• 멤브레인
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• 제23권6호
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• pp.432-438
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• 2013

본 연구에서는 metal organic frameworks (MOFs)의 한 종류인 MIL-100(Fe)을 이용하여 혼합기질막(mixed matrix membranes, MMMs)을 제조하였다. MIL-100(Fe)의 함량을 고분자 대비 0~30 wt%까지 변화시키면서 첨가된 MOF의 함량에 따른 기체의 투과 특성을 살펴보았다. $H_2$, $CO_2$, $O_2$, $N_2$, $CH_4$의 기체 투과도는 MIL-100(Fe) 첨가량이 증가함에 따라 투과도가 증가하는 경향을 보여주었으며, 상대적으로 큰 입자크기를 가진 $SF_6$의 투과도는 MIL-100(Fe)의 첨가량이 증가함에 따라 투과도가 감소하였다. 이상 선택도는 $N_2/SF_6$의 경우 폴리이미드막 대비 약 40% 증가하였으며, 이를 통해 $N_2/SF_6$ 분리에 적합한 분리막임을 확인할 수 있었다.

• 비파괴검사학회지
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• 제23권4호
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• pp.322-327
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• 2003

초고밀도 자기기록 reading head로 사용되고 있는 거대자기저항(GMR, Giant Magnetoresistance) NiO 다층박막을 제작하고 이를 공기중에서 80 일간 자연산화시킨후, 형성된 산화층과 잔류응력 변화에 따른 NiO 스핀밸브 박막의 자기저항 특성을 연구하였다. $NiO(60nm)/Ni_{81}Fe_{19}(5nm)/Co(0.7nm)/Cu(2nm)/Co(0.7nm)/Ni_{81}Fe_{19}(7nm)$의 구조를 갖는 다층박막을 공기중에서 약 80일간 자연산화 시켰을 때, 자기저항비(MR)와 교환결합력$(H_{ex})$이 각각 4.9%와 110 Oe에서 7.3%와 170 Oe로 증가하였다. 이때, 스핀밸브박막의 비저항(P) 값은 $28{\mu}{\Omega}m$로 감소하였지만 박막의 비저항 값의 변화량$({\Delta}p)$는 크기변화가 거의 없는 것을 알 수 있었다. 그러므로, 자기저항비의 증가는 aging시간에 따른 비저항 값의 감소에 기인한 것으로 생각되며, 저항의 감소는 표면산화에 따라 전도전자의 반사율증가에 의한 것으로 사료된다. 또한 교환결합력의 증가는 반강자성체/자성체 박막사이 계면에서 발생한 잔류응력이 aging시간이 경과함에 따라 감소하여 특성이 강화된 것으로 생각된다.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.51-59
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• 2002

In this study, cycle simulation was performed to investigate the effect of EGR on combustion characteristics and emissions including NO and soot using a two-zone model in a DI diesel engine. The NO formation was well predicted for different EGR rate and temperature using a two-zone model. The oxygen in the inlet charge was replaced by CO$_2$ and H$_2$O with EGR. The reduction in the inlet charge oxygen resulted in very large reduction in NO level at the same inlet charge temperature. The effect of EGR was to reduce the burned gas temperature. When EGR was increased from 0% to 15%, the peak flame temperature was decreased by 50$\^{C}$ and it caused about 57% NO reduction. EGR caused increase of the overall inlet charge temperature which offset some of benefit of lower flame temperature resulting from O$_2$ displacement. Cooling the EGR was confirmed to provide additional benefits by lowering NO emission. It also reduced soot emission.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.237-240
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• 2002

Micro catalytic reactors are alternative propulsion device that can be used on a nano satellite. When used with a monopropellant, $H_2O_2$, a micro catalytic reactor needs only one supply system as the monopropellant reacts spontaneously on contact with catalyst and releases heat without external ignition, while separate supply lines for fuel and oxidizer are needed for a bipropellant rocket engine. Additionally, $H_2O_2$ is in liquid phase at room temperature, eliminating the burden of storage for gaseous fuel and carburetion of liquid fuel. In order to design a micro catalytic reactor, an appropriate catalyst material must be selected. Considering the safety concern in handling the monopropellants and reaction performance of catalyst, we selected hydrogen peroxide at volume concentration of 70% and perovskite redox catalyst of lantanium cobaltate doped with strondium. Perovskite catalysts are known to have superior reactivity in reduction-oxidation chemical processes. In particular, lantanium cobaltate has better performance in chemical reactions involving oxygen atom exchange than other perovskite materials. In the present study, a process to prepare perovskite type catalyst, $La_{0.8}Sr_{0.2}CoO_3$, and measurement of its propellant decomposition performance in a test reactor are described.

• 한국세라믹학회지
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• 제43권3호
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• pp.173-176
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• 2006

${Sr_{1-x}Ba_xNb_2O_6$(SBN) have been obtained in Pt crucible by melting and cooling in air atmosphere. Some SBNs being at the bottom of the crucible are black and transparent, and the other SBNs colorless. The black SBN became to be colorless by oxidation heat treatment $1,300^{\circ}C$ for 4 h, Curie temperature is changed by colorless change of black SBN. The reason seems to be $Nb^{5+}$ oxidation of some $Nb^{4+}$ ions in SBN or effect of unknown impurities. Diffused Phase Transition (DPT) was appeared during heating and cooling process. Various sintered SBN ceramics specimen showed relaxor characteristics.

• International Journal of Automotive Technology
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• 제6권6호
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• pp.591-598
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• 2005

A three-way catalyst system of a natural gas vehicle (NGV) has characteristics of higher fuel consumption and higher thermal load than a lean-bum catalyst system. To meet stringent emission standards in the future, NGV with the lean-bum engine may need a catalyst system to reduce the amounts of HC, CO and NOx emission, although natural gas system has low emission characteristics. We conducted experiments to evaluate the conversion efficiency of the NOx reduction catalyst for the lean-burn natural gas engine. The NOx reduction catalysts were prepared with the ${\gamma}-Al_{2}O_3$ washcoat including Ba based on Pt, Pd and Rh precious metal. In the experiments, effective parameters were space velocity, spike duration of the rich condition, and the temperature of flowing model gas. From the results of the experiments, we found that the temperature for maximum NOx reduction was around $450^{\circ}C$, and the space velocity for optimum NOx reduction was around $30,000\;h^{-1}$ And we developed an evaluation model of the NOx reduction catalyst to evaluate the conversion performance of each other catalysts.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.18-28
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• 2007

Three diesel engines were fueled with BDF 20, a blend of 80% diesel fuel and 20% biodiesel fuel by volume, and run in excess of 200 h to evaluate their combustion characteristics and durability. The engines used for this study were a 4-cylinder 2476-cc displacement IDI diesel engine(Engine 1), a 4-cylinder l732-cc displacement IDI diesel engine(Engine 2), and a single cylinder 673-cc displacement DI diesel engine(Engine 3). Engine dynamometer testing was performed on each engine at regularly scheduled intervals to monitor the performance and exhaust emissions, which were sampled at 1h intervals for analysis, The peak combustion pressure with BDF 20 increased in Engines 1 and 3 over that measured when burning pure diesel fuel, but that in Engine 2 remained constant. Combustion parameters, such as the maximum combustion pressure and corresponding crank angle, did not change over the long-term dynamometer testing. The BSFC with BDF 20 in Engine 1 was less than that measured with pure diesel fuel. The amount of smoke produced with BDF 20 was less for all engines ; the greatest reduction was observed for Engine 3. The NOx emissions were lower in the IDI engines than the DI engine. The traditional trade-off between smoke and NOx emissions was maintained for BDF 20 fuel for Engines 1 and 3. There was not a big difference in the $CO_2\;and\;O_2$ emissions for BDF 20, as compared to pure diesel fuel, but more $CO_2$ was exhausted by Engine 1 than by Engines 2 or 3 and less $O_2$ was exhausted by Engine 1 than by Engines 2 or 3. The engine parts remained clean, except for some carbon attached to the area surrounding the nozzle hole of the DI diesel engine.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.285-285
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• 2010

Zinc oxide (ZnO) is a direct band gap semiconductor with 3.37 eV, which has in a hexagonal wurtzite structure. ZnO is a good candidate for a photocatalyst because it has physical and chemical stability, high oxidative properties, and absorbs of ultraviolet light. During ZnO is irradiated by UV light, redox (reduction and oxidation) reactions will occur on the ZnO surface, generating the radicals O2- and OH. These two powerful oxidizing agents have been proven to be effective in decomposition of harmful organic materials, converting them into CO2 and H2O. Therefore, we assume that oxygen on the surface of ZnO is a very important factor in the photocatalytic activities of ZnO nanoparticles. Recently, ZnO nanoparticles are studied in various application fields by many researchers. Photocatalyst research is progressing much in various application fields. But the ZnO nanoparticles have disadvantage that is unstable in water in comparison titanium dioxide (TiO2). The Zn(OH)2 was formed at the ZnO surface and ZnO become inactive as a photocatalyst when ZnO is present in the solution. Therefore, we prepared synthesized ZnO nanoaprticles that were immersed in the water and dried in the oven. After that, we measured photocatalytic activities of prepared samples and find the cause of their phtocatalytic activity changes. The characterization of ZnO nanoparticles were analyzed by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and BET test. Also we defined the photocatalytic activity of ZnO nanoparticles using UV-VIS Spectroscopy. And we explained changing of photocatalytic activity after the water treatment using X-ray Photoelectron Spectroscopy (XPS).

• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.519-525
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• 2010

Ethanol was used as reductant to remove $NO_x$ over Ag/$Al_2O_3$ catalyst via SCR from stationary emission source. Among the tested hydrocarbon reductants, ethanol showed highest de-$NO_x$ performance over the Ag/$Al_2O_3$ catalyst. De-$NO_x$ efficiency of about 83% was obtained in the condition of GHSV 20,000 $hr^{-1}$, $NO_x$ 200 ppm, CO 200 ppm, $O_2$ 13%, $H_2O$ 5% and mole ratio of ethanol/$NO_x$ = 2 between temperature of $300^{\circ}C$ and $400^{\circ}C$. While $SO_2$ presence in the $NO_x$ exhaust suppressed the catalytic activity, catalyst with acid (0.7% $H_2SO_4$) treatment of catalyst showed higher catalytic activity, where In-Situ DRIFT showed S presence over catalyst surface was increased after acid treatment of catalyst. From in-situ DRIFT and SCR results, it was concluded that sulfur presence over the surface of Ag/$Al_2O_3$ catalyst was the dominant factor to control the de-$NO_x$ reaction yield via HC-SCR from the exhausted gas including $SO_2$.

• 한국작물학회지
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• 제47권3호
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• pp.167-173
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• 2002

호남평야지에서 건답직파재배와 무경운기계이앙 재배시 적정 연속재배 년수 및 윤환재배법을 구명하고자 '95년부터 '00년까지 호남농업시험장 수도포장인 전북통(미사질양토)에서 동진벼를 공시하여 시험한 결과를 요약하면 다음과 같다. 1. 무경운 기계이앙재배시 표층의 공극율이 건답직파에 비해 높았고 가비중은 무경운 재배시 가벼웠으며 무경운 재배를 계속할수록 표토는 볏짚의 환원에 따른 유기물 함량이 높아지고 물리성이 개선되나 심토는 경운 생략에 따른 물리성 악화와 유기물 함량의 감소로 벼 뿌리가 표층에 많이 분포하는 경향이었다. 2. $m^2$당 경수는 건답직파보다 무경운이앙에서 많았고 5년연속 건답직파시 275개로 경수의 감소가 현저하였으며 유효경비율은 재배양식간 큰 차이없이 60%내외였다. 3. 무경운재배를 계속 할 경우 잡초의 발생량이 크게 증가하였는데 1년생 잡초인 사마귀풀, 둑새풀이 많이 발생하였고, 다년생 잡초인 나도겨풀의 발생량이 많았으며 잡초성벼는 경운이앙재배에 비해 많이 발생하였지만 무경운 연속 재배년수에 관계없이 2-3%였다. 4. 건답직파를 3년 연속 했을 경우 잡초성벼 발생율은 3.7%가 되었으며 이듬해 담수직파로 윤환재배를 한 결과 2%로 감소하였지만 다시 건답직파재배를 했을 때 7.2%가 발생하여 윤환재배의 효과가 적었다. 5. 도복은 담수직파에서는 3으로 재배양식중 가장 심하였고 다음으로 무경운 기계이앙 순이었으며 건답직파와 경운이앙재배에서는 경미하였는데 도복 정도는 재배년차간 차이보다는 재배양식에 따라 발생정도가 다르게 나타났다. 6. 출수기는 무경운 이앙에서는 경운이앙과 비슷하였으나 건답직파와 담수직파에서는 년차간 변이가 심하였으며 쌀수량은 담수직파의 경우 년차간 큰 차이없이 경운이앙에 비해 약간 낮았고 무경운이앙에서는 5년연속 재배시 다소 감소되었으며 건답직파에서는 5년연속 재배시 62%로 크게 감소되었다.다.0일이었다.환경적응성이 낮은 경향이었다.은 모두 경운 유 ㆍ무에 관계없이 시비수준이 높을수록 높은 경향을 보였고, 10일에 최고수준을 보인 후 완만한 감소를 나타냈으며, $K^{+}$, $Ca^{2+}$에 비해 $Mg^{2+}$이 보다 낮은 함량을 보였다.989년산 일반계를 10분도와 12분도로 도정하였을 때 도정도에 따른 밥맛의 차이는 없었다.X>$CoO_x$는 $Co_3O_4$로 존재하고, 반응 전의 경우에는 이와는 다른 chemical state를 보여주었다. XRD 및 XPS 결과를 바탕으로, 촉매표면에 존재하는 $Co_3O_4$의 외부표면이 $Co_2TiO_4$와 $CoTiO_3$ 같은 $CoTiO_x$로 encapsulation되어 있는 모델구조를 제안할 수 있고, 이는 반응시간의 함수로 나타나는 촉매활성에 있어서 전이영역의 존재를 잘 설명할 수 있을 뿐만 아니라, XRD와 XPS에서 얻어진 촉매의 물리화학적인 특성을 잘 반영할 수 있다. 나타냈고, 골격근과 눈 조직에서 피루브산에 대한 LDH의 친화력이 상당히 크므로 LDH가 혐기적 조건에서 효율적으로 기능을 하는 것으로 사료된다.5) and "Cleanliness of clothes ＆ features" (p ＜0.05) of VIP ward were significantly higher than those of a general ward.tive to apply.아울러 고려(考慮)해야 한다. 이것은 고무기술자(技術者)가 당면(當面)해야할 과제(課題)에 속(屬)하며 바람직 한것은 본장(本章)의 내용(內容)이 여러 상황하(狀況下)에서 당면(當面)한 문제(問題)에 대(對)해 어떻게 대처(對處)해 야 할지를 모르는 여러 기술자(技術者)