• Proceedings of the IEEK Conference
• /
• 2001.06b
• /
• pp.29-32
• /
• 2001

In this paper, the thermal oxidation behaviors and the electrical characteristics of the thermal oxide grown on SiC are discussed. For these studies the oxide layers with various thickness were on SiC in wet $O_2$ or dry $O_2$ at l15$0^{\circ}C$ and the MOS capacitors using the 350$\AA$ gate oxide grown in wet $O_2$ were fabricated and electrically characterized. It was found from the experimental results that the oxidation rate of SiC with the Si-face and with the carbon-face were about 10% and 50% of oxidation rate of Si. The C-V measurement results of the SiC oxide showed abnormal hysterisis properties which had ever been not observed for the Si oxide. And the hysterisis behavior was seen more significant when initial bias voltage was more negative or more positive. The hysterisis property of the SiC oxide was believed to be due the substantial amount of the deep level traps to exist at the interface between the oxide and the SiC substrate. The leakage of the SiC oxide was found to be one order larger than the Si oxide, but the breakdown strength was almost equal to that of the Si oxide.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.9 s.114
• /
• pp.919-925
• /
• 2006

An accurate mathematical model for complex stiffness of the pneumatic spring would be necessary for an efficient design of a pneumatic spring used in vibration isolation tables for precision instruments such as optical devices or nano-scale equipments. A diaphragm, often employed for prevention of air leakage, plays a significant role of complex stiffness element as well as the pressurized air itself Therefore, effects of the diaphragm need to be included in the dynamic model for a more faithful description of dynamic behavior of pneumatic spring. But the complex stiffness of diaphragm is difficult to predict In an analytical way, since it is a rubber membrane of complicated shape in itself. Moreover, the diaphragm should be expandable in response to pressurization inside a chamber, which makes direct measurement of complex stiffness of diaphragm extremely difficult. In our earlier research, the complex stiffness of diaphragm was indirectly measured, which was just to eliminate the theoretical stiffness of pressurized air from the measured complex stiffness of the pneumatic spring. In order to reflect complex stiffness of inflated diaphragm on the total stiffness at the initial design or design improvement stage, however. it is required to be able to predict beforehand. In this paper, how to predict the complex stiffness of inflated rubber diaphragm by commercial FE codes (e.g. ABAQUS) will be discussed and the results will be compared with the indirectly measured values.

• Journal of the Korean Vacuum Society
• /
• v.5 no.1
• /
• pp.62-66
• /
• 1996

$(Ba_{1-x}Sr_xTiO_3$ (BST) thin films have been grown on Pt-coated MgO by metal -organic chemical vapor deposition. X-ray diffraction results showed that BST films were grown on a Pt/MgO substrate with (100) preferred orientation perpendicular to the surface. The lineawr relationship of P-E curve obtained form hysteresis loop measurement indicated that the BST films had a Curie transitions below room temperature . Films deposited at $900^{\circ}C$ exhibited a smooth and dense microstructure, a dielectric constant of 202, and a dissipation facotr of 0.02 at 100kHz. The leakage current density of the BST films is about $2\times10^{-10} \;A/\textrm{cm}^2$$ at an applied electric field of 0.2 MV/cm. The electrical behavior on the current-voltage characteristics is well explained by the bulk-limited Pool-Frenkel emission.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.8
• /
• pp.78-85
• /
• 1995

We fabricated the Pb$_{1-0.28{\alpha}}La_{0.28}TiO_{3}$ (PLT(28)) thin film successfully by using the sol-gel method and characterized it to evaluate its potential for being utilized as the capacitor dielectrics of ULSI DRAMs. In our sol-gel process, the acetates were used as the starting materials. Through the TGA-DTA analysis, we established the excellent fabrication conditions of the sol-gel method for the PLT(28) thin film. We obtained the dense and crack-free PLT(28) thin film of 100% perovskite phase by drying at 350$^{\circ}C$ after each coating and final annealing at 650$^{\circ}C$. Its electrical properties were measured from the planar capacitors fabricated on the Pt/Ti/SiO$_{2}$/Si substrate. By the P-E hysteresis measurement, its paraelectric phase was identified and its dielectric constant and leakage current density were measured as 936 and 1.1${\mu}A/cm^{2}$, respectively. Those electrical values indicate that the PLT(28) thin film is the most successful candidate for the capacitor dielectrics of ULSI DRAMs at the present.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2009.05a
• /
• pp.255-256
• /
• 2009

The anti suck back centering (ASBC) for preventing backflow of oil for oil rotary pump was designed in the power failure. To evaluate the evacuation characteristics, we manufactured the mini vacuum system, personal computer, AD converter (National instrument, NI-6009), and automatic controller with touch panel for a basis. In this study, we measured the evacuation characteristics of ABSC and analyzed the flow field of viscous flow regime using a commercial software, CFD-ACE+. Also, the leakage of the advaced ASBC for leveling was measured.

• The KSFM Journal of Fluid Machinery
• /
• v.15 no.6
• /
• pp.5-10
• /
• 2012

The effect of pressure-side opening length on three-dimensional flow fields and aerodynamic losses downstream of a cavity squealer tip has been investigated in a turbine rotor cascade for the squealer rim height-to-chord ratio and tip gap height-tochord ratio of $h_{st}/c$ = 5.05% and h/c = 2.0% respectively. The opening length-to-camber ratio is changed to be $OL/c_c$ = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.7 The results show that longer OL leads not only to weaker secondary flow but also to lower aerodynamic loss in the tip leakage vortex region, while it significantly widens the area with high aerodynamic loss in the passage vortex region. The aerodynamic loss coefficient mass-averaged all over the measurement plane is kept almost constant for $0.0{\leq}OL/c_c{\leq}0.3$, whereas it increases rapidly for $OL/c_c$ > 0.3 in proportion to $OL/c_c$. There is little deterioration in flow turning with increasing $OL/c_c$.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.2
• /
• pp.48-53
• /
• 2014

A low-noise regenerative blower is developed for fuel cell application by combining the FANDAS-Regen code and design optimization algorithm under several performance constraints for flow capacity, static pressure, efficiency and power consumption. The optimized blower design model is manufactured with some impeller modification based on low noise design concept and tested by using aerodynamic performance chamber facility and narrow-band noise measurement apparatus. The measured results of the optimized blower satisfy the performance requirements and are also compared favorably with the FANDAS-Regen prediction results within a few percent relative error. Furthermore, the present study shows the remarkable noise reduction by 26 dBA can be achieved through design optimization and low noise design concept.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.844-849
• /
• 2006

Accurate modeling of complex dynamic stiffness of the pneumatic springs is crucial for an efficient design of vibration isolation tables for precision instruments such as optical devices or nano-technology equipments. Besides pressurized air itself, diaphragm made of rubber materials, essentially employed for prevention of air leakage, plays a significant contribution to the total complex stiffness. Therefore, effects of the diaphragm should be taken care of precisely. The complex stiffness of an inflated diaphragm is difficult to predict or measure, since it is always working together with the pressurized air. In our earlier research, the complex stiffness of a diaphragm was indirectly estimated simply by subtracting stiffness of the pressurized air from measurement of the total complex stiffness for a single chamber pneumatic spring. In order to reflect dynamic stiffness of inflated diaphragm on the total stiffness at the initial design or design improvement stage, however, it is required to be able to predict beforehand. In this presentation, how to predict the complex stiffness of inflated rubber diaphragm by commercial FE codes(e.g. ABAQUS) will be discussed and the results will be compared with the indirectly measured values.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.4
• /
• pp.83-93
• /
• 2007

This paper represents the development of 3-axises loadcell for measuring the side-force of suspension module of MPV(Multi Purposed Vehicle). The side force causes the failure of damper, such as leakage. The loadcell was developed using strain gauges, and the Wheastone bridge circuit to compensate for the cross-talk between the each axises and the measurement error by temperature. Structure analysis of loadcell was accomplished with FEM(Finite Element Method) to optimize the location of strain gages. The design optimization for important factors that have an effect on performance of loadcell was accomplished by using DOE(Design of Experiment). Loadcell was produced and successfully tested, showing good sensitivity and low cross-talk. The cross-talk of the developed loadcell is bellow 5%. The load history was measured at proving ground. The maximum side-force, the longitudinal force, and vertical force of MPV are 4.2 kN, 8.0 kN, and 17.0 kN, respectively, at Belgian road.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.55 no.4
• /
• pp.196-201
• /
• 2006

A electrical fault that may generate an electrical disaster is defined as any abnormal condition caused by reduction in the insulation strength. To find out the abnormal condition, periodical inspections have being performed every 3 years. Recently, the number of empty houses during normal working hours is rising by dramatic increase in the number of nuclear families and double income families. To define the potential risk of the electric installation, measurement of zero phase current has been being considered. But the measured value could not be adapted to an absolute reference to the installation because the measured zero phase current value also contained capacitive leakage current. Therefore, in this paper, the correlation between the condition of the electrical installation and the zero phase current was analyzed. The result focuses on to detect them in a cost efficient way.