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박형민,채종철,송동욱,양희수,장비호,박영득,나자경,조경석,안광수,Park, Hyungmin,Chae, Jongchul,Song, Donguk,Yang, Heesu,Jang, Bi-Ho,Park, Young-Deuk,Nah, Jakyoung,Cho, Kyung-Suk,Ahn, Kwangsu 한국천문학회 2012 天文學會報 Vol.37 No.2
For the study of fine-scale structure and dynamics in the solar chromosphere, the Fast Imaging Solar Spectrograph (FISS) was installed in 1.6m New Solar Telescope at Big Bear Solar Observatory in 2010. The instrument, installed at a vertical table of the Coude lab, is properly working and producing data for science. From the analysis of the data, however, we noticed that a couple of problems exist that deteriorate image quality : lower light level and poorer resolution of the CaII band data. After several tests, we found that the relay optics at the right position is crucial role for the spatial resolution of raster-scan images. By using resolution target, we re-aligned relay optics and other components of the spectrograph. Here we present the result of optical test and new data taken by the FISS.
학습이론으로서의 문화역사활동이론의 의미와 ‘학습’의 개념에 대한 비판적 고찰
박형민(Hyungmin Park) 학습자중심교과교육학회 2019 학습자중심교과교육연구 Vol.19 No.10
본 연구의 목적은 인간학습의 집단적, 역동적 속성을 포착, 분석하기 위한 유용한틀로서 문화역사활동이론이 갖는 학습이론으로서의 면모를 드러내는데 있다. 활동이론에서는 인간의 학습과 그 결과로서의 의식의 발달이 사회문화적 최소 맥락으로 서의 ‘활동(activity)’에 참여함으로써 비롯된다고 보고, 학습과정을 분석하는 최소단위로 ‘활동체계(activity system) 를 제시하고 있다. 활동이론은 인간의 학습을 3가지 수준으로 개념화하고 있으며, 학습주체가 특정 ’활동‘에 참여하면서 그 구성요소 와의 상호작용을 통해 ’활동‘과 함께 성장, 변화해 나가는 과정을 포착하는데 있어 유용한 이론적 틀을 제공하고 있다. 그러나 활동이론이 복잡다단한 학습현상을 이해하는데 있어 보다 정교하고 엄밀한 이론적 도구로 자리매김하기 위해서는 3가지 학습수준의 구체적인 발생맥락과 학습수준간 상호관계, 인간의 정신·심리활동과 ’활동‘과의 관계성 등에 대한 심도깊은 이론적 논의와 활동이론을 활용한 실천연구가 필요하다. This study explored the Cultural Historical Activity Theory(CHAT) as a learning theory and especially examined the concept of activity and learning in the CHAT. CHAT argues that human learning and its result of development of human consciousness takes place as a result of a subject’s participation in the ‘Activity’ as the minimal socio-cultural context of learning and suggests the ‘Activity System’ as a unit of analysis of human learning. CHAT conceptualizes human learning at three levels and emphasizes that the subject(s) in the specific activity and the activity itself grow and change with through dynamic interactions with the constituent elements of the activity. In this regard, CHAT is a useful tool for identifying and grasping collective aspects of human learning. However, in order for CHAT to be a more sophisticated and rigorous theoretical tool for understanding the complicated human learning phenomena, further studies should be conducted on the issues; (1) the occurrence context of three levels of learning in the CHAT and the relationship among them, (2) the status of human mental and psychological process in the activity system.
날개표면의 요철이 공중 정지 비행하는 잠자리의 공력에 미치는 영향
박형민(Hyungmin Park),최해천(Haecheon Choi) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In nature, the profile of the wings in many orders of insects is corrugated and it has been found to affect the aerodynamic forces in gliding flight. In the present study, the effect of spanwise corrugation on the aerodynamic force generation of dragonfly wing in hovering motion is investigated using a one-paired dynamically scaled mechanical dragonfly wing model which performs an inclined hovering motion by wing flapping in a white-oil tank. We consider smooth and corrugated wings whose wing sections are based on the forewing of Aeshna juncea. We measure the normal and tangential forces on the wing at the Reynolds number of 1,900. We find that, with the corrugation, the drag force slightly increases during a downstroke (high angle of attack) and the lift force increases during an upstroke (small angle of attack), respectively, resulting in the increase of the mean vertical force by 10 ~ 30% depending on the wing trajectory.
박형민(Hyungmin Park),배기수(Kisoo Bae),전우평(Woo-Pyung Jeon),최해천(Haecheon Choi) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
Among the various nature’s flyers, the butterfly is known as one of the excellent aerial species that are very good at both gliding and flapping flight. Considering the aerodynamically poorly-shaped wings of the butterfly (cross section of flat-plate and low aspect ratio), the high flight capability of the butterfly wing is worthwhile to be noted. Several researchers have studied the effects of the wing morphology on the aerodynamic performances of the butterfly, based on the idea that the wing should have additional devices to overcome the disadvantages and enhance the aerodynamic performance. The hind-wing tails of swallowtail butterfly has been also reported to affect the gliding flight of the butterfly, but the detailed evidences supporting the conjectured aerodynamic function of the tails have not been given. Therefore, in the present study, the effect of hind-wing tails on the aerodynamic performance of a swallowtail butterfly is experimentally investigated in a wind tunnel. The butterfly model is made of a thin brass sheet and its shape is precisely duplicated from a specimen of real swallowtail butterfly (Papilio Ulysses). With the tails, the lift and drag increase by about 10~20% and 5%, respectively, at the angles of attack larger than 15°, which results in the enhancement of lift-to-drag ratio in a wide range of attack angles. Also due to the tails, the slope of pitching moment curve with respect to the attack angle is more negative (steeper), which indicates the enhanced longitudinal static stability. From the flow visualization, the wake width is increased at the spanwise location near the tails and thus modifying the vortical structure behind the wing as a V-shaped one. This change in vortical structure induces the vortex core-region with low-pressure near the upper-surface of the wing, thereby increases the lift force.