• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.549-550
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• 2006

Mobile fuel cell is highlighted in these days because mobile fuel cell can contain more energy than existing batteries. Nowadays mobile devices like cellular phone, PMP(portable multi-media player), notebook, and etc. need more energy, But existing batteries like Li-ion or Ni-MH batteries are not going to satisfy such demands. In this paper, mobile fuel cell is developed. Its size is 50*70*8mm and it is made of aluminium plates. The fuel cell type is PEM and the fuel is pure hydrogen and oxygen.

• Journal of the Optical Society of Korea
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• v.19 no.2
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• pp.199-205
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• 2015

We investigated the effects of the thickness and doping concentration in p- and n-type poly-Si layers on the performance of a solar cell based on a carbon fiber in order to improve the energy conversion efficiency of the cell. The short-circuit current density and open-circuit voltage of the carbon fiber-based solar cell were significantly influenced by the thickness and doping concentration in the p- and n-type poly-Si layers. The solar cell efficiency was successfully enhanced to ~10.5%.

• Journal of Society of Preventive Korean Medicine
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• v.5 no.1
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• pp.134-143
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• 2001

The oxidative modification of low density lipoprotein(LDL) has been implicated in the development of atherosclerosis. Oxidized LDL are found in macrophage foam cell, and it can induce an macrophage proliferation in atherosclerotic plaque. In this study, we investigated the hypothesis that gamisoyosan(GS) may reduce atherosclerosis by lowering the oxidiazability of LDL, To achive this goal, we examined the effect of GS on LDL oxidation, nitric oxide production in mouse macrophage cell line, RAW264.7, and the effect of GS on cupuric sulfate-induced cytotoxicity, LDH release, and macrophage activity. GS inhibited the generation of oxidized LDL from native LDL in RAW264.7 cell culture, and decreased the release of LDH from cupric sulfate-stimulated RAW264.7 cell. In other experiments, GS activated RAW264.7 cell, and prolonged the survival time, and increased nitric oxide production in Raw 264.7 cells.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.579-582
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• 2008

PEM Fuel cell system was designed and constructed to use as a power source of unmanned aerial vehicles(UAV) in the present study. Sodium borohydride was selected as a hydrogen source and was decomposed by catalytic hydrolysis reaction. Fuel cell system consists of a fuel cell stack, a hydrogen generation system(HGS), and power management system(PMS). HGS was composed of a catalytic reactor, micropump, fuel cartridge, and separator. Hybrid power system between lithium-polymer battery and fuel cell was developed. The fuel cell system was integrated and packaged into a blended wing-body UAV. Energy density of the total system was 1,000 $W{\cdot}hr/kg$ and high endurance more than 5 hours was accomplished in the ground tests.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1870-1872
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• 1999

Performance of 20-cell stack for direct methanol fuel cell (DMFC) was tested at constant temperature. Electrode evaluation used to the stack was tested by the performance of a single cell. A new composite electrode prepared from active carbon cloth and high porous active carbon was developed for hydrophilic layer of the cell. Characteristics of a single cell using the composite electrode showed the current density of $500mA/cm^2$ at the cell voltage of 0.4V at $120^{\circ}C$. For the operating of 20 days. the cell voltage at constant cell current densty of $100mA/cm^2$ was slightly reduced from 0.62V to 0.53V with the cell voltage decay rate of 14.5%. Power of 20-cell stack at 5.3V, $100^{\circ}C$ was about 180W.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.161-170
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• 2012

There are many factors to consider when attempting to improve the efficiency of fuel cell operation, such as the operation temperature, humidity, stoichiometry, operation pressure, geometric features, etc. In this paper, the effects of the operation pressure were investigated to find the current density and water saturation behavior on a cross section designated by the design geometry. A two-dimensional geometric model was established with a gas channel that can provide $H_2$ to the anode and $O_2$ and water vapor to the cathode gas diffusion layer (GDL). The results from this numerical modeling revealed that higher operation pressures would produce a higher current density than lower ones, and the water saturation behavior was different at operation pressures of 2 atm and 3 atm in the cathode GDL. In particular, the water saturation ratios are higher directly below the collector than in other areas. In addition, this paper presents the dependence of the velocity behavior in the cathode on pressure changes, and the velocity fluctuations through the GDL are higher in the output area than in inlet area. This conclusion will be utilized to design more efficient fuel cell modeling of real fuel cell operation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.4
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• pp.351-361
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• 2023

The purpose of this paper is to help those who research and develop solar cells in university laboratories and industrial sites understand the most basic and important quantum efficiency measurement and analysis method in analyzing solar cell performance. Starting with the definition of quantum efficiency, we calculate the theoretical current density according to the band gap of the solar cell material from the solar spectrum, along with a detailed introduction to the measurement and analysis methods, and measure and analyze the theoretical current density and quantum efficiency. We discuss in depth how to analyze the performance of solar cells through Quantum efficiency measurement and analysis of solar cells is a very useful method that can give intuition to solar cell performance analysis as it can analyze solar cells according to depth (front emitter, bulk, rear surface). Students and researchers who study solar cells with a deep understanding of theoretical current density and quantum efficiency measurement analysis are expected to use it as a basis for analyzing solar cell performance.

• Journal of Naturopathy
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• v.7 no.2
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• pp.63-69
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• 2018

Purpose: The purpose of this study was to investigate the effects of Bacillus fermentation broth (ENM) on the human NK cell activity, and bone matrix density, matrix content and area of hamsters fed ENM. Methods: NK cell activity was tested, and bone mineral density were measured by x-ray. Results: NK cell activity was significantly higher in the control group (644.71 pg/ml) and in the test group (1796.37 pg/ml) (p<.004). Test groups were significantly increased by 1110.37 pg/ml in the pre-test and 1796.37 pg/ml in the post-test(p<.001). Behavioral observations after feeding ENM to hamsters showed normal behavior with no difference between control and test groups. The hamster body weight of the control was 106 g at the initial and final 27 days. In the test group, the initial weight was 96.6 g and the final 27 days was 114 g. No morphological changes were observed in the X-ray photographs of the hamster hind legs. The bone matrix density was 0.059 g/cm³ in control and 0.062 g/cm³ in the test, which was increased by 0.003 g/cm³. The bone matrix content was 0.175 g in the control and 0.196 g in the test. The bone area was 2.95 cm² in the control and 3.19 cm² in the test, which was increased by 0.19 cm². In the autopsy, neither the control nor the test group showed any remarkable abnormality, and each organ was normal. Conclusions: It is thought that ingestion of ENM is useful for immunity enhancement.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.66-69
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• 2001

Previously we developed a CHO cell line (CHO-OTC1-A19) expressing the first two enzymes of urea cycle. This cell line showed higher ammonia removal activity and faster growth rate than the vector controlled CHO cells (CHO-neo-5). The purpose of this study was to develop a cell line with higher ammonia removal activity than the cell line developed previously. To accomplish this, we constructed stable CHO cell lines expressing the first three, the first four, or all five enzymes of urea cycle by the stable transfection method. We finally selected CHO-AL-19 cell line expressing the first three, the first four enzymes of the cycle with higher ammonia activity than CHO-OTC1-A19 and CHO-n대-5 cell lines: 40% and 15% higher than those of CHO-neo-5 and CHO-OTC1-A19 cell lines 72 hour after culture started, respectively. It also showed 44% and 10% higher cell viability than CHO-neo-5 and CHO- OTC1-A19 cell lines at higher cell density. In addition, CHO-AL-19 cells showed 45%-60% and about 20% lower ammonia concentration per cell than those of CHO-neo-% and CHO-OTC1-A19 cell lines, respectively. These results indicate that CHO-AL-19 could be used in the production of human therapeutic proteins with higher efficiency.

• KSBB Journal
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• v.4 no.1
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• pp.11-14
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• 1989

A study on the continuous fermentation with cell recycle by a tower fermentor to produce ethanol has been carried out. ethanol fermentation was conducted with flocculating yeast strain, Saccharomyces cerevisiae TS4, to compare the ethanol productivity with conventional continuous process. Employing a 15% glucose feed, a cell density of 50 g/l was obtaind. The ethanol productivity of the cell recycle system was found to be 26.5g EtOH/1-hr, which was nearly 7.5 times higher than the conventional continuous process without cell recycle. A cell recycle ratio of 7 to 8 resulted in the highest ethanol productivity and cell concentration. Thus the cell recycle ratio was found to be a key factor in controlling the production of clarified overflow liquid. An aeration rate above 3.8 $\times$ 10-3 VVM seemed to decrease the ethanol productivity. The continuous fermentation with cell recycle was successfully used in the separation of cells from fermentation broth with enhancement of mixing in the tower fermentor.