• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 춘계학술대회 논문집
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• pp.141-146
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• 1999

A new method, so called MMA(Method of Moving Asymptotes) was applied to the optimization problems of non-linear functions and non-linear structures. In each step of the iterative process, tile MMA generates a strictly convex approximation subproblems and solves them by using the dual problems. The generation of these subproblems is controlled by so called 'moving asymptotes', which may both make no oscillation and speed up tile convergence rate of optimization process. By contrast in generalized dual function, the generated function by MMA is always explicit type. Both the objective and behaviour constraints which were approximated are optimized by dual function. As the results of some examples, it was found that this method is very effective to obtain the global solution for problems with many local solutions. Also it was found that MMA is a very effective approximate method using the original function and its 1st derivatives.

• 충청수학회지
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• 제10권1호
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• pp.57-70
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• 1997

In this paper two preconditioned GMRES and QMR methods are applied to the non-Hermitian system from the Petrov-Galerkin procedure for the Poisson equation and compared to each other. To our purpose the ILUT and the SSOR preconditioners are used.

• 충청수학회지
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• 제24권3호
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• pp.437-447
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• 2011

In this paper we present a new variant of the Euler-Chebyshev method for solving nonlinear equations. Analysis of convergence is given to show that the presented methods are at least fifth-order convergent. Several numerical examples are given to illustrate that newly presented methods can be competitive to other known fifth-order methods and the Newton method in the efficiency and performance.

• 한국멀티미디어학회논문지
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• 제14권8호
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• pp.1000-1009
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• 2011

영상 보간법은 영상의 크기변환에서 할당되지 못한 화소에 대한 값을 추정하는 기술로써, 보간된 결과 영상에서 나타나는 화질 열화 현상을 최소화하면서도 낮은 계산복잡도를 가지는 것이 필요하다. 본 논문에서는 반복적 오차 제거를 이용한 영상 보간법을 제안한다. 제안하는 방법은 5단계로 구성되며, 각각 손실 정보 계산 단계, 손실 정보 추정 단계 손실 정보 적용 단계 오차 계산 단계 오차 적용 단계이다. 실험을 통해서 기존의 방법보다 평균 3.3dB이상 PSNR(peak signal to noise rate)이 향상된 것을 알 수 있었고, 주관적인 화질도 개선된 것을 확인하였으며 계산복잡도가 최소 83% 이상 감소한 것을 측정하였다. 제안한 영상 보간 방법은 영상 복원 및 확대를 위한 다양한 응용 환경에서 유용하게 사용될 수 있다.

• 한국정밀공학회지
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• 제12권7호
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• pp.99-106
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• 1995

Frequency response functions are of great use in dynamic analysis of structural systems. The present paper proposes an efficient method for computation of the frequency rewponse functions of linear structural dynamic models with a sparse, non-proportional damping matrix. An exact condensation procedure is proposed which enables the present method to condense the matrices without resulting in any errors. Also, an iterative scheme is proposed to be able to avoid matrix inversion in computing frequency response matrix. The proposed method is illustrated through a numerical example.

• 한국음향학회지
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• 제39권4호
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• pp.246-254
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• 2020

본 논문에서는 학습 기반 압축 센싱 기법을 이용한 측면주사 소나 영상의 비균일 잡음 제거 알고리즘을 제안한다. 제안하는 기법은 Iterative Shrinkage and Thresholding Algorithm(ISTA) 알고리즘을 기반으로 하고 있으며 성능 향상을 위해 학습네트워크의 비선형성을 강화시키는 전략을 선택하였다. 제안된 구조는 입력 신호를 비선형 변환과 초기화 하는 부분, Sparse 공간으로 변환 및 역변환하는 ISTA block, 특징 공간에서 픽셀 공간으로 변환하는 부분으로 구성된다. 제안된 기법은 다양한 모의 실험을 통해 잡음 제거 성능 및 메모리 효율성 측면에서 우수함이 입증되었다.

• Journal of information and communication convergence engineering
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• 제5권1호
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• pp.54-58
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• 2007

A real-time frame-layer rate control algorithm with a token bucket traffic shaper is proposed for distortion variation minimization. The proposed rate control method uses a non-iterative optimization method for low computational complexity, and performs bit allocation at the frame level to minimize the average distortion over an entire sequence as well as variations in distortion between frames. The proposed algorithm does not produce time delay from encoding, and is suitable for real-time low-complexity video encoder. Experimental results indicate that the proposed control method provides better visual and PSNR performances than the existing rate control method.

• East Asian mathematical journal
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• 제40권1호
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• pp.109-118
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• 2024

This paper proposes a numerical method based on domain decomposition to find approximate solutions for one-dimensional convection-diffusion equations with Neumann boundary conditions. First, the equations are transformed into convection-diffusion equations with Dirichlet conditions. Second, the author introduces the Prediction/Correction Domain Decomposition (PCDD) method and estimates errors for the interface prediction scheme, interior scheme, and correction scheme using known error estimations. Finally, the author compares the PCDD algorithm with the fully explicit scheme (FES) and the fully implicit scheme (FIS) using three examples. In comparison to FES and FIS, the proposed PCDD algorithm demonstrates good results.

• Journal of applied mathematics & informatics
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• 제42권3호
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• pp.607-623
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• 2024

This article studies the effects of heat generation/absorption and thermal radiation on the unsteady magnetohydrodynamic (MHD) Casson fluid flow past a vertical plate through rotating porous medium with constant temperature and mass diffusion. It is assumed that the plate temperature and concentration level are raised uniformly. For finding the exact solution, a set of non-dimensional partial differential equations is solved analytically using the Laplace transform technique. The influence of various non-dimensional parameters on the velocity are discussed, including the effects of the magnetic parameter M, heat generation/absorption Q, thermal radiation parameter R, Prandtl number Pr, Schmidt number Sc, permeability of porous medium parameter, Casson fluid parameter γ, on velocity, temperature, and concentration profiles, which are discussed through several figures. It is found that velocity, temperature, and concentration profiles in the case of heat generation parameter Q, Casson fluid parameter γ, thermal Grashof number Gr, mass Grashof number Gc, Permeability Porous medium parameter K, and time t have retarding effects. It is also seen that the magnetic field M, Thermal Radiation parameter R, Prandtl field Pr, Schmidt number Sc have reverse effects on it.

• Interaction and multiscale mechanics
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• 제2권3호
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• pp.263-276
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• 2009

This paper is intended to investigate interaction response of a train running over a suspension bridge undergoing support settlements. The suspension bridge is modeled as a single-span suspended beam with hinged ends and the train as successive moving oscillators with identical properties. To conduct this dynamic problem with non-homogeneous boundary conditions, this study first divides the total response of the suspended beam into two parts: the static and dynamic responses. Then, the coupled equations of motion for the suspended beam carrying multiple moving oscillators are transformed into a set of nonlinearly coupled generalized equations by Galerkin's method, and solved using the Newmark method with an incremental-iterative procedure including the three phases: predictor, corrector, and equilibrium-checking. Numerical investigations demonstrate that the present iterative technique is available in dealing with the dynamic interaction problem of vehicle/bridge coupling system and that the differential movements of bridge supports will significantly affect the dynamic response of the running vehicles but insignificant influence on the bridge response.