model was validated against field measurements of BOD, TN, TP, and flow at the downstream location, where the model results showed a reasonable agreement with the field measurements at all parameters. From this study, it was shown that the stream water quality would change along with elapsed time from rainfall start as well as rainfall intensity. The model results indicated that the water quality would significantly upgrade due to the first flush and high sewage ratio of CSO at the beginning of rainfall event, but become degraded along with the runoff increase due to dilution effect.

• Journal of Korea Water Resources Association
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• v.30 no.4
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• pp.317-326
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• 1997

The Palmer Drought Severity Index has been ectensively used to quantitatively evaluate the drought severity at a location for both agricultural and water resources management purposes. In the present study the Palmer-type formula for drought index is drived for the whole country by analyzing the monthly rainfall and meteorological data at nine stations with a long period of records. The formula is then used to compute the monthly drought severity index at sixty-eight rainfall stations located throughout the country. For the past five significant drought periods the spatial variation of each drought is shown as a nationwide drought index map of a specified duration from which the relative severity of drought throughout the country is identifiable for a specific drought period. A comparative study is made to evaluate the relative severity of the significant droughts occurred in Korea since 1960's. It turned out that '94-'95 drought was one of the worst both in the areal extent and drought severity. It is found that the Palmer-type formula is a very useful tool in quantitatively evaluating the severity of drought over an area as well as at a point. When rainfall and meteorological forecast become feasible on a long-term basis the method could also be utilized as a tool for drought forecasting.

• Journal of Wetlands Research
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• v.15 no.1
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• pp.105-114
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• 2013

Recently, Due to Climate change, extreme rainfall occurs frequently. In many preceding studies, Because of extreme hydrological events changes, it is expected that peak flood Magnitude and frequency of drainage infrastructures changes. However, at present, probability rainfall in the drainage facilities design is assumed to Stationary which are not effected from climate change and long-term fluctuation. In the future, flood control safety standard should be reconsidered about the valid viewpoint. In this paper, in order to assess impact of climate change on drainage system, Future climate change information has been extracted from RCP 8.5 Climate Change Scenario for IPCC AR5, then estimated the design rainfall for various durations at return periods. Finally, the design flood estimated through the HEC-HMS Model which is being widely used in the practices, estimated the effect of climate change on the Design Flood of Mihochen basin. The results suggested that the Design Flood increase by climate change. Due to this, the Flood risk of Mihochen basin can be identified to increase comparing the present status.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.170-170
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• 2020

Due to the development of technologies, complex computation of huge data set is possible with a prevalent personal computer. Therefore, machine learning methods have been widely applied in the hydrologic field such as regression-based regional frequency analysis (RFA). The main purpose of this study is to compare two frameworks of RFA based on the artificial neural network (ANN) models: quantile regression technique (QRT-ANN) and parameter regression technique (PRT-ANN). As an output layer of the ANN model, the QRT-ANN predicts quantiles for various return periods whereas the PRT-ANN provides prediction of three parameters for the generalized extreme value distribution. Rainfall gauging sites where record length is more than 20 years were selected and their annual maximum rainfalls and various hydro-meteorological variables were used as an input layer of the ANN model. While employing the ANN model, 70% and 30% of gauging sites were used as training set and testing set, respectively. For each technique, ANN model structure such as number of hidden layers and nodes was determined by a leave-one-out validation with calculating root mean square error (RMSE). To assess the performances of two frameworks, RMSEs of quantile predicted by the QRT-ANN are compared to those of the PRT-ANN.

• Korean Journal of Agricultural and Forest Meteorology
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• v.3 no.1
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• pp.55-70
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• 2001

It was unusual crop weather for 1998 and 1999 compared with normal in Korea. The consecutive days of the optimum ripening period for rice plant that had daily mean temperature 21~23$^{\circ}C$ for 40 days after flowering, increased with long anomalies in 1998~99. The air temperature during ripening period was much higher than the optimum temperature and lower sunshine hour than norm in the local adaptability tests of newly developed rice lines during those years. In response of rice cultivation to warming and cloudy weather during crop season, the yield shall be decreased. Most scientists agree that the rate of heating is accelerating and temperature change could become increasingly disruptive. Weather patterns should also become more erratic. Agrometeorologists could be analyzed yearly variations of temperature, sunshine hour and rainfall pattern focused on transient agroclimate change for last a decade. Rice agronomists could be established taking advantage of real time agricultural meteorology information system for fertilization, irrigation, pest control and harvest. Also they could be analyzed the characteristics of flowering response of the recommended and newly bred rice cultivars for suitable cropping plan such as cultural patterns and sowing or transplanting date. Rice breeders should be deeply considered introducing the characteristics of basic vegetative type of flowering response like Togil rices as prospective rice cultivars corresponding to global warming because of the rices needed higher temperature at ripening stage than japonica rices, photoperiod-sensitive and thermo-sensitive ecotypes.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.649-654
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• 2005

Shallow slope failures in residual soil during periods of prolonged infiltration are common over the world. One of the key factors that dominate slope stability is hydrological response associated with infiltration. Hence, the soil-water profile during rainfall infiltration into unsaturated soil must me examined to evaluate slope stability. However, the hydraulic response of unsaturated soil is complicated by inherent uncertainties of the soil hydraulic properties. This study presents a methodology for assessing the effects of parameter uncertainty of hydraulic properties on the response of a analytical infiltration model using first-order reliability method. The unsaturated soil properties are considered as uncertain variables with means, standard deviations, and marginal probability distributions. Sensitivities of the probabilistic outcome to the basic uncertainties in the input random variables are provided through importance factors.

• Journal of Korean Society of Rural Planning
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• v.11 no.1 s.26
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• pp.17-24
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• 2005

The purpose of this study is to evaluate the hydrological impact due to temporal land cover change by gradual urbanization of Anseong-cheon Gongdo watershed ($371.8km^2$). Land covers of 1981, 1990, 2000 Landsat TM images were classified by maximum likelihood method. The watershed showed a trend that forest & paddy areas decreased about $33km^2$ and $27km^2$, respectively and urban area increased about $11km^2$ during the periods. To identify the impact of streamflow due to urbanization, WMS HEC-1 was used. According to apply Huffs quartile storm events by changing land cover data, peak runoff discharge of each frequency rainfall (50, 100, 500 years) increased about 56, 36, $192m^3/sec$, respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.151-151
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• 2019

Because drought is a complex and stochastic phenomenon in nature, statistical approaches for drought assessment receive great attention for water resource planning and management. Generally drought characteristics such as severity, duration and intensity are modelled separately. This study aims to develop a relationship between drought characteristics using a bivariate copula model. To achieve the objective, we calculated the Standardized Precipitation Index (SPI) using rainfall data at 6 rain gauge stations for the period of 1961-1999 in Jehlum River Basin, Pakistan, and investigated the drought characteristics. Since there is a significant correlation between drought severity and duration, they are usually modeled using different marginal distributions and joint distribution function. Using exponential distribution for drought severity and log-logistic distribution for drought duration, the Galambos copula was recognized as best copula to model joint distribution of drought severity and duration based on the KS-statistic. Various return periods of drought were calculated to identify time interval of repeated drought events. The result of this study can provide useful information for effective water resource management and shows superiority against univariate drought analysis.

• Korean Journal of Environmental Agriculture
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• v.42 no.4
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• pp.311-323
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• 2023

Miscanthus sinensis Andersson (Poaceae) cultivars exhibit excellent visual appeal as ornamental grasses and adapt well to diverse environmental conditions. This study focused on assessing the growth response and landscape durability of seven popular Miscanthus cultivars ('Gold Breeze', 'Strictus', 'Morning Light', 'Variegatus', 'Gracillimus', 'Kleine Fontäne', 'Common') under drought, rainfall and low temperature condition. The test cultivars were transplanted and cultivated on research plots in 2013, with data collected from June 2017 to February 2018. Plant materials were categorized into three types based on the amount of the water lost; group I ('Kleine Fontäne', 'Variegatus', 'Strictus'), experiencing the most significant water loss; group II ('Common', 'Gracillimus'); and group III ('Gold Breeze', 'Morning Light') where the least water loss occurred. The drought resistance index (DRI) remained low as water shortage conditions persisted. The lodged angle underwent more pronounced changes in reproductive growth stage than in vegetative growth stage, notably decreasing after heading. Discoloration patterns were classified into two types: group I ('Common', 'Gold Breeze', 'Kleine Fontäne', 'Strictus') and group II ('Gracillimus', 'Morning Light', 'Variegatus') based on the periods of peak duration.

• Proceedings of the KIEE Conference
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• summer
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• pp.527-529
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• 2004

This paper researched leakage current characteristics of EHW insulators(36,000lbs) to artificially contaminated clay and kaolin through construction of long-periods testing facility. Insulators were contaminated and classified into the ESDD level(B, C and D) under IEC Pub. 60507 standards method. As a result of tests, leakage current of the heavily contaminated D level to clay was approximately 2,260 $[\muA]$, which is contaminated to kaolin was approximately 3,200 $[\muA]$, during initial rainfall. However after raining, leakage current of naturally washed contamination insulators was lower at approximately 300 $[\muA]$. As regular temperature $20^{\circ}C$, leakage current increased greatly in case humidity density was over $72\%$. But, leakage current was not influenced by temperature variation in case of regular $\%$ humidity.