• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.202-205
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• 2010

In this study, the etch properties of $Al_2O_3$ thin films deposited by atomic layer deposition were investigated as a function of the $O_2$ content in $BCl_3$/Ar inductively coupled plasma. The experiments were performed by comparing the etch rates and selectivity of $Al_2O_3$ over the hard mask materials as functions of the input plasma parameters, such as the gas mixing ratio, DC-bias voltage, ratio-frequency (RF) power and process pressure. The highest obtained etch rate was 477 nm/min at an RF power of 700 W, $O_2$ to $BCl_3$/Ar gas ratio of 15%, DC-bias voltage of -100 V and process pressure of 15 mTorr. The deposition occurred on the surfaces when the amount of $O_2$ added to the $BCl_3$/Ar gas was too high at a low DC-bias voltage or high process pressure. X-ray photoelectron spectroscopy was used to investigate the chemical reactions on the etched surface.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.26-35
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• 1996

In this paper, characteristics of the electromagnetically coupled broadband microstrip antennas are analyzed by the Finite Difference Time Domain (FDTD) method, and antenna para- meters are optimized to get maximum bnadwidth. By using short radial tuning stub in microstrip feedline, electromagnetically coupled microstrip antenna shows broadband ($\simeq$13%) characteristics, and the characteristics are varied as a function of radius, radial angle, and position of the radial tuning stub. Operating frequency, return loss, VSWR and input impedance are calculated by Fourier transforming the time domain results. After optimization of the parameters, maximum bandwidth of the radial stub tuning microstrip antenna is about 15% and the ripple char- acteristic of the VSWR is better than the rectangular tuning stub microstrip antenna.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.12
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• pp.93-102
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• 2004

This paper presents a general theory for the analysis of an aperture-coupled cavity-fed microstrip patch antenna to develop a simple but accurate equivalent circuit model. The developed equivalent circuit consists of ideal transformers, admittance elements, and transmission lines. These circuit element values are computed by applying the complex power concept, the Fourier transform and series representation, and the spectral-domain immittance approach. The input impedance of the antenna is calculated and compared with the published data. Good agreements validate the simplicity and accuracy of the developed equivalent circuit model.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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• pp.560-566
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• 2004

In this paper, the electrical and emission properties of electrodeless fluorescent lamp were discussed using the inductively coupled plasma (ICP) with the variation of argon gas pressure and RF power. The RF output was applied to the antenna in the range of 5∼50 W at 13.56 MHz. The internal plasma voltage of the chamber and the probe current were measured while varying the supply voltage to the Langmuir probe in the range of －100V∼＋100V. When the pressure of argon gas was increased, electric current was decreased. There was a significant electric current increase from 10 to 30 W. Also, when the RF power was increased, electron density was increased. Also, the emission spectrum, Ar- I lins, luminance were investigated. At this time, the input parameter for ICP RF plasma, Ar gas pressure and RF power were applied in the range of 10∼60 mTorr, 10∼300 W, respectively. This implies that this method can be used to find an optimal RF power for efficient light illumination in an electrodeless fluorescent lamp.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.229-233
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• 2007

In this study, we carried out an investigation of the etching characteristics(etch rate, selectivity) of $HfO_2$ thin films in the $CH_4/Ar$ inductively coupled plasma. It was found that variations of input power and negative dc-bias voltage are investigated by the monotonic changes of the $HfO_2$ etch rate as it generally expected from the corresponding variations of plasma parameters. At the same time, a change in either gas pressure or in gas mixing ratio result in non-monotonic etch rate that reaches a maximum at 2 Pa and for $CH_4(20%)/Ar(80%)$ gas mixture, respectively. The X-ray photoelectron spectroscopy analysis showed an efficient destruction of the oxide bonds by the ion bombardment as well as showed an accumulation of low volatile reaction products on the etched surface. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the $CH_4-containing$ plasmas.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1998.11a
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• pp.131-133
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• 1998

Electron temperature, electron density and electron energy distribution function were measured in Radio-Frequency Inductively Coupled Plasma(RFICP) using a probe method. Measurements were conducted in argon discharge for pressure from 10 mTorr to 40 mTorr and input rF power from 100W to 600W and flow rate from 3 sccm to 12 sccm. Spatial distribution of electron temperature, electron density and electron energy distribution function were measured for discharge with same aspect ratio (R/L=2). Electron temperature was found to depend on pressure, but only weakly on power. Electron density and electron energy distribution function strongly depended on both pressure and power. Electron density and electron energy distribution function increased with increasing flow rate. Radial distribution of the electron density and electron energy distribution function were peaked in the plasma center. Normal distribution of the electron density, electron energy distribution function were peaked in the center between quartz plate and substrate. These results were compared to a simple model of ICP, finally, we found out the generation mechanism of Radio-Frequency Inductively Coupled Plasma.

• Steel and Composite Structures
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• v.7 no.4
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• pp.279-301
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• 2007

When coupling beams are proportioned appropriately in coupled core wall (CCW) systems, the input energy from ground motions is dissipated primarily through inelastic deformations in plastic hinge regions at the ends of the coupling beams. It is desirable that the plastic hinges form at the beam ends while the base wall piers remain elastic. The strength and stiffness of the coupling beams are, therefore, crucial if the desired global behavior of the CCW system is to be achieved. This paper presents the results of nonlinear response history analysis of two 20-story CCW buildings. Both buildings have the same geometric dimensions, and the components of the buildings are designed based on the equivalent lateral force procedure. However, one building is fitted with steel coupling beams while the other is fitted with diagonally reinforced concrete coupling beams. The force-deflection relationships of both beams are based on experimental data, while the moment-curvature and axial load-moment relationships of the wall piers are analytically generated from cross-sectional fiber analyses. Using the aforementioned beam and wall properties, nonlinear response history analyses are performed. Superiority of the steel coupling beams is demonstrated through detailed evaluations of local and global responses computed for a number of recorded and artificially generated ground motions.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.10
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• pp.754-764
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• 2001

Class A bipolar second-generation current conveyor (CCII) with low current-input impedance and its offset-compensated CCII for high-accuracy current-mode signal processing are proposed. The CCIIs consist of a regulated current-cell for current input, a emitter follower for voltage input, and a cascode current mirror lot current output. In these architecture, the two input stages are coupled by current mirror to reduce the current input impedance. Experiments show that the CCII has impedance of 8.4 Ω and offset voltage of 40 mV at current input terminal. To reduce this offset, the offset-compensated CCII adopts diode-connected npn and pnp transistor in the proposed CCII. Experiments show that the offset-compensated CCII has current input impedance of 2.1 Ω and offset voltage of 0.05 mV. The 3-dB cutoff frequency of the CCIIs when used as a voltage follower extends beyond 30 MHz. The power dissipation is 7.0 mW

• Journal of the Korean Society for Precision Engineering
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• v.30 no.7
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• pp.733-740
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• 2013

The high-velocity electromagnetic forming (EMF) process is based on the Lorentz force and the energy of the magnetic field. The advantages of EMF include improved formability, wrinkle reduction, and non-contact forming. In this study, numerical simulations were conducted to determine the practical parameters for the EMF process. A 2-D axis-symmetric electromagnetic model was used, based on a spiral-type forming coil. In the numerical simulation, an RLC circuit was coupled to the spiral coil to measure various design parameters, such as the system input current and the electromagnetic force. The simulation results show that even though the input peak current levels were at the same level in each case, the forming condition varied due to differences in the frequency of the input current. Thus, the electromagnetic forming force was affected by the input current frequency, which in turn, determined the magnitude of the current density and the magnetic flux density.

• Journal of Power Electronics
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• v.13 no.4
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• pp.592-599
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• 2013

This paper investigates a new isolated single-phase AC-DC converter, which integrates a modified AC-DC buck-boost converter with a DC-DC forward converter. The front semi-stage is operated in discontinuous conduction mode (DCM) to achieve an almost unity power factor and a low total harmonic distortion of the input current. The rear semi-stage is used for step-down voltage conversion and electrical isolation. The front semi-stage uses a coupled inductor with the same winding-turn in the primary and secondary sides, which is charged in series during the switch-on period and is discharged in parallel during the switch-off period. The discharging time can be shortened. In other words, the duty ratio can be extended. This semi-stage can be operated in a larger duty-ratio range than the conventional AC-DC buck-boost converter for DCM operation. Therefore, the proposed converter is suitable for universal input voltage (90~264 $V_{rms}$) and a wide output-power range. Moreover, the voltage stress on the DC-link capacitor is low. Finally, a prototype circuit is implemented to verify the performance of the proposed converter.