Science.gov

Sample records for rough surface scattering

  1. Modeling surface roughness scattering in metallic nanowires

    SciTech Connect

    Moors, Kristof; Sorée, Bart; Magnus, Wim

    2015-09-28

    Ando's model provides a rigorous quantum-mechanical framework for electron-surface roughness scattering, based on the detailed roughness structure. We apply this method to metallic nanowires and improve the model introducing surface roughness distribution functions on a finite domain with analytical expressions for the average surface roughness matrix elements. This approach is valid for any roughness size and extends beyond the commonly used Prange-Nee approximation. The resistivity scaling is obtained from the self-consistent relaxation time solution of the Boltzmann transport equation and is compared to Prange-Nee's approach and other known methods. The results show that a substantial drop in resistivity can be obtained for certain diameters by achieving a large momentum gap between Fermi level states with positive and negative momentum in the transport direction.

  2. Surface roughness scattering in multisubband accumulation layers

    NASA Astrophysics Data System (ADS)

    Fu, Han; Reich, K. V.; Shklovskii, B. I.

    2016-06-01

    Accumulation layers with very large concentrations of electrons where many subbands are filled became recently available due to ionic liquid and other new methods of gating. The low-temperature mobility in such layers is limited by the surface roughness scattering. However, theories of roughness scattering so far dealt only with the small-density single subband two-dimensional electron gas (2DEG). Here we develop a theory of roughness-scattering limited mobility for the multisubband large concentration case. We show that with growing 2D electron concentration n the surface dimensionless conductivity σ /(2 e2/h ) first decreases as ∝n-6 /5 and then saturates as ˜(d aB/Δ2)≫1 , where d and Δ are the characteristic length and height of the surface roughness and aB is the effective Bohr radius. This means that in spite of the shrinkage of the 2DEG thickness and the related increase of the scattering rate the 2DEG remains a good metal.

  3. Modeling stray light from rough surfaces and subsurface scatter

    NASA Astrophysics Data System (ADS)

    Harvey, James E.; Goshy, John J.; Pfisterer, Richard N.

    2014-09-01

    Over the years we have developed an adequate theory and understanding of surface scatter from smooth optical surfaces (Rayleigh-Rice), moderately rough surfaces with paraxial incident and scattered angles (Beckmann- Kirchhoff) and even for moderately rough surfaces with arbitrary incident and scattered angles where a linear systems formulation requiring a two-parameter family of surface transfer functions is required to characterize the surface scatter process (generalized Harvey-Shack). However, there is always some new material or surface manufacturing process that provides non-intuitive scatter behavior. The linear systems formulation of surface scatter is potentially useful even for these situations. In this paper we will present empirical models of several classes of rough surfaces or materials (subsurface scatter) that allow us to accurately model the scattering behavior at any incident angle from limited measured scatter data. In particular, scattered radiance appears to continue being the natural quantity that exhibits simple, elegant behavior only in direction cosine space.

  4. Scattering of light by molecules over a rough surface.

    PubMed

    Long, Maureen; Khine, Michelle; Kim, Arnold D

    2010-05-01

    We present a theory for the multiple scattering of light by obstacles situated over a rough surface. This problem is important for applications in biological and chemical sensors. To keep the formulation of this theory simple, we study scalar waves. This theory requires knowledge of the scattering operator (t-matrix) for each of the obstacles as well as the reflection operator for the rough surface. The scattering operator gives the field scattered by the obstacle due to an exciting field incident on the scatterer. The reflection operator gives the field reflected by the rough surface due to an exciting field incident on the rough surface. We apply this general theory for the special case of point scatterers and a slightly rough surface with homogeneous Dirichlet and Neumann boundary conditions. We show examples that demonstrate the utility of this theory. PMID:20448766

  5. Surface roughness scattering of electrons in bulk mosfets

    SciTech Connect

    Zuverink, Amanda Renee

    2015-11-01

    Surface-roughness scattering of electrons at the Si-SiO2 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 on 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

  6. Electromagnetic scattering from rough surfaces covered with short branching vegetation

    NASA Astrophysics Data System (ADS)

    Chiu, Tsen-Chieh

    1998-11-01

    Retrieval of vegetation and underlying ground surface parameters has become one of the major applications of microwave remote sensing. To accomplish this task, a necessary step is to construct high-fidelity scattering models by which the relationship between all target parameters to the radar backscatter can be established. Many scattering models have been proposed for both rough surfaces and vegetation canopies. However, many important issues such as the dielectric inhomogeneity of the underlying rough surfaces, and the near-field scattering interaction among the vegetation particles and rough surfaces, have not been addressed yet. This dissertation provides electromagnetic scattering solutions for (1) slightly rough surfaces with inhomogeneous dielectric profiles and (2) rough surfaces covered with short branching vegetation. The rough surface scattering model presented in Chapter 2 is the first analytical model which includes surface scattering up to the second order and accounts for the dielectric inhomogeneity of dielectric medium. The scattering model for short branching vegetation is a polarimetric and fully coherent model which accounts for the near-field scattering interaction between vegetation particles and underlying rough surfaces (in Chapter 3) and among vegetation particles (in Chapter 4). The construction of the scattering model for short branching vegetation and the characterization of its performance are presented in Chapter 5. Soybean plants which possess the desired branching structure are chosen as the test targets. Realistic computer-generated vegetation structures, which are essential when considering the coherence effect of the vegetation structure and the scattering interaction among particles, are used in this model. The statistics of the polarimetric radar backscatter of vegetation medium is characterized by performing Monte-Carlo simulations. The scattering models developed for individual components and the overall scattering model have

  7. Depolarization of light by rough surface of scattering phantoms

    NASA Astrophysics Data System (ADS)

    Tchvialeva, Lioudmila; Markhvida, Igor; Lee, Tim K.; Doronin, Alexander; Meglinski, Igor

    2013-02-01

    The growing interest in biomedical optics to the polarimetric methods push researchers to better understand of light depolarization during scattering in and on the surface of biological tissues. Here we study the depolarization of light propagated in silicone phantoms. The phantoms with variety of surface roughness and bulk optical properties are designed to imitate human skin. Free-space speckle patterns in parallel (III) and perpendicular (I⊥) direction in respect to incident polarization are used to get the depolarization ratio of backscattered light DR = (III - I⊥)/( III + I⊥). The Monte Carlo model developed in house is also applied to compare simulated DR with experimentally measured. DR dependence on roughness, concentration and size of scattering particles is analysed. A weak depolarization and negligible response to scattering of the medium are observed for phantoms with smooth surfaces, whereas for the surface roughness in order to the mean free path the depolarization ratio decreases and reveals dependence on the bulk scattering coefficient. In is shown that the surface roughness could be a key factor triggering the ability of tissues' characterization by depolarization ratio.

  8. Gaussian beam scattering from arbitrarily shaped objects with rough surfaces

    NASA Astrophysics Data System (ADS)

    Chen, Hui; Wu, Zhensen; Yang, Ruike; Bai, Lu

    2004-07-01

    The scattered field of Gaussian beam scattering from arbitrarily shaped dielectric objects with rough surfaces is investigated for optical and infrared frequencies by using the plane wave spectrum method and the Kirchhoff approximation, and the formulae for the coherent and incoherent scattering cross sections are obtained theoretically based on geometrical optics and tangent plane approximations. The infrared laser scattering cross sections of a rough sphere are calculated at 1.06 µm, and the influence of the beam size is analysed numerically. It is shown that when the beam size is much larger than the size of the object, the results in this paper will be close to those of an incident plane wave.

  9. Coherence of light scattered from a randomly rough surface.

    PubMed

    Leskova, T A; Maradudin, A A; Munõz-Lopez, J

    2005-03-01

    We study the coherence of p-polarized light scattered from a one-dimensional weakly rough random metal surface in contact with vacuum. The mutual coherence function of the single nonzero component of the scattered magnetic field is calculated in planes parallel to, and at increasing distances from, the mean scattering surface in the vacuum region. It is found to be the sum of a contribution that is independent of the distance from the mean surface and a contribution that is a function of this distance and decays to zero over a distance of the order of the wavelength of the incident light. It is also shown that the spatial coherence of the electromagnetic field in the far field in a plane at a fixed distance from the mean surface, as a function of the relative distance along it, mimics the surface height autocorrelation function at short relative distances and oscillates with two periods, T(1) = lambda and T(2) = lambda/sin theta(0), where theta(0) is the angle of incidence. The former is due to the excitation of lateral waves, while the latter is due to the coherent interference of the multiple scattering processes that lead to the enhanced backscattering effect. In the near field the spatial coherence of the electromagnetic field measured at a fixed distance from the mean surface displays oscillations that are due to the excitation of surface plasmon polaritons. The period of these oscillations equals the wavelength of the surface plasmon polaritons, while the exponential decay of their amplitude is determined by the energy mean free path of the surface plasmon polaritons.

  10. The phenomenon of simplified scattering from rough surfaces to reflection in fractional space

    NASA Astrophysics Data System (ADS)

    Safdari, Hadiseh; Vahabi, Mahsa; Jafari, Gholamreza

    2015-11-01

    In this paper, the scattering of incident plane waves from rough surfaces has been modeled in a fractional space. It is shown how wave scattering from a rough surface could correspond to a simple reflection problem in a fractional space. In an integer dimensional space, fluctuations of the surface result in wave scattering, while in the fractional space, these fluctuations are compensated by the geometry of space. In the fractional space, reflection is equivalent to scattering from the integer dimensional space. Comparing scattered wave functions from different self-affine rough surfaces in the framework of the Kirchhoff theory with the results from the fractional space, we see good agreement between them.

  11. Coherent effects in the scattering of light from two-dimensional rough metal surfaces.

    PubMed

    Letnes, Paul Anton; Nordam, Tor; Simonsen, Ingve

    2013-06-01

    We investigate numerically multiple light-scattering phenomena for two-dimensional randomly rough metallic surfaces, where surface plasmon polaritons (SPPs) mediate several surface scattering effects. The scattering problem is solved by numerical solution of the reduced Rayleigh equation for reflection. The multiple scattering phenomena of enhanced backscattering and enhanced forward scattering are observed in the same system, and their presence is due to the excitation of SPPs. The numerical results discussed are qualitatively different from previous results for one-dimensionally rough surfaces, as one-dimensional surfaces have a limited influence on the polarization of light.

  12. Retrieval of terahertz spectroscopic signatures in the presence of rough surface scattering using wavelet methods

    NASA Astrophysics Data System (ADS)

    Arbab, M. H.; Winebrenner, D. P.; Thorsos, E. I.; Chen, A.

    2010-11-01

    Scattering of terahertz waves by surface roughness can obscure spectral signatures of chemicals at these frequencies. We demonstrate this effect using controlled levels of surface scattering on α-lactose monohydrate pellets. Furthermore, we show an implementation of wavelet methods that can retrieve terahertz spectral information from rough surface targets. We use a multiresolution analysis of the rough-surface-scattered signal utilizing the maximal overlap discrete wavelet transform (MODWT) to extract the resonant signature of lactose. We present a periodic extension technique to circumvent the circular boundary conditions of MODWT, which can be robustly used in an automated terahertz stand-off detection device.

  13. Forward scattering of pulses from a rough sea surface by Fourier synthesis of parabolic equation solutions.

    PubMed

    Miles, David A; Hewitt, Robin N; Donnelly, Marcus K; Clarke, Timothy

    2003-09-01

    A variable depth step implementation of the range-dependent acoustic model (RAM) is applied to the modeling of forward scattering from a rough sea surface. The sea surface is treated within RAM simply as an internal interface between a water layer and an air upper halfspace. A comparison with a numerically exact integral equation is undertaken for the scattering of single frequencies from Pierson-Moskowitz sea surfaces. The method is extended to model the variability of linear frequency modulated pulses from a series of frozen sea surfaces in a shallow water waveguide. The subsequent effect of rough boundary scattering on the replica correlation process is investigated. PMID:14514180

  14. An iterative analytic—numerical method for scattering from a target buried beneath a rough surface

    NASA Astrophysics Data System (ADS)

    Xu, Run-Wen; Guo, Li-Xin; Wang, Rui

    2014-11-01

    An efficiently iterative analytical—numerical method is proposed for two-dimensional (2D) electromagnetic scattering from a perfectly electric conducting (PEC) target buried under a dielectric rough surface. The basic idea is to employ the Kirchhoff approximation (KA) to accelerate the boundary integral method (BIM). Below the rough surface, an iterative system is designed between the rough surface and the target. The KA is used to simulate the initial field on the rough surface based on the Fresnel theory, while the target is analyzed by the boundary integral method to obtain a precise result. The fields between the rough surface and the target can be linked by the boundary integral equations below the rough surface. The technique presented here is highly efficient in terms of computational memory, time, and versatility. Numerical simulations of two typical models are carried out to validate the method.

  15. On high-frequency radiation scattering sensitivity to surface roughness in particulate media

    NASA Astrophysics Data System (ADS)

    Zohdi, T. I.

    2016-06-01

    This paper analyzes the sensitivity of high-frequency radiation scattering in particulate media, to particle surface roughness. Ray-tracing theory and computation are employed. Since the magnitude of the Poynting vector ray, the irradiance, is the appropriate quantity to be tracked, the behavior of the reflectance, which controls the ratio of the reflected and incident Poynting vector magnitudes, is of primary concern. The reflectance is a highly nonlinear function of the refractive indices and angle of incidence. The present work first addresses the relationship between a single scatterer's sensitivity to its surface roughness and then the response of a large number of scatterers to the surface roughness. The analysis indicates that, for a single scatterer, the sensitivity of the response to roughness decreases, up to a point, and then increases again, i.e., it is nonmonotone. However, for a system of multiple scatterers, this effect vanishes, due to multiple internal reflections which dominate the overall response characteristics. While it was relatively straightforward to compute the overall sensitivity of a single scattering body, for example a sphere, when multiple reflecting bodies are considered, numerical simulations are necessary because the reflected rays from one "rough" body will, in turn, be reflected to another "rough" body, etc. Examples are given for a system of randomly distributed scatterers.

  16. The IEM2M rough-surface scattering model for complex-permittivity scattering media

    NASA Astrophysics Data System (ADS)

    Álvarez-Pérez, José L.

    2012-05-01

    The integral equation model (IEM) was developed in the late 1980s and arguably became the most cited and implemented rough-surface scattering model in the field of radar remote sensing for Earth observation. It was derived by applying a second-order iteration in the incident electromagnetic field to the integral equations of the surface fields as given by Poggio and Miller. It is thus an extension of the first-order, Born approximation of these equations that produce the classical Kirchhoff approximation. The IEM has been subject to numerous amendments and variations over the last 20 years due to the imperfect introduction and handling of the Weyl representation of the spherical wave in its first version. The work presented here is a further development of the contribution made by the same author in 2001 (IEM2M), which was the first version of IEM able to blend analytically both the Kirchhoff and the small-perturbation approximations for the bistatic case. The improvement reported in this article is concerned with the inclusion of evanescent waves in the formulation of the model and the extension of the range of applicability of the second-order scattering terms to interfaces with complex-permittivity scattering media.

  17. Interference between magnetism and surface roughness in coherent soft X-ray scattering

    SciTech Connect

    Rahmim, A.; Tixier, S.; Tiedje, T.; Eisebitt, S.; Lorgen, M.; Scherer, R.; Eberhardt, W.; Luning, J.; Scholl, A.

    2002-06-15

    In coherent soft x-ray scattering from magnetically ordered surfaces there are contributions to the scattering from the magnetic domains, from the surface roughness, and from the diffraction associated with the pinhole aperture used as a coherence filter. In the present work, we explore the interplay between these contributions by analyzing speckle patterns in diffusely scattered x rays from the surface of magnetic thin films. Magnetic contrast from the surface of anti ferro magnetically ordered LaFeO3 films is caused by magnetic linear dichroism in resonant x-ray scattering. The samples studied possess two types of domains with their magnetic orientations perpendicular to each other. By tuning the x-ray energy from one of the two Fe-L3 resonant absorption peaks to the other, the relative amplitudes of the x-ray scattering from the two domains is inverted which results in speckle pattern changes. A theoretical expression is derived for the intensity correlation between the speckle patterns with the magnetic contrast inverted and not inverted. The model is found to be in good agreement with the x-ray-scattering observations and independent measurements of the surface roughness. An analytical expression for the correlation function gives an explicit relation between the change in the speckle pattern and the roughness, and magnetic and aperture scattering. Changes in the speckle pattern are shown to arise from beating of magnetic scattering with the roughness scattering and diffraction from the aperture. The largest effect is found when the surface roughness scatter is comparable in intensity to the magnetic scatter.

  18. Scattering of surface plasmon-polaritons and volume waves by a rough gold film.

    PubMed

    Sterligov, V A; Grytsaienko, I A; Men, Y

    2016-08-15

    A discrepancy between the theories of volume and surface plasmon-polaritons (SPPs) wave scattering was found. Its tentative explanation is related to the resonance-like emission of SPPs energy due to SPPs diffraction by a surface relief Fourier decomposition component. It was also shown that the sum of surface wave scattered intensity along a plane of incidence is proportional to surface roughness value. PMID:27519069

  19. Diffuse scattered field of elastic waves from randomly rough surfaces using an analytical Kirchhoff theory

    NASA Astrophysics Data System (ADS)

    Shi, F.; Lowe, M. J. S.; Xi, X.; Craster, R. V.

    2016-07-01

    We develop an elastodynamic theory to predict the diffuse scattered field of elastic waves by randomly rough surfaces, for the first time, with the aid of the Kirchhoff approximation (KA). Analytical expressions are derived incorporating surface statistics, to represent the expectation of the angular distribution of the diffuse intensity for different modes. The analytical solutions are successfully verified with numerical Monte Carlo simulations, and also validated by comparison with experiments. We then apply the theory to quantitatively investigate the effects of the roughness and the shear-to-compressional wave speed ratio on the mode conversion and the scattering intensity, from low to high roughness within the valid region of KA. Both the direct and the mode converted intensities are significantly affected by the roughness, which leads to distinct scattering patterns for different wave modes. The mode conversion effect is very strong around the specular angle and it is found to increase as the surface appears to be more rough. In addition, the 3D roughness induced coupling between the out-of-plane shear horizontal (SH) mode and the in-plane modes is studied. The intensity of the SH mode is shown to be very sensitive to the out-of-plane correlation length, being influenced more by this than by the RMS value of the roughness. However, it is found that the depolarization pattern for the diffuse field is independent of the actual value of the roughness.

  20. Scattering of electromagnetic waves from a periodic surface with random roughness

    NASA Technical Reports Server (NTRS)

    Yueh, H. A.; Shin, R. T.; Kong, J. A.

    1988-01-01

    Equations for the scattering of electromagnetic waves from a randomly perturbed periodic surface have been formulated using the extended boundary condition method and solved using the small perturbation method. Surface currents and scattered fields are solved for up to the second order. The results indicate that as the correlation length of the random roughness increases, the bistatic scattering patterns of the scattered fields show several beams associated with each Bragg diffraction direction of the periodic surface. The beam shape becomes broader with smaller correlation length. Results obtained using the Kirchhoff approximation are found to agree well with the present results for the hh and vv polarized backscattering coefficients for small angles of incidence.

  1. Double-scatter cross sections for two-dimensional random rough surfaces that exhibit backscatter enhancement.

    PubMed

    Bahar, E; El-Shenawee, M

    2001-01-01

    Full-wave solutions are given for the single- and double-scatter radar cross sections for two-dimensional random rough surfaces. High-frequency approximations are used for the double-scatter cross sections in order to express them as numerically tractable four-dimensional integrals. The major contributions to the double-scatter cross sections are associated with the quasi-parallel and quasi-antiparallel double-scatter paths. They come from the neighborhoods of specular points. The enhancement of the backscatter cross sections, which is associated with the quasi-antiparallel double-scatter paths, is observed for both the like- and cross-polarized cross sections.

  2. Reciprocal path scattering due to the combination of atmospheric turbulence and rough surfaces

    NASA Astrophysics Data System (ADS)

    Murphy, Robert A.; Phillips, Ronald L.

    1995-06-01

    The topic of enhanced backscattering (EBS) from random media has generated considerably research interest for the last two decades in Eastern Europe and for the last decade in the West. Two distinct scattering phenomena that are unique to scattering by random media are capable of producing enhanced backscatter: coherent reciprocal path scattering (RPS) and incoherent random focusing events. When coherent RPS is responsible for EBS, the maximum enhancement factor is two. Several theoretical models exist for EBS from random rough surfaces and by atmospheric turbulence individually; however, no theoretical model exists for the EBS due to the combination of rough surface and atmospheric turbulence enhancement. Simple geometrical optics models are presented that illustrate the EBS due to RPS by the combination of saturated atmospheric turbulence and a rough surface target upon a monostatic laser radar system.

  3. A study of scattering characteristics for micro-scale rough surfaces

    NASA Astrophysics Data System (ADS)

    Won, Yonghee

    Defining the scatter characteristics of surfaces plays an important role in various technology industries such as the semiconductor, automobile, and military industries. Scattering can be used to inspect products for problems created during the manufacturing process and to generate the specifications for engineers. In particular, scattering measurement systems and models have been developed to define the surface properties of a wide variety of materials used in manufacturing. However, most previous research has been focused on very smooth surfaces as a nano-scale roughness. The research in this paper uses the Bidirectional Reflectance Distribution Function (BRDF) and focuses on defining the scattering properties of micro-scale rough and textured surfaces for three different incident angles. Also, the parameters of ABg and Harvey-Shack models are obtained for input into optical design software.

  4. Backscattering of linearly polarized light from turbid tissue-like scattering medium with rough surface

    NASA Astrophysics Data System (ADS)

    Doronin, Alexander; Tchvialeva, Lioudmila; Markhvida, Igor; Lee, Tim K.; Meglinski, Igor

    2016-07-01

    In the framework of further development of a unified computational tool for the needs of biomedical optics, we introduce an electric field Monte Carlo (MC) model for simulation of backscattering of coherent linearly polarized light from a turbid tissue-like scattering medium with a rough surface. We consider the laser speckle patterns formation and the role of surface roughness in the depolarization of linearly polarized light backscattered from the medium. The mutual phase shifts due to the photons' pathlength difference within the medium and due to reflection/refraction on the rough surface of the medium are taken into account. The validation of the model includes the creation of the phantoms of various roughness and optical properties, measurements of co- and cross-polarized components of the backscattered/reflected light, its analysis and extensive computer modeling accelerated by parallel computing on the NVIDIA graphics processing units using compute unified device architecture (CUDA). The analysis of the spatial intensity distribution is based on second-order statistics that shows a strong correlation with the surface roughness, both with the results of modeling and experiment. The results of modeling show a good agreement with the results of experimental measurements on phantoms mimicking human skin. The developed MC approach can be used for the direct simulation of light scattered by the turbid scattering medium with various roughness of the surface.

  5. Effect of shadowing on electromagnetic scattering from rough ocean wavelike surfaces at small grazing angles

    SciTech Connect

    West, J.C.

    1997-03-01

    A hybrid moment-method/geometrical-theory-of-diffraction technique (MM/GTD) has been implemented to numerically calculate the electromagnetic scattering from one-dimensionally rough surfaces at extreme illumination angles (down to 0{degree} grazing). The hybrid approach allows the extension of the modeled scattering surface to infinity, avoiding the artificial edge diffraction that prevents use of the standard moment method at the smallest grazing angles. Numerical calculation of the backscattering from slightly rough large-scale surfaces approximating ocean wave features shows that roughness in strongly shadowed regions can contribute significantly to the total backscatter at vertical polarization. This is observed when the shadowing obstacle is several wavelengths high, and the magnitude of the shadow-region contribution does not depend on the radius-of-curvature of the shadowing feature. Strongly shadowed roughness does not significantly contribute to the backscatter at horizontal polarization, although weakly shadowed roughness near the incidence shadow boundary does. The calculations indicate that a shadowing-corrected two-scale model may be able to predict the distributed-surface portion of the sea-surface scattering from the ocean surface at grazing angles down to about 15{degree}, but at lower grazing the shadowing and large-scale curvature of the surface prevent the establishment of a Bragg resonance and invalidate the model.

  6. [Multiple scattering of visible and infrared light by sea fog over wind driving rough sea surface].

    PubMed

    Sun, Xian-Ming; Wang, Hai-Hua; Lei, Cheng-Xin; Shen, Jin

    2013-08-01

    The present paper is concerned with computing the multiple scattering characteristics of a sea fog-sea surface couple system within this context. The single scattering characteristics of sea fog were studied by Mie theory, and the multiple scattering of sunlight by single sea fog layer was studied by radiative transfer theory. The reflection function of a statistically rough ocean surface was obtained using the standard Kirchhoff formulation, with shadowing effects taken into account. The reflection properties of the combined sea fog and ocean surface were obtained employing the adding method, and the results indicated that the reflected light intensity of sea fog increased with the sea background.

  7. Optical scattering simulation of ice particles with surface roughness modeled using the Edwards-Wilkinson equation

    NASA Astrophysics Data System (ADS)

    Zhang, Jianing; Bi, Lei; Liu, Jianping; Panetta, R. Lee; Yang, Ping; Kattawar, George W.

    2016-07-01

    Constructing an appropriate particle morphology model is essential for realistic simulation of optical properties of atmospheric particles. This paper presents a model for generating surface roughness based on a combination of methods from discrete differential geometry combined with a stochastic partial differential equation for surface evolution introduced by Edwards and Wilkinson. Scattering of light by roughened particles is simulated using the Invariant Imbedding T-Matrix (II-TM) method. The effects of surface roughness on the single-scattering properties, namely, the phase matrix, asymmetry factor, and extinction efficiency, are investigated for a single wavelength in the visible range and for a range of size parameters up to x=50. Three different smooth shapes are considered: spherical, spheroidal, and hexagonal, the latter two in just the "compact particle" case of unit aspect ratio. It is shown that roughness has negligible effects on the optical scattering properties for size parameters less than 20. For size parameters ranging from 20 to 50, the phase matrix elements are more sensitive to the surface roughness than are two important integral optical properties, the extinction efficiency and asymmetry factor. As has been seen in studies using other forms of roughening, the phase function is progressively smoothed as roughness increases. The effect on extinction efficiency is to increase it, and on asymmetry factor is to decrease it. Each of these effects is relatively modest in the size range considered, but the trend of results suggests that greater effects will be seen for size parameters larger than ones considered here.

  8. Impact of phonon-surface roughness scattering on thermal conductivity of thin si nanowires.

    PubMed

    Martin, Pierre; Aksamija, Zlatan; Pop, Eric; Ravaioli, Umberto

    2009-03-27

    We present a novel approach for computing the surface roughness-limited thermal conductivity of silicon nanowires with diameter D<100 nm. A frequency-dependent phonon scattering rate is computed from perturbation theory and related to a description of the surface through the root-mean-square roughness height Delta and autocovariance length L. Using a full phonon dispersion relation, we find a quadratic dependence of thermal conductivity on diameter and roughness as (D/Delta)(2). Computed results show excellent agreement with experimental data for a wide diameter and temperature range (25-350 K), and successfully predict the extraordinarily low thermal conductivity of 2 W m(-1) K-1 at room temperature in rough-etched 50 nm silicon nanowires. PMID:19392295

  9. Light scattering by a rough surface of human skin. 2. Diffuse reflectance

    SciTech Connect

    Barun, V V; Ivanov, A P

    2013-10-31

    Based on the previously calculated luminance factors, we have investigated the integral characteristics of light reflection from a rough surface of the skin with large-scale inhomogeneities under various conditions of the skin illumination. Shadowing of incident and scattered beams by relief elements is taken into account. Diffuse reflectances by the Gaussian and the quasi-periodic surfaces are compared and, in general, both these roughness models are shown to give similar results. We have studied the effect of the angular structure of radiation multiply scattered deep in the tissue and the refraction of rays as they propagate from the dermis to the surface of the stratum corneum on the reflection characteristics of the skin surface. The importance of these factors is demonstrated. The algorithms constructed can be included in the schemes of calculation of the light fields inside and outside the medium in solving various direct and inverse problems of optics of biological tissues. (biophotonics)

  10. Double-scatter cross sections for two-dimensional random rough surfaces that exhibit backscatter enhancement.

    PubMed

    Bahar, E; El-Shenawee, M

    2001-01-01

    Full-wave solutions are given for the single- and double-scatter radar cross sections for two-dimensional random rough surfaces. High-frequency approximations are used for the double-scatter cross sections in order to express them as numerically tractable four-dimensional integrals. The major contributions to the double-scatter cross sections are associated with the quasi-parallel and quasi-antiparallel double-scatter paths. They come from the neighborhoods of specular points. The enhancement of the backscatter cross sections, which is associated with the quasi-antiparallel double-scatter paths, is observed for both the like- and cross-polarized cross sections. PMID:11151986

  11. Retrieving the size of particles with rough and complex surfaces from two-dimensional scattering patterns

    NASA Astrophysics Data System (ADS)

    Ulanowski, Z.; Hirst, E.; Kaye, P. H.; Greenaway, R.

    2012-12-01

    Scattered intensity measurement is a commonly used method for determining the size of small particles. However, it requires calibration and is subject to errors due to changes in incident irradiance or detector sensitivity. Analysis of two-dimensional scattering patterns offers an alternative approach. We test morphological image processing operations on patterns from a diverse range of particles with rough surfaces and/or complex structure, including mineral dust, spores, pollen, ice analogs and sphere clusters from 4 to 88 μm in size. It is found that the median surface area of intensity peaks is the most robust measure, and it is inversely proportional to particle size. The trend holds well for most particle types, as long as substantial roughness or complexity is present. One important application of this technique is the sizing of atmospheric particles, such as ice crystals.

  12. Multi-hybrid method for investigation of EM scattering from inhomogeneous object above a dielectric rough surface

    NASA Astrophysics Data System (ADS)

    Li, Jie; Guo, LiXin; He, Qiong; Wei, Bing

    2012-10-01

    An iterative strategy combining Kirchhoff approximation^(KA) with the hybrid finite element-boundary integral (FE-BI) method is presented in this paper to study the interactions between the inhomogeneous object and the underlying rough surface. KA is applied to study scattering from underlying rough surfaces, whereas FE-BI deals with scattering from the above target. Both two methods use updated excitation sources. Huygens equivalence principle and an iterative strategy are employed to consider the multi-scattering effects. This hybrid FE-BI-KA scheme is an improved and generalized version of previous hybrid Kirchhoff approximation-method of moments (KA-MoM). This newly presented hybrid method has the following advantages: (1) the feasibility of modeling multi-scale scattering problems (large scale underlying surface and small scale target); (2) low memory requirement as in hybrid KA-MoM; (3) the ability to deal with scattering from inhomogeneous (including coated or layered) scatterers above rough surfaces. The numerical results are given to evaluate the accuracy of the multi-hybrid technique; the computing time and memory requirements consumed in specific numerical simulation of FE-BI-KA are compared with those of MoM. The convergence performance is analyzed by studying the iteration number variation caused by related parameters. Then bistatic scattering from inhomogeneous object of different configurations above dielectric Gaussian rough surface is calculated and the influences of dielectric compositions and surface roughness on the scattering pattern are discussed.

  13. Statistical multiple diffuse scattering from rough surfaces in RHEED — beyond the distorted-wave Born approximation

    NASA Astrophysics Data System (ADS)

    Wang, Z. L.

    1996-10-01

    In reflection high-energy electron diffraction (RHEED) of growing surfaces in molecular beam epitaxy (MBE), diffuse scattering is generated by atom vibrations, point vacancies and growth islands (or surface roughness). Most of the existing RHEED theories have been developed under the first-order diffuse scattering approximation, and thus they are restricted for surfaces whose roughness is relatively low. In fact, crystal surfaces grown by MBE are usually rough; the change of surface coverage from 0 to 1 monolayer accounts for the observed RHEED oscillation. In this paper, a formal dynamical theory of RHEED has been developed to calculate the diffuse scattering produced by both atom vibrations and point vacancies at surfaces. The theory is aimed at recovering the multiple diffuse scattering that has been dropped by the distorted-wave Born approximation (DWBA). With the inclusion of a complex potential in the dynamical calculation, a rigorous proof is given to show that the high-order diffuse scattering terms are recovered in the calculation using the equation originally derived under the DWBA. This conclusion establishes the basis for expanding the RHEED theories developed under the first-order diffuse scattering to cases where the degree of surface roughness is high, allowing dynamical calculation of RHEED rocking curves for any growing surface. The statistical time and structure averages over the distorted crystal potential are evaluated analytically before numerical calculation. The dynamic form factor is calculated with consideration of anisotropic surface atom vibration and point vacancies at a growing surface.

  14. Determination of volume and surface scattering from saline ice using ice sheets with precisely controlled roughness parameters

    SciTech Connect

    Bredow, J.W.; Porco, R.L.; Fung, A.K.; Tjuatja, S.; Jezek, K.C.; Gogineni, S.; Gow, A.J.

    1995-09-01

    Experiments were performed at the US Army Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, NH, to precisely determine the relative contributions of surface and volume scattering from saline ice that has well-known surface roughness characteristics. The ice growth phase of the experiment made use of two 6-ft diameter tanks and a 6-ft diameter mold with known roughness statistical parameters of rms height = 0.25 cm and Gaussian correlation (correlation length = 2.0 cm). One tank was used for growing a moderately thick saline ice sheet with very smooth surface, and the other was used for growing a thin layer of freshwater ice over the surface mold. The latter resulted in a layer with one statistically known rough boundary and one smooth boundary. Wide-bandwidth, multiple incidence angle backscattering measurements were performed, first on the bare saline ice sheet and then on the same sheet after the thin freshwater ice sheet was placed on top of it. Results indicate that the surface scattering dominates over saline ice volume scattering at all frequencies for low incidence angles for both the very smooth and Gaussian rough surfaces. The significance of volume scattering depends strongly on angle of incidence, frequency, volume scattering albedo, surface roughness, and surface correlation function.

  15. MOLA-derived Roughness Data Used to Predict Surface Scattering for Mars Subsurface Radar Sounding

    NASA Technical Reports Server (NTRS)

    Plaut, J. J.; Garneau, S.

    1999-01-01

    The Mars Express orbiter, to be launched by the European Space Agency in 2003, will carry a low-frequency radar sounding instrument, MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding). The primary goal of MARSIS is to map the distribution of water, both solid and (if present) liquid, in the upper several km of the martian crust. Detecting discontinuities in the crust, such as an ice-water transition, presents many challenges for a Mars orbital radar sounder. One challenge that must be overcome is the presence of radar scattering (echoes) from the surface of Mars, expected to be detected by the sounder antennas at the same time as any echoes aris-ing from subsurface interfaces. As the transmitted spherical wavefront spreads within the crust of Mars,. it also interacts with surface topography at off-nadir positions, creating a "clutter" signal that can mask the subsurface echoes. The MARSIS instrument will utilize Doppler filtering to limit the off-nadir clutter in the along-track direction, and a nadir-null secondary antenna to identify strong off-nadir clutter from the cross-track direction. To evaluate the effects of off-nadir surface clutter and the capability of these schemes to reduce the clutter, it is necessary to predict the range of scattering behavior that may be expected from martian surface topography. In this paper, we utilize Mars Orbital Laser Altimeter (MOLA) data from the current Mars Global Surveyor mission to characterize the topographic roughness of a variety of martian terrain types, at scales relevant to the MARSIS clutter problem. Segments of MOLA altimetry profiles are reduced to the topographic parameters rms slope and fractal dimension, which then are used as inputs to a near-nadir radar scattering model to predict the strength of the clutter signal. Additional information is contained in the original extended abstract.

  16. Electromagnetic wave scattering at near-grazing incidence from a gently undulating, rough surface

    NASA Technical Reports Server (NTRS)

    Vesecky, J. F.; Sperley, E. J.; Zebker, H. A.

    1988-01-01

    Models to estimate the reflection coefficient of a statistically rough surface, for example the works of Beckmann, Smith, and Vesecky are discussed. Bistatic radar experiments carried out during the Apollo 16 mission provide a data set with which to compare theoretical models and experimental data. These bistatic S-band radar experiments provide experimental estimates of the Moon's bistatic, forward scatter, reflection coefficient for grazing angles of 2.5 to 78 deg. Theoretical expressions for the reflection coefficient are developed for comparison with these experimental data. At grazing angles below 10 deg the models of Smith and Vesecky compare favorably with the data. Beckmann's model falls significantly more rapidly with decreasing grazing angle than does the data.

  17. Scattering of Rarefied Gas Atoms from Rough Surface Simulated with Fractals

    NASA Astrophysics Data System (ADS)

    Aksenova, Olga A.

    2003-05-01

    The fractal approach to the model of surface roughness in the problem of gas-surface interaction is developed on the base of the generalization of two-dimensional model of roughness proposed by Blackmore and Zhou. The relation between the parameters of the model and the values influencing the aerodynamic coefficients is investigated. Computed results are compared with the values obtained using statistical model of roughness — the isotropic Gaussian random field.

  18. Effects on the Electromagnetic Scattering of a Plane Wave due to the Surface Roughness of a Buried Perfectly Conducting Pipeline

    NASA Astrophysics Data System (ADS)

    Frezza, Fabrizio; Mangini, Fabio; Stoja, Endri; Tedeschi, Nicola

    2013-04-01

    In this work we present a numerical study of the effects that can be observed in the electromagnetic scattering of a plane wave due to the surface roughness of a buried scatterer. The latter is supposed to be a metallic pipeline modeled as a perfect-electric conducting cylinder immersed in a half-space occupied by a lossy medium. Considering the pipeline's cross-section, the surface roughness is modeled as a sinusoidal variation of the radius of the cylinder's surface with respect to the revolution angle. A linearly-polarized plane wave impinging normally to the interface between air and the previously-mentioned medium excites the structure. As a result, we monitor the three components of the scattered electric field along a line just above the interface between the two media. To perform the study, a commercially available simulator which implements the Finite Element Method was adopted. In order to discriminate the effects due only to the surface roughness, we compare the results obtained by the rough surface scatterers with the reference case of a perfect cylinder in which the surface roughness is absent, for a fixed depth and a fixed mean radius of the cylinder. In our study, we vary the amplitude and the angular frequency of the sinusoidal disturbance to model different surface roughness scenarios. For all the scenarios taken in consideration, a frequency sweep of the impinging radiation is performed. This allows us to investigate the relation between the excitation frequency and the sinusoidal disturbance frequency of the rough surface. The study has several implications in the field of civil engineering. One example might be the one in which the geometrical characteristics of the buried pipeline are known in advance, and it is important to continuously monitor the structural variations of its external surface due to the deterioration in time under the action of various environmental factors.

  19. Sound scattering from rough bubbly ocean surface based on modified sea surface acoustic simulator and consideration of various incident angles and sub-surface bubbles' radii

    NASA Astrophysics Data System (ADS)

    Bolghasi, Alireza; Ghadimi, Parviz; Chekab, Mohammad A. Feizi

    2016-09-01

    The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator (SSAS) developed based on optimization of the Helmholtz-Kirchhoff-Fresnel (HKF) method. The improved acoustic simulator, hereby known as the Modified SSAS (MSSAS), is capable of determining sound scattering from the sea surface and includes an extended Hall-Novarini model and optimized HKF method. The extended Hall-Novarini model is used for considering the effects of sub-surface bubbles over a wider range of radii of sub-surface bubbles compared to the previous SSAS version. Furthermore, MSSAS has the capability of making a three-dimensional simulation of scattered sound from the rough bubbly sea surface with less error than that of the Critical Sea Tests (CST) experiments. Also, it presents scattered pressure levels from the rough bubbly sea surface based on various incident angles of sound. Wind speed, frequency, incident angle, and pressure level of the sound source are considered as input data, and scattered pressure levels and scattering coefficients are provided. Finally, different parametric studies were conducted on wind speeds, frequencies, and incident angles to indicate that MSSAS is quite capable of simulating sound scattering from the rough bubbly sea surface, according to the scattering mechanisms determined by Ogden and Erskine. Therefore, it is concluded that MSSAS is valid for both scattering mechanisms and the transition region between them that are defined by Ogden and Erskine.

  20. Sound scattering from rough bubbly ocean surface based on modified sea surface acoustic simulator and consideration of various incident angles and sub-surface bubbles' radii

    NASA Astrophysics Data System (ADS)

    Bolghasi, Alireza; Ghadimi, Parviz; Chekab, Mohammad A. Feizi

    2016-08-01

    The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator (SSAS) developed based on optimization of the Helmholtz-Kirchhoff-Fresnel (HKF) method. The improved acoustic simulator, hereby known as the Modified SSAS (MSSAS), is capable of determining sound scattering from the sea surface and includes an extended Hall-Novarini model and optimized HKF method. The extended Hall-Novarini model is used for considering the effects of sub-surface bubbles over a wider range of radii of sub-surface bubbles compared to the previous SSAS version. Furthermore, MSSAS has the capability of making a three-dimensional simulation of scattered sound from the rough bubbly sea surface with less error than that of the Critical Sea Tests (CST) experiments. Also, it presents scattered pressure levels from the rough bubbly sea surface based on various incident angles of sound. Wind speed, frequency, incident angle, and pressure level of the sound source are considered as input data, and scattered pressure levels and scattering coefficients are provided. Finally, different parametric studies were conducted on wind speeds, frequencies, and incident angles to indicate that MSSAS is quite capable of simulating sound scattering from the rough bubbly sea surface, according to the scattering mechanisms determined by Ogden and Erskine. Therefore, it is concluded that MSSAS is valid for both scattering mechanisms and the transition region between them that are defined by Ogden and Erskine.

  1. Efficiently computational techniques for solving large- scale electromagnetic problems: Microstrip interconnects and rough surface scattering

    NASA Astrophysics Data System (ADS)

    Lin, Chien-Min

    Systematically numerical implementations for solving the large-scale electromagnetic problems of microstrip interconnects and rough surface scattering are explored and demonstrated in this dissertation by comparing with the traditional methods. Having circumvented the major difficulties of numerous storage and computational complexity, the proposed methods had validated themselves on the affordable computer platforms whenever both the analytical approaches and conventional numerical methods are not applicable. In use of the Method of Moments, an integro-differential equation is first formulated in terms of surface unknowns related to the boundary conditions. Following Garlerkin's procedures, a matrix equation with a finite discretization of N unknowns is constructed. In the full- wave analysis of microstrip interconnects, Complex Image Method is used to reduce the matrix fill-time while the Mixed-Potential Integral Equation with Rao, Wilton, and Glisson triangular discretization is concerned. The impedance matrix is decomposed into a pair of strong and weak interaction matrix accounting for the separation while the integral kernels are sufficiently approximated. Recalling the Fast Fourier Transform, the weak- interaction contributions are conferred in a canonical grid using the Taylor's series expansion. A Screening Window Wavelet Transform scheme is applied to the strong- interaction matrix for the data compression and high sparsity. Based on Multiresolution Analysis, the Matrix- Vector Multiplication can be efficiently performed by the Subband Filtering Scheme in the wavelet domain. Finally, the Banded or Sparse Matrix Iterative Approach in conjunction with the Conjugate Gradient iterative method is employed to solve for the matrix equation. In addition to investigating the validity of analytical theories, the proposed methods are corroborated to study the backscattering enhancement, conical diffraction, and Stokes parameters in remote sensing and induced surface

  2. Effects of surface roughness with two scales on light scattering by hexagonal ice crystals large compared to the wavelength: DDA results

    NASA Astrophysics Data System (ADS)

    Collier, C. T.; Hesse, E.; Taylor, L.; Ulanowski, Z.; Penttilä, A.; Nousiainen, T.

    2016-10-01

    The effect of ice crystal surface roughness on light scattering by ice crystals which are large compared to the wavelength was studied, in particular changes to the 2D scattering patterns, azimuthally averaged phase functions, degree of linear polarisation patterns and asymmetry parameters for a range of orientations and roughness scales. It was found that roughness has an effect on light scattering by hexagonal prisms, particularly when the roughness features are of comparable size to the wavelength. The roughness model that has the most effect on light scattering takes account of more than one roughness scale. Rough geometry was implemented by a Gaussian roughness method that took roughness parameters derived from sand grains, which have been reported to be suitable proxies for rough ice crystals. Light scattering data for these geometries was computed using the ADDA discrete dipole approximation method.

  3. Numerical Solution of Light Scattered from and Transmitted through a Rough Dielectric Surface with Applications to Periodic Roughness and Isolated Structures

    NASA Technical Reports Server (NTRS)

    Sun, Wenbo; Videnn, Gorden; Lin, Bing; Hu, Yongxiang

    2007-01-01

    Light scattering and transmission by rough surfaces are of considerable interest in a variety of applications including remote sensing and characterization of surfaces. In this work, the finite-difference time domain technique is applied to calculate the scattered and transmitted electromagnetic fields of an infinite periodic rough surface. The elements of Mueller matrix for scattered light are calculated by an integral of the near fields over a significant number of periods of the surface. The normalized Mueller matrix elements of the scattered light and the spatial distribution of the transmitted flux for a monolayer of micron-sized dielectric spheres on a silicon substrate are presented. The numerical results show that the nonzero Mueller matrix elements of the system of the monolayer of dielectric spheres on a silicon substrate have specific maxima at some scattering angles. These maxima may be used in characterization of the feature of the system. For light transmitted through the monolayer of spheres, our results show that the transmitted energy focuses around the ray passing through centers of the spheres. At other locations, the transmitted flux is very small. The technique also may be used to calculate the perturbance of the electromagnetic field due to the presence of an isolated structure on the substrate.

  4. Random rough surface photofabrication

    NASA Astrophysics Data System (ADS)

    Brissonneau, Vincent; Escoubas, Ludovic; Flory, François; Berginc, Gérard

    2011-10-01

    Random rough surfaces are of primary interest for their optical properties: reducing reflection at the interface or obtaining specific scattering diagram for example. Thus controlling surface statistics during the fabrication process paves the way to original and specific behaviors of reflected optical waves. We detail an experimental method allowing the fabrication of random rough surfaces showing tuned statistical properties. A two-step photoresist exposure process was developed. In order to initiate photoresist polymerization, an energy threshold needs to be reached by light exposure. This energy is brought by a uniform exposure equipment comprising UV-LEDs. This pre-exposure is studied by varying parameters such as optical power and exposure time. The second step consists in an exposure based on the Gray method.1 The speckle pattern of an enlarged scattered laser beam is used to insolate the photoresist. A specific photofabrication bench using an argon ion laser was implemented. Parameters such as exposure time and distances between optical components are discussed. Then, we describe how we modify the speckle-based exposure bench to include a spatial light modulator (SLM). The SLM used is a micromirror matrix known as Digital Micromirror Device (DMD) which allows spatial modulation by displaying binary images. Thus, the spatial beam shape can be tuned and so the speckle pattern on the photoresist is modified. As the photoresist photofabricated surface is correlated to the speckle pattern used to insolate, the roughness parameters can be adjusted.

  5. Investigation on wide-band scattering of a 2-D target above 1-D randomly rough surface by FDTD method.

    PubMed

    Li, Juan; Guo, Li-Xin; Jiao, Yong-Chang; Li, Ke

    2011-01-17

    Finite-difference time-domain (FDTD) algorithm with a pulse wave excitation is used to investigate the wide-band composite scattering from a two-dimensional(2-D) infinitely long target with arbitrary cross section located above a one-dimensional(1-D) randomly rough surface. The FDTD calculation is performed with a pulse wave incidence, and the 2-D representative time-domain scattered field in the far zone is obtained directly by extrapolating the currently calculated data on the output boundary. Then the 2-D wide-band scattering result is acquired by transforming the representative time-domain field to the frequency domain with a Fourier transform. Taking the composite scattering of an infinitely long cylinder above rough surface as an example, the wide-band response in the far zone by FDTD with the pulsed excitation is computed and it shows a good agreement with the numerical result by FDTD with the sinusoidal illumination. Finally, the normalized radar cross section (NRCS) from a 2-D target above 1-D rough surface versus the incident frequency, and the representative scattered fields in the far zone versus the time are analyzed in detail.

  6. The relationship between radar scattering and surface roughness of lunar volcanic features

    NASA Astrophysics Data System (ADS)

    Jawin, Erica R.; Kiefer, Walter S.; Fassett, Caleb I.; Bussey, D. Benjamin J.; Cahill, Joshua T. S.; Dyar, M. Darby; Lawrence, Samuel J.; Spudis, Paul D.

    2014-11-01

    Lunar roughness measurements derived from the Lunar Orbiter Laser Altimeter are compared to 12.6 cm wavelength radar data collected by the Miniature Radio Frequency instrument and 70 cm wavelength radar data collected by the Arecibo Observatory. These data are compared to assess how surface and subsurface roughness are correlated and affected by parameters including age and composition at length scales between 0.1 and 100 m. A range of features are analyzed including volcanic domes (Marius Hills, Rümker Hills, Gruithuisen, and Mairan Domes); mare (Imbrium, Serenitatis, and Oceanus Procellarum); pyroclastic dark mantle deposits (Sinus Aestuum, Sulpicius Gallus, and Mare Vaporum); and two young craters (Copernicus and Tycho). Statistically significant positive correlations exist between topographic roughness and both P- and S-band circular polarization ratios. The strongest correlation is observed at the longest length scales. Correlations weaken as length scales become less similar, potentially due to distinct processes controlling surface modification. Roughness is not significantly correlated with local slope. Although the Marius Hills are compositionally distinct from the Gruithuisen and Mairan domes, they are indistinguishable in roughness characteristics. Conversely, the Rümker Hills, mare, and dark mantle deposits are smoother at the length scales examined, possibly due to fine-grained mantling of regolith or pyroclastic deposits. The floor and ejecta of Tycho are the roughest surfaces measured in this study, while the floor and ejecta of Copernicus overlap the roughness distribution of the volcanic features. This study shows that many factors control the evolution of roughness over time on various length scales.

  7. Using waveguide scattering of laser radiation for determining the autocorrelation function of statistical surface roughness within a wide range of changes of the roughness correlation interval

    SciTech Connect

    Egorov, Alexander A

    2002-04-30

    An electrodynamic problem of laser radiation scattering in an integrated-optical waveguide containing small statistical irregularities (interface roughness and irregularities of the refractive indices of the waveguide-forming media) is considered. The possibility of using the waveguide scattering of laser radiation for extracting the information on the statistical properties of irregularities from noisy data of the scattering diagram in a far-field zone is shown. An algorithm for reconstructing the autocorrelation function of irregularities for the correlation interval changing within a wide range is described. The possibility of restoring a given Gaussian autocorrelation function that describes statistical irregularities of the waveguide substrate surface for a correlation interval changing between 10 nm and 10 {mu}m and a high-level additive white real noise is shown by computer simulation. (laser applications and other topics in quantum electronics)

  8. Fast method to compute scattering by a buried object under a randomly rough surface: PILE combined with FB-SA.

    PubMed

    Bourlier, Christophe; Kubické, Gildas; Déchamps, Nicolas

    2008-04-01

    A fast, exact numerical method based on the method of moments (MM) is developed to calculate the scattering from an object below a randomly rough surface. Déchamps et al. [J. Opt. Soc. Am. A23, 359 (2006)] have recently developed the PILE (propagation-inside-layer expansion) method for a stack of two one-dimensional rough interfaces separating homogeneous media. From the inversion of the impedance matrix by block (in which two impedance matrices of each interface and two coupling matrices are involved), this method allows one to calculate separately and exactly the multiple-scattering contributions inside the layer in which the inverses of the impedance matrices of each interface are involved. Our purpose here is to apply this method for an object below a rough surface. In addition, to invert a matrix of large size, the forward-backward spectral acceleration (FB-SA) approach of complexity O(N) (N is the number of unknowns on the interface) proposed by Chou and Johnson [Radio Sci.33, 1277 (1998)] is applied. The new method, PILE combined with FB-SA, is tested on perfectly conducting circular and elliptic cylinders located below a dielectric rough interface obeying a Gaussian process with Gaussian and exponential height autocorrelation functions. PMID:18382488

  9. Energy conservation of the scattering from one-dimensional random rough surfaces in the high-frequency limit.

    PubMed

    Pinel, Nicolas; Bourlier, Christophe; Saillard, Joseph

    2005-08-01

    Energy conservation of the scattering from one-dimensional strongly rough dielectric surfaces is investigated using the Kirchhoff approximation with single reflection and by taking the shadowing phenomenon into account, both in reflection and transmission. In addition, because no shadowing function in transmission exists in the literature, this function is presented here in detail. The model is reduced to the high-frequency limit (or geometric optics). The energy conservation criterion is investigated versus the incidence angle, the permittivity of the lower medium, and the surface rms slope. PMID:16092248

  10. 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.

  11. Light scattering by a rough surface of human skin. 1. The luminance factor of reflected light

    SciTech Connect

    Barun, V V; Ivanov, A P

    2013-08-31

    Based on the analytical solution of Maxwell's equations, we have studied the angular structure of the luminance factor of light reflected by the rough skin surface with large-scale relief elements, illuminated by a directed radiation beam incident at an arbitrary angle inside or outside the medium. The parameters of the surface inhomogeneities are typical of human skin. The calculated angular dependences are interpreted from the point of view of the angular distribution function of micro areas. The results obtained can be used for solving direct and inverse problems in biomedical optics, in particular for determining the depth of light penetration into a biological tissue, for studying the light action spectra on tissue chromophores under the in vivo conditions, for developing diagnostic methods of structural and biophysical parameters of a medium, and for optimising the mechanisms of interaction of light with biological tissues under their noninvasive irradiation through skin. (biomedical optics)

  12. Examination of surface roughness on light scattering by long ice columns by use of a two-dimensional finite-difference time-domain algorithm.

    PubMed

    Sun, Wenbo; Loeb, Norman G; Videen, Gorden; Fu, Qiang

    2004-03-20

    Natural particles such as ice crystals in cirrus clouds generally are not pristine but have additional microroughness 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 microm, respectively, the errors in the FDTD results in the extinction, scattering, and absorption efficiencies are smaller than approximately 0.5%. The errors in the FDTD results in the asymmetry factor are smaller than approximately 0.05%. The errors in the FDTD results in the phase-matrix elements are smaller than approximately 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.

  13. Fast Numerical Algorithms for 3-D Scattering from PEC and Dielectric Random Rough Surfaces in Microwave Remote Sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Lisha

    We present fast and robust numerical algorithms for 3-D scattering from perfectly electrical conducting (PEC) and dielectric random rough surfaces in microwave remote sensing. The Coifman wavelets or Coiflets are employed to implement Galerkin's procedure in the method of moments (MoM). Due to the high-precision one-point quadrature, the Coiflets yield fast evaluations of the most off-diagonal entries, reducing the matrix fill effort from O(N2) to O( N). The orthogonality and Riesz basis of the Coiflets generate well conditioned impedance matrix, with rapid convergence for the conjugate gradient solver. The resulting impedance matrix is further sparsified by the matrix-formed standard fast wavelet transform (SFWT). By properly selecting multiresolution levels of the total transformation matrix, the solution precision can be enhanced while matrix sparsity and memory consumption have not been noticeably sacrificed. The unified fast scattering algorithm for dielectric random rough surfaces can asymptotically reduce to the PEC case when the loss tangent grows extremely large. Numerical results demonstrate that the reduced PEC model does not suffer from ill-posed problems. Compared with previous publications and laboratory measurements, good agreement is observed.

  14. A laboratory study of the electromagnetic bias of rough surface scattering by water waves

    NASA Technical Reports Server (NTRS)

    Parsons, Chester L.; Miller, Lee S.

    1990-01-01

    The design, development, and use of a focused-beam radar to measure the electromagnetic bias introduced by the scattering of radar waves by a roughened water surface are discussed. The bias measurements were made over wide ranges of environmental conditions in a wavetank laboratory. Wave-elevation data were provided by standard laboratory capacitance probes. Backscattered radar power measurements coincident in time and space with the elevation data were produced by the radar. The two data sets are histogrammed to produce probability density functions for elevation and radar reflectivity, from which the electromagnetic bias is computed. The experimental results demonstrate that the electromagnetic bias is quite variable over the wide range of environmental conditions that can be produced in the laboratory. The data suggest that the bias is dependent upon the local wind field and on the amplitude and frequency of any background wave field that is present.

  15. Scattering from rough thin films: discrete-dipole-approximation simulations.

    PubMed

    Parviainen, Hannu; Lumme, Kari

    2008-01-01

    We investigate the wave-optical light scattering properties of deformed thin circular films of constant thickness using the discrete-dipole approximation. Effects on the intensity distribution of the scattered light due to different statistical roughness models, model dependent roughness parameters, and uncorrelated, random, small-scale porosity of the inhomogeneous medium are studied. The suitability of the discrete-dipole approximation for rough-surface scattering problems is evaluated by considering thin films as computationally feasible rough-surface analogs. The effects due to small-scale inhomogeneity of the scattering medium are compared with the analytic approximation by Maxwell Garnett, and the results are found to agree with the approximation.

  16. Scattering of near normal incidence SH waves by sinusoidal and rough surfaces in 3-D: comparison to the scalar wave approximation.

    PubMed

    Jarvis, Andrew J C; Cegla, Frederic B

    2014-07-01

    The challenge of accurately simulating how incident scalar waves interact with rough boundaries has made it an important area of research within many scientific disciplines. Conventional methods, which in the majority of cases focus only on scattering in two dimensions, often suffer from long simulation times or reduced accuracy, neglecting phenomena such as multiple scattering and surface self-shadowing. A simulation based on the scalar wave distributed point source method (DPSM) is presented as an alternative which is computationally more efficient than fully meshed numerical methods while obtaining greater accuracy than approximate analytical techniques. Comparison is made to simulated results obtained using the finite element method for a sinusoidally periodic surface where scattering only occurs in two dimensions, showing very good agreement (<0.2 dB). In addition to two-dimensional scattering, comparison to experimental results is also carried out for scattering in three dimensions when the surface has a Gaussian roughness distribution. Results indicate that for two-dimensional scattering and for rough surfaces with a correlation length equal to the incident wavelength (λ) and a root mean square height less than 0.2λ, the scalar wave approximation predicts reflected pulse shape change and envelope amplitudes generally to within 1 dB. Comparison between transducers within a three-element array also illustrate the sensitivity pulse amplitude can have to sensor position above a rough surface, differing by as much as 17 dB with a positional change of just 1.25λ. PMID:24960707

  17. Scattering of near normal incidence SH waves by sinusoidal and rough surfaces in 3-D: comparison to the scalar wave approximation.

    PubMed

    Jarvis, Andrew J C; Cegla, Frederic B

    2014-07-01

    The challenge of accurately simulating how incident scalar waves interact with rough boundaries has made it an important area of research within many scientific disciplines. Conventional methods, which in the majority of cases focus only on scattering in two dimensions, often suffer from long simulation times or reduced accuracy, neglecting phenomena such as multiple scattering and surface self-shadowing. A simulation based on the scalar wave distributed point source method (DPSM) is presented as an alternative which is computationally more efficient than fully meshed numerical methods while obtaining greater accuracy than approximate analytical techniques. Comparison is made to simulated results obtained using the finite element method for a sinusoidally periodic surface where scattering only occurs in two dimensions, showing very good agreement (<0.2 dB). In addition to two-dimensional scattering, comparison to experimental results is also carried out for scattering in three dimensions when the surface has a Gaussian roughness distribution. Results indicate that for two-dimensional scattering and for rough surfaces with a correlation length equal to the incident wavelength (λ) and a root mean square height less than 0.2λ, the scalar wave approximation predicts reflected pulse shape change and envelope amplitudes generally to within 1 dB. Comparison between transducers within a three-element array also illustrate the sensitivity pulse amplitude can have to sensor position above a rough surface, differing by as much as 17 dB with a positional change of just 1.25λ.

  18. Satellite peaks in the scattering of light from the two-dimensional randomly rough surface of a dielectric film on a planar metal surface.

    PubMed

    Nordam, T; Letnes, P A; Simonsen, I; Maradudin, A A

    2012-05-01

    A nonperturbative, purely numerical, solution of the reduced Rayleigh equation for the scattering of p- and s-polarized light from a dielectric film with a two-dimensional randomly rough surface deposited on a planar metallic substrate, has been carried out. It is found that satellite peaks are present in the angular dependence of the elements of the mean differential reflection coefficient in addition to an enhanced backscattering peak. This result resolves a conflict between the results of earlier approximate theoretical studies of scattering from this system.

  19. Bistatic scattering from a three-dimensional object above a two-dimensional randomly rough surface modeled with the parallel FDTD approach.

    PubMed

    Guo, L-X; Li, J; Zeng, H

    2009-11-01

    We present an investigation of the electromagnetic scattering from a three-dimensional (3-D) object above a two-dimensional (2-D) randomly rough surface. A Message Passing Interface-based parallel finite-difference time-domain (FDTD) approach is used, and the uniaxial perfectly matched layer (UPML) medium is adopted for truncation of the FDTD lattices, in which the finite-difference equations can be used for the total computation domain by properly choosing the uniaxial parameters. This makes the parallel FDTD algorithm easier to implement. The parallel performance with different number of processors is illustrated for one rough surface realization and shows that the computation time of our parallel FDTD algorithm is dramatically reduced relative to a single-processor implementation. Finally, the composite scattering coefficients versus scattered and azimuthal angle are presented and analyzed for different conditions, including the surface roughness, the dielectric constants, the polarization, and the size of the 3-D object.

  20. Water-scattered signal to compensate for the rough sea surface effect on bottom lidar imaging.

    PubMed

    Dolin, Lev S; Luchinin, Alexander G

    2008-12-20

    We investigate the possibility of using the water-backscattered radiation from a bottom sounding airborne imaging light detection and ranging (lidar) system to determine the surface slope at the point where the laser beam intersects the surface. We show that the refraction angle of the beam can be determined using receivers whose sensitivities vary linearly over their field of view. Equations are derived to estimate the statistical mean and variance values of this refracted angle. We demonstrate that the proposed algorithm improves lidar imaging. Numerical examples with reference to typical marine conditions are given. PMID:19104538

  1. Simple ray-tracing model for a rough surface of an ink layer including internal scattering particles printed on a light guide plate.

    PubMed

    Sekiguchi, Yoshifumi; Kaneko, Hiroki

    2016-02-01

    For simulating light guide lighting systems, we have developed a ray-tracing model for an ink layer extracting light from a light guide. The model consists of the volume and the rough surface scattering calculated on the basis of Mie theory and the facet model, respectively. The model of an ink layer was required to conserve energy for analyzing how much light loss occurs in each component in the lighting system. Though a single-scattering rough surface model with a shadowing/masking function successfully describes the scattering distribution, shadowing light violates the energy conservation law because of a lack of multiple scattering. We developed the rough surface ray-tracing model (RSRT model), which includes the multiple scattering instead of the shadowing/masking effect. We investigated the applicability of the RSRT model for an ink layer by comparing the RSRT model with recent physical and facet models. Finally, we compared the calculated and measured scattering distributions of an ink layer, applied the developed ink layer model to the lighting system, and confirmed the developed model to be valid.

  2. A rough earth scattering model for multipath prediction

    NASA Technical Reports Server (NTRS)

    Page, L. J.; Chestnut, P. C.

    1970-01-01

    The most important phenomena to be considered in a model of radio wave communication between earth satellites are scattering from the surface of the earth. A model is derived and implemented on a computer to predict the field received after reflection from a rough, spherical earth. The scattering integrals are computed numerically; the domain of integration is the appropriate region on the surface of the earth. Calculations have been performed at VHF frequencies and for terrain which could be described as marshy land. Rough surface scattering calculations must be performed over a spherical earth when satellites are involved. There is a definite dependence on the values of the roughness, and the correlation length.

  3. Electron mobility limited by surface and interface roughness scattering in AlxGa1-xN/GaN quantum wells

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Xia; Yang, Shao-Yan; Wang, Jun; Liu, Gui-Peng; Li, Zhi-Wei; Li, Hui-Jie; Jin, Dong-Dong; Liu, Xiang-Lin; Zhu, Qin-Sheng; Wang, Zhan-Guo

    2013-07-01

    The electron mobility limited by the interface and surface roughness scatterings of the two-dimensional electron gas in AlxGa1-xN/GaN quantum wells is studied. The newly proposed surface roughness scattering in the AlGaN/GaN quantum wells becomes effective when an electric field exists in the AlxGa1-xN barrier. For the AlGaN/GaN potential well, the ground subband energy is governed by the spontaneous and the piezoelectric polarization fields which are determined by the barrier and the well thicknesses. The thickness fluctuation of the AlGaN barrier and the GaN well due to the roughnesses cause the local fluctuation of the ground subband energy, which will reduce the 2DEG mobility.

  4. Surface roughness measurements

    NASA Technical Reports Server (NTRS)

    Howard, Thomas G.

    1994-01-01

    The Optics Division is currently in the research phase of producing grazing-incidence mirrors to be used in x-ray detector applications. The traditional method of construction involves labor-intensive glass grinding. This also culminates in a relatively heavy mirror. For lower resolution applications, the mirrors may be of a replicated design which involves milling a mandrel as a negative of the final shape and electroplating the cylindrical mirror onto it. The mirror is then separated from the mandrel by cooling. The mandrel will shrink more than the 'shell' (mirror) allowing it to be pulled from the mandrel. Ulmer (2) describes this technique and its variations in more detail. To date, several mirrors have been tested at MSFC by the Optical Fabrication Branch by focusing x-ray energy onto a detector with limited success. Little is known about the surface roughness of the actual mirror. Hence, the attempt to gather data on these surfaces. The test involves profiling the surface of a sample, replicating the surface as described above, and then profiling the replicated surface.

  5. Reconstruction of scattering properties of rough air-dielectric boundary

    NASA Astrophysics Data System (ADS)

    Sokolov, V. G.; Zhdanov, D. D.; Potemin, I. S.; Garbul, A. A.; Voloboy, A. G.; Galaktionov, V. A.; Kirilov, N.

    2016-10-01

    The article is devoted to elaboration of the method of reconstruction of rough surface scattering properties. The object with rough surface is made of transparent dielectric material. Typically these properties are described with bi-directional scattering distribution function (BSDF). Direct measurement of such function is either impossible or very expensive. The suggested solution provides physically reasonable method for the rough surface BSDF reconstruction. The method is based on Monte-Carlo ray tracing simulation for BSDF calculation. Optimization technique is further applied to correctly reconstruct the BSDF. The results of the BSDF reconstruction together with measurement results are presented in the article as well.

  6. Reconstruction of scattering properties of rough air-dielectric boundary

    NASA Astrophysics Data System (ADS)

    Sokolov, V. G.; Zhdanov, D. D.; Potemin, I. S.; Garbul, A. A.; Voloboy, A. G.; Galaktionov, V. A.; Kirilov, N.

    2016-08-01

    The article is devoted to elaboration of the method of reconstruction of rough surface scattering properties. The object with rough surface is made of transparent dielectric material. Typically these properties are described with bi-directional scattering distribution function (BSDF). Direct measurement of such function is either impossible or very expensive. The suggested solution provides physically reasonable method for the rough surface BSDF reconstruction. The method is based on Monte-Carlo ray tracing simulation for BSDF calculation. Optimization technique is further applied to correctly reconstruct the BSDF. The results of the BSDF reconstruction together with measurement results are presented in the article as well.

  7. Complete Bistatic (4 Pi) Polarimetric Characterization of Waves Scattered from and across Two-Dimensional Random Rough Surfaces Using the Full Wave Approach.

    NASA Astrophysics Data System (ADS)

    Lee, Bom Son

    1995-01-01

    In this work, the full wave approach (Bahar, 1981a, 1991; Bahar and Lee, 1994a, 1995a) is used to obtain the expressions for the scatter cross sections for two-dimensional random rough surfaces. Formally, it involves 10-dimensional integrals. Under certain justifiable conditions, this expression can be reduced to a tractable form. This work is strictly restricted to rough surfaces with large radii of curvature compared to wavelength. The limitations of the generalized full wave solutions that have been recently cited in the technical literature (Thompson and Chapman, 1993; Collin, 1994) are not addressed in this work. The large radii of curvature restriction is introduced in order to reduce to three, the dimension of the multiple integrals used to compute the cross sections for two dimensional rough surfaces. If, in addition to the large radii of surface curvature assumption, the rough surface is homogeneous and isotropic, the 10-dimensional integral can be expressed as a 3-dimensional integral. This integral accounts for the surface height/slope correlation through the use of the conditional joint characteristic functions (Bahar, 1991; Bahar and Lee, 1994a). This full wave solution is shown to reduce to the small perturbation solution (Rice, 1951) and reduce to the physical optics solution (Beckmann and Spizzichino, 1963) in their appropriate regions of validity. The full wave results are compared with the associated small perturbation and physical/geometrical optics results as well as the experimental (O'Donell and Mendez, 1987) and numerical (Sanchez-Gil and Nieto-Vesperinas, 1991) results. The scattering cross sections are the top left 2 x 2 elements of the modified Mueller matrix. The Mueller matrix elements are related to the like and cross polarized radar cross sections as well as to the relative phase of the vertically and horizontally polarized waves. The 4 x 4 Mueller matrix completely characterizes the scattered fields from the target. These Mueller

  8. Reconstruction of the experimental autocorrelation function and determination of the parameters of the statistical roughness of a surface from laser radiation scattering in an integrated-optical waveguide

    SciTech Connect

    Egorov, Aleksei A

    2003-04-30

    The possibility of using the waveguide scattering of laser radiation for obtaining information on the statistical properties of irregularities from the noisy data obtained in the far-field zone is shown. A complex algorithm for reconstructing the experimental autocorrelation function of the surface roughness of an integrated-optical waveguide substrate is described. This algorithm is based on a combination of the classical regularisation and quasi-optimal filtering. (waveguides)

  9. Incorporation of a rough ocean surface and semi-infinite water body in multiple scattering computations of polarized light in an atmosphere-ocean system

    NASA Astrophysics Data System (ADS)

    Chowdhary, Jacek; Travis, Larry D.; Lacis, Andrew A.

    1995-01-01

    The use of accurate space-born polarimetric measurements to retrieve tropospheric aerosol characteristics is a promising remote sensing tool, but also imposes strong requirements on the atmosphere-ocean model in terms of its adequacy and on computational techniques in terms of their accuracy and efficiency. The present work is concerned with computing the reflection matrix of an atmosphere-ocean system within this context. We use the Ambartsumyan non- linear integral equation to obtain the reflection matrix for a semi-infinite homogeneous ocean body containing hydrosols. The reflection and transmission matrices of a statistically rough ocean surface are obtained using the standard Kirchhoff formulation, with shadowing effects taken into account. The reflection properties of the combined ocean body and ocean surface are obtained employing the adding method. We use the Fourier decomposition of the scattering matrices and separation of the first-order scattering to substantially reduce the computational burden. An atmospheric model containing aerosols and molecules is computed and added on the top of the ocean system using the adding/doubling method. We report preliminary computational data and discuss the variation of the degree of linear polarization of singly and multiply scattered radiation as a function of scattering geometry, surface roughness, and aerosol and molecular optical depth.

  10. Incorporation of a rough ocean surface and semi-infinite water body in multiple scattering computations of polarized light in an atmosphere-ocean system

    SciTech Connect

    Chowdhary, J. |; Travis, L.D.; Lacis, A.A.

    1995-12-31

    The use of accurate space-born polarimetric measurements to retrieve tropospheric aerosol characteristics is a promising remote sensing tool, but also imposes strong requirements on the atmosphere-ocean model in terms of its adequacy and on computational techniques in terms of their accuracy and efficiency. The present work is concerned with computing the reflection matrix of an atmosphere-ocean system within this context. The authors use the Ambartsumyan non-linear integral equation to obtain the reflection matrix for a semi-infinite homogeneous ocean body containing hydrosols. The reflection and transmission matrices of a statistically rough ocean surface are obtained using the standard Kirchhoff formulation, with shadowing effects taken into account. The reflection properties of the combined ocean body and ocean surface are obtained employing the adding method. They use the Fourier decomposition of the scattering matrices and separation of the first-order scattering to substantially reduce the computational burden. An atmosphere model containing aerosols and molecules is computed and added on the top of the ocean system using the adding/doubling method. They report preliminary computational data and discuss the variation of the degree of linear polarization of singly and multiply scattered radiation as a function of scattering geometry, surface roughness, and aerosol and molecular optical depth.

  11. Message-passing-interface-based parallel FDTD investigation on the EM scattering from a 1-D rough sea surface using uniaxial perfectly matched layer absorbing boundary.

    PubMed

    Li, J; Guo, L-X; Zeng, H; Han, X-B

    2009-06-01

    A message-passing-interface (MPI)-based parallel finite-difference time-domain (FDTD) algorithm for the electromagnetic scattering from a 1-D randomly rough sea surface is presented. The uniaxial perfectly matched layer (UPML) medium is adopted for truncation of FDTD lattices, in which the finite-difference equations can be used for the total computation domain by properly choosing the uniaxial parameters. This makes the parallel FDTD algorithm easier to implement. The parallel performance with different processors is illustrated for one sea surface realization, and the computation time of the parallel FDTD algorithm is dramatically reduced compared to a single-process implementation. Finally, some numerical results are shown, including the backscattering characteristics of sea surface for different polarization and the bistatic scattering from a sea surface with large incident angle and large wind speed.

  12. Surface Roughness, Optical Shadowing, and Radar Backscatter

    NASA Astrophysics Data System (ADS)

    Shepard, M. K.; Campbell, B. A.

    1996-03-01

    The topography of natural surfaces at scales of a few meters or less is commonly referred to as roughness. These variations in height and slope, their magnitude, and the changes in structure as a function of scale length are of fundamental importance to interpretation of geologic emplacement regimes and subsequent modification. For most planetary studies and many terrestrial situations, no in situ observations of the ground are available, and remote sensing data are used to infer the nature of the terrain. For optical, infrared, and microwave measurements, surface roughness and its scale-dependence have a large impact on the brightness, polarization, angular scattering properties, and wavelength-dependence of reflected energy. The link between surface roughness and specific remote sensing properties for many types of observations, however, remains elusive. We focus here on the nature of roughness and its scale-dependence for terrestrial rocky surfaces, and the effect of such changes on optical shadowing and radar backscatter.

  13. Does surface roughness amplify wetting?

    SciTech Connect

    Malijevský, Alexandr

    2014-11-14

    Any solid surface is intrinsically rough on the microscopic scale. In this paper, we study the effect of this roughness on the wetting properties of hydrophilic substrates. Macroscopic arguments, such as those leading to the well-known Wenzel's law, predict that surface roughness should amplify the wetting properties of such adsorbents. We use a fundamental measure density functional theory to demonstrate the opposite effect from roughness for microscopically corrugated surfaces, i.e., wetting is hindered. Based on three independent analyses we show that microscopic surface corrugation increases the wetting temperature or even makes the surface hydrophobic. Since for macroscopically corrugated surfaces the solid texture does indeed amplify wetting there must exist a crossover between two length-scale regimes that are distinguished by opposite response on surface roughening. This demonstrates how deceptive can be efforts to extend the thermodynamical laws beyond their macroscopic territory.

  14. Surface roughness considerations for atmospheric correction of ocean color sensors. I - The Rayleigh-scattering component. II - Error in the retrieved water-leaving radiance

    NASA Technical Reports Server (NTRS)

    Gordon, Howard R.; Wang, Menghua

    1992-01-01

    The first step in the Coastal Zone Color Scanner (CZCS) atmospheric-correction algorithm is the computation of the Rayleigh-scattering (RS) contribution, L sub r, to the radiance leaving the top of the atmosphere over the ocean. In the present algorithm, L sub r is computed by assuming that the ocean surface is flat. Calculations of the radiance leaving an RS atmosphere overlying a rough Fresnel-reflecting ocean are presented to evaluate the radiance error caused by the flat-ocean assumption. Simulations are carried out to evaluate the error incurred when the CZCS-type algorithm is applied to a realistic ocean in which the surface is roughened by the wind. In situations where there is no direct sun glitter, it is concluded that the error induced by ignoring the Rayleigh-aerosol interaction is usually larger than that caused by ignoring the surface roughness. This suggests that, in refining algorithms for future sensors, more effort should be focused on dealing with the Rayleigh-aerosol interaction than on the roughness of the sea surface.

  15. Scattering of s-polarized electromagnetic plane waves from a film with a shallow random rough surface on a perfect conductor.

    PubMed

    García-Llamas, R; Márquez-Beltran, C

    2000-09-01

    Scattering of s-polarized electromagnetic planes waves from a film, with a shallow random rough one-dimensional surface, bounded by vacuum and a perfect conductor is calculated. An integral equation that relates the amplitude of the scattered field to the incident wave is found by use of the Rayleigh hypothesis. The integral equation is solved numerically and by use of the perturbation theory, up to the fourth order in the surface profile function. In the angular dependence of the incoherent part of the differential reflection coefficient, the backscattering peak and two additional satellite peaks are observed, owing to two guided waves supported by the film. Analysis of the perturbation solution reveals that the background scattering exhibits minima and maxima as functions of the thickness. By studying the behavior of the scattering as a function of the absorption index of the film, it is shown that the amplitudes of the peaks are low when k approximately 10(-2) and high when k approximately 10(-4).

  16. Extreme ultraviolet mask substrate surface roughness effects on lithography patterning

    SciTech Connect

    George, Simi; Naulleau, Patrick; Salmassi, Farhad; Mochi, Iacopo; Gullikson, Eric; Goldberg, Kenneth; Anderson, Erik

    2010-06-21

    In extreme ultraviolet lithography exposure systems, mask substrate roughness induced scatter contributes to LER at the image plane. In this paper, the impact of mask substrate roughness on image plane speckle is explicitly evaluated. A programmed roughness mask was used to study the correlation between mask roughness metrics and wafer plane aerial image inspection. We find that the roughness measurements by top surface topography profile do not provide complete information on the scatter related speckle that leads to LER at the image plane. We suggest at wavelength characterization by imaging and/or scatter measurements into different frequencies as an alternative for a more comprehensive metrology of the mask substrate/multilayer roughness effects.

  17. Surface roughness of anodized titanium coatings.

    SciTech Connect

    Dugger, Michael Thomas; Chinn, Douglas Alan

    2010-10-01

    Samples of grade five 6Al4V titanium alloy were coated with two commercial fluoropolymer anodizations (Tiodize and Canadize) and compared. Neither coating demonstrates significant outgassing. The coatings show very similar elemental analysis, except for the presence of lead in the Canadize coating, which may account for its lower surface friction in humid environments. Surface roughness has been compared by SEM, contact profilometry, optical profilometry, power spectral density and bidirectional scattering distribution function (BSDF). The Tiodize film is slightly smoother by all measurement methods, but the Canadize film shows slightly less scatter at all angles of incidence. Both films exhibited initial friction coefficients of 0.2 to 0.4, increasing to 0.4 to 0.8 after 1000 cycles of sliding due to wear of the coating and ball. The coatings are very similar and should behave identically in most applications.

  18. The neutral surface layer above rough surfaces

    NASA Astrophysics Data System (ADS)

    Smedman, Ann-Sofi; Sahlee, Erik

    2014-05-01

    It is generally accepted that turbulent fluxes (momentum and scalar fluxes) are approx. constant with height above horizontal surfaces with low roughness. But what will happen when the roughness sub-layer is large as found over cities, forests and rough seas? In a study of the kinematic structure of the near neutral atmospheric surface layer, Högström, Hunt and Smedman, 2002, it was demonstrated that a model with detached eddies from above the surface layer impinging on to the surface (Hunt and Morison, 2000) could explain some of the observed features in the neutral atmospheric boundary layer. Thus the detached eddy model proved successful in explaining the dynamic structure of the near neutral atmospheric surface layer, especially the shape of the spectra of the wind components and scalars and corresponding fluxes. Here we make the hypothesis that the detached-eddy model can also be used to explain the experimental results related to the 3-dimensional turbulence structure above rough surfaces. Measurements are taken both over land (grass and forest) and over sea (Baltic Sea and hurricane Fabian in the Atlantic) above the roughness sub-layer. Analysis of the turbulence structure shows a striking similarity between the different sites. Hunt, J.C.R and Morrison, J.F., 2000: Eddy structure in turbulent boundary layers, Euro. J. Mech. B-Fluids, 19, 673-694. Högström, U., Hunt, J.C.R., and Smedman, A., 2002: Theory and measurements for turbulence spectra and variances in the atmospheric neutral surface layer, Bound.-Layer Meteorol., 103,101-124.

  19. Modeling Radar Scatter from Icy and Young Rough Lunar Craters

    NASA Technical Reports Server (NTRS)

    Thompson, Thomas (Tommy); Ustinov, Eugene; Spudis, Paul; Fessler, Brian

    2012-01-01

    For lunar orbital synthetic aperture radars, such as the Chandrayaan Mini-RF operating at S- band (13-cm) wavelength and the Lunar Reconnaissance Orbiter Mini-RF operating at S- band and X-band (3-cm) wavelengths, it is important to understand the radar backscattering characteristics of the icy and young, rough craters. Assuming a mixing model consisting of diffuse and quasi-specular scattering components, we have modeled the opposite-sense circular (OC) and same-sense circular (SC) backscattering characteristics. The specular component, consisting of only OC echoes, represents the echoes from the surface and subsurface layers that are oriented perpendicular to the radar's line-of-sight. The diffuse component, consisting of both SC and OC echoes, represents the echoes associated with either rocks or ice. Also, diffuse echoes have backscatter that is proportional to the cosine of the incidence angle. We modeled how these two (specular and diffuse) radar scattering components could be modulated by factors such as surface roughness associated with young craters. We also modeled how ice radar scattering components could be modulated by a thin regolith covering, and/or by the situation where ice occupies small patches within a larger radar pixel. We tested this modeling by examining 4 nonpolar craters and 12 polar craters using LRO Mini-RF data. Results indicate that icy and young rough craters can be distinguished based upon their SC enhancements (Alpha) and OC enhancements (Gamma). In addition, we also examined the craters that have unusual circular polarization ratios (CPRs) that likely result from a double bounce mode of scattering. Blocky fresh craters, icy craters, and craters exhibiting double bounce scattering can be separated based on the values of Alpha, Gamma, the ratio of Alpha/Gamma and the weighted sum of Alpha and Gamma.

  20. Calibration of surface roughness standards

    NASA Astrophysics Data System (ADS)

    Thalmann, R.; Nicolet, A.; Meli, F.; Picotto, G. B.; Matus, M.; Carcedo, L.; Hemming, B.; Ganioglu, O.; De Chiffre, L.; Saraiva, F.; Bergstrand, S.; Zelenika, S.; Tonmueanwai, A.; Tsai, C.-L.; Shihua, W.; Kruger, O.; de Souza, M. M.; Salgado, J. A.; Ramotowski, Z.

    2016-01-01

    The key comparison EURAMET.L-K8.2013 on roughness was carried out in the framework of a EURAMET project starting in 2013 and ending in 2015. It involved the participation of 17 National Metrology Institutes from Europe, Asia, South America and Africa representing four regional metrology organisations. Five surface texture standards of different type were circulated and on each of the standards several roughness parameters according to the standard ISO 4287 had to be determined. 32 out of 395 individual results were not consistent with the reference value. After some corrective actions the number of inconsistent results could be reduced to 20, which correspond to about 5% of the total and can statistically be expected. In addition to the material standards, two softgauges were circulated, which allow to test the software of the instruments used in the comparison. The comparison results help to support the calibraton and measurement capabilities (CMCs) of the laboratories involved in the CIPM MRA. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  1. Wind tunnel model surface gauge for measuring roughness

    NASA Technical Reports Server (NTRS)

    Vorburger, T. V.; Gilsinn, D. E.; Teague, E. C.; Giauque, C. H. W.; Scire, F. E.; Cao, L. X.

    1987-01-01

    The optical inspection of surface roughness research has proceeded along two different lines. First, research into a quantitative understanding of light scattering from metal surfaces and into the appropriate models to describe the surfaces themselves. Second, the development of a practical instrument for the measurement of rms roughness of high performance wind tunnel models with smooth finishes. The research is summarized, with emphasis on the second avenue of research.

  2. Wetting properties of molecularly rough surfaces

    SciTech Connect

    Svoboda, Martin; Lísal, Martin; Malijevský, Alexandr

    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 by 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.

  3. Three-Dimensional Electromagnetic Scattering from Layered Media with Rough Interfaces for Subsurface Radar Remote Sensing

    NASA Astrophysics Data System (ADS)

    Duan, Xueyang

    The objective of this dissertation is to develop forward scattering models for active microwave remote sensing of natural features represented by layered media with rough interfaces. In particular, soil profiles are considered, for which a model of electromagnetic scattering from multilayer rough surfaces with or without buried random media is constructed. Starting from a single rough surface, radar scattering is modeled using the stabilized extended boundary condition method (SEBCM). This method solves the long-standing instability issue of the classical EBCM, and gives three-dimensional full wave solutions over large ranges of surface roughnesses with higher computational efficiency than pure numerical solutions, e.g., method of moments (MoM). Based on this single surface solution, multilayer rough surface scattering is modeled using the scattering matrix approach and the model is used for a comprehensive sensitivity analysis of the total ground scattering as a function of layer separation, subsurface statistics, and sublayer dielectric properties. The buried inhomogeneities such as rocks and vegetation roots are considered for the first time in the forward scattering model. Radar scattering from buried random media is modeled by the aggregate transition matrix using either the recursive transition matrix approach for spherical or short-length cylindrical scatterers, or the generalized iterative extended boundary condition method we developed for long cylinders or root-like cylindrical clusters. These approaches take the field interactions among scatterers into account with high computational efficiency. The aggregate transition matrix is transformed to a scattering matrix for the full solution to the layered-medium problem. This step is based on the near-to-far field transformation of the numerical plane wave expansion of the spherical harmonics and the multipole expansion of plane waves. This transformation consolidates volume scattering from the buried random

  4. Influence of Nanoscale Surface Roughness on Colloidal Force Measurements.

    PubMed

    Zou, Yi; Jayasuriya, Sunil; Manke, Charles W; Mao, Guangzhao

    2015-09-29

    Forces between colloidal particles determine the performances of many industrial processes and products. Colloidal force measurements conducted between a colloidal particle AFM probe and particles immobilized on a flat substrate are valuable in selecting appropriate surfactants for colloidal stabilization. One of the features of inorganic fillers and extenders is the prevalence of rough surfaces-even the polymer latex particles, often used as model colloidal systems including the current study, have rough surfaces albeit at a much smaller scale. Surface roughness is frequently cited as the reason for disparity between experimental observations and theoretical treatment but seldom verified by direct evidence. This work reports the effect of nanoscale surface roughness on colloidal force measurements carried out in the presence of surfactants. We applied a heating method to reduce the mean surface roughness of commercial latex particles from 30 to 1 nm. We conducted force measurements using the two types of particles at various salt and surfactant concentrations. The surfactants used were pentaethylene glycol monododecyl ether, Pluronic F108, and a styrene/acrylic copolymer, Joncryl 60. In the absence of the surfactant, nanometer surface roughness affects colloidal forces only in high salt conditions when the Debye length becomes smaller than the surface roughness. The adhesion is stronger between colloids with higher surface roughness and requires a higher surfactant concentration to be eliminated. The effect of surface roughness on colloidal forces was also investigated as a function of the adsorbed surfactant layer structure characterized by AFM indentation and dynamic light scattering. We found that when the layer thickness exceeds the surface roughness, the colloidal adhesion is less influenced by surfactant concentration variation. This study demonstrates that surface roughness at the nanoscale can influence colloidal forces significantly and should be taken

  5. Terahertz NDE for Metallic Surface Roughness Evaluation

    NASA Technical Reports Server (NTRS)

    Madaras, Eric I.; Anastasi, Robert F.

    2006-01-01

    Metallic surface roughness in a nominally smooth surface is a potential indication of material degradation or damage. When the surface is coated or covered with an opaque dielectric material, such as paint or insulation, then inspecting for surface changes becomes almost impossible. Terahertz NDE is a method capable of penetrating the coating and inspecting the metallic surface. The terahertz frequency regime is between 100 GHz and 10 THz and has a free space wavelength of 300 micrometers at 1 THz. Pulsed terahertz radiation, can be generated and detected using optical excitation of biased semiconductors with femtosecond laser pulses. The resulting time domain signal is 320 picoseconds in duration. In this application, samples are inspected with a commercial terahertz NDE system that scans the sample and generates a set of time-domain signals that are a function of the backscatter from the metallic surface. Post processing is then performed in the time and frequency domains to generate C-scan type images that show scattering effects due to surface non-uniformity.

  6. Rough surface mitigates electron and gas emission

    SciTech Connect

    Molvik, A

    2004-09-03

    Heavy-ion beams impinging on surfaces near grazing incidence (to simulate the loss of halo ions) generate copious amounts of electrons and gas that can degrade the beam. We measured emission coefficients of {eta}{sub e} {le} 130 and {eta}{sub 0} {approx} 10{sup 4} respectively, with 1 MeV K{sup +} incident on stainless steel. Electron emission scales as {eta}{sub e} {proportional_to} 1/cos({theta}), where {theta} is the ion angle of incidence relative to normal. If we were to roughen a surface by blasting it with glass beads, then ions that were near grazing incidence (90{sup o}) on smooth surface would strike the rims of the micro-craters at angles closer to normal incidence. This should reduce the electron emission: the factor of 10 reduction, Fig. 1(a), implies an average angle of incidence of 62{sup o}. Gas desorption varies more slowly with {theta} (Fig. 1(b)) decreasing a factor of {approx}2, and along with the electron emission is independent of the angle of incidence on a rough surface. In a quadrupole magnet, electrons emitted by lost primary ions are trapped near the wall by the magnetic field, but grazing incidence ions can backscatter and strike the wall a second time at an azimuth where magnetic field lines intercept the beam. Then, electrons can exist throughout the beam (see the simulations of Cohen, HIF News 1-2/04). The SRIM (TRIM) Monte Carlo code predicts that 60-70% of 1 MeV K{sup +} ions backscatter when incident at 88-89{sup o} from normal on a smooth surface. The scattered ions are mostly within {approx}10{sup o} of the initial direction but a few scatter by up to 90{sup o}. Ion scattering decreases rapidly away from grazing incidence, Fig. 1(c ). At 62 deg. the predicted ion backscattering (from a rough surface) is 3%, down a factor of 20 from the peak, which should significantly reduce electrons in the beam from lost halo ions. These results are published in Phys. Rev. ST - Accelerators and Beams.

  7. Influence of surface roughness on gecko adhesion.

    PubMed

    Huber, Gerrit; Gorb, Stanislav N; Hosoda, Naoe; Spolenak, Ralph; Arzt, Eduard

    2007-07-01

    In this study we show the influence of surface roughness on gecko adhesion on both the nano- and macroscales. We present experimental data for the force necessary to pull off single spatulae from hard rough substrates and also detail observations on living geckos clinging to various surfaces. Both experiments consistently show that the effective adhesion shows a minimum for a root mean square roughness ranging from 100 to 300nm.

  8. Measurement and modeling of rough surface effects on terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Henry, S. C.; Schecklman, S.; Kniffin, G. P.; Zurk, L. M.; Chen, A.

    2010-02-01

    Recent improvements in sensing technology have driven new research areas within the terahertz (THz) portion of the electromagnetic (EM) spectrum. While there are several promising THz applications, several outstanding technical challenges need to be addressed before robust systems can be deployed. A particularly compelling application is the potential use of THz reflection spectroscopy for stand-off detection of drugs and explosives. A primary challenge for this application is to have sufficient signal-to-noise ratio (SNR) to allow spectroscopic identification of the target material, and surface roughness can have an impact on identification. However, scattering from a rough surface may be observed at all angles, suggesting diffuse returns can be used in robust imaging of non-cooperative targets. Furthermore, the scattering physics can also distort the reflection spectra, complicating classification algorithms. In this work, rough surface scattering effects were first isolated by measuring diffuse scattering for gold-coated sandpaper of varying roughness. Secondly, we measured scattering returns from a rough sample with a spectral signature, namely α-lactose monohydrate mixed with Teflon and pressed with sandpaper to introduce controlled roughness. For both the specular and diffuse reflection measurements, the application of traditional spectroscopy techniques provided the ability to resolve the 0.54 THz absorption peak. These results are compared with results from a smooth surface. Implications of the results on the ability to detect explosives with THz reflection spectroscopy are presented and discussed. In addition, the Small Perturbation Method (SPM) is employed to predict backscatter from lactose with a small amount of roughness.

  9. Physically-based Ice Thickness and Surface Roughness Retrievals over Rough Deformed Sea Ice

    NASA Astrophysics Data System (ADS)

    Li, Li; Gaiser, Peter; Allard, Richard; Posey, Pamela; Hebert, David; Richter-Menge, Jacqueline; Polashenski, Christopher; Claffey, Keran

    2016-04-01

    The observations of sea ice thickness and ice surface roughness are critical for our understanding of the state of the changing Arctic. Currently, the Radar and/or LiDAR data of sea ice freeboard are used to infer sea ice thickness via isostasy. The underlying assumption is that the LiDAR signal returns at the air/snow interface and radar signal at the snow/ice interface. The elevations of these interfaces are determined based on LiDAR/Radar return waveforms. However, the commonly used threshold-based 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. Both the ice thickness and surface roughness retrievals are validated using in-situ data. 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

  10. ANALYZING SURFACE ROUGHNESS DEPENDENCE OF LINEAR RF LOSSES

    SciTech Connect

    Reece, Charles E.; Kelley, Michael J.; Xu, Chen

    2012-09-01

    Topographic structure on Superconductivity Radio Frequency (SRF) surfaces can contribute additional cavity RF losses describable in terms of surface RF reflectivity and absorption indices of wave scattering theory. At isotropic homogeneous extent, Power Spectrum Density (PSD) of roughness is introduced and quantifies the random surface topographic structure. PSD obtained from different surface treatments of niobium, such Buffered Chemical Polishing (BCP), Electropolishing (EP), Nano-Mechanical Polishing (NMP) and Barrel Centrifugal Polishing (CBP) are compared. A perturbation model is utilized to calculate the additional rough surface RF losses based on PSD statistical analysis. This model will not consider that superconductor becomes normal conducting at fields higher than transition field. One can calculate the RF power dissipation ratio between rough surface and ideal smooth surface within this field range from linear loss mechanisms.

  11. 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.

  12. Surface roughness effects on bidirectional reflectance.

    NASA Technical Reports Server (NTRS)

    Smith, T. F.; Hering, R. G.

    1973-01-01

    An experimental study of surface roughness effects on bidirectional reflectance of metallic surfaces is presented. Samples consisting of glass, aluminum alloy, and stainless steel materials were roughened using standard grinding techniques and coated with a radiatively opaque layer of pure aluminum. Surface roughness parameters, rms height and rms slope, were evaluated from digitized surface profile measurements and are less than 1.0 micron, and 0.28, respectively. Rough-surface specular, bidirectional, and directional reflectance measurements for selected values of polar angle and wavelength of incident energy within the range from 10 to 80 deg and from 1 to 14 microns, respectively, are reported. The influence of surface roughness is discussed in terms of rms height and rms slope.

  13. Effect of Surface Roughness on Hydrodynamic Bearings

    NASA Technical Reports Server (NTRS)

    Majumdar, B. C.; Hamrock, B. J.

    1981-01-01

    A theoretical analysis on the performance of hydrodynamic oil bearings is made considering surface roughness effect. The hydrodynamic as well as asperity contact load is found. The contact pressure was calculated with the assumption that the surface height distribution was Gaussian. The average Reynolds equation of partially lubricated surface was used to calculate hydrodynamic load. An analytical expression for average gap was found and was introduced to modify the average Reynolds equation. The resulting boundary value problem was then solved numerically by finite difference methods using the method of successive over relaxation. The pressure distribution and hydrodynamic load capacity of plane slider and journal bearings were calculated for various design data. The effects of attitude and roughness of surface on the bearing performance were shown. The results are compared with similar available solution of rough surface bearings. It is shown that: (1) the contribution of contact load is not significant; and (2) the hydrodynamic and contact load increase with surface roughness.

  14. Specular Reflection from Rough Surfaces Revisited

    NASA Astrophysics Data System (ADS)

    Yasuda, Kensei; Kim, Alvin; Cho, Hayley; Timofejev, Timofej; Walecki, Wojciech J.; Klep, James; Edelson, Amy S.; Walecki, Abigail S.; Walecki, Eve S.; Walecki, Peter S.

    2016-10-01

    In his beautiful paper, Hasan Fakhruddin reported observations of mirror-like reflections in the rough surface of a ground glass plate. Similar effects have been recently employed for metrology of the roughness of optical diffusers used in modern light emitting device illumination systems. We report the observations of specular reflection in nontransparent rough surfaces at oblique angles, where roughness was treated as a variable. We present a simple trigonometry-based model explaining the observed phenomenon, which we experimentally validated using aluminum surfaces that have controlled roughness. The reported demonstration requires no special equipment, other than cellphone cameras, dielectric or metal plate, and sandpaper, and serves as an introduction to wave optics. This activity can be used to get further insight into everyday applications of wave optics for students already familiar with wave optics fundamentals.

  15. Roughness Perception of Haptically Displayed Fractal Surfaces

    NASA Technical Reports Server (NTRS)

    Costa, Michael A.; Cutkosky, Mark R.; Lau, Sonie (Technical Monitor)

    2000-01-01

    Surface profiles were generated by a fractal algorithm and haptically rendered on a force feedback joystick, Subjects were asked to use the joystick to explore pairs of surfaces and report to the experimenter which of the surfaces they felt was rougher. Surfaces were characterized by their root mean square (RMS) amplitude and their fractal dimension. The most important factor affecting the perceived roughness of the fractal surfaces was the RMS amplitude of the surface. When comparing surfaces of fractal dimension 1.2-1.35 it was found that the fractal dimension was negatively correlated with perceived roughness.

  16. Specular Reflection from Rough Surfaces Revisited

    ERIC Educational Resources Information Center

    Yasuda, Kensei; Kim, Alvin; Cho, Hayley; Timofejev, Timofej; Walecki, Wojciech J.; Klep, James; Edelson, Amy S.; Walecki, Abigail S.; Walecki, Eve S.; Walecki, Peter S.

    2016-01-01

    In his beautiful paper, Hasan Fakhruddin reported observations of mirror-like reflections in the rough surface of a ground glass plate. Similar effects have been recently employed for metrology of the roughness of optical diffusers used in modern light emitting device illumination systems. We report the observations of specular reflection in…

  17. Rough surface reconstruction for ultrasonic NDE simulation

    SciTech Connect

    Choi, Wonjae; Shi, Fan; Lowe, Michael J. S.; Skelton, Elizabeth A.; Craster, Richard V.

    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. 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.

  18. Replicated mask surface roughness effects on EUV lithographic pattering and line edge roughness

    SciTech Connect

    George, Simi A.; Naulleau, Patrick P.; Gullikson, Eric M.; Mochi, Iacopo; Salmassi, Farhad; Goldberg, Kenneth A.; Anderson, Erik H.

    2011-03-11

    To quantify the roughness contributions to speckle, a programmed roughness substrate was fabricated with a number of areas having different roughness magnitudes. The substrate was then multilayer coated. Atomic force microscopy (AFM) surface maps were collected before and after multilayer deposition. At-wavelength reflectance and total integrated scattering measurements were also completed. Angle resolved scattering based power spectral densities are directly compared to the AFM based power spectra. We show that AFM overpredicts the roughness in the picometer measurements range. The mask was then imaged at-wavelength for the direct characterization of the aerial image speckle using the SEMATECH Berkeley Actinic Inspection Tool (AIT). Modeling was used to test the effectiveness of the different metrologies in predicting the measured aerial-image speckle. AIT measured contrast values are 25% or more than the calculated image contrast values obtained using the measured rms roughness input. The extent to which the various metrologies can be utilized for specifying tolerable roughness limits on EUV masks is still to be determined. Further modeling and measurements are being planned.

  19. Effect of Surface Roughness on Optical Heating of Metals

    NASA Astrophysics Data System (ADS)

    Auinger, M.; Ebbinghaus, P.; Blümich, A.; Erbe, A.

    2014-01-01

    Heating by absorption of light is a commonly used technique to ensure a fast temperature increase of metallic samples. The rate of heating when using optical heating depends critically on the absorption of light by a sample. Here, the reflection and scattering of light from UV to IR by surfaces with different roughness of iron-based alloy samples (Fe, 1 wt-% Cr) is investigated. A combination of ellipsometric and optical scattering measurements is used to derive a simplified parametrisation which can be used to obtain the absorption of light from random rough metal surfaces, as prepared through conventional grinding and polishing techniques. By modelling the ellipsometric data of the flattest sample, the pseudodielectric function of the base material is derived. Describing an increased roughness by a Maxwell-Garnett model does not yield a reflectivity which follows the experimentally observed sum of scattered and reflected intensities. Therefore, a simple approach is introduced, based on multiple reflections, where the number of reflections depends on the surface roughness. This approach describes the data well, and is subsequently used to estimate the fraction of absorbed energy. Using numerical modelling, the effect on the heating rate is investigated. A numerical example is analysed, which shows that slight changes in roughness may result in big differences of the energy input into a metallic sample, with consequences on the achieved temperatures. Though the model oversimplifies reality, it provides a physically intuitive approach to estimate trends.

  20. The effect of roughness model on scattering properties of ice crystals

    NASA Astrophysics Data System (ADS)

    Geogdzhayev, Igor; van Diedenhoven, Bastiaan

    2016-07-01

    We compare stochastic models of microscale surface roughness assuming uniform and Weibull distributions of crystal facet tilt angles to calculate scattering by roughened hexagonal ice crystals using the geometric optics (GO) approximation. Both distributions are determined by similar roughness parameters, while the Weibull model depends on the additional shape parameter. Calculations were performed for two visible wavelengths (864 nm and 410 nm) for roughness values between 0.2 and 0.7 and Weibull shape parameters between 0 and 1.0 for crystals with aspect ratios of 0.21, 1 and 4.8. For this range of parameters we find that, for a given roughness level, varying the Weibull shape parameter can change the asymmetry parameter by up to about 0.05. The largest effect of the shape parameter variation on the phase function is found in the backscattering region, while the degree of linear polarization is most affected at the side-scattering angles. For high roughness, scattering properties calculated using the uniform and Weibull models are in relatively close agreement for a given roughness parameter, especially when a Weibull shape parameter of 0.75 is used. For smaller roughness values, a shape parameter close to unity provides a better agreement. Notable differences are observed in the phase function over the scattering angle range from 5° to 20°, where the uniform roughness model produces a plateau while the Weibull model does not.

  1. Simplified Approach to Predicting Rough Surface Transition

    NASA Technical Reports Server (NTRS)

    Boyle, Robert J.; Stripf, Matthias

    2009-01-01

    Turbine vane heat transfer predictions are given for smooth and rough vanes where the experimental data show transition moving forward on the vane as the surface roughness physical height increases. Consiste nt with smooth vane heat transfer, the transition moves forward for a fixed roughness height as the Reynolds number increases. Comparison s are presented with published experimental data. Some of the data ar e for a regular roughness geometry with a range of roughness heights, Reynolds numbers, and inlet turbulence intensities. The approach ta ken in this analysis is to treat the roughness in a statistical sense , consistent with what would be obtained from blades measured after e xposure to actual engine environments. An approach is given to determ ine the equivalent sand grain roughness from the statistics of the re gular geometry. This approach is guided by the experimental data. A roughness transition criterion is developed, and comparisons are made with experimental data over the entire range of experimental test co nditions. Additional comparisons are made with experimental heat tran sfer data, where the roughness geometries are both regular as well a s statistical. Using the developed analysis, heat transfer calculatio ns are presented for the second stage vane of a high pressure turbine at hypothetical engine conditions.

  2. Multiple scattering in the high-frequency limit with second-order shadowing function from 2D anisotropic rough dielectric surfaces: II. Comparison with numerical results

    NASA Astrophysics Data System (ADS)

    Bourlier, C.; Berginc, G.

    2004-07-01

    This second part presents illustrative examples of the model developed in the companion paper, which is based on the first- and second-order optics approximation. The surface is assumed to be Gaussian and the correlation height is chosen as anisotropic Gaussian. The incoherent scattering coefficient is computed for a height rms range from 0.5lgr to 1lgr (where lgr is the electromagnetic wavelength), for a slope rms range from 0.5 to 1 and for an incidence angle range from 0 to 70°. In addition, simulations are presented for an anisotropic Gaussian surface and when the receiver is not located in the plane of incidence. For a metallic and dielectric isotropic Gaussian surfaces, the cross- and co-polarizations are also compared with a numerical approach obtained from the forward-backward method with a novel spectral acceleration algorithm developed by Torrungrueng and Johnson (2001, JOSA A 18).

  3. Thermal smoothing of rough surfaces in vacuo

    NASA Technical Reports Server (NTRS)

    Wahl, G.

    1986-01-01

    The derivation of equations governing the smoothing of rough surfaces, based on Mullins' (1957, 1960, and 1963) theories of thermal grooving and of capillarity-governed solid surface morphology is presented. As an example, the smoothing of a one-dimensional sine-shaped surface is discussed.

  4. Ghost imaging for a reflected object with a rough surface

    SciTech Connect

    Wang Chunfang; Zhang Dawei; Chen Bin; Bai Yanfeng

    2010-12-15

    Ghost imaging for the reflected object with rough surface is investigated. The surface height variance {sigma}{sub h}{sup 2} and the correlation length l{sub c} have been introduced to characterize the rough surface. Based on a simple scattering model, we derive the analytical expressions which are used to describe the effects of {sigma}{sub h}{sup 2} and l{sub c} on ghost imaging. The results show that both {sigma}{sub h}{sup 2} and l{sub c} have no influence on the image resolution, while the convergence of the correlation decreases as {sigma}{sub h}{sup 2} increases. Additionally, the bucket detector used in the test arm can dramatically improve the visibility of ghost images. The results are backed up by numerical simulations, in which a Monte Carlo approach to generate a rough surface has been used.

  5. Identifying Changes in Snowpack Surface Roughness Characteristics

    NASA Astrophysics Data System (ADS)

    Fassnacht, S. R.; Corrao, M. V.; Deems, J. S.; Stednick, J. D.

    2006-12-01

    The flow of air over a surface is influenced by its roughness. The surface of a snowpack is smooth relative to the underlying ground surface. The relative roughness of the snowpack surface changes directionally, spatially, and temporally, due to deposition, erosion, and melt. To examine these changes in snowpack surface roughness at the microtopographic scale for a Northern Colorado site, the surface was photographed using a darker-coloured roughness board that was inserted into the snowpack so that a black (board) versus white (snow) contrast existed along the entire length of the board. The board was 1-m long and was inserted 11 times at 10-cm intervals to create a 1-m by 1-m mesh. The orientation of the boards was rotated 90 degrees to provide finer resolution data in perpendicular directions. For the 1-m boards, the pixel resolution was approximately 0.4 mm. To measure the snow grain scale, a crystal card was photographed and yielded a pixel resolution of approximately 0.1 mm. Incorporating image processing issues such as image contrast and brightness, the digital images were translated into individual lines. These lines were used to compute semi- variograms in log-log space, from which the magnitude of semi-variance, the fractal dimensions, and the scale break were computed. The semi-variogram characteristics were used to illustrate directional, spatial, and temporal changes in snowpack surface roughness.

  6. A rough-surface thermophysical model for airless planets

    NASA Technical Reports Server (NTRS)

    Spencer, John R.

    1990-01-01

    A model for determining diurnal temperatures in spherical-section depressions and which encompasses both subsurface heat-flow and direct and scattered sunlight effects is presently applied to the disk-integrated thermal emission of a rough planetary surface with nonzero thermal inertia. Attention is given to the variation with roughness and thermal inertia of the beaming parameter eta, which characterizes zero-phase thermal emission by comparison with a smooth, nonrotating body and is almost independent of albedo for a given surface roughness. The thermal phase curve of Ceres is noted to be well matched by the model features of (1) prograde rotation, (2) 44-deg rms surface slope, and (3) a thermal inertia that is 30 percent of the lunar value.

  7. Degree of ice particle surface roughness inferred from polarimetric observations

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    The degree of surface roughness of ice particles within thick, cold ice clouds is inferred from multi-directional, 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 extratropics, 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.

  8. Adsorption of Polymers on Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Venkatakrishnan, Abishek; Kuppa, Vikram

    2014-03-01

    Most of the surfaces encountered in nature display irregularity and self-similarity at certain length scales. Such real surfaces can be mimicked via fractal surfaces using an algorithm that produces random surfaces. The problem of polymer chains adsorbed on smooth surfaces has been well understood whereas adsorption on rough surfaces still remains unclear due to the complexity involved in equilibration and sampling of molecules in such systems. The enthalpic interactions between the monomers and the entropic penalty arising due to adsorption on rough surfaces are significantly different from smooth surfaces. In this study, we investigate the adsorption of freely rotating polymer chains on fractal surfaces by Monte-Carlo molecular simulations. Random fractal surfaces are generated using the diamond-square algorithm for different values of the Hurst parameter. Properties like monomer-surface interaction, density profiles, chain orientation profiles and distribution of adsorbed chain fractions are investigated. We also demonstrate the significant effect of fractal dimension on adsorption of polymers on rough surfaces.

  9. Venus surface roughness and Magellan stereo data

    NASA Technical Reports Server (NTRS)

    Maurice, Kelly E.; Leberl, Franz W.; Norikane, L.; Hensley, Scott

    1994-01-01

    Presented are results of some studies to develop tools useful for the analysis of Venus surface shape and its roughness. Actual work was focused on Maxwell Montes. The analyses employ data acquired by means of NASA's Magellan satellite. The work is primarily concerned with deriving measurements of the Venusian surface using Magellan stereo SAR. Roughness was considered by means of a theoretical analyses based on digital elevation models (DEM's), on single Magellan radar images combined with radiometer data, and on the use of multiple overlapping Magellan radar images from cycles 1, 2, and 3, again combined with collateral radiometer data.

  10. Surface roughness modulations by submesoscale currents

    NASA Astrophysics Data System (ADS)

    Rascle, Nicolas; Chapron, Bertrand; Nouguier, Frederic; Ponte, Aurelien; Mouche, Alexis; Molemaker, Jeroen

    2016-04-01

    At times, high resolution images of sea surface roughness can provide stunning details of submesoscale upper ocean dynamics. As interpreted, transformations of short scale wind waves by horizontal current gradients are responsible for those spectacular observations. Here we present two major advances towards the quantitative interpretation of those observations. First, we show that surface roughness variations mainly trace two particular characteristics of the current gradient tensor, the divergence and the strain in the wind direction. Local vorticity and shear in the wind direction should not affect short scale roughness distribution and would not be detectable. Second, we discuss the effect of the viewing direction using sets of quasi-simultaneous sun glitter images, taken from different satellites to provide different viewing configurations. We show that upwind and crosswind viewing observations can be markedly different. As further confirmed with idealized numerical simulations, this anisotropy well traces surface current strain area, while more isotropic contrasts likely trace areas dominated by surface divergence conditions. These findings suggest the potential to directly observe surface currents at submesoscale by using surface roughness observations at multiple azimuth viewing angles. They also pave the way towards a better understanding of the coupling between ocean, waves and atmosphere at high resolution.

  11. Surface roughness limited contrast to clutter ratios THz medical imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Sung, Shijun; Bajwa, Neha; Goell, Jacob; Taylor, Zachary

    2016-03-01

    The THz electromagnetic properties of rough surface are explored and their effect on the observed contrast in THz images is quantified. Rough surface scatter is a major source of clutter in THz imaging as the rough features of skin and other tissues result in non-trivial reflection signal modulation. Traditional approaches to data collection utilize dielectric windows to flatten surfaces for THz imaging. However, there is substantial interest surrounding window free imaging as contact measurements are not ideal for a range of candidate diseases and injuries. In this work we investigate the variation in reflected signal in the specular direction from rough surfaces targets with known roughness parameters. Signal to clutter ratios are computed and compared with that predicted by Rayleigh Rough surface scattering theory. It is shown that Rayleigh rough surface scattering theory, developed for rough features larger than the interacting wavelength, holds acceptable at THz frequencies with rough features much smaller than the wavelength. Additionally, we present some biological tissue imaging examples to illustrate the impact of rough surface scattering in image quality.

  12. Surface forces: Surface roughness in theory and experiment

    SciTech Connect

    Parsons, Drew F. Walsh, Rick B.; Craig, Vincent S. J.

    2014-04-28

    A method of incorporating surface roughness into theoretical calculations of surface forces is presented. The model contains two chief elements. First, surface roughness is represented as a probability distribution of surface heights around an average surface height. A roughness-averaged force is determined by taking an average of the classic flat-surface force, weighing all possible separation distances against the probability distributions of surface heights. Second the model adds a repulsive contact force due to the elastic contact of asperities. We derive a simple analytic expression for the contact force. The general impact of roughness is to amplify the long range behaviour of noncontact (DLVO) forces. The impact of the elastic contact force is to provide a repulsive wall which is felt at a separation between surfaces that scales with the root-mean-square (RMS) roughness of the surfaces. The model therefore provides a means of distinguishing between “true zero,” where the separation between the average centres of each surface is zero, and “apparent zero,” defined by the onset of the repulsive contact wall. A normal distribution may be assumed for the surface probability distribution, characterised by the RMS roughness measured by atomic force microscopy (AFM). Alternatively the probability distribution may be defined by the histogram of heights measured by AFM. Both methods of treating surface roughness are compared against the classic smooth surface calculation and experimental AFM measurement.

  13. Tear Film Interferometry and Corneal Surface Roughness

    PubMed Central

    King-Smith, P. Ewen; Kimball, Samuel H.; Nichols, Jason J.

    2014-01-01

    Purpose. Previous studies of optical interference from the whole thickness of the precorneal tear film showed much lower contrast than from the pre–contact lens tear film. It is hypothesized that the recorded low contrast is related to roughness of the corneal surface compared with the smooth contact lens surface. This hypothesis is tested, and characteristics of this roughness are studied. Methods. Reflectance spectra were recorded from 20 healthy individuals using a silicon-based sensor used in previous studies (wavelength range, 562–1030 nm) and an indium-gallium-arsenide (InGaAs) sensor responding at longer wavelengths (912–1712 nm). Interference from the whole thickness of the precorneal tear film caused oscillations in the reflectance spectra. Results. Spectral oscillations recorded with the InGaAs sensor were found to decay as a Gaussian function of wave number (1/wavelength). This is consistent with a rough corneal surface, whose distribution of surface height is also a Gaussian function. Contrast of spectral oscillations for the InGaAs sensor was, on average, approximately four times greater than that for the silicon sensor. Conclusions. For the Gaussian roughness model based on InGaAs spectra, the corneal surface was characterized by a surface height SD of 0.129 μm. Spectral oscillations recorded with a silicon-based camera can have higher contrast than expected from this Gaussian roughness model, indicating some reflectance from a smoother or more compact surface. The results also indicate that InGaAs cameras could provide whole-thickness interference images of higher contrast than silicon-based cameras. PMID:24692127

  14. ROUGHNESS ANALYSIS OF VARIOUSLY POLISHED NIOBIUM SURFACES

    SciTech Connect

    Ribeill, G.; Reece, C.

    2008-01-01

    Niobium superconducting radio frequency (SRF) cavities have gained widespread use in accelerator systems. It has been shown that surface roughness is a determining factor in the cavities’ effi ciency and maximum accelerating potential achievable through this technology. Irregularities in the surface can lead to spot heating, undesirable local electrical fi eld enhancement and electron multipacting. Surface quality is typically ensured through the use of acid etching in a Buffered Chemical Polish (BCP) bath and electropolishing (EP). In this study, the effects of these techniques on surface morphology have been investigated in depth. The surface of niobium samples polished using different combinations of these techniques has been characterized through atomic force microscopy (AFM) and stylus profi lometry across a range of length scales. The surface morphology was analyzed using spectral techniques to determine roughness and characteristic dimensions. Experimentation has shown that this method is a valuable tool that provides quantitative information about surface roughness at different length scales. It has demonstrated that light BCP pretreatment and lower electrolyte temperature favors a smoother electropolish. These results will allow for the design of a superior polishing process for niobium SRF cavities and therefore increased accelerator operating effi ciency and power.

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

    SciTech Connect

    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 applied in numerical DSMC methods as well as in analytical investigations.

  16. Boltzmann active walkers and rough surfaces

    NASA Astrophysics Data System (ADS)

    Pochy, R. D.; Kayser, D. R.; Aberle, L. K.; Lam, L.

    1993-06-01

    An active walker model (AWM) was recently proposed by Freimuth and Lam for the generation of various filamentary patterns. In an AWM, the walker changes the landscape as it walks, and its steps are in turn influenced by the changing landscape. The landscape so obtained is a rough surface. In this paper, the properties of such a rough surface (with average height conserved) generated by a Boltzmann active walker in 1 + 1 dimensions is investigated in detail. The scaling properties of the surface thickness σ T is found to belong to a new class quite different from other types of fractal surfaces. For example, σ T is independent of the system size L, but is a function of the “temperature” T. Soliton propagation is found when T = 0.

  17. Backscattering from a Gaussian distributed, perfectly conducting, rough surface

    NASA Technical Reports Server (NTRS)

    Brown, G. S.

    1977-01-01

    The problem of scattering by random surfaces possessing many scales of roughness is analyzed. The approach is applicable to bistatic scattering from dielectric surfaces, however, this specific analysis is restricted to backscattering from a perfectly conducting surface in order to more clearly illustrate the method. The surface is assumed to be Gaussian distributed so that the surface height can be split into large and small scale components, relative to the electromagnetic wavelength. A first order perturbation approach is employed wherein the scattering solution for the large scale structure is perturbed by the small scale diffraction effects. The scattering from the large scale structure is treated via geometrical optics techniques. The effect of the large scale surface structure is shown to be equivalent to a convolution in k-space of the height spectrum with the following: the shadowing function, a polarization and surface slope dependent function, and a Gaussian factor resulting from the unperturbed geometrical optics solution. This solution provides a continuous transition between the near normal incidence geometrical optics and wide angle Bragg scattering results.

  18. Surface roughness effects in elastohydrodynamic contacts

    NASA Technical Reports Server (NTRS)

    Tripp, J. H.; Hamrock, B. J.

    1985-01-01

    Surface roughness effects in full-film EHL contacts were studied. A flow factor modification to the Reynolds equation was applied to piezoviscous-elastic line contacts. Results for ensemble-averaged film shape, pressure distribution, and other mechanical quantities were obtained. Asperities elongated in the flow direction by a factor exceeding two decreased both film shape and pressure extrema at constant load; isotropic or transverse asperities increased these extrema. The largest effects are displayed by traction, which increased by over 5% for isotropic or transverse asperities and by slightly less for longitudinal roughness.

  19. Wetting on rough self-affine surfaces

    NASA Astrophysics Data System (ADS)

    Palasantzas, George

    1995-05-01

    In this paper, we present a general investigation of the effective potential for complete wetting on self-affine rough surfaces. The roughness effect is investigated by means of the height-height correlation model in Fourier space ~(1+aξ2q2)-1-H. The parameters H and ξ are, respectively, the roughness exponent and the substrate in-plane correlation length. It is observed that the effect of H on the free interface profile is significant for ξ>ξ) regime is characterized by a power-law scaling ~Y-2.

  20. The Relative Surface Roughness of the two Sides of Iapetus

    NASA Astrophysics Data System (ADS)

    Lee, J.; Buratti, B.; Mosher, J.

    2007-12-01

    We apply Cassini ISS (Imaging Science Subsystem) data from the January 1st, 2005 flyby of Iapetus to a surface roughness model originally developed by Buratti and Veverka (1985). Since macroscopic features of topography alter the scattering properties of a planetary surface (Schoenberg, 1925; Hameen-Antilla et al., 1965; Hapke, 1966, 1984; Veverka and Wasserman, 1972; Lumme and Bowell, 1981; Buratti et al., 1985), this model uses the observed scattering behavior to provide a depth to radius factor q quantifying the size of craters on the surface. Relative surface roughness of the low albedo (leading) hemisphere and high albedo (trailing) hemisphere can then be determined by comparing the value for the two hemispheres, and any differences observed will provide an estimate of the depth of the dark material. Our preliminary findings show marked differences in macroscopic roughness between the high and low albedo hemispheres, indicating that the surface on the dark side is much smoother than the bright. Our results further suggest that the dark material is substantial enough to cause significant infilling of the craters on the dark side. Funded by the NASA Space Grant.

  1. Soil Surface Roughness through Image Analysis

    NASA Astrophysics Data System (ADS)

    Tarquis, A. M.; Saa-Requejo, A.; Valencia, J. L.; Moratiel, R.; Paz-Gonzalez, A.; Agro-Environmental Modeling

    2011-12-01

    Soil erosion is a complex phenomenon involving the detachment and transport of soil particles, storage and runoff of rainwater, and infiltration. The relative magnitude and importance of these processes depends on several factors being one of them surface micro-topography, usually quantified trough soil surface roughness (SSR). SSR greatly affects surface sealing and runoff generation, yet little information is available about the effect of roughness on the spatial distribution of runoff and on flow concentration. The methods commonly used to measure SSR involve measuring point elevation using a pin roughness meter or laser, both of which are labor intensive and expensive. Lately a simple and inexpensive technique based on percentage of shadow in soil surface image has been developed to determine SSR in the field in order to obtain measurement for wide spread application. One of the first steps in this technique is image de-noising and thresholding to estimate the percentage of black pixels in the studied area. In this work, a series of soil surface images have been analyzed applying several de-noising wavelet analysis and thresholding algorithms to study the variation in percentage of shadows and the shadows size distribution. Funding provided by Spanish Ministerio de Ciencia e Innovación (MICINN) through project no. AGL2010- 21501/AGR and by Xunta de Galicia through project no INCITE08PXIB1621 are greatly appreciated.

  2. 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

  3. Studies on argon collisions with smooth and rough tungsten surfaces.

    PubMed

    Ozhgibesov, M S; Leu, T S; Cheng, C H; Utkin, A V

    2013-09-01

    The aim of this work is to investigate argon scattering behaviors on the smooth and rough tungsten surfaces. Current work deals with numerical simulation of nanoscale heat transfer process accompanying with rarefied gas-solid substrate interactions using molecular dynamics (MD) method. Taking into account that this method is very time consuming, MD simulation using CUDA capable Graphic Cards is implemented. The results found that imperfection of the surface significantly influences on gas atom's momentum change upon collision. However, the energy exchange rate remains unchanged regardless to the surface roughness. This finding is in contrast with the results in extant literatures. We believed the results found in this paper are important for both numerical and theoretical analyses of rarefied gas flow in micro- and nano-systems where the choice of boundary conditions significantly influences flow. PMID:24007943

  4. Studies on argon collisions with smooth and rough tungsten surfaces.

    PubMed

    Ozhgibesov, M S; Leu, T S; Cheng, C H; Utkin, A V

    2013-09-01

    The aim of this work is to investigate argon scattering behaviors on the smooth and rough tungsten surfaces. Current work deals with numerical simulation of nanoscale heat transfer process accompanying with rarefied gas-solid substrate interactions using molecular dynamics (MD) method. Taking into account that this method is very time consuming, MD simulation using CUDA capable Graphic Cards is implemented. The results found that imperfection of the surface significantly influences on gas atom's momentum change upon collision. However, the energy exchange rate remains unchanged regardless to the surface roughness. This finding is in contrast with the results in extant literatures. We believed the results found in this paper are important for both numerical and theoretical analyses of rarefied gas flow in micro- and nano-systems where the choice of boundary conditions significantly influences flow.

  5. Flow over a Biomimetic Surface Roughness Microgeometry

    NASA Astrophysics Data System (ADS)

    Warncke Lang, Amy; Hidalgo, Pablo; Westcott, Matthew

    2006-11-01

    Certain species of sharks (e.g. shortfin mako and common hammerhead) have a skin structure that could result in a bristling of their denticles (scales) during increased swimming speeds (Bechert, D. W., Bruse, M., Hage, W. and Meyer, R. 2000, Fluid mechanics of biological surfaces and their technological application. Naturwissenschaften 80:157-171). This unique surface geometry results in a three-dimensional array of cavities* (d-type roughness geometry) forming within the surface and has been given the acronym MAKO (Micro-roughness Array for Kinematic Optimization). Possible mechanisms leading to drag reduction over the shark's body by this unique roughness geometry include separation control thereby reducing pressure drag, skin friction reduction (via the `micro-air bearing' effect first proposed by Bushnell (AIAA 83-0227)), as well as possible transition delay in the boundary layer. Initial work is confined to scaling up the geometry from 0.2 mm on the shark skin to 2 cm, with a scaling down in characteristic velocity from 10 - 20 m/s to 10 - 20 cm/s for laminar flow boundary layer water tunnel studies. Support for this research by NSF SGER grant CTS-0630489 and a University of Alabama RAC grant is gratefully acknowledged. * Patent pending.

  6. Effects of surface roughness and absorption on light propagation in graded-profile waveguides

    SciTech Connect

    Danilenko, S S; Osovitskii, A N

    2011-06-30

    This paper examines the effects of surface roughness and absorption on laser light propagation in graded-profile waveguiding structures. We derive analytical expressions for the scattering and absorption coefficients of guided waves and analyse these coefficients in relation to parameters of the waveguiding structure and the roughness of its boundary. A new approach is proposed to measuring roughness parameters of precision dielectric surfaces. Experimental evidence is presented which supports the main conclusions of the theory. (integraled-optical waweguides)

  7. Robust surface roughness indices and morphological interpretation

    NASA Astrophysics Data System (ADS)

    Trevisani, Sebastiano; Rocca, Michele

    2016-04-01

    Geostatistical-based image/surface texture indices based on variogram (Atkison and Lewis, 2000; Herzfeld and Higginson, 1996; Trevisani et al., 2012) and on its robust variant MAD (median absolute differences, Trevisani and Rocca, 2015) offer powerful tools for the analysis and interpretation of surface morphology (potentially not limited to solid earth). In particular, the proposed robust index (Trevisani and Rocca, 2015) with its implementation based on local kernels permits the derivation of a wide set of robust and customizable geomorphometric indices capable to outline specific aspects of surface texture. The stability of MAD in presence of signal noise and abrupt changes in spatial variability is well suited for the analysis of high-resolution digital terrain models. Moreover, the implementation of MAD by means of a pixel-centered perspective based on local kernels, with some analogies to the local binary pattern approach (Lucieer and Stein, 2005; Ojala et al., 2002), permits to create custom roughness indices capable to outline different aspects of surface roughness (Grohmann et al., 2011; Smith, 2015). In the proposed poster, some potentialities of the new indices in the context of geomorphometry and landscape analysis will be presented. At same time, challenges and future developments related to the proposed indices will be outlined. Atkinson, P.M., Lewis, P., 2000. Geostatistical classification for remote sensing: an introduction. Computers & Geosciences 26, 361-371. 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. Lucieer, A., Stein, A., 2005. Texture-based landform segmentation of LiDAR imagery

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

    SciTech Connect

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

  9. Grinding surface roughness measurement based on the co-occurrence matrix of speckle pattern texture

    SciTech Connect

    Lu, R.-S.; Tian, G.-Y.; Gledhill, Duke; Ward, Steve

    2006-12-10

    Surface speckle pattern intensity distribution resulting from laser light scattering from a rough surface contains various information about the surface geometrical and physical properties.A surface roughness measurement technique based on the texture analysis of surface speckle pattern texture images is put forward. In the surface roughness measurement technique, the speckle pattern texture images are taken by a simple setup configuration consisting of a laser and a CCD camera. Our experimental results show that the surface roughness contained in the surface speckle pattern texture images has a good monotonic relationship with their energy feature of the gray-level co-occurrence matrices. After the measurement system is calibrated by a standard surface roughness specimen, the surface roughness of the object surface composed of the same material and machined by the same method as the standard specimen surface can be evaluated from a single speckle pattern texture image. The robustness of the characterization of speckle pattern texture for surface roughness is also discussed. Thus the surface roughness measurement technique can be used for an in-process surface measurement.

  10. Adhesive contact of randomly rough surfaces

    NASA Astrophysics Data System (ADS)

    Pastewka, Lars; Robbins, Mark

    2012-02-01

    The contact area, stiffness and adhesion between rigid, randomly rough surfaces and elastic substrates is studied using molecular statics and continuum simulations. The surfaces are self-affine with Hurst exponent 0.3 to 0.8 and different short λs and long λL wavelength cutoffs. The rms surface slope and the range and strength of the adhesive potential are also varied. For parameters typical of most solids, the effect of adhesion decreases as the ratio λL/λs increases. In particular, the pull-off force decreases to zero and the area of contact Ac becomes linear in the applied load L. A simple scaling argument is developed that describes the increase in the ratio Ac/L with increasing adhesion and a corresponding increase in the contact stiffness [1]. The argument also predicts a crossover to finite contact area at zero load when surfaces are exceptionally smooth or the ratio of surface tension to bulk modulus is unusually large, as for elastomers. Results that test this prediction will be presented and related to the Maugis-Dugdale [2] theories for individual asperities and the more recent scaling theory of Persson [3]. [1] Akarapu, Sharp, Robbins, Phys. Rev. Lett. 106, 204301 (2011) [2] Maugis, J. Colloid Interface Sci. 150, 243 (1992) [3] Persson, Phys. Rev. Lett. 74, 75420 (2006)

  11. Interactions between surface roughness and airflow turbulence affecting drying dynamics of rough porous surfaces

    NASA Astrophysics Data System (ADS)

    Haghighi, Erfan; Kirchner, James; Or, Dani

    2016-04-01

    Evaporative drying of porous surfaces interacting with turbulent airflows is common in various industrial and natural applications. The intrinsic relief and roughness of natural porous surfaces are likely to influence the structure of interacting turbulent airflow boundary layers, and thus affect rates and patterns of heat and vapor fluxes from the surface. These links have been formalized in new mechanistic models that consider intermittent and localized turbulence-induced boundary layers, resulting in rich surface evaporation and energy exchange dynamics. The models were evaluated experimentally by systematically varying surface roughness elements in drying experiments of wavy and bluff-body covered sand surfaces in a wind tunnel. Thermal infrared signatures of localized evaporative fluxes as well as mean evaporative mass losses were recorded. The resulting patterns were in good agreement with model predictions for local and surface averaged turbulent exchange rates. Experimental and theoretical results suggest that evaporative water losses from wavy sand surfaces can be either enhanced or suppressed (relative to a flat surface), due to the complex interplay between the local boundary layer thickness and internal limitations on water flow to the evaporating surface. For sand surfaces covered by isolated cylindrical elements (bluff bodies), model predictions and measurements show persistent enhancement of evaporative fluxes from bluff-rough surfaces compared to a flat surface under similar conditions. This enhancement is attributed to the formation of vortices that thin the boundary layer over part of the interacting surface footprint. The implications of this study for interpreting and upscaling evapotranspiration rates from terrestrial surfaces will be discussed.

  12. Speckle pattern texture analysis method to measure surface roughness

    NASA Astrophysics Data System (ADS)

    Kuznetsov, I.; Sadovoy, A.; Doronin, A.; Meglinski, I.

    2013-02-01

    Speckle pattern texture analysis method is applied to measure surface roughness of human skin. The method is based on analyzing of a gray level co-occurrence matrix occurred from a speckle image of a rough surface. Paper with different surface roughness is used as a skin phantom. The roughness is controlled by profilometry measurements. The developed methodology could find wide application in dermatology and tissue diagnostics.

  13. Theory of adhesion: Role of surface roughness

    NASA Astrophysics Data System (ADS)

    Persson, B. N. J.; Scaraggi, M.

    2014-09-01

    We discuss how surface roughness influences the adhesion between elastic solids. We introduce a Tabor number which depends on the length scale or magnification, and which gives information about the nature of the adhesion at different length scales. We consider two limiting cases relevant for (a) elastically hard solids with weak (or long ranged) adhesive interaction (DMT-limit) and (b) elastically soft solids with strong (or short ranged) adhesive interaction (JKR-limit). For the former cases we study the nature of the adhesion using different adhesive force laws (F ˜ u-n, n = 1.5-4, where u is the wall-wall separation). In general, adhesion may switch from DMT-like at short length scales to JKR-like at large (macroscopic) length scale. We compare the theory predictions to results of exact numerical simulations and find good agreement between theory and simulation results.

  14. 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.

  15. The roughness of the Martian surface: A scale dependent model

    NASA Technical Reports Server (NTRS)

    Shepard, M. K.; Guinness, E. A.; Arvidson, R. E.

    1993-01-01

    In the coming decade, several lander missions to Mars are planned (e.g., MESUR Pathfinder, MESUR). One of the dangers facing planners of these missions is the rough topography observed at both Viking Lander sites. Both landing sites are ubiquitously covered with meter-scale boulders. Objects of this size pose obvious threats to soft landers, especially at Mars where the distance from Earth causes prohibitive time lags between the transmission of commands and feedback from the spacecraft. An obvious solution is to scout for a 'smooth' site prior to the landing. However, the best resolutions realizable on current and future missions (i.e., Mars Observer) are on the order of several meters. Even at this scale, boulders of 1-2 meters in size are unresolvable. Additionally, the amount of time and spacecraft resources required to search even a small area of the planet are unrealistic given other mission objectives. An alternative is to determine the 'roughness' of the surface at a subpixel scale using bidirectional reflectance observations. Much larger areas of the planet can be searched, and much of the search can easily be automated. The morphology of the martian plains observed by the Viking Landers is physically simple. The surface is covered with a layer (approximately flat lying) of aeolian sediment from which numerous outcrops of bedrock and boulders protrude. This morphology, while simple, will be difficult to characterize from orbit using traditional bidirectional reflectance models for two reasons. First, modeling the surface as facets with Gaussian or exponential slope distributions is not realistic given the morphology described above. Second, the roughness parameter is an 'average' of the roughness at scales ranging from the wavelength of light being scattered to the pixel size of the observation. Thus, there is no definite scale of roughness that can be extracted from the Hapke roughness parameter. Using the concepts of geometric and boolean models

  16. Rough surface scattering based on facet model

    NASA Technical Reports Server (NTRS)

    Khamsi, H. R.; Fung, A. K.; Ulaby, F. T.

    1974-01-01

    A model for the radar return from bare ground was developed to calculate the radar cross section of bare ground and the effect of the frequency averaging on the reduction of the variance of the return. It is shown that, by assuming that the distribution of the slope to be Gaussian and that the distribution of the length of the facet to be in the form of the positive side of a Gaussian distribution, the results are in good agreement with experimental data collected by an 8- to 18-GHz radar spectrometer system. It is also shown that information on the exact correlation length of the small structure on the ground is not necessary; an effective correlation length may be calculated based on the facet model and the wavelength of the incident wave.

  17. The dependence of sea surface roughness on wind-waves

    NASA Astrophysics Data System (ADS)

    Lange, B.; Johnson, H. K.; Larsen, S. E.; Højstrup, J.

    2003-04-01

    The wave age dependency of the non-dimensional sea surface roughness (also called Charnock parameter) is investigated with data from the new field measurement program at Rødsand in the Danish Baltic Sea. An increasing Charnock parameter with inverse wave age is found, which can be described by a power law relation of the form proposed by Johnson et al. (1998) and others. Friction velocity is a common quantity in both Charnock parameter and wave age. Thus self-correlation effects are unavoidable in the relation between them. The significance of self-correlation is investigated by employing an artificial 'data' set with randomised wave parameters. It is found that self-correlation severely influences the relation. For the Rødsand data set the difference between real and randomised 'data' was found to be within the measurement uncertainty. By using a small sub-set of the data it was found that the importance of self-correlation increases for a narrower range of wave age values. This agrees with the conclusion of Johnson et al. (1998), that due to the scatter and self-correlation problems the coefficients of the power law relation can only be obtained from the analysis of an aggregated data set with a wide wave age range combining measurements from several sites. The dependency between wave age and sea roughness has been discussed extensively in the literature with different and sometimes conflicting results. A wide range of coefficients has been found for the power law relation between Charnock parameter and wave age for different data sets. It is shown that self-correlation contributes to such differences, since it depends on the range of wave age values present in the data sets. Also, data are often selected for rough flow conditions with the Reynolds roughness number. It is shown that for data sets with large scatter this can lead to misleading results of the relation of wave age and Charnock parameter. Two different methods to overcome this problem are presented

  18. Reconstruction of Two-Dimensional Randomly Rough Surfaces Based on Bidirectional Reflectance Distribution Function

    NASA Astrophysics Data System (ADS)

    Xuan, Yimin; Han, Yuge; Zhou, Yue

    2013-03-01

    This article presents an inverse method for reconstructing two-dimensional randomly rough surfaces based on the available (experimental or given) data of the bidirectional reflectance distribution function (BRDF). The Maxwell's equations of electromagnetic waves are applied to describe the light scattering process of rough surfaces by accounting for the near-field effect. Such a forward problem is numerically solved with the finite-difference time-domain algorithm. The inverse scattering problem of reconstructing the surface profile is handled by means of an optimization technique—the particle swarm optimizer algorithm. As an example, reconstruction of a Gaussian rough surface is conducted based on the experimental data of BRDFs. The retrieved results of the surface profile are compared with those measured by atomic force microscopy from the samples, which shows that the reconstruction algorithm can provide the credible prediction of surface profiles. The reconstruction approach studied in this study can make reliable predictions of the actual or required surface profiles.

  19. Application of wavelet transforms in terahertz spectroscopy of rough surface targets

    NASA Astrophysics Data System (ADS)

    Arbab, M. Hassan; Winebrenner, Dale P.; Thorsos, Eric I.; Chen, Antao

    2010-02-01

    Previously, it has been shown that scattering of terahertz waves by surface roughness of a target can alter the terahertz absorption spectrum and thus obscure the detection of some chemicals in both transmission and reflection geometries. In this paper it is demonstrated that by employing Maximal Overlap Discrete Wavelet Transform (MODWT) coefficients, wavelet-based methods can be used to retrieve spectroscopic information from a broadband terahertz signal reflected from a rough surface target. It is concluded that while the commonly used direct frequency domain deconvolution method fails to accurately characterize and detect the resonance in the dielectric constant of rough surface lactose pellets, wavelet techniques were able to successfully identify such features.

  20. Interactions of light with rough dielectric surfaces - Spectral reflectance and polarimetric properties

    NASA Technical Reports Server (NTRS)

    Yon, S. A.; Pieters, C. M.

    1988-01-01

    The nature of the interactions of visible and NIR radiation with the surfaces of rock and mineral samples was investigated by measuring the reflectance and the polarization properties of scattered and reflected light for slab samples of obsidian and fine-grained basalt, prepared to controlled surface roughness. It is shown that the degree to which radiation can penetrate a surface and then scatter back out, an essential criterion for mineralogic determinations based on reflectance spectra, depends not only upon the composition of the material, but also on its physical condition such as sample grain size and surface roughness. Comparison of the experimentally measured reflectance and polarization from smooth and rough slab materials with the predicted models indicates that single Fresnel reflections are responsible for the largest part of the reflected intensity resulting from interactions with the surfaces of dielectric materials; multiple Fresnel reflections are much less important for such surfaces.

  1. A Statistical Study for Optimum Surface Roughness and Engraving Depth

    NASA Astrophysics Data System (ADS)

    Kasman, Şefika; Saklakoǧlu, I. Etem

    2011-01-01

    The aim of this study is to investigate the effect of scan times on surface roughness and engraving depth an experimental design was implemented to AISI H13 tool steed workpiece using fiber laser. For this purpose, an experimental design plan was constituted using full factorial design and results were evaluated for surface roughness and engraving depth. The results showed that the scan times and the scan speed significantly affect both surface roughness and engraving depth. In order to characterize the surface roughness and engraving depth, two linear regression models were constituted.

  2. Quantification of soil surface roughness evolution under simulated rainfall

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  3. Relativistic scattering from moving fractally corrugated surfaces.

    PubMed

    De Cupis, P

    2003-05-15

    The solution to the problem of optical or electromagnetic-wave scattering from perfectly conducting rough surfaces modeled by a multiscale fractal function is generalized to the case of relative uniform translating motion with respect to the observer. The presence of motion can be treated by the relativistic frame hopping method by means of plane-wave simplification techniques, since the solution relevant to the static case is expressed in terms of a generalized expansion of Floquet modes.

  4. Drag force and surface roughness measurements on freshwater biofouled surfaces.

    PubMed

    Andrewartha, J; Perkins, K; Sargison, J; Osborn, J; Walker, G; Henderson, A; Hallegraeff, G

    2010-05-01

    The detrimental effect of biofilms on skin friction for near wall flows is well known. The diatom genera Gomphonema and Tabellaria dominated the biofilm mat in the freshwater open channels of the Tarraleah Hydropower Scheme in Tasmania, Australia. A multi-faceted approach was adopted to investigate the drag penalty for biofouled 1.0 m x 0.6 m test plates which incorporated species identification, drag measurement in a recirculating water tunnel and surface characterisation using close-range photogrammetry. Increases in total drag coefficient of up to 99% were measured over clean surface values for biofouled test plates incubated under flow conditions in a hydropower canal. The effective roughness of the biofouled surfaces was found to be larger than the physical roughness; the additional energy dissipation was caused in part by the vibration of the biofilms in three-dimensions under flow conditions. The data indicate that there was a roughly linear relationship between the maximum peak-to-valley height of a biofilm and the total drag coefficient.

  5. Impact of EUVL mask surface roughness on an actinic blank inspection image and a wafer image

    NASA Astrophysics Data System (ADS)

    Yamane, Takeshi; Terasawa, Tsuneo

    2012-11-01

    An impact of EUVL mask surface roughness on actinic inspection was studied. The background level (BGL) of an actinic inspection image is caused by the light scattered from the mask blank surface roughness. The BGL is found to be proportional to the square of the mask surface roughness measured by AFM. By using this proportionality coefficient, a global distribution of the surface roughness can be obtained at the same time while inspection a mask. On the other hand, any local variation of BGL indicates variation of the mask surface roughness at each pixel. Assuming that the roughness at a center pixel is 0.15 nm rms (SEMI standard specification) and those at the surrounding pixels are 0.1 nm rms, the signal intensity at the center pixel is found to be approximately the same as that of a 1.2 nm-high and 40 nm-wide programmed defect. In that case, CD error on a wafer image due to the reflectivity loss by the roughness is found to be not critical. This means that the local roughness should be less than 0.15 nm rms, and that the inspection system can detect such a local variation of the roughness with 100 % probability.

  6. Backscattering of waves of a two-scale rough surface with allowance for rereflections

    NASA Astrophysics Data System (ADS)

    Zavorotnyi, V. U.

    An analysis is made of wave scattering by a surface with small-scale and large-scale (as compared with the wavelength) roughnesses. Kur'ianov's method is refined by allowing for rereflections. An expression is derived for the mean intensity of the diffuse component of the scattered field in the case of an arbitrary configuration of the large-scale component of the surface. In the case of backscattering there occurs coherent summation of several field components, which is connected with the presence of rereflections on the surface. The results are pertinent to wave scattering by the sea surface.

  7. Light scattering by a reentrant fractal surface.

    PubMed

    Mendoza-Suárez, A; Méndez, E R

    1997-05-20

    Recently, rigorous numerical techniques for treating light scattering problems with one-dimensional rough surfaces have been developed. In their usual formulation, these techniques are based on the solution of two coupled integral equations and are applicable only to surfaces whose profiles can be described by single-valued functions of a coordinate in the mean plane of the surface. In this paper we extend the applicability of the integral equation method to surfaces with multivalued profiles. A procedure for finding a parametric description of a given profile is described, and the scattering equations are established within the framework of this formalism. We then present some results of light scattering from a sequence of one-dimensional flat surfaces with defects in the form of triadic Koch curves. Beyond a certain order of the prefractal, the scattering patterns become stationary (within the numerical accuracy of the method). It can then be argued that the results obtained correspond to a surface with a fractal structure. These constitute, to our knowledge, the first rigorous calculations of light scattering from a reentrant fractal surface. PMID:18253371

  8. 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.

  9. Surface roughness evolution of nanocomposite thin films

    SciTech Connect

    Turkin, A. A.; Pei, Y. T.; Shaha, K. P.; Chen, C. Q.; Vainshtein, D. I.; Hosson, J. Th. M. de

    2009-01-01

    An analysis of dynamic roughening and smoothening mechanisms of thin films grown with pulsed-dc magnetron sputtering is presented. The roughness evolution has been described by a linear stochastic equation, which contains the second- and fourth-order gradient terms. Dynamic smoothening of the growing interface is explained by ballistic effects resulting from impingements of ions to the growing thin film. These ballistic effects are sensitive to the flux and energy of impinging ions. The predictions of the model are compared with experimental data, and it is concluded that the thin film roughness can be further controlled by adjusting waveform, frequency, and width of dc pulses.

  10. Rough surface improves stability of air- sounding balloons

    NASA Technical Reports Server (NTRS)

    Scoggins, J. R.

    1965-01-01

    Aerodynamic stability of balloons used for measuring the intensity and direction of atmospheric winds at various elevations is improved by incorporating a rough surface on the balloons. The rough-surfaced balloon is useful for collecting wind profiles and other meteorological data.

  11. Counterintuitive MCNPX Results for Scintillator Surface Roughness Effect

    SciTech Connect

    2012-08-12

    We have reported on our recent MCNPX simulation results of energy deposition for a group of 8 scintillation detectors, coupled with various rough surface patterns. The MCNPX results generally favored the detectors with various rough surface patterns. The observed MCNPX results are not fully explained by this work.

  12. The role of surface roughness in the measurement of slipperiness.

    PubMed

    Chang, W R; Kim, I J; Manning, D P; Bunterngchit, Y

    2001-10-20

    Surface roughness has been shown to have substantial effects on the slip resistance between shoe heels and floor surfaces under various types of walking environments. This paper summarizes comprehensive views of the current understanding on the roles of surface roughness on the shoe and floor surfaces in the measurement of slipperiness and discusses promising directions for future research. Various techniques and instruments for surface roughness measurements and related roughness parameters are reviewed in depth. It is suggested that a stylus-type profilometer and a laser scanning confocal microscope are the preferred instruments for surface roughness measurements in the field and laboratory, respectively. The need for developing enhanced methods for reliably characterizing the slip resistance properties is highlighted. This could be based on the principal understanding of the nature of shoe and floor interface and surface analysis techniques for characterizing both surfaces of shoe and floor. Therefore, surface roughness on both shoe and floor surfaces should be measured and combined to arrive at the final assessment of slipperiness. While controversies around the friction measurement for slipperiness assessment still remain, surface roughness measurement may provide an objective alternative to overcoming the limitations of friction measurements.

  13. Prediction of Frictional Drag over Rough Walls using Surface Statistics

    NASA Astrophysics Data System (ADS)

    Flack, Karen; Schultz, Michael

    2014-11-01

    Although the frictional drag of rough-wall-bounded flows has been studied extensively, several practical questions remain largely unresolved. First, the relationship between the shape of the roughness function in transitionally-rough regime and the surface topography which gives rise to it are not well understood. Second, it is not completely clear which textural parameters best describe a rough surface in a hydraulic sense. Furthermore, the range of roughness wavelengths that influence the skin-friction is not well established. The focus of the present work is to attempt to address these questions with a systematic study of the skin-friction of fifteen rough surfaces that were generated by grit blasting. The hydrodynamic tests were carried out over a large Reynolds number range. Five surfaces were prepared by grit blasting with a single scale blast media. These underwent hydrodynamic testing and were subsequently blasted with secondary and tertiary scale media in order to investigate the role that the incorporation of additional roughness length scales plays in determining the shape of the roughness function and the resulting hydraulic length scale. The presentation will focus on the appropriate statistical scales for prediction of the roughness function. Spatial filtering prior to the calculation of surface statistics will also be discussed. Work supported by the Office of Naval Research.

  14. 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.

  15. Comparing Vesta's Surface Roughness to the Moon Using Bistatic Radar Observations by the Dawn Mission

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The first orbital bistatic radar (BSR) observations of a small body have been conducted opportunistically by NASA's Dawn spacecraft at Asteroid Vesta using the telecommunications antenna aboard Dawn to transmit and the Deep Space Network 70-meter antennas on Earth to receive. Dawn's high-gain communications antenna continuously transmitted right-hand circularly polarized radio waves (4-cm wavelength), and due to the opportunistic nature of the experiment, remained in a fixed orientation pointed toward Earth throughout each BSR observation. As a consequence, Dawn's transmitted radio waves scattered from Vesta's surface just before and after each occultation of the Dawn spacecraft behind Vesta, resulting in surface echoes at highly oblique incidence angles of greater than 85 degrees, and a small Doppler shift of ~2 Hz between the carrier signal and surface echoes from Vesta. We analyze the power and Doppler spreading of Vesta's surface echoes to assess surface roughness, and find that Vesta's area-normalized radar cross section ranges from -8 to -17 dB, which is notably much stronger than backscatter radar cross section values reported for the Moon's limbs (-20 to -35 dB). However, our measurements correspond to the forward scattering regime--such that at high incidence, radar waves are expected to scatter more weakly from a rough surface in the backscatter direction than that which is scattered forward. Using scattering models of rough surfaces observed at high incidence, we report on the relative roughness of Vesta's surface as compared to the Moon and icy Galilean satellites. Through this, we assess the dominant processes that have influenced Vesta's surface roughness at centimeter and decimeter scales, which are in turn applicable to assisting future landing, sampling and orbital missions of other small bodies.

  16. 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.

  17. Shape reconstruction of the multi-scale rough surface from multi-frequency phaseless data

    NASA Astrophysics Data System (ADS)

    Bao, Gang; Zhang, Lei

    2016-08-01

    We consider the problem of reconstructing the shape of multi-scale sound-soft large rough surfaces from phases measurements of the scattered field generated by tapered waves with multiple frequencies impinging on a rough surface. To overcome both the ill-posedness and nonlinearity of this problem for a single frequency, the Landweber regularization method based on the adjoint of the nonlinear objective functional is used. When the multi-frequency data is available, an approximation method is introduced to estimate the large-scale structure of the rough surface using the data measurements at the lowest frequency. The obtained estimate serves as an initial guess for a recursive linearization algorithm in frequency, which is used to capture the small scale structure of the rough surface. Numerical experiments are presented to illustrate the effectiveness of the method.

  18. Effect of surface roughness on the microwave emission from soils

    NASA Technical Reports Server (NTRS)

    Choudhury, B. J.; Schmugge, T. J.; Newton, R. W.; Chang, A. T. C.

    1978-01-01

    The effect of surface roughness on the brightness temperature of a moist terrain was studied through the modification of Fresnel reflection coefficient and using the radiative transfer equation. The modification involves introduction of a single parameter to characterize the roughness. It is shown that this parameter depends on both the surface height variance and the horizontal scale of the roughness. Model calculations are in good quantitative agreement with the observed dependence of the brightness temperature on the moisture content in the surface layer. Data from truck mounted and airborne radiometers are presented for comparison. The results indicate that the roughness effects are greatest for wet soils where the difference between smooth and rough surfaces can be as great as 50K.

  19. Roughness-Based Superhydrophobic Surfaces: Fundamentals and Future Directions

    NASA Astrophysics Data System (ADS)

    Patankar, Neelesh

    2011-11-01

    Superhydrophobicity of rough surfaces has attracted global interest through the past decade. There are naturally occurring instances of such surfaces, e.g., lotus leaves, which led to the popular term ``lotus effect.'' Numerous applications in wide ranging areas such as drag reduction, self-cleaning, heat exchangers, energy conversion, condensation, anti-icing, textile, desalination, etc., are being explored by researchers worldwide. The signature configuration for superhydrophobicity has been ``bead-like'' drops on rough surfaces that roll-off easily. This becomes possible if the liquid does not impale the roughness grooves, and if the contact angle hysteresis is low. Finding appropriate surface roughness is therefore necessary. A thermodynamic framework to enable analysis of this problem will be presented. It will be noted that the success of rough superhydrophobic substrates relies on the presence of gas pockets in the roughness grooves underneath the liquid. These gas pockets could be those of air from the surrounding environment. Current design strategies rely on the availability of air. However, if the rough substrates are fully submerged in the liquid then the trapped air in the roughness grooves may not be sustained. A design approach based on sustaining a vapor phase of the liquid itself in the roughness grooves, instead of relying on the presence of air, will be presented. The resulting surfaces, referred to as vapor stabilizing substrates, are deemed to be robust against wetting transition even if no air is present. Applications of this approach include low drag surfaces, nucleate boiling at dramatically low superheats, among others. The concept can be generalized to other transitions on the phase diagram, thus enabling the design of rough surfaces for phase manipulation in general.

  20. Scattering of waves from periodic surfaces

    NASA Technical Reports Server (NTRS)

    Chuang, S.-L.; Kong, J. A.

    1981-01-01

    In order to study the scattering of waves from periodic surfaces, the basic grating equations are reviewed, and a general approach for scattering from impenetrable and penetrable media is formulated. Three analytical methods for scattering on a conducting sinusoidal surface for both TE and TM polarized waves are compared. In The Masel, Merrill, and Miller (MMM) method for quantum scattering of atoms (1975, 1976), the surface field expansions are expressed in terms of Fourier series. The Modified Physical Optics (MPO) method (DeSanto, 1975; Whitman and Schwering, 1977) uses surface field expansions consisting of a leading term proportional to the physical optics approximation multiplied by a Fourier series expansion. The Waterman's Plane Harmonics (WPH) approach (1975) makes use of basis functions which are downward plane harmonics evaluated on the surface. The MMM method proved to be the most efficient one in terms of rate and range of convergence. For dielectric media with periodic rough surfaces, an improved method is developed for calculating the reflected and transmitted powers, and the results are compared with experimental data obtained at optical frequencies.

  1. Surface Roughness of the Moon Derived from Multi-frequency Radar Data

    NASA Astrophysics Data System (ADS)

    Fa, W.

    2011-12-01

    Surface roughness of the Moon provides important information concerning both significant questions about lunar surface processes and engineering constrains for human outposts and rover trafficabillity. Impact-related phenomena change the morphology and roughness of lunar surface, and therefore surface roughness provides clues to the formation and modification mechanisms of impact craters. Since the Apollo era, lunar surface roughness has been studied using different approaches, such as direct estimation from lunar surface digital topographic relief, and indirect analysis of Earth-based radar echo strengths. Submillimeter scale roughness at Apollo landing sites has been studied by computer stereophotogrammetry analysis of Apollo Lunar Surface Closeup Camera (ALSCC) pictures, whereas roughness at meter to kilometer scale has been studied using laser altimeter data from recent missions. Though these studies shown lunar surface roughness is scale dependent that can be described by fractal statistics, roughness at centimeter scale has not been studied yet. In this study, lunar surface roughnesses at centimeter scale are investigated using Earth-based 70 cm Arecibo radar data and miniature synthetic aperture radar (Mini-SAR) data at S- and X-band (with wavelengths 12.6 cm and 4.12 cm). Both observations and theoretical modeling show that radar echo strengths are mostly dominated by scattering from the surface and shallow buried rocks. Given the different penetration depths of radar waves at these frequencies (< 30 m for 70 cm wavelength, < 3 m at S-band, and < 1 m at X-band), radar echo strengths at S- and X-band will yield surface roughness directly, whereas radar echo at 70-cm will give an upper limit of lunar surface roughness. The integral equation method is used to model radar scattering from the rough lunar surface, and dielectric constant of regolith and surface roughness are two dominate factors. The complex dielectric constant of regolith is first estimated

  2. Reflection of X-rays from a rough surface at extremely small grazing angles.

    PubMed

    Wen, Mingwu; Kozhevnikov, Igor V; Wang, Zhanshan

    2015-09-21

    Peculiarities of X-ray diffraction from a rough surface at an extremely small grazing angle of an incident beam are theoretically studied. The interrelation of four diffraction channels (coherent reflectance, coherent transmittance, diffuse scattering in vacuum, and scattering into the matter depth) is analyzed for different limiting cases (large and small correlation length of roughness and large and extremely small grazing angle of incident radiation). Both the Debye-Waller and the Nevot-Croce factors are demonstrated to describe improperly the features of X-ray diffraction at extremely small grazing angles. More appropriate simple analytic expressions for the specular reflectivity and total integrated scattering in vacuum are obtained instead. Transformation of one limiting diffraction regime into another one with variation in the correlation length of roughness is discussed.

  3. Phonon thermal conductivity in silicon nanowires: The effects of surface roughness at low temperatures

    NASA Astrophysics Data System (ADS)

    Hyun Oh, Jung; Shin, Mincheol; Jang, Moon-Gyu

    2012-02-01

    Using a Green's function method based on an elastic wave equation, the effects of surface roughness and the nanowire-contact interface scattering on phonon thermal conductivity are studied at low temperatures. It is found that the interface geometry between a nanowire and its contacts affects the transmission function at small energies related to the gapless modes and it gives rise to deviated results from the universal conductance. It is also shown that the surface roughness is crucial in the suppression of phonon thermal conductivity with reducing the nanowire size by averaging the transmission function over the rough-surface configurations. Furthermore, the phonon mean free path is proportional to the ratio of the correlation length and roughness heights quadratically as well as the cross-section area of the nanowire.

  4. Modeling of surface roughness effects on glaze ice accretion

    NASA Technical Reports Server (NTRS)

    Hansman, R. John, Jr.; Yamaguchi, Keiko; Berkowitz, Brian M.; Potapczuk, Mark

    1990-01-01

    A series of experimental investigations focused on studying the cause and effect of roughness on accreting glaze ice surfaces were conducted. Detailed microvideo observations were made of glaze ice accretions on 1 to 4 inch diameter cylinders in three icing wind tunnels (the Data Products of New England six inch test facility, the NASA Lewis Icing Research Tunnel, and the B. F. Goodrich Ice Protection Research Facility). Infrared thermal video recordings were made of accreting ice surfaces in the Goodrich facility. Distinct zones of surface water behavior were observed; a smooth wet zone in the stagnation region with a uniform water film; a rough zone where surface tension effects caused coalescence of surface water into stationary beads; a horn zone where roughness elements grow into horn shapes; a runback zone where surface water ran back as rivulets; and a dry zone where rime feathers formed. The location of the transition from the smooth to the rough zone was found to migrate with time towards the stagnation point. The behavior of the transition appeared to be controlled by boundary layer transition and bead formation mechanisms at the interface between the smooth and rough zones. Regions of wet ice growth and enhanced heat transfer were clearly visible in the infrared video recordings of glaze ice surfaces. A simple multi-zone modification to the current glaze ice accretion model was proposed to include spatial variability in surface roughness.

  5. Radar scattering laws and wavelength dependence of the lunar surface

    NASA Technical Reports Server (NTRS)

    Simpson, R. A.

    1978-01-01

    Data from Apollo lunar bistatic radar experiments have been processed to give probability density functions for surface slopes. These show best agreement with a Hagfors scattering law, though data having both gaussian and exponential characteristics also exist. Surface roughness estimates range from 4 deg in maria to at least 8 deg in highlands, values which are appropriate to 25 m horizontal scales and which are areal averages over tens of square kilometers. Roughness varies with wavelength, most strongly in maria.

  6. Computer simulation of RBS spectra from samples with surface roughness

    NASA Astrophysics Data System (ADS)

    Malinský, P.; Hnatowicz, V.; Macková, A.

    2016-03-01

    A fast code for the simulation of common RBS spectra including surface roughness effects has been written and tested on virtual samples comprising either a rough layer deposited on a smooth substrate or smooth layer deposited on a rough substrate and simulated at different geometries. The sample surface or interface relief has been described by a polyline and the simulated RBS spectrum has been obtained as the sum of many particular spectra from randomly chosen particle trajectories. The code includes several procedures generating virtual samples with random and regular (periodical) roughness. The shape of the RBS spectra has been found to change strongly with increasing sample roughness and an increasing angle of the incoming ion beam.

  7. Counterintuitive MCNPX Results for Scintillator Surface Roughness Effect

    SciTech Connect

    Yuan, Ding; Guss, Paul

    2012-10-01

    We performed a number of comparative MCNPX simulations of gamma energy depositions of scintillation crystals with smooth and rough surfaces. In the study, nine surface patterns (8 micro-roughness + 1 smooth) were coupled with eight common scintillation crystals for a total of 72 possible combinations. Although this was a preliminary study, the outcome was counterintuitive; results generally favored surfaces with micro-roughness over a conventional smooth surface as measured in terms of average energy depositions. The advantage gained through surface roughness is less significant for CdSe and LaCl3, but is most significant for the common NaI and the glass-like SiO2 scintillators. Based on the results of the 64 rough-surface coupled MCNPX simulations, 57 of the 64 (~89%) simulations showed some improvement in energy deposition. The mean improvement in energy deposition was 2.52%. The maximum improvement was about 8.75%, which was achieved when roughening the surface of a SiO2 scintillator using a micro cutting pattern. Further, for a conventional NaI scintillator, MCNPX results suggest that any roughness pattern would improve the energy deposition, with an average improvement of 3.83%. Although the likely causes remain unclear, we intend to focus on presenting simulation results instead of offering a sound explanation of the underlying physics.

  8. Influence of particle surface roughness on creeping granular motion.

    PubMed

    Sheng, Li-Tsung; Chang, Wei-Ching; Hsiau, Shu-San

    2016-07-01

    A core is formed at the center of a quasi-two-dimensional rotating drum filled more than half with granular material. The core rotates slightly faster than the drum (precession) and decreases in radius over time (erosion) due to the granular creeping motion that occurs below the freely flowing layer. This paper focuses on the effect of the surface roughness of particles on core dynamics, core precession, and core erosion. Two different surface roughness of glass particles having the same diameter were used in the experiments. The surface structures of the particles were quantitatively compared by measuring the coefficients of friction and using a simple image contrast method. The experiments were performed with five different filling levels in a 50-cm-diameter rotating drum. According to the results, core precession and core erosion are both dependent on the particle surface roughness. Core precession becomes weaker and erosion becomes stronger when using particles having a rough surface in the experiments. To explain the physics of core dynamics, the particles' surface roughness effect on the freely flowing layer and the creeping motion region were also investigated. The granular bed velocity field, maximum flowing layer depth δ, shear rate in the flowing layer γ[over ̇], and the creeping region decay constant y_{0} were also calculated in this paper. The effect of the particles' surface roughness on these physical variables well illustrates the physics of core dynamics and creeping granular motion.

  9. Influence of particle surface roughness on creeping granular motion

    NASA Astrophysics Data System (ADS)

    Sheng, Li-Tsung; Chang, Wei-Ching; Hsiau, Shu-San

    2016-07-01

    A core is formed at the center of a quasi-two-dimensional rotating drum filled more than half with granular material. The core rotates slightly faster than the drum (precession) and decreases in radius over time (erosion) due to the granular creeping motion that occurs below the freely flowing layer. This paper focuses on the effect of the surface roughness of particles on core dynamics, core precession, and core erosion. Two different surface roughness of glass particles having the same diameter were used in the experiments. The surface structures of the particles were quantitatively compared by measuring the coefficients of friction and using a simple image contrast method. The experiments were performed with five different filling levels in a 50-cm-diameter rotating drum. According to the results, core precession and core erosion are both dependent on the particle surface roughness. Core precession becomes weaker and erosion becomes stronger when using particles having a rough surface in the experiments. To explain the physics of core dynamics, the particles' surface roughness effect on the freely flowing layer and the creeping motion region were also investigated. The granular bed velocity field, maximum flowing layer depth δ , shear rate in the flowing layer γ ˙, and the creeping region decay constant y0 were also calculated in this paper. The effect of the particles' surface roughness on these physical variables well illustrates the physics of core dynamics and creeping granular motion.

  10. Influence of particle surface roughness on creeping granular motion.

    PubMed

    Sheng, Li-Tsung; Chang, Wei-Ching; Hsiau, Shu-San

    2016-07-01

    A core is formed at the center of a quasi-two-dimensional rotating drum filled more than half with granular material. The core rotates slightly faster than the drum (precession) and decreases in radius over time (erosion) due to the granular creeping motion that occurs below the freely flowing layer. This paper focuses on the effect of the surface roughness of particles on core dynamics, core precession, and core erosion. Two different surface roughness of glass particles having the same diameter were used in the experiments. The surface structures of the particles were quantitatively compared by measuring the coefficients of friction and using a simple image contrast method. The experiments were performed with five different filling levels in a 50-cm-diameter rotating drum. According to the results, core precession and core erosion are both dependent on the particle surface roughness. Core precession becomes weaker and erosion becomes stronger when using particles having a rough surface in the experiments. To explain the physics of core dynamics, the particles' surface roughness effect on the freely flowing layer and the creeping motion region were also investigated. The granular bed velocity field, maximum flowing layer depth δ, shear rate in the flowing layer γ[over ̇], and the creeping region decay constant y_{0} were also calculated in this paper. The effect of the particles' surface roughness on these physical variables well illustrates the physics of core dynamics and creeping granular motion. PMID:27575202

  11. Ice friction: The effects of surface roughness, structure, and hydrophobicity

    SciTech Connect

    Kietzig, Anne-Marie; Hatzikiriakos, Savvas G.; Englezos, Peter

    2009-07-15

    The effect of surface roughness, structure, and hydrophobicity on ice friction is studied systematically over a wide range of temperature and sliding speeds using several metallic interfaces. Hydrophobicity in combination with controlled roughness at the nanoscale is achieved by femtosecond laser irradiation to mimic the lotus effect on the slider's surface. The controlled roughness significantly increases the coefficient of friction at low sliding speeds and temperatures well below the ice melting point. However, at temperatures close to the melting point and relatively higher speeds, roughness and hydrophobicity significantly decrease ice friction. This decrease in friction is mainly due to the suppression of capillary bridges in spite of the presence of surface asperities that facilitate their formation. Finally, grooves oriented in the sliding direction also significantly decrease friction in the low velocity range compared to scratches and grooves randomly distributed over a surface.

  12. Ice friction: The effects of surface roughness, structure, and hydrophobicity

    NASA Astrophysics Data System (ADS)

    Kietzig, Anne-Marie; Hatzikiriakos, Savvas G.; Englezos, Peter

    2009-07-01

    The effect of surface roughness, structure, and hydrophobicity on ice friction is studied systematically over a wide range of temperature and sliding speeds using several metallic interfaces. Hydrophobicity in combination with controlled roughness at the nanoscale is achieved by femtosecond laser irradiation to mimic the lotus effect on the slider's surface. The controlled roughness significantly increases the coefficient of friction at low sliding speeds and temperatures well below the ice melting point. However, at temperatures close to the melting point and relatively higher speeds, roughness and hydrophobicity significantly decrease ice friction. This decrease in friction is mainly due to the suppression of capillary bridges in spite of the presence of surface asperities that facilitate their formation. Finally, grooves oriented in the sliding direction also significantly decrease friction in the low velocity range compared to scratches and grooves randomly distributed over a surface.

  13. 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

  14. Surface roughness measurement on a wing aircraft by speckle correlation.

    PubMed

    Salazar, Félix; Barrientos, Alberto

    2013-09-05

    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.

  15. 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.

  16. Equilibrium of wetting layers on rough surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Kuang-Yu

    The objective of this dissertation is to study physical adsorption on solids with complex surface geometry--especially on self-similar and self-affine fractal surfaces--in the context of three phase equilibria. Such studies will facilitate the prediction of the adsorbed film from known surface properties, e.g., topography or interactions (direct problem), and the inference of unknown surface properties from experimental data (inverse problem). These results will then be compared against wetting phenomena on planar surfaces and with other methods of probing complex surface geometries of solids. Chapter One offers the basic context, including wetting phenomena on planar surfaces, the cornerstone prediction of wetting transition on planar surfaces by Cahn, the concepts of fractal geometry, and the formation of fractal objects, for later comparison. The rest of this dissertation will be devoted to the study of multilayer adsorption on fractal surfaces. When a liquid film completely wets the surface, the number of adsorbed molecules as a function of the vapor pressure will depend strongly on the underlying surface geometry. The fractal structure leads to the Frenkel-Halsey-Hill type isotherms with the exponents in the corresponding power laws depending on the fractal dimension and on whether the dominant influence is from the substrate potential (van der Waals wetting) or from the film-vapor surface tension (capillary wetting). The transition between the two is the analog of Cahn's transition: The thermal disorder is replaced by the quenched disorder. This analogy is studied in Chapter Two for self-similar surfaces, and in Chapter Four for self-affine surfaces. In Chapter Two the derivation framework also automatically identifies well-defined coexistence lines in the pressure-dimension diagram. The effect of the repulsive part is examined there too. A simple analysis of adsorption/desorption hysteresis on self-similar surfaces in Chapter Three concludes that the

  17. Effects of Nanoscale Surface Roughness on Colloid Detachment

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Recent advances in colloid transport science have demonstrated the importance of surface roughness on colloid attachment; however, few studies have investigated the influence of nano-scale roughness on colloid detachment. This study explores the effects of flow perturbations on a variety of mineral surfaces, as well as NaOH treated (i.e. rough, Figure 1a) and untreated (i.e. smooth, Figure 1b) surfaces for colloids of various sizes attached in an impinging jet system under flowing and stagnant conditions. These experiments showed minimal detachment from the roughened surfaces (treated glass) and significant detachment from the smooth surfaces (untreated glass and mica). A correlation between residence time and attachment irreversibility was also revealed, indicating that the particles that spent the longest time attached to the surface developed the strongest adhesion. The representative surface-heterogeneity model developed by Pazmino et al. (2014) was used to conduct detachment simulations under similar geochemical and flow conditions. While simulated results show qualitative agreement with experimental results, they tend to over-predict detachment, highlighting differences among simulated versus real surfaces, which may be related to surface roughness. These results suggest that more sophisticated models that incorporate surface roughness and time-based adhesion are needed to accurately predict colloid detachment in environmental systems.

  18. 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

  19. A possibility of avoiding surface roughness due to insects

    NASA Technical Reports Server (NTRS)

    Wortmann, F. X.

    1984-01-01

    Discussion of a method for eliminating turbulence caused by the formation of insect roughness upon the leading edges and fuselage, particularly in aircraft using BLC. The proposed technique foresees the use of elastic surfaces on which insect roughness cannot form. The operational characteristics of highly elastic rubber surface fastened to the wing leading edges and fuselage edges are examined. Some preliminary test results are presented. The technique is seen to be advantageous primarily for short-haul operations.

  20. Surface Roughness Parameter Uncertainties on Radar Based Soil Moisture Retrievals

    NASA Technical Reports Server (NTRS)

    Joseph, A. T.; vanderVelde, R.; O'Neill, P. E.; Lang, R.; Su, Z.; Gish, T.

    2012-01-01

    Surface roughness variations are often assumed to be negligible for the retrieval of sol moisture. Although previous investigations have suggested that this assumption is reasonable for natural vegetation covers (i.e. Moran et al. 2002), in-situ measurements over plowed agricultural fields (i.e. Callens et al. 2006) have shown that the soil surface roughness can change considerably due to weathering induced by rain.

  1. The influence of surface treatment on the implant roughness pattern

    PubMed Central

    ROSA, Marcio Borges; ALBREKTSSON, Tomas; FRANCISCHONE, Carlos Eduardo; SCHWARTZ FILHO, Humberto Osvaldo; WENNERBERG, Ann

    2012-01-01

    An important parameter for the clinical success of dental implants is the formation of direct contact between the implant and surrounding bone, whose quality is directly influenced by the implant surface roughness. A screw-shaped design and a surface with an average roughness of Sa of 1-2 µm showed a better result. The combination of blasting and etching has been a commonly used surface treatment technique. The versatility of this type of treatment allows for a wide variation in the procedures in order to obtain the desired roughness. Objectives To compare the roughness values and morphological characteristics of 04 brands of implants, using the same type of surface treatment. In addition, to compare the results among brands, in order to assess whether the type of treatment determines the values and the characteristics of implant surface roughness. Material and methods Three implants were purchased directly from each selected company in the market, i.e., 03 Brazilian companies (Biomet 3i of Brazil, Neodent and Titaniumfix) and 01 Korean company (Oneplant). The quantitative or numerical characterization of the roughness was performed using an interferometer. The qualitative analysis of the surface topography obtained with the treatment was analyzed using scanning electron microscopy images. Results The evaluated implants showed a significant variation in roughness values: Sa for Oneplant was 1.01 µm; Titaniumfix reached 0.90 µm; implants from Neodent 0.67 µm, and Biomet 3i of Brazil 0.53 µm. Moreover, the SEM images showed very different patterns for the surfaces examined. Conclusions The surface treatment alone is not able to determine the roughness values and characteristics. PMID:23138742

  2. Heat Transfer Variation on Protuberances and Surface Roughness Elements

    NASA Technical Reports Server (NTRS)

    Henry, Robert C.; Hansman, R. John, Jr.; Breuer, Kenneth S.

    1995-01-01

    In order to determine the effect of surface irregularities on local convective heat transfer, the variation in heat transfer coefficients on small (2-6 mm diam) hemispherical roughness elements on a flat plate has been studied in a wind funnel using IR techniques. Heat transfer enhancement was observed to vary over the roughness elements with the maximum heat transfer on the upstream face. This heat transfer enhancement increased strongly with roughness size and velocity when there was a laminar boundary layer on the plate. For a turbulent boundary layer, the heat transfer enhancement was relatively constant with velocity, but did increase with element size. When multiple roughness elements were studied, no influence of adjacent roughness elements on heat transfer was observed if the roughness separation was greater than approximately one roughness element radius. As roughness separation was reduced, less variation in heat transfer was observed on the downstream elements. Implications of the observed roughness enhanced heat transfer on ice accretion modeling are discussed.

  3. Characteristics of density currents over regular and irregular rough surfaces

    NASA Astrophysics Data System (ADS)

    Bhaganagar, K.

    2013-12-01

    Direct numerical simulation is used as a tool to understand the effect of surface roughness on the propagation of density currents. Simulations have been performed for lock-exchange flow with gate separating the dense and the lighter fluid. As the lock is released the dense fluid collapses with the lighter fluid on the top, resulting in formation of horizontally evolving density current. The talk will focus on the fundamental differences between the propagation of the density current over regular and irregular rough surfaces. The flow statistics and the flow structures are discussed. The results have revealed the spacing between the roughness elements is an important factor in classifying the density currents. The empirical relations of the front velocity and location for the dense and sparse roughness have been evaluated in terms of the roughness height, spacing between the elements and the initial amount of lock fluid. DNS results for a dense current flowing over a (a) smooth and (b) rough bottom with egg-carton roughness elements in a regular configuration. In these simulations the lock-exchange box is located in the middle of the channel and has two gates which allow two dense currents to be generated, one moving to the right and one to the left side of the channel. Note how the dense current interface presents smaller structures when over a rough bottom (right).

  4. Surface roughness of minerals and implications for dissolution studies

    NASA Astrophysics Data System (ADS)

    Anbeek, Chris

    1992-04-01

    Large, naturally weathered mineral fragments are often ground and sieved to obtain samples for dissolution studies. If the fragments are ground to much smaller dimensions, the samples are normally assumed to contain one type of (fresh) surface only. A model has been developed to test the validity of this assumption. The model describes the surface roughness factor of ground mineral material as a function of grain size and can be used to: (1) estimate the roughness factors of the freshly created and the naturally weathered surfaces; (2) estimate the ratio of fresh to total surface area for the ground samples, both for geometric and for actual surfaces; and (3) check the internal consistency of surface area measurements. Literature data were evaluated for intensively ground size fractions of nine different naturally weathered feldspars. Roughness factors of freshly created surfaces ranged from 2.5-11. Roughness factors of naturally weathered surfaces ranged from 130-2600, which is much higher than is generally recognized for feldspars. Comparison with surface roughness estimates from Scanning Electron Microscopy strongly suggests that etch pit formation plays a minor role in the increase in actual surface area during natural weathering. Instead, virtually all increase in surface area must be attributed to the formation of internal surface structures like micropores. The model also showed that for these ground samples, the assumption of one type of (fresh) surface is approximately correct for the geometric surfaces. For the actual (BET) surfaces, ratios of fresh to total surface area varied over almost the entire range from 0 to 1. This demonstrates that, even after intensive grinding, samples from large, naturally weathered mineral fragments can still contain substantial proportions of weathered BET surface area. Thus, previous dissolution studies in terms of fresh BET surface only may have been misinterpreted.

  5. Effect of Acidic Agents on Surface Roughness of Dental Ceramics

    PubMed Central

    Kukiattrakoon, Boonlert; Hengtrakool, Chanothai; Kedjarune-Leggat, Ureporn

    2011-01-01

    Background: An increase in surface roughness of ceramics may decrease strength and affect the clinical success of ceramic restorations. However, little is known about the effect of acidic agents on ceramic restorations. The aim of this study was to evaluate the surface roughness of dental ceramics after being immersed in acidic agents. Methods: Eighty-three ceramic disk specimens (12.0 mm in diameter and 2.0 mm in thickness) were made from four types of ceramics (VMK 95, Vitadur Alpha, IPS Empress Esthetic, and IPS e.max Ceram). Baseline data of surface roughness were recorded by profilometer. The specimens were then immersed in acidic agents (citrate buffer solution, pineapple juice and green mango juice) and deionized water (control) at 37°C for 168 hours. One group was immersed in 4% acetic acid at 80°C for 168 hours. After immersion, surface roughness was evaluated by a profilometer at intervals of 24, 96, and 168 hours. Surface characteristics of specimens were studied using scanning electron microscopy (SEM). Data were analyzed using two-way repeated ANOVA and Tukey's multiple comparisons (α = 0.05). Results: For all studied ceramics, all surface roughness parameters were significantly increased after 168 hours immersion in all acidic agents (P < 0.05). After 168 hours in 4% acetic acid, there were significant differences for all roughness parameters from other acidic agents of all evaluated ceramics. Among all studied ceramics, Vitadur Alpha showed significantly the greatest values of all surface roughness parameters after immersion in 4% acetic acid (P < 0.001). SEM photomicrographs also presented surface destruction of ceramics in varying degrees. Conclusion: Acidic agents used in this study negatively affected the surface of ceramic materials. This should be considered when restoring the eroded tooth with ceramic restorations in patients who have a high risk of erosive conditions. PMID:22132009

  6. Surface roughness and breaking wave properties retrieved from polarimetric microwave radar backscattering

    NASA Astrophysics Data System (ADS)

    Hwang, Paul A.; Fois, Franco

    2015-05-01

    Ocean surface roughness and wave breaking are the two main contributors of radar backscattering from the ocean surface. The relative weightings of the two contributions vary with the microwave polarization: the VV (vertical transmit vertical receive) is dominated by the Bragg resonance scattering mechanism, and the HH (horizontal transmit horizontal receive) and VH (horizontal transmit vertical receive or vertical transmit horizontal receive) contain nontrivial non-Bragg contributions mainly produced by breaking features. A method is developed to obtain the short-scale properties of ocean surface roughness and wave breaking from Ku, C, and L band polarimetric sea returns. The results are used for quantitative evaluation of the ocean surface roughness spectral models and for deriving understanding of the breaking contribution important to microwave ocean remote sensing, in particular its dependence on wind speed, microwave frequency, and incidence angle. Implications of the results to air-sea interaction applications are discussed.

  7. Improved detection of rough defects for ultrasonic NDE inspections based on finite element modeling of elastic wave scattering

    SciTech Connect

    Pettit, J. R.; Walker, A.; Lowe, M. J. S.

    2014-02-18

    Defects which posses rough surfaces greatly affect ultrasonic wave scattering behaviour, often reducing the magnitude of reflected signals. Ultrasonic inspections rely upon this response for detecting and sizing flaws. For safety critical components reliable characterisation is crucial. Therefore, providing an accurate means to predict reductions in signal amplitude is essential. An extension of Kirchhoff theory has formed the basis for the UK power industry inspection justifications. However, it is widely recognised that these predictions are pessimistic owing to analytical approximations. A numerical full field modelling approach does not fall victim to such limitations. Here, a Finite Element model is used to aid in setting a non-conservative reporting threshold during the inspection of a large pressure vessel forging that might contain embedded rough defects. The ultrasonic response from multiple rough surfaces defined by the same statistical class is calculated for normal incident compression waves. The approach is validated by comparing coherent scattering with predictions made by Kirchhoff theory. At lower levels of roughness excellent agreement is observed, whilst higher values confirm the pessimism of Kirchhoff theory. Furthermore, the mean amplitude in the specular direction is calculated. This represents the information obtained during an inspection, indicating that reductions due to increasing roughness are significantly less than the coherent component currently being used.

  8. 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.

  9. Parametric optical surface roughness measurement by means of polychromatic speckle autocorrelation

    NASA Astrophysics Data System (ADS)

    Patzelt, Stefan; Ciossek, Andreas; Lehmann, Peter; Schoene, Armin

    1998-10-01

    A method for determining surface roughness of engineering surfaces that is applicable to in-process measurements under harsh circumstances of industrial production plants (e.g. vibrations, humidity) is introduced. The rough surface is illuminated with polychromatic laser light. The angular distribution of scattered light intensities, i.e. a polychromatic speckle pattern, is the result of an incoherent superposition of monochromatic speckle intensities. The angular dispersion leads to increasing speckle widths with an increasing distance to the optical axis an effect called speckle elongation. This gives rise to a radial structure of the speckle pattern. However, with increasing surface roughness the radial structure vanishes because of a decreasing similarity of the monochromatic speckle patterns of the different wavelengths. The markedness of this effect is analyzed by digital image processing algorithms, e.g. the procedure of polychromatic speckle autocorrelation. The latest approach to an in-process roughness measurement device was made by the use of singlemode fiber-pigtailed laser diodes in order to supply a trichromatic, temporally partially coherent laser beam. A brief introduction to the theoretical background is followed by the presentation of the experimental setup. The image processing algorithms for calculating an optical roughness measure from digitalized speckle patterns are explained, and first results of surface roughness determination are presented.

  10. Site-specific retention of colloids at rough rock surfaces.

    PubMed

    Darbha, Gopala Krishna; Fischer, Cornelius; Luetzenkirchen, Johannes; Schäfer, Thorsten

    2012-09-01

    The spatial deposition of polystyrene latex colloids (d = 1 μm) at rough mineral and rock surfaces was investigated quantitatively as a function of Eu(III) concentration. Granodiorite samples from Grimsel test site (GTS), Switzerland, were used as collector surfaces for sorption experiments. At a scan area of 300 × 300 μm(2), the surface roughness (rms roughness, Rq) range was 100-2000 nm, including roughness contribution from asperities of several tens of nanometers in height to the sample topography. Although, an increase in both roughness and [Eu(III)] resulted in enhanced colloid deposition on granodiorite surfaces, surface roughness governs colloid deposition mainly at low Eu(III) concentrations (≤5 × 10(-7) M). Highest deposition efficiency on granodiorite has been found at walls of intergranular pores at surface sections with roughness Rq = 500-2000 nm. An about 2 orders of magnitude lower colloid deposition has been observed at granodiorite sections with low surface roughness (Rq < 500 nm), such as large and smooth feldspar or quartz crystal surface sections as well as intragranular pores. The site-specific deposition of colloids at intergranular pores is induced by small scale protrusions (mean height = 0.5 ± 0.3 μm). These protrusions diminish locally the overall DLVO interaction energy at the interface. The protrusions prevent further rolling over the surface by increasing the hydrodynamic drag required for detachment. Moreover, colloid sorption is favored at surface sections with high density of small protrusions (density (D) = 2.6 ± 0.55 μm(-1), asperity diameter (φ) = 0.6 ± 0.2 μm, height (h) = 0.4 ± 0.1 μm) in contrast to surface sections with larger asperities and lower asperity density (D = 1.2 ± 0.6 μm(-1), φ = 1.4 ± 0.4 μm, h = 0.6 ± 0.2 μm). The study elucidates the importance to include surface roughness parameters into predictive colloid-borne contaminant migration calculations.

  11. Site-specific retention of colloids at rough rock surfaces.

    PubMed

    Darbha, Gopala Krishna; Fischer, Cornelius; Luetzenkirchen, Johannes; Schäfer, Thorsten

    2012-09-01

    The spatial deposition of polystyrene latex colloids (d = 1 μm) at rough mineral and rock surfaces was investigated quantitatively as a function of Eu(III) concentration. Granodiorite samples from Grimsel test site (GTS), Switzerland, were used as collector surfaces for sorption experiments. At a scan area of 300 × 300 μm(2), the surface roughness (rms roughness, Rq) range was 100-2000 nm, including roughness contribution from asperities of several tens of nanometers in height to the sample topography. Although, an increase in both roughness and [Eu(III)] resulted in enhanced colloid deposition on granodiorite surfaces, surface roughness governs colloid deposition mainly at low Eu(III) concentrations (≤5 × 10(-7) M). Highest deposition efficiency on granodiorite has been found at walls of intergranular pores at surface sections with roughness Rq = 500-2000 nm. An about 2 orders of magnitude lower colloid deposition has been observed at granodiorite sections with low surface roughness (Rq < 500 nm), such as large and smooth feldspar or quartz crystal surface sections as well as intragranular pores. The site-specific deposition of colloids at intergranular pores is induced by small scale protrusions (mean height = 0.5 ± 0.3 μm). These protrusions diminish locally the overall DLVO interaction energy at the interface. The protrusions prevent further rolling over the surface by increasing the hydrodynamic drag required for detachment. Moreover, colloid sorption is favored at surface sections with high density of small protrusions (density (D) = 2.6 ± 0.55 μm(-1), asperity diameter (φ) = 0.6 ± 0.2 μm, height (h) = 0.4 ± 0.1 μm) in contrast to surface sections with larger asperities and lower asperity density (D = 1.2 ± 0.6 μm(-1), φ = 1.4 ± 0.4 μm, h = 0.6 ± 0.2 μm). The study elucidates the importance to include surface roughness parameters into predictive colloid-borne contaminant migration calculations. PMID:22861645

  12. Scatter of X-rays on polished surfaces

    NASA Technical Reports Server (NTRS)

    Hasinger, G.

    1981-01-01

    In investigating the dispersion properties of telescope mirrors used in X-ray astronomy, the slight scattering characteristics of X-ray radiation by statistically rough surfaces were examined. The mathematics and geometry of scattering theory are described. The measurement test assembly is described and results of measurements on samples of plane mirrors are given. Measurement results are evaluated. The direct beam, the convolution of the direct beam and the scattering halo, curve fitting by the method of least squares, various autocorrelation functions, results of the fitting procedure for small scattering, and deviations in the kernel of the scattering distribution are presented. A procedure for quality testing of mirror systems through diagnosis of rough surfaces is described.

  13. Surface roughness and wear of resin cements after toothbrush abrasion.

    PubMed

    Ishikiriama, Sérgio Kiyoshi; Ordoñéz-Aguilera, Juan Fernando; Maenosono, Rafael Massunari; Volú, Fernanda Lessa Amaral; Mondelli, Rafael Francisco Lia

    2015-01-01

    Increased surface roughness and wear of resin cements may cause failure of indirect restorations. The aim of this study was to evaluate quantitatively the surface roughness change and the vertical wear of four resin cements subjected to mechanical toothbrushing abrasion. Ten rectangular specimens (15 × 5 × 4 mm) were fabricated according to manufacturer instructions for each group (n = 10): Nexus 3, Kerr (NX3); RelyX ARC, 3M ESPE (ARC); RelyX U100, 3M ESPE (U100); and Variolink II, Ivoclar/Vivadent (VL2). Initial roughness (Ra, µm) was obtained through 5 readings with a roughness meter. Specimens were then subjected to toothbrushing abrasion (100,000 cycles), and further evaluation was conducted for final roughness. Vertical wear (µm) was quantified by 3 readings of the real profile between control and brushed surfaces. Data were subjected to analysis of variance, followed by Tukey's test (p < 0.05). The Pearson correlation test was performed between the surface roughness change and wear (p < 0.05). The mean values of initial/final roughness (Ra, µm)/wear (µm) were as follows: NX3 (0.078/0.127/23.175); ARC (0.086/0.246/20.263); U100 (0.296/0.589/16.952); and VL2 (0.313/0.512/22.876). Toothbrushing abrasion increased surface roughness and wear of all resin cements tested, although no correlation was found between those variables. Vertical wear was similar among groups; however, it was considered high and may lead to gap formation in indirect restorations.

  14. Surface roughness and wear of resin cements after toothbrush abrasion.

    PubMed

    Ishikiriama, Sérgio Kiyoshi; Ordoñéz-Aguilera, Juan Fernando; Maenosono, Rafael Massunari; Volú, Fernanda Lessa Amaral; Mondelli, Rafael Francisco Lia

    2015-01-01

    Increased surface roughness and wear of resin cements may cause failure of indirect restorations. The aim of this study was to evaluate quantitatively the surface roughness change and the vertical wear of four resin cements subjected to mechanical toothbrushing abrasion. Ten rectangular specimens (15 × 5 × 4 mm) were fabricated according to manufacturer instructions for each group (n = 10): Nexus 3, Kerr (NX3); RelyX ARC, 3M ESPE (ARC); RelyX U100, 3M ESPE (U100); and Variolink II, Ivoclar/Vivadent (VL2). Initial roughness (Ra, µm) was obtained through 5 readings with a roughness meter. Specimens were then subjected to toothbrushing abrasion (100,000 cycles), and further evaluation was conducted for final roughness. Vertical wear (µm) was quantified by 3 readings of the real profile between control and brushed surfaces. Data were subjected to analysis of variance, followed by Tukey's test (p < 0.05). The Pearson correlation test was performed between the surface roughness change and wear (p < 0.05). The mean values of initial/final roughness (Ra, µm)/wear (µm) were as follows: NX3 (0.078/0.127/23.175); ARC (0.086/0.246/20.263); U100 (0.296/0.589/16.952); and VL2 (0.313/0.512/22.876). Toothbrushing abrasion increased surface roughness and wear of all resin cements tested, although no correlation was found between those variables. Vertical wear was similar among groups; however, it was considered high and may lead to gap formation in indirect restorations. PMID:25466330

  15. Chemical monitors based on Surface-Enhanced Raman Scattering (SERS)

    SciTech Connect

    Vo-Dinh, T.; Alarie, J.P.; Sutherland, W.S.; Stokes, D.L.; Miller, G.H.

    1992-12-31

    This paper presents an overview of the development of chemical monitors using the Surface-Enhanced Raman Scattering (SERS) technique. The SERS effect is based on recent experimental observations, which have indicated enhancement of the Raman scattering efficiency by factors up to 10{sup 8} when a compound is adsorbed on rough metallic surfaces having submicron protrusions. The focus of our research efforts is on the development of SERS-active sensors and instrumentation capable of field analysis and remote sensing.

  16. Investigation Into the Accuracy of 3D Surface Roughness Characteristics

    NASA Astrophysics Data System (ADS)

    Kumermanis, M.; Rudzitis, J.; Mozga, N.; Ancans, A.; Grislis, A.

    2014-04-01

    The existing standards for surface roughness cover only two dimensions, while in reality this is three-dimensional (3D). In particular, the 3D surface roughness parameters are important for solving the contact surface mechanics problems as related to the accuracy of 3D surface roughness characteristics. One of the most important factors for determination of 3D characteristics is the number of data points (NDP) on the x- and y-axes (i.e. in cut-off length). The NDP has a profound effect on the accuracy of measurement results, measuring time and volume of the output data (especially along the y-axis, where the NDP is identical to the number of parallel profiles). At a too small NDP the results will be incorrect and with too broad scatter, while a too large NDP - though not enlarging the range of basic information - considerably increases the measuring time. Therefore, the aim of the work was to find the optimal NDP for such surface processing methods as grinding, spark erosion and shot methods of surface treatment. Eksistējošie virsmas raupjuma standarti apskata virsmas raupjumu tikai divās dimensijās. Tomēr reālais virsmas raupjums pēc savas dabas ir trīsdimensiju (3D) objekts. Līdz ar to virsmas raupjums ir jāraksturo ar 3D parametriem. Un no šo parametru noteikšanas precizitātes ir atkarīgi tālākie virsmas aprēķini, piemēram, virsmu kontaktēšanās process. Viens no svarīgākajiem faktoriem, raksturojot virsmas raupjumu 3D, pielietojot kontakta tipa mēriekārtas, ir datu punktu skaits pa abām mērīšanas asīm x un y. Ar datu punktu skaitu mēs saprotam to skaitu mērīšanas bāzes garumā. Datu punktu skaits būtiski ietekmē sagaidāmo mērījumu rezultātu precizitāti, mērīšanai nepieciešamo laiku un izejas datu faila izmērus (sevišķi y-ass virzienā, kur katrs datu punkts ir paralēls profils). Datu punktu skaitam ir jābūt optimālam. Pārāk mazs punktu skaits noved pie neprecīziem rezultātiem un lielas to izkliedes, savuk

  17. Experiments to test theoretical models of the polarization of light by rough surfaces

    NASA Technical Reports Server (NTRS)

    Geake, J. E.; Geake, M.; Zellner, B. H.

    1984-01-01

    A number of attempts have been made to provide theoretical models of the physical processes involved in the polarization of light scattered by a rough surface, such as the regolith of an atmosphereless planet. Some laboratory experiments designed to test different aspects of these models are described. It is concluded that double Fresnel reflection is usually the dominant process in producing negative polarization, but that diffraction effects may play a significant part in double events involving small-scale surface features.

  18. Controlling adhesion force by means of nanoscale surface roughness.

    PubMed

    Ramakrishna, Shivaprakash N; Clasohm, Lucy Y; Rao, Akshata; Spencer, Nicholas D

    2011-08-16

    Control of adhesion is a crucial aspect in the design of microelectromechanical and nanoelectromechanical devices. To understand the dependence of adhesion on nanometer-scale surface roughness, a roughness gradient has been employed. Monomodal roughness gradients were fabricated by means of silica nanoparticles (diameter ∼12 nm) to produce substrates with varying nanoparticle density. Pull-off force measurements on the gradients were performed using (polyethylene) colloidal-probe microscopy under perfluorodecalin, in order to restrict interactions to van der Waals forces. The influence of normal load on pull-off forces was studied and the measured forces compared with existing Hamaker-approximation-based models. We observe that adhesion force reaches a minimum value at an optimum particle density on the gradient sample, where the mean particle spacing becomes comparable with the diameter of the contact area with the polyethylene sphere. We also observe that the effect on adhesion of increasing the normal load depends on the roughness of the surface.

  19. Reflection of polarized light by rough surfaces: Monte Carlo modeling compared to measurements

    NASA Astrophysics Data System (ADS)

    Guirado, Daniel; Marcos Sanz, Juan; María Saiz, José; Muñoz, Olga; Stam, Daphne M.

    2013-04-01

    A Monte Carlo model of light scattering in a dense medium was developed in order to simulate the reflection of polarized light by rough surfaces [1]. This model calculates all four Stokes parameters of light scattered in all directions by a surface made of any material. Although multiple scattering is allowed, there is a limitation in the packing density of the medium, as independent scattering is assumed. The model can be applied to the study of light scattering by fluffy icy/dusty surfaces, e.g., various types of planetary or lunar regolith-type surfaces, icy moons or comets. The main goal of this work is to test the model by comparing scattering matrix elements calculated with the Monte Carlo model to experimentally measured scattering matrix elements as functions of the phase angle. We use a Sahara sand surface for this. The experimental scattering matrix is measured at the new apparatus developed at the University of Cantabria (Spain) [2]. Sample surfaces are prepared by putting together dust grains with a water-diluted glue coating. A surface's top layer was made with pure sand, to preserve the air-sand refractive index ratio. Calibration measurements have already been carried out successfully by using Spectralon as a Lambertian surface. After calibration, measurements of a surface made of Sahara sand were performed. In such measurements, deviations from Lambertian behavior were found, as well as a very prominent forward peak in the (1,1)-element of the matrix for grazing illumination angles. The values of I and -Q/I calculated by the model for the vertical scattering plane and non-polarized incident light were compared to the measured F11 and -F21/F11 elements for several incident directions. A good agreement between measurements and calculations was achieved. The forward-scattering peak of the (1,1)-element can be interpreted as a result of single scattering of horizontally incident light by the small features of the non-flat surface. In this case, light

  20. Response Ant Colony Optimization of End Milling Surface Roughness

    PubMed Central

    Kadirgama, K.; Noor, M. M.; Abd Alla, Ahmed N.

    2010-01-01

    Metal cutting processes are important due to increased consumer demands for quality metal cutting related products (more precise tolerances and better product surface roughness) that has driven the metal cutting industry to continuously improve quality control of metal cutting processes. This paper presents optimum surface roughness by using milling mould aluminium alloys (AA6061-T6) with Response Ant Colony Optimization (RACO). The approach is based on Response Surface Method (RSM) and Ant Colony Optimization (ACO). The main objectives to find the optimized parameters and the most dominant variables (cutting speed, feedrate, axial depth and radial depth). The first order model indicates that the feedrate is the most significant factor affecting surface roughness. PMID:22294914

  1. Analysis of surface roughness generation in aircraft ice accretion

    NASA Technical Reports Server (NTRS)

    Hansman, R. J., Jr.; Reehorst, Andrew; Sims, James

    1992-01-01

    Patterns of roughness evolution have been studied analysis of high magnification video observations of accreting ice surfaces provided by the NASA Lewis Research Center. Three distinct patterns of surface roughness generation have been identified within the parametric regions studied. They include: Rime, Multi-Zone Glaze, and Uniform Glaze. Under most icing conditions, a brief period of transient rime ice growth was observed caused by heat conduction into the body. The resulting thin rime layer explains previously observed insensitivity of some ice accretions to substrate insensitivity of some ice accretions to substrate surface chemistry and may provide justification for simplifying assumptions in ice accretion sailing and modeling effects.

  2. Surface roughness effects with solid lubricants dispersed in mineral oils

    NASA Technical Reports Server (NTRS)

    Cusano, C.; Goglia, P. R.; Sliney, H. E.

    1983-01-01

    The lubricating effectiveness of solid-lubricant dispersions are investigated in both point and line contacts using surfaces with both random and directional roughness characteristics. Friction and wear data obtained at relatively low speeds and at room temperature, indicate that the existence of solid lubricants such as graphite, MoS2, and PTFE in a plain mineral oil generally will not improve the effectiveness of the oil as a lubricant for such surfaces. Under boundary lubrication conditions, the friction force, as a function of time, initially depends upon the directional roughness properties of the contacting surfaces irrespective of whether the base oil or dispersions are used as lubricants.

  3. Simulation Study of the Flow Boundary Condition for Rough Surfaces

    NASA Astrophysics Data System (ADS)

    He, Gang; Robbins, Mark O.

    2001-03-01

    In order to solve a flow problem with the continuum Navier-Stokes equation, a boundary condition must be assumed. In most cases, a no-slip condition is used, i.e. the velocity of the fluid is set equal to that of a bounding solid at their interface. Deviations from this condition can be quantified by a slip length S that represents the additional width of fluid that would be needed to accomodate any velocity difference at the interface. Previous simulations with atomically flat surfaces show that S can be very large in certain limits. (P. A. Thompson and M. O. Robbins, Phys. Rev. A, 41), 6830(1990). ( J.-L. Barrat and L. Bocquet, Phys. Rev. Lett., 82), 4671(1999). A dramatic divergence with S as shear rate increases has also been seen.( P. A. Thompson and S. M. Troian, Nature, 389), 360(1997) We have extended these simulations to surfaces with random roughness, steps, and angled facets typical of twin boundaries. In all cases, S decreases rapidly as the roughness increases. When peak-to-peak roughness is only two atomic diameters, values of S have dropped from more than 20 diameters to only one or two. In addition, the non-linear regime where S diverges with shear rate is supressed by surface roughness. These results suggest that the experimental behavior of atomically flat surfaces such as mica may be very different than that of more typical rough surfaces.

  4. Studies of the 3D surface roughness height

    NASA Astrophysics Data System (ADS)

    Avisane, Anita; Rudzitis, Janis; Kumermanis, Maris

    2013-12-01

    Nowadays nano-coatings occupy more and more significant place in technology. Innovative, functional coatings acquire new aspects from the point of view of modern technologies, considering the aggregate of physical properties that can be achieved manipulating in the production process with the properties of coatings' surfaces on micro- and nano-level. Nano-coatings are applied on machine parts, friction surfaces, contacting parts, corrosion surfaces, transparent conducting films (TCF), etc. The equipment available at present for the production of transparent conducting oxide (TCO) coatings with highest quality is based on expensive indium tin oxide (ITO) material; therefore cheaper alternatives are being searched for. One such offered alternative is zink oxide (ZnO) nano-coatings. Evaluating the TCF physical and mechanical properties and in view of the new ISO standard (EN ISO 25178) on the introduction of surface texture (3D surface roughness) in the engineering calculations, it is necessary to examine the height of 3D surface roughness, which is one of the most significant roughness parameters. The given paper studies the average values of 3D surface roughness height and the most often applied distribution laws are as follows: the normal distribution and Rayleigh distribution. The 3D surface is simulated by a normal random field.

  5. Studies of the 3D surface roughness height

    SciTech Connect

    Avisane, Anita; Rudzitis, Janis; Kumermanis, Maris

    2013-12-16

    Nowadays nano-coatings occupy more and more significant place in technology. Innovative, functional coatings acquire new aspects from the point of view of modern technologies, considering the aggregate of physical properties that can be achieved manipulating in the production process with the properties of coatings’ surfaces on micro- and nano-level. Nano-coatings are applied on machine parts, friction surfaces, contacting parts, corrosion surfaces, transparent conducting films (TCF), etc. The equipment available at present for the production of transparent conducting oxide (TCO) coatings with highest quality is based on expensive indium tin oxide (ITO) material; therefore cheaper alternatives are being searched for. One such offered alternative is zink oxide (ZnO) nano-coatings. Evaluating the TCF physical and mechanical properties and in view of the new ISO standard (EN ISO 25178) on the introduction of surface texture (3D surface roughness) in the engineering calculations, it is necessary to examine the height of 3D surface roughness, which is one of the most significant roughness parameters. The given paper studies the average values of 3D surface roughness height and the most often applied distribution laws are as follows: the normal distribution and Rayleigh distribution. The 3D surface is simulated by a normal random field.

  6. Plasmonic pressure in profile-modulated and rough surfaces

    NASA Astrophysics Data System (ADS)

    Noginova, N.; LePain, M.; Rono, V.; Mashhadi, S.; Hussain, R.; Durach, M.

    2016-09-01

    The electromagnetic momentum loss approach is applied to predict the plasmon drag effect in profile-modulated gold films at different amplitudes of surface modulations. Direct proportionality of energy and momentum transfer in interactions of plasmons and free electrons in metal is proven to be valid for surfaces with relatively low height modulation amplitudes. An equivalent circuit model is discussed, which can provide qualitative description of the plasmon-induced electrical effects in modulated surfaces and surfaces with random roughness.

  7. Thermal Transport across a Substrate-Thin-Film Interface: Effects of Film Thickness and Surface Roughness

    NASA Astrophysics Data System (ADS)

    Liang, Zhi; Sasikumar, Kiran; Keblinski, Pawel

    2014-08-01

    Using molecular dynamics simulations and a model AlN-GaN interface, we demonstrate that the interfacial thermal resistance RK (Kapitza resistance) between a substrate and thin film depends on the thickness of the film and the film surface roughness when the phonon mean free path is larger than film thickness. In particular, when the film (external) surface is atomistically smooth, phonons transmitted from the substrate can travel ballistically in the thin film, be scattered specularly at the surface, and return to the substrate without energy transfer. If the external surface scatters phonons diffusely, which is characteristic of rough surfaces, RK is independent of film thickness and is the same as RK that characterizes smooth surfaces in the limit of large film thickness. At interfaces where phonon transmission coefficients are low, the thickness dependence is greatly diminished regardless of the nature of surface scattering. The film thickness dependence of RK is analogous to the well-known fact of lateral thermal conductivity thickness dependence in thin films. The difference is that phonon-boundary scattering lowers the in-plane thermal transport in thin films, but it facilitates thermal transport from the substrate to the thin film.

  8. Average wave function method for gas-surface scattering

    NASA Astrophysics Data System (ADS)

    Singh, Harjinder; Dacol, Dalcio K.; Rabitz, Herschel

    1986-02-01

    The average wave function method (AWM) is applied to scattering of a gas off a solid surface. The formalism is developed for both periodic as well as disordered surfaces. For an ordered lattice an explicit relation is derived for the Bragg peaks along with a numerical illustration. Numerical results are presented for atomic clusters on a flat hard wall with a Gaussian-like potential at each atomic scattering site. The effect of relative lateral displacement of two clusters upon the scattering pattern is shown. The ability of AWM to accommodate disorder through statistical averaging over cluster configurations is illustrated. Enhanced uniform backscattering is observed with increasing roughness on the surface.

  9. Validity of the Rayleigh hypothesis for two-dimensional randomly rough metal surfaces

    NASA Astrophysics Data System (ADS)

    Nordam, T.; Letnes, P. A.; Simonsen, I.

    2013-08-01

    The Rayleigh hypothesis is the assumption that the field in the region above (below) a rough surface can be expressed as a weighted sum of upwards (downwards) propagating scattered (transmitted) modes, and that these expressions can be used to satisfy the boundary conditions on the fields at the surface. This hypothesis is expected to be valid for surfaces of sufficiently small slopes. For one-dimensional sinusoidal surfaces, the region of validity is known analytically, while for randomly rough surfaces in one and two dimensions, the limits of validity of the Rayleigh hypothesis are not known. In this paper, we perform a numerical study of the validity of the Rayleigh hypothesis for two-dimensionally rough metal and perfectly conducting surfaces by considering the conservation of energy. It is found for a perfect electric conductor that the region of validity is defined by the ratio of the root-mean-square roughness, δ, over the correlation length, α, being less than about 0.2, while for silver we find δ/α lesssim 0.08 for an incident wavelength λ = 457.9 nm. Limitations in our simulations made us unable to check the Rayleigh hypothesis for roughness where δ gtrsim 0.13λ.

  10. How surface roughness affects chemical transfer from soil to surface runoff?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil surface roughness affects transport processes, e.g., runoff generation, infiltration, sediment detachment, etc., occurring on the surface. Nevertheless, how soil roughness affects chemical transport is less known. In this study, we partitioned roughness elements into mounds which diverge water ...

  11. Effects of surface roughness and oxide layer on the thermal boundary conductance at aluminum/silicon interfaces

    NASA Astrophysics Data System (ADS)

    Hopkins, Patrick E.; Phinney, Leslie M.; Serrano, Justin R.; Beechem, Thomas E.

    2010-08-01

    In nanosystems, the primary scattering mechanisms occur at the interfaces between the material layers. As such, the structure and composition around these interfaces can affect scattering rates and, therefore, thermal resistances. In this work, we measure the room-temperature thermal boundary conductance of aluminum films grown on silicon substrates subjected to various pre-Al-deposition surface treatments with a pump-probe thermoreflectance technique. The Si surfaces are characterized with atomic force microscopy to determine mean surface roughness. The measured thermal boundary conductances decrease as Si surface roughness increases. In addition, stripping of the native oxide layer from the surface of the Si substrate immediately prior to Al film deposition causes the thermal boundary conductance to increase. The measured data are compared to an extension of the diffuse mismatch model that accounts for interfacial mixing and structure around the interface in order to better elucidate the thermal scattering processes affecting thermal boundary conductance at rough interfaces.

  12. Analysis of microwave backscatter measured by radar altimeter on land to study surface aerodynamic roughness

    NASA Astrophysics Data System (ADS)

    Yang, Le; Liu, Qinhuo

    2012-10-01

    The aerodynamic surface roughness z0 is a key parameter for climate and land-surface models to study surfaceatmosphere exchanges of mass and energy. The roughness length is difficult to estimate without wind speed profile data, which is intractable at regional to global scale. Theoretical formulations of roughness have been developed in terms of canopy attributes such as frontal area, height, and drag coefficient. This paper discusses the potential of radar altimetry, which provides the backscatter coefficient of the land surface at nadir view, to characterise the surface roughness at km scale. The AIEM model and ProSARproSIM are employed to simulate the backscatter coefficient under different surface condition and different observation geometry at bare soil and at pine forest, respectively. The altimetry backscatter decreases with increase of geometric roughness. The microwave backscatter measured at the nadir view is more sensitive to the surface roughness than that at the oblique observation, especially for the smooth surface. The direct forest return is the dominated scattering mechanism for normal incidence at forest area. Since we failed to collect the z0 measurement at arid and semi-arid area with sparse vegetation, the backscatter measurements at Ku and C band of altimeter Jason1 were analyzed with the ground measured aerodynamic surface roughness at three vegetated sites (Da yekou, Yin ke, and Chang Baisan) of China. The relationships we found between Jason1 sigma0 and z0 is not significant, since Jason1 lost track seriously at the three sites. Further research using the altimeter data of Jason2 and Cryosat is possible to demonstrate the potential to map z0 from orbit using radar altimeters.

  13. Dispersion and Attenuation of Surface Acoustic Waves of Various Polarizations on a Stress-Free Randomly Rough Surface of Solid

    NASA Astrophysics Data System (ADS)

    Kosachev, V. V.; Shchegrov, A. V.

    1995-06-01

    An approach to obtaining the dispersion equation of surface acoustic waves (SAWs) on a stress-free, randomly rough surface of an anisotropic elastic medium is suggested. The problem is solved in the approximation of a weakly rough surface using Green's function technique. The dispersion and attenuation of sagittally and shear horizontally (SH) polarized SAWs are investigated both analytically and numerically for a three-dimensionally (3D) and a two-dimensionally (2D) rough surface of an isotropic medium. The results for 2D roughness are shown to be contained in the more general expressions for the 3D case, and the connection between the results for the 3D and the 2D cases is pointed out. Dispersion relations are derived for SAWs of both polarizations propagating in an arbitrary direction along a 2D rough surface. The SAW attenuation mechanisms are investigated at various incidence angles. It is concluded that all three mechanisms (viz. scattering into bulk transverse, longitudinal, and Rayleigh surface acoustic waves) are involved for the Rayleigh and SH polarized SAWs at certain incidence angles, whereas at the other angles only some of the mechanisms are. The criterion for the existence of SH polarized SAWs on a rough surface is considered. A possible increase of the SAW phase velocity on a rough surface compared with that for a flat boundary is discussed. In the limit λ ≫ a (where a is the roughness correlation length) simple explicit expressions for the phase velocities of Rayleigh and SH polarized SAWs are derived. A comparison of the results obtained herein with those of other workers is presented.

  14. Scaling of surface roughness in perfectly plastic disordered media

    SciTech Connect

    Barai, Pallab; Nukala, Phani K; Sampath, Rahul S; Simunovic, Srdjan

    2010-01-01

    This paper investigates surface roughness characteristics of localized plastic yield surface in a perfectly plastic disordered material. We model the plastic disordered material using perfectly plastic random spring model. Our results indicate that plasticity in a disordered material evolves in a diffusive manner until macroscopic yielding, which is in contrast to the localized failure observed in brittle fracture of disordered materials. On the other hand, the height-height fluctuations of the plastic yield surfaces generated by the spring model exhibit roughness exponents similar to those obtained in the brittle fracture of disordered materials, albeit anomalous scaling of plastic surface roughness is not observed. The local and global roughness exponents ({zeta}{sub loc} and {zeta}, respectively) are equal to each other, and the two-dimensional crack roughness exponent is estimated to be {zeta}{sub loc} = {zeta} = 0.67 {+-} 0.03. The probability density distribution p[{Delta}h({ell})] of the height differences {Delta}h({ell}) = [h(x+{ell})-h(x)] of the crack profile follows a Gaussian distribution.

  15. Simulation of synthetic gecko arrays shearing on rough surfaces.

    PubMed

    Gillies, Andrew G; Fearing, Ronald S

    2014-06-01

    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.

  16. Improved x-ray reflectivity calculations for rough surfaces and interfaces

    NASA Astrophysics Data System (ADS)

    Fujii, Yoshikazu

    2011-09-01

    We have investigated the fact that the calculated x-ray reflectivity based on the Parratt formalism, coupled with the use of the Nevot-Croce representation of roughness, show a strange phenomenon where the amplitude of the oscillation due to interference effects increases for a rougher surface. Here, we propose that the strange result has its origin in a currently used equation due to a serious mistake in which the Fresnel transmission coefficient in the reflectivity equation is increased at a rough interface, and the increase in the transmission coefficient completely overpowers any decrease in the value of the reflection coefficient because of a lack of consideration of diffuse scattering. The mistake in Nevot and Croce's treatment originates in the fact that the modified Fresnel coefficients were calculated based on the theory which contains the x-ray energy conservation rule at surface and interface. In their discussion, the transmission coefficients were replaced approximately by the reflection coefficients by the ignoring diffuse scattering term at the rough interface, and according to the principle of conservation energy at the rough interface also. The errors of transmittance without the modification cannot be ignored. It is meaningless to try to precisely match the numerical result based on a wrong calculating formula even to details of the reflectivity profile of the experimental result. Thus, because Nevot and Croce's treatment of the Parratt formalism contains a fundamental mistake regardless of the size of roughness, this approach needs to be corrected. In the present study, we present a new accurate formalism that corrects this mistake, and thereby derive an accurate analysis of the x-ray reflectivity from a multilayer surface, taking into account the effect of roughness-induced diffuse scattering. The calculated reflectivity obtained by the use of this accurate reflectivity equation gives a physically reasonable result, and should enable the

  17. Rigorous and asymptotic models of coherent scattering from random rough layers with applications to roadways and geoscience

    NASA Astrophysics Data System (ADS)

    Pinel, Nicolas; Bourlier, Christophe; Le Bastard, Cédric

    2014-05-01

    This paper presents the rigorous efficient PILE (Propagation-Inside-Layer Expansion) numerical method [1] and an extension of the Ament model [2] to calculate the field scattered by three homogeneous media separated by two random rough surfaces. Here, the study is applied to ground penetrating radar (GPR) (nadir angle, wide band) for nondestructive survey by taking the roughness of the surfaces into account and by calculating the contribution of each echo coming from the multiple scattering inside the layer. Applications to roadways and geoscience are investigated. The PILE method starts from the Method of Moments (MoM), and the impedance matrix is inverted by blocks from the Taylor series expansion of the inverse of the Schur complement. Its great advantage is that it is rigorous, with a simple formulation and has a straightforward physical interpretation. Actually, this last property relies on the fact that each block of the impedance matrix is linked to a particular and quasi-independent physical process occurring during the multiple scattering between the two rough surfaces. Furthermore, the PILE method allows us to use any acceleration algorithm (MLFMM, BMIA/CAG, Forward-Backward with or without Spectral Acceleration, etc.) developed for a single interface. In addition, an asymptotic approach is extended to rough layered media: the scalar Kirchhoff-tangent plane approximation (SKA), for calculating the coherent scattering from the rough layer. The numerical rigorous PILE method is used as a reference to validate this asymptotic model. The study focuses on 2D problems with so-called 1D surfaces, for computational ease of the reference numerical method. Nevertheless, it must be highlighted that the SKA approach can readily be applied to 3D problems. This approach is applied to rough layers with two slightly rough surfaces characterized by either Gaussian or exponential correlation functions. The height probability density function (PDF) is assumed to be Gaussian

  18. Light depolarization in off-specular reflection on submicro rough metal surfaces with imperfectly random roughness.

    PubMed

    Liu, Linsheng; Li, Xuefeng; Nonaka, Kazuhiro

    2015-02-01

    Depolarization at a rough surface relates to its roughness and irregularity (e.g., sags and crests) besides the material property. However, there is still lack of general theory to clearly describe the relationship between depolarization ratios and surface conditions, and one important reason is that the mechanism of depolarization relates to geometric parameters such as microcosmic height/particle distributions of sub-micro to nm levels. To study the mechanism in more detail, a compact laser instrument is developed, and depolarization information of a linearly polarized incident light is used for analyzing the roughness, during which a He-Ne laser source (λ = 632.8 nm) is used. Three nickel specimens with RMS roughness (Rq) less than λ/4 are fabricated and tested. Six different areas in each specimen are characterized in detail using an AFM. Rq are in the range of 34.1-155.0 nm, and the heights are non-Gaussian distribution in the first specimen and near-Gaussian distribution in the others. Off-specular inspection is carried out exactly on these 18 characterized areas, and results show that the cross-polarization ratios match quite well with Rq values of the first sample that has Rq ≤ λ/10 (or Rt ≤ λ), while they match well with maximum height, Rt, values of the other two that have Rt > λ (the maximum derivation is 11%). In addition, since this instrument is simple, portable, stable, and low-cost, it has great potential for practical online roughness testing after a linear calibration.

  19. 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.

  20. A technique for measuring convective heat transfer at rough surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Zuolan; Ireland, P. T.; Jones, T. V.

    1990-06-01

    A new method has been developed for measuring local heat transfer coefficients at rough surfaces. The technique was applied to an idealized section of a large scaled model of a turbine blade cooling passage to assess the effect of surface irregularities which result from the blade manufacturing process. The experimental method is described in full and the results are presented for tests on an isolated pin-fin situated in fully developed channel flow. The effect of the thermal conductivity of the roughness elements is discussed.

  1. Surface roughness effect on ultracold neutron interaction with a wall and implications for computer simulations

    SciTech Connect

    Steyerl, A.; Malik, S. S.; Desai, A. M.; Kaufman, C.

    2010-05-15

    We review the diffuse scattering and the loss coefficient in ultracold neutron reflection from slightly rough surfaces, report a surprising reduction in loss coefficient due to roughness, and discuss the possibility of transition from quantum treatment to ray optics. The results are used in a computer simulation of neutron storage in a recent neutron lifetime experiment that reported a large discrepancy of neutron lifetime with the current particle data value. Our partial reanalysis suggests the possibility of systematic effects that were not included in this publication.

  2. Coherent light scattering of heterogeneous randomly rough films and effective medium in the theory of electromagnetic wave multiple scattering

    SciTech Connect

    Berginc, G

    2013-11-30

    We have developed a general formalism based on Green's functions to calculate the coherent electromagnetic field scattered by a random medium with rough boundaries. The approximate expression derived makes it possible to determine the effective permittivity, which is generalised for a layer of an inhomogeneous random medium with different types of particles and bounded with randomly rough interfaces. This effective permittivity describes the coherent propagation of an electromagnetic wave in a random medium with randomly rough boundaries. We have obtained an expression, which contains the Maxwell – Garnett formula at the low-frequency limit, and the Keller formula; the latter has been proved to be in good agreement with experiments for particles whose dimensions are larger than a wavelength. (coherent light scattering)

  3. Physical Interpretation of the Sensitivity of Polarisation Coherence to Soil Surface Roughness

    NASA Astrophysics Data System (ADS)

    Mattia, F.; Le Toan, T.

    2003-04-01

    Surface roughness is an important geo-physical parameter required for numerous applications such as agronomy, geology, risk assessment, etc. In addition, the estimate of soil roughness may provide valuable a priori information to simplify the problem of soil moisture retrieval from SAR data. In the past, roughness discriminators based on the ratio between soil backscatter at different polarisations (i.e. sigmaHH/ sigmaVV ) and on the correlation coefficient between HH and VV channels (i.e. rhoHHVV) have been suggested. More recently, the potential of the correlation coefficient between co-polarised channels (i.e. polarisation coherence) in an arbitrary state of polarisation has been investigated. In particular, the correlation coefficient between co-polarised channels at circular polarisation (i.e. rhoRRLL ) has been found extremely sensitive to surface roughness and weakly sensitive to soil moisture content. However, notwithstanding these observations have been confirmed by several experimental studies a complete physical understanding of the phenomenon is still missing, at least in the remote sensing community. One of the main reasons for this lack of understanding is that in general, only lowest order approximations of theoretical surface scattering models are exploited in remote sensing applications. These approximations do not include the effect of multiple reflections. They cannot therefore predict accurately the whole covariance matrix often required to synthesise roughness discriminators, such as rhoRRLL. In this respect, despite the fact that higher order approximations of theoretical surface scattering models are mathematically very complex, they are necessary to give indications to understand the phenomenon and they can provide physical guidelines to develop semi-empirical approaches. In this context, the objective of this paper is to present a simple physical framework to interpret the sensitivity of different roughness discriminators to soil roughness

  4. Soil surface roughness and porosity under different tillage systems

    NASA Astrophysics Data System (ADS)

    Rodriguez-Gonzalez, J.; Saa-Requejo, A.; Gómez, J. A.; Valencia, J. L.; Zarco, P.; Tarquis, A. M.

    2012-04-01

    Both soil porosity and surface elevation can be altered by tillage operation. Even though the surface porosity is an important parameter of a tilled field, however, no practical technique for rapid and non-contact measurement of surface porosity has been developed yet. On the contrary, the surface elevation of tilled soil can be quickly determined with a laser profiler. Working under the assumption that the surface elevation of a tilled field is a complicated superposition of the soil terrain profile at a larger-scale and the roughness at a fine-scale, this study included three aspects: (i) to establish an index (Roughness Index, RI) at a fine-scale to associate the surface roughness with porosity; (ii) to examine the correlation between surface porosity and the proposed RI by three types of tillage treatment in the field; and (iii) to check the scaling/multiscaling behavior among different grid sizes of calculating RI on predicting surface porosity. Consequently, the statistical results from each tilled plot show a strong correlation between the surface porosity and the defined RI in an early stage (ca. 2 days) after tillage. Acknowledgements Funding provided by CEIGRAM (Research Centre for the Management of Agricultural and Environmental Risks)and Spanish Ministerio de Ciencia e Innovación (MICINN) through project AGL2010-21501/AGR is greatly appreciated.

  5. NDT and E for the surface roughness of marble

    NASA Astrophysics Data System (ADS)

    Avdelidis, Nicolas P.; Moropoulou, Antonia; Delegou, Ekaterini T.; Almond, Darryl P.

    2004-04-01

    Two non-contact NDT and E (non-destructive testing and evaluation) techniques were employed in the inspection of quarry Pentelic marble samples; surface profilometry and infrared thermography. The samples were processed with different roughness treatments (i.e. 60, 80, 100, 220, 400 and 600 mesh) and were evaluated in the laboratory. Furthermore, different surface cleaning treatments were applied to a Pentelic marble surface in situ and then representative samples were collected and evaluated in the laboratory by the means of these two non-destructive techniques. Quantitative analysis of all samples was performed. In particular, the surface roughness parameter Rq at a specific length scale and 3-D micro-topography plots were attained by the use of the laser profilometry scanning approach, whilst temperature - time plots displaying the intensity of pixels as a function of time on the obtained thermal images were also obtained with the intention of distinguishing the influence of the applied roughness treatments. Results indicate that these two non-destructive techniques can be used for the assessment of surface roughness.

  6. Observing submesoscale currents from high resolution surface roughness images

    NASA Astrophysics Data System (ADS)

    Rascle, N.; Chapron, B.; Nouguier, F.; Mouche, A.; Ponte, A.

    2015-12-01

    At times, high resolution sea surface roughness variations can provide stunning details of submesoscale upper ocean dynamics. As interpreted, transformations of short scale wind waves by horizontal current gradients are responsible for those spectacular observations. Here we present tow major advances towards the quantitative interpretation of those observations. First, we show that surface roughness variations mainly trace two particular characteristics of the current gradient tensor, the divergence and the strain in the wind direction. Local vorticity and shear in the wind direction should not affect short scale roughness distribution and would not be detectable. Second, we discuss the effect of the viewing direction using sets of quasi-simultaneous sun glitter images, taken from different satellites to provide different viewing configurations. We show that upwind and crosswind viewing observations can be markedly different. As further confirmed with idealized numerical simulations, this anisotropy well traces surface current strain area, while more isotropic contrasts likely trace areas dominated by surface divergence conditions. These findings suggest the potential to directly observe surface currents at submesoscale by using high resolution roughness observations at multiple azimuth viewing angles.

  7. Study of turbulent boundary layers over rough surfaces with emphasis n the effects of roughness character and Mach number

    NASA Astrophysics Data System (ADS)

    Finson, M. L.

    1982-02-01

    A Reynolds stress model for turbulent boundary layers on rough walls is used to investigate the effects of roughness character and compressibility. The flow around roughness elements is treated as form drag. A method is presented for deriving the required roughness shape and spacing from profilometer surface measurements. Calculations based on the model compare satisfactorily with low speed data on roughness character and hypersonic measurements with grit roughness. The computer model is exercised systematically over a wide range of parameters to derive a practical scaling law for the equivalent roughness. In contrast to previous correlations, for most roughness element shapes the effective roughness is not predicted to show a pronounced maximum as the element spacing decreases. The effect of roughness tends to be reduced with increasing edge Mach number, primarily due to decreasing density in the vicinity of the roughness elements. It is further shown that the required roughness Reynolds number for fully rough behavior increases with increasing Mach number, explaining the small roughness effects observed in some hypersonic tests.

  8. Adhesion of echinoderm tube feet to rough surfaces.

    PubMed

    Santos, Romana; Gorb, Stanislav; Jamar, Valérie; Flammang, Patrick

    2005-07-01

    Echinoderms attach strongly and temporarily to the substratum by means of specialized organs, the podia or tube feet. The latter consist of a basal extensible cylinder, the stem, which bears an apical flattened disc. The disc repeatedly attaches to and detaches from the substratum through adhesive and de-adhesive secretions. In their activities, echinoderms have to cope with substrata of varying degrees of roughness as well as with changing hydrodynamic conditions, and therefore their tube feet must adapt their attachment strength to these environmental constraints. This study is the first attempt to evaluate the influence of substratum roughness on the temporary adhesion of echinoderm tube feet and to investigate the material properties of their contact surface. It was demonstrated that tube foot discs are very soft (E-modulus of 6.0 and 8.1 kPa for sea stars and sea urchins, respectively), have viscoelastic properties and adapt their surface to the substratum profile. They also show increased adhesion on a rough substratum in comparison to its smooth counterpart, which is due mostly to an increase in the geometrical area of contact between the disc and the surface. Tenacity (force per unit area) increases with roughness [e.g. 0.18 and 0.34 MPa on smooth polymethyl-methacrylate (PMMA), 0.21 and 0.47 MPa on rough PMMA for sea stars and sea urchins, respectively] if only the projected surface area of the adhesive footprint is considered. However, if this tenacity is corrected to take into account the actual substratum 3-D profile, surface roughness no longer influences significantly the corrected adhesion strength (e.g. 0.18 and 0.34 MPa on smooth PMMA, 0.19 and 0.42 MPa on rough PMMA for sea stars and sea urchins, respectively). It can be hypothesized that, under slow self-imposed forces, disc material behaves viscously to adapt to substratum roughness while the adhesive fills out only very small surface irregularities (in the nanometer range). It is deposited as a

  9. Controlling Surface Roughness to Enhance Mass Flow Rates in Nanochannels

    NASA Astrophysics Data System (ADS)

    Zimon, Malgorzata; Emerson, David; Reese, Jason

    2012-11-01

    A very active field of research in fluid mechanics and material science is predicting the behavior of Newtonian fluids flowing over porous media with different wettabilities. Opposite effects have been observed: some state that wall roughness always suppresses fluid-slip, whereas others show that for some cases roughness may reduce the surface friction. In this work, MD simulations were carried out to further investigate physical mechanisms for liquid slip, and factors affecting it. A rough wall was formed by either periodically spaced rectangular protrusions or was represented by a cosine wave. The MD simulations were conducted to study Poiseuille and Couette flow of liquid argon in a nanochannel with hydrophilic kryptonian walls. The effect of wall roughness and interface wettability on the streaming velocity, and the slip-length at the walls, is observed to be significant. Our results show a dependency of mass flow rate on the type of flow and topography of the channel walls. For a fixed magnitude of the driving force, an increase in the mass flow rate, compared to the smooth surface, was observed for the wavy roughness, whereas the opposite effect was observed for Couette flow where a higher slip was obtained for rectangular gaps. The study is funded in the UK by the Engineering and Physical Sciences Research Council.

  10. Near grazing scattering from non-Gaussian ocean surfaces

    NASA Technical Reports Server (NTRS)

    Kim, Yunjin; Rodriguez, Ernesto

    1993-01-01

    We investigate the behavior of the scattered electromagnetic waves from non-Gaussian ocean surfaces at near grazing incidence. Even though the scattering mechanisms at moderate incidence angles are relatively well understood, the same is not true for near grazing rough surface scattering. However, from the experimental ocean scattering data, it has been observed that the backscattering cross section of a horizontally polarized wave can be as large as the vertical counterpart at near grazing incidence. In addition, these returns are highly intermittent in time. There have been some suggestions that these unexpected effects may come from shadowing or feature scattering. Using numerical scattering simulations, it can be shown that the horizontal backscattering cannot be larger than the vertical one for the Gaussian surfaces. Our main objective of this study is to gain a clear understanding of scattering mechanisms underlying the near grazing ocean scattering. In order to evaluate the backscattering cross section from ocean surfaces at near grazing incidence, both the hydrodynamic modeling of ocean surfaces and an accurate near grazing scattering theory are required. For the surface modeling, we generate Gaussian surfaces from the ocean surface power spectrum which is derived using several experimental data. Then, weakly nonlinear large scale ocean surfaces are generated following Longuet-Higgins. In addition, the modulation of small waves by large waves is included using the conservation of wave action. For surface scattering, we use MOM (Method of Moments) to calculate the backscattering from scattering patches with the two scale shadowing approximation. The differences between Gaussian and non-Gaussian surface scattering at near grazing incidence are presented.

  11. Partial-slip frictional response of rough surfaces

    PubMed Central

    Paggi, Marco; Pohrt, Roman; Popov, Valentin L.

    2014-01-01

    If two elastic bodies with rough surfaces are first pressed against each other and then loaded tangentially, sliding will occur at the boundary of the contact area while the inner parts may still stick. With increasing tangential force, the sliding parts will expand while the sticking parts shrink and finally vanish. In this paper, we study the fractions of the contact area, tangential force and tangential stiffness, associated with the sticking portion of the contact area, as a function of the total applied tangential force up to the onset of full sliding. For the numerical analysis randomly rough, fractal surfaces are used, with the Hurst exponent H ranging from 0.1 to 0.9. Numerical simulations by boundary element method are compared with an analytical analysis in the framework of the Greenwood and Williamson (GW) model. In both cases, a universal linear dependency between the real contact area fraction in stick condition and the applied tangential force is found, regardless of the Hurst exponent of the rough surfaces. Regarding the dependence of the differential tangential stiffness on the tangential force, a linear relation is found in the GW case. For randomly rough surfaces, a nonlinear relation depending on H is derived. PMID:24898988

  12. Snow Bedforms Create the Surface Roughness of Polar Snow

    NASA Astrophysics Data System (ADS)

    Filhol, S.; Sturm, M.

    2015-12-01

    Polar snow surfaces are rough. The wind moves, piles up, and scours snow grains from the snow surface, and recombines them into various shapes also called bedforms. Individual bedforms may have shapes that can be readily described and perhaps understood, but one storm event after another generate a complex compound surface whose roughness is the sum of both deposition and erosion. Characterizing and understanding the origin of this bedform roughness is one key toward a better estimation of precipitation at a global scale from microwave remote sensing, and also a better understanding of two critical sea ice processes; the transfer of momentum from the atmosphere to ice floes, and the spatial distribution of melt ponds in springtime. During this presentation, we will describe the dynamics of snow bedform formation and we will explore how the basic palette of bedforms combined with a unique weather history can reveal the genesis of a rough snow surface. Detailed laser scanner maps of bedforms measured in Arctic Alaska will be used to illustrate these processes and forms.

  13. Influence of surface roughness on nonlinear flow behaviors in 3D self-affine rough fractures: Lattice Boltzmann simulations

    NASA Astrophysics Data System (ADS)

    Wang, Min; Chen, Yi-Feng; Ma, Guo-Wei; Zhou, Jia-Qing; Zhou, Chuang-Bing

    2016-10-01

    This study investigates the impacts of surface roughness on the nonlinear fluid flow through three-dimensional (3D) self-affine rock fractures, whose original surface roughness is decomposed into primary roughness (i.e. the large-scale waviness of the fracture morphology) and secondary roughness (i.e. the small-scale unevenness) with a wavelet analysis technique. A 3D Lattice Boltzmann method (LBM) is adopted to predict the flow physics in rock fractures numerically created with and without consideration of the secondary roughness, respectively. The simulation results show that the primary roughness mostly controls the pressure distribution and fracture flow paths at a large scale, whereas the secondary roughness determines the nonlinear properties of the fluid flow at a local scale. As the pressure gradient increases, the secondary roughness enhances the local complexity of velocity distribution by generating and expanding the eddy flow and back flow regions in the vicinity of asperities. It was found that the Forchheimer's law characterizes well the nonlinear flow behavior in fractures of varying roughness. The inertial effects induced by the primary roughness differ only marginally in fractures with the roughness exponent varying from 0.5 to 0.8, and it is the secondary roughness that significantly enhances the nonlinear flow and leads to earlier onset of nonlinearity. Further examined were the effects of surface roughness on the transmissivity, hydraulic aperture and the tortuosity of flow paths, demonstrating again the dominant role of the secondary roughness, especially for the apparent transmissivity and the equivalent hydraulic aperture at high pressure gradient or high Reynolds number. The results may enhance our understanding of the role of surface roughness in the nonlinear flow behaviors in natural rock fractures.

  14. The apparent state of droplets on a rough surface

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoling; Lu, Tian

    2009-02-01

    The factors influencing the state and wetting transition of droplets on a rough surface are both complex and obscure. The change in wetting is directly reflected by changes under the contact condition of the droplets with the surface. The recent study about the wettability of the superhydrophobic surface under the condensing condition arouses the new understanding about the apparent state of droplets on a rough surface. In this work, to validate the existence of droplets in an intermediate state, a microscale pillar topological polydimethylsiloxane (PDMS) surface was manufactured and its wettability under various conditions was studied. According to the experimental data, it is proposed that the wetting state of a rough surface may be embodied using the contact area ratio of a solid/liquid/gas droplet with the projective plane. A general calculation model for the apparent contact angle of droplets is given and expressed diagrammatically. It is found that the measured apparent contact angles of droplets at different states on the surface falls within the range predicted by our proposed equation.

  15. Nonlinear Actuation Dynamics of Driven Casimir Oscillators with Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Broer, Wijnand; Waalkens, Holger; Svetovoy, Vitaly B.; Knoester, Jasper; Palasantzas, George

    2015-11-01

    At separations below 100 nm, Casimir-Lifshitz forces strongly influence the actuation dynamics of microelectromechanical systems (MEMS) in dry vacuum conditions. For a micron-size plate oscillating near a surface, which mimics a frequently used setup in experiments with MEMS, we show that the roughness of the surfaces significantly influences the qualitative dynamics of the oscillator. Via a combination of analytical and numerical methods, it is shown that surface roughness leads to a clear increase of initial conditions associated with chaotic motion, that eventually lead to stiction between the surfaces. Since stiction leads to a malfunction of MEMS oscillators, our results are of central interest for the design of microdevices. Moreover, stiction is of significance for fundamentally motivated experiments performed with MEMS.

  16. Abrasive wear and surface roughness of contemporary dental composite resin.

    PubMed

    Han, Jian-min; Zhang, Hongyu; Choe, Hyo-Sun; Lin, Hong; Zheng, Gang; Hong, Guang

    2014-01-01

    The purpose of this study was to evaluate the abrasive wear and surface roughness of 20 currently available commercial dental composite resins, including nanofilled, supra-nanofilled, nanohybrid and microhybrid composite resins. The volume loss, maximum vertical loss, surface roughness (R(a)) and surface morphology [Scanning electron microscopy (SEM)] were determined after wear. The inorganic filler content was determined by thermogravimetric analysis. The result showed that the volume loss and vertical loss varied among the materials. The coefficients of determination (R(2)) of wear volume loss and filler content (wt%) was 0.283. SEM micrographs revealed nanofilled composites displayed a relatively uniform wear surfaces with nanoclusters protrusion, while the performance of nanohybrid composites varied. The abrasive wear resistance of contemporary dental composite resins is material-dependent and cannot be deduced from its category, filler loading and composite matrix; The abrasive wear resistance of some flowable composites is comparable to the universal/posterior composite resins.

  17. Surface roughness when diamond turning RSA 905 optical aluminium

    NASA Astrophysics Data System (ADS)

    Otieno, T.; Abou-El-Hossein, K.; Hsu, W. Y.; Cheng, Y. C.; Mkoko, Z.

    2015-08-01

    Ultra-high precision machining is used intensively in the photonics industry for the production of various optical components. Aluminium alloys have proven to be advantageous and are most commonly used over other materials to make various optical components. Recently, the increasing demand from optical systems for optical aluminium with consistent material properties has led to the development of newly modified grades of aluminium alloys produced by rapid solidification in the foundry process. These new aluminium grades are characterised by their finer microstructures and refined mechanical and physical properties. However the machining database of these new optical aluminium grades is limited and more research is still required to investigate their machinability performance when they are diamond turned in ultrahigh precision manufacturing environment. This work investigates the machinability of rapidly solidified aluminium RSA 905 by varying a number of diamond-turning cutting parameters and measuring the surface roughness over a cutting distance of 4 km. The machining parameters varied in this study were the cutting speed, feed rate and depth of cut. The results showed a common trend of decrease in surface roughness with increasing cutting distance. The lowest surface roughness Ra result obtained after 4 km in this study was 3.2 nm. This roughness values was achieved using a cutting speed of 1750 rpm, feed rate of 5 mm/min and depth of cut equal to 25 μm.

  18. Surface roughness stabilizes the clustering of self-propelled triangles

    NASA Astrophysics Data System (ADS)

    Ilse, Sven Erik; Holm, Christian; de Graaf, Joost

    2016-10-01

    Self-propelled particles can spontaneously form dense phases from a dilute suspension in a process referred to as motility-induced phase separation. The properties of the out-of-equilibrium structures that are formed are governed by the specifics of the particle interactions and the strength of the activity. Thus far, most studies into the formation of these structures have focused on spherical colloids, dumbbells, and rod-like particles endowed with various interaction potentials. Only a few studies have examined the collective behavior of more complex particle shapes. Here, we increase the geometric complexity and use molecular dynamics simulations to consider the structures formed by triangular self-propelled particles with surface roughness. These triangles either move towards their apex or towards their base, i.e., they possess a polarity. We find that apex-directed triangles cluster more readily, more stably, and have a smoother cluster interface than their base-directed counterparts. A difference between the two polarities is in line with the results of Wensink et al. [Phys. Rev. E 89, 010302 (2014)]; however, we obtain the reversed result when it comes to clustering, namely, that apex-directed triangles cluster more successfully. We further show that reducing the surface roughness negatively impacts the stability of the base-directed structures, suggesting that their formation is in large part due to surface roughness. Our results lay a solid foundation for future experimental and computational studies into the effect of roughness on the collective dynamics of swimmers.

  19. Lunar Surface Imaging Polarimetry: I. Roughness and Grain Size

    NASA Astrophysics Data System (ADS)

    Dollfus, Audouin

    1998-11-01

    Imaging polarimetry characterizes the physical nature of the lunar surface by the median size of the grains and by the roughness of the surface. A video-polarimeter was designed at Observatoire de Paris to produce at the telescope images of planetary surfaces in intensity, degree of linear polarization, flux of polarized light, and other relevant photo-polarimetric images. With these images, the median grain sizeMdand mean roughness slope angle θ have been derived and mapped over characteristic lunar features. The method is explained. Terrains of anomalous surface textures have been discovered. The Imbrian and Eratosthenian mare surfaces, worked by the long term accumulation of impacts and by space exposure, produce a “mature” morphology characterized byMd= 47 μm and θ = 10°, irrespective of the composition of the material. Ejecta blankets around craters of Copernican age or younger show smoother surfaces and larger grains. Pyroclastic deposits have the same roughness, θ = 10°, but consist of grains too small to have been produced by mechanical impact comminution. Very specific terrain types have been discovered along the cliff of Rupes Recta and the crater Birt, which indicate clean rocks depleted of dust. These anomalies may result from seismic action when an impact formed the recent nearby crater Thebit A.

  20. AFM-measured surface roughness of SU-8 structures produced by deep x-ray lithography

    NASA Astrophysics Data System (ADS)

    Vora, K. D.; Lochel, B.; Harvey, E. C.; Hayes, J. P.; Peele, A. G.

    2006-10-01

    Deep x-ray lithography is a well-known technique used to pattern ultra high aspect ratio microstructures. It relies on the fact that higher energy synchrotron x-rays have the ability to penetrate millimeters of resist layers. However, the spectral shape of the beam will vary as a function of penetration depth, sometimes by design, so as to distribute the dose differently for different thickness structures and always as a result of filtering of lower energies. Some studies have shown that in PMMA sidewall roughness can be affected by spectral issues. SU-8 is now the resist of choice for certain high aspect ratio structures due to its high sensitivity and contrast. As sidewall roughness is a key parameter in several potential applications of high aspect ratio structures, we therefore investigated the surface roughness of 500 µm thick SU-8 structures exposed using beam spectra with peak energies between 3 keV and 12 keV. Results indicate that as the x-ray energy increases so too does the surface roughness. The surface roughness also increases as a function of feature depth. We attribute this to the random secondary physical processes of photo and Auger electron scattering both of which are strongly energy dependent.

  1. 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.

  2. 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.

  3. Delayed lubricant depletion on liquid-infused randomly rough surfaces

    NASA Astrophysics Data System (ADS)

    Kim, Jeong-Hyun; Rothstein, Jonathan P.

    2016-05-01

    In this study, pressure drops on liquid-infused superhydrophobic surfaces were measured through a microchannel. A number of different superhydrophobic surfaces were prepared and tested. These surfaces included several PDMS surfaces containing precisely patterned microposts and microridges as well as a number of PTFE surfaces with random surface roughness created by sanding the PTFE with different sandpapers. Silicone oil was selected as the lubricant fluid and infused into the microstructures of the superhydrophobic surfaces. Several aqueous glycerin solutions with different viscosities were used as working fluids so that the viscosity ratio between the lubricant and the working fluid could be varied. The lubricant layer trapped within the precisely patterned superhydrophobic PDMS surfaces was found to be easily depleted over a short period of time even in limit of low flow rates and capillary numbers. On the other hand, the randomly rough superhydrophobic PTFE surfaces tested were found to maintain the layer of lubricant oil even at moderately high capillary numbers resulting in drag reduction that was found to increase with increasing viscosity ratio. The pressure drops on the liquid-infused PTFE surfaces were measured over time to determine the longevity of the lubricant layer. The pressure drops for the randomly rough PTFE surfaces were found to initially diminish with time before reaching a short-time plateau which is equivalent to maximum drag reduction. This minimum pressure drop was maintained for at least three hours in all cases regardless of feature size. However, as the depletion of the oil from the lubricant layer was initiated, the pressure drop was observed to grow slowly before reaching a second long-time asymptote which was equivalent to a Wenzel state.

  4. The variation of ice adhesion strength with substrate surface roughness

    NASA Astrophysics Data System (ADS)

    Hassan, M. F.; Lee, H. P.; Lim, S. P.

    2010-07-01

    The purpose of this study is to determine whether a relationship exists between the mean surface roughness Ra of an aluminium sample and the interfacial bonding strength σ between it and ice that has been frozen onto its surface. A method of forced vibration of a cantilevered composite beam at 10.0 Hz was used to study the interfacial fracture of the metal-ice interface. Low-cost strain gauges instead of piezoelectric PVDF sensors used in other reported studies were used for the adhesion strength measurements. It was found that increasing surface roughness would lead to a higher interfacial bonding strength, although there was no clearly defined mathematical relationship between Ra and σ. For smooth beams, the adhesion strength was found to be between 0.142 and 0.267 MPa, which was in good agreement with the range of values reported in other studies.

  5. Roughness Scaling of Fracture Surfaces in Polycrystalline Materials

    SciTech Connect

    Seppala, E; Reed, B; Kumar, M; Minich, R; Rudd, R

    2004-04-26

    The roughness scaling of fracture surfaces in two-dimensional grain boundary networks is studied numerically. Grain boundary networks are created using a Metropolis method in order to mimic the triple junction distributions from experiments. Fracture surfaces through these grain boundary networks are predicted using a combinatorial optimization method of maximum flow - minimum cut type. We have preliminary results from system sizes up to N = 22500 grains suggesting that the roughness scaling of these surfaces follows a random elastic manifold scaling exponent {zeta} = 2/3. We propose a strong dependence between the energy needed to create a crack and the special boundary fraction. Also the special boundaries at the crack and elsewhere in the system can be tracked.

  6. Hot-rolling nanowire transparent electrodes for surface roughness minimization.

    PubMed

    Hosseinzadeh Khaligh, Hadi; Goldthorpe, Irene A

    2014-01-01

    Silver nanowire transparent electrodes are a promising alternative to transparent conductive oxides. However, their surface roughness presents a problem for their integration into devices with thin layers such as organic electronic devices. In this paper, hot rollers are used to soften plastic substrates with heat and mechanically press the nanowires into the substrate surface. By doing so, the root-mean-square surface roughness is reduced to 7 nm and the maximum peak-to-valley value is 30 nm, making the electrodes suitable for typical organic devices. This simple process requires no additional materials, which results in a higher transparency, and is compatible with roll-to-roll fabrication processes. In addition, the adhesion of the nanowires to the substrate significantly increases.

  7. 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.

  8. Real-time studies of surface roughness development and reticulation mechanism of advanced photoresist materials during plasma processing

    NASA Astrophysics Data System (ADS)

    Pal, A. R.; Bruce, R. L.; Weilnboeck, F.; Engelmann, S.; Lin, T.; Kuo, M.-S.; Phaneuf, R.; Oehrlein, G. S.

    2009-01-01

    Surface roughness development of photoresist (PR) films during low pressure plasma etching has been studied using real-time laser light scattering from photoresist materials along with ellipsometric and atomic force microscopy (AFM) characterization. We show that evolution of the intensity of light scattered from a film surface can be used to study the development of surface roughness for a wide range of roughness starting from subnanometer to few hundred nanometers. Laser light scattering in combination with ellipsometry and AFM is also used to study the reticulation mechanism of 193 and 248 nm PRs during argon plasma processing. We employ a three-layer model (modified layer, rough layer, and bulk film) of the modified PR surface (193 and 248 nm PRs) to simulate and understand the behavior of ellipsometric Ψ-Δ trajectories. Bruggeman's effective medium approximation is employed to study the roughness that develops on the surface after reticulation. When the glass transition temperature of the organic materials is reached during Ar plasma processing, the PR films reticulate and roughness develops rapidly. Roughness development is more pronounced for 248 nm PR than for 193 nm PR. Simulation of Ψ-Δ shows that the growth of roughness is accompanied by strong expansion in the materials, which is stronger for 248 nm PR than 193 nm PR. The leading factors responsible for reticulation are found to be compressive stress that develops in the modified surface layer as it is created along with strong molecular chain motion and expansion of the material when the temperature is increased past the glass transition temperature. Reticulation leads to a significantly different surface morphology for 248 nm PR as compared to 193 nm PR and can be related to differences in molecular structure and composition leading to different responses when a modified surface layer is formed by ion bombardment accompanying plasma etching.

  9. Numerical studies of the scattering of light from a two-dimensional randomly rough interface between two dielectric media

    NASA Astrophysics Data System (ADS)

    Hetland, Ø. S.; Maradudin, A. A.; Nordam, T.; Simonsen, I.

    2016-05-01

    The scattering of polarized light incident from one dielectric medium on its two-dimensional randomly rough interface with a second dielectric medium is studied. A reduced Rayleigh equation for the scattering amplitudes is derived for the case where p- or s-polarized light is incident on this interface, with no assumptions being made regarding the dielectric functions of the media. Rigorous, purely numerical, nonperturbative solutions of this equation are obtained. They are used to calculate the reflectivity and reflectance of the interface, the mean differential reflection coefficient, and the full angular distribution of the intensity of the scattered light. These results are obtained for both the case where the medium of incidence is the optically less dense medium and in the case where it is the optically more dense medium. Optical analogs of the Yoneda peaks observed in the scattering of x rays from metal surfaces are present in the results obtained in the latter case. Brewster scattering angles for diffuse scattering are investigated, reminiscent of the Brewster angle for flat-interface reflection, but strongly dependent on the angle of incidence. When the contribution from the transmitted field is added to that from the scattered field it is found that the results of these calculations satisfy unitarity with an error smaller than 10-4.

  10. PREFACE: Atom-surface scattering Atom-surface scattering

    NASA Astrophysics Data System (ADS)

    Miret-Artés, Salvador

    2010-08-01

    It has been a privilege and a real pleasure to organize this special issue or festschrift in the general field of atom-surface scattering (and its interaction) in honor of J R Manson. This is a good opportunity and an ideal place to express our deep gratitude to one of the leaders in this field for his fundamental and outstanding scientific contributions. J R Manson, or Dick to his friends and colleagues, is one of the founding fathers, together with N Cabrera and V Celli, of the 'Theory of surface scattering and detection of surface phonons'. This is the title of the very well-known first theoretical paper by Dick published in Physical Review Letters in 1969. My first meeting with Dick was around twenty years ago in Saclay. J Lapujoulade organized a small group seminar about selective adsorption resonances in metal vicinal surfaces. We discussed this important issue in surface physics and many other things as if we had always known each other. This familiarity and warm welcome struck me from the very beginning. During the coming years, I found this to be a very attractive aspect of his personality. During my stays in Göttingen, we had the opportunity to talk widely about science and life at lunch or dinner time, walking or cycling. During these nice meetings, he showed, with humility, an impressive cultural background. It is quite clear that his personal opinions about history, religion, politics, music, etc, come from considering and analyzing them as 'open dynamical systems'. In particular, with good food and better wine in a restaurant or at home, a happy cheerful soirée is guaranteed with him, or even with only a good beer or espresso, and an interesting conversation arises naturally. He likes to listen before speaking. Probably not many people know his interest in tractors. He has an incredible collection of very old tractors at home. In one of my visits to Clemson, he showed me the collection, explaining to me in great detail, their technical properties

  11. Friction and roughness of a melting rock surface

    NASA Astrophysics Data System (ADS)

    Nielsen, S.; di Toro, G.; Griffith, W. A.

    2010-07-01

    Under extreme conditions like those encountered during earthquake slip, frictional melt is likely to occur. It has been observed on ancient faults that the melt is mostly extruded toward local extensional jogs or lateral tension cracks. In the case of laboratory experiments with a rotary shear apparatus, melt is extruded from the sample borders. When this happens, a thin and irregular melt layer is formed whereby the normal load is still in part supported by contact asperities under an incipient yield condition (as in dry friction models), but also, in the interstices between asperities, by the pressure of the viscous fluid wetting the interface. In addition, roughness of the surface is dynamically reshaped by the melting process of an inhomogeneous material (polymineralic rock). In particular, we argue that the roughness of the melting surface decreases with melting rate and temperature gradient perpendicular to the fault. Taking into account the above conditions, we obtain an expression for the average melt layer thickness and viscous pressure that may be used in estimates of friction in the presence of melt. We argue that the ratio of melt thickness to roughness depends on sliding velocity; such a ratio may be used as a gauge of slip-rate during fossil earthquakes on faults bearing pseudotachylite (solidified melt). Finally, we derive an improved analytical solution for friction in the presence of melt including the effect of roughness evolution.

  12. Estimation of Bare Surface Soil Moisture and Surface Roughness Parameter Using L-Band SAR Image Data

    NASA Technical Reports Server (NTRS)

    Shi, Jian-Cheng; Wang, James; Hsu, Ann Y.; ONeill, Peggy E.; Engman, Edwin T.

    1997-01-01

    An algorithm based on a fit of the single-scattering Integral Equation Method (IEM) was developed to provide estimation of soil moisture and surface roughness parameter (a combination of rms roughness height and surface power spectrum) from quad-polarized synthetic aperture radar (SAR) measurements. This algorithm was applied to a series of measurements acquired at L-band (1.25 GHz) from both AIRSAR (Airborne Synthetic Aperture Radar operated by the Jet Propulsion Laboratory) and SIR-C (Spaceborne Imaging Radar-C) over a well- managed watershed in southwest Oklahoma. Prior to its application for soil moisture inversion, a good agreement was found between the single-scattering IEM simulations and the L band measurements of SIR-C and AIRSAR over a wide range of soil moisture and surface roughness conditions. The sensitivity of soil moisture variation to the co-polarized signals were then examined under the consideration of the calibration accuracy of various components of SAR measurements. It was found that the two co-polarized backscattering coefficients and their combinations would provide the best input to the algorithm for estimation of soil moisture and roughness parameter. Application of the inversion algorithm to the co-polarized measurements of both AIRSAR and SIR-C resulted in estimated values of soil moisture and roughness parameter for bare and short-vegetated fields that compared favorably with those sampled on the ground. The root-mean-square (rms) errors of the comparison were found to be 3.4% and 1.9 dB for soil moisture and surface roughness parameter, respectively.

  13. Scattering from very rough layers under the geometric optics approximation: further investigation.

    PubMed

    Pinel, Nicolas; Bourlier, Christophe

    2008-06-01

    Scattering from very rough homogeneous layers is studied in the high-frequency limit (under the geometric optics approximation) by taking the shadowing effect into account. To do so, the iterated Kirchhoff approximation, recently developed by Pinel et al. [Waves Random Complex Media17, 283 (2007)] and reduced to the geometric optics approximation, is used and investigated in more detail. The contributions from the higher orders of scattering inside the rough layer are calculated under the iterated Kirchhoff approximation. The method can be applied to rough layers of either very rough or perfectly flat lower interfaces, separating either lossless or lossy media. The results are compared with the PILE (propagation-inside-layer expansion) method, recently developed by Déchamps et al. [J. Opt. Soc. Am. A23, 359 (2006)], and accelerated by the forward-backward method with spectral acceleration. They highlight that there is very good agreement between the developed method and the reference numerical method for all scattering orders and that the method can be applied to root-mean-square (RMS) heights at least down to 0.25lambda. PMID:18516140

  14. Survey of surface roughness properties of synchrotron radiation optics

    SciTech Connect

    Takacs, P.Z.; Colbert, J.; Church, E.L.

    1986-03-01

    Measurements of surface roughness were made on a large number of grazing incidence mirrors delivered for use at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory. The measurements were made with a WYKO optical profiler using a 2.5X and a 10X objective and analyzed with our PROFILE code to generate an average periodogram representation for each surface. The data is presented in the form of representative profiles with all of the periodogram curves arranged according to figure type. Analysis of the periodograms allows one to compute bandwidth-limited values for RMS roughness and slope, to provide valuable feedback information to manufacturers regarding compliance with specifications, and to predict the performance of the optic at x-ray wavelengths.

  15. SECONDARY EMISSION FROM NON-SPHERICAL DUST GRAINS WITH ROUGH SURFACES: APPLICATION TO LUNAR DUST

    SciTech Connect

    Richterova, I.; Nemecek, Z.; Beranek, M.; Safrankova, J.; Pavlu, J.

    2012-12-20

    Electrons impinging on a target can release secondary electrons and/or they can be scattered out of the target. It is well established that the number of escaping electrons per primary electron depends on the target composition and dimensions, the energy, and incidence angle of the primary electrons, but there are suggestions that the target's shape and surface roughness also influence the secondary emission. We present a further modification of the model of secondary electron emission from dust grains which is applied to non-spherical grains and grains with defined surface roughness. It is shown that the non-spherical grains give rise to a larger secondary electron yield, whereas the surface roughness leads to a decrease in the yield. Moreover, these effects can be distinguished: the shape effect is prominent for high primary energies, whereas the surface roughness predominantly affects the yield at the low-energy range. The calculations use the Lunar Highlands Type NU-LHT-2M simulant as a grain material and the results are compared with previously published laboratory and in situ measurements.

  16. The Influence of Roughness on Gear Surface Fatigue

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy

    2005-01-01

    Gear working surfaces are subjected to repeated rolling and sliding contacts, and often designs require loads sufficient to cause eventual fatigue of the surface. This research provides experimental data and analytical tools to further the understanding of the causal relationship of gear surface roughness to surface fatigue. The research included evaluations and developments of statistical tools for gear fatigue data, experimental evaluation of the surface fatigue lives of superfinished gears with a near-mirror quality, and evaluations of the experiments by analytical methods and surface inspections. Alternative statistical methods were evaluated using Monte Carlo studies leading to a final recommendation to describe gear fatigue data using a Weibull distribution, maximum likelihood estimates of shape and scale parameters, and a presumed zero-valued location parameter. A new method was developed for comparing two datasets by extending the current methods of likelihood-ratio based statistics. The surface fatigue lives of superfinished gears were evaluated by carefully controlled experiments, and it is shown conclusively that superfinishing of gears can provide for significantly greater lives relative to ground gears. The measured life improvement was approximately a factor of five. To assist with application of this finding to products, the experimental condition was evaluated. The fatigue life results were expressed in terms of specific film thickness and shown to be consistent with bearing data. Elastohydrodynamic and stress analyses were completed to relate the stress condition to fatigue. Smooth-surface models do not adequately explain the improved fatigue lives. Based on analyses using a rough surface model, it is concluded that the improved fatigue lives of superfinished gears is due to a reduced rate of near-surface micropitting fatigue processes, not due to any reduced rate of spalling (sub-surface) fatigue processes. To complete the evaluations, surface

  17. X-ray Magnetic Scattering From Surfaces^*

    NASA Astrophysics Data System (ADS)

    Gibbs, Doon

    1997-03-01

    In the last several years, there have been continuing efforts to probe long-ranged magnetic order at surfaces by x-ray and neutron diffraction, following many earlier studies by low energy electron diffraction. The main motivation has been to discover how bulk magnetic structures are modified near a surface, where the crystal symmetry is broken. In this talk, we describe x-ray scattering studies of the magnetic structure observed near the (001) surface of the antiferromagnet uranium dioxide.(G. M. Watson, Doon Gibbs, G. H. Lander, B. D. Gaulin, L.E. Berman, Hj. Matzke and W. Ellis, Phys. Rev. Lett. 77), 751 (1996). Within about 50 Åof the surface, the intensity of the magnetic scattering decreases continuously as the bulk Neel temperature is approached from below. This contrasts with the bulk magnetic ordering transition which is discontinuous. Recent measurements of the specular magnetic reflectivity suggest that the width of the magnetic interface diverges as a power-law in reduced temperature reminiscent of surface induced disorder. Related experiments concerned with magnetic crystallography of Co_3-Pt(111) surfaces(S. Ferrer, P. Fajardo, F. de Bergevin, J. Alvarez, X. Torrelles, H. A. van der Vegt and V. H. Etgens, Phys. Rev. Lett. 77), 747 (1996). and interfacial magnetic roughness of Co/Cu multilayers(J. F. MacKay, C. Teichert, D.E. Savage and M.G. Lagally, Phys. Rev. Lett. 77), 3925 (1996). will also be discussed. ^* Work at Brookhaven National Laboratory is supported by the U.S. DOE under Contract No. DE-AC02-CH7600016.

  18. Estimation of Bare Surface Soil Moisture and Surface Roughness Parameter Using L-Band SAR Image Data

    NASA Technical Reports Server (NTRS)

    Shi, Jian-Cheng; Wang, James; Hsu, Ann; ONeill, Peggy; Engman, Edwin T.

    1997-01-01

    An algorithm based on a fit of the single-scattering Integral Equation Method (IEM) was developed to provide estimation of soil moisture and surface roughness parameter (a combination of rms roughness height and surface power spectrum) from quasi-polarized synthetic aperture radar (SAR) measurements. This algorithm was applied to a series of measurements acquired at L-band (1.25 GHz) from both AIRSAR (Airborne Synthetic Aperture Radar operated by Jet Propulsion Laboratory) and SIR-C (Spaceborne Imaging Radar-C) over a well-managed watershed in southwest Oklahoma. It was found that the two co-polarized backscattering coefficients and their combinations would provide the best input to the algorithm for estimation of soil moisture and roughness parameter. Application of the inversion algorithm to the co-polarized measurements of both AIRSAR and SIR-C resulted in estimated values of soil moisture and roughness parameter for bare and short-vegetated fields that compared favorably with those sampled on the ground. The root-mean-square (rms) errors of the comparison were found to be 3.4% and 1.9 dB for soil moisture and surface roughness parameter, respectively.

  19. Friction and roughness of a melting rock surface

    NASA Astrophysics Data System (ADS)

    Nielsen, Stefan; di Toro, Giulio; Griffith, Ashley

    2010-05-01

    Under extreme conditions like those encountered during earthquake slip, frictional melt is likely to occur. It has been observed on fossil faults that the melt is mostly extruded toward local extensional jogs or lateral tension cracks. A similar condition is reproduced in laboratory experiments with a rotary shear apparatus. When this happens, a thin and irregular melt layer is formed whereby the normal load is still in part supported by contact asperities under an incipient yield condition (as in dry friction models), but also, in the interstices between asperities, by the pressure of the viscous fluid wetting the interface. In addition, roughness of the surface is dynamically reshaped by the melting process of an inhomogeneous material (polymineral rock). In particular, we argue that the roughness decreases with temperature gradient and the melting rate. Taking into account the above conditions, we obtain an expression for the average melt layer thickness and viscous pressure that may be used in estimates of friction in the presence of melt. We argue that the ratio of melt thickness to roughness depends on sliding velocity; such a ratio may be used as a gauge of slip-rate during fossil earthquakes on faults bearing pseudotachylite (solidified melt). Finally, we derive an improved analytical solution for friction in the presence of melt including the effect of roughness evolution.

  20. 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.

  1. Structure of turbulent wedges created by isolated surface roughness

    NASA Astrophysics Data System (ADS)

    Kuester, Matthew S.; White, Edward B.

    2016-04-01

    Isolated surface roughness in a laminar boundary layer can create a wedge of turbulence that spreads laterally into the surrounding laminar flow. Some recent studies have identified high- and low-speed streaks along the exterior of turbulent wedges. In this experiment, developing turbulent wedges are measured to observe the creation of these streaks. Naphthalene shear stress surface visualization and hotwire measurements are utilized to investigate the details of turbulent wedges created by cylinders in a laminar flat-plate boundary layer. Both the surface visualization and the hotwire measurements show high- and low-speed streaks in the wake of the cylinder that devolve into a turbulent wedge. The turbulent wedge spreading is associated with the emergence of these high- and low-speed streaks along the outside of the wedge. As the wedge evolves in the streamwise direction, these streaks persist inside of the core of the wedge, while new, lower amplitude streaks form along the outside of the wedge. Adding asymmetry to the cylinder moved the virtual origin closer to the roughness and increased the vortex shedding frequency, while adding small-scale roughness features did not strongly affect turbulent wedge development. Intermittency calculations additionally show the origin of the turbulent core inside of the wedge. The structure and spacing of the high-speed streaks along the extremities of the turbulent wedge give insight into the spreading angle of the turbulent wedge.

  2. Numerical surface-scattering laws for asteroid applications

    NASA Astrophysics Data System (ADS)

    Wilkman, O.; Muinonen, K.; Penttilä, A.; Peltoniemi, J.

    2014-07-01

    We present a database of numerically computed surface-scattering laws for surfaces consisting of close-packed spherical volume elements of particles. Simple analytical scattering laws, such as the Lommel-Seeliger law, are commonly used to model the scattering of sunlight by asteroid surfaces. In their simple form, however, they are only valid for smooth surfaces, while the surfaces of asteroids are roughened by a loose regolith. The particulate surface structure causes subtle photometric features [1], but taking them into account is difficult with a simple analytic scattering law. Our intention is to allow a user to efficiently simulate light scattering from this type of surfaces by using pre-computed values. We use a ray-tracing technique [2] to compute the scattering of light from a surface medium composed of spherical volume elements of particles. The medium has a variable volume-element size distribution, packing density, and macroscale roughness. The scattering is discretized over the angles of incidence, emergence, and azimuth using an efficient and simple hemisphere discretization scheme. The numerical scattering laws are provided as data files containing the sky hemisphere and descriptive metadata. In practice, the user will load the hemisphere array from the file and compute the scattering-law values in his/her software through interpolation between the array values, then multiplying by a desired phase function. The first release of data contains scattering laws computed for media of low-to-moderate geometric albedo, with packing densities in the range of 0.15 to 0.55 and a uniform size distribution. Documentation and example source code are also provided to help users integrate our scattering-law approach to their software.

  3. Improvement of PET surface hydrophilicity and roughness through blending

    SciTech Connect

    Kolahchi, Ahmad Rezaei; Ajji, Abdellah; Carreau, Pierre J.

    2015-05-22

    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 content 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.

  4. Statistical characteristics of simulated radar imagery from bare soil surfaces: Effects of surface roughness and soil moisture variability

    SciTech Connect

    Narayanan, R.M.; Rundquist, D.C. ); Pardipuram, R. )

    1994-01-01

    The potential of high-resolution radar imagery to estimate various hydrological parameters, such as soil moisture, has long been recognized. Image simulation is one approach to study the interrelationships between the radar response and the underlying ground parameters. In order to perform realistic simulations, the authors incorporated the effects of naturally occurring spatial variability and spatial correlations of those ground parameters that affect the radar response, primarily surface roughness and soil moisture. Surface roughness and soil moisture images were generated for a hypothetical 100 x 100 m bare soil surface area at 1 m resolution using valid probability distribution and correlation lengths, These values were then used to obtain copolarized radar scattering coefficients at 2 GHz (L band) and 10 GHz (X band) frequencies using appropriate backscatter models, which were then converted to a digital number within 0--255 gray scale in order to generate radar images. The effect of surface roughness variability causes variability in the radar image, which is more apparent under smooth soil conditions. On the other hand, the inherent spatial pattern in soil moisture tends to cause similar patterns in the radar image under rougher soil conditions. The maximum difference between contrast-enhanced mean values of the radar image digital number due to moisture variations occurs at surface roughness values in the 1.5--2.0 cm range.

  5. Radiometric Trouble with Rough Surfaces? ... The von Neumann Series can Help!

    NASA Astrophysics Data System (ADS)

    Davis, A. B.

    2004-05-01

    Operational retrieval methods used in surface remote sensing will generally assume that the interrogated terrain is uniform as well as flat (if not outright horizontal) at least at sub-pixel scales. Both assumptions are highly questionable. There are spectral techniques (linear un-mixing, end-members, etc.) designed to address the non-uniformity issue and adjacency effects (nonlinear mixing) near large gradients in surface albedo can be unraveled with techniques using the Green function of the aerosol atmosphere. But strong deviations from local flatness define a challenging problem in three-dimensional radiative transfer; this is especially true when the terrain has a very rough fractal shape with height variability over a wide range of scales. The source of the problem is the multiple reflections between surface elements in view of each other and is mathematically akin to the problem of multiple scattering in heterogeneous turbid media like clouds. The fundamental solution to the multiple scattering/reflection problem in transport theory is called ``successive orders-of-scattering/reflection'' by physicists and a ``von Neumann expansion'' by mathematicians. I have applied this method to the analysis of two remote sensing problems that appear to be vastly different: (1) angular dependence of effective emissivity in thermal remote sensing, and (2) biases in fine laser altimetry (such as attempted by NASA's present GLAS mission which focuses on polar ice caps). The thermal problem can be reduced to a question of mean aspect ratio in the macro-roughness of the surface. The altimetry problem calls furthermore for a roughness scale. In both cases, corrections can be made to obtain the surface property of interest: actual emissivity, and actual altitude. In both cases, Monte Carlo simulation ---another seminal contribution of John von Neumann, with others--- was the key to first inspiring and then validating the proposed analytical models with one or two free parameters

  6. Rough spacecraft surfaces -a threat to Planetary Protection issues

    NASA Astrophysics Data System (ADS)

    Probst, Alexander; Facius, Rainer; Wirth, Reinhard; Moissl-Eichinger, Christine

    Inadvertent introduction of terrestrial microorganisms to foreign solar bodies could compromise the integrity of present and future life detection missions. For Planetary Protection purposes space agencies measure the aerobic, mesophilic spore load of a spacecraft as a proxy indicator in order to determine its bioload. Emerging novel hardware in space science implicates novel surface structures and materials that need to be controlled with regard to contaminations. For instance (roughened) carbon fiber reinforced plastic and Vectran fabric for construction of landing platforms and airbags, respectively, have been used in some Mars exploration missions. These materials have different levels of roughness and their potential risk to retain spores for insufficient sampling success has never been in scope of investigation. In this comprehensive study we evaluated ESA's novel nylon flocked swab protocol on stainless steel and other tech-nical surfaces with regard to Bacillus spore recovery. Low recovery efficiencies of the ESA standard wipe assay for large surface sampling were demonstrated with regard to Bacillus at-rophaeus spore detection. Therefore another protocol designed for rough surface sampling was evaluated on Vectran fabric and (roughened) carbon fiber reinforced plastic. Moreover, scan-ning electron micrographs of the technical surfaces studied allowed a more detailed view on their properties. The evaluated sampling protocols and the corresponding results are of high interest for future life detection missions in order to preserve their scientific integrity throughout spacecraft assembly.

  7. A full-field perturbation approach to scattering and reverberation in range-dependent environments with rough interfaces.

    PubMed

    Ivakin, Anatoliy N

    2016-07-01

    A perturbation approach to roughness scattering and reverberation in range-dependent environments is developed treating each interface as a superposition of a smooth reference interface, which may include large-scale deterministic features (such as bathymetry changes), and small compared to the acoustic wavelength vertical deviations from this interface that are considered as random roughness perturbations. The reference interface is assumed to be smooth enough to allow analytic or numerical solution for the field in the vicinity of this interface that can then be used in perturbation theory. Expressions for both the reverberation field and average reverberation intensity in a general case of an arbitrary number of rough interfaces are obtained in a form convenient for numerical simulations. In the case of long-range ocean reverberation, several approximations for these expressions are developed, relevant to various environmental scenarios and different types of interfaces: sea-surface, water-sediment interface, buried sediment interfaces, and bottom basement. The results are presented in a simple form and provide a direct relationship of the reverberation intensity with three critical characteristics defined at each interface: (1) local spectrum of roughness, (2) local contrast of acoustic parameters, and (3) two-way full-field transmission intensity calculated taking into account only large-scale changes of the environment.

  8. Subsurface Sounding of Mars: The Effects of Surface Roughness

    NASA Technical Reports Server (NTRS)

    Plaut, J. J.; Jordan, R.; Safaeinili, A.; Safaenelli, A.; Seu, R.; Orosei, R.

    2001-01-01

    The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) will conduct a global survey of Mars from the Mars Express Orbiter starting in 2004. The primary objective of the subsurface observations is to detect material interfaces in the upper several kilometers of the crust of Mars, with a particular emphasis on mapping the 3D distribution of water and ice in that portion of the crust. In order to detect subsurface interfaces, the returned echo from the subsurface must be distinguished from noise and clutter, which can arise from a variety of sources. One source of clutter is surface topography that generates backscattered energy at the same time delay as the subsurface region of interest. Surface topography can affect the detectability of subsurface features in several other ways. Surface roughness at scales comparable or somewhat smaller than the radar wavelength reduces the coherency of the wave as it passes the upper interface. Also, surface slope (tilt) at scales of the radar footprint and larger (> 5 km) affects the apparent Doppler signature of the echoes, and effectively disperses the wave transmitted into the subsurface, making processing and interpretation difficult. In this paper, we report on the roughness characteristics of Mars at these various scales as measured by the Mars Global Surveyor Laser Altimeter (MOLA), and consider the implications for achieving the subsurface sounding goals of MARSIS. Additional information is contained in the original extended abstract.

  9. Decoupling single nanowire mobilities limited by surface scattering and bulk impurity scattering

    SciTech Connect

    Khanal, D. R.; Levander, A. X.; Wu, J.; Yu, K. M.; Liliental-Weber, Z.; Walukiewicz, W.; Grandal, J.; Sanchez-Garcia, M. A.; Calleja, E.

    2011-08-01

    We demonstrate the isolation of two free carrier scattering mechanisms as a function of radial band bending in InN nanowires via universal mobility analysis, where effective carrier mobility is measured as a function of effective electric field in a nanowire field-effect transistor. Our results show that Coulomb scattering limits effective mobility at most effective fields, while surface roughness scattering only limits mobility under very high internal electric fields. High-energy {alpha} particle irradiation is used to vary the ionized donor concentration, and the observed decrease in mobility and increase in donor concentration are compared to Hall effect results of high-quality InN thin films. Our results show that for nanowires with relatively high doping and large diameters, controlling Coulomb scattering from ionized dopants should be given precedence over surface engineering when seeking to maximize nanowire mobility.

  10. The effects of shadowing on modelling forward radar propagation over a rough sea surface

    NASA Astrophysics Data System (ADS)

    Freund, D. E.; Woods, N. E.; Ku, H. C.; Awadallah, R. S.

    In order to accurately predict the effects of ocean roughness on forward radar propagation, it is important to incorporate the relevant physical scattering mechanisms. Shadowing is one such mechanism that is particularly important for low-grazing incidence yet it is often not taken into account. One broad class of approximations defines a roughness reduction factor in terms of an ensemble average over surface heights of a Rayleigh phase factorE The widely used Ament approximation and Miller-Brown approximation are two examples from this class of approximations that do not incorporate shadowing. In this paper, we use this class of approximations to develop a `shadowed' approximation that implements a probability density function (PDF) for a rough sea surface illuminated at grazing incidence. A rigorous method of moments calculation is used to compare and quantitatively assess the accuracy of the Ament, Miller-Brown, and shadowed approximations at horizontal polarization. It is shown that the shadowed approximation yields significantly more accurate results than either the Ament or Miller-Brown approximation. In addition, these three approximations are compared with experimental data and it is shown that the shadowed approximation is in good agreement with the data. Finally, numerical curve fitting is used to develop a simple analytical expression for a roughness reduction factor that incorporates shadowing.

  11. Investigations of rough surface effects on friction factors in turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Taylor, Robert P.; Coleman, Hugh W.; Scaggs, W. F.

    1988-02-01

    The results of an experimental investigation of the effects of surface roughness on turbulent pipe flow friction factors are presented and compared with predictions from a discrete element roughness model which had been developed previously. Friction factor data were acquired over a pipe Reynolds number range from 10,000 to 600,000 for eleven different rough surfaces, nine of which had uniform roughness elements and two of which were roughened nonuniformly. These surfaces covered a range of roughness element sizes, spacings and shapes. Predictions from the discrete element roughness model were in very good agreement with the data for both the uniform and nonuniform roughness cases.

  12. Nanostructures increase water droplet adhesion on hierarchically rough superhydrophobic surfaces.

    PubMed

    Teisala, Hannu; Tuominen, Mikko; Aromaa, Mikko; Stepien, Milena; Mäkelä, Jyrki M; Saarinen, Jarkko J; Toivakka, Martti; Kuusipalo, Jurkka

    2012-02-14

    Hierarchical roughness is known to effectively reduce the liquid-solid contact area and water droplet adhesion on superhydrophobic surfaces, which can be seen for example in the combination of submicrometer and micrometer scale structures on the lotus leaf. The submicrometer scale fine structures, which are often referred to as nanostructures in the literature, have an important role in the phenomenon of superhydrophobicity and low water droplet adhesion. Although the fine structures are generally termed as nanostructures, their actual dimensions are often at the submicrometer scale of hundreds of nanometers. Here we demonstrate that small nanometric structures can have very different effect on surface wetting compared to the large submicrometer scale structures. Hierarchically rough superhydrophobic TiO(2) nanoparticle surfaces generated by the liquid flame spray (LFS) on board and paper substrates revealed that the nanoscale surface structures have the opposite effect on the droplet adhesion compared to the larger submicrometer and micrometer scale structures. Variation in the hierarchical structure of the nanoparticle surfaces contributed to varying droplet adhesion between the high- and low-adhesive superhydrophobic states. Nanoscale structures did not contribute to superhydrophobicity, and there was no evidence of the formation of the liquid-solid-air composite interface around the nanostructures. Therefore, larger submicrometer and micrometer scale structures were needed to decrease the liquid-solid contact area and to cause the superhydrophobicity. Our study suggests that a drastic wetting transition occurs on superhydrophobic surfaces at the nanometre scale; i.e., the transition between the Cassie-Baxter and Wenzel wetting states will occur as the liquid-solid-air composite interface collapses around nanoscale structures. Consequently, water adheres tightly to the surface by penetrating into the nanostructure. The droplet adhesion mechanism presented in

  13. Roughness of human enamel surface submitted to different prophylaxis methods.

    PubMed

    Castanho, Gisela Muassab; Arana-Chavez, Victor E; Fava, Marcelo

    2008-01-01

    The purpose of this in vitro study was to evaluate alterations in the surface roughness and micromorphology of human enamel submitted to three prophylaxis methods. Sixty-nine caries-free molars with exposed labial surfaces were divided into three groups. Group I was treated with a rotary instrument set at a low speed, rubber cup and a mixture of water and pumice; group II with a rotary instrument set at a low speed, rubber cup and prophylaxis paste Herjos-F (Vigodent S/A Indústria e Comércio, Rio de Janeiro, Brazil); and group III with sodium bicarbonate spray Profi II Ceramic (Dabi Atlante Indústrias Médico Odontológicas Ltda, Ribeirão Preto, Brazil). All procedures were performed by the same operator for 10 s, and samples were rinsed and stored in distilled water Pre and post-treatment surface evaluation was completed using a surface profilometer (Perthometer S8P, Marh, Perthen, Germany) in 54 samples. In addition, the other samples were coated with gold and examined in a scanning electron microscope (SEM). The results of this study were statistically analyzed with the paired t-test (Student), the Kruskal-Wallis test and the Dunn (5%) test. The sodium bicarbonate spray led to significantly rougher surfaces than the pumice paste. The use of prophylaxis paste showed no statistically significant difference when compared with the other methods. Based on SEM analysis, the sodium bicarbonate spray presented an irregular surface with granular material and erosions. Based on this study, it can be concluded that there was an increased enamel surface roughness when teeth were treated with sodium bicarbonate spray when compared with teeth treated with pumice paste. PMID:18767461

  14. Roughness of human enamel surface submitted to different prophylaxis methods.

    PubMed

    Castanho, Gisela Muassab; Arana-Chavez, Victor E; Fava, Marcelo

    2008-01-01

    The purpose of this in vitro study was to evaluate alterations in the surface roughness and micromorphology of human enamel submitted to three prophylaxis methods. Sixty-nine caries-free molars with exposed labial surfaces were divided into three groups. Group I was treated with a rotary instrument set at a low speed, rubber cup and a mixture of water and pumice; group II with a rotary instrument set at a low speed, rubber cup and prophylaxis paste Herjos-F (Vigodent S/A Indústria e Comércio, Rio de Janeiro, Brazil); and group III with sodium bicarbonate spray Profi II Ceramic (Dabi Atlante Indústrias Médico Odontológicas Ltda, Ribeirão Preto, Brazil). All procedures were performed by the same operator for 10 s, and samples were rinsed and stored in distilled water Pre and post-treatment surface evaluation was completed using a surface profilometer (Perthometer S8P, Marh, Perthen, Germany) in 54 samples. In addition, the other samples were coated with gold and examined in a scanning electron microscope (SEM). The results of this study were statistically analyzed with the paired t-test (Student), the Kruskal-Wallis test and the Dunn (5%) test. The sodium bicarbonate spray led to significantly rougher surfaces than the pumice paste. The use of prophylaxis paste showed no statistically significant difference when compared with the other methods. Based on SEM analysis, the sodium bicarbonate spray presented an irregular surface with granular material and erosions. Based on this study, it can be concluded that there was an increased enamel surface roughness when teeth were treated with sodium bicarbonate spray when compared with teeth treated with pumice paste.

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

    NASA Technical Reports Server (NTRS)

    Stahl, Mark T.

    2015-01-01

    Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces grinding saving both time and money and allows the science requirements to be better defined. In this study various materials are polished from a fine grind to a fine polish. Each sample's RMS surface roughness is measured at 81 locations in a 9x9 square grid using a Zygo white light interferometer at regular intervals during the polishing process. Each data set is fit with various standard distributions and tested for goodness of fit. We show that the skew in the RMS data changes as a function of polishing time.

  16. Radar, visual and thermal characteristics of Mars - Rough planar surfaces

    NASA Technical Reports Server (NTRS)

    Schaber, G. G.

    1980-01-01

    High-resolution Viking Orbiter images contain significant information on Martian surface roughness at 25- to 100-m lateral scales, while 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 are qualitatively confirmed by the Viking image data. Large-scale, curvilinear 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 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.

  17. Influence of Surface Roughness in Electron Beam Welding

    NASA Astrophysics Data System (ADS)

    Wiednig, C.; Stiefler, F.; Enzinger, N.

    2016-03-01

    The requirements of welded components are rising continuously through increasing demands in engineering. But in engineering not only the quality of welds is important also an economic and timesaving production is crucial. Especially in welding of large cross sections economization potential is existing and significant. Beside the welding technique itself the joint preparation is a major part of work. Electron beam welding has some major advantages in this area. Due the high energy density a very short welding time as well as a small heat affected zone can be achieved. Furthermore the joint preparation can be held simple. Nevertheless, a careful machining and cleaning of the joint surfaces is recommended in literature. In addition to geometric tolerances a specific surface roughness should be kept. These statements are quite general and unspecific. In this contribution a systematic investigation on the influence of joint preparation on the joint properties is presented. By performing several welding experiments with different surface roughness this study provides empirical conclusions. Beside the microscopic investigation of different cross sections and mechanical tests of the welded samples also the process stability during welding was reviewed.

  18. The Turbulent Boundary Layer on a Rough Curvilinear Surface

    NASA Technical Reports Server (NTRS)

    Droblenkov, V. F.

    1958-01-01

    A number of semiempirical approximate methods exist for determining the characteristics of the turbulent boundary layer on a curvilinear surface. At present, among these methods, the one proposed by L. G. Loitsianskii is given frequent practical application. This method is sufficiently effective and permits, in the case of wing profiles with technically smooth surfaces, calculating the basic characteristics of the boundary layer and the values of the overall drag with an accuracy which suffices for practical purposes. The idea of making use of the basic integral momentum equation ((d delta(sup xx))/dx) + ((V' delta(sup xx))/V) (2 + H) = (tau(sub 0))/(rho V(exp 2)) proves to be fruitful also for the solution of the problems in the determination of the characteristics of the turbulent boundary layer on a rough surface.

  19. Surface roughness measurement of tooling spheres for laser measurements

    NASA Astrophysics Data System (ADS)

    Sarr, Dennis P.; Reed, Paul W.

    2001-02-01

    The usage of chrome or highly polished precision tooling (reference) spheres is common in the calibration and operational characterization of measurement systems such as a Coordinate Measurement Machine (CMM). The usage of a three-dimensional, (3D) laser triangulation, non-contact measurement system on CMMs and other scanning systems pose several obstacles. The highly specular mirror finish on the tooling sphere provides an accurate mechanical entity that has adverse results with laser sensors. The development of tooling spheres with a diffuse surface would benefit laser based measurement systems. The surface roughness and reflectivity properties have an effect on the laser measurements' accuracy. Efforts to develop spheres and establish meaningful measurements of spheres with modified surface finishes are investigated.

  20. Role of Surface Roughness in Hysteresis during Adhesive Elastic Contact

    PubMed Central

    Kesari, Haneesh; Doll, Joseph C.; Pruitt, Beth L.; Cai, Wei; Lew, Adrian J.

    2010-01-01

    In experiments that involve contact with adhesion between two surfaces, as found in atomic force microscopy or nanoindentation, two distinct contact force (P) vs. indentation-depth (h) curves are often measured depending on whether the indenter moves towards or away from the sample. The origin of this hysteresis is not well understood and is often attributed to moisture, plasticity or viscoelasticity. Here we report experiments that show that hysteresis can exist in the absence of these effects, and that its magnitude depends on surface roughness. We develop a theoretical model in which the hysteresis appears as the result of a series of surface instabilities, in which the contact area grows or recedes by a finite amount. The model can be used to estimate material properties from contact experiments even when the measured P-h curves are not unique. PMID:21152108

  1. Leakage current in quantum-cascade lasers through interface roughness scattering

    NASA Astrophysics Data System (ADS)

    Flores, Y. V.; Kurlov, S. S.; Elagin, M.; Semtsiv, M. P.; Masselink, W. T.

    2013-10-01

    The impact of interface roughness (IFR)-scattering on the quantum efficiency of quantum-cascade lasers (QCLs) is demonstrated and analyzed both experimentally and theoretically. An InGaAs/InAlAs strain-compensated QCL emitting at λ ˜ 5.4 μm is analyzed in pulsed mode at liquid nitrogen temperatures. Measurements of the differential slope efficiency as a function of laser resonator length allow the pumping efficiency to be measured as a function of electron temperature. Excellent agreement is obtained when comparing the data to a calculation of the leakage current into higher-lying states via IFR-scattering, providing evidence of the importance of IFR-scattering on the QCLs quantum efficiency.

  2. Single-scatter vector-wave scattering from surfaces with infinite slopes using the Kirchhoff approximation.

    PubMed

    Bruce, Neil C

    2008-08-01

    This paper presents a new formulation of the 3D Kirchhoff approximation that allows calculation of the scattering of vector waves from 2D rough surfaces containing structures with infinite slopes. This type of surface has applications, for example, in remote sensing and in testing or imaging of printed circuits. Some preliminary calculations for rectangular-shaped grooves in a plane are presented for the 2D surface method and are compared with the equivalent 1D surface calculations for the Kirchhoff and integral equation methods. Good agreement is found between the methods.

  3. Effects of surface roughness on evaporation from porous surfaces into turbulent airflows

    NASA Astrophysics Data System (ADS)

    Haghighi, Erfan; Or, Dani

    2014-05-01

    The ubiquitous and energy intensive mass transfer between wet porous surfaces and turbulent airflows is of great importance for various natural and industrial applications. The roughness of natural surfaces is likely to influence the structure of adjacent boundary layer and thus affecting heat and mass fluxes from surfaces. These links were formalized in a new model that considers the intermittent turbulence-induced boundary layer with local mass and energy exchange rates. We conducted experiments with regular surface roughness patterns subjected to constant turbulent airflows and monitored mass loss and thermal signatures of localized evaporative fluxes using infrared thermography. The resulting patterns were in good agreement with model predictions for local and surface averaged turbulent exchange rates. Preliminary results obtained for evaporation from sinusoidal wavy soil surfaces reveal that evaporative fluxes can be either enhanced or suppressed (relative to a flat surface) owing to relative contribution of downstream (separation zone) and rising (reattachment zone) surfaces of the wave with thick and thin viscous sublayer thicknesses, respectively. For isolated roughness elements (bluff bodies) over a flat evaporating surface, the resulting fluxes are enhanced (relative to a smooth surface) due to formation of vortices that induce thinner boundary layer. Potential benefits of the study for interpretation and upscaling of evaporative and heat fluxes from natural (rough) terrestrial surfaces will be discussed. Keywords: Turbulent Evaporation, Porous Media, Surface Roughness, Infrared Thermography.

  4. Correlation between x-ray reflectivity measurements and surface roughness of AXAF coated witness samples

    NASA Astrophysics Data System (ADS)

    Clark, Anna M.; Bruni, Ricardo J.; Romaine, Suzanne E.; Schwartz, Daniel A.; van Speybroeck, Leon P.; Yip, P. W.; Drehman, A. J.; Shapiro, Alan P.

    1996-07-01

    One of the specifications used to polish the AXAF witness samples was that the rms surface roughness be scatter to a minimum. However, it is not necessarily the best indication of the expected performance of the soft x-ray reflectivity of the surfaces. In particular, the reflectivity data from the AXAF flight optic witness samples indicate sample to sample differences of a few percent which do not correlate with the optical profilometry results for these samples. Further investigations were carried out to measure rms surface roughness using atomic force microscopy (AFM). The differences shown by AFM surface roughness measurements correlates to differences found in reflectivity for these same samples. One-dimensional power spectral density data is presented from both AFM and WYKO measurements along with the reflectivity results at 8 keV for the AXAF witness samples. The results indicate that to obtain accurate prediction of x-ray performance it is necessary to look at the scanning probe metrology data provided by the AFM, in addition to the optical profilometry data.

  5. On the effect of surface roughness and frequency on the planetary radar echo

    NASA Astrophysics Data System (ADS)

    Virkki, Anne

    2016-10-01

    Planetary radar is a strong tool for revealing surface properties of near-Earth asteroids, such as the geometric composition, or surface roughness, with implications on the chemical composition. For some asteroids and comets visited with spacecrafts, local variations of the size distribution of surface particles have been observed (Michikami et al., Earth Planets Space 60, 2008). The variations can be observed using radar through variations of circular-polarization ratio (Virkki et al. In Asteroids, Comets, Meteors 2014, 2014).We model radar scattering by planetary surfaces using an algorithm of geometric optics with Fresnelian reflections and refractions as well as diffuse scattering (Muinonen et al., JQSRT 110, 2009). Previously, we have shown the effect of various surface properties, such as the material, geometry, and size of the scatterers, e.g., wavelength-scale boulders on the asteroid surface, on the observed radar albedo and circular-polarization ratio when a power-law (r-3) size distribution of irregular particles is used (Virkki and Muinonen, Icarus 269, 2016). In this study, we show how different size distributions affect the radar albedo and circular-polarization ratio. Also, we discuss the effect that the choice of the observation frequency (2380 or 8560 MHz) may have on the echo. As materials, we compare different types of rock and ice.

  6. Variation of soil surface roughness under simulated rainfall

    NASA Astrophysics Data System (ADS)

    Tarquis, A. M.; Saa-Requejo, A.; Valencia, J. L.; Moratiel, R.; Paz-Gonzalez, A.

    2012-04-01

    Soil surface micro-topography or roughness (SSR) defines the physical boundary between overland flow and soil. Due to its unique position, soil roughness potentially affects surface processes such as infiltration, flow routing, erosion and sedimentation. Thus the decay of SSR under different rainfall intensities is of most interest in soil erosion. While some authors have chosen exponent function of cumulative rainfall to describe the decay of SSR, others have used the kinetic energy of rainfall. SSR at the field level is an easy visually perceptible notion, but difficult to describe numerically. In this study we didn't use pin-meter or laser techniques to quantify SSR. Percentage of micro-topographic shadows, under fixed sunlight conditions, has been applied based on former works that proved it is an easy and reliable method to estimate SSR. Two experimental plots, of 1m x 1m, were subjected to successive simulated rainfall events with an intensity of 67 mm/h and a height of 2 m. Both plots were a harrowed plot with an oriented roughness and 6% slope. Images were obtained each 15 minutes of rainfall with an incident angle of light of 45° approximately. The image was acquired by an OLYMPUS X-925, having a size of 2976x3968 pixels and corresponding to an area of 75 cm x 100 cm. For denoising process, the image was cropped to 590x800 pixels and for image binarization Indicator Kriging (IK) method was used. Comparisons of both plots respect to SSR evolution, runoff accumulation and shadows morphology are showed. Acknowledgements Funding provided by Spanish Ministerio de Ciencia e Innovación (MICINN) through project no. AGL2010-21501/AGR is greatly appreciated.

  7. The Global Surface Roughness of 433 Eros from the NEAR-Shoemaker Laser Altimeter (NLR)

    NASA Astrophysics Data System (ADS)

    Meyer Susorney, Hannah Celine; Barnouin, Olivier S.

    2016-10-01

    Surface roughness is the quantitative measure of the change in topography at a given scale. Previous studies have used surface roughness to map geologic units, choose landing sites, and understand the relative contribution of different geologic processes to topography. In this study we focus on understanding how surface roughness is linked to the geologic processes acting on asteroids, with a case study of 433 Eros through the generation of global surface roughness maps. The scale that surface roughness is measured at will dictate the geologic processes studied; the majority of studies of the surface roughness of asteroids have focused on centimeter scale roughness (derived from radar measurements). Spacecraft that rendezvous with asteroids and carry laser altimeters on board provide topographic data that allows surface roughness to be measured at the scale of meters to hundreds of meters.To calculate surface roughness on 433 Eros from 1 m to 300 m, we use the Near Earth Asteroid Rendezvous (NEAR)-Shoemaker's laser altimeter (NLR). We measure surface roughness as Root-Mean Square (RMS) deviation, which is simply the RMS difference in height over a given scale. RMS deviation is then used to calculate the Hurst exponent, which quantifies the fractal behavior of the surface and is indicative of the type of geologic processes controlling topography at that scale. The surface roughness on 433 Eros varies regionally, with smaller roughness values where regolith has accumulated, and more elevated roughness values along the walls of large craters or near linear grooves. The roughness seen in crater walls may be evidence for subsurface structures (visible as aligned blocks protruding from the crater walls). The surface roughness of 433 Eros is also remarkably fractal relative to other asteroids and planets. To understand in greater detail the geological origin of the surface roughness and fractal nature of Eros, this study presents the first global maps of surface roughness

  8. Grazing-incidence small-angle X-ray scattering in a twofold rough-interface medium: a new theoretical approach using the q-eigenwave formalism.

    PubMed

    Chukhovskii, F N; Roshchin, B S

    2015-11-01

    Based on the rigorous Green function formalism to describe the grazing-incidence small-angle X-ray scattering (GISAXS) problem, a system of two linked integral equations is derived with respect to amplitudes of the reflected and transmitted plane q-eigenwaves (eigenstate functions) propagating through two homogeneous media separated from each other by a rough surface interface. To build up the coupled solutions of these basic equations beyond the perturbation theory constraint 2kσθ0 < 1, a simple iteration procedure is proposed as opposed to the self-consistent wave approach [Chukhovskii (2011). Acta Cryst. A67, 200-209; Chukhovski (2012). Acta Cryst. A68, 505-512]. Using the first-order iteration, analytical expressions for the averaged specular and non-specular scattering intensity distributions have been obtained. These expressions are further analysed in terms of the GISAXS parameters {k, θ, θ0} and surface finish ones {σ, l, h}, where θ and θ0 are the scattering and incidence angles of the X-rays, respectively, σ is the root-mean-square roughness, l is the correlation length, h is the fractal surface model index, k = 2π/λ, and λ is the X-ray wavelength. A direct way to determine the surface finish parameters from the experimental specular and diffuse scattering indicatrix scan data is discussed for an example of GISAXS measurements from rough surfaces of α-quartz and CdTe samples. PMID:26522410

  9. The effect of surface roughness on Triton's volatile distribution

    NASA Technical Reports Server (NTRS)

    Yelle, Roger V.

    1992-01-01

    Calculations of radiative equilibrium temperatures on Triton's rough surface suggest that significant condensation of N2 may be occurring in the northern equatorial regions, despite their relatively dark appearance. The bright frost is not apparent in the Voyager images because it tends to be concentrated in relatively unilluminated facets of the surface. This patchwork of bright frost-covered regions and darker bare ground may be distributed on scales smaller than that of the Voyager resolution; as a result the northern equatorial regions may appear relatively dark. This hypothesis also accounts for the observed wind direction in the Southern Hemisphere because it implies that the equatorial regions are warmer than the south polar regions.

  10. Tennis ball fuzziness: assessing textile surface roughness using digital imaging

    NASA Astrophysics Data System (ADS)

    Steele, C.; Jones, R.; Leaney, P. G.

    2006-06-01

    Wear plays an important role in the game of tennis as it affects both ball performance and player perceived ball quality. Visual appearance can be used in ball differentiation, but has so far been limited to subjective assessments used to estimate ball wear and performance characteristics. A metric for ball surface condition will allow performance and perception data from varied testing set-ups to be objectively compared and analysed. A versatile new method of assessing surface roughness using digital imaging has been developed to allow the quantitative assessment of tennis ball condition. This metric allows manufacturers and researchers to predict ball performance and player perception from worn ball samples, developing acceptable wear limits. In the successful implementation of this metric, several key factors, including lighting, image thresholding, algorithm implementation and camera specifications, were identified to aid future alternative implementations.

  11. Using ASTER Stereo Images to Quantify Surface Roughness

    NASA Astrophysics Data System (ADS)

    Mushkin, Amit; Gillespie, Alan

    The unresolved topographic expression of surfaces, surface roughness (SR), is a fundamental surface property that conveys useful information for a wide range of Earth and planetary sciences. Yet, this information is difficult to measure remotely because most spaceborne imagers have resolutions on the order of meters to hundreds of meters and SR can vary significantly below these scales. One way to measure SR is to exploit differential shadowing in stereo images, and in particular, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), with its nadir (3N) and backward-looking (3B) near-infrared channels. We have proposed a simple ratio of land-leaving radiance in those two channels as a measure of relative SR at scales <15 m/pixel. This "two-look" relative SR measure is simple, robust, and insensitive to atmospheric conditions, and thus ASTER 3B/3N ratio images are suggested as a useful and readily accessible tool for photo-interpretation. Moreover, one could calibrate the ratio data to physical parameters, such as RMS height, and translate to SR maps at 15 m/pixel resolution. Two calibration schemes enable this translation: empirical calibration against independent in situ roughness measurements and model-based calibration against forward simulations of ­two-look ratios from very high-resolution (<5 mm) digital elevation models of natural ­surfaces, measured with a ground-based light detection and ranging ­system. Here, we focus on the latter scheme that enables construction of calibration curves for any given viewing and illumination geometries encountered by ASTER. ASTER now ­provides a global archive of images, and the two-look approach with ASTER stereo data enables a unique quantitative mapping capability of SR at 15 m/pixel spatial resolution for almost anywhere on Earth.

  12. Texture descriptions of lunar surface derived from LOLA data: Kilometer-scale roughness and entropy maps

    NASA Astrophysics Data System (ADS)

    Li, Bo; Ling, Zongcheng; Zhang, Jiang; Chen, Jian; Wu, Zhongchen; Ni, Yuheng; Zhao, Haowei

    2015-11-01

    The lunar global texture maps of roughness and entropy are derived at kilometer scales from Digital Elevation Models (DEMs) data obtained by Lunar Orbiter Laser Altimeter (LOLA) aboard on Lunar Reconnaissance Orbiter (LRO) spacecraft. We use statistical moments of a gray-level histogram of elevations in a neighborhood to compute the roughness and entropy value. Our texture descriptors measurements are shown in global maps at multi-sized square neighborhoods, whose length of side is 3, 5, 10, 20, 40 and 80 pixels, respectively. We found that large-scale topographical changes can only be displayed in maps with longer side of neighborhood, but the small scale global texture maps are more disorderly and unsystematic because of more complicated textures' details. Then, the frequency curves of texture maps are made out, whose shapes and distributions are changing as the spatial scales increases. Entropy frequency curve with minimum 3-pixel scale has large fluctuations and six peaks. According to this entropy curve we can classify lunar surface into maria, highlands, different parts of craters preliminarily. The most obvious textures in the middle-scale roughness and entropy maps are the two typical morphological units, smooth maria and rough highlands. For the impact crater, its roughness and entropy value are characterized by a multiple-ring structure obviously, and its different parts have different texture results. In the last, we made a 2D scatter plot between the two texture results of typical lunar maria and highlands. There are two clusters with largest dot density which are corresponded to the lunar highlands and maria separately. In the lunar mare regions (cluster A), there is a high correlation between roughness and entropy, but in the highlands (Cluster B), the entropy shows little change. This could be subjected to different geological processes of maria and highlands forming different landforms.

  13. On the Mean Flow Behaviour in the Presence of Regional-Scale Surface Roughness Heterogeneity

    NASA Astrophysics Data System (ADS)

    Yang, Xiang I. A.

    2016-10-01

    A suite of large-eddy simulations of the neutral atmospheric boundary layer is conducted to study the mean flow response to the presence of surface roughness heterogeneity at regional scales (surface roughness heterogeneity on the scale of several boundary-layer heights). The roughness heterogeneity is imposed using alternating rough wall patches with numerically resolved rectangular roughness elements of different packing densities. The flow near the surface is found to adjust rapidly, reaching equilibrium conditions at distances on the order of a single inter-roughness element spacing. Despite the regional heterogeneity in surface roughness, it is often desirable to parametrize the entire rough wall using one single effective roughness height. To develop such a parametrization the model of Bou-Zeid et al. [Water Resources Research 40(2):1, 2004] is extended to incorporate the displacement height, d. Predictions from this parametrization are compared with the simulations, with reasonably good agreement.

  14. On the Mean Flow Behaviour in the Presence of Regional-Scale Surface Roughness Heterogeneity

    NASA Astrophysics Data System (ADS)

    Yang, Xiang I. A.

    2016-05-01

    A suite of large-eddy simulations of the neutral atmospheric boundary layer is conducted to study the mean flow response to the presence of surface roughness heterogeneity at regional scales (surface roughness heterogeneity on the scale of several boundary-layer heights). The roughness heterogeneity is imposed using alternating rough wall patches with numerically resolved rectangular roughness elements of different packing densities. The flow near the surface is found to adjust rapidly, reaching equilibrium conditions at distances on the order of a single inter-roughness element spacing. Despite the regional heterogeneity in surface roughness, it is often desirable to parametrize the entire rough wall using one single effective roughness height. To develop such a parametrization the model of Bou-Zeid et al. [Water Resources Research 40(2):1, 2004] is extended to incorporate the displacement height, d. Predictions from this parametrization are compared with the simulations, with reasonably good agreement.

  15. The SIR-B observations of microwave backscatter dependence on soil moisture, surface roughness, and vegetation covers

    NASA Technical Reports Server (NTRS)

    Wang, J. R.; Shiue, J. C.; Engman, E. T.; Rusek, M.; Steinmeier, C.

    1986-01-01

    An experiment was conducted from an L-band SAR aboard Space Shuttle Challenger in October 1984 to study the microwave backscatter dependence on soil moisture, surface roughness, and vegetation cover. The results based on the analyses of an image obtained at 21-deg incidence angle show a positive correlatlion between scattering coefficient and soil moisture content, with a sensitivity comparable to that derived from the ground radar measurements reported by Ulaby et al. (1978). The surface roughness strongly affects the microwave backscatter. A factor of two change in the standard deviation of surface roughness height gives a corresponding change of about 8 dB in the scattering coefficient. The microwave backscatter also depends on the vegetation types. Under the dry soil conditions, the scattering coefficient is observed to change from about -24 dB for an alfalfa or lettuce field to about -17 dB for a mature corn field. These results suggest that observations with a SAR system of multiple frequencies and polarizations are required to unravel the effects of soil moisture, surface roughness, and vegetation cover.

  16. Classical And Quantum Rainbow Scattering From Surfaces

    SciTech Connect

    Winter, H.; Schueller, A.; Busch, M.; Seifert, J.; Wethekam, S.

    2011-06-01

    The structure of clean and adsorbate covered surfaces as well as of ultrathin films can be investigated by grazing scattering of fast atoms. We present two recent experimental techniques which allow one to study the structure of ordered arrangements of surface atoms in detail. (1) Rainbow scattering under axial surface channeling conditions, and (2) fast atom diffraction. Our examples demonstrate the attractive features of grazing fast atom scattering as a powerful analytical tool in studies on the structure of surfaces. We will concentrate our discussion on the structure of ultrathin silica films on a Mo(112) surface and of adsorbed oxygen atoms on a Fe(110) surface.

  17. Surface wave dispersion from small vertical scatterers

    NASA Astrophysics Data System (ADS)

    van Wijk, K.; Levshin, A. L.

    2004-10-01

    Heterogeneity in the subsurface creates conflicting types of dispersion of seismic waves. A laboratory and numerical experiment show that multiple scattering of elastic waves from isolated heterogeneities near the surface not only attenuates, but also delays coherent events. Because scattering off these impedance contrasts is frequency dependent, multiple scattering is a source of dispersion. If ignored, multiple scattering dispersion could be erroneously attributed to a model with horizontal homogeneous layers of different wave speeds.

  18. 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.

  19. A numerical study of electromagnetic scattering from ocean like surfaces

    NASA Technical Reports Server (NTRS)

    Lentz, R. R.

    1972-01-01

    The integral equations describing electromagnetic scattering from one dimensional conducting surfaces are formulated and numerical results are presented. The results are compared with those obtained using approximate methods such as physical optics, geometrical optics, and perturbation theory. The integral equation solutions show that the surface radius of curvature must be greater than 2.5 wavelengths for either the physical optics or geometric optics to give satisfactory results. It has also been shown that perturbation theory agrees with the exact fields as long as the root mean square surface roughness is less than one-tenth of a wavelength.

  20. Dynamics of Wetting and Wicking on Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Antao, Dion; Preston, Daniel; Adera, Solomon; Zhu, Yangying; Wang, Evelyn

    Micro/nano engineering of surfaces to enhance the performance of phase-change heat transfer processes has recently gained wide interest. Interfacial phenomena at the micro/nanoscale play an important role in defining the dynamic wetting and wicking characteristics of the surfaces. Here we report experiments that characterize the dynamic wetting and wicking processes on microstructured silicon surfaces. We investigated cylindrical micropillar arrays in a square pattern with various diameter, pitch, and height to characterize key interfacial behavior over a wide range of surface roughness. The experiments were performed by dipping the microstructured sample vertically into a reservoir of de-ionized water and the spreading dynamics were captured with a high speed camera. We observed that both wetting and wicking exhibit a power law dependence on time, however they occur at different time scales. The instantaneous (~10-100 ms) wetting behavior occurs due to the interfacial tensions, and the resultant force acting at the three-phase contact line. The longer time scale (>100 ms) wicking behavior results from the balance of the capillary pressure generated within the microstructure and the viscous pressure loss from flow through the micropillar array. We develop analytical models to predict these different time scale behavior and compare them to experimental results. This work provides insight into key dynamic processes affecting micro/nanostructure enhanced phase-change heat transfer devices.

  1. Enhancement of Friction against a Rough Surface by a Ridge-Channel Surface Microstructure.

    PubMed

    Bai, Ying; Hui, Chung-Yuen; Levrard, Benjamin; Jagota, Anand

    2015-07-14

    We report on a study of the sliding friction of elastomeric surfaces patterned with ridges and channels (and unstructured flat controls), against both smooth and roughened spherical indenters. Against the smooth spherical indenter, all of the structured surfaces have highly reduced sliding friction due to the reduction in actual area of contact. Against roughened spherical indenters, however, the sliding force for structured samples can be up to 50% greater than that of an unstructured flat control. The mechanism of enhanced friction against a rough surface is due to a combination of increased actual area of contact, interlocking between roughness and the surface structure, and attendant dynamic instabilities that dissipate energy.

  2. Measurement of defects by measuring of light scattering from surfaces using focused illumination

    NASA Astrophysics Data System (ADS)

    Rodríguez-Núñez, O.; Bruce, Neil C.

    2016-04-01

    Light scattering has been used as a method of characterizing material or surface roughness in different areas of the science and technology, usually the surface is illuminated with light and the pattern of scattering is measured above the surface. In the literature, the scattered light has been measured using an incident beam with a diameter on the order of a few cm for surfaces with roughness scales of the order of microns, mainly to avoid problems with the speckle pattern of light. However, this kind of measurement does not give information on local variations in roughness or defects present in the sample. Also, it has been reported in many studies that the polarization of the scattered light is affected by the surface material and roughness. In this paper we present a novel experimental device used to identify local defects on surfaces by the measurement of the scattered light pattern using laser light focused onto the surface. We present results of experimental measurements for two surfaces with roughness and defects of the order of 6 to 60 microns using sizes of incident beam of the same order and we compare the results of experimental cases with results of numerical calculation based on the Kirchhoff Approximation of light scattering by rough surfaces. We include preliminary results from the effect on the pattern of light scattering as a function of the polarization state by using focused light to illuminate the surface, we calculate the Mueller matrix for the equivalent period of the surface micro-manufactured experimentally. Finally we conclude about the validity of the method.

  3. The effect of surface roughness on the fretting corrosion of 316L stainless steel biomaterial surfaces

    NASA Astrophysics Data System (ADS)

    Shenoy, Aarti

    The medical device industry is still seeking answers to the mechanically-assisted corrosion (MAC) problem, which becomes increasingly important due to modularity in design. MAC manifests in various forms, some of which are fretting corrosion, crevice corrosion and stress corrosion. Several studies have been conducted to understand the causes and the factors that affect fretting corrosion. Some of the factors are the applied load, surface potential, oxide film characteristics and solution chemistry near the interface. Surface properties such as surface roughness determine the topography of the surface and the nature of asperity-asperity contact, which is a factor that would determine the mechanically assisted corrosion behavior of the interface, like the stem-neck and head-neck taper junctions in modular hip replacement devices. This study aims to understand the correlation between surface roughness of 316L stainless steel samples and fretting corrosion behavior using a variable load pin-on-disc test. It was found that the smoother surfaces are associated with lower fretting currents. However, smoother surfaces also created the conditions for fretting initiated crevice corrosion to occur more readily. Fretting corrosion regimes and the severity are thus dependent upon the surface roughness. A possible explanation could be due to the inverse relationship between the interasperity distance parameter, Delta, and fretting currents. The coefficient of friction between the two surfaces in contact however remained unaffected by surface roughness, but decreased with increasing load. Smoother surfaces, while lowering fretting corrosion reactions can enhance crevice corrosion reactions in 316L stainless steel interfaces.

  4. Development of sol-gel icephobic coatings: effect of surface roughness and surface energy.

    PubMed

    Fu, Qitao; Wu, Xinghua; Kumar, Divya; Ho, Jeffrey W C; Kanhere, Pushkar D; Srikanth, Narasimalu; Liu, Erjia; Wilson, Peter; Chen, Zhong

    2014-12-10

    Sol-gel coatings with different roughness and surface energy were prepared on glass substrates. Methyl triethoxysilane (MTEOS), 3-Glycidyloxypropyl trimethoxysilane (GLYMO) and fluoroalkylsilane (FAS) were used to obtain a mechanically robust icephobic coating. Different amount of hydrophobic silica nano particles was added as fillers to introduce different roughness and surface energy to the coatings. The microstructure, roughness, and surface energy, together with elemental information and surface chemical state, were investigated at room temperature. The contact angle and sliding angle were measured at different temperatures to correlate the wetting behavior at low temperature with the anti-icing performance. The ice adhesion shear strength was measured inside an ice chamber using a self-designed tester. The factors influencing the ice adhesion were discussed, and the optimum anti-icing performance found in the series of coatings. It was found that lower surface energy leads to lower ice adhesion regardless of the roughness, while the roughness plays a more complicated role. The wetting behavior of the droplet on surface changes as temperature decreases. The anti-icing performance is closely related to the antiwetting property of the surfaces at subzero temperatures.

  5. Fractal reconstruction of rough membrane surface related with membrane fouling in a membrane bioreactor.

    PubMed

    Zhang, Meijia; Chen, Jianrong; Ma, Yuanjun; Shen, Liguo; He, Yiming; Lin, Hongjun

    2016-09-01

    In this paper, fractal reconstruction of rough membrane surface with a modified Weierstrass-Mandelbrot (WM) function was conducted. The topography of rough membrane surface was measured by an atomic force microscopy (AFM), and the results showed that the membrane surface was isotropous. Accordingly, the fractal dimension and roughness of membrane surface were calculated by the power spectrum method. The rough membrane surface was reconstructed on the MATLAB platform with the parameter values acquired from raw AFM data. The reconstructed membrane was much similar to the real membrane morphology measured by AFM. The parameters (including average roughness and root mean square (RMS) roughness) associated with membrane morphology for the model and real membrane were calculated, and a good match of roughness parameters between the reconstructed surface and real membrane was found, indicating the feasibility of the new developed method. The reconstructed membrane surface can be potentially used for interaction energy evaluation. PMID:27318159

  6. Fractal reconstruction of rough membrane surface related with membrane fouling in a membrane bioreactor.

    PubMed

    Zhang, Meijia; Chen, Jianrong; Ma, Yuanjun; Shen, Liguo; He, Yiming; Lin, Hongjun

    2016-09-01

    In this paper, fractal reconstruction of rough membrane surface with a modified Weierstrass-Mandelbrot (WM) function was conducted. The topography of rough membrane surface was measured by an atomic force microscopy (AFM), and the results showed that the membrane surface was isotropous. Accordingly, the fractal dimension and roughness of membrane surface were calculated by the power spectrum method. The rough membrane surface was reconstructed on the MATLAB platform with the parameter values acquired from raw AFM data. The reconstructed membrane was much similar to the real membrane morphology measured by AFM. The parameters (including average roughness and root mean square (RMS) roughness) associated with membrane morphology for the model and real membrane were calculated, and a good match of roughness parameters between the reconstructed surface and real membrane was found, indicating the feasibility of the new developed method. The reconstructed membrane surface can be potentially used for interaction energy evaluation.

  7. Surface roughness effects on the solar reflectance of cool asphalt shingles

    SciTech Connect

    Akbari, Hashem; Berdahl, Paul; Akbari, Hashem; Jacobs, Jeffry; Klink, Frank

    2008-02-17

    We analyze the solar reflectance of asphalt roofing shingles that are covered with pigmented mineral roofing granules. The reflecting surface is rough, with a total area approximately twice the nominal area. We introduce a simple analytical model that relates the 'micro-reflectance' of a small surface region to the 'macro-reflectance' of the shingle. This model uses a mean field approximation to account for multiple scattering effects. The model is then used to compute the reflectance of shingles with a mixture of different colored granules, when the reflectances of the corresponding mono-color shingles are known. Simple linear averaging works well, with small corrections to linear averaging derived for highly reflective materials. Reflective base granules and reflective surface coatings aid achievement of high solar reflectance. Other factors that influence the solar reflectance are the size distribution of the granules, coverage of the asphalt substrate, and orientation of the granules as affected by rollers during fabrication.

  8. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: A Model for Fractal Dimension of Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Li, Jian-Hua; Yu, Bo-Ming; Zou, Ming-Qing

    2009-11-01

    We report a model for the fractal dimension Ds of rough surfaces based on the fractal distribution of roughness elements on surfaces and the fractal character of surface profiles. The proposed model for the fractal dimension Ds is expressed as a function of the fractal dimensions D for conic roughness diameter/height and Dp for surface profile, maximum roughness base diameter λmax, the ratio β of conic roughness height to its base radius as well as the ratio λminλmax of the minimum to the maximal base diameter.

  9. Graphene thickness dependent adhesion force and its correlation to surface roughness

    SciTech Connect

    Pourzand, Hoorad; Tabib-Azar, Massood

    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 adhesion force measurement results.

  10. Fabrication and qualification of roughness reference samples for industrial testing of surface roughness levels below 0.5 nm Sq

    NASA Astrophysics Data System (ADS)

    Faehnle, O.; Langenbach, E.; Zygalsky, F.; Frost, F.; Fechner, R.; Schindler, A.; Cumme, M.; Biskup, H.; Wünsche, C.; Rascher, R.

    2015-08-01

    Applying reactive ion beam etching (RIBE) processes at the Leibniz Institute of Surface Modification (IOM), several reference samples to be used in industry for calibrating of roughness testing equipment have been generated with the smoothest sample featuring 0.1 nm rms Sq. Subsequently these reference samples have been measured cross-site applying atomic force microscopy (AFM), white light interferometry (WLI), Nomarski1 microscopy (NM) and scatterometry (iTIRM2) determining the appropriate range of measurable rms surface roughness for each industrial measuring device.

  11. Comparison of finite source and plane wave scattering from corrugated surfaces

    NASA Technical Reports Server (NTRS)

    Levine, D. M.

    1977-01-01

    The choice of a plane wave to represent incident radiation in the analysis of scatter from corrugated surfaces was examined. The physical optics solution obtained for the scattered fields due to an incident plane wave was compared with the solution obtained when the incident radiation is produced by a source of finite size and finite distance from the surface. The two solutions are equivalent if the observer is in the far field of the scatterer and the distance from observer to scatterer is large compared to the radius of curvature at the scatter points, condition not easily satisfied with extended scatterers such as rough surfaces. In general, the two solutions have essential differences such as in the location of the scatter points and the dependence of the scattered fields on the surface properties. The implication of these differences to the definition of a meaningful radar cross section was examined.

  12. The effect of surface roughness on the transmission of microwave radiation through a planetary surface

    NASA Technical Reports Server (NTRS)

    Golden, L. M.

    1979-01-01

    To account for surface roughness, the transmission of microwave radiation through a planetary surface to an observer is treated by a Monte Carlo technique. Sizable effects are found near the limb of the planet, and they should be included in analyses of high-resolution observations and high-precision integrated disk observations.

  13. Polarimetric passive microwave remote sensing of wind vectors with foam-covered rough ocean surfaces

    NASA Astrophysics Data System (ADS)

    Zhou, Lin; Tsang, Leung; Chen, Dong

    2003-08-01

    In this paper, polarimetric microwave emissions from wind-generated foam-covered ocean surfaces are investigated. The foam is treated as densely packed air bubbles coated with thin seawater coating. The absorption, scattering and extinction coefficients are calculated by Monte Carlo simulations of solutions of Maxwell equations of a collection of coated particles. The effects of boundary roughness of ocean surface are included by using the second-order small perturbation method (SPM) describing the reflection coefficients between foam and ocean. An empirical wavenumber spectrum is used to represent the small-scale wind-generated sea surfaces. The iterative method is employed to solve dense media radiative transfer (DMRT) equations, and is applied to calculate results of all four Stokes parameters of rough ocean surfaces. The theoretical results of four Stokes brightness temperatures with typical parameters of foam in passive remote sensing at 10.8 GHz, 19 GHz and 36.5 GHz are illustrated. The azimuth variations of polarimetric brightness temperature are calculated. Emission with various wind speed and foam layer thickness is studied. The results are also compared with those based on Quasi-Crystalline Approximation (QCA).

  14. Effect of fracture surface roughness on shear crack growth

    SciTech Connect

    Gross, T.S.; Watt, D.W. . Dept. of Mechanical Engineering); Mendelsohn, D.A. . Dept. of Engineering Mechanics)

    1992-12-01

    A model of fracture surface interference for Mode I fatigue crack profiles was developed and evaluated. Force required to open the crack faces is estimated from point contact expressions for Mode I stress intensity factor. Force transfer across contacting asperities is estimated and used to calculate Mode II resistance stress intensity factor (applied factor is sum of effective and resistance factors). Electro-optic holographic interferometry was used to measure 3-D displacement field around a Mode I fatigue pre-crack in Al loaded in Mode II shear. Induced Mode I crack face displacements were greater than Mode II displacements. Plane stress shear lip caused displacement normal to surface as the crack faces are displaced. Algorithms are being developed to track the displacements associated with the original coordinate system in the camera. A 2-D boundary element method code for mixed mode I and II loading of a rough crack (sawtooth asperity model) has been completed. Addition of small-scale crack tip yielding and a wear model are completed and underway, respectively.

  15. Flow Measurements over a Biomimetic Surface Roughness Microgeometry

    NASA Astrophysics Data System (ADS)

    Lang, Amy; Hidalgo, Pablo; Westcott, Matthew

    2007-11-01

    Certain species of sharks (e.g. shortfin mako) have a skin structure that results in a bristling of their denticles (scales) during increased swimming speeds. This unique surface geometry results in the formation of a 3D array of cavities* (d-type roughness geometry) within the shark skin, thus causing it to potentially act as a means of boundary layer control. Initial work is confined to scaling up the geometry from 0.2 mm on the shark skin to 2 cm, with a scaling down in characteristic velocity from 10 - 20 m/s to 10 - 20 cm/s for laminar flow boundary layer water tunnel studies over a shark skin model. The hypothesized formation of cavity vortices within the shark skin replica has been measured using DPIV. We have also shown that with the sufficient growth of a boundary layer upstream of the model (local Re = 200,000), transition is not tripped by the surface and the flow skips over the cavities. Support for this research by a NSF SGER grant (CTS-0630489), Lindbergh Foundation Grant and a University of Alabama RAC grant is gratefully acknowledged. * Patent pending.

  16. Influence of surface roughness on the polarimetric characteristics of a wire-grid grating polarizer.

    PubMed

    Ryu, Hojeong; Joon Yoon, Soon; Kim, Donghyun

    2008-10-20

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

  17. On the effect of surface roughness on the vapor flow under Leidenfrost-levitated droplets

    SciTech Connect

    Prat, M.; Schmitz, P.; Poulikakos, D.

    1995-09-01

    In this paper a theoretical investigation is reported on the effect of surface roughness on the phenomenon of Leidenfrost-levitation of droplets above a hot surface. The problem is solved first approximately using a macroscopic approach in which the roughness is replaced by a semi-empirical slip conditions of the Beavers-Joseph type. Next, a microscopic model which determines the vapor flow in the close vicinity of the rough surface is solved numerically. Three basic periodic roughnesses are examined: triangular, rectangular, and semi-cylindrical. The effect of the relative size of the droplet and the roughness elements on the vapor flow is investigated in the course of the study.

  18. Symmetric and asymmetric capillary bridges between a rough surface and a parallel surface.

    PubMed

    Wang, Yongxin; Michielsen, Stephen; Lee, Hoon Joo

    2013-09-01

    Although the formation of a capillary bridge between two parallel surfaces has been extensively studied, the majority of research has described only symmetric capillary bridges between two smooth surfaces. In this work, an instrument was built to form a capillary bridge by squeezing a liquid drop on one surface with another surface. An analytical solution that describes the shape of symmetric capillary bridges joining two smooth surfaces has been extended to bridges that are asymmetric about the midplane and to rough surfaces. The solution, given by elliptical integrals of the first and second kind, is consistent with a constant Laplace pressure over the entire surface and has been verified for water, Kaydol, and dodecane drops forming symmetric and asymmetric bridges between parallel smooth surfaces. This solution has been applied to asymmetric capillary bridges between a smooth surface and a rough fabric surface as well as symmetric bridges between two rough surfaces. These solutions have been experimentally verified, and good agreement has been found between predicted and experimental profiles for small drops where the effect of gravity is negligible. Finally, a protocol for determining the profile from the volume and height of the capillary bridge has been developed and experimentally verified.

  19. 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

  20. Visual and digital comparative tooth colour assessment methods and atomic force microscopy surface roughness.

    PubMed

    Grundlingh, A A; Grossman, E S; Shrivastava, S; Witcomb, M J

    2013-10-01

    This study compared digital and visual colour tooth colour assessment methods in a sample of 99 teeth consisting of incisors, canines and pre-molars. The teeth were equally divided between Control, Ozicure Oxygen Activator bleach and Opalescence Quick bleach and subjected to three treatments. Colour readings were recorded at nine intervals by two assessment methods, VITA Easyshade and VITAPAN 3D MASTER TOOTH GUIDE, giving a total of 1782 colour readings. Descriptive and statistical analysis was undertaken using a GLM test for Analysis of Variance for a Fractional Design set at a significance of P < 0.05. Atomic force micros copy was used to examine treated ename surfaces and establish surface roughness. Visual tooth colour assessment showed significance for the independent variables of treatment, number of treatments, tooth type and the combination tooth type and treatment. Digital colour assessment indicated treatment and tooth type to be of significance in tooth colour change. Poor agreement was found between visual and digital colour assessment methods for Control and Ozicure Oxygen Activator treatments. Surface roughness values increased two-fold for Opalescence Quick specimens over the two other treatments, implying that increased light scattering improved digital colour reading. Both digital and visual colour matching methods should be used in tooth bleaching studies to complement each other and to compensate for deficiencies.

  1. Rough surface wavelength measurement through self mixing of Doppler microwave backscatter. [from ocean waves

    NASA Technical Reports Server (NTRS)

    Weissman, D. E.; Johnson, J. W.

    1979-01-01

    A microwave backscatter technique is presented that has the ability to sense the dominant surface wavelength of a random rough surface. The purpose of this technique is to perform this measurement from an aircraft or spacecraft, wherein the horizontal velocity of the radar is an important parameter of the measurement system. Attention will be directed at water surface conditions for which a dominant wavelength can be defined, then the spatial variations of reflectivity will have a two dimensional spectrum that is sufficiently close to that of waves to be useful. The measurement concept is based on the relative motion between the water waves and a nadir looking radar, and the fact that while the instantaneous Doppler frequency at the receiver returned by any elementary group of scatterers on a water wave is monotonically changing, the difference in the Doppler frequency between any two scattering 'patches' stays approximately constant as these waves travel parallel to the major axis of an elliptical antenna footprint. The results of a theoretical analysis and a laboratory experiment with a continuous wave (CW) radar that encompasses several of the largest waves in the illuminated area show how the structure in the Doppler spectrum of the backscattered signal is related to the surface spectrum and its parameters in an especially direct and simple way when an incoherent envelope detector is the receiver.

  2. 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.

  3. 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. PMID:24972882

  4. 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.

  5. The effect of roughness elements on wind erosion: The importance of surface shear stress distribution

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Representation of surface roughness effects on aeolian sediment transport is a key source of uncertainty in wind erosion models. Drag partitioning schemes are used to account for roughness by scaling the soil entrainment threshold by the ratio of shear stress on roughness elements to that on the veg...

  6. Roughness Reduction in AISI 316L Stainless Steel after Surface Mechanical Attrition Treatment (SMAT)

    NASA Astrophysics Data System (ADS)

    Arifvianto, B.; Suyitno, Suyitno; Mahardika, M.

    2011-12-01

    Surface mechanical attrition treatment (SMAT) enhances the strength of metals by generating nanocrystallites at the surface layer. During the treatment, multiple impacts of milling balls are subjected to the treated surface. Consequently, the structure and roughness of the treated surface are also modified. In this paper, the effect of SMAT on the surface structure and roughness of an initially rough AISI 316L stainless steel is investigated. The SMAT was conducted for 0-20 minutes. The surface morphology, roughness, and volume loss due to the SMAT were studied. The result shows a decreasing roughness by the SMAT. An apparently deformed structure is also observed after 15 minutes of the treatment. However, no significant change in the volume loss is reported due to this treatment. Deformation by the multiple impacts is proposed to be the mechanism of the roughness reduction instead of microcutting by the milling balls during the SMAT.

  7. Obtaining Seasonal Snow Surface Roughness from Sub-Millimeter to Kilometer Scale Using Plate Photography and Mobile Laser Scanning

    NASA Astrophysics Data System (ADS)

    Anttila, K.; Manninen, T.; Kukko, A.; Kaartinen, H.; Hakala, T.; Kaasalainen, S. M.; Karjalainen, T.; Lahtinen, P.; Krooks, A.; Siljamo, N.; Riihelä, A.

    2013-12-01

    Seasonal snow surface roughness affects the brightness of snow surface and through that the albedo of Earth. It also affects the satellite and radar data of snow surfaces and the wind near the surface. The roughness depends on the direction and distance measured. We have developed a plate-photography method for measuring microscale surface roughness at a resolution of 0.01 mm. The concept is similar to the plate photography method described in Manninen et al. 2012 that can be used to study scales from millimeter to 1-meter scale. Preliminary test measurements were made in different directions daily during one week at the beginning of April 2013. The results have been analysed using multiscale parameters derived from root mean square height (Manninen et al. 1997 &2003). The method proved to be a working concept. For scales longer than one meter we have developed a mobile laser scanning based method for obtaining snow surface roughness (Kukko et al. 2013). In this method we have mounted FGI ROAMER (Kukko et al. 2007) on a sledge driven by a snow mobile. Together these methods will provide means to measure snow surface roughness from sub-millimeter to kilometer scales. Kukko, A., K. Anttila, T. Manninen, H. Kaartinen and S. Kaasalainen (subm.), Snow surface roughness from mobile laser scanning data. Kukko, A., Andrei, C.-O., Salminen, V.-M., Kaartinen, H., Chen, Y., Rönnholm, P., Hyyppä, H., Hyyppä, J., Chen, R., Haggrén, H., Kosonen, I., and Capek K. Road Environment Mapping System of the Finnish Geodetic Institute - FGI Roamer, Int. Arch. Photogramm. Remote Sens., 36, 241-247, 2007. Manninen, A.T. (1997), Surface roughness of Baltic sea ice, Journal of Geophysical Research, Oceans, 102(C1), 1119 -1139. Manninen, A.T. (2003), Multiscale surface roughness description for scattering modeling of bare soil, Physica A, 319, 535 - 551. Manninen, T., K. Anttila, T. Karjalainen, and P. Lahtinen (2012), Automatic snow surface roughness estimation using digital photos

  8. Turbulent boundary layer over solid and porous surfaces with small roughness

    NASA Technical Reports Server (NTRS)

    Kong, F. Y.; Schetz, J. A.; Collier, F.

    1982-01-01

    Skin friction and profiles of mean velocity, axial and normal turbulence intensity, and Reynolds stress in the untripped boundary layer were measured directly on a large diameter, axisymmetric body with: (1) a smooth, solid surface; (2) a sandpaper-roughened, solid surface; (3) a sintered metal, porous surface; (4) a smooth, perforated titanium surface; (5) a rough solid surface made of fine, diffusion bonded screening, and (6) a rough, porous surface of the same screening. Results obtained for each of these surfaces are discussed. It is shown that a rough, porous wall simply does not influence the boundary layer in the same way as a rough solid wall. Therefore, turbulent transport models for boundary layers over porous surfaces either with or without injection or suction, must include both surface roughness and porosity effects.

  9. Electride Mediated Surface Enhanced Raman Scattering (SERS)

    NASA Technical Reports Server (NTRS)

    Anderson, Mark S. (Inventor)

    2016-01-01

    An electride may provide surface enhanced Raman scattering (SERS). The electride, a compound where the electrons serve as anions, may be a ceramic electride, such as a conductive ceramic derived from mayenite, or an organic electride, for example. The textured electride surface or electride particles may strongly enhance the Raman scattering of organic or other Raman active analytes. This may also provide a sensitive method for monitoring the chemistry and electronic environment at the electride surface. The results are evidence of a new class of polariton (i.e., a surface electride-polariton resonance mechanism) that is analogous to the surface plasmon-polariton resonance that mediates conventional SERS.

  10. Deposition of latex colloids at rough mineral surfaces: an analogue study using nanopatterned surfaces.

    PubMed

    Krishna Darbha, Gopala; Fischer, Cornelius; Michler, Alex; Luetzenkirchen, Johannes; Schäfer, Thorsten; Heberling, Frank; Schild, Dieter

    2012-04-24

    Deposition of latex colloids on a structured silicon surface was investigated. The surface with well-defined roughness and topography pattern served as an analogue for rough mineral surfaces with half-pores in the submicrometer size. The silicon topography consists of a regular pit pattern (pit diameter = 400 nm, pit spacing = 400 nm, pit depth = 100 nm). Effects of hydrodynamics and colloidal interactions in transport and deposition dynamics of a colloidal suspension were investigated in a parallel plate flow chamber. The experiments were conducted at pH ∼ 5.5 under both favorable and unfavorable adsorption conditions using carboxylate functionalized colloids to study the impact of surface topography on particle retention. Vertical scanning interferometry (VSI) was applied for both surface topography characterization and the quantification of colloidal retention over large fields of view. The influence of particle diameter variation (d = 0.3-2 μm) on retention of monodisperse as well as polydisperse suspensions was studied as a function of flow velocity. Despite electrostatically unfavorable conditions, at all flow velocities, an increased retention of colloids was observed at the rough surface compared to a smooth surface without surface pattern. The impact of surface roughness on retention was found to be more significant for smaller colloids (d = 0.3, 0.43 vs. 1, 2 μm). From smooth to rough surfaces, the deposition rate of 0.3 and 0.43 μm colloids increased by a factor of ∼2.7 compared to a factor of 1.2 or 1.8 for 1 and 2 μm colloids, respectively. For a substrate herein, with constant surface topography, the ratio between substrate roughness and radius of colloid, Rq/rc, determined the deposition efficiency. As Rq/rc increased, particle-substrate overall DLVO interaction energy decreased. Larger colloids (1 and 2 μm) beyond a critical velocity (7 × 10(-5) and 3 × 10(-6) m/s) (when drag force exceeds adhesion force) tend to detach from the surface

  11. Deposition of latex colloids at rough mineral surfaces: an analogue study using nanopatterned surfaces.

    PubMed

    Krishna Darbha, Gopala; Fischer, Cornelius; Michler, Alex; Luetzenkirchen, Johannes; Schäfer, Thorsten; Heberling, Frank; Schild, Dieter

    2012-04-24

    Deposition of latex colloids on a structured silicon surface was investigated. The surface with well-defined roughness and topography pattern served as an analogue for rough mineral surfaces with half-pores in the submicrometer size. The silicon topography consists of a regular pit pattern (pit diameter = 400 nm, pit spacing = 400 nm, pit depth = 100 nm). Effects of hydrodynamics and colloidal interactions in transport and deposition dynamics of a colloidal suspension were investigated in a parallel plate flow chamber. The experiments were conducted at pH ∼ 5.5 under both favorable and unfavorable adsorption conditions using carboxylate functionalized colloids to study the impact of surface topography on particle retention. Vertical scanning interferometry (VSI) was applied for both surface topography characterization and the quantification of colloidal retention over large fields of view. The influence of particle diameter variation (d = 0.3-2 μm) on retention of monodisperse as well as polydisperse suspensions was studied as a function of flow velocity. Despite electrostatically unfavorable conditions, at all flow velocities, an increased retention of colloids was observed at the rough surface compared to a smooth surface without surface pattern. The impact of surface roughness on retention was found to be more significant for smaller colloids (d = 0.3, 0.43 vs. 1, 2 μm). From smooth to rough surfaces, the deposition rate of 0.3 and 0.43 μm colloids increased by a factor of ∼2.7 compared to a factor of 1.2 or 1.8 for 1 and 2 μm colloids, respectively. For a substrate herein, with constant surface topography, the ratio between substrate roughness and radius of colloid, Rq/rc, determined the deposition efficiency. As Rq/rc increased, particle-substrate overall DLVO interaction energy decreased. Larger colloids (1 and 2 μm) beyond a critical velocity (7 × 10(-5) and 3 × 10(-6) m/s) (when drag force exceeds adhesion force) tend to detach from the surface

  12. The forward scattering of microwave solar radiation from a water surface

    NASA Technical Reports Server (NTRS)

    Wentz, F. J.

    1978-01-01

    The forward scattering of microwave solar radiation from both smooth and rough water surfaces is computed. The smooth surface is assumed specular, and the rough surface is represented by a two-scale surface, for which two small-scale perturbation parameters, 0.10 and 0.25, are considered. The contribution of the scattered sunlight to the antenna temperature is found using the scalar approximation, and the results are compared with radiometer measurements. The overall agreement is good, but in some cases the smooth-surface measurements are higher than the computations. This discrepancy possibly indicates an absolute calibration error or a slight misalignment of the antennas' boresights. The computations for the two perturbation parameters bracket the rough-surface measurements except when the sun's mirror image is far removed from the boresight direction. The small disagreement in this case may be due to a peaked large-scale slope distribution.

  13. [Polarization Modeling and Analysis of Light Scattering Properties of Multilayer Films on Slightly Rough Substrate].

    PubMed

    Gao, Hui; Gao, Jun; Wang, Ling-mei; Wang, Chi

    2016-03-01

    To satisfy the demand of multilayer films on polarization detection, polarized bidirectional reflectance distribution function of multilayer films on slightly rough substrate is established on the basis of first-order vector perturbation theory and polarization transfer matrix. Due to the function, light scattering polarization properties are studied under multi-factor impacts of two typical targets-monolayer anti-reflection film and multilayer high-reflection films. The result shows that for monolayer anti-reflection film, observing positions have a great influence on the degree of polarization, for the left of the peak increased and right decreased compared with the substrate target. Film target and bare substrate can be distinguished by the degree of polarization in different observation angles. For multilayer high-reflection films, the degree of polarization is significantly associated with the number and optical thickness of layers at different wavelengths of incident light and scattering angles. With the increase of the layer number, the degree of polarization near the mirror reflection area decreases. It reveals that the calculated results coincide with the experimental data, which validates the correctness and rationality of the model. This paper provides a theoretical method for polarization detection of multilayer films target and reflection stealth technology. PMID:27400497

  14. [Polarization Modeling and Analysis of Light Scattering Properties of Multilayer Films on Slightly Rough Substrate].

    PubMed

    Gao, Hui; Gao, Jun; Wang, Ling-mei; Wang, Chi

    2016-03-01

    To satisfy the demand of multilayer films on polarization detection, polarized bidirectional reflectance distribution function of multilayer films on slightly rough substrate is established on the basis of first-order vector perturbation theory and polarization transfer matrix. Due to the function, light scattering polarization properties are studied under multi-factor impacts of two typical targets-monolayer anti-reflection film and multilayer high-reflection films. The result shows that for monolayer anti-reflection film, observing positions have a great influence on the degree of polarization, for the left of the peak increased and right decreased compared with the substrate target. Film target and bare substrate can be distinguished by the degree of polarization in different observation angles. For multilayer high-reflection films, the degree of polarization is significantly associated with the number and optical thickness of layers at different wavelengths of incident light and scattering angles. With the increase of the layer number, the degree of polarization near the mirror reflection area decreases. It reveals that the calculated results coincide with the experimental data, which validates the correctness and rationality of the model. This paper provides a theoretical method for polarization detection of multilayer films target and reflection stealth technology.

  15. A method to evaluate the three-dimensional roughness of fracture surfaces in brittle geomaterials.

    PubMed

    Tatone, Bryan S A; Grasselli, Giovanni

    2009-12-01

    Conventionally, the evaluation of fracture surface roughness in brittle geomaterials, such as concrete and rock, has been based on the measurement and analysis of two-dimensional profiles rather than three-dimensional (3D) surfaces. The primary reason for doing so was the lack of tools capable of making 3D measurements. However, in recent years, several optical and mechanical measurement tools have become available, which are capable of quickly and accurately producing high resolution point clouds defining 3D surfaces. This paper provides a methodology for evaluating the surface roughness and roughness anisotropy using these 3D surface measurements. The methodology is presented step-by-step to allow others to easily adopt and implement the process to analyze their own surface measurement data. The methodology is demonstrated by digitizing a series of concrete fracture surfaces and comparing the estimated 3D roughness parameters with qualitative observations and estimates of the well-known roughness coefficient, R(s).

  16. Surface-induced resistivity of thin metallic films bounded by a rough fractal surface

    NASA Astrophysics Data System (ADS)

    Munoz, Raúl C.; Finger, Ricardo; Arenas, Claudio; Kremer, German; Moraga, Luis

    2002-11-01

    We have extended the modified formalism of Sheng, Xing, and Wang [J. Phys.: Condens. Matter 11 L299 (1999)] to allow the calculation of the conductivity of a thin metallic film bounded by a rough fractal surface. We utilized the so-called k-correlation model proposed by Palasantzas and Barnas [Phys. Rev. B 48, 14 472 (1993); 56, 7726 (1997)], to describe the height-height autocorrelation function corresponding to a self-affine roughness. This extension permits the calculation of the conductivity of the film as a function of the r.m.s. roughness amplitude δ, of the lateral correlation length ξ, of the mean free path in the bulk l, and of the roughness exponent H. We found that the degree of surface irregularity, represented by the roughness exponent H characterizing the surface, does influence the conductivity of the film, as first discovered by Palasantzas and Barnas. However, this influence manifests itself for large bulk mean free paths l~1000 nm and for large correlation lengths ξ~5 nm, in which case the conductivity of the film for H=1 exceeds by about 30% the conductivity for H=0.2, an effect which is smaller than that reported by Palasantzas and Barnas. For correlation lengths ξ below 1 nm and mean free paths l~100 nm, the influence of the roughness exponent H on the conductivity is reduced to below 10%, and for smaller mean free paths and correlation lengths the conductivity becomes insensitive to H. We also found that Mathiessen's rule is severily violated in the case of thin metallic films. The resistivity of the film coincides roughly with the surface-limited resistivity only in the case of ultrathin films t<5 nm. For thicker films 100 nm>t>5 nm, the resistivity of the film exceeds by some 20 to 30 % the value dictated by Mathiessen's rule. And conversely, the apparent surface-induced resistivity estimated assuming the validity of Mathiessen's rule, exceeds by nearly one order of magnitude the true surface-induced resistivity, except in the case of

  17. Measuring grinding surface roughness based on the sharpness evaluation of colour images

    NASA Astrophysics Data System (ADS)

    Huaian, Y. I.; Jian, L. I. U.; Enhui, L. U.; Peng, A. O.

    2016-02-01

    Current machine vision-based detection methods for metal surface roughness mainly use the grey values of images for statistical analysis but do not make full use of the colour information and ignore the subjective judgment of the human vision system. To address these problems, this paper proposes a method to measure surface roughness through the sharpness evaluation of colour images. Based on the difference in sharpness of virtual images of colour blocks that are formed on grinding surfaces with different roughness, an algorithm for evaluating the sharpness of colour images that is based on the difference of the RGB colour space was used to develop a correlation model between the sharpness and the surface roughness. The correlation model was analysed under two conditions: constant illumination and varying illumination. The effect of the surface textures of the grinding samples on the image sharpness was also considered, demonstrating the feasibility of the detection method. The results show that the sharpness is strongly correlated with the surface roughness; when the illumination and the surface texture have the same orientation, the sharpness clearly decreases with increasing surface roughness. Under varying illumination, this correlation between the sharpness and surface roughness was highly robust, and the sharpness of each virtual image increased linearly with the illumination. Relative to the detection method for surface roughness using gray level co-occurrence matrix or artificial neural network, the proposed method is convenient, highly accurate and has a wide measurement range.

  18. Improving the Surface Roughness of Pickled Steel Strip by Control of Rolling Temperature

    NASA Astrophysics Data System (ADS)

    Chang, Yao-Nan; Lin, Szu-Ning; Liou, Horng-Yih; Chang, Chu-Wei; Wu, Chia-Chan; Wang, Ying-Chun

    2013-01-01

    This investigation is to analyze the surface roughness problem of low carbon pickled steel strips from the view points of prior hot rolling conditions and the hot-rolled scales. The results showed that, compared with other parameters, the most important factor in hot rolling to affect the surface roughness was the rolling temperature. As the temperature was increased, the amount of the outer brittle α-Fe2O3 increased, leading to rough scale/substrate interface and rough surface after pickling. However, the effect of coiling temperature was almost negligible because no further rolling existed after that stage. Quantitative estimation showed that decrease in rolling temperature in this investigation reduced the surface roughness, Ra, from 1.06-1.78 μm to 0.88-1.10 μm after pickling in laboratory. Similar degree of improvement in roughness was also observed after pickling in mill.

  19. Fractal Surfaces of Molecular Crystals Mimicking Lotus Leaf with Phototunable Double Roughness Structures.

    PubMed

    Nishimura, Ryo; Hyodo, Kengo; Sawaguchi, Haruna; Yamamoto, Yoshiaki; Nonomura, Yoshimune; Mayama, Hiroyuki; Yokojima, Satoshi; Nakamura, Shinichiro; Uchida, Kingo

    2016-08-17

    Double roughness structure, the origin of the lotus effect of natural lotus leaf, was successfully reproduced on a diarylethene microcrystalline surface. Static superwater-repellency and dynamic water-drop-bouncing were observed on the surface, in the manner of natural lotus leaves. Double roughness structure was essential for water-drop-bouncing. This ability was not observed on a single roughness microcrystalline surface showing the lotus effect of the same diarylethene derivative. The double roughness structure was reversibly controlled by alternating irradiation with UV and visible light. PMID:27455376

  20. Surface-enhanced Raman scattering from surface and subsurface oxygen species at microscopically well-defined Ag surfaces

    NASA Astrophysics Data System (ADS)

    Pettinger, B.; Bao, X.; Wilcock, I. C.; Muhler, M.; Ertl, G.

    1994-03-01

    Ag(111) and Ag(110) surfaces exposed to oxygen at elevated temperatures (~800 K) exhibit strongly enhanced Raman bands at 803 and 627 cm-1 which are attributed to O atoms strongly chemisorbed on the surface (Oγ) or held in subsurface sites (Oβ), respectively. In contrast to usual experience, surface-enhanced Raman scattering is occurring here under well-defined conditions up to temperatures of 900 K which is attributed to the joint operation of delocalized electromagnetic enhancement (caused by surface roughness provided by oxygen-induced faceting) and local resonance due to the particular electronic properties of the surface sites.

  1. Massively Parallel Computation of Soil Surface Roughness Parameters on A Fermi GPU

    NASA Astrophysics Data System (ADS)

    Li, Xiaojie; Song, Changhe

    2016-06-01

    Surface roughness is description of the surface micro topography of randomness or irregular. The standard deviation of surface height and the surface correlation length describe the statistical variation for the random component of a surface height relative to a reference surface. When the number of data points is large, calculation of surface roughness parameters is time-consuming. With the advent of Graphics Processing Unit (GPU) architectures, inherently parallel problem can be effectively solved using GPUs. In this paper we propose a GPU-based massively parallel computing method for 2D bare soil surface roughness estimation. This method was applied to the data collected by the surface roughness tester based on the laser triangulation principle during the field experiment in April 2012. The total number of data points was 52,040. It took 47 seconds on a Fermi GTX 590 GPU whereas its serial CPU version took 5422 seconds, leading to a significant 115x speedup.

  2. Effects of the roughness characteristics on the wire tool surface for the electrical discharge machining properties

    SciTech Connect

    Fukuzawa, Yasushi; Yamashita, Masahide; Mamuro, Hiroaki; Yamashita, Ken; Ogata, Masayoshi

    2011-01-17

    Wire electrical discharge machining (WEDM) has been investigated to obtain the better discharge machining properties of the removal rate and the surface roughness in a few decades. Recently, it revealed that the rough tool electrodes can improve the WEDM properties for some sort of materials. In this study, the rough wire electrodes using a wet blasting method was developed and evaluated the machining performance for the insulated Si{sub 3}N{sub 4} in the WEDM processes. As the results, it could not recognize the advantage of roughness wire electrode under the high-energy condition, but it found that the electro-conductive layer thickness became thinner in comparison with those of normal wires. On the contrary, it could be obtained the better surface roughness in the low energy condition. It was supposed that the roughed wire surface generates the homogeneous dispersion discharges on the workpiece.

  3. 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.

  4. Skid resistance and surface roughness testing of historic stone surfaces: advantages and limitations

    NASA Astrophysics Data System (ADS)

    Török, Ákos

    2013-04-01

    Skid resistance tests are mostly applied for testing road surfaces and almost never applied for testing stones at cultural heritage sites. The present study focuses on the possibilities of using these techniques in assessing the surface roughness of paving stones at a historic site. Two different methods were used in a comparative way to evaluate the surface properties of various types of stones ranging from travertine to non-porous limestone and granite. The applied techniques included the use of SRT pendulum (Skid Resistance Tester) providing USRV values and a mobile equipment to analyze the surface properties (Floor Slide Control) by surface profiling and providing angle of friction. The main aims of tests were to understand the wearing of stone materials due to intense pedestrian use and to detect surface changes/surface roughness and slip resistance within few year periods. The measured loss in surface slip resistance (i.e. USRV values) was in the order of 20% for granites, while most limestones lost at least 40% in terms of USRV values. An opposite trend was detected for a porous travertine type, where the surface became rougher after years of use. The limitations of these techniques are also addressed in the paper. The tests have shown that the introduction of the use of these equipments in heritage studies provide useful information on the longevity of historic stone pavements that are open for public use.

  5. Modification of the surface state of rough substrates by two different varnishes and influence on the reflected light

    NASA Astrophysics Data System (ADS)

    Elias, Mady; René de la Rie, E.; Delaney, John K.; Charron, Eric; Morales, Kathryn M.

    2006-10-01

    Modification of the visual appearance when a rough surface is covered by a varnish is mostly attributed to the levelling of the substrate surface, which depends on the molecular weight of the varnish. The topography of varnished surfaces, however, has never been measured directly. Surfaces of varnishes applied over glass substrates of varying roughness were studied, therefore, using mechanical profilometry. Two different varnishes made with a low and a high molecular weight resin were studied. Both varnishes lower the r.m.s. roughness of the substrates and filter the high spatial frequencies. These results are amplified for the varnish containing the low molecular weight resin. The light reflected by the varnished samples is modelled from these topographical data. Its angular distribution, calculated from the probability density of slopes is presented, taking into account separately the air/varnish and the varnish/substrate interfaces. These analyses are presented in a back-scattering configuration. They show that varnishing significantly reduces the angular width of the reflected light and that this effect is magnified for the low molecular weight resin. Modelling furthermore shows that the influence of the roughness of the varnish/substrate interface is negligible in the total reflected light.

  6. Improved the Surface Roughness of Silicon Nanophotonic Devices by Thermal Oxidation Method

    NASA Astrophysics Data System (ADS)

    Shi, Zujun; Shao, Shiqian; Wang, Yi

    2011-02-01

    The transmission loss of the silicon-on-insulator (SOI) waveguide and the coupling loss of the SOI grating are determined to a large extent by the surface roughness. In order to obtain smaller loss, thermal oxidation is a good choice to reduce the surface roughness of the SOI waveguide and grating. Before the thermal oxidation, the root mean square of the surface roughness is over 11 nm. After the thermal oxidation, the SEM figure shows that the bottom of the grating is as smooth as quartz surface, while the AFM shows that the root mean square of the surface is less than 5 nm.

  7. Investigation of Surface Roughness Effect on Transition Edge Sensor Microcalorimeters Using Multilayer Readout Wiring

    NASA Astrophysics Data System (ADS)

    Kuromaru, G.; Kuwabara, K.; Miyazaki, N.; Suzuki, S.; Hosoya, S.; Koizumi, Y.; Ohashi, T.; Ishisaki, Y.; Ezoe, Y.; Yamada, S.; Mitsuda, K.; Hidaka, M.; Satoh, T.

    2016-07-01

    We are developing a transition edge sensor (TES) using multilayer readout wiring for future X-ray astronomy satellites. Although we fabricated a first full 20 × 20 pixels TES array, we could not confirm transition of the TES. Considering possible causes, we focused on surface roughness of the TES film. We checked the fabrication process steps that can influence the surface roughness step by step, and changed wiring material (Al to Nb) and also a process condition of an ion milling. As a result, we succeeded to reduce the surface roughness from 4.5 to 2.5 nm rms at 1 \\upmu m scale. However, the transition was not observed probably because the TES films in our samples with surface roughness more than {˜ }1 nm rms tend not to show the transition. Therefore, to suppress the surface roughness even more, we discuss possible process effects and mitigations.

  8. Novel Approach to Surface Plasmon Resonance: A Third Dimension in Data Interpretation Through Surface Roughness Changes.

    PubMed

    Manole, Claudiu Constantin; Pîrvu, C; Maury, F; Demetrescu, I

    2016-06-01

    In a Surface Plasmon Resonance (SPR) experiment two key parameters are classically recorded: the time and the angle of SPR reflectivity. This paper brings into focus a third key parameter: SPR reflectivity. The SPR reflectivity is proved to be related to surface roughness changes. Practical investigations on (i) gold anodizing and (ii) polypyrrole film growth in presence of oxalic acid is detailed under potentiostatic conditions. These experimental results reveal the potential of using the SPR technique to investigate real-time changes both on the gold surface, but also in the gold film itself. This extends the versatility of the technique in particular as sensitive in-situ diagnostic tool. PMID:27427713

  9. Marius Hills: Surface Roughness from LROC and Mini-RF

    NASA Astrophysics Data System (ADS)

    Lawrence, S.; Hawke, B. R.; Bussey, B.; Stopar, J. D.; Denevi, B.; Robinson, M.; Tran, T.

    2010-12-01

    The Lunar Reconnaissance Orbiter Camera (LROC) Team is collecting hundreds of high-resolution (0.5 m/pixel) Narrow Angle Camera (NAC) images of lunar volcanic constructs (domes, “cones”, and associated features) [1,2]. Marius Hills represents the largest concentration of volcanic features on the Moon and is a high-priority target for future exploration [3,4]. NAC images of this region provide new insights into the morphology and geology of specific features at the meter scale, including lava flow fronts, tectonic features, layers, and topography (using LROC stereo imagery) [2]. Here, we report initial results from Mini-RF and LROC collaborative studies of the Marius Hills. Mini-RF uses a hybrid polarimetric architecture to measure surface backscatter characteristics and can acquire data in one of two radar bands, S (12 cm) or X (4 cm) [5]. The spatial resolution of Mini-RF (15 m/pixel) enables correlation of features observed in NAC images to Mini-RF data. Mini-RF S-Band zoom-mode data and daughter products, such as circular polarization ratio (CPR), were directly compared to NAC images. Mini-RF S-Band radar images reveal enhanced radar backscatter associated with volcanic constructs in the Marius Hills region. Mini-RF data show that Marius Hills volcanic constructs have enhanced average CPR values (0.5-0.7) compared to the CPR values of the surrounding mare (~0.4). This result is consistent with the conclusions of [6], and implies that the lava flows comprising the domes in this region are blocky. To quantify the surface roughness [e.g., 6,7] block populations associated with specific geologic features in the Marius Hills region are being digitized from NAC images. Only blocks that can be unambiguously identified (>1 m diameter) are included in the digitization process, producing counts and size estimates of the block population. High block abundances occur mainly at the distal ends of lava flows. The average size of these blocks is 9 m, and 50% of observed

  10. Experimental research of surface roughness effects on highly-loaded compressor cascade aerodynamics

    NASA Astrophysics Data System (ADS)

    Chen, Shao-wen; Xu, Hao; Wang, Song-tao; Wang, Zhong-qi

    2014-08-01

    Aircraft engines deteriorate during continuous operation under the action of external factors including fouling, corrosion, and abrasion. The increased surface roughness of compressor passage walls limits airflow and leads to flow loss. However, the partial increase of roughness may also restrain flow separation and reduce flow loss. It is necessary to explore methods that will lower compressor deterioration, thereby improving the overall performance. The experimental research on the effects of surface roughness on highly loaded compressor cascade aerodynamics has been conducted in a low-speed linear cascade wind tunnel. The different levels of roughness are arranged on the suction surface and pressure surface, respectively. Ink-trace flow visualization has been used to measure the flow field on the walls of cascades, and a five-hole probe has been traversed across one pitch at the outlet. By comparing the total pressure loss coefficient, the distributions of the secondary-flow speed vector, and flow fields of various cases, the effects of surface roughness on the aerodynamics of a highly loaded compressor cascade are analyzed and discussed. The results show that adding surface roughness on the suction surface and pressure surface make the loss decrease in most cases. Increasing the surface roughness on the suction surface causes reduced flow speed near the blade, which helps to decrease mixing loss at the cascades outlet. Meanwhile, adding surface roughness on the suction surface restrains flow separation, leading to less flow loss. Various levels of surface roughness mostly weaken the flow turning capacity to various degrees, except in specific cases.

  11. Small-angle and surface scattering from porous and fractal materials.

    SciTech Connect

    Sinha, S. K.

    1998-09-18

    We review the basic theoretical methods used to treat small-angle scattering from porous materials, treated as general two-phase systems, and also the basic experimental techniques for carrying out such experiments. We discuss the special forms of the scattering when the materials exhibit mass or surface fractal behavior, and review the results of recent experiments on several types of porous media and also SANS experiments probing the phase behavior of binary fluid mixtures or polymer solutions confined in porous materials. Finally, we discuss the analogous technique of off-specular scattering from surfaces and interfaces which is used to study surface roughness of various kinds.

  12. Soil surface roughness decay in contrasting climates, tillage types and management systems

    NASA Astrophysics Data System (ADS)

    Vidal Vázquez, Eva; Bertol, Ildegardis; Tondello Barbosa, Fabricio; Paz-Ferreiro, Jorge

    2014-05-01

    Soil surface roughness describes the variations in the elevation of the soil surface. Such variations define the soil surface microrelief, which is characterized by a high spatial variability. Soil surface roughness is a property affecting many processes such as depression storage, infiltration, sediment generation, storage and transport and runoff routing. Therefore the soil surface microrelief is a key element in hydrology and soil erosion processes at different spatial scales as for example at the plot, field or catchment scale. In agricultural land soil surface roughness is mainly created by tillage operations, which promote to different extent the formation of microdepressions and microelevations and increase infiltration and temporal retention of water. The decay of soil surface roughness has been demonstrated to be mainly driven by rain height and rain intensity, and to depend also on runoff, aggregate stability, soil reface porosity and soil surface density. Soil roughness formation and decay may be also influenced by antecedent soil moisture (either before tillage or rain), quantity and type of plant residues over the soil surface and soil composition. Characterization of the rate and intensity of soil surface roughness decay provides valuable information about the degradation of the upper most soil surface layer before soil erosion has been initiated or at the very beginning of soil runoff and erosion processes. We analyzed the rate of decay of soil surface roughness from several experiments conducted in two regions under temperate and subtropical climate and with contrasting land use systems. The data sets studied were obtained both under natural and simulated rainfall for various soil tillage and management types. Soil surface roughness decay was characterized bay several parameters, including classic and single parameters such as the random roughness or the tortuosity and parameters based on advanced geostatistical methods or on the fractal theory. Our

  13. Review of Surface Roughness Effect on Beam Quality

    NASA Astrophysics Data System (ADS)

    Mostacci, A.; Palumbo, L.; Alesini, D.

    2003-12-01

    In recent years a strong attention arose around the problem of the e.m. interaction of an ultra-relativistic beam with the residual roughness inside a beam tube, in particular in the framework of future 4th generation coherent light sources. The main concern was the effect of the wake-fields on the relative energy spread of the beam which has to be of the order of 10-4, as for example in the LCLS and TESLA case. Although the real roughness has a stochastic feature, most studies dealt with periodic structure, or dielectric-equivalent layer which are considered to be conservative with respect the stochastic case. In this paper we will review the main theoretical models, and the most significant measurements trying to provide to the reader a complete picture of the present status of understanding.

  14. 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.

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

    NASA Technical Reports Server (NTRS)

    Amer, Tahani Reffet; Selby, Gregory V.

    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 (T-S) 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 nonlinear 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 nonlinear receptivity effects for certain combinations of surface roughness elements.

  16. 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.

  17. Effect of Organic Additive on Surface Roughness of Polycrystalline Silicon Film after Chemical Mechanical Polishing

    NASA Astrophysics Data System (ADS)

    Hwang, Hee-Sub; Park, Jin-Hyung; Yi, Sok-Ho; Paik, Ungyu; Park, Jea-Gun

    2010-01-01

    The effect of an organic additive on the surface roughness of a polycrystalline silicon (poly-Si) film was investigated by chemical mechanical polishing (CMP). The surface roughness of the polished poly-Si film was markedly reduced by adding 0.001 wt % hydroxyl ethyl cellulose (HEC) and then decreased slightly with further addition of HEC. We concluded that the reduction of surface roughness was attributed to the formation of a hydroplane layer on the poly-Si surface. Evidence of the hydroplane layer was verified by contact angle and X-ray photoelectron spectroscopy (XPS) measurements.

  18. The effectiveness of polishing kits: influence on surface roughness of zirconia.

    PubMed

    Preis, Verena; Grumser, Katharina; Schneider-Feyrer, Sibylle; Behr, Michael; Rosentritt, Martin

    2015-01-01

    This study investigated the effectiveness of intraoral and technical polishing kits. Zirconia specimens were sintered, ground, and polished with 14 different two-step or three-step polishing kits. Surface roughness (Ra, Rz) after each treatment step was determined, and scanning electron micrographs were made. Except for one system, all polishing kits were effective in reducing the surface roughness of ground zirconia. Differences in surface roughness were high after the first polishing step but were reduced to Ra/Rz values similar to or lower than those of the sintered reference after the final polishing step. Achieving smooth surfaces depended on a sequential application of all polishing steps. PMID:25822299

  19. Surface roughness of rock faces through the curvature of triangulated meshes

    NASA Astrophysics Data System (ADS)

    Lai, P.; Samson, C.; Bose, P.

    2014-09-01

    In this paper, we examine three different measures of roughness based on a geometric property of surfaces known as curvature. These methods were demonstrated using an image of a large rock face made up of a smooth blocky limestone in contact with a rough friable dolostone. The point cloud analysed contained 10,334,288 points and was acquired at a distance of 3 m from the rock face. The point cloud was first decimated using an epsilon-net and then meshed using the Poisson surface reconstruction method before the proposed measures of roughness were applied. The first measure of roughness is defined as the difference in curvature between a mesh and a smoothed version of the same mesh. The second measure of roughness is a voting system applied to each vertex which identifies the subset of vertices which represent rough regions within the mesh. The third measure of roughness uses a combination of spatial partitioning data structures and data clustering in order to define roughness for a region in the mesh. The spatial partitioning data structure allows for a hierarchy of roughness values which is related to the size of the region being considered. All of the proposed measures of roughness are visualised using colour-coded displays which allows for an intuitive interpretation.

  20. 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.

  1. Low-coherence interferometry based roughness measurement on turbine blade surfaces using wavelet analysis

    NASA Astrophysics Data System (ADS)

    Zou, Yibo; Li, Yinan; Kaestner, Markus; Reithmeier, Eduard

    2016-07-01

    In this paper, a non-contact optical system, a low-coherence interferometer (LCI), is introduced for the purpose of measuring the surface roughness of turbine blades. The designed system not only possesses a high vertical resolution and is able to acquire the roughness topography, but also it has a large vertical scanning range compared to other commonly used optical systems. The latter characteristic allows us to measure turbine blades surfaces with large curvature without collisions between the lens and the measurement object. After obtaining the surface topography, wavelet analysis is applied to decompose the original surface into multiple bandwidths to conduct a multiscale analysis. The results show that the developed LCI system proofs a good performance not only in obtaining the surface topography in the roughness scale but also in being able to measure surfaces of objects that possess a complex geometry in a large vertical range. Furthermore, the applied biorthogonal wavelet in this study has performed good amplitude and phase properties in extracting the roughness microstructures from the whole surface. Finally, the traditional roughness parameters, such as the mean surface roughness Sa and the Root Mean Square (RMS) roughness Sq, are evaluated in each decomposed subband and their correlations with the scale of each subband are analyzed.

  2. The boundary layer over turbine blade models with realistic rough surfaces

    NASA Astrophysics Data System (ADS)

    McIlroy, Hugh M., Jr.

    The impact of turbine blade surface roughness on aerodynamic performance and heat loads is well known. Over time, as the turbine blades are exposed to heat loads, the external surfaces of the blades become rough. Also, for film-cooled blades, surface degradation can have a significant impact on film-cooling effectiveness. Many studies have been conducted on the effects of surface degradation/roughness on engine performance but most investigations have modeled the rough surfaces with uniform or two-dimensional roughness patterns. The objective of the present investigation is to conduct measurements that will reveal the influence of realistic surface roughness on the near-wall behavior of the boundary layer. Measurements have been conducted at the Matched-Index-of-Refraction (MIR) Facility at the Idaho National Engineering and Environmental Laboratory with a laser Doppler velocimeter. A flat plate model of a turbine blade has been developed that produces a transitional boundary layer, elevated freestream turbulence and an accelerating freestream in order to simulate conditions on the suction side of a high-pressure turbine blade. Boundary layer measurements have been completed over a smooth plate model and over a model with a strip of realistic rough surface. The realistic rough surface was developed by scaling actual turbine blade surface data that was provided by U.S. Air Force Research Laboratory. The results indicate that bypass transition occurred very early in the flow over the model and that the boundary layer remained unstable throughout the entire length of the test plate; the boundary layer thickness and momentum thickness Reynolds numbers increased over the rough patch; and the shape factor increased over the rough patch but then decreased downstream of the patch relative to the smooth plate case; in the rough patch case the flow experienced two transition reversals with laminar-like behavior achieved by the end of the test plate; streamwise turbulence

  3. Electron Scattering at Surfaces and Interfaces of Transition Metals

    NASA Astrophysics Data System (ADS)

    Zheng, Pengyuan

    , the growth of epitaxial W(001) layers on MgO(001) substrates by ultra-high vacuum magnetron sputtering is studied, in order to obtain an alternative W layer orientation in addition to the well-known growth of epitaxial W(011) on Al2O3 substrates. X-ray diffraction o-2theta scans, o-rocking curves, and pole figures show that 5-400 nm thick W(001) layers grown at Ts = 900 °C are monocrystalline with a relaxed lattice constant of 3.167+/-0.001 nm, as determined from high resolution reciprocal space mapping. The magnitude of the residual in-plane compressive strain decreases from -1.2+/-0.1% to 0.1+/-0.1% with increasing dw. This is attributed to the glide of threading dislocations which increases the average misfit dislocation length, causing relaxation of the stress associated with differential thermal contraction. X-ray reflectivity measurements indicate smooth surfaces with a root-mean-square surface roughness ≤1.0 nm and a roughness exponent of 0.38 for dw below 20 nm. Secondly, the effect of surface roughness on surface scattering is investigated to ensure its contribution to the resistivity size effect is properly included when comparing W films grown on different substrates. In fact it is found the rho of in situ annealed 4-20 nm thick epitaxial W(001) layers grown on MgO(001) samples show weaker dw dependence than that of unannealed samples in vacuum and air at both 295 and 77 K although completely diffuse surface scattering are present on both sets of films. No significant change in the structural quality of the samples after annealing is observed for d ≤ 20 nm. While a combination of X-ray reflectivity and Atomic Force Microscope study on surface morphology shows flatter surface mounds after annealing. Consequently, in situ annealing treatment is carried out on both epitaxial W(110) and W(001) from dw =4-320 nm to obtain surface with comparable rms roughness and lateral correlation length. Thus the rho increase due to the surface roughness is estimated in

  4. Surface-integral formulation of scattering theory

    SciTech Connect

    Kadyrov, A.S. Bray, I.; Mukhamedzhanov, A.M.; Stelbovics, A.T.

    2009-07-15

    We formulate scattering theory in the framework of a surface-integral approach utilizing analytically known asymptotic forms of the two-body and three-body scattering wavefunctions. This formulation is valid for both short-range and long-range Coulombic interactions. New general definitions for the potential scattering amplitude are presented. For the Coulombic potentials, the generalized amplitude gives the physical on-shell amplitude without recourse to a renormalization procedure. New post and prior forms for the Coulomb three-body breakup amplitude are derived. This resolves the problem of the inability of the conventional scattering theory to define the post form of the breakup amplitude for charged particles. The new definitions can be written as surface-integrals convenient for practical calculations. The surface-integral representations are extended to amplitudes of direct and rearrangement scattering processes taking place in an arbitrary three-body system. General definitions for the wave operators are given that unify the currently used channel-dependent definitions.

  5. Friction and adhesion of gecko-inspired PDMS flaps on rough surfaces.

    PubMed

    Yu, Jing; Chary, Sathya; Das, Saurabh; Tamelier, John; Turner, Kimberly L; Israelachvili, Jacob N

    2012-08-01

    Geckos have developed a unique hierarchical structure to maintain climbing ability on surfaces with different roughness, one of the extremely important parameters that affect the friction and adhesion forces between two surfaces. Although much attention has been paid on fabricating various structures that mimic the hierarchical structure of a gecko foot, yet no systematic effort, in experiment or theory, has been made to quantify the effect of surface roughness on the performance of the fabricated structures that mimic the hierarchical structure of geckos. Using a modified surface forces apparatus (SFA), we measured the adhesion and friction forces between microfabricated tilted PDMS flaps and optically smooth SiO(2) and rough SiO(2) surfaces created by plasma etching. Anisotropic adhesion and friction forces were measured when sliding the top glass surface along (+y) and against (-y) the tilted direction of the flaps. Increasing the surface roughness first increased the adhesion and friction forces measured between the flaps and the rough surface due to topological matching of the two surfaces but then led to a rapid decrease in both of these forces. Our results demonstrate that the surface roughness significantly affects the performance of gecko mimetic adhesives and that different surface textures can either increase or decrease the adhesion and friction forces of the fabricated adhesives.

  6. Mathematical modeling of surface roughness in magnetic abrasive finishing of BK7 optical glass.

    PubMed

    Pashmforoush, Farzad; Rahimi, Abdolreza; Kazemi, Mehdi

    2015-10-01

    Magnetic abrasive finishing (MAF) is one of the advanced machining processes efficiently used to finish hard-to-machine materials. Simulation and modeling of the process is of particular importance to understand the mechanics of material removal and consequently achieve a high-quality surface with a minimum of surface defects. Hence, in this paper, we performed a numerical-experimental study to mathematically model the surface roughness during the MAF of BK7 optical glass. For this purpose, the initial roughness profile was estimated using fast Fourier transform (FFT) and a Gaussian filter. We obtained the final surface profile based on the material removal mechanisms and the corresponding chipping depth values evaluated by finite element analysis. We then validated experimentally the simulation results in terms of the arithmetic average surface roughness (R(a ). The comparison between the obtained results demonstrates that the theoretical and experimental findings are in good agreement when predicting the parameters' effect on surface roughness behavior. PMID:26479596

  7. Surface Roughness Model Based on Force Sensors for the Prediction of the Tool Wear

    PubMed Central

    de Agustina, Beatriz; Rubio, Eva María; Sebastián, Miguel Ángel

    2014-01-01

    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. PMID:24714391

  8. 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.

  9. Mathematical Modeling of Surface Roughness of Castings Produced Using ZCast Direct Metal Casting

    NASA Astrophysics Data System (ADS)

    Chhabra, M.; Singh, R.

    2015-04-01

    Aim of this investigation is to develop a mathematical model for predicting surface roughness of castings produced using ZCast process by employing Buckingham's π-theorem. A relationship has been proposed between surface roughness of castings and shell wall thickness of the shell moulds fabricated using 3D printer. Based on model, experiments were performed to obtain the surface roughness of aluminium, brass and copper castings produced using ZCast process based on 3D printing technique. Based on experimental data, three best fitted third-degree polynomial equations have been established for predicting the surface roughness of castings. The predicted surface roughness values were then calculated using established best fitted equations. An error analysis was performed to compare the experimental and predicted data. The average prediction errors obtained for aluminium, brass and copper castings are 10.6, 2.43 and 3.12 % respectively. The obtained average surface roughness (experimental and predicted) values of castings produced are acceptable with the sand cast surface roughness values range (6.25-25 µm).

  10. The Effect of Remin Pro and MI Paste Plus on Bleached Enamel Surface Roughness

    PubMed Central

    Heshmat, Haleh; Ganjkar, Maryam Hoorizad; Jaberi, Solmaz; Fard, Mohammad Javad Kharrazi

    2014-01-01

    Objective The growing demand for enhanced esthetic appearance has led to great developments in bleaching products. The exposure of hard tissues of the tooth to bleaching agents can affect the roughness of the enamel surface. The freshly bleached enamel surface exposed to various surface treatments such as fluoride and other remineralizing agents have been assessed in this study. The aim of this experimental study was to compare the effect of Casein Phosphopeptide-Amorphous Calcium Phosphate with Fluoride (MI Paste Plus) and Remin Pro on the enamel surface roughness after bleaching. Materials and Methods: Thirty enamel samples of sound human permanent molars were prepared for this study. After initial roughness measurement with profilometer, the samples were exposed to 37% carbamide peroxide bleaching agent 20 minutes twice, and randomly divided into three groups of ten. In group 1, a CPP-ACPF containing paste (MI Paste Plus) and in group 2, Remin Pro were applied to the teeth during a 15 day period for 5 minutes, twice a day. Samples of group 3 (control) were immersed in artificial saliva for 15 days. The roughness of all samples were measured at the beginning, after bleaching and after the study intervention and statistically analyzed. Results: The surface roughness significantly increased in all groups following bleaching, and then it showed a decrease after application of both Remin Pro and CPP-ACPF in comparison to using bleaching agent (P<0.005). The surface roughness after using Remin Pro and CPP-ACPF was statistically similar to each other (P>0.05). Conclusion: There was no difference between surface roughness of MI Paste Plus and Remin Pro groups. Also the surface roughness was decreased compared to the initial enamel surface roughness. PMID:24910687

  11. Deposition at glancing angle, surface roughness, and protein adsorption: Monte Carlo simulations.

    PubMed

    Zhdanov, Vladimir P; Rechendorff, Kristian; Hovgaard, Mads B; Besenbacher, Flemming

    2008-06-19

    To generate rough surfaces in Monte Carlo simulations, we use the 2 + 1 solid-on-solid model of deposition with rapid transient diffusion of newly arrived atoms supplied at glancing angle. The surfaces generated are employed to scrutinize the effect of surface roughness on adsorption of globular and anisotropic rodlike proteins. The obtained results are compared with the available experimental data for Ta deposition at glancing angle and for the bovine serum albumin and fibrinogen uptake on the corresponding Ta films.

  12. Ion scattering experiment on Ni(110) surface

    SciTech Connect

    Nicholas, B.; Rambabu, B.; Collins, W.E.

    1986-01-01

    Light emission from excited neutral scattered Ne and sputtered Ni were investigated using the LEIS method. A 5-keV Ne/sup +/ beam was used to bombard a Ni(110) surface. Results of the light emission data is presented and compared with neutral production of Ne. 4 refs., 3 figs.

  13. Understanding and eliminating artifact signals from diffusely scattered pump beam in measurements of rough samples by time-domain thermoreflectance (TDTR).

    PubMed

    Sun, Bo; Koh, Yee Kan

    2016-06-01

    Time-domain thermoreflectance (TDTR) is a pump-probe technique frequently applied to measure the thermal transport properties of bulk materials, nanostructures, and interfaces. One of the limitations of TDTR is that it can only be employed to samples with a fairly smooth surface. For rough samples, artifact signals are collected when the pump beam in TDTR measurements is diffusely scattered by the rough surface into the photodetector, rendering the TDTR measurements invalid. In this paper, we systemically studied the factors affecting the artifact signals due to the pump beam leaked into the photodetector and thus established the origin of the artifact signals. We find that signals from the leaked pump beam are modulated by the probe beam due to the phase rotation induced in the photodetector by the illumination of the probe beam. As a result of the modulation, artifact signals due to the leaked pump beam are registered in TDTR measurements as the out-of-phase signals. We then developed a simple approach to eliminate the artifact signals due to the leaked pump beam. We verify our leak-pump correction approach by measuring the thermal conductivity of a rough InN sample, when the signals from the leaked pump beam are significant. We also discuss the advantages of our new method over the two-tint approach and its limitations. Our new approach enables measurements of the thermal conductivity of rough samples using TDTR.

  14. Application of IEM model on soil moisture and surface roughness estimation

    NASA Technical Reports Server (NTRS)

    Shi, Jiancheng; Wang, J. R.; Oneill, P. E.; Hsu, A. Y.; Engman, E. T.

    1995-01-01

    Monitoring spatial and temporal changes of soil moisture are of importance to hydrology, meteorology, and agriculture. This paper reports a result on study of using L-band SAR imagery to estimate soil moisture and surface roughness for bare fields. Due to limitations of the Small Perturbation Model, it is difficult to apply this model on estimation of soil moisture and surface roughness directly. In this study, we show a simplified model derived from the Integral Equation Model for estimation of soil moisture and surface roughness. We show a test of this model using JPL L-band AIRSAR data.

  15. Effects of surface roughness on the VIRTIS/Rosetta thermal measurements

    NASA Astrophysics Data System (ADS)

    Leyrat, C.; Erard, S.; Capria, M.; Capaccioni, F.

    2014-07-01

    Thermal emission from planetary surfaces depends on many physical processes/parameters such as the Bond albedo, the heat capacity, the thermal inertia, the sublimation of ices at the surfaces, but also on the small-scale surface roughness. Distinguishing the effect of both thermal inertia and surface roughness on the infrared measurements is not trivial. In particular, surface roughness, that cannot be resolved within the pixels of instruments frame, can produce both shadows at small scales and mutual heating, which affect the thermal flux and the temperature estimations. The effect of roughness also varies with local incidence and emission angles, and local time, being significantly stronger closed to terminator when the local hills cast their shadows at far distances. In this poster, we present a thermo-physical model based on thermal conduction of heat over several diurnal and seasonal skin depths and show how surface roughness affects the retrieved temperature, especially, in the near-infrared domain [1--5 microns], where the VIRTIS/Rosetta instrument will observe comet CG 67/P starting in July 2014. We first compute the surface temperature of CG 67P using a simple thermo-physical model that takes into account the global shape of the nucleus. Then, we investigate (1) how the surface roughness can modify the apparent surface temperature and the thermal inertia, and (2) what are the best geometries of observation to distinguish between topographic effects and physical thermal processes.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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 rate 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.

  17. Mathematical model for strip surface roughness of stainless steel in cold rolling process

    NASA Astrophysics Data System (ADS)

    Chen, Jinshan; Li, Changsheng; Zhu, Tao; Han, Wenlong; Cao, Yong

    2013-05-01

    Surface roughness control is one of the most important subjects during producing stainless steel strips. In this paper, under the conditions of introducing to the concepts of transferring ratio and genetic factor and through the further theoretical analysis, a set of theoretical models about strip surface roughness were put forward in stainless steel cold tandem rolling. Meanwhile, the lubrication experiment in cold rolling process of SUS430 stainless steel strip was carried out in order to comprehensively study surface roughness. The effect of main factors on transferring ratio and genetic factor was analyzed quantitatively, such as reduction, initial thickness, deformation resistance, emulsion technological parameters and so on. Attenuation function equations used for describing roll surface roughness were set up, and also strip surface roughness at the entry of last mill was solved approximately. Ultimately, mathematical model on strip surface roughness for cold tandem rolling of stainless steel was built, and then it was used into the practical production. A great number of statistical results show that experimental data is in excellent agreement with the given regression equations, and exactly, the relative deviation on roughness between calculated and measured is less than 6.34%.

  18. Roughness Characterization of and Turbulent Boundary Layer Flow over flat Snow Surfaces

    NASA Astrophysics Data System (ADS)

    Gromke, C.; Guala, M.; Manes, C.; Walter, B.; Lehning, M.

    2009-12-01

    The surface roughness is essential for all turbulent exchange processes within the lower part of the atmospheric boundary layer. Consequently, a proper representation of the surfaces roughness is needed in every mathematical description of near surface mass-, energy- and momentum exchange processes. Considering the vertical mean velocity profile of turbulent boundary layer flow, this is done by assigning an aerodynamic roughness length z0 to the surface. We followed two procedures to describe the roughness of freshly fallen snow surfaces. First, photographs of snow surfaces have been taken and evaluated using digital image analysis giving snow surface contour line coordinates. Applying structure functions to the snow surface coordinates and statistical fitting procedures, resulted in classes of surface characteristic length scales and scaling exponents. These results allow to identify the deposition process of snow fall as scaling exponents corresponded to that of Ballistic Deposition. Moreover, the resulting characteristic length scales can be assigned to typical particle size and aggregation size length scales consistent with results found by Lowe et al. (2007) and Manes et al. (2008). Second, aerodynamic roughness lengths z0 have been estimated from log-law fitting of velocity profiles over the snow surfaces measured in the SLF cold atmospheric boundary layer wind tunnel. The aerodynamic roughness lengths found are in general agreement with available literature data and suggest the presence of aerodynamically rough regimes with flow independent z0. In the synthesis of both approaches, we found evidence for a linear relationship between one class of surface characteristic length scales, which is associated with typical snow particle sizes, and aerodynamic roughness lengths z0. The correlation with the aggregation length scale is weaker for the few (4) samples analyzed thus far. The relatively weak pronounced scale separation between particle and aggregation size

  19. FEM/SPH simulation research and experiment of surface roughness based on traditional polishing process

    NASA Astrophysics Data System (ADS)

    Li-Jun, Shen; Yong-Jian, Wan; Kai, Meng; Chuan-Ke, Huang

    2015-06-01

    Surface roughness is one of the most important parameters of surface quality and a difficult technical issue in glass polishing, especially for traditional polishing. In this paper, the coupled algorithm of FEM/SPH has been used to simulate the deformation of brittle K9 glass in traditional polishing. The influences of polishing particle size and insert depth on surface roughness are analyzed in detail. Then, experiment is carried out on a ∅100 mm flat K9 mirror with three sorts of particle, ceria abrasive particle with 1.2, 1.6 and 2 μm. Simulation and experiment results show that surface roughness of brittle glass has direct relationship with particle size during traditional polishing process. The surface roughness is better as the particle size is smaller.

  20. Femtoliter silver cups as surface enhanced Raman scattering active containers.

    PubMed

    Bhuvana, T; Kulkarni, G U

    2009-01-28

    Femtoliter capacity Ag cups formed by the pulsed laser ablation of an Ag foil have been tried out as substrates for surface enhanced Raman scattering (SERS) measurements. The cups are formed as the impinging droplets from the laser plume undergo a flow pattern before freezing into cup-like structures, resulting in a surface roughness (approximately 35 nm) that makes them ideal for SERS studies. The internal volume of the cups is in the femtoliter (10(-15) l) range, well suited for small-scale reactions, particularly in biological studies. The cups exhibit enhancement factors of the order of 10(6) with the analyte molecule thiophenol. Individual cups have been dosed attoliter quantities (10(-18) l) of the analyte and detected. PMID:19417320

  1. The effects of crushing surface roughness on the crushing characteristics of composite tubes

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.; Wolterman, Richard L.; Kennedy, John M.

    1992-01-01

    The effects of crushing-surface roughness on the energy-absorption capability of graphite and glass-epoxy composite tubes were investigated. Fifty different combinations of fiber, matrix, and specimen ply orientation were evaluated. Two different crushing surface roughnesses were used in this investigation. Crushing surface significantly influences the energy-absorption capability only of tubes that crush in the lamina bending crushing mode; tubes that crush in other modes are not influenced because their lamina bundles do not slide against the crushing surface. Those tubes that crush in the lamina bending mode can achieve higher, lower, or no change in energy-absorption capability as crushing surface roughness increases. If the fiber failure strain of tubes that crush in the lamina bending crushing mode exceeds the matrix failure strain then the energy-absorption capability increases as crushing surface roughness increases. However, if the matrix failure strain exceeds the fiber failure strain then the energy-absorption capability increases as crushing surface roughness decreases. Energy-absorption capability is uninfluenced by crushing surface roughness for tubes that have equal fiber and matrix failure strains.

  2. Surface characteristics of Venus derived from Pioneer Venus altimetry, roughness, and reflectivity measurements

    NASA Astrophysics Data System (ADS)

    Head, J. W.; Peterfreund, A. R.; Garvin, J. B.

    1985-07-01

    The three primary data sets for the Pioneer Venus orbiter radar experiment (topography, roughness, and reflectivity) contain important information about the geological and textural characteristics of the surface of Venus. The authors have subdivided the range of roughness and reflectivity values into three categories as follows: roughness, in degrees rms slope: relatively smooth (1° - 2.5°), transitional from smooth to rough (2.5° - 5°), and relatively rough (>5°); and Fresnel reflectivity: surface dominated by soil or porous material (<0.1), surfaces dominated by rock material (0.1 - 0.2), and surfaces with a significant percentage of anomalously high dielectric material (>0.2). The authors have analyzed each of these data sets and their relationships to each other in order to define areas of the surface that are characterized by distinctive properties (e.g., rough rocky surfaces, smooth soil surfaces). They then describe the abundance and areal distribution of such areas and locally calibrate the geological significance of some of the surface types by examining high-resolution images from spacecraft and earth-based observatories.

  3. Surface slope and roughness measurement using ICESat/GLAS elevation and laser waveform

    NASA Astrophysics Data System (ADS)

    Li, Xiaolu; Xu, Kai; Xu, Lijun

    2016-09-01

    Surface slope and roughness are important geomorphological variables which have been used in the Earth and planetary sciences to infer material properties. For the ICESat/GLAS measurement, roughness and slope are two surface properties for broadening the width of the returned pulse. Based on this, a new method (GLAS waveform-derived roughness, GWR in short) is investigated to invert roughness from waveform broadening after excluding slope effect. Surface slope is estimated from the repeat tracks elevation of ICESat/GLAS, which is verified to be coincidence with geography facts (Landsat-7 images). Extensive experiments are performed using the proposed methods to evaluate the performance of surface properties (roughness, slope and elevation) in the Jakobshavn area. The experimental results demonstrate that, compared with the elevation-derived roughness method (GER in short), GWR is more sensitive to local surface properties in the gentle slope zone because it is a small-scale estimation. Additionally, GWR is a more stable roughness estimation which is immune to a strong elevation change.

  4. Deterministic forward scatter from surface gravity waves.

    PubMed

    Deane, Grant B; Preisig, James C; Tindle, Chris T; Lavery, Andone; Stokes, M Dale

    2012-12-01

    Deterministic structures in sound reflected by gravity waves, such as focused arrivals and Doppler shifts, have implications for underwater acoustics and sonar, and the performance of underwater acoustic communications systems. A stationary phase analysis of the Helmholtz-Kirchhoff scattering integral yields the trajectory of focused arrivals and their relationship to the curvature of the surface wave field. Deterministic effects along paths up to 70 water depths long are observed in shallow water measurements of surface-scattered sound at the Martha's Vineyard Coastal Observatory. The arrival time and amplitude of surface-scattered pulses are reconciled with model calculations using measurements of surface waves made with an upward-looking sonar mounted mid-way along the propagation path. The root mean square difference between the modeled and observed pulse arrival amplitude and delay, respectively, normalized by the maximum range of amplitudes and delays, is found to be 0.2 or less for the observation periods analyzed. Cross-correlation coefficients for modeled and observed pulse arrival delays varied from 0.83 to 0.16 depending on surface conditions. Cross-correlation coefficients for normalized pulse energy for the same conditions were small and varied from 0.16 to 0.06. In contrast, the modeled and observed pulse arrival delay and amplitude statistics were in good agreement.

  5. CdTe surface roughness by Raman spectroscopy using the 830 nm wavelength.

    PubMed

    Frausto-Reyes, C; Molina-Contreras, J Rafael; Medina-Gutiérrez, C; Calixto, Sergio

    2006-09-01

    A Raman spectroscopic study was performed to detect the surface roughness of a cadmium telluride (CdTe) wafer sample, using the 514.5, 632.8 and 830.0 nm excitations wavelengths. To verify the relation between the roughness and the structure of Raman spectra, in certain zones of the sample, we measured their roughness with an atomic force microscopy. It was found that, using the 830 nm wavelength there is a direct correspondence between the spectrum structure and the surface roughness. For the others wavelengths it was found, however, that there is not a clearly correspondence between them. Our results suggest that, using the excitation wavelength of 830 nm the Raman spectroscopy can be used as an on-line roughness monitor on the CdTe growth.

  6. Critical instability and friction scaling of fluid flows through pipes with rough inner surfaces.

    PubMed

    Tao, Jianjun

    2009-12-31

    It has been shown experimentally over nearly 80 years that surface fine roughness of circular pipes has a crucial effect on the natural transition to turbulence. In this Letter, a theoretical explanation is suggested for the roughness-induced instability. Once the nonlinear effect of roughness is introduced (through a pipe with fine corrugation surface), the mean velocity profile becomes unstable to three-dimensional, asymmetric, and helical traveling waves at moderate Reynolds numbers. The threshold of the aspect ratio or shape factor of the roughness element required to cause instability scales as Re-2. Inspired by the current model, a scaling form is proposed and the scaled friction factor measurements in rough pipes collapse onto a universal curve.

  7. Sol-gel replicated optics made from single point diamond turned masters exhibit fractal surface roughness

    SciTech Connect

    Bernacki, B.E.; Miller, A.C. Jr.; Evans, B.M. III; Moreshead, W.V.; Nogues, J.L.R.

    1996-05-01

    Deterministic optics manufacturing, notably single point diamond turning (SPDT) has matured such that the current generation of machines is capable of producing refractive and reflective optics for the visible wavelength region that are quite acceptable for many applications. However, spiral tool marks are still produced that result in unwanted diffractive scattering from grating-like features having a spatial frequency determined by the machine feed, tool radius, and other influences such as vibration and material removal effects. Such regular artifacts are the characteristic of deterministic manufacturing methods such as SPDT. The authors present some initial findings suggesting that fractal, or non-deterministic surfaces can be produced by SPDT through sol-gel replication. The key is the large isotropic shrinkage that occurs through monolithic sol-gel replication (a factor of 2.5) that results in all features, including tooling marks, being reduced by that amount. The large shrinkage itself would be a laudable-enough feature of the replication process. However, by an as-yet-not understood manner, the replication process itself seems to alter the roughness character of the replicated surface such that it appears to be fractal when analyzed using contact profilometry and the power spectrum approach.

  8. 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.

  9. Surface roughness and wettability of dentin ablated with ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Lü, Peijun; Sun, Yuchun; Wang, Yong

    2015-05-01

    The aim of this study was to evaluate the surface roughness and wettability of dentin following ultrashort pulsed laser ablation with different levels of fluence and pulse overlap (PO). Twenty-five extracted human teeth crowns were cut longitudinally into slices of approximately 1.5-mm thick and randomly divided into nine groups of five. Samples in groups 1 to 8 were ablated with an ultrashort pulsed laser through a galvanometric scanning system. Samples in group 9 were prepared using a mechanical rotary instrument. The surface roughness of samples from each group was then measured using a three-dimensional profile measurement laser microscope, and wettability was evaluated by measuring the contact angle of a drop of water on the prepared dentin surface using an optical contact angle measuring device. The results showed that both laser fluence and PO had an effect on dentin surface roughness. Specifically, a higher PO decreased dentin surface roughness and reduced the effect of high-laser fluence on decreasing the surface roughness in some groups. Furthermore, all ablated dentin showed a contact angle of approximately 0 deg, meaning that laser ablation significantly improved wettability. Adjustment of ultrashort pulsed laser parameters can, therefore, significantly alter dentin surface roughness and wettability.

  10. Observation of the rose petal effect over single- and dual-scale roughness surfaces.

    PubMed

    Yeh, Kuan-Yu; Cho, Kuan-Hung; Yeh, Yu-Hao; Promraksa, Arwut; Huang, Chung-Hsuan; Hsu, Cheng-Che; Chen, Li-Jen

    2014-08-29

    Rose petals exhibit superhydrophobicity with strong adhesion to pin water drops, known as the 'petal effect.' It is generally believed that the petal effect is attributed to dual-scale roughness, that is, the surface possesses both a nanostructure and a microstructure (Feng et al 2008 Langmuir 24 4114). In this study, we demonstrate that the dual-scale roughness is not a necessary condition for a surface of the petal effect. A surface of single-scale roughness, either at the nanoscale or the microscale alone, within a certain roughness region may also exhibit the petal effect. The surface roughness plays the essential role on the wetting behavior and governs the contact angle in the Wenzel or Cassie state, as well as the contact angle hysteresis. A water drop on the surface of the petal effect under the condition of the advancing and receding contact angle would fall into, respectively, the Cassie and Wenzel state, which leads to a contact angle hysteresis large enough to pin the water drop. On both single and dual textured hydrophobic surfaces, a sequence of wetting transitions: Wenzel state → petal state (sticky superhydrophobic state) → lotus state (slippery superhydrophobic state) is consistently observed by simply increasing the surface roughness. PMID:25100802

  11. Observation of the rose petal effect over single- and dual-scale roughness surfaces

    NASA Astrophysics Data System (ADS)

    Yeh, Kuan-Yu; Cho, Kuan-Hung; Yeh, Yu-Hao; Promraksa, Arwut; Huang, Chung-Hsuan; Hsu, Cheng-Che; Chen, Li-Jen

    2014-08-01

    Rose petals exhibit superhydrophobicity with strong adhesion to pin water drops, known as the ‘petal effect.’ It is generally believed that the petal effect is attributed to dual-scale roughness, that is, the surface possesses both a nanostructure and a microstructure (Feng et al 2008 Langmuir 24 4114). In this study, we demonstrate that the dual-scale roughness is not a necessary condition for a surface of the petal effect. A surface of single-scale roughness, either at the nanoscale or the microscale alone, within a certain roughness region may also exhibit the petal effect. The surface roughness plays the essential role on the wetting behavior and governs the contact angle in the Wenzel or Cassie state, as well as the contact angle hysteresis. A water drop on the surface of the petal effect under the condition of the advancing and receding contact angle would fall into, respectively, the Cassie and Wenzel state, which leads to a contact angle hysteresis large enough to pin the water drop. On both single and dual textured hydrophobic surfaces, a sequence of wetting transitions: Wenzel state → petal state (sticky superhydrophobic state) → lotus state (slippery superhydrophobic state) is consistently observed by simply increasing the surface roughness.

  12. Surface roughness and wettability of dentin ablated with ultrashort pulsed laser.

    PubMed

    Liu, Jing; Lü, Peijun; Sun, Yuchun; Wang, Yong

    2015-05-01

    The aim of this study was to evaluate the surface roughness and wettability of dentin following ultrashort pulsed laser ablation with different levels of fluence and pulse overlap (PO). Twenty-five extracted human teeth crowns were cut longitudinally into slices of approximately 1.5-mm thick and randomly divided into nine groups of five. Samples in groups 1 to 8 were ablated with an ultrashort pulsed laser through a galvanometric scanning system. Samples in group 9 were prepared using a mechanical rotary instrument. The surface roughness of samples from each group was then measured using a three-dimensional profile measurement laser microscope, and wettability was evaluated by measuring the contact angle of a drop of water on the prepared dentin surface using an optical contact angle measuring device. The results showed that both laser fluence and PO had an effect on dentin surface roughness. Specifically, a higher PO decreased dentin surface roughness and reduced the effect of high-laser fluence on decreasing the surface roughness in some groups. Furthermore, all ablated dentin showed a contact angle of approximately 0 deg, meaning that laser ablation significantly improved wettability. Adjustment of ultrashort pulsed laser parameters can, therefore,significantly alter dentin surface roughness and wettability.

  13. On the Correlation of Effective Terahertz Refractive Index and Average Surface Roughness of Pharmaceutical Tablets

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mousumi; Bawuah, Prince; Tan, Nicholas; Ervasti, Tuomas; Pääkkönen, Pertti; Zeitler, J. Axel; Ketolainen, Jarkko; Peiponen, Kai-Erik

    2016-08-01

    In this paper, we have studied terahertz (THz) pulse time delay of porous pharmaceutical microcrystalline compacts and also pharmaceutical tablets that contain indomethacin (painkiller) as an active pharmaceutical ingredient (API) and microcrystalline cellulose as the matrix of the tablet. The porosity of a pharmaceutical tablet is important because it affects the release of drug substance. In addition, surface roughness of the tablet has much importance regarding dissolution of the tablet and hence the rate of drug release. Here, we show, using a training set of tablets containing API and with a priori known tablet's quality parameters, that the effective refractive index (obtained from THz time delay data) of such porous tablets correlates with the average surface roughness of a tablet. Hence, THz pulse time delay measurement in the transmission mode provides information on both porosity and the average surface roughness of a compact. This is demonstrated for two different sets of pharmaceutical tablets having different porosity and average surface roughness values.

  14. 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°.

  15. Procedure for estimating fracture energy from fracture surface roughness

    DOEpatents

    Williford, Ralph E.

    1989-01-01

    The fracture energy of a material is determined by first measuring the length of a profile of a section through a fractured surface of the material taken on a plane perpendicular to the mean plane of that surface, then determining the fractal dimensionality of the surface. From this, the yield strength of the material, and the Young's Modulus of that material, the fracture energy is calculated.

  16. Characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data

    NASA Astrophysics Data System (ADS)

    Frankel, Kurt L.; Dolan, James F.

    2007-06-01

    Range-front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages. These distinct landforms are often defined by descriptions of their surface morphology, desert varnish accumulation, clast rubification, desert pavement formation, soil development, and stratigraphy. Although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past, high-resolution airborne laser swath mapping (ALSM) digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail. Here we use ALSM data to calculate surface roughness on two alluvial fans in northern Death Valley, California. We define surface roughness as the standard deviation of slope in a 5-m by 5-m moving window. Comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99% confidence level. Furthermore, there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10Be and 36Cl surface exposure ages of ˜70 ka. Beyond 70 ka, alluvial landforms become progressively rougher with age. These data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces.

  17. Surface Roughness Characterization of Niobium Subjected to Incremental BCP and EP Processing Steps

    SciTech Connect

    Hui Tian; Guihem Ribeill; Charles Reece; Michael Kelley

    2008-02-12

    The surface of niobium samples polished under incremental Buffered Chemical Polish (BCP) and Electro-Polishing (EP) have been characterized through Atomic Force Microscopy (AFM) and stylus profilometry across a range of length of scales. The results were analyzed using Power Density Spectral (PSD) technique to determine roughness and characteristic dimensions. This study has shown that the PSD method is a valuable tool that provides quantitative information about surface roughness at different length scales.

  18. Surface roughness analysis after machining of direct laser deposited tungsten carbide

    NASA Astrophysics Data System (ADS)

    Wojciechowski, S.; Twardowski, P.; Chwalczuk, T.

    2014-03-01

    In this paper, an experimental surface roughness analysis in machining of tungsten carbide is presented. The tungsten carbide was received using direct laser deposition technology (DLD). Experiments carried out included milling of tungsten carbide samples using monolithic torus cubic boron nitride (CBN) tool and grinding with the diamond cup wheel. The effect of machining method on the generated surface topography was analysed. The 3D surface topographies were measured using optical surface profiler. The research revealed, that surface roughness generated after the machining of tungsten carbide is affected by feed per tooth (fz) value related to kinematic-geometric projection only in a minor extent. The main factor affecting machined surface roughness is the occurrence of micro grooves and protuberances on the machined surface, as well as other phenomena connected, inter alia, with the mechanism for material removal.

  19. Scattering effects of machined optical surfaces

    NASA Astrophysics Data System (ADS)

    Thompson, Anita Kotha

    1998-09-01

    Optical fabrication is one of the most labor-intensive industries in existence. Lensmakers use pitch to affix glass blanks to metal chucks that hold the glass as they grind it with tools that have not changed much in fifty years. Recent demands placed on traditional optical fabrication processes in terms of surface accuracy, smoothnesses, and cost effectiveness has resulted in the exploitation of precision machining technology to develop a new generation of computer numerically controlled (CNC) optical fabrication equipment. This new kind of precision machining process is called deterministic microgrinding. The most conspicuous feature of optical surfaces manufactured by the precision machining processes (such as single-point diamond turning or deterministic microgrinding) is the presence of residual cutting tool marks. These residual tool marks exhibit a highly structured topography of periodic azimuthal or radial deterministic marks in addition to random microroughness. These distinct topographic features give rise to surface scattering effects that can significantly degrade optical performance. In this dissertation project we investigate the scattering behavior of machined optical surfaces and their imaging characteristics. In particular, we will characterize the residual optical fabrication errors and relate the resulting scattering behavior to the tool and machine parameters in order to evaluate and improve the deterministic microgrinding process. Other desired information derived from the investigation of scattering behavior is the optical fabrication tolerances necessary to satisfy specific image quality requirements. Optical fabrication tolerances are a major cost driver for any precision optical manufacturing technology. The derivation and control of the optical fabrication tolerances necessary for different applications and operating wavelength regimes will play a unique and central role in establishing deterministic microgrinding as a preferred and a

  20. Coherent scattering of a spherical wave from an irregular surface. [antenna pattern effects

    NASA Technical Reports Server (NTRS)

    Fung, A. K.

    1983-01-01

    The scattering of a spherical wave from a rough surface using the Kirchhoff approximation is considered. An expression representing the measured coherent scattering coefficient is derived. It is shown that the sphericity of the wavefront and the antenna pattern can become an important factor in the interpretation of ground-based measurements. The condition under which the coherent scattering-coefficient expression reduces to that corresponding to a plane wave incidence is given. The condition under which the result reduces to the standard image solution is also derived. In general, the consideration of antenna pattern and sphericity is unimportant unless the surface-height standard deviation is small, i.e., unless the coherent scattering component is significant. An application of the derived coherent backscattering coefficient together with the existing incoherent scattering coefficient to interpret measurements from concrete and asphalt surfaces is shown.

  1. Effect finishing and polishing procedures on the surface roughness of IPS Empress 2 ceramic

    PubMed Central

    Nishida, Rodrigo; Elossais, André Afif; Lima, Darlon Martins; Reis, José Mauricio Santos Nunes; Campos, Edson Alves; de Andrade, Marcelo Ferrarezi

    2013-01-01

    Objective. To evaluate the surface roughness of IPS Empress 2 ceramic when treated with different finishing/polishing protocols. Materials and methods. Sixteen specimens of IPS Empress 2 ceramic were made from wax patterns obtained using a stainless steel split mold. The specimens were glazed (Stage 0–S0, control) and divided into two groups. The specimens in Group 1 (G1) were finished/polished with a KG Sorensen diamond point (S1), followed by KG Sorensen siliconized points (S2) and final polishing with diamond polish paste (S3). In Group 2 (G2), the specimens were finished/polished using a Shofu diamond point (S1), as well as Shofu siliconized points (S2) and final polishing was performed using Porcelize paste (S3). After glazing (S0) and following each polishing procedure (S1, S2 or S3), the surface roughness was measured using TALYSURF Series 2. The average surface roughness results were analyzed using ANOVA followed by Tukey post-hoc tests (α = 0.01) Results. All of the polishing procedures yielded higher surface roughness values when compared to the control group (S0). S3 yielded lower surface roughness values when compared to S1 and S2. Conclusions. The proposed treatments negatively affected the surface roughness of the glazed IPS Empress 2 ceramic. PMID:22724660

  2. Overlap region in turbulent boundary layer over a rough surface

    NASA Astrophysics Data System (ADS)

    Afzal, Noor

    2010-11-01

    The one term non-linear outer layer in George & Castillo (1997, AMR 50, 689), based on their AIP argument, was matched with inner wall layer leading to power law velocity, which denied very existence of traditional log law, while Clauser (1956) patched same outer layer with inner wall log law. Jones, Nickles & Marusic (2008, JFM 616, 195) proposal that free stream velocity (in GC97) and friction velocity (in Coles 1956) are potentially valid scalings according to their theoretical criterion in the outer layer, is misleading, being not correct. Further, in Nishioka (2010, FDR 42, 45502-5) and Prandtl (1935, AT) the additive constant in power law velocity is singular at large Reynolds numbers is also not correct, and this constant is shown to be zero. In the present work, two terms outer layer expansion is considered where leading term scales with free steam velocity and first order with friction velocity. The leading term turns out to be a non-linear wake type equation through application of Izakson-Millikan- Kolmogorov hypothesis. The first order terms lead to alternate functional equations, arising from ratios of two successive derivatives of the functional equations, each of which admits two functional solutions, the power law velocity profile in addition to log law velocity profile. The comparison with extensive data on rough & smooth walls also provide strong support to present work.

  3. Dropwise condensation on superhydrophobic surfaces with two-tier roughness

    NASA Astrophysics Data System (ADS)

    Chen, Chuan-Hua; Cai, Qingjun; Tsai, Chialun; Chen, Chung-Lung; Xiong, Guangyong; Yu, Ying; Ren, Zhifeng

    2007-04-01

    Dropwise condensation can enhance heat transfer by an order of magnitude compared to film condensation. Superhydrophobicity appears ideal to promote continued dropwise condensation which requires rapid removal of condensate drops; however, such promotion has not been reported on engineered surfaces. This letter reports continuous dropwise condensation on a superhydrophobic surface with short carbon nanotubes deposited on micromachined posts, a two-tier texture mimicking lotus leaves. On such micro-/nanostructured surfaces, the condensate drops prefer the Cassie state which is thermodynamically more stable than the Wenzel state. With a hexadecanethiol coating, superhydrophobicity is retained during and after condensation and rapid drop removal is enabled.

  4. Geometrical evolution of interlocked rough slip surfaces: The role of normal stress

    NASA Astrophysics Data System (ADS)

    Badt, Nir; Hatzor, Yossef H.; Toussaint, Renaud; Sagy, Amir

    2016-06-01

    We study the evolution of slip surface topography using direct shear tests of perfectly mating surfaces. The tests are performed under imposed constant normal stress and constant slip rate conditions, to a sliding distance comparable to the roughness scale of the studied surfaces. Prismatic limestone blocks are fractured in tension using four-point bending and the generated surface topographies are measured using a laser profilometer. The initially rough fracture interfaces are tested in direct shear while ensuring a perfectly mating configuration at the beginning of each test. The predetermined sliding distance in all tests is 10 mm and the sliding velocity is 0.05 mm/s. A constant normal stress is maintained throughout the tests using closed loop servo control. The range of normal stresses applied is between 2 MPa and 15 MPa. After shearing, the surface topographies are re-scanned and the geometrical evolution is analyzed. We find that surface roughness increases with increasing normal stress: under normal stresses below 5 MPa the surfaces become smoother compared to the original geometry, whereas under normal stresses between 7.5 MPa and 15 MPa the surfaces clearly become rougher following shear. Statistical spectral analyses of the roughness profiles indicate that roughness increases with length-scale. Power spectral density values parallel to the slip orientation are fitted by power-law with typical power value of 2.6, corresponding to a Hurst exponent of 0.8, assuming self-affine roughness. This power value is consistent for the post-sheared surfaces and is obtained even when the original surface roughness does not follow initially a power-law form. The value of the scaling-law prefactor however increases with increasing normal stress. We find that the deformation associated with shearing initially rough interlocked surfaces extends beyond the immediate tested surface, further into the intact rock material. The intensity of the damage and its spatial

  5. The relationship of surface roughness and cell response of chemical surface modification of titanium

    PubMed Central

    Zareidoost, Amir; Ghaseme, Behrooz

    2012-01-01

    Implant surface topography influences osteoblastic proliferation, differentiation and extracellular matrix protein expressions. Previous researches proved that chemical surface modification of titanium implants could be used to improve Bone-to-implant contact. In this study, the surface topography, chemistry and biocompatibility of polished titanium surfaces treated with mixed solution of three acids containing HCl, HF and H3PO4 with different etched conditions for example concentration, time and addition of calcium chloride were studied. Osteoblast cells (MG-63) were cultured on different groups of titanium surfaces. In order to investigate titanium surfaces, SEM, AFM and EDS analyses were carried out. The results showed that surfaces treated with HCl–HF–H3PO4 had higher roughness, lower cytotoxicity level and better biocompatibility than controls. Moreover, addition of calcium chloride into mixed solution of three acids containing HCl, HF and H3PO4 is an important, predominant and new technique for obtaining biofunction in metals for biomedical use including dentistry. PMID:22460230

  6. Monte Carlo simulation of the effects of anode surface roughness on x-ray spectra

    SciTech Connect

    Kakonyi, Robert; Erdelyi, Miklos; Szabo, Gabor

    2010-11-15

    Purpose: Spectral and angular distribution of the x-ray beam generated by medical x-ray tubes as a function of anode surface roughness was analyzed. Methods: Different sets of profiles such as ideal flat, regular profiles, and measured profiles adopted from the literature were analyzed by means of MCNPX Monte Carlo simulator. The geometry used was simplified to separate different physical effects. A sphere centered on the origin of the coordinate system was divided into two hemispheres filled with tungsten and a vacuum, respectively. The studied anode surfaces were placed at the center of the plane of the hemisphere. The profiles were realized by means of the general lattice structure of the MCNPX. The energy and angular distributions of the excited photons were recorded with energy and angular resolutions of 0.5 keV and 1 deg., respectively, by means of point detectors. The range of the studied anode surface roughness was 0-550 {mu}m R{sub a}. The emission angle dependencies of the following quantities were analyzed: Half value layer (HVL) value, intensity, and spectral photon flux. Results: The analysis of the HVL of the x-ray beam showed that around an emission angle of 5 deg., the hardness of the beam was practically independent of the surface roughness. The value of this emission angle depends on the filtration. Below this critical angle, the HVL value decreases, while at a higher emission angle, the beam becomes harder with increasing surface roughness. The intensity degradation saturates with increasing roughness. The position of the maximum spectral photon flux shifts to higher emission angles as the anode surface roughness increases. The surface roughness (R{sub a}) was found to be an inadequate quantity to describe the effect of anode surface roughness on x-ray spectra since no definite connection was found between the values of the intensity degradation and surface roughness. At 120 kVp tube voltage and at a 3.84 {mu}m R{sub a} roughness value, the

  7. Enhancement of vortex induced forces and motion through surface roughness control

    DOEpatents

    Bernitsas, Michael M.; Raghavan, Kamaldev

    2011-11-01

    Roughness is added to the surface of a bluff body in a relative motion with respect to a fluid. The amount, size, and distribution of roughness on the body surface is controlled passively or actively to modify the flow around the body and subsequently the Vortex Induced Forces and Motion (VIFM). The added roughness, when designed and implemented appropriately, affects in a predetermined way the boundary layer, the separation of the boundary layer, the level of turbulence, the wake, the drag and lift forces, and consequently the Vortex Induced Motion (VIM), and the fluid-structure interaction. The goal of surface roughness control is to increase Vortex Induced Forces and Motion. Enhancement is needed in such applications as harnessing of clean and renewable energy from ocean/river currents using the ocean energy converter VIVACE (Vortex Induced Vibration for Aquatic Clean Energy).

  8. Reduction in surface roughness and aperture size effect for XeF2 etching of Si

    NASA Astrophysics Data System (ADS)

    Sugano, Koji; Tabata, Osamu

    2003-01-01

    Low etching pressure and addition of buffer gas successfully decrease the etched surface roughness and the aperture effect which represent challenges toward the application of silicon etching with XeF2 to MEMS fabrication. Etched roughness and aperture effect are extremely high and limit factors for the design rules of MEMS. By lowering the charge pressure of XeF2 from 390 to 65 Pa, the etched roughness decreased from 870.8 and 174.4 Å and the uniformity ((depth for 25 μm mask aperture)(depth for 175 μm mask aperture)× 100 %) improved from 71.3 to 88.7%. By adding N2 or reaction products including Xe and SiF4 as buffer gas, surface roughness was reduced and the surface morphology changed.

  9. Reduction of vortex induced forces and motion through surface roughness control

    SciTech Connect

    Bernitsas, Michael M; Raghavan, Kamaldev

    2014-04-01

    Roughness is added to the surface of a bluff body in a relative motion with respect to a fluid. The amount, size, and distribution of roughness on the body surface is controlled passively or actively to modify the flow around the body and subsequently the Vortex Induced Forces and Motion (VIFM). The added roughness, when designed and implemented appropriately, affects in a predetermined way the boundary layer, the separation of the boundary layer, the level of turbulence, the wake, the drag and lift forces, and consequently the Vortex Induced Motion (VIM), and the fluid-structure interaction. The goal of surface roughness control is to decrease/suppress Vortex Induced Forces and Motion. Suppression is required when fluid-structure interaction becomes destructive as in VIM of flexible cylinders or rigid cylinders on elastic support, such as underwater pipelines, marine risers, tubes in heat exchangers, nuclear fuel rods, cooling towers, SPAR offshore platforms.

  10. Significance of the Casimir force and surface roughness for actuation dynamics of MEMS

    NASA Astrophysics Data System (ADS)

    Broer, Wijnand; Palasantzas, George; Knoester, Jasper; Svetovoy, Vitaly B.

    2013-03-01

    Using the measured optical response and surface roughness topography as inputs, we perform realistic calculations of the combined effect of Casimir and electrostatic forces on the actuation dynamics of microelectromechanical systems (MEMS). In contrast with the expectations, roughness can influence MEMS dynamics, even at distances between bodies significantly larger than the root-mean-square roughness. This effect is associated with statistically rare high asperities that can be locally close to the point of contact. It is found that even though surface roughness appears to have a detrimental effect on the availability of stable equilibria, it ensures that those equilibria can be reached more easily than in the case of flat surfaces. Hence our findings play a principal role for the stability of microdevices such as vibration sensors, switches, and other related MEM architectures operating at distances below 100 nm.

  11. Contact mechanics for layered materials with randomly rough surfaces.

    PubMed

    Persson, B N J

    2012-03-01

    The contact mechanics model of Persson is applied to layered materials. We calculate the M function, which relates the surface stress to the surface displacement, for a layered material, where the top layer (thickness d) has different elastic properties than the semi-infinite solid below. Numerical results for the contact area as a function of the magnification are presented for several cases. As an application, we calculate the fluid leak rate for laminated rubber seals.

  12. Method for Fabricating Soft Tissue Implants with Microscopic Surface Roughness

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor); Rutledge, Sharon K. (Inventor)

    1999-01-01

    A method for fabricating soft tissue implants using a mold. The cavity surface of an initially untextured mold. made of an organic material such as epoxy. is given a thin film coating of material that has pinholes and is resistant to atomic particle bombardment. The mold cavity surface is then subjected to atomic particle bombardment, such as when placed in an isotropic atomic oxygen environment. Microscopic depressions in the mold cavity surface are created at the pinhole sites on the thin film coating. The thin film coating is removed and the mold is then used to cast the soft tissue implant. The thin film coating having pinholes may be created by chilling the mold below the dew point such that water vapor condenses upon it; distributing particles, that can partially dissolve and become attached to the mold cavity surface, onto the mold cavity surface; removing the layer of condensate, such as by evaporation; applying the thin film coating over the entire mold surface; and, finally removing the particles, such as by dissolving or brushing it off. Pinholes are created in the thin film coating at the sites previously occupied by the particles.

  13. A new method for modeling rough membrane surface and calculation of interfacial interactions.

    PubMed

    Zhao, Leihong; Zhang, Meijia; He, Yiming; Chen, Jianrong; Hong, Huachang; Liao, Bao-Qiang; Lin, Hongjun

    2016-01-01

    Membrane fouling control necessitates the establishment of an effective method to assess interfacial interactions between foulants and rough surface membrane. This study proposed a new method which includes a rigorous mathematical equation for modeling membrane surface morphology, and combination of surface element integration (SEI) method and the composite Simpson's approach for assessment of interfacial interactions. The new method provides a complete solution to quantitatively calculate interfacial interactions between foulants and rough surface membrane. Application of this method in a membrane bioreactor (MBR) showed that, high calculation accuracy could be achieved by setting high segment number, and moreover, the strength of three energy components and energy barrier was remarkably impaired by the existence of roughness on the membrane surface, indicating that membrane surface morphology exerted profound effects on membrane fouling in the MBR. Good agreement between calculation prediction and fouling phenomena was found, suggesting the feasibility of this method.

  14. Turbulent boundary layer over solid and porous surfaces with small roughness

    NASA Technical Reports Server (NTRS)

    Kong, F. Y.; Schetz, J. A.; Collier, F.

    1982-01-01

    The wind tunnel models and instrumentation used as well as data reduction and error analysis techniques employed are described for an experimental study conducted to measure directly skin friction and obtain profiles of mean velocity, axial and normal turbulence intensity, and Reynolds stress in the untripped boundary on a large diameter axisymmetric body. Results are given for such a body with a (1) smooth, solid surface; (2) a sandpaper roughened, solid surface; (3) a sintered metal, porous surface; (4) a ""smooth'' performated titanium surface; (5) a rough, solid surface made of fine diffusion bonded screening; and (6) a rough, porous surface made of the same screening. The roughness values were in low range (k+ 5 to 7) just above what is normally considered ""hydraulically smooth''. Measurements were taken at several axial locations and tow or normal stream freestream velocities, 45.1 m/sec and 53.5 m/sec.

  15. Use of upscaled elevation and surface roughness data in two-dimensional surface water models

    USGS Publications Warehouse

    Hughes, J.D.; Decker, J.D.; Langevin, C.D.

    2011-01-01

    In this paper, we present an approach that uses a combination of cell-block- and cell-face-averaging of high-resolution cell elevation and roughness data to upscale hydraulic parameters and accurately simulate surface water flow in relatively low-resolution numerical models. The method developed allows channelized features that preferentially connect large-scale grid cells at cell interfaces to be represented in models where these features are significantly smaller than the selected grid size. The developed upscaling approach has been implemented in a two-dimensional finite difference model that solves a diffusive wave approximation of the depth-integrated shallow surface water equations using preconditioned Newton–Krylov methods. Computational results are presented to show the effectiveness of the mixed cell-block and cell-face averaging upscaling approach in maintaining model accuracy, reducing model run-times, and how decreased grid resolution affects errors. Application examples demonstrate that sub-grid roughness coefficient variations have a larger effect on simulated error than sub-grid elevation variations.

  16. Comparative analysis of different measurement techniques for characterizing soil surface roughness in agricultural soils

    NASA Astrophysics Data System (ADS)

    Martinez-Agirre, Alex; Álvarez-Mozos, Jesús; Valle, José Manuel; Rodríguez, Álvaro; Giménez, Rafael

    2016-04-01

    Soil surface roughness can be defined as the variation in soil surface elevations, and as such, it is a key element in hydrology and soil erosion processes. In agricultural soils, roughness is mainly an anthropic factor determined by the type of tillage and management. Roughness is also a property with a high spatial variability, since the same type of tillage can result in surfaces with different roughness depending on the physical characteristics of the soil and atmospheric conditions. In order to quantify roughness and to parameterize its role in different processes, different measurement techniques have been used and several parameters have been proposed in the literature. The objective of this work is to evaluate different measurement techniques and assess their accuracy and suitability for quantifying surface roughness in agricultural soils. With this aim, a comparative analysis of three roughness measurement techniques has been carried out; (1) laser profilometer, (2) convergent photogrammetry and (3) terrestrial laser scanner. Roughness measurements were done in 3 experimental plots (5x5 meters) with different tillage treatments (representing different roughness conditions) obtained with typical agricultural tools. The laser profilometer registered vertically the distance from a reference bar down to the surface. It had a vertical accuracy of 1.25 mm, a sampling interval of 5 mm and a total length profile of 5 m. Eight profiles were taken per plot, four in parallel to tillage direction and four in perpendicular. Convergent photogrammetry consisted of 20-30 images taken per plot from a height of 5-10 m above ground (using an elevation platform), leading to point clouds of ~25 million points per plot. Terrestrial laser scanner measurements were taken from the four sides of each plot at a measurement height of ~1.75 m above ground. After orientating and corregistering the four scans, point clouds of ~60 million points were obtained per plot. The comparative

  17. Effect of surface roughness on erosion rates of pure copper coupons in pulsed vacuum arc system

    NASA Astrophysics Data System (ADS)

    Rao, Lakshminarayana; Munz, Richard J.

    2007-12-01

    Vacuum arc erosion measurements were performed on copper cathodes having different surface roughness and surface patterns in 10-5 Torr vacuum (1.3324 mPa), in an external magnetic field of 0.04 T. Different surface patterns and surface roughness were created by grit blasting with alumina grits (G-cathodes) and grinding with silicon carbide emery paper (E-cathodes). The erosion rates of these cathodes were obtained by measuring the weight loss of the electrode after igniting as many as 135 arc pulses, each of which was 500 µs long at an arc current of 125 A. The erosion rates measured indicate that erosion rates decrease with decreasing roughness levels. Results obtained indicate that both surface roughness and surface patterns affect the erosion rate. Having patterns perpendicular to the direction of cathode spot movement gives lower erosion rates than having patterns parallel to arc movement. Isotropic surfaces give lower erosion rates than patterned surfaces at the same roughness.

  18. Performance of a novel polishing rubber wheel in improving surface roughness of feldspathic porcelain.

    PubMed

    Han, Geum-Jun; Kim, Jae-Hoon; Lee, Mi-Ae; Chae, So-Yeon; Lee, Yun-Hee; Cho, Byeong-Hoon

    2014-01-01

    Replacing glazing with polishing is still controversial in terms of the surface roughness of dental porcelains. This study investigated the polishing performance of a ceramic-polishing rubber wheel (CP-RW), which contains large uniform and rounded silicon carbide particles and small diamond particles, in improving the surface roughness of two feldspathic porcelains for sintering and CAD/CAM milling. Using a confocal laser scanning microscopy, the changes in the surface roughness parameters were evaluated before and after polishing or glazing for three surface treatment groups: SofLex polishing, CP-RW polishing, and Glazing. Regardless of the parameters, all treatments reduced roughness values (repeated measures ANOVA, p<0.05). The roughness values obtained after CP-RW polishing were lower than those obtained after SofLex polishing and glazing (2-way ANOVA, p<0.05). Polishing both ceramics with CP-RW made the surfaces smooth with the lowest roughness values in all parameters. The effect was dependent on the materials used.

  19. Simulation of surface roughness during the formation of thermal spray coatings

    SciTech Connect

    Kanouff, M.P.

    1996-07-01

    The formation of a thermal spray coating was analyzed to identify methods to reduce the surface roughness of the coating. A new methodology was developed which uses a string of equally spaced node points to define the shape of the coating surface and to track the shape change as the thermal spray mass is deposited. This allows the calculation of arbitrary shapes for the coating surface which may be very complex. The model simulates the stochastic deposition of a large number of thermal spray droplets, where experimental data is used for the mass flux distribution on the target surface. This data shows that when the thermal spray mass impinges on the target surface, a large fraction of it (over-spray) splashes off the target and is re-deposited with a small spray angle, resulting in a large coating roughness. This analysis was used in a parameter study to identify methods for reducing the coating roughness. Effect of the shape of the profile for the pre-roughened substrate was found to be small. Decreasing the droplet size by a factor of 2 decreased the roughness by 13%. Increasing the spray angle for the over-spray by a factor of 2 decreased the roughness by 50%, and decreasing the amount of over- spray by a factor of 2 decreased the roughness by 51%.

  20. Phase Transition to a Time-Reversal Symmetry-Breaking State in d-Wave Superconducting Films with Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Higashitani, Seiji; Miyawaki, Nobumi

    2015-03-01

    The normal-superconducting phase transition in d-wave superconducting films is discussed with a focus on the effect of diffuse surface scattering. A specularity parameter S characterizing the boundary condition is introduced for systematic analysis of the surface effect. When S = 1 (the specular limit), the film can exhibit a novel superconductivity that spontaneously breaks time-reversal symmetry, as was shown by Vorontsov [Phys. Rev. Lett. 102, 177001 (2009)]. We find that this superconducting phase is suppressed as the degree of surface roughness increases, i.e., as the specularity S decreases. In particular, it is completely suppressed when S = 0 (the diffusive limit). Those results are explained from the viewpoint of surface odd-frequency pairing.

  1. 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.

  2. Effect of surface roughness on the texture and oxidation behavior of Zircaloy-4 cladding tube

    NASA Astrophysics Data System (ADS)

    Akhiani, Hamed; Szpunar, Jerzy A.

    2013-11-01

    Conventional pressure water reactors like CANDU use Zircaloy-4 as a fuel cladding tube. Surface roughness that arises from the manufacturing process, pilgering, may alter these tubes' properties in various ways. This paper presents a comparative study of cladding tubes with different surface conditions in order to investigate their effect on the Zircaloy-4 substrate and oxide textures as well as the oxidation kinetic. The experimental results reveal that surface roughness affects the oxidation rate and weight gain of the cladding tubes. Although surface polishing slightly changes the substrate texture, it induces no significant change in the oxide texture. Moreover, oxidation time does not significantly change the preferred orientation of the zirconium oxide.

  3. Influence of the atomic force microscope tip on the multifractal analysis of rough surfaces.

    PubMed

    Klapetek, Petr; Ohlídal, Ivan; Bílek, Jindrich

    2004-12-01

    In this paper, the influence of atomic force microscope tip on the multifractal analysis of rough surfaces is discussed. This analysis is based on two methods, i.e. on the correlation function method and the wavelet transform modulus maxima method. The principles of both methods are briefly described. Both methods are applied to simulated rough surfaces (simulation is performed by the spectral synthesis method). It is shown that the finite dimensions of the microscope tip misrepresent the values of the quantities expressing the multifractal analysis of rough surfaces within both the methods. Thus, it was concretely shown that the influence of the finite dimensions of the microscope tip changed mono-fractal properties of simulated rough surface to multifractal ones. Further, it is shown that a surface reconstruction method developed for removing the negative influence of the microscope tip does not improve the results obtained in a substantial way. The theoretical procedures concerning both the methods, i.e. the correlation function method and the wavelet transform modulus maxima method, are illustrated for the multifractal analysis of randomly rough gallium arsenide surfaces prepared by means of the thermal oxidation of smooth gallium arsenide surfaces and subsequent dissolution of the oxide films. PMID:15556700

  4. Modeling interface roughness scattering in a layered seabed for normal-incident chirp sonar signals.

    PubMed

    Tang, Dajun; Hefner, Brian T

    2012-04-01

    Downward looking sonar, such as the chirp sonar, is widely used as a sediment survey tool in shallow water environments. Inversion of geo-acoustic parameters from such sonar data precedes the availability of forward models. An exact numerical model is developed to initiate the simulation of the acoustic field produced by such a sonar in the presence of multiple rough interfaces. The sediment layers are assumed to be fluid layers with non-intercepting rough interfaces.

  5. Numerical simulations of sink-flow boundary layers over rough surfaces

    NASA Astrophysics Data System (ADS)

    Yuan, J.; Piomelli, U.

    2014-01-01

    Turbulent sink flows over smooth or rough walls with sand-grain roughness are studied using large-eddy and direct numerical simulations. Mild and strong levels of acceleration are applied, yielding a wide range of Reynolds number (Reθ = 372 - 2748) and cases close to the reverse-transitional state. Flow acceleration and roughness are shown to exert opposite effects on boundary-layer integral parameters, on the Reynolds stresses, budgets of turbulent kinetic energy, and properties of turbulent structures in the vicinity of the rough surface; statistics exhibit similarity when plotted using inner scaling for cases with the same roughness Reynolds number, k+. Acceleration leads to a decrease of k+, while roughness increases it. For cases with higher k+, the low-speed streaks become destabilized, and turbulent structures near the wall are distributed more uniformly in the wall-parallel plane; they are less extended in the streamwise direction, but more densely packed. Higher k+ also causes decorrelation of the outer-layer hairpin packets with the near-wall structures, probably due to the direct impact of random roughness elements on the hairpin legs. Wall-similarity applies for the fully turbulent cases, in which the outer-layer turbulent statistics are affected by acceleration only. It is shown that being in the hydraulically smooth regime is a necessary condition for reverse-transition, supporting the idea that relaminarization starts from the inner region, where roughness effects dominate.

  6. Influence of polishing procedures on the surface roughness of dental ceramics made by different techniques.

    PubMed

    Oliveira-Junior, Osmir Batista; Buso, Leonardo; Fujiy, Fábio Hiroshi; Lombardo, Geraldo Henrique Leao; Campos, Fernanda; Sarmento, Hugo Ramalho; Souza, Rodrigo Othavio Assuncao

    2013-01-01

    The aim of this study was to evaluate the influence of 2 different surface polishing procedures-glazing and manual polishing-on the roughness of ceramics processed by computer-aided design/computer-aided manufacturing (CAD/CAM) and conventional systems (stratification technique). Eighty ceramic discs (diameter: 8 mm, thickness: 1 mm) were prepared and divided among 8 groups (n = 10) according to the type of ceramic disc and polishing method: 4 GZ and 4 MP. Specimens were glazed according to each manufacturer's recommendations. Two silicone polishing points were used on the ceramic surface for manual polishing. Roughness was measured using a surface roughness tester. The roughness measurements were made along a distance of 2 mm on the sample surface and the speed of reading was 0.1 mm/s. Three measurements were taken for each sample. The data (μm) were statistically analyzed using analysis of variance (ANOVA) and Tukey's test (α = 0.05). Qualitative analysis was performed using scanning electron microscopy (SEM). The mean (± SD) roughness values obtained for GZ were: 1.1 ± 0.40 μm; 1.0 ± 0.31 μm; 1.6 ± 0.31 μm; and 2.2 ± 0.73 μm. For MP, the mean values were: 0.66 ± 0.13 μm; 0.43 ± 0.14 μm; 1.6 ± 0.55 μm; and 2.0 ± 0.63 μm. The mean roughness values were significantly affected by the ceramic type (P = 0.0001) and polishing technique (P = 0.0047). The SEM images confirmed the roughness data. The manually polished glass CAD/CAM ceramics promoted lower surface roughness than did the glazed feldspathic dental ceramics.

  7. Investigation on three-dimensional surface roughness evaluation of engineering ceramic for rotary ultrasonic grinding machining

    NASA Astrophysics Data System (ADS)

    Wei, Shiliang; Zhao, Hong; Jing, Juntao

    2015-12-01

    Surface roughness has considerable influence on its quality and function of products in precision and ultra-precision machining, and the same situation applies to engineering ceramic for rotary ultrasonic grinding machining (RUGM). This paper presents a new parameter, called fractal root mean square deviation, for evaluating engineering ceramic three-dimensional (3D) surface roughness of RUGM. Based on engineering ceramics surface of RUGM is typical isotropic, the mathematical model of fractal root mean square deviation was established, and it possesses double characteristics of absolute measurement and multi-scale. Then validation has been implemented, and fractal root mean square deviation is superior to evaluate engineering ceramic 3D surface roughness with better resolution and sensitivity. Furthermore, the relationship between main factor parameters and fractal root mean square deviation was proposed. The evaluation parameter and the results could be implemented in practice to get higher quality surface.

  8. Time Invariant Surface Roughness Evolution during Atmospheric Pressure Thin Film Depositions

    PubMed Central

    Merkh, Thomas; Spivey, Robert; Lu, Toh Ming

    2016-01-01

    The evolution of thin film morphology during atmospheric pressure deposition has been studied utilizing Monte Carlo methods. Time invariant root-mean-squared roughness and local roughness morphology were both observed when employing a novel simulation parameter, modeling the effect of the experimental high pressure condition. This growth regime, where the surface roughness remains invariant after reaching a critical value, has not been classified by any existing universality class. An anti-shadowing growth mechanism responsible for this regime occurs when particles undergo binary collisions beneath the surface apexes. Hence, this mechanism is applicable when the mean free path of the depositing species is comparable to the amplitude of the surface features. Computationally this has been modeled by allowing particles to change direction at a specified height above the local film surface. This modification of the incoming flux trajectory consequently has a dramatic smoothening effect, and the resulting surfaces appear in agreement with recent experimental observations. PMID:26814165

  9. Roughness gradients on zirconia for rapid screening of cell-surface interactions: Fabrication, characterization and application.

    PubMed

    Flamant, Quentin; Stanciuc, Ana-Maria; Pavailler, Hugo; Sprecher, Christoph Martin; Alini, Mauro; Peroglio, Marianna; Anglada, Marc

    2016-10-01

    Roughness is one of the key parameters for successful osseointegration of dental implants. The understanding of how roughness affects cell response is thus crucial to improve implant performance. Surface gradients, which allow rapid and systematic investigations of cell-surface interactions, have the potential to facilitate this task. In this study, a novel method aiming to produce roughness gradients at the surface of zirconia using hydrofluoric acid etching was implemented. The topography was exhaustively characterized at the microscale and nanoscale by white light interferometry and atomic force microscopy, including the analysis of amplitude, spatial, hybrid, functional, and fractal parameters. A rapid screening of the influence of roughness on human mesenchymal stem cell morphology was conducted and potential correlations between roughness parameters and cell morphology were investigated. The roughness gradient induced significant changes in cell area (p < 0.001), aspect ratio (p = 0.01), and solidity (p = 0.026). Nanoroughness parameters were linearly correlated to cell solidity (p < 0.005), while microroughness parameters appeared nonlinearly correlated to cell area, highlighting the importance of multiscale optimization of implant topography to induce the desired cell response. The gradient method proposed here drastically reduces the efforts and resources necessary to study cell-surface interactions and provides results directly transferable to industry. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2502-2514, 2016. PMID:27227541

  10. Thermal emission spectroscopy of microcrystalline sedimentary phases: Effects of natural surface roughness on spectral feature shape

    NASA Astrophysics Data System (ADS)

    Hardgrove, C. J.; Rogers, A. D.; Glotch, T. D.; Arnold, J. A.

    2016-03-01

    Distinguishing between microcrystalline and macrocrystalline mineral phases can help constrain the conditions under which those minerals formed or the degree of postdepositional alteration. This study demonstrates the effects of crystal size and surface roughness on thermal infrared emission spectra of micro and macrocrystalline phases of the two most common minerals on Earth, quartz and calcite. Given the characteristic depositional and environmental conditions under which microcrystalline minerals form, and the recent observations of high-silica deposits on Mars, it is important to understand how these unique materials can be identified using remote infrared spectroscopy techniques. We find that (a) microcrystalline minerals exhibit naturally rough surfaces compared to their macrocrystalline counterparts at the 10 µm scale; and that (b) this roughness causes distinct spectral differences within the Reststrahlen bands of each mineral. These spectral differences occur for surfaces that are rough on the wavelength scale, where the absorption coefficient (k) is large. Specifically, the wavelength positions of the Reststrahlen features for microcrystalline phases are narrowed and shifted compared to macrocrystalline counterparts. The spectral shape differences are small enough that the composition of the material is still recognizable, but large enough such that a roughness effect could be detected. Petrographic and topographic analyses of microcrystalline samples suggest a relationship between crystal size and surface roughness. Together, these observations suggest it may be possible to make general inferences about microcrystallinity from the thermal infrared spectral character of samples, which could aid in reconstructions of sedimentary rock diagenesis where corresponding petrographic or microimaging is not available.

  11. Experimental analysis of the surface roughness evolution of etched glass for micro/nanofluidic devices

    NASA Astrophysics Data System (ADS)

    Ren, J.; Ganapathysubramanian, B.; Sundararajan, S.

    2011-02-01

    Roughness of channel surfaces, both deterministic and random, is known to affect the fluid flow behavior in micro/nanoscale fluidic devices. This has relevance particularly for applications involving non-Newtonian fluids, such as in biomedical lab-on-chip devices. While several studies have investigated effects of relative large, deterministic surface structures on fluid flow, the effect of random roughness on microfluidic flow remains relatively unexplored. In this study, the effects of processing conditions for wet etching of glass including etching time and etching orientation on centre-line average (Ra) and the autocorrelation length (ACL) were investigated. Statistical distribution of the roughness was also studied. Results indicated that ACL can be tailored in the range of 1-4 µm by changing etching time in horizontal etching while Ra was found to increase weakly with etching time in all three etching orientations. Analysis of the experimental data using the Kolmogorov-Smirnov goodness-of-fit hypothesis test shows that the glass surface roughness does not follow a Gaussian distribution, as is typically assumed in the literature. Instead, the T location-scale distribution fits the roughness data with 1.11% error. These results provide promising insights into tailoring surface roughness for improving microfluidic devices.

  12. Effects of hydraulic roughness on surface textures of gravel-bed rivers

    USGS Publications Warehouse

    Buffington, J.M.; Montgomery, D.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 (??0(bf)), representing a hypothetical reference condition of low hydraulic roughness. For a given ??0(bf), 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 of D50 can be up to 90% smaller than those predicted from ??0(bf). 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.

  13. On the calibration of Mars Orbiter Laser Altimeter surface roughness estimates using high-resolution DTMs

    NASA Astrophysics Data System (ADS)

    Poole, W.; Muller, J.-P.; Gupta, S.

    2012-04-01

    Planetary surface roughness is critical in the selection of suitable landing sites for robotic lander or roving missions. It has also been used in the identification of terrain, for better calibration of radar returns and improved understanding of aerodynamic roughness [1]. One of the secondary science goals of the Mars Orbiter Laser Altimeter (MOLA) was the study of surface roughness at 100 m, using the backscatter pulse width of the laser pulse, which has a footprint of 168 m in diameter [2]. The pulse width values in the final release (version L) of the MOLA Precision Experiment Data Record (PEDR) have been corrected for across track slopes and the removal of 'bad points', and footprint diameter was revised to 75 m, with a 35 m response length in [3]. We look here at comparing surface roughness values derived from the MOLA pulse-width data with surface roughness estimates derived at various scales from high-resolution digital terrain models (DTMs) to determine if these theoretically derived surface roughness lengths are physically meaningful. The final four potential landing sites for Mars Science Laboratory were used in this study, as they have extensive HiRISE (1m) and HRSC (50m) DTM coverage [4]. Pulse width data from both the MOLA PEDR (version L) and the data used in [3] was collected and compared for each of the sites against surface roughness estimates at various scales from HiRISE, and HRSC, DTMs using the RMS height. This assumed a circular footprint for each MOLA footprint and that the horizontal geolocation of the PEDR MOLA footprints was sufficiently accurate to only extract those DTM points which lay inside the footprints. Results from the MOLA PEDR data were extremely poor, and show no correlation with surface roughness measurements from DTMs. Results using the corrected data in [3] were mixed. Eberswalde and Holden Craters both show significantly improved correlations for a variety of surface roughness scales. The best correlations were found to

  14. Infrared Low Temperature Turbine Vane Rough Surface Heat Transfer Measurements

    NASA Technical Reports Server (NTRS)

    Boyle, R. J.; Spuckler, C. M.; Lucci, B. L.; Camperchioli, W. P.

    2000-01-01

    Turbine vane heat transfer distributions obtained using an infrared camera technique are described. Infrared thermography was used because noncontact surface temperature measurements were desired. Surface temperatures were 80 C or less. Tests were conducted in a three vane linear cascade, with inlet pressures between 0.14 and 1.02 atm., and exit Mach numbers of 0.3, 0.7, and 0.9, for turbulence intensities of approximately 1 and 10%. Measurements were taken on the vane suction side, and on the pressure side leading edge region. The designs for both the vane and test facility are discussed. The approach used to account for conduction within the vane is described. Midspan heat transfer distributions are given for the range of test conditions.

  15. Surface-Enhanced Raman Scattering and Biophysics

    NASA Astrophysics Data System (ADS)

    Kneipp, Katrin

    2001-03-01

    Surface-enhanced Raman scattering (SERS) is a phenomenon resulting in strongly increased Raman signals from molecules which have been attached to metallic nanostructures such as colloidal silver or gold particles. The effect combines the structural information content of a vibrational spectroscopy with extremely high sensitivity and in some cases, it showes promise in overcoming the low-sensitivity problems inherent in Raman spectroscopy. Cross sections effective in SERS can reach 10 16 to 10 15 cm2 per molecule corresponding to enhancement factors of about fourteen orders of magnitude compared with “normal” non-resonant Raman scattering. Such extremely large cross sections are sufficient for single molecule Raman spectroscopy. The high sensitivity and particularly the single molecule capabilities open up exciting perspectives for SERS as tool for basic research in biophysics, biochemistry and in laboratory medicine, where it allows to study extremely small amounts of biolomedically relevant molecules in order to understand development of diseases, treatment and therapy control based on molecular structural information at the single molecule level. The most spectacular applications might appear in rapidly spectroscopic characterization of specific DNA fragments down to structurally sensitive detection of single bases in order to elucidate the human genome sequence without any labeling technology. I will briefly introduce the SERS effect and report experiments with Raman scattering of single molecules. Potential and limitations of surface-enhanced Raman techniques as a tool in biophysics and biomedical spectroscopy will be considered.

  16. A wind tunnel study of flows over idealised urban surfaces with roughness sublayer corrections

    NASA Astrophysics Data System (ADS)

    Ho, Yat-Kiu; Liu, Chun-Ho

    2016-08-01

    Dynamics in the roughness (RSLs) and inertial (ISLs) sublayers in the turbulent boundary layers (TBLs) over idealised urban surfaces are investigated analytically and experimentally. In this paper, we derive an analytical solution to the mean velocity profile, which is a continuous function applicable to both RSL and ISL, over rough surfaces in isothermal conditions. Afterwards, a modified mixing-length model for RSL/ISL transport is developed that elucidates how surface roughness affects the turbulence motions. A series of wind tunnel experiments are conducted to measure the vertical profiles of mean and fluctuating velocities, together with momentum flux over various configurations of surface-mounted ribs in cross flows using hot-wire anemometry (HWA). The analytical solution agrees well with the wind tunnel result that improves the estimate to mean velocity profile over urban surfaces and TBL dynamics as well. The thicknesses of RSL and ISL are calculated by monitoring the convergence/divergence between the temporally averaged and spatio-temporally averaged profiles of momentum flux. It is found that the height of RSL/ISL interface is a function of surface roughness. Examining the direct, physical influence of roughness elements on near-surface RSL flows reveals that the TBL flows over rough surfaces exhibit turbulence motions of two different length scales which are functions of the RSL and ISL structure. Conclusively, given a TBL, the rougher the surface, the higher is the RSL intruding upward that would thinner the ISL up to 50 %. Therefore, the conventional ISL log-law approximation to TBL flows over urban surfaces should be applied with caution.

  17. Surface roughness due to residual ice in the use of low power deicing systems

    NASA Technical Reports Server (NTRS)

    Shin, Jaiwon; Bond, Thomas H.

    1993-01-01

    Thicknesses of residual ice are presented to provide information on surface contamination and associated roughness during deicing events. Data was obtained from low power ice protection systems tests conducted in the Icing Research Tunnel at NASA Lewis Research Center (LeRC) with nine different deicing systems. Results show that roughness associated with residual ice is not characterized by uniformly distributed roughness. Results also show that deicing systems require a critical mass of ice to generate a sufficient expelling force to remove the ice.

  18. Effect of wettability and surface roughness on ice-adhesion strength of hydrophilic, hydrophobic and superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Bharathidasan, T.; Kumar, S. Vijay; Bobji, M. S.; Chakradhar, R. P. S.; Basu, Bharathibai J.

    2014-09-01

    The anti-icing properties of hydrophilic, hydrophobic and superhydrophobic surfaces/coatings were evaluated using a custom-built apparatus based on zero-degree cone test method. The ice-adhesion reduction factor (ARF) of these coatings has been evaluated using bare aluminium alloy as a reference. The wettability of the surfaces was evaluated by measuring water contact angle (WCA) and sliding angle. It was found that the ice-adhesion strength (τ) on silicone based hydrophobic surfaces was ∼ 43 times lower than compared to bare polished aluminium alloy indicating excellent anti-icing property of these coatings. Superhydrophobic coatings displayed poor anti-icing property in spite of their high water repellence. Field Emission Scanning Electron Microscope reveal that Silicone based hydrophobic coatings exhibited smooth surface whereas the superhydrophobic coatings had a rough surface consisting of microscale bumps and protrusions superimposed with nanospheres. Both surface roughness and surface energy play a major role on the ice-adhesion strength of the coatings. The 3D surface roughness profiles of the coatings also indicated the same trend of roughness. An attempt is made to correlate the observed ice-adhesion strength of different surfaces with their wettability and surface roughness.

  19. Effects of surface roughness on the average heat transfer of an impinging air jet

    SciTech Connect

    Beitelmal, A.H.; Saad, M.A.; Patel, C.D.

    2000-01-01

    Localized cooling by impinging flow has been used in many industrial applications such as in cooling of gas turbine blades and drying processes. Here, effect of surface roughness of a uniformly heated plate on the average heat transfer characteristics of an impinging air jet was experimentally investigated. Two aluminum plates, one with a flat surface and the second with some roughness added to the surface were fabricated. The roughness took the shape of a circular array of protrusions of 0.5mm base and 0.5mm height. A circular Kapton heater of the same diameter as the plates (70mm) supplied the necessary power. The surfaces of the plates were polished to reduce radiation heat losses and the back and sides insulated to reduce conduction heat losses. temperatures were measured over a Reynolds number ranging from 9,600 to 38,500 based on flow rate through a 6.85mm diameter nozzle. The temperature measurements were repeated for nozzle exit-to-plate spacing, z/d, ranging from 1 to 10. The average Nusselt number for both cases was plotted versus the Reynolds number and their functional correlation was determined. The results indicate an increase of up to 6.0% of the average Nusselt number due to surface roughness. This modest increase provides evidence to encourage further investigation and characterization of the surface roughness as a parameter for enhancing heat transfer.

  20. An Analytical Solution of Radiative Transfer in the Coupled Atmosphere-Ocean System with Rough Surface

    NASA Technical Reports Server (NTRS)

    Jin, Zhonghai; Charlock, Thomas P.; Rutledge, Ken; Knut Stamnes; Wang, Yingjian

    2006-01-01

    Using the efficient discrete-ordinate method, we present an analytical solution for radiative transfer in the coupled atmosphere-ocean system with rough air-water interface. The theoretical formulations of the radiative transfer equation and solution are described. The effects of surface roughness on radiation field in the atmosphere and ocean are studied and compared with measurements. The results show that ocean surface roughness has significant effects on the upwelling radiation in the atmosphere and the downwelling radiation in the ocean. As wind speed increases, the angular domain of sunglint broadens, the surface albedo decreases, and the transmission to ocean increases. The downward radiance field in the upper ocean is highly anisotropic, but this anisotropy decreases rapidly as surface wind increases and as depth in ocean increases. The effects of surface roughness on radiation also depend greatly on both wavelength and angle of incidence (i.e., solar elevation); these effects are significantly smaller throughout the spectrum at high sun. The model-observation discrepancies may indicate that the Cox-Munk surface roughness model is not sufficient for high wind conditions.

  1. Rock surface roughness measurement using CSI technique and analysis of surface characterization by qualitative and quantitative results

    NASA Astrophysics Data System (ADS)

    Mukhtar, Husneni; Montgomery, Paul; Gianto; Susanto, K.

    2016-01-01

    In order to develop image processing that is widely used in geo-processing and analysis, we introduce an alternative technique for the characterization of rock samples. The technique that we have used for characterizing inhomogeneous surfaces is based on Coherence Scanning Interferometry (CSI). An optical probe is first used to scan over the depth of the surface roughness of the sample. Then, to analyse the measured fringe data, we use the Five Sample Adaptive method to obtain quantitative results of the surface shape. To analyse the surface roughness parameters, Hmm and Rq, a new window resizing analysis technique is employed. The results of the morphology and surface roughness analysis show micron and nano-scale information which is characteristic of each rock type and its history. These could be used for mineral identification and studies in rock movement on different surfaces. Image processing is thus used to define the physical parameters of the rock surface.

  2. Instruments and MethodsIn situ measurements of snow surface roughness using a laser profiler

    NASA Astrophysics Data System (ADS)

    Lacroix, P.; Legrésy, B.; Langley, K.; Hamran, S. E.; Kohler, J.; Roques, S.; Rémy, F.; Dechambre, M.

    The snow surface roughness at centimetre and millimetre scales is an important parameter related to wind transport, snowdrifts, snowfall, snowmelt and snow grain size. Knowledge of the snow surface roughness is also of high interest for analyzing the signal from radar sensors such as SAR, altimeters and scatterometers. Unfortunately, this parameter has seldom been measured over snow surfaces. The techniques used to measure the roughness of other surfaces, such as agricultural or sand soils, are difficult to implement in polar regions because of the harsh climatic conditions. In this paper we develop a device based on a laser profiler coupled with a GPS receiver on board a snowmobile. This instrumentation was tested successfully in midre Lovénbreen, Svalbard, in April 2006. It allowed us to generate profiles of 3 km sections of the snow-covered glacier surface. Because of the motion of the snowmobile, the roughness signal is mixed with the snowmobile signal. We use a distance/frequency analysis (the empirical mode decomposition) to filter the signal. This method allows us to recover the snow surface structures of wavelengths between 4 and 50 cm with amplitudes of >1 mm. Finally, the roughness parameters of snow surfaces are retrieved. The snow surface roughness is found to be dependent on the scales of the observations. The retrieved RMS of the height distribution is found to vary between 0.5 and 9.2 mm, and the correlation length is found to be between 0.6 and 46 cm. This range of measurements is particularly well adapted to the analysis of GHz radar response on snow surfaces.

  3. Effect of Cigarette Smoke on Surface Roughness of Different Denture Base Materials

    PubMed Central

    Mahross, Hamada Zaki; Mohamed, Mahmoud Darwish; Hassan, Ahmed Mohammed

    2015-01-01

    Background Surface roughness is an important property of denture bases since denture bases are in contact with oral tissues and a rough surface may affect tissues health due to microorganism accumulation. Therefore, the effect of cigarette smoke on the surface roughness of two commercially available denture base materials was evaluated to emphasize which type has superior properties for clinical use. Materials and Methods A total numbers of 40 specimens were constructed from two commercially available denture base materials; heat-cured PMMA and visible light cured UDMA resins (20 for each). The specimens for each type were randomly divided into: Group I: Heat cured resin control group; Group II: Heat cured acrylic resin specimens exposed to cigarette smoking; Group III: Light cured resin control group; Group IV: Light cured resin specimens exposed to cigarette smoking. The control groups used for immersion in distilled water and the smoke test groups used for exposure to cigarette smoking. The smoke test groups specimens were exposed to smoking in a custom made smoking chamber by using 20 cigarettes for each specimen. The surface roughness was measured by using Pocket SurfPS1 profilometer and the measurements considered as the difference between the initial and final roughness measured before and after smoking. Results The t-test for paired observation of test specimens after exposure to smoking was indicated significant change in surface roughness for Group II (p< 0.05) but has no significance with Group IV. Otherwise, there were no significant differences with control groups (Group I and III). Conclusion The surface roughness of the dentures constructed from heat cured acrylic resin had been increased after exposure to cigarette smoke but had no impact on the dentures constructed from visible light cured resin. PMID:26501010

  4. Surface Roughness of Composite Resins after Simulated Toothbrushing with Different Dentifrices

    PubMed Central

    Monteiro, Bruna; Spohr, Ana Maria

    2015-01-01

    Background: The aim of the study was to evaluate, in vitro, the surface roughness of two composite resins submitted to simulated toothbrushing with three different dentifrices. Materials and Methods: Totally, 36 samples of Z350XT and 36 samples of Empress Direct were built and randomly divided into three groups (n = 12) according to the dentifrice used (Oral-B Pro-Health Whitening [OBW], Colgate Sensitive Pro-Relief [CS], Colgate Total Clean Mint 12 [CT12]). The samples were submitted to 5,000, 10,000 or 20,000 cycles of simulated toothbrushing. After each simulated period, the surface roughness of the samples was measured using a roughness tester. Results: According to three-way analysis of variance, dentifrice (P = 0.044) and brushing time (P = 0.000) were significant. The composite resin was not significant (P = 0.381) and the interaction among the factors was not significant (P > 0.05). The mean values of the surface roughness (µm) followed by the same letter represent no statistical difference by Tukey's post-hoc test (P <0.05): Dentifrice: CT12 = 0.269a; CS Pro- Relief = 0.300ab; OBW = 0.390b. Brushing time: Baseline = 0,046ª; 5,000 cycles = 0.297b; 10,000 cycles = 0.354b; 20,000 cycles = 0.584c. Conclusion: Z350 XT and Empress Direct presented similar surface roughness after all cycles of simulated toothbrushing. The higher the brushing time, the higher the surface roughness of composite resins. The dentifrice OBW caused a higher surface roughness in both composite resins. PMID:26229362

  5. Evaluation of surface roughness of different restorative composites after polishing using atomic force microscopy

    PubMed Central

    Kumari, C Meena; Bhat, K Manohar; Bansal, Rahul

    2016-01-01

    Introduction: Resin based composites are widely used aesthetic restorative materials in clinical restorative dentistry. The filler size and the percentage of fillers affects smooth surface, clinical durability, aesthetics, better optical properties, compatibility with natural enamel tissue, surface gloss, and preventing the discoloration of the restoration. The finishing and polishing of tooth-coloured restorations are necessary clinical steps for better aesthetics and longevity of restored teeth. Aim: In this study nano composites were chosen, because these contain nano particles which provide better overall composites features, including the quality of polished surface. The aim of this study was to evaluate the surface roughness of different newer posterior composites. Material and Method: Five commercially available posterior restorative composite were tested in this study. All the specimens were polished with shofu multi step polishing system. After polishing the samples were all analyzed by atomic force microscopy which is used to study surface topography and surface morphology of materials. Results: The values of surface roughness of each specimen were statistically analyzed using Kruskal Wallis ANOVA, and Pair wise comparisons by Mann-Whitney U test setting the statistical significance at p ≤ 0.05. Conclusion: Tetric Evo Ceram, Z350 exhibited less surface roughness compared to Ever X, Clearfil Majesty and Sure fil SDR. There was no statistical difference between groups regarding surface rough ness between groups. PMID:26957795

  6. Surface roughness and translucency of resin composites after immersion in coffee and soft drink.

    PubMed

    de Gouvea, Cresus V Depes; Bedran, Luciane M; de Faria, Márcia Aguiar; Cunha-Ferreira, Neli

    2011-01-01

    The aim of this study was to evaluate the in vitro changes in color and surface roughness of different composite resins when subjected to cycles of immersion in three coloring solutions: coffee, soft drink, and coffee plus soft drink. Sixty test specimens were made of each material, all in shade A3. Translucency and initial roughness measurements were taken by spectrophotometer and roughness meter. Then the samples were submitted to three cycles per day of exposure to potentially coloring solutions for a period of 15 days. Final roughness and translucency measurements were taken, the mean and standard deviation calculated for each resin and each variable. Data were initially analyzed by the one away ANOVA test, which showed significant differences between groups (p<0.05). Subsequently the post hoc and Tukey tests were performed with level of significance of 0.05. The results showed that the coloring substances altered translucency and surface roughness. DURAFILL resin immersed in the soft drink (M3) was the least pigmented, while CONCEPT resin immersed in the coffee (M2) showed the the least loss of surface smoothness. The Spearman and Pearson coefficients were 0.38 and 0.04 respectively, signifying that there is no correlation between roughness and translucency. PMID:22010399

  7. Scattering by Artificial Wind and Rain Roughened Water Surfaces at Oblique Incidences

    NASA Technical Reports Server (NTRS)

    Craeye, C.; Sobieski, P. W.; Bliven, L. F.

    1997-01-01

    Rain affects wind retrievals from scatterometric measurements of the sea surface. To depict the additional roughness caused by rain on a wind driven surface, we use a ring-wave spectral model. This enables us to analyse the rain effect on K(u) band scatterometric observations from two laboratory experiments. Calculations based on the small perturbation method provide good simulation of scattering measurements for the rain-only case, whereas for combined wind and rain cases, the boundary perturbation method is appropriate.

  8. Effect of surface roughness of chitosan-based microspheres on cell adhesion

    NASA Astrophysics Data System (ADS)

    Zan, Qingfeng; Wang, Chen; Dong, Limin; Cheng, Peng; Tian, Jiemo

    2008-11-01

    Microspheres are novel candidate materials for microcarriers and tissue-engineering scaffolds. Chitosan microspheres were selected as the base materials because of their excellent properties for biomedical applications. But their smooth surfaces were not adapted for cell attachment. Hence, in order to improve the roughness of chitosan microspheres, β-TCP/chitosan composite microspheres were developed. From SEM photographs, the coarse surfaces of composite microspheres were observed, there were some ceramic particles standing out of the chitosan matrix. And their roughness measured by profilometers was about 2.0 μm. Mouse MC3T3-E1 osteoblasts were seeded on the microspheres for evaluating the attachment interaction between cells and materials. According to the ESEM photographs and MTT assay, the adherence and proliferation of osteoblasts on the surfaces of modified microspheres were better than those on the chitosan microspheres, which were mainly attributed to the improved roughness of surface.

  9. Surface roughness and gloss study of prints: application of specular reflection at near infrared

    NASA Astrophysics Data System (ADS)

    Silfsten, P.; Dutta, R.; Pääkkönen, P.; Tåg, C.-M.; Gane, P. A. C.; Peiponen, K.-E.

    2012-12-01

    Absolute reflectance data were measured with a spectrophotometer in the visible and near infrared (NIR) spectral range. The specular reflectance data in the NIR were used for the assessment of the surface roughness of magenta, yellow, cyan and black prints on paper. In addition, surface roughness data obtained from the prints with a mechanical diamond stylus, an optical profiling system and the spectrophotometer are compared with each other. The surface roughness obtained with the aid of the spectrophotometer data suggests a smoother surface than when measured with the diamond stylus and the optical profiling system. The gloss of the prints can be obtained from the absolute specular reflectance spectra in the spectral region of visible light. It is shown that specular reflection data at a fixed wavelength in the NIR are useful also in the interpretation of gloss in the visible spectral range, but using an unconventional grazing angle of incidence.

  10. Rough surface electrical contact resistance considering scale dependent properties and quantum effects

    SciTech Connect

    Jackson, Robert L.; Crandall, Erika R.; Bozack, Michael J.

    2015-05-21

    The objective of this work is to evaluate the effect of scale dependent mechanical and electrical properties on electrical contact resistance (ECR) between rough surfaces. This work attempts to build on existing ECR models that neglect potentially important quantum- and size-dependent contact and electrical conduction mechanisms present due to the asperity sizes on typical surfaces. The electrical conductance at small scales can quantize or show a stepping trend as the contact area is varied in the range of the free electron Fermi wavelength squared. This work then evaluates if these effects remain important for the interface between rough surfaces, which may include many small scale contacts of varying sizes. The results suggest that these effects may be significant in some cases, while insignificant for others. It depends on the load and the multiscale structure of the surface roughness.

  11. 3D surface roughness measurement for scaliness scoring of psoriasis lesions.

    PubMed

    Ahmad Fadzil, M Hani; Prakasa, Esa; Asirvadam, Vijanth Sagayan; Nugroho, Hermawan; Affandi, Azura Mohd; Hussein, Suraiya Hani

    2013-11-01

    Psoriasis is an incurable skin disorder affecting 2-3% of the world population. The scaliness of psoriasis is a key assessment parameter of the Psoriasis Area and Severity Index (PASI). Dermatologists typically use visual and tactile senses in PASI scaliness assessment. However, the assessment can be subjective resulting in inter- and intra-rater variability in the scores. This paper proposes an assessment method that incorporates 3D surface roughness with standard clustering techniques to objectively determine the PASI scaliness score for psoriasis lesions. A surface roughness algorithm using structured light projection has been applied to 1999 3D psoriasis lesion surfaces. The algorithm has been validated with an accuracy of 94.12%. Clustering algorithms were used to classify the surface roughness measured using the proposed assessment method for PASI scaliness scoring. The reliability of the developed PASI scaliness algorithm was high with kappa coefficients>0.84 (almost perfect agreement).

  12. Determination of surface roughness of a proglacial floodplain using TLS data. What to consider!

    NASA Astrophysics Data System (ADS)

    Baewert, Henning; Morche, David

    2015-04-01

    The determination of surface roughness of channel reaches and floodplains is a part of geomorphologic studies since decades. Usually, the grain roughness determination requires knowledge about the grain size distribution of the study site. However, in some cases this approach is impractical, especially when investigating large areas (when form roughness is more important) or even impossible due to inaccessibility. In addition, the particles within the channel are usually covered by other particles or incorporated into finer sediment. Removing the particles from the channel bottom already means a disturbance of the system under investigation and thus possible falsification of the results. Here, the application of terrestrial laser scanning (TLS) offers new possibilities. The indirect recording of the surface leads to a significant reduction of the workload in the field. Furthermore, form roughness and burial/imbrication are taken into account. However, there are numerous factors which may influence the results. Therefore, this study focuses on the following questions: 1) Is the application of several filter techniques influencing the calculation of the roughness height? 2) How crucial is the point density of the point cloud? The roughness height is determined by standard deviation of the height values (Z) within a grid cell. Due to this the third question is: 3) How does the grid cell size influence the roughness height? To answer these questions a floodplain in the proglacial zone of the Gepatschferner glacier, Austria was surveyed using the terrestrial laser scanner ILRIS-36D. The floodplain was scanned from two different directions and with three different resolutions (20 mm, 50 mm, and 100 mm). When processing the raw data different filters were used. The influence of the cell size was examined by using different grid cell sizes (10 mm, 50 mm, 100 mm, 250 mm, 430 mm, 690 mm, and 1085 mm) when calculating the roughness height. A pebble count was carried out to

  13. Surface roughness and packaging tightness affect calcium lactate crystallization on Cheddar cheese.

    PubMed

    Rajbhandari, P; Kindstedt, P S

    2014-01-01

    Calcium lactate crystals that sometimes form on Cheddar cheese surfaces are a significant expense to manufacturers. Researchers have identified several postmanufacture conditions such as storage temperature and packaging tightness that contribute to crystal formation. Anecdotal reports suggest that physical characteristics at the cheese surface, such as roughness, cracks, and irregularities, may also affect crystallization. The aim of this study was to evaluate the combined effects of surface roughness and packaging tightness on crystal formation in smoked Cheddar cheese. Four 20-mm-thick cross-section slices were cut perpendicular to the long axis of a retail block (~300g) of smoked Cheddar cheese using a wire cutting device. One cut surface of each slice was lightly etched with a cheese grater to create a rough, grooved surface; the opposite cut surface was left undisturbed (smooth). The 4 slices were vacuum packaged at 1, 10, 50, and 90kPa (very tight, moderately tight, loose, very loose, respectively) and stored at 1°C. Digital images were taken at 1, 4, and 8 wk following the first appearance of crystals. The area occupied by crystals and number of discrete crystal regions (DCR) were quantified by image analysis. The experiment was conducted in triplicate. Effects of storage time, packaging tightness, surface roughness, and their interactions were evaluated by repeated-measures ANOVA. Surface roughness, packaging tightness, storage time, and their 2-way interactions significantly affected crystal area and DCR number. Extremely heavy crystallization occurred on both rough and smooth surfaces when slices were packaged loosely or very loosely and on rough surfaces with moderately tight packaging. In contrast, the combination of rough surface plus very tight packaging resulted in dramatic decreases in crystal area and DCR number. The combination of smooth surface plus very tight packaging virtually eliminated crystal formation, presumably by eliminating available

  14. Radioisotope Deposition on Interior Building Surfaces: Air Flow and Surface Roughness Influences

    SciTech Connect

    Leonard, Bobby E

    2005-12-15

    Interior surface deposition effects of vaporized radioactive aerosols are important in understanding their behavior in accident conditions such as the Japanese nuclear laboratory accident in 1999 and the Chernobyl nuclear power plant accident in 1986, where entire communities had to be abandoned because of surface contamination, and the hopefully unlikelihood of a terrorist dirty nuclear bomb attack. Airborne radon progeny offers an opportunity to study radioisotope surface deposition. A significant annual lung cancer rate is also attributed to airborne radon progeny in the interior domestic environment. Surface deposition rates influence the airborne progeny levels. Here, we report extensive {sup 218}Po deposition rates over typical air change rates (ACHs) from 0.02 to 1.0 h{sup -1} for interior furnishings surfaces in a 0.283-m{sup 3} test chamber to supplement earlier reported deposition rates for interior wall, ceiling, and floor surfaces. In analyzing the deposition results from the different materials, it is found that they correlate in terms of roughness with relative static friction and aerodynamic shear stress. Extrapolation to perfectly smooth surfaces provides a good estimate of the Fick's law value. Contrary to prior radon analysis at higher air flow, where the Crump and Seinfeld (CS) turbulent deposition models seemed to fit, at low ACH below 0.5 h{sup -1} the deposition data found excellent agreement with a new Brownian diffusive deposition model for laminar flow. A composite model using the Brownian diffusive laminar flow and the CS turbulent flow models provides an excellent fit to all data. These results provide insight into contamination issues relative to other airborne radioisotopes, with the relative effects being dependent on the airborne contaminant particle sizes and their respective diffusion coefficients as seen in the two deposition models.

  15. Effects of electrode surface roughness on motional heating of trapped ions

    NASA Astrophysics Data System (ADS)

    Lin, Kuan-Yu; Low, Guang Hao; Chuang, Isaac L.

    2016-07-01

    Electric-field noise is a major source of motional heating in trapped-ion quantum computation. While the influence of trap-electrode geometries on electric-field noise has been studied in patch potential and surface adsorbate models, only smooth surfaces are accounted for by current theory. The effects of roughness, a ubiquitous feature of surface electrodes, are poorly understood. We investigate its impact on electric-field noise by deriving a rough-surface Green's function and evaluating its effects on adsorbate-surface binding energies. At cryogenic temperatures, heating-rate contributions from adsorbates are predicted to exhibit an exponential sensitivity to local surface curvature, leading to either a large net enhancement or suppression over smooth surfaces. For typical experimental parameters, orders-of-magnitude variations in total heating rates can occur depending on the spatial distribution of adsorbates. Through careful engineering of electrode surface profiles, our results suggests that heating rates can be tuned over orders of magnitudes.

  16. Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions

    NASA Astrophysics Data System (ADS)

    Magee, N. B.; Miller, A.; Amaral, M.; Cumiskey, A.

    2014-11-01

    Here we show high-magnification images of hexagonal ice crystals acquired by environmental scanning electron microscopy (ESEM). Most ice crystals were grown and sublimated in the water vapor environment of an FEI-Quanta-200 ESEM, but crystals grown in a laboratory diffusion chamber were also transferred intact and imaged via ESEM. All of these images display prominent mesoscopic topography including linear striations, ridges, islands, steps, peaks, pits, and crevasses; the roughness is not observed to be confined to prism facets. The observations represent the most highly magnified images of ice surfaces yet reported and expand the range of conditions in which rough surface features are known to be conspicuous. Microscale surface topography is seen to be ubiquitously present at temperatures ranging from -10 °C to -40 °C, in supersaturated and subsaturated conditions, on all crystal facets, and irrespective of substrate. Despite the constant presence of surface roughness, the patterns of roughness are observed to be dramatically different between growing and sublimating crystals, and transferred crystals also display qualitatively different patterns of roughness. Crystals are also demonstrated to sometimes exhibit inhibited growth in moderately supersaturated conditions following exposure to near-equilibrium conditions, a phenomenon interpreted as evidence of 2-D nucleation. New knowledge about the characteristics of these features could affect the fundamental understanding of ice surfaces and their physical parameterization in the context of satellite retrievals and cloud modeling. Links to supplemental videos of ice growth and sublimation are provided.

  17. Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions

    NASA Astrophysics Data System (ADS)

    Magee, N. B.; Miller, A.; Amaral, M.; Cumiskey, A.

    2014-03-01

    Here we show high-magnification images of hexagonal ice crystals acquired by Environmental Scanning Electron Microscopy (ESEM). Most ice crystals were grown and sublimated in the water vapor environment of an FEI-Quanta-200 ESEM, but crystals grown in a laboratory diffusion chamber were also transferred intact and imaged via ESEM. All of these images display prominent mesoscopic topography including linear striations, ridges, islands, steps, peaks, pits, and crevasses; the roughness is not observed to be confined to prism facets. The observations represent the most highly magnified images of ice surfaces yet reported and expand the range of conditions where the rough surface features are known to be conspicuous. Microscale surface topography is seen to be ubiquitously present at temperatures ranging from -10 °C to -40 °C, at super-saturated and sub-saturated conditions, on all crystal facets, and irrespective of substrate. Despite the constant presence of surface roughness, the patterns of roughness are observed to be dramatically different between growing and sublimating crystals, and transferred crystals also display qualitatively different patterns of roughness. Crystals are also demonstrated to sometimes exhibit inhibited growth in moderately supersaturated conditions following exposure to near-equilibrium conditions, a phenomena interpreted as evidence of 2-D nucleation. New knowledge of the characteristics of these features could affect the fundamental understanding of ice surfaces and their physical parameterization in the context of satellite retrievals and cloud modeling. Links to Supplement videos of ice growth and sublimation are provided.

  18. Impact of surface roughness of gypsum materials on adaptation of zirconia cores

    PubMed Central

    Kim, Ki-Baek; Kim, Sa-Hak

    2015-01-01

    PURPOSE The present study investigated the influences of various gypsum materials on the precision of fit of CAD/CAM-fabricated prostheses and analyzed their correlation with surface roughness. MATERIALS AND METHODS The master model of the mandibular right first molar was replicated, and four experimental groups based on two types of Type IV stone (GC Fujirock EP, Die keen) and two types of scannable stone (Aesthetic-Basegold, Everest Rock) were created to include a total of 40 specimens, 10 in each group. The surface roughness of the working models for the respective experimental groups was measured. Once the zirconia cores had been fabricated, the marginal and internal fits were measured with a digital microscope using the silicone replica technique. The mean and standard deviation of the respective points of measurement were computed and analyzed through the one-way ANOVA and Tukey's HSD test. The correlation between surface roughness and the precision of fit of the zirconia core was analyzed using the Pearson correlation analysis (α=.05). RESULTS The zirconia cores fabricated from the scannable stone working models exhibited a superior precision of fit as compared to those fabricated from the Type IV stone working models. The correlation analysis results showed a clear positive correlation between surface roughness and the precision of fit of zirconia cores in all of the experimental groups (P<.05). CONCLUSION The results confirmed that the surface roughness of dental working models has a decisive influence on the precision of fit of zirconia cores. PMID:26140171

  19. Effects of Yb:KYW thin-disk femtosecond laser ablation on enamel surface roughness

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Sun, Yuchun; Wang, Yong; Lü, Peijun

    2014-07-01

    This study aimed to quantitatively evaluate the surface roughness of enamel following ablation with a Yb:KYW thin-disk femtosecond pulsed laser at different fluences (F), scanning speeds and scanning line spacings. Thirty human extracted teeth were sectioned into crowns and roots along the cementum-enamel junction, and then the crowns were cut longitudinally into sheets about 1.5 mm thick. The samples were randomly divided into ten groups (n=3). Samples of groups 1-8 were irradiated with a femtosecond pulsed laser. These enamel samples were fixed on a stage at focus plane, and a laser beam irradiated onto the samples through a galvanometric scanning system, with which rectangular movement could be achieved. Samples of groups 9 and 10 were prepared with grinding instruments. Following ablation and preparation, the samples were examined for surface roughness with a three-dimensional laser profile measurement microscope. The results showed that scanning speed and scanning line spacing had little influence on the surface roughness of femtosecond pulsed laser-ablated enamel, except when F=4 J/cm2. When a lower fluence was used, the enamel surface roughness was higher, and vice versa. This study showed that various laser fluences, scanning speeds and scanning line spacings can affect and alter enamel surface roughness. Therefore, adequate parameters should be chosen to achieve the proper therapeutic benefits.

  20. Vortex shedding and morphodynamic response of bed surfaces containing non-erodible roughness elements

    NASA Astrophysics Data System (ADS)

    McKenna Neuman, Cheryl; Sanderson, Robert Steven; Sutton, Stephen

    2013-09-01

    A series of wind tunnel experiments was carried out to investigate particle entrainment from surfaces in which one or more roughness elements were embedded. Thin sand strips were employed to eliminate impact and ejection, and thus isolate entrainment by fluid drag. The pattern of erosion is consistent with the presence of coherent vortices, inclusive of trailing vortices in the wake flow. The shape and orientation of the roughness element strongly influence this pattern. When an upwind supply of saltators is introduced, the majority of particles within the bed are entrained through impact, with the exception of a sand tail to the lee of the roughness element. That is, the effect of coherent structures within the airflow, as related to spatial variation in the fluid drag exerted on the bed surface, is completely overprinted by the saltation cloud and the blocking of particle trajectories by the upwind face of the roughness element. In a repeated set of experiments, the bed was allowed to fully adjust its morphology to the transport system. In this case, particle entrainment did not selectively occur within the zone of wake flow, and by inference the fluid stress across the test surface appeared to be uniform. These experiments support the hypothesis that vortex annihilation occurs on morphodynamically adjusted surfaces. In summary, the system response to the emergence of non-erodible roughness elements on surfaces affected by wind erosion involves a suite of geophysical processes, each of which attains varied levels of dominance within a given morphodynamic domain.

  1. Effects of Er: YAG laser irradiation on wettability, surface roughness, and biocompatibility of SLA titanium surfaces: an in vitro study.

    PubMed

    Ayobian-Markazi, Nader; Karimi, Mohammadreza; Safar-Hajhosseini, Ali

    2015-02-01

    The erbium: yttrium-aluminum-garnet (Er: YAG) laser has been introduced as an effective method in the decontamination of implant surfaces. Data concerning the effects of the Er: YAG laser on the biological and surface properties of titanium are conflicting. Cellular behavior is greatly affected by surface properties, including composition, roughness, wettability, and morphology of the titanium surface. The aim of this study was to investigate the influence of the Er: YAG laser on the biocompatibility, surface roughness, and wettability of sandblasted and acid-etched (SLA) titanium surfaces. Twenty-one SLA titanium disks were irradiated by the Er: YAG laser at a pulse energy of 100 mJ, with a pulse frequency of 10 Hz under water irrigation for 1 min. Cell viability, surface roughness, and wettability alterations were evaluated. Thirteen nonirradiated SLA disks were used as the control groups. Human osteoblast-like SaOs-2 cells were seeded onto the disks in culture media. Cell viability was evaluated using the methylthiazol tetrazolium assay. The surface roughness and wettability of the test and control groups were measured using profilometer and tensiometer devices, respectively. A significantly higher cell viability rate was observed in the test group (p = 0.032). The surface roughness was significantly reduced in the test group compared with the control group (p = 0.008). The surface wettability was significantly higher in the test group (p = 0.004). Within the limits of this study, the application of the Er: YAG laser with the previously described properties did not appear to have adverse effects on the biocompatibility of the SLA titanium surfaces. Application of this laser decreased the surface roughness and increased the wettability of the SLA titanium surfaces.

  2. Effect of triple antibiotic paste with or without ethylenediaminetetraacetic acid on surface loss and surface roughness of radicular dentine.

    PubMed

    Nerness, A Z; Ehrlich, Y; Spolnik, K; Platt, J A; Yassen, G H

    2016-05-01

    This study aimed to compare the effect of two concentrations of triple antibiotic paste (TAP) with or without ethylenediaminetetraacetic acid (EDTA) on surface loss and surface roughness of radicular dentine. Human radicular dentine specimens were randomized into six experimental groups (n = 16 per group). The first and second groups were treated with 1,000 mg/mL or 1 mg/mL of TAP for 4 weeks. The third and fourth groups were treated with 1,000 mg/mL or 1 mg/mL of TAP for 4 weeks followed by 17 % EDTA for 5 min. The fifth group was treated with 17 % EDTA for 5 min and the sixth group received no treatment (control). Dentine surface loss and surface roughness were quantified after various treatments using optical and contact profilometry, respectively. One-way ANOVA followed by Fisher's protected least significant differences was used for statistical analyses. All treatment groups showed significantly higher surface loss compared to the untreated dentine. Dentine treated with 1,000 mg/mL had significant increase in surface loss and surface roughness compared to dentine treated with 1 mg/mL of TAP. The use of EDTA after both concentrations of TAP did not have significant additive effect on surface loss and surface roughness of dentine. The clinically used concentration of TAP (1,000 mg/mL) caused significantly higher surface loss and surface roughness of radicular dentine compared to the use of 1 mg/mL of TAP. Furthermore, the substantial amount of dentine surface loss and surface roughness detected in the current study may be attributed to TAP rather than EDTA.

  3. Finite Element Method Simulations of the Near-Field Enhancement at the Vicinity of Fractal Rough Metallic Surfaces

    SciTech Connect

    Micic, Miodrag; Klymyshyn, Nicholas A.; Lu, H PETER.

    2004-03-04

    Near-field optical enhancement at metal surfaces and methods such as surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS), fluorescent quenching and enhancement, and various near-field scanning microscopies (NSOM) all depend on a metals surface properties, mainly on its morphology and SPR resonant frequency. We report on simulations of the influence of different surface morphologies on electromagnetic field enhancements at the rough surfaces of noble metals and also evaluate the optimal conditions for the generation of a surface-enhanced Raman signal of absorbed species on a metallic substrate. All simulations were performed with a classical electrodynamics approach using the full set of Maxwells equations, which were solved with the three-dimensional finite element method (FEM). Two different classes of surfaces where modeled using fractals, representing diffusion limited aggregation growth dendritic structures, such as one on the surface of electrodes, and second one representing the sponge-like structure used to model surfaces of particles with high porosity, such as metal coated catalyst supports. The simulations depict the high inhomogeneity of an enhanced electromagnetic field as both a field enhancement and field attenuation near the surface. While the diffusion limited aggregation dendritical fractals enhanced the near-field electromagnetic field, the sponge fractals significantly reduced the local electromagnetic field intensity. Moreover, the fractal orders of the fractal objects did not significantly alter the total enhancement, and the distribution of a near-field enhancement was essentially invariant to the changes in the angle of an incoming laser beam.

  4. Effect of surface roughness on the microwave brightness temperature of soils

    NASA Technical Reports Server (NTRS)

    Choudhury, B. J.; Schmugge, T. J.; Chang, A.

    1977-01-01

    The effect of surface roughness on the brightness temperature of a moist terrain was studied through the modification of Fresnel reflection coefficient and using the radiative transfer equation. Model calculations are in good qualitative agreement with the observed dependence of the brightness temperature on the moisture content in the surface layer.

  5. Surface-Roughness-Based Virtual Textiles: Evaluation Using a Multi-Contactor Display.

    PubMed

    Philpott, Matthew; Summers, Ian R

    2015-01-01

    Virtual textiles, generated in response to exploratory movements, are presented to the fingertip via a 24-contactor vibrotactile array. Software models are based on surface-roughness profiles from real textiles. Results suggest that distinguishable "textile-like" surfaces are produced, but these lack the necessary accuracy for reliable matching to real textiles.

  6. 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

  7. Surface roughness of zirconia for full-contour crowns after clinically simulated grinding and polishing.

    PubMed

    Hmaidouch, Rim; Müller, Wolf-Dieter; Lauer, Hans-Christoph; Weigl, Paul

    2014-12-01

    The aim of this study was to evaluate the effect of controlled intraoral grinding and polishing on the roughness of full-contour zirconia compared to classical veneered zirconia. Thirty bar-shaped zirconia specimens were fabricated and divided into two groups (n=15). Fifteen specimens (group 1) were glazed and 15 specimens (group 2) were veneered with feldspathic ceramic and then glazed. Prior to grinding, maximum roughness depth (Rmax) values were measured using a profilometer, 5 times per specimen. Simulated clinical grinding and polishing were performed on the specimens under water coolant for 15 s and 2 N pressure. For grinding, NTI diamonds burs with grain sizes of 20 µm, 10 µm, and 7.5 µm were used sequentially. The ground surfaces were polished using NTI kits with coarse, medium and fine polishers. After each step, Rmax values were determined. Differences between groups were examined using one-way analysis of variance (ANOVA). The roughness of group 1 was significantly lower than that of group 2. The roughness increased significantly after coarse grinding in both groups. The results after glazing were similar to those obtained after fine grinding for non-veneered zirconia. However, fine-ground veneered zirconia had significantly higher roughness than venerred, glazed zirconia. No significant difference was found between fine-polished and glazed zirconia, but after the fine polishing of veneered zirconia, the roughness was significantly higher than after glazing. It can be concluded that for full-contour zirconia, fewer defects and lower roughness values resulted after grinding and polishing compared to veneered zirconia. After polishing zirconia, lower roughness values were achieved compared to glazing; more interesting was that the grinding of glazed zirconia using the NTI three-step system could deliver smooth surfaces comparable to untreated glazed zirconia surfaces.

  8. Effect of whitening dentifrices on the surface roughness of a nanohybrid composite resin

    PubMed Central

    da Rosa, Gabriela Migliorin; da Silva, Luciana Mendonça; de Menezes, Márcio; do Vale, Hugo Felipe; Regalado, Diego Ferreira; Pontes, Danielson Guedes

    2016-01-01

    Objectives: The present study verified the influence of whitening dentifrices on the surface roughness of a nanohybrid composite resin. Materials and Methods: Thirty-two specimens were prepared with Filtek™ Z350 XT (3M/ESPE) and randomly divided into four groups (n = 08) that were subjected to brushing simulation equivalent to the period of 1 month. The groups assessed were a control group with distilled water (G1), Colgate Total 12 Professional Clean (G2), Sensodyne Extra Whitener Extra Fresh (G3), and Colgate Luminous White (G4). A sequence of 90 cycles was performed for all the samples. The initial roughness of each group was analyzed by the Surface Roughness Tester (TR 200-TIME Group Inc., CA, USA). After the brushing period, the final roughness was measured, and the results were statistically analyzed using nonparametric Kruskal–Wallis and Dunn tests for intergroup roughness comparison in the time factor. For intragroup and “Δ Final − Initial” comparisons, the Wilcoxon test and (one-way) ANOVA were, respectively, performed (α = 0.05). Results: The roughness mean values before and after brushing showed no statistically significant difference when the different dentifrices were used. None of the dentifrices analyzed increased significantly the nanohybrid composite resin surface roughness in a 1 month of tooth brushing simulation. Conclusions: These results suggest that no hazardous effect on the roughness of nanohybrid composite resin can be expected when whitening dentifrices are used for a short period. Similar studies should be conducted to analyze other esthetic composite materials. PMID:27095891

  9. Surface roughness of zirconia for full-contour crowns after clinically simulated grinding and polishing.

    PubMed

    Hmaidouch, Rim; Müller, Wolf-Dieter; Lauer, Hans-Christoph; Weigl, Paul

    2014-12-01

    The aim of this study was to evaluate the effect of controlled intraoral grinding and polishing on the roughness of full-contour zirconia compared to classical veneered zirconia. Thirty bar-shaped zirconia specimens were fabricated and divided into two groups (n=15). Fifteen specimens (group 1) were glazed and 15 specimens (group 2) were veneered with feldspathic ceramic and then glazed. Prior to grinding, maximum roughness depth (Rmax) values were measured using a profilometer, 5 times per specimen. Simulated clinical grinding and polishing were performed on the specimens under water coolant for 15 s and 2 N pressure. For grinding, NTI diamonds burs with grain sizes of 20 µm, 10 µm, and 7.5 µm were used sequentially. The ground surfaces were polished using NTI kits with coarse, medium and fine polishers. After each step, Rmax values were determined. Differences between groups were examined using one-way analysis of variance (ANOVA). The roughness of group 1 was significantly lower than that of group 2. The roughness increased significantly after coarse grinding in both groups. The results after glazing were similar to those obtained after fine grinding for non-veneered zirconia. However, fine-ground veneered zirconia had significantly higher roughness than venerred, glazed zirconia. No significant difference was found between fine-polished and glazed zirconia, but after the fine polishing of veneered zirconia, the roughness was significantly higher than after glazing. It can be concluded that for full-contour zirconia, fewer defects and lower roughness values resulted after grinding and polishing compared to veneered zirconia. After polishing zirconia, lower roughness values were achieved compared to glazing; more interesting was that the grinding of glazed zirconia using the NTI three-step system could deliver smooth surfaces comparable to untreated glazed zirconia surfaces. PMID:25059249

  10. Degradation Characteristics of MgO Based Magnetic Tunnel Junction Caused by Surface Roughness of Ta/Ru Buffer Layers.

    PubMed

    Lee, Jung Min; Choi, Chul Min; Sukegawa, Hiroaki; Lee, Jeong Yong; Mitani, Seiji; Song, Yun-Heub

    2016-01-01

    We investigated how surface roughness of a Ta/Ru buffer layer affects the degradation characteristics on MgO-based magnetic tunnel junctions (MTJs). MTJs with worse surface roughness on the buffer layer showed increased resistance drift and degraded time-dependent dielectric breakdown (TDDB) characteristics. We suggest that this resulted from reduced MgO thickness on the MTJ with worse surface roughness on the buffer layer, which was estimated by the TDDB and analytic approach. As a result, surface roughness of the buffer layer is a critical factors that impacts the reliability of MTJs, and it should be controlled to have the smallest roughness value as possible. PMID:27398503

  11. Parameterization of albedo, thermal inertia, and surface roughness of desert scrub/sandy soil surface

    NASA Technical Reports Server (NTRS)

    Otterman, J.; Mccumber, M.

    1986-01-01

    Spectral albedo, A sub n, for the direct solar beam is defined as A sub n (r sub i,s, theta sub 0) = r sub i exp(-s tan theta sub 0)1-I(s) where I(s) is the integral over all reflection angles describing the interception by the absorbing plants of the flux reflected from the soil, r sub i soil reflectance, assumed Lambertian, S the projection on a vertical plane of plants per unit surface area, and theta sub 0 is the solar zenith angle. Hemispheric reflectance for the direct solar beam equals 1-I(s) times the reflectance to the zenith. The values of s of 0.1, 0.2, and 0.3 respectively quantify sparse, moderately dense, and very dense desert scrub. Thin plants are assumed to be of negligible thermal inertia, and thus directly yield the absorbed insolation to the atmosphere. Surface thermal inertia is therefore effectively reduced. The ratio of surface roughness height to plant height is parameterized for sparse, moderately dense, and very dense desert-scrub as a function of s based on data expressing the dependence of this ratio on plant silhouette.

  12. The effects of extraoral porcelain polishing sequences on surface roughness and color of feldspathic porcelain.

    PubMed

    Yuzugullu, Bulem; Celik, Cigdem; Erkut, Selim; Ozcelik, Tuncer Burak

    2009-01-01

    The aim of this study was to evaluate the surface properties and color of porcelain modified by extraoral polishing sequences. Six different surface treatment regimens (diamond burs, self-glaze, overglaze, reglaze, Pearl Surface polishing system, and Diamond Twist SCL) were applied to 60 porcelain disks (n = 10 per group). Profilometry and atomic force microscopy (AFM) were used for the determination of surface roughness (Ra); color changes (deltaE*) were investigated by spectrophotometry. Statistical comparisons were made using analysis of variance, the Kruskal-Wallis test, and the Pearson correlation coefficient test. Surface treatments significantly affected Ra values (P < .001) but had no effect on color (P > .05). AFM findings were consistent with Ra values. Color did not appear to be correlated with surface roughness (P > .05). The findings concluded that the Pearl Surface system helps to decrease chairside time and may be used as an alternative to overglazing. PMID:20095196

  13. Effect ofartificial accelerated aging on color stability and surface roughness of indirect composites.

    PubMed

    Zanin, Fabíola Rejane; Garcia, Lucas da Fonseca Roberti; Casemiro, Luciana Assirati; Pires-de-Souza, Fernanda de Carvalho Panzeri

    2008-03-01

    Direct and indirect composite resins have different forms of polymerization. Some materials require a post-cure system associating light and heat enhancing clinical properties. This study assessed the changes in color and surface roughness of three indirect composite resins after accelerated aging. Twelve specimens (15 x 2 mm) were obtained for each tested material. Subsequently, the first measurements for roughness tests and colorimetric spectrophotometry (CIE L*a*b* scale) were performed. Specimens were subject to accelerated aging for 384 hours. New measurements were then performed to evaluate the resulting change. Accelerated aging produced color change and increased surface roughness in all composite resins. Solidex resin showed color changes above the clinically accepted value (DeltaE = 4.31 +/- 0.22), and roughness values (Ra = 0.088 +/- 0.008 microm) statistically lower than that of Artglass (Ra = 0.141 +/- 0.026 microm) and Targis (Ra = 0.124 +/- 0.02 microm) (p<0.001). All the indirect resins tested showed color change and increased roughness after accelerated aging. Solidex showed color stability above a quantitative level considered clinically acceptable and lower roughness values compared to the other resins.

  14. Surface roughness and dislocation density in InP/InGaAs layers

    NASA Astrophysics Data System (ADS)

    Masson, Denis P.; Laframboise, Sylvain

    2004-12-01

    A subtle roughening of the surface of a buried 60 nm InGaAs epitaxial layer was detected using a combination of sample cleaving, selective chemical etching and Field Emission Scanning Electron Microscopy (FESEM). In our technology, InGaAs is the photo-absorbing layer of Metal Organic Chemical Vapor Deposition (MOCVD) grown layers used in the monolithic integration of active photo detectors and a passive mux/demux. Conventional Photo-Luminescence (PL) and X-Ray Diffraction (XRD) techniques used to monitor and optimize the growth of epitaxial layers did not show this microscopic surface roughness. The appearance of roughness in the InGaAs layer was linked to very large changes in the dislocation density of the layers grown over the rough surface. Increases of up to three orders of magnitude in the Etch Pit Density (EPD from 104 to 107 cm-2) were revealed using a standard Huber Etch. The Huber Etch also showed the preferred formation of "pairs" of dislocations threading out from a common point on the rough InGaAs surface. Changes in growth conditions resulted in the complete elimination of roughness and of excessive dislocation densities

  15. 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.

  16. Evaluation of surface roughness and hardness of different glass ionomer cements

    PubMed Central

    Bala, Oya; Arisu, Hacer Deniz; Yikilgan, Ihsan; Arslan, Seda; Gullu, Abdulkadir

    2012-01-01

    Objectives: The aim of this study was to evaluate surface roughness and hardness of a nanofiller GIC, a resin-modified GIC, three conventional GICs, and a silver-reinforced GIC. Methods: For each material, 11 spcecimens were prepared and then stored in distilled water at 37 °C for 24 h. The surface roughness of 5 specimens was measured using a surface profilometer before polishing and after polishing with coarse, medium, fine, superfine aluminum oxide abrasive Sof-Lex discs respectively. The hardness of the upper surfaces of the remaining 6 specimens was measured with a Vickers microhardness measuring instrument. Results: All tested GICs showed lower surface roughness values after the polishing procedure. Surface finish of nanofiller GIC was smoother than the other tested GICs after polishing. This was followed by resin-modified GIC, Fuji II LC; then silver-reinforced GIC, Argion Molar, conventional GICs, Aqua Ionofil Plus, Fuji IX, and Ionofil Molar, respectively. The result of the hardness test indicated that the microhardness value of silver-reinforced GIC was greater than that of the other GICs. When the hardness values of all tested GICs were compared, the differences between materials (except Aqua Ionofil Plus with Ionofil Molar and Ketac N100 with Fuji II LC (P>.05)) were found statistically significant (P<.05). Conclusions: According to the results of this study, it can be concluded that the differences in the composition of GICs may affect their surface roughness and hardness. PMID:22229011

  17. Large Wind Farms and the Scalar Flux over an Heterogeneously Rough Land Surface

    NASA Astrophysics Data System (ADS)

    Calaf, Marc; Higgins, Chad; Parlange, Marc B.

    2014-12-01

    The influence of surface heterogeneities extends vertically within the atmospheric surface layer to the so-called blending height, causing changes in the fluxes of momentum and scalars. Inside this region the turbulence structure cannot be treated as horizontally homogeneous; it is highly dependent on the local surface roughness, the buoyancy and the horizontal scale of heterogeneity. The present study analyzes the change in scalar flux induced by the presence of a large wind farm installed across a heterogeneously rough surface. The change in the internal atmospheric boundary-layer structure due to the large wind farm is decomposed and the change in the overall surface scalar flux is assessed. The equilibrium length scale characteristic of surface roughness transitions is found to be determined by the relative position of the smooth-to-rough transition and the wind turbines. It is shown that the change induced by large wind farms on the scalar flux is of the same order of magnitude as the adjustment they naturally undergo due to surface patchiness.

  18. Effects of internal bremsstrahlung of tritium β-decay and surface roughness in the BIXS method

    NASA Astrophysics Data System (ADS)

    Mao, L.; An, Z.; Liang, J. H.; Long, X. G.; Peng, S. M.; Zhang, W. G.

    2011-01-01

    We have studied the effects of the internal bremsstrahlung of tritium β-decay, sample surface roughness and tritium content as well on the tritium β-decay induced X-ray spectroscopy (BIXS) for tritium measurements based on Monte Carlo simulations. The Knipp-Uhlenbeck-Bloch theoretical model was adopted for the internal bremsstrahlung. It is found that the contributions of internal bremsstrahlung of tritium β-decays are approximately 30%, 10%, 4% and 2% of the corresponding external bremsstrahlung for C, Ti, Mo and W materials, respectively, and the sample surface roughness may cause an error of several percent in the BIXS method if the surface roughness of a sample is in a reasonable range. Moreover, the effect of tritium content should be taken into account when a sample contains a large amount of tritium, otherwise, the tritium contents measured by the BIXS method will be underestimated, for example, by up to ˜15% for Ti metal.

  19. Surface roughness and gloss of current CAD/CAM resin composites before and after toothbrush abrasion.

    PubMed

    Koizumi, Hiroyasu; Saiki, Osamu; Nogawa, Hiroshi; Hiraba, Haruto; Okazaki, Tomoyo; Matsumura, Hideo

    2015-01-01

    The purpose of this study was to evaluate the gloss and surface roughness behaviors of newly developed CAD/CAM composite blocks with different filler contents and characteristics. The gloss and surface roughness were quantified before and after a toothbrush dentifrice abrasion test; the results were compared to the gloss and surface roughness of a ceramic CAD/CAM block. Knoop hardness was determined before abrasion test. The results were analyzed by ANOVA, Tukey HSD, and Dunnett t test (p<0.05). The rank order of Knoop hardness was as follows: Vita Mark II>Vita Enamic>Gradia block>Shofu Block HC, Lava Ultimate≥Katana Avencia block≥Cerasmart. After toothbrush abrasion, a significant difference in the gloss unit was detected between the Shofu Block HC material and the ceramic block. The Ra and Rz of the Cerasmart and Shofu Block HC materials were significantly larger than those of the ceramic block after toothbrush abrasion.

  20. Dual frequency microwave radiometer measurements of soil moisture for bare and vegetated rough surfaces

    NASA Technical Reports Server (NTRS)

    Lee, S. L.

    1974-01-01

    Controlled ground-based passive microwave radiometric measurements on soil moisture were conducted to determine the effects of terrain surface roughness and vegetation on microwave emission. Theoretical predictions were compared with the experimental results and with some recent airborne radiometric measurements. The relationship of soil moisture to the permittivity for the soil was obtained in the laboratory. A dual frequency radiometer, 1.41356 GHz and 10.69 GHz, took measurements at angles between 0 and 50 degrees from an altitude of about fifty feet. Distinct surface roughnesses were studied. With the roughness undisturbed, oats were later planted and vegetated and bare field measurements were compared. The 1.4 GHz radiometer was less affected than the 10.6 GHz radiometer, which under vegetated conditions was incapable of detecting soil moisture. The bare surface theoretical model was inadequate, although the vegetation model appeared to be valid. Moisture parameters to correlate apparent temperature with soil moisture were compared.

  1. A light load model combining surface roughness and waviness to predict thermal contact conductance

    NASA Astrophysics Data System (ADS)

    Yovanovich, M. M.; Fisher, N. J.; Saabas, H. J.

    1983-06-01

    Thermal contact conductance data of wavy-rough stainless steel surfaces are compared with the theoretical values of the Clausing-Chao point contact model (PCM) and of the Cooper-Mikic-Yovanovich conforming, rough surface model (CRM). Neither model accurately predicts the conductances over all contact pressures; however they appear to represent the light and heavy load bounds on the conductances. The PCM is modified to include the effects of surface roughness, the lateral boundaries of the test specimen, and the constriction parameter. The CRM is modified to include the effectiveness of waviness. Both modified PCM and CRM are combined in a contact conductance correl