• Journal of applied mathematics & informatics
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• 제16권1_2호
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• pp.307-321
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• 2004

In this paper, the unsteady Stokes problem is considered and also the pressure-correction method for the problem is described. At a fixed time level, we reduce the problem to two symmetric positive definite problems which depend on a time step parameter. Linear systems that arise from the problems are large, sparse, symmetric, positive definite and ill-conditioned as the time step tends to zero. Preconditioned problems based on an additive Schwarz method for solving the symmetric positive definite problems are derived and preconditioners are defined implicitly. It will be shown that the rate of convergence is independent of the mesh parameters as well as the time step size.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.206-209
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• 1999

This paper presents an improved method of calculating the penalty factors for economic load dispatch based on B-coefficient and AC load flow and their performance comparison. The algorithm for calculating B-coefficients by Meyer is improved and its performance is compared with that of AC load flow. The B-coefficient method is superior to the load flow method in its simplicity and computation speed. However accuracy of the B-coefficient method is not satisfactory when it is applied to the ill-conditioned systems where generators produce excessive reactive power.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.297-299
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• 1999

The B-coefficient method is well-known and universally used method for its simplicity and computation speed. However, the B-coefficient method has a weak point of accuracy when it is applied to the ill-conditioned systems where generators produce excessive reactive power. This paper describes the developed module to be applied to commercial program package of calculating the penalty factors by Jacobian method. The effectiveness of the proposed program has been demonstrated using the IEEE 30 bus system.

• 한국생산제조학회지
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• 제20권2호
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• pp.139-144
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• 2011

This paper presents a boundary element application to determine the optimal impressed current densities at defect position on the pipe line. In this protection paint, enough current must be impressed to lower the potential distribution on the metal surface to the critical values. The optimal impressed current densities are determined in order to minimize the power supply for protection. This inverse problem was formulated by employing the boundary element method. Since the system of linear equations obtained was ill-conditioned, including singular value decomposition, conjugate gradient method were applied and the accuracies of these estimation. Several numerical examples are presented to demonstrate the practical applicability of the proposed method.

• 자원환경지질
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• 제18권3호
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• pp.217-224
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• 1985

Householder변환을 비저항반전 문제에 응용하여 해의 안전성을 조사하였다. 비저항탐사의 데이터를 해석할 때, 정규방정식을 통하여 지하구조모델을 구하는 종래의 비저항반전법은 수치적으로 불안정성을 야기시킬 경우가 간혹 있다. 이에 반하여 관측방정식의 해를 직접 구하는 Householder변환을 이용한 비저항반전법은 종래의 방법보다 수치적으로 더 안정하다. 본 논문에서는 Householder변환을 이용한 비저항반전법이 종래의 방법으로는 안정된 지하구조모델을 구할 수 없을 정도로 잡음이 포함된 이론적인 Schlumberger탐사 데이터의 경우에도 안정된 모델을 구할 수 있음을 보여 주었다.

• International Journal of Control, Automation, and Systems
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• 제6권4호
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• pp.544-550
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• 2008

In this paper, an efficient positioning algorithm is proposed for a local positioning system using ultrasound and RF in WSN. The proposed positioning algorithm is the modified Savarese method where measurement noise characteristics are included as a weighting. Furthermore the ill-conditioned and the singularity problem occurred when all beacons are installed at the same height are removed. And the method is applicable to 2D positioning with 2 beacons only. The experiments with implemented system show the accurate seamless positioning less than 2cm error both static and dynamic experiments while the original Savarese method can not provide positions.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2009년도 추계학술대회
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• pp.223-229
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• 2009

The engine backfire leading to the damage to the intake system is observed in the mixer-type LPG engines. The hot spot flowing back into the intake manifold from the engine cylinder during the valve overlap period is known to give rise to the backfire. This backfire is known to be the main cause of the abrupt stop of the vehicle leading to the accidents on the streets. In this study, the cylinder pressure buildup at the later stage of combustion due to the prolonged burning is presumed to be the main cause of the backflow leading to the backfire. This is experimentally observed by creating the engine misfire using the ill-conditioned ignition systems.

• 충청수학회지
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• 제25권2호
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• pp.367-377
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• 2012

The goal of the image restoration is to find a good approximation of the original image for the degraded image, the blurring matrix, and the statistics of the noise vector given. Fast truncated Lagrange (FTL) method has been proposed by G. Landi as a image restoration method for large-scale ill-conditioned BTTB linear systems([3]). We implemented FTL method for the image restoration problem with reflective boundary condition which gives better reconstructions of the unknown, the true image.

• 충청수학회지
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• 제31권1호
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• pp.137-149
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• 2018

In this paper, under the assumption of the symmetry point spread function, antireflective boundary conditions(AR-BCs) are considered in connection with the fast truncated Lagrange(FTL) method. The FTL method is proposed as an image restoration method for large-scale ill-conditioned BTTB(block Toeplitz with Toeplitz block) and BTHHTB(block Toeplitz-plus-Hankel matrix with Toeplitz-plus-Hankel blocks) linear systems([13, 17]). The implementation and efficiency of the FTL method in the AR-BCs are further illustrated. Especially, by employing the AR-BCs, both the continuity of the image and the continuity of its normal derivative are preserved at the boundary. A reconstructed image with less artifacts at the boundary is obtained as a result.

• 전기학회논문지
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• 제60권1호
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• pp.150-155
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• 2011

In an active noise control systems, an IIR filter may cause a problem in stability beacause of its poles. For IIR filter, its poles goes sometimes out of a unit circle in a z-plane in the transition state, where the adaptive algorithm converges to the optimum value, which causes the system to diverge. Fuzzy LMS algorithm has a better convergence property than conventional LMS algorithms, but is not applicable to IIR filter because of the reasons. Stabilized adaptive algorithm could be improves stability by moving the pole of IIR filer toward the origin forcibly in the transient state, and by introducing forgetting factor to maintain the optimum convergence when it reaches to the steady state. In this paper, We proposed stabilized adaptive fuzzy LMS algorithms with IIR filter structures, for single channel active noise control with ill conditioned signal case. Computer simulations were performed to show the effectiveness of a proposed algorithm.