• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.7
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• pp.317-323
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• 2001

We investigated the stability of cryocooler-cooled high-temperature superconducting (HTS) coils by using a computer program based on FEM. In this study, the current at which "thermal runaway" occurs, which depends on the relationship between the cooling power of the cryocooler and the heat generation in HTS coils, was adopted as a stability criterion of cryocooler operating HTS coils. It was shown that cryocooler-cooled HTS coil was stable in operating current above the critical current from the numerical analysis results by HTS model coil. And also, if we efficiently remove the heat generation from HTS coils by potimizing heat drain, the ramp-rate limitation can be mitigated because the effect of AC loss by the current rise was too small. Furthermore, in the case of pulsed operation; the HTS model coil is ramped from zero to the peak value in one second and back to zero current in one second, such as the operation of SMES device, the peak value of poerating current is 1.5-2 times greater than that of the thermal runaway current.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.4
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• pp.152-157
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• 2002

This paper describes an effect of a single- and a quadruple-lightning impulse currents on electrical characteristics of ZnO blocks, and an expert system to diagnose arrestor deterioration. To deduce the parameters needed for diagnosing arrester deterioration, an accelerate deterioration teat is carried out. In the experiment, leakage current components are measured. Also, wave height distribution of the leakage current according to the progress of arrester deterioration is analyzed. From the experimental results, the wave height distribution of the leakage current showed conspicuous difference even in an immaterial leakage current increase. Therefore, the use of wave height distribution of the leakage current in deterioration diagnostic technique makes more accurate diagnosis than the conventional method by using only a leakage currant value. Finally, the expert system based on the experimental results is developed and the system can diagnose arrestor deterioration by measuring the leakage current and its wade height distribution.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.389-392
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• 2020

In order to accurately predict the losses in the power cable, analysis of the eddy current losses in the metal sheath is required. The copper loss is easily calculated by the resistance and current of the conductor, but it is difficult to measure and predict the eddy current generated from the metal sheath. For this purpose, the previous study analyzed the eddy current loss in single phase cable, but there is a limit to apply it because three phase cables are used in real environment. Therefore, in this paper, the eddy current loss occurring in the metal sheath of three phase cable according to the cause was analyzed theoretically. In addition, the eddy current loss occurring in the triangular and horizontal array were predicted through electromagnetic numerical analysis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.123-128
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• 2014

This paper analyzed the change of subthreshold current for channel dimension of double gate(DG) MOSFET. The nano-structured DGMOSFET to reduce the short channel effect had to be preciously analyze. Poisson's equation had been used to analyze the potential distribution in channel, and Gaussian function had been used as carrier distribution. The subthreshold current had been analyzed for device parameters such as channel dimension, and projected range and standard projected deviation of Gaussian function. Since this potential model was verified in the previous papers, we used this model to analyze the subthreshold current. Resultly, we know the subthreshold current was influenced on parameters of Gaussian function and channel dimension for DGMOSFET.

• Development and Reproduction
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• v.4 no.2
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• pp.243-250
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• 2000

To find the mechanism underlying the ADP-induced increase in the outward current in ovulated mouse oocytes, we examined changes in voltage-dependent currents using the whole cell voltage clamp technique and the internal perfusion technique. Eggs were collected from the oviduct of superovulated mice with PMSG and hCG. Membrane potential was held at -60 mV (or -80 mV in the case of recording $Ca^{2＋}$ currents) and step depolarizations or hyperpolarizations were applied for 300 ms. By step depolarizations, outward currents comprising steady-state and time-dependent components were elicited. They were generated in response to the positive potential more than 20 mV with severe outward rectification and were blocked by external TEA, a specific $K^{＋}$ channel blocker, suggesting that they be carried via $K^{＋}$ channels. Internally-perused 5 mM ADP gradually increased outward $K^{＋}$ currents (IK) 1 min after perfusion of ADP and reached slowly to maximum (150~170％) 5 min later over the positive potential range, implying that ADP might not be acted directly to the $K^{＋}$ channels. IK were decreased by 5 mM ATP without affecting the steady-state component of outward current. In contrast to the effect of ADP and ATP on IK, both effect of ATP and ADP on inward $Ca^{2＋}$ currents (ICa) could not be detected due to the continuous decrease in current amplitudes with time-lapse ("run-down" phenomena). To check if there is a G protein-involved regulation in the ionic current of mouse oocytes, 1 mM GTP was applied to the cytoplasmic side, and the outward current and inward currents were recorded. ICa was promptly increased in the presence of GTP whereas IK was not changed. from these results, it is concluded that the ATP-dependent regulation is likely linked in the ADP-induced increase in the outward $K^{＋}$ current, and G protein-involved cellular signalling might affect ion channels carrying $Ca^{2＋}$ and $K^{＋}$ in mouse oocytes.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.6
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• pp.615-621
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• 1999

In spite many evidences has supported the cardioprotective effect of bradykinin, its direct effects at the cell level are still under question. We investigated the both effects of bradykinin (BK) on $Ca^{2+}-related$ ionic currents using whole cell voltage clamp technique in rabbit cardiomyocytes and on the intracellular $Ca^{2+}$ transient using calcium sensitive fluorescence dye, indo-1AM. Simultaneously with recording intracellular $Ca^{2+}$ transients, cell contractility was estimated from the changes in length of the electrical stimulated rat cardiac myocytes. L-type $Ca^{2+}$ current decreased by bradykinin at the entire voltage range. Inward tail current increased initially up to its maximum about 4 min after exposing myocytes to BK, and then gradually decreased again by further exposure to BK. This tail current decreased remarkably at washing BK off but slowly recovered ca. 20 min later. The change in cell contractility was similar to that in tail current showing initial increase followed by gradual decrease. Removal of BK brought remarkable decrease in contractility, which was recovered $15{\sim}20$ min after cessation of electrical stimulation. Bradykinin increased $Ca^{2+}$ transient initially but after some time $Ca^{2+}$ transient also decreased coincidentally with contractility. From these results, it is suggested that bradykinin exerts directly its cardioprotective effect on the single myocytes by decreasing the intracellular $Ca^{2+}$ level followed by an initial increase in $Ca^{2+}$ transient.

• Journal of the Korean Applied Science and Technology
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• v.23 no.4
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• pp.347-354
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• 2006

Generally, it has been known that positive plate efficiency is the most influential effect on the initial current capacity of lead acid battery. Thus, in this study, we have investigated the curing effect of the positive plate, which is one of the important lead acid battery processes. The curing process of the positive plate is performed either with the separation of each plate with 1mm gap or with no gap of plate. As a result, when there is no interval between each plate, the higher temperature current happened than expected, resulting in the changes in the initial current efficiency of the lead acid battery. The chemical composition and crystal structure of a material coated on the positive plate were identified with XRD and SEM. It was resulted that were only there not a lot of 4BS (tetrabasic-lead sulfate, $4PbO{\cdot}PbSO_4)$ on the plate in case of curing of plates without interval, but a large quantity of $Pb_3O_4$ also formed on the surface. On the other hand, it was observed that 3BS (tribasic-lead sulface, $3PbO{\cdot}PbSO_4{\cdot}H_2O)$ was the main product on the plate in case of typical curing process with some interval. From the initial current capacity test, the positive plate having 3BS was approximately 40% higher in initial current capacity than that having 4BS. It was concluded that 4BS and $Pb_3O_4$ on the plate surface were harmful to the initial current capacity of lead acid battery.

• Journal of the Korean Institute of Gas
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• v.10 no.1 s.30
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• pp.43-47
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• 2006

This study attempted to examine how the hydrogen embrittlement susceptibility of the STS 444 stainless steel varies under different welding conditions and how its effect on hydrogen embrittlement differs by the impressed current density levels. For doing so, U bend test specimens was used to impress the current density at 5,10, 15, and 20 $mA/cm^2$ in the $0.5M\;H_2SO_4+0.001M\;As_2O_3$ solution with an electrochemical corrosion tester. The hydrogen embrittlement was assessed by observing the time to failure, and then the microphotographs of metal structures were compared to investigate the metal- related structural properties. The study findings suggest that the effect on hydrogen embrittlement for the STS 444 steel significantly depends on both the welding conditions, or variations in the amount of shield gas, and the levels of current density. In particular, as the impressed current density increases, the hydrogen embrittlement increases rapidly.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.31-37
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• 2000

In the case of metal-induced lateral crystallization (MILC) for low temperature poly-Si TFT, offset length between Ni-thin film and the sides of gate could be modified to control the location of MILC boundary. Electrical characteristics were compared to analyze the effect of MILC boundary that was located either in or out of the channel region of the TFT. By removing the MILC boundary from channel region, on current, subthreshold slope and leakage current properties could be improved. When MILC boundary was located in the channel region, leakage current was reduced with electrical stress biasing. The amount of reduction increased as the channel width increased, but it was independent of the channel length.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.753-756
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• 2013

This paper analyzed the change of subthreshold current for channel dimension of double gate(DG) MOSFET. The nano-structured DGMOSFET to reduce the short channel effect had to be preciously analyze. Poisson's equation had been used to analyze the potential distribution in channel, and Gaussian function had been used as carrier distribution. The subthreshold current had been analyzed for device parameters such as channel dimension, and projected range and standard projected deviation of Gaussian function. Since this potential model was verified in the previous papers, we used this model to analyze the subthreshold current. Resultly, we know the subthreshold current was influenced on parameters of Gaussian function and channel dimension for DGMOSFET.