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      • 편대비행 하는 항공기 날개들에서 발생하는 후류말림 연구

        한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2020 융ㆍ복합기술연구소 논문집 Vol.10 No.1

        The wake shapes behind wings in formation flight are very important to the aerodynamics and performances of aircrafts. In the present study, a discrete vortex methood is extended to handle the wake rollups behind multiple wings. It was found that the relative distance between the wings and the rotational direction of the wingtip vortices have significant effect on the movement of the wingtip vortices. When the wings are close to each other, the wingtip vortices moved faster than the wings of large relative distances. The vortex pair of opposite signs generated from each wingtip has an effect of moving the wingtip vortices upward. The relative height between the wings has an effect of moving the wingtips along the centerline of each vortex. The wakeshape behind multiple wings is a function of the relative distances and thus is dependent on the configuration of the formation flight. In the futhre, a study on the vortex movement pattern will be studied.

      • KCI등재

        사용자 선호에 기반한 효율적 최대 휘소가시화 알고리즘의 선택 방법

        한철희,계희원 한국멀티미디어학회 2018 멀티미디어학회논문지 Vol.21 No.2

        Maximum intensity projection (MIP) is a common visualization technique in medical imaging system. A typical method to improve the performance of MIP is empty space leaping, which skips unnecessary area. This research proposes a new method to improve the existing empty space leaping. In order to skip more regions, we introduce a variety of acceleration strategies that use some tolerance given by the user to take part in image quality loss. Each proposed method shows various image quality and speed, and this study compares them to select the best one. Experimental results show that it is most efficient to add a constant tolerance function when the image quality required by the user is low. Conversely, when the user required image quality is high, a function with a low tolerance of volume center is most effective. Applying the proposed method to general MIP visualization can generate a relatively high quality image in a short time.

      • 지면효과의 공력해석

        한철희 忠州大學校 2008 한국교통대학교 논문집 Vol.43 No.-

        Aerodynamic characteristics of a wing or wings in ground effect are investigated using a vortex lattice method. The surface of the wing is discretized as quadrilateral elements over which vortex line singularity elements are distributed. The pressure on the wing's surface is obtained by using Bernoulli's equation. The effect of the ground height on the aerodynamic characteristics of a single wing or wings in formation flight is investigated. It is found that the wings in formation flight experience the increased roll moment with the distance between the wings. Aileron and ground effect have the effect of augmenting the generation of the rolling moment. It is believed that present method can be applied to the aerodynamic analysis of wings in formation flight near the ground.

      • KCI등재
      • KCI등재

        차량환경에서 음성인식 성능 향상을 위한 마이크로폰 어레이 빔형성 기법

        한철희,강홍구,황영수,윤대희,Han Chul-Hee,Kang Hong-Goo,Hwang Youngsoo,Youn Dae-Hee 한국음향학회 2005 韓國音響學會誌 Vol.24 No.7

        본 논문에서는 차량환경에서 잔향과 근접장 효과에 의해 발생하는 목적 음성 신호의 왜곡을 감소시킬 수 있는 마이크로폰 어레이 빔형성 기법을 제안하였다. 온라인으로 추정하기 어려운 소스와 마이크간의 전달함수 대신 상대적으로 추정이 용이한 기준 마이크와 다른 마이크간의 상대전달함수를 조향 벡터로 이용함으로써, 원격장 모델의 조향 벡터를 이용한 빔형성기에 비해 목적 음성 신호의 왜곡을 감소시킬 수 있는 준최적 빔형성 기법을 제안하였다. 제안된 방법의 성능을 검증하기 위해, 실제 차량에서 녹음된 음성 DB를 구축하고, 이를 이용하여 HTK를 통한 음성인식 실험을 수행하였다. 음성인식 실험 결과 원격장 모델을 이용한 방법보다 인식률이 최대 $15\%$까지 향상됨을 확인하였다. In this paper. a microphone array beamforming algorithm that reduces the signal distortion caused by reverberation and near-field effect in car environment is proposed. When reverberation or near-field effect is present, an optimum beamformer should be constructed with a steering vector consisting of transfer functions between source and microphones, but it is generally difficult to estimate transfer functions on-line without knowledge of the source signal. Instead, a sub-optimal beamforming algorithm that reduces signal distortion is proposed. It is constructed with steering vectors consisting of relative transfer functions between reference sensor and other sensors. In order to evaluate the performance of the proposed algorithm. we had recorded noisy speech database in a car, and performed speech recognition experiments with HMM Toolkit (HTK) released by Cambridge University. The recognition rate of the proposed algorithm was 15 percents higher than that of the conventional far-field beamformers in best case.

      • KCI등재후보

        채널 내를 비행하는 가변스팬 날개 공력특성 I (가로세로비 및 안내로 영향)

        한철희 항공우주시스템공학회 2016 항공우주시스템공학회지 Vol.10 No.4

        In this paper, an experimental study on the aerodynamic characteristics of a variable span wing flying inside a channel guideway is accomplished using wind tunnel testing. A variable span wing with a NACA 0012 airfoil section was fabricated and actuated using a linear servo motor. The aerodynamic effects of 1) wing aspect ratio, 2) ground effect, and 3) the gap between the wingtip and the wing fence were investigated. It was found that both ground effect and wing fence gap increased lift. Also, the wing fence gap does not significantly affect drag. Therefore, it was found that a variable span mechanism can be used as an effective high lift device when flap use is limited. 본 논문에서 채널 안내로를 비행하는 가변스팬 날개의 공력특성에 관한 실험연구를 수행하였다. NACA 0012익형을 가진 가변스팬 날개를 제작하였으며 선형서보모터를 사용하여 작동시켰다. 날개의 가로세로비, 지면효과, 날개와 펜스사이의 거리가 날개의 공력특성에 미치는 영향을 조사하였다. 연구결과 지면 및 펜스 모두 항공기 날개의 양력을 증가시켰으며 지면효과와 달리 펜스는 날개의 항력에 큰 영향을 미치지 않았다. 가변스팬 메커니즘이 플랩사용이 제한되는 상황에서 효과적인 고양력 장치로 사용가능할 것으로 판단된다.

      • The effect of structural changes of electron donor-acceptor complex on the dynamics of contact radical ion pair separation

        한철희 선문대학교 자연과학대학 2001 자연과학논총 Vol.4 No.-

        The objective of this paper is to design and implement an engineering database for integrated structural design system of the pre-engineered buildings, and to represent the methodology of it. In this paper an object model was developed by OMT and IDEFO and converted to an relational database. The database in this paper is confined to the structural design process arid contains the analysis data and design data.

      • 인간동력 항공기 안정성 해석

        한철희 한국교통대학교 2015 한국교통대학교 논문집 Vol.50 No.-

        In this paper, the longitudinal static stability of a human powered aircraft is analyzed using the aerodynamic coefficients and inertia of TORUK MAKTO I. The aerodynamic coefficients are obtained using a free software, XFOIL and a lifting line theory. The inertias are obtained using the commercial software, CATIA. The effects of the ground and the change of the center of gravity on the static stability are evaluated. It was found that the vertical distance between the AC and the CG had the effect of increasing the longitudinal static stability during the climb and cruse flight. When the position of the AC of the main wing is placed behind the CG of the aircraft, the longitudinal static stability was also increased. It was also found that the aerodynamic ground effect moved the neutral point backward. In future, the lateral and directional stability will be studied.

      • KCI등재

        The Secularization of Higher Education: Narratives in Twentieth Century America

        한철희 한국기독교교육정보학회 2014 Journal of Christian education information tech Vol.0 No.26

        This study attempts to explore the process of secularization in Protestant higher education in twentieth century America. This study also acknowledges that most of the colleges and universities founded in the United States before the 20th century were strongly Protestant Christian. However, they were profoundly changed by the development of secular modern culture in the wake of the Enlightenment, and radically declined in power, popularity and prestige of religion in higher education, and then finally lost their religious character. The process of secularization was composed of the dialectic courses such as primal principle, rising reaction, and the resolving consequence. For this purpose, this study provides the narratives of the leading figures connected with the movement toward secularization of American higher education. The cooperative relationships between Christianity and higher education which continued to the twentieth century gradually deteriorated into a loss of major roles in the American academic circles, and also in Korea. Follow-up research is required for the pattern of Korean Christian higher education.

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