• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1876-1878
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• 1999

Developed was a 5kW-class polymer electrolyte membrane fuel cell(PEMFC) system comprised of fuel cell stack, fuel processing, thermal and water management subsystems and ancillary equipments. Several large single cells have been fabricated with different gas flow field patterns and paths, and the gas flow field pattern for the stack has been determined based on the single cell performance of thin film membrane electrode assembly (MEA). The PEMFC stack was consisted of 100 cells with an electrode area of $300cm^2$, having serpentine flow pattern. Fuel processing was developed including an autothermal methanol reformer and two preferential CO oxidation reactors. The fuel processing was combined to PEMFC operation system consisted of air compressor and thermal and water management subsystems. The PEMFC stack showed performance of 5kW under the supply of $H_2$ and air, but its performance was lowered to 3.5kW under the supply of reformed gas.

• KSBB Journal
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• 제11권1호
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• pp.52-57
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• 1996

평활근 세포에 대한 shear stress의 영향을 알아보기 위해 슬라이드 글라스위에 배양된 牛 대통맥의 평활근 세포를 120시간 동안 0~26 dyn/$cm^2$의 각기 다른 일정한 shear stress의 유체에 노출하였다. 실험 장치를 순환하는 배지의 lactate dehydrogen­a ase의 농도측정 결과, 본 연구에서 적용된 shear stress 범위에서는 유체의 흐름으로 인하여 세포가 슬라이드 글라스 표면으로부터 이탈되는 현상은 없었다. 표면 $cm^2$ 당 존재하는 세포의 수를 측정한 결과, 평활근 세포는 정체배양시 가장 빨리 성장하였다. 표변에서의 shear stress가 증가할수록 i영활근 세포의 성장은 늦었으며, shear stress가 17 dyn/$cm^2$ 이상에서는 세포의 성장이 관찰되지 않았다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.90.2-90.2
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• 2011

This paper describes performance enhancement of a fuel cell's blower by controlling flow path. Different duct diameter at the inlet and outlet of the blower is selected for reducing blower noise level and input power. Hole diameter and the number of hole at the check valve are tested to reduce the input power of the blower. Two types of blower, fuel pressurized blower and cathode blower, are considered in the present study. Throughout experimental measurements of the test blowers, it is found that duct diameter is effective to reduce noise level and input power in the fuel cell blower. Noise reduction due to the optimal duct diameter at the outlet is more effective when flow rate is relatively large. That is, cathode blower has larger noise reduction compared to fuel pressurized blower because of larger flower rate. Input power of the blower can be reduced by controlling the hole diameter and the number of hole at the check valve.

• 약학회지
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• 제44권2호
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• pp.149-154
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• 2000

Flavin mononucleotide (1,4-butanediamine) Pt(II) complex (7FMN) was synthesized and screened anticancer activity [J. Pharm. Soc. Korea 43(6),762-770 (1999)]. 7FMN have good water solubility and moderate anticancer activiy In this paper cell-cycle specificity and nephrotoxicity were studied. Interaction of DNA with cisplatin and synthesized 7FMN was analyzed by flow cytometry and showed G2 arrest in L1210 cell line. It means that cell-cycle on L1210 was inhibit in S phase by cisplatin and 7FMN. In order to biochemically analyze nephrotoxicity of cisplatin and 7FMN, after injecting each agent intraperitoneally, blood was exsanguinated after 6 hours, 1 day, 3 days and 7 days, respectively. Then, serum was separated from the blood. The serum level of BUN, creatinine and uric acid in cisplatin and 7FMN administated mice (25~35 g, ICR strain, a dose each 8,12 and 16 times of the $IC_{50}$/ value, cisplatin; 7 times) were determined by autochemistry analyzer. In cisplatinadministered mice group, BUN level was elevated than normal control group at 3rd day and repaired at 7th day. In 7FMN administrated group was not elevated. Creatinine and uric acid level were no difference with the normal control group. Therefore synthesized 7FMN is less toxic than cisplatin in nephrotoxiciaty.

• 한국동물번식학회:학술대회논문집
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• 한국동물번식학회 2001년도 춘계학술발표대회
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• pp.69-69
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• 2001

The cell cycle phase in which donor nuclei exist prior to nuclear transfer is an important factor governing developmental rates of reconstituted embryos. It was suggested that quiescent G0 and cycling G1 cells could support normal development of reconstituted embryos. In a quest of optimized donor nuclei treatment prior to nuclear transfer, this study was undertaken to examine the cell cycle characteristics of bovine fetal and adult somatic cells when cultured under a variety of culture treatments and the cell cycle change with the lapse of time after trypsinization. This was archived by measuring the DNA content of cells using flow cytometry, Cultured fetal fibroblast cells, adult skin and muscle cells, and cumulus cells were divided by 3 culture treatments; 1) grown to 60-70% confluency (cycling), 2) serum starved culture, 3) culture to confluency. Trypsinized cells were fixed by 70% ethanol and stained with propidium iodide. For one experiment, trypsinized cells were resuspended in DMEM＋10% FBS and incubated for 1.5, 3 and 6 h with occasional shaking before ethanol fixation. Cell cycle phases were determined by flow cytometry enabling calculation of percentages of G0＋G1, S and G2＋M. The majority of cells were in G0＋Gl stage regardless of origin of cells. Cultures that were serum starved or cultured to confluency contained significantly (P<0.05) higher percentages of cells in G0＋G1 (89.5-95.4%). For every cell lines and culture treatments, percentages of cells in existing in G0＋G1 increased with decreasing of the cell size from large to small. In the serum starved and confluency groups, about 98% of small cells were in G0＋G1 Serum starved culture contained higher percentages of small-sized cells (38.5-66.9%) than cycling and confluent cultures regardless of cell lines (P<0.05). After trypsinization of fetal fibroblast and adult skin cells that were serum starved and cultured to confluency, the percentages of cells in G0＋G1 significantly increased by incubation for 1.5(95.7-99.5%) and 3.0 h (95.9-98.6%). The results suggest that the efficient synchronization of bovine somatic cells in G0＋G1 for nuclear transfer can be established by incubation for a limited time period after trypsinization of serum starved or confluent cells.

• Journal of Power Electronics
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• 제11권2호
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• pp.194-201
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• 2011

The air flow supplied to a fuel cell system is one of the most significant factors in determining fuel efficiency. The conventional method of controlling the air flow is to fix the oxygen supply at an estimated constant rate for optimal efficiency. However, the actual optimal point can deviated from the pre-set value due to temperature, load conditions and so on. In this paper, the maximum efficiency point tracking (MEPT) algorithm is proposed for finding the optimal air supply rate in real time to maximize the net-power generation of fuel cell systems. The fixed step MEPT algorithm has slow dynamics, thus it affects the overall efficiency. As a result, the variable step MEPT algorithm is proposed to compensate for this problem instead of a fixed one. The complete small signal model of a PEM Fuel cell system is developed to perform a stability analysis and to present a design guideline. For a design example, a 1kW PEM fuel cell system with a DSP 56F807 (Motorola Inc) was built and tested using the proposed MEPT algorithm. This control algorithm is very effective for a soft current change load like a grid connected system or a hybrid electric vehicle system with a secondary energy source.

• 대한수의학회지
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• 제39권1호
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• pp.169-176
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• 1999

The purposes of this study were to set up the method of the natural killer(NK) cell activity assay using the flow cytometer and to examine the characteristics and distribution of the NK cell during rat hepatocarcinogenesis. Forty five male 6 week-old specific pathogen free(SPF) Sprague-Dawley rats were randomly divided into three groups. Group I was the non-treated control and given normal diet and water. Group II was treated with diethylnitrosamine(DEN, 200mg/kg, i.p.) and partial hepatectomy. Group III was treated with DEN, partial hepatectomy and 0.05% phenobarbital sodium in water from 3 to 16 weeks. All animals were examined the morphology of the large granular lymphocyte(LGL), the LGL percent of the total lymphocytes and the LGL conjugation rate with YAC-1 cell in peripheral blood, spleen and liver. Moreover, activity of the LGL isolated from peripheral blood lymphocytes was determined using the flow cytometer. As results, LGL were observed in the peripheral blood, spleen and liver. LGL were observed the relatively faintly staining basophilic cytoplasm with granules, and eccentric, often kidney-shaped nuclei in Giemsa stain. Its size was $11{\sim}13{\mu}m$. LGL percentage of the isolated lymphocytes in peripheral blood, spleen and liver were 1.8~2.3%, 1.3~1.4% and 0.87~0.99%, respectively. LGL conjugation rate with YAC-1 cell was shown to be peripheral blood(9.3~10.3 %) > spleen(7.7~8.7%) > liver(5.6~7.0%). The activity of the LGL isolated from peripheral blood lymphocytes in Group I, II and III was 33.7%, 30.5% and 35.4%, respectively. However, all values were not significantly between groups.

• 대한한의학회지
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• 제20권1호
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• pp.91-105
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• 1999

The effects of Yinjin and Yinjinsaryongsangagambang on a DNA damaging agent, etoposide-induced apoptosis, cell viability, cell cycle progression, and mRNA expression of apoptosis-related genes of human hepatocyte cell line HepG2 were investigated using tryphan blue exclusion assay, MTT assay, flow cytometry, immunocytometric analysis of PCNA, and quantitative RT-PCR analysis. MTT assay showed that Yinjin and Yinjinsaryongsangagambang increases cellular viability of HepG2 cells in a dosage-dependent manner. Stimulation of cell cycle progression by Yinjin or Yinjinsaryongsangagambang was detected by flow cytometric analysis of the DNA content and immunocytometric analysis of PCNA expression. A significant reduction of a DNA-damaging agent, etoposide-induced apoptosis were found in both Yinjin and Yinjinsaryongsangagambang-treated cells in dosage-dependent manner. In overall, 3-fold reduction of apoptosis was recognized in $10.0\;{\mu}g/ml$ of Yinjin or Yinjinsaryongsangagambang-treated cells compared to untreated cells. Although the difference is not significant, Yinjinsaryongsangagambang showed slightly higher effect on the inhibition of apoptosis than Yinjin. From flow cytometric analysis of apoptosis, while 39.9% of untreated cells showed etoposide-induced apoptotic cell death, only 19.6% or 17.4% of Yinjin or Yinjinsaryongsangagambang-treated cells were fond at apoptotic sub G1 phase, respectively. Interestingly, strong induction of Gadd45-mRNA was observed from Yinjin or Yinjinsaryongsangagambang-treated cells. However, no changes in expression levels of p53 and Waf1 were detected, demonstrating that induction of Gadd45 mRNA expression by Yinjin or Yinjinsaryongsangagambang occurs by p53-independent mechanism. Marked mRNA inductions of two apoptosis-inhibiting genes, Bcl-2 and Bcl- XL, were found in both Yinjin or Yinjinsaryongsangagambang-treated HepG2 cells while no changes was detected in expression levels of an apoptosis-promoting gene, Bax.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2367-2369
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• 2004

It is well known that an indirect methanol based fuel cell system imposes a performance limitation on the fuel cell electric vehicle (FCEV) due to the reformer lag. An optional battery system can be used together with fuel cell to improve this performance limitation and it is called a fuel cell hybrid electric vehicle (FCHEV) this paper first describes the configuration of FCHEV with explanation of the energy flow between subsystems. Mathematical modeling of each subsystem such as a fuel cell system, a battery system, a driving motor with the transmission are formulated and coded using Matlab/simulink software. It is illustrated by simulation results that fuel cell modeling yields appropriate stack voltage in order to get the required current quantity with varying hydrogen flow.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.82.2-82.2
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• 2011

A channel design which is closely related with the mass transport overpotential is one of the most important procedures to optimize the whole fuel cell performance. In this study, three dimensional results of a numerical study for gas distribution in channels of a molten carbonate fuel cell (MCFC) unit cell for a 1kW class stack was presented. The relationship between the fuel and air distribution in the anode and cathode channels of the unit cell and the electric performance was observed. A charge balance model in the electrodes and the electrolyte coupled with a heat transfer model and a fluid flow model in the porous electrodes and the channels was solved for the mass, momentum, energy, species and charge conservation. The electronic and ionic charge balance in the anode and cathode current feeders, the electrolyte and GDEs were solved for using Ohm's law, while Butler-Volmer charge transfer kinetics described the charge transfer current density. The material transport was described by the diffusion and convection equations and Navier-Stokes equations govern the flow in the open channel. It was assumed that heat is produced by the electrochemical reactions and joule heating due to the electrical currents.