• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.601-610
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• 2016

The light-emitting diode (LED) has been used in a variety of industrial fields and for general 0lighting purposes on account of its high efficiency, low power consumption and long lifespan. The LED is driven by direct current; therefore, an AC/DC converter is typically required for its use. An electrolytic capacitor is generally used for stabilizing DC voltage during use of the AC/DC converter. However, this capacitor has a short lifespan, which makes it a limiting factor in LED lighting. Furthermore, LED lighting requires a dimmable control to enable energy savings and fulfil a growing consumer demand. In this paper, the dimmable single-stage power factor correction (PFC) continuous conduction mode (CCM) flyback converter that employs no electrolytic capacitor is presented. The LC resonant filter is alternatively applied to reduce the 120[Hz] ripple on the output. And the optimum value of the LC resonant filter parameters considering both efficient and performance is analysed. Simulation and experimental results verify the satisfactory operation of the converter.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.382-384
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• 2013

LED is much brighter than the traditional incandescent, and low power consumption. Development and commercialization of LED fluorescent lamp is made in order to improve efficient fluorescent lamps with this existing and environmental problems. Because, unlike fluorescent lamps, it is not possible to directly use AC power to the unidirectional element having a polarity, LED requires a power supply. The power supply function is lowered as compared with the fluorescent lamp common in terms of maintenance costs because of the high price large. In this study, we constructed a circuit that can be controlled with a constant current in order to eliminate a phenomenon that brightness of the light which rectifies the AC power supply easy to place in the power supply due to the current change due to the voltage fluctuation is changed, in maintenance, I would like to propose how to develop a device which can be easily replaced less expensive composed of interchangeable modules of Plug in / out method to distinguish the LED module this.

• The Journal of Society for e-Business Studies
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• v.3 no.1
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• pp.95-115
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• 1998

The growth of the internet shopping mall has led to a critical mass of consumers and firms participating in a global online marketplace. This study is devoted to providing a conceptual framework for describing and analyzing the characteristics of internet shopping mall. We proposed a model which classifies internet shopping mall into four types, including (1) general intermediary (2) general direct-sales (3) specialized intermediary (4) specialized direct-sales. Our framework facilitates greater understanding of the internet shopping mall as commercial medium and allows examination of internet shopping mall in terms of the opportunities and challenges firms facing online business.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.120-126
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• 2014

Translucent green colored opal glass was fabricated to substitute polycarbonate diffuser of LED lighting in order to solve the durability problem. Batch materials of green colored opal glass with the composition of calcium phosphate for opacifier and iron oxide for colorant were made and melted at $1550^{\circ}C$. As the results, translucent green colored opal glass was obtaind, which had excellent optical properties compare with nomal color glass for the diffuser of LED lighting, with no dazzling from direct light by high haze value over 90 % and low parallel transmittance value about 1 %. Therefore, it is concluded that this translucent green colored opal glass can be used for the glass diffuser materials of LED lighting with high heat resistance and high durability to substitute polycarbonate diffuser.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.2
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• pp.217-223
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• 2015

In this paper, the performance of a system was analyzed according to the design parameters of a LED secondary lens that can be applied at a very close range, e.g., for direct lighting or display systems. We designed the secondary lens of the very-close-range LED using an aspheric equation and analyzed its performance-particularly the angle of the beam spread, central luminous intensity, and light uniformity-with respect to the thickness of lens, radius, conic constant, and asphericity (4th). Our analysis shows that four parameters affect the performance. The simulation results indicate an optimal thickness of 1 mm and show that a larger radius yields higher performance. The optimal range for the conic constant was determined as -1.21 to -1.25, the optimal range for the asphericity was determined as 0.0047xx to 0.0049xx (4th).

• Journal of the Semiconductor & Display Technology
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• v.11 no.1
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• pp.21-27
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• 2012

The optical diffuser for direct-lit LED backlight unit was prepared by using extrusion compounding followed by thermoforming process. Poly(methyl methacrylate) (PMMA) with superior optical characteristics and polycarbonate (PC) with good thermal property were used as base resins, and crosslinked polystyrene (PS) and PMMA beads as diffusing agents were incorporated into resin matrix to derive light scattering and diffusing action. In the compounded plate, the diffusing beads were observed to be dispersed uniformly and distinctly in the continuous phase. The inclusion of polymeric beads up to 3 wt% substantially enhanced the optical characteristics such as luminance, luminance uniformity, haze for the diffuser. Two different diffusers of PC and PMMA-based compound with various compositions were compared in terms of measured optical, thermal, and mechanical properties, which would be expected to be utilized for the industrial application of LED backlight unit.

• Asian-Australasian Journal of Animal Sciences
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• v.10 no.5
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• pp.510-513
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• 1997

This study examined the effects of ignoring inbreeding depression on (co)variance components for weaning weight through the use of Monte Carlo simulation. Weaning weight is of particular interest as a trait for which additive direct and maternal genetic components exist and there then is the potential for a direct-maternal genetic covariance. Ignoring inbreeding depression in the analytical model (.8 kg reduction of phenotypic value per 1% inbreeding) led to biased estimates of all genetic (co) variance components, all estimates being larger than the true values of the parameters. In particular, a negative bias in the direct-maternal genetic covariance was observed in analyses that ignored inbreeding depression. A small spurious sire-by-year interaction variance was also observed.

• The korean journal of orthodontics
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• v.34 no.4 s.105
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• pp.333-342
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• 2004

The purpose of this study was to evaluate the clinical effectiveness of a plasma arc light and light emitting diode (LED), compared with shear bond strength and the failure pattern of brackets bonded with visible light in direct bonding. Brackets were bonded with Transbond XT to 60 human premolars embedded in the resin blocks according to different light-curing methods. Then, the shear bond strength of each group was measured using a universal testing machine (Instron) and the adhesive failure pattern after debonding was visually examined by light microscope. The results were as follows: 1. The shear bond strength showed no significant difference between the visible light and light emitting diode, but the plasma arc light exhibited a significantly lower shear bond strength compared with the visible light and light emitting diode. 2. In the visible light and light emitting diode, adhesive failure patterns were similar. Bond failure occurred more frequently at the enamel-adhesive interface. 3. The bonding failure of brackets bonded with plasma arc light occurred more frequently at the bracket-adhesive interface. The results of this study suggest that plasma arc light, light emitting diode and visible light are all clinically useful in the direct bonding of orthodontic brackets.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.169-174
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• 2014

This paper proposes a novel beehive-shaped reflector for application to light-emitting diode (LED) transceivers for illumination and bi-directional visible light communication (VLC). By using a diffuse propagation model extended to line-of-sight and direct signals, the distribution of illuminance and the path loss of the transceiver are investigated to evaluate the performance of the beehive-shaped reflector. To verify bi-directional communication, a VLC-based image capture system, comprising a complementary metal-oxide semiconductor (CMOS) image sensor and video processor unit, is demonstrated. Real-time images captured by the CMOS camera are successfully transmitted to the monitoring system via a free-space channel at a rate of 115.2 kbps.

• The Transactions of the Korea Information Processing Society
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• v.6 no.5
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• pp.1351-1361
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• 1999

The wide spread of multimedia system demands a large area viewing display device which can inform a message to many people in open area. This paper is about the design of a large area viewing LED panel control system. The control system runs on 16 bit microprocessor MC68EC000 and has following functions: 16 line clock and time, 2 channel priority interrupt, 2 channel direct memory access, 2 channel 12 bit clock and timer, 2 channel infrared remocon receiver, 2 channel RS-232C with 16 byte FIFO, IBM PC/AT compatible keyboard interface, ISA bus, battery backuped real time clock, battery backuped 256 byte SRAM and watch dog timer. The core circuits are implemented to ASIC, considering lower cost, higher reliability, higher performance, smaller dimension, and lower power consumption. This is verified by simulation and fabricated in 0.6 um CMOS SOG processes. The total gate count is 39,083 and the clock frequency is 48 MGz. The fabricated ASIC is mounted on test board.