• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2113-2115
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• 2000

It is necessary to install the arc generation facility in order to obtain the important technology for the design of breakers and switches, and for the improvement of their performance and reliability. With this facility, it is possible, to study the characteristics of Arc in air/gas/vacuum insulation environment. The facility briefly consists of capacitor bank which can charge enormous energy, an air-core reactor, experimental arc-chamber, and several measurement equipments. This facility can simulates the arc phenomena in breakers and switches by means of generating high currents. In order to study the arc phenomena in SF6 gas and vacuum and to test the quenching performance of the extinguishing chambers which are developing. we made experimental $SF_6$gas/vacuum chambers and measured several parameter's of chambers. And besides we visualized arc ignition and arc movement by means of high speed camera.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.28-34
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• 2008

A magnetic field detector as a potential MRI receiver is proposed. The proposed device is composed of SRR(split ring resonator) which is a kind of LC resonator first introduced as a negative permeability material and a simple loop antenna. The proposed device showed similar degree of performance to commercial one with a simpler circuit.

• Journal of Magnetics
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• v.12 no.1
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• pp.35-39
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• 2007

A highly sensitive magnetic sensor using the Giant MagnetoImpedance effect has been developed. The sensor performance is studied and estimated. The sensor circuitry consists of a square wave generator (driving source), a sensing element in a form of composite wire of a 25 $\mu$m copper core electrodeposited with a thin layer of soft magnetic material ($Ni_{80}Fe_{20}$), and two amplifier stages for improving the gain, switching mechanism, scaler circuit, an AC power source driving the permeability of the magnetic coating layer of the sensing element into a dynamic state, and a signal pickup LC circuit formed by a pickup coil and an capacitor. Experimental studies on sensor have been carried out to investigate the key parameters in relation to the sensor sensitivity and resolution. The results showed that for high sensitivity and resolution, the frequency and magnitude of the ac driving current through the sensing element each has an optimum value, the resonance frequency of the signal pickup LC circuit should be equal to or twice as the driving frequency on the sensing element, and the anisotropy of the magnetic coating layer of the sensing wire element should be longitudinal.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1782-1789
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• 2008

This paper presents the design of acoustic resonance(AR) free and dimmable electronic ballast for 1kW Metal-Halide Lamp(MHL). The proposed Ballast consists of a Full-Bridge(FB) rectifier, a passive power factor correction(PFC) circuit, a full-bridge inverter, an ignitor using LC resonance and a control circuit for frequency modulation and dimming control. Whereas a passive PFC provides advantages in terms of high reliability and low cost for constructing the circuit, it is difficult to supply a stable voltage because of the output voltage ripple that occurs with a period of 120Hz. Although the ballast can be designed with a small size and a light weight if it is driven at a switching frequency between 1 and 100 kHz, AR will occur if the eigenvalue frequency of the lamp coincides with the inverter's operation frequency. The operation frequency was modulated in real time according to the output voltage ripple to compensate for the variation in power supplied to the lamp and eliminate AR. For dimming, the method, which modulated drive frequency of FB inverter using the control of DC level by microprocessor, was used. The Dimming ranged at least from 600W to 1kw as rated power of the lamp with 4 stages. Performance of the proposed technique was validated through numerical analysis, computer simulation using Pspice and by applying it to an electronic ballast for a prototype 1kW MHL.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.10
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• pp.123-130
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• 2016

High-frequency induction heating equipment can heat the metal by applying a High-Frequency power to the resonant circuit. The resonance circuit is composed of the work coil and the conduction-cooled power capacitor, it influences the performance of the heat treatment equipment according to the characteristics of the capacitor. However, dependence on conduction-cooled power capacitor's import is high due to lack of core technology research and development. Minimizing the generation of internal heat transmitted inside during LC resonance, reduce the reactive power loss, there is a need for a capacitor within the voltage characteristic outstanding. To implement localization it is vital that prior study of the analysis on the frequency response characteristic for the finished capacitor advanced manufacturer be implemented. Studying the interpolation method to read the value at any point of the characteristic curve for a given log-log scale was applied to the analysis tool of the capacitor by my proposed algorithm. The simulation for reproducing frequency response curves was attempted by assuming a capacitor in a simplified series equivalent RC circuit to obtain the equivalent series resistance value. It was confirmed that the reproduction rate was the result value above 83% as compared to the simulation of the properties and characteristics on the actual reactive power for Peak value, and that the algorithm can be applicable when analyzing and predicting the characteristic curves of a simpled model capacitor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1466-1477
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• 2016

This paper analyzes the electrical characteristic such as the impedance(Z), inductance(L), and cable resistance($R_p$) according to the change of cable length in order to move the electrical sorting device for distinguishing between AF non-insulated track circuits from the center of railway to outside railway. The simulation is performed to check the voltage difference between the voltage of sender and the voltage of receiver and determine the possibility of the voltage restoration availability in the frequency filter band through the capacitor compensation. It was applied to the results of the simulation to the sorting devices installed in the actual field. It is proved the availability by checking the measured voltage characteristic according to the capacitor compensating change of $10{\mu}F$ and $16{\mu}F$ before, and after the length of cable is increased with 6 meters. Through this, the prevention of breakdown and damage to facilities and the prevention the safety-related accidents of line workers from the train are expected according to moving the sorting devices of AR non-insulated track circuits to outside railway.

• Natural Product Sciences
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• v.24 no.4
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• pp.235-240
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• 2018

Betula platyphylla var. japonica (Betulaceae), also known as Asian white birch, is an endemic medicinal tree, the bark of which has been used in Chinese traditional medicine for the treatment of various inflammatory diseases. In our continuing search for bioactive compounds from Korean natural resources, a phytochemical investigation of the bark of B. platyphylla var. japonica led to the isolation of 7-oxo-${\beta}$-sitosterol (1) and soyacerebroside I (2) from its ethanol extract as main components by liquid chromatography (LC)/mass spectrometry (MS)-based analysis. The structures of isolates were identified by comparison of $^1H$ and $^{13}C$ nuclear magnetic resonance spectroscopic data and physical data with the previously reported values and LC/MS analyses. To the best of our knowledge, this is the first study to demonstrate that the isolated compounds, 7-oxo-${\beta}$-sitosterol and soyacerebroside I, were isolated in B. platyphylla var. japonica. We examined the effects of the isolates on the regulation of adipocytes and osteoblast differentiation. These isolates (1 and 2) produced fewer lipid droplets compared to the untreated negative control in Oil Red O staining of the mouse mesenchymal stem cell line without altering the amount of alkaline phosphatase staining. The results demonstrated that both compounds showed marginal inhibitory effects on adipocyte differentiation but did not affect osteoblast differentiation.

• Korean Journal of Medicinal Crop Science
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• v.27 no.3
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• pp.208-217
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• 2019

Background: In the present study, we identified two cytotoxic compounds from the root of Rumex crispus L. using a bioassay-based method. Methods and Results: Compared with the other fractions, the diethyl ether ($Et_2O$) fraction of R. crispus root extract exhibited the strongest of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging effect [scavenging concentration 50% $(SC_{50})=63.8{\pm}1.47{\mu}g/m{\ell}$], nitric oxide (NO) production inhibitory effect on the mouse macrophage cell line RAW264.7 [inhibitory concentration 50% $(IC_{50})=60.9{\pm}7.52{\mu}g/m{\ell}$] and cytotoxicity effect on the human hepatoma cell line, HepG2 [lethal concentration 50% $(LC_{50})=115.4{\pm}1.86{\mu}g/m{\ell}$]. According to the bioassay-based method, two cytotoxic compounds were purified from the $Et_2O$ fraction by using column chromatography and preparative high performance liquid chromatography (prep-HPLC). These two compounds were identified as parietin and chrysophanol by using nuclear magnetic resonance (NMR) and liquid chromatography quadruple time of flight mass spectrometry (LC-QTOF-MS). In addition, both parietin and chrysophanol exhibited a cytotoxicity effect on HepG2 cells, their $LC_{50}$ values were $169.1{\pm}17.67{\mu}M$ and $111.5{\pm}6.62{\mu}M$, respectively. Conclusions: Parietin and chrysophanol isolated from the $Et_2O$ fraction of the R. crispus root extract showed cytotoxicity in HepG2 cell.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1654-1663
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• 2015

Compared to LC resonance, LCL resonance has distinct advantages such as a large resonant capability, low voltage and current stresses of the power device, constant voltage or current output characteristics, and fault-tolerance capability. Thus, LCL resonant compensation is employed for a movable Inductive Contactless Power Transfer (ICPT) system with a multi-load in this paper, which achieves constant current output characteristics. Peculiarly, the primary side adopts a much larger compensation inductor than the primary leakage inductor to lower the reactive power, reduce the input current ripple, generate a large current in the primary side, and realize soft-switching. Furthermore, this paper proposes an approximate resonant point for large inductor-ratio LCL resonant compensation through fundamental wave analysis. In addition, the PWM control strategy is used for this system to achieve constant current output characteristics. Finally, an experimental platform is built, whose secondary E-Type coils can ride and move on a primary rail. Simulations and experiments are conducted to verify the effectiveness and accuracy of both the theory and the design method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.1
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• pp.46-51
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• 2004

The cause for the variation of the initial permeability according to the Co substitution of Ni-Zn ferrite used in the LC resonance filter for the power line communication is studied. The initial permeability decreases as the quantity of Co diminishes, and the saturation magnetization increases as the quantity increases. Because the sintering density and the microstructure of ferrite show little change, the variation of the initial permeability can't be explained by the density, microstructure nor the saturation magnetization factor. The magnetocrystalline anisotropy increases, similar with the saturation magnetization, as the quantity of Co increases. The increase of magnetocrystalline anisotropy value makes the domain wall energy grow, which leads to the decrease of the initial permeability, because there's linear law between the magnetocrystalline anisotropy and the domain wall energy. The resonance frequency to Co substitution moved to high frequency band, due to the close relationship with domain wall energy, Initial permeability decreaed a little with an increase of Co contents, but resonace frequency moved to high frequency band. as a result of that, when Co was added 0.05 mol, initial permeability and resonace frequency was 75 and 25 MHz respectively.