• 한국구조물진단유지관리공학회 논문집
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• 제19권4호
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• pp.49-56
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• 2015

초고성능 콘크리트는 높은 강도와 유동성을 갖는 우수한 재료 특성을 나타내는 콘크리트이다. 그러나 고연성 시멘트 복합체에 비하여 낮은 연성을 나타낸다. 이 연구에서는 강섬유와 마이크로섬유의 조합이 초고성능 콘크리트의 인장거동에 미치는 영향을 조사하였다. 이를 위하여 강섬유와 폴리에틸렌, 폴리비닐알코올, 현무암섬유 조합에 따라 4가지 초고성능 콘크리트 배합을 결정하였고, 인장거동을 평가하기 위하여 직접인장 실험을 수행하였다. 또한 마이크로섬유가 제조과정에서 의도하지 않은 과도한 기포를 생성하는지를 확인하기 위하여 밀도실험을 수행하였다. 실험결과 인장강도가 높은 폴리에틸렌섬유는 초고성능 콘크리트의 인장거동을 향상시키는데 효과적임을 확인하였고, 현무암섬유는 초고성능 콘크리트의 균열강도 및 인장강도를 증가시키는데 효과적임을 확인하였다. 또한 마이크로섬유가 의도하지 않은 기포를 생성하지 않는다는 것도 확인하였다.

• 한국환경과학회지
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• 제26권6호
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• pp.711-717
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• 2017

Dielectric Barrier Discharge (DBD) plasma is a new technique for use in environmental pollutant degradation, which is characterized by the production of hydroxyl radicals as the primary degradation species. Due to the short lifetime of the chemically active species generated during the plasma reaction, the dissolution of the plasma gas has a significant effect on the reaction performance. The plasma reaction performance can be enhanced by combining the basic plasma reactor with a homogenizer system in which the bubbles are destroyed and turned into micro-bubbles. For this purpose, the improvement of the dissolution of plasma gas was evaluated by measuring the RNO (N-dimethyl-4-nitrosoaniline, an indicator of the generation of OH radicals). Experiments were conducted to evaluate the effects of the diameter, rotation speed, and height of the homogenizer, pore size, and number of the diffuser and the applied voltage on the plasma reaction. The results showed that the RNO removal efficiency of the plasma reactor combined with a homogenizer is two times higher than that of the conventional one. The optimum rotor size and rotation speed of the homogenizer were 15.1 mm, and 19,700 rpm, respectively. Except for the lowest pore size distribution of $10-16{\mu}m$, the pore size of the diffuser showed little effect on RNO removal.

• Carbon letters
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• 제10권3호
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• pp.181-189
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• 2009

Activated carbon spheres (ACS) were prepared at different heating rates by carbonization of the resole-type phenolic beads (PB) at $950^{\circ}C$ in $N_2$ atmosphere followed by activation of the resultant char at different temperatures for 5 h in $CO_2$ atmosphere. Influence of heating rate on porosity and temperature on carbon structure and porosity of ACS were investigated. Effect of heating rate and temperature on porosity of ACS was also studied from adsorption isotherms of nitrogen at 77 K using BET method. The results revealed that ACS have exhibited a BET surface area and pore volume greater than $2260\;m^2/g$ and $1.63\;cm^3/g$ respectively. The structural characteristics variation of ACS with different temperature was studied using Raman spectroscopy. The results exhibited that amount of disorganized carbon affects both the pore structure and adsorption properties of ACS. ACS were also evaluated for structural information using Fourier Transform Infrared (FTIR) Spectroscopy. ACS were evaluated for chemical composition using CHNS analysis. The ACS prepared different temperatures became more carbonaceous material compared to carbonized material. ACS have possessed well-developed pores structure which were verified by Scanning Electron Microscopy (SEM). SEM micrographs also exhibited that ACS have possessed well-developed micro- and meso-pores structure and the pore size of ACS increased with increasing activation temperature.

• Ocean Science Journal
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• 제43권1호
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• pp.61-65
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• 2008

Feeding apparatus, mechanism and passage of ingested prey were described for Nemopilema nomurai (Scyphozoa: Rhizostomeae). N. nomurai medusae without central mouths have developed complicated canal systems connecting the tip of the tentacle and oral arm to the gut cavity. The number of junctions in the canal system increases with the bell diameter. The prey is gathered by paralyzing nematocyst at the tentacles and by adhering cirri at the oral arms and scapulets. They are engulfed into the terminal pore located at the oral arms and scapulets, and entered into the gut cavity via the canal system. The estimated digestion time is 1 hour and 20 min. The diameter of terminal pore is always about 1 mm, implying that they could not eat prey larger than that pore size. On the other hand, ephyrae have central mouths and could swallow prey as large as adults could. Exploitation of the same size of food by adult and ephyra implies that N. nomurai can affect seriously the whole food web, massively ingesting micro- and mesozooplankton and cutting the energy transfer toward the higher level of carnivores.

• 한국표면공학회지
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• 제51권6호
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• pp.344-353
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• 2018

Plasma electrolytic oxidation of Ti-25Ta-xHf alloy in electrolyte containing Ca and P for dental implants was investigated using various experimental techniques. Ti-25Ta-xHf (x=0 and 15 wt.%) alloys were manufactured in an arc-melting vacuum furnace. Micropores were formed in PEO films on Ti-25Ta-xHf alloys in 0.15 M calcium acetate monohydrate + 0.02 M calcium glycerophosphate at 240 V, 270 V and 300 V for 3 min, respectively. The microstructure of Ti-25Ta-xHf alloys changed from (${\alpha}^{\prime}+{\alpha}^{{\prime}{\prime}}$) phase to (${\alpha}^{{\prime}{\prime}}+{\beta}$) phase by addition of Hf. As the applied potential increased, the number of pore and the area ratio of occupied by micro-pore decreased, whereas the pore size increased. The anatase phase increase as the applied potential increased. Also, the crystallite size of anatase-$TiO_2$ can be controlled by applied voltage.

• 마이크로전자및패키징학회지
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• 제10권1호
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• pp.7-11
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• 2003

반도체 칩이나 전자제품에 사용되는 부품들은 작동할 때 발열을 하게 되며 발생한 열이 적절히 제거되지 않을 경우 제품 오작동의 원인이 된다. 이러한 열을 제거하기 위해 히트싱크(heatsink)와 냉각 팬 (cooling fan)을 조합한 냉각 구조가 사용된다. 그러나 히트싱크와 냉각 팬의 조합 구조는 복잡한 형상을 취하기 때문에 전기 전자 제품의 소형화 추세에 부응하기에는 어려움이 따른다. 냉각 효율은 히트싱크의 표면적과 히트싱크 제조시 사용된 재료에 따라 달라진다. 일반적인 냉각 구조의 한계를 극복하기 위한 방안으로써, Trach-etched 멤브레인의 표면과 기공(pore)에 무전해 금도금과 구리 도금을 실행하여 크기는 작으면서 표면적을 증가시킨 마이크로 히트싱크를 제조하였다. 제조한 마이크로 히트싱크의 구조는 주사현미경(SEM)과 광학 현미경으로 관찰하였으며, 일반적인 구리보다 열효율이 우수함을 방열 특성 실험을 통해 관찰하였다.

• 한국연초학회지
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• 제18권1호
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• pp.85-91
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• 1996

Commercially available activated carbon was treated with 0.2N NaOH/0.1N HCl to decrease the ash contents and to analyze the effect of demineralization. We have studied their properties and adsorptivity to solvents such as benzene, acetone, toluene and carbon tetrachloride, ammonia and also aldehydes of cigarette smoke. By demineralization with NaOH/HCl, surface area and pore volume were increased up to 10 - 20% according to developement of micro-pore and pH of activated carbon was also changed from 10.2 to 6.3. Surface acidity of the activated carbon treated with chemicals increased slightly. The chemical treatment led to small increase in adsorptioil properties of solvents, ammonia and aldehydes of cigarette smoke, but content of chlorine and sulfur in activated carbon were reduced. As the results of smoking test, charcoal taste caused by the activated carbon was reduced significantly by the treatment with NaOH/HCl.

• 대한치과기공학회지
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• 제37권4호
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• pp.235-242
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• 2015

Purpose: The aims of this study are compare with microstructure and mechanical properties of Co-Cr-Mo alloys fabricated by powder metallurgy(P/M) process and casting process respectively. Methods: Microstructure and micro-hardness were tested by SEM and Vickers Hardness Tester. The sintered specimen was produced by furnace-coolling after sintering, however the casting specimen were produced thru air-cooling and water-cooling after the casting. For observation of phase transformation during sintering, DSC analyzing was carried out. Results: Mean pore size of sintered Co-Cr-Mo alloy was $4.32{\mu}m$ and that of casting alloy was $1.63{\mu}m$. Hardness of sintered alloy was lower than water-quenched casting alloy. Conclusion: Proper sintering temperature of Co-Cr-Mo alloy was above $1,200^{\circ}C$ and pore size of casting specimen were finer than sintered specimen, but hardness were similar.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.659-664
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• 2001

This paper was studied to effects of fatigue by low flexural load on micro structures and carbonation of mortar. Mortar specimens cured at various conditions were first subjected to bending repeated loads, and it was made clear that insufficient cure reduced fatigue resistance of them. Next, fatigue tests that the stress levels are lower than the ones of fatigue rupture were carried out, The effect of curing conditions in early age on carbonation was furthermore studied using the scale, and it was made clear that insufficient cure is also susceptible to carbonation of them. Finally, the reason for rapid carbonation of fatigued mortars insufficiently outed was discussed from the view point of changes in pore structure of them.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.73-76
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• 2007

In this study, methane gas adsorption ability of activated carbon (AC) with surface functional group effect, adsorbed methane amount was evaluated after nitric acid and ureatreatment of AC surface. Specific surface area and pore distribution of AC were studied though nitrogen adsorption isotherm at 77 K. Micro pore volume was calculated through H-K method. Adsorbed methane amount was evaluated through volume method at room temperature by using auto adsorption apparatus. Adsorbed methane amount of AC was found to increase with to specific surface area increase.Correlation proposed between the methane adsorption amount and surface nature indicates that the surface nature plays an important role on the adsorption amount at a given temperature.