• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.662-670
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• 2005

With highly oxygenated fuels the smoke emissions decreased sharply and linearly with increases in the fuel oxygen content and entirely disappeared at an oxygen content of $38wt-\%$ even at stoichiometric mixture conditions The NOx also decreased monotonically with increases in oxygen content. and thermal efficiency slightly improved because of a reduction in cooling loss and improvement in the degree of constant volume combustion. The mechanisms of the significant reductions in emissions and improvement in engine performance were analyzed with a bottom view type DI diesel engine. Together with direct flame images, flame images were taken through an optical fetter passing only two wavelengths for use in 2-D two-color analysis. The results showed that luminous flame decreased significantly with increases in oxygen content and was not detected for neat dimethoxy methane(DMM). The decrease in flame luminosity with highly oxygenated fuels corresponds with decreases in soot and cooling losses, including those due to heat radiation. The 2-D two-color flame analysis indicated that the high temperature flame and high KL factor areas apparently decreased with increasing fuel oxygen content. These results correspond strongly with decreases in NOx. smoke. and cooling loss with increases in oxygen content.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.569-575
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• 2011

Since the high heat generation of LED chips can cause a reduction in lifetime, degradation of luminous efficiency, and variation of color temperature, studies have been carried out on the optimization of LED packaging and heat sinks. Recently, LED packages have been applied to high-power lights such as car headlamps or street lights, and it is known that cooling using only free convection is not at all efficient. Thus, in this study, a heat pipe with forced convection was examined for the optimization of the cooling performance in high-power LED lights. In addition, optimal on-off control of a fan was adopted to increase the fan lifetime, since the lifetime of the fan is generally shorter than that of the LEDs.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.357-361
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• 2009

The authors have demonstrated white oraganic light-emitting diodes (WOLED) using 1,4-bis[2-(4'-diphenylaminobiphenyl-4-yl)vinyl]benzene as fluorescent blue emitter and iridium(III) bis(5-acetyl-2-phenylpyridinato-N,C2') acetylacetonate as phosphorescent red emitter. The optimized WOLED using red host material as bis(2-methyl-8-quinolinato) -4-phenylphenolate exhibited proper color stability in comparison with the control device using 4,4'-N,N'-dicarbazole-biphenyl as red host. The white device showed a maximum luminance of 21100 $cd/m^2$ at 14 V, luminous efficiency of 9.7 cd/A at 20 $mA/cm^2$, and Commission Internationale de I'Eclairage ($CIE_{x,y}$)coordinates of (0.32, 0.34) at 1000 $cd/m^2$. The devices also exhibited the color shift with ${\Delta}CIE_{x,y}$ coordinates of ${\pm}$ (0.01,0.01) from 100 to 20000 $cd/m^2$.

• KIEAE Journal
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• v.13 no.2
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• pp.47-52
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• 2013

The problems of light pollution first became an issue in the 1970s when astronomers identified the degradation of the night sky due to the increase in lighting associated with development and growth. As more impacts to the environment by lighting have been identified, many attempts have been made for reducing light pollutions. To prevent light pollution and increase energy efficiency, Seoul Metropolitan Government(SMG) replaced metal halide road lighting to LED luminaire in four arterial highway in Seoul. The present study compared the lighting characteristics of metal halide and LED luminaire in terms of Korea Standard for road lighting(KS A 3701) and BUG rating from Illuminating Engineering Society of North America(IESNA). The results showed that LED luminaire increased road surface luminance up to 2 times in average compared to the metal halide environment. Also, LED luminaire reduced the glare value by 2 times and luminous flux over 50% than the metal halide luminaire. In comparison with the BUG ratings, LED luminaire rated 1 degree lower for the backlight ratings and 3-4 degrees lower for the uplight ratings. The measured values testified that the LED luminaire is effective for roadway lighting and light pollution reduction.

• Journal of the Korean Institute of Rural Architecture
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• v.10 no.3
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• pp.27-34
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• 2008

Recently, the outdoor lighting of architectural Facade has increased for the improvement of night-scape in urban and coastal resort. The purpose of this research is to analyze lighting characteristics; Luminance, Illuminance, Color Temperature, Chromaticity in Gyengpo Park of Eastern famous coastal resort. The result of this paper is as follows: 1) The Luminance ratio was measured that compare to the 1:10 criterion(IESNA) was in excess to the most building except "K". Because of these condition, Luminance environments was injurious to visual health the overuse of the outdoor lighting or glare to the eyes. 2) The level of vertical Illuminance value was insufficient 33.3% among the cases of survey with 4Lux standard of CIE. 3) The kinds of outdoor lighting of BLDG were increased lighting emitting diode(LED), metal halide(MH) instead of reduction trend of neon, fluorescent light, halogen. As the crisis of Energy resources we will be investigate adapt method of outdoor lighting, which design is based on economical efficiency by the use of optimum lighting.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.2
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• pp.180-186
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• 2005

As a driving method of AC-PDP, Address-Display Separated(ADS) driving has been widely adopted for its simple architecture and low discharge failure rate. However, a high definition like a HDTV has defect of long addressing time by reason of a number of pixels. Priming effect isn't fully sustained because of long addressing time during the address period. Therefore, it has different wall charge and luminance of each addressing time in the sustain period. In this study, we suggest a new driving waveform on the address period to improve these defects. We applied a ramp waveform, instead of a square waveform, to an address period in ADS, for operating on the AC-PDP, which used the conventional gas [He-Ne-Xe]. When the ramp waveform is applied to the address period, we experimented for uniform wall charge and the improved luminance by sustained Priming effect at each addressing time in the sustain period.

• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.8
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• pp.679-687
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• 2001

It is known that amorphous BaTiO$_3$ thin films have good insulating properties[1][2]. In this investigation, amorphous BaTiO$_3$ thin films were deposited by rf magnetron sputtering on thick BaTiO$_3$ films of AC powder EL devices which were fabricated by screen-printing. The electrical and optical properties of the EL devices were then investigated. Adding amorphous BaTiO$_3$ thin film, it showed that leakage current density was decreased. Especially, leakage current density was decreased more with he sample of 0.5-hour deposition than the sample of 4-hours deposition. This result led to the improvement of luminous efficiency by 11%. It could be concluded that proper amorphous BaTiO$_3$ thin film deposition improved the surface property of dielectric layer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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• pp.716-719
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• 2007

The effects of the evaporation rate of MgO films using an electron beam on the MgO properties and the discharge characteristics of a plasma display panel (PDP) were investigated and analyzed. MgO films were deposited with the various MgO evaporation rates. The MgO properties such as the crystal orientation, the surface roughness, and the film structure were inspected using XRD (X-ray diffraction), AFM (atomic force microscopy). From the experiments and Paschen law, the maximum value of the secondary electron emission coefficient $({\gamma})$ was obtained at the evaporation rate of $5{\AA}/sec$. The XRD results and cathode-luminescence (CL) spectra show the ${\gamma}$ values are correlated with F/F+ centers of the molecular structure of MgO films. The minimum firing voltage and the maximum luminous efficiency were obtained at an evaporation rate of $5{\AA}/sec$. In the MgO film deposited at $5{\AA}/sec$, the (200) orientation and F+ center were most intensive.

• Journal of Convergence for Information Technology
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• v.10 no.2
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• pp.96-101
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• 2020

In micro-sized light emitting diodes, which are increasingly attentions as the light sources of displays and semiconductor lighting, increasing the amount of light and improving the luminous efficiency are very important and various development directions and methods have been proposed. In this study, the design of 3-dimensional nano structures through nano frame formation and the application of a nano pattern and a reactive etching method were proposed. And it will also be discussed that nano pillar arrays with nano cavities having improved verticality can be applied to semiconductor light sources through the development of nano frame structures.