• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.21-27
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• 2008

Triangular structure is used as basic shape of artificial structures for generating the upwelling current in order to make rich fishing ground at sea. Artificial upwelling current could bring the deep sea water containing a lot of nutrients from the bottom up to the surface. The purpose of this study is to examine the flow characteristics around underwater triangular structure with various stratification parameter. An experimental study was carried out for the triangular structure model in the circulating water channel to investigate flow characteristics by flow visualization method. A velocity fields around the underwater structure were measured by particle image velocimetry(PIV). The experimental results showed that the upwelling effect at the back and upper region of the structure could be best when the water depth was 2 times of the structure height and the stratification parameter was approximately 3.0. These quantitative data will be useful to determine the functional efficiency cf artificial upwelling structures.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1634-1638
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• 2008

하천의 2차원 흐름 해석, 유사이동 해석, 오염확산 해석을 위한 유체의 수치해석법에는 유한요소법, 유한차분법, 유한차분법의 변형인 유한체적법, 경계적분법 등이 있다. 유체에 대한 수치해석 기법으로 전통적으로 가장 많이 사용되고 있는 방법은 유한차분법이지만, 비구조적 요소망(unstructured mesh)을 이용하여 복잡한 형상을 표현하기가 상대적으로 용이한 유한요소법이 다양한 형태의 하천 해석에는 더욱 적합할 것이다. 본 연구에서는 비구조적 요소망을 advanced front method를 이용하여 생성해 보았다. Advanced front method는 해석하고자 하는 영역에 적절한 절점들을 생성한 후 삼각 요소망을 구성하는 grid based advanced front method와 절점들을 생성하지 않고 해석 영역에 삼각 요소를 바로 구성하는 element based advanced front method로 나눌 수 있다. Grid based advanced front method에서 해석 영역에 적절한 절점을 생성하는 방법으로는 일반적인 격자 구조의 절점 생성 방법을 적용하였으며 경계와의 거리가 가까운 절점은 생성되지 않으며, 삼각 요소를 구성할 때에는 두 개의 인접 절점을 비교하여 최적의 삼각 요소를 구성하게 된다. 단 두 개의 인접 절점만을 비교함으로서 비교적 빠른 시간 안에 최적의 삼각 요소망을 구성할 수 있다. 삼각 요소망을 생성한 후에는 Laplacian smoothing을 이용하여 삼각 요소망의 형질을 개선하였다. Element based advanced front method는 외부 경계에서부터 시작된 Front가 내부 영역으로 확대되어지며 각 Front에서 적절한 절점을 직접 생성하여 바로 삼각 요소를 구성하게 된다. Front에서 생성된 절점은 인접 절점들이 있는지 검색하여 인접 절점이 있다면 생성된 절점은 삭제되어지며 인접 절점이 삼각 요소를 위한 나머지 한 점으로 채택되어진다. Front는 외부 경계와 교차되어지지 않아야 하며 또한 연속된 Front를 효율적으로 관리하기 위해 list 자료 구조를 활용하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.8 no.2
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• pp.1-8
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• 1990

A regular grid or a triangulated irregular network is generally used as the data structure of digital terrain models. A Regular grid is simple and easy to manipulate, but it can't describe well terrain surface features and requires vast volumes of data. In the meantime, a triangulated irregular network has complex data structure, but it can describe well terrain surface features and can achieve the accuracy suitable to its application with relatively little data. This paper aims at the construction of efficient digital terrain models by the improvment of a triangulated irregular network based on Delaunay triangulation. Regular and irregular data set are sampled from existing contour maps, and the efficiency and the accuracy of the two data structures are compared.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.241-246
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• 2014

The purpose of this study is to investigate the flow characteristics around underwater triangular structure with various inclination and Reynolds number. A flow fields around the triangular structure model were measured by visualization method and PIV in the circulating water channel. The result of the experiment is where the triangular structure that has a inclination of $45^{\circ}$ and the reynolds number at $Re=2.9{\times}10^3$ showed rising velocity component to 2.7 times of the structure height. When the reynolds number is steady and when the inclination is greater the descending velocity component of the structure's rears current form is greatly shown and for the areas where it's more than y/hs=1.75 has a change in the angle of inclination but it doesn't give a great effect to it.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.238-239
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• 2003

2차원 슬랩 형태의 단일 결함 레이저는 낮은 발진 문턱값과 작은 모드 부피로 인해 문턱 없는 레이저의 동작 가능성, 광자 집적 회로에서의 광원 소자 등으로 각광을 받고 있다. 광결정은 결정 구조에 따라 삼각격자와 사각격자로 나눌 수 있는데, 특히 삼각격자의 경우 사각격자에 비해 밴드갭이 보다 넓은 주파수 영역에 걸쳐 나타나므로, 공진기와 도파로서의 응용에 더 적합한 소재로 연구되고 있다. 2차원 삼각구조 단일 결함 광결정은 60$^{\circ}$회전에 대하여 대칭성을 가지므로, 군론에 따라 기본적으로 60$^{\circ}$,120$^{\circ}$,180$^{\circ}$,360$^{\circ}$의 회전 대칭성을 가지고 있는 네 종류의 모드가 존재한다. (중략)

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1997.10a
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• pp.114-121
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• 1997

회전 열파이프의 열전달 성능은 액막 두께 및 증발부로 귀환되는 응축 액막 유동율에 의해 결정된다. 그 동안 응축액 유동율을 촉진시키기 위하여 용기 내벽에 groove, 테이퍼 및 나선형 코일을 삽입하여 유동율을 높이는 방법들이 연구되었다. 본 연구도 회전 열파이프의 내부 관벽 구조에 관한 것으로써 삼각 단면을 갖는 회전 열파이프의 열전달 특성을 파악하고자 하였다. 삼각 단면을 갖는 회전 열파이프는 고속 회전 영역에서 모서리 부분으로 액막이 집중되어 관 내벽에 형성되는 액막 두께를 줄일 수 있으나 증발부에서 국부적인 과열이 발생되어 불안정한 작동 상태를 나타내었다. 따라서 본 연구에서는 개선방안으로 증발부에 부분적으로 원형관을 접합하였으며, 그 결과 dry-out의 억제와 함께 삼각 유동 단면에 의한 액막 두께 감소 효과를 볼 수 있었다. 회전체 발열부 냉각에 적용시키기 위해서는 앞으로 최적의 기하학적 형상에 따른 충전율 및 액막에서의 열전달에 대한 정량적인 해석 연구가 필요할 것으로 생각된다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.12 no.2
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• pp.209-218
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• 1994

This study aims to generate triangulated irregular network in a form of digital terrain model which is being increasingly used. In general, grid digital elevation model and triangulated irregular network are reasonable units for solving terrain problems. But, triangulated irregular network is an efficient alternative to grid digital elevation model because of their efficiency in storing data and their convenient data structure for accommodating irregularly spaced elevation data. Various methods represented for extracting triangulated irregular networks from grid digital elevation model, and then algorithm that get accurate results for triangulation with their data set was introduced. The new approach for triangulation in this study uses the Elevation and Changeable Distance criterion, and adding interpolation points and restricted constraint lines can generate triangulated irregular network which is more close to real surface. This made database efficient construction and could be used for many applications of geo-spatial information system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.8
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• pp.1-7
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• 2005

This paper proposes a local improvement method that combines extended topological clean up and optimization-based smoothing for homogenizing triangular grid system. First extended topological clean up procedures are applied to improve the connectivities of grid elements. Then, local optimization-based smoothing is performed for maximizing the distortion metric that measures grid quality. Using the local improvement strategy, we implement the grid homogenizations for two triangular grid examples. It is shown that the suggested algorithm improves the quality of the triangular grids to a great degree in an efficient manner and also can be easily applied to the remeshing algorithm in adaptive mesh refinement technique.

• Journal of Educational Research in Mathematics
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• v.24 no.4
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• pp.607-622
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• 2014

The purpose of this paper is that it analyzes the historical development of the concept of trigonometric functions and discuss some didactical implications. The results of the study are as follows. First, the concept of trigonometric functions is developed from line segments measuring ratios to numbers representing the ratios. Geometry, arithmetic, algebra and analysis has been integrated in this process. Secondly, as a result of developing from practical calculation to theoretical function, periodicity is formalized, but 'trigonometry' is overlooked. Third, it must be taught trigonometry relationally and structurally by the principle of similarity. Fourth, the conceptual generalization of trigonometric functions must be recognized as epistemological obstacle, and it should be improved to emphasize the integration revealed in history. The results of these studies provide some useful suggestions to teaching and learning of trigonometry.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.655-662
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• 2023

Big data research plays a role of supplementing existing social science research methods. If the survey and experimental methods are somewhat inaccurate because they mainly rely on recall memories, big data are more accurate because they are real-time records. Social science research so far, which mainly conducts sample research for reasons such as time and cost, but big data research analyzes almost total data. However, it is not easy to repeat and reproduce social research because the social atmosphere can change and the subjects of research are not the same. While social science research has a strong triangular structure of 'theory-method-data', big data analysis shows a weak theory, which is a serious problem. Because, without the theory as a scientific explanation logic, even if the research results are obtained, they cannot be properly interpreted or fully utilized. Therefore, in order for big data research to become a methodological innovation, I proposed big thinking along with researchers' efforts to create new theories(black boxes).