• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1421-1423
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• 2003

The relationship between magnetic properties of BiPbSrCaCuo superconductor and externally applied magnetic field was studied to develop a magnetic field polarity sensor. The behavior was related to the magnetic flux trapped in the superconductor, which penetrates through the material by the external magnetic field. Some portion of the superconductor was changed to a normal state by the trapped magnetic flux. Electrical characteristics of the superconductor with trapped magnetic flux were extremely sensitive to the external magnetic field and showed different responses depending on the direction of the magnetic field.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2007년도 추계학술연구발표회 및 정기총회
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• pp.32-32
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• 2007

• 대한기계학회논문집A
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• 제32권8호
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• pp.654-659
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• 2008

This paper is to suggest a concept design of the permanent magnet type magnetic resonance imaging (MRI) device based on the parameter optimization method. Pulse currents in the gradient coils will introduce the effect of eddy currents in the ferromagnetic material, which will worsen the quality of imaging. In order to equalize the magnetic flux in the MRI device for good imaging, the eddy current effect in the ferromagnetic material must be taken into account. This study attempts to use the design of experiment (DOE) and the response surface method (RSM) for equalizing the magnetic flux of the permanent magnet type MRI device using that the magnetic flux can be calculated directly using a commercial finite element analysis package. As a result, optimal shapes of the pole and the yoke of the PM type MRI device can be obtained. The commercial package, ANSYS, is used for analyzing the magnetic field problem and obtaining the resultant magnetic flux.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.905-908
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• 2001

The microstructure and the magnetic properties of Mn-Zn ferrite, which were power loss and saturation magnetic flux density, were investigated as the function of the process before firing. The highest initial permeability and the lowest power loss were attained to the specimen with CaO 400 ppm as a resulted from the highest solubility to SiO$_2$and the creation of liquid phase which improved sintering. The biggest grain size, the highest saturation magnetic flux density and the lowest power loss, which was resulted from that the eddy current loss increased as grain size increased but the hysteresis loss much more decreased and the hysteresis loss strongly influenced on the total power loss rather than the eddy current loss, were obtained to the Mn-Zn ferrite added 2wt% PVA. The power loss was lowest and the saturation magnetic flux density was highest in case of 1 ton/$\textrm{cm}^2$ and the grain size was not influenced.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.186-187
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• 2006

The development of SFCL (Superconducting Fault Current Limiter) is getting more important as the power demand is increased rapidly. Up to now, several kinds of SFCL have been proposed and it is expected that they will be applied to appropriate position considering their own properties. Amongst those proposed SFCL, flux-lock type SFCL using the magnetic cancelation for current limiting has the advantages of overcoming the technical difficulties that other types of SFCLs have. In this paper, the integrated three-phase flux-lock type SFCL was fabricated and its operational modes were investigated through the short circuit tests. The operational mode were to divided into four mode according to the variation of the currents flowing into the secondary winding connected the superconducting elements and the speed of the quench generation. It was expected that the improvement of current limiting characteristics of the SFCL could be possible through control of the operational mode.

• 한국전기전자재료학회논문지
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• 제22권8호
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• pp.694-697
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• 2009

The separated three-phase flux-coupling type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO coated conductor. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO coated conductor was connected with secondary coil in parallel. In this paper, we investigated the current limiting characteristics through winding number of coil 2 and winding direction in the flux-coupling type SFCL. Through the analysis, it was shown that additive polarity condition and lower winding number of coil 2 have advantaged from the point of view of fault current limiting and burned of YBCO coated conductor.

• 대한기계학회논문집
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• 제12권3호
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• pp.622-629
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• 1988

본 연구에서는 박판형 열유속 센서의 감도를 높임과 동시에 두께와 면적을 줄 이기 위한 방안으로서 시벡 계수(Seebeck doefficient)가 일반 열전대재료보다 월등히 큰 반도체 열전재료를 이용하여 박판형 센서를 제작하고 그 성능을 조사하였다. 센 서의 제작에 사용한 열전재료는 Melcor 사에서 열전 열펌프 생산에 사용하기 위하여 개발한 소자로서 통상 텔루루화 비스무스(bismuth telluride)라 불리우며 그 조성은 비스무스, 텔루륨, 셀레늄, 안티몬의 4가지 합금에 미량의 불순물(dopent)이 첨가된 것으로 불순물의 종류에 따라 전기적인 P형 또는 N형의 반도체가 되는 것으로 알려져 있으며 Table 1에 물성치가 나타나 있다.

• Nuclear Engineering and Technology
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• 제32권4호
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• pp.379-394
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• 2000

As an in-vessel retention (IVR) design concept in coping with a severe accident in the nuclear power plant during which time a considerable amount of core material may melt, external cooling of the reactor vessel has been suggested to protect the lower head from overheating due to relocated material from the core. The efficiency of the ex-vessel management may be estimated by the thermal margin defined as the ratio of the critical heat flux (CHF）to the actual heat flux from the reactor vessel. Principal factors affecting the thermal margin calculation are the amount of heat to be transferred downward from the molten pool, variation of heat flux with the angular position, and the amount of removable heat by external cooling In this paper a thorough literature survey is made and relevant models and correlations are critically reviewed and applied in terms of their capabilities and uncertainties in estimating the thermal margin to potential failure of the vessel on account of the CHF Results of the thermal margin calculation are statistically treated and the associated uncertainties are quantitatively evaluated to shed light on the issues requiring further attention and study in the near term. Our results indicated a higher thermal margin at the bottom than at the top of the vessel accounting for the natural convection within the hemispherical molten debris pool in the lower plenum. The information obtained from this study will serve as the backbone in identifying the maximum heat removal capability and limitations of the IVR technology called the Cerium Attack Syndrome Immunization Structures (COASISO) being developed for next generation reactors.

• 전기전자학회논문지
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• 제22권3호
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• pp.759-766
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• 2018

This paper presents a high-speed axial-flux machine which utilizes the idea of sinusoidal shaped pole combined with a consequent iron-pole. The target of the proposed machine is the cost reduction of the relatively expensive Samarium-Cobalt (SmCo) permanent magnet (PM) material and the torque per PM volume improvement by using sinusoidal consequent-pole rotor. The effectiveness of the proposed machine is validated by comparing it with conventional consequent-pole and with conventional PM machines using 3-D finite element method (FEM) simulations. The comparison and analysis is done in terms of back electro-motive force (back-EMF) harmonic contents, torque per PM volume and torque ripple characteristics. The simulation results show that the proposed machine is suitable and cost-effective for high-speed and high torque per PM volume applications. Furthermore, due to the consequent pole, the magnetic flux saturation and the overload current torque-capability are also presented and discussed in the paper.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.8-12
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• 1994

Solid solutions $Sr_2$($Ta_{1-x}$$Nb_{x}$)$_2$$O_{7}$ (x = 0.0 - 1.0) composed of strontium-tantalate (low Curie temperature) and strontium-niobate (high Curie temperature) were prepared by the conventional mixed oxide method and the molten salt synthesis method (flux method). Phase relation, sintering temperature, grain-orientation and dielectric properties were investigated for sintered ceramic samples with different compositions. Both Curie temperature and dielectric constant at Curie temperature were increased, and sintering behavior and the degree of grain-orientation were improved with the increase of Nb content. Single phase $Sr_2$$Nb_2$$O_{7}$ powder was synthesized by using flux method at lower temperatures, and sintering temperature was also reduced by using flux method derived powder than using mixed-oxide derived powder. Sintering characteristics and dielectric properties of specimens prepared by flux method were better than those derived through the conventional method.