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하이브리드 해상풍력 파일 기초 콘크리트 지지구조(MCF) 개발
김현기,김범준,김기두,Kim, Hyun Gi,Kim, Bum Jun,Kim, Ki Du 한국강구조학회 2013 韓國鋼構造學會 論文集 Vol.25 No.3
기존 해상풍력발전 지지구조물의 단점을 보완한 신형식의 파일 기초 하이브리드 지지구조물을 본 연구에서 제안하였다. 이 지지구조는 콘크리트 자중을 이용한 중력식 기초의 개념으로부터 수정되어 4개의 파일로 지지되며, 강재 샤프트와 원추형 콘크리트가 결합된 하이브리드 형식이다. 규모가 크고 두꺼운 콘크리트의 3차원 해석을 위해, 정확한 기하형상 모델링과 응력의 절점 보간이 가능한 솔리드-쉘 입체요소를 개발하였다. 해양구조물 전용 유한요소 프로그램인 XSEA에 탑재된 솔리드-쉘 요소와 Stream Function 파랑 이론을 적용하여, 제안한 하이브리드 지지구조물에 대해 서남해안 지역의 환경조건을 적용한 준정적 해석 및 고유진동수 해석을 실시하였다. 해석결과, 수평변위가 허용변위 이내로 나타났고, 고유진동수 해석을 통해 하이브리드 구조형식의 동적거동에 대한 우수성을 입증하였다. 결과적으로, 파일지지 하이브리드 지지구조물은 우리나라 서남해안 지역과 같이 연약지반에 적용 할 수 있는 충분한 안정성을 가진 것으로 평가 되었고, 각 부재에 대한 최적화 연구를 통해 경제성 확보가 가능한 것으로 검토되었다. This paper proposes a new hybrid support structure by the driven piles which removes disadvantages of the existing type of support structure for offshore wind turbines. The hybrid type of support structure is combined with concrete cone and steel shaft, and is supported not only by gravity type foundations but also by driven piles. For three dimensional analysis of the huge and thick concrete structure, a solid-shell element that is capable of exact modeling and node interpolations of stresses is developed. By applying wave theory of stream function and solid-shell element in XSEA simulation software for fixed offshore wind turbines, a quasi-static analysis and natural frequency analysis of proposed support structure are performed with the environmental condition on Southwest Coast in Korea. In the result, lateral displacement is not exceed allowable displacement and a superiority of dynamic behavior of new hybrid support structure is validated by natural frequency analysis. Consequently, the hybrid support structure presented in this study has a structural stability enough to be applied on real-site condition in Korea. The optimized structures based on the preliminary design concept resulted in an efficient structure, which reasonably reduces fabrication costs.
광디스크 드라이브 공기베어링 슬라이더의 형상민감도 해석
김현기,장혁,김광선,임경화,Kim, Hyun-Ki,Jang, Hyuk,Kim, Kwang-Sun,Lim, Kyong-Hwa 한국마이크로전자및패키징학회 2000 마이크로전자 및 패키징학회지 Vol.7 No.4
고성능과 고속화의 면에서 광저장장치의 관심은 상당히 높다. 그러나 하드디스크와 비교하여 광저장장치는 임의의 데이터에 대한 탐색속도가 매우 늦다. 따라서, 광저장장치에서의 새로운 형태의 연구가 필요하다. 본 연구는 하드디스크 장치와 유사한 스윔 암 구동기를 사용한 광저장장치의 공기베어링의 특성에 관해 연구하였다. 광저장장치에서 요구되어지는 최적의 슬라이더 형상을 구하기 위하여 공기 베어링면의 형상변화에 따른 부상상태에 관한 민감도를 연구하였다. The optical storage device has recently experienced significant improvements, especially for the aspects of high capacity and fast transfer rate. However, it is the fact that the optical storage device has the lower access time for the randomly scattered data compared to the hard disk drives. It is, therefore, necessary to develop a new type of optical storage system. In this study, we investigate the air bearing characteristics for the optical disk drives which have the swing arm actuator similar to the hard disk drives. Considering the requirements of the optical disk drives, we parameterize the shape of the air bearing surface and investigate its sensitivity to the flying characteristics for further optimized design outputs.
김현기,신민호,김수삼,Kim. Hyun-Ki,Shin. Min-Ho,Kim. Soo-Sam 한국방재학회 2004 한국방재학회논문집 Vol.4 No.1
강우침투는 철도성토사면의 불안정성을 유발하는 요인으로 작용하여 때때로 파괴의 결과로 나타나게 된다. 강우량과 철도성토사면 안정성과의 기본적인 상관성이 강우에 의한 성토사면의 불안정성을 분석하여 제안되었다. 사면내부로의 강우침투속도를 규명하기 위하여 실내시험을 수행하였으며, 강우침투실험결과에서 강우침투량은 강우침투속도가 사면경사에 의해 지배되기 때문에 저수지 등의 경우에 있어서의 침투와는 상당히 다르다는 것을 알 수 있었다. 이와 같은 견과에 근거하여 강우의 경계조건을 변화시켜 적용한 후, 다양한 수치해석을 수행하였다. 이를 통해 강우시 철도 성토사면의 전단강도, 포화도 그리고 간극수압의 변화를 예측할 수 있었으며, 철도사면의 안전율이 강우량-강우지수의 함수로서 표현될 수 있었다. 따라서 이 강우지수가 강우시 열차운전규제기준을 설정하기 위해 유용함을 밝혔다. Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the rainfall and stability of railway embankment is defined to analyze the stability of embankment by rainfall. An experimental study for defining of infiltration rate of rainfall into slope is conducted in the lab. The results of Rainfall Infiltration show that rainfall Infiltration is not equal to infiltration as like reservoir because rate of rainfall infiltration is controlled by slope angle. Based on these results, boundary condition of rainfall is altered and various numerical analysis are performed. The variation of shear strength, the degree of saturation and pore-water pressure for railway slope during rainfall can be predicted and the safety factor of railway slope can be expressed as the function of rainfall amount, namely rainfall index. Therefore, it is judged that this rainfall index can be a good tool for the rail-transport operation control.
회전익기용 연료탱크 Slosh & Vibration 인증시험
김현기,김성찬,이종원,황인희,장기원,전필선,정태경,하병근,이기천,신동우,Kim, Hyun-Gi,Kim, Sung-Chan,Lee, Jong-Won,Hwang, In-Hee,Jang, Ki-Won,Jun, Pil-Sun,Jung, Tae-Kyung,Ha, Byung-Kun,Lee, Gui-Cheon,Shin, Dong-Woo 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.1
Rapid turning and accelerated movement of a rotorcraft leads to the slosh and vibration effect of fuel in the fuel tank. Due to the slosh load, the internal component of a fuel tank can be broken and fuel tank skin can be damaged. This is directly related to human survivability. Military specification(MIL-DTL-27422D) requires the verification of the stability of aircraft fuel tank and internal component against slosh & vibration load through the qualification test. This report shows the establishment of slosh and vibration test facility and KUH fuel tank qualification test result.
김현기(Hyun-Ki Kim),이성혁(Sung-Hyouk Lee),이진욱(Jin-Wook Lee) 한국지반신소재학회 2013 한국토목섬유학회 학술발표회 Vol.2013 No.4
Evaluation of stability in traditional designing of reinforced soil structures is executed by examination of internal and external stability. Analysis of internal stability is for pull-out and ductile strength. Analysis of external stability is for settlement, overturning and sliding. Though reliability analysis has been developed to minimize inherent uncertainties of soil properties and analytical model, it is not welcomed by field engineer and designer because of its difficulty. In this study, system reliability analysis method for various failure modes of internal and external stability is proposed. Reliability method(U. S. COE, 1999) is adopted to calculate failure probability for each failure modes as a practical method and then, uni-modal bounds was used to evaluate system reliability. Because of complex consideration for various failure modes, it is possible to secure advanced safety by using simultaneous failure probability.
다항식 방사형기저함수 신경회로망을 이용한 ASP 모델링 및 시뮬레이터 설계
김현기(Hyun-Ki Kim),이승주(Seung-Joo Lee),오성권(Sung-Kwun Oh) 대한전기학회 2013 전기학회논문지 Vol.62 No.4
In this paper, we introduce a modeling and a process simulator developed with the aid of pRBFNNs for activated sludge process in the sewage treatment system. Activated sludge process(ASP) of sewage treatment system facilities is a process that handles biological treatment reaction and is a very complex system with non-linear characteristics. In this paper, we carry out modeling by using essential ASP factors such as water effluent quality, the manipulated value of various pumps, and water inflow quality, and so on. Intelligent algorithms used for constructing process simulator are developed by considering multi-output polynomial radial basis function Neural Networks(pRBFNNs) as well as Fuzzy C-Means clustering and Particle Swarm Optimization. Here, the apexes of the antecedent gaussian functions of fuzzy rules are decided by C-means clustering algorithm and the apexes of the consequent part of fuzzy rules are learned by using back-propagation based on gradient decent method. Also, the parameters related to the fuzzy model are optimized by means of particle swarm optimization. The coefficients of the consequent polynomial of fuzzy rules and performance index are considered by the Least Square Estimation and Mean Squared Error. The descriptions of developed process simulator architecture and ensuing operation method are handled.
무선 멀티홉 네트워크 환경에서의 공평하고 효율적인 게임 이론 기반 멀티채널 할당 알고리즘
김현기(Hyun-Ki Kim),이태진(Tae-Jin Lee) 대한전자공학회 2007 대한전자공학회 학술대회 Vol.2007 No.11
Equipping wireless routers with multiple radios improves the bandwidth by transmitting over multiple radios simultaneously using orthogonal channels. Fair and efficient channel assignment algorithms can alleviate the interference effect of nearby transmissions. We show that intelligent channel assignment is critical to the performance of our proposed algorithm. Simulation results are presented to illustrate the effectiveness of the algorithms.