• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.452-458
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• 2003

This paper presents a robust vibration control methodology of smart structural systems. The governing equations and associated boundary conditions are derived by Hamilton's principle. A robust controller is designed using a linear matrix inequality (LMI) approach to the multiobjective synthesis. The design objectives are to achieve a mix of H$\sub$$\infty$/ performance and H$_2$ performance satisfying constraints on the closed-loop pole locations in the face of model uncertainties. Numerical examples are presented to demonstrate the effectiveness of LMI approach in damping out the multiple modes of vibration of the piezo/beam system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.1108-1113
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• 2004

‘Set’ is a tool that is used frequently in designing computer programs. Because of the reason, ‘set constraints languages’ have been developed recently. In this research, we introduce ‘(Ab)(Cl) set unification’ problem and implement it using the ‘set equation rewriting in Prolog’. In this research we shows that the set unification, that is considered to be difficult to be implemented in procedural languages, ran be implemented easily using the non-deterministic control structure and the list data structure in logic language like Prolog. Our research uses the Ciao Prolog with GNU GPL, this is compared with other existing implementations which used expensive commercial Prolog, so anyone can use the result freely. Currently the result is being used for implementing a set constraint language.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.4
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• pp.469-476
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• 2007

A domain/boundary decomposition technique is applied to carry out efficient finite element analyses of 3-D contact problems. Appropriate penalty functions are selected for connecting an interface and contact interfaces with neighboring subdomains that satisfy continuity constraints. As a consequence, all the effective stiffness matrices have positive definiteness, and computational efficiency can be improved to a considerable degree. If necessary, any complex-shaped 3-D domain can be divided into several simple-shaped subdomains without considering the conformity of meshes along the interface. With a set of numerical examples, the basic characteristics of computational efficiency are investigated carefully.

• Korean Architects
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• no.3 s.347
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• pp.72-76
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• 1998

본 특집은 지방시대에 지역건축문화가 어떻게 변화하고 정착되고 있는가? 그 지역만의 갖고 있는 도시+건축문화의 아이덴티티는 무엇이고, 현대화과정에서 그 지역의 고유한 문화경관요소가 개발과 보존이라는 병립된 사회요구속에서 어떻게 적응되고 있는가에 대해 살펴봄을 의도하고 있다. 특히 백제문화권의 중심도시인 아산, 부여, 공주의 도시특성을 이루고 있는 도시공간구조 및 구성요소와 그 속에 내포되어 있는 문화경관요소의 현황을 살펴본다. 본고는 현대화하는 과정 속에서 전통성이 있는 문화요소를 지역성의 개념과 상관적으로 관련시켜 정리하기 위한 것이다. 문화가 지역을 초월하여 국제적으로 교류되면서, 생활의 편익성을 추구하는 현대인들은 국가와 민족의 차이를 넘어 동일한 지구문화형성의 과정으로 급속히 진행하고 있다. 현대화는 서구화라는 등식은 서구문화의 간결한 편익성이 낳은 전세계적 현상이다. 따라서 현대화를 생활의 변화로 이해할 때에 전통논의의 여유가 있고, 전통논의에 대한 객관성이 있으며, 편협된 전통관으로부터 자유로와질 수 있다. 시간의 변화에 따라서 생활이 변하고, 특히 생활을 담는 그룻으로서 건축환경이 변한다. 오랜 시간을 통해서 서서히 건축환경이 변하지만, 누적된 변화는 커다란 차이로서 나타나고, 이에 따라 적응과정에서의 여러 문제점이 발생한다. 그러므로 현재까지 많이 논의되어온 보전과 보존의 방법론적 세분화에 의한 적극적인 대책이 요구되는 시점에 있다고 할 수 있다. 해서 '전통성을 갖춘' 도시ㆍ건축구조물을 단순한 유적, 유물로 보존할 것인가, 실생활과 관련된 생활과 함께 하는 문화현상으로 적응시킬 것인가 하는 문제점이 우리의 과제인 것이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.7-14
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• 2005

A subdomain-interface finite element method is suggested to solve a class of fully- coupled thermomechanical problems with contact boundaries. The penalty method is used for connecting subdomains that satisfy interface compatibility conditions. As a result, effective stiffness matrices are always positive definite, and computational efficiency can be improved to a considerable degree. Moreover, any complex-shaped domain can be divided into independently modeled subdomains without considering the conformity of meshes on interfaces. Using a computer code based on the present method, these advantageous features are shown through a set of numerical studies.

• Journal of KIISE:Software and Applications
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• v.31 no.10
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• pp.1304-1319
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• 2004

We can significantly reduce the cost o# program testing by automating the process of test data generation. Test data generation usually concerns identifying input values on which a selected path is executed. Although lots of research has been done so far, there still remains a lot of issues to be addressed. One of the issues is the shape problem. The shape problem refers to the problem of figuring out a shape of the input data structure required to cause the traversal of a given path. In this paper, we introduce a new method for the shape problem. The method converts the selected path into static single assignment (SSA) form without pointer dereferences. This allows us to consider each statement in the selected path as a constraint involving equality or inequality. We solve the constraints to get a solution which will be represented in terms of the points-to relations for each input variable. Simple, but illustrative examples are given to explain the proposed method.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.267-272
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• 2012

This paper propose the implementation of robust fuzzy controller for controlling an active magnetic bearing (AMB) system with 6 degree of freedom (DOF). A basic model with 6 DOF rotor dynamics and electromagnetic force equations for conical magnetic bearings is proposed. The developed model has severe nonlinearity and uncertainty so that it is not easy to obtain the control objective. For solving this problem, we use the Takagi-Sugeno (T-S) fuzzy model which is suitable for designing fuzzy controller. The control object in the AMB system enables the rotor to rotate without any phsical contact by using magnetic force. In this paper, we analyze the nonlinearity of the active magnetic bearing system by using fuzzy control algorithm and desing the robust control algorithm for solving the parameter variation. Simulation results for AMB are demonstrated to visualize the feasibility of the proposed method.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.401-404
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• 2003

In this paper, $H_2$, $H_{\infty}$, and mixed $H_2/H_{\infty}$ FIR filters are newly proposed for discrete-time state space signal models. The proposed filters require linearity, unbiased property, FIR structure, and independence of the initial state information in addition to the performance criteria in both $H_2$ and $H_{\infty}$ sense. It is shown that $H_2$, $H_{\infty}$, and mixed $H_2/H_{\infty}$ FIR filter design problems can be converted into convex programming problems via linear matrix inequalities (LMIs) with a linear equality constraint. Simulation studies illustrat that the proposed FIR filter is more robust against uncertainties and has faster convergence than the conventional IIR filters. the conventional IIR filters.

• Journal of the Korean School Mathematics Society
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• v.8 no.3
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• pp.367-382
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• 2005

In this paper, we deal with various contents relating to the group concept in school mathematics and teaching of algebraic structures indirectly by combining these contents. First, we consider structure of knowledge based on Bruner, and apply these discussions to the teaching of algebraic structure in school algebra. As a result of these analysis, we can verify that the essence of algebraic structure is group concept. So we investigate the previous researches about group concept: Piaget, Freudenthal, Dubinsky. In our school, the contents relating to the group concept have been taught from elementary level indirectly. Tn elementary school, the commutative law and associative law is implicitly taught in the number contexts. And in middle school, various linear equations are taught by the properties of equality which include group concept. But these algebraic contents is not related to the high school. Though we deal with identity and inverse in the binary operations in high school mathematics, we don't relate this algebraic topics with the previous learned contents. In this paper, we discussed algebraic structure focusing to the group concept to obtain a connectivity among school algebra. In conclusion, the group concept can take role in relating these algebraic contents and teaching the algebraic structures in school algebra.

• Education of Primary School Mathematics
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• v.19 no.3
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• pp.223-247
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• 2016

Given the importance of developing algebraic thinking from early grades, this study investigated an overall performance and main characteristics of algebraic thinking from a total of 197 third grade students. The national elementary mathematics curriculum in Korea does not emphasize directly essential elements of algebraic thinking but indicates indirectly some of them. This study compared our students' performance related to algebraic thinking with results of Blanton et al. (2015) which reported considerable progress of algebraic thinking by emphasizing it through a regular curriculum. The results of this study showed that Korean students solved many items correctly as compatible to Blanton et al. (2015). However, our students tended to use 'computational' strategies rather than 'structural' ones in the process of solving items related to equation. When it comes to making algebraic expressions, they tended to assign a particular value to the unknown quantity followed by the equal sign. This paper is expected to explore the algebraic thinking by elementary school students and to provide implications of how to promote students' algebraic thinking.