• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.27.2-27.2
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• 2011

본 연구에서는 저저항/고투과 플렉시블 투명 전극 개발을 위해 금속 그리드가 적용된 투명 전극을 개발하였다. Lift off 공정을 도입하여 플렉시블 PET 기판 위에 Ag grid를 성막하고 이후 연속 공정이 가능한 Roll-to-Roll sputtering system을 이용하여 최적화된 ITO(40nm)/Ag(12nm)/ITO(40nm) 다층 투명 전극을 성막하였다. 제작된 플렉시블 투명 전극의 전기적, 광학적, 구조적 특성 및 기계적/전기적 안정성 평가를 위해 four-point probe measurement, Hall effect measurement, UV/Vis spectrometer, scanning electron microscopy 및 bending tester를 이용하여 각각의 특성을 분석하였다. Ag grid가 적용된 ITO/Ag/ITO 투명 전극에서 Ag의 배선 간격이 0.75 mm일 때 0.18 ohm/sq. 의 낮은 면 저항과 가시광선 영역에서 80% 이상의 높은 투과율을 나타내었으며, 이러한 저저항 및 고투과율 특성으로 인해 최적화된 배선 간격 0.75 mm에서 $538.11{\times}10^{-3}\;ohm^{-1}$의 매우 높은 figure of merit ($T^{10}/R_{sh}$) 값을 확보할 수 있었다. 기계적 응력에 따른 전기적 안정성 특성 분석 결과 5,000회 이상의 bending cycle 에서도 초기 저항 값과 유사한 전기적 특성을 나타냄으로써 Ag grid가 적용된 ITO/Ag/ITO 플렉시블 투명 전극의 기계적 응력에 따른 전기적 안정성을 확인할 수 있었다. Ag grid가 적용된 ITO/Ag/ITO 투명 전극의 투명 안테나 적용 가능성을 타진하기 위해 low band 및 high band 영역에서의 안테나 효율을 측정하였으며, 모든 영역에서 상용화된 copper 안테나와 유사한 효율을 나타내었다. Ag grid를 이용한 플렉시블 투명 전극의 저저항/고투과율 특성은 플렉시블 광전소자의 투명 안테나로의 적용 가능성을 나타낸다.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.75-81
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• 2021

This study analyzes the resonance characteristics caused by the mutual interference between LCL filters and the grid impedance under the parallel operation of the grid-connected inverter using the LCL filter. These characteristics are verified through simulation and experiment. Two inverters are used to connect to the grid in parallel, and the system parameters, including the LCL filter, are set to the same conditions. In the case of inverters running in parallel at the point of common coupling, the presence of grid impedance causes mutual interference between the LCL filters of each inverter, and the deviation of the filter resonance frequency is analyzed to understand the parallel inverter. The correlation between the number of devices and the size of grid impedance is simulated by PSIM and verified by MATLAB. By connecting the real-time digital simulator Typhoon HILS to the DSP 28377 control board, the mutual interference characteristics are tested under the condition of two inverters running in parallel. The experimental and analysis results are the same, indicating the validity of the analysis.

• Journal of radiological science and technology
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• v.46 no.2
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• pp.89-97
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• 2023

With the introduction of the D.R system, the grid with high removal rate of scattered radiation is selected and used without considering the grid performance evaluation. Despite the high removal rate of scattered radiation belonging to high grid ratio, it is also possible to see the cut-off phenomenon in which the primary ray involved in the formation of image could be removed as well. Thus, the purpose of this study is to provide the basic data for researches on the usefulness of using the grid by presenting the appropriate grid ratio in the D.R system through the measurement of image in grid such as non-grid, 6:1, 8:1, 10:1, 12:1. The equipments used for this study were radiation generator with grid in 12:1, 10:1, 8:1, 6:1, indirect-type detector, and acryl phantom. As the study for image evaluation, this study measured the SNR, PSNR, MSE, and Entropy. In the results of this study, the PSNR was the highest in 6:1 and the lowest in 8:1. The SNR was high in 6:1 and 8:1, and the lowest in 12:1. In case of Entropy, it was high in 8:1 and 10:1, and the lowest in 12:1. Therefore, when the grid is used, it would be more proper to choose the grid in 8:1 or 10:1 with less loss in information content of primary ray rather than the high grid ratio showing the increased patient exposure dose.

• International Journal of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.78-86
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• 2017

In this paper, we propose an energy-efficient scheduling scheme for real-time periodic tasks on a heterogeneous Grid computing system. The Grid system consists of heterogeneous processors providing the DVFS mechanism with a finite set of discrete clock frequencies. In order to save energy consumption, the proposed scheduling scheme assigns each real-time task to a processor with the least energy increment. Also the scheme activates a part of all available processors with unused processors powered off. Evaluation shows that the proposed scheme saves up to 70% energy consumption of the previous method.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.85-86
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• 2011

In this paper, the virtual power grid of Jeju in 2020 is modelled including not only VSC HVDC(Voltage Source Current-High Voltage Direct Current) but also wind power generators as 200MW for onshore and 500MW for offshore by PSCAD/EMTDC. Each active power and reactive power are able to controlled by the VSC HVDC. In addition, to verify the characteristic of the modeling VSC HVDC, those wind power generators are cut off from the grid. The result show that the modeling power grid of Jeju become stabilized after 0.1second from failure.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.85-89
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• 2016

Wing is the most important part of aircraft which produces lift. In general when aircraft takes off or lands, high lift is required and additional devices are adopted in front and aft-side of wing, which constitute so-called multi element airfoils. The objective of this research is to develop a specialized grid generation program to help engineers in reducing human labor and eliminating time-consuming process for mesh regeneration by deforming the initially-given grid system with efficient deforming method. This paper describes briefly about the mesh deformation methods, and provides some results to verify the quality of deformed mesh and eventually correctness of current approach.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.213-215
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• 2002

This paper presents grid connected photovoltaic inverter system using a new Zero-Current-Transition(ZCT) technique. The main switches of the proposed grid connected inverter are turned off under the zero current condition by operating the auxiliary circuit and also all semiconductor devices, switches and diodes, are applied to low rated voltage regardless of the load condition. In additionally, the proposed ZCT scheme has advantages, which are without the additional current stresses and the conduction losses on the main switches during the resonance period of the auxiliary circuit. The simulation was performed to verify the validity of the proposed grid connected photovoltaic ZCT inverter system.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1264-1266
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• 2009

We introduce a location-based routing model applied for grid backbone nodes in wireless mesh network. The number of paths with nearest distance between two nodes is calculated and used as key parameter to execute routing algorithm. Node will increase the transmission range that makes a trade off with data rate to reach its neighbors when node itself is isolated. The routing model is lightweight and oriented thanks to the simple but efficient routing algorithm.

• International Area Studies Review
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• v.22 no.1
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• pp.261-284
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• 2018

Global changeover to renewable energy is an inaugurate initiatives as one of the UN sustainable development goals. But the State alone can not achieve its goal, in particular, countries classified as bad governance. However, when the combination of innovative public-private partnerships including technology and operational innovation can be made, it can provide with rural remote villages of developing countries with more sustainable environment. In other words, we tried to show examples of success in energy supply by reducing costs and increasing marketability through various partnerships(technological innovation benefits). Base on the question, this paper examines the cases of Steama.Co, Ewang'an in Kenya, and Grameen Shakti in Bangladesh, and analyzes the developmental effects of differences in partnership types.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.16-22
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• 2020

The characteristics of the LCL filter for grid-connected inverters have been discussed in academia and industry. An online simulation tool was applied to compare and analyze the difference between the LCL filter and L filter. LCL filters were modeled and simulated using a range of professional simulation simulators, and the LCL filters were found to have good filtering effects for high-frequency harmonics. First, this paper summarizes the transfer functions of the LCL filter and provides the Bode plot diagram. The accuracy and validity of the filter attenuation characteristics were confirmed by a fast Fourier transform based on off-line simulation tools, such as PSIM and MATLAB, depending on the given parameters of the LCL filter. Finally, the Typhoon HIL402 real-time simulation was performed for hardware in the loop simulation to verify the actual filtering characteristics of the LCL filter.