• The Korean Journal of Physiology and Pharmacology
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• v.2 no.4
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• pp.529-539
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• 1998

The effects of membrane surface charge originated from lipid head groups on ion channels were tested by analyzing the activity of single large conductance $Ca^{2+}-activated\;K^+$ (maxi K) channel from rat skeletal muscle. The conductances and open-state probability ($P_o$) of single maxi K channels were compared in three types of planar lipid bilayers formed from a neutral phosphatidylethanolamine (PE) or two negatively-charged phospholipids, phosphatidylserine (PS) and phosphatidylinositol (PI). Under symmetrical KCl concentrations $(3{\sim}1,000\;mM)$, single channel conductances of maxi K channels in charged membranes were $1.1{\sim}1.7$ times larger than those in PE membranes, and the differences were more pronounced at the lower ionic strength. The average slope conductances at 100 mM KCl were $251{\pm}9.9$, $360{\pm}8.7$ and $356{\pm}12.4$ $(mean{\pm}SEM)$ pS in PE, PS and PI membranes respectively. The potentials at which $P_o$ was 1/2, appeared to have shifted left by 40 mV along voltage axis in the membranes formed with PS or PI. Such shift was consistently seen at pCa 5, 4.5, 4 and 3.5. Estimation of the effect of surface charge from these data indicated that maxi K channels sensed the surface potentials at a distance of $8{\sim}9\;{\AA}$ from the membrane surface. In addition, similar insulation distance ($7{\sim}9\;{\AA}$) of channel mouth from the bilayer surface charge was predicted by a 3-barrier-2-site model of energy profile for the permeation of $K^+$ ions. In conclusion, despite the differences in structure and fluidity of phospholipids in bilayers, the activities of maxi K channels in two charged membranes composed of PS or PI were strikingly similar and larger than those in bilayers of PE. These results suggest that the enhancement of conductance and $P_o$ of maxi channels is mostly due to negative charges in the phospholipid head groups.

• Journal of the Korean Ceramic Society
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• v.30 no.5
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• pp.397-403
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• 1993

Widely used dielectrics, barium titanate was promising material for ceramic capacitor. It was produced by specific formulation with various dopants-La2O3, ZrO2, SnO2, CaZrO3, CaTiO3, CaSnO3, Bi2O3, and etc.-according to demanded properties of capacitor. In this study, we would examinate the study of dielectric properties and temperatuer characteristics (T.C.) with the amount of Bi2O3. The sample was prepared with [BaTiO3]10＋[BaZrO3, SnO2, La2O3, ZrO2]10 and Bi2O3 varied from 1.0, 1.5, 2.0, 2.5 to 3.0wt%. After milling and mixing for 15hrs, each sample was dried and then pressed at 700kg/$\textrm{cm}^2$ into pellets. Pellets were fired at 131$0^{\circ}C$, for 3hrs in air. As the result of measurements, dielectric constant, break down voltage, and insulation resistance were increased with the amount of Bi2O3, and the resonant frequency was shifted from high frequency to low frequency range. In the case of temperature characteristics, capacitance change rate was symmetrically changed at -$25^{\circ}C$ and ＋85$^{\circ}C$ respectively. Therefore, it is recognized that the temperature characteristics can be moderated with doping Bi2O3 in our study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.232-235
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• 2002

Recently developed liquid silicone rubber (LSR) can be cured by platinum catalyzed additional hydrosilylation mechanism and has the advantage of no byproduct compared to traditional millable peroxide curing silicone rubber. We investigated the characteristics of dielectric breakdown of silicone rubber and adhesion properties between semi-conductive LSR and insulating LSR for high voltage application of pre-molded joint (PMJ). In order to understand the dielectric breakdown characteristics, we used the sheet samples and the paired type rogowski insert electrode system. The breakdown strength and adhesion strength of LSR (E-3) were superior to those of several silicone rubbers. Adhesion strength could be improved by curing at high temperature without post-curing process or enhanced by post-curing process. When LSR (E-3) was cured at $(150^{\circ}C{\times}10min$ semi-conductive )${\times}$ ($175^{\circ}C{\times}10min$ insulation), it showed the high breakdown strength with low standard deviation, and good adhesion strength. In this results, we could apply this process to the fabrication of PMJ without post-curing.

• Journal of the Korea Safety Management & Science
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• v.15 no.1
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• pp.109-120
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• 2013

As information-oriented industry has been developed and electronic devices has come to be smaller, lighter, multifunctional, and high speed, the components used to the devices need to be much high density and should have find pattern due to high integration. Also, diverse reliability problems happen as user environment is getting harsher. For this reasons, establishing and securing products and components reliability comes to key factor in company's competitiveness. It makes accelerated test important to check product reliability in fast way. Out of fine pattern failure modes, failure of Electrochemical Migration(ECM) is kind of degradation of insulation resistance by electro-chemical reaction, which it comes to be accelerated by biased voltage in high temperature and high humidity environment. In this thesis, the accelerated life test for failure caused by ECM on fine pattern substrate, $20/20{\mu}m$ pattern width/space applied by Semi Additive Process, was performed, and through this test, the investigation of failure mechanism and the life-time prediction evaluation under actual user environment was implemented. The result of accelerated test has been compared and estimated with life distribution and life stress relatively by using Minitab software and its acceleration rate was also tested. Through estimated weibull distribution, B10 life has been estimated under 95% confidence level of failure data happened in each test conditions. And the life in actual usage environment has been predicted by using generalized Eyring model considering temperature and humidity by developing Arrhenius reaction rate theory, and acceleration factors by test conditions have been calculated.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.2
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• pp.190-195
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• 2009

This paper introduces experimental investigates of an electrical accident of the distributing cable termination with simulated a shoddy construction. We prepared two termination kites, one is built-in type, the other is heat contraction type. Also, we manufactured cable termination that have simulated defect by badness construction and investigated their insulation characteristics such as ac (35[kV], 1[min]) and impulse (95[kV], $1.2{\times}50[{\mu}s]$) withstand test. The influence of defects such as thickness decrease, the gap between stress-con of housing and semiconductor and heating time on insulating properties of the termination have been studied. The thickness decrease of an insulator decreases ac breakdown strength suddenly and the breakdown traces of the insulator that is damaged by knife displayed elliptic shape. The gap of between stress-con and semiconductor deteriorates dielectric strength of insulator seriously. In heat contraction type, the ac breakdown voltage became low when the heating time is short.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.3
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• pp.172-177
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• 2014

Industrial, medical, environment and agriculture application of pulse power technology have been developing rapidly in many field. In order to make use in the form of pulses is applied to the pulse forming technique. At this time, spark gap is generally used for the pulse forming. Spark gap may be possible to simulate the shape of the electrode, to know the uniform or non-uniform electric field of the electrode structure. Further, it can be determined using Paschen's law applied pressure of the insulating gas in accordance with the voltage which is created using the value of the electric field. In this paper, we tried to found using a formula and the simulation process to determine the pressure. The value of the electric field is different according to the shape of the electrode. So, the range of pressure applied also varies. In order to withstand the 100 kV with a gap of 5 mm, the nitrogen gas must be applied to about 7 bar in the electrode structure. On the other hand, in the same conditions, Sulfur hexafluoride gas must be applied to about 2 bar. Consequently, the Sulfur hexafluoride gas has a higher insulation properties than nitrogen gas may be applied to low pressure at the same conditions.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.141-144
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• 2015

The superconducting fault current limiter (SFCL) is an electric power device that limits the fault current immediately in a power grid. Korea Electric Power Corporation (KEPCO) has been developing a 154 kV, 2 kA SFCL since 2011 to protect power grids from increasing fault current and improve the stability and quality of electric power. This SFCL adopts 2G YBCO wires and operates at 71 K and 5 bars. In this paper, a cooling system for the 154 kV SFCL and its cooling test results are reported. This cooling system uses a Stirling-type cooler to make sub-cooled liquid nitrogen ($LN_2$), which cools the superconductor modules of the SFCL. The $LN_2$ is circulated between the cooler and the cryostat that contains superconductor modules. The $LN_2$ also plays the role of a high voltage insulator between the modules and the cryostat, so the pressure was maintained at 5 bars for high insulation performance. After installation in a test site, the cooling characteristics of the system were tested. In this operation test, some important data were measured such as temperature distribution in $LN_2$, pressure change, performance of the heat exchanger, and cooling capacity of the total system. Consequently, the results indicate that the cooling system operates well as designed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.425-431
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• 2011

The harmonic distortion level may be significant in electric propulsion systems, as the main loads usually are variable speed propulsion/thruster drives. Distortion of currents and supply voltage waveforms may lead to: Increased power dissipation(losses) in equipment connected to the network, such as generators, motors, transformers, cables, etc., from the harmonic currents, may cause overheating and deterioration of the insulation, and reduced life time of the equipment. In this paper introduced the canceling method of harmonic currents by a multipulse drive with phase shifting transformer. The simulation results indicated a good speed response to the middle speed range of electric propulsion motor. And also, THD(total harmonic distortion) and torque ripple could be reduced in comparing the 12-pulse drive with 6-pulse drive.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.93-94
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• 2007

An essential step for SERGI is to show the TRANSFORMER PROTECTOR (TP) efficacy for all transformers and all types of rupture of insulation. Its research program philosophy is thus to maintain a strong connection between experiments and the theoretical developments. Up to now, two TP test campaigns have been performed, both under the worst conditions by creating low impedance faults leading to electrical arcs inside the transformer tank dielectric oil. In 2002, Electricite de France performed 28 TP tests. Then, in 2004, a second campaign of 34 TP tests was carried out by CEPEL, the Brazilian independent High Voltage Laboratory. For the 62 tests, each transformer was equipped with the TP, which reacts directly to the moving dynamic pressure peak, shock wave, caused by the low impedance fault. When an electrical arc occurs, only one pressure peak is generated. The initial energy transfer is almost instantaneous, and so is the phase change. Because of the oil inertia, the gas is very quickly pressurised. As it is more difficult to vaporise a liquid than to crack oil-vapour into smaller molecules, the arc location would mainly remain in the gaseous phase after and less gas will be produced. As a result, when comparing tests for which pressure peaks are respectively equal to 8 bar (116 psi) and 8.8 bar (127 psi), the corresponding arc energies vary by an order 10 of magnitude (0.1 MJ and 1 MJ respectively). The correlation of the results obtained between arc energy and dynamic pressure demonstrates that the arc energy is not the key parameter during transformer tank explosion, which is in opposition with the common electrical engineers belief.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.834-838
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• 2011

This research shows the electrical characteristic using excellent epoxy nano-composite of MgO 5.0 wt% and $SiO_2$ 0.4 wt% in mechanical strength test depending on nano-additive. First of all, volume resistance depending on nano-additive and temperature using high resistance meter (HP. 4329A) by increasing 10, 100, 1,000 V of applying voltage was measured. Moreover, temperature range of $25{\sim}120^{\circ}C$ with virgin sample was tested using TO-9B oven by Ando Company. The result showed that virgin and the samples added with MgO and $SiO_2$ had similar value of volume resistance in low temperature and low electric field region and reduced with slow slope. The nano-composite's volume resistance of sample added with MgO and $SiO_2$ had higher value than virgin sample's volume resistance in high temperature region more than $80^{\circ}C$. Moreover, the slope has steeply reduced. The volume resistance of sample added with MgO 5.0 wt% was $8.38{\times}10^{13}\;{\Omega}{\cdot}cm$ and it was 6.8 times more than virgin sample in high temperature at $120^{\circ}C$. The insulation characteristics were constant although filler has changed in low temperature region. But, in high temperature region, the value of volume resistance of sample with MgO 5.0 wt% was 7.6 times more than the virgin sample's volume resistance.