http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
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>
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.
Kang Jin Lee,Giwoo Jeung,Chang-Seob Yang,Hyun-Ju Chung,Joon Goo Park,Heung-Geun Kim,Dong-Hun Kim IEEE 2009 IEEE transactions on magnetics Vol.45 No.3
<P>This paper deals with the numerical implementation of the material sensitivity analysis, which is used to efficiently determine an optimal magnetization distribution on a ship hull. A material sensitivity formula for the forward problem formulated in terms of the equivalent magnetic charge method is analytically derived. Then, the components of the adjoint system including the magnetic pseudo-source are thoroughly investigated in order to obtain the first-order gradient information of an objective function with respect to the magnetic charge. The formula facilitates applying the deterministic approach to searching for an optimal charge distribution and also it yields stable and reliable solutions to magnetostatic inverse problems in three dimensions. Finally, the proposed method has been successfully applied to a scale model ship and the predicted results on the underwater field disturbance due to the remanent magnetization of the hull have been compared to real measurements.</P>
Nak-Sun Choi,Giwoo Jeung,Sang Sik Jung,Chang-Seob Yang,Hyun-Ju Chung,Dong-Hun Kim IEEE 2012 IEEE transactions on magnetics Vol.48 No.2
<P>This paper presents an efficient methodology for optimizing degaussing coil currents in ships to minimize the anomaly of underwater magnetic fields due to the hull magnetization induced under the Earth's magnetic field. To achieve this, first, the shielding effect of the hull on the underwater fields is thoroughly examined. Then, for a fast search of optimum degaussing currents, a sensitivity formula of an objective function with respect to the magnetomotive force is adopted. The feature of the proposed method is that it does not require any numerical field analyses to assess an objective function during optimization process providing experimental field data for each coil are given. The validity and effectiveness of the method has been tested with a model ship.</P>
Nak-Sun Choi,Giwoo Jeung,Chang-Seob Yang,Hyun-Ju Chung,Dong-Hun Kim IEEE 2012 IEEE transactions on applied superconductivity Vol.22 No.3
<P>This paper presents an efficient methodology for optimizing degaussing coil currents in a ship with ferromagnetic hull to minimize magnetic field anomaly underwater. For fast search for an optimum, a magnetomotive force sensitivity formula is adopted. The feature of the method does not require any numerical field analyses to assess an objective function during optimization process providing experimental field data on each coil with respect to the reference magnetomotive force are given. Especially, the shielding effect of the hull on degaussing fields is thoroughly investigated. The validity of the proposed method has been tested with a model ship.</P>