• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1086-1089
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• 2006

We have developed 2.4" QVGA wide color gamut LCD module using RGB-LED backlight. The color gamut is achieved 100% of NTSC compared to 70% of NTSC when used with White-LED backlight. But RGB LED backlight is difficult to maintain its color balance since RGB LED is gradually degraded by the change of ambient temperature and a long term aging characteristic, etc. This paper describes a feasibility study of our optical feedback system developed for preventing such a color shift.

• 수산해양기술연구
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• 제51권2호
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• pp.163-170
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• 2015

Recently LED fish-attracting lamps have been more widely used in fisheries as low-cost and high-efficiency fishing gear, and development of long-life high-efficiency lamps is required through the design of LED packages to optimize heat resistance. This study developed an improved LED fish-attracting lamp with excellent heat performance, which was verified using a numerical model. Heat-resistance design factors such as the heat-radiation fin shape, PCB type, and LED chip count were investigated and optimized. Comparison with a commercial 180-W LED fishing lamp showed that the increase in initial temperature was 40% higher than that of the surrounding LED chip because of design errors in contact thermal resistance. The 250-W LED lamp developed in this study has a characteristic with thermal rising in linearly stable according to the heat source. In addition, luminance efficiency was improved by 20-65% by using flow-visualization simulation. A decrease of 45% in total power consumption with a fuel-cost reduction of over 55% can be expected when using these optimized heat release design factors.

• 한국신뢰성학회지:신뢰성응용연구
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• 제13권3호
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• pp.207-216
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• 2013

This paper, we classified LED failure mechanisms that occur due to the delamination and analyzed each of the mechanism that gives the LED PKGs the effect. Usually, the LED is composed of several materials which are LED chips, gold wire, phosphor, epoxy resin, adhesive, reflector and lead frame. These different materials are usually delaminated in trouble conditions which are huge temperature difference, hot and humid or mechanical shocked. When the components are delaminated, a luminance will be lost and moisture be absorbed easily, a thermal resistance be increased attendantly. In this paper, we experimented to investigate failure mechanism of the thermal resistance and failure mechanism of the decrease of luminance that occur due to the delamination. A thermal shock test was performed to reproduce this phenomena by subjecting samples to a cold-hot cyclling process between $-30^{\circ}C$(15min) and $110^{\circ}C$(15min). The samples were inspected at 200, 600 and 1,000 cycles. We measured feature of LED using the spatial analyzer, optical microscope, thermal resistance, photometer, scanning electron microscope (SEM). As a result, the progression of the crack and the thermal resistance and decrease in luminance are proportional to number of thermal shock.

• Design & Manufacturing
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• 제7권1호
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• pp.60-63
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• 2013

Recently, Silicone that one of the thermo-sets is used to making optical products such as LED lenses because of excellent thermal properties. LED lenses are required to keep the precise dimensions, so they must be molded to have the minimum deformation. Thermo-sets have the expansion characteristic on the part of thermal property, it is important to optimize the cure condition so that the deformation of the part become minimum. In this study, to investigate the relationship between the shrinkage by the curing and expansion by the thermal properties of the resin, reactive injection experiment was performed by setting the variables such as mold setting temperature, cure time. As a result, it was confirmed that there was a interval while the thermal properties were transferred to more active during the cure process. It is expected to help in determining the reactive injection molding conditions of the thermo-set parts as well as LED lens in order to reduce the amount of deformation.

• Design & Manufacturing
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• 제15권3호
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• pp.50-55
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• 2021

Solar power generation, which is one of the methods of using solar energy, has a high possibility of practical implementation compared to other renewable energy power generation, and it has the characteristic that it can generate as much power as needed in necessary places. In addition, maintenance is easy, unmanned operation is possible, and power management can be performed more efficiently if operated in a hybrid method with existing electric energy. Therefore, in this study, numerical analysis using a computer program was performed to analyze the efficient operation and performance improvement of solar energy of the rotating condensing type solar LED street lamp. As a result, the two-axis tracking type could obtain 15.23 % more electricity per year than the fixed type, and additional auxiliary power generation was required for the fixed type by 19 % per year than the tracking type. As a result of computational fluid dynamics(CFD) simulation for PV module surface temperature prediction, the The surface temperature of the Photovoltaics(PV) module incident surface was predicted to be about 10℃ higher than that of the fixed type.

• 한국산학기술학회논문지
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• 제13권10호
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• pp.4398-4404
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• 2012

본 논문은 자동차 LED head lamp의 방열을 위한 히트싱크(heat sink)의 설계요소를 변화시켜 방열특성을 알아보고자 수치해석을 수행하였다. 수치해석에 적용한 히트싱크는 LED를 광원으로 사용하는 기존제품(Type 1)을 바탕으로 한정된 내부공간에 적합하도록 설계하여 5가지 Type으로 설계하였다. 설계된 히트싱크의 수치해석은 ANSYS CFD V12.1을 사용하여 히트싱크의 변화에 따른 온도분포와 평균온도, 공기유동특성, 열유속 등을 분석하였다. 수치해석을 통하여 방열판의 구조와 휜 형상에 따른 방열특성의 상관관계를 도출할 수 있었으며, 설계된 히트싱크의 온도분포, 공기의 유동특성, 열유속 등을 분석한 결과, 히트싱크 Type 2가 다른 Type들에 비해 LED head lamp의 방열을 위해 적합한 특성을 나타내었다.

• 한국초전도ㆍ저온공학회논문지
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• 제16권2호
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• pp.54-58
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• 2014

High-temperature superconducting (HTS) rotating machines always require an electric current of from several hundreds to several thousand amperes to be led from outside into cold region of the field coil. Heat losses through the current leads then assume tremendous importance. Consequently, it is necessary to acquire optimal design for the leads which would achieve minimum heat loss during operation of machines for a given electrical current. In this paper, conduction cooled current lead type of 10 MW-Class HTS rotating machine will be chosen, a conceptual design will be discussed and performed relied on the least heat lost estimation between conventional metal lead and partially HTS lead. In addition, steady-state thermal characteristic of each one also is considered and illustrated.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.38-46
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• 2010

For the development of 100[W] stage lighting, quantitative and uniform color mixing that applied through color adopted Simple-Inverse matching so that color mixing can be possible along Black Body Locus. R,G,B(Red, Green, Blue) LED(Light Emitting Diode) arrangement through LED package character analysis, LED module, and the characteristic of device were considered for uniform color mixing. A distance changeable optical device was built to assure high uniformity and high diffusion of not only the middle of diffusion side but also the border side. Also, we developed the control power circuit that can expand up to 6 channels which are possible for quantitative color mixing, and the high uniformity and high quantified border light for color mixing control and the verification of color mixing characteristics by composing GUI(Graphical user interface) including color mixing simulator. By presenting the experimental results of light color control, we proved the usefulness of our developed border light and the proposed color mixing method.

• 한국전기전자재료학회논문지
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• 제30권8호
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• pp.520-524
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• 2017

Electrical relay in an essential part of smart grids, electrical vehicles, and LED lightning systems. Therefore, studying relay reliability is important. Relays using permanent magnet actuators (PMAs), which are energy efficient, are also in the spotlight. However, most of the permanent magnets used in PMAs have a characteristic wherein the magnetic flux decreases as the temperature increases. When the magnetic flux is reduced, the force acting on the actuator is reduced. Therefore, in this study, we measured the decrease in the relay operating speed with permanent magnet reduction due to temperature rise. In addition, changes in the bouncing phenomena due to magnetic flux reduction were analyzed. As a result, the operating speed of the relay has decreased and the bouncing phenomenon has not significantly changed.

• 한국분말재료학회지
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• 제9권3호
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• pp.148-152
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• 2002

The microstructures and indentation fracture of pressureless-sintered $DyNbO_4$ crystalline were investigated as a basic study for the application of weak phase of fibrous monolithic composites. They were comprised with many lamella twins as well as micro-cracks at the grain boundaries. The hardness at room temperature was remarkably low value(575 Hv) due to the low relative density and existence of microcracks at grain boundaries. The main fracture mode was a typical intergranular fracture, and showed remarkable micro-cracking effect. The heavy plastic deformation was observed around the site of indentation. In addition, the $DyNbO_4$ was expected to apply as a weak phase in the fibrous monolithic composites because of the low hardness and easily plastic deformation that could be led the preferable pulled-out and microcracking toughening under the failure.