• Journal of the Korean Society of Visualization
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• v.17 no.3
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• pp.12-18
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• 2019

Direct numerical simulation of a fully developed turbulent plane Couette-Poiseuille flow with a two-dimensional (2-D) rod-roughened wall is performed to investigate the impacts of the surface roughness. It is shown that the logarithmic region in the mean velocity profile over the rough wall Couette-Poiseuille flow is significantly shortened by the surface roughness compared to that over a turbulent Couette-Poiseuille flow with smooth wall. The Reynolds shear stress over the rough wall Couette-Poiseuille flow is decreased compared to that for a smooth case in the outer layer. These results are attributed to weakened turbulence activity or roll-cell mode over the rough wall Couette-Poiseuille flow near the channel centerline due to suppressed development of u'-structure on the top wall, as documented through spanwise energy spectra of the streamwise velocity fluctuations. Inspection of congregation motion near the bottom wall and time evolution of u'-structure reveal weakened co-supporting cycle for the rough wall case.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1333-1334
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• 2007

Al thin film was the most popular electrode in semiconductor and flat panel display world, because of its electrical conductivity, selectivity and easy to apply to thin film. However, Al thin films were not good to use on the bottom electrode about the crystalline growth of inorganic compound materials such as ZnO, AlN and GaN, because of its surface roughness and melting points. In this paper, we investigated Ar plasma surface treatment of Al thin film to enhance the surface roughness and electrical conductivity using the reactive ion etching system. Several process conditions such as RF power, working pressure and process time were controlled. In results, the surface roughness showed $15.53\;{\AA}$ when RF power was 100 W, working pressure was 50 mTorr and process time was 10 min. Also, we tried to deposit ZnO thin films on the each Al thin films, the upper conditions showed the best crystalline characteristics by x-ray diffraction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.107-116
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• 2014

A volume density of roughness correction blocks in a channel is defined and the corresponding roughness coefficient(n) is estimated by analyzing the diverse hydraulic characteristics of VR, the product of the average velocity and the hydraulic radius, block Reynolds number ($Re^*$), drag coefficient ($\acute{C}_D$), and the roughness coefficient ($n_b$) of bottom shear. The increase of VR and block Reynolds number causes the exponential decrease of roughness coefficient converged to a constant value as expected. The drag coefficient also exponentially decreases as block Reynolds number increases as well. The drag force is governed by the block shape defined by volume density in high block Reynolds number of turbulent flow region. For more accurate estimation of roughness coefficient the use of the correlation equation of it is required by block Reynolds number and volume density. The regression equations for n-VR, $\acute{C}_D-Re^*$, and $n_b-\acute{C}_D$ are presented. The regression equations of roughness coefficient are also presented by block Reynolds number and volume density. The developed equation of roughness coefficient by block Reynolds number and volume density has practical use by confirming the coincidence between the experimental results and the results of HEC-RAS using the developed equation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.1
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• pp.23-33
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• 2020

In this study, the effect of surface roughness distribution and its influence on the inflight icing code was investigated. Previous numerical studies focused on the magnitude of surface roughness, and the effects were only addressed in terms of changes in thermal boundary layers with fully turbulent assumption. In addition, the empirical formula was used to take account the turbulent transition due to surface roughness, which was regarded as reducing the accuracy of ice shape prediction. Therefore, in this study, the turbulent transition model based on the two-equation turbulence model was applied to consider the effects of surface roughness. In order to consider the effect of surface roughness, the transport equation for roughness amplification parameter was applied, and the surface roughness distribution model was implemented to consider the physical properties. For validation, the surface roughness, convective heat transfer coefficient, and ice shape were compared with experimental results and other numerical methodology. As a result, it was confirmed that the excessive prediction of the heat transfer coefficient at the leading edge and the ice horn shape at the bottom of the airfoil were improved accordingly.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.2001-2003
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• 1996

In this study, Allied Signal 211 SOG was used as a sacrificial material. After researching its etching properties, we adapted it to bottom-drive micrometers. SOG was superior etch rate and roughness to them of PSG or CVD-oxide and possible to low-temperature processing. Etching properties of SOG depended on the temperature and duration of its bake and cure. SOG used in the fabrication of bottom-drive micrometers showed us usefulness as a sacrificial layer and haying a least influence on machines on it in comparison with conventional sacrificial materials.

• Transactions on Electrical and Electronic Materials
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• v.6 no.1
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• pp.14-17
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• 2005

The SrRuO_{3}$ films for application of the bottom electrode were deposited on p-Si (001) substrates by metalorganic chemical vapor deposition (MOCVD). The films are characterized by various deposition parameters. The optimum deposition condition for SRO films is the deposition temperature of $500{\circ}C$, Sr/Ru input mol ratio of 1.0, and a flow rate of precursors of 15 ml/h. The films deposited by an optimum condition exhibited a single phase of SrRuO_{3}$, an rms roughness of 8 nm, and a resistivity of approximately $900{\mu}{\Omega}{\cdot}cm$. The high resistivity of the films for application of a bottom electrode should be improved through a characterization of an interface.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1996.10a
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• pp.14-14
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• 1996

In order to understand the tidal hydrodynamics of the Yellow Sea and Parts of the East China Sea, we have developed a three-dimensional, fine resolution, nonlinear, harmonic finite element model. Major four tidal constituents, M$_2$, S$_2$, K$_1$ and O$_1$ are used as forcing along the open boundary. Due to the shallowness of the region, tidal results are strongly affected by the bottom roughness coefficients, especially for the quadratic form. (omitted)

• Journal of the Society of Cosmetic Scientists of Korea
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• v.45 no.4
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• pp.373-380
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• 2019

There are many differences in tran-epidermal water loss (TEWL), skin water contents, and skin elasticity, etc between face and forearm skin. In particular, our previous studies showed that elasticity of face skin was significantly differed from forearm depending on full hydration. So, we have studied the surface properties of corneocyte using atomic force microscopy (AFM), assuming that the differences between face and forearm skin would be associated with the surface properties of corneocyte. The surface roughness of corneocyte and villus-like projections (VPs) were measured. Furthermore, qualitative comparison among the surface of face, forearm, and lip corneocyte was performed. Corneocytes were collected by tape-stripping on both face and forearm of 8 volunteers, and the bottom surface of corneocytes were measured at 40 ㎛ × 40 ㎛ using AFM. Results showed that the lower surface roughness of face corneocytes was 388.34 ± 86.189 nm, and that of forearm corneocytes was 662.27 ± 224.257 nm, which confirmed that the lower surface of forearm corneocytes was more rough than that of face corneocytes (p < 0.001). Compared with the amount of VPs, lip corneocytes were the highest followed by face corneocytes, and forearm corneocytes were the lowest. From these results, it is conclued that the surface properties of corneocytes are somewhat involved in the property differences between the face and the forearm skin and VPs can be a useful parameter for the study of corneocyte by site. In addition, AFM is a very useful device for the comparative study of nano-structural differences on the surface of corneocytes. More studies can lead to develop a new evaluation method of corneocytes.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.93-99
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• 2011

We investigated how the surface roughness of electrode affects the charge injection at the pentacene/Au interface. After depositing Au film on the Si substrate by sputtering, we annealed the sample to control the Au surface roughness. Pentacene and Au top electrode were subsequently deposited to complete the sample. The nucleation density of pentacene was slightly higher on the rougher Au electrode, but surface morphologies of thick pentacene films were similar on both the as-prepared and the roughened Au electrodes. The current-voltage curves obtained from the Au/pentacene/Au structure measured as a function of temperature indicated that the interface barrier was higher for the rougher Au bottom-electrode. We propose that the higher barrier was caused by the lower work function of rougher electrode surface and the higher trap density at the interface.

• Journal of Dental Rehabilitation and Applied Science
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• v.16 no.3
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• pp.197-210
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• 2000

Surface roughness is one of implant surface topography and it's found that surface roughness characterizations, such as surface energy, oxide layer thickness and its chemical composition, are closely correlated if the roughness is changed. Several studies showed the importance of analyzing surface structure so the surface structure of thread implant was analyzed to measure the implant quality exactly. In this study, surface roughness of 4 implants - MK $II^{(R)}$(Nobel Biocare), $RBM^{(R)}$(Life-Core, USA), $Osseotite^{(R)}$(3i, USA), $TPS^{(R)}$(Life-Core, USA) - were measured using $Accura^{(R)}$ and 40 implants were installed into 4 sets of ten bovine ribs based on the parameters from the measurements. From this test, the following conclusions for the initial stability were drawn by measuring and comparing RFA, Periotest Value (PTV), Removal Torgue Value (RTV). 1. $R_a$ value in surface roughness measurement was increasing by the order of $MKII^{(R)}$, $Osseotite^{(R)}$, $RBM^{(R)}$, $TPS^{(R)}$ and $R_q$ value was the same order. 2. $R_q$ value in each section was observed to increase by the order of $MKII^{(R)}$, $Osseotite^{(R)}$, $RBM^{(R)}$, $TPS^{(R)}$ in top and $MKII^{(R)}$, $RBM^{(R)}$, $Osseotite^{(R)}$, $TPS^{(R)}$ in mid-section but the value of $MKII^{(R)}$ bottom was the lowest, followed by $Osseotite^{(R)}$, $RBM^{(R)}$ and $TPS^{(R)}$. 3. RFA increased by the order of $RBM^{(R)}$(7042Hz), $MKII^{(R)}$(7047Hz), $Osseotite^{(R)}$(7076Hz), $TPS^{(R)}$(7168Hz) and there was no significance between each group. 4. PTV was increasing by the order of $MKII^{(R)}$(-1.62), $TPS^{(R)}$(-1.92), $Osseotite^{(R)}$ & $RBM^{(R)}$(-2.08) and there was no significance, either. 5. Removal torque in RTV measurement showed the increasing order of $MKII^{(R)}(5.31kgf{\cdot}cm)$, $Oeeotite^{(R)}(5.71kgf{\cdot}cm)$, $TPS^{(R)}(5.92kgf{\cdot}cm)$ and $RBM^{(R)}(7.24kgf{\cdot}cm)$ and there was no significance among groups. Above observations explains that surface roughness does not make any impact on the initial stability of implants installation.