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Purpose: The aim of this work was to estimate the multifractal spectra of 3D surface roughness for unworn hydrogel contact lenses (CL), obtained with atomic force microscopy (AFM) analysis. Materials and methods: Contact lenses made from vifilcon A (Focus® Monthly Toric Visitint® model, CIBA Vision Corp.) were investigated. CL surface roughness was studied by AFM in tapping-mode™, in an aqueous environment, on square areas ranging from 1 to 4 µ[m.sup.2]. A detailed methodology for CL surface multifractal characterization, which may be applied for AFM data, was presented. Results: The CL surface roughness revealed multifractal geometry at various magnifications. The generalized dimension [D.sub.q] and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of CL surface geometry at nanometer scale. Conclusions: Multifractal analysis provides different yet complementary information to that offered by traditional surface statistical parameters. POLYM. ENG. SCI., 54:1066-1080, 2014. © 2013 Society of Plastics Engineers, INTRODUCTION Fractal and multifractal theories are efficient tools to better describe biomaterials' surface geometry used in biomedical applications, based on image analysis methods [1-3]. In the field of polymer science, [...]

A neural network can use the surface roughness of a painting to tell one person's brushstrokes from another's. A neural network can use the surface roughness of a painting to tell one person's brushstrokes from another's., Author Affiliations: Paintings of flowers honed a neural network's ability to link a work to a specific artist. Credit: F. Ji et al./Herit. Sci. (CC BY 4.0) An artist painting [...]

The aim of this study was to qualitatively and quantitatively characterize the optic surface topography of unworn hydrogel contact lenses (CLs) using atomic force microscopy (AFM) analysis and methods of modern metrology. The CLs used in this study were vifilcon A (Focus® Monthly Toric Visitint® model, CIBA Vision Corp.). AFM analysis was performed in Tapping Mode™ in an aqueous environment. The surface roughness analysis was based on six quantitative statistical parameters: arithmetic mean deviation of the surface ([S.sub.a]), root mean square deviation of the surface ([S.sub.q]), skewness of the topography height distribution ([S.sub.sk]), kurtosis of the topography height distribution ([S.sub.ku]), 10-point average of the absolute heights ([S.sub.z]), and vertical distance between highest peak and lowest surface point ([S.sub.t]). These parameters were determined across different square areas (1,4, 9, 16, and 25 µ[m.sup,2]). The surface roughness parameter values were found to be dependent on the examined surface area. The values of [S.sub.a], [S.sub.q], |[S.sub.sk]|, [S.sub.z], and [S.sub.t] parameters increase with the increasing size of the scanning area, an opposite effect of that observed for the [S.sub.ku] parameter values. The proposed methodology might potentially have implications for the future testing of contact lens hydrophilic polymers. POLYM. ENG. SCI., 53:2141-2150, 2013. @ 2013 Society of Plastics Engineers, INTRODUCTION Digital image analysis and mathematical morphology is broadly used in many areas, including material science, medicine, and biology (1-3). In material science, the microstructure of machined surface topography, as [...]

A step by step transformation of the low frequency small height and slope perturbation solution into the high frequency reciprocal and dual, physical and geometrical optic solutions is presented. The familiar Kirchhoff approximations for the fields impressed by the incident plane wave upon the rough surfaces results in nonreciprocal solutions. It is shown that the surface element scattering coefficients based on the Kirchhoff approximations agree with the corresponding reciprocal physical optics solutions only at the stationary phase, specular points on the rough surfaces. While the Kirchhoff approximations and physical optics approximations are based on the characterization of the surface fields by Fresnel reflection coefficients, the corresponding surface element scatter coefficient derived for the small perturbation solution and the full wave solutions are based on the imposition of boundary conditions for the tangential components of the electric and magnetic fields. A flow graph schematically depicting the relationships between these solutions for the scattered fields is also presented. PACS Nos: 02.00, 41.00, 42.00, 84.00, 89.00 Nous presentons une transformation etape par etape da la solution de petite amplitude de basse frequence et de perturbation de pente vers des solutions reciproques de haute frequence et a la fois d'optique physique et geometrique. Les approximations habituelles de Kirchhoff pour les champs marques par l'onde plane incidente sur les surfaces rugueuses donnent des solutions non reciproques. Nous montrons que les coefficients de diffusion d'element de surface bases sur les approximations de Kirchhoff n'agreent avec les solutions d'optique physique reciproques correspondantes qu'a la phase stationnaire, les points speculaires des surfaces rugueuses. Alors que les approximations de Kirchhoff et les approximations d'optique physique sont basees sur la caracterisation des champs de surface par les coefficients de reflexion de Fresnel, les coefficients de diffusion des elements de surface correspondants obtenus de la solution en faible perturbation et les solutions ondulatoires completes sont basees sur l'imposition de conditions limites pour les composantes tangentielles des champs electrique et magnetique. Nous presentons aussi un graphe de flot qui montre schematiquement entre les solutions pour les champs diffuses. [Traduit par la Redaction], 1. Introduction In this paper the relationships between rough surface (see Figs. 1a and 1b) scattering solutions based on (i) the Kirchhoff approximation, (ii) the physical optics approximations, (iii) the [...]

A comprehensive study was carried out to understand the effect of roughness on the turbulence characteristics of flow in an open channel. To this end, tests were conducted with four different types of bed surface conditions at two different Reynolds number (Re = 47 500 and 31 000). This includes the use of an impermeable smooth bed, impermeable rough bed, permeable sand bed, and an impermeable bed with distributed roughness. The roughness is generated using sand grains of median diameter 2.46 mm. The effect of bed roughness is seen to have penetrated through most of the flow depth, disputing the conventional 'wall similarity' hypothesis. The results show that the distributed roughness generates the largest roughness effect. The differences in the characteristics as noted by the velocity triple products exceed 200% between the flow over the smooth and rough beds. Although the same sand grain is used to create the different rough bed conditions, there are differences in turbulence characteristics, which is an indication that specific geometry of the roughness has an influence. A quadrant analysis indicates that roughness increases the contribution of the extreme turbulent events that produce very large instantaneous Reynolds shear stress and consequently influence the flow. Key words: turbulence, rough bed, Reynolds shear stress, shear stress correlations, higher-order moments, quadrant analysis, open channel flow. Une etude complete a ete realisee afin de mieux comprendre l'effet de la rugosite sur les caracteeristiques de turbulence d'un ecoulement dans un canal a surface libre. Des essais ont ainsi ete realises en utilisant quatre diffeerents types de conditions de surface de lit a deux differents nombres de Reynolds (Re = 47 500 et 31 000). Cela comprend l'utilisation d'un lit lisse impermeable, d'un lit rugueux impermeable, d'un lit de sable permeable et d'un lit impermeable comportant une rugosite repartie. La rugosite est generee par des grains de sable d'un diametre moyen de 2,46 mm. L'effet de la rugosite; du lit semble avoir influence: presque tout le tirant d'eau, contestant ainsi l'hypothese conventionnelle de << similarite des parois >>. Selon les resultats, le plus fort effet de rugosite decoule de la rugosite repartie. Les differences, telles que notees par le cube de la velocitee, entre les caracteristiques de l'eecoulement passant sur des lits lisses et rugueux deepassent 200 %. Bien que la meme granulometrie de sable soit utilisee pour engendrer les differentes conditions de rugosite,il existe certaines differences dans les caracteeristiques de turbulence, ce qui indique que la geomeetrie speecifique de la rugosite avait une influence. Une analyse des quadrants indique que la rugosite augmente la contribution des evenements turbulents extremes, lesquels produisent de tres grandes tensions de Reynolds instantanees et, en consequence, influencent l'ecoulement. Mots-cles: turbulence, lit rugueux, tension de Reynolds, correlations contrainte de cisaillement, moments d'ordre superieur, analyse des quadrants, ecoulement a surface libre. [Traduit par la Redaction], 1. Introduction Understanding the structure and dynamics of flow in an open channel that comprises a sheared boundary layer like flow is of importance to the modeling of transport and [...]

Direct numerical simulation is employed in order to describe the subsonic flow past an array of micron-sized discrete roughness elements, which were mounted near the leading edge of a 30-degree swept wing at a chord Reynolds number of 7.4 x [10.sup.6]. The flow conditions correspond to flight receptivity experiments that were conducted to investigate the effects of roughness on crossflow instabilities. To make the computations tractable, the geometry is scaled by the radius of the wing leading edge, which magnifies the region of interest and enhances resolution. The leading-edge region is then approximated by the flow past an infinite parabolic cylinder. The numerical method is based upon a sixth-order-accurate time-implicit scheme to attain high fidelity and was used in conjunction with an eighth-order low-pass Pade-type nondispersive filter operator to maintain stability. A high-order overset-grid approach preserved spatial accuracy on a local mesh system representing the roughness elements, using domain decomposition to perform calculations on a parallel computing platform. The direct simulation for the flow about the roughness elements was used to capture crossflow vortices and served as input to the nonlinear parabolized stability equations, which were then solved in order to determine receptivity of the flow to the geometric perturbations. Three different geometric roughness elemental shapes were investigated in the study. For one shape, the effect of element height was examined. Features of the roughness-element flowfields are elucidated, and findings of the stability calculations are compared. Results are presented for receptivity of the crossflow instability to the size and shape of elements, as obtained by the direct numerical simulation and by two different stability approaches. DOI: 10.2514/1.J050548

For detailed hydraulic modeling, accurate spatial information of riparian vegetation patterns needs to be derived in automatic fashion. We propose a supervised classification for heterogeneous riparian corridors with a low number of spectrally separate classes using data fusion of a Quickbird image and LIDAR data. The approach considers nine land cover classes including three woody riparian species, brush, cultivated areas, grassland, urban infrastructures, bare soil and water. The classical 'stacked vector' approach is adopted for data fusion, while the nonparametric weighted feature-extraction method and the pixel-oriented maximum likelihood algorithm are used for feature-reduction and classification purposes, respectively. We test the approach over a 14-km stretch of the Sieve River (Tuscany Region, Italy). A one-dimensional river modeling is applied over the study reach comparing the results of a classification- derived hydraulic roughness map and a traditional ground-based approach. Despite the complex study reach, the classification method produced encouraging accuracies (OKS = 0.77) and represents a useful tool to delineate application domains of flow resistance models suited to different hydrodynamic patterns (e.g., stiff/flexible vegetation). Hydraulic modeling results showed that the remotely derived floodplain roughness parameterization captures the equivalent Manning coefficient over 20 test cross sections with uncertainty distributions described by low mean and standard deviation values. DOI: 10.1061/(ASCE)HY.1943-7900.0000254 CE Database subject headings: Flow resistance; Hydrodynamics; Hydrologic models; Remote sensing; Vegetation; Hydraulic roughness. Author keywords: Flow resistance; Manning; Quickbird; LIDAR; Hydrodynamic modeling; Remote sensing.

Interaction between the free surface and the bed material in flow over rock chutes under macroroughness conditions leads to a high air entrainment into the flow. The note reports on an experimental study about air diffusion features in the flow over a long rock chute. Air concentration profiles and water depths over a uniform bed material were measured. An empirical equation for the average air concentration in macroroughness condition for steep slopes is proposed. A new Darcy-Weisbach equivalent friction factor for long chutes as a function of the slope and the relative equivalent depth has also been found. DOI: 10.1061/(ASCE)HY.1943-7900.0000270 CE Database subject headings: Hydraulic roughness; Aeration; Two phase flow; Friction; Uniform flow; Rocks. Author keywords: Rock chute; Macroroughness; Self-aeration; Two-phase flow; Air concentration; Equivalent friction factor.

A tidal bore is a wave propagating upstream as the tidal flow turns to rising. It forms during spring tide conditions when the flood tide is confined to a narrow funneled channel. To date, theoretical and numerical studies rely upon physical experiments to validate the developments, but the experimental data are limited mostly to visual observations and sometimes free-surface measurements. Herein turbulent velocity measurements were obtained in a large-size laboratory facility with a fine spatial and temporal resolution. The instantaneous velocity measurements showed rapid flow deceleration at all vertical elevations, and large fluctuations of all velocity components were recorded beneath the bore and secondary waves. A comparison between undular (nonbreaking) and breaking bores suggested some basic differences. In an undular bore, large velocity fluctuations were recorded beneath the first wave crest and the secondary waves showing a long-lasting effect after the bore passage. In a breaking bore, some large turbulent stresses were observed next to the shear zone in a region of high velocity gradients, while some transient flow recirculation was recorded next to the bed. The effects of bed roughness were tested further. The boundary friction contributed to some wave attenuation and dispersion, and the free-surface data showed some agreement with the wave dispersion theory for intermediate gravity waves. The instantaneous velocity data showed however a significant effect of the boundary roughness on the velocity field next to the boundary (z/[d.sub.0] < 0.2) for both undular and breaking bores. Overall the findings were consistent with field observations of tidal bores and highlighted the significant impact of undular (nonbreaking) bores on natural systems. DOI: 10.1061/(ASCE)WW.1943-5460.0000048 CE Database subject headings: Turbulence; Bed roughness; Tidal currents; Wave propagation. Author keywords: Tidal bores; Turbulence; Bed roughness; Physical modeling.

An important element of achieving quality in a road network is the control of vehicle vibration due to pavement roughness and road irregularities. Scientific literature and international standards suggest that we evaluate these phenomena by measuring the whole body vibration (WBV) on the road user, but, for the practical aims of road engineering, this expression has to be related to road unevenness indexes, especially the most common one (the international roughness index, IRI). This index, in turn, is obtained from measured pavement geometric data using a conventional model of a mechanical system representing part of a vehicle. To better investigate the problem of user comfort, more complex models and analyses are needed. In this paper, a model of a real and common vehicle is presented and used, after a calibration process, to perform many dynamic simulations. The obtained results, in terms of weighted vertical acceleration ([a.sub.wz], that is, the WBV index, according to ISO standard), show good correlations ([R.sup.2] from 0.75 to 0.93, depending on vehicle speed) with the IRI values of the examined road sections. On the basis of this correlation, authors propose threshold values for both vibration and roughness indexes; these thresholds could be used for road users' comfort evaluation and adopted in technical standards. DOI: 10.1061/(ASCE)TE.1943-5436.0000143 CE Database subject headings: Surface roughness: Pavements; Deterioration: Surveys; Highways and roads; Vibration. Author keywords: Road roughness; Pavement deterioration; Surveys; Highways; Comfort limits.

Applications involving highly loaded elastohydrodynamic lubrication (EHL), particularly when the lubricant experiences shear thinning, operating with small film thicknesses may necessitate consideration of surface asperities. A modified Reynolds equation with provision for surface roughness and shear thinning is treated to predict the pressure and surface asperity effect in an EHL line-contact. The unknown in the Reynolds equation is the hydrodynamic pressure instead of the total pressure to ensure that the pressure boundary condition at the outlet is properly posed. The Carreau viscosity model is used for characterizing the shear thinning behavior, Patir and Cheng flow factors for taking into the influence of roughness on the lubricating film, and Greenwood--Trip for determination of pressure at the asperity level. The modified Reynolds equation is solved for the hydrodynamic pressure instead of the total pressure with appropriately defined boundary conditions. [DOI: 10.1115/1.4001787]

Design of a near contact air bearing interface such as that created by a recording head slider and data storage disk requires consideration of a lubrication equation that is appropriate for high Knudsen number flows. The Poiseuille flow database reported by Fukui and Kaneko, 1990 ['A Database for Interpolation of Poiseuille Flow Rates for High Knudsen Number Lubrication Problems,' ASME J. Tribol., 112, pp. 78-83] is appropriate over a wide range of Knudsen numbers and is used throughout the data storage industry for analysis of the low flying recording head slider air bearing. However, at such low clearances, the topography of the air bearing surfaces also comes into question, making it important to consider both rarefaction and surface roughness effects in the air bearing design. In order to simplify the air bearing analysis of rough surfaces, averaging techniques for the lubrication equation have been developed for situations where the number of roughness elements (or waves) is either much greater or much less than the gas bearing number. Between these two extremes there are currently no roughness averaging methods available. Although some analytical and numerical studies have been reported for continuum and first-order slip conditions with simple geometries, little or no results have appeared that include both surface roughness and high Knudsen number flows outside the limited ranges where surface averaging techniques are used. In order to better understand the influence of transverse surface roughness over a wide range of Knudsen numbers and the relationship of key parameters involved, this paper describes a primarily analytical air bearing study of a wide, rough surface slider bearing using the Poiseuille flow database reported by Fukui and Kaneko. The work is focused outside the limited ranges where current surface averaging methods for the lubrication equation are expected to be valid. [DOI: 10.1115/1.4001848] Keywords: lubrication equation, high Knudsen number, rough surface, hydrodynamic lubrication, air bearing interface, data storage

Asymmetric height distribution in surface roughness is important in many engineering surfaces, such as in constant velocity ( CV) joints, where specific manufacturing processes could result in such surfaces. Even if the initial surfaces exhibit symmetric roughness, the running-in and sliding processes could result in asymmetric roughness distributions. In this paper, the effect of asymmetric asperity height distribution on the static friction coefficient is investigated theoretically and experimentally. The asymmetry of the surface roughness is modeled using the Pearson system of frequency curves. Two elastic-plastic static friction models, the Kogut--Etsion (KE) and Cohen--Kligerman--Etsion (CKE) models are adapted to account for asymmetric roughness and employed to obtain the tangential and normal contact forces. Static friction experiments using CV joint roller and housing surfaces, which exhibit different levels of surface roughness, were performed and directly compared with the KE and CKE static friction models using both a symmetric Gaussian as well as Pearson distributions of asperity heights. It is found that the KE model with the Pearson distribution compares favorably with the experimental measurements. [DOI: 10.1115/1.4001547] Keywords: static friction coefficient, friction model, surface roughness, asymmetric height distribution

Roughness of a pavement surface is commonly correlated to its serviceability. On the other hand, on many occasions, investigators have attributed pavement roughness to inadequate skid resistance (friction) as well. However, current pavement friction evaluation and standardization models have yet to incorporate effects of pavement roughness. Hence a study was conducted to investigate and quantify the effects of pavement roughness on the skid number (SN) (or 100 coefficient of friction). First, an experimental program was executed to evaluate SN measured from a locked wheel tester (LWT) on pavement sections with similar micro- and macrotexture conditions but different levels of roughness. The measured average SN was seen to be significantly lower on relatively rougher pavement sections. To explain the above observations, a second set of experiments was conducted to study the effect of the normal load on the LWT tire on SN. Statistical analysis including regression and ANOVA was used to validate the nonlinear reciprocal relationship found between SN and the normal load which contradicts the general perception of constant SN with respect to the normal load. Then, a one-dimensional two-degrees-of-freedom vibration model was formulated to incorporate the significant dynamic fluctuations of the normal load of the LWT induced by pavement roughness and the vehicle speed. The variation of the normal load and its nonlinear relation to SN was used to explain lower SN values measured on relatively rougher surfaces. The feasibility of using the international roughness index and the dynamic load coefficient as predictors of the reduction in SN due to pavement roughness was also investigated. Assurance of adequate skid resistance is a vital factor considered in allocating pavement rehabilitation funds at the network level. Since excessively rough pavements also create skid hazards, it is concluded that roughness effects must be considered in pavement management systems not only for serviceability purposes, but also in safety evaluations. DOI: 10.1061/(ASCE)TE.1943-5436.0000118 CE Database subject headings: Roughness; Dynamic loads; Coefficients; Pavements. Author keywords: Roughness; Skid number; Dynamic load coefficient; Locked wheel tester; International roughness index.

This paper presents an experimental investigation of roughness effects on aerodynamic performance in a low-speed linear compressor cascade. Equivalent sandgrain roughnesses of 12 [micro]m, 180 [micro]m, 300 [micro]m, 425 [micro]m, and 850 [micro]m have been tested. In nondimensional terms, these roughnesses represent compressor blade roughnesses found in actual gas turbines. Downstream pressure, velocity, and angle have been measured with a five-hole probe at 0.3 chord downstream of the blade trailing edge. For the tested roughnesses of 180 [micro]m, 300 [micro]m, 425 [micro]m, and 850 [micro]m, the axial velocity ratio across the blade row decreases by 0.1%, 2.1%, 2.5%, and 5.4%, respectively. For the same cases, the exit flow angle deviation increases by 24%, 38%, 51%, and 70%, respectively. Finally, the mass-averaged total pressure loss increases by 12%, 44%, 132%, and 217%, respectively. Also, the loss increases more rapidly in the transitionally rough region. Thus, among the three parameters, the loss responds most sensitively to changes in compressor blade roughness. [DOI: 10.1115/1.4001788]

This paper describes the derivation and numerical solution of a lubrication equation appropriate for high Knudsen number flows and certain types of striated rough surfaces. The derivation begins with the compressible form of the lubrication equation together with the nonlinear series form of the Poiseuille flow reported by Fukui and Kaneko (1990, 'A Database for Interpolation of Poiseuille Flow Rates for High Knudsen Number Lubrication Problems,' ASME J. Tribol., 112, pp. 78-83.). A multiple-scale analysis is performed on the lubrication equation for a finite-width time-dependent bearing and is limited to either stationary-transverse or longitudinal striated surface roughness of very. short length scale. The rough surface averaging that takes place within the multiple-scale analysis includes a fully coupled treatment of the Poiseuille flow. What results is an especially nonlinear lubrication equation with averaged surface roughness effects that is appropriate for high Knudsen number analysis. A rotational transformation is also introduced to provide the roughness averaged lubrication equation in a form that allows analysis of the skewed orientation of a recording head slider with roughness defined relative to the direction of disk motion but with the lubrication equation conveniently expressed in the coordinate system of the slider. A factored-implicit numerical algorithm is described that provides the solution of the roughness averaged lubrication equation. Even though the lubrication equation is highly nonlinear, the numerical scheme is crafted to be fully second-order, time-accurate, and noniterative for tracking the solution in time either to an asymptotic steady-state or in response to a dynamic event. Numerical solutions of several simple geometry bearings are presented that utilize parameters that are typical of the slider-disk interface of current hard disk drives. It is anticipated that the primary benefit of this work may be the ability to accurately and efficiently include the influence of discrete disk data tracks in the air bearing design of very low clearance recording head sliders. [DOI: 10.1115/1.4001023] Keywords: data storage, high Knudsen number, rough surface, air bearing interface, lubrication equation

Glass surface roughness can be considered positive for certain applications in optics. Results of maskless (i.e., lithography-free) reactive-ion-etch runs are given, where (depending on etch parameters) self-masking leads to very different surface morphologies. The latter's variety allows for virtually any desired scattered visible light power portion, a result that we term dosed scattering. The surfaces are characterized, for example, by the root-mean-square roughness [[delta].sub.rms], while their optical scattering is described by the diffuse transmission as well as the Harvey parameters. Since the wavelengths [lambda] in glass are around [[delta].sub.rms], the shapes of the individual scatterers account for local refraction adding up to the usual scattering. OCIS codes: 240.0240, 290.0290.

The working features of innovative coastal defense structures that can dissipate the energy of incoming waves by the action of large-scale bottom unevennesses (rigid blades covering the lower half of the water depth) were investigated by means of a laboratory experimental campaign. The goal of the study was to characterize the ability of the structures to efficiently reduce the wave height with a minimal change in the mean water superelevations. Similar wave height reductions were achieved for both vertical and inclined blades; their efficiency was slightly superior to that of traditional submerged rubble-mound breakwaters of the same cross-shore extension. For the incident waves examined, very low mean water elevations were observed inshore of the structures, with the inclined blades producing the smallest values. These results suggest that the structures analyzed here could represent an alternative to submerged rubble-mound breakwaters from a hydrodynamic point of view to protect coastlines prone to erosion with minimal risk of dangerous rip currents. DOI: 10.1061/(ASCE)WW.1943-5460.0000028 CE Database subject headings: Coastal structures; Dissipating submerged structures. Author keywords: Coastal structures; Submerging; Hydraulic roughness; Wave forces.

In this paper the Arehard model and classical results of mean square calculus are used to derive two Cauchy problems in terms of the expected value and covariance of the worn height stochastic process. The uncertainty is present in the wear and roughness coefficients. In order to model the uncertainty, random variables or stochastic processes are used. In the latter case, the expected value and covariance of the worn height stochastic process are obtained for three combinations of correlation models for the wear and roughness coefficients. Numerical examples for both models are solved. For the model based on a random variable, a larger dispersion in terms of worn height stochastic process was observed. [DOI: 10.1115/1.3173603] Keywords: constitutive modeling of materials, mechanical properties of materials

The paper investigates the influence of the resistance coefficient variability onto the spatial development of roll-waves. Two models, based on time-asymptotic solutions of the linearized St. Venant equations, subject to either impulsive or oscillating perturbation, have been modified by including the dependence of the resistance coefficient on flow conditions, wall roughness, and fluid viscosity. Independently of the perturbation type, it has been shown that the hypothesis of constant resistance coefficient leads to underestimate the disturbance spatial growth. Theoretical predictions are finally compared with results of a fully nonlinear model and with literature experimental data for several combinations of Froude and Reynolds numbers and relative roughness values. The representation of variability of the resistance coefficient fundamentally improves the performance of minimum channel length criteria, whereas its neglect may lead to noncautious channel design. DOI: 10.1061/(ASCE)HY.1943-7900.0000139 CE Database subject headings: Bed roughness: Friction: Open channel flow; Stability; Water waves; Reynolds number; Flow resistance. Author keywords: Bed roughness: Friction; Open channel flow; Stability; Water waves.

In the present investigation, a tip test based on upsetting and backward extrusion was utilized to characterize the effect of surface roughness of the billet and forming tools, and the type of lubricants on friction. For the test, cylindrical specimens made of aluminum alloys of 6061-O and 2024-O, and single punch and two die sets with different surface topologies, were used with four lubricants such as VG32, VG100, corn oil, and grease. The load levels and tip distances were measured for both materials, and compared with each other to determine shear friction factors at the punch and counter punch interfaces separately, depending on the variation in surface topologies and lubrications using finite element simulations. As a result, a linear relationship among the dimensionless load, tip distance, and shear friction factors at the punch and counter punch interfaces was derived for the experimental conditions investigated. The slope change of this linear relationship from negative to positive clearly depends on the variation in surface conditions at the billet/punch and billet/counter punch interfaces. Also, it was demonstrated that the dimensionless tip distance for the frictionless case can be extrapolated from the experimental data. This value can be used for characterizing the relative effect on friction due to surface conditions at the punch and counter punch, and lubrication quality of the lubricant for the given processing conditions. [DOI: 10.1115/1.4000273] Keywords: tip test, friction measurement, tip distance, backward extrusion, surface roughness, surface topology

Surface texture plays an important role in the frictional behavior and transfer layer formation of contacting surfaces. In the present investigation, basic experiments were conducted using an inclined pin-on-plate sliding apparatus to better understand the role of surface texture on the coefficient of friction and the formation of a transfer layer. In the experiments, soft HCP materials such as pure Mg and pure Zn were used for the pins and a hardened 080 M40 steel was used for the plate. Two surface parameters of the steel plates--roughness and texture--were varied in tests that were conducted at a sliding speed of 2 mm/s in ambient conditions under both dry and lubricated conditions. The morphologies of the worn surfaces of the pins and the formation of the transfer layer on the counter surfaces were observed using a scanning electron microscope. In the experiments, the occurrence of stick-slip motion, the formation of a transfer layer, and the value of friction were recorded. With respect in the friction, both adhesion and plowing components were analyzed. Based on the experimental results, the effect of surface texture on the friction was attributed to differences in the amount of plowing. Both the plowing component of friction and the amplitude of stick-slip motion were determined to increase surface textures that promote plane strain conditions and decrease the textures that favor plane stress conditions. [DOI: 10.1115/1.3142904] Keywords: friction, transfer layer, stick-slip, surface texture, HCP metals

The objective of this work was to improve our understanding of pulsed laser micropolishing (PL[micro]P) by studying the effects of laser pulse length and feed rate (pulses per millimeter) on surface roughness. PL[micro]P experiments were conducted with a multimode neodymium-doped yttrium aluminum garnet (Nd: YAG) laser (1064 nm wavelength) that was focused down to approximately 50 [micro]m diameter and scanned over the stationary workpiece surface. Simulation results presented here and previous work suggest that longer laser pulses result in smoother surfaces. Results on microfabricated nickel samples using laser pulse durations of 300 ns and 650 ns test this hypothesis. Polishing with 300 ns and 650 ns pulse durations results in an average surface roughness of 66 nm and 47 nm, respectively; reductions of 30% and 50% compared with the original surface. Furthermore, PL[micro]P is shown to introduce a minor artifact on the sample surface whose spatial frequency (1/mm) is directly related to the laser feed rate (pulses/mm). [DOI: 10.1115/1.3106033] Keywords: pulsed laser, polishing, nickel, surface roughness

This paper is based on a microinteraction principle of fabricating a RB-SiC material with a fixed abrasive. The influence of the depth formed on a RB-SiC workpiece by a diamond abrasive on the material removal rate and the surface roughness of an optical component are quantitatively discussed. A mathematical model of the material removal rate and the simulation results of the surface roughness are achieved. In spite of some small difference between the experimental results and the theoretical anticipatiom which is predictable, the actual removal rate matches the theoretical prediction very well. The fixed abrasive technology's characteristic of easy prediction is of great significance in the optical fabrication industry, so this brand-new fixed abrasive technology has wide application possibilities. OCIS codes: 220.0220, 220.4000, 220.4610, 220.5450.

Most of the methods for generating regular surface texture (RST) consist of shaping a set of regular grooves (cavities) arranged in a regular way. This paper presents possibilities for regular surface texture generation by so-called 'pattern grinding' with the wheel prepared in a special way. The simple variant of the method involves grinding with the wheel having helical grooves. The grooves shaped on the work material are the result of specific wheel surface reproduction. The ratio between work-material feed and wheel speed is an important factor, determining the layout of the grooves generated on the work-material and the shape of the groove sides. Surface texture consists of two components: deterministic, resulting from the nominal wheel active surface, and random, resulting from the random shape and arrangement of abrasive grains. The limited contribution of the random component of surface texture is discussed based on the ratio between the undeformed chip thickness and the sizes of the grooves. Kinematical analysis of the wheel reproduction process is performed for description of nominal surface texture. Experimental results of flat and cylindrical surfaces, obtained with pattern grinding are also provided. Two critical values of the ratio between work-material feed and wheel speed were derived, and three ranges of this ratio are discussed. The kinematical approach provided relationships between input data of the process (wheel shape and grinding parameters) and nominal groove dimensions and groove layout. The geometrical characteristics of the work-material nominal surface texture are presented for each of the three types of surface texture. It is important to ensure that the work feeds are greater than the lower critical value. For achievable work feeds the shape of the sides of the grooves is cycloid. Experiments revealed the limited contribution of the random component of the surface structure of the work material. Random arrangement of abrasive grains is important only at local (micro-) level and affects the roughness of groove bottoms, while the dimensions and arrangement of the grooves are affected only to a minimal degree. [DOI: 10.1115/1.3070511] Keywords: grinding, regular surface texture

A formula is derived for the total width of the angle spread function in an imaging optical system, the performance of which is degraded by surface roughness. The derivation is done in the framework of the scalar theory of diffraction, but it does not rely on the small roughness approximation. The contribution of scattering from surface roughness to the total width of the angle spread function is found to depend only on the variance of the roughness slope. It is also shown that the common rule of obtaining the total width of the angle spread function as a square sum of the pure scattering component and the pure specular component is actually incorrect and does not fully account for the contribution of the specular component. OCIS codes: 110.4850, 260.1960, 290.5825, 290.5880.

We investigated the effect of surface roughness on the sensor performance of extinction-based localized surface plasmon resonance (LSPR) biosensors. The sensor measures resonance wavelength shifts in transmittance caused by biomolecular interactions that are amplified by periodic nanostructures. The numerical computation was conducted using rigorous coupled-wave analysis with Gaussian random surface profiles. The results suggest that, when a surface has a roughness smaller than 2 nm in height deviation, the sensitivity of a LSPR biosensor is not significantly influenced regardless of correlation length (CL). However, we found that the extinction peak amplitude and curve width are affected substantially by a decrease in CL. At a less than 100 nm CL, surface roughness can induce interference between localized surface plasmons excited by the surface and nanowires, which can lead to major degradation of sensor performance. OCIS codes: 050.2770, 130.6010, 240.5770, 240.6680.

The influence of surface roughness on the polarimetric performance of a wire-grid polarizer (WGP) is numerically investigated using rigorous coupled-wave analysis over 100 random surface realizations. Surface roughness is modeled with a Gaussian surface, represented by two independent parameters: surface height deviation and correlation length of a profile. The results show that WGP performance can suffer from significant degradation as well as increased deviation with surface roughness, although the extent varies with specific parameters. The influence of roughness was also examined with respect to grating period as a WGP parameter and incident light properties, such as wavelength and angle. OCIS codes: 050.1950, 120.5410, 230.5440, 240.5770, 260.5430.

Chemical frosting is used as a surface decorating method by many glass package producers. After immersion in an acid frosting bath, glass items present the desired frosted effect. The perception of this particular effect is due to the formation of a microscopic crystalline pattern on the glass surface, which scatters light passing through the glass surface. The chemical composition of the frosting bath influences these properties by modifying the surface roughness, the depth, and the average slopes of the crystalline pattern. Perception of the final aspect can be modified according to the chemical composition of the frosting bath. Different correlations between all these parameters exist and have been quantified. OCIS codes: 240.5770, 120.6650.

White-light interferometry measuring an optically rough surface commonly does not resolve the lateral structure of the surface. This means that there are height differences within one resolution cell that exceed one-fourth of the wavelength of the light used. Thus the following questions arise: Which height is measured by white-light interferometry? How does the surface roughness affect the measurement uncertainty? The goal of the presented paper is to answer these questions by means of numerical simulations. Before the aforementioned questions can be answered, the distribution of the intensity of individual speckles, the influence of surface roughness, and the spectral width of the light source used are discussed. OCIS codes: 030.6140, 030.6600, 120.3180, 120.6650.

Optical scattering arising from interface roughness and interference effects is a dominant loss mechanism of thin film coatings for 193 nm. A procedure is presented where at-wavelength scatter measurements in combination with atomic force microscopy are used as a tool for the in-depth characterization of the origins of scattering. For highly reflective coatings, the influence of the substrate roughness on the growth properties is analyzed. Moreover, the effects of interface roughness and optical thickness deviations on the scattering properties are separated. Furthermore, the procedure was used to investigate scattering properties of coatings at 45[degrees] incidence and of coatings applied in immersion fluid that so far could not be accessed by direct measurement. OCIS codes: 120.5820, 120.6660, 240.0240, 290.5820, 240.0310.

Past studies have shown that initial pavement roughness greatly affects future pavement roughness and roughness progression rate. Initial pavement roughness is also an important input to the roughness prediction model in mechanistic-empirical design guide. This study analyzed the design and construction factors affecting initial pavement roughness. Initial international roughness index of 90 concrete pavements constructed in Wisconsin from 2000 to 2004 were analyzed using multiple regression method. The factors considered in this study included concrete pavement slab thickness, project location, dowel bar placement, joint spacing, base type, and pavement length. The factors affecting initial pavement roughness were identified. CE Database subject headings: Roughness; Concrete pavements; Pavement design.

A remarkable characteristic of the cathode spot of a low-pressure arc is that it can remove an oxide layer preferentially. Recently, the cathode spot of a low-pressure arc has been used for cleaning metal oxide surfaces before thermal spraying or surface modification. However, few reports have described the cathode spot movement or the oxide removal process. This experiment was carried out using the SS400 cathode workpiece and a cylindrical copper anode. The cathode spot movement was recorded using a high-speed video camera. The images were later analyzed using plasma image processing. The workpiece surface was covered with a thick oxide of 9.67 [micro]m. The workpiece surface was analyzed using a laser microscope after processing. The cathode spot movement shows differences as the processing time increases and as the oxide layer roughness changes. Index Terms--Cathode spot movement, low-pressure arc, moved distance, oxide layer, processing time, surface roughness, tracks of cathode spots, vacuum arc.

The paper analyses the etch rate and surface roughness of polished and lapped AT-cut quartz subjected to hot, concentrated ammonium bifluoride. The etch rates correlated well and allowed for a polishing and preserving.

Approximate closed-form equations are derived for normal and tangential contact forces of rough surfaces in dry friction. Using an extension of the Greenwood and Tripp (1970, Proc, Inst. Mech. Eng., 185, pp. 625-633) model, in which the derivations permit asperity shoulder-to-shoulder contact and viscoelastic asperity behavior, mathematical formulae are derived for normal and tangential components of the contact force that depend not only on the proximity of the two surfaces but also the rate of approach and relative sliding. A statistical approach is forwarded in which dependence of the asperity tangential contact force on relative tangential velocity of two asperities can be cast as corrective factors in the mathematical description of tangential force. In this regard two corrective coefficients are derived: force directionality corrective coefficient and force-velocity directionality corrective coefficient. The results show that for a moderate to high load ranges the contact force can be analytically described to within 20% accuracy of that from a numerical integration of the contact equations, well below the uncertainties due to surface profile measurement. [DOI: 10.1115/1.2736730] Keywords: kinetic friction, viscoelastic contact model, rough surfaces

Preferential surface texturing is expected to significantly improve tribological performance of ultralow flying magnetic storage head-disk interfaces (HDIs) by modifying the roughness and reducing the contact area preferentially, thereby reducing the relevant interfacial forces, such as friction, contact, and adhesive forces. Because of the different etch rates in the titanium carbide (top surface) and alumina (bottom surface) portions of the slider air-bearing surface (ABS), during reactive ion etching the surface heights possess a distinct bimodal distribution. In order to accurately and realistically capture the interfacial phenomena of the ultralow flying HDI with a preferentially textured slider ABS, a probability density function was proposed by linking two different Gaussian asperity distributions. The proposed bimodal asperity distribution was then directly incorporated into a previously developed rough surface contact model to calculate the corresponding interfacial forces. The results were then directly compared to a single Gaussian approximation (ignoring the bimodality) as well as a high-order polynomial curve-fit approximation (encompassing the bimodality). Comparative studies revealed that the proposed bimodal distribution method has a main advantage of being able to resolve the top and bottom asperity contributions separately, which is physically more accurate, and thereby providing interfacial force estimates that are more physically accurate. Other simpler methods, by assuming a single continuous distribution over the entire surface, are not able to isolate the top and bottom asperity distributions and thus are more likely to overestimate the interfacial forces in sub-5 nm flying HDIs. [DOI: 10.1115/1.2736440] Keywords: magnetic storage, surface roughness, preferential texturing, head-disk interfaces

A nylon bar with different surface roughness is used as a simulation sample of biological tissue for the determination of optical properties by using the spatially resolved steady-state diffuse reflection technique. The results obtained indicate that surface roughness has some effects on the determination of the optical properties of the nylon bar. The determined reduced scattering coefficient decreases with the decrease of the surface roughness of the nylon bar and goes to a constant for the lower surface roughness, and the determined absorption coefficient increases with the decrease of the surface roughness of the nylon bar. Consequently, the optical properties of the tissues obtained by the spatially resolved steadystate diffuse reflection technique should be modified. OCIS codes: 170.3660, 290.5880, 170.7050.

The surface morphology of the niobium (Nb) films, as well as the microstructure of Nb/AlOx-Al/Nb trilayers is studied. The results show that the diffusion of the Al at the Al/Nb interface increases with the increasing roughness of the base Nb layer.

The studies about the effect of substrate surface roughness on the critical current and temperature of niobium thin film strip-line circuits is presented. It showed decrease in a critical current with increase in surface roughness, which is attributed to the decrease in critical current to penetration barrier at the strip-line edge that decreases with increasing surface roughness.

We investigated the charging characteristics of alumina in vacuum with varying surface roughness, and the electric field distribution. The charging on the alumina surface in vacuum is, in general, strongly influenced by field electron emission (FEE) and secondary electron emission avalanche (SEEA). We varied the surface roughness and the electric field distribution on the alumina surface in order to control the FEE and the SEEA. Under these conditions, we measured the 2-dimensional distribution of surface charging potential on the alumina surface. From the measurement results, we quantitatively discussed charge polarity and charge density on the surface for various types of electric field distributions. Finally, we successfully propose a concept of a charging control technique on the alumina insulator in vacuum for the improvement of electrical insulation performance on the alumina surface. Index Terms--Charging characteristics, vacuum, surface roughness, alumina insulator, electric field distribution, secondary electron emission avalanche (SEEA).

It has been clarified by researchers that insulators having contact angles, e.g. [+ or -] 45 [degrees] with regard to the plane electrodes, is hard to acquire charge when they are exposed to high voltages in vacuum. For example, an insulator in the shape of a truncated frustum is free from charging. However, since such insulator has inevitably large volume, it obstructs the compactness. On the other hand, roughening insulator surface is also effective to prevent the surface from charging. In this case, the cost for roughening the entire surface may be high when the insulator is large. In this paper we review our previous investigation results and describe new experimental results aimed at developing feasible and compact insulators used in vacuum. Surface charging characteristics of partially and mechanically processed insulators have been studied for this purpose. That is, the charging phenomena when such insulators are exposed to a ramped dc or ac voltage have been observed by using a capacitive probe embedded in the cathode. Firstly, we describe of a partially roughened cylindrical insulator, where the height of the roughened surface measured from the cathode is varied keeping the total length constant. Secondly, we describe a cylindrical insulator having a truncated conical frustum or a chamfer at its cathode-side end. Based on these experimental and simulation results we prove that the partial mechanical processing is effective to control and suppress the insulator charging in vacuum. Index Terms = Surface charge, flashover, depression and control of charging, dc and ac high voltages, roughening, truncated conical frustum, partial processing, vacuum.

Carrier transport in undoped ultrathin-silicon bodies/channels is examined using a process/physics-based double-gate (DG) MOSFETs model (UFDG). Calibration of UFDG to undoped p- and n-channel DG FinFETs yields consistent results, demonstrating very high mobilities in contemporary FinFETs.

This work aims at characterizing the probability of wave impact and determining the position of impact on an FPSO (floating production storage and offloading platform) bow geometry. In order to determine the instants when impact occurs, an experimental program was performed on a specific bow shape. The bow was instrumented with pressure transducers and the test program, also making use of video recordings, was designed such that it was possible to determine the correlation between undisturbed wave shape and the impact pressure time traces. It has been found that the wave impact at the bow is highly correlated with the local wave steepness, which for very high waves has at least second-order effects. A comparison between the probability distributions of local wave steepness of the experimental undisturbed wave time trace and numerical simulations of second-order wave theory is provided and it confirmed that the latter is very adequate for calculations. The experimental results were further used to determine how the probability of impact varies with free surface vertical velocity. It was found that the significant wave height of the sea state itself does not have significant influence on the result and a regression model was derived for the bow type in the experiments. The proposed model for determining the probability of having an impact is based on combining distributions, adjusted a priori to the numerically generated second-order free surface vertical velocity, and the experimental probability of impact of a known certain seastate and free surface velocity. The analytical description makes it fast and easy to expand to other cases of interest and some example calculations are shown to demonstrate the relative ease of the procedure proposed. The position of the impact is determined by the nonlinear wave crests and the ship motions. The ship motions can be determined based on a linear response to the nonlinear waves considered. [DOI: 10.1115/1.2426983]

Surface roughness is one of the important quality characteristic of a micromachined component. This paper presents a model to predict surface roughness of micro-Dmachined surfaces. The model is based on the configuration of a single-spark cavity formed as a function of process parameters. Assuming the normal distribution of surface heights, the [mu] and [sigma] ([R.sub.q]) of the surface profile are evaluated after every spark. The model was further extended to capture the role of debris in micro-EDM in changing electric potential at the micropeaks on the cathode surfaces. The chemical kinetics approach was used to evaluate the change in plasma enthalpy and composition as a result of debris inclusion in the dielectric. The corresponding energy distribution between the electrodes was used to predict configuration of the single-spark cavity and the consequent surface roughness using the earlier surface roughness model. The modeling results were found to agree well with the micro-EDM validation experiments performed without and with the inclusion of artificial debris (iron particles) in the dielectric. [DOI: 10.1115/1.2540683] Keywords: Micro-EDM, surface roughness, single-spark, plasma, spark erosion, debris inclusion