• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.5C
• /
• pp.403-412
• /
• 2008

This paper presents the methods which obtain the solution of Wiener-Hopf equation by LMS algorithm and get the coefficient of TDL filter in lattice filter directly. For this result, we apply an orthogonal input signal generated by lattice filter into an equivalent Wiener-Hopf equation and shows the scheme that can obtain the solution by using the MMSE algorithm. Conventionally, the method like aforementioned scheme can get an error and regression coefficient recursively. However, in this paper, we can obtain an error and the coefficients of TDL filter recursively. And, we make an theoretical analysis on the convergence characteristics of the proposed algorithm. Then we can see that the result is similar to conventional analysis. Also, by computer simulation, we can make sure that the proposed algorithm has an excellent performance.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.6
• /
• pp.27-38
• /
• 2012

In this paper, we introduce CoMP in 3GPP LTE-Advanced Release 11 to take care of shadowing effects appearing in cell-edge areas to meet rapidly increasing demand for high speed transmission and multi-media data. In order to mitigate interference, orthogonalizing is ideal but it is slightly difficult to be applied to real systems. Therefore, interference alignment and avoidance are used in practical applications. Interference alignment is a scheme enabling us to consider interference our friend not enemy. We show lattice codes in Gaussian channel achieve Shannon capacity where strong interference exists. In addition, we show the relationship between channel parameter a and DoF(Degree of Freedom) applying lattice codes to interference alignment for interference channel with three users.

• Journal of Advanced Navigation Technology
• /
• v.15 no.3
• /
• pp.349-354
• /
• 2011

In this paper, H-polarized scattering problems by a resistive strip grating with zero resistivity at strip-edges over a grounded dielectric plane according to the strip width and grating period, the relative permittivity and thickness of a dielectric layer, and incident angles of a transverse electric (TE) plane wave are analyzed by applying the Fourier-Galerkin Moment Method (FGMM). The tapered resistivity of resistive strips has zero resistivity at strip edges, then the induced surface current density on the resistive strip is expanded in a series of Chebyshev polynomials of the second kind as a orthogonal ploynomials. The sharp variations of the reflected power are due to resonance effects were previously called wood's anomallies, the numerical results for the reflected power are compared with those of uniform resistivity in the existing papers.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.6A
• /
• pp.551-557
• /
• 2011

We investigate lattice-reduction-aided precoding techniques using Look-Up table (LUT) for multi-user multiple-input multiple-output(MIMO) systems. Lattice-reduction-aided vector perturbation (VP) gives large sum capacity with low encoding complexity. Nevertheless lattice-reduction process based on the LLL-Algorithm still requires high computational complexity since it involves several iterations of size reduction and column vector exchange. In this paper, we apply the LUT-aided lattice reduction on VP and propose a scheme to generate the LUT efficiently. Simulation results show that a proposed scheme has similar orthogonality defect and Bit-Error-Rate(BER) even with lower memory size.

• Journal of Advanced Navigation Technology
• /
• v.15 no.4
• /
• pp.543-548
• /
• 2011

In this paper, H-polarized electromagnetic scattering problems by a resistive strip grating over a grounded dielectric plane according to the strip width and grating period, the relative permittivity and thickness of a dielectric layer, and incident angles of a TE (transverse electric) plane wave are analyzed by applying the FGMM (Fourier-Galerkin Moment Method). The tapered resistivity of resistive strips in this paper varies from finite resistivity at one edge to zero resistivity at the other edge, then the induced surface current density on the resistive strip is expanded in a series of Jacobi polynomials of the order ${\alpha}=1$, ${\beta}=0$ as a kind of orthogonal polynomials. The numerical results of the normalized reflected power show in good agreement with those of existing papers.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.2
• /
• pp.668-676
• /
• 1991

Turbulent flows around tube banks and in the diffuser were studied using a non-orthogonal boundary fitted coordinate system and the modified K-.epsilon. turbulence model. In these cases, many problems emerge which stem from the geometrical complexity of the flow domain and the physical complexity of turbulent flow itself. To treat the complex geometry, governing equations were reformulated in a non-orthogonal coordinate system with Cartesian velocity components and discretised by the finite volume method with a non-staggered variable arrangement. The modified K-.epsilon. model of Hanjalic and Launer was applied to solve above two cases under the condition of strong and mild pressure gradient. The results using the modified K-.epsilon. model results in both test cases.

• Journal of Ocean Engineering and Technology
• /
• v.7 no.2
• /
• pp.150-161
• /
• 1993

원초변수를 이용한 Navier-Stokes 방정식의 수치계산기법을 개발하고, 이를 응용하여 backward facing step의 층류 유동을 계산하였다. 직교좌표계에서의 비압축성 Navier-Stokes방정식을 풀기위해 시간과 공간항을 2차 정도의 유한 차분을 사용하여 이산화하였고 비교차격자계를 사용하여 양해법으로 수치 계산하였다. 운동량방정식과 연속방정식으로 부터 유도된 압력방정식(pressure-poisson equation)을 이용하여 무발산 조건을 만족시켰ㄲ다. Backward facing step의 층류 유동을 100.$\leq$R$_e$$\leq$1000 범위에 대해서 수치 계산하였으며 실험결과와 잘 일치하는 결과를 구할 수 있었다. 특히 step뒤에서 생기는 박리구간의 길이는 다른 계산결과들보다 실험치에 가까운 값을 얻을 수 있었으며, Re가 600보다 클때는 위쪽 벽에 또 다른 박리 유동이 발생되는 현상이 예측되었다.

• 한국전산유체공학회:학술대회논문집
• /
• 1995.10a
• /
• pp.82-89
• /
• 1995

In the present paper, a method of nearly orthogonal grid generation in an arbitrary simply-connected 3D domain will be presented. The method is a new direct and non-iterative scheme based on the concept of the decomposition of the global orthogonal transformation into consecutive mapping of a conformal mapping and an auxiliary orthogonal mapping, which was suggested by King and Leal [4]. In our numerical scheme. Kang and Leal's method is extended from 2D problems to 3D problems while the advantage of the non-iterative algorithm is maintained. The essence of the present mapping method is that an iterative scheme can be avoided by introducing a preliminary step. This preliminary step corresponds to a conformal map and is based on the boundary element method(BEM). This scheme is applied to generate several nearly-orthogonal grid systems which are orthogonal at boundaries.

• Korean Journal of Computational Design and Engineering
• /
• v.13 no.6
• /
• pp.450-458
• /
• 2008

Recently, Cartesian grid approach has been popular to generate grid meshes for complex geometries in CFD (Computational Fluid Dynamics) because it is based on the non-body-fitted technique. This paper presents a method of an octree generation and boundary cell clipping using section curves for fast octree generation and elimination of redundant intersections between boundary cells and triangles from 3D triangular mesh. The proposed octree generation method uses 2D Scan-Converting line algorithm, and the clipping is done by parameterization of vertices from section curves. Experimental results provide octree generation time as well as Cut-cell clipping time of several models. The result shows that the proposed octree generation is fast and has linear relationship between grid generation time and the number of cut-cells.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1397-1401
• /
• 2007

낙동강에 위치한 하회마을의 점사주는 상류에 안동 및 임하 다목적댐이 건설되면서, 수량이 조절됨에 따라 토사수리학적 특성이 상당히 변화되었으며, 식생이 발생하는 등 옛 모습을 상실해 가고 있는 지역이다. 이 연구는 낙동강의 중상류에 위치한 하회지구에 평면 이차원 하상변동 및 수질예측 수치모형인 KU-RLMS 모형을 적용하여 하회마을 앞의 점사주에 영향을 미치는 수리학적 특성 변화를 규명할 목적으로 수행하였다. KU-RLMS 모형은 하천 및 저수지의 국부적인 수리, 수질, 유사이동 해석을 위해 개발된 평면 이차원 비정상 수치모형이다. 직사각형 격자를 사용하는 유한차분법의 단점을 보완하기 위해, 흐름 계산을 위한 지배 방정식은 3차원 Reynolds 방정식으로부터 수심적분된 2차원 연속방정식과 운동량방정식을 불규칙한 경계를 현실적으로 모사할 수 있는 직교곡선 좌표계로 변환한 방정식을 사용한다. 안동다목적댐과 임하다목적댐의 방류량, 수공구조물 설치 여부 등을 고려하여 수치모의조건을 결정하였으며, 각 조건에 대한 흐름 변화특성을 분석하였다.