• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1459-1460
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• 2011

자성유체에 60Hz의 교류자기장을 인가할 때 발생되는 냉각효과를 해석하기 위해 유한요소법을 결합하였다. 열원으로는 전류가 코일에 흐를 때 생성되는 줄열과 닐운동과 브라운운동으로 야기되는 전력손실에 의한 발열이 있다. 교류자기장은 주파수가 낮기 때문에 줄열이 주요한 열원이 된다. 그러므로 코일에서 자성유체로 일어나는 열전달과 자연대류현상은 코일의 표면에서 일어난다. 자연대류현상을 해석하기 위해서는 자성유체의 부력밀도를 고려해야 한다. 부가적으로 자계의 세기와 온도에 관한 함수인 자화와 자기체적력밀도로 인해 자기대류현상과 같은 강제대류가 일어난다. 이러한 두 가지 대류현상으로 인해 교류자기장을 인가한 자성유체에서 냉각효과가 일어난다. 자기체적력밀도는 유한요소법으로 보간된 가상공극개념을 이용하여 켈빈전자기력밀도를 이끌어 낸 후 이를 수치적으로 이용하여 구하였다. 랑제방함수는 켈빈전자기력밀도와 전력손실을 계산하는데 필요한 비선형 자화율을 고려하기 위해 사용하였다.

• Journal of the Korean Society of Radiology
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• v.8 no.5
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• pp.231-240
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• 2014

The purpose of this study were to analyze that the Seoul neuropsychological screening battery (SNSB) for the evaluating cognitive assessment of the Parkinson's disease patients with mild cognitive impairment (PD-MCI) and the changes of the cerebral ventricle volume in the brain magnetic resonance imaging (MRI), and we has been bring forward the guideline to determine the diagnostic criteria for the PD-MCI. To achieve this, we was diagnosed with Parkinson's disease patients (PD-MCI group: 34 patients; Parkinson's disease with normal cognition, PD-NC group: 34 patients) to perform the SNSB test for the attention, language, memory, visuospatial, and frontal/executive functions and the brain MRI. Additionally, to compared the change of the cerebral ventricle volume, we performed the brain MRI for the 32 normal control (NC) group. The volumetric analysis for a specific cerebral ventricle performed by using Freesurfer Ver. 5.1 (Massachusetts general Hospital, Boston MA, USA). As a results, compared to the PD-NC group, the PD-MCI group were statistically significant reduction in the ability to perform the memory and the visuospatial function (p<0.05). The volumetric changes for a specific cerebral ventricle were statistically significant variation in the left and right lateral ventricle, left and right inferior lateral ventricle, and 3rd ventricle. Although, in order to compared the objectification, the normalized percentage applied to the volumetric changes showed to extend the PD-MCI group than the PD-NC group. Specially, the left and right ventricle extension for the PD-MCI patients conspicuously had showed a quantitative linear relationship between the memory and the visuospatial function for the SNSB (r>0.5, p<0.05). Therefore, we were able to judge the diagnostic criteria of the PD-MCI through that can observe the volumetric variation of the specific cerebral ventricle by using Freesurfer in brain MRI, and to analyze the correlation between the SNSB.

• Journal of the Korean Magnetics Society
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• v.21 no.5
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• pp.174-179
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• 2011

Magnetic force calculation methods such as Maxwell stress, virtual work principle, equivalent magnetic charge, and equivalent magnetizing current are widely used until now. The force density is still controversial issue even though it is common sense that all of these methods have legitimate results. The surface force densities of each method are quite different with each other in the point of numerical result and final expression. In this paper, it is shown that a unified expression of body force density is derived using virtual air-gap scheme for an analytic model in which cylindrical magnetic material with a vertical current runs through its center.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.30-32
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• 2003

본 논문은 LCD 제조 공정 라인에서 LCD용 원판을 다른 여러 공정으로 이송하는데 사용하기 위한 수평형 스토크 시스템의 설계 및 제작에 관한 연구이다. 구동원으로 제작된 영구 자석 여자 횡자속형 전동기는 높은 공극 자속 밀도를 얻을 수 있는 구조로 일반 선형 유도 전동기나 선형 등기기에 비해 단위 체적당 높은 출력 밀도를 얻을 수 있는 장점을 가지고 있다. 3차원 등가 자기 회로망법을 사용하여 기자력 변화에 따른 추력 및 흡인력과 같은 특성을 해석하였으며 정특성 실험을 통하여 설계 및 해석의 타당성을 검토하였다.

• Journal of the Korean Magnetics Society
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• v.11 no.6
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• pp.245-249
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• 2001

Natural convection of a magnetic fluid is different from that of Newtonian fluids because magnetic body force exists in an addition to gravity and buoyancy. In this paper, natural convection of a magnetic fluids (W-40) in annular pipes was studied by experimentally. Inside wall was kept at a constant temperature (25 $^{\circ}C$), and outside wall was also held at a constant but lower temperature (20 $^{\circ}C$). The magnetic fields of various magnitude were applied up. This study has resulted in the following fact that the natural convection of a magnetic fluids was controlled by the direction and intensity of the magnetic fields.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.2
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• pp.31-37
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• 2008

In this paper, we analyzed the dynamic behavior of magnetic fluid in a circular pipe with multiple permanent magnets. Magnetic fluid react on magnetic field against the normal fluid. In other words, magnetic fluid flow has the electromagnetism and fluid mechanics. So magnetic fluids has studied about the fluids properties and experiment. In this paper we studied the magnetic fluids velocity and pressure distribution for the novel type actuator. Because the velocity and pressure distribution is the important element of the magnetic fluids flow. First, we analyzed the Maxwell equation for the multiple permanent magnet and then concluded the governing equations for the magnetic fluid flow using the equation of Navier-Stokes. And, we simulated the dynamic behavior of magnetic fluid flow using the FEM(Finite Element Method). And we illustrated the relation between magnetic field and dynamic behavior of magnetic fluid flow.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.127-132
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• 2003

Natural convection of a magnetic fluid is different from that of Newtonian fluids because magnetic-body force exists in addition to gravity and buoyancy. In this paper, natural convection of a magnetic fluids (W-40) in a cubic cavity was examined by experimental method. One side wall was kept at a constant temperature (25 $^{\circ}C$), and the opposite side wall was also held at a constant but lower temperature (20 $^{\circ}C$). The magnetic fields of various magnitude were applied up and down by permanent magnets. We measured temperatures at 5 points which are the most suitable places in cavity by the analysis record. The thermo-sensitive liquid crystal film (R20C5A) was utilized in order to visualize wall-temperature distributions. Several kinds of experiments were carried out in order to clarify the influence of direction and intensity of magnetic fields on the natural convection. It was found that the natural convection of a magnetic fluids could be controlled by the direction and intensity of the magnetic fields.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.26-30
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• 2013

This article is experimentally to investigate thermal-flow characteristics of the magnetic fluid for concentric annuli under externally fixed magnetic fields using visualization technique. Temperatures of the inner tube and outer tube in the tested concentric annuli were constantly maintained at both $30^{\circ}C$ and $25^{\circ}C$ and the middle tube was filled with the magnetic fluid. Magnetic field was uniformly applied using 4 permanent magnets at 4 directions of the concentric annuli. As a result, the thermal-flow characteristics of the magnetic fluid for concentric annuli could be controlled by directions of the external magnetic fields.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.133-146
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• 2001

We report the results of structural field observation and measurement of anisotropy of magnetic susceptibility (AMS) of the diamictitic Hwanggangri Formation distributed in Chungju-Suanbo area of the Okchon Belt, Korea. The outcrops of the Hwanggangri Formation show two types of cleavage in general: slaty cleavage (SI) and crenulation cleavage (5z). 5] cleavage is, however, well observable only in the notheastem (NE) part of study area, while overwhelmed by 52 cleavage in the southwestern (5W) part, indicating stronger later deformation in 5W part of the study area. This partitioning of the study area is corroborated by both IRM and AMS parameters: NE part of the study area is characterized by higher IRM intensity, higher bulk magnetic susceptibility, higher AM5 degree, and by oblate shape of magnetic susceptibility ellipsoid. Their values become drastically lowered toward southwest, and reach to a stable minimum in the whole 5W part of the study area. In addition, degree of both metamorphism and deformation tends to increase gradually from northeast toward southwest and also from northwest toward southeast in the study area. Based on the distribution pattern of the principal axes ( $k_1, k_2, k_3$ axes) of magnetic anisotropy ellipsoids revealed in the NE part of the study area, three episodes of deformation ( $D_1, D_2, D_3$ ) are recognized: D_1$ deformation produced $S_2$ cleavage with NE-5W trend, which is caused by a strong NW-SE tlattening of a coaxial pure shear. $D_2$ deformation produced 5z cleavage characterized by a non-coaxial deformation. It was caused by a ductile or semi-ductile thrusting toward NW and concurrent sinistral shearing along $S_2$ cleavage plane. Lastly, $D_3$ deformation produced tlexural folding of all previous structures with a nearly horizontal NE fold axis. Distribution pattern of the principal axes of magnetic anisotropy ellipsoid from the SW part of the study area, on the other hand, does not show any coherency among sites or samples. We interpret that this dispersed pattern of $k_1, k_2, k_3$ axes together with lower anisotropy strength indicates that magnetic fabrics in the SW part have been disturbed either by a superposition of strong deformation/metamorphism or by a kind of reciprocal strain due to an overlapping of $D_1$ and $D_2$ or by both processes.

• Korean Journal of Microbiology
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• v.38 no.3
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• pp.153-161
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• 2002

Sox4, a transcription factor, consists of three functional domains: an HMG-box domain as a DNA binding domain, serine rich region as a transactivation domain and glycine rich region (GRR), an unknown functional domain. Although Sox4 is known to be functionally involved in heart, B-cell and reproductive system development, its physiological function remains to be elucidated. We used pGEX expression system to develop a simple and rapid method for purifying Sox4 protein in suitable forms for biochemical studies of their functions. Unexpectedly, we observed that full-length Sox4 appears to be protease-sensitive during expression and purification in E. coli. To map the protease-sensitive site in Sox4, we generated various constructs with each of functional domains of Sox4 and purified as the GST-Sox4 fusion proteins using glutathione beads. We found that the specific cleavage site for the proteolytic enzyme, which exists in E. coli, is localized within the novel GRR of Sox4. Our study suggest that the GRR of Sox4 may a target for the cellular protease action and this cleavage in the GRR may be involved in regulating physiological function of Sox4. Additionally, our study may provide a useful method for investigating the proteolytic cleavage of the target molecule in E. coli.