• 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.

• 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.

• 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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1312-1319
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• 1988

Internal gear is the important part of the planetary reduction gear system. This study aims at developing the numerical analysis method for design of spherical hob to manufacture internal gear. Methods of calculation of hob tooth profile, generating tooth profile and tooth profile errors such as the errors of pressure angle, tooth thickness and pitch of spherical hob must be made smaller than those of standard tooth profile. And, the smaller the pressure angle and the number of equivalent pinion tooth become, the larger the tooth profile errors are. One design example of spherical hob is proposed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.457-465
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• 1988

The inside contact characteristics in abrasive belt drives were investigated analytically and experimentally for (1) driver pulley contact wheel and (2) driven pulley contact wheel. The concentrated contact forces in the grinding zone divided the entire belt-pulley contact are by three distinct areas and the tangential friction forces in the active areas caused the normal forces to change, which resulted in the different belt force distribution compared with those of the ordinary flat belt drives. The experimental results for the normal pressure (belt tension) distribution were in good agreement with the theoretical results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.837-846
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• 1989

Belt tension distribution for an abrasive blet grinding was investigated analytically and experimentally for (1) slack side and (2) tight side blet grinding. Classical Eytelwein equation was used to predict the belt tension distribution with dividing contact angles into (1) inactive and (2) active angles. General friction theory was modified based on the friction force between the belt and the support in the grinding contact area that was obtained by experiments. It was found that analytical results were in good agreement with the experimental results. Also, the tight side belt grinding was recommended since it could carry out more grinding load than that of slack side belt grinding.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1159-1162
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• 2009

브로드캐스팅 프로토콜은 무선 애드 혹 네트워크에서 컨트롤 메시지를 전체 노드에 전송하기 위한 목적으로 널리 사용된다. 전통적인 브로드캐스팅 프로토콜은 모든 노드가 처음 받은 메시지를 재전송 하기 때문에 극심한 중복전송과 충돌문제가 발생한다. 이러한 문제를 해결하기 위해 최근에 효율적으로 재전송노드를 줄이기 위한 브로드캐스팅 기법들이 제안되었지만 여전히 다수의 불필요한 재전송이 발생한다. 제안 기법은 1-홉 이웃노드의 위치정보를 이용하여 전파반경에 내접하는 정삼각형의 꼭짓점을 구하고 각 꼭짓점에 가장 가까운 이웃노드를 재전송노드로 선택한다. 우리는 먼저 재전송 노드를 최소화하기 위한 이상적인 모델을 제시하고 이상적인 모델에 근접하기 위한 방법을 설명한다. 시뮬레이션 결과를 통해 제안 기법이 기존의 효율적인 브로드캐스팅 프로토콜보다 성능이 우수하며 재전송 노드수가 lower bound에 근접하는 것을 보여준다.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.541-546
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• 2006

3차원 관상동맥을 분석하기 위해서는 혈관의 분기점, 극단점, 혈관의 계층적 구조 관계를 함축적으로 표현하는 것이 매우 중요하다. 본 논문에서는3차원 CT 혈관 조영 영상으로부터 관상동맥의 3차원 골격을 자동으로 추출하는 방법을 개발하였다. 먼저, CT혈관 조영술에 의해 획득된 슬라이스 이미지로부터 3차원 조작 및 수술 시뮬레이션 등을 위하여 혈관의 3차원 표면에 대한 메쉬 모델을 생성한다. 생성된 메쉬 모델이 임의로 변형된 후에도 자동으로 골격을 쉽게 추출할 수 있도록 메쉬 모델을 복셀화하는 단계를 거친다. 이렇게 얻어진 복셀 모델로부터 표면복셀을 결정하고 표면 복셀로부터 객체 복셀까지의 유클리드 거리값를 계산하여 유클리드 거리맵(EDM)을 계산한다. 계산된 EDM 으로부터 객체 복셀이 가지게 되는 최대 내접 구를 계산하여 Discrete Medial Surface을 생성하게 되는데 이것은 골격의 후보가 된다. 골격의 후보집합 복셀에 대하여 Dijkstra 최단 경로 결정 알고리즘을 적용하여 골격을 자동으로 추출하게 된다. 이렇게 추출된 3차원 골격은 관상동맥 수술 시뮬레이션 등의 다양한 형상 분석에 유용하게 사용될 수 있다.

• The Journal of the Korean Society for Microbiology
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• v.7 no.1
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• pp.29-41
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• 1972

To grow Myocbacterium leprae in cultured mouse peritoneal macrophages, studies were made with trypsin-purified Myco. laprae on 1) the dynamics of infection of mouse peritonal macrophages in vivo with Myco. leprae by intraperitoneal inoculation, 2) growth experiment of Myco. leprae in cultured mouse peritoneal macrophages by in vivo infection and in vitro cultivation and 3) the observation of pathological changes in spleens of mice induced by intraperitoneal inoculation of Myco. leprae. Results are summarized as follows; 1. Continuing and significant decreases were observed in the numbers of both acid-fast bacilli in cultured macrophage and of macrophages harboring.acid-fast bacilli by the length of inter vats between the time of intraperitoneal inoculation of Myco. leprae and the time of initiation of macrophage culture. 2. No evidence of multiplication of Myco. leprae in the peritoneal macrophages in vivo was found up to 5 months after intraperitoneal inoculation. 3. With cultures of macrophages made 24 hours and 1 week after intraperitoneal inoculation of Myco. leprae and maintained in vitro up to 2 to 3 months, microscopic examination of the stained preparations of cultured macrophages indicated that an apparent increase in the number of acid-fast bacilli in the macrophages did occur. 4. Quantitative experiment with in vivo infected-in vitro cultured macrophages revealed certain features of increase in the number of total acid-fast bacilli in the cultured macrophages 7 and 9 weeks after initiation of the cultures. 5. Pathological changes in the spleens mice inoculated with Myco. leprae were of mainly degenerative nature in the red pulp. No multiplication of Myco. leprae was observed in the spleens of mice up to 5 months after intraperitoneal inoculation.

• Journal of the Korean Data and Information Science Society
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• v.28 no.4
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• pp.831-841
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• 2017

The irrational number ${\pi}$ is defined as the ratio of circumference of a circle to its radius and always becomes constant. This article does Monte Carlo approximation of its value using the famous Buffon's needle experiment and shows that its convergence is not always proportional to the sample size. We also do Monte Carlo simulations to see the convergence of the computed ${\pi}$ values from the random walk series with independent normal increment. Finally we apply the theoretical derivation to various financial time series data such as KOSPI, stock prices of Korean big firms, global stock indices and major foreign exchange rates. The historical data shows that log transformed data random walk process but most of their first lagged data don't follow a normal distribution. More importantly the computed value from the ratio of the regression coefficient ${\pi}$ tend to converge a constant, unfortunately not ${\pi}$. Using this result we could doubt on the efficient market hypothesis, and relate the degree of the hypothesis with the amount of deviation of the estimated ${\pi}$ values.