• The KIPS Transactions:PartB
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• v.14B no.7
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• pp.549-558
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• 2007

Collaborative filtering systems have problems when users rate items and the rated results depend on their feelings, as there is a possibility that the results include noise. The method proposed in this paper optimizes the matrix by excluding irrelevant ratings as information for recommendations from a user-item matrix using dispersion. It reduces the noise that results from predicting preferences based on original user ratings by inflecting the information for items and users on the matrix. The method excludes the ratings values of the utmost limits using a percentile to supply the defects of coefficient of variance and composes a weighted user-item matrix by combining the user coefficient of variance with the median of ratings for items. Finally, the preferences of the active user are predicted based on the weighted matrix. A large database of user ratings for movies from the MovieLens recommender system is used, and the performance is evaluated. The proposed method is shown to outperform earlier methods significantly.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.335-338
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• 1988

A numerical method is presented for the scattering by the perfectly conducting cylinder with arbitrary cross sections. The relevant integral equation considered by the E-field formulation is solved by method of moments, and thereby the surface current induced as well as the radar cross section of the scatterer are numerically computed to specify the scattering nature of the scatterer. Two separate methods, one with point matching and the other Galerkin's method, are considered to make cross checks to the results obtained. Taking two half pulses suggested to expand the surface current shows savings in computation time and accurate solutions for the corners on the scatterer.

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.78-81
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• 1987

The scattering characteristics are analysed for the dielectric cylinder with arbitrary cross section partially covered by thin conductors. The integro differential equations consistant with boundary conditions of conductor and dielectric boundaries are derived by the equivalence principle. They are transformed into matrix equations by moment method. The circular dielectric cylinder covered by conductors at the upper and bottom side of the cylinder is chosen for the numerical example. Current distributions on conductors and scattering cross section by the cylinder are computed for incident wave perpendicular to the conductor plane.

• Journal of KSNVE
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• v.7 no.4
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• pp.571-578
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• 1997

Recently, many general-purpose packages for fluid-structure interaction problems have been announced. However, they have a lot of limitations to model structures in the fluid-structure interaction problems reasonably. Utilizing general-purpose packages such as MSC/NASTRAN and SYSNOISE, in this paper, a method to slove the radiation scattering problems with some accuracy in the fluid-structure interaction problems was developed. Using a simple model, the results from the presented method here are compared with those from SYSNOISE. The result shows quite a good agreement between the two methods. The problems, which could not be solved by SYSNOISE, were tried to solve with the presented method and results were presented. It was proved that this method could be safely used to solve fluid-structure interaction problems.

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.408-412
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• 2007

Combining the analytical transfer matrix method with supersymmetry algebra, a new quantization condition is suggested. To demonstrate the efficiency of the new quantization condition, the eigenenergies of the Coulomb potential are analytically derived. The scattering-led phase shifts are also determined and they are the same for all Coulomb potential states. It is found that the new quantization condition is mathematically simple and exact.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.337-344
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• 2000

The wavelet analysis technique is applied in the spectral domain to efficiently represent the multi-scale features of the impedance matrices. In this scheme, the 2-D quadtree decomposition (applying the wavelet transform to only the part of the matrix) method often used in image processing area is applied for a sparse moment matrix. CG(Conjugate-Gradient) method is also applied for saving memory and computation time of wavelet transformed moment matrix. Numerical examples show that for rectangular cylinder case the non-zero elements of the transformed moment matrix grows only as O($N^{1.6}$).

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.5
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• pp.65-72
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• 1994

We resolve the suboptimal $\infty$ control problem using (J,J')-lossless coprime factorization by transforming the linear fractional transformation (LFT) into chain scattering description (CSD) in discrete-time systems. The condition transformed LFT into CSD is that the inverse matrix of $P_{21}$ of standard plant exists. But, this paper presents the method of transforming LFT into CSD for 4-block problem in case that the inverse matrix of $P_{21}$ of standard plant does not exist and parameterization of the all suboptimal $\infty$T controllers using (J,J')-lossless coprime factorization. It is shown that this method can resolve the suboptimal $\infty$ control problem solving only two Riccati equations in discrete-time systems.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.3
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• pp.7-12
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• 1990

A rigorous analysis of the scattering problem by the perfectly conducting strip loaded with a dielectric cylinder of different permittivity is presented. By introducing auxiliary electromagnetic fields and applying the reciprocity theorem, integral equations for the unknown electric field are derived. These integral equations are transformed into an equivalent matrix equation of infinite order with proper boundary conditions. By calculating inverse matrix of unknown coefficients from this equation, scattered electric fields are determined. In particular case of the dielectric with the same permittivity, the results of this paper correspond to well-known results.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.1
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• pp.69-79
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• 2001

A volume integral equation method(VIEM) is applied for the effective analysis of elastic wave scattering problems in unbounded solids containing general anisotropic inclusions. It should be noted that this newly developed numerical method does not require the Green's function for anisotropic inclusions to solve this class of problems since only the Green's function for the unbounded isotropic matrix is Involved In their formulation for the analysis. nis new method can also be applied to general two-dimensional elastodynamic problems with arbitrary shapes and number of anisotropic inclusions. Through the analysis of plane elastodynamic problems in unbounded isotropic matrix with an orthotropic inclusion, it is established that this new method is very accurate and effective for solving plane elastic problems in unbounded solids containing general anisotropic inclusions.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.1
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• pp.29-34
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• 2022

In this paper, thr H-polarized scattering problems by a resistive strip grating in a grounded double dielectric layer are analyzed by applying the PMM(point matching method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients, the scattered electromagnetic fields are expanded in a series of Floquet mode functions, and the resistive boundary condition is applied to analysis of the resistive strip. The %error of the convergence of the reflected power according to the relative permittivity of the dielectric layer and the size of the number of rows in the square matrix was compared, as the size of the number of rows in the square matrix increased, the accuracy of the reflected power increased. As the resistivity of the resistive strip decreased, the thickness of the dielectric layers decreased, and the relative permittivity of the dielectric layers increased, the reflected power increased. The numerical results for the presented structure of this paper having a grounded double dielectric layer are shown in good agreement compared to those of the existing papers.