• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1243-1244
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• 2006

Five kinds of double stacked 385 (55 x7) filamentary Bi2212/Ag round wires and 55 filamentary tapes with different Ag ratios (silver area/superconductor area) have been fabricated via PIT method, and the effects of Ag ratio and processing factors on critical current density were studied. The effects of the maximum temperature and average filament diameter on critical current density were also studied. The wire of 0.74 mm diameter having Ag ratio 3.7 showed critical current density of $2,218\;A/mm^2$ at 4.2 K, 0 T.

• 대한전기학회논문지:전력기술부문A
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• 제53권8호
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• pp.461-465
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• 2004

This paper analysed the induced current density by electric field of human body under the 765 kV transmission line considering permittivity and conductivity. As permittivity of human body is very high as $10^6$ at 60 Hz, special numerical computation technique in Surface Charge Method(SCM) for composite media with extremely different properties is applied to reduce calculation error of induced current density and electric field inside the human body. Calculation results show that the average of the induced current density inside human body is about 3mA/$m^2$, which is less than ICNIRP criterion (10mA/$m^2$).

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.449-453
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• 2005

Electrochemical systems find widespread technical application. Industrial electrolytic process include electroplating, electroforming, and electropolishing. Electroforming and electroplating is widely used in the manufacture of metal parts. This paper based on the basic equations of electrics and electrochemical kinetics, was employed for a theoretical explanation of the current density distribution on electroforming process. We calculated current density distribution and potential distribution on cathode. Also, calculated current density distribution of vertical direction. It was shown that current density is related with distance of between anode and cathode and mass transfer process. And make an experiment on its relation and electroformed thickness. It shows that it is useful method using FEM with multi-physics to estimate electroformed thickness.

• 한국표면공학회지
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• 제51권1호
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• pp.62-70
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• 2018

Sulfamate plating solution containing a small amount of chloride bath was fabricated to study the properties of the electrodeposited Ni thin films. Effects of the changes of current density and additive concentration on current efficiency, residual stress, surface morphology and microstructure of Ni thin films electrodeposited from Ni sulfamate-chloride baths were investigated. The current efficiency was measured to be more than about 95%, independent of the changes of current density and saccharin concentration in the baths. Residual stress of Ni thin film was appeared to be the compressive stress modes in the range of $5{\sim}30mA/cm^2$ current density. Maximum compressive stress was observed at the current density of $10mA/cm^2$. Compressive stress values of Ni thin/thick films were increased to be about -85~-100 MPa with increasing saccharin concentration from 0 to 0.0195 M(4 g/L). Surface morphology was changed from smooth to nodule surface appearance with increasing the current density. Smooth surface morphology of Ni thin films electrodeposited from the baths containing saccharin was observed, independent of the saccharin concentration. Ni thin/thick films consist of FCC(111), FCC(200), FCC(220), FCC(311) and FCC(222) peaks. It was revealed that the FCC(200) peak of Ni thin films is the preferred orientation in the range of $5{\sim}30mA/cm^2$ current density. The intensity of FCC(200) peak was gradually decreased and the intensity of FCC(111) peak was increased with increasing saccharin concentration in the baths.

• 한국표면공학회지
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• 제53권4호
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• pp.190-199
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• 2020

Copper pyrophosphate baths were employed in order to study the dependencies of current efficiency, residual stress, surface morphology and microstructure of electrodeposited Cu thin layers on applied current density. The current efficiency was obtained to be more than about 90 %, independent of the applied current density. Residual stress of Cu electrodeposits was measured to be in the range of -30 MPa and 25 MPa with the increase of applied current density from 0.5 to 15 mA/㎠. Relatively smooth surface morphologies of the electodeposited Cu layers were obtained at an intermediate current range between 3 and 4 mA/㎠. The Cu electrodeposits showed FCC(111), FCC(200), and FCC(220) peaks and any preferred orientation was not observed in this study. The average crystalline size of Cu thin layers was measured to be in the range of 44~69 nm.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권2호
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• pp.59-64
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• 2001

The distribution of current in the conductors influenced by the armature geometry and velocity is an important parameter for determining performance of an electromagnetic launcher(EML). the electric current in the early launching stage tends to flow on the outer surfaces of the conductors, resulting in very high local electric current density. However, the tendency for current to concentrate on the surface is driven by the velocity skin effect later in launching stage. The high current density produces high local heating and, consequently, increases armature wear which causes several defects on EML system. This paper investigates the effects of rail/armature geometry on current density distribution, launcher inductance gradient (L'), and contact force. Three geometrical parameters are used here to characterize the railgun system. These are the ratio of contact length to root length, relative position of contact leading edge to root trailing edge, and the ratio of rail overhang to the rail height. The distribution of current density, L', contact force between various configurations of the armature and the rail are analyzed and compared by using the EMAP3D program.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 초전도 자성체
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• pp.37-40
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• 2002

Superconductor wire fabricated by electrophoresis showed its critical current density depended on parameters such as applied voltage and deposition time. Substrate and suspension solutions. and its properties are also important parameters. When same optimal parameter and condition was used, deposition density of superconductor film affect directly its critical current density. In this study, therefore, electrophoretic deposition technique was utilized for a densification of YBCO superconducting wire, and researches on electrophoretic suspension solutions and additive were experimentally performed for an improvement of the critical current density of fabricated electrophoretically superconducting wire. The samples fabricated in the solution with the additive, 8 vol.% of 1% PEG(1000), showed the highest critical current density.

• 소성∙가공
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• 제29권1호
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• pp.37-43
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• 2020

Increasing the critical current density of superconducting wire is one of the difficult challenges in the field of superconductivity. It is well known that the higher volume fraction of uniformly dispersed α-Ti is able to enhance the critical current density of superconducting material NbTi because α-Ti serves as a flux pinning center. The volume fraction of α-Ti highly depends on the grain size of NbTi because α-Ti precipitates at the grain boundaries or triple points. For this purpose, we investigated the effect of initial microstructures of NbTi obtained from hot rolling in various temperature conditions on the critical current density. In addition, subsequent heat treatment was assigned to precipitate α-Ti and groove rolling/cold drawing was adopted to produce a wire with a diameter of about 1.0 mm. It was observed that the band structure was formed after hot rolling at 500~600℃. It was also found that the volume fraction of α-Ti after hot rolling at 500~600℃ was higher and it led to the highest critical current density.

• International Journal of Precision Engineering and Manufacturing
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• 제2권1호
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• pp.18-25
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• 2001

Electrolytic polishing is the anodic dissolution process in the transpassive state. It removes non-metallic inclusion and improves mechanical and corrosion resistance of stainless steel. If there is a Bailby layer, it will be removed and the true structure of the surface will be restored. Electrolytic polishing is normally used to remove a very thin layer of material from the surface of metal object. A new electrolyte composed of phosphoric, sulfuric and distilled water has been developed in this study. Two current density, high & low current density regions, have been applied in this study. In this study, In the region of high current density, there is no plateau region but excellent electrolytic polishing effect can be accomplished in short machining time because material removel process and leveling process occur simultaneously. In the low current density region, there can be found plateau region. The material removal process and leveling process occur successively. The aim of this work is to determine electrolytic polishing for stainless steel in terms of high & low current density and workpiece surface roughness.

• 전력전자학회논문지
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• 제10권6호
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• pp.618-625
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• 2005

본 논문은 CRT 표시장치에서 고전류밀도를 구현하기 위한 전자총의 히터와 캐소드의 최적의 저전력설계와 실험을 수행하였다. CRT 표시장치에서 밝기, 고휘도, 고해상도와 대화면화를 위해서는 전자총 캐소드(cathode)의 고전류밀도가 필수적이다. 이를 위해서는 함침형 캐소드가 사용되며, 고전류밀도를 얻기 위해 히터의 동작온도를 높여야하는데 이에 비례하여 소비전력도 증가한다. 본 논문에서는 고전류밀도 캐소드 히터의 저전력 설계를 위하여 히터의 리드형태(Lead Type), 코팅(Coating)법, 발열부의 1차 및 2차 코일링의 피치와 권선수를 달리한 샘플을 제작, 시험하였다.