• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.771-772
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• 2006

Mechanical properties of metal injection molded titanium and titanium alloy parts were investigated in this study. Material powders with low oxygen content and spherical shape were obtained by electrode induction-melting gas atomization which could melt and atomize titanium and titanium alloy bars with no touch on crucible or tundish. Tensile specimens were fabricated from obtained powders by metal injection molding process. Tensile strength of the specimens increases with increasing oxygen content. This result corresponds to a tendency of wrought metal.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.407-410
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• 1998

During the past decade, substantial research effort has been directed into the development of rechargeable lithium batteries. Although some improvements in cycle life and efficiency have been achieved, the reversibility of the lithium electrode remains as a significant problem in aprotic solvent based electrolyte. The major problems limiting cycle life are short circuits resulting from growth of lithium dendrites, and macroscopic shape changes during the recharge process. As an anode material of lithium rechargeable battery, amorphous carbon materials have been studied extensively because of their high electrochemical performance. The polyacene materials prepared from phenol refine at relatively low temperature(550∼750$^{\circ}C$) show a highly Li-doped state up C$_2$Li state without liberation of Li cluster. So it has largely layered distance 4${\AA}$. The Li storage mechanism as well as the large hysterisis observed in the voltage-capacity profile of the amorphous carbone materials are still the subjects of controversy. We prepared each polyacene material various temperature and investigated electrochemical property. The mole ratio of [H]/[C] is 0.027∼0.015 range.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.49-51
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• 2005

This paper presents the potential interferences in various grounding electrode systems. The ground potential rise and potential interference coefficients were calculated as a function of the configuration and size of grounding electrodes and the distance between grounding electrodes. The potential rise and potential interference coefficient strongly depend on the distance between grounding electrodes, the shape and size of grounding electrodes.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.163-167
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• 2007

A field emission electron gun including 3 electrodes including one cathode and two anodes is very important for high resolution electron microscope. To have functions to control the initially-emitted electron beam, two anodes act as an electrostatic lens according to equipotential lines by adjusting the spot size, intensity, and working distance. To verify the action of the electron beam by the electrostatic lens by changing several parameters such as electrode shape, displacement and applied voltage to the electrodes, the two lenses were design and simulated and then their performances were analyzed with angular beam intensity(distribution), electrical optic axis variation and their stability.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.15-22
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• 2019

Metallic nanowires (MNWs) have recently been considered as one of the most promising candidates for flexible electrodes of advanced electronics including wearable devices, electronic skins, and soft robotics, since they have high aspect ratio in physical shape, low percolation threshold, high ductility and optical transparency. Herein, we review the latest findings related to the MNWs and discuss the properties and potentials of this material that can be used in implementation of various advanced electronic devices.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.9
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• pp.1300-1305
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• 2012

A triaxial Blumlein pulse forming line has been designed to generate a pulse whose voltage is ~300 kV, pulse duration is ~5 ns, and rise time is ~500 ps. It turns out, however, that the rise time of the pulse becomes much longer than 500 ps due to parasitic inductances and capacitances existing inside the system. A peaking switch has been developed to shorten the rise time of the pulse from Blumlein pulse forming line. In the peaking switch, a wedge-shaped dielectric material (MC 901 nylon) is employed to surround the electrode on the antenna side. This shape inhibits an abrupt change of the output impedance, thereby minimizing the reflection of the output pulse. Experimental results show that the peaking switch is capable of improving the rise time of the pulse at a level of 500 ps.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1849-1851
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• 2003

To obtain a low ground resistance in high resistivity soil, long vertical ground rods are often used. However, if the lightning current or fault current with high frequency flow into the grounding system, the ground impedance is significantly increased because of the inductive behavior. This paper presents how the impulse current works on the long vertical ground electrodes. The different shape of current was impressed between ground rods and auxiliary electrode by using impulse generator and the ground impedance was calculated from the ground potential rise.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.363-369
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• 2017

This paper presents the experimental results related to soil ionization and electrical breakdown in a concentric hemispherical electrode system under lightning impulse voltages. Dynamic voltage-current and impedance-time characteristics of soil ionization were measured and analyzed. Also the electrical breakdowns of the soil gap were investigated. The time-lag to the peak current corresponds to the soil ionization propagation. The time of ionization propagation in wet sand is found to decrease with increasing the impulse currents. A drastic decrease in ground resistance was observed during the impulse current spreading in sand. The electrical breakdown appears at the wave tail of impulse voltage and results in a wide scatter in V-t curves. The voltage-current curves have a fan-like shape attributed to ionization processes which result in increasing current and decreasing voltage.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.79-84
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• 2011

In this study, breakdown characteristics of a vertical sphere-plane air gap in the presence of combustion flame were examined under the application of a.c. and d.c. high-voltages in order to investigate the effect of flame on the dielectric strength of air. Propane gas is used as the fuel of the flame, and the temperature distribution of air around the flame is measured. The polarity effects for the d.c. voltages and breakdown voltages of air when applied both of a.c. and d.c. voltages were examined in the case of the variation of the gap length and the horizontal distance between the flame and the high-voltage sphere electrode. The influence of relative air density, electrification and shape changes of the flame as factors that affect the breakdown voltages were discussed.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.88-91
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• 2009

For lightning currents, a grounding system shows the transient grounding impedance characteristics. A grounding system for protection against lightning should be evaluated by the transient grounding impedance, not it's ground resistance. The transient grounding impedance varies with the shape of ground electrode and earth characteristics as well as the waveform of lightning surge current. For the analysis and practical use of transient grounding impedance, the characteristics of transient grounding impedance should be analyzed theoretically and this paper suggests the theoretical analysis for the transient grounding impedance of counterpoise by using the distributed parameter circuit model. EMTP and Matlab are used to simulate the distributed parameter circuit model of counterpoise and the adequacy of the distributed parameter model of counterpoise is examined by comparing the simulated results with the measured results.