• Proceedings of the Korea Contents Association Conference
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• 2003.05a
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• pp.403-405
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• 2003

An iterative Green's function method (IGFM) is introduced to analyze complex electromagnetic waveguide structures in view of the university student. The IGFM utilizes the Green's function and iteration scheme. The physical mechanism with simple mathematical equations is used to formulate the IGFM. Scattering characteristics of a standard E-plane T-junction in a parallel-plate waveguide are theoretically investigated in terms of the IGFM. Numerical computations illustrate the characteristics of resection and transmission powers versus frequency. A dominant-mode solution is presented and compared with the higher-mode solutions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.10
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• pp.2303-2309
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• 1997

This paper presents a convergence analysis of the stocastic gradient adaptive algorithm based on the least mean absolute third (LMAT) error criteriohn. Under the assumption that the signals involved are zero-mean, wide-sense sateionaryand gaussian, a set of nonlinear difference equations that characterizes the mean and mean-squared behavior of the algorithm is derived. Computer simulation resutls show fairly good agreements between the theoetical and empirical behaviors of the algorithm.

• Journal of the KSME
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• v.34 no.7
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• pp.517-526
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• 1994

복합재료가 점차 최근에 항공기에서 이차적인 구조요소에서 일차적으로 힘을 받는 구조물에 사 용됨으로써 두꺼운 복합재료 구조판과 셸의 정확한 동적, 정적거동을 예측하는 것이 중요한 문 제가 되었다. 특히 전산구조역학의 한 분야로서 복합재료 적층판의 문제는 inhomogeneity와 anisotropy 문제를 가지고 있어서 복잡하며 일차구조 (primary structrue)에서는 100장-200장의 적층도 드물지 않게 볼 수 있어서 정확한 계산을 위해서는 방대한 기억용량과 빠른 계산속도를 요구한다. 그러므로 복합재료 적층판의 거동을 정확하고 값싸고 빠르게 계산할 수 있는 이론과 수치방법의 개발이 중요한 문제이다. 이 문제는 E. Reissner, R. K. Kapania & S. Raciti, A. K. Noor & W. S., Burton, L. Librescu & J. N. Reddy, J. N. Reddy 등에 의해서 review가 행하 여졌고 이 분야의 모든 paper들의 비교적 현재까지 연구동향을 잘 묘사하고 있다. 여러 review paper들이 시간흐름상으로 여러 연구들을 잘 정리하고 있으므로 이 글에서는 논문들을 다시 review하는 것이 아니라 지난 20여 년간 이 분야에서 계속되어 온 연구중 주요한 것을 고찰하고 소개하는 것을 그 목적으로 한다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1551-1552
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• 2008

본 논문은 네트워크 기반 제어시스템(NCS: Networked Control Systems)에 모델매칭 제어기법을 적용한 효율적인 제어알고리즘을 제안한다. 비선형의 특징을 가지는 제어기 및 관측기의 시간지연을 Taylor 근사법으로 선형화하여 선형시스템 이론을 적용한 모델매칭 제어기를 설계하였다. 또한, 제어기의 차수를 우세극 기법과 극,영점 상쇄기법(Pole-Zero Cancelation)을 통해 저차화한 후 그 타당성을 검증하였다. 제안한 제어알고리즘의 컴퓨터 시뮬레이션을 실시하였으며 기존의 고차 모델매칭 제어기와 비교분석하여 타당성 및 신뢰성을 검증하였다.

• 전기의세계
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• v.34 no.11
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• pp.654-665
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• 1985

현재 전자군의 매개변수해석에 많이 이용되고 있는 방법과 이들의 실측을 하기 위한 실험방법으로는 몇가지가 있다. 대체로 정상Townsend실험, 퍼스Townsend실험, 비행시간관측실험 등이 있으며, 본 고찰에서는 이들을 중심적으로 취급하였다. 그러나 이들은 측정실험방법이 각각 다름에 따라 이론적 해석방법도 다르다. 또한 본 논문에서는 에너지분포를 2차근사 방법으로 해석한 것을 서술하고, 그 이상의 고차항까지 고려하여 해석결과와 비교한예는 그림7과 같다. 이와 같이 기체방전현상의 이론적 해석이 실험치와 잘일치되는 것으로 보아 기체계의 절연설계나 특성 예측이 가능하기 때문에 공학적 응용이 기대되는 모델화도 이루어질 수가 있다. 기체방전simulation이 응용되어지고 있는 분야는 이외에도 가장 현대적인 응용인 gas laser의해석, laser조사에 의한 방전트리거기구의 해석 등 상당히 광범위하게 응용되어지고 있으므로 이에 대한 연구가 활성화되어져야 하겠다.

• Geotechnical Engineering
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• v.13 no.3
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• pp.53-62
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• 1997

Analytical studies were conducted to develop the Spectral-Analysis-of-Surface-Waves (SASW) method for underwater use. For the precise estimation of the in-situ soil stiffness profile from SASW measurements, it is essential to determine economical and reasonable theoretical dispersion curves reflecting various experimental conditions. In this paper, therefore, analytical methods are mainly discussed, which were developed to determine theoretical dispersion curves of surface waves propagated along the soil-water interface. Application of the analytical methods is then illustrated by an example involving estimation of a stiffness profile through a forward modeling process of SASW measurements. Applicabilities of the SASW method as well as the developed analytical methods are evaluated, respectively, from the example.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.317-326
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• 1998

This paper describes a reduced finite element formulation for nonlinear transient heat transfer analysis based on Lanczos Algorithm. In the proposed reduced formulation all material nonlinearities of irradiation boundary element are included using the pseudo force method and numerical time integration of the reduced formulation is conducted by Galerkin method. The results of numerical examples demonstrate the applicability and the accuracy of the proposed method for the nonlinear transient heat transfer analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.381-387
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• 2016

In this paper, the methodology applied to the improvement of stress analyses is extended to free vibration and buckling analyses. The essence of the methodology is the Saint-Venant's principle that is applicable to beam and plate models. The principle allows one to dimensionally reduce three-dimensional elasticity problems. Thus the methodology can be employed to vibration and buckling as well as stress analysis. First, the principle is briefly revisited, and then the formations of classical beam theories are presented. To improve the predictions, the perturbed terms (unknowns) are introduced together with the warping functions that are calculated by stress equilibrium equations. The unknowns are then calculated by applying the equivalence of stress resultants (i.e., Saint-Venant's principle). As numerical examples, cantilever and simply supported beams are analytically solved. The results obtained are compared with those of the classical beam theories. It is shown that the methodology can be used to improve the predictions without introducing shear correction factors.

• Journal of Korean Association for Spatial Structures
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• v.5 no.3 s.17
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• pp.65-74
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• 2005

An analytical model was developed to investigate the flexural behavior of a pultruded fiber-reinforced plastic deck of rectangular unit module. The model is based on first-order shea. deformable plate theory (FSDT), and capable of predicting deflection of the deck of arbitrary laminate stacking sequences. To formulate tile problem, two-dimensional plate finite element method is employed. Numerical results are obtained for FRP decks under uniformly-distributed loading, addressing the effects of fiber angle and span-to-height ratio. It is found that the present analytical model is accurate and efficient for solving flexural behavior of FRP decks. Also, as the height of FRP deck plate is higher, the necessity of higher order Shear deformable plate theory(HSDT) is announced, not the FSDT in the plate analysis theory.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.3 no.1
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• pp.3-10
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• 1992

Flux-drive waveguide phase shifter is designed by twin-slab model. Measured differential phase shifts are smaller than the theoretical values by 8-9 percents. Measured insertion loss and VSWR of the phase shifter using TT73-2200 ferite are less than 0.45dB and 1.25 respectively, within pass band. The phase shifter using double-setup transformer shows wider bandwidth characteristics. Finally the reduced-height waveguide phase shifter using TT3-2900 ferrite shows very efficient suppression of higher-oreder modes.