• Tribology and Lubricants
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• 제4권1호
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• pp.69-73
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• 1988

The effects of journal speed and bearing load on pressure distribution and the temperature distribution of bearing surface are investigated experimentally. The journal bearing which has 219.94mm diameter, length-to-diameter ratio of L/D=0.8 and clearance ratio of 0.004 is used. Journal has a built-in pressure transducer for the measurement of pressure distribution in the mid plane of bearing. Bearing surface temperatures are measured at 60 points. The bearing load is varied from 300 N to 5900 N and journal speed from 300 rpm to 2500 rpm. As the load is increased under constant speed, the location of maximum pressure moves to the site of minimum film thickness, and maximum pressure and absolute value of minimum pressure are increased. The temperature distribution in vicinity of oil inlet shows that heated lubricant's carry-over exists around the oil inlet.

• 대한기계학회논문집
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• 제13권3호
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• pp.419-423
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• 1989

본 연구에서는 담금유의 냉각능에 관한 상세한 연구는 우리나라에서는 아직 미비한 상태에 있으나, 저자 등은 제1보에서 서술한 실험장치 및 은시편을 사용하여 여러 광.식물성유의 냉각곡선을 구하고, 이로부터 냉각성능을 나타내는 파라미터들을 구하여, 객관적인 냉각성능을 평가하였다.

• 한국식품영양과학회지
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• 제29권1호
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• pp.120-127
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• 2000

Deep-fat frying is a common cooking practice. There has been considerable concern regarding the mutagenic and carcinogenic potential of thermally oxidized oils. Studies on deep-fried foods so far have revealed not much on the mutagenicity of the oils in the foods. Therefore, in the present study, it was attempted to investigate the mutagenicity ofthe thermally oxidized safflower oil. Oil was heated in a home-fryer at a temperature of 180$\pm$3$^{\circ}C$ for 48 hours. Oil samples were taken at 0, 8, 16, 24, 32, 40 and 48 hours of heating, respectively. Each sample was used to study the changes in peroxide value (POV), acid value (AV), iodine value (IV), conjugated dienoic acid (CDA) content, %, and fatty acid composition. Another series of samples were fractionated into non-polar and polar fractions by column chromatography. The mutagenicity of the samples taken from the thermally oxidized oils, as well as the non-polar and polar fractions of the thermally oxidized oils, was investigated with the Ames test. The Ames test was carried out with and without metabolic activation. Bacterial tester strains used in the present study were the histidine auxotrophic strains of Salmonella typhimurium TA100, TA1535 and TA102 were used for the detection of base pair mutations, and TA98 and TA1537 for frame shift mutations. Each series of samples was dissolved in tetraphydrofuran (inhibitor-free) and tested at doses ranging from 0.05 to 5 mg/plate. None of the oil samples taken during the 48 hour oxidation period showed any mugagenic activity. This was the case, even after the activaton with 59 mix. Also, none of the polar and non-polar fractions showed any mutagenic activity on all the strains tested.

• 한국식품과학회지
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• 제38권1호
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• pp.16-21
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• 2006

본 연구는 야자유를 190, $220^{\circ}C$에서 24시간 가열한 후 6개의 MOS로 구성된 전자코로 산패정도를 판별하였다. 주성분분석 결과 제1주성분 값이 열처리 시간에 따라 +0.952에서 0.325로 감소하였다. 가열 온도를 높임에 따라 야자유의 산패정도도 증가하였다. 또 다른 방법에 하나로 GC를 바탕으로 한 SAW센서가 부착된 전자코를 사용한 결과 후각이미지가 뚜렷하게 차이가 나는 것을 보여주었다. 160, $220^{\circ}C$에서 가열한 야자유로부터 휘발 성분에 대한 GC peak의 수와 넓이가 가열온도와 가열 처리 시간에 따라 증가함을 보여주었다. 이러한 방법은 신속하면서도 곧바로 알기 쉽게 데이터를 이미지화함으로써 가열 처리된 야자유의 휘발성분을 전자코로 신속하고 간편하게 분석하여 가열 처리 정도가 예측 가능하였다.

• Elastomers and Composites
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• 제52권3호
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• pp.187-193
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• 2017

In this study, the effect of the cure, mechanical properties, and oil resistance of NBR (acrylonitrile-butadiene rubber)/peroxide compounds were investigated for various co-agents. NBR compounds were characterized using a swelling test, a rheometer (MDR), and a compression set test. Mechanical properties were tested with original compounds, heated in air and exposed to the ASTM No.1, IRM 903 oil. NBR compounds were prepared using peroxide as the crosslinking agent. Trimethylolpropane trimethacrylate (TMPTMA), triallyl isocyanurate (TAIC), and 1,2-polybutadiene (HVPBD) were used as co-agents. The NBR compounds containing TMPTMA and HVPBD lowered the scorch time, while the addition of TAIC did not significantly change the scorch time. NBR compounds containing TMPTMA increased the crosslinking density, while the addition of TAIC and HVPBD lowered the crosslinking density. Moreover, the addition of TMPTMA improved the oil resistance of the NBR compound.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.60-65
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• 2001

Bomb calorimeter was developed for measuring the calorific value of combustible matter such as wastes. The calorimeter consist of bomb, stirred-water type bucket, thermometer and ignition circuit. Operation and performance of the calorimeter have been tested experimentally. In the present study, calorific values of light oil, lamp oil and bunker C oil is measured using the bomb calorimeter. Mass of the sample is fixed at lg, and oxygen pressure in the bomb is used as an experimental parameter. Sample in the oxygen bomb is burned with electrically heated Ni-Cr wire of 100mm in length, and temperature of water in the bucket become increased by $5^{\circ}C$ during about 30min. Calorific value of the sample is calculated with the temperature difference of water. Combustion tests, such as the record of temperature history and the inspection of remnants, are performed at 4, 6, 8 and 10 atm of the oxygen pressure. From the test results, oxygen pressure in the bomb must be over 10atm for complete combustion.

• 한국식품영양학회지
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• 제15권4호
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• pp.342-349
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• 2002

유채유에 코코넛유와 팜유를 각각 30%, 50%, 70%의 비율로 단순혼합한 혼합유와 ester 교환에 의한 혼합유를 제조하였고, 180$\pm$5$^{\circ}C$에서 가열산화시키면서 산값, 과산화물값, 요오드값, 공액이중산값 및 굴절율의 변화를 측정한 결과는 다음과 같았다. 1. 코코넛유의 산값은 25시간 가열 시까지 증가하였다가 그 이후 다소 낮아진 경향을 보였다. 또한 혼합비율에 따라 커다란 차이는 없었으나, 코코넛유와 혼합인 경우 코코넛유보다 낮은 산값을 보여주었다. 2. Ester교환에 의한 혼합유의 과산화물 초기값이 단순혼합유의 초기값보다 다소 높게 나타났으나, 증가폭에 있어서는 커다란 차이가 없었다. 코코넛유와 팜유의 혼합비율에 따라서 커다란 차이를 보이지 않았으나 혼합유의 경우가 유채유보다 낮은 값을 나타냈다. 3. 코코넛유와 팜유의 혼합시에 요오드 값의 감소가 나타났으나, 혼합방법이 요오드값의 감소현상에 크게 영향을 미치지 않는 것으로 나타났다. 4. 코코넛유와 팜유의 혼합비율이 증가함에 따라 공액이중산값의 증가폭이 다소 작아지는 현상이 나타났다. 단순혼합유와 ester 교환에 의한 혼합유의 차이는 ester교환에 의한 혼합유의 초기값이 단순혼합유의 초기값보다 다소 높은 경향이었으며 35시간 가열후의 증가폭은 커다란 차이가 없는 것으로 나타났다. 5. 코코넛유와 팜유의 혼합비율이 증가됨에 따라서는 큰 차이 없이 비슷한 정도의 굴절율 증가를 나타내고 있었다. 혼합방법의 차이에 따른 굴절율은 ester 교환에 의 한 혼합유가 단순혼합유보다 초기값에서 다소 낮은 굴절율 값을 보였다. 유채유를 포화지방산의 함량이 큰 유지와 혼합하면 유채유의 산화 안정성이 향상되는 것으로 나타났으며, 혼합방법에 따라 산화 안정성에 미치는 영향이 거의 없으므로 코코넛유나 팜유 같은 유지를 유채유에 혼합하면 튀김유로의 활용이 가능할 것으로 생각된다.

• 대한기계학회논문집B
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• 제37권8호
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• pp.725-732
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• 2013

본 논문에서는 가는 열선 주위를 흐르는 나노유체의 대류열전달 특성을 실험을 통하여 검토하였다. 입자 혼합 농도가 다른 4개의 나노엔진오일에 대하여 열선온도가 증가하는 경우, 유체온도가 증가하는 경우 그리고 막온도가 일정하게 유지되는 경우 등 세가지 온도경계조건에 대하여 대류열전달계수를 측정하였다. 내부유동에서 나노유체의 대류열전달계수 상승이 열전도율 상승을 초과한다는 결과가 최근 발표되기도 했지만 본 연구에서는 이 결과를 확인할 수 없었다. 온도조건에 따른 대류열전달계수의 변화 거동을 분석함으로써 나노유체의 열전도율과 경계층두께의 관계를 설명할 수 있었다.

• Fibers and Polymers
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• 제3권1호
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• pp.38-42
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• 2002

Polypropylene filaments were spun from a mixture of PP chips of two different Melt Flow Index (MFI) (3 MFI and 35 MFI). A significant difference was observed in the melting characteristics of the resultant filaments from either of the individual components as observed from the DSC. The main difference being in the degree of melting achieved at any temperature in the initial stages of the melting range, which was found to be higher in case of the filaments spun from the b]end. These filaments were then thermally bonded using silicon oil bath and heated roller method. Subsequently the bond strength of the filaments was measured on the Instron Tensile Tester using the loop technique. The values of the world strengths obtained from the blend were compared with those made from the individual component. It was found that the bond strength of the bonds obtained from the blended filament at a given temperature was higher than that of the bonds made from the filaments of either of the individual components, which is also suggested by the DSC curves. The difference in the bond strength was found to be as high as 25% in case of the blend with 60:40 composition ratios of the 3 MFI and 35 MFI components respectively.

• 한국식품조리과학회지
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• 제18권6호
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• pp.603-612
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• 2002

The study was carried out to compare the relation between the color intensity and antioxidant activity of caramelization products using xylose(XY), glucose(GL). sucrose(SU), glucose＋citric acid(GLCA), glucose＋sodium citrate(GLSC), heated at 80, 120 and 140$\^{C}$ for 24hrs, respectively. The color intensity(absorbance at 490nm) of the browning mixtures increased as the browning temperature and time increased. But the degrees of color intensity of SU and GLCA changed very little. The hydrogen donating ability(HDA) of browning reaction products was generally enhanced as the browning temperature and time increased. When browning mixtures were heated at 80$\^{C}$, the HDA of GLGC was the highest, but the HDA of GLSC was the highest when heated at 120 and 140$\^{C}$. The antioxidant activities for the corn oil substrate containing the anhydrous ethanol extracts from the browning mixtures was inferior to that of SU, but was superior to that of GLCA. The relations among the color intensity, the antioxidant activity, and the hydrogen donating ability(HDA, reducing power) of the browning reaction mixtures were as follows: As the color intensity increased, the antioxidant activity decreased. The correlation coefficient of the color intensity and the antioxidant activity by regression equation was -0.73 ∼ -0.82. As the reducing power increased, the antioxidant activity decreased. The correlation coefficient between the reducing power and the antioxidant activity by regression equation was -0.98 ∼ -0.99. Therefore, the antioxidant activity of browning reaction mixtures seemed not correlated with the color intensity and the reducing power.