• Macromolecular Research
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• v.17 no.7
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• pp.528-532
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• 2009

The size and shape of free volume (FV) holes available in membrane materials control the rate of gas diffusion and its permeability. Based on this principle, a segmented, thermo-sensitive polyurethane (TSPU) membrane with functional gate, i.e., the ability to sense and respond to external thermo-stimuli, was synthesized. This smart membrane exhibited close-open characteristics to the size of the FV hole and water vapor permeation and thus can be used as smart food packaging materials. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), positron annihilation lifetimes (PAL) and water vapor permeability (WVP) were used to evaluate how the morphological structure of TSPU and the temperature influence the FV holes size. In DSC and DMA studies, TSPU with a crystalline transition reversible phase showed an obvious phase-separated structure and a phase transition temperature at $53^{\circ}C$ (defined as the switch temperature and used as a functional gate). Moreover, the switch temperature ($T_s$) and the thermal-sensitivity of TSPU remained available after two or three thermal cyclic processes. The PAL study indicated that the FV hole size of TSPU is closely related to the $T_s$. When the temperature varied cyclically from $T_s-10{\circ}C$ to $T_s+10^{\circ}C$, the average radius (R) of the FV holes of the TSPU membrane also shifted cyclically from 0.23 to 0.467 nm, exhibiting an "open-close" feature. As a result, the WVP of the TSPU membrane also shifted cyclically from 4.30 to $8.58\;kg/m^2{\cdot}d$, which produced an "increase-decrease" response to the thermo-stimuli. This phase transition accompanying significant changes in the FV hole size and WVP can be used to develop "smart materials" with functional gates and controllable water vapor permeation, which support the possible applications of TSPU for food packaging.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1959-1961
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• 1999

We prepared the $Ag[100\AA])/Sb_2S_3[3000\AA]$ films using the thermal evaporator. The films were exposed by the blue-pass filtered mercury lamp and the polarized He-Ne laser. We have investigated the dependence of the induced optical energy with Ag-doping and have observed the transmittance variation near the optical absorption edge with the light source. It was shown that the energy gap of this thin film was largely changed by exposing He-Ne laser, the light source of the near energy gap of this thin film. It is because of the structural change from Ag-doping. It is investigated that the dissolution, the diffusion, and the field effect of the Ag thin film generate the Ag spatial distribution.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.50.1-50.1
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• 2009

Transparent conductive oxides (TCOs) play an important role in thin-film solar cells in terms of low cost and performance improvement. Al-doped ZnO (AZO) is a very promising material for thin-film solar cellfabrication because of the wide availability of its constituent raw materials and its low cost. In this study, AZO films were prepared by low pressurechemical vapor deposition (LPCVD) using trimethylaluminum (TMA), diethylzinc(DEZ), and water vapor. In order to improve the absorbance of light, atypical surface texturing method is wet etching of front electrode using chemical solution. Alternatively, LPCVD can create a rough surface during deposition. This "self-texturing" is a very useful technique, which can eliminate additional chemical texturing process. The introduction of a TMA doping source has a strong influence on resistivity and the diffusion of light in a wide wavelength range.The haze factor of AZO up to a value of 43 % at 600 nm was achieved without an additional surface texturing process by simple TMA doping. The use of AZO TCO resulted in energy conversion efficiencies of 7.7 % when it was applied to thep-i-n a-Si:H thin film solar cell, which was comparable to commercially available fluorine doped tin oxide ($SnO_2$:F).

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1489-1490
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• 2011

The $O_2$ plasma treatment is used as improvement of ITO roughness glass for organic light-emitting diodes and organic photovoltaic cells. This study examined the effect of the electrical properties of OLED according to variation of $O_2$ plasma power. In experiment, we found that the electrical characteristics of device are excellent when the power of $O_2$ plasma is 250 W. And when the power of $O_2$ plasma increases over 250 W, the electrical properties were getting worse. $O_2$ plasma treatment not only prevents the diffusion of indium, a metal constituent, to an organic layer but also plays a significant role as improvement of ITO roughness. By considering organic light-emitting diodes treating $O_2$ plasma, it could contribute to the improvement of the efficiency of the device.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1437-1439
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• 2007

We fabricated white organic light emitting device (WOLED) with the layered fluorescent blue material and phosphorescent green/red dye-doped materials. Addition of the non-doped phosphorescent host material between the fluorescent and phosphorescent light emitting layers provided the result of broadband white spectrum, with improved balance, higher efficiency, and lower power consumption. In our devices, there was no need of exciton-blocking layer between the each emission layer for the further confinement of the diffusion of excitons.

• Journal of the Korean Solar Energy Society
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• v.24 no.2
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• pp.39-50
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• 2004

One of the challenge for successful daylighting design might be to capture sunlighting that varies in both intensity and position and to deliver the luminous flux into the inner space as deep as possible. Conventional glazing apertures allow daylight in the outer 3.5m of a perimeter spaces. More advanced daylighting technologies can extend this daylighting depth by reflecting sunlight further from the windows within a deep floor area. For this purpose, this study developed light shelves based on performance evaluation with a mock-up model that constructed recently and measured under real sky condition. All these daylighting devices have a customized geometry developed from the solar path at a given latitude and utilize unique reflecting finishing to maximize the amount of redirection and diffusion of the daylight. This paper tells that the best daylighting penetration typically can be expected from using light-colored sloped external shelves.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.239.1-239.1
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• 2011

Dye sensitized solar cells (DSC) are promising devices for inexpensive, nontoxic, transparent, and large-scale solar energy conversion. Generally thick $TiO_2$ nanoporous films act as efficient photoanodes with their large surface area for absorbing light. However, electron transport through nanoparticle networks causes the slowdown and the loss of electron transport because of a number of interparticle boundaries inside the conduction path. We have studied DSCs with precisely dimension-controlled $TiO_2$ nanotubes array as photoanode. $TiO_2$ nanotubes array is prepared by template-directed fabrication method with atomic layer deposition. Well-ordered nanotubes array provides not only large surface area for light absorbing but also direct pathway for electrons with minimalized grain boundaries. Large enlongated anatase grains in the nanotubes could enhance the conductivity of electrons, but also suppress the recombination with holes through defect sites during diffusion into the electrode. To study the effect of grain boundaries, we fabricated two kinds of nanotubes which have different grain sizes by controlling deposition conditions. And we studied electron conduction through two kinds of nanotubes with different grain structures. The solar cell performance was studied as a function of thickness and grain structures. And overall solar-to-electric energy conversion efficiencies of up to 7% were obtained.

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.357-363
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• 1999

A frequency domain spectroscopic system was constructed to investigate the optical properties of multiple scattering media. The alternating current (AC) and phase lag components of backscattered light were measured by using the heterodyne detection method. Absorption and transport scattering coefficients were computed from the values based on diffusion theory. Predictions showed excellent matches in comparison with actual values of absorption and scattering. Predictable ranges of the optical coefficients were analyzed in terms of the distance between light source and detector, and modulation frequencies. A proposed compact experimental set-up using laser diodes can be utilized to estimate non-invasively the optical properties of multiple scattering media such as biological tissues.

• Fashion & Textile Research Journal
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• v.5 no.4
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• pp.324-330
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• 2003

The purpose of this study is on the meaning and variety about gender expressed in modern fashion. The results are as follows ; First, the typical masculine gender was authority, discretion as a result of heteropatriarchy focused on the western reason. It was conservative and the symbolic image type of the meaning excluded masculine sexual expression. Dress and its ornament was expressed as the style of straight silhouette, dark color, rough and stiff material. Second, the typical feminine gender was the symbolic image type of a mother and a wife defined relatively by man as a result of western heteropatriarchy and the image type which men regarded women as sexual objects. Dress and its ornament was expressed as the style of silhouette which let bodily curve out, light color, soft material. The most typical item is dress and suit. Third, androgyny has been described as the feminie gender of androgynous, which shows masculine image as the effect of feminism and social success of professional women. Dress and its ornament is expressed as the style of business suit, the symple of typical man's one. The masculine gender of androgynous is showed man's suit as silhouette that let bodily curve out, light color, exposure and soft material, which is the symbol of feminine dress, Fourth, unisex is the area of dress and its ornament used the sexless symbol which there has been no gender more because of the spread of sports and diffusion of leisure in life style.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1770-1772
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• 1998

This study is concluded under by investigation about the lighting environment on a blackboard in elementary, middle, high school of inchon metropolitan. 1. The illumination was approximated to standard value in the side of quantity by the result of the Mimistry of Education's command. However, the uniformity of illuminescence was relatively increased. 2. In order to raise the blackboard lighting, we installed local lighting fixture for blackboard but most of schools are directly adopted to the way of sticking to the blackboard and the lower part of the blackboard is not effective. So that it is desirable of teacher and students to put the local lighting in front of the higher part of the blackboard or install in setting the perfect diffusion light from the ceiling. 3. Deviation of luminance is also more groat when local lighting exist for blackboard. And, regardless of local lighting, luminance of blackboard in side of window, from direction of floor is high because of regular reflected light. Therefore a curtain or blind must be installed pertinently.