• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.501-517
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• 2016

Synchronized switch damping (SSD) is a structural vibration control technique in which a piezoelectric patch attached to or embedded into the structure is connected to or disconnected from the shunt circuit in order to dissipate the vibration energy of the host structure. The switching process is performed by a digital signal processor (DSP) which detects the displacement extrema and generates a command to operate the switch in synchronous with the structure motion. Recently, autonomous SSD techniques have emerged in which the work of DSP is taken up by a low pass filter, thus making the whole system autonomous or self-powered. The control performance of the previous autonomous SSD techniques heavily relied on the electrical quality factor of the shunt circuit which limited their damping performance. Thus in order to reduce the influence of the electrical quality factor on the damping performance, a new autonomous SSD technique is proposed in this paper in which a negative capacitor is used along with the inductor in the shunt circuit. Only a negative capacitor could also be used instead of inductor but it caused saturation of negative capacitor in the absence of an inductor due to high current generated during the switching process. The presence of inductor in the shunt circuit of negative capacitor limits the amount of current supplied by the negative capacitance, thus improving the damping performance. In order to judge the control performance of proposed autonomous SSDNCI, a comparison is made between the autonomous SSDI, autonomous SSDNC and autonomous SSDNCI techniques for the control of an aluminum cantilever beam subjected to both single mode and multimode excitation. A value of negative capacitance slightly greater than the piezoelectric patch capacitance gave the optimum damping results. Experiment results confirmed the effectiveness of the proposed autonomous SSDNCI technique as compared to the previous techniques. Some limitations and drawbacks of the proposed technique are also discussed.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.457-460
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• 2005

When a hearing aid' s user is listening through telephone or cellular phone, he/she usually suffers from severe electrical magnetic interference noise. It is because hearing aids amplify voice signal as well as background noise. A telecoil, an induction coil, is a possible solution for the problem. Because a telecoil has the characteristic of high pass filter, it has some problem of resulting increased high frequency noise. For solving this problem, we can use a capacitor connected with the telecoil in parallel. According to capacitance, receiving signal quality may change. In this paper, proper capacitor values for the best sound quality are investigated by experimental work.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.1
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• pp.15-22
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• 2001

In this paper, a VSC(Voltage Sag Corrector) is discussed for the purpose of power quality enhancement. A fast detecting technique of voltage sag is accomplished through the detection of instantaneous value on synchronous reference frame. A robust characteristic against the noise is available by inserting the first order low pass filter in the detection circuit. The formula and the filter design process is described properly with the mathematical equations. Because the VSC system supply the active power to load, it is required to design the proper size of the energy storage system, In this paper, the capacitor bank is used as an energy storage system, and the size of the capacitor is designed from the point of view of input/output energy as the output power rating and the amplitude and duration time of the voltage sag. The simulation is accomplished by PSCAD/EMTDC.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.3
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• pp.90-94
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• 2004

The variation of electrical properties of (Ba,Sr)$TiO_3$ [BST] thin films for Metal-Insulator-Semiconductor (MIS) capacitors was investigated. BST thin films were deposited on p-Si(100) substrates by the RF magnetron sputtering with temperature range of 500~$600^{\circ}C$. The dielectric properties of MIS capacitors consisting of AUBST/$SiO_2$/Si sandwich structure were measured for various conditions. We examined the characteristics of MIS capacitor with various oxygen pressure, substrate temperature and (Ba+Sr)/Ti ratio. It was found that the leakage current was reduced in MIS capacitor with high quality $SiO_2$ layer was grown on bare p-Si substrate by thermal oxidation. The BST MIS structure showed relatively high capacitance even though it is the combination of high-dielectric BST thin films and $SiO_2$ layer. The charge state densities of the MIS capacitors and Current-voltage characteristics of the MIS capacitor were investigated. By applying $SiO_2$ layer between BST thin films and Si substrate, low leakage current of $10^{-10}$ order was observed.

• Journal of Sensor Science and Technology
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• v.16 no.2
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• pp.97-103
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• 2007

Crystallized carbon nitride film that has many stable physical and/or chemical properties has been expected potentially by a new electrical material. However, one of the most significant problems degrading the quality of carbon nitride films is an existence of N-H and C-H bonds from the deposition environment. The possibility of these reactions with hydroxyl group in carbon nitride films, caused by a hydrogen attack, was suggested and proved in our previous reports that this undesired effect could be applied for fabricating micro-humidity sensors. In this study, MIS capacitor and MIM capacitor with $5{\mu}m{\times}5{\mu}m$ meshes were fabricated. As an insulator, carbon nitride film was deposited on a $Si_{3}N_{4}/SiO_{2}/Si$ substrate using reactive magnetron sputtering system, and its dielectric constant, C-V characteristics and humidity sensing properties were investigated. The fabricated humidity sensors showed a linearity in the humidity range of 0 %RH to 80 %RH. These results reveal that MIS and MIM $CN_{X}$ capacitive humidity sensors can be used for Si based micro-humidity sensors.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2227-2236
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• 2017

In order to solve the neutral-point voltage fluctuation problem of three-phase three-level T-type inverters (TPTLTIs), the unbalance characteristics of capacitor voltages under different switching states and the mechanism of neutral-point voltage fluctuation are revealed. Based on the mathematical model of a TPTLTI, a feed-forward voltage balancing control strategy of DC-link capacitor voltages error is proposed. The strategy generates a DC bias voltage using a capacitor voltage loop with a proportional integral (PI) controller. The proposed strategy can suppress the neutral-point voltage fluctuation effectively and improve the quality of output currents. The correctness of the theoretical analysis is verified through simulations. An experimental prototype of a TPTLTI based on Digital Signal Processor (DSP) is built. The feasibility and effectiveness of the proposed strategy is verified through experiment. The results from simulations and experiment match very well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.313-313
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• 2008

Aerosol Deposition(AD) method is based on the impact consolidation phenomenon of ceramic fine particles at room temperature. AD is promising technology for the room temperature deposition of the dielectrics thin films with high quality. Embedding of passive components such as capacitors into printed circuit board is becoming an important strategy for electronics miniaturization and device reliability, manufacturing cost reduction. So, passive integration using aerosol deposition. In this study, we examine the effects of the characteristics of raw powder on the thickness, roughness, electrical properties of $BaTiO_3$ thin films. Thin films were deposited on the copper foil and copper plate. Electrical and material properties was investigated as a change of annealing temperature. We final aim the effects of before and after of laminated on the electrical properties and suit of embedded capacitor.

• Transactions on Electrical and Electronic Materials
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• v.11 no.3
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• pp.126-129
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• 2010

(1-X) $(Na_{0.5}K_{0.5})NbO_3-X$ $K_4CuNb_8O_{23}$ (NKN-X KCN) ceramics were produced using the conventional solid state sintering method, and their sinterability and electric properties were investigated. The density, dielectric constant (${\varepsilon}_r$), piezoelectric constant $d_{33}$, electromechanical coupling factor $k_p$ and mechanical quality factor $Q_m$ value of the NKN ceramics depended upon the KCN content and the sintering temperature. In particular, the KCN addition to the NKN greatly improved the mechanical quality factor $Q_m$ value. The ceramic with X = 2.0 mol% sintered at $1,150^{\circ}C$ possesses the optimum properties (${\varepsilon}_r=241$, $d_{33}=78$, $k_p=0.34$ and $Q_m=1,121$). These results indicate that the ceramic is a promising candidate material for applications in lead free piezoelectric transformer and filter materials.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.1
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• pp.35-42
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• 2016

Developments in power electronics have enabled the widespread application of Pulse Width Modulation (PWM) inverters, notably for connecting renewable systems to the grid. This study demonstrates that a high-quality power can be achieved using a stand-alone inverter, whereby the comparison between the power quality of the stand-alone inverter with battery storage (off-grid) and the power quality of the utility network is presented. Multi-loop control techniques for a single phase stand-alone inverter are used. A capacitor current control is used to give active damping and enhance the transient and steady state inverter performance. A capacitor current control is cheaper than the inductor current control, where a small current sensing resistor is used. The output voltage control is used to improve the system performance and also control the output voltage. The inner control loop uses a proportional gain current controller and the outer loop is implemented using internal model control proportional-integral-derivative to ensure stability. The optimal controls are achieved by using the Sisotool tool in MATLAB/Simulink. The outcome of the control scheme of the numerical model of the stand-alone inverter has a smooth and good dynamic performance, but also a strong robustness to load variations. The numerical model of the stand-alone inverter and its power quality are presented, and the power quality is shown to meet the IEEE 519-2014. Furthermore, the power quality of the off-grid system is measured experimentally and compared with the grid power, showing power quality of off-grid system to be better than that of the utility network.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1587-1588
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• 2006

Tn this paper, PCB (Printed Circuit Board) embedded $BaTiO_3$ MIM capacitors were designed, fabricated, and characterized for low cost organic SOP applications by using 3-D EM simulator and low temperature processes. Size of electrodes and thickness of high dielectric films are optimized for improving the performance characteristics of the proposed embedded MIM capacitors at high frequency regime. The selected thicknesses of the $BaTiO_3$ film are $12{\mu}m$, $16{\mu}m$, and $20{\mu}m$. The fabricated MIM capacitor with dielectric constant of 30 and thickness of $12{\mu}m$ has capacitance density of $21.5p\;F/mm^2$ at 100MHz, maximum quality factor of 37.4 at 300 MHz, a quality factor of 30.9 at 1GHz, self resonant frequency of 5.4 GHz, respectively. The measured capacitances and quality factors are well matched with 3-D EM simulated ones. These embedded capacitors are promising for SOP based advanced electronic systems with various functionality, low cost, small size and volume.