• 정보처리학회논문지A
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• 제13A권2호
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• pp.177-184
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• 2006

옷감 시뮬레이션에서 explicit 방법은 시간격(time step)이나 스프링 인장력이 큰 경우 안정적이지 않아 사용할 수 없기 때문에, 느리지만 안정성이 높은 implicit 방법이 사용되어 왔다. 시간격을 크게 하는 것은 시뮬레이션을 빠르게 진행시키는 효과가 있고, 큰 인장력의 스프링으로는 잘 늘어나지 않는 옷감을 표현할 수 있다. 다른 방법으로는 explicit 방법처럼 계산이 빠르면서도 implicit 방법처럼 안정적인 특성을 가지는 semi-implicit 방법들을 찾는 연구가 진행되어 왔다. 본 논문에서는 Kang(Kang and Cho 2002)의 방법을 개선하여 거의 explicit 방법에서 완전한 implicit 방법까지 조절이 가능한 실시간 옷감 시뮬레이션 방법을 제안한다. 이 방법은 explicit 방법처럼 간단하고 빠르면서 implicit 방법처럼 시간격(time step)이나 스프링 인장력이 큰 경우에도 안정적으로 작동한다. 또한 기존의 semi-implicit 방법과 비교해서 비교적 작은 인공적 감쇠(artificial damping) 현상을 가진다.

• 한국정밀공학회지
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• 제13권12호
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• pp.86-98
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• 1996

An combined implicit/explicit scheme for the analysis of sheet forming problems has been proposed in this work. In finite element simulation of sheet metal forming processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. The implicit scheme dmploys a more reliable and rigorous scheme in considering the equilibrium at each step of deformation, while in the explict scheme the problem of convergency is elimented at thecost of solution accuracy. The explicit approach and the implicit approach have merits and demerits, respectively. In order to combine the merits of these two methods a step-wise combined implici/explicit scheme has been developed. In the present work, the rigid-plastic finite element method using bending energy augmented membraneelements(BEAM)(1) is employed for computation. Computations are carried out for some typical sheet forming examples by implicit, combined implicit/explicit schemes including deep drawing of an oil pan, front fender and fuel tank. From the comparison between the methods the advantages and disadvantages of the methods are discussed.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제25권4호
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• pp.262-295
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• 2021

This paper introduces mono-implicit general linear methods, a special class of general linear methods, which are implicit in the output solution for the numerical integration of differential algebraic equations. We show how L-stable inherent Runge-Kutta members can be derived. The procedures for implementation have been discussed. The numerical test on the problem considered shows that the methods have improved accuracy when compared to RADAU IIA and the results from MATLAB ode15s, which have been taken as our reference solution.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제25권4호
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• pp.224-261
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• 2021

The interest in implicit-explicit (IMEX) integration methods has emerged as an alternative for dealing in a computationally cost-effective way with stiff ordinary differential equations arising from practical modeling problems. In this paper, we introduce implicit-explicit second derivative linear multi-step methods (IMEX SDLMM) with error control. The proposed IMEX SDLMM is based on second derivative backward differentiation formulas (SDBDF) and recursive SDBDF. The IMEX second derivative schemes are constructed with order p ranging from p = 1 to 8. The methods are numerically validated on well-known stiff equations.

• 한국항공우주학회지
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• 제30권3호
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• pp.8-16
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• 2002

헬리콥터 비행 시뮬레이션을 위한 로터 운동방정식을 implicit formulation 형태로 유도하였다. 좌표계 사이의 상대운동을 고려한 일반화된 벡터 kinematics 를 유도하고 이를 적용하여 브레이드 임의 위치 에서 관성속도 및 관성가속도를 구하였다. 유도된 속도 및 가속도 벡터를 이용하여 플래핑, 리드래그 및 토오크 방정식 등을 implicit form으로 유도하였다. 브레이드 스팬에 따른 공간 적분 방법을 살펴보고, 다양한 힌지형상 및 힌지배열 순서에 관계없이 응용영역을 확장할 수 있음을 밝혔다. DAE(Differential Algebraic Equation) 형태를 갖는 본 연구의 결과식을 이용하여 동특성 계산을 위한 시간적분법을 검토하였다.

• 한국CDE학회논문집
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• 제13권3호
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• pp.187-199
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• 2008

This paper describes a C++ class hierarchy of implicit objects for geometry modeling and processing. This class structure provides a software kernel for integrating many various models and methods found in current implicit modeling areas. The software kernel includes primitive objects playing a role of unit element in creating a complex shape, and operator objects used to construct more complex shape of implicit object formed with the primitive objects and other operators. In this paper, class descriptions of these objects are provided to better understand the details of the algorithm or implementation, and its instance examples to show the capabilities of the object classes for constructive shape geometry. In addition, solid modeling system shown as an application example demonstrates that the proposed implicit object classes allow us to carry out modern solid modeling techniques, which means they have the capabilities to extend to various applications.

• Journal of applied mathematics & informatics
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• 제4권2호
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• pp.341-378
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• 1997

We consider three classes of numerical methods for solv-ing the semi-explicit differential-algebraic equations of index 1 and higher. These methods use implicit multistep fixed stepsize methods and several iterative processes including simple iteration, full a2nd modified Newton iteration. For these methods we prove convergence theorems and derive error estimates. We consider different ways of choosing initial approximations for these iterative methods and in-vestigate their efficiency in theory and practice.

• 호남수학학술지
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• 제37권4호
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• pp.441-455
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• 2015

In this paper, we perform a comparison study of explicit and implicit numerical methods for the equity-linked securities (ELS). The option prices of the two-asset ELS are typically computed using an implicit finite diffrence method because an explicit finite diffrence scheme has a restriction for time steps. Nowadays, the three-asset ELS is getting popularity in the real world financial market. In practical applications of the finite diffrence methods in computational finance, we typically use relatively large space steps and small time steps. Therefore, we can use an accurate and effient explicit finite diffrence method because the implementation is simple and the computation is fast. The computational results demonstrate that if we use a large space step, then the explicit scheme is better than the implicit one. On the other hand, if the space step size is small, then the implicit scheme is more effient than the explicit one.

• 한국어교육
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• 제25권1호
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• pp.115-144
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• 2014

The purpose of this paper is to compare the two different instruction methods for Korean learners of academic purposes in learning request expression. Participants were divided into two groups, explicit and implicit group. Both groups viewed several scenes from the drama that involved native speakers interacting in different situations. The instructional treatment for the explicit group included metapragmatic information while the treatment for the implicit group did not. On the other hand, the treatment for the implicit group followed implicit techniques, which were repetition of the video presentation and a script reading activity. This study was made up of a pre-test, a post-test, and a delayed-test. The pre-test was conducted prior to the instructional treatment. The post-test was administered a day after the last instruction and the delayed-test was conducted five weeks after the treatments. Two types of tests, speaking and writing, were used in this study to examine subjects' knowledge of Korean request. The result of this research reveals that implicit treatment was more effective than explicit treatment in Korean learners' request acquisition. This results might have been due to the operationalization of the implicit condition in this study. Implicit instruction may help language learners make rules by themselves through tasks.

• 한국멀티미디어학회논문지
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• 제12권6호
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• pp.842-855
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• 2009

We present a physics-based blending method for the second order algebraic implicit surface. Unlike other traditional blending techniques, the proposed method avoids complex mathematical operations and unwanted artifacts like bulge, which have highly limited the application of the second order algebraic implicit surface as a modeling primitive in spite of lots of its excellent properties. Instead, the proposed method provides the designer with flexibility to control the shapes of the blending surface on interactive basis; the designer can check and design the shape of blending surfaces accurately by simply adjusting several physics parameter in real time, which was impossible in the traditional blending methods. In the later parts of this paper, several results are also presented.