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마이크로 pin fin 화학반응기에서 수소화붕소나트륨 수용액의 압력강하 및 탈수소 화학반응 연구
정기문(Ki Moon Jung),최석현(Seok Hyun Choi),정문선(Moon-Sun Chung),이희준(Hee Joon Lee) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Many types of hydrogen storages have been studied recently paying attention to hydrogen storage and release. Among those, dehydrogenation from the hydrolysis of a sodium borohydride (NaBH₄) solution has been of much interest owing to its high theoretical hydrogen storage capacity (10.8 wt.%) and potentially safe operation. However, most of researchers have focused on chemical characteristics such as NaBH4 hydrolysis, catalysts, and synthesis, but not on the mechanical design of a chemical reactor for hydrogen generation. To design an efficient chemical reactor, size (which should be compact) and pressure drop, reaction rate are of great importance. Therefore, a microchannel is promising for the design of a dehydrogenation reactor owing to its very large reacting surface area per unit volume. Moreover, micro size pin fin structures could be manufactured on the bottom of microchannel surface for even more extended reacting surface area and contact catalytic reaction. An experiment study has been performed on catalytic reaction rate and pressure drop of NaBH4 solution over both a single microchannel with a hydraulic diameter of 300 ㎛ and a staggered array of micro pin fins with hydraulic diameter of 50 ㎛ in the microchannel. Catalytic reaction rates and pressure drops were obtained over Reynolds numbers from 1 to 60 and solution concentration from 5 to 20 wt.%. Moreover, reacting flows were visualized using a high-speed camera with a macro zoom lens. As a result, both the amount of hydrogenation and pressure drop are 2.45 times and 1.5 times more in pin fin microchannel than in a single microchannel, respectively.
췌장암과 염증성 췌장질환의 감별진단에 있어서 혈청 CA 19 - 9 의 진단적 가치
정기문(Ki Mun Jung),장세호(Se Ho Chang),심상군(Sang Gun Sim),우성경(Sung Kyung Woo),이재구(Jae Gu Lee),조중현(Joong Hyeon Cho),김영채(Young Chai Kim),최진학(Jin Hak Choi) 대한내과학회 1990 대한내과학회지 Vol.39 No.3
N/A To evaluate the diagnostic value of CA 19-9 in pancreatic cancer, serum levels of 19 subjects with pancreatic cancer and 15 subjects with inflammatory pancreatic diseases were measured by sandwiched radioim-munometric assay. We also studied the influence of serum alkaline phos-phatase and serum bilirubin to CA 19-9 levels in the same subjects. The results were as follows; 1) With a recommended reference cut off value of 37 U/ml, serum CA 19-9 differentiate pancreatic cancer from inflammatory pancreatic diseases with 84%. sensitivity, 67% specificity, and 67% negative predictive value. With a higher cut off value of 100 U/ml, the diagnostic specificity was increased up to 89%, 2) A significant linear correlation was observed between serum bilirubin and serum CA 19-9 (r=0.3764, p<0.05), between serum alkaline phrosphatase, and serum CA 19-9 (r=0.6531, p<0.0001). We concluded that the measurement of serum CA 19 -9 was a simple and useful method in differential diagnosis of pancreatic cancer, and by increasing the cut-off value up to 100 U/ml, its diagnostic specificity was markedly increased. Our study also revealed that there was a significant correlation bewteen serum CA 19-9 and serum bilirubin and serum alkaline phosphatase.
마이크로 Pin Fin 화학반응기에서 수소화붕소나트륨 수용액의 압력강하 및 탈수소 화학반응 연구
정기문(Ki Moon Jung),최석현(Seok Hyun Choi),이희준(Hee Joon Lee) 대한기계학회 2017 大韓機械學會論文集B Vol.41 No.6
수소화붕소나트륨은 안정적으로 수소가 저장된 물질이며, 촉매반응으로 수소를 용이하게 분리할 수 있다. 본 연구에서는 탈수소 반응률을 높이기 위해 비표면적이 큰 마이크로 pin fin 화학반응기를 제작하여 수소화붕소나트륨 수용액의 압력강하 및 탈수소 화학반응 실험을 수행하였다. 나노공정을 이용하여 실리콘웨이퍼에 높이 300 μm, 직경 50 μm의 pin fin을 축간격 1.3, 횡간격 1.5으로 엇갈림 배열하였다. 수소화붕소나트륨 수용액은 5~20 wt.% 농도로 Re수 1~60으로 공급되었으며, 초고속카메라를 이용하여 탈수소반응 유동양상을 관찰하였다. 실험 결과 마이크로 pin fin 화학반응기는 동일 수력학적직경을 가지는 직관 마이크로채널 화학반응기보다 화학반응 성능이 2.45배 우수한 반면, 압력강하는 1.5배 증가하였다. Dehydrogenation from the hydrolysis of a sodium borohydride (NaBH4) solution has been of interest owing to its high theoretical hydrogen storage capacity (10.8 wt.%) and potentially safe operation. An experimental study has been performed on the catalytic reaction rate and pressure drop of a NaBH4 solution over both a single microchannel with a hydraulic diameter of 300 μm and a staggered array of micro pin fins in the microchannel with hydraulic diameter of 50 μm. The catalytic reaction rates and pressure drops were obtained under Reynolds numbers from 1 to 60 and solution concentrations from 5 to 20 wt.%. Moreover, reacting flows were visualized using a high-speed camera with a macro zoom lens. As a result, both the amount of hydrogenation and pressure drop are 2.45 times and 1.5 times larger in a pin fin microchannel array than in a single microchannel, respectively.
저류특성을 고려한 북한강수계 발전용댐의 유형 구분방안 제시
최정욱,정기문,강두선,안정환,김태순,Choi, Jeongwook,Jeong, Gimoon,Kang, Doosun,Ahn, Jeonghwan,Kim, Taesoon 한국수자원학회 2021 한국수자원학회논문집 Vol.54 No.8
Climate change threatens the security of domestic water resources in South Korea. To overcome the potential water shortage, various approaches are being studied by alterning the operation of dams or by integrated operation of multiple dams and reservoirs. However, most of the related researches were developed and applied for multi-purpose dams, and few studies were conducted for the hydropower dams. The main purpose of the hydropower dam is to generate electric energy; however, the potential water shortage due to prolonged droughts brings the idea to supply water from the hydropower dam in the basin. To that end, it is required to estimate the water supply ability of the hydropower dams. In this study, we proposed a methodology to classify the hydropower dam into a "storage-type" and "run-of-river type" dam. The proposed approach was demonstrated using the hydropower dams located in North-han River basin. The results of this study are expected to contribute for further analysis of the hydropower dams, such as evaluation of water supply capacity and drought mitigation purpose operation of the hydropower dams.