• Journal of the Korean Ceramic Society
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• v.43 no.3 s.286
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• pp.177-184
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• 2006

Dy $L_3$-edge XANES and EXAFS spectra of chalcogenide Ge-As-S glass doped with ca. 0.2 wt% dysprosium have been investigated along with some reference Dy-containing crystals. Amplitude of the white-line peak in XANES spectrum of the glass sample turns out to be stronger than that of other reference crystals, i.e., $DY_2S_3,\;Dy_2O_3\;and\;DyBr_3$. It has been verified from the Dy $L_3$-edge EXAFS spectra that a central Dy atom is surrounded by $6.7{\pm}0.5$ sulfur atoms in its first coordination shell in the Ge-As-S glass, which is relatively smaller than 7.5 of the $Dy_2S_3$ crystal. Averaged Dy-S inter-atomic-distance of the glass ($2.78{\pm}0.01{\AA}$) also turns out to be somewhat shorter than that of the $Dy_2S_3$ crystal ($2.82{\pm}0.01{\AA}$). Such nanostructural changes occurring at Dy atoms imply there being stronger covalency of Dy-S chemical bonds in the Ge-As-S glass than in the crystal counterpart. The enhanced covalency in the nanostructural environment of $Dy^{3+}$ ions inside the glass would then be responsible for optical characteristics of the $4f{\leftrightarrow}4f$ transitions of the dopants, i.e., increase of oscillator strengths and spontaneous radiative transition probabilities.

• Korean Journal of Materials Research
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• v.27 no.9
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• pp.501-506
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• 2017

Surface morphology and optical properties such as transmittance and haze effect of glass etched by physical and chemical etching processes were investigated. The physical etching process was carried out by pen type sandblasting process with $15{\sim}20{\mu}m$ dia. of $Al_2O_3$ media; the chemical etching process was conducted using HF-based mixed etchant. Sandblasting was performed in terms of variables such as the distance of 8 cm between the gun nozzle and the glass substrate, the fixed air pressure of 0.5bar, and the constant speed control of the specimen stage. The chemical etching process was conducted with mixed etching solution prepared by combination of BHF (Buffered Hydrofluoric Acid), HCl, and distilled water. The morphology of the glass surface after sandblasting process displayed sharp collision vestiges with nonuniform shapes that could initiate fractures. The haze values of the sandblasted glass were quantitatively acceptable. However, based on visual observation, the desirable Anti-Glare effect was not achieved. On the other hand, irregularly shaped and sharp vestiges transformed into enlarged and smooth micro-spherical craters with the subsequent chemical etching process. The curvature of the spherical crater increased distinctly by 60 minutes and decreased gradually with increasing etching time. Further, the spherical craters with reduced curvature were uniformly distributed over the etched glass surface. The haze value increased sharply up to 55 % and the transmittance decreased by 90 % at 60 minutes of etching time. The ideal haze value range of 3~7 % and transmittance value range of above 90 % were achieved in the period of 240 to 720 minutes of etching time for the selected concentration of the chemical etchant.

• Current Optics and Photonics
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• v.3 no.5
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• pp.423-428
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• 2019

Visibility of road-surface markings is one of the critical issues that should be secured for self-driving cars as well as human drivers. Glass beads are taking on the role of retroreflectors, and therefore are considered a necessity in modern pavements. In this context, retroreflectance is sensitively dependent not only on the refractive index of glass beads but also on that of the surrounding medium. This implies that the optimum refractive index of glass beads immersed in water, i.e. under wet conditions, is different from that of glass beads surrounded by air, i.e. under dry conditions. A refractive index of approximately 1.9, which is known to maximize retroreflectance under dry conditions, actually exhibits much poorer retroreflectance under wet conditions. This suggests that glass beads with optimal refractive index for wet conditions need to be installed together with those for dry conditions. We propose a facile but practical model capable of calculating retroreflectance of glass beads surrounded by an arbitrary medium, here water in particular, and experimentally verify its capability of assessing the refractive index of commercial glass beads. Changes in retroreflectance according to the mixing ratio of glass beads with different refractive indices are also discussed, in an effort to propose the proper use of glass beads produced for dry and wet conditions.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.499-502
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• 2004

The temperature distribution of a glass plate heated in the infrared heating chamber has been investigated. Temperature of the glass panel is measured using a set of thermocouples and the optical pyrometer. Temperatures measured by thermocouples have good agreement with those by the pyrometer. The temperature uniformity of the panel is improved with wall reflectivity, which is one of the important factors to uniformly heat the panel

• Korean Journal of Optics and Photonics
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• v.24 no.1
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• pp.39-44
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• 2013

In this study, we assessed the hydrophilic characteristics of the surface of toughened glass used in smartphones by investigating the optical properties and contact angle characteristics of the plasma device. In this study, the characteristics were different depending on the partial pressure of the gas, input voltage, and degree of ionization of argon gas. In this study, the surface of the toughened glass became more hydrophilic, as indicated by contact angle and light spectrum, after plasma treatment than before the treatment.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.18-24
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• 2010

Efforts to obtain more efficient coupling of light from a laser diode to a single mode fiber have continued for various applications such as links for optical fiber communication systems. In TO-can package, configuration of optimized aspherical lens is bi-aspheric and its diameter is 2.4mm. We designed and fabricated aspherical coupling lens by means of glass molding technique under consideration of glass shrinkage. By controlling the aspherical profile error and surface roughness which were below 90nm and 10nm, respectively, we obtained the low coupling loss, 5.40dB, which was able to use for coupling a single mode fiber to laser diode.

• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.497-502
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• 2005

This study investigated the effects of the substrate and powder content on the fabrication of SiO$_{2}$ photonic crystals by evaporation method. Photonic crystals were self-assembled on quartz, Corning 1737 glass, slide glass, and ITa glass to verify the effects of the wetting angle and surface morphology. The powder contents of the solution were varied from 0.2 to 2.0 wt$\%$. The number of photonic crystal layers increased according to the decrease of wetting angle and surface roughness. The resultant photonic crystals showed the best optical characteristics when the number of photonic crystal layers was within 40 and 50. In addition, the intensity peak of Fabry¡?Perot fringes increased when the wetting angle was large and the particle size was small. Photonic crystals coated on ITO glass showed the highest reflectance peak of 63$\%$ relative intensity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.64-64
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• 2010

This paper presents the results of changes of optical properties of front materials in crystalline PV modules. If PV modules on the outdoor, transmittance of front materials is reduced by solar light. That is UV, IR included Solar spectrum will have change the properties of glass. Therefore decrease in transmittance leads to loss of the PV modules output. All the PV modules showed the loss in Isc by 1~5% within few hors. To investigate the changes we are analyzed using spectrophotometer from raw glass to laminated glass.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.761-766
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• 2012

Abrasive fluid jet polishing processes have been used for the polishing of optical surfaces with complex shapes. However, unstable and unpredictable polishing spots can be generated due to the fundamental property of an abrasive fluid jet that it begins to lose its coherence as the jet exits a nozzle. To solve such problems, MR fluid jet polishing has been suggested using a mixture of abrasives and MR fluid whose flow properties can be readily changed according to imposed magnetic field intensity. The MR fluid jet can be stabilized by imposed magnetic fields, thus it can remain collimated and coherent before it impinges upon the workpiece surface. In this study, MR fluid jet polishing characteristics of fused silica glass were investigated according to injection time and magnetic field intensity variations. Material removal rates and 3D profiles of the generated polishing spots were investigated. From the results, it can be confirmed that the developed MR fluid polishing system can be applied for stable and predictable precise polishing of optical parts.

• The Journal of the Korea Contents Association
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• v.6 no.12
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• pp.163-168
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• 2006

Hg-free fluorescent lamps were fabricated and electro-optical characterization were measured for using LCD backlight. PDP phosphors, nitro-cellulose and n-butyl acetate were mixed and coated uniformly in glass tube without stain. The glass tubes were sintered at $550^{\circ}C$ for 20 minutes, vacuumed to $10^{-6}$ torr and supplied discharge gas by using a gas mixture. After various experiment about phosphors thickness and inner diameter of glass tube, the appropriate phosphors thickness and inner diameter of glass tube were obtained. The luminance and luminous efficiency of manufactured fluorescent lamps with Ne+Xe discharge gas were $6,270cd/m^2$, 13 lm/W under 75 kHz sinusoidal wave voltage, respectively.