• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2016.11a
• /
• pp.3-32
• /
• 2016

High power impulse magnetron sputtering (HiPIMS) technique has been developed for more than 15 years. It is characterized by its ultra-high peak current and peak power density to obtain unique thin film properties, such as high hardness, good adhesion and tribological performance. However, its low deposition rate makes it hard to be applied in industries. In this work, the development of HiPIMS system and integration of radio frequency (RF) or mid-frequency (MF) power supplies were introduced. Effects of duty cycle and repetition frequency on the microstructure, mechanical property, optical and electrical properties of some binary, ternary and quarternary nitride coatings and oxide thin films were discussed. It can be observed that the deposition rate was effectively increased by the superimposed HiPIMS with RF or MF power. High hardness, good adhesion and sufficient wear resistance can be obtained through a proper adjustment of processing parameters of HiPIMS power system.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.1
• /
• pp.93-98
• /
• 2002

It is a present situation that the control on automobile emission is getting more restrictive and also the regulations for emission are changing greatly up to level of those advanced foreign countries. Specially, it has been many years that exhaust gases from gasoline automobile rather than from diesel is the major object concerned by Korea and other countries, and it is strongly required on the reduction techniques on harmful NOx and PM among those compositions. Thus, this research focused on the Exhaust Gas Recirculation (EGR) and the target fur this research is heavy-duty turbo-diesel engine with EGR, and conducted with numerical simulation to get engine performance and the characteristics of emission. Furthermore. the results obtained under different conditions such as rpm, power, EGR rate are compared and investigated with the numerical simulation using KIVA-3.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.11
• /
• pp.1925-1930
• /
• 2016

Fuel cell power generation system, unlike conventional energy sources, converts chemical energy into electrical energy through electrochemical reaction of hydrogen and oxygen. This paper presents the control of interleaved multi-phase boost converter as the feasibility study on small-scale prototype electric railway vehicle application using fuel cell generation system. PSIM simulation program is to be used to implement the modeling of the electrical fuelcell as well as traction motor control with interleaved multi-phase boost converter. Comparing the input current ripple rate, two-phase interleaved boost converter is less than the boost converter. But the more multi-phase not less proportional to the ripple factor. we confirmed that the amplitude of the input current ripple rate of converter depend on duty ratio.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.1023-1025
• /
• 1998

This paper presents the fabrication of a micro pump consisting of a pair of Al f1ap wave and a phase change actuator. The phase change actuator is composed of a heater, a silicone rubber diaphragm and a working liquid chamber. The diaphragm is actuated by the evaporation and the condensation of the working liquid. The actuator pumps fluid through the valves. The micro pump is fabricated by the anisotropic etch, the boron deposition and the metal evaporation. The forward and the backward flow characteristics of the f1ap valves were obtained. Also, the flow rate of the micro pump has been measured. When the square wave input of 12 V, 60% duty ratio and 0.2 Hz is applied, the average flow rate is $0.15{\mu}{\ell}/sec$ for zero pressure difference.

• Proceedings of the KIEE Conference
• /
• 2002.07a
• /
• pp.206-208
• /
• 2002

The transmission system is designed to be protected by 40 kA rate of circuit breaker fer 345 tV system and 31.5 kA and 50 kA rate of circuit breaker for 154 kV system. The short circuit current shows the tendency of exceeding circuit breaker duty for some substations and the tendency will continue if an appropriate countermeasure will not be applied to. In order to solve this problem from the viewpoint of system operation, the 154 kV system is under reconfiguration to be radial systems. This paper presents application effect of resistive and inductive SCFL (Superconducting Fault Current Limiter to Korea power systems. An algorithm of SCFL site decision is suggested.

• Proceedings of the KIEE Conference
• /
• 2005.11a
• /
• pp.116-118
• /
• 2005

열공압 방식으로 동작하는 마이크로 펌프와 밸브가 집적된 (polydimethylsiloxane)PDMS 미 세 유체 시스템을 제작하였다. 본 실험에서 제안한 미세 유체 시스템은 PDMS 마이크로 채널, PDMS membrane, 열공압 챔버, indium tin oxide(ITO) 히터로 구성되어 있다. 마이크로 펌프의 경우 가해주는 펄스 전압의 변화를 통해 유속을 최적화 하였고 마이크로 밸브의 경우 가해주는 직류 전압을 변화시켜 유체의 흐름을 제어할 수 있었다. 미세 유체 시스템의 최적화된 조건은 마이크로 펌프의 경우 duty 4%와 주파수 4Hz에서 최대 pumping rate을 나타냈고 그때의 pumping rate 68nl/min이었다. 마이크로 밸브의 유체를 closing 전력은 450mW이었다.

• Journal of Sensor Science and Technology
• /
• v.15 no.1
• /
• pp.47-52
• /
• 2006

This paper describes the design, fabrication and characteristics of a buckling microvalve using a MCA (multilayer ceramic actuator). The mechanical and fluidic analysis are done by finite element method. The designed structure is normally closed microvalve using buckling effect, which is consist of three separate structures; a valve seat die, an actuator die and a small piezoelectric actuator. The flow rate of the fabricated MCA valve was 0-8.13 ml/min at the applied pressure of 0-50 kPa. Maximum non-linearity was 2.24 % FS at a duty cycle of 50 %. The maximum pressure was 230 kPa and the leak rate was $3.03{\times}10^{-8}\;Pa{\cdot}m^{3}/cm^{2}$ at a supply voltage of 100 V.

• Journal of the Korean Ceramic Society
• /
• v.34 no.10
• /
• pp.1092-1098
• /
• 1997

Electrical discharge machining (EDM) was attempted on a ceramic matrix composite containing non-conductive alumina as a matrix and conductive titania as a second phase, and was found successful. As the current or duty factor increased, the material removal rate (MRR) increased and the surface roughness also increased. The EDMed surface was covered with a number of craters of a circular shape having 100-200 microns of diameter. The melting and evaporation was suggested for the EDM mechanism. The bending strength decreased 44% after EDM, but the Weibull modulus increased more than twice. Combination of EDM and barre이 polishing resulted in the maintenance of the bending strength level. Temperature distribution near a spark in the sample was computer-simulated by use of finite element method, and was found to have similar shape to the one which the observed craters have.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2006.11a
• /
• pp.143-146
• /
• 2006

There has been growing concern regarding IAQ(Indoor Air Quality) recently, and IAQ problems from the air-tightness and use of chemical materials addition to the building materials have become increasingly important factors in the built environment. Ventilation is supposed as the solution of healthy indoor quality, and Korea government requests that all new apartment buildings must have a ventilation system as a matter of duty since January, 2006. The purpose of this study is to investigate the indoor concentration change of VOCs include the Formaldehyde according to many different ventilation supply types. Results showed that the reduction effect of target pollutants by the ventilation system was very slight. The cause of these results was attribute to increase the emission rate of building materials by increasing the ventilation rate.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.53 no.6
• /
• pp.342-346
• /
• 2004

A thermopneumatic-actuated polydimethylsiloxane (PDMS) micropump has been fabricated and their properties are characterized. The diffusers are used as a flow-rectifying element instead of passive check valves. The advantages of the proposed microvalve are of the low cost fabrication process and the transparent optical property using PDMS and indium tin oxide (ITO) glass. We presented the PDMS micropump that is easily integrated with the in-channel PDMS microvalves on the same substrate. The flowrate of the micropump increases linearly as the applied pulse voltage to the ITO heater increases. The fabricated ITO heater resistance is 6.54k$\Omega$. The peak of the flow rate is observed at the duty ratio of 10% for the applied pulse voltage of 55V at 6Hz and the maximum flow rate of 78nl/min is measured.