• 대한조선학회지
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• 제18권1호
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• pp.9-18
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• 1981

The wave-pattern analysis has been one of important research tools in the towing tank, and applied for hull form design. The longitudinal-cut method of Newman and Sharma is adopted in KRIS deep towing tank. Instrumentations and data acquisition systems are developed for that. Local effects and truncation effects are estimated by using calculated wave patterns of simple source distributions. Wigley model of 2m is used to check the accuracy of the whole system. Cut positions and truncation points are changed to investigate characteristics of the wave-pattern analysis. Coefficients of wave-pattern resistance are low-estimated in comparison with those of Maruo and Ikehata. The general quality of the system is very good, but some more efforts to increase the accuracy are required. Two full-form models(one basic form, the other with bulbous bow) are tested to show high application-possibilities of the wave-pattern analysis for the hull form design.

• Ocean Systems Engineering
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• 제5권3호
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• pp.139-160
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• 2015

The global performance of the 5MW OC4 semisubmersible floating wind turbine in random waves was numerically simulated by using the turbine-floater-mooring fully coupled and time-domain dynamic analysis program FAST-CHARM3D. There have been many papers regarding floating offshore wind turbines but the effects of second-order wave-body interactions on their global performance have rarely been studied. The second-order wave forces are actually small compared to the first-order wave forces, but its effect cannot be ignored when the natural frequencies of a floating system are outside the wave-frequency range. In the case of semi-submersible platform, second-order difference-frequency wave-diffraction forces and moments become important since surge/sway and pitch/roll natural frequencies are lower than those of typical incident waves. The computational effort related to the full second-order diffraction calculation is typically very heavy, so in many cases, the simplified approach called Newman's approximation or first-order-wave-force-only are used. However, it needs to be justified against more complete solutions with full QTF (quadratic transfer function), which is a main subject of the present study. The numerically simulated results for the 5MW OC4 semisubmersible floating wind turbine by FAST-CHARM3D are also extensively compared with the DeepCWind model test results by Technip/NREL/UMaine. The predicted motions and mooring tensions for two white-noise input-wave spectra agree well against the measure values. In this paper, the numerical static-offset and free-decay tests are also conducted to verify the system stiffness, damping, and natural frequencies against the experimental results. They also agree well to verify that the dynamic system modeling is correct to the details. The performance of the simplified approaches instead of using the full QTF are also tested.

• Journal of electromagnetic engineering and science
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• 제2권2호
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• pp.81-86
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• 2002

This paper presents the full wave analysis of microwave circuits with nonlinear device using the finite difference time domain method. The equivalent current source is used to model nonlinear device and all the electric field components at the nonlinear device are updated by FDTD algorithm. The currents and voltages of nonlinear device are calculated by the state equations and iteration method. To validate the proposed method, the S-parameters of NEC NE72089 MESFET in various conditions are analyzed and the results are compared with those of the ADS. The proposed method is applied to the analysis of a microwave amplifier, which includes NEC NE72089 MESFET. The analysis results obtained by the present method show good agreement with those of the ADS.

• 한국해안·해양공학회논문집
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• 제20권4호
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• pp.401-412
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• 2008

본 연구에서는 3차원수치파동수로내에 쇄파후의 파랑이 대형연직원주구조물에 작용할 때 작용파력과 구조물에 의한 파랑변형을 수치적으로 해석한다. 수치해석법으로 파랑과 구조물과의 비선형상호간섭에 따른 쇄파현상을 포함하는 복잡한 자유수면의 거동특성을 고정도로 해석할 수 있는 3차원Navier-Stokes운동방정식과 자유수면추적에 3차원VOF(Volume Of Fluid)법을 결합한 강비선형해석법을 적용한다. 3차원파동장내에서 해저는 쇄파를 상대적으로 쉽게 발생시킬 수 있는 경사스텝의 해저(변수심의 경사수역과 일정수심역으로 구성)로 이루어진 경우를 고려하며, 파고의 변화에 따라 쇄파가 경사수역 또는 일정수심역에서 발생하여 일정수심역의 대형연직원주구조물에는 쇄파후의 파랑만이 작용하는 경우로 한정한다. 구조물의 위치 및 입사파랑의 파고변화가 구조물에 작용하는 파력 및 파랑변형에 미치는 특성을 쇄파전후의 파랑을 중심으로 검토하고, 쇄파후 파랑의 전파에 따른 파랑에너지의 변화와 구조물에 작용하는 파력특성과를 연관시켜 논의하여 3차원파동장에서 파랑과 구조물과의 강비선형간섭현상의 특성을 규명한다.

• 한국전자파학회논문지
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• 제17권2호
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• pp.148-151
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• 2006

PCB에서의 전자파 간섭원으로 DC power-bus의 공진이 자주 지목된다. 이것은 결국, 전도성 또는 전파 방사의 형태로, 하나 또는 인접한 시스템에서 디지털 SI를 저하시키게 된다. 따라서 PCB의 방사 문제를 파악하는 것은 중요하므로, 본 논문은 DC power-bus 공진 모드에 대한 방사를 면밀히 살펴본다. 엄밀한 주파수 영역 해석법을 이용하여 임피던스와 방사 전계를 구하고, 이는 물리와 전자파 해석 모의시험에 의해 타당성이 검토된다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.149-152
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• 2005

The DC power-bus' resonance is frequently attributed to EMI sources in the PCBs. Subsequently, it will ruin the digital signal integrity within one system or between adjacent systems in the form of conducted or radiated emission. Hence, since it is of importance to examine the PCB's emission, this paper sheds a light on the radiated emission from the power-bus with regards to its resonance modes. A full-wave analysis method is used to calculate the impedance and radiated electric fields and is validated by physics and an EM analysis tool.

• 전기학회논문지
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• 제59권1호
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• pp.116-119
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• 2010

In this work, we presented the characterization of 3 dB branch type directional couplers by using High-Tc superconducting thin films. To do this, we deposited YBCO superconducting thin films on MgO substrates by using rf-magnetron sputtering techniques. The designed center frequency was 408 MHz and the designed passband was 20 MHz. Also we designed 3 dB Power difference and $90^{\circ}$ of phase difference between port 3 and port 4. The even and odd mode analysis were used to characterize our directional couplers and em Sonnet (full wave analysis program) was utilized to the optimum design. We reported experimental results, including a center frequency, passband, half power characteristics and phase differences. We confirmed that experimental results were in good agreements with characterization by using full wave analysis program.

• 한국전자파학회논문지
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• 제24권3호
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• pp.337-347
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• 2013

고 출력 전자기장(HPEM)의 영향은 시스템의 오작동, 고장 및 장비의 심각한 훼손을 야기시킬 수 있다. 따라서 업무 환경이 각종 전자 장비들로 대체 및 구성되어 가는 요즘, 인명과 재산을 보호하기 위해 고 출력 전자장에 대한 대책 연구가 필요하다. 이에 반해, 위상학적 해석 방법(topological analysis)은 해석 대상 구조에 대해 전자장의 이동 경로와 해석을 원하는 지점을 단순화시켜 해석하며, 대표적으로 Baum-Liu-Tesche(BLT) 방정식 기반의 해석법과 구역 설정(zoning)에 기반한 해석 방법 그리고 확률에 기초하고 있는 Power Balance Method(PWB)를 연동시킴으로써 효율적으로 해석할 수 있다. PWB 방법은 기존의 EM 시뮬레이션 방법의 비효율성을 극복하기 위한 하나의 대안으로 제시된 방법이다. 본 논문에서는 기존의 위상학적 해석 방법에 적용되는 기초기술을 바탕으로 대형 구조에 적용될 수 있는 전자파 해석 방법을 제안한다. 그리고 최종적으로 PWB 방법과 full wave analysis 방법을 비교함으로써 PWB 방법의 장점과 이 방법의 도입 필요성에 대해 제안한다.

• Coupled systems mechanics
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• 제1권2호
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• pp.183-204
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• 2012

A method for the analysis of wave scattering in 3-D elastic full space is developed by means of the coupled boundary-volume integral equation, which takes into account the effects of both the boundary of inclusions and the uctuation of the wave field. The wavenumber domain formulation is used to construct the Krylov subspace by means of FFT. In order to achieve the wavenumber domain formulation, the boundary-volume integral equation is transformed into the volume integral equation. The formulation is also focused on this transform and its numerical implementation. Several numerical results clarify the accuracy and effectiveness of the present method for scattering analysis.

• 대한조선학회논문집
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• 제40권3호
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• pp.22-28
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• 2003

In rough seas, bow-flare regions of the full ships (tanker and bulk carrier) are subiect to high impact pressures due to the on-coming breaking waves. And many ships suffer structural damages in that region, even though they were built under the bow structure strengthening rules of the ship classes. So, a new design method for bow-flare structure is highly required. In this paper, a new prediction method of the bow-flare impact pressure (in terms of equivalent static pressure) acting on the full ships' bow is presented. This method is based on the 6 full ships' damage analysis and the breaking wave impact mechanism. Calculation results of the bow-flare impact pressure and the shell plate thickness are shown and discussed. Through the example calculations, it was found that the present method is useful for the structure design of the full ships' bow.