• Journal of the Korean earth science society
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• v.40 no.6
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• pp.624-638
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• 2019

A questionnaire was administered, and all responses were analyzed to examine prospective teachers' conceptual understanding of the relationship between dew point temperature and absolute humidity in air parcels. The responses revealed that many prospective teachers have substantial misconceptions about the relationship. For example, some thought that the absolute humidity and the dew point temperature are proportional to each other, and that the dew point temperature is proportional to the water vapor mass in the parcel. The misconceptions seemingly stemmed from inadequate descriptions on the relationship in middle-school science textbooks of the 7th and 2007 revised curricula. The study notes that the first year students' textbook of the 2015 revised curriculum introduced the concepts of evaporation, condensation, and volume changes as a function of gaseous pressure and temperature, from a perspective of molecular motion. It is suggested that keeping this perspective in the middle school curriculum, while introducing water vapor pressure as the measure of water vapor amount and dew point temperature, should help prevent middle school teachers and students from having misconceptions. There should be a concerted effort to make the science curriculum more consistent and coherent across the grade levels.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.255-262
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• 2014

To investigate the effect of oil on evaporation heat transfer of plate heat exchanger, evaporation heat transfer experiment was carried out using experimental apparatus for micro gear pumped R134a-oil circulation. By varying oil circulation rate of POE oil from 0 to 5%, evaporation heat transfer performance of plate heat exchanger was investigated. As OCR(Oil Circulation Ratio) increases, the evaporation heat transfer coefficient of R134a decreases and pressure drop increases. When the evaporating temperature is $30^{\circ}C$ and the refrigerant mass flow rate is 80 g/s, evaporation heat transfer rate decreases by 10 % and pressure drop increases by 10% at 2% of OCR condition.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.62-66
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• 2009

Utilization and interest of unconventional fuel and process residue such as oil sand and its residue, oil sand coke, have been increased because of the continuous rise of fuel price and conventional fuel availability. In this study, the gasification of oil sand coke produced from coking process of oil sand was performed to utilize as an energy resource using lab-scale fixed bed gasification system. The combustion characteristics of oil sand bitumen and oil sand coke were investigated by using TGA and lab-scale gasification system was applied to reveal the characteristics of produced syngas composition with oxygen/fuel ratio, temperature and steam injection rate. Oil sand coke shows a high carbon content, heating value and sulfur content and low ash content and reactivity. In case of oil sand coke gasification, generally with increasing temperature, the amount of steam introduced and decreasing oxygen injection rate, $H_2$ content in product gas increased while the $CO_2$ content decreased. The calorific value of syngas shows about $2100kcal/Nm^3$ and this result indicates that the oil sand coke can be used as a resource of hydrogen and fuel.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.130-130
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• 2002

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.778-784
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• 2005

It has been found that the addition of cosurfactant is necessary in order to expand three phase region containing middle phase microemulsion in ternary systems containing alkyl ethoxylate (AEO) nonionic surfactant, commercial lubricant and water. Phase behavior in the surfactant systems with addition of cosurfactant over a temperature range of 30 to $60^{\circ}C$ showed different trends depending on surfactant, temperature and chain length of alcohol added. For the $C_{12}E_4$ system, addition of n-pentanol and n-hexanol both produced a three phase region over a wide range of temperatures but the middle-phase formed was found to be a $L_3$ or D' phase which would not facilitate solubilization of high molecular weight lubricants. On the other hand, for the $C_{12}E_5$ system, the middle-phase microemulsion was found to be formed with addition of a rather long-chain alcohol such as n-hexanol, n-heptanol, n-octanol, or n-nonanol. The results shown with the addition of cosurfactant was understood in connection with interfacial tension measurements and composition analysis. The inability of the hydrocarbon region of the surfactant films to incorporate the large lubricant molecules and high solubility of a hydrophobic surfactant are thought to be the chief reasons for poor solubilization with D' phase.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.233-237
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• 1994

매스콘크리트에서는 수화열에 의하여 유발된 높은 온도가 열응력을 일으키는 원인이 되며 구속의 정도에 따라 인장응력이 발생되어 균열이 발생하게 된다. 따라서, 매스콘크리트 타설시 시멘트의 수화열에 의한 균열이 심각한 문제가 된다. 본 연구에서는 매스콘크리트 기초 및 교각구조에 대한 수화열 실험을 통해 온도분포 및 변형분포를 측정하고 이에 대한 온도 및 열응력 해석을 통해 매스콘크리트에 대한 수화열 특성을 규명하였다.

• Applied Chemistry for Engineering
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• v.29 no.3
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• pp.350-355
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• 2018

In this study, the effect of biomass torrefaction on the thermal and catalytic pyrolysis of cork oak was investigated. The thermal and catalytic pyrolysis behavior of cork oak (CO) and torrefied CO (TCO) were evaluated by comparing their thermogravimetric (TG) analysis results and product distributions of bio-oils obtained from the fast pyrolysis using a fixed bed reactor. TG and differential TG (DTG) curves of CO and TCO revealed that the elimination amount of hemicellulose in CO increased by applying the higher torrefaction temperature and longer torrefaction time. CO torrefaction also decreased the oil yield but increased that of solid char during the pyrolysis because the contents of cellulose and lignin in CO increased due to the elimination of hemicellulose during torrefaction. Selectivities of the levoglucosan and phenolics in TCO pyrolysis oil were higher than those in CO pyrolysis oil. The content of aromatic hydrocarbons in bio-oil increased by applying the catalytic pyrolysis of CO and TCO over HZSM-5 ($SiO_2/Al_2O_3=30$). Compared to CO, TCO showed the higher efficiency on the formation of aromatic hydrocarbons via the catalytic pyrolysis over HZSM-5 and the efficiency was maximized by applying the higher torrefaction and catalytic pyrolysis reaction temperatures of 280 and $600^{\circ}C$, respectively.

• Monthly Duck's Village
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• s.59
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• pp.38-40
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• 2008

• 전기의세계
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• v.51 no.9
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• pp.14-18
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• 2002

• Journal of the Korean Wood Science and Technology
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• v.39 no.1
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• pp.86-94
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• 2011

Pyrolytic lignin was obtained from biooil produced with yellow poplar wood. Fast pyrolysis was performed under various temperature ranges and residence times using fluidized bed type reactor. Several analytical methods were adopted to characterize the structure of pyrolytic lignin as well as the effect of pyrolysis temperature and residence time on the modification of the lignin. The yield of pyrolytic lignin increased as increasing pyrolysis temperature and decreasing residence time of pyrolysis products. The molecular weight of pyrolytic lignin determined by gel permeation chromatography (GPC) was approximately 1,200 mol/g, which was approximately a tenth of milled wood lignin (MWL) purified from the same woody biomass. Based on analytical data, demethoxylation and side chain cleavage reaction were dominantly occurred during fast pyrolysis.