• 대한수학회논문집
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• 제11권1호
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• pp.209-214
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• 1996

A flat space is characterized by tube volumes about geodesic balls. Similar characterizations are also given for other rank one symmetric spaces.

• 천문학논총
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• 제30권3호
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• pp.833-833
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• 2015

• 한국항공우주학회지
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• 제44권6호
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• pp.477-483
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• 2016

본 연구는 Particle Image Velocimetry(PIV) 기법을 이용하여 마하수 2.96의 평판에 대해 층류, 천이, 난류 경계층의 속도 분포를 측정하였다. Schlieren 가시화 기법과 PIV 기법을 이용하여 앞전에서 발생한 경사 충격파가 평판 위의 유동장에 영향을 주는지 확인하였다. 층류 경계층의 경우, 실험에서 측정한 속도 분포가 압축성 Blasius 속도 분포를 만족하였다. 천이 경계층의 속도 분포는 벽면 부근부터 이론적인 난류 속도 분포로 변했으며, Re = $1.41{\times}10^6$에서 천이가 시작되었다. 난류 경계층 영역에서는 압축성 효과를 고려한 Van Driest 변환 속도가 비압축성 로그 법칙을 만족하였다. 또한 로그 구간이 끝나는 위치($y/{\delta}{\approx}0.28$)가 비압축성 난류 경계층($y/{\delta}{\approx}0.2$)에 비해 벽면에서 더 멀어진 것을 확인하였다.

• 건축역사연구
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• 제21권4호
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• pp.7-24
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• 2012

The Buddhist cave temple carved into the rock provides a large space for the ritual in general in which a structure of Stupa is built in the center of the space purely for religious worship empty of Sarira, and the temple is formed around this Stupa. Relief-Stupa of the cave temple indicates the similar shape that of Relief-religious worship of flat land temple. However, there appears a small difference in representation since the background of formation of the cave temple differs in that of flat land temple. Specially, Caitya Stupa of currently existing cave temples have been damaged to lose of their original shape only possible to be analyzed the stylistic development through Relief-Stupa from which the characteristic of Stupa could be understood. The early cave temple could be characterized with a balanced structure consists of upturn bowl, steeple stone with simple drum & Hamikawasnagae, in which it appears strongly the detail factor characteristics of drum & steeple of having system with Caitya Stupa. In the post cave temple, the subject of worship moved to statue of Buddha due to the influence of Gandhara, Mathura art which reduced the importance of Stupa. This illustrates in Relief-stupa as well the style change as well as changes in detail factor. The sculpture appeared at the limited location either the wall of Caitya shrine or pillar in vihara cave with stronger decorative meaning. Contrast to the Relief Stupa of early flat land temples or the cave temples mentioned above sculptured with symbolism, however, the post cave temple showed the relief structure based on the plan of flat plan.

• 한국항공우주학회지
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• 제37권6호
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• pp.562-570
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• 2009

불어내기식 극초음속 풍동을 이용하여 2차원형 돌출물 주위의 유동 및 공력가열 특성에 대한 실험적 연구를 수행하였다. 실험의 유입 유동 조건은 마하수 7, 단위 레이놀즈수 $2.0{\times}10^6/m$ 이다. 실험 조건은 길이가 다른 두 개의 평판에 세 가지 돌출물이 높이에 따라 변화되며, 실험데이터는 쉴리렌 이미지 가시화 기법과 돌출물 전면에서의 열유속 게이지를 이용한 열유속 측정을 통해 획득되었다. 또한, 본 논문에서는 경계층 천이 탐지기법과 같은 극초음속 유동 실험 기법도 함께 제시하였다. 실험 결과 돌출물 전방에 큰 박리 영역이 관찰되었으며, 박리 영역은 돌출물의 높이와 평판의 길이에 따라 민감하게 변화 하였다. 가장 큰 돌출물의 경우에서만, 돌출물 상부 측정점에서 열유속 측정치의 급격한 점프가 있는 것으로 관찰되었다. 또한 측정된 열유속은 돌출물의 높이가 크고 평판의 길이가 길수록 증가하는 경향성을 보였다.

• 문화기술의 융합
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• 제9권2호
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• pp.105-112
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• 2023

3차원의 세계를 작품으로 구현해내려는 시도는 시대와 매체를 구분하지 않고 계속되어왔으며, 그 목적은 현실의 재현보다도 몰입 상태의 구현이다. 본 연구는 디지털미디어아트에서 최종적으로 관람자와 마주하는 매체인 평면스크린이 완전한 몰입을 방해한다고 보고, 스크린의 한계를 벗어나 공간의 현실감을 주는 작품들의 사례를 조사하고 분석하였다. 분석한 결과를 작품 제작에 활용한 결과, 디지털미디어아트 분야에서 현실적 공간의 제시와 몰입의 강화는 스크린 내의 시각적 영상 콘텐츠뿐만 아니라 전시 환경에 맞는 설치, 결과적으로 구성되는 공간 그 자체까지 작업으로 보아야 한다는 것을 알 수 있었다.

• 천문학회보
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• 제40권1호
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• pp.65.3-66
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• 2015

The determination of three dimensional parameters (e.g., radial speed, angular width, source location) of Coronal Mass Ejections (CMEs) is very important for space weather forecast. To estimate these parameters, several cone models based on a flat cone or a shallow ice-cream cone with spherical front have been suggested. In this study, we investigate which cone model is proper for halo CME morphology using 33 CMEs which are identified as halo CMEs by one spacecraft (SOHO or STEREO-A or B) and as limb CMEs by the other ones. From geometrical parameters of these CMEs such as their front curvature, we find that near full ice-cream cone CMEs (28 events) are dominant over shallow ice-cream cone CMEs (5 events). So we develop a new full ice-cream cone model by assuming that a full ice-cream cone consists of many flat cones with different heights and angular widths. This model is carried out by the following steps: (1) construct a cone for given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, (4) minimize the difference between the estimated projection points with the observed ones. We apply this model to several halo CMEs and compare the results with those from other methods such as a Graduated Cylindrical Shell model and a geometrical triangulation method.

• 대한조선학회지
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• 제5권1호
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• pp.1-7
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• 1968

In this problem the ragid punch in the form of a flat-ended circular cylinder of unit radius is cemented to the stress free surface of an elastic half-space. An axial load P is then applied to the punch to force it into half-space to depth $\varepsilon$. It is assumed that the adhesive between the punch and can be reduced to the system of Abel type integral equations which are equation (13) and (14). It is also shown that the stress and displacement components on the portions of boundary where they are not prescribed can be expressed in terms of $\phi(t)$ and/or $\phi(t)$ which are introduced in equation (9) and (10). Those functions can be obtained from the solution of the system of integral equations (13) and (14).

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.215-221
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• 2017

An electromagnetic (EM) wave absorber reduces the possibility of radar detection by minimizing the radar cross section (RCS) of structures. In this study, a radar absorbing structure (RAS) was applied to the leading edge of a blended wing body aircraft to reduce RCS in X-band (8.2~12.4GHz) radar. The RAS was composed of a periodic pattern resistive sheet with conductive lossy material and glass-fiber/epoxy composite as a spacer. The applied RAS is a multifunctional composite structure which has both electromagnetic (EM) wave absorbing ability and load-bearing ability. A two dimensional unit absorber was designed first in a flat-plate shape, and then the fabricated leading edge structure incorporating the above RAS was investigated, using simulated and free-space measured reflection loss data from the flat-plate absorber. The leading edge was implemented on the aircraft, and its RCS was measured with respect to various azimuth angles in both polarizations (VV and HH). The RCS reduction effect of the RAS was evaluated in comparison with a leading edge of carbon fabric reinforced plastics (CFRP). The designed leading edge structure was examined through static structural analysis for various aircraft load cases to check structural integrity in terms of margin of safety. The mechanical and structural characteristics of CFRP, RAS and CFRP with RAM structures were also discussed in terms of their weight.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.29.2-29.2
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• 2011

Earth's bow shock is a transition layer across which properties of plasmas change irreversibly. Although some features of the bow shock are well described by continuities of fluxes of various macroscopic quantities, particle dynamics across the transition layer is very complicated. Observed phase space distributions show multiple ion beams and partially thermalized ions around the transition layer. In some cases, both hot magnetosheath ions and cold solar wind ions simultaneously exist in the magnetosheath. Electrons around the transition layer usually have flat-top distributions with temperature anisotropy. From the observed properties of the phase space distributions we will discuss thermalization processes that occur across the shock transition.