• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.2
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• pp.197-203
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• 2001

Micro-defects induced by design and production failure or working environments are known as the cause of SCC(Stress Corrosion Cracking) in aged structures. Therefore, the evaluation of structural integrity based on micro-cracks is required not only a manufacturing step but also in-service term. So we introduce a new nondestructive inspection method using the magneto-optical film to detect micro-cracks. The method has some advantage such as high testing speed, real time data acquistion and the possibility of remote sensing by using of a magneto-optical film that takes advantage of the change of magnetic domains and domain walls. This paper introduces the concept of the new nondestructive inspection method using the magneto-optical film, also proves the possibility of this method as a remote testing system under oscillating load considering application on real fields by applying the method to four types of specimens.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.253-255
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• 2007

비파괴검사방식 중 자기누설 탐상법(Magnetic Flux Leakage, MFL)은 선박의 표면이나 인간의 손이 닿지 않는 곳의 부식상태를 파악하기에 적합한 방법이다. 실시간 모니터링 가능한 자기누설 탐상 시스템은 빠르고 정확한 검사가 요구되는 대형 선박의 교면 검사에서 유용하게 사용될 것으로 예상된다. 본 논문에서는 스파이더형의 소형 비파괴 검사기를 실시간 모니터링이 가능하도록 제작하였다.

• Journal of Satellite, Information and Communications
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• v.9 no.1
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• pp.90-96
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• 2014

This paper is about increasing transfer efficiency of wireless power transmission. The new method is proposed to detect the alignment of transmitter and receiver of wireless charger and so smart phone can display the position of wireless charging receiver on its LCD panel for the maximum charging efficiency. The previous method is only to show the transfer efficiency, but this method is to show not only the efficiency but also coordinates of receiver. The apparatus of the wireless charger is based on WPC(Wireless Power Consortium) standard and has planar air coil combined with magnet shield in Tx and Rx device so that the leakage flux is minimized on condition of under hundreds of kHz operating frequency. In this paper, it's showed that relation of magnet field and distance of each coils can be linearized and position information of Tx and Rx device is calculated thru trigonometry. Through the experiment, the obstacles of linearity are discovered and also showed that it can be optimized. and so the presented method is suitable for alignment detection method of Tx and Rx device in WPC wireless charger.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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• pp.508-514
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• 2004

A fluxgate magnetic sensor consists of a solenoid excitation coil, pick-up coil, and magnetic core. We presents the effect of magnetic core shape in a micromachined fluxgate sensor. To observe the performance of fluxgate sensor with magnetic core side width and gap, side width of 125 ${\mu}{\textrm}{m}$, 250 ${\mu}{\textrm}{m}$, and 500 ${\mu}{\textrm}{m}$ were designed in a rectangular-ring shaped core and the gaps of 0 ${\mu}{\textrm}{m}$, 50 ${\mu}{\textrm}{m}$, and 100 ${\mu}{\textrm}{m}$ were also fabricated in a racetrack shaped core. The solenoid coils and magnetic core were separated by benzocyclobutane(BCB) which had high insulation and good planarization characters. Copper coil patterns of 10 ${\mu}{\textrm}{m}$ width and 6${\mu}{\textrm}{m}$ thickness were electroplated on Ti(300 $\AA$) / Cu(1500 $\AA$) seed layers. 3 ${\mu}{\textrm}{m}$ thick N $i_{0.8}$F $e_{0.2.}$(permalloy) film for the magnetic core was also electroplated under 2000 gauss to induce the magnetic anisotropy. The magnetic core had the high DC effective permeability of ∼1,300 and coercive field of ∼0.1 Oe. Because the magnetic cores of 500 ${\mu}{\textrm}{m}$ side width and 0 gap had a low magnetic flux leakage, high sensitivity of ∼350 V/T were measured at excitation condition of 3 $V_{P-P}$ and 2 MHz square wave. The power consumption of ∼14 ㎽ was measured. The fabricated fluxgate sensor had the very small actual size of 3.0${\times}$1.7 $\textrm{mm}^2$. When two fluxgates were perpendicularly aligned in terrestrial field, their two-axis output signals were very useful to commercialize an electronic azimuth compass for the portable navigation system.m.m.m.

• The Korean Journal of Nuclear Medicine
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• v.28 no.2
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• pp.227-233
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• 1994

Irradiation of 20mg of natural $Dy(NO_3)_3$ in a neutron flux of $2{\times}10^{13}n/cm^2$ sec for 4 hours gave 5.76 Ci of $^{165}Dy$(specific activity, 610mCi/mg Dy) with high radionuclidic purity (>99.9 %). $^{165}Dy-MA$ was prepared in a quantitative yield by reacting the aqueous solution of $^{165}Dy(NO_3)_3$ with sodium borohydride solution in 0.2N NaOH. Coulter particle analyzer exhibited mean particle size of $2.6{\mu}m$ (range $1{\sim}6{\mu}m$), Even though the $^{165}Dy-MA$ suspension in saline was stored at $37^{\circ}C$ for 24 hours or autoclaved at $121^{\circ}C$ for 30minutes, there was no significant change in particle size and leakage problem indicating the prepared $^{165}Dy-MA$ is sufficiently stable. In-vivo retention studies were carried out by administering $^{165}Dy-MA$ into the knee joint space of normal rabbits. Gamma camera analysis showed high retention in joint space of normal rabbits. Gamma camera analysis showed high retention in joint space even at 24 hours after administration (> 99.9%). The ease with which the $^{165}Dy-MA$ can be made in the narrow size range and their high invitro and vivo stability make them attractive agents for radiation synovectomy.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.483-489
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• 2016

The typical methods used for inspecting ferromagnetic pipes include the ultrasonic testing (UT) contact method and the following non-contact methods: magnetic flux leakage (MFL), electromagnetic acoustic transducers (EMAT), and remote field eddy current testing (RFECT). Among these methods, the RFECT method has the advantage of being able to establish a system smaller than the diameter of a pipe. However, the method has several disadvantages as well, including different sensitivities and difficult-to-repair coil sensors which comprise its array system. Therefore, a giant magneto-resistance (GMR) sensor was applied to address these issues. The GMR sensor is small, easy to replace, and has uniform sensitivity. In this experiment, the GMR sensor was used to measure remote field and defect signal characteristics (in the axial and radial directions) in a ferromagnetic pipe. These characteristics were measured in an effort to investigate standard defects at changing depths within a pipe. The results show that the experiment successfully demonstrated the applicability of the GMR sensor to RFECT signal detection in ferromagnetic pipe.

• Journal of the Korean Magnetics Society
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• v.23 no.2
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• pp.68-76
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• 2013

Currently, wireless power transmission technology based on magnetic induction was employed in battery charger for smart phone application. The system consists of wireless power transmitter in base station and receiver in smart phone. Size and thickness of receiver was strictly limited in the newest smart phone. In order to achieve high efficiency of a tiny small wireless power receiver module, sub-millimeter thick electromagnetic wave shielding sheet having high permeability and Q was essential component. It was found that magnetic field from transmitter to receiver can be intensified by sufficient shielding cause to minimize leakage magnetic flux by those magnetic properties. This leads to high efficiency of wireless power transmission and protects crucial integrated circuit of main board from electromagnetic noise. The important soft magnetic materials were introduced and summarized for the current small-power wireless power charger and NFC application and mid-power home appliance and high-power automotive application in the near future.

• Nuclear Engineering and Technology
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• v.47 no.3
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• pp.380-387
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• 2015

A lead slowing-down spectrometer (LSDS) system is a promising nondestructive assay technique that enables a quantitative measurement of the isotopic contents of major fissile isotopes in spent nuclear fuel and its pyroprocessing counterparts, such as $^{235}U$, $^{239}Pu$, $^{241}Pu$, and, potentially, minor actinides. The LSDS system currently under development at the Korea Atomic Energy Research Institute (Daejeon, Korea) is planned to utilize a high-flux ($>10^{12}n/cm^2{\cdot}s$) neutron source comprised of a high-energy (30 MeV)/high-current (~2 A) electron beam and a heavy metal target, which results in a very intense and complex radiation field for the facility, thus demanding structural shielding to guarantee the safety. Optimization of the structural shielding design was conducted using MCNPX for neutron dose rate evaluation of several representative hypothetical designs. In order to satisfy the construction cost and neutron attenuation capability of the facility, while simultaneously achieving the aimed dose rate limit (< $0.06{\mu}Sv/h$), a few shielding materials [high-density polyethylene (HDPE)eBorax, $B_4C$, and $Li_2CO_3$] were considered for the main neutron absorber layer, which is encapsulated within the double-sided concrete wall. The MCNP simulation indicated that HDPE-Borax is the most efficient among the aforementioned candidate materials, and the combined thickness of the shielding layers should exceed 100 cm to satisfy the dose limit on the outside surface of the shielding wall of the facility when limiting the thickness of the HDPE-Borax intermediate layer to below 5 cm. However, the shielding wall must include the instrumentation and installation holes for the LSDS system. The radiation leakage through the holes was substantially mitigated by adopting a zigzag-shape with concrete covers on both sides. The suggested optimized design of the shielding structure satisfies the dose rate limit and can be used for the construction of a facility in the near future.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.6
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• pp.542-553
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• 2011

A magnetic cable that can safely deliver high frequency AC electric power in flammable or sensitive workplaces by preventing from arcs and electric shocks is firstly proposed in this paper. Several new magnetic cable structures with magnetic shields, which are composed of such cancel coil, cancel copper plate, and cancel copper pipe, were compactly implemented by considering and analyzing fringe field and thus the parallel leakage flux is drastically reduced. The output power and efficiency of a prototype magnetic cable with 1.5 m length and 5 cm gap were measured as 353.8W and 68%, where the source current and switching frequency were 10 $A_{rms}$ and 20 kHz, respectively. The proposed magnetic cables are fully analyzed and verified by finite-element method (FEM) simulations and experiments. The results are in a good agreement.

• Membrane Journal
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• v.21 no.4
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• pp.321-328
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• 2011

$PrBa_{0.9}Sr_{0.1}Co_2O_{5+{\delta}}$ oxide was synthesized by soild state reaction method. Dense ceramic membrane was prepared using as-prepared powder by pressing and sintering at $1250^{\circ}C$. XRD result of membrane showed double perovskite structure. Leakage and oxygen permeation test were conducted on the membrane sealed by pyrex ring as a sealing material. Oxygen permeation was measured in the temperature range from 850 to $950^{\circ}C$. The oxygen flux of $PrBa_{0.9}Sr_{0.1}Co_2O_{5+{\delta}}$ membrane was increased with the temperature from 0.15 to $0.32mL/cm^2{\cdot}min$.