• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.463-472
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• 2007

This paper presents theoretical and finite element analysis results for the lateral-torsional buckling of I-girders with corrugated web under uniform bending. Lateral-torsional buckling is a major design aspect for flexural members composed of thin-walled I-section. However, torsional rigidities such as the warping constants of the I-girders with corrugated web are not fully understood yet. In this paper, bending and pure torsional rigidities of I-girders with corrugated web are first described using the results of previous researchers. Then, the location of the shear center and the warping constants are derived. Using the derived section properties of I-girders with corrugated web, the lateral-torsional buckling strength is determined. Finite element analyses are conducted and the proposed lateral-torsional buckling strength of I-girders with corrugated web is successfully verified. Finally, the effects of corrugation profiles of the web on the lateral-torsional buckling load of I-girders with corrugated web are discussed.

• The Journal of the Acoustical Society of Korea
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• v.9 no.3
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• pp.56-61
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• 1990

A New theoretical energy spectrum model for underwater explosive sound is introduced in order to calculate the precise spectral energy levels. This model is obtained by Fourier analysis of Gaussian formula which accurately represents the pressure wave generated from Underwater explosions. In case that explosive energy is very low. The spectrum levels which are obtained from the new theoretical model are in good agreement with the experimental spectrum levels, while the Weston model using impulse formula cannot interpret the experimental results.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.6
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• pp.71-78
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• 1994

본 연구에서는 결합계수(K)를 고려한 D급 고주파 공진형 인버터를 연구대상으로 하여 회로구성 및 동작원리에 대해 기술하였다. 본 회로의 기본적인 정상동작특성을 무차원화 제어변수를 도입하여 범용성있게 도설하였고, 부하시정수와 결합계수를 변수로 채용하여 인버터의 운전특성을 평가하였다. 특성평가를 통해 얻어진 자료를 기초로 하여 주회로의 설계기법의 일례를 제시하고, 실험에 의한 실측파형과 이론파형을 비교하여 회로해석의 정당성을 뒷받침 하였고, 제안회로가 전자식 안정기, 전자조리기 등의 실제응용에 적용가능함을 보여주고 있다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.11-20
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• 2014

This paper aims at comparing and analyzing shear buckling characteristics between sinusoidal corrugation shape and trapezoidal one. For this, I adopted the equal-length trapezoidal corrugation and sinusoidal one for the analytical models, and analyzed their shear buckling characteristics through linear buckling analysis and on its theory. Generally, the shear buckling shapes of corrugated steel plates are classified into local buckling, global buckling, and interactive buckling from the two buckling modes. Sinusoidal corrugation shape, unlike trapezoidal corrugation, does not have flat sides, which causes another tendency in shear buckling mode. Especially, the changes and different aspects of shear buckling on the boundary between local buckling and global buckling appear in different corrugation shapes. According to the analysis results, interactive buckling mode appeared on the boundary of local buckling and global bucking in trapezoidal corrugation. However, in the case of corrugated steel plates with sinusoidal configuration, interactive buckling mode appeared in the part where global bucking takes place. Besides, trapezoidal shapes are of advantages on shear buckling resistance in the local buckling section, and so are sinusoidal shapes in the global buckling section.

• Korean Journal of Optics and Photonics
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• v.24 no.2
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• pp.58-63
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• 2013

A theoretical analysis of the impact of rise time of a Q-switch on the output pulse performance is carried out in an Ytterbium-doped actively Q-switched fiber laser. The finite difference time domain (FDTD) method is used to numerically simulate the Q-switched fiber laser. It is shown that stable Gaussian-like pulse shape can be generated when the Q-switch rise time is increased and pulse repetition rate is enlarged.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.5
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• pp.521-528
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• 1992

this paper a new PAM-PWM Inverter using IGBT Is described. The output waveforms in the proposed PAM-PWM inverter are investigated both theoretiically and experimentally. The line-voltage waveform is composed of fundamental component and the sidebands of carrier frequency. The lower order harmonics are not included In the output waveform. As each inverter arm does not operate during two-thirds period, the heats, generated in the devices are reduced. That is the size of the inverter system can be minimized because of the reduction In the heat dissipating equipemnt.

• Journal of Korea Water Resources Association
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• v.35 no.1
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• pp.91-96
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• 2002

The present research describes the Bragg reflection of obliquely incident waves propagating over sinusoidally varying topographies. A numerical model based on the boundary element method is employed. Wave numbers providing Bragg reflection are calculated and compared to theoretical predictions. The reflection coefficients obtained from this model are also compared with those of the eigenfunction expansion method. A very good agreement is observed.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.202-204
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• 2007

영구자석을 이용한 다상 브러시리스 전동기의 역기전력의 파형은 정현파나 이상적인 사다리꼴 파형과는 다른 형태를 갖는다. 또한 다상 전동기의 경우 상호인덕턴스에 대한 이론적 해석이 쉽지 않아 시뮬레이션을 위한 모델 구현이 어렵다. 본 논문에서는 임의의 역기전력 파형을 갖는 7상 영구자석 브러시리스 전동기의 시뮬레이션 모델 구현 방법으로 회로 및 수식 을 기반으로 FEA(Finite Element Analysis)를 이용한 모델을 제안하고 시뮬레이션과 실험을 통해 제안된 모델의 타당성을 입증한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.259-267
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• 2000

This paper presents the method for an estimation of discharge current waveshapes in short gap discharge by radiated electromagnetic fields. The method of current waveform estimation described is using the one antenna method(single field method) and two antennal method(complex field method) with a measured electric or magnetic fields at given field point by a time domain antenna. In order to verify the availability of the estimation theory, the discharge current waveshape estimation was performed by one and two antenna methods using the measured electric fields of Wilson & Ma and compared with experiments.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.83-83
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• 2022

여러 분야의 연구자들이 지진해일의 위험에 대한 경각심을 가지고, 지진해일의 발생, 전파 그리고 수리현상을 해석하기 위해 많은 노력을 기울이고 있다. 해안지역에서 직접적인 피해를 입히는 지진해일의 충격파, 처오름, 월파, 침수 등에 관한 연구에 유사한 파형 특성을 가진 고립파를 많이 사용한다. 고립파는 비선형성과 분산이 균형을 이루는 가정에서 Korteweg-de Vries(KdV) 방정식을 만족하는 안정적인 이론파이다. 고립파의 파형분포는 수심에 의해 결정되고, 일정 수심 이상에서는 지진해일을 대신해 사용할 수 있다. 그러나 수심이 낮은 천해에서는 주기와 파장이 비현실적으로 짧아짐으로 지진해일을 대신하기에는 무리가 있다. 본 연구에서는 지진해일의 처오름 특성을 분석하기 위한 1:20 불투과성 경사면이 포함된 수치파동수조를 구성한다. 먼저, 일본 NOWPHAS(Nationwide Ocean Wave information network for Ports and HArbourS)의 관측자료를 이용하여 2011 동일본 지진해일과 고립파의 파형분포를 비교한다. 그리고 다양한 파형의 지진해일 생성할 수 있게 개발된 조파방법을 수치파동수조에 도입하여 수치해석을 수행한다. 수치해석결과, 지진해일의 처오름 높이가 고립파에 비해 최대 1.8배, 최소 1.13배, 평균 1.56배 증가한다.