• Journal of Magnetics
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• 제2권2호
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• pp.58-66
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• 1997

Recently, artificially modulated magnetic multilayer materials, for examples giant magnetoresistant magnetic head materials and magneto-optic recording materials in the wavelength of a blue laser beam, attract great attention in the electronics industry due to their unique properties derived from the modulated multilayer structure. Since the multilayer structure as well as amorphous structure, is non-equilibrium state in terms of free energy, an assessment of the thermal staibility in the multilayer structure is crucially importnat both for basic research and applications. In this review paper, effective microscopic interdiffusion process in the two dimensional multilayer structure will be described in terms of steep concentration gradient effect, strain effect and magnetic transition effect.

• Journal of Magnetics
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• 제3권3호
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• pp.96-98
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• 1998

In this paper a structurally coupled and magnetically decoupled Ba-ferrite thin film medium is proposed to evade the superparamagnetic limit and reduce media noise. The proposed medium consists of ferrimagnetic Ba-ferrite nano-grains (< 10 nm) and a non-magnetic grain boundary material. Magnetic grains are crystallographically matched with the grain boundary material. Spherical or cubic shaped Ba-ferrite particle is also proposed for above 100 Kfci particulate recording application.

• Journal of Magnetics
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• 제16권3호
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• pp.276-280
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• 2011

This paper presents a non-destructive evaluation study on a radiator with cooling fins as a complex shaped specimen. Radiator structures are used in various heat exchangers, such as automobiles, air conditioners and refrigerators. An eddy current testing method, namely multi-frequency excitation and spectrogram method (MFES), was employed to detect a defect on the radiator tube surrounded by cooling fins. Overall, experimental results suggested that the influence of cooling fin is not as noticeable as that of the defect signals.

• Journal of Magnetics
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• 제4권4호
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• pp.128-130
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• 1999

We have measured the magnetization of Ni/Ag(Ni at %)/Ni (50$\AA$/30 $\AA$/50 $\AA$) trilayered films including Ni atoms inserted in non-magnetic Ag spacer. The magnetization as a function of applied field at 5 K and as a function of temperature at 100 Oe were investigated respectively using SQUID magnetometer. In these measurements peaks of magnetization at some critical temperatures were observed in all the samples. The antiferromagnetic coupling energy between neighboring Ni layers showed oscillatory behaviors according to the amounts of the Ni atoms inserted in Ag spacer. Loose spin model suggested by slonczews야 was used to explain such results.

• 한국자기학회지
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• 제5권5호
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• pp.395-398
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• 1995

For the core loss measurement under arbitrary waveform of magnetic induction, we have constructed a single sheet core loss measuring system which consists of yoke apparatus for single sheet of $10\;cm{\times}10\;cm$, arvitrary waveform synthesizer, B-feedback system, and two channel transient recorder. Using the constructed measuring system, we can measure core loss including higher harmonics up to 2 kHz. Core loss of non-oreinted electrical steel was increased exponentially when higher harmonic frequency was increased or amplitude of harmonic induction was increased.

• 한국자기학회지
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• 제1권2호
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• pp.89-93
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• 1991

회전축에 부착된 두 코아가 회전축의 토오크에 의하여 인장응력과 압축응력을 받게하여 두 코아의 최대자기유도 차이를 피측정량으로 하는 새로운 비접촉 토오크 센서를 제작하였다. 제작된 토오 크센서는 선형도가 1% 정도였으며 과도현상적인 토오크를 자화주파수와 동일한 10 kHz 의 샘플링주파수 로 측정 가능하게 하였다.

• The Journal of the Acoustical Society of Korea
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• 제16권1E호
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• pp.9-14
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• 1997

Check valves used in industrial and Nuclear Power Plant safety systems are susceptible to failure modes generally associated with wear of internal parts. Specifically, hinge pins, disc studs, pistons, and other mechanical parts may degrade over time, and in some cases, may which might produce a disabling event leading to plant or process shutdown. The primary diagnostic technique in the past has been to disassemble the valves. This procedure is costly, time consuming, and in the nuclear industry, it can lead to radiation exposure in some situations. Additionally repair and reassembly of a valve does not ensure proper operation. Non-intrusive diagnostic technologies including acoustics and magnetics with a digital signal analysis allow to evaluate check valve performance without a disassembly and is able to help the user detect degraded valve conditions.

• Journal of Magnetics
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• 제6권1호
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• pp.31-35
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• 2001

This paper describes the design method of a magnetic system to maximize the magnetic flux leakage (MFL) in a non-destructive testing (NDT) system. The defect signals in a MFL type NDT system mainly depend on the change of the magnetic leakage flux in the region of a defect. The characteristics of the B-H curves are analysed and a design method to define the operating point on B-H curves for maximum leakage is performed. The computed MFL signal by a nonlinear finite element method is verified by measurement using Hall sensors mounted on the 6 legs PIG, the traveling detector unit in gas pipe, in an 8 inch test tube with defects. The rhombic defects could be successfully identified from the defect signals.

• Journal of Magnetics
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• 제20권4호
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• pp.460-465
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• 2015

The paper presents methodologies and results concerning one- and two-dimensional numerical modeling of radio frequency oscillations in a coaxial transmission line fed with a short pulse of electric current. The line is partially filled with a ferrite material, magnetized longitudinally close to saturation. The 2D model has permitted analyzing, for the first time in the art, the spatial structure and dynamics of the wave field within the radially non-uniform cross-section planes of the non-linear and dispersive guiding structure. This opens ways for optimizing size parameters of the line and the extent to which it is filled with the ferromagnetic material, thus increasing the line's electric strength and intensity of the r.f. oscillations.

• Journal of Magnetics
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• 제20권4호
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• pp.360-365
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• 2015

Spatial distributions of magnetic flux density in a newly designed magnetized inductively coupled plasma (M-ICP) etcher were investigated. Radial and axial magnetic flux densities as well as the magnetic flux density on the center of the substrate holder were controllable by placing multiple circular coils around the etcher properly. The plasma density non-uniformity in M-ICP (25 Gauss) can be reduced (1.4%) compared to that in ICP (16.7%) when the neutral gas pressure was 0.67 Pa and a right-hand circularly polarized wave (R-wave) can be propagated in to the etcher by making magnetic flux density increases both radially and axially from the center of the substrate holder.