• Title/Summary/Keyword: Marching square

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Terrain Reconstruction from Contour Lines (등고선을 이용한 지형 재구성)

  • Kim, Sung-Soo;Lee, Seong-Ho;Lee, Jong-Hun;Yang, Young-Kyu
    • Proceedings of the Korea Information Processing Society Conference
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    • 2001.10a
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    • pp.641-644
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    • 2001
  • 기존의 종이지도를 수치지도 처리과정으로 얻어진 등고선(contour line) 데이터는 원격탐사(Remote Sensing)와 지리정보시스템(GIS)의 응용분야에서 주로 사용되어지는 데이터이다. 이러한 등고선은 해당 지역의 DTM(Digital Terrain Model) 데이터 생성을 위해 보간(interpolation)하여 생성하는 데 연구가 집중되어 왔다. 본 논문에서는 DEM(Digital Elevation Model)으로부터 얻어진 등고선 데이터를 이용하여 사용자에게 3 차원으로 가시화 해 줄 수 있는 기법을 소개한다. 등고선 추출을 위한 방법으로는 기존의 소개되어진 Marching Square 알고리즘을 적용하였고, 지역적인 최고점(local minimum)과 최소점(maximum)을 구하기 위해 등고선을 열린 등고선(open contour)과 닫힌 등고선(closed contour)으로 분류하게 된다. 지역적 최고, 최소점을 찾기 위한 탐색공간을 줄이기 위해 닫힌 등고선만을 대상으로 등고선 트리를 생성하였으며, 생성된 트리의 리프노드에 대해서 최고, 최소점에 대한 근사(approximation)를 수행하게 된다. 이렇게 구해진 근사된 정점들과 등고선 데이터를 입력으로 하여 제한된 딜로니 삼각분할(Constrained Delaunay Triangulation)을 수행함으로써, 3 차원 지형을 재구성할 수 있다. 실험에서 USGS 로부터 획득한 지형 데이터를 이용하여 속도 측정을 하였다. 결과적으로 저장공간 측면에서 적은 량의 데이터를 가지면서 등고선을 표현할 수 있는 3 차원 지형을 렌더링 할 수 있음을 알 수 있다.

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Dynamic Characteristics of Thermal Stratification Build-up by Unsteady Natural Convection (비정상 자연대류에 의한 온도성층화의 동특성에 관한 연구)

  • Kang, B.S.;Lee, J.S.;Lee, T.S.;Ro, S.T.
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.17 no.4
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    • pp.382-394
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    • 1988
  • Dynamic characteristics of thermally-forced stratification process in a square enclosure with a linear temperature profile at the side walls have been investigated through flow visualization experiment and numerical analysis. The experiment was performed on air with the Rayleigh numbers of order $10^5$. A particle tracer method is used for the flow visualization and to obtain a sudden linear temperature profile at the side walls copper blocks which already have a linear temperature profile are come into contact with the thin copper plates of the test section. Immediately a meridional circulation is developed and heat transfer takes place from the wall to the interior region by circulation of fluid and finally a thermal stratification is achieved. In the numerical study, QUICK scheme for convective terms, SIMPLE algorithm for pressure correction, and the implicit method for the time marching are adopted for the integration of conservation equations. Comparison of flow visualization and numerical results shows that the developing flow patterns are very similar in dynamic nature even though there is a time lag due to the inevitable time delay in setting up a linear temperature profile. For high Rayleigh numbers, the oscillatory motion is likely to take place and stratified region is extended. However, initial temperature adjustment process is much slower than that for low Rayleigh numbers.

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Socialist Pop After Cultural Revolution (문화혁명기 이후의 중국의 사회주의 팝아트)

  • Park, Se-Youn
    • The Journal of Art Theory & Practice
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    • no.6
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    • pp.27-50
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    • 2008
  • This thesis examines contemporary Chinese painting after the Cultural Revolution(1966~76), focusing upon so-called "Chinese Pop art", which I termed as "Socialist Pop art". I considered the art of this period within the broader context of social changes especially after the Tienanmen incident of 1989. After the Cultural Revolution during which idolization of Chairman Mao was at its peak, one of the major changes in communist China was that an anti-Mao wave was generated in almost every social class. For example, novels that revealed the hardships during the Cultural Revolution were published. Posters that openly criticized the Maoism were also produced and displayed on the walls, and demand for democracy spurred widespread activist movements among young generations. These broad social changes were also reflected in art. A variety of art movements were introduced from the West to China, and after a period of experimentation with the new imported styles, artists began to apply the new artistic idiom to their works in order to visualize their own social and political realities they lived in. It was a shift from earlier Socialist Realism to a new expression either directly or indirectly, "Socialist Pop", an amalgam of Socialist Realism and Pop art tradition. After the 1989 crackdown of Tienanmen Square protest, when communist government quelled with brutal measures the students, workers, and ordinary people who rose for democracy, greater urge to protest the Deng Xiaoping regime emerged. This time coincided with the gradual emergence of art using Pop art vocabulary to satirize the social reality, the Socialist Pop art, along with many other art forms all with avant-garde spirit. One of the most frequent subjects of Chinese Pop art was visual images of Chairman Mao and his Cultural Revolution, and new China that was saturated with capitalism, which tainted the Chinese way of life with a Western way of consumerism and commercialism. The reason for the popularity of Mao's image was spurred by the "Mao Craze" in the early 1990's. People suddenly began to fall in a kind of nostalgia for the past, and once again, Mao Zedong was idolized as an entity who can heal the problems of modern China who had been marching towards their ultimate destination, the economic development. But this time Chairman Mao was no more an idol but just a popular, commercial product. He is no more an object of worship of almost religious nature but he has become an iconography symbolizing the complex nature of present Chinese society. During this process of depicting the social reality, Chinese artists are making the authority and sanctity of Maoism ineffective. Dealing with this new trend of contemporary Chinese art in view of "Socialist Pop art" two manners of re-creating Pop art can be illustrated: one that incorporates the propaganda posters of the Cultural Revolution; the other borrows from Chinese traditional popular imagery or mass media, such as photos taken during Mao era. What is worth mentioning is that these posters and photos of the Cultural Revolution can be identified as 'popular' media, as they were directed to educate the popular mass, thus combination of this ingenuous pop media with Western Pop art can be fully justified as a genre unique to China. Through this genre, we can discover a new chapter of the Chinese contemporary painting and its society, as their Pop art can be considered as self-portraits true to their present appearances.

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