• Structural Engineering and Mechanics
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• 제51권4호
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• pp.685-705
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• 2014

This paper presents a new formulation for forward scalar wave simulations in semi-infinite media. Perfectly-Matched-Layers (PMLs) are used as a wave absorbing boundary layer to surround a finite computational domain truncated from the semi-infinite domain. In this work, a hybrid formulation was developed for the simulation of scalar wave motion in two-dimensional PML-truncated domains. In this formulation, displacements and stresses are considered as unknowns in the PML domain, while only displacements are considered to be unknowns in the interior domain. This formulation reduces computational cost compared to fully-mixed formulations. To obtain governing wave equations in the PML region, complex coordinate stretching transformation was introduced to equilibrium, constitutive, and compatibility equations in the frequency domain. Then, equations were converted back to the time-domain using the inverse Fourier transform. The resulting equations are mixed (contain both displacements and stresses), and are coupled with the displacement-only equation in the regular domain. The Newmark method was used for the time integration of the semi-discrete equations.

• 대한수학회논문집
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• 제11권2호
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• pp.495-501
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• 1996

There is currently a regain of interest in ADI (Alternating Direction Implicit) method as a preconditioner for iterative Method for solving large sparse linear systems, because of its suitability for parallel computation. However the classical ADI is not applicable to FE(Finite Element) matrices. In this paper wer propose a Block-ADI method, which is applicable to Finite Element metrices. The new approach is a combination of classical ADI method and domain decompositi on. Also, we provide a partial proof of the convergence based on the results from the regular splittings, in case the discretization metrix is symmetric positive definite.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.437-443
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• 2003

The object of this paper is the treatment of how to make the vorticity boundary condition instead of pressure in the primitive variable case. An improved algorithm for solving the vorticity-stream function equation is presented. The linear finite element approximation for the solution of Wavier-Stokes and Stokes flows is constructed. Not only regular domain but also complicate domain can be analyze d, using this formulation.

• 대한수학회지
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• 제61권3호
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• pp.515-545
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• 2024

Consider a Noetherian domain R₀ with quotient field K₀. Let K be a finitely generated regular transcendental field extension of K₀. We construct a Noetherian domain R with Quot(R) = K that contains R₀ and embed Spec(R₀) into Spec(R). Then, we prove that key properties of abelian varieties and smooth geometrically integral projective curves over K are preserved under reduction modulo p for "almost all" p ∈ Spec(R₀).

• 한국수학교육학회지시리즈A:수학교육
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• 제45권2호
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• pp.191-204
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• 2006

Computer technology has a potential to change the contents of school mathematics and the way of teaching mathematics. But in our country, the problem whether computer technology should be introduced into mathematics classroom or not was not resolved yet. As a tool, computer technology can be used by teachers who are confident of the effectiveness and who can use it skillfully and can help students to understand mathematics. The purpose of this study was to investigate the effective way to introduce and utilize computer technology based on the status quo of mathematics classroom setting. One possible way to utilize computer technology in mathematics classroom in spite of the lack of computer and the inaccessibility of useful software is using domain specific simulation software like 'Polyhedron'. 'Polyhedron', as we can guess from the name, can be used to explore regular and semi regular polyhedra and the relationship between them. Its functions are limited but it can visualize regular polyhedra, transform regular polyhedra into other polyhedra. So it is easier to operate than other dynamic geometry software like GSP. To investigate the effect of using this software in mathematics class, three classes(one in 6th grade from science education institute for the gifted, two in 7th grade) were chosen. Activities focused on the relationship between regular and semi regular polyhedra. After the class, several conclusions were drawn from the observation. First, 'Polyhedron' can be used effectively to explore the relationship between regular and semi regular polyhedra. Second, 'Polyhedron' can motivate students. Third, Students can understand the duality of polyhedra. Fourth, Students can visualize various polyhedra by reasoning. To help teachers in using technology, web sites like NCTM's illuminations and NLVM of Utah university need to be developed.

• 과학교육연구지
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• 제41권1호
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• pp.98-110
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• 2017

이 연구의 목적은 대학부설과학영재교육원과 일반학교 수업에서 영재학생이 인식하는 교우기대감을 비교하기 위한 것이다. 경기도에 소재하고 있는 A 대학부설과학영재교육원의 영재 121명에게 친밀성, 능력 유사성, 도덕성을 하위 영역으로 하는 교우기대감 검사를 실시하였다. 연구 결과는 다음과 같다. 대학부설 과학영재교육원과 일반학교에서 영재학생이 인식하는 교우기대감은 친밀성, 도덕성의 하위 영역에서 통계적으로 유의한 차이가 있었고, 능력 유사성의 하위 영역에서는 통계적으로 유의한 차이를 보이지 않았다. 일반학급에서는 친밀성에 대한 교우 기대감이 높았고, 영재학급에서는 도덕성에 대한 교우기대감이 높았다. 또한, 교우기대감의 각 하위 영역의 일부 세부문항에서 통계적으로 유의한 차이를 보이는 교우기대감도 있었다. 그리고 대학부설과학영재교원의 영재학생은 지역교육청부설영재교육원과 단위학교 영재학급의 영재학생이 보이는 교우기대감과 다른 특징도 보였다. 연구 결과를 토대로 영재학생의 교우기대감이 주는 시사점에 대하여 논의하였다.

• 영재교육연구
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• 제26권1호
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• pp.37-51
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• 2016

이 연구는 일반학급에서 과학영재와 일반학생이 지각하는 교우기대감과 영재학급 및 일반학급에서 초등과학영재가 지각하는 교우기대감을 조사한 것이다. 연구 대상은 지역교육청부설 영재교육원과 단위학교 영재학급의 5, 6학년 과학영재 233명과 과학영재와 같은 지역에 위치한 초등학교 5, 6학년 일반학생 329명이다. 검사도구로는 친밀성, 능력/유사성, 도덕성의 하위영역을 범주로 하는 교우기대감 척도 설문지를 사용하였다. 연구 결과는 다음과 같다. 첫째, 일반학급에서의 교우기대감에서 과학영재는 일반학생에 비하여 친밀성과 도덕성의 하위 영역에서 통계적으로 유의하게 교우기대감이 높았으나 능력/유사성에서는 두 집단 간에 차이를 보이지 않았다. 둘째, 영재학급과 일반학급에서 과학영재가 지각하는 교우기대감에서는 일반학급에 비하여 영재학급에서 친밀성의 하위 영역에서 통계적으로 유의하게 교우기대감이 높았고, 능력/유사성과 도덕성의 하위 영역에서는 유의한 차이를 보이지 않았다. 연구 결과를 토대로 학습 환경에 따른 과학영재의 교우기대감이 주는 시사점에 대하여 논의하였다.

• 한국해양공학회지
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• 제20권5호
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• pp.30-35
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• 2006

In tire presence of incident waves with different frequencies, there are second order sum and difference frequency wave exciting forces due to the nonlinearity of tire incident waves. Although the magnitude of these nonlinear wave forces are small, they act on TLPs at sum and difference frequencies away from those of the incident waves. So, the second order sum and difference frequency waveexciting forces occurring close to tire natural frequencies of TLPs often give greater contributions to high and law frequency resonant responses. Nonlinear motion responses and tension variations in the time domain are analyzed by solving the motion equations with nonlinear wave exciting forces using tire numerical analysismethod. The numerical results of time domain analysis for the nonlinear wave exciting forces on the ISSC TLP in regular waves are compared with the numerical and experimental ones of frequency domain analysis. The results of this comparison confirmed tire validity of the proposed approach.

• Journal of Advanced Research in Ocean Engineering
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• 제3권4호
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• pp.174-183
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• 2017

Numerical simulations were performed about the green water problem of a FPSO. Three regular waves in head sea were tested. A rectangular box-shaped FPSO was considered and it is assumed there is a vertical wall on the deck. For the numerical simulations, an open-source CFD code, OpenFOAM, was applied to solve the present problems. Focus is on wave fields around the FPSO, water flows and impact pressures on the deck. For the validation, the present calculation results were compared with the existing experimental of Lee et al. (2012) and Changwon university in KTTC Cooperative Study Report (2015). The statistical values and spatial distribution of the peak pressures are directly compared with the experimental data. Some discussions are made on the effects of the domain breadth on the Green water impact pressure.

• Korean Journal of Mathematics
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• 제28권1호
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• pp.65-73
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• 2020

This article concerns a property of local rings and domains. A ring R is called weakly local if for every a ∈ R, a is regular or 1-a is regular, where a regular element means a non-zero-divisor. We study the structure of weakly local rings in relation to several kinds of factor rings and ring extensions that play roles in ring theory. We prove that the characteristic of a weakly local ring is either zero or a power of a prime number. It is also shown that the weakly local property can go up to polynomial (power series) rings and a kind of Abelian matrix rings.