• 대한수학회보
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• 제55권6호
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• pp.1811-1822
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• 2018

In this paper, we exhibit the explicit forms of continued fraction expansions of a family of algebraic power series over a finite field and we study their asymptotic distribution of approximation exponents.

• 대한수학회보
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• 제53권3호
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• pp.699-709
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• 2016

Our paper is devoted to the study of certain diophantine equations on the ring of polynomials over a finite field, which are intimately related to algebraic formal power series which have partial quotients of unbounded degree in their continued fraction expansion. In particular it is shown that there are Pisot formal power series with degree greater than 2, having infinitely many large partial quotients in their simple continued fraction expansions. This generalizes an earlier result of Baum and Sweet for algebraic formal power series.

• 대한수학회보
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• 제48권1호
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• pp.79-83
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• 2011

In the present paper we introduce the lower autocentral series of autocommutator subgroups of a given group. Following our previous work on the subject in 2009, it is shown that every finite abelian group is isomorphic with $n^{th}$-term of the lower autocentral series of some finite abelian group.

• Structural Engineering and Mechanics
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• 제16권6호
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• pp.655-674
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• 2003

Investigated in this study are the natural vibration characteristics of the coaxial cylindrical shells coupled with a fluid. Theoretical method is developed to find the natural frequencies of the shell using the finite Fourier series expansion, and their results are compared with those of finite element method to verify the validation of the method developed. The effect of the fluid-filled annulus and the boundary conditions on the modal characteristics of the coaxial shells is investigated using a finite element modeling.

• 한국수학사학회지
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• 제19권2호
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• pp.1-24
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• 2006

조선 산학의 퇴타술의 역사를 연구한다. 이상혁(李尙爀)$(1810\sim?)$의 익산(翼算)(1868)이 출판되기 전의 역사와 익산(翼算)의 결과로 나누어 연구한다. 경선징(慶善徵)$(1616\sim?)$의 묵사집산법(默思集算法)부터 남병길(南秉吉)$(1820\sim1869)$의 산학정의(算學正義)(1867)까지의 산서를 통하여 익산(翼算) 이전의 퇴타술은 큰 발전을 이루지 못한 것을 조사한다. 이상혁(李尙爀)은 조선(朝鮮) 산학(算學)에서 가장 독창적인 방법을 써서 새로운 결과를 얻어낸다. 그는 퇴타술을 구조적으로 해결하고, 또 새로운 문제인 절적(截積)과 이를 위한 분적법(分積法)을 도입하여 이의 구조도 완전히 밝혀내었다.

• 소음진동
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• 제6권3호
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• pp.297-303
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• 1996

The general approach using sine series expansions was represented to evaluate the radiation loading from a vibrating surface on a simply supported cylinder. In this paper, the fluid-loading coefficients (radiation impedance) for a submerged finite cylindrical shell with an arbitrary end condition are defined and evaluated. The vibrations of cylindrical shell are expressed by using cosine series expansions to analyze the radiation impedance for a finite cylindrical shell. It is possible to represent the displacements at both ends of cylindrical shell in comparison with sine series. The direct and cross modal components of fluid-loading coefficients are shown and the validity of cosine series expansions are verified from the results of numerical computations. This approach and results are directly applicable in the analysis of sound radiation from subemerged finite cylindrical shell with arbitrary end conditions.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.418-422
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• 2005

In this study, the die design and die series on the surface residual stress of cold drawn eutectoid steel wire has been investigated. Test pieces were fabricated using die series with different mean and final reduction ratio. Surface residual stresses in the axial direction were measured by X-ray diffraction, Broker's 2-dimensional GADDS system. Results were compared with stress profiles which were calculated by 3D and 2D finite element simulation, Hibbitt's ABAQUS 6.4 program in Finite Element Analysis. By means of FEA method, optimal die shape considering delta-parameter were induced and applied in order to determine die sequence designs. Balance of the drawing stresses was also introduced to optimize die sequence.

• 소성∙가공
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• 제15권2호
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• pp.153-157
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• 2006

In this study, the die design and die series on the surface residual stress of cold drawn eutectoid steel wire have been investigated. Test pieces were fabricated using die series with different mean and final reduction ratios. Surface residual stresses in the axial direction were measured by X-ray diffraction, Bruker's 2-dimensional GADDS system. The results were compared with stress profiles that were calculated by 3D and 2D finite element simulations, ABAQUS 6.4 program in finite element analysis(FEA). By means of the FEA method, optimal die shape considering delta-parameter were induced and applied in order to determine die sequence designs. Balance of the drawing stresses was also introduced to optimize die sequence.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.18-23
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• 1993

In this paper, we attempt to estimate the state of a finite state system. In such system, we can observe time series data which has some significant behaviors corresponding to its system states. The behavior is characterized by feature parameters extracted from time series. Our thought is that the system output time series data is expressed as a sequence of behavior patterns which are represented by clusters in feature parameters space. An algorithm jointing fuzzy clustering to fuzzy finite state transition model is suggested.

• Journal of Magnetics
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• 제18권2호
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• pp.130-134
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• 2013

Most electrical machines like motor, generator and transformer are symmetric in terms of magnetic field distribution and mechanical structure. In order to analyze these problems effectively, many coupling techniques have been introduced. This paper deals with a coupling scheme for open boundary problem of symmetric and periodic structure. It couples an analytical solution of Fourier series expansion with the standard finite element method. The analytical solution is derived for the magnetic field in the outside of the boundary, and the finite element method is for the magnetic field in the inside with source current and magnetic materials. The main advantage of the proposed method is that it retains sparsity and symmetry of system matrix like the standard FEM and it can also be easily applied to symmetric and periodic problems. Also, unknowns of finite elements at the boundary are coupled with Fourier series coefficients. The boundary conditions are used to derive a coupled system equation expressed in matrix form. The proposed algorithm is validated using a test model of a bush bar for the power supply. And the each result is compared with analytical solution respectively.