• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.43-46
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• 2000

In this paper, the stress and transient currents associated with the on and off time of applied voltage were used to measure the density and distribution of high voltage stress induced traps in thin silicon oxide films. The transient currents were due to the discharging of traps generated by high stress voltage in the silicon oxides. The trap distributions were relatively uniform near both cathode and anode interface. The trap densities were dependent on the stress polarity. The stress generated trap distributions were relatively uniform the order of $10^{11}\sim10^{21}$[states/eV/$cm^2$] after a stress. The trap densities at the oxide silicon interface after high stress voltages were in the $10^{10}\sim10^{13}$[states/eV/$cm^2$]. It appear that the stress and transient current that flowed when the stress voltage were applied to the oxide was caused by carriers tunneling through the silicon oxide by the high voltage stress generated traps.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.37-42
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• 2007

We are developing a 22.9 kV/25 MVA superconducting fault current limiting(SFCL) system for a power distribution network. A Bi-2212 bulk SFCL element, which has the merits of large current capacity and high allowable electric field during fault of the power network, was selected as a candidate for our SFCL system. In this work, we experimentally investigated important characteristics of the 190 kVA Bi-2212 SFCL element in its application to the power grid e.g. DC voltage-current characteristic, AC loss, current limiting characteristic during fault, and so on. Some experimental data related to thermal and electromagnetic behaviors were also compared with the calculated ones based on numerical method. The results show that the total AC loss at rated current of the 22.9 kV/25 MVA SFCL system, consisting of one hundred thirty five 190 kVA SFCL elements, becomes likely 763 W, which is excessively large for commercialization. Numerically calculated temperature of the SFCL element in some sections is in good agreement with the measured one during fault. Local temperature distribution in the190 kVA SFCL element is greatly influenced by non-uniform critical current along the Bi-2212 bulk SFCL element, even if its non-uniformity becomes a few percentages.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.865-868
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• 1993

This paper describes a simple random signal generator employing by CMOS analog technology in current mode. The system is a nonlinear dynamical system described by a difference equation, such as x(t＋1) = f(x(t)) , t = 0,1,2, ... , where f($.$) is a nonlinear function of x(f). The tent map is used as a nonlinear function to produce the random signals with the uniform distribution. The prototype is implemented by using transistor array devices fabricated in a mass product line. It can be easily realized on a chip. Uniform randomness of the signal is examined by the serial correlation test and the $\chi$2 test.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.35-39
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• 2003

A typical HTS power transmission cable has multi-layer conductor structure to increase the current capacity. The tapes of the innermost layer are wound on a round former, and adjacent tapes of another layer are separated by a thin insulating film. However, usually the current is not evenly distributed among the layers because of inductance difference of each layer, and the inductance is provided by the winding pitch of each layer's tape. Consequently n method to make the current distribution more uniform is a adjusting the tape winding pitch, hence reduce the AC loss. This paper describes a current distribution by adjusting a tape winding pitch of each layer. Also, this paper shows recommendations for future cable conductor prototypes.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.1
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• pp.38-42
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• 2004

In this paper we analyzed the electromagnetic behavior of a superconducting fault current limiter (SFCL) under the quench state using FEM. The analysis model used in this work is 5.5 KVA meander-line type SFCLs which are currently developed by Superconductor Power System Lab in Korea Electric Power Research Institute. Meshes of 3,650 triangular elements were used in the analysis of this SFCL. Analysis results showed that the distribution of current density was concentrated to inner curved line in meander-line type SFCL and the maximum current density was 14.61 A/$m^2$ and also the maximum Joule heat was 2,030 W/$m^2$ in this region. We think that the new and the modified structure must be considered for an uniform distribution of the electromagnetic field.

• Journal of the Korean Electrochemical Society
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• v.12 no.4
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• pp.317-323
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• 2009

Theoretical calculations for the secondary current distributions for the electrode with a projection part in electroplating were performed. Two kinds of electrodes were considered. One is a electrode with the overall conducting surfaces(Case 1) and the other is an electrode in which only a projection part has a conducting surface(Case 2). The effects of applied potential, the ratio of ion exchange current to conductivity, $\xi$ and the aspect ratio on the current distribution were examined. The increase of applied current or the value of $\xi$ decreased the uniformity of current distribution. The small value of aspect ratio resulted the more uniform current distribution and Case 2 showed the better uniformity than Case 2. When this model was applied into an electrode with various projection parts, the local current distribution along the electrode surface were obtained successfully. In this case, the decrease of $\xi$ also increase the uniformity of current distribution as seen previously.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.7
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• pp.626-630
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• 2007

The AC loss is an important issue in the design of the high temperature superconductor (HTS) power cables and fault current limiters. In these applications, a cylindrical HTS conductor is often used. In commercialization of these apparatuses, AC loss is a critical factor but not elucidated completely because of complexities in its measurement, e.g. non-uniform current distribution and phase difference between currents flowing in an individual HTS tape. We have prepared two cylindrical conductors composed of a Bi-2223 tape with different critical current density. In this paper, the AC loss characteristics of the conductors have been experimentally investigated and numerically analyzed. The result show that the measured losses for two conductors are not dependent on both arrangements and contact positions of a voltage lead. This implies that most of loss flux is only in the conductors. The loss for the Bi-2223 conductor with low critical current density is in good agreement with the calculated loss from Monoblock model, whereas the loss measured for the Bi-2223 conductor with high critical current density doesn't coincide with the loss calculated from the Monoblock model. The measured loss is also different from numerically calculated one based on the polygon model especially in low transport current.

• Journal of the Korean Society of Clothing and Textiles
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• v.46 no.5
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• pp.910-926
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• 2022

Suitability for the human body, freedom to move and thermal insulation are important design considerations in military clothing. This study investigates the performance and wearer-satisfaction of the functional inner winter uniform currently used in Korea; it is hoped that our data can inform the development of a future version. Interviews were conducted, in which the participants suggested various improvements. The uniforms were mainly worn for guard duty or as daily attire in cold weather. The participants chose how many layers to wear according to the current situation, rather than sticking to the layering recommended in the manual. Layering choices did not significantly affect combat efficiency but were found to affect wearers' comfort. Wearers' satisfaction was found to depend on the convenience of the clothing, whether it was in the appropriate size, freedom to move and thermal insulation. Also, this study suggests a problem with the current size system, as the analysis of size distribution, across all sizes, the range of current production is insufficient to cover the demand.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.2050-2058
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• 2018

Impulse characteristic of transmission tower grounding grid is needed for lightning protection of transmission line. This paper describes an outdoor experimental test facility established for large-scale grounding grid of transmission tower, made up of four impulse current generators and a circle current return electrode. The amplitude of impulse current is up to 100 kA. The results of the CDEGS simulation and GPR measurement reveal the uniform current distribution in the test arrangement. An impulse test for a square electrode with extended conductors is carried out in condition of three current waveforms with different amplitude. Based on the electrical network model and iterative algorithm method, a calculation model is proposed to simulate the impulse characteristic of large-scale grounding grid considering soil ionization. The curve of impulse resistance against the current amplitude shows the soil ionization both from the simulation and test. Deviation between the simulation and test result is less than 15%.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.750-752
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• 2002

An HTS power cable has multi-layer conductor structure to increase the current capacity. However, usually the current is not evenly distributed among the layers. This paper describes a method to make the current distribution more uniform and hence reduce the AC loss. Also. this paper shows recommendation for future cable conductor prototypes.