• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.191-195
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• 2001

The applications of magnetic fluid can be normally made by 1) using changes of a property of matter caused by applied magnetic field; 2) preserving magnetic fluid at a certain position or in a magnetic fluid keeping the body in a floating condition; 3) controlling the flow of magnetic fluid by means of magnetic field. However, these are usually made by using their methods together. In this study, the natural convection flow of a magnetic fluid in annular pipes is experimentally analyzed. High temperature is kept constantly inside of a circular pipe of experimental model, on the other hand, low temperature is kept constantly outside of it. In experiments, several cases are carried out in order to clarify the fluence of direction and intensity of magnetic fields on the natural convection of magnetic fluid. Therefore magnetic fields are applied in various intensity and up and down directions by permanent magnets.

• 대한기계학회논문집B
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• 제23권1호
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• pp.25-32
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• 1999

In the present paper, we theoretically analyze the flow of magnetic fluids in a circular pipe with a vertical magnetic field and investigate the magnetic response by the external magnetic field. Theoretical study through the governing equation derived by Siliomis is carried out with numerical analysis by the Gauss Elimination Method. Using polar and magnetic effect parameters, theoretical equations and distributions for the velocity, vorticity, internal angular momentum and induced magnetization as the magnetic response are shown. Especially, in the region of strong magnetic field the specific property is appeared by finding a critical magnetic effect parameter for a polar effect parameter.

• 한국기계가공학회지
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• 제7권2호
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• pp.38-44
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• 2008

In the present paper, we theoretically analyze the flow of magnetic fluids in a circular pipe with a vertical magnetic field and investigate the magnetic response by the external magnetic field. Theoretical study through the governing equation derived by Siliomis is carried out with numerical analysis by the Gauss Elimination Method. Using polar and magnetic effect parameters, theoretical equations and distributions for the velocity, apparent viscosity as the magnetic response are shown. Especially, in the region of strong magnetic field the specific property is appeared by finding a critical magnetic effect parameter for a polar effect parameter.

• 비파괴검사학회지
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• 제20권3호
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• pp.231-237
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• 2000

공업용 서멧 절삭공구는 다성분계 탄화물과 강자성체(ferromagnetic material)인 철족의 Co, Ni 결합상 금속으로 구성 되어 있다. 본 연구에서는 새로운 시도로서 금속 결합상 량과 소결조건에 따른 TiCN계 서멧의 자기적 특성의 측정에 의한 기계적 성질의 평가방법을 연구하였다. 실험에서는 결합상이 다른 상용 서멧조성의 합금을 분말 야금법에 의해 제조하였다. 소결된 서멧의 자기적 특성은 합금의 조직과 탄소량에 따라 크게 변화하였다. 포화자화(magnetic saturation, $4{\pi}\;{\sigma}$)와 항자력(coercive force, Hc)은 비례하였으며, 고탄소 소결합금에 있어서는 Co-Ni 결합상에서의 W, Mo, Ti등의 용매원자의 농도가 낮아짐에 따라 포화자화는 증가하였다 항자력이 높을수록 경도는 증가하였고, 서멧의 강도 및 인성은 포화자화가 증가할수록 우수하였다. 서멧공구에서 자기적 특성을 측정하여 기계적 성질을 비파괴적으로 평가할 수 있었다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권12호
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• pp.617-622
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• 2006

It is necessary to measure precisely the magnetic characteristics of electrical steel sheets under rotating magnetic fields, to obtain an accurate numerical performance analysis of electric machines made of electrical steel sheets. In this paper, the two dimensional magnetic characteristics of an electrical steel sheet are measured and explained under rotating magnetic fields using a two-axes-excitation type single sheet tester (SST). Through experiments, the magnetic properties, under rotating magnetic fields, of a non-oriented and grain oriented electrical steel sheet were measured respectively. In addition, the iron losses due to not only the alternating magnetic fields, but also rotating magnetic fields were measured. These experimentally measured results can evidently be applied to the analysis of iron losses in electrical machines.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.439-440
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• 2008

An inductive coupler, which feeds communication to the electric power transmission line, is required to establish Power Line Communication(PLC). The electro-magnetic property of magnetic core and design technology for coupler are very important to manufacture an inductive coupler for power transmission line. The magnetic core with superior electro-magnetic property was manufactured by using nano-crystalline alloy and an inductive coupler, which can operate at the maximum 2,000 A current, was designed and manufactured by establishment of current saturation, signal out winding, and electro-magnetic simulation in this study. Communication speed of 14 Mbps in 600 m communication distance of the real electric power transmission line was obtained by using the inductive coupler and application possibility of the inductive coupler for the electric power transmission line was certified.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.388-389
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• 2009

The use of arc tubes made of ceramic material further enhanced some of the metal halide lamp's properties. These properties translate into higher efficacy with better color rendering, stable color through lamp long life. Recently, due to an increase in the application of the ceramic metal-halide lamp, the study for the property etc. according to Ballast's driving scheme and the study for arc tube material, optimization of gas and so on are being proceeded to improve the property of the lamp. Especially, to control ceramic metal-halide lamp, the vigorous study and practical use with respect to Electronic Ballast, which has been improved in the disadvantages of the conventional Magnetic Ballast are made. In this paper, Electrical characteristics and gas insulation destroy time are analyzed by comparing magnetic ballast with electronic ballast.

• Current Applied Physics
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• 제18권12호
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• pp.1465-1472
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• 2018

The magnetic and optical properties of Ce-doped ZnO systems have been widely demonstrated, but the effects of different strains of Ce-doped ZnO systems remain unclear. To solve these problems, this study identified the effects of biaxial strain on the electronic structure, absorption spectrum, and magnetic properties of Ce-doped ZnO systems by using a generalized gradient approximation + U (GGA + U) method with plane wave pseudopotential. Under unstrained conditions, the formation energy decreased, the system became stable, and the doping process became easy with the increase in the distances between two Ce atoms. The band gap of the systems with different strains became narrower than that of undoped ZnO without strain, and the absorption spectra showed a red shift. The band gap narrowed, and the red shift became weak with the increase of compressive strain. By contrast, the band gap widened, and the red shift became significant with the increase of tensile strain. The red shift was significant when the tensile strain was 3%. The systems with -1%, 0%, and 1% strains were ferromagnetic. For the first time, the magnetic moment of the system with -1% strain was found to be the largest, and the system showed the greatest beneficial value for diluted magnetic semiconductors. The systems with -3%, -2%, 2%, and 3% strains were non-magnetic, and they had no value for diluted magnetic semiconductors. The ferromagnetism of the system with -1% strain was mainly caused by the hybrid coupling of Ce-4f, Ce-5d, and O-2p orbits. This finding was consistent with Zener's Ruderman-Kittel-Kasuya-Yosida theory. The results can serve as a reference for the design and preparation of new diluted magnetic semiconductors and optical functional materials.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.173.1-173.1
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• 2014

The variations of electronic and magnetic properties of ultrathin Fe overlayers on a W(001) surface as a function of Fe film thickness (1.0~4.0 ML) has been investigated using x-ray magnetic circular dichroism (XMCD) in conjunction with ultraviolet photoelectron spectroscopy (UPS) and low energy electron diffraction (LEED). We found that the ferromagnetic property of Fe film started to build up over 2.0 ML, as we confirmed the spin and angular moment contribution to the magnetic moment using XMCD experiments. We will systematically demonstrate that the occurrence of ferromagnetic property of Fe film on a W(001) surface is closely correlated to a themally stable layer of Fe film on a W(001) surface.

• 열처리공학회지
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• 제14권6호
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• pp.323-329
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• 2001

Artificial aging was performed to simulate the microstructural degradation in 2.25CrMo steel arising from long time exposure at $540^{\circ}C$. The carbide morphologies were classified as acicular, pipe and globular type, and the number of carbides per unit area was measured for each type of carbides. The fine acicular carbides were found to diminish drastically in the initial stage of aging. An attempt was made to evaluate the microstructural degradation in artificially aging heat treated 2.25CrMo steel by the magnetic property measurements such as saturation magnetization, coercivity and remanence. The saturation magnetization showed no distinct trend with aging time. However, the coercivity and remanence were observed to decrease rapidly in initial 920 hours of aging time and then decrease slowly afterwards.