• 대한수학회보
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• 제52권2호
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• pp.377-394
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• 2015

In this paper, we generalize some results about Bertrand curves and Razzaboni surfaces in Euclidean 3-space to the case that the ambient space is Minkowski 3-space. Our discussion is divided into three different cases, i.e., the parent Bertrand curve being timelike, spacelike with timelike principal normal, and spacelike with spacelike principal normal. For each case, first we show that Razzaboni surfaces and their mates are related by a reciprocal transformation; then we give B$\ddot{a}$cklund transformations for Bertrand curves and for Razzaboni surfaces; finally we prove that the reciprocal and B$\ddot{a}$cklund transformations on Razzaboni surfaces commute.

• Applied Microscopy
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• 제34권4호
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• pp.211-221
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• 2004

물질을 이루고 있는 원자의 집합체에서 단 한번의 회절이 일어나는 경우의 회절이론의 개발을 소개하였다. Fourier transform으로 이루어지는 역 격자 공간에서의 역격자 공간 분포와 실 공간에서의 패터슨 함수와의 관계를 유도하고 이어 여러 가지 물질을 예로 들어 고찰하였다.

• 한국과학교육학회지
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• 제12권2호
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• pp.31-42
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• 1992

The purposes of this study were to find out the degree of formation of the concept of density for the junior high students. The changing pattern of concept in acquiring the concept of density and the degree of development of INRC transformation ability related to the concept of density were also analyzed according to cognitive level and teaching method. The results of this study were as follows. 1) The experimental group were more effective than control group in the formation of the concept of density. 2) Even though students had been taught the concept of density, the various types of preconception were remained and persisted. Especially, the students at concrete level had persisted misconceptions and these misconceptions had been changed to the other misconceptions. 3) In the degree of the formation of the transformation ability of INRC group related to the concept of density in solid phase, the experimental group developed much better on both the abilities of Reciprocal transformation, Correlative transformation and the abilities to manipulate two variables such as volume and mass than control group. 4) The correlation coefficient between GALT score and achivement of the concept of density was 0.67. The correlation coefficient between achivement of the concept of density and the formation the transformation of INRC group related to the concept of density was 0.78.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.195-197
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• 1987

A new method of model reduction, based on the differentiation of polynomials, is Introduced by Gutman(1982). Without the reciprocal transformation, and the differentiation of the numerator and denominator polynomials of the transfer function, used by Gutman, the lower-order system can be obtained by the permutation of the order of numerator and denominator and the number of differentiation.

• 열처리공학회지
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• 제4권3호
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• pp.39-46
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• 1991

The effects of austenitizing temperatures and times and cooling rate on the characteristics of continuous air cooling have been investigated for 0.3%C-Mn steels microalloyed with vanadium. Transformation start temperatures have been found to be measured from temperature-time curve directly obtained with continuous air cooling and to decrease with increasing austenitizing temperature, cooling rate and Mn contents. The coarsening behavior of austenite grain size has been measured to abnormally grow at $1050^{\circ}C$ and rapidly grow at $1200^{\circ}C$. It has been found that the volume fraction of pearlite was linealy proportional to the reciprocal square root of austenite grain size. The hardness has been measured to increase with increasing cooling rate up to $250^{\circ}C/min.$ and to remain relatively unchanged in the range of $250{\sim}400^{\circ}C/min.$ showing that hardness valves for steel with a higher Mn content increase more than those for steel with a lower Mn content. The impact property has been found to decrease with increasing of austenite grain size but does not linealy change with the reciprocal square root of austenite grain size.

• 한국정보통신학회논문지
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• 제7권7호
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• pp.1462-1470
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• 2003

정보통신의 발달과 인터넷의 확산으로 인해 정보보안의 필요성이 증대되면서 다양한 암호알고리즘이 개발되어 활용되고 있다. 이와 더불어 암호 공격 기술도 발전하여서, 공격에 강한 알고리즘에 대한 연구가 활발하게 진행되고 있다. Substitution Permutation Networks(SPN)등의 블록 암호알고리즘에서 교환계층의 선형변환행렬이 Maximum Distance Separable(MDS) 코드를 생성하면 차분공격과 선형공격에 강한 특성을 보인다. 본 논문에서는 선형변환행렬이 MDS 코드를 생성하는가를 판단하는 새로운 알고리즘을 제안한다. 선행변환행렬의 입력코드는 GF(2$^n$)상의 원소들로 이들을 변수로 해석할 수 있다. 하나의 변수를 다른 변수들의 대수식으로 변환하고 대입하여 변수를 하나씩 소거한다. 변수가 하나이고 모든 계수가 ‘0’이 아니면 선형변환 행렬은 MDS 코드를 생성한다. 본 논문에서 제안한 알고리즘은 기존의 모든 정방부분행렬이 정칙인지를 판단하는 알고리즘과 비교하여 곱셈 및 역수 연산수를 많이 줄임으로서 수행 시간을 크게 감소 시켰다.

• 한국의상디자인학회지
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• 제9권2호
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• pp.167-178
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• 2007

The purpose of this study is to systematically examine fusion phenomenon in the cultural aspect aiming to grasp the characteristics of fusion phenomenon, which has a steady impact on fashion trend. A reason for fusion to be noted as a cultural code is because diversely cultural interpretations are impossible from one viewpoint. Therefore, it is aimed to inquire into the characteristics of fusion culture, which is one phenomenon of newly mass culture, and to examine which cultural fusion phenomenon in modern fashion is being displayed in fashion design. First, the culturally fusion phenomenon, which was indicated in modern fashion, is displayed as repetition. The fusion, which integrates into fashion as a cultural code, is a trend of pursuing the experience with different culture. The needs of consumers are shown as fusion fashion that repeatedly uses the traditional detail and the modern detail through cultural repetition. Second, it is displayed as transformation. A concept of fusion is not the simple aggregate in [1+1=2], but the creation of new culture called [1+1=1]. In modern fashion, the cultures in the East and the West are harmoniously transformed, and through transformation, each culture is being compressively delivered. Third, it is displayed as interdependency. The fusion fashion which was newly re-interpreted while having reciprocal influence upon mutual culture, is re-interpreted by forming the equal relationship in heterogeneous elements without destroying fashion that was made previously.

• 열처리공학회지
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• 제10권2호
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• pp.93-100
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• 1997

Effect of austenite grain size on starting temperature of ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation($M_s$) has been studied in an Fe-18%Mn alloy. Particular attention was paid on the variation of stacking fault energy with austenite grain size, which is considered to be a important factor affecting ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation. Austenite grain size was increased in a wide range from $13{\mu}m$ to $185{\mu}m$ with increasing solution treatment temperature from $700^{\circ}C$ to $1100^{\circ}C$. Hardness was decreased with increasing austenite grain size while the volume fraction of ${\varepsilon}$ martensite showed a reverse tendency, which indicates that the hardness is more dependent on austenite grain size than ${\varepsilon}$ martensite content. No significant change was found in $M_s$ temperature when the grain size was larger than about $30{\mu}m$. In case that, the austenite grain size was smaller than about $30{\mu}m$, however, $M_s$ temperature was marlkedly decreased with decreasing austenite grain size. A linear relationship between $M_s$ temperature and the stacking fault formation probability, i.e. the reciprocal of the stacking fault energy was obtained, which suggests that the variation of $M_s$ temperature with austenite grain size is closely related to the change in stacking fault energy.

• 대한전자공학회논문지
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• 제24권6호
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• pp.948-955
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• 1987

The model reduction method of the high order linear time invariant systems is proposed. The continuous fraction expansion of Auxiliary denominator polynomial is used to obtain denominator polynomial of the reduced order model, and the numerator polynomial of the reduced order model is obtained by equating the first some moments of the original and the reduced order model, using simplified moment function. This methiod does not require the calculation of the reciprocal transformation which should be calculated in Routh approximation, furthemore the stability of the reduced order model is guaranted if original system is stable. Responses of this method showed us good characteristics.

• 대한전자공학회논문지
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• 제24권4호
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• pp.583-589
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• 1987

A new approximation method is proposed for the linear model reduction of high order dynamic systems. This mehtod is based upon the denominator table(D-table) and time moment-matching technique. The denominator table(D-table) is used to obtain the denominator polynomial of reduced-order model, and the numerator polynomial is obtained by time moment-matching method. This proposed method does not require the calculation of the alpha-beta expansion and reciprocal transformation which should be calculadted by Routh approximation method. The advantages of the proposed method are that it is computationally every attractive better than Routh approximation method and the reduced model is stable Il the original system is stable.