• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.188-192
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• 1994

This paper presenta new method for tool interference acoidance using rectanguar approximation in NC machining of scuptured surface. The procedure of algorithm for approximation of sculptured surface to rectangular surface is described. Using this algorithm, we can check concave, convex, and side interference region and avoid these interferenes.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.2
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• pp.93-99
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• 1998

Parabolic approximation and sponge layer are applied as open boundary condition for elliptic finite difference wave model. Generalized conjugate gradient method is used as a solution procedure. Using parabolic approximation a large part of spurious reflection is removed at the spherical shoal experiment and sponge layer boundary condition needs more than 2 wave lengths of sponge layer to give similar results. Simulating the propagation of waves on a rectangular harbor, it is identified that iterative scheme can be applied easily for the non-rectangular computational region.

• Communications for Statistical Applications and Methods
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• v.4 no.3
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• pp.629-635
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• 1997

An approximation for multivariate t probability for an orhant region(i.e., a rectangular resion with lower limits of $-\infty$ for all margins) is proposed. It is based on conditional expectations, a regression with binary variables, and the exact formula for the evalution of the bivariate t integrals by Dunnett and Sobel. It is noted that the proposed approximation method is espicially useful for evaluating the multivariate t integrals where there is no simple method available until now.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.719-724
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• 1994

This paper describes a hybrid surface-based method for smooth 3D surface approximation to a sequence of 2D cross sections. The resulting surface is a hybrid G $^{1}$ surface represented by a mesh of triangular and rectangular Bezier patches defined on skinning, branching, or capping regions. Each skinning region is approximated with a closed B_spline surface, which is transformed into a mesh of Bezier patches. Triangular G $^{1}$ surfaces are constructed over brabching and capping regions such that the transitions between each capping regions such that the transitions between each triangular surface and its neighboring skinning surfaces are G $^{1}$ continuous. Since each skinning region is represented by an approximated rectangular C $^{2}$ suface instead of an interpolated trctangular G $^{[-1000]}$ surface, the proposed method can provide more smooth surfaces and realize more efficient data reduction than triangular surfacebased method.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.45-52
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• 2000

We present a novel method for simple and efficient analysis of the rectangular MQW waveguide. Preferentially two-dimensional structure is transformed into one-dimensional structure by using the effective index method. Then, the characteristic matrix of the resultant planar MQW waveguide is analyzed by scanning angle method. The effective index, modal intensity, and optical confinement factor of rectangular MQW waveguide can be effectively obtained by this method. Our simulation results show excellent agreement with the accurate solutions based on the finite element method. We also introduce the approximation methods for the analysis of rectangular MQW waveguide and investigate their validity. By using perturbation approach, modal power loss of guided wave in rectangular MQW waveguide is newly investigated and compared with the conventional method using the approximation of planar MQW waveguide.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.11
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• pp.898-908
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• 1990

This paper applies the moment method to analyze the transverse electromagnetic(TEM) cell with an inner conductor (septum) of arbitrary rectangular shape and location by employing quast static approximation. The EM field and the characteristic impedance so obtained are shown to be in good agreement with the available data from the previously published papers about the typical TEM cell structure with center septum of zero thickness.

• Journal of information and communication convergence engineering
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• v.2 no.3
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• pp.187-192
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• 2004

A method using two dimension Haar functions approximation for solving the problem of a partial differential equation and estimating the parameters of a non-linear distributed parameter system (DPS) is presented. The applications of orthogonal functions, including Haar functions, and their transforms have been given much attention in system control and communication engineering field since 1970's. The Haar functions set forms a complete set of orthogonal rectangular functions similar in several respects to the Walsh functions. The algorithm adopted in this paper is that of estimating the parameters of non-linear DPS by converting and transforming a partial differential equation into a simple algebraic equation. Two dimension Haar functions approximation method is introduced newly to represent and solve a partial differential equation. The proposed method is supported by numerical examples for demonstration the fast, convenient capabilities of the method.

• ETRI Journal
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• v.6 no.2
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• pp.18-26
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• 1984

Among the various forms of interpolating polynomial for approximation, this paper is a study about the characteristics of piecewise Lagrange interpolating polynomials. And throughout the study, an attempt is made to construct the two-dimensional ap proximating function over Rectangular Grid and Triangular Grid by using the one-dim ensional interpolating polynomials.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.741-744
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• 2005

A numerical scattering model for artificial metal structure based on physical optics approximation is developed to identify the height of phase center, and the result is compared with interferometric SAR DEM. The interferometric SAR data were gathered by AIRSAR during PACRIM- II campaign on Jeju Island. Power transmission towers on piedmont pasture along the slopes of Mt. Halla look like elliptic risings in TOPSAR DEM. The heights of risings are quantitatively analyzed using a scattering model in the way of achieving the height of phase centers of power transmission towers. A numerical algorithm is developed on the basis of physical optics approximation. The structure of power transmission tower was decomposed into hundreds of rectangular metal plates, of which the scattering matrix is known in analytic form, and the calculated scattering fields were summed coherently. The effect of direct backscattering component, ground-scatterer component and scatterer-ground component are decomposed and computed individually for each rectangular metal plate. The $\Deltak-radar$ equivalent was used to calculate height of phase center of the scatterer. The heights of a selected power transmission tower and scattering algorithm results give existence and location of the transmission towers but not actual tower heights.

• The KSFM Journal of Fluid Machinery
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• v.5 no.2 s.15
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• pp.29-35
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• 2002

The present study is concerned with the flow patterns induced by various impellers in a rectangular tank. Impellers are FBT (Flat blade turbine), PBT (Pitched blade turbine), Shroud turbine, Rushton turbine, and Helical ribbon turbine types. The solutions of flows in moving reference frames require the use of 'moving' cell zone. The moving zone approaches are based on MRF (Multiple reference frame), which is a steady-state approximation and sliding method, which is an unsteady-state approximation. Numerical results using two moving zone approaches we compared with experiments by Ranade & Joshi, which have done extensive LDA measurements of the flow generated by a standard six-bladed Rushton turbine in a cylindrical baffled vessel. In this paper, we simulated the flow patterns with above-mentioned moving zone approaches and impellers. Turbulence model used is RNG $k-{\epsilon}$ model. Sliding-mesh method is more effective than MRF for simulating the rectangular tank with inlet and outlet. RNG $k-{\epsilon}$ model strongly underestimates the velocity of experimental data and velocity by Chen & Kim's model, but it seems to be correctly predicted in overall distribution.