• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.72-83
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• 2013

The paper proposes a new multilevel variable output voltage AC/DC Converter for power supply of power amplifiers used in underwater acoustic sensors. The proposed multilevel variable output voltage AC/DC Converter is composed of two parts. One as the input section is the high efficiency phase-shifted PWM full bridge DC-DC converter to get multiport power sources. The other as the output section is composed of two flying-capacitor 3-level DC-DC converters and a diode bridge circuit to get fast-response and multilevel variable output voltage for an envelope amplifier. Also the paper suggests the detailed circuit topology and design guideline of multilevel variable output voltage AC/DC converter. It also proposes the power balanced control method between 3-level converters and the voltage balanced algorithm for flying capacitors. Its characteristics should be verified by the detailed simulation results. It is anticipated that the proposed converter will be used very well for power amplifiers used in underwater acoustic sensors.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.863-866
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• 1999

(Ba,Sr)$TiO_3$ thin films have attracted groat interest as new dielectric materials of capacitors for ultra-large-scale integrated dynamic random access memories (ULSI-DRAMs) such as 1 Gbit or 4 Gbit. In this study, inductively coupled $BCl_3/Cl_2$/Ar plasmas was used to etch (Ba,Sr)$TiO_3$ thin films. RF power/dc bias voltage = 600 W/-250 V and chamber pressure was 10 mTorr. The $Cl_2/(Cl_2+Ar)$ was fixed at 0.2, the (Ba,Sr)$TiO_3$ thin films were etched adding $BCl_3$. The highest (Ba,Sr)$TiO_3$ etch rate is 480$\AA/min$ at 10 % $BCl_3$ adding to $Cl_2$/Ar. The characteristics of the plasmas were estimated using optical emission spectroscopy (OES). The change of Cl, B radical density measured by OES as a function of $BCl_3$ percentage in $Cl_2$/Ar. The highest Cl radical density was shown at the addition of 10% $BCl_3$ to $Cl_2$/Ar. To study on the surface reaction of (Ba,Sr)$TiO_3$ thin films was investigated by XPS analysis. Ion enhancement etching is necessary to break Ba-O bond and to remove $BaCl_2$. There is a little chemical reaction between Sr and Cl, but Sr is removed by physical sputtering. There is a chemical reaction between Ti and Cl, and Tic14 is removed with ease. The cross-sectional of (Ba,Sr)$TiO_3$ thin film was investigated by scanning electron microscopy (SEM), the etch slope is about $65\;{\sim}\;70$.

• Fire Science and Engineering
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• v.29 no.6
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• pp.91-97
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• 2015

Skyscrapers, large business buildings, and IT consumers use many appliances, and the electrical power stems can cause fires by overheating. This can result in damaged capacitors, lost data, rising ground potential, and communication obstacles from linear or nonlinear high frequency. To make sure of that we investigated 7 spots of a building, among which 6-spots were fair but the other one needed high frequency control. Spots 3, 6, and 7 needed diagnostic workup, and spots 2, 3, and 5 considered 5 high frequency currents. A phase is all of good but the high frequency current is greater than the standard level except for spot 1. As a result, a zigzag transformer or active filter needs to be installed, and the efficiency needs to be upgraded by investigating load unbalance factors and power factors.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.567-567
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• 2012

Since the carbon nanotubes (CNTs) have extraordinary material properties, many researchers are trying to make a practical application in various fields [1]. In particular, the high surface area of CNTs was fascinated for nano-template on the catalytic system. $RuO_2$ coated CNTs are useful functional nano-composites in many applications, including super capacitors, fuel cells, biosensors, and field emitters. However, the research of interaction between CNTs and $RuO_2$ was not satisfied with various fields [2]. In this study, we will introduce the change of chemical and electrical state of $RuO_2$/CNTs at different temperatures by synchrotron radiation photoemission spectroscopy (SRPES). The t-MWCNTs used in this experiment were grown on the Ni/TiN/Si substrates by chemical vapor deposition. $RuO_2$ of 4-20 nm in thickness was deposited on the t-MWNTs by sputter. The SRPES measurements were carried out at the 4B1 beamline of the Pohang Accelerator Laboratory in Korea. The result of XPS measurement indicates that the deposited $RuO_2$ on the CNTs was reduced into pure Ru at above $300^{\circ}C$. And we confirmed that the effective work function of $RuO_2$/CNTs was decreased with increasing temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.333-333
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• 2011

We have investigated the breakdown properties in liquids by high voltage pulse system. High voltage pulse power system is consisted of the Marx-generator with two capacitors (0.5 ${\mu}F$, withstanding voltage is 40 kV), to which the charging voltage can be applied to maximum 30 kV DC, spark gap switch and charging resistor of 20 $M{\Omega}$. We have made use of tungsten pin electrodes of anode-cathode (A-K), which are immersed into the liquids. The breakdown voltage and current signals are measured by high voltage probe (Tektronix P6015A) and current monitor (IPC CM-1.S). Especially the high speed breakdown or plasma propagation characteristics in the pulsed A-K gap have been investigated by using the high speed ICCD camera. We have measured the electron temperature through the Boltzmann plot method from the breakdown spectrums. Here the A-K gap has been changed by 1 mm, 2 mm, and 3 mm. The used liquids are distilled water and solution of salt (0.9 %). The output voltage and current signals at breakdown in distilled water are shown to be bigger than those in saline solution. The breakdown voltage and current characteristics in liquids will be discussed in accordance with A-K gap distances. It is also found that the electron temperatures and plasma densities in liquids are decreased in conformity with A-K gap.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.10
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• pp.58-67
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• 2006

In this paper, real-time reactive power/power factor compensating equipment is suggested for improving power quality at electrical railway's substation in marshalling yard and designing optimal capacity of compensating equipment for actual apply at current marshalling yard. For this purpose, several kind of real-time reactive power/power factor compensating equipments are introduced and SVG(Static Var Generator) as optimal compensating equipment that is suitable for load characteristics of substation in marshalling yard is suggested. This paper shows proper simulations by suggested equipment using PSIM software and describe basic compensating principle and simulation results. Optimal capacity design for applying current marshalling yard is based on real measured power quality data. Power quality improvement that is performed by SVG as real-time reactive power/power factor compensating equipment is estimated at electrical railway's substation in marshalling yard. As reference, real-time reactive power/power factor compensating equipment is composed by voltage source inverter and DC capacitors.

• Analytical Science and Technology
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• v.18 no.3
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• pp.206-215
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• 2005

Polychlorinated biphenyls (PCBs) were commercially produced as complex mixtures beginning in 1929. The PCBs manufactured commercially are known by a variety of trade names including; Aroclor (USA), Phenoclor (France), Kaneclor (Japan), Sovol (USSR) and so on. PCBs are a class of 209 congeners that were widely used in a wide variety of applications, including dielectric fluid in transformers and large capacitors; heat transfer fluids; hydraulic fluids; lubricating and cutting oils; and as additives in pesticides, paints, adhesives, sealants, and plastics. The quantification methods of peak matching and coefficient comparison were compared using the Aroclor 1242, 1248, 1254, 1260 standards. Also, six transformer oils were analyzed as a main source of polychlorinated biphenyls (PCBs) emission into the environment. The transformer oils contained the pure and mixed of Aroclor 1242, Aroclor 1254, and Aroclor 1260. The analytical results using two quantification methods showed the little difference between the measured results.

• Journal of Sensor Science and Technology
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• v.7 no.2
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• pp.103-110
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• 1998

Pyroelectric infrared detectors based on La-modified $PbTiO_{3}$ (PLT) thin films have been fabricated by RF magnetron sputtering and rnicrornachining technology. The detectors form $Pb_{l-x}La_{x}Ti_{1-x/4}O_{3}$ (x=0.05) thin film ferroelectric capacitors epitaxially grown by RF magnetron sputtering on Pt/MgO (100) substrate. The sputtered PLT thin film exhibits highly c-axis oriented crystal structure that no poling treatment for sensing applications is required. This is an essential factor to increase the yield for realization of an infrared image sensor. Micromachining technology is used to lower the thermal mass of the detector by giving maximum sensor efficiency. Polymide is coated on top of the sensing elements to support the fragile structure and the backside of the MgO substrate is selectively etched to reduce the heat loss. The sensing element exhibited a very high detectivity D* of $8.5{\times}10^{8}cm{\cdot}\sqrt{Hz}/W$ at room temperature and it is about 100 times higher than the case of micromachining technology is not used. A sensing system that detects the position as well as the existence of a human body is realized using the array sensor.

• Journal of the Korean Ceramic Society
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• v.46 no.2
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• pp.175-180
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• 2009

Multilayer ceramic capacitors (MLCCs) have continually been made smaller in size and larger in capacity in resent years. However, the end termination electrode is still thick in many MLCCs. In this study, we used small grain glass frit to embody thin film and highly densification in the end termination by improve sintering driving force with well-dispersion and rising surface energy. Pastes were fabricated using size changed glass frit, such as 0.1 ${\mu}m$, 0.5 ${\mu}m$, 1.0 ${\mu}m$, 4.0 ${\mu}m$. Fabricated pastes were applied 05A475KQ5 chip and fired various sintering temperatures to analyze sintering behavior of pastes. Consequently, small glass frit used pastes have many merits than larger, such as well-dispersion, improve cornercoverage and surface roughness, possibility of low temperature sintering. However, we confirmed that small glass frit used pastes have narrow sintering window by rapid completion of sintering densification.

• Journal of the Korean Electrochemical Society
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• v.8 no.1
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• pp.1-5
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• 2005

Electric double layer capacitors(EDLCS) based on the charge stored at the interface between a hi팀 surface area carbon electrode and an organic electrolyte solution are widely used as a maintenance-free power source for IC memories and microcomputers. The achievement of the excellent performance of the capacitor requires an electrolyte solution which provides high conductivities over a wide temperature range and good electrochemical stabilities to allow the capacitor to be operated at high voltage. The electrochemical capacitor using a carbon material as electrodes and using an organic electrolyte with $1M-LiPF_6$ in PC-GBL-DEC(volume ratio 1:1:2) has specific capacitance of 64F/g.