• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2158-2167
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• 2018

This paper analyzed the magnetic field produced by the cylindrical stator coils of permanent magnet spherical motor (PMSM). The elliptic equations about the vector magnetic potential were given. Given that the eddy current effects are neglected, the magnet field of the PMSM is regarded as irrotational field, which can be calculated by scalar magnetic potential. The current density of cylindrical stator coil was proposed based on the definition of current density. The expression of current density of stator coil was obtained according to the double Fourier series decomposition and spherical harmonic functions. Then the magnetic flux density for scalar magnetic potential was derived. Further, the influence of different parameters on radial flux density was also analyzed. Finally, the results by the analytical method in this paper were validated by finite element analysis (FEA).

• 한국초전도ㆍ저온공학회논문지
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• 제21권4호
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• pp.29-33
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• 2019

2G HTS wire with high engineering current density is desired for applications where compact, high power density superconducting equipment is important. We have succeeded in enhancing engineering current density of commercial SuperOx 2G HTS wire based on GdBCO by increasing the HTS layer thickness without fast degradation of the HTS film microstructure. This was possible after improving the temperature uniformity along the HTS film deposition zone. In particular, the wire engineering current density was increased from 700-770 A/㎟ (for a 65 ㎛-thick wire without stabilisation) or 430-480 A/㎟ (for a 105 ㎛-thick stabilised wire) at the beginning of this study to almost 1200 A/㎟ (for a 67 ㎛-thick wire without stabilisation) or 770 A/㎟ (for a 107 ㎛-thick stabilised wire) at completion of this study.

• 대한토목학회논문집
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• 제11권2호
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• pp.27-37
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• 1991

음부력을 갖는 유체가 소규모 저수지로 유입되어 일어나는 밀도류의 거동 및 순환이 차원해석과 수리실험을 이용하여 해석된다. 무차원침강점 및 밀도류전면속도, 밀도류전면이동거리, 머리 뒤의 밀도층내회석 등은 유입밀도후르드수, Fre의 영향을 받으며 밀도층의 두께, 흐름양상 및 저수지내 밀도의 변화는 밀도류전면이 하류단에 도달하여 반사되기 전과 후의 양상이 현저하게 다르다. 밀도층의 두께는 전자의 경우에는 Fre, 후자의 경우는 시간과 Fre의 영향을 받으며 이들은 지수식으로 표현할 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.252-255
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• 1996

Superconducting current lead is one of the promising applications of the oxide high-Tc superconductors, because they have the advantage of decreasing heat conduction to low temperature region, comparing with a conventional cooper alloy lead. High critical current density is a key factor for the applications such as current lead. (Bi,Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$\_$x/ high Tc superconductor haute been investigated in terms of critical current density. Bi-2223 superconducting current lead made by CIP and solid state sintering process. Bi-2223 current lead that heat treated at 836$^{\circ}C$ for 240 h in 1/13 P$\_$O$_2$/ had over 150 A/$\textrm{cm}^2$ of critical current density at 77K. We knew that the superconducting properties of tube type current leads were better than rods type of them. And we investigated the relation of Bi-2223 formation and heat treatment condition by XRD and SEM analysis.

• 한국표면공학회지
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• 제27권6호
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• pp.340-346
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• 1994

The method of uniforming current distribution in Hull cell are studied by using auxiliary anode, current shield bipolar electrode, and combinings bipolar electrode with current shield in order to find a way of uni-form deposition. The current density distributions are measured by each ammeter of the same inner resistance connected to divided cathode pannel respectively. The current density distributions of cathode electrode divided into five sections with 5mm width have a tendency of linear inclination, and that of twenty sections have a tendency of smoother curve than the curve of original Hull cell pannel. Their results showed lower value on the high current density portion and higher value on the low portion than that original Hull cell pannel. The current distribution in Hull cell is able to unify by using auxiliary anode, or combining bipo-lar electrode with current shield, but not efficient in using one of both individually.

• Transactions on Electrical and Electronic Materials
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• 제1권1호
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• pp.12-16
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• 2000

In this paper, we analyze self field effects of Bi-2223 tape-stacked cable assuming constant current density in the cross section of stacked cable. Generally, the critical current of Bi-2223 tape-stacked-cable in much less than the total summation of critical currents of each tape, which is mainly due to the self magnetic fields of the cable itself. Therefore, to predict the critical current of Bi-2223 tape-stacked-cable, we needs to analyze the self filed effects on the stacked cable as well as critical current density data(J$\_$C/) of one tape. To make it more complex, the critical current degradation of Bi-2223 tape is an-isotropic; the critical current is lower in the normal magnetic field(to the tape surface) than in the parallel field. In the paper, a novel approach to predict the critical current of a Bi-2223 tape-stacked-cable from a J$\_$C/-B curve of one tape is presented with the assumption of constant current density across the stacked cable, The approach basically includes the load analysis of the stacked tapes, and its usefulness is confirmed by the experimental data.

• 한국환경과학회지
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• 제7권2호
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• pp.223-232
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• 1998

득량만의 조석주기에 따른 성층특성을 연구하기 위하여 우선 30여개 관측점에서 관측된 수온, 염분, 밀도, 해류, 열수지, 바람, 밀도류 자료를 조사하였다. 이 관측자료를 토대로 성층현상을 규명할 수 있는 해석적 모델을 개발하였으며 이 해석적모델을 이용하여 얻어진 연구결과에 따르면, 득량만의 성층을 이루는 요인은 조석, 태양열, 밀도,류인 것으로 나타났으며, 성층을 파과할 수 있는 조석에너지의 혼합에너지의 에너지 기여율 $\varepsilon$ 은 약 0.020 - 0.021정도 되는 것으로 나타났다.

• 대한기계학회논문집A
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• 제39권7호
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• pp.659-663
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• 2015

본 연구에서는 다른 게이지 체적을 가지는 시편들의 동일한 에너지밀도 하에서의 통전소성 인장 거동을 실험을 통하여 비교하였다. 5052-H32 알루미늄 합금의 통전소성 인장실험의 결과는 시편의 게이지 길이나 폭 혹은 체적에 상관없이 동일한 에너지밀도가 가해질 때 거의 유사한 통전소성 특성을 보여준다. 특히 통전소성 인장시험의 전형적인 현상인 stress-drop 의 크기를 비교할 때, 소재의 통전소성이 개별적인 전류밀도와 통전시간이 아닌 에너지밀도에 의해서 영향을 받는다는 것을 확인할 수 있다. 본 논문의 결과는 통전소성 현상을 응용한 제조공정의 개발 시 공정설계변수들 중 전류밀도와 통전시간 두 가지를 에너지밀도 하나로 줄일 수 있다는 것을 의미하며 이는 향 후 다양한 통전소성 기반 제조기술의 개발에 이바지 할 것으로 예상된다.

• 한국환경과학회지
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• 제32권6호
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• pp.465-475
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• 2023

In this study, we evaluated the treatment efficiency of livestock wastewater by altering the current density using boron-doped diamond (BDD) electrodes. As the current density was adjusted from 10 to 35 mA/cm2, the removal efficiency of organic matter increased from 22.2 to 71.5%. Similar to that of organic matter, the removal efficiency of color increased with increasing current density up to 85.7%, indicating a higher removal efficiency for color than that of organic matter. The removal efficiency of ammonia nitrogen increased from 14.6 to 53.3% as the current density increased, but it was lower than that of organic matter. In addition, the removal of organic matter, color, and ammonia nitrogen followed first-order reactions, according to the reaction rate analysis. The energy consumption ranged from 4.87 to 8.33 kWh/kg COD, and it was found that the organic matter removal efficiency was more efficient at high current densities. Based on various analyses, the optimal current density was 20 mA/cm2, and the corresponding energy consumption was 6.824 kWh/kg COD.

• 한국표면공학회지
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• 제57권1호
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• pp.8-13
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• 2024

Anodizing of Al6061 alloy was conducted in two different electrolytes of 20% sulfuric acid and 8% sulfuric acid + 3 % oxalic acid solutions at a constant current or decreasing current density conditions, and its dielectric breakdown voltage was measured. The surface morphology of anodic oxide films was observed by TEM and thermal treatment was carried out at 400 ℃ for 2 h to evaluate the resistance of the anodic oxide films to crack initiation. The anodic oxide film formed in 8% sulfuric acid + 3 % oxalic acid solution showed higher dielectric breakdown voltage and better resistance to crack initiation at 400 ℃ than that formed in 20% sulfuric acid solution. The dielectric breakdown voltage increased 6 ~12% by applying decreasing current density comparing with a constant current density.