• Proceedings of the Korea Information Processing Society Conference
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• 2019.10a
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• pp.907-910
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• 2019

본 연구에서는 X-ray 영상에서 비산란 그리드 장치의 영향으로 인한 아티팩트를 제거하기 위하여 이산코사인변환(DCT: discrete cosine transform) 기반의 주파수 분석 기법과 딥러닝 네트워크의 학습 기법을 상호 보완적으로 결합하는 방법론을 제안한다. 피사체의 특성에 따라 다양하게 나타나는 그리드 라인의 억제 기능을 학습하기 위하여 서로 다른 특성을 반영하는 3 종류의 학습데이터를 생성한다. 학습에 사용되는 그리드 라인 영상의 타겟 데이터를 산출하기 위하여 DCT 기반의 밴드스톱 필터링 기법을 사용하였으며 학습데이터의 양적인 부족을 해결하기 위하여 패치 기반의 학습 방법을 적용하였다. 제안된 방법에 대해 기존의 방법과 비교하여 피사체 경계선 영역에서 발생하는 성능저하 현상, 분할의 가장자리에서 발생하는 블로킹 현상, 배경 영상에서의 성능저하 현상 등을 상대적으로 개선할 수 있음을 실험적으로 평가하였다.

• Smart Structures and Systems
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• v.33 no.2
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• pp.105-118
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• 2024

In order to realize tiny bridge crack discovery by UAV-based machine vision, a novel method combining deep learning and tensor voting is proposed. Firstly, the grid images of crack are detected and descripted based on SE-ResNet50 to generate feature points. Then, the probability significance map of crack image is calculated by tensor voting with feature points, which can define the direction and region of crack. Further, the crack detection anchor box is formed by non-maximum suppression from the probability significance map, which can improve the robustness of tiny crack detection. Finally, a case study is carried out to demonstrate the effectiveness of the proposed method in the Xiangjiang-River bridge inspection. Compared with the original tensor voting algorithm, the proposed method has higher accuracy in the situation of only 1-2 pixels width crack and the existence of edge blur, crack discontinuity, which is suitable for UAV-based bridge crack discovery.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.3
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• pp.10-16
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• 2004

Untypical unstable burning with very low frequency was observed at firing test of a gas generator using bundle cylindrical grain. The pressure unbalance between inside and outside of cylindrical grain brought such a low unstable burning. The grains were radially holed so that the high pressure gas inside of grain could quickly moved outward of gain, resulting dissipation of the pressure unbalance However too many holes were required to let the burning be stable for all operation regime from low to high temperature of grain and resultantly deteriorate the Progressive increase of gas amount produced by a gas generator. So another idea using grids located both sides of a bundle grain was applied to dissipate actively large vorticities enhanced by unbalance pressure distribution in a combustor. Finally stable burning with progressively increase of gas was established by application of 5${\times}$5 grid slightly away bundle grain to move bundle gain freely in case pressure unbalance were occurred inside of combustor.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1969-1982
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• 2015

The virtual inertia control (VIC) of wind turbine with directly-driven permanent-magnet synchronous generator (D-PMSG) can act similarly to the conventional synchronous generator in inertia response and frequency control, thereby supporting the system frequency stability. However, because the wind speed is inconstant and changeable to a certain extent and the D-PMSG is a complex nonlinear system, there are great difficulties in the virtual inertia optimal control of the D-PMSG. Based on the design principle of the active disturbance rejection control (ADRC), this paper presents a new VIC strategy for the D-PMSG from the perspective of power disturbance suppression in the system. The strategy helps fulfill the power grid disturbance estimation and compensation by means of the extended state observer (ESO) so as to improve the disturbance-resisting performance of the system. Compared with conventional proportional-derivative virtual inertia control (PDVIC), this method, which is of better adaptability and robustness, can not only improve the property of the D-PMSG responding to the system frequency but also reduce the influence of wind speed disturbance. The simulation and experiment results have verified the effectiveness and feasibility of the VIC based on the ADRC.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.254-259
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• 2014

In this paper, we describe construction of a wind stabilization demo-site and effects of output power control of wind turbines for suppression of ramp rate using ESS (Energy Storage System). It is difficult to control the output power of distributed generator such as wind turbine which of variation is very large. If the large capacity wind farm be interconnected into power system may cause blackout due to Power Quality. For these reasons, the international standards such as Grid-Code is limited to less than 10 [%/min] of renewable energy ramp rate. The case of Korea, government actively conducts propagating large-scale renewable energy for green growth policy, to interconnecting more renewable energy into power system is necessary for stabilization technology. For these reasons, the POSCO consortium has constructed a wind stabilization demo-site that is configured as 500 [kWh] battery energy storage systems can output up to 3 [C-Rate] and two wind turbines rated 750 [kW]. In POSCO consortium, which implements various methods stabilizing output power of wind turbine such as smoothing, section firming and ramp control, we derive the results of long-term demonstration that can be controlled to satisfy to the international standard about ramp rate [%/kW] of wind turbine output power.