• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.429-437
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• 2017

Micro hollow plate type silica with low refraction properties was synthesized and its hollow structure was applied as an optical structure to develop a light diffusion material that simultaneously satisfies the requirements of good light diffusibility, high transmissibility, and high luminance. The developed light diffusion material was applied to a light diffusion film and the film's optical properties were assessed. Hollow silica was synthesized by precipitation method using $Mg(OH)_2$ core particles, sodium silicate, and ammonium sulfate as the silica precursors. The concentration of the silica precursor was adjusted to control hollow silica shell thickness. The total light transmittance of the light diffusion film composed of the hollow silica was 94.55%, which was 4.57% higher than that of the PC film; new film's haze was 71.20%, which was 70.9% higher. Furthermore, the luminance increased by 5.34% compared to that of the light source. The reason for the results is not only that the micro plate type hollow silica, which has a low refractive property, played a role in reducing the difference in refractive index between the medium boundaries, but also that there was a light-concentrating effect due to the changing of light paths to the front direction inside the hollow structure. Optical simulation verified the enhanced optical properties when hollow silica was applied to the light diffusion film.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.5
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• pp.299-304
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• 2004

Influence of Ca addition on microstructure and room temperature mechanical properties has been studied for AZ31(Mg-3%Al-1%Zn-0.2%Mn)-(0~0.5)%Ca wrought alloys, based on experimental results from metallography, X-ray diffractometry and mechanical tests. Yield strength, ultimate tensile strength and hardness of the alloys increased remarkably with increasing Ca content, whereas elongation was deteriorated continuously. Microstructural examination revealed that Ca addition efficiently refined grains of ${\alpha}$(Mg) phase and that some of the Ca dissolved in ${\beta}(Mg_{17}Al_{12})$ precipitates. The former and the latter facts are thought to be responsible for improved strength and loss of ductility of the AZ31+Ca wrought alloys, respectively.

• Applied Chemistry
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• v.15 no.1
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• pp.17-20
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• 2011

A disposable light exposure detector kit has been developed by UV curing of a hydrogel material. The devised light exposure detector kit consisted of light sensitive structures, bottom plate, character sheet and sticky back plate. A light exposure detector kit has a serial light sensitive structures that contain various light sensitive dyes such as rhodamine and fluorescein. The light sensitive structure composed of UV curable hydrogel polymer material as a supporing material and photosensitive dye in a certain concentration. The fabrication procedure of the ligh exposure detector kit is very simple and fast due to UV curing procedure of a photopolymerizable hydrogel material such as poly(ethylene glycol) methyl ether acrylate (PEGMEA) and poly(ethylene glycol) diacrylate (PEGDA) with a photosensitive dye. By the proposed fabrication method, various size and shape of a light exposure detector kit could be fabricated using a flexible elastomer mold. Due to a fast and inexpensive fabrication method, the light exposure detector kit could be use a single use for various industrial applications. According to light irradation, the light sensitive structure on a light exposure detector kit could be lose its color by decomposition of a photosensitive dye chemical in the structure. Thus the amount of the exposed light on a substrate could easily be recognised by changing color or transparency of the structure.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.133-137
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• 2003

When a light is projected upon a material, part of its radiation energy is absorbed and the rest is reflected or transmitted according to the nature of the material. The molecules of the substance absorbing a light obtains the radiation energy to the wavelength of the light to make photochemical degradation by ultraviolet ray or thermal reactions like physical damage by infrared ray. The degree of damage by radiation energy varies to the substances of materials, the spectral power distribution of the light source and the duration of irradiation. Because the damage brings about a devaluation of material and once damaged, it is irretrievable, it is necessary to minimize the damage and conserve the native quality of a material by a protective lighting system. A measuring system was set up to measure the temperature rise of each sample by infrared radiation from light sources. And the temperature rise and temperature distribution by various infrared lamps were measured with varying time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05b
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• pp.37-40
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• 2005

Light reflectance and arc resistance of PTFE composites were investigated. PTFE composites have been used widely as a material for circuit breaker nozzle. Arc energy is transported to the nozzle material by radiation. It is needed to add some fillers to PTFE to avoid energy penetration into the nozzle material. In this paper, some fillers that have endurance in the high temperature arc environment were added into PTFE. The light reflectance and arc resistance of PTFE composites according to the kinds and content of fillers were investigated.

• Journal of Environmental Science International
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• v.15 no.7
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• pp.677-688
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• 2006

Currently, the application of $TiO_2$ photocatalyst has been focused on purification and treatment of wastewater. However, the use of conventional $TiO_2$ slurry photocatalyst results in disadvantage of stirring during the reaction and of separation after the reaction. And the usage of artificial UV lamp has made the cost of photocatalyst treatment system high. Consequently, we studied that solar light/$TiO_2$ film system was designed and developed in order to examine disinfection characteristics of sewage wastewater treatment. The optimum conditions for disinfection such as solar light intensity, characteristic of sewage wastewater, amounts of $TiO_2$ and comparison of solar ligth/$TiO_2$ systems with UV light/$TiO_2$ system was examined. The results are as follows: (1) photocatalytic disinfection process with solar light in the presence of $TiO_2$ film more effectively killed total coliform (TC) than solar light or $TiO_2$ film absorption only. (2) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with remain resistant material. (3) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with the increase of amounts of $TiO_2$. (4) TC survival ratio decreased linearly with increasing UV light intensity. (5) The disinfection effect of solar light/$TiO_2$ slurry system decreased more than UV light/$TiO_2$ film systems. (6) The disinfection reaction followed first-order kinetics. We suggest that solar light instead of using artificial UV light was conducted to investigate the applicability of alternative energy source in the disinfection of TC and the degradation of organic material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.606-609
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• 1999

We fabricated white light-emitting diode which have a mixed single emitting layer containing poly(N-vinylcarbazole), trois(8-hydroxyquinoline)aluminum and poly(3-hexylthiophene) and investigated the emission properties of it. It is possible to obtain a blue light from poly(N-vinylcarbazole). green light from tris(8-hydroxyquinoline)aluminum and red light from poly(3-hexylthiophene). The fabricated device emits white light with slight orange light. We think that the energy transfer in a mixed layer occurred from PVK to Alq₃ and P3HT resulted in decreasing the blue light intensity from PVK. We find that the efficiency of the white light electroluminescent device can be improved by injecting electron more effectively and blue light need to improve the color purity of white light.

• Journal of Magnetics
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• v.15 no.2
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• pp.91-98
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• 2010

The paper presents results of a study on the selective separation technology of ferrous and non-ferrous metals from broken light bulbs. The proposed method is to use magnetic fluids to obtain a magnetic fluid based- separation. [1] The study was conducted using three types of waste materials: regular light bulbs, auto light bulbs and neon tubes. In order to process the waste materials, a six stages technologic flow was developed: a) separation of light bulbs components; b) Physical and chemical analysis of raw materials; c) grain conditioning of the raw material; d) dry magnetic separation of ferrous components; e) magnetic fluid separation of non-magnetic material; f) recovery of the magnetic fluid adhered to the surface of the separated material grains. [2] This study shows that magnetic fluid separation is only profitable for regular and auto light bulbs and is not profitable in the case of neon tubes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.214-217
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• 2002

The internal quantum efficiency of organic light emitting devices(OLEDs) using fluorescent organic materials is limited within 25% because of the triplet excitons which can hardly emit light. So there has been considerable interest in finding ways to obtain light emission from triplet excitons. One approach has been to add phosphorescent compounds to one of the layers in OLEDs. Then triplet excitons can transfer to these phosphorescent molecules and emit light. In this study, multilayer OLEDs with phosphorescent emitter, Iridium complexes were prepared. The devices with a structure of ITO/TPD/Ir complex doped in the host material/Alq3/Li:Al/Al were fabricated, and its electrical and optical characteristics were studied. Using various Ir complexes and the host materials, we fabricated several devices and investigated the device characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.550-553
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• 2010

The enhancement of quantum efficiency using a surface modified Ag anode in top-emitting organic light emitting diodes (TEOLEDs) is reported. The operation voltage at the current density of $1\;mA/cm^2$ of TEOLEDs decreased from 9.3 V to 4.3 V as the surface of anode coated with $CuO_x$ layer. The work function of these structures were quantitatively determined using synchrotron radiation photoemission spectroscopy. Secondary electron emission spectra revealed that the work function of the Ag/$CuO_x$ structure is higher by 0.6 eV than that of Ag. Thus, the $CuO_x$ structure acts as a role in reducing the hole injection barrier by about 0.6 eV, resulting in a decrease of the turn-on voltage of top-emitting light emitting diodes.