• Title/Summary/Keyword: geodesic space

Search Result 84, Processing Time 0.017 seconds

LINEAR POLARIZATION OF A DOUBLE PEAKED BROAD EMISSION LINE IN ACTIVE GALACTIC NUCLEI

  • Lee, Hee-Won
    • Journal of The Korean Astronomical Society
    • /
    • v.44 no.2
    • /
    • pp.59-65
    • /
    • 2011
  • A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles that are well-fitted by a relativistic accretion disk model. We develop a Monte Carlo code to compute the linear polarization of a double peaked broad emission line arising from Thomson scattering. A Keplerian accretion disk is adopted for the double peak emission line region and the geometry is assumed to be Schwarzschild. Far from the accretion disk where flat Minkowski geometry is appropriate, we place an azimuthally symmetric scattering region in the shape of a spherical shell sliced with ${\Delta}{\mu}=0.1$. Adopting a Monte Carlo method we generate line photons in the accretion disk in arbitrary directions in the local rest frame and follow the geodesic paths of the photons until they hit the scattering region. The profile of the polarized flux is mainly determined by the relative location of the scattering region with respect to the emission source. When the scattering region is in the polar direction, the degree of linear polarization also shows a double peak structure. Under favorable conditions we show that up to 0.6% linear polarization may be obtained. We conclude that spectropolarimetry can be a powerful probe to reveal much information regarding the accretion disk geometry of these active galactic nuclei.

An Experimental Study on the Application of Shelter Structure Using Deployable Scissors Systems (전개가능형 가위구조시스템을 이용한 쉘터구조물에의 적용성 검토에 관한 실험적 연구)

  • Lim, Ji-Sub;Choi, Sang-Soon;Jeong, Eul-Seok;Kim, Seung-Deog
    • Journal of Korean Association for Spatial Structures
    • /
    • v.14 no.3
    • /
    • pp.101-108
    • /
    • 2014
  • Recently, natural disasters such as earthquake, tsunami, typhoon and tornado are increasing, and cause huge economical loses and victim. Thus, when the disaster occurs, it is important to prepare emergency evacuation shelters for fast and easy construction compared to general building system. And, deployable structures will provide a great help for such aim. Deployable structures have the great advantage of being faster and easier to erect and dismantle compared to conventional building forms. In this study, we confirm the possibility of deployment for shelter structures using scissor structure system. First, Basic model was performed to recognize the appllicability of the deployable systems of the dome-shaped structure. Second, Advanced model that more improved inner space and deployment mechanism was confirmed.

A Study on Cutting Pattern Generation of Membrane Structures Using Spline Curves (스플라인 곡선을 이용한 막구조물의 재단도 작성에 관한 연구)

  • Shon, Su-Deok;Lee, Seung-Jae
    • Journal of Korean Association for Spatial Structures
    • /
    • v.12 no.1
    • /
    • pp.109-119
    • /
    • 2012
  • For membrane structure, there are three main steps in design and construction, which are form finding, statistical load analysis, and cutting patterning. Unlike the first two stages, the step of cutting pattern involves the translation of a double-curved surface in 3D space into a 2D plane with minimal error. For economic reasons, the seam lines of generated cutting patterns rely greatly on the geodesic line. Generally, as searching regions of the seam line are plane elements in the step of shape analysis, the seam line is not a smooth curve, but an irregularly divided straight line. So, it is how we make an irregularly divided straight line a smooth curve that defines the quality of the pattern. Accordingly, in this paper, we analyzed interpolation schemes using spline, and apply these methods to cutting pattern generation on the curved surface. To generate the pattern, three types of spline functions were used, i.e., cubic spline function, B-spline, and least-square spline approximation, and simple model and the catenary-shaped membrane was adopted to examine the result of generation. The result of comparing the approximation curves by the number of elements and the number of extracted nodes of simple model revealed that the seam line for less number of extracted nodes with large number of elements were more efficient, and the least-square spline approximation provided smoother seam line than other methods.

A Study on the Effects of Wind Load of Membrane Roof Structures according to External Form (외형에 따른 지붕 막구조물의 풍하중 영향 고찰)

  • Ko, Kwang-Woong;Jang, Myung-Ho;Lee, Jang-Bog;Sur, Sam-Yeol
    • Proceeding of KASS Symposium
    • /
    • 2008.05a
    • /
    • pp.15-18
    • /
    • 2008
  • A Spatial structure, having a curvature with a curved surface, is an extremely efficient mechanical creation considering the external load. It is resisted the out-of-plane direction load by in-plane forces using the structure's curvature. Spatial Structures include many types of structures, such as: space frames or grids; cable-and-strut and tensegrity; air-supported or air-inflated; self-erecting and deployable; cable net; tension membrane; lightweight geodesic domes; folded plates; and thin shells. Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. It is very important that effects by wind load than seismic and dead load. And, wind load is different by surrounding and shape of building In this study, we analyze the results of design wind load and wind tunnel tests about the 2 stadiums which are constructed on sensitive sites by effect of wind loads.

  • PDF