• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1134-1139
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• 2006

Electrical, optical, and structural properties of indium zinc oxide (IZO) anode films grown by a RF magnetron sputtering were investigated as functions of RF power and working pressure in pure Ar ambient. To investigate electrical, optical and structural properties of IZO anode films, 4-point probe and UV/VIS spectrometry, and X-ray diffraction (XRD) were performed, respectively. A sheet resistance of $15.2{\Omega}/{\square}$, average transmittance above 80 % in visible range, expecially above 85 % in 550 nm, and root mean square roughness of 1.13 nm were obtained from optimized IZO anode films grown in oxygen free ambient. All samples show amorphous structure regardless of RF power and working pressure due to low substrate temperature. In addition, XPS depth profile obtained from IZO/PES exhibits that there is no obvious evidence of interfacial reaction between IZO and PES substrate. Furthermore, current-voltage-luminance of the flexible phosphorescent flexible OLEDs fabricated on IZO anode shows dependence on sheet resistance of the IZO anode. These results indicate that the IZO anode is a promising candidate to substitute conventional ITO anode for high-quality flexible displays.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.11 no.4
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• pp.247-253
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• 2011

A sustainability of electricity supply has emerged as a critical issue for low carbon green growth in South Korea. Wind power is the fastest growing source of renewable energy. However, due to its own intermittency and volatility, the power supply generated from wind energy has variability in nature. Hence, accurate forecasting of wind speed and power plays a key role in the effective harvesting of wind energy and the integration of wind power into the current electric power grid. This paper presents a short-term wind speed prediction method based on support vector regression. Moreover, particle swarm optimization is adopted to find an optimum setting of hyper-parameters in support vector regression. An illustration is given by real-world data and the effect of model regularization by particle swarm optimization is discussed as well.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.4
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• pp.182-187
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• 2017

Synchronous generators have been significantly applied in large-scale power plants and its monitoring systems are additionally established to sequentially observe states and outputs. We develop a computer based monitoring device for three-phase synchronous power generators in this paper. First, a test-bed of such generator system is created and then a interface board is constructed to transfer electric signals including the output voltage and the current from generators into a computer system via a data acquisition device. Its RMS(root-mean-square) values are continuously shown on a screen of computer systems and its time-histories graphs are additionally illustrated under a graphic user interface(GUI) mode. Lastly, we carry out real-time experiments using the generator system with the monitoring device to demonstrate its reliability and superiority by comparing results of a generic power analyzer which is well-used in measuring various power systems practically.

• Journal of Forest and Environmental Science
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• v.31 no.3
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• pp.202-206
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• 2015

Site index curves were developed for Larix kaempferi and Pinus koraiensis in Gangwon and North Gyeongsang provinces in Korea. For the development of site index, Schumacher and Chapman-Richards model were applied using the data collected from 2012 to 2014. Base age was set to 40 years for Larix kaempferi and Pinus koraiensis in site index of this study. Coefficient of determination and root mean square error of site index models were provided by species, and the models were compared with the previous studies to check the suitability. Overall, site index models developed in this study fitted in the current data well. Thus, the site indexes are considered to be properly used in Gangwon and North Gyeongsang provinces.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.1093-1096
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• 1999

In this paper, video image segmentation algorithm based on color histogram and change detector is proposed. Color histograms are calculated from both changed region which is detected in the previous and current frame and unchanged region. With each histogram, modes and valleys are detected. Then, color vectors are calculated by averaging pixels in modes. Markers are extracted by labeling color vectors that represent modes, the watershed algorithm is applied to determine uncertain region. In growing region, the root mean square(RMS) of the distance between average pixel in marker region and adjacent pixel is used as a measure. The proposed algorithm based on color histogram and change detector segments video image fastly and effectively. And simulation results show that the proposed method determines the exact boundary between background and foreground.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.19-24
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• 1997

In this study, we extend the application of the interface-matrix(IM) method for reflector modeling to Analytic Flux Expansion Nodal (AFEN) method. This include the modifications of the surface-averaged net current continuity and the net leakage balance conditions for IM method in accordance with AFEN fomular. AFEN-interface matrix (AFEN-IM) method has been tested against ZION-1 benchmark problem. The numerical result AFEN-IM method shows 1.24% of maximum error and 0.42% of root-mean square error in assembly power distribution, and 0.006%Δk of neutron multiplication factor. This result proves that the interface-matrix method for reflector modeling can be useful in AFEN method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.8
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• pp.373-378
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• 2001

This paper introduces a new online index to quantify the harmonic distortion. The proposed index based on VI product can represent the harmonic distortion of both voltage and current, and it includes the effect of interharmonic distortion. Also, the new index is suitable to online harmonic distortion evaluation since it only requires the r.m.s. (root mean square) value and fundamental frequency value of the signals. Case studies are presented to show the availability of the proposed index using the comparison with the THD (Total Harmonic Distortion).

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.451-452
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• 2014

본 논문에서는 단상 계통연계형 컨버터의 전원 위상각을 추종함에 있어 필수적인 전압 센서의 옵셋 오차에 대한 영향을 분석하고 이를 검출 및 보상하기 위한 알고리즘을 제안하였다. 전원전압 측정에 따른 옵셋 오차는 전원 주파수의 1배 맥동을 야기하여 전원 위상각이 왜곡된다. 왜곡된 전원 위상각에 의한 좌표변환시 동기 좌표계 dq축 전류에 전원 주파수 1배의 맥동을 야기하며 이는 계통측 상전류에 직류성분과 전원 주파수 2배의 고조파 성분을 발생시키게 된다. 따라서, 본 논문에서는 전원측정시 야기되는 옵셋 오차의 영향을 분석하고 이의 검출신호로 전원 위상각 제어기의 적분출력을 선정하였다. 또한 RMS(Root Mean Square) 기법을 이용하여 옵셋 성분을 검출 및 보상하는 알고리즘을 제안하였다. 제안된 알고리즘의 성능은 시뮬레이션과 실험을 통하여 검증하였다.

• Current Optics and Photonics
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• v.4 no.6
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• pp.516-523
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• 2020

The normal low-cost manufacturing process for freeform vehicle side mirrors causes deviations from the design curvature. Here, an improved manufacturing process is proposed, combining photorealistic ray-traced visualization of each deviation and subsequent analysis of its deviated reflective scene compared to that of the original design. The proposed mechanism successfully highlights the overlap and mismatch regions of deviated reflected scenes with reference to the desired reflective scenes. We benchmarked the robustness of freeform mirror manufacturing by evaluating the 10, 20, and 30% root-mean-square (RMS) deviated curvature, and concluded that the acceptable deviation needs to be below RMS20% to avoid mismatched regions that could mislead the driver.

• Current Optics and Photonics
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• v.7 no.6
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• pp.708-713
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• 2023

A robust all-fiber nonlinear amplifying loop-mirror-based mode-locked femtosecond laser is demonstrated. Power-dependent nonlinear phase shift in a Sagnac loop enables stable and power-efficient mode-locking working as an artificial saturable absorber. The pump power is adjusted to achieve the lowest intensity noise for stable long-term operation. The minimum pump power for mode-locking is 180 mW, and the optimal pump power is 300 mW. The lowest integrated root-mean-square relative intensity noise of a free-running mode-locked laser is 0.009% [integration bandwidth: 1 Hz-10 MHz]. The long-term repetition-rate instability of a free-running mode-locked laser is 10^-7 over 1,000 s averaging time. The repetition-rate phase noise scaled at 10-GHz carrier is -122 dBc/Hz at 10 kHz Fourier frequency. The demonstrated method can be applied as a seed source in high-precision real-time mid-infrared molecular spectroscopy.