• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.3
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• pp.283-289
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• 2014

This paper carries out a series of analysis of power system using Gallium Nitride (GaN) FET which has wide band gap (WBG) characteristics comparing to conventional Si MOSFET-used power system. At first, for comparison of each semiconductor device, the switching-transient parameter is quantitatively extracted from released information of GaN FET. And GaN FET model which reflect this dynamic property is configured. By using this model, the performance of GaN FET is analyzed comparing to Si MOSFET. Also, in order to enable a representative assessment on the power system level, Si MOSFET and GaN FET are applied to the most common structure of power system, full-bridge, and each power systems are compared based on various criteria, such as performance, efficiency and power density. The entire process is verified with the aid of mathematical analysis and simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1168-1171
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• 2003

In contrast to a conventional transformer, the flat transformer is made using a number of small ferrite cores. Two cores for transformer and one core for inductor, which composed one module. Many modules can be connected together to form a flat matrix transformer. This structural arrangement eliminates the single hot spot problem in conventional transformers and permits high current density pertains at high frequency. In this study, the ferrite magnetic cores of Mn-Zn system for the Flat transformer were manufactured and the electrical and magnetic characteristics of its tested. The power loss of sample FO2(Mn-Zn ferrite) sintered at $1350^{\circ}C$ was $350kW/m^3$ in test conditions of 250kHz, 200mT and $100^{\circ}C$, which showed the good power loss property in high frequency. The power loss of FO2 samples has been studied as a function of magnetic flux density and frequency. Steinmetz exponent was 2.82 at 250kHz and 2.73 at 500kHz. These results illustrated the switching of power loss mechanism in ferrite core from hysteresis losses to eddy current losses or others.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.180-180
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• 2010

The design and implementation of high rate deposition process and anti-scratch property of silicon oxide film by PECVD with UHF power were investigated according to the effect of UHF input power with HF bias. New regime of high rate deposition of SiOx films by hybrid plasma process was investigated. The dissociation of OMCTS (C8H24Si4O4) precursor was controlled by plasma processes. SiOx films were deposited on polyethylene terephthalate (PET) and polycarbonate substrate by plasma enhanced chemical vapor deposition (PECVD) using OMCTS with oxygen carrier gas. As the input energy increased, the deposition rate of SiOx film increased. The plasma diagnostics were performed by optical emission spectrometry. The deposition rate was characterized by alpha-step. The mechanical properties of the coatings were examined by nano-indenter and pencil hardness, respectively. The deposition rate of the SiOx films could be controlled by the appropriate intensity of excited neutrals, ionized atoms and UHF input power with HF bias at room temperature, as well as the dissociation of OMCTS.

• Food Science and Biotechnology
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• v.16 no.2
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• pp.275-280
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• 2007

The effect of using Korean wheat flour versus Australian wheat flour on noodle quality as a result of differing physical and chemical properties of the flours was investigated. The results provided appropriate technical information for selection of wheat varieties to produce high quality Korean salted noodles. Noodle quality was quantified based on measurement of the appearance and texture of noodles. When consumer preference tests were conducted, a firmer and more elastic texture was preferred for Korean white salted noodles, however, when appearance was included in the consumer tests, noodles made with Australian wheat were favored over Korean wheats. Korean flour was found to produce firmer and more elastic noodles, whereas Australian flour produced brighter, creamier colored noodles. In flour quality tests, Korean flours were found to have a higher setback viscosity and lower swelling power than Australian flour. Additionally, Korean flours had higher water absorption values. Protein content of flour was an important parameter affecting the firmness of Korean noodles, whereas setback viscosity and swelling power were the major determinants of elasticity. Overall, the important parameters for determination of the quality of Korean salted noodles were high setback viscosity, low swelling power, and high protein content.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.4
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• pp.55-61
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• 1995

Variable structure control (VSC) can be used for the control of power plants required stability and robustness such as elevator control. It has no overshoot and is insensitive to parameter variations and disturbances in the sliding mode where the system structure is changed with the sliding surface in the center. But in the real system, VSC has a high frequency chattering which has a bad influence upon the control system proformances. In this paper, to alleviate the high frequency chattering, a binary controller (BC) with inertial type external loop is implemented by DSP and applied to position control of brushless DC motor. Binary controller has external loop to generate the continuous control input with the flexible variation of primary loop gain. Thus it has the property of chattering alleviation in addition to advantages of the conventional variable structure control.

• Journal of Power System Engineering
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• v.10 no.2
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• pp.111-116
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• 2006

Tribologcal property of the ceramics used in severe condition was investigated and both $Al_2O_3$ ball and Al/SiC composite made by thermal spray process[TSP] were used as a specimen in this study. Four kinds of material couple in ball and disk specimens were tested in the dry condition by using ball-on-disk type tribo-tester. Friction coefficient, surface roughness, wear rate, and photograph of the worn surface were investigated. Generally, High SiC contents[$40{\sim}50%$] specimens showed very low friction coefficient below 0.05 and little wear rate in dry condition. And also, low SiC contents[0%] specimens showed a moderate wear rate and high coefficient of friction at the same condition.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.6-10
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• 2013

We investigate the electrical and thermal transport properties of a sesquicarbide superconductor $La_2C_3$, including electrical resistivity, thermoelectric power, and thermal conductivity. The electrical resistivity exhibits a typical metallic character with a saturation behavior at high temperatures. The thermoelectric power shows a metallic behavior with pronounced phonon-drag effect, comparable with pure metals. The broad peak of the thermal conductivity is observed in the superconducting state, which is rapidly suppressed by magnetic fields. These observations suggest that the electron-phonon scattering is significant in $La_2C_3$, which is relevant with the relatively high-$T_c$ in $La_2C_3$ through strong electron-phonon coupling with low frequency phonon modes.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2121-2123
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• 1998

In recent years, A PWM Converter or Switched Mode Converter with high power factor and sinusoidal input current have got widespread studied. But, Almost all of studies is based on linear load. This paper reports on research aimed at achieving high power factor and sinusoidal input current waveform for electronic arc welder, which has nonlinear dynamic characteristics. It is shown that simulation result yield its property.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.18-22
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• 2000

The partial discharge testing is widely used in insulation property measurement because it gives low stress to high voltage equipment which is undertaken tests. Therefore it is very useful method compare to previous destructive methods and effective diagnosis method in power transformer that requires live-line diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In recent, the study of partial discharge is carrying out discover of initial defect of power equipment through condition diagnosis and system development of degradation diagnosis using HFPD(High Frequency Partial Discharge) detection. In this study, simulated transformer is manufactured and HFPD occurred from transformer is measured with broad band antenna in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.29-32
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• 2000

The partial discharge testing is widely used in insulation property measurement because it gives low stress to high voltage equipment which is undertaken tests. Therefore it is very useful method compare to previous destructive methods and effective diagnosis method in power transformer that requires on-line & on-site diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In recent, the study of partial discharge is carrying out discover of initial defect of power equipment through condition diagnosis and system development of degradation diagnosis using HFPD(High Frequency Partial Discharge) detection. In this study, simulated transformer is manufactured and PD/HFPD occurred from transformer is measured with broad band antenna in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages.