• 한국세라믹학회지
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• 제34권4호
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• pp.351-356
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• 1997

The origin of the variation of initial permeability in manganese-zinc ferrite polycrystals with a content of hematite was investigated. Initial permeability showed maximum with hematite content while there was no significant change in microstructure. Saturation magnetization increased with hematite content. So the variation of initial permeability was not explained on the basis of microstructural change or saturation magnetization. Temperature dependence of initial permeability revealed magnetocrystalline anisotropy was the origin of the variation of initial permeability. The change in magnetocrystalline anisotropy was ascribed to the variation in ferrous ion concentration. Therefore the variation of initial permeability in manganese-zinc ferrite polycrystals with a content of hematite was due to ferrous ion concentration via magnetocrystalline anisotropy.

• 한국재료학회지
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• 제30권11호
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• pp.589-594
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• 2020

Many electronic applications require magnetic materials with high permeability and frequency properties. We improve the magnetic permeability of soft magnetic powder by controlling the shape magnetic anisotropy of the powders and through the preparation of amorphous nanoparticles. For this purpose, the effect of the shape magnetic anisotropy of amorphous Fe-B-P nanoparticles is observed through a magnetic field and the frequency characteristics and permeability of these amorphous nanoparticles are observed. These characteristics are investigated by analyzing the composition of particles, crystal structure, microstructure, magnetic properties, and permeability of particles. The composition, crystal structure, and microstructure of the particles are analyzed using inductively coupled plasma optical emission spectrometry-, X-ray diffraction, scanning electron microscopy and focused ion beam analysis. The saturation magnetization and permeability are measured using a vibrating sample magnetometer and an LCR meter, respectively. It is confirmed that the shape magnetic anisotropy of the particles influences the permeability. Finally, the permeability and frequency characteristics of the amorphous Fe-B-P nanoparticles are improved.

• Geomechanics and Engineering
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• 제21권2호
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• pp.103-109
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• 2020

The inflow rate is of interest in the design of underground structures such as tunnels and buried pipes below the groundwater table. Soil permeability governing the inflow rate significantly affects the hydro-geological behavior of soils but is difficult to estimate due to its wide range of distribution, nonlinearity and anisotropy. Volume changes induced by stress can cause nonlinear stress-strain behavior, resulting in corresponding permeability changes. In this paper, the nonlinearity and anisotropy of permeability are investigated by conducting Rowe cell tests, and a nonlinear permeability model considering anisotropy was proposed. Model modification and parameter evaluation for field application were also addressed. Significance of nonlinear permeability was illustrated by carrying out numerical analysis of a tunnel. It is highlighted that the effect of nonlinear permeability is significant in soils of which volume change is considerable, and particularly appears in the short-term flow behavior.

• 한국전기전자재료학회논문지
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• 제17권1호
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• pp.46-51
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• 2004

The cause for the variation of the initial permeability according to the Co substitution of Ni-Zn ferrite used in the LC resonance filter for the power line communication is studied. The initial permeability decreases as the quantity of Co diminishes, and the saturation magnetization increases as the quantity increases. Because the sintering density and the microstructure of ferrite show little change, the variation of the initial permeability can't be explained by the density, microstructure nor the saturation magnetization factor. The magnetocrystalline anisotropy increases, similar with the saturation magnetization, as the quantity of Co increases. The increase of magnetocrystalline anisotropy value makes the domain wall energy grow, which leads to the decrease of the initial permeability, because there's linear law between the magnetocrystalline anisotropy and the domain wall energy. The resonance frequency to Co substitution moved to high frequency band, due to the close relationship with domain wall energy, Initial permeability decreaed a little with an increase of Co contents, but resonace frequency moved to high frequency band. as a result of that, when Co was added 0.05 mol, initial permeability and resonace frequency was 75 and 25 MHz respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.443-446
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• 2001

MI(Magneto-Impedance) sensor which is made by thin films has significantly high detecting sensitivity in weak magnetic field. It also has a merit to be able to build in low power system. Its structure is simple, which makes it easier to prepare a miniature. In this study, its magnetic permeability and anisotropy field(H$\sub$k/) as a function of a thickness of sputtered amorphous CoZrNb thin film with high saturation magnetostriction and excellent soft magnetic property are investigated. In order to make a uniaxial anisotropy, thin film was subjected to post annealing with a static magnetic field with 1KOe intensity at 250, 300, and 320$^{\circ}C$ for 2 hour. Anisotropy field(H$\sub$k/)of thin film is measured by using MH loop tracer. Its magnetic permeability of thin film is measured over the frequency range from 1 MHz to 750MHz. It has shown that the magnetic permeability of amorphous CoZrNb thin film is decreased due to the skin effect with increasing a thickness of CoZrNb thin film, and hence its driving frequency is lowered.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.778-781
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• 2002

MI(Magneto-Impedance) sensor which is made by thin films has significantly high detecting sensitivity in weak magnetic field. It also has a merit to be able to build in the low power system. Its structure is simple, which makes it easier to prepare a miniature. In this study, its magnetic permeability and anisotropy field$(H_k)$ as a function of a thickness of sputtered amorphous CoZrNb films with zero-magnetostriction and excellent soft magnetic property are investigated. In order to make a uniaxial anisotropy, film was subjected to the post annealing in a static magnetic field with 1KOe intensity at 250, 300, and $320^{\circ}C}$ respectively for 2 hours. Anisotropy field$(H_k)$ of film is measured by using a MH loop tracer. Its magnetic permeability of a film is measured over the frequency range from 1 MHz to 750MHz. It has shown that the magnetic permeability of amorphous CoZrNb film is decreased due to the skin effect with increasing a thickness of the CoZrNb film, and hence its driving frequency is lowered. And, it was examined on the permeability and impedance to fabricate the MI sensor which acts at a low frequency by thickening a CoZrNb film relatively.

• 한국지반공학회지:지반
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• 제2권3호
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• pp.27-36
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• 1986

뒷채움 다짐한 옹벽에 저해 침투빙가 주동토압에 미치는 영향을 관찰하기 위하여 책험과 이론해석에 의하여 연구가 수행되었다. 다짐방법이 모래의 투빙성에 미치는 영향을 관찰하기 위하여 특별히 고안된 정수두 투수시험장치와 전기전도도 측정법에 의하여 실험이 행해졌다. 실험결과, 다짐방상에 직각인 방향과 평행한 방향의 투수계수의 비(kz/ky)는 공소비와 반대수방안지에서 직선관계로 보이고, 상대밀도가 90% 이상에서는 kz/ky의 값이 2-4로 나타났다. 이 때 다짐방법은 투수계수에 별다른 영향을 주지 않았으며, 굵은 모래보다 가는 모래에서 이방성이 크게 나타났다. 이방성 침투가 주동토압에 미치는 영향을 관찰하기 위하여 확장된 Gray 이론에 실험결과를 적용하여 보았다. kz/ky의 값이 클수록 주동토압의 크기는 작아지고, 벽면마찰의 영향은 크지 않았다.

• 한국지반공학회논문집
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• 제36권11호
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• pp.149-156
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• 2020

약액 그라우팅은 지반의 강도 증진 및 차수 공법에 성공적으로 이용되어 왔으나, 그라우트의 유동은 지층의 투구계수 이방성에 크게 영향을 받는다. 따라서, 본 연구에서는 전산 유체 역학법을 이용하여 투수계수의 이방성이 수평 약액 그라우팅의 유효 반경에 미치는 영향을 알아보았다. 먼저 수평 방향 약액 주입 시뮬레이션을 위하여 공극 매질내 2상 점성 유체의 유동을 모델링하였고, 경화에 따른 확산과 점성 변화 또한 고려했다. 수치해석 결과, 투수계수의 이방성으로 인해 그라우트 구근의 형태가 타원체로 발달했고, 용해에 따른 확산 때문에 그라우트 구근의 모서리로 갈수록 공극내 그라우트 포화도가 점진적으로 감소했다. 이 결과를 바탕으로 10, 50, 90의 임계포화도를 설정하여 그에 따른 수평 방향 및 수직 방향 유효 반경을 산출하였다. 또한, 0.01 - 100의 수평·수직 방향 투수계수비에 따른 유효 반경을 산출하여 회귀식을 개발했다. 본 연구 결과는 투수계수 이방성을 가진 지층의 특성을 이용한 보다 효율적인 약액 그라우트 주입 전략 계획에 기여할 것으로 기대한다.

• 터널과지하공간
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• 제23권3호
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• pp.228-240
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• 2013

퇴적암에서 나타나는 이방성은 층리에 의한 영향이 크며, 암석의 수리적 특성에도 영향을 주게 된다. 본 연구에서는 층리가 발달한 다공질 사암을 대상으로, 층리구조에 의해 발생한 공극구조 이방성이 사암의 수리 이방성에 미치는 영향을 분석하였다. 사암의 공극구조 이방성 파악을 위해 X-ray CT(computed tomography)를 이용하여 내부 공극률의 변화양상을 분석하였다. 층리방향에 따른 수리이방성은 층리면과 수평면이 이루는 각도를 $0^{\circ}$에서 $90^{\circ}$까지 $15^{\circ}$간격으로 코어링한 샘플을 제작하여 투수실험을 통해 파악하였다. 투수실험 결과 층리면과 투수방향이 수직인 경우 투수율이 가장 작은 값을 나타낸 반면, 층리면과 투수방향이 평행일 때 가장 높은 투수율을 나타내었으며, 평균 수리이등방비($k_{90^{\circ}}/k_{0^{\circ}}$)가 1.8로 층리에 따른 수리 이방성이 확연하게 나타났다. 또한, 이러한 사암의 수리이방특성은 층리에 의해 공극특성이 서로 다른 층상구조가 형성되기 때문임을 확인하였다.

• 한국자기학회지
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• 제7권4호
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• pp.186-190
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• 1997

2축 Helmholtz 코일을 이용해서 연자성박막의 이방성 분산을 측정할 수 있는 장치를 제작하여 TBP(Transverse Biased Permeability) 측정 방법으로 rf 스파터방법으로 제작한 퍼말로이박막의 이방성 불균일성을 측정하였다. 각도불균일분포함수의 경우 Lorentz 함수형태를 띄며, 크기불균일 분포함수의 경우 자장이 큰 영역에서의 분산 값이 커져 대칭분포에서 벗어난다. 퍼말로이 박막의 두께가 증가할수록 이방성의 각도 및 크기분산이 커지고 각도 분산의 경우 이것은 두께 증가에 따른 결정립 크기의 증대와 국소이방성의 증가로 설명할 수 있었다.