• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2415-2423
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• 2015

Experiments were conducted on sine wave fin-and-tube heat exchangers having oval tubes under wet condition. Oval tubes having an aspect ratio of 0.6 were made, by deforming 12.7mm round tubes. Twelve samples, having different fin pitch and tube row, were tested. Results showed that, for oval tube samples, the effect of fin pitch on j and f factor was not significant. As for the effect of tube row, the lowest j factor was obtained for one row configuration(81% of two row configuration), which is clear contrast to round tube samples, where the highest j factor was obtained for one row configuration. Possible reasoning is provided considering the flow and heat transfer characteristics of sine wave channel combined with connecting oval tubes. Comparison of $j/f^{1/3}$ with plain fin-and-tube heat exchanger having 15.9mm O.D. round tube reveals that present oval fin-and-tube heat exchanger shows superior thermal performance except for one row configuration. In other words, $j/f^{1/3}$ of the two row oval tube heat exchanger was 1.6~2.5 times larger than those of round tube heat exchanger, 1.4~2.4 times larger for three row configuration and 1.2~2.8 times for four row configuration.

• Journal of the Korean Ceramic Society
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• v.24 no.6
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• pp.572-578
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• 1987

The vacuum evaporated Au films on soda-lime glasses were measured by the electrical conductivity with the variation of the annealing time, relative humidity, and temperature. Au films structures were observed by scanning Electron Microscope and X-ray Diffractometer. As the annealing time and temperature increased, the electrical conductivity was increased due to the migration or annihilation of defects, but the electrical conductivity was decreased as with the relative humidity increased. Au films by XRD and SEM examination showed the negligible effect of chemical reactions.

• Proceedings of the SAREK Conference
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• 2007.06a
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• pp.127-127
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• 2007

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.71-74
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• 2001

폴리에스테르 섬유는 섬도가 가늘어질수록 전체 표면적이 증가하므로 염색시 초기 염색속도가 빨라져 불균염의 원인이 되며, 겉보기 염착량은 감소하여 많은 염료를 사용해야 된다. 그래서 해도형 초극세 폴리에스테르 섬유는 레규라 폴리에스테르보다 세탁견뢰도 및 습마찰견뢰도가 현저히 저하하게 된다[1-3]. 또한 초극세 폴리에스테르 섬유는 환원세정을 하더라도 마무리 열고정이나 가공시에 가해주는 열로 인해 열이행이 많이 일어나는 것이 세탁견뢰도를 저하시키는 원인으로 지적되고 있다[4, 5]. (중략)

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.188-188
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• 2016

GZO 박막은 상업적으로 사용되는 ITO를 경제적으로 대체할 수 있는 유망한 투명 전도 물질이며, 인체에 무해하고, 공급이 쉬우며, 화학적으로 안정하다. 특히, CIGS와 같은 광전변환 소자 전극에서는 부식 저항이 매우 중요한데, 습한 환경에서 견뎌낼 수 있다는 장점이 있다. GZO는 3가 갈륨이 2가 아연에 도핑된 n타입의 반도체 물질이다. 그리고 육각형의 황화아연 물질의 전기 전도도는 산소 결핍에 매우 의존한다. GZO의 수소는 산소 결핍 집중에 영향을 끼친다. 따라서 이 연구에서는 RF 마그네트론 스퍼터링 실험 동안 수소 함유량을 다양화 시키고, 면 저항, 광 투과도, 부식저항의 효과를 조사한다. 수소량이 증가할수록, 면 저항은 향상되어지고, 특정 지점을 넘으면 감소한다. 분극 실험에 의해 측정되어진 부식 저항은 박막의 미세조직과 결정립계의 특성에 더 의존되어진다. 훨씬 더 많은 수소를 함량한 비정질이 부식 저항성에 있어서 유효한 차이를 나타내지 못하는 동안 결정 내에서 많은 수소를 지닌 작은 결정의 결정립계는 낮은 분극저항, 즉 낮은 부식 저항성의 결과를 도출한다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1171-1172
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• 2015

송전선이나 전기기기의 나선(裸線)부분을 절연하고 동시에 기계적으로 유지 또는 지지하기 위한 절연체와 이것과 일체로 조립된 금구류로 구성된 절연지지물인 애자는 전기적으로 충분한 절연내력을 가지게 하기 위하여 다수의 주름을 만들어 표면에 따른 거리를 크게 한다. 이는 표면이 습하였을 때, 염분이나 먼지 등이 부착하였을 때 절연내력이 저하되는 것을 방지하는 데 효과가 있다. 그리고 재질별(세라믹, 유리, 합성수지 등), 모양별(원판형, 원주형, 중공, 갓형 등), 용도별(전차 선로용, 발전소 또는 변전소용, 통신 선로용 등) 및 사용방법(현수용, 내장용, 인류용, 고정용 등)에 따라 다양하게 분류된다. 본 논문에서는 복합 애자류(composite insulators)의 여러 가지 성능평가 시험방법 중에서 복합 애자의 여러 계면과 연결 금구의 접속부(interfaces and connections of end fittings)에 대한 이상 유무를 확인하는 시험인 수분침투시험평가기술에 대해 고찰하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.317.1-317.1
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• 2013

유기 태양전지는 다른 무기계 태양전지에 비해 물질 자체의 쉬운 가공성과 유연한 특성으로 차세대 플렉시블 태양전지로 각광받고 있지만 상대적으로 짧은 수명으로 상용화에 걸림돌이 되고 있다. 현재까지 알려진 유기 태양전지의 짧은 수명의 원인으로는 수분과 산소에 의한 광활성층의 화학적 열화 및 표면의 변화, 전극의 열화, 전자-전공 수송층의 흡습현상 등이 있다 [1]. 본 연구에서는 이러한 이론적인 열화 메커니즘에 기초하여 일정한 수분과 산소 분위기에서 각 단위층들이 열화되는 현상을 광학적, 화학적 분석을 통해 짧은 수명의 원인을 밝혀내고자 한다. 유기 태양전지의 가혹시험은 $85^{\circ}C$의 온도와 85%의 습도 조건에서 이뤄졌으며, 가혹시간에 따른 열화현상 비교를 위해 0, 50, 100, 250, 500 h 동안 시험을 진행하였다. C-O, C=O 결합 형성에 의한 광활성층의 ${\pi}$공액의 변형은 FT-IR(fourier transform infrared spectroscopy)과 XRD (X-ray diffraction) 측정을 통해 분석하였고 변화된 표면 형상은 FE-SEM (field emission scanning electron microscopy) 측정을 통해 관찰하였다.

• Journal of Food Hygiene and Safety
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• v.28 no.3
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• pp.272-278
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• 2013

To evaluate the effect of surface contaminated with Escherichia coli O157:H7 (E. coli O157:H7) on the microbiological safety of lettuce, this study was conducted to investigate the attachment, biofilm producing, survival, and cross-contamination of E. coli O157:H7 on stainless steel and polyvinyl chloride (PVC). The attachment rate of E. coli O157:H7 on PVC was 10 times higher than that on stainless steel after exposure 1 h in cell suspension. However, there was not a difference between two types of surface after exposure for 6 h and 24h. The biofilm producing of E. coli O157:H7 was TSB > 10% lettuce extracts > 1% lettuce extracts > phosphate buffer. When two kinds of materials were stored at various conditions ($20^{\circ}C$ and $30^{\circ}C$, relative humidity (RH) 43%, 69%, and 100%), the numbers of E. coli O157:H7 at $30^{\circ}C$, RH 43% or RH 69% were reduced by 5.0 log CFU/coupon within 12 h regardless of material type. Conversely, the survival of E. coli O157:H7 at RH 100% was lasted more than 5 days. In addition, the reduction rate of E. coli O157:H7 was decreased in the presence of organic matter. The transfer efficiency of E. coli O157:H7 from the contaminated surface to lettuce was dependent upon the water amount of the surface of lettuce. Especially, the transfer rate of E. coli O157:H7 was increased by 10 times in the presence of water on the lettuce surface. From this study, the retention of E. coli O157:H7 on produce contact surfaces increase the risk cross-contamination of this pathogen to produce. Thus, it is important that the surface in post harvest facility is properly washed and sanitized after working for prevention of cross-contamination from surface.

• Membrane Journal
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• v.20 no.1
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• pp.76-86
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• 2010

This study investigated the effect of 2-butoxyethanol (BE) as a nonsolvent additive, relative humidity and air contact time on the structure formation of microfiltration membranes, permeation and morphology properties in phase inversion process. The membranes were prepared by using polyethersulfone (PES)/Dimethyl formamide (DMF)/p-toluenesulfonic acid (TSA)/Polyvinylpyrrolidone (PVP)/BE casting solution and water coagulant. Casting solutions containing various concentration of BE were exposed to a water vapor, under 60 and 80% of relative humidity for 40 and 90 sec, which would be absorbed on. The correlations between the membrane permeation properties and surface/inner structures of membrane were investigated. The characterization of membranes was carried out by a capillary flow porometer, a FE-SEM and a water permeation test apparatus. The surface structure of PES membranes was affected by the exposure time as well as the relative humidity strongly. Furthermore, the addition of BE helped control surface and inner structure at certain humidity and exposure time.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.2
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• pp.244-250
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• 2019

We investigated the relationship between morphological characteristics and individual dry weight to develop a method for estimating the individual dry weight of sheet form macroalgae: Ulva australis, Ulva linza, Pachymeniopsis lanceolata, and Pyropia yezoensis. In Total, 319 thalli of various sizes were collected at six sites from February 2017 to December 2018. An interspecific allometric exponent of 0.28 was found for length-biomass allometry in four sheet form macroalgae, corresponding to a 1/4-power law for primary producers. The relationships between surface area and individual dry weight, as well as between individual fresh weight and individual dry weight, were found to fit significantly using linear regression equations. This explained 94-99 % of individual dry weight, indicating that surface area and individual fresh weight can be used to accurately estimate individual dry weight. We propose the use of this method when experimental processes do not allow individual dry weight to be measured directly, so researchers can save both time and expense.