• 한국환경농학회지
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• 제36권3호
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• pp.184-192
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• 2017

BACKGROUND: This study was performed to evaluate the residue dissipation of boscalid and spinetoram on crown daisy and sweet pepper affected by the morphology of the crop. The half-lives and dissipation rate constants for boscalid and spinetoram on crown daisy and sweet pepper were calculated. And then lower limit of 95% confidence interval for dissipation rate constant could be used to propose the pre-harvest residue limit. METHODS AND RESULTS: The pesticide products diluted according to the pesticide label were applied one time on crown daisy and sweet pepper at 2 field sites, respectively. Initial concentration of boscalid and spinetoram on crown daisy after application were in the range of 72.80~117.15 mg/kg and 2.82~4.67 mg/kg, respectively. And Initial concentration of boscalid and spinetoram on sweet pepper were in the range of 1.58~1.62 mg/kg and 0.10~0.21 mg/kg, respectively. Boscalid and spinetoram for crown daisy dissipted below the maximum residue limit(MRL) at 10 and 2 days after application, respectively. All residues concentration of boscalid and spinetoram for sweet pepper below the MRL at 0 day after application. The half-lives based on dissipation rate constant for boscalid and spinetoram on crown daisy were 4.2~4.9 days and 3.0~2.4 days respectively. And the half-lives for boscalid and spinetoram on sweet pepper were 6.7~7.0 days and 2.8~4.0 days respectively. CONCLUSION: The difference in initial concentration of boscalid and spinetoram among crop commodities were due to different crop morphology with larger surface areas. This study was suggested that pre-harvest residue limit would be calculated from lower limit of 95% confidence interval for dissipation rate constant and would be useful to protect consumers by controlling the pesticide residues in crop.

• 한국환경농학회지
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• 제37권2호
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• pp.97-103
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• 2018

BACKGROUND: Dissipation of acetamiprid and thiamethoxam in greenhouse grown chard samples was evaluated at 5 intervals including the pre-harvest interval after application. This study was conducted to determine the residue levels, the biological half-lives and dissipation rate of acetamiprid and thiamethoxam in chard under controlled conditions. METHODS AND RESULTS: Acetamiprid and thiamethoxam were applied in accordance with good agricultural practices for chard. Chard samples were collected at 0, 1, 2, 3, 5, 7, 10 and 14 days after application. Quantitaion was performed by HPLC-DAD system with C18 column. Limit of quantification (LOQ) of acetamiprid and thiamethoxam were both 0.02 mg/kg for chard. The recovery of acetamiprid and thiamethoxam were 77.8~107.5% and 94.3~108.6% at two concentration levels. The half-lives of pesticide dissipation in chard for two fields were 11.9 and 8.2 days for acetamiprid and 3.6 and 3.3 days for thiamethoxam respectively. The dissipation rate of acetamiprid and thiamethoxam were estimated according to the statistics method with a 95% confidence. CONCLUSION: Dissipation of acetamiprid and thiamethoxam in chard were determined under greenhouse. The concentration of acetamiprid and thiamethoxam in chards at 0 days after application were below specified by Korean MRL. Dissipation rate constant will be useful to set the pre-harvest residue limit for public health and consumer protection.

• Journal of Applied Biological Chemistry
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• 제63권3호
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• pp.267-274
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• 2020

상추 중 살균제 mandipropamid 및 살충제 thiamethoxam의 생산단계 잔류허용기준(PHRLs)를 추정하기 위해 3곳의 상추 시설재배지에서 두 약제의 경시적 잔류량 감소특성을 조사하였다. 상추 중 농약 잔류량은 HPLC-PDA 또는 UVD를 이용하여 분석하였으며 우수한 회수율 및 변이값을 보여 분석의 유효성을 확보하였다. 농약안전사용기준에 따라 약제살포 권고량을 살포한 후 살포 후 수확일(PHI)을 포함한 10일 동안 출하시기에 적합한 개체를 채취하여 잔류량을 분석하였다. 포장별 초기 평균 잔류량은 mandipropamid 6.68-17.87 mg/kg, thiamethoxam 4.96-8.31 mg/kg이었고 10일 경과 후 각각 초기잔류량의 16-54 및 14-44% 수준으로 감소하였다. Thiamethoxam의 대사산물인 clothianidin은 <0.02-0.37 mg/kg으로 검출되었다. 상추 중 두 약제의 잔류량은 단순 1차 감쇄반응처럼 감소하였으며 포장구분없이 일자별 잔류량 회귀식을 산출한 결과, 평균 감소상수 및 생물학적 반감기는 mandipropamid의 경우 -0.1060 및 6.5일이었고 thiamethoxam은 -0.1236 및 5.6일이었다. 상추 잔류량 감소상수의 95% 신뢰구간 상한치는 mandipropamid -0.0746 및 thiamethoxam -0.1091이었으며, 출하 10일 및 5일 전 PHRLs은 mandipropamid의 경우 63.24 및 43.56 mg/kg, thiamethoxam은 44.66 및 25.88 mg/kg으로 산출되었다. 본 연구결과는 농가에서 농작물 출하시기를 조절하는데 활용될 수 있으며 농가의 소득 안정화에 기여할 것으로 판단된다.

• 한국초전도ㆍ저온공학회논문지
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• 제3권1호
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• pp.35-39
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• 2001

The optimum cross-sectional area profile of gas-cooled high-temperature superconductor(HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant satiety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-stacking HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-stacking current leads are discussed.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.84-88
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• 2001

The optimum cross-sectional area Profile of gas-cooled high-temperature superconductor (HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant safety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-step HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-step current leads are discussed.

• 한국연소학회지
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• 제8권3호
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• pp.15-23
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• 2003

Partial quenching structure of turbulent diffusion flames in a turbulent mixing layer is investigated by the method of flame hole dynamics in order to develop a prediction model for turbulent flame lift off. The essence of flame hole dynamics is derivation of the random walk mapping, from the flame-edge theory, which governs expansion or contraction of flame holes initially created by local quenching events. The numerical simulation for flame hole dynamics is carried out in two stages. First, a direct numerical simulation is performed for constant-density fuel-air channel mixing layer to obtain the turbulent flow and mixing fields, from which a time series of two dimensional scalar dissipation rate array is extracted at a fixed virtual flame surface horizontally extending from the end of split plate to the downstream. Then, the Lagrangian simulation of the flame hole random walk mapping projected to the scalar dissipation rate array yields temporally evolving turbulent extinction process and its statistics on partial quenching characteristics. The statistical results exhibit that the chance of partial quenching is strongly influenced by the crossover scalar dissipation rate while almost unaffected by the iteration number of the mapping that can be regarded as a flame-edge speed.

• 한국가스학회지
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• 제13권3호
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• pp.33-42
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• 2009

부상화염에 대한 연소반응 유동 수치해석을 수행하여 부상높이에 대한 기존 연구 결과들과 비교를 통하여 수치해석 결과의 신뢰성을 검정하였다. 화염전파속도를 결정하는 유동방향변환점을 기존의 연구에서처럼 연료분출속도에 상관없이 일률적인 위치로 선정할 경우 많은 오차를 유발하기 때문에 본 연구에서는 부상화염에서 이론당량비선을 따라 유동속도와 스칼라 소산율 특성을 살펴보았고 화염전파속도를 선정하는 유동방향변환점을 타당하게 선정하는 방법을 정립하였다. 이를 토대로 화염전파속도와 스칼라소산율의 관계식을 도출하여 부상화염에서 화염전파속도 특성을 규명하였다.

• 오토저널
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• 제3권2호
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• pp.34-42
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• 1981

The feasibility of using fluidic components for improving certain performance characteristics of the suspension systems for tracked vehicle is investigated. This study describes three variable damping systems for which the damping coefficients are function of relative velocity and absolute a of the vehicle body. Through the comparison analysis between constant damping coefficient damper and each of variable dampers. the followings were found: (1)Fluidic Diode Damper gave less accelerations, (2)Both Fluidic Diode Damper and Relative Velocity Damper gave the less time for which the wheel is off the ground, (3) At low vehicle velocity Fluidic Diode Damper gave low energy dissipation rate, while at high vehicle velocity Turbulence Accelerometer Damper gave low energy dissipation rate.

• 한국연소학회지
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• 제20권3호
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• pp.35-42
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• 2015

Investigating coal combustion in a large-scale boiler using computational fluid dynamics (CFD) requires a combination of flow and reaction models. These models include a number of rate constants which are often difficult to determine or validate for particular coals or furnaces. Nonetheless, CFD plays an important role in developing new combustion technologies and improving the operation. In this study, the model selection and rate constants for coal devolatilization, char conversion, and turbulent reaction were evaluated for a commercial wall-firing boiler. The influence of devolatilization and char reaction models was found not significant on the overall temperature distribution and heat transfer rate. However, the difference in the flame shapes near the burners were noticeable. Compared to the coal conversion models, the rate constant used for the eddy dissipation rate of gaseous reactions had a larger influence on the temperature and heat transfer rate. Based on the operation data, a value for the rate constant was recommended.

• 한국환경농학회지
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• 제39권2호
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• pp.122-129
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• 2020

BACKGROUND: Dissipation patterns of insecticides (acequinocyl, clothianidin, diflubenzuron, thiacloprid, and thiamethoxam) on strawberry grown in plastic-covered greenhouse were evaluated at 7 intervals including the preharvest interval after application. This study was performed to determine the residue concentrations, half-lives and dissipation rates in strawberry for the harvest periods. METHODS AND RESULTS: Acequinocyl, clothianidin, diflubenzuron, thiacloprid, and thiamethoxam were applied in accordance with critical good agricultural practices for strawberry. Strawberry samples were collected at 0, 1, 2, 3, 5, 7 and 10 days after application. Quantitaion was performed by HPLC/DAD and HPLC-MSMS system with C₁₈ column. The limit of quantitation (LOQ) values varied between were 0.00025~0.05 mg/kg on strawberry. The recoveries of acequinocyl, clothianidin, diflubenzuron, thiacloprid and thiamethoxam at two concentrations ranged from 70.9~104.9% on strawberry. The half-lives of pesticide dissipation on strawberry for two fields ranged from 1.3~8.2 days. The dissipation rates were evaluated according to the statistics method with a 95% confidence. CONCLUSION: The residue levels of insecticides (acequinocyl, clothianidin, diflubenzuron, thiacloprid, and thiamethoxam) on strawberry at 0-day after application were below the specified values by Korean MRL. To estimate dissipation rate constant of pesticides on crop for harvest periods, it is important to set the pre-harvest residue limit for human health and consumer protection in Korea.