• 한국환경농학회지
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• 제27권1호
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• pp.10-17
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• 2008

The objective of this study was to estimate the pollutant loads from paddy fields by cultivation practices using a non-point-sources models. One of them is CREAMS-PADDY model that was developed considering the water balance and mass balance of paddy fields. The CREAMS-PADDY model was applied to provide basic data to reduce runoff loadings under various scenarios such as various water management control and various fertilizer condition. The model was verified against T-N, T-P and runoff flow data collected during cropping periods at 2000. The model results agreed well with the measured data in verification. The results showed that the model could be used for estimating the runoff loadings from irrigated paddy fields by cultivation practices was possible. Comparison of simulated the standard height and the sluice management of T-N and T-P runoff loadings from paddy fields were +32.4%, +10.3% in 10 mm below the standard height, -29.2%, -35.9% in 20 mm above the standard height, 52.6%, 59.0% in 40 mm above the standard height, respectively. Comparison of simulated the standard fertilizer and the fertilizer control of T-N and T-P runoff loadings from paddy fields were -1.3%, -21.7%in reduction of conventional fertilizer 30%, -1.0%, -12.5% in reduction of standard fertilizer 30%, respectively. Therefore, reducing nonpoint-sources nutrient loading by reducing fertilization may not work well in the range of normal paddy rice farming practices, and instead it could be achieved by reducing surface drainage outflow.

• Journal of Biosystems Engineering
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• 제41권4호
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• pp.342-356
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• 2016

Purpose: The drying of a thin layer of native cassava starch in a tray dryer was modeled to establish an equation for predicting the drying behavior under given conditions. Methods: Drying tests were performed using samples of native cassava starch over a temperature range of $40-60^{\circ}C$. We investigated the variation in the drying time, dynamic equilibrium moisture content, drying rate period, critical moisture content, and effective diffusivity of the starch with temperature. The starch diffusion coefficient and drying activation energy were determined. A modification of the model developed by Hii et al. was devised and tested alongside fourteen other models. Results: For starch with an initial moisture content of 82% (db), the drying time and dynamic equilibrium moisture content decreased as the temperature increased. The constant drying rate phase preceded the falling rate phase between $40-55^{\circ}C$. Drying at $60^{\circ}C$ occurred only in the falling rate phase. The critical moisture content was observed in the $40-55^{\circ}C$ range and increased with the temperature. The effective diffusivity of the starch increased as the drying temperature increased from 40 to $60^{\circ}C$. The modified Hii et al. model produced randomized residual plots, the highest $R^2$, and the lowest standard error of estimates. Conclusions: Drying time decreased linearly with an increase in the temperature, while the decrease in the moisture content was linear between $40-55^{\circ}C$. The constant drying rate phase occurred without any period of induction over a temperature range of $40-55^{\circ}C$ prior to the falling rate period, while drying at $60^{\circ}C$ took place only in the falling rate phase. The effective diffusivity had an Arrhenius relationship with the temperature. The modified Hii et al. model proved to be optimum for predicting the drying behavior of the starch in the tray dryer.

• 한국환경농학회지
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• 제40권2호
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• pp.127-133
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• 2021

BACKGROUND: Dithiocarbamte fungicides have been used in crop cultivation for diseases protection and treatment. And cultivated agricultrual products were used as feedstuff, and residual pesticides are likely to be absorbed and transferred to livestock. But the maximum residue limits (MRLs) were not established for dithiocarbate fungicides in livestock products, and thus an analysis method was developed and validated for dithiocarbamate fungicides to establish MRLs. METHODS AND RESULTS: Samples were prepared using CS₂ trap method and detected with UV/VIS spectrophotometer. Calibration line (0.1 ~ 10 ㎍/mL) was linear with r² > 0.99. For validation, the recovery tests were carried out at three fortification levels (MLOQ, 10 MLOQ and 50 MLOQ) from livestock samples (egg, milk, beef, pork, and chicken). The results for mancozeb, propineb, and thiram ranged between 76.8 to 109.6%, 79.4 to 108.8%, and 80.2 to 107.8%, respectively and % RSD (relative standard deviation) values were below 9.5%. Furthermore, inter-laboratory analysis was performed to validate the method. CONCLUSION: All values were corresponded with the criteria ranges requested by both the CODEX (CAC/GL 40-1993, 2003) and MFDS guidelines (2016). This might be used as an official analytical method for determination of dithiocarbamate fungicides at established MRLs and monitoring.

• 한국구조물진단유지관리공학회 논문집
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• 제23권2호
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• pp.20-27
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• 2019

건전자제품의 개발과 생산기술에 비교하여 폐유리의 재활용을 위한 기술개발은 상대적으로 미흡하여 자원낭비와 환경오염이 가속화되고 있다. 해외에서는 이 분야에 대한 기술개발이 활발하게 이루어지고 있으나 국내의 경우, 그 관심도가 부족하여 폐유리를 불법투기 또는 매립으로 처리하고 있는 실정이다. 폐유리는 시멘트와 수화반응시 포졸란 반응가능성이 있는 것으로 확인되어 경화 콘크리트의 물리적 성질을 향상시키고 굳지 않은 콘크리트의 레올로지 특성을 개선하여 블리딩의 저감 및 수화열 발생의 억제 등에 효과적인 것으로 보고되고 있다. 따라서 본 논문에서는 폐유리를 잔골재로 사용한 차폐콘크리트의 알칼리-실리카반응이 팽창에 미치는 영향을 분석하고 폐유리 혼입에 의한 알칼리-실리카반응의 팽창을 억제하기 위한 방안으로 적정 혼화재료를 사용하여 차폐콘크리트의 내구성능을 평가하였다.

• 한국산림과학회지
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• 제109권4호
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• pp.438-445
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• 2020

본 연구는 산림소유역에 시공되어 있는 사방댐내의 토사유출량에 영향을 미치는 산림환경 인자를 분석하고 수량 화이론(I)를 이용하여 예방적인 측면에서 사방댐 시공적지를 선정하고 예측하였다. 각 산림환경 인자의 범위를 추정한 결과, 준설경과년수(0.7495)가 가장 높게 나타나 산림소유역 토사유출량에 큰 영향을 미치는 것으로 추정되었으며, 다음으로는 경급(0.6000), 소밀도(0.5318), 유역면적(0.3416), 사면경사(0.3207), 강수량(0.3160), 고도(0.2990), 토양형(0.2192)순으로 나타났다. 각 인자의 범주별 상대점수를 74개 사방댐의 각종 인자에 반응시켜 사방댐의 시공적지를 예측할 수 있는 판정표를 개발하였고, 판정표를 이용하여 시공적지를 I급지(Very suitable site) 2.2496 이상, II급지(Suitable site) 1.1248~2.2495, III급지(Poor suitable site) 1.1247 이하로 구분하였다.

• Geomechanics and Engineering
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• 제28권5호
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• pp.437-454
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• 2022

The hydro-mechanical (HM) two-way sequential coupling in the TOUGH2-FLAC3D linking algorithm is validated completely and successfully in both M to H and H to M directions, which are initiated by mechanical surface loading for geomechanical validation and hydrological groundwater pumping for hydrogeological validation, respectively. For such complete and successful validation, a TOUGH2-FLAC3D linked numerical model is developed first by adopting the TOUGH2-FLAC3D linking algorithm, which uses the two-way (fixed-stress split) sequential coupling scheme and the implicit backward time stepping method. Two geomechanical and two hydrogeological validation problems are then simulated using the linked numerical model together with basic validation strategies and prerequisites. The second geomechanical and second hydrogeological validation problems are also associated with the Mandel effect and the Noordbergum and Rhade effects, respectively, which are three phenomenally well-known but numerically challenging HM effects. Finally, sequentially coupled numerical solutions are compared with either analytical solutions (verification) or fully coupled numerical solutions (benchmarking). In all the four validation problems, they show almost perfect to extremely or very good agreement. In addition, the second geomechanical validation problem clearly displays the Mandel effect and suggests a proper or minimum geometrical ratio of the height to the width for the rectangular domain to maximize agreement between the numerical and analytical solutions. In the meantime, the second hydrogeological validation problem clearly displays the Noordbergum and Rhade effects and implies that the HM two-way sequential coupling scheme used in the linked numerical model is as rigorous as the HM two-way full coupling scheme used in a fully coupled numerical model.

• 한국환경농학회지
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• 제41권3호
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• pp.177-184
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• 2022

BACKGROUND: Recently, the inflow of nonpoint pollutants into rivers caused by rapid urban and industrialization promotes the proliferation of algae, which causes eutrophication of rivers. This study was conducted to evaluate the seasonal variation of water quality characteristics and cryptomonads growth in the Oncheon River. METHODS AND RESULTS: The water quality and distribution characteristics of cryptomonads in the Oncheon River were investigated monthly for 12 months from January 2021. The cell number of cryptomonads was intensively developed in January-April, and it decreased sharply in the summer with heavy rainfall. In particular, cryptomonads moved to the downstream side of the river depending on the time, and as a result, significant differences were shown for each investigation point. The Korean trophic state index (Tsi_KO) in Oncheon River was classified as eutrophy all year round, indicating that cryptomonads can grow year-round. Distribution characteristics of cryptomonads in Oncheon River showed high correlations with DO (r=0.678), BOD (r=0.826) and chlorophyll-a (r=0.613) in water. CONCLUSION(S): In order to reduce cryptomonads in the Oncheon River, it is judged that a complex countermeasure considering the residence time, insolation and precipitation along with water quality factors is required.

• 한국농공학회논문집
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• 제65권3호
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• pp.57-67
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• 2023

A flash drought is a rapid-onset drought that develops over a short period of time as weather and environmental factors change rapidly, unlike general droughts, due to meteorological abnormalities. Abnormally high evapotranspiration rates and rapid declines in soil moisture increase vegetation stress. In addition, crop yields may decrease due to flash droughts during crop growth and may damage agricultural and economic ecosystems. In this study, Flash Drought Intensity Index (FDII) based on soil moisture data from Gravity Recovery Climate Experiment (GRACE) was used to analyze flash drought. FDII, which is calculated using soil moisture percentile, is expressed by multiplying two factors: the rate of intensification and the drought severity. FDII was developed for domestic flash drought events from 2014 to 2018. The flash drought that occurred in 2018, Chungcheongbuk-do showed the highest FDII. FDII was higher in heat wave flash drought than in precipitation deficit flash drought. The results of this study show that FDII is reliable flash drought analysis tool and can be applied to quantitatively analyze the characteristics of flash drought in South Korea.

• 대한토목학회논문집
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• 제26권1B호
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• pp.1-6
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• 2006

낙동강, 섬진강, 영산강, 그리고 금강 권역의 충적 대수층에서 해안선을 통하여 바다로 유출되는 지하수 해안유출량이 평가되었다. 증반산, 하천 유출과 같은 수문학적 주요 인자와 양적으로 비교하면 지하수 해안유출량은 상대적으로 많은 양이 아니다. 하지만 수문순환 과정에서 최하류라는 특징에 의하여 지하수 해안 유출의 개발은 환경적인 영향을 상대적으로 적게 받으며, 현재 물 부족으로 어려움을 겪고 있는 많은 해안지역에서 유용하게 사용될 수 있는 중요한 수자원이다. 유출량 평가를 위하여 기 조사된 지하수위 조사 자료와 Darcy의 법칙에 기반을 둔 평가방법을 이용하였다. 주요 변수의 산정에는 해안선의 복잡성과 해수쐐기의 영향을 고려할 수 있는 기술을 적용하였다. 연구결과 조사 대상 4개 하천 권역의 지하수 해안 유출량은 연간 18억$m^3$에 달하는 것으로 나타났다. 이는 권역별 강수총량의 2.3%에 이르는 수치이다. 지하수 개발 측면에서 는 낙동강 권역이 가장 유리한 것으로 나타났다.

• 산업경영시스템학회지
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• 제46권spc호
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• pp.31-38
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• 2023

In this study, in order to develop a method to efficiently inject essential nutrients necessary for plant growth into wood chips, which are simply used as soil covering materials in the agriculture, landscaping and horticultural industries, the atmospheric pressure dipping method and the vacuum pressure impregnating method are used to improve the plant nutrients injectability and impregnation amount were comparatively analyzed. Nutrient ingredients and 8 major heavy metal contents of wood chips injected with nutrients were analyzed, and soil covering effects were examined by covering wood chips injected with nutrients on soil. Comparing the dipping method and the vacuum pressure impregnation method, it took about 48 hours or more to inject 1,500 g or more of the nutrient aqueous solution into 1 kg of wood chips in the dipping method, but the vacuum pressure impregnation method could be impregnated in about 5 minutes. Components of the impregnated nutrients were detected in proportion to the diluted concentration. As a result of covering the wood chips developed in this study on soil, they showed weakly acidic pH, and the heat insulation and moisturizing effects during the winter season were evaluated to be superior to those of uncovered soil. In the future, wood chips impregnated with nutrients are expected to contribute to the more efficient use of waste wood resources and the long-term supply of nutrients essential for plant growth, reducing excessive use of chemical fertilizers and reducing costs.