• Proceedings of the Korea Multimedia Society Conference
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• 2000.04a
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• pp.137-140
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• 2000

카메라의 렌즈 등 광학장비의 성능 제한으로 인하여 초점이 맞지 않아 흐려지고 잡음으로 훼손된 영상을 복원하는데 일반적으로 반복복원방법이 사용된다. 이 경우에 가속변수는 훼손영상에 관계없이 영상전체에 일률적으로 적용되기 때문에 흐려짐 훼손이 심한 윤곽부분도 훼손이 작은 평면영역이 같이 일정하게 처리되어 수렴속도가 느려지고 시각적으로 중요한 윤곽부분의 복원에는 효율적이지 못하다. 이러한 문제점을 해결하기 위하여 본 논문에서는 흐려짐 훼손이 작은 평면영역은 가속변수를 작게하고 훼손이 큰 윤곽영역은 가속변수를 크게 하여 영상의 국부적인 특성에 따라 적응적으로 반복 복원하는 방법을 제안하였다. 제안한 복원방법은 기존의 방법과 비교하여 수렴속도가 빨라지고 시각적으로 중요한 윤곽정보의 복원에도 효율적임을 실험결과를 통해 할 수 있었으며, MSE면에서도 우수하였다.

• Journal of Korea Multimedia Society
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• v.3 no.4
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• pp.365-371
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• 2000

To restore image degraded by out-of-focus blur and additive noise, an iterative restoration is used. Acceleration parameter is usually applied equally to all over the image without considering the local characteristics of degraded images. As a result, the conventional methods are not effective in restoring severely degraded edge region and shows slow convergence rate. To solve this problem we propose an adaptive iterative restoration according to local degradation, in which the acceleration parameter has low value in flat region that is less degraded and high value in edge region that is more degraded. Through experiments, we verified that the proposed method showed better results with fast convergence rate, showed Visually better image in edge region and lower MSE than the conventional methods.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.1-7
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• 2003

Mode superposition method(MSM) is the most commonly used for solving linear response problems of structural dynamics. The major advantage of MSM is that usually a small number of lower mode is sufficient to analysis the response. However, the convergence is slow and many modes would be needed to give an accurate MSM in large structure with many degrees of freedom. The inaccuracies of MSM are caused by mode truncation in the solution. These demerits can be overcome by use of the mode acceleration method(MAM). Example analyses are carried out in simple beam subjected to harmonic loadings and compared the convergence of the joint displacements by the two methods. For relatively low frequency loadings, a good results was obtained by the lowest one mode in MAM, so the method is more economic in numerical analysis on an accurate solution.

• The KIPS Transactions:PartD
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• v.13D no.3 s.106
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• pp.369-376
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• 2006

This paper presents a new method of significantly improving conventional Bayesian statistical text classifier by incorporating accelerated EM(Expectation Maximization) algorithm. EM algorithm experiences a slow convergence and performance degrade in its iterative process, especially when real online-textual documents do not follow EM's assumptions. In this study, we propose a new accelerated EM algorithm with uncertainty-based selective sampling, which is simple yet has a fast convergence speed and allow to estimate a more accurate classification model on Naive Bayesian text classifier. Experiments using the popular Reuters-21578 document collection showed that the proposed algorithm effectively improves classification accuracy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.10
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• pp.2001-2013
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• 1994

In this paper, the method of processing a blurred noisy image has been researched. The conventional method of processing signal has faluts which are slow convergence speed and long time-consuming process at the singular point and or in the ill condition. There is the process, the Gauss Seidel's method to remove these faults, but it takes too much time because it processed singnal repeatedly. For overcoming the faults, this paper shows a image restoration method which takes shorter than the Gauss-Seidel's by comparing the Gauss Seidel's with proposed alogorithm and accelerating convergence speed at the singular point and/or in the ill condition. In this paper, the conventional process method(Gauss-Seidel) and proposed optimal algorithm were used to get a standard image($256{\times}56{\times}bits$). and then the results are simulated and compared each other in order to examine the variance of MSE(Mean Square Error) by the acceleration parameter in the proposed image restoration. The result of the signal process and the process time was measured at all change of acceleration parameter in order to verify the effectveness of the proposed algorithm.

• Journal of the Korea Computer Industry Society
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• v.2 no.6
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• pp.817-826
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• 2001

In this paper, the method of processing a blurred noisy signal has been researched. The conventional method of processing signal has faults which are slow-convergence speed and long time-consuming process at the singular point and in the ill condition. There is the process, the Gauss-Seidel's method to remove these faults, but it takes too much time because it processes signal repeatedly. For overcoming the faults, this paper shows a signal process method which takes shorter than the Tikhnov-Miller's by comparing the Tikhnov-Miller's with proposed algorithm and accelerating convergence speed at the singular point in the ill condition. In this paper, the conventional process method and proposed optimal algorithm were used to get a standard image (256 ＊ 256 ＊ 8bits),and then the results are simulated and compared each other in order to examine the variance of MSE ( Mean-Square Error ) by the acceleration parameter in the proposed two dimensional signal procedures. The result of the signal process and the processing time was measured at all change of acceleration parameter in order to verify the effectiveness of the proposed algorithm.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.4
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• pp.191-197
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• 2021

To calculate the induced charge of atoms in molecular dynamics, linear equations for the induced charges need to be solved. As induced charges are determined at each time step, the process involves considerable computational costs. Hence, an efficient method for calculating the induced charge distribution is required when analyzing large systems. This paper introduces the Uzawa method for solving saddle point problems, which occur in linear systems, for the solution of the Lagrange equation with constraints. We apply the accelerated Uzawa algorithm, which reduces computational costs noticeably using the Schur complement and preconditioned conjugate gradient methods, in order to overcome the drawback of the Uzawa parameter, which affects the convergence speed, and increase the efficiency of the matrix operation. Numerical models of molecular dynamics in which two gold nanoparticles are placed under external electric fields reveal that the proposed method provides improved results in terms of both convergence and efficiency. The computational cost was reduced by approximately 1/10 compared to that for the Gaussian elimination method, and fast convergence of the conjugate gradient, as compared to the basic Uzawa method, was verified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.3
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• pp.266-272
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• 2004

In this paper, an observer-based adaptive controller is proposed to control the longitudinal motion of vehicles. The standard gradient method will be used to estimate the vehicle parameters such as mass, time constant, etc. The nonlinear model between the driving force and the vehicle acceleration will be chosen to design the state observer for the vehicle velocity and acceleration. It will be shown that the proposed observer is exponentially stable, and that the adaptive controller proposed in this paper is stable by the Lyapunov function candidate. It will be proved that the errors of the relative distance, velocity and acceleration converge to zero asymptotically fast, and that the overall system is also asymptotically stable. The simulation results are presented to investigate the effectiveness of the proposed method.

• Journal of the Korea Computer Graphics Society
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• v.24 no.5
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• pp.11-19
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• 2018

In this paper, we propose an algorithm for improving the accuracy and rate of convergence when two point clouds with noise and a low overlapping area are registered to each other. We make the most use of the geometric information of the underlying geometry of the point clouds with noise for better accuracy. We select a reasonable region from the noisy point cloud for registration and combine a modified acceleration algorithm to improve its speed. The conventional accuracy improvement method was not possible in a lot of noise, this paper resolves the problem by selecting the reasonable region for the registration. And this paper applies acceleration algorithm for a clone to low overlap point cloud pair. A simple algorithm is added to the conventional method, which leads to 3 or 4 times faster speed. In conclusion, this algorithm was developed to improve both the speed and accuracy of point cloud registration in noisy and low overlap case.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.41-50
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• 1994

An iterative time marching procedure for solving incompressible viscous flows has been applied to the flow around a propeller. This procedure solves three-dimensional Navier-Stokes equations on a moving, body-fitted, non-orthogonal grid using first-order accurate scheme for the time deivatives and second-and third-order accurate schemes for the spatial derivatives. To accelerate iterative process, a multigrid technique has been applied. This procedure is suitable for efficient execution on the current generation of vector or massively parallel computer architectures. Generally good agreement with published experimental and numerical data has been obtained. It was also found that the multigrid technique was efficient in reducing the CPU time needed for the simulation and improved the solution quality.