• Tribology and Lubricants
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• 제25권5호
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• pp.342-347
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• 2009

This paper presents EHL analysis for rough surfaces with directional roughness. Three different types of surfaces with pure longitudinal roughness, pure transversal roughness and isotropic roughness are generated. For the surfaces with longitudinal and transversal roughness, two cases are analyzed; one is a case of asperity peak on a spherical contact center, the other one is of valley on a spherical contact center. As a results, the surface with pure transversal roughness gives higher pressure and smaller minimum film thickness than the surface with pure longitudinal roughness, and the surface with isotropic roughness has similar EHL behavior with the surface with pure transversal roughness.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.323-328
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• 2004

Finish machining of a curved surface is often carried out by an NC system with curved interpolation in a high speed machining strategies. This study aims to develop the NURBS interpolator for the PC-NC based machine tools. In the case of a finish cut using a ball-end mill in high speed machining, low machinability at the bottom of a tool produces a harmful effect on surface roughness. The developed interpolator considers the relation between inclined angle, surface roughness, and feed rate, and adjusts real-time feed rate in order to generate surfaces which have isotropic surface roughness. The proposed interpolator is fully implemented and an experimental results are shown.

• 반도체디스플레이기술학회지
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• 제10권4호
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• pp.31-35
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• 2011

For high efficiency of Si-cells, Si wafers were textured by the KOH and NaOH etching solution to decreas the reflectance at surfaces of the cells. The textured surfaces were shown various types such as isotropic and anisotropic depending on the etching solution. The reflectance at sample of an anisotropic form with pyramid type was lower than that of isotropic form. The surface with isotropic form of general tiny circles on the surface increased the efficiency, however, the reflectance of it was increased. The efficiency was increased on surface with low roughness.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.859-865
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• 2001

This paper reports on the theoretical analysis of mixed lubrication for the piston ring. The analytical model is presented by using the average flow and asperity contact model. The cyclic variations of the nominal minimum oil film thickness are obtained by numerical iterative method. The total friction is calculated by using the hydrodynamic and asperity contact theory. The effect of the roughness height, pattern, and engine speed on the nominal minimum film thickness, friction force, ad frictional power losses are investigated. As the roughness height increases, the nominal oil film thickness and total friction force increase. Also, the effect of the surface roughness on the boundary friction is dominant at low engine speed and high asperity height. The longitudinal roughness pattern shows lower mean oil film pressure and thinner oil film thickness compared to the case of the isotropic and transverse roughness patterns.

• Geomechanics and Engineering
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• 제11권4호
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• pp.515-530
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• 2016

In this paper, five different quantitative parameters were proposed for the characterization of the primary roughness which is the component of surface morphology that prevails during large strike-slip faults of more than 50 m. These parameters are mostly the anisotropic properties of rock surface morphology at various scales: (i) coefficient ($k_a$) and degree (${\delta}_a$) of apparent structural anisotropy of surface; (ii) coefficient ($k_r$) and degree (${\delta}_r$) of real structural anisotropy of surface; (iii) surface anisotropy function P(${\varphi}$); and (iv) degree of surface waviness ($W_s$). The coefficient and degree of apparent structural anisotropy allow qualifying the anisotropy/isotropy of a discontinuity according to a classification into four classes: anisotropic, moderately anisotropic/isotropic and isotropic. The coefficient and degree of real structural anisotropy of surface captures directly the actual surface anisotropy using geostatistical method. The anisotropy function predicts directional geometric properties of a surface of discontinuity from measurements in two orthogonal directions. These predicted data may subsequently be used to highlight the anisotropy/isotropy of the surface (radar plot). The degree of surface waviness allows qualifying the undulation of anisotropic surfaces. The proposed quantitative parameters allows their application at both lab and field scales.

• 대한금속재료학회지
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• 제49권7호
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• pp.557-564
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• 2011

This paper reports the relationship between the surface roughness and thermal emissivity of graphite (IG-11) in nuclear reactors. The roughness was controlled by changing the oxidization time, resulting in 0, 6, and 11% losses of mass. The levels of roughness were 0.40, 0.72 and 1.09${\mu}m$ for the weight loss of 0, 6 and 11%, respectively. The binders and graphite fillers were found to have sequentially oxidized with a higher thermal emission for the highly oxidized sample, but with a lower emission when measured at a higher temperature. Our study suggests a method for predicting the thermal emission rate of graphite in a nuclear reactor based on roughness measurement.

• 한국세라믹학회지
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• 제43권10호
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• pp.613-618
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• 2006

Graphite is suitable materials as a moderator, reflector, and supporter of a nuclear reactor because of high tolerance to the high temperature and neutron irradiations. Because graphite is so weak to the oxidation, its oxidation study is essentially demanded for the operation and design of the nuclear reactor. This work focuses on the effect of the surface oxidation of graphite according to the surface treatment. With thermogravimeter (TG), oxidation characteristics of the isotropic graphite are measured at the three temperature areas, and oxidation ratio and amounts are estimated as changing the surface roughness. Furthermore, the polished graphite surface produced fom the surface treatment is investigated with the Raman spectroscopic study. Oxidation behaviors of the surface are also evaluated as elimination the polished layer by washing with strong sonication.

• 대한금속재료학회지
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• 제50권4호
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• pp.338-343
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• 2012

The early osseointegration of titanium (Ti) dental implants is related to the initial cell morphology. The morphology of the cells (mesenchymal stem cells, MSC) was observed on three different Ti disc surfaces, which were mechanically treated by polishing, blasting, and scratching. A non-directional surface (isotropic texture) was obtained by the blasting of HA grits on cp-Ti discs, and a unidirectional surface (anisotropic texture) was obtained by the scratching of SiC papers. The cell attachment and arrangement in the initial periods were quite similar, but those in the later periods were significantly affected by the texture of the cp-Ti discs. After 1 week, the blasted Ti discs showed non-directional arrangement or spreading of the cells, whereas the scratched cp-Ti discs showed unidirectional properties parallel to the direction of the scratched grooves on the surface. The surface roughness of the cp-Ti discs significantly affects cell proliferation. Cell proliferation on the blasted and scratched surfaces was about 60% and 40% higher compared to the control result (polishing group) after 1 week (P<0.05). Cell proliferation on the blasted and scratched surfaces after 1 week was slightly enhanced with increasing surface roughness. It is believed that the direction of cell attachment and arrangement is closely related to the surface texture of the substrate surfaces, but cell proliferation after a relatively long period of time is directly enhanced by the surface roughness, not by the surface texture.

• 한국표면공학회지
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• 제33권4호
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• pp.273-280
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• 2000

Silver was deposited on glass by electroless plating and electroplating. Surface properties were investigated using the AFM. Crystal structure of deposit layers was confirmed by TEM and XRD. Electroplating is performed by DC plating and pulse plating, respectively. This study resulted in followings, first, deposit of electroless plating showed fine grain and was similar to the amorphous structure. Second, electrodeposit on the electroless layer was revealed following results ; (1) more uniform layer and finer grains were obtained with increasing frequency (2) more isotropic structure was obtained with increasing frequency (3) finer grains at 25% duty cycle was obtained (4) grain size and roughness of the silver deposit was decreased with increasing frequency.

• The Journal of the Acoustical Society of Korea
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• 제25권2E호
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• pp.60-68
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• 2006

High-frequency bistatic scattering measurements from a corrugated surface were made in an acoustic water tank. First the azimuthal scattering pattern was measured from an artificially corrugated surface which has varying impedance. The corrugated surface was installed both transverse to the direction of incident wave and longitudinal to the direction of incident wave. The angle between the corrugated surface and the direction of the incident wave was about $45^{\circ}$. Second, the scattering strengths were measured from the flat sediment and the corrugated sediment. A critical angle of about $37^{\circ}$ was calculated in the acoustic water tank. The measurements were made at three fixed grazing angles: $33^{\circ}$ (lower than critical angle), $37^{\circ}$ (critical angle), and $41^{\circ}$ (higher than critical angle). The scattering angle and the grazing angle are equal in each measurement. Frequencies were from 50 kHz to 100 kHz with an increment of 1 kHz. The corrugated sediment was made transverse to the direction of the incident wave. The first measurement indicates that the scattering patterns depend on the relations between the corrugated surface and the direction of the incident wave. In the second measurement, the data measured from the flat sediment were compared to the APL-UW model and to the NRL model. The NRL model's output shows more favorable comparisons than the APL-UW model. In case of the corrugated sediment, the model and the measured data are different because the models used an isotropic wave spectrum of sediment roughness in the scattering calculations. The isotropic wave spectrum consists of $w_2$ and ${\gamma}_2$. These constants derived from sediment names or bulk size. The model which used the constants didn't consider the effect of a corrugated surface. In order to consider a corrugated surface, the constants were varied in the APL-UW model.