• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.141.1-141.1
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• 2014

오일 증기의 제트를 분사하여 잔류가스를 배기하는 오일확산펌프는, 구조가 간단하여 고장이 적고 저렴하며 소음 및 전기노이즈가 적게 발생하는 많은 장점을 가지고 있다. 그러나 오일의 증기압에 의해 그 도달압력이 10-9 Torr 이상으로 제한되어, 액체질소로 냉각되는 배플형태의 저온 트랩을 사용하지 않는 한 10-10 Torr영역의 초고진공 배기용으로는 사용하지 못하는 것으로 알려져 있다. 유회전펌프로 뒷받침 배기(foreline pumping)하는 700l/s의 배기속도를 가진 오일확산펌프에 300 liter/sec의 컨덕턴스를 가진 액체질소 트랩을 부착하여 메탈 실링을 사용하는 초고진공 챔버를 배기하였다. 액체질소트랩에 액체질소를 투입하면 $1{\times}10-8Pa$이하의 초고진공이 얻어졌으나, 액체질소가 증발하여 트랩의 온도가 상온으로 상승하면 압력도 $1{\times}10-7Pa$ 이상으로 상승하였다. 50 liter/sec의 배기속도를 가진 터보분자펌프로 오일확산펌프를 뒷받침 배기하면 액체질소를 투입하지 않은 상태에서 $5{\times}10-9Pa$이하의 초고진공이 얻어졌으며, 액체질소를 투입하여도 압력은 거의 변화하지 않았다. 잔류가스분석장치로 얻은 잔류가스 성분 스펙트럼은 수소가 잔류가스의 대부분을 차지하는 것을 보여주었다.

• 기계와재료
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• 제22권1호
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• pp.54-64
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• 2010

공작기계의 고속화, 다축화, 복잡화에 따른 열변형 오차가 공작기계에서 발생하는 오차의 대부분을 차지하고 있다. 이러한 열변형 오차를 최소화 하기 위해 공작기계의 발열부에 차가운 오일을 공급하여 냉각함으로써, 열변형을 제거하는 장치가 오일쿨러이다. 오일쿨러는 제어 방법에 따라 On-off, 가스 바이패스, 인버터 방식 등이 사용된다. 초정밀 공작기계에는 주로 가스 바이패스 및 인버터 방식이 사용되는데, 인버터 방식의 경우 고가(高價)인 관계로 주로 옵션 형태로 사용된다. 가스 바이패스 방식 오일쿨러는 인버터 방식에 비해 가격이 저렴하고 구조가 간다하며 정밀한 온도제어를 할 수 있지만 부하가 낮은 경우 구조적인 한계로 인해 온도제어 불안정을 발생시킨다. 본 연구에서는 기존 바이패스 방식 오일쿨러에서 나타나는 문제점을 해결하고 보다 정밀한 온도제어를 위해 2개의 전자밸브를 갖는 듀얼 밸브 방식 오일쿨러 시스템을 개발하였다. 개발된 듀얼 밸브 오일쿨러 시스템의 성능검증을 위해 정격운전, DIN 8602 규격, ISO/DIS 230-3 운전모드에서 성능을 비교/분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권7호
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• pp.9-15
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• 2018

The turbochargers, which are used widely in diesel and gasoline engines, are an effective device to reduce fuel consumption and emissions. On the other hand, turbo-lag is one of the main problems of a turbocharger. Bearing friction losses is a major cause of turbo lag and is particularly intense in the lower speed range of the engine. Current turbochargers are mostly equipped with floating bearings: two journal bearings and one thrust bearing. This study focused on the bearing friction at the lower speed range and the experimental equipment was established with a drive-motor, load-cell, magnetic coupling, and oil control system. Finally, the friction losses of turbochargers were measured considering the influence of the rotating speed from 30,000rpm to 90,000rpm, oil temperature from $50^{\circ}C$ to $100^{\circ}C$, and oil supply pressure of 3bar and 4bar. The friction power losses were increased exponentially to 1.6 when the turbocharger speed was increased. Friction torques decreased with increasing oil temperature and increased with increasing oil pressure. Therefore, the oil temperature and pressure must be maintained at appropriate levels.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권4호
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• pp.57-62
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• 2018

This study was designed to analyze the chemical composition and antioxidant activity of various vegetable oils (pumpkin seed oil, camellia seed oil, red pepper seed oil and peanut oil) using adsorbents (active carbon, acid clay, kaolin). Their chemical composition was analyzed by GCMS. Their antioxidant activity was evaluated by measuring their DPPH and ABTS radical scavenging activity. After the treatment with the adsorbents, the contents of most of the fatty acids and active ingredients contained in the four kinds of vegetable oils were reduced. After the treatment with the three adsorbents, the linoleic acid and erythrodiol contents of the pumpkin seed oil were reduced. In the case of the camellia seed oil, the fatty acids content was decreased, but there was no loss of vitamin E after the acid clay treatment. The content of the compound capsaicin, which forms part of the spicy component of red pepper seed oil, was reduced by 53.33% after the acid clay treatment. The peanut oil showed the lowest loss of sitosterol compound in the group treated with active carbon. The antioxidant activity was observed to be in the order of pumpkin seed oil (kaolin>acid clay>active carbon), camellia seed oil (acid clay>kaolin>active carbon), red pepper seed oil (kaolin>acid clay>active carbon) and peanut oil (active carbon>acid clay>kaolin).

• Korean Journal of Food Science and Technology
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• 제40권3호
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• pp.303-310
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• 2008

This study was performed to verify the effects of encapsulation against oil oxidation. Thiobarbituric acid (TBA) values of samples were compared during storage at $60^{\circ}C$, indicating that the encapsulated avocado oil had lower TBA values than the free avocado oil. Microcapsules consisting of a whey protein isolate (WPI)-only wall system had slightly improved oxidative stability; however, spray-dried particles containing a high proportion of maltodextrin (MD) clearly offered better protection from oxidation than the other forms of encapsulation. The chlorophyll (Chl) content of the encapsulated avocado oil was higher than that of the free oil sample. When compared to the control, all wall systems protected the change of the chlorophyll content storage. No large differences were observed between the encapsulated powders according to the various wall materials. The color of the encapsulated oil changed from green to yellowish-green, indicating the formation of pheophytin from chlorophyll. The yellowish color of the oil correlated with a reduced total Chl content. In conclusion, encapsulation with spray drying for avocado oil could lead to improved stability during storage with respect to oxidation and the preservation of chlorophyll.

• Journal of Convergence for Information Technology
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• 제9권3호
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• pp.56-67
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• 2019

The aim of this study was to investigate the influence of rosemary oil inhalation on memory, attention and autonomic nervous system according to the concentration difference in the aged. The research design was non-equivalent control group non-synchronized design. Participants were 89 individuals aged 65 or older who live in the community. Participants inhaled almond carrier oil(control group), 10%(experimental group A) and 100%(experimental group B) rosemary oil. Memory, attention, and autonomic nervous system responses were measured. Data were analyzed by SPSS win 24.0. The differences of the group and time were analyzed through repeated measure ANOVA. There were no significant differences in immediate recall (F=.42, p =.656), delayed recall (F=.45, p=.639), recognition (F=1.45, p=.242), digit span-forward (F=1.53, p=.223), digit span-backward (F=.46, p=.636), activities of sympathetic nerve system (LF)(F=.19, p=.828), activities of parasympathetic nerve system (HF)(F=.37, p=.694), LH/HF(F=1.39, p=.256), systolic blood pressure (F=.37, p=.694), diastolic blood pressure (F=1.25, p=.291). The inhalation of 10% and 100% rosemary oil for five minutes showed no significant effects on memory, attention and automatic nervous system in the aged.

• Analytical Science and Technology
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• 제33권6호
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• pp.262-273
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• 2020

A fluorine content analysis method for krill oils, which is a representative oil formulation in foods, was developed in compliance with the Korea Food and Drug Ministry's "Guidelines for Validation of Testing Methods Related to Food". Using this method for krill oils, the presence of impurities was evaluated via combustion-ion chromatography (C-IC). A review of published technical data on fluorine in krill oils showed that while the traditional wet potentiometric method was typically used, it was not reliable. Moreover, there was no food testing/analysis laboratory in Korea to perform a fluorine test analysis on such an oil matrix. Therefore, we identified halogen (fluorine) tests, developed to national and international standards, and developed a test method suitable for krill oils by selecting a C-IC method that is sufficiently applicable to the oil matrix. Based on the characteristics of the oil matrix, the optimal test method was established through various experiments by reviewing the concerns related to loss and interference in the preparation and introduction of samples. The fluorine content test was carried out on 11 krill oil products that were purchased online. Most products (with the exception of only one) were found to contain less than the reporting limit obtained by the test method. Furthermore, after additional testing, a high fluorine content of approximately 2,000 ~ 3,000 mg/kg was detected on the krill surface, although the concentration varied depending on the area of the krill. A comparison with samples from two ISO/IEC 17025 testing laboratories confirmed that there was no significant difference in the statistical analysis results obtained by ANOVA among the three laboratories. A testing guide for fluorine content analysis was completed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2003년도 추계학술대회 논문요약집
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• pp.87-87
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• 2003

• Communications for Statistical Applications and Methods
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• 제4권1호
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• pp.75-90
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• 1997

본 연구는 범주형자료의 오분류에 관한 연구로, 2$\times$2분할표의 자료에 오분류가 있다고 생각되는 조사와 반복조사를 통해 정확하게 분류한 새로운 범주형자료를 시간이라는 새변수의 결합을 통해 오분류 여부를 탐색하는 방법에 대한 연구이다.

• Journal of the KSME
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• 제55권6호
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• pp.34-37
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• 2015

이 글에서는 유전체 배리어 방전 플라즈마를 활용하여 오일 미스트를 1차 집진한 뒤에 2차적으로 $CO/CO_2$로 전환하여 저감하는 기술에 대해 소개하고자 한다.