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0.96(Na0.5K0.5)NbO3-0.04(Ba(1-x)Srx)TiO3 무연 세라믹스의 유전 및 압전 특성
김미로 ( Mi Ro Kim ),윤석진 ( Seok Jin Yoon ),최지원 ( Ji Won Choi ) 한국센서학회 2010 센서학회지 Vol.19 No.2
0.96(Na0.5K0.5)NbO3-0.04(Ba(1-x)Srx)TiO3 lead free piezoelectric ceramics were synthesized to enhance the piezoelectric properties of (Na,K)NbO3. The systhesis and sintering method were the conventional solid state reaction method and general sintering method in air atmosphere. The polymorphic phase transition(PPT) was observed at all composition(0≤ x ≤0.05) when (Ba(1-x)Srx)TiO3 were added in the (Na0.5K0.5)NbO3. As Sr concentration was increased, grain size, dielectric loss(tanδ) and mechanical quality factor(Qm) were decreased and piezoelectric constant(d33) and electromechanical coupling factor(kp) were increased within a limited value. The optimized piezoelectric and properties, d33, kp, Qm, and tand, of 0.96(Na0.5K0.5)NbO3-0.04(Ba(1-x)Srx)TiO3 were 139 pC/N, 0.31%, 95, 0.04 at the composition of x=0.04.
냉각수유로가 포함된 열적조건이 PEMFC 성능에 미치는 영향
김미로(Mi-Ro Kim),안병재(Byung-Jae Ahn),최영민(Young-Min Choi) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_1
There are several types of fuel cells available to transform chemical energy directly to electrical energy. One of these, the proton exchange membrane fuel cell, operates at a lower temperature than other types of fuel cells and it may be a useful power source for future automobiles and stationary power plant. For the development of high performance fuel cell, water and heat management of the PEMFC is important. To investigate the influence of coolant passage, three types of coolant passage models are studied numerically. The model results notify that optimal shape of cooling passage strongly depends on shape of gas channel of its geometrical type. The effects of operating conditions like humidity, including temperature effect are also studied. The extremely high inlet humidity may cause cathode flooding issues and increases the load of auxiliary devices, such as humidifier systems. On the contrary, the excessively low humidity may lead to membrane dehydrating problem. From a thermal point of view, the extremely high cell temperature may cause critical performance problem. So optimized coolant passage design is important.
김미로(Mi-Ro Kim),조남효(Nam-Hyo Cho) 한국전산유체공학회 1996 한국전산유체공학회 학술대회논문집 Vol.1996 No.-
Characteristics of heat and fluid flow in an automotive HVAC module was investigated and design parameters like the distribution of air flow rates through the module outlets were studied. Commercial CFD tools called Star-CD and ICEM CFD/CAE were used for a solver and a mesh generator respective]y, An evaporator and a heater core were modelled as porous regions where complete flow equations were not solved but a simple Darcy's law was applied. Different modes of ventilating, defrosting, and temperature mixing were investigated. The prediction of air flow rate distribution among different outlets showed a good agreement with experimental data.
[가솔린엔진부문] 엔진실린더 내부 유동해석을 통한 정상유동 실험결과의 분석
김미로(Mi-Ro Kim),조남효(Nam-Hyo Cho) 한국자동차공학회 1999 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1999 No.11_1
Three-dimensional transient in-cylinder flow in a 4-valve DOHC engine with an intake port blocked by a swirl control valve was analyzed by CFD, The calculated transient variation of swirl ratios were with measured values form steady port flow rig test for three intake ports with different swirl strength. The transit in-cylinder flow was calculated for an engine speed interpreted by the steady port flow rig test. The swirl ratios from the transient CFD calculation and the port flow test were compared very well with the maximun error under 10%
김미로(Mi-Ro Kim),안병재(Byung-Jae Ahn),최영민(Young-Min Choi) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_1
A three-dimensional computational fluid dynamics(3-D CFD) model of the proton exchange membrane fuel cell(PEMFC) is presented to explain the characteristic of its behavior. Many researchers have numerically studied small(~10-50㎠) PEMFC systems. But 3-D numerical model of a commercial-sized PEMFC with reacting area on the order of 200~ ㎠ is still hard to perform effectively. This study applies 3-D CFD model to a commercial-sized(250㎠) PEMFC selected from research models to show its usefulness. Various types of bi-polar plate channel including standard serpentine shaped gas flow channel are proposed and examined. The effects of operating conditions like humidity, including temperature effect, and gas flow rates are also studied. Cathode flooding or membrane dehydrating conditions could be expected through numerical analysis.
권혁수(Hyck-Su Kweon),김미로(Mi-Ro Kim),최희진(Hee-Jin Choi) 대한전자공학회 2015 대한전자공학회 학술대회 Vol.2015 No.6
In this paper, we used the ACU products to simulate PCB regarding the general PCB design. Here we compared the SCE Test result (CISPR 25 3<SUP>nd</SUP> Edition)with Simulation Result. We got rid of the resonance point by getting ReturnPath, Via, Decap. tuning and decreased impedance. After all we confirmed that EMC Test result improved a lot due to the power and ground stabilization.
가솔린 직접분사엔진의 흡기과급에 따른 성층화 연소에 미치는 영향
박형철(Hyung-Cheul Park),김미로(Mi-Ro Kim),조남효(Nam-Hyo Cho) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_1
The effects of pressure charge on combustion stability and emissions have been analyzed in a GDI single cylinder engine. A late injection mode of stratified condition at 1200~2400rpm was tested and the charge pressure ratio was increased up to 1.5: 1. In-cylinder CFD analysis has been also performed to understand in-cylinder flow and fuel spray behavior. With a higher charge pressure ratio and a constant air-fuel ratio of 40:1 IMEP was increased greatly due to the increased amount of intake air mass. ISFC was improved by increasing the engine load, and the limiting stratification zone was extended to a higher engine speed, but a stable ignition timing zone was limited. ISCO was increased slightly with the increase of IMEP while ISHC was decreased. Intercooling was not used in this study but natural air cooling by a long flexible intake hose, therefore an appropriate turbocharging condition should be studied further to understand the effect of charge intake temperature on NOx emissions etc.