• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.7
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• pp.308-314
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• 2005

The 2 GHz film bulk acoustic wave resonator(FBAR), one of the most necessary device of the next generation mobile communication system, consisted of solidly mounted resonator(SMR) structure using Brags reflector, was researched in this paper The FBAR applied SiO$_{2}$ and W had large difference of the acoustic impedance to reflector Al to electrode and ZnO to piezoelectric layer. Specially, the FBAR applied the two-step deposition method to improve the c-axis orientation and increase reproducibility of the fabrication device had good performance. The electrical properties of plasma such as impedance, resistance, reactance, $V_{pp},\;I{pp}$, VSWR and phase difference of voltage and current, was analyzed and measured by RF sensor with the variable experiment process factors such as gas ratio, RF power and base vacuum level about concerning the thickness, c-axis orientation, adhesion and roughness. The FBAR device about the optimum condition resulted reflection loss(S$_{11}$) of -17 dB, resonance frequency of 1.93 GHz, electric-mechanical coefficient(k$_{eff}$) of 2.38 $\%$ and Qualify factor of 580. It was seen better qualify than the common dielectric filter at present and expected on business to the filter device of 2 GHz bandwidth with the MMIC technology.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.712-721
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• 2023

While hydrogen is widely used, it has a low minimum ignition energy, raising safety concerns when using it. This research studied which parameters are the key variables in the hydrogen release and diffusion. These parameters were divided into six process variables in the initial release and two environmental variables in the dispersion. One hundred and twenty cases were selected through design of experiment, and the end-point in each case were analyzed using PHAST. Afterwards, an end-point prediction model was developed using RSM and ANOVA, and the impact of each variable on the endpoint was analyzed. As a result, the influence of eight variables was graded. The nozzle diameter had the greatest influence on the end-point, while the pipe roughness coefficient had no effect on the end-point. It is expected that these results will be used as basic data to improve safety across all fields of hydrogen handling facilities.

• Journal of Korea Water Resources Association
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• v.56 no.spc1
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• pp.1007-1014
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• 2023

Two-dimensional flow analysis, a fundamental component of hydrodynamics, plays a pivotal role in numerically simulating fluid behavior in rivers and waterways. This modeling approach heavily relies on parameters such as eddy viscosity and roughness coefficient to accurately represent flow characteristics. Therefore, combination of appropriate parameters is very important to accurately simulate flow characteristics. In this study, an automation algorithm was developed and applied to find the optimal combination of parameters. Previously, when applying a two-dimensional flow analysis model, former researchers usually depend on the empirical approach, which causes many difficulties in finding optimal variable values. Using the experimental data, we tracked errors according to the combination of various parameters and applied the algorithm that can determine the optimal combination of parameters with the Python language. The automation algorithm can easily determine the most accurate combination by comparing the flow velocity error values among the two-dimensional flow analysis results among the combinations of 121 (11×11) parameters. In the perspective of utilizing automation algorithm, there is an expected high utility in promptly and straightforwardly determining the optimal combination of parameters with the smallest error.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.193-197
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• 2002

The tribological properties and van der Waals attractive forces and the thermal stability of films are very important characteristics of highly hydrophobic fluorocarbon (FC) films for the long-term reliability of nano system. The effect of thermal annealing on films and van der Waals attractive forces and friction coefficient of films have been investigate d in this study. It was coated Al wafer which was treated O2 and Ar that ocatfluorocyclobutane ($C_4_{8}$) and Ar were supplied to the CVD chamber in the ratio of 2:3 for deposition of FC Films. Static contact angle and dynamic contact angle were used to characterize FC films. Thickness of films was measured by variable angle spectroscopy ellipsometer (VASE). Nanotribological data was got by atomic force microscopy (AFM) to measure roughness, lateral force microscopy (LFM) to measure friction force, and force vs. distance (FD) curve to evaluate adhesion force. FC films were cured in N2 and vacuum. The film showed the slight changes in its properties after 3 hr annealing. FTIR ATR studies showed the decrease of C-F peak intensity in the spectra as the annealing time increased. A significant decrease of film thickness has been observed. The friction force of Al surface was at least thirty times higher than ones with FC films. The adhesive force of bare Al was greater than 100 nN. After deposit FC films adhesive force was decreased to 40 nN. The adhesive force of films was decreased down to 10 nN after 24 hr annealing. During 24 hr annealing in $N_2$and vacuum at $100^{\circ}C$ film properties were not changed so much.