• 한국수소및신에너지학회논문집
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• 제20권4호
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• pp.283-290
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• 2009

This study focuses on the performance characteristics of polymer electrolyte membrane fuel cell (PEMFC) using the AC impedance technique. The experiment was carried out to investigate the optimal operating conditions of PEMFC such as cell temperature, flow rate, humidified temperature and back-pressure. The fuel cell performance was analyzed by DC electronic-loader with constant voltage mode and expressed by voltage-current density. Additionally, AC impedance was measured to analysis of ohmic and activation loss and expressed by Nyquist plot. The results showed that the cell performance increased with increase of cell temperature, air flow rate, humidified temperature and backpressure. Also, the activation loss decreased as the increase of cell temperature, air flow rate, humidified temperature and backpressure.

• 한국정밀공학회지
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• 제22권8호
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• pp.159-164
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• 2005

The Hot Embossing Lithography(HEL) as a method fur the fabrication of the nanostructure with polymer is becoming increasingly important because of its simple process, low cost, high replication fidelity and relatively high throughput. In this paper, we carried out experimental studies and numerical simulations in order to understand the viscous flow of the polymer (PMMA) film during the hot embossing process. To grasp the characteristics of the micro patterning rheology by process parameters (embossing temperature, pressure and time), we have carried out various experiments by using the nickel-coated master fabricated by the deep RIE process and the plasma sputtering. During the hot embossing process, we have observed the characteristics of the viscoelastic behavior of polymer. Also, the viscous flow during the hot embossing process has been simulated by the continuum based FDM(Finite Difference Method) analysis considering the micro effect, such as a surface tension and a contact angle.

• E2M - 전기 전자와 첨단 소재
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• 제10권8호
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• pp.770-777
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• 1997

Some polymer materials including epoxy resin are being instead of porcelain for outdoor insulating materials such as insulators bushings cable terminators and surge arrester housing. And the largest problem to be overcomed is the tracking and erosion of the outdoor polymer material brought about by dry band arcing during prolonged exposure to contaminations. In this paper the effect of surface tension wettability flow rate of contaminants with varying surfactant content and frequency of applied voltage on the tracking breakdown of epoxy insulating materials were investigated. As the flow rate of contaminant is increased the surface resistivity is decreased and the leakage current is increased the time to tracking breakdown is decreased. It is found that time to tracking breakdown depends on the surface tension of contaminant that is difference of wettability. And as the frequency of applied voltage is increased time to tracking breakdown decreased.

• 태양에너지
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• 제19권3호
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• pp.1-11
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• 1999

Previous researchers have studied how to reduce a pumping power in order to save energy in the fluid transporting system. Especially, it has been studied a lot about reducing the pressure drop among parameters related to the energy saving for fluid transport. This study is to investigate the effect of a substantial drag reduction caused by the polymer(A611P, A601P) when the working fluids flow to the vertical and horizontal direction in the vertical cylindrical equipment of closed flow system. In this experiment, we mount a visualization equipment on the test section and take pictures. With using the PIV system, instrument and analyzing the movement of bubble for different polymer concentration are observed and some mechanism of the drag reduction effect is clarified.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 봄 학술발표회 논문집
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• pp.87-92
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• 1991

Since the material property of binder in polyester polymer concrete has a viscous mechanism, the workability of polyester polymer concrete mixture showed different characteristics from that of cement concretes. Therefore, this study was devised to evaluate workability characteristics of polyester polymer concrete using slump and flow tests. Study results showed that the test temperature and ST/UP ratio were the most dominantly affecting factor on the viscosity of binder, and viscosity of the binder was strongly correlated with the workability of polyester polymer concrete mixture.

• 한국공작기계학회논문집
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• 제11권5호
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• pp.81-87
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• 2002

The existing compressor steel seal used in automotive air-conditioner has the problem of oil leakage and deterioration in shielding performance, due to the abrasion and corrosion of the material. A new type of polymer resin seal studied in this research has the characteristics of high anti-abrasiveness and anti-corrosiveness, which can oversome the defects of the steel seal. In addition, the seal needs lower manufacturing cost and is appropriate to mass production, because it is made by the injection molding method requiring no mechanical processing. The profile generation program for seal mold has been developed using the gradient method, and the molding characteristics of the seal have analyzed through the flow analysis and the warpage analysis. The program has been verified by comparing the analysis results with the measured data of the test product. The research might be said to provide the basic method to produce the polymer resin seals with various types and dimensions.

• 태양에너지
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• 제19권1호
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• pp.37-45
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• 1999

As polymer added in flow, the phenomenon of drag reduction effect was found by many experiments and studies. We divided polymer into three molecular weight($2{\times}10^5,\;4{\times}10^5,\;5{\times}10^5$) and into four concentration(1, 5, 10, 20wppm), then we measured the drag reduction effect in the range Reynolds Number with $30000{\sim}60000$. Finally we found that the most effect drag reduction was that molecular weight is $2{\times}10^5$ with 10wppm concentration. Then the concentration was according to PEO molecular weight, and in general DR increase according to Reynolds Number.

• 반도체디스플레이기술학회지
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• 제12권2호
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• pp.19-25
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• 2013

Extrusion is one of the most important operations in the polymer-processing industry. Balancing the distribution of flow through a die to achieve a uniform velocity distribution is the primary objective and one of the most difficult tasks of extrusion die design. If the manifold in a coat-hanger die is not properly designed, the exit velocity distribution may be not uniform; this can affect the thickness across the width of the die. Yet, no procedure is known to optimize the coat hanger die with respect to an even velocity profile at the exit. While optimizing the exit velocity distribution, the constraint optimization used in this work with allowable pressure drop in the die; according to this constraint we can control the pressure in the die. The computational approach incorporates three-dimensional finite element simulations software STAR-CCM+. These simulations are used with numerical optimization to design polymer coat hanger dies with pressure drop, uniform velocity and temperature variation across the die exit.

• 폴리머
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• 제35권3호
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• pp.254-259
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• 2011

고분자 용액의 전기분무에서 금속 샘플 포집기들은 분무된 입자로부터 흔히 용매를 충분히 제거하거나 재분산이 가능한 분무 입자를 회수하는데 효과적이지 못하다. 단백질 약물의 캡슐화(encapsulation)를 위해 본 연구에서는 입자를 분산매(응고액제)의 층류 안으로 분무하는 새로운 전기분무시스템을 설계하였다. 캡슐화용 물질로 키토산과 폴리아크릴산이 사용되었다. 이 새로운 시스템을 사용하여 입자의 응집을 방지할 수 있었으며, 4~16 kV의 전압과 같은 유속에서 unimodal한 입도분포를 관찰할 수 있었다. 반면에 가한 전압이 평균 입자 크기에 미치는 영향은 크지 않았다.

• 설비공학논문집
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• 제13권3호
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• pp.194-199
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• 2001

The turbulent flow resistance of water solution with polymer is reduced as compared with that of pure water. This effects is named th drag reduction and offers the significant reduction of the pumping power and the energy consumption. But the intense shear forces and the high temperature experienced by the polymer solution when passing through the pipes cause the degradation a loss of drag reduction effectiveness. Especially, the degradation behavior is found to be strongly dependent on temperature. This mechanical and thermal degradation can be avoided by adding materials such as surfactant to the polymer solution, which enhance the bonding force between molecules. In the present study, Copolymer and SDS were utilized and they were mixed in 10 different mixture ratios, while total concentration was fixed as 100wppm. Degradation of Copolymer-SDS mixture solutions was investigated experimentally in closed loop at the temperature of $10^{\circ}C\; and\; 80^{\circ}C$ with various flow average velocities of 1.5 m/sec, 3.0m/sec, and 4.5m/sec. Degradation characteristics of polymer solution without surfactant show a radical loss of drag reduction effectiveness at high temperature. Degradation alleviation ability of surfactant is especially effective at high temperature. Consequently, this results show that the addition of surfactant to the polymer solution can control unfavorable degradation phenomena for high temperature systems.