• Journal of Sensor Science and Technology
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• v.5 no.1
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• pp.71-77
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• 1996

Considering that polycrystalline silicon, a structural material of the micromachining, is affected by a sacrificial oxide layer, the poly-oxide obtained by the thermal oxidation of polycrystalline silicon is newly proposed and estimated as the sacrificial oxide layer. The grain size of the polycrystalline silicon grown on the poly-oxide is larger than that of poly crystalline silicon grown on the conventional sacrificial oxide layer. As a result of XRD, increase of (111) textures and formation of additional (220) textures are observed on the polycrystaIline silicon deposited on the poly-oxide. Also, the polycrystalline silicon grown on the poly-oxide represents small and uniform stress.

• Journal of Powder Materials
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• v.19 no.3
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• pp.196-203
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• 2012

$TiO_2$ was successfully formed on a Ti specimen by MAO (Micro-Arc-Oxidation) method treated in $Na_3PO_4$ electrolyte. This study deals with the influence of voltage and working time on the change of surface microstructure and phase composition. Voltage affected the forming rate of the oxidized layer and surface microstructure where, a low voltage led to a high surface roughness, more holes and a thin oxidized layer. On the other hand, a high voltage led to more dense surface structure, wider surface holes, a thick layer and fewer holes. Higher voltage increases photocatalytic activity because of better crystallization of the oxidized layer and good phase composition with anatase and rutile $TiO_2$, which is able to effectively separate excited electrons and holes at the surface.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1435-1440
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• 2009

Geotechnical variability is a complex feature that results from many independent sources of uncertainties, and is mainly affected by inherent variability and measurement errors. This study evaluates the coefficient of variation (COV) of soil properties at Song-do region in Korea for evaluating inherent soil variability. Since soil variability is sensitive to soil layers and soil types, the COVs by soil layers (reclaimed layer and marine layer) and the COVs by soil types (clay and silt) were separately evaluated. It is observed that geotechnical variability of marine layer and clay is relatively smaller than that of reclamation layer and silt.

• Journal of Surface Science and Engineering
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• v.22 no.4
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• pp.185-196
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• 1989

The surface modification of a mild and stainless steel by alumina sprayed coating were studied. The effects of surface roughness and bond coating layer on the adhesive strengthy and durability of sprayed specimens were also investiated. The adhesive strength of ceramic coating was affected by surface roughness and bond coating layer thinkness. That showed excellent undergrit blast time and bond coating layer; 60 sec and 0.15-0.33mm, respectively. The adhesive strength and densification of sprayed coating with air pressure were superior to those of without and fracture was mainly occured at alumina-bond coating interface. Under ambient atmosphere at $800^{\circ}C$, the oxides existed within bond coating layer promote diffusion of oxygen to lower durability of sprayed specimens. In this case, fracure was occured at sudstrate-bond coating interface.

• Transactions on Electrical and Electronic Materials
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• v.18 no.3
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• pp.144-147
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• 2017

In this study, two- and three-layer ceramic piezoelectric actuators were designed and simulated according to SUS316 thickness, actuator width, and mass using ATILA software in order to develop a piezoelectric actuator for haptic application. Numerical modelling based on the finite element method was performed to find the resonance frequencies and modal shapes of the actuator. The resonance frequency was affected by the thickness of the SUS316 plate and mass. On the other hand, the width of the actuator did not have a significant impact. Maximum displacements were generated at the center of a haptic three-layer ceramic piezoelectric actuator. The two-layer ceramic piezoelectric actuator with a mass of 2.6 g was suitable as $16.28{\mu}m$ at 265 Hz for haptic sensation application.

• Structural Engineering and Mechanics
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• v.88 no.6
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• pp.609-623
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• 2023

The objective of this study is to investigate the distribution of von Mises stress, peeling stress, and shear stress in the adhesive layer used to bond two composite panels, considering various parameters using a three-dimensional finite element method. The stiffness of the materials and the effect of the stacking order on the amount of load transferred to the adhesive layer were examined to determine which type of laminate generates less stress at the bond line. The study analyzed six different stacking sequences, all with a common first layer in contact with the adhesive and a 0° orientation. Additionally, the impact of using hybrid composites on reducing bond line stress was investigated.

• The Korean Journal of Ecology
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• v.23 no.3
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• pp.241-253
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• 2000

The degree to which microenvironmental factors are linked to spatial patterns of vegetational factors within ecosystems has important consequences for our understanding of how ecosytems are structured and for conservation of rare species in ecosystems. We studied this relationships between the spatial patterns of microenvironmental factors and vegetational factors in temperate hardwood forest in Mt. Jumbong Biological Reserve Area, Korea. To do this, environmental and vegetational factors from 196 micropoints in a 0.49 ha plot were investigated. Most of all environmental factors and vegetational factors showed the variations among micropoints. Microtopographic factors, litter depth, soil moisture content and relative light intensity at this site were spatially dependent at a scale of 14∼62 m. Coverage of tree and shrub layer and species diversity of herb layer in autumn were spatially dependent at a scale of < 15 m. Species richness and species diversity of herb layer in spring and species richness of herb layer in autumn were spatially dependent at a scale of 28∼48 m. Multiple regression analysis showed that spatial patterns of species richness and species diversity of herb layer in spring and autumn were affected by litter depth, slope, subtree layer, shrub, Sasa borealis etc. The best predictor for the spatial patterns of species richness and species diversity of herb layer at this site was the spatial pattern of litter depth. Species richness and species diversity of herb layer showed strongly negative correlation with litter depth. We estimate that the spatial pattern of litter depth at this site were affected by direction of wind, microtopography and spatial pattern of shrub layer.

• Korean Journal of Materials Research
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• v.22 no.4
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• pp.190-194
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• 2012

The formation of high-quality polycrystalline silicon (poly-Si) on relatively low cost substrate has been an important issue in the development of thin film solar cells. Poly-Si seed layers were fabricated by an inverse aluminum-induced crystallization (I-AIC) process and the properties of the resulting layer were characterized. The I-AIC process has an advantage of being able to continue the epitaxial growth without an Al layer removing process. An amorphous Si precursor layer was deposited on Corning glass substrates by RF magnetron sputtering system with Ar plasma. Then, Al thin film was deposited by thermal evaporation. An $SiO_2$ diffusion barrier layer was formed between Si and Al layers to control the surface orientation of seed layer. The crystallinity of the poly-Si seed layer was analyzed by Raman spectroscopy and x-ray diffraction (XRD). The grain size and orientation of the poly-Si seed layer were determined by electron back scattering diffraction (EBSD) method. The prepared poly-Si seed layer showed high volume fraction of crystalline Si and <100> orientation. The diffusion barrier layer and processing temperature significantly affected the grain size and orientation of the poly Si seed layer. The shorter oxidation time and lower processing temperature led to a better orientation of the poly-Si seed layer. This study presents the formation mechanism of a poly seed layer by inverse aluminum-induced crystallization.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.48 no.1
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• pp.27-33
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• 2016

This study was carried out in order to investigate the effect of binder properties in pre-coating layer on the characteristics of top-coating layer and print mottle of coated paper. Four different latices were used as a binder in pre-coating layer, and coating color prepared with a same formulation was applied for top-coating. The properties and print mottle of coated paper were evaluated. It was found that glass transition temperature (Tg) was the important factor to control the properties of pre- and top-coating layer. PPS roughness of coated paper was decreased and paper gloss was increased with applying binder which has lower Tg. Properties of top-coating layer were affected by the binder used in pre-coating layer. Print mottle of coated paper was improved with using binder which has lower Tg in pre-coating layer. These results indicate that final printability and properties of top-coating layer can be improved with using suitable binder in pre-coating layer.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.267-279
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• 1996

Microorganisms are implicated the endodontic treatment failures. Persistent endodontic infection may be the result of retention of microorganisms in the dentin of the root canal walls. Dentinal tubules of the root canal walls have been shown to harbor microorganisms. The purpose of this study was to investigate the invasion of microorganism into the root dentin and dentinal tubules. The effects of irrigation solutions and smear layer on bacterial colonization of root canal were evaluated using a scanning electron microscopy. Canals of extracted human teeth with single and straight canals were stepback prepared using normal saline. Tooth samples were divided into four groups according to the irrigation solutions -5 % sodium hypochlorite and normal saline-and smear layer treatment. The smear layer was removed by 5% NaOCl and 20% EDTA for 10 min respectively. After sterilization, they were incubated with each strains of Streptococcus sanguis, Enterococcus faecalis, Staphylococcus aureus and Escherichia coli. Sodium hypochlorite solution reduced the adhesion of microorganisms effectively compared to normal saline. The smear layer inhibited colonization of E. faecalis, S. aureus and E. coli in the root canals due to their blocking of dentianl tubules. But S. sanguis invaded dentinal tubules in the root canals without smear layer. It was suggested that bacterial attachment might be different according to the strains. Sodium hypochlorite inhibited bacterial attachment in the dentinal tubules dramatically. The absence or presence of smear layer affected bacterial invasion of the dentinal tubules.