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Measurement of grain surface roughness
Fr???…czek J.,Kaczorowski J.,?…??lipek Z.
International Agrophysics , 2000,
Abstract: In the research on the friction of vegetative grain-structure, an essential problem lies in the appropriate determination of the condition of the surface layer of elements in mutual contact. The analysis must define both tensile strength parameters and the surface topography. Most frequently, surface geometry is defined by roughness. Compared to the traditional methods applied for the construction materials, the measurement of roughness in this case is more difficult due to the cellular structure and multifarious shapes of individual skeletons, while low surface hardness (especially at significant humidity) excludes the possibility of applying mechanical methods. For these reasons, an attempt was made to develop a rapid and simple method for the measurement of grain surface roughness relying on the optical procedure. The measurement bench consists of a stereo-microscope with a trinoculare and a camera linked to the computer through an analogue-digital processor. The entire measurement set is equipped with a MultiScan software, where a special picture processing was applied as described below in the paper. A computer analysis of the picture allows to carry out an automatic and precise measurement of the profile roughness in any selected point on the grain surface.
Influence of surface roughness on superhydrophobicity  [PDF]
C. Yang,U. Tartaglino,B. N. J. Persson
Physics , 2006, DOI: 10.1103/PhysRevLett.97.116103
Abstract: Superhydrophobic surfaces, with liquid contact angle theta greater than 150 degree, have important practical applications ranging from self-cleaning window glasses, paints, and fabrics to low-friction surfaces. Many biological surfaces, such as the lotus leaf, have hierarchically structured surface roughness which is optimized for superhydrophobicity through natural selection. Here we present a molecular dynamics study of liquid droplets in contact with self-affine fractal surfaces. Our results indicate that the contact angle for nanodroplets depends strongly on the root-mean-square surface roughness amplitude but is nearly independent of the fractal dimension D_f of the surface.
Stochastic analysis of surface roughness  [PDF]
M. Waechter,F. Riess,H. Kantz,J. Peinke
Physics , 2003, DOI: 10.1209/epl/i2003-00616-4
Abstract: For the characterization of surface height profiles we present a new stochastic approach which is based on the theory of Markov processes. With this analysis we achieve a characterization of the complexity of the surface roughness by means of a Fokker-Planck or Langevin equation, providing the complete stochastic information of multiscale joint probabilities. The method was applied to different road surface profiles which were measured with high resolution. Evidence of Markov properties is shown. Estimations for the parameters of the Fokker-Planck equation are based on pure, parameter free data analysis.
Role of surface roughness in superlubricity  [PDF]
Ugo Tartaglino,Vladimir N. Samoilov,Bo N. J. Persson
Physics , 2006, DOI: 10.1088/0953-8984/18/17/004
Abstract: We study the sliding of elastic solids in adhesive contact with flat and rough interfaces. We consider the dependence of the sliding friction on the elastic modulus of the solids. For elastically hard solids with planar surfaces with incommensurate surface structures we observe extremely low friction (superlubricity), which very abruptly increases as the elastic modulus decreases. We show that even a relatively small surface roughness may completely kill the superlubricity state.
Effect of filler particles on surface roughness of experimental composite series
Marghalani, Hanadi Yousif;
Journal of Applied Oral Science , 2010, DOI: 10.1590/S1678-77572010000100011
Abstract: objective: the purpose of this study was to evaluate the effect of different filler sizes and shapes on the surface roughness of experimental resin-composite series. material and methods: thirty-three disc-shaped specimens of the series (spherical-rzd 102, 105, 106, 107, 114 and irregular-rzd 103, 108, 109, 110, 111, 112) were prepared in a split teflon mold and irradiated with an halogen light-curing unit (450 mw/cm2 for 40 s) at both top and bottom surfaces. the specimens were stored for 3 months in distilled water. the surface roughness values in form of surface finish-vertical parameter (ra), maximum roughness depth (rmax) and horizontal roughness parameter (sm) were recorded using a contact profilometer. the data were analyzed by one-way anova and the means were compared by scheffé post-hoc test (a=0.05). results: the lowest surface roughness (ra) was observed in s-100 (0.079±0.013), while the roughest surface was noted in i-450/700/1000 (0.125±0.011) and i-450/1000 (0.124±0.004). the spherical-shape series showed the smoothest surface finish compared to the irregular-shape ones with higher significant difference (p>0.05). the vertical surface roughness parameter (ra) values increased as the filler size increased yielding a linear relation (r2=0.82). on the contrary, the horizontal parameter (sm) was not significantly affected by the filler size (r2=0.24) as well as the filler shape. conclusions: filler particle's size and shape have a great effect on the surface roughness parameters of these composite series.
Comparative study of the surface roughness of Ormocer-based and conventional composites
Cunha, Leonardo Gon?alves;Alonso, Roberta Caroline Bruschi;Santos, Paulo Henrique dos;Sinhoreti, Mário Alexandre Coelho;
Journal of Applied Oral Science , 2003, DOI: 10.1590/S1678-77572003000400014
Abstract: the aim of this study was to evaluate the surface roughness of two ormocer-based resin composites before and after mechanical toothbrushing. the study compared the brands admira and definite with composites based on conventional monomer systems (bis-gma, bis-ema, uedma e tegdma), z250 and a110. eight samples of each material with 4mm in diameter and 2mm in height were prepared using a metallic mold. after 24 hours they were polished and examined with a profilometer for measurement of the initial surface roughness (ra, mm) before mechanical toothbrushing (30,000 cycles). after toothbrushing, the samples were taken to the profilometer once again to check the final surface roughness. the results were submitted to anova and tukey test (5%). the admira composite presented a higher mean of surface roughness before toothbrushing (0.132mm), with a statistical difference from the composite a110 (0.082mm). definite (0.110mm) and z250 (0.105mm) composites showed no differences between themselves or among the other composites. no statistical differences were observed after toothbrushing between the composites definite (0.178mm), z250 (0.187mm), admira (0.181mm), and a110 (0.193mm). all composites showed a statistically significant increase in the surface roughness after toothbrushing.
General Regularities of Wood Surface Roughness
Acta Silvatica & Lignaria Hungarica , 2008,
Abstract: The surface roughness of wood products is depending on many factors related both towood properties and wood working operational parameters. Probably this is the reason why there areno generally valid correlation determining surface roughness parameters as a function of influencingfactors. In particular, the account of wood structure in the surface roughness interpretation proved tobe difficult.In the last years an important progress was made in recognizing the role of the anatomicalstructure of wood species in the attainable surface roughness. The introduction of a structure numbermade it possible to express and characterize the different wood species numerically.The aim of these studies was the separation of roughness components due to the anatomicalstructure and the woodworking operation. Using a special finishing technique, the roughnesscomponent due to woodworking operations was not significant and could be separated. The samespecimens were also subjected to different woodworking operations using cutting velocities between10 and 50 m/s. The processing of experimental data resulted in a chart showing the minimumroughness component due to different woodworking operations. Special experimental investigationwas conducted to clear the influence of edge dullness on the surface roughness, especially on itsAbbott-parameters. The measurements showed that the Rk-parameter is a good indicator to predictedge dullness.
Does surface roughness amplify wetting?  [PDF]
Alexandr Malijevsky
Physics , 2014, DOI: 10.1063/1.4901128
Abstract: Any solid surface is intrinsically rough on the microscopic scale. In this paper, we study the effect of this roughness on the wetting properties of hydrophilic substrates. Macroscopic arguments, such as those leading to the well-known Wenzel's law, predict that surface roughness should \emph{amplify} the wetting properties of such adsorbents. We use a fundamental measure density functional theory (DFT) to demonstrate the opposite effect from roughness for microscopically corrugated surfaces, i.e., wetting is \emph{hindered}. Based on three independent analyses we show that microscopic surface corrugation increases the wetting temperature or even makes the surface hydrophobic. Since for macroscopically corrugated surfaces the solid texture does indeed amplify wetting there must exist a crossover between two length-scale regimes that are distinguished by opposite response on surface roughening. This demonstrates how deceptive can be affords to extend the thermodynamical laws beyond their macroscopic territory.
Spin Hall effect by surface roughness  [PDF]
Lingjun Zhou,Vahram L. Grigoryan,Sadamichi Maekawa,Xuhui Wang,Jiang Xiao
Physics , 2014, DOI: 10.1103/PhysRevB.91.045407
Abstract: The spin Hall effect and its inverse effect, caused by the spin orbit interaction, provide the interconversion between spin current and charge current. Since the effects make it possible to generate and manipulate spin current electrically, how to realize the large effects is an important issue in both physics and applications. To do so, materials with heavy elements, which have strong spin orbit interaction, have been examined so far. Here, we propose a new mechanism to enhance the spin Hall effect without heavy elements, \ie surface roughness in metallic thin films. We examine Cu and Al thin films with surface roughness and find that they give the spin Hall effect comparable to that in bulk Au. We demonstrate that the spin Hall effect induced by surface roughness has the side jump contribution but not skew scattering.
Effect of surface roughness and adsorbates on superlubricity  [PDF]
V. N. Samoilov,C. Yang,U. Tartaglino,B. N. J. Persson
Physics , 2006,
Abstract: We study the sliding of elastic solids in adhesive contact with flat and rough interfaces. We consider the dependence of the sliding friction on the elastic modulus of the solids. For elastically hard solids with planar surfaces with incommensurate surface structures we observe extremely low friction (superlubricity), which very abruptly increases as the elastic modulus decreases. We show that even a relatively small surface roughness or a low concentration of adsorbates may completely kill the superlubricity state.
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