• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.321-326
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• 2022

As the thickness of the polymer membrane of PEMFC(Proton Exchange Membrane Fuel Cells) is getting thinner for PEMFC performance and price reduction, research on improving durability has become more important. In the durability evaluation of membranes, the mechanical durability evaluation time is more than twice that of the chemical durability evaluation time, so it is necessary to select the durability evaluation conditions well. In this study, we tried to check how much the mechanical durability evaluation time changes when there is a difference in the inflow gas type and flow rate in the mechanical durability evaluation protocol (Wet/Dry). When nitrogen was used at a flow rate of 2,000 mL/min, the evaluation time increased by 1.25 times compared to when air was used. An increase in the degradation rate of the electrode Pt was the main factor when air was used. When the flow rate was reduced to 800 mL/min, the air and nitrogen evaluation times increased by 1.5 times and 1.2 times, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.95-101
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• 2015

This paper presents experimental results about characteristics of soil discharge as a function of moisture content when the $1.2/50{\mu}s$ lightning impulse voltage is applied. The laboratory experiments, for this study, were carried out based on factors affecting the transient behavior in soils. The electrical breakdown in soils was measured over a 0-6% range of moisture content for sands and a 0-4% range of moisture content for gravels. Needle-plane electrode systems was used As a result, the conduction current prior to ionization growth in dry soil is a little, but it in wet soil is increased with the applied voltage because the wet soil particles act as conductors. The soil impedance curves show an abrupt reduction just after breakdown. The general tendency measured in different soils is that the higher the water content, the lower the breakdown voltage and the shorter the time-lag to breakdown.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.98.2-98.2
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• 2011

For optimal performance of a proton exchange membrane fuel cell (PEMFC), the membrane electrode assembly (MEA) requires hydration, and the membrane's conductivity depends on water content. A humidifier is required to ensure that the reactant gas, usually hydrogen and air, is hydrated before entering the fuel cell. Dry membrane operation or improper hydration causes performance degradation. Typically, the humidification of a fuel cell is carried out by means of an internal or external humidifier. A membrane humidifier is applied to the external humidification of transportation or residential power generation fuel cell due to its convenience and high performance. In this study, The experiments were constructed with a plate-type membrane humidifier in terms of geometric parameters and operating parameters. The results show that the temperature and pressure, the channel length, the membrane thickness and gas flow rate are critical parameters affecting the performance of the humidifier.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.275-278
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• 2001

Ferroelectric PZT thin films were fabricated on the RuO$_2$/Pt, Pt bottom electrode with a PZT(53/47) metal alkoxide solutions. All PZT thin films showed a uniform grain structure without the presence of rosette structure. The PZT thin films were etched as a function of Cl$_2$/Ar and additive CF$_4$ into Cl$_2$(80%)/Ar(20%). The etch rates of PZT thin films were 1970 ${\AA}$/min at 30 % additive CF$_4$ into Cl$_2$(80%)/Ar(20%). The remanent polarization and leakage current density in PZT thin film on the RuO$_2$/Pt were 64.2 ${\mu}$C/cm$^2$, 1.4${\times}$10$\^$-6/ respectively.

• Korean Journal of Crystallography
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• v.2 no.2
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• pp.32-40
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• 1991

The effects of compositional variation, rotation speel and pulling rate on the growth of optical quality Bi120e02(1 crystals were examined. It was found to flatten the shape of crystal-melt interface for yowing a single crystals less than about 30mm in diameter at the rotation speed of 50rpm. Diameter of crystals with flat interface was increased as the pulling rate. The precipitation of Bi40e3012 phase set limits to pulling rate of BGO crystals. Precipitate-free BGO crystals were grown under pulling rate of 2mm l hr which released the stress resulted from too hi어 Pulling rate, and from 6. IBi203·GeO2 batch composition obtained by addition of 0.1 mole Bi203 into Bi-deficient melts to fill up the deficiency resulted from gradual volatilization of Bi2O). The pale-yellow colored crystals had good quality in that dislocation density was less than 103pits/cm, and it also exhibited transmittance of 70% and optical activity of 23°/mm. and SAW velosity was measured 1700m/sec on 111 cut 110 propagating BGO crystals. The SAW filter with electrode thickness of 9.8um was fabricated by using the electron beam and dry etching technique, it makes Bi12GeO20 devices intersting for color TV IF with half device size.

• KSBB Journal
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• v.13 no.1
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• pp.71-76
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• 1998

Tissue biosensor for mearsuring sodium channel blockers, such tetrodotoxin(TTX), saxitoxin (STX) and paralytic shellfish poisoning(PSP) consisted of frog bladder membrane, and $Na^{+}$ electrode. The proposed biosensor was applied to determine Chinese drug and dry or wet Porphyra yezonesis $Na^{+}$ channel blockers below the detection limit of the standard mouse bio-assay while the observed detection limit didn't cause human poisoning. The proposed biosensor system may be used for future $Na^{+}$ channel blockers monitoring within the marine environment.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.425-432
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• 2002

This study was carried out to develop an automatic mixing system of nutrient solution for closed-loop hydroponics using ion electrodes. The results of the study are summarized as follows: 1. It appeared that ion-electrodes had not to be soaked into nutrient solution for a long time since it was much less durable than EC or PH sensors. Once ion-electrodes were soaked into real nutrient solution for a long time, they became unstable. 2. ion measurement modules, which were able to sample recirculated nutrient solution and easily wash and dry ion-electrodes, were developed in order to use ion-electrodes continuously. 3. The results of calibration tests on three kinds of ion electrodes presented that the time required to read measurement data was over 30 seconds. Using the calibration data the regression equations for the ion electrodes were developed. 4. An automatic nutrient-solution mixing system using the three kinds of ion electrodes was developed and then its accuracy was examined. The control errors of the mixing system using ion electrodes were in the range of 9.8 to 12%.

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2365-2370
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• 2009

A working electrode in dye-sensitized solar cells was fabricated using $TiO_2$ colloidal sol prepared from titanium isopropoxide used as a starting material by applying the sol-gel method. The effect of aging times and temperatures on physical and chemical properties of $TiO_2$ sol particles was systematically investigated. Results showed that the crystallinity and average particle size of $TiO_2$ colloidal sol can be successfully controlled by the adjustment of aging time and temperature. The conversion efficiency of the repetitive dry coating films fabricated using the dried $TiO_2$ colloidal sol particles and hydroxypropyl cellulose binder (15%) was 10.31% with a high transparency.

• Fisheries and Aquatic Sciences
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• v.15 no.3
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• pp.203-207
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• 2012

The amount of fluoride removed from Antarctic krill via organic acid extraction depends on the extraction time, concentration, extraction volume, and the nature of the acid itself. The fluoride content in Euphausia superba was determined by measuring the concentration of fluoride ion in acidic extracts using an ion-selective electrode. The best results were obtained by adding 50 mL of 0.01 M citric acid to 0.3-0.5 g of krill and extracting for 5 min. Under these conditions, recoveries of fluoride from frozen whole krill and krill meat were 95.6-99.5% and 97.5-101.3%, respectively. The dry basis fluoride contents of krill by-product, krill meat and the boiled krill were 705, 298, and 575 ppm, respectively. These levels were significantly reduced by citric acid extraction.

• Journal of Electrochemical Science and Technology
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• v.1 no.1
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• pp.10-18
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• 2010

Controlled electrodeposition of dendritic nano-structured gold-platinum (AuPt) alloy onto an electrochemically pretreated carbon paper substrate was conducted in an attempt to improve catalyst utilization and to secure an electronic percolation network toward formic acid (FA) fuel cell application. The AuPt catalysts were obtained by potentiostatic deposition. AuPt catalysts synthesized as bimetallic alloys with 60% Au content exhibited the highest catalytic activity towards formic acid electro-oxidation. The origin of this high activity and the role of Au were evaluated, in particular, by XPS analysis. Polarization and stability measurements with 1 mg $cm^{-2}$ AuPt catalyst (only 0.4 mg $cm^{-2}$ Pt) showed 52 mW $cm^{-2}$ and sustainable performance using 3M formic acid and dry air at $40^{\circ}C$.