• 한국도로학회논문집
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• 제18권6호
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• pp.123-130
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• 2016

OBJECTIVES : The objective of this research is to determine the moisture resistance of the freeze-thaw process occurring in low-noise porous pavement using either hydrated-lime or anti-freezing agent. Various additives were applied to low-noise porous asphalt, which is actively paved in South Korea, to overcome its disadvantages. Moreover, the optimum contents of hydrated-lime and anti-freezing agent and behavior properties of low-noise porous asphalt layer are determined using dynamic moduli via the freeze-thaw test. METHODS : The low-noise porous asphalt mixtures were made using gyratory compacters to investigate its properties with either hydrated-lime or anti-freezing agent. To determine the dynamic moduli of each mixture, impact resonance test was conducted. The applied standard for the freeze-thaw test of asphalt mixture is ASTM D 6857. The freeze-thaw and impact resonance tests were performed twice at each stage. The behavior properties were defined using finite element method, which was performed using the dynamic modulus data obtained from the freeze-thaw test and resonance frequencies obtained from non-destructive impact test. RESULTS : The results show that the coherence and strength of the low-noise porous asphalt mixture decreased continuously with the increase in the temperature of the mixture. The dynamic modulus of the normal low-noise porous asphalt mixture dramatically decreased after one cycle of freezing and thawing stages, which is more than that of other mixtures containing additives. The damage rate was higher when the freeze-thaw test was repeated. CONCLUSIONS : From the root mean squared error (RMSE) and mean percentage error (MPE) analyses, the addition rates of 1.5% hydrated-lime and 0.5% anti-freezing agent resulted in the strongest mixture having the highest moisture resistance compared to other specimens with each additive in 1 cycle freeze-thaw test. Moreover, the freeze-thaw resistance significantly improved when a hydrated-lime content of 0.5% was applied for the two cycles of the freeze-thaw test. Hence, the optimum contents of both hydrated-lime and anti-freezing agent are 0.5%.

• Transactions on Electrical and Electronic Materials
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• 제14권6호
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• pp.312-316
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• 2013

In this study, short-circuit preventive layer (blocking layer) was deposited between conductive transparent electrode and porous $TiO_2$ film in the DSSCs. As blocking layer, we selected the metal-oxide such as $TiO_2$, $Nb_2O_5$ and ZnO. The sheet resistance with each different blocking layers were 18 ${\Omega}/sq.$ for the $TiO_2$, 10 ${\Omega}/sq.$ for the $Nb_2O_5$ and 8 ${\Omega}/sq.$ for the ZnO, while the RMS (Root Mean Square) roughness value of DSSCs were 39.61 nm for the $TiO_2$, 41.84 nm for the $Nb_2O_5$ and 36.14 nm for the ZnO respectively. From the results of photocurrent-voltage curves, a sputtered $Nb_2O_5$ blocking layer showed higher performance on 2.64% of photo-electrochemical properties. The maximum of conversion efficiency which was achieved under 1 sun irradiation by depositing the blocking layer increased up to 0.56%.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.319.1-319.1
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• 2013

Solid oxide fuel cells (SOFCs) have been recognized as one of emerging renewable energy sources, due to minimized pollutant production and high efficiency in operation. The performance of SOFCs is largely dependent on the electrode polarization which involves the oxidation/reduction in cathodes and anodes along with the charge transport of ions and electronic carriers. Atomic layer deposition is based on the alternate chemical surface reaction occurring at low temperatures with high uniformity and superior step coverage. Such features can be extended into the coating of metal oxide and/or metal layer onto the porous materials. In particular, the atomic layer deposition is can manipulated in controlling the charge transport in terms of triple phase boundaries, in order to control artificially the electrochemical polarization in electrodes of SOFC. The current work applied atomic layer deposition of metal oxides intro the electrodes of SOFCs. The corresponding effect was monitored in terms of the electrochemical characterization. The roles of atomic layer deposition in solid oxide fuel cells are discussed towards optimized towards long-term durability at intermediate temperature.

• 한국세라믹학회지
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• 제39권11호
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• pp.1011-1016
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• 2002

Colloidal particles of silica (100 nm in size) were electrostatically dispersed and adsorbed on a glass substrate coated with silica sol or alumina sol. Stability of the suspensions and microstructure of the adsorbed particle layers were discussed in terms of total potential energies between the particles and the substrate. Well-dispersed suspension resulted in a layer with densely packed and regularly arranged particles, whereas less stable suspension resulted in a porous layer with loosely packed and irregularly arranged particles. Despite repulsive interactions between the particles and the substrate coated with silica sol, the observed adsorption can be attributed to chemical bonds formed at the interface between the particle and silica sol. In contrast, the adsorption of the particles on the substrate coated with alumina sol formed a layer with strongly adhered and densely packed particles, due to large attractive interactions between the particles and alumina sol.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.207-210
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• 2005

In this paper, a two-dimensional cross-channel model was applied to investigate influence of the gas diffusion layer(GDL) property and flow field geometry in the anode side for proton exchange membrane fuel cell(PEMFC). The GDL is made of a porous material such as carbon cloth, carbon paper, or metal wire mesh. To the simplicity, the GDL is represented as a block of material containing numerous pathways through which gaseous reactants and liquid water can pass. The purpose of present work was to study the effect of the GDL thickness and the porosity, and flow field geometry by computational fluid dynamics(CFD)

• Transactions on Electrical and Electronic Materials
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• 제5권4호
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• pp.143-147
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• 2004

Surface defects and bulk defects on SOI wafers are studied. Two new metrologies have been proposed to characterize surface and bulk defects in epitaxial layer transfer (ELTRAN) wafers. They included the following: i) laser scattering particle counter and coordinated atomic force microscopy (AFM) and Cu-decoration for defect isolation and ii) cross-sectional transmission electron microscope (TEM) foil preparation using focused ion beam (FIB) and TEM investigation for defect morphology observation. The size of defect is 7.29 urn by AFM analysis, the density of defect is 0.36 /cm$^2$ at as-direct surface oxide defect (DSOD), 2.52 /cm$^2$ at ox-DSOD. A hole was formed locally without either the silicon or the buried oxide layer (Square Defect) in surface defect. Most of surface defects in ELTRAN wafers originate from particle on the porous silicon.

• 한국해양공학회지
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• 제20권6호
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• pp.35-40
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• 2006

In recent years, there's been strong demand for seawalls that havea gentle slope and permeability that serveswater affinity and disaster prevention from wave attack. The aim of this study is to examine wave transformation, including wave run-up that propagates on the coastal structures. A numerical model based on the weak nonlinear dispersive Boussinesq equation, together with the unsteady nonlinear Darcy law for fluid motion in permeable layer, is developed. The applicability of this numerical model is examined through Deguchi and Moriwaki's hydraulic model test on the permeable slopes. From this study, it is found that the proposed numerical model can predict wave transformation and run-up on the gentle slope with a permeable layer, but can't show accurate results for slopes steeper than about 1:10.

• 대한치과기공학회지
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• 제32권4호
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• pp.297-305
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• 2010

Purpose: The purpose of this study was to observe the change of metal-mold reaction and surface roughness in titanium casting specimens for phosphate-silica alumina bonded investment with mold temperatures. Methods: The metal-phosphate silica alumina bonded mold interface reaction and surface roughness of titanium casting specimens according to mold temperatures were investigated. The Specimens were analysed by scanning electron microscopy and surface roughness tester. Results: The oxidation behavior indicated by the growth of oxide thickness. The titanium-oxide layer were consisted two layer of a porous external and a dense internal one. The reaction layer and surface roughness increased with increasing investment material temperature. Conclusion: In this work, The most suitable mold temperature in casting of pure titanium was $200^{\circ}C$.

• Current Photovoltaic Research
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• 제3권3호
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• pp.91-96
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• 2015

Optical modeling and characterization of transparent dye-sensitized solar cells (DSC) are presented to design and estimate DSC devices numerically. In order to model the inhomogeneous active layer of DSC, the porous structure of titanium oxide ($TiO_2$) and dye mixture, we prepared films consisting of layer by layer of the DSC's basic materials sequentially, and characterized the optical parameters of the films with the effective refractive index, which was extracted from the transmittance and reflectance measurements in ultra violet to near infra-red range. By using the effective refractive index, we made the optical model for DSC, and demonstrated that the optical model based on effective refractive index can be used to design and evaluate the performance of transparent-type DSC modules.

• 한국세라믹학회지
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• 제54권6호
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• pp.525-529
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• 2017

To improve the thermal resistance of a porous borosilicate lining block, we prepared and applied polysiloxane-fumed silica-ethanol slurry on top of the block and fired the coating layer using a torch for 5 minutes at $800^{\circ}C$. We conducted magnified characterizations using a microscope and XRD analysis to observe phase transformations, and TGA-DTA analysis to determine the thermal resistance. Thermal characterizations showed improved heat resistance with relatively high polysiloxane content slurry. Cross-sectional optical microscope observation showed less melting near the surface and decreased pore formation area with higher polysiloxane content slurry. XRD analysis revealed that the block and coating layer were amorphous phases. TGA-DTA analysis showed an endothermic reaction at around $550^{\circ}C$ as the polysiloxane in the coating layer reacted to form SiOC. Therefore, coating polysiloxane on a borosilicate block contributes to preventing the melting of the block at temperatures above $800^{\circ}C$.