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- 저자 : Koomson, Emmanuel (검색결과 5 건)
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Effect of sulfur on the cell performance in a molten carbonate fuel cell
이기정,Samuel Koomson,이충곤 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.4
This study evaluated the performance characteristics of a molten carbonate fuel cell (MCFC) under sulfur poisoning condition. A 100 cm2 bench-scale MCFC was used for the performance test. The performance of the cell at the normal operation condition was measured at 620 oC under atmospheric pressure. To evaluate the sulfur poisoning effect, 50 ppm H2S/Balanced N2 gas mixture at a flow rate of 30 ml/min was injected into the anode. The cell performance was analyzed via steady-state polarization (SSP) and inert gas step addition (ISA) methods. The overpotential of the cell was observed to have been changed by the injection of H2S gas, and an overpotential increase of ca. 40% was recorded after about 100 hours from the point of addition of the H2S gas. A voltage reduction rate of 2.62×104 mV/s was recorded at a current density of 150mA/cm2 after about 240 hours. The steady-state polarization characteristics of the cell showed that the sulfur poisoning was relatively slow. In addition, the effect of H2S gas on the cell performance was quantitatively measured by the ISA method.
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Abdallah Abdul-Mumuni,Isaac Koomson 한양대학교 경제연구소 2019 JOURNAL OF ECONOMIC RESEARCH Vol.24 No.2
This paper investigates the effect of household remittance inflows onchild education in Ghana using data from the Ghana LivingStandards Survey Six (GLSS 6). Employing an instrumental variableapproach and including children at the nursery and kindergartenlevels in our study, the following findings are established. First,remittance inflows generally reduce household liquidity constraints,translating into increased number of school hours for their children. Second, while remittance inflow improves child education in the urbanareas, it reduces school hours for their counterparts in ruralcommunities. Third, gains in school hours from remittance inflows aremuch greater for boys but do not make any or much of a difference inimproving that of the girl-child. We call for financial systemregulations that help to substantially reduce transaction costs on (orrigidities in) remittance inflows so that its influence on child educationoutcomes will be improved.
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이기정,김태균,Samuel Koomson,이충곤 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.10
The cell performance of Li-K and Li-Na carbonate electrolytes was compared using a coin type molten carbonate fuel cell operated at the extremely high temperature of 800oC. It was an acceleration test to compare the performance in a short period. Electrochemical techniques such as steady state polarization (SSP) and impedance from the Nyquist plot were used in the cell performance analysis. The initial performance of both electrolytes was similar, but the performance of the Li-K electrolyte decreased drastically after 180h. The results from SSP showed that the total overpotential of the Li-K electrolyte increased sharply, whereas that of Li-Na electrolyte had a continuous performance up to 340h. The impedance analysis showed that the internal resistance of the Li-K electrolyte increased with time, but that of Li-Na electrolyte remained unchanged. The remaining amount of each electrolyte was determined, and it was observed that the electrolyte loss rate of the Li-K electrolyte was 0.0072g/hr, and that of Li-Na electrolyte was 0.0028g/ hr. This implies that the electrolyte depletion rate of the Li-K electrolyte is about 1.5 times faster than that of the Li-Na electrolyte at the high-temperature condition. Thus, the cell of a Li-Na electrolyte containing MCFC according to the consumption of electrolyte is expected to be longer than one that uses Li-K electrolyte.
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Alam, Md Kowsar,Koomson, Emmanuel,Zou, Heng,Yi, Changqing,Li, Cheuk-Wing,Xu, Tao,Yang, Mengsu Elsevier Pub. Co 2018 Analytica Chimica Acta Vol. No.
<P><B>Abstract</B></P> <P>The pivotal role of microfluidic technology in life science and biomedical research is now widely recognized. Indeed, microfluidics as a research tool is unparalleled in terms of its biocompatibility, robustness, efficient reagent consumption, and controlled fluidic, surface, and structure environments. The controlled environments are essential in assessing the complex behavior of cells in response to microenvironmental cues. The strengths of microfluidics also reside in its amenability to integration with other analytical platforms and its capacity for miniaturization, parallelization and automation of biochemical assays. Following previous review on the applications of microfluidic devices for cell-based assays in 2006, we have monitored the progress in the field and summarized the advances in microfluidic technology from 2007 to 2017, with a focus on microfluidics development for applications in cell manipulation, cell capture and detection, and cell treatment and analysis. Moreover, we highlighted novel commercial microfluidic products for biomedical and clinical purposes that were introduced in the review period. Thus, this review provides a comprehensive source for recent developments in microfluidics and presents a snapshot of its remarkable contribution towards basic biomedical research and clinical science. We recognize that although enormous amounts of evidence have reinforced the promise of microfluidic technology across diverse applications, much remains to be done to realize its full potential in mainstream biomedical science and clinical practice.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Advances in microfluidic technology for cell analysis in the last decade were reviewed. </LI> <LI> Microfluidic platforms exhibited superior spatiotemporal resolution for cell manipulation and monitoring of cellular responses.. </LI> <LI> Commercialization of microfluidic technology has gained traction in biomedical research and diagnostic applications. . </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Lee, Ki-Jeong,Kim, Yu-Jeong,Koomson, Samuel,Lee, Choong-Gon The Korean Electrochemical Society 2018 Journal of electrochemical science and technology Vol.9 No.2
This study evaluated the performance characteristics of varied electrolyte species and amounts in a molten carbonate fuel cell (MCFC). Coin-type MCFCs were used at the condition of $650^{\circ}C$ and 1 atm. In order to measure the effects of varied electrolyte species and amounts, electrolytes of $(Li+K)_2CO_3$ and $(Li+Na)_2CO_3$ were selected and the amounts of 1.5 g, 2.0 g, 3.0 g, and 4.0 g were used. Insignificant performance differences were observed in the cell using different electrolytes, but the cell performance was sensitive to the amount of the electrolyte used. The pore-filling ratio (PFR), a ratio of pore filling in the components by the liquid carbonate electrolytes, was used to determine the optimum performance range. Consequently, 77% PFR demonstrated the optimum performance for both electrolytes. Thus, the MCFC had a permissible but narrow optimum performance range. The remaining amounts of electrolyte in the cells were determined using the weight reduction ratio (WRR) method after several hours of cell operation. The WRR used the relationship between the initial loaded amount of electrolyte and weight reduction of components in 10 wt% acetic acid. The relationships were linear and identical between the two electrolyte species.
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