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함현식,Sung-Hwan Ahn,Song-Hyoung Kim,Kwang-Bo Jung 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.3
The effect of pressure on the direct synthesis of dimethyl ether (DME) from syngas over metal (Cu, Zn) pillared ilerites and metal (Cu, Zn) impregnated metal-pillared ilerites was explored. The prepared catalysts were characterized by XRD, BET, ICP-AES, SEM and FT-IR. The direct DME synthesis reaction was carried out in a differential fixed bed reactor with the prepared catalysts at various pressures (10, 20, 30 bar), 250 oC and H2/CO ratio of 2. The Cu/Zn-pillared ilerite catalyst showed the highest catalytic activity among the prepared catalysts at 20 bar, in which CO conversion was about 62% and DME selectivity was about 89%. CO conversion increased with pressure, and DME selectivity increased with pressure in the range of 10-20 bar, and above the pressure slightly decreased with pressure. The optimum pressure for this reaction was 20 bar.
함현식(Hyun-sik Ham),김동현(Dong-hyun Kim),채정우(Jung-woo Chae),이신애(Sin-ae Lee),김윤지(Yun-ji Kim),조현욱(Hyun Uk Cho),조현종(Hyun-chong Cho) 대한전기학회 2020 전기학회논문지 Vol.69 No.2
The early detection of plant disease is important in that it enhances the quality and productivity of crops. A large amount of research has considered machine learning classifiers to protect tomato plants from diseases, but the reliability of early disease diagnoses in this way remains uncertain due to the use of small datasets. Therefore, to enhance the dependability of them, this study examined a tomato disease classification system based on a deep learning using a dataset containing 17,063 images of tomato leaves infected with eight diseases. The deep learning model used in this classifier consisted of symmetric and asymmetric building blocks including convolutions, average pooling, max pooling, concats, dropouts, and fully connected layers. The obtained result indicated a high degree of accuracy (98.9%) which is high enough to be used as a proper diagnosis tool for farmers who lack professional knowledge of tomato diseases.
도전성 카본블랙/PVdF 복합재의 제조 및 전기적 특성
김명찬 ( Kim Myeong Chan ),문승환 ( Mun Seung Hwan ),임재석 ( Im Jae Seog ),함현식 ( Ham Hyeon Sig ),박홍수 ( Park Hong Su ),김명수 ( Kim Myeong Su ) 한국유화학회 2003 한국응용과학기술학회지 Vol.20 No.3
N/A Electrical properties of carbon filler/PVdF {poly(vinylidene fluoride)}composite were investigated as a funtion of carbon filler/PVdF ratio in the range of 0.2~0.5. Three kinds of comercialzied conductive carbon blacks such as Hiblack 41Y, KE300J, and KE600J, and carbon nanofibers prepared by the catalytic chemical vapor deposition of C_(2)H_(4) over Ni-Cu catalysts were in the range of 0.65 to 13.5 S/cm depending the fillers` electrical conductivity ranging from 5.6 to 23.1 S/cm. Among the carbon fillers used, the KE600J carbon black showed the highest conductivity both in the composite and filler itself because of its high degree of graphitization due to the high-temperature thermal treatment and its high surface area due to the activation treatment.
김상범 ( Kim Sangbeom ),박은석 ( Park Eun Seog ),천한진 ( Cheon Han Jin ),김영국 ( Kim Yeong Gug ),임연수 ( Im Yeon Su ),박홍수 ( Park Hong Su ),함현식 ( Ham Hyeon Sig ) 한국유화학회 2003 한국응용과학기술학회지 Vol.20 No.4
N/A Synthesis gas is produced commercially by a steam reforming process. However, the process is highly endothermic and energy intensive. Thus, this study was conducted to produce synthesis gas by the partial oxidation of methane to cut down the energy cost. Supported Ni catalysts were prepared by the impregnation method. To examine the activity of the catalysts, a differential fixed bed reactor was used, and the reaction was carried out at 750~850℃ and 1 atm. The fresh and used catalysts were characterized by XRD, XPS, TGA and AAS. The highest catalytic activity was obtained with the 13wt% Ni/MgO catalyst, with which methane conversion was 81%, and H_(2) and CO selectivities were 94% and 93%, respectively. 13wt% Ni/MgO catalyst showed the best MgNiO_(2) solid solution state, which can explain the highest catalytic activity of the 13wt% Ni/MgO catalyst.
김상범 ( Kim Sang Beom ),박은석 ( Park Eun Seog ),천한진 ( Cheon Han Jin ),김영국 ( Kim Yeong Gug ),김명수 ( Kim Myeong Su ),박홍수 ( Park Hong Su ),함현식 ( Ham Hyeon Sig ) 한국유화학회 2003 한국응용과학기술학회지 Vol.20 No.3
N/A Syntheses gas is commercially produced by a steam reforming process. However, the process is highly endothermic and energy-consuming. Thus, this study was conducted to produce syntheses gas by the partial oxidation of methane to decrease the energy cost. Supported Ni catalysts were prepared by the impregnation method. To examine the activity of the catalysts, a differential fixed bed reactor was used, and the reaction was carried out at 750~850℃ and 1 atm. The fresh and used catalysts were characterized by XRD, XPS, TGA and AAS. The highest catalytic activity was obtained with the 13wt% Ni/MgO catalyst, with which methane conversion was 81%, and H_(2) and CO selectivities were 94% and 93%, respectively. 13wt% Ni/MgO catalyst showed the best MgNiO_(2) solid solution state, which can explain the highest catalytic activity of the 13wt% Ni/MgO catalyst.
고정층 반응기에서 합성가스 생성에 미치는 반응온도와 반응물 유속의 영향
김상범 ( Kim Sang Beom ),김영국 ( Kim Yeong Gug ),황재영 ( Hwang Jae Yeong ),김명수 ( Kim Myeong Su ),함현식 ( Ham Hyeon Sig ) 한국유화학회 2004 한국응용과학기술학회지 Vol.21 No.1
N/A The effects of reaction temperature and flow rate of reactants on the methane conversion, product selectivity, product ratio, and carbon deposition were investigated with 13wt% Ni/MgO catalyst. Reaction temperatures were changed from 600 to 850℃, and reactants flow rates were changed from 100 to 200 mL/mim. There were no significant changes in the methane conversion observed in the range of temperatures used. It is possibly stemmed from the nearly total exhaustion of oxygen introduced. The selectivities of hydrogen and carbon monoxide did not largely depend on the reaction temperature. The selectivities of hydrogen and carbon monoxide were 96 and 90% respectively. Carbon deposition observed was the smallest at 750℃ and the largest at 850℃. It is found that the proper reaction temperature is 750℃. the best reactant flow rate was 150 ml/min.
메탄 플라즈마 CVD법으로 합성한 탄소나노튜브의 구조적 특성
김명찬 ( Myung Chan Kim ),문승환 ( Seung Hwan Moon ),임재석 ( Jae Seok Lim ),함현식 ( Hyun Sik Hahm ),박홍수 ( Hong Soo Park ),김명수 ( Myung Soo Kim ) 한국유화학회 2004 한국응용과학기술학회지 Vol.21 No.4
N/A Multi-walled carbon nanotubes (CNTs) were prepared by microwave plasma chemical vapor deposition (MPCVD) using various combination of binary catalysts and methane precursor. The maximum yield (10.3 %) of CNTs was obtained using a methane-hydrogen-nitrogen mixture with volume ratio of 1:1:2 at 1000 W of microwave power. As the microwave power increased up to 1000 W, the deposition yield of CNTs raised from 4.1 % to 10. 3 %. However, the prepared CNTs at 800 W showed the more crystalline structure than those prepared at 1000 W. The prepared CNTs over different binary catalysts had various structural conformations such as aligned cylinder, bamboo, and nanofibers. The Id/Ig value of CNTs over Fe-Fe/Al₂O₃, Co-Co/Al₂O₃, and Co-Cu/Al₂O₃ were in the range of 0.89~0.93. Among the various binary catalysts used, Fe-Co./Al₂O₃ showed the highest yield.