• Communications of Mathematical Education
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• v.24 no.1
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• pp.145-158
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• 2010

In this paper we study tetrahedron's properties related with center of inscribed sphere using the center of mass. We show that the center of mass of four mass points (A,a), (B,b), (C,c), (D,d) coincide with center of tetrahedron's inscribed sphere, suggest equalities and inequalities related with center of inscribed sphere, and prove theses using the center of mass. Our results can be used in research and education programs, various types of gifted student education.

• Journal of the Korean School Mathematics Society
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• v.20 no.4
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• pp.445-464
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• 2017

This study targeting 10 high school 3rd grade students who have studied space figures in natural sciences track analyzes the process of analogical discovery from the construction of inscribed and circumscribed circles of a triangle to that of inscribed and circumscribed spheres of a tetrahedron through the analytical method using Geogebra. The subjects are divided into two groups of five, the experimental group consisting of those who have experienced analytical method and the comparative group consisting of those who haven't. This research analyzing the process of constructing inscribed and circumscribed spheres of a tetrahedron. Although students of both groups all have an accurate preliminary knowledge of inscribed and circumscribed circles of a triangle, they have difficulty in constructing inscribed and circumscribed spheres of a tetrahedron. However, the students of experimental group who have studied the constructing process of inscribed and circumscribed circles of a triangle in reverse using analytical method and Geogebra can perform analogical discovery finding out the way to construct inscribed and circumscribed spheres of a tetrahedron using analogy by themselves. They can control and explore space figures by visualization. Also, they can immediately examine and provide feedback on the analogizing process of their own. In addition, the process affects the attitude of students toward mathematics positively as well as gives validity to the result of analogy.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2009.03a
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• pp.153-159
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• 2009

불연속변형해석(DDA)은 유한요소법(FEM)과 개별요소법(DEM)의 장점을 모두 가지고 있는 해석법이다. 3차원 불연속변형해석의 안정성과 해석속도는 접촉찾기(Contact Detection) 알고리즘과 벌칙스프링(Penalty spring)을 이용한 접촉처리 알고리즘에 의해 크게 좌우되는데, 블록의 꼭지점(vertex) 간의 접촉이 발생할 경우, 적합한 접촉면을 결정하는 과정에서 많은 해석오류와 시간적 손실이 발생할 가능성이 있다. 본 연구에서는 블록의 꼭지점에 내접하는 구(inscribed sphere)를 삽입하여 가상의 접촉점과 접촉면을 생성하는 알고리즘을 연구하였다. 이로 인해 발생할 수 있는 해석의 오차의 크기를 확인하고, 간단한 불연속 변형해석의 해석 실례에 적용해 보았다.

• Korean journal of communication and information
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• v.16
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• pp.36-70
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• 2001

The purpose of this study is to investigate women's radio talk program and evaluate its possibilities and limitation from the point of feminist perspective. The theoretical framework is based on feminist studies and text analysis of talk show. Existing studies regarding talk show are mainly focused on television. But radio talk show is one of general entertainment and it's influences on minorities are still significant. is the most representative women's radio talk program in Korea. It has been broadcasted over 10 years and very popular among Korean housewives. The audience of this program call themselves schoolfellow, and call the program 'school of women'. The media text of is mainly consisted of letters from women audiences, and they are selected by producers. So the text is made by both audiences and producers. The unique combination of this process produces complicated discourses which contain women's experiences in letters and station's considerations through safekeeping. The problems investigated in this study are as follows: First, What discourses are produced in this program? Second, Alternative possibilities can be seen in this program in feminist perspectives? Text analysis of 1week(2000.9.18-9.24) and interview with producers are accomplished to this purposes. In the text analysis, subject matters, inscribed women's position, values of the letters are revealed. Most of the subject matters are family affairs. Some are socially oriented but family and home are the predominant category of women's letters. And the position of women subject is defined in the domestic network. They are nameless but the mother, wife, daughter, daughter-in-law of other people. In value, family-oriented value and small happiness in everyday life are generally appeared. But these values are essentially coincide with the values of status quo. The answers of the conflict are not public but individualized. And acception the status quo is presented as the wisest decision, But ` has many implications in relation to women's sharing of their experience, and construction of imagined community in media. Women continuously interact each other revealing and discussing their experiences and sometimes their social practices are stirred through this media sphere. So we see the 'emotional union' among women are formed through radio. The limitation of this program is very apparent: it's patriarchic values, acception of status quo, and individualization of the women's problems. But in the same time we can read coexisting it's latent possibilities: the possibilities of women's public sphere. But it is completely alternative women's sphere in feminist perspectives. It renders women opportunities to participate public media and share with other women, and collaborate with their problem.

• International Journal of CAD/CAM
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• v.7 no.1
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• pp.71-80
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• 2007

Recently, feature-based solid modeling systems have been widely used in product design. However, for engineering analysis of a product model, an ed CAD model composed of mid-surfaces is desirable for conditions in which the ed model does not affect analysis result seriously. To meet this requirement, a variety of solid ion methods such as MAT (medial axis transformation) have been proposed to provide an ed CAE model from a solid design model. The algorithm of the MAT approach can be applied to any complicated solid model. However, additional work to trim and extend some parts of the result is required to obtain a practically useful CAE model because the inscribed sphere used in the MAT method generates insufficient surfaces with branches. On the other hand, the mid-surface ion approach supports a practical method for generating a two-dimensional ed model, even though it has difficulties in creating a mid-surface from some complicated parts. In this paper, we propose a dimension reduction approach on solid models based on the midsurface abstraction approach. This approach simplifies the solid model by abbreviating or removing trivial features first such as the fillet, mounting, or protrusion. The geometry of each face is replaced with mid-patches from the simplified model, and then unnecessary topological entities are deleted to generate a clean ed model. Also, additional work, such as extending and stitching mid-patches, completes the generation of a mid-surface model from the patches.