• Journal of the Korean Vacuum Society
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• v.16 no.2
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• pp.91-98
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• 2007

The Korea Research Institute of Standards and Science (KRISS) has developed a residual gas analyzer (RGA) calibration system and measured gas sensitivities for two different types QMSs using nitrogen, argon, and helium. Different gas sensitivities were identified according to mass and pressure, so it was revealed that the gas sensitivity correction is necessary for proper use of mass spectrometers.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.12-19
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• 1994

The crystallization behavior of the amorphous $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_{6}$ alloy with isothermal annealing at $552^{\circ}C$ was studied by $M\"{o}ssbauer$ spectroscopy. The amorphous phase was revealed to coexist together with $Do_{3}-FeSi$ nanocrystalline and Cu-duster in annealed alloys by $M\"{o}ssbauer$ spectrum analysis. At the early stage of crystallization, Si content of FeSi is high due to the creation of Cu-cluster, and decreases with annealing until 60 minutes, which results in the increase in the mean hyperfine field of FeSi, and thereafter keeps constant. After 60 minutes, the decrease in the mean hyperfine field of the residual armrphous, in spite of a slight change in the volume fraction of the FeSi and the residual armrphous, is caused by the increase in the content of Nb and B in residual amorphous phase. Both directions of the hyperfine field, those of the FeSi and the residual amorphous, become randomly oriented in about 60 minutes. For FeSi and Cu-duster, the Avrami exponents are 0.51 and O.65, the activation energies are 2.35 eV and 2.44 eV, and the incubation times are 2.4 minutes and 0.8 minutes respectively. Earlier formation of Cu-duster than that of FeSi is coincidence with the fact that Cu atom promotes the nucleation of the FeSi.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.11
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• pp.1515-1522
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• 2008

Monitoring the pesticide residues in agricultural products is essential to protect consumers, obtain data for risk assessment, and ensure fair trade practices. We developed a multi-residue method for the analysis of 37 pesticides with different physico-chemical properties in agricultural products and analyzed the amount of pesticide residues on about 1,000 samples circulated in South Korea. The samples consisted of 26 different types of agricultural products selected at markets in 14 major cities; cereals (2 species), nuts (1 species) potatoes (1 species), beans (2 species), fruits (3 species), vegetables (16 species), and mushrooms (1 species). In this study, residual pesticides were detected in 23 samples (2.2%) and one sample was detected to be over maximum residue limits (MRLs, 0.1%) for pesticides in foods by the Korea food code. In leafy vegetables such as pepper leaves, radish leaves, cham-na-mul, shin-sun-cho, crown daisy, chwi-na-mul and citrus fruits such as kumquat, 8 kinds of pesticides were detected. Specially, diazinon were detected over MRLs and also, endosulfan, ethoprophos and phenthoate were detected frequently. Based on these results, we investigated the risk assesment from amount of residual pesticide, total %ADI was 1.262%, but the value has not effected on human health.

• Korean Journal of Environmental Agriculture
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• v.29 no.4
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• pp.388-395
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• 2010

In order to decrease level of an organophosphorus fungicide, tolclofos-methyl, from in situ ginseng cultivating soil, we isolated a tolclofos-methyl degrading bacteria from ginseng cultivating soil samples. The bacterial strain removed tolclofos-methyl around 95% after 3 days incubation with complete liquid media. The strain was identified as Sphingomonas sp. by 16S rDNA sequence comparison, and designated as Sphingomonas sp. 224. Through the GC-MS analysis, Sphingomonas sp. 224 was proposed to have an initiative degradation pathway generating the metabolite such as 2,6-dichloro-4-methyl phenol compound from tolclofos-methyl. In addition, Sphingomonas sp. 224 was confirmed representing the effective degrading capability to tolclofosmethyl in situ soil.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2005.10a
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• pp.310-316
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• 2005

축산식품(우유)내의 잔류항생물질을 신속하고 간편하고 정확하게 분석하기 위한 시험법 개발을 목적으로 하였다. 축산식품내의 일반적인 잔류항생물질에 대한 지금까지의 분석법으로는 Bioassay법, TLC법, ELISA법, GC법 및 HPLC법 등이 있지만 Streptomycin/dihydrostreptomycin, neomycin에 대한 HPLC법은 거의 확립되어 있지 않은 실정이다. 우리나라의 공인 검사법으로는 Bioassay법 및 HPLC법등이 있지만 그러나 지금까지의 방법으로는 검출감도가 낮은 것이 큰 문제점으로 되어 왔다. 본 연구에서는 STP에 대한 HPLC법에 대한 보고한 Edder 방법 중에 clean-up 과정 및 이동상 조건을 대폭 수정하여 STP의 분리 및 검출감도를 낮추려고 시도하였다. 본 연구에 사용된 유도체화 장치 Post-Column Derivatization Instrument PCX 5100 (Pickering La-boratories, Inc.)의 컬럼 온도는 $40^{\circ}C$, 오븐온도 $55^{\circ}C$, 유도체화 용매 유속 0.6ml/min 이동상 유속 0.8ml/min으로 검출기는 형광검출기를 이용하여 STP 검출에 대해 만족할 만한 결과를 얻었다. 이때의 분석소요시간은 약 15분이었다. 표준시료 STP의 검량선은 넓은 농도범위(0.02${\sim}$1.0ppm)에서 양호한 직선성을 나타냈다. 본 시험법에 의한 검출한계는 limit of detection(LOD)은 0.02ppm이었으며, 적어도 우유에서의 MRL이 0.6ppm임을 감안하면 STP를 정량적으로 정도 좋게 측정할 수 있다는 것을 확인했다. 상기의 조건하에서 실제시료인 우유에 표준 STP를 0.5ppm을 spiking한 후 SPE상에서 SCX(Strong cation exchange column)을 통한 clean-up과정을 거친 후의 STP의 limit of quantification(LOQ)는 약 0.44ppm이었으며, 이에 대한 회수율은 89.7${\pm}$2.3%(n=6)를 나타냈다. 실제 CODEX에서 권장한 우유의 MRL이 0.6ppm인 점을 감안하면 CODEX권고치에 도달할 수 있는 것으로 판단되었다. 따라서 본 연구에서 개발 된 시험법은 지금까지 국내적으로 STP에 대한 시험법이 확립되어 있지 않은 것으로 이와 아울러 간편한 parallux와 병용해 STP에 대한 정량 및 정성 분석을 유도체화 장치 및 형광검출기를 이용해 잔류항생물질 STP에 대한 분석시험법을 개발하였다.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.248-251
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• 2018

Catalytic pyrolysis of the waste paper cup containing coffee residual (WPCCCR) was performed using a fixed bed reactor and pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS). Non-catalytic pyrolysis of WPCCCR produced a large amount of oil together with gas and char. The use of both HZSM-5 and HY decreased the yields of oil and increased the yield of gas due to the additional catalytic cracking. Owing to the acidic catalytic properties of HZSM-5 and HY, catalytic Py-GC/MS analysis of WPCCCR increased the selectivity to aromatic hydrocarbons in product oil. Owing to properties of HZSM-5 having a stronger acidity and medium pore size, the catalytic pyrolysis of WPCCR over HZSM-5 produced much larger amounts of aromatic hydrocarbons than that of using HY.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.282-287
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• 2023

The effect of stress relief heat treatment temperature and duration time on the microstructure, residual stress and Vickers hardness of additively manufactured Ti-6Al-4V alloy using laser powder bed fusion process was clarified. As a result of stress relief heat treatment for 240 minutes at 823 K and 60 minutes or more at 873 K, residual stress was decreased less than 30 MPa without grain growth and phase transformation which causes dimensional distortion and deterioration of mechanical properties. In addition, hardness was increased with increasing heat treatment temperature and duration time. It was deduced that the refinement of acicular martensitic α' phase due to the increasing duration time of isothermal heat treatment at 773~873 K, which was not detected by XRD and phase map analysis using SEM-EBSD, probably increases the hardness.

• Korean journal of applied entomology
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• v.16 no.4 s.33
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• pp.221-227
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• 1977

Polychlorinated Biphenyls (PCBs) interfere with gas chromatographic analysis of multiple organochlorine pesticide residues. In the present work, existing Florisil column chromatographic method has been modified as to improve separation of organochlorine pesticides and their metabolites from PCBs. It was amply demonstrated that separation of $\alpha-BHC,\; \gamma-BHC$ Heptachlor epoxide Dieldrin, p.p-DDD, p.p'-DDT from PCBs such as Aroclor 1254 is complete and recovery of the pesticides is found quantitative. Aldrin and Heptachlor in the Aroclor eluant can be separately analyzed by comparison of the chromatographic pattern of standard Aroclor 1254 with that of Aroclor 1254 a dmixed with the two pesticides. The Florsil column technique can be utilized in the routine evaluation of the organochlorine pesticide residues by gas chromatography.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.175-181
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• 2000

월성원자력4호기가 '99.06.09일 11:53분 경 전출력 소외전원상실시험시 주발전기 병입차단기 및 기동용변압기 차단기의 트립과 동시에 예상 밖의 13.8Kv 원자로 냉각재펌프모터#3(9.000HP)이 순시과전류 보호계전기(50Y) 동작으로 트립되어 이로 인한 냉각재 저유량으로 원자로 제1정지계통이 동작되고 원자로가 비상정지 되어 동 시험이 실패되었음. 이 비정상적인 고장은 예비디젤발전기의 수동 기동 병입과 터빈 수동 정지 및 주발전기 트립후 적절한 조치로 소내전원은 정상적으로 복구되었음. 이에 대해 냉각재펌프모터#3의 순시과전류 동작 원인을 유도전동기의 전원상실 후 발생되는 잔류전압(Residual Voltage)과 공급 모선전압(Bus Voltage) 측면에서 분석하며, 모터의 회전속도, 위상각, 잔류전압크기 변화 및 신속개방 절체시 냉각재펌프모터의 돌입 기동전류를 계산하고, PSS/E 프로그램을 사용한 간략한 모의 사례로 검증하였으며 이에 대한 재발방지를 위한 대책을 제시함.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.864-873
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• 1995

Amorphous $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_{6}$ ribbons were annealed for different time at $500^{\circ}C$ and $552^{\circ}C$, just before and after the exothermic reaction in DSC curve. The development of nanocrystalline phase was investigated by means of $M\"{o}ssbsuer$ spectroscopy. The crystalline phase consists mainly of $DO_{3}Fe-Si$. Though slight in amount (5%), another ferromagnetic phase which could be presumed $t-Fe_{3}B$ was detected Si content of $DO_{3}Fe-Si$, Si/(Fe+Si), was 0.218 under the heat treatment at $500^{\circ}C$ for 60 min and 0.222 at $552^{\circ}C$ for 10 min. Since then both of those values decreased with time until 120 min and finally these two values remained constant at 0.210. The variation in Si content with annealing time results in the variation in the hyperfine field and the isomer shift. The increase in the mean hyperfine fields and the decrease in the mean isomer shifts of Fe-Si are caused by the increase in Si content. The volume fractions of residual amorphous phase rapidly decrease during the early stage of annealing and come nearer to saturation after 120 min both at $500^{\circ}C$ and $552^{\circ}C$. The decrease in the mean hyperfine field of residual amorphous. in spite of slight changes in the volume fractions of Fe-Si and of residual amorphous after 120 min. is caused by the increase in the content of Nb and B in residual amorphous phase. The saturated volume fraction of the crystalline phase was 81% for $500^{\circ}C$ (180 min) and 77% for $552^{\circ}C$ (960 min), different from expectation.