• Korean Journal of Environmental Agriculture
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• v.31 no.4
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• pp.318-327
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• 2012

BACKGROUND: For Non-Point Source(NPS) loads reduction, pollutant loads need to be quantified for major farming methods. The objective of this study was to evaluate impacts of farming methods on NPS pollutant loads from a paddy rice field during the growing season. METHODS AND RESULTS: The height of drainage outlet, amount of fertilizer, irrigation water quality were considered as farming factors for scenarios development. The control was derived from conventional farming methods and four different scenarios were developed based combination of farming factors. A field scale model, CREAMS-PADDY(Chemicals, Runoff, and Erosion from Agricultural Management Systems for PADDY), was used to calculate pollutant nutrient loads. The data collected from an experimental plot located downstream of the Idong reservoir were used for model calibration and validation. The simulation results agreed well with observed values during the calibration and validation periods. The calibrated model was used to evaluate farming scenarios in terms of NPS loads. Pollutant loads for T-N, T-P were reduced by 5~62%, 8~37% with increasing the height of drainage outlet from 100 mm of 100 mm, respectively. When amount of fertilizer was changed from standard to conventional, T-N, T-P pollutant loads were reduced by 0~22%, 0~24%. Irrigation water quality below water criteria IV of reservoir increased T-N of 9~65%, T-P of 9~47% in comparison with conventional. CONCLUSION(S): The results indicated that applying increased the height of drainage after midsummer drainage, standard fertilization level during non-rainy seasons, irrigation water quality below water criteria IV of reservoir were effective farming methods to reduce NPS pollutant loads from paddy in Korea.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.421-421
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• 2019

본 연구의 목적은 HSPF 모델을 이용하여 비점오염물질이 수질에 미치는 영향을 평가하는 것이다. 합천댐 유역을 연구대상지역으로 선정하였으며, 입력자료는 유역도, 하천도, 토지이용도, 수치표고모델 및 기상자료 등을 이용하였다. HSPF 모형은 2000년부터 2016년까지의 실측값을 이용하여 보정 및 검증이 이루어졌다. 수문 보정을 위한 매개변수는 사용자 설명서와 참고문헌에 근거하여 선정하였으며, 시행착오법에 의해 수행되었다. 모델의 적용성 평가는 $R^2$, RMSE, RMAE, NSE를 사용하였고 $R^2$가 0.78에서 0.83, RMSE는 2.55에서 2.76mm/day, RMAE는 0.46에서 0.48mm/day, NSE는 0.81에서 0.82까지의 범위로 나타났으며, 연간 유출량이 ${\pm}4%$ 오차 이내로 산정되었다. 수질 모형을 구동하기 위한 수질 자료는 환경부에서 제시한 지침에 따라 생활계, 축산계, 산업계, 토지이용량에 따른 발생 부하량과 배출부하량을 산정하였다. 수질 모형 또한 수문과 같은 기간의 자료를 이용하여 보정 및 검정이 이루어졌다. 보정 결과 연평균 BOD의 차이가 0.22mg/L이고 오차범위는 13%였으며, T-N과 T-P는 0.66mg/L, 0.027mg/L의 차이를 가지며 오차범위는 각각 16%, 13%로 나타났다. 수질항목 중에서도 비점오염 관리의 효과를 평가하기 위해 비점오염물질 중 가장 큰 비중을 차지하는 축산계에 감소 시나리오를 적용하였다. 축산계의 배출부하량 감소율이 20%일때의 BOD, T-N, T-P는 각각 3%, 1%, 3% 감소하였으며 40% 감소율을 적용하였을때는 5%, 3%, 4% 감소하였다. 이러한 수질 해석을 결과를 토대로 효과적인 오염물질 방법을 적용하여 수질 개선과 합천댐 유역의 목표수질을 달성 할 수 있을 것으로 판단된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.327-327
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• 2010

In this paper, an investigation of factors affecting piezoelectric transformers is presented by ATILA software. These transformers are multi-layer piezoelectric transformers in square shape $28\;{\times}\;28\;mm$ and operate in first vibration mode for step-down function. The piezoelectric transformers were modeled in 3D-dimension and analyzed using finite element method in ATILA software, a popular software in piezoelectric analysis. Modal and harmonic modules were used in this process. Effective factors to the properties of piezoelectric transformers including different input electrode patterns, directions of polarization, sizes of connective comer, number of layers were examined on the simulated model using input voltage of 20 V and load resistance of $100\;{\Omega}$. Moreover, thermal analysis was also obtained with conditions of input voltage of 5 V and no-load.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.6
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• pp.233-241
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• 2005

The present model of a SF6 arc accounts for the copper vapour contamination from the electrodes inside a Laval nozzle of a circuit breaker. Steady state simulations have been done for the arc with electrode gap of 60mm and DC electric current of 500A, 1000A and 1500A for both cases with and without copper contamination. The effects of electrode polarity are considered for the arc current of 1000A. It was found out that evaporation of copper from the anode results in a cooling of the arc in a region close to the electrodes. The electrical potential across the electrodes is not sensitive to the presence of copper vapour, typically less than $4\%$ difference. Transient analysis has been done in order to obtain the arc properties at current zero. The arc current is increased linearly from -1000 to 0A when the upstream electrode is cathode with constant dI/dt of $27.0A/{\mu}s$ (or decreased linearly from 1000 to 0A when upstream electrode is anode). It has been predicted that the presence of copper vapour reduces the interruption capability of the breaker.

• Atmosphere
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• v.25 no.4
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• pp.623-637
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• 2015

The accurate analysis of water vapor in initial of numerical weather prediction (NWP) model is required as one of the necessary conditions for the improvement of heavy rainfall prediction and reduction of spin-up time on a very-short-range forecast. To study this effect, the impact of a ground-based Global Positioning System (GPS)-Precipitable Water Vapor (PWV) on very-short-range forecast are examined. Data assimilation experiments of GPS-PWV data from 19 sites over the Korean Peninsula were conducted with Advanced Storm-scale Analysis and Prediction System (ASAPS) based on the Korea Meteorological Administration's Korea Local Analysis and Prediction System (KLAPS) included "Hot Start" as very-short-range forecast system. The GPS total water vapor was used as constraint for integrated water vapor in a variational humidity analysis in KLAPS. Two simulations of heavy rainfall events show that the precipitation forecast have improved in terms of ETS score compared to the simulation without GPS-PWV data. In the first case, the ETS for 0.5 mm of rainfall accumulated during 3 hrs over the Seoul-Gyeonggi area shows an improvement of 0.059 for initial forecast time. In other cases, the ETS improved 0.082 for late forecast time. According to a qualitative analysis, the assimilation of GPS-PWV improved on the intensity of precipitation in the strong rain band, and reduced overestimated small amounts of precipitation on the out of rain band. In the case of heavy rainfall during the rainy season in Gyeonggi province, 8 mm accompanied by the typhoon in the case was shown to increase to 15 mm of precipitation in the southern metropolitan area. The GPS-PWV assimilation was extremely beneficial to improving the initial moisture analysis and heavy rainfall forecast within 3 hrs. The GPS-PWV data on variational data assimilation have provided more useful information to improve the predictability of precipitation for very short range forecasts.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.3
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• pp.284-299
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• 2008

Emission input modules was developed to produce emission input data and change some profiles for Sparse Matrix Operator Kernel Emissions (SMOKE) using Clean Air Policy Support System (CAPSS)'s activities and previous studies. Specially, this study was focused to improve chemical speciation and temporal allocation profiles of SMOKE. At first, SCC cord mapping was done. 579 SCC cords of CAPSS were matched with EPA's one. Temporal allocation profiles were changed using CAPSS monthly activities. And Chemical speciation profiles were substituted using Kang et al. (2000) and Lee et al. (2005) studies and Kim et al. (2005) study. Simulation in Seoul Metropolitan Area (Seoul, Incheon, Gyeonggi) using MM5, SMOKE and CMAQ modeling system was done for effect analysis of changed input modules of SMOKE. Emission model results adjusted with new input modules were slightly changed as compared to using EPA's default modules. SMOKE outputs shows that aldehyde emissions were decreased 4.78% after changing chemical profiles, increased 0.85% after implementing new temporal profiles. Toluene emissions were decreased 18.56% by changing chemical speciation profiles, increased 0.67% by replacing temporal profiles as well. Simulated results of air quality were also slightly elevated by using new input modules. Continuous accumulation of domestic data and studies to develop input system for air quality modeling would produce more improved results of air quality prediction.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.1
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• pp.77-81
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• 2014

Purpose : In the current whole brain Radiation Therapy, Optimold was used to immobilize the head. However, skin dose was increased about 22% due to the scattering radiation by the Optimold. Since the minimum dose causing cataracts was 2 Gy, it could be seen that the effects were large especially on the lens. Therefore, in the whole brain Radiation Therapy, it was to compare and to evaluate the lens absorbed dose according to the presence of Optimold in the eyeball part. Materials and Methods : In order to compare and to evaluate the lens absorbed dose according to the presence of Optimold in the eyeball part, the Optimold mask was made ??up to 5mm bolus on the part of the eye lens in the human model phantom (Anderson Rando Phantom, USA). In the practice treatment, to measure the lens dose, the simulation therapy was processed by placing the GafChromic EBT3 film under bolus, and after the treatment plan was set up through the treatment planning system (Pinnacle, PHILIPS, USA), the treatments were measured repeatedly three times in the same way. After removing the Optimold mask in the eyeball part, it was measured in the same way as above. After scanning the film and measuring the dose by using the Digital Flatbed Scanner (Expression 10000XL, EPSON, USA), the doses were compared and evaluated according to the presence of Optimold mask in the eyeball part. Results : When there was the Optimold mask in the eyeball part, it was measured at $10.2cGy{\pm}1.5$ in the simulation therapy, and at $24.8cGy{\pm}2.7$ in the treatment, and when the Optimold mask was removed in the eye part, it was measured at $12.9cGy{\pm}2.2$ in the simulation therapy, and at $17.6cGy{\pm}1.5$ in the treatment. Conclusion : In case of removing the Optimold mask in the eyeball part, the dose was increased approximately 3 cGy in the simulation therapy and was reduced approximately 7 cGy in the treatment in comparison to the case that the Optimold mask was not removed. During the whole treatment, since the lens absorbed dose was reduced about 27%, the chance to cause cataracts and side effects was considered to be reduced due to decrease of the absorbed dose to the eye lens which had the high sensitivity on the radiation.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.10 no.S_4
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• pp.197-206
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• 2001

The long-range transport mechanisms of Asian dust were analyzed based on the synoptic weather system and numerical simulation by using NCEP/NCAR reanalysis and TOMS data during the periods of 1996-2001. We classified the whole weather types of eastern Asia during spring and created the representative weather types during the yellow sand events using cluster analysis and weather charts for the last 6 years(1996~2001). These long-range transport mechanisms were related to various pressure patterns including high and low, trough and ridge, and upper-level fronts. Case studies of the yellow sand events have performed by the simulation of MM5 with meteorological elements such as the horizontal wind of u and v component, potential temperature, potential vorticity, and vertical circulation during the episodic days(2~8 March 2001). In addition, the origin of the long-range transport was examined with the estimation of backward trajectory using HYSPLIT4 Model. In this paper, we concluded that three weather types at 1000 hPa, 850 hPa, 500 hPa, and 300 hPa levels were classified respectively. The dominant features were the extending continental outflow from China to Korea at 1000 hPa and 850 hPa levels, the deep trough passage and cold advection at 500 hPa and 300 hPa levels during the yellow sand events. And also, we confirmed the existence of pola $r_tropical jets in the upper-level, the behavior of potential vorticity over Korea, the estimation of potential vorticity through vertical cross section, and the transport of yellow sand through backward trajectories.es.

• Journal of Environmental Science International
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• v.19 no.7
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• pp.829-841
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• 2010

The estimation of a biogenic volatile organic compound (BVOC, especially isoprene) and the influence of isoprene emissions on ozone concentrations in the Greater Busan Area (GBA) were carried out based on a numerical modeling approach during a high ozone episode. The BVOC emissions were estimated using a biogenic emission information system (BEIS v3.14) with vegetation data provided by the forest geographical information system (FGIS), land use data provided by the environmental geographical information system (EGIS), and meteorological data simulated by the MM5. Ozone simulation was performed by two sets of simulation scenarios: (1) without (CASE1) and (2) with isoprene emissions (CASE2). The isoprene emission (82 ton $day^{-1}$) in the GBA was estimated to be the most dominant BVOC followed by methanol (56) and carbon monoxide (28). Largest impacts of isoprene emissions on the ozone concentrations (CASE2-CASE1) were predicted to be about 4 ppb in inland locations where a high isoprene was emitted and to be about 2 ppb in the downwind and/or convergence regions of wind due to both the photochemical reaction of ozone precursors (e.g., high isoprene emissions) and meteorological conditions (e.g., local transport).

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.281-281
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• 2017

하천에서 하도불안정(stream instability)으로 인하여 하상의 형태가 변화하고 하상파(sand wave)가 발생한다. 사련(ripple), 사구(dune) 등과 같은 하상파는 흐름저항을 유발하여 홍수시 수위를 증가시킨다. 수리실험 및 수치모형을 이용하여 사련 및 사구의 발달과정 그리고 이를 지나는 난류흐름에 대한 연구가 국외에서는 이루어지고 있지만 국내의 경우 거의 찾아보기 힘들다. 수치모형을 활용한 연구는 주로 횡방향으로 하상파가 일정하다는 가정하에 연직 2차원 수치모형을 적용하였으나 최근 컴퓨터 기술 및 수치기법의 고도화로 3차원 RANS(Reynolds averaged Navier-Stokes) 또는 LES(Large eddy simulation)를 이용한 수치모형이 개발되고 있다. 본 연구에서는 LES에 유사이송 및 하상변동 모형과 결합하여 사구발달에 대한 수치모의를 수행하였다. LES와 유사이송 및 하상변동 모형의 결합은 순간유속성분을 하상변동모형에 직접 적용되기 때문에 난류영향을 고려할 수 있는 것이 장점이다. 특히 사구의 발달에 따라 복잡한 흐름이 발생하며 3차원 와구조가 발생하므로 난류특성의 고려는 필수적이다. 수치모의는 Delft Hydraulics (Bakker et al., 1986)에서 수행한 수리실험 T39를 활용하였다. 수리실험은 길이 100 m, 폭 0.5 m 개수로에서 수행되었으며 평균유속은 0.611 m/s, 수심은 0.436 m이다. 하상파 실험에 사용된 유사입경은 0.78 mm 균일사를 사용하였다. 수치모의 조건은 수리실험과 동일하게 하였으나 계산시간의 효율을 고려하여 흐름방향의 계산영역은 4.0 m로 하고 주기경계조건(periodic boundary condition)을 부여하여 계산을 수행하였다. 수치모의 계산은 사구의 길이 및 파고가 평형상태에 이를 때까지 수행되었다. 수치모의 통해 사구발달에 따른 흐름 및 하상변동 특성을 분석하였다.