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Giwoo Jeung,Nak-Sun Choi,Chang-Seob Yang,Hyun-Ju Chung,Dong-Hun Kim 한국자기학회 2014 Journal of Magnetics Vol.19 No.1
This paper proposes an indirect fault detection method for an onboard degaussing coil system, installed to reduce the underwater magnetic field from the ferromagnetic hull. The method utilizes underwater field signals measured at specific magnetic treatment facilities instead of using time-consuming numerical field solutions in a three-dimensional space. An equivalent magnetic charge model combined with a material sensitivity formula is adopted to predict fault coil locations. The purpose of the proposed method is to yield reliable data on the location and type of a coil breakdown even without information on individual degaussing coils, such as dimension, location and number of turns. Under several fault conditions, the method is tested with a model ship equipped with 20 degaussing coils.
Giwoo Jeung,Dong-Wook Kim,Young Hwa Sung,Heung-Geun Kim,Dong-Hun Kim 한국자기학회 2012 Journal of Magnetics Vol.17 No.1
A reliability-based optimization method for electromagnetic design is presented to take uncertainties of design parameters into account. The method can provide an optimal design satisfying a specified confidence level in the presence of uncertain parameters. To achieve the goal, the reliability index approach based on the firstorder reliability method is adopted to deal with probabilistic constraint functions and a double-loop optimization algorithm is implemented to obtain an optimum. The proposed method is applied to the TEAM Workshop Problem 22 and its accuracy and efficiency is verified with reference of Monte Carlo simulation results.
Giwoo Jeung,Chang-Seob Yang,Hyun-Ju Chung,Se-Hee Lee,Dong-Hun Kim IEEE 2009 IEEE transactions on magnetics Vol.45 No.10
<P>This paper presents an efficient methodology for determining the underwater field anomaly due to the remanent magnetization of a ferromagnetic ship hull by utilizing a magnetic dipole modeling technique combined with material sensitivity analysis. The complicated 3D structure of the hull is replaced with an equivalent magnetic dipole array placed in a 2D plane, of which the optimal dipole moment values will be easily sought out with the aid of material sensitivity analysis. To achieve this, a material sensitivity formula, which contains the first-order gradient information of an objective function with respect to the magnetic dipoles, is analytically derived by exploiting the augmented objective function and adjoint variable method. The proposed method leads to easy numerical implementation and also dramatically reducing system unknowns of the 3D inverse problem considered. Finally, the validity of the method has been tested with real measurements of a scale model ship as well as numerical results of our previous work, which adopted the magnetic charge method in conjunction with material sensitivity analysis.</P>
김기우(Giwoo Kim),장재덕(Jaeduk Jang) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_2
Lock-Up Clutches of Torque Convener in an automotive automatic transmission have been recently designed with a significant purpose of achieving a more fuel economy. In order to suppress torsional vibration of the engine torque. lock-up clutch has been also employed with damper composed with several springs. Due to the resonance, however. NVH problems occur in low speed driving condition. The torsional vibration analysis of the vehicle is investigated by the dynamic modeling using EASYS5®. In addition, its application to damper performance is also investigated This study provides useful information for optimum damper design.
[동력전달계부문] 3차원 유동해석을 이용한 자동변속기 토크 컨버터 설계
김기우(Giwoo Kim),장재덕(Jaeduk Jang) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_2
Automotive torque converters have recently been designed with a significant purpose of achieving a more efficient performance. In order to evaluate the change of the overall performance such as torque capacity and torque ratio, the complex circulating flow characteristics of the different torque converterst were investigated by three dimensional flow analysis using CFD code, STAR-CD. The experimental analysis is also performed to compare with computational results. In addition, It's design application to hydraulic performance is investigated. This study provides useful information for optimal design
Nam-Kyung Kim,Giwoo Jeung,Chang-Seob Yang,Hyun-Ju Chung,Dong-Hun Kim 한국자기학회 2011 Journal of Magnetics Vol.16 No.2
This paper presents a magnetization modeling method combined with material sensitivity information to identify the unknown magnetization distribution of a hull and improve the accuracy of the predicted fields. First, based on the magnetization modeling, the hull surface was divided into three-dimensional sheet elements, where the individual remanent magnetization was assumed to be constant. For a fast search of the optimum magnetization distribution on the hull, a material sensitivity formula containing the first-order gradient information of an objective function was combined with the magnetization modeling method. The feature of the proposed method is that it can provide a stable and accurate field solution, even in the vicinity of the hull. Finally, the validity of the method was tested using a scale model ship.