• Asian Journal of Atmospheric Environment
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• 제9권1호
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• pp.57-65
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• 2015

We measured the concentrations of five aromatic hydrocarbons (benzene, toluene, ethylbenzene, m,p-xylene, and styrene) in the atmosphere during four seasonal campaigns at Deokjeok and Jeju Islands in the Yellow Sea from October 2005 to June 2006. Toluene was the most abundant aromatic hydrocarbon, with median of 0.24 ppb at Deokjeok and 0.20 ppb at Jeju, followed by benzene (0.21 ppb, 0.15 ppb) and m,p-xylene (0.06 ppb, 0.06 ppb). Aromatic hydrocarbon measurements exhibited the typical seasonality of the major emission sources, such as vehicle exhaust, solvent evaporation, and regional circulation patterns. The ratios of m,p-xylene/ethylbenzene of 1.57 at Deokjeok and 1.05 at Jeju reflected the degree of proximity to outflows of each source region, South Korea and China. The toluene/benzene ratios of 1.0 were consistently both on field observations and on the 3-D chemical model simulation, which is slightly higher than that in the Western Pacific area. It implied that the air over the Yellow Sea was influenced to a great extent by the surrounding areas. We confirmed that current emission inventories of aromatic hydrocarbons in Northeast Asia reasonably reproduced temporal and spatial variations of toluene and benzene over the Yellow Sea.

• Tribology and Lubricants
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• 제22권5호
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• pp.260-268
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• 2006

The dielectric constants of used gasoline engine oils were obtained at a few temperatures and a frequency. Through analyzing the characteristics of dielectric constant, the related correlation between the changes in dielectric constants of oil and the degree of oil deterioration is going to be found. The dielectric constant was calculated using cross capacitances measured by a sensor tube. As results of the measurement of the fresh engine oil's dielectric constant, it was found that the value of dielectric constant was set down below $60^{\circ}C$ regardless changing frequency. Further, above 6 kHz, the dielectric constant was set down even if temperature was above $100^{\circ}C$ Therefore, for the measurement of used oils, it was selected the frequency of 6 kHz,,and the temperature of $80^{\circ}C$ preventing a certain ionic-conduction effects on the measured dielectric constant and the evaporation of a certain fluid mixed with engine oil. Specially, the effects of the mixing fluid like coolant, water and fuel on the fresh engine oil's dielectric constant were studied. It was found that the oil mixed with coolant showed the highest value, next water, and the lowest fuel. As results of the measurement of the used engine oil's dielectric constant, it was found that the possible changed rate of the used engine oil's dielectric constant based on the warning limit for engine oil in service was below 4% for gasoline engine oil.

• Tribology and Lubricants
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• 제22권5호
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• pp.290-300
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• 2006

The dielectric constants of used diesel engine oils were obtained at a few temperatures and a frequency. Through analyzing the characteristics of dielectric constant, the related correlation between the changes in dielectric constants of oil and the degree of oil deterioration is going to be found. The dielectric constant was calculated using cross capacitances measured by a sensor tube. As results of the measurement of the fresh engine oil's dielectric constant, it was found that the value of dielectric constant was set down below $60^{\circ}C$ regardless changing frequency. Further, above 6 kHz, the dielectric constant was set down even if temperature was above $100^{\circ}C$. Therefore, for the measurement of used oils, it was selected the frequency of 6 kHz, and the temperature of $80^{\circ}C$ preventing a certain ionic-conduction effects on the measured dielectric constant and the evaporation of a certain fluid mixed with engine oil. Specially, the effects of the mixing fluid like coolant, water and fuel on the fresh engine oil's dielectric constant were studied. It was found that the oil mixed with coolant showed the highest value, next water, and the lowest fuel. As results of the measurement of the used engine oil's dielectric constant, it was found that the possible changed rate of the used engine oil's dielectric constant based on the warning limit for engine oil in service was below 10% for diesel engine oil.

• 대한금속재료학회지
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• 제49권4호
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• pp.321-328
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• 2011

The 30 nm-thick Ni layers was deposited on a flexible polyimide substrate with an e-beam evaporation. Subsequently, we deposited a Si layer using a catalytic CVD (Cat-CVD) in a hydride amorphous silicon (${\alpha}$-Si:H) process of $T_{s}=180^{\circ}C$ with varying thicknesses of 55, 75, 145, and 220 nm. The sheet resistance, phase, degree of the crystallization, microstructure, composition, and surface roughness were measured by a four-point probe, HRXRD, micro-Raman spectroscopy, FE-SEM, TEM, AES, and SPM. We confirmed that our newly proposed Cat-CVD process simultaneously formed both NiSi and crystallized Si without additional annealing. The NiSi showed low sheet resistance of < $13{\Omega}$□, while carbon (C) diffused from the substrate led the resistance fluctuation with silicon deposition thickness. HRXRD and micro-Raman analysis also supported the existence of NiSi and crystallized (>66%) Si layers. TEM analysis showed uniform NiSi and silicon layers, and the thickness of the NiSi increased as Si deposition time increased. Based on the AES depth profiling, we confirmed that the carbon from the polyimide substrate diffused into the NiSi and Si layers during the Cat-CVD, which caused a pile-up of C at the interface. This carbon diffusion might lessen NiSi formation and increase the resistance of the NiSi.

• 보존과학회지
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• 제34권4호
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• pp.283-293
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• 2018

This study involved a comparative analysis of the correlation between meteorological elements and the concentration of airborne fungi(CFU) in relation to biological damage to two temples on piedmonts, which is a cultural heritage building. The work compared Beopjusa temple in Boeun(Chungcheongbuk-do Province) and Seonamsa temple in Suncheon(Jeollanam-do Province). Twelve meteorological elements and the CFU were measured and the Pearson correlation analysis was used to determine the degree of the relationship between them. The results showed that Beopjusa temple had high wind speed, high total horizontal radiation, high evaporation, and large number of days with precipitation. Seonamsa temple had high air temperature, high relative humidity, high dew point temperature, high sea level pressure, high precipitation, and high CFU. The CFU at Beopjusa temple did not have a linear correlation with meteorological elements, but at Seonamsa temple it was highly positive correlated with the number of days with precipitation, relative humidity, and precipitation, and was highly negative correlated with total horizontal radiation. In addition, Beopju and Seonamsa temple had a common linear relationship between factors not affected by the topographical conditions, and had a individual linear correlation between factors affected by the topographical conditions.

• 한국구조물진단유지관리공학회 논문집
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• 제11권2호
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• pp.155-163
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• 2007

고강도 콘크리트(HSC)는 화재 시 폭렬현상과 함께 부재가 취성적인 거동을 하게 되는 단점을 지니고 있다. 폭렬현상은 화재 시 $100{^{\circ}C}$이상에서 부재내부의 수분 증발로 인하여 발생한 수증기가 수밀한 콘크리트에 갇혀 발생한다. 따라서 콘크리트 강도가 증가 할수록 수밀성이 높아져 폭렬의 정도가 심해진다. 콘크리트의 폭렬을 제어할 수 있는 방안으로는 폴리프로필렌 섬유(PP섬유)를 혼입하는 방법이 가장 효율적인 것으로 보고 되었다. 본 연구에서는 콘크리트 강도와 PP섬유 함유량을 변수로 하는 기둥 실험체에 대한 내화실험과 잔존강도실험을 수행하여 폭렬현상을 관찰하고 잔존강도를 측정하였다. 그 결과 콘크리트 강도가 60MPa에서 85MPa로 증가할 때 기둥 실험체의 잔존 축 강도는 10%증가하였다. 또한, PP섬유 함유량이 0%에서 0.2%까지 증가 할수록 잔존 축강도비는 68%에서 85%까지 증가하였으나, PP섬유 함유량이 0.2%이상에서는 잔존강도의 증가가 거의 나타나지 않았다.

• 현장농수산연구지
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• 제6권1호
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• pp.81-89
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• 2004

포도 "캠벨얼리" 송이에 새로 개발된 봉지를 괘대하여 봉지 내부의 미기상의 변화, 생리장해 및 병 발생, 과실품질, 수확기 판정의 편이성을 조사하였다. 개발봉지의 미기상은 온도 및 광투과율은 차이가 없었으나, 상대습도 및 봉지 표면의 수분 증발량은 변화를 주었다. 수정불량과, 착색불량과, 동녹 발생율 및 회색곰광이 발생율은 처리 간 큰 차이가 없었다. 열과 및 탄저병 발생은 무대과에 비하여 개발봉지가 현저히 감소하였다. 특히 탄저병 발생정도는 개발봉지가 현저히 덜 심하였다. 과방, 과립 및 과경의 생장 및 가용성고형물, 산 함량, 과색과 과분 발생에는 큰 차이가 없었다. 개발봉지는 수확기 판정의 편이성이 우수하였으며, 과색 및 과분 발생정도가 높아 과실의 품질을 향상시킬 수 있었다.

• 대한기계학회논문집
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• 제14권3호
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• pp.702-715
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• 1990

본 연구에서는 개수로 후래시 증발기 내부를 단순화된 형태로 가정하여 앞서 언급된 운전조건 및 유입되는 기포의 갯수유량(혹은 기공률)에 따라 증발기 내부의 속 도 및 온도분포를 수치적으로 계산해 보고자 한다. 이를 위해 유동을 정상상태의 난 류유동으로 가정하였으며, 구형의 기포에 대해 평균적인 운동 및 성장을 지배하는 방 정식을 세우고 상변화에 의한 증발량을 구하였다. 즉 입구에서 유입된 기포들이 성 장하면서 자유표면을 통해서 빠져나가는 운동 궤적을 추적함으로써 증발기 내부 유동 의 속도 및 온도분포를 구하고 이를 바탕으로 총 증발량 및 증발성능을 예측해 보고자 하는 것이다. 그리고 이렇게 계산된 결과들을 기존의 실험값과 비교하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제13권1호
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• pp.1-5
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• 2011

[ $CeO_2$ ]has been widely used for single buffer layer of coated conductor because of superior chemical and structural compatibility with $ReBa_2Cu_3O_{7-{\delta}}$(Re=Y, Nd, Sm, Gd, Dy, Ho, etc.). But, the surface of $CeO_2$ layer showed cracks because of the large difference in thermal expansion coefficient between metal substrate and deposited $CeO_2$ layer, when thickness of $CeO_2$ layer exceeds 100 nm on the biaxially textured Ni-3%W substrate. The deposition rate has been limited to be less than 6 $\AA$/sec in order to get a good epitaxy. In this research, we deposited $CeO_2$ single buffer layers on biaxially textured Ni-3%W substrate with 2-step process such as thin nucleation layer(>10 nm) with low deposition rate(3 $\AA$/sec) and thick homo epitaxial layer(>240 nm) with high deposition rate(30 $\AA$/sec). Effect of deposition temperature on degree of texture development was tested. Thick homo epitaxial $CeO_2$ layer with good texture without crack was obtained at $600^{\circ}C$, which has ${\Delta}{\phi}$ value of $6.2^{\circ}$, ${\Delta}{\omega}$ value of $4.3^{\circ}$ and average surface roughness(Ra) of 7.2 nm within $10{\mu}m{\times}10{\mu}m$ area. This result shows the possibility of preparing advanced Ni substrate with simplified architecture of single $CeO_2$ layer for low cost coated conductor.

• 동력기계공학회지
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• 제20권6호
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• pp.87-92
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• 2016

This research dealt with performance characteristics of OTEC system applying an ejector and additional pump. Each system using five kinds of working fluids was analyzed, and primary parameters with respect to entrainment ratio were examined: Turbine gross power, evaporation capacity, pump work, efficiency and volume flow ratio. The primary results were as following. The efficiency of ejector-pump OTEC system was dependent on entrainment of the ejector. The degree of efficiency change was different from applied working fluid, and amount of pump work was turned out to be primary factor affected system efficiency. Meanwhile, optimized entrainment ratio was different from applied working fluid since their different vapor density. System efficiency at optimized entrainmet ratio of each working fluid was around 5%, showing minor difference each other.