• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.2
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• pp.199-207
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• 2001

In this paper, we suggest an edge-based surface segmentation algorithm of 3D image using curvature. For the first, in this proposed method, we approximate 3D depth data to second order curves by each scan line and decide splitting points of 3D edges by curvature of the approximated curves. And finally make a group as 3D surface with the region of input image by the 3D edges. In the conventional algorithms, there are some difficulties in detecting 3D edge with the separated processes for the jump edge and the crease edge and especially, in deciding the ambiguous discontinuity of surface directions about the crease edge. The proposed algorithm decides curvature discontinuity using curvature which is simply calculated by a geometrical approximation. Furthermore, the algorithm has a cooperated process to calculate the jump and crease edges. The results of computer simulations with several 3D images show that the proposed method yields better performance as comparing with the conventional methods.

• Geophysics and Geophysical Exploration
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• v.17 no.2
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• pp.95-103
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• 2014

This paper presents a practical inversion method for recovering a three-dimensional (3D) resistivity model and static shifts simultaneously. Although this method is based on a Gauss-Newton approach that requires a sensitivity matrix, the computer time can be greatly reduced by implementing a simple and effective procedure for updating the sensitivity matrix using the Broyden's algorithm. In this research, we examine the approximate inversion procedure and the weighting factor ${\beta}$ for static shifts through inversion experiments using synthetic MT data. In methods using the full sensitivity matrix constructed only once in the iteration process, a procedure using the full sensitivity in the earlier stage is useful to produce the smallest rms data misfit. The choice of ${\beta}$ is not critical below some threshold value. Synthetic examples demonstrate that the method proposed in this paper is effective in reconstructing a 3D resistivity structure from static-shifted MT data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.387-397
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• 1992

The spatial domain design of 2-dimensional separable denominator digital filters(SDDF) based on the reduced dimensional decomposition can be realized when the given 2-D impulse response specifications are decomposed into a pair of 1-D specifications via singular value decompositions(SVD). Because of use of the balaned approximation and equivalent transform as 1-D design algorithm, 2-D design algorithm retains the advantage that is numerically stable and can minimize quantization errors. In this paper in order to analyze and reduce these errors, minimum comfficient quantization realization is directly derived from impulse response specification. And using the equivalent trans form relation between mininum coefficient quantization error and minimum roundoff error realizations, we optimally realize a SDDF. This algorithm is analyzed by the simulation, which shows that it is superior to direct or balanced realization in quantization errors.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.667-669
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• 2003

특징 형상의 조합으로 표현될 수 없는 자유 형상을 가진 제품이 늘어남에 따라 자유형상을 효율적으로 변형시키는 기법이 필요하다. 여러 가지 자유형상 변형기법(FFD) 가운데에서 자유 형상을 파라메트릭하게 컨트롤하기 위해서는 조정 다각형 기반의 형상 변형 기법이 적합하다. 이에 따라 본 연구에서는 FFD 기법을 적용하여 자유형상 모델을 파라메트릭하게 컨트롤하기 위해 입력 모델에 대한 조정 다각형을 자동으로 생성하는 알고리즘을 제안하였다. 제안된 알고리즘은 크게 기본 조정 다각형 생성과 조정 다각형 최적화 단계로 나누어진다. 기본 다각형 생성에서는 1)입력모델을 직교 3방향에 투영, 2)투영된 결과에 대해 2차원 조정 다각형을 생성, 3)2차원 조정 다각형을 조합하여 3차원 기본 조정 다각형 생성의 단계를 거친다. 조정 다각형 최적화 단계에서는 기본 조정 다각형에 에지 및 면 연산자를 적용하여 입력 모델에 더욱 근사하는 최종 조정 다각형을 생성한다. 예제에서는 제안된 알고리즘을 통해 자동으로 생성된 조정다각형을 자동차 모델에 적용하여 모델의 형상을 변화시킨 결과를 보였다.

• Journal of KIISE:Software and Applications
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• v.32 no.9
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• pp.868-877
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• 2005

Arcs are usually treated as significant features in the field of pattern recognition. This paper presents a method to detect arcs from digital planar curves and estimate their arc centers and radii by using geometric analysis. The deviation of distance between the original curve and the detected arc by the proposed method does not exceed a tolerant error. The experimental results show that the proposed method is available for the detection of arcs iron not only smooth but also heavily noisy curves.

• Geophysics and Geophysical Exploration
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• v.21 no.1
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• pp.1-7
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• 2018

In the two-dimensional (2D) modeling of electrical method, the potential in the space domain is reconstructed with the calculated potentials in the wavenumber domain using inverse Fourier transform. The inverse Fourier integral is numerically evaluated using the transformed potential at different wavenumbers. In order to improve the precision of the integration, either the logarithmic or exponential approximation has been used depending on the size of wavenumber. Two numerical methods have been generally used to evaluate the integral; interval integration and Gaussian quadrature. However, both methods do not consider the distance from the current source. Thus the resulting potential in the space domain shows some error. Especially when the distance from the current source is very small or large, the error increases abruptly and the evaluated potential becomes extremely unstable. In this study, we developed a new method to calculate the integral accurately by introducing the distance from the current source to the rescaled Gauss abscissa and weight. The numerical tests for homogeneous half-space model show that the developed method can yield the error level lower than 0.4 percent over the various distances from the current source.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1332-1336
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• 2007

댐 제방 붕괴파는 갑작스러운 유량의 증가가 발생하여 불연속적인 흐름특성을 가지는 충격파(shock wave)가 전파되며, 갈수기 저수기에는 중소하천의 상류, 여울과 소에서의 흐름 또는 낙차공이나 보, 댐 여수로 등의 수공구조물에서 부분적인 사류 흐름이 발생된다. 이 때 흐름은 한계수위를 통과하게 되므로 기존 수치해법의 적용에 어려움이 존재한다. 본 연구에서는 실제하천에 적용될 수 있는 1차원 HLL, Roe Riemann 근사해법들을 간단히 소개하고, 시간공간적으로 2차의 고정확도 기법으로 확장하는 방법에 대하여 소개하였다. 각 기법을 정확해가 존재하는 댐붕괴 및 마른하도 전파의 경우에 적용하여 각 기법의 적용성 및 정확성을 비교하였다. 그리고 기존 Lax-Friedrichs 기법과 Lax-Wendroff 기법의 적용결과를 비교하였다. 적용결과 Lax-Friedrichs 기법을 제외한 모든 기법이 정확해와 잘 일치하였으며 특히 HLL 기법을 2차 정확도로 확장한 WAF 기법이 가장 높은 정확도로 계산되었다. 그러나 비선형 생성항이 존재하는 실제하천에 있어서 MUSCL 기법을 이용한 2차 정확도 기법이 합리적일 것으로 판단된다.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.8
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• pp.3-9
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• 2015

Under the maximum transmit power constraint and the minimum rate constraint, we propose the optimal number of transmit antennas and transmit power which maximize energy-efficiency (EE) in multi-user multiple-input multiple-output (MIMO) downlink system with the maximal ratio transmission (MRT) precoding. Because the optimization problem for the instantaneous channel is difficult to solve, we use independence of individual channel, average channel gain and path loss to approximate the objective function. Since the approximated EE optimization problem is two-dimensional search problem, we find the optimal number of transmit antennas and transmit power using Lagrange multipliers and our proposed algorithm. Simulation results show that the number of transmit antennas and power obtained by proposed algorithm are almost identical to the value by the exhaustive search.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.428-432
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• 2007

댐 제방 등의 붕괴로 인하여 발생하는 급격한 유량의 변화와 흐름영역의 변화로 인한 천이류 및 도수의 발생, 불규칙한 하천단면에서 갈수기 저수기의 흐름해석은 기존의 수치해법의 한계로 인하여 수리모형실험 및 경험식 또는 단면의 단순화 등에 의존하고 있는 실정이다. 본 연구에서는 자연하천에서 비선형 흐름율 계산에 불연속초기조건의 해석해인 Riemann 근사해법을 사용하여 수치적으로 안정되고 정확한 1차원 모형을 개발하고자 한다. 이를 위하여 유한체적법을 사용하였고, 수위와 유량의 계산을 위하여 요구되는 유한체적을 유출입하는 흐름율의 계산에 HLL Riemann 해법을 사용하였으며, MUSCL 기법으로 2차 정확도기법으로 확장하였다. Riemann 해법을 통하여 계산된 비선형의 흐름율과 보존 특성을 만족시켜줄 수 있는 하상 및 하폭변화로 인한 생성항을 처리하는 기법을 제안함으로서 새로운 1차원 수치해석모형을 개발하였다. 개발된 모형의 실제하천의 적용성을 확인하기 위하여 하상과 하폭이 변화하는 부정류 흐름에 적용하여 모형의 적용성 및 정확성을 검증하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.123-131
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• 2005

According to ow previous study, we confirmed That the Petrov-Galerkin natural element method(PG-NEM) completely resolves the numerical integration inaccuracy in the conventional Bubnov-Galerkin natural element method(BG-NEM). This paper is an extension of PG-NEM to two-dimensional geometrically nonlinear problem. For the analysis, a linearized total Lagrangian formulation is approximated with the PS-NEM. At every load step, the grid points ate updated and the shape functions are reproduced from the relocated nodal distribution. This process enables the PG-NEM to provide more accurate and robust approximations. The representative numerical experiments performed by the test Fortran program, and the numerical results confirmed that the PG-NEM effectively and accurately approximates The large deformation problem.