• Journal of information and communication convergence engineering
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• v.13 no.1
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• pp.50-55
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• 2015

We report design and simulation of a two-dimensional (2D) silicon-based nanophotonic crystal as an optical insulator to enhance the light emission efficiency of light-emitting diodes (LEDs). The device was designed in a manner that a triangular array silicon photonic crystal light insulator has a square trench in the middle where LED can be placed. By varying the normalized radius in the range of 0.3-0.5 using plane wave expansion method (PWEM), we found that the normalized radius of 0.45 creates a large band gap for transverse electric (TE) polarization. Subsequently a series of light propagation simulation were carried out using 2D and three-dimensional (3D) finite-difference time-domain (FDTD). The designed silicon-based light insulator device shows optical characteristics of a region in which light propagation was forbidden in the horizontal plane for TE light with most of the visible light spectrum in the wavelength range of 450 nm to 600 nm.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.9
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• pp.444-449
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• 2001

In this paper, a novel ultraviolet sensor is presented based on a photoluminescent porous silicon. Porous silicon layer was formed by chemical etching of surface of pn junction in a $HF(48%)-HNO_3(60%)-H_20$ solution. Incident ultraviolet(UV) light is converted to visible light by photoluminescent porous silicon layer, and then this visible light generates electron-hole pairs in the pn junction, which produces a photocurrent flow through the device. In order to maximize detection efficiency, the peak sensitivity wavelength of the pn junction diode was matched with the peak wavelength of Photoluminescence from porous silicon layer. The porous silicon ultraviolet sensor showed a large output current as UV intensity increases and but very low sensitivity to visible light. The detection sensitivity of porous silicon sensor was calculated as 2.91mA/mW. These results are expected to open up a possibility that the present porous silicon sensor can be used for detecting UV light in a visible background, compared to silicon UV detectors which have an undesirable response to visible light.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.89.2-89.2
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• 2010

The dye-sensitized solar cell (DSSC) is a device for the conversion of visible light into electricity, based on the sensitization of wide bandgap semiconductors. The performance of the cell mainly depends on a dye used as sensitizer. The absorption spectrum of the dye and the anchorage of the dye to the surface of $TiO_2$ are important parameters determining the efficiency of the cell. Generally, transition metal coordination compounds(ruthenium polypyridyl complexes) are used as the effective sensitizers, due to their intense charge-transfer absorption in the whole visible range and highly efficient metal-to ligand charge transfer. However, ruthenium polypyridyl complexes contain a heavy metal, which is undesirable from point of view of the environmental aspects. Moreover, the process to synthesize the complexes is complicated and costly. Alternatively, organic dyes can be used for the same purpose with an acceptable efficiency. The advantages of organic dyes include their availability and low cost. We designed and synthesized a series of organic sensitizers containing long wavelength absorption-chromophores for the dye sensitized solar cell. The DSSC composed of Blue-chromophores for the sensitization absorbed long wavelength region which is different also applied into the dye-cocktail (mixing) system. The photovoltaic property of DSSCs organic long wavelength absorption-chromophores were measured and evaluated by comparison with that of individual chromophores.

• Restorative Dentistry and Endodontics
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• v.14 no.1
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• pp.149-159
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• 1989

The purpose of this study was to assess the effects of wavelength and intensity of light curing units on the curing of composite resin. The wavelength and intensity of nine units were evaluated with Optical Multichannel Analyzer and Radiometer. Two-part split stainless steel mold with a cylindrical hole-3.0mm in diameter, 6.0mm in hgieht-was prepared. After placing a Mylar strip between two parts, 100 specimens were made by inserting each of four composite resins into the mold and irradiating for 20 seconds with five light units alternatively. The curing depths were measured by scraping method and evaluated by two-way ANOVA. And Vicker's hardness measurements were made on the longitudinally sectioned surface at 0.5mm interval. The results were as follows: 1. Visilux 2 showed a narrow spectral band within the effective wavelength in initiating polymerization and the highest intensity. Translux showed the diffuse spectrum of wavelength and the lower light intensity. 2. Visilux 2 showed the highest curing effect in any composite resin and then followed by Optilux, Efos 35, Heliomat and Translux. (p < 0.01) 3. Durafill showed the deepest curing depth in any light unit and then followed by Bisfil M, Silux and Heliosit. (p < 0.01). 4. Maximum hardness values showed 0.1mm and 0.5mm under top surface and then gradually decreased with depth.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.770-775
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• 2018

In this study, the characteristics of muscle relaxation were analyzed by the experimental and numerical method. A skin tissue was produced by imitational biological tissue using the agar powder, saline solution and sugar. The tissue was exposed to three types of wavelength-blue visible radiation(410 nm), red visible radiation(635 nm), and infrared ray(830 nm). The temperature results along the depth of tissue were measured according to the variation of light wavelength and irradiation time. The temperature change of the tissue shown up similar pattern regardless of the light wavelength kinds. The wavelength of infrared ray penetrated strongly into tissue between 3.2 mm and 11.4 mm. Also, the temperature change with the irradiation time was small, and the temperature value of the infrared ray was the largest. As a result, the muscle relaxation will occur mainly at the infrared wavelength.

• Journal of the Optical Society of Korea
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• v.12 no.2
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• pp.79-87
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• 2008

We have developed a miniature fisheye lens with $190^{\circ}$ field of view operating simultaneously in the visible and the near infrared wavelengths. The modulation transfer function characteristic for the visible wavelength is sufficient for a mega-pixel-grade image sensor. The lens also has a fair resolution in the infrared wavelength region. The calibrated $f-{\theta}$ distortion is less than 5%, and the relative illumination is over 90%. In consequence, a sharp wide-angle image can be obtained which is uniform in brightness over the entire range of field angles. The real image heights for the visible and the near infrared wavelengths have been fitted to polynomial functions of incidence angle with sub-pixel accuracies. Combined with the near equidistance projection scheme of the lens, this lens can be advantageously employed in various image-processing applications requiring a wide-angle lens.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1998.11a
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• pp.138-141
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• 1998

To evaluate the color change of the opaque resin materials, a measuring system including PAS(photodegradation acceleration system) was constructed. Xenon lamp is used as a light source in the PAS, and the radiant energy from the lamp is irradiated to the samples through serveral high-pass filters with cut-off wavelength in UV and visible region. The color difference of the samples were measured by using the measuring system with a spectrophotometer(CM-2002) and a computer. The result showed that the opaque resin materials changed severely in their color in the wavelength of UV region and changed a little in the wavelength of visible region.

• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.27-31
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• 1998

We investigated visible light radiated from Plasma focus device by time-resolved analyzed method and time-integrated analyzed method. Plasma focus consisted of two coaxial electrodes is a device that translated from electric energy of maximum 40 kV/20 kJ in capacitor banks into visible light by electric discharge. Spectral analysis is using Monochromator(f =0.5m). Time-resolved spectrum is analyzed with a oscilloscope the light pulse of constant wavelength and time-integrated spectrum does with densitometer the film which developed a constant range of wavelength. The optimum condition of visible emission was that the discharging voltage was 17kV and the gas pressure 0.5 torr Ar.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.118.1-118.1
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• 2011

The dye-sensitized solar cell (DSSC) is a device for the conversion of visible light into electricity, based on the sensitization of wide bandgap semiconductors. The performance of the cell mainly depends on a dye used as sensitizer. The absorption spectrum of the dye and the anchorage of the dye to the surface of TiO2 are important parameters determining the efficiency of the cell. Generally, transition metal coordination compounds(ruthenium polypyridyl complexes) are used as the effective sensitizers, due to their intense charge-transfer absorption in the whole visible range and highly efficient metal-to ligand charge transfer. However, ruthenium polypyridyl complexes contain a heavy metal, which is undesirable from point of view of the environmental aspects. Moreover, the process to synthesize the complexes is complicated and costly. Alternatively, organic dyes can be used for the same purpose with an acceptable efficiency. The advantages of organic dyes include their availability and low cost. We designed and synthesized a series of organic sensitizers containing long wavelength absorption-chromophores for the dye sensitized solar cell. The DSSC composed of Blue-chromophores for the sensitization absorbed long wavelength region which is different also applied into the dye-cocktail (mixing) system. The photovoltaic property of DSSCs organic long wavelength absorption-chromophores were measured and evaluated by comparison with that of individual chromophores.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.237-242
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• 2012

At present, crystalline solar cells take up a significant percentage of the solar industry. The ways of increasing the efficiency of crystalline solar cell are texturing and AR(Anti-Reflection) coating, and the purpose of these technologies is to increase the amount of available light on the solar cell by reducing the reflectivity. The reflectance of crystalline silicon solar cell combined with such technologies will be able to predict using the proposed simulation in this paper. The simulation algorithm was made using MATLAB, and it is a combination of the theories of reflection in textured wafer and in anti-reflection coated wafer. The simulation results were divided into three wavelength band and were compared with actual reflectance measured by a spectrometer. The wavelength band from 300 to 380 was named ultraviolet region and the wavelength band from 380 to 780 is named visible region. Finally, the wavelength band from 780 to 1200 named infrared region. When compared with measured reflection data, the simulation results had a small error from 0.4 to 0.5[%] in visible region. The error occurred in the rest two regions is larger than visible region. The extreme error occurred the infrared region is due to internal reflection effect, but in the ultraviolet region, the rationale on reduction phenomenon of reflectance occurred in small range did not proved. If these problem will be solve, this simulation will have high reliability more than now and be able to predict the reflectance of solar cells.