• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1925-1931
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• 2011

This paper suggests an approach to the subtle concept, "good", through the fuzzy logic and the design of the Canny edge detector of Gray scale images based on the rules of fuzzy anisotropic diffusion. The Canny edge detection algorithms design is to divide the gray levels into pixels and then calculate the diffusion coefficients at each pixel of non-edgy regions. Based on this processing, we present the Canny edge detector implementing fuzzy logic and comparing the results to other existing methods. The proposed approach is the narrow dynamic range of the gray-level image Sharpening the edge detection and has the advantage.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.1
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• pp.83-90
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• 1991

The method, which is introduced here, is an approximation derived by an application of the slender body theory, which has achieved a great success in the field of aeronautical engineering. However numerical results for wave resistance by this theory have been very disappointing. A slender body formulation for a ship in uniform forward motion si presented. It is based on the asymptotic expansion of the Kelvin source and the result is quite different from the existing slender ship theory developed by Vossers, Tuck and Maruo. It is equivalent to an approximation for the kernel function of the Neumann-Kelvin problem which assumes the linearized free surface condition but deals with the body boundary condition in its exact from. The velocity field and pressure distribution can be calculated simply by the differentiation of the two-dimensional velocity potential. A formula for the wave resistance of slender ships is also presented.

• The Journal of the Korea Contents Association
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• v.12 no.3
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• pp.434-441
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• 2012

An analytic solution to the extended mild-slope equation was derived for waves propagating over an axi-symmetric pit. The water depth inside the pit was in proportion to a power of radial distance from the center of pit. The equation was transformed into the ordinary differential equation using the method of separation of variables. The coefficients of differential terms were expressed as an explicit form composing of the phase and group velocities. The bottom curvature and the square of bottom slope terms, which were added to the extended mild-slope equation, were expressed as power series. Finally, using the Frobenius series, the analytic solution to the extended mild-slope equation was derived. The present analytic solution was validated by comparing with the numerical solution obtained from FEM.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.25-32
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• 2004

We propose a hierarchical disparity estimation algorithm with edge-preserving energy-based regularization. Initial disparity vectors are obtained from downsampled stereo images using a feature-based region-dividing disparity estimation technique. Dense disparities are estimated from these initial vectors with shape-adaptive windows in full resolution images. Finally, the vector fields are regularized with the minimization of the energy functional which considers both fidelity and smoothness of the fields. The first two steps provide highly reliable disparity vectors, so that local minimum problem can be avoided in regularization step. The proposed algorithm generates accurate disparity map which is smooth inside objects while preserving its discontinuities in boundaries. Experimental results are presented to illustrate the capabilities of the proposed disparity estimation technique.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.127-136
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• 2007

In this paper, the equations of the scaled boundary finite element method are derived for non-homogeneous half plane and analyzed numerically In the scaled boundary finite element method, partial differential equations are weaken in the circumferential direction by approximation scheme such as the finite element method, and the radial direction of equations remain in analytical form. The scaled boundary equations of non-homogeneous half plane, its elastic modulus varies as power function, are newly derived by the virtual work theory. It is shown that the governing equation of this problem is the Euler-Cauchy equation, therefore, the logarithm mode used in the half plane problem is not valid in this problem. Two numerical examples are analysed for the verification and the feasibility.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.131-135
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• 2006

A seismic waveform inversion for prestack seismic data based on the Gauss-Newton method is presented. The Gauss-Newton method for seismic waveform inversion was proposed in the 80s but has rarely been studied. Extensive computational and memory requirements have been principal difficulties. To overcome this, we used different sizes of grids in the inversion stage from those of grids in the wave propagation simulation, temporal windowing of the simulation and approximation of virtual sources for calculating partial derivatives, and implemented this algorithm on parallel supercomputers. We show that the Gauss-Newton method has high resolving power and convergence rate, and demonstrate potential applications to real seismic data.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.155-166
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• 1988

An "equivalent homogeneous, orthotropic" model that includes edge effects and an accompanying finite element analysis is presented for elastomeric bearings. The model is developed for two-dimensional configurations with horizontal layers, and for linear, elastic, small deformation conditions. The equivalent homogeneous theory, in addition to capturing the overall response characteristics of the layered elastomeric bearing system, approximately models the important edge effects, which occur at and near boundaries that cut the layers, and the stress concentrations at layer interfaces. The primary dependent variables for the theory have been selected such that the highest derivatives appearing in the strain energy function are first-order, thus requiring only $C_0$ continuity of the finite element approximations. As a result, the finite element analysis is simple and computationally efficient. Numerical examples are presented to verify the theory and to illustrate potential applications of the analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.8B
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• pp.1129-1140
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• 2001

본 논문에서는 블록기반 동영상 부호화에서 나타나는 양자화 잡음을 그 특성에 맞게 모델링을 하고, 이를 기반으로 웨이블렛 변환(wavelet transform)을 이용하여 양자화 잡음을 제거하는 후처리 방법을 제안한다. 제안된 방법에서는 양자화 잡음을 특정 프로화일(profile)로 표현되는 블록화 잡음과 비에지 화소(non-edge pixel)에서 백색 가우시안 특성을 가지는 나머지 잡음의 합으로 모델링 한다. 이러한 양자화 잡음의 모델을 기반으로 정칙화 미분(regularized differentiation)을 표현하는 Mallat의 1차원 웨이브렛 변환을 이용하여 영상복원 관점에서 각각의 잡음을 제거한다. 먼저, 웨이브렛 영역의 블록경계에서 임펄스로 나타나는 블록화 잡음 성분들의 크기를 추정하여 줄임으로 해서 블록화 잡음을 제거한다. 이때 임펄스 크기의 추정은 메디안 필터와 양자화 파라미터(quantization parameter), 그리고 국부 활동도(local activity)를 이용하여 이루어진다. 그리고 나머지 잡음은 비에지 화소에서 연역치화(soft-thresholding)을 수행함으로써 제거한다. 이러한 후처리 방법의 구현은 실시간 응용을 위해 웨이브렛 필터를 이용하여 근사적으로 공간 영역에서 이루어진다. 실험 결과, 제안된 방법이 다양한 영상과 압축률에 대해 MPEG-4 VM(verification model) 후처리 필터(post-filter)보다 PSNR 성능뿐만 아니라 주관적 화질면에서도 우수함을 확인하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.193-201
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• 2004

The aim of this study is focused on getting an almost exact solution which is the simplicity and exactness of an axisymmetrically loaded cylindrical shell. This method replaces the finite element method which is a very powerful tool for analysis of any kind of structure which has an arbitrary shape, but is still a numerical analysis. Instead, this study uses the method of distribution of end actions which is a kind of iteration technique to implement the leading matrix method. The distribution and carry-over factors of a cylinder are calculated by the theory of a differential equation of a beam on an elastic foundation. The results are satisfactory when this method is applied to a cylinder that is subjected to a concentrated load and hydrostatic pressure when compared with the BEF analogy separately.

• Nuclear Engineering and Technology
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• v.4 no.4
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• pp.280-293
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• 1972

The differential fast neutron spectra above 0.5 Mev at particular spatial positions in tile reactor(TRIGA MARK-II) core has been determined experimentally using several threshold activation detectors. The series expansion technique utilizing the concept of least squares optimization was used to obtain an approximate solution to the set of integral equations which are defined by the experimentally determined activation data. The influence of use of different weighting functions in the solution was analyzed in each measurement. To carry out the necessary mathematical calculations, a computer code for the UNIVAC 1106 digital computer has been prepared. Good agreement was achieved between the differential fast neutron spectra determined in this work and the computed flux determined independently using space-independent multigroup transport theory.