• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.245-248
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• 2003

We construct a universal derivation module of an R-algebra which is constructed by means of a tensor product of three copies of the algebras.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.81-89
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• 2004

The vibration analysis of the circular arch as a member of a structure has been an important subject of mechanics due to its various applications to many industrial fields. In particular, circular arches with variable cross section are widely used to optimize the distribution of weight and strength and to satisfy special architectural and functional requirements. The Generalized Differential Quadrature Method (GDQM) and Differential Transformation Method (DTM) were recently proposed by Shu and Zou, respectively. In this study, GDQM and DTM were applied to the vibration analysis of circular arches with variable cross section. The governing equations of motion for circular arches with variable cross section were derived. The concepts of Differential Transformation and Generalized Differential Quadrature were briefly introduced. The non-dimensionless natural frequencies of circular arches with variable cross section were obtained for various boundary conditions. The results obtained using these methods were compared with those of previous works. GDQM and DTM showed fast convergence, accuracy, efficiency, and validity in solving the vibration problem of circular arches with variable cross section.

• Korean journal of food and cookery science
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• v.11 no.1
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• pp.69-76
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• 1995

This study was concentrated on the subject of chou formation and physicochemical characteristics on medium flour mixed with 0, 25, 50, 75, 100% of rice flour in order to clarify the possibility to substitute rice flour for wheat flour on chou preparation. The water holding capacity, swelling power, and maximum viscosity were higher in rice flour than those in medium flour but the initial pasting temperature was equal to 65$^{\circ}C$ in the two flour groups. The ratio of setback during cooling became 0.94 in the rice flour and 1.14 in the medium flour. So, the rice flour showed a slow tendency during gel formation as compared with the medium flour. The volumes of the rice choux were ranged from 80.0% to 89.0% according to the mixing ratio of medium flour as compared with that of the chou of wheat flour. But, the choux formation were increased as much as 108.8% out the paste added gelation of glutinous substance and 124.4% at the paste added Span20 of emulsifier compared to the non-addition treatment. The paste of rice flour added gelatin and Span20 showed better dispersion of components, especially, the small granules of lipid were fairly or plentifully dispersed in the paste added Span20 due to emulsifying activity. In sensory evaluation, the chou of l00% rice flour was inferior to that of medium flour on cavity-forming but the choux of wheat flour mixed with 25%, 50%, and 75% of rice flour were equal or superior to that of medium flour on all characteristics tested such as appearance, surface color, cavity-forming, chewiness, and taste. There were no significant differences on the cavity-forming expansion and taste between choux of rice flour and wheat flour Therefore, the results of this study made conclusion that rice flour would be substituted for wheat flour on the chou preparation.

• Journal of Educational Research in Mathematics
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• v.21 no.1
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• pp.33-55
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• 2011

This study explores the characteristics of calculus students' and instructors' discourses on the derivative using a communicational approach to cognition. The data were collected from surveys, classroom observations, and interviews. The results show that the instructors did not explicitly address some aspects of the derivative such as the relationship between the derivative function (f'(x)) and the derivative at a point (f'(a)), and f'(x) as a function, and that students incorrectly described or used these aspects for problem solving. It is also found that both implicitness in the instructors' discourse, and students' incorrect descriptions were closely related to their use of the word, "derivative" without specifying it as "the derivative function" or "the derivative at a point." Comparison between instructors' and students' discourses suggests that explicit discussion about the derivative including exact use of terms will help students see the relationship that f'(a) is a number, a point-specific value of f'(x) that is a function, and overcome their mixed and incorrect notion "the derivative" such as the tangent line at a point.

• Journal of the Korea Institute of Building Construction
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• v.18 no.6
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• pp.551-558
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• 2018

This study evaluate the fluidity and hardening properties of mortar by replacement ratio of ferronickel slag powder to estimate the applicability of ferronickel slag powder for cement replacement materials. Ferronickel slag powder was replaced by 0, 5, 10, 15 and 20% of the cement weight. In addition, blast furnace slag powder and fly ash were also used for comparing with the mixtures using ferronickel slag powder. As the test results, the micro-hydration heat of the mixture containing the ferronickel slag powder was lower than that of the mixtures containing the same amount of blast furnace slag powder and fly ash. The flow of the sample with ferronickel slag powder was relatively higher than the other mixtures. In all ages, the compressive strength of the mixture with ferronickel slag powder and fly ash was similar to that of the mix containing only fly ash. In case of drying shrinkage, the mixture containing ferronickel slag powder exhibited lower drying shrinkage than the mixture using blast furnace slag powder, and similar to the mixture containing fly ash.

• Communications of Mathematical Education
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• v.33 no.3
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• pp.335-354
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• 2019

The purpose of this study is to explore alternative ways of teaching derivatives in a way that emphasizes intuition. For this purpose, the contents related to derivatives in Korean curriculum and textbooks were analyzed by comparing with contents in Singapore Curriculum and textbooks. Singapore, where the curriculum deals with derivatives relatively earlier than Korea, introduces the concept of derivatives and differentiation as the slope of tangent instead of the rate of instantaneous change in textbook. Also, Singapore use technology and inductive extrapolation to emphasize intuition rather than form and logic. Further, from the results of the exploration of other foreign cases, we confirm that the UK and Australia also emphasized intuition in teaching derivatives and differentiation. Based on the results, we discuss the meaning and implication of introducing derivatives and teaching differentiation in a way that emphasizes intuition. Finally, we propose the implications for the alternative way of teaching differentiation.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.10 no.1
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• pp.21-29
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• 2006

The method to construct a surface from point data are widely known. But the way to make a surface from derivative data is not usually used since derivative data in engineering appears very often. In this paper, if more than one types of data among three possible data such as point data, first derivative data, second derivative data are given, we can construct a surface. If only first derivative data are given, we add a function value at the one point. If only second derivative data are given, we add a linear function.

• Proceedings of the Korea Society for Simulation Conference
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• 1994.10a
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• pp.4-4
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• 1994

미분방정식은 많은 학문에서 현실 세계의 대상을 모형화하고 시뮬레이션하는 데에 매우 유용하게 사용되는 도구이다. 그 중에서도 현실 세계에서 적용되는 물리적 법칙에 근거해서 가상 세계를 만드는 컴퓨터 애니메이션이나 과학적 가시화등의 분양에서는 미분방정식으로 다루고자하는 대상을 모형화하고 시뮬레이션을 통해서 필요한 자료를 추출하는 과정이 필수적이다. 본 연구에서는 현실 세계에 근거한 가상세계를 만들기 위해서 요구되는 물리적 시뮬레이션을 수행하기 위한 방법을 연구하고, 그 소프트웨어를 개발한다. 현실세게를 모형화하는데에 많이 쓰이는 물리학적 방법은 역학에 근거한 미분방정식들이다. 그 중에서도 연립 상미분방정식의 형태로 많이 나타나는 Newton 방정식은 거시적인 물체들간의운동ㅇㄹ 표현하는데에 많이 사용도니다. 그리고 편미분방정식의 형태로 나타나는 Lagrange 방정식은 Hamilton의 원리를 운동방정식에 적용하여 얻은 것으로 Newton 방정식과 관계가 없는 광버무이한 물리적 현상을 표현하는데에 사용된다. 본 연구에서 개발하는 시물레이션 소프트웨어는 연립 상미분방정식으로 모형화되는 대상을 시뮬레이션할 수 있는 방법과 2c, 편미분방정식으로 모형화되는 대상을 시뮬레이션 할 수 있는 방법을 제공한다.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.50-56
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• 1997

본 논문은 다물체동역학에서의 민감도해석을 위하여 개발된 혼합법(Mixed method)을 보여준다. 이 방법은 해석적인 미분의 유도와 수치적인 미분의 장점을 함께 사용한다. 해석적인 유도는 기본적인 전체의 미분에서 사용 되며 여기서 나온 각 세부 미분항은 수치적인 미분방법에 의존한다. 이로인하여 세부미분항을 다물체의 운동방정식 에서 유도할 때 발생하는 어려움을 제거한다. 여기서 사용되는 운동 방정식은 Joint Coordinate 방정식을 사용하며, 이 방정식의 계산시간과 정확도에 의해 민감도해석에서도 정확도와 계산시간의 효율을 향상시킬 수 있게 된다. 예제로서 자동차 Suspension 시스템의 승차감을 최적화하기 위한 민감도 해석을 수행하였으며, 여기서 혼합법이 차등미분법과 상응한 결과를 보였다.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1988_1989
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• 2009

본 논문은 이차 미분 맥파(SDPTG, Second Derivation of Photoplethysmogram)를 측정하여 이차 미분 맥파의 5개의 특징점을 검출하는 방법에 대한 내용을 기술한다. 본 논문에서는 측정된 신호의 신호대 잡음비(SNR)을 높이는 방법과 기존의 미분을 이용한 변곡점 추출의 한계적인 부분, 그리고 본 논문에서 제안하는 이차 미분 맥파의 특징점의 분포를 이용한 특징점 추출 알고리즘에 대해서 설명한다.