• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.215-224
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• 2018

Influences of the magnetic field on 5, 10 and 15 wt% (1.5, 3 and 4.5 M) HCl solution behaviour, which has widespread applications in petroleum well acidizing, were investigated in various conditions. Differences in the pH of magnetized hydrochloric acid compared to that of normal hydrochloric acid were measured. Taguchi design of experimental (DoE) method were used to model effects of the magnetic field intensity, concentration, velocity and temperature of acid in addition to the elapsed time. The experimental results showed that the magnetic field decreases [$H^+$] concentration of hydrochloric acid up to 42% after magnetization. Increasing the magnetic field intensity (with 28% contribution), concentration (with 42% contribution), and velocity of acid increases the effect of magnetic treatment. The results also demonstrated that the acid magnetization was-not influenced by the fluid velocity and heating. It was also displayed that the acid preserves its magnetic memory during time. The optimum combination of factors with respect to the highest change of [$H^+$] concentration was obtained as an acid concentration of 10% and an applied magnetic field of 4,300 Gauss. Due to the reduction of HCl reaction rate under the magnetization process, it can be proposed that the magnetized HCl is a cost effective and reliable alternative retarder in the matrix acidizing of hydrocarbon (crude oil and natural gas) wells.

• Journal of the Korean institute of surface engineering
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• v.36 no.6
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• pp.461-465
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• 2003

The microstructures and magnetic properties of electrodeposited Fe-45 wt%Ni-P alloys have been investigated. The structures of electrodeposited Fe-45 wt%Ni alloy was FCC i.e. ${\gamma}$ phase and the size of crystallite was 10 nm. The structure of electrodeposited Fe-45 wt%Ni-1 wt%P alloy showed ${\gamma}$ phase and 7 nm sized nanocrystalline. The electrodeposited Fe-45 wt%Ni-P alloys containing 2∼3 wt% of P exhibited ${\gamma}$ ＋ $\alpha$ dual phases. The electrodeposited Fe-45 wt%Ni-P alloys above 3.5 wt% showed an amorphous structure. P in the alloys acted grain refining and phase changing element. The resistivity of the electrodeposited alloys increased with P contents. Effective permeability at high frequency (above 1 MHz) increased with P contents up to 2 wt% and this was ascribed to the easier magnetization rotation owing to the reduction of eddy current. Effective permeability decreased with P contents above 3 wt% and this was ascribed to the transformation of the ferromagnetism of Fe-45 wt%Ni alloy gradually into paramagnetism with the introduction of P into the electrodeposited alloy matrix.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1021-1022
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• 2011

This paper presents the double side PM synchronous motor/generator for core loss reduction in flywheel energy storage system. The use of double PM rotor causes the elimination of core loss in no-load state of machine. Because flywheel rotational speed is reduced by core loss, double PM rotor is very effective in flywheel system. This paper suggests two types of double side PM rotor, Halbach magnetized array and parallel magnetized array. And characteristic comparison according to thickness of rotor back core is performed.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.67-69
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• 2004

This paper describes an approach to design a interior permanent magnet motor(IPM motor) for the reduction of cogging torque. The magnitude of the torque ripple and cogging torque in a interior permanent magnet motor(IPM motor) are generally dependent on several major factors: the shape of stator tooth tip, slot opening width, air gap length, the shape of barrier preventing flux leakage of magnets, magnet configuration and magnetization distribution or magnet poles. In this paper, the IPM BLDC motor is designed considering a saturated leakag flux between the barriers on the rotor for increasing the efficiency and decreasing the magnitude of the cogging torque. Analytical model is developed for the IPM BLDC motor with a concentrated winding stator. The results verifies that the proposed design approach is very efficient and effective in reducing the cogging torque and the torque ripple of the IPM BLDC motor to be used in an electric vehicle.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.6
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• pp.1110-1115
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• 2009

We studied on the design of electrical parameters for ICP(Inductively Coupled Plasma) light sources which can be effective to improve the electrical power efficiency of it. These parameters were derivated from Barkhausen theory about the oscillating condition of a ballaster. The relationships of $f-I_p$ and f-n were calculated theoretically and then these relationships were compared with the measured results about $I_p$ and power depending to a discharge length(l) of ICP light source. Finally, we can see that a specific range of induced current depending to a discharge length would be necessary to minimize the change of magnetization inductance and driving frequency at driving.

• Journal of Magnetics
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• v.9 no.2
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• pp.37-39
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• 2004

Polycrystalline Ni-Mn-Ga films have been deposited onto mica substrates held at 720 K by flash-evaporation method. At room temperature the films have a tetragonal structure with a = b = 0.598 and c = 0.576 nm typical for bulk $Ni_2MnGa$ below a martensitic transformation. Temperature measurements of ferromagnetic resonance reveal a martensitic phase transformation at 310 K. The transformation brings about a substantial decrease in the effective magnetization and a drastic increase in the ferromagnetic resonance linewidth due to a strong increase in the magnetic anisotropy in the martensitic phase.

• Journal of Magnetics
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• v.12 no.4
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• pp.152-155
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• 2007

Spin dependent transport was investigated in lateral $Py(Ni_{81}Fe_{19})/Au/Py$ spin valve devices. Clear spin valve effect was observed in conventional four-terminal measurement geometry. Higher resistance was found in antiparallel magnetization field of two Py electrodes which is determined by anisotropy magnetoresistance (AMR) measurements. The rectangular shape of spin signal together with good agreement of switching field convinces observed spin valve signal is resulted from effective spin injection and detection. The magnetoresistance ratio decays exponentially with channel length by which spin diffusion length of Au channel was estimated to be 76 nm.

• Journal of Magnetics
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• v.4 no.2
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• pp.69-72
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• 1999

Magnetic properties and crystallographic structure of e-beam evaporated Co/Cr and Co/Mo multilayer thin films were investigated using VSM and XRD. Co/Cr and Co/Mo multilayer thin films are confirmed as an alternating layered structure. The structure of films with thicker Co layers than Cr and Mo layers are found to be a hcp structure with the c-axis perpendicular to the film plane. The direction of the film plane is the easy magnetization one. There is a no significant difference in shape of hysteresis loops between Co/Cr and Co/Mo multilayer films. It is found that Mo layer is more effective than Cr for preparing Co layer with c-axis normal to the film plane.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.303-305
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• 2000

The effect of anisotropy field on the high frequency magnetic characteristics of FeTaN films was investigated. Those films show good magnetic properties : 4$\pi$Ms of 13KG, Hc of 0.6 Oe, effective permeability(${\mu}$') of 800 with a stable frequency response up to 800MHz. The films also show a large anisotropy field(Hk) over 21Oe. It result from the increased anisotropy of patterned FeTaN films. The combination of high saturation magnetization and relatively high Hk in these films is believed to the partly responsible for FeTaN for the excellent high-frequency behavior.

• Journal of Korea Foundry Society
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• v.40 no.4
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• pp.113-117
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• 2020

A series of Fe-P-B and Fe-Si-B amorphous alloys with high Fe contents exceeding 90 wt.% was successfully prepared by combining flux treatment and melt-spinning technique. The effects of Fe content and the flux treatment on the thermal and magnetic properties of amorphous alloys were studied. The glass-forming ability and the thermal stability of amorphous ribbons can be improved by a flux treatment, revealing the effective removal of heterogeneous nucleation sites in the ribbons through the flux treatment. It was found that Fe-Si-B ribbons exhibit higher saturation magnetization levels than Fe-P-B ribbons.