• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.50-60
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• 1999

In order to design a safe and economic catamaran, it is of clime importance to rigorously estimate the dynamic loads on the catamaran in waves. In this paper, the 2-D strip method by Lee et al.[3] is. extended to a 3-D method which can estimate the dynamic loads(horizontal and vertical shear forses, and bending and torsional moments) acting on the center of the cross deck of the catamaran travelling in an arbitrary wave heading angle. The computational results are compared with Wahab et al's experimental data[2], and also 2-D and 3-D numerical results published. It is found that in general, the 3-D method give much improved correlations with the experimental data compared with 2-D methods, but there are some discrcrepancy between the same 3-D results used by the same theory. In order to improve the accuracy, the effect of the viscous flow and the rigid consideration of the forward speed effect seem to be necessary.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.878-885
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• 2009

One of important factors in designing MEMS resonators for RF filters is obtaining a desired frequency response function (FRF) within a specific frequency range of interest. Because various array-type MEMS resonators have been recently introduced to improve the filter characteristics such as bandwidth, pass-band, and shape factor, the degrees of freedom (DOF) of finite elements for their FRF calculation dramatically increases and therefore raises computational difficulties. In this paper the Krylov subspace-based model order reduction using moment-matching with non-zero expansion points is represented as a numerical solution to perform the frequency response analyses of those array-type MEMS resonators in an efficient way. By matching moments at a frequency around the specific operation range of the array-type resonators, the required FRF can be efficiently calculated regardless of their operating frequency from significantly reduced systems. In addition, because of the characteristics of the moment-matching method, a minimal order of reduced system with a prearranged accuracy can be determined through an error indicator using successive reduced models, which is very useful to automate the order reduction process and FRF calculation for structural optimization iterations. We also found out that the presented method could obtain the FRF of a $6\times6$ array-type resonator within a seventieth of the computational time necessary for the direct method and in addition FRF calculation by the mode superposition method could not even be completed because of a data overflow with a half after calculation of 9,722 eigenmodes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.939-947
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• 2001

This paper presents the penetrated electric fields and resonant frequencies inside a metallic enclosure with aperture excited by an external dipole source. In the theoretical analysis, integral equations for the current distribution and electric field distributions on the aperture are solved by applying Galerkin\`s method of moments. The results show that the electric fields inside metallic enclosure is maximum at the near the aperture and resonant frequencies are the same as calculated of the enclosure without aperture. To verify the theoretical analysis the electric field inside enclosure and resonant frequencies are compared with the experimental results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.273-288
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• 1997

In this work, the electromagnetic waves scattered from 2-dimensional random rough surfaces are characterized by the $4\times4$ Mueller matrix elements. The full wave solutions are used to compute these elements. The results of the full wave solutions for 1-dimensional random rough surfaces were shown to agree well with those of the experiment and the method of moments. The Mueller matrix elements are related to the like and cross polarized radar cross sections as well as to the relative phase of the vertically and horizontally polarized waves. The $4\times4$ Mueller matrix elements completely characterize electromagnetic scattering from target. The computed results of this paper can be useful to the field of active remote sensing or RCS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1600-1606
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• 2001

Resonant frequency in rectangular microstrip patch antenna on anisotropic substrates with airgap and superstrate are analyzed. Dyadic Green function is derived for selected anisotropic material by constitutive relation. From these results, integral equations of electric fields are formulated using Fourier transform in space region. The electric field integral equations are discretized into the matrix form by applying Galerkin\`s moment method. Sinusoidal functions are selected as basis functions because they resemble in the actual standing wave on the patch. To verify the validity of numerical result, we compare our result with existing one and get a good agreement between them. From the numerical results, the resonant frequency in the variation of air gap, patch length and anisotropy ratio are presented and analysed.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.8
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• pp.340-348
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• 2003

In this paper, we propose a novel formulation to solve a time-domain combined field integral equation (CFIE) for analyzing the transient electromagnetic scattering response from closed conducting bodies. Instead of the conventional marching-on in time (MOT) technique, tile solution method in this paper is based on the moment method that involves separate spatial and temporal testing procedures. Triangular patch vector functions are used for spatial expansion and testing functions for three-dimensional arbitrarily shaped closed structures. The time-domain unknown coefficient is approximated as a basis function set that is derived from tile Laguerre functions with exponentially decaying functions. These basis functions are also used as the temporal testing. Numerical results computed by the proposed method arc stable without late-time oscillations and agree well with the frequency-domain CFIE solutions.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.9
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• pp.29-39
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• 2001

Dielectric cover effect of rectangular microstrip patch antenna on uniaxial substrates with airgap are studied. First, we derive Dyadic Green function for selected anisotropic material by constitutive relation and then formulate integral equations of electric fields using Fourier transform in space region. Using Galerkin's moment method, we discretize the electric field integral equations into the matrix form and select sinusoidal functions as basis functions. We verify the validity of numerical results and compare the results with existing ones in showing a good agreement between them. When the dielectric cover thickness is varied, the resonant frequencies and input impedances in the variation of air gap, patch length and thickness and permittivity of superstrate are presented and analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.186-196
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• 2000

In this paper, modified square loop frequency selective surface for dualband communication antenna systems is proposed, and the scattering characteristics is discussed. The analysis for the problem of scattering by periodic structures with a dielectric slab is formulated using the spectral-domain immittance approach and Floquet's theorem. The method of moments which uses rooftop subdomain basis function is employed to solve the equations. Numerical results include the comparison between the transmission characteristic of general square loop and that of modified square loop. Also, the transmission characteristics of modified square loop for arbitrary incident angle and polarization is presented. To verify analysis results, modified square loop frequency selective surface was fabricated and the calculated results were compared with the measured results. The measured results showed good agreement with the calculated results.

• Journal of IKEEE
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• v.5 no.1 s.8
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• pp.91-99
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• 2001

Spectral domain of resonant frequency rectangular microstrip patch antenna on anisotropic substrates and superstrate with airgap are analyzed. First, we derive dyadic Green function for selected anisotropic material by constitutive relation and then formulate integral equations of electric fields using Fourier transform in space region. Using Galerkin's moment method, we discretize the electric field integral equations Into the matrix form and select sinusoidal functions as basis functions. We verify the validity of numerical results and compare the results with existing ones in showing a good agreement between them. The resonant frequencies in the variation of air gap, patch length and permittivity of superstrate anisotrpy ratio of anisotrpic superstrate are presented and analyzed.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.3
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• pp.68-74
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• 1995

In this paper, E-polarized electromagnetic scattering by a conducting strip grating with 2 dielectric layers is analyzed to calculate the geometrical reflected and transmitted power by applying the Fourier-Galerkin moment mothed. The induced current density is expanded in a Fourier series using a simple exponential func- tion, and we applied the boundary conditions to the electromagnetic fields at the boundary planes. The sca- ttered electromagnetic fields are expanded in a series of Floquet mode functions. To examine the accuracy of the present method, the geometrically reflected and transmitted power are evaluated and compared with those of the existing papers, and then the numerical results are found in good agreement with those of the existing paper.