Estimating small-scale roughness of a rock joint using TLS data

NASA Astrophysics Data System (ADS)

Bitenc, Maja; Kieffer, D. Scott; Khoshelham, Kourosh

2016-04-01

Roughness of a rock joint is an important parameter influencing rock mass stability. Besides the surface amplitude, also the roughness direction- and scale-dependency should be observed (i.e. 3D roughness). Up to now most of roughness measurements and parameters rely on point or profile data obtained on small samples, mostly in a laboratory. State-of-the-art remote sensing technologies supply 3D measurements of an in-situ rock surface and therefore enable a 3D roughness parameterization. Detailed morphology of a remote large-scale vertical structure can be best observed by Terrestrial Laser Scanning (TLS). In a short time and from distances of a few hundred meters, TLS provides relatively dense and precise point cloud. Sturzenegger and Stead [2009] showed that the TLS technology and careful fieldwork allow the extraction of first-order roughness profiles, i.e. the surface irregularities with a wavelength greater than about 10 cm. Our goal is to find the lower limit; this is, to define the smallest discernible detail, and appropriate measuring and processing steps to extract this detail from the TLS data. The smallest observable roughness amplitude depends on the TLS data precision, which is limited mostly by an inherent range error (noise). An influence of the TLS noise on the rock joint roughness was analyzed using highly precise reference data acquired by Advanced TOpometric Sensor (ATOS) on a 20x30 cm rock joint sample. ATOS data were interpolated into 1 mm grid, to which five levels (0.5, 1, 1.5, 2, 2.5 mm) of normally distributed noise were added. The 3D surfaces entered direction-dependent roughness parameter computation after Grasselli [2001]. Average roughness of noisy surfaces logarithmically increase with the noise level and is already doubled for 1 mm noise. Performing Monte Carlo simulation roughness parameter noise sensitivity was investigated. Distribution of roughness differences (roughness of noisy surfaces minus roughness of reference ATOS surface) is approximately normal. Standard deviation of differences on average slightly increases with the noise level, but is strongly dependent on the analysis direction. As proved by different researches within the field of signal, image and also TLS data processing, noise can be, to a certain extent, removed by a post-processing step called denoising. In this research, four denoising methods, namely discrete WT (DWT) and stationary WT (SWT), and classic NLM (NLM) and probabilistic NLM (PNLM), were used on noisy ATOS data. Results were compared based on the (i) height and (ii) roughness differences between denoised surfaces and reference ATOS surface, (iii) the peak signal-to-noise ratio (PSNR) and (iv) the visual check of denoised surface. Increased PSNRs and reduced roughness differences prove the importance of the TLS data denoising procedure. In case of SWT, NLM and PNLM the surface is mostly over smoothed, whereas in case of DWT some noise remains. References: - Grasselli, G. (2001). Shear strength of rock joints based on quantified surface description. École Polytechnique Fédérale de Lausanne. Lausanne, EPFL. - Sturzenegger, M. and D. Stead (2009). "Close-range terrestrial digital photogrammetry and terrestrial laser scanning for discontinuity characterization on rock cuts." Engineering Geology 106(3-4): 163-182.

Cassini/VIMS observes rough surfaces on Titan's Punga Mare in specular reflection.

PubMed

Barnes, Jason W; Sotin, Christophe; Soderblom, Jason M; Brown, Robert H; Hayes, Alexander G; Donelan, Mark; Rodriguez, Sebastien; Mouélic, Stéphane Le; Baines, Kevin H; McCord, Thomas B

Cassini /VIMS high-phase specular observations of Titan's north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 6°±1°. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geographic distribution, and uniform appearance at low phase, we prefer a waves interpretation. Applying theoretical wave calculations based on Titan conditions our slope determination allows us to infer winds of 0.76±0.09 m/s and significant wave heights of [Formula: see text] cm at the time and locations of the observation. If correct, these would represent the first waves seen on Titan's seas, and also the first extraterrestrial sea-surface waves in general.

The effect of brushing with toothpaste containing nano calcium carbonate upon nanofill composite resin surface roughness

NASA Astrophysics Data System (ADS)

Ramadhani, A. M.; Herda, E.; Triaminingsih, S.

2017-08-01

This study aims to determine the effect of brushing with toothpaste containing nanocalcium carbonate on the roughness of nanofill composite resin surface. Brushing was conducted with 3 types of materials for 3 consecutive brushing periods of 10 minutes each. Surface roughness was measured using a surface-roughness tester and the results were analyzed using the repeated ANOVA and the one-way ANOVA test. The surface morphology was observed using SEM after 3 months’ worth of brushing with the 3 materials. It was found that the nanofill composite resin surface-roughness value increased significantly (p<0.005) after brushing with toothpaste containing nano calcium carbonate for 3 months, but the value was not as high as that obtained when brushing with other types of toothpaste.

Surface Forces Apparatus Measurements of Interactions between Rough and Reactive Calcite Surfaces.

PubMed

Dziadkowiec, Joanna; Javadi, Shaghayegh; Bratvold, Jon E; Nilsen, Ola; Røyne, Anja

2018-06-26

nm-Range forces acting between calcite surfaces in water affect macroscopic properties of carbonate rocks and calcite-based granular materials and are significantly influenced by calcite surface recrystallization. We suggest that the repulsive mechanical effects related to nm-scale surface recrystallization of calcite in water could be partially responsible for the observed decrease of cohesion in calcitic rocks saturated with water. Using the surface forces apparatus, we simultaneously followed the calcite reactivity and measured the forces in water in two surface configurations: between two rough calcite surfaces (CC) and between rough calcite and a smooth mica surface (CM). We used nm-scale rough, polycrystalline calcite films prepared by atomic layer deposition. We measured only repulsive forces in CC in CaCO 3 -saturated water, which was related to roughness and possibly to repulsive hydration effects. Adhesive or repulsive forces were measured in CM in CaCO 3 -saturated water depending on calcite roughness, and the adhesion was likely enhanced by electrostatic effects. The pull-off adhesive force in CM became stronger with time, and this increase was correlated with a decrease of roughness at contacts, the parameter which could be estimated from the measured force-distance curves. That suggested a progressive increase of real contact areas between the surfaces, caused by gradual pressure-driven deformation of calcite surface asperities during repeated loading-unloading cycles. Reactivity of calcite was affected by mass transport across nm- to μm-thick gaps between the surfaces. Major roughening was observed only for the smoothest calcite films, where gaps between two opposing surfaces were nm-thick over μm-sized areas and led to force of crystallization that could overcome confining pressures of the order of MPa. Any substantial roughening of calcite caused a significant increase of the repulsive mechanical force contribution.

Effect of various tooth whitening modalities on microhardness, surface roughness and surface morphology of the enamel.

PubMed

Kwon, So Ran; Kurti, Steven R; Oyoyo, Udochukwu; Li, Yiming

2015-09-01

The purpose of this study was to evaluate the effect of four whitening modalities on surface enamel as assessed with microhardness tester, profilometer, and scanning electron microscopy (SEM). Whitening was performed according to manufacturer's directions for over-the-counter (OTC), dentist dispensed for home use (HW) and in-office (OW) whitening. Do-it-yourself (DIY) whitening consisted of a strawberry and baking soda mix. Additionally, negative and positive controls were used. A total of 120 enamel specimens were used for microhardness testing at baseline and post-whitening. Following microhardness testing specimens were prepared for SEM observations. A total of 120 enamel specimens were used for surface roughness testing at baseline and post-whitening (n = 20 per group). Rank-based Analysis of Covariance was performed to compare microhardness and surface roughness changes. Tests of hypotheses were two-sided with α = 0.05. There was a significant difference in Knoop hardness changes (ΔKHN) among the groups (Kruskal-Wallis test, p < 0.0001). Significant hardness reduction was observed in the positive control and DIY group (p < 0.0001). Mean surface roughness changes (ΔRa) were significantly different among the groups (Kruskal-Wallis test, p < 0.0001). Surface roughness increased in the OTC group (p = 0.03) and in the positive control (p < 0.0001). The four whitening modalities-DIY, OTC, HW and OW induced minimal surface morphology changes when observed with SEM. It can be concluded that none of the four whitening modalities adversely affected enamel surface morphology. However, caution should be advised when using a DIY regimen as it may affect enamel microhardness and an OTC product as it has the potential to increase surface roughness.

Correlation of Windspeed and Antarctic Surface Roughness

NASA Astrophysics Data System (ADS)

Stockham, Mark; Anita Collaboration

2015-04-01

When electromagnetic waves interact with a media interface the transmitted and reflected portions of the incoming wave depend on the incident angle of the wave and wavelength (as well as the material properties of the media). The roughness of the surface of Antarctica affects the radio frequency signals received by airborne experiments, such as the balloon-borne experiment ANITA (ANtarctic Impulsive Transient Antenna) which observes the reflected radio waves from cosmic ray-induced extensive air showers (EAS). Roughness of a given scale can cause decoherence of the reflected signal and is an important effect to understand when estimating the amplitude of the incoming wave based on the reflected wave. It is challenging to get a survey of surface roughness over many of the areas that these experiments are likely to pass over. Correlating historical wind speed records with statistical roughness as observed by the backscatter of satellite [Rémy F, Parouty S. Remote Sensing. 2009] and airborne experiments operating at different frequencies can possibly be used to predict time-dependent surface roughness with surface wind speed as the input. These correlations will be presented for a variety of areas on the Antarctic ice shelf. NASA Grant NNX11AC47G.

Critical surface roughness for wall bounded flow of viscous fluids in an electric submersible pump

NASA Astrophysics Data System (ADS)

Deshmukh, Dhairyasheel; Siddique, Md Hamid; Kenyery, Frank; Samad, Abdus

2017-11-01

Surface roughness plays a vital role in the performance of an electric submersible pump (ESP). A 3-D numerical analysis has been carried out to find the roughness effect on ESP. The performance of pump for steady wall bounded turbulent flows is evaluated at different roughness values and compared with smooth surface considering a non-dimensional roughness factor K. The k- ω SST turbulence model with fine mesh at near wall region captures the rough wall effects accurately. Computational results are validated with experimental results of water (1 cP), at a design speed (3000 RPM). Maximum head is observed for a hydraulically smooth surface (K=0). When roughness factor is increased, the head decreases till critical roughness factor (K=0.1) due to frictional loss. Further increase in roughness factor (K>0.1) increases the head due to near wall turbulence. The performance of ESP is analyzed for turbulent kinetic energy and eddy viscosity at different roughness values. The wall disturbance over the rough surface affects the pressure distribution and velocity field. The roughness effect is predominant for high viscosity oil (43cP) as compared to water. Moreover, the study at off-design conditions showed that Reynolds number influences the overall roughness effect.

Surface roughness of Saturn's rings and ring particles inferred from thermal phase curves

NASA Astrophysics Data System (ADS)

Morishima, Ryuji; Turner, Neal; Spilker, Linda

2017-10-01

We analyze thermal phase curves of all the main rings of Saturn (the A, B, C rings, and the Cassini division) measured by both the far-IR and mid-IR detectors of the Cassini Composite InfraRed Spectrometer (CIRS). All the rings show temperature increases toward zero phase angle, known as an opposition effect or thermal beaming. For the C ring and Cassini division, which have low optical depths, intra-particle shadowing is considered the dominant mechanism causing the effect. On the other hand, the phase curves of the optically thick B and A rings steepen significantly with decreasing absolute solar elevation angle from 21° to 14°, suggesting inter-particle shadowing plays an important role in these rings. We employ an analytic roughness model to estimate the degrees of surface roughness of the rings or ring particles. For optically thin rings, an isolated particle covered by spherical segment craters is employed while for the thick rings we approximate a packed particle layer as a slab covered by craters. The particles in the thin rings are found to have generally rough surfaces, except in the middle C ring. Across the C ring, the optical depth correlates with the degree of surface roughness. This may indicate that surface roughness comes mainly from particle clumping, while individual particles have rather smooth surfaces. For the optically thick rings, the surface roughness of the particle layer is found to be moderate. The modeled phase curves of optically thick rings are shallow if the phase angle change is primarily due to change of observer azimuthal angle. On the other hand, the phase curves are steep if the phase angle change is due to change of observer elevation angle, as inter-particle shadows become visible at higher observer elevation. In addition, the area of shadowed facets increases with decreasing solar elevation angle. These combined effects explain the large seasonal change of the phase curve steepness observed for the thick rings. The degrees of surface roughness inferred from the thermal phase curves are generally less than those from the phase curves in visible light. This is probably explained by different roughness scales seen in thermal and visible light or by dilution of thermal phase curve steepnesses due to particle motion.

Experimental Investigation of Minimum Quantity Lubrication in Meso-scale Milling with Varying Tool Diameter

NASA Astrophysics Data System (ADS)

Yusof, M. Q. M.; Harun, H. N. S. B.; Bahar, R.

2018-01-01

Minimum quantity lubrication (MQL) is a method that uses a very small amount of liquid to reduce friction between cutting tool and work piece during machining. The implementation of MQL machining has become a viable alternative to flood cooling machining and dry machining. The overall performance has been evaluated during meso-scale milling of mild steel using different diameter milling cutters. Experiments have been conducted under two different lubrication condition: dry and MQL with variable cutting parameters. The tool wear and its surface roughness, machined surfaces microstructure and surface roughness were observed for both conditions. It was found from the results that MQL produced better results compared to dry machining. The 0.5 mm tool has been selected as the most optimum tool diameter to be used with the lowest surface roughness as well as the least flank wear generation. For the workpiece, it was observed that the cutting temperature possesses crucial effect on the microstructure and the surface roughness of the machined surface and bigger diameter tool actually resulted in higher surface roughness. The poor conductivity of the cutting tool may be one of reasons behind.

Nanoscale Roughness and Morphology Affect the IsoElectric Point of Titania Surfaces

PubMed Central

Borghi, Francesca; Vyas, Varun; Podestà, Alessandro; Milani, Paolo

2013-01-01

We report on the systematic investigation of the role of surface nanoscale roughness and morphology on the charging behaviour of nanostructured titania (TiO2) surfaces in aqueous solutions. IsoElectric Points (IEPs) of surfaces have been characterized by direct measurement of the electrostatic double layer interactions between titania surfaces and the micrometer-sized spherical silica probe of an atomic force microscope in NaCl aqueous electrolyte. The use of a colloidal probe provides well-defined interaction geometry and allows effectively probing the overall effect of nanoscale morphology. By using supersonic cluster beam deposition to fabricate nanostructured titania films, we achieved a quantitative control over the surface morphological parameters. We performed a systematical exploration of the electrical double layer properties in different interaction regimes characterized by different ratios of characteristic nanometric lengths of the system: the surface rms roughness Rq, the correlation length ξ and the Debye length λD. We observed a remarkable reduction by several pH units of IEP on rough nanostructured surfaces, with respect to flat crystalline rutile TiO2. In order to explain the observed behavior of IEP, we consider the roughness-induced self-overlap of the electrical double layers as a potential source of deviation from the trend expected for flat surfaces. PMID:23874708

Smoothed particle hydrodynamics study of the roughness effect on contact angle and droplet flow.

PubMed

Shigorina, Elena; Kordilla, Jannes; Tartakovsky, Alexandre M

2017-09-01

We employ a pairwise force smoothed particle hydrodynamics (PF-SPH) model to simulate sessile and transient droplets on rough hydrophobic and hydrophilic surfaces. PF-SPH allows modeling of free-surface flows without discretizing the air phase, which is achieved by imposing the surface tension and dynamic contact angles with pairwise interaction forces. We use the PF-SPH model to study the effect of surface roughness and microscopic contact angle on the effective contact angle and droplet dynamics. In the first part of this work, we investigate static contact angles of sessile droplets on different types of rough surfaces. We find that the effective static contact angles of Cassie and Wenzel droplets on a rough surface are greater than the corresponding microscale static contact angles. As a result, microscale hydrophobic rough surfaces also show effective hydrophobic behavior. On the other hand, microscale hydrophilic surfaces may be macroscopically hydrophilic or hydrophobic, depending on the type of roughness. We study the dependence of the transition between Cassie and Wenzel states on roughness and droplet size, which can be linked to the critical pressure for the given fluid-substrate combination. We observe good agreement between simulations and theoretical predictions. Finally, we study the impact of the roughness orientation (i.e., an anisotropic roughness) and surface inclination on droplet flow velocities. Simulations show that droplet flow velocities are lower if the surface roughness is oriented perpendicular to the flow direction. If the predominant elements of surface roughness are in alignment with the flow direction, the flow velocities increase compared to smooth surfaces, which can be attributed to the decrease in fluid-solid contact area similar to the lotus effect. We demonstrate that classical linear scaling relationships between Bond and capillary numbers for droplet flow on flat surfaces also hold for flow on rough surfaces.

Optimization of Surface Roughness and Wall Thickness in Dieless Incremental Forming Of Aluminum Sheet Using Taguchi

NASA Astrophysics Data System (ADS)

Hamedon, Zamzuri; Kuang, Shea Cheng; Jaafar, Hasnulhadi; Azhari, Azmir

2018-03-01

Incremental sheet forming is a versatile sheet metal forming process where a sheet metal is formed into its final shape by a series of localized deformation without a specialised die. However, it still has many shortcomings that need to be overcome such as geometric accuracy, surface roughness, formability, forming speed, and so on. This project focus on minimising the surface roughness of aluminium sheet and improving its thickness uniformity in incremental sheet forming via optimisation of wall angle, feed rate, and step size. Besides, the effect of wall angle, feed rate, and step size to the surface roughness and thickness uniformity of aluminium sheet was investigated in this project. From the results, it was observed that surface roughness and thickness uniformity were inversely varied due to the formation of surface waviness. Increase in feed rate and decrease in step size will produce a lower surface roughness, while uniform thickness reduction was obtained by reducing the wall angle and step size. By using Taguchi analysis, the optimum parameters for minimum surface roughness and uniform thickness reduction of aluminium sheet were determined. The finding of this project helps to reduce the time in optimising the surface roughness and thickness uniformity in incremental sheet forming.

A lattice Boltzmann simulation of coalescence-induced droplet jumping on superhydrophobic surfaces with randomly distributed structures

NASA Astrophysics Data System (ADS)

Zhang, Li-Zhi; Yuan, Wu-Zhi

2018-04-01

The motion of coalescence-induced condensate droplets on superhydrophobic surface (SHS) has attracted increasing attention in energy-related applications. Previous researches were focused on regularly rough surfaces. Here a new approach, a mesoscale lattice Boltzmann method (LBM), is proposed and used to model the dynamic behavior of coalescence-induced droplet jumping on SHS with randomly distributed rough structures. A Fast Fourier Transformation (FFT) method is used to generate non-Gaussian randomly distributed rough surfaces with the skewness (Sk), kurtosis (K) and root mean square (Rq) obtained from real surfaces. Three typical spreading states of coalesced droplets are observed through LBM modeling on various rough surfaces, which are found to significantly influence the jumping ability of coalesced droplet. The coalesced droplets spreading in Cassie state or in composite state will jump off the rough surfaces, while the ones spreading in Wenzel state would eventually remain on the rough surfaces. It is demonstrated that the rough surfaces with smaller Sks, larger Rqs and a K at 3.0 are beneficial to coalescence-induced droplet jumping. The new approach gives more detailed insights into the design of SHS.

Dynamic evolution of interface roughness during friction and wear processes.

PubMed

Kubiak, K J; Bigerelle, M; Mathia, T G; Dubois, A; Dubar, L

2014-01-01

Dynamic evolution of surface roughness and influence of initial roughness (S(a) = 0.282-6.73 µm) during friction and wear processes has been analyzed experimentally. The mirror polished and rough surfaces (28 samples in total) have been prepared by surface polishing on Ti-6Al-4V and AISI 1045 samples. Friction and wear have been tested in classical sphere/plane configuration using linear reciprocating tribometer with very small displacement from 130 to 200 µm. After an initial period of rapid degradation, dynamic evolution of surface roughness converges to certain level specific to a given tribosystem. However, roughness at such dynamic interface is still increasing and analysis of initial roughness influence revealed that to certain extent, a rheology effect of interface can be observed and dynamic evolution of roughness will depend on initial condition and history of interface roughness evolution. Multiscale analysis shows that morphology created in wear process is composed from nano, micro, and macro scale roughness. Therefore, mechanical parts working under very severe contact conditions, like rotor/blade contact, screws, clutch, etc. with poor initial surface finishing are susceptible to have much shorter lifetime than a quality finished parts. © Wiley Periodicals, Inc.

Molecular dynamics simulation of nanobubble nucleation on rough surfaces

NASA Astrophysics Data System (ADS)

Liu, Yawei; Zhang, Xianren

2017-04-01

Here, we study how nanobubbles nucleate on rough hydrophobic surfaces, using long-time standard simulations to directly observe the kinetic pathways and using constrained simulations combined with the thermodynamic integration approach to quantitatively evaluate the corresponding free energy changes. Both methods demonstrate that a two-step nucleation route involving the formation of an intermediate state is thermodynamically favorable: at first, the system transforms from the Wenzel state (liquid being in full contact with the solid surface) to the Cassie state (liquid being in contact with the peaks of the rough surface) after gas cavities occur in the grooves (i.e., the Wenzel-to-Cassie transition); then, the gas cavities coalesce and form a stable surface nanobubble with pinned contact lines (i.e., the Cassie-to-nanobubble transition). Additionally, the free energy barriers for the two transitions show opposing dependencies on the degree of surface roughness, indicating that the surfaces with moderate roughness are favorable for forming stable surface nanobubbles. Moreover, the simulation results also reveal the coexistence and transition between the Wenzel, Cassie, and nanobubble states on rough surfaces.

Influence of Roughness-Induced Slip on Colloid Transport: Experimental and Modelling Insights

NASA Astrophysics Data System (ADS)

Rasmuson, J. A.; Johnson, W. P.

2017-12-01

A limitation of classic colloid filtration theory is that it applies only to smooth surfaces, yet most natural surfaces present some degree of nano- to micro-scale roughness. A large volume of research has been dedicated to understanding the effects of roughness on particle attachment at the nano-scale since these interactions dictate field scale transport behavior. It has been previously demonstrated that roughness imposes a finite slip vector at the surface that causes particles to experience higher near-surface velocities than would be expected over a smooth surface. Slip near a rough surface can affect two primary mechanisms of particle attenuation: 1) interception of the surface (finding a landing spot) and 2) arrest on the surface (sticking the landing). However, a clear designation on how slip affects particle transport near rough surfaces is missing. The goal of this study was to provide a guide for the height of the slip layer and contact surface in reference to the mean-plane for rough surfaces. Direct observation was used to measure near-surface velocities of particles translating near surfaces of varying roughness spanning three orders of magnitude. The influence of roughness on particle transport was investigated using computational fluid dynamics (CFD) modeling with rough surfaces measured with atomic force microscopy (AFM). The CFD and experimental results were used to calibrate a Lagrangian particle transport model that utilizes simple modifications to the flow field for a smooth surface using statistically based roughness parameters. Advantages of the Lagrangian model are significantly decreased computation times and applicability to a wide range of natural surfaces without explicitly simulating individual asperities. The results suggest that the no-slip boundary should be placed at the bottom of the maximum asperity valleys, and that the contact surface should be placed at the root mean square (RMS) roughness above the mean plane. Collector surfaces with the greatest RMS roughness had the highest sensitivity to the placement of the contact surface. These findings highlight the need for accurate and representative AFM measurements and have important implications for future transport models.

Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment

PubMed Central

Pacifici, Edoardo; Bossù, Maurizio; Giovannetti, Agostino; La Torre, Giuseppe; Guerra, Fabrizio; Polimeni, Antonella

2013-01-01

Summary Background Even today, use of Glass Ionomer Cements (GIC) as restorative material is indicated for uncooperative patients. Aim The study aimed at estimating the surface roughness of different GICs using or not their proprietary surface coatings and at observing the interfaces between cement and coating through SEM. Materials and methods Forty specimens have been obtained and divided into 4 groups: Fuji IX (IX), Fuji IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finishing Gloss (VFG). Samples were obtained using silicone moulds to simulate class I restorations. All specimens were processed for profilometric evaluation. The statistical differences of surface roughness between groups were assessed using One-Way Analysis of Variance (One-Way ANOVA) (p<0.05). The Two-Way Analysis of Variance (Two-Way ANOVA) was used to evaluate the influence of two factors: restoration material and presence of coating. Coated restoration specimens (IXC and VFG) were sectioned perpendicular to the restoration surface and processed for SEM evaluation. Results No statistical differences in roughness could be noticed between groups or factors. Following microscopic observation, interfaces between restoration material and coating were better for group IXC than for group VFG. Conclusions When specimens are obtained simulating normal clinical procedures, the presence of surface protection does not significantly improve the surface roughness of GICs. PMID:24611090

Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment.

PubMed

Pacifici, Edoardo; Bossù, Maurizio; Giovannetti, Agostino; La Torre, Giuseppe; Guerra, Fabrizio; Polimeni, Antonella

2013-01-01

Even today, use of Glass Ionomer Cements (GIC) as restorative material is indicated for uncooperative patients. The study aimed at estimating the surface roughness of different GICs using or not their proprietary surface coatings and at observing the interfaces between cement and coating through SEM. Forty specimens have been obtained and divided into 4 groups: Fuji IX (IX), Fuji IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finishing Gloss (VFG). Samples were obtained using silicone moulds to simulate class I restorations. All specimens were processed for profilometric evaluation. The statistical differences of surface roughness between groups were assessed using One-Way Analysis of Variance (One-Way ANOVA) (p<0.05). The Two-Way Analysis of Variance (Two-Way ANOVA) was used to evaluate the influence of two factors: restoration material and presence of coating. Coated restoration specimens (IXC and VFG) were sectioned perpendicular to the restoration surface and processed for SEM evaluation. No statistical differences in roughness could be noticed between groups or factors. Following microscopic observation, interfaces between restoration material and coating were better for group IXC than for group VFG. When specimens are obtained simulating normal clinical procedures, the presence of surface protection does not significantly improve the surface roughness of GICs.

Effects of hydraulic roughness on surface textures of gravel‐bed rivers

USGS Publications Warehouse

Buffington, John M.; Montgomery, David R.

1999-01-01

Field studies of forest gravel‐bed rivers in northwestern Washington and southeastern Alaska demonstrate that bed‐surface grain size is responsive to hydraulic roughness caused by bank irregularities, bars, and wood debris. We evaluate textural response by comparing reach‐average median grain size (D50) to that predicted from the total bank‐full boundary shear stress (т0bf), representing a hypothetical reference condition of low hydraulic roughness. For a given т0bf, channels with progressively greater hydraulic roughness have systematically finer bed surfaces, presumably due to reduced bed shear stress, resulting in lower channel competence and diminished bed load transport capacity, both of which promote textural fining. In channels with significant hydraulic roughness, observed values D50 can be up to 90% smaller than those predicted from т0bf. We find that wood debris plays an important role at our study sites, not only providing hydraulic roughness but also influencing pool spacing, frequency of textural patches, and the amplitude and wavelength of bank and bar topography and their consequent roughness. Our observations also have biological implications. We find that textural fining due to hydraulic roughness can create usable salmonid spawning gravels in channels that otherwise would be too coarse.

EM Bias-Correction for Ice Thickness and Surface Roughness Retrievals over Rough Deformed Sea Ice

NASA Astrophysics Data System (ADS)

Li, L.; Gaiser, P. W.; Allard, R.; Posey, P. G.; Hebert, D. A.; Richter-Menge, J.; Polashenski, C. M.

2016-12-01

The very rough ridge sea ice accounts for significant percentage of total ice areas and even larger percentage of total volume. The commonly used Radar altimeter surface detection techniques are empirical in nature and work well only over level/smooth sea ice. Rough sea ice surfaces can modify the return waveforms, resulting in significant Electromagnetic (EM) bias in the estimated surface elevations, and thus large errors in the ice thickness retrievals. To understand and quantify such sea ice surface roughness effects, a combined EM rough surface and volume scattering model was developed to simulate radar returns from the rough sea ice `layer cake' structure. A waveform matching technique was also developed to fit observed waveforms to a physically-based waveform model and subsequently correct the roughness induced EM bias in the estimated freeboard. This new EM Bias Corrected (EMBC) algorithm was able to better retrieve surface elevations and estimate the surface roughness parameter simultaneously. In situ data from multi-instrument airborne and ground campaigns were used to validate the ice thickness and surface roughness retrievals. For the surface roughness retrievals, we applied this EMBC algorithm to co-incident LiDAR/Radar measurements collected during a Cryosat-2 under-flight by the NASA IceBridge missions. Results show that not only does the waveform model fit very well to the measured radar waveform, but also the roughness parameters derived independently from the LiDAR and radar data agree very well for both level and deformed sea ice. For sea ice thickness retrievals, validation based on in-situ data from the coordinated CRREL/NRL field campaign demonstrates that the physically-based EMBC algorithm performs fundamentally better than the empirical algorithm over very rough deformed sea ice, suggesting that sea ice surface roughness effects can be modeled and corrected based solely on the radar return waveforms.

Bioactive treatment promotes osteoblast differentiation on titanium materials fabricated by selective laser melting technology.

PubMed

Tsukanaka, Masako; Fujibayashi, Shunsuke; Takemoto, Mitsuru; Matsushita, Tomiharu; Kokubo, Tadashi; Nakamura, Takashi; Sasaki, Kiyoyuki; Matsuda, Shuichi

2016-01-01

Selective laser melting (SLM) technology is useful for the fabrication of porous titanium implants with complex shapes and structures. The materials fabricated by SLM characteristically have a very rough surface (average surface roughness, Ra=24.58 µm). In this study, we evaluated morphologically and biochemically the specific effects of this very rough surface and the additional effects of a bioactive treatment on osteoblast proliferation and differentiation. Flat-rolled titanium materials (Ra=1.02 µm) were used as the controls. On the treated materials fabricated by SLM, we observed enhanced osteoblast differentiation compared with the flat-rolled materials and the untreated materials fabricated by SLM. No significant differences were observed between the flat-rolled materials and the untreated materials fabricated by SLM in their effects on osteoblast differentiation. We concluded that the very rough surface fabricated by SLM had to undergo a bioactive treatment to obtain a positive effect on osteoblast differentiation.

Investigation of Wall Shear Stress Behavior for Rough Surfaces with Blowing

NASA Astrophysics Data System (ADS)

Helvey, Jacob; Borchetta, Colby; Miller, Mark; Martin, Alexandre; Bailey, Sean

2014-11-01

We present an experimental study conducted in a turbulent channel flow wind tunnel to determine the modifications made to the turbulent flow over rough surfaces with flow injection through the surfaces. Hot-wire profile results from a quasi-two-dimensional, sinusoidally-rough surface indicate that the effects of roughness are enhanced by momentum injection through the surface. In particular, the wall shear stress was found to show behavior consistent with increased roughness height when surface blowing was increased. This observed behavior contradicts previously reported results for regular three-dimensional roughness which show a decrease in wall shear stress with additional blowing. It is unclear whether this discrepancy is due to differences in the roughness geometry under consideration or the use of the Clauser fit to estimate wall shear stress. Additional PIV experiments are being conducted for a three-dimensional fibrous surface to obtain Reynolds shear stress profiles. These results provide an additional method for estimation of wall-shear stress and thus allow verification of the use of the Clauser chart approach for flows with momentum injection through the surface. This research is supported by NASA Kentucky EPSCoR Award NNX10AV39A, and NASA RA Award NNX13AN04A.

Investigation of ellipsometric parameters of 2D microrough surfaces by FDTD.

PubMed

Qiu, J; Ran, D F; Liu, Y B; Liu, L H

2016-07-10

Ellipsometry is a powerful method for measuring the optical constants of materials and is very sensitive to surface roughness. In previous ellipsometric measurement of optical constants of solid materials with rough surfaces, researchers frequently used effective medium approximation (EMA) with roughness already known to fit the complex refractive index of the material. However, the ignored correlation length, the other important parameter of rough surfaces, will definitely result in fitting errors. Hence it is necessary to consider the influence of surface roughness and correlation length on the ellipsometric parameters Δ (phase difference) and Ψ (azimuth) characterizing practical systems. In this paper, the influence of roughness of two-dimensional randomly microrough surfaces (relative roughness σ/λ ranges from 0.001 to 0.025) of silicon on ellipsometric parameters was simulated by the finite-difference time-domain method which was validated with experimental results. The effects of incident angle, relative roughness, and correlation length were numerically investigated for two-dimensional Gaussian distributed randomly microrough surfaces, respectively. The simulated results showed that compared with the smooth surface, only tiny changes of the ellipsometric parameter Δ could be observed for microrough silicon surface in the vicinity of the Brewster angle, but obviously changes of Ψ occur especially in the vicinity of the Brewster angle. More differences between the ellipsometric parameters of the rough surface and smooth surface can been seen especially in the vicinity of the Brewster angle as the relative roughness σ/λ increases or correlation length τ decreases. The results reveal that when we measure the optical constants of solid materials by ellipsometry, the smaller roughness, larger correlation length and larger incident wavelength will lead to the higher precision of measurements.

Numerical simulation of electroosmotic flow in rough microchannels using the lattice Poisson-Nernst-Planck methods

NASA Astrophysics Data System (ADS)

Kamali, Reza; Soloklou, Mohsen Nasiri; Hadidi, Hooman

2018-05-01

In this study, coupled Lattice Boltzmann method is applied to solve the dynamic model for an electroosmotic flow and investigate the effects of roughness in a 2-D flat microchannel. In the present model, the Poisson equation is solved for the electrical potential, the Nernst- Planck equation is solved for the ion concentration. In the analysis of electroosmotic flows, when the electric double layers fully overlap or the convective effects are not negligible, the Nernst-Planck equation must be used to find the ionic distribution throughout the microchannel. The effects of surface roughness height, roughness interval spacing and roughness surface potential on flow conditions are investigated for two different configurations of the roughness, when the EDL layers fully overlap through the microchannel. The results show that in both arrangements of roughness in homogeneously charged rough channels, the flow rate decreases by increasing the roughness height. A discrepancy in the mass flow rate is observed when the roughness height is about 0.15 of the channel width, which its average is higher for the asymmetric configuration and this difference grows by increasing the roughness height. In the symmetric roughness arrangement, the mass flow rate increases until the roughness interval space is almost 1.5 times the roughness width and it decreases for higher values of the roughness interval space. For the heterogeneously charged rough channel, when the roughness surface potential ψr is less than channel surface potential ψs , the net charge density increases by getting far from the roughness surface, while in the opposite situation, when ψs is more than ψr , the net charge density decreases from roughness surface to the microchannel middle center. Increasing the roughness surface potential induces stronger electric driving force on the fluid which results in larger velocities in the flow.

Fractal characterization and wettability of ion treated silicon surfaces

NASA Astrophysics Data System (ADS)

Yadav, R. P.; Kumar, Tanuj; Baranwal, V.; Vandana, Kumar, Manvendra; Priya, P. K.; Pandey, S. N.; Mittal, A. K.

2017-02-01

Fractal characterization of surface morphology can be useful as a tool for tailoring the wetting properties of solid surfaces. In this work, rippled surfaces of Si (100) are grown using 200 keV Ar+ ion beam irradiation at different ion doses. Relationship between fractal and wetting properties of these surfaces are explored. The height-height correlation function extracted from atomic force microscopic images, demonstrates an increase in roughness exponent with an increase in ion doses. A steep variation in contact angle values is found for low fractal dimensions. Roughness exponent and fractal dimensions are found correlated with the static water contact angle measurement. It is observed that after a crossover of the roughness exponent, the surface morphology has a rippled structure. Larger values of interface width indicate the larger ripples on the surface. The contact angle of water drops on such surfaces is observed to be lowest. Autocorrelation function is used for the measurement of ripple wavelength.

Comparative Study of Lunar Roughness from Multi - Source Data

NASA Astrophysics Data System (ADS)

Lou, Y.; Kang, Z.

2017-07-01

The lunar terrain can show its collision and volcanic history. The lunar surface roughness can give a deep indication of the effects of lunar surface magma, sedimentation and uplift. This paper aims to get different information from the roughness through different data sources. Besides introducing the classical Root-mean-square height method and Morphological Surface Roughness (MSR) algorithm, this paper takes the area of the Jurassic mountain uplift in the Sinus Iridum and the Plato Crater area as experimental areas. And then make the comparison and contrast of the lunar roughness derived from LRO's DEM and CE-2 DOM. The experimental results show that the roughness obtained by the traditional roughness calculation method reflect the ups and downs of the topography, while the results obtained by morphological surface roughness algorithm show the smoothness of the lunar surface. So, we can first use the surface fluctuation situation derived from RMSH to select the landing area range which ensures the lands are gentle. Then the morphological results determine whether the landing area is suitable for the detector walking and observing. The results obtained at two different scales provide a more complete evaluation system for selecting the landing site of the lunar probe.

Degree of Ice Particle Surface Roughness Inferred from Polarimetric Observations

NASA Technical Reports Server (NTRS)

Hioki, Souichiro; Yang, Ping; Baum, Bryan A.; Platnick, Steven; Meyer, Kerry G.; King, Michael D.; Riedi, Jerome

2016-01-01

The degree of surface roughness of ice particles within thick, cold ice clouds is inferred from multidirectional, multi-spectral satellite polarimetric observations over oceans, assuming a column-aggregate particle habit. An improved roughness inference scheme is employed that provides a more noise-resilient roughness estimate than the conventional best-fit approach. The improvements include the introduction of a quantitative roughness parameter based on empirical orthogonal function analysis and proper treatment of polarization due to atmospheric scattering above clouds. A global 1-month data sample supports the use of a severely roughened ice habit to simulate the polarized reflectivity associated with ice clouds over ocean. The density distribution of the roughness parameter inferred from the global 1- month data sample and further analyses of a few case studies demonstrate the significant variability of ice cloud single-scattering properties. However, the present theoretical results do not agree with observations in the tropics. In the extra-tropics, the roughness parameter is inferred but 74% of the sample is out of the expected parameter range. Potential improvements are discussed to enhance the depiction of the natural variability on a global scale.

Comparative bone tissue integration of nanostructured and microroughened dental implants.

PubMed

Salou, Laëtitia; Hoornaert, Alain; Stanovici, Julien; Briand, Sylvain; Louarn, Guy; Layrolle, Pierre

2015-01-01

The aim was to compare osteointegration of nanostructured implants to a microsurface widely used for titanium dental implants. Commercial titanium dental implants with smooth or microroughened surfaces were nanostructured. Implants were inserted into the femoral condyles of rabbits. After 2 and 4 weeks, histomorphometry calculation was performed. Nanotubes measuring 60 nm in diameter were observed on both S-NANO (roughness: 0.05 μm) and R-NANO (roughness: 0.40 μm) surfaces. The MICRO surface exhibited typical random cavities (roughness: 2.09 μm). At 4 weeks, bone-to-implant contact values were significantly higher for the R-NANO than for the MICRO surface while no differences were observed at 2 weeks. Overall, this study shows that the nanostructured surfaces improved osteointegration similar or higher than the MICRO.

2D scaling behavior of nanotextured GaN surfaces: A case study of hillocked and terraced surfaces

NASA Astrophysics Data System (ADS)

Mutta, Geeta Rani; Carapezzi, Stefania

2018-07-01

The 2D scaling properties of GaN surfaces have been studied by means of the 2D height-height correlation function (HHCF). The GaN layers under investigation presented exemplar morphologies, generated by distinct growth methods: a molecular beam epitaxy (MBE) grown surface decorated by hillocks and a metal organic vapor phase epitaxy (MOVPE) grown surface with terraced structure. The 2D statistical analysis of these surfaces has allowed assessing quantitatively the degree of morphological variability along all the different directions across each surface, their corresponding roughness exponents and correlation lengths. A scaling anisotropy as well as correlation length anisotropy has been detected for both hillocked and terraced surfaces. Especially, a marked dependence of correlation length from the direction across the terraced surface has been observed. Additionally, the terraced surfaces showed the lower root mean square (RMS) roughness value and at the same time, the lower roughness exponent value. This could appear as a contradiction, given that a low RMS value is associated to a smooth surface, and usually the roughness exponent is interpreted as a "measure" of the smoothness of the surface, the smoother the surface, the higher (approaching the unity) is the roughness exponent. Our case study is an experimental demonstration in which the roughness exponent should be, more appropriately, interpreted as a quantification of how the roughness changes with length scale.

Optical mapping of surface roughness by implementation of a spatial light modulator

NASA Astrophysics Data System (ADS)

Aulbach, Laura; Pöller, Franziska; Lu, Min; Wang, Shengjia; Koch, Alexander W.

2017-08-01

It is well-known that the surface roughness of materials plays an important role in the operation and performance of technological systems. The roughness influences key parameters, such as friction and wear, and is directly connected to the functionality and durability of the respective system. Tactile methods are widely used for the measurement of surface roughness, but a destructive measurement procedure and the lack of feasibility of online monitoring are crucial drawbacks. In the last decades, several non-contact, usually optical systems for surface roughness measurements have been developed, e.g., white light interferometry, light scatter analysis, or speckle correlation. These techniques are in turn often unable to assign the roughness to a certain surface area or involve inappropriate adjustment procedures. One promising and straightforward optical measurement method is the surface roughness measurement by analyzing the fringe visibility of an interferometric fringe pattern. In our work, we employed a spatial light modulator in the interferometric setup to vary the fringe visibility and provide a stable and reliable measurement system. In previous research, either the averaged fringe visibility or the fringe visibility along a defined observation profile were analyzed. In this article, the analysis of the fringe visibility is extended to generate a complete roughness map of the measurement target. Thus, surface defects or areas of different roughness can be easily located.

Surface and Basal Roughness in Radar Sounding Data: Obstacle and Opportunity

NASA Astrophysics Data System (ADS)

Schroeder, D. M.; Grima, C.; Haynes, M.

2015-12-01

The surface and basal roughness of glaciers, ice sheets, and ice shelves can pose a significant obstacle to the visual interpretation and quantitative analysis of radar sounding data. Areas of high surface roughness - including grounding zones, shear margins, and crevasse fields - can produce clutter and side-lobe signals that obscure the interpretation of englacial and subglacial features. These areas can also introduce significant variation in bed echo strength profiles as a result of losses from two-way propagation through rough ice surfaces. Similarly, reflections from rough basal interfaces beneath ice sheets and ice shelves can also result in large, spatially variable losses in bed echo power. If unmitigated and uncorrected, these effects can degrade or prevent the definitive interpretation of material and geometric properties at the base of ice sheets and ice shelves using radar reflectivity and bed echo character. However, these effects also provide geophysical signatures of surface and basal interface character - including surface roughness, firn density, subglacial bedform geometry, ice shelf basal roughness, marine-ice/brine detection, and crevasse geometry - that can be observed and constrained by exploiting roughness effects in radar sounding data. We present a series of applications and approaches for characterizing and correcting surface and basal roughness effects for airborne radar sounding data collected in Antarctica. We also present challenges, insights, and opportunities for extending these techniques to the orbital radar sounding of Europa's ice shell.

Surface roughness of polyvinyl siloxane impression materials following chemical disinfection, autoclave and microwave sterilization.

PubMed

Al Kheraif, Abdulaziz Abdullah

2013-05-01

Autoclave sterilization and microwave sterilization has been suggested as the effective methods for the disinfection of elastomeric impressions, but subjecting elastomeric impressions to extreme temperature may have adverse effects on critical properties of the elastomers. To evaluate the effect of chemical disinfection as well as autoclave and microwave sterilization on the surface roughness of elastomeric impression materials. The surface roughness of five commercially available polyvinyl siloxane impression materials (Coltene President, Affinis Perfect impression, Aquasil, 3M ESPE Express and GC Exafast) were evaluated after subjecting them to chemical disinfection, autoclaving and microwave sterilization using a Talysurf Intra 50 instrument. Twenty specimens from each material were fabricated and divided into four equal groups, three experimental and one control (n=25). The differences in the mean surface roughness between the treatment groups were recorded and statistically analyzed. No statistically significant increase in the surface roughness was observed when the specimens were subjected to chemical disinfection and autoclave sterilization, increase in roughness and discoloration was observed in all the materials when specimens were subjected to microwave sterilization. Chemical disinfection did not have a significant effect but, since it is less effective, autoclave sterilization can be considered effective and autoclaving did not show any specimen discoloration as in microwave sterilization. Microwave sterilization may be considered when impressions are used to make diagnostic casts. A significant increase in surface roughness may produce rougher casts, resulting in rougher tissue surfaces for denture and cast restorations. Autoclave sterilization of vinyl polysiloxane elastomeric impressions for 5 minutes at 134°C at 20 psi may be considered an effective method over chemical disinfection and microwave sterilization, because chemical disinfection does not eliminate all disease-causing microorganisms and microwave sterilization leads to a rougher impression surface.

The influence of surface roughness of deserts on the July circulation - A numerical study

NASA Technical Reports Server (NTRS)

Sud, Y. C.; Smith, W. E.

1985-01-01

The effect of the low surface roughness characteristics of deserts on atmospheric circulation in July is examined using numerical simulations with the GCM of the Goddard Laboratory for Atmospheric Science (GLAS). Identical sets of simulations were carried out with the model starting from the initial state of the atmosphere on June 15, for the years 1979 and 1980. The first simulation included a surface roughness factor of 45 cm, and the second set had a surface roughness factor of 0.02 cm for desert regions, and 45 cm for all other land. A comparative analysis of the numerical data was carried out in order to study the variations for the desert regions. It is shown that rainfall in the Sahara desert was reduced significantly in the data set with the nonuniform surface roughness factor in comparison with the other data set. The inter-tropical convergence zone (ITCZ) moved southward to about 15 degrees, which was close to its observed location at about 10 degrees N. In other deserts, the North American Great Plains, Rajputana in India, and the Central Asian desert, no similar changes were observed. Detailed contour maps of the weather conditions in the different desert regions are provided.

The observation of the physicochemical change of rock under freeze-thawing experiment: CLSM, XRD and ICP analysis

NASA Astrophysics Data System (ADS)

Choi, J.; Chae, B.; Chon, C.; Jeong, J.

2013-12-01

Abstract : In order to understand the progress of the physical weathering of rock sample, we managed freeze-thawing experiment at temperature of up to 40C from -20C taking into account of South Korea. In this study, the time was held by two hours the temperature of the maximum (40C) and minimum (-20C) and the experiments were carried out at intervals of one hour rising and falling. We have run the experiment about 120 cycle with the cycle of -20C from 40C experiment. We measured the physical properties of rock samples after each 20 cycle has elapsed by using confocal laser scanning microscope (CLSM) and observed changes in roughness of rock samples surface. We also analyzed the mineral of rock sample using the XRD analysis and observing the change in chemical composition of solution used in the experiment by using ICP analysis. Through the above process, we observed physico-chemical changes in the rock sample due to freeze-thaw cycles. To analysis of the line roughness parameter we used set by the 10 vertical and horizontal cross section line on the surface and surface roughness parameter was analyzed by using the area on the surface. Through such a process, while the freeze-thawing experiment is advanced, it was studied how the physical roughness and chemical composition were changed. As a result, it was possible to observe a change in the mineral component of the particular dissolved in the solution and it was able to observe the characteristic changes of the parameters of the roughness of the lines and surfaces.

Contribution of Nano- to Microscale Roughness to Heterogeneity: Closing the Gap between Unfavorable and Favorable Colloid Attachment Conditions.

PubMed

Rasmuson, Anna; Pazmino, Eddy; Assemi, Shoeleh; Johnson, William P

2017-02-21

Surface roughness has been reported to both increase as well as decrease colloid retention. In order to better understand the boundaries within which roughness operates, attachment of a range of colloid sizes to glass with three levels of roughness was examined under both favorable (energy barrier absent) and unfavorable (energy barrier present) conditions in an impinging jet system. Smooth glass was found to provide the upper and lower bounds for attachment under favorable and unfavorable conditions, respectively. Surface roughness decreased, or even eliminated, the gap between favorable and unfavorable attachment and did so by two mechanisms: (1) under favorable conditions attachment decreased via increased hydrodynamic slip length and reduced attraction and (2) under unfavorable conditions attachment increased via reduced colloid-collector repulsion (reduced radius of curvature) and increased attraction (multiple points of contact, and possibly increased surface charge heterogeneity). Absence of a gap where these forces most strongly operate for smaller (<200 nm) and larger (>2 μm) colloids was observed and discussed. These observations elucidate the role of roughness in colloid attachment under both favorable and unfavorable conditions.

Radar characteristics of Viking 1 landing sites

USGS Publications Warehouse

Tyler, G.L.; Campbell, D.B.; Downs, G.S.; Green, R.R.; Moore, H.J.

1976-01-01

Radar observations of Mars at centimeter wavelengths in May, June, and July 1976 provided estimates of surface roughness and reflectivity in three potential landing areas for Viking 1. Surface roughness is characterized by the distribution of surface landing slopes or tilts on lateral scales of the order of 1 to 10 meters; measurements of surface reflectivity are indicators of bulk surface density in the uppermost few centimeters. By these measures, the Viking 1 landing site at 47.5??W, 22.4??N is rougher than the martian average, although it may be near the martian average for elevations accessible to Viking, and is estimated to be near the Mars average in reflectivity. The AINW site at the center of Chryse Planitia, 43.5??W, 23.4??N, may be an area of anomalous radar characteristics, indicative of extreme, small-scale roughness, very low surface density, or a combination of these two characteristics. Low signal-to-noise ratio observations of the original Chryse site at 34??W, 19.5??N indicate that that area is at least twice as rough as the Mars average.

Retrieval of Soil Moisture and Roughness from the Polarimetric Radar Response

NASA Technical Reports Server (NTRS)

Sarabandi, Kamal; Ulaby, Fawwaz T.

1997-01-01

The main objective of this investigation was the characterization of soil moisture using imaging radars. In order to accomplish this task, a number of intermediate steps had to be undertaken. In this proposal, the theoretical, numerical, and experimental aspects of electromagnetic scattering from natural surfaces was considered with emphasis on remote sensing of soil moisture. In the general case, the microwave backscatter from natural surfaces is mainly influenced by three major factors: (1) the roughness statistics of the soil surface, (2) soil moisture content, and (3) soil surface cover. First the scattering problem from bare-soil surfaces was considered and a hybrid model that relates the radar backscattering coefficient to soil moisture and surface roughness was developed. This model is based on extensive experimental measurements of the radar polarimetric backscatter response of bare soil surfaces at microwave frequencies over a wide range of moisture conditions and roughness scales in conjunction with existing theoretical surface scattering models in limiting cases (small perturbation, physical optics, and geometrical optics models). Also a simple inversion algorithm capable of providing accurate estimates of soil moisture content and surface rms height from single-frequency multi-polarization radar observations was developed. The accuracy of the model and its inversion algorithm is demonstrated using independent data sets. Next the hybrid model for bare-soil surfaces is made fully polarimetric by incorporating the parameters of the co- and cross-polarized phase difference into the model. Experimental data in conjunction with numerical simulations are used to relate the soil moisture content and surface roughness to the phase difference statistics. For this purpose, a novel numerical scattering simulation for inhomogeneous dielectric random surfaces was developed. Finally the scattering problem of short vegetation cover above a rough soil surface was considered. A general scattering model for grass-blades of arbitrary cross section was developed and incorporated in a first order random media model. The vegetation model and the bare-soil model are combined and the accuracy of the combined model is evaluated against experimental observations from a wheat field over the entire growing season. A complete set of ground-truth data and polarimetric backscatter data were collected. Also an inversion algorithm for estimating soil moisture and surface roughness from multi-polarized multi-frequency observations of vegetation-covered ground is developed.

The In vitro Evaluation of the effect of xyliwhite, probiotic, and the conventional toothpastes on the enamel roughness and microhardness.

PubMed

Maden, E Arat; Altun, C; Polat, G Guven; Basak, F

2018-03-01

The aim of this study was to evaluate the effect of fluoride, Xylitol, Probiotic, and Whitening toothpastes on the permanent teeth enamel roughness and microhardness. One hundred and twenty teeth were randomly divided into 2 groups, each group having 60 samples. G1: The group in which enamel roughness was examined (n = 60). G2: The group in which enamel microhardness was examined (n = 60). Then, these groups were randomly divided into 4 groups among themselves (n = 15). Each group was brushed using four different toothpastes for 1 week with a battery-powered toothbrush in the morning and evening for 2 min. Vicker's hardness tester was used to measure the changes in microhardness, and the profilometer was used to measure the changes in surface roughness. No statistically significant differences were found on surface roughness and microhardness values measured after tooth brushing process in group brushed with Colgate MaxFresh toothpaste (P > 0.01). Statistically significant decrease was observed on Vicker's hardness values measured after tooth brushing process in groups brushed with Ipana White Power Carbonate toothpaste, Xyliwhite Toothpaste Gel, and Periobiotic Probiotic Toothpaste (P < 0.01). Statistically significant increase was observed on surface roughness values in groups brushed with Ipana White Power Carbonate toothpaste, Xyliwhite Toothpaste Gel, Periobiotic Probiotic Toothpaste (P < 0.01). As a result, Colgate MaxFresh abrasive-free toothpaste with fluoride has no effect on permanent tooth enamel surface roughness and microhardness. Xyliwhite, Periobiotic, and Ipana White Power Carbonate-containing abrasive toothpastes led to changes negatively on permanent tooth enamel surface roughness and microhardness.

Effect of surface roughness on the heating rates of large-angled hypersonic blunt cones

NASA Astrophysics Data System (ADS)

Irimpan, Kiran Joy; Menezes, Viren

2018-03-01

Surface-roughness caused by the residue of an ablative Thermal Protection System (TPS) can alter the turbulence level and surface heating rates on a hypersonic re-entry capsule. Large-scale surface-roughness that could represent an ablated TPS, was introduced over the forebody of a 120° apex angle blunt cone, in order to test for its influence on surface heating rates in a hypersonic freestream of Mach 8.8. The surface heat transfer rates measured on smooth and roughened models under the same freestream conditions were compared. The hypersonic flow-fields of the smooth and rough-surfaced models were visualized to analyse the flow physics. Qualitative numerical simulations and pressure measurements were carried out to have an insight into the high-speed flow physics. Experimental observations under moderate Reynolds numbers indicated a delayed transition and an overall reduction of 17-46% in surface heating rates on the roughened model.

Effect of multiple autoclave cycles on the surface roughness of HyFlex CM and HyFlex EDM files: an atomic force microscopy study.

PubMed

Yılmaz, K; Uslu, G; Özyürek, T

2018-02-13

To compare the effect of autoclave cycles on the surface topography and roughness of HyFlex CM and HyFlex EDM instruments using atomic force microscopy (AFM) analysis. Eight new files of each brand were subdivided into four subgroups (n = 2/each subgroup). One group was allocated as the control group and not subjected to autoclave sterilization. The other three groups were subjected to different numbers (1, 5, and 10) of autoclave sterilization cycles. After the cycle instruments were subjected to AFM analysis. Roughness average (Ra) and the root mean square (RMS) values were chosen to investigate the surface features of endodontic files. The data was analyzed using one-way ANOVA and post hoc Tamhane tests at 5% significant level. The lowest Ra and RMS values were observed in the HyFlex EDM files that served as the control and in those subjected to a single cycle of autoclave sterilization (P < 0.05). The highest Ra and RMS values were observed in the HyFlex CM and HyFlex EDM files that were subjected to 10 cycles of autoclave sterilization (P < 0.05). The surface roughness values of the HyFlex CM group showed a significant increase after ten autoclave cycles, whereas those of the HyFlex EDM group exhibited a significant change after five autoclave cycles (P < 0.05). Although the initial surface roughness values of the HyFlex EDM files were lower than those of the HyFlex CM files, the surface roughness values of the EDM files showed a statistically significant increase after 5 cycles of autoclave sterilization. In contrast, the surface roughness values of the HyFlex CM files did not increase until 10 cycles of autoclave sterilization. Present study indicated that autoclave sterilization negatively affected the surface roughness of the tested NiTi files.

Stability of micro-Cassie states on rough substrates

NASA Astrophysics Data System (ADS)

Guo, Zhenjiang; Liu, Yawei; Lohse, Detlef; Zhang, Xuehua; Zhang, Xianren

2015-06-01

We numerically study different forms of nanoscale gaseous domains on a model for rough surfaces. Our calculations based on the constrained lattice density functional theory show that the inter-connectivity of pores surrounded by neighboring nanoposts, which model the surface roughness, leads to the formation of stable microscopic Cassie states. We investigate the dependence of the stability of the micro-Cassie states on substrate roughness, fluid-solid interaction, and chemical potential and then address the differences between the origin of the micro-Cassie states and that of surface nanobubbles within similar models. Finally, we show that the micro-Cassie states share some features with experimentally observed micropancakes at solid-water interfaces.

Effects of ice crystal surface roughness and air bubble inclusions on cirrus cloud radiative properties from remote sensing perspective

NASA Astrophysics Data System (ADS)

Tang, Guanglin; Panetta, R. Lee; Yang, Ping; Kattawar, George W.; Zhai, Peng-Wang

2017-07-01

We study the combined effects of surface roughness and inhomogeneity on the optical scattering properties of ice crystals and explore the consequent implications to remote sensing of cirrus cloud properties. Specifically, surface roughness and inhomogeneity are added to the Moderate Resolution Imaging Spectroradiometer (MODIS) collection 6 (MC6) cirrus cloud particle habit model. Light scattering properties of the new habit model are simulated using a modified version of the Improved Geometric Optics Method (IGOM). Both inhomogeneity and surface roughness affect the single scattering properties significantly. In visible bands, inhomogeneity and surface roughness both tend to smooth the phase function and eliminate halos and the backscattering peak. The asymmetry parameter varies with the degree of surface roughness following a U shape - decreases and then increases - with a minimum at around 0.15, whereas it decreases monotonically with the air bubble volume fraction. Air bubble inclusions significantly increase phase matrix element -P12 for scattering angles between 20°-120°, whereas surface roughness has a much weaker effect, increasing -P12 slightly from 60°-120°. Radiative transfer simulations and cirrus cloud property retrievals are conducted by including both the factors. In terms of surface roughness and air bubble volume fraction, retrievals of cirrus cloud optical thickness or the asymmetry parameter using solar bands show similar patterns of variation. Polarimetric simulations using the MC6 cirrus cloud particle habit model are shown to be more consistent with observations when both surface roughness and inhomogeneity are simultaneously considered.

Speckle patterns produced by an optical vortex and its application to surface roughness measurements.

PubMed

Passos, M H M; Lemos, M R; Almeida, S R; Balthazar, W F; da Silva, L; Huguenin, J A O

2017-01-10

In this work, we report on the analysis of speckle patterns produced by illuminating different rough surfaces with an optical vortex, a first-order (l=1) Laguerre-Gaussian beam. The generated speckle patterns were observed in the normal direction exploring four different planes: the diffraction plane, image plane, focal plane, and exact Fourier transform plane. The digital speckle patterns were analyzed using the Hurst exponent of digital images, an interesting tool used to study surface roughness. We show a proof of principle that the Hurst exponent of a digital speckle pattern is more sensitive with respect to the surface roughness when the speckle pattern is produced by an optical vortex and observed at a focal plane. We also show that Hurst exponents are not so sensitive with respect to the topological charge l. These results open news possibilities of investigation into speckle metrology once we have several techniques that use speckle patterns for different applications.

An Investigation of the Influence of Initial Roughness on the Friction and Wear Behavior of Ground Surfaces

PubMed Central

Liang, Guoxing; Schmauder, Siegfried; Lyu, Ming; Schneider, Yanling; Zhang, Cheng; Han, Yang

2018-01-01

Friction and wear tests were performed on AISI 1045 steel specimens with different initial roughness parameters, machined by a creep-feed dry grinding process, to study the friction and wear behavior on a pin-on-disc tester in dry sliding conditions. Average surface roughness (Ra), root mean square (Rq), skewness (Rsk) and kurtosis (Rku) were involved in order to analyse the influence of the friction and wear behavior. The observations reveal that a surface with initial roughness parameters of higher Ra, Rq and Rku will lead to a longer initial-steady transition period in the sliding tests. The plastic deformation mainly concentrates in the depth of 20–50 μm under the worn surface and the critical plastic deformation is generated on the rough surface. For surfaces with large Ra, Rq, low Rsk and high Rku values, it is easy to lose the C element in, the reciprocating extrusion. PMID:29401703

Global Scale Simultaneous Retrieval of Smoothened Vegetation Optical Depth and Surface Roughness Parameter using AMSR-E X-band Observations

NASA Astrophysics Data System (ADS)

Lanka, Karthikeyan; Pan, Ming; Konings, Alexandra; Piles, María; D, Nagesh Kumar; Wood, Eric

2017-04-01

Traditionally, passive microwave retrieval algorithms such as Land Parameter Retrieval Model (LPRM) estimate simultaneously soil moisture and Vegetation Optical Depth (VOD) using brightness temperature (Tb) data. The algorithm requires a surface roughness parameter which - despite implications - is generally assumed to be constant at global scale. Due to inherent noise in the satellite data and retrieval algorithm, the VOD retrievals are usually observed to be highly fluctuating at daily scale which may not occur in reality. Such noisy VOD retrievals along with spatially invariable roughness parameter may affect the quality of soil moisture retrievals. The current work aims to smoothen the VOD retrievals (with an assumption that VOD remains constant over a period of time) and simultaneously generate, for the first time, global surface roughness map using multiple descending X-band Tb observations of AMSR-E. The methodology utilizes Tb values under a moving-time-window-setup to estimate concurrently the soil moisture of each day and a constant VOD in the window. Prior to this step, surface roughness parameter is estimated using the complete time series of Tb record. Upon carrying out the necessary sensitivity analysis, the smoothened VOD along with soil moisture retrievals is generated for the 10-year duration of AMSR-E (2002-2011) with a 7-day moving window using the LPRM framework. The spatial patterns of resulted global VOD maps are in coherence with vegetation biomass and climate conditions. The VOD results also exhibit a smoothening effect in terms of lower values of standard deviation. This is also evident from time series comparison of VOD and LPRM VOD retrievals without optimization over moving windows at several grid locations across the globe. The global surface roughness map also exhibited spatial patterns that are strongly influenced by topography and land use conditions. Some of the noticeable features include high roughness over mountainous regions and heavily vegetated tropical rainforests, low roughness in desert areas and moderate roughness value over higher latitudes. The new datasets of VOD and surface roughness can help improving the quality of soil moisture retrievals. Also, the methodology proposed is generic by nature and can be implemented over currently operating AMSR2, SMOS, and SMAP soil moisture missions.

Characterising soil surface roughness with a frequency modulated polarimetric radar

NASA Astrophysics Data System (ADS)

Seeger, Manuel; Gronz, Oliver; Beiske, Joshua; Klein, Tobias

2014-05-01

Soil surface roughness is considered crucial for soil erosion as it determines the effective surface exposed to the raindrop impact. It regulates surface runoff velocity and it causes runoff concentration. But a comprehensive characterisation of the shape of the soils' surface is still difficult to achieve. Photographic systems and terrestrial laser-scanning are nowadays able to generate high resolution DEMs, but the derivation of roughness parameters is still not clear. Spaceborne radar systems are used for about 3 decades for earth survey. Spatial soil moisture distribution, ice sheet monitoring and earth-wide topographic survey are the main objectives of these radar systems, working generally with frequencies <10 GHz. Contrasting with this, technologies emitting frequencies up to 77 GHz are generally used for object tracking purposes. But it is known, that the reflection characteristics, such as intensity and polarisation, strongly depend on the properties of the target object. A new design of a frequency modulated continuous wave radar, emitting a right hand shaped circular polarization and receiving both polarization directions, right and left-hand shaped, is tested here for its ability to detect and quantify different surface roughness. The reflection characteristics of 4 different materials 1) steel, 2) sand (0,5-1 mm), 3) fine (2-4 mm) and 4) coarse (15-30 mm) rock-fragments and different roughness as well as moisture content are analysed. In addition, the signals are taken at 2 different angles to the soil's surface (90° and 70°). For quantification of the roughness, a photographic method (Structure-from-Motion) is applied to generate a detailed DEM and random roughness (RR) is calculated. To characterise the radar signal, different ratios of the reflected channels and polarisations are calculated. The signals show differences for all substrates, also clearly visible between sand and fine rock fragments, despite a wavelength of 1 cm of the electromagnetic waves. A systematic change of the signals with changing roughness is also observed. Measurements show a significant influence of the angle of observation. Soil moisture shows also an influence on the reflected signal, but is quite well differentiable to the effects of the shape of the soil's surface. The results show that polarimetric radar technology may be suitable to characterise the surface of soils, but still faces a big lack of knowledge on how to quantify and differentiate the different signals, how to handle variable observation angles, and finally how to characterise roughness.

Dust lifting in GEM-Mars using a roughness length map

NASA Astrophysics Data System (ADS)

Daerden, F.; Neary, L.; Whiteway, J. A.; Hébrard, E.

2013-09-01

Lifting of size distributed dust due to surface wind stress and dust devils has been implemented in the GEM-Mars 3D-GCM. It turned out that a detailed surface roughness length map was necessary to bring the simulated dust opacities in accordance with observations.

Interaction of Waves and Currents.

DTIC Science & Technology

1983-03-01

glitter due to the greater surface roughness on the current. This surface roughness has value in remote sensing, particularly when infrared observations...34Pneumatic Breakwaters to Protect Dredges," Journal of Waterways and Harbors Division, Vol. 87, No. WW2 , May 1961, pp. 67- 87. Discussion 87 (Nov.) 127

Derivation of Mars Surface Scattering Properties from OMEGA Spot Pointing Observations

NASA Astrophysics Data System (ADS)

Pinet, P. C.; Daydou, Y.; Cord, A.; Chevrel, S. C.; Poulet, F.; Erard, S.; Bibring, J.-P.; Langevin, Y.; Melchiorri, R.; Bellucci, G.; Altieri, F.; Arvidson, R. E.; OMEGA Co-Investigator Team

2005-03-01

OMEGA emission phase function (EPF) observation shows that one may access from orbit to geology-driven surface scattering properties such as surface roughness. It has implications for spectroscopic interpretation and for CRISM observations to come.

Unveiling the mechanisms of dressed-photon-phonon etching based on hierarchical surface roughness measure

NASA Astrophysics Data System (ADS)

Naruse, Makoto; Yatsui, Takashi; Nomura, Wataru; Kawazoe, Tadashi; Aida, Masaki; Ohtsu, Motoichi

2013-02-01

Dressed-photon-phonon (DPP) etching is a disruptive technology in planarizing material surfaces because it completely eliminates mechanical contact processes. However, adequate metrics for evaluating the surface roughness and the underlying physical mechanisms are still not well understood. Here, we propose a two-dimensional hierarchical surface roughness measure, inspired by the Allan variance, that represents the effectiveness of DPP etching while conserving the original two-dimensional surface topology. Also, we build a simple physical model of DPP etching that agrees well with the experimental observations, which clearly shows the involvement of the intrinsic hierarchical properties of dressed photons, or optical near-fields, in the surface processing.

Study on surface roughness evolvement of Nd-doped phosphate glass after IBF

NASA Astrophysics Data System (ADS)

Li, Furen; Xie, Xuhui; Zhou, Lin; Tie, Guipeng; Hu, Hao

2016-10-01

Nd doped phosphate glass is widely used as gain media in high power laser system. It is traditionally polished with the annular polishing technology. The edge effect is inevitable in annular polishing process and it results in the low manufacturing efficiency. Ion Beam Figuring (IBF) is a highly deterministic, non-contact method for the ultra-precision optics fabrication. So the edge effect is avoided. Nanometer and sub-nanometer precision is realizable in IBF. In this paper, Nd doped phosphate glass was polished with IBF, and the evolvement of surface roughness was emphasized. The roughness of surface polished with ion beam at normal and oblique incidence was researched. The oblique incident angle was 45°. The surface roughness was measured with the white light interferometer. No evident change was observed. This means that the pre-finish roughness can be preserved in IBF. The results denote that IBF is a feasible method to correct the contour errors of Nd doped phosphate glass, and the roughness will not be coarsened.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Praveen Kumar, E-mail: praveenyadav@rrcat.gov.in; Nayak, Maheswar; Rai, Sanjay Kumar

The authors report the effect of argon ion to molybdenum atom ratio (r) on the microstructure of low energy (70 eV) argon ion assisted electron beam evaporated Mo thin films. Surface roughness, morphology, and crystallinity of Mo films are found to strongly depend on “r.” Increase of “r” from 0 to 100 induces gradual loss in crystallinity, reduction in surface roughness and systematic increase in density of the film. For “r” ∼ 100, average atomic density of the film approaches the bulk value (97%) with lowest surface roughness. Further, increasing “r” up to 170 reduces the atomic density, increases roughness, and increase inmore » crystallinity induced by low energy Ar ion beam. The observed surface roughness and grain size determined by x-ray reflectivity and glancing incidence x-ray diffraction correlate well with atomic force microscopy measurements. This study demonstrates that for r = 100 one gets lowest roughness Mo film with highest density and nearly amorphous microstructure. The growth model is discussed by structural zone model.« less

Sea ice roughness: the key for predicting Arctic summer ice albedo

NASA Astrophysics Data System (ADS)

Landy, J.; Ehn, J. K.; Tsamados, M.; Stroeve, J.; Barber, D. G.

2017-12-01

Although melt ponds on Arctic sea ice evolve in stages, ice with smoother surface topography typically allows the pond water to spread over a wider area, reducing the ice-albedo and accelerating further melt. Building on this theory, we simulated the distribution of meltwater on a range of statistically-derived topographies to develop a quantitative relationship between premelt sea ice surface roughness and summer ice albedo. Our method, previously applied to ICESat observations of the end-of-winter sea ice roughness, could account for 85% of the variance in AVHRR observations of the summer ice-albedo [Landy et al., 2015]. Consequently, an Arctic-wide reduction in sea ice roughness over the ICESat operational period (from 2003 to 2008) explained a drop in ice-albedo that resulted in a 16% increase in solar heat input to the sea ice cover. Here we will review this work and present new research linking pre-melt sea ice surface roughness observations from Cryosat-2 to summer sea ice albedo over the past six years, examining the potential of winter roughness as a significant new source of sea ice predictability. We will further evaluate the possibility for high-resolution (kilometre-scale) forecasts of summer sea ice albedo from waveform-level Cryosat-2 roughness data in the landfast sea ice zone of the Canadian Arctic. Landy, J. C., J. K. Ehn, and D. G. Barber (2015), Albedo feedback enhanced by smoother Arctic sea ice, Geophys. Res. Lett., 42, 10,714-10,720, doi:10.1002/2015GL066712.

Deviation characteristics of specular reflectivity of micro-rough surface from Fresnel's equation

NASA Astrophysics Data System (ADS)

Zhang, W. J.; Qiu, J.; Liu, L. H.

2015-07-01

Specular reflectivity is an important radiative property in thermal engineering applications and reflection-based optical constant determinations, yet it will be influenced by surface micro-roughness which cannot be completely removed during the polishing process. In this work, we examined the deviation characteristics of the specular reflectivity of micro-rough surfaces from that predicted by the Fresnel's equation under the assumption of smooth surface. The effects of incident angle and relative roughness were numerically investigated for both 1D and 2D micro randomly rough surfaces using full wave analysis under the condition that the relative roughness is smaller than 0.05. For transverse magnetic (TM) wave incidence, it is observed that the deviation of specular reflectivity dramatically rises as the incident angle approaches to the pseudo Brewster's angle, which violates the prediction based on Rayleigh criterion. While for the transverse electric (TE) wave incidence, the deviation of the specular reflectivity is much smaller and decreases monotonically with the increase of incident angle, which agrees with the predication from Rayleigh criterion. Generally, the deviation of specular reflectivity for both TM and TE increases with the relative roughness as commonly expected.

Phase formation in selected surface-roughened plasma-nitrided 304 austenite stainless steel.

PubMed

Singh, Gajendra Prasad; Joseph, Alphonsa; Raole, Prakash Manohar; Barhai, Prema Kanta; Mukherjee, Subroto

2008-04-01

Direct current (DC) glow discharge plasma nitriding was carried out on three selected surface-roughened AISI 304 stainless steel samples at 833 K under 4 mbar pressures for 24 h in the presence of N 2 :H 2 gas mixtures of 50 : 50 ratios. After plasma nitriding, the phase formation, case depth, surface roughness, and microhardness of a plasma-nitrided layer were evaluated by glancing angle x-ray diffractogram, optical microscope, stylus profilometer, and Vickers microhardness tester techniques. The case depth, surface hardness, and phase formation variations were observed with a variation in initial surface roughness. The diffraction patterns of the plasma-nitrided samples showed the modified intensities of the α and γ phases along with those of the CrN, Fe 4 N, and Fe 3 N phases. Hardness and case depth variations were observed with a variation in surface roughness. A maximum hardness of 1058 Hv and a case depth of 95 μm were achieved in least surface-roughened samples.

Silica nano-particle super-hydrophobic surfaces: the effects of surface morphology and trapped air pockets on hydrodynamic drainage forces.

PubMed

Chan, Derek Y C; Uddin, Md Hemayet; Cho, Kwun L; Liaw, Irving I; Lamb, Robert N; Stevens, Geoffrey W; Grieser, Franz; Dagastine, Raymond R

2009-01-01

We used atomic force microscopy to study dynamic forces between a rigid silica sphere (radius approximately 45 microm) and a silica nano-particle super-hydrophobic surface (SNP-SHS) in aqueous electrolyte, in the presence and absence of surfactant. Characterization of the SNP-SHS surface in air showed a surface roughness of up to two microns. When in contact with an aqueous phase, the SNP-SHS traps large, soft and stable air pockets in the surface interstices. The inherent roughness of the SNP-SHS together with the trapped air pockets are responsible for the superior hydrophobic properties of SNP-SHS such as high equilibrium contact angle (> 140 degrees) of water sessile drops on these surfaces and low hydrodynamic friction as observed in force measurements. We also observed that added surfactants adsorbed at the surface of air pockets magnified hydrodynamic interactions involving the SNP-SHS. The dynamic forces between the same silica sphere and a laterally smooth mica surface showed that the fitted Navier slip lengths using the Reynolds lubrication model were an order of magnitude larger than the length scale of the sphere surface roughness. The surface roughness and the lateral heterogeneity of the SNP-SHS hindered attempts to characterize the dynamic response using the Reynolds lubrication model even when augmented with a Navier slip boundary.

Mars radar clutter and surface roughness characteristics from MARSIS data

NASA Astrophysics Data System (ADS)

Campbell, Bruce A.; Schroeder, Dustin M.; Whitten, Jennifer L.

2018-01-01

Radar sounder studies of icy, sedimentary, and volcanic settings can be affected by reflections from surface topography surrounding the sensor nadir location. These off-nadir ;clutter; returns appear at similar time delays to subsurface echoes and complicate geologic interpretation. Additionally, broadening of the radar echo in delay by surface returns sets a limit on the detectability of subsurface interfaces. We use MARSIS 4 MHz data to study variations in the nadir and off-nadir clutter echoes, from about 300 km to 1000 km altitude, R, for a wide range of surface roughness. This analysis uses a new method of characterizing ionospheric attenuation to merge observations over a range of solar zenith angle and date. Mirror-like reflections should scale as R-2, but the observed 4 MHz nadir echoes often decline by a somewhat smaller power-law factor because MARSIS on-board processing increases the number of summed pulses with altitude. Prior predictions of the contributions from clutter suggest a steeper decline with R than the nadir echoes, but in very rough areas the ratio of off-nadir returns to nadir echoes shows instead an increase of about R1/2 with altitude. This is likely due in part to an increase in backscatter from the surface as the radar incidence angle at some round-trip time delay declines with increasing R. It is possible that nadir and clutter echo properties in other planetary sounding observations, including RIME and REASON flyby data for Europa, will vary in the same way with altitude, but there may be differences in the nature and scale of target roughness (e.g., icy versus rocky surfaces). We present global maps of the ionosphere- and altitude-corrected nadir echo strength, and of a ;clutter; parameter based on the ratio of off-nadir to nadir echoes. The clutter map offers a view of surface roughness at ∼75 m length scale, bridging the spatial-scale gap between SHARAD roughness estimates and MOLA-derived parameters.

Acoustic imaging in application to reconstruction of rough rigid surface with airborne ultrasound waves

NASA Astrophysics Data System (ADS)

Krynkin, A.; Dolcetti, G.; Hunting, S.

2017-02-01

Accurate reconstruction of the surface roughness is of high importance to various areas of science and engineering. One important application of this technology is for remote monitoring of open channel flows through observing its dynamic surface roughness. In this paper a novel airborne acoustic method of roughness reconstruction is proposed and tested with a static rigid rough surface. This method is based on the acoustic holography principle and Kirchhoff approximation which make use of acoustic pressure data collected at multiple receiver points spread along an arch. The Tikhonov regularisation and generalised cross validation technique are used to solve the underdetermined system of equations for the acoustic pressures. The experimental data are collected above a roughness created with a 3D printer. For the given surface, it is shown that the proposed method works well with the various number of receiver positions. In this paper, the tested ratios between the number of surface points at which the surface elevation can be reconstructed and number of receiver positions are 2.5, 5, and 7.5. It is shown that, in a region comparable with the projected size of the main directivity lobe, the method is able to reconstruct the spatial spectrum density of the actual surface elevation with the accuracy of 20%.

Acoustic imaging in application to reconstruction of rough rigid surface with airborne ultrasound waves.

PubMed

Krynkin, A; Dolcetti, G; Hunting, S

2017-02-01

Accurate reconstruction of the surface roughness is of high importance to various areas of science and engineering. One important application of this technology is for remote monitoring of open channel flows through observing its dynamic surface roughness. In this paper a novel airborne acoustic method of roughness reconstruction is proposed and tested with a static rigid rough surface. This method is based on the acoustic holography principle and Kirchhoff approximation which make use of acoustic pressure data collected at multiple receiver points spread along an arch. The Tikhonov regularisation and generalised cross validation technique are used to solve the underdetermined system of equations for the acoustic pressures. The experimental data are collected above a roughness created with a 3D printer. For the given surface, it is shown that the proposed method works well with the various number of receiver positions. In this paper, the tested ratios between the number of surface points at which the surface elevation can be reconstructed and number of receiver positions are 2.5, 5, and 7.5. It is shown that, in a region comparable with the projected size of the main directivity lobe, the method is able to reconstruct the spatial spectrum density of the actual surface elevation with the accuracy of 20%.

Variation in bed level shear stress on surfaces sheltered by nonerodible roughness elements

NASA Astrophysics Data System (ADS)

Sutton, Stephen L. F.; McKenna-Neuman, Cheryl

2008-09-01

Direct bed level observations of surface shear stress, pressure gradient variability, turbulence intensity, and fluid flow patterns were carried out in the vicinity of cylindrical roughness elements mounted in a boundary layer wind tunnel. Paired corkscrew vortices shed from each of the elements result in elevated shear stress and increased potential for the initiation of particle transport within the far wake. While the size and shape of these trailing vortices change with the element spacing, they persist even for large roughness densities. Wake interference coincides with the impingement of the upwind horseshoe vortices upon one another at a point when their diameter approaches half the distance between the roughness elements. While the erosive capability of the horseshoe vortex has been suggested for a variety of settings, the present study shows that the fluid stress immediately beneath this coherent structure is actually small in comparison to that caused by compression of the incident flow as it is deflected around the element and attached vortex. Observations such as these are required for further refinement of models of stress partitioning on rough surfaces.

Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes

PubMed Central

Li, Zhiyang; Leung, Calvin; Gao, Fan; Gu, Zhiyong

2015-01-01

In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM−1·cm−2) among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors. PMID:26404303

Bacterial adhesion on conventional and self-ligating metallic brackets after surface treatment with plasma-polymerized hexamethyldisiloxane.

PubMed

Tupinambá, Rogerio Amaral; Claro, Cristiane Aparecida de Assis; Pereira, Cristiane Aparecida; Nobrega, Celestino José Prudente; Claro, Ana Paula Rosifini Alves

2017-01-01

Plasma-polymerized film deposition was created to modify metallic orthodontic brackets surface properties in order to inhibit bacterial adhesion. Hexamethyldisiloxane (HMDSO) polymer films were deposited on conventional (n = 10) and self-ligating (n = 10) stainless steel orthodontic brackets using the Plasma-Enhanced Chemical Vapor Deposition (PECVD) radio frequency technique. The samples were divided into two groups according to the kind of bracket and two subgroups after surface treatment. Scanning Electron Microscopy (SEM) analysis was performed to assess the presence of bacterial adhesion over samples surfaces (slot and wings region) and film layer integrity. Surface roughness was assessed by Confocal Interferometry (CI) and surface wettability, by goniometry. For bacterial adhesion analysis, samples were exposed for 72 hours to a Streptococcus mutans solution for biofilm formation. The values obtained for surface roughness were analyzed using the Mann-Whitney test while biofilm adhesion were assessed by Kruskal-Wallis and SNK test. Significant statistical differences (p< 0.05) for surface roughness and bacterial adhesion reduction were observed on conventional brackets after surface treatment and between conventional and self-ligating brackets; no significant statistical differences were observed between self-ligating groups (p> 0.05). Plasma-polymerized film deposition was only effective on reducing surface roughness and bacterial adhesion in conventional brackets. It was also noted that conventional brackets showed lower biofilm adhesion than self-ligating brackets despite the absence of film.

Unpolarized emissivity with shadow and multiple reflections from random rough surfaces with the geometric optics approximation: application to Gaussian sea surfaces in the infrared band.

PubMed

Bourlier, Christophe

2006-08-20

The emissivity from a stationary random rough surface is derived by taking into account the multiple reflections and the shadowing effect. The model is applied to the ocean surface. The geometric optics approximation is assumed to be valid, which means that the rough surface is modeled as a collection of facets reflecting locally the light in the specular direction. In particular, the emissivity with zero, single, and double reflections are analytically calculated, and each contribution is studied numerically by considering a 1D sea surface observed in the near infrared band. The model is also compared with results computed from a Monte Carlo ray-tracing method.

Modelling of surface roughness effects on impurity erosion and deposition in TEXTOR with a code package SURO/ERO/SDPIC

NASA Astrophysics Data System (ADS)

Dai, Shuyu; Kirschner, A.; Sun, Jizhong; Tskhakaya, D.; Wang, Dezhen

2014-12-01

The roughness-induced uneven erosion-deposition behaviour is widely observed on plasma-wetted surfaces in tokamaks. The three-dimensional (3D) angular distribution of background plasma and impurities is expected to have an impact on the local erosion-deposition characteristic on rough surfaces. The investigations of 13C deposition on rough surfaces in TEXTOR experiments have been re-visited by 3D treatment of surface morphology to evaluate the effect of 3D angular distribution and its connection with surface topography by the code package SURO/ERO/SDPIC. The simulation results show that the erosion/deposition patterns and evolution of surface topography are strongly affected by the azimuthal direction of incident flux. A reduced aspect ratio of rough surface leads to an increase in 13C deposition due to the enhanced trapping ability at surface recessions. The shadowing effect of rough surface has been revealed based on the relationship between 3D incident direction and surface topography properties. The more realistic surface structures used by 3D SURO can well reproduce the experimental results of the increase in the 13C deposition efficiency by a factor of 3-5 on a rough surface compared with a smooth one. The influence of sheath electric field on the local impact angle and resulting 13C deposition has been studied, which indicates that the difference in 13C deposition caused by sheath electric field can be alleviated by the use of more realistic surface structures. The difference in 13C deposition on smooth graphite and tungsten substrates has been specified by consideration of effects of kinetic reflection, enhanced physical sputtering and nucleation.

Influence of epoxy, polytetrafluoroethylene (PTFE) and rhodium surface coatings on surface roughness, nano-mechanical properties and biofilm adhesion of nickel titanium (Ni-Ti) archwires

NASA Astrophysics Data System (ADS)

Asiry, Moshabab A.; AlShahrani, Ibrahim; Almoammar, Salem; Durgesh, Bangalore H.; Kheraif, Abdulaziz A. Al; Hashem, Mohamed I.

2018-02-01

Aim. To investigate the effect of epoxy, polytetrafluoroethylene (PTFE) and rhodium surface coatings on surface roughness, nano-mechanical properties and biofilm adhesion of nickel titanium (Ni-Ti) archwires Methods. Three different coated (Epoxy, polytetrafluoroethylene (PTFE) and rhodium) and one uncoated Ni-Ti archwires were evaluated in the present study. Surface roughness (Ra) was assessed using a non-contact surface profilometer. The mechanical properties (nano-hardness and elastic modulus) were measured using a nanoindenter. Bacterial adhesion assays were performed using Streptococcus mutans (MS) and streptococcus sobrinus (SS) in an in-vitro set up. The data obtained were analyzed using analyses of variance, Tukey’s post hoc test and Pearson’s correlation coefficient test. Result. The highest Ra values (1.29 ± 0.49) were obtained for epoxy coated wires and lowest Ra values (0.29 ± 0.16) were obtained for the uncoated wires. No significant differences in the Ra values were observed between the rhodium coated and uncoated archwires (P > 0.05). The highest nano-hardness (3.72 ± 0.24) and elastic modulus values (61.15 ± 2.59) were obtained for uncoated archwires and the lowest nano-hardness (0.18 ± 0.10) and elastic modulus values (4.84 ± 0.65) were observed for epoxy coated archwires. No significant differences in nano-hardness and elastic modulus values were observed between the coated archwires (P > 0.05). The adhesion of Streptococcus mutans (MS) to the wires was significantly greater than that of streptococcus sobrinus (SS). The epoxy coated wires demonstrated an increased adhesion of MS and SS and the uncoated wires demonstrated decreased biofilm adhesion. The Spearman correlation test showed that MS and SS adhesion was positively correlated with the surface roughness of the wires. Conclusion. The different surface coatings significantly influence the roughness, nano-mechanical properties and biofilm adhesion parameters of the archwires. The evaluated parameters were most influenced by epoxy coating followed by PTFE and rhodium coating. A positive correlation was detected between surface roughness and biofilm adhesion.

Particles induced surface nanoroughness of titanium surface and its influence on adhesion of osteoblast-like MG-63 cells

NASA Astrophysics Data System (ADS)

Solař, P.; Kylián, O.; Marek, A.; Vandrovcová, M.; Bačáková, L.; Hanuš, J.; Vyskočil, J.; Slavínská, D.; Biederman, H.

2015-01-01

Titanium is one of the most common materials employed for production of implants, which is due to its good biocompatibility. However, the colonization of titanium surface by osteoblast cells may be influenced by its roughness and therefore precise control of roughness of titanium surface as well as identification of its optimal value for growth of cells is of high importance. In this study the nanorough titanium surfaces were prepared on polished disks of TiAlV by two step method of deposition. In the first step TiAlV were coated by nanoparticles generated by gas aggregation sources. Such prepared films of nanoparticles were subsequently covered with a titanium overlayer. Different values of surface roughness in the range 1-100 nm were achieved by variation of the size and number of the nanoparticles. Such prepared surfaces were subsequently used for investigation of influence of roughness of titanium surfaces on the adhesion of human osteoblast-like MG-63 cells. It was found out that 7 days after seeding the highest number of adhering cells was observed for samples with root-mean-square roughness of 30 nm.

Influence of surface roughness on cetyltrimethylammonium bromide adsorption from aqueous solution.

PubMed

Wu, Shuqing; Shi, Liu; Garfield, Lucas B; Tabor, Rico F; Striolo, Alberto; Grady, Brian P

2011-05-17

The influence of surface roughness on surfactant adsorption was studied using a quartz crystal microbalance with dissipation (QCM-D). The sensors employed had root-mean-square (R) roughness values of 2.3, 3.1, and 5.8 nm, corresponding to fractal-calculated surface area ratios (actual/nominal) of 1.13, 1.73, and 2.53, respectively. Adsorption isotherms measured at 25 °C showed that adsorbed mass of cetyltrimethylammonium bromide per unit of actual surface area below 0.8 cmc, or above 1.2 cmc, decreases as the surface roughness increases. At the cmc, both the measured adsorbed amount and the measured dissipation increased dramatically on the rougher surfaces. These results are consistent with the presence of impurities, suggesting that roughness exacerbates well-known phenomena reported in the literature of peak impurity-related adsorption at the cmc. The magnitude of the increase, especially in dissipation, suggests that changes in adsorbed amount may not be the only reason for the observed results, as aggregates at the cmc on rougher surfaces are more flexible and likely contain larger amounts of solvent. Differences in adsorption kinetics were also found as a function of surface roughness, with data showing a second, slower adsorption rate after rapid initial adsorption. A two-rate Langmuir model was used to further examine this effect. Although adsorption completes faster on the smoother surfaces, initial adsorption at zero surface coverage is faster on the rougher surfaces, suggesting the presence of more high-energy sites on the rougher surfaces.

Effect of leading-edge roughness on stability and transition of wind turbine blades

NASA Astrophysics Data System (ADS)

Kutz, Douglas; Freels, Justin; Hidore, John; White, Edward

2011-11-01

Over time, wind turbine blades erode due to impacts with sand and other debris. The resulting surface roughness degrades the blades' aerodynamic performance. Experimental studies conducted at the Texas A&M University Low-Speed Wind Tunnel examine roughness effects using a 2D NACA 63-418 airfoil with interchangeable leading edges of varying roughness at chord Reynolds numbers up to 3 . 0 ×106 . These data reveal decreased CL , max and increased CD , min as roughness increases. At very high roughness levels, even the lift curve slope is reduced. To better understand these findings and improve modeling of roughness effects, extensive boundary layer measurements including surface-mounted hotfilms and boundary-layer velocity profiles are used to assess how laminar-to-turbulent transition is promoted by roughness. As expected, roughness accelerates transition. Tollmien-Schlichting (TS) transition is observed only for a smooth leading edge while bypass transition is observed for the moderate and high roughness levels. Results are compared to N-factor transition predictions generated with software used by the wind industry. Predictions are successful for the smooth leading edge but even the low roughness level prevents correct transition prediction using TS-based methods. Support for this work by Vestas Technology Americas, Inc., is gratefully acknowledged as is the support of the wind-energy research group and the Low-Speed Wind Tunnel staff.

Surface Roughness and Morphology Customization of Additive Manufactured Open Porous Ti6Al4V Structures

PubMed Central

Pyka, Grzegorz; Kerckhofs, Greet; Papantoniou, Ioannis; Speirs, Mathew; Schrooten, Jan; Wevers, Martine

2013-01-01

Additive manufacturing (AM) is a production method that enables the building of porous structures with a controlled geometry. However, there is a limited control over the final surface of the product. Hence, complementary surface engineering strategies are needed. In this work, design of experiments (DoE) was used to customize post AM surface treatment for 3D selective laser melted Ti6Al4V open porous structures for bone tissue engineering. A two-level three-factor full factorial design was employed to assess the individual and interactive effects of the surface treatment duration and the concentration of the chemical etching solution on the final surface roughness and beam thickness of the treated porous structures. It was observed that the concentration of the surface treatment solution was the most important factor influencing roughness reduction. The designed beam thickness decreased the effectiveness of the surface treatment. In this case study, the optimized processing conditions for AM production and the post-AM surface treatment were defined based on the DoE output and were validated experimentally. This allowed the production of customized 3D porous structures with controlled surface roughness and overall morphological properties, which can assist in more controlled evaluation of the effect of surface roughness on various functional properties. PMID:28788357

Surface Roughness and Morphology Customization of Additive Manufactured Open Porous Ti6Al4V Structures.

PubMed

Pyka, Grzegorz; Kerckhofs, Greet; Papantoniou, Ioannis; Speirs, Mathew; Schrooten, Jan; Wevers, Martine

2013-10-22

Additive manufacturing (AM) is a production method that enables the building of porous structures with a controlled geometry. However, there is a limited control over the final surface of the product. Hence, complementary surface engineering strategies are needed. In this work, design of experiments (DoE) was used to customize post AM surface treatment for 3D selective laser melted Ti6Al4V open porous structures for bone tissue engineering. A two-level three-factor full factorial design was employed to assess the individual and interactive effects of the surface treatment duration and the concentration of the chemical etching solution on the final surface roughness and beam thickness of the treated porous structures. It was observed that the concentration of the surface treatment solution was the most important factor influencing roughness reduction. The designed beam thickness decreased the effectiveness of the surface treatment. In this case study, the optimized processing conditions for AM production and the post-AM surface treatment were defined based on the DoE output and were validated experimentally. This allowed the production of customized 3D porous structures with controlled surface roughness and overall morphological properties, which can assist in more controlled evaluation of the effect of surface roughness on various functional properties.

Scaling behavior of the surface roughness of platinum films grown by oblique angle deposition

NASA Astrophysics Data System (ADS)

Dolatshahi-Pirouz, A.; Hovgaard, M. B.; Rechendorff, K.; Chevallier, J.; Foss, M.; Besenbacher, F.

2008-03-01

Thin platinum films with well-controlled rough surface morphologies are grown by e-gun evaporation at an oblique angle of incidence between the deposition flux and the substrate normal. Atomic force microscopy is used to determine the root-mean-square value w of the surface roughness on the respective surfaces. From the scaling behavior of w , we find that while the roughness exponent α remains nearly unchanged at about 0.90, the growth exponent β changes from 0.49±0.04 to 0.26±0.01 as the deposition angle approaches grazing incidence. The values of the growth exponent β indicate that the film growth is influenced by both surface diffusion and shadowing effects, while the observed change from 0.49 to 0.26 can be attributed to differences in the relative importance of diffusion and shadowing with the deposition angle.

Radiographic evaluation of marginal bone level around implants with different neck designs after 1 year.

PubMed

Shin, Young-Kyu; Han, Chong-Hyun; Heo, Seong-Joo; Kim, Sunjai; Chun, Heoung-Jae

2006-01-01

To evaluate the influence of macro- and microstructure of the implant surface at the marginal bone level after functional loading. Sixty-eight patients were randomly assigned to 1 of 3 groups. The first group received 35 implants with a machined neck (Ankylos); the second group, 34 implants with a rough-surfaced neck (Stage 1); and the third, 38 implants with a rough-surfaced neck with microthreads (Oneplant). Clinical and radiographic examinations were conducted at baseline (implant loading) and 3, 6, and 12 months postloading. Two-way repeated analysis of variance (ANOVA) was used to test the significance of marginal bone change of each tested group at baseline, 3, 6, and 12 month follow-ups and 1-way ANOVA was also used to compare the bone loss of each time interval within the same implant group (P < .05). At 12 months, significant differences were noted in the amount of alveolar bone loss recorded for the 3 groups (P < .05). The group with the rough-surfaced microthreaded neck had a mean crestal bone loss of 0.18 +/- 0.16 mm; the group with the rough-surfaced neck, 0.76 +/- 0.21 mm; and the group with the machined neck, 1.32 +/- 0.27 mm. In the rough-surfaced group and the rough-surfaced microthreaded group, no statistically significant changes were observed after 3 months, whereas the machined-surface group showed significant bone loss for every interval (P < .05). To minimize marginal bone loss, in addition to the use of a rough surface at the marginal bone level, a macroscopic modification such as the addition of microthreads could be recommended. A rough surface and microthreads at the implant neck not only reduce crestal bone loss but also help with early biomechanical adaptation against loading in comparison to the machined neck design. A rough surface with microthreads at the implant neck was the most effective design to maintain the marginal bone level against functional loading.

The machined surface of magnesium AZ31 after rotary turning at air cooling condition

NASA Astrophysics Data System (ADS)

Akhyar, G.; Purnomo, B.; Hamni, A.; Harun, S.; Burhanuddin, Y.

2018-04-01

Magnesium is a lightweight metal that is widely used as an alternative to iron and steel. Magnesium has been applied in the automotive industry to reduce the weight of a component, but the machining process has the disadvantage that magnesium is highly flammable because it has a low flash point. High temperature can cause the cutting tool wear and contributes to the quality of the surface roughness. The purpose of this study is to obtain the value of surface roughness and implement methods of rotary cutting tool and air cooling output vortex tube cooler to minimize the surface roughness values. Machining parameters that is turning using rotary cutting tool at speed the workpiece of (Vw) 50, 120, 160 m/min, cutting speed of rotary tool of (Vt) 25, 50, 75 m/min, feed rate of (f) 0.1, 0.15, 0.2 mm/rev, and depth of cut of 0.3 mm. Type of tool used is a carbide tool diameter of 16 mm and air cooling pressure of 6 bar. The results show the average value of the lowest surface roughness on the speed the workpiece of 80 m/min, cutting speed of rotary tool of 50 m/min, feed rate of 0.2 mm/rev, and depth of cut of 0.3 mm. While the average value of the highest surface roughness on the speed the workpiece of 160 m/min, cutting speed of rotary tool of 50 m/min, feed rate of 0.2 mm/rev, and depth of cut of 0.3 mm. The influence of machining parameters concluded the higher the speed of the workpiece the surface roughness value higher. Otherwise the higher cutting speed of rotary tool then the lower the surface roughness value. The observation on the surface of the rotary tool, it was found that no uniform tool wear which causes non-uniform surface roughness. The use of rotary cutting tool contributing to lower surface roughness values generated.

Preliminary evaluation of the SIR-B response to soil moisture, surface roughness, and crop canopy cover

NASA Technical Reports Server (NTRS)

Dobson, M. C.; Ulaby, F. T.

1986-01-01

Two predawn ascending data-takes by the Shuttle Imaging Radar-B (SIR-B) were used to evaluate the effects of surface roughness, crop canopy, and soil moisture on radar backscatter. The two images, separated by three days, were both obtained at 30-deg local angle of incidence, but with opposite azimuth viewing directions. The imagery was externally calibrated with respect to the radar backscattering coefficient sigma(0) via response to arrays of point and area-extended targets of known radar cross section. Three land-cover classes: (1) corn, (2) corn stubble and plowed bare soil, and (3) disked bare soil, soybeans, soybean stubble, alfalfa, and clover could be readily separated for either observation date on the basis of image tone alone. The dependence of sigma(0) on the surface roughness and canopy brightness inhibits the capability of SIR to globally estimate the near-surface soil moisture from the value of sigma(0) for single date observations, unless the surface roughness or canopy cover conditions are accounted for. However, within given ranges of these conditions, the sigma(0) was found to be highly correlated with the soil moisture.

Effect of Surface Roughness on Characteristics of Spherical Shock Waves

NASA Technical Reports Server (NTRS)

Huber, Paul W.; McFarland, Donald R.

1959-01-01

Measurements of peak overpressure and Mach stem height were made at four burst heights. Data were obtained with instrumentation capable of directly observing the variation of shock wave movement with time. Good similarity of free air shock peak overpressure with larger scale data was found to exist. The net effect of surface roughness on shock peak overpressures slightly. Surface roughness delayed the Mach stem formation at the greatest charge height and lowered the growth at all burst heights. A similarity parameter was found which approximately correlates the triple point path at different burst heights.

Curb Mounting, Vertical Mobility, and Inverted Mobility on Rough Surfaces Using Microspine-Enabled Robots

NASA Technical Reports Server (NTRS)

Parness, Aaron

2012-01-01

Three robots that extend microspine technology to enable advanced mobility are presented. First, the Durable Reconnaissance and Observation Platform (DROP) and the ReconRobotics Scout platform use a new rotary configuration of microspines to provide improved soldier-portable reconnaissance by moving rapidly over curbs and obstacles, transitioning from horizontal to vertical surfaces, climbing rough walls and surviving impacts. Next, the four-legged LEMUR robot uses new configurations of opposed microspines to anchor to both manmade and natural rough surfaces. Using these anchors as feet enables mobility in unstructured environments, from urban disaster areas to deserts and caves.

Polarimetric scattering behavior of materials at terahertz frequencies

NASA Astrophysics Data System (ADS)

DiGiovanni, David Anthony

Terahertz spectroscopic techniques have long been used to characterize the electromagnetic behavior of materials for use in radar, astronomy, and remote sensing applications. Spectroscopic information is valuable, but additional information about materials is present in the polarization of the scattered radiation. This thesis has investigated the polarimetric scattering behavior of various rough dielectric and metallic materials from 100 GHz to 1.55 THz. Common building materials and terrain, such as sand, gravel, soil, concrete, and roofing shingles, were studied. In order to obtain a better understanding of basic rough surface scattering phenomenology in this region of the spectrum, roughened metal and plastic samples were studied as well. The scattering behavior of these materials was studied as a function of incident angle, roughness, frequency, and polarization. Theoretical scattering models were used to compare measured results to theoretical predictions. Good agreement was observed between scattering measurements and theoretical predictions based on the small perturbation theory for the roughened metal surfaces. However, a substantial disagreement was observed for the rough dielectric surfaces and is discussed.

Micromorphology of cactus-pear (Opuntia ficus-indica (L.) Mill) cladodes based on scanning microscopies.

PubMed

Ben Salem-Fnayou, Asma; Zemni, Hassène; Nefzaoui, Ali; Ghorbel, Abdelwahed

2014-01-01

Cladode ultrastructural features of two prickly and two spineless Opuntia ficus-indica cultivars were examined using environmental scanning electron and atomic force microscopies. Observations focused on cladode as well as spine and glochid surface micromorphologies. Prickly cultivars were characterized by abundant cracked epicuticular wax deposits covering the cladode surface, with an amorphous structure as observed by AFM, while less abundant waxy plates were observed by ESEM on spineless cultivar cladodes. Further AFM observations allowed a rough granular and crystalloid epicuticular wax structure to be distinguished in spineless cultivars. Regarding spine micromorphology, prickly cultivars had strong persistent spines, observed by ESEM as a compact arrangement of oblong epidermal cells with a rough granular structure. However, deciduous spines in spineless cultivars had a broken transversely fissured epidermis covering a parallel arrangement of fibres. Through AFM, the deciduous spine surface presented an irregular hilly and smooth microrelief while persistent spines exhibited rough helical filamentous prints. ESEM and AFM studies of cladode surfaces from prickly and spineless cactus pear cultivars revealed valuable micro-morphological details that ought to be extended to a large number of O. ficus-indica cultivars. Copyright © 2013 Elsevier Ltd. All rights reserved.

Modeling interface shear behavior of granular materials using micro-polar continuum approach

NASA Astrophysics Data System (ADS)

Ebrahimian, Babak; Noorzad, Ali; Alsaleh, Mustafa I.

2018-01-01

Recently, the authors have focused on the shear behavior of interface between granular soil body and very rough surface of moving bounding structure. For this purpose, they have used finite element method and a micro-polar elasto-plastic continuum model. They have shown that the boundary conditions assumed along the interface have strong influences on the soil behavior. While in the previous studies, only very rough bounding interfaces have been taken into account, the present investigation focuses on the rough, medium rough and relatively smooth interfaces. In this regard, plane monotonic shearing of an infinite extended narrow granular soil layer is simulated under constant vertical pressure and free dilatancy. The soil layer is located between two parallel rigid boundaries of different surface roughness values. Particular attention is paid to the effect of surface roughness of top and bottom boundaries on the shear behavior of granular soil layer. It is shown that the interaction between roughness of bounding structure surface and the rotation resistance of bounding grains can be modeled in a reasonable manner through considered Cosserat boundary conditions. The influence of surface roughness is investigated on the soil shear strength mobilized along the interface as well as on the location and evolution of shear localization formed within the layer. The obtained numerical results have been qualitatively compared with experimental observations as well as DEM simulations, and acceptable agreement is shown.

Experimental study of surface integrity and fatigue life in the face milling of inconel 718

NASA Astrophysics Data System (ADS)

Wang, Xiangyu; Huang, Chuanzhen; Zou, Bin; Liu, Guoliang; Zhu, Hongtao; Wang, Jun

2018-06-01

The Inconel 718 alloy is widely used in the aerospace and power industries. The machining-induced surface integrity and fatigue life of this material are important factors for consideration due to high reliability and safety requirements. In this work, the milling of Inconel 718 was conducted at different cutting speeds and feed rates. Surface integrity and fatigue life were measured directly. The effects of cutting speed and feed rate on surface integrity and their further influences on fatigue life were analyzed. Within the chosen parameter range, the cutting speed barely affected the surface roughness, whereas the feed rate increased the surface roughness through the ideal residual height. The surface hardness increased as the cutting speed and feed rate increased. Tensile residual stress was observed on the machined surface, which showed improvement with the increasing feed rate. The cutting speed was not an influencing factor on fatigue life, but the feed rate affected fatigue life through the surface roughness. The high surface roughness resulting from the high feed rate could result in a high stress concentration factor and lead to a low fatigue life.

Effects of plaque lengths on stent surface roughness.

PubMed

Syaifudin, Achmad; Takeda, Ryo; Sasaki, Katsuhiko

2015-01-01

The physical properties of the stent surface influence the effectiveness of vascular disease treatment after stent deployment. During the expanding process, the stent acquires high-level deformation that could alter either its microstructure or the magnitude of surface roughness. This paper constructed a finite element simulation to observe the changes in surface roughness during the stenting process. Structural transient dynamic analysis was performed using ANSYS, to identify the deformation after the stent is placed in a blood vessel. Two types of bare metal stents are studied: a Palmaz type and a Sinusoidal type. The relationship between plaque length and the changes in surface roughness was investigated by utilizing three different length of plaque; plaque length longer than the stent, shorter than the stent and the same length as the stent. In order to reduce computational time, 3D cyclical and translational symmetry was implemented into the FE model. The material models used was defined as a multilinear isotropic for stent and hyperelastic for the balloon, plaque and vessel wall. The correlation between the plastic deformation and the changes in surface roughness was obtained by intermittent pure tensile test using specimen whose chemical composition was similar to that of actual stent material. As the plastic strain is achieved from FE simulation, the surface roughness can be assessed thoroughly. The study found that the plaque size relative to stent length significantly influenced the critical changes in surface roughness. It was found that the length of stent which is equal to the plaque length was preferable due to the fact that it generated only moderate change in surface roughness. This effect was less influential to the Sinusoidal stent.

Long-term erosion of plasma-facing materials with different surface roughness in ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Hakola, A.; Karhunen, J.; Koivuranta, S.; Likonen, J.; Balden, M.; Herrmann, A.; Mayer, M.; Müller, H. W.; Neu, R.; Rohde, V.; Sugiyama, K.; The ASDEX Upgrade Team

2014-04-01

The effect of surface roughness on the long-term erosion patterns of tungsten coatings was investigated in the outer strike-point region of ASDEX Upgrade during its 2010-11 plasma operations. The net erosion rates of rough coatings (Ra = 5-6 μm) were three to seven times smaller than those of smooth coatings (Ra = 0.4-0.8 μm). This is because rough surfaces are largely modified and damaged in the microscopic scale but the material is re-deposited together with boron, deuterium and carbon on the shadowed sides of the most prominent surface features. In addition, we observed that W coatings were eroded on average at a rate of 0.03 nm s-1, which was three to four times smaller than the value for Cr, simulating here steel.

Fabricating Superhydrophobic and Superoleophobic Surfaces with Multiscale Roughness Using Airbrush and Electrospray

NASA Astrophysics Data System (ADS)

AL-Milaji, Karam N.

Examples of superhydrophobic surfaces found in nature such as self-cleaning property of lotus leaf and walking on water ability of water strider have led to an extensive investigation in this area over the past few decades. When a water droplet rests on a textured surface, it may either form a liquid-solid-vapor composite interface by which the liquid droplet partially sits on air pockets or it may wet the surface in which the water replaces the trapped air depending on the surface roughness and the surface chemistry. Super water repellent surfaces have numerous applications in our daily life such as drag reduction, anti-icing, anti-fogging, energy conservation, noise reduction, and self-cleaning. In fact, the same concept could be applied in designing and producing surfaces that repel organic contaminations (e.g. low surface tension liquids). However, superoleophobic surfaces are more challenging to fabricate than superhydrophobic surfaces since the combination of multiscale roughness with re-entrant or overhang structure and surface chemistry must be provided. In this study, simple, cost-effective and potentially scalable techniques, i.e., airbrush and electrospray, were employed for the sake of making superhydrophobic and superoleophobic coatings with random and patterned multiscale surface roughness. Different types of silicon dioxide were utilized in this work to in order to study and to characterize the effect of surface morphology and surface roughness on surface wettability. The experimental findings indicated that super liquid repellent surfaces with high apparent contact angles and extremely low sliding angles were successfully fabricated by combining re-entrant structure, multiscale surface roughness, and low surface energy obtained from chemically treating the fabricated surfaces. In addition to that, the experimental observations regarding producing textured surfaces in mask-assisted electrospray were further validated by simulating the actual working conditions and geometries using COMSOL Multiphysics.

The joint effect of mesoscale and microscale roughness on perceived gloss.

PubMed

Qi, Lin; Chantler, Mike J; Siebert, J Paul; Dong, Junyu

2015-10-01

Computer simulated stimuli can provide a flexible method for creating artificial scenes in the study of visual perception of material surface properties. Previous work based on this approach reported that the properties of surface roughness and glossiness are mutually interdependent and therefore, perception of one affects the perception of the other. In this case roughness was limited to a surface property termed bumpiness. This paper reports a study into how perceived gloss varies with two model parameters related to surface roughness in computer simulations: the mesoscale roughness parameter in a surface geometry model and the microscale roughness parameter in a surface reflectance model. We used a real-world environment map to provide complex illumination and a physically-based path tracer for rendering the stimuli. Eight observers took part in a 2AFC experiment, and the results were tested against conjoint measurement models. We found that although both of the above roughness parameters significantly affect perceived gloss, the additive model does not adequately describe their mutually interactive and nonlinear influence, which is at variance with previous findings. We investigated five image properties used to quantify specular highlights, and found that perceived gloss is well predicted using a linear model. Our findings provide computational support to the 'statistical appearance models' proposed recently for material perception. Copyright © 2015 Elsevier Ltd. All rights reserved.

Investigation of surface water behavior during glaze ice accretion

NASA Technical Reports Server (NTRS)

Hansman, R. John, Jr.; Turnock, Stephen R.

1988-01-01

Microvideo observations of glaze ice accretions on 1-in-diameter cylinders in a closed-loop refrigerated wind tunnel were obtained to study factors controlling the behavior of unfrozen surface water during glaze ice accretion. Three zones of surface water behavior were noted, each with a characteristic roughness. The effect of substrate thermal and roughness properties on ice accretions was also studied. The contact angle and hysteresis were found to increase sharply at temperatures just below 0 C, explaining the high resistance to motion of water beads observed on accreting glaze ice surfaces. Based on the results, a simple multizone modification to the current glaze ice accretion model is proposed.

Nanoindentation of orthodontic archwires: The effect of decontamination and clinical use on hardness, elastic modulus and surface roughness.

PubMed

Alcock, Joseph P; Barbour, Michele E; Sandy, Jonathan R; Ireland, Anthony J

2009-08-01

The purpose of this research was to investigate the effects of decontamination and clinical exposure on the elastic moduli, hardness and surface roughness of two frequently used orthodontic archwires, namely 0.020in.x0.020in. heat activated (martensitic active) nickel titanium archwires and 0.019in.x0.025in. austenitic stainless steel archwires. This study was a prospective clinical trial in which 20 consecutive patients requiring an archwire change as part of their course of orthodontic fixed appliance therapy, had either a nickel titanium or stainless steel archwire fitted as deemed clinically necessary. The effect of clinical use was determined by comparing distal end cuts of the "as received" archwires before and after decontamination, with the same retrieved archwires following clinical use and decontamination. Hardness, elastic modulus and surface roughness were determined using an atomic force microscope (AFM) coupled with a nanoindenter. The results showed that the decontamination regimen and clinical use had no statistically significant effect on the nickel titanium archwires, but did have a statistically significant effect on the steel archwires. Decontamination of the steel wires significantly increased the observed surface hardness (p=0.01) and reduced the surface roughness (p=0.02). Clinical use demonstrated a statistically significant increase in the observed elastic modulus (p<0.001) and a decrease in surface roughness (p=0.001). At present it is difficult to predict the clinical significance of these statistically significant changes in archwire properties on orthodontic tooth movement.

Smoothing of Fault Slip Surfaces by Scale Invariant Wear

NASA Astrophysics Data System (ADS)

Dascher-Cousineau, K.; Kirkpatrick, J. D.

2017-12-01

Fault slip surface roughness plays a determining role in the overall strength, friction, and dynamic behavior of fault systems. Previous wear models and field observations suggest that roughness decreases with increasing displacement. However, measurements have yet to isolate the effect of displacement from other possible controls, such as lithology or tectonic setting. In an effort to understand the effect of displacement, we present comprehensive qualitative and quantitative description of the evolution of fault slip surfaces in and around the San-Rafael Desert, S.E. Utah, United States. In the study area, faults accommodated regional extension at shallow (1 to 3 km) depth and are hosted in the massive, well-sorted, high-porosity Navajo and Entrada sandstones. Existing displacement profiles along with tight displacement controls readily measureable in the field, combined with uniform lithology and tectonic history, allowed us to isolate for the effect of displacement during the embryonic stages of faulting (0 to 60 m in displacement). Our field observations indicate a clear compositional and morphological progression from isolated joints or deformation bands towards smooth, continuous, and mirror-like fault slip surfaces with increasing displacement. We scanned pristine slip surfaces with a white light interferometer, a laser scanner, and a ground-based LiDAR. We produce and analyses more than 120 individual scans of fault slip surfaces. Results for the surfaces with the best displacement constraints indicate that roughness as defined by the power spectral density at any given length scale decreases with displacement according to a power law with an exponent of -1. Roughness measurements associated with only maximum constraints on displacements corroborate this result. Moreover, maximum roughness for any given fault is bounded by a primordial roughness corresponding to that of joint surfaces and deformation band edges. Building upon these results, we propose a multi-scale wear model to explain the evolution of faults with displacement. We suggest that together, asperity failure as a scale invariant process, and the stochastic strength of host rocks are consistent with qualitative and quantitative observational constraints made in this study.

Surface roughness analysis of SiO2 for PECVD, PVD and IBD on different substrates

NASA Astrophysics Data System (ADS)

Amirzada, Muhammad Rizwan; Tatzel, Andreas; Viereck, Volker; Hillmer, Hartmut

2016-02-01

This study compares surface roughness of SiO2 thin layers which are deposited by three different processes (plasma-enhanced chemical vapor deposition, physical vapor deposition and ion beam deposition) on three different substrates (glass, Si and polyethylene naphthalate). Plasma-enhanced chemical vapor deposition (PECVD) processes using a wide range of deposition temperatures from 80 to 300 °C have been applied and compared. It was observed that the nature of the substrate does not influence the surface roughness of the grown layers very much. It is also perceived that the value of the surface roughness keeps on increasing as the deposition temperature of the PECVD process increases. This is due to the increase in the surface diffusion length with the rise in substrate temperature. The layers which have been deposited on Si wafer by ion beam deposition (IBD) process are found to be smoother as compared to the other two techniques. The layers which have been deposited on the glass substrates using PECVD reveal the highest surface roughness values in comparison with the other substrate materials and techniques. Different existing models describing the dynamics of clusters on surfaces are compared and discussed.

3D Micro-topography of Transferred Laboratory and Natural Ice Crystal Surfaces Imaged by Cryo and Environmental Scanning Electron Microscopy

NASA Astrophysics Data System (ADS)

Magee, N. B.; Boaggio, K.; Bancroft, L.; Bandamede, M.

2015-12-01

Recent work has highlighted micro-scale roughness on the surfaces of ice crystals grown and imaged in-situ within the chambers of environmental scanning electron microscopes (ESEM). These observations appear to align with theoretical and satellite observations that suggest a prevalence of rough ice in cirrus clouds. However, the atmospheric application of the lab observations are indeterminate because the observations have been based only on crystals grown on substrates and in pure-water vapor environments. In this work, we present details and results from the development of a transfer technique which allows natural and lab-grown ice and snow crystals to be captured, preserved, and transferred into the ESEM for 3D imaging. Ice crystals were gathered from 1) natural snow, 2) a balloon-borne cirrus particle capture device, and 3) lab-grown ice crystals from a diffusion chamber. Ice crystals were captured in a pre-conditioned small-volume (~1 cm3) cryo-containment cell. The cell was then sealed closed and transferred to a specially-designed cryogenic dewer (filled with liquid nitrogen or crushed dry ice) for transport to a new Hitachi Field Emission, Variable Pressure SEM (SU-5000). The cryo-cell was then removed from the dewer and quickly placed onto the pre-conditioned cryo transfer stage attached to the ESEM (Quorum 3010T). Quantitative 3D topographical digital elevation models of ice surfaces are reported from SEM for the first time, including a variety of objective measures of statistical surface roughness. The surfaces of the transported crystals clearly exhibit signatures of mesoscopic roughening that are similar to examples of roughness seen in ESEM-grown crystals. For most transported crystals, the habits and crystal edges are more intricate that those observed for ice grown directly on substrates within the ESEM chamber. Portions of some crystals do appear smooth even at magnification greater than 1000x, a rare observation in our ESEM-grown crystals. The transported crystals hint at some significant differences in roughness morphology, but they do provide evidence that crystals grown in air/water mixtures and with minimal substrate influence also exhibit mesoscopic roughness with similarity to that observed in ESEM-grown crystals.

S. sanguinis adhesion on rough titanium surfaces: effect of culture media.

PubMed

Rodríguez-Hernández, Ana G; Muñoz-Tabares, José A; Godoy-Gallardo, Maria; Juárez, Antonio; Gil, Francisco-Javier

2013-03-01

Bacterial colonization plays a key role in dental implant failure, because they attach directly on implant surface upon implantation. Between different types of bacteria associated with the oral environment, Streptococcus sanguinis is essential in this process since it is an early colonizer. In this work the relationship between titanium surfaces modified by shot blasting treatment and S. sanguinis adhesion; have been studied in approached human mouth environment. Bacteria pre-inoculated with routinary solution were put in contact with titanium samples, shot-blasted with alumina and silicon carbide, and adhesion results were compared with those obtained when bacteria were pre-inoculated with modified artificial saliva medium and on saliva pre-coated titanium samples. Our results showed that bacterial adhesion on titanium samples was influenced by culture conditions. When S. sanguinis was inoculated in routinary culture media, colonies forming unities per square millimeter presented an increment correlated with roughness and surface energy, but separated by the type of particle used during shot-blasting treatment; whereas in modified artificial saliva only a relationship between bacteria adhered and the increment in both roughness and surface energy were observed, regardless of the particle type. Finally, on human saliva pre-coated samples no significant differences were observed among roughness, surface energy or particle. Copyright © 2012 Elsevier B.V. All rights reserved.

Error in Radar-Derived Soil Moisture due to Roughness Parameterization: An Analysis Based on Synthetical Surface Profiles

PubMed Central

Lievens, Hans; Vernieuwe, Hilde; Álvarez-Mozos, Jesús; De Baets, Bernard; Verhoest, Niko E.C.

2009-01-01

In the past decades, many studies on soil moisture retrieval from SAR demonstrated a poor correlation between the top layer soil moisture content and observed backscatter coefficients, which mainly has been attributed to difficulties involved in the parameterization of surface roughness. The present paper describes a theoretical study, performed on synthetical surface profiles, which investigates how errors on roughness parameters are introduced by standard measurement techniques, and how they will propagate through the commonly used Integral Equation Model (IEM) into a corresponding soil moisture retrieval error for some of the currently most used SAR configurations. Key aspects influencing the error on the roughness parameterization and consequently on soil moisture retrieval are: the length of the surface profile, the number of profile measurements, the horizontal and vertical accuracy of profile measurements and the removal of trends along profiles. Moreover, it is found that soil moisture retrieval with C-band configuration generally is less sensitive to inaccuracies in roughness parameterization than retrieval with L-band configuration. PMID:22399956

Innovative potential of plasma technology

NASA Astrophysics Data System (ADS)

Budaev, V. P.

2017-11-01

The review summarizes recent experimental observations of materials exposed to extreme hot plasma loads in fusion devices and plasma facilities with high-temperature plasma. Plasma load on the material in such devices lead to the stochastic clustering and fractal growth of the surface on scales from tens of nanometers to hundreds of micrometers forming statistical self-similarity of the surface roughness with extremely high specific area. Statistical characteristics of hierarchical granularity and scale invariance of such materials surface qualitatively differ from the properties of the roughness of the ordinary Brownian surface which provides a potential of innovative plasma technologies for synthesis of new nanostructured materials with programmed roughness properties, for hypersonic technologies, for biotechnology and biomedical applications.

Surface roughness in XeF{sub 2} etching of a-Si/c-Si(100)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevens, A.A.E.; Beijerinck, H.C.W.

2005-01-01

Single wavelength ellipsometry and atomic force microscopy (AFM) have been applied in a well-calibrated beam-etching experiment to characterize the dynamics of surface roughening induced by chemical etching of a {approx}12 nm amorphous silicon (a-Si) top layer and the underlying crystalline silicon (c-Si) bulk. In both the initial and final phase of etching, where either only a-Si or only c-Si is exposed to the XeF{sub 2} flux, we observe a similar evolution of the surface roughness as a function of the XeF{sub 2} dose proportional to D(XeF{sub 2}){sup {beta}} with {beta}{approx_equal}0.2. In the transition region from the pure amorphous to themore » pure crystalline silicon layer, we observe a strong anomalous increase of the surface roughness proportional to D(XeF{sub 2}){sup {beta}} with {beta}{approx_equal}1.5. Not only the growth rate of the roughness increases sharply in this phase, also the surface morphology temporarily changes to a structure that suggests a cusplike shape. Both features suggest that the remaining a-Si patches on the surface act effectively as a capping layer which causes the growth of deep trenches in the c-Si. The ellipsometry data on the roughness are corroborated by the AFM results, by equating the thickness of the rough layer to 6 {sigma}, with {sigma} the root-mean-square variation of the AFM's distribution function of height differences. In the AFM data, the anomalous behavior is reflected in a too small value of {sigma} which again suggests narrow and deep surface features that cannot be tracked by the AFM tip. The final phase morphology is characterized by an effective increase in surface area by a factor of two, as derived from a simple bilayer model of the reaction layer, using the experimental etch rate as input. We obtain a local reaction layer thickness of 1.5 monolayer consistent with the 1.7 ML value of Lo et al. [Lo et al., Phys. Rev. B 47, 648 (1993)] that is also independent of surface roughness.« less

Randomized clinical study of alterations in the color and surface roughness of dental enamel brushed with whitening toothpaste.

PubMed

de Moraes Rego Roselino, Lourenço; Tirapelli, Camila; de Carvalho Panzeri Pires-de-Souza, Fernanda

2018-03-30

This clinical study evaluated the influence of whitening toothpaste on color and surface roughness of dental enamel. Initially, the abrasiveness of the toothpastes used (Sorriso Dentes Brancos [SDB]; Colgate Luminous White and Close up White Now) was tested on 30 (n = 10) plexiglass acrylic plates that were submitted to mechanical tooth brushing totalizing 29,200 cycles. Subsequently, 30 participants were selected, and received a toothbrush and nonwhitening toothpaste (SDB). The participants used these products for 7 days and initial color readouts (Spectrophotometer) and surface roughness of one maxillary central incisors was performed after this period of time. For surface roughness readouts, one replica of the maxillary central incisor was obtained by a polyvinyl siloxane impression material (Express) and polyurethane resin. After baseline measurements, participants were separated into three groups (n = 10), according to the toothpaste used. The participants returned after 7, 30, and 90 days when new color readouts and surface roughness were recorded. The measured values were statistically analyzed (2-way-ANOVA, repeated measures, Tukey, P < .05). Whitening toothpastes did not promote significant (P > .05) color alteration and nor increased the surface roughness of the dental enamel in brushing time of the study. The abrasiveness of whitening toothpaste and the brushing trial period did not affect the surface roughness of dental enamel. However, color changes observed on enamel were above the perceptibility and acceptability thresholds reported in the literature. The over-the-counter toothpastes tested had an effect on dental enamel color above the perceptibility and acceptability thresholds but did not change the surface roughness of the teeth. © 2018 Wiley Periodicals, Inc.

Bacterial adhesion on conventional and self-ligating metallic brackets after surface treatment with plasma-polymerized hexamethyldisiloxane

PubMed Central

Tupinambá, Rogerio Amaral; Claro, Cristiane Aparecida de Assis; Pereira, Cristiane Aparecida; Nobrega, Celestino José Prudente; Claro, Ana Paula Rosifini Alves

2017-01-01

ABSTRACT Introduction: Plasma-polymerized film deposition was created to modify metallic orthodontic brackets surface properties in order to inhibit bacterial adhesion. Methods: Hexamethyldisiloxane (HMDSO) polymer films were deposited on conventional (n = 10) and self-ligating (n = 10) stainless steel orthodontic brackets using the Plasma-Enhanced Chemical Vapor Deposition (PECVD) radio frequency technique. The samples were divided into two groups according to the kind of bracket and two subgroups after surface treatment. Scanning Electron Microscopy (SEM) analysis was performed to assess the presence of bacterial adhesion over samples surfaces (slot and wings region) and film layer integrity. Surface roughness was assessed by Confocal Interferometry (CI) and surface wettability, by goniometry. For bacterial adhesion analysis, samples were exposed for 72 hours to a Streptococcus mutans solution for biofilm formation. The values obtained for surface roughness were analyzed using the Mann-Whitney test while biofilm adhesion were assessed by Kruskal-Wallis and SNK test. Results: Significant statistical differences (p< 0.05) for surface roughness and bacterial adhesion reduction were observed on conventional brackets after surface treatment and between conventional and self-ligating brackets; no significant statistical differences were observed between self-ligating groups (p> 0.05). Conclusion: Plasma-polymerized film deposition was only effective on reducing surface roughness and bacterial adhesion in conventional brackets. It was also noted that conventional brackets showed lower biofilm adhesion than self-ligating brackets despite the absence of film. PMID:28902253

Effect of surface morphology on drag and roughness sublayer in flows over regular roughness elements

NASA Astrophysics Data System (ADS)

Placidi, Marco; Ganapathisubramani, Bharathram

2014-11-01

The effects of systematically varied roughness morphology on bulk drag and on the spatial structure of turbulent boundary layers are examined by performing a series of wind tunnel experiments. In this study, rough surfaces consisting of regularly and uniformly distributed LEGO™ bricks are employed. Twelve different patterns are adopted in order to methodically examine the individual effects of frontal solidity (λF, frontal area of the roughness elements per unit wall-parallel area) and plan solidity (λP, plan area of roughness elements per unit wall-parallel area), on both the bulk drag and the turbulence structure. A floating element friction balance based on Krogstad & Efros (2010) was designed and manufactured to measure the drag generated by the different surfaces. In parallel, high resolution planar and stereoscopic Particle Image Velocimetry (PIV) was applied to investigate the flow features. This talk will focus on the effects of each solidity parameter on the bulk drag and attempt to relate the observed trends to the flow structures in the roughness sublayer. Currently at City University London.

The impact of climate and composition on playa surface roughness: Investigation of atmospheric mineral dust emission mechanisms

NASA Astrophysics Data System (ADS)

Tollerud, H. J.; Fantle, M. S.

2011-12-01

Atmospheric mineral dust has a wide range of impacts, including the transport of elements in geochemical cycles, health hazards from small particles, and climate forcing via the reflection of sunlight from dust particles. In particular, the mineral dust component of climate forcing is one of the most uncertain elements in the IPCC climate forcing summary. Mineral dust is also an important component of geochemical cycles. For instance, dust inputs to the ocean potentially affect the iron cycle by stimulating natural iron fertilization, which could then modify climate via the biological pump. Also dust can transport nutrients over long distances and fertilize nutrient-poor regions, such as island ecosystems or the Amazon rain forest. However, there are still many uncertainties in quantifying dust emissions from source regions. One factor that influences dust emission is surface roughness and texture, since a weak, unconsolidated surface texture is more easily ablated by wind than a strong, hard crust. We are investigating the impact of processes such as precipitation, groundwater evaporation, and wind on surface roughness in a playa dust source region. We find that water has a significant influence on surface roughness. We utilize ESA's Advanced Synthetic Aperture Radar (ASAR) instrument to measure roughness in the playa. A map of roughness indicates where the playa surface is smooth (on the scale of centimeters) and potentially very strong, and where it is rough and might be more sensitive to disturbance. We have analyzed approximately 40 ASAR observations of the Black Rock Desert from 2007-2011. In general, the playa is smoother and more variable over time relative to nearby areas. There is also considerable variation within the playa. While the playa roughness maps changed significantly between summers and between observations during the winters, over the course of each summer, the playa surface maintained essentially the same roughness pattern. This suggests that there were no active processes during the summers that changed surface roughness. Images from NASA's MODIS instrument (1640 nm, band 6) delineate winter flooding on the playa. Areas of water in the winter tend to be smoother in the summer. In particular, a smooth area of the play in summer 2010 aligns very closely with ponded water in February 2010. This indicates that standing water disrupts the playa surface, reducing roughness. We also compared the distribution of surface roughness across the playa to playa composition. X-ray diffraction (XRD) of samples from the Black Rock Desert demonstrates that the playa surface is composed of approximately 30% quartz, 45% clays, 10% calcite, and 5% halite. Calcite and halite concentrations vary significantly between samples. We produced a map of calcite concentration in the Black Rock Desert based on hyperspectral data from NASA's EO-1 Hyperion instrument. We find that calcite concentrations are higher in smooth areas that have been inundated by water. Without an understanding of the surface processes associated with dust emission, it is difficult to model atmospheric dust, especially in the past or future when there is much less data for an empirical dust model.

Effects of Surface Roughness, Oxidation, and Temperature on the Emissivity of Reactor Pressure Vessel Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, J. L.; Jo, H.; Tirawat, R.

Thermal radiation will be an important mode of heat transfer in future high-temperature reactors and in off-normal high-temperature scenarios in present reactors. In this work, spectral directional emissivities of two reactor pressure vessel (RPV) candidate materials were measured at room temperature after exposure to high-temperature air. In the case of SA508 steel, significant increases in emissivity were observed due to oxidation. In the case of Grade 91 steel, only very small increases were observed under the tested conditions. Effects of roughness were also investigated. To study the effects of roughening, unexposed samples of SA508 and Grade 91 steel were roughenedmore » via one of either grinding or shot-peening before being measured. Significant increases were observed only in samples having roughness exceeding the roughness expected of RPV surfaces. While the emissivity increases for SA508 from oxidation were indeed significant, the measured emissivity coefficients were below that of values commonly used in heat transfer models. Based on the observed experimental data, recommendations for emissivity inputs for heat transfer simulations are provided.« less

The Effect of Hydrofluoric Acid Etching Duration on the Surface Micromorphology, Roughness, and Wettability of Dental Ceramics

PubMed Central

Ramakrishnaiah, Ravikumar; Alkheraif, Abdulaziz A.; Divakar, Darshan Devang; Matinlinna, Jukka P.; Vallittu, Pekka K.

2016-01-01

The current laboratory study is evaluating the effect of hydrofluoric acid etching duration on the surface characteristics of five silica-based glass ceramics. Changes in the pore pattern, crystal structure, roughness, and wettability were compared and evaluated. Seventy-five rectangularly shaped specimens were cut from each material (IPS e-max™, Dentsply Celtra™, Vita Suprinity™, Vita mark II™, and Vita Suprinity FC™); the sectioned samples were finished, polished, and ultrasonically cleaned. Specimens were randomly assigned into study groups: control (no etching) and four experimental groups (20, 40, 80 and 160 s of etching). The etched surfaces’ microstructure including crystal structure, pore pattern, pore depth, and pore width was studied under a scanning electron microscope, and the surface roughness and wettability were analyzed using a non-contact surface profilometer and a contact angle measuring device, respectively. The results were statistically analyzed using one-way analysis of variance (ANOVA) and the post hoc Tukey’s test. The results showed a significant change in the pore number, pore pattern, crystal structure, surface roughness, and wettability with increased etching duration. Etching for a short time resulted in small pores, and etching for longer times resulted in wider, irregular grooves. A significant increase in the surface roughness and wettability was observed with an increase in the etching duration. The findings also suggested a strong association between the surface roughness and wettability. PMID:27240353

Is fault surface roughness indicative of fault mechanisms? Observations from experimental Limestone faults

NASA Astrophysics Data System (ADS)

Sagy, A.; Tesei, T.; Collettini, C.

2016-12-01

Geometrical irregularity of contacting surfaces is a fundamental factor controlling friction and energy dissipation during sliding. We performed direct shear experiments on 20x20 cm limestone surfaces by applying constant normal load (40-200 kN) and sliding velocity 1-300 µm/s. Before shearing, the surfaces were polished with maximal measured amplitudes of less than 0.1 mm. After shear, elongated islands of shear zones are observed, characterized by grooves ploughed into the limestone surfaces and by layers of fine grain wear. These structures indicate that the contact areas during shear are scattered and occupy a limited portion of the entire surface area. The surfaces was scanned by a laser profilometer that measures topography using 640 parallel beams in a single run, offer up to 10 µm accuracy and working ranges of 200 mm. Two distinctive types of topographical end members are defined: rough wavy sections and smooth polished ones. The rough zones display ridges with typical amplitudes of 0.1-1 mm that cross the grooves perpendicular to the slip direction. These features are associated with penetrative brittle damage and with fragmentation. The smoother zones display reflective mirror-like surfaces bordered by topographical sharp steps at heights of 0.3-0.5 mm. These sections are localized inside the wear layer or between the wear layer and the host rock, and are not associated with observed penetrative damage. Preliminary statistical analysis suggests that the roughness of the ridges zones can be characterized using a power-low relationship between profile length and mean roughness, with relatively high values of Hurst exponents (e.g. H > 0.65) parallel to the slip direction. The polished zones, on the other hand, corresponded to lower values of Hurst exponents (e.g. H ≤ 0.6). Both structural and roughness measurements indicate that the distinctive topographic variations on the surfaces reflect competing mechanical processes which occur simultaneously during shear. The wavy ridged zone is the surface expression of penetrative cracking and fragmentation which widen the shear zone, while the smooth zones reflect localized flow and plastic deformation of the wear material. The similarity in topography of shear structures between experimental and natural faults suggests similar mechanical processes.

Large-eddy simulations of surface roughness parameter sensitivity to canopy-structure characteristics

DOE PAGES

Maurer, K. D.; Bohrer, G.; Kenny, W. T.; ...

2015-04-30

Surface roughness parameters, namely the roughness length and displacement height, are an integral input used to model surface fluxes. However, most models assume these parameters to be a fixed property of plant functional type and disregard the governing structural heterogeneity and dynamics. In this study, we use large-eddy simulations to explore, in silico, the effects of canopy-structure characteristics on surface roughness parameters. We performed a virtual experiment to test the sensitivity of resolved surface roughness to four axes of canopy structure: (1) leaf area index, (2) the vertical profile of leaf density, (3) canopy height, and (4) canopy gap fraction.more » We found roughness parameters to be highly variable, but uncovered positive relationships between displacement height and maximum canopy height, aerodynamic canopy height and maximum canopy height and leaf area index, and eddy-penetration depth and gap fraction. We also found negative relationships between aerodynamic canopy height and gap fraction, as well as between eddy-penetration depth and maximum canopy height and leaf area index. We generalized our model results into a virtual "biometric" parameterization that relates roughness length and displacement height to canopy height, leaf area index, and gap fraction. Using a decade of wind and canopy-structure observations in a site in Michigan, we tested the effectiveness of our model-driven biometric parameterization approach in predicting the friction velocity over heterogeneous and disturbed canopies. We compared the accuracy of these predictions with the friction-velocity predictions obtained from the common simple approximation related to canopy height, the values calculated with large-eddy simulations of the explicit canopy structure as measured by airborne and ground-based lidar, two other parameterization approaches that utilize varying canopy-structure inputs, and the annual and decadal means of the surface roughness parameters at the site from meteorological observations. We found that the classical representation of constant roughness parameters (in space and time) as a fraction of canopy height performed relatively well. Nonetheless, of the approaches we tested, most of the empirical approaches that incorporate seasonal and interannual variation of roughness length and displacement height as a function of the dynamics of canopy structure produced more precise and less biased estimates for friction velocity than models with temporally invariable parameters.« less

Large-eddy simulations of surface roughness parameter sensitivity to canopy-structure characteristics

NASA Astrophysics Data System (ADS)

Maurer, K. D.; Bohrer, G.; Kenny, W. T.; Ivanov, V. Y.

2015-04-01

Surface roughness parameters, namely the roughness length and displacement height, are an integral input used to model surface fluxes. However, most models assume these parameters to be a fixed property of plant functional type and disregard the governing structural heterogeneity and dynamics. In this study, we use large-eddy simulations to explore, in silico, the effects of canopy-structure characteristics on surface roughness parameters. We performed a virtual experiment to test the sensitivity of resolved surface roughness to four axes of canopy structure: (1) leaf area index, (2) the vertical profile of leaf density, (3) canopy height, and (4) canopy gap fraction. We found roughness parameters to be highly variable, but uncovered positive relationships between displacement height and maximum canopy height, aerodynamic canopy height and maximum canopy height and leaf area index, and eddy-penetration depth and gap fraction. We also found negative relationships between aerodynamic canopy height and gap fraction, as well as between eddy-penetration depth and maximum canopy height and leaf area index. We generalized our model results into a virtual "biometric" parameterization that relates roughness length and displacement height to canopy height, leaf area index, and gap fraction. Using a decade of wind and canopy-structure observations in a site in Michigan, we tested the effectiveness of our model-driven biometric parameterization approach in predicting the friction velocity over heterogeneous and disturbed canopies. We compared the accuracy of these predictions with the friction-velocity predictions obtained from the common simple approximation related to canopy height, the values calculated with large-eddy simulations of the explicit canopy structure as measured by airborne and ground-based lidar, two other parameterization approaches that utilize varying canopy-structure inputs, and the annual and decadal means of the surface roughness parameters at the site from meteorological observations. We found that the classical representation of constant roughness parameters (in space and time) as a fraction of canopy height performed relatively well. Nonetheless, of the approaches we tested, most of the empirical approaches that incorporate seasonal and interannual variation of roughness length and displacement height as a function of the dynamics of canopy structure produced more precise and less biased estimates for friction velocity than models with temporally invariable parameters.

[Observation of topography and analysis of surface contamination of titanium implant after roughness treatment].

PubMed

Cao, Hongdan; Yang, Xiaodong; Wu, Dayi; Zhang, Xingdong

2007-04-01

The roughness treatment of dental implant surface could improve the bone bonding and increase the success rate of implant, but the difference of diverse treatments is still unknown. In this study using scanning electron microscopy (SEM), energy disperse spectrometer (EDS) and the test of contact angle, we studied the microstructure, surface contamination and surface energy, and hence conducted a comparative analysis of the following surface roughness treatments: Polished Treatment (PT), Sandblasting with Alumina(SA), Sandblasting with Aluminia and Acid-etched (SAA), Sandblasting with Titanium Acid-etched (STA), Electro-erosion Treatment(ET). The result of SEM showed that the surface displayed irregularities after roughness treatments and that the surface properties of different roughness treatments had some distinctions. SAA and SA had some sharp edges and protrutions; the STA showed a regular pattern like honeycomb, but the ET sample treated by electric erosion exhibited the deeper pores of different sizes and the pores with a perforated secondary structure. The EDS indicated that the surface was contaminated after the treatment with foreign materials; the SA surface had some embedded contaminations even after acid etching. The measurement of water contact angle indicated that the morphology correlated with the surface treatments. These findings suggest that the distinction of surface structure and composition caused by different treatments may result in the disparity in biological behavior of dental implant.

Profilometric analysis of two composite resins' surface repolished after tooth brush abrasion with three polishing systems.

PubMed

Uppal, Mudit; Ganesh, Arathi; Balagopal, Suresh; Kaur, Gurleen

2013-07-01

To evaluate the effect of three polishing protocols that could be implemented at recall on the surface roughness of two direct esthetic restorative materials. Specimens (n = 40) measuring 8 mm (length) × 5 mm (width) × 4 mm (height) were fabricated in an acrylic mold using two light-cured resin-based materials (microfilled composite and microhybrid composite). After photopolymerization, all specimens were finished and polished with one of three polishing protocols (Enhance, One Gloss, and Sof-Lex polishing systems). The average surface roughness of each treated specimen was determined using 3D optical profilometer. Next all specimens were brushed 60,000 times with nylon bristles at 7200 rpm using crosshead brushing device with equal parts of toothpaste and water used as abrasive medium. The surface roughness of each specimen was measured after brushing followed by repolishing with one of three polishing protocols, and then, the final surface roughness values were determined. The data were analyzed using one-way and two-factor analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD). Significant difference (P < 0.05) in surface roughness was observed. Simulated brushing following initial polishing procedure significantly roughened the surface of restorative material (P < 0.05). Polishing protocols can be used to restore a smooth surface on esthetic restorative materials following simulated tooth brushing.

Simulation of synthetic gecko arrays shearing on rough surfaces

PubMed Central

Gillies, Andrew G.; Fearing, Ronald S.

2014-01-01

To better understand the role of surface roughness and tip geometry in the adhesion of gecko synthetic adhesives, a model is developed that attempts to uncover the relationship between surface feature size and the adhesive terminal feature shape. This model is the first to predict the adhesive behaviour of a plurality of hairs acting in shear on simulated rough surfaces using analytically derived contact models. The models showed that the nanoscale geometry of the tip shape alters the macroscale adhesion of the array of fibres by nearly an order of magnitude, and that on sinusoidal surfaces with amplitudes much larger than the nanoscale features, spatula-shaped features can increase adhesive forces by 2.5 times on smooth surfaces and 10 times on rough surfaces. Interestingly, the summation of the fibres acting in concert shows behaviour much more complex that what could be predicted with the pull-off model of a single fibre. Both the Johnson–Kendall–Roberts and Kendall peel models can explain the experimentally observed frictional adhesion effect previously described in the literature. Similar to experimental results recently reported on the macroscale features of the gecko adhesive system, adhesion drops dramatically when surface roughness exceeds the size and spacing of the adhesive fibrillar features. PMID:24694893

Ultrastructural evaluation of enamel after dental bleaching associated with fluoride.

PubMed

Dominguez, John A; Bittencourt, Bruna; Michel, Milton; Sabino, Nilson; Gomes, João Carlos; Gomes, Osnara M M

2012-08-01

This study evaluated the effects on human enamel after two bleaching procedures: with a fluoridated bleaching agent and with topical fluoride application postbleaching. It used 43 enamel blocks (3 mm(2) ) that were ground flat (600-2,000 grit) and polished with polishing paste (one and one-fourth). Specimens were randomly divided into three groups according to the bleaching procedure: (1) control group, (2) hydrogen peroxide 35% (HPF) and topical application of fluoride 1.23%, and (3) HP 38% (OP) with fluoride in its composition. Bleaching agents were used according to the manufacturer's instructions. Three methodologies were used: nanoindentation, to observe surface hardness and elastic modulus; atomic force microscopy, to observe surface roughness (R(a) - R(z)); and scanning electron microscopy, to observe the enamel surface effects. Group OP had a decrease in the elastic modulus after bleaching, which was recovered at 14 days. An increased roughness (R(a); 32%) was observed on group HPF and had an increased erosion on enamel surface (67%). It was concluded that topical application of fluoride, after using the nonfluoridated whitening agent, increased the roughness values and erosion of enamel. Copyright © 2012 Wiley Periodicals, Inc.

Secondary flows in turbulent boundary layers over longitudinal surface roughness

NASA Astrophysics Data System (ADS)

Hwang, Hyeon Gyu; Lee, Jae Hwa

2018-01-01

Direct numerical simulations of turbulent boundary layers over longitudinal surface roughness are performed to investigate the impact of the surface roughness on the mean flow characteristics related to counter-rotating large-scale secondary flows. By systematically changing the two parameters of the pitch (P) and width (S) for roughness elements in the ranges of 0.57 ≤P /δ ≤2.39 and 0.15 ≤S /δ ≤1.12 , where δ is the boundary layer thickness, we find that the size of the secondary flow in each case is mostly determined by the value of P - S, i.e., the valley width, over the ridge-type roughness. However, the strength of the secondary flows on the cross-stream plane relative to the flow is increased when the value of P increases or when the value of S decreases. In addition to the secondary flows, additional tertiary and quaternary flows are observed both above the roughness crest and in the valley as the values of P and S increase further. Based on an analysis using the turbulent kinetic energy transport equation, it is shown that the secondary flow over the ridge-type roughness is both driven and sustained by the anisotropy of turbulence, consistent with previous observations of a turbulent boundary layer over strip-type roughness [Anderson et al., J. Fluid Mech. 768, 316 (2015), 10.1017/jfm.2015.91]. Careful inspection of the turbulent kinetic energy budget reveals that the opposite rotational sense of the secondary flow between the ridge- and strip-type roughness elements is primarily attributed to the local imbalance of energy budget created by the strong turbulent transport term over the ridge-type roughness. The active transport of the kinetic energy over the ridge-type roughness is closely associated with the upward deflection of spanwise motions in the valley, mostly due to the roughness edge.

Rough-surface model for surface temperature calculations on Vesta

NASA Astrophysics Data System (ADS)

Palmer, E.; Sykes, M.

2014-07-01

We model observations by the Dawn Visual and Infrared spectrometer (VIR) [1] to reproduce the observed surface temperature of Vesta. The VIR instrument has collected over 3,700 spectral cubes of Vesta out to 5.1 microns. The observed surface temperature is derived by matching the irradiance near 5 microns with a grey body, the Planck function after removing a reflected-light component per previous procedures [2--5] with similar results. We noted that the observed surface temperatures are significantly hotter than what simple theoretical models would predict [2]. To better understand this, we used a high-resolution topographic model of Vesta [6] that provided exact phase, incidence, and emission angles for every VIR pixel. We assume an emissivity of 0.9, Bond albedo of between 0.16 and 0.22 [5], and a variety of thermal inertia values for a low-contrast, highly degraded, homogenous crater. We have created a ''rough-surface'' thermal model that takes into account how irregular grains create sub-pixel variations in the thermal spectrum and describe the effect it has on the observed surface temperatures of Vesta. We have applied this method to the VIR observations of Vesta, which produced a high level of agreement with the observed surface temperatures.

Static and sliding contact of rough surfaces: Effect of asperity-scale properties and long-range elastic interactions

NASA Astrophysics Data System (ADS)

Hulikal, Srivatsan; Lapusta, Nadia; Bhattacharya, Kaushik

2018-07-01

Friction in static and sliding contact of rough surfaces is important in numerous physical phenomena. We seek to understand macroscopically observed static and sliding contact behavior as the collective response of a large number of microscopic asperities. To that end, we build on Hulikal et al. (2015) and develop an efficient numerical framework that can be used to investigate how the macroscopic response of multiple frictional contacts depends on long-range elastic interactions, different constitutive assumptions about the deforming contacts and their local shear resistance, and surface roughness. We approximate the contact between two rough surfaces as that between a regular array of discrete deformable elements attached to a elastic block and a rigid rough surface. The deformable elements are viscoelastic or elasto/viscoplastic with a range of relaxation times, and the elastic interaction between contacts is long-range. We find that the model reproduces the main macroscopic features of evolution of contact and friction for a range of constitutive models of the elements, suggesting that macroscopic frictional response is robust with respect to the microscopic behavior. Viscoelasticity/viscoplasticity contributes to the increase of friction with contact time and leads to a subtle history dependence. Interestingly, long-range elastic interactions only change the results quantitatively compared to the meanfield response. The developed numerical framework can be used to study how specific observed macroscopic behavior depends on the microscale assumptions. For example, we find that sustained increase in the static friction coefficient during long hold times suggests viscoelastic response of the underlying material with multiple relaxation time scales. We also find that the experimentally observed proportionality of the direct effect in velocity jump experiments to the logarithm of the velocity jump points to a complex material-dependent shear resistance at the microscale.

Surface Roughness Retrieval By Inversion Of Hapke Model: A Multi-scale Approach

NASA Astrophysics Data System (ADS)

Labarre, S.; Ferrari, C. C.; Jacquemoud, S.

2015-12-01

Surface roughness is a key property of soils that affects the various processes involved in their evolution such as solar absorption, erosion or moisture, both on Earth and other Solar System surfaces. In the 80's, B.Hapke provided an approximate analytic solution for the bidirectional reflectance distribution function (BRDF) of a particulate medium and, later on, included the effect of surface roughness as a correction factor for the BRDF of a smooth surface. The effect of roughness on the BRDF is modeled as a shadowing function of the so-called roughness parameter, which is the mean slope angle of the facets composing the surface integrated over all scales from the sub-millimeter to the kilometer scales. Hapke model is widely used in planetary sciences to retrieve the roughness parameter from observed BRDFs. Yet the physical meaning of the retrieved roughness is not clear as the scale at which it happens is not defined. This work aims at understanding the relative impact of the roughness defined at each scale to the BRDF in order to test the ability of the singly retrieved roughness parameter at describing the ground truth. We propose to perform a wavelet analysis on meter-sized digital elevation models (DEM) generated from various volcanic and sedimentary terrains at high-mm-scale spatial resolution. It consists in splitting the DEM in several spatial frequencies and in simulating the BRDF at each scale with a ray-tracing code. Also the global BRDF is simulated so that the relative contribution of each scale can be studied. Then the Hapke model is fitted to the global BRDF to retrieve the roughness parameter. We will expose and discuss the results of this study. Figure: BRDF of a'a lava DEM simulated at varying azimut (φi) and incidence angles (i), in the principal plan. The direction of the light source is given by the colored squares. Mean slope angle of the surface is 36°.

Cleaning of optical surfaces by capacitively coupled RF discharge plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, P. K., E-mail: praveenyadav@rrcat.gov.in; Rai, S. K.; Nayak, M.

2014-04-24

In this paper, we report cleaning of carbon capped molybdenum (Mo) thin film by in-house developed radio frequency (RF) plasma reactor, at different powers and exposure time. Carbon capped Mo films were exposed to oxygen plasma for different durations at three different power settings, at a constant pressure. After each exposure, the thickness of the carbon layer and the roughness of the film were determined by hard x-ray reflectivity measurements. It was observed that most of the carbon film got removed in first 15 minutes exposure. A high density layer formed on top of the Mo film was also observedmore » and it was noted that this layer cannot be removed by successive exposures at different powers. A significant improvement in interface roughness with a slight improvement in top film roughness was observed. The surface roughness of the exposed and unexposed samples was also confirmed by atomic force microscopy measurements.« less

Effect of bleaching agents and whitening dentifrices on the surface roughness of human teeth enamel.

PubMed

Özkan, Pelin; Kansu, Gülay; Özak, Sule Tuğba; Kurtulmuş-Yilmaz, Sevcan; Kansu, Pelin

2013-01-01

The aim of this in vitro study was to evaluate the surface roughness of human enamel bleached with 10% carbamide peroxide or 10% hydrogen peroxide bleaching agents at different times and also subjected to different superficial cleaning treatments. One hundred and forty flat enamel samples were divided into 14 groups, Group 1-Group 14 (G1-G14). G1-G7 were treated with 10% carbamide peroxide and different dentifrices, G8-G14 were treated with 10% hydrogen peroxide and different dentifrices (G1 and G8: not brushed as control groups; G2 and G9: brushed with Ipana® toothpaste; G3 and G10: brushed with Clinomyn® toothpaste; G4 and G11: brushed with Moos Dent® toothpaste; G5 and G12: brushed with Signal® toothpaste; G6 and G13: brushed with Colgate® toothpaste; G7 and G14: brushed without dentifrice). A profilometer was used to measure average roughness values of the initial surface roughness and at each 7-day-interval. The bleaching was performed for 6 h a day and the surface cleaning treatment was performed 3-times a day, 2 min each time, for 4 weeks. The samples were stored in distilled water during the test period. Statistical analysis revealed significant differences in surface roughness values over time for all groups except G1 and G8 (not brushed). The results of the surface roughness of all groups were nearly the same. The bleaching with 10% hydrogen peroxide and 10% carbamide peroxide did not alter the enamel surface roughness, but when the bleaching treatment was performed combined with abrasive dentifrices, a significant increase in roughness values was observed.

Sub ablative Er: YAG laser irradiation on surface roughness of eroded dental enamel.

PubMed

Curylofo-Zotti, Fabiana Almeida; Lepri, Taísa Penazzo; Colucci, Vivian; Turssi, Cecília Pedroso; Corona, Silmara Aparecida Milori

2015-11-01

This study evaluated the effects of Er:YAG laser irradiation applied at varying pulse repetition rate on the surface roughness of eroded enamel. Bovine enamel slabs (n = 10) were embedded in polyester resin, ground, and polished. To erosive challenges, specimens were immersed two times per day in 20mL of concentrated orange juice (pH = 3.84) under agitation, during a two-day period. Specimens were randomly assigned to irradiation with the Er:YAG laser (focused mode, pulse energy of 60 mJ and energy density of 3.79 J/cm(2) ) operating at 1, 2, 3, or 4 Hz. The control group was left nonirradiated. Surface roughness measurements were recorded post erosion-like formation and further erosive episodes by a profilometer and observed through atomic force microscopy (AFM). Analysis of variance revealed that the control group showed the lowest surface roughness, while laser-irradiated substrates did not differ from each other following post erosion-like lesion formation. According to analysis of covariance, at further erosive episodes, the control group demonstrated lower surface roughness (P > 0.05), than any of the irradiated groups (P < 0.05). The pulse repetition rate of the Er:YAG laser did not affect roughness of dental enamel eroded. The AFM images showed that the specimens irradiated by the Er:YAG laser at 1 Hz presented a less rough surface than those irradiated at 2, 3, and 4 Hz. © 2015 Wiley Periodicals, Inc.

Impact of gyro-motion and sheath acceleration on the flux distribution on rough surfaces

NASA Astrophysics Data System (ADS)

Schmid, K.; Mayer, M.; Adelhelm, C.; Balden, M.; Lindig, S.; ASDEX Upgrade Team

2010-10-01

As was already observed experimentally, the erosion of tungsten (W) coated graphite (C) tiles in ASDEX-Upgrade (AUG) exhibits regular erosion patterns on the micrometre rough surfaces whose origin is not fully understood: surfaces inclined towards the magnetic field direction show strong net W erosion while surfaces facing away from the magnetic field are shadowed from erosion and may even exhibit net W deposition. This paper presents a model which explains the observed erosion/deposition pattern. It is based on the calculation of ion trajectories dropping through the plasma sheath region to the rough surface with combined magnetic and electrical fields. The surface topography used in the calculations is taken from atomic force microscope measurement of real AUG tiles. The calculated erosion patterns are directly compared with secondary electron microscopy images of the erosion zones from the same location. The erosion on surfaces inclined towards the magnetic field is due to ions from the bulk plasma which enter the sheath gyrating along the magnetic field lines, while the deposition of W on surfaces facing away from the magnetic field is due to promptly re-deposited W that is ionized still within the magnetic pre-sheath.

Nanotextured PDMS Substrates for Enhanced Roughness and Aptamer Immobilization for Cancer Cell Capture

NASA Astrophysics Data System (ADS)

Islam, Muhymin; Mahmood, Arif; Bellah, Md.; Kim, Young-Tae; Iqbal, Samir

2014-03-01

Detection of circulating tumor cells (CTCs) in the early stages of cancer is requires very sensitive approach. Nanotextured polydimethylsiloxane (PDMS) substrates were fabricated by micro reactive ion etching (Micro-RIE) to have better control on surface morphology and to improve the affinity of PDMS surfaces to capture cancer cells using surface immobilized aptamers. The aptamers were specific to epidermal growth factor receptors (EGFR) present in cell membranes, and overexpressed in tumor cells. We also investigated the effect of nano-scale features on cell capturing by implementing various surfaces of different roughnesses. Three different recipes were used to prepare nanotextured PDMS by micro-RIE using oxygen (O2) and carbon tetrafluoride (CF4). The measured average roughness of three nanotextured PDMS surfaces were found to impact average densities of captured cells. In all cases, nanotextured PDMS facilitated cell capturing possibly due to increased effective surface area of roughened substrates at nanoscale. It was also observed that cell capture efficiency was higher for higher surface roughness. The nanotextured PDMS substrates are thus useful for cancer cytology devices.

A quantitative AFM analysis of nano-scale surface roughness in various orthodontic brackets.

PubMed

Lee, Gi-Ja; Park, Ki-Ho; Park, Young-Guk; Park, Hun-Kuk

2010-10-01

In orthodontics, the surface roughnesses of orthodontic archwire and brackets affect the effectiveness of arch-guided tooth movement, corrosion behavior, and the aesthetics of orthodontic components. Atomic force microscopy (AFM) measurements were used to provide quantitative information on the surface roughness of the orthodontic material. In this study, the changes in surface roughness of various orthodontic bracket slots before and after sliding movement of archwire in vitro and in vivo were observed through the utilization of AFM. Firstly, we characterized the surface of four types of brackets slots as follows: conventional stainless steel (Succes), conventional ceramic (Perfect), self-ligating stainless steel (Damon) and self-ligating ceramic (Clippy-C) brackets. Succes) and Damon brackets showed relatively smooth surfaces, while Perfect had the roughest surface among the four types of brackets used. Secondly, after in vitro sliding test with beta titanium wire in two conventional brackets (Succes and Perfect), there were significant increases in only stainless steel bracket, Succes. Thirdly, after clinical orthodontic treatment for a maximum of 2 years, the self-ligating stainless steel bracket, Damon, showed a significant increase in surface roughness. But self-ligating ceramic brackets, Clippy-C, represented less significant changes in roughness parameters than self-ligating stainless steel ones. Based on the results of the AFM measurements, it is suggested that the self-ligating ceramic bracket has great possibility to exhibit less friction and better biocompatibility than the other tested brackets. This implies that these bracket slots will aid in the effectiveness of arch-guided tooth movement.

Optimization of Machining Process Parameters for Surface Roughness of Al-Composites

NASA Astrophysics Data System (ADS)

Sharma, S.

2013-10-01

Metal matrix composites (MMCs) have become a leading material among the various types of composite materials for different applications due to their excellent engineering properties. Among the various types of composites materials, aluminum MMCs have received considerable attention in automobile and aerospace applications. These materials are known as the difficult-to-machine materials because of the hardness and abrasive nature of reinforcement element-like silicon carbide particles. In the present investigation Al-SiC composite was produced by stir casting process. The Brinell hardness of the alloy after SiC addition had increased from 74 ± 2 to 95 ± 5 respectively. The composite was machined using CNC turning center under different machining parameters such as cutting speed (S), feed rate (F), depth of cut (D) and nose radius (R). The effect of machining parameters on surface roughness (Ra) was studied using response surface methodology. Face centered composite design with three levels of each factor was used for surface roughness study of the developed composite. A response surface model for surface roughness was developed in terms of main factors (S, F, D and R) and their significant interactions (SD, SR, FD and FR). The developed model was validated by conducting experiments under different conditions. Further the model was optimized for minimum surface roughness. An error of 3-7 % was observed in the modeled and experimental results. Further, it was fond that the surface roughness of Al-alloy at optimum conditions is lower than that of Al-SiC composite.

Dimensional accuracy and surface property of titanium casting using gypsum-bonded alumina investment.

PubMed

Yan, Min; Takahashi, Hidekazu; Nishimura, Fumio

2004-12-01

The aim of the present study was to evaluate the dimensional accuracy and surface property of titanium casting obtained using a gypsum-bonded alumina investment. The experimental gypsum-bonded alumina investment with 20 mass% gypsum content mixed with 2 mass% potassium sulfate was used for five cp titanium castings and three Cu-Zn alloy castings. The accuracy, surface roughness (Ra), and reaction layer thickness of these castings were investigated. The accuracy of the castings obtained from the experimental investment ranged from -0.04 to 0.23%, while surface roughness (Ra) ranged from 7.6 to 10.3microm. A reaction layer of about 150 microm thickness under the titanium casting surface was observed. These results suggested that the titanium casting obtained using the experimental investment was acceptable. Although the reaction layer was thin, surface roughness should be improved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maurer, K. D.; Bohrer, G.; Kenny, W. T.

Surface roughness parameters, namely the roughness length and displacement height, are an integral input used to model surface fluxes. However, most models assume these parameters to be a fixed property of plant functional type and disregard the governing structural heterogeneity and dynamics. In this study, we use large-eddy simulations to explore, in silico, the effects of canopy-structure characteristics on surface roughness parameters. We performed a virtual experiment to test the sensitivity of resolved surface roughness to four axes of canopy structure: (1) leaf area index, (2) the vertical profile of leaf density, (3) canopy height, and (4) canopy gap fraction.more » We found roughness parameters to be highly variable, but uncovered positive relationships between displacement height and maximum canopy height, aerodynamic canopy height and maximum canopy height and leaf area index, and eddy-penetration depth and gap fraction. We also found negative relationships between aerodynamic canopy height and gap fraction, as well as between eddy-penetration depth and maximum canopy height and leaf area index. We generalized our model results into a virtual "biometric" parameterization that relates roughness length and displacement height to canopy height, leaf area index, and gap fraction. Using a decade of wind and canopy-structure observations in a site in Michigan, we tested the effectiveness of our model-driven biometric parameterization approach in predicting the friction velocity over heterogeneous and disturbed canopies. We compared the accuracy of these predictions with the friction-velocity predictions obtained from the common simple approximation related to canopy height, the values calculated with large-eddy simulations of the explicit canopy structure as measured by airborne and ground-based lidar, two other parameterization approaches that utilize varying canopy-structure inputs, and the annual and decadal means of the surface roughness parameters at the site from meteorological observations. We found that the classical representation of constant roughness parameters (in space and time) as a fraction of canopy height performed relatively well. Nonetheless, of the approaches we tested, most of the empirical approaches that incorporate seasonal and interannual variation of roughness length and displacement height as a function of the dynamics of canopy structure produced more precise and less biased estimates for friction velocity than models with temporally invariable parameters.« less

Micro and sub-micron surface structuring of AZ31 by laser re-melting and dimpling

NASA Astrophysics Data System (ADS)

Furlan, Valentina; Demir, Ali Gökhan; Previtali, Barbara

2015-12-01

In this work, the use of ns-pulsed fibre laser for surface structuring of AZ31 Mg alloy is investigated. Surface re-melting was employed to change surface morphology, especially in terms of surface roughness. Dimpling by percussion microdrilling was investigated to control the hole geometry.. With surface remelting mono-directional and homogeneous surfaces were obtained with Fl<500 J/cm2. Above 500 J/cm2 particle generation was observed, which induced sub-micron structure growth with nano-fibrous features. Moreover, surface roughness could be controlled below the initial value and much higher. With dimpling, transformation from gentle to strong ablation was observed at F0=10.3 J/cm2. XRD analysis was employed to link oxide growth to the surface morphology. Tensile tests were carried out to assess the damage on the mechanical properties after surface structuring.

Surface Roughening Behavior of 6063 Aluminum Alloy during Bulging by Spun Tubes

PubMed Central

Cai, Yang; Wang, Xiaosong; Yuan, Shijian

2017-01-01

Severe surface roughening during the hydroforming of aluminum alloy parts can produce surface defects that severely restrict their application in the automobile and aerospace industry. To understand the relation between strain, grain size and surface roughness under biaxial stress conditions, hydro-bulging tests of aluminum alloy tubes were carried out, and the tubes with different grain sizes were prepared by a spinning and annealing process. The surface roughness was measured by a laser scanning confocal microscope to evaluate the surface roughening macroscopical behavior, and the corresponding microstructures were observed using electron back-scattered diffraction (EBSD) to reveal the roughening microscopic behavior. The results obtained show that the surface roughness increased with both strain and grain size under biaxial stress. No surface defects were observed on the surface when the grain size was less than 105 μm if the strain was less than 18%, or when the grain size was between 130 and 175 μm if the strain was less than 15.88% and 7.15%, respectively. The surface roughening microscopic behavior was identified as an inhomogeneous grain size distribution, which became more pronounced with increasing grain size and resulted in greater local deformation. Concentrated grain orientation also results in severe inhomogeneous deformation during plastics deformation, and serious surface roughening. PMID:28772658

Combined Radar-Radiometer Surface Soil Moisture and Roughness Estimation

NASA Technical Reports Server (NTRS)

Akbar, Ruzbeh; Cosh, Michael H.; O'Neill, Peggy E.; Entekhabi, Dara; Moghaddam, Mahta

2017-01-01

A robust physics-based combined radar-radiometer, or Active-Passive, surface soil moisture and roughness estimation methodology is presented. Soil moisture and roughness retrieval is performed via optimization, i.e., minimization, of a joint objective function which constrains similar resolution radar and radiometer observations simultaneously. A data-driven and noise-dependent regularization term has also been developed to automatically regularize and balance corresponding radar and radiometer contributions to achieve optimal soil moisture retrievals. It is shown that in order to compensate for measurement and observation noise, as well as forward model inaccuracies, in combined radar-radiometer estimation surface roughness can be considered a free parameter. Extensive Monte-Carlo numerical simulations and assessment using field data have been performed to both evaluate the algorithms performance and to demonstrate soil moisture estimation. Unbiased root mean squared errors (RMSE) range from 0.18 to 0.03 cm3cm3 for two different land cover types of corn and soybean. In summary, in the context of soil moisture retrieval, the importance of consistent forward emission and scattering development is discussed and presented.

Combined Radar-Radiometer Surface Soil Moisture and Roughness Estimation.

PubMed

Akbar, Ruzbeh; Cosh, Michael H; O'Neill, Peggy E; Entekhabi, Dara; Moghaddam, Mahta

2017-07-01

A robust physics-based combined radar-radiometer, or Active-Passive, surface soil moisture and roughness estimation methodology is presented. Soil moisture and roughness retrieval is performed via optimization, i.e., minimization, of a joint objective function which constrains similar resolution radar and radiometer observations simultaneously. A data-driven and noise-dependent regularization term has also been developed to automatically regularize and balance corresponding radar and radiometer contributions to achieve optimal soil moisture retrievals. It is shown that in order to compensate for measurement and observation noise, as well as forward model inaccuracies, in combined radar-radiometer estimation surface roughness can be considered a free parameter. Extensive Monte-Carlo numerical simulations and assessment using field data have been performed to both evaluate the algorithm's performance and to demonstrate soil moisture estimation. Unbiased root mean squared errors (RMSE) range from 0.18 to 0.03 cm3/cm3 for two different land cover types of corn and soybean. In summary, in the context of soil moisture retrieval, the importance of consistent forward emission and scattering development is discussed and presented.

Are superhydrophobic surfaces best for icephobicity?

PubMed

Jung, Stefan; Dorrestijn, Marko; Raps, Dominik; Das, Arindam; Megaridis, Constantine M; Poulikakos, Dimos

2011-03-15

Ice formation can have catastrophic consequences for human activity on the ground and in the air. Here we investigate water freezing delays on untreated and coated surfaces ranging from hydrophilic to superhydrophobic and use these delays to evaluate icephobicity. Supercooled water microdroplets are inkjet-deposited and coalesce until spontaneous freezing of the accumulated mass occurs. Surfaces with nanometer-scale roughness and higher wettability display unexpectedly long freezing delays, at least 1 order of magnitude longer than typical superhydrophobic surfaces with larger hierarchical roughness and low wettability. Directly related to the main focus on heterogeneous nucleation and freezing delay of supercooled water droplets, the observed ensuing crystallization process consisted of two distinct phases: one very rapid recalescent partial solidification phase and a subsequent slower phase. Observations of the droplet collision process employed for the continuous liquid mass accumulation up to the point of ice formation reveal a previously unseen atmospheric-pressure, subfreezing-temperature regime for liquid-on-liquid bounce. On the basis of the entropy reduction of water near a solid surface, we formulate a modification to the classical heterogeneous nucleation theory, which predicts the observed freezing delay trends. Our results bring to question recent emphasis on super water-repellent surface formulations for ice formation retardation and suggest that anti-icing design must optimize the competing influences of both wettability and roughness.

Effect of prophylactic polishing protocols on the surface roughness of esthetic restorative materials.

PubMed

Neme, A L; Frazier, K B; Roeder, L B; Debner, T L

2002-01-01

Many polishing protocols have been evaluated in vitro for their effect on the surface roughness of restorative materials. These results have been useful in establishing protocols for in vivo application. However, limited research has focused on the subsequent care and maintenance of esthetic restorations following their placement. This investigation evaluated the effect of five polishing protocols that could be implemented at recall on the surface roughness of five direct esthetic restorative materials. Specimens (n=25) measuring 8 mm diameter x 3 mm thick were fabricated in an acrylic mold using five light-cured resin-based materials (hybrid composite, microfilled composite, packable composite, compomer and resin-modified glass ionomer). After photopolymerization, all specimens were polished with Sof-Lex Disks to produce an initial (baseline) surface finish. All specimens were then polished with one of five prophylactic protocols (Butler medium paste, Butler coarse paste, OneGloss, SuperBuff or OneGloss & SuperBuff). The average surface roughness of each treated specimen was determined from three measurements with a profilometer (Surface 1). Next, all specimens were brushed 60,000 times at 1.5 Hz using a brush-head force of 2 N on a Manly V-8 cross-brushing machine in a 50:50 (w/w) slurry of toothpaste and water. The surface roughness of each specimen was measured after brushing (Surface 2) followed by re-polishing with one of five protocols, then final surface roughness values were determined (Surface 3). The data were analyzed using repeated measures ANOVA. Significant differences (p=0.05) in surface roughness were observed among restorative materials and polishing protocols. The microfilled and hybrid resin composite yielded significantly rougher surfaces than the other three materials following tooth brushing. Prophylactic polishing protocols can be used to restore a smooth surface on resin-based esthetic restorative materials following simulated tooth brushing.

Non-Thermal Atmospheric Plasma: Can it Be Taken as a Common Solution for the Surface Treatment of Dental Materials?

NASA Astrophysics Data System (ADS)

Emre, Seker; Mehmet, Ali Kilicarslan; Serdar, Polat; Emre, Ozkir; Suat, Pat

2016-04-01

This study aimed to evaluate the surface roughness and wetting properties of various dental prosthetic materials after different durations of non-thermal atmospheric plasma (NTAP) treatment. One hundred and sixty discs of titanium (Ti) (n:40), cobalt chromium (Co-Cr) (n:40), yttrium stabilized tetragonal zirconia polycrystals (Y-TZP) (n:40) and polymethylmethacrylate (PMMA) (n:40) materials were machined and smoothed with silicon carbide papers. The surface roughness was evaluated in a control group and in groups with different plasma exposure times [1-3-5 s]. The average surface roughness (Ra) and contact angle (CA) measurements were recorded via an atomic force microscope (AFM) and tensiometer, respectively. Surface changes were examined with a scanning electron microscope (SEM). Data were analyzed with two-way analysis of variance (ANOVA) and the Tukey HSD test α=0.05). According to the results, the NTAP surface treatment significantly affected the roughness and wettability properties (P < 0.05). SEM images reveal that more grooves were present in the NTAP groups. With an increase in the NTAP application time, an apparent increment was observed for Ra, except in the PMMA group, and a remarkable reduction in CA was observed in all groups. It is concluded that the NTAP technology could enhance the roughening and wetting performance of various dental materials. supported by the Department of Scientific Research, Eskisehir Osmangazi University, Turkey (No. 201441045)

Spatial characteristics of secondary flow in a turbulent boundary layer over longitudinal surface roughness

NASA Astrophysics Data System (ADS)

Hwang, Hyeon Gyu; Lee, Jae Hwa

2017-11-01

Direct numerical simulations of turbulent boundary layers (TBLs) over spanwise heterogeneous surface roughness are performed to investigate the characteristics of secondary flow. The longitudinal surface roughness, which features lateral change in bed elevation, is described by immersed boundary method. The Reynolds number based on the momentum thickness is varied in the range of Reθ = 300-900. As the TBLs over the roughness elements spatially develop in the streamwise direction, a secondary flow emerges in a form of counter-rotating vortex pair. As the spanwise spacing between the roughness elements and roughness width vary, it is shown that the size of the secondary flow is determined by the valley width between the roughness elements. In addition, the strength of the secondary flow is mostly affected by the spanwise distance between the cores of the secondary flow. Analysis of the Reynolds-averaged turbulent kinetic energy transport equation reveals that the energy redistribution terms in the TBLs over-the ridge type roughness play an important role to derive low-momentum pathways with upward motion over the roughness crest, contrary to the previous observation with the strip-type roughness. This research was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2017R1D1A1A09000537) and the Ministry of Science, ICT & Future Planning (NRF-2017R1A5A1015311).

[Influence of different surface roughness of opaque porcelain on reflectance and L* value of porcelain fused to metal].

PubMed

Wang, Hui; Xiong, Fang; Yu, Hai-yang; Luo, Zhen-hua

2009-08-01

The purpose of this study was to investigate how different surface roughness of opaque porcelain influence reflectance and CIE L* value of porcelain fused to metal (PFM) restorations. 48 casted Ni-Cr alloy metal specimens (12.0 mm x 1.0 mm) were fabricated with ShoFu Vintage Halo porcelain and divided into six groups, eight pieces for each group. The specimens in the first group without polishing were used as control. Other groups were polished against 200-, 400-, 600-, 800-, and 1000-grit sandpaper after sintered, respectively. Surface roughness and color parameters of the specimens were measured with a Surface Roughometer EX2154-13 and a spectrocolorimeter, respectively. Ra (arithmetical mean deviation of the profile) was the main standard value to describe the surface roughness of many kinds of meatal or porcelain materials, and here we used it to express surface roughness of opaque porcelain. The data were statistically analyzed by one-way analysis of variance (alpha = 0.05) in SPSS 13.0. The reflectance value increased from 72.386 +/- 3.953 to 78.671 +/- 3.408, and CIE L* value from 90.189 +/- 1.200 to 93.496 +/- 1.070 with the increasing of surface roughness (Ra) of opaque porcelain from (0.226 +/- 0.069) microm to (0.706 +/- 0.082) microm. The same magnitude were also observed after body porcelain and enamel porcelain were sintered on with reflectance increased from 76.301 +/- 3.097 to 81.529 +/- 4.028, and CIE L* value from 80.694 +/- 1.564 to 84.604 +/- 2.964. The surface roughness of opaque porcelain had effects on the reflectance and value of PFM restorations. Within the limitation of this study, the recommended Ra range of opaque porcelain was 0.23-0.50 microm.

Characterizing the SWOT discharge error budget on the Sacramento River, CA

NASA Astrophysics Data System (ADS)

Yoon, Y.; Durand, M. T.; Minear, J. T.; Smith, L.; Merry, C. J.

2013-12-01

The Surface Water and Ocean Topography (SWOT) is an upcoming satellite mission (2020 year) that will provide surface-water elevation and surface-water extent globally. One goal of SWOT is the estimation of river discharge directly from SWOT measurements. SWOT discharge uncertainty is due to two sources. First, SWOT cannot measure channel bathymetry and determine roughness coefficient data necessary for discharge calculations directly; these parameters must be estimated from the measurements or from a priori information. Second, SWOT measurement errors directly impact the discharge estimate accuracy. This study focuses on characterizing parameter and measurement uncertainties for SWOT river discharge estimation. A Bayesian Markov Chain Monte Carlo scheme is used to calculate parameter estimates, given the measurements of river height, slope and width, and mass and momentum constraints. The algorithm is evaluated using simulated both SWOT and AirSWOT (the airborne version of SWOT) observations over seven reaches (about 40 km) of the Sacramento River. The SWOT and AirSWOT observations are simulated by corrupting the ';true' HEC-RAS hydraulic modeling results with the instrument error. This experiment answers how unknown bathymetry and roughness coefficients affect the accuracy of the river discharge algorithm. From the experiment, the discharge error budget is almost completely dominated by unknown bathymetry and roughness; 81% of the variance error is explained by uncertainties in bathymetry and roughness. Second, we show how the errors in water surface, slope, and width observations influence the accuracy of discharge estimates. Indeed, there is a significant sensitivity to water surface, slope, and width errors due to the sensitivity of bathymetry and roughness to measurement errors. Increasing water-surface error above 10 cm leads to a corresponding sharper increase of errors in bathymetry and roughness. Increasing slope error above 1.5 cm/km leads to a significant degradation due to direct error in the discharge estimates. As the width error increases past 20%, the discharge error budget is dominated by the width error. Above two experiments are performed based on AirSWOT scenarios. In addition, we explore the sensitivity of the algorithm to the SWOT scenarios.

Influence of Structural Features and Fracture Processes on Surface Roughness: A Case Study from the Krosno Sandstones of the Górka-Mucharz Quarry (Little Beskids, Southern Poland)

NASA Astrophysics Data System (ADS)

Pieczara, Łukasz

2015-09-01

The paper presents the results of analysis of surface roughness parameters in the Krosno Sandstones of Mucharz, southern Poland. It was aimed at determining whether these parameters are influenced by structural features (mainly the laminar distribution of mineral components and directional distribution of non-isometric grains) and fracture processes. The tests applied in the analysis enabled us to determine and describe the primary statistical parameters used in the quantitative description of surface roughness, as well as specify the usefulness of contact profilometry as a method of visualizing spatial differentiation of fracture processes in rocks. These aims were achieved by selecting a model material (Krosno Sandstones from the Górka-Mucharz Quarry) and an appropriate research methodology. The schedule of laboratory analyses included: identification analyses connected with non-destructive ultrasonic tests, aimed at the preliminary determination of rock anisotropy, strength point load tests (cleaved surfaces were obtained due to destruction of rock samples), microscopic analysis (observation of thin sections in order to determine the mechanism of inducing fracture processes) and a test method of measuring surface roughness (two- and three-dimensional diagrams, topographic and contour maps, and statistical parameters of surface roughness). The highest values of roughness indicators were achieved for surfaces formed under the influence of intragranular fracture processes (cracks propagating directly through grains). This is related to the structural features of the Krosno Sandstones (distribution of lamination and bedding).

A Low-Speed Experimental Investigation of the Effect of a Sandpaper Type of Roughness on Boundary-Layer Transition

NASA Technical Reports Server (NTRS)

Von Doenhoff, Albert E; Horton, Elmer A

1958-01-01

An investigation was made in the Langley low-turbulence pressure tunnel to determine the effect of size and location of a sandpaper type of roughness on the Reynolds number for transition. Transition was observed by means of a hot-wire anemometer located at various chordwise stations for each position of the roughness. These observations indicated that when the roughness is sufficiently submerged in the boundary layer to provide a substantially linear variation of boundary-layer velocity with distance from the surface up to the top of the roughness, turbulent "spots" begin to appear immediately behind the roughness when the Reynolds number based on the velocity at the top of the roughness height exceeds a value of approximately 600. At Reynolds numbers even slightly below the critical value (value for transition), the sandpaper type of roughness introduced no measurable disturbances into the laminar layer downstream of the roughness. The extent of the roughness area does not appear to have an important effect on the critical value of the roughness Reynolds number.

Estimation of gloss from rough surface parameters

NASA Astrophysics Data System (ADS)

Simonsen, Ingve; Larsen, Åge G.; Andreassen, Erik; Ommundsen, Espen; Nord-Varhaug, Katrin

2005-12-01

Gloss is a quantity used in the optical industry to quantify and categorize materials according to how well they scatter light specularly. With the aid of phase perturbation theory, we derive an approximate expression for this quantity for a one-dimensional randomly rough surface. It is demonstrated that gloss depends in an exponential way on two dimensionless quantities that are associated with the surface randomness: the root-mean-square roughness times the perpendicular momentum transfer for the specular direction, and a correlation function dependent factor times a lateral momentum variable associated with the collection angle. Rigorous Monte Carlo simulations are used to access the quality of this approximation, and good agreement is observed over large regions of parameter space.

Role of roughness parameters on the tribology of randomly nano-textured silicon surface.

PubMed

Gualtieri, E; Pugno, N; Rota, A; Spagni, A; Lepore, E; Valeri, S

2011-10-01

This experimental work is oriented to give a contribution to the knowledge of the relationship among surface roughness parameters and tribological properties of lubricated surfaces; it is well known that these surface properties are strictly related, but a complete comprehension of such correlations is still far to be reached. For this purpose, a mechanical polishing procedure was optimized in order to induce different, but well controlled, morphologies on Si(100) surfaces. The use of different abrasive papers and slurries enabled the formation of a wide spectrum of topographical irregularities (from the submicro- to the nano-scale) and a broad range of surface profiles. An AFM-based morphological and topographical campaign was carried out to characterize each silicon rough surface through a set of parameters. Samples were subsequently water lubricated and tribologically characterized through ball-on-disk tribometer measurements. Indeed, the wettability of each surface was investigated by measuring the water droplet contact angle, that revealed a hydrophilic character for all the surfaces, even if no clear correlation with roughness emerged. Nevertheless, this observation brings input to the purpose, as it allows to exclude that the differences in surface profile affect lubrication. So it is possible to link the dynamic friction coefficient of rough Si samples exclusively to the opportune set of surface roughness parameters that can exhaustively describe both height amplitude variations (Ra, Rdq) and profile periodicity (Rsk, Rku, Ic) that influence asperity-asperity interactions and hydrodynamic lift in different ways. For this main reason they cannot be treated separately, but with dependent approach through which it was possible to explain even counter intuitive results: the unexpected decreasing of friction coefficient with increasing Ra is justifiable by a more consistent increasing of kurtosis Rku.

Relation between skin micro-topography, roughness, and skin age.

PubMed

Trojahn, C; Dobos, G; Schario, M; Ludriksone, L; Blume-Peytavi, U; Kottner, J

2015-02-01

The topography of the skin surface consists of lines, wrinkles, and scales. Primary and secondary lines form a network like structure that may be identified as polygons. Skin surface roughness measurements are widely applied in dermatological research and practice but the relation between roughness parameters and their anatomical equivalents are unclear. This study aimed to investigate whether the number of closed polygons (NCP) per measurement field can be used as a reliable parameter to measure skin surface topography. For this purpose, we analysed the relation between skin surface roughness parameters and NCP in different age groups. Images of the volar forearm skin of 38 subjects (14 children, 12 younger, and 12 older adults) were obtained with the VisioScan VC98. The NCP was counted by three independent researchers and selected roughness parameters were measured. Interrater reliability of counting the number of closed polygons and correlations between NCP, roughness parameters, and age were calculated. The mean NCP/mm² in children was 3.1 (SD 1.1), in younger adults 1.0 (SD 0.7), and in older adults 1.0 (SD 0.9). The interrater reliability was 0.9. A negative correlation of NCP/mm² with age was observed, whereas measured roughness parameters were positively associated with age. NCP/mm² was weakly related to skin roughness. The NCP/mm² is a reproducible parameter for characterizing the skin surface topography. It is proposed as an additional parameter in dermatological research and practice because it represents distinct aspects of the cutaneous profile not covered by established roughness parameters. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Laboratory observations and simulations of phase reddening

NASA Astrophysics Data System (ADS)

Schröder, S. E.; Grynko, Ye.; Pommerol, A.; Keller, H. U.; Thomas, N.; Roush, T. L.

2014-09-01

The visible reflectance spectrum of many Solar System bodies changes with changing viewing geometry for reasons not fully understood. It is often observed to redden (increasing spectral slope) with increasing solar phase angle, an effect known as phase reddening. Only once, in an observation of the martian surface by the Viking 1 lander, was reddening observed up to a certain phase angle with bluing beyond, making the reflectance ratio as a function of phase angle shaped like an arch. However, in laboratory experiments this arch-shape is frequently encountered. To investigate this, we measured the bidirectional reflectance of particulate samples of several common rock types in the 400-1000 nm wavelength range and performed ray-tracing simulations. We confirm the occurrence of the arch for surfaces that are forward scattering, i.e. are composed of semi-transparent particles and are smooth on the scale of the particles, and for which the reflectance increases from the lower to the higher wavelength in the reflectance ratio. The arch shape is reproduced by the simulations, which assume a smooth surface. However, surface roughness on the scale of the particles, such as the Hapke and van Horn (Hapke, B., van Horn, H. [1963]. J. Geophys. Res. 68, 4545-4570) fairy castles that can spontaneously form when sprinkling a fine powder, leads to monotonic reddening. A further consequence of this form of microscopic roughness (being indistinct without the use of a microscope) is a flattening of the disk function at visible wavelengths, i.e. Lommel-Seeliger-type scattering. The experiments further reveal monotonic reddening for reflectance ratios at near-IR wavelengths. The simulations fail to reproduce this particular reddening, and we suspect that it results from roughness on the surface of the particles. Given that the regolith of atmosphereless Solar System bodies is composed of small particles, our results indicate that the prevalence of monotonic reddening and Lommel-Seeliger-type scattering for these bodies results from microscopic roughness, both in the form of structures built by the particles and roughness on the surface of the particles themselves. It follows from the singular Viking 1 observation that the surface in front of the lander was composed of semi-transparent particles, and was smooth on the scale of the particle size.

Corroded surface roughness of copper analyzed by Fourier transform infrared mapping microscopy and optical profilometric study.

PubMed

Kasperek, J; Lefez, B; Beucher, E

2004-02-01

This study shows the effects of roughness on infrared spectra shapes of thin corrosion products on metallic substrates. The calculated spectra show that the baseline is mainly affected by increasing roughness and that such effects do not shift the position of the absorption bands. The model obtained has been used to extract data of artificial patina on a copper surface. Surface defects of copper substrates can be distinguished on the whole surface, from the morphological and chemical points of view, using optical profilometry and infrared microspectroscopy. An homogeneous layer of cuprite covers the surface except in the linear defects. Fourier transform infrared (FT-IR) analysis indicates that a mixture of atacamite and clinoatacamite is mainly located in these scratches. The width of these particular areas is in good agreement with profilometric observations.

Modeling and measurement of microwave emission and backscattering from bare soil surfaces

NASA Technical Reports Server (NTRS)

Saatchi, S.; Wegmuller, U.

1992-01-01

A multifrequency ground-based radiometer-scatterometer system working at frequencies between 3.0 GHz and 11.0 GHz has been used to study the effect of soil moisture and roughness on microwave emission and backscattering. The freezing and thawing effect of the soil surface and the changes of the surface roughness due to rain and erosion are reported. To analyze the combined active and passive data, a scattering model based on physical optics approximation for the low frequency and geometrical optics approximation for high frequency has been developed. The model is used to calculate the bistatic scattering coefficients from the surface. By considering the conservation of energy, the result has been integrated over a hemisphere above the surface to calculate the emissivity. The backscattering and emission model has been coupled with the observed data in order to extract soil moisture and surface roughness.

Effect of natural ageing on surface of silver loaded TPE and its influence in antimicrobial efficacy

NASA Astrophysics Data System (ADS)

Tomacheski, Daiane; Pittol, Michele; Simões, Douglas Naue; Ribeiro, Vanda Ferreira; Santana, Ruth Marlene Campomanes

2017-05-01

The aim of this study is to characterize the modifications in silver loaded TPE surfaces exposed to weathering and their relation to susceptibility to microbial attack. Silver loaded TPE materials were exposed to natural ageing for nine months and modifications in antimicrobial properties and surface characteristics were evaluated. Chemical changes were investigated by using the infrared spectra. The average surface roughness and topography were determined by atomic force microscopy. Contact angle was measured to verify wettability conditions and surface free energy (SFE). After nine months of exposure, a decrease in the antimicrobial properties of loaded TPE compounds was observed. A reduction in surface roughness and improvement in wettability and high values of polar component of SFE were verified. The best antibacterial action was noticed in the sample with high Lewis acid force, lower roughness and lower carbonyl index.

Surface roughness control by extreme ultraviolet (EUV) radiation

NASA Astrophysics Data System (ADS)

Ahad, Inam Ul; Obeidi, Muhannad Ahmed; Budner, Bogusław; Bartnik, Andrzej; Fiedorowicz, Henryk; Brabazon, Dermot

2017-10-01

Surface roughness control of polymeric materials is often desirable in various biomedical engineering applications related to biocompatibility control, separation science and surface wettability control. In this study, Polyethylene terephthalate (PET) polymer films were irradiated with Extreme ultraviolet (EUV) photons in nitrogen environment and investigations were performed on surface roughness modification via EUV exposure. The samples were irradiated at 3 mm and 4 mm distance from the focal spot to investigate the effect of EUV fluence on topography. The topography of the EUV treated PET samples were studied by AFM. The detailed scanning was also performed on the sample irradiated at 3 mm. It was observed that the average surface roughness of PET samples was increased from 9 nm (pristine sample) to 280 nm and 253 nm for EUV irradiated samples. Detailed AFM studies confirmed the presence of 1.8 mm wide period U-shaped channels in EUV exposed PET samples. The walls of the channels were having FWHM of about 0.4 mm. The channels were created due to translatory movements of the sample in horizontal and transverse directions during the EUV exposure. The increased surface roughness is useful for many applications. The nanoscale channels fabricated by EUV exposure could be interesting for microfluidic applications based on lab-on-a-chip (LOC) devices.

Gas discharge plasma treatment of poly(ethylene glycol-co-1,3/1,4 cyclohexanedimethanol terephthalate) for enhanced paint adhesion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salapare, Hernando S., E-mail: hssalapare@up.edu.ph; Department of Physical Sciences and Mathematics, College of Arts and Sciences, University of the Philippines Manila, Manila City 1000; College of Science, Pamantasan ng Lungsod ng Maynila, Intramuros, Manila City 1002

Low-energy hydrogen-ions and tetrafluoromethane-ions produced from a gas discharge ion source were irradiated to poly(ethylene glycol-co-1,3/1,4 cyclohexanedimethanol terephthalate) (PETG) sheets for enhancing paint adhesion. The ion beams were characterized using a cast steel mass spectrometer, while the untreated and treated samples were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, contact angle measurements, and profilometry. The paint adhesion was determined by using the standard method for evaluating adhesion by knife [ASTM D6677-07, Standard Test Method for Evaluating Adhesion by Knife (ASTM International, West Conshohocken, PA, 2012)] and was correlated with the calculation of the work of adhesion derived frommore » the Young–Dupré equation. After plasma treatment, a significant decrease in the contact angle was observed in all samples, except for the CF{sub 4} ion-treated samples with the discharge current of 3 mA and an irradiation time of 30 min. At longer irradiation times, the treated samples showed lesser changes in the contact angle measurement. The increase in the average and root-mean-square surface roughness was observed on the samples after plasma treatment. The samples treated with either H{sub 2} or CF{sub 4} ions for 15 min showed a direct correlation between the discharge current and surface roughness. The samples treated for 30 min showed no significant correlation between the surface roughness and discharge current, which can be attributed to the possible melting of the samples since PETG has a low melting point. The observation made in this study on the relationship of wettability and surface roughness is consistent with the Wenzel wetting mode. Scanning electron micrographs showed surface etching on the hydrogen ion-treated samples while no significant surface changes were observed for the CF{sub 4} ion-treated samples. In general, paint adhesion was stronger for samples that exhibited enhanced wettability and high work of adhesion. The optimal work of adhesion to double the paint adhesion performance was at least 84.79 mN/m. The increase in the surface roughness after the treatment provided an increased friction between the paint and the PETG surface. The increase in the paint adhesion was also due to the covalent, hydrogen, and van der Waals bonding that are typically observed for highly wettable surfaces.« less

The distribution of particulate material on Mars

NASA Technical Reports Server (NTRS)

Christensen, Philip R.

1991-01-01

The surface materials on Mars were extensively studied using a variety of spacecraft and Earth-based remote sensing observations. These measurements include: (1) diurnal thermal measurements, used to determine average particle size, rock abundance, and the presence of crusts; (2) radar observations, used to estimate the surface slope distributions, wavelength scale roughness, and density; (3) radio emission observations, used to estimate subsurface density; (4) broadband albedo measurements, used to study the time variation of surface brightness and dust deposition and removal; and (5) color observations, used to infer composition, mixing, and the presence of crusts. Remote sensing observations generally require some degree of modeling to interpret, making them more difficult to interpret than direct observations from the surface. They do, however, provide a means for examining the surface properties over the entire planet and a means of sampling varying depths within the regolith. Albedo and color observations only indicate the properties of the upper-most few microns, but are very sensitive to thin, sometimes emphemeral dust coatings. Thermal observations sample the upper skin depth, generally 2 to 10 cm. Rock abundance measurements give an indirect indication of surface mantling, where the absence of rocks suggests mantles of several meters. Finally, radar and radio emission data can penetrate several meters into the surface, providing an estimate of subsurface density and roughness.

Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

PubMed Central

Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L.; Emelko, Monica B.

2015-01-01

Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or “sag effect” was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition. PMID:26658159

Evaluation of the surface roughness of three heat-cured acrylic denture base resins with different conventional lathe polishing techniques: A comparative study.

PubMed

Rao, Duggineni Chalapathi; Kalavathy, N; Mohammad, H S; Hariprasad, A; Kumar, C Ravi

2015-01-01

Surface roughness promotes adhesion and colonization of denture plaque. Therefore, it is important to know the effects of polishing and finishing on the surface roughness of various acrylic resin materials. To evaluate and compare the effects of different conventional lathe polishing techniques on heat cured acrylic resins in producing surface roughness. Three different commercially available heat-cured acrylic resin materials namely DPI, Meliodent and Trevalon Hi were selected. 30 Specimens of each acrylic material (30 x 3 = 90, 10 x 60 x 2mm) were prepared and divided into 5 groups, each group consisted of 6 Nos. of specimens per material(6x3=18) and were grouped as Group A(unfinished), Group B (finished), Group C (Polishing Paste), Group D (Polishing Cake) and Group E (Pumice and Gold rouge). The resulted surface roughness (μm) was measured using Perthometer and observed under Scanning Electron Microscope. The values obtained were subjected statistical analyses. Among the materials tested, better results were obtained with Trevalon Hi followed by Meliodent and DPI. Among the polishing methods used, superior results were obtained with universal polishing paste followed by polishing cake; Pumice and Gold rouge. Although Pumice and Gold rouge values produced greater roughness value, they were well within the threshold value of 0.2 mm.

Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

NASA Astrophysics Data System (ADS)

Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L.; Emelko, Monica B.

2015-12-01

Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or “sag effect” was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition.

Rupture preparation process controlled by surface roughness on meter-scale laboratory fault

NASA Astrophysics Data System (ADS)

Yamashita, Futoshi; Fukuyama, Eiichi; Xu, Shiqing; Mizoguchi, Kazuo; Kawakata, Hironori; Takizawa, Shigeru

2018-05-01

We investigate the effect of fault surface roughness on rupture preparation characteristics using meter-scale metagabbro specimens. We repeatedly conducted the experiments with the same pair of rock specimens to make the fault surface rough. We obtained three experimental results under the same experimental conditions (6.7 MPa of normal stress and 0.01 mm/s of loading rate) but at different roughness conditions (smooth, moderately roughened, and heavily roughened). During each experiment, we observed many stick-slip events preceded by precursory slow slip. We investigated when and where slow slip initiated by using the strain gauge data processed by the Kalman filter algorithm. The observed rupture preparation processes on the smooth fault (i.e. the first experiment among the three) showed high repeatability of the spatiotemporal distributions of slow slip initiation. Local stress measurements revealed that slow slip initiated around the region where the ratio of shear to normal stress (τ/σ) was the highest as expected from finite element method (FEM) modeling. However, the exact location of slow slip initiation was where τ/σ became locally minimum, probably due to the frictional heterogeneity. In the experiment on the moderately roughened fault, some irregular events were observed, though the basic characteristics of other regular events were similar to those on the smooth fault. Local stress data revealed that the spatiotemporal characteristics of slow slip initiation and the resulting τ/σ drop for irregular events were different from those for regular ones even under similar stress conditions. On the heavily roughened fault, the location of slow slip initiation was not consistent with τ/σ anymore because of the highly heterogeneous static friction on the fault, which also decreased the repeatability of spatiotemporal distributions of slow slip initiation. These results suggest that fault surface roughness strongly controls the rupture preparation process, and generally increases its complexity with the degree of roughness.

Roughness threshold for cell attachment and proliferation on plasma micro-nanotextured polymeric surfaces: the case of primary human skin fibroblasts and mouse immortalized 3T3 fibroblasts

NASA Astrophysics Data System (ADS)

Bourkoula, A.; Constantoudis, V.; Kontziampasis, D.; Petrou, P. S.; Kakabakos, S. E.; Tserepi, A.; Gogolides, E.

2016-08-01

Poly(methyl methacrylate) surfaces have been micro-nanotextured in oxygen plasmas with increasing ion energy, leading to micro-nanotopography characterized by increased root mean square roughness, correlation length and fractal dimension. Primary human skin fibroblasts and mouse immortalized 3T3 fibroblasts were cultured on these surfaces and the number of adhering cells, their proliferation rate and morphology (cytoplasm and nucleus area) were evaluated as a function of roughness height, correlation length, and fractal dimension. A roughness threshold behavior was observed for both types of cells leading to dramatic cell number decrease above this threshold, which is almost similar for the two types of cells, despite their differences in size and stiffness. The results are discussed based on two theoretical models, which are reconciled and unified when the elastic moduli and the size of the cells are taken into account.

Visual Inspection of Surfaces

NASA Technical Reports Server (NTRS)

Hughes, David; Perez, Xavier

2007-01-01

This presentation evaluates the parameters that affect visual inspection of cleanliness. Factors tested include surface reflectance, surface roughness, size of the largest particle, exposure time, inspector and distance from sample surface. It is concluded that distance predictions were not great, particularly because the distance at which contamination is seen may depend on more variables than those tested. Most parameters estimates had confidence of 95% or better, except for exposure and reflectance. Additionally, the distance at which surface is visibly contaminated decreases with increasing reflectance, roughness, and exposure. The distance at which the surface is visually contaminated increased with the largest particle size. These variables were only slightly affected the observer.

New horizons in selective laser sintering surface roughness characterization

NASA Astrophysics Data System (ADS)

Vetterli, M.; Schmid, M.; Knapp, W.; Wegener, K.

2017-12-01

Powder-based additive manufacturing of polymers and metals has evolved from a prototyping technology to an industrial process for the fabrication of small to medium series of complex geometry parts. Unfortunately due to the processing of powder as a basis material and the successive addition of layers to produce components, a significant surface roughness inherent to the process has been observed since the first use of such technologies. A novel characterization method based on an elastomeric pad coated with a reflective layer, the Gelsight, was found to be reliable and fast to characterize surfaces processed by selective laser sintering (SLS) of polymers. With help of this method, a qualitative and quantitative investigation of SLS surfaces is feasible. Repeatability and reproducibility investigations are performed for both 2D and 3D areal roughness parameters. Based on the good results, the Gelsight is used for the optimization of vertical SLS surfaces. A model built on laser scanning parameters is proposed and after confirmation could achieve a roughness reduction of 10% based on the S q parameter. The Gelsight could be successfully identified as a fast, reliable and versatile surface topography characterization method as it applies to all kind of surfaces.

Effect of whitening dentifrices on the surface roughness of commercial composites.

PubMed

Barbieri, Guilherme Machado; Mota, Eduardo Gonçalves; Rodrigues-Junior, Sinval Adalberto; Burnett, Luiz Henrique

2011-10-01

Our study aimed to test the null hypothesis that whitening and non-whitening dentifrices affect similarly the surface roughness of commercial microhybrid composites, independent of the brushing time. One hundred and ninety-two disc-shaped specimens of Filtek Z250 (3 M/ESPE, St. Paul, MN, USA) and Rok (SDI, Australia) were built up and randomly assigned to 24 groups, based on the dentifrices used (two whitening dentifrices: Colgate Max White-Colgate-Palmolive, São Bernardo do Campo, São Paulo, Brazil and Close Up Extra Whitening-Unilever, Brasil Higiene Pessoal e Limpeza Ltda, Ipojuca, Pernambuco, Brazil; and one non-whitening dentifrice: Colgate Total 12 Clean Mint-Colgate-Palmolive), and on the simulated brushing times (24 hours, 6, 12 and 24 months). The specimens were submitted to the toothbrushing regimens after which the surface roughness (Ra) was measured. Data was submitted to analysis of variance and Tukey test (α=0.05). The composite's surface roughness was significantly affected by the composites (p=0.0007), the dentifrices (p=0.0001), and the simulated brushing time (p=0.0001). Higher roughness was observed when the whitening dentifrices were used and when the brushing time increased. Filtek Z250 was more affected than Rok, especially after 24 months of simulated brushing. Whitening dentifrices produced higher surface roughness in the composites tested. The degree of surface compromising increased with brushing time and depends on the composite's microstructure and composition. © 2011 Wiley Periodicals, Inc.

Effect of artificial aging on the surface roughness and microhardness of resin-based materials.

PubMed

Santos, M Jacinta M C; Rêgo, Heleine Maria Chagas; Mukhopadhyay, Anuradha; El Najjar, Mai; Santos, Gildo C

2016-01-01

This study sought to verify the effects of aging on the surface roughness (Ra) and microhardness (Knoop hardness number [KHN]) of resin-based restorative materials protected with a surface sealer. Disc specimens of 2 resin-modified glass ionomers (RMGIs) and 1 composite resin (CR) were fabricated in a metal mold. Specimens of each material were divided into 1 group that was covered with surface sealer and 1 group that was not. Both groups of each material were then subdivided according to whether they were stored (aged) in cola or distilled water. Surface roughness and KHN values were obtained from each specimen before and after storage. After aging of the specimens, significantly higher Ra values were observed in the 2 RMGIs when they were not covered with a surface sealer, while the CR was not affected. The KHN values varied by materials and storage conditions (with and without a surface sealer). All the groups with a surface sealer exhibited increased Ra values after aging.

Macro and micro wettability of hydrophobic siloxane films with hierarchical surface roughness

NASA Astrophysics Data System (ADS)

Terpilowski, Konrad; Goncharuk, Olena; Gun’ko, Vladimir M.

2018-07-01

A method has been proposed to control the macro- and micro-wetting properties of hydrophobic surfaces through changes in the roughness due to modifying siloxane films with silica microparticles (MP). An experimental and theoretical analysis of macro- and micro-wettability dependence on the roughness of a film surface was carried out by combination of SEM and XPS methods with evaluation of equilibrium contact angles from Tadmor’s equation. SEM images (environmental mode) allowed characterizing the mosaic hydrophobicity/hydrophilicity of the siloxane film surface. Hydrophobic siloxane films filled with silica MP were synthesized on the plasma activated and non-activated glass substrates by the sol-gel dip-coating method using tetraethylorthosilicate based precursor compositions with subsequent reaction with hexamethyldisilazane. The values of water contact angles higher than 150° indicating a superhydrophobic effect were observed for films with combining nano- and micro-hierarchical roughness. Moreover, considering wettability on the micro scale the hybrid effect was discovered and confirmed by the SEM and XPS studies showing the presence of not only hydrophobic but also hydrophilic surface domains.

Effect of root planing on surface topography: an in-vivo randomized experimental trial.

PubMed

Rosales-Leal, J I; Flores, A B; Contreras, T; Bravo, M; Cabrerizo-Vílchez, M A; Mesa, F

2015-04-01

The root surface topography exerts a major influence on clinical attachment and bacterial recolonization after root planing. In-vitro topographic studies have yielded variable results, and clinical studies are necessary to compare root surface topography after planing with current ultrasonic devices and with traditional manual instrumentation. The aim of this study was to compare the topography of untreated single-rooted teeth planed in vivo with a curette, a piezoelectric ultrasonic (PU) scraper or a vertically oscillating ultrasonic (VOU) scraper. In a randomized experimental trial of 19 patients, 44 single-rooted teeth were randomly assigned to one of four groups for: no treatment; manual root planing with a curette; root planing with a PU scraper; or root planing with a VOU scraper. Post-treatment, the teeth were extracted and their topography was analyzed in 124 observations with white-light confocal microscopy, measuring the roughness parameters arithmetic average height, root-mean-square roughness, maximum height of peaks, maximum depth of valleys, absolute height, skewness and kurtosis. The roughness values arithmetic average height and root-mean-square roughness were similar after each treatment and lower than after no treatment ( p < 0.05). Absolute height was lower in the VOU group than in the untreated ( p = 0.0026) and PU (p = 0.045) groups. Surface morphology was similar after the three treatments and was less irregular than in the untreated group. Values for the remaining roughness parameters were similar among all treatment groups ( p > 0.05). Both ultrasonic devices reduce the roughness, producing a similar topography to that observed after manual instrumentation with a curette, to which they appear to represent a valid alternative. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiusheng, Y., E-mail: qsyan@gdut.edu.cn; Senkai, C., E-mail: senkite@sina.com; Jisheng, P., E-mail: panjisheng@gdut.edu.cn

Different machining processes were used in the single crystal SiC wafer machining. SEM was used to observe the surface morphology and a cross-sectional cleavages microscopy method was used for subsurface cracks detection. Surface and subsurface cracks characteristics of single crystal SiC wafer in abrasive machining were analysed. The results show that the surface and subsurface cracks system of single crystal SiC wafer in abrasive machining including radial crack, lateral crack and the median crack. In lapping process, material removal is dominated by brittle removal. Lots of chipping pits were found on the lapping surface. With the particle size becomes smaller,more » the surface roughness and subsurface crack depth decreases. When the particle size was changed to 1.5µm, the surface roughness Ra was reduced to 24.0nm and the maximum subsurface crack was 1.2µm. The efficiency of grinding is higher than lapping. Plastic removal can be achieved by changing the process parameters. Material removal was mostly in brittle fracture when grinding with 325# diamond wheel. Plow scratches and chipping pits were found on the ground surface. The surface roughness Ra was 17.7nm and maximum subsurface crack depth was 5.8 µm. When grinding with 8000# diamond wheel, the material removal was in plastic flow. Plastic scratches were found on the surface. A smooth surface of roughness Ra 2.5nm without any subsurface cracks was obtained. Atomic scale removal was possible in cluster magnetorheological finishing with diamond abrasive size of 0.5 µm. A super smooth surface eventually obtained with a roughness of Ra 0.4nm without any subsurface crack.« less

Effects of delayed finishing/polishing on surface roughness, hardness and gloss of tooth-coloured restorative materials.

PubMed

Yazici, A Ruya; Tuncer, Duygu; Antonson, Sibel; Onen, Alev; Kilinc, Evren

2010-01-01

The aim of this study was to investigate the effect of delayed finishing/polishing on the surface roughness, hardness and gloss of tooth-coloured restorative materials. Four different tooth-coloured restoratives: a flowable resin composite- Tetric Flow, a hybrid resin composite- Venus, a nanohybrid resin composite- Grandio, and a polyacid modified resin composite- Dyract Extra were used. 30 specimens were made for each material and randomly assigned into three groups. The first group was finished/polished immediately and the second group was finished/polished after 24 hours. The remaining 10 specimens served as control. The surface roughness of each sample was recorded using a laser profilometer. Gloss measurements were performed using a small-area glossmeter. Vickers microhardness measurements were performed from three locations on each specimen surface under 100g load and 10s dwell time. Data for surface roughness and hardness were analyzed by Kruskal Wallis test and data for gloss were subjected to one-way ANOVA and Tukey test (P <.05). The smoothest surfaces were obtained under Mylar strip for all materials. While there were no significant differences in surface roughness of immediate and delayed finished/polished Dyract Extra samples, immediately finished/polished Venus and Grandio samples showed significantly higher roughness than the delayed polished samples (P <.05). In Tetric Flow samples, immediately finishing/polishing provided smoother surface than delayed finishing/polishing (P <.05). The highest gloss values were recorded under Mylar strip for all materials. While delayed finishing/polishing resulted in a significantly higher gloss compared to immediate finishing/polishing in Venus samples (P <.05), no differences were observed between delayed or immediate finishing/polishing for the other materials (P>.05). The lowest hardness values were found under Mylar strip. Delayed finishing/polishing significantly increased the hardness of all materials. The effect of delayed finishing/polishing on surface roughness, gloss and hardness appears to be material dependent.

Ultrastructural investigation of intact orbital implant surfaces using atomic force microscopy.

PubMed

Choi, Samjin; Lee, Seung Jun; Shin, Jae-Ho; Cheong, Youjin; Lee, Hui-Jae; Paek, Joo Hee; Kim, Jae Sik; Jin, Kyung-Hyun; Park, Hun-Kuk

2011-01-01

This study examined the surface nanostructures of three orbital implants: nonporous poly(methyl methacrylate) (PMMA), porous aluminum oxide and porous polyethylene. The morphological characteristics of the orbital implants surfaces were observed by atomic force microscopy (AFM). The AFM topography, phase shift and deflection images of the intact implant samples were obtained. The surface of the nonporous PMMA implant showed severe scratches and debris. The surface of the aluminum oxide implant showed a porous structure with varying densities and sizes. The PMMA implant showed nodule nanostructures, 215.56 ± 52.34 nm in size, and the aluminum oxide implant showed crystal structures, 730.22 ± 341.02 nm in size. The nonporous PMMA implant showed the lowest roughness compared with other implant biomaterials, followed by the porous aluminum oxide implant. The porous polyethylene implant showed the highest roughness and severe surface irregularities. Overall, the surface roughness of orbital implants might be associated with the rate of complications and cell adhesion. Copyright © 2011 Wiley Periodicals, Inc.

Influence of SMAT Parameters on Microstructural and Mechanical Properties of Al-Mg-Si Alloy AA 6061

NASA Astrophysics Data System (ADS)

Anand Kumar, S.; Satish Kumar, P.; Ganesh Sundara Raman, S.; Sankara Narayanan, T. S. N.

2017-04-01

In the present work, the influence of surface mechanical attrition treatment (SMAT) parameters on the microstructural and mechanical properties of an aluminum-magnesium-silicon alloy AA 6061 was studied using design of experiment technique. Balls of three different diameters were used, and SMAT was done for three different durations. The microstructural features of the surface layer fabricated by SMAT were characterized by cross-sectional scanning electron microscopic observations, x-ray diffraction technique and transmission electron microscopy. The microindentation hardness, nanoindentation hardness and surface roughness were determined. Due to SMAT, nanocrystallites formed on the surface and near-surface regions, and hardness and surface roughness increased. The ball diameter was the most influencing SMAT parameter compared to the treatment duration. However, interaction between ball diameter and treatment duration could not be ignored. Regression equations were developed relating the process parameters to the surface properties. The ball diameter and treatment duration could thus be properly selected as per the required values of roughness and/or the hardness.

Experimental Investigation of Roughness Effects on Transition Onset and Turbulent Heating Augmentation on a Hemisphere at Mach 6 and Mach 10

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

2017-01-01

An experimental investigation of the effects of distributed surface roughness on boundary-layer transition and turbulent heating has been conducted. Hypersonic wind tunnel testing was performed using hemispherical models with surface roughness patterns simulating those produced by heat shield ablation. Global aeroheating and transition onset data were obtained using phosphor thermography at Mach 6 and Mach 10 over a range of roughness heights and free stream Reynolds numbers sufficient to produce laminar, transitional and turbulent flow. Upstream movement of the transition onset location and increasing heating augmentation over predicted smooth-wall levels were observed with both increasing roughness heights and increasing free stream Reynolds numbers. The experimental heating data are presented herein, as are comparisons to smooth-wall heat transfer distributions from computational flow-field simulations. The transition onset data are also tabulated, and correlations of these data are presented.

Evidence for ground-ice occurrence on asteroid Vesta using Dawn bistatic radar observations

NASA Astrophysics Data System (ADS)

Palmer, E. M.; Heggy, E.; Kofman, W. W.

2017-12-01

From 2011 to 2012, the Dawn spacecraft orbited asteroid Vesta, the first of its two targets in the asteroid belt, and conducted the first bistatic radar (BSR) experiment at a small-body, during which Dawn's high-gain communications antenna is used to transmit radar waves that scatter from Vesta's surface toward Earth at high incidence angles just before and after occultation of the spacecraft behind the asteroid. Among the 14 observed mid-latitude forward-scatter reflections, the radar cross section ranges from 84 ± 8 km2 (near Saturnalia Fossae) to 3,588 ± 200 km2 (northwest of Caparronia crater), implying substantial spatial variation in centimeter- to decimeter-scale surface roughness. The compared distributions of surface roughness and subsurface hydrogen concentration [H]—measured using data from Dawn's BSR experiment and Gamma Ray and Neutron Spectrometer (GRaND), respectively—reveal the occurrence of heightened subsurface [H] with smoother terrains that cover tens of square kilometers. Furthermore, unlike on the Moon, we observe no correlation between surface roughness and surface ages on Vesta—whether the latter is derived from lunar or asteroid-flux chronology [Williams et al., 2014]—suggesting that cratering processes alone are insufficient to explain Vesta's surface texture at centimeter-to-decimeter scales. Dawn's BSR observations support the hypothesis of transient melting, runoff and recrystallization of potential ground-ice deposits, which are postulated to flow along fractures after an impact, and provide a mechanism for the smoothing of otherwise rough, fragmented impact ejecta. Potential ground-ice presence within Vesta's subsurface was first proposed by Scully et al. [2014], who identified geomorphological evidence for transient water flow along several of Vesta's crater walls using Dawn Framing Camera images. While airless, differentiated bodies such as Vesta and the Moon are thought to have depleted their initial volatile content during the process of differentiation, evidence to the contrary is continuing to change our understanding of the distribution and preservation of volatiles during planetary formation in the early solar system.

Effect of surface roughness on droplet splashing

NASA Astrophysics Data System (ADS)

Hao, Jiguang

2017-12-01

It is well known that rough surfaces trigger prompt splashing and suppress corona splashing on droplet impact. Upon water droplet impact, we experimentally found that a slightly rough substrate triggers corona splashing which is suppressed to prompt splashing by both further increase and further decrease of surface roughness. The nonmonotonic effect of surface roughness on corona splashing weakens with decreasing droplet surface tension. The threshold velocities for prompt splashing and corona splashing are quantified under different conditions including surface roughness, droplet diameter, and droplet surface tension. It is determined that slight roughness significantly enhances both prompt splashing and corona splashing of a water droplet, whereas it weakly affects low-surface-tension droplet splashing. Consistent with previous studies, high roughness triggers prompt splashing and suppresses corona splashing. Further experiments on droplet spreading propose that the mechanism of slight roughness enhancing water droplet splashing is due to the decrease of the wetted area with increasing surface roughness.

Growth of contact area between rough surfaces under normal stress

NASA Astrophysics Data System (ADS)

Stesky, R. M.; Hannan, S. S.

1987-05-01

The contact area between deforming rough surfaces in marble, alabaster, and quartz was measured from thin sections of surfaces bonded under load with low viscosity resin epoxy. The marble and alabaster samples had contact areas that increased with stress at an accelerating rate. This result suggests that the strength of the asperity contacts decreased progressively during the deformation, following some form of strain weakening relationship. This conclusion is supported by petrographic observation of the thin sections that indicate that much of the deformation was cataclastic, with minor twinning of calcite and kinking of gypsum. In the case of the quartz, the observed contact area was small and increased approximately linearly with normal stress. Only the irreversible cataclastic deformation was observed; however strain-induced birefringence and cracking of the epoxy, not observed with the other rocks, suggests that significant elastic deformation occurred, but recovered during unloading.

Rough surfaces: Is the dark stuff just shadow?. ;Who knows what evil lurks in the hearts of men? The shadow knows!;☆

NASA Astrophysics Data System (ADS)

Cuzzi, Jeffrey N.; Chambers, Lindsey B.; Hendrix, Amanda R.

2017-06-01

Remote observations of the surfaces of airless planetary objects are fundamental to inferring the physical structure and compositional makeup of the surface material. A number of forward models have been developed to reproduce the photometric behavior of these surfaces, based on specific, assumed structural properties such as macroscopic roughness and associated shadowing. Most work of this type is applied to geometric albedos, which are affected by complicated effects near zero phase angle that represent only a tiny fraction of the net energy reflected by the object. Other applications include parameter fits to resolved portions of some planetary surface as viewed over a range of geometries. The spherical albedo of the entire object (when it can be determined) captures the net energy balance of the particle more robustly than the geometric albedo. In most treatments involving spherical albedos, spherical albedos and particle phase functions are often treated as if they are independent, neglecting the effects of roughness. In this paper we take a different approach. We note that whatever function captures the phase angle dependence of the brightness of a realistic rough, shadowed, flat surface element relative to that of a smooth granular surface of the same material, it is manifested directly in both the integral phase function and the spherical albedo of the object. We suggest that, where broad phase angle coverage is possible, spherical albedos may be easily corrected for the effects of shadowing using observed (or assumed) phase functions, and then modeled more robustly using smooth-surface regolith radiative transfer models without further imposed (forward-modeled) shadowing corrections. Our approach attributes observed "powerlaw" phase functions of various slope (and "linear" ranges of magnitude-vs.-phase angle) to shadowing, as have others, and goes in to suggest that regolith-model-based inferences of composition based on shadow-uncorrected spherical albedos overestimate the amount of absorbing material contained in the regolith.

Rough Surfaces: Is the Dark Stuff Just Shadow?: "Who knows what evil lurks in the hearts of men? The shadow knows!"

NASA Technical Reports Server (NTRS)

Cuzzi, Jeffrey N.; Chambers, Lindsey B.; Hendrix, Amanda R.

2016-01-01

Remote observations of the surfaces of airless planetary objects are fundamental to inferring the physical structure and compositional makeup of the surface material. A number of forward models have been developed to reproduce the photometric behavior of these surfaces, based on specific, assumed structural properties such as macroscopic roughness and associated shadowing. Most work of this type is applied to geometric albedos, which are affected by complicated effects near zero phase angle that represent only a tiny fraction of the net energy reflected by the object. Other applications include parameter fits to resolved portions of some planetary surface as viewed over a range of geometries. The spherical albedo of the entire object (when it can be determined) captures the net energy balance of the particle more robustly than the geometric albedo. In most treatments involving spherical albedos, spherical albedos and particle phase functions are often treated as if they are independent, neglecting the effects of roughness. In this paper we take a different approach. We note that whatever function captures the phase angle dependence of the brightness of a realistic rough, shadowed, flat surface element relative to that of a smooth granular surface of the same material, it is manifested directly in both the integral phase function and the spherical albedo of the object. We suggest that, where broad phase angle coverage is possible, spherical albedos may be easily corrected for the effects of shadowing using observed (or assumed) phase functions, and then modeled more robustly using smooth-surface regolith radiative transfer models without further imposed (forward-modeled) shadowing corrections. Our approach attributes observed "power law" phase functions of various slope (and "linear" ranges of magnitude-vs.-phase angle) to shadowing, as have others, and goes on to suggest that regolith-model-based inferences of composition based on shadow-uncorrected spherical albedos overestimate the amount of absorbing material contained in the regolith.

Experimental and simulation study of growth of TiO2 films on different substrates and its applications

NASA Astrophysics Data System (ADS)

Ghogare, Trupti T.; Kartha, Moses J.; Kendre, Subhash D.; Pathan, Habib M.

2018-04-01

Monte-Carlo Ballistic Deposition simulations have done on substrates with different initial roughness. The grown films were observed to be porous. The initial growths of the films with seed like initiations are observed for substrate with high initial roughness. In order to confirm this effect TiO2 films were deposited on different substrates using chemical bath deposition. The surface morphological and optical properties were measured using scanning electron microscopy and a UV-Vis spectrophotometer. Flower like porous structure are obtained on glass substrate and continuous porous morphology is formed on ITO substrate. The morphology of the surfaces was successfully reconstructed and the surface porosity was calculated after digitalising images and reconstructed the surfaces. The TiO2 film formed on ITO is observed to be 10% more porous than on the film formed on glass substrate. Diffusion Limited Aggregation simulations with multiple seeds confirms that the observed flower like structure formed are due to the screening effects of the diffusing ion by already deposited particles.

Plastic strain and grain size effects in the surface roughening of a model aluminum alloy

NASA Astrophysics Data System (ADS)

Moore, Eric Joseph

To address issues surrounding improved automotive fuel economy, an experiment was designed to study the effect of uniaxial plastic tensile deformation on surface roughness and on slip and grain rotation. Electron backscatter diffraction (EBSD) and scanning laser confocal microscopy (SLCM) were used to track grain size, crystallographic texture, and surface topography as a function of incremental true strain for a coarse-grained binary alloy that is a model for AA5xxx series aluminum alloys. One-millimeter thick sheets were heat treated at 425°C to remove previous rolling texture and to grow grains to sizes in the range ˜10-8000 mum. At five different strain levels, 13 sample regions, containing 43 grains, were identified in both EBSD and SLCM micrographs, and crystallographic texture and surface roughness were measured. After heat treatment, a strong cube texture matrix emerged, with bands of generally non-cube grains embedded parallel to the rolling direction (RD). To characterize roughness, height profiles from SLCM micrographs were extracted and a filtered Fourier transform approach was used to separate the profiles into intergranular (long wavelength) and intragranular (short wavelength) signatures. The commonly-used rms roughness parameter (Rq) characterized intragranular results. Two important parameters assess intergranular results in two grain size regimes: surface tilt angle (Deltatheta) and surface height discontinuity (DeltazH) between neighboring grains at a boundary. In general, the magnitude of Rq and Deltatheta increase monotonically with strain and indicate that intergranular roughness is the major contributor to overall surface roughness for true strains up to epsilon = 0.12. Surface height discontinuity DeltazH is defined due to exceptions in surface tilt angle analyses. The range of observed Deltatheta= 1-10° are consistent with the observed 3-12° rotation of individual grains as measured with EBSD. For some grain boundaries with Deltatheta< 4°, the surface height discontinuity DeltazH characterizes the response of adjacent grains in which one or more are large (˜1000-2000 mum), making a 3-12° rotation of the grain highly unlikely. This can be understood by postulating that the energy associated with rotating large grains would exceed the energy to shear along the boundary. Slip and grain boundary shearing are the active mechanisms in these instances.

Surface and subsurface cracks characteristics of single crystal SiC wafer in surface machining

NASA Astrophysics Data System (ADS)

Qiusheng, Y.; Senkai, C.; Jisheng, P.

2015-03-01

Different machining processes were used in the single crystal SiC wafer machining. SEM was used to observe the surface morphology and a cross-sectional cleavages microscopy method was used for subsurface cracks detection. Surface and subsurface cracks characteristics of single crystal SiC wafer in abrasive machining were analysed. The results show that the surface and subsurface cracks system of single crystal SiC wafer in abrasive machining including radial crack, lateral crack and the median crack. In lapping process, material removal is dominated by brittle removal. Lots of chipping pits were found on the lapping surface. With the particle size becomes smaller, the surface roughness and subsurface crack depth decreases. When the particle size was changed to 1.5µm, the surface roughness Ra was reduced to 24.0nm and the maximum subsurface crack was 1.2µm. The efficiency of grinding is higher than lapping. Plastic removal can be achieved by changing the process parameters. Material removal was mostly in brittle fracture when grinding with 325# diamond wheel. Plow scratches and chipping pits were found on the ground surface. The surface roughness Ra was 17.7nm and maximum subsurface crack depth was 5.8 µm. When grinding with 8000# diamond wheel, the material removal was in plastic flow. Plastic scratches were found on the surface. A smooth surface of roughness Ra 2.5nm without any subsurface cracks was obtained. Atomic scale removal was possible in cluster magnetorheological finishing with diamond abrasive size of 0.5 µm. A super smooth surface eventually obtained with a roughness of Ra 0.4nm without any subsurface crack.

Lacunarity study of speckle patterns produced by rough surfaces

NASA Astrophysics Data System (ADS)

Dias, M. R. B.; Dornelas, D.; Balthazar, W. F.; Huguenin, J. A. O.; da Silva, L.

2017-11-01

In this work we report on the study of Lacunarity of digital speckle patterns generated by rough surfaces. The study of Lacunarity of speckle patterns was performed on both static and moving rough surfaces. The results show that the Lacunarity is sensitive to the surface roughness, which suggests that it can be used to perform indirect measurement of surface roughness as well as to monitor defects, or variations of roughness, of metallic moving surfaces. Our results show the robustness of this statistical tool applied to speckle pattern in order to study surface roughness.

Surface correlations of hydrodynamic drag for transitionally rough engineering surfaces

NASA Astrophysics Data System (ADS)

Thakkar, Manan; Busse, Angela; Sandham, Neil

2017-02-01

Rough surfaces are usually characterised by a single equivalent sand-grain roughness height scale that typically needs to be determined from laboratory experiments. Recently, this method has been complemented by a direct numerical simulation approach, whereby representative surfaces can be scanned and the roughness effects computed over a range of Reynolds number. This development raises the prospect over the coming years of having enough data for different types of rough surfaces to be able to relate surface characteristics to roughness effects, such as the roughness function that quantifies the downward displacement of the logarithmic law of the wall. In the present contribution, we use simulation data for 17 irregular surfaces at the same friction Reynolds number, for which they are in the transitionally rough regime. All surfaces are scaled to the same physical roughness height. Mean streamwise velocity profiles show a wide range of roughness function values, while the velocity defect profiles show a good collapse. Profile peaks of the turbulent kinetic energy also vary depending on the surface. We then consider which surface properties are important and how new properties can be incorporated into an empirical model, the accuracy of which can then be tested. Optimised models with several roughness parameters are systematically developed for the roughness function and profile peak turbulent kinetic energy. In determining the roughness function, besides the known parameters of solidity (or frontal area ratio) and skewness, it is shown that the streamwise correlation length and the root-mean-square roughness height are also significant. The peak turbulent kinetic energy is determined by the skewness and root-mean-square roughness height, along with the mean forward-facing surface angle and spanwise effective slope. The results suggest feasibility of relating rough-wall flow properties (throughout the range from hydrodynamically smooth to fully rough) to surface parameters.

Percolation characteristics of solvent invasion in rough fractures under miscible conditions

NASA Astrophysics Data System (ADS)

Korfanta, M.; Babadagli, T.; Develi, K.

2017-10-01

Surface roughness and flow rate effects on the solvent transport under miscible conditions in a single fracture are studied. Surface replicas of seven different rocks (marble, granite, and limestone) are used to represent different surface roughness characteristics each described by different mathematical models including three fractal dimensions. Distribution of dyed solvent is investigated at various flow rate conditions to clarify the effect of roughness on convective and diffusive mixing. After a qualitative analysis using comparative images of different rocks, the area covered by solvent with respect to time is determined to conduct a semi-quantitative analysis. In this exercise, two distinct zones are identified, namely the straight lines obtained for convective (early times) and diffusive (late times) flow. The bending point between these two lines is used to point the transition between the two zones. Finally, the slopes of the straight lines and the bending points are correlated to five different roughness parameters and the rate (Peclet number). It is observed that both surface roughness and flow rate have significant effect on solvent spatial distribution. The largest area covered is obtained at moderate flow rates and hence not only the average surface roughness characteristic is important, but coessentially total fracture surface area needs to be considered when evaluating fluid distribution. It is also noted that the rate effect is critically different for the fracture samples of large grain size (marbles and granite) compared to smaller grain sizes (limestones). Variogram fractal dimension exhibits the strongest correlation with the maximum area covered by solvent, and display increasing trend at the moderate flow rates. Equations with variogram surface fractal dimension in combination with any other surface fractal parameter coupled with Peclet number can be used to predict maximum area covered by solvent in a single fracture, which in turn can be utilized to model oil recovery, waste disposal, and groundwater contamination processes in the presence of fractures.

Ocean Surface Wave Optical Roughness - Innovative Measurement and Modeling

DTIC Science & Technology

2008-01-01

e.g. Jessup and Phadnis , 2005) have been reported. Our effort seeks to provide a more comprehensive description of the physical and optical roughness...1986: Statistics of breaking waves observed as whitecaps in the open sea, Journal of Physical Oceanography, 16, 290-297. Jessup, A.T. and Phadnis

Microtopographic evolution of lava flows at Cima volcanic field, Mojave Desert, California

NASA Technical Reports Server (NTRS)

Farr, Tom G.

1992-01-01

Microtopographic profiles were measured and power spectra calculated for dated lava flow surfaces at Cima volcanic field in the eastern Mojave Desert of California in order to quantify changes in centimeter- to meter-scale roughness as a function of age. For lava flows younger than about 0.8 m.y., roughness over all spatial scales decreases with age, with meter-scale roughness decreasing slightly more than centimeter scales. Flows older than about 0.8 m.y. show a reversal of this trend, becoming as rough as young flows at these scales. Modeling indicates that eolian deposition can explain most of the change observed in the offset, or roughness amplitude, of power spectra of flow surface profiles up to 0.8 m.y. Other processes, such as rubbing and stone pavement development, appear to have a minor effect in this age range. Changes in power spectra of surfaces older than about 0.8 m.y. are consistent with roughening due to fluvial dissection. These results agree qualitatively with a process-response model that attributes systematic changes in flow surface morphology to cyclic changes in the rates of eolian, soil formation, and fluvial processes. Identification of active surficial processes and estimation of the extent of their effects, or stage of surficial evolution, through measurement of surface roughness will help put the correlation of surficial units on a quantitative basis. This may form the basis for the use of radar remote sensing data to help in regional correlations of surficial units.

Effects of rf power on chemical composition and surface roughness of glow discharge polymer films

NASA Astrophysics Data System (ADS)

Zhang, Ling; He, Xiaoshan; Chen, Guo; Wang, Tao; Tang, Yongjian; He, Zhibing

2016-03-01

The glow discharge polymer (GDP) films for laser fusion targets were successfully fabricated by plasma enhanced chemical vapor deposition (PECVD) at different radio frequency (rf) powers. The films were deposited using trans-2-butene (T2B) mixed with hydrogen as gas sources. The composition and state of plasma were diagnosed by quadrupole mass spectrometer (QMS) and Langmuir probe during the deposition process. The composition, surface morphology and roughness were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and white-light interferometer (WLI), respectively. Based on these observation and analyses, the growth mechanism of defects in GDP films were studied. The results show that, at low rf power, there is a larger probability for secondary polymerization and formation of multi-carbon C-H species in the plasma. In this case, the surface of GDP film turns to be cauliflower-like. With the increase of rf power, the degree of ionization is high, the relative concentration of smaller-mass hydrocarbon species increases, while the relative concentration of larger-mass hydrocarbon species decreases. At higher rf power, the energy of smaller-mass species are high and the etching effects are strong correspondingly. The GDP film's surface roughness shows a trend of decrease firstly and then increase with the increasing rf power. At rf power of 30 W, the surface root-mean-square roughness (Rq) drops to the lowest value of 12.8 nm, and no ;void; defect was observed.

Estimating Discharge, Depth and Bottom Friction in Sand Bed Rivers Using Surface Currents and Water Surface Elevation Observations

NASA Astrophysics Data System (ADS)

Simeonov, J.; Czapiga, M. J.; Holland, K. T.

2017-12-01

We developed an inversion model for river bathymetry estimation using measurements of surface currents, water surface elevation slope and shoreline position. The inversion scheme is based on explicit velocity-depth and velocity-slope relationships derived from the along-channel momentum balance and mass conservation. The velocity-depth relationship requires the discharge value to quantitatively relate the depth to the measured velocity field. The ratio of the discharge and the bottom friction enter as a coefficient in the velocity-slope relationship and is determined by minimizing the difference between the predicted and the measured streamwise variation of the total head. Completing the inversion requires an estimate of the bulk friction, which in the case of sand bed rivers is a strong function of the size of dune bedforms. We explored the accuracy of existing and new empirical closures that relate the bulk roughness to parameters such as the median grain size diameter, ratio of shear velocity to sediment fall velocity or the Froude number. For given roughness parameterization, the inversion solution is determined iteratively since the hydraulic roughness depends on the unknown depth. We first test the new hydraulic roughness parameterization using estimates of the Manning roughness in sand bed rivers based on field measurements. The coupled inversion and roughness model is then tested using in situ and remote sensing measurements of the Kootenai River east of Bonners Ferry, ID.

Surface roughness: A review of its measurement at micro-/nano-scale

NASA Astrophysics Data System (ADS)

Gong, Yuxuan; Xu, Jian; Buchanan, Relva C.

2018-01-01

The measurement of surface roughness at micro-/nano-scale is of great importance to metrological, manufacturing, engineering, and scientific applications given the critical roles of roughness in physical and chemical phenomena. The surface roughness of materials can significantly change the way of how they interact with light, phonons, molecules, and so forth, thus surface roughness ultimately determines the functionality and property of materials. In this short review, the techniques of measuring micro-/nano-scale surface roughness are discussed with special focus on the limitations and capabilities of each technique. In addition, the calculations of surface roughness and their theoretical background are discussed to offer readers a better understanding of the importance of post-measurement analysis. Recent progress on fractal analysis of surface roughness is discussed to shed light on the future efforts in surface roughness measurement.

A geometrical optics polarimetric bidirectional reflectance distribution function for dielectric and metallic surfaces.

PubMed

Hyde, M W; Schmidt, J D; Havrilla, M J

2009-11-23

A polarimetric bidirectional reflectance distribution function (pBRDF), based on geometrical optics, is presented. The pBRDF incorporates a visibility (shadowing/masking) function and a Lambertian (diffuse) component which distinguishes it from other geometrical optics pBRDFs in literature. It is shown that these additions keep the pBRDF bounded (and thus a more realistic physical model) as the angle of incidence or observation approaches grazing and better able to model the behavior of light scattered from rough, reflective surfaces. In this paper, the theoretical development of the pBRDF is shown and discussed. Simulation results of a rough, perfect reflecting surface obtained using an exact, electromagnetic solution and experimental Mueller matrix results of two, rough metallic samples are presented to validate the pBRDF.

Refurbishing of carbon contaminated pre-mirror of reflectivity beam line at Indus-1

NASA Astrophysics Data System (ADS)

Yadav, P. K.; Kumar, M.; Gupta, R. K.; Sinha, M.; Patel, H. S.; Modi, M. H.

2018-04-01

In recent days optics contamination and its refurbishing is a serious issue for synchrotron radiation beam line community. Here we refurbished a carbon contaminated mirror by Ar and O2 gas mixed (1:1) radio frequency plasma. For structural analysis pre and post characterization of the mirror was done by Soft X-ray reflectivity (SXRR), Raman Spectroscopy (RS) and Atomic force microscopy (AFM). Before refurbishing mirror, a low density graphitic carbon layer of thickness 400 Å with surface roughness about 55 Å and Au surface roughness 14Å was estimated by SXRR. After one hour RF plasma exposure it is observed by SXRR and Raman spectroscopy that carbon layer is completely removed. The AFM and SXRR results show that roughness of Au surface not increase after plasma exposure.

The effect of row structure on soil moisture retrieval accuracy from passive microwave data.

PubMed

Xingming, Zheng; Kai, Zhao; Yangyang, Li; Jianhua, Ren; Yanling, Ding

2014-01-01

Row structure causes the anisotropy of microwave brightness temperature (TB) of soil surface, and it also can affect soil moisture retrieval accuracy when its influence is ignored in the inversion model. To study the effect of typical row structure on the retrieved soil moisture and evaluate if there is a need to introduce this effect into the inversion model, two ground-based experiments were carried out in 2011. Based on the observed C-band TB, field soil and vegetation parameters, row structure rough surface assumption (Q p model and discrete model), including the effect of row structure, and flat rough surface assumption (Q p model), ignoring the effect of row structure, are used to model microwave TB of soil surface. Then, soil moisture can be retrieved, respectively, by minimizing the difference of the measured and modeled TB. The results show that soil moisture retrieval accuracy based on the row structure rough surface assumption is approximately 0.02 cm(3)/cm(3) better than the flat rough surface assumption for vegetated soil, as well as 0.015 cm(3)/cm(3) better for bare and wet soil. This result indicates that the effect of row structure cannot be ignored for accurately retrieving soil moisture of farmland surface when C-band is used.

Atomic force microscopy studies of homoepitaxial GaN layers grown on GaN template by laser MBE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choudhary, B. S.; Rajasthan Technical University, Rawatbhata Road, Kota 324010; Singh, A.

We have grown homoepitaxial GaN films on metal organic chemical vapor deposition (MOCVD) grown 3.5 µm thick GaN on sapphire (0001) substrate (GaN template) using an ultra-high vacuum (UHV) laser assisted molecular beam epitaxy (LMBE) system. The GaN films were grown by laser ablating a polycrystalline solid GaN target in the presence of active r.f. nitrogen plasma. The influence of laser repetition rates (10-30 Hz) on the surface morphology of homoepitaxial GaN layers have been studied using atomic force microscopy. It was found that GaN layer grown at 10 Hz shows a smooth surface with uniform grain size compared to the rough surfacemore » with irregular shape grains obtained at 30 Hz. The variation of surface roughness of the homoepitaxial GaN layer with and without wet chemical etching has been also studied and it was observed that the roughness of the film decreased after wet etching due to the curved structure/rough surface.« less

Detection and interpretation of ocean roughness variations across the Gulf Stream inferred from radar cross section observations

NASA Technical Reports Server (NTRS)

Weissman, D. E.; Thompson, T. W.

1977-01-01

Radar cross section data shows that the Gulf Stream has a higher cross section per unit area (interpreted here as a greater roughness) than the water on the continental shelf. A steep gradient in cross section was often seen at the expected location of the western boundary. There were also longer-scale (10-20 km) gradual fluctuations within the stream of significant magnitude. These roughness variations are correlated with the surface shear stress that the local wind imposes on the sea. Using the available surface-truth information concerning the wind speed and direction, an assumed Gulf Stream velocity profile, and high-resolution ocean-surface temperature data obtained by the VHRR onboard a NOAA-NESS polar-orbiting satellite, the present study demonstrates that the computed surface stress variation bears a striking resemblance to the measured radar cross-section variations.

Progress in radar snow research. [Brookings, South Dakota

NASA Technical Reports Server (NTRS)

Stiles, W. H.; Ulaby, F. T.; Fung, A. K.; Aslam, A.

1981-01-01

Multifrequency measurements of the radar backscatter from snow-covered terrain were made at several sites in Brookings, South Dakota, during the month of March of 1979. The data are used to examine the response of the scattering coefficient to the following parameters: (1) snow surface roughness, (2) snow liquid water content, and (3) snow water equivalent. The results indicate that the scattering coefficient is insensitive to snow surface roughness if the snow is drv. For wet snow, however, surface roughness can have a strong influence on the magnitude of the scattering coefficient. These observations confirm the results predicted by a theoretical model that describes the snow as a volume of Rayleig scatterers, bounded by a Gaussian random surface. In addition, empirical models were developed to relate the scattering coefficient to snow liquid water content and the dependence of the scattering coefficient on water equivalent was evaluated for both wet and dry snow conditions.

Effect of Reduced Phosphoric Acid Pre-etching Times 
on Enamel Surface Characteristics and Shear Fatigue Strength Using Universal Adhesives.

PubMed

Tsujimoto, Akimasa; Fischer, Nicholas; Barkmeier, Wayne; Baruth, Andrew; Takamizawa, Toshiki; Latta, Mark; Miyazaki, Masashi

2017-01-01

To examine the effect of reduced phosphoric acid pre-etching times on enamel fatigue bond strength of universal adhesives and surface characteristics by using atomic force microscopy (AFM). Three universal adhesives were used in this study (Clearfil Universal Bond [C], G-Premio Bond [GP], Scotchbond Universal Adhesive [SU]). Four pre-etching groups were employed: enamel pre-etched with phosphoric acid and immediately rinsed with an air-water spray, and enamel pre-etched with phosphoric acid for 5, 10, or 15 s. Ground enamel was used as the control group. For the initial bond strength test, 15 specimens per etching group for each adhesive were used. For the shear fatigue test, 20 specimens per etching group for each adhesive were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred. Initial shear bond strengths and fatigue shear strengths of composite adhesively bonded to ground and pre-etched enamel were determined. AFM observations of ground and pre-etched enamel were also conducted, and surface roughness as well as surface area were evaluated. The initial shear bond strengths and fatigue shear strengths of the universal adhesives in the pre-etched groups were significantly higher than those of the control group, and were not influenced by the pre-etching time. Significantly higher surface roughness and surface area of enamel surfaces in pre-etched groups were observed compared with those in the control group. While the surface area was not significantly influenced by etching time, surface roughness of the enamel surfaces in the pre-etched groups significantly increased with pre-etching time. The results of this in vitro study suggest that reduced phosphoric acid pre-etching times do not impair the fatigue bond strength of universal adhesives. Although fatigue bond strength and surface area were not influenced by phosphoric-acid etching times, surface roughness increased with increasing etching time.

Diversity of dermal denticle structure in sharks: Skin surface roughness and three-dimensional morphology.

PubMed

Ankhelyi, Madeleine V; Wainwright, Dylan K; Lauder, George V

2018-05-29

Shark skin is covered with numerous placoid scales or dermal denticles. While previous research has used scanning electron microscopy and histology to demonstrate that denticles vary both around the body of a shark and among species, no previous study has quantified three-dimensional (3D) denticle structure and surface roughness to provide a quantitative analysis of skin surface texture. We quantified differences in denticle shape and size on the skin of three individual smooth dogfish sharks (Mustelus canis) using micro-CT scanning, gel-based surface profilometry, and histology. On each smooth dogfish, we imaged between 8 and 20 distinct areas on the body and fins, and obtained further comparative skin surface data from leopard, Atlantic sharpnose, shortfin mako, spiny dogfish, gulper, angel, and white sharks. We generated 3D images of individual denticles and measured denticle volume, surface area, and crown angle from the micro-CT scans. Surface profilometry was used to quantify metrology variables such as roughness, skew, kurtosis, and the height and spacing of surface features. These measurements confirmed that denticles on different body areas of smooth dogfish varied widely in size, shape, and spacing. Denticles near the snout are smooth, paver-like, and large relative to denticles on the body. Body denticles on smooth dogfish generally have between one and three distinct ridges, a diamond-like surface shape, and a dorsoventral gradient in spacing and roughness. Ridges were spaced on average 56 µm apart, and had a mean height of 6.5 µm, comparable to denticles from shortfin mako sharks, and with narrower spacing and lower heights than other species measured. We observed considerable variation in denticle structure among regions on the pectoral, dorsal, and caudal fins, including a leading-to-trailing edge gradient in roughness for each region. Surface roughness in smooth dogfish varied around the body from 3 to 42 microns. © 2018 Wiley Periodicals, Inc.

Development of AISI 316L stainless steel coronary stent

NASA Astrophysics Data System (ADS)

García-López, Erika; Siller, Héctor R.; Rodríguez, Ciro A.

2018-02-01

Coronary stents are manufactured through a sequence of processes and each step demands the process control to assure surface quality. This study is focused on the influence of laser cutting parameters and electropolishing on average surface roughness and back wall dross percentage for fiber laser cutting of AISI 316L coronary struts. A preliminary test and a design of experiments (DOE) were implemented to determine the limiting cutting conditions and the effect of these parameters on quality indicators. Preliminary results identify four cutting zones from a non-cut zone to a burned zone, in a frequency range between 1000 and 1500 Hz and a peak power between 160 to 180 W for clean cuts. From the DOE results, several interactions between factors were observed; however, a laser frequency of 1000 to 1500 Hz and a cutting speed of 250 mm/min minimize the backwall dross percentage and the surface roughness to values less than 2% and 0.9 μm, respectively. After the laser conditions selection, coronary stents were manufactured and electropolished to reduce the surface roughness on the strut edge. Electropolishing results indicate a surface roughness reduction from 0.9 μm to 0.3 μm after 300 s of electropolishing time.

Roughness influence on human blood drop spreading and splashing

NASA Astrophysics Data System (ADS)

Smith, Fiona; Buntsma, Naomi; Brutin, David

2017-11-01

The impact behaviour of complex fluid droplets is a topic that has been extensively studied but with much debate. The Bloodstain Pattern Analysis (BPA) community is encountering this scientific problem with daily practical cases since they use bloodstains as evidence in crime scene reconstruction. We aim to provide fundamental explanations in the study of blood drip stains by investigating the influence of surface roughness and wettability on the splashing limit of droplets of blood, a non-Newtonian colloidal fluid. Droplets of blood impacting perpendicularly different surfaces at different velocities were recorded. The recordings were analysed as well as the surfaces characteristics in order to find an empirical solution since we found that roughness plays a major role in the threshold of the splashing/non-splashing behaviour of blood compared to the wettability. Moreover it appears that roughness alters the deformation of the drip stains. These observations are key in characterising features of drip stains with the impacting conditions, which would answer some forensic issues.

Incorporation of a high-roughness lower boundary into a mesoscale model for studies of dry deposition over complex terrain

NASA Astrophysics Data System (ADS)

Physick, W. L.; Garratt, J. R.

1995-04-01

For flow over natural surfaces, there exists a roughness sublayer within the atmospheric surface layer near the boundary. In this sublayer (typically 50 z 0 deep in unstable conditions), the Monin-Obukhov (M-O) flux profile relations for homogeneous surfaces cannot be applied. We have incorporated a modified form of the M-O stability functions (Garratt, 1978, 1980, 1983) in a mesoscale model to take account of this roughness sublayer and examined the diurnal variation of the boundary-layer wind and temperature profiles with and without these modifications. We have also investigated the effect of the modified M-O functions on the aerodynamic and laminar-sublayer resistances associated with the transfer of trace gases to vegetation. Our results show that when an observation height or the lowest level in a model is within the roughness sublayer, neglect of the flux-profile modifications leads to an underestimate of resistances by 7% at the most.

Near-surface bulk densities of asteroids derived from dual-polarization radar observations

NASA Astrophysics Data System (ADS)

Virkki, A.; Taylor, P. A.; Zambrano-Marin, L. F.; Howell, E. S.; Nolan, M. C.; Lejoly, C.; Rivera-Valentin, E. G.; Aponte, B. A.

2017-09-01

We present a new method to constrain the near-surface bulk density and surface roughness of regolith on asteroid surfaces using planetary radar measurements. The number of radar observations has increased rapidly during the last five years, allowing us to compare and contrast the radar scattering properties of different small-body populations and compositional types. This provides us with new opportunities to investigate their near-surface physical properties such as the chemical composition, bulk density, porosity, or the structural roughness in the scale of centimeters to meters. Because the radar signal can penetrate into a planetary surface up to a few decimeters, radar can reveal information that is hidden from other ground-based methods, such as optical and infrared measurements. The near-surface structure of asteroids and comets in centimeter-to-meter scale is essential information for robotic and human space missions, impact threat mitigation, and understanding the history of these bodies as well as the formation of the whole Solar System.

Stability of smooth and rough mini-implants: clinical and biomechanical evaluation - an in vivostudy

PubMed Central

Vilani, Giselle Naback Lemes; Ruellas, Antônio Carlos de Oliveira; Elias, Carlos Nelson; Mattos, Cláudia Trindade

2015-01-01

Objective: To compare in vivo orthodontic mini-implants (MI) of smooth (machined) and rough (acid etched) surfaces, assessing primary and secondary stability. Methods: Thirty-six (36) MI were inserted in the mandibles of six (6) dogs. Each animal received six (6) MI. In the right hemiarch, three (3) MI without surface treatment (smooth) were inserted, whereas in the left hemiarch, another three (3) MI with acid etched surfaces (rough) were inserted. The two distal MI in each hemiarch received an immediate load of 1.0 N for 16 weeks, whereas the MI in the mesial extremity was not subject to loading. Stability was measured by insertion and removal torque, initial and final mobility and by inter mini-implant distance. Results: There was no statistical behavioral difference between smooth and rough MI. High insertion torque and reduced initial mobility were observed in all groups, as well as a reduction in removal torques in comparison with insertion torque. Rough MI presented higher removal torque and lower final mobility in comparison to smooth MI. MI did not remain static, with displacement of rough MI being smaller in comparison with smooth MI, but with no statistical difference. Conclusions: MI primary stability was greater than stability measured at removal. There was no difference in stability between smooth and rough MI when assessing mobility, displacement and insertion as well as removal torques. PMID:26560819

High frequency acoustic propagation under variable sea surfaces

NASA Astrophysics Data System (ADS)

Senne, Joseph

This dissertation examines the effects of rough sea surfaces and sub-surface bubbles on high frequency acoustic transmissions. Owing to the strong attenuation of electromagnetic waves in seawater, acoustic waves are used in the underwater realm much in the same way that electromagnetic waves are used in the atmosphere. The transmission and reception of acoustic waves in the underwater environment is important for a variety of fields including navigation, ocean observation, and real-time communications. Rough sea surfaces and sub-surface bubbles alter the acoustic signals that are received not only in the near-surface water column, but also at depth. This dissertation demonstrates that surface roughness and sub-surface bubbles notably affect acoustic transmissions with frequency ranges typical of underwater communications systems (10-50 kHz). The influence of rough surfaces on acoustic transmissions is determined by modeling forward propagation subject to sea surface dynamics that vary with time scales of less than a second to tens of seconds. A time-evolving rough sea surface model is combined with a rough surface formulation of a parabolic equation model for predicting time-varying acoustic fields. Linear surface waves are generated from surface wave spectra, and evolved in time using a Runge-Kutta integration technique. This evolving, range-dependent surface information is combined with other environmental parameters and fed into the acoustic model, giving an approximation of the time-varying acoustic field. The wide-angle parabolic equation model manages the rough sea surfaces by molding them into the boundary conditions for calculations of the near-surface acoustic field. The influence of sub-surface bubbles on acoustic transmissions is determined by modeling the population of bubbles near the surface and using those populations to approximate the effective changes in sound speed and attenuation. Both range-dependent and range-independent bubble models are considered, with the range-dependent model varying over the same time scales as the sea surface model and the range-independent model invariant over time. The bubble-induced sound speed and attenuation fluctuations are read in by the parabolic equation model, which allows for the effects of surface roughness and sub-surface bubbles to be computed separately or together. These merged acoustic models are validated using concurrently-collected acoustic and environmental information, including surface wave spectra. Data to model comparisons demonstrate that the models are able to approximate the ensemble-averaged acoustic intensity at ranges of at least a kilometer for acoustic signals of 10-20 kHz. The rough surface model is shown to capture variations due to surface fluctuations occurring over time scales of less than a second to tens of seconds. The separate bubble models demonstrate the abilities to account for the intermittency of bubble plumes and to determine overall effect of bubbly layers, respectively. The models are shown to capture variations in the acoustic field occurring over time scales of less than a second to tens of seconds. Comparisons against data demonstrate the ability of the model to track acoustic transmissions under evolving sea surfaces. The effects of the evolving bubble field are demonstrated through the use of idealized test cases. For frequency ranges important to communications, surface roughness is shown to have the more dominant effect, with bubbles having an ancillary effect.

Thickness and surface roughness study of co-sputtered nanostructured alumina/tungsten (Al2O3/W) thin films

NASA Astrophysics Data System (ADS)

Naveen, A.; Krishnamurthy, L.; Shridhar, T. N.

2018-04-01

Tungsten (W) and Alumina (Al2O3) thin films have been developed using co-sputtering technique on SS304, Copper (Cu) and Glass slides using Direct Current magnetron sputtering (DC) and Radio Frequency (RF) magnetron sputtering methods respectively. Central Composite Design (CCD) method approach has been adopted to determine the number of experimental plans for deposition and DC power, RF power and Argon gas flow rate have been input parameters, each at 5 levels for development of thin films. In this research paper, study has been carried out determine the optimized condition of deposition parameters for thickness and surface roughness of the thin films. Thickness and average Surface roughness in terms of nanometer (nm) have been characterized by thickness profilometer and atomic force microscopy respectively. The maximum and minimum average thickness observed to be 445 nm and 130 respectively. The optimum deposition condition for W/Al2O3 thin film growth was determined to be at 1000 watts of DC power and 800 watts of RF power, 20 minutes of deposition time, and almost 300 Standard Cubic Centimeter(SCCM) of Argon gas flow. It was observed that average roughness difference found to be less than one nanometer on SS substrate and one nanometer on copper approximately.

Full wave two-dimensional modeling of scattering and inverse scattering for layered rough surfaces with buried objects

NASA Astrophysics Data System (ADS)

Kuo, Chih-Hao

Efficient and accurate modeling of electromagnetic scattering from layered rough surfaces with buried objects finds applications ranging from detection of landmines to remote sensing of subsurface soil moisture. The formulation of a hybrid numerical/analytical solution to electromagnetic scattering from layered rough surfaces is first presented in this dissertation. The solution to scattering from each rough interface is sought independently based on the extended boundary condition method (EBCM), where the scattered fields of each rough interface are expressed as a summation of plane waves and then cast into reflection/transmission matrices. To account for interactions between multiple rough boundaries, the scattering matrix method (SMM) is applied to recursively cascade reflection and transmission matrices of each rough interface and obtain the composite reflection matrix from the overall scattering medium. The validation of this method against the Method of Moments (MoM) and Small Perturbation Method (SPM) is addressed and the numerical results which investigate the potential of low frequency radar systems in estimating deep soil moisture are presented. Computational efficiency of the proposed method is also discussed. In order to demonstrate the capability of this method in modeling coherent multiple scattering phenomena, the proposed method has been employed to analyze backscattering enhancement and satellite peaks due to surface plasmon waves from layered rough surfaces. Numerical results which show the appearance of enhanced backscattered peaks and satellite peaks are presented. Following the development of the EBCM/SMM technique, a technique which incorporates a buried object in layered rough surfaces by employing the T-matrix method and the cylindrical-to-spatial harmonics transformation is proposed. Validation and numerical results are provided. Finally, a multi-frequency polarimetric inversion algorithm for the retrieval of subsurface soil properties using VHF/UHF band radar measurements is devised. The top soil dielectric constant is first determined using an L-band inversion algorithm. For the retrieval of subsurface properties, a time-domain inversion technique is employed together with a parameter optimization for the pulse shape of time delay echoes from VHF/UHF band radar observations. Numerical studies to investigate the accuracy of the proposed inversion technique in presence of errors are addressed.

Direct observation of bacterial deposition onto clean and organic-fouled polyamide membranes.

PubMed

Subramani, Arun; Huang, Xiaofei; Hoek, Eric M V

2009-08-01

Nanofiltration (NF) and reverse osmosis (RO) membranes are commonly applied to produce highly purified water from municipal wastewater effluents. In these applications, biofouling limits overall process performance and increases the cost of operation. Initial bacteria adhesion onto a membrane surface is a critical early step in the overall process of membrane biofouling. However, adsorption of effluent organic matter onto the membrane may precede bacterial deposition and change membrane surface properties. Herein we employed direct microscopic observation to elucidate mechanisms governing bacterial cell deposition onto clean and organic-fouled NF and RO membranes. Bovine serum albumin (BSA) and alginic acid (AA) were used as models for protein and polysaccharide rich organic matter in secondary wastewater effluents. In all experiments, organic fouling increased membrane hydraulic resistance and salt rejection, in addition to interfacial hydrophilicity and roughness. Even though surface hydrophilicity increased, the rougher surfaces presented by organic-fouled membranes produced nano-scale features that promoted localized bacterial deposition. An extended DLVO analysis of bacterial cells and membrane surface properties suggested that bacterial deposition correlated most strongly with the Lewis acid-base free energy of adhesion and root mean square (RMS) roughness, whereas van der Waals and electrostatic free energies were weakly correlated. This was true for both clean and organic-fouled membranes. Bacterial deposition rates were clearly influenced by an antagonistic interplay between macroscopic surface hydrophilicity and nano-scale surface roughness.

Connections Between the Spring Breakup of the Southern Hemisphere Polar Vortex, Stationary Waves, and Air-sea Roughness

NASA Technical Reports Server (NTRS)

Garfinkel, Chaim I.; Oman, Luke David; Barnes, Elizabeth A.; Waugh, Darryn W.; Hurwitz, Margaret H.; Molod, Andrea M.

2013-01-01

A robust connection between the drag on surface-layer winds and the stratospheric circulation is demonstrated in NASA's Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM). Specifically, an updated parameterization of roughness at the air-sea interface, in which surface roughness is increased for moderate wind speeds (4ms to 20ms), leads to a decrease in model biases in Southern Hemispheric ozone, polar cap temperature, stationary wave heat flux, and springtime vortex breakup. A dynamical mechanism is proposed whereby increased surface roughness leads to improved stationary waves. Increased surface roughness leads to anomalous eddy momentum flux convergence primarily in the Indian Ocean sector (where eddies are strongest climatologically) in September and October. The localization of the eddy momentum flux convergence anomaly in the Indian Ocean sector leads to a zonally asymmetric reduction in zonal wind and, by geostrophy, to a wavenumber-1 stationary wave pattern. This tropospheric stationary wave pattern leads to enhanced upwards wave activity entering the stratosphere. The net effect is an improved Southern Hemisphere vortex: the vortex breaks up earlier in spring (i.e., the spring late-breakup bias is partially ameliorated) yet is no weaker in mid-winter. More than half of the stratospheric biases appear to be related to the surface wind speed biases. As many other chemistry climate models use a similar scheme for their surface layer momentum exchange and have similar biases in the stratosphere, we expect that results from GEOSCCM may be relevant for other climate models.

Effect of ultraviolet light irradiation on bond strength of fiber post: Evaluation of surface characteristic and bonded area of fiber post with resin cement.

PubMed

Reza, Fazal; Ibrahim, Nur Sukainah

2015-01-01

Fiber post is cemented to a root canal to restore coronal tooth structure. This research aims to evaluate the effect of ultraviolet (UV) irradiation on bond strength of fiber post with resin cement. A total of 40 of the two types of fiber posts, namely, FRC Prostec (FRC) and Fiber KOR (KOR), were used for the experiment. UV irradiation was applied on top of the fiber post surface for 0, 15, 20, and 30 min. The irradiated surface of the fiber posts (n = 5) were immediately bonded with resin cement (Rely X U200) after UV irradiation. Shear bond strength (SBS) MPa was measured, and the dislodged area of post surfaces was examined with scanning electron microscopes. Changes in surface roughness (Ra) of the FRC group after UV irradiation were observed (n = 3) using atomic force microscopy. Data of SBS were statistically analyzed using one-way analysis of variance, followed by multiple comparisons (P < 0.05). SBS was significantly higher for 20 min of UV irradiation of the FRC group while significantly higher SBS was observed with 15 min of UV irradiation of the KOR group. Resin cement was more evident (cohesive failure) on the dislodged post surface of the UV treated groups compared with the control. The surface roughness of the FRC post was Ra = 175.1 nm and Ra = 929.2 nm for the control and the 20 min group, respectively. Higher surface roughness of the UV irradiated group indicated formation of mechanical retention on the fiber post surface. Evidence of cohesive failure was observed which indicated higher SBS of fiber post with the UV irradiated group.

Effect of ultraviolet light irradiation on bond strength of fiber post: Evaluation of surface characteristic and bonded area of fiber post with resin cement

PubMed Central

Reza, Fazal; Ibrahim, Nur Sukainah

2015-01-01

Objective: Fiber post is cemented to a root canal to restore coronal tooth structure. This research aims to evaluate the effect of ultraviolet (UV) irradiation on bond strength of fiber post with resin cement. Materials and Methods: A total of 40 of the two types of fiber posts, namely, FRC Prostec (FRC) and Fiber KOR (KOR), were used for the experiment. UV irradiation was applied on top of the fiber post surface for 0, 15, 20, and 30 min. The irradiated surface of the fiber posts (n = 5) were immediately bonded with resin cement (Rely X U200) after UV irradiation. Shear bond strength (SBS) MPa was measured, and the dislodged area of post surfaces was examined with scanning electron microscopes. Changes in surface roughness (Ra) of the FRC group after UV irradiation were observed (n = 3) using atomic force microscopy. Data of SBS were statistically analyzed using one-way analysis of variance, followed by multiple comparisons (P < 0.05). Results: SBS was significantly higher for 20 min of UV irradiation of the FRC group while significantly higher SBS was observed with 15 min of UV irradiation of the KOR group. Resin cement was more evident (cohesive failure) on the dislodged post surface of the UV treated groups compared with the control. The surface roughness of the FRC post was Ra = 175.1 nm and Ra = 929.2 nm for the control and the 20 min group, respectively. Conclusions: Higher surface roughness of the UV irradiated group indicated formation of mechanical retention on the fiber post surface. Evidence of cohesive failure was observed which indicated higher SBS of fiber post with the UV irradiated group. PMID:25713488

An Experimental Study of Fretting of Gear Teeth

NASA Technical Reports Server (NTRS)

Krantz, Timothy L.

2008-01-01

Experiments were conducted to study fretting of gears. The gears were made from case-carburized AISI 9310 alloy to match the material of a flight actuator gearbox of interest. The objective of the testing was to produce damage representative of that observed on flight hardware. The following correlations and observations were noted. The amplitude of dithering motion very strongly influenced the type and magnitude of damage. Sliding amounts on the order of 30% of the width of the line contact were judged to most readily produce fretting damage. There was observed an incubation period on the order of tens-of-thousands of cycles, and the incubation period was influenced by surface roughness, torque, and the motion extent. Fretting damage could be produced for any of the torques tested, and the severity of damage increased slightly with torque. Gear teeth having surface roughness of 0.7-0.8 micrometer were somewhat more resistant to fretting than were smoother surfaces.

A lattice Boltzmann model for substrates with regularly structured surface roughness

NASA Astrophysics Data System (ADS)

Yagub, A.; Farhat, H.; Kondaraju, S.; Singh, T.

2015-11-01

Superhydrophobic surface characteristics are important in many industrial applications, ranging from the textile to the military. It was observed that surfaces fabricated with nano/micro roughness can manipulate the droplet contact angle, thus providing an opportunity to control the droplet wetting characteristics. The Shan and Chen (SC) lattice Boltzmann model (LBM) is a good numerical tool, which holds strong potentials to qualify for simulating droplets wettability. This is due to its realistic nature of droplet contact angle (CA) prediction on flat smooth surfaces. But SC-LBM was not able to replicate the CA on rough surfaces because it lacks a real representation of the physics at work under these conditions. By using a correction factor to influence the interfacial tension within the asperities, the physical forces acting on the droplet at its contact lines were mimicked. This approach allowed the model to replicate some experimentally confirmed Wenzel and Cassie wetting cases. Regular roughness structures with different spacing were used to validate the study using the classical Wenzel and Cassie equations. The present work highlights the strength and weakness of the SC model and attempts to qualitatively conform it to the fundamental physics, which causes a change in the droplet apparent contact angle, when placed on nano/micro structured surfaces.

Improvement of the GEOS-5 AGCM upon Updating the Air-Sea Roughness Parameterization

NASA Technical Reports Server (NTRS)

Garfinkel, C. I.; Molod, A.; Oman, L. D.; Song, I.-S.

2011-01-01

The impact of an air-sea roughness parameterization over the ocean that more closely matches recent observations of air-sea exchange is examined in the NASA Goddard Earth Observing System, version 5 (GEOS-5) atmospheric general circulation model. Surface wind biases in the GEOS-5 AGCM are decreased by up to 1.2m/s. The new parameterization also has implications aloft as improvements extend into the stratosphere. Many other GCMs (both for operational weather forecasting and climate) use a similar class of parameterization for their air-sea roughness scheme. We therefore expect that results from GEOS-5 are relevant to other models as well.

An in vitro evaluation of wear and surface roughness of particulate filler composite resin after tooth brushing.

PubMed

Al Khuraif, Abdul Aziz A

2014-11-01

To evaluate the influence of tooth brushing on wear and surface roughness of four different particulate filler composite resins. Six specimens (2 mm thick and 8 mm in diameter) of each tested material (Filtek Z250-Microhybrid, SpectrumTPH3-Submicron hybrid, Filtek Z350XT Nanofiller and Filtek P90- Microhybrid) were prepared according to the manufacturer's directions. A brushing sequence of 5000, 10,000 and 20,000 cycles was performed for all the samples. A non-contact profilometer was used to determine average surface roughness (Ra) and wear of the material assessed using an analytic electronic balance at baseline and each cycle interval. The data obtained were analyzed using one-way ANOVAs and post-hoc multiple comparison tests. Paired t-test was used for comparisons between cycle intervals for each material. Analyses with scanning electron microscopy (SEM) were also performed. The resin composite Filtek P 90 presented an increase in percentage weight loss after final toothbrushing cycles over the rest of the materials. Brushing significantly increased roughness (Ra) for all composites. Filtek Z250, after brushing, was significantly rougher than the other resins followed by Filtek P 90, Spectrum TPH 3 and Filtek Z350 XT. However, SEM images indicated severe change in surface topography of 'sub-micron hybrid' specimen compared to each other after tooth brushing. Wear and surface roughness increased with each cycle interval for all the materials and one composite resin demonstrated a higher increase in surface roughness than the other three tested brands of composite resins. Not much difference was observed in the weight loss between tested samples.

The VHCF experimental investigation of FV520B-I with surface roughness Ry

NASA Astrophysics Data System (ADS)

Wang, J. L.; Zhang, Y. L.; Ding, M. C.; Zhao, Q. C.

2018-05-01

Different surface roughness type (Ra and Ry) has different effect on the VHCF failure and life. Ra is widely employed as the quantitative expression of the surface roughness, but there are few fatigue failure mechanism analysis and experimental study under surface roughness Ry. The VHCF experiment is conducted out using the specimen with different surface roughness values. The surface roughness Ry is employed as the major research object to investigate the relationship and distribution tendency between the Ry, fatigue life and the distance between internal inclusion and surface, and a new VHCF failure character is proposed.

Smoothed particle hydrodynamics study of the roughness effect on contact angle and droplet flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shigorina, Elena; Kordilla, Jannes; Tartakovsky, Alexandre M.

We employ a pairwise force Smoothed Particle Hydrodynamics (PF-SPH) model to simulate sessile and transient droplets on rough hydrophobic and hydrophilic surfaces. PF-SPH allows for modeling of free surface flow without discretizing the air phase, which is achieved by imposing the surface tension and dynamic contact angles with pairwise interaction forces. We use the PF-SPH model to study the effect of surface roughness and microscopic contact angle on the effective contact angle and droplet dynamics. In the first part of this work, we investigate static contact angles of sessile droplets on rough surfaces in a shape of a sinusoidal functionmore » and made of rectangular bars placed on top of a flat surface. We find that the effective static contact angles of Cassie and Wenzel droplets on a rough surface are greater than the corresponding microscale static contact angles. As a result, microscale hydrophobic rough surfaces also show effective hydrophobic behavior. On the other hand, microscale hydrophilic surfaces may be macroscopically hydrophilic or hydrophobic, depending on the type of roughness. Next, we study the impact of the roughness orientation (i.e., an anisotropic roughness) and surface inclination on droplet flow velocities. Simulations show that droplet flow velocities are lower if the surface roughness is oriented perpendicular to the flow direction. If the predominant elements of surface roughness are in alignment with the flow direction, the flow velocities increase compared to smooth surfaces, which can be attributed to the decrease in fluid-solid contact area similar to the classical lotus effect. We demonstrate that linear scaling relationships between Bond and capillary number for droplet flow on flat surfaces also hold for flow on rough surfaces.« less

[Silicate coating of cemented titanium-based shafts in hip prosthetics reduces high aseptic loosening].

PubMed

Marx, R; Faramarzi, R; Jungwirth, F; Kleffner, B V; Mumme, T; Weber, M; Wirtz, D C

2009-01-01

For cemented hip prostheses, all requirements can be fulfilled by using forged Co/Cr/Mo stems. Co/Cr/Mo alloys, however, are contraindicated for allergy sufferers. For these patients, a cemented prosthesis made of titanium (alloy) would be indicated. Cemented stems from titanium (alloy), depending on the geometry of the prosthesis and its specific surface texture, however, may have loosening rates which are clinically not tolerable. In comparison to Co/Cr/Mo alloys, the greater roughness in conjunction with lesser abrasion resistance of titanium-based alloys leads to high loosening rates caused by abrasion. On the other hand, the greater surface roughness permits good mechanical retention of bone cement to the surface. Good mechanical retention enhances migration behaviour and reduces micromotions. However, there is no stable hydrolytic bond between bone cement and metallic surface; intermediate-term debonding between metal and bone cement is predictable. This debonding results in relative movements, consequently in wear particles which have their origin both from the rough metallic surface and from the PMMA cement. The roughness of the metallic surface operates as emery and with that, a rubbing wear from the PMMA. For the above reasons, a low or moderate roughness is essential for easily abradable implants such as shafts made of titanium (alloy) because low roughness provides a fail-safe running function in case of debonding. Thus, one must allow for inappropriate migration behaviour accompanied by greater micromotions due to insufficient mechanical retention in the case of low roughness. This can be accomplished by a silicate layer coating applied to the metal shaft surface via electrochemical "ECD" or physical vapour deposition "PVD". For analysis, specimens (screws for pull-out, cones for push-out tests) were sand-blasted, so that roughnesses between Ra = 0.8 microm (Rz = 4 microm) and Ra = 2.0 microm (Rz = 9 microm) were generated. The bond strengths observed in tensile tests for roughnesses of Ra = 1.7 mm were always well above 25 MPa for all periods of hydrolytic load. Therefore, the investigation shows that surfaces of moderate roughness (Ra = 1.7 microm), however coated, provide a steady retention. Cave-in and micromotions should widely be prevented. The abrasion, which is a consequence of and reason for debonding and loosening at the same time, should be avoidable if the bonding of cement on the metallic shaft is stabilised with the help of a suitable chemical bond system.

Quantitative flaw characterization with scanning laser acoustic microscopy

NASA Technical Reports Server (NTRS)

Generazio, E. R.; Roth, D. J.

1986-01-01

Surface roughness and diffraction are two factors that have been observed to affect the accuracy of flaw characterization with scanning laser acoustic microscopy. In accuracies can arise when the surface of the test sample is acoustically rough. It is shown that, in this case, Snell's law is no longer valid for determining the direction of sound propagation within the sample. The relationship between the direction of sound propagation within the sample, the apparent flaw depth, and the sample's surface roughness is investigated. Diffraction effects can mask the acoustic images of minute flaws and make it difficult to establish their size, depth, and other characteristics. It is shown that for Fraunhofer diffraction conditions the acoustic image of a subsurface defect corresponds to a two-dimensional Fourier transform. Transforms based on simulated flaws are used to infer the size and shape of the actual flaw.

A Novel Multi-Phosphonate Surface Treatment of Titanium Dental Implants: A Study in Sheep

PubMed Central

von Salis-Soglio, Marcella; Stübinger, Stefan; Sidler, Michéle; Klein, Karina; Ferguson, Stephen J.; Kämpf, Käthi; Zlinszky, Katalin; Buchini, Sabrina; Curno, Richard; Péchy, Péter; Aronsson, Bjorn-Owe; von Rechenberg, Brigitte

2014-01-01

The aim of the present study was to evaluate a new multi-phosphonate surface treatment (SurfLink®) in an unloaded sheep model. Treated implants were compared to control implants in terms of bone to implant contact (BIC), bone formation, and biomechanical stability. The study used two types of implants (rough or machined surface finish) each with either the multi-phosphonate Wet or Dry treatment or no treatment (control) for a total of six groups. Animals were sacrificed after 2, 8, and 52 weeks. No adverse events were observed at any time point. At two weeks, removal torque showed significantly higher values for the multi-phosphonate treated rough surface (+32% and +29%, Dry and Wet, respectively) compared to rough control. At 52 weeks, a significantly higher removal torque was observed for the multi-phosphonate treated machined surfaces (+37% and 23%, Dry and Wet, respectively). The multi-phosphonate treated groups showed a positive tendency for higher BIC with time and increased new-old bone ratio at eight weeks. SEM images revealed greater amounts of organic materials on the multi-phosphonate treated compared to control implants, with the bone fracture (from the torque test) appearing within the bone rather than at the bone to implant interface as it occurred for control implants. PMID:25215424

Titan: Preliminary results on surface properties and photometry from VIMS observations of the early flybys

USGS Publications Warehouse

Buratti, B.J.; Sotin, Christophe; Brown, R.H.; Hicks, M.D.; Clark, R.N.; Mosher, J.A.; McCord, T.B.; Jaumann, R.; Baines, K.H.; Nicholson, P.D.; Momary, T.; Simonelli, D.P.; Sicardy, B.

2006-01-01

Cassini observations of the surface of Titan offer unprecedented views of its surface through atmospheric windows in the 1-5 ??m region. Images obtained in windows for which the haze opacity is low can be used to derive quantitative photometric parameters such as albedo and albedo distribution, and physical properties such as roughness and particle characteristics. Images from the early Titan flybys, particularly T0, Ta, and T5 have been analyzed to create albedo maps in the 2.01 and 2.73 ??m windows. We find the average normal reflectance at these two wavelengths to be 0.15??0.02 and 0.035??0.003, respectively. Titan's surface is bifurcated into two albedo regimes, particularly at 2.01 ??m. Analysis of these two regimes to understand the physical character of the surface was accomplished with a macroscopic roughness model. We find that the two types of surface have substantially different roughness, with the low-albedo surface exhibiting mean slope angles of ???18??, and the high-albedo terrain having a much more substantial roughness with a mean slope angle of ???34??. A single-scattering phase function approximated by a one-term Henyey-Greenstein equation was also fit to each unit. Titan's surface is back-scattering (g???0.3-0.4), and does not exhibit substantially different backscattering behavior between the two terrains. Our results suggest that two distinct geophysical domains exist on Titan: a bright region cut by deep drainage channels and a relatively smooth surface. The two terrains are covered by a film or a coating of particles perhaps precipitated from the satellite's haze layer and transported by eolian processes. Our results are preliminary: more accurate values for the surface albedo and physical parameters will be derived as more data is gathered by the Cassini spacecraft and as a more complete radiative transfer model is developed from both Cassini orbiter and Huygens Lander measurements. ?? 2006 Elsevier Ltd. All rights reserved.

Heat Transfer Enhancement by Finned Heat Sinks with Micro-structured Roughness

NASA Astrophysics Data System (ADS)

Ventola, L.; Chiavazzo, E.; Calignano, F.; Manfredi, D.; Asinari, P.

2014-04-01

We investigated the benefits of micro-structured roughness on heat transfer performance of heat sinks, cooled by forced air. Heat sinks in aluminum alloy by direct metal laser sintering (DMLS) manufacturing technique were fabricated; values of the average surface roughness Ra from 1 to 25 microns (standard milling leads to roughness around 1 micron) under turbulent regimes (Reynolds number based on heating edge from 3000 to 17000) have been explored. An enhancement of 50% in thermal performances with regards to standard manufacturing was observed. This may open the way for huge boost in the technology of electronic cooling by DMLS.

Superhydrophobicity of electrospray-synthesized fluorinated silica layers.

PubMed

Kim, Eun-Kyeong; Lee, Chul-Sung; Kim, Sang Sub

2012-02-15

The preparation of superhydrophobic SiO(2) layers through a combination of a nanoscale surface roughness and a fluorination treatment is reported. Electrospraying SiO(2) precursor solutions that had been prepared by a sol-gel chemical route produced very rough SiO(2) layers. Subsequent fluorination treatment with a solution containing trichloro(1H,1H,2H,2H-perfluorooctyl)silane resulted in highly rough, fluorinated SiO(2) layers. The fluorinated rough SiO(2) layers exhibited excellent repellency toward various liquid droplets. In particular, water repellency of 168° was observed. On the bases of Cassie-Baxter and Young-Dupre equations, the surface fraction and the work of adhesion of the rough, fluorinated SiO(2) layers were respectively estimated. In light of the durability in water, ultraviolet resistance, and thermal stability, the superhydrophobic SiO(2) layers prepared in this work hold promise in a range of practical applications. Copyright © 2011 Elsevier Inc. All rights reserved.

How does substrate roughness affect the service life of a superhydrophobic coating?

NASA Astrophysics Data System (ADS)

Zhang, Xin; Mo, Jiliang; Si, Yifan; Guo, Zhiguang

2018-05-01

Although the development of superhydrophobic coatings is rapidly maturing, issues related to their low mechanical durability persist. In this context, the effect of substrate roughness on the service life of superhydrophobic coatings was studied. In this study, superhydrophobic coatings were fabricated on sandpapers of different roughness and reciprocating wear tests were conducted. The wear-resistance number of the superhydrophobic coating, defined as the maximum number of friction cycles after which the superhydrophobic surface started to lose its superhydrophobicity, increased from 50 to 24,000 with an increase in the substrate roughness from 2000 CW to 240 CW (CW is defined as the number of particles arranged in an inch), while it decreased from 24,000 to 17,000 with a further increase in the substrate roughness from 240 CW to 60 CW. Observations of the surface structure and wear analyses indicated that the superhydrophobic material infiltrated the spaces between the sand grains, and the rough peaks could consequently protect the superhydrophobic material during the wear tests. However, this protection weakens when the substrate roughness increases or decreases beyond certain values. Furthermore, these phenomena and results were also verified by applying the superhydrophobic coatings to different types of common substrates.

Formulation of glutaraldehyde disinfectant for alginate impressions.

PubMed

Unemori, M; Matsuya, Y; Matsuya, S; Akashi, A; Mizuno, K; Akamine, A

1999-12-01

The effect of buffer agents incorporated in glutaraldehyde disinfectants on the surface quality of dental models was examined by the measurement of surface roughness, X-ray diffraction analysis and SEM observation. Seven experimental glutaraldehyde disinfectants were prepared using two buffer agents, potassium acetate alone or potassium acetate and sodium hydrogen carbonate in combination. Four kinds of sulfate--zinc, calcium, potassium and magnesium sulfate--were added to these disinfectants in order to accelerate the hydration of calcium sulfate hemihydrate. The impressions treated with the experimental disinfectants for 1 h produced stone surfaces which had significantly lower surface roughness values than those treated with the commercial disinfectants (p < 0.05). The X-ray diffraction analysis and SEM observation showed that these superior surfaces were produced as a result of significant reductions in the amount of residual calcium sulfate hemihydrate. Replacement of buffer agents in commercial glutaraldehyde disinfectants with chemicals such as those studied in the present study will improve the surface quality of dental stone.

Wetting Transition of Nonpolar Neutral Molecule System on a Neutral and Atomic Length Scale Roughness Substrate

NASA Astrophysics Data System (ADS)

Zhou, Shiqi

2018-03-01

One recently proposed new method for accurately determining wetting temperature is applied to the wetting transition occurring in a single component nonpolar neutral molecule system near a neutral planar substrate with roughness produced by cosinusoidal modulation(s). New observations are summarized into five points: (i) for a planar substrate superimposed with one cosinusoidal modulation, with increasing of the periodicity length or the surface attraction force field, or decreasing of the amplitude, wetting temperature T_W drops accordingly and the three parameters show multiplication effect; moreover, both the periodicity length and amplitude effect curves display pole phenomena and saturation phenomena, and the T_W saturation occurs at small (for case of large amplitude) or large (for case of small amplitude) periodicity length side, respectively. (ii) In the case of the planar substrate superimposed with two cosinusoidal modulations with equal periodicity length, the initial phase difference is critical issue that influences the T_W, which decreases with the initial phase difference. (iii) In the case of the planar substrate superimposed with two cosinusoidal modulations with zero phase difference, change of the T_W with one periodicity length under the condition of another periodicity length unchanged is non-monotonous. (iv) When the parameters are chosen such that the T_W draws ever closer to the bulk critical temperature, wetting transition on the roughness substrate eventually does not occur. (v) The present microscopic calculation challenges traditional macroscopic theory by confirming that the atomic length scale roughness always renders the surface less hydrophilic and whereas the mesoscopical roughness renders the surface more hydrophilic. All of these observations summarized can be reasonably explained by the relative strength of the attraction actually enjoyed by the surface gas molecules to the attraction the gas molecules can get when in bulk.

CO2 adhesion on hydrated mineral surfaces.

PubMed

Wang, Shibo; Tao, Zhiyuan; Persily, Sara M; Clarens, Andres F

2013-10-15

Hydrated mineral surfaces in the environment are generally hydrophilic but in certain cases can strongly adhere CO2, which is largely nonpolar. This adhesion can significantly alter the wettability characteristics of the mineral surface and consequently influence capillary/residual trapping and other multiphase flow processes in porous media. Here, the conditions influencing adhesion between CO2 and homogeneous mineral surfaces were studied using static pendant contact angle measurements and captive advancing/receding tests. The prevalence of adhesion was sensitive to both surface roughness and aqueous chemistry. Adhesion was most widely observed on phlogopite mica, silica, and calcite surfaces with roughness on the order of ~10 nm. The incidence of adhesion increased with ionic strength and CO2 partial pressure. Adhesion was very rarely observed on surfaces equilibrated with brines containing strong acid or base. In advancing/receding contact angle measurements, adhesion could increase the contact angle by a factor of 3. These results support an emerging understanding of adhesion of, nonpolar nonaqueous phase fluids on mineral surfaces influenced by the properties of the electrical double layer in the aqueous phase film and surface functional groups between the mineral and CO2.

Getting the temperature right: Understanding thermal emission from airless bodies

NASA Astrophysics Data System (ADS)

Bandfield, J.; Greenhagen, B. T.; Hayne, P. O.; Williams, J. P.; Paige, D. A.

2016-12-01

Thermal infrared measurements are crucial for understanding a wide variety of processes present on airless bodies throughout the solar system. Although these data can be complex, they also contain an enormous amount of useful information. By building a framework for understanding thermal infrared datasets, significant advances are possible in the understanding of regolith development, detection of H2O and OH-, characterizing the nature and magnitude of Yarkovsky and YORP effects, and determination of the properties of newly identified asteroids via telescopic measurements. Airless bodies can have both extremely rough and insulating surfaces. For example, these two properties allow for sunlit and shaded or buried lunar materials separated by just a few centimeters to vary by 200K. In this sense, there is no "correct" temperature interpretable from orbital, or even in-situ, measurements. The surface contains a wide mixture of temperatures in the field of view, and rougher surfaces greatly enhance this anisothermality. We have used the Lunar Reconnaissance Orbiter Diviner Radiometer to characterize these effects by developing new targeting and analysis methods, including extended off-nadir observations and combined surface roughness and thermal modeling (Fig. 1). These measurements and models have shown up to 100K brightness temperature differences from measurements that differ only in the viewing angle of the observation. In addition, the thermal emission near 3 μm can be highly dependent on the surface roughness, resulting in more extensive and prominent lunar 3 μm H2O and OH-absorptions than indicated in data corrected by isothermal models. The datasets serve as a foundation for the derivation and understanding of surface spectral and thermophysical properties. Roughness and anisothermality effects are likely to dominate infrared measurements from many spacecraft, including LRO, Dawn, BepiColombo, OSIRIS-REx, Hayabusa-2, and Europa Clipper.

Ripple formation on atomically flat cleaved Si surface with roughness of 0.038 nm rms by low-energy Ar{sup 1+} ion bombardment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pahlovy, Shahjada A.; Mahmud, S. F.; Yanagimoto, K.

The authors have conducted research regarding ripple formation on an atomically flat cleaved Si surface by low-energy Ar{sup +} ion bombardment. The cleaved atomically flat and smooth plane of a Si wafer was obtained by cutting vertically against the orientation of a Si (100) wafer. Next, the cleaved surface was sputtered by a 1 keV Ar{sup +} ion beam at ion-incidence angles of 0 deg., 60 deg., 70 deg., and 80 deg. The results confirm the successful ripple formation at ion-incidence angles of 60 deg. - 80 deg. and that the wavelength of the ripples increases with the increase ofmore » the ion-incidence angle, as well as the inverse of ion doses. The direction of the ripple also changes from perpendicular to parallel to the projection of the ion-beam direction along the surface with the increasing ion-incidence angle. The authors have also observed the dose effects on surface roughness of cleaved Si surface at the ion-incidence angle of 60 deg., where the surface roughness increases with the increased ion dose. Finally, to understand the roughening mechanism, the authors studied the scaling behavior, measured the roughness exponent {alpha}, and compared the evolution of scaling regimes with Cuerno's one-dimensional simulation results.« less

Adsorption of silica colloids onto like-charged silica surfaces of different roughness

DOE PAGES

Dylla-Spears, R.; Wong, L.; Shen, N.; ...

2017-01-17

Particle adsorption was explored in a model optical polishing system, consisting of silica colloids and like-charged silica surfaces. The adsorption was monitored in situ under various suspension conditions, in the absence of surfactants or organic modifiers, using a quartz crystal microbalance with dissipation monitoring (QCM-D). Changes in surface coverage with particle concentration, particle size, pH, ionic strength and ionic composition were quantified by QCM-D and further characterized ex situ by atomic force microscopy (AFM). A Monte Carlo model was used to describe the kinetics of particle deposition and provide insights on scaling with particle concentration. Transitions from near-zero adsorption tomore » measurable adsorption were compared with equilibrium predictions made using the Deraguin-Verwey-Landau-Overbeek (DLVO) theory. In addition, the impact of silica surface roughness on the propensity for particle adsorption was studied on various spatial scale lengths by intentionally roughening the QCM sensor surface using polishing methods. It was found that a change in silica surface roughness at the AFM scale from 1.3 nm root-mean-square (rms) to 2.7 nm rms resulted in an increase in silica particle adsorption of 3-fold for 50-nm diameter particles and 1.3-fold for 100-nm diameter particles—far exceeding adsorption observed by altering suspension conditions alone, potentially because roughness at the proper scale reduces the total separation distance between particle and surface.« less

Evaluate the Effect of Commercially Available Denture Cleansers on Surface Hardness and Roughness of Denture Liners at Various Time Intervals

PubMed Central

Mohammed, Hilal S.; Singh, Sumeet; Hari, Prasad A.; Amarnath, G. S.; Kundapur, Vinaya; Pasha, Naveed; Anand, M.

2016-01-01

Background and objective: Chemical cleansing by denture cleansers is first choice for denture plaque control. The most common problems while using denture cleansers are hardening, porosity, odor sorption, water sorption, solubility, and colour change, bacterial and fungal growth. Chemical cleansing procedures have been found to have an effect on the physical and mechanical properties of denture liners. Thus, this study was conducted to evaluate the effect of commercially available denture cleansers on surface hardness and roughness of acrylic and silicon based denture liners at various time interval. Method: Two autopolymerising denture liners Kooliner (acrylic) and GC reline soft (silicon) were tested with two commercially available denture cleansers, polident and efferdent plus. Total of 120 specimens were prepared and all the specimens were divided into six groups based on the relining materials and denture cleansers used. Surface hardness and surface roughness was tested using Shore A durometer and profilometer respectively at the end of day 1, day 7, day 30 and day 90. All the specimens were stored in artificial saliva throughout the study. Cleanser solution was prepared daily by adding Polident and Efferdent plus denture cleanser tablet into 250ml of enough very warm (not hot) water. Acrylic and silicon liner groups were cleansed in a solution of denture cleanser and water for 15 minutes daily, rinsed with water and stored in artificial saliva at room temperature. The data was analyzed with one way ANOVA and independent t-test. Result: The acrylic soft lining showed gradual hardening and increase in surface roughness after immersion in denture cleanser and also with time. Acrylic liner material showed maximum hardness and roughness with Polident followed by Efferdent plus and water (control group). Silicone lining material showed a slight difference in hardness and roughness between the test group and control group. There was a slight increase in hardness in all the groups with time. Very slight increase in mean surface roughness of all the silicon liner groups from day 1 to day 90 was observed. A statistically significant change was noted between and within the all silicon liner groups on day 7, day 30 and day 90. Conclusion: The average surface hardness and surface roughness were lower in silicon liner material than acrylic liner material. Maximum surface roughness was noted by Polident followed by Efferdent Plus and Water for both acrylic liner group and silicon liner group. PMID:28190983

Effect of specific surface area of MWCNTS on surface roughness and delamination in drilling Epoxy/Glass Fabric Composite

NASA Astrophysics Data System (ADS)

Ponnuvel, S.; Ananth, M. Prem

2018-03-01

In this study the effect of specific surface area of the MWCNTs on the drilled hole qualities was investigated. Epoxy araldite LY556 with hardener HY951 and E-glass coarse plain weave fabric are used for the fabrication of reference material (specimen A). Multi-WalledCarbon Nanotubes (MWCNTs) with diameters <8 nm and 20–30 nm are used for the fabrication of study materials, namely specimen B and specimen C respectively. In specimen B the epoxy resin was filled with MWCNTs having a specific surface area >500 m2 g‑1. MWCNTs in specimen C had a specific surface area >110 m2 g‑1. Drilling experiments were conducted on all the three specimens. Two dimensional delamination factor and the surface roughness of the inner wall of the drilled holes were investigated using Grey Relational Analysis (GRA) and Analysis of variance (ANOVA). Two dimensional delamination factor showed better performance from specimen B and specimen C in comparison with specimen A suggesting improvement in the bonding between epoxy and the glass fiber in the presence of MWCNTs. Similar observations were made for surface roughness of the inner wall of the drilled holes at 1250 rpm. Whereas the presence of MWCNTs (Specimen B and specimen C) produced poor surface finish at 500 rpm in comparison with specimen A. Variations in the hole quality characteristics between specimen B and specimen C was marginal with better observations in specimen C.

Surface roughness measurement in the submicrometer range using laser scattering

NASA Astrophysics Data System (ADS)

Wang, S. H.; Quan, Chenggen; Tay, C. J.; Shang, H. M.

2000-06-01

A technique for measuring surface roughness in the submicrometer range is developed. The principle of the method is based on laser scattering from a rough surface. A telecentric optical setup that uses a laser diode as a light source is used to record the light field scattered from the surface of a rough object. The light intensity distribution of the scattered band, which is correlated to the surface roughness, is recorded by a linear photodiode array and analyzed using a single-chip microcomputer. Several sets of test surfaces prepared by different machining processes are measured and a method for the evaluation of surface roughness is proposed.

Analysis of the coherent and turbulent stresses of a numerically simulated rough wall pipe

NASA Astrophysics Data System (ADS)

Chan, L.; MacDonald, M.; Chung, D.; Hutchins, N.; Ooi, A.

2017-04-01

A turbulent rough wall flow in a pipe is simulated using direct numerical simulation (DNS) where the roughness elements consist of explicitly gridded three-dimensional sinusoids. Two groups of simulations were conducted where the roughness semi-amplitude h+ and the roughness wavelength λ+ are systematically varied. The triple decomposition is applied to the velocity to separate the coherent and turbulent components. The coherent or dispersive component arises due to the roughness and depends on the topological features of the surface. The turbulent stress on the other hand, scales with the friction Reynolds number. For the case with the largest roughness wavelength, large secondary flows are observed which are similar to that of duct flows. The occurrence of these large secondary flows is due to the spanwise heterogeneity of the roughness which has a spacing approximately equal to the boundary layer thickness δ.

Fabrication of surface micro- and nanostructures for superhydrophobic surfaces in electric and electronic applications

NASA Astrophysics Data System (ADS)

Xiu, Yonghao

In our study, the superhydrophobic surface based on biomimetic lotus leave is explored to maintain the desired properties for self-cleaning. Parameters in controlling bead-up and roll-off characteristics of water droplets were investigated on different model surfaces. The governing equations were proposed. Heuristic study is performed. First, the fundamental understanding of the effect of roughness on superhydrophobicity is performed. The effect of hierarchical roughness, i.e., two scale roughness effect on roughness is investigated using systems of (1) monodisperse colloidal silica sphere (submicron) arrays and Au nanoparticle on top and (2) Si micrometer pyramids and Si nanostructures on top from KOH etching and metal assisted etching of Si. The relation between the contact area fraction and water droplet contact angles are derived based on Wenzel and Cassie-Baxter equation for the systems and the two scale effect is explained regarding the synergistic combination of two scales. Previously the microscopic three-phase-contact line is thought to be the key factor in determining contact angles and hystereses. In our study, Laplace pressure was brought up and related to the three-phase-contact line and taken as a key figure of merit in determining superhydrophobicity. In addition, we are one of the first to study the effect of tapered structures (wall inclination). Combining with a second scale roughness on the tapered structures, stable Cassie state for both water and low surface energy oil may be achieved. This is of great significance for designing both superhydrophobicity and superoleophobicity. Regarding the origin of contact angle hysteresis, study of superhydrophobicity on micrometer Si pillars was performed. The relation between the interface work of function and contact angle hysteresis was proposed and derived mathematically based on the Young-Dupre equation. The three-phase-contact line was further related to a secondary scale roughness induced. Based on our understanding of the roughness effect on superhydrophobicity (both contact angle and hysteresis), structured surfaces from polybutadiene, polyurethane, silica, and Si etc. were successfully prepared. For engineering applications of superhydrophobic surfaces, stability issues regarding UV, mechanical robustness and humid environment need to be investigated. Among these factors, UV stability is the first one to be studied. However, most polymer surfaces we prepared failed the purpose. Silica surfaces with excellent UV stability were prepared. This method consists of preparation of rough silica surfaces, thermal treatment and the following surface hydrophobization by fluoroalkyl silane treatment. Fluoroalkyl groups are UV stable and the underlying species are silica which is also UV stable (UV transparent). UV stability on the surface currently is 5,500 h according the standard test method of ASTM D 4329. No degradation on surface superhydrophobicity was observed. New methods for preparing superhydrophobic and transparent silica surfaces were investigated using urea-choline chloride eutectic liquid to generate fine roughness and reduce the cost for preparation of surface structures. Another possible application for self-cleaning in photovoltaic panels was investigated on Si surfaces by construction of the two-scale rough structures followed by fluoroalkyl silane treatment. Metal (Au) assisted etching was employed to fabricate nanostructures on micrometer pyramid surfaces. The light reflection on the prepared surfaces was investigated. After surface texturing using KOH etching for micrometer pyramids and the following nanostructure using metal assisted etching, surface light reflection reduced to a minimum value which shows that this surface texturing technique is highly promising for improving the photovoltaic efficiency while imparting photovoltaics the self-cleaning feature. This surface is also expected to be UV stable due to the same fluoroalkyl silane used. Regarding the mechanical robustness, epoxy-silica superhydrophobic surfaces were prepared by O2 plasma etching to generate enough surface roughness of silica spheres followed by fluoroalkyl silane treatment. A robustness test method was proposed and the test results showed that the surface is among the most robust surfaces for the superhydrophobic surfaces we prepared and currently reported in literature.

Understanding EUV mask blank surface roughness induced LWR and associated roughness requirement

NASA Astrophysics Data System (ADS)

Yan, Pei-Yang; Zhang, Guojing; Gullikson, Eric M.; Goldberg, Ken A.; Benk, Markus P.

2015-03-01

Extreme ultraviolet lithography (EUVL) mask multi-layer (ML) blank surface roughness specification historically comes from blank defect inspection tool requirement. Later, new concerns on ML surface roughness induced wafer pattern line width roughness (LWR) arise. In this paper, we have studied wafer level pattern LWR as a function of EUVL mask surface roughness via High-NA Actinic Reticle Review Tool. We found that the blank surface roughness induced LWR at current blank roughness level is in the order of 0.5nm 3σ for NA=0.42 at the best focus. At defocus of ±40nm, the corresponding LWR will be 0.2nm higher. Further reducing EUVL mask blank surface roughness will increase the blank cost with limited benefit in improving the pattern LWR, provided that the intrinsic resist LWR is in the order of 1nm and above.

Monostable superrepellent materials

NASA Astrophysics Data System (ADS)

Li, Yanshen; Quéré, David; Lv, Cunjing; Zheng, Quanshui

2017-03-01

Superrepellency is an extreme situation where liquids stay at the tops of rough surfaces, in the so-called Cassie state. Owing to the dramatic reduction of solid/liquid contact, such states lead to many applications, such as antifouling, droplet manipulation, hydrodynamic slip, and self-cleaning. However, superrepellency is often destroyed by impalement transitions triggered by environmental disturbances whereas inverse transitions are not observed without energy input. Here we show through controlled experiments the existence of a “monostable” region in the phase space of surface chemistry and roughness, where transitions from Cassie to (impaled) Wenzel states become spontaneously reversible. We establish the condition for observing monostability, which might guide further design and engineering of robust superrepellent materials.

Backscattering from a two-scale rough surface with application to radar sea return

NASA Technical Reports Server (NTRS)

Chan, H. L.; Fung, A. K.

1973-01-01

A two-scale composite surface scattering theory was developed without using the noncoherent assumption. The surface is assumed electrically homogeneous and finitely conducting; the surface roughness may be nonuniform geometrically. The special forms of the terms for excluding the non-coherent assumption and the meanings of these terms are discussed. To gain insight into the mechanisms of backscattering, the results are compared with those obtained by previous theories. The comparison with NRL data shows satisfactory agreement for both horizontal and vertical polarization, especially for incident angles larger than 30 deg. For smaller incident angles, NASA/JSC data have been chosen for comparison and close agreement is again observed.

Research of Surface Roughness Anisotropy

NASA Astrophysics Data System (ADS)

Bulaha, N.; Rudzitis, J.; Lungevics, J.; Linins, O.; Krizbergs, J.

2017-04-01

The authors of the paper have investigated surfaces with irregular roughness for the purpose of determination of roughness spacing parameters perpendicularly to machining traces - RSm1 and parallel to them - RSm2, as well as checking the relationship between the surface anisotropy coefficient c and surface aspect ratio Str from the standard LVS EN ISO 25178-2. Surface roughness measurement experiments with 11 surfaces show that measuring equipment values of mean spacing of profile irregularities in the longitudinal direction are not reliable due to the divergence of surface mean plane and roughness profile mean line. After the additional calculations it was stated that parameter Str can be used for determination of parameter RSm2 and roughness anisotropy evaluation for grinded, polished, friction surfaces and other surfaces with similar characteristics.

Determination and interpretation of the optical constants for solar cell materials

NASA Astrophysics Data System (ADS)

Fujiwara, Hiroyuki; Fujimoto, Shohei; Tamakoshi, Masato; Kato, Masato; Kadowaki, Hideyuki; Miyadera, Tetsuhiko; Tampo, Hitoshi; Chikamatsu, Masayuki; Shibata, Hajime

2017-11-01

Solar cell materials in thin film form often exhibit quite rough surface, which makes the accurate determination of the optical constants using spectroscopic ellipsometry (SE) quite difficult. In this study, we investigate the effect of the rough surface on the SE analysis and establish an analysis procedure, which is quite helpful for the correction of the underestimated roughness contribution. As examples, the roughness analyses for CuInSe2 and CH3NH3PbI3 hybrid-perovskite thin films are presented. Moreover, to interpret the dielectric functions of emerging solar cell materials, such as CH3NH3PbI3 and Cu2ZnSnSe4, the optical transition analyses are performed based on density functional theory (DFT). The excellent agreement observed between the experimental and DFT results allows the detailed assignment of the transition peaks, confirming the importance of DFT for revealing fundamental optical characteristics.

Non-linear boundary-layer receptivity due to distributed surface roughness

NASA Technical Reports Server (NTRS)

Amer, Tahani Reffet

1995-01-01

The process by which a laminar boundary layer internalizes the external disturbances in the form of instability waves is known as boundary-layer receptivity. The objective of the present research was to determine the effect of acoustic excitation on boundary-layer receptivity for a flat plate with distributed variable-amplitude surface roughness through measurements with a hot-wire probe. Tollmien-Schlichting mode shapes due to surface roughness receptivity have also been determined, analyzed, and shown to be in agreement with theory and other experimental work. It has been shown that there is a linear relationship between the surface roughness and receptivity for certain roughness configurations with constant roughness wavelength. In addition, strong non-linear receptivity effects exist for certain surface roughness configurations over a band where the surface roughness and T-S wavelength are matched. The results from the present experiment follow the trends predicted by theory and other experimental work for linear receptivity. In addition, the results show the existence of non-linear receptivity effects for certain combinations of surface roughness elements.

Role of urban surface roughness in road-deposited sediment build-up and wash-off

NASA Astrophysics Data System (ADS)

Zhao, Hongtao; Jiang, Qian; Xie, Wenxia; Li, Xuyong; Yin, Chengqing

2018-05-01

Urban road surface roughness is one of the most important factors in estimation of surface runoff loads caused by road-deposited sediment (RDS) wash-off and design of its control measures. However, because of a lack of experimental data to distinguish the role of surface roughness, the effects of surface roughness on RDS accumulation and release are not clear. In this study, paired asphalt and concrete road surfaces and rainfall simulation designs were used to distinguish the role of surface roughness in RDS build-up and wash-off. Our results showed that typical asphalt surfaces often have higher depression depths than typical concrete surfaces, indicating that asphalt surfaces are relatively rougher than concrete surface. Asphalt surfaces can retain a larger RDS amount, relative higher percentage of coarser particles, larger RDS wash-off loads, and lower wash-off percentage, than concrete surfaces. Surface roughness has different effects in RDS motilities with different particle sizes during rainfall runoff, and the settleable particles (44-149 μm) were notably influenced by it. Furthermore, the first flush phenomenon tended to be greater on relatively smooth surfaces than relatively rough surfaces. Overall, surface roughness plays an important role in influencing the complete process of RDS build-up and wash-off on different road characteristics.

Pt thermal atomic layer deposition for silicon x-ray micropore optics.

PubMed

Takeuchi, Kazuma; Ezoe, Yuichiro; Ishikawa, Kumi; Numazawa, Masaki; Terada, Masaru; Ishi, Daiki; Fujitani, Maiko; Sowa, Mark J; Ohashi, Takaya; Mitsuda, Kazuhisa

2018-04-20

We fabricated a silicon micropore optic using deep reactive ion etching and coated by Pt with atomic layer deposition (ALD). We confirmed that a metal/metal oxide bilayer of Al 2 O 3 ∼10  nm and Pt ∼20  nm was successfully deposited on the micropores whose width and depth are 20 μm and 300 μm, respectively. An increase of surface roughness of sidewalls of the micropores was observed with a transmission electron microscope and an atomic force microscope. X-ray reflectivity with an Al Kα line at 1.49 keV before and after the deposition was measured and compared to ray-tracing simulations. The surface roughness of the sidewalls was estimated to increase from 1.6±0.2  nm rms to 2.2±0.2  nm rms. This result is consistent with the microscope measurements. Post annealing of the Pt-coated optic at 1000°C for 2 h showed a sign of reduced surface roughness and better angular resolution. To reduce the surface roughness, possible methods such as the annealing after deposition and a plasma-enhanced ALD are discussed.

Atmospheric stability analysis over statically and dynamically rough surfaces

NASA Astrophysics Data System (ADS)

Maric, Emina; Metzger, Meredith; Singha, Arindam; Sadr, Reza

2011-11-01

The ratio of buoyancy flux to turbulent kinetic energy production in the atmospheric surface layer is investigated experimentally for air flow over two types of surfaces characterized by static and dynamic roughness. In this study, ``static'' refers to the time-invariant nature of naturally-occurring roughness over a mud/salt playa; while, ``dynamic'' refers to the behavior of water waves along an air-water interface. In both cases, time-resolved measurements of the momentum and heat fluxes were acquired from synchronized 3D sonic anemometers mounted on a vertical tower. Field campaigns were conducted at two sites, representing the ``statically'' and ``dynamically'' rough surfaces, respectively: (1) the SLTEST facility in Utah's western desert, and (2) the new Doha airport in Qatar under construction along the coast of the Persian Gulf. Note, at site 2, anemometers were located directly above the water by extension from a tower secured to the end of a 1 km-long pier. Comparisons of the Monin-Obukhov length, flux Richardson number, and gradient Richardson number are presented, and discussed in the context of the observed evolution of the turbulent spectra in response to diurnal variations of atmospheric stability. Supported by the Qatar National Research Fund.

Effects of size reduction on deformation, microstructure, and surface roughness of micro components for micro metal injection molding

NASA Astrophysics Data System (ADS)

Liu, Lin; Wang, Xin-da; Li, Xiang; Qi, Xiao-tong; Qu, Xuan-hui

2017-09-01

The fabrication of 17-4PH micro spool mandrils by micro metal injection molding was described here. The effects of size reduction on deformation, microstructure and surface roughness were studied by comparing a ϕ500 μm micro post and a ϕ1.7 mm cylinder after debinding and sintering. Experimental results show that slumping of the micro posts occurred due to a dramatic increase in outlet vapor pressure initiated at the thermal degradation onset temperature and the moment of gravity. Asymmetrical stress distribution within the micro component formed during the cooling stage may cause warping. Prior solvent debinding and adjustment in a thermal debinding scheme were useful for preventing the deformation of the micro components. Smaller grain size and higher micro hardness due to impeded grain growth were observed for the micro posts compared with the ϕ1.7 mm cylinder. Surface roughness increased with distance from the gate of the micro spool mandril due to melt front advancement during mold filling and the ensuing pressure distribution. At each position, surface roughness was dictated by injection molding and increased slightly after sintering.

Switchable static friction of piezoelectric composite—silicon wafer contacts

NASA Astrophysics Data System (ADS)

van den Ende, D. A.; Fischer, H. R.; Groen, W. A.; van der Zwaag, S.

2013-04-01

The meso-scale surface roughness of piezoelectric fiber composites can be manipulated by applying an electric field to a piezocomposite with a polished surface. In the absence of an applied voltage, the tips of the embedded piezoelectric ceramic fibers are below the surface of the piezocomposite and a silicon wafer counter surface rests solely on the matrix region of the piezocomposite surface. When actuated, the piezoelectric ceramic fibers protrude from the surface and the wafer rests solely on these protrusions. A threefold decrease in engineering static friction coefficient upon actuation of the piezocomposite was observed: from μ* = 1.65 to μ* = 0.50. These experimental results could be linked to the change in contact surface area and roughness using capillary adhesion theory, which relates the adhesive force to the number and size of the contacting asperities for the different surface states.

Influence of implant surface topography on bone-regenerative potential and mechanical retention in the human maxilla and mandible.

PubMed

Wei, Niu; Bin, Shi; Jing, Zhou; Wei, Sun; Yingqiong, Zhao

2014-06-01

To evaluate the short- and mid-term effects of commercial pure (cp) titanium implant surface topography on osseointegration, bone-regenerative potential and mechanical retention in the human maxilla and mandible. 32 micro-implants with the same geometry but with four different surface treatments were implanted in the maxilla and mandible of eight patients. Each patient received four micro-implants, one of each type. Percentage of bone-to-implant contact analysis and histological evaluation was carried 3, 6 and 12 weeks after implantation. Furthermore, reverse removal torque tests were conducted 3 and 6 weeks after implantation to analyze functional bone attachment. Implant surfaces tested were: machined, grit-blasted, acid-etched, and grit-blasted with acid-etch. One-way ANOVA was performed using the multiple comparison Fisher's test to determine significance of observed differences among test groups. The level of significance was established at 5% (P < 0.05). Mean and standard deviations of the test groups were calculated. Surface roughness had a significant correlation with the evolution of bone regeneration. The surfaces with roughness Ra approximately 4 microim (grit-blasted and grit-blasted with acid-etch), showed rapid tissue colonization compared to machine and acid-etched surfaces. The results of reverse removal torque tests confirmed a significant correlation between surface roughness and functional bone attachment. Grit-blasted and grit-blasted with acid etched surfaces showed higher retention values compared to machine and acid-etched implants. This finding was supported by higher bone-to-implant contact observed for rougher surfaces (grit-blasted and grit-blasted with acid etching).

Poly-Gaussian model of randomly rough surface in rarefied gas flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aksenova, Olga A.; Khalidov, Iskander A.

2014-12-09

Surface roughness is simulated by the model of non-Gaussian random process. Our results for the scattering of rarefied gas atoms from a rough surface using modified approach to the DSMC calculation of rarefied gas flow near a rough surface are developed and generalized applying the poly-Gaussian model representing probability density as the mixture of Gaussian densities. The transformation of the scattering function due to the roughness is characterized by the roughness operator. Simulating rough surface of the walls by the poly-Gaussian random field expressed as integrated Wiener process, we derive a representation of the roughness operator that can be appliedmore » in numerical DSMC methods as well as in analytical investigations.« less

Roughness transitions of diamond(100) induced by hydrogen-plasma treatment

NASA Astrophysics Data System (ADS)

Koslowski, B.; Strobel, S.; Wenig, M. J.; Ziemann, P.

To investigate the influence of hydrogen-plasma treatment on diamond(100) surfaces, heavily boron (B)-doped HPHT diamond crystals were mechanically and chemo-mechanically polished, and exposed to a microwave-assisted hydrogen plasma on a time scale of several minutes. The resulting surface morphology was analyzed on macroscopic scales by stylus profilometry (PFM) and on microscopic scales by STM and AFM. The polished samples have a roughness of typically 100 pmrms (PFM), with no obvious anisotropic structures at the surface. After exposure of the B-doped diamond(100) to the H-plasma, the roughness increases dramatically, and pronounced anisotropic structures appear, these being closely aligned with the crystallographic axis' and planes. An exposure for 3 minutes to the plasma leads to an increase of the roughness to 2-4 nmrms (STM), and a `brick-wall' pattern appears, formed by weak cusps running along <110>. Very frequently, the cusps are replaced by `negative' pyramids that are bordered by {11X} facets. After an exposure of an additional 5 minutes, the surface roughness of the B-doped samples increases further to 20-40 nmrms (STM), and frequently exhibits a regular pattern with structures at a characteristic length scale of about 100 nm. Those structures are aligned approximately with <110> and they are faceted with faces of approximately {XX1}. These results will be discussed in terms of strain relaxation, similar to the surface roughening observed on SiGe/Si and anisotropic etching.

Analogies to Demonstrate the Effect of Roughness on Surface Wettability

ERIC Educational Resources Information Center

Yolcu, Hasan

2017-01-01

This article presents an analogy to illustrate the effect of surface roughness on surface wettability. I used a water-filled balloon to represent water droplet, a toothpick to represent surface roughness and Styrofoam as the surface. The analogies presented in this article will help visualize how roughness affects the wettability of the surface…

Supersonic turbulent boundary layers with periodic mechanical non-equilibrium

NASA Astrophysics Data System (ADS)

Ekoto, Isaac Wesley

Previous studies have shown that favorable pressure gradients reduce the turbulence levels and length scales in supersonic flow. Wall roughness has been shown to reduce the large-scales in wall bounded flow. Based on these previous observations new questions have been raised. The fundamental questions this dissertation addressed are: (1) What are the effects of wall topology with sharp versus blunt leading edges? and (2) Is it possible that a further reduction of turbulent scales can occur if surface roughness and favorable pressure gradients are combined? To answer these questions and to enhance the current experimental database, an experimental analysis was performed to provide high fidelity documentation of the mean and turbulent flow properties along with surface and flow visualizations of a high-speed (M = 2.86), high Reynolds number (Retheta ≈ 60,000) supersonic turbulent boundary layer distorted by curvature-induced favorable pressure gradients and large-scale ( k+s ≈ 300) uniform surface roughness. Nine models were tested at three separate locations. Three pressure gradient models strengths (a nominally zero, a weak, and a strong favorable pressure gradient) and three roughness topologies (aerodynamically smooth, square, and diamond shaped roughness elements) were used. Highly resolved planar measurements of mean and fluctuating velocity components were accomplished using particle image velocimetry. Stagnation pressure profiles were acquired with a traversing Pitot probe. Surface pressure distributions were characterized using pressure sensitive paint. Finally flow visualization was accomplished using schlieren photographs. Roughness topology had a significant effect on the boundary layer mean and turbulent properties due to shock boundary layer interactions. Favorable pressure gradients had the expected stabilizing effect on turbulent properties, but the improvements were less significant for models with surface roughness near the wall due to increased tendency towards flow separation. It was documented that proper roughness selection coupled with a sufficiently strong favorable pressure gradient produced regions of "negative" production in the transport of turbulent stress. This led to localized areas of significant turbulence stress reduction. With proper roughness selection and sufficient favorable pressure gradient strength, it is believed that localized relaminarization of the boundary layer is possible.

Comparison of PARASOL Observations with Polarized Reflectances Simulated Using Different Ice Habit Mixtures

NASA Technical Reports Server (NTRS)

Cole, Benjamin H.; Yang, Ping; Baum, Bryan A.; Riedi, Jerome; Labonnote, Laurent C.; Thieuleux, Francois; Platnick, Steven

2012-01-01

Insufficient knowledge of the habit distribution and the degree of surface roughness of ice crystals within ice clouds is a source of uncertainty in the forward light scattering and radiative transfer simulations required in downstream applications involving these clouds. The widely used MODerate Resolution Imaging Spectroradiometer (MODIS) Collection 5 ice microphysical model assumes a mixture of various ice crystal shapes with smooth-facets except aggregates of columns for which a moderately rough condition is assumed. When compared with PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) polarized reflection data, simulations of polarized reflectance using smooth particles show a poor fit to the measurements, whereas very rough-faceted particles provide an improved fit to the polarized reflectance. In this study a new microphysical model based on a mixture of 9 different ice crystal habits with severely roughened facets is developed. Simulated polarized reflectance using the new ice habit distribution is calculated using a vector adding-doubling radiative transfer model, and the simulations closely agree with the polarized reflectance observed by PARASOL. The new general habit mixture is also tested using a spherical albedo differences analysis, and surface roughening is found to improve the consistency of multi-angular observations. It is suggested that an ice model incorporating an ensemble of different habits with severely roughened surfaces would potentially be an adequate choice for global ice cloud retrievals.

Probing cluster surface morphology by cryo spectroscopy of N2 on cationic nickel clusters

NASA Astrophysics Data System (ADS)

Dillinger, Sebastian; Mohrbach, Jennifer; Niedner-Schatteburg, Gereon

2017-11-01

We present the cryogenic (26 K) IR spectra of selected [Nin(N2)m]+ (n = 5-20, m = 1 - mmax), which strongly reveal n- and m-dependent features in the N2 stretching region, in conjunction with density functional theory modeling of some of these findings. The observed spectral features allow us to refine the kinetic classification [cf. J. Mohrbach, S. Dillinger, and G. Niedner-Schatteburg, J. Chem. Phys. 147, 184304 (2017)] and to define four classes of structure related surface adsorption behavior: Class (1) of Ni6+, Ni13+, and Ni19+ are highly symmetrical clusters with all smooth surfaces of equally coordinated Ni atoms that entertain stepwise N2 adsorption up to stoichiometric N2:Nisurface saturation. Class (2) of Ni12+ and Ni18+ are highly symmetrical clusters minus one. Their relaxed smooth surfaces reorganize by enhanced N2 uptake toward some low coordinated Ni surface atoms with double N2 occupation. Class (3) of Ni5+ and Ni7+ through Ni11+ are small clusters of rough surfaces with low coordinated Ni surface atoms, and some reveal semi-internal Ni atoms of high next-neighbor coordination. Surface reorganization upon N2 uptake turns rough into rough surface by Ni atom migration and turns octahedral based structures into pentagonal bipyramidal structures. Class (4) of Ni14+ through Ni17+ and Ni20+ are large clusters with rough and smooth surface areas. They possess smooth icosahedral surfaces with some proximate capping atom(s) on one hemisphere of the icosahedron with the other one largely unaffected.

Surface topography and roughness of high-speed milled AlMn1Cu

NASA Astrophysics Data System (ADS)

Wang, Zhenhua; Yuan, Juntang; Yin, Zengbin; Hu, Xiaoqiu

2016-10-01

The aluminum alloy AlMn1Cu has been broadly applied for functional parts production because of its good properties. But few researches about the machining mechanism and the surface roughness were reported. The high-speed milling experiments are carried out in order to improve the machining quality and reveal the machining mechanism. The typical topography features of machined surface are observed by scan electron microscope(SEM). The results show that the milled surface topography is mainly characterized by the plastic shearing deformation surface and material piling zone. The material flows plastically along the end cutting edge of the flat-end milling tool and meanwhile is extruded by the end cutting edge, resulting in that materials partly adhere to the machined surface and form the material piling zone. As the depth of cut and the feed per tooth increase, the plastic flow of materials is strengthened and the machined surface becomes rougher. However, as the cutting speed increases, the plastic flow of materials is weakened and the milled surface becomes smoother. The cutting parameters (e.g. cutting speed, feed per tooth and depth of cut) influencing the surface roughness are analyzed. It can be concluded that the roughness of the machined surface formed by the end cutting edge is less than that by the cylindrical cutting edge when a cylindrical flat-end mill tool is used for milling. The proposed research provides the typical topography features of machined surface of the anti-rust aluminum alloy AlMn1Cu in high speed milling.

Dielectric properties of Asteroid Vesta's surface as constrained by Dawn VIR observations

NASA Astrophysics Data System (ADS)

Palmer, Elizabeth M.; Heggy, Essam; Capria, Maria T.; Tosi, Federico

2015-12-01

Earth and orbital-based radar observations of asteroids provide a unique opportunity to characterize surface roughness and the dielectric properties of their surfaces, as well as potentially explore some of their shallow subsurface physical properties. If the dielectric and topographic properties of asteroid's surfaces are defined, one can constrain their surface textural characteristics as well as potential subsurface volatile enrichment using the observed radar backscatter. To achieve this objective, we establish the first dielectric model of asteroid Vesta for the case of a dry, volatile-poor regolith-employing an analogy to the dielectric properties of lunar soil, and adjusted for the surface densities and temperatures deduced from Dawn's Visible and InfraRed mapping spectrometer (VIR). Our model suggests that the real part of the dielectric constant at the surface of Vesta is relatively constant, ranging from 2.3 to 2.5 from the night- to day-side of Vesta, while the loss tangent shows slight variation as a function of diurnal temperature, ranging from 6 × 10-3 to 8 × 10-3. We estimate the surface porosity to be ∼55% in the upper meter of the regolith, as derived from VIR observations. This is ∼12% higher than previous estimation of porosity derived from previous Earth-based X- and S-band radar observation. We suggest that the radar backscattering properties of asteroid Vesta will be mainly driven by the changes in surface roughness rather than potential dielectric variations in the upper regolith in the X- and S-band.

Roughness evolution of metallic implant surfaces under contact loading and nanometer-scale chemical etching.

PubMed

Ryu, J J; Letchuman, S; Shrotriya, P

2012-10-01

Surface damage of metallic implant surface at taper lock and clamped interfaces may take place through synergistic interactions between repeated contact loading and corrosion. In the present research, we investigated the influence of surface roughness and contact loading on the mechanical and chemical damage phenomena. Cobalt-chromium (CoCrMo) specimens with two different roughness configurations created by milling and grinding process were subjected to normal and inclined contact loading. During repeated contact loading, amplitude of surface roughness reached a steady value after decreasing during the first few cycles. During the second phase, the alternating experiment of rough surface contact and micro-etching was conducted to characterize surface evolution behavior. As a result, surface roughness amplitude continuously evolved-decreasing during contact loading due to plastic deformation of contacting asperities and increasing on exposure to corrosive environment by the preferential corrosion attack on stressed area. Two different instabilities could be identified in the surface roughness evolution during etching of contact loaded surfaces: increase in the amplitude of dominant wavenumber and increase in amplitude of a small group of roughness modes. A damage mechanism that incorporates contact-induced residual stress development and stress-assisted dissolution is proposed to elucidate the measured instabilities in surface roughness evolution. Copyright © 2012 Elsevier Ltd. All rights reserved.

Influences of multiple firings and aging on surface roughness, strength and hardness of veneering ceramics for zirconia frameworks.

PubMed

Tang, Xuehua; Luo, Huinan; Bai, Yang; Tang, Hui; Nakamura, Takashi; Yatani, Hirofumi

2015-09-01

To evaluate the effects of multiple firings and aging on surface roughness, strength, and hardness of veneering ceramics for zirconia frameworks. Five different veneering ceramics for zirconia frameworks were used: Vintage ZR (ZR), Cerabien ZR (CZR), VitaVM9 (VM9), Cercon ceram KISS (KISS), and IPS e.max ceram (e.max). Specimens were fired 2 or 10 times in order to accelerate aging. Surface roughness was evaluated using laser profilometry. Flexural strength and Vickers hardness were also measured. Surface topography was observed using scanning electron microscopy. After accelerated aging, the surface roughness of all specimens fired 10 times was significantly lower than that of the same specimens fired 2 times (P=0.000). Except for VM9, the flexural strength of all specimens fired 10 times was greater than that of the same specimens fired 2 times, and the differences were significant for ZR and CZR (P<0.01). The flexural strength of VM9 fired 10 times was significantly lower than that of VM9 fired 2 times (P=0.034). The Vickers hardness of ZR and VM9 fired 10 times was significantly higher than that of the same specimens fired 2 times (P<0.05), but that of KISS fired 10 times was significantly lower than that of KISS fired 2 times (P=0.000). Multiple firings had a positive effect on the surface roughness of all aged veneering ceramics used for zirconia restorations and on the strength and hardness of many aged veneering ceramics used for zirconia restorations. Copyright © 2015 Elsevier Ltd. All rights reserved.

Residual Stress Distribution and Microstructure of a Multiple Laser-Peened Near-Alpha Titanium Alloy

NASA Astrophysics Data System (ADS)

Umapathi, A.; Swaroop, S.

2018-04-01

Laser peening without coating (LPwC) was performed on a Ti-2.5 Cu alloy with multiple passes (1, 3 and 5), using a Nd:YAG laser (1064 nm) at a constant overlap rate of 70% and power density of 6.7 GW cm-2. Hardness and residual stress profiles indicated thermal softening near the surface (< 100 μm) and bulk softening due to adiabatic heating. Maximum hardness (235 HV at 500 μm) and maximum residual stress (- 890 MPa at 100 μm) were observed for LPwC with 1 pass. Surface roughness and surface 3-D topography imaging showed that the surface roughness increased with the increase in the number of passes. XRD results indicated no significant β phases. However, peak shifts, broadening and asymmetry were observed and interpreted based on dislocation activity. Microstructures indicated no melting or resolidification or refinement of grains at the surface. Twin density was found to increase with the increase in the number of passes.

Residual Stress Distribution and Microstructure of a Multiple Laser-Peened Near-Alpha Titanium Alloy

NASA Astrophysics Data System (ADS)

Umapathi, A.; Swaroop, S.

2018-05-01

Laser peening without coating (LPwC) was performed on a Ti-2.5 Cu alloy with multiple passes (1, 3 and 5), using a Nd:YAG laser (1064 nm) at a constant overlap rate of 70% and power density of 6.7 GW cm-2. Hardness and residual stress profiles indicated thermal softening near the surface (< 100 μm) and bulk softening due to adiabatic heating. Maximum hardness (235 HV at 500 μm) and maximum residual stress (- 890 MPa at 100 μm) were observed for LPwC with 1 pass. Surface roughness and surface 3-D topography imaging showed that the surface roughness increased with the increase in the number of passes. XRD results indicated no significant β phases. However, peak shifts, broadening and asymmetry were observed and interpreted based on dislocation activity. Microstructures indicated no melting or resolidification or refinement of grains at the surface. Twin density was found to increase with the increase in the number of passes.

L Band Brightness Temperature Observations over a Corn Canopy during the Entire Growth Cycle

PubMed Central

Joseph, Alicia T.; van der Velde, Rogier; O’Neill, Peggy E.; Choudhury, Bhaskar J.; Lang, Roger H.; Kim, Edward J.; Gish, Timothy

2010-01-01

During a field campaign covering the 2002 corn growing season, a dual polarized tower mounted L-band (1.4 GHz) radiometer (LRAD) provided brightness temperature (TB) measurements at preset intervals, incidence and azimuth angles. These radiometer measurements were supported by an extensive characterization of land surface variables including soil moisture, soil temperature, vegetation biomass, and surface roughness. In the period May 22 to August 30, ten days of radiometer and ground measurements are available for a corn canopy with a vegetation water content (W) range of 0.0 to 4.3 kg m−2. Using this data set, the effects of corn vegetation on surface emissions are investigated by means of a semi-empirical radiative transfer model. Additionally, the impact of roughness on the surface emission is quantified using TB measurements over bare soil conditions. Subsequently, the estimated roughness parameters, ground measurements and horizontally (H)-polarized TB are employed to invert the H-polarized transmissivity (γh) for the monitored corn growing season. PMID:22163585

Microstructure and physical properties of nano-biocomposite films based on cassava starch and laponite.

PubMed

Valencia, Germán Ayala; Luciano, Carla Giovana; Lourenço, Rodrigo Vinicius; do Amaral Sobral, Paulo José

2018-02-01

The aim of this research was to study the effects of laponite concentrations on some properties of nano-biocomposite films based on cassava starch, focusing mainly the relation between the properties of the surface microstructure and roughness, water contact angle and gloss. Nano-biocomposite films were produced by casting. We analyzed gloss, color, opacity, water contact angle, crystallinity by X-ray diffraction, and microstructure by scanning electron microscopy and atomic force microscopy. Texture parameters (energy, entropy and fractal dimension) were extracted from micrographs. We observed a great impact of laponite in the morphology of nano-biocomposite films. Texture parameters correlated with surface heterogeneity and roughness. Finally, surface roughness affected the surface hydrophilicity of nano-biocomposite films. Laponite platelets were exfoliated and/or intercalated with amylose and amylopectin chains. This research reports new information on the effects of laponite concentrations on the morphological, optical and wetting properties of nano-biocomposite films aiming future industrial applications. Copyright © 2017 Elsevier B.V. All rights reserved.

L Band Brightness Temperature Observations Over a Corn Canopy During the Entire Growth Cycle

NASA Technical Reports Server (NTRS)

Joseph, Alicia T.; O'Neill, Peggy E.; Choudhury, Bhaskar J.; vanderVelde, Rogier; Lang, Roger H.; Gish, Timothy

2011-01-01

During a field campaign covering the 2002 corn growing season, a dual polarized tower mounted L-band (1.4 GHz) radiometer (LRAD) provided brightness temperature (T(sub B)) measurements at preset intervals, incidence and azimuth angles. These radiometer measurements were supported by an extensive characterization of land surface variables including soil moisture, soil temperature, vegetation biomass, and surface roughness. During the period from May 22, 2002 to August 30, 2002 a range of vegetation water content (W) of 0.0 to 4.3 kg/square m, ten days of radiometer and ground measurements were available. Using this data set, the effects of corn vegetation on surface emissions are investigated by means of a semi-empirical radiative transfer model. Additionally, the impact of roughness on the surface emission is quantified using T(sub B) measurements over bare soil conditions. Subsequently, the estimated roughness parameters, ground measurements and horizontally (H)-polarized T(sub B) are employed to invert the H-polarized transmissivity (gamma-h) for the monitored corn growing season.

Cement paste surface roughness analysis using coherence scanning interferometry and confocal microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apedo, K.L., E-mail: apedo@unistra.fr; Munzer, C.; He, H.

2015-02-15

Scanning electron microscopy and scanning probe microscopy have been used for several decades to better understand the microstructure of cementitious materials. Very limited work has been performed to date to study the roughness of cementitious materials by optical microscopy such as coherence scanning interferometry (CSI) and chromatic confocal sensing (CCS). The objective of this paper is to better understand how CSI can be used as a tool to analyze surface roughness and topography of cement pastes. Observations from a series of images acquired using this technique on both polished and unpolished samples are described. The results from CSI are comparedmore » with those from a STIL confocal microscopy technique (SCM). Comparison between both optical techniques demonstrates the ability of CSI to measure both polished and unpolished cement pastes. - Highlights: • Coherence scanning interferometry (CSI) was used to analyze cement paste surfaces. • The results from the CSI were compared with those from a confocal microscopy. • 3D roughness parameters were obtained using the window resizing method. • Polished and unpolished cement pastes were studied.« less

Corrosion of Nickel-Titanium Orthodontic Archwires in Saliva and Oral Probiotic Supplements

PubMed Central

Turco, Gianluca; Contardo, Luca; Serdarević, Nikolina Leona; Otmačić, Helena; Ćurković; Špalj, Stjepan

2017-01-01

Objectives The aim of the study was to examine how probiotic supplements affect the corrosion stability of orthodontic archwires made of nickel-titanium alloy (NiTi). Materials and Methods NiTi archwires (0.508x0.508 and having the length of 2.5 cm) were tested. The archwires (composition Ni=50.4%, Ti=49.6%) were uncoated, nitrified and rhodium coated. Surface microgeometry was observed by using scanning electron microscope and surface roughness was measured by profilometer through these variables: roughness average, maximum height and maximum roughness depth. Corrosion was examined by electrochemical method of cyclic polarisation. Results Rhodium coated alloy in saliva has significantly higher general corrosion in saliva than nitrified alloy and uncoated alloy, with large effect size (p=0.027; η2=0.700). In the presence of probiotics, the result was even more pronounced (p<0.001; η2=0.936). Probiotic supplement increases general and localised corrosion of rhodium coated archwire and slightly decreases general corrosion and increases localised corrosion in uncoated archwire, while in the case of nitrified archwire the probability of corrosion is very low. The differences in surface roughness between NiTi wires before corrosion are not significant. Exposure to saliva decreases roughness average in rhodium coated wire (p=0.015; η2=0.501). Media do not significantly influence surface microgeometry in nitrified and uncoated wires. Conclusion Probiotic supplement affects corrosion depending on the type of coating of the NiTi archwire. It increases general corrosion of rhodium coated wire and causes localised corrosion of uncoated and rhodium coated archwire. Probiotic supplement does not have greater influence on surface roughness compared to that of saliva. PMID:29872237

Modeling Surface Roughness to Estimate Surface Moisture Using Radarsat-2 Quad Polarimetric SAR Data

NASA Astrophysics Data System (ADS)

Nurtyawan, R.; Saepuloh, A.; Budiharto, A.; Wikantika, K.

2016-08-01

Microwave backscattering from the earth's surface depends on several parameters such as surface roughness and dielectric constant of surface materials. The two parameters related to water content and porosity are crucial for estimating soil moisture. The soil moisture is an important parameter for ecological study and also a factor to maintain energy balance of land surface and atmosphere. Direct roughness measurements to a large area require extra time and cost. Heterogeneity roughness scale for some applications such as hydrology, climate, and ecology is a problem which could lead to inaccuracies of modeling. In this study, we modeled surface roughness using Radasat-2 quad Polarimetric Synthetic Aperture Radar (PolSAR) data. The statistical approaches to field roughness measurements were used to generate an appropriate roughness model. This modeling uses a physical SAR approach to predicts radar backscattering coefficient in the parameter of radar configuration (wavelength, polarization, and incidence angle) and soil parameters (surface roughness and dielectric constant). Surface roughness value is calculated using a modified Campbell and Shepard model in 1996. The modification was applied by incorporating the backscattering coefficient (σ°) of quad polarization HH, HV and VV. To obtain empirical surface roughness model from SAR backscattering intensity, we used forty-five sample points from field roughness measurements. We selected paddy field in Indramayu district, West Java, Indonesia as the study area. This area was selected due to intensive decreasing of rice productivity in the Northern Coast region of West Java. Third degree polynomial is the most suitable data fitting with coefficient of determination R2 and RMSE are about 0.82 and 1.18 cm, respectively. Therefore, this model is used as basis to generate the map of surface roughness.

Numerical analysis of the bucket surface roughness effects in Pelton turbine

NASA Astrophysics Data System (ADS)

Xiao, Y. X.; Zeng, C. J.; Zhang, J.; Yan, Z. G.; Wang, Z. W.

2013-12-01

The internal flow of a Pelton turbine is quite complex. It is difficult to analyse the unsteady free water sheet flow in the rotating bucket owing to the lack of a sound theory. Affected by manufacturing technique and silt abrasion during the operation, the bucket surface roughness of Pelton turbine may be too great, and thereby influence unit performance. To investigate the effect of bucket roughness on Pelton turbine performance, this paper presents the numerical simulation of the interaction between the jet and the bucket in a Pelton turbine. The unsteady three-dimensional numerical simulations were performed with CFX code by using the SST turbulence model coupling the two-phase flow volume of fluid method. Different magnitude orders of bucket surface roughness were analysed and compared. Unsteady numerical results of the free water sheet flow patterns on bucket surface, torque and unit performance for each bucket surface roughness were generated. The total pressure distribution on bucket surface is used to show the free water sheet flow pattern on bucket surface. By comparing the variation of water sheet flow patterns on bucket surface with different roughness, this paper qualitatively analyses how the bucket surface roughness magnitude influences the impeding effect on free water sheet flow. Comparison of the torque variation of different bucket surface roughness highlighted the effect of the bucket surface roughness on the Pelton turbine output capacity. To further investigate the effect of bucket surface roughness on Pelton turbine performance, the relation between the relative efficiency loss rate and bucket surface roughness magnitude is quantitatively analysed. The result can be used to predict and evaluate the Pelton turbine performance.

Surface deterioration of dental materials after simulated toothbrushing in relation to brushing time and load.

PubMed

Heintze, S D; Forjanic, M; Ohmiti, K; Rousson, V

2010-04-01

(1) To evaluate the changes in surface roughness and gloss after simulated toothbrushing of 9 composite materials and 2 ceramic materials in relation to brushing time and load in vitro; (2) to assess the relationship between surface gloss and surface roughness. Eight flat specimens of composite materials (microfilled: Adoro, Filtek Supreme, Heliomolar; microhybrid: Four Seasons, Tetric EvoCeram; hybrid: Compoglass F, Targis, Tetric Ceram; macrohybrid: Grandio), two ceramic materials (IPS d.SIGN and IPS Empress polished) were fabricated according to the manufacturer's instructions and optimally polished with up to 4000 grit SiC. The specimens were subjected to a toothbrushing (TB) simulation device (Willytec) with rotating movements, toothpaste slurry and at three different loads (100g/250g/350g). At hourly intervals from 1h to 10h TB, mean surface roughness Ra was measured with an optical sensor and the surface gloss (Gl) with a glossmeter. Statistical analysis was performed for log-transformed Ra data applying two-way ANOVA to evaluate the interaction between load and material and load and brushing time. There was a significant interaction between material and load as well as between load and brushing time (p<0.0001). The microhybrid and hybrid materials demonstrated more surface deterioration with higher loads, whereas with the microfilled resins Heliomolar and Adoro it was vice versa. For ceramic materials, no or little deterioration was observed over time and independent of the load. The ceramic materials and 3 of the composite materials (roughness) showed no further deterioration after 5h of toothbrushing. Mean surface gloss was the parameter which discriminated best between the materials, followed by mean surface roughness Ra. There was a strong correlation between surface gloss and surface roughness for all the materials except the ceramics. The evaluation of the deterioration curves of individual specimens revealed a more or less synchronous course suspecting hinting specific external conditions and not showing the true variability in relation to the tested material. The surface roughness and gloss of dental materials changes with brushing time and load and thus results in different material rankings. Apart from Grandio, the hybrid composite resins were more prone to surface changes than microfilled composites. The deterioration potential of a composite material can be quickly assessed by measuring surface gloss. For this purpose, a brushing time of 10h (=72,000 strokes) is needed. In further comparative studies, specimens of different materials should be tested in one series to estimate the true variability. Copyright (c) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Wetting properties of molecularly rough surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Svoboda, Martin; Lísal, Martin, E-mail: lisal@icpf.cas.cz; Department of Physics, Institute of Science, J. E. Purkinje University, 400 96 Ústí n. Lab.

2015-09-14

We employ molecular dynamics simulations to study the wettability of nanoscale rough surfaces in systems governed by Lennard-Jones (LJ) interactions. We consider both smooth and molecularly rough planar surfaces. Solid substrates are modeled as a static collection of LJ particles arranged in a face-centered cubic lattice with the (100) surface exposed to the LJ fluid. Molecularly rough solid surfaces are prepared by removing several strips of LJ atoms from the external layers of the substrate, i.e., forming parallel nanogrooves on the surface. We vary the solid-fluid interactions to investigate strongly and weakly wettable surfaces. We determine the wetting properties bymore » measuring the equilibrium droplet profiles that are in turn used to evaluate the contact angles. Macroscopic arguments, such as those leading to Wenzel’s law, suggest that surface roughness always amplifies the wetting properties of a lyophilic surface. However, our results indicate the opposite effect from roughness for microscopically corrugated surfaces, i.e., surface roughness deteriorates the substrate wettability. Adding the roughness to a strongly wettable surface shrinks the surface area wet with the liquid, and it either increases or only marginally affects the contact angle, depending on the degree of liquid adsorption into the nanogrooves. For a weakly wettable surface, the roughness changes the surface character from lyophilic to lyophobic due to a weakening of the solid-fluid interactions by the presence of the nanogrooves and the weaker adsorption of the liquid into the nanogrooves.« less

The improvement of surface roughness by polishing method of arcylic door panel at Taishi Tech Sdn Bhd

NASA Astrophysics Data System (ADS)

Basirin, Hammadi bin Mohd; Nawi, Ismail bin Haji Mohd

2017-04-01

This research is an approach to improve the surface roughness for acrylic door panel by using polishing process. The polishing process involve is sanding process by 3 types of sand paper. The sanding process used to improve the surface roughness by using the different grit sizes of sand paper. The experiment was done by using two types of material s, that is plywood and medium density board (MDF). These two materials are the main materials in producing the arcrylic door panel. The surface roughness of these two materials affects the qualities and quantities of the acrylic door panel. The surface structure was measured by using Optical Microscope and Scanning Electron Microscope (SEM) and the surface roughness was measured by using Mitutoyo surfest SJ 400 Tester. Results indicates that using the different types of grit are influence the surface roughness of the material. When the higher types of grit sizes had been used, the average roughness of the surface are decrease. In summary, a good surface roughness condition produced when using the higher types of grit sizes sand paper.

Clouds Versus Carbon: Predicting Vegetation Roughness by Maximizing Productivity

NASA Technical Reports Server (NTRS)

Olsen, Lola M.

2004-01-01

Surface roughness is one of the dominant vegetation properties that affects land surface exchange of energy, water, carbon, and momentum with the overlying atmosphere. We hypothesize that the canopy structure of terrestrial vegetation adapts optimally to climate by maximizing productivity, leading to an optimum surface roughness. An optimum should exist because increasing values of surface roughness cause increased surface exchange, leading to increased supply of carbon dioxide for photosynthesis. At the same time, increased roughness enhances evapotranspiration and cloud cover, thereby reducing the supply of photosynthetically active radiation. We demonstrate the optimum through sensitivity simulations using a coupled dynamic vegetation-climate model for present day conditions, in which we vary the value of surface roughness for vegetated surfaces. We find that the maximum in productivity occurs at a roughness length of 2 meters, a value commonly used to describe the roughness of today's forested surfaces. The sensitivity simulations also illustrate the strong climatic impacts of vegetation roughness on the energy and water balances over land: with increasing vegetation roughness, solar radiation is reduced by up to 20 W/sq m in the global land mean, causing shifts in the energy partitioning and leading to general cooling of the surface by 1.5 K. We conclude that the roughness of vegetated surfaces can be understood as a reflection of optimum adaptation, and it is associated with substantial changes in the surface energy and water balances over land. The role of the cloud feedback in shaping the optimum underlines the importance of an integrated perspective that views vegetation and its adaptive nature as an integrated component of the Earth system.

The influence of surface roughness on volatile transport on the Moon

NASA Astrophysics Data System (ADS)

Prem, P.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.

2018-01-01

The Moon and other virtually airless bodies provide distinctive environments for the transport and sequestration of water and other volatiles delivered to their surfaces by various sources. In this work, we conduct Monte Carlo simulations of water vapor transport on the Moon to investigate the role of small-scale roughness (unresolved by orbital measurements) in the migration and cold-trapping of volatiles. Observations indicate that surface roughness, combined with the insulating nature of lunar regolith and the absence of significant exospheric heat flow, can cause large variations in temperature over very small scales. Surface temperature has a strong influence on the residence time of migrating water molecules on the lunar surface, which in turn affects the rate and magnitude of volatile transport to permanently shadowed craters (cold traps) near the lunar poles, as well as exospheric structure and the susceptibility of migrating molecules to photodestruction. Here, we develop a stochastic rough surface temperature model suitable for simulations of volatile transport on a global scale, and compare the results of Monte Carlo simulations of volatile transport with and without the surface roughness model. We find that including small-scale temperature variations and shadowing leads to a slight increase in cold-trapping at the lunar poles, accompanied by a slight decrease in photodestruction. Exospheric structure is altered only slightly, primarily at the dawn terminator. We also examine the sensitivity of our results to the temperature of small-scale shadows, and the energetics of water molecule desorption from the lunar regolith - two factors that remain to be definitively constrained by other methods - and find that both these factors affect the rate at which cold trap capture and photodissociation occur, as well as exospheric density and longevity.

The frictional properties of a simulated gouge having a fractal particle distribution

USGS Publications Warehouse

Biegel, R.L.; Sammis, C.G.; Dieterich, J.H.

1989-01-01

The frictional properties of a layer of simulated Westerly granite fault gouge sandwiched between sliding blocks of Westerly granite have been measured in a high-speed servo-controlled double-direct shear apparatus. Most gouge layers were prepared to have a self-similar particle distribution with a fractal dimension of 2.6. The upper fractal limit was varied between 45 and 710 ??m. Some gouges were prepared with all particles in the range between 360 and 710 ??m. In each experiment the sliding velocity was cyclically alternated between 1 and 10 ??ms-1 and the coefficient of friction ??m and its transient parameters a, b and Dc were measured as functions of displacement. In addition to the particle size distribution, the following experimental variables were also investigated: the layer thickness (1 and 3 mm), the roughness of the sliding surfaces (Nos 60 and 600 grit) and the normal stress (10 and 25 MPa). Some of the sample assemblies were epoxy impregnated following a run so the gouge structure could be microscopically examined in thin section. We observed that gouges which were initially non-fractal evolved to a fractal distribution with dimension 2.6. Gouges which had an initial fractal distribution remained fractal. When the sliding blocks had smooth surfaces, the coefficient of friction was relatively low and was independent of the particle distribution. In these cases, strong velocity weakening was observed throughout the experiment and the transient parameters a, b and Dc, remained almost constant. When the sliding blocks had rough surfaces, the coefficient of friction was larger and more dependent on the particle distribution. Velocity strengthening was observed initially but evolved to velocity weakening with increased sliding displacement. All three transient parameters changed with increasing displacement. The a and b values were about three times as large for rough surfaces as for smooth. The characteristic displacement Dc was not sensitive to surface roughness but was the only transient parameter which was sensitive to the normal stress. For the case of rough surfaces, the coefficient of friction of the 1 mm thick gouge was significantly larger than that for the 3 mm thick layers. Many of these observations can be explained by a micromechanical model in which the stress in the gouge layer is heterogeneous. The applied normal and shear stresses are supported by 'grain bridges' which span the layer and which are continually forming and failing. In this model, the frictional properties of the gouge are largely determined by the dominant failure mode of the bridging structures. ?? 1989.

Wind-Tunnel Study of Scalar Transfer Phenomena for Surfaces of Block Arrays and Smooth Walls with Dry Patches

NASA Astrophysics Data System (ADS)

Chung, Juyeon; Hagishima, Aya; Ikegaya, Naoki; Tanimoto, Jun

2015-11-01

We report the result of a wind-tunnel experiment to measure the scalar transfer efficiency of three types of surfaces, wet street surfaces of cube arrays, wet smooth surfaces with dry patches, and fully wet smooth surfaces, to examine the effects of roughness topography and scalar source allocation. Scalar transfer coefficients defined by the source area {C}_{E wet} for an underlying wet street surface of dry block arrays show a convex trend against the block density λ _p. Comparison with past data, and results for wet smooth surfaces including dry patches, reveal that the positive peak of {C}_{E wet} with increasing λ _p is caused by reduced horizontal advection due to block roughness and enhanced evaporation due to a heterogeneous scalar source distribution. In contrast, scalar transfer coefficients defined by a lot-area including wet and dry areas {C}_{E lot} for smooth surfaces with dry patches indicate enhanced evaporation compared to the fully wet smooth surface (the oasis effect) for all three conditions of dry plan-area ratio up to 31 %. Relationships between the local Sherwood and Reynolds numbers derived from experimental data suggest that attenuation of {C}_{E wet} for a wet street of cube arrays against streamwise distance is weaker than for a wet smooth surface because of canopy flow around the blocks. Relevant parameters of ratio of roughness length for momentum to scalar {B}^{-1} were calculated from observational data. The result implies that {B}^{-1} possibly increases with block roughness, and decreases with the partitioning of the scalar boundary layer because of dry patches.

Understanding Volatile Occurrence on Vesta Using Bistatic Radar and GRaND Observations by the Dawn Mission

NASA Astrophysics Data System (ADS)

Palmer, E. M.; Heggy, E.; Kofman, W. W.

2016-12-01

The first orbital bistatic radar experiment was conducted by Dawn at Asteroid Vesta, where Dawn's HGA was used to transmit X-band radio waves and Earth's Deep Space Network (DSN) 70-meter antennas were used to receive. Due to the opportunistic nature of the experiment, the HGA remained in a fixed orientation toward the Earth such that surface radar reflections occurred at grazing incidence angles of 89° just before and after Dawn's occultation behind Vesta. Among the 16 observed echo sites, we find that σ0ranges from -12 dB to -20 dB and has corresponding RMS slopes ranging from 1°- 8°. To assess potential volatile presence, we compare the distribution of RMS slopes to subsurface hydrogen concentrations observed by Dawn's Gamma Ray and Neutron Detector (GRaND) to 1 m depth. While Vesta's surface is thought to have been largely depleted of volatiles during its differentiation, observations by Dawn'sGRaND and VIR instruments suggest the potential introduction of hydrated material through meteoritic impacts. We identify seven sites of potential volatile occurrence—where low roughness (<5°) is observed to be coupled with high content of hydrated materials (0.025 - 0.04 wt%). Such sites support the possibility of volatile presence, as the regolith should otherwise be particularly rough in the absence of smoothening processes such as the melting, run-off and recrystallization of water ice after an impact. The sites correspond to occultation entry orbit numbers 635, 644 and 719—which overlap Divalia Fossae, Marcia crater ejecta and Octavia crater, respectively—and exit orbit numbers 377, 406, 407 and 720—overlapping northern cratered trough terrain, dark material near Aruntia crater and the cratered highlands. Toward comparing volatile occurrence on other small bodies, Dawn'sBSR experiment at Asteroid Ceres raises new questions. How does the range of decimeter-scale RMS slopes compare with Vesta's surface? How well does the distribution of RMS slopes correlate with GRaND's map of subsurface hydrogen concentration? In addition to optimizing future missions' landing and surface trafficability, characterizing small body surface roughness using BSR will enable further investigation into the relationship between volatile presence and decimeter-scale surface roughness.

Influence of denture surface roughness and host factors on dental calculi formation on dentures: a cross-sectional study.

PubMed

Matsumura, Keisuke; Sato, Yuji; Kitagawa, Noboru; Shichita, Toshiharu; Kawata, Daisuke; Ishikawa, Mariko

2018-05-04

Dental calculi formation on dentures can worsen the oral cavity environment by complicating oral hygiene. However, few studies have investigated the effect of how patients use and manage their dentures, denture surface roughness, and host factors such as oral cavity dryness and saliva properties on denture cleanliness and denture dental calculi formation. Accordingly, we conducted the present survey to evaluate these factors to clarify the strength of the influence of each factor. We enrolled 53 patients who had used dentures for at least 3 months and used a dental prosthesis that covered at least the six front teeth including the left and right mandibular canines. After staining the dentures, we divided the participants into a group that was positive for dental calculi (DCP group) and a group that was negative for dental calculi (DCN group). After removing all the stains, we evaluated the surface roughness of the dentures. A questionnaire was used to survey how the participants used and managed their dentures. Oral cavity dryness was evaluated, and resting saliva samples were collected to assess saliva properties. Correlations between the presence or absence of dental calculi and denture use and management were evaluated using a chi-square test. Correlations with denture surface roughness, oral cavity dryness, and saliva properties were evaluated using the Mann-Whitney U test. Correlations between the presence or absence of dental calculi and all factors were analyzed using multivariate analysis (quantification II). Surface roughness was significantly greater in the DCP group (p < 0.01), and the DCP group members wore their dentures during sleep significantly more often and used a denture cleaner when storing their dentures significantly less often (both p < 0.01). No significant differences were observed for oral cavity dryness or saliva properties. The multivariate analysis showed significant correlations of dental calculi formation with denture surface roughness and items related to denture use and management, but not for oral cavity dryness or saliva properties. Our findings indicate that dental calculi formation is influenced by how dentures are used and managed and by denture surface roughness, but not by oral cavity dryness and saliva properties.

Global statistics of microphysical properties of cloud-top ice crystals

NASA Astrophysics Data System (ADS)

van Diedenhoven, B.; Fridlind, A. M.; Cairns, B.; Ackerman, A. S.; Riedi, J.

2017-12-01

Ice crystals in clouds are highly complex. Their sizes, macroscale shape (i.e., habit), mesoscale shape (i.e., aspect ratio of components) and microscale shape (i.e., surface roughness) determine optical properties and affect physical properties such as fall speeds, growth rates and aggregation efficiency. Our current understanding on the formation and evolution of ice crystals under various conditions can be considered poor. Commonly, ice crystal size and shape are related to ambient temperature and humidity, but global observational statistics on the variation of ice crystal size and particularly shape have not been available. Here we show results of a project aiming to infer ice crystal size, shape and scattering properties from a combination of MODIS measurements and POLDER-PARASOL multi-angle polarimetry. The shape retrieval procedure infers the mean aspect ratios of components of ice crystals and the mean microscale surface roughness levels, which are quantifiable parameters that mostly affect the scattering properties, in contrast to "habit". We present global statistics on the variation of ice effective radius, component aspect ratio, microscale surface roughness and scattering asymmetry parameter as a function of cloud top temperature, latitude, location, cloud type, season, etc. Generally, with increasing height, sizes decrease, roughness increases, asymmetry parameters decrease and aspect ratios increase towards unity. Some systematic differences are observed for clouds warmer and colder than the homogeneous freezing level. Uncertainties in the retrievals will be discussed. These statistics can be used as observational targets for modeling efforts and to better constrain other satellite remote sensing applications and their uncertainties.

Global Statistics of Microphysical Properties of Cloud-Top Ice Crystals

NASA Technical Reports Server (NTRS)

Van Diedenhoven, Bastiaan; Fridlind, Ann; Cairns, Brian; Ackerman, Andrew; Riedl, Jerome

2017-01-01

Ice crystals in clouds are highly complex. Their sizes, macroscale shape (i.e., habit), mesoscale shape (i.e., aspect ratio of components) and microscale shape (i.e., surface roughness) determine optical properties and affect physical properties such as fall speeds, growth rates and aggregation efficiency. Our current understanding on the formation and evolution of ice crystals under various conditions can be considered poor. Commonly, ice crystal size and shape are related to ambient temperature and humidity, but global observational statistics on the variation of ice crystal size and particularly shape have not been available. Here we show results of a project aiming to infer ice crystal size, shape and scattering properties from a combination of MODIS measurements and POLDER-PARASOL multi-angle polarimetry. The shape retrieval procedure infers the mean aspect ratios of components of ice crystals and the mean microscale surface roughness levels, which are quantifiable parameters that mostly affect the scattering properties, in contrast to a habit. We present global statistics on the variation of ice effective radius, component aspect ratio, microscale surface roughness and scattering asymmetry parameter as a function of cloud top temperature, latitude, location, cloud type, season, etc. Generally, with increasing height, sizes decrease, roughness increases, asymmetry parameters decrease and aspect ratios increase towards unity. Some systematic differences are observed for clouds warmer and colder than the homogeneous freezing level. Uncertainties in the retrievals will be discussed. These statistics can be used as observational targets for modeling efforts and to better constrain other satellite remote sensing applications and their uncertainties.

Effect of surface treatments on shear bond strength of resin composite bonded to CAD/CAM resin-ceramic hybrid materials

PubMed Central

Güngör, Merve Bankoğlu; Bal, Bilge Turhan; Ünver, Senem; Doğan, Aylin

2016-01-01

PURPOSE The purpose of this study was to assess the effect of surface treatments on shear bond strength of resin composite bonded to thermocycled and non-thermocycled CAD/CAM resin-ceramic hybrid materials. MATERIALS AND METHODS 120 specimens (10×10×2 mm) from each material were divided into 12 groups according to different surface treatments in combination with thermal aging procedures. Surface treatment methods were airborne-particle abrasion (abraded with 50 micron alumina particles), dry grinding (grinded with 125 µm grain size bur), and hydrofluoric acid (9%) and silane application. According to the thermocycling procedure, the groups were assigned as non-thermocycled, thermocycled after packing composites, and thermocycled before packing composites. The average surface roughness of the non-thermocycled specimens were measured after surface treatments. After packing composites and thermocycling procedures, shear bond strength (SBS) of the specimens were tested. The results of surface roughness were statistically analyzed by 2-way Analysis of Variance (ANOVA), and SBS results were statistically analyzed by 3-way ANOVA. RESULTS Surface roughness of GC were significantly lower than that of LU and VE (P<.05). The highest surface roughness was observed for dry grinding group, followed by airborne particle abraded group (P<.05). Comparing the materials within the same surface treatment method revealed that untreated surfaces generally showed lower SBS values. The values of untreated LU specimens showed significantly different SBS values compared to those of other surface treatment groups (P<.05). CONCLUSION SBS was affected by surface treatments. Thermocycling did not have any effect on the SBS of the materials except acid and silane applied GC specimens, which were subjected to thermocycling before packing of the composite resin. PMID:27555894

Optimization of Surface Roughness Parameters of Al-6351 Alloy in EDC Process: A Taguchi Coupled Fuzzy Logic Approach

NASA Astrophysics Data System (ADS)

Kar, Siddhartha; Chakraborty, Sujoy; Dey, Vidyut; Ghosh, Subrata Kumar

2017-10-01

This paper investigates the application of Taguchi method with fuzzy logic for multi objective optimization of roughness parameters in electro discharge coating process of Al-6351 alloy with powder metallurgical compacted SiC/Cu tool. A Taguchi L16 orthogonal array was employed to investigate the roughness parameters by varying tool parameters like composition and compaction load and electro discharge machining parameters like pulse-on time and peak current. Crucial roughness parameters like Centre line average roughness, Average maximum height of the profile and Mean spacing of local peaks of the profile were measured on the coated specimen. The signal to noise ratios were fuzzified to optimize the roughness parameters through a single comprehensive output measure (COM). Best COM obtained with lower values of compaction load, pulse-on time and current and 30:70 (SiC:Cu) composition of tool. Analysis of variance is carried out and a significant COM model is observed with peak current yielding highest contribution followed by pulse-on time, compaction load and composition. The deposited layer is characterised by X-Ray Diffraction analysis which confirmed the presence of tool materials on the work piece surface.

Rock discontinuity surface roughness variation with scale

NASA Astrophysics Data System (ADS)

Bitenc, Maja; Kieffer, D. Scott; Khoshelham, Kourosh

2017-04-01

ABSTRACT: Rock discontinuity surface roughness refers to local departures of the discontinuity surface from planarity and is an important factor influencing the shear resistance. In practice, the Joint Roughness Coefficient (JRC) roughness parameter is commonly relied upon and input to a shear strength criterion such as developed by Barton and Choubey [1977]. The estimation of roughness by JRC is hindered firstly by the subjective nature of visually comparing the joint profile to the ten standard profiles. Secondly, when correlating the standard JRC values and other objective measures of roughness, the roughness idealization is limited to a 2D profile of 10 cm length. With the advance of measuring technologies that provide accurate and high resolution 3D data of surface topography on different scales, new 3D roughness parameters have been developed. A desirable parameter is one that describes rock surface geometry as well as the direction and scale dependency of roughness. In this research a 3D roughness parameter developed by Grasselli [2001] and adapted by Tatone and Grasselli [2009] is adopted. It characterizes surface topography as the cumulative distribution of local apparent inclination of asperities with respect to the shear strength (analysis) direction. Thus, the 3D roughness parameter describes the roughness amplitude and anisotropy (direction dependency), but does not capture the scale properties. In different studies the roughness scale-dependency has been attributed to data resolution or size of the surface joint (see a summary of researches in [Tatone and Grasselli, 2012]). Clearly, the lower resolution results in lower roughness. On the other hand, have the investigations of surface size effect produced conflicting results. While some studies have shown a decrease in roughness with increasing discontinuity size (negative scale effect), others have shown the existence of positive scale effects, or both positive and negative scale effects. We hypothesize that roughness can increase or decrease with the joint size, depending on the large scale roughness (or waviness), which is entering the roughness calculation once the discontinuity size increases. Therefore, our objective is to characterize roughness at various spatial scales, rather than at changing surface size. Firstly, the rock surface is interpolated into a grid on which a Discrete Wavelet Transform (DWT) is applied. The resulting surface components have different frequencies, or in other words, they have a certain physical scale depending on the decomposition level and input grid resolution. Secondly, the Grasselli Parameter is computed for the original and each decomposed surface. Finally, the relative roughness change is analyzed with respect to increasing roughness wavelength for four different rock samples. The scale variation depends on the sample itself and thus indicates its potential mechanical behavior. References: - Barton, N. and V. Choubey (1977). "The shear strength of rock joints in theory and practice." Rock Mechanics and Rock Engineering 10(1): 1-54. - Grasselli, G. (2001). Shear strength of rock joints based on quantified surface description. École Polytechnique Fédérale de Lausanne. Lausanne, EPFL. - Tatone, B. S. A. and G. Grasselli (2009). "A method to evaluate the three-dimensional roughness of fracture surfaces in brittle geomaterials." Review of Scientific Instruments 80(12) - Tatone, B. and G. Grasselli (2012). "An Investigation of Discontinuity Roughness Scale Dependency Using High-Resolution Surface Measurements." Rock Mechanics and Rock Engineering: 1-25.

Determining Surface Roughness in Urban Areas Using Lidar Data

NASA Technical Reports Server (NTRS)

Holland, Donald

2009-01-01

An automated procedure has been developed to derive relevant factors, which can increase the ability to produce objective, repeatable methods for determining aerodynamic surface roughness. Aerodynamic surface roughness is used for many applications, like atmospheric dispersive models and wind-damage models. For this technique, existing lidar data was used that was originally collected for terrain analysis, and demonstrated that surface roughness values can be automatically derived, and then subsequently utilized in disaster-management and homeland security models. The developed lidar-processing algorithm effectively distinguishes buildings from trees and characterizes their size, density, orientation, and spacing (see figure); all of these variables are parameters that are required to calculate the estimated surface roughness for a specified area. By using this algorithm, aerodynamic surface roughness values in urban areas can then be extracted automatically. The user can also adjust the algorithm for local conditions and lidar characteristics, like summer/winter vegetation and dense/sparse lidar point spacing. Additionally, the user can also survey variations in surface roughness that occurs due to wind direction; for example, during a hurricane, when wind direction can change dramatically, this variable can be extremely significant. In its current state, the algorithm calculates an estimated surface roughness for a square kilometer area; techniques using the lidar data to calculate the surface roughness for a point, whereby only roughness elements that are upstream from the point of interest are used and the wind direction is a vital concern, are being investigated. This technological advancement will improve the reliability and accuracy of models that use and incorporate surface roughness.

Effect of surface roughness of trench sidewalls on electrical properties in 4H-SiC trench MOSFETs

NASA Astrophysics Data System (ADS)

Kutsuki, Katsuhiro; Murakami, Yuki; Watanabe, Yukihiko; Onishi, Toru; Yamamoto, Kensaku; Fujiwara, Hirokazu; Ito, Takahiro

2018-04-01

The effects of the surface roughness of trench sidewalls on electrical properties have been investigated in 4H-SiC trench MOSFETs. The surface roughness of trench sidewalls was well controlled and evaluated by atomic force microscopy. The effective channel mobility at each measurement temperature was analyzed on the basis of the mobility model including optical phonon scattering. The results revealed that surface roughness scattering had a small contribution to channel mobility, and at the arithmetic average roughness in the range of 0.4-1.4 nm, there was no correlation between the experimental surface roughness and the surface roughness scattering mobility. On the other hand, the characteristics of the gate leakage current and constant current stress time-dependent dielectric breakdown tests demonstrated that surface morphology had great impact on the long-term reliability of gate oxides.

A new fiber optic sensor for inner surface roughness measurement

NASA Astrophysics Data System (ADS)

Xu, Xiaomei; Liu, Shoubin; Hu, Hong

2009-11-01

In order to measure inner surface roughness of small holes nondestructively, a new fiber optic sensor is researched and developed. Firstly, a new model for surface roughness measurement is proposed, which is based on intensity-modulated fiber optic sensors and scattering modeling of rough surfaces. Secondly, a fiber optical measurement system is designed and set up. Under the help of new techniques, the fiber optic sensor can be miniaturized. Furthermore, the use of micro prism makes the light turn 90 degree, so the inner side surface roughness of small holes can be measured. Thirdly, the fiber optic sensor is gauged by standard surface roughness specimens, and a series of measurement experiments have been done. The measurement results are compared with those obtained by TR220 Surface Roughness Instrument and Form Talysurf Laser 635, and validity of the developed fiber optic sensor is verified. Finally, precision and influence factors of the fiber optic sensor are analyzed.

Roughness Effects on Fretting Fatigue

NASA Astrophysics Data System (ADS)

Yue, Tongyan; Abdel Wahab, Magd

2017-05-01

Fretting is a small oscillatory relative motion between two normal loaded contact surfaces. It may cause fretting fatigue, fretting wear and/or fretting corrosion damage depending on various fretting couples and working conditions. Fretting fatigue usually occurs at partial slip condition, and results in catastrophic failure at the stress levels below the fatigue limit of the material. Many parameters may affect fretting behaviour, including the applied normal load and displacement, material properties, roughness of the contact surfaces, frequency, etc. Since fretting damage is undesirable due to contacting, the effect of rough contact surfaces on fretting damage has been studied by many researchers. Experimental method on this topic is usually focusing on rough surface effects by finishing treatment and random rough surface effects in order to increase fretting fatigue life. However, most of numerical models on roughness are based on random surface. This paper reviewed both experimental and numerical methodology on the rough surface effects on fretting fatigue.

Effects of roughness and compressibility of flooring on cow locomotion.

PubMed

Rushen, J; de Passillé, A M

2006-08-01

We examined the effects of roughness and degree of compressibility of flooring on the locomotion of dairy cows. We observed 16 cows walking down specially constructed walkways with materials that differed in surface roughness and degree of compressibility. Use of a commercially available soft rubber flooring material decreased slipping, number of strides, and time to traverse the corridor. These effects were most apparent at difficult sections of the corridor, such as at the start, at a right-angle turn, and across a gutter. Covering the walkway with a thin layer of slurry increased frequency of slipping, number of strides, and time taken to traverse the walkway. Effects of adding slurry were not overcome by increasing surface roughness or compressibility. Placing more compressible materials under a slip-resistant material reduced the time and number of steps needed to traverse the corridor but did not reduce slips, and the effects on cow locomotion varied nonlinearly with the degree of compressibility of the floor. Use of commercially available rubber floors improved cow locomotion compared with concrete floors. However, standard engineering measures of the floor properties may not predict effects of the floor on cow behavior well. Increasing compressibility of the flooring on which cows walk, independently of the roughness of the surface, can improve cow locomotion.

Sputtering of rough surfaces: a 3D simulation study

NASA Astrophysics Data System (ADS)

von Toussaint, U.; Mutzke, A.; Manhard, A.

2017-12-01

The lifetime of plasma-facing components is critical for future magnetic confinement fusion power plants. A key process limiting the lifetime of the first-wall is sputtering by energetic ions. To provide a consistent modeling of the sputtering process of realistic geometries, the SDTrimSP-code has been extended to enable the processing of analytic as well as measured arbitrary 3D surface morphologies. The code has been applied to study the effect of varying the impact angle of ions on rough surfaces on the sputter yield as well as the influence of the aspect ratio of surface structures on the 2D distribution of the local sputtering yields. Depending on the surface morphologies reductions of the effective sputter yields to less than 25% have been observed in the simulation results.

Towards predictive models for transitionally rough surfaces

NASA Astrophysics Data System (ADS)

Abderrahaman-Elena, Nabil; Garcia-Mayoral, Ricardo

2017-11-01

We analyze and model the previously presented decomposition for flow variables in DNS of turbulence over transitionally rough surfaces. The flow is decomposed into two contributions: one produced by the overlying turbulence, which has no footprint of the surface texture, and one induced by the roughness, which is essentially the time-averaged flow around the surface obstacles, but modulated in amplitude by the first component. The roughness-induced component closely resembles the laminar steady flow around the roughness elements at the same non-dimensional roughness size. For small - yet transitionally rough - textures, the roughness-free component is essentially the same as over a smooth wall. Based on these findings, we propose predictive models for the onset of the transitionally rough regime. Project supported by the Engineering and Physical Sciences Research Council (EPSRC).

Novel Zirconia Surface Treatments for Enhanced Osseointegration: Laboratory Characterization

PubMed Central

Ewais, Ola H.; Al Abbassy, Fayza; Ghoneim, Mona M.; Aboushelib, Moustafa N.

2014-01-01

Purpose. The aim of this study was to evaluate three novel surface treatments intended to improve osseointegration of zirconia implants: selective infiltration etching treatment (SIE), fusion sputtering (FS), and low pressure particle abrasion (LPPA). The effects of surface treatments on roughness, topography, hardness, and porosity of implants were also assessed. Materials and Methods. 45 zirconia discs (19 mm in diameter × 3 mm in thickness) received 3 different surface treatments: selective infiltration etching, low pressure particle abrasion with 30 µm alumina, and fusion sputtering while nontreated surface served as control. Surface roughness was evaluated quantitatively using profilometery, porosity was evaluated using mercury prosimetry, and Vickers microhardness was used to assess surface hardness. Surface topography was analyzed using scanning and atomic force microscopy (α = 0.05). Results. There were significant differences between all groups regarding surface roughness (F = 1678, P < 0.001), porosity (F = 3278, P < 0.001), and hardness (F = 1106.158, P < 0.001). Scanning and atomic force microscopy revealed a nanoporous surface characteristic of SIE, and FS resulted in the creation of surface microbeads, while LPPA resulted in limited abrasion of the surface. Conclusion. Within the limitations of the study, changes in surface characteristics and topography of zirconia implants have been observed after different surface treatment approaches. Thus possibilities for enhanced osseointegration could be additionally offered. PMID:25349610

Effective Wettability of Heterogenous Fracture Surfaces Using the Lattice-Boltzmann Method

NASA Astrophysics Data System (ADS)

E Santos, J.; Prodanovic, M.; Landry, C. J.

2017-12-01

Fracture walls in the subsurface are often structured by minerals of different composition (potentially further altered in contact with fluids during hydrocarbon extraction or CO2 sequestration), this yields in a heterogeneous wettability of the surface in contact with the fluids. The focus of our work is to study how surfaces presenting different mineralogy and roughness affect multiphase flow in fractures. Using the Shan-Chen model of the lattice-Boltzmann method (LBM) we define fluid interaction and surface attraction parameters to simulate a system of a wetting and a non-wetting fluid. In this work, we use synthetically created fractures presenting different arrangements of wetting and non-wetting patches, and with or without roughness; representative of different mineralogy, similar workflow can be applied to fractures extracted from X-ray microtomography images of fractures porous media. The results from the LBM simulations provide an insight on how the distribution of mineralogy and surface roughness are related with the observed macroscopic contact angle. We present a comparison between the published analytical models, and our results based on surface areas, spatial distribution and local fracture aperture. The understanding of the variables that affect the contact angle is useful for the comprehension of multiphase processes in naturally fractured reservoirs like primary oil production, enhanced oil recovery and CO2 sequestration. The macroscopic contact angle analytical equations for heterogeneous surfaces with variable roughness are no longer valid in highly heterogeneous systems; we quantify the difference thus offering an alternative to analytical models.

Accurate potential drop sheet resistance measurements of laser-doped areas in semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinrich, Martin, E-mail: mh.seris@gmail.com; NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore 117456; Kluska, Sven

2014-10-07

It is investigated how potential drop sheet resistance measurements of areas formed by laser-assisted doping in crystalline Si wafers are affected by typically occurring experimental factors like sample size, inhomogeneities, surface roughness, or coatings. Measurements are obtained with a collinear four point probe setup and a modified transfer length measurement setup to measure sheet resistances of laser-doped lines. Inhomogeneities in doping depth are observed from scanning electron microscope images and electron beam induced current measurements. It is observed that influences from sample size, inhomogeneities, surface roughness, and coatings can be neglected if certain preconditions are met. Guidelines are given onmore » how to obtain accurate potential drop sheet resistance measurements on laser-doped regions.« less

Variability in radar returns from Martian debris-covered glaciers attributed to surface debris layer roughness and composition: implications for the regional distribution of massive subsurface ice and near-surface pore-filling ice.

NASA Astrophysics Data System (ADS)

Petersen, E.; Holt, J. W.; Levy, J. S.; Lalich, D.

2017-12-01

Lobate debris aprons, lineated valley fill, and concentric crater fill are a class of Martian landform thought to be glaciers blanketed by a lithic debris layer. They are found in the mid latitudes (roughly 30-50°N and S) where surface ice is presently unstable. Shallow Radar (SHARAD) sounder observations are in many cases able to resolve the basal contact between the glacier and underlying bedrock, showing that the bulk composition of these features is water ice with < 20% lithic debris; they are thus often referred to as debris-covered glaciers (DCG). The basal contact of candidate glaciers is not always present in SHARAD radargrams, and variable reflection power between glacier sites suggests that non-detections may be due to a reduction of echo power below the noise floor. A likely candidate for signal loss is the variable roughness of different glacial surface textures. We test this mechanism of signal reduction via analysis of SHARAD reflections augmented by surface roughness analyses generated from HiRISE stereo DEMs. This method provides a means of constraining the electrical properties of the surface debris. We show that measured surface roughness is sufficient to explain basal reflection signal loss for five glacier sites in the region of Deuteronilus/Protonilus Mensae (R2 = 0.90), with the dielectric constant for the surface debris layer constrained to 4.9 ± 0.3. Assuming debris formed of basalt rock, this value is consistent with a porous debris layer containing up to 64% ice, or an ice-free debris layer with porosity of 28-34%. From this work, we conclude that (1) weak or non-existent basal reflections at these sites are due to roughness-induced radar signal loss and not due to differing properties of the basal interface, (2) all DCG candidates in this study exhibit similar bulk compositions of relatively pure water ice, and (3) the surface debris layer is formed of porous lithic debris which may contain a significant fraction of pore ice.

Cellular Behavior of Human Adipose-Derived Stem Cells on Wettable Gradient Polyethylene Surfaces

PubMed Central

Ahn, Hyun Hee; Lee, Il Woo; Lee, Hai Bang; Kim, Moon Suk

2014-01-01

Appropriate surface wettability and roughness of biomaterials is an important factor in cell attachment and proliferation. In this study, we investigated the correlation between surface wettability and roughness, and biological response in human adipose-derived stem cells (hADSCs). We prepared wettable and rough gradient polyethylene (PE) surfaces by increasing the power of a radio frequency corona discharge apparatus with knife-type electrodes over a moving sample bed. The PE changed gradually from hydrophobic and smooth surfaces to hydrophilic (water contact angle, 90º to ~50º) and rough (80 to ~120 nm) surfaces as the power increased. We found that hADSCs adhered better to highly hydrophilic and rough surfaces and showed broadly stretched morphology compared with that on hydrophobic and smooth surfaces. The proliferation of hADSCs on hydrophilic and rough surfaces was also higher than that on hydrophobic and smooth surfaces. Furthermore, integrin beta 1 gene expression, an indicator of attachment, and heat shock protein 70 gene expression were high on hydrophobic and smooth surfaces. These results indicate that the cellular behavior of hADSCs on gradient surface depends on surface properties, wettability and roughness. PMID:24477265

Geometrical considerations in analyzing isotropic or anisotropic surface reflections.

PubMed

Simonot, Lionel; Obein, Gael

2007-05-10

The bidirectional reflectance distribution function (BRDF) represents the evolution of the reflectance with the directions of incidence and observation. Today BRDF measurements are increasingly applied and have become important to the study of the appearance of surfaces. The representation and the analysis of BRDF data are discussed, and the distortions caused by the traditional representation of the BRDF in a Fourier plane are pointed out and illustrated for two theoretical cases: an isotropic surface and a brushed surface. These considerations will help characterize either the specular peak width of an isotropic rough surface or the main directions of the light scattered by an anisotropic rough surface without misinterpretations. Finally, what is believed to be a new space is suggested for the representation of the BRDF, which avoids the geometrical deformations and in numerous cases is more convenient for BRDF analysis.

Measuring Skew in Average Surface Roughness as a Function of Surface Preparation

NASA Technical Reports Server (NTRS)

Stahl, Mark

2015-01-01

Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces polishing time, saves money and allows the science requirements to be better defined. This study characterized statistics of average surface roughness as a function of polishing time. Average surface roughness was measured at 81 locations using a Zygo white light interferometer at regular intervals during the polishing process. Each data set was fit to a normal and Largest Extreme Value (LEV) distribution; then tested for goodness of fit. We show that the skew in the average data changes as a function of polishing time.

Emulation of Forward-looking Radar Technology for Threat Detection in Rough Terrain Environments: A Scattering and Imaging Study

DTIC Science & Technology

2012-12-01

a) Ground with flat surface; (b) Ground with randomly rough surface, hrms =1.2 cm, lc=14.93 cm; (c) Ground with randomly rough surface, hrms =1.6 cm...horizontal-horizontal (hh)-polarized images for 20 m×10 m scene: (a) Ground with flat surface; (b) Ground with randomly rough surface, hrms =1.2 cm...lc=14.93 cm; (c) Ground with randomly rough surface, hrms =1.6 cm, lc=14.93 cm. Ground electrical properties: εr=6, σd=10 mS/m. Frequency span: 0.3

Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging

NASA Technical Reports Server (NTRS)

Carter, Lynn M.; Campbell, Donald B.; Campbell, Bruce A.

2010-01-01

Radar is a useful remote sensing tool for studying planetary geology because it is sensitive to the composition, structure, and roughness of the surface and can penetrate some materials to reveal buried terrain. The Arecibo Observatory radar system transmits a single sense of circular polarization, and both senses of circular polarization are received, which allows for the construction of the Stokes polarization vector. From the Stokes vector, daughter products such as the circular polarization ratio, the degree of linear polarization, and linear polarization angle are obtained. Recent polarimetric imaging using Arecibo has included Venus and the Moon. These observations can be compared to radar data for terrestrial surfaces to better understand surface physical properties and regional geologic evolution. For example, polarimetric radar studies of volcanic settings on Venus, the Moon and Earth display some similarities, but also illustrate a variety of different emplacement and erosion mechanisms. Polarimetric radar data provides important information about surface properties beyond what can be obtained from single-polarization radar. Future observations using polarimetric synthetic aperture radar will provide information on roughness, composition and stratigraphy that will support a broader interpretation of surface evolution.

Theoretical and experimental models of the diffuse radar backscatter from Mars

NASA Technical Reports Server (NTRS)

England, A. W.

1995-01-01

The general objective for this work was to develop a theoretically and experimentally consistent explanation for the diffuse component of radar backscatter from Mars. The strength, variability, and wavelength independence of Mars' diffuse backscatter are unique among our Moon and the terrestrial planets. This diffuse backscatter is generally attributed to wavelength-scale surface roughness and to rock clasts within the Martian regolith. Through the combination of theory and experiment, the authors attempted to bound the range of surface characteristics that could produce the observed diffuse backscatter. Through these bounds they gained a limited capability for data inversion. Within this umbrella, specific objectives were: (1) To better define the statistical roughness parameters of Mars' surface so that they are consistent with observed radar backscatter data, and with the physical and chemical characteristics of Mars' surface as inferred from Mariner 9, the Viking probes, and Earth-based spectroscopy; (2) To better understand the partitioning between surface and volume scattering in the Mars regolith; (3) To develop computational models of Mars' radio emission that incorporate frequency dependent, surface and volume scattering.

Prenatally administered HMB modifies the enamel surface roughness in spiny mice offspring: An atomic force microscopy study.

PubMed

Świetlicka, Izabela; Muszyński, Siemowit; Tomaszewska, Ewa; Dobrowolski, Piotr; Kwaśniewska, Anita; Świetlicki, Michał; Skic, Anna; Gołacki, Krzysztof

2016-10-01

The aim of this research was to check the effect of the prenatally administered β-hydroxy β-methylbutyrate (HMB) on the development of enamel surface of the spiny mice offspring. The spiny mice dams were randomly assigned into three groups: control group (not supplemented with HMB) and two experimental groups in which powdered HMB was given at the daily dosage of 0.2g/kg of body weight (group I) and 0.02g/kg of body weight (group II) during the last period of gestation. Newborn pups were euthanized by CO 2 inhalation. The morphology of incisor teeth was analysed using atomic force microscopy (AFM) in semi-contact mode in the height, magnitude and phase domains. Height images became a basis for determination of surface roughness parameters. Conducted study indicated that maternal HMB administration markedly influences enamel development. Enamel of offspring's teeth in both experimental groups was characterized by significantly smaller values of indices describing surface roughness and profile. HMB supplementation influenced the calculated parameters regardless of the diet type and offspring sex, however higher dose of HMB caused stronger changes in enamel surface's physical properties and could be observed in higher intensity in the male group. HMB administration caused reduction in the irregularities of enamel surface, thereby possibly reducing the probability of bacteria adhesion and caries development. These observations may serve to improve nutrition and supplementation of animals and could be a lead for further research. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of physico-chemical, mechanical and morphological fingerpad properties on the frictional distinction of sticky/slippery surfaces

PubMed Central

Cornuault, Pierre-Henri; Carpentier, Luc; Bueno, Marie-Ange; Cote, Jean-Marc; Monteil, Guy

2015-01-01

This study investigates how the fingerpad hydrolipid film, shape, roughness and rigidity influence the friction when it rubs surfaces situated in the slippery psychophysical dimension. The studied counterparts comprised two ‘real’ (physical) surfaces and two ‘virtual’ surfaces. The latter were simulated with a tactile stimulator named STIMTAC. Thirteen women and 13 men rubbed their right forefingers against the different surfaces as their arms were displaced by a DC motor providing constant velocity and sliding distance. Tangential and normal forces were measured with a specific tribometer. The fingerpad hydrolipid film was characterized by Fourier transform infrared spectroscopy. The shape and roughness of fingers were extrapolated from replicas. Indentation measurements were carried out to determine fingerpad effective elastic modulus. A clear difference was observed between women and men in terms of friction behaviour. The concept of tactile frictional contrast (TFC) which was introduced quantifies an individual's propensity to distinguish two surfaces frictionally. The lipids/water ratio and water amount on the finger skin significantly influenced the TFC. A correlation was observed between the TFC and fingerpad roughness, i.e. the height of the fingerpad ridges. This is essentially owing to gender differences. A significant difference between men's and women's finger topography was also noted, because our results suggested that men have rougher fingers than women. The friction measurements did not correlate with the fingerpad curvature nor with the epidermal ridges' spatial period. PMID:26269232

Taguchi Optimization of Cutting Parameters in Turning AISI 1020 MS with M2 HSS Tool

NASA Astrophysics Data System (ADS)

Sonowal, Dharindom; Sarma, Dhrupad; Bakul Barua, Parimal; Nath, Thuleswar

2017-08-01

In this paper the effect of three cutting parameters viz. Spindle speed, Feed and Depth of Cut on surface roughness of AISI 1020 mild steel bar in turning was investigated and optimized to obtain minimum surface roughness. All the experiments are conducted on HMT LB25 lathe machine using M2 HSS cutting tool. Ranges of parameters of interest have been decided through some preliminary experimentation (One Factor At a Time experiments). Finally a combined experiment has been carried out using Taguchi’s L27 Orthogonal Array (OA) to study the main effect and interaction effect of the all three parameters. The experimental results were analyzed with raw data ANOVA (Analysis of Variance) and S/N data (Signal to Noise ratio) ANOVA. Results show that Spindle speed, Feed and Depth of Cut have significant effects on both mean and variation of surface roughness in turning AISI 1020 mild steel. Mild two factors interactions are observed among the aforesaid factors with significant effects only on the mean of the output variable. From the Taguchi parameter optimization the optimum factor combination is found to be 630 rpm spindle speed, 0.05 mm/rev feed and 1.25 mm depth of cut with estimated surface roughness 2.358 ± 0.970 µm. A confirmatory experiment was conducted with the optimum factor combination to verify the results. In the confirmatory experiment the average value of surface roughness is found to be 2.408 µm which is well within the range (0.418 µm to 4.299 µm) predicted for confirmatory experiment.

Cheap and fast measuring roughness on big surfaces with an imprint method

NASA Astrophysics Data System (ADS)

Schopf, C.; Liebl, J.; Rascher, R.

2017-10-01

Roughness, shape and structure of a surface offer information on the state, shape and surface characteristics of a component. Particularly the roughness of the surface dictates the subsequent polishing of the optical surface. The roughness is usually measured by a white light interferometer, which is limited by the size of the components. Using a moulding method of surfaces that are difficult to reach, an imprint is taken and analysed regarding to roughness and structure. This moulding compound method is successfully used in dental technology. In optical production, the moulding compound method is advantageous in roughness determination in inaccessible spots or on large components (astrological optics). The "replica method" has been around in metal analysis and processing. Film is used in order to take an impression of a surface. Then, it is analysed for structures. In optical production, compound moulding seems advantageous in roughness determination in inaccessible spots or on large components (astrological optics). In preliminary trials, different glass samples with different roughness levels were manufactured. Imprints were taken from these samples (based on DIN 54150 "Abdruckverfahren für die Oberflächenprüfung"). The objective of these feasibility tests was to determine the limits of this method (smallest roughness determinable / highest roughness). The roughness of the imprint was compared with the roughness of the glass samples. By comparing the results, the uncertainty of the measuring method was determined. The spectrum for the trials ranged from rough grind (0.8 μm rms), over finishing grind (0.6 μm rms) to polishing (0.1 μm rms).

Exploring a new method for the retrieval of urban thermophysical properties using thermal infrared remote sensing and deterministic modeling

NASA Astrophysics Data System (ADS)

De Ridder, K.; Bertrand, C.; Casanova, G.; Lefebvre, W.

2012-09-01

Increasingly, mesoscale meteorological and climate models are used to predict urban weather and climate. Yet, large uncertainties remain regarding values of some urban surface properties. In particular, information concerning urban values for thermal roughness length and thermal admittance is scarce. In this paper, we present a method to estimate values for thermal admittance in combination with an optimal scheme for thermal roughness length, based on METEOSAT-8/SEVIRI thermal infrared imagery in conjunction with a deterministic atmospheric model containing a simple urbanized land surface scheme. Given the spatial resolution of the SEVIRI sensor, the resulting parameter values are applicable at scales of the order of 5 km. As a study case we focused on the city of Paris, for the day of 29 June 2006. Land surface temperature was calculated from SEVIRI thermal radiances using a new split-window algorithm specifically designed to handle urban conditions, as described inAppendix A, including a correction for anisotropy effects. Land surface temperature was also calculated in an ensemble of simulations carried out with the ARPS mesoscale atmospheric model, combining different thermal roughness length parameterizations with a range of thermal admittance values. Particular care was taken to spatially match the simulated land surface temperature with the SEVIRI field of view, using the so-called point spread function of the latter. Using Bayesian inference, the best agreement between simulated and observed land surface temperature was obtained for the Zilitinkevich (1970) and Brutsaert (1975) thermal roughness length parameterizations, the latter with the coefficients obtained by Kanda et al. (2007). The retrieved thermal admittance values associated with either thermal roughness parameterization were, respectively, 1843 ± 108 J m-2 s-1/2 K-1 and 1926 ± 115 J m-2 s-1/2 K-1.

Changes to Glazed Dental Ceramic Shade, Roughness, and Microhardness after Bleaching and Simulated Brushing.

PubMed

Rodrigues, Carlos Roberto Teixeira; Turssi, Cecilia Pedroso; Amaral, Flávia Lucisano Botelho; Basting, Roberta Tarkany; França, Fabiana Mantovani Gomes

2017-09-05

To evaluate shade stability, surface roughness, microhardness, and compressive strength of a glazed feldspathic ceramic subjected to bleaching and simulated brushing. Eighty-eight glazed feldspathic ceramic specimens were made from microparticulate leucite and divided into eight groups (n = 10). The whitening products used were: Opalescence Trèswhite Supreme (Ultradent), Opalescence®\\ PF 15% (Ultradent), and Oral-B 3D White Whitestrips. All substances for whitening were used for 4 hours/day for a period of 14 days; the control group was not bleached. Next, half of the specimens were individually brushed. Microhardness and surface roughness data were subjected to three-way ANOVA and Tukey test. The diametrical tensile strength data were subjected to two-way ANOVA. The shade change data were analyzed using Kruskal-Wallis, Mann-Whitney, and the Student-Newman-Keuls test. The significance level was set at 5%. Glazed feldspathic ceramic surface microhardness was significantly affected by bleaching agents (p = 0.007). Initially, glazed ceramic microhardness was significantly higher than that observed after contact with the bleaching agents, whether or not brushing was performed. The specimens submitted to bleaching in preloaded trays presented lower surface roughness values after brushing (p = 0.037). The surface roughness was significantly lower in the brushed specimens (p = 0.044). The diametrical tensile strength was not significantly affected by the application of bleaching agents (p = 0.563) or by brushing (p = 0.477). When the specimens were brushed, however, shade change was significantly influenced by the bleaching agent used (p = 0.041). Bleaching agents associated with brushing cycles can alter surface properties and shade stability of glazed feldspathic ceramics, though such findings may not reflect the performance of unglazed feldspathic ceramics. © 2017 by the American College of Prosthodontists.

The evolution of fracture surface roughness and its dependence on slip

NASA Astrophysics Data System (ADS)

Wells, Olivia L.

Under effective compression, impingement of opposing rough surfaces of a fracture can force the walls of the fracture apart during slip. Therefore, a fracture's surface roughness exerts a primary control on the amount of dilation that can be sustained on a fracture since the opposing surfaces need to remain in contact. Previous work has attempted to characterize fracture surface roughness through topographic profiles and power spectral density analysis, but these metrics describing the geometry of a fracture's surface are often non-unique when used independently. However, when combined these metrics are affective at characterizing fracture surface roughness, as well as the mechanisms affecting changes in roughness with increasing slip, and therefore changes in dilation. These mechanisms include the influence of primary grains and pores on initial fracture roughness, the effect of linkage on locally increasing roughness, and asperity destruction that limits the heights of asperities and forms gouge. This analysis reveals four essential stages of dilation during the lifecycle of a natural fracture, whereas previous slip-dilation models do not adequately address the evolution of fracture surface roughness: (1) initial slip companied by small dilation is mediated by roughness controlled by the primary grain and pore dimensions; (2) rapid dilation during and immediately following fracture growth by linkage of formerly isolated fractures; (3) wear of the fracture surface and gouge formation that minimizes dilation; and (4) between slip events cementation that modifies the mineral constituents in the fracture. By identifying these fundamental mechanisms that influence fracture surface roughness, this new conceptual model relating dilation to slip has specific applications to Enhanced Geothermal Systems (EGS), which attempt to produce long-lived dilation in natural fractures by inducing slip.

Numerical investigation of roughness effects in aircraft icing calculations

NASA Astrophysics Data System (ADS)

Matheis, Brian Daniel

2008-10-01

Icing codes are playing a role of increasing significance in the design and certification of ice protected aircraft surfaces. However, in the interest of computational efficiency certain small scale physics of the icing problem are grossly approximated by the codes. One such small scale phenomena is the effect of ice roughness on the development of the surface water film and on the convective heat transfer. This study uses computational methods to study the potential effect of ice roughness on both of these small scale phenomena. First, a two-dimensional condensed layer code is used to examine the effect of roughness on surface water development. It is found that the Couette approximation within the film breaks down as the wall shear goes to zero, depending on the film thickness. Roughness elements with initial flow separation in the air induce flow separation in the water layer at steady state, causing a trapping of the film. The amount of trapping for different roughness configurations is examined. Second, a three-dimensional incompressible Navier-Stokes code is developed to examine large scale ice roughness on the leading edge. The effect on the convective heat transfer and potential effect on the surface water dynamics is examined for a number of distributed roughness parameters including Reynolds number, roughness height, streamwise extent, roughness spacing and roughness shape. In most cases the roughness field increases the net average convective heat transfer on the leading edge while narrowing surface shear lines, indicating a choking of the surface water flow. Both effects show significant variation on the scale of the ice roughness. Both the change in heat transfer as well as the potential change in surface water dynamics are presented in terms of the development of singularities in the surface shear pattern. Of particular interest is the effect of the smooth zone upstream of the roughness which shows both a relatively large increase in convective heat transfer as well as excessive choking of the surface shear lines at the upstream end of the roughness field. A summary of the heat transfer results is presented for both the averaged heat transfer as well as the maximum heat transfer over each roughness element, indicating that the roughness Reynolds number is the primary parameter which characterizes the behavior of the roughness for the problem of interest.

The evolution of slip surface roughness during earthquake propagation in carbonate faults

NASA Astrophysics Data System (ADS)

Zhu, B.; De Paola, N.; Llewellin, E. W.; Holdsworth, R.

2014-12-01

Slip surface roughness is understood to control the dynamics of earthquake propagation. Quantifying the micro- and nano-scale roughness of slip surfaces can give insight into the grain-scale processes controlling the strength of faults during earthquake propagation. Friction experiments were performed on fine-grained calcite gouges, at speed 1 ms-1, normal stress 18 MPa, displacements 0.009-1.46 m, and room temperature and humidity. Results show a two stage-evolution (S1-2) of the fault strength, with an initial increase up to peak value 0.82 (S1), followed by a sudden decrease to a low, steady-state value 0.18 (S2). Samples retrieved at the end of S1 show the development of a cohesive slip zone (SZ), made of micron-scale, angular clasts formed by brittle fracturing and cataclasis. The SZ of samples deformed up to S2, is composed of nanograin aggregates which exhibit polygonal grain boundaries indicating high temperature grain boundary sliding creep deformation. In both cases, the SZ is bounded by a sharply defined slip surface. The 3-D geometry of seven experimental slip surfaces (40μm×40μm) has been reconstructed by digital processing of sets of 1800 images of SZ cross sections acquired at 20 nm intervals perpendicular to the slip direction, using a slicing (Focussed Ion Beam) and viewing (Field Emission Scanning Electron Microscope) technique. Spectrum power density analyses show that nano- and micron-scale slip surface roughness is anisotropic for both S1 and S2 slip surfaces. At the nano- and micron-scale, root mean square values decrease with length for S1 slip surfaces, but only slightly for S2 surfaces, and are anisotropic in the slip-normal and slip-parallel directions. The anisotropy is reduced at the nano-scale, although S2 slip surfaces are still smoother parallel to slip than normal to slip. Hurst exponents vary through scales, and are anisotropic in the directions parallel and normal to slip. Variable Hurst exponents indicate that slip surface roughness is scale-dependent with anisotropic, not self-affine behaviour at the micro/nano-scale, in contrast to the self-affine behaviour inferred at the mm to km scales. Dynamic weakening and creep deformation, observed during S2, coincide with an evolution towards less anisotropic and scale-dependent slip surface roughness at the nanoscale.

A Transport Equation Approach to Modeling the Influence of Surface Roughness on Boundary Layer Transition

NASA Astrophysics Data System (ADS)

Langel, Christopher Michael

A computational investigation has been performed to better understand the impact of surface roughness on the flow over a contaminated surface. This thesis highlights the implementation and development of the roughness amplification model in the flow solver OVERFLOW-2. The model, originally proposed by Dassler, Kozulovic, and Fiala, introduces an additional scalar field roughness amplification quantity. This value is explicitly set at rough wall boundaries using surface roughness parameters and local flow quantities. This additional transport equation allows non-local effects of surface roughness to be accounted for downstream of rough sections. This roughness amplification variable is coupled with the Langtry-Menter model and used to modify the criteria for transition. Results from flat plate test cases show good agreement with experimental transition behavior on the flow over varying sand grain roughness heights. Additional validation studies were performed on a NACA 0012 airfoil with leading edge roughness. The computationally predicted boundary layer development demonstrates good agreement with experimental results. New tests using varying roughness configurations are being carried out at the Texas A&M Oran W. Nicks Low Speed Wind Tunnel to provide further calibration of the roughness amplification method. An overview and preliminary results are provided of this concurrent experimental investigation.

Skin friction measurements of systematically-varied roughness: Probing the role of roughness amplitude and skewness

NASA Astrophysics Data System (ADS)

Barros, Julio; Flack, Karen; Schultz, Michael

2017-11-01

Real-world engineering systems which feature either external or internal wall-bounded turbulent flow are routinely affected by surface roughness. This gives rise to performance degradation in the form of increased drag or head loss. However, at present there is no reliable means to predict these performance losses based upon the roughness topography alone. This work takes a systematic approach by generating random surface roughness in which the surface statistics are closely controlled. Skin friction and roughness function results will be presented for two groups of these rough surfaces. The first group is Gaussian (i.e. zero skewness) in which the root-mean-square roughness height (krms) is varied. The second group has a fixed krms, and the skewness is varied from approximately -1 to +1. The effect of the roughness amplitude and skewness on the skin friction will be discussed. Particular attention will be paid to the effect of these parameters on the roughness function in the transitionally-rough flow regime. For example, the role these parameters play in the monotonic or inflectional nature of the roughness function will be addressed. Future research into the details of the turbulence structure over these rough surfaces will also be outlined. Research funded by U.S. Office of Naval Research (ONR).

Chemical resistance and cleanability of glazed surfaces

NASA Astrophysics Data System (ADS)

Hupa, Leena; Bergman, Roger; Fröberg, Linda; Vane-Tempest, Stina; Hupa, Mikko; Kronberg, Thomas; Pesonen-Leinonen, Eija; Sjöberg, Anna-Maija

2005-06-01

Adhesion of soil on glazed surfaces and their cleanability depends on chemical composition, phase composition, and roughness of the surface. The surface can be glossy consisting mainly of a smooth glassy phase. A matt and rough surface consists of a glassy phase and one or more crystalline phases. The origin and composition of the crystalline phases affect the chemical resistance and the cleanability of the surface. Fifteen experimental glossy and matt glazes were soaked in a slightly alkaline cleaning agent solution. The surfaces were spin-coated with sebum, i.e. a soil component typical for sanitary facilities. After wiping out the soil film in a controlled manner, the surface conditions and the soil left were evaluated with colour measurements, SEM/EDXA and COM. The results show that wollastonite-type crystals in the glaze surfaces were attacked in aqueous solutions containing typical cleaning agents. This corrosion led to significant decrease in the cleanability of the surface. The other crystal types observed, i.e. diopside and quartz crystals were not corroded, and the cleanability of glazes containing only these crystals was not changed in the cleaning agent exposures. Also the glassy phase was found to be attacked in some formulations leading to a somewhat decreased cleanability. The repeated soiling and cleaning procedures indicated that soil is accumulated on rough surfaces and surfaces which were clearly corroded by the cleaning agent.

Spin relaxation in graphene nanoribbons in the presence of substrate surface roughness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaghazardi, Zahra; Faez, Rahim; Touski, Shoeib Babaee

2016-08-07

In this work, spin transport in corrugated armchair graphene nanoribbons (AGNRs) is studied. We survey combined effects of spin-orbit interaction and surface roughness, employing the non-equilibrium Green's function formalism and multi-orbitals tight-binding model. Rough substrate surfaces have been statistically generated and the hopping parameters are modulated based on the bending and distance of corrugated carbon atoms. The effects of surface roughness parameters, such as roughness amplitude and correlation length, on spin transport in AGNRs are studied. The increase of surface roughness amplitude results in the coupling of σ and π bands in neighboring atoms, leading to larger spin flipping ratemore » and therefore reduction of the spin-polarization, whereas a longer correlation length makes AGNR surface smoother and increases spin-polarization. Moreover, spin diffusion length of carriers is extracted and its dependency on the roughness parameters is investigated. In agreement with experimental data, the spin diffusion length for various substrate ranges between 2 and 340 μm. Our results indicate the importance of surface roughness on spin-transport in graphene.« less

Wetting Hysteresis at the Molecular Scale

NASA Technical Reports Server (NTRS)

Jin, Wei; Koplik, Joel; Banavar, Jayanth R.

1996-01-01

The motion of a fluid-fluid-solid contact line on a rough surface is well known to display hysteresis in the contact angle vs. velocity relationship. In order to understand the phenomenon at a fundamental microscopic level, we have conducted molecular dynamics computer simulations of a Wilhelmy plate experiment in which a solid surface is dipped into a liquid bath, and the force-velocity characteristics are measured. We directly observe a systematic variation of force and contact angle with velocity, which is single-valued for the case of an atomically smooth solid surface. In the microscopically rough case, however, we find (as intuitively expected) an open hysteresis loop. Further characterization of the interface dynamics is in progress.

Insect adhesion on rough surfaces: analysis of adhesive contact of smooth and hairy pads on transparent microstructured substrates

PubMed Central

Zhou, Yanmin; Robinson, Adam; Steiner, Ullrich; Federle, Walter

2014-01-01

Insect climbing footpads are able to adhere to rough surfaces, but the details of this capability are still unclear. To overcome experimental limitations of randomly rough, opaque surfaces, we fabricated transparent test substrates containing square arrays of 1.4 µm diameter pillars, with variable height (0.5 and 1.4 µm) and spacing (from 3 to 22 µm). Smooth pads of cockroaches (Nauphoeta cinerea) made partial contact (limited to the tops of the structures) for the two densest arrays of tall pillars, but full contact (touching the substrate in between pillars) for larger spacings. The transition from partial to full contact was accompanied by a sharp increase in shear forces. Tests on hairy pads of dock beetles (Gastrophysa viridula) showed that setae adhered between pillars for larger spacings, but pads were equally unable to make full contact on the densest arrays. The beetles' shear forces similarly decreased for denser arrays, but also for short pillars and with a more gradual transition. These observations can be explained by simple contact models derived for soft uniform materials (smooth pads) or thin flat plates (hairy-pad spatulae). Our results show that microstructured substrates are powerful tools to reveal adaptations of natural adhesives for rough surfaces. PMID:24990289

Insect adhesion on rough surfaces: analysis of adhesive contact of smooth and hairy pads on transparent microstructured substrates.

PubMed

Zhou, Yanmin; Robinson, Adam; Steiner, Ullrich; Federle, Walter

2014-09-06

Insect climbing footpads are able to adhere to rough surfaces, but the details of this capability are still unclear. To overcome experimental limitations of randomly rough, opaque surfaces, we fabricated transparent test substrates containing square arrays of 1.4 µm diameter pillars, with variable height (0.5 and 1.4 µm) and spacing (from 3 to 22 µm). Smooth pads of cockroaches (Nauphoeta cinerea) made partial contact (limited to the tops of the structures) for the two densest arrays of tall pillars, but full contact (touching the substrate in between pillars) for larger spacings. The transition from partial to full contact was accompanied by a sharp increase in shear forces. Tests on hairy pads of dock beetles (Gastrophysa viridula) showed that setae adhered between pillars for larger spacings, but pads were equally unable to make full contact on the densest arrays. The beetles' shear forces similarly decreased for denser arrays, but also for short pillars and with a more gradual transition. These observations can be explained by simple contact models derived for soft uniform materials (smooth pads) or thin flat plates (hairy-pad spatulae). Our results show that microstructured substrates are powerful tools to reveal adaptations of natural adhesives for rough surfaces.

SEM and AFM studies of dip-coated CuO nanofilms.

PubMed

Dhanasekaran, V; Mahalingam, T; Ganesan, V

2013-01-01

Cupric oxide (CuO) semiconducting thin films were prepared at various copper sulfate concentrations by dip coating. The copper sulfate concentration was varied to yield films of thicknesses in the range of 445-685 nm by surface profilometer. X-ray diffraction patterns revealed that the deposited films were polycrystalline in nature with monoclinic structure of (-111) plane. The surface morphology and topography of monoclinic-phase CuO thin films were examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. Surface roughness profile was plotted using WSxM software and the estimated surface roughness was about ∼19.4 nm at 30 mM molar concentration. The nanosheets shaped grains were observed by SEM and AFM studies. The stoichiometric compound formation was observed at 30 mM copper sulfate concentration prepared film by EDX. The indirect band gap energy of CuO films was increased from 1.08 to 1.20 eV with the increase of copper sulfate concentrations. Copyright © 2012 Wiley Periodicals, Inc.

Graphene thickness dependent adhesion force and its correlation to surface roughness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pourzand, Hoorad; Tabib-Azar, Massood, E-mail: azar.m@utah.edu; Biomedical Engineering, University of Utah, Salt Lake City, Utah 84112

2014-04-28

In this paper, adhesion force of graphene layers on 300 nm silicon oxide is studied. A simple model for measuring adhesion force for a flat surface with sub-nanometer roughness was developed and is shown that small surface roughness decreases adhesion force while large roughness results in an effectively larger adhesion forces. We also show that surface roughness over scales comparable to the tip radius increase by nearly a factor of two, the effective adhesion force measured by the atomic force microscopy. Thus, we demonstrate that surface roughness is an important parameter that should be taken into account in analyzing the adhesionmore » force measurement results.« less

Effect of drop volume and surface statistics on the superhydrophobicity of randomly rough substrates

NASA Astrophysics Data System (ADS)

Afferrante, L.; Carbone, G.

2018-01-01

In this paper, a simple theoretical approach is developed with the aim of evaluating shape, interfacial pressure, apparent contact angle and contact area of liquid drops gently deposed on randomly rough surfaces. This method can be useful to characterize the superhydrophobic properties of rough substrates, and to investigate the contact behavior of impacting drops. We assume that (i) the size of the apparent liquid-solid contact area is much larger than the micromorphology of the substrate, and (ii) a composite interface is always formed at the microscale. Results show apparent contact angle and liquid-solid area fraction are slightly influenced by the drop volume only at relatively high values of the root mean square roughness h rms, whereas the effect of volume is practically negligible at small h rms. The main statistical quantity affecting the superhydrophobic properties is found to be the Wenzel roughness parameter r W, which depends on the average slope of the surface heights. Moreover, transition from the Cassie-Baxter state to the Wenzel one is observed when r W reduces below a certain critical value, and theoretical predictions are found to be in good agreement with experimental data. Finally, the present method can be conveniently exploited to evaluate the occurrence of pinning phenomena in the case of impacting drops, as the Wenzel critical pressure for liquid penetration gives an estimation of the maximum impact pressure tolerated by the surface without pinning occurring.

Performance assessment of femoral knee components made from cobalt-chromium alloy and oxidized zirconium.

PubMed

Brandt, J-M; Guenther, L; O'Brien, S; Vecherya, A; Turgeon, T R; Bohm, E R

2013-12-01

The surface characteristics of the femoral component affect polyethylene wear in modular total knee replacements. In the present retrieval study, the surface characteristics of cobalt-chromium (CoCr) alloy and oxidized zirconium (OxZr) femoral components were assessed and compared. Twenty-six retrieved CoCr alloy femoral components were matched with twenty-six retrieved OxZr femoral components for implantation period, body-mass index, patient gender, implant type, and polyethylene insert thickness. The surface damage on the retrieved femoral components was evaluated using a semi-quantitative assessment method, scanning electron microscopy, and contact profilometry. The retrieved CoCr alloy femoral components showed less posterior surface gouging than OxZr femoral components; however, at a higher magnification, the grooving damage features on the retrieved CoCr alloy femoral components confirmed an abrasive wear mechanism. The surface roughness values Rp, Rpm, and Rpk for the retrieved CoCr alloy femoral components were found to be significantly higher than those of the retrieved OxZr femoral components (p≤0.031). The surface roughness values were higher on the medial condyles than on the lateral condyles of the retrieved CoCr alloy femoral components; such a difference was not observed on the retrieved OxZr femoral components. The surface roughness of CoCr alloy femoral components increased while the surface roughness of the OxZr femoral components remained unchanged after in vivo service. Therefore, the OxZr femoral components' resistance to abrasive wear may enable lower polyethylene wear and ensure long-term durability in vivo. Level IV. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

Optimum surface roughness prediction for titanium alloy by adopting response surface methodology

NASA Astrophysics Data System (ADS)

Yang, Aimin; Han, Yang; Pan, Yuhang; Xing, Hongwei; Li, Jinze

Titanium alloy has been widely applied in industrial engineering products due to its advantages of great corrosion resistance and high specific strength. This paper investigated the processing parameters for finish turning of titanium alloy TC11. Firstly, a three-factor central composite design of experiment, considering the cutting speed, feed rate and depth of cut, are conducted in titanium alloy TC11 and the corresponding surface roughness are obtained. Then a mathematic model is constructed by the response surface methodology to fit the relationship between the process parameters and the surface roughness. The prediction accuracy was verified by the one-way ANOVA. Finally, the contour line of the surface roughness under different combination of process parameters are obtained and used for the optimum surface roughness prediction. Verification experimental results demonstrated that material removal rate (MRR) at the obtained optimum can be significantly improved without sacrificing the surface roughness.

Influence of Cutting Parameters and Tool Wear on the Surface Integrity of Cobalt-Based Stellite 6 Alloy When Machined Under a Dry Cutting Environment

NASA Astrophysics Data System (ADS)

Yingfei, Ge; de Escalona, Patricia Muñoz; Galloway, Alexander

2017-01-01

The efficiency of a machining process can be measured by evaluating the quality of the machined surface and the tool wear rate. The research reported herein is mainly focused on the effect of cutting parameters and tool wear on the machined surface defects, surface roughness, deformation layer and residual stresses when dry milling Stellite 6, deposited by overlay on a carbon steel surface. The results showed that under the selected cutting conditions, abrasion, diffusion, peeling, chipping and breakage were the main tool wear mechanisms presented. Also the feed rate was the primary factor affecting the tool wear with an influence of 83%. With regard to the influence of cutting parameters on the surface roughness, the primary factors were feed rate and cutting speed with 57 and 38%, respectively. In addition, in general, as tool wear increased, the surface roughness increased and the deformation layer was found to be influenced more by the cutting parameters rather than the tool wear. Compressive residual stresses were observed in the un-machined surface, and when machining longer than 5 min, residual stress changed 100% from compression to tension. Finally, results showed that micro-crack initiation was the main mechanism for chip formation.

Monitoring of Surface Roughness in Aluminium Turning Process

NASA Astrophysics Data System (ADS)

Chaijareenont, Atitaya; Tangjitsitcharoen, Somkiat

2018-01-01

As the turning process is one of the most necessary process. The surface roughness has been considered for the quality of workpiece. There are many factors which affect the surface roughness. Hence, the objective of this research is to monitor the relation between the surface roughness and the cutting forces in aluminium turning process with a wide range of cutting conditions. The coated carbide tool and aluminium alloy (Al 6063) are used for this experiment. The cutting parameters are investigated to analyze the effects of them on the surface roughness which are the cutting speed, the feed rate, the tool nose radius and the depth of cut. In the case of this research, the dynamometer is installed in the turret of CNC turning machine to generate a signal while turning. The relation between dynamic cutting forces and the surface roughness profile is examined by applying the Fast Fourier Transform (FFT). The experimentally obtained results showed that the cutting force depends on the cutting condition. The surface roughness can be improved when increasing the cutting speed and the tool nose radius in contrast to the feed rate and the depth of cut. The relation between the cutting parameters and the surface roughness can be explained by the in-process cutting forces. It is understood that the in-process cutting forces are able to predict the surface roughness in the further research.

Super Water-Repellent Fractal Surfaces of a Photochromic Diarylethene Induced by UV Light

NASA Astrophysics Data System (ADS)

Izumi, Norikazu; Minami, Takayuki; Mayama, Hiroyuki; Takata, Atsushi; Nakamura, Shinichiro; Yokojima, Satoshi; Tsujii, Kaoru; Uchida, Kingo

2008-09-01

Photochromic diarylethene forms super water-repellent surfaces upon irradiation with UV light. Microfibril-like crystals grow on the solid diarylethene surface after UV irradiation, and the contact angle of water on the surface becomes larger with increasing surface roughness with time. The fractal analysis was made by the box-counting method for the rough surfaces. There are three regions in the roughness size having the fractal dimension of ca. 2.4 (size of roughness smaller than 5 µm), of ca. 2.2 (size of roughness between 5-40 µm), and of ca. 2.0 (size of roughness larger than 40 µm). The fractal dimension of ca. 2.4 was due to the fibril-like structures generated gradually by UV irradiation on diarylethene surfaces accompanied with an increase in the contact angle. The surface structure with larger fractal dimension mainly contributes to realizing the super water-repellency of the diarylethene surfaces. This mechanism of spontaneous formation of fractal surfaces is similar to that for triglyceride and alkylketene dimer waxes.

Measuring skew in average surface roughness as a function of surface preparation

NASA Astrophysics Data System (ADS)

Stahl, Mark T.

2015-08-01

Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces polishing time, saves money and allows the science requirements to be better defined. This study characterized statistics of average surface roughness as a function of polishing time. Average surface roughness was measured at 81 locations using a Zygo® white light interferometer at regular intervals during the polishing process. Each data set was fit to a normal and Largest Extreme Value (LEV) distribution; then tested for goodness of fit. We show that the skew in the average data changes as a function of polishing time.

Nano-textured fluidic biochip as biological filter for selective survival of neuronal cells.

PubMed

Han, Hsieh-Cheng; Lo, Hung-Chun; Wu, Chia-Yu; Chen, Kuei-Hsien; Chen, Li-Chyong; Ou, Keng-Liang; Hosseinkhani, Hossein

2015-06-01

This is an innovative study to engineer biological filter to evaluate the effect of template surface structure and physiochemical properties that can be used for wide variety of applications in biological, health care as well as environmental protection. Specifically, planar silicon (Si) wafer and arrayed Si nano-tips (SiNT) templates were fabricated and coated with gold for various lengths of time to study the effect of surface charge, surface roughness, and hydrophilicity on biological activity of rat pheochromocytoma cell lines PC12. The initial growth and proliferation of PC12 cells on Si and SiNT templates showed an antipathy for the ultra-sharp SiNTs templates. In contrast, the same cells demonstrated a preferable adherence to and proliferation on planar Si templates, resulting in higher cell densities by three orders of magnitude than those on SiNT templates. It is hypothesized that SiNTs array does generate nano-fluidic effect such that the effective contact region for aqueous solution on SiNTs is lower than that on planar Si templates, thus decreasing adsorbable area for cell viability and survival. Moreover, the effect of the gold coating on cell number density was analyzed in terms of the surface roughness, zeta potential and wetting properties of the templates. It was determined that surface charge, as measured by the zeta potential, strongly correlated with the trend observed in the surface cell density, whereas no such correlation was observed for surface roughness or wetting properties in the ranges of our experiment conditions. © 2014 Wiley Periodicals, Inc.

Quantification of the optical surface reflection and surface roughness of articular cartilage using optical coherence tomography

NASA Astrophysics Data System (ADS)

Saarakkala, Simo; Wang, Shu-Zhe; Huang, Yan-Ping; Zheng, Yong-Ping

2009-11-01

Optical coherence tomography (OCT) is a promising new technique for characterizing the structural changes of articular cartilage in osteoarthritis (OA). The calculation of quantitative parameters from the OCT signal is an important step to develop OCT as an effective diagnostic technique. In this study, two novel parameters for the quantification of optical surface reflection and surface roughness from OCT measurements are introduced: optical surface reflection coefficient (ORC), describing the amount of a ratio of the optical reflection from cartilage surface with respect to that from a reference material, and OCT roughness index (ORI) indicating the smoothness of the cartilage surface. The sensitivity of ORC and ORI to detect changes in bovine articular cartilage samples after enzymatic degradations of collagen and proteoglycans using collagenase and trypsin enzymes, respectively, was tested in vitro. A significant decrease (p < 0.001) in ORC as well as a significant increase (p < 0.001) in ORI was observed after collagenase digestion. After trypsin digestion, no significant changes in ORC or ORI were observed. To conclude, the new parameters introduced were demonstrated to be feasible and sensitive to detect typical OA-like degenerative changes in the collagen network. From the clinical point of view, the quantification of OCT measurements is of great interest since OCT probes have been already miniaturized and applied in patient studies during arthroscopy or open knee surgery in vivo. Further studies are still necessary to demonstrate the clinical capability of the introduced parameters for naturally occurring early OA changes in the cartilage.

Surface roughness retrieval by inversion of the Hapke model: A multiscale approach

NASA Astrophysics Data System (ADS)

Labarre, S.; Ferrari, C.; Jacquemoud, S.

2017-07-01

Surface roughness is a key property of soils that controls many surface processes and influences the scattering of incident electromagnetic waves at a wide range of scales. Hapke (2012b) designed a photometric model providing an approximate analytical solution of the Bidirectional Reflectance Distribution Function (BRDF) of a particulate medium: he introduced the effect of surface roughness as a correction factor of the BRDF of a smooth surface. This photometric roughness is defined as the mean slope angle of the facets composing the surface, integrated over all scales from the grain size to the local topography. Yet its physical meaning is still a question at issue, as the scale at which it occurs is not clearly defined. This work aims at better understanding the relative influence of roughness scales on soil BRDF and to test the ability of the Hapke model to retrieve a roughness that depicts effectively the ground truth. We apply a wavelet transform on millimeter digital terrain models (DTM) acquired over volcanic terrains. This method allows splitting the frequency band of a signal in several sub-bands, each corresponding to a spatial scale. We demonstrate that sub-centimeter surface features dominate both the integrated roughness and the BRDF shape. We investigate the suitability of the Hapke model for surface roughness retrieval by inversion on optical data. A global sensitivity analysis of the model shows that soil BRDF is very sensitive to surface roughness, nearly as much as the single scattering albedo according to the phase angle, but also that these two parameters are strongly correlated. Based on these results, a simplified two-parameter model depending on surface albedo and roughness is proposed. Inversion of this model on BRDF data simulated by a ray-tracing code over natural targets shows a good estimation of surface roughness when the assumptions of the model are verified, with a priori knowledge on surface albedo.

Numerical analysis of the effect of surface roughness on mechanical fields in polycrystalline aggregates

NASA Astrophysics Data System (ADS)

Guilhem, Yoann; Basseville, Stéphanie; Curtit, François; Stéphan, Jean-Michel; Cailletaud, Georges

2018-06-01

This paper is dedicated to the study of the influence of surface roughness on local stress and strain fields in polycrystalline aggregates. Finite element computations are performed with a crystal plasticity model on a 316L stainless steel polycrystalline material element with different roughness states on its free surface. The subsequent analysis of the plastic strain localization patterns shows that surface roughness strongly affects the plastic strain localization induced by crystallography. Nevertheless, this effect mainly takes place at the surface and vanishes under the first layer of grains, which implies the existence of a critical perturbed depth. A statistical analysis based on the plastic strain distribution obtained for different roughness levels provides a simple rule to define the size of the affected zone depending on the rough surface parameters.

Characteristics of surface roughness associated with leading edge ice accretion

NASA Technical Reports Server (NTRS)

Shin, Jaiwon

1994-01-01

Detailed size measurements of surface roughness associated with leading edge ice accretions are presented to provide information on characteristics of roughness and trends of roughness development with various icing parameters. Data was obtained from icing tests conducted in the Icing Research Tunnel (IRT) at NASA Lewis Research Center (LeRC) using a NACA 0012 airfoil. Measurements include diameters, heights, and spacing of roughness elements along with chordwise icing limits. Results confirm the existence of smooth and rough ice zones and that the boundary between the two zones (surface roughness transition region) moves upstream towards stagnation region with time. The height of roughness grows as the air temperature and the liquid water content increase, however, the airspeed has little effect on the roughness height. Results also show that the roughness in the surface roughness transition region grows during a very early stage of accretion but reaches a critical height and then remains fairly constant. Results also indicate that a uniformly distributed roughness model is only valid at a very initial stage of the ice accretion process.

Stick-slip friction and wear of articular joints

PubMed Central

Lee, Dong Woog; Banquy, Xavier; Israelachvili, Jacob N.

2013-01-01

Stick-slip friction was observed in articular cartilage under certain loading and sliding conditions and systematically studied. Using the Surface Forces Apparatus, we show that stick-slip friction can induce permanent morphological changes (a change in the roughness indicative of wear/damage) in cartilage surfaces, even under mild loading and sliding conditions. The different load and speed regimes can be represented by friction maps—separating regimes of smooth and stick-slip sliding; damage generally occurs within the stick-slip regimes. Prolonged exposure of cartilage surfaces to stick-slip sliding resulted in a significant increase of surface roughness, indicative of severe morphological changes of the cartilage superficial zone. To further investigate the factors that are conducive to stick-slip and wear, we selectively digested essential components of cartilage: type II collagen, hyaluronic acid (HA), and glycosaminoglycans (GAGs). Compared with the normal cartilage, HA and GAG digestions modified the stick-slip behavior and increased surface roughness (wear) during sliding, whereas collagen digestion decreased the surface roughness. Importantly, friction forces increased up to 2, 10, and 5 times after HA, GAGs, and collagen digestion, respectively. Also, each digestion altered the friction map in different ways. Our results show that (i) wear is not directly related to the friction coefficient but (ii) more directly related to stick-slip sliding, even when present at small amplitudes, and that (iii) the different molecular components of joints work synergistically to prevent wear. Our results also suggest potential noninvasive diagnostic tools for sensing stick-slip in joints. PMID:23359687

Incorporating Skew into RMS Surface Roughness Probability Distribution

NASA Technical Reports Server (NTRS)

Stahl, Mark T.; Stahl, H. Philip.

2013-01-01

The standard treatment of RMS surface roughness data is the application of a Gaussian probability distribution. This handling of surface roughness ignores the skew present in the surface and overestimates the most probable RMS of the surface, the mode. Using experimental data we confirm the Gaussian distribution overestimates the mode and application of an asymmetric distribution provides a better fit. Implementing the proposed asymmetric distribution into the optical manufacturing process would reduce the polishing time required to meet surface roughness specifications.

Soil roughness, slope and surface storage relationship for impervious areas

NASA Astrophysics Data System (ADS)

Borselli, Lorenzo; Torri, Dino

2010-11-01

SummaryThe study of the relationships between surface roughness, local slope gradient and maximum volume of water storage in surface depressions is a fundamental element in the development of hydrological models to be used in soil and water conservation strategies. Good estimates of the maximum volume of water storage are important for runoff assessment during rainfall events. Some attempts to link surface storage to parameters such as indices of surface roughness and, more rarely, local gradient have been proposed by several authors with empirical equations often conflicting between them and usually based on a narrow range of slope gradients. This suggests care in selecting any of the proposed equations or models and invites one to verify the existence of more realistic experimental relationships, based on physical models of the surfaces and valid for a larger range of gradients. The aim of this study is to develop such a relation for predicting/estimating the maximum volume of water that a soil surface, with given roughness characteristics and local slope gradient, can store. Experimental work has been carried out in order to reproduce reliable rough surfaces able to maintain the following properties during the experimental activity: (a) impervious surface to avoid biased storage determination; (b) stable, un-erodible surfaces to avoid changes of retention volume during tests; (c) absence of hydrophobic behaviour. To meet the conditions a-c we generate physical surfaces with various roughness magnitude using plasticine (emulsion of non-expansible clay and oil). The plasticine surface, reproducing surfaces of arable soils, was then wetted and dirtied with a very fine timber sawdust. This reduced the natural hydrophobic behaviour of the plasticine to an undetectable value. Storage experiments were conducted with plasticine rough surfaces on top of large rigid polystyrene plates inclined at different slope gradient: 2%, 5%, 10%, 20%, 30%. Roughness data collected on the generated plasticine surfaces were successfully compared with roughness data collected on real soil surfaces for similar conditions. A set of roughness indices was computed for each surface using roughness profiles measured with a laser profile meter. Roughness indices included quantiles of the Abbot-Firestone curve, which is used in surface metrology for industrial application to characterize surface roughness in a non-parametric approach ( Whitehouse, 1994). Storage data were fitted with an empirical equation (double negative exponential of roughness and slope). Several roughness indices resulted well related to storage. The better results were obtained using the Abbot-Firestone curve parameter P100. Beside this storage empirical model (SEM) a geometrical model was also developed, trying to give a more physical basis to the result obtained so far. Depression geometry was approximated with spherical cups. A general physical model was derived (storage cup model - SCM). The cup approximation identifies where roughness elevation comes in and how it relates to slope gradient in defining depression volume. Moreover, the exponential decay used for assessing slope effect on storage volume in the empirical model of Eqs. (8) and (9) emerges as consistent with distribution of cup sizes.

Cemented fixation with PMMA or Bis-GMA resin hydroxyapatite cement: effect of implant surface roughness.

PubMed

Walsh, W R; Svehla, M J; Russell, J; Saito, M; Nakashima, T; Gillies, R M; Bruce, W; Hori, R

2004-09-01

Implant surface roughness is an important parameter governing the overall mechanical properties at the implant-cement interface. This study investigated the influence of surface roughness using polymethylmethcrylate (PMMA) and a Bisphenol-a-glycidylmethacyrlate resin-hydroxyapatite cement (CAP). Mechanical fixation at the implant-cement interface was evaluated in vitro using static shear and fatigue loading with cobalt chrome alloy (CoCr) dowels with different surface roughness preparations. Increasing surface roughness improved the mechanical properties at the implant-cement interface for both types of cement. CAP cement fixation was superior to PMMA under static and dynamic loading.

Investigation of the influence of a step change in surface roughness on turbulent heat transfer

NASA Technical Reports Server (NTRS)

Taylor, Robert P.; Coleman, Hugh W.; Taylor, J. Keith; Hosni, M. H.

1991-01-01

The use is studied of smooth heat flux gages on the otherwise very rough SSME fuel pump turbine blades. To gain insights into behavior of such installations, fluid mechanics and heat transfer data were collected and are reported for a turbulent boundary layer over a surface with a step change from a rough surface to a smooth surface. The first 0.9 m length of the flat plate test surface was roughened with 1.27 mm hemispheres in a staggered, uniform array spaced 2 base diameters apart. The remaining 1.5 m length was smooth. The effect of the alignment of the smooth surface with respect to the rough surface was also studied by conducting experiments with the smooth surface aligned with the bases or alternatively with the crests of the roughness elements. Stanton number distributions, skin friction distributions, and boundary layer profiles of temperature and velocity are reported and are compared to previous data for both all rough and all smooth wall cases. The experiments show that the step change from rough to smooth has a dramatic effect on the convective heat transfer. It is concluded that use of smooth heat flux gages on otherwise rough surfaces could cause large errors.

Inference of effective river properties from remotely sensed observations of water surface

NASA Astrophysics Data System (ADS)

Garambois, Pierre-André; Monnier, Jérôme

2015-05-01

The future SWOT mission (Surface Water and Ocean Topography) will provide cartographic measurements of inland water surfaces (elevation, widths and slope) at an unprecedented spatial and temporal resolution. Given synthetic SWOT like data, forward flow models of hierarchical-complexity are revisited and few inverse formulations are derived and assessed for retrieving the river low flow bathymetry, roughness and discharge (A0, K, Q) . The concept of an effective low flow bathymetry A0 (the real one being never observed) and roughness K , hence an effective river dynamics description, is introduced. The few inverse models elaborated for inferring (A0, K, Q) are analyzed in two contexts: (1) only remotely sensed observations of the water surface (surface elevation, width and slope) are available; (2) one additional water depth measurement (or estimate) is available. The inverse models elaborated are independent of data acquisition dynamics; they are assessed on 91 synthetic test cases sampling a wide range of steady-state river flows (the Froude number varying between 0.05 and 0.5 for 1 km reaches) and in the case of a flood on the Garonne River (France) characterized by large spatio-temporal variabilities. It is demonstrated that the most complete shallow-water like model allowing to separate the roughness and bathymetry terms is the so-called low Froude model. In Case (1), the resulting RMSE on infered discharges are on the order of 15% for first guess errors larger than 50%. An important feature of the present inverse methods is the fairly good accuracy of the discharge Q obtained, while the identified roughness coefficient K includes the measurement errors and the misfit of physics between the real flow and the hypothesis on which the inverse models rely; the later neglecting the unobserved temporal variations of the flow and the inertia effects. A compensation phenomena between the indentifiedvalues of K and the unobserved bathymetry A0 is highlighted, while the present inverse models lead to an effective river dynamics model that is accurate in the range of the discharge variability observed. In Case (2), the effective bathymetry profile for 80 km of the Garonne River is retrieved with 1% relative error only. Next, accurate effective topography-friction pairs and also discharge can be inferred. Finally, defining river reaches from the observation grid tends to average the river properties in each reach, hence tends to smooth the hydraulic variability.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Pei-Yang; Zhang, Guojing; Gullickson, Eric M.

Extreme ultraviolet lithography (EUVL) mask multi-layer (ML) blank surface roughness specification historically comes from blank defect inspection tool requirement. Later, new concerns on ML surface roughness induced wafer pattern line width roughness (LWR) arise. In this paper, we have studied wafer level pattern LWR as a function of EUVL mask surface roughness via High-NA Actinic Reticle Review Tool. We found that the blank surface roughness induced LWR at current blank roughness level is in the order of 0.5nm 3σ for NA=0.42 at the best focus. At defocus of ±40nm, the corresponding LWR will be 0.2nm higher. Further reducing EUVL maskmore » blank surface roughness will increase the blank cost with limited benefit in improving the pattern LWR, provided that the intrinsic resist LWR is in the order of 1nm and above.« less

An investigation of the observability of ocean-surface parameters using GEOS-3 backscatter data

NASA Technical Reports Server (NTRS)

Miller, L. S.; Priester, R. W.

1978-01-01

The degree to which ocean surface roughness can be synoptically observed through use of the information extracted from the GEOS-3 backscattered waveform data was evaluated. Algorithms are given for use in estimating the radar sensed waveheight distribution or ocean-surface impulse response. Other factors discussed include comparisons between theoretical and experimental radar cross section values, sea state bias effects, spatial variability of significant waveheight data, and sensor-related considerations.

Efficiency of different protocols for enamel clean-up after bracket debonding: an in vitro study

PubMed Central

Sigilião, Lara Carvalho Freitas; Marquezan, Mariana; Elias, Carlos Nelson; Ruellas, Antônio Carlos; Sant'Anna, Eduardo Franzotti

2015-01-01

Objective: This study aimed to assess the efficiency of six protocols for cleaning-up tooth enamel after bracket debonding. Methods: A total of 60 premolars were divided into six groups, according to the tools used for clean-up: 12-blade bur at low speed (G12L), 12-blade bur at high speed (G12H), 30-blade bur at low speed (G30L), DU10CO ORTHO polisher (GDU), Renew System (GR) and Diagloss polisher (GD). Mean roughness (Ra) and mean roughness depth (Rz) of enamel surface were analyzed with a profilometer. Paired t-test was used to assess Ra and Rz before and after enamel clean-up. ANOVA/Tukey tests were used for intergroup comparison. The duration of removal procedures was recorded. The association between time and variation in enamel roughness (∆Ra, ∆Rz) were evaluated by Pearson's correlation test. Enamel topography was assessed by scanning electron microscopy (SEM). Results: In Groups G12L and G12H, original enamel roughness did not change significantly. In Groups G30L, GDU, GR and GD, a smoother surface (p < 0.05) was found after clean-up. In Groups G30L and GD, the protocols used were more time-consuming than those used in the other groups. Negative and moderate correlation was observed between time and (∆Ra, ∆Rz); Ra and (∆Ra, ∆Rz); Rz (r = - 0.445, r = - 0.475, p < 0.01). Conclusion: All enamel clean-up protocols were efficient because they did not result in increased surface roughness. The longer the time spent performing the protocol, the lower the surface roughness. PMID:26560825

The balance between keystone clustering and bed roughness in experimental step-pool stabilization

NASA Astrophysics Data System (ADS)

Johnson, J. P.

2016-12-01

Predicting how mountain channels will respond to environmental perturbations such as floods requires an improved quantitative understanding of morphodynamic feedbacks among bed topography, surface grain size and sediment sorting. In boulder-rich gravel streams, transport and sorting often lead to the development of step pool morphologies, which are expressed both in bed topography and coarse grain clustering. Bed stability is difficult to measure, and is sometimes inferred from the presence of step pools. I use scaled flume experiments to explore feedbacks among surface grain sizes, coarse grain clustering, bed roughness and hydraulic roughness during progressive bed stabilization and over a range of sediment transport rates. While grain clusters are sometimes identified by subjective interpretation, I quantify the degree of coarse surface grain clustering using spatial statistics, including a novel normalization of Ripley's K function. This approach is objective and provides information on the strength of clustering over a range of length scales. Flume experiments start with an initial bed surface with a broad grain size distribution and spatially random positions. Flow causes the bed surface to progressively stabilize in response to erosion, surface coarsening, roughening and grain reorganization. At 95% confidence, many but not all beds stabilized with coarse grains becoming more clustered than complete spatial randomness (CSR). I observe a tradeoff between topographic roughness and clustering. Beds that stabilized with higher degrees of coarse-grain clustering were topographically smoother, and vice-versa. Initial conditions influenced the degree of clustering at stability: Beds that happened to have fewer initial coarse grains had more coarse grain reorganization during stabilization, leading to more clustering. Finally, regressions demonstrate that clustering statistics actually predict hydraulic roughness significantly better than does D84 (the size at which 84% of grains are smaller). In the experimental data, the spatial organization of surface grains is a stronger control on flow characteristics than the size of surface grains.

Refined BCF-type boundary conditions for mesoscale surface step dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Renjie; Ackerman, David M.; Evans, James W.

Deposition on a vicinal surface with alternating rough and smooth steps is described by a solid-on-solid model with anisotropic interactions. Kinetic Monte Carlo (KMC) simulations of the model reveal step pairing in the absence of any additional step attachment barriers. We explore the description of this behavior within an analytic Burton-Cabrera-Frank (BCF)-type step dynamics treatment. Without attachment barriers, conventional kinetic coefficients for the rough and smooth steps are identical, as are the predicted step velocities for a vicinal surface with equal terrace widths. However, we determine refined kinetic coefficients from a two-dimensional discrete deposition-diffusion equation formalism which accounts for stepmore » structure. These coefficients are generally higher for rough steps than for smooth steps, reflecting a higher propensity for capture of diffusing terrace adatoms due to a higher kink density. Such refined coefficients also depend on the local environment of the step and can even become negative (corresponding to net detachment despite an excess adatom density) for a smooth step in close proximity to a rough step. Incorporation of these refined kinetic coefficients into a BCF-type step dynamics treatment recovers quantitatively the mesoscale step-pairing behavior observed in the KMC simulations.« less

Refined BCF-type boundary conditions for mesoscale surface step dynamics

DOE PAGES

Zhao, Renjie; Ackerman, David M.; Evans, James W.

2015-06-24

Deposition on a vicinal surface with alternating rough and smooth steps is described by a solid-on-solid model with anisotropic interactions. Kinetic Monte Carlo (KMC) simulations of the model reveal step pairing in the absence of any additional step attachment barriers. We explore the description of this behavior within an analytic Burton-Cabrera-Frank (BCF)-type step dynamics treatment. Without attachment barriers, conventional kinetic coefficients for the rough and smooth steps are identical, as are the predicted step velocities for a vicinal surface with equal terrace widths. However, we determine refined kinetic coefficients from a two-dimensional discrete deposition-diffusion equation formalism which accounts for stepmore » structure. These coefficients are generally higher for rough steps than for smooth steps, reflecting a higher propensity for capture of diffusing terrace adatoms due to a higher kink density. Such refined coefficients also depend on the local environment of the step and can even become negative (corresponding to net detachment despite an excess adatom density) for a smooth step in close proximity to a rough step. Incorporation of these refined kinetic coefficients into a BCF-type step dynamics treatment recovers quantitatively the mesoscale step-pairing behavior observed in the KMC simulations.« less

Reducing the influence of the surface roughness on the hardness measurement using instrumented indentation test

NASA Astrophysics Data System (ADS)

Maslenikov, I.; Useinov, A.; Birykov, A.; Reshetov, V.

2017-10-01

The instrumented indentation method requires the sample surface to be flat and smooth; thus, hardness and elastic modulus values are affected by the roughness. A model that accounts for the isotropic surface roughness and can be used to correct the data in two limiting cases is proposed. Suggested approach requires the surface roughness parameters to be known.

Role of Integrin Subunits in Mesenchymal Stem Cell Differentiation and Osteoblast Maturation on Graphitic Carbon-coated Microstructured Surfaces

PubMed Central

Olivares-Navarrete, Rene; Rodil, Sandra E.; Hyzy, Sharon L.; Dunn, Ginger R.; Almaguer-Flores, Argelia; Schwartz, Zvi; Boyan, Barbara D.

2015-01-01

Surface roughness, topography, chemistry, and energy promote osteoblast differentiation and increase osteogenic local factor production in vitro and bone-to-implant contact in vivo, but the mechanisms involved are not well understood. Knockdown of integrin heterodimer alpha2beta1 (α2β1) blocks the osteogenic effects of the surface, suggesting signaling by this integrin homodimer is required. The purpose of the present study was to separate effects of surface chemistry and surface structure on integrin expression by coating smooth or rough titanium (Ti) substrates with graphitic carbon, retaining surface morphology but altering surface chemistry. Ti surfaces (smooth [Ra<0.4μm], rough [Ra≥3.4μm]) were sputter-coated using a magnetron sputtering system with an ultrapure graphite target, producing a graphitic carbon thin film. Human mesenchymal stem cells and MG63 osteoblast-like cells had higher mRNA for integrin subunits α1, α2, αv, and β1 on rough surfaces in comparison to smooth, and integrin αv on graphitic-carbon-coated rough surfaces in comparison to Ti. Osteogenic differentiation was greater on rough surfaces in comparison to smooth, regardless of chemistry. Silencing integrins β1, α1, or α2 decreased osteoblast maturation on rough surfaces independent of surface chemistry. Silencing integrin αv decreased maturation only on graphitic carbon-coated surfaces, not on Ti. These results suggest a major role of the integrin β1 subunit in roughness recognition, and that integrin alpha subunits play a major role in surface chemistry recognition. PMID:25770999

Determination of the Wave Parameters from the Statistical Characteristics of the Image of a Linear Test Object

NASA Astrophysics Data System (ADS)

Weber, V. L.

2018-03-01

We statistically analyze the images of the objects of the "light-line" and "half-plane" types which are observed through a randomly irregular air-water interface. The expressions for the correlation function of fluctuations of the image of an object given in the form of a luminous half-plane are found. The possibility of determining the spatial and temporal correlation functions of the slopes of a rough water surface from these relationships is shown. The problem of the probability of intersection of a small arbitrarily oriented line segment by the contour image of a luminous straight line is solved. Using the results of solving this problem, we show the possibility of determining the values of the curvature variances of a rough water surface. A practical method for obtaining an image of a rectilinear luminous object in the light rays reflected from the rough surface is proposed. It is theoretically shown that such an object can be synthesized by temporal accumulation of the image of a point source of light rapidly moving in the horizontal plane with respect to the water surface.

Comparison of surface roughness and chip characteristics obtained under different modes of lubrication during hard turning of AISI H13 tool work steel.

NASA Astrophysics Data System (ADS)

Raj, Anil; Wins, K. Leo Dev; Varadarajan, A. S.

2016-09-01

Surface roughness is one of the important parameters, which not only affects the service life of a component but also serves as a good index of machinability. Near Dry Machining, methods (NDM) are considered as sustainable alternative for workshops trying to bring down their dependence on cutting fluids and the hazards associated with their indiscriminate usage. The present work presents a comparison of the surface roughness and chip characteristics during hard turning of AISI H13 tool work steel using hard metal inserts under two popular NDM techniques namely the minimal fluid application and the Minimum Quantity Lubrication technique(MQL) using an experiment designed based on Taguchi's techniques. The statistical method of analysis of variance (ANOVA) was used to determine the relative significance of input parameters consisting of cutting speed, feed and depth of cut on the attainable surface finish and the chip characteristics. It was observed that the performance during minimal fluid application was better than that during MQL application.

Au-nanoparticles grafted on plasma treated PE

NASA Astrophysics Data System (ADS)

Švorčík, V.; Chaloupka, A.; Řezanka, P.; Slepička, P.; Kolská, Z.; Kasálková, N.; Hubáček, T.; Siegel, J.

2010-03-01

Polyethylene (PE) surface was treated with Ar plasma. Activated surface was grafted from methanol solution of 1,2-ethanedithiol. Then the sample was immersed into freshly prepared colloid solution of Au-nanoparticles. Finally Au layer was sputtered on the samples. Properties of the modified PE were studied using various methods: AFM, EPR, RBS and nanoindentation. It was shown that the plasma treatment results in degradation of polymer chain (AFM) and creation of free radicals by EPR. After grafting with dithiol, the concentration of free radicals declines. The presence of Au and S in the surface layer after the coating with Au-nanoparticles was proved by RBS. Plasma treatment changes PE surface morphology and increases surface roughness, too. Another significant change in surface morphology and roughness was observed after deposition of Au-nanoparticles. Nanoindentation measurements show that the grafting with Au-nanoparticles increases adhesion of subsequently sputtered Au layer.

Character of the opposition effect and negative polarization

NASA Technical Reports Server (NTRS)

Pieters, Carle M.; Shkuratov, Yu. G.; Stankevich, D. G.

1991-01-01

Photometric and polarimetric properties at small phase angles were measured for silicates with controlled surface properties in order to distinguish properties that are associated with surface reflection from those that are associated with multiple scattering from internal grain boundaries. These data provide insight into the causes and conditions of photometric properties observed at small phase angles for dark bodies of the solar system. Obsidian was chosen to represent a silicate dielectric with no internal scattering boundaries. Because obsidian is free of internal scatterers, light reflected from both the rough and smooth obsidian samples is almost entirely single and multiple Fresnel reflections form surface facets with no body component. Surface structure alone cannot produce an opposition effect. Comparison of the obsidian and basalt results indicates that for an opposition effect to occur, surface texture must be both rough and contain internal scattering interfaces. Although the negative polarization observed for the obsidian samples indicates single and multiple reflections are part of negative polarization, the longer inversion angle of the multigrain inversion samples implies that internal reflections must also contribute a significant negative polarization component.

Effects of Surface Roughness on Conical Squeeze Film Bearings with Micropolar fluid

NASA Astrophysics Data System (ADS)

Rajani, C. B.; Hanumagowda, B. N.; Shigehalli, Vijayalaxmi S.

2018-04-01

In the current paper, a hypothetical analysis of the impact of surface roughness on squeeze film lubrication of rough conical bearing using Micropolar fluid is examined using Eringen’sMicropolar fluid model. The generalized averaged Reynolds type equation for roughness has been determined analytically using the Christensen’s stochastic theory of roughness effects and the closed form expressions are obtained for the fluid film pressure, load carrying capacity and squeezing time. Further, the impacts of surface roughness using micropolar fluids on the squeeze film lubrication of rough conical bearings has been discussed and according to the outcomes arrived, pressure, load carrying capacity and squeezing time increases for azimuthal roughness pattern and decreases for radial roughness patterns comparatively to the smooth case.

Generalizing roughness: experiments with flow-oriented roughness

NASA Astrophysics Data System (ADS)

Trevisani, Sebastiano

2015-04-01

Surface texture analysis applied to High Resolution Digital Terrain Models (HRDTMs) improves the capability to characterize fine-scale morphology and permits the derivation of useful morphometric indexes. An important indicator to be taken into account in surface texture analysis is surface roughness, which can have a discriminant role in the detection of different geomorphic processes and factors. The evaluation of surface roughness is generally performed considering it as an isotropic surface parameter (e.g., Cavalli, 2008; Grohmann, 2011). However, surface texture has often an anisotropic character, which means that surface roughness could change according to the considered direction. In some applications, for example involving surface flow processes, the anisotropy of roughness should be taken into account (e.g., Trevisani, 2012; Smith, 2014). Accordingly, we test the application of a flow-oriented directional measure of roughness, computed considering surface gravity-driven flow. For the calculation of flow-oriented roughness we use both classical variogram-based roughness (e.g., Herzfeld,1996; Atkinson, 2000) as well as an ad-hoc developed robust modification of variogram (i.e. MAD, Trevisani, 2014). The presented approach, based on a D8 algorithm, shows the potential impact of considering directionality in the calculation of roughness indexes. The use of flow-oriented roughness could improve the definition of effective proxies of impedance to flow. Preliminary results on the integration of directional roughness operators with morphometric-based models, are promising and can be extended to more complex approaches. Atkinson, P.M., Lewis, P., 2000. Geostatistical classification for remote sensing: an introduction. Computers & Geosciences 26, 361-371. Cavalli, M. & Marchi, L. 2008, "Characterization of the surface morphology of an alpine alluvial fan using airborne LiDAR", Natural Hazards and Earth System Science, vol. 8, no. 2, pp. 323-333. Grohmann, C.H., Smith, M.J., Riccomini, C., 2011. Multiscale Analysis of Topographic Surface Roughness in the Midland Valley, Scotland. IEEE Transactions on Geoscience and Remote Sensing 49, 1220-1213. Herzfeld, U.C., Higginson, C.A., 1996. Automated geostatistical seafloor classification - Principles, parameters, feature vectors, and discrimination criteria. Computers and Geosciences, 22 (1), pp. 35-52. Smith, M.W. 2014, "Roughness in the Earth Sciences", Earth-Science Reviews, vol. 136, pp. 202-225. Trevisani, S., Cavalli, M. & Marchi, L. 2012, "Surface texture analysis of a high-resolution DTM: Interpreting an alpine basin", Geomorphology, vol. 161-162, pp. 26-39. Trevisani S., Rocca M., 2014. Geomorphometric analysis of fine-scale morphology for extensive areas: a new surface-texture operator. Geophysical Research Abstracts, Vol. 16, EGU2014-5612, 2014. EGU General Assembly 2014.

Comparison of four methods of surface roughness assessment of corneal stromal bed after lamellar cutting

PubMed Central

Jumelle, Clotilde; Hamri, Alina; Egaud, Gregory; Mauclair, Cyril; Reynaud, Stephanie; Dumas, Virginie; Pereira, Sandrine; Garcin, Thibaud; Gain, Philippe; Thuret, Gilles

2017-01-01

Corneal lamellar cutting with a blade or femtosecond laser (FSL) is commonly used during refractive surgery and corneal grafts. Surface roughness of the cutting plane influences postoperative visual acuity but is difficult to assess reliably. For the first time, we compared chromatic confocal microscopy (CCM) with scanning electron microscopy, atomic force microscopy (AFM) and focus-variation microscopy (FVM) to characterize surfaces of variable roughness after FSL cutting. The small area allowed by AFM hinders conclusive roughness analysis, especially with irregular cuts. FVM does not always differentiate between smooth and rough surfaces. Finally, CCM allows analysis of large surfaces and differentiates between surface states. PMID:29188095

Analysis of multi lobe journal bearings with surface roughness using finite difference method

NASA Astrophysics Data System (ADS)

PhaniRaja Kumar, K.; Bhaskar, SUdaya; Manzoor Hussain, M.

2018-04-01

Multi lobe journal bearings are used for high operating speeds and high loads in machines. In this paper symmetrical multi lobe journal bearings are analyzed to find out the effect of surface roughnessduring non linear loading. Using the fourth order RungeKutta method, time transient analysis was performed to calculate and plot the journal centre trajectories. Flow factor method is used to evaluate the roughness and the finite difference method (FDM) is used to predict the pressure distribution over the bearing surface. The Transient analysis is done on the multi lobe journal bearings for threedifferent surface roughness orientations. Longitudinal surface roughness is more effective when compared with isotopic and traverse surface roughness.

Early Onset of Kinetic Roughening due to a Finite Step Width in Hematin Crystallization

NASA Astrophysics Data System (ADS)

Olafson, Katy N.; Rimer, Jeffrey D.; Vekilov, Peter G.

2017-11-01

The structure of the interface of a growing crystal with its nutrient phase largely determines the growth dynamics. We demonstrate that hematin crystals, crucial for the survival of malaria parasites, transition from faceted to rough growth interfaces at increasing thermodynamic supersaturation Δ μ . Contrary to theoretical predictions and previous observations, this transition occurs at moderate values of Δ μ . Moreover, surface roughness varies nonmonotonically with Δ μ , and the rate constant for rough growth is slower than that resulting from nucleation and spreading of layers. We attribute these unexpected behaviors to the dynamics of step growth dominated by surface diffusion and the loss of identity of nuclei separated by less than the step width w . We put forth a general criterion for the onset of kinetic roughening using w as a critical length scale.

Disinfection procedures: their efficacy and effect on dimensional accuracy and surface quality of an irreversible hydrocolloid impression material.

PubMed

Rentzia, A; Coleman, D C; O'Donnell, M J; Dowling, A H; O'Sullivan, M

2011-02-01

This study investigated the antibacterial efficacy and effect of 0.55% ortho-phthalaldehyde (Cidex OPA(®)) and 0.5% sodium hypochlorite (NaOCl) on the dimensional accuracy and surface quality of gypsum casts retrieved from an irreversible hydrocolloid impression material. A simulated clinical cast and technique was developed to compare the dimensional accuracy and surface quality changes of the test gypsum casts with controls. Dimensional accuracy measurements were completed between fixed points using a travelling microscope under low angle illumination at a magnification of ×3. Surface quality changes of "smooth" and "rough" areas on the cast were evaluated by means of optical profilometry. The efficacy of the disinfection procedures against Pseudomonas aeruginosa was evaluated by determining the number of colony forming units (cfu) recovered after disinfection of alginate discs inoculated with 1×10⁶cfu for defined intervals. The dimensional accuracy of the gypsum casts was not significantly affected by the disinfection protocols. Neither disinfectant solution nor immersion time had an effect on the surface roughness of the "smooth" area on the cast, however, a significant increase in surface roughness was observed with increasing immersion time for the "rough" surface. Complete elimination of viable Pseudomonas aeruginosa cells from alginate discs was obtained after 30 and 120 s immersion in Cidex OPA(®) and NaOCl, respectively. Immersion of irreversible hydrocolloid impressions in Cidex OPA(®) for 30 s was proved to be the most effective disinfection procedure. Copyright © 2010 Elsevier Ltd. All rights reserved.

Microwave radiation is effective at disinfecting dental stone surfaces without changing their physical properties.

PubMed

Bona, Ariel José; Amaral-Brito, Mauro Gustavo; Rodrigues, José Augusto; Peruzzo, Daiane Cristina; França, Fabiana Mantovani Gomes

2017-01-01

The aims of this study were to evaluate the effectiveness of different microwave radiation regimens for disinfection of type IV dental stone surfaces and to assess the influence of these regimens on surface roughness and dimensional change following disinfection. Three hundred cylindrical (20 × 2-mm) test specimens were made in type IV stone and divided into subgroups of 20 according to the microorganisms tested (Staphylococcus aureus, Escherichia coli, or Candida albicans) and the 900-W microwave radiation protocol (cycles of 3, 5, or 7 minutes; a positive control; or a negative control). To test physical changes, 80 test specimens were made with the same dimensions except that they had 2 parallel and symmetrical indentations measuring 8 × 4 mm. These specimens were divided into 4 subgroups of 20 each (a subgroup for each radiation time and a negative control). The mean dimensional change and roughness data were analyzed by mixed models for repeated measures and Tukey-Kramer tests. Disinfection was analyzed with descriptive statistics. For E coli and C albicans, all radiation times proved effective at sterilizing the test specimens. For S aureus, sterilization was achieved with 5 and 7 minutes of exposure; however, colonies were observed in 10 Petri dishes (50%) exposed to 3 minutes of microwave radiation. No statistically significant difference in dimensional change or surface roughness was observed for any radiation regimen (P > 0.05).

Pressure variation of developed lapping tool on surface roughness

NASA Astrophysics Data System (ADS)

Hussain, A. K.; Lee, K. Q.; Aung, L. M.; Abu, A.; Tan, L. K.; Kang, H. S.

2018-01-01

Improving the surface roughness is always one of the major concerns in the development of lapping process as high precision machining caters a great demand in manufacturing process. This paper aims to investigate the performance of a newly designed lapping tool in term of surface roughness. Polypropylene is used as the lapping tool head. The lapping tool is tested for different pressure to identify the optimum working pressure for lapping process. The theoretical surface roughness is also calculated using Vickers Hardness. The present study shows that polypropylene is able to produce good quality and smooth surface roughness. The optimum lapping pressure in the present study is found to be 45 MPa. By comparing the theoretical and experimental values, the present study shows that the newly designed lapping tool is capable to produce finer surface roughness.

Universal emulsion stabilization from the arrested adsorption of rough particles at liquid-liquid interfaces

PubMed Central

Zanini, Michele; Marschelke, Claudia; Anachkov, Svetoslav E.; Marini, Emanuele; Synytska, Alla; Isa, Lucio

2017-01-01

Surface heterogeneities, including roughness, significantly affect the adsorption, motion and interactions of particles at fluid interfaces. However, a systematic experimental study, linking surface roughness to particle wettability at a microscopic level, is currently missing. Here we synthesize a library of all-silica microparticles with uniform surface chemistry, but tuneable surface roughness and study their spontaneous adsorption at oil–water interfaces. We demonstrate that surface roughness strongly pins the particles' contact lines and arrests their adsorption in long-lived metastable positions, and we directly measure the roughness-induced interface deformations around isolated particles. Pinning imparts tremendous contact angle hysteresis, which can practically invert the particle wettability for sufficient roughness, irrespective of their chemical nature. As a unique consequence, the same rough particles stabilize both water-in-oil and oil-in-water emulsions depending on the phase they are initially dispersed in. These results both shed light on fundamental phenomena concerning particle adsorption at fluid interfaces and indicate future design rules for particle-based emulsifiers. PMID:28589932

Universal emulsion stabilization from the arrested adsorption of rough particles at liquid-liquid interfaces

NASA Astrophysics Data System (ADS)

Zanini, Michele; Marschelke, Claudia; Anachkov, Svetoslav E.; Marini, Emanuele; Synytska, Alla; Isa, Lucio

2017-06-01

Surface heterogeneities, including roughness, significantly affect the adsorption, motion and interactions of particles at fluid interfaces. However, a systematic experimental study, linking surface roughness to particle wettability at a microscopic level, is currently missing. Here we synthesize a library of all-silica microparticles with uniform surface chemistry, but tuneable surface roughness and study their spontaneous adsorption at oil-water interfaces. We demonstrate that surface roughness strongly pins the particles' contact lines and arrests their adsorption in long-lived metastable positions, and we directly measure the roughness-induced interface deformations around isolated particles. Pinning imparts tremendous contact angle hysteresis, which can practically invert the particle wettability for sufficient roughness, irrespective of their chemical nature. As a unique consequence, the same rough particles stabilize both water-in-oil and oil-in-water emulsions depending on the phase they are initially dispersed in. These results both shed light on fundamental phenomena concerning particle adsorption at fluid interfaces and indicate future design rules for particle-based emulsifiers.

Novel low-cost millimeter-wave system for road surface characterization

NASA Astrophysics Data System (ADS)

Busuioc, Dan; Anstey, Kyle; Rappaport, Carey; Birken, Ralf; Doughty, Jeffrey; Wang, Ming

2011-04-01

A novel low-cost low-complexity design based on Radar technology operating at millimeter wave is presented for the characterization of road surface conditions in real-time. At frequencies of 24-77 GHz the wavelength is long enough to obtain slight penetration in the top 1-2" of asphalt or concrete surface, but is also short enough to resolve details such as crack or pothole depth/etc. The Radar system operates by continuously outputting radiation and sampling the roadway-reflected radiation through a receiver-downconverter-sampler system. In initial laboratory testing, the received signal strength was observed to obey the inverse distance 1/R2 relationship. The received signal is further dependent on the incidence angle between the plane of the sensor and the plane of the roadway. One observation from this is the need of auxiliary sensors for determining the distance above the road surface as well as providing incident angle data. The sensor was further mounted on a movable cart used to measure the reflected signal on a variety of road surfaces (smooth, rough, surface defects, and environment factors such as various levels of moisture). By comparing measurements of the material after soaking to measurements in the dry state, there is substantial differentiation in measurements, which indicates the ability to measure the porosity of various materials. Lastly the sensor bandwidth provides the capability to measure surface roughness illustrated in the standard deviation of measurement data. On a macroscopic level, the aggregate in a roadway acts as a series of random scatterers and rough roadways or roadways with surface voids show a large variance between measurements of nearby points.

Effect of parameters on picosecond laser ablation of Cr12MoV cold work mold steel

NASA Astrophysics Data System (ADS)

Wu, Baoye; Liu, Peng; Zhang, Fei; Duan, Jun; Wang, Xizhao; Zeng, Xiaoyan

2018-01-01

Cr12MoV cold work mold steel, which is a difficult-to-machining material, is widely used in the mold and dye industry. A picosecond pulse Nd:YVO4 laser at 1064 nm was used to conduct the study. Effects of operation parameters (i.e., laser fluence, scanning speed, hatched space and number of scans) were studied on ablation depth and quality of Cr12MoV at the repetition rate of 20 MHz. The experimental results reveal that all the four parameters affect the ablation depth significantly. While the surface roughness depends mainly on laser fluence or scanning speed and secondarily on hatched space or number of scans. For laser fluence and scanning speed, three distinct surface morphologies were observed experiencing transition from flat (Ra < 1.40 μm) to bumpy (Ra = 1.40 - 2.40 μm) eventually to rough (Ra > 2.40 μm). However, for hatched space and number of scan, there is a small bumpy and rough zone or even no rough zone. Mechanisms including heat accumulation, plasma shielding and combustion reaction effects are proposed based on the ablation depth and processing morphology. By appropriate management of the laser fluence and scanning speed, high ablation depth with low surface roughness can be obtained at small hatched space and high number of scans.

Roughness Versus Charge Contributions to Representative Discrete Heterogeneity Underlying Mechanistic Prediction of Colloid Attachment, Detachment and Breakthrough-Elution Behavior Under Environmental Conditions.

NASA Astrophysics Data System (ADS)

Johnson, William; Farnsworth, Anna; Vanness, Kurt; Hilpert, Markus

2017-04-01

The key element of a mechanistic theory to predict colloid attachment in porous media under environmental conditions where colloid-collector repulsion exists (unfavorable conditions for attachment) is representation of the nano-scale surface heterogeneity (herein called discrete heterogeneity) that drives colloid attachment under unfavorable conditions. The observed modes of colloid attachment under unfavorable conditions emerge from simulations that incorporate discrete heterogeneity. Quantitative prediction of attachment (and detachment) requires capturing the sizes, spatial frequencies, and other properties of roughness asperities and charge heterodomains in discrete heterogeneity representations of different surfaces. The fact that a given discrete heterogeneity representation will interact differently with different-sized colloids as well as different ionic strengths for a given sized colloid allows backing out representative discrete heterogeneity via comparison of simulations to experiments performed across a range of colloid size, solution IS, and fluid velocity. This has been achieved on unfavorable smooth surfaces yielding quantitative prediction of attachment, and qualitative prediction of detachment in response to ionic strength or flow perturbations. Extending this treatment to rough surfaces, and representing the contributions of nanoscale roughness as well as charge heterogeneity is a focus of this talk. Another focus of this talk is the upscaling the pore scale simulations to produce contrasting breakthrough-elution behaviors at the continuum (column) scale that are observed, for example, for different-sized colloids, or same-sized colloids under different ionic strength conditions. The outcome of mechanistic pore scale simulations incorporating discrete heterogeneity and subsequent upscaling is that temporal processes such as blocking and ripening will emerge organically from these simulations, since these processes fundamentally stem from the limited sites available for attachment as represented in discrete heterogeneity.

Remote sensing of soil moisture content over bare fields at 1.4 GHz frequency

NASA Technical Reports Server (NTRS)

Wang, J. R.; Choudhury, B. J.

1980-01-01

A simple method of estimating moisture content (W) of a bare soil from the observed brightness temperature (T sub B) at 1.4 GHz is discussed. The method is based on a radiative transfer model calculation, which has been successfully used in the past to account for many observational results, with some modifications to take into account the effect of surface roughness. Besides the measured T sub B's, the three additional inputs required by the method are the effective soil thermodynamic temperature, the precise relation between W and the smooth field brightness temperature T sub B and a parameter specifying the surface roughness characteristics. The soil effective temperature can be readily measured and the procedures of estimating surface roughness parameter and obtaining the relation between W and smooth field brightness temperature are discussed in detail. Dual polarized radiometric measurements at an off-nadir incident angle are sufficient to estimate both surface roughness parameter and W, provided that the relation between W and smooth field brightness temperature at the same angle is known. The method of W estimate is demonstrated with two sets of experimental data, one from a controlled field experiment by a mobile tower and the other, from aircraft overflight. The results from both data sets are encouraging when the estimated W's are compared with the acquired ground truth of W's in the top 2 cm layer. An offset between the estimated and the measured W's exists in the results of the analyses, but that can be accounted for by the presently poor knowledge of the relationship between W and smooth field brightness temperature for various types of soils. An approach to quantify this relationship for different soils and thus improve the method of W estimate is suggested.

Sustaining dry surfaces under water

PubMed Central

Jones, Paul R.; Hao, Xiuqing; Cruz-Chu, Eduardo R.; Rykaczewski, Konrad; Nandy, Krishanu; Schutzius, Thomas M.; Varanasi, Kripa K.; Megaridis, Constantine M.; Walther, Jens H.; Koumoutsakos, Petros; Espinosa, Horacio D.; Patankar, Neelesh A.

2015-01-01

Rough surfaces immersed under water remain practically dry if the liquid-solid contact is on roughness peaks, while the roughness valleys are filled with gas. Mechanisms that prevent water from invading the valleys are well studied. However, to remain practically dry under water, additional mechanisms need consideration. This is because trapped gas (e.g. air) in the roughness valleys can dissolve into the water pool, leading to invasion. Additionally, water vapor can also occupy the roughness valleys of immersed surfaces. If water vapor condenses, that too leads to invasion. These effects have not been investigated, and are critically important to maintain surfaces dry under water. In this work, we identify the critical roughness scale, below which it is possible to sustain the vapor phase of water and/or trapped gases in roughness valleys – thus keeping the immersed surface dry. Theoretical predictions are consistent with molecular dynamics simulations and experiments. PMID:26282732

Membrane fouling in a submerged membrane bioreactor: An unified approach to construct topography and to evaluate interaction energy between two randomly rough surfaces.

PubMed

Cai, Xiang; Shen, Liguo; Zhang, Meijia; Chen, Jianrong; Hong, Huachang; Lin, Hongjun

2017-11-01

Quantitatively evaluating interaction energy between two randomly rough surfaces is the prerequisite to quantitatively understand and control membrane fouling in membrane bioreactors (MBRs). In this study, a new unified approach to construct rough topographies and to quantify interaction energy between a randomly rough particle and a randomly rough membrane was proposed. It was found that, natural rough topographies of both foulants and membrane could be well constructed by a modified two-variable Weierstrass-Mandelbrot (WM) function included in fractal theory. Spatial differential relationships between two constructed surfaces were accordingly established. Thereafter, a new approach combining these relationships, surface element integration (SEI) approach and composite Simpson's rule was deduced to calculate the interaction energy between two randomly rough surfaces in a submerged MBR. The obtained results indicate the profound effects of surface morphology on interaction energy and membrane fouling. This study provided a basic approach to investigate membrane fouling and interface behaviors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electromagnetic wave scattering from rough terrain

NASA Astrophysics Data System (ADS)

Papa, R. J.; Lennon, J. F.; Taylor, R. L.

1980-09-01

This report presents two aspects of a program designed to calculate electromagnetic scattering from rough terrain: (1) the use of statistical estimation techniques to determine topographic parameters and (2) the results of a single-roughness-scale scattering calculation based on those parameters, including comparison with experimental data. In the statistical part of the present calculation, digitized topographic maps are used to generate data bases for the required scattering cells. The application of estimation theory to the data leads to the specification of statistical parameters for each cell. The estimated parameters are then used in a hypothesis test to decide on a probability density function (PDF) that represents the height distribution in the cell. Initially, the formulation uses a single observation of the multivariate data. A subsequent approach involves multiple observations of the heights on a bivariate basis, and further refinements are being considered. The electromagnetic scattering analysis, the second topic, calculates the amount of specular and diffuse multipath power reaching a monopulse receiver from a pulsed beacon positioned over a rough Earth. The program allows for spatial inhomogeneities and multiple specular reflection points. The analysis of shadowing by the rough surface has been extended to the case where the surface heights are distributed exponentially. The calculated loss of boresight pointing accuracy attributable to diffuse multipath is then compared with the experimental results. The extent of the specular region, the use of localized height variations, and the effect of the azimuthal variation in power pattern are all assessed.

In situ evaluation of surface roughness and micromorphology of temporary soft denture liner materials at different time intervals.

PubMed

Araújo, Célio U; Basting, Roberta T

2018-03-01

To perform an in situ evaluation of surface roughness and micromorphology of two soft liner materials for dentures at different time intervals. The surface roughness of materials may influence the adhesion of micro-organisms and inflammation of the mucosal tissues. The in situ evaluation of surface roughness and the micromorphology of soft liner materials over the course of time may present results different from those of in vitro studies, considering the constant presence of saliva and food, the changes in temperature and the pH level in the oral cavity. Forty-eight rectangular specimens of each of the two soft liner materials were fabricated: a silicone-based material (Mucopren Soft) and an acrylic resin-based material (Trusoft). The specimens were placed in the dentures of 12 participants (n = 12), and the materials were evaluated for surface roughness and micromorphology at different time intervals: 0, 7, 30 and 60 days. Roughness (Ra) was evaluated by means of a roughness tester. Surface micromorphology was evaluated by scanning electron microscopy. Analysis of variance for randomised block design and Tukey's test showed that surface roughness values were lower in the groups using the silicone-based material at all the time intervals (P < .0001). The average surface roughness was higher at time interval 0 than at the other intervals, for both materials (P < .0001). The surface micromorphology showed that the silicone material presented a more regular and smoother surface than the acrylic resin-based material. The surface roughness of acrylic resin-based and silicone-based denture soft liner materials decreased after 7 days of evaluation, leading to a smoother surface over time. The silicone-based material showed lower roughness values and a smoother surface than the acrylic resin-based material, thereby making it preferred when selecting more appropriate material, due its tendency to promote less biofilm build-up. © 2017 John Wiley & Sons A/S and The Gerodontology Association. Published by John Wiley & Sons Ltd.

Hydrogen peroxide bleaching induces changes in the physical properties of dental restorative materials: Effects of study protocols.

PubMed

Yu, Hao; Zhang, Chang-Yuan; Wang, Yi-Ning; Cheng, Hui

2018-03-01

The purpose of this study was to evaluate the influence of study protocols on the effects of bleaching on the surface roughness, substance loss, flexural strength (FS), flexural modulus (FM), Weibull parameters, and color of 7 restorative materials. The test materials included 4 composite resins, 1 glass-ionomer cement, 1 dental ceramic, and 1 polyacid-modified composite. The specimens were randomly divided into 4 groups (n = 20) according to different study protocols: a bleaching group at 25°C (group 25B), a bleaching group at 37°C (group 37B), a control group at 25°C (group 25C), and a control group at 37°C (group 37C). The specimens in the bleaching group were treated with 40% hydrogen peroxide for 80 min at the respective environmental temperatures. The surface roughness, substance loss, FS, FM, and color of the specimens were measured before and after treatment. FS data were also subjected to Weibull analysis, which was used to estimate of the Weibull modulus (m) and the characteristic strength (σ 0 ). Surface roughness increased and significant color changes were observed for all tested specimens after bleaching treatment, except for the ceramic. After bleaching at 37°C, the polyacid-modified composite showed significantly reduced FS, FM, m, and σ 0 values in comparison to the control specimens stored at 37°C in whole saliva. Significant differences were also found between the 37B and 25B polyacid-modified composite groups in terms of surface roughness, FS, m, σ 0 , and color changes. Varying effects of bleaching on the physical properties of dental restorative materials were observed, and the influences of the study protocols on bleaching effects were found to be material-dependent. The influence of study protocols on the effects of bleaching on the surface roughness, flexural properties, and color of dental restorative materials are material-dependent and should be considered when evaluating the effects of bleaching on dental restorative materials. © 2017 Wiley Periodicals, Inc.

Effect of Finishing and Polishing on Roughness and Gloss of Lithium Disilicate and Lithium Silicate Zirconia Reinforced Glass Ceramic for CAD/CAM Systems.

PubMed

Vichi, A; Fonzar, R Fabian; Goracci, C; Carrabba, M; Ferrari, M

To assess the efficacy of dedicated finishing/polishing systems on roughness and gloss of VITA Suprinity and IPS e.max CAD. A total of 24 blocks of Suprinity and 24 of e.max were cut into a wedge shape using an InLab MC-XL milling unit. After crystallization, the 24 Suprinity wedges were divided into four subgroups: group A.1: Suprinity Polishing Set Clinical used for 30 seconds and group A.2: for 60 seconds; group A.3: VITA Akzent Plus Paste; and group A.4: spray. The 24 e.max wedges (group B) were divided into four subgroups according to the finishing procedure: group B.1: Optrafine Ceramic Polishing System for 30 seconds and group B.2: for 60 seconds; group B.3: IPS e.max CAD Crystall/Glaze paste; and group B.4: spray. After finishing/polishing, gloss was assessed with a glossmeter and roughness evaluated with a profilometer. Results were analyzed by applying a two-way analysis of variance for gloss and another for roughness (α=0.05). One specimen per each subgroup was observed with a scanning electron microscope. For roughness, materials and surface were significant factors ( p<0.001). Suprinity exhibited significantly lower roughness than e.max. Also the Material-Surface Treatment interaction was statistically significant ( p=0.026). For gloss, both material and surface treatment were significant factors ( p<0.001). VITA Suprinity showed significantly higher gloss than e.max. Also the Material-Surface Treatment interaction was statistically significant ( p<0.001). Manual finishing/polishing for 60 seconds and glazing paste are the most effective procedures in lowering the roughness of CAD/CAM silica-based glass ceramics. Manual finishing/polishing for 60 seconds allows milled silica-based glass ceramics to yield a higher gloss. VITA Suprinity displayed higher polishability than IPS e.max CAD.

Impact of Surface Roughness on AMSR-E Sea Ice Products

NASA Technical Reports Server (NTRS)

Stroeve, Julienne C.; Markus, Thorsten; Maslanik, James A.; Cavalieri, Donald J.; Gasiewski, Albin J.; Heinrichs, John F.; Holmgren, Jon; Perovich, Donald K.; Sturm, Matthew

2006-01-01

This paper examines the sensitivity of Advanced Microwave Scanning Radiometer (AMSR-E) brightness temperatures (Tbs) to surface roughness by a using radiative transfer model to simulate AMSR-E Tbs as a function of incidence angle at which the surface is viewed. The simulated Tbs are then used to examine the influence that surface roughness has on two operational sea ice algorithms, namely: 1) the National Aeronautics and Space Administration Team (NT) algorithm and 2) the enhanced NT algorithm, as well as the impact of roughness on the AMSR-E snow depth algorithm. Surface snow and ice data collected during the AMSR-Ice03 field campaign held in March 2003 near Barrow, AK, were used to force the radiative transfer model, and resultant modeled Tbs are compared with airborne passive microwave observations from the Polarimetric Scanning Radiometer. Results indicate that passive microwave Tbs are very sensitive even to small variations in incidence angle, which can cause either an over or underestimation of the true amount of sea ice in the pixel area viewed. For example, this paper showed that if the sea ice areas modeled in this paper mere assumed to be completely smooth, sea ice concentrations were underestimated by nearly 14% using the NT sea ice algorithm and by 7% using the enhanced NT algorithm. A comparison of polarization ratios (PRs) at 10.7,18.7, and 37 GHz indicates that each channel responds to different degrees of surface roughness and suggests that the PR at 10.7 GHz can be useful for identifying locations of heavily ridged or rubbled ice. Using the PR at 10.7 GHz to derive an "effective" viewing angle, which is used as a proxy for surface roughness, resulted in more accurate retrievals of sea ice concentration for both algorithms. The AMSR-E snow depth algorithm was found to be extremely sensitive to instrument calibration and sensor viewing angle, and it is concluded that more work is needed to investigate the sensitivity of the gradient ratio at 37 and 18.7 GHz to these factors to improve snow depth retrievals from spaceborne passive microwave sensors.

On the uniqueness of the receding contact angle: effects of substrate roughness and humidity on evaporation of water drops.

PubMed

Pittoni, Paola G; Lin, Chia-Hui; Yu, Teng-Shiang; Lin, Shi-Yow

2014-08-12

Could a unique receding contact angle be indicated for describing the wetting properties of a real gas-liquid-solid system? Could a receding contact angle be defined if the triple line of a sessile drop is not moving at all during the whole measurement process? To what extent is the receding contact angle influenced by the intrinsic properties of the system or the measurement procedures? In order to answer these questions, a systematic investigation was conducted in this study on the effects of substrate roughness and relative humidity on the behavior of pure water drops spreading and evaporating on polycarbonate (PC) surfaces characterized by different morphologies. Dynamic, advancing, and receding contact angles were found to be strongly affected by substrate roughness. Specifically, a receding contact angle could not be measured at all for drops evaporating on the more rugged PC surfaces, since the drops were observed strongly pinning to the substrate almost until their complete disappearance. Substrate roughness and system relative humidity were also found responsible for drastic changes in the depinning time (from ∼10 to ∼60 min). Thus, for measurement observations not sufficiently long, no movement of the triple line could be noted, with, again, the failure to find a receding contact angle. Therefore, to keep using concepts such as the receding contact angle as meaningful specifications of a given gas-liquid-solid system, the imperative to carefully investigate and report the inner characteristics of the system (substrate roughness, topography, impurities, defects, chemical properties, etc.) is pointed out in this study. The necessity of establishing methodological standards (drop size, measurement method, system history, observation interval, relative humidity, etc.) is also suggested.

Surface roughness analysis of fiber post conditioning processes.

PubMed

Mazzitelli, C; Ferrari, M; Toledano, M; Osorio, E; Monticelli, F; Osorio, R

2008-02-01

The chemo-mechanical surface treatment of fiber posts increases their bonding properties. The combined use of atomic force and confocal microscopy allows for the assessment and quantification of the changes on surface roughness that justify this behavior. Quartz fiber posts were conditioned with different chemicals, as well as by sandblasting, and by an industrial silicate/silane coating. We analyzed post surfaces by atomic force microscopy, recording average roughness (R(a)) measurements of fibers and resin matrix. A confocal image profiler allowed for the quantitative assessment of the average superficial roughness (R(a)). Hydrofluoric acid, potassium permanganate, sodium ethoxide, and sandblasting increased post surface roughness. Modifications of the epoxy resin matrix occurred after the surface pre-treatments. Hydrofluoric acid affected the superficial texture of quartz fibers. Surface-conditioning procedures that selectively react with the epoxy-resin matrix of the fiber post enhance roughness and improve the surface area available for adhesion by creating micro-retentive spaces without affecting the post's inner structure.

Influence of Surface Texture and Roughness of Softer and Harder Counter Materials on Friction During Sliding

NASA Astrophysics Data System (ADS)

Menezes, Pradeep L.; Kishore; Kailas, Satish V.; Lovell, Michael R.

2015-01-01

Surface texture influences friction during sliding contact conditions. In the present investigation, the effect of surface texture and roughness of softer and harder counter materials on friction during sliding was analyzed using an inclined scratch testing system. In the experiments, two test configurations, namely (a) steel balls against aluminum alloy flats of different surface textures and (b) aluminum alloy pins against steel flats of different surface textures, are utilized. The surface textures were classified into unidirectionally ground, 8-ground, and randomly polished. For a given texture, the roughness of the flat surfaces was varied using grinding or polishing methods. Optical profilometer and scanning electron microscope were used to characterize the contact surfaces before and after the experiments. Experimental results showed that the surface textures of both harder and softer materials are important in controlling the frictional behavior. The softer material surface textures showed larger variations in friction between ground and polished surfaces. However, the harder material surface textures demonstrated a better control over friction among the ground surfaces. Although the effect of roughness on friction was less significant when compared to textures, the harder material roughness showed better correlations when compared to the softer material roughness.

Effect of surface topographic features on the optical properties of skin: a phantom study

NASA Astrophysics Data System (ADS)

Liu, Guangli; Chen, Jianfeng; Zhao, Zuhua; Zhao, Gang; Dong, Erbao; Chu, Jiaru; Xu, Ronald X.

2016-10-01

Tissue-simulating phantoms are used to validate and calibrate optical imaging systems and to understand light transport in biological tissue. Light propagation in a strongly turbid medium such as skin tissue experiences multiple scattering and diffuse reflection from the surface. Surface roughness introduces phase shifts and optical path length differences for light which is scattered within the skin tissue and reflected from the surface. In this paper, we study the effect of mismatched surface roughness on optical measurement and subsequent determination of optical properties of skin tissue. A series of phantoms with controlled surface features and optical properties corresponding to normal human skin are fabricated. The fabrication of polydimethylsiloxane (PDMS) phantoms with known surface roughness follows a standard soft lithography process. Surface roughness of skin-simulating phantoms are measured with Bruker stylus profiler. The diffuse reflectance of the phantom is validated by a UV/VIS spectrophotometer. The results show that surface texture and roughness have considerable influence on the optical characteristics of skin. This study suggests that surface roughness should be considered as an important contributing factor for the determination of tissue optical properties.

The effect of toothbrush bristle stiffness on nanohybrid surface roughness

NASA Astrophysics Data System (ADS)

Zairani, O.; Irawan, B.; Damiyanti, M.

2017-08-01

The surface of a restoration can be affected by toothpaste containing abrasive agents and the stiffness of toothbrush bristles. Objective: To identify the effect of toothbrush bristle stiffness on nanohybrid surface roughness. Methods: Sixteen nanohybrid specimens were separated into two groups. The first group was brushed using soft-bristle toothbrushes, and the second group was brushed using medium-bristle toothbrushes. Media such as aqua bides was used for brushing in both groups. Brushing was done 3 times for 5 minutes. Surface roughness was measured initially and at 5, 10, and 15 minutes using a surface roughness tester. Results: The results, tested with One-Way ANOVA and Independent Samples t Test, demonstrated that after brushing for 15 minutes, the soft-bristle toothbrush group showed a significantly different value (p < 0.05) of nanohybrid surface roughness. The group using medium-bristle toothbrushes showed the value of nano hybrid surface roughness significant difference after brushing for 10 minutes. Conclusion: Roughness occurs more rapidly when brushing with medium-bristle tooth brushes than when brushing with soft-bristle toothbrushes.

The Backscattering Phase Function for a Sphere with a Two-Scale Relief of Rough Surface

NASA Astrophysics Data System (ADS)

Klass, E. V.

2017-12-01

The backscattering of light from spherical surfaces characterized by one and two-scale roughness reliefs has been investigated. The analysis is performed using the three-dimensional Monte-Carlo program POKS-RG (geometrical-optics approximation), which makes it possible to take into account the roughness of objects under study by introducing local geometries of different levels. The geometric module of the program is aimed at describing objects by equations of second-order surfaces. One-scale roughness is set as an ensemble of geometric figures (convex or concave halves of ellipsoids or cones). The two-scale roughness is modeled by convex halves of ellipsoids, with surface containing ellipsoidal pores. It is shown that a spherical surface with one-scale convex inhomogeneities has a flatter backscattering phase function than a surface with concave inhomogeneities (pores). For a sphere with two-scale roughness, the dependence of the backscattering intensity is found to be determined mostly by the lower-level inhomogeneities. The influence of roughness on the dependence of the backscattering from different spatial regions of spherical surface is analyzed.

Large-Eddy Simulations of Fully Developed Turbulent Channel and Pipe Flows with Smooth and Rough Walls

NASA Astrophysics Data System (ADS)

Saito, Namiko

Studies in turbulence often focus on two flow conditions, both of which occur frequently in real-world flows and are sought-after for their value in advancing turbulence theory. These are the high Reynolds number regime and the effect of wall surface roughness. In this dissertation, a Large-Eddy Simulation (LES) recreates both conditions over a wide range of Reynolds numbers Retau = O(102) - O(108) and accounts for roughness by locally modeling the statistical effects of near-wall anisotropic fine scales in a thin layer immediately above the rough surface. A subgrid, roughness-corrected wall model is introduced to dynamically transmit this modeled information from the wall to the outer LES, which uses a stretched-vortex subgrid-scale model operating in the bulk of the flow. Of primary interest is the Reynolds number and roughness dependence of these flows in terms of first and second order statistics. The LES is first applied to a fully turbulent uniformly-smooth/rough channel flow to capture the flow dynamics over smooth, transitionally rough and fully rough regimes. Results include a Moody-like diagram for the wall averaged friction factor, believed to be the first of its kind obtained from LES. Confirmation is found for experimentally observed logarithmic behavior in the normalized stream-wise turbulent intensities. Tight logarithmic collapse, scaled on the wall friction velocity, is found for smooth-wall flows when Re tau ≥ O(106) and in fully rough cases. Since the wall model operates locally and dynamically, the framework is used to investigate non-uniform roughness distribution cases in a channel, where the flow adjustments to sudden surface changes are investigated. Recovery of mean quantities and turbulent statistics after transitions are discussed qualitatively and quantitatively at various roughness and Reynolds number levels. The internal boundary layer, which is defined as the border between the flow affected by the new surface condition and the unaffected part, is computed, and a collapse of the profiles on a length scale containing the logarithm of friction Reynolds number is presented. Finally, we turn to the possibility of expanding the present framework to accommodate more general geometries. As a first step, the whole LES framework is modified for use in the curvilinear geometry of a fully-developed turbulent pipe flow, with implementation carried out in a spectral element solver capable of handling complex wall profiles. The friction factors have shown favorable agreement with the superpipe data, and the LES estimates of the Karman constant and additive constant of the log-law closely match values obtained from experiment.

The effect of cutting parameters on the performance of ZTA-MgO cutting tool

NASA Astrophysics Data System (ADS)

Ali, A. M.; Hamidon, N. E.; Zaki, N. K. M.; Mokhtar, S.; Azhar, A. Z. A.; Bahar, R.; Ahmad, Z. A.

2018-01-01

The effect of cutting parameters on the performances of ZTA-MgO ceramic cutting tool investigated. The aim of this project is to discover the effect of cutting speed and feedrate on the performance of the ZTA-MgO cutting tool via wear and surface roughness measurement. CNC turning machining performed using the cutting speed, Vc range from 354 to 471 m/min and the feed rate, f 0.1, 0.3 and 0.5 mm/rev while the depth of cut, d is kept constant at 0.2 mm. The flank wear, crater wear, and chipping were measured accordingly using optical microscope, Matlab programming and SEM. Surface roughness of machined stainless steel 316L surface were measured using the surface roughness tester (Mitutoyo MTR097-8. The result showing the increment trend of flank wear with increment of cutting speed and feed rate with the lowest value of flank wear, 0.061 mm achieved at Vc = 354 m/min and f = 0.1 mm/rev while the highest flank wear is 0.480 mm at Vc = 471 m/min and f = 0.5 mm/rev. The increasing pattern also observed in the crater wear results. The lowest area of crater wear is 2.2736 mm2 at Vc = 354 m/min and f = 0.1 mm/rev while the highest value is 4.8524 mm2 at Vc = 471 m/min and f = 0.5 mm/rev. As for the surface roughness, the higher the cutting speed, the lower the average roughness (Ra) value. Cutting speed, Vc = 471 m/min with f = 0.1 mm/rev has the lowest value of Ra which is 0.72µm.

Addressing scale dependence in roughness and morphometric statistics derived from point cloud data.

NASA Astrophysics Data System (ADS)

Buscombe, D.; Wheaton, J. M.; Hensleigh, J.; Grams, P. E.; Welcker, C. W.; Anderson, K.; Kaplinski, M. A.

2015-12-01

The heights of natural surfaces can be measured with such spatial density that almost the entire spectrum of physical roughness scales can be characterized, down to the morphological form and grain scales. With an ability to measure 'microtopography' comes a demand for analytical/computational tools for spatially explicit statistical characterization of surface roughness. Detrended standard deviation of surface heights is a popular means to create continuous maps of roughness from point cloud data, using moving windows and reporting window-centered statistics of variations from a trend surface. If 'roughness' is the statistical variation in the distribution of relief of a surface, then 'texture' is the frequency of change and spatial arrangement of roughness. The variance in surface height as a function of frequency obeys a power law. In consequence, roughness is dependent on the window size through which it is examined, which has a number of potential disadvantages: 1) the choice of window size becomes crucial, and obstructs comparisons between data; 2) if windows are large relative to multiple roughness scales, it is harder to discriminate between those scales; 3) if roughness is not scaled by the texture length scale, information on the spacing and clustering of roughness `elements' can be lost; and 4) such practice is not amenable to models describing the scattering of light and sound from rough natural surfaces. We discuss the relationship between roughness and texture. Some useful parameters which scale vertical roughness to characteristic horizontal length scales are suggested, with examples of bathymetric point clouds obtained using multibeam from two contrasting riverbeds, namely those of the Colorado River in Grand Canyon, and the Snake River in Hells Canyon. Such work, aside from automated texture characterization and texture segmentation, roughness and grain size calculation, might also be useful for feature detection and classification from point clouds.

ROV dives under Great Lakes ice

USGS Publications Warehouse

Bolsenga, S.J.; Gannon, John E.; Kennedy, Gregory; Norton, D.C.; Herdendorf, Charles E.

1989-01-01

Observations of the underside of ice have a wide variety of applications. Severe under-ice roughness can affect ice movements, rough under-ice surfaces can scour the bottom disturbing biota and man-made structures such as pipelines, and the flow rate of rivers is often affected by under-ice roughness. A few reported observations of the underside of an ice cover have been made, usually by cutting a large block of ice and overturning it, by extensive boring, or by remote sensing. Such operations are extremely labor-intensive and, in some cases, prone to inaccuracies. Remotely operated vehicles (ROV) can partially solve these problems. In this note, we describe the use, performance in a hostile environment, and results of a study in which a ROV was deployed under the ice in Lake Erie (North American Great Lakes).

Effects of intraoral aging of arch-wires on frictional forces: An ex vivo study.

PubMed

Kumar, Avinash; Khanam, Arifa; Ghafoor, Hajra

2016-01-01

Archwires act as gears to move teeth with light, continuous forces. However, the intraoral use of orthodontic archwires is liable to surface deposits which alter the mechanical properties of archwires, causing an increase in the friction coefficient. To evaluate the surface changes of the stainless steel archwires after 6 weeks of intraoral use and its influence on frictional resistance during sliding mechanics. As-received rectangular 0.019" × 0.025" stainless steel orthodontic archwires (control) were compared with the archwires retrieved after the final phase of leveling and alignment stage of orthodontic treatment collected after 6 weeks of intraoral exposure (test samples) from 10 patients undergoing treatment. The control and test samples were used to evaluate surface debris using Scanning Electron Microscopy, surface roughness was assessed using Atomic Force Microscope and frictional forces were measured using Instron Universal Testing Machine in the buccal inter-bracket region that slides through the molar tube for space closure. Unpaired t -test and Pearson correlation tests were used for statistical analysis ( P < 0.05 level of significance). Significant increase was observed in the level of debris ( P = 0.0001), surface roughness ( P = 0.0001), and friction resistance ( P = 0.001) of orthodontic archwires after their intraoral exposure. Significant positive correlations ( P < 0.05) were also observed between these three variables. Stainless steel test archwires showed a significant increase in the degree of debris and surface roughness, increasing the frictional forces between the archwire-bracket interfaces which would considerably reduce the normal orthodontic forces. Thus, continuing the same archwire after levelling and alignment for space closure is not recommended.

The importance of media roughness considerations for describing particle deposition in porous media

NASA Astrophysics Data System (ADS)

Jin, C.; Emelko, M.

2016-12-01

The morphology of media/collector surfaces (i.e., roughness) is one of the most important factors that has been recognized for decades; however, literature has been, for the most part, contradictory, non-mechanistic, and non-quantitative. A one-site kinetic model for attachment/detachment using a convection-diffusion model was used to evaluate particle deposition on collector surfaces in the packed beds. Rigorous controlled experiments addressing the impacts of surface roughness on particle deposition were conducted in parallel plate and packed bed systems; they demonstrated that a) surface roughness consistently influenced colloid deposition in a nonlinear, non-monotonic manner such that a critical roughness size associated with minimum particle deposition could be identified and b) collector surface roughness and background ionic strength concurrently influenced particle deposition. Excellent agreement between experimental data and numerical simulations was found when the most current knowledge representing hydrodynamic and interfacial forces associated with collector media roughness was represented. Although surface roughness also had a non-linear, non-monotonic impact on DLVO interaction energy at all separation distances, it was inadequate for describing and simulating particle deposition on surfaces with variable roughness. Notably, this work demonstrates that hydrodynamic effects can significantly alter particle deposition relative to expectations when only the DLVO force is considered. Moreover, the combined effects of hydrodynamics and interaction forces on particle deposition on rough, spherical media are not additive, but synergistic. Consideration of hydrodynamic contributions to particle deposition may help to explain discrepancies between model-based expectations and experimental outcomes and improve descriptions of particle deposition during physicochemical filtration in systems with non-smooth collector surfaces.

River discharge estimation from synthetic SWOT-type observations using variational data assimilation and the full Saint-Venant hydraulic model

NASA Astrophysics Data System (ADS)

Oubanas, Hind; Gejadze, Igor; Malaterre, Pierre-Olivier; Mercier, Franck

2018-04-01

The upcoming Surface Water and Ocean Topography satellite mission, to be launched in 2021, will measure river water surface elevation, slope and width, with an unprecedented level of accuracy for a remote sensing tool. This work investigates the river discharge estimation from synthetic SWOT observations, in the presence of strong uncertainties in the model inputs, i.e. the river bathymetry and bed roughness. The estimation problem is solved by a novel variant of the standard variational data assimilation, the '4D-Var' method, involving the full Saint-Venant 1.5D-network hydraulic model SIC2. The assimilation scheme simultaneously estimates the discharge, bed elevation and bed roughness coefficient and is designed to assimilate both satellite and in situ measurements. The method is tested on a 50 km-long reach of the Garonne River during a five-month period of the year 2010, characterized by multiple flooding events. First, the impact of the sampling frequency on discharge estimation is investigated. Secondly, discharge as well as the spatially distributed bed elevation and bed roughness coefficient are determined simultaneously. Results demonstrate feasibility and efficiency of the chosen combination of the estimation method and of the hydraulic model. Assimilation of the SWOT data results into an accurate estimation of the discharge at observation times, and a local improvement in the bed level and bed roughness coefficient. However, the latter estimates are not generally usable for different independent experiments.

Estimation of surface soil moisture and roughness from multi-angular ASAR imagery in the Watershed Allied Telemetry Experimental Research (WATER)

NASA Astrophysics Data System (ADS)

Wang, S. G.; Li, X.; Han, X. J.; Jin, R.

2010-06-01

Radar remote sensing has demonstrated its applicability to the retrieval of basin-scale soil moisture. The mechanism of radar backscattering from soils is complicated and strongly influenced by surface roughness. Furthermore, retrieval of soil moisture using AIEM-like models is a classic example of the underdetermined problem due to a lack of credible known soil roughness distributions at a regional scale. Characterization of this roughness is therefore crucial for an accurate derivation of soil moisture based on backscattering models. This study aims to directly obtain surface roughness information along with soil moisture from multi-angular ASAR images. The method first used a semi-empirical relationship that connects the roughness slope (Zs) and the difference in backscattering coefficient (Δσ) from ASAR data in different incidence angles, in combination with an optimal calibration form consisting of two roughness parameters (the standard deviation of surface height and the correlation length), to estimate the roughness parameters. The deduced surface roughness was then used in the AIEM model for the retrieval of soil moisture. An evaluation of the proposed method was performed in a grassland site in the middle stream of the Heihe River Basin, where the Watershed Allied Telemetry Experimental Research (WATER) was taken place. It has demonstrated that the method is feasible to achieve reliable estimation of soil water content. The key challenge to surface soil moisture retrieval is the presence of vegetation cover, which significantly impacts the estimates of surface roughness and soil moisture.

Soft X-ray multilayers produced by sputtering and molecular beam epitaxy (MBE) - Substrate and interfacial roughness

NASA Astrophysics Data System (ADS)

Kearney, Patrick A.; Slaughter, J. M.; Powers, K. D.; Falco, Charles M.

1988-01-01

Roughness measurements were made on uncoated silicon wafers and float glass using a WYKO TOPO-3D phase shifting interferometry, and the results are reported. The wafers are found to be slightly smoother than the flat glass. The effects of different cleaning methods and of the deposition of silicon 'buffer layers' on substrate roughness are examined. An acid cleaning method is described which gives more consistent results than detergent cleaning. Healing of the roughness due to sputtered silicon buffer layers was not observed on the length scale probed by the WYKO. Sputtered multilayers are characterized using both the WYKO interferometer and low-angle X-ray diffraction in order to yield information about the roughness of the top surface and of the multilayer interfaces. Preliminary results on film growth using molecular beam epitaxy are also presented.

Surface smoothening effects on growth of diamond films

NASA Astrophysics Data System (ADS)

Reshi, Bilal Ahmad; Kumar, Shyam; Kartha, Moses J.; Varma, Raghava

2018-04-01

We have carried out a detailed study of the growth dynamics of the diamond film during initial time on diamond substrates. The diamond films are deposited using Microwave Plasma Chemical Vapor Deposition (MPCVD) method for different times. Surface morphology and its correlation with the number of hours of growth of thin films was invested using atomic force microscopy (AFM). Diamond films have smooth interface with average roughness of 48.6873nm. The initial growth dynamics of the thin film is investigated. Interestingly, it is found that there is a decrease in the surface roughness of the film. Thus a smoothening effect is observed in the grown films. The film enters into the growth regime in the later times. Our results also find application in building diamond detector.

Modeling of surface roughness effects on Stokes flow in circular pipes

NASA Astrophysics Data System (ADS)

Song, Siyuan; Yang, Xiaohu; Xin, Fengxian; Lu, Tian Jian

2018-02-01

Fluid flow and pressure drop across a channel are significantly influenced by surface roughness on a channel wall. The present study investigates the effects of periodically structured surface roughness upon flow field and pressure drop in a circular pipe at low Reynolds numbers. The periodic roughness considered exhibits sinusoidal, triangular, and rectangular morphologies, with the relative roughness (i.e., ratio of the amplitude of surface roughness to hydraulic diameter of the pipe) no more than 0.2. Based upon a revised perturbation theory, a theoretical model is developed to quantify the effect of roughness on fully developed Stokes flow in the pipe. The ratio of static flow resistivity and the ratio of the Darcy friction factor between rough and smooth pipes are expressed in four-order approximate formulations, which are validated against numerical simulation results. The relative roughness and the wave number are identified as the two key parameters affecting the static flow resistivity and the Darcy friction factor.

Studies of SERS efficiency of gold coated porous silicon formed on rough silicon backside

NASA Astrophysics Data System (ADS)

Dridi, H.; Haji, L.; Moadhen, A.

2017-12-01

Starting from a rough backside of silicon wafer, we have formed a porous layer by electrochemical anodization and then coated by a thin film of gold. The morphological characteristics of the porous silicon and in turn the metal film are governed by the anodization process and also by the starting surface. So, in order to investigate the Plasmonic aspect of such rough surface which combines roughness inherent to the porous nature and that due to rough starting surface, we have used a dye target molecule to study its SERS signal using a porous silicon layer obtained on the rough backside surface. The use of unusual backside of silicon wafer could be, beside the others, an interesting way to made SERS effective substrate thanks to reproducible rough porous gold on porous layer from this starting face. The morphological results correspond to the silicon rough surface as a function of the crystallographic orientation showed the presence of two different substrate structure. The optical reflectivity results obtained of gold deposited on oxidized porous silicon showed a dependence of its Localized Surface Plasmon band frequency of the deposit time. SERS results, obtained for a dye target molecule (Rhodamine 6G), show a higher intensities in the case of the 〈110〉 orientation, which characterized by the higher roughness surface. Voici "the most relevant and important aspects of our work".

Mineral loss and morphological changes in dental enamel induced by a 16% carbamide peroxide bleaching gel.

PubMed

Soares, Diana Gabriela; Ribeiro, Ana Paula Dias; Sacono, Nancy Tomoko; Loguércio, Alessandro Dourado; Hebling, Josimeri; Costa, Carlos Alberto de Souza

2013-01-01

The aim of this study was to compare the effect of a 16% carbamide peroxide (CP) gel and a 10% CP gel on mineralized enamel content and morphology. Enamel blocks from bovine incisors were subjected to a 14-day treatment (8 h/day) with 10% or 16% CP gels. Knoop microhardness was evaluated before bleaching and at 1, 7 or 14 days after this treatment (50 g/15 s). Mineral content (energy-dispersive x-ray spectroscopy), surface roughness and topography (atomic force microscopy) were evaluated at the 14-day period. Data were analyzed statistically by two-way ANOVA and Tukey's test (α=0.05). Significant microhardness reduction was observed at the 7 th and 14 th days for 10% CP gel, and for all bleaching times for 16% CP gel (p<0.05). At the 14-day period, a significant decrease in Ca and P content, increase on surface roughness (p<0.05) as well as on picks and valleys distance were observed when both bleaching gels were used. These enamel alterations were more intense for 16% CP gel. It was concluded that both CP-based gels promoted loss of mineral structure from enamel, resulting in a rough and porous surface. However, 16% CP gel caused the most intense adverse effects on enamel.

In vivo surface roughness evolution of a stressed metallic implant

NASA Astrophysics Data System (ADS)

Tan, Henry

2016-10-01

Implant-associated infection, a serious medical issue, is caused by the adhesion of bacteria to the surface of biomaterials; for this process the surface roughness is an important property. Surface nanotopography of medical implant devices can control the extent of bacterial attachment by modifying the surface morphology; to this end a model is introduced to facilitate the analysis of a nanoscale smooth surface subject to mechanical loading and in vivo corrosion. At nanometre scale rough surface promotes friction, hence reduces the mobility of the bacteria; this sessile environment expedites the biofilm growth. This manuscript derives the controlling equation for surface roughness evolution for metallic implant subject to in-plane stresses, and predicts the in vivo roughness changes within 6 h of continued mechanical loading at different stress level. This paper provides analytic tool and theoretical information for surface nanotopography of medical implant devices.

Cu self-sputtering MD simulations for 0.1-5 keV ions at elevated temperatures

NASA Astrophysics Data System (ADS)

Metspalu, Tarvo; Jansson, Ville; Zadin, Vahur; Avchaciov, Konstantin; Nordlund, Kai; Aabloo, Alvo; Djurabekova, Flyura

2018-01-01

Self-sputtering of copper under high electric fields is considered to contribute to plasma buildup during a vacuum breakdown event frequently observed near metal surfaces, even in ultra high vacuum condition in different electric devices. In this study, by means of molecular dynamics simulations, we analyze the effect of surface temperature and morphology on the yield of self-sputtering of copper with ion energies of 0.1-5 keV. We analyze all three low-index surfaces of Cu, {1 0 0}, {1 1 0} and {1 1 1}, held at different temperatures, 300 K, 500 K and 1200 K. The surface roughness relief is studied by either varying the angle of incidence on flat surfaces, or by using arbitrary roughened surfaces, which result in a more natural distribution of surface relief variations. Our simulations provide detailed characterization of copper self-sputtering with respect to different material temperatures, crystallographic orientations, surface roughness, energies, and angles of ion incidence.

Study on micro fabricated stainless steel surface to anti-biofouling using electrochemical fabrication

NASA Astrophysics Data System (ADS)

Hwang, Byeong Jun; Lee, Sung Ho

2017-12-01

Biofilm formed on the surface of the object by the microorganism resulting in fouling organisms. This has led to many problems in daily life, medicine, health and industrial community. In this study, we tried to prevent biofilm formation on the stainless steel (SS304) sheet surface with micro fabricated structure. After then forming the microscale colloid patterns on the surface of stainless steel by using an electrochemical etching forming a pattern by using a FeCl3 etching was further increase the surface roughness. Culturing the Pseudomonas aeruginosa on the stainless steel fabricated with a micro structure on the surface was observed a relationship between the surface roughness and the biological fouling of the micro structure. As a result, the stainless steel surface with a micro structure was confirmed to be the biological fouling occurs less. We expect to be able to solve the problems caused by biological fouling in various fields such as medicine, engineering, using this research.

Arecibo radar observations of Mars surface characteristics in the Northern Hemisphere

NASA Technical Reports Server (NTRS)

Simpson, R. A.; Tyler, G. L.; Campbell, D. B.

1978-01-01

Mars surface characteristics at and near the Viking Chryse and Tritonis Lacus landing areas were determined by radio scatter using the 12.6-cm radar at the Arecibo Observatory during 1975-76. Interpretation of each power spectrum suggests rms surface tilts of 4 deg at the final A1WNW (47.9 deg W, 22.5 deg N) site, 5 deg near the original A1 site, and 6 deg between the two. At the back-up site (A2) surface-roughness estimates were about 4 deg. Striking changes in surface texture have been found near the eastern bases of Tharsis Montes and Albor Tholus, each volcanic feature marking the western boundary of very smooth surface units. The roughness sensed at 1- to 100-m scales by radar appears to be relatively independent of the surface units defined at large scale lengths by photogeologists. Radar properties thus provide an additional means by which planetary surfaces may be characterized.

A study of the interactions between glass-ionomer cement and S. sanguis biofilms

NASA Astrophysics Data System (ADS)

Hengtrakool, Chanotai

Glass-ionomer cements (GIC) have been used for dental procedures for many years and more recently in other medical applications such as bone cements, for bone reconstruction and also as drug release agents. The postulated caries-preventive activities of GIC are thought to result from their sealing ability, remineralization potential and antibacterial effects. Extensive 'in vitro' investigations have attempted to quantify these effects. In this study, an artificial mouth model, simulating 'in vivo' conditions at the tooth surface, was used to achieve a better understanding of the interaction of oral bacteria with the cements. This study investigated the interaction of Streptococcus sanguis, a common mouth commensal, with two glass-ionomer formulations (one containing fluoride and the other without fluoride ion) with particular reference to bacterial growth, changes in surface roughness and hardness of the glass-ionomer cement with respect to time. Restorative materials with rough surfaces will promote bacterial accumulation 'in vivo' and plaque formation is one factor in surface degradation. The constant depth film fermenter (CDFF) permits the examination of these phenomena and was used to investigate glass-ionomer/S. sanguis biofilm interaction over periods up to 14 days. In conjunction with these studies, surface roughness was measured using a 3-dimension laser profilometer and the surface hardness evaluated using a micro-indenter. Fluoride release from the cement was measured over 84 days. The results showed that autoclaving the CDFF prior to bacterial innoculate did not appear to affect the long-term fluoride release of the GIC. Laser profilometry revealed that the initial roughness and surface area of the GICs was significantly greater than the hydroxyapatite control. S. sanguis viable counts were significantly reduced for both glass-ionomer formulations in the shortterm, the greater reduction being with fluoride-GIC. S. sanguis biofilms produced similar hardness reduction on the surface of GIC:A to those observed with lactic acid pH 5 and artificial saliva whereas the effect on GIC:B was equivalent to that of lactic acid pH between 4 and 5. GICs showed changes in surface roughness after removal the biofilms. This indicates that while S. sanguis biofilm is affected by the GIC, there is also an increase in roughness of the cement indicating some degradation.

A comparison between measured surface microtopography and observed scattering in the extreme ultraviolet

NASA Technical Reports Server (NTRS)

Green, James; Jelinsky, Sharon; Bowyer, Stuart; Malina, Roger F.

1988-01-01

The paper presents comparative measurements of surface roughness on prepared samples. These measurements have been made with both Talystep profilometers and WYKO interferometers. In addition, the scattering distribution from these samples was measured at extreme ultraviolet wavelengths. The utility of the WYKO interferometer and Talystep device for specifying extreme ultraviolet mirror surface quality is discussed.

Frictional heating processes during laboratory earthquakes

NASA Astrophysics Data System (ADS)

Aubry, J.; Passelegue, F. X.; Deldicque, D.; Lahfid, A.; Girault, F.; Pinquier, Y.; Escartin, J.; Schubnel, A.

2017-12-01

Frictional heating during seismic slip plays a crucial role in the dynamic of earthquakes because it controls fault weakening. This study proposes (i) to image frictional heating combining an in-situ carbon thermometer and Raman microspectrometric mapping, (ii) to combine these observations with fault surface roughness and heat production, (iii) to estimate the mechanical energy dissipated during laboratory earthquakes. Laboratory earthquakes were performed in a triaxial oil loading press, at 45, 90 and 180 MPa of confining pressure by using saw-cut samples of Westerly granite. Initial topography of the fault surface was +/- 30 microns. We use a carbon layer as a local temperature tracer on the fault plane and a type K thermocouple to measure temperature approximately 6mm away from the fault surface. The thermocouple measures the bulk temperature of the fault plane while the in-situ carbon thermometer images the temperature production heterogeneity at the micro-scale. Raman microspectrometry on amorphous carbon patch allowed mapping the temperature heterogeneities on the fault surface after sliding overlaid over a few micrometers to the final fault roughness. The maximum temperature achieved during laboratory earthquakes remains high for all experiments but generally increases with the confining pressure. In addition, the melted surface of fault during seismic slip increases drastically with confining pressure. While melting is systematically observed, the strength drop increases with confining pressure. These results suggest that the dynamic friction coefficient is a function of the area of the fault melted during stick-slip. Using the thermocouple, we inverted the heat dissipated during each event. We show that for rough faults under low confining pressure, less than 20% of the total mechanical work is dissipated into heat. The ratio of frictional heating vs. total mechanical work decreases with cumulated slip (i.e. number of events), and decreases with increasing confining pressure and normal stress. Our results suggest that earthquakes are less dispersive under large normal stress. We linked this observation with fault roughness heterogeneity, which also decreases with applied normal stress. Keywords: Frictional heating, stick-slip, carbon, dynamic rupture, fault weakening.

Calculations of microwave brightness temperature of rough soil surfaces: Bare field

NASA Technical Reports Server (NTRS)

Mo, T.; Schmugge, T. J.; Wang, J. R.

1985-01-01

A model for simulating the brightness temperatures of soils with rough surfaces is developed. The surface emissivity of the soil media is obtained by the integration of the bistatic scattering coefficients for rough surfaces. The roughness of a soil surface is characterized by two parameters, the surface height standard deviation sigma and its horizontal correlation length l. The model calculations are compared to the measured angular variations of the polarized brightness temperatures at both 1.4 GHz and 5 GHz frequences. A nonlinear least-squares fitting method is used to obtain the values of delta and l that best characterize the surface roughness. The effect of shadowing is incorporated by introducing a function S(theta), which represents the probability that a point on a rough surface is not shadowed by other parts of the surface. The model results for the horizontal polarization are in excellent agreement with the data. However, for the vertical polarization, some discrepancies exist between the calculations and data, particularly at the 1.4 GHz frequency. Possible causes of the discrepancy are discussed.

Quantification of soil surface roughness evolution under simulated rainfall

USDA-ARS?s Scientific Manuscript database

Soil surface roughness is commonly identified as one of the dominant factors governing runoff and interrill erosion. The objective of this study was to compare several existing soil surface roughness indices and to test the Revised Triangular Prism surface area Method (RTPM) as a new approach to cal...

Effect of surface roughness on osteogenesis in vitro and osseointegration in vivo of carbon fiber-reinforced polyetheretherketone–nanohydroxyapatite composite

PubMed Central

Deng, Yi; Liu, Xiaochen; Xu, Anxiu; Wang, Lixin; Luo, Zuyuan; Zheng, Yunfei; Deng, Feng; Wei, Jie; Tang, Zhihui; Wei, Shicheng

2015-01-01

As United States Food and Drug Administration-approved implantable material, carbon fiber-reinforced polyetheretherketone (CFRPEEK) possesses an adjustable elastic modulus similar to cortical bone and is a prime candidate to replace surgical metallic implants. The bioinertness and inferior osteogenic properties of CFRPEEK, however, limit its clinical application as orthopedic/dental implants. In this study, CFRPEEK–nanohydroxyapatite ternary composites (PEEK/n-HA/CF) with variable surface roughness have been successfully fabricated. The effect of surface roughness on their in vitro cellular responses of osteoblast-like MG-63 cells (attachment, proliferation, apoptosis, and differentiation) and in vivo osseointegration is evaluated. The results show that the hydrophilicity and the amount of Ca ions on the surface are significantly improved as the surface roughness of composite increases. In cell culture tests, the results reveal that the cell proliferation rate and the extent of osteogenic differentiation of cells are a function of the size of surface roughness. The composite with moderate surface roughness significantly increases cell attachment/proliferation and promotes the production of alkaline phosphatase (ALP) activity and calcium nodule formation compared with the other groups. More importantly, the PEEK/n-HA/CF implant with appropriate surface roughness exhibits remarkably enhanced bioactivity and osseointegration in vivo in the animal experiment. These findings will provide critical guidance for the design of CFRPEEK-based implants with optimal roughness to regulate cellular behaviors, and to enhance biocompability and osseointegration. Meanwhile, the PEEK/n-HA/CF ternary composite with optimal surface roughness might hold great potential as bioactive biomaterial for bone grafting and tissue engineering applications. PMID:25733834

The physics of water droplets on surfaces: exploring the effects of roughness and surface chemistry

NASA Astrophysics Data System (ADS)

Eid, K. F.; Panth, M.; Sommers, A. D.

2018-03-01

This paper explores the fluid property commonly called surface tension, its effect on droplet shape and contact angle, and the major influences of contact angle behaviour (i.e. surface roughness and surface chemistry). Images of water droplets placed on treated copper surfaces are used to measure the contact angles between the droplets and the surface. The surface wettability is manipulated either by growing a self-assembled monolayer on the surface to make it hydrophobic or by changing the surface roughness. The main activities in this experiment, then, are (1) preparing and studying surfaces with different surface wettability and roughness; (2) determining the shape and contact angles of water droplets on these surfaces; and (3) demonstrating the spontaneous motion of water droplets using surface tension gradients.

Comparative histomorphometry and resonance frequency analysis of implants with moderately rough surfaces in a loaded animal model.

PubMed

Al-Nawas, B; Groetz, K A; Goetz, H; Duschner, H; Wagner, W

2008-01-01

Test of favourable conditions for osseointegration with respect to optimum bone-implant contact (BIC) in a loaded animal model. The varied parameters were surface roughness and surface topography of commercially available dental implants. Thirty-two implants of six types of macro and microstructure were included in the study (total 196). The different types were: minimally rough control: Branemark machined Mk III; oxidized surface: TiUnite MkIII and MkIV; ZL Ticer; blasted and etched surface: Straumann SLA; rough control: titanium plasma sprayed (TPS). Sixteen beagle dogs were implanted with the whole set of the above implants. After a healing period of 8 weeks, implants were loaded for 3 months. For the evaluation of the BIC areas, adequately sectioned biopsies were visualized by subsurface scans with confocal laser scanning microscopy (CLSM). The primary statistical analysis testing BIC of the moderately rough implants (mean 56.1+/-13.0%) vs. the minimally rough and the rough controls (mean 53.9+/-11.2%) does not reveal a significant difference (P=0.57). Mean values of 50-70% BIC were found for all implant types. Moderately rough oxidized implants show a median BIC, which is 8% higher than their minimally rough turned counterpart. The intraindividual difference between the TPS and the blasted and etched counterparts revealed no significant difference. The turned and the oxidized implants show median values of the resonance frequency [implant stability quotients (ISQ)] over 60; the nonself-tapping blasted and etched and TPS implants show median values below 60. In conclusion, the benefit of rough surfaces relative to minimally rough ones in this loaded animal model was confirmed histologically. The comparison of different surface treatment modalities revealed no significant differences between the modern moderately rough surfaces. Resonance frequency analysis seems to be influenced in a major part by the transducer used, thus prohibiting the comparison of different implant systems.

The Budget of Turbulent Kinetic Energy in the Urban Roughness Sublayer

NASA Astrophysics Data System (ADS)

Christen, Andreas; Rotach, Mathias W.; Vogt, Roland

2009-05-01

Full-scale observations from two urban sites in Basel, Switzerland were analysed to identify the magnitude of different processes that create, relocate, and dissipate turbulent kinetic energy (TKE) in the urban atmosphere. Two towers equipped with a profile of six ultrasonic anemometers each sampled the flow in the urban roughness sublayer, i.e. from street canyon base up to roughly 2.5 times the mean building height. This observational study suggests a conceptual division of the urban roughness sublayer into three layers: (1) the layer above the highest roofs, where local buoyancy production and local shear production of TKE are counterbalanced by local viscous dissipation rate and scaled turbulence statistics are close to to surface-layer values; (2) the layer around mean building height with a distinct inflexional mean wind profile, a strong shear and wake production of TKE, a more efficient turbulent exchange of momentum, and a notable export of TKE by transport processes; (3) the lower street canyon with imported TKE by transport processes and negligible local production. Averaged integral velocity variances vary significantly with height in the urban roughness sublayer and reflect the driving processes that create or relocate TKE at a particular height. The observed profiles of the terms of the TKE budget and the velocity variances show many similarities to observations within and above vegetation canopies.

Theory connecting nonlocal sediment transport, earth surface roughness, and the Sadler effect

NASA Astrophysics Data System (ADS)

Schumer, Rina; Taloni, Alessandro; Furbish, David Jon

2017-03-01

Earth surface evolution, like many natural phenomena typified by fluctuations on a wide range of scales and deterministic smoothing, results in a statistically rough surface. We present theory demonstrating that scaling exponents of topographic and stratigraphic statistics arise from long-time averaging of noisy surface evolution rather than specific landscape evolution processes. This is demonstrated through use of "elastic" Langevin equations that generically describe disturbance from a flat earth surface using a noise term that is smoothed deterministically via sediment transport. When smoothing due to transport is a local process, the geologic record self organizes such that a specific Sadler effect and topographic power spectral density (PSD) emerge. Variations in PSD slope reflect the presence or absence and character of nonlocality of sediment transport. The range of observed stratigraphic Sadler slopes captures the same smoothing feature combined with the presence of long-range spatial correlation in topographic disturbance.

Effect of Polishing Systems on Surface Roughness and Topography of Monolithic Zirconia.

PubMed

Goo, C L; Yap, Auj; Tan, Kbc; Fawzy, A S

2016-01-01

This study evaluated the effect of different chairside polishing systems on the surface roughness and topography of monolithic zirconia. Thirty-five monolithic zirconia specimens (Lava PLUS, 3M ESPE) were fabricated and divided into five groups of seven and polished with the following: Group 1 (WZ)-Dura white stone followed by Shofu zirconia polishing kit; Group 2 (SZ)-Shofu zirconia polishing kit; Group 3 (CE)-Ceramiste porcelain polishers; Group 4 (CM)-Ceramaster porcelain polishers; and Group 5 (KZ)-Komet ZR zirconia polishers. All specimens were ground with a fine-grit diamond bur prior to polishing procedures to simulate clinical finishing. Baseline and post-polishing profilometric readings were recorded and delta Ra values (difference in mean surface roughness before and after polishing) were computed and analyzed using one-way analysis of variance and Scheffe post hoc test (p<0.05). Representative scanning electron microscopy (SEM) images of the ground but unpolished and polished specimens were acquired. Delta Ra values ranged from 0.146 for CE to 0.400 for KZ. Delta Ra values for KZ, WZ, and SZ were significantly greater than for CE. Significant differences in delta Ra values were also observed between KZ and CM. The SEM images obtained were consistent with the profilometric findings. Diamond-impregnated polishing systems were more effective than silica carbide-impregnated ones in reducing the surface roughness of ground monolithic zirconia.

The effect of multiple autoclave cycles on the surface of rotary nickel-titanium endodontic files: An in vitro atomic force microscopy investigation

PubMed Central

Nair, Ashish Shashikant; Tilakchand, Mahima; Naik, Balaram Damodar

2015-01-01

Aims: To observe and study the effect of multiple autoclave sterilization cycles, on the surface of nickel-titanium (NiTi) files. Materials and Methods: The file used for this study was the Mtwo file (VDW) and ProTaper (Dentsply). The apical 5 mm of the files were attached to a silicon wafer and subjected to autoclave cycles under standardized conditions. They were scanned with an AFM after 1, 5, and 10 cycles. The unsterilized files were used as control, before start of the study. Three vertical topographic parameters namely maximum height (MH), root mean square (RMS) of surface roughness, and arithmetic mean roughness (AMR)were measured with the atomic force microscope (AFM). Analysis of variance along with Tukey's test was used to test the differences. Results: The vertical topographic parameters were higher for both the files, right after the first cycle, when compared with the control (P < 0.01). The surface roughness increased sharply for Mtwo when compared to ProTaper, though ProTaper had a rougher surface initially. Conclusions: The study confirmed that the irregularities present on the surface of the file became more prominent with multiple autoclave cycles, a fact that should be kept in mind during their reuse. PMID:26069408

The effect of multiple autoclave cycles on the surface of rotary nickel-titanium endodontic files: An in vitro atomic force microscopy investigation.

PubMed

Nair, Ashish Shashikant; Tilakchand, Mahima; Naik, Balaram Damodar

2015-01-01

To observe and study the effect of multiple autoclave sterilization cycles, on the surface of nickel-titanium (NiTi) files. The file used for this study was the Mtwo file (VDW) and ProTaper (Dentsply). The apical 5 mm of the files were attached to a silicon wafer and subjected to autoclave cycles under standardized conditions. They were scanned with an AFM after 1, 5, and 10 cycles. The unsterilized files were used as control, before start of the study. Three vertical topographic parameters namely maximum height (MH), root mean square (RMS) of surface roughness, and arithmetic mean roughness (AMR)were measured with the atomic force microscope (AFM). Analysis of variance along with Tukey's test was used to test the differences. The vertical topographic parameters were higher for both the files, right after the first cycle, when compared with the control (P < 0.01). The surface roughness increased sharply for Mtwo when compared to ProTaper, though ProTaper had a rougher surface initially. The study confirmed that the irregularities present on the surface of the file became more prominent with multiple autoclave cycles, a fact that should be kept in mind during their reuse.

The effect of brushing with nano calcium carbonate and calcium carbonate toothpaste on the surface roughness of nano-ionomer

NASA Astrophysics Data System (ADS)

Anisja, D. H.; Indrani, D. J.; Herda, E.

2017-08-01

Nanotechnology developments in dentistry have resulted in the development of nano-ionomer, a new restorative material. The surface roughness of restorative materials can increase bacteria adhesion and lead to poor oral hygiene. Abrasive agents in toothpaste can alter tooth and restorative material surfaces. The aim of this study is to identify the effect of brushing with nano calcium carbonate, and calcium carbonate toothpaste on surface roughness of nano-ionomer. Eighteen nano-ionomer specimens were brushed with Aquabidest (doubledistilled water), nano calcium carbonate and calcium carbonate toothpaste. Brushing lasted 30 minutes, and the roughness value (Ra) was measured after each 10 minute segment using a surface roughness tester. The data was analyzed using repeated ANOVA and one-way ANOVA test. The value of nano-ionomer surface roughness increased significantly (p<0.05) after 20 minutes of brushing with the nano calcium carbonate toothpaste. Brushing with calcium carbonate toothpaste leaves nano-ionomer surfaces more rugged than brushing with nano calcium carbonate toothpaste.

Influence of surface roughness and waviness on film thickness and pressure distribution in elastohydrodynamic contacts

NASA Technical Reports Server (NTRS)

Chow, L. S. H.; Cheng, H. S.

1976-01-01

The Christensen theory of a stochastic model for hydrodynamic lubrication of rough surfaces was extended to elastohydrodynamic lubrication between two rollers. Solutions for the reduced pressure at the entrance as a function of the ratio of the average nominal film thickness to the rms surface roughness, were obtained numerically. Results were obtained for purely transverse as well as purely longitudinal surface roughness for cases with or without slip. The reduced pressure was shown to decrease slightly by considering longitudinal surface roughness. The same approach was used to study the effect of surface roughness on lubrication between rigid rollers and lubrication of an infinitely wide slider bearing. Using the flow balance concept, the perturbed Reynolds equation, was derived and solved for the perturbed pressure distribution. In addition, Cheng's numerical scheme was modified to incorporate a single two-dimensional elastic asperity on the stationary surface. The perturbed pressures obtained by these three different models were compared.

A study examining the effects of water-miscible cutting fluids for end milling process of carbon fiber reinforced plastic

NASA Astrophysics Data System (ADS)

Anan, Ruito; Matsuoka, Hironori; Ono, Hajime; Ryu, Takahiro; Nakae, Takashi; Shuto, Schuichi; Watanabe, Suguru; Sato, Yuta

2017-04-01

This study examined the improvements to the tool life and finished surface roughness by using water-miscible cutting fluids in carbon fiber reinforced plastics end milling. In cutting tests, it was found that the use of emulsion type, soluble type, and solution type cutting fluids improved tool life compared with the case of dry cutting. Specifically, significant differences in tool life were observed at a high cutting speed of 171 m/min. In addition, the finished surface exhibited a low level of roughness when the solution type cutting fluid was used, regardless of the cutting speed.

Nanoscale Roughness of Faults Explained by the Scale-Dependent Yield Stress of Geologic Materials

NASA Astrophysics Data System (ADS)

Thom, C.; Brodsky, E. E.; Carpick, R. W.; Goldsby, D. L.; Pharr, G.; Oliver, W.

2017-12-01

Despite significant differences in their lithologies and slip histories, natural fault surfaces exhibit remarkably similar scale-dependent roughness over lateral length scales spanning 7 orders of magnitude, from microns to tens of meters. Recent work has suggested that a scale-dependent yield stress may result in such a characteristic roughness, but experimental evidence in favor of this hypothesis has been lacking. We employ an atomic force microscope (AFM) operating in intermittent-contact mode to map the topography of the Corona Heights fault surface. Our experiments demonstrate that the Corona Heights fault exhibits isotropic self-affine roughness with a Hurst exponent of 0.75 +/- 0.05 at all wavelengths from 60 nm to 10 μm. If yield stress controls roughness, then the roughness data predict that yield strength varies with length scale as λ-0.25 +/ 0.05. To test the relationship between roughness and yield stress, we conducted nanoindentation tests on the same Corona Heights sample and a sample of the Yair Fault, a carbonate fault surface that has been previously characterized by AFM. A diamond Berkovich indenter tip was used to indent the samples at a nominally constant strain rate (defined as the loading rate divided by the load) of 0.2 s-1. The continuous stiffness method (CSM) was used to measure the indentation hardness (which is proportional to yield stress) and the elastic modulus of the sample as a function of depth in each test. For both samples, the yield stress decreases with increasing size of the indents, a behavior consistent with that observed for many engineering materials and recently for other geologic materials such as olivine. The magnitude of this "indentation size effect" is best described by a power-law with exponents of -0.12 +/- 0.06 and -0.18 +/- 0.08 for the Corona Heights and Yair Faults, respectively. These results demonstrate a link between surface roughness and yield stress, and suggest that fault geometry is the physical manifestation of a scale-dependent yield stress.

Influence of the three-dimensional heterogeneous roughness on electrokinetic transport in microchannels.

PubMed

Hu, Yandong; Werner, Carsten; Li, Dongqing

2004-12-15

Surface roughness has been considered as a passive means of enhancing species mixing in electroosmotic flow through microfluidic systems. It is highly desirable to understand the synergetic effect of three-dimensional (3D) roughness and surface heterogeneity on the electrokinetic flow through microchannels. In this study, we developed a three-dimensional finite-volume-based numerical model to simulate electroosmotic transport in a slit microchannel (formed between two parallel plates) with numerous heterogeneous prismatic roughness elements arranged symmetrically and asymmetrically on the microchannel walls. We consider that all 3D prismatic rough elements have the same surface charge or zeta potential, the substrate (the microchannel wall) surface has a different zeta potential. The results showed that the rough channel's geometry and the electroosmotic mobility ratio of the roughness elements' surface to that of the substrate, epsilon(mu), have a dramatic influence on the induced-pressure field, the electroosmotic flow patterns, and the electroosmotic flow rate in the heterogeneous rough microchannels. The associated sample-species transport presents a tidal-wave-like concentration field at the intersection between four neighboring rough elements under low epsilon(mu) values and has a concentration field similar to that of the smooth channels under high epsilon(mu) values.

Prediction of an internal boundary layer on a flat plate after a step change in roughness using a near-wall RANS model

NASA Astrophysics Data System (ADS)

Chu, Minghan; Meng, Fanxiao; Bergstrom, Donald J.

2017-11-01

An in-house computational fluid dynamics code was used to simulate turbulent flow over a flat plate with a step change in roughness, exhibiting a smooth-rough-smooth configuration. An internal boundary layer (IBL) is formed at the transition from the smooth to rough (SR) and then the rough to smooth (RS) surfaces. For an IBL the flow far above the surface has experienced a wall shear stress that is different from the local value. Within a Reynolds-Averaged-Navier-Stokes (RANS) formulation, the two-layer k- ɛ model of Durbin et al. (2001) was implemented to analyze the response of the flow to the change in surface condition. The numerical results are compared to experimental data, including some in-house measurements and the seminal work of Antonia and Luxton (1971,72). This problem captures some aspects of roughness in industrial and environmental applications, such as corrosion and the earth's surface heterogeneity, where the roughness is often encountered as discrete distributions. It illustrates the challenge of incorporating roughness models in RANS that are capable of responding to complex surface roughness profiles.

Effect of Shot Peening in Different Shot Distance and Shot Angle on Surface Morphology, Surface Roughness and Surface Hardness of 316L Biomaterial

NASA Astrophysics Data System (ADS)

Umbu Kondi Maliwemu, Erich; Malau, Viktor; Iswanto, Priyo Tri

2018-01-01

Shot peening is a mechanical surface treatment with a beneficial effect to generate compressive residual stress caused by plastic deformation on the surface of material. This plastic deformation can improve the surface characteristics of metallic materials, such as modification of surface morphology, surface roughness, and surface hardness. The objective of this study is to investigate the effect of shot peening in different shot distance and shot angle on surface morphology, surface roughness, and surface hardness of 316L biomaterial. Shot distance was varied at 6, 8, 10, and 12 cm and shot angle at 30, 60, and 90°, working pressure at 7 kg/cm2, shot duration for 20 minutes, and using steel balls S-170 with diameter of 0.6 mm. The results present that the shot distance and shot angle of shot peening give the significant effect to improve the surface morphology, surface roughness, and surface hardness of 316 L biomaterial. Shot peening can increase the surface roughness by the increasing of shot distance and by the decreasing of shot angle. The nearest shot distance (6 cm) and the largest shot angle (90°) give the best results on the grain refinement with the surface roughness of 1.04 μm and surface hardness of 534 kg/mm2.

Light-induced V{sub oc} increase and decrease in high-efficiency amorphous silicon solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stuckelberger, M., E-mail: michael.stuckelberger@epfl.ch; Riesen, Y.; Despeisse, M.

High-efficiency amorphous silicon (a-Si:H) solar cells were deposited with different thicknesses of the p-type amorphous silicon carbide layer on substrates of varying roughness. We observed a light-induced open-circuit voltage (V{sub oc}) increase upon light soaking for thin p-layers, but a decrease for thick p-layers. Further, the V{sub oc} increase is enhanced with increasing substrate roughness. After correction of the p-layer thickness for the increased surface area of rough substrates, we can exclude varying the effective p-layer thickness as the cause of the substrate roughness dependence. Instead, we explain the observations by an increase of the dangling-bond density in both themore » p-layer—causing a V{sub oc} increase—and in the intrinsic absorber layer, causing a V{sub oc} decrease. We present a mechanism for the light-induced increase and decrease, justified by the investigation of light-induced changes of the p-layer and supported by Advanced Semiconductor Analysis simulation. We conclude that a shift of the electron quasi-Fermi level towards the conduction band is the reason for the observed V{sub oc} enhancements, and poor amorphous silicon quality on rough substrates enhances this effect.« less

Surface roughness mediated adhesion forces between borosilicate glass and gram-positive bacteria.

PubMed

Preedy, Emily; Perni, Stefano; Nipiĉ, Damijan; Bohinc, Klemen; Prokopovich, Polina

2014-08-12

It is well-known that a number of surface characteristics affect the extent of adhesion between two adjacent materials. One of such parameters is the surface roughness as surface asperities at the nanoscale level govern the overall adhesive forces. For example, the extent of bacterial adhesion is determined by the surface topography; also, once a bacteria colonizes a surface, proliferation of that species will take place and a biofilm may form, increasing the resistance of bacterial cells to removal. In this study, borosilicate glass was employed with varying surface roughness and coated with bovine serum albumin (BSA) in order to replicate the protein layer that covers orthopedic devices on implantation. As roughness is a scale-dependent process, relevant scan areas were analyzed using atomic force microscope (AFM) to determine Ra; furthermore, appropriate bacterial species were attached to the tip to measure the adhesion forces between cells and substrates. The bacterial species chosen (Staphylococci and Streptococci) are common pathogens associated with a number of implant related infections that are detrimental to the biomedical devices and patients. Correlation between adhesion forces and surface roughness (Ra) was generally better when the surface roughness was measured through scanned areas with size (2 × 2 μm) comparable to bacteria cells. Furthermore, the BSA coating altered the surface roughness without correlation with the initial values of such parameter; therefore, better correlations were found between adhesion forces and BSA-coated surfaces when actual surface roughness was used instead of the initial (nominal) values. It was also found that BSA induced a more hydrophilic and electron donor characteristic to the surfaces; in agreement with increasing adhesion forces of hydrophilic bacteria (as determined through microbial adhesion to solvents test) on BSA-coated substrates.

Effect of two in-office whitening agents on the enamel surface in vivo: a morphological and non-contact profilometric study.

PubMed

Cadenaro, Milena; Breschi, Lorenzo; Nucci, Cesare; Antoniolli, Francesca; Visintini, Erika; Prati, Carlo; Matis, Bruce A; Di Lenarda, Roberto

2008-01-01

This study evaluated the morphological effects produced in vivo by two in-office bleaching agents on enamel surface roughness using a noncontact profilometric analysis of epoxy replicas. The null hypothesis tested was that there would be no difference in the micromorphology of the enamel surface during or after bleaching with two different bleaching agents. Eighteen subjects were selected and randomly assigned to two treatment groups (n=9). The tooth whitening materials tested were 38% hydrogen peroxide (HP) (Opalescence Xtra Boost) and 35% carbamide peroxide (CP) (Rembrandt Quik Start). The bleaching agents were applied in accordance with manufacturer protocols. The treatments were repeated four times at one-week intervals. High precision impressions of the upper right incisor were taken at baseline as the control (CTRL) and after each bleaching treatment (T0: first application, T1: second application at one week, T2: third application at two weeks and T3: fourth application at three weeks). Epoxy resin replicas were poured from impressions, and the surface roughness was analyzed by means of a non-contact profilometer (Talysurf CLI 1000). Epoxy replicas were then observed using SEM. All data were statistically analyzed using ANOVA and differences were determined with a t-test. No significant differences in surface roughness were found on enamel replicas using either 38% hydrogen peroxide or 35% carbamide peroxide in vivo. This in vivo study supports the null hypothesis that two in-office bleaching agents, with either a high concentration of hydrogen or carbamide peroxide, do not alter enamel surface roughness, even after multiple applications.

The relationship among sea surface roughness variations, oceanographic analyses, and airborne remote sensing analyses

NASA Technical Reports Server (NTRS)

Oertel, G. F.; Wade, T. L.

1981-01-01

The synthetic aperture radar (SAR) was studied to determine whether it could image large scale estuaries and oceanic features such as fronts and to explain the electromagnetic interaction between SAR and the individual surface front features. Fronts were observed to occur at the entrance to the Chesapeake Bay. The airborne measurements consisted of data collection by SAR onboard an F-4 aircraft and real aperture side looking radar (SLAR) in Mohawk aircraft. A total of 89 transects were flown. Surface roughness and color as well as temperature and salinity were evaluated. Cross-frontal surveys were made. Frontal shear and convergence flow were obtained. Surface active organic materials, it was indicated, are present at the air-sea interface. In all, 2000 analyses were conducted to characterize the spatial and temporal variabilities associated with water mass boundaries.

Microwave remote sensing of snowpacks

NASA Technical Reports Server (NTRS)

Stiles, W. H.; Ulaby, F. T.

1980-01-01

The interaction mechanisms responsible for the microwave backscattering and emission behavior of snow were investigated, and models were developed relating the backscattering coefficient (sigma) and apparent temperature (T) to the physical parameters of the snowpack. The microwave responses to snow wetness, snow water equivalent, snow surface roughness, and to diurnal variations were investigated. Snow wetness was shown to have an increasing effect with increasing frequency and angle of incidence for both active and passive cases. Increasing snow wetness was observed to decrease the magnitude sigma and increase T. Snow water equivalent was also observed to exhibit a significant influence sigma and T. Snow surface configuration (roughness) was observed to be significant only for wet snow surface conditions. Diurnal variations were as large as 15 dB for sigma at 35 GHz and 120 K for T at 37 GHz. Simple models for sigma and T of a snowpack scene were developed in terms of the most significant ground-truth parameters. The coefficients for these models were then evaluated; the fits to the sigma and T measurements were generally good. Finally, areas of needed additional observations were outlined and experiments were specified to further the understanding of the microwave-snowpack interaction mechanisms.

Wetting failure of hydrophilic surfaces promoted by surface roughness

PubMed Central

Zhao, Meng-Hua; Chen, Xiao-Peng; Wang, Qing

2014-01-01

Wetting failure is of vital importance to many physical phenomena, such as industrial coating and drop emission. Here we show when and how the surface roughness promotes the destabilization of a moving contact line on a hydrophilic surface. Beyond the balance of the driving force and viscous resistance where a stable wetting interface is sustained, wetting failure occurs and is modified by the roughness of the surface. The promoting effect arises only when the wetting velocity is high enough to create a gas-liquid-solid composite interface in the vicinity of the moving contact line, and it is a function of the intrinsic contact angle and proportion of solid tops. We propose a model to explain splashes of rough solid spheres impacting into liquids. It reveals a novel concept that dynamic wetting on hydrophilic rough surfaces can be similar to that on hydrophobic surfaces, and brings a new way to design surfaces with specific wetting properties. PMID:24948390

Comparison of Predicted and Measured Turbine Vane Rough Surface Heat Transfer

NASA Technical Reports Server (NTRS)

Boyle, R. J.; Spuckler, C. M.; Lucci, B. L.

2000-01-01

The proposed paper compares predicted turbine vane heat transfer for a rough surface over a wide range of test conditions with experimental data. Predictions were made for the entire vane surface. However, measurements were made only over the suction surface of the vane, and the leading edge region of the pressure surface. Comparisons are shown for a wide range of test conditions. Inlet pressures varied between 3 and 15 psia, and exit Mach numbers ranged between 0.3 and 0.9. Thus, while a single roughened vane was used for the tests, the effective rougness,(k(sup +)), varied by more than a factor of ten. Results were obtained for freestream turbulence levels of 1 and 10%. Heat transfer predictions were obtained using the Navier-Stokes computer code RVCQ3D. Two turbulence models, suitable for rough surface analysis, are incorporated in this code. The Cebeci-Chang roughness model is part of the algebraic turbulence model. The k-omega turbulence model accounts for the effect of roughness in the application of the boundary condition. Roughness causes turbulent flow over the vane surface. Even after accounting for transition, surface roughness significantly increased heat transfer compared to a smooth surface. The k-omega results agreed better with the data than the Cebeci-Chang model. However, the low Reynolds number k-omega model did not accurately account for roughness when the freestream turbulence level was low. The high Reynolds number version of this model was more suitable when the freestream turbulence was low.

Study on Surface Roughness of Modified Silicon Carbide Mirrors polished by Magnetorheological Finishing

NASA Astrophysics Data System (ADS)

Du, Hang; Song, Ci; Li, Shengyi

2018-01-01

In order to obtain high precision and high surface quality silicon carbide mirrors, the silicon carbide mirror substrate is subjected to surface modification treatment. In this paper, the problem of Silicon Carbide (SiC) mirror surface roughness deterioration by MRF is studied. The reasons of surface flaws of “Comet tail” are analyzed. Influence principle of MRF polishing depth and the surface roughness of modified SiC mirrors is obtained by experiments. On this basis, the united process of modified SiC mirrors is proposed which is combined MRF with the small grinding head CCOS. The united process makes improvement in the surface accuracy and surface roughness of modified SiC mirrors.

Study on Plastic Deformation Characteristics of Shot Peening of Ni-Based Superalloy GH4079

NASA Astrophysics Data System (ADS)

Zhong, L. Q.; Liang, Y. L.; Hu, H.

2017-09-01

In this paper, the X-ray stress diffractometer, surface roughness tester, field emission scanning electron microscope(SEM), dynamic ultra-small microhardness tester were used to measure the surface residual stress and roughness, topography and surface hardness changes of GH4079 superalloy, which was processed by metallographic grinding, turning, metallographic grinding +shot peening and turning + shot peening. Analysized the effects of shot peening parameters on shot peening plastic deformation features; and the effects of the surface state before shot peening on shot peening plastic deformation characteristics. Results show that: the surface residual compressive stress, surface roughness and surface hardness of GH4079 superalloy were increased by shot peening, in addition, the increment of the surface residual compressive stress, surface roughness and surface hardness induced by shot peening increased with increasing shot peening intensity, shot peening time, shot peening pressure and shot hardness, but harden layer depth was not affected considerably. The more plastic deformation degree of before shot peening surface state, the less increment of the surface residual compressive stress, surface roughness and surface hardness induced by shot peening.

Characterization, modeling and simulation of fused deposition modeling fabricated part surfaces

NASA Astrophysics Data System (ADS)

Taufik, Mohammad; Jain, Prashant K.

2017-12-01

Surface roughness is generally used for characterization, modeling and simulation of fused deposition modeling (FDM) fabricated part surfaces. But the average surface roughness is not able to provide the insight of surface characteristics with sharp peaks and deep valleys. It deals in the average sense for all types of surfaces, including FDM fabricated surfaces with distinct surface profile features. The present research work shows that kurtosis and skewness can be used for characterization, modeling and simulation of FDM surfaces because these roughness parameters have the ability to characterize a surface with sharp peaks and deep valleys. It can be critical in certain application areas in tribology and biomedicine, where the surface profile plays an important role. Thus, in this study along with surface roughness, skewness and kurtosis are considered to show a novel strategy to provide new transferable knowledge about FDM fabricated part surfaces. The results suggest that the surface roughness, skewness and kurtosis are significantly different at 0° and in the range (0°, 30°], [30°, 90°] of build orientation.

Spin Hall effect originated from fractal surface

NASA Astrophysics Data System (ADS)

Hajzadeh, I.; Mohseni, S. M.; Movahed, S. M. S.; Jafari, G. R.

2018-05-01

The spin Hall effect (SHE) has shown promising impact in the field of spintronics and magnonics from fundamental and practical points of view. This effect originates from several mechanisms of spin scatterers based on spin–orbit coupling (SOC) and also can be manipulated through the surface roughness. Here, the effect of correlated surface roughness on the SHE in metallic thin films with small SOC is investigated theoretically. Toward this, the self-affine fractal surface in the framework of the Born approximation is exploited. The surface roughness is described by the k-correlation model and is characterized by the roughness exponent H , the in-plane correlation length ξ and the rms roughness amplitude δ. It is found that the spin Hall angle in metallic thin film increases by two orders of magnitude when H decreases from H  =  1 to H  =  0. In addition, the source of SHE for surface roughness with Gaussian profile distribution function is found to be mainly the side jump scattering while that with a non-Gaussian profile suggests both of the side jump and skew scatterings are present. Our achievements address how details of the surface roughness profile can adjust the SHE in non-heavy metals.

Characterizing near-surface firn using the scattered signal component of the glacier surface return from airborne radio-echo sounding

NASA Astrophysics Data System (ADS)

Rutishauser, Anja; Grima, Cyril; Sharp, Martin; Blankenship, Donald D.; Young, Duncan A.; Cawkwell, Fiona; Dowdeswell, Julian A.

2016-12-01

We derive the scattered component (hereafter referred to as the incoherent component) of glacier surface echoes from airborne radio-echo sounding measurements over Devon Ice Cap, Arctic Canada, and compare the scattering distribution to firn stratigraphy observations from ground-based radar data. Low scattering correlates to laterally homogeneous firn above 1800 m elevation containing thin, flat, and continuous ice layers and below 1200 m elevation where firn predominantly consists of ice. Increased scattering between elevations of 1200-1800 m corresponds to firn with inhomogeneous, undulating ice layers. No correlation was found to surface roughness and its theoretical incoherent backscattering values. This indicates that the scattering component is mainly influenced by the near-surface firn stratigraphy, whereas surface roughness effects are minor. Our results suggest that analyzing the scattered signal component of glacier surface echoes is a promising approach to characterize the spatial heterogeneity of firn that is affected by melting and refreezing processes.

Rough surface reconstruction for ultrasonic NDE simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Wonjae; Shi, Fan; Lowe, Michael J. S.

2014-02-18

The reflection of ultrasound from rough surfaces is an important topic for the NDE of safety-critical components, such as pressure-containing components in power stations. The specular reflection from a rough surface of a defect is normally lower than it would be from a flat surface, so it is typical to apply a safety factor in order that justification cases for inspection planning are conservative. The study of the statistics of the rough surfaces that might be expected in candidate defects according to materials and loading, and the reflections from them, can be useful to develop arguments for realistic safety factors.more » This paper presents a study of real rough crack surfaces that are representative of the potential defects in pressure-containing power plant. Two-dimensional (area) values of the height of the roughness have been measured and their statistics analysed. Then a means to reconstruct model cases with similar statistics, so as to enable the creation of multiple realistic realizations of the surfaces, has been investigated, using random field theory. Rough surfaces are reconstructed, based on a real surface, and results for these two-dimensional descriptions of the original surface have been compared with those from the conventional model based on a one-dimensional correlation coefficient function. In addition, ultrasonic reflections from them are simulated using a finite element method.« less

Relationships between aerodynamic roughness and land use and land cover in Baltimore, Maryland

USGS Publications Warehouse

Nicholas, F.W.; Lewis, J.E.

1980-01-01

Urbanization changes the radiative, thermal, hydrologic, and aerodynamic properties of the Earth's surface. Knowledge of these surface characteristics, therefore, is essential to urban climate analysis. Aerodynamic or surface roughness of urban areas is not well documented, however, because of practical constraints in measuring the wind profile in the presence of large buildings. Using an empirical method designed by Lettau, and an analysis of variance of surface roughness values calculated for 324 samples averaging 0.8 hectare (ha) of land use and land cover sample in Baltimore, Md., a strong statistical relation was found between aerodynamic roughness and urban land use and land cover types. Assessment of three land use and land cover systems indicates that some of these types have significantly different surface roughness characteristics. The tests further indicate that statistically significant differences exist in estimated surface roughness values when categories (classes) from different land use and land cover classification systems are used as surrogates. A Level III extension of the U.S. Geological Survey Level II land use and land cover classification system provided the most reliable results. An evaluation of the physical association between the aerodynamic properties of land use and land cover and the surface climate by numerical simulation of the surface energy balance indicates that changes in surface roughness within the range of values typical of the Level III categories induce important changes in the surface climate.

Surface treatment of dental porcelain: CO2 laser as an alternative to oven glaze.

PubMed

Sgura, Ricardo; Reis, Mariana Cavalcante; Hernandes, Antonio Carlos; de Abreu Fantini, Márcia Carvalho; Andreeta, Marcello Rubens Barsi; Medeiros, Igor Studart

2015-02-01

This work tested continuous CO2 laser as a surface treatment to dental porcelain and compared it to oven glaze (auto-glaze) by means of roughness and color parameters. Three commercial veneering porcelains with different crystalline content were tested: VM7, VM9, and VM13. Porcelain discs (3.5 × 2.0 mm, diameter × height) were sintered and had one side ground by a diamond bur (45 μm) simulating a chairside adjustment in a clinical office. Specimens (n = 7) were divided into the following groups: C--control (no treatment), G--auto-glaze (oven), and L--surface continuous irradiation with CO2 laser (Gem Laser, Coherent; λ = 10.6 μm). Laser was tested in three exposure times (3, 4, or 5 min) and two irradiances (45 and 50 W/cm(2)). Roughness parameters (Ra, Rz, and Rpm/Rz) were measured using a rugosimeter (Surftest 301, Mitutoyo). Color differences (ΔE) between the G and L groups were calculated (VITA Easyshade); ΔE values up to 3.3 were considered as not perceivable. A surface analysis was conducted by stereomicroscopy (Olympus SZ61) and SEM (Stereoscan 440, LEO). Crystalline content of specimens from groups C and L (50 W/cm(2), 5 min) was assessed by X-ray diffraction and then compared. Surface roughness (Ra and Rz) observed for laser-irradiated groups was similar to G for all studied porcelains. Rpm/Rz ratios were near 1.0 for all groups that indicated a sharp ridge profile for all specimens. Only one laser condition studied (50 W/cm(2), 3 min) from VM7 porcelain resulted in color difference (ΔE = 3.5) to G. Specimens irradiated with 50 W/cm(2) for 5 min presented the smoother surface observed by SEM, comparable to G. X-ray diffraction data revealed an increase in leucite crystallite size for VM9 and VM13 porcelains after laser treatment. Regarding roughness, continuous CO2 laser applied on porcelain surface was as effective as conventional oven auto-glaze.

Direct numerical simulation of flow over dissimilar, randomly distributed roughness elements: A systematic study on the effect of surface morphology on turbulence

NASA Astrophysics Data System (ADS)

Forooghi, Pourya; Stroh, Alexander; Schlatter, Philipp; Frohnapfel, Bettina

2018-04-01

Direct numerical simulations are used to investigate turbulent flow in rough channels, in which topographical parameters of the rough wall are systematically varied at a fixed friction Reynolds number of 500, based on a mean channel half-height h and friction velocity. The utilized roughness generation approach allows independent variation of moments of the surface height probability distribution function [thus root-mean-square (rms) surface height, skewness, and kurtosis], surface mean slope, and standard deviation of the roughness peak sizes. Particular attention is paid to the effect of the parameter Δ defined as the normalized height difference between the highest and lowest roughness peaks. This parameter is used to understand the trends of the investigated flow variables with departure from the idealized case where all roughness elements have the same height (Δ =0 ). All calculations are done in the fully rough regime and for surfaces with high slope (effective slope equal to 0.6-0.9). The rms roughness height is fixed for all cases at 0.045 h and the skewness and kurtosis of the surface height probability density function vary in the ranges -0.33 to 0.67 and 1.9 to 2.6, respectively. The goal of the paper is twofold: first, to investigate the possible effect of topographical parameters on the mean turbulent flow, Reynolds, and dispersive stresses particularly in the vicinity of the roughness crest, and second, to investigate the possibility of using the wall-normal turbulence intensity as a physical parameter for parametrization of the flow. Such a possibility, already suggested for regular roughness in the literature, is here extended to irregular roughness.

STS-55 Earth observation of the Timor Sea

NASA Technical Reports Server (NTRS)

1993-01-01

STS-55 Earth observation taken from Columbia, Orbiter Vehicle (OV) 102, shows the Timor Sea along the south coast of Timor. The sunglint pattern shows a sharp boundary in sea surface temperature, with cooler water along the coast and warmer water offshore. The sunglint brightness reveals water surface roughness with bright indicating smooth water and dark representing rough water. Cooler water is smoother because it acts to stabilize the atmospheric boundary layer, while the warm water acts to destabilize the atmosphere. Another indication of water temperature is the cloud pattern. Advection within the atmosphere as a result of warming at the sea surface forms low-level clouds with the small, popcorn-like appearance seen in upper right corner of the photograph. The cool water, on the other hand, is relatively free of the popcorn-like clouds. The distribution of the clouds indicates that the wind is blowing toward the upper right corner of the photograph. Also note the line of low-level

Microwave emission measurements of sea surface roughness, soil moisture, and sea ice structure

NASA Technical Reports Server (NTRS)

Gloersen, P.; Wilheit, T. T.; Schmugge, T. J.

1972-01-01

In order to demonstrate the feasibility of the microwave radiometers to be carried aboard the Nimbus 5 and 6 satellites and proposed for one of the earth observatory satellites, remote measurements of microwave radiation at wavelengths ranging from 0.8 to 21 cm have been made of a variety of the earth's surfaces from the NASA CV-990 A/C. Brightness temperatures of sea water surfaces of varying roughness, of terrain with varying soil moisture, and of sea ice of varying structure were observed. In each case, around truth information was available for correlation with the microwave brightness temperature. The utility of passive microwave radiometry in determining ocean surface wind speeds, at least for values higher than 7 meters/second has been demonstrated. In addition, it was shown that radiometric signatures can be used to determine soil moisture in unvegetated terrain to within five percentage points by weight. Finally, it was demonstrated that first year thick, multi-year, and first year thin sea ice can be distinguished by observing their differing microwave emissivities at various wavelengths.

Evidence of a metal-rich surface for the Asteroid (16) Psyche from interferometric observations in the thermal infrared

NASA Astrophysics Data System (ADS)

Matter, Alexis; Delbo, Marco; Carry, Benoit; Ligori, Sebastiano

2013-09-01

We describe the first determination of thermal properties and size of the M-type Asteroid (16) Psyche from interferometric observations obtained with the Mid-Infrared Interferometric Instrument (MIDI) of the Very Large Telescope Interferometer. We used a thermophysical model to interpret our interferometric data. Our analysis shows that Psyche has a low macroscopic surface roughness. Using a convex 3-D shape model obtained by Kaasalainen et al. (Kaasalainen, M., Torppa, J., Piironen, J. [2002]. Icarus 159, 369-395), we derived a volume-equivalent diameter for (16) Psyche of 247 ± 25 km or 238 ± 24 km, depending on the possible values of surface roughness. Our corresponding thermal inertia estimates are 133 or 114 J m-2 s-0.5 K-1, with a total uncertainty estimated at 40 J m-2 s-0.5 K-1. They are among the highest thermal inertia values ever measured for an asteroid of this size. We consider this as a new evidence of a metal-rich surface for the Asteroid (16) Psyche.

Study of the effect of tribo-materials and surface finish on the lubricant performance of new halogen-free room temperature ionic liquids

NASA Astrophysics Data System (ADS)

Saurín, N.; Minami, I.; Sanes, J.; Bermúdez, M. D.

2016-03-01

The present work evaluates different materials and surface finish in the presence of newly designed, hydrophobic halogen-free room temperature ionic liquids (RTILs) as lubricants. A reciprocating tribo-tester was employed with steel-ceramic and steel-thermosetting epoxy resin contacts under boundary lubrication conditions. Four different tetraalkylphosphonium organosilanesulfonate RTILs provided excellent lubricating performance, with friction coefficients as low as 0.057, and non-measurable wear for the higher roughness machine-finish stainless steel flat against sapphire balls, in the case of the lubricants containing the 2-trimethylsilylethanesulfonate anion. Higher friction coefficients of the order of 0.1 and wear volumes of the order of 10-4 mm3 were observed for the lower roughness fine-finished flat stainless steel surface. All RTILs prevent wear of epoxy resin against stainless steel balls, with friction coefficients in the range of 0.03-0.06. EDX analysis shows the presence of RTILs on the stainless steel surfaces after the tribological tests. Under the experimental conditions, no corrosive processes were observed.

Assessing and Mapping of Road Surface Roughness based on GPS and Accelerometer Sensors on Bicycle-Mounted Smartphones

PubMed Central

Shen, Jie; Wan, Mi; Shi, Jiafeng

2018-01-01

The surface roughness of roads is an essential road characteristic. Due to the employed carrying platforms (which are often cars), existing measuring methods can only be used for motorable roads. Until now, there has been no effective method for measuring the surface roughness of un-motorable roads, such as pedestrian and bicycle lanes. This hinders many applications related to pedestrians, cyclists and wheelchair users. In recognizing these research gaps, this paper proposes a method for measuring the surface roughness of pedestrian and bicycle lanes based on Global Positioning System (GPS) and accelerometer sensors on bicycle-mounted smartphones. We focus on the International Roughness Index (IRI), as it is the most widely used index for measuring road surface roughness. Specifically, we analyzed a computing model of road surface roughness, derived its parameters with GPS and accelerometers on bicycle-mounted smartphones, and proposed an algorithm to recognize potholes/humps on roads. As a proof of concept, we implemented the proposed method in a mobile application. Three experiments were designed to evaluate the proposed method. The results of the experiments show that the IRI values measured by the proposed method were strongly and positively correlated with those measured by professional instruments. Meanwhile, the proposed algorithm was able to recognize the potholes/humps that the bicycle passed. The proposed method is useful for measuring the surface roughness of roads that are not accessible for professional instruments, such as pedestrian and cycle lanes. This work enables us to further study the feasibility of crowdsourcing road surface roughness with bicycle-mounted smartphones. PMID:29562731

Wear behavior of pressable lithium disilicate glass ceramic.

PubMed

Peng, Zhongxiao; Izzat Abdul Rahman, Muhammad; Zhang, Yu; Yin, Ling

2016-07-01

This article reports effects of surface preparation and contact loads on abrasive wear properties of highly aesthetic and high-strength pressable lithium disilicate glass-ceramics (LDGC). Abrasive wear testing was performed using a pin-on-disk device in which LDGC disks prepared with different surface finishes were against alumina pins at different contact loads. Coefficients of friction and wear volumes were measured as functions of initial surface finishes and contact loads. Wear-induced surface morphology changes in both LDGC disks and alumina pins were characterized using three-dimensional laser scanning microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The results show that initial surface finishes of LDGC specimens and contact loads significantly affected the friction coefficients, wear volumes and wear-induced surface roughness changes of the material. Both wear volumes and friction coefficients of LDGC increased as the load increased while surface roughness effects were complicated. For rough LDGC surfaces, three-body wear was dominant while for fine LDGC surfaces, two-body abrasive wear played a key role. Delamination, plastic deformation, and brittle fracture were observed on worn LDGC surfaces. The adhesion of LDGC matrix materials to alumina pins was also discovered. This research has advanced our understanding of the abrasive wear behavior of LDGC and will provide guidelines for better utilization and preparation of the material for long-term success in dental restorations. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 968-978, 2016. © 2015 Wiley Periodicals, Inc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mourey, Odile; Petit-Etienne, Camille; Cunge, Gilles, E-mail: gilles.cunge@cea.fr

Pulsed plasmas are promising candidates to go beyond limitations of continuous waves' plasma. However, their interaction with surfaces remains poorly understood. The authors investigated the silicon etching mechanism in inductively coupled plasma (ICP) Cl{sub 2} operated either in an ICP-pulsed mode or in a bias-pulsed mode (in which only the bias power is pulsed). The authors observed systematically the development of an important surface roughness at a low duty cycle. By using plasma diagnostics, they show that the roughness is correlated to an anomalously large (Cl atoms flux)/(energetic ion flux) ratio in the pulsed mode. The rational is that themore » Cl atom flux is not modulated on the timescale of the plasma pulses although the ion fluxes and energy are modulated. As a result, a very strong surface chlorination occurs during the OFF period when the surface is not exposed to energetic ions. Therefore, each energetic ion in the ON period will bombard a heavily chlorinated silicon surface, leading to anomalously high etching yield. In the ICP pulsed mode (in which the ion energy is high), the authors report yields as high as 40, which mean that each individual ion impacts will generate a “crater” of about 2 nm depth at the surface. Since the ion flux is very small in the pulsed ICP mode, this process is stochastic and is responsible for the roughness initiation. The roughness expansion can then be attributed partly to the ion channeling effect and is probably enhanced by the formation of a SiClx reactive layer with nonhomogeneous thickness over the topography of the surface. This phenomenon could be a serious limitation of pulsed plasma processes.« less

Self-assembly of fatty acids on hydroxylated Al surface and effects of their stability on wettability and nanoscale organization.

PubMed

Liascukiene, Irma; Steffenhagen, Marie; Asadauskas, Svajus J; Lambert, Jean-François; Landoulsi, Jessem

2014-05-27

The self-assembly of fatty acids (FA) on the surfaces of inorganic materials is a relevant way to control their wetting properties. While the mechanism of adsorption on model flat substrate is well described in the literature, interfacial processes remain poorly documented on nanostructured surfaces. In this study, we report the self-assembly of a variety of FA on a hydroxylated Al surface which exhibits a random nanoscale organization. Our results revealed a peculiar fingerprint due to the FA self-assembly which consists in the formation of aligned nanopatterns in a state of hierarchical nanostructuration, regardless of the molecular structure of the FA (chain length, level of unsaturation). After a significant removal of adsorbed FA using UV/O3 treatment, a complete wetting was reached, and a noticeable disturbance of the surface morphology was observed, evidencing the pivotal role of FA molecules to maintain these nanostructures. The origin of wetting properties was investigated prior to and after conditioning of FA-modified samples taking into account key parameters, namely the surface roughness and its composition. For this purpose, the Wenzel roughness, defined as the third moment of power spectral density, was used, as it is sensitive to high spatial frequency and thus to the obtained hierarchical level of nanostructuration. Our results revealed that no correlation can be made between water contact angles (θ(w)) and the Wenzel roughness. By contrast, θ(w) strongly increased with the amount of -CHx- groups exhibited by adsorbed FA. These findings suggest that the main origin of hydrophobization is the presence of self-assembled molecules and that the surface roughness has only a small contribution to the wettability.

Effect of 100 MeV Ag+7 ion irradiation on the bulk and surface magnetic properties of Co-Fe-Si thin films

NASA Astrophysics Data System (ADS)

Hysen, T.; Geetha, P.; Al-Harthi, Salim; Al-Omari, I. A.; Lisha, R.; Ramanujan, R. V.; Sakthikumar, D.; Avasthi, D. K.; Anantharaman, M. R.

2014-12-01

Thin films of Co-Fe-Si were vacuum evaporated on pre-cleaned float glass substrates employing thermal evaporation. The films were subsequently irradiated with 100 MeV Ag+7 ions at fluences of 1×1011, 1×1012 and 1×1013 ions/cm2. The pristine and irradiated samples were subjected to surface analysis using Atomic Force Microscopy (AFM), Vibrating Sample Magnetometry (VSM) and Magneto Optic Kerr Effect (MOKE) measurements. The as deposited film has a root mean square roughness (Rq) of 8.9 nm and an average roughness of (Ra) 5.6 nm. Irradiation of the as deposited films with 100 MeV Ag7+ ions modifies the surface morphology. Irradiating with ions at fluences of 1×1011 ions/cm2 smoothens the mesoscopic hill-like structures, and then, at 1×1012 ions/cm2 new surface structures are created. When the fluence is further increased to 1×1013 ions/cm2 an increase in the surface roughness is observed. The MOKE loop of as prepared film indicated a squareness ratio of 0.62. As the film is irradiated with fluences of 1×1011 ions/cm2, 1×1012 ions/cm2 and 1×1013 ions/cm2 the squareness ratio changes to 0.76, 0.8 and 0.86 respectively. This enhancement in squareness ratio towards 1 is a typical feature when the exchange interaction starts to dominates the inherent anisotropies in the system. The variation in surface magnetisation is explained based on the variations in surface roughness with swift heavy ion (SHI) irradiation.

Detection of longitudinal ulcer using roughness value for computer aided diagnosis of Crohn's disease

NASA Astrophysics Data System (ADS)

Oda, Masahiro; Kitasaka, Takayuki; Furukawa, Kazuhiro; Watanabe, Osamu; Ando, Takafumi; Goto, Hidemi; Mori, Kensaku

2011-03-01

The purpose of this paper is to present a new method to detect ulcers, which is one of the symptoms of Crohn's disease, from CT images. Crohn's disease is an inflammatory disease of the digestive tract. Crohn's disease commonly affects the small intestine. An optical or a capsule endoscope is used for small intestine examinations. However, these endoscopes cannot pass through intestinal stenosis parts in some cases. A CT image based diagnosis allows a physician to observe whole intestine even if intestinal stenosis exists. However, because of the complicated shape of the small and large intestines, understanding of shapes of the intestines and lesion positions are difficult in the CT image based diagnosis. Computer-aided diagnosis system for Crohn's disease having automated lesion detection is required for efficient diagnosis. We propose an automated method to detect ulcers from CT images. Longitudinal ulcers make rough surface of the small and large intestinal wall. The rough surface consists of combination of convex and concave parts on the intestinal wall. We detect convex and concave parts on the intestinal wall by a blob and an inverse-blob structure enhancement filters. A lot of convex and concave parts concentrate on roughed parts. We introduce a roughness value to differentiate convex and concave parts concentrated on the roughed parts from the other on the intestinal wall. The roughness value effectively reduces false positives of ulcer detection. Experimental results showed that the proposed method can detect convex and concave parts on the ulcers.

Bacterial plaque retention on oral hard materials: effect of surface roughness, surface composition, and physisorbed polycarboxylate.

PubMed

McConnell, Marla D; Liu, Yu; Nowak, Andrew P; Pilch, Shira; Masters, James G; Composto, Russell J

2010-03-15

Bacterial adhesion to oral hard materials is dependent on various factors, for example, surface roughness and surface composition. In this study, bacteria retention on three oral hard substrates, hydroxyapatite (HAP), enamel, and polished enamel (p-enamel) were investigated. The surface morphology and roughness of the three substrates were measured by scanning probe microscopy. HAP had the roughest surface, followed by enamel and polished enamel. For each individual substrate type, the roughness was shown to increase with scan size up to 50 microm x 50 microm. For HAP and enamel, roughness decreased considerably after formation of a pellicle, while addition of polymer coating to the pellicle layer reduced roughness much less in comparison. Bacterial surface coverage was measured at 30 min, 3 h, and 24 h on both native and surface-modified substrates, which were coated with two different polycarboxylate-based polymers, Gantrez S97 and Carbopol 940. As a result, the polymer coated surfaces had reduced bacteria coverage compared with the native surfaces over all time points and substrates measured. The reduction is the combined effect of electrostatic repulsion and sequestering of Ca(2+) ions at the surface, which plays a key role in the initial adhesion of bacteria to enamel surfaces in models of plaque formation. (c) 2009 Wiley Periodicals, Inc.

Effect of sealant agents on the color stability and surface roughness of nanohybrid composite resins.

PubMed

Dede, Doğu Ömür; Şahin, Onur; Koroglu, Aysegül; Yilmaz, Burak

2016-07-01

The effect of sealant agents on the surface roughness and color stability of nanohybrid composite resins is unknown. The purpose of this in vitro study was to evaluate the effect of sealant agents on the surface roughness and color stability of 4 nanohybrid composite resin materials. Forty disks (10×2 mm) were fabricated for each nanohybrid composite resin material (Z-550, Tetric EvoCeram, Clearfill Majesty, Ice) (N=160) and divided into 4 surface treatment groups: 1 conventional polishing (control) and 3 different sealant agent (Palaseal, Optiglaze, BisCover) coupling groups (n=10). The specimens were thermocycled, and surface roughness (Ra) values were obtained with a profilometer. Scanning electron microscope images were also recorded. CIELab color parameters of each specimen were measured with a spectrophotometer before and after 7 days of storage in a coffee solution. Color differences were calculated by the CIEDE 2000 (ΔE00) formula. The data were statistically analyzed by 2-way ANOVA and by the Tukey HSD test (α=.05). The surface treatment technique significantly affected the Ra values of the composite resins tested (P<.001). The interaction between the surface treatment technique and composite resin material was also significant for ΔE00 values (P<.05). Within the composite resin groups, significant decreases in Ra were observed only for the Palaseal agent coupled composite resin groups (except Ice) compared with the control groups (P<.05). Scanning electron microscope images revealed rougher surfaces with conventionally polished groups compared with test groups. Conventionally polished groups had the highest ΔE00 (3.09 to 3.49) values for each composite resin group, except for BisCover applied Clearfill Majesty (P<.05). Within the composite resin groups, significant differences were observed between the color change seen with BisCover and other sealants for Clearfill Majesty composite resin (P<.05). Using Palaseal agent on all tested composite resins except for Ice produced smoother surfaces. All surface sealant agents provided less discoloration of nanohybrid composite resins after coffee staining compared with conventional polishing except for BisCover applied Clearfill Majesty composite resin. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Numerical simulation of adverse-pressure-gradient boundary layer with or without roughness

NASA Astrophysics Data System (ADS)

Mottaghian, Pouya; Yuan, Junlin; Piomelli, Ugo

2014-11-01

Large-eddy and direct numerical simulations are carried out on flat-plate boundary layer over smooth and rough surfaces, with adverse pressure gradient.The deceleration is achieved by imposing a wall-normal freestream velocity profile, and is strong enough to cause separation at the wall. The Reynolds number based on momentum thickness and freestream velocity at inlet is 600. Numerical sandgrain roughness is applied based on an immersed boundary method, yielding a flow that is transitionally rough. The turbulence intensity increases before separation, and reaches a higher value for the rough case, indicating stronger mixing. Roughness also causes higher momentum deficit near the wall, leading to earlier separation. This is consistent with previous observation made on rough-wall flow separation over a ramp. In both cases, the turbulent kinetic energy peaks inside the shear layer above the detachment region, with higher values in the rough case; it then decreases approaching the reattachment region. Near the wall inside the separation bubble, the near-zero turbulent intensity indicates that the turbulent structures are lifted up in the separation region. Compared with the smooth case, the shear layer is farther from the wall and the reattachment length is longer on the rough wall.

Assessment of physiological performance and perception of pushing different wheelchairs on indoor modular units simulating a surface roughness often encountered in under-resourced settings.

PubMed

Sasaki, Kotaro; Rispin, Karen

2017-01-01

In under-resourced settings where motorized wheelchairs are rarely available, manual wheelchair users with limited upper-body strength and functionalities need to rely on assisting pushers for their mobility. Because traveling surfaces in under-resourced settings are often unpaved and rough, wheelchair pushers could experience high physiological loading. In order to evaluate pushers' physiological loading and to improve wheelchair designs, we built indoor modular units that simulate rough surface conditions, and tested a hypothesis that pushing different wheelchairs would result in different physiological performances and pushers' perception of difficulty on the simulated rough surface. Eighteen healthy subjects pushed two different types of pediatric wheelchairs (Moti-Go manufactured by Motivation, and KidChair by Hope Haven) fitted with a 50-kg dummy on the rough and smooth surfaces at self-selected speeds. Oxygen uptake, traveling distance for 6 minutes, and the rating of difficulty were obtained. The results supported our hypothesis, showing that pushing Moti-Go on the rough surface was physiologically less loading than KidChair, but on the smooth surface, the two wheelchairs did not differ significantly. These results indicate wheelchair designs to improve pushers' performance in under-resourced settings should be evaluated on rough surfaces.

Correlation of bond strength with surface roughness using a new roughness measurement technique.

PubMed

Winkler, M M; Moore, B K

1994-07-01

The correlation between shear bond strength and surface roughness was investigated using new surface measurement methods. Bonding agents and associated resin composites were applied to set amalgam after mechanically roughening its surface. Surface treatments were noe (as set against glass), 80 grit, and 600 grit abrasive paper. Surface roughness (R(a) as measured parallel and perpendicular (+) to the direction of the polishing scratches and true profile length were measured. A knife-edge was applied (rate = 2.54 mm/min) at the bonding agent/amalgam interface of each sample until failure. Coefficients of determination for mean bond strength vs either roughness (R(a), of profile length were significantly higher for measurements in parallel directions than for those measurements in (+) directions. The shear bond strength to set amalgam for a PENTA-containing adhesives system (L.D. Caulk Division) was not significantly different from that of a PENTA-free adhesive (3M Dental Products Division), even though PENTA has been reported to increase bond strength to nonprecious metals. The shear bond strength of resin composite to amalgam is correlated to surface roughness when it is measured parallel to the polishing scratches. This correlation is significantly lower when surface roughness is measured in the typical manner, perpendicular to the polishing scratches.

Fast, Statistical Model of Surface Roughness for Ion-Solid Interaction Simulations and Efficient Code Coupling

NASA Astrophysics Data System (ADS)

Drobny, Jon; Curreli, Davide; Ruzic, David; Lasa, Ane; Green, David; Canik, John; Younkin, Tim; Blondel, Sophie; Wirth, Brian

2017-10-01

Surface roughness greatly impacts material erosion, and thus plays an important role in Plasma-Surface Interactions. Developing strategies for efficiently introducing rough surfaces into ion-solid interaction codes will be an important step towards whole-device modeling of plasma devices and future fusion reactors such as ITER. Fractal TRIDYN (F-TRIDYN) is an upgraded version of the Monte Carlo, BCA program TRIDYN developed for this purpose that includes an explicit fractal model of surface roughness and extended input and output options for file-based code coupling. Code coupling with both plasma and material codes has been achieved and allows for multi-scale, whole-device modeling of plasma experiments. These code coupling results will be presented. F-TRIDYN has been further upgraded with an alternative, statistical model of surface roughness. The statistical model is significantly faster than and compares favorably to the fractal model. Additionally, the statistical model compares well to alternative computational surface roughness models and experiments. Theoretical links between the fractal and statistical models are made, and further connections to experimental measurements of surface roughness are explored. This work was supported by the PSI-SciDAC Project funded by the U.S. Department of Energy through contract DOE-DE-SC0008658.

Real time measurements of surface growth evolution in magnetron sputtered single crystal Mo/V superlattices using in situ reflection high energy electron diffraction analysis

NASA Astrophysics Data System (ADS)

Svedberg, E. B.; Birch, J.; Edvardsson, C. N. L.; Sundgren, J.-E.

1999-07-01

The use of video recording of reflection high energy electron diffraction (RHEED) patterns for assessing the dynamic evolution of the surface morphology and crystallinity during growth was evaluated. As an example, Mo/V(001) superlattices with varying layer thickness (with periods Λ of 2.5 to 8.9 nm and a constant Mo:V ratio of 1:1) were examined. During the deposition, changes from two- to three-dimensional growth were observed in situ. From prior transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies, it is known that this transition is associated with a critical thickness and concurrent roughening of the V layer. Video recording and subsequent image and data processing allowed the surface morphology to be continuously followed during growth. Post-growth analyses of the recorded data provided the evolution of surface lattice parameters and short range [1-2 monolayer (ML)] surface roughnesses with a time resolution of 200-400 ms (0.02-0.04 nm thickness resolution). During growth of Mo, a smoothening effect could be observed while the growth of V evidently increased the surface roughness from 1 to 2 ML. Furthermore, the onset of coherency strain relaxation of the topmost growing layers was observed to occur at 2.0-2.5 nm layer thicknesses for both materials, which is in qualitative agreement with theoretical predictions.

Surface roughness manifestations of deep-seated landslide processes

NASA Astrophysics Data System (ADS)

Booth, A. M.; Roering, J. J.; Lamb, M. P.

2012-12-01

In many mountainous drainage basins, deep-seated landslides evacuate large volumes of sediment from small surface areas, leaving behind a strong topographic signature that sets landscape roughness over a range of spatial scales. At long spatial wavelengths of hundreds to thousands of meters, landslides tend to inhibit channel incision and limit topographic relief, effectively smoothing the topography at this length scale. However, at short spatial wavelengths on the order of meters, deformation of deep-seated landslides generates surface roughness that allows expert mappers or automated algorithms to distinguish landslides from the surrounding terrain. Here, we directly connect the characteristic spatial wavelengths and amplitudes of this fine scale surface roughness to the underlying landslide deformation processes. We utilize the two-dimensional wavelet transform with high-resolution, airborne LiDAR-derived digital elevation models to systematically document the characteristic length scales and amplitudes of different kinematic units within slow moving earthflows, a common type of deep-seated landslide. In earthflow source areas, discrete slumped blocks generate high surface roughness, reflecting an extensional deformation regime. In earthflow transport zones, where material translates with minimal surface deformation, roughness decreases as other surface processes quickly smooth short wavelength features. In earthflow depositional toes, compression folds and thrust faults again increase short wavelength surface roughness. When an earthflow becomes inactive, roughness in all of these kinematic zones systematically decreases with time, allowing relative dating of earthflow deposits. We also document how each of these roughness expressions depends on earthflow velocity, using sub-pixel change detection software (COSI-Corr) and pairs of orthorectified aerial photographs to determine spatially extensive landslide surface displacements. In source areas, the wavelength of slumped blocks tends to correlate with velocity as predicted by a simple sliding block model, but the amplitude is insensitive to velocity, suggesting that landslide depth rather than velocity sets this characteristic block amplitude. In both transport zones and depositional toes, the amplitude of the surface roughness is higher where the longitudinal gradient in velocity is higher, confirming that differential movement generates and maintains this fine scale roughness.

Implementation and analysis of relief patterns of the surface of benign and malignant lesions of the skin by microtopography

NASA Astrophysics Data System (ADS)

López Pacheco, María del Carmen; Filipe Pereira da Cunha Martins-Costa, Manuel; Pérez Zapata, Aura Judith; Domínguez Cherit, Judith; Ramón Gallegos, Eva

2005-12-01

The objective of this study was to be able to distinguish between healthy skin tissue and malignant ones, furthermore determining a unique pattern of roughness for each skin lesion by microtopographic analysis of the skin surface of Mexican patients during the period from April to October 2002. The standard technique used in this study for the diagnosis of skin cancer and the comparison of the results was the haematoxylin eosin histopathological technique. Latex impressions were taken from skin lesions as well as from the healthy skin of each patient to serve as control samples. These impressions were analysed by the MICROTOP.03.MFC microtopographic system inspection. It was observed that when the tumour becomes rougher, more malign will be the lesion. On average, the melanoma present an increase of roughness of 67% compared to healthy skin, obtaining a roughness relation of 1:2.54. The percentage decreases to 49% (49%, 1:60) in the case of basal cell carcinoma and to 40% in pre-malignant lesions such as melanocytic nevus (40%, 1:150). In benign lesions such as the seborrhoea keratosis only a small increase in roughness was noted (4%, 1:0.72). Microtopographic inspection of the skin surface can be considered as a complementary diagnostic technique for skin cancer.

Using Multi-Dimensional Microwave Remote Sensing Information for the Retrieval of Soil Surface Roughness

NASA Astrophysics Data System (ADS)

Marzahn, P.; Ludwig, R.

2016-06-01

In this Paper the potential of multi parametric polarimetric SAR (PolSAR) data for soil surface roughness estimation is investigated and its potential for hydrological modeling is evaluated. The study utilizes microwave backscatter collected from the Demmin testsite in the North-East Germany during AgriSAR 2006 campaign using fully polarimetric L-Band airborne SAR data. For ground truthing extensive soil surface roughness in addition to various other soil physical properties measurements were carried out using photogrammetric image matching techniques. The correlation between ground truth roughness indices and three well established polarimetric roughness estimators showed only good results for Re[ρRRLL] and the RMS Height s. Results in form of multitemporal roughness maps showed only satisfying results due to the fact that the presence and development of particular plants affected the derivation. However roughness derivation for bare soil surfaces showed promising results.

Analysis of Surface Roughness at Overlapping Laser Shock Peening

NASA Astrophysics Data System (ADS)

Dai, F. Z.; Zhang, Z. D.; Zhou, J. Z.; Lu, J. Z.; Zhang, Y. K.

2016-02-01

The overlapping effects on surface roughness are studied when samples are treated by laser shock peening (LSP). Surface roughness of overlapped circular laser spot is calculated by ISO 25178 height parameters. The usually used overlapping styles namely isosceles-right-triangle-style (AAP) and equilateral-triangle-style (AAA) are carefully investigated when the overlapping degree in x-axis (ηx) is below 50%. Surface roughness of isosceles-right-triangle-style attains its minimum value at ηx of 29.3%, and attains its maximum value at ηx of 43.6%. Surface roughness of equilateral-triangle-style attains its minimum value at ηx of 42.3%, and attains its maximum value at ηx of 32%. Experimental results are well consistent with theoretical analysis.

Effect of the addition of antimicrobial agents on Shore A hardness and roughness of soft lining materials.

PubMed

Urban, Vanessa M; Lima, Thiago F; Bueno, Mirian G; Giannini, Marcelo; Arioli Filho, João N; de Almeida, Ana Lúcia P F; Neppelenbroek, Karin H

2015-04-01

While the incorporation of antimicrobial agents into soft denture liners has been suggested as a reliable alternative treatment for denture stomatitis, it may affect the liner's properties. The effect of addition of antimicrobial agents for the treatment of denture stomatitis on the surface roughness and Shore A hardness of soft lining materials was evaluated. The test groups comprised specimens (36 × 7 × 6 mm(3) ) of soft materials (Softone and Trusoft) without (control) or with incorporation of drugs (nystatin, miconazole, ketoconazole, chlorhexidine diacetate, and itraconazole). Hardness (Shore A) and roughness (Ra) were evaluated after immersion of specimens (n = 10) in distilled water at 37°C for 24 hours, 7 and 14 days. Data were analyzed by 3-way ANOVA/Tukey's test (α = 0.05). After 14 days, an increase (p < 0.05) was observed in the hardness of soft materials with time for the modified specimens, except for itraconazole. Addition of drugs increased the Softone roughness only for the addition of miconazole and chlorhexidine (p < 0.05), and did not increase the roughness of Trusoft with time. Only chlorhexidine and itraconazole altered the roughness compared to the control for each material (p < 0.05). The smallest changes of hardness and roughness with time in the modified groups compared to controls were observed for itraconazole groups for both materials. © 2014 by the American College of Prosthodontists.

Effect of sandblasting on surface roughness of zirconia-based ceramics and shear bond strength of veneering porcelain.

PubMed

He, Min; Zhang, Zutai; Zheng, Dongxiang; Ding, Ning; Liu, Yan

2014-01-01

This study aims to investigate the effect of sandblasting on the surface roughness of zirconia and the shear bond strength of the veneering porcelain. Pre-sintered zirconia plates were prepared and divided into four groups. Group A were not treated at all; group B were first sandblasted under 0.2 MPa pressure and then densely sintered; group C and D were sintered first, and then sandblasted under 0.2 MPa and 0.4 MPa pressures respectively. Surface roughness was measured and 3D roughness was reconstructed for the specimens, which were also analyzed with X-ray diffractometry. Finally after veneering porcelain sintering, shear bond tests were conducted. Sandblasting zirconia before sintering significantly increased surface roughness and the shear bond strength between zirconia and veneering porcelain (p<0.05). Sandblasting zirconia before sintering is a useful method to increase surface roughness and could successfully improve the bonding strength of veneering porcelain.

Comparison of aerodynamically and model-derived roughness lengths (zo) over diverse surfaces, central Mojave Desert, California, USA

USGS Publications Warehouse

MacKinnon, D.J.; Clow, G.D.; Tigges, R.K.; Reynolds, R.L.; Chavez, P.S.

2004-01-01

The vulnerability of dryland surfaces to wind erosion depends importantly on the absence or the presence and character of surface roughness elements, such as plants, clasts, and topographic irregularities that diminish wind speed near the surface. A model for the friction velocity ratio has been developed to account for wind sheltering by many different types of co-existing roughness elements. Such conditions typify a monitored area in the central Mojave Desert, California, that experiences frequent sand movement and dust emission. Two additional models are used to convert the friction velocity ratio to the surface roughness length (zo) for momentum. To calculate roughness lengths from these models, measurements were made at 11 sites within the monitored area to characterize the surface roughness element. Measurements included (1) the number of roughness species (e.g., plants, small-scale topography, clasts), and their associated heights and widths, (2) spacing among species, and (3) vegetation porosity (a measurement of the spatial distribution of woody elements of a plant). Documented or estimated values of drag coefficients for different species were included in the modeling. At these sites, wind-speed profiles were measured during periods of neutral atmospheric stability using three 9-m towers with three or four calibrated anemometers on each. Modeled roughness lengths show a close correspondence (correlation coefficient, 0.84-0.86) to the aerodynamically determined values at the field sites. The geometric properties of the roughness elements in the model are amenable to measurement at much higher temporal and spatial resolutions using remote-sensing techniques than can be accomplished through laborious ground-based methods. A remote-sensing approach to acquire values of the modeled roughness length is particularly important for the development of linked surface/atmosphere wind-erosion models sensitive to climate variability and land-use changes in areas such as the southwestern United States, where surface roughness has large spatial and temporal variations. ?? 2004 Elsevier B.V. All rights reserved.

Numerical Model Sensitivity to Heterogeneous Satellite Derived Vegetation Roughness

NASA Technical Reports Server (NTRS)

Jasinski, Michael; Eastman, Joseph; Borak, Jordan

2011-01-01

The sensitivity of a mesoscale weather prediction model to a 1 km satellite-based vegetation roughness initialization is investigated for a domain within the south central United States. Three different roughness databases are employed: i) a control or standard lookup table roughness that is a function only of land cover type, ii) a spatially heterogeneous roughness database, specific to the domain, that was previously derived using a physically based procedure and Moderate Resolution Imaging Spectroradiometer (MODIS) imagery, and iii) a MODIS climatologic roughness database that like (i) is a function only of land cover type, but possesses domain specific mean values from (ii). The model used is the Weather Research and Forecast Model (WRF) coupled to the Community Land Model within the Land Information System (LIS). For each simulation, a statistical comparison is made between modeled results and ground observations within a domain including Oklahoma, Eastern Arkansas, and Northwest Louisiana during a 4-day period within IHOP 2002. Sensitivity analysis compares the impact the three roughness initializations on time-series temperature, precipitation probability of detection (POD), average wind speed, boundary layer height, and turbulent kinetic energy (TKE). Overall, the results indicate that, for the current investigation, replacement of the standard look-up table values with the satellite-derived values statistically improves model performance for most observed variables. Such natural roughness heterogeneity enhances the surface wind speed, PBL height and TKE production up to 10 percent, with a lesser effect over grassland, and greater effect over mixed land cover domains.

How surface mounds and depressions change during rainfall events

USDA-ARS?s Scientific Manuscript database

The soil roughness, or microrelief, controls processes occurring on the surface. Although there are numerous studies on how soil roughness affects soil erosion processes, little are focused on quantifying different roughness functions on surface hydrology and erosion, i.e., water diverging and soil...

Quantifying surface roughness effects on phonon transport in silicon nanowires.

PubMed

Lim, Jongwoo; Hippalgaonkar, Kedar; Andrews, Sean C; Majumdar, Arun; Yang, Peidong

2012-05-09

Although it has been qualitatively demonstrated that surface roughness can reduce the thermal conductivity of crystalline Si nanowires (SiNWs), the underlying reasons remain unknown and warrant quantitative studies and analysis. In this work, vapor-liquid-solid (VLS) grown SiNWs were controllably roughened and then thoroughly characterized with transmission electron microscopy to obtain detailed surface profiles. Once the roughness information (root-mean-square, σ, correlation length, L, and power spectra) was extracted from the surface profile of a specific SiNW, the thermal conductivity of the same SiNW was measured. The thermal conductivity correlated well with the power spectra of surface roughness, which varies as a power law in the 1-100 nm length scale range. These results suggest a new realm of phonon scattering from rough interfaces, which restricts phonon transport below the Casimir limit. Insights gained from this study can help develop a more concrete theoretical understanding of phonon-surface roughness interactions as well as aid the design of next generation thermoelectric devices.

Influence of polishing on surface roughness following toothbrushing wear of composite resins.

PubMed

Dalla-Vecchia, Karine Battestin; Taborda, Talita Damas; Stona, Deborah; Pressi, Heloísa; Burnett Júnior, Luiz Henrique; Rodrigues-Junior, Sinval Adalberto

2017-01-01

This study aimed to evaluate the influence of different polishing systems on the surface roughness of composite resins following procedures to simulate the effects of toothbrushing over time. Four currently available commercial composites were used to make 128 cylindrical specimens. The specimens were randomly allocated to polishing with a 1-step polisher or 1 of 3 multistep polishers (n = 8 per group). The baseline surface roughness was measured, and the specimens were submitted to 5000, 10,000, and 20,000 brushing cycles to represent toothbrushing throughout 6, 12, and 24 months, respectively. Results showed that surface roughness was influenced by the type of composite and polishing system and was not influenced by the simulated toothbrushing time. However, the surface roughness, as challenged by toothbrushing wear, was affected by the interaction among the composite, the polisher, and the toothbrushing time. The 1-step polisher produced the highest surface roughness and influenced toothbrushing wear resistance of some composites.

Surface roughness model based on force sensors for the prediction of the tool wear.

PubMed

de Agustina, Beatriz; Rubio, Eva María; Sebastián, Miguel Ángel

2014-04-04

In this study, a methodology has been developed with the objective of evaluating the surface roughness obtained during turning processes by measuring the signals detected by a force sensor under the same cutting conditions. In this way, the surface quality achieved along the process is correlated to several parameters of the cutting forces (thrust forces, feed forces and cutting forces), so the effect that the tool wear causes on the surface roughness is evaluated. In a first step, the best cutting conditions (cutting parameters and radius of tool) for a certain quality surface requirement were found for pieces of UNS A97075. Next, with this selection a model of surface roughness based on the cutting forces was developed for different states of wear that simulate the behaviour of the tool throughout its life. The validation of this model reveals that it was effective for approximately 70% of the surface roughness values obtained.

Surface roughness effects on bidirectional reflectance

NASA Technical Reports Server (NTRS)

Smith, T. F.; Hering, R. G.

1972-01-01

An experimental study of surface roughness effects on bidirectional reflectance of metallic surfaces is presented. A facility capable of irradiating a sample from normal to grazing incidence and recording plane of incidence bidirectional reflectance measurements was developed. Samples consisting of glass, aluminum alloy, and stainless steel materials were selected for examination. Samples were roughened using standard grinding techniques and coated with a radiatively opaque layer of pure aluminum. Mechanical surface roughness parameters, rms heights and rms slopes, evaluated from digitized surface profile measurements are less than 1.0 micrometers and 0.28, respectively. Rough surface specular, bidirectional, and directional reflectance measurements for selected values of polar angle of incidence and wavelength of incident energy within the spectral range of 1 to 14 micrometers are reported. The Beckmann bidirectional reflectance model is compared with reflectance measurements to establish its usefulness in describing the magnitude and spatial distribution of energy reflected from rough surfaces.

Shear Model Development of Limestone Joints with Incorporating Variations of Basic Friction Coefficient and Roughness Components During Shearing

NASA Astrophysics Data System (ADS)

Mehrishal, Seyedahmad; Sharifzadeh, Mostafa; Shahriar, Korosh; Song, Jae-Jon

2017-04-01

In relation to the shearing of rock joints, the precise and continuous evaluation of asperity interlocking, dilation, and basic friction properties has been the most important task in the modeling of shear strength. In this paper, in order to investigate these controlling factors, two types of limestone joint samples were prepared and CNL direct shear tests were performed on these joints under various shear conditions. One set of samples were travertine and another were onyx marble with slickensided surfaces, surfaces ground to #80, and rough surfaces were tested. Direct shear experiments conducted on slickensided and ground surfaces of limestone indicated that by increasing the applied normal stress, under different shearing rates, the basic friction coefficient decreased. Moreover, in the shear tests under constant normal stress and shearing rate, the basic friction coefficient remained constant for the different contact sizes. The second series of direct shear experiments in this research was conducted on tension joint samples to evaluate the effect of surface roughness on the shear behavior of the rough joints. This paper deals with the dilation and roughness interlocking using a method that characterizes the surface roughness of the joint based on a fundamental combined surface roughness concept. The application of stress-dependent basic friction and quantitative roughness parameters in the continuous modeling of the shear behavior of rock joints is an important aspect of this research.

Surface roughness estimation by inversion of the Hapke photometric model on optical data simulated using a ray tracing code

NASA Astrophysics Data System (ADS)

Champion, J.; Ristorcelli, T.; Ferrari, C. C.; Briottet, X.; Jacquemoud, S.

2013-12-01

Surface roughness is a key physical parameter that governs various processes (incident radiation distribution, temperature, erosion,...) on Earth and other Solar System objects. Its impact on the scattering function of incident electromagnetic waves is difficult to model. In the 80's, Hapke provided an approximate analytic solution for the bidirectional reflectance distribution function (BRDF) of a particulate medium and, later on, included the effect of surface roughness as a correction factor for the BRDF of a smooth surface. This analytical radiative transfer model is widely used in solar system science whereas its ability to remotely determine surface roughness is still a question at issue. The validation of the Hapke model has been only occasionally undertaken due to the lack of radiometric data associated with field measurement of surface roughness. We propose to validate it on Earth, on several volcanic terrains for which very high resolution digital elevation models are available at small scale. We simulate the BRDF of these DEMs thanks to a ray-tracing code and fit them with the Hapke model to retrieve surface roughness. The mean slope angle of the facets, which quantifies surface roughness, can be fairly well retrieved when most conditions are met, i.e. a random-like surface and little multiple scattering between the facets. A directional sensitivity analysis of the Hapke model confirms that both surface intrinsic optical properties (facet's reflectance or single scattering albedo) and roughness are the most influential variables on ground BRDFs. Their interactions in some directions explain why their separation may be difficult, unless some constraints are introduced in the inversion process. Simulation of soil surface BRDF at different illumination and viewing angles

Surface roughness scattering of electrons in bulk mosfets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuverink, Amanda Renee

2015-11-01

Surface-roughness scattering of electrons at the Si-SiO 2 interface is a very important consideration when analyzing Si metal-oxide-semiconductor field-effect transistors (MOSFETs). Scattering reduces the mobility of the electrons and degrades the device performance. 250-nm and 50-nm bulk MOSFETs were simulated with varying device parameters and mesh sizes in order to compare the effects of surface-roughness scattering in multiple devices. The simulation framework includes the ensemble Monte Carlo method used to solve the Boltzmann transport equation coupled with a successive over-relaxation method used to solve the two-dimensional Poisson's equation. Four methods for simulating the surface-roughness scattering of electrons were implemented onmore » both devices and compared: the constant specularity parameter, the momentum-dependent specularity parameter, and the real-space-roughness method with both uniform and varying electric fields. The specularity parameter is the probability of an electron scattering speculariy from a rough surface. It can be chosen as a constant, characterizing partially diffuse scattering of all electrons from the surface the same way, or it can be momentum dependent, where the size of rms roughness and the normal component of the electron wave number determine the probability of electron-momentum randomization. The real-space rough surface method uses the rms roughness height and correlation length of an actual MOSFET to simulate a rough interface. Due to their charge, electrons scatter from the electric field and not directly from the surface. If the electric field is kept uniform, the electrons do not perceive the roughness and scatter as if from a at surface. However, if the field is allowed to vary, the electrons scatter from the varying electric field as they would in a MOSFET. These methods were implemented for both the 50-nm and 250-nm MOSFETs, and using the rms roughness heights and correlation lengths for real devices. The current-voltage and mobility-electric field curves were plotted for each method on the two devices and compared. The conclusion is that the specularity-parameter methods are valuable as simple models for relatively smooth interfaces. However, they have limitations, as they cannot accurately describe the drastic reduction in the current and the electron mobility that occur in MOSFETs with very rough Si-SiO 2 interfaces.« less

Improvement of PET surface hydrophilicity and roughness through blending

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolahchi, Ahmad Rezaei; Ajji, Abdellah; Carreau, Pierre J.

Controlling the adhesion of the polymer surface is a key issue in surface science, since polymers have been a commonly used material for many years. The surface modification in this study includes two different aspects. One is to enhance the hydrophilicity and the other is to create the roughness on the PET film surface. In this study we developed a novel and simple approach to modify polyethylene terephthalate (PET) film surface through polymer blending in twin-screw extruder. One example described in the study uses polyethylene glycol (PEG) in polyethylene terephthalate (PET) host to modify a PET film surface. Low contentmore » of polystyrene (PS) as a third component was used in the system to increase the rate of migration of PEG to the surface of the film. Surface enrichment of PEG was observed at the polymer/air interface of the polymer film containing PET-PEG-PS whereas for the PET-PEG binary blend more PEG was distributed within the bulk of the sample. Furthermore, a novel method to create roughness at the PET film surface was proposed. In order to roughen the surface of PET film, a small amount of PKHH phenoxy resin to change PS/PET interfacial tension was used. The compatibility effect of PKHH causes the formation of smaller PS droplets, which were able to migrate more easily through PET matrix. Consequently, resulting in a locally elevated concentration of PS near the surface of the film. The local concentration of PS eventually reached a level where a co-continuous morphology occurred, resulting in theinstabilities on the surface of the film.« less

Homogeneous dielectric barrier discharges in atmospheric air and its influencing factor

NASA Astrophysics Data System (ADS)

Ran, Junxia; Li, Caixia; Ma, Dong; Luo, Haiyun; Li, Xiaowei

2018-03-01

The stable homogeneous dielectric barrier discharge (DBD) is obtained in atmospheric 2-3 mm air gap. It is generated using center frequency 1 kHz high voltage power supply between two plane parallel electrodes with specific alumina ceramic plates as the dielectric barriers. The discharge characteristics are studied by a measurement of its electrical discharge parameters and observation of its light emission phenomena. The results show that a large single current pulse of about 200 μs duration appearing in each voltage pulse, and its light emission is radially homogeneous and covers the entire surface of the two electrodes. The homogeneous discharge generated is a Townsend discharge during discharge. The influences of applied barrier, its thickness, and surface roughness on the transition of discharge modes are studied. The results show that it is difficult to produce a homogeneous discharge using smooth plates or alumina plate surface roughness Ra < 100 nm even at a 1 mm air gap. If the alumina plate is too thin, the discharge also transits to filamentary discharge. If it is too thick, the discharge is too weak to observe. With the increase of air gap distance and applied voltage, the discharge can also transit from a homogeneous mode to a filamentary mode. In order to generate stable and homogeneous DBD at a larger air gap, proper dielectric material, dielectric thickness, and dielectric surface roughness should be used, and proper applied voltage amplitude and frequency should also be used.

Radar, visual and thermal characteristics of Mars: Rough planar surfaces

USGS Publications Warehouse

Schaber, G.G.

1980-01-01

High-resolution Viking Orbiter images (10 to 15 m/pixel) contain significant information on Martian surface roughness at 25- to 100-m lateral scales, whereas Earth-based radar observations of Mars are sensitive to roughness at lateral scales of 1 to 30 m, or more. High-rms slopes predicted for the Tharsis-Memnonia-Amazonis volcanic plains from extremely weak radar returns (low peak radar cross section) are qualitatively confirmed by the Viking image data. Large-scale, curvilinear (but parallel) ridges on lava flows in the Memnonia Fossae region are interpreted as innate flow morphology caused by compressional foldover of moving lava sheets of possible rhyolite-dacite composition. The presence or absence of a recent mantle of fine-grained eolian material on the volcanic surfaces studied was determined by the visibility of fresh impact craters with diameters less than 50 m. Lava flows south and west of Arsia Mons, and within the large region of low thermal inertia centered on Tharsis Montes (H. H. Kieffer et al., 1977, J. Geophys. Res.82, 4249-4291), were found to possess such a recent mantle. At predawn residual temperatures ??? -10K (south boundary of this low-temperature region), lava flows are shown to have relatively old eolian mantles. Lava flows with surfaces modified by eolian erosion and deposition occur west-northwest of Apollinaris Patera at the border of the cratered equatorial uplands and southern Elysium Planitia. Nearby yardangs, for which radar observations indicate very high-rms slopes, are similar to terrestrial features of similar origin. ?? 1980.

Atomic force microscopy analysis of different surface treatments of Ti dental implant surfaces

NASA Astrophysics Data System (ADS)

Bathomarco, Ti R. V.; Solorzano, G.; Elias, C. N.; Prioli, R.

2004-06-01

The surface of commercial unalloyed titanium, used in dental implants, was analyzed by atomic force microscopy. The morphology, roughness, and surface area of the samples, submitted to mechanically-induced erosion, chemical etching and a combination of both, were compared. The results show that surface treatments strongly influence the dental implant physical and chemical properties. An analysis of the length dependence of the implant surface roughness shows that, for scan sizes larger than 50 μm, the average surface roughness is independent of the scanning length and that the surface treatments lead to average surface roughness in the range of 0.37 up to 0.48 μm. It is shown that the implant surface energy is sensitive to the titanium surface area. As the area increases there is a decrease in the surface contact angle.

Neutron imaging with lithium indium diselenide: Surface properties, spatial resolution, and computed tomography

NASA Astrophysics Data System (ADS)

Lukosi, Eric D.; Herrera, Elan H.; Hamm, Daniel S.; Burger, Arnold; Stowe, Ashley C.

2017-11-01

An array of lithium indium diselenide (LISe) scintillators were investigated for application in neutron imaging. The sensors, varying in thickness and surface roughness, were tested using both reflective and anti-reflective mounting to an aluminum window. The spatial resolution of each LISe scintillator was calculated using the knife-edge test and a modulation transfer function analysis. It was found that the anti-reflective backing case yielded higher spatial resolutions by up to a factor of two over the reflective backing case despite a reduction in measured light yield by an average of 1.97. In most cases, the use of an anti-reflective backing resulted in a higher spatial resolution than the 50 μm-thick ZnS(Cu):6 LiF comparison scintillation screen. The effect of surface roughness was not directly correlated to measured light yield or observed spatial resolution, but weighting the reflective backing case by the random surface roughness revealed that a linear relationship exists between the fractional change (RB/ARB) of the two. Finally, the LISe scintillator array was used in neutron computed tomography to investigate the features of halyomorpha halys with the reflective and anti-reflective backing.

Tool wear compensation scheme for DTM

NASA Astrophysics Data System (ADS)

Sandeep, K.; Rao, U. S.; Balasubramaniam, R.

2018-04-01

This paper is aimed to monitor tool wear in diamond turn machining (DTM), assess effects of tool wear on accuracies of the machined component, and develop compensation methodology to enhance size and shape accuracies of a hemispherical cup. In order to find change in the centre and radius of tool with increasing wear of tool, a MATLAB program is used. In practice, x-offsets are readjusted by DTM operator for desired accuracy in the cup and the results of theoretical model show that change in radius and z-offset are insignificant however x-offset is proportional to the tool wear and this is what assumed while resetting tool offset. Since we could not measure the profile of tool; therefore we modeled our program for cup profile data. If we assume no error due to slide and spindle of DTM then any wear in the tool will be reflected in the cup profile. As the cup data contains surface roughness, therefore random noise similar to surface waviness is added. It is observed that surface roughness affects the centre and radius but pattern of shifting of centre with increase in wear of tool remains similar to the ideal condition, i.e. without surface roughness.

Effect of denture cleansers on color stability, surface roughness, and hardness of different denture base resins

PubMed Central

Porwal, Anand; Khandelwal, Meenakshi; Punia, Vikas; Sharma, Vivek

2017-01-01

Aim: The purpose of this study was to evaluate the effect of different denture cleansers on the color stability, surface hardness, and roughness of different denture base resins. Materials and Methods: Three denture base resin materials (conventional heat cure resin, high impact resin, and polyamide denture base resin) were immersed for 180 days in commercially available two denture cleansers (sodium perborate and sodium hypochlorite). Color, surface roughness, and hardness were measured for each sample before and after immersion procedure. Statistical Analysis: One-way analysis of variance and Tukey's post hoc honestly significant difference test were used to evaluate color, surface roughness, and hardness data before and after immersion in denture cleanser (α =0.05). Results: All denture base resins tested exhibited a change in color, surface roughness, and hardness to some degree in both denture cleansers. Polyamides resin immersed in sodium perborate showed a maximum change in color after immersion for 180 days. Conventional heat cure resin immersed in sodium hypochlorite showed a maximum change in surface roughness and conventional heat cure immersed in sodium perborate showed a maximum change in hardness. Conclusion: Color changes of all denture base resins were within the clinically accepted range for color difference. Surface roughness change of conventional heat cure resin was not within the clinically accepted range of surface roughness. The choice of denture cleanser for different denture base resins should be based on the chemistry of resin and cleanser, denture cleanser concentration, and duration of immersion. PMID:28216847

Examination of Surface Roughness on Light Scattering by Long Ice Columns by Use of a Two-Dimensional Finite-Difference Time-Domain Algorithm

NASA Technical Reports Server (NTRS)

Sun, W.; Loeb, N. G.; Videen, G.; Fu, Q.

2004-01-01

Natural particles such as ice crystals in cirrus clouds generally are not pristine but have additional micro-roughness on their surfaces. A two-dimensional finite-difference time-domain (FDTD) program with a perfectly matched layer absorbing boundary condition is developed to calculate the effect of surface roughness on light scattering by long ice columns. When we use a spatial cell size of 1/120 incident wavelength for ice circular cylinders with size parameters of 6 and 24 at wavelengths of 0.55 and 10.8 mum, respectively, the errors in the FDTD results in the extinction, scattering, and absorption efficiencies are smaller than similar to 0.5%. The errors in the FDTD results in the asymmetry factor are smaller than similar to 0.05%. The errors in the FDTD results in the phase-matrix elements are smaller than similar to 5%. By adding a pseudorandom change as great as 10% of the radius of a cylinder, we calculate the scattering properties of randomly oriented rough-surfaced ice columns. We conclude that, although the effect of small surface roughness on light scattering is negligible, the scattering phase-matrix elements change significantly for particles with large surface roughness. The roughness on the particle surface can make the conventional phase function smooth. The most significant effect of the surface roughness is the decay of polarization of the scattered light.

Comparison of two metrological approaches for the prediction of human haptic perception

NASA Astrophysics Data System (ADS)

Neumann, Annika; Frank, Daniel; Vondenhoff, Thomas; Schmitt, Robert

2016-06-01

Haptic perception is regarded as a key component of customer appreciation and acceptance for various products. The prediction of customers’ haptic perception is of interest both during product development and production phases. This paper presents the results of a multivariate analysis between perceived roughness and texture related surface measurements, to examine whether perceived roughness can be accurately predicted using technical measurements. Studies have shown that standardized measurement parameters, such as the roughness coefficients (e.g. Rz or Ra), do not show a one-dimensional linear correlation with the human perception (of roughness). Thus, an alternative measurement method was compared to standard measurements of roughness, in regard to its capability of predicting perceived roughness through technical measurements. To estimate perceived roughness, an experimental study was conducted in which 102 subjects evaluated four sets of 12 different geometrical surface structures regarding their relative perceived roughness. The two different metrological procedures were examined in relation to their capability to predict the perceived roughness of the subjects stated within the study. The standardized measurements of the surface roughness were made using a structured light 3D-scanner. As an alternative method, surface induced vibrations were measured by a finger-like sensor during robot-controlled traverse over a surface. The presented findings provide a better understanding of the predictability of human haptic perception using technical measurements.

Effects of surface roughness and electrokinetic heterogeneity on electroosmotic flow in microchannel

NASA Astrophysics Data System (ADS)

Masilamani, Kannan; Ganguly, Suvankar; Feichtinger, Christian; Bartuschat, Dominik; Rüde, Ulrich

2015-06-01

In this paper, a hybrid lattice-Boltzmann and finite-difference (LB-FD) model is applied to simulate the effects of three-dimensional surface roughness and electrokinetic heterogeneity on electroosmotic flow (EOF) in a microchannel. The lattice-Boltzmann (LB) method has been employed to obtain the flow field and a finite-difference (FD) method is used to solve the Poisson-Boltzmann (PB) equation for the electrostatic potential distribution. Numerical simulation of flow through a square cross-section microchannel with designed roughness is conducted and the results are critically analysed. The effects of surface heterogeneity on the electroosmotic transport are investigated for different roughness height, width, roughness interval spacing, and roughness surface potential. Numerical simulations reveal that the presence of surface roughness changes the nature of electroosmotic transport through the microchannel. It is found that the electroosmotic velocity decreases with the increase in roughness height and the velocity profile becomes asymmetric. For the same height of the roughness elements, the EOF velocity rises with the increase in roughness width. For the heterogeneously charged rough channel, the velocity profile shows a distinct deviation from the conventional plug-like flow pattern. The simulation results also indicate locally induced flow vortices which can be utilized to enhance the flow and mixing within the microchannel. The present study has important implications towards electrokinetic flow control in the microchannel, and can provide an efficient way to design a microfluidic system of practical interest.

Influence of Wire Electrical Discharge Machining (WEDM) process parameters on surface roughness

NASA Astrophysics Data System (ADS)

Yeakub Ali, Mohammad; Banu, Asfana; Abu Bakar, Mazilah

2018-01-01

In obtaining the best quality of engineering components, the quality of machined parts surface plays an important role. It improves the fatigue strength, wear resistance, and corrosion of workpiece. This paper investigates the effects of wire electrical discharge machining (WEDM) process parameters on surface roughness of stainless steel using distilled water as dielectric fluid and brass wire as tool electrode. The parameters selected are voltage open, wire speed, wire tension, voltage gap, and off time. Empirical model was developed for the estimation of surface roughness. The analysis revealed that off time has a major influence on surface roughness. The optimum machining parameters for minimum surface roughness were found to be at a 10 V open voltage, 2.84 μs off time, 12 m/min wire speed, 6.3 N wire tension, and 54.91 V voltage gap.

Osteoblast response to magnesium ion-incorporated nanoporous titanium oxide surfaces.

PubMed

Park, Jin-Woo; Kim, Youn-Jeong; Jang, Je-Hee; Song, Hwangjun

2010-11-01

This study investigated the surface characteristics and in vitro osteoconductivity of a titanium (Ti) surface incorporated with the magnesium ions (Mg) produced by hydrothermal treatment for future application as an endosseous implant surface. Mg-incorporated Ti oxide surfaces were produced by hydrothermal treatment using Mg-containing solution on two different microstructured surfaces--abraded minimally rough (Ma) or grit-blasted moderately rough (RBM) samples. The surface characteristics were evaluated using scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, optical profilometry, and inductively coupled plasma atomic emission spectroscopy (ICP-AES). MC3T3-E1 pre-osteoblast cell attachment, proliferation, alkaline phosphatase (ALP) activity, and quantitative analysis of osteoblastic gene expression on Ma, RBM, Mg-incorporated Ma (Mg), and Mg-incorporated grit-blasted (RBM/Mg) Ti surfaces were evaluated. Hydrothermal treatment produced an Mg-incorporated Ti oxide layer with nanoporous surface structures. Mg-incorporated surfaces showed surface morphologies and surface roughness values almost identical to those of untreated smooth or micro-rough surfaces at the micron scale. ICP-AES analysis showed Mg ions released from treated surfaces into the solution. Mg incorporation significantly increased cellular attachment (P=0 at 0.5 h, P=0.01 at 1 h) on smooth surfaces, but no differences were found on micro-rough surfaces. Mg incorporation further increased ALP activity in cells grown on both smooth and micro-rough surfaces at 7 and 14 days of culture (P=0). Real-time polymerase chain reaction analysis showed higher mRNA expressions of the osteoblast transcription factor gene (Dlx5), various integrins, and the osteoblast phenotype genes (ALP, bone sialoprotein and osteocalcin) in cells grown on micro-rough (RBM) and Mg-incorporated (Mg and RBM/Mg) surfaces than those on Ma surfaces. Mg incorporation further increased the mRNA expressions of key osteoblast genes and integrins (α1, α2, α5, and β1) in cells grown on both the smooth and the micro-rough surfaces. These results indicate that an Mg-incorporated nanoporous Ti oxide surface produced by hydrothermal treatment may improve implant bone healing by enhancing the attachment and differentiation of osteoblastic cells. © 2010 John Wiley & Sons A/S.

Comparison of the effect of plasma treatment and gamma ray irradiation on PS-Cu nanocomposite films surface

NASA Astrophysics Data System (ADS)

Farag, O. F.

2018-06-01

Polystyrene-copper (PS-Cu) nanocomposite films were treated with DC N2 plasma and gamma rays irradiations. The plasma treatment of PS-Cu film surface was carried out at different treatment times, gas pressure 0.4 Torr and the applied power 3.5 W. On the other hand, the treatment with gamma rays irradiation were carried out at irradiation doses 10, 30 and 50 kGy. The induced changes in surface properties of PS-Cu films were investigated with UV-viss spectroscopy, scanning electron microscopy (SEM) and FTIR spectroscopy techniques. In addition, the wettability property, surface free energy, spreading coefficient and surface roughness of the treated samples were studied by measuring the contact angle. The UV-viss spectroscopy analysis revealed that the optical band gap decreases with increasing the treatment time and the irradiation dose for plasma and gamma treatments, respectively. SEM observations showed that the particle size of copper particles was increased with increasing the treatment time and the irradiation dose, but gamma treatment changes the copper particles size from nano scale to micro scale. The contact angle measurements showing that the wettability property, surface free energy, spreading coefficient and surface roughness of the treated PS-Cu samples were increased remarkably with increasing the treatment time and the irradiation dose for plasma and gamma treatments, respectively. The contact angle, surface free energy, spreading coefficient and surface roughness of the treated PS-Cu samples are more influenced by plasma treatment than gamma treatment.

Factors Affecting Optimal Surface Roughness of AISI 4140 Steel in Turning Operation Using Taguchi Experiment

NASA Astrophysics Data System (ADS)

Novareza, O.; Sulistiyarini, D. H.; Wiradmoko, R.

2018-02-01

This paper presents the result of using Taguchi method in turning process of medium carbon steel of AISI 4140. The primary concern is to find the optimal surface roughness after turning process. The taguchi method is used to get a combination of factors and factor levels in order to get the optimum surface roughness level. Four important factors with three levels were used in experiment based on Taguchi method. A number of 27 experiments were carried out during the research and analysed using analysis of variance (ANOVA) method. The result of surface finish was determined in Ra type surface roughness. The depth of cut was found to be the most important factors for reducing the surface roughness of AISI 4140 steel. On the contrary, the other important factors i.e. spindle speed and rake side angle of the tool were proven to be less factors that affecting the surface finish. It is interesting to see the effect of coolant composition that gained the second important factors to reduce the roughness. It may need further research to explain this result.

Ion radiation albedo effect: influence of surface roughness on ion implantation and sputtering of materials

NASA Astrophysics Data System (ADS)

Li, Yonggang; Yang, Yang; Short, Michael P.; Ding, Zejun; Zeng, Zhi; Li, Ju

2017-01-01

In fusion devices, ion retention and sputtering of materials are major concerns in the selection of compatible plasma-facing materials (PFMs), especially in the context of their microstructural conditions and surface morphologies. We demonstrate how surface roughness changes ion implantation and sputtering of materials under energetic ion irradiation. Using a new, sophisticated 3D Monte Carlo (MC) code, IM3D, and a random rough surface model, ion implantation and the sputtering yields of tungsten (W) with a surface roughness varying between 0-2 µm have been studied for irradiation by 0.1-1 keV D+, He+ and Ar+ ions. It is found that both ion backscattering and sputtering yields decrease with increasing roughness; this is hereafter called the ion radiation albedo effect. This effect is mainly dominated by the direct, line-of-sight deposition of a fraction of emitted atoms onto neighboring asperities. Backscattering and sputtering increase with more oblique irradiation angles. We propose a simple analytical formula to relate rough-surface and smooth-surface results.

Simple model of surface roughness for binary collision sputtering simulations

NASA Astrophysics Data System (ADS)

Lindsey, Sloan J.; Hobler, Gerhard; Maciążek, Dawid; Postawa, Zbigniew

2017-02-01

It has been shown that surface roughness can strongly influence the sputtering yield - especially at glancing incidence angles where the inclusion of surface roughness leads to an increase in sputtering yields. In this work, we propose a simple one-parameter model (the "density gradient model") which imitates surface roughness effects. In the model, the target's atomic density is assumed to vary linearly between the actual material density and zero. The layer width is the sole model parameter. The model has been implemented in the binary collision simulator IMSIL and has been evaluated against various geometric surface models for 5 keV Ga ions impinging an amorphous Si target. To aid the construction of a realistic rough surface topography, we have performed MD simulations of sequential 5 keV Ga impacts on an initially crystalline Si target. We show that our new model effectively reproduces the sputtering yield, with only minor variations in the energy and angular distributions of sputtered particles. The success of the density gradient model is attributed to a reduction of the reflection coefficient - leading to increased sputtering yields, similar in effect to surface roughness.

Effects of soil surface roughness on interrill erosion processes and sediment particle size distribution

USDA-ARS?s Scientific Manuscript database

Soil surface roughness significantly impacts runoff and erosion under rainfall. Few previous studies on runoff generation focused on the effects of soil surface roughness on the sediment particle size distribution (PSD), which greatly affects interrill erosion and sedimentation processes. To address...

Roughness based perceptual analysis towards digital skin imaging system with haptic feedback.

PubMed

Kim, K

2016-08-01

To examine psoriasis or atopic eczema, analyzing skin roughness by palpation is essential to precisely diagnose skin diseases. However, optical sensor based skin imaging systems do not allow dermatologists to touch skin images. To solve the problem, a new haptic rendering technology that can accurately display skin roughness must be developed. In addition, the rendering algorithm must be able to filter spatial noises created during 2D to 3D image conversion without losing the original roughness on the skin image. In this study, a perceptual way to design a noise filter that will remove spatial noises and in the meantime recover maximized roughness is introduced by understanding human sensitivity on surface roughness. A visuohaptic rendering system that can provide a user with seeing and touching digital skin surface roughness has been developed including a geometric roughness estimation method from a meshed surface. In following, a psychophysical experiment was designed and conducted with 12 human subjects to measure human perception with the developed visual and haptic interfaces to examine surface roughness. From the psychophysical experiment, it was found that touch is more sensitive at lower surface roughness, and vice versa. Human perception with both senses, vision and touch, becomes less sensitive to surface distortions as roughness increases. When interact with both channels, visual and haptic interfaces, the performance to detect abnormalities on roughness is greatly improved by sensory integration with the developed visuohaptic rendering system. The result can be used as a guideline to design a noise filter that can perceptually remove spatial noises while recover maximized roughness values from a digital skin image obtained by optical sensors. In addition, the result also confirms that the developed visuohaptic rendering system can help dermatologists or skin care professionals examine skin conditions by using vision and touch at the same time. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effect of sealer coating and storage methods on the surface roughness of soft liners.

PubMed

Usta Kutlu, Ilknur; Yanikoğlu, Nuran Dinckal; Kul, Esra; Duymuş, Zeynep Yesïl; Sağsöz, Nurdan Polat

2016-03-01

A soft lining is applied under a removable prosthesis for various reasons. The porosity of the lining material may increase colonization by microorganisms and cause tissue inflammation. The purpose of this in vitro study was to evaluate the effect of sealer coating on the surface roughness of soft lining materials under 4 different conditions. A total of 125 specimens were prepared. One high-temperature silicone-based soft lining material and 2 room-temperature-polymerized soft lining materials (1 silicone-based and 1 methacrylate-based) were used. Twenty-five specimens of each room-temperature soft lining material were coated with 2 layers of surface sealer. Additionally, 5 specimens of each material were stored in either distilled water, Coca-Cola, denture cleanser, saliva, or air. The surface roughness was measured at baseline and after 1, 7, 14, and 28 days. Surface roughness values were analyzed with repeated measures analysis of variance, and the Bonferroni multiple comparison test was performed using time-dependent groups and storage methods. In the time-dependent groups, methacrylate-based sealer-coated soft liners exhibited a significant increase in roughness (1.74-2.09 μm, P<.001), and silicone-based sealer-coated soft liners exhibited a decrease in roughness, but it was not significant (2.16-2.02 μm, P>.05). Therefore, the sealer coating was not effective in reducing surface roughness. Among the time-dependent storage methods, the denture cleanser exhibited an almost significant increase in roughness (1.83-1.99 μm, P=.054). Coca-Cola and artificial saliva did not show a significant difference (P>.05). However, a significant decrease in roughness was found with distilled water (P=.02) and air (P<.001). Statistically significant differences in surface roughness were found among the different types of soft liners. The sealer coating had no significant effect, and denture cleanser slightly increased the surface roughness. Contrary to expectations, the roughness did not increase in all groups over time. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Mesoscale model response to random, surface-based perturbations — A sea-breeze experiment

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Pielke, R. A.; Miller, W. F.; Lee, T. J.

1990-09-01

The introduction into a mesoscale model of random (in space) variations in roughness length, or random (in space and time) surface perturbations of temperature and friction velocity, produces a measurable, but barely significant, response in the simulated flow dynamics of the lower atmosphere. The perturbations are an attempt to include the effects of sub-grid variability into the ensemble-mean parameterization schemes used in many numerical models. Their magnitude is set in our experiments by appeal to real-world observations of the spatial variations in roughness length and daytime surface temperature over the land on horizontal scales of one to several tens of kilometers. With sea-breeze simulations, comparisons of a number of realizations forced by roughness-length and surface-temperature perturbations with the standard simulation reveal no significant change in ensemble mean statistics, and only small changes in the sea-breeze vertical velocity. Changes in the updraft velocity for individual runs, of up to several cms-1 (compared to a mean of 14 cms-1), are directly the result of prefrontal temperature changes of 0.1 to 0.2K, produced by the random surface forcing. The correlation and magnitude of the changes are entirely consistent with a gravity-current interpretation of the sea breeze.

The effect of heat treatments applied to superstructure porcelain on the mechanical properties and microstructure of lithium disilicate glass ceramics.

PubMed

Özdemir, Hatice; Özdoğan, Alper

2018-01-30

The aim of this study was to investigate that heat treatments with different numbers applied to superstructure porcelain whether effects microstructure and mechanical properties of lithium disilicate ceramic (LDC). Eighty disc-shaped specimens were fabricated from IPS e.max Press. Specimens were fired at heating values of porcelain in different numbers and divided four groups (n=5). Initial Vickers hardness were measured and X-ray diffraction (XRD) analysis was performed. Different surface treatment were applied and then Vickers hardness, surface roughness and environmental scanning electron microscopy (ESEM) analysis were performed. Data were analyzed with Varyans analysis and Tukey HSD test (α=0.05). Initial hardness among groups was no significant different (p>0.05), but hardness and surface roughness after surface treatments were significant different (p<0.05). Lithium disilicate (LD) peaks decrease depended on firing numbers. ESEM observations showed that firing number and surface treatments effect microstructure of LDC. Increasing firing numbers and surface treatments effect the microstructure of LDC.

Spallation-induced roughness promoting high spatial frequency nanostructure formation on Cr

NASA Astrophysics Data System (ADS)

Abou-Saleh, A.; Karim, E. T.; Maurice, C.; Reynaud, S.; Pigeon, F.; Garrelie, F.; Zhigilei, L. V.; Colombier, J. P.

2018-04-01

Interaction of ultrafast laser pulses with metal surfaces in the spallation regime can result in the formation of anisotropic nanoscale surface morphology commonly referred to as laser-induced periodic surface structures (LIPSS) or ripples. The surface structures generated by a single pulse irradiation of monocrystalline Cr samples are investigated experimentally and computationally for laser fluences that produce high spatial frequency nanostructures in the multi-pulse irradiation regime. Electron microscopy reveals distinct response of samples with different crystallographic surface orientations, with (100) surfaces exhibiting the formation of more refined nanostructure by a single pulse irradiation and a more pronounced LIPSS after two laser pulses as compared to (110) surfaces. A large-scale molecular dynamics simulation of laser interaction with a (100) Cr target provides detailed information on processes responsible for spallation of a liquid layer, redistribution of molten material, and rapid resolidification of the target. The nanoscale roughness of the resolidified surface predicted in the simulation features elongated frozen nanospikes, nanorims and nanocavities with dimensions and surface density similar to those in the surface morphology observed for (100) Cr target with atomic force microscopy. The results of the simulation suggest that the types, sizes and dimensions of the nanoscale surface features are defined by the competition between the evolution of transient liquid structures generated in the spallation process and the rapid resolidification of the surface region of the target. The spallation-induced roughness is likely to play a key role in triggering the generation of high-frequency LIPSS upon irradiation by multiple laser pulses.

Fabrication of surfaces with extremely high contact angle hysteresis from polyelectrolyte multilayer.

PubMed

Wang, Liming; Wei, Jingjing; Su, Zhaohui

2011-12-20

High contact angle hysteresis on polyelectrolyte multilayers (PEMs) ion-paired with hydrophobic perfluorooctanoate anions is reported. Both the bilayer number of PEMs and the ionic strength of deposition solutions have significant influence on contact angle hysteresis: higher ionic strength and greater bilayer number cause increased contact angle hysteresis values. The hysteresis values of ~100° were observed on smooth PEMs and pinning of the receding contact line on hydrophilic defects is implicated as the cause of hysteresis. Surface roughness can be used to further tune the contact angle hysteresis on the PEMs. A surface with extremely high contact angle hysteresis of 156° was fabricated when a PEM was deposited on a rough substrate coated with submicrometer scale silica spheres. It was demonstrated that this extremely high value of contact angle hysteresis resulted from the penetration of water into the rough asperities on the substrate. The same substrate hydrophobized by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane exhibits high advancing contact angle and low hysteresis. © 2011 American Chemical Society

Moisture condensation behavior of hierarchically carbon nanotube-grafted carbon nanofibers.

PubMed

Park, Kyu-Min; Lee, Byoung-Sun; Youk, Ji Ho; Lee, Jinyong; Yu, Woong-Reol

2013-11-13

Hierarchical micro/nanosurfaces with nanoscale roughness on microscale uneven substrates have been the subject of much recent research interest because of phenomena such as superhydrophobicity. However, an understanding of the effect of the difference in the scale of the hierarchical entities, i.e., nanoscale roughness on microscale uneven substrates as opposed to nanoscale roughness on (a larger) nanoscale uneven surface, is still lacking. In this study, we investigated the effect of the difference in scale between the nano- and microscale features. We fabricated carbon nanotube-grafted carbon nanofibers (CNFs) by dispersing a catalyst precursor in poly (acrylonitrile) (PAN) solution, electrospinning the PAN/catalyst precursor solution, carbonization of electrospun PAN nanofibers, and direct growth of carbon nanotubes (CNTs) on the CNFs. We investigated the relationships between the catalyst concentrations, the size of catalyst nanoparticles on CNFs, and the sizes of CNFs and CNTs. Interestingly, the hydrophobic behavior of micro/nano and nano/nano hierarchical surfaces with water droplets was similar; however a significant difference in the water condensation behavior was observed. Water condensed into smaller droplets on the nano/nano hierarchical surface, causing it to dry much faster.

Characterizing low-Z erosion and deposition in the DIII-D divertor using aluminum

DOE PAGES

Chrobak, Chris P.; Doerner, R. P.; Stangeby, Peter C.; ...

2017-01-28

Here, we present measurements and modeling of aluminum erosion and redeposition experiments in separate helium and deuterium low power, low density L-mode plasmas at the outer divertor strike point of DIII-D to provide a low-Z material benchmark dataset for tokamak erosion-deposition modeling codes. Coatings of Al ~100nm thick were applied to ideal (smooth) and realistic (rough) surfaces and exposed to repeat plasma discharges using the DiMES probe. Redeposition and re-erosion in all cases was primarily in the downstream toroidal field direction, evident from both in-situ spectroscopic and post-mortem non spectroscopic measurements. The gross Al erosion yield estimated from both Hemore » and D plasma exposures was ~40-70% of the expected erosion yield based on theoretical physical sputtering yields. However, the multi-step redeposition and re-erosion process, and hence the measured net erosion yield and material migration, was found to be influenced by the surface roughness and/or porosity. On rough surfaces, the fraction of the eroded Al coating found redeposited outside the original coating area was 25x higher than on smooth surfaces. The amount of Al found redeposited on the rough substrate was in fact proportional to the net eroded Al, suggesting an accumulation of deposited Al in surface pores and other areas shadowed from re-erosion. In order to determine the fraction and distribution of eroded Al returning to the surface, a simple model for erosion and redeposition was developed and fitted to the measurements. The model presented here reproduces many of the observed results in these experiments by using theoretically calculated sputtering yields, calculating surface composition changes and erosion rates in time, assuming a spatial distribution function for redepositing atoms, and accounting for deposit trapping in pores. The results of the model fits reveal that total redeposition fraction increases with higher plasma temperature (~30% for 15-18eV plasmas, and ~45% for 25-30eV plasmas), and that 50% of the atoms redepositing on rough surfaces accumulated in shadowed areas.« less

Observations of internal waves in the Gulf of California by SEASAT SAR

NASA Technical Reports Server (NTRS)

Fu, L. L.; Holt, B.

1983-01-01

Internal waves which are among the most commonly observed oceanic phenomena in the SEASAT SAR imagery are discussed. These waves are associated with the vertical displacements of constant water density surfaces in the ocean. Their amplitudes are maximum at depths where the water density changes most rapidly usually at depths from 50 to 100 m, whereas the horizontal currents associated with these waves are maximum at the sea surface where the resulting oscillatory currents modulate the sea surface roughness and produce the signatures detected by SAR.

Observations of internal waves in the Gulf of California by SEASAT SAR

NASA Astrophysics Data System (ADS)

Fu, L. L.; Holt, B.

1983-07-01

Internal waves which are among the most commonly observed oceanic phenomena in the SEASAT SAR imagery are discussed. These waves are associated with the vertical displacements of constant water density surfaces in the ocean. Their amplitudes are maximum at depths where the water density changes most rapidly usually at depths from 50 to 100 m, whereas the horizontal currents associated with these waves are maximum at the sea surface where the resulting oscillatory currents modulate the sea surface roughness and produce the signatures detected by SAR.

Boundary-layer transition on cones at angle of attack in a Mach-6 Quiet Tunnel

NASA Astrophysics Data System (ADS)

Swanson, Erick O.

It is desirable for the boundary layer on a re-entry vehicle (RV) to be laminar during as much of its flight as possible, since a turbulent boundary layer causes several problems, such as high heat flux to the vehicle and larger drag forces. Nosetip roughness can cause the boundary layer to transition downstream on the cone. Surface roughness and nosetip bluntness may cause windside-forward transition on maneuvering RVs. The crossflow instability may also influence transition on yawed RVs. The mechanisms through which these phenomena induce transition are poorly understood. Several experiments have been conducted to study these phenomena. The temperature-sensitive-paint (TSP) and oil-flow techniques were used to observe transition and crossflow vortices on cones at angle of attack in the Purdue Boeing/AFOSR Mach-6 Quiet Tunnel. The high-Reynolds number capability of the tunnel was developed to facilitate these experiments. Improvements were made in the use of the temperature-sensitive-paint technique in the Purdue Mach-6 Quiet Tunnel. The measured heat transfer to cones with sharp and spherically-blunt nosetips at 0° angle-of-attack was within 60% of the values from Navier-Stokes computations. Transition was observed on sharp and spherically-blunt cones at 6° angle-of-attack in noisy flow. Crossflow vortices were observed with both TSP and oil flow under noisy conditions in the turbulent boundary layer on a sharp cone. The vortex angles were about 50% of the surface-streamline angles observed using oil dots. TSP was also used to observe crossflow vortices in quiet flow. The vortices were similar to those seen in noisy flow. An array of roughness elements at x = 2 inches (axially) with a spacing of 9° on a yawed sharp cone in noisy flow influenced transition that was apparently induced by the crossflow instability. No influence of the roughness array was observed in quiet flow.

[Modeling and Simulation of Spectral Polarimetric BRDF].

PubMed

Ling, Jin-jiang; Li, Gang; Zhang, Ren-bin; Tang, Qian; Ye, Qiu

2016-01-01

Under the conditions of the polarized light, The reflective surface of the object is affected by many factors, refractive index, surface roughness, and so the angle of incidence. For the rough surface in the different wavelengths of light exhibit different reflection characteristics of polarization, a spectral polarimetric BRDF based on Kirchhof theory is proposee. The spectral model of complex refraction index is combined with refraction index and extinction coefficient spectral model which were got by using the known complex refraction index at different value. Then get the spectral model of surface roughness derived from the classical surface roughness measuring method combined with the Fresnel reflection function. Take the spectral model of refraction index and roughness into the BRDF model, then the spectral polarimetirc BRDF model is proposed. Compare the simulation results of the refractive index varies with wavelength, roughness is constant, the refraction index and roughness both vary with wavelength and origin model with other papers, it shows that, the spectral polarimetric BRDF model can show the polarization characteristics of the surface accurately, and can provide a reliable basis for the application of polarization remote sensing, and other aspects of the classification of substances.

Eggshell structure in Caiman latirostris eggs improves embryo survival during nest inundation.

PubMed

Cedillo-Leal, César; Simoncini, Melina S; Leiva, Pamela M L; Larriera, Alejandro; Lang, Jeffrey W; Piña, Carlos I

2017-05-17

Egg inundation often results in poor hatching success in crocodylians. However, how tolerant eggs are to submergence, and/or how eggshell ultrastructure may affect embryo survival when inundated, are not well understood. In this study, our objective was to determine if embryo survival in Caiman latirostris is affected by eggshell surface roughness, when eggs are submerged under water. Tolerance to inundation was tested early (day 30) versus late (day 60) in development, using eight clutches (four per time treatments), subdivided into four groups: ( N = 9 per clutch per treatment; 9 × 4 = 36 eggs per group). 'Rough' eggshell represented the natural, unmodified eggshell surface structure. 'Smooth' eggshell surface structure was created by mechanically sanding the natural rough surface to remove surface columnar elements and secondary layer features, e.g. irregularities that result in 'roughness'. When inundated by submerging eggs under water for 10 h at day 30, 'smooth' eggshell structure resulted in more than twice as many dead embryos (16 versus 6, smooth versus rough; N = 36), and fewer than half as many healthy embryos (6 versus 13, smooth versus rough, respectively; N = 36). By contrast, at day 60, inundation resulted in very low hatching success, regardless of eggshell surface structure. Only two hatchlings survived the inundation, notably in the untreated group with intact, rough eggshells. Inundation produced a high rate of malformations (58% at day 30), but did not affect hatchling size. Our results indicate that eggshell roughness enhances embryo survival when eggs are inundated early in development, but not late in development. Apparently, the natural surface 'roughness' entraps air bubbles at the eggshell surface during inundation, thereby facilitating gas exchange through the eggshell even when the egg is submerged under water. © 2017 The Author(s).

Development of the Navy’s Next-Generation Nonhydrostatic Modeling System

DTIC Science & Technology

2013-09-30

e.g. surface roughness, land- sea mask, surface albedo ) are needed by physical parameterizations. The surface values will be read and interpolated...characteristics (e.g. albedo , surface roughness) is now available to the model during the initialization stage. We have added infrastructure to the...six faces (Fig 3). 4 Figure 3: Topography (top left, in meters), surface roughness (top right, in meters), albedo (bottom left, no units

Effect of Pd Surface Roughness on the Bonding Process and High Temperature Reliability of Au Ball Bonds

NASA Astrophysics Data System (ADS)

Huang, Y.; Kim, H. J.; McCracken, M.; Viswanathan, G.; Pon, F.; Mayer, M.; Zhou, Y. N.

2011-06-01

A 0.3- μm-thick electrolytic Pd layer was plated on 1 μm of electroless Ni on 1 mm-thick polished and roughened Cu substrates with roughness values ( R a) of 0.08 μm and 0.5 μm, respectively. The rough substrates were produced with sand-blasting. Au wire bonding on the Ni/Pd surface was optimized, and the electrical reliability was investigated under a high temperature storage test (HTST) during 800 h at 250°C by measuring the ball bond contact resistance, R c. The average value of R c of optimized ball bonds on the rough substrate was 1.96 mΩ which was about 40.0% higher than that on the smooth substrate. The initial bondability increased for the rougher surface, so that only half of the original ultrasonic level was required, but the reliability was not affected by surface roughness. For both substrate types, HTST caused bond healing, reducing the average R c by about 21% and 27%, respectively. Au diffusion into the Pd layer was observed in scanning transmission electron microscopy/ energy dispersive spectroscopy (STEM-EDS) line-scan analysis after HTST. It is considered that diffusion of Au or interdiffusion between Au and Pd can provide chemically strong bonding during HTST. This is supported by the R c decrease measured as the aging time increased. Cu migration was indicated in the STEM-EDS analysis, but its effect on reliability can be ignored. Au and Pd tend to form a complete solid solution at the interface and can provide reliable interconnection for high temperature (250°C) applications.

Effect of vital tooth bleaching on solubility and roughness of dental cements.

PubMed

Londono, Jimmy; Abreu, Amara; Nelson, Steve; Hernandez, Jorge; Torres, Carlos; Mettenburg, Donald; Looney, Stephen; Rueggeberg, Frederick

2009-09-01

Vital tooth bleaching may affect properties of dental cements used for fixed prostheses. The purpose of this study was to examine the effect of a combined in-office and at-home bleaching regimen on changes in surface roughness and depth loss of a variety of commercially available dental cements. Five cement classifications were tested: glass ionomer, resin-modified glass ionomer, resin,self-adhesive resin cement, and zinc phosphate. Cements were placed in multiple wells in plastic blocks. After setting,the surface profile of each block was determined, and average roughness and vertical height of cement surface from the specimen holder were recorded. Blocks were water stored (control) or subjected to in-office and at-home bleaching(n=12). Surfaces were rescanned and pre- and posttest parameter changes were calculated. Statistical analysis consisted of Mann-Whitney-Wilcoxon Rank Sum and Student t tests applied to control and bleaching parameterc hanges within the same cements. A family-wise alpha of .05 was maintained by using a Bonferroni-adjusted level of significance preset to .01 per test. Zinc phosphate showed the only significant depth increase (P=.004) from bleaching: 0.9 +/- 0.7 microm deeper than the water-control group. Only resin-modified glass ionomer showed a significant (P=.004) increase in roughness from bleaching; values increased by 0.05 +/- 0.03 microm over the water-control group. In-office and at-home bleaching significantly increased depth loss of zinc phosphate and increased resinmodified glass ionomer roughness. However, the absolute values of differences observed, as compared to the wateronly control, were considered to be clinically insignificant. (J Prosthet Dent 2009;102:148-154)

Gloss measurements and rugometric inspection in dental biomaterials

NASA Astrophysics Data System (ADS)

Fernández-Oliveras, Alicia; Costa, Manuel F. M.; Yebra, Ana; Rubiño, Manuel; Pérez, María. M.

2013-11-01

In dental applications, optimizing appearance is desirable and increasingly demanded by patients. The specular gloss is among the major appearance properties of dental biomaterials, and its relationship with surface roughness has been reported. Roughness and gloss are key surface aspects that complement each other. We have experimentally analyzed the specular gloss and surface roughness of two different types of dental-resin composites and pre-sintered and sintered zirconia ceramics. We have studied two shades of both composite types and two sintered zirconia ceramics: colored and uncolored. Moreover, a surface treatment was applied to one specimen of each dental resin. Gloss measurements were performed with a standardized reflectometer and the corresponding gloss percentages were calculated. All the samples were submitted to rugometric non-invasive inspection with the MICROTOP.06.MFC laser microtopographer in order to determine meaningful statistical parameters such as the average roughness (Ra) and the root-mean-square deviation (Rq). For a comparison of the different biomaterials, the uncertainties associated to the measure of the surface gloss and roughness were also determined. The differences between the two shades of both kinds of composites proved significant in the case of the roughness parameters but not for the specular gloss. The surface treatment applied to the dental-resin composites increased the average roughness but the changes in the specular gloss were significant only for the A2 enamel nano-composite. For the zirconia ceramic the sintered process resulted in an increase in the surface roughness with a decrease of the specular gloss, corroborating that the relationship between the gloss and the roughness shows the expected behavior.

RANS Based Methodology for Predicting the Influence of Leading Edge Erosion on Airfoil Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Langel, Christopher M.; Chow, Raymond C.; van Dam, C. P.

The impact of surface roughness on flows over aerodynamically designed surfaces is of interested in a number of different fields. It has long been known the surface roughness will likely accelerate the laminar- turbulent transition process by creating additional disturbances in the boundary layer. However, there are very few tools available to predict the effects surface roughness will have on boundary layer flow. There are numerous implications of the premature appearance of a turbulent boundary layer. Increases in local skin friction, boundary layer thickness, and turbulent mixing can impact global flow properties compounding the effects of surface roughness. With thismore » motivation, an investigation into the effects of surface roughness on boundary layer transition has been conducted. The effort involved both an extensive experimental campaign, and the development of a high fidelity roughness model implemented in a R ANS solver. Vast a mounts of experimental data was generated at the Texas A&M Oran W. Nicks Low Speed Wind Tunnel for the calibration and validation of the roughness model described in this work, as well as future efforts. The present work focuses on the development of the computational model including a description of the calibration process. The primary methodology presented introduces a scalar field variable and associated transport equation that interacts with a correlation based transition model. The additional equation allows for non-local effects of surface roughness to be accounted for downstream of rough wall sections while maintaining a "local" formulation. The scalar field is determined through a boundary condition function that has been calibrated to flat plate cases with sand grain roughness. The model was initially tested on a NACA 0012 airfoil with roughness strips applied to the leading edge. Further calibration of the roughness model was performed using results from the companion experimental study on a NACA 63 3 -418 airfoil. The refined model demonstrates favorable agreement predicting changes to the transition location, as well as drag, for a number of different leading edge roughness configurations on the NACA 63 3-418 airfoil. Additional tests were conducted on a thicker S814 airfoil, with similar roughness configurations to the NACA 63 3-418. Simulations run with the roughness model compare favorably with the results obtained in the experimental study for both airfoils.« less

Surface Roughness and Gloss of Actual Composites as Polished With Different Polishing Systems.

PubMed

Rodrigues-Junior, S A; Chemin, P; Piaia, P P; Ferracane, J L

2015-01-01

This in vitro study evaluated the effect of polishing with different polishing systems on the surface roughness and gloss of commercial composites. One hundred disk-shaped specimens (10 mm in diameter × 2 mm thick) were made with Filtek P-90, Filtek Z350 XT, Opallis, and Grandio. The specimens were manually finished with #400 sandpaper and polished by a single operator using three multistep systems (Superfix, Diamond Pro, and Sof-lex), one two-step system (Polidores DFL), and one one-step system (Enhance), following the manufacturer's instructions. The average surface roughness (μm) was measured with a surface profilometer (TR 200 Surface Roughness Tester), and gloss was measured using a small-area glossmeter (Novo-Curve, Rhopoint Instrumentation, East Sussex, UK). Data were analyzed by two-way analysis of variance and Tukey's test (α=0.05). Statistically significant differences in surface roughness were identified by varying the polishing systems (p<0.0001) and by the interaction between polishing system and composite (p<0.0001). Pairwise comparisons revealed higher surface roughness for Grandio when polished with Sof-Lex and Filtek Z250 and Opallis when polished with Enhance. Gloss was influenced by the composites (p<0.0001), the polishing systems (p<0.0001), and the interaction between them (p<0.0001). The one-step system, Enhance, produced the lowest gloss for all composites. Surface roughness and gloss were affected by composites and polishing systems. The interaction between both also influenced these surface characteristics, meaning that a single polishing system will not behave similarly for all composites. The multistep systems produced higher gloss, while the one-step system produced the highest surface roughness and the lowest gloss of all.

Effect of surface pre-treatments on biocompatibility of magnesium.

PubMed

Lorenz, Carla; Brunner, Johannes G; Kollmannsberger, Philip; Jaafar, Leila; Fabry, Ben; Virtanen, Sannakaisa

2009-09-01

This study reports the influence of Mg surface passivation on the survival rate of human HeLa cells and mouse fibroblasts in cell culture experiments. Polished samples of commercially pure Mg show high reactivity in the cell culture medium, leading to a pH shift in the alkaline direction, and therefore cell adhesion and survival is strongly impaired. Passivation of the Mg surface in 1M NaOH can strongly enhance cell survival. The best initial cell adhesion is observed for Mg samples incubated in simulated body fluid (M-SBF), which leads to the formation of a biomimetic, amorphous Ca/Mg-phosphate layer with high surface roughness. This surface layer, however, passivates and seals the Mg surface only partially. Subsequent Mg dissolution leads to a significantly stronger pH increase compared to NaOH-passivated samples, which prevents long-term cell survival. These results demonstrate that surface passivation with NaOH and M-SBF together with the associated changes of surface reactivity, chemistry and roughness provide a viable strategy to facilitate cell survival on otherwise non-biocompatible Mg surfaces.

Analysis of composite/difference field scattering properties between a slightly rough optical surface and multi-body defects.

PubMed

Gong, Lei; Wu, Zhensen; Gao, Ming; Qu, Tan

2018-03-20

The effective extraction of optical surface roughness and defect characteristic provide important realistic values to improve optical system efficiency. Based on finite difference time domain/multi-resolution time domain (FDTD/MRTD) mixed approach, composite scattering between a slightly rough optical surface and multi-body defect particles with different positions is investigated. The scattering contribution of defect particles or the slightly rough optical surface is presented. Our study provides a theoretical and technological basis for the nondestructive examination and optical performance design of nanometer structures.

Surface Roughness Measurement on a Wing Aircraft by Speckle Correlation

PubMed Central

Salazar, Félix; Barrientos, Alberto

2013-01-01

The study of the damage of aeronautical materials is important because it may change the microscopic surface structure profiles. The modification of geometrical surface properties can cause small instabilities and then a displacement of the boundary layer. One of the irregularities we can often find is surface roughness. Due to an increase of roughness and other effects, there may be extra momentum losses in the boundary layer and a modification in the parasite drag. In this paper we present a speckle method for measuring the surface roughness on an actual unmanned aircraft wing. The results show an inhomogeneous roughness distribution on the wing, as expected according to the anisotropic influence of the winds over the entire wing geometry. A calculation of the uncertainty of the technique is given. PMID:24013488

Surface changes of enamel after brushing with charcoal toothpaste

NASA Astrophysics Data System (ADS)

Pertiwi, U. I.; Eriwati, Y. K.; Irawan, B.

2017-08-01

The aim of this study was to determine the surface roughness changes of tooth enamel after brushing with charcoal toothpaste. Thirty specimens were brushed using distilled water (the first group), Strong® Formula toothpaste (the second group), and Charcoal® Formula toothpaste for four minutes and 40 seconds (equivalent to one month) and for 14 minutes (equivalent to three months) using a soft fleece toothbrush with a mass of 150 gr. The roughness was measured using a surface roughness tester, and the results were tested with repeated ANOVA test and one-way ANOVA. The value of the surface roughness of tooth enamel was significantly different (p<0.05) after brushing for an equivalent of one month and an equivalent of three months. Using toothpaste containing charcoal can increase the surface roughness of tooth enamel.