• Journal of Magnetics
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• v.22 no.1
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• pp.85-92
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• 2017

This research is proposed with the efficient searching method of deperming protocol for magnetic silence. The deperming protocol has been changed depending on the initial magnetic field, the final magnetic field, and the shot number, so deciding parameter is highly important. Therefore, in this paper, the value of the initial magnetic field is supposed to be fixed to that of the saturation field, and excluding the initial magnetic field in the variable, the deperming protocol has been analyzed depending on the final magnetic field and the change of the shot number. In the result of this experiment, the final magnetic field gets high performance to the reverse of the direction of the initial magnetization, and it is resulted that the shot number inverse proportion to the size of the final magnetic field.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1693-1699
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• 2011

In this paper, for magnetic silence technology of naval vessel, is to make lab deperm system and to evaluate the deperm capacity of naval vessel regarding deperm protocol. Initial permanent magnetic field of naval vessel is magnetized before deperm, having the magnetic field of the same size, to evaluate the deperm capacity regarding a variety of deperm protocol for experimental reliability growth. Current dead time effect of deperm protocol is measured at the different initial current, which are 8A, 6A and 4A respectively. Furthermore, the experiment under the same condition except changing duty cycle into 50% is carried out. As a result, it is possible to compare the six different experiment outcomes. The result shows that the experiment with dead time improve the deperm capacity more than 48.51 percent comparing to the case without dead time.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.24-28
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• 2009

In this study, we investigated whether the anhysteretic demagnetization process would be applicable to remove a complicated magnetization of a steel tube as a part of the experimental earlier study for a deperming of naval vessel. The magnetic tube used in this study was a 10cm-long and 1cm-diameter steel tube, and magnetized with a E-shape ferrite core to form a nonuniform magnetization in it. In the anhysteretic demagnetization process, a dc magnetic field applied along the longitudinal direction of the tube decreased from ${\pm}$3kA/m to zero-field with the step of ${\pm}$300A/m. At the same time, an ac bias magnetic field with the frequency of 60Hz and the field intensity of 300A/m was excited along the circumstantial direction of the tube. It was found that the anhysteretic process was useful to demagnetize a small-object like a steel tube from the experimental results showing the residual magnetization reduced over 90%.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1065-1066
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• 2011

본 논문에서는 함정의 피탐지 성능 개선을 위한 기초 연구로 dead time 적용시 탈자 프로토콜 변화에 따른 탈자 성능 분석에 관한 연구를 하였다. 함정의 재질은 SM45C로 원통의 형태이다. 자기장 측정에 사용한 자기센서는 영국 Bartington Instruments사의 MAG-03MCB70(Three-Axis Fluxgate Magnetometer)을 사용하였으며, inter-cardinal run 방법을 이용하여 유도자기장과 영구자기장을 분리하였다. Anhyteretic deperm 프로토콜을 적용하여 탈자를 진행하였고 전류의 지속시간이 증가하는 경우에 비하여 dead time을 적용하였을 경우 탈자 성능이 향상된 결과를 얻을 수 있었다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.700-701
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• 2015

본 논문은 함정 피탐지 성능 개선을 위하여 함정의 효율적인 탈자 프로토콜 탐색 기법에 관한 연구를 하였다. 탈자 프로토콜은 정해진 장비와 시간내에서 영구자기장 성분을 최소화 해야하는 방법으로써 본 논문에서는 탈자 초기 전류와 탈자 종료 전류의 자화 방향을 이용하여 최적의 탈자 프로토콜을 탐색하는 기법에 대하여 연구하였다. 실험을 위해서 탈자 처리 시설을 제작하였으며, 실험의 오차를 줄이기 위하여 지구자기장을 보상하는 3축방향의 코일을 이용하였다. 실험 결과 초기 전류와 종료 전류의 자화방향을 이용하여 최적의 탈자 프로토콜을 탐색할 수 있었다.

• Journal of Magnetics
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• v.18 no.3
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• pp.326-330
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• 2013

Magnetic treatment of surface vessels and submarines (Deperm) is required to camouflage them against magnetic detection from enemy marine force. So far, deperm has been accomplished by applying an alternating magnetic field of which amplitude decreases linearly. However, the reduction of the residual flux density in the direction of magnetic field is not linear in the case of the linear protocol, since the ferromagnetic material used to construct a surface vessel, mainly Fe-C, shows a nonlinear behavior in an alternating magnetic field. This is one of main reasons to make an ordinary deperm protocol inefficient. In this paper, we propose the exponential deperming protocol and compare the exponential protocol to conventional linear protocol within the framework of deperm performance. We found out that step number could be reduced in the exponential protocol compare with in the linear protocol, because the larger numbers of deperm steps are dedicated in the irreversible domain process region on the magnetic hysteresis.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.3
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• pp.359-363
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• 2011

An orthogonal magnetic field is often used for a military vessel in the deperm process such as Flash D deperm protocol and Anhysteretic deperm protocol. The effect of the orthogonal magnetic field on a deperm performance was investigated for a sample with strain-induced magnetization and field-induced magnetization given to different direction. A 70mm wide, 110mm long and 0.25mm thick rectangular steel plate was bent to have U-shape and to generate a strong strain on the bottom region of U-shaped steel plate. Field-induced magnetization was attached by NdFeB permanent magnet. Demagnetization was performed by applying magnetic field with a step decrement from the first field(the first shot) under the action of DC bias field.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.445-450
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• 2016

This paper studied on the influence of naval vessel shape on vertical magnetic field after the vessel was demagnetized. The triangular shape, the rectangular shape and circular shape were adaped from vessel's structual drawings. Magneto-static FEM analysis was performed to obtain the iduced magnetic field due to earth magnetic field for those shapes. During demagnetization process, magnetic field of residual magnetization was observed. The holizontal and vertical magnetic field were calculated depending on vertical bias magnetic field through magnetc component seperation. To demagnetize naval vessel ship, demagnetizing coils shoud be wound more finely in the vow and stern of the ship than it should be in the mid-part of the ship.