• The Korean Journal of Pesticide Science
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• v.21 no.1
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• pp.17-25
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• 2017

Dissipation pattern and biological half-lives of fungicides boscalid and pyraclostrobin were calculated on jujube. The pesticides were sprayed on jujube in two different field at the standard rate, respectively. The raw agricultural commodities were harvested at 0 (2 hr), 1, 3, 5, 7, 10 and 14 days after treatment, and analyzed by HPLC/DAD. The method limit of quantification (MLOQ) was $0.02mg\;kg^{-1}$ for boscalid and pyraclostrobin. The recovery ranged 101.8~109.3% with below 5% of CV (Coefficient of variation) for boscalid and 104.2~115.4% with below 5% of CV for pyraclostrobin. An average initial deposit at field 1 and field 2 samples were observed 0.40 and $0.48mg\;kg^{-1}$ for boscalid and, 0.76 and $0.57mg\;kg^{-1}$ for pyraclostrobin, respectively. The biological half-lives of field 1 and field 2 were 11.0 and 13.2 day for boscalid, and 6.1 and 12.7 days for pyraclostrobin.

• Korean Journal of Environmental Agriculture
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• v.34 no.4
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• pp.328-335
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• 2015

BACKGROUND: The present investigation was aimed to predict the pre-harvest residue limits (PHRLs) of the fluopicolide and metrafenone on cherry tomato and to estimate their half-life and characteristics of the residues.METHODS AND RESULTS: Pesticides were treated once on cherry tomato in field 1 and 2 under the standard application rate. The samples were collected 7 times at the end of 0(2 hours after pesticides spaying), 1, 2, 3, 5, 7 and 10 days before harvest. Residues of fluopicolide and metrafenone were analyzed by the LC-MS/MS. In this study, the method limit of quantification (MLOQ) for both fluopicolide and metrafenone in cherry tomato was found to be 0.005 mg kg-1. Their recovery levels were 92.7∼94.8% and 82.6∼88.0%, shown with coefficient of variation of less than 10%. Half-life of fluopicolide and metrafenone in field 1 and 2 were found to be 15.0 days and 12.8 days, 18.9 days and 21.5 days, respectively.CONCLUSION: Based on the results, this study shows the level of PHRL on cherry tomato is 0.27 mg/kg for fluopicolide and 2.29 mg/kg for metrafenone at 10 days before harvesting. The present study indicates the residues of both pesticides on cherry tomato will be below maximum residue limit (MRL) at harvest.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.220-223
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• 2001

Pb가 10% 과잉되고 Zr : Ti = 52 : 48 조성을 갖는 PZT sol이 Pt(3500Å)/Ti(400Å)/SiO₂(3000Å)Si(525㎛)기판 위에 스핀 코팅법으로 반복 코팅된 후, 450℃에서 10분, 650℃에서 2분간 반복 열처리되었다. 이와 같이 다양한 두께로 적층된 박막은 각 시편에 대해 최종적으로 650℃ 30분 동안 어닐링 처리되었다. 제조된 PZT 박막의 두께는 4100Å에서 1.75㎛사이의 4종이었다. 이어서 스퍼터링법으로 Pt전극이 PZT 막 위에 증착되었다. 제조된 PZT 박막의 결정 구조 조사를 위해 XRD, 그리고 미세 구조 및 전기적 특성을 알아보기 위해 FESEM과 P-E 이력 곡선이 각각 관찰되었다. 4100Å에서 1.75㎛까지 두께 증가에 따른 장비상의 포화 이력 한계로 잔류 분극(Pr)값이 25μC/㎠에서 다소 감소되었다. 측정된 X선 회절 결과에서 최초 4회 코팅시 perovskite 결정 구조로 성장한 결정립은 (111)배향이 우세하었으나, 두께가 증가됨에 따라 (111)/(110)값이 감소되었으며, 이를 통해 두께 증가에 따른 (111)배향성이 다소 감소됨을 알 수 있었다. 이상의 결과로부터 제조된 PZT 박막은 큰 힘과 높은 내전압 특성을 갖는 마이크로 압전 액츄에이터에 적용될 수 있을 것으로 생각되었다.

• Journal of Food Hygiene and Safety
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• v.34 no.1
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• pp.30-39
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• 2019

An analytical method was developed for the determination of sedaxane in agricultural products using liquid chromatograph-tandem mass spectrometry (LC-MS/MS). The samples were extracted with acetonitrile and partitioned with dichloromethane to remove the interference, and then purified by using silica SPE cartridges to clean up. The analytes were quantified and confirmed by using LC-MS/MS in positive ion mode using multiple reaction monitoring (MRM). The matrix-matched calibration curves were linear over the calibration ranges ($0.001-0.25{\mu}g/mL$) into a blank extract with $r^2$>0.99. For validation, recovery tests were carried out at three different concentration levels (LOQ, 10LOQ, and 50LOQ, n=5) with five replicates performed at each level. The recoveries were ranged between 74.5 to 100.8% with relative standard deviations (RSDs) of less than 12.1% for all analytes. All values were consistent with the criteria ranges requested in the Codex guidelines (CAC/GL 40, 2003) and Food Safety Evaluation Department guidelines (2016). The proposed analytical method was accurate, effective and sensitive for sedaxane determination in agricultural commodities.

• Journal of Food Hygiene and Safety
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• v.34 no.2
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• pp.115-123
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• 2019

An analytical method was developed for the determination of fenpropimorph, a morpholine fungicide, in hulled rice, potato, soybean, mandarin and green pepper using QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) sample preparation and LC-MS/MS (liquid chromatography-tandem mass spectrometry). The QuEChERS extraction was performed with acetonitrile followed by addition of anhydrous magnesium sulfate and sodium chloride. After centrifugation, d-SPE (dispersive solid phase extraction) cleanup was conducted using anhydrous magnesium sulfate, primary secondary amine sorbents and graphitized carbon black. The matrix-matched calibration curves were constructed using seven concentration levels, from 0.0025 to 0.25 mg/kg, and their correlation coefficient ($R^2$) of five agricultural products were higher than 0.9899. The limits of detection (LOD) and quantification (LOQ) were 0.001 and 0.0025 mg/kg, respectively, and the limits of quantification for the analytical method were 0.01 mg/kg. Average recoveries spiked at three levels (LOQ, $LOQ{\times}10$, $LOQ{\times}50$, n=5) and were in the range of 90.9~110.5% with associated relative standard deviation values less than 5.7%. As a result of the inter-laboratory validation, the average recoveries between the two laboratories were 88.6~101.4% and the coefficient of variation was also below 15%. All optimized results were satisfied the criteria ranges requested in the Codex guidelines and Food Safety Evaluation Department guidelines. This study could serve as a reference for safety management relative to fenpropimorph residues in imported and domestic agricultural products.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.279-288
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• 2001

암반내에 존재하는 불연속면은 지하구조물의 안정성에 큰 영향을 미친다. 불연속면을 해석하기 위한 구성법칙에 대한 많은 연구가 진행되어 왔으나, 객관적인 거칠기 파라미터를 이용한 전단거동 모사에 관한 연구는 아직 미흡한 실정이다. 본 연구에서는 정량적인 거칠기 파라미터를 이용한 두 가지의 새로운 구성방정식을 만들어 절리 거동을 모사하였다. 첫 번째 구성법칙은 탄소성 이론에 근거하여 두께가 없는 개별절리요소 이용한 방법이고, 두 번째 구성법칙은 3차원 레이저 변위 측정 데이터를 직접 이용하여 Ohnishi가 제안한 거칠기 손상모델을 도입하였다. 제안된 두 모델을 가지고 직접 전단시험을 모사해본 결과 실제 실험에 나타나는 변형률 경화 및 연화현상 그리고 잔류전단강도와 같은 현상을 볼 수 있었다.

• Horticultural Science & Technology
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• v.34 no.4
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• pp.644-654
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• 2016

Supervised residue trials for mandipropamid in Korean cabbage(Brassica campestris L.) were conducted to establish its pre-harvest residue limit (PHRL), a criterion to ensure the safety of the terminal pesticide residue during cabbage production. Tissues of Korean cabbage were collected at 0, 1, 3, 5, 7, and 10 days after mandipropamid application and subjected to residue analysis. The analytical method was validated by recoveries ranging from 88.2-92.2% at two levels (0.4 and $2.0mg{\cdot}kg^{-1}$), and a limit of quantitation (LOQ) of $0.04mg{\cdot}kg^{-1}$. Mandipropamid residues in Korean cabbage gradually decreased over time. The dissipation rate of the residue would be affected by intrinsic degradation of the compound along with dilution resulting from the fast growth of Korean cabbage. The decay pattern was well fitted by simple first-order kinetics. Biological half-lives of mandipropamid in Korean cabbage ranged from 3.9-4.0 days in two field conditions. Calculated by the regression curve of mandipropamid dissipation, the PHRLs of mandipropamid in Korean cabbage were recommended as 11.07-12.19 and $5.76-6.05mg{\cdot}kg^{-1}$ for 10 and 5 days prior to harvest, respectively.

• Restorative Dentistry and Endodontics
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• v.33 no.5
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• pp.457-462
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• 2008

"Residual stress" can be developed during polymerization of the dental composite and it can be remained after this process was completed. The total amount of the force which applied to the composite restoration can be calculated by the sum of external and internal force. For the complete understanding of the restoration failure behavior. these two factors should be considered. In this experiment. I compared the residual stress of the recently developed nanofilled dental composite by ring slitting methods. The composites used in this study can be categorized in two groups. one is microhybrid type-Z250, as control group, and nanofilled type-Grandio, Filtek Supreme. Ceram-X, as experimental ones. Composite ring was made and marked two reference points on the surface. Then measure the change of the distance between these two points before and after ring slitting. From the distance change, average circumferential residual stress $({\sigma}{\theta})$ was calculated. In 10 minutes and 1 hour measurement groups, Filtek Supreme showed higher residual stress than Z250 and Ceram-X. In 24 hour group, Filtek showed higher stress than the other groups. Following the result of this experiment, nanofilled composite showed similar or higher residual stress than Z250, and when comparing the Z250 and Filtek Supreme, which have quite similar matrix components. Filtek Supreme groups showed higher residual stress.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.384-387
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• 2004

강원도 지역 탄산수에 대해 혼합에 의한 용존 희유원소의 거동특성 및 탄산염 침전물 형성에 따른 REE 분별작용을 살펴보았다. 탄산수들은 화학적으로 $Na-HCO_3형,\; Ca-Na-HCO_3형\; 및\; Ca-HCO_3$형으로 구분되며, 동위원소조성도 유형에 따라 명확히 구분되는 특징을 보인다. 지화학 및 동위원소 자료의 해석 결과, $Na-HCO_$형 탄산수는 지하심부에서 심부 기원 $CO_2$의 공급에 의해 형성된 반면, 다른 두 유형의 탄산수들은 $Na-HCO_$ 형 탄산수와 천부지하수 간의 혼합에 의해 생성되었음을 지시하였다. 탄산수 내 용존 REE 함량은 물 유형에 따라 변화하지만, ∑REE 함량은 TDS, pH, alkalinity, $\delta^{18}O$$\delta^{18}O$ 및 tritium 함량과 좋은 상관성을 보여주어, 천부 지하수와의 혼합된 특징을 나타내었다. Na-HCO$_3$형 탄산수의 용존 REE 패턴은 강한 HREE 부화를 보여주어 이른바 'S-shape'을 나타내는 반면, $Na-HCO_$ 형은 분산되어 있으며 LREE 부화를 보여주었다. $Ca-Na-HCO_3$형은 약한 HREE 분화 패턴을 보여주었다. 탄산수로부터 침전된 침전물과 침전물을 제거한 잔류물의 REE 패턴은 원 탄산수와 거의 유사한 형태를 보여주어, 탄산염 침전물과 잔류물 간의 REE 분별작용은 일어나지 않았음을 나타낸다.지 않았음을 나타낸다.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.136-136
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• 1999

박막의 탄성특성을 평가하는 방법으로 nano-indentation, Brillouin light scattering measurement, ultrasonic surface wave measurement, bulge test, vibration membrane method 등 여러 가지가 제시되어 왔다. 최근에는 탄성특성을 평가할 수 있는 간단한 방법으로 기판 식각 기법을 이용한 freehang, bridge 방법이 제시되었다. 이중에서 bridge 방법은 간단한 식각 기법을 이용하여 얇은 박막에서도 탄성 특성을 평가할 수 있는 방법으로 제시되었다. 그러나 식각 과정에서 발생하는 patch 부분의 under-cut으로 인해 정확한 bridge의 길이를 측정할 수 없게 되어 오차가 발생하고 있다. 본 연구에서는 bridge 방법에서 발생하는 오차를 줄이기 위한 방법으로, patch 부분에 etch-stop을 제작해 줌으로서 식각 과정에서 발생하는 under-cut을 효과적으로 제거시켰다. Etch-stop은 2장의 mask를 align key를 이용하여 제작하였다. 먼저 산화막이 형성되어 있는 Si 기판위에 mask 1을 이용하여 patch 부분을 lithography 작업하고, 습식 식각 공정을 한 뒤 DLC 필름을 증착시킨다. 다음으로 mask 2를 이용하여 bridge pattern을 제작하고, DLC 필름을 증착시킨 후 lift-off 기술과 산화막 등방식각 공정을 통해 bridge를 제작하였다. 이렇게 제작된 bridge를 통해 필름이 기판에 부착되기 위해 필요한 변형률을 측정하고, 독립적으로 측정된 필름의 잔류응력과 함께 박막의 응력-변형률 관계식에 적용시켜 biaxial elastic modulus, E/(1-v)를 구할 수 있었다. Sidl 첨가된 DLC 필름은 rf-PACVD 장비를 이용하여 증착하였다. 이때 전극과 플라즈마 사이의 바이어스 음전압은 -400V로 합성압력은 10mTorr로 고정하였다. 사용한 반응가스는 벤젠(C6H6)과 희석된 실렌(SiH4:2H=10:90)이며, 희석된 실렌의 첨가량을 조절하여 필름 내에 함유된 Si의 양을 조절하였다. 각각의 조건에서 증착시간을 조절하여 필름의 두께를 조절하였다. 필름의 잔류응력은 압축잔류 응력에 의해 발생한 필름/기판 복합체의 곡률을 laser 반사법을 이용하여 측정하고, 이 결과를 Brenner 등에 의해 유도된 식을 대입하여 계산하였다.