• Journal of Magnetics
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• 제8권1호
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• pp.13-17
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• 2003

The longitudinal magnetooptical Kerr effect was used to analyse magnetic domains in soft magnetic ${(Fe_{97}A1_3)}_{85}N_{15}$/$Al_{2}O_{3}$ multilayers in order to get microscopic understanding of interlayer exchange coupling. The measuring system consists of a Kerr microscope, a CCIR camera (with an 8-bit framegrabber), 16 bit digital camera and computer system for real-time image processing and to control external magnetic field and cameras. The strength of ferromagnetic (EM) coupling as a function of the spacer thickness of $Al_2O_3$ was investigated. It was found that strong FM-coupling, strong uniaxial anisotropy and coherent rotation of the magnetization have been observed for the spacer thickness in the range of 0.2 nm $\leq$ t $\leq$ 1 m, however, weak FM-coupling, patch domains and $360^{\circ}$-walls occur for the spacer thickness of t = 2.5 nm. At a spacer thickness of t $\geq$ 5 nm transition takes place from weak FM-coupling to the decoupled state where complex interlayer interactions and different types of the domain walls were observed.

• Journal of Magnetics
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• 제11권4호
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• pp.156-159
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• 2006

We have studied the magnetic properties of the CuNi nanoparticles for three different sizes prepared by plasma and chemical techniques. The magnetization is enormously enhanced with decreasing the nanoparticle size. This enhanced magnetic moment shows almost inversely linear temperature dependence, which could be interpreted by the Langevin-type superparamagnetism. The field dependence exhibits ferromagnetic-like behavior with weak hysteresis, which could described in terms of uncompensated spin and/or surface anisotropy. In addition, the magnetic data suggest that the CuNi nanoparticles produced by the plasma method result in significantly less oxidized metallic nanoparticles than those prepared by other techniques.

• 한국초전도ㆍ저온공학회논문지
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• 제21권4호
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• pp.6-8
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• 2019

Iron-based superconductors (IBSs) possess nematic phases in which rotational symmetry of the electronic structure is spontaneously broken. This novel phase has attracted much attention as it is believed to be closely linked to the superconductivity. However, observation of the symmetry broken phase by using a macroscopic experimental tool is a hard task because of naturally formed twin domains. Here, we report on a novel detwinning method by using a magnetic field on FeTe single crystal. Detwinning effect was measured by resistivity anisotropy using the Montgomery method. Our results show that FeTe was detwinned at 2T, which is a relatively weak field compared to the previously reported result. Furthermore, detwinning effect is retained even when the field is turned off after field cooling, making it an external stimulation-free detwinning method.

• Asian-Australasian Journal of Animal Sciences
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• 제13권2호
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• pp.167-175
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• 2000

This paper describes the magnetic orientation of bull sperm separated into the head and the flagellum treated by DTT or heparin in a 5,400G static field. Semen samples collected from four bulls (Japanese Black) were mixed to the same sperm density. One percentage triton X-100 was used to extract the plasma membrane. The intact and demembranated sperm suspensions were treated with 20, 200, 2,000 mM DTT, 100, 1,000 or 10,000 units heparin solutions at $4^{\circ}C$ for 6 days. The decondensation of the sperm nuclei treated by DTT or heparin was examined by measuring the head area at 1, 3 and 6 days. After measuring the area, each sample was exposed to a 5,400G static magnetic field generated by Nd-Fe-B permanent magnets for 24 hours at room temperature. Results showed that the sperms were separated into the head and the flagellum through the DTT treatment. Almost of the separated heads showed that their long axis oriented perpendicularly to the magnetic lines of force, and most of the long axis perpendicularly oriented heads showed that their flat plane oriented perpendicularly in a 5,400G magnetic field. Also, the demembranation of the head tended to increase those perpendicular orientations, while those perpendicular orientations of the head declined with the decondensation of the sperm nuclei. These findings suggest that strong magnetic anisotropy for the perpendicular orientation of the long axis and the flat plane of the head occurs in the sperm nuclei in a 5,400G magnetic field. The separated flagellum showed lower parallel orientation, and the separated and demembranated flagellum showed parallel orientation to the magnetic lines of force in this magnetic field. These findings suggest that weak magnetic anisotropy of the parallel orientation of the flagellum occurs in the inside components in a 5,400G field.

• The Korean Journal of Ceramics
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• 제6권3호
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• pp.315-317
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• 2000

A magnetoplumbite type of Ba ferrite(BaM) layers were deposited on Pt(111) and Pt(200) layers, and their c-axis orientation and magnetic characteristics were compared each other. The as-deposited BaM layer on Pt(111) one at the substrate temperature $T_s$ above $500^{\circ}C$ revealed remarkable c-axis orientation. The saturation magnetization 4$\piM_s$ and the perpendicular coercivity $H_{c⊥}$ of the films as-deposited at $T_s$ of $600^{\circ}C$ were 4.0kG and 2.5kOe, respectively. On the other hand, BaM ferrite layer deposited on Pt(200) layer at $T_s$ as relatively low as $500^{\circ}C$ also revealed weak c-axis orientation as well as (107) one and the films as-deposited at $T_s$ of $600^{\circ}C$ exhibited 4$\piMs_{and}$ $H_{c⊥}$ of 2.8kG and 2.5kOe, respectively. It was suggested that although chemical activity of Pt surface was effective for the formation of BaM crystallites, the lattice matching was also important for obtaining BaM layer with good c-axis orientation and large perpendicular anisotropy.sotropy.

• 한국지리정보학회지
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• 제9권1호
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• pp.168-178
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• 2006

최근 울진원자력 발전소에 대량의 해파리가 유입되어 냉각용수 공급을 위한 취수구를 막고 발전장애를 일으키는데, 이에 대한 사전 방지 대책 중 하나로 해양생물 대량유입의 감시 및 예보의 필요성이 제기되고 있다. 자체 이동 능력이 약한 보름달 물해파리와 같은 해양생물체에 대해서는 해수유동이 중요한 유입 요소로 작용하며, 울진주변해역에서 표층 해류방향이 북서향일 때에는 대마난류를 타고 올라온 해파리가 발전소 쪽으로 이동하여 피해를 주게 된다. 난류수의 유동방향 탐지를 위해 울진해역 $25km{\times}25km$ 공간범위를 설정하여 NOAA 해수면온도 관측자료를 수집하였다. 통계적 분석을 위해 수온자료는 GIS point 데이터로 만들고 ArcGIS의 geostatistical analyst를 사용하였으며, 수온 point 데이터에 대해 방향성 반베리오그램(directional semivariogram) 계산과 이방성(anisotropy)으로 해수면 난류수 유동방향을 탐지하였다. 이러한 실험적 결과는 발전소 취수구에 해양생물 대량유입을 감시하는 요소기술로 해파리유입 조기경보시스템 개발에 활용될 수 있을 것으로 기대한다.

• 대한금속재료학회지
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• 제48권6호
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• pp.498-505
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• 2010

Wrought magnesium alloys show a low formability at room temperature, and a remarkable anisotropy of mechanical properties make it difficult to use them in a deformation process in industry. The microstructure and crystallographic texture of metals are developed during thermo-mechanical processes, and they are significant to the understanding of the mechanical properties of metals. This work studies the microstructure, texture development and tensile properties of the extruded AZ31 Mg alloy after rolling at 100 and $300^{\circ}C$. After 40% rolling at $100^{\circ}C$, many deformed twins were observed and a relatively weak texture developed. The basal poles were split and rotated towards the rolling direction about $20^{\circ}$. During 60% rolling at $300^{\circ}C$, the dynamic recrystallization (DRX) took place and developed a strong <0001>II ND fiber texture, which influenced the poor formability at room temperature.

• 지질공학
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• 제32권1호
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• pp.85-99
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• 2022

Rock discontinuities, as weak interfaces in rock, control mechanical properties of rock mass. Presence of discontinuities complicates the engineering properties of rock, which is the root of anisotropy and heterogeneity that have nonnegligible influences on the rock engineering. Morphological characteristics of discontinuities in natural rock are an important factor influencing the mechanical properties, particularly roughness, of discontinuities. Therefore, the accurate measurement and characterization of morphologies of discontinuities are preconditions for studying mechanical properties of discontinuities. Taking discontinuities in red sandstone as research objects, the research obtained three-dimensional (3D) morphologies of discontinuities in natural rock by carrying out 3D morphological scanning tests. The waviness and roughness were separated from 3D morphologies of rock discontinuities through wavelet transform. In addition, the calculation method for the overall slope root mean square (RMS) as well as slope RMSs of waviness and roughness of 3D morphologies of discontinuities considering the shear direction was proposed. The research finally determined an evaluation method for 3D morphologies of discontinuities by quantitatively characterizing 3D morphologies with the mean value of the three slope RMSs.

• 대한토목학회논문집
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• 제28권6B호
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• pp.643-651
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• 2008

본 연구에서는 횡방향 언덕-저면의 하상형상을 갖는 개수로 흐름을 수치모의 하였다. 곡선좌표계에 대한 지배방정식을 유도하고, 난류폐합을 위해 Speziale(1987)가 제안한 비선형 $k-{\varepsilon}$ 모형을 이용하였다. 개발된 모형의 개수로 흐름에 대한 적용성 및 모형 상수의 민감도를 분석하기 위해 직사각형 개수로 흐름을 수치모의 하였다. 그 결과 모형상수 $C_D$와 $C_E$는 각각 이차흐름 강도 및 난류의 비등방성에 영향을 미치는 것으로 확인되었다. 또한 비선형 $k-{\varepsilon}$ 모형이 자유수면에서 발생되는 난류의 비등방성을 정확히 모의할 수 없는 것으로 나타났으나, 전반적인 이차흐름 분포는 비교적 잘 예측하는 것으로 확인되었다. 한편 개발된 모형을 이용하여 횡방향 하상형상을 갖는 개수로 흐름을 수치모의하고 기존의 실험 결과와 비교하였다. 그 결과 비선형 $k-{\varepsilon}$ 모형이 하상형상의 언덕과 저면에서 발생되는 상향류 및 하향류를 비교적 정확히 예측하는 것으로 나타났으며, 계산된 주흐름방향 평균유속 및 난류구조 역시 기존의 실험 결과와 잘 일치하였다. 그러나 비선형 $k-{\varepsilon}$ 모형은 하상형상의 저면을 향하는 하향류를 과소 산정하는 것으로 확인되었다.

• 전기의세계
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• 제23권2호
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• pp.55-61
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• 1974

Nature of magnetic creep phenomena in low coercive force films(Ni 80%-Fe 20%) in form of narrow channels imbedded in high coercive force films is studied in this work. Aluminium is evaporated on the hot glass substrate and eched free in the shape of narrow channels by photoetoetching method. then, Permalloy(Ni 80%, Fe 20%) is deposited on these Aluminium substrate under the uniform field of 30(Oe) to introduce anisotropy. Permalloy film on Al has a high coercive force and one on the substrate devoid of Al has how coercive force. Magnetic revers domain which is introduced at the end of channel grows under the a.c field in hard axis direction, in spite of very weak d.c field in easy axis direction. This creeping is investigated as a function of external fields and channel widths. Permalloy film thickness is 500.angs.-900.angs. and channel widths are 40, 51, 65, 81, 115.mu. respectively. Creeping increases as external field increases while it decreases with channel width decrease. Creep velocity in channels depends on the a.c field along hard axis, d.c field along easy axis and channel widths and its range is 1-10cm/sec in this experiment. From study of dependence of creep velocity on channel width, it can be concluded that creep velocity is expressed in form of v=v$_{0}$ exp .alpha.(H-H$_{0}$) where .alpha. is a function of a.c field along hard axis and H is driving d.c field along easy axis, H$_{0}$ is not a coercive force of film as usuall expected but the d.c threshold field along easy axis which is a function of channel width. This characteristic is also confirmed by the study of dependence of creep velocity upon easy axis field strength. Value of .alpha. obtained is 1.3-2.3cm/sec We depending upon film charactor, hard axis field strength and frequency.uency.