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Development of a new free wake model using finite vortex element for a horizontal axis wind turbine
Hyungki Shin,Jiwoong Park,Soogab Lee 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.1
The treatment of rotor wake has been a critical issue in the field of the rotor aerodynamics. This paper presents a new free wake model for the unsteady analysis for a wind turbine. A blade-wake-tower interaction is major source of unsteady aerodynamic loading and noise on the wind turbine. However, this interaction can not be considered in conventional free wake model. Thus, the free wake model named Finite Vortex Element (FVE hereafter) was devised in order to consider the interaction effects. In this new free wake model, the wake-tower interaction was described by dividing one vortex filament into two vortex filaments, when the vortex filament collided with a tower. Each divided vortex filaments were remodeled to make vortex ring and horseshoe vortex to satisfy Kelvin’s circulation theorem and Helmholtz’s vortex theorem. This model was then used to predict aerodynamic load and wake geometry for the horizontal axis wind turbine. The results of the FVE model were compared with those of the conventional free wake model and the experimental results of SNU wind tunnel test and NREL wind tunnel test under various inflow velocity and yaw condition. The result of the FVE model showed better correlation with experimental data. It was certain that the tower interaction has a strong effect on the unsteady aerodynamic load of blades. Thus, the tower interaction needs to be taken into account for the unsteady load prediction. As a result, this research shows a potential of the FVE for an efficient and versatile numerical tool for unsteady loading analysis of a wind turbine.
Nanocomb Architecture Design Using Germanium Selenide as High-Performance Lithium Storage Material
Kim, Hyungki,Son, Yeonguk,Lee, Jinho,Lee, Minkyung,Park, Seungkyu,Cho, Jaephil,Choi, Hee Cheul American Chemical Society 2016 Chemistry of materials Vol.28 No.17
<P>A key to improve the electrochemical performance of anode materials is to exploit the rational nanostructure designing beneficial for structural toughness and high rate capability. As a nanostructure design in accordance with this criterion, we introduced GeSe nanocomb architecture with well-developed nanocomb teeth on the backbone. In this unique nanocomb architecture, the free space between nanocomb teeth effectively alleviates tremendous volume expansion during lithiation, and anisotropic structure with a short Li+ diffusion length of tens of nanometer scale guarantees the favorable lithiation/delithiation kinetics. These structural advantages of GeSe nanocomb architecture lead to significantly improved electrochemical performance compared to the GeSe nanopowder counterpart. This GeSe nanocomb architecture exhibits electrochemical performance with the reversible capacity of 726 mA.h.g(-1), showing superior capacity retention of 89% even after 1000 cycles at 1.0 C (1.01 A.g(-1)).</P>
관세법상 실화주(實貨主)와 실질과세원칙에 관한 소고 - 대법원 2015. 11. 27. 선고 2014두2270 판결을 중심으로 -
권형기(Hyungki Kwon) 한국국제조세협회 2020 조세학술논집 Vol.36 No.1
본 논문은 대법원 2015. 11. 27. 선고 2014두2270 판결에 대한 평석과 함께 관세법상 실화주(實貨主) 및 실질과세원칙에 대해 연구한 것이다. 이에 관세법상 실질과세원칙과 그 논란의 연혁을 검토하고, 다른 세목에서의 실질과세원칙과의 비교, 일본의 판결과 학설의 비교, 관세법상 실화주와 구매자의 비교 등을 논의하였다. 연구 결과, 관세법상 실질과세원칙을 적용하더라도 사법상의 소유권자를 실화주로 보아야 하며, 그 외의 경제적 이해관계 등에 따라 실화주를 판단할 수 없다는 점을 확인할 수 있었다. 이는 다른 간접세에서의 실질과세원칙과 비교해 보더라도 확인할 수 있고, 일본의 판결 역시 이와 유사한 것으로 보인다. 관세법상 실화주와 구매자는 구분되는 개념인데, 사실 판단에 있어서는 구매자에 관한 여러 판단 기준이 관세법상 실화주 여부를 판단함에 있어 간접적인 참고가 될 수 있다고 본다. 결론적으로 볼 때, 관세법상 납세의무자를 법률상 소유권에 따라 판단한 대상판결의 법리 설시에는 동의하나, 구체적 사실관계를 따져볼 때 원고를 실화주로 인정하지 않는 결론에 이른 것에는 의문이 있으며, 대법원 역시 이로 인해 동 사안을 입증책임의 문제로서 판시한 것으로 보인다. This study is a study on the Supreme Court’s decision 2014du2270 dated November 27, 2015, which reviews the concept of cargo owner and substance over form principle under the Customs Law. In this regard, the Court reviewed the substance over form principle under the Customs Law, the history of its controversy, the application trend of the substance over form principle under the Customs Law, comparison with the application of the substance over form principle in other excise taxes, comparison with rulings and theories in Japan, and comparison between the buyer and cargo owner under the Customs law. This study identifies that even if the substance over form principle is applied to a cargo owner under the Customs Law, the legal owner should be regarded as the cargo owner, and the cargo owner cannot be viewed differently according to other economic interests. It is also confirmed that the application of the substance over form principle in other indirect taxes, and the rulings in Japan have similar perspectives. The Customs Law seems to distinguish the cargo owner and buyer, but in fact, various discussions on the buyer can be helpful in determining the cargo owner under the Customs Law. In conclusion, while agreeing on the legal explanation of the decision that the taxpayer under the Customs law follows the legal ownership, upon reviewing the specific facts, there are questions about the conclusion that the plaintiff is not regarded as the cargo owner. Thus, the Supreme Court also appears to have judged this case as a matter of burden of proof.
수평축 풍력블레이드의 비대칭 환경에서의 공력 해석을 위한 자유후류기법에 관한 연구
신형기(Hyungki Shin),박지웅(Jiwoong Park),이수갑(Soogab Lee),김석우(Seokwoo Kim) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
풍력 발전기의 블레이드는 다른 회전기와는 달리 항상 지면의 경계층, 요-에러에 의한 어긋난 유입류, 타워와의 간섭효과의 환경에서 운영된다. 따라서 정상운전상태에서도 이와 같은 환경에서 겪게 되는 공력하중의 해석이 블레이드의 설계에서 중요하게 요구된다. 본 연구에서는 이의 비정상 공력하중해석을 위하여 자유후류기법을 이용한 방법을 연구하였다. 특히, 타워와의 간섭해석을 위하여 FVE라 명명한 후류 모델을 개발하여 적용하였다.