• 한국수소및신에너지학회논문집
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• 제24권5호
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• pp.353-358
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• 2013

To develop preferential CO oxidation reaction (PROX) catalyst for small scale hydrogen generation system, supported Pt catalysts have been applied for the target reaction. The supports were systematically changed to optimize supported Pt catalysts. $Pt/Al_2O_3$ catalyst showed the highest CO conversion among the catalysts tested in this study. This is due to easier reducibility, the highest dispersion, and smallest particle diameter of $Pt/Al_2O_3$. It has been found that the catalytic performance of supported Pt catalysts for PROX depends strongly on the reduction property and depends partly on the Pt dispersion of supported Pt catalysts. Thus, $Pt/Al_2O_3$ can be a promising catalyst for PROX for small scale hydrogen generation system.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2011년도 후기공동학술대회 논문집
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• pp.41-41
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• 2011

국제해사기구(IMO)에서2016년에 건조되는 선박부터 Tier III 규제를 예고하고 있다. 이 규 제를 만족하기 위하여 엔진 전처리 기술 및 후처리 기술 개발과 실증 연구가 활발히 진행되고 있다. 이중 SCR(Selective Catalytic Reduction) 반응을 이용한 질소산화물 저감기술이 80% 이상의 Tier III NOx 규제치를 만족할 수 있는 유일한 기술이다. 육상 플랜트에서 실증과 검증이 확보된 SCR 기술의 선박 엔진에 대한 적용을 위해서는 선박의 급격한 운전조건 변화와 엔진에 의한 저주파 진동에 대한 촉매 내구성 확보가 중요하다. 본 연구에서 기공 분포면에서 마이크로 기공보다는 메죠 및 매크로 기공쪽으로 구조를 개선함으로써 촉매 사용시 우려되는 배기가스중의 Soot 또는 2차 합성물질에 의한 촉매기공 막힘을 최대한 방지한 상용 SCR 촉매를 개발하였다. 또한 촉매에 대한 내구성 실증을 위하여 현재 운항 선박(한진피츠버그호)에 장착하여 실증 실험을 수행하였다. 기존 corrugate 타입의 촉매보다 40% 정도의 부피 감소와 차압 감소를 달성하였고 이로 인하여 선박내 제한된 공간에 효율적으로 SCR 시스템 설치가 가능할 것으로 생각된다. 그리고 본 연구에서는 가이드 베인 설치 없이 유동 균일화를 달성하여 반응기 전체의 크기 축소가 가능하다. 이는 추가적인 비용 및 압력 손실 저감, 유지 보수 공간 확보 등의 장점이 있다.

• BMB Reports
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• 제46권12호
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• pp.567-574
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• 2013

Liver plays a major role in maintaining glucose homeostasis in mammals. Under fasting conditions, hepatic glucose production is critical as a source of fuel to maintain the basic functions in other tissues, including skeletal muscle, red blood cells, and the brain. Fasting hormones glucagon and cortisol play major roles during the process, in part by activating the transcription of key enzyme genes in the gluconeogenesis such as phosphoenol pyruvate carboxykinase (PEPCK) and glucose 6 phosphatase catalytic subunit (G6Pase). Conversely, gluconeogenic transcription is repressed by pancreatic insulin under feeding conditions, which effectively inhibits transcriptional activator complexes by either promoting post-translational modifications or activating transcriptional inhibitors in the liver, resulting in the reduction of hepatic glucose output. The transcriptional regulatory machineries have been highlighted as targets for type 2 diabetes drugs to control glycemia, so understanding of the complex regulatory mechanisms for transcription circuits for hepatic gluconeogenesis is critical in the potential development of therapeutic tools for the treatment of this disease. In this review, the current understanding regarding the roles of two key transcriptional activators, CREB and FoxO1, in the regulation of hepatic gluconeogenic program is discussed.

• 대한기계학회논문집B
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• 제24권12호
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• pp.1596-1607
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• 2000

The optimal design of auto-catalyst needs a good compromise between the pressure drop and flow uniformity in the substrate. One of the effective methods to achieve this goal is to use the concept of radially variable cell density. But this method has not been examined its usefulness in terms of chemical behavior and conversion performance. In this work, two-dimensional performance prediction of catalyst coupled with turbulent reacting flow simulation has been used to evaluated the benefits of this method n the flow uniformity and conversion efficiency. The results showed that two cell combination of 93cpsc and 62 cpsc was the most effective for improved pressure drop and conversion efficiency due to balanced space velocity and efficient usage of geometric surface area of channels. It was also found that large temperature difference between the bricks in case that the edge of the frontal face of brick has too much lower cell density(less than 67% of cell density of the center of the brick). This study has also demonstrated that the present computational results show the better prediction accuracy in terms of CO, HC and NO conversion efficiencies compared to those of conventional 1-D adiabatic model by comparison with experimental results.

• 한국분무공학회지
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• 제24권4호
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• pp.178-184
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• 2019

Diesel engines have the advantages of higher thermal efficiency and lower CO2 emissions than gasoline engines, but have the disadvantages that particulate matter (PM) and nitrogen oxides (NOx) emissions are greater than those of gasoline engines. In particular, nitrogen oxides (NOx) emitted from diesel engines generates secondary ultrafine dust (PM2.5) through photochemical reactions in the atmosphere, which is fatal to humans. In order to reduce nitrogen oxides (NOx), pre-treatment systems such as EGR, post-treatment systems such as LNT and Urea SCR have been actively studied. The Urea SCR consists of an injection device injecting urea agent and a catalytic device for reducing nitrogen oxides (NOx). The nitrogen oxide (NOx) reduction performance varies greatly depending on the urea uniformity in the exhaust pipe. In this study, spray characteristics according to the spray hole structure were confirmed, and the influence of spray uniformity on spray characteristics was studied through engine evaluation.

• Environmental Engineering Research
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• 제20권2호
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• pp.155-161
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• 2015

Experimental research shows that the nitric oxides ($NO_X$) concentration track at the outlet of selective catalytic reduction (SCR) catalyst with a transient variation of Adblue dosage has a time delay and it features a characteristic of resistance-capacitance (RC). The phenomenon brings obstacles to get the simultaneously $NO_X$ expected to be reduced and equi-molar ammonia available to SCR reaction, which finally inhibits $NO_X$ conversion efficiency. Generally, engine loads change frequently, which triggers a rapid changing of Adblue dosage, and it aggravates the air quality that are caused by $NO_X$ emission and ammonia slip. In order to increase the conversion efficiency of $NO_X$ and avoid secondary pollution, the paper gives a comprehensive analysis of the SCR system and tells readers the key factors that affect time delay and RC characteristics. Accordingly, a map of time delay is established and a solution method for time constant and proportional constant is carried out. Finally, the paper accurately describes the input-output state relation of SCR system by using "variable RC model with time delay". The model can be used for a real-time correction of Adblue dosage, which can increase the conversion efficiency of $NO_X$ in SCR system and avoid secondary pollution forming. Obviously, the results of the work discover an avenue for the SCR control strategy.

• 한국대기환경학회지
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• 제20권3호
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• pp.291-302
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• 2004

The CuO/$3AL_2O_3{\cdot}2SiO_2$ catalyst impregnated ceramic candle filters for nitrogen oxides removal were prepared by porous mullite($3AL_2O_3{\cdot}2SiO_2$) support and CuO catalyst deposited on this support to achieve uniformly dispersed CuO deposition, which are impregnated into the pores of available alumino-silicate ceramic candle filter. The CuO/3$AL_2O_3{\cdot}2SiO_2$ catalyst impregnated ceramic candle filters were characterized by XRD, BET, air permeability, pore size, SEM and catalytic tests in the reduction of NOx by NH$_3$. The observed effects of CuO/3$AL_2O_3{\cdot}2SiO_2$ impregnated ceramic candle filters in SCR reaction are as follows : (1) when the content of CuO catalyst increased further, activity of NO increased. (2) NO conversion at first increased with temperature and then decreased at high temperatures (above 40$0^{\circ}C$), possibly due to the occurrence of the ammonia oxidation reaction. (3) In pilot plant test for 3 months, NO conversion was greater than 90%.

• 한국소음진동공학회논문집
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• 제17권9호
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• pp.826-834
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• 2007

A 7K60MC-S low speed diesel engine in a power plant has frequently experienced high vibration since the unit completed construction works. Up to date, no fundamental vibration solutions were reached. Hence, several vibration tests and analyses were conducted to identify the root cause of this high vibration and to suggest the optimal countermeasures for diesel engine. The 9.25 Hz and 25.4 Hz vibrations have been observed on main body during operation. The magnitude of engine upper structural vibration is generally similar in horizontal transverse direction. However, differences in the 'Fore' and 'After' vibration magnitude with the same vibration phase angle at 9.25 Hz occur due to the explosion pulsations of 7 cylinders and the Inertia momentum added by the SCR (selective catalytic reduction) duct system. It was analyzed that the excess structural vibration occurred when the natural frequency of engine body is affected by the exciting sources due to the explosion pressure and the discharge pulsation of the seven cylinders in resonance range.

• 공업화학
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• 제8권2호
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• pp.191-196
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• 1997

$Pt/MoO_3/SiO_2$ 촉매계에서의 $50^{\circ}C$ 등온 환원 실험에서 hydrogen spillover는 소성 온도가 증가함에 따라 더욱 빠른 속도로 진행된다. 이는 Pt 표면위에 형성되는 overlayer에 기인하는 것임을 TEM과 CO chemisorption 측정으로 알 수 있었다. 1-butene의 iso-butene으로의 골격이성질화 반응 mechanism은 carbonium ion의 형성과 methyl기의 골격 치환의 2 step으로 알려져 있다. $Pt/MoO_3/SiO_2$ 촉매계에서 약 $250^{\circ}C$에서 calcination하면 iso-butene 수율이 증가한다. 이는 $PtCl_x$ precursor 내에 존재하는 chlorine의 감소에 의한 것과 overlayer 생성에 따라 Pt 표면으로부터 $MoO_3/SiO_2$로의 hydrogen spillover의 증가에 의한 것으로 추측된다.

• Molecules and Cells
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• 제27권3호
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• pp.299-305
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• 2009

Over-expression of phospholipase D (PLD) 1 or PLD2 down-regulated CKII activity in NIH3T3 cells. The same results were found with catalytically inactive mutants of PLD isozymes, indicating that the catalytic activity of PLD is not required for PLD-mediated CKII inhibition. Consistent with this, 1-butanol did not alter CKII activity. The reduction in CKII activity in PLD-over-expressing NIH3T3 cells was due to reduced protein level, but not mRNA level, of the $CKII{\beta}$ subunit. This PLD-induced $CKII{\beta}$ degradation was mediated by ubiquitin-proteasome machinery, but MAP kinase and mTOR were not involved in $CKII{\beta}$ degradation. PLD isozymes interacted with the $CKII{\beta}$ subunit. Immunocytochemical staining revealed that PLD and $CKII{\beta}$ colocalize in the cytoplasm of NIH3T3 cells, especially in the perinuclear region. PLD binding to $CKII{\beta}$ inhibited $CKII{\beta}$ autophosphorylation, which is known to be important for $CKII{\beta}$ stability. In summary, the current data indicate that PLD isozymes can down-regulate CKII activity through the acceleration of $CKII{\beta}$ degradation by ubiquitin-proteasome machinery.