• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.161-171
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• 2001

점성토의 압밀거동은 투수성뿐만 아니라 변형 특성에 따라 크게 영향을 받으며, 변형 특성은 재하 방법에 따른 변형조건과 흙의 특성, 특히 이방성에 따라 다르게 나타난다. 이 논문에서는 점성토의 이방적 변형 특성이 압밀거동에 미치는 영향을 분석하기 위하여 다양한 변형 조건에 대한 압밀방정식과 압밀계수를 직교 이방성 탄성이론을 이용하여 유도하였다. 다양한 변형 조건에서 등방과 이방적 변형 특성하의 압밀계수를 평가하였으며, 그 결과 탄성계수의 이방성이 압밀계수에 미치는 영향이 매우 크고, 특히 수평방향의 변위가 허용되고, 수직방향의 변위가 구속될수록 크게 나타났다. 따라서 점성토 지반에 대한 하중 재하시 압밀소요시간의 정확한 예측을 위해서는 발생 가능한 변형 조건과 이방적 변형 특성에 대한 적절한 고려가 매우 중요함을 알 수 있었다.

• Journal of the Korean institute of surface engineering
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• v.31 no.3
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• pp.151-156
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• 1998

코발트계 비정질 합금을 여러 온도 구간 및 시간에 대해서 열처리하며 표면 결정화 현상이 자기 이방성에 미치는 영향을 탐구하였다. 자기 이방성은 비정질 표면의 결정 구조에 민감한 변화를 보였는데 면심입방점 코발트에 많은 결함이 존재할 경우 자기이방성이 최대치를 나타내였다.

• The Journal of Engineering Geology
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• v.3 no.3
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• pp.231-239
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• 1993

This paper presents a result on the determination of velocity distribution by a tomographic inversion of crosshole seismic traveltimes in transversely isotropic(aniso tropic) media. The crosshole traveltimes used in this study are synthetic ones computed by ray tracing for some models having isotropic and transversely isotropic velocity distributions. The traveltimes are inverted by a general ART and ansotropic ART which considers the transversely isotropic effect during inver sion. The aniotropic ART gives accurate velodty distributions of transversely isotropic and isotropic models, while the isotropic ART determines accurate velocities only for the isotropic model but inaccurate for the transversely isotropic one. Therefore, the anisotropic ART may be used in case where no information is known on the isotropy or transverse isotropy of a survey area.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.25-29
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• 2005

Magnetic properties of YIG films grown by solid phase epitaxy (SPE) was measured as a function of temperature with focus on magneto-crystalline and perpendicular magnetic anisotropy. Perpendicular magnetic anisotropy was not induced in the SPE YIG films annealed at low temperature by relaxing residual stress through formation of dislocation. On the contrary the films annealed at high temperature showed perpendicular magnetic anisotropy which shows very low density of dislocation. Perpendicular magnetic anisotropy field decreased linearly up to a high temperature of $230^{\circ}C$ above which magneto-crystalline anisotropy disappeared. Coercivity also decreased linearly with temperature up 세 $230^{\circ}C$. Magneto-crystalline anisotropy of perpendicular anisotropy induced epitaxial (111) YIG films can be measured using $H_k=4K_1/3M_s$. Temperature behavior of initial susceptibility can be successfully explained by Hopkinson effects. Curie temperature of YIG films grown on GGG substrate with high paramagnetic susceptibility can be easily measured using the results.

• Tunnel and Underground Space
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• v.11 no.1
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• pp.72-78
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• 2001

A method to determine elastic constants for transversely isotropic rock using a single uniaxial compression test was proposed by Kim(1995). However, some problems were found when this method was applied. We derived two different equations in determination of elastic constants using V$\sub$12/ and V$\sub$21/ and performed uniaxial compression tests for two specimens whose angles between transversely isotropic plane and horizontal plane are 30$^{\circ}C$ and 65$^{\circ}C$. The anisotropic elastic constants should be calculated with different equations depend on the angle. If the anisotropic angle is lower than 45$^{\circ}$, V$\sub$21/ may be used. However, if the anisotropic angle is higher than 45$^{\circ}$, V$\sub$12/ may be used.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.229-240
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• 2007

In this study, seismic anisotropic tomography algorithm was developed for imaging the seismic velocity anisotropy of the subsurface. This algorithm includes several inversion schemes in order to make the inversion process stable and robust. First of all, the set of the inversion parameters is limited to one slowness, two ratios of slowness and one direction of the anisotropy symmetric axis. The ranges of the inversion parameters are localized by the pseudobeta transform to obtain the reasonable inversion results and the inversion constraints are controlled efficiently by ACB(Active Constraint Balancing) method. Especially, the inversion using the Fresnel volume is applied to the anisotropic tomography and it can make the anisotropic tomography more stable than ray tomography as it widens the propagation angle coverage. The algorithm of anisotropic tomography is verified through the numerical experiments. And, it is applied to the real field data measured at limestone region and the results are discussed with the drill log and geological survey data. The anisotropic tomography algorithm will be able to provide the useful tool to evaluate and understand the geological structure of the subsurface more reasonably with the anisotropic characteristics.

• Journal of the Korean Magnetics Society
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• v.9 no.2
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• pp.71-77
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• 1999

본 연구에서는 이방성 Nd-Fe-B계 자성분말과 바인더로 polypropylene을 사용하여 compound를 제조한 후 사출성형에 의해 이방성 Nd-Fe-B 레진본드자석을 제조하여 자성분말의 함량, 인가자장 및 사출성형 온도에 따른 자기적 특성 및 유변학적 특성을 조사하였다. Torque sensor에 의해 측정한 본 연구에 사용된 이방상 Nd-Fe-B계 자성분말의 최대 분말함량은 70.7vol%이었다. Compound의 자성분말 함량이 증가함에 따라 레진본드자석의 잔류자속밀도와 최대자기에너지적은 증가하여 54vol%에서 최대값을 보인후 다시 감소하였고, 보자력은 변화가 없었다. 54vol% 자성분말 함량 이상에서 잔류자속밀도와 최대자기에너지적이 다시 감소하는 것은 사출성형시 자성분말의 배향도 저하에 기인한다. 이것은 compound의 자성분말 함량이 증가함에 따라 compound의 유동성이 저하되어 사출성형시 자성분말의 이방화를 어렵게 만들기 때문이다. 사출성형 온도가 증가함에 따라 레진본드자석의 자기적 특성은 증가하였다. 이는 성형온도가 증가함에 따라 compound의 유동성이 향상되어 자성분말의 배향도가 증가되었기 때문이다. 따라서 사출성형에 의해 이방성 Nd-Fe-B계 레진본드자석 제조시 자기적 특성을 향상시키기 위해서는 compound의 자성말 함량 뿐만 아니라 compound의 유동성이 중요하게 고려되어야 한다.

• Journal of the Korean Magnetics Society
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• v.25 no.4
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• pp.101-105
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• 2015

Recent theoretical calculations predicted that a system composed exclusively of 3d transition metals without 4d/5d transition metals or rare earth metals can have strong perpendicular magnetocrystalline anisotropy (MCA) if Fe and Ni layers are arranged appropriately. They considered only Fe-terminated surfaces, noting that Fe/MgO(001) and CoFeB/MgO(001) show strong perpendicular MCA. In this paper, we investigate magnetism and MCA of Ni/Fe(001) surface where Ni layer is positioned at the surface, by using complementarily the first principles calculational methods of Vienna Ab-initio Simulation Package (VASP) and Full-potential Linearized Augmented Plane Wave (FLAPW) method. Comparing results of magnetism and MCA obtained by VASP with the results by FLAPW method, we find the VASP results do not show big difference from results by FLAPW method. Magnetic moments of Fe and Ni are enhanced due to strong hybridization between Fe and Ni bands. MCA of Ni/Fe(001) is parallel to the surface, which implies the surface termination plays a crucial role in determining MCA of a system.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.393-398
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• 2007

Seismic traveltime tomography technique was conducted at a site composed of black shale. It is well known that black shale has strong anisotropic property. Therefore, the anisotropic property of black shale has to be considered to obtain the appropriate subsurface velocity model by an inversion process. To estimate the anisotropic constant of the velocity of the black shale in the survey area, the relation between the velocity, which is calculated by the straight ray path and the first arrival time, and the angle of the ray propagation was examined. The elliptically shaped relation was found and it reveals that the black shale contains the anisotropic property of velocity. It was also noticed that the horizontal velocity is faster than the vertical velocity. When the estimated anisotropic constant was applied in the process of the velocity inversion for three sets of field data, we could obtain the appropriate velocity structures of the site that is consistent with the result of the geological survey.

• Geophysics and Geophysical Exploration
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• v.18 no.4
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• pp.232-240
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• 2015

Magnetotelluric (MT) survey investigates electrical structure of subsurface by measuring natural electromagnetic fields on the earth surface. For the accurate interpretation of MT data, the precise three-dimensional (3-D) modeling algorithm is prerequisite. Since MT responses are affected by electrical anisotropy of medium, the modeling algorithm has to incorporate the electrical anisotropy especially when analyzing time-lapse MT data sets, for monitoring engineered geothermal system (EGS) reservoir, because changes in different-vintage MT-data sets are small. This study developed a MT modeling algorithm for the simulation MT responses in the presence of electrical anisotropy by improving a pre-existing staggered-grid finite-difference MT modeling algorithm. After verifying the developed algorithm, we analyzed the effect of vertical transversely isotropic (VTI) anisotropy on MT responses. In addition, we are planning to extend the applicability of the developed algorithm which can simulate not only the horizontal transversely isotropic (HTI) anisotropy, but also the tiled transversely isotropic (TTI) anisotropy.