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등가 자기모델과 매질민감도법을 이용한 강자성체 판에 분포하는 영구자화에 기인한 자기장 신호분석
정기우(Gi-Woo Jeung),김동욱(Dong-Wook Kim),김동훈(Dong-Hun Kim),양창섭(Chang-Seob Yang),정현주(Hyun-Ju Chung) 한국자기학회 2010 韓國磁氣學會誌 Vol.20 No.3
For predicting magnetic signals due to the remanent magnetization distributed on a ferromagnetic ship hull, this paper presents an efficient methodology for solving inverse problems, where the material sensitivity analysis based on the continuum mechanics is combined with the equivalent magnetic models. To achieve this, the 3D magnetic charge model and the magnetic dipole moment model are introduced and material sensitivity formulae applicable to each equivalent model are derived. The formulae offer the firstorder gradient information of an objective function with respect to the variation of the magnetic charge or magnetic dipole and so an optimal solution can be easily obtained regardless of the number of design variables. To validate the proposed method, the numerical results are comparison with the real measurements of a mock-up model.
부드러운 경계 위상 최적설계기법을 이용한 유전체 형상 및 위상 최적설계
정기우(Gi-Woo Jeung),최낙선(Nak-Sun Choi),김남경(Nam-Kyung Kim),김동훈(Dong-Hun Kim) 대한전기학회 2009 전기학회논문지 Vol.58 No.10
This paper deals with a new methodology for topology optimization in which the topology of the design domain may change during the shape optimization process. To achieve this, the concept of the topological gradient is introduced to compute the sensitivity of an objective function when a small hole is drilled in the domain. Based on shape and topological sensitivity values, the shape and topology of the design domain may be simultaneously changed during design iterations if necessary. To verify the advantages and also to facilitate understanding of the method itself, two electrostatic design problems have been tested by using 2D finite element analysis: the first is the inverse problem of a simple dielectric model and the second is the rotor design of a MEMS actuator.
분전반 모선에 의해 발생되는 극저주파 자기장 저감을 위한 차폐판 최적 설계
鄭起宇(Gi-Woo Jeung),崔洛善(Nak-Sun Choi),金東勳(Dong-Hun Kim),張樂元(Nakwon Jang),李東映(Dong-Young Lee) 대한전기학회 2009 전기학회논문지 Vol.58 No.1
This paper deals with the optimal design of a shield plate in order to minimize Extremely-Low-Frequency(ELF) magnetic fields generated from three-phase bus bars. Combining an evolutionary strategy with a 3D finite element analysis tool, the main dimensions of the shield plate are sought out. The optimization procedure consists of two separated design stages to take into account all foreseen structures of the plate. In the first stage, the basic dimensions of the plate are optimized including the distance between the plate and the bus bars. Then the usefulness of the additional structures such as a slit and fillet is investigated in the second stage. Finally the optimum design of the shield plate is suggested from the viewpoint of the shielding effectiveness and manufacturing cost.
전자파의 집중도를 이용한 바이모달 트램의 전자파 차폐 성능 분석
최낙선(Nak-Sun Choi),정기우(Gi-Woo Jeung),김남경(Nam-Kyung Kim),송명곤(Myung Kon Song),이강원(Kang-Won Lee),목재균(Jai-Kyun Mok),김동훈(Dong-Hun Kim) 대한전기학회 2011 전기학회논문지 Vol.60 No.7
In this paper, the electromagnetic shielding performance of a BiMODAL Tram is investigated by means of an electromagnetic analysis tool, called HFSS. For the purposed of doing this, first, three-dimensional finite element modeling for the tram including electronic devices and engine room is carried out. Then, for quantitatively assessing the electromagnetic shielding performance of the tram’s body, concentration indexes for electric field magnitude and time-average stored electric energy are introduced. From numerical results, it is inferred that the tram’s body can protect the electronic devices and engine room against external electromagnetic waves from 30 ㎒ to 100 ㎒.
최낙선(Nak-Sun Choi),정기우(Gi-Woo Jeung),김동욱(Dong-Wook Kim),양창섭(Chang-Seop Yang),정현주(Hyun-Ju Jun),김동훈(Dong-Hun Kim) 대한전기학회 2012 전기학회논문지 Vol.61 No.10
This paper analyzes re-degaussing performances of various breakdown conditions of degaussing coils in a ship to reduce underwater magnetic field anomaly due to the hull magnetization induced under the Earth’s magnetic field. To achieve this, first, it is implemented to optimize degaussing coil currents by a magnetomotive force sensitivity formula combined with the coil effects. The re-degaussing processes are then executed when a breakdown occurs in degaussing coils, one by one. Finally, the re-degaussing performances are examined with the results of normal degaussing and coil breakdown conditions.
2차 전자방출 효과를 고려한 기체방전의 과도상태 유한요소해석
김남경(Nam-Kyung Kim),정기우(Gi-Woo Jeung),최낙선(Nak-Sun Choi),이세희(Se-Hee Lee),김동훈(Dong-Hun Kim) 대한전기학회 2010 전기학회논문지 Vol.59 No.7
To analyze the gas discharge phenomena in parallel-plane electrodes, the fully coupled finite element method (FEM) considering secondary electron emission effects in discharge column was adopted in this paper. Two coupled equations of the hydrodynamic diffusion-drift equations for three carriers and the Poisson’s equation for electric scalar potential should be solved as a system equation. The proposed method including two secondary electron processes of the photoemission and background ionization has been successfully applied to evaluating the breakdown voltage in parallel-plane electrodes and is verified by comparing its numerical results with the experimental ones. From the obtained results, it is inferred that the proposed numerical scheme will be useful for predicting and understanding streamer transient phenomena.
정밀 3차원 수중 운동체의 전자기파 전파 특성 해석 기법
김동욱(Dong-Wook Kim),정기우(Gi-Woo Jeung),양창섭(Chang-Seob Yang),정현주(Hyun-Ju Chung),김동훈(Dong-Hun Kim) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
본 논문에서는 수중 운동체에 의한 전자기파 전파 특성을 해석하고자 유한요소법을 기반으로 하는 상용 전자기 해석 도구를 사용하여 정밀 3차원 수중 전자기파 전파 특성 해석 기법을 제시하였다. 이를 위하여 3차원 수중 운동체 운용 환경을 구축하였고 전자기 해석의 효율성을 높이고자 Surface Impedance Boundary Condition(SIBC) 기법을 적용하였다. 제안된 해석 기법의 타당성을 검증하기 위하여 동일 조건의 영상자기모멘트법과 비교를 통하여 신뢰성과 정확성을 검증하였다.
일차근사신뢰도법을 이용한 신뢰도 기반 최적설계 기법 개발
김동욱(Dong-Wook Kim),정기우(Gi-Woo Jeung),정상식(Sang Sik Jung),성영화(Young Hwa Sung),김동훈(Dong-Hun Kim) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.10
본 논문에서는 제품의 설계과정에서 발생하는 불확실 요소를 고려하기 위하여 확률정보를 이용한 신뢰도 기반 최적설계 기법을 제시하였다. 일차근사신뢰도법(first order reliability method : FORM)을 사용하여 신뢰도 지수를 계산하여 설계에 적용하였다. 제안된 설계 기법의 타당성을 검증하기 위해 정확성이 높은 몬테카를로 수치모사기법(Monte Carlo simulation method : MCS)을 통하여 제안된 기법의 적합성을 검증하였다.
주파수 영역에서 연속체 민감도법을 이용한 유전체 저대역 필터 최적 설계
최낙선(Nak-Sun Choi),정기우(Gi-Woo Jeung),김남경(Nam-Kyung Kim),변진규(Jin-Kyu Byun),김동훈(Dong-Hun Kim) 대한전기학회 2010 전기학회논문지 Vol.59 No.8
This paper presents a new methodology for designing a dielectric waveguide filter with the cutoff frequency of 2.4 ㎓ based on the continuum design sensitivity analysis. An analytical sensitivity formula is derived in frequency domain and then unified program architecture applicable to the optimal design of high-frequency devices is proposed. A three-dimensional dielectric resonator used in waveguide filters has been tested to illustrate the validity of the proposed method.