• Journal of IKEEE
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• v.23 no.2
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• pp.524-528
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• 2019

Although different types of discharge cells exist, in common it is the primary goal for all discharge cells to have lower drive voltages and higher efficiency characteristics. To improve these factors, many studies are conducted that prolong the discharge path inside the discharge cell or change the composition of the working gas. In this paper, the two-dimensional fluid simulation was used to calculate the discharge voltage (firing voltage and sustain voltage) and the change in luminance and luminous efficacy according to the change in gap distance between discharge electrodes. In addition, we looked at changes in various charged particles, exciting particles and VUV particles, and studied the causes of the resulting values.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.93-97
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• 2022

We report highly efficient quantum dot light-emitting diodes (QLEDs) with TiO₂ nanoparticles (NPs) as an alternative electron transport layer (ETL) and poly (methyl methacrylate) (PMMA) as an insulating layer. TiO₂ NPs were applied as ETLs of inverted structured QLEDs and the effect of the addition of PMMA between ETL and emission layer (EML) on device characteristics was studied in detail. A thin PMMA layer supported to make the charge balance in the EML of QLEDs due to its insulating property, which limits electron injection effectively. Green QLEDs with a PMMA layer produced the maximum luminance of 112,488 cd/m² and a current efficiency of 25.92 cd/A. We expect the extended application of TiO₂ NPs as the electron transport layer in inverted structured QLEDs device in the near future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.6
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• pp.681-687
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• 2013

This study analyzed characteristics of 240 W high power LED lamps by comparing with those of traditional metal halide lamps. In addition, it analyzed the propriety of LED lamps as a source of light, considering seawater transmission characteristics. When Applying white LED package with the color temperature color temperature of 6500K, a 240W-LED fishing lamp has a characteristics of the luminous angle to be expanded to ${\pm}45^{\circ}$, the illumination change was improved to 0.8, as well as the luminance efficiency was improved to 98.8lm/W. As results of comparison between one 1,500W-metal halide lamp and four 240W-LED lamp with considering a seawater transmission and a luminous efficiency of scotopic vision, the radiant flux of two lamps were almost equal level at 50m depth and the luminous flux was 5% higher LED lamp than metal-halide lamp even if only applying the luminous efficiency of scotopic vision. As the luminous flux of LED lmap was 14% higher than that of metal-halide lamp with applying the luminous efficiency of scotopic vision to radiant flux at 50m depth, so LED fishing lamp was verified to alternative possibility of metal-halide lamp.

• Journal of Surface Science and Engineering
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• v.46 no.3
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• pp.111-115
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• 2013

To study the encapsulation method for large-area organic light emitting devices (OLEDs), OLED of ITO / 2-TNATA / NPB / $Alq_3$:Rubrene / $Alq_3$ / LiF / Al structure was fabricated, which on $Alq_3$/LiF/Al as protective layer of OLED was deposited to protect the damage of OLED, and subsequently it was encapsulated using attaching film and flat glass. The current density and luminance of encapsulated OLED using attaching film and flat glass has similar characteristics compared with non-encapsulated OLED when thickness of Al as a protective layer was 1200 nm, otherwise power efficiency of encapsulated OLED was better than non-encapsulated OLED. Encapsulation process using attaching film and flat glass did not have any effects on the emission spectrum and the Commission International de L'Eclairage (CIE) coordinate. The lifetime of encapsulated OLED using attaching film and flat glass was 287 hours in 1200 nm Al thickness, which was increased according to thickness of Al protective layer, and was improved 54% compared with 186 hours in same Al thickness, lifetime of encapsulated OLED using epoxy and flat glass. As a result, it showed the improved efficiency and the long lifetime, because the encapsulation method using attaching film and flat glass could minimize the impact on OLED caused through UV hardening process in case of glass encapsulation using epoxy.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.147-154
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• 2015

In this paper, we employed a model which defines the sensitivity according to the background luminance, so called JND (Just Noticeable Difference), and applied to the video coding. The proposed method finds out the maximum possible quantization parameter for the current unit based on the threshold of JND model and reduce the bitrate with similar perceptual quality. It selects the higher quantization parameter and reduce the bitrate when the reconstructed signal which is coded with higher quantization parameter is in a range of allowance based on the JND threshold, i.e. the signal has the similar perceptual quality compared to that is coded with the initial quantization parameter. The proposed algorithm was implemented on HM16.0, which is a reference software of the latest video coding standard HEVC (High Efficiency Video Coding) and the coding performance was evaluated. Compared to HM16.0, the proposed algorithm achieved maximum 20.21% and 6.18% of average bitrate reduction with the similar perceptual quality.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.116-123
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• 2007

This paper proposed a new amplitude width modulation for OLED data driver IC. The data driver controls brightness of OLED by adjusting amplitude and width of the data drive current pulse. There were two conventional methods; pulse amplitude modulation(PAM) and pulse width modulation(PWM). The PWM method suffered from lower light emitting time efficiency at low luminance signal. The PAM method suffered from large chip area using DACs for each column. The proposed method was aiming at accurately controlling of the current level by MSB data and light emitting efficiency by LSB data to improve the inefficiencies of the PAM and a PWM. The proposed AWM driver circuit implemented using $0.35-{\mu}m$ 3-poly 4-metal CMOS high voltage process. The simulation result shows the improvement in the accuracy of the gray level control even though the driver circuit is smaller than the PAM.

• Macromolecular Research
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• v.13 no.2
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• pp.114-119
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• 2005

We synthesized two new series of alternating copolymers, poly[bis(2-(4-phenylenevinylene)-2-cyanoethenyl)-9,9-dihexyl-9H-fluoren-2,7-yl-alt-1,4-phenylene](Polymer-I)and poly[bis(2-(4-phenylenevinylene)-2­cyanoethenyl)-9,9-dihexyl-9H-fluoren-2,7-yl-alt-2,7-(9,9-dihexylfluorene)](Polymer-II), via the Suzuki coupling reaction, for use in light-emitting diodes (LEDs). Defect-free uniformly thin films of these polymers were found to be easily formed on indium-tin oxide (ITO) coated glass substrates. Multi-layer LEDs with ITO/PEDOT/Polymer/ LiF/Al configurations with or without an $Alq_3$ electron transport layer were fabricated with these polymers. The maximum EL emissions of Polymer-I and Polymer-II with an $Alq_3/LiF/Al$ cathode were observed at 516 and 533 nm, respectively. The maximum brightness and external luminance efficiency of the devices fabricated with the EL polymers were found to be $411 cd/m^2$ and 0.16 cd/A, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1343-1346
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• 2005

Self assembled monolayers (SAM) are generally used at the anode/organic interface to enhance the carrier injection in organic light emitting devices, which improves the electroluminescence performance of organic devices. This paper reports the use of SAM of 1-decanethiol (H-S(CH2)9CH3) at the cathode/organic interface to enhance the electron injection process for organic light emitting devices. Aluminum (Al), tris-(8-hydroxyquionoline) aluminum (Alq3), N,N'-diphenyl-N,N'-bis(3 -methylphenyl)-1,1'- diphenyl-4,4'-diamine (TPD) and indium-tin-oxide (ITO) were used as bottom cathode, an emitting layer (EML), a hole-transporting layer (HTL) and a top anode, respectively. The results of the capacitancevoltage (C-V), current density -voltage (J-V) and brightness-voltage (B-V), luminance and quantum efficiency measurements show a considerable improvement of the device performance. The dipole moment associated with the SAM layer decreases the electron schottky barrier between the Al and the organic interface, which enhances the electron injection into the organic layer from Al cathode and a considerable improvement of the device performance is observed. The turn-on voltage of the fabricated device with SAM layer was reduced by 6V, the brightness of the device was increased by 5 times and the external quantum efficiency is increased by 0.051%.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.773-776
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• 2002

Efficient organic white light-emitting diodes are fabricated by doping [bis(2-methyl-8-quinolinolato) (tripheny-siloxy)aluminium (III)] (SAlq), a blue-emitting layer, with a red fluorescent dye of 4-dicyanomethylene-2-methyl-6-{2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-8-yl)vinyl}-4H-pyran (DCM2). The incomplete energy transfer from blue-emitting SAlq to red-emitting DCM2 enables to obtain a balanced white light-emission. A device with the structure of ITO/TPD (50 nm)/SAlq:DCM2 (30 nm, 0.5 %)/$Alq_3$ (20 nm)/LiF (0.5 nm)/AI shows emission peaks at 456 nm and 482 nm from SAlq and at 570 nm from DCM2. The white light-emitting device shows an external quantum efficiency of about 2.3 %, a luminous efficiency of about 2.4 lm/W, and the CIE chromaticity coordinates of (0.32, 0.37) at 100 cd/m^2. A maximum luminance of about 23,800 cd/m^2. is obtained at 15 V and the current density of 782 mA/cm^2.

• Journal of the Korea Society of Computer and Information
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• v.12 no.4
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• pp.87-94
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• 2007

Imbalances in focus, luminance and color between stereo Pairs could cause disparity vector estimation error and increment of transmission data. If the distribution of errors in residual image is large, it may influence to lowering of compression performance. Therefore, in this paper, we propose an efficient balancing method between stereo pairs to reduce the effect. For this, we registrated stereo images using a FFT based method to consider the pixels in the occluded region, we eliminated the pixels of blocks which has large error of disparity vector estimation in balancing function estimation. The balancing function has estimated using histogram specification, local information of target image and residual image between stereo images. Experiments show that the proposed method is effective in error distribution, PSNR and disparity vector estimation. We expect that our method can be improving compression efficiency in stereo coding system.