• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.5
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• pp.416-423
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• 2007

To drive the CCFL In LCD backlight inverter, a new transformer structure with small volume is proposed which have a boosting voltage and a lamp current balancing functions. The proposed transformer structure has been verified through experimental test with 40inch LCD backlight inverter.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.11
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• pp.495-502
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• 1986

The change of the discharge characteristics of the high-pressure sodium (HPS) lamps is investigated over a power source frequency range of 60 Hz to 30, 000 Hz. As the frequency increases, the light and electrical characteristics of the HPS lamps are improved since the re-ignition is not needed due to the constant electron density, and the cathode fall is reduced. But at the certain frequency range, the arc instability called acoustic resonance occurs, and the arc tube is damaged. Regarding these characteristics and the kind of the illuminating system, a proper frequency is selected to operate the HPS lamps. And a new measuring system using a computer and the storage-scope is developed to avoid the error of the ordinary gauges at high frequency power.

• Electrical & Electronic Materials
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• v.8 no.3
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• pp.254-260
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• 1995

A method is described for the design and fabrication of the sensor interface circuits on the Clark electrodes for the dissolved oxygen(DO). The discussion includes a method for the +5 V single-supply driving for the sensor circuits, which has low power comsumption for the front-end electronics. DO probe under test is composed of the Clark electrode with silver anode, gold cathode and the electrolyte of half saturated KCI solution and the FEP teflon memtrance for the oxygen penetration. Typical polarograms for the DO probes by using this sensor circuit reveals high accuracy over 99% of the I to V conversion. Partial pressure of oxygen obtained from the polarograms are well suited to the results calculated. It is expected that the proposed sensor circuits can be utilized into the customized IC for the battery-driven small-size DO meters.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.3
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• pp.197-204
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• 2008

DMFC(Direct Methanol Fuel Cell) is one of promising candidates for power sources of small mobile IT devices like notebook, cell phone, and so on. Efficient operation of fuel cell system is very important for long-sustained power supply because of limited fuel tank size. It is necessary to investigate operation characteristics of fuel cell stack for optimal control of DMFC system. The generated voltage was modeled according to various operating condition; methanol concentration, stack temperature, and load current. It is inevitable for methanol solution at anode to cross over to cathode through MEA(membrane electrode assembly), which reduces the system efficiency and increases fuel consumption. In this study, optimal operation conditions are proposed by analyzing stack performance model, cross-over phenomenon, and system efficiency.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.71.2-71.2
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• 2012

There are rising demands for developing more efficient energy materials to stem the depletion of fossil fuels, which have prompted significant research efforts on proton exchange fuel cells (PEFCs) and lithium ion batteries (LIBs). To date, both PEFCs and LIBs are being widely developed to power small electronics, however, their utilization to medium-large sized electric power resources such as vehicle and stationary energy storage systems still appears distant. These technologies increasingly rely upon polymer electrolyte membranes (PEMs) that transport ions from the anode to the cathode to balance the flow of electrons in an external circuit, and therefore play a central role in determining the efficiency of the devices; as ion transport is a kinetic bottleneck compared to electrical conductivity, enormous efforts have been devoted to improving the transport properties of PEMs. In present study, we carried out an in-depth analysis of the morphology effects on transport properties of PEMs. How parameters such as self-assembled nanostructures, domain sizes, and domain orientations affect conductivities of PEMs will be presented.

• Transactions on Electrical and Electronic Materials
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• v.8 no.2
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• pp.93-96
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• 2007

LCD (liquid crystal display) industry is needed to goods of high reliability and is interested in products without harmful material. In this experiment, we made the LED backlight unit for Automotive-navigation. And for making this backlight unit we used to eight side emitting type white LEDs with 1 W high power of the lumileds company. We could know that this backlight unit releases to 6500 nit in 14 W power consumption and start up voltage time is under the 15ms in the ambient temperature $-20\;^{\circ}C$.

• Journal of the Korean Professional Engineers Association
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• v.44 no.1
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• pp.48-52
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• 2011

The KEPCO Research Institute has developed Molten Carbonate Fuel Cell(MCFC) since 1993. Recently, an 125-kW MCFC system was operated at Boryeong thermal power plant, Korea from December, 2009 to March, 2010, This system is composed of an 125-kW stack, mechanical balance of plant (MBOP), and Power Conditioning System. The stack has 200 unit cells of which effective area is 10,000 cm2. Especially, MBOP is mainly made up of ejector and catalytic combustor which help this system to be supplied with cathode inlet gas using anode tail gas and fresh air. After the pretreatment of this system was performed for about 20 days, initial load operation was performed at January. 2010. Moreover, this system had been operated for 3,270 hours.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.197-201
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• 2001

Measuring of the dissolved oxygen is widely used for the environmental control of natural waters, sewage waste treatment, medical and biochemical studies, soil husbandry, food and drug process control, and prevention of corrosion in boilers. Especially, a power plants need special management for preventing accidents from corrosion, therefore, it is essential to measure the concentration of dissolved oxygen in real-time. In this paper we present a method of measuring dissolved oxygen very accurately up to ppb units. This method, called polarographic method, is based on the measures of the electric current generated by the oxidation process in cathode and de-oxidation process in anode, assuming that the amount of the current is proportional to the density of dissolved oxygen.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.281-288
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• 2010

This study examined the carbon corrosion at Pt/C interface in proton exchange membrane fuel cell environment. The Pt nano particles were electrodeposited on carbon substrate, and then the corrosion behavior of the carbon electrode was examined. The carbon electrodes with Pt nano electrodeposits exhibited the higher oxidation rate and lower oxidation overpotential compared with that of the electrode without Pt. This phenomenon was more active at $75^{\circ}C$ than $25^{\circ}C$. In addition, the current transients and the corresponding power spectral density (PSD) of the carbon electrodes with Pt nano electrodeposits were much higher than those of the electrode without Pt. The carbon corrosion at Pt/C interface was highly accelerated by Pt nano electrodeposits. Furthermore, the polarization and power density curves of PEMFC showed degradation in the performance due to a deterioration of cathode catalyst material and Pt dissolution.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.406-407
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• 2007

We prepared indium zinc oxide (IZO) thin film for cathode electrode such as an application of flat panel display by using the facing targets sputtering (FTS) method at room temperature. The effects of input power and film thickness were investigated with respect to physical and optical properties of films such as deposition rate, electrical properties, microstructure and transmittance. We could obtain properties of IZO thin films of under $10^{-3}\;{\Omega}-cm$ in resistivity and the thin films of over 90% in transmittance. Also, we obtained IZO thin films which were an amorphous structure.