• 전기의세계
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• v.29 no.1
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• pp.21-27
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• 1980

The effect of electric shock on human body is enormousness, which leads to warmth, tingling, and even death. The mean values of perception currents obtained on 91 men and 39 women are about 0.77(mA) for men and 0.57(mA) for women. The mean value for women is approximately seven tenths that of men. An individual can tolerate, with no adverse effects, repeated exposure to the reactions associated with currents of his let-go level, and the mean value of let-go currents obtained from 27 normal men is 6.29(mA). Lethal currents flowing human body is very dangerous even for a short time. So, it is necessary to have recourse to animal experiments ot determine lethal current for human. An analysis of experimental data indicates that body weight and shock duration are important factors in determining the lethal current. It is suggested that the relationship between current and shock duration is given by I=K/.root.T, and lethal current is proportional to body weight, where I is the current in milliampere, and T is the time in seconds.

• 전기의세계
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• v.24 no.1
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• pp.55-62
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• 1975

A single-phase induction motor with it's stator winding splitted into two series windings, of which the terminals of one winding is switched pulsationally by a thyristor type ON-OFF device so that the motor may operate as a pulsational shaded-pole motor, can modulate current waveforms of it's two series windings. In view of current waveform modulation method, a single-phase single-winding motor operates as a two-phase induction motor with asymmetrical axis windings where the starting torque can be obtained effectively without an auxiliary capacitor attached and it's running speed controlled by shifting phase between current waveforms differently. Equivalent circuit for analysis is modified from a double revolving field equivalent circuit of a single-phase induction motor with asymmetrical windings whose angle is 45.deg.C elet. degrees. Analysis and test results show that ON-OFF action of the pulsational shaded-pole winding has the same effect of a series capacitor, and then at heavy loads this motor operates with a small amonut of the input current than that having the fixed shaded-pole winding.

• Electrical & Electronic Materials
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• v.8 no.1
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• pp.27-34
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• 1995

The analysis of nonlinear equivalent circuit and the resonance characteristics of input current and output voltage were simulated, and their electrical properties are discussed in the transverse-type piezoelectric ceramic transformer. The nonlinear resonance characteristics of input current and output voltage showed by the thermal effect due to a higher driving current, the nonlinearity increased greatly as driving current increased. When load resistor was 100[M.ohm.], the nonlinear coefficient was -1.3. The nonlinear resonance curve of input current and output voltage for a variation of input voltage and load resistor agreed with the discussed theory. The output voltage increased nearly proportioned to input voltage when load resistors were below 50[M.ohm.], the voltage step-up ratio decreased when a load resistor was 100[M.ohm.] and their maximum value was 950.

• Journal of Life Science
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• v.9 no.2
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• pp.82-85
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• 1999

The effects of ethanol on 5-hydrosytryptamine(5-HT3) receptor-mediated ion current were evaluated in whole-cell patch-clamp recordings from NCB-20 neuroblastoma cells. The physiologic and pharmacologic properties of 5-HT-activated ion current in NCB-20 cells indicated that it was mediated by 5-HT3 receptors. Ethanol(25-100mM) potentiated 5-HT3 receptor-mediated current in a concentration-dependent manner.

• Journal of the Korean Solar Energy Society
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• v.29 no.5
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• pp.73-80
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• 2009

A tidal current turbine is designed and analyzed numerically by using blade element momentum theory. The rated power has a limitation because the diameter of the tidal current turbine cannot exceed the depth of sea water. This study investigates a horizontal axis tidal-current turbine with a rated power of 500 kW. NACA-6 series laminar foil shape is used for basic airfoil along the blade span. The distributions of chord length and twist angle along the blade span are obtained from the hydrodynamic optimization procedure. Prandtl's tip loss correction and angle of attack correction considering the three-dimensional effect are applied for this study. The power coefficient curve shows maximum peak at the rated tip speed ratio of 6.0, and the maximum torque coefficient is developed at the tip speed ratio of 4. The drag coefficient reaches about 0.85 at the design tip speed ratio.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.4
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• pp.255-261
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• 2000

Experiments were carried out to measure the corrosion potential and current density variations in the polarization curves of polypropylene. In particular, the results were examined to identify those influences affecting the corrosion potential, such as temperature, pH, salt, and oxygen. The Tafel slope for the anodic dissolution was determined based on the polarization effect under various conditions. Furthermore, the optimum conditions for the most rapid transformation were establish based on a variety of conditions, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(I(sub)r/I(sub)f). This I(sub)r/I(sub)f value was then used to measure the critical corrosion sensitivity of polypropylene. The potentiodynamic parameters of corrosion were obtained using a Tafel plot.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.505-507
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• 1995

Applications of the fiber optic sensing are glowing rapidly, particularly in situations where size, weight, speed, and immunity to electromagnetic interference are important considerations. The fiber optic current sensors have been developed for low frequency(60Hz) metering in electric power systems. But we try measure to high frequency large current by fiber optic current sensor based on Bi substituted rare earth iron garnet. In this paper, we report the linearity to 500 amperes and frequency response of signal processor and a result of detection the standard impulse large current of fiber optic impulse sensor system.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1430-1431
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• 2008

In this paper, a optical current transformer has been designed and favricated to improve temperature stability caused materials properties and insulation in measuring system, suing single crystal as faraday effect cells. We used 850[nm] Laser diode as the light source and PIN Photodiode as receiver. For the experiment, the temperature transformation device make by aluminum. The range of current was from 0[A]$\sim$1600[A] and the range of temperature was from -20[$^{\circ}C$] to 50[$^{\circ}C$]. In a same experimental condition magnitude increased input current increase follow by increasing proportion of input current. The result of this study shows that characteristics of OCT are good, and it can be reflected for practical optical sensors.

• Journal of Korea Multimedia Society
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• v.21 no.9
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• pp.1068-1075
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• 2018

We propose a method for driving loudspeakers from class D audio power amplifiers in current mode, instead of in conventional voltage mode, which was impossible with the feedback circuitry. Unlike analog audio amplifiers, Class D audio power amplifiers have signal delay between the input and output signals, which makes it difficult to apply the feedback circuitry for current-mode driving. The idea of the pre-distortion scheme used for the compensation of the non-linearity of RF power amplifiers is adapted to remedy the impedance variation effect of the loudspeakers for current driving. The method uses the speaker model for the pre-distorter to compensate for the speaker impedance variation with frequency. The simulation and test results confirms the validity of the proposed method.

• Journal of Power Electronics
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• v.12 no.3
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• pp.477-486
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• 2012

This paper proposes a novel current control scheme for vector-controlled induction machine (IM) drives in the overmodulation (OVM) range, with which the voltage utilization of the voltage-source inverter (VSI) can be maximized. In the OVM region, the original voltage reference is modified by changing its magnitude and angle, which causes the motor current to be distorted, resulting in a deterioration of the current control performance. To meet with this situation, the harmonic components in the feedback currents should be eliminated before being input to the PI current controllers. For this, a composite observer is applied to extract the fundamental and harmonic components from the distorted currents, which gives a good performance without a delay and the effect of a fundamental frequency variation. In addition, through a detailed analysis of the response of the PI current controllers in the OVM range, the effectiveness of using the composite observer is demonstrated. Simulation and experimental results for a 3-kW induction motor drive are shown to verify the validity of the proposed method.