• Journal of Welding and Joining
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• 제15권3호
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• pp.36-46
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• 1997

Dynamics of molten drop detachment in the Gas Metal Arc (GMA) welding is investigated using the Volume of Fluid(VOF) method. The electromagnetic effects are included in the formulation of the VOF method which has been widely used to analyze the dynamics of the fluid having a free surface. The molten drop geometry, pressure and velocity profiles within the drop are calculated numerically in the cases of globular and spray transfer modes. It appears that the velocity and current distribution affect metal detachment. It is found that the taper is formed and maintained during the spray transfer by the electromagnetic force. Predicted results show reasonably good agreement with the available experimental data which validates the application of the VOF method to metal transfer analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.531-533
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• 2000

In compared with air insulated switchgear, GIS has a high efficiency and confidence So the transformer substation can be reduced the size to 1/10. Insulation method using $SF_6$ gas has a very excellent insulation characteristics for high pressure equipment but has a characteristics that insulation heredity is changed for internal unequal electric field. So analysis of electromagnetic field in GIS is very important basic data for structure design and trouble diagnosis process. In compared with established method, SNM in this paper observes variation of the electromagnetic field with real time and get result very similar to measurement. In order to know the variation of electromagnetic field distribution for transient response for time and position, variations are observed when the spacer is bonded and metal particles are moving fast.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1431-1434
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• 1994

The annular induction electromagnetic pump with maximum flowrate of $60{\ell}/min$ for the sodium coolant system of liquid metal fast breeder reacters has been designed using the equivalent circuit method. The final optimum values of geometrical and electromagnetic parameters were obtained for an annular induction pump from the relation of the electrical variables giving the developing force to the fluid and the pressure drops between both sides of the pump. The physical properties of the core, coil condoctor materials in the high temperature and pump cooling systems under operation have been taken into account in the design of the pump. The structural material were also selected considering the reaction with sodium and the magnetic field distortion.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.2067-2073
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• 2018

This paper will present the design of a novel-type velocity-controllable electromagnetic coil launcher (EMCL). By studying the influence of initial capacitor voltage on the velocity of an EMCL, the launcher voltage can be set to precisely adjust the velocity of projectile launching. The simulation of voltage and velocity in relation to time is obtained by Maxwell software. The experimental data show that for the launch accuracy to be achievable, the actual precision is 2%. Because of the excellent performance of Velocity-controllable EMCL, it can replace the air gun and applied to split Hopkinson pressure bar (SHPB).

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3919-3927
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• 2022

This study presents an optimal design of the coolant system of a non-refueling full-life small reactor by analyzing the space-integrated geometrical and electromagnetic variables of an extra vessel electromagnetic pump (EVEMP) for the circulation of a lead-bismuth eutectic (LBE) coolant. The EVEMP is an ideal alternative to the thermal-hydraulic system of non-refueling full-life micro reactors as it possesses no internal structures, such as impellors or sealing structures, for the transportation of LBE. Typically, the LBE passes through the annular flow channel of a reactor, is cooled by the heat exchanger, and then circulates back to the EVEMP flow channel. This thermal-hydraulic flow method is similar to natural circulation, which enhances thermal efficiency, while providing a golden time for cooling cores in the event of an emergency. When the forced circulation technology of the EVEMP was applied, the non-refueling full-life micro reactor achieve an output power of 60 MWt, which is higher than that achievable via the natural circulation method (30 MWt). Accordingly, an optimized EVEMP for Micro URANUS with a flow rate of 4196 kg/s and developed pressure of 73 kPa under a working temperature of 250 ℃ was designed.

• 한국항행학회논문지
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• 제26권6호
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• pp.464-473
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• 2022

본 논문에서는 자율무인잠수정에 사용되는 UHF-GPS 안테나의 성능을 만족하는 경량화 설계에 대해 제안하였다. 설계 프로세스에 사용된 구조해석, 수밀외압시험 그리고 비파괴 검사는 수중운용 환경에서 발생하는 외력에 대한 구조 안전성을 고려하여 결정하였다. 먼저 수상에서 모함과 통신을 위한 UHF-GPS 안테나 성능과 수중 운용 시 발생하는 20 bar 압력을 고려한 레이돔 재질을 선정하였으며, 전자기장해석 및 구조해석을 수행하여 무게 대비 강도 및 강성이 높고 유전율이 우수한 PA-GF 소재를 선정하였다. 그리고 UHF-GPS 안테나의 요구 중량을 만족하기 위한 레이돔 두께별 전자기장해석 및 구조해석을 추가 수행하였으며, 최종 모델 선정 후 수밀외압시험 및 비파괴 검사를 통해 구조 안전성을 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1098-1101
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• 1995

NbTi thin films were prepared on Si wafer and Cu substrate by rf magnetron sputtering in the range of sputtering pressure $3{\times}10^{-2}$torr to $3{\times}10^{-4}$torr at room temperature. The influence of sputtering pressure and substrate type on crystallographic orientation and morphology of NbTi thin films was investigated by using X-ray diffraction(XRD) and scanning electron microscopy(SEM), respectively. And the effect of crystallographic orientation and morphology of NbTi film on electromagnetic behaviors was estimated by measuring critical current in various applied magnetic field. The film morphology changed from porous structure consisting of tapered crystallites to densely deposited film decreasing with sputtering pressure. The change of crystallographic orientation with the sputtering pressure and rf power was calculated from the texture coefficient of(002) plane based on XRD patterns. It was found that a change of texture coefficient of(002) plane increased with decreasing sputtering pressure. From observation of critical current in various applied magnetic field, we have identified that the change of critical current abruptly decrease applying with magnetic field and NbTi film produced at high sputtering pressure does not exhibit superconductivity but at low sputtering pressure shows superconductivity.

• Journal of Welding and Joining
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• 제17권6호
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• pp.70-77
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• 1999

Surface depression in the arc welding is calculated numerically to analyze its influence on pool convection and oscillation. The magnitude of surface depression due to arc pressure on the stationary GTA pool surface is relatively small, and fluctuations of the surface and velocity are caused mainly by arc pressure. The inward flow on the surface due to the electromagnetic force and positive surface tension gradient acts to decrease surface depression. Surface depression appears to have minor effects on average flow velocity and thus pool geometry. Pool oscillation occurs due to surface vibration, and oscillation frequencies are affected mainly by the surface tension and pool width. The input parameters such as arc pressure and current have negligible effects on the oscillation frequency, and the surface tension gradient has limited effects. Since the oscillation frequency varies slightly according to penetration, pool oscillation for the partial penetration weld pool is applicable to monitor the pool width.

• Journal of Magnetics
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• 제18권2호
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• pp.168-172
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• 2013

We have developed a high-field and high-frequency ESR system using a commercially available magnetometer equipped with the superconducting quantum interference device (SQUID). This is magnetization detection type ESR and ESR is observed as a change of the magnetization at the resonance condition under irradiation of the electromagnetic wave. The frequency range is from 70 to 315 GHz and the maximum magnetic field is 5 T. The sensitivity is estimated to be $10^{13}$ spins/G. The advantage of this system is that the high-field ESR measurements can be made very easily and quantitatively. Moreover, this high-field ESR can be applied to the measurements under pressure by using a widely used piston-cylinder pressure cell.

• Computers and Concrete
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• 제8권4호
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• pp.425-443
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• 2011

Most previous studies have generally overlooked the contribution of thermal stresses generated within the concrete mass when subjected to microwave heating and reported on pore-pressure as being the dominant cause of surface spalling. Also, the variation in electromagnetic properties of concrete and its effects on the microwave heating process have not been studied in detail. In this paper, finite element modeling is used to examine the simultaneous development of compressive thermal stresses and pore-pressure arising from the microwave heating of concrete. A modified Lambert's Law formulation is proposed to estimate the microwave power dissipation in the concrete mass. Moreover, the effects of frequency and concrete water content on the concrete heating rate and pattern are investigated. Results show high compressive stresses being generated especially in concrete with a high water content when heated by microwaves of higher frequencies. The results also reveal that the water content of concrete plays a crucial role in the microwave heating process.