• Korean Journal of Materials Research
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• v.28 no.8
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• pp.474-477
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• 2018

$Ca_3MgSi_2O_8:Eu^{2+}$(x = 0.003, 0.005, 0.007, 0.01, 0.03 mol) white phosphors for Light Emitting Diodes(LED) are synthesized with different concentrations of $Eu^{2+}$ ions using a solid state reaction method. The crystal structures, surface and optical properties of the phosphors are investigated using X-Ray Diffraction(XRD), Scanning Electron Microscope(SEM) and photoluminescence(PL). The X-Ray Diffraction results reveals that the crystal structure of the $Ca_3MgSi_2O_8:Eu^{2+}$ is a monoclinic system. The particle size of $Ca_3MgSi_2O_8:Eu^{2+}$ white phosphors is about $1{\sim}5{\mu}m$, as confirmed by SEM images. The maximum emission spectra of the phosphors are observed at 0.01 mol $Eu^{2+}$ concentration. The decrease in PL intensity in the $Ca_3MgSi_2O_8:Eu^{2+}$ white phosphors with $Eu^{2+}$ concentration is interpreted by concentration quenching. The International Commission on Illumination(CIE) coordinate of 0.01 mol Eu doped $Ca_3MgSi_2O_8$ is X = 0.2136, Y = 0.3771.

• Journal of Multimedia Information System
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• v.5 no.2
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• pp.105-110
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• 2018

Autonomous cars require the integration of multiple communication systems for driving safety. Many carmakers unveil mirrorless concept cars aiming to replace rear and sideview mirrors in vehicles with camera monitoring systems, which eliminate blind spots and reduce risk. This paper presents optical vehicle-to-vehicle (V2V) communications for autonomous mirrorless cars. The flicker-free light emitting diode (LED) light sources, providing illumination and data transmission simultaneously, and a high speed camera are used as transmitters and a receiver in the OCC link, respectively. The rear side vehicle transmits both future action data and vehicle type data using a headlamp or daytime running light, and the front vehicle can receive OCC data from the camera that replaces side mirrors so as not to prevent accidents while driving. Experimental results showed that action and vehicle type information were sent by LED light sources successfully to the front vehicle's camera via the OCC link and proved that OCC-based V2V communications for mirrorless cars can be a viable solution to improve driving safety.

• Journal of the Korean Solar Energy Society
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• v.34 no.3
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• pp.66-74
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• 2014

In this paper, the performance of Hybrid Dimming control system for Daylighting system is evaluated by accredited tests. The system controls the balance of illuminance of daylight between daylight system and LED light system. It makes the normal illuminance of interior without the effects of weather by controlling the LED depending on the brightness of outside. For the tests, 6 diffusers($600{\times}300mm$) were installed in lighting area($36m^2$) and normal operation of the system sensors were tested about the interference of sunlight. The results of the examinations were satisfied with the criteria of accredited tests. Further research is the verification of energy saving effect by comparing the Hybrid Dimming control system to current artificial light system.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.8
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• pp.1247-1255
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• 2013

In this paper, We proposes multipurpose function electronic measurement reference station prototype system based on LED and Gyro Sensor. This system have developed to possible with real time data collection and landscape illumination and surrounding diastrophism monitoring for that analyze problems of existing planted reference station. Hardware for the proposed system consists of a gyro sensor module to detect diastrophism, GPS module to process location information, environment sensor module to process surrounding environmental data and CDMA wireless data communication to send the collected data to server. In addition, this paper intends to enhance system management and future usability in a way that applies LED, QR-code, RFID and Solar cell module to outer side of electronic measurement reference station to improve usability of H/W for electronic measurement reference station. Lastly, this paper conducted current amount evaluation to supply stabilized electricity with its various functions in the proposed multipurpose function electronic measurement reference station and it's proved that this system can be stably operated with its electricity loss factor of 2.29% loss factor. And this paper conducted a qualitative comparison with existing electronic measurement reference station system in order to evaluate superiority of the proposed electronic measurement reference station.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.12
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• pp.2836-2843
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• 2015

Due to metallicity of materials, a vessel has a limitation to adopt RF-based wireless communication technologies for the inner communication means. Visible Light Communication(VLC) can be a sound alternative to dissolve such a limitation. Using a visual light as a transmission medium, VLC is free from radio interferences and restriction of radio usages which are typically related to RF-based wireless communications. In addition, VLC can not only require the facility cost relatively low because of being possibly converged with existing LED illumination, but also be harmless to the human body. This paper proposes an indoor location-based emergency call service system solution for ships using the VLC technology that supports 256Kbps data rate and 5m transmission distance. This paper presents real implementation and testing results of the solution which verifies the propriety of the proposal.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.3-10
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• 2012

The visible light communication takes advantages of LED and PD for communication and is considered as a next generation wireless communication technology. It can support variety indoor applications. Especially, Visible LAN service has drawn much attention due to high data rate and no interference with existing WPAN system as well as high efficiency in illumination. However, existing MAC protocol occurs a high communication delay due to uplink collision and backoff time. In this paper, to reduce packet delay, we propose an enhanced MAC protocol based on FDD where the time difference between uplink frame and downlink frame transmission is utilized. Through computer simulations, we verified that the proposed MAC protocol outperforms the existing MAC protocol in terms of average packet delay.

• Animal Bioscience
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• v.35 no.12
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• pp.1967-1976
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• 2022

Objective: The aim of this study was to characterize the fecal microbiota of broiler chickens reared in the presence of different shades of light-emitting diode (LED) lights, correlating this information with biochemical and molecular evidence that allowed drawing conclusions on the state of health of the animals. Methods: Overall, the metagenomic approach on fecal samples was associated with evaluations on enzymes involved in the cellular response to oxidative stress: glutathione peroxidase (GPX), superoxide dismutase and catalase; while the inflammatory aspect was studied through the dosage of a proinflammatory cytokine, the interleukin 6 (IL-6), and the evaluation of the matrix metalloproteinases 2 (MMP-2) and 9 (MMP-9). Specifically, analysis was performed on distinct groups of chickens respectively raised in the presence of neutral (K = 3,300 to 3,700), cool (K = 5,500 to 6,000), and warm (K = 3,000 to 2,500) LED lightings, and a direct comparison was performed with animals reared with traditional neon lights. Results: The metagenomic analysis highlighted the presence of two most abundant bacterial phyla, the Firmicutes and the Bacteroidetes, with the latter characterized by a greater relative abundance (p<0.05) in the group of animals reared with Neutral LED light. The analysis on the enzymes involved in the antioxidant response showed an effect of the LED light, regardless of the applied shade, of reducing the expression of GPX (p<0.01), although this parameter is not correlated to an effective reduction in the tissue amount of the enzyme. Regarding the inflammatory state, no differences associated with IL-6 and MMP-9 were found; however, is noteworthy the significant reduction of MMP-2 activity in tissue samples obtained from animals subjected to illumination with neutral LED light. Conclusion: This evidence, combined with the metagenomic findings, supports a potential positive effect of neutral LED lighting on animal welfare, although these considerations must be reflected in more targeted biochemical evaluations.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.11
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• pp.53-61
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• 1996

In this paper, efficient techniques for solder joint inspection have been described. Using three layers of ring shaped LED's with different illumination angles, three frames of images are sequentially obtained. From these images the regions of interest (soldered regions) are segmented, and their characteristic features including the average gray level and the percentage of highlights - refereed to as 2D features - are extracted. Based on the backpropagation algorithm of neural networks, each solder joint is classified intor one of the pre-defined types. If the output value is not in the confidence interval, the distribution of tilt angles-referred to as 3D features - is claculated, and the solder joint is classified based on the bayes classfier. The second classifier requires more computation while providing more information and better performance. The proposed inspection system has been implemented and tested with various types of solder joints in SMDs. The experimental results have verified the validity of this scheme in terms of speed and recognition rate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.55-56
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• 2008

The photo leakage currents of a conventional hydrogenated amorphous silicon(a-Si:H) thin film transistor(TFT) were investigated and analyzed in the case of illumination from various lightsources such as halogen lamp, cold cathode fluorescent lamp(CCFL) backlight, and white light emitting diode(LED) backlight The photo leakage characteristics showed the apparent differences in the leakage level and in the $I_{on}/I_{off}$ ratio in spite of the similar luminances of light sources. This leakage level is expected to be related to the wavelength of the lowest intensity peak from spectral analysis of light sources.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.190-192
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• 2006

The clinical characteristics of photodamaged skin, such as coarse and fine wrinkle are not accurately evaluable with previous methods. Public awareness for wrinkle treatment and prevention which rely on proper assessment and evaluation of the underlying skin changes has been increased as the population ages. In this paper, we suggest an in-vivo method and instrument that allow us to acquire a wrinkle-enhanced image to improve the accuracy of quantitative and qualitative analysis for skin wrinkle. The method used involved white LED illumination and photography through polarizing filters. Finally, the polarized light photography yields an accurate and evaluable parameter of photodamaged skin, especially fine and coarse wrinkle.