• Polymer(Korea)
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• v.29 no.2
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• pp.204-210
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• 2005

We describe a colorless, transparent polyimide films for plastic display substrate which should have heat resistance, roll-to-roll processability and low CTE (coefficient of thermal expansion) property. Colorless polyimides were synthesized from 3,3',4,4'-oxydiphthalic anhydride (ODPA) 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and diamines such as sulfonyldianiline, aminophenoxybenzene (TPE-p, TPE-q, TPE-r) and bis[4-(3-aminophen oxy)phenyl] sulfone (m-BAPS). Their optical properties were measured by UV spectrophotometer, colormeter and hazemeter. We prepared polyimide/organophilic layered silicate nanocomposite to improve dimension stability. These colorless polyimide films showed UV transmittance by the level upper $89\%$, at 440 nm and excellent optical property having the value under yellow index (YI)=7. In addition, polyimide nanocomposite films also showed an improvement of CTE value as decreased according to the amount of layered silicate contents.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.713-719
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• 2000

In order to Prepare the$Ge_xSi_{1-x}/Si$(111) heterosructure by solid phase epitaxy (SPE), about 1000A of Au and about 1000A Ge were sequentially deposited on the Si(111) substrate. The resulting Ge/Au/Si(111) samples were isochronically annealed in the high vacuum condition. The behaviors of Au and Ge during thermal annealing and the structural Properties of $Ge_xSi_{1-x}$ films were characterized by Auger electron spectroscopy (AES), X-ray diffraction (XRD) and high resolution transmission electron microscopy (TEM). The a-Ge/Au/Si(111) structure was converted to the Au/GeSi/Si(111) structure. Defects such as stacking faults, point defects and dislocations were found at the GeXSil-X(111) interface, but the film was grown epitaxially with the matching face relationship of $Ge_xSi_{1-x}/$(111)/Si(111). Twin crystals were also found in the $Ge_xSi_{1-x}/$(111) matrix.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.1
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• pp.1-8
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• 2014

In this study, a field monitoring on Namae beach erosion countermeasure in the east coast of Korea is conducted to verify its efficiency and effectiveness. The Namae Beach project has been carried out for six years with three years for planning and three years for actual construction. The planning phase of numerical model tests and investigations had been reported by Kim et al. (2008, 2011). The field monitoring confirms increase in the beach width after the submerged artificial reefs construction and is due to its wave energy dissipation effects. The field monitoring is performed at the seaward and landward of the countermeasures. The wave height reduction from the seaward side (depth h = 10.5 m) to the landward side (h = 3.7 m) of the reef is measured for wave transmission coefficient (Kt) analysis. The analysis shows 60% of deduction in wave energy due to the submerged artificial reefs.

• Journal of Pharmaceutical Investigation
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• v.36 no.6
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• pp.385-392
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• 2006

Paclitaxel is an important chemotherapeutic agent for the treatment of human solid tumors. Multicellular resistance(MCR) is considered to be a major mechanism of resistance of human solid tumors to chemotherapeutic agent such as paclitaxel, which includes barriers to drug penetration through tumor tissues. Multicellular layers(MCL) cultures resemble in vivo tumor condition in terms of MCR and has been used successfully to produce clinically relevant data. In the present study, we evaluated the penetration characteristics and post-penetration anti-proliferative activity of paclitaxel using MCL of human colorectal cancer cells(DLD-1 and HT-29) grown in Transwell inserts. The penetration of $[^{14}C]-paclitaxel$ was slower than that of mannitol which penetrates via paracellular pathway in DLD-1 MCL. The penetration of $[^{14}C]-paclitaxel$ was faster in HT-29 MCL compared to DLD-1 MCL, i.e., at 10 ${\mu}M$ 100% and 40% penetration were observed after 48 hr incubation for HT-29 and DLD-1 cells, respectively. When calculated using anti-proliferative activity in the conditioned media of bottom chamber, the penetration after 24 hr was very limited(less than 50%) and concentration-dependent at the concentrations tested in both MCL's. These results suggest that limited and differential penetration of paclitaxel in tumor tissues may contribute to lower and differential efficacy against human solid tumors.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.36.2-36.2
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• 2011

최근 나노기술의 비약적인 발전을 바탕으로 그 동안 구현이 쉽지 않았던 마이크로-나노 단위의 생체모사(biomimetics) 기술이 큰 각광을 받고 있다. 그 중에서도 특히 연잎 효과(lotus-effect)로 대표되는 접촉각 $150^{\circ}$ 이상의 초소수성(superhydrophobicity) 표면 구현은 생물, 화학, 물질 등의 다양한 분야에 있어 큰 사용가치를 가지기 때문에 연구가 전세계적으로 활발히 진행되고 있다. 초소수성을 가지는 표면을 구현하기 위해서는 표면의 화학적인 조성을 변화시켜 표면의 거칠기를 증대시키는 방법과 표면에너지를 낮추는 방법으로 구분될 수 있으며, 이를 위해 표면에 나노구조체를 형성시켜 표면 거칠기를 증대시키는 방법과 silane 계열의 자가-형성 단일막(Self-assembled monolayer)을 코팅하여 표면에너지를 낮추는 방법이 사용되어 왔다. 그러나 표면에 나노구조체를 형성시키는 과정에서 비싼 공정 비용이 발생하며, 대면적 구현이 쉽지 않다는 단점이 있으며, silane 계열의 자가-형성 단일막의 경우에는 제거가 쉽지 않아 추후 다양한 소자에의 적용이 어렵다는 단점을 가지고 있다. 본 연구에서는 무전해 식각법(Aqueous Electroless Etching)을 이용하여 대면적으로 합성시킨 실리콘 나노와이어의 표면 산소 흡착 처리를 통해 $156^{\circ}$ 이상의 초소수성 표면을 구현하였다. 액상 기반으로 형성된 실리콘 나노와이어의 표면은 열처리 공정을 통해 OH-기에서 O-기로 치환되어 낮은 표면에너지를 가지게 되며, 낮아진 표면에너지와 산화과정에서 증대된 표면 거칠기를 통해 Wenzel-state의 초소수성 표면 성질을 보였다. 변화된 나노와이어의 표면 거칠기는 주사전자현미경 (FE-SEM)과 주사투과현미경 (HR-TEM)을 통해 관찰되었다. 또한, 나노와이어의 길이와 열처리 공정 조건에 따라 나노와이어의 표면을 접촉각 $0^{\circ}$의 초친수성(superhydrophilicity) 특성부터 접촉각 $150^{\circ}$ 이상의 초소수성 특성까지 변화시킬 수 있었으며, 나노와이어의 길이에 따라 표면 난반사율을 조절하여 90% 이상의 매우 높은 흡수율을 가지는 나노와이어 표면을 구현할 수 있었다. 이러한 산소 흡착법을 이용한 초소수성 표면 구현은 기존 자가-형성 단일막 코팅을 이용한 방법에 비해 소자 제작 및 활용에 있어 매우 유리하며, 바이오칩, 수광소자 등의 다양한 응용 분야에 적용 가능할 것으로 예상된다.

• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.156-161
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• 1998

We developed aerosol flame deposition method and made stress-free Pyrex-based optical waveguide on silicon substrate using this method. Zr is doped to control the refractive index of Pyrex waveguide layers. The refractive index of the film changes from 1.460 to 1.475 as the content of Zr changes from 0 to 3 wt%. Er is doped to see the possibility of applying this Pyrex waveguide as PLC-type (Planar Lightwave Circuit) optical amplifier. The refractive index of the film changes from 1.460 to 1.465 as the content of Zr changes from 0 to 1 wt%. Light launching using a prism coupler to the fabricated waveguide showed good quality for application to PLC. The polarization dependence of refractive-index of the Pyrex film is measured to be less than $2{\times}10^{-4}$.

• Korean Journal of Optics and Photonics
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• v.23 no.4
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• pp.135-142
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• 2012

We have developed a measurement method of the refractive index profile of an optical fiber by using diffraction phase microscopy. In the microscope system, the reference light was extracted directly from the probe light that passed through the sample by means of pinhole filtering with a diffraction grating. The spatial interference pattern produced by the probe light and the reference light was processed to generate the phase image of the sample fiber. The index profile was obtained by the inverse Abel transform of the phase profile. In order to remove the background phase that originated from the index difference between the cladding and the surrounding medium, the background phase was calculated from the phase data of the cladding to make a core phase profile that can be directly transformed to the index profile of the core without the full phase image that includes the entire cladding part.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.1
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• pp.20-29
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• 1992

In $BaTiO_3-NaNbO_3$ system, complete series of solid solution occurs and $30BaTiO_3{cdot}70NaNbO_3$ composition is congruently melted. Single crystals of $30BaTiO_3{cdot}70NaNbO_3$, composition were grown by Czochralski method in this investigation. Single crystals with dimensions of 15 - 20mm diameter and 20 - 30mm length, were grown at the pulling rate of 2.0mm/h and the rotation rate of 5.0 -l0rpm. Core structures were found in the grown crystals and inclusions, cellular boundaries existed at the core region. The origin of core occuring was unstability of the crystal- melt interface due to the poor conductivity of latent heat through the crystal during the crystal growing process. Obtained crystals were optically homogeneous except the core region and showed high optical transmittance in the visible range.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1289-1294
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• 1999

To identify the effect of packaging film on browning reaction of dried squid, 3 kinds of packaging film$(NYLON\;12\;{\mu}m/LDPE\;80\;{\mu}m)$ including transparency, white, black film were tested about browning degree of dried squid during storage at ambient temperature for 50 days. During storage period, water content and water activity were maintained almost constant, and microbial count was not changed. When color index was measured by color difference meter, L value and ${\Delta}E$ value were the highest in the dried squid packaged with transparency film. ${\Delta}E$ value was rapidly increased in early packaging period(within 10 day). TBA value was showed same tendency with ${\Delta}E$ value in early storage period. So, the browning was supposed to originated from lipid oxidation by UV light transmitted through packaging film in the early storage period.

• Journal of the Korean Electrochemical Society
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• v.12 no.3
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• pp.239-244
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• 2009

This paper aims to report the effect of surface treatment on graphite and its effect on the improvement of $Al_2O_3$ and $nano-Li_4Ti_5O_{12}$. The structure and property of surface treatment on graphite were determined by scanning electron microscopy, transmission electron microscopy and electrochemical property and safety were determined by charge/discharge cycler, accelerating rate calorimeter. The composite with different metallic oxide exhibited the first efficiency of 82.5% and specific capacity of 350 mAh/g. Although the composite showed same efficiency and specific capacity at first cycle, surface treatment on graphite by $nano-Li_4Ti_5O_{12}$ exhibited a higher charge/discharge rate, cycle life and thermal stability.