• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.494-497
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• 2006

For commercialization of polymer electrolytemembrane fuel cell (PEMFC), durability of membrane electrode assemblies (MEAs) has to be improved. Especially, long-term stability of MEA is one of the most important issues for frequent shut-down and start-up processes of PEMFC. The degradation of MEA could be attributed to chemical attack of hydrogen peroxide radicals that are formed at high cell voltages without any special treatment to remove residual hydrogen from anode gas channel after shut-down of the fuel cell. In this study, we investigated the long-term stability of MEA under different on/off operation conditions. Residential hydrogen gas was removed from the anode flow channel by purging air or nitrogen. Also, a dummy resistance was applied to the fuel cell to exhaust residential hydrogen at the anode. In these cases, MEA showed much more stable durability. Electrochemical characteristics of the fuel cell were measured byrepeating the on/off cycles with the hydrogen removal processes. Also, degradation of MEA components was examined by SEM, TEM and XRD analyses.

• Journal of Pharmaceutical Investigation
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• 제35권3호
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• pp.165-171
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• 2005

Itraconazole is a triazole antifungal agent to inhibit most fungal pathogens. However, it is difficult for itraconazloe to be delivered by topical system due to its poor aqueous solubility. First, niosomes containing drug were prepared with span 60, cholesterol. tocopherol and poloxamer 407 as vesicle forming agents in an effort to increase solubility of itraconazole. And then prepared niosomes were dispersed in O/W creams (containing xanthan gum, glycerin, vaseline, glyceryl monostearate and $Cerix^{\circledR}-5$) or gels (containing xanthan gum and poloxamer 407). Both creams and gels were evaluated with respect to their rheological properties, in vitro permeation through excised skin of hairless mouse. Creams or gels containing niosome showed pseudoplastic flow and hysteresis loop. For both creams and gels, viscosity was increased with increasing the content of glycerine or vaseline and the content of gel forming polymer, respectively. In creams, the permeability of drug to skin was decreased with increasing the viscosity of cream. The permeability of drug was affected by pH as well as viscosity of gel. In vitro permeation test results demonstrated that cream formulations showed better permeability than gels. In conclusion, these results suggest that creams formulation containing niosome can be useful for the topical delivery of intraconazole.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.183-187
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• 1997

The Thin films were obtained by plasma polymerization of phenyl isothiocyanate. Polymerizations were carried out in rf(13.56 [MHz]) glow discharge generated in an inter-electrode capacitively coupled gas flow system. It was fecund that this monomer produces uniform films with a wide range of thicknesses, from hundreds of nanometers to tens of micrometers. The deposition rate appeared to be dependent on the substrate distance from the monomer inlet. The IR data revealed significant decrease in -NCS groups content in the polymer as compared with the monomer spectrum and indicated for the appearance of new absorption bands corresponding to the -CN and C-H aliphatic groups. The soluble fraction by GC was found to be composed of numerous low molecular-weight compounds.

• ETRI Journal
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• 제35권6호
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• pp.1152-1155
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• 2013

A cost-effective and simple solder on pad (SoP) process is proposed for a fine-pitch microbump interconnection. A novel solder bump maker (SBM) material is applied to form a 60-${\mu}m$ pitch SoP. SBM, which is composed of ternary Sn3.0Ag0.5Cu (SAC305) solder powder and a polymer resin, is a paste material used to perform a fine-pitch SoP through a screen printing method. By optimizing the volumetric ratio of the resin, deoxidizing agent, and SAC305 solder powder, the oxide layers on the solder powder and Cu pads are successfully removed during the bumping process without additional treatment or equipment. Test vehicles with a daisy chain pattern are fabricated to develop the fine-pitch SoP process and evaluate the fine-pitch interconnection. The fabricated Si chip has 6,724 bumps with a 45-${\mu}m$ diameter and 60-${\mu}m$ pitch. The chip is flip chip bonded with a Si substrate using an underfill material with fluxing features. Using the fluxing underfill material is advantageous since it eliminates the flux cleaning process and capillary flow process of the underfill. The optimized bonding process is validated through an electrical characterization of the daisy chain pattern. This work is the first report on a successful operation of a fine-pitch SoP and microbump interconnection using a screen printing process.

• 한국수소및신에너지학회논문집
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• 제18권4호
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• pp.422-431
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• 2007

Polymer electrolyte membrane fuel cell(PEMFC) is very interesting power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, improvement of performance and effect of temperature. These problems can be approached to be solved by using mathematical models which are useful tools for analysis and optimization of fuel cell performance and for heat and water management. In this paper, the present work is to develop an electrochemical model to examine the electrochemical process inside PEM fuel cell. A complete set of considerations of mass, momentum, species and charge is developed and solved numerically with proper account of electrochemical kinetics. When depth of gas channel becomes thinner, diffusion of reactant makes well into gas diffusion layer(GDL) and the performance increases. Although at low current region there is little voltage difference between experimental data of PEM fuel cell and numerical data. When the porosity size of gas diffusion layer for PEM fuel cell is bigger, oxygen diffusion occurs well and oxygen mass fraction appears high in catalyst layer.

• 한국세라믹학회지
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• 제55권2호
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• pp.126-134
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• 2018

Using aqueous solution free radical polymerization with glacial acrylic acid (GAA), maleic anhydride (MA) and sodium methallyl disulfonate (SMADS), a novel linear polycarboxylate dispersant was synthesized for ceramics. Dispersant linear structural characterization was done by FTIR, $^1H$ NMR, HPLC and GPC, and the ratio of monomers was determined using an orthogonal experiment. This research is focused on the effects of polymerization temperature, monomer mole ratios and dosage of initiator on ceramic slurry viscosity with linear polycarboxylate dispersant for ceramic dosage rate of 0.30% (based on dry slurry), all of which were investigated by single factor test. The best polymerization conditions for linear GAA-MA-SMADS are when n(AA) : n(MA) : n(SMADS) equals 3.0 : 1.0 : 0.5, the molecular weight of the polymer is 4600 daltons, the initiator sodium persulfate accounts for 7% of the total mass of polymerized monomers, the polymerization temperature is $90^{\circ}C$ and the reaction time is 2 h. The ceramic body slurry viscosity drops from $820mPa{\cdot}s$ to $46mPa{\cdot}s$ when the concentration of the polycarboxylate dispersant is 0.30%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.892-895
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• 2003

This paper describes on RIE(Reactive Ion Etching) characteristics of 3C-SiC(Silicon Carbide) grown on Si(100) wafers. During RIE of 3C-SiC films in this work, $CHF_3$ gas is used to form of polymer as a side wall for excellent anisotropy etching. From this process, etch rates are obtained a $60{\sim}980{\AA}/min$ by various conditions such as $CHF_3$ gas flux, $O_2$ addition ratio, RF power and electrode distance. Also, approximately $40^{\circ}$ mesa structures are successfully formed at 100 mTorr $CHF_3$ gas flow ratio, 200 W RF power and 30 mm electrode distance. Moreover, vertical side wall is fabricated by anisotropy etching with 50% $O_2$ addition ratio and 25 mm electrode distance. Therefore, RIE of 3C-SiC films using $CHF_3$ could be applicable as fabrication process technology for high-temperature 3C-SiC MEMS applications.

• Journal of Electrochemical Science and Technology
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• 제9권2호
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• pp.93-98
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• 2018

$MnO_2$, a metal oxide used as an electrode material in electrochemical capacitors (EDLCs), has been applied in binary oxide and conducting polymer hybrid electrodes to increase their stability and capacitance. We developed a method for electrodepositing Mn-Ni oxide/PANI, Mn-Ni oxide/PEDOT, and Mn-Ni-Ru oxide/PEDOT films on carbon paper in a single step using a mixed bath. Mn-Ni oxide/PEDOT and Mn-Ni-Ru oxide/PEDOT electrodes used in an electro-osmotic pump (EOP) have shown better efficiency compared to Mn-Ni oxide and Mn-Ni oxide/PANI electrodes through testing in water as a pumping solution. EOP using a Mn-Ni-Ru oxide/PEDOT electrode was also tested in a 0.5 mM $Li_2SO_4$ solution as a pumping solution to confirm the effect of the $Li^+$ insertion/de-insertion reaction of Ruthenium oxide on the EOP. Experimental results show that the flow rate increases with the increase in current in a 0.5 mM $Li_2SO_4$ solution compared to that obtained when water was used as a pumping solution.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.778-784
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• 2001

Injection molding is a very important industrial process for the manufacturing of plastics objects. During an injection molding process of composites, the fiber-matrix separation and fiber orientation are caused by the flow of molten polymer/fiber mixture. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation orientation and injection molding conditions. So far, there is no research on the measurement of fiber orientation using image processing. In this study, the effects of fiber content ratio and molding condition on the fiber orientation-angle distributions are studied experimentally. Using the image processing method, the fiber orientation distribution of weld-line parts in injection-molded products is assessed. And the effects of fiber content and injection molding conditions on the fiber orientation functions are also discussed.

• 한국정밀공학회지
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• 제18권9호
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• pp.192-203
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• 2001

The design of gate and runner(delivery system) is one of the most important subject in injection molding. Delivery system is a channel to flow the polymer melt from the injection molding machine to the mold cavities. Also, delivery system affect quality and productivity of the part. The synthesis of delivery system of injection molding has been done empirically, since it requires profound knowledge about the moldability and causal effects on the properties of the part, which are not available to designers through the current CAD systems. GATEWAY is a knowledge module which contains knowledge to permit non-experts as well as mold design experts to generate the acceptable geometries of gate and runner far injection molded parts. A knowledge-based CAD system is constructed by adding the knowledge module, GATEWAY, to an existing geometric modeler. A knowledge-based CAD system is a new tool which enables the concurrent design and CIM with integrated and balanced design decisions at the initial design of injection molding.