• 한국정밀공학회지
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• 제16권11호
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• pp.234-242
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• 1999

In this paper, a method for assessment of the anisotropic machined surfaces is proposed. Fractal dimension (FD) is calculated using structure function and an index of the anisotropy is obtained as a ratio of its maximum and minimum value. The upper limit of fractal region on the structure function is determined as the length of the lag where the autocorrelation function shows 20% of its maximum value. The model of the structure function is derived from that of the auto correlation function. And, it shows that the new method and the proposed index of anisotropy are useful.

• Geomechanics and Engineering
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• 제11권4호
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• pp.515-530
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• 2016

In this paper, five different quantitative parameters were proposed for the characterization of the primary roughness which is the component of surface morphology that prevails during large strike-slip faults of more than 50 m. These parameters are mostly the anisotropic properties of rock surface morphology at various scales: (i) coefficient ($k_a$) and degree (${\delta}_a$) of apparent structural anisotropy of surface; (ii) coefficient ($k_r$) and degree (${\delta}_r$) of real structural anisotropy of surface; (iii) surface anisotropy function P(${\varphi}$); and (iv) degree of surface waviness ($W_s$). The coefficient and degree of apparent structural anisotropy allow qualifying the anisotropy/isotropy of a discontinuity according to a classification into four classes: anisotropic, moderately anisotropic/isotropic and isotropic. The coefficient and degree of real structural anisotropy of surface captures directly the actual surface anisotropy using geostatistical method. The anisotropy function predicts directional geometric properties of a surface of discontinuity from measurements in two orthogonal directions. These predicted data may subsequently be used to highlight the anisotropy/isotropy of the surface (radar plot). The degree of surface waviness allows qualifying the undulation of anisotropic surfaces. The proposed quantitative parameters allows their application at both lab and field scales.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2012년도 자성 및 자성재료 국제학술대회
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• pp.104-105
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• 2012

The temperature dependence of the effective magnetic anisotropy constant K(T) of ferrite nanoparticles is obtained based on the measurements of SQUID magnetometry. For this end, a very simple but intuitive and direct method for determining the temperature dependence of anisotropy constant K(T) in nanoparticles is introduced in this study. The anisotropy constant at a given temperature is determined by associating the particle size distribution f(r) with the anisotropy energy barrier distribution $f_A(T)$. In order to estimate the particle size distribution f(r), the first quadrant part of the hysteresis loop is fitted to the classical Langevin function weight-averaged with the log?normal distribution, slightly modified from the original Chantrell's distribution function. In order to get an anisotropy energy barrier distribution $f_A(T)$, the temperature dependence of magnetization decay $M_{TD}$ of the sample is measured. For this measurement, the sample is cooled from room temperature to 5 K in a magnetic field of 100 G. Then the applied field is turned off and the remanent magnetization is measured on stepwise increasing the temperature. And the energy barrier distribution $f_A(T)$ is obtained by differentiating the magnetization decay curve at any temperature. It decreases with increasing temperature and finally vanishes when all the particles in the sample are unblocked. As a next step, a relation between r and $T_B$ is determined from the particle size distribution f(r) and the anisotropy energy barrier distribution $f_A(T)$. Under the simple assumption that the superparamagnetic fraction of cumulative area in particle size distribution at a temperature is equal to the fraction of anisotropy energy barrier overcome at that temperature in the anisotropy energy barrier distribution, we can get a relation between r and $T_B$, from which the temperature dependence of the magnetic anisotropy constant was determined, as is represented in the inset of Fig. 1. Substituting the values of r and $T_B$ into the $N{\acute{e}}el$-Arrhenius equation with the attempt time fixed to $10^{-9}s$ and measuring time being 100 s which is suitable for conventional magnetic measurement, the anisotropy constant K(T) is estimated as a function of temperature (Fig. 1). As an example, the resultant effective magnetic anisotropy constant K(T) of manganese ferrite decreases with increasing temperature from $8.5{\times}10^4J/m^3$ at 5 K to $0.35{\times}10^4J/m^3$ at 125 K. The reported value for K in the literatures is $0.25{\times}10^4J/m^3$. The anisotropy constant at low temperature region is far more than one order of magnitude larger than that at 125 K, indicative of the effects of inter?particle interaction, which is more pronounced for smaller particles.

• 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.

• Macromolecular Research
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• 제8권6호
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• pp.268-275
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• 2000

After imposing a large pre-strain, anisotropy increases with increasing residual extension ratio. Gums have very low residual extension ratio and exhibit little anisotropy, while black filled SBR and especially sulfur-cured carbon black filled NR have large set and anisotropy. For carbon black filled rubber, samples subjected to tensile loading in perpendicular to the pre-strain direction have the same stress-strain curves shape as the sample without pre-strain (=isotropic samples), but slightly lower modulus. However, compared to isotropic or perpendicular directional samples to pre-strain direction, samples subjected to tensile loading in parallel to the pre-strain direction show low stress at low deformation, but have high stiffness at high deformation. Normalized anisotropy changes with strain. The normalized anisotropy for various deformations is a linear function of residual extension ratio.

• Bulletin of the Korean Chemical Society
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• 제23권6호
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• pp.865-872
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• 2002

A systematic way of determining the equilibrium orientation of carbon monoxide (CO) in heme proteins using time-resolved polarized mid-IR spectroscopy is presented. The polarization anisotropy at pump-probe delay time of zero in the limit of zero photolysis and the angular distrbution function of CO are required to obtain the equilibrium orientation of CO. An approach is developed for determining the polarization anisotropy in the zero-photolysis limit from the anisotropy measured under finite photolysis conditions in an optically thick sample where the fraction of molecules photolyzed decreased as the pump pulse passes through and is absorbed by the sample. This approach is verified by measuring the polarization anisotropy of CO of carbonmonoxy myoglobin at various levels of photolysis. This method can be readily applied to other photoselection experiments determining precise angle between transition dipoles.

• 한국자동차공학회논문집
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• 제18권2호
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• pp.56-60
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• 2010

Since the forming process involves the strain rate effect, a yield function considering the strain rate is indispensible to predict the accurate final blank shape in the forming simulation. One of the most widely used in the forming analysis is the Hill48 quadratic yield function due to its simplicity and low computing cost. In this paper, static and dynamic uni-axial tensile tests according to the loading direction have been carried out in order to measure the yield stress and the r-value. Based on the measured results, the Hill48 yield loci have been constructed, and their performance to describe the plastic anisotropy has been quantitatively evaluated. The Hill48 quadratic yield function has been modified using convex combination in order to achieve accurate approximation of anisotropy at the rolling and transverse direction.

• 한국세라믹학회지
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• 제39권10호
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• pp.907-911
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• 2002

Using the two-dimensional Wulff plot, the equilibrium shape of a sapphire crystal was investigated as a function of surface energy anisotropy. Depending on the relative values of surface energy for various facet planes, the projected shape of equilibrium sapphire was determined to be rectangle, parallelogram, hexagon or octagon. The results are compared with the experimentally observed shapes of internal cavities of submicron range in sapphire single crystals.

• Journal of Magnetics
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• 제10권4호
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• pp.133-136
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• 2005

The NiMn/NiFe bilayer structure which was short time annealed in order to induce unidirectional anisotropy were studied as a function of annealing temperature. The maximum exchange bias field of NiMn/NiFe bilayer was presented at $250^{\circ}C$ after short time annealing process with no external field. The appearance of exchange bias was due to phase transformation of NiMn layer. In plane angular dependence of a resonance field distribution which measured by FMR was analysed as a combined effect of unidirectional anisotropy and uniaxial anisotropy. The resonance field and the line width from FMR measurement were also analysed with annealing temperature.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.959-965
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• 2002

Effective hydraulic conductivity of a statistically anisotropic heterogeneous medium is obtained for steady two-dimensional flows employing stochastic analysis. Flow equations are solved up to second order and the effective conductivity is obtained in a semi-analytic form depending only on the spatial correlation function and the anisotropy ratio of the hydraulic conductivity field, hence becoming a true intrinsic property independent of the flow field. Results are obtained using a statistically anisotropic Gaussian correlation function where the anisotropy is defined as the ratio of integral scales normal and parallel to the mean flow direction. Second order results indicate that the effective conductivity of an anisotropic medium is greater than that of an isotropic one when the anisotropy ratio is less than one and vice versa. It is also found that the effective conductivity has upper and lower bounds of the arithmetic and the harmonic mean conductivities.