• Journal of the Optical Society of Korea
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• v.16 no.1
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• pp.42-46
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• 2012

We have developed a fluorescence optical detection system using a digital micromirror device (DMD) for monitoring 3D cell culture matrices in situ. Full 3D imaging with fast scanning speed was implemented by the combined action of a DMD and a motorized stage. Imaging results with fluorescent microbeads measure the minimum axial resolution of the system as $6.3{\mu}m$, while full 1-mm scanning through 3D alginate-based matrix was demonstrated. For cell imaging, improved images were obtained by removing background fluorescence although the scanning distance was reduced because of low intracellular fluorescence efficiency. The system is expected to be useful to study various dynamics and behaviors of 3-dimensionally cultured cells in microfluidic systems.

• Applied Science and Convergence Technology
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• v.26 no.6
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• pp.214-217
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• 2017

AlSb is a promising material for optical devices, particularly for high-frequency and nonlinear-optical applications. We report the effect of growth temperature on structural properties of AlSb grown on GaAs substrate. In particular we studied the surface of AlSb with the growth temperature by atomic force microscopy, and concluded that optimized growth temperature of AlSb is $530^{\circ}C$. We also show the result of real-time monitoring of AlSb growth by in situ ellipsometry. The results of the structural study are good agreement with the previous reported ellipsometric data.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.283-289
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• 1999

Multilayer thin film reference materials for the sputter depth profiling analysis are used to calibrate the sputter depth scale by measuring the sputtering rate and to optimize the sputtering conditions for the best depth resolution. Surface analysis group of Korea Research Institute of Standards and science (KRISS) have developed various types of multilayer thin films by using an ion beam sputter deposition and in-situ surface analysis system. The chemical states of the thin films reference materials were certified by in-situ XPS and the thicknesses were certified by transmission electron microscopy (TEM).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.224-229
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• 2013

Vanadium oxide thin films were deposited on $c-Al_2O_3$ (001) substrate by in-situ RF magnetron sputtering. Oxygen partial pressure was adjusted to prepare thermochromic $VO_2$ phase. X-ray diffraction patterns and scanning electron microscopy convincingly showed that plate-like $V_2O_5$ grains were changed into round-shape $VO_2$ grains as oxygen partial pressure decreased. After the optimized deposition conditions were fixed, the effect of substrate temperature and orientation on the optical properties of $VO_2$ thin films was analyzed.

• International Journal of Korean Welding Society
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• v.3 no.2
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• pp.29-39
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• 2003

The durability and reliability of thermal barrier coatings (TBCs) play an important role in the service reliability, availability and maintainability (RAM) of hot­section components in advanced turbine engines for aero and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary non­destructive evaluation (NDE) techniques for quality control and life­remain assessment of TBCs. This paper overviews the governing principles and applications of the luminescence and the impedance examined in the light of residual stress, phase constituents and resistance (or capacitance) in TBC constituents including the thermally grown oxide (TGO) scale. Results from NDE by PSLS and EIS are discussed and related to the microstructural development during high temperature thermal cycling, examined by using a variety of microscopic techniques including focused ion beam (FIB) in­situ lift­out (INLO), transmission and scanning transmission electron microscopy (TEM and STEM).

• Applied Microscopy
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• v.47 no.3
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• pp.101-104
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• 2017

In this investigation, synchrotron X-ray imaging was used to investigate the water distribution inside newly developed gas diffusion media in polymer electrolyte membrane fuel cells. In-situ radiography was used to reveal the relationship between the structure of the microporous layer (MPL) and the water flow in a newly developed MPL equipped with randomly arranged holes. A strong influence of these holes on the overall water transport was found. This contribution provides a brief overview to some of our recent activities on this research field.

• Food Science and Biotechnology
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• v.18 no.2
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• pp.432-435
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• 2009

The preventive effect of chewing gum containing maltitol, xylitol, gum base, and sugar on remineralization were investigated. The clinical study consisted of 8 weeks' randomized, double blind, controlled, cross-over clinical trials including 24 healthy adults had chew gum. After each test week, remineralization effect was evaluated by measuring microhardness and scanning electron microscopy (SEM). Microhardness of experimental chewing gum containing maltitol or xylitol was significantly higher than that of sugar gum (p<0.005). Images of SEM showed the remineralization effect of gum containing gum base, maltitol, or xylitol compared with sugar gum. Maltitol and xylitol gums were more effective in remineralization than sugar gum. It was concluded that maltitol and xylitol can be used as sugar substitute to prevent dental caries.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.558-561
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• 2005

In-situ photopolymerization of alkyl acrylate monomers in the presence of a nematic fluid provides a cellular matrix of liquid crystalline droplets in which the chemical structure of the encapsulating polymer exerts control over the alignment (anchoring) of the liquid crystalline molecules. Control is obtained by variation of the alkyl side chains and through copolymerization of two dissimilar monofunctional acrylates. Two monofunctional acrylates with opposing tendencies on copolymerization provide control over the tunability of anchoring over a wide temperature range. Using various acrylates we show that a uniform vertical alignment can be achieved over a large area. Utilizing this technique and a nematic with negative dielectric anisotropy, we have fabricated highly flexible liquid crytal based devices, with high contrast and fast response time, without using any alignment layer.

• 한국전자현미경학회:학술대회논문집
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• 2005.05a
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• pp.66-69
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• 2005

• Applied Microscopy
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• v.36 no.spc1
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• pp.57-61
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• 2006

High-resolution microscopy was applied for surveying hydride stability in Vanadium alloys, which are candidate for hydrogen storage materials of advanced hydrogen energy systems. $V_2H$ hydride in V alloys was stable at room temperature under the vacuum condition, but it was decomposed during heating up to $100^{\circ}C$. It was confirmed from HRTEM image and FFT that $V_2H$ has a BCT structure, where hydrogen atoms locate at octahedral sites. Crystal orientation was <110> beta// <110> mat., and lattice strain is about 10%. After the decomposition of the hydride, relatively large lattice expansion was observed in the matrix, which suggests that hydrogen atoms should be trapped by lattice defects and included in the matrix. Intensive electron beam also enhanced the decomposition.