• 전기화학회지
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• 제6권1호
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• pp.28-35
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• 2003

상용 유체 전산모사 코드인 FLUENT ver.6.0을 이용하여 직접 메탄을 연료전지의 전기화학적 해석 및 유로 내에서의 유체의 유동특성을 분석하였다 본 전산모사를 통해 유로 내의 유속, 압력, 온도, 농도 및 전류밀도 분포에 대한 다양한 정보를 얻을 수 있었으며, 유로 디자인에 따른 반응물 및 생성물의 유동에 대한 정보로부터 최적의 유로 형태를 결정할 수 있었다. 이와 같은 전산모사 방법을 사용하면 직접 메탄을 연료전지의 전극과 분리판 유로의 구조를 최적화하는데 매우 유리하다.

• 공업화학
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• 제32권4호
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• pp.442-448
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• 2021

고분자전해질 연료전지에서 분리판 유로 형상은 유체 공급과 물 및 열 확산, 접촉 저항 등에 영향을 주는 중요한 요소이다. 본 연구에서는 25 cm² 단위 전지를 이용하여 공기극에 구리폼을 적용한 분리판을 이용하여 연료전지 성능 평가를 수행하였다. 압력과 상대습도 조건에 대한 영향을 분극 곡선과 전기화학적 임피던스 분광법을 이용하여 분석하였다. 구리폼의 ohmic 저항이 높아 사형유로형상 보다 연료전지 성능은 낮았지만, 다공성 구조로 인한 균일한 연료 분포로 활성화 손실과 물질전달 손실이 적은 것을 확인하였다. 구리폼의 소수성이 높아 물 배출이 유리한 장점이 있지만, 저가습 조건에서는 사형유로에 비하여 전해질막 수화도가 낮은 것을 확인하였다. 다공성 금속 분리판은 균일한 압력 분포와 효과적인 수분 배출로 연료전지 성능을 개선할 수 있을 것으로 판단되며, 저항을 최소화할 수 있도록 금속폼의 물성에 대한 연구가 수행되어야 할 것이다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.358-358
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• 2012

The application of BZO (Boron-doped Zinc Oxide) films use as the TCO(Transparent Conductive Oxide) material for display and solar cell industries, where the conductivity of the BZO films plays a critical role for improvement of cell performance. Thin BZO films are deposited on glass substrates by using RF sputter system. Then charging flow rates of O2 gas from zero to 10 sccm, thereby controlling the impurity concentration of BZO. BZO deposited on soda lime glass and RF power was 300 W, frequency was 13.56 MHz, and working pressure was $5.0{\times}10-6$ Torr. The Substrate and glass between distance 200 mm. We measured resistivity, conductivity, mobility by hall measurement system. Optical properties measured by photo voltaic device analysis system. We measured surface build according to oxygen flow rate from XPS (X-ray Photoelectron Spectroscopy) system. The profile of the energy distribution of the electrons emitted from BZO films by the Auger neutralization is measured and rescaled so that Auger self-convolution arises, revealing the detail structure of the valence band. It may be observed coefficient ${\gamma}$ of the secondary electron emission from BZO by using ${\gamma}$-FIB (Gamma-Focused Ion Beam) system. We observed the change in electrical conductivity by correlation of the valence band structure. Therefore one of the key issues in BZO films may be the valence band that detail structure dominates performance of solar cell devices. Demonstrating the secondary electron emission by the Auger neutralization of ions is useful for the determination of the characteristics of BZO films for solar cell and display developments.

• 설비공학논문집
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• 제24권10호
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• pp.739-744
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• 2012

This paper describes the blower performance used for single-stage high pressure regenerative blower. The blower considered is widely applied to the field of a fuel cell system, a medical equipment and a sewage treatment plant. Flow rate and rotating frequency of a impeller of the blower are considered as design parameters for the proper operation of the blower. Three-dimensional Navier-Stokes equations are introduced to analyze the performance and internal flow of the blower. Relatively good agreement between experimental measurements and numerical simulation is obtained. Throughout a numerical simulation, it is found that small and stable vortical flow generated inside the blade passage is effective to increase pressure and efficiency of the blower. Large local recirculation flow having low velocity in the blade passage obstructs the generation of stable vortical flow, thus increases the pressure loss of the blower. Detailed flow field inside the blower is also analyzed and discussed.

• 한국환경과학회지
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• 제7권3호
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• pp.349-360
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• 1998

Effects of uniform flow on a two-dimensional mesoscale horizontal convection were investigated by using the vorticity and thermodynamic equations. For thins purpose, We simulated properties of a thermal convection m a stably stratified Boussinesq flued caused by partial heating at the center of a lower boundary If we don't consider effects of the uniform flow, the convection takes the form of aidsymmetrlc with respect to the z-alds. But when uniform flow Is strong, velocity field and temperature field consist of a sin91e cell structure which spreads upstream side of the partial heating area. The flow pattern for strong uniform flows takes the form of positive temperatue near the ground and negative temperature perturbation soft over the partial heating area, and downward motion directly over the upwind portion of the partial heating area and upward motion on the downstream side. The downstream edge of the upstream cell Is shifted in the downstream direction with the Increase of uniform flow almost linearly.

• 전기화학회지
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• 제15권2호
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• pp.74-82
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• 2012

고분자전해질 연료전지의 성능은 매우 복잡한 물리 현상들에 의해 변화하게 된다. 반응면적이 25 $cm^2$인 5-pass, 4-turn 사행성 유동유로의 립 부분에 보조유동유로를 가지는 형상에 대하여 물관리 측면에서의 연료전지 성능을 수치해석을 통해 비교하였다. 보조유동유로를 추가함에 따라 촉매층 공급 대류의 유동 방향이 변경되어 유로 내부의 물 배출 특성을 향상시키는 결과를 나타내었다. 또한 입구에서의 공급기체를 보조유동유로로 분산시킴에 따라 입구에서의 전류 밀도는 낮아지며 보조유동유로로 이동하는 공급기체들은 주 유동유로의 내에서의 체류시간보다 길어져서 전체적인 전류밀도 분포가 균일해지는 것을 확인하였다.

• Korea-Australia Rheology Journal
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• 제19권3호
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• pp.157-164
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• 2007

Microencapsulation of cells within microfluidic devices enables explicit control of the membrane thickness or cell density, resulting in improved viability of the transplanted cells within an aggressive immune system. In this study, living cells (3T3 and L929 fibroblast cells) are encapsulated within a semi-permeable membrane (calcium crosslinked alginate gel) in two different device designs, a flow focusing and a core-annular flow focusing geometry. These two device designs produce a bead and a long microfibre, respectively. For the alginate bead, an alginate aqueous solution incorporating cells flows through a flow focusing channel and an alginate droplet is formed from the balance of interfacial forces and viscous drag forces resulting from the continuous (oil) phase flowing past the alginate solution. It immediately reacts with an adjacent $CaCl_2$ drop that is extruded into the main flow channel by another flow focusing channel downstream of the site of alginate drop creation. Depending on the flow conditions, monodisperse microbeads of sizes ranging from $50-200\;{\mu}m$ can be produced. In the case of the microfibre, the alginate solution with cells is extruded into a continuous phase of $CaCl_2$ solution. The diameter of alginate fibres produced via this technique can be tightly controlled by changing both flow rates. Cell viability in both forms of alginate encapsulant was confirmed by a LIVE/DEAD cell assay for periods of up to 24 hours post encapsulation.

• Asian Pacific Journal of Cancer Prevention
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• 제14권12호
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• pp.7645-7649
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• 2013

Background: Immune functions and their relation to prognosis in breast cancer patients have become areas of great interest in recent years. Correlations between survival outcomes and peripheral blood flow cytometry parameters are therefore of interest. Here we focused on patients with non-metastatic breast cancer (BC). Materials and Methods: A total of 29 patients with pathological confirmed breast carcinoma and flow cytometry data were assessed for overall survival (OS) and progression free survival (PFS). Results: The median age of the patients was 54 years (range, 29-83). Multivariate analysis revealed that OS was significantly associated with absolute cytotoxic T cell count (95%CI, coef 2.26, p=0.035), tumor size (95%CI, coef -14.5, p 0.004), chemotherapy (95%CI, coef 12.9, p 0.0001), MFI of CD4 (95%CI, coef -5.1, P 0.04), MFI of HLA DR (95%CI, coef -5.9, p 0.008) and tumor grade (95%CI, coef -13, P 0.049) with R-Sq(adj)=67%. Similar findings were obtained for PFS. Conclusions: OS and PFS were significantly associated with tumor grade, tumor size, chemotherapy, MFI of CD4, HLA DR and absolute cytotoxic T cell count. The study revealed that MFI of basic CD markers and absolute cytotoxic T cell number may be a prognostic factors in women with non-metastatic BC.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.147-151
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• 2007

A serpentine channel geometry often used in a polymer electrolyte membrane fuel cell has a strong pressure gradient between adjacent channels in specific regions. The pressure gradient helps some amount of reactant gas penetrate through a gas diffusion layer(GDL). As a result, the overall serpentine flow structure is slightly different from intention of a designer. The purpose of this paper is to examine the effect of serpentine flow structure on current density distribution. By using a commercial code, STAR-CD, a numerical simulation is performed to analyze the fuel cell with relatively high aspect ratio active area. To increase the accuracy of the numerical simulation, GDL permeabilities are measured with various compression conditions. Three-dimensional flow field and current density distribution are calculated. For the verification of the numerical simulation results, water condensation process in the cathode channel is observed through a transparent bipolar plate. The result of this study shows that the region of relatively low current density corresponds to that of dropwise condensation in cathode channels.

• 대한기계학회논문집
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• 제17권1호
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• pp.182-189
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• 1993

본 연구에서는 한곳에 적응효과가 중복되는 것을 피하고 해의 변화율이 상대 적으로 큰 곳에 대해 대등한 격자 적응효과를 주는 방법을 연구하였다. 전 유동장에 서 해의 변화율을 계산하여 하한값(threshold) 보다 큰 값을 갖는 cell에 대해 같은 크기의 가중함수(weight function) 값을 갖게 한다. 하한값(threshold)은 전체 cell 수에 대해 상위의 변화율을 갖는 cell의 백분율(percentage)로부터 구한다. 이 방법 은 하한값을 직접 대입해야 한다는 단점은 있으나 변황율이 상대적으로 큰 영역에 대 해 고른 격자 적응 효과를 줌으로 해서 격자 적응의 회수를 줄일 수 있으며 해의 발달 에 긍정적인 격자를 생성할 수 있다.