• 대한기계학회논문집A
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• 제27권9호
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• pp.1562-1570
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• 2003

The prediction of the inelastic behavior of the structure is an essential part of reliability assessment procedure, because most of the failures are induced by the inelastic deformation, such as creep and plastic deformation. During decades, there has been much progress in understanding of the inelastic behavior of the materials and a lot of inelastic constitutive equations have been developed. The complexity of these constitutive equations generally requires a stable and accurate numerical method. The radial return mapping is one of the most robust integration scheme currently used. Nonlinear kinematic hardening model of Armstrong-Fredrick type has recovery term and the direction of kinematic hardening increment is not parallel to that of plastic strain increment. In this case, The conventional radial return mapping method cannot be applied directly. In this investigation, we expanded the radial return mapping method to consider the nonlinear kinematic hardening model and implemented this integration scheme into ABAQUS by means of UMAT subroutine. The solution of the non-linear system of algebraic equations arising from time discretization with the generalized midpoint rule is determined using Newton method and bisection method. Using dynamic yield condition derived from linearization of flow rule, the integration scheme for elastoplastic and viscoplastic constitutive model was unified. Several numerical examples are considered to demonstrate the efficiency and applicability of the present method.

• 한국해안해양공학회지
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• 제4권3호
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• pp.161-167
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• 1992

서로 다른 유한수심을 갖는 두 영역을 연결하는 해저단위로 전파하는 비분산 유한진폭장파를 고려한다. 2차원 운동을 가정하고, 파봉선이 단과 평행하며, 비점성류체에서의 비회전운동으로 본다. 유한진폭파의 변형을 기술하기 위하여 유한진폭 천해정식과, 단위의 연결부에서 Riemann 변수로 나타낸 질양보존 및 압력연속조건들을 사용한다. 식들에 의하면 Riemann 불변양이 일정한 네 조의 특성유선과 입사, 반사 및 전달파의 진폭을 관련지어 주는 2개의 비선형방정식이 정의된다. 얻어진 방정식계는 통상의 형태로는 해석하기가 어려워 지진 해일파에 실용적으로 사용할 수 있는 특수한 경우만 고려한다. 얻어진 결과들을 장파이론과 비교하였고 아주 작은 진폭의 파인 경우에도 뚜렷한 비선형 효과가 제시되었다.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.838-849
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• 2017

This paper proposes penalty factor equations that take into consideration the weld strength over-match given in the classified form similar to the revised equations presented in the Code Case N-779 via cyclic elastic-plastic finite element analysis. It was found that the $K_e$ analysis data reflecting elastic follow-up can be consolidated by normalizing the primary-plus-secondary stress intensity ranges excluding the nonlinear thermal stress intensity component, $S_n$ to over-match degree of yield strength, $M_F$. For the effect of over-match on $K_n{\times}K_{\nu}$, dispersion of the $K_n{\times}K_{\nu}$ analysis data can be sharply reduced by dividing total stress intensity range, excluding local thermal stresses, $S_{p-lt}$ by $M_F$. Finally, the proposed equations were applied to the weld between the safe end and the piping of a pressurizer surge nozzle in pressurized water reactors in order to calculate a cumulative usage factor. The cumulative usage factor was then compared with those derived by the previous $K_e$ factor equations. The result shows that application of the proposed equations can significantly reduce conservatism of fatigue assessment using the previous $K_e$ factor equations.

• Transactions on Control, Automation and Systems Engineering
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• 제4권2호
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• pp.169-175
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• 2002

A sliding mode control of spacecraft attitude tracking with actuator, especially reaction wheel, is presented. The sliding mode controller is derived based on quaternion parameterization for the kinematic equations of motion. The reaction wheel dynamic equations represented by wheel input voltage are presented. The input voltage to wheel is calculated from the sliding mode controller and reaction wheel dynamics. The global asymptotic stability is shown using a Lyapunov analysis. In addition the robustness analysis is performed for nonlinear system with parameter variations and disturbances. It is shown that the controller ensures control objectives for the spacecraft with reaction wheels.

• 충청수학회지
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• 제19권1호
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• pp.101-110
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• 2006

In this paper, we develop existence and uniqueness criteria to certain class of three point boundary value problems associated with third order nonlinear fuzzy differential equations, with the help of Green's functions and contraction mapping principle.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2581-2584
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• 2003

In this paper, we propose a self-localization algorithm using vertical line segments. Indoor environment is consist of horizontal and vertical line features such as doors, furniture, and so on. From the input image, vertical line edges are detected by an edge operator, Then, line segments are obtained by projecting edge image vertically and detecting local maximum from the projected histogram. From the relation of horizontal position of line segments and the location of the robot, nonlinear equations are come out Localization is done by solving the equations by using Newton's method. Experimental results show that the proposed algorithm using one camera is simple and applicable to indoor environment.

• Journal of applied mathematics & informatics
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• 제10권1_2호
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• pp.119-130
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• 2002

An extended Jacobin elliptic function method is presented for constructing exact travelling wave solutions of nonlinear partial differential equations(PDEs) in a unified way. The main idea of this method is to take full advantage of the elliptic equation that Jacobin elliptic functions satisfy and use its solutions to replace Jacobin elliptic functions in Jacobin elliptic function method. It is interesting that many other methods are special cases of our method. Some illustrative equations are investigated by this means.

• Journal of applied mathematics & informatics
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• 제26권1_2호
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• pp.299-306
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• 2008

Finite difference schemes are considered for a $Ca^{2+}$ diffusion equations, which discribe $Ca^{2+}$ buffering by using stationary and mobile buffers. Stability and $L^\infty$ error estimates of approximate solutions for the corresponding schemes are obtained using the extended Lax-Richtmyer equivalence theorem.

• 대한수학회보
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• 제47권3호
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• pp.455-465
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• 2010

In this paper, by using the semi-order method, two new existence theorems of coupled quasi-solutions for a class of nonlinear operator equations in Banach spaces are proved under some suitable conditions.

• 대한수학회보
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• 제53권6호
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• pp.1725-1739
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• 2016

Abstract. Numerical solutions for the evolutionary space fractional order differential equations are considered. A predictor corrector method is applied in order to obtain numerical solutions for the equation without solving nonlinear systems iteratively at every time step. Theoretical error estimates are performed and computational results are given to show the theoretical results.