• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.29-35
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• 2001

Direct current corrosion have being investigated by lots of scientists but alternating current corrosion was ignored because the corrosion rate by AC was very small. Recently however, AC corrosion accidents have been reported in many other countries. So the study of AC corrosion is to be necessary In these days. In this paper, several experiments which intentionally imposed the AC or DC to the specimens also imposed AC and DC at the same time was carried out in the laboratory to examine the AC corrosion characteristics and in addition applied the same way in the field. Moreover, while the field investigations of the abnormal corrosion failures, It was the AC that caused one of corrosion failures.

• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.398-404
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• 2017

In order to study the AC driving mechanism for OLED lighting, the fluorescent OLEDs were fabricated and the electroluminescent characteristics of the OLEDs by AC forward bias were analyzed. In the case of the driving method of OLED by AC forward bias under the same voltage and the same current density, degradation of luminescent characteristics for elapsed time progressed faster than in the case of the driving method by DC bias. These phenomena were caused by the peak voltage of AC forward bias which is ${\sqrt{2}}$ times higher than the DC voltage. In addition, the degradation of the OLED was accelerated because the AC forward bias had come close to the upper limit of the allowable voltage range even though the peak voltage didn't exceed the allowable range of the OLED. However, the fabricated fluorescent OLED showed little degradation of OLED characteristics due to AC forward bias from 0 V to 6.04 V. Therefore, OLED lighting by AC driving will become commercialized if sufficient luminance is realized at a voltage at which the characteristics of the OLED are not degradation by the AC driving method.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.135-140
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• 2005

Although it was recently observed that severe fatigue damage was formed in Al or Cu interconnects due to the cyclic temperatures generated by Joule heating of the metal lines by the passage of alternating currents (AC), AC loading frequency effect on the damage evolution characteristics are not known so far. This work focused on the effect of AC loading frequency (100 Hz vs. 10 kHz) on the thermo-mechanical fatigue characteristics by using polycrystalline sputtered Cu lines with temperature cycles with amplitudes from 100 to $300^{\circ}C$. It was consistently observed that higher loading frequency accelerated damaged grain growth and led to earlier failure irrespective of Cu grain sizes. The frequency effect is believed to result from differences in the concentration of defects created by the deformation-induced motion of dislocations to the grain boundaries.

• Advances in nano research
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• v.1 no.3
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• pp.171-182
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• 2013

The alternating current (AC) conductivity in semiconductor crystals with an open-core screw dislocation is studied in the current work. The screw dislocation in crystalline media results in an effective potential field which affects the electronic transport properties of the system. Therefore, from a technological view point, it is interesting to investigate properties of AC conductivity at frequencies of a few terahertz. To quantify the screw-induced potential effect, we calculated the AC conductivity of dislocated crystals using the Kubo formula. The conductivity showed peaks within the terahertz frequency region, where the amplitude of the AC conductivity was large enough to be measured in experiments. The measurable conductivity peaks did not arise in dislocation-free crystals threaded by a magnetic flux tube. These results imply different conductivity mechanisms in crystals with a screw dislocation than those threaded by a magnetic flux tube, despite the apparent similarity in their electronic eigenstates.

• Journal of Power Electronics
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• v.15 no.4
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• pp.876-885
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• 2015

High frequency alternating current (HFAC) has been widely used in a wide range of power distribution systems (PDS) due to its superior performance. A high frequency AC/DC converter plays the role of converting HFAC voltage to DC voltage. In this paper, a new LCL-T resonant AC/DC converter has been proposed, and an easier control method based on input voltage comparison is presented, without the complicated calculation of the zero-crossing point. Both a low distortion and near-to-unity power factor can be achieved by the proposed resonant converter and control strategy. The operational principle and steady-state analysis are given for the proposed resonant converter. A simulation model and experimental prototype are implemented with an operation frequency of 25kHz and a rated power of 20W. The simulation and experimental results verify the accuracy of the analysis and the excellent performance of the proposed topology.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.1
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• pp.111-119
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• 2022

This paper is about power transfer between heterogeneous systems in zero-energy buildings. Currently, electricity used in buildings, from renewable energy generation power in buildings, consists of alternating current networks. In order to use electricity, alternating current must be converted to direct current, which typically results in a loss of 10%. In order to solve this problem, research is needed to reduce power loss as much as possible by implementing both a DC network and an AC network in a zero-energy building. Therefore, in this paper, an inter-link converter capable of bidirectional power transfer between DC and AC networks applied to zero-energy buildings is developed. The structure of the inter-link converter to be developed was proposed and its feasibility was verified through simulations and experiments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.5
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• pp.466-470
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• 2022

In order to widely disseminate LED lighting, LED lighting technology that directly uses AC commercial power has been recently introduced. AC powered LED lighting technology has a problem in that the light brightness of the LED changes because the voltage applied to the LED and the current flowing through the LED continuously change. In this study, when the LED current is greater than the design current, the current control signal generated by the controller is supplied to the current source to supply only the design current to the LED by increasing the voltage drop at the current source. If it is smaller than the design current, the controller is adjusted so that the current is supplied only to the LED without a voltage drop in the current source. It can be seen that the higher the maximum rectified voltage, the faster the lighting time of the LED light emitting block is, so that the power factor of the LED lighting is improved. The LED lighting technology proposed in this study enables LED lighting with constant light brightness, reduced power consumption, and long lifetime.

• Journal of Power Electronics
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• v.16 no.1
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• pp.66-73
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• 2016

The quantity of alternating current (AC) leakage and the value of distortion factor in capacitor currents are discussed with regard to a new power component called variable capacitance device (VCD). This component has terminals for controlling its capacitance. Nonlinear dielectric characteristics are utilized in this device to vary the capacitance. When VCD operates in an AC circuit, the AC leakage from this device through direct current (DC) control voltage source increases according to the conditions of DC control voltage and so on. To solve this problem, we propose techniques for suppressing AC leakage. Although VCD has strong nonlinear characteristics, the current through the capacitor is not distorted significantly. The relations between AC leakage and the distortion in current waveforms are investigated. An application example for an AC power regulator is also introduced to evaluate the distortion in waveforms.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.63-72
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• 2001

An alternating current (AC) corrosion using coupon and electric resistance (ER) probe has been studied. Coupon coupled with ER probe were applied in terms of AC voltage from high value to low value through the survey of AC voltages on buried gas transmission pipeline over the country. Parameters such as AC current density of coupon, AC voltage, cathodic protection potential, soil resistivity and frequency were monitored continually. Corrosion induced by AC was observed even under cathodically protected condition that met cathodic protection criterion (below -850mv vs. CSE). Corrosion rate was affected mainly not by AC voltage but by both of frequency and AC current density. An experimental corrosion rate relationship could be obtained statistically, In which AC corrosion rate increased linearly with effective AC current density and its slope was 0.619 in case of coupon and 0.885 in case of ER probe.

• Korean Journal of Materials Research
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• v.32 no.7
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• pp.320-325
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• 2022

Single OLED and tandem OLED was manufactured to analyze the electroluminescence characteristics of DC driving, AC driving, and full-wave rectification driving. The threshold voltage of OLED was the highest in DC driving, and the lowest in full-wave rectification driving due to an improvement of current injection characteristics. The luminance at a driving voltage lower than 10.5 V (8,534 cd/m²) of single OLED and 20 V (7,377 cd/m²) of a tandem OLED showed that the full-wave rectification drive is higher than that of DC drive. The luminous efficiency of OLED is higher in full-wave rectification driving than in DC driving at low voltage, but decrease at high voltage. The full-wave rectification power source may obtain higher current density, higher luminance, and higher current efficiency than the AC power source. In addition, it was confirmed that the characteristics of AC driving and full-wave rectification driving can be predicted from DC driving characteristics by comparing the measured values and calculated values of AC driving and full-wave rectification driving emission characteristics. From the above results, it can be seen that OLED lighting with improved electroluminescence characteristics compared to DC driving is possible using full-wave rectification driving and tandem OLED.