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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.
Theory of adhesion: role of surface roughness  [PDF]
Bo N. J. Persson,Michele Scaraggi
Physics , 2014, DOI: 10.1063/1.4895789
Abstract: We discuss how surface roughness influence the adhesion between elastic solids. We introduce a Tabor number which depends on the length scale or magnification, and which gives information about the nature of the adhesion at different length scales. We consider two limiting cases relevant for (a) elastically hard solids with weak adhesive interaction (DMT-limit) and (b) elastically soft solids or strong adhesive interaction (JKR-limit). For the former cases we study the nature of the adhesion using different adhesive force laws ($F\sim u^{-n}$, $n=1.5-4$, where $u$ is the wall-wall separation). In general, adhesion may switch from DMT-like at short length scales to JKR-like at large (macroscopic) length scale. We compare the theory predictions to the results of exact numerical simulations and find good agreement between theory and the simulation results.
Role of Surface Roughness during Natural Convection  [PDF]
M. Yousaf, S. Usman
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33C021

A computational study was performed in a two-dimensional square cavity in the presence of roughness using an algorithm based on mesoscopic method known as Lattice Boltzmann Method (LBM). A single relaxation time Bhatnagar-Gross-Krook (BGK) model of LBM was used to perform numerical study. Sinusoidal roughness elements of dimensionless amplitude of 0.1 were located on both the hot and cold walls of a square cavity. A Newtonian fluid of the Prandtl number (Pr) 1.0 was considered. The range of the Rayleigh (Ra) number explored was from 103 to 106 in a laminar region. Thermal and hydrodynamic behaviors of fluid were studied using sinusoidal roughness elements. Validation of computational algorithm was performed against previous benchmark studies, and a good agreement was found. Average Nu (Nusselt number) has been calculated to observe the effects of the surface roughness on the heat transfer. Results showed that sinusoidal roughness elements considerably affect the thermal and hydrodynamic behaviors of fluid in a square cavity. The maximum reduction in the average heat transfer in the presence of roughness was calculated to be 23.33%.

Fluid contact angle on solid surfaces: role of multiscale surface roughness  [PDF]
Francesco Bottiglione,Giuseppe Carbone,Bo N. J. Persson
Physics , 2015, DOI: 10.1063/1.4932104
Abstract: We present a simple analytical model and an exact numerical study which explain the role of roughness on different length scales for the fluid contact angle on rough solid surfaces. We show that there is no simple relation between the distribution of surface slopes and the fluid contact angle. In particular, surfaces with the same distribution of slopes may exhibit very different contact angles depending on the range of length-scales over which the surfaces have roughness.
Role of surface roughness in hard x-ray emission from femtosecond laser produced copper plasmas  [PDF]
P. P. Rajeev,S. Banerjee,A. S. Sandhu,L. C. Tribedi,G. R. Kumar
Physics , 2001, DOI: 10.1103/PhysRevA.65.052903
Abstract: The hard x-ray emission in the energy range of 30-300 keV from copper plasmas produced by 100 fs, 806 nm laser pulses at intensities in the range of 10$^{15}-10^{16}$ W cm$^{-2}$ is investigated. We demonstrate that surface roughness of the targets overrides the role of polarization state in the coupling of light to the plasma. We further show that surface roughness has a significant role in enhancing the x-ray emission in the above mentioned energy range.
Electron Transport in Silicon Nanowires: The Role of Acoustic Phonon Confinement and Surface Roughness Scattering  [PDF]
E. B. Ramayya,D. Vasileska,S. M. Goodnick,I. Knezevic
Physics , 2008, DOI: 10.1063/1.2977758
Abstract: We investigate the effects of electron and acoustic-phonon confinement on the low-field electron mobility of thin square silicon nanowires (SiNWs) that are surrounded by SiO$_2$ and gated. We employ a self-consistent Poisson-Schr\"{o}dinger-Monte Carlo solver that accounts for scattering due to acoustic phonons (confined and bulk), intervalley phonons, and the Si/SiO$_2$ surface roughness. The wires considered have cross sections between 3 $\times$ 3 nm$^2$ and 8 $\times$ 8 nm$^2$. For larger wires, as expected, the dependence of the mobility on the transverse field from the gate is pronounced. At low transverse fields, where phonon scattering dominates, scattering from confined acoustic phonons results in about a 10% decrease of the mobility with respect to the bulk phonon approximation. As the wire cross-section decreases, the electron mobility drops because the detrimental increase in both electron--acoustic phonon and electron--surface roughness scattering rates overshadows the beneficial volume inversion and subband modulation. For wires thinner than 5 $\times$ 5 nm$^2$, surface roughness scattering dominates regardless of the transverse field applied and leads to a monotonic decrease of the electron mobility with decreasing SiNWs cross section.
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.
Surface roughness influence on the quality factor of high frequency nanoresonators  [PDF]
G. Palasantzas
Physics , 2008, DOI: 10.1063/1.2874790
Abstract: Surface roughness influences significantly the quality factor of high frequency nanoresonators for large frequency - relaxation times within the non-Newtonian regime, where a purely elastic dynamics develops. It is shown that the influence of sort wavelength roughness, which is expressed by the roughness exponent H for the case of self-affine roughness, plays significant role in comparison with the effect of the long wavelength roughness parameters such as the rms roughness amplitude and the lateral roughness correlation length. Therefore, the surface morphology can play important role in designing high-frequency resonators operating within the non-Newtonian regime.
Atul Kumar,,Dr. Sudhir Kumar,,Dr. Rohit Garg
International Journal of Engineering Science and Technology , 2011,
Abstract: The surface roughness plays an important role in product quality and manufacturing process planning, which is also a technical requirement. The effects of turning process parameters on surface roughness have been analyzed. The main effects (independent parameters), quadratic effects (square of the independent variables), and interaction effects of the variables have been considered separately to build best subset of the model. Three different values of the feed, three values of the depth of cut, two different types of cutting tools have been used to generate a total 18 readings in a single set. Three different types of work piece material havebeen used for the experimentation, which generates a total 54 readings of the data. After having the data from the experiments, output (surface roughness, Ra) of the test samples was taken on a Taylor Hobson made Talysurf surface roughness tester. To analyze the data set, statistical tool of MATLAB (Software) has been used to reduce the manipulation and help to arrive at proper improvement plan of the Manufacturing process & Techniques. Feed and depth of cut has a major effect on the surface roughness. Hypothesis testing was also done to check the goodness of fit of the data. A comparison between the observed and predicted data was made, which shows a close relationship.
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.
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