• Geophysics and Geophysical Exploration
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• v.23 no.4
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• pp.223-229
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• 2020

Small-loop EM techniques have been used in many geophysical investigations, including shallow engineering and environmental surveys. Even though geometric and frequency soundings have been widely used, there is a debate regarding the effectiveness of frequency sounding, especially when the coil spacing is small. In this study, we analyzed the effectiveness of geometric as well as frequency soundings via the one-dimensional modeling of small-loop EM surveys. The numerical results reveal that geometric sounding can effectively provide underground information. Conversely, the frequency soundings are only effective when the loop spacing is relatively large, that is, when the induction number is large. On the contrary, the frequency soundings fail to provide any information concerning the subsurface layers if the loop spacing is not large.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.74-86
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• 1997

With continued miniaturization and development of new devices, the highly nonuniform oxidation of three-dimensional non-planar silicon structures plays an increasingly important role. In this paper, the three-dimensional finite element numerical simulator. Grwoth of oxide is a coupled process of diffusion of oxidant and deformation of oxide. Because boundaries of oxide are moved in each time step and LOCOS structure is formed three-dimensional shape of sruface, it is necessary to develope an efficient node control algorithm that can locally generate and eliminate the node. Therefore we have developed the optimized three-dimensional mesh generator which is cpable of refining and eliminating the meshes at the moving boundary of oxide, and hve developed three-dimensional finite element oxidation solver.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.1
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• pp.55-62
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• 1983

The error rate performance of phase shift Keyed(PSK) signal has been evaluated in terms of carrier-to-noise ratio(CNR), carrier-to-interferer ratio(CIR), impulsive index, and the phase difference between signal and interferer in the environment of cochannel PSK inter-ference and impulsive noise. We hays derived a general equation of the probability density function (p.d.f.) of output of coherent phase detector. And the error rate of the received binary PSK(BPSK) signal has been numerically evaluated. The graphic results show us that the best case is the situation of the signal and the inter- ferer meet with orthogonal phase.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.3
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• pp.225-232
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• 2018

This paper proposed the optimization method of the extremely low numerical-dispersion finite-difference time-domain (ELND-FDTD) method based on the H(2,4) scheme for wideband and extremely accurate electromagnetic properties of lossy material, which has a constant conductivity and relative permittivity. The optimized values of three variables are calculated for the minimum numerical dispersion errors of the proposed FDTD method. The excellent accuracy of the proposed method is verified by comparing the calculated results of three different FDTD methods and the analytical results of the two-dimensional dielectric cylinder scattering problem.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.458-465
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• 2003

In this paper, we analyze the transient electromagnetic response from three-dimensional(3-D) dielectric bodies using a time-domain electric field integral equation formulation. The solution method in this paper is based on the Galerkin＇s method that involves separate spatial and temporal testing procedures. Triangular patch basis functions are used for spatial expansion and testing functions for arbitrarily shaped 3-D dielectric structures. The time-domain unknown coefficients of the equivalent electric and magnetic currents are approximated as an orthonormal basis function set that is derived from the Laguerre functions. These basis functions are also used as the temporal testing. Numerical results involving equivalent currents and far fields computed by the proposed method are presented.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.1096-1103
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• 2003

In this paper, we analyze the transient electromagnetic response from three-dimensional(3-D) dielectric bodies using a time-domain PMCHW(Poggio, Miller, Chang, Harrington, Wu) formulation. The solution method in this paper is based on the Galerkin's method that involves separate spatial and temporal testing procedures. Triangular patch basis functions are used for spatial expansion and testing functions for arbitrarily shaped 3-D dielectric structures. The time-domain unknown coefficients of the equivalent currents are approximated by a set of orthonormal basis functions that are derived from the Laguerre polynomials. These basis functions are also used as the temporal testing. Numerical results involving equivalent currents and far fields computed by the proposed method are presented.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.11
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• pp.171-179
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• 2013

This paper presents a comparative study on application of Routh-Hurwitz and Llewellyn absolute stability criteria to a scaled telerobotic system. The dynamic equations of the telerobotic system are given, and the transfer function of the system is obtained for further stability analysis. The stable margins of controller gains are obtained using both stability analysis methods, and the differences in the results are described and explained. The paper is concluded by a numerical example verifying performed stability analysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.961-968
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• 2004

In this paper, we present a set of numerical schemes to solve the Muller integral equation for the analysis of electromagnetic scattering from arbitrarily shaped three-dimensional dielectric bodies by applying the method of moments(Mon. The piecewise homogeneous dielectric structure is approximated by planar triangular patches. A set of the RWG(Rao, Wilton, Glisson) functions is used for expansion of the equivalent electric and magnetic current densities and a combination of the RWG function and its orthogonal component is used for testing. Numerical results for a dielectric sphere are presented and compared with solutions obtained using other formulations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.145-152
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• 2011

The performance of flat-tube radiators with louvered fins was numerically investigated for different tube insertion lengths. The results of numerical analysis using CFX-11 were compared with experimental results. In this study, three types of flat-tube radiators with louvered fins were considered. An experiment was conducted to validate the numerical results. Flow rate ratio (FR) and Stotal were introduced to understand the uniformity of flow distribution easily. The results of numerical analysis revealed that the heat transfer rate and pressure drop increased as the mass flow rate increased. Further, the results showed that the heat transfer rate of sample 3 with h/D = 0.5 was higher than that of the other samples. The pressure drop increased as the insertion length toward the header part increased, and the pressure drop in the case of sample 3 appeared to be the highest. The factor Stotal showed that the uniformity of the flow distribution in the case of sample 1 with h/D = 0 was higher than that in the case of the other samples.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.4 s.95
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• pp.373-379
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• 2005

Papers on improvement of electromagnetic field uniformity in a reverberation chamber with 1D Quadratic Residue Diffuser of Schroeder method has been published several times. In this paper, to obtain improved electromagnetic field characteristics and field uniformity in a reverberation chamber, cubical residue diffuser sets of Schroeder type are designed for a chamber in $2.3\;\cal{GHz}\~3\;\cal{GHz}$. The FDTD(Finite-Difference Time-Domain) technique is used to analyze the field characteristics in a chamber. Cubical residue algorithm and 2D arrangement show more randomness than the previous study results. The characteristics of tolerance, polarity, deviations, as well as power efficency, are improved with cubical residue diffuser sets in a chamber.