• Journal of Integrative Natural Science
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• v.3 no.3
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• pp.148-152
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• 2010

Photoluminescence properties and surface morphologies of porous silicon etched with various applied current densities at fixed etching times. FE-SEM image of porous silicon surface indicated that the porous silicon prepared at currents below 200 mA exhibited very bright red photoluminescence properties. As the applied current densities increased, the photoluminescence efficiencies of porous silicon prepared at applied current densities above 300 mA decreased, and displayed the cracked surface on porous silicon. This cracked surface start to collapsed to give cracked domains.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.260-270
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• 2012

This work aims to present a theoretical analysis of the electric and magnetic surface current densities of a circular microstrip antenna (CMSA) as a body of revolution. The rigorous analysis of these problems begins with the application of the equivalence principle, which introduces an unknown electric current density on the conducting surface and both unknown equivalent electric and magnetic surface current densities on the dielectric surface. These current densities satisfy the integral equations (IEs) obtained by canceling the tangential components of the electric field on the conducting surface and enforcing the continuity of the tangential components of the fields across the dielectric surface. The formulation of the radiation problems is based on the combined field integral equation. This formulation is coupled with the method of moments (MoMs) as a numerical solution for this equation. The numerical results of the electric and magnetic surface current densities on the outside boundary of a CMSA excited by $TM_{11^-}$ and $TM_{21^-}$ modes are presented. The radiation pattern is calculated numerically in the two principle planes for a CMSA and gives a good results compared with measured results published by other research workers.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.433-438
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• 2008

This paper analyses current densities induced inside a worker using AC arc welder. Applying the boundary element method, we calculate current densities induced in organs inside a worker in case he was located at 1cm, 3cm, 5cm, 10cm, 15cm, 20cm far from a power cable of AC arc welder. As results of study, we find a maximum current density induces at a heart surface and may be higher than $10mA/m^2$ of ICNIRP guideline if he works within 15cm from a power cable.

• Progress in Superconductivity
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• v.11 no.2
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• pp.128-134
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• 2010

The magnetic flux profiles in SmBCO and YBCO coated conductors(CC) in the presence of the external field were comparatively investigated by magneto-optic image and scanning hall probe measurements. The current distributions calculated by using the inversion method from measured field profiles show that the decrease of current densities near the edges of SmBCO CC is more significant than those of YBCO CC. Through the comparison of the numerical analysis based on Kim's critical state model and the Brandt and Indenbom's solution, we found that this feature is related to their different field dependant properties of the critical current densities.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1410-1411
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• 2007

This paper analyses current densities induced inside a worker using AC arc welder. Applying the boundary element method, we calculate current densities induced in organs inside a worker in case he was located at 1[cm], 3[cm], 5[cm], 10[cm], 15[cm], 20[cm] far from a power cable of AC arc welder. As results of study, we find a maximum current density induces at a heart surface and may be higher than 10[$mA/m^2$] of ICNIRP guideline if he works within 15[cm] from a power cable.

• Progress in Superconductivity and Cryogenics
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• v.14 no.2
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• pp.1-7
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• 2012

In this review paper, we report the characteristics of the critical current density in FeAs based superconductors which is newly discovered by Hosono group of Tokyo Institute of Technology on 2008. Since the many specimens in present stage are not single crystals, there are two kinds of critical current density observed in the specimens which are so-called local and global critical current densities. Therefore, it is necessary to evaluate both kinds of critical current densities. The history effect in which the global critical current density shows different values in increasing and decreasing magnetic field is also observed when the specimens have the local and the global critical current densities. The wire which critical current is 180 A is successfully developed with using the knowledge of abovementioned characteristics of two kinds of critical current densities and the history effect.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.136-139
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• 2000

The relations between tensile stresses and critical current densities (J$_c$) of coated conductors were measured. Around 320 MPa of tensile stress, the critical current densities of coated conductor fabricated on pure Ni tape were reduced to zero at 77K, where J$_c$ for zero stress was order of 10$^5$A/cm. The critical tensile stress was much enhanced for the coated conductors fabricated on NiCr alloy tapes. However fabrication conditions for the growth on such alloys are much different from those on the pure Ni and it was not easy to get good textures and large critical currents. The detailed fabrication methods on those alloys will be presented.

• Corrosion Science and Technology
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• v.16 no.3
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• pp.109-114
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• 2017

Monitoring of corrosion is in most cases based on simulation of environmental conditions on a large and complex structure such as a buried pipeline using a small probe, and the measurement of thermodynamics and kinetics of corrosion processes occurring on the probe surface. This paper presents a hybrid corrosion monitoring probe designed for simulating deteriorating conditions wrought by disbonded coatings and for measuring current densities and distribution of such densities on a simulated pipeline surface. The concept of the probe was experimentally evaluated using immersion tests under cathodic protection (CP) in high resistivity aqueous solution. Underneath the disbonded area, anodic currents and cathodic currents were carefully measured. Anodic current densities were used to calculate metal loss according to Faraday's law. Calculated corrosion patterns were compared with corrosion damage observed at the surface of the probe after a series of stringent tests. The capability of the probe to measure anodic current densities under CP, without requiring interruption, was demonstrated in high resistivity aqueous solution. The pattern of calculated metal loss correlated well with corrosion products distribution observed at the array surface. Working principles of the probe are explained in terms of electrochemistry.

• Proceedings of the IEEK Conference
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• summer
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• pp.343-347
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• 2004

High oxidation temperature of SiC shows a tendency of carbide formation at the interface which results in poor MOSFET transfer characteristics. Thus we developed oxidation processes in order to get low interface charge densities. N-type 6H-SiC MOS capacitors were fabricated by different oxidation processes: dry, wet, and dry­reoxidation. Gate oxidation and Ar anneal temperature was $1150^{\circ}C.$ Ar annealing was performed after gate oxidation for 30 minutes. Dry-reoxidation condition was $950^{\circ}C,$ H2O ambient for 2 hours. Gate oxide thickness of dry, wet and dry-reoxidation samples were 38.0 nm, 38.7 nm, 38.5 nm, respectively. Mo was adopted for gate electrode. To investigate quality of these gate oxide films, high frequency C- V measurement, gate oxide leakage current, and interface trapped charge densities (Dit) were measured. The interface trapped charge densities (Dit) measured by conductance method was about $4\times10^{10}[cm^{-1}eV^{-1}]$ for dry and wet oxidation, the lowest ever reported, and $1\times10^{11}[cm^{-1}eV^{-1}]$ for dry-reoxidation

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.3-6
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• 2003

We have developed a small-sized superconducting magnetic energy storage (SMES) device, which provides electric power with high quality to sensitive electric loads. In large magnets such as the SMES magnets the stability, which is determined by several factors, e.g. conductors cooling condition and operating current, magnets winding structure, is a crucial problem. The effect of the cooling condition, the copper ratio, and the conductor's size upon the recovery currents was investigated experimentally. The results indicate that the recovery current characteristics of the strands vary considerably according to their insulation method. In the fully insulated strands with a low copper ratio, the recovery current densities range from 10 to 20 % of their engineering critical current densities. The recovery current density of the 30-conductor with a cooling channel is about a factor of 1.8 higher than that without a cooling channel.