• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.184-186
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• 2012

In this work, 3-dimensional, non-isothermal numerical simulation was performed to analyse the effects of contact resistance and electric conductivity of GDL on the fuel cell performance. For numerical simulation contact resistance of Carbon and Stainless steel was measured. The simulation results reveal that 10 times change of electric conductivity leads only 6.5% decrease of PEMFC performance. But stainless steel which has high contact resistance decrease fuel cell performance over 25% at a high current density region than carbon. This results show that suitable Surface treatment technology is needed for metal bipolar plate, especially stainless steel.

• Journal of the Korean Applied Science and Technology
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• v.23 no.2
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• pp.160-168
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• 2006

The conductances of trimethyltetradecylammonium bromide (TTAB) plus triphenyltetradecyl phosphonium bromide (TTPB) and TTAB plus trimethylhexadecylammonium bromide (HTAB) over the entire mole fraction range of TTAB were measured in water and in cyclodextrin plus water mixtures at fixed 4 and 8 mM of cyclodextrin at $30^{\circ}C$. The conductivity plot for both binary mixtures shows a single break from which the mixed critical micelle concentration and degree of micelle ionization were computed. From the slope of the conductivity curve, the equivalent ionic conductivities of the monomeric, associated, and the micelle states were calculated and discussed with respect to the surfactant-cyclodextrin complexation in the whole mole fraction range of both surfactant binary mixtures. The association constant K between the respective monomeric surfactant and cyclodextrin cavity of fixed 4 mM cyclodextrin was computed by considering 1:1 association from the surface tension measurement. A comparison among the K values for HTAB-cyclodetrin, TTAB-cyclodextrin, and TTPB-cyclodextrin shows that the former complexation is significantly stronger in comparison to the other ones due to the longer hydrophobic tail.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1426-1433
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• 2005

In this paper, reliability analysis of surface settlement by ground water drawdown is performed using a reliability-groundwater flow numerical model. The result is compared with that of the deterministic model to evaluate the influence of the uncertainty from hydraulic conductivity in the soft ground as well as to determine the range of hydraulic conductivity of grouted ground. From the analyses, it was found that probability of failure to exceed the tolerable settlement was very high, if the hydraulic conductivity of grouted ground is decided from the deterministic flow model only. Reliability analysis which evaluates variance of hydraulic conductivity should be used together with the deterministic model for grouting design of tunnels to prevent ground water drawdown.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.1
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• pp.17-22
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• 2011

The conventional coated paper has many functional problems for printed RFID tag. This study was carried out in order to evaluate the effect of coating color components on conductivity of printed coated paper. It has been well known that the efficiency of printed RFID tag is influenced by surface properties of substrate. The required properties for suitable substrate of printed RFID tag are high smoothness and waterproof property. In this study high grammage base paper surface sized with PVA was used. Coated paper was manufactured with five different formulations. Types of coating pigments and dosage of latex were varied. It was obtained high smoothness and also less binder demand with clay than GCC. On the other hand, suitable surface resistance and smoothness of coated paper for RFID tag was obtained with 20% of latex. Besides it shows the possibility of using coated paper for printed RFID tag.

• Polymer(Korea)
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• v.24 no.5
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• pp.673-681
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• 2000

Electrically conductive composites have been prepared by treating fabrics with oxidizing agent and exposing them to aniline, which deposited a substantial amount of conductive polymer within the interstices of the material. However the conductivity of the composite fabrics was limited by the irregular deposition of the conductive polymer layer. To improve the conductivity of polyaniline/nylon 6 composite fabrics, we modified the surface characteristics of nylon 6 fabrics by various plasma treatments and increased diffusion and adsorption of aniline by ultrasonic treatments. By the oxygen plasma treatment, attachment of functional groups such as C-O and C-OH increased on the surface of nylon 6 fiber, which promoted adhesion to polyaniline resulting in the higher add-on and electrical conductivity. Electrical conductivities of polyaniline/nylon 6 composite fabrics were highly increased by ultrasonic treatment, which assisted the diffusion of aniline into the inside of nylon fabrics by cavitation and vibration. Also, the effects of monomer concentration and the number of deposition cycles on the nylon 6 fabric conductivity Were investigated. As a result, the fabric conductivity increased with the monomer concentration and the number of polymerization deposition cycles.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.7
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• pp.382-386
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• 2004

A study has been made of surface modification of organic materials by ion implantation to increase the surface electrical properties. The substrate used were PET(polyethylene teraphtalate). N$^{＋}$, Ar$^{＋}$ implantation was peformed at energies of 40 keV and 50 keV with fluences from $5{\times}10^{15}$, $1{\times}10^{16}$,$7{\times}10^{16}$, $1{\times}10^{17}$/ ions/$cm^2$. UV/Vis, FT-IR and XPS spectroscopy measured for surface structure changes. Surface resistance decrease of implanted polymers was affected by ion implantation energy, ion species and ion dose rate. Surface conductivity of PET increased $2{\times}10^{9}$/∼$2{\times}10^{10}$/$\Omega$/sq by ion implantation. Result of various spectroscopy analysis, the cause of increasing PET surface conductivity was expected to breaking C=O bonds. It was formation carbon network structure by promote cross-linking and create C-C, C=C bonds.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1845-1847
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• 2013

The lateral photovoltaic effect (LPE) can be observed in semiconductors by irradiating a light spot position between electrodes on sample's surface. Because lateral photovoltaic voltage (LPV) is sensitively changed by light spot position, a LPE device has been tried as a position-sensitive detector. This study discusses the correlation between LPV and conductivity in p-type silicon and nano-structured Au deposited p-type silicon (nano-Au silicon), respectively. Conductivity measurement of the sample was carried out using the four-wire method to eliminate contact resistance, and conductivity dependence on LPV was simultaneously measured by changing the light irradiation position. The result showed a strong correlation between conductivity and LPV in the p-type silicon sample. The correlation coefficient was 0.87. The correlation coefficient between LPV and conductivity for the nano-Au silicon sample was 0.41.

• The Journal of Engineering Geology
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• v.30 no.2
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• pp.147-160
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• 2020

Unsaturated hydraulic conductivity of near-surface unconsolidated layers depends on the physical properties and water content of the unconsolidated layers. So far, many studies have been conducted on the unsaturated hydraulic conductivity of near-surface unconsolidated layers. However, researches on hydraulic conductivity of unsaturated fractured rocks have been relatively rare. In relation to the construction of a low/intermediate level radioactive waste surface-disposal facility, this study compared and analyzed van Genuchten parameters (α, n) in the laboratory and the hydraulic conductivity obtained in field tests for fractured hornfels at a radioactive-waste disposal site of Korea. The relationship between the field hydraulic conductivity and van Genuchten parameters using data from the ten depth intervals of three boreholes resulted in that the correlation coefficient (R) between the hydraulic conductivity and the van Genuchten parameter α was 0.7607, showing positive correlation whereas the R between the hydraulic conductivity and the van Genuchten shape-defining parameter n was -0.8720, showing negative correlation. Hence, this study confirmed the relationship between the field hydraulic conductivity and the van Genuchten unsaturated functions for the unsaturated fractured hornfels.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.308-314
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• 2018

Among the fuel cell electrolyte candidates in the intermediate temperature range, glass materials show stable physical properties and are also expected to have higher ion conductivity than crystalline materials. In particular, phosphate glass has a high mobility of protons since such a structure maintains a hydrogen bond network that leads to high proton conductivity. Recently, defects like volatilization of phosphorus and destruction of the bonding structure have remarkably improved with introduction of cations, such as Zr4+ and Nb5+, into phosphate. In particular, niobium has proton conductivity on the surface because of higher surface acidity. It can also retain phosphorus content during heat treatment and improve chemical stability by bonding with phosphorus. In this study, we fabricate niobium phosphate glass thin films through sol-gel processing, and we report the chemical stability and electrical properties. The existence of the hydroxyl group in the phosphate is confirmed and found to be preserved at the intermediate temperature region of $150-450^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2967-2972
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• 2010

Poly-N-vinylcarbazole/polyaniline (PVK-PANI) composites are synthesized by varying target loading concentrations of aniline (0.025 - 0.1 M). The surface morphology of the composites is studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The temperature-dependent DC conductivity of PVK-PANI composite films was studied at the temperature range of 300 - 500 K. The data suggest that the conductivity increase with an increase in aniline concentration in the composite with an increase in temperature. Further based on the conductivity behavior we can suggest that the PVK-PANI composites show a semiconducting behavior with a positive temperature coefficient of resistivity (TCR). The enhanced conductivity and the positive TCR of the PVK-PANI composite films may be due to the strong interaction between PANI and PVK in the composite films.